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Biomedical subjects

H Schulz

Publications and source records attributed to H Schulz.

At least 271 records · Page 15Linked to original sources
PubMed1991

The distribution of slow-wave sleep across the night: a comparison for infants, children, and adults.

This study describes the temporal distribution of slow-wave sleep (SWS) (defined as the visually scored stages 3 + 4) across the night for 16 infants aged between 20 weeks and 1 year, 17 children between 1 and 6 years, and 17 adults between 20 and 36 years. In all three groups the amounts of SWS peaked during the first nonrapid eye movement (NREM) episode. SWS decreased across the night for adults and children, but not for infants. In infants the amounts of SWS remained at a fairly constant level from the second cycle onward, although many cycles were observed with zero SWS. The latter was evident from the very low tendency for SWS to appear in consecutive NREM/REM cycles. Rather, SWS was observed in alternate cycles. In children this phenomenon was less prominent but still well visible, and the tendency for SWS to appear in consecutive cycles had increased. In adults SWS occurred predominantly in consecutive cycles. The results suggest that whereas REM recurrence time increases twofold from infancy to adulthood, SWS recurrence time remains of similar length in infants, children, and adults.

Adult↗
PubMed1990

D-3-hydroxyacyl coenzyme A dehydratase from rat liver peroxisomes. Purification and characterization of a novel enzyme necessary for the epimerization of 3-hydroxyacyl-CoA thioesters.

Rat liver peroxisomal D-3-hydroxyacyl-CoA dehydratase, which in combination with enoyl-CoA hydratase catalyzes the epimerization of 3-hydroxyacyl-CoA, was purified by a five-step procedure to yield a highly purified preparation as judged by gel electrophoresis of the native and denatured enzyme. Since the molecular mass of the native dehydratase was estimated to be twice that of its 44-kDa subunit, the enzyme seems to be composed of two, possibly identical subunits. This dehydratase catalyzes the reversible dehydration of D-3-hydroxyacyl-CoA to 2-trans-enoyl-CoA, but, in contrast to enoyl-CoA hydratase, does not act on 2-cis-enoyl-CoA. The dehydratase is virtually inactive toward crotonyl-CoA, but exhibits high activity with 2-trans-hexenoyl-CoA as a substrate and acts with decreasing efficiency on all 2-enoyl-CoAs tested from 2-hexenoyl-CoA to 2-hexadecenoyl-CoA. The pH optimum of the enzyme is close to 8. Equilibrium ratios of 3-hydroxyoctanoyl-CoA/2-trans-octenoyl-CoA and 3-hydroxyoctanoyl-CoA/2-cis-octenoyl-CoA were found to be close to 3 and 137, respectively. It is suggested that 2-cis-enoyl-CoA intermediates formed during the beta-oxidation of polyunsaturated fatty acids in peroxisomes are hydrated by enoyl-CoA hydratase to D-3-hydroxyacyl-CoAs which are epimerized to their L-isomers by the sequential actions of D-3-hydroxyacyl-CoA dehydratase and enoyl-CoA hydratase.

Animals↗
PubMed1990

Nucleotide sequence of the fadA gene. Primary structure of 3-ketoacyl-coenzyme A thiolase from Escherichia coli and the structural organization of the fadAB operon.

The DNA insert of plasmid pK52 contains the fadAB operon coding for the Escherichia coli fatty acid oxidation complex. Studies on the operon's structure and organization revealed that the initiator codon (ATG) of the structural gene for 3-ketoacyl-CoA thiolase, the fadA gene, is located 109 nucleotides 3' to the stop codon (TGA) of the fadB gene that encodes the alpha-subunit, a multifunctional polypeptide. The direction of transcription of this operon is thus from fadB to fadA. The orientation of the fadA and fadB genes is the reverse of what had been published previously. The structural gene for thiolase is 1,164 nucleotides long and starts six nucleotides downstream from a Shine-Dalgarno sequence. 109 nucleotides of 5'-noncoding and 321 nucleotides of 3'-noncoding regions are also reported. The 3-ketoacyl-CoA thiolase beta-subunit is composed of 388 residues and has a calculated Mr of 40,889. The alpha- and beta-subunits were separated by gel filtration in formic acid, and the sequence of the amino-terminal 10 amino acids of the beta-subunit coincided with that deduced from the nucleotide sequence data. Sequence comparisons suggest that Cys-91 of the E. coli enzyme is the active-site cysteine residue and that the consensus sequence of the active sites of 3-ketoacyl-CoA thiolases is Asn-Arg-X1-Cys-X2-Ser-X3-X4-Gln. Although the quaternary structure of E. coli 3-ketoacyl-CoA thiolase is different from that of other thiolases, the sequence is homologous to rat and human peroxisomal and rat mitochondrial 3-ketoacyl-CoA thiolases, to the extent of 42, 41, and 37%, identity, respectively. An evolutionary tree of thiolases was constructed; it suggests that the genes of E. coli and peroxisomal 3-ketoacyl-CoA thiolases diverged after the appearance of eukaryotic cells.

Acetyl-CoA C-Acyltransferase↗
PubMed1990

Cardiogenic oscillations of He and SF6 in expired gas in dogs.

Quantitative analysis of cardiogenic oscillations of He and SF6 during airway and venous loading demonstrated that both VA/Q and VA/VA inequalities were involved in the lung gas inhomogeneity producing cardiac oscillations in the expirogram. Both inequalities were coupled in such a manner that low VA/Q units had high VA/VA. The oscillations were modified in conducting airways where SF6 oscillations were attenuated more than He oscillations, probably by laminar Taylor dispersion.

Animals↗
PubMed1990

Sloping alveolar plateaus of CO2, O2, and intravenously infused C2H2 and CHClF2 in the dog.

To investigate the role of the various mechanisms assumed to contribute to the slope of the alveolar plateau, two test gases exhibiting identical solubility but two-fold differing diffusivity, acetylene (C2H2) and chlorodifluoromethane (Freon 22, CHClF2), dissolved in saline were intravenously infused in 10 anesthetized, paralyzed, artificially ventilated dogs (mean body mass, 18 kg). The partial pressures of C2H2, CHClF2, CO2 and O2 during a constant-flow single-breath washout maneuver were recorded by mass spectrometry and analyzed in terms of slope of the alveolar plateau (phase III) and series (Fowler) dead space. The slope of the alveolar plateau (S) was determined as the relative alveolar slope normalized to mixed-expired partial pressure and referred to expired volume (VE), S(V) = delta PE/(PE - PI)/delta VE or expiration time (tE), S(t) = delta PE/(PE - PI)/delta tE (subscripts I, E, and E refer to inspired, instantaneous expired and mixed-expired gas, respectively). The effects of expiratory flow rate (VE), and time of breath-hold (BH) were studied with reference to control conditions (VI = 0.5 L.sec-1, VE = 0.1 L.sec-1, VI = 50% and VE = 75% of volume at FRC, BH = 0 sec). In control conditions, the following significantly different S(V) values (units: L-1), grouped in ascending order, were obtained (means +/- SD): CO2, 0.83 +/- 0.26; C2H2, 0.93 +/- 0.18; CHClF2, 1.00 +/- 0.20; O2, 1.07 +/- 0.29. The mean C2H2/CHClF2 ratio for S(V), 0.94 (SD +/- 0.03), was statistically different from unity. In line with model calculations, the experimental findings suggest that three mechanisms contribute to the sloping alveolar plateaus: 1, continuing gas exchange during expiration; 2, ventilation-perfusion inequality combined with sequential emptying; 3, intrapulmonary diffusion limitation.

Acetylene↗
PubMed1990

ESWL and gallstone dissolution with MTBE via a naso-vesicular catheter.

Endoscopic placement of a naso-vesicular catheter was successful in 90% (45/50) of patients with cholecystolithiasis. The first 7 patients were treated by MTBE dissolution alone. Dissolution was discontinued after a maximum of 14 days, as only two patients were rendered stone free. In one patient, 3 tiny pigment stones were sucked out through the catheter, and in another inoperable patient a pigtail endoprosthesis was finally inserted into the gallbladder. In the remaining 36 patients, combined ESWL and MTBE dissolution therapy was carried out. Treatment was broken off by one patient after one week, and interrupted in another due to catheter dislodgement. After an average of 10 days with 1-9 ESWL sessions (average: 3) complete stone clearance was achieved in 60% (20/34) of patients. Fourteen of the patients who completed treatment, and the one with catheter dislodgement still have sludge in the gallbladder, which is being treated with oral bile acids. The procedure-related complication rate was 10% (3 pancreatitis, 1 cystic duct perforation and 1 guidewire impaction). The mortality rate was zero. There was no evident complication due to either ESWL or MTBE dissolution.

Catheterization↗
PubMed1990

The influence of two behavioral regimens on the distribution of sleep and wakefulness in narcoleptic patients.

Thirty-two hours (night-day-night) of polygraphic recordings were performed on 14 patients with a diagnosis of narcolepsy-cataplexy. Half of the patients stayed in bed during the day, whereas the other half were seated at a table. Patients were free to nap whenever they wanted to. Patients under continuous bedrest slept 2-3 times more during the day than patients who were sitting at the table. Rapid-eye-movement (REM) sleep and slow-wave sleep (SWS, stages 3 and 4) were nearly absent during daytime sleep in the table group, but not in the bed group. The differential behavioral regimes during the day resulted in different amounts of SWS in the consecutive night sleep. Although SWS increased from the first to the second night in the table group, it decreased in the bed group. This result suggests that the presumably homeostatic regulation of SWS is intact in narcoleptic patients.

Adult↗
PubMed1990

DR2-positive monozygotic twins discordant for narcolepsy.

Narcolepsy runs in families, and recent research has revealed the human leukocyte antigen (HLA) DR2 to be a genetic marker closely associated with the disease. But, as indicated by family studies, other factors contribute to the pathogenesis of narcolepsy. The investigation of monozygotic twins is the most specific research tool for distinguishing between a multigenetic and a multifactorial pathogenetic model. We present clinical and sleep polygraphic data from two pairs of monozygotic twins, and in addition, from some of their first-degree relatives. In both pairs only one twin suffered from the clinical symptoms of narcolepsy/cataplexy. Only in these subjects did night sleep recordings and a multiple sleep latency test reveal both multiple sleep onset rapid-eye-movement periods (SOREMPs) and short mean sleep onset latencies. However, in two of the asymptomatic, HLA DR2+ relatives, short mean sleep onset latencies during the multiple sleep latency test (MSLT) were observed, and one, HLA DR2- relative showed REM sleep two times during the MSLT. Our results strongly favor a multifactorial pathogenetic model for narcolepsy.

Adult↗
PubMed1990

Pulmonary diffusing capacities for nitric oxide and carbon monoxide determined by rebreathing in dogs.

Pulmonary diffusing capacities (DL) of NO and CO were determined simultaneously from rebreathing equilibration kinetics in anesthetized paralyzed supine dogs (mean body wt 20 kg) after denitrogenation (replacement of N2 by Ar). During rebreathing the dogs were ventilated in closed circuit with a gas mixture containing 0.06% NO, 0.06% 13C18O, and 1% He in Ar for 15 s, with tidal volume of 0.5 liter and frequency of 60/min. The partial pressures of NO, 13C18O, 16O18O, N2, Ar, CO2, and He in the trachea were continuously analyzed by mass spectrometry. Measurements were performed at various O2 levels characterized by the mean end-expired PO2 during rebreathing (PE'O2). In control conditions ("normoxia," PE'O2 = 67 +/- 8 Torr) the following mean +/- SD values were obtained (in ml.min-1.Torr-1): DLNO = 52.4 +/- 11.0 and DLCO = 15.4 +/- 2.9. In hypoxia (PE'O2 = 24 +/- 7 Torr) DLNO increased by 11 +/- 8% and DLCO by 19 +/- 10%, and in hyperoxia (PE'O2 = 390 +/- 26 Torr) DLNO decreased to 87 +/- 3% and DLCO to 56 +/- 8% with respect to values in normoxia. DLNO/DLCO of 3.24 +/- 0.06 (hypoxia), 3.38 +/- 0.31 (normoxia), and 5.54 +/- 1.04 (hyperoxia) were significantly higher than the NO/CO Krogh diffusion constant ratio (1.92) predicted for simple diffusion through aqueous layers. With increasing O2 uptake elicited by 2,4-dinitrophenol, DLNO and DLCO increased and DLNO/DLCO remained close to unchanged. The results suggest that the combined effects of diffusion and chemical reaction with hemoglobin limit alveolar-capillary transport of CO. If it is assumed that reaction kinetics of NO with hemoglobin (known to be extremely fast) are not rate limiting for NO uptake, the contribution of the slow chemical reaction with hemoglobin to the total CO uptake resistance (= 1/DLCO) was estimated to be 38% in hypoxia, 41% in normoxia, and 64% in hyperoxia. The various factors expected to restrict the validity of this analysis are discussed, in particular the effects of functional inhomogeneity.

2,4-Dinitrophenol↗
PubMed1990

Alveolar slope and dead space of He and SF6 in dogs: comparison of airway and venous loading.

Series (Fowler) dead space (VD) and slope of the alveolar plateau of two inert gases (He and SF6) with similar blood-gas partition coefficients (approximately 0.01) but different diffusivities were analyzed in 10 anesthetized paralyzed mechanically ventilated dogs (mean body wt 20 kg). Single-breath constant-flow expirograms were simultaneously recorded in two conditions: 1) after equilibration of lung gas with the inert gases at tracer concentrations [airway loading (AL)] and 2) during steady-state elimination of the inert gases continuously introduced into venous blood by a membrane oxygenator and partial arteriovenous bypass [venous loading (VL)]. VD was consistently larger for SF6 than for He, but there was no difference between AL and VL. The relative alveolar slope, defined as increment of partial pressure per increment of expired volume and normalized to mixed expired-inspired partial pressure difference, was larger by a factor of two in VL than in AL for both He and SF6. The He-to-SF6 ratio of relative alveolar slope was generally smaller than unity in both VL and AL. Whereas unequal ventilation-volume distribution combined with sequential emptying of parallel lung regions appears to be responsible for the sloping alveolar plateau during AL, the steeper slope during VL is attributed to the combined effects of continuing gas exchange and ventilation-perfusion inequality coupled with sequential emptying. The differences between He and SF6 point at the contributing role of diffusion-dependent mechanisms in intrapulmonary gas mixing.

Administration, Inhalation↗
PubMed1990

Cardiogenic oscillations in He and SF6 expirograms during airway and venous loading.

Cardiogenic oscillations in the expired partial pressure profiles of two inert gases (He and SF6) were monitored in seven anesthetized paralyzed mechanically ventilated dogs. He and SF6 were administered either intravenously by a membrane oxygenator and partial arteriovenous bypass [venous loading (VL)] or by washin into lung gas [airway loading (AL)]. The single-breath expirograms obtained during constant-flow expiration after inspiration of test gas-free air displayed distinct and regular cardiogenic oscillations. The relative oscillation amplitude (ROA), calculated as oscillation amplitude divided by mixed expired-inspired partial pressure difference, was in the range of 1-8%. The ROA for both He and SF6 was approximately 4.2 times higher in VL than in AL, which indicated that among lung units that emptied sequentially in the cardiac cycle, the effects of alveolar ventilation-perfusion (VA/Q) inequality were more pronounced than those of alveolar ventilation-alveolar volume (VA/VA) inequality. In AL, He and SF6 oscillations were 180 degrees out of phase compared with CO2 and O2 oscillations and with He and SF6 oscillations in VL, which suggests that regions with low VA/VA had high VA/Q and very low Q/VA. The ROA was practically unaffected by breath holding in both AL and VL, which indicates that there was little diffusive or convective (cardiogenic) mixing between the lung units that were responsible for cardiogenic oscillations. The ROA was consistently higher for He than for SF6, and the He-to-SF6 ratio was independent of route of test gas loading, averaging 1.6 in both AL and VL. This result may be explained by laminar Taylor dispersion, whereby oscillations generated in peripheral lung regions are dissipated in inverse proportion to diffusion coefficient during transit through the proximal (larger) airways.

Administration, Inhalation↗
PubMed1990

2,4-Dienoyl-coenzyme A reductase deficiency: a possible new disorder of fatty acid oxidation.

Several inherited disorders of fatty acid beta-oxidation have been described that relate mainly to saturated precursors. This study is the first report of an enzyme defect related only to unsaturated fatty acid oxidation and provides the first in vivo evidence that fat oxidation in humans proceeds by the reductase-dependent pathway. The patient was a black female, presenting in the neonatal period with persistent hypotonia. Biochemical studies revealed hyperlysinemia, hypocarnitinemia, normal organic acid profile, and an unusual acylcarnitine species in both urine and blood. The new metabolite was positively identified by mass spectrometry as 2-trans,4-cis-decadienoylcarnitine, derived from incomplete oxidation of linoleic acid. In spite of dietary therapy, the patient died of respiratory acidosis at four months of age. Samples of liver and muscle from the autopsy were assayed for 2,4-dienoyl-coenzyme A reductase activity. Using the substrate 2-trans,4-cis-decadienoylcoenzyme A, the reductase activity was 40% of the control value in liver and only 17% of that found in normal muscle. It is suggested that unsaturated substrates should be used for in vitro testing to cover the full range of potential beta-oxidation defects and that acylcarnitine species identification be used for in vivo detection of this disorder.

Fatty Acid Desaturases↗