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Biomedical subjects

K Beck

Publications and source records attributed to K Beck.

At least 91 records · Page 5Linked to original sources
PubMed1988

Multiple lipid islands of the colonic mucosa. A light and electron microscopic study.

Light and electron microscopic findings in a case of multiple lipid islands of the sigmoid mucosa are described. The patient apparently represents the second case with these lesions published in the medical literature. Lipid droplets were found in histiocytes, pericytes, smooth muscle cells, and Schwann cells. Pathological alterations of the nervous system in lipid islands have not been described before. The accumulation of lipids in different cell types of the colonic mucosa and the alterations of nervous elements are probably due to toxic factors reaching the cells either from the intestinal lumen or from the blood stream. The term "lipid proctitis (colitis)" does not appear to be useful because the lipid islands are obviously no disease sui generis but an epiphenomenon of other pathological processes. Pathological differential diagnosis and clinico-pathological correlation of colorectal lipid islands are briefly discussed.

Colon, Sigmoid↗
PubMed1988

Attachment to an endogenous laminin-like protein initiates sprouting by leech neurons.

Leech neurons in culture sprout rapidly when attached to extracts from connective tissue surrounding the nervous system. Laminin-like molecules that promote sprouting have now been isolated from this extracellular matrix. Two mAbs have been prepared that react on immunoblots with a approximately equal to 220- and a approximately equal to 340-kD polypeptide, respectively. These antibodies have been used to purify molecules with cross-shaped structures in the electron microscope. The molecules, of approximately equal to 10(3) kD on nonreducing SDS gels, have subunits of approximately equal to 340, 220, and 160-180 kD. Attachment to the laminin-like molecules was sufficient to initiate sprouting by single isolated leech neurons in defined medium. This demonstrates directly a function for a laminin-related invertebrate protein. The mAbs directed against the approximately equal to 220-kD chains of the laminin-like leech molecule labeled basement membrane extracellular matrix in leech ganglia and nerves. A polyclonal antiserum against the approximately equal to 220-kD polypeptide inhibited neurite outgrowth. Vertebrate laminin did not mediate the sprouting of leech neurons; similarly, the leech molecule was an inert substrate for vertebrate neurons. Although some traits of structure, function, and distribution are conserved between vertebrate laminin and the invertebrate molecule, our results suggest that the functional domains differ.

Animals↗
PubMed1988

Gastric motor responses elicited by vagal stimulation and purine compounds in the atropine-treated rabbit.

1. The effects of vagal inhibitory stimulation and of purine compounds were studied in the rabbit stomach. 2. Gastric motility was assessed by the balloon method. Vagal nerves were electrically stimulated at the neck. Purine compounds were injected intra-arterially. 3. In the atropine-treated rabbit, vagal stimulation caused relaxant motor responses followed by a rebound contraction. 4. Among the purine compounds, only ADP and ATP caused relaxant motor responses similar to the effects of vagal inhibitory stimulation. However, the relaxation produced by ATP was more powerful than that due to ADP, especially at lower infusion rates. 5. Vagal inhibitory responses were recorded during and after infusion of ATP. When relaxation by ATP was fully developed, vagal inhibitory stimulation was ineffective. At the highest infusion rates of ATP, a depression of the vagal inhibitory motility was also observed after cessation of the infusion. 6. Relaxant responses to ATP and vagal inhibitory stimulation were not influenced by theophylline, scarcely affected by alpha,beta-methylene ATP, but were reduced or blocked by reactive blue 2. 7. The results are consistent with ATP being an inhibitory neurotransmitter in the stomach of the rabbit.

Adenosine↗
PubMed1987

[What does laparoscopy contribute to explaining fever of unknown origin?].

The diagnostic value of laparoscopy with biopsy under vision was analysed retrospectively in 70 patients with persisting or recurrent fever of at least six weeks' duration which had remained unexplained despite detailed noninvasive studies. In 42 of these patients an intra-abdominal process had been suspected. The cause of fever was directly or indirectly diagnosed by the laparoscopy in 31 patients (44%), 29 of whom had clinical findings or abnormal biochemical results pointing to an involvement of abdominal organs. The most common laparoscopic diagnosis was granulomatous disease, isolated liver disease or malignant lymphoma. If clinical signs pointing to abdominal involvement are absent, laparoscopy is unlikely to aid in the diagnosis of fever of unknown origin.

Adolescent↗
PubMed1987

Laminin-nidogen complex. Extraction with chelating agents and structural characterization.

Large quantities of intact laminin-nidogen complex could be extracted from a mouse tumor basement membrane with a physiological buffer containing EDTA. Analysis of the purified complex demonstrated that the two proteins occur in an equimolar ratio and that anchoring of these complexes to the extracellular matrix requires divalent cations. Reversible dissociation of the complex was achieved with 2 M guanidine X HCl and has been used for purification of the individual components. Electron microscopy and binding studies using laminin fragments demonstrated that nidogen interacts specifically with the center of the cross-shaped laminin molecule as represented by the short-arm structure fragment 1. The complex was also useful to confirm and refine a previously proposed dumb-bell structure of nidogen and to prepare and characterize the cell-binding fragment 8 from the long arm of laminin.

Animals↗
PubMed1987

Laminin is structurally conserved in the sea urchin basal lamina.

The extracellular matrix is involved in the regulation of differentiation and morphogenesis. Here we report the identification of a sea urchin embryonic extracellular matrix protein by means of a monoclonal antibody BL1 (Mab BL1) and the isolation of the protein from basal lamina preparations. In paraffin sections of fixed embryos, the antibody can be detected on the basal surfaces of cells after the blastula stage. Immunoprecipitation from embryo lysates and salt extracts of metabolically labeled basal lamina preparations demonstrates that the basal lamina antigen is a large mol. wt protein of approximate mol. wt 10 which consists of disulfide-linked subunits of mol. wts 480 000 and 260 000. Electron microscopic images show that the Mab BL1 basal lamina antigen is structurally related to the vertebrate extracellular matrix protein laminin.

Journal Article↗
PubMed1984

Coevolution: mathematical analysis of host-parasite interactions.

An S----I----S epidemic transmitted by two similar strains of parasite acting on a host population of three genotypes which differ in their reaction to the disease is modelled and analyzed. Singular perturbation techniques are used to reduce the original system of nine differential equations to a coupled system of two equations describing the slowtime coevolution of gene frequency and parasite strain frequency.

Animals↗
PubMed1984

The effect of epidemics on genetic evolution.

Mathematical models of a vector-borne infectious disease acting on a host population consisting of three genotypes which differ in susceptibility to, recovery from, and death due to the disease are presented and analyzed. Singular perturbation techniques are used to obtain a single differential equation describing the slow time evolution of gene frequencies.

Biological Evolution↗
PubMed1984

[The use of short-term tests for oxidation studies of drugs. 2. Kinetics of 2-mercaptobenzthiazole oxidation].

By the example of 2-mercapto-benzthiazole it has been ascertained how far the k25 value obtained by extrapolation from the Arrhenius equation corresponds with the k25 value of the long-term test. To record besides oxidation products the 2-mercapto-benzthiazole, a UV-spectrophotometric method has been produced. The isothermal short-term test has been performed at 50, 60, 70, 80 and 90 degrees C after identification of the temperature independence of the reaction mechanism and of the reaction rate pH dependence.

Benzothiazoles↗
PubMed1983

[Laparoscopic sonography. A new dimension in the diagnostic approach to internal organs].

A newly developed laparoscopic sonography probe was used for assessment of upper abdominal and retroperitoneal organs. A linear array instrument with a frequency of 7 MHz was used. The cross-sectional width is 3.5 cm and the high frequency permits excellent dissolution. Thus the accepted loss of penetration depth is fully compensated by the possibility of placing the probe directly onto the organs. This method seems to be particularly suitable for detailed assessment of intraabdominal and retroperitoneal organs and of pathological changes. Laparoscopic ultrasonography-directed collection of tissues for histologic evaluation is equally easily done.

Abdomen↗
PubMed1983

Translational diffusion in phospholipid monolayers measured by fluorescence microphotolysis.

A method is described that eliminates surface flow in monolayers at the air-water interface and makes possible diffusion measurements by fluorescence microphotolysis ("photobleaching"). In contrast to previous studies that did not account for surface flow, lipid probe diffusion has been found to be similar in densely packed monolayers and in related bilayers. Furthermore, it seems that lipid diffusion is based on the same molecular mechanism in monolayers, bilayers, and potentially also cell membranes. In monolayers of L-alpha-dilauroylphosphatidylcholine (Lau2-PtdCho) the translational diffusion coefficient D of the fluorescent lipid probe N-4-nitrobenzo-2-oxa-1,3 diazole egg phosphatidylethanolamine decreased from 110 microns2/s at a surface pressure II = 1 mN/m to 15 microns2/s at II = 38 mN/m (T = 21-22 degrees C). Data could be fitted by the "free volume model." In monolayers of L-alpha-dipalmitoylphosphatidylcholine (Pam2-PtdCho) D decreased by greater than 3 orders of magnitude upon increasing II at constant temperature, thus indicating a fluid-to-crystalline phase transition. In Lau2-PtdCho/Pam2-PtdCho monolayers phase separation has been visualized in the fluorescence microscope and the effect on D measured. These results suggest that monolayers are a promising model system for studying the molecular mobility of lipids and other cell membrane components.

Liposomes↗
PubMed1981

Effect of furosemide on parathyroid hormone stimulated guinea pig renal adenylate cyclase and thyrotrophin and fluoride stimulated human thyroid adenylate cyclase.

The effect of furosemide 8 X 10(-4) mol/l an 8 X 10(-5) mol/l on parathyroid hormone stimulated adenylate cyclase was studied in renal tissue slices from guinea pigs. Furosemide caused a dose-dependent inhibition of the effect of parathyroid hormone on production of cyclic AMP, without having any significant effect on the basal cyclic AMP production. Furosemide in similar concentrations did not inhibit the stimulatory effect of thyrotrophin and fluoride in human thyroid homogenates suggesting that furosemide is not an universal inhibitor of adenylate cyclase and that the inhibition is not caused by a direct action of furosemide on the adenylate cyclase enzyme. Furosemide did not interfere with binding of cyclic AMP to cyclic AMP binding protein kinase from rabbit muscle. The results indicate that furosemide exerts an inhibitory influence either upon binding of parathyroid hormone to renal receptors or upon transmission of impulse from receptor to adenylate cyclase. The inhibitory influence of furosemide on parathyroid hormone action in kidney could explain the value of furosemide in the acute treatment of hypercalcaemia, but also suggest that chronic treatment with furosemide might interfere with normal calcium metabolism.

Adenylyl Cyclases↗
PubMed1981

Functional aspects of canine bronchial-pulmonary vascular communications.

Experiments in anesthetized open-chest dogs indicated that blood from the canine bronchial circulation may drain into both the arterial and venous sides of the alveolar drain into both the arterial and venous sides of the alveolar vessel bed. Evan's blue dye injected into the systemic circulation appeared in the effluent from a left lower lobe pulmonary arterial segment in which inflow was stopped with a snare and outflow through the alveolar vessel bed was stopped by maintaining zone 1 conditions. To determine the influence of mean systemic arterial pressure on lobar bronchial flow, flows from arterial and venous cannulas were measured at different mean systemic arterial pressures (lung volume history constant). Influence of lung volume and transpulmonary pressure (Ptp) change were each examined utilizing the hysteresis characteristics of the lung pressure-volume curve. Mean total flows ranged from 2.26 to 5.26 ml/min with 43.61% draining through the arterial side. Flow decreased with lower systemic arterial pressure, high Ptp, and higher lung volume. Distribution of flow was influenced only by lung volume changes. Results indicate that the communication sites contributing to the arterial drainage are located within the alveolar vessel bed. Since bronchial flow drains to both sides of the alveolar vessel bed, it must be considered when interpreting results from "isolated" pulmonary circulation preparations.

Animals↗