A new Technique for Measurement of Myocardial O2-Utilization

The coronary reserve of mammalian hearts is significantly heterogeneous. From this phenomenon we conclude on a heterogeneous energy-demand, i.e., ATP-demand and therefore on a nonuniform ischemic tolerance of cardiomyocytes.

Our aim was to establish a method for direct quantification of cardiomyocyte energy production. According to Langendorff, 10 isolated rabbit hearts were perfused with oxygen enriched Krebs-Henseleit solution. Using the stable oxygen isotope ¹⁸O₂, respiratory water of 7 hearts was labelled, and samples were taken from the coronary venous effluent. Defined cardiac tissue areas were lyophylized. Using the guanidine-hydrochloride technique, μl-water samples from the tissue and the coronary venous effluent were quantitatively converted to CO₂. With the help of mass-spectrometry the δ¹⁸O/¹⁶O-isotope ratios were determined and related to the SMOW-scale.

Compared to control hearts, a significant shift to higher SMOW-values within respiratory water from ¹⁸O-labelled hearts was detected (mean = 14.61%). Control hearts (maximal scatter = 1.42%) as well as ¹⁸O-labelled hearts (4.06%) showed high reproducibilit, of the method. With the employed experimental setup, significant regional differences were not detected. The kinetics of the coronary venous effluent showed a tendency toward saturation with H₂ ¹⁸O within 2 min after starting the ¹⁸O₂-perfusion. After 50 s perfusion increase in SMOW-values reached statistical significance.     

Studies upon Qualification of Meat from Animals Irradiated and Contaminated with Radiocaesium

Abstract

The problem concerning qualification of food originated from animals irradiated and contaminated with ¹³⁷caesium appeared especially after the Chernobyl accident. So, it was a reason to undertake respective studies on 108 rabbits divided into three groups: group I – non-irradiated rabbits, group II – irradiated with a dose of 103 mCkg^?1 (400 R), group III – irradiated with a dose of 206 mCkg^?1 (800 R). All animals were contaminated intragastrically with an aqueous solution of ¹³⁷CsCl. After slaughter samples of the muscles were cured in 1, 3, 5, 10, and 15% brine or were cooked for 2 hrs. In the case of curing the radioactivities of meat and brine, and the concentrations of salt in cured meat were estimated after 7, 14, and 21 days. The radioactivities of cooked meat, broth, and condensed water vapour were estimated after 1 and 2 hrs. Taking into account the decrease of the radioactivities, duration of curing, and concentrations of salt in cured meat the optimum results were achieved when the meat from non-irradiated rabbits was cured for 7 days in 3% brine, and that of irradiated rabbits in 5% brine with regard to a lower stability of this meat. The decontamination effectiveness of cooking was similar in all examined rabbits. Radiocaesium penetrates into the brine or broth and escapes with water vapour thereafter.     

替拉扎明在家兔体内的代谢研究

进行了替拉扎明（TPZ）在家兔体内的代谢研进行了研究。化学合成了TPZ的去氧代谢物SR4317和SR4330,由HPLC、TLC、MS、^1H NMR及IR分析证实,SR4317和SR4330是TPZ经逐步还原的去氧化合物;采用HPLC梯度洗脱法同时测定家兔血浆中TPZ及其代谢物SR4317、SR4330的含量,得到TPZ及其代谢物的均值血药浓度-时间关系曲线。由此可推知,TPZ在家兔体内的代谢途径为还原代谢,即TPZ逐步还原为4位去氧的代谢物SR4317和1、4位去氧的代谢物SR4330。该研究结果可为TPZ在人体内的代谢研究提供参考。     

高功率微波对家兔视觉电生理功能及组织结构的影响

采用高功率电磁波直接辐照家免全身后,即刻分别测试家兔的视网膜电流图（Electro-retinogram,ERG）;随后即刻取材,包埋固定,分别在光学显微镜和透射电镜下观察其视觉器官的组织结构。结果表明,高场强的高功率微波辐照可造成家兔眼视网膜组织的即刻损伤,对家兔视觉电生理功能可产生明显的抑制作用,其作用强度与辐照剂量和辐照时间存在一定的量效、时效关系。     

Review: Reactive selenium metabolites as targets of toxic metals/metalloids in mammals: a molecular toxicological perspective

Human activities have been contaminating the environment with toxic heavy metal and metalloid compounds. Since the toxicity of one metal or metalloid can be dramatically modulated by the simultaneous ingestion of another, studies addressing the molecular basis of chemical interactions between toxic and essential elements are increasingly important. The intravenous injection of rabbits with selenite and arsenite or with selenite and mercuric mercury resulted in the in vivo formation of the seleno‐bis (S‐glutathionyl) arsinium ion, [(GS)₂AsSe]^?, or a glutathione‐coated mercuric selenide, (GS)₅(HgSe)_core, in blood. The formation of these species (and the formation of a cadmium–selenium species in blood after the exposure of rats to selenite and cadmium) critically involves reactive selenite metabolites, such as GS–Se^? and/or HSe^?, which indicates that these physiologically important metabolites are molecular targets of ingested toxic metals and metalloids. The fate and stability of [(GS)₂AsSe]^? and (GS)₅(HgSe)_core in vivo imply that the chronic exposure of mammals to inorganic arsenic and mercury will cumulatively affect the bioavailability of selenium, which could lead to selenium deficiency. Since selenium deficiency is significantly associated with the etiology of cancer in humans, the GSH‐driven in vivo formation of selenium‐containing metal and metalloid species provides a likely molecular mechanism for the chronic toxicity of environmentally persistent inorganic arsenic, mercury and cadmium. Copyright © 2002 John Wiley & Sons, Ltd.     

Formulation and Preliminary in vivo Testing of Rufloxacin-Cyclodextrin Ophthalmic Solutions

Aim of the present work was to investigate the effect of somecyclodextrins (CDs) on the solubility and ocular bioavailability of rufloxacin base (RUF), with theultimate goal of developing an ophthalmic formulation. Phase solubility studies of RUF inpH 7.4 buffer were carried out in the presence of -cyclodextrin (-CD),hydroxypropyl--cyclodextrin (HP--CD) and -cyclodextrin(-CD). The effect of hydroxypropyl methylcellulose (HPMC) on RUF solubility was evaluated after heating the solutionscontaining HP--CD at 120 °C.A significant enhancement of RUF solubility was achieved by associatingthe drug with CDs, particularly HP--CD. This CD formed with RUF a less stablecomplex than that formed by -CD, but did not suffer the solubility limitations ofthe parent CD, and showed a higher solubilizing capacity than -CD. Addition of 0.25%(w/v) HPMC to solutions containing HP--CD increased the solubilizing effect of this CD,thus allowing reduction of the amount necessary for solubilization of 0.3% (w/v) RUF.Preliminary pharmacokinetic data in rabbits indicated that theocular bioavailability of 0.3% (w/v) RUF solubilized by HP--CD was higher when compared witha 0.3% (w/v) RUF suspension used as reference.     

Dendroaspis natriuretic peptide regulates the cardiac L-type Ca2+ channel activity by the phosphorylation of α1c proteins

Dendroaspis natriuretic peptide (DNP), a new member of the natriuretic peptide family, is structurally similar to atrial, brain, and C-type natriuretic peptides. However, the effects of DNP on the cardiac function are poorly defined. In the present study, we examined the effect of DNP on the cardiac L-type Ca(2+) channels in rabbit ventricular myocytes. DNP inhibited the L-type Ca(2+) current (I(Ca,L)) in a concentration dependent manner with a IC(50) of 25.5 nM, which was blocked by an inhibitor of protein kinase G (PKG), KT5823 (1 μM). DNP did not affect the voltage dependence of activation and inactivation of I(Ca,L). The α(1c) subunit of cardiac L-type Ca(2+) channel proteins was phosphorylated by the treatment of DNP (1 μM), which was completely blocked by KT5823 (1 μM). Finally, DNP also caused the shortening of action potential duration in rabbit ventricular tissue by 22.3 ± 4.2% of the control (n = 6), which was completely blocked by KT5823 (1 μM). These results clearly indicate that DNP inhibits the L-type Ca(2+) channel activity by phosphorylating the Ca(2+) channel protein via PKG activation.     

Determination of 3-n-butylphthalide in rabbit plasma by HPLC with fluorescence detection and its application in pharmacokinetic study

A rapid, sensitive and specific reversed-phase high-performance liquid chromatographic method was developed for the determination of 3-n-butylphthalide, a drug currently being developed for treatment of stroke, in rabbit plasma. Fluorescence detection at an excitation wavelength of 280 nm and an emission wavelength of 304 nm was used for quantification of 3-n-butylphthalide. Ibuprofen was used as internal standard. Plasma samples were extracted with diethyl ether under acidic conditions. After evaporation of the organic phase, the extract was dissolved in mobile phase and injected into the chromatograph with C(18) column and a mobile phase of 0.05 mol/L sodium acetate buffer (pH 4.5)-acetonitrile (400:600). The peak area ratio vs concentration in plasma was linear over the range of 0.0212-4.24 microg/mL (correlation coefficient r = 0.9984) and the limit of quantification was 0.0212 microg/mL. Mean recovery was determined as 101.0% by analysis of plasma standard samples containing 0.0424, 0.424, 2.12 and 4.24 microg/mL of 3-n-butylphthalide. The intra-day relative standard deviations (RSDs) ranged from 3.6 to 8.9% and inter-day RSDs were within 8.0%. Pharmacokinetics of a single intravenous dose of 3-n-butylphthalide to the rabbits was presented to illustrate the applicability of this method. 3-n-Butylphthalide exhibited linear pharmacokinetics after intravenous administration to rabbits over the dose range 1-10 mg/kg.