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Biomedical subjects

J Jacobi

Publications and source records attributed to J Jacobi.

At least 19 recordsLinked to original sources
PubMed1991

Cell kinetics in parathyroid adenomas: evidence for decline in rates of cell birth and tumour growth, assuming clonal origin.

OBJECTIVE: We aimed to provide a cell kinetic explanation for the demonstrated lack of disease progression in most patients with mild, asymptomatic primary hyperparathyroidism. DESIGN: We compared cell birth rates, estimated at the time of adenoma excision, with the lowest birth rates needed to grow tumours of the observed size. PATIENTS: Sixty-three patients with primary hyperparathyroidism due to a single chief cell adenoma who had normal renal function were followed up for long enough to demonstrate cure after surgical excision. MEASUREMENTS: Fresh adenoma tissue was incubated with tritiated thymidine. The proportion of cells synthesizing DNA was determined directly by radioautography in 18 cases, and indirectly from the regression of label index on rate of DNA synthesis in 45 cases. The birth rate of new cells was calculated assuming the duration of S phase to be 12 hours. The number of cells in each adenoma was estimated both from parenchymal weight and from total DNA content, and the minimum birth rate needed to produce this number of cells from a single cell, beginning in utero, was calculated on an exponential model. RESULTS: The mean observed birth rate of new cells (mean (SD)) was 17.3 (11.1)%/year, and the minimum needed birth rate was 42.8 (21.6)%/year, significantly, (P less than 0.001) higher than the observed birth rate. CONCLUSIONS: The rate of mitosis had fallen substantially during the life span of most parathyroid adenomas. To account for this, we propose that the mutation implied by a clonal origin increases the secretory setpoint. Because proliferation, as well as hormone secretion, is influenced by calcium in parathyroid cells, the expected result would be rapid initial growth, slowing down as tumour size reached an asymptotic value corresponding to the total rate of hormone secretion needed to raise the plasma calcium to the new setpoint.

Adenoma↗
PubMed1983

Loss of nitroglycerin to cardiopulmonary bypass apparatus.

An in vitro model of a cardiopulmonary bypass (CPB) circuit using a bubble oxygenator was developed to assess the potential of this system to extract nitroglycerin (NTG). A NTG solution (100 ng/ml) was circulated through a CPB circuit at 5 L/min for 60 min. Samples obtained for NTG analysis revealed a significant loss of drug to the circuit. By 60 min, only 18% of the initial NTG concentration was present. In a separate experiment, the bubble oxygenator was shown to be the major source of drug extraction because less than 15% of the drug concentration infused directly into the oxygenator appeared in the arterial outlet. These results indicate that patients may not receive the expected dose of NTG during CPB even if caution is taken to administer the drug through nonadsorbing iv tubing.

Biological Availability↗
PubMed1979

[Cadmium content of vegetable foods in the effective range of a lead smelting plant].

In the effective range of a lead smelting plant, the repercussions of cadmium emissions (mainly past) on vegetables, fruit, soil and drinking water as well as of immissions were investigated by means of atomic absorption spectrometry. As compared to the "normal" cadmium level, the cadmium contents in vegetables and fruit were some 2- to 85-fold higher; and those in soils, some 70- to 230-fold. The mean contents in vegetables ranged from 0.4 to 25.5 p.p.m. (on a dry-weight basis); those in fruit, from 0.09 to 1.17 p.p.m. Cadmium concentrations varying from 6.8 to 22.8 p.p.m. were found in soil samples. The drinking water contained 0.009 p.p.m. of cadmium. The mean cadmium contents in the atmosphere and the sedimentary dust were 0.007 mg/m3 and 0.550 mg/m2/30d, respectively. In the territory investigated, the total human uptake of cadmium supplied by vegetables, fruit, potatoes, drinking water and air is 3.3-32.6 microgram/d. The following cadmium levels were found in human organ samples obtained at necropsy: right and left renal cortex, 33.99 and 35.98 p.p.m., respectively; liver, 3.14 p.p.m.; lungs, 0.63 p.p.m.; pancreas, 1.47 p.p.m.; brain stem, 0.16 p.p.m.

Brain Stem↗
PubMed1979

[Fluoride contents of rat molars following the administration of amine-fluoride-containing caries preventives (author's transl)].

Experiments on fifty Wistar rats were conducted with the object of studying the incorporation of fluoride into the enamel of molars subsequent to the administration of amine-fluoride-containing caries preventives. - Use of two toothpastes with low fluoride contents of 0.125% and 0.18% F, respectively, and two higher-fluoride (1% F) solutions resulted in a marked increase in the concentration of fluoride in the superficial layers of dental enamel.

Animals↗
PubMed1978

[Evaluation of the cadmium content in sedimented and floating dust as factors in contamination of the biosphere].

In a territory being 3.500 km2, the cadmium deposits from the atmosphere were determined at 63 sites in 52 towns and communities. These determinations yielded a mean value ranging from 0.13 to 0.15 mg/m2 . 30 d. On the contrary, the mean value (-x) was 0.33 mg/m2. 30 d in the region of heavy-metal-emitting industries. The mean cadmium content in the aerosol was between 0.003 and 0.004 microgram m-3 and, respectively, 0.016 microgram m-3 in case of cadmium emission. It was calculated that the mean proportion of cadmium in the sedimentary dust was between 13 and 16 p.p.m. The cadmium burden, as estimated as cadmium sediment, correlated with the extent of the developmental area. The authors recommend for the present the following maximum permissible values: 0.05 microgram m-3 in the aerosol, and 0.15 mg/m2. 30 d. The cadmium content in the sedimentary dust may be considered to be a permanent burden applied via the food chain, whereas the content in the aerosol is of less importance to the total uptake in man. The calculation of the daily pulmonary uptake yielded a value of 0.075 microgram, from which an absorption of 0.038 microgram is estimated.

Air Pollutants, Occupational↗
PubMed1977

Onset of oestrogen-induced prolactin secretion and DNA synthesis by the rat pituitary gland.

The times of onset of oestrogen-induced prolactin secretion and DNA synthesis were studied in the pituitary gland of the male rat. At intervals from 3 to 96 h after injection of 10 mg diethylstilboestrol dipropionate, serum and pituitary prolactin concentrations were measured by radioimmunoassay and pituitary DNA synthesis by incorporation of [3H]-thymidine in vitro. Serum prolactin was raised significantly from 6 h onwards and DNA synthesis was increased from 30 h onwards. Pituitary prolactin concentration began to increase at 30 h. Significant correlations were obtained between serum prolactin and DNA synthesis from 24 to 72 h but not during the period of prolactin secretion from 6 to 24 h.

Animals↗
PubMed1977

Hyporeninemia and hypoaldosteronism in diabetes mellitus.

The changes in plasma renin activity (PRA) and plasma aldosterone concentration (PA) in response to postural stimuli were evaluated in 12 patients with stable diabetes mellitus and in five volunteers. Seven diabetic patients had hyperkalemia, and several had renal insufficiency and neurological complications. Five diabetics and had normal serum potassium concentration, a mean creatinine clearance within the normal range, and few complications. PRA and PA were measured in these patients and in the control subjects, all of whom were receiving a diet containing 10 mEq of sodium and 50 mEq of potassium while they were in a supine position, after they were tilted to a 90 degrees position, and after upright posture for two hours. The results indicate that impaired responsiveness of PRA and PA may occur in patients with complicated and those with uncomplicated diabetes and may be responsible in part for a relatively high prevalence of hyperkalemia especially in those diabetic patients with reduced renal function.

Adult↗
PubMed1976

[Lead content of vegetable foods in vicinity of lead emitting industry].

By means of atomic absorption spectrophotometry, the authors determined the lead content in vegetable, fruit and soil samples from the environments of a lead-smelting plant. The lead values obtained were some 10- to 100-fold higher than those found normally. The mean lead content in vegetables varied from 2 to 150 p.p.m. in dry matter; that in fruits, from 4 to 35 p.p.m. Lead concentrations ranging from 575 to 2900 p.p.m. were detected in the soil samples. The mean lead content in the atmosphere was between 0.62 and 0.95 mug/m3 (maximum value 12 mug/m3). From these data it was calculated that the total resorption of lead from vegetables, fruits, potatoes and air varied from 0.04 to 0.49 mg/day in the territory under investigation. To protect the population against increased intake of lead, it is recommended to abandon individual and commercial vegetable and fruit growing, especially leaf vegetables. Since the contamination of the soil persists for generations, the authors discuss its replacement by non-contaminated surface soil.

Air Pollution↗