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Biomedical subjects

H Kolb

Publications and source records attributed to H Kolb.

At least 361 records · Page 20Linked to original sources
PubMed1978

The pyridoxal-binding site in pyridoxamine-pyruvate transaminase.

The enzyme-substrate complex formed between pyridoxamine-pyruvate transaminase (EC 2.6.1.30) and pyridoxal was reduced with NaBH4. After carboxymethylation and tryptic digestion, pyridoxyl-lysine-containing peptides were isolated by a combination of Sephadex and Dowex 50 chromatography. Analysis of these peptides shows the structure around the pyridoxal-binding lysine residues to be Ala-Asp-Ile-Tyr-Val-Thr-Gly-Pro-Asx-Lys(Pxy)-Cys-Leu(Pro2, Gly2, Ala2, Met)(Thr, Leu2)Gly-Val-Ser-Glu-Arg. This structure differs from those found for the corresponding peptides from pyridoxal phosphate-dependent enzymes.

Amino Acids↗
PubMed1978

Cellular recognition by rat liver cells of neuraminidase-treated erythrocytes. Demonstration and analysis of cell contacts.

Freshly isolated rat liver cells adhere firmly to neuraminidase-treated rat or mouse erythrocytes but not to untreated erythrocytes. Binding between cells occurs only in the presence of calcium and is specially inhibited by D-galactose. We therefore suggest that cell adherence is mediated by a galactose-specific hepatic membrane receptor. Ultrastructural analysis of contact regions revealed point-like interactions between hepatic microvilli and erythrocytes and no broad areas of membrane contact. When liver cells are cultivated in vitro they lose their ability to bind erythrocytes within 24 h.

Animals↗
PubMed1978

Histopathology of hepatic acute graft-versus-host disease in the dog. A double blind study confirms the specificity of small bile duct lesions.

To test the association of small bile duct destructive lesions in the liver with acute graft-versus-host disease, a blind (coded) histological study was done comparing liver tissue from three groups of dogs given 1,200 R of total-body irradiation: one not given marrow infusions after irradiation, another given autologous hemopoietic grafts, and a third given marrow grafts from DLA-nonidentical unrelated donors. The dogs with unrelated grafts all developed graft-versus-host disease, and their liver histology was distinguished from that of the dogs in the other two groups by three findings: (1) extensive small bile ductule necrosis and atypia; (2) infiltrates of mononuclear cells around and in ductules; and (3) individual hepatocyte necrosis scattered throughout the lobules. Thus, bile duct lesions appear to be a good marker for assessing the presence and severity of hepatic graft-versus-host disease in dogs.

Animals↗
PubMed1978

Intracellular staining reveals different levels of stratification for on- and off-center ganglion cells in cat retina.

1. Ganglion cells in the retina of the cat were stained by intracellular dye injection after recording their responses to photic stimulation. 2. All cells encountered were divided into those giving on-responses and those producing off-responses, and the level of dendritic branching of these two groups was compared. Cells giving off-responses were found to branch high in the inner plexiform layer (IPL), near the amacrine cell bodies (sublamina a); those giving on-responses were found to branch lower in the inner plexiform layer (sublamina b). 3. Dye-injected cells varied widely in morphology and size, having cell bodies ranging in diameter from 8 to 32 micrometer and dendritic fields ranging from 25 to 490 micrometer in diameter; yet the sign of the response of each unit correlated only with the level of dendritic branching. Thus, no other morphological feature except stratification appears to be important in determining the sign of the response of these cells. 4. The stratification of ganglion cells into on- and off-layers parallels the distribution of the axon terminals of the flat and invaginating cone bipolars. Flat cone bipolars are in a position to contact off-center ganglion cells (in sublamina a) and invaginating cone bipolars are in a position to contact on-center ganglion cells (in sublamina b). 5. The rod and cone inputs to some cells were characterized by comparing their responses to deep red and blue rod-matched stimuli over a 2-log unit range starting at dark-adapted threshold. About half the cells appeared to be rod dominated under these conditions, whereas the others appeared to have mixed rod and cone signals. 6. The nature of the rod and cone pathways to ganglion cells is discussed.

Animals↗
PubMed1978

Chloroquine retinopathy in the rhesus monkey.

Chloroquine was administered intramuscularly 5 days a week to rhesus monkeys for as long as 4 1/2 years. No clinical, fluorescein angiographic, or electrophysiological evidence of retinal damage was observed. Yet chloroquine/chloroquine byproduct analysis of the ocular tissues revealed an enormous binding capacity of the pigmented tissues of the eye (choroid plus RPE, ciliary body, and iris) with eventual accumulation observed in the retina. Despite the normal ophthalmic appearance and function, extensive pathological changes occurred in the retinas and choroids of these experimental monkeys. The chloroquine caused an initial dramatic effect on the ganglion cells, with the photoreceptors affected shortly thereafter. Patching degeneration of the ganglion cells and photoreceptors then progressed over several years, with the choroid and pigment epithelium ultimately deteriorating as well.

Animals↗
PubMed1977

Characterization of syngeneic anti-idiotypic antibody against the idiotype fo BALB/c myeloma protein J558.

BALB/c mice were immunized against the idiotype of BALB/c myeloma J55,. Syngeneic, specific anti-idiotypic antibodies against this germ line idiotype were shown by the isoelectric focusing technique to be markedly heterogeneous. In fact, the heterogeneity of isogeneic anti-idiotypic sera appeared to be comparable to those of allogeneic anti-J558 sera, raised in A/J and CB20 mice. As a rule, individual mice exhibit different clonal spectra. By spleen cell transfer experiments, each individual spectrum of clones could be expanded in order to arrive at an estimate of the size of anti-idiotypic repertoires. These were found to be of the order of 7-16 different anti-idiotypic clones for an individual BALB/c mouse. From the infrequency of clonal repetition we conclude that the repertoire of the BALB/c strain must be well in excess of one hundred anti-idiotypic molecular species.

Animals↗
PubMed1977

The organization of the outer plexiform layer in the retina of the cat: electron microscopic observations.

The outer plexiform layer of the cat retina has been examined by electron microscopy of random and serial ultrathin sections in order that neural profiles might be positively identified and their synaptic relationships studied. Photoreceptors are interconnected by means of gap junctions as are the A horizontal cells. B horizontal cells and axon terminals do not appear to be engaged in any synapses apart from those with photoreceptors, while A horizontal cells make rare 'junctions' with cone bipolars only. Interplexiform cell processes probably account for all the conventional chemical synapses in the outer plexiform layer of cat retina.

Animals↗
PubMed1977

Synaptic connections of the interplexiform cell in the retina of the cat.

Electron microscopy of Golgi-impregnated material and of well fixed, ultrathin serial sections has revealed the synaptic connections of interplexiform cells in cat retina. In the inner plexiform layer these cells are postsynaptic to amacrine cells and probably presynaptic to both bipolars and amacrines. In the outer plexiform layer they are presynaptic to rod and cone bipolar cells and also pre- and postsynaptic to other interplexiform cell dendrites. The interplexiform cell in cat retina appears to be concerned with feeding back information from the inner plexiform layer to the dendrites of bipolar cells in the outer plexiform layer.

Animals↗
PubMed1977

Clones producing antibodies of more than one class.

Clones producing antibodies directed against oligo-D-alanine (D-ala) determinants have been demonstrated in X-irradiated recipient mice after transfer of limited numbers of spleen and thymus cells. Seven out of eighty-one recipients were found to have donor allotype clones, all of which produced IgG1 antibodies to D-ala; two of these clones also produced small quantities of IgG2a antibodies. In addition, each of the seven responder mice contained IgM antibodies to D-ala. Isoelectric focusing (IEF) patterns of anti-D-ala antibodies from each of the seven responder mice were restricted and compatible with one to three antibody types. Most of these IEF patterns were significiantly different from each other. Five mice have been used for a comparison of IgM and IgG1 combining sites by affinity and specifity measurements. In each case affinity and specificity of IgM and IgG1 antibodies were alike. No similarity was found when comparing IgM from one clone with IgG1 from another one. These data led us to conclude that a single precursor cell can give rise to a clone producing antibodies of the IgM class and different IgG subclasses all of which share combininig sites.

Animals↗
PubMed1977

A receptor for 'self' on lymphocytes.

A large population of lymphocytes is able to form rosettes with syngeneic, allogeneic or closely related xenogeneic erythrocytes. Similar results were found with spleen cells from mice, rats and rabbits. The highest numbers were found in mice where up to 30% of lymphocytes bound autologous erythrocytes. Rosette formation is probably due to stereospecific cell surface receptors since erythrocytes of distant xenogeneic origin were not recognized. Rosette forming cells do not seem to be restricted to the B-cell or T-cell compartment since mouse thymus cells as well as spleen cells from congenitally athymic (nude) mice bound erythrocytes to a similar degree.

Alpha-Globulins↗
PubMed1977

Ir-gene control of antibody class production.

The antibody response in mice to DNP-insulin is under Ir-gene control. The Ir gene defects in two strains have been analyzed. In both cases the IgG immune response was impaired whereas the IgM response was not affected. One H-2 gene haplotype was characterized by lack of IgG response, independent of the immunization protocol. A second H-2 haplotype manifested a low response of IgG after immunization with Bordetella pertussis as an adjuvant but a high response after complete Freund's adjuvant. It is proposed that a low level of T cell help induces the production of IgM antibodies, intermediate levels allow few IgG clones to develop, and high levels induce a heterogeneous IgG response.

Animals↗
PubMed1976

Structural basis for ON-and OFF-center responses in retinal ganglion cells.

The inner plexiform layer of the mammalian retina has a bisublaminar organization determined by restricted branching of the terminals of cone bipolar cells and dendrites of class I (large) and class II (small) ganglion cells. Comparison of dendritic field diameters and receptive fiedl center sizes of large ganglion cells suggests that neural circuitry in sublamina a conveys "OFF"-center properties and connections in sublamina b "ON"-center properties to retinal ganglion cells.

Animals↗