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Biomedical subjects

A Weber

Publications and source records attributed to A Weber.

At least 739 records · Page 41Linked to original sources
PubMed1966

The effect of the replacement of calcium by strontium on excitation-contraction coupling in frog skeletal muscle.

1. In frog skeletal muscle strontium can replace calcium in potassium contractures for 5 hr, though it is less effective than Ca. Sr can restore the responsiveness to K after it had been lost in the presence of Mn.2. Muscles refractory to caffeine following repeated exposure to it in the absence of Ca, recover in part following addition of Sr.3. The uptake of (85)Sr was increased during mechanical activity, whereas the uptake of (58)Co was not changed. Resting uptake of (58)Co was 3-4 times greater than that of (85)Sr.4. Sr fully activated the myofibrillar adenosine triphosphatase (ATP-ase), though its affinity was about 30 times less than Ca.5. The sarcoplasmic reticulum took up Sr, though less effectively than Ca.

Adenosine Triphosphatases↗
PubMedDate not supplied

In utero allotransplantation of retrovirally transduced fetal hepatocytes in primates: feasibility and short-term follow-up.

In utero allotransplantation of fetal hepatocytes into a preimmune fetus could be used in early treatment of many inherited hepatic metabolic diseases. This study was designed to assess the tolerance to hepatocyte transplantation and to test the feasability and toxicity of such an injection in a primate model. Fetal hepatocytes were obtained from two 120-day-old Macaca mulatta fetuses and cryopreserved. They were thawed, cultured in vitro, and transduced with a recombinant retrovirus expressing beta-galactosidase. Transduction efficiency was 75-85%. Three unrelated fetuses (90, 100, and 104 days old) were each given 1-2 x 10(7) transduced cells via the umbilical vein. This caused vasospasm and severe bradycardia. Two fetuses died in the 48 hours after transplantation; the third survived and was killed at the end of gestation. No evidence of the infused cells was found. Three fetuses (90 days old) were, therefore, given 3-4 10(7) hepatocytes by direct intrahepatic injection. All the fetuses survived without side effect. Donor cells were not apparent from histochemical staining and PCR reactions. There was no evidence of inflammatory reaction. These findings indicate that the protocole could be improved by increasing the number of transplanted cells and using specific hepatic promoters in the retroviral vectors to achieve an effective postnatal chimerism.

Animals↗
PubMedDate not supplied

Resistance of the suckling guinea pig to lithocholic acid-induced cholestasis.

Although immaturity of the liver and synthesis of monohydroxy bile acids have been implicated as pathogenic factors in neonatal cholestasis, there is no direct evidence to show that these bile acids induce cholestasis in the newborn. In the present investigation, we compared the effects of lithocholic acid (LCA) injection on bile flow in suckling (2-week-old) and adult (12-week-old) guinea pigs. Bile flow was not modified by LCA in 2-week-old animals, but it was reduced by 50 to 80% in the adults, the decrease being dose-dependent. In the newborn, the injected LCA was mainly secreted in bile (greater than 90%), while in the adults it was distributed between the liver and bile. The percentage of biliary bile acids (as determined by gas-liquid chromatography) in the two groups was similar before and after LCA injection. Morphologic lesions characteristic of LCA-induced cholestasis were observed only in the adult guinea pigs. This study demonstrates that the newborn guinea pig is less susceptible to cholestasis induced by 90 to 180 mumoles per kg body weight of lithocholate and that, in the neonatal liver, there is no defect in the transport of this bile acid from blood to bile.

Age Factors↗
PubMedDate not supplied

Effect of complete sulfation of bile acids on bile formation in rats.

The effect of sulfation of common bile acids on the formation of bile was investigated in male rats by infusing them with the sulfate esters of cholic, chenodeoxycholic, deoxycholic, lithocholic or dehydrocholic acid in four step-wise, increasing doses. Each dose was infused for 30 min and bile collected every 10 min. Control studies were performed by using either albumin solution (the bile acid carrier) or corresponding nonsulfated bile acids at concentrations similar to those of the sulfated products. The secretion of sulfated bile acids was slower and less than that of nonsulfated bile acids, demonstrating transport maximum kinetics rather than the secretory rate maximum characteristic of nonsulfated bile acids. Sulfation significantly increased bile salt-independent bile flow and the choleretic potency of the bile acids tested. With the exception of deoxycholic acid, which had a slight stimulatory effect, bile acid sulfation generally prevented a rise in bile acid-dependent phospholipid and cholesterol secretion. In fact, it reduced biliary phospholipid and cholesterol secretion associated with the secretion of endogenous bile acids. These data are in agreement with the physicochemical properties of sulfated bile acids. They indicate that sulfation prevents the cholestatic action of nonsulfated bile acids, perhaps by increasing bile flow via a high choleretic potential and/or by stimulating bile acid-independent bile flow. The effect of sulfated bile acids on the secretion of biliary phospholipids may protect the canalicular membrane from the detergent properties of bile acids and may thus block the cholestasis which results from high, nonsulfated bile acid concentrations.

Animals↗
PubMedDate not supplied

[Air pollution due to cigarette smoke: physiological and irritating effects].

We assessed the effects on the judgement of air quality, eye blinking rate,and lung functions of air pollution due to cigarette smoke. At the same time, subjective irritations were recorded. The measured effects were brought into relationship with the concentration of some pollutants in the air.

Air Pollutants↗