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Biomedical subjects

H Kolb

Publications and source records attributed to H Kolb.

At least 217 records · Page 12Linked to original sources
PubMed1991

Notes on technical progress in veterinary public health.

Scientific and technical progress in the field of veterinary public health (VPH) over the last one hundred years has contributed to the protection of consumer health and the environment. This report presents examples of the success achieved in the control of epizootics of tuberculosis, brucellosis, rabies and trichinellosis, which are also zoonotic diseases. The discussion also considers hygiene measures in relation to Listeria in food as well as certain challenges resulting from the spread of latent infections among farm animals. The increasing incidence of Salmonella infections among humans is also considered. Other important VPH tasks include the control of chemical residues of varying origin and of toxic biological substances in foods. Examples are also presented of measures taken and problems which arise in connexion with ensuring that meat is produced under hygienic conditions (meat inspection). The principles involved in efficient controls of establishments and products are outlined. Technical progress in consumer protection is exemplified by the processes of pasteurisation, cooling and freezing, and the limitation of additives. Other important tasks arise in the disposal of animal carcasses and wastes, and in the fields of animal welfare and genetic engineering. Future activities in VPH will depend upon proper education, onward and postgraduate training for veterinarians, and suitable infrastructures for research, examination and surveillance.

Animals↗
PubMed1991

Decreased expression of adhesion molecules on monocytes in recent onset IDDM.

The expression of adhesion molecules in monocytes of patients with recent onset type I diabetes was analysed. Monocytes were identified as CD14-positive cells by flow cytometry. The percentage of monocytes expression LFA-1 alpha, ICAM-1 and HLA-DR was slightly lower in recent onset type I diabetes (n = 13) compared to normal subjects (n = 15) and was significantly decreased after activation of cells with lipopolysaccharide and interferon-gamma for 5-24 hr. Receptor densities on adhesion molecule-positive monocytes and the expression of LFA-1 beta were normal. These data indicate that monocyte trafficking is abnormal in recent onset type 1 diabetes.

Adolescent↗
PubMed1991

Analysis of IL-2 receptor positive CD8(+)-T-lymphocytes grown from islets of NOD mice.

IL-2 receptor positive T-cells from leukocyte-infiltrated pancreatic islets of diabetes prone or acutely diabetic NOD mice were propagated in vitro by culture in interleukin-2 containing medium. Of 13 lines obtained after limiting dilution all were positive for the T-cell marker Thy-1 and for CD8. Considerable heterogeneity in T-cell receptor usage was noted. Seven lines expressed T-cell receptors using V beta 8, one line was positive for V beta 5 and two lines expressed a non V beta 5, non V beta 8 receptor. Finally, two further lines lacked T-cell receptors. None of the cell lines were cytotoxic to islet cells although 10 lines showed non MHC restricted lysis of one or more tumour cells including rat insulinoma cells. We conclude that IL-2 receptor positive CD8+ T-lymphocytes from NOD islets are heterogenous with respect to V beta T-cell receptor usage. The majority of these cells are not cytotoxic to islet cells.

Animals↗
PubMed1991

Analysis of TNF alpha-induced DNA strand breaks at the single cell level.

Treatment of L929 cells with TNF alpha initiates apoptosis and subsequent cell death. The authors have visualized sites of DNA damage in situ by using DNA polymerase to synthesize new strands from the DNA strands breaks as starting point. Biotin-dUTP was incorporated into the newly synthesized strand and visualized by immunocytochemistry. DNA strand breaks were first observed 3 to 4 hours after contact with TNF alpha and preceded cell death. Limiting doses of TNF alpha caused DNA strand breaks only in a subpopulation of L929 cells. At a low dose, TNF alpha led to DNA damage without any subsequent loss of cell viability. The new assay also detects DNase-induced single strand breaks and thus is able to visualize apoptotic as well as non-apoptotic types of DNA damage.

Animals↗
PubMed1991

[Local therapy measures in HIV-associated Kaposi's sarcoma with special reference to fractionation radiotherapy].

In 23 patients with HIV-associated Kaposi's sarcoma 53 tumor lesions were treated with fractioned radiotherapy. Indication for the radiotherapy were mostly cosmetic reasons in stigmatizing tumors, but also in several cases pain, oedema or functional deficits as a result of the tumor lesions. 21 patients received orthovoltage irradiation, the remaining four patients were treated with telecobalt therapy. A complete response was observed in 17%, a partial response in 76% and unchanged lesions in 4%. In two cases (4%), both were treated with telecobalt-therapy by large tumor masses, there occurred a further tumor progression inspite of the radiotherapy. In ten lesions, all with partial remission, we later observed a repeated tumor progression. Important side effects were signs of inflammation as mucositis and edema or hyperpigmentation. The occurrence of acute side effects can be reduced by fractionating of the radiotherapy.

Adult↗
PubMed1990

Distribution of immunoreactivity to protein kinase C in the turtle retina.

Immunocytochemical staining procedures using the HRP-complexed antibody to protein kinase C (PKC) have been carried out on the turtle retina. Wholemounts and frozen sections of retina have been studied by light microscopy to evaluate PKC immunoreactivity after stimulation of the retina with light and neurotransmitters known to be active in the vertebrate retina. The most dramatically stained sites are cone synaptic pedicles and bipolar cells under all conditions. Ganglion cells stain weakly under certain conditions. Applying the antibody to a 'control' retina under dark adapted conditions results in uniform background staining of both hyperpolarizing and depolarizing bipolar pathways, while stimulating the retina with K+ under dim light conditions results in discretely stained bipolar cells and a prominent band of staining in stratum 4 of the inner plexiform layer. Stronger stimulation of bipolar cells with their terminals contributing to strata 3 and 4 and the continuous dominant band in stratum 4 can be elicited with incubation of the retina in neurotransmitter agonists, GABA and dopamine. Incubation with dopamine, in particular, brings out the putative dopaminergic amacrine cell. The only condition in which a strong band in stratum 2 can be demonstrated is under stimulation with a flashing bar of spot of light. Thus K+ and neurotransmitter stimulation elicit PKC staining in neurons contributing to the ON or depolarizing sublamina of the IPL, while intermittent flashing light stimulus is required to elicit PKC staining in the OFF or hyperpolarizing sublamina of the IPL.

Animals↗
PubMed1990

Identification of pedicles of putative blue-sensitive cones in the human retina.

Cone photoreceptor pedicles from midperipheral regions of the human retina (6 mm from the foveal center) have been studied by light and electron microscopy. Three areas of cone pedicle mosaic were serially thin-sectioned, in the tangential plane, from the inner border of the outer plexiform layer to the emergence of the cone axons from the cone pedicles. Semithin sections were then collected from the cone axon level through the cone cell bodies to the cone inner segment level. Two hundred twenty-one cone pedicles were followed by this means to their respective inner segments. Eight percent of the cone pedicles were from cones with inner segment characteristics of the blue cones. All 221 cone pedicles were reconstructed by tracing images from electron micrographs. The cone pedicle locations, surface areas, telodendrial projections, and synaptic ribbons could then be measured by morphometry and analyzed by statistical methods. Some selected cone pedicles were reconstructed by computer graphics methods. The cone pedicles identified as belonging to the blue cone type could be distinguished from the surrounding longer wavelength types on the following morphological criteria: 1) they were smaller (50% the area of the surrounding pedicles), 2) they contained shorter synaptic ribbons, 3) they exhibited essentially no telodendrial contact to neighboring cone pedicles, 4) they were positioned slightly more vitread in the outer plexiform layer than neighboring pedicles, and 5) their irregular occurrence in the cone mosaic coincided with the distribution criteria established in our previous paper (Ahnelt et al: J. Comp. Neurol. 255:18-34, '87) for putative blue sensitive cones in midperipheral human retina.

Color Perception↗
PubMed1990

Tumour necrosis factor alpha production is upregulated in diabetes prone BB rats.

Following activation peritoneal macrophages from diabetes prone BB rats secreted strikingly higher amounts of tumour necrosis factor alpha than found for macrophages from diabetes resistant or normal Wistar rats. Enhanced tumour necrosis factor alpha production was detected prior to the occurrence of insulitis. Cultures of macrophages derived from precursor cells in diabetes prone BB rat bone marrow also showed upregulated tumour necrosis factor alpha secretion upon challenge with endotoxin and interferon gamma. Tumour necrosis factor alpha hypersecretion may contribute to autoimmune diabetes by affecting thymic and post-thymic T-cell maturation and by promoting pancreatic islet inflammation.

Animals↗
PubMed1990

The synaptic organization of the dopaminergic amacrine cell in the cat retina.

The dopaminergic amacrine cells of the cat retina have been stained by immunocytochemistry using an antibody to tyrosine hydroxylase (Toh). The complete population of Toh+ cells has been studied by light microscopy of retinal wholemounts to evaluate morphological details of dendritic structure and branching patterns. Selected Toh+ amacrine cells have been studied by serial-section electron microscopy to analyse synaptic input and output relationships. The majority of Toh+ amacrine cells occur in the amacrine cell layer of the retina and have their dendrites ramifying and forming the characteristic rings in stratum 1 of the inner plexiform layer. A minority of Toh+ cells have cell bodies displaced to the ganglion cell layer but their dendrites also stratify in stratum 1. All Toh+ cells have some dendritic branches running in stratum 2 as well as in stratum 1, and frequently they have long 'axon-like' processes (500-1000 microns long) dipping down to run in stratum 5 before passing up to rejoin the major dendritic arbors in stratum 1. In addition Toh+ stained processes follow blood vessels in the inner plexiform layer and in the ganglion cell layer. A population of Toh+ cells found in the inferior retina appears to give rise to stained processes that pass to the outer plexiform layer and therein to run for as far as one millimeter. Electron microscopy reveals that Toh+ amacrine cells are postsynaptic to amacrine cells and a few bipolar cell terminals in stratum 1 of the inner plexiform layer and are primarily presynaptic to AII amacrine cell bodies and lobular appendages, and to another type of amacrine cell body and amacrine dendrites hypothesized to be the A17 amacrine cell. The Toh+ dendrites in stratum 2 are presynaptic to AII lobular appendages primarily. Stained 'axon-like' processes running in stratum 5 prove to be presynaptic to AII amacrine dendrites as they approach the rod bipolar axon terminals and they may also be presynaptic to the rod bipolar terminal itself. The Toh+ stained dendrites that have been followed in the outer plexiform layer run along the top of the B-type horizontal cell somata and may have small synapses upon them. The only clear synapses seen in the outer plexiform layer are from the Toh+ profiles upon vesicle filled amacrine-like profiles that are in turn presynaptic to bipolar cell dendrites in the outer plexiform layer. We presume the cells postsynaptic to the Toh+ dendrites in the outer plexiform layer are interplexiform cells.(ABSTRACT TRUNCATED AT 400 WORDS)

Animals↗
PubMed1990

A 'puff and advance' technique for visually controlled staining of turtle retinal ganglion cells.

We describe a 'puff and advance' technique for visually controlled staining of retinal ganglion cells (GCs) in the unfixed, living retina for light and electron microscopy. Glass microelectrodes are filled with rhodamine-isothiocyanate labeled horseradish peroxidase (Rh-HRP), or Lucifer yellow (LY), or a mixture of both, or with 5,6-carboxytetramethylrhodamine (5,6-Rh) and advanced tangentially through the GC layer with microscopic observation using epifluorescence. Brief "puffs" of LY or 5,6-Rh are constantly ejected from the advancing electrode tip by a train of negative current pulses. GC penetration is signaled by virtually instantaneous staining of its soma (and eventually its axon and dendrites if the electrode is not advanced further). An impaled GC can be electron densely stained with the Rh-HRP complex by switching to positive current pulses. The extent of dye filling is monitored through the microscope using a filter combination appropriate for the dye. After fixation, standard histochemical procedures reveal HRP stained GCs in wholemount views for light microscopical examination. Furthermore, the preservation of the labeled cells and the neuropil is of a quality to allow electron microscopic analysis for synaptic input. This technique can be used in combination with LY backfiling of GCs from the optic nerve and with retinas in which GCs have been prelabeled with rhodamine beads retrogradely transported from the optic tectum as well.

Animals↗
PubMed1990

Proinsulin autoantibodies: association with type I diabetes but not with islet cell antibodies, insulin autoantibodies or HLA-DR type.

Antibodies reacting with proinsulin but not with insulin determinants have been observed recently in Type I diabetes. We describe here that ELISA-determined proinsulin autoantibodies (IgG-PAA) also occur in first-degree relatives of IDDM patients (38/513, 7.4% vs 1.9% in controls, P less than 0.025). In contrast to insulin autoantibodies (IgG-IAA) and islet cell antibodies (ICA) no association with HLA type was found. Furthermore, IgG-PAA occur independently of IgG-IAA and ICA. We conclude that the humoral autoimmune response to proinsulin determinants is under separate genetic control.

Autoantibodies↗
PubMed1990

Essential contribution of macrophages to islet cell destruction in vivo and in vitro.

A number of observations indicate an essential role of macrophage activity in the development of hyperglycemia in animal models of Type I diabetes. Administration of macrophage-toxic silica particles prevents spontaneous diabetes development in BB rats or NOD mice. The same result was noted in the low-dose streptozotocin-induced diabetes model in mice. Macrophages appear to be the first immune cells infiltrating islets during early insulitis. Macrophages in inflamed islets of BB rats bear the ED1 marker, whereas resident islet macrophages are ED2-positive. In vitro, ED1-positive macrophages were found to lyse pancreatic islet cells to a similar degree to various tumor cells but not normal thyrocytes. Macrophage-mediated lysis of islet cells was inhibited in the presence of 10-100 mM nicotinamide.

Animals↗