Archives internationales de physiologie, de biochimie et de biophysique最新文献

Fluorescence spectroscopy of plasma soluble melanin derived from 3-hydroxyanthranilic acid discloses an emission (em) maximum at approximately 413 nm [excitation (ex) maximum approximately 324 nm]; plasma melanins derived from dopa, catecholamines, catechol and 3-hydroxykynurenine have em maxima at approximately 445 nm (ex maxima approximately 345 nm). All of these melanins are present in human plasma. For the present study, plasma samples were obtained from 120 healthy Caucasian, Hispanic, Mongoloid and Negroid males and females, ranging from 19 to 92 years of age, with 12 or more subjects in each racial and sex group. The average relative fluorescence intensities of all samples (diluted 1 to 50 with water) were 34.6 +/- 7.4 (standard deviation) at 413 nm and 40.8 +/- 8.2 at 445 nm. Individual intensity values in samples from women below 50 years in age were in the lower range of the values observed; at age 50 and higher no difference was seen in samples from women and men. No clear cut relationships to race or age were seen.

Dopamine addition to the internal fluid bathing the isolated frog skin results in a strong increase of short circuit current (SCC) across this tissue. The effect is dose-dependent, 10(-4) M being the dose resulting in maximal effect. The measure of transepithelial fluxes of both 22Na+ and 36Cl- across symmetrical parts of skin short-circuited in permanence demonstrates that this effect is due to stimulation of Na+ adsorption and Cl- secretion. The former effect, but not the latter one, is mimicked by both SKF89124A and SKF82525J (D1 and D2 agonists, respectively). Moreover the effect of dopamine on SCC and Na+ net flux is wider than that of its synthetic agonists even when both D1 and D2 agonists were added together. It is suggested that the extraeffect of dopamine on SCC is due to a stimulation of Cl- secretion, probably mediated by dopamine interaction with another receptor.

We studied the putative inhibitory activity of about 50 synthetic molecules on the biosynthesis of ecdysone. Most of these molecules had been synthesized according to the conceptual framework of suicide substrate type inhibitors. They potentially react either with well-known catalytic mechanisms (hydroxylations at C-22 and C-25) or with more hypothetic ones (introduction of the keto group at C-6 and the hydroxylation at C-14). The two hydroxylations which take place on the side chain at C-22 and C-25 in the last steps of the ecdysone biosynthetic pathway, and which are catalysed by cytochrome P-450 dependent monooxygenases, can be effectively affected. The essential chemical arrangement which produced a consequent inhibitory effect included an acteylenic or an allenic inhibitory function, near the hydroxylation to inhibit, with a hydroxyl group, preferably grafted in C-20. In order to increase the inhibitory effect, several characteristics gradually appeared: shortness of the side chain, hydroxyl group in position (R) at C-20 and at C-22, if necessary; in the proximal shortening side chain molecules, hydroxyl group at C-17 in position beta; lowering steric hindrance at C-20. It seemed that a molecule bearing a side chain in a relative position behind the midplan of the steroid nucleus induced a more important inhibitory effect. On the contrary, the form of the steroid nucleus itself (as in cholesterol, 7-dehydrocholesterol, 3-dehydrocholesterol, or in a molecule with a saturated B cycle) did not play a deciding part in the activity of the compound. Only the molecules with a typical ecdysteroid nucleus showed a poor inhibitory effect. Molecules acting as suicide substrate type inhibitors on the ecdysone biosynthesis should produce an irreversible inactivation of the enzyme and show a biosynthetic inhibition specifically linked to ecdysteroid. It was not the case of all the tested molecules. Some of them induced a very important inhibition without possessing the other characteristics of a suicide substrate type compound. Other derived chemicals, which were not synthesized according to the framework of the suicide substrate type molecules, showed all the characteristics of this type of molecules. In the course of this work, it has been possible to point out several molecules showing an important inhibitory effect on ecdysone biosynthesis.

The aim of this work is to determine the effect of low frequency current (L) versus medium frequency current (M) in order to generate a different force level on soleus and gastrocnemius muscles. The experiment was conducted on 10 healthy, male volunteer subjects aged from 19 to 21 who provided informed consent to participate in the experiment. None of the subjects had experienced electrostimulation (ES) procedures before. The subjects were seated with vertical legs and horizontal thighs. Isometric force of the gastrocnemius and soleus muscles was measured using a strain gage dynamometer (100 daN). The transducer was adjusted on the knee, along the vertical axis of the leg. For the conditions of ES, a bi-phasic, symmetrical square wave signal was applied at each of five low frequencies: 20, 40, 60, 80 and 100 Hz and at each of six medium frequencies (2222 Hz) modulated or not, to yield 20, 40, 60, 80, 100 bursts of pulses. Maximum voluntary contraction (MVC) was also recorded. The phase duration was constant throughout 180 microseconds. The current level was set individually for each subject at the maximum that could be tolerated and applied during 10 s. Each contractile condition was randomly chosen. The forces produced by the different regimen of ES used are significantly different (P < 0.001). For each type of stimulation we got tetanic contractions. After an initial ramp, a nearly flat curve corresponding to tetanus was reached. For a 60 hz low frequency current, the force production reached 76% of MVC for a mean intensity of 58 mA, corresponding to a charge of 1253 microC.(ABSTRACT TRUNCATED AT 250 WORDS)

We tested the hypothesis that the variable functional properties of rat versus guinea pig hearts are due to differences in intracellular Ca2+ handling. Hearts isolated from rats and guinea pigs were perfused with physiological saline, and isovolumic left ventricular (LV) pressure as well as coronary perfusion pressure were recorded simultaneously with Ca2+ transients from aequorin-loaded cells. Guinea pig hearts developed 47% less LV pressure than rat hearts, and the time to peak pressure was prolonged by 71% at similar heart rates. Diastolic and systolic levels of myoplasmic Ca2+ were approximately the same in both species at normal external Ca2+ concentration (1 mM); however, at low Ca2+ concentration (0.5 mM), guinea pig hearts maintained a higher level of myoplasmic Ca2+ than rat hearts, and the relative depression of LV systolic pressure was less. Guinea pig hearts also exhibited higher resistance to the negative inotropic effect of caffeine and did not respond to increments in perfusion pressure with increases in LV-developed pressure and systolic Ca2+ levels as did rat hearts. These contrasting findings with regard to intracellular Ca2+ handling may be attributed to a different organization of the ionic transport system with higher dependence of rat cardiomyocytes on normal function of the sarcoplasmic reticulum.

Small doses of NaCN (250 micrograms.kg-1) intravenously injected into normal anesthetized Wistar rats, provoked immediate hyperventilation, bradycardia and systemic hypotension. These effects resulted mostly from peripheral chemoreceptor (PCR) stimulation. In totally baro- and chemodenervated rats (CDN), the drug induced hypoventilation, reduction in O2 consumption, prolonged bradycardia and systemic hypotension, characteristics of direct intoxication. In hyperoxic rats, hyperventilation was reduced. Bradycardia was suppressed with reduction in the systemic hypotension. These modifications arose partly from a reduction in PCR excitability and partly from a direct O2 activity counteracting cyanide poisoning. After chemical sympathetic denervation, rats presented prolonged and enlarged hyperventilation, bradycardia and systemic hypotension due to loss of adaptive baroreflex responses. Cyanide effects are predominantly reflexes in intact rats but these reactions mask the direct toxic effect of the drug which cannot be totally neglected.

Effects of oxytocin (0.25 IU OT/100 g/d for 3 days) on accessory sex glands structure and catecholamine content were examined in rats kept on two different light regimens. In 12 h light/12 h dark conditions ventral prostate responded to OT by a regression of the epithelial component and an increase in dopamine content. Coagulating gland structure was not affected, but noradrenaline content of the seminal vesicle+coagulating gland complex was enhanced. Constant lighting per se caused atrophic changes in the prostatic epithelium, evident by decreased total volume and by increased percentage of acini containing cuboidal epithelium. OT treatment considerably prevented the epithelial atrophy without affecting catecholamines level. In the seminal vesicle+coagulating gland complex it reduced the dopamine content. Since this light regimen elevated the plasma ACTH, the altered accessory sex gland response to OT seems to be due to the stress-induced changes in the neuro-endocrine factors conditioning their function. The effects of OT on accessory glands catecholamine content indicate interferences with their autonomic control.

The technique of the universal film agarose electrophoresis has been used to detect biochemical characteristics of the body extract proteins in 3 different species and 2 genera of the pseudoscorpion family Neobisiidae. The migration rate of these proteins as well as their relative abundance for Neobisium carpaticum Beier, Neobisium macrodactylum (Daday) and Roncus pannonius Curcić, Dimitrijević & Karamata, from Yugoslavia, were compared. Electrophoretic identifications of these species showed both species-specific and (probably) intergeneric differences. It is assumed that body protein electrophoresis can be also used: (a) to differentiate species in any stage of their life cycle, (b) to reveal the presence of sibling species, and to differentiate the taxonomic and evolutionary interrelations both in congeneric as well as in other, more distant taxa.

A naturally occurring hemagglutinin (HA) was detected in the serum of the freshwater crab Parathelphusa hydrodromus using mammalian erythrocytes (RBC) as indicator cells. The serum gave the highest HA titer with rabbit RBC. In cross adsorption tests, this RBC type completely adsorbed all HA activities from serum. An analysis of the physico-chemical properties of HA showed it to be specifically dependent on the presence of Ca2+ for its activity, irreversibly sensitive to EDTA, stable between pH 7.5 and 10.0, and heat-labile. Further studies demonstrated that the HA is proteinaceous as it was precipitable by conventional deproteinizing agents, and susceptible to the action of proteases and 2-mercaptoethanol. HA-inhibition assays performed with 44 carbohydrates revealed that the serum HA was specific for non-reducing terminal glucose with alpha 1-2 glycosidic linkage. Thus this agglutinin appears to be unique among all the known crustacean agglutinins.