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Biomedical subjects

M Hahn

Publications and source records attributed to M Hahn.

At least 235 records · Page 13Linked to original sources
PubMed1989

[Comparison of the readings of the digital decompression meter with hyperbaric chamber tests].

An estimation of the risk incurred through the use of digital decompression computers used by the diver must be based on comparisons with hyperbaric chamber tests. We compared the decompression indications displayed by different commercial devices to depth/bottom time profiles for which hyperbaric chamber experiments have given us the relevant information on types and frequency of decompression sickness.

Decompression↗
PubMed1988

Isolation of pyroGlu-Leu-Leu-Gly-Gly-Arg-Phe-NH2 (Pol-RFamide), a novel neuropeptide from hydromedusae.

The hydromedusa Polyorchis penicillatus is a good model system to study neurotransmission in coelenterates. Using a radioimmunoassay for the peptide sequence Arg-Phe-NH2 (RFamide), two peptides have now been purified from acetic acid extracts of this medusa. The structure of one of these peptides was established as pyroGlu-Leu-Leu-Gly-Gly-Arg-Phe-NH2, and was named Pol-RFamide. This peptide belongs to the same peptide family as a recently isolated neuropeptide from sea anemones (pyroGlu-Gly-Arg-Phe-NH2). Using antisera to Pol-RFamide, the peptide was found to be exclusively localized in neurones of Polyorchis, among them neurones associated with smooth-muscle fibres. This suggests that Pol-RFamide might be a transmitter or modulator at neuromuscular junctions.

Amino Acid Sequence↗
PubMed1988

The effect of four narcotics on cholecystokinin octapeptide stimulated gallbladder contraction.

In an attempt to find the ideal analgesic to treat biliary tract pain we compared the effects of saline and equianalgesic doses of morphine, pentazocine, pethidine, and butorphanol on CCK-OP stimulated gallbladder emptying in healthy volunteers. Morphine produced a profound delay in gallbladder emptying while the other narcotics produced a significant delay in comparison to saline, but less than morphine. None of the drugs affected common bile duct diameter, bilirubin, liver enzymes or amylase. We recommend avoiding the use of morphine in the treatment of biliary and pancreatic pain, but although pethidine, pentazocine and butorphanol may be potentially detrimental we could find no definite superiority of one versus the others.

Adolescent↗
PubMed1988

Absence of missense mutations in activated c-myc genes in avian leukosis virus-induced B-cell lymphomas.

We have determined the nucleotide sequences of two independent DNA clones which contained the activated c-myc genes from avian leukosis virus-induced B-cell lymphomas. Neither of these c-myc genes contained missense mutations. This strongly supports the notion that the c-myc proto-oncogene in avian leukosis virus-induced B-cell lymphomas can be oncogenically activated by altered expression of the gene without a change in the primary structure of the gene product.

Animals↗
PubMed1988

[Bone structure changes in hip joint endoprosthesis implantation over the course of many years. A quantitative study].

The stability of implanted artificial joints is limited. One main factor for this is the change of the bone tissue near the implant. Therefore we studied femura with stem endoprostheses derived from autopsy. All specimens were cut in horizontal and longitudinal sections. X-rays were made of all sections. Then the specimens were embedded undecalcified and ground to 10 microns. The wellknown phenomenons at the bone cement border were found too. Direct bone cement contact is about 5%. The 4 studied femura show a higher porosity of cortical bone as controls. The loss of cortical bone is up to 40% after 55 months. There is a correlation between new load situation and the localisation of bone loss.

Aged↗
PubMed1987

Mapping of a Bradyrhizobium japonicum DNA Region Carrying Genes for Symbiosis and an Asymmetric Accumulation of Reiterated Sequences.

Spontaneous kanamycin-sensitive derivatives were obtained from Bradyrhizobium japonicum (strain 110) carrying Tn5 insertions in symbiotic gene cluster I; the derivatives were shown to have deletions of cluster I plus flanking DNA which was indicated by the absence of different copies of the repeated sequences RSalpha and RSbeta. The deletion endpoints were mapped using cloned wild-type DNA fragments containing RSalpha copies which also served as origins for overlapped cosmid cloning. The majority of the deletions resulted from recombinational fusion of two remote RSalpha copies. Novel types of repeated sequences (RSgamma, RSdelta, and RSepsilon) occurring in 12, 10, and 4 copies per genome were detected. Seven, nine, and three copies of RSgamma, RSdelta, and RSepsilon, respectively, were located near cluster I. It is concluded that the B. japonicum genome has an unusual DNA segment of >230 kilobase pairs characterized by the presence of repeated sequences and genes for symbiotic N(2) fixation.

Journal Article↗
PubMed1987

Conservation of a symbiotic DNA region in soybean root nodule bacteria.

Bradyrhizobium japonicum USDA 3I1b110 contains a DNA region in which symbiotic genes and many repeated sequences are closely linked. Hybridization analysis revealed that this region was highly conserved in some B. japonicum strains (USDA 24, USDA 122, USDA 123, ATCC 10324, 61A24) but not in others (USDA 76, 61A76, 61A101). The genomic presence of multiple copies of one of the repeated sequences (RSalpha) appeared to be specifically characteristic for soybean root nodule bacteria, including the fast-growing Rhizobium fredii, which carries most of these RSalpha copies on the symbiotic plasmid.

Journal Article↗
PubMed1987

[Preparation of hip joint endoprostheses for qualitative and quantitative morphologic assessment].

The morphological investigation of endoprostheses and the evaluation of the reaction with the surrounding bone tissue require the use of new preparation techniques. A standardized procedure of preparation is suggested to enable a comparison among various study groups. After removing the specimens (at autopsy), x-rays are taken, followed by separation into horizontal and longitudinal sections. These sections are undecalcified embedded retaining the implant/bone interface and grounded to thickness of 5-10 mu. First results of a quantitative analysis of bone loss are presented.

Bone Resorption↗
PubMed1986

Three-dimensional structure of the regular surface layer (HPI layer) of Deinococcus radiodurans.

The low-resolution structure of the regular surface layer of Deinococcus radiodurans has been determined from negatively stained specimens by three-dimensional electron microscopy. The layer has P6 symmetry, a lattice constant of 18 nm and a thickness of 6.5 nm. Three-dimensional reconstruction was performed by a hybrid real space/Fourier space approach that incorporates partial compensation of lattice distortions: The model obtained is discussed in the light of independent information about the surface structure of this layer, derived from metal shadowing and surface relief reconstruction. While agreement is quite satisfactory for the apparently more rigid inner surface, the outer surface shows severe flattening effects. The structure of the HPI layer is compared with other bacterial surface layers using a classification scheme that is outlined in the Appendix.

Bacteria↗