Reliability of serum separator blood drawing tubes under routine conditions.
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Blood Cells↗
Biomedical subjects
G Kirchner
Publications and source records attributed to G Kirchner.
'Interoception' of heart rate, blood pressure, and myocardial metabolism during ergometric work load in healthy young subjects.
In a laboratory experiment intensities of 25, 50, and 75% of the individual range of a cardiovascular parameter (heart rate, blood pressure, and Robinson-index as an index of myocardial metabolism) were demonstrated during bicycle ergometer testing with healthy young subjects. In a subsequent phase they had to reproduce the same value of the parameter in question by regulating the physical work load of the ergometer. Reproduction accuracy was taken as an interoceptive index. We concluded from our data that subjects reproduced heart rate with high internal consistency but with a systematic bias. There is no linear consistency in blood pressure reproduction, and a moderate one in the reproduction of the index of myocardial metabolism. The physiological processes, upon which the interoception and reproduction is based, remain a question of further research.
Adult↗
Toxicity indices of radioactive waste.
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Humans↗
Transport of iodine and cesium via the grass-cow-milk pathway after the Chernobyl accident.
More than 150 data sets giving time-dependent concentrations of 131I and 137Cs in feed and milk of cows after the Chernobyl accident are evaluated using a minimal compartmental modeling approach. Transfer of cesium via the grass-cow-milk pathway is adequately described by a three-compartmental model. No unique model results for 131I, as a compartment with slow secretion of 131I into milk, are identified for some datasets only. Frequency distributions of weathering half-lives on grass and of equilibrium feed-to-milk transfer coefficients are approximately lognormal. Mean values of weathering half-lives on plants are 9.1 +/- 0.6 d for iodine and 11.1 +/- 0.8 d for cesium, in good agreement with means established from experiments performed before 1986. Mean values of equilibrium feed-to-milk transfer coefficients are 3.4 +/- 0.4 10(-3) d L-1 for 131I and 5.4 +/- 0.5 10(-3) d L-1 for 137 Cs. Both are lower than means calculated from the pre-Chernobyl data base. Plausible explanations of the differences include (1) reduced availability of fallout compared to soluble tracer; (2) underestimation of post-Chernobyl transfer coefficients by some experiments concluded too early to record slow transport processes; and (3) reduced transfer of 131I compared to long-lived iodine isotopes due to decay during fixation in the thyroid. Feed-to-milk transfer of 131I is related to milk yield, but no influence of milk yield and type of feed on transfer is apparent for cesium.
Accidents↗
[Assessment of current cardiovascular stress in healthy, young people].
Forty-three young healthy subjects' estimates of their own heart rate, systolic blood pressure, and myocardial oxygen consumption at various intensities of physical work load were investigated. Their estimates were assessed using an ipsative scale, while the physiological parameters were measured continuously and simultaneously. Subjects tended to underestimate their heart rate at every intensity level, men misinterpreting less than women. Blood pressure was underestimated only at moderate physical work loads; with increasing work load blood pressure was overestimated. Estimates of myocardial oxygen consumption were the least biased. This result indicates that parameters other than the heart rate influence cardiac interoception. It seems that estimation of cardiovascular parameters influences the self regulation of physical activities.
Adult↗
Zonation of glucokinase in rat liver changes during postnatal development.
In the liver many metabolic pathways are preferentially localized in different zones of the acinus. It is assumed that this zonation allows an efficient adaptation to different states of nutrition, because alternative pathways can be regulated independently. It is reported that the rate limiting enzyme for the glycolytic pathway, glucokinase (EC 2.7.1.2), is predominantly located in the pericentral zone. The gene expression of glucokinase is induced to a maximum level after a carbohydrate-rich diet. In starved or diabetic rats glucokinase gene expression is barely detectable. In postnatal development glucokinase is induced to significant levels only from day 14 onwards. The distribution of the glucokinase protein in the rat liver lobule in the first 4 weeks of postnatal life was investigated by immunohistochemistry and compared to the distribution observed in adult rats. In adult rats considerably high levels of glucokinase are measureable as shown by immunoblotting utilizing a monospecific antibody and a photometric assay of glucokinase enzyme activity, respectively. Immunohistochemically the hepatic glucokinase protein is detected in the perivenous area. During postnatal development, the quantities of hepatic glucokinase protein and glucokinase enzyme activity start to increase significantly from day 15 onwards. Subsequently, glucokinase levels rise further until day 29. In contrast to the results obtained by immunoblotting, glucokinase is already detectable in some liver cells in sections from 6-day-old rats by immunohistochemistry. The liver lobule structure at this age is not completely developed, therefore it is not possible to definitely assign these cells to periportal or pericentral areas. At day 10 post partum the number of glucokinase expressing cells, which appear to be localized preferentially in the periportal zone, increases. In agreement with the immunoblotting, an immense increase in glucokinase activity was observed at day 14. The periportal zonation, clearly detectable at this time, remains stable until day 24. In sections from 29-day-old rats the periportal zonation begins to change into a more homogeneous pattern with a slight preference for periportal areas. The observed appearance of the periportal zonation of glucokinase during neonatal development is obviously in contrast to the perivenous expression of glucokinase in adult rats.
Aging↗
Enkephalin-containing neurons in the inferior mesenteric ganglion projecting to the distal colon of cat: evidence from combined retrograde tracing by fluorescent microspheres and immunohistochemistry.
Retrograde tracing with rhodamine fluorescent microspheres combined with fluorescein immunolabelling of methionine-enkephalin showed the presence of enkephalin-like material in neurons of the inferior mesenteric ganglion (sympathetic prevertebral ganglion) projecting to the distal colon in cat. Two weeks after injecting the microspheres into the wall of the distal colon, the inferior mesenteric ganglion was dissected out and incubated for 24 hours in a colchicine-containing culture medium in order to facilitate the detection of enkephalins in the soma of ganglion neurons. It was observed that retrogradely labelled ganglion cells contained enkephalin-like immunoreactive material. These ganglion cells corresponded to enkephalin-like postganglionic neurons, the terminals of which were located inside the wall of the distal colon. These enkephalin-like neurons were numerous and scattered throughout the ganglion. Sometimes enkephalin-like immunoreactive fibers, probably originating from spinal preganglionic neurons, ran close to immunoreactive and non-immunoreactive retrogradely labelled ganglion cells. This suggests that enkephalin-like immunoreactive fibers may make synaptic connections with enkephalin-like and non-enkephalin-like postganglionic neurons projecting to the distal colon. The present study establishes for the first time the existence of an enkephalin-like postganglionic pathway to the digestive tract originating from a sympathetic prevertebral ganglion. This finding indicates that the enkephalinergic innervation of the cat digestive tract may have at least two possible sources: (i) the sympathetic prevertebral ganglia; and (ii) the enteric nervous ganglia.
Animals↗
An algorithm establishing a defined ergometric cardiovascular load.
A computer-aided procedure is presented to regulate the workload on an ergometric bicycle to an individually fixed level of heart rate as the criterion, applying an integral controller algorithm. The workload is incremented in a few variable steps asymptotically to the target heart rate. A free parameter of the algorithm has been fixed empirically. In the empirical evaluation of the quality of this procedure, a strictly linear relationship of individual Watt increment and rise in heart rate was found in 27 subjects, with a median correlation of 0.95. The procedure is recommended for specific ergometric workload regulation in which an upper limit of rise in heart rate should not be surpassed, e.g. in cardiac rehabilitation. The procedure can also be generalized to comparable regulation tasks, e.g. in the management of blood pressure to avoid an hypertensive crisis.
Adult↗
Migration rates of radionuclides deposited after the Chernobyl accident in various North German soils.
In three soils typical for Northern Germany including Eutric Cambisol, Orthic Podsol and Eutric Histosol (Food and Agriculture Organization nomenclature), distributions of 90Sr, 134Cs, 137Cs and 239Pu + 240Pu in the soil profiles were determined. Sampling was performed more than 3 years after deposition of Chernobyl fallout nuclides. Migration rates calculated with a compartmental model showed no significant differences between Cs originating from either atomic weapons or Chernobyl fallout. This result indicates that Chernobyl Cs may have reached sorption equilibrium with the soil matrix 3 years after the accident. Both the compartmental model and the dispersion equation reproduce distributions of most of the activities, but fail to reproduce some (minor) activity fractions that show increased mobility.
Accidents↗
Purification and properties of yeast ATP (CTP):tRNA nucleotidyltransferase from wild type and overproducing cells.
ATP (CTP):tRNA nucleotidyltransferase (EC 2.7.7.25) has been purified from wild type cells of the yeast Saccharomyces cerevisiae, as well as from a strain that overproduces the activity. Purification from the wild type strain was accomplished with a multistep protocol including ammonium sulfate fractionation, anion exchange chromatography, gel filtration, and affinity chromatography. The purified enzyme is near homogeneity as evidenced by sodium dodecyl sulfate-polyacrylamide gel electrophoresis and at 59,000 Da is smaller than reported previously. A similar molecular mass is obtained by gel filtration demonstrating that the enzyme is active as a monomer. The pH optimum for the enzyme is around 9.5. The apparent KM values for ATP and CTP were determined to be 5.6 x 10(-4) M and 1.8 x 10(-4) M, respectively. Purification of the enzyme from the overproducing cells was accomplished by a three step protocol with high yield. The nucleotidyltransferase activity from the overproducing cells had a KM for CTP indistinguishable from that of the wild type enzyme, and the mobility of the protein on sodium dodecyl sulfate gels was the same regardless of the source. Thus, the overproducing strain appears to be a good source for large amounts of yeast nucleotidyltransferase for further biochemical and structural studies.
Chromatography↗
Isolation of a temperature-sensitive mutant with an altered tRNA nucleotidyltransferase and cloning of the gene encoding tRNA nucleotidyltransferase in the yeast Saccharomyces cerevisiae.
We have isolated a yeast mutant, ts352, that is temperature-sensitive for growth. The mutation has a general effect on mRNA metabolism and a specific effect on tRNA biosynthesis. Cells shifted to the nonpermissive temperature accumulate tRNAs that are shorter than mature tRNAs. The increased ability of these tRNAs to accept ATP demonstrates that growth of the ts352 mutant at the nonpermissive temperature results in accumulation of tRNA with defective 3' ends. The activity of ATP (CTP):tRNA-specific tRNA nucleotidyltransferase can readily be measured in extracts from wild type but not mutant cells. We have cloned and sequenced the wild type allele of the ts352 gene and find significant similarity between the yeast protein sequence predicted from the DNA sequence and the protein predicted from the sequence of the Escherichi coli tRNA nucleotidyltransferase gene. Expression of the yeast gene on a multicopy plasmid increases the activity of the tRNA nucleotidyltransferase in extracts. We conclude that the defect in the ts352 mutant is in the gene coding for yeast tRNA nucleotidyltransferase and that we have isolated the yeast gene that codes for this enzyme.
Amino Acid Sequence↗
Active bacterial luciferase from a fused gene: expression of a Vibrio harveyi luxAB translational fusion in bacteria, yeast and plant cells.
The luxA and luxB genes encoding the luciferase from Vibrio harvey were fused by site-directed mutagenesis so that one polypeptide was encoded by the fused gene. The fused gene facilitated light production in Escherichia coli, Saccharomyces cerevisiae, and Nicotiana plumbaginifolia when the substrates decanal and reduced flavin mononucleotide were present. The specific activity of the encoded enzyme is not known. In E. coli and S. cerevisiae cells the light emission could be measured in viable, intact cells. The luxAB fusion provides a simple reporter gene for in vivo measurement of promoter strength in these species and may be useful in other systems as well.
Base Sequence↗
Genotoxic activity of the aminophenols as evidenced by the induction of sister chromatid exchanges.
1 Most hair dyes contain the structural isomers ortho-, meta- and para- aminophenol which were investigated concerning their ability to induce sister chromatid exchanges (SCE) in cultured human lymphocytes in vitro and in Chinese hamster bone marrow cells in vivo. 2 In vitro only ortho-aminophenol significantly induced SCE in a dose-dependent manner. 3 In vivo none of the structural isomers increased significantly the SCE frequency. 4 It is concluded that ortho-aminophenol is a weak directly acting compound which is detoxified during its metabolism.
Aminophenols↗
[Fermentation of pyruvate by 7 species of phototrophic purple bacteria].
The dark, anaerobic fermentation of pyruvate under growth conditions was examined with the following species of phototrophic purple bacteria: Rhodospirillum rubrum strains Ha and S1, Rhodopseudomonas gelatinosa strain 2150, Rhodopseudomonas acidophila strain 7050, Rhodopseudomonas palustris strain ATCC 17001, Rhodopseudomonas capsulata strains Kb1 and 6950, Rhodopseudomonas sphaeroides strain ATCC 17023, and Chromatium vinosum strain D. Fermentation balances were established for all experiments. Under fermentative conditions cell protein and dry weight increased only slightly, if at all. The species differed considerably in their fermentative activity; R. rubrum and R. gelatinosa exhibited the highest rates (2-8 mumoles pyruvate/mg protein-h). R. acidophila and R. capsulata showed an intermediate fermentation rate (0.4--2.0 mumoles pyruvate/mg protein-h), while the other strains tested fermented at quite low rates (0.2-0.4 mumoles pyruvate/mg protein-h). The extremes of fermentation times were from 30-380 hours. Based on the products of fermentation which were formed in addition to acetate, formate, and CO2, the species can be grouped as follows: a) R. rubrum, R. gelatinosa, and R. sphaeroides additionally form propionate. b) R. gelatinosa, R. palustris, R. capsulata, R. sphaeroides, and C. vinosum additionally form lactate. R. palustris also produces butyrate. c) R. acidophila and R. capsulata additionally form much 2,3-butanediol, acetoin, and diacetyl. Small amounts of acetoin were formed by the rest of the strains. A comparison of the fermentation of pyruvate by normal and starved cells (4 days in the light without a carbon source) of R. rubrum and R. gelatinosa shows that the latter ferment more slowly and produce less acetate and formate, but more propionate or lactate. The fermentation of pyruvate by R. rubrum was also studied in cultures in which the pH fell (7.2--6.6). Compared with the fermentation at neutral pH (7.3, 7.4), the following differences were found: a slower fermentation rate, an increased production of dry weight, an increased formation of propionate, but a reduced formation of acetate and a very low production of formate.
Acetates↗
[The anomeric benzylglycosides of N-acetyl-neuraminic acid].
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Alcohols↗
Zonal turnover of cell poles of Bacillus subtilis.
Turnover of cell walls of Bacillus subtilis occurs in three distinct phases: a lag phase, a relatively rapid phase persisting for 2-3 generations and a much slower phase continuing for several additional generations. A lectin probe revealed that cell pole material was lost during the slow phase of turnover and that the loss of wall occurred in zones, beginning at the cylinder-pole junction and continuing to the cell tip. This is in contrast to cell wall turnover in cylinders where turnover occurs randomly at many surface sites.
Acetylglucosamine↗
How does a Bacillus split its septum right down the middle?
This is a speculative paper which considers the possible ways that Gram-positive cells might employ to achieve an even thickness of the two daughter poles resulting from the fission of the cross-wall. The first is that the protonmotive force generated by the extrusion of protons at the cytoplasmic membrane acts to inhibit autolysins to a distance of about 25 nm. The second has to do with the stresses that develop as the poles form. On the tacit assumption that the autolysins will function faster when their substrates are under tension, it is shown how this, too, can lead to even bisection of the cross-wall. These possibilities are not alternative, both probably function.
Bacillus↗