Search PubMed⌕ Search

Biomedical subjects

G Schuler

Publications and source records attributed to G Schuler.

At least 361 records · Page 20Linked to original sources
PubMed1979

[Unusual variants of blue naevi--a report of four cases (author's transl)].

This paper presents four unusual variants of blue naevus: a giant-sized blue naevus, a blue naevus assuming the clinical and histological appearance of a histiocytoma, a plaque-type blue naevus, and a pedunculated cellular blue naevus. Two of these lesions were studied at the ultrastructural level: in one case the dermal melanocytes contained malanosomes of all stages, thus documenting active melanin synthesis. In the other lesion, melanocytes of identical appearance were found in the superficial portions, whereas inactive melanocytes, densely packed with mature melanosomes, predominated in the deeper portions. It is concluded that blue naevi may vary considerably, both clinically and in histological appearance, as well as in regard to melanin synthesis activity.

Adult↗
PubMed1979

Profiles of radionuclide left ventricular ejection fraction changes induced by supine bicycle exercise in normals and patients with coronary heart disease.

This paper presents the profiles of left ventricular ejection fraction (EF) during and following supine bicycle exercise in normal subjects and in patients with coronary heart disease, as well as the relationship of the described patterns to clinical parameters. Twenty normal men and 40 patients with coronary artery disease were studied using gated equilibrium radionuclide angiography (EQ-EF). In the normals, during exercise, EF increased by a mean of 25% of the resting value, with an increase of no less than 11%. The exercise-limiting symptom in patients with coronary artery disease was angina pectoris in 20 and fatique in the other 20 patients. In the angina patients, there was a mean decrease in EF of 20%, and in the other coronary artery disease patients ejection fraction change little. Only two patients with coronary artery disease increased from a normal resting value to peak exercise by more than 11%, and they had isolated right coronary lesions. An "overshoot" elevation of ejection fraction above resting levels was demonstrated following termination of exercise in most patients. The patients with a significant fall in exercise ejection fraction more frequently had abnormal exercise-induced ECG changes as well as abnormal left ventriculograms and more severe coronary artery disease at cardiac catheterization than the patients with little change in ejection fraction. We conclude that 1) normals could be separated from most patients with significant coronary artery disease in this study population; 2) ejection fraction must be measured at maximal exercise for it to have diagnostic value, since there could be normal rise before and after peak exercise and an abnormal response missed; and 3) the ejection fraction response to exercise reflects the severity of the underlying coronary artery disease. The described patterns of exercise-induced changes in left ventricular ejection fraction are important to consider when using this new technique to diagnose and evaluate patients with coronary artery disease.

Adult↗
PubMed1979

A critical revaluation of fibre arrangement in the mid-zone (stratum reticulare) of human corium.

Investigation of in situ fixed skin clearly showed distinct arrangement and orientation of collagenous fibre bundles clearly visible only after in situ fixation of whole bodies. Light microscopy seems especially useful to study gross fibre and fibre bundle arrangement, whereas scanning electron microscopy is better suited to study the finer details of fibres and fibre bundles and their arrangement. 2 main directions of fibre bundles were found. The orientation was corresponding to the main mechanical stresses exerted to the skin. No clear start and ending of the fibre bundles could be distinguished. They seem to be arranged in a 3 dimensional texture. Fibres are branching off from one bundle and merge again either with a branch of the same bundle or with a branch of another bundle, in a higher or a lower layer of this 3 dimensional texture. In addition to the 2 main directions of the bundle orientation thin fibres are penetrating the whole texture in various directions. This is especially prominent in regions where vessels, hairbulbs or glands are protruding into the stratum reticulare. A quantitative study of fibre and fibre bundle orientation using semithin sections is under current investigation applying an automatic image analysis system.

Aged↗
PubMed1979

Validity of left-ventricular ejection fractions measured at rest and peak exercise by equilibrium radionuclide angiography using short acquisition times.

To validate ejection fraction (EF) calculations from 5 and 2 minutes of multiple-gated equilibrium radionuclide angiographic data and to establish its utility during alterations in cardiac performance, we studied 38 patients with chest pain suggestive of coronary artery disease. Twenty-four patients underwent contrast ventriculography (CV) as well as first-pass (FP) and equilibrium (EQ) radionuclide angiography at rest, and 14 additional patients had both radionuclide tests performed at rest as well as during peak supine bicycle exercise. The resting 5-min acquisition ejection fractions were compared between each method and the following correlations were generated: r = .92, n = 24 (CV-EQ), r = .92, n = 24 (CV-FP), and r = .95, n = 38 (FP-EQ). The variability of EQ-EF calculations between two independent observers was less than 2%; the mean absolute difference between two sequential 2-min acquisitions and the 5-min recordings was -.1 +/- 1.6%, and the reproducibility of sequential 2-min ejection fractions was excellent (r = .98). EQ and FP ejection fractions at symptom-limited exercise correlated well (r = .96, n = 14). We conclude that equilibrium radionuclide angiography is a valid method to measure EF both at rest as well as during peak exercise even when 2-min acquisition periods are used.

Adult↗
PubMed1978

Particle segregation in chromaffin granule membranes by forced physical contact.

Bovine chromaffin granules were exposed to different isotonic non-ionic and ionic solutions (sucrose; Ca2+- and Mg2+-free phosphate-buffered saline; Tris-HCl + NaCl; Ca2+- and Mg2+-free phosphate-buffered saline + sucrose; Tris-HCl + sucrose) at pH 7 and then frozen either in suspension or as firm pellets. Freezing was performed without prefixation or antifreeze treatments either by 'standard' techniques (approx. 1 mm3 suspended or pelleted material on gold specimen supports dipped into liquid Freon) or with increased cooling rates by spraying suspensions into liquid propane ('spray-freezing'). Regardless of the freezing method, membrane-intercalated particles were always randomly distributed when chromaffin granules were frozen in suspension. In contrast, forced physical contact between granules produced by centrifugation (12000 X g, 25 min) provoked dispersal of membrane-intercalated particles, but only in the presence of ions. Sucrose or EDTA in an ionic environment had no inhibitory effect. The following conclusions are derived: (1) Even below the reported phase transition region particle clustering is possible. (2) Chromaffin granule membranes are not liable to thermotropic segregation of membrane-intercalated particles. (3) Although the low freezing rates of 'standard' freezing techniques produce large-scale segregation artefacts (by which suspended chromaffin granules are pushed together within the segregated solute) this does not result in intramembraneous particle segregation. (4) Forced physical contact produces a Ca2+-independent particle segregation, but only when repulsive electrostatic forces of membrane components are partially screened in an ionic environment. (5) This does not invalidate results obtained by others, showing Ca2+-mediated chromaffin granules agglomeration and segregation of membrane-intercalated particles, but it might indicate the occurrence of another, not directly Ca2+-dependent particle segregation mechanism in a prefusional stage of close membrane-to-membrane contact during exocytosis.

Animals↗
PubMed1978

Renal function and intrarenal hemodynamics in acutely hypoxic and hypercapnic rats.

On the basis of microsphere distribution, inert gas washout, and standard clearance data, the effects of acute hypoxia and hypercapnia on the kidney were studied in anesthetized, mechanically ventilated rats. Moderate hypoxia (mean PO2, 48 mm Hg) did not significantly change diuresis, GFR, and tubular sodium rejection. Due to a decrease in renal vascular resistance (R) from 40.1 to 31.8 mm Hg ml-1 min, mean renal blood flow stayed constant in spite of a significant drop in mean arterial blood pressure. Hypoxic changes in R were not accompanied by significant changes in intrarenal distribution of blood flow (IDBF). In severe hypoxia (PO2 less than 45 mm Hg) with oliguria and marked arterial hypotension, R was the lowest of all groups (28.8 mm Hg ml-1 min). Hypercapnia did not significantly change the renal excretory parameters, although an increase in R (without change in IDBF), together with a decrease in MAP caused a marked drop in mean renal blood flow. From these studies we conclude: 1) in the anestheized rat, acute hypoxia caused significant changes in intrarenal hemodynamics without changes in excretory function, 2) hypoxic renal vasodilation persists even in severe hypotension with oliguria and anuria, 3) in acute hypoxia and hypercapnia, changes in renal blood flow and renal vascular resistance are not accompanied by significant changes in IDBF.

Animals↗
PubMed1976

[Comparative study on the effect of anticholinergic substances on basic gastric secretion as well as on gastric secretion stimulated by pentagastrin or hypoglycemia (author's transl)].

The effect of orally administered ipratropiumbromide and propanthelinbromide on the basic gastric secretion as well as on the gastric secretion stimulated by pentagastrin or hypoglycemia due to application of insulin was tested intraindividually in a double blind comparative study. Drug dosage and time after the drug effect was measured varied. In addition the anticholinergic effect of ipratropiumbromide on the basic as well as on the gastric secretion stimulated by pentagastrin was compared to that of oxacepam. The inhibitory effect of ipratropiumbromide on the basic gastric secretion as well as on the secretion stimulated by pentagastrin and hypoglycemia is more pronounced than that of propanthelinbromid. The effect on the basic secretion reached its peak 450 min after drug application whereas the maximal effect on pentagastrin stimulated secretion showed earlier. The effect described was only seen with a dose of the anticholinergic drug of at least 30 mg. A combination of ipratropiumbromide+oxacepam has no effect stronger than ipratropiumbromide alone. On the contrary, it rather seems to have an augementative effect on pentagastrin stimulated gastric secretion that may be compensated completely by ipratropiumbromide. On the basic of these results a direct influence of anticholinergic substances on the parietal cell is discussed.

Adult↗
PubMed1966

Low-noise, interference-resistant amplifier suitable for biological signals.

Minor changes in conventional low-noise amplifier circuits decrease circuit noise and attenuate the unwanted effects of varying impedances and potentials which exist between commonly employed electrodes and the tissues of biological subjects. The resulting reduction of intrinsic amplifier noise and reduced susceptibility to external interference is helpful in the study of low-frequency signals of microvolt level.

Electrophysiology↗
PubMedDate not supplied

Tamm-Horsfall-Protein excretion as a marker of ascending limb transport indicates early renal tubular damage in diabetes mellitus type I.

Tamm-Horsfall Protein (THP) is a 95 kD glycoprotein which is secreted in the thick ascending loop of Henle (TALH) of the kidney. After renal tubular damage the secretion of THP is reduced. In diabetes mellitus (DM), TALH has not been studied. To differentiate between glomerular (albumin), proximal tubular microglobulinuria (alpha 1-microglobulin), and TALH function (THP), we investigated 65 patients 4-61 years of age. In well-controlled DM, mean hemoglobin A1 equalled 7.4% and proximal tubular parameters indicated reversible damage early after onset. THP excretion (per 24 hrs or per day) was significantly elevated in DM duration of greater than ten years, suggesting enhanced TALH ion transport (glomerular hyperfiltration). THP secretion decreased in DM duration of greater than 15 years despite normal albumin excretion. Thus, renal THP excretion indicates early medullary dysfunction (TALH) in DM type I.

Adolescent↗