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Biomedical subjects

H P Buscher

Publications and source records attributed to H P Buscher.

At least 19 recordsLinked to original sources

[Medical expert systems and clinical needs].

The rapid expansion of computer-based systems for problem solving or decision making in medicine, the so-called medical expert systems, emphasize the need for reappraisal of their indication and value. Where specialist knowledge is required, in particular where medical decisions are susceptible to error these systems will probably serve as a valuable support. In the near future computer-based systems should be able to aid the interpretation of findings of technical investigations and the control of treatment, especially where rapid reactions are necessary despite the need of complex analysis of investigated parameters. In the distant future complete support of diagnostic procedures from the history to final diagnosis is possible. It promises to be particularly attractive for the diagnosis of seldom diseases, for difficult differential diagnoses, and in the decision making in the case of expensive, risky or new diagnostic or therapeutic methods. The physician needs to be aware of certain dangers, ranging from misleading information up to abuse. Patient information depends often on subjective reports and error-prone observations. Although basing on problematic knowledge computer-born decisions may have an imperative effect on medical decision making. Also it must be born in mind that medical decisions should always combine the rational with a consideration of human motives.

Artificial Intelligence

The acinar location of the sodium-independent and the sodium-dependent component of taurocholate uptake. A histoautoradiographic study of rat liver.

The acinar location of tritium-labelled taurocholate taken up from sodium-containing and sodium-free perfusion media in isolated perfused rat liver was made visible by means of histoautoradiography on cryoslices at low, medium and high bile salt concentrations. In antegrade perfusion studies, in the presence of sodium, with taurocholate concentrations of 1 and 20 microM, respectively, the silver grain label was mainly restricted to acinar zones 1. At an 80 microM concentration, zones 2 and 3 were also labelled but with decreasing intensities towards the terminal hepatic venules. At 120 microM taurocholate, all acinar zones were nearly equally labelled. In the absence of sodium, antegrade liver perfusions with 1, 20 and 120 microM taurocholate resulted in an almost homogenous labelling of all acinar zones and retrograde perfusions in a silver grain density slightly decreasing towards the terminal portal venules. The results indicate that hepatocytes of all acinar zones are capable of taking up taurocholate by both a sodium-dependent and a sodium-independent pathway. The contribution of the sodium-independent uptake to the overall uptake of taurocholate increases with increasing zonal recruitment at higher concentrations. The sodium-dependent uptake, however, is always dominant.

Animals

Hepatic uptake of fluorescein, investigated by video fluorescence microscopy and digital image analysis.

We evaluated fluorescence microscopy combined with digitized image analysis for the investigation of fluorescein transport in the intact rat liver. The images of the surface of isolated rat livers which were perfused directly under a microscope were projected onto a silicone-intensified target camera, stored on a video tape and analyzed with a microcomputer equipped with an image digitizer. It was shown that, after correction of the day-to-day variability of the optical and electronical system, the increase in fluorescence intensity of the liver surface following fluorescein infusion depended linearly on the fluorescein concentration in the perfusion medium up to 1 mM. Since, under the conditions used, biliary secretion and metabolic influences were found to be insignificant the uptake mechanism is probably predominantly simple diffusion.

Animals

Functional hepatocyte heterogeneity in glutamate, aspartate and alpha-ketoglutarate uptake: a histoautoradiographical study.

[3H]glutamate, [3H]alpha-ketoglutarate or [3H]aspartate was injected in physiological concentrations into antegrade (from portal to hepatic vein) or retrograde (from hepatic to portal vein) perfused rat liver, and the tissue distribution of radioactivity was studied by histoautoradiography. Independent of the direction of perfusion, radioactivity was accumulated in a small perivenous liver parenchymal cell population, which surrounded the terminal hepatic venules as a layer of about two to five cells thick. In contrast, accumulation of radioactivity in periportal hepatocytes was low and sometimes not detectable. This distribution pattern roughly resembled that described for the immunohistochemical distribution of glutamine synthetase in liver. The present histoautoradiographic findings demonstrate a predominant uptake of vascular glutamate, aspartate and ketoglutarate into a small perivenous cell population. They confirm previous label incorporation studies in the metabolically intact liver, demonstrating an almost exclusive uptake of vascular glutamate and alpha-ketoglutarate into perivenous glutamine synthetase containing hepatocytes. In addition, evidence is presented suggesting that perivenous uptake of alpha-ketoglutarate may be one determinant for hepatic glutamine synthesis, at least under the experimental conditions used here.

Animals

[Immunologic defects in the lymphatic system of the intestinal mucosa in common variable immunodeficiency (CVID) syndrome].

The humoral immune system of the intestinal mucosa of patients with common variable immuno deficiency (CVID) syndrome was studied immunohistologically using antibodies against immunoglobulin (Ig) A1-2, M and G1-4, against the J chain and the secretory component. In 9/13 CVID-patients IgA-positive cells were totally absent whereas a total IgM-defect was found only in 3/14 patients. Considerable numbers of J chain-positive cells were present in all CVID-patients irrespective of the extent of the Ig-defect indicating the presence of early B-cells unable to differentiate and to produce Ig. There was a strong expression of the secretory component in the cytoplasm and at the surface of enterocytes even in those CVID-patients who were totally defective in IgA- and IgM-positive cells.

Humans

Fluorescent derivatives of bile salts. I. Synthesis and properties of NBD-amino derivatives of bile salts.

In order to visualize bile salt transport, fluorescent bile salt derivatives were synthesized by introduction of the relatively small fluorescent 4-nitrobenzo-2-oxa-1,3-diazol (NBD)-amino group in either the 3-, 7-, or 12-position of the steroid structure, thus providing a complete set of diastereomeric derivatives, 3 alpha-NBD-amino-7 alpha,12 alpha-dihydroxy-5 beta-cholan-24-oic acid, 3 beta-NBD-amino-7 alpha,12 alpha-dihydroxy-5 beta-cholan-24-oic acid, 7 alpha-NBD-amino-3 alpha,12 alpha-dihydroxy-5 beta-cholan-24-oic acid, 7 beta-NBD-amino-3 alpha,12 alpha-dihydroxy-5 beta-cholan-24-oic acid, 12 alpha-NBD-amino-3 alpha,7 alpha-dihydroxy-5 beta-cholan-24-oic acid, 12 beta-NBD-amino-3 alpha,7 alpha-dihydroxy-5 beta-cholan-24-oic acid, as well as their taurine conjugates. Their optical properties with absorption maxima at about 490 nm and emission maxima at 550 nm make them suitable for fluorescent microscopic studies. Fluorescence of the NBD-derivatives is strongly dependent on polarity of the solvent, on the concentration of the bile salt derivatives, and only slightly on temperature.

Bile Acids and Salts

Fluorescent derivatives of bile salts. II. Suitability of NBD-amino derivatives of bile salts for the study of biological transport.

Interaction of unconjugated and taurine-conjugated NBD-amino-dihydroxy-5 beta-cholan-24-oic acids bearing the fluorophor in the 3 alpha, 3 beta, 7 alpha, 7 beta, 12 alpha, or 12 beta position with albumin results in a small hypsochromic shift of the emission maximum and an increase in quantum yield, suggesting binding by hydrophobic interactions. The different unconjugated fluorescent bile salt derivatives are metabolized by intact rat liver in different ways. The unconjugated 3 beta-NBD-amino derivative is completely transformed to its taurine conjugate and secreted as such, whereas the 3 alpha-NBD-amino derivative is completely transformed to a polar fluorescent compound not identical with its taurine conjugate. The unconjugated 7 alpha- and 7 beta-NBD-amino derivatives are only partially conjugated with taurine and mainly secreted in unmetabolized form. The unconjugated 12 alpha- and 12 beta-NBD-amino derivatives are not at all transformed to their taurine conjugates, but are partially metabolized to unidentified compounds. They are predominantly secreted as the unmetabolized compounds. In contrast to the unconjugated derivatives, all taurine-conjugated fluorescent bile salt derivatives are secreted into bile unmetabolized. With the exception of the 3 alpha-compound, all synthesized taurine-conjugated fluorescent derivatives interfere with the secretion of cholyltaurine. Differential photoaffinity labeling studies using (7,7-azo-3 alpha,12 alpha- dihydroxy-5 beta-cholan-24-oyl)-2'-[2'-3H(N)]aminoethanesulfonate as a photolabile derivative revealed that in liver cells all fluorescent bile salt derivatives interact with the same polypeptides as the physiological bile salts. The hepatobiliary transport of taurine-conjugated NBD-amino bile salt derivatives is, due to hydrophobic interactions, accompanied by an increase in fluorescence intensity which is favorable for the study of biological bile salt transport by fluorescence microscopy.

Albumins

Defective drug uptake contributing to multidrug resistance in hepatoma cells can be evaluated in vitro.

In clinical practice the acquired or de novo resistance of tumors to antitumor chemotherapy remains a big problem. However, in the past few years some progress has been made in understanding the two principal mechanisms: metabolic alterations leading to a reduced cytostatic or cytotoxic effect of drugs, and reduced accumulation of drugs within the tumor cells [15, 34, 35]. The second phenomenon is usually attributed to the ability of tumor cells to accelerate the efflux of various xenobiotics. This phenomenon is considered primarily responsible for the development of multidrug resistance (MDR). However, loss or impairment of drug uptake by the tumor cells may also contribute to resistance to antitumor drugs. This paper focuses on recent findings with hepatoma cells, which support this view.

Antineoplastic Agents

[The place of ERCP in pancreatic diagnosis. The change caused by sonography and computed tomography].

Based on 1099 endoscopic retrograde cholangiopancreatograms (ERCP), 659 examinations conducted in 1973-1980 prior to the introduction of computed tomography (CT) and 440 performed in 1988-1989, the impact of sonography and CT on ERCP is studied. The availability of CT did not cause any significant change in the frequency of and indications for ERCP. The rate of successful ERCP examinations increased from 73.6% to 92%. Complications occurred in 2.3%, and the mortality rate was 0.4% and was similar in both periods. ERCP was the third imaging procedure, being applied after sonography and CT, in most patients. The diagnostic value of ERCP in pancreatic disease is compared with that of sonography and CT in 116 patients with histologically or clinically proven diagnosis. The sensitivity is 79% for ERCP and 78% for CT. Indeterminate findings were recorded in 11% of the ERCP and 8% of the CT examinations; these rates can be decreased by complementary use of both imaging modalities.

Cholangiopancreatography, Endoscopic Retrograde

[Cholelithiasis--non-surgical intervention. Definitive and combined use].

New endoscopic and radiological techniques, together with pharmacological developments, prompted by high-surgical risk patients or those developing bile duct stones after prior cholecystectomy--but also by the wish to have less invasive alternatives available, have led to a variety of non-operative therapeutic modalities in gallstone diseases. Both endoscopic and radiological procedures are employed to remove stones from the biliary tract and gallbladder. Extracorporeal lithotripsy and chemical litholysis are being increasingly employed to treat gallbladder stones. Laparoscopic cholecystectomy is a new operative possibility. These different approaches, sometimes used in combination, are associated with different preconditions for success. Indications and results must be measured against the gold standard of cholecystectomy.

Cholelithiasis

The histoautoradiographic localization of taurocholate in rat liver after bile duct ligation. Evidence for ongoing secretion and reabsorption processes.

To determine whether in complete obstructive cholestasis taurocholate is taken up by hepatocytes and if so whether it is secreted into bile, tritium-labelled taurocholate was localized by histoautoradiography on cryoslices from normal rat livers and from those after bile duct ligation. In non-cholestatic livers the hepatocytes of acinar zones 1 as well as the lumina and the epithelia of bile ductules and ducts became intensely labelled directly after injection of [3H]taurocholate into a mesenterial vein. Four hours and 4 days after bile duct ligation, hepatocytes of all three acinar zones became labelled, but in contrast to the normal state, pericanalicular concentration of silver grains was not observed, not even within 5 min. Fifteen days after bile duct obstruction, cryoslices taken 2 min after injection of [3H]taurocholate exhibited an intense silver grain labelling of all acinar zones, with the highest density at bile canalicular areas of the liver cell plates as well as the proliferated bile ductules and bile ducts. The biliary epithelium of small bile ductules and ducts of non-cholestatic and of bile duct-obstructed livers were also covered with silver grains; the epithelium of larger ducts exhibited significant labelling predominantly at the lateral sites of the cells. The biliary epithelium of the common bile duct was not significantly labelled. The results indicate that in complete obstructive cholestasis (a) taurocholate continues to be taken up from blood by hepatocytes and secreted into bile, but in terms of varying duration of obstruction, (b) all acinar zones are involved in bile salt transport, (c) in the initial phase (4 h and 4 days respectively after bile duct obstruction) hepatocytes fail to concentrate taurocholate at the canalicular site, (d) in a consecutive phase, in which bile ductules and ducts proliferate (demonstrated for a 15-day cholestasis), the taurocholate concentration at the canalicular site of hepatocytes is re-established and biliary secretion seems to be enhanced, (e) the biliary epithelium of bile ductules and ducts may play a significant role in the reabsorption and/or regurgitation of bile salts from bile to blood. Reabsorption/regurgitation of biliary constituents may also be operative in the non-cholestatic state but may become significantly enhanced with bile ductular proliferation.

Animals

Transport systems for amphipathic compounds in normal and neoplastic hepatocytes.

Photoaffinity labeling of plasma membrane subfractions from liver and of intact liver tissue with a photolabile bile salt derivative, the sodium salt of (7,7-azo-3 alpha,12 alpha-dihydroxy-5 beta-cholan-24-oyl)-2-aminoethanesulfonic acid, revealed that the hepatobiliary transport of bile salts is accomplished by transport systems different for sinusoidal uptake and canalicular secretion. Polypeptides with apparent Mr values 54,000 and 48,000 interact with bile salts at sinusoidal membrane, whereas a polypeptide with an apparent Mr of 100,000 is involved in bile salt secretion through the canalicular membrane. Photoaffinity labeling with photolabile derivatives of uncharged and cationic compounds provided evidence that the sinusoidal membrane polypeptides exhibit a broad binding specificity. Photoaffinity labeling studies and kinetic studies suggest that hepatic uptake of different amphipathic anions, uncharged compounds and even of cations is mediated by the sinusoidal transport systems which are involved in the uptake of bile salts. Relatively little is known about the specificity of the canalicular bile salt transport system. The fluorescent bile salt derivative, the sodium salt of (N-[7-(4-nitrobenzo-2-oxa-1,3-diazol)]-3 beta-amino-7 alpha, 12 alpha-dihydroxy-5 beta-cholan-24-oyl)-2-aminoethanesulfonic acid, is readily taken up into the hepatocytes of all acinar zones and may be used for the evaluation of the functional state of bile salt transport by fluorescence microscopy. Fluorescent microscopic studies with the fluorescent bile salt derivative showed that ascites hepatoma AS 30D cells do not have the ability to take up bile salts and demonstrated the absence of hepatobiliary bile salt transport in the solid Morris hepatoma 7777. Photoaffinity labeling studies revealed that in both tumor cell models, in hepatoma AS 30D and in Morris hepatoma 7777, the plasma membranes were devoid of the polypeptides having affinities to bile salts and amphipathic cations. A slight labeling of bile salt binding membrane polypeptides in plasma membranes from Morris hepatomas 9618A and TC 5123 opens the possibility to study transport in neoplastic hepatocytes.

Animals

[Cholestasis].

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Bile Acids and Salts

Bile salt binding to serum components. Taurocholate incorporation into high-density lipoprotein revealed by photoaffinity labelling.

1. Photoaffinity labelling of human serum albumin with the sodium salts of (3 beta-azido-7 alpha,12 alpha-dihydroxy-5 beta-cholan-24-oyl)-2-amino[2(-3)H (N)]ethanesulfonic acid, (7,7-azo-3 alpha,12 alpha-dihydroxy-5 beta-cholan-24-oyl)-2-amino[2(-3)H (N)]ethanesulfonic acid and (11 zeta-azido-12-oxo-3 alpha,7 alpha-dihydroxy-5 beta-cholan-24-oyl)-2-amino[2(-3)H (N)]ethanesulfonic acid resulted, in each case, in a considerable covalent incorporation of radioactivity into the protein. 2. Photoaffinity labelling of whole serum, obtained from fasting test persons, revealed with all three photolabile derivatives of taurocholate at the physiological concentration of 2.1 microM the incorporation of radioactivity not only into albumin but also into high-density lipoprotein, as demonstrated by density gradient centrifugation and by immunological characterization. 3. The bulk of radioactivity incorporated into high-density lipoprotein by photoaffinity labelling of whole serum was found to have been associated with the lipids. Only 10-20% of the label was covalently bound to apolipoproteins, predominantly to the apolipoproteins A-I and A-II. 4. The interaction of taurocholate with high-density lipoprotein has been confirmed by density gradient centrifugation using 14C-labelled taurcholate. It is assumed that the interaction of taurocholate with high-density lipoprotein is physiologically of significance.

Adult

[Intrahepatic cholestasis due to N-propyl ajmaline].

In two patients intrahepatic cholestasis and cholestatic liver disease probably due to N-propyl ajmaline were observed. In both cases there was a four-week-interval between the first ingestion of the drug and the onset of jaundice. In one case with rigors there was a temporary rise in temperature and cholestasis. In the other there was a two to three week prodromal period of pruritus and gastro-intestinal symptoms. Both cases were characterised by blood and pronounced tissue eosinophilia in the periportal zones, a marked increase of cholestatic and hepatic cell enzymes, serum bilirubin and cholesterol, a moderate increase in erythrocyte sedimentation rate and absence of leucocytosis. Pathological laboratory findings returned to normal spontaneously within 5 weeks in one case and within two weeks under steroid therapy in the other.

Adult