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Biomedical subjects

H C Bauer

Publications and source records attributed to H C Bauer.

At least 109 records · Page 6Linked to original sources
PubMed1986

DNA microspectrophotometry of bone sarcomas in tissue sections as compared to imprint and flow DNA analysis.

The aim of the present study was to establish an upper limit of diploidy for microspectrophotometric (MSP) DNA measurements in sections of mesenchymal tissue analyzing DNA data of a large number of normal cell populations. The reliability of this upper limit of diploidy for discriminating between diploid and hyperploid bone sarcomas was tested by analyzing the same tumors by MSP in imprint preparations and flow cytometry (FCM). The median DNA value of control cells in tissue sections was given arbitrary value of DNA index (DI) 1.0, denoting the diploid DNA content. The proportion of cells with DNA values exceeding DI 1.25 (greater than DI 1.25) was determined for each normal cell population. The maximum percentage of cells with DNA values exceeding DI 1.25, encountered by analysis of 91 normal cell populations in tissue sections, was 31%. This percentage was set as an upper limit of diploidy. Hence, tumors with a higher percentage of cells greater than DI 1.25 were classified as hyperploid. When we applied this criterion, 31 of 36 sarcomas analyzed by MSP in tissue sections were hyperploid, which was in complete agreement with FCM and MSP in imprints of the same tumors. Apart from discriminating between diploid and hyperploid tumors, an attempt was made to determine peak DNA values of sarcomas analyzed in tissue sections. Peak DNA values, as defined by a minimum of 30% of the cells within a class width of DI 0.25, could be determined for 23 of 36 tumors. These peak DNA values correlated well with corresponding peaks obtained by FCM.(ABSTRACT TRUNCATED AT 250 WORDS)

Bone Neoplasms↗
PubMed1986

Murine cortical brain cells are autoantigenic from a distinct developmental stage onwards.

The expression of autoantigens on murine cortical brain cells and their first appearance during development was studied. Autoreactivity was analyzed by weight increase and lymphocyte proliferation in the popliteal lymph node (PLN). Cortical brain cells or defined plasma membrane preparations were injected s.c. without adjuvant into syngeneic recipients. Weak, but significant T cell-dependent PLN enlargement was triggered with brain cells from adult mice. A stronger reaction could be elicited with one defined fraction of purified plasma membranes. The earliest appearance of the antigenic material in the plasma membrane fraction was observed on day 15 after birth. This time point correlates exactly with the completion of the blood-brain barrier in large parts of the central nervous system.

Animals↗
PubMed1986

Growth and ploidy of human osteosarcoma xenografts in serial passage in nude mice.

Six human osteosarcoma tumors have been transplanted to and maintained as xenografts in serial passage in nude mice. The xenografts, characterized by growth rate, histologic appearance, and DNA flow cytometric data, are now in the 6-17 passages in mice. Histologic appearances and growth rates of the xenografts were unchanged through all passages except for one xenograft in which the growth rate doubled in passage 3. All six tumors had hyperploid DNA contents. The ploidy levels were unchanged, compared to their original tumors, in all passages of five xenografts. One xenograft, concomitantly with the increase in growth rate, also doubled the ploidy from 2.8 to 5.6C. There was a good agreement between the proportion of S-phase cells and mitotic indices of the six xenografts. The growth rate, depending also on cell loss, was less related to the proliferative activity of the xenografts. It was concluded that osteosarcomas have a stable aneuploid DNA content in nude mice, but polyploidization can occur after a number of passages.

Animals↗
PubMed1986

Effects of bisphosphonates on the incorporation of calcium-45 and 3H-proline in orthotopic and in demineralized matrix-induced bone in rats.

The influence of the two bisphosphonates, 1-hydroxyethylidene-1, 1-bisphosphonate (HEBP) and dichloromethylene bisphosphonate (Cl2MBP), on bone formation was studied in demineralized matrix-induced bone in young rats. Cl2MBP was given in doses of 0.3 and 3 mg P/kg per day and HEBP 2,4, and 8 mg P/kg per day starting immediately after implantation of the bone matrix and continued until sacrifice at 3 weeks. Rates of collagen synthesis and mineralization of implants, femurs, and incisor teeth were quantified by assay of 3H-proline and 45Ca injected 24 h before death. New bone formation in implants was also evaluated by histologic examinations. Implants from Cl2MBP-treated animals had wider bone trabeculae than controls but were colonized by normal appearing hematopoietic tissue. Implants and femurs from both Cl2MBP groups had a higher ash content than controls, but uptake of the two isotopes was not affected. These results indicate that Cl2MBP, at these dose levels, inhibits bone resorption without affecting bone formation in rats. The uptake of 45Ca in implants decreased with increasing doses of HEBP; almost no ash or 45Ca activity was encountered with the highest dose. The bone in implants from this group appeared less mature, and only scanty areas of bone marrow were seen. The uptake of 3H-proline was not affected by HEBP. It appears that, in rats, HEBP primarily inhibits mineralization and resorption, whereas matrix formation remains largely unaffected.

Animals↗
PubMed1986

Influence of indomethacin on induced heterotopic bone formation in rats. Importance of length of treatment and of age.

The effect of indomethacin on heterotopic and orthotopic bone formation in rats was analyzed with respect to (1) length of treatment after implantation, (2) duration of the indomethacin induced inhibition of heterotopic bone formation, and (3) influence of age of the implant recipient. Three weeks after implantation of demineralized bone matrix, the ash weight of implants from rats receiving indomethacin 2 mg/kg body weight during the entire experiment was 31% lower than that of controls. Animals treated for only six days after implantation exhibited an almost equally pronounced inhibition. However, six weeks after implantation, the inhibition caused by six days of indomethacin treatment had almost dissipated. In older rats the implants of demineralized bone matrix induces smaller volumes of new bone than in younger rats, but indomethacin causes approximately the same degree of inhibition of osteoinduction. Orthotopic bone is not affected by indomethacin treatment. This study shows that a short period of indomethacin treatment at the time of implantation of demineralized bone matrix is sufficient to reduce experimental bone formation, but the inhibitory effect slowly diminishes if the inductive process is continuous. The results indicate that the inhibition of heterotopic new bone formation by indomethacin may be mediated through reduction of the initial inflammatory response or by reduced mesenchymal cell proliferation.

Aging↗
PubMed1985

Three secretory rates in human hepatoma cells.

It is presently unknown what factors regulate the rate of intracellular transport of secretory proteins. The human hepatoma cell line Hep G2 is highly differentiated and secretes many of the proteins characteristic of normal hepatocytes. The secretion kinetics of nine proteins by Hep G2 cells in culture was investigated using pulse-chase techniques and immunoisolation of proteins with monospecific antibodies. Our results show that the export of nine proteins falls into three discrete kinetic classes: (i) a rapidly secreted class with an intracellular retention half-time of 30-40 min (albumin, fibronectin, alpha-fetoprotein and alpha 1-proteinase inhibitor), (ii) an intermediate secreted class with a half-time of 75-80 min (ceruloplasmin, alpha 2-macroglobulin and plasminogen), (iii) and a slowly secreted class with an intracellular retention half-time of 110-120 min (fibrinogen and transferrin). Our findings that there are three distinct kinetic classes of secretory proteins strongly suggests that intracellular transport is selective and that proteins of the same secretory class share structural features which influence their rate of export.

Albumins↗
PubMed1985

Role of carbohydrate in glycoprotein secretion by human hepatoma cells.

We have previously shown that export of nine proteins by human hepatoma cells falls into three discrete kinetic classes with intracellular retention half-times of approximately 35 min, 77 min and 115 min. To determine if carbohydrate on secretory glycoproteins determines the secretory class we have measured the kinetics of export of the nine proteins after tunicamycin-treatment of cultures. We found no apparent correlation between the kinetic class of a secretory protein and sensitivity of secretion to tunicamycin-treatment. For example, three glycoproteins are exported with rapid kinetics and secretion of only one, alpha 1-protease inhibitor, is inhibited by tunicamycin treatment. In addition, three glycoproteins are secreted with intermediate kinetics and tunicamycin-treatment inhibits the secretion of two of these proteins, alpha 2-macroglobulin and ceruloplasmin but not the third, plasminogen.

Blood Proteins↗
PubMed1985

Specificity of neuronal factors which aggregate acetylcholine receptors on cultured myotubes.

Neuronal factors from conditioned medium of neuroblastoma X glioma hybrid cells or isolated from embryonic pig brain aggregate acetylcholine receptors (AChR) on cultured chicken and rat myotubes. A membrane surface protein labelled with a fluorescent monospecific antibody was not aggregated with the same treatment. Antibodies against AChR block the action of the aggregating factors but do not produce large aggregates themselves. These findings indicate that the factors specifically react with the AChR on developing myotubes.

Animals↗
PubMed1985

Influence of human alpha-interferon on four human osteosarcoma xenografts in nude mice.

Growth-inhibiting effects of human alpha-interferon (HuIFN-alpha) were investigated in four human osteosarcoma xenografts in nude mice. In addition to effects on growth, the HuIFN-alpha treatment was evaluated by histological examination and DNA flow cytometric analysis. Daily doses of 2 X 10(5) IU HuIFN-alpha completely arrested the growth of two osteosarcoma xenografts and partially inhibited one, whereas 1 X 10(6) IU/day were necessary to arrest the growth of the fourth. Growth inhibition was reversible and tumor size independent. The histological appearance, including mitotic indices, and S-phase proportions were unchanged in three xenografts. The mechanism of the HuIFN-alpha-induced growth inhibition of these three xenografts was therefore not considered to be a direct antiproliferative effect, but rather due to increased cell loss and/or increased cell cycle time. The modal DNA value of one xenograft was changed from aneuploid to diploid during HuIFN-alpha treatment. Histologically, these xenografts were partly replaced by normal appearing bone and bone marrow. The S-phase proportion was also reduced in these xenografts, implying that HuIFN-alpha can also have a direct antiproliferative effect.

Animals↗
PubMed1984

Three cholinergic neuroblastoma hybrid cell lines that form few synapses on myotubes are deficient in acetylcholine receptor aggregation molecules and large dense core vesicles.

Three neuroblastoma X glioma hybrid cell lines that synthesize and release acetylcholine but that form few or no synapses with cultured skeletal muscle cells lack two characteristics of neuroblastoma or hybrid cell lines that do form many synapses with myotubes: large dense core vesicles and the ability to increase the number of nicotinic acetylcholine receptor clusters on co-cultured myotube membranes. Functional synapse formation on myotubes was increased by co-culturing myotubes and cells from one of the defective lines with neuroblastoma cells that induce myotube acetylcholine receptor aggregation but which synthesize little or no acetylcholine.

Animals↗
PubMed1984

A few axonal proteins distinguish ventral spinal cord neurons from dorsal root ganglion neurons.

A series of proteins putatively involved in the generation of axonal diversity was identified. Neurons from ventral spinal cord and dorsal root ganglia were grown in a compartmented cell-culture system which offers separate access to cell somas and axons. The proteins synthesized in the neuronal cell somas and subsequently transported into the axons were selectively analyzed by 2-dimensional gel electrophoresis. The patterns of axonal proteins were substantially less complex than those derived from the proteins of neuronal cell bodies. The structural and functional similarity of axons from different neurons was reflected in a high degree of similarity of the gel pattern of the axonal proteins from sensory ganglia and spinal cord neurons. Each axonal type, however, had several proteins that were markedly less abundant or absent in the other. These neuron-population enriched proteins may be involved in the implementation of neuronal diversity. One of the proteins enriched in dorsal root ganglia axons had previously been found to be expressed with decreased abundance when dorsal root ganglia axons were co-cultured with ventral spinal cord cells under conditions in which synapse formation occurs (P. Sonderegger, M. C. Fishman, M. Bokoum, H. C. Bauer, and P.G. Nelson, 1983, Science [Wash. DC], 221:1294-1297). This protein may be a candidate for a role in growth cone functions, specific for neuronal subsets, such as pathfinding and selective axon fasciculation or the initiation of specific synapses. The methodology presented is thus capable of demonstrating patterns of protein synthesis that distinguish different neuronal subsets. The accessibility of these proteins for structural and functional studies may contribute to the elucidation of neuron-specific functions at the molecular level.

Animals↗
PubMed1983

Axonal proteins of presynaptic neurons during synaptogenesis.

Changes occur in the synthesis and axonal transport of neuronal proteins in dorsal-root ganglia axons as a result of contact with cells from the spinal cord during synapse formation. Dorsal-root ganglia cells were cultured in a compartmental cel culture system that allows separate access to neuronal cell bodies and their axons. When cells from the ventral spinal cord were cultured with the dorsal-root ganglia axons, synapses were established within a few days. Metabolic labeling and two-dimensional electrophoresis revealed that four of more than 300 axonal proteins had changed in their expression by the time synapses were established. The highly selective nature of these changes suggests that the proteins involved may be important in the processes of axon growth and synapse formation and their regulation by the regional environment.

Animals↗
PubMed1983

Laminin induces acetylcholine receptor aggregation on cultured myotubes and enhances the receptor aggregation activity of a neuronal factor.

The effect of several basement membrane components on the aggregation of acetylcholine (ACh) receptors on cultured myotubes was studied. Cultures were incubated for 16 to 24 hr with laminin, a heparan sulfate proteoglycan, collagen types IV and V, or fibronectin, alone, or together with medium conditioned by NG108-15 neuroblastoma X glioma hybrid cells (NCM). The number of ACh receptor aggregates per myotube was assayed by fluorescence microscopy of cultures stained with tetramethylrhodamine-labeled alpha-bungarotoxin. Laminin induced ACh receptor aggregation on primary rat myotubes and on myotubes formed by G8-1 clonal rat muscle cells. Laminin enhanced the receptor-aggregating activity of NCM in a concentration-dependent manner (0.6 to 6.0 micrograms/ml) and the number of aggregates formed in the presence of laminin and NCM together was greater than the sum of the aggregates induced by NCM and laminin separately. The aggregation factor in NCM is probably not laminin, since less than 10 ng/ml of laminin-like immunoreactivity was detected in NCM, and antiserum against laminin blocked the effects of laminin but had little effect on NCM aggregation activity. Collagen type V enhanced the receptor aggregation activity of NCM, but less strongly than laminin, and had little or no effect by itself. The other basement membrane components did not induce receptor aggregation or enhance the effect of NCM. Experiments in which ACh receptors were labeled before exposure of cultures to NCM and laminin indicated that laminin enhanced the rearrangement of receptors at the cell surface. Immunofluorescence microscopy indicated that laminin binds to the myotubes within 30 min and forms patches on the cell surface over a period of hours. Laminin bound to the myotube surface enhanced receptor aggregation as well as laminin continuously present in the culture medium. The results suggest the possibility that laminin could enhance the receptor aggregation activity of a neuronal factor(s) released at the developing neuromuscular junction.

Animals↗
PubMed1982

Modulation of morphology and plasma-membrane enzyme activities of rat thymocytes induced by specific antisera.

Lewis rat thymocytes were incubated with different ligands: specific rat alloantisera, rabbit xenoantisera against whole-rat thymocytes or against thymocyte plasma-membrane vesicles and the two mitogens: concanavalin A and the Ca++ ionophore A 23187. After treatment, a crude plasma-membrane fraction was repaired, and the activities of two plasma-membrane marker enzymes, alkaline phosphatase and gamma-glutamyl transferase, and a general membrane marker enzyme, lysolecithin acyltransferase, were determined. An increase of all marker enzyme activities was observed only when thymocytes had been incubated with alloantiserum directed against the gene products of their major histocompatibility complex (MHC) or with rabbit antiserum against syngeneic thymocytes. Anti-MHC alloantiserum against a nonrelevant haplotype increased moderately the gamma-glutamyltransferase activity. Alloantiserum directed against the weak histocompatibility antigens had no significant effect as had rabbit antiserum raised against thymocyte plasma-membrane vesicles. The mitogens concanavalin A and A 23187 both increased the activity of the alkaline phosphatase and lysolecithin acyltransferase. Scanning electron microscopy showed that treatment with alloantisera did not alter the cell shape drastically. In contrast, incubation with rabbit xenoantiserum against thymocytes resulted in cell rounding and deformation. Rabbit xenoantiserum against the plasma-membrane vesicles of thymocytes resulted in markedly disturbed or damaged plasma membranes.

1-Acylglycerophosphocholine O-Acyltransferase↗
PubMed1981

Changes of the internal organization of the plasma membrane correlated to the regeneration potency of the cell.

Internal organization of the plasma-membrane of rat thymocytes and pituitary tumor cells (GH3) was experimentally altered by low temperature and either changing osmolarity or adding drugs destroying the cytoskeleton. These treatments induce reversible aggregation of intramembrane particles of the plasma membrane. Thin section electron microscopy of the hypotonically shocked cells show all the cell organelles to be extremely swollen and the cytoplasmic space to be rather empty. Returned to physiological conditions, the cells show normal morphological aspects, accompanied by 'normal' permeability properties of the plasma membrane; the aggregation of intramembrane particles is reversed. The proliferation behaviour of GH3-cell is not affected by this treatment. This demonstrates a high regeneration potency of the mammalian cell and leads to the assumption that molecular components which are important for the survival of the cell must be structural (membrane) bound.

Animals↗
PubMed1981

Characterization and partial purification of a neuronal factor which increases acetylcholine receptor aggregation on cultured muscle cells.

Medium conditioned by NG108-15 neuroblastoma x glioma hybrid cells contains a factor which increases the number of acetylcholine receptor (AChR) aggregates on cultured myotubes. Protease digestion indicates that the AChR aggregation factor is a protein, and the molecular weight is from 150,000 to 250,000 daltons as estimated by ultrafiltration and gel filtration. Preparative isoelectrofocusing indicates that the aggregation factor has a pI of about 4.7. The factor is found in the soluble cytoplasmic fraction but not in the plasma membrane fraction of NG108-15 cells. Aggregation activity is not detected in the cytoplasm of liver cells or in the cytoplasm of C6BU-1 glioma cells. A possible developmental role for the aggregation factor is suggested by its presence in embryonic rat brain but not in adult rat brain. AChR aggregation factors found in the cytoplasm or conditioned medium of NG108-15 cells or in the cytoplasmic fraction of fetal brain have similar molecular weights and isoelectric points.

Acetylcholine↗
PubMed1981

A factor from neurons induces partial immobilization of nonclustered acetylcholine receptors on cultured muscle cells.

A factor or factors released by cultured NG108-15 neuroblastoma X glioma hybrid cells and added to the medium of rat myotube primary cultures was found to immobilize some of the previously mobile acetylcholine receptors in the myotube membrane. Partial receptor immobilization occurred within 3 h after the beginning of treatment with the NG108-15-conditioned medium factor and persisted for at least 24 h of continuous treatment. A similarly derived conditioned medium concentrate from the non-neuronal parent glioma cell line did not immobilize receptors, relative to untreated controls. Acetylcholine receptors were visualized by fluorescent alpha-bungarotoxin and their lateral motion was observed by the technique of fluorescence photobleaching recovery.

Animals↗