Search PubMed⌕ Search

Biomedical subjects

P Bergmann

Publications and source records attributed to P Bergmann.

At least 73 records · Page 4Linked to original sources
PubMed1990

Circadian and pulsatile TSH secretion under physiological and pathophysiological conditions.

In addition to the well known circadian rhythm of TSH secretion a pulsatile pattern of release has been shown. Analysis of the pulsatile release by different computer-assisted methods revealed systematic differences in the number and distribution of TSH pulses. Using the same approximation of false positive pulses (less than 1%) in any of the 21 healthy male volunteers tested a lower number of pulses was found by the Pulsar method (mean 5.1 +/- 2.0/24 h) than by the Cluster (10.6 +/- 1.8) or the DESADE program (13.6 +/- 4.6). The results of the Cluster and Desade analysis fit well to that of Fourier transformation which revealed a dominant frequency at 160 min. In addition dominant frequencies in comparison to a noise series were found at 24 h and at 33 min. Analysis of the data in 8 h segments between 2000 and 0400 h, 0400 and 1200 h and 1200 and 2000 h by Desade and cluster revealed that app. 50% of pulses occurred between 2000 and 0400 h, suggesting an important role of pulsatile TSH release in the generation of the circadian TSH rhythm. In 3 patients with TSH-induced hyperthyroidism the circadian and pulsatile pattern of TSH secretion was similar to that in healthy controls. In contrast, in a patient with a TSH producing pituitary tumor the circadian variation of TSH secretion was abolished. Patients with a non-toxic goitre revealed a significantly lower mean TSH serum level as the control group of healthy subjects. The number of TSH pulses was slightly but significantly lower when analyzed by the DESADE program but not when analyzed with any other method.

Adult↗
PubMed1990

[Effect of cavity design on the marginal fit of Class I composite fillings].

16 butt joint (Group A) and 16 beveled (Group B) class I cavities were prepared in extracted molars and filled with two hybrid composite resin materials using the enamel etching technique. Replicas were obtained before and after thermocycling (TC) and a computerized quantitative margin analysis was carried out in the SEM. Statistical analysis revealed significant differences (p less than 0.01) between the two groups only after TC. Group B showed significantly less marginal openings than Group A (A: 50.7%, B: 8.4%) after TC. Class I cavities for hybrid composite resin materials should be beveled.

Acid Etching, Dental↗
PubMed1990

Long-term irreversibility of bone loss after surgery for primary hyperparathyroidism.

We reported previously that radial bone mineral content was decreased in patients with primary hyperparathyroidism and remained subnormal 1 year after surgery. In this study, we reviewed the results of sequential measurements of the radial bone mineral content, performed up to 107 months after removal of the parathyroid adenoma in 71 patients suffering from primary hyperparathyroidism. Bone mineral content increased during the first year after surgery. During the period 1 to 8 months after removal of the adenoma, the mean monthly increment was 0.009 +/- 0.0022 g/cm for the radial epiphysis and 0.0084 +/- 0.0023 g/cm for the shaft. However, in 39 patients seen at the end of 1 year after surgery, the bone mineral content of the epiphysis remained more than 1 SD below the normal mean in 61% (24) of the patients and more than 2 SDs in 36% (14) of the patients. For the shaft, those percentages were 59% (23) and 26% (10), respectively. Thereafter, the monthly increment rate of bone mineral content decreased rapidly with time, so that only minor further increase could be expected. Data show that patients with a low bone mineral content when diagnosed with primary hyperparathyroidism will conserve life long an irreversible loss of bone as compared with a matched control population.

Adenoma↗
PubMed1989

Correction of low circulating levels of 1,25-dihydroxyvitamin D by 25-hydroxyvitamin D during reversal of hypomagnesaemia.

The effect of 25-hydroxyvitamin D (25OHD), given orally during the reversal of hypomagnesaemia, was studied in five patients with hypomagnesaemic hypocalcaemia and low serum levels of 25OHD and 1,25-dihydroxyvitamin D (1,25(OH)2D). The results were compared to those obtained in five other patients with similar initial levels of magnesium, calcium, 25OHD and 1,25(OH)2D who did not receive 25OHD. Serum levels of 1,25(OH)2D in the ten hypomagnesaemic patients were lower than in ten control subjects with low serum levels of 25OHD. The reversal of hypomagnesaemia was similar in the two groups of patients and elicited a similar increase of circulating iPTH levels. The expected increase of circulating 25OHD was observed in patients supplemented with 25OHD; their circulating 1,25(OH)2D rose within 48 h to normal levels, contrasting with the delayed and poor increase of 1,25(OH)2D in patients receiving no 25OHD. The evolution of serum calcium was however identical in the two groups. Our results suggest that vitamin D deficiency was a significant factor leading to low circulating levels of 1,25(OH)2D in hypomagnesaemic hypocalcaemic patients. The biological consequences of low serum 1,25(OH)2D in these patients remain unclear, but clearly, normal levels of 1,25(OH)2D are not essential for the correction of hypomagnesaemic hypocalcaemia.

Adult↗
PubMed1989

Low basal thyrotropin with normal thyroid function in primary hyperparathyroidism.

TSH serum levels and thyroid function in 32 patients with primary hyperparathyroidism and hypercalcemia were compared to those of 30 age and sex-matched normal subjects. Serum T3 and T4 concentrations in hyperparathyroidism were not different from normal. However, basal serum TSH concentrations measured with an ultrasensitive immunoradiometric assay were significantly lower than normal (1.09 +/- 0.49 vs 2.06 +/- 0.85 mU/l, p less than 0.001). In hyperparathyroidism, TSH, but not T4 or T3, was negatively correlated with serum calcium, not with iPTH. The increase in TSH (delta TSH) 30 min after the iv injection of TRH was also significantly blunted in patients with primary hyperparathyroidism; delta TSH was highly correlated with basal TSH in hypercalcemic patients. The basal TSH concentration was higher and no longer different from normal (1.70 +/- 1.2 mU/l) 2 to 12 months after removal of the parathyroid adenoma, when serum calcium was normalized, whereas T3 and T4 did not change. A low basal TSH with normal T4 and low T3 was found in 13 patients with hypercalcemia of malignancy. In these patients, TSH increased after treatment of hypercalcemia with 3-amino-l,hydroxypropylidene-1, 1-bisphosphonate, whereas T4 did not change. The results suggest that the set point of pituitary thyroid feedback control could be decreased in chronic hypercalcemia and that hypercalcemia could render the thyroid more sensitive to TSH.

Adenoma↗
PubMed1989

[Local factors in bone repair].

Besides the systemic hormones (parathyroid hormone, calcitonin...), several local factors act on bone resorption and formation. These factors are released by cells of the bone microenvironment (hematopoietic cells, fibroblasts, endothelial cells...) and also by bone cells, mainly of the osteoblastic lineage. Among the factors which increase locally bone resorption ("osteoclastic activating factors, OAF"), interleukin 1, acting alone or synergistically with tumor necrosis factor, seems to be the most potent. As parathyroid hormone, it does not act directly on osteoclasts, but stimulates cells of the osteoblastic lineage to secrete unknown factors stimulating resorption. Prostaglandins E have been thought to be among these soluble factors secreted by osteoblasts or osteoblast precursors which stimulate bone resorption directly, but it appears now that the direct effect of prostaglandins on the osteoclasts is inhibitory. Several growth factors are secreted by cells of the osteoblastic lineage and by other bone cells. They are stored in the bone matrix, from which they are released and activated during resorption. The most important are IGF-I, IGF-II, and TGF beta. These growth factors stimulate replication of the osteoblast precursors and collagen synthesis by osteoblasts, and could be responsible for the well known coupling between resorption and formation. TGF beta also seems to inhibit replication of osteoclast precursors, and could thus stop the resorption process. It seems now that estrogens and physical stress act on bone at least in part by modulating the equilibrium between these local factors which act on resorption and formation.

Bone Development↗
PubMed1988

Bone loss and bone blood flow in paraplegic rats treated with calcitonin, diphosphonate, and indomethacin.

Sham-operated (SO) and paraplegic rats were treated from the day of operation during a period of 4 or 6 weeks with salmon calcitonin 4 IU/kg/day or a diphosphonate (APD) 1mM/kg/day or indomethacin 2.5 mg/kg/day. The consequence of spinal cord section on the femur and tibia is a loss of mineral which affects predominantly trabecular bone (-24 and -13% in calcium content for the tibial metaphysis and the whole bone, respectively, when compared with the SO controls), a twofold increase in bone blood flow as measured by the technique of the microspheres trapping, a moderate decrease of the 72 hour 45Ca accretion rate in the bone shaft, and an increase in the number of metaphyseal osteoclasts in the tibia. In paraplegics, all three drugs inhibit bone loss to some degree, calcitonin and indomethacin being mostly effective on the cortical bone of the shaft, and APD tremendously increasing the trabecular network of the metaphysis. APD is the only drug to exhibit a significant effect on the calcium content of the bones of the SO controls, but some effect is apparent for calcitonin on X-rays and histological preparations. The increase in bone blood flow in paraplegics is unaffected, this point being discussed in view of the hypothesis of the resorptive action of prostaglandins produced by newly formed vessels. 45Ca accretion rate increases in the shaft of calcitonin-treated paraplegics, whereas it decreases in APD-treated controls and paraplegics. The number of osteoclasts decreases in paraplegics treated with calcitonin and indomethacin, and increases in both controls and paraplegics treated with APD.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1988

Penetration of aminoglycosides in uninfected pleural exudates and in pleural empyemas.

The concentrations of gentamicin, netilmicin, and amikacin were determined after one single intravenous injection in uninfected pleural fluid after thoracotomy and in purulent pleural empyemas. The mean peak concentrations in the pleural fluid after the injection of gentamicin (1.5 mg/kg), netilmicin (2.0 mg/kg), and amikacin (7.5 mg/kg) were 2.9 +/- 0.3 mg/L, 3.7 +/- 0.8 mg/L, and 11.0 +/- 3.1 mg/L, respectively. The pleural penetration of the drugs was very high (from 80.0 to 99.1 percent). By contrast, gentamicin and netilmicin were not detectable in empyema pus; in this exudate the mean peak level of amikacin was 5.7 +/- 2.2 mg/L, with the penetration of this drug being 31.0 percent. The concentrations of parenterally administered aminoglycosides are substantially lower in empyema pus than in sterile pleural fluid. The possibility of poor pleural penetration of some aminoglycosides, as well as the presence of local conditions in pleural empyema unfavorable to the bioactivity of these drugs, must be kept in mind when treating pleural infections.

Amikacin↗
PubMed1988

Continuous ambulatory peritoneal dialysis vs haemodialysis: a lesser risk of amyloidosis?

We compared plasma beta-2-microglobulin (beta 2M) at a 1-year interval in 25 CAPD patients and 25 patients haemodialysed with cuprophane membranes and matched for residual renal function and duration of renal replacement therapy. Plasma beta 2M remained lower in CAPD patients throughout the study, and increased significantly with time both in CAPD and haemodialysis patients, as renal function decreased. In both groups, plasma beta 2M was negatively correlated with residual creatinine clearance, the influence of the latter being much greater in haemodialysis, as demonstrated by comparison of the regression lines. In haemodialysis, but not in CAPD, plasma beta 2M also correlated with time on dialysis. In CAPD patients, the daily peritoneal output averaged 38 mg (range 16-59 mg), and was directly correlated with plasma beta 2M. CAPD thus allows a significant peritoneal removal of beta 2M, which progressively takes over from the declining renal function, resulting in lower plasma beta 2M than in matched haemodialysis patients. However, the peritoneal removal of beta 2M remains insufficient and values increase with time as renal function declines. Thus, if beta 2M amyloidosis is related to raised plasma levels, the risk of beta 2M amyloidosis in CAPD should simply be delayed as compared to haemodialysis.

Adult↗
PubMed1988

Are tuberculous patients at a great risk from hypercalcemia?

The risk of tuberculous patients to develop hypercalcemia was investigated in 33 patients aged 19 to 80. Twenty-two of the 33 received no vitamin D supplements. Before antituberculous chemotherapy serum calcium corrected for albumin and urinary calcium levels were normal, serum 25-hydroxyvitamin D (25(OH)D) levels were low, but serum 1,25(OH)2D levels, oral calcium load test and intestinal 47Ca absorption were normal. After 17 to 34 days of chemotherapy serum calcium corrected for albumin and 1,25(OH)2D levels were lower without change in serum D-binding protein. In 11 patients 25(OH)D, 50 micrograms/day, was given orally for two months. 25(OH)D given three days before chemotherapy in five patients induced an increase of levels of 1,25(OH)2D which was greater than in 10 control patients with similar serum levels of 25(OH)D. When chemotherapy was added to 25(OH)D, the five patients showed high normal 1,25(OH)2D levels. The last six patients received 25(OH)D together with or after starting chemotherapy. None of the 33 patients developed hypercalcemia, even when supplemented with 25(OH)D for two months. It appears that hypercalcemia is uncommon in tuberculosis.

Adult↗
PubMed1987

[Drug transport through artificial lipoid membranes. 21. Ion pair transport with alkyl salicylic acids].

Using hexylsalicylic acid it was demonstrated that alkylated derivatives of salicylic acid are able to increase partition and transport of ionized basic drugs across lipophilic membranes. The influence of different donor concentrations on the relation of transport was studied by means of pholedrine in combination with hexylsalicylic acid. In order to explain the mechanism of the ion-pair-transport experiments were carried out which show beside the mentioned increase of transport the occurrence of a countertransport of protons and lithium-ions, respectively. The lipophilic counterion hexylsalicylate acts inside of this mechanism as a carrier for the ionized drugs.

Chemical Phenomena↗
PubMed1986

[Characterization of lectin receptors on cell surfaces with regard to functional aspects].

The actual definitions of lectins are presented and discussed and lectins are classified as one group of the affinitins. The ability of lectins to bind carbohydrates serves as a widely used principle in the nature for cell recognition and adhesion processes. By means of labelled glycoconjugates the identification, localization and quantitation of receptor bound lectins can be investigated as by lectinological as by a combination of lectinological and immunological reactions. The special properties of toxic lectins are discussed by use of the lectin I from mistletoe as characteristic example. The coupling of A-chains with antibodies (immunotoxins) or other haptomers (affinotoxins) leads to agents render it possible to influence directly cell functions.

Animals↗