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Biomedical subjects

H Kolb

Publications and source records attributed to H Kolb.

At least 145 records · Page 8Linked to original sources
PubMed1994

Fusidic acid suppresses nitric oxide toxicity in pancreatic islet cells.

Earlier preclinical and clinical trials indicate that fusidic acid, a triterpenoid compound originally described as an antimicrobial drug may protect islet beta cells from destruction in type I (insulin-dependent) diabetes mellitus. Since nitric oxide appears to be an important mediator of inflammatory islet cell death we analyzed whether fusidic acid interferes with nitric oxide production or action. We report here that fusidic acid dose-dependently inhibits lysis of isolated islet cells by activated macrophages, a process mediated by nitric oxide. In the presence of 100 microM fusidic acid macrophage-mediated islet cell lysis was reduced from 52.5 to 1.7% (P < 0.001). Fusidic acid only slightly affected macrophage function and did not inhibit the release of nitric oxide. We therefore tested whether fusidic acid suppresses nitric oxide toxicity in target cells. Isolated islet cells were exposed to the nitric oxide donor nitroprusside which led to DNA strand breaks and plasma membrane lysis. DNA strand breaks were reduced from 54.6 to 34.9% (P < 0.001) in the presence of 100 microM fusidic acid and cell lysis was reduced from 60.1 to 27.5% with 100 microM (P < 0.001). In the presence of 500 microM fusidic acid DNA strand breaks and cell lysis were reduced further to 27.1 and 10.7%, respectively (P < 0.001). No protection by fusidic acid was observed when cells were exposed to oxygen radicals or the alkylating beta cell toxin streptozotocin. The suppression of nitric oxide toxicity by fusidic acid was not due to its known inhibitory action on protein biosynthesis and thus represents a hitherto unknown activity of this drug.

Animals↗
PubMed1994

Ultrastructural and immunocytochemical analysis of the circuitry of two putative directionally selective ganglion cells in turtle retina.

Two well-stained, horseradish peroxidase-filled varieties of putative ON-OFF directionally selective ganglion cells, G14a and G15, that project to the dorsolateral optic tectum (Guiloff and Kolb [1992a] Vis. Neurosci. 8:295-313) were studied qualitatively and quantitatively. Both were bistratified ganglion cells with one tier of dendrites in the OFF sublamina and the other in the ON sublamina of the inner plexiform layer (IPL). The cells were serially sectioned and examined for synaptic inputs by electron microscopy. Portions of the dendritic trees were also analyzed after postembedding immunocytochemistry for neurotransmitter candidates gamma aminobutyric acid (GABA), glycine, choline acetyltransferase (ChAT), and glutamate in presynaptic neurons. Both G14a and G15 are dominated by amacrine cell inputs and have only minor bipolar cell involvement. Probably at least two different types of bipolar cell are presynaptic. Both ganglion cells receive some GABA-positive (GABA+) amacrine inputs and G14a receives ChAT+ amacrine inputs. Glycine+ and glutamate+ inputs could not be detected in either cell. The GABA+ inputs appeared to be regionally arranged in the dendritic trees. The general distribution of amacrine and bipolar inputs to the two tiers of dendrites in both cell types appeared to be asymmetrical, both along the radial extent of the dendritic trees and within the depth of the IPL. Our data support some aspects of the current models for directional selectivity. We suggest candidate bipolar and amacrine cells that could have input to these ganglion cells. Since many of the putative presynaptic amacrine cells coincide with directionally selective types recorded and stained by other authors, we propose that in turtle retina directional selectivity arises in neurons presynaptic to the ganglion cells.

Animals↗
PubMed1994

Complexity and scaling properties of amacrine, ganglion, horizontal, and bipolar cells in the turtle retina.

In the present study we have evaluated the complexity and scaling properties of the morphology of retinal neurons using fractal dimension as a quantitative parameter. We examined a large number of cells from Pseudemys scripta and Mauremys caspica turtles that had been labeled using Golgi-impregnation techniques, intracellular injection of Lucifer Yellow followed by photooxidation, intracellular injection of rhodamine conjugated horseradish peroxidase, or intracellular injection of Lucifer Yellow or horseradish peroxidase alone. The fractal dimensions of two-dimensional projections of the cells were calculated using a box counting method. Discriminant analysis revealed fractal dimension to be a significant classification parameter among several other parameters typically used for placing turtle retinal neurons in different cell classes. The fractal dimension of amacrine cells was significantly correlated with dendritic field diameters, while the fractal dimensions of ganglion cells did not vary with dendritic field span. There were no significant differences between the same cell types in two different turtle species, or between the same types of neurons in the same species after labeling with different techniques. The application of fractal dimension, as a quantitative measure of complexity and scaling properties and as a classification criterion of neuronal types, appears to be useful and may have wide applicability to other parts of the central nervous system.

Animals↗
PubMed1994

Soluble forms of intercellular adhesion molecule-1 in insulin-dependent diabetes mellitus.

Soluble adhesion molecules are detectable at low levels in healthy people but are increased in various disorders. However, their physiological role is unknown. Circulating intercellular adhesion molecule-1 (cICAM-1) may modulate inflammation or arise as a consequence of inflammation. We have described elevated concentrations of cICAM-1 in subjects at risk of developing insulin-dependent diabetes mellitus (IDDM), compared with recent-onset IDDM patients and healthy controls. Here we tested the ability of a monomeric soluble recombinant form of ICAM-1 (rICAM-1), to prevent the proliferation of T cells to islet-cell and other antigens. We also tested the ability of two multivalent ICAM-1-immunoglobulin (ICAM-1-Ig) fusion proteins to stop proliferation of T cells in vitro. Autoreactive T-cell proliferation was suppressed by monoclonal antibodies directed against ICAM-1 or lymphocyte-function antigen-1 (LFA-1). Furthermore, 100 mumol rICAM-1 blocked T-cell proliferation in response to an islet-cell autoantigen, and multivalent ICAM-1-Ig fusion proteins were approximately 1,000-fold more effective. The usual interleukin-2-induced proliferation of T cells was unaffected by ICAM or ICAM-Ig. In addition, rICAM-1 blocked primary T-cell responses from peripheral blood mononuclear cells of newly diagnosed IDDM patients in concentrations similar to elevated cICAM-1 concentrations in individuals at risk for the disease. Thus, naturally circulating ICAM-1 may downregulate inflammation in subjects at risk of developing IDDM. Ig-ICAM-1 fusion proteins may thus provide novel means to intervene in the pathogenesis of autoimmune diseases.

Autoantigens↗
PubMed1994

Regulation of 92-kD gelatinase release in HL-60 leukemia cells: tumor necrosis factor-alpha as an autocrine stimulus for basal- and phorbol ester-induced secretion.

Matrix metalloproteinase 9 (MMP-9), also known as 92-kD type IV collagenase/gelatinase, is believed to play a critical role in tumor invasion and metastasis. Here, we report that MMP-9 was constitutively released from the human promyelocytic cell line HL-60 as determined by zymographic analysis. Tumor necrosis factor-alpha (TNF-alpha) enhanced the enzyme release threefold to fourfold and the protein kinase C (PKC) activator and differentiation inducer 12-O-tetradecanoylphorbol-13-acetate (TPA) eightfold to ninefold. Gelatinase induction by TNF-alpha and TPA was inhibited by actinomycin D or cycloheximide, indicating that de novo protein synthesis was required. Neutralizing monoclonal antibodies to TNF-alpha (anti-TNF-alpha) decreased the basal MMP-9 release of these cells. In addition, these antibodies also significantly interfered with the TPA-induced enzyme release. Agents that inhibit TNF-alpha expression in HL-60 cells, such as pentoxifylline and dexamethasone, completely abrogated both the constitutive and TPA-evoked MMP-9 release. Diethyldithiocarbamate, which is known to stimulate TNF-alpha production in HL-60 cells, exerted a positive effect on MMP-9 release in untreated cells but was inhibitory in TPA-treated HL-60 cells. The PKC inhibitor staurosporine at low concentrations (100 ng/mL) caused a significant augmentation of MMP-9 release in untreated cultures that was blocked by the addition of anti-TNF-alpha. High concentrations (2 mumol/L) of staurosporine completely abolished the extracellular enzyme activity both in untreated and TPA-stimulated cells. These results suggest, that TNF-alpha is required for basal and PKC-mediated MMP-9 release in HL-60 leukemia cells. Thus, MMP-9 secretion may be regulated by TNF-alpha not only in a paracrine but also in an autocrine fashion. This may potentiate the matrix degradative capacity of immature leukemic cells in the processes of bone marrow egress and the evasion of these cells into peripheral tissue.

Alkaloids↗
PubMed1994

Are there three types of horizontal cell in the human retina?

Golgi-impregnated horizontal cells (HCs) as viewed in whole mount human retinas have been studied by light microscopic (LM) techniques. Impregnated HCs have been drawn by camera lucida and by the Eutectics neuron tracing method to provide quantitative data on dendritic tree sizes, dendritic tree shapes, and dendritic terminals for statistical treatment and cluster analysis. In addition, fractal analyses of HC dendritic branching patterns have been performed. Three significantly different HCs can be classified on both subjective and objective morphological criteria in central and peripheral human retina. In the fovea all HCs are so small that it is difficult to achieve a clear separation of the subtypes, although they can be distinguished by the experienced observer. HI types are the classic HCs of Polyak (The Retina, Chicago: University of Chicago Press, 1941) with distinct dendritic terminal clusters going to cones and a fan-shaped axon terminal consisting of large numbers of rod-destined terminals. HII cells have profusely branched, overlapping dendrites, with poorly defined terminals going to cones and a short curled axon bearing small terminals also going to cones. The HIII types exhibit larger diameter, more asymmetrically shaped dendritic trees and 30% more dendritic terminal clusters than HI cells at any location on the retina. Many HIII cells appear to emit a process from the cell body in the inner nuclear layer (INL) that descends into the outer strata of the inner plexiform layer (IPL). The axon of the HIII cell may end in a loosely organized, sprawling arborization. Fractal dimensions of the horizontal cells also show significant differences between the three groups. HII cells exhibit the highest fractal dimension followed by HI and HIII cells with lower and lowest fractal dimensions, respectively. The fractal dimension of HII cells of rhesus monkey, as determined from drawings by other authors in other publications, are the same as HII cells of human retina.

Dendrites↗
PubMed1994

Horizontal cells and cone photoreceptors in primate retina: a Golgi-light microscopic study of spectral connectivity.

The relationship of primate horizontal cells (HC) to cone pedicles was assessed by superimposing the cone inner segment mosaic upon Golgi-impregnated HC dendritic terminal clusters in a light microscope (LM) study. The HI, HII, and HIII types of HC were identified, hand-drawn, photographed, and analyzed by computer graphics methods. Blue cone (B-cones) inner segments and their projected pedicles were distinguished from red (R-cones) and green (G-cones) cones on morphological criteria. Thus the inclusion or avoidance of B-cone pedicles by the various HC types' dendritic terminal clusters establishes whether there is any color specificity to their connections. In addition, we made counts of the number of dendritic terminals in the clusters going to cone pedicles in the various HCs' dendritic fields and plotted these against distances the cone pedicles lay from the cell body. In this way we could evaluate the weighting of spectral type of cone input. In general, the three HC types made the majority of their dendritic contacts with cones lying closest to their cell bodies at the center of their dendritic fields. However, HI and HIII cells, with their distinct terminal clusters, did not contact all the centrally located cones uniformly. They either avoided completely (HIII cells) or made only sparse dendritic connections (HI cells) with certain cones. The avoided or sparsely innervated cones were identified as B-cones. HII cells, on the other hand, with their more profuse and diffusely branched dendrites, appeared to contact all overlying cone pedicles and, in contrast to HI and HIII cells, directed a relatively larger number of dendrites to B-cone positions. Axon terminals of HII cells appeared to contact B-cones exclusively.

Animals↗
PubMed1994

Horizontal cells and cone photoreceptors in human retina: a Golgi-electron microscopic study of spectral connectivity.

Connections of the three human horizontal cell (HC) types with overlying cone pedicles have been studied via electron microscopy (EM). Because blue cones (B-cones) can be recognized on distinctive morphological criteria, we could determine their presence by light microscopy (LM) in the mosaic overlying HC dendritic trees. Then we could confirm the presence or absence of dendritic contacts to B-cone pedicles by examining EM serial sections and making reconstructions of examples of the three HC types. Three HI cells have been reconstructed. Their dendritic terminals ended as lateral elements of ribbon synapses in green and red cone pedicles (G- and R-cones) primarily. B-cone pedicles in HI cell dendritic fields received no more than one or two contacts. Six reconstructed HII cells were found to contact all the pedicles within their dendritic field. However, their dendrites reached especially for B-cone pedicles and innervated them with disproportionately large numbers of terminals compared with G- and R-cones. HII axons appeared to contact B-cones exclusively. The four reconstructed HIII cells were found to avoid completely B-cones in their dendritic fields. Data have been collected on synaptic ribbon lengths at HI and HII lateral elements in the B-cone as compared with G- and R-cone pedicles. HII dendritic terminals end almost exclusively at the smaller ribbons and HI dendrites at the larger ribbons. The number of dendritic terminals provided by the three HCs to G- and R-cone pedicles as compared B-cone pedicles has been more accurately quantitated than was possible in the LM analysis (accompanying paper). New findings on the morphology of B-cone pedicles in peripheral retina have revealed that 1) B-cone pedicles end further vitread in the outer plexiform layer (OPL) than other cone pedicles, thereby forming a sublayer of the OPL neuropil, here named OPLb, in comparison to OPLa, where the G- and R-cone pedicles end; 2) B-cone pedicles have very few telodendrial connections; and 3) in peripheral retina (probably beyond 8 mm from the fovea to the ora serrata), they are bi- or trilobed, with each lobe containing separate synaptic invaginations. The vitread position and unique morphology of B-cone pedicles appear to relate directly to the unique morphology and unusual connectivity patterns of both their B-cone-specific bipolar and B-cone-related horizontal cell, the HII cell.(ABSTRACT TRUNCATED AT 400 WORDS)

Axons↗
PubMed1994

Nitric oxide toxicity in islet cells involves poly(ADP-ribose) polymerase activation and concomitant NAD+ depletion.

Previous studies have shown that DNA strand breaks are an early consequence of nitric oxide toxicity in pancreatic islet cells. We show here that exposure of islet cells to chemical NO donors causes the formation of ADP-ribose polymers in cell nuclei, with concomitant depletion of intracellular NAD+. Islet cell lysis was largely prevented by the ADP-ribosylation inhibitors nicotinamide, 3-aminobenzamide, and 4-amino-1,8-naphthalimide, the latter being a potent new-generation compound with high selectivity for poly(ADP-ribosyl)-ation. These findings indicate a key role of poly(ADP-ribose) polymerase activation in NO toxicity in islet cells.

1-Naphthylamine↗
PubMed1994

Human osteosarcoma (U-2 OS) cells express both insulin-like growth factor-I (IGF-I) receptors and insulin-like growth factor-II/mannose-6-phosphate (IGF-II/M6P) receptors and synthesize IGF-II: autocrine growth stimulation by IGF-II via the IGF-I receptor.

UNLABELLED: Recently, insulin-like growth factor-I and -II (IGF-I and -II) have been implicated in the growth promotion of tumors in vivo and tumor cells in vitro. We have studied the human osteosarcoma cell line U-2 OS in order 1) to gain more insight into the growth promoting actions of the IGFs and 2) to establish an in vitro tissue culture model of IGF action in human tumor cells. Specific binding of 125I-IGF-I and 125I-IGF-II to IGF-I receptors and IGF-II/mannose-6-phosphate (M6P) receptors on U-2 OS cells was demonstrated in competitive binding experiments and in affinity crosslinking experiments. Western blotting of cell extracts confirmed the expression of the IGF-II/M6P receptor. In addition, in Northern blotting experiments using total RNA from U-2 OS cells IGF-I receptor RNA of 11 kb and IGF-II/M6P receptor RNA of approximately 9 kb were detected. Solution hybridization experiments confirmed the presence of IGF-I receptor and IGF-II/M6P receptor RNA. In a subset of experiments DNA synthesis was measured as 3H-thymidine uptake into cellular DNA of U-2 OS cells. Normal rat serum stimulated DNA synthesis maximally. IGF-I-deficient serum from hypophysectomized rats as well as IGF-I or IGF-II without serum were approximately twofold and tenfold, respectively, less potent than serum in stimulating 3H-thymidine uptake. The concentrations of IGF-I and IGF-II needed for half maximal stimulation of DNA synthesis corresponded well with the respective concentrations required for half maximal inhibition of 125I-IGF-I binding to U-2 OS cells. The anti-IGF-I receptor antibody alpha IR3 blocked the IGF-I and IGF-II stimulated increase of 3H-thymidine uptake. In addition, basal DNA synthesis was partially inhibited by the anti-IGF-I receptor antibody. These data suggest that U-2 OS cells synthesize and secrete IGF-like peptides. Northern blotting experiments confirmed that U-2 OS cells express an IGF-II RNA species of 5.3 kb but no IGF-I transcripts. In a series of RNase protection assays, protected RNA fragments were detected with an IGF-II riboprobe. Also, cell-conditioned medium from U-2 OS cells contained 1-2 ng/ml IGF-II immunoreactivity as measured in an IGF-binding protein blocked IGF-II radioimmunoassay. IN CONCLUSION: 1) U-2 OS cells express IGF-I and IGF-II/M6P receptors. 2) U-2 OS tumor cells respond to the addition of exogenous IGF-I and IGF-II with an increase of DNA synthesis.(ABSTRACT TRUNCATED AT 400 WORDS)

Animals↗
PubMed1994

Cyclophosphamide treatment of female non-obese diabetic mice causes enhanced expression of inducible nitric oxide synthase and interferon-gamma, but not of interleukin-4.

In pancreatic lesions of non-obese diabetic (NOD) mice the expression of inducible nitric oxide synthase (iNOS) and of the cytokines interferon-gamma and interleukin-4 were studied. Strong iNOS expression as determined at the level of transcription, translation and of enzyme activity was associated with destructive insulitis as seen 8-10 days after cyclophosphamide treatment of 70- to 80-day-old female NOD mice. Immunohistochemistry showed iNOS associated with infiltrating macrophages but not in endocrine cells. The enhancement of iNOS after cyclophosphamide correlated with an increase of T-helper type 1 (Th1) associated interferon-gamma expression while T-helper type 2 (Th2) associated interleukin-4 was the dominant cytokine prior to cyclophosphamide and after diabetes onset. We conclude that insulitis in young NOD mice is carried by Th2 cells while cyclophosphamide enhanced insulitis is determined by Th1 cells. Macrophages show two different functional states in insulitis; strong iNOS expression in macrophages is associated with destructive insulitis.

Amino Acid Oxidoreductases↗
PubMed1994

Inflammatory islet damage in patients bearing HLA-DR 3 and/or DR 4 haplotypes does not lead to islet autoimmunity.

The hypothesis was tested that islet autoimmunity is induced by ongoing islet cell destruction in subjects with susceptibility genes HLA-DR 3 and/or DR 4. Sixty-one patients with confirmed chronic pancreatitis were analysed, 30 of whom expressed HLA-DR 3 and/or DR 4. Electron microscopy studies in 10 patients showed that the inflammatory process also affected islets, as recognisable from islet cell lysis, intrainsular fibrosis and immune cell infiltrates. None of the sera tested contained any of three markers of islet autoimmunity, ICA, IAA or GAD antibodies. A correlation was seen between the loss of exocrine function, as determined by the ALTAB-test, and of beta-cell function, as determined by the C-peptide response to i.v. glucagon. However, there was no preferential loss of beta-cell function in patients with HLA-DR 3 and/or DR 4. We conclude that islet cell destruction occurs during chronic pancreatitis, but does not trigger islet autoimmunity, even in the presence of HLA-DR 3 and/or DR 4.

Adult↗
PubMed1994

Identification of the synaptic pedicles belonging to the different spectral types of photoreceptor in the turtle retina.

In this paper we describe the morphology of the different spectral types of photoreceptor pedicles in the outer plexiform layer (OPL) of the Pseudemys turtle as studied by light (LM) and electron microscopy (EM). Tangential serial thick sections were cut from the oil droplet region to the level where the axons emerge from cell bodies and then serial thin sections through the axons and the entire pedicles were collected and examined. Thus photoreceptor pedicles could be identified by tracing cells from their oil droplets to their synapses in the OPL. Double cone pedicles consisted of closely applied pairs with the principal member's pedicle wrapping around the accessory member's pedicle. Each pedicle was approx. 104 microns 2 in area and contained 12 and 8 synaptic ribbons respectively. Rods comprised 8% of the pedicles in the field, were small (84 microns 2), contained closely packed synaptic vesicles, and on average, 9 long ribbons. Single red and green cone pedicles could not be told apart without following them from their oil droplets, however, both were about the same size (106-127 microns 2) and contained 10-12 ribbons. Blue cone pedicles were small and round (80 microns 2) and arose from short oblique axons giving off from large, greenish, clear oil droplet-containing cell bodies (13% of the cone population). The least common pedicle types (5% of the cone population) were identified tentatively as UV cones because they originated from small, clear oil droplet-containing cell bodies. UV cones had spherical pedicles, elongated in the vertical axis, that arose from extremely long, angled axons. Their very small pedicles (64 microns 2) exhibited characteristic "horns" that projected from the top sides of the pedicle. Both putative UV and blue cone pedicles ended more vitread in the OPL than other pedicles and contained only 5-6 and 8-10 ribbons respectively. Understanding the ultrastructural features that distinguish the different types of photoreceptor pedicle will allow us to begin a study of spectral connections to second order neutrons in the turtle OPL in the future.

Animals↗
PubMed1994

Effect of lipoic acid on cyclophosphamide-induced diabetes and insulitis in non-obese diabetic mice.

In an animal model of type I diabetes, the non-obese diabetic (NOD) mouse, the influence of the antioxidant lipoic acid (LA) on the development of diabetes was investigated. Acceleration of diabetes development with cyclophosphamide (CY) resulted in 60% diabetic animals with severely infiltrated islets within 1-3 weeks. Daily administration of lipoic acid for 20 or 30 days around cyclophosphamide treatment suppressed the incidence of diabetes to 30% (P < 0.05) and 33%, respectively. Semiquantitative analysis of islet infiltration showed a reduction of severe intraislet infiltration and an increase in the percentage of islets with mild per-insular and periductular infiltrates (from 8.4 to 29.6 and 25.9%, respectively, P < 0.01) after lipoic acid treatment. These results show that the protective effect of lipoic acid on diabetes development correlates with partial suppression of islet inflammation. The anti-inflammatory action of lipoic acid may be due to its ability to scavenge oxygen radicals and to suppress nitric oxide production.

Animals↗