Fat body in some genera of leaf-cutting ants (Hymenoptera: Formicidae). Proteins, lipids and polysaccharides detection

The comparative histochemical analysis of the fat body of workers belonging to the basal species Cyphomyrmex rimosus and Mycetarotes parallelus and to derived species Acromyrmex disciger and Atta laevigata revealed that this tissue is constituted mainly by cells denominated trophocytes and oenocytes. The trophocytes of all species studied here were characterized mainly by the proteins and lipids synthesis and storage, being the derived species the ones who have presented higher quantity of lipids in the trophocytes when compared to the trophocytes of basal species. In workers M. parallelus and A. laevigata, besides proteins and lipids, there has being observed the presence of polysaccharides, however, in C. rimosus and A. disciger these elements were detected in lower quantities. The histochemical studies of the oenocytes of basal and derived species revealed significant presence of proteins as well as lipids in these cells. In the oenocytes of derived species A. disciger and A. laevigata a higher quantity of lipidic inclusions has being observed, when compared to the basal species.     

New morphological data on fat bodies of semi-engorged females of Amblyomma cajennense (Acari: Ixodidae)

The present ultramorphological, histological and ultrastructural study on the fat body of semi-engorged females of Amblyomma cajennense revealed that this tissue is diffuse and consists of strands of cells surrounding the tracheal trunks. Morphometric analysis showed that the cellular and nuclear areas of round-shaped trophocytes are larger than those of cuboidal trophocytes, indicating that the arrangement of the former provides more contact area with the haemolymph. In this species, the fat body is found right underneath the integument and around organs. It consists of two cell types that despite distinct morphological characteristics and locations in the tissue, present the same histological features. In this study, these cells were termed cuboidal trophocytes when arranged as strands of cells and present in larger numbers, and round-shaped trophocytes when lying on these strands and observed in fewer numbers. Histological observations revealed that both types of trophocytes have one nucleus in their cytoplasm and also exhibit numerous vacuoles of different sizes and contents. Ultrastructural examination revealed that the organelles more frequently observed were the vesicular and lamellar rough endoplasmic reticulum, and mitochondria with tubular crests, indicating that they might be involved in lipid synthesis. Smooth endoplasmic reticulum was not observed. Cuboidal trophocytes arranged in strands, despite being closely associated, do not exhibit fused plasma membranes. Rather, the fusion of basal lamina of two neighboring cells is occasionally observed, acting as a selective permeability barrier. Here, a new terminology for tick fat body is proposed. It is based on fat body location (parietal, when located right underneath the integument instead of peripheral; and perivisceral, when located around organs instead of central) terminologies previously suggest by Obenchain and Oliver and for the cells constituting them, cuboidal trophocytes when arranged as strands, and round-shaped trophocytes when lying on these strands. Nephrocytes were not observed in semi-engorged females of A. cajennense.     

Dehiscent organs used for defensive behavior of kamikaze termites of the genus Ruptitermes (Termitidae,Apicotermitinae) are not glands

During Isoptera evolution, the caste of soldiers disappeared in some Apicotermitinae termites as in the Neotropical Ruptitermes. Paired dorsolateral structures located between the metathorax and abdomen of foraging workers of Ruptitermes were previously denominated dehiscent glands, and are responsible for releasing an adhesive secretion that immobilizes enemies, causing their death. In this study, we investigated the morphology of dehiscent organs of workers of Ruptitermes reconditus, Ruptitermes xanthochiton, and Ruptitermes pitan and also second instar larvae of R. reconditus using light, laser scanning confocal, and transmission electron microscopy. Additionally, we performed a preliminary protein analysis using SDS-PAGE to further characterize the secretion of Ruptitermes dehiscent organs. Our results showed that the dehiscent organs do not exhibit the typical characteristics of the exocrine glandular cells class I, II or III of insects, suggesting that they constitute a new type of defensive organ. Thus, the denomination dehiscent gland was not used but dehiscent organ. Dehiscent organs in larvae are formed by fat body cells. In workers, dehiscent organs are composed by compact masses of cells that accumulate a defensive secretion and are poor in organelles related to the production of secretion. Since the dehiscent organs are not glands, we hypothesize that the dehiscent organs originate from larval fat body. The defensive secretion may have been produced at younger developmental stages of worker or the defensive compounds were absorbed from food and accumulated in the worker fat body. Histochemical techniques and SDS-PAGE revealed that the secretion of Ruptitermes dehiscent organs is constituted mainly by a protein of high molecular weight (200 kDa). In conclusion, the dehiscent organs are extremely different from the exocrine glands of termites and other insects described until now. In fact, they seem to be a specialized fat body that is peculiar and exclusive of Ruptitermes termites.     

Heparan sulfate is the main sulfated glycosaminoglycan species in internal organs of the male cockroach, Periplaneta americana

Sulfated glycosaminoglycans (GAGs) were isolated and characterized in thoracic muscle, fat body, whole digestive tract (stomach+intestine) and reproductive tract of adult male cockroaches, Periplaneta americana. Heparan sulfate (HS) was the predominant sulfated GAG species in the tissues analyzed, corresponding to more than 90% of the total sulfated GAG content. In both the thoracic muscle and fat body it was the only sulfated GAG species detected. We also determined the location of sulfated GAGs in most of these organs by histochemical analysis using 1,9-dimethylmethylene blue. In the thoracic muscle, sulfated GAG metachromatic staining was detected only in the connective tissue that surrounds the muscle bundles or fascicles. In the intestinal tract, metachromatic staining was observed in both epithelial and lining columnar cells. Only spermatozoa presented metachromatic material in the male reproductive tract. Since, HS corresponds to 90-100% of total sulfated GAGs in these tissues, the metachromatic staining specifically reflects the location of this particular sulfated GAG in these organs. In conclusion, the present study extends previous observations on the GAG composition in cockroaches providing new information on the tissue distribution and location of HS in several internal organs of adult males of the cockroach P. americana.     

Snow white and the seven dwarfs: a multivariate approach to classification of cold tolerance

Two main cold hardiness strategies of insects - freeze tolerance in some species, and overwintering in a supercooled state without tolerance of freezing in many others - were recently reclassified. However, I present several problems with the current systems. My suggested classification is based on clearer definitions of the causes of cold injury. I recognize three main mortality factors: freezing of body liquids, cold shock, and cumulative chill injury. Presence or absence of each of these factors produce eight combinations. I have named the eight classes after Snow White and the Seven Dwarfs to avoid nomenclatural confusion. Some of these classes are probably not used as tactics against cold injury by any insect species. Other classes contain so many species that they might be reclassified in more detail, using values of supercooling point and other quantitative parameters. However, widely comparable parameters, like the upper limit of cold injury zone and the sum of injurious temperatures are still rarely published, thus we still lack comprehensive data for multivariate analyses. Every cold hardiness strategy should be characterized by a meaningful class or subclass together with the physiological, biochemical, and behavioural mechanisms employed by the insects. I also point out the existence of strategies that combine two tactics - either a switching strategy (during preparation for winter, population "chooses" which tactic will be used), or a dual strategy (individuals are ready to use one of the tactics depending on the prevailing environmental conditions).     

Establishment of a concept of visceral fat syndrome and discovery of adiponectin

Although obesity is a major background of life style-related diseases such as diabetes mellitus, lipid disorder, hypertension and cardiovascular disease, the extent of whole body fat accumulation does not necessarily the determinant for the occurrence of these diseases. We developed the method for body fat analysis using CT scan and established the concept of visceral fat obesity, in other word metabolic syndrome in which intra-abdominal visceral fat accumulation has an important role in the development of diabetes, lipid disorder, hypertension and atherosclerosis. In order to clarify the mechanism that visceral fat accumulation causes metabolic and cardiovascular diseases, we have analyzed gene expression profile in subcutaneous adipose tissue and visceral adipose tissue. From the analysis, we found that adipose tissue, especially visceral adipose tissue expressed abundantly the genes encoding bioactive substances such as cytokines, growth factors and complements. In addition to known bioactive substances, we found a novel collagen-like protein which we named adiponectin. Adiponectin is present in plasma at a very high concentration and is inversely associated with visceral fat accumulation. Adiponectin has anti-diabetic, anti-hypertensive and anti-atherogenic properties and recent studies revealed that this protein has an anti-inflammatory and anti-oncogenic function. Therefore hypoadiponectinemia induced by visceral fat accumulation should become a strong risk factor for metabolic and cardiovascular diseases and also some kinds of cancers.In this review article, I would like to discuss the mechanism of life style-related diseases by focusing on the dysregulation of adiponectin related to obesity, especially visceral obesity.     

Ergastoplasmic paracrystalline inclusion bodies in the adipose gonadal envelope and fat body of the glow worm, Lampyris noctiluca (Insecta, Coleoptera).

The gonads of glow worm larvae are enveloped by adipose tissue which represents a specialized fat body. The adipose gonadal envelope, and also to a lesser extent the fat body cells, contain tubular paracrystalline inclusion bodies (PIBs). Cells of other tissues are devoid of such inclusions. The PIBs form in the cisternae of rough ER. In young larvae PIB formation is sparse, but at advanced larval stages PIBs often occur as bundles in stacks of ergastoplasm. Typically, a PIB within a cisterna consists of four to seven parallel tubules. The outer diameter of a tubule is ca 28.8 nm and the width of the tubule lumen ca 12.2 nm. The "wall" of a tubule contains globular protein subunits of ca 8.3 nm diameter; the subunits are arranged helically. Since the adipose gonadal envelope progresses through a cytological differentiation process during differentiation and maturation of the gonads, the increased number of PIBs may indicate enhanced metabolic activity of the tissue related to nutrition of the growing gonads.     

Ultrasonic assessment of tissue hydration status

Tissue water content is an important diagnostic parameter that can be used for estimation of water loss in muscles such as common dehydration during high endurance exercises. It could be also applied for evaluation of the increased fluids content in the tissue caused by the variety of pathological conditions or edemas. Ultrasonic method for tissue water content monitoring is based on the premise that the speed of a bulk or compression sound wave is determined mainly by the molecular content of the tissue. Most soft tissues, including muscles that consist of about 70-80% water, exhibit shift of the ultrasound velocity associated with the change in their water content. In the present paper, we tested the feasibility of assessing changes in tissue water content by measurements of ultrasound velocity in ex vivo animal muscle tissues. An increase in the ultrasound velocity correlated with the volumetric water loss in the tissue was observed when other tissue components (proteins, fat) remained constant. Possibility to assess muscle dehydration with 1% accuracy was confirmed in model dehydration experiments, where ultrasound velocity slope of about 3 m/s per 1% of water loss was revealed at measurement error less than 2 m/s. Hence, the ultrasonic approach can provide basis for a convenient, lightweight system in sports medicine for monitoring total body hydration during long-term endurance exercise in hot conditions, as well as for edemas monitoring and other medical applications.     

Ultra-structure and histochemistry of digestive cells of Podisus nigrispinus (Hemiptera: Pentatomidae) fed with prey reared on bt-cotton

The toxic effects of Bt proteins from the body of the prey/host to predators and parasitoids have been investigated as a route of impact on non-target insects of Bt crops. This research aimed to analyze ultrastructural changes and histochemistry in digestive cells of the middle region of the midgut of Podisus nigrispinus fed, since its second instar, with Spodoptera frugiperda reared on Bt cotton variety Acala90 B, which expresses the toxin Cry 1Ac, and its non-Bt isoline Acala 90. Fragments of the midgut of P. nigrispinus were analyzed by electron microscopy. For the histochemical analysis, Bromophenol Blue, Periodic Acid Schiff von Kossa, Alcian Blue pH 2.5 and Sudan Black were used. The Cry1Ac toxin of Bt cotton ingested by S. frugiperda promotes a disorganization in the perimicrovillar matrix of P. nigrispinus (third trophic level), thus generating ultrastructural changes in the digestive cells, as elongation of microvilli, presence of spherocrystals and granules of different electron densities, in addition to altering the distribution pattern of glycogen, lipids and calcium of these cells in the median region of the midgut. Thus, we conclude that species moderately susceptible to Cry1Ac toxin, such as S. frugiperda, can acquire this toxin and expose it to P. nigrispinus, which can interfere with your ability to predation.     

Protein transfer to membranes upon shape deformation

Red blood cells, milk fat droplets, or liposomes all have interfaces consisting of lipid membranes. These particles show significant shape deformations as a result of flow. Here we show that these shape deformations can induce adsorption of proteins to the membrane. Red blood cell deformability is an important factor in several diseases involving obstructions of the microcirculatory system, and deformation induced protein adsorption will alter the rigidity of their membranes. Deformation induced protein transfer will also affect adsorption of cells onto implant surfaces, and the performance of liposome based controlled release systems. Quantitative models describing this phenomenon in biomaterials do not exist. Using a simple quantitative model, we provide new insight in this phenomenon. We present data that show convincingly that for cells or droplets with diameters upwards of a few micrometers, shape deformations induce adsorption of proteins at their interface even at moderate flow rates.     

Biological surface science

Biological surface science (BioSS), as defined here is the broad interdisciplinary area where properties and processes at interfaces between synthetic materials and biological environments are investigated and biofunctional surfaces are fabricated. Six examples are used to introduce and discuss the subject: Medical implants in the human body, biosensors and biochips for diagnostics, tissue engineering, bioelectronics, artificial photosynthesis, and biomimetic materials. They are areas of varying maturity, together constituting a strong driving force for the current rapid development of BioSS. The second driving force is the purely scientific challenges and opportunities to explore the mutual interaction between biological components and surfaces.

Model systems range from the unique water structures at solid surfaces and water shells around proteins and biomembranes, via amino and nucleic acids, proteins, DNA, phospholipid membranes, to cells and living tissue at surfaces. At one end of the spectrum the scientific challenge is to map out the structures, bonding, dynamics and kinetics of biomolecules at surfaces in a similar way as has been done for simple molecules during the past three decades in surface science. At the other end of the complexity spectrum one addresses how biofunctional surfaces participate in and can be designed to constructively participate in the total communication system of cells and tissue.

Biofunctional surfaces call for advanced design and preparation in order to match the sophisticated (bio) recognition ability of biological systems. Specifically this requires combined topographic, chemical and visco-elastic patterns on surfaces to match proteins at the nm scale and cells at the micrometer scale. Essentially all methods of surface science are useful. High-resolution (e.g. scanning probe) microscopies, spatially resolved and high sensitivity, non-invasive optical spectroscopies, self-organizing monolayers, and nano- and microfabrication are important for BioSS. However, there is also a need to adopt or develop new methods for studies of biointerfaces in the native, liquid state.

For the future it is likely that BioSS will have an even broader definition than above and include native interfaces, and that combinations of molecular (cell) biology and BioSS will contribute to the understanding of the “living state”.     

Identification of fly eggs using scanning electron microscopy for forensic investigations

Forensic entomology is the science that studies the role of insects in decomposing corpses and one of the most common uses is to estimate the post-mortem interval (PMI) based on insect activity on a decomposing body. Usually, flies are the first insects to reach a carcass and are able to oviposit on carrion within a few hours after death. Scanning electron microscopy (SEM) gives detailed information about morphological characters helping to identify the immature forms of flies and consequently serves as a tool in crime scene investigations. Sometimes, only eggs and larvae are found in corpses. Some dipteral species are important because their larvae develop in organic matter. The aim of this study is to identify eggs of species of forensic importance, such as Chrysomya megacephala, Chrysomya putoria, Lucilia cuprina, Lucilia eximia and Ophyra aenescens, using scanning electron microscopy (SEM). C. megacephala had no anastomosis or holes at the top of the islands and C. putoria had few anastomoses and no holes, whereas L. eximia and O. aenescens were found to have anastomoses and holes and L. cuprina had only anastomoses. The median area was bifurcated anteriorly in C. megacephala, L. eximia and O. aenescens and rounded in C. putoria and L. cuprina. Also the sculptures observed in the chorionic cells, the length and the way that median area ends up posteriorly are characteristics of great diagnostic value to identify muscoids of forensic importance.     

Frequency-Selective Fat Suppression Radiofrequency Pulse Train to Remove Olefinic Fats

CHESS pulse can suppress the signal originating from aliphatic fat protons but cannot suppress the signal from olefinic fat protons, which is near the resonance frequency of water protons. Adipose tissue contains various fat species; aliphatic fat comprises about 90 % and olefinic fat about 10 % of adipose tissue. Thus, CHESS pulse cannot be used to suppress the signal from adipose tissue completely. The purpose of this study was to find a method to suppress the signal from adipose tissue completely. The Fatsat train pulse, created with an arbitrary flip angle and insensitive to B1 inhomogeneity, was used. Because B1 inhomogeneity is larger on higher field magnetic resonance imaging, the fat suppression radiofrequency pulse needs to be B1-insensitive. To investigate a percentage of olefinic fat in adipose tissues, the excitation frequency of the Fatsat train pulse was varied from ?240 to +400 Hz and the images and fat-suppressed images were obtained. The presence of olefinic fat comprising about 10 % of abdominal adipose tissue was identified. The result agreed with some previous papers. Complete fat suppression could be achieved by partial (10 %) inversion of longitudinal aliphatic fat magnetization and by canceling out the two fat magnetizations. The flip angle was identified to about 95°. In conclusion, the cause that the signal from adipose tissues cannot be suppressed completely has been found. Improved images that signals from adipose tissues were suppressed completely have been demonstrated. This technique can also be applied to several pulse sequences.     

Impact of ultrasound processing on alternative protein systems: Protein extraction,nutritional effects and associated challenges

Proteins from alternative sources including terrestrial and aquatic plants, microbes and insects are being increasingly explored to combat the dietary, environmental and ethical challenges linked primarily to conventional sources of protein, mainly meat and dairy proteins. Ultrasound (US) technologies have emerged as a clean, green and efficient methods for the extraction of proteins from alternative sources compared to conventional methods. However, the application of US can also lead to modifications of the proteins extracted from alternative sources, including changes in their nutritional quality (protein content, amino acid composition, protein digestibility, anti-nutritional factors) and allergenicity, as well as damage of the compounds associated with an increased degradation resulting from extreme US processing conditions. This work aims to summarise the main advances in US equipment currently available to date, including the main US parameters and their effects on the extraction of protein from alternative sources, as well as the studies available on the effects of US processing on the nutritional value, allergenicity and degradation damage of these alternative protein ingredients. The main research gaps identified in this work and future challenges associated to the widespread application of US and their scale-up to industry operations are also covered in detail.     

Noninvasive assessment of abdominal adipose tissues and quantification of hepatic and pancreatic fat fractions in type 2 diabetes mellitus

The purpose of this study was to evaluate adipose tissue distributions and hepatic and pancreatic fat contents using a 6-point Dixon MRI technique in type 2 diabetes mellitus (T2DM), and to assess associations between fat distributions and biochemical markers of insulin resistance. Intra-abdominal MRI was investigated in 14 T2DM patients, 13 age- and sex-matched healthy controls (HC) and 11 young HC using a 3 T Prisma MRI scanner. All T2DM subjects completed a fasting comprehensive metabolic panel, and demographic measurements were taken according to standardized methodologies. We observed excellent correlation (R² = 0.94) between hepatic fat fraction quantified using 6-point Dixon MRI and gold standard MRS, establishing the accuracy and reliability of the Dixon technique. Significantly increased visceral adipose tissue (VAT) volumes were found in T2DM patients compared to age-matched HC (1569.81 ± 670.62 cm³ vs. 1106.60 ± 566.85 cm³, p = .04). We also observed a trend of increasing subcutaneous adipose tissues (SAT), and total abdominal fat (TAT) volumes in T2DM compared to age-matched HC. Hepatic fat fraction percentage (HFF%) was 44.6% higher in T2DM compared to age-matched HC and 64.4% higher compared to young HC. Pancreatic fat fractions in the head and body/tail were higher in T2DM patients compared to both healthy cohorts. We also observed correlations between fat contents of the liver and pancreas in T2DM patients, and association between biochemical markers of T2DM with HFF, indicating a risk for non-alcoholic fatty liver disease among T2DM. In summary, this study provides evidence of T2DM patients having increased liver and pancreatic fat, as well as increased adipose tissues.     

Experimental investigations on the strategies of fighting crickets Velarifictorus micado to manipulate air resistance

Fighting crickets,one species of flightless insects optimally chosen by nature for millions of years,have evolved to fairly smooth and streamlined body surfaces.This article tries to answer the question how the insects manipulate air resistance when travelling through air after take-off without using their wings and meanwhile keep a high efficiency.We found that fighting crickets,Velarifictorus micado,performed two types of movements through air:stable and unstable.The two types both have a high moving efficiency.For the stable type,the moving efficiency is larger than 95%.As a typical example,focusing on the stable type,we firstly predicted each component of aerodynamic drag applied on the crickets and analysed the drag contributions to the initial kinetic energy dissipation.Further investigation revealed the mechanisms of the efficiently moving strategy against air resistance for the insects.The results show that the crickets can spin their hind legs to adjust body posture,thereby changing(increasing or decreasing)the air drag acting on the body to raise the efficiency during aerial movements.This work may advance the understanding of the significance of hind legs to insects’evolution and provide inspiration for future robot or micro aerial vehicle designs.     

Ultrasound velocity in human muscle in vivo: perspective for edema studies

The present study examines the association of the changes in ultrasound velocity measured at 1 MHz using 1.5 micros duration tone burst in the human soleus muscle in vivo with several pathologies including patients with chronic renal failure (CRF) and disorders of the cardiovascular system. Total 127 subjects were investigated, with approximately equal number of male and female subjects uniformly distributed by age, from 15 to 70 years old. Since molecular composition of the tissue is thought to have greater effect on the bulk ultrasound velocity, potential contribution of both water and fat, two main variable components of a muscle, were taken into account. Observed negative correlation of ultrasound velocity with the body mass index was considered a result of an elevated fat content. Based on the obtained data, presence of leg edemas results in a measurably lower ultrasound velocity in the soleus muscle. Unless patients had visibly detected leg edema, no difference between healthy individuals, patients with chronic heart failure, or CRF was found. Despite relatively high individual variations in velocity, ranging from 1530 to 1615 m/s, a statistically significant gender correlated difference between average values of the velocity was observed. No dependence of velocity on subject age was detected. An indirect confirmation of the muscle fluid homeostasis was revealed in patients with CRF undergoing hemodialysis procedure. After hemodialysis, a significantly smaller increase (0.3% in average) of ultrasound velocity in the soleus muscle was observed than otherwise could be expected if a uniform relative loss of total body fluids was assumed (1-1.3%). In general, the study findings set a premise for using ultrasound velocity as a potential quantitative parameter for edema assessment.     

在多层结构的生物组织中近红外光子迁移的研究

在无损近红外光学诊断领域中,研究光子在多层生物组织中的迁移十分重要。本文以猪的脂肪和肌肉组成的两层结构作为研究的样品。将近红外光源和检测器置于脂肪的表面,由光源发出被两层组织反射的光子的一部分由检测器所接收。本文给出了光电流与光源到检测器的距离的关系以及光电流与脂肪厚度的关系。为了分析实验结果,用蒙特卡罗仿真计算光子在均匀介质中迁移轨迹,用菲涅耳定律来决定光子包在脂肪和肌肉边界处的折射分量和反射分量。结果表明,仿真数据与实验符合得很好。结论是：本文中所提供的实验和仿真方法对于分析光子在生物组织中的迁移以及优化传感器设计十分有用。     

13C/12C-Untersuchungen an Tumorzellen

Abstract

The metabolism of tumor-cells differs in many ways from normal (healthy) cells. One of the major differences is the high glycolytic activity in tumor-cells with the subsequent formation of lactate from glucose, even in the presence of oxygen. The question whether this high rate of glycolysis has any effect on the ¹³C/¹²C-relation of the cells is examined in experiments with a tumor-cell line (HT29) and in specimens of human breast cancer.

The HT29 cells show a clear decrease in ¹³C content compared to their culture medium (Δδ = 3.28‰).

Tissue from human breast cancer has more ¹³C than normal breast tissue taken from the same patient ((Δδ = 2.74‰). But the content of fat is much higher in the normal tissue and its δ-value is negatively correlated with its fat content. It is concluded that the difference between normal and tumor tissue is due to the heterogeneous composition of the normal tissue samples.     

Muscle and fat quantification in MRI gradient echo images using a partial volume detection method. Application to the characterization of pig belly tissue

Complete dissection is the current reference method to quantify muscle and fat tissue on pig carcasses. Magnetic resonance imaging (MRI) is an appropriate nondestructive alternative method that can provide reliable and quantitative information on pig carcass composition without losing the spatial information. We have developed a method to quantify the amount of fat tissue and muscle in gradient echo MR images. This method is based on the method proposed by Shattuck et al. [12]. It provides segmentation of pure tissue and partial volume voxels, which allows separation of muscle and fat tissue including the fine insertions of intermuscular fat. Partial volume voxel signal is expected to be proportional to the signals of pure tissue constituting them or at least to vary monotonously with the proportion of each tissue. However, it is not always the case with gradient echo sequence due to the chemical shift effect. We studied this effect on a fat tissue/muscle interface model with variable proportion of water in the fat tissue and variable TE. We found that at TE=8 ms, for a 0.2-T MRI system, the requirement of Shattuck's method were filled thanks to the presence of water in fat tissue. Moreover, we extended the segmentation method with a simple correction scheme to compute more accurately the proportions of each tissue in partial volume voxels. We used this method to evaluate the fat tissue and muscle on 24 pig bellies using a gradient echo sequence (TR 700 ms, TE 8 ms, slice thickness 8 mm, number of averages 8, flip angle 90 degrees , FOV 512 mm, matrix 512*512, Rect. FOV 4/8, 19 slices, space between slices 2 mm). The image analysis results were compared with dissection results giving a prediction error of the muscle content (mean=2.7 kg) of 88.9 g and of the fat content (mean=2.7 kg) of 115.8 g without correction of the chemical shift effect in the computation of partial volume fat content. The correction scheme improved these results to, respectively, 81.5 and 107.1 g.