Biomedical subjects

H Kolb

Publications and source records attributed to H Kolb.

At least 199 records · Page 11Linked to original sources

PubMed1992

Nitric oxide: a pathogenetic factor in autoimmunity.

Nitric oxide (NO) has been identified recently as a multifunctional mediator, produced by, and acting on, most cells of the body. Besides its function as endothelium-derived relaxing factor, as a neurotransmitter and as an immune defence molecule, evidence is accumulating that NO participates in inflammatory- and autoimmune-mediated tissue destruction. Modulation of NO synthesis and action represents a new approach to the treatment of inflammatory and autoimmune conditions.

Amino Acid Oxidoreductases↗

PubMed1992

Low dose streptozotocin-induced diabetes in mice: reduced IL-2 production and modulation of streptozotocin-induced hyperglycemia by IL-2.

The possible role of interleukin 2(IL-2) in the pathogenesis of multiple low dose streptozotocin (Sz)-induced diabetes in mice was analysed. Spleen cells from diabetic male C57Bl/6 mice showed diminished mitogen-induced IL-2 production as determined by bioassay using the IL-2-dependent T-cell line CTLL-2. In parallel the proliferative response was reduced. Systemic daily administration of human recombinant IL-2 for 3 weeks had dose-dependent effects on the development of hyperglycemia in Sz-treated (5 x 40 mg) mice: while IL-2 at doses of 1 x 2, 1 x 10, 2 x 10 micrograms/kg body weight caused partial suppression of hyperglycemia, higher doses (2 x 20, 2 x 40 micrograms/kg) had an enhancing effect. Treatment with the lowest dose (1 x 1 micrograms/kg) or with a control preparation from bacteria (2 x 10 micrograms/kg) did not significantly alter the course of diabetes. Effects of IL-2 were similar when treatment was started concomitantly with or only after streptozotocin injections. This observation argues against the direct interaction between IL-2 and streptozotocin but suggests modulation of immune reactivity by IL-2. Our findings of decreased mitogen-stimulated IL-2 production by splenic lymphocytes, and the disease-modulating effect of IL-2 in the low-dose streptozotocin diabetes extend our previous observations in spontaneously diabetic BB rats and further support the notion of an involvement of IL-2 in the control of autoimmune diseases.

Animals↗

PubMed1992

Ganglion cell types of the turtle retina that project to the optic tectum: Intracellular HRP injections of retrogradely, rhodamine-marked cell bodies.

The turtle retina has been shown to have a variety of different morphological ganglion cell types as well as distinct physiological ganglion cell types. The major projection of the retina to the brain in nonmammalian vertebrates is to the optic tectum. In this study, we address the question of which retinal ganglion cell types project to the optic tectum in the turtle. Fluorescent rhodamine-labeled microspheres were used to trace the retinal ganglion cell projection to the superficial layers of the optic tectum. The fluorescent ganglion cell somata, retrogradely marked by transport from the contralateral optic tectum, were impaled with micropipettes containing rhodamine-horseradish peroxidase solution and this dye was iontophoresed into the cells under visual control. Most of the morphological ganglion cell types described in Golgi studies (Kolb, 1982; Kolb et al., 1988) were stained. Thus, the small cell types G1, G2, G3, G5, G6, and G7; the medium-sized types G10, G11, G12, G13, and G14; and the large-sized types G15, G16, G19, G20, and G21 project to the optic tectum in the turtle. We have added a new type, G2a, which proves to have some differences from the original G2 in branching pattern. We were unable to stain the small type G4, the medium-sized types G8 and G9, and the large cell types G17 and G18: this suggests that they might not project to the superficial layers of the dorsolateral optic tectum, at least, in the turtle.

Animals↗

PubMed1992

Diabetes manifestation in BB rats is preceded by pan-pancreatic presence of activated inflammatory macrophages.

Pancreata of normoglycemic diabetes-prone (dp) and diabetes-resistant (dr) BB rats and normal Wistar rats were screened for macrophage infiltration by immunohistochemistry and by electron microscopy. Inflammatory macrophages were found in the endocrine as well as the exocrine part of the pancreata from dp BB rats. In the exocrine tissue they had a different phenotype (ED1+, ED2+, W3/25+, Ox17+) from that found in pancreata from dr BB and Wistar rats (predominantly ED1-, ED2+, W3/25+, Ox17-). The number of macrophages in exocrine portions of pancreata from the various rat strains were not different. By electron microscopy scattered macrophage-associated tissue lesions and phagocytosis of cell debris were found throughout the exocrine tissue and in islets of dp BB rats. Such lesions were low or absent in biopsies of animals that later did not develop diabetes. We conclude that macrophage-mediated cytotoxicity during the early phases of diabetes development in BB rats is not restricted to islets, but is a generalized, pan-pancreatic event.

Animals↗

PubMed1992

Insulin autoantibodies measured by radioimmunoassay methodology are more related to insulin-dependent diabetes mellitus than those measured by enzyme-linked immunosorbent assay: results of the Fourth International Workshop on the Standardization of Insulin Autoantibody Measurement.

Insulin autoantibodies (IAA) have been identified in newly diagnosed insulin-dependent diabetes mellitus (IDDM) patients and in individuals at high risk of developing the disease. However, the literature is not in agreement regarding the prevalence, significance, and predictive value of IAA. Previous workshops have shown that certain sera give markedly different results depending upon assay methodology and, therefore, have suggested that these discrepancies may be due to variations in the assay methodologies used: either the fluid phase RIA or the solid phase enzyme-linked immunosorbent assay (ELISA). Sera from controls (n = 61), newly diagnosed IDDM patients (n = 30), healthy subjects who later became diabetic (n = 8), and first degree relatives of diabetic probands (n = 22) were randomly numbered and sent without category identification to 19 RIA and 10 ELISA laboratories. Each laboratory's raw data from the control sera were used to determine the cut-off point for positive (3 SD above the mean of control sera) in the disease relevant categories. RIA and ELISA methods were comparable in obtaining a low frequency of IAA in control sera. However, the laboratories using RIA methods found a much higher percentage of sera to be IAA positive among both newly diagnosed patients and healthy individuals who later developed diabetes than laboratories using ELISA methods (P less than 0.005). In contrast, there was considerable overlap in the percentage of sera from first degree relatives found positive by both assays. These data strongly suggest that IAA measured by RIA methodology are more disease related than those measured by ELISA methods. Consequently, RIA assays or assays proven to perform as well should be used to measure IAA associated with IDDM.

Autoantibodies↗

PubMed1992

Elevated levels of circulating adhesion molecules in IDDM patients and in subjects at risk for IDDM.

Serum levels of recently discovered circulating forms of adhesion molecules, ICAM-1 and L-selectin, were found to be elevated in IDDM patients and in subjects at risk for developing IDDM compared with 100 normal, nondiabetic blood donors. Both adhesion molecules were determined by sandwich ELISA. Serum concentrations of either clCAM-1 or cL-selectin were > 2SD of normal mean in 10 of 14 recent-onset IDDM patients (P < 0.05). Serum levels of clCAM-1 and cL-selectin did not correlate. In first-degree relatives, elevated adhesion molecule levels were observed in the 6 ICA+ individuals and in the ICA- individuals all (n = 14) with a genetic risk of IDDM (sharing HLA-DR3 and/or-DR4 with the diabetic relative) but not in the HLA-DR3- and/or -DR4- relatives (n = 13). We conclude that elevated clCAM-1 and cL-selectin levels occur independently of ICA status and probably reflect ongoing immune processes in recent-onset IDDM patients and first-degree relatives at risk for IDDM.

Adult↗

PubMed1992

Abnormal TNF production in prediabetic BB rats is linked to defective CD45R expression.

The genetic basis and diabetes association of aberrant tumour necrosis factor-alpha (TNF-alpha) production by activated peritoneal macrophages in diabetes-prone (dp) biobreeding (BB) rats was analysed. Southern blot analysis could not detect a restriction fragment length polymorphism for the TNF gene distinguishing dp BB rats from Wistar (Wi) rats and diabetes resistant (dr) BB rats. The contiguous genetic arrangement of lymphotoxin (LT) and TNF genes described in mouse and man was also found in the rat by cloning a chromosomal region covering both genes. In search of a polymorphic marker we amplified a (CA)n:(GT)n microsatellite in the TNF promoter region by polymerase chain reaction (PCR). We detected two alleles, (CA)26 and (CA)33, but no correlation with diabetes risk was seen. Crosses between dp BB rats and Wi or Lewis. 1A (Lew. 1A) rats, respectively, indicated that aberrant TNF-alpha production of activated macrophages is inherited dominantly with only weak penetrance. Analysis of the F2 generation and backcrosses with the two parental strains showed that aberrant TNF production co-segregates with lymphopaenia and defective CD45R expression, markers known to reflect a diabetes predisposing gene(s) outside the RT1 complex. We conclude that a single linkage group is responsible for both aberrant TNF production and defective T-cell maturation in dp BB rats.

Animals↗

PubMed1991

Postembedding immunocytochemistry for GABA and glycine reveals the synaptic relationships of the dopaminergic amacrine cell of the cat retina.

Postembedding electron microscope immunocytochemistry of glycine and GABA conjugated to colloidal gold has been applied to pre-embedded cat retina stained with the antibody against tyrosine hydroxylase (Toh+). Toh+ stained cells are the equivalent of A18 amacrine cells of Golgi descriptions (Kolb et al., '81). The dendrites of Toh+ cells synapse upon several different types of glycine-positive amacrine cell bodies. We suggest that these are the A8, A3/A4, and AII amacrine cell varieties by analogous immunocytochemical staining intensity, to glycine autoradiographic labeling intensity (Pourcho and Goebel, '85). The greatest number of synapses from Toh+ dendrites are directed at the least glycine-positive amacrine, which is the AII cell by all morphological criteria. A few glycine-positive profiles are also presynapatic to the Toh+ stained cell body itself. Toh+ profiles are also presynaptic to GABA-positive amacrine cell bodies. The commonest amacrine synapsed upon is very heavily labeled with GABA immunocytochemistry. We consider it to be the A17 amacrine cell, which is known to label strongly by [3H] muscimol autoradiography (Pourcho and Goebel, '83). The cell body of the Toh+ amacrine cell also receives many synapses, which appear to be GABA-positive, and Toh+ profiles running in stratum 1 of the inner plexiform layer (IPL) are both pre- and postsynaptic to GABA-positive amacrine cell profiles. In addition, the cell body and primary dendrites of the Toh+ cell receive input from a bipolar type and GABA- or glycine-negative profiles. GABA-positive profiles, belonging to the interplexiform cell (IPC), are synapsed upon by Toh+ profiles that run in the outer plexiform layer (OPL).(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗

PubMed1991

Activated macrophages kill pancreatic syngeneic islet cells via arginine-dependent nitric oxide generation.

IL-1 and TNF alpha are assumed to be major mediators of islet cell destruction during the pathogenesis of type 1 diabetes. Here we show by neutralization of the two cytokines with excess antibody that IL-1 and TNF alpha do not contribute to the cytotoxic activity of activated macrophages towards isolated islet cells. However, islet cells can be protected from lysis by depleting the culture medium of L-arginine or by adding the antagonist NG-monomethyl-L-arginine, both of which inhibit the generation of nitric oxide by activated macrophages. These results indicate a role of nitric oxide or its equivalent, the endothelium-derived relaxing factor in the development of type 1 diabetes. This is the first report showing that nitric oxide may damage normal cells and thus may be a hitherto unrecognized pathogenetic factor in tissue inflammation and autoimmune disence.

Animals↗

PubMed1991

Midget ganglion cells of the parafovea of the human retina: a study by electron microscopy and serial section reconstructions.

In this study we used serial section electron microscopy and three-dimensional reconstructions to examine four midget ganglion cells of the human retina. The four cells were located in the parafoveal retina 2.5 mm or 8 degrees from the foveal center. Both type a (with dendritic trees in distal inner plexiform layer) and type b (with dendritic trees in proximal inner plexiform layer) midget ganglion cells have been studied. These cells have dendritic trees of 7-9 microns diameter, and their complete dendritic trees in the neuropil of the inner plexiform layer can be analyzed, as well as the bipolar cell axon terminals having synaptic input, by a study of 100-150 serial ultrathin sections. Type a midget ganglion cells appear to be in a one-to-one relationship with flat midget bipolar cell axon terminals ending in distal inner plexiform layer. Type b midget ganglion cells are in a one-to-one synaptic relationship with invaginating midget bipolar cell axon terminals in proximal inner plexiform layer. The midget bipolar cells primarily involved with the midget ganglion cells do not contact other ganglion cell dendrites. In other words, midget bipolar cells appear to be in exclusive contact with single midget ganglion cells in the human retina. The midget ganglion cells receive most of their input from their associated midget bipolar cells in the form of ribbon synapses at dyads or monads (55-81 ribbons total), although ribbonless synapses are seen occasionally. In all four midget ganglion cells reconstructed, one or two other bipolar cell axon terminals, presumed to be from wide-field bipolar types, provide 1-3 ribbon synapses each. The number of amacrine synapses upon a midget ganglion cell's dendritic tree is approximately equal to the number of bipolar ribbon inputs (43%-56% bipolar ribbons: 44%-57% amacrine synapses). We assume from our knowledge of response characteristics of ganglion cells in other mammalian retinas (Nelson et al., '78: J. Neurophysiol. 41:427-483), that the type a midget ganglion cell and its exclusive connectivity with a flat midget bipolar cell forms a single cone connected OFF-center pathway, whereas the type b midget ganglion cell with its exclusive connectivity to an invaginating midget bipolar cell forms a single cone connected ON-center pathway, through the retina to the brain.

Animals↗

PubMed1991

Pharmacokinetics and metabolism of cyclophosphamide administered after total body irradiation of bone marrow transplant recipients.

High-dose cyclophosphamide is used immediately after total body irradiation (TBI) in conditioning for bone marrow transplantation (BMT). Possible interactions of the two treatment modalities were sought by measuring the blood pharmacokinetics of CP and 4-hydroxy-cyclophosphamide (4-HOCP) in patients undergoing BMT. There was a non-significant trend to a shorter half-life of CP compared to reported values. Exposure to 4-HOCP, the major metabolite of CP, did not appear to be altered by prior TBI of the patient.

Adolescent↗

PubMed1991

Macrophage cytotoxicity towards isolated rat islet cells: neither lysis nor its protection by nicotinamide are beta-cell specific.

In animal models of Type 1 (insulin-dependent) diabetes mellitus macrophages were shown to be the first immunocytes that infiltrate the pancreatic Langerhans islets in the autoimmune process. We now show direct macrophage cytotoxicity against isolated rat islet cells in an electron microscopical study, which permits investigation of the specificity of this process. Freshly isolated islet cells were co-incubated with syngeneic peritoneal macrophages at a target: effector-cell ratio of 1:2. After various time periods, the cells were directly fixed and embedded; the ratio of live and dead cells was evaluated by electron microscopy. Our results demonstrate that activated but not resident macrophages lyse islet cells in a time-dependent manner. After 15 h of co-incubation lysis of islet cells is complete. No islet cell-macrophage contacts and no differences between the lysis of Beta cells or non-Beta cells were observed during the observation period. Islet cells encapsulated in alginate were also lysed by macrophages as a direct proof for soluble mediator(s) of cytotoxicity. Nicotinamide protected islet cells from lysis in a dose-dependent manner. As a result of this electron microscopic study we conclude that even at very low target: effector ratios, activated macrophages lyse syngeneic islet cells regardless of islet cell type via secretion of humoral mediator(s).

Animals↗

PubMed1991

Proinsulin autoantibodies are more closely associated with type 1 (insulin-dependent) diabetes mellitus than insulin autoantibodies.

The disease association of autoantibodies to proinsulin and insulin was compared in patients with Type 1 (insulin-dependent) diabetes mellitus and first-degree relatives. Following the recommendation of the Fourth International Workshop on the Standardization of insulin autoantibodies, autoantibodies were determined by fluid-phase radioimmunoassay using equimolar concentrations of mono-125I-A14-insulin or -proinsulin to detect insulin or proinsulin autoantibodies, respectively. A higher prevalence of proinsulin autoantibodies vs insulin autoantibodies was found in 97 patients with Type 1 diabetes prior to insulin treatment (34.0% vs 22.7%, p less than 0.05) and in 16 islet cell antibody-positive relatives (43.8% vs 31.3%, NS). There was only one serum positive for insulin and proinsulin autoantibodies in 110 islet cell antibody-negative first degree relatives (0.9%). None of 88 normal sera contained proinsulin autoantibodies or insulin autoantibodies. There was a close correlation of proinsulin autoantibody and insulin autoantibody titres in individual sera (r = 0.95, p less than 0.01) due to crossreaction of all insulin autoantibodies with proinsulin. However, some proinsulin autoantibodies did not crossreact with insulin. Background binding in normal sera was lower for proinsulin autoantibodies. We conclude that proinsulin autoantibodies have a higher association to acute Type 1 diabetes than insulin autoantibodies.

Adult↗

PubMed1991

Suppression of low dose streptozotocin induced diabetes in mice by administration of a nitric oxide synthase inhibitor.

Nitric oxide has recently been identified as the primary toxic effector molecule in the lysis of islet cells by inflammatory macrophages. We show here that N-nitro-L-arginine-methylester (NAME), an inhibitor of endothelial and macrophage NO synthase partially suppresses diabetes development in the low dose streptozotocin induced diabetes model in C57BL/6J mice. Mean blood glucose levels were lower in the group receiving NAME throughout the observation period of 30d (p less than 0.05-0.001). Similar concentrations of NAME as expected in vivo were tested in vitro in macrophage-islet cell cocultures and were found to partially suppress NO production and islet cell lysis. We conclude that NO synthase activity is a pathogenetic factor in diabetes development.

Amino Acid Oxidoreductases↗

PubMed1991

Methimazole treatment aggravates low-dose streptozotocin-induced diabetes.

Treatment of mice with methimazole was found to modulate diabetes development following low-dose (5 x 40 mg/kg body weight) streptozotocin administration. The administration of 0.2 or 1 mg methimazole per kg body weight for 1-3 weeks significantly enhanced hyperglycemia. The enhancing effect of methimazole was also seen when administration began only after termination of streptozotocin injections. Methimazole treatment did not potentiate diabetes induced by a single high dose of streptozotocin (175 mg/kg). Serum thyroxin levels were not affected due to the short period of thyrostatic treatment. Semiquantitative immunocytochemistry of inflamed islets did not show a stronger influx of immune cells but rather a high activation state of infiltrated macrophages (M1/70 positive). We conclude that methimazole enhances the development of immune-mediated diabetes.

Animals↗

PubMed1991

Genetic analysis of susceptibility to diabetes mellitus in F2-hybrids between diabetes-prone BB and various MHC-recombinant congenic rat strains.

The occurrence of diabetes mellitus was analysed in F2 hybrids bred from diabetic BB male rats and females of congenic rat strains carrying different major histocompatibility (RT1) haplotypes on the common LEW strain genetic background. Permissiveness for the disease in BB rats is probably determined by class II genes of the RT1 complex, which are also present in normal rats. Class I and class III genes, notably the Hsp70 genes in the class III region, do not appear to be involved. Among the diabetic F2 hybrids, about 90% are shown by DNA analysis to be homozygous for the class II genes of the permissive RT1 haplotype. The segregation patterns are in accord with the action of two independent recessive genes, one of them being RT1-linked.

Animals↗

PubMed1991

Synaptic inputs to physiologically defined turtle retinal ganglion cells.

Two physiologically distinct, HRP-marked turtle retinal ganglion cells were examined for their morphology, GABAergic, glycinergic, and bipolar cell synaptic inputs, using electron-microscopic autoradiography and postembedding immunocytochemistry. One cell was a color-opponent, transient ON/OFF ganglion cell. Its center response to red was a sustained hyperpolarization, and its center response to green was a depolarization with increased spiking at onset. The HRP-injected cell most resembled G6, from previous Golgi-impregnation studies (Kolb, 1982; Kolb et al., 1988). It was a narrow-field bistratified cell, whose two broad dendritic strata peaked at approximately levels L20-25 (sublamina a) and L60 (sublamina b) of the inner plexiform layer. Bipolar cell synapses onto G6 were found evenly distributed between its distal and proximal dendritic strata, spanning L20-75. These inputs probably originated from several different bipolar cells, reflecting the complexity of the center response. GABAergic inputs were found onto both the distal and proximal strata, from near L20-L85. Only a few glycinergic inputs, confined to dendrites at L50-70, were observed. A second ganglion cell type that we physiologically characterized and HRP-injected had sustained ON-center, sustained OFF-surround responses. Two examples were studied; both were bistratified in sublamina b, near L60-70 and L85-100, with branches up to near L40. They resembled G10, from previous Golgi-impregnation studies (Kolb, 1982; Kolb et al., 1988). One cell was partially reconstructed to look at the distributions of GABAergic and glycinergic amacrine cell, and bipolar cell inputs. Although synapses from bipolar cells were equally divided between the two major dendritic strata of G10, the inputs to the distal stratum were close to the soma, and the inputs to the more proximal stratum were on the peripheral dendrites. This arrangement may reflect input from two distinct types of ON-bipolar cell. GABAergic and glycinergic inputs to G10 costratified to both strata and to the distal branches; but where glycinergic inputs were found distributed throughout the arbor, GABAergic inputs appeared to be confined to peripheral dendrites. We hypothesize on the neural elements involved and the circuitry that may underlie the physiologically recorded receptive fields of these two very different ganglion cell types in the turtle retina.

Animals↗

PubMed1991

Low dose streptozotocin causes stimulation of the immune system and of anti-islet cytotoxicity in mice.

Multiple low doses of streptozotocin are known to induce immune-mediated insulin deficient diabetes and depression of immune reactivity. We show here that immune depression by streptozotocin is not general but that some parts of the immune system are stimulated. Spleen cells from streptozotocin-treated mice showed enhanced cytotoxicity against syngeneic islet cells and various tumour cells including insulinoma cells. Several cell types served as effector cells, including macrophages, asialo GM1+ and Lyt-2+ lymphocytes. The increased cytotoxic activity towards islet cells was mostly due to macrophages and to non-asialo GM1+ and non-Lyt-2+ lymphocytes. A higher activation state of macrophages in low dose streptozotocin-treated mice was demonstrated by measurements of superoxide anion release. We conclude that multiple low doses of streptozotocin stimulate 'natural cytotoxicity', i.e. the non-MHC restricted cytotoxic activity of macrophages, T cells and natural killer lymphocytes.

Animals↗