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  • 1
    ISSN: 1432-1971
    Schlagwort(e): PDA ; Echocardiography ; Fluid balance ; VLBW infants
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Notizen: Summary Fifty very low birth weight (VLBW) infants (750–1500 g, 27–33 weeks gestational age) were assigned at random to one of two groups of negative fluid balance and underwent prospective clinical and echocardiographic examinations during the first month of life. The purpose was to determine: (a) the effect of fluid restriction on the incidence of ductal shunting, (b) the reliability of the physical examination in diagnosing significant ductal shunting, and (c) the relationship between significant ductal shunting and outcome in such infants. None of the infants had manipulations to close the ductus during the first week of life. Using routine structural and functional echocardiographic indices as criteria for the diagnosis of hemodynamically significant ductal shunting (hsPDA), we found that the two fluid-balance groups (8%–10% weight loss vs 13%–15% weight loss) did not significantly differ in incidence of hsPDA, duration of ventilation, or development of BPD. These two groups were then combined for further analysis: 32 (64%) of 50 VLBW infants had hsPDA during the first week of life. The group of infants with hsPDA did not differ significantly from that without hsPDA in birth weight or gestational age, but had a significantly lower Apgar score (P〈0.04) and was significantly more likely to require ventilator support for RDS (P〈0.01). Although when present a typical ductal murmur was specific for the development of significant ductal shunting, no murmur was heard in 21 (66%) of 32 infants with early hsPDA. Of the infants requiring ventilator support for RDS, the group with early hsPDA needed ventilation for 13.8±9.4 days, significantly longer than the group without early hsPDA (3.2±2.6 days,P〈0.001), and had a higher incidence of BPD and death than the group without early hsPDA (P〈0.04). In our study of a large group of prospectively identified VLBW infants, we did not find that significant ductal shunting was altered by more stringent fluid restriction, but we did find that such shunting was frequently inapparent clinically, and was associated with significantly increased morbidity and mortality.
    Materialart: Digitale Medien
    Standort Signatur Einschränkungen Verfügbarkeit
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  • 2
    ISSN: 1432-1971
    Schlagwort(e): Radionuclide ; Echocardiography ; Ventricular septal defect
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Notizen: Summary Pulmonary to systemic blood flow ratios (Qp:Qs) were estimated in 16 children with ventricular septal defects using simultaneous echocardiography and radionuclide angiography, and compared to Qp:Qs measured at cardiac catheterization by the Fick principle method (Fick). When ratios of echographic left atrial dimensions (LAD) to body surface area (LAD/M2), body length (LAD/ht), and aortic root diameter (LAD/Ao) were compared to the Qp:Qs determined by Fick, the correlation coefficients were r=0.70 for LAD/M2, r=0.66 for LAD/ht, and r=0.54 for LAD/Ao. The correlation coefficients between Qp:Qs by Fick, and left ventricular dimensions/M2 and fractional shortening of the left ventricle were not significant. The correlation coefficients between Qp:Qs and the ratios estimated by gamma-variate and area-ratio analysis of radioisotope pulmonary dilution curves were r=0.92 and r=0.84, respectively. Thus, radionuclide angiography provided more accurate quantitation of left to right shunting through a ventricular septal defect than echocardiography. However, difficulty in obtaining adequate bolus injections of the radioisotope may result in technical failures whereas echocardiographic measurement is possible in almost all pediatric patients. Finally, the gamma-variate method cannot accurately quantitate shunt ratios greater than 3.5 to 1.
    Materialart: Digitale Medien
    Standort Signatur Einschränkungen Verfügbarkeit
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  • 3
    ISSN: 1432-1971
    Schlagwort(e): Sickle cell anemia ; Exercise ; ST-segment depression
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Notizen: Summary In order to evaluate potential electrocardiographic (ECG) correlates of ST-segment depression during exercise in patients with sickle cell anemia (SS), 43 subjects, aged 5–23 years, underwent submaximal exericse testing. Eight (19%) had ST-segment depression on the exercise ECG during submaximal exercise. These eight patients had significantly lower hemoglobin levels than the 35 subjects without evidence of ST-segment depression. These eight subjects also had significantly higher peak blood pressures and peak heart rates than the 35 subjects without ST-segment depression. The product of peak heart rate and peak systolic blood pressure, the maximal double product, is a correlate of myocardial oxygen consumption and was significantly higher in the patients with ST-segment depression than in the patients without ST-segment depression. These results indicate that patients with SS and evidence of exercise-induced ST-segment depression may have decreased myocardial oxygen supply due to low hemoglobin levels and increased myocardial oxygen demand (elevated double products) when compared to subjects with SS who do not have exercise-induced ST-segment depression.
    Materialart: Digitale Medien
    Standort Signatur Einschränkungen Verfügbarkeit
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  • 4
    ISSN: 1432-072X
    Schlagwort(e): Rhodopseudomonas sphaeroides ; tRNAphe ; Intracytoplasmic membrane induction ; RPC-5 reversed phase chromatography ; BDEAE cellulose chromatography
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Abstract A new iso-accepting tRNAphe from extracts of chemoheterotrophic and photoheterotrophic cells of Rhodopseudomonas sphaeroides has been identified by both BDEAE cellulose and RPC-5 chromatography. Rechromatography of each of the tRNAphe species in either the acylated or deacylated state shows that they migrate as single homogeneous peaks. In steady-state chemoheterotrophic cultures of R. sphaeroides tRNA I–II phe account for 25–30% of the total phenylalanine accepting activity while in steadystate photoheterotrophic cultures tRNA I–II phe account for no more than 10% of the total phenylalanine accepting activity. During the transition from chemoheterotrophic to photoheterotrophic growth conditions the levels of tRNA I–II phe fall in an exponential manner during the first half of the intracytoplasmic membrane induction period. tRNA I phe then remains at a level 10% that of its steady-state chemoheterotrophic level as long as photoheterotrophic growth conditions remain. tRNA II phe , after dropping to 10% of its former chemoheterotrophic level then returns to a level 50% that of its chemoheterotrophic level as long as photoheterotrophic growth conditions remain.
    Materialart: Digitale Medien
    Standort Signatur Einschränkungen Verfügbarkeit
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  • 5
    Digitale Medien
    Digitale Medien
    Springer
    Molecular genetics and genomics 120 (1973), S. 191-200 
    ISSN: 1617-4623
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Summary By making certain assumptions, we have provided evidence which indicates that: amber and ochre codons function in vivo, the bulk of the E. coli mRNA is polycistronic, intercistronic space may correspond to no more than 12–24 nucleotides and ochre is used twenty five times more frequently than amber, for chain termination.
    Materialart: Digitale Medien
    Standort Signatur Einschränkungen Verfügbarkeit
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  • 6
    Digitale Medien
    Digitale Medien
    Springer
    Molecular genetics and genomics 151 (1977), S. 41-47 
    ISSN: 1617-4623
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Summary The expression and stability of Escherichia coli F-primes in Proteus mirabilis is examined. It is possible to consecutively introduce, and stably maintain, the DNA of several E. coli F-primes in P. mirabilis in the absence of selective pressure for all or some of the plasmids. Additionally, we can recover more than one F-prime from certain P. mirabilis recipient strains which carry DNA derived from several independent matings with E. coli F-prime donors.
    Materialart: Digitale Medien
    Standort Signatur Einschränkungen Verfügbarkeit
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  • 7
    Digitale Medien
    Digitale Medien
    Springer
    Photosynthesis research 19 (1988), S. 63-71 
    ISSN: 1573-5079
    Schlagwort(e): CO2 fixation ; gene expression
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Abstract From studies conducted in both our laboratory and by Gibson, Tabita and colleagues, as well as drawing on the recent studies with Alcaligenes eutrophus, we describe two genetic regions which have been identified on the chromosome of Rhodobacter sphaeroides which code for a number of enzymes involved in CO2 fixation. One region was found to contain the genes coding for fructose 1,6-bisphosphatase (fbpA), phosphoribulokinase (prkA), a 37 kDa polypeptide (cfxA), and form I ribulose 1,5-bisphosphate carboxylase/oxygenase (rbcL, S). These genes appear to be expressed in the same transcriptional direction and are tandomly arranged. A second, apparently unlinked region of the chromosome contains a duplicate (with respect to functionality of gene products) but not identical set of these same four genes. Although the gene order in both regions is apparently identical, there is approximately 4 kb of DNA separating the 3′-end of prkB and the beginning of cfxB. The specific genetic organizations and proposed roles of these two genetic regions are discussed.
    Materialart: Digitale Medien
    Standort Signatur Einschränkungen Verfügbarkeit
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  • 8
    Digitale Medien
    Digitale Medien
    Springer
    Photosynthesis research 19 (1988), S. 39-61 
    ISSN: 1573-5079
    Schlagwort(e): Bacteriochlorophyll-protein complex ; gene expression ; light-harvesting complex ; reaction center ; Rhodospirillaceae ; transcriptional control ; translational control
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Abstract The puf operon of the purple nonsulfur photosynthetic bacterium, Rhodobacter sphaeroides, contains structural gene information for at least two functionally distinct bacteriochlorophyll-protein complexes (light harvesting and reaction center) which are present in a fixed ratio within the photosynthetic intracytoplasmic membrane. Two proximal genes (pufBA) specify subunits of a long wavelength absorbing (i.e., 875 nm) light harvesting complex which are present in the photosynthetic membrane in ≃15 fold excess relative to the reaction center subunits which are encoded by the pufLM genes. This review summarizes recent studies aimed at determining how expression of the R. sphaeroides puf operon region relates to the ratio of individual bacteriochlorophyll-protein complexes found within the photosynthetic membrane. These experiments indicate that puf operon expression may be regulated at the transcriptional, post-transcriptional, translation and post-translational levels. In addition, this review discusses the possible role(s) of newly identified loci upstream of pufB which may be involved in regulating either synthesis or assembly of individual bacteriochrlorophyll-protein complexes as well as the pufX gene, the most distal genetic element within the puf operon whose function is still unknown.
    Materialart: Digitale Medien
    Standort Signatur Einschränkungen Verfügbarkeit
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