Search PubMed⌕ Search

Biomedical subjects

H Stark

Publications and source records attributed to H Stark.

At least 163 records · Page 9Linked to original sources
PubMed1988

Hypercalciuria as a cause of persistent or recurrent haematuria.

Of 91 children with idiopathic persistent or recurrent haematuria, eight also had hypercalciuria. This was transient in three and persistent in five. Persistent hypercalciuria was a rare cause of microscopic haematuria (two of 80), but common in association with gross haematuria (three of 11).

Adolescent↗
PubMed1988

Shape estimation in computer tomography from minimal data.

In computerized tomography, line integrals of the absorptivity are used to reconstruct the object. In some applications only the locations, sizes, and shapes of internal opacities or near-opacities are needed. For these applications it is unnecessary to reconstruct an image by convolution backprojection [O(N3)] or by direct Fourier methods [O(N2log N)]. We propose an algorithm suitable for this problem that requires only O(N) operations (N is of the order of the number of views). We analyze and demonstrate the high performance of the algorithm but show that the performance of the algorithm depends strongly on an appropriate choice of system parameters. These parameters, the number of view N theta, and the detector spacing deltas are shown to be linked, and a choice of deltas strongly constrains the choice of N theta. We show how an optimum N theta can be determined for a fixed deltas, including practical values of deltas. A series of experiments that reinforce the theory is simulated on a computer.

Humans↗
PubMed1988

Metabolism of D-proline beta-casomorphin derivatives in the rat brain.

The aim of the present study was to evaluate the metabolic breakdown of two biologically active derivatives of beta-casomorphin (beta CM)-i.e. D-proline4-beta CM (D-Pro4-beta CM) and des-tyrosine 1-D-proline4-beta CM (DT-D-Pro4-beta CM)- in the rat brain. After intracerebroventricular (icv.) administration of 0.78 nmoles of both [3H]D-Pro4-beta CM and [3H]DT-D-Pro4-beta CM, the concentration of the intact peptides and their metabolites was estimated in brain stem and corpus striatum. Both peptides were degraded in brain tissue forming a common metabolite. Phe-D-Pro-Gly. The metabolic half-lives of DT-D-Pro4-beta CM in brain stem and c. striatum were 22.6 min and 28.6 min, whereas those of D-Pro4-beta CM were 7.8 min and 8.2 min, respectively. According to both half-lives of the intact peptide and the kinetics of the formation of the stable metabolite Phe-D-Pro-Gly. DT-D-Pro4-beta CM seemed to be more resistant to biological degradation in brain tissue than D-Pro4-beta CM. In the case of D-Pro4-beta CM, the dipeptidylpeptidase IV (DP IV) (EC 3.4.14.-) is presumed to be the cardinal enzyme for the breakdown. Since the degradation of these peptides in brain tissue results in the unique metabolite Phe-D-Pro-Gly, the differences in the pattern of biological activities between D-Pro4-beta CM and DT-D-Pro4-beta CM may be due to the action of the corresponding intact peptide.

Animals↗
PubMed1987

[Fluctuations and stable elements in the visual field in glaucoma].

In glaucomatous visual fields there are more fluctuations than stable elements. High-amplitude fluctuations of stimulus threshold values are characteristic of glaucoma. The correlation between sensitivity and the mean loss can be demonstrated by the ABC test. The structure of scotomas is explained. There is a stable, relatively small nucleus (a) of individual defects which stay in the same location for three years and mainly have the most severe loss (greater than or equal to 2.0 logE). However, accompanying and border fluctuations (b and c) predominate. They are detected by recording individual defects. The results of a study lasting several years are communicated, in which 1124 visual field examinations were performed in 146 patients using the Peritest computer-controlled perimeter.

Age Factors↗
PubMed1987

Metabolism of beta-casomorphin and its derivatives in rat brain and liver homogenates.

Derivatives of opiate-like acting beta-casomorphin (beta-CM), (Tyr-Pro-Phe-Pro-Gly), were prepared by substitution of D-amino acids. The metabolism of these analogs was studied in brain and liver homogenates. Their half-lives and the metabolites resulting from their biological degradation were determined by means of the HPLC-technique. Resistance to biological degradation, which was considerably enhanced in some derivatives, was shown to depend on the position of the D-amino acids. The following substances proved to be particularly stable: D-Pro2-beta-CM, Des-Tyr-D-Pro2-beta-CM, Des-Tyr-D-Phe3-beta-CM. The resulting metabolites suggest that the activity of proline-specific peptidases is predominant in the catabolic process. The degradation pattern of beta-CM-pentapeptides produced by peptidases in the brain and liver is completely different from that of the enkephalin-pentapeptides, which are likewise protected by substitution of D-stereoisomers for certain L-amino acids. The different degradation kinetics of beta-CM-pentapeptides in neuronal and non-neuronal tissue homogenates (liver) reflect the variation in activity of certain peptidases. Considering the half-lives that we have estimated, we suggest which of the peptides tested has a high resistance against biological degradation in vivo.

Amino Acid Sequence↗
PubMed1986

Direct measurement of TP/GFR: a simple and reliable parameter of renal phosphate handling.

As the Walton-Bijvoet nomogram for estimating renal phosphate (P) threshold (TmP/GFR) is not applicable to children of all ages, we sought an alternative method for measuring renal handling of P. Recognizing that the nomogram represents an indirect correlation between TmP/GFR and TP/GFR under fasting conditions, we examined this directly in 26 children. An excellent correlation was found, expressed as TmP/GFR = (fasting TP/GFR X 1.1) -0.3 (r = 0.95). The regression line in adults, expressed as TmP/GFR = (fasting TP/GFR X 1.4) -0.9 (calculated from published studies) is markedly different at the higher values typical for children. Since no advantage could be seen in the use of a mathematically derived TmP, we investigated the direct use of measured TP/GFR (tubular P reabsorption per 100 ml glomerular filtrate) as a measure of renal P handling in clinical practice. No differences were found between morning fasting and nonfasting values. Measurements in 151 healthy subjects aged 3 days to 53 years established normal values in relation to age. The use of this parameter in patients is shown to accurately reflect defects and changes in renal P handling. We believe it to be the preferred parameter because it represents a directly measured physiologic function applicable to all age-groups.

Adolescent↗
PubMed1986

Degradation of beta-casomorphin in the rat brain in vivo.

The degradation of beta-casomorphin 1-5 (Tyr-Pro-Phe-Pro-Gly (beta CM]--an opiate-like acting pentapeptide--was investigated in brain stem and corpus striatum of male Wistar rats during the first 20 min after an intracerebroventricular (i.c.v.) application of 166 nmol [3H]Phe3-beta CM. Dependent on the time after [3H]Phe3-beta CM injection, the radioactivity carried by beta CM and its metabolites was estimated in the HCl-soluble tissue fraction of these brain structures. The separation of the intact pentapeptide from its metabolites was performed using HPLC-technique. In both brain regions a rapid decrease in the concentration of beta CM was observed during the first 10 min after [3H]Phe3-beta CM application (1st phase). 10 to 20 min after injection, the decrease in beta CM concentration was found to be considerably smaller (2nd phase). Moreover, beta CM is rapidly degraded forming phenylalanine and tyrosine as the main metabolites. Furthermore, at any time, small amounts of Phe-Pro-Gly, Phe-Pro, Pro-Phe-Pro-Gly and Tyr-Pro-Phe-Pro were estimated. From these results, the analgesic effect by i.c.v. application of 166 nmol beta CM is assumed to be caused rather by the intact pentapeptide molecule than by one of its metabolites.

Animals↗
PubMed1986

Reconstruction of the ulnar collateral ligament in athletes.

Reconstruction of the ulnar collateral ligament using a free tendon graft was performed on sixteen athletes. All participated in sports that involved throwing (mostly professional baseball), and all had valgus instability of the elbow. After reconstruction and rehabilitation, ten of the sixteen patients returned to their previous level of participation in sports, one returned to a lower level of participation, and five retired from professional athletics. Despite precautions, there was a high incidence of complications related to the ulnar nerve. Two patients had postoperative ulnar neuropathy (one late and one early) that required a secondary operation, but they eventually recovered completely. Three others reported some transient postoperative hypoesthesia along the ulnar aspect of the forearm that resolved after a few weeks or months.

Adult↗
PubMed1985

The use of the portal system for the transplantation of a neonate kidney graft in a child with Wilms' tumor.

A single an-encephalus neonate kidney graft was transplanted into the portal system of a 6-year-old recipient who had previously undergone removal of the right kidney and inferior vena cava because of Wilms tumor. The left kidney ceased to function shortly thereafter. The child was supported very poorly on hemodialysis, and showed repeated very high levels of cytotoxic antibodies in her serum. The first cross-negative kidney graft that was available harbored two main arteries and duplicate collecting system with two very thin ureters. These vascular anatomic and pathologic variations of both donor graft and recipient necessitated the use of the portal system for renal graft venous drainage and the aorta for the graft revascularization. The ureters that had pinpoint-like lumen were inserted together into the lumen of the native ureter stump and fixated. One year after the transplantation the serum creatinine level is 1.8 mg/dL.

Aorta↗
PubMed1985

[Long-term treatment of senile macular degeneration with Cosaldon A+E].

During the early phase of senile degeneration of the macula treatment with Cosaldon A+E offers real changes of improvement. In the later phases long-term Cosaldon therapy can bring about an appreciable improvement when other vasoactive substances are administered at intervals. The addition of the vitamins A and E improves the efficacy of Cosaldon. Results in 157 patients are supported by statistics.

Adult↗
PubMed1985

[Studies with the computer-guided perimeter "Peritest" on the effect of Cosaldon A+E on glaucomatous visual field defects].

Investigations on 114 glaucoma patients with the computerized perimeter 'Peritest' showed that treatment with Cosaldon A + E resulted in a decrease or elimination of visual field defects. Favourable results were also obtained with statistical significance for severe visual field defects of defect class greater than or equal to 2.0 log U. Treatment time was generally 4-5 months. During the first 6-10 weeks of treatment strong fluctuations were observed regarding individual sensitivity of light perception as well as number of defect positions.

Adult↗
PubMed1985

Levan-induced glomerulitis in rabbits: a possible role for direct complement activation in situ.

Since high-molecular-weight levan is known to reduce capillary permeability to large molecules, an experiment was designed to investigate whether this agent may attenuate the glomerulonephritis associated with acute serum sickness in rabbits. The study, in fact, demonstrated an enhancing effect of levan, which caused increased glomerular proliferative changes and leucocyte infiltration and, possibly, increased IgG deposition in this experimental model. In addition, rabbits injected only with levan also demonstrated mild glomerulitis and C3 deposition. In one of four rabbits examined, this was accompanied by a marked fall in the serum level of total haemolysing complement. Levan was demonstrated to cause activation of complement when incubated with normal rabbit serum in vitro. We believe that these findings are best explained on the basis of complement activation in situ by levan in the glomeruli, probably via the alternative pathway, with the resulting inflammatory response. In the case of BSA-injected rabbits, this response is believed to be additive to that of the classical immune complex-mediated complement activation.

Animals↗
PubMed1983

[Eye changes in Gaucher's disease].

In a patient with Gaucher's disease multiple, chalky-white, randomly distributed, circular spots were observed in the superficial layers of the retina or directly on the vessel walls. There are indications that these changes of the retina, which have also been described by other authors, are characteristic of the juvenile form of Gaucher's disease. By carrying out a long-term study over an 11-year period it was possible to prove that these spots were caused by defective healing of minute hemorrhages which were initially still visible as red and white concentric target lesions in the center of the spot. The macula was not cherry-red in this case.

Adolescent↗