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Biomedical subjects

B Koch

Publications and source records attributed to B Koch.

At least 91 records · Page 5Linked to original sources
PubMed1995

[Initial studies of the prevalence of human Herpesvirus 7 (HHV-7) in Mexican blood donors].

Human herpesvirus 7 (HHV-7) has been recently isolated from CD4-positive peripheral blood lymphocytes of a healthy person. The present study was performed to find the antibody prevalence of this virus in the healthy Mexican population. Two hundred blood samples from candidates for blood donation at the General Hospital of Mexico were studied with the indirect immunofluorescence test (IFA) in HHV-7 infected SupT1 cells. 83.5% were male persons and 16.5% female, the mean age for the male group was 28.8 years and for the female group 31.5. The donors came from 12 different states in Mexico, predominantly from the city (60.8%), and had different occupations. Almost all samples (98.5%) were positive to HHV-7. Other studies done revealed 1% positive to brucella, 1% positive to Hepatitis B, 2% positive to syphilis, hepatitis C and HIV test were negative in the whole group studied. There was a high incidence of HHV-7 in the group studied: more than 50% of the subject had high titers. This results should be further studied determine titers indicative of an active infection and to search for any association with illnesses.

Adult↗
PubMed1995

Multifactorial regulation of pituitary adenylate cyclase-activating polypeptide (PACAP)-induced production of cyclic AMP in ATT-20 corticotrophs: major involvement of Rolipram-sensitive and insensitive phosphodiesterases.

Cyclic nucleotide phosphodiesterases (PDEs) appear to play a major role in the modulation of cellular accumulations of cAMP/cGMP and hence the magnitude of the cell response to a hormone signal. These enzymes are present in cells as multiple isoforms and lie under control of various protein kinases. Because PACAP, unlike corticotropin-releasing factor (CRF), may stimulate a dual signalling pathway in pituitary cells (activating both adenylyl cyclase and phospholipase C), we used AtT-20 corticotrophs and primary cultures of rat pituitary cells to study the effect and possible differential influence of these peptides on cAMP formation. Time-course analysis indicated that, both in the absence and the presence of Rolipram (a selective type IV PDE inhibitor), PACAP stimulated a rapid and short-lived accumulation of cAMP in tumor corticotrophs, while in the presence of the non-selective inhibitor IBMX, the peptide produced a sustained high plateau level of second messenger (10 times the level generated with Rolipram at 20 min). On the contrary, when exposed to CRF, cAMP production augmented in parallel, irrespective of whether Rolipram or IBMX were present. The differential effects of the PDE inhibitors were seen with PACAP concentrations ranging from 0.1 to 100 nM, and could also be demonstrated in primary cultures of pituitary cells. Co-incubation of AtT-20 cells with Rolipram along with inhibitors of type I (but not of type III) PDEs, enhanced cAMP formation elicited by PACAP to a level significantly higher than that induced by CRF.(ABSTRACT TRUNCATED AT 250 WORDS)

1-Methyl-3-isobutylxanthine↗
PubMed1995

Characterization of cytochrome P450TYR, a multifunctional haem-thiolate N-hydroxylase involved in the biosynthesis of the cyanogenic glucoside dhurrin.

The haem-thiolate N-hydroxylase cytochrome P450TYR involved in the biosynthesis of the tyrosine-derived cyanogenic glucoside dhurrin in Sorghum bicolor had recently been isolated. Reconstitution of enzyme activity by insertion of cytochrome P450TYR and NADPH-cytochrome P450-reductase into L-alpha-dilauroylphosphatidylcholine micelles and using tyrosine as substrate results in the formation of p-hydroxyphenylacetaldehyde oxime. Quantitative substrate binding spectra demonstrate that tyrosine and N-hydroxytyrosine are mutually exclusive substrates that bind to the same active site of cytochrome P450TYR. The multifunctionality of cytochrome P450TYR has been confirmed in reconstitution experiments using recombinant cytochrome P450TYR expressed in Escherichia coli. It was earlier reported that an in vitro microsomal system catalyzing all but the last step in the biosynthetic pathway for cyanogenic glucosides exhibits catalytic facilitation (channelling). This observation is explained by the multifunctionality of cytochrome P450TYR. The cytochrome P450TYR sequence represents the first amino acid sequence of a functionally characterized cytochrome P-450 enzyme from a monocotyledonous plant and the first sequence of an N-hydroxylase with high substrate specificity. Multifunctional N-hydroxylases of the cytochrome P-450 type have not previously been reported in living organisms.

Cloning, Molecular↗
PubMed1995

Azure B-eosin APAAP staining: a method for simultaneous hematological and immunological cell analysis.

Azure B-eosin APAAP staining allows simultaneous analysis of peripheral blood and bone marrow cells for hematological characteristics and immunological cell marker profiles. A defined sequence of staining procedures maintains characteristic components of the Romanowsky-Giemsa stain whereas cell antigens can be detected immunologically using the alkaline phosphatase-anti-alkaline phosphatase (APAAP) detection system. Antigens are visualized by the staining product of the substrate-naphthol AS GR phosphate and variamine blue salt. The usefulness of the azure B-eosin APAAP method was demonstrated on blood and bone marrow smears of patients with various hematological disorders.

Alkaline Phosphatase↗
PubMed1995

[Results of resection and adjuvant therapy of liver metastases of primary colorectal tumors--a review of the literature].

Natural history of patients with colorectal liver metastases is not significantly changed even by curative resection. The majority unfortunately relapse. The results of adjuvant treatment after resection were evaluated by analysis of 17 publications as well as by own data (60 patients). 340 patients were either treated by intraarterial (n = 201), systemic (n = 82), intraportal (n = 29) or intraperitoneal (n = 28) chemoinfusion (5-Fluorouracil or Floxuridine). An alternative approach was the treatment with specific immunotherapy using tumor vaccination (n = 35) or monoclonal antibodies (n = 20). Morbidity of adjuvant treatment includes local (chemical hepatitis, biliary sclerosis) and systemic (diarrhea, stomatitis) side effects. Technical complications could reach a level of up to 50% in case of local administration. With exception of 6 studies no comparison with a resection only group was performed. Despite postulated increase of survival and recurrence free time with historical controls the results of current ongoing studies are needed before general use of adjuvant treatment can be recommended.

Antibodies, Monoclonal↗
PubMed1995

Characterisation of the neurosensory elements of the feline cranial cruciate ligament.

The identification and distribution of mechanoreceptors in the cranial cruciate ligament of the cat (analogous to the anterior cruciate ligament in other species) was studied histologically using a modified celloidin embedding technique to achieve serial sectioning of bone-ligament-bone preparations with gold chloride staining. We identified distinctive large elongated structures situated between the collagen bundles of the ligament (resembling endings described as Freeman and Wyke type III; also termed Golgi tendon receptors). These endings were found near the middle of the ligament well away from the bone-ligament junction. Axons seen entering only one end of each type III ending helped to confirm its neural basis. While we saw structures resembling types I and II endings (i.e. Ruffini and pacinian endings, respectively) in individual sections, serial sections failed to reveal convincing evidence of their existence. Such structures almost always appeared to be vascular in nature on adjacent sections, with vessels entering and exiting. We conclude that serial sections are critical to interpreting the presence or absence of mechanoreceptors.

Animals↗
PubMed1994

Isolation of the heme-thiolate enzyme cytochrome P-450TYR, which catalyzes the committed step in the biosynthesis of the cyanogenic glucoside dhurrin in Sorghum bicolor (L.) Moench.

The cytochrome P-450 enzyme (hemethiolate enzyme) that catalyzes the N-hydroxylation of L-tyrosine to N-hydroxytyrosine, the committed step in the biosynthesis of the cyanogenic glucoside dhurrin, has been isolated from microsomes prepared from etiolated seedlings of Sorghum bicolor (L.) Moench. The cytochrome P-450 enzyme was solubilized with the detergents Renex 690, reduced Triton X-100, and 3-[(3-cholamidopropyl)dimethylammonio]-1-propanesulfonate and isolated by ion-exchange (DEAE-Sepharose) and dye (Cibacron blue and reactive red 120) column chromatography. To prevent irreversible aggregation of the cytochrome P-450 enzyme, the isolation procedure was designed without any concentration step--i.e., with dilution of the ion-exchange gel with gel filtration material. The isolated enzyme, which we designate the cytochrome P-450TYR enzyme, gives rise to the specific formation of a type I substrate binding spectrum in the presence of L-tyrosine. The microsomal preparation contains 0.2 nmol of total cytochrome P-450/mg of protein. The cytochrome P-450TYR enzyme is estimated to constitute approximately 20% of the total cytochrome P-450 content of the microsomal membranes and about 0.2% of their total protein content. The apparent molecular mass of the cytochrome P-450TYR enzyme is 57 kDa, and the N-terminal amino acid sequence is ATMEVEAAAATVLAAP. A polyclonal antibody raised against the isolated cytochrome P-450TYR enzyme is specific as monitored by Western blot analysis and inhibits the in vitro conversion of L-tyrosine to p-hydroxymandelonitrile catalyzed by the microsomal system. The cytochrome P-450TYR enzyme exhibits high substrate specificity and acts as an N-hydroxylase on a single endogenous substrate. The reported isolation procedure based on dye columns constitutes a gentle isolation method for cytochrome P-450 enzymes and is of general use as indicated by its ability to separate cytochrome P-450TYR from the cytochrome P-450 enzyme catalyzing the C-hydroxylation of p-hydroxyphenylacetonitrile and from cinnamic acid 4-hydroxylase.

Amino Acid Sequence↗
PubMed1994

Isolation of autophagocytosis mutants of Saccharomyces cerevisiae.

Protein degradation in the vacuole (lysosome) is an important event in cellular regulation. In yeast, as in mammalian cells, a major route of protein uptake for degradation into the vacuole (lysosome) has been found to be autophagocytosis. The discovery of this process in yeast enables the elucidation of its mechanisms via genetic and molecular biological investigations. Here we report the isolation of yeast mutants defective in autophagocytosis (aut mutants), using a rapid colony screening procedure.

Microscopy, Electron↗
PubMed1994

Evidence for an inhibitory effect of nitric oxides on neuropeptide secretion from isolated neural lobe of the rat pituitary gland.

The present study aims at investigating the effect of pharmacological manipulation of nitric oxides (NOs) formation in the rat neurohypophysis on the secretion of vasopressin (AVP). We found that the NO synthase antagonist L-NAME and free-ferrous hemoglobin (an NO inactivator) produced a transient and significant enhancement of basal secretion of AVP from incubated glands. Conversely, the NO precursor L-arginine (but not its inactive counterpart D-arginine) antagonized the stimulatory influence of L-NAME on both AVP and oxytocin (OT) output. Elevation of NOs formation triggered by means of the NO donor SIN-1 likewise dampened spontaneous, as well as stimulated, AVP release. It is concluded that NOs molecules show up as potent regulators of neuropeptide secretion at the level of nerve terminals in the neurohypophysis.

Amino Acid Oxidoreductases↗
PubMed1994

Inhibition of protein phosphatases by okadaic acid and calyculin-A differentially modulates hormonal- and forskolin-stimulated formation of cyclic AMP in AtT-20 corticotrophs: effect of pituitary adenylate activating polypeptide and corticotropin-releasing factor.

The effect of phosphatase inhibitors okadaic acid and calyculin-A on cAMP formation and adrenocorticotropic hormone (ACTH) secretion in AtT-20 corticotrophs was investigated. Both okadaic acid and calyculin-A inhibited dose-dependently the accumulation of cAMP in cells stimulated with pituitary adenylate cyclase activating factor (PACAP) and corticotropin-relating hormone (CRF). While in the case of okadaic acid the half-maximum inhibiting concentration was similar for both peptides (IC50 = 4 x 10(-7) M), it appeared that calyculin-A was about one order of magnitude more efficient in inhibiting the effect of PACAP than that of CRF (IC50 = 3.8 x 10(-9) M vs 2.0 x 10(-8) M, respectively). Importantly, the inhibitors blocked the activation by cholera toxin (which acts on Gs-like proteins) of cAMP formation, but failed to alter the effect of forskolin (which bypasses the receptor-G protein complex and activates adenylyl cyclase directly). Treatment of cells with calyculin-A significantly dampened adenylyl cyclase activity in cell membrane fraction, though to a lesser extent than it blocked cAMP formation in the whole cell. Both okadaic acid and calyculin-A inhibited CRF- and PACAP-induced secretion of ACTH. Our data hint that in AtT-20 corticotrophs, inhibition of phosphatases by modulating the state of phosphorylation of the receptor-G proteins complexes for CRF and PACAP, regulates cAMP formation and ACTH secretion.

Adenylyl Cyclases↗
PubMed1994

Antagonistic effects of retinoic acid and triiodothyronine in the expression of corticoid-binding globulin (CBG) by cultured fetal hepatocytes.

Cultures of rat fetal hepatocytes were used to investigate the effects and interplay of triiodothyronine (T3) and retinoic acid (RA) in the regulation of gene expression of CBG, compared to that of alpha-fetoprotein (AFP). The cultured cells showed cytological features typical to hepatocytes and actually synthesized CBG and AFP, as evidenced from in situ hybridization with specific radioactive probes. Time course studies indicated that CBG (but not AFP) binding capacity in culture medium and cell mRNA levels disappeared with a half-life of about 2 days, thereby reflecting the decrease previously seen in hepatic CBG mRNA contents during embryonic life. The Kd values for CBG binding were unchanged under these conditions. Culturing of hepatocytes in the presence of T3 resulted in dose-dependent stimulations of both medium CBG and cell mRNA levels, with an EC50 concentration of about 10(-9) M. In sharp contrast, RA caused a reduction in CBG biosynthesis (IC50 = 1.7 x 10(-7) M) and, in addition, antagonized the stimulatory influence of T3. Under the same experimental conditions, AFP synthesis failed to be affected in a similar fashion. We conclude that thyroid hormones and RA directly act on hepatocytes to specifically regulate the expression of CBG in an antagonistic way.

Animals↗
PubMed1994

From ill-defined extracts to the immunomodulatory lectin: will there be a reason for oncological application of mistletoe?

There is an obvious discrepancy between the popularity of mistletoe extracts and their classification as a non-conventional treatment modality with unproven efficacy in oncology. The commercial preparations suffer from several major drawbacks: lack of precise declarations for the molecular characteristics and the concentrations of diverse extract constituents; the composition of extracts can even be influenced by the different methods of preparation, the time of harvest, and the type of host tree; lack of experimentally substantiated instructions for the dose of supposedly effective substance(s) and the schedule of applications to clinically trigger an undisputably documented antitumoral activity; lack of thorough clinical studies according to the generally accepted criteria as the measure for responsible recommendations. To provide the indispensable set of data for a rational decision, the immunomodulatory galactoside-specific lectin was biochemically characterized and its antitumoral/antimetastatic activity was documented in three murine tumor model systems, occurring within a narrow dose range. Biweekly treatment with s.c. injections of a lectin dose of 1 ng/kg caused no notable harmful side-effects in patients, who showed modulation of selected immune parameters. In a group of 23 patients with advanced cancer no at least partial remission was seen. In principle, enhancement of factors like cytokine availability or NK-cell activity is not necessarily linked to therapeutic benefit. Factors such as growth promotion of certain tumor cell lines by cytokines, occurrence of respective insensitivity in advanced stages or varying levels of target sensitivity to cell-mediated cytotoxicity with significant interindividual differences deserve attention. Each tumor class has to be considered separately for its responsiveness.(ABSTRACT TRUNCATED AT 250 WORDS)

Adjuvants, Immunologic↗
PubMed1994

Glucocorticoids, but not dopamine, negatively regulate the melanotrophic activity of the rabbit pituitary intermediate lobe.

The leporidae (rabbit and hare) pituitary intermediate lobe (IL) differs from that of other mammals by its neuroendocrine regulation. In particular, it is not submitted to the classic dopaminergic inhibitory control, which has been considered as a repressive factor for the expression of glucocorticoid receptors (GR) in the mammalian IL. Hence, the present experiments aimed at examining the rabbit IL for the possible existence of GR. Using both immunocytochemistry and binding studies with (3H)-dexamethasone, we localized GR in the nuclei of IL cells and showed the presence of saturable and high-affinity type II receptor sites, with Kd approximately 3.9 nM. Also, exposure of cultured IL cells to 10 nM dexamethasone (DEX) resulted in the blockade of melanocyte-stimulating hormone (alpha MSH) secretion stimulated by oxytocin (OT). Importantly, the inhibitory effect was reversed by a 100-fold excess of the glucocorticoid antagonist RU 38486. This is the first study which clearly demonstrates in a mammalian IL, namely the rabbit, the presence of functional GR, involved in the negative regulation of the melanotrophic activity of this gland.

Animals↗
PubMed1994

Precocious and reversible expression of sucrase-isomaltase unrelated to intestinal cell turnover.

The effect of starvation and refeeding on the developmental pattern of intestinal sucrase-isomaltase (SI) was analyzed in preweaned rats. Starvation at postnatal day 12 caused a precocious expression of SI activity and mRNA. Alkaline phosphatase activity was slightly reduced, and no significant change was observed for aminopeptidase and lactase activities. Immunostaining showed that SI molecules appear in cells at the base of the villus. Sucrase expression was further increased by prolonged food deprivation, whereas enzyme activity as well as the amount of SI mRNA dropped to reach the low level found in control sucklings when 48 h-starved pups were refed by returning them to their dams. During the refeeding period, the enterocytes that were committed to produce SI by starvation continued to express the enzyme while migrating up the villi. However, the new epithelial cells arising from the crypts no longer synthesized the disaccharidase. The starvation-evoked appearance of SI was preceded by a transient burst of expression of the protooncogene c-fos, an event that may be correlated to the ontogenic rise of c-fos mRNA observed before weaning. However, in contrast to the normal weaning condition, SI induction by starvation occurred without obvious increase of epithelial cell proliferation and turnover. During the starvation and refeeding period, patterns of sucrase activity and SI mRNA paralleled the serum level of glucocorticoids.(ABSTRACT TRUNCATED AT 250 WORDS)

Animal Feed↗
PubMed1994

Pituitary adenyl cyclase-activating peptide: a hypophysiotropic factor that stimulates proopiomelanocortin gene transcription, and proopiomelanocortin-derived peptide secretion in corticotropic cells.

The biological effects of pituitary adenylate cyclase-activating peptide (PACAP) 27 and 38 on peptide secretion and gene regulation were studied in the mouse corticotrope-derived cell line AtT20. Treatment of these cells with PACAP 27/38 led to a dose-dependent increase in cAMP content and ACTH accumulation in the medium with an apparent ED50 value close to 10(-9) M. The genomic effects of PACAP were first investigated by using a reporter gene containing a cAMP responsive element (CRE: TGACGTCA) PACAP 27/38 stimulate transcription from this construction and the effect is further increased when cells are cotreated with the phosphodiesterase inhibitor rolipram. Furthermore, we show by measuring nuclear heterologous proopiomelanocortin (POMC) RNA levels or by using a reporter gene containing the POMC promoter region, that PACAP stimulates POMC transcription. This transcriptional stimulation is mediated by the cAMP-dependent protein kinase (PKA) since genetic inactivation of PKA by a dominant inhibitory mutant of this enzyme completely abolished the effect of PACAP on POMC transcription. Finally, we show that the transcriptional stimulation of POMC by PACAP is repressed by the glucocorticoid receptor agonist dexamethasone. Taken together, these data suggest that PACAP is a hypophysiotropic hormone that exert similar if not identical functions as corticotropin-releasing hormone (CRH) on corticotrope cells.

Adrenocorticotropic Hormone↗
PubMed1994

[Testing the hydrodynamic properties of heart valve prostheses with a new test apparatus].

A new test apparatus for the testing of artificial heart valves makes it possible to realize both physiological flow through the valve during the flow period, and physiological pressure differences across the artificial valve during the closing phase, both for aortic and mitral valve positions, with freely selectable stroke volume and heart frequency. The major hydraulic parameters of the valve are measured directly (pressure drop, closing volume and closing time, leakage volume) or are calculated (e. g. energy loss). In association with the demonstration of the suitability of the HKP+ test apparatus for the measurement of hydraulic parameters in accordance with ISO 5840, the hydraulic properties of various types and sizes of valve with respect to pressure drop (resistance), together with their closing behaviour and leakage flow, are described for different fluids, and the correlations shown.

Aortic Valve↗
PubMed1993

A further case of acute nonlymphocytic leukemia with tetrasomy 8.

In very rare patients tetrasomy of chromosome 8 is observed as the only karyotypic event. We present a 74-year-old man with acute monocytic leukemia (FAB M5) displaying 46,XY/48,XY, +8, +8 in unstimulated bone marrow cells. The patient died 2 weeks after diagnosis. Tetrasomy 8 appears to identify a subgroup of acute nonlymphocytic leukemia. It may indicate a poor prognosis.

Aged↗