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Biomedical subjects

B Koch

Publications and source records attributed to B Koch.

At least 19 recordsLinked to original sources
PubMed1992

[Intra-arterial calcium provocation for the preoperative diagnosis of the location of an occult insulinoma].

Blood-sugar levels below 40 mg/dl were measured during syncope in two female patients (aged 59 and 73 years). Suspected organic hyperinsulinism was confirmed by a fasting test. Ultrasound examination and computed tomography failed to demonstrate an insulinoma. Coeliacomesentericography was then undertaken together with a selective intra-arterial calcium provocation test of the pancreas (0.4 or 0.5 mmol calcium in physiological saline was injected into the pancreas-supplying arteries--proximal and distal splenic, superior mesenteric and gastroduodenal). The insulin level was determined in simultaneously obtained hepatic venous blood. In case 1, the insulin level rose tenfold after calcium injection into the proximal splenic artery, indicating a process in the body of the pancreas. In case 2, a steep rise in insulin occurred after injection into the truncus coeliacus and the proximal and distal splenic artery, suggesting an insulinoma in the tail of the pancreas. The site of the insulinoma was confirmed in both cases at surgery. The adenoma was enucleated in case 1, removed by partial resection of the tail of the pancreas in case 2.--These observations show that occult insulinomas can be localized preoperatively by intraarterial calcium injection with measurement of insulin concentration in simultaneously obtained hepatic venous blood.

Aged↗
PubMed1992

Pituitary adenylate cyclase-activating polypeptide (PACAP) stimulates cyclic AMP formation as well as peptide output of cultured pituitary melanotrophs and AtT-20 corticotrophs.

The present study was aimed at investigating whether PACAP stimulates accumulation of cAMP, as well as hormonal secretion of homogeneous populations of pituitary proopiomelanocortin (POMC) cells, namely melanotrophs and AtT-20 corticotrophs. PACAP was shown to enhance cAMP accumulation in a dose-dependent fashion in both cell types (with EC50 values of approx. 10(-10) M) and elicited additive increases of cAMP production with CRF in melanotrophs, but not in corticotrophs. PACAP also stimulated dose-dependently the secretion of alpha-MSH and ACTH, with EC50 concentrations of about 10(-9) M. In melanotrophs, bromocriptine significantly depressed PACAP-induced cAMP formation and blunted by more than 90% stimulated alpha-MSH release. This study shows that (1) pituitary POMC cells did respond to PACAP by enhancing cAMP accumulation and elevating hormone secretion as well; (2) the effect of PACAP was additive with CRF on cAMP production in melanotrophs, but not in corticotrophs, while there was no additivity on peptide output from both cell types; (3) activation of dopamine receptors in melanotrophs dampened both cAMP formation and peptide secretion. These findings are consistent with PACAP playing a possible hypophysiotropic role in the regulation of pituitary POMC cell activity.

Adrenocorticotropic Hormone↗
PubMed1992

Application of newly synthesized detergents in the side chain degradation of plant sterols by Mycobacterium fortuitum.

Newly synthesized detergents of polyoxyethylene polyoxypropylene co-polymers (Co-EOPO), polyoxyethylene polyoxypropylene adducts of the diethylene triamine (DETA-EOPO), and steroidal detergents (SDD) stimulate significantly side chain degradation of plant sterols referring to both the sterol degradation and the formation of the product, 9 alpha-hydroxy-androsta-4-ene-3,17-dione (9 OH-AD), by Mycobacterium fortuitum NRRL-B-8119. Highest stimulative effects were observed with derivatives of the DETA-EOPO group. Using compounds of the Co-EOPO group optimal sterol transformation rates were found for polymers with a polyoxypropylene domain of 1400-2000 in molecular weight and with a polyoxyethylene content of 20-50%. Mostly efficient steroidal detergents tested were the 4-cholesten-3-(O-carboxymethyl)-oxime and the amino acid adducts of sterol-3 beta-chlorocarbonates. Detergents were favourably applied as pre-formed sterol-detergent complexes (9:1/w:w) in submers fermentation procedures. By treating harvested resting cells of M. fortuitum with derivatives of Co-EOPO or DETA-EOPO a considerable activation of the cells takes place concerning the sterol degradation and the formation of 9 OH-AD at a high yield in subsequent transformation process on buffer. In solubilization experiments we revealed that there is no correlation between the detergent mediated solubilization of the hydrophobic sterol substrate in the aqueous medium and the transformation activity of the bacterial cells. The detergents are assumed to interact with a multicomponent mesophase (FMCM) which is placed between cells and sterol surface and mediates the transport.

DEET↗
PubMed1992

[The effectiveness of physical therapy techniques. Possibilities of electromyography evaluation].

The purpose of this study is to verify the efficiency of selected physiotherapeutic techniques. EMG analysis with surface electrodes was performed in order to obtain sufficient data about the process of local strain. Furthermore, the local strain of the muscles surrounding a healthy knee is compared with the local strain of muscles after a knee injury (ACL-rupture) with resultant atrophy. The results prove modifications of progress and amplitudes of local strain and of coordination affected by atrophy/non-atrophy. On account of the first results additional research is recommended to investigate the specific aims of the different techniques.

Anterior Cruciate Ligament↗
PubMed1992

The biosynthesis of cyanogenic glucosides in seedlings of cassava (Manihot esculenta Crantz).

A microsomal system catalyzing the in vitro synthesis of the aglycones of the two cyanogenic glucosides linamarin and lotaustralin has been isolated from young etiolated seedlings of cassava (Manihot esculenta Crantz). A prerequisite to obtain active preparations is the complete removal of the endosperm pellicle covering the cotyledons before seedling homogenization. The rates of conversion of the parent amino acids valine and isoleucine to their cyanohydrins are 19 and 6 nmol/h/mg protein, respectively. The conversion rates for the corresponding oximes (2-methylpropanal oxime and 2-methylbutanal oxime) are 475 and 440 nmol/h/mg protein and for the nitriles (2-methylpropionitrile and 2-methylbutyronitrile) 45 and 75 nmol/h/mg protein. With the exception of 2-cyclopentenylglycine, none of the additionally tested amino acids are metabolized, whereas a broad substrate specificity is observed using oximes and nitriles as substrates. The in vitro biosynthesis is photoreversibly inhibited by carbon monoxide, demonstrating the involvement of cytochrome P450 in the hydroxylation processes. All tissues of the cassava seedling contain cyanogenic glucosides. The microsomal enzyme system responsible for their synthesis is restricted to the cotyledons and their petioles. This demonstrates that the cyanogenic glucosides are actively transported to other parts of the seedling. The enzyme activity decreases with the height of the etiolated seedling and is barely detectable in seedlings above 75 mm.

Glucosides↗
PubMed1992

Polychlorinated and polybrominated biphenyl congeners and retinoid levels in rat tissues: structure-activity relationships.

The purpose of this study was to examine the structural requirements of polychlorinated and polybrominated biphenyls (PCBs and PBBs) for altering tissue levels of retinoids. Seven congeneric PCBs and PBBs were studied: 3,3',4,4'-tetrachlorobiphenyl (TCB), 2',3,3',4,5- and 3,3',4,4',5-pentachlorobiphenyls (-PeCBs), 3,3',4,4'- and 3,3',5,5'-tetrabromobiphenyls (-TBBs), 2,2',3,3',5,5'-hexachlorobiphenyl (-HCB), and 3,3',4,4',5,5'-hexabromobiphenyl (-HBB). Male Sprague-Dawley rats were fed a vitamin A-adequate diet (1.3 mg/kg) for 30 days before being given a single IP injection of one of seven polyhalogenated biphenyls (150 mumol/kg) in corn oil (10 ml/kg) or vehicle alone. Rats were killed 1 week later. Except for 3,3',4,4',5,5'-HBB, all PCBs and PBBs studied significantly decreased serum retinol levels and, except for 3,3',4,4',5,5'-HBB and 2,2',3,3',5,5'-HCB, all PCBs and PBBs also lowered the serum retinol-binding-protein (RBP) content. The activity of hepatic retinyl ester hydrolase (REH) was reduced by the treatment of 3,3',4,4',5-PeCB, 3,3',4,4'-TBB, and 3,3',4,4',5,5'-HBB. The levels of hepatic retinol were decreased by 2,2',3,3',5,5'-HCB, 2',3,3',4,5-PeCB, and 3,3',4,4',5-PeCB, while levels of hepatic retinyl palmitate were decreased by 2',3,3',4,5-PeCB, 3,3',4,4',5-PeCB, 3,3',4,4'-TCB, 3,3',4,4'-TBB, and 3,3',4,4',5,5'-HBB. The substantial decreases in hepatic retinyl palmitate levels could not be explained solely on the basis of hepatomegaly caused by acutely toxic PCBs and PBBs. All halogenated biphenyls which caused a decrease in hepatic retinyl palmitate also caused an increase in renal retinyl palmitate except 3,3',4,4',5-PeCB. In summary, the acutely toxic (nonortho substituted) congeners had pronounced effects on hepatic, renal, and serum retinoids whereas other biphenyls only decreased serum retinol levels. The effects of these seven compounds on REH activity were not correlated with the effects on serum retinol or RBP levels. Therefore, this study shows that the structure-activity relationships for altering hepatic retinoids differ from those for serum retinol, implying the involvement of multiple mechanisms.

Animals↗
PubMed1992

Pituitary adenylate cyclase polypeptide (PACAP) stimulates cyclic AMP formation in pituitary fibroblasts and 3T3 tumor fibroblasts: lack of enhancement by protein kinase C activation.

A number of neuropeptides were shown to produce potent mitogenic effects on Swiss 3T3 fibroblasts by activating the phospholipase C pathway. Here we provide evidence for the activation by PACAP of the adenylate cyclase pathway in 3T3, as well as in non-tumoral pituitary fibroblasts, similarly to what was seen in pituitary endocrine cells. In these cells, PACAP triggered elevation of both intracellular and extracellular contents of cAMP and the effect was time- and dose-dependent, with half-maximal stimulations being induced with about 0.1 nM. Following activation of protein kinase C (PKC) by the phorbol ester phorbol 12-myristate 13-acetate (PMA), PACAP-induced cAMP production was amplified in pituitary endocrine cells, but was either unchanged or dampened in 3T3 and pituitary fibroblasts, respectively. Pretreatment of cells with pertussis toxin (PT) failed to change the effect of PMA on PACAP-stimulated adenylate cyclase activity, irrespective of the cell type being used. However, PT dramatically reduced the potentiation by PMA of cAMP production enhanced by forskolin in 3T3 cells. These results provide new evidence pointing to the presence in fibroblasts of receptors for PACAP, coupled to cAMP production, which may play a role in the modulation of the mitogenic signal. They also indicate that, compared with pituitary endocrine cells, PKC activation in fibroblasts differentially affected PACAP-induced cAMP formation and that these effects were unaltered upon inhibition by PT of Gi-like proteins.

1-Methyl-3-isobutylxanthine↗
PubMed1992

Biosynthesis of hepatic corticosteroid-binding globulin: ontogeny and effect of thyroid hormone.

The present study reports on the ontogeny and the effect of thyroid hormones on liver corticosteroid-binding globulin (CBG) biosynthesis, in relation to plasma CBG binding capacity in the rat. We show that mRNACBG contents were high in liver of 18-day-old fetuses and decreased with age to reach almost undetectable levels by postnatal day 1. Interestingly, at the latter time point plasma CBG concentration remained elevated and disappeared thereafter from the circulation with a half-life of about 3 days. The messenger was localized in parenchymatous cells and not in hematopoietic ones, although the latter constitute the major cell population in fetal liver. It is not until after 10 days of age that mRNACBG and plasma CBG levels increased in concert, with a sex-difference being noticed by postnatal day 30. Treatment of rats with 3,3',5-triiodo-L-thyronine (T3), but not reverse T3 (rT3) (the predominant form present in fetal serum), enhanced CBG biosynthesis. These findings show that liver mRNACBG contents undergo dramatic changes during ontogeny and suggest the existence of a differential regulation of the messenger in fetal and neonatal rats.

Animals↗
PubMed1992

Enhanced production of platelet activating factor by peripheral granulocytes from children with asthma.

Granulocytes from 23 asthmatic children aged 4-15 years and 32 age-matched healthy children were studied. Cells were purified by Dextran sedimentation and Percoll gradient centrifugation from heparinized blood. After in vitro stimulation by ionophore A23187 the amount of newly synthesized PAF and LTC4 was assessed by radio receptor assay or radioimmunoassay respectively. Eight patients had symptoms of asthma within the last 3 weeks before examination. Granulocytes from the symptomatic patients showed a significantly higher PAF generation (median 125 ng/10(6) cells, range 7-189 ng/10(6) cells) when compared to asymptomatic patients (p less than 0.001, median 14 ng/10(6) cells, range 6-33 ng/10(6) cells) or controls (p less than 0.001, median 11 ng/10(6) cells, range 3-26 ng/10(6) cells). In contrast, LTC4 generation was increased in both patient groups. The results suggest a regulatory role of PAF in the exacerbation of asthma.

Adolescent↗
PubMed1992

[Acute abdominal pain--standardized findings as diagnostic support. Results of a prospective multicenter intervention study and testing of a computer-assisted diagnosis system].

Despite powerful diagnostic tools (e.g. ultrasound, special laboratory investigations), the diagnosis of acute abdominal pain is still a considerable problem. Several studies in the UK have shown that the diagnostic accuracy can be improved by structured and standardized history taking and clinical examination and by computer-aided diagnosis. In the framework of a concerted action of the European Community we have conducted a prospective multicenter interventional trial comparing two consecutive phases: a) a baseline phase in clinical routine without additional intervention, b) a test phase with structured and standardized history and clinical examination (questionnaire, documentation programme). In addition, a computer-aided diagnostic system developed in the UK was applied to the cases in the test phase. Outcome criteria were the diagnostic accuracy of the initial and the final examiner, the perforated appendix rate, the negative appendectomy rate, the negative laparotomy rate and the rates of diagnostic errors with missing indication to operation and of delayed urgent operations. No differences could be found between the phases with respect to the outcome criteria. In the baseline phase (test phase) diagnostic accuracy was 59% (59%), diagnostic accuracy after investigation (senior examiner) was 77% (78%), perforated appendix rate was 11% (16%), negative appendectomy rate was 13% (15%), negative laparotomy rate was 7% (8%), the rate of missed urgent indications to operation was 1.1% (1.9%) and the rate of delayed urgent operations was 3.4% (2.4%). Major differences between the centers were recorded. Computer-aided diagnosis resulted in a diagnostic accuracy of 51%. The introduction of structured and standardized history taking and clinical examination has not brought any improvement of the good results in clinical routine. It is doubtful, whether existing systems of computer-aided diagnosis are able to significantly decrease the still remaining error rate of 20%.

Abdomen, Acute↗
PubMed1991

[Limited surgical radicality in occult cancer of Vater's papilla].

Nine histologically proven benign adenomas of the papilla of Vater were consecutively treated by transduodenal full thickness excision and simultaneous staging of regional lymph nodes without severe postoperative complications. 4 patients had a small well differentiated (pT1 GIpN0) carcinoma, although there was neither macroscopically nor by frozen sections any suspicion of a malignant tumour. A more radical pancreatoduodenectomy was not carried out and the 4 patients are without tumour recurrence or metastases 1-8 years postoperatively.

Adenoma↗
PubMed1991

Inhibition of protein kinase C activity in cultured pituitary cells attenuates both cyclic AMP-independent and -dependent secretion of ACTH.

The present study examines the effect of reduction of protein kinase C (PKC) activity, as induced by either phorbol ester (PMA) down-regulation or staurosporine inhibition, on the secretion of ACTH from cultured anterior pituitary (AP) cells. Short-term (3 h) exposure of cells to 5 nM PMA resulted in almost complete desensitization to both PMA and vasopressin (AVP), while there was only a minor incidence on the effect of corticotropin-releasing factor (CRF). In contrast, long-term (12-24 h) exposure of cells to PMA, as well as pretreatment with staurosporine, dramatically reduced the stimulatory influence of CRF. This was shown not to be due to a decline in ACTH cells' stores, nor to the toxicity of phorbol ester or to a negative autofeedback of ACTH. Pretreatment of corticotrophs with PMA failed to dampen the CRF-induced cyclic AMP formation, while it caused a decline in the effects of forskolin and 8-bromoadenosine cyclic AMP. Stimulated ACTH secretion subsequent to either veratridine- or high K(+)-induced cell depolarization was likewise decreased. We conclude that in corticotrophs the stimulatory action of not only AVP, but also of that of CRF on ACTH secretion strongly relies on PKC activity. In the case of CRF, however, this may not be a primary consequence of receptor occupation, as evidence suggests an indirect relationship which may involve PKC regulation of Ca2+ channels and/or the ion's intracellular messenger function.

8-Bromo Cyclic Adenosine Monophosphate↗
PubMed1991

Tumor of follicular infundibulum.

Tumor of the follicular infundibulum is a rare, benign proliferative follicular disorder. A case of multiple lesions in a 37-year-old woman is reported. The diagnosis was made histologically.

Adult↗
PubMed1991

In vitro effects of an imidazole antifungal, prochloraz, on spectral and catalytic properties of microsomal cytochromes P-450.

1. The imidazole antifungal agent, prochloraz, elicited type II spectral interactions with microsomal cytochromes P-450 from rats pretreated with phenobarbital (PB), 3-methyl-cholanthrene (MC) and dexamethasone (DEX). 2. Prochloraz interacts strongly with type I binding sites of both PB- and DEX-induced cytochromes P-450 and to a lesser extent with cytochromes P-450 from MC-induced rats. 3. The antifungal derivative was a more potent inhibitor of the troleandomycin-nitrosoalkyl-cytochrome P-450 complex formation in DEX-induced microsomes than of the isosafrole-carbene-cytochrome P-450 complex formation in MC-pretreated rats. 4. Prochloraz is a strong inhibitor of the cytochrome P-450-dependent mixed-function oxidases in rat liver microsomal preparations.

Animals↗