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Biomedical subjects

H Mayer

Publications and source records attributed to H Mayer.

At least 181 records · Page 10Linked to original sources
PubMed1990

Morphological, biochemical, and molecular biological characterization of a rat rhabdomyosarcoma cell line during differentiation induction in vitro.

BA-HAN-1C is a clonal rat rhabdomyosarcoma cell line consisting of proliferating mononuclear tumor cells, some of which spontaneously fuse to form terminally differentiated postmitotic myotubelike giant cells. Exposure to retinoic acid resulted in an inhibition of proliferation and a marked increase in cellular differentiation. The number of myotubelike giant cells significantly increased, and about 30% of the mononuclear tumor cells exhibited morphological features of rhabdomyogenic differentiation which were not observed in the mononuclear cells of untreated cultures. Morphological differentiation was paralleled by an increase in total creatine kinase activity as a biochemical marker of differentiation. These effects of retinoic acid were preceded by an increased expression of proto-oncogene raf and transient expression of proto-oncogene fos. The maximum level of fos expression was observed at 15 min and of raf at 12 hr after exposure to retinoic acid. No expression of the proto-oncogenes src, myb, myc, ros, mos, erbA, and erbB was detected.

Animals↗
PubMed1990

Effects of parathyroid hormone fragments on the growth of murine mandibular condylar cartilage in vitro.

The present study showed that the fragment hPTH (1-34) is mitogenic in organ cultures of neonatal mandibular condylar cartilage, and even more so in late fetal condyles. Three fragments of hPTH were used to clarify which part of the molecule possesses a mitogenic effect alike that of the native hormone: hPTH (1-34), (28-48) and (53-84). [3H]thymidine incorporation into trichloracetic acid insoluble material and quantitative autoradiography were employed in a serum-free medium to assess the effects of these fragments while light and electron microscopy studies served for morphological evaluations. It became evident that the fragment hPTH (1-34) enhanced the incorporation of [3H]thymidine, a fact that could be noted only in serum-free medium. The putative target cells for the effects of hPTH (1-34) were the chondroporogenitor cells which also appeared to have experienced a blockage in their differentiation into chondroblasts. Ultrastructurally, the latter cells responded in the formation of adherent profiles of plasma membranes, whereas the differentiated zone of the cartilage reduced its size. Using serum-free medium, hPTH (1-34) also brought about an inhibition in alkaline phosphatase activity, a fact that was not encountered in medium containing serum. By contrast, hPTH (28-48) had no mitogenic effect, although treated specimens revealed morphological changes in the chondroprogenitor cell zone along with an enhancement of cartilage cells hypertrophy. No significant effects on either mitogenecity or morphology could be noted in hPTH (53-84)-treated cultures.

Animals↗
PubMed1989

Heterogeneous response to differentiation induction in different clonal subpopulations of a rat rhabdomyosarcoma cell line (BA-HAN-1).

Three clonal subpopulations (A, B, C) isolated from the same rhabdomyosarcoma of the rat were tested and compared for their susceptibility to differentiation induction using retinoic acid (RA), dimethylformamide (DMF), and N-monomethylformamide (NMF). These subpopulations differ in that a block to spontaneous differentiation is imposed at different stages which are characteristic for each subpopulation. Whereas tumor cell proliferation was significantly inhibited (P less than 0.001) in all three subpopulations, the effects of RA, DMF, and NMF on tumor cell differentiation were strikingly heterogeneous. The response was most marked in subpopulation C, as evidenced by a significant increase in the number of terminally differentiated myotube-like giant cells (P less than 0.001) and in biochemical differentiation, as indicated by the creatine kinase activity (P less than 0.05). Between 5% (DMF and NMF) and 30% (RA) of the mononuclear cells in subpopulation C exhibited thick and thin myofilaments, which were never observed in the mononuclear cells of the control. In contrast, subpopulation A and B responded to RA, DMF, and NMF quite heterogeneously with an increase in biochemical differentiation, whereas terminally differentiated myotube-like giant cells were never observed. These results demonstrate that the therapeutic potential of differentiation induction in malignant tumors may be impaired by tumor heterogeneity.

Animals↗
PubMed1989

The core region of Proteus mirabilis R110/1959 lipopolysaccharide.

The complete core structure present in the lipopolysaccharide of the R mutant R110/1959 from Proteus mirabilis (Proteus type II core) was investigated using methylation analysis and a number of degradation methods such as Smith degradation and beta-elimination. These studies combined with earlier work on a Rc-type mutant of P. mirabilis O28 (R4/O28) which shares the same inner core region, allowed formulation of the complete core structure of the Proteus type II core as shown in Scheme 1. (formula; see text) A characteristic feature of the Proteus core of type II is the presence of two units of D-galacturonic acid (DGalA); one in terminal, the other one in a chain-linked position. In addition, the presence of the two isomers of glycero-D-manno-heptose (LDHep and DDHep) and the lack of galactose are conspicuous. DDHep occupies a terminal position in the external core region, whereas the three units of LDHep in addition to dOclA form, as in other enterobacterial core types, the internal core region. The taxonomic significance of the presence of DGalA in the Proteus type II core, but also in all R cores of other Proteeae investigated so far, will be discussed.

Carbohydrate Conformation↗
PubMed1989

The central part of parathyroid hormone stimulates thymidine incorporation of chondrocytes.

The stimulation of DNA synthesis in primary cell cultures of chicken chondrocytes by parathyroid hormone was studied by assaying [3H]thymidine incorporation into DNA. Optimal assay conditions were determined by varying cell age, plating density, and incubation time. Under these conditions DNA synthesis was significantly stimulated by parathyroid hormone (PTH) and some of its fragments: cells treated with human (h)PTH(1-84), bovine (b)PTH(1-34) and [Nle8,18,Tyr34]bPTH(3-34)amide and hPTH(13-34) displayed 2.6-fold enhanced [3H]thymidine incorporation in a dose-dependent manner. The fragment hPTH(28-48) led to a similar stimulation, whereas [Tyr43]hPTH(43-68) and [Tyr52,Asp76]hPTH(52-84) had no effect. Using a series of synthetic hPTH peptides covering the central region of the hormone molecule (residues 25-47), we could delimitate further this putative mitogenic functional domain to a core region between amino acid residues 30 and 34. The effect of PTH on [3H]thymidine incorporation could not be mimicked by forskolin, indicating that the corresponding signal is not mediated by cAMP. It is, however, inhibited by EGTA and cannot be provoked in the absence of calcium ions in the medium. Therefore, the results presented indicate a hitherto unidentified functional domain of PTH in the central part of the molecule which exerts its mitogenic effect on chondrocytes in a cAMP-independent manner but seems to involve calcium ions for signal transduction.

Amino Acid Sequence↗
PubMed1989

Purification and characterisation of a growth factor from porcine bone.

A growth factor was extracted from porcine bone matrix by demineralisation and purified by heat and acid treatment, hydroxyapatite chromatography and gel filtration under dissociative conditions and reverse-phase HPLC. Using the mitogenic response of osteoblast-progenitor cells from embryonic chicken, a mitogenic activity was purified 3000-fold. The mitogenic protein thus purified shows an apparent molecular mass of 13.5 kDa in both the nonreduced and reduced form on sodium dodecyl sulfate/polyacrylamide gel electrophoresis. The mitogenic activity is sensitive to proteinase K, dithiothreitol, and resistant to DNAse, RNase, heat (70 degrees C) and pH (3-10). The factor stimulates the proliferation of osteoblast-progenitor cells from embryonic chick at a concentration of 1 ng/ml. It is active on cells from skin, periosteum and sternum and has no or little activity on cells of the calvaria, intestine or kidney of embryonic chick or on mouse AKR-2B/Balb c/3T3 cell line.

Animals↗
PubMed1989

Structural analysis of the nontoxic lipid A of Rhodobacter capsulatus 37b4.

Lipid A from Rhodobacter capsulatus 37b4 consists of a D-glucosaminyl-(beta 1-6)-D-glucosamine disaccharide backbone, carrying diphosphorylethanolamine at C-1 of the reducing glucosamine and phosphorylethanolamine at C-4' of the nonreducing glucosamine. 1,4'-Bisphosphorylated lipid A, lacking the polar head groups, was also encountered and contributed to the observed microheterogeneity in the phosphate substitution. The amino functions of both glucosamines are substituted almost entirely by the rare 3-oxotetradecanoic acid, which is a characteristic constituent of lipid A in the genus Rhodobacter. 3-Hydroxydecanoic acid is ester-bound at C-3 and C-3' of the glucosamine disaccharide and the one at the nonreducing glucosamine (C-3') is partially substituted by dodecenoic acid to form an ester-bound diester. In free lipid A, hydroxy groups at C-4 and C-6' of the glucosamine disaccharide are unsubstituted. C-6' being the putative attachment point of the lipopolysaccharide core. The nontoxic Rhodobacter capsulatus lipid A shows extensive serological cross-reaction with the toxic Salmonella lipid A. Structural similarities in the hydrophilic part of both types of lipid A, dissimilarities in the hydrophobic part and their impacts on serologic properties are discussed.

Binding Sites↗
PubMed1989

Expression of human parathyroid hormone in Escherichia coli.

Human parathyroid hormone (PTH) has been expressed in Escherichia coli as a cro-beta-galactosidase-hPTH fusion protein under temperature-sensitive control of the lambda phage PR promoter. The lacZ gene has been truncated to a different extent revealing an optimal length of the prokaryotic peptide portion between 199 and 407 amino acid residues. Up to 250 mg of pure fusion protein have been obtained from 1-liter E. coli culture by stepwise solubilization with urea. The linkage between the prokaryotic and the eukaryotic protein moiety consists of an Asp-Pro peptide bond and therefore is easily cleavable by acid treatment. A simple procedure for the purification of the hormone is described. The resulting recombinant hormone reacts with anti-PTH antibodies and stimulates renal adenylate cyclase identically to bovine or human PTH.

Adenylyl Cyclases↗
PubMed1989

Lipid A with 2,3-diamino-2,3-dideoxy-glucose in lipopolysaccharides from slow-growing members of Rhizobiaceae and from "Pseudomonas carboxydovorans".

Lipid A's from two Bradyrhizobium species and from the phylogenetically closely related species "Pseudomonas carboxydovorans" were found to contain 2,3-diamino-2,3-dideoxy-glucose as lipid A backbone sugar. In contrast, three representatives of the genus Rhizobium, as well as the phylogenetically related species Agrobacterium tumefaciens, contain solely glucosamine as lipid A backbone sugar. These findings support independent studies on the phylogenetical relatedness based on 16S rRNA-data of the genus Bradyrhizobium with "Pseudomonas carboxydovorans" and Rhodopseudomonas palustris, which form a tight phylogenetical cluster and which all contain the 2,3-diamino-2,3-dideoxy-glucose-containing lipid A. The relatedness of these species to the glucosamine-containing species of the genus Rhizobium and to Agrobacterium tumefaciens is rather distant as documented by 16S rRNA studies.

Electrophoresis, Polyacrylamide Gel↗
PubMed1989

Temperature-dependent incorporation of 4-amino-L-arabinose in lipid A of distinct gram-negative bacteria.

The presence and the relative amount of 4-amino-L-arabinose in lipopolysaccharides of members of the Enterobacteriaceae family and in a single strain of Chromobacterium violaceum has been studied with regard to growth-temperature dependent variations. Changes in the presence and the amount of 4-amino-L-arabinose (4-AA) were observed in almost all cases, but the variations observed were not consistent among different species. While Salmonella minnesota and Proteus mirabilis showed higher levels of incorporation at higher temperatures, the S- and R-forms of Yersinia enterocolitica showed the opposite effect, i.e. only marginal incorporation by growth at 10 degrees C. Chromobacterium violaceum, however, showed no significant alteration in the 4-amino-L-arabinose content when growth either at 14 or at 37 degrees C. DOC-PAGE pattern of isolated lipopolysaccharides showed characteristic profiles indicating that the O-chain-synthesis of distinct Enterobacteriaceae is also differently influenced by changes in growth temperature.

Arabinose↗
PubMed1989

Detection of enterobacterial common antigen on bacterial cell surfaces by colony-immunoblotting: effect of its linkage to lipopolysaccharide.

A colony-immunoblotting procedure is described which allows a quick screening of high numbers of bacteria for their Enterobacterial Common Antigen phenotype. In this assay the intensity of reaction is dependent on the carrier to which ECA is linked and which anchors ECA in the outer membrane. Bacteria containing LPS-linked ECA react stronger in this and in other immunoassays than bacteria containing only the phospholipid-linked ECA.

Antigens, Bacterial↗
PubMed1989

Heterogeneous response to differentiation induction with different polar compounds in a clonal rat rhabdomyosarcoma cell line (BA-HAN-1C).

The clonal rat rhabdomyosarcoma cell line BA-HAN-1C was tested for its susceptibility to differentiation induction with different polar compounds. This cell line is composed of proliferating mononuclear tumour cells, some of which spontaneously fuse to form terminally differentiated postmitotic myotube-like giant cells. Exposure of BA-HAN-1C cells to dimethylsulphoxide (DMSO), hexamethylene bisacetamide (HMBA), sodium butyrate (NaBut) and N-monomethylformamide (NMF) resulted in a significant inhibition of proliferation (P less than 0.001) and in a simultaneous increase in differentiation. The response was most pronounced after exposure to NMF as evidenced by a marked increase in the creatine kinase activity used as a biochemical marker of differentiation (P less than 0.05) and the number of terminally differentiated myotube-like giant cells (P less than 0.001). Furthermore, about 5% of the mononuclear cells exhibited thick and thin myofilaments which were never observed in the mononuclear cells of the control. In contrast, the effects of DMSO, HMBA and NaBut were exclusively confined to a significant increase in biochemical differentiation (P less than 0.05), whereas no increase in morphological differentiation was observed and the number of myotube-like giant cells even significantly (P less than 0.001) decreased. This heterogeneous response to differentiation induction with different polar compounds probably indicates different mechanisms of action and suggests that the induction of biochemical differentiation might be independently regulated from events leading to cell fusion and terminal differentiation.

Acetamides↗
PubMed1989

A psychosociomedical prediction model of response to treatment by chronically disabled workers with low-back pain.

There has been much interest in identifying variables that can predict which individuals are susceptible to developing chronic low-back pain. There currently are a number of studies that are evaluating primary predictors (which uninjured workers are likely to develop chronic low-back pain) and secondary predictors (which workers with acute episodes will develop chronic pain). The present study reports the first results from a large-scale investigation of tertiary predictors. Specifically, it addresses the issue of what psychosociomedical variables are predictive of success/failure in response to a comprehensive Functional Restoration treatment program by workers who are chronically disabled with low-back pain. Three stages were involved in the development of this prediction model. First, a group of treatment and research professionals who had extensive experience in the area of chronic low-back pain identified an array of 42 variables, from a larger pool of quantified physical, psychosocial, and medical parameters rated to be important with this patient population.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1989

Calcium regulates parathyroid hormone messenger ribonucleic acid (mRNA), but not calcitonin mRNA in vivo in the rat. Dominant role of 1,25-dihydroxyvitamin D.

In vivo 1,25-dihydroxyvitamin D3 (1,25(OH)2D3) decreased PTH and calcitonin gene transcription. A low calcium is the major signal for PTH secretion, and a high calcium for calcitonin secretion. We report here that calcium has no effect on calcitonin messenger RNA (mRNA) levels in vivo in the rat, but that a low calcium markedly stimulates PTH mRNA levels. Serum calcium was decreased by ip phosphorus and increased by calcium gluconate (ip or iv infusion) and demonstrated that a low serum calcium markedly increased PTH mRNA levels whereas a high serum calcium had no effect. There was no change in mRNAs for calcitonin or actin in the same thyroparathyroid extracts. After phosphorus ip serum calcium decreased from 10.4 to 8.5 mg/dl and PTH mRNA increased up to 3-fold at 1, 3, and 6 h. Gel blots showed that a low calcium increased PTH mRNA levels with no change in its size (833 base pairs). Calcitonin ip decreased both serum calcium and phosphorus with an up to 5-fold increase in PTH mRNA at 1 h, thus demonstrating that the effect of phosphorus on PTH mRNA was due to the low serum calcium and not the high serum phosphorus. When phosphorus and 1,25(OH)2D3 (100 pmol/100 g) were injected together, despite the low serum calcium, there was a decrease in PTH mRNA levels. These results show a linear relationship between calcium and PTH gene expression, but not calcitonin or actin, with a dominant role for 1,25(OH)2D3.

Animals↗
PubMed1989

Quantifying postoperative deficits of physical function following spinal surgery.

This study evaluates the degree of objectively quantified physical deconditioning of spinal surgery patients. The object is to evaluate the data in terms of the pain and disability claimed by 35 male and 11 female patients three months after spinal surgery. Among the males, two subgroups (i.e., disc excision or spinal fusion) were evaluated. All patients reported subjective indices of pain/disability and completed quantified tests of lumbar motion, sagittal trunk strength, lifting capacity, and bicycle ergometry. In general, true lumbar motion was markedly restricted to 50%-60% and trunk strength means were below 50% of gender-specific normative values. There were similar deficits for lifting capacity. Those who had spinal fusions tended to perform poorly, with a relatively high incidence of pain/disability. There were no differences found between the male group and subgroups who were gainfully employed or had a brief period of disability prior to surgery or had low subjective pain/disability. These results indicate that a patient's subjective pain/disability were not a reliable measure of functional capacity by three months postoperatively. Regardless of working status, pain level, or brevity of disability, there was a significant loss of performance ability and risk of persistent dysfunction after surgical treatment.

Adult↗
PubMed1988

Increased synthesis of human parathyroid hormone in Escherichia coli through alterations of the 5' untranslated region.

The expression of human parathyroid hormone (hPTH) in Escherichia coli was optimized by variations of the spacing sequence between the ribosome-binding site (RBS) and the beginning of the gene (ATG) and by increasing the complementarity of the RBS to the 16 S rRNA. The expression level of 3 micrograms/liter increased more than 100-fold to 475 micrograms/liter as a direct consequence of modifications in the region 5' of the gene.

Base Sequence↗
PubMed1988

Structural studies on the core and lipid A region of a 4-amino-L-arabinose-lacking Rc-type mutant of Proteus mirabilis.

The structure of the 4-amino-L-arabinose-lacking lipopolysaccharide of the Proteus mirabilis Rc-type mutant R4, derived from wild-type O28, was elucidated. The lipopolysaccharide core structure has previously been partially characterized. The linkage between heptose and deoxyoctulosonic acid(dOclA) is now reported, as well as the structure of the lipid A moiety of this mutant strain. Besides the tentative identification of an alpha-linked glucosamine disaccharide in the lipid A backbone accompanying the usual beta 1----6-linked glucosamine-disaccharide, the only significant structural variation to previous studies was the lack of substitution of the C-4' phosphate by 4-amino-L-arabinose. In addition, the substitution at C-8 of one dOclA unit by 4-amino-L-arabinose, previously reported for the R45 mutant of P. mirabilis 1959, is lacking in this R mutant. Also in addition to previous findings, the terminal unit of heptose was found to be substituted at C-7 with phosphorylethanolamine (PEtN) and not only with phosphate, although this substitution is not complete as demonstrated by the relevant signals in 31P-NMR. Additional studies with the wild-type strain P. mirabilis O28 revealed the presence of 4-amino-L-arabinose in both the core and the lipid A regions suggesting that the R4 mutant is defective in the biosynthesis of this amino sugar rather than in its transfer. Otherwise the lipid A regions of the mutant and the wild-type strain show no structural differences. The following formula is proposed for the lipopolysaccharide of 4-amino-L-arabinose-lacking mutant R4/O28 P. mirabilis: (Formula; see text)

Electrophoresis, Polyacrylamide Gel↗