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Biomedical subjects

P Schwarz

Publications and source records attributed to P Schwarz.

At least 19 recordsLinked to original sources
PubMed1992

Normal pattern of parathyroid response to blood calcium lowering in primary hyperparathyroidism: a citrate clamp study.

OBJECTIVE: The objective of the present study was to elucidate the parathyroid responsiveness by measurements of blood ionized calcium and serum intact parathyroid hormone (PTH) concentrations, before and during trisodium citrate induced hypocalcaemia. PATIENTS AND CONTROLS: Sixteen patients with primary hyperparathyroidism and 32 healthy volunteers. DESIGN: Blood ionized calcium concentration was lowered by about 0.20 mmol/l and maintained at this level for 2 hours by blood ionized calcium controlled trisodium citrate infusion. MEASUREMENTS: Serum PTH(1-84) was measured by an immunoradiometric assay. RESULTS: In patients and controls, baseline measurements of blood ionized calcium were 1.39 +/- 0.07 vs 1.24 +/- 0.04 mmol/l (mean +/- SD) (P < 0.001) and of serum PTH (1-84) 9.7 +/- 5.4 vs 3.2 +/- 1.1 pmol/l (P < 0.001). During a trisodium citrate clamp, serum PTH(1-84) rose to a maximal concentration after 5-10 minutes in both groups, the patients to 2-10 times baseline, whereas controls rose to 4-7 times baseline values. In both groups the peak of serum PTH(1-84) declined to a steady state concentration around 2-4 times baseline. CONCLUSIONS: In conclusion, adenoma cells seem to react in almost the same way as normal parathyroid cells. They respond to initiation of hypocalcaemia by the release of preformed PTH(1-84), and continue to secrete increased amounts of PTH(1-84) during the maintenance of relative hypocalcaemia. The increased baseline concentrations of blood ionized calcium and serum PTH(1-84) and the serum PTH(1-84) response during blood ionized calcium lowering all suggest a shift upwards in the calcium set point.

Adenoma↗
PubMed1992

Regulation of acute parathyroid hormone release in normal humans: combined calcium and citrate clamp study.

The objective of the present study was to elucidate the dynamics of parathyroid hormone regulation, with particular reference to the mechanism controlling the acute parathyroid hormone release. Through utilization of the citrate clamp technique and the calcium clamp technique we were able, in a standardized way, to stimulate and suppress the parathyroid hormone secretion. Precise bedside measurements of blood ionized calcium and measurements of intact parathyroid hormone were performed. Twelve healthy young volunteers participated in two trials 6-12 wk apart, a citrate clamp (delta-blood ionized calcium -0.19 mmol/l) and a calcium plus citrate clamp (delta-blood ionized calcium +0.22 mmol/l and -0.19 mmol/l). During the citrate clamp, preceded by normal calcemia, serum intact parathyroid hormone peaked to a maximum after 5-10 min, four to six times above baseline concentration and then declined to a steady state two to three times above baseline concentration. During the citrate clamp, preceded by hypercalcemia induced by a calcium clamp, serum intact parathyroid hormone also peaked immediately to about five to nine times above its suppressed level, approximately two times above the baseline concentration. Subsequently, serum intact parathyroid hormone declined to a steady state just below the baseline concentration. In conclusion, within the range studied, the mechanism eliciting the acute serum intact parathyroid hormone release from its depot is a fall in blood ionized calcium, not the absolute concentration of ionized calcium.

Adult↗
PubMed1992

Hypocalcemia and parathyroid hormone responsiveness in diabetes mellitus: a tri-sodium-citrate clamp study.

The aim of this study was to elucidate the diabetic hypocalcemia and PTH responsiveness, investigated by measuring blood ionized calcium and serum intact parathyroid hormone (S-PTH(1-84)) concentrations, before and during an induced and maintained controlled hypocalcemia. In 15 patients with insulin-dependent diabetes mellitus and 19 healthy volunteers the blood ionized calcium concentration was lowered by about 0.20 mmol/l and maintained at this level by blood ionized calcium controlled tri-sodium-citrate infusion. In patients vs controls, baseline measurements averaged for blood ionized calcium (mmol/l) 1.18 +/- 0.08 vs 1.24 +/- 0.03 (p less than 0.01), for S-magnesium (mmol/l) 0.73 +/- 0.07 vs 0.81 +/- 0.07 (p less than 0.01) and for S-PTH (1-84) (pmol/l) 3.0 +/- 1.0 vs 3.1 +/- 1.0 (p greater than 0.75). During the clamp, S-PTH (1-84) peaked to comparable maximums after 5-10 min in both groups and then declined to constant concentrations two to three times above their control levels. In conclusion, we found a diabetic hypocalcemia and hypomagnesemia, though baseline levels of PTH and PTH responsiveness were normal. This may be taken to indicate a mild shift downwards in the set-point for PTH secretion in patients with insulin-dependent diabetes mellitus.

Adult↗
PubMed1992

Calcium clamp technique: suppression of serum intact PTH by induced hypercalcaemia in normal man and primary hyperparathyroidism.

The aim of the study was to investigate the interrelation between induced hypercalcaemia and serum intact parathyroid hormone (S-PTH(1-84)) in normal man and in patients with primary hyperparathyroidism (PHPT) by measuring blood ionized calcium (B-Ca++) and S-PTH(1-84) before and during a controlled calcium infusion. Guided by frequent measurements of B-Ca++, we adjusted the calcium infusion rate continuously, thereby keeping B-Ca++ in a steady state at a pre-determined level approximately 0.25 mmol l-1 above baseline values. This calcium clamp technique (CCT) applied to 14 normal volunteers for 120 min established a standardized reference for parathyroid suppression and the renal physiological PTH response. The reproducibility of the method and the results obtained by the CCT were satisfactorily assessed in six of the 14 normal subjects. In normal subjects B-Ca++ was raised from 1.25 +/- 0.3 mmol l-1 (mean +/- SD) to 1.49 +/- 0.02 mmol l-1 suppressing S-PTH(1-84) to 264 +/- 9.9% of pre-infusion levels. We applied the CCT to 10 patients with PHPT for 120 min raising B-Ca++ from 1.41 +/- 0.09 mmol l-1 to 1.69 +/- 0.08 mmol l-1, thereby suppressing S-PTH(1-84) to 47.9 +/- 16.3% of pre-infusion levels. The renal handling of calcium and phosphate during CCT demonstrates the biological effects of suppressed activity of PTH on the renal tubules showing increments in the maximal tubular phosphate reabsorption in relation to the glomerular filtration rate (TmP/GFR) and decreased tubular reabsorption fraction of calcium. The described CCT is a safe and reliable dynamic test.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1991

[How precise is the optical Cerec impression?].

The purpose of this investigation was to evaluate the precision of optical impressio obtained with the Cerec-device. Cerec provides a linear correlation between z-data and altitude (r = 1), one bit representing 49 microns. Repeated measurements deliver pixel-z-data within a range of +/- 49 microns and surfaceaverages (484 pixel) within +/- 5 microns. Deviations occur near areas with parallel orientation to the direction of measurement.

Ceramics↗
PubMed1990

Induced hypocalcaemia controlled by a citrate clamp technique, and the intact parathyroid hormone response obtained.

In order to investigate (1) the possibility of controlled induction and maintenance of hypocalcaemia, and (2) the intact parathyroid hormone (PTH(1-84)) response obtained thereby, 14 healthy individuals were administered an i.v. infusion of trisodiumcitrate. The reproducibility of the method established was assessed in five of the 14 individuals. Aiming at a steady-state level of blood ionized calcium (B-Ca2+) = 1.00 mmol/l, obtained within 30 min and subsequently maintained for 90 min, the infusion was guided by frequent determinations B-Ca2+. The method established was as follows: infusion of 0.85 mmol citrate/kg body weight/h during the first 10 min, followed by 0.44 mmol citrate/kg body wt h 1.26 exp. ((actual B-Ca2(+)--target B-Ca2+)/0.02) mmol/l, until B-Ca2+ = 1.00 mmol/l. In the steady-state period the infusion rate was 0.29 mmol citrate/kg body wt. h 1.26 exp. ((actual B-Ca2(+)--target B-Ca2+)/0.02) mmol/l. The method showed reproducibility by an overall difference in B-Ca2+ measurements of -0.03 mmol/l, which did not statistically differ from zero (p less than 0.05). No severe side effects were observed during a total of 21 infusions. Intact serum parathyroid hormone concentrations (S-PTH(1-84)) obtained during induced hypocalcaemia rose to a peak within 5-10 min, and then declined to a steady-state level about three times the initial. The serum (S) PTH(1-84) response could be caused by a burst of S-PTH(1-84) from a depot source while the steady-state level may indicate a stimulated secretion from parathyroid glands. The S-PTH(1-84) response was shown to be reproducible by an overall difference in S-PTH(1-84) measurements of -0.52 pmol/l, which did not statistically differ from zero (p less than 0.10).

Calcium↗
PubMed1990

[Evaluation of the new radiovisiography system].

The latest version of the Radiovisiography-system was evaluated in comparison to its predecessor and a high speed periapical film (Agfa Dentus M4). Both RVG-systems proved to have the same sensitivity and are capable of displaying a similar contrast range. Nevertheless additional functions of the new system allow a much better visualisation of the radiographed structure. Compared with Dentus M4 periapical films the RVG-System provides less sensitivity but a wider range of contrast.

Evaluation Studies as Topic↗
PubMed1990

[Comparative study of the Interplak tooth cleansing instrument].

Unlike manual and electric toothbrushes, the brush head of the Interplak instruments remains stationary while ten tufts of bristle rotate. The efficacy of this new system was evaluated in comparison to a conventional electric toothbrush (Braun dental d3). When used for the first time the Interplak instrument proved to be more effective in reducing plaque. After training periods of 2 and 4 weeks there was, however, no significant difference between products.

Adult↗
PubMed1989

[Systemic lupus erythematosus and pregnancy].

The literature about pregnancies in patients with systemic lupus erythematosus (SLE) was reviewed. Information about 1,164 pregnancies was compiled. Fifty-four per cent of the pregnancies were normal, 15 per cent of the babies were premature, and 29 per cent of the pregnancies resulted in fetal wastage. In a background population of 50,000 women the corresponding figures were 80, 4 and 16 per cent, respectively. The neonatal mortality of babies borne by women with SLE was 2 per cent. About one third of the patients had an exacerbation of their disease, mostly post-partum or during the last trimester of the pregnancy. The risk of a exacerbation for patients with active disease at the time of conception was double that of patients with inactive disease. Therapeutic abortions were followed by improvement as well as deterioration of the disease. Two per cent of the patients died during pregnancy or post-partum. Cardiolipin-antibody may be a marker of fetal wastage and Ro-antibody may be a marker of fetal heart block in babies borne by women with SLE. Pregnancy was previously considered inadvisable in all patients with SLE. During recent years, the attitude to this problem has been less rigid. However the patients should be fully informed about the risk of exacerbation, fetal wastage, and premature delivery and patients with active disease should be advised to postpone pregnancy until a remission has been achieved.

Female↗
PubMed1989

[Histiocytosis X. Review of the literature and a case report].

Histiocytosis X is a non-lipid reticuloendotheliosis, characterized by histiocyte proliferation. The proliferating cells resemble the Langerhan's cells in the epidermis. The main clinical types include eosinophile granuloma, Hand-Schüller-Christian's disease (HSC) and Letterer-Siwe's disease (LS). Eosinophile granuloma is localized to the skeleton and runs a spontaneously benign course. HSC and LS are serious, generalized conditions. HSC runs a chronic and occasionally lethal course. LS usually runs a rapidly lethal course. LS commences before the age of three years while HSC occurs both in children and young adults. A case of HSC is described.

Adult↗