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Biomedical subjects

W Arnold

Publications and source records attributed to W Arnold.

At least 19 recordsLinked to original sources
PubMed1992

The Rhizobium meliloti pmi gene encodes a new type of phosphomannose isomerase.

Interspecific complementation of a Xanthomonas campestris pv. campestris phosphomannose isomerase (PMI) mutant was used to isolate a cosmid from a genomic library of Rhizobium meliloti 2011 carrying the pmi gene of this strain. Subcloning experiments localized the coding region to a 2.0-kb SalI-ClaI fragment. Nucleotide sequence analysis of this fragment indicated the presence of two open reading frames (ORFs), coding for 18- and 43-kDa polypeptides. The analysis of the gene function by gene disruption experiments showed that ORF2 codes for pmi. A comparison of the deduced amino acid sequence with the corresponding sequences of the Pseudomonas aeruginosa and Escherichia coli PMIs revealed no significant homology, indicating that the isolated gene encodes a new type of PMI. The construction of a pmi-deficient mutant of R. meliloti using the sacB-sacR cassette technique showed that the loss of PMI activity does not affect the symbiotic properties of this strain.

Amino Acid Sequence↗
PubMed1992

Investigations of droloxifene and other hormone manipulations on N-nitrosomethylurea-induced rat mammary tumours. 1. Influence on tumour growth.

The effect of droloxifene, a new anti-oestrogenic drug, on N-nitrosomethylurea-induced mammary tumours of Sprague-Dawley rats was investigated and compared with that of tamoxifen. The response of tumour growth to ovariectomy or to treatment with aminoglutethimide or high doses of oestradiol was also studied. Ovariectomy was by far the most effective treatment for mammary-tumour-bearing animals. More than 75% of the tumours in ovariectomized rats did not grow progressively but remained in remission for up to 12 weeks after castration when the experiment was terminated. The inhibitory effects of droloxifene and tamoxifen on mammary tumour growth were similar, but body weight loss of animals treated with tamoxifen was more marked than that of animals treated with droloxifene at the same dose and schedule.

Animals↗
PubMed1992

Investigations of droloxifene and other hormonal manipulations on N-nitrosomethylurea-induced rat mammary tumours. 2. Influence on oestrogen receptor.

In N-nitrosomethylurea-induced rat mammary tumours, tamoxifen is found to compete at the binding sites of the oestradiol receptor if a receptor determination is performed 1 day following the last drug application to animals. Despite a higher binding affinity of droloxifene (3-OH-tamoxifen) to oestradiol receptor, compared to tamoxifen, its influence on the measurable receptor quantity is only very weak or not demonstrable. Therefore, binding affinity is not a valid explanation for the different influences of the two anti-oestrogens on the receptor. These only can be attributed to different behaviour patterns of both substances in relation to their half-lives and metabolism and accumulation in the organism. Owing to the short half-life of droloxifene, even 1 day after the last application too little drug is available to compete for oestradiol binding sites. In the case of both anti-oestrogenic substances, cessation of drug application for 8 weeks abolished any influence on the oestradiol receptor. Furthermore, failure of aminoglutethimide to influence the oestradiol receptor could be observed because this substance does not act via this receptor. The experiments performed confirm literature data regarding the effect of aminoglutethimide therapy on oestradiol receptors in breast tumour tissue of human beings. In summary: receptor investigations of N-nitrosomethylurea-induced rat mammary tumours, used as a model to test therapy regimens with droloxifene or other drugs with a short half-life, may be of limited value only.

Aminoglutethimide↗
PubMed1992

Immunohistochemical characterization of the human endolymphatic sac and its associated cell populations.

The use of monoclonal and polyclonal antibodies as specific markers for the localization of tissue constituents in situ allows the characterization of cells according to their state of differentiation and the detection of cellular antigens related to the function of cells and tissues. Our studies focus on the immunohistochemical characterization of the human endolymphatic sac (ES) and its associated cell populations. A panel of 37 monoclonal and polyclonal antibodies were used on frozen sections and fixed material from 64 ES of 32 persons without any clinically known inner ear disorders. The ES were removed at the time of autopsy; case histories were available. The results of our studies on the extraosseous part of the human ES support the assumption that the epithelium is metabolically active and capable of both secretion and absorption. The reactivity of the epithelial cells with antibodies against neuron specific enolase, chromogranin and somatostatin, respectively, implies a paracrine activity of the ES. Further results obtained with antibodies specific for cells of the immune system indicate a possible role of the human ES in the inner ear immune defence and a functional relationship of the ES to the common mucosa-associated immune system.

Adolescent↗
PubMed1992

Genetics of xanthan production in Xanthomonas campestris: the xanA and xanB genes are involved in UDP-glucose and GDP-mannose biosynthesis.

The nucleotide sequence of a 3.4-kb EcoRI-PstI DNA fragment of Xanthomonas campestris pv. campestris revealed two open reading frames, which were designated xanA and xanB. The genes xanA and xanB encode proteins of 448 amino acids (molecular weight of 48,919) and 466 amino acids (molecular weight of 50,873), respectively. These genes were identified by analyzing insertion mutants which were known to be involved in xanthan production. Specific tests for the activities of enzymes involved in the biosynthesis of UDP-glucose and GDP-mannose indicated that the xanA gene product was involved in the biosynthesis of both glucose 1-phosphate and mannose 1-phosphate. The deduced amino acid sequence of xanB showed a significant degree of homology (59%) to the phosphomannose isomerase of Pseudomonas aeruginosa, a key enzyme in the biosynthesis of alginate. Moreover, biochemical analysis and complementation experiments with the Escherichia coli manA fragment revealed that xanB encoded a bifunctional enzyme, phosphomannose isomerase-GDP-mannose pyrophosphorylase.

Amino Acid Sequence↗
PubMed1992

Functional morphology of the human endolymphatic sac. A review.

Modern immunohistochemical methods allow a functional characterization of the human endolymphatic sac (ES) and its associated cell populations. The currently available immunohistochemical data on the extraosseous part of the human ES support the assumption that the epithelium is metabolically active and capable of both secretion and absorption. The reactivity of some epithelial cells with antibodies against neuroendocrine antigens implies a paracrine activity of the human ES. Further results provide evidence for a possible role of the human ES in inner ear immune defense and indicate a putative functional relationship of the human ES to the common mucosa-associated immune system.

Endolymphatic Sac↗
PubMed1992

Case report: top hearing performances of a postlingually deaf cochlear implant user.

On the occasion of the Cochlear Implant Symposium in Geneva in October 1991, top hearing results attained by a young postlingually deaf woman with cochlear implant systems were presented in video recordings. These data are centered on demanding hearing performances in test situations and in a telephone conversation. For various reasons, two reimplantations were necessary in this deaf patient. Initially, she was provided with a single-channel extra-cochlear electrode of the Vienna type, which she found to improve her lipreading substantially, and she attained an unexpectedly good understanding of speech on a purely auditory basis. Today, this postlingually deaf women uses a multichannel intracochlear electrode of the Nucleus type. The excellent results with the first extracochlear system are clearly surpassed with the intracochlear system. Not least because of her above-average speech competence, the cochlear implant user attains a high degree of open speech understanding. Her verbal hearing efficiency is comparable to that of a person with mild to moderately severe hearing loss.

Adolescent↗
PubMed1992

[Immunohistochemical findings in otosclerotic lesions].

Despite numerous scientific efforts, the etiology of otosclerosis still remains unknown. Pathogenically, there are several signs of a chronic inflammatory process of the bony otic capsule. In this study, we tried to characterize the components of chronic inflammation by immunohistochemical techniques. Within otosclerotic lesions a mixed cellular infiltrate can be observed, consisting of lymphocytes, macrophages and plasma cells. Macrophages which are capable of presenting antigen in association with major histocompatibility antigens (MHC) class I and class II to CD8(+)-, and CD4(+)-T cells, respectively, were found in otosclerotic lesions based on their expression of the MAC387 antigen. Furthermore, HLA-DR positive cells and complement C3 have been found in resorption lacunae of otosclerotic lesions. Several osteoblasts and chondrocytes in active otosclerotic lesions reveal a strong surface expression of beta-2-microglobulin, indicating an increased MHC class I antigen expression in active otosclerotic lesions. In agreement with recently published data we found that a large fraction of the lymphoid cells are antigen-primed T-cells expressing an alpha/beta T-cell receptor in association with CD3 molecules on their surfaces. CD4+ lymphocytes which functionally represent lymphokine-secreting cells are activated through the specific recognition of antigen, presented in context with MHC class II molecules such as HLA-DR. Therefore, the presence of MHC class II positive cells are crucial for the initiation of a local immune response. Thus, our observation of HLA-DR positive cells in otosclerotic lesions is of particular interest.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1992

Stimulation of cell division and fibroblast focus formation by antisense repression of retinoblastoma protein synthesis.

Circumstantial evidence supports a role for the retinoblastoma susceptibility gene, Rb-1, in the maintenance of normal cell growth, in that loss of its function results in abnormal growth and malignancy. Here we report that a high rate of mitosis and efficient dense focus formation in human embryonic lung fibroblasts (HEL cells) is induced by antisense oligonucleotide-directed inhibition of synthesis of p105-Rb, the product of the Rb-1 gene. mRNA specific for p105-Rb is truncated at the site of base pairing with the antisense oligonucleotide, and no synthesis of p105-Rb is observed. The rate of mitosis is considerably increased and the frequency of dense focus formation is extremely high in treated cells. However, although phosphothioate oligodeoxyribonucleotides taken up by the cells remain stable for at least 4 weeks, the recipient cells do not become immortal; nor are they able to induce tumor formation in nude mice. Thus, loss of Rb-1 function is not sufficient per se to allow malignant transformation.

Base Sequence↗
PubMed1992

[Gait analysis in patients with total hip endoprostheses. Part I: Gait analysis--the electroichnograph--(EKIG-3) Riga].

The pace analysis of patients with a total hip replacement has been carried out by means of the electroichnograph EKIG-3 of the Riga Institute of Orthopaedics and Traumatology. It comprises foot analysis (heel torsion, sole exercise, ball torsion, contact ability by using special sandals) on an electrically flowed carpet. Furthermore, angular changes in the knee-joint have been registered by means of goniometers, and the trunk deviation to the lateral an sagittal direction has also been measured.

Biomechanical Phenomena↗
PubMed1992

[Gait analysis in patients with total hip endoprosthesis. Part II: Pre- and postoperative gait analysis].

35 patients have been examined before the implantation of a total hip replacement, about 7 days postoperatively and again after 12 weeks by means of the electro-ichnograph EKIG-3 of the Riga Institute of Orthopaedics and Traumatology. Before the hip-joint substitution the normal values could not approximately be attained. The step duration has postoperatively increased, and it has decreased to pre-operative values by the time of the follow-up examination. The best results were obtained concerning the change of the trunk deviation in the frontal plane. The hip mobility measured passively was remarkably better after the operation and almost reached normal values. Regarding the results it should above all be taken into consideration, that the most important fact for the patient is the alleviation and elimination of pain, respectively.

Adult↗
PubMed1991

Characterization of recA genes and recA mutants of Rhizobium meliloti and Rhizobium leguminosarum biovar viciae.

DNA fragments carrying the recA genes of Rhizobium meliloti and Rhizobium leguminosarum biovar viciae were isolated by complementing a UV-sensitive recA- Escherichia coli strain. Sequence analysis revealed that the coding region of the R. meliloti recA gene consists of 1044 bp coding for 348 amino acids whereas the coding region of the R. leguminosarum bv. viciae recA gene has 1053 bp specifying 351 amino acids. The R. meliloti and R. leguminosarum bv. viciae recA genes show 84.8% homology at the DNA sequence level and of 90.1% at the amino acid sequence level. recA- mutant strains of both Rhizobium species were constructed by inserting a gentamicin resistance cassette into the respective recA gene. The resulting recA mutants exhibited an increased sensitivity to UV irradiation, were impaired in their ability to perform homologous recombination and showed a slightly reduced growth rate when compared with the respective wild-type strains. The Rhizobium recA strains did not have altered symbiotic nitrogen fixation capacity. Therefore, they represent ideal candidates for release experiments with impaired strains.

Amino Acid Sequence↗
PubMed1991

Ribonucleotide reductase in melanoma tissue. EPR detection in human amelanotic melanoma and quenching of the tyrosine radical by 4-hydroxyanisole.

The characteristic EPR doublet of tyrosine radicals of the growth-regulating enzyme ribonucleotide reductase was detected in human melanoma tissue grown in nude mice. This was possible through the use of an amelanotic melanoma that does not exhibit disturbing EPR signals from melanin. The content of tyrosine radicals is higher in young tumor tissues than in older ones. The clinically applied antimelanotic drug, 4-hydroxyanisole, inhibits ribonucleotide reductase in Ehrlich ascites tumor cells as demonstrated by a pronounced quenching of tyrosine radicals (IC50 = 5 microM). In amelanotic melanoma tissue tyrosine radicals of the enzyme are also quenched by 4-hydroxyanisole in concentrations down to 50 microM. Thus, the inactivation of ribonucleotide reductase, which provides deoxyribonucleotides for DNA synthesis, may be a hitherto unexpected mechanism for the antitumor action of 4-hydroxyanisole.

Animals↗
PubMed1991

Detection of hepatitis B virus DNA in serum with nucleic acid probes labelled with 32P, biotin, alkaline phosphatase or sulphone.

To facilitate the clinical application of dot-blot hybridization for assaying hepatitis B virus (HBV) DNA, we compared the ability of nucleic acid probes labelled with 32P or with various non-radioactive markers to detect HBV DNA in patient serum. Cloned HBV DNA was hybridized with (1) 32P-labelled HBV DNA cloned in M13, (2) the 32P-labelled HBV RNA probe included in the HepProbe kit, (3) an alkaline phosphatase-labelled synthetic oligonucleotide of HBV, (4) biotin-labelled HBV DNA, and (5) sulphonated HBV DNA. Detection was either by autoradiography or an enzymatic colour reaction. The lowest level of detection of cloned HBV DNA was achieved with the 32P-labelled HBV RNA probe (0.3 pg HBV DNA, corresponding to 3 x 10(4) genomes in 50 microliters), followed by the 32P-labelled DNA probe (0.3-2 pg), sulphonated DNA (1-2 pg), biotin-labelled DNA (4 pg), and an alkaline phosphatase-labelled synthetic oligonucleotide (30 pg). Subsequently, sera from 159 patients with various constellations of HBsAg, HBeAg, and anti-HBe were tested with the most sensitive radioactive method (HepProbe) and the corresponding nonradioactive method (sulphonation). The overall concordance rate was 71% (r = 0.42). Compared with HepProbe results, sulphonation showed a sensitivity of 80% and a specificity of 67%. We conclude that radiolabelling (in particular 32P-labelling of HBV RNA) still allows the most sensitive and reliable detection of HBV DNA in patient serum using conventional dot-blot hybridization.

Alkaline Phosphatase↗
PubMed1991

Biogenesis of transverse tubules and triads: immunolocalization of the 1,4-dihydropyridine receptor, TS28, and the ryanodine receptor in rabbit skeletal muscle developing in situ.

Our previous immunofluorescence studies support the conclusion that the temporal appearance and subcellular distribution of TS28 (a marker of transverse (T) tubules and caveolae in adult skeletal muscle [Jorgensen, A. O., W. Arnold, A. C.-Y. Shen. S. Yuan, M. Gover, and K. P. Campbell, 1990, J. Cell Biol. 110:1173-1185]), correspond very closely to those of T-tubules forming de novo in developing rabbit skeletal muscle (Yuan, S., W. Arnold, and A. O. Jorgensen, 1990, J. Cell Biol. 110:1187-1198). To extend our morphological studies of the biogenesis of T-tubules and triads, the temporal appearance and subcellular distribution of the alpha 1-subunit of the 1,4-dihydropyridine receptor (a marker of the T-tubules and caveolae) was compared to (a) that of TS28; and (b) that of the ryanodine receptor (a marker of the junctional sarcoplasmic reticulum) in rabbit skeletal muscle cells developing in situ (day 19 of gestation to 10 d newborn) by double immunofluorescence labeling. The results presented show that the temporal appearance and relative subcellular distribution of the alpha 1-subunit of the 1,4-dihydropyridine receptor (alpha 1-DHPR) are distinct from those of TS28 at the onset of the biogenesis of T-tubules. Thus, in a particular developing myotube the alpha 1-DHPR appeared before TS28 (secondary myotubes; day 19-24 of gestation). Furthermore, the alpha 1-DHPR was distributed in discrete foci at the outer zone of the cytosol, while TS28 was confined to foci and rod-like structures at the cell periphery. As development proceeded (primary myotubes; day 24 of gestation) approximately 50% of the foci were positively labeled for both TS28 and the alpha 1-DHPR, while approximately 20 and 30% of the foci were uniquely labeled for TS28 and the alpha 1-DHPR, respectively. The foci labeled for both TS28 and the alpha 1-DHPR and the foci uniquely labeled for TS28 were generally confined to the cell periphery, while the foci uniquely labeled for the alpha 1-DHPR were mostly confined to the outer zone of the cytosol. 1-2 d after birth, TS28 was distributed in a chickenwire-like network throughout the cytosol, while the alpha 1-DHPR was confined to cytosolic foci. In contrast, the temporal appearance and subcellular distribution of the alpha 1-DHPR and the ryanodine receptor were very similar, if not identical, throughout all the stages of the de novo biogenesis of T-tubules and triads examined.(ABSTRACT TRUNCATED AT 400 WORDS)

Animals↗