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Biomedical subjects

B Sommer

Publications and source records attributed to B Sommer.

At least 91 records · Page 5Linked to original sources
PubMed1996

Typical and atypical fractures of the odontoid process in young children. Report of two cases and a review of the literature.

The most common injury to the odontoid process in children under the age of seven years is a fracture through the synchondrosis with or without anterior displacement of the odontoid process, but this is not the only type of fracture of the odontoid process in this age-group. Fractures above and below the synchondrosis and fractures with posterior displacement were described. Typical clinical features of these fractures are: (1) major and blunt trauma, (2) neck pain and resistance to active and passive head movements; and (3) no or only slight neurological deficits. Conservative treatment had excellent results in the majority of cases. Nevertheless, there are a few specific indications for surgery.

Child, Preschool↗
PubMed1996

[Development of squamous cell carcinoma in chronic anal eczema and therapeutic consequences].

We report two cases of chronic anal eczema. In one case a squamous cell carcinoma developed at the site of inflammation. This carcinoma was treated by wide local excision. The second case was treated in the same way for prophylactic reasons. These two cases demonstrate the importance of biopsies and surgical intervention when dealing with a therapy-resistant chronic anal eczema.

Aged↗
PubMed1996

Differential regional distribution of AMPA receptor subunit messenger RNAs in the human spinal cord as visualized by in situ hybridization.

The electrophysiological characteristics of alpha-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA) receptors vary with their subunit composition. The establishment of the subunit distribution is an essential step in the understanding of the function of these receptors. In the spinal cord, AMPA receptors are involved in normal and, possibly, pathological processes. Using in situ hybridization histochemistry with radiolabelled oligonucleotides as probes, we have studied the distribution of AMPA receptor subunit messenger RNAs (spliced flip and flop variants of glutamate receptor subunits A-D) in the human post mortem spinal cord. Transcripts for flip variants were preferentially expressed in the superficial dorsal horn, with a dorsoventral decreasing gradient of the signals. Transcripts for flop variants were also abundantly present in all layers of the gray matter, with the highest signal being observed for glutamate receptor subunit Bflop. Accordingly, flop forms were predominant in areas other than the superficial dorsal horn. This differential distribution of transcripts in the dorsal horn suggests that the subunit composition of AMPA receptors varies with the afferent inputs; AMPA receptors on neurons in the superficial dorsal horn, where terminals of thin primary afferents conducting noxious information are located, contain more flip forms, whereas neurons in the deep dorsal horn, where thick primary afferents mediating innocuous stimuli terminate, have AMPA receptors which are mainly composed of flop forms of glutamate receptor subunits A and B. The relatively high abundance of glutamate receptor subunit B transcripts in the superficial laminae of the dorsal horn indicates that AMPA receptors in these laminae have lower Ca2+ permeability. In addition, the relative abundance of glutamate receptor subunits Bflip and Dflop may show that AMPA receptors in the superficial dorsal horn have slow desensitization, while those of motor neurons have rapid desensitization.

Adult↗
PubMed1996

Expression of matrix proteins during the development of mineralized tissues.

The specific properties of mineralized tissues are defined by the composition of the fraction of the noncollagenous matrix proteins. Because these proteins play a pivotal role in the processes of cell differentiation and activation and of mineralization, their temporal and spatial expression is tightly regulated. Within this study, the expression of the enamel protein amelogenin and of the bone matrix proteins osteopontin, bone sialoprotein, osteocalcin, and osteonectin was investigated by in situ hybridization. Two models that allow observation of the formation of mineralized tissues were chosen. The development of bone and cartilage was observed on murine metatarsals from 15-day-old embryos up to 1-day-old mice. This time covers the periods of initial bone formation as well as onset of resorption of mineralized cartilage and bone. To study gene expression in the mineralized tissues of the dental organ, enamel, dentin, and cementum, developing molars ranging in age from 16-day-old embryos to 14 days after delivery were chosen. Within this time frame, the molars develop from an immature state to the differentiated organ which erupts through the mandibular bone. In the developing metatarsals, osteopontin and bone sialoprotein mRNAs were detected in osteoblasts and hypertrophic chondrocytes at the onset of mineralization. In the tooth organ, only cementoblasts expressed transcripts encoding the two proteins; odontoblasts and ameloblasts did not express these genes. Osteonectin was expressed by osteoblasts and hypertrophic chondrocytes as well, whereas in the molars it was produced exclusively by odontoblasts. Osteocalcin was expressed specifically by osteoblasts in the developing metatarsals. In tooth, osteocalcin transcripts were detected in odontoblasts. Finally, amelogenin was a specific product of ameloblasts. Thus, a sequential and cell type-restricted expression of matrix proteins takes place during the development of the mineralized tissues. The expression patterns of the transcripts encoding the bone matrix proteins suggest different biological roles depending on the time and site of expression.

Amelogenin↗
PubMed1996

Modulation of the immunologic response to acute stress in humans by beta-blockade or benzodiazepines.

Acute stress evokes immediate responses in the cardiovascular endocrine, and immune systems. In particular, the number and activity of natural killer (NK) lymphocytes increase after stress. Here, we investigate the possibility to pharmacologically interfere with these stress-induced immunologic changes. Twenty-five healthy males were subjected to an acute stressor, a first-time tandem parachute jump. Subjects were randomly assigned to a beta-adrenoceptor antagonist (propranolol), a benzodiazepine (alprazolam), or placebo group. To analyze the role of the spleen in lymphocyte redistribution, splenectomized subjects performed a parachute jump. Propranolol, but no alprazolam, inhibited the heart rate increase during jumping. Increases in epinephrine and cortisol in the propranolol group were comparable to placebo, but were attenuated by alprazolam. The number and activity of NK cells significantly increased in the placebo group but not in the propranolol group immediately after stress. Alprazolam treatment did not alter the increase in NK cell numbers but did inhibit the increase in NK activity. In splenectomized subjects, NK cell numbers, but not NK activity, increased as in placebo subjects. We conclude that stress-induced changes in the immune system are controlled by beta-adrenergic mechanisms and only partly depend on the spleen; central interference with alprazolam differentially affects stress-induced changes in the NK cell compartment.

Adrenergic beta-Antagonists↗
PubMed1996

Low birthweight in Germany 1990-92.

The reunification in 1990 of the German Democratic Republic (GDR) and the Federal Republic of Germany (FRG) produced profound social transformations. Changes in the distribution of low birthweight (LBW, < 2500 g) in the two parts of the country between 1990 and 1992 have been studied by analysing vital statistics for the period. In absolute numbers, livebirths in the former FRG remained stable, while those in the former GDR declined by 51%. Numbers of LBW livebirths increased slightly in the former FRG and decreased in the former GDR; those in the category between 500 and 999 g remained stable in the former GDR and increased in the former FRG. However in terms of proportion, livebirths in this category doubled in the former GDR. Migration rates for the same period showed a shifting population from East to West particularly of young people, and maternal age-specific numbers of livebirths decreased in both countries. Psychosocial stress may have contributed to the rise in ELBW, but it is also possible that the improvement and sharing of perinatal management strategies may have led to increased survival of babies < 1000 g. Most importantly, the observed rise in the proportion of ELBW births (except those < 500 g) could be a result of the introduction of the more comprehensive definition of livebirth into the former GDR.

Adult↗
PubMed1995

Calpain inhibitor I decreases beta A4 secretion from human embryonal kidney cells expressing beta-amyloid precursor protein carrying the APP670/671 double mutation.

We have investigated the effects of the cell-penetrating cysteine protease inhibitors calpain inhibitor I (N-acetyl-Leu-Leu-norleucinal) and calpain inhibitor II (N-acetyl-Leu-Leu-methioninal) on the secretion of the beta-amyloid peptide (beta A4) using transiently transfected cells expressing beta-amyloid precursor protein (APP) with the NL670/671 double mutation. Calpain inhibitor I markedly reduced the amounts of immunoprecipitable beta A4 and p3 peptide released into the culture medium. Within the cells C-terminal APP fragments accumulated. Since beta A4 secretion by cells expressing the 100 amino acid long APP C-terminus was also reduced by calpain inhibitor I, we conclude that this substance directly or indirectly interferes with the gamma-secretase activity responsible for generating the beta A4 and p3 C-termini.

Amino Acid Sequence↗
PubMed1995

Alternative splicing of AMPA receptor subunits: regulation in clonal cell lines.

Alternative splicing of AMPA receptors was investigated in rat PC12 and human SH-SY5Y cells. PC12 cells predominantly expressed GluR-B flip mRNA before and after differentiation. In SH-SY5Y cells, each AMPA-receptor subunit showed a distinct splice variant expression profile throughout differentiation. GluR-B mRNA was comparable in expression levels for flip and flop splice variants. In the other AMPA-receptor subunit transcripts the flip form was the more prominent splice variant. After three days post induction a transient elevation of GluR-B and -D flop mRNA expression could be observed.

Alternative Splicing↗
PubMed1995

Ligand binding profile of the rat metabotropic glutamate receptor mGluR3 expressed in a transfected cell line.

A cDNA clone encoding the rat metabotropic glutamate receptor mGluR3 was stably transfected into human embryonic kidney 293 cells. Receptor-expressing cell lines were characterized by centrifugation binding assays using [3H]glutamate as radioligand. The rank order of affinity was L-glutamate > (1S,3R)-1-aminocyclopentane-1,3-dicarboxylic acid (1S,3R-ACPD) > L(+)-2-amino-3-phosphonopropionic acid (L-AP3) > quisqualic acid > L(+)-2-amino-4-phosphonobutyric acid (L-AP4) > ibotenic acid. The active enantiomers of several phenylglycines displayed Ki values of 300 to 400 microM. The nonactive enantiomers and the standard ionotropic glutamate receptor ligands N-methyl-D-aspartic acid (NMDA), (R,S)-alpha-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA) and kainic acid only weakly displaced [3H]glutamate. In this cell line, L-glutamate and (2S,3S,4S)-alpha-(Carboxycyclopropyl)-glycine (L-CCG-I) reduced cAMP levels in a dose-dependent manner. The sensitivity of this system and its easy applicability make it feasible to envisage ligand binding assays on cell lines expressing cloned receptors as useful screening tools to discover and characterize new and specific agonists and antagonists.

Animal Population Groups↗
PubMed1995

Special considerations for Orthodox Jewish patients in the emergency department.

Orthodox Jews are a special cultural group; their entire lives revolve around the teaching of the Torah. Their religious beliefs are reflected in all aspects of their lives, in both health and illness. The emergency department at Maimonides Medical Center has strived to serve this community and has modified common patient care practices to meet the needs of this special population.

Emergency Nursing↗
PubMed1995

[Effect of acetylsalicylic acid on platelet aggregation and capillary bleeding in healthy cats].

The influence of acetylsalicylic acid (ASA) in vitro and in vivo on several parameters of the hemostatic system was evaluated in healthy cats. The aggregation response of cat platelets in vitro was not influenced by 10 micrograms ASA/ml plasma, whereas ASA concentrations of 35, 70, 100 micrograms/ml and of 1 mg/ml consistently inhibited the platelet aggregation induced by 0.1 (n = 4 cats) and 0.25 micrograms collagen/ml (n = 6 cats). The aggregation response to ADP and thrombin was partially (n = 2) or completely (n = 8) inhibited by an ASA concentration of 5 mg/ml. Administration of ASA at a dosage of 10 and 25 mg/kg BW orally and intravenously yielded a plasma concentration of salicylic acid of 30-42 micrograms/ml (10 mg/kg BW) and 50-70 micrograms/ml (25 mg/kg BW). All the dosages of ASA produced an inconsistent inhibition of the collagen-induced platelet aggregation (1/5 and 2/5 for the respective groups), whereas the response to ADP and thrombin was not altered. Capillary bleeding time was not significantly altered after the ASA administration. Platelet count and screening tests were not influenced by ASA application. According to the results of this study, ASA as a platelet aggregation inhibitor is not useful for the prophylaxis of thromboembolism in cats.

Adenosine Diphosphate↗
PubMed1994

Identification of negative-acting and protein-binding elements in the mouse alpha A-crystallin -1556/-1165 region.

The mouse alpha A-crystallin-encoding gene (alpha A-cry) is expressed in a highly lens-preferred manner. To date, it has been shown that this lens-preferred expression is controlled by four proximal positive-acting transcriptional regulatory elements: DE1 (-111/-97), alpha A-CRYBP1 (-66/-57), PE1/TATA (-35/-19) and PE2 (+24/+43). The present study extends our knowledge of mouse alpha A-cry transcriptional regulatory elements to the far upstream region of that gene by demonstrating that the -1556 to -1165 region contains negative-acting sequence elements which function in transfected lens cells derived from mouse, rabbit and chicken. This is the first negative-acting regulatory region identified in mouse alpha A-cry. The -1556 to -1165 region contains sequences similar to repressor/silencer elements identified in other genes, including those highly expressed in the lens, such as the delta 1-crystallin (delta 1-cry) and vimentin (vim) genes. The -1480 to -1401 region specifically interacts with nuclear proteins isolated from the alpha TN4-1 mouse lens cell line. Contained within this protein-binding region and positioned at -1453 to -1444 is a sequence (RS1) similar to the chicken delta 1-cry intron 3 repressor, and which competes for the formation of -1480 to -1401 DNA-protein complexes. Our findings suggest that lens nuclear proteins bind to the mouse alpha A-cry RS1 region. We demonstrate that the chicken delta 1-cry intron repressor binds similar nuclear proteins in chicken embryonic lens cells and mouse alpha TN4-1 lens cells.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1994

Molecular biology of glutamate receptors.

The ligand-gated receptors for L-glutamate play a central role in acute neuronal degeneration. Recently cDNAs have been isolated for subunits of several glutamate receptor subtypes. By sequence homology all these subunits clearly belong to one large gene family. Several subfamilies exist and match roughly previously pharmacologically and electrophysiologically defined subtypes of glutamate receptors. Currently four genes (GluR A, B, C and D) are known that code for the AMPA subtypes of glutamate receptors. Recombinant expression of wild type and mutated sequences identified a critical residue in the putative TM2 channel-lining segment that controls Ca2+ ion permeability. The arginine (R) found in GluR B subunits at that position renders AMPA channels impermeable for Ca2+ ions, whereas glutamine (Q) containing GluR A, C and D subunits give rise to Ca2+ permeable channels. RNA editing converts the genomically encoded glutamine codon into the arginine codon found in GluR B cDNAs for the Q/R site. NMDA subtypes of glutamate receptors are formed after coexpression of the NR1 cDNA with a cDNA of the NR2 family. Depending on the member of the NR2 family used, NMDA receptors with different kinetical and pharmacological properties are generated. Common to all channels of these NMDA receptors is a high permeability for Ca2+ ions and a voltage dependent block by Mg2+ ions. All currently known NMDA receptor subunits have an asparagine at the Q/R homologous position. We found that this residue is critical for Mg2+ block and Ca2+ permeability of NMDA receptor channels.

Amino Acid Sequence↗