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Biomedical subjects

G Schubert

Publications and source records attributed to G Schubert.

At least 73 records · Page 4Linked to original sources
PubMed1988

[Surgical possibilities in recurrence of colorectal carcinoma].

Locoregional recurrences occur in 10 to 15% of curatively operated rectal carcinomas. Technically conditioned relapses can be largely avoided by proper procedure, such as taking into consideration the localisation, staging, grading, safety zones and step-by-step procedure, e.g. "no-touch-isolation" technique, radicular approach and rinsing with cytocides. In this manner, locoregional relapses can be reduced to about 10%. Only technically conditioned relapses can be cured by surgery, but, as already stated above, these should be avoided by an appropriate technique. It is quite out of place to indulge in euphoria in respect of treating locoregional recurrences, as shown by long-term examination of actual survival rates; calculated survival rates are certainly inappropriate for spreading euphoria. Such locoregional relapses can be recognised relatively early and reoperated "curatively" only if aftercare follow-up is regular and intensive. It seems that endorectal sonography is of special diagnostic importance for the early detection of relapses while being a relatively simple method. It must be stated quite clearly that efficient preventive measures during the first operation will be much more effective than any efforts put into follow-up or aftercare. Every surgeon should therefore know that it is imperative to proceed subtly and carefully during the first operation so as to avoid any relapses due to faulty technique, the more so since all relapses have a poor prognosis even with so-called "curative" operations.

Colonic Neoplasms↗
PubMed1987

Quantitative structure-activity relationships of estrogenic steroids substituted at C14, C15.

The uterotropic activity of thirty 3-methoxyestradiol derivatives is measured and discussed on the basis of X-ray crystallographic results and quantitative structure-activity relationship analyses involving hydrophobic substituent constants pi and f as well as steric parameters Pr and L. In addition, estrogenicity is compared to data of interceptive activity and receptor binding affinity. All the biological data exhibit a high degree of intercorrelation. 17 beta-Hydroxysteroids having 14 alpha configuration reveal a generally better capability of high-affinity binding than those being 14 beta configurated. Between the uterotropic activity and the hydrophobicity of C14, C15 substituents, statistically significant correlations are found which suggest a close contact between the steroidal D-ring subsite and the receptor protein (e.g. for 14 alpha steroids: log UDD = -0.996 pi -0.392; n = 9, r = -0.943, s = 0.235, t = -7.5, alpha less than 0.001). The hydrophobic nature of both 14 alpha and 14 beta medium-sized substituents employed is shown by QSAR regressions to exert a stronger influence than steric effects. Furthermore, there are indications to additional hydrogen bonding and steric repulsion phenomena. As to the receptor-binding models discussed in the literature, it is concluded that the receptor protein has a high conformational flexibility to accommodate very different drug structures all having the common phenolic ring A. But, if an appropriate spacing of steroidal key atoms is recognized by the receptor and, consequently, the steroid-receptor complex is formed, the binding is complemented by hydrophobic interactions also in the D-ring region.

Animals↗
PubMed1987

Evidence for an involvement of dopamine receptors in the natriuretic response to atrial natriuretic peptide.

Intravenous injection of atrial natriuretic peptides (ANP) induces a preferential vasodilatation of the renal resistance vessels. A similar effect is exerted by dopamine. Exogenous administration of this catecholamine induces, like the atrial peptides, diuresis and natriuresis, an effect prevented by dopamine receptor antagonists. In view of these parallels, the influence of dopamine antagonists on the diuretic response of anaesthetized rats to ANP was tested. The unselective dopamine antagonists haloperidol (50 micrograms, i.v.) and chlorpromazine (50 micrograms, i.v.) prevented the diuretic and natriuretic effect of a partially purified atrial extract, and significantly blunted that of alpha-hANP (1 microgram). Dopamine receptors are classified as DA-1 and DA-2. The DA-2 receptor antagonists metoclopramide (50 micrograms, i.v.) and sulpiride (50 micrograms, i.v.) did not affect ANP induced natriuresis. The DA-1 receptor antagonists SCH 23390 and SK&F 83566 dose-dependently counteracted the renal response to the intravenous administration of ANP. The administration of haloperidol (25, 50 and 100 micrograms, i.v.) to rats undergoing a putative ANP dependent natriuresis (isotonic saline loading) dose-dependently reduced both urine volume and sodium excretion. Atriopeptin II (10(-9)-10(-10) M) displaced tritiated spiperone, a dopamine antagonist, from specific binding sites in homogenates of renal medulla, papilla and cortex. These results suggest that dopamine receptors, most probably of the DA-1 subclass, are involved in the natriuretic response to ANP. The present experiments do not allow the conclusion as to whether ANP directly interacts with the dopamine receptors or whether it affects these receptors by releasing dopamine.

Animals↗
PubMed1986

Composition and texture of calcium oxalate calculi in children.

An analysis is made of the frequency distribution of calcium oxalate calculi in children according to age, the occurrence of both hydrate forms and the four basic texture types. With the exception of the first year of age, weddellite is found more frequently than whewellite. In contrast to a general survey, children show a greater share of weddellite texture types versus the concentric texture of whewellite.

Adolescent↗
PubMed1986

Tubuloglomerular feedback and glomerular morphology in Goldblatt hypertensive rats on varying protein diets.

The present experiments were performed to examine the effect of variation in protein intake on renal function and morphology in the non-clipped kidneys of Goldblatt hypertensive rats. After renal artery clipping, rats were put on diets containing 5 (LP), 17.5 (NP), or 51% (HP) protein. After 4 to 5 weeks, all rats had developed hypertension. GFR was directly correlated with protein intake (1.47 +/- 0.15 in HP, 1.19 +/- 0.14 in NP, and 0.93 +/- 0.08 ml/min in LP), as was SNGFR (44.2 +/- 1.89, 39.1 +/- 2.23, and 27.9 +/- 0.86 nl/min in HP, NP, and LP rats). The response of SNGFR to changes in loop of Henle flow rate was attenuated in NP and HP rats: the maximum decrease was reduced (30.0 +/- 5.2% in NP, 22.1 +/- 4.2% in HP) and higher tubular flow rates were required to elicit responses (V1/2, the flow rate at which the response is half-maximum, was 28.9 +/- 2.6 nl/min in NP and 28.2 +/- 1.4 nl/min in HP). In LP rats, the maximum response was a decrease of 47.7 +/- 2.5%, and V1/2 was 18.1 +/- 1.2 nl/min, values similar to those found in normal control rats. The weights of the non-clipped kidneys were 0.96 +/- 0.04 g (LP), 1.06 +/- 0.05 g (NP), and 1.36 +/- 0.06 g (HP). In the LP rats there was no difference between the non-clipped and clipped kidneys. Light microscopic evaluation showed a high incidence of focal glomerulosclerosis in non-clipped kidneys of HP rats, but no glomerular lesions in the non-clipped kidneys of LP rats.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1986

Tubuloglomerular feedback responses with native and artificial tubular fluid.

Experiments were performed to compare the tubuloglomerular feedback response to native and artificial tubular fluid. The change in early proximal flow rate produced by changes in loop of Henle flow rate was measured in anesthetized rats using micropuncture techniques. Loop perfusion fluid was either an artificial solution with an electrolyte composition similar to that of proximal fluid (ATF) or native tubular fluid (NTF) collected from the late proximal tubule. In control rats, in rats on a low NaCl diet, in rats on restricted food intake, and in acutely saline-expanded rats no differences were detected between ATF- and NTF-perfused nephrons. In rats receiving 10 g NaCl/100 g, diet, responses with ATF and NTF to a flow change from 0 to 15 nl/min did not differ significantly; maximum feedback responses (flow change from 0 to 40 nl/min) were, however, significantly greater with ATF (-25.4%) than NTF (-12.9%). Chloride absorption was not different with the two perfusates. With both ATF and NTF a significant negative correlation was found between maximum responses and NaCl intake, with the slope being steeper with NTF. We conclude that some unidentified constituent of tubular fluid affects maximum feedback responses during very high NaCl intake, but feedback responses to physiological flow rate changes appear to be independent of luminal factors.

Animals↗
PubMed1986

[Nonspecific pyelonephritis and the formation of urinary calculi in urogenital tuberculosis].

The course of urogenital tuberculosis is complicated by unspecific bacterial infections of the urinary tract and nephrolithiasis. Among 605 patients with bacteriological or histological verified urogenital tuberculosis, 122 patients (20%) developed unspecific bacterial urinary infection--commonly caused by E. coli, proteus and pseudomonas--and 57 patients (9.4%) showed nephrolithiasis. In 42% of the lithiasis patients an urinary tract infection simultaneously occurred. 22 calculi are analyzed by the combined crystal-optical and x-ray-diffraction method with following results: 9 X struvite/carbonate apatite, 6 X calcium phosphate, 7 X calcium oxalate. The texture of 12 calculi was investigated on thin sections by polarization microscopy and a high concentration of organic material was found in both calcium oxalate and struvite/carbonate apatite calculi.

Bacteria↗
PubMed1985

Dopamine receptor antagonists inhibit the natriuretic response to atrial natriuretic factor (ANF).

The diuretic and natriuretic response of anesthetized rats to low doses of semi-purified atrial extracts or synthetic alpha-hANP was completely blocked by intravenous injection of 50 micrograms of haloperidol or chlorpromazine. Sulpiride or metoclopramide at the same doses did not show this effect. We conclude from these results that dopamine receptors, probably of the D1-type, are involved in the natriuretic effect of the atrial peptides.

Adenylyl Cyclases↗