Acta physiologica Academiae Scientiarum Hungaricae最新文献

Low body weight premature babies born before the 32nd gestational week were studied to analyse the postnatal fall in plasma haemoglobin and in quantitative changes in amino acid levels. Red blood cells of premature low body weight infants were found to disintegrate more rapidly than those of mature newborns. Thin-layer ion-exchange chromatographic studies showed that amino acids originating from the degrading haemoglobin-F lead to rise in plasma amino acids. These amino acids might play a role as substrates for gluconeogenesis in the energy supply of low body weight premature babies during the special fasting state just after birth.

The unknown enzymatic mechanism of enhanced protein breakdown in steroid myopathy was studied in functionally and biochemically different muscles of rabbits treated with dexamethasone for three weeks. After glucocorticoid administration the fast-twitch glycolytic semimembraneous muscle of treated animals was atrophied, whereas the weight of the slow-twitch oxidative soleus muscle was not altered. The specific activity of the lysosomal endo- and exopeptidases (cathepsin D, E, B and L, lysosomal carboxypeptidase A and dipeptidylpeptidase I) was increased about 2-fold in the atrophied white muscle. The activity of the cytosol enzyme Ca++-activated neutral proteinase was also elevated, whereas that of the other cytosol endopeptidase, chymotrypsin-like enzyme, was unaltered. The level of alanine aminopeptidase was only slightly increased. On the other hand, there were no unequivocal changes in protease activity in the soleus muscle. These findings are in agreement with the known differences in glucocorticoid-sensitivity of the various muscles. Our results suggest that the lysosomal proteolytic system and the Ca++-activated neutral proteinase may play an important role in the glucocorticoid-induced intracellular protein catabolism in muscle. The inhibitor capacities of cathepsin B and trypsin detectable in muscle cytosol were not altered after steroid treatment. Consequently, the increase in cathepsin B activity was not due to the loss of its inhibitor.

Results of this study showed that in a considerable number of patients with duodenal ulcer a globulin of the IgG class was responsible for the enhancement of HCl secretion. This secretagogue globulin appeared to combine directly with the H2 receptors of the parietal cells thereby increasing hydrochloric acid output without the formation of antigen-antibody complex.

Following stimulation with NaCl of different concentrations, responses from one, two or three receptor cells of the sensillae could be recorded, one of them being always "dominant". The other one or two secondary cells showed a lower frequency and a faster adaptation. The responses of the dominant cells proved to be variable, even to repeated stimulations using the same concentration of the same substance. Increasing the concentration from 0.01 mol/l to 1.0 mol/l, the initial frequency may increase or decrease, however, frequency minimum or maximum may also occur at an intermediate concentration. These findings indicate a less specialized stage of the receptor cells. The individual characteristics of the receptor cells may be surpassed when averaging the responses of sufficiently high number of cells.

The effects of lithocholic acid (LCA), chenodeoxycholic acid (CDCA), deoxycholic acid (DOCA), cholic acid (CA) and dehydrocholic acid (DHCA) on the biliary excretion of amaranth (AM) in rats and on the respiration of isolated liver mitochondria were investigated. Bile acids diminished the biliary excretion of AM, and in vitro they enhanced the state 4 mitochondrial respiration and inhibited DNP- and ADP-stimulated oxygen consumption. The ID50 values (mumol/kg i.v.) and I50 concentrations (X 10(-5) M) of the bile acids for inhibiting AM excretion and ADP-stimulated mitochondrial respiration, respectively, were as follows: for LCA 16 and 3.3, for CDCA 160 and 24, for DOCA 230 and 31, for CA 680 and 105, and for DHCA 700 and 260. LCA, CDCA and DOCA inhibited the biliary excretion of AM uncompetitively. It is concluded that the toxic effect of LCA, CDCA and DOCA on mitochondria might play a role in their inhibitory action on the biliary transport of AM.

In acute immobilized rats, the effect on the EEG of thermal and chemical (capsaicin microinjection) stimulation of the warm sensors in the preoptic region, mid-hypothalamic area and posterior hypothalamus were studied. Both localized heating and capsaicin resulted in a sleep-like EEG with spindles and slow waves. Stimulation of the posterior hypothalamus was the most effective and stimulation in the mid-hypothalamus was the least effective in inducing spindle activity. Since capsaicin is regarded as a specific stimulant for the hypothalamic warm sensors, the results suggest that the EEG effect, and probably the sleep-inducing effect, of heat are mediated via the central thermoreceptors, and cannot be due to a non-specific activation of the basal forebrain hypnogenic mechanisms.

The effect of native serum samples from schizophrenic and control patients on the electrically induced contractions of the isolated mouse vas deferens (MVD) preparations was investigated. It was demonstrated that only the samples of schizophrenic origin elicited a naloxone dependent inhibition on the contractions of the MVD preparations, while sera from healthy individuals and those from non schizophrenic but mentally ill patients proved to be ineffective in this respect. By using ultrafiltration and gel chromatographic techniques, four fractions disclosing MVD related biological activity could be separated from schizophrenic samples. Chemical analysis revealed an elevated quantity of ninhydrin and Lowry positive materials as well as of unidentified carbohydrate components in the active fractions. Molecular mass of the serum ingredients carrying opioid activity was found to range between 0.5 and 5.0 KD. It is speculated that new appearance or the accumulation in the sera of several, and partly at least, unknown peptides and glycopeptides disclosing opioid activity might be characteristic of schizophrenia.

Rats were exposed to whole body vibration horizontally for four hours at 5 Hz frequency and 2 cm amplitude. Of the components of the plasma kallikrein-kinin system the free (spontaneous) and kaolin-activated kallikrein (prekallikrein) activities, the concentration of bradykinin, the bradykinin splitting total kininase activity, total kallikrein-inhibitor activity and the concentration of alpha 2-macroglobulin, a major plasma kallikrein inhibitor, were estimated. Results showed that in response to acute vibration plasma free kallikrein activity was increased significantly in association with a significant reduction of prekallikrein concentration. The concentrations of bradykinin and total kininase activity were significantly elevated, too. Neither total kallikrein-inhibitor activity nor the concentration of alpha 2-macroglobulin were changed indicating that the plasma kallikrein inhibitors did not play a role in the alterations of plasma free kallikrein and prekallikrein activities. During acute vibration the plasma kallikrein-kinin system was activated probably by the enhanced catecholamine secretion. We suggest that the biological importance of this phenomenon is in the defense against the impaired microcirculation caused by catecholamines.

The regulation of Na+ and water metabolism was studied in sheep with rumen fistula after water deprivation for 48 hours. Na+ and K+ concentrations were determined in blood plasma, blood, urine and saliva, with or without NaCl load. The results showed that the water content of the ruminal fluid plays an important role in the control of electrolyte and water metabolism. The absorption of water and Na+ from the rumen favours the maintenance of isosmolality and isovolaemia until the concentration of Na+ in the ruminal fluid has exceeded that in blood plasma. Thereafter the balance of water movement between rumen and extravascular space is shifted towards the rumen inhibiting thereby a further increase of Na+ concentration and ensuring the life conditions for the ruminal microbial population. During water deprivation not only water is lost but as a result of Na+ excretion relative hyponatraemia also ensues as can readily be assessed from the ratio of salivary Na+ and K+ concentrations. Upon NaCl load the salivary Na+/K+ ratio was increased indicating the extent of Na+ supply.