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Biomedical subjects

A Weber

Publications and source records attributed to A Weber.

At least 451 records · Page 25Linked to original sources
PubMed1986

Thyroid status during pregnancy and post partum in regions of iodine deficiency and endemic goiter.

During pregnancy the thyroid is subjected to increased demands which is associated with a tendency to endogenous iodine deficiency. Under the conditions of insufficient iodine supply in the GDR the pathophysiological changes result in: 1. prevalence of goiter in about 60% of pregnant women; 2. enlargement of the extent of neck in more than 50% of all pregnant women examined only returning to the prepregnant status in 25%-40%; 3. prevalence of goiter in newborn with 5%; 12.8% of 1948 stilborn had macroscopically an enlarged thyroid gland, the highest weight being 45 g. More than 53% of the stilborn examined by autopsy had a thyroid weight of over 3 g; 4. in contrast to the regions with sufficient iodine supply renal iodine excretion was steadily decreasing during pregnancy and post partum, changing the iodine deficiency from grade II to grade III; 5. low iodine excretion in newborn: 1.3 +/- 0.2 microgram I/day in goitrous (1.2 +/- 0.2 nmol I/mmol creatinine) 2.2 +/- 0.4 micrograms I/day in non-goitrous (2.0 +/- 0.4 nmol I/mmol creatinine); 6. according to ETR more than 50% of the pregnant examined showed a hypothyroid tendency. The pathophysiological changes during pregnancy caused by insufficient iodine supply can be met efficiently by careful thyroid hormone treatment or by the administration of 150 micrograms I daily. A mandatory iodine salt prophylaxis is demanded.

Adolescent↗
PubMed1986

[Occurrence of phenylalanine hydroxylase in the human kidney].

Phenylalanine hydroxylase activity, determined by fluorimetric procedure in human kidney (cortex) of 17 patients, who had a kidney operation, was on the average 4.7 nkat tyr/g protein (25 degrees C), which is 28% in comparison to the enzyme activity in human liver. This is in good accordance with the results of AYLING et al. who investigated 15 human kidneys. They found by the spectrophotometric method 22% of the liver enzyme activity. A nonspecific hydroxylation could be excluded by tests with the inhibitors p-Cl-phenylalanine, 3-I-tyrosine and 6-F-tryptophan.

Adult↗
PubMed1985

Removal of tropomyosin overlap and the co-operative response to increasing calcium concentrations of the acto-subfragment-1 ATPase.

The co-operative response of regulated actomyosin ATPase to increasing concentrations of calcium has been attributed to nearest-neighbor interactions, presumably between troponin-tropomyosin complexes. The degree of co-operativity was not decreased after the carboxy-terminal 11 amino acid residues had been removed from tropomyosin by carboxypeptidase A. This indicates that the interactions between neighboring troponin-tropomyosin complexes do not occur through the overlapping tropomyosin ends.

Actins↗
PubMed1985

Plasma and gamma-globulin infusion in chronic inflammatory polyneuropathy.

We treated 17 patients with chronic inflammatory polyneuropathy (CIP) with infusions of fresh-frozen plasma (FFP). Thirteen patients had a beneficial response: 12 improved considerably and one moderately. The first signs of improvement were seen within 8 days of the onset of treatment. None of these patients had had spontaneous remissions for 2 months prior to treatment, and none had received immunosuppressive medication during the plasma infusions. The treatment effect was short-lasting in 9 patients. Re-institution of the FFP infusions was always followed by improvement. The same effect could be achieved by intravenous gamma-globulin. We conclude that infusions with FFP, of which the IgG fraction is the effective part, may induce a rapid and clinically important improvement in patients with CIP.

Adolescent↗
PubMed1985

Effects of various organic chemicals on the regreening of red colored Chlorella zofingiensis.

Under nitrogen-deficient culture conditions Chlorella zofingiensis decomposes the chlorophylls, synthesizes secondary cartenoids, and thus develops red colored resting stages (akinetes). On transfer of the akinetes into nitrogen-containing fresh culture medium the algae regreen completely within a short period. The results of the experiments presented in this study show that the regreening process reacts with high sensitivity to the addition of environmentally hazardous chemicals. This system proved to be much more sensitive than other methods of testing for ecotoxicity. This screening test is universally applicable and offers, in addition, the possibility of testing volatile compounds since it is carried out in air-tight culture vessels. A phytotoxicity of 50% calculated as inhibition of the chlorophyll biosynthesis during exposure for 48 hr was found for paraquat at concentrations of 0.15 microM (added as methysulfate) and 0.28 microM (added as chloride) and for pentachlorophenol (PCP) at 0.16 microM. The chemicals 2- and 4-nitrophenol, however, proved to be much less toxic. Here, a 50% inhibition of chlorophyll biosynthesis was observed at 49 and 75 microM. When exposed to 4-chloroaniline even concentrations of 200 microM were not sufficient to cause a 50% inhibition of the regreening process. In additional experiments the influence of increasing salt concentrations (NaCl stress) and simultaneous exposure to the toxicants was examined. A step-by-step increase in the salinity of the experimental medium resulted in a drastic reduction of the toxicity caused by the addition of paraquat. This effect was much less pronounced when PCP was employed as toxicant. A different result was obtained with 2-nitrophenol: Here the toxic action was slightly enhanced. Differences in the time-dependent toxic response were also observed using the diverse toxicants. Probable causes are discussed.

Aniline Compounds↗
PubMed1985

Maxillary ameloblastoma with orbital invasion. A clinicopathologic study.

A 72-year-old white man presented to Massachusetts Eye and Ear Infirmary with proptosis of the right eye. Computerized tomography (CT) scan revealed a mass which filled the right maxillary sinus and invaded the orbital and middle cranial cavities. Six years earlier, the patient had excision of an ameloblastoma of the right maxillary antrum. The tumor recurred, requiring maxillectomy, local radiotherapy and finally exenteration. Ameloblastoma is a relatively rare epithelial tumor arising from embryonal tooth elements. It is locally invasive and recurrent but rarely metastasizes and extension to the orbit is extremely unusual. The clinical features, histopathologic findings and treatment of this tumor are discussed. Differential diagnosis of jaw tumors, which may invade the orbit, is reviewed.

Aged↗
PubMed1985

Distribution of 125I-thyroxine in different organs and tissues of dietically obese rats.

The distribution of 125I-thyroxine (% dose/g tissue; tissue/plasma radioactivity ratio) was investigated in different tissues of 28-week-old obese Wistar rats. Obesity was induced by high-fat diet (HFD) and confirmed by carcass analysis; in heavy obese animals the relative and absolute fat content is increased twofold and threefold, respectively, compared to control rats fed on a low-fat diet (LFD). Heavy HFD rats exhibit diminished 125I-T4 distribution in the "slow pool" (fat tissue, muscle) and unchanged values in the "fast pool" (liver, kidney) in comparison with LFD rats with low body weight. The differences in distribution presented here are not caused by the diet per se, but they are the consequence of the obesity of the animal, because no differences in the 125I-T4 distribution were found in the 125I-T4 between HFD and LFD rats with relatively equal body weight and body composition. The reduced T4 distribution in the fat tissue of obese rats is discussed in connection with possibly decreased lipolysis in this tissue and possible causal participation in the beginning of obesity.

Adipose Tissue↗
PubMed1985

Quantitation of ciprofloxacin in body fluids by high-pressure liquid chromatography.

We describe a reverse-phase high-pressure liquid chromatography method for the quantitation of a new quinoline carboxylic acid antimicrobial agent, ciprofloxacin (Bay o 9867). This assay utilizes the intrinsic fluorescence of ciprofloxacin for primary detection but employs UV absorption as a secondary detection system. Mobile phases contained methanol and phosphate buffer and used a common C18 mu Bondapak column. A single precipitation step of a 50-microliter specimen was the only sample preparation necessary. The assay is linear from 2,000 to 10 ng/ml and sensitive to 5 ng/ml. The mean recovery of ciprofloxacin from serum was 105.7%. The coefficient of variation was less than or equal to 3.1% for same-day precision and less than or equal to 6.3% for assay-to-assay precision. Because the assay requires only small specimen volumes and minimal sample preparation and because of its defined characteristics, this assay would be ideal for clinical trials and pharmacokinetics studies of ciprofloxacin.

Anti-Infective Agents↗
PubMed1985

Pharmacokinetics of three oral formulations of ciprofloxacin.

We compared the absorption of three formulations of ciprofloxacin after oral administration in 18 normal adult male volunteers. Each subject received 500 mg of ciprofloxacin as two 250-mg tablets, one 500-mg tablet, or a solution in a randomized crossover sequence. Pharmacokinetic parameters were determined by model independent methods. Because a solution is considered to be the ideal oral dosage form, the results determined for the tablets were compared to those for the solution. Mean values for the maximum concentration of drug in serum, the time to maximum concentration of drug in serum, and the elimination half-life were 3.23 micrograms/ml, 1.00 h, and 5.04 h, respectively, for the solution. The mean renal clearance of ciprofloxacin was 372 ml/min and accounted for at least 50% of the total clearance. We recovered 44.4, 48.6, and 55.8% of the administered ciprofloxacin from the urine as unchanged drug within 24 h after dosing with the 250-mg tablets, 500-mg tablets, or solution, respectively. The 500-mg tablets were found to be bioequivalent to the solution with regard to all pharmacokinetic parameters. The 250-mg tablet was not bioequivalent to either of the other formulations; the relative bioavailability values were 78.7 and 74.1%, respectively, for the 500-mg tablet and the solution. The clinical significance of this difference in bioavailability is yet to be determined.

Administration, Oral↗
PubMed1985

Radioenzymatic assays for aminoglycosides with kanamycin 6'-acetyltransferase.

To facilitate the rapid and accurate quantitation of parenterally administered aminoglycosides, we defined the optimum conditions (pH, duration of incubation, and cofactor concentrations) to permit radioenzymatic assays with kanamycin acetyltransferase. The accuracy in quantitating tobramycin, netilmicin, kanamycin, and amikacin at concentrations in the therapeutic range was greater than 90%, with a mean recovery of 102.8%. The mean of the interassay coefficient of variation was 7.8%. Typical standard curves at six different concentrations resulted in a correlation coefficient (r value) of greater than 0.99 for each aminoglycoside. The radioenzymatic assay correlates well with the bioassay (tobramycin and netilmicin) and radioimmunoassay (amikacin and kanamycin); the correlation coefficient is greater than 0.90 for all. We conclude that the radioenzymatic assay utilizing kanamycin 6'-acetyltransferase is feasible for all commercially available parenterally administered aminoglycosides.

Acetyl Coenzyme A↗
PubMed1985

Aminoglycoside penetration, inactivation, and efficacy in cystic fibrosis sputum.

We studied sputum tobramycin concentrations after intravenous administration in 10 cystic fibrosis patients. Tobramycin concentrations were determined by a bioassay and a radioenzymatic assay (REA). The bacterial density of Pseudomonas aeruginosa in sputum was examined serially during therapy. Bioactivity of tobramycin in the sputum was low and increased little during treatment. In contrast, tobramycin content (as assayed by REA) showed a progressive accumulation of the drug to high concentrations: a mean of 82 micrograms/g sputum after 3 wk of therapy in 4 patients. Pseudomonas aeruginosa was eradicated from the sputum in 3 of 4 patients receiving antibiotic therapy for 3 wk. Eradication correlated with tobramycin sputum concentrations measured by REA, which were 20-fold greater than the apparent tobramycin inhibitory concentration. A bactericidal effect of aminoglycosides in the presence of sputum in vitro could only be reliably produced with concentrations 25-fold the MIC. We conclude that tobramycin penetrates cystic fibrosis (CF) sputum and accumulates over time. Although CF sputum antagonized the bioactivity of aminoglycosides, 3 wk of intravenous therapy combined with an antipseudomonal beta-lactam antibiotic may be effective in eradication of P. aeruginosa from sputum of certain CF patients.

Adolescent↗