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Biomedical subjects

J Beckmann

Publications and source records attributed to J Beckmann.

At least 73 records · Page 4Linked to original sources
PubMed1983

Resonance Raman studies of ETE dehydrogenase (an iron sulfur flavoprotein).

ETF Dehydrogenase is an iron sulfur flavoprotein responsible for the transfer of electrons between electron transfer flavoprotein (ETF) and CoQ of the electron transport chain. We have determined the resonance Raman spectrum of this enzyme observing in the process at least seven of thirteen flavin bands in the 1100cm-1-1600 cm-1 region of the Raman spectrum. The positions of three of these bands, II, IX, and X (see Figure I and Table I for band numbering system) in ETF dehydrogenase is very similar to their positions in aqueous solution of flavins in which water is hydrogen bonded to N-1, N-5, C=0(2), C=0(4), and N-H(3) of flavin. Conversely the positions of the flavin Raman bands are considerably shifted from those of flavin in nonhydrogen bonding solvent. The positions of bands II, IX, and X are nearly identical to those in the flavoprotein glutathione reductase; x-ray structural investigations on this enzyme indicate that there is extensive hydrogen bonding between FAD and protein in this molecule. A previous study in our laboratory has demonstrated that metal complexation at N-5 and C=0(4) with either Ru or Ag produces large shifts in the positions of Raman bands II, VI, IX, and X. None of these shifts are observed in ETF dehydrogenase indicating that there is no direct inner sphere coordination of Fe to flavin. In addition to the Raman bands of flavin observed in our spectrum, we also observe one band that is in the Fe-S stretching region observed for a variety of Fe-S proteins. This band is located at 331 cm-1. The frequency of the band corresponds to the 335 cm-1 band associated with the strongest Fe-S stretching mode in the 4Fe-4S protein ferrodoxin from C. pasterianum. The observed frequency is quite different from that of the 3Fe-3S proteins such as ferrodoxin(II) from D. gigas. Finally, ETF dehydrogenase shows no loss of activity or visual evidence of photodegradation in the laser beam as most other FeS proteins do.

Animals↗
PubMed1983

Intellectual and social function of patients surviving cardiac arrest outside the hospital.

Thirteen survivors of cardiac arrest outside the hospital were examined by clinical and psychological tests 1-3 years after the incidence, and compared to a matched control group of 13 patients with acute myocardial infarction without cardiac arrest. Psychological tests revealed that 7 patients with previous cardiac arrest and 4 control patients had mild-moderate to moderate-severe dementia. The demential symptoms were not detectable by a clinical interview. Four patients in each group exhibited pronounced anxiety symptoms. There were no clear differences between the two groups in respect of changes in cardiac function and social status after the incidence.

Adult↗
PubMed1982

Phantom breast syndrome in young women after mastectomy for breast cancer. Physical, social and psychological aspects.

Phantom breast syndrome (PBS) developed in 11 out of 31 (35.5%) consecutive young women, who had undergone mastectomy for breast cancer. Six to 21 months after operation the patients were asked to take part in a follow-up investigation in which physical sequelae, social condition, and psychological reactions were assessed and related to the presence of PBS. There was no correlation between PBS and postsurgical physical sequelae, those who had received adjuvant radiotherapy, or the side on which mastectomy was performed. Socially, the group with PBS was dominated by women with an occupation outside the home. The psychological examination showed that the group with PBS had a definite predominance of women with a severely damaged body image and impaired sexual function in comparison to the group without PBS. However, the predominance did not reach a statistically significant level. Sexual identity, anxiety, affective disorder or changes in close family relationships did not reveal any distinct pattern. In our opinion, the appearance of PBS should be seen in relation to complex psychological reactions to the mastectomy.

Adult↗
PubMed1981

Quantification of cells in islets of Langerhans using DNA determination.

DNA content seems to be an ideal reference parameter for data on secretory function or metabolism of pancreatic islets. The approved fluorometric DNA assay with diaminobenzoic acid (DABA) of Kissane and Robins comprises repeated ethanol extractions of the tissue for removal of lipids from which some DABA-reactive aldehydes may originate. In the present study it is demonstrated that only negligible amounts of DABA-positive material are extractable from islets of Langerhans. Furthermore, it is shown that various substances used in experiments on the endocrine pancreas do not interfere with the DABA-DNA reaction. A modification of the original DABA procedure which does not include ethanol extractions and which is thus more simple and accurate is described for application to pancreatic islets in the absence as well as in the presence of incubation medium. A close linear correlation between islet dry weight and islet DNA content is demonstrated. Islets from rats, normal mice, and ob/ob mice contain 38.3-39.2 ng DNA per microgram dry weight.

Aminobenzoates↗
PubMed1980

Dimeric tRNA precursors in yeast.

Two DNA fragments, each containing tRNA(Arg)3 and a tRNA(Asp) gene in close conjunction, have been isolated from different genomic regions of Saccharomyces cerevisiae. Nucleotide Nucleotide sequence analysis of the gene regions revealed that in both fragments the tRNA(Arg)3 coding region is located 5'-proximal to the tRNA(Asp) coding region. They are separated by an identical spacer of 10 nucleotides. Although the 5'-flanking sequences are different in the two plasmids, some similarities are observed. To test the mode of expression of this gene configuration, we transcribed the DNA fragments in a Xenopus oocyte nuclear extract. Specific transcription of the yeast tRNA genes took place in an RNA precursor which comprised both tRNA species. We report here that the precursor RNA was processed to the mature-sized tRNA molecules, indicating the presence of an enzyme activity in the Xenopus nucleus capable of cutting a dimeric tRNA precursor. This is the first observation of a eukaryotic dimeric tRNA precursor.

Animals↗
PubMed1980

On the relation of glucose and insulin secretion in the fasting state.

In the isolated perfused rat pancreas the relationship between glucose concentration and insulin release was altered by fasting for 1-3 days. The maximum effect decreased progressively, while there was no change in the glucose concentration, yielding half of maximum response. Prolonged perfusion of the pancreas from fasting rats with glucose (20 mM) failed to restore the reduced secretion. The insulin content of the pancreas gland decreased after the second day of starvation. Blood glucose, however, was unchanged for 4 days after an initial fall. It is concluded that the capacity of the secretory mechanism, rather than its sensitivity to glucose, is reduced by starvation.

Animals↗
PubMed1980

Inhibitory effect of deuterium oxide on glucose oxidation by pancreatic islets.

The inhibition of insulin release by deuterium oxide has been interpreted by its stabilizing action on the microtubular system of the beta-cell. Because only indirect information exists about beta-cell metabolism in the presence of D2O, the effect of D2O (99.7%) on glucose oxidation by pancreatic islets was studied. Heavy water reduced 14CO2 formation from [U-14C]glucose (16.7 mM) by ob/ob mouse and rat islets by 50 and 30%, resp. Omission of calcium from H2O-containing media resulted in a 40% diminished glucose oxidation by ob/ob mouse islets. In the absence of calcium, D2O led to a further decrease in 14CO2 production (60%). Erythrocytes oxidized similar amounts of glucose in the absence and presence of D2O. Effects of D2O on glucose transport and mitochondrial respiration are discussed as possible causes of the decreased 14CO2 formation in islet tissue. It is concluded that the inhibition of insulin release by D2O need not necessarily be ascribed to its stabilizing effect on microtubules, but may also be due--at least in part--to the reduction of islet glucose oxidation.

Animals↗
PubMed1980

Neurotoxic effects of heavy lead exposure determined with psychological tests.

Nine men exposed to high concentrations of lead in their work at a battery plant were examined with the aid of psychological tests. Intelligence tests indicated normal intellectual potential, but memory, attention, concentration and psychomotor performance were severely impaired. The clinical picture indicated an organic mental syndrome. Psychological tests are recommended for clinical evaluation of neurotoxic effects of lead exposure.

Adult↗
PubMed1978

Psychological dysfunctions in lead-exposed workers. Relation to biological parameters of exposure.

Insidious neurotoxic effects of lead have been studied in a population of 42 lead-exposed workers and a reference group of 22 comparable workers with no lead exposure. The age of the individuals ranged from 18 to 50 years. The complete Wechler Adult Intelligence Scale, as well as psychomotor and memory tests, was included in the test battery. The exposure was assessed by means of the lead concentration in blood and hair and the ratio between zinc protoporphyrin and hemoglobin in the blood. Significant differences were found between the two groups of workers, especially concerning long-term memory, verbal and visuospatial abstraction, and psychomotor speed. Decreased performance in these tests was in most cases associated with indices of increased lead exposure, not only in the total population studied, but also within the lead-exposed group alone. Blood lead and zinc protoporphyrin appeared to correlate better with the intellectual impairment than did hair lead, and thus these analyses are probably better predictors for neurotoxic effects of lead. Age and exposure time were not found to be significant confounding factors in this study.

Adolescent↗
PubMed1976

Inhibition of insulin and glucagon release from the perfused rat pancreas by cyproheptadine (Periactinol, Nuran).

The tricyclic compound cyproheptadine (Periactinol, Nuran) inhibited glucose-induced insulin release from the perfused rat pancreas. Tolbutamide-stimulated insulin release was significantly reduced in the presence and completely suppressed in the absence of a substimulatory glucose concentration (5 mM). Arginine produced a slow rise of insulin release, which was completely abolished by cyproheptadine. Furthermore the biphasic glucagon release due to the stimulus was inhibited. Oxidation of 14C-glucose in isolated islets was unaltered in the presence of cyproheptadine, and pyruvate added to the perfusion medium failed to reverse the inhibitory effect on glucose induced insulin release, indicating that impaired glucose metabolism is not responsible for the inhibition. In addition, the inhibition remained unchanged when phentolamine was present, suggesting that the effect is not mediated by inhibitory adrenergic alpha receptors. Theophylline, in contrast, partly overcame the inhibition. When the calcium concentration of the medium was enhanced, the inhibitory effect of cyproheptadine was still visible, although the relative inhibition had become smaller. The results suggest that cyproheptadine blocks insulin release by affecting a fundamental step of the stimulus-secretion coupling common to peptide hormones. A participation of a calcium-antagonizing effect in the inhibition is discussed.

Animals↗