A molecular scheme for the reaction between γ-aminobutyric acid and the most abundant chloride channel on crayfish deep extensor abdominal muscle

Single-channel measurements were performed with the aim of constructing a detailed molecular scheme for the reaction between -aminobutyric acid (GABA) and a chloride channel of crayfish deep extensor abdominal muscle (DEAM). GABA was applied in pulses to outside-out patches of muscle membrane, and, based on the dose-response of the peak currents and of their rise times, a linear model with five binding steps has been proposed. Evaluation of the single-channel kinetics indicated at least three open states. Two of them originate most probably from the fully liganded receptor state and are grouped in mixed bursts due to their different life times. The third one appears independently, outside the bursts, and originates from a lower liganded receptor state. Simulations of the dose-responses and the open time distributions with this model led to a set of rate constants which generated relatively optimal fits.     

An evaluation of seven postural reactions ("lagereflexe" selected by Vojta) in twenty-five healthy infants

Twenty-five healthy infants were followed from the newborn period to the age of eighteen months, by evaluation of their neuromotor performance. Evaluation of the specific postural reaction patterns (as described by Vojta) did not seem to be any use as a "short-cut" for the early diagnosis of neuromotor abnormalities, a considerable number of deviations from the normal/optimal pattern being noted even in completely normal infants.     

Induction of vascular haemostasis by Nd:YAG laser light in melanin-rich and melanin-free tissue

Haemostasis was effected in vessels of melanin-rich (MR: choroid) and melanin-free (MF: mesentery) rabbit tissue irradiated with a cw-Nd: YAG laser. The following parameters were employed: - pulse duration: 200 ms (MR) and 100ms (MF); focal spot diameter: 200 m (MR) and 80 m (MF); pulse energies: 100–250 mJ (MR) and 0.5-1J (MF); irradiances: 1.6–4.0kWcm^–2 (MR) and 1–2 × 10²kWcm² (MF). In melanin-rich tissue, laser energy is absorbed principally by melanin granules contained within the stromal melanocytes. The heat generated in these structures radiates into the surrounding tissue where it is dissipated. The damage thus incurred by the endothelium of blood vessels encompassed within this field triggers the haemostatic mechanism whereby blood flow is arrested. This effect is realized by the formation of an occluding plug of platelets, which is stabilized by the deposition of fibrin, particularly in capillaries, and to a lesser degree in larger vessels of the vascular lamina. In melanin-free tissue, haemoglobin serves as the primary site of energy absorption, which is thus shifted from the stroma to the vessel lumen. Irradiation of vessels in such tissue leads to thermocoagulation of plasma proteins and consequent stasis of blood flow.     

Differences in the response of Sprague-Dawley and Lewis rats to bezafibrate: The hypolipidemic effect and the induction of peroxisomal enzymes

The effects of bezafibrate administered at 10 and 50 mg/kg/day for 7 days to male Sprague-Dawley (SD) and Lewis rats were investigated in order to determine the interrelation between the changes in serum and hepatic lipid contents and activities of selected peroxisomal, microsomal and mitochondrial enzymes in the two rat strains. In both strains, bezafibrate effectively reduced serum and hepatic lipids, increased the liver weight, induced a proliferation of peroxisomes, and selectively elevated the activities of carnitine acetyltransferase and of the enzymes of the peroxisomal -oxidation system. Moreover, immunoblotting revealed that the drug specifically enhanced the concentration of only those peroxisomal enzymes involved in fatty acid -oxidation. The data obtained demonstrate that although the responses initiated by bezafibrate are qualitatively similar in both strains, they differ in their magnitude in a dose-dependent manner, with the Lewis strain exhibiting a more pronounced response than the SD rats. These results show that dose-dependent strain differences as well as the generally known species differences should be taken into account in pharmacological and toxicological evaluations of fibrates in rodents. Furthermore, generalization and extrapolation from rodent studies should be treated with great caution.     

Continuous monitoring of extracellular lactate concentration by microdialysis lactography for the study of rat muscle metabolism in vivo

A method is described for the measurement and on-line monitoring of muscular extracellular lactate concentration in both anaesthetized and freely moving rats. This method is based on microdialysis sampling and lactic dehydrogenase-catalysed nicotinamide adenine dinucleotide, reduced (NADH)-fluorescence detection techniques. In vivo calibration revealed a resting extracellular lactate concentration of 1.92±0.13 mmol/l (± SEM) in the gastrocnemius muscle of adult male Wistar rats (n=6), while the average whole-blood lactate level was 0.76±0.12 mmol/l (± SEM). This measured extracellular lactate concentration was 1.73-times higher than that deduced from the arterial lactate concentration. Blocking glycolysis with iodoacetate reduced the extracellular lactate concentration to 52±6% (± SEM, n= 4) of the resting level. The extracellular lactate concentration in rat gastrocnemius muscle had increased to significantly (P0.05) different levels, 2.4±0.03 (± SEM) or 4.0±0.55 (± SEM) times the control value, 1 h after aortic clamping (n=3) or cardiac arrest (n=3), respectively. Stimulation of the sciatic nerve induced elevations of the extracellular lactate concentration in the tibialis anterior muscle which were linearly related to the recorded isometric force-time integral. We also monitored on-line the changes in extracellular lactate concentration in the tibialis anterior muscle of a swimming rat. Our results indicate that microdialysis lactate reflects also intracellular metabolism. Lactography may be a useful alternative to biopsies and nuclear magnetic resonance spectroscopy in clinical medicine and physiology for the monitoring of metabolism in vivo.     

A quantitative study in the rat on the relationship between imipramine levels in brain and serum

Serum and brain levels of the tricyclic antidepressant drug imipramine (IMI) were studied in the rat under a variety of conditions. IV doses (range 1 nmol kg^-1 to 15 mol kg^-1, 350 ng–5mg kg^-1) and administered 5 min before death, were linearly correlated with IMI levels in serum, frontal cortex, and cerebellum. In this experiment, the highest levels of IMI were achieved in the frontal and occipital cortex and the lowest levels were found in the brain stem. The regional distribution was more even in rats pretreated with thiopental or -hydroxybutyric acid, drugs that alter cerebral blood flow. After 20 min or more, tracer amounts of IMI injected IV to IMI-pretreated rats [1 or 17 days, daily dose 2×36 mol kg^-1 (10 mg kg^-1), last dose 89 mol kg^-1 (25 mg kg^-1), 2–3 h before death] exhibited a distribution pattern in serum and various brain regions similar to that of the unlabeled drug. In the latter experiments, content (per volume) of the tracer or unlabeled IMI was more than 25-fold higher in various brain areas than in serum. It is concluded that despite large differences in drug levels in serum or brain, a close relationship is maintained under the conditions studied.deceased     

Rapid and sensitive enzyme-linked immunosorbent assay for the microsomal epoxide hydrolase

A rapid and sensitive indirect enzyme-linked immunosorbent assay(ELISA) was developed for micrsomal epoxide hydrolase of ratliver. The assay, which is easily and readily performed, issignificantly more sensitive than most enzymatic epoxide hydrolaseassays routinely used and electroimmunoassays previously developed.The limit of sensitivity of the ELISA is between 2–5 ngof microsomal epoxide hydrolase. Using the ELISA microsomalepoxide hydrolases of mouse and rat liver were shown to be antigenicallyvery similar, while microsomal epoxide hydrolases of guineapig, monkey and human liver are antigenically distinct fromthose of rat and mouse. The ELISA developed here is capableof detecting microsomal epoxide hydrolase of rat and mouse livereven when significant enzymatic activity is lost. These resultsindicate that the antigenic sites recognized by the antibodiesused are distinct from the catalytic site of the epoxide hydrolase.Approximately 1.9% of rat microsomal protein was quantifiedas microsomal epoxide hydrolase by the ELISA. Low levels ofmicrosomal epoxide hydrolase were also detected in rat livercytosol (0.02% of the cytosolic protein) demonstrating thatmicrosomal epoxide hydrolase is not totally membrane bound orthat an immunologically related protein occurs in the cytosolof normal rat liver. The ELISA developed here will be valuablein investigating further the role of microsomal epoxide hydrolase.     

Medullary Carcinoma of the Thyroid Gland

Medullary thyroid carcinoma (MTC) is an uncommon thyroid tumor that has attracted a great deal of interest because of its frequent presentation as a familial tumor and its primary involvement in the type II multiple endocrine neoplasia (MEN) syndromes MEN-IIA and MEN-IIB and familial medullary thyroid carcinoma (FMTC). The MTC tumor cells secrete the polypeptide hormone calcitonin, which serves as an excellent tumor marker, useful for defining the presence of disease, preoperatively or following thyroidectomy. The discovery that mutations in the RET proto-oncogene are associated with MEN-II syndromes was highly significant in that it demonstrated a clear correlation between genotype and phenotype; and most importantly it provided a mechanism whereby family members at risk could be identified by direct DNA analysis. Virtually all patients with MEN-IIA, MEN-IIB, and FMTC develop MTC; therefore there is a clear rationale for performing thyroidectomy as soon as a RET mutation has been identified. Because MTC appears to be much more aggressive in patients with MEN-IIB, thyroidectomy is performed during the first year of life in this setting, whereas in patients with MEN-IIA, where the tumor appears to be more indolent, the procedure can be safety delayed until age 5 years. Reoperative neck exploration in patients with evidence of persistent or recurrent MTC has been effective in a significant number of patients, although the success of the operation requires careful patient selection and preoperative assessment. MTC, as expressed in the MEN-II syndromes, is an excellent model to evaluate the usefulness of interventional therapy in patients demonstrated to have a genetic predisposition for cancer.