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Biomedical subjects

A Weber

Publications and source records attributed to A Weber.

At least 415 records · Page 23Linked to original sources
PubMed1988

Syngeneic transplantation of thyroid tissue encapsulated in a cellulose sulphate membrane.

A new, simple encapsulation method, the precipitation of a polyelectrolyte complex membrane of cellulose sulphate and poly(dimethyldiallylammoniumchloride) was investigated in syngeneic thyroid transplantation. Half a thyroid gland was placed beneath the kidney capsule either after being encapsulated or as a non-encapsulated control graft. In normo-thyroid as well as hypothyroid recipients, the grafted tissue was viable for up to 12 weeks. Furthermore, the hypothyroid state, which was characterized by a markedly diminished 125iodine incorporation into the thyroid, no body weight gain and undetectable serum thyroxin concentrations, was compensated by the grafted tissue. The encapsulated grafts showed lower iodine incorporation, T4 secretion and body weight gain when compared with non-encapsulated control grafts. This may be due to a partial restriction of TSH by the capsule membrane. It was concluded that the cellulose sulphate membrane is biocompatible and enables the functional survival of syngeneic grafted tissue.

Animals↗
PubMed1988

Comparison of ciprofloxacin assays.

Two high pressure liquid chromatography methods developed independently and two different microbiological methods assayed samples containing ciprofloxacin derived from four volunteers: 46 sera, 19 saliva and 27 urine specimens. Each subject had received 500 mg of ciprofloxacin by mouth, with the samples collected in the ensuing six hours. Fifteen mock unknowns, prepared by adding known amounts of ciprofloxacin to normal human serum, were also assayed by the four procedures. The limits of sensitivity of the HPLC assays were less than 0.01 microgram/ml; the sensitivity limits of the bioassay were 0.02 microgram/ml (disc method) and 0.06 microgram/ml (well method). The inter-assay data was analyzed by linear regression. Ciprofloxacin concentrations in serum samples correlated well (R = 0.90) with all methods. Values obtained with urine samples also correlated well (R greater than or equal to 0.80). We conclude that either microbiological assay or quantitation by HPLC is satisfactory for quantitation of ciprofloxacin.

Chromatography, High Pressure Liquid↗
PubMed1988

Reference interval for prealbumin for children two to 36 months old.

To define a reference value for serum prealbumin (transthyretin) concentration, we used a rate immunonephelometric microassay to quantify it in 76 healthy children, ranging in age from two to 36 months. Age-specific ranges (+/- 2 SD from the mean) are: 2-5.9 months, 142-330 mg/L; 6-11.9 months, 120-274 mg/L; 12-17.9 months, 115-259 mg/L; 18-23.9 months, 143-243 mg/L; 24-36 months, 108-258 mg/L. When the data were grouped into those for subjects younger and older than 12 months of age, the mean for the 2-11.9 month age group (210 mg/L) significantly (P less than 0.01) exceeded that of the 12-36 month age group (187 mg/L). We propose that in spite of a decrease in prealbumin concentration with increasing age, it is acceptable to use the reference interval 116-281 mg/L (+/- 2 SD from the mean) for children from two to 36 months old. We also compared concentrations of prealbumin in serum and plasma of 41 individuals, finding the mean difference to be +11.7 mg/L; concentrations in plasma averaged 6.7% greater than those in serum.

Aging↗
PubMed1987

Nucleation of actin polymerization by villin and elongation at subcritical monomer concentration.

We have obtained a quantitative description of villin-nucleated actin polymerization in physiological salt by determining the concentrations of free villin (V), villin-actin monomer (VA), villin-actin dimer (VA2), and villin-actin oligomer (VAn). Over a range of actin-villin ratios from 0.1 to 20 we determined the concentration of actin-bound villin by measuring the low-intensity pyrenylactin fluorescence of the two terminal actins in each villin-actin polymer. (To this end we first showed that each villin-actin oligomer and polymer contains two low-intensity pyrenylactin molecules.) We determined the concentration of free villin using a calibrated cutting activity assay. The pattern of increase in bound villin together with the pattern of increase in high-intensity pyrenylactin fluorescence with increasing G-actin concentration indicated, first, that villin-actin monomers were not formed at detectable levels even at a 12-fold villin excess over actin. Second, there was no stoichiometric villin-actin dimer formation at actin-villin ratios of 2. Instead there was an equilibrium between free villin, VA2, and VAn. Defining K1 = [VA]/[V][A] and K2 = [VA2]/[VA][A], a good fit of the data was obtained with K1 much less than K2 and a value of K1K2 = Kv = 10(12)-10(13) M-2 = [VA2]/[V][A]2, i.e., 1/Kv1/2 = (0.3-1) X 10(-6) M. We have assumed here that the monomer binding constant of VA2 to form VA3 was equal to the monomer binding constant of pointed filament ends, K infinity = 1/c infinity, obtained as described below.(ABSTRACT TRUNCATED AT 250 WORDS)

Actins↗
PubMed1987

Kinetics of actin elongation and depolymerization at the pointed end.

We measured the rate of elongation at the pointed filament end with increasing concentrations of G-actin [J(c) function] using villin-capped actin filaments of very small (actin/villin = 3, VA3) and relatively large size (actin/villin = 18, VA18) as nuclei for elongation. The measurements were made under physiological conditions in the presence of both Mg2+ and K+. In both cases the J(c) function was nonlinear. In contrast to the barbed filament end, however, the slope of the J(c) function sharply decreased rather than increased when the monomer concentration was lowered to concentrations near and below the critical concentration c infinity. At zero monomer concentration, depolymerization at the pointed end was very slow with a rate constant of 0.02 s-1 for VA18. When VA3 was used, the nonlinearity of the J(c) function was greatly exaggerated, and the nuclei elongated at actin concentrations below the independently measured critical concentration for the pointed end. This is consistent with and confirms our previous finding [Weber, A., Northrop, J., Bishop, M. F., Ferrone, F. A., & Mooseker, M. S. (1987) Biochemistry (preceding paper in the issue)] that at an actin-villin ratio of 3 a significant fraction of the villin is free and that a series of steady states exist between villin-actin complexes of increasing size and G-actin. The rate constant of elongation seems to increase with increasing G-actin concentrations because of increasing conversion of free villin into villin-actin oligomers during the period of the measurement of the initial elongation rate. The villin-actin oligomers have a much higher rate constant of actin binding than does free villin.(ABSTRACT TRUNCATED AT 250 WORDS)

Actins↗
PubMed1987

[Passive smoking. Acute effects on the lung function of sensitive persons].

From the relationship between the degree of air pollution due to tobacco and its acute effects on healthy persons it is possible to estimate the still tolerable level of air pollution for healthy adults. The results and conclusions of the studies published by now on acute effects of passive smoking on patients with bronchial asthma are partially contradictory and do not allow a reliable estimation of the upper limit of tobacco smoke exposure for this particularly sensitive group. Because of methodological problems in studies with symptomatic asthmatics, further studies should be conducted which investigate patients with hayfever and asthma out of the pollen season, clinically healthy subjects with nonspecific bronchial hyperreactivity upon pharmacological challenge, and subjects who claim sensitivity to tobacco smoke.

Acute Disease↗
PubMed1987

The modulating effect of estrogens on luteinizing hormone release in complete androgen insensitivity syndrome before and after gonadectomy and cyclic steroid application.

The response of LH release to exogenous estrogens was studied in three patients with androgen insensitivity syndrome (AIS) before and after gonadectomy and a prolonged treatment with a sequential pill. Estrogen provocation tests were performed in which 0.05 mg/kg body weight estradiol benzoate was administered intramuscularly and serum FSH and LH levels were assessed every 12 hours for 96 hours after gonadectomy, three months after a prolonged treatment with a sequential pill (16 cycles: 9 days mestranol 100 micrograms, 12 days mestranol 80 micrograms and chlormadinone acetate 2 mg) and in one patient before gonadectomy. The control group consisted of 10 normal females during the follicular phase. A positive feedback effect was induced in normal females and in AIS patients after prolonged treatment with a sequential pill.

Adolescent↗
PubMed1987

Specific interaction of IgE antibodies with a carbohydrate epitope of honey bee venom phospholipase A2.

Phospholipase A2 (E.C. 3.1.1.4.) is a major allergen of honey bee venom. It exists in a glycosylated and an unglycosylated variant. Both forms and the glycopeptide isolated after exhaustive proteolytic digestion were tested in RAST and RAST inhibition studies. IgE from 11 of 14 bee venom allergy sera exhibited significantly higher, and in two cases exclusive, affinity towards glycosylated phospholipase. In RAST inhibition experiments using phospholipase coupled to discs five of the sera were completely inhibited by glycopeptide at 0.1 mg/ml; four sera were partially inhibited and two sera could not be inhibited. Glycoasparagine, lacking all amino acids except the carbohydrate-linking asparagine, inhibits IgE-binding to glycopeptide discs up to 100%. These data clearly demonstrate that an oligosaccharide of a structural type frequently found in glycoproteins can represent an epitope which is recognized by IgE antibodies from allergic patients, which are specifically directed against the parent glycoprotein.

Animals↗
PubMed1987

Pharmacokinetics of ciprofloxacin in cystic fibrosis.

We studied the pharmacokinetics of ciprofloxacin in 12 adult males with and 12 adult males without cystic fibrosis (CF). In a randomized crossover sequence, the subjects received 200 mg intravenously or 750 mg orally. With intravenous dosing, subjects also received 651 mg of iothalamate, a marker of glomerular filtration, and 700 mg of antipyrine, an indicator of hepatic oxidative drug metabolism. Pharmacokinetic parameters were determined by model independent methods. In the CF subjects, the ciprofloxacin concentration in serum during the first hour after intravenous administration was higher, and the oral absorption rate was slower. Other parameters did not differ between the groups. Mean concentrations in serum 5 min postinfusion were 3.08 and 2.14 micrograms/ml, and mean peak concentrations after oral dosing were 3.24 and 3.34 micrograms/ml in subjects with and without CF, respectively. Mean values for elimination half-life in all subjects were 4.8 and 5.0 h after intravenous and oral administration, respectively. The mean renal clearances in all subjects after intravenous and oral administration were 19.4 and 14.5 liters/h and accounted for 64 and 47% of the total clearance, respectively. These values were significantly greater than renal iothalamate clearance, indicating that tubular secretion contributed to the renal clearance of ciprofloxacin. A total of 69 and 35.4% of the administered ciprofloxacin was recovered from the urine within 48 h after intravenous and oral administration, respectively. The mean bioavailability was 71.2% and did not differ between the groups. We conclude that similar dosing regimens can be used to treat patients with CF and their normal counterparts.

Administration, Oral↗
PubMed1987

Surgical portosystemic shunts in children: assessment with duplex Doppler US. Work in progress.

The patency of 12 surgical portosystemic shunts in 11 children with portal hypertension was assessed with duplex Doppler ultrasonography. Results were compared with surgical, angiographic, and clinical findings. Seven of nine patent shunts were directly seen, and flow in them was assessed. One proximal splenorenal and one mesentericocaval shunt were not directly seen because of intestinal meteorism. The obstructed shunts were not seen, and no flow could be detected at their site. The presence and direction of flow in the splanchnic venous system were determined in all children, obviating the need for further angiographic studies.

Adolescent↗
PubMed1987

Liver cell membrane solubilization may control maximum secretory rate of cholic acid in the rat.

The factors modulating the maximum secretory rate of cholic acid were investigated. Rats were infused intravenously with cholic acid in measured stepwise increasing doses (1, 2, 3, and 4 mumol X min-1 X 100 g body wt-1). Each dose was infused for 30 min and bile samples were collected every 10 min. Bile flow, bile acid, cholesterol, individual biliary phospholipids, and the fatty acid profiles of the biliary phospholipids were determined. Microsomal and bile canalicular membrane-enriched fractions were isolated from cholic acid-treated rats at the end of the experiment. Membranes were analyzed for cholesterol, phospholipid, and phospholipid fatty acid composition. During cholic acid infusion, the secretion rates of bile acid, cholesterol, phospholipid, and bile flow initially increased and then declined. No evidence of liver cell damage was observed by light or electron microscopy. Maximum phospholipid secretion rate (13.5 nmol X min-1 X g-1) occurred before peak bile flow and bile acid secretory rate maximum (4.72 microliter X min-1 X g-1 and 375 nmol X min-1 X g-1). When phospholipid output declined, the proportion of sphingomyelins and phosphatidylethanolamine relative to phosphatidylcholine increased. This was also reflected in the fatty acid composition. Cholic acid infusion caused a decline in microsomal and bile canalicular membrane phospholipid content without affecting their phospholipid composition. Depletion of membrane phospholipid resulted in an increase in the cholesterol:phospholipid ratio, which is suggested to be the underlying mechanism for modulating cholic acid secretion.

Animals↗
PubMed1987

Hemodynamic changes in portal circulation after portosystemic shunts: use of duplex sonography in 43 patients.

Forty-five patients with 46 surgical portosystemic shunts were examined by duplex Doppler sonography, and the results were compared with those of esophageal endoscopy, angiography, surgery, and clinical follow-up. Thirty-eight shunts were patent, and in 33 of these, the shunt was directly visualized and flow was observed with Doppler sonography. Eight shunts were obstructed. After a successful portosystemic shunt procedure, flow in the shunted splanchnic vein was directed toward the shunt and the systemic vein. We studied the intrahepatic portal venous circulation in all of the patients; we found that in the presence of patent portosystemic shunt, portal flow is hepatofugal. This reversal of blood flow occurred in all but four patients. In the end-to-side portacaval shunt, where the portal vein is ligated, blood in intrahepatic portal branches presumably reaches the shunt through perihepatic collaterals. In the presence of a thrombosed shunt, intrahepatic portal venous flow was hepatopetal. To our knowledge, this is the first noninvasive in vivo study of intrahepatic portal circulation after portosystemic shunt surgery. The duplex Doppler evaluation of portosystemic shunts appears to be reliable and should be the method of choice for shunt patency assessment in patients with recurrent signs of portal hypertension. In addition to demonstrating flow at the site of the anastomosis, the Doppler study may yield an easy and reliable sign of shunt patency: reversed flow (hepatofugal flow) in the intrahepatic portal veins probably signals a patent shunt, even if the site of the anastomosis cannot be visualized directly by sonography.

Adolescent↗
PubMed1987

[Can changes in the gonadotropin response in androgen insensitivity syndrome be detected with the GnRH test following gonadectomy and steroid administration?].

Information about the reaction of the hypothalamic pituitary axis by Gn-Rh-stimulation dependent from gonadectomy and steroid substitution in 3 patients with androgen insensitivity syndrome. The test was done before and after gonadectomy, under receipt of within the intake of a sequential hormonal contraceptive (Sequenz-Ovosiston) in the 16th cycle and after a pill free interval of 3 months, LH and FSH were estimated with a RIA-method. The LH-base-concentration is independent from the moment of the gonadectomy normogonadotrop and indicate after Gn-Rh-stimulation a regular LH-answer. The FSH-reaction is clearly dependent from the moment of gonadectomy. Not the gonadectomy but the steroid substitution over a long time is decisive about the reaction of the adenohypophysis.

Adolescent↗