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Biomedical subjects

B Mayer

Publications and source records attributed to B Mayer.

At least 217 records · Page 12Linked to original sources
PubMed1995

Distribution of mast cells in human ileocecal region.

The number and histochemistry of mast cells were analyzed in surgical specimens of the ileocecal junction and neighboring intestinal segments. All the basophilic cells contained tryptase and some were immunoreactive for chymase, vasoactive intestinal polypeptide, or nitric oxide synthase. The medium density of mast cells per square millimeter was 31.90, 110.38, 72.83, 29.80, and 32.70, in the mucosa, submucosa, inner circular, outer circular, and longitudinal muscle layers, respectively. Mast cell density was higher at the ileocecal junction (for all layers together, 79.29 mast cells/mm2) than elsewhere (mast cells/mm2: ileum, 52.29; cecum, 59.22; cecocolonic junction, 54.65; ascending colon, 48.63). The differences among layers and among segments were significant and might be due to layer- and region-specific mast cell roles. Mast cell richness in the muscle coat, especially in the inner circular muscle layer, might be important in regulating its motility.

Cell Count↗
PubMed1995

Pentamidine does not interfere with nitrite formation in activated RAW 264.7 macrophages but inhibits constitutive brain nitric oxide synthase.

Pentamidine effects on the interferon-gamma- or interferon-gamma plus bacterial lipopolysaccharide-induction of nitric oxide synthase in the macrophage cell line RAW 264.7, determined by measuring nitrite release into culture supernatants, were investigated. At concentrations above 10 microM, pentamidine caused visible toxic effects including cell lysis which also was assessed by measuring lactic dehydrogenase release. A progressive inhibitory effect of pentamidine could not be clearly dissociated from these toxic and lytic effects which were extensive at 100 microM. At 1 microM pentamidine, the dose response dependence of nitrite formation on interferon-gamma was not affected. Tumor necrosis factor-alpha caused some enhancement of interferon-gamma-induced nitrite release only at high doses of 100 and 10,000 unit/ml. Pentamidine had no effect on isolated inducible nitric oxide synthase from RAW 264.7 cells but inhibited the constitutive enzyme from pork cerebellum non-competitively. The lack of any stimulatory effect of pentamidine on nitrite production in RAW 264.7 cells suggests that NOS induction and NO production by macrophages is not the mechanism of the antimicrobial effects of this drug.

Animals↗
PubMed1995

Demonstration of nitric oxide synthase (NOS) in marmosets by NADPH diaphorase (NADPH-d) histochemistry and NOS immunoreactivity.

Since species interdiversity often prevents the extrapolation of laboratory rodent data to man and similar problems may exist for nitric oxide synthase (NOS), NADPH-d activity and immunohistochemistry of NOS were investigated in the New World monkey Callithrix jacchus (marmoset), which has been shown to be close to the human situation in many respects. Using the NADPHd reaction with beta-NADPH and nitroblue tetrazolium (NBT) on acetone-chloroform pretreated cryosections, NBT formazan was found in many neural and non-neural (e.g. diverse epithelia, striated muscle fibers, vascular endothelium) cells in numerous tissues and organs. Prefixation with formaldehyde lowered the number of NADPH-d active sites and the amount of formazan with the exception of neuronal NADPH-d as did incubation of fresh or acetone-chloroform-pretreated sections for NADPH-d in the presence of 0.5% formaldehyde. When 1% formaldehyde or 0.5 mM permanganate were used significant amounts of formazan appeared only in central and peripheral neurons, vasal endothelial cells, small intestinal enterocytes, plasma membrane region of striated muscle fibers as well as arteriolar cells in the kidney; except for enterocytes, these observations were confirmed by NOS-immunohistochemistry which revealed in addition reactive cells in the thymus and intestinal lamina propria.

Acetone↗
PubMed1995

Characterization of neuronal amino acid transporters: uptake of nitric oxide synthase inhibitors and implication for their biological effects.

In the present study we investigated uptake of the nitric oxide (NO) synthase inhibitors NG-methyl-L-arginine and NG-nitro-L-arginine by the mouse neuroblastoma x rat glioma hybrid cell line NG108-15. Uptake of NG-methyl-L-arginine was characterized by biphasic kinetics (Km1 = 8 mumol/L, Vmax1 = 0.09 nmol x mg-1 x min-1; Km2 = 229 mumol/L, Vmax2 = 2.9 nmol x mg-1 x min-1) and was inhibited by basic but not by neutral amino acids. Uptake of NG-nitro-L-arginine followed Michaelis-Menten kinetics (Km = 265 mumol/L, Vmax = 12.8 +/- 0.86 nmol x mg-1 x min-1) and was selectively inhibited by aromatic and branched chain amino acids. Further characterization of the transport systems revealed that uptake of NG-methyl-L-arginine is mediated by system y+, whereas systems L and T account for the transport of NG-nitro-L-arginine. In agreement with these data on uptake of the inhibitors, L-lysine and L-ornithine antagonized the inhibitory effects of NG-methyl-L-arginine on bradykinin-induced intracellular cyclic GMP accumulation, whereas L-tryptophan, L-phenylalanine, and L-leucine interfered with the effects of NG-nitro-L-arginine. These data suggest that rates of uptake are limiting for the biological effects of NO synthase inhibitors.

Amino Acid Oxidoreductases↗
PubMed1995

The effect of NO-donors in bovine and rat pineal cells: stimulation of cGMP and cGMP-independent inhibition of melatonin synthesis.

The presence of soluble guanylate cyclase in the pineal and its regulation by adrenergic pathways has been well documented. Recent evidence points to adrenergically stimulated nitric oxide generation as a mechanism for coupling this pathway. To what extent nitric oxide (NO) signalling can influence adrenergically stimulated melatonin synthesis has not been investigated. Cyclic guanosine 3',5'-monophospate (cGMP) signal transduction in the bovine pineal has also received little attention. We describe in the present report: 1) a dose-dependent elevation of cGMP in response to the nitrovasodilators, sodium nitroprusside (SNP) and 3-morpholino-sydnonimine (SIN-1), 2) a dose-dependent inhibition of melatonin synthesis by SNP and SIN-1, but not by 8-Br-cGMP in both bovine and rat pineal cell cultures, which is not due to cytotoxicity as judged by two different approaches, and 3) immunohistochemical evidence for the presence of nitric oxide synthase (NOS) (EC 1.14.23.-) in the intact bovine pineal gland and in cultured bovine pinealocytes. These data support the view that NOS is a component of the cGMP-generating system in mammalian pinealocytes. Although NO-donor molecules are also potent activators of cGMP accumulation, they may have other important actions in the pineal, namely the inhibition of adrenergic-stimulated melatonin synthesis. As SNP and SIN-1 exerted this inhibitory effect on cells regardless of whether they were stimulated by isoproterenol, forskolin or 8-Br-cAMP it would appear that NO-donors can act 'downstream' from the receptor/adenylate cyclase level.

Animals↗
PubMed1995

Morphology of incipient mesoderm formation in the rabbit embryo: a light- and retrospective electron-microscopic study.

Mesoderm formation is a hallmark of vertebrate gastrulation and, at the same time, one of the prime examples for epithelio-mesenchymal transformation. Recent advances in experimental embryology and molecular biology have clarified the role of growth factors and genes in this process; however, its microscopic anatomy in higher vertebrates is still far from clear. Therefore, the present study describes the morphology of mesoderm formation in the rabbit embryo, a species which may be representative for both the avian and the mammalian embryo in this respect. Serial semithin sections were correlated with topographical landmarks in surface views of embryonic discs at 6.4, 6.5, and 6.6 days post conceptionem, and selected semithin sections were reembedded for ultrastructural analysis. Mesoderm cells are shown to be generated by ingression of bottle-shaped epiblast cells in the area of the posterior node and the primitive streak. Here, basal endocytotic pits and absence or discontinuity of the basal lamina are taken as suggestive evidence for specific removal of extracellular matrix material. Within the bottle-shaped cells most organelles are concentrated in a narrow apical neck which will subsequently constitute the 'trailing end' of the ingressing mesoderm cells. These features support the assumption that most principles of epithelio-mesenchymal transformation seen during primary mesenchyme formation in the sea urchin also apply to mesoderm formation in vertebrates. However, transient tripartite zonula adherens-type junctions are formed apically between ingressing mesoderm cells and the neighboring epiblast cells. They are interpreted here as being responsible for maintaining supracellular integrity of the embryonic disc during the shedding of mesoderm cells in the amniote embryo.

Animals↗
PubMed1995

Nitric oxide synthase (NOS-I) in Leydig cells of the human testis.

By means of immunocytochemical methods, immunoreactivity for the brain isoform of nitric oxide synthase (NOS-I) was recognized in numerous Leydig cells of the human testis as well as in MA-10 tumor and TM3 non-tumor mouse Leydig cell lines. Within the Leydig cell cytoplasm, immunocytochemical results suggested the occurrence of factors known to activate NOS-I such as glutamate and aspartate, as well as molecules involved in the regulation of the NOS-I activity such as calmodulin and Ca2+/calmodulin-dependent protein kinase II. Leydig cells, Sertoli cells, some endothelial cells of the testis, MA-10- and TM3 mouse Leydig cell lines exhibited a relatively strong NADPH-diaphorase enzyme activity as well. Double sequential immunostainings provided evidence that NOS-like immunoreactivity of the testicular Leydig cells is colocalized with testosterone, calmodulin, aspartate, glutamate, and Ca2+/calmodulin-dependent protein kinase II. Sodium nitro-prusside treatment did not result in increased cGMP formation by MA-10- or TM3 mouse Leydig cells, suggesting that NO produced by these cells acts primarily in a paracrine fashion. The NO produced by NOS-I immunoreactive Leydig cells may act as a messenger: 1) between neighbouring NOS-I positive and/or negative Leydig cells as well as to mediate the action of numerous intracellular and extracellular neuroactive substances and growth factors; 2) between Leydig cells and the muscle cells or pericytes of blood vessels to regulate local blood flow and permeability; and 3) between Leydig cells and pertibular myofibroblasts to influence their contraction and the permeability of the lamina propria.

Adult↗
PubMed1995

Nerve cells in the human ciliary muscle: ultrastructural and immunocytochemical characterization.

PURPOSE: Intrinsic nerve cells in the human ciliary muscle were identified and characterized by immunohistochemical and ultrastructural methods. METHODS: Serial sections through the ciliary muscle of 10 human donors (age range, 53 to 91 years) were investigated by electron microscopy, NADPH-diaphorase (NADPH-d) staining, and immunohistochemistry. Antibodies against nitric oxide synthase (NOS), protein gene product 9.5 (PGP 9.5), neurofilament proteins, tyrosine hydroxylase (TH), neuropeptide Y (NPY), vasoactive intestinal peptide (VIP), substance P (SP) and calcitonin gene-related peptide (CGRP) were used. Nerve cell density per millimeter of circumferential width was analyzed in three eyes, and in one eye the total number of neurons in the entire ciliary muscle was evaluated. RESULTS: Small (70% of the total; longitudinal diameter 10 to 14 microns) and large (longitudinal diameter 20 to 30 microns) ganglion cells were identified in the inner parts of the muscles' reticular and circular portions. No nerve cells were observed in the anterior longitudinal portion. The cells were in contact with unmyelinated axons and synaptic boutons containing small agranular and large granular vesicles. Axo-somatic and axo-dendritic synapses were observed. Histochemically and ultrahistochemically, the neurons stained intensely for NADPH-d. Both cell types were multipolar and expressed long filamentous processes. Axonal processes with periodic swellings suggesting varicosities ran close and parallel to neighboring muscle bundles. Some nerve cells were connected with each other by axonal processes. No perivascular NADPH-d-positive nerves were seen around ciliary muscle vessels, but they were present in the wall of the major arterial circle of the iris. A small number of ganglion cells contributed to this perivascular network. NADPH-d-positive neurons stained for PGP 9.5 and NOS. No TH, NPY, or VIP-positive ciliary muscle neurons were observed. In double labeling experiments, 70% of the nerve cells were in contact with nerve endings expressing SP-like and CGRP-like immunoreactivity. Seventeen to 32 NADPH-d-positive neurons were counted per millimeter of ciliary muscle circumferential width, with 923 in the entire ciliary muscle of one donor eye. CONCLUSIONS: The presence of intrinsic NOS-positive nerve cells concentrated in the inner parts of the ciliary muscle might indicate a physiological role of nitric oxide for disaccommodation or fluctuations during accommodation.

Aged↗
PubMed1995

Potent and selective inhibition of nitric oxide-sensitive guanylyl cyclase by 1H-[1,2,4]oxadiazolo[4,3-a]quinoxalin-1-one.

In brain and other tissues, nitric oxide (NO) operates as a diffusible second messenger that stimulates the soluble form of the guanylyl cylase enzyme and so elicits an accumulation of cGMP in target cells. Inhibitors of NO synthesis have been used to implicate NO in a wide spectrum of physiological and pathophysiological mechanisms in the nervous system and elsewhere. The function of cGMP in most tissues, however, has remained obscure. We have now identified a compound, 1H-[1,2,4]oxadiazolo[4,3-a]quinoxalin-1-one (ODQ), that potently and selectively inhibits NO-stimulated guanylyl cyclase activity. In incubated slices of cerebellum, ODQ reversibly inhibited the NO-dependent cGMP response to glutamate receptor agonists (IC50 approximately nM) but did not affect NO synthase activity. The compound did not affect synaptic glutamate receptor function, as assessed in hippocampal slices, nor did it chemically inactivate NO. ODQ did, however, potentially inhibit cGMP generation in response to NO-donating compounds. An action on NO-stimulated soluble guanylyl cyclase was confirmed in studies with the purified enzyme. ODQ failed to inhibit NO-mediated macrophage toxicity, a phenomenon that is unrelated to cGMP, nor did it affect the activity of particulate guanylyl cyclase or adenylyl cyclase. ODQ is the first inhibitor that acts selectively at the level of a physiological NO "receptor" and, as such, it is likely to prove useful for investigating the function of the cGMP pathway in NO signal transduction.

Amino Acid Oxidoreductases↗
PubMed1995

Are CD44 variant isoforms involved in human tumour progression?

The transmembrane glycoprotein CD44 exists in a variety of isoforms generated by alternative splicing of the pre-mRNA. In a rat metastasis model, certain variant isoforms (containing exon 6v) are causally involved in lung metastasis formation. We have summarized the data obtained to date on the expression of CD44 variant isoforms in human tumour progression. In non-Hodgkin lymphomas, expression of exon 6v containing isoforms is an independent prognostic factor indicating an adverse prognosis. Upregulation of exon 9v containing isoforms in gastric and renal cell carcinomas relates to a poor prognosis of patients. In colorectal carcinomas, CD44-9v isoforms are strongly expressed already in early adenomas; CD44-6v isoforms are upregulated in late adenomas along with ras and TP53 mutations. No expression of variant isoforms has been detectable in neuroblastomas, but significant downregulation of CD44s correlates inversely with tumour progression and N-myc amplification. Only in breast carcinoma has no correlation of CD44 expression with survival or any other prognostic marker been established. Evaluation of CD44 isoform expression by immunohistochemistry in cases of non-Hodgkin lymphoma, gastric, colon and renal cell carcinomas, as well as neuroblastomas, may be a useful diagnostic parameter indicating invasive processes.

Breast Neoplasms↗
PubMed1995

A modified method allows for correlation between NADPH-diaphorase histochemistry and immunohistochemistry for the demonstration of neuronal nitric oxide synthase (nNOS).

Results obtained with the conventional nitro blue tetrazolium salt method for the visualization of the NADPH-diaphorase (NADPH-d) activity of nitric oxide synthase (NOS) are not specific for this particular enzyme, since this activity represents only a fraction of the total cellular NADPH-d pool. Therefore, the standard NADPH-d procedure was modified by performing the incubation in the presence of formaldehyde. Parallel application of the modified NADPH-d staining technique and the indirect immunofluorescence using an antibody against the neuronal isoenzyme (nNOS) on rat, mouse and guinea-pig tissues showed a correlation between histochemical and immunocytochemical staining. It can thus be concluded that the modified NADPH-d procedure allows for a more specific detection of the histochemical nNOS activity than the conventional method.

Animals↗
PubMed1995

Postnatal development of NADPH-diaphorase/nitric oxide synthase positive nerve cells in the visual cortex of the rat.

The postnatal development of NADPH-diaphorase (NADPH-d)/nitric oxide synthase (NOS) positive nerve cells was studied in the visual cortex of rats on postnatal day 1, 5, 10, 15, 20, 30 and at the age of 1 year. NADPH-d was demonstrated enzymhistochemically and NOS immunohistochemically using a polyclonal antibody. NADPH-d is localized in nerve cell somata, dendrites, axons and blood vessels, whereas NOS immunoreactivity is only detectable in nerve cells. The identity of NADPH-d cells with those which contain NOS was proved in double labelling experiments in the cortex of rats on postnatal day 5, 15 and at the age of 1 year. The results of these experiments have shown that in the cortex of rats NADPH-d positive cells are identical with NOS-positive cells in the different stages. Therefore we have used NADPH-d histochemistry in all other postnatal stages as a marker for neurons which contain NOS. NOS positive nerve cells appear very early on postnatal day 1 in the intermediate (white matter) and subplate (layers V and VI) region as small undifferentiated neurons. During the following postnatal differentiation these neurons reached their typical morphology in the second week and appeared in all layers. Neurons in layers V and VI preceded those in the superficial layers. Nerve cells in the white matter seem to have their own differentiation pattern because they showed characteristic features of immaturated varicose dendrites for a longer time. The investigation of soma size with the computerized "Kontron Videoplan" system (Zeiss, Germany) showed the largest cell bodies on postnatal day 20 which then decreased towards adulthood. Between postnatal day 10 and 20 some NOS-positive neurons especially in the deep layers displayed symptoms of degeneration, like shrunken cell bodies, corkscrew and twisted dendrites. Furthermore, NOS-positive neurons in layer I are not detectable in adult neocortex. These observations could suggest that some NOS-positive cells in the cerebral cortex of rats may occur only transiently. Also in the neuropil some alterations in the localization of NOS positive axonal boutons were observed. On postnatal day 10 NOS negative cell somata were shadowy surrounded by boutons. During the further development from postnatal day 20 until adulthood this particular position was no longer visible. Beside the NOS cells which played a transient role, the majority of these cells survived to adulthood and are a morphological (Martinotti-cells with ascending axons) and chemical (GABAergic, NADPH-d/NOS positive, peptide containing cells) defined cell type in the neuronal network of the cortex of the rat.

Aging↗
PubMed1995

Innervation of myofibroblast-like scleral spur cells in human monkey eyes.

PURPOSE: To study the innervation of the presumably contractile, myofibroblast-like scleral spur cells in human and cynomolgus monkey eyes. METHODS: Serial tangential sections of the scleral spur region of the eyes of 16 human donors and 6 cynomolgus monkeys were investigated with immunocytochemical methods. Antibodies against acetylcholinesterase, synaptophysin, alpha-smooth muscle actin, calcitonin gene-related peptide (CGRP), neuropeptide Y (NPY), nitric oxide synthase (NOS), substance P (SP), tyrosine hydroxylase (TH), and vasoactive intestinal peptide (VIP) were used. In addition, sections were processed for glyoxylic acid-induced catecholamine fluorescence (CF) and for NADPH-diaphorase (NADPH-d). RESULTS: In the eyes of both species, circumferentially oriented varicose axons were observed in the scleral spur region of all quadrants. Double labeling showed that most of these scleral spur axons were in close contact with the alpha-smooth muscle actin-positive, myofibroblast-like scleral spur cells. In human eyes, the axons showed like-immunoreactivity (LI) for SP, CGRP, NPY, VIP, and NOS. In addition, numerous scleral spur axons stained for NADPH-d. Most SP-LI scleral spur axons were double-labeled for CGRP-LI, and none for VIP-LI. All NPY-LI scleral spur axons were double labeled for VIP-LI but lacked immunoreactivity to TH. Some VIP-LI axons were not labeled for NPY-LI. Nerve fibers immunoreactive (IR) for TH or positively stained for CF were not observed in association with scleral spur cells. In contrast, in cynomolgus monkey eyes, circumferentially oriented TH-IR and CF-positive varicose axons were observed frequently in the scleral spur region. In addition, SP-LI, CGRP-LI, and NPY-LI/TH-IR axons were present in the chamber angle of monkey eyes, whereas VIP-LI, VIP-LI/NPY-LI, NOS-positive, or NADPH-d-positive nerve fibers were absent. In both species, positive staining for acetylcholinesterase was seen only in the ciliary muscle, not in the scleral spur region. CONCLUSIONS: The close association of varicose axons with the myofibroblast-like scleral spur cells indicates that nervous signals modulate scleral spur cell tone. A sympathetic scleral spur cell innervation is present only in cynomolgus monkeys but seems to be absent in humans. Conversely, scleral spur axons of presumably parasympathetic origin (NOS-IR or NADPH-d-positive, VIP-LI, and VIP-LI/NPY-LI) are absent in the cynomolgus monkeys but present in humans. In both species, a cholinergic innervation of the scleral spur cells seems to be rare or absent.

Adult↗
PubMed1995

Promiscuity of heme groups in the cyanobacterial cytochrome-C oxidase.

The cyanobacteria Nostoc sp. strain Mac, Anabaena 7937, Synechocystis 6803, and Anacystis nidulans (Synechococcus 6301) were grown and incubated in the light under three different oxygen regimes: Phase-A cells were harvested from photoautotrophically growing cultures at a cell density of 2.8-3.2 microliter packed cell mass/ml and an oxygen concentration of approx. 350 microM (corresponding to > 150% air saturation). Phase-B cells were harvested 24 hrs after 20 microM 3-(3,4-dichlorophyl)-1,1-dimethylurea had been added to the culture and gassing switched to 1% oxygen (< 10 microM). Phase-C cells originated from phase-B cells after 12 hrs of gassing the illuminated, yet non-growing cultures with air (21% oxygen or 200-220 microM in the medium). Cytoplasmic membranes were isolated and purified from each of the three cell types. Non-covalently bound hemes were extracted and identified by reversed-phase high performance liquid chromatography. Besides ubiquitous heme B only heme A was detected in phase-A membranes while phase-B and phase-C membranes contained both hemes A and O proportions of which depended on the oxygen status of the cells. CO/difference spectra, photo-action spectra of CO-inhibited oxygen uptake, and polarographic determination of oxygen-affinities clearly showed that both hemes A and O were part of a functional form of cytochrome-c oxidase which, however, exhibited a single subunit-I apoprotein as verified by immunoblotting. Also electron transport characteristics did not give evidence for a quinol or any other alternate oxidase functioning in cyanobacteria.

Chromatography, High Pressure Liquid↗
PubMed1995

Nitric oxide synthase and vasoactive intestinal polypeptide colocalization in neurons innervating the human penile circulation.

The question which neurotransmitters mediate penile erection in humans is still unsettled. Although functional studies have established a role of vasoactive intestinal polypeptide (VIP) and nitric oxide (NO) in human penile smooth muscle relaxation, they did not allow a conclusion as to whether they are released by neurons or other cells. This article outlines the identification of numerous nitric oxide synthase (NOS) and VIP-containing axons in the human penis. More than 50% of the perivascular nerve fibres and more than 90% of the trabecular nerve fibres within the corpus cavernosum stained positive for both NOS and VIP. In contrast, endothelial cells stained only faintly for NOS-immunoreactivity, NOS/VIP-immunoreactivity was reduced (diabetes) or absent (lesion of the cavernous nerve) in penile tissue taken from patients with neurogenic impotence. These findings support the concept that NO and VIP act as neural comediators of penile erection in humans.

Humans↗