[Training of sport-divers and directions on its methods].
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Diving↗
Biomedical subjects
A Jensen
Publications and source records attributed to A Jensen.
Heterologous expression and characterization of wild-type and mutant forms of a 26 kDa endochitinase from barley (Hordeum vulgare L.).
To investigate structure-function relationships in plant chitinases, we have developed a heterologous expression system for the 26 kDa endochitinase from Hordeum vulgare L. (barley). Escherichia coli cells harbouring the gene in a T7 RNA polymerase-based expression vector synthesized completely insoluble recombinant protein under standard induction conditions at 37 degrees C. However, a concentration of soluble recombinant protein of approx. 15 mg/l was achieved by inducing bacteria at low temperature (15 degrees C). Recombinant endochitinase was purified to homogeneity and shown to be structurally and functionally identical to the seed protein. An average of three disulphide bonds are present in the recombinant enzyme, consistent with the number found in the natural form. The seed and recombinant proteins showed the same specific activity towards a high-molecular-mass substrate and exhibited similar anti-fungal activity towards Tricoderma reesei. Site-directed mutagenesis was used to replace residues that are likely to be involved in the catalytic event, based on structural similarities with lysozyme and on sequence alignments with related chitinases. The Glu67-->Gln mutation resulted in a protein with undetectable activity, while the Glu89-->Gln mutation yielded an enzyme with 0. 25% of wild-type specific activity. This suggests that two acidic residues are essential for catalytic activity, similar to the situation with many other glycosyl hydrolases. Examination of conserved residues stretching into the proposed substrate binding cleft suggests that Asn124 also plays an important functional role.
Chitinases↗
Peri/intraventricular haemorrhage: a cranial ultrasound study on 5286 neonates.
OBJECTIVE: We launched a prospective cranial ultrasound study at the Department of Obstetrics and Gynaecology of the University of Giessen. In this study we examined the incidence and severity of brain damage in neonates and related them to various obstetrical risk factors. STUDY DESIGN: More than 90% of all neonates born between 1984 and 1988 were included in the study (n = 5286) and were screened by ultrasound for cerebral abnormalities on 5-8 days post-partum. The relation between the incidence of peri/intraventricular haemorrhages (PIVH) and obstetrical risk factors were analyzed by contingency tables. RESULTS: The most frequent abnormality was PIVH (3.6%) of various degrees (grade I-III). Periventricular leucomalacia, porencephalia, subarachnoidal haemorrhages, and hydrocephali were rare (< or = 0.2%). The incidence of PIVH increased progressively with decreasing gestational age, e.g. from 1.6% at 38-43 weeks up to 50.0% at 24-30 weeks of gestation. A large percentage of babies with PIVH were clinically normal. In immature neonates there was a close inverse relationship between Apgar score at 1, 5 and 10 min and both incidence and severity of PIVH. This was in contrast to findings in mature neonates where a marked increase in the incidence of PIVH was found only with Apgar scores as low as 0-4 points. The relation between the incidence of PIVH and both cardiotocography and arterial cord blood pH was poor, independent of the gestational age. The incidence of PIVH was increased in growth retarded fetuses (pH < or = 7.29), premature rupture of membranes, fever sub partu and gestosis. It is interesting to note that in mature fetuses there was no difference in the incidence of PIVH between vaginally delivered (0.8%) and sectioned breech presentations (2.1%). In preterms at 35-37 weeks with prolonged labour and secondary cesarean section, the incidence of PIVH was very high (11.2%). CONCLUSION: From the present study we conclude that the incidence of PIVH especially in immature neonates is highly associated with low Apgar scores at birth. Since the Apgar score reflects the clinical condition and the degree of circulatory centralisation of neonates that is influenced by various ante- and intranatal risk factors, a protective obstetrical management is necessary to reduce the incidence of PIVH in neonates.
Acid-Base Equilibrium↗
Regional cerebral glucose utilization in immature fetal guinea pigs during maternal isocapnic hypoxemia.
Recent studies in immature fetal animals demonstrated only a slight or variable increase in the cerebral glycolytic rate during moderate isocapnic hypoxemia. However, the methods used in those studies did not allow for detection of small differences or of regional redistributions of the cerebral glycolytic rate. Hence, a global increase or a regional redistribution of the cerebral glycolytic rate during hypoxemia accompanied by a severe increase in tissue lactate concentration in a few brain areas may have been overlooked in these studies. Because these pathophysiologic mechanisms seem to considerably exacerbate neuronal cell damage due to hypoxic/ischemic insults, we were keen to clarify this point. We, therefore, applied the 2-deoxyglucose method to fetal guinea pigs in utero and measured total and regional cerebral glucose utilization in fetuses of this species at 0.75 of gestation during maternal isocapnic hypoxemia. At 0.75 of gestation guinea pig dams were chronically catheterized. Control groups were exposed to room air, whereas study groups were exposed to a hypoxic atmosphere (10% oxygen, 2% carbon dioxide, and 88% nitrogen). To measure total and regional cerebral glucose utilization during normoxemia and isocapnic hypoxemia, we injected i.v. 100 microCi of 2-[3H]deoxyglucose into the dams. Total and regional cerebral glucose utilization were determined from the steady-state clearance of 2-deoxyglucose between the maternal arterial plasma and the fetal brain, the glucose concentration in the maternal arterial plasma, and the "lumped constant." During isocapnic hypoxemia, total fetal cerebral glucose utilization was not significantly higher than that previously measured during normoxemia (8 +/- 0.8 versus 8 +/- 1.0 micromol/100 g/min). Furthermore, no redistribution of cerebral glucose utilization could be detected. We conclude that moderate isocapnic hypoxemia in the immature fetal brain does not lead to any significant increase or redistribution of glucose utilization or to any major lactate accumulation. This may be related to the low cerebral metabolic demands of brain tissue at this stage of development. Whether this is the main reason for the known resistance of the immature fetal brain toward ischemic neuronal cell damage remains to be established.
Animals↗
Lead concentrations in human plasma, urine and whole blood.
OBJECTIVES: Blood-lead levels (B-Pb), and to some extent urinary lead (U-Pb), are the most employed measures of lead exposure and risk. However, the small fraction of lead present in plasma (usually below 1% of that in blood) is probably more relevant to lead exposure and toxicity. Nevertheless, the lead content of plasma lead (P-Pb) has only seldom been used, mainly due to analytical limitations, which have now been overcome. We examined P-Pb in occupationally exposed subjects, as well as its relationship with B-Pb and U-Pb. METHODS: Blood samples were obtained from 145 male workers, 110 of whom were employed in lead work. After a simple dilution of plasma, P-Pb was determined by inductively coupled plasma mass spectrometry. The detection limit was 0.04 microg/l, and the imprecision was 5%. RESULTS: The lead concentration ranges were 0.20-37 microg/l for P-Pb, 0.9-176 microg/l (density adjusted) for U-Pb, and 9-930 microg/l for B-Pb. A close exponential relation was obtained between B-Pb and P-Pb. When B-Pb was plotted versus log P-Pb, a straight line (log P-Pb = 0.00225 x B-Pb - 0.58; r = 0.97) was obtained. Both the relation between U-Pb and P-Pb and that between U-Pb and B-Pb showed a large scattering (r = 0.78 in both cases). The relation to B-Pb appeared to be exponential, while that to P-Pb appeared to be linear. CONCLUSIONS: The low detection limit and good precision of P-Pb determinations make it possible to use P-Pb in assessments of lead exposure and risk. Furthermore, in relative terms, P-Pb is a more sensitive measure than B-Pb, especially at high lead levels. This development is of importance for studies of exposure, possibly also for studies of risks.
Adult↗
Ontogenetic differences in energy metabolism and inhibition of protein synthesis in hippocampal slices during in vitro ischemia and 24 h of recovery.
The present study was designed to clarify whether ontogenetic differences in the vulnerability of the brain towards hypoxic-ischemic insults are only caused by the low cerebral energy demand of immature animals or whether there are additional mechanisms, such as protein synthesis (PSR), that may be involved in this phenomenon. We therefore measured tissue levels of adenylates and PSR in hippocampal slices from immature (E40) and mature (E60) guinea pigs fetuses and from adult guinea pigs during in vitro ischemia and 24 h of recovery using a recently modified method. Hippocampal slices were incubated in a temperature controlled flow-through chamber, gassed with 95% O2/5% CO2. In vitro ischemia was induced by transferring slices to a glucose-free artificial cerebrospinal fluid (aCSF) equilibrated with 95% N2/5% CO2. The duration of ischemia ranged from 10 to 40 min. Adenylates were measured by HPLC after extraction with perchloric acid. PSR was evaluated as the incorporation rate of [14C]leucine into proteins. Under control conditions, tissue levels in adenylates did not change, whereas PSR increased slightly in hippocampal slices from mature fetuses and adult animals during a 24-h control incubation period. In slices from immature fetuses ATP levels were only maintained for 2 h. During in vitro ischemia the decline in ATP, total adenylate pool, and adenylate energy charge was much slower in slices from immature fetuses than in slices from mature fetuses or adults. After in vitro ischemia, ATP and the total adenylate pool did not completely recover in mature fetuses and adults, whereas adenylate energy charge almost returned to control values independently of the developmental stage. Two hours after in vitro ischemia PSR was undisturbed in slices from immature fetuses, but severely inhibited in slices from mature fetuses and adults. With ongoing recovery, PSR in mature fetuses returned to control values, while in adults it was still inhibited even 24 h after in vitro ischemia. From these results we conclude that hippocampal slices prepared from mature guinea pig fetuses as well as from adult guinea pigs can be held metabolically stable during long-term incubation using a recently modified technique. However, in slices from immature fetuses a stable energy state could not be maintained for more than 2 h. We further conclude that postischemic disturbances in PSR closely reflect the ontogenetic changes in the vulnerability of the brain to ischemia and that low energy metabolism is certainly not the only cause of the increased vulnerability of the fetal brain to ischemia.
Adenosine Triphosphate↗
The brain of the asphyxiated fetus--basic research.
The question whether asphyxia may be harmful to the brain of the fetus and newborn is largely related to the gestational age. Experimental studies on chronically prepared fetal sheep suggest that the resistance to asphyxia associated with maturity is not only related to structural changes in the fetal brain during development. Also, maturational changes of the sympathetic nervous system seem to be involved, which provide the neurohumoral basis for an effective circulatory and metabolic centralization to ensure intact survival of asphyxia (Jensen and Berger, 1991). This review will summarize the peculiarities of the fetal circulation, the redistribution of organ blood flow during hypoxaemia and asphyxia and its changes during development. Finally, it will focus on direct effects of asphyxia on the fetal brain. Future work in this field will have to concentrate on the important question how the fetal brain can be protected against the adverse effects of asphyxia.
Brain↗
Local cerebral glucose utilization in fetal guinea pigs at 0.75 gestation.
OBJECTIVE: Using the 2-deoxyglucose method, measurements of local cerebral glucose utilization in large fetal animals are very difficult and expensive. To circumvent these problems we recently modified the 2-deoxyglucose method for use in the fetal guinea pig in utero (Berger et al., J Neurochem 1994; 63: 271-279). The present study was designed to measure the rates of local cerebral glucose utilization in fetal guinea pigs at 0.75 of gestation. STUDY DESIGN: After intravenous injection of 14C 2-deoxyglucose into the dams, local cerebral glucose utilization of the fetuses was measured from the time integral of the tracer in the maternal plasma and the autoradiographically determined concentration of the tracer in various parts of the fetal brain. RESULTS: Fetal cerebral glucose utilization was low as compared to adult animals and varied in different brain structures from 19 +/- 4 to 29 +/- 7 mumol/100 g/min. CONCLUSION: This study demonstrates the feasibility to measure local cerebral glucose utilization in undisturbed fetal guinea pigs in utero. We conclude that the low rate of cerebral glucose utilization and its small overall variability may reflect the neurological immaturity of the fetal brain.
Animals↗
Relation between cerebral oxygen delivery and neuronal cell damage in fetal sheep near term.
Asphyxia is one of the major causes for fetal brain damage. Although the quality of life of the so affected children is mostly very limited, the pathogenesis of hypoxic fetal brain damage is poorly understood. Particularly, there is a lack of studies, in which cerebral oxygen delivery is directly correlated to the extent of neuronal cell damage in the same brain specimens. Therefore, we measured cerebral oxygen delivery before (- 1 h), during (+3 min & +27 min) and after (+10 min, +4 h, +72 h) 30 min of ischaemia in 5 chronically catheterized normoxemic fetal sheep at 129 +/- 1 days gestation (term is at 147 days) using the microsphere method. In contrast to previous studies (Williams et al. 1990), we arrested carotid arterial blood flow above the lingual artery for 30 min during surgery. Seventy-two hours later the fetal brains were fixed in vivo under barbiturate anaesthesia of both the fetus and the ewe. After cerebral blood flow analysis neuronal cell damage was assessed with light microscopy in 43 specimens of the fetal brain after cresyl violet/fuchsin staining using a scoring system. After arrest of carotid arterial blood flow cerebral blood flow was reduced by 80%. Neuronal cell damage was focussed on the cerebral cortex. Almost no damage could be detected in deeper parts of the brain. In the cerebrum there was threshold oxygen delivery of 3 ml O2/100 g tissue/min, below which neuronal damage occurred. However, there was no correlation between cerebral oxygen delivery and neuronal cell damage in specimens of the cerebrum, in which oxygen delivery was less than 3 ml O2/100 g tissue/min, suggesting selective vulnerability. Therefore, in addition to the reduction in cerebral oxygen delivery, other variables, e.g. neurotransmitter release, receptor pattern or oxygen radicals, may be involved in the development of brain damage.
Analysis of Variance↗
Catecholamine and serotonin concentrations in fetal guinea-pig brain: relation to regional cerebral blood flow and oxygen delivery in the growth-restricted fetus.
To test the hypothesis that intrauterine growth restriction (IUGR) would lead to altered neurotransmitter metabolism in the brain because of poorer oxygenation, blood flows and tissue concentrations of noradrenaline, dopamine, serotonin and their metabolites were measured in 14 parts of the brain of guinea-pig fetuses at 61-64 days' gestation. Eight fetuses with IUGR induced by uterine artery ligation were compared with 8 controls. Regional brain blood flows were determined by the microsphere method and tissue concentrations of monoamines by HPLC with electrochemical detection. The oxygen content of preductal arterial blood was significantly lower in IUGR fetuses than in controls (2.3 +/- 0.6 v. 3.5 +/- 0.5 mM; P < 0.001). Although this was compensated by increases in blood flow to many areas of the brain, significant decreases occurred in oxygen delivery to the temporal and occipital cortex, hippocampus and cerebellum of IUGR fetuses. In contrast, oxygen delivery to brainstem areas was maintained. Noradrenaline concentrations were closely similar in brains from the two groups, except for an increase in the caudate nucleus of IUGR fetuses. Dopamine concentrations were significantly elevated in brainstem areas. Concentrations of 3,4-dihydroxyphenylglycol (DOPEG), a noradrenaline metabolite, and 3,4-dihydroxyphenylacetic acid (DOPAC), a dopamine metabolite, showed a similar pattern of increase in brains of IUGR fetuses, possibly resulting from increased synthesis of noradrenaline and dopamine rather than from decreased degradation. Concentrations of serotonin were significantly higher in frontal and temporal cortex of IUGR fetuses, and the serotonin metabolite 5-HIAA increased significantly in cortical areas. Changes in neurotransmitter metabolism could not be related to oxygen supply, since serotonin concentrations increased in the forebrain, despite reduced oxygen delivery and the known dependence of tryptophan-5-hydroxylase on tissue PO2, and dopamine levels were elevated in the brainstem, where the oxygen supply was maintained.
Animals↗
Tools for the production and purification of full-length, N- or C-terminal 32P-labeled protein, applied to HIV-1 Gag and Rev.
We have constructed two new vectors for the production of foreign proteins in Escherichia coli. The vectors, pGEX-GTH and pET-HTG, produce protein fused to glutathione S-transferase (GST) at the N- and C-termini, respectively, allowing one-step purification on glutathione-Sepharose. Furthermore, they carry the recognition sequence (RRASV) for the catalytic subunit of cAMP-dependent heart muscle kinase (HMK) at the terminus distal to the GST tag, enabling specific 32P labeling in vitro. By positioning the GST and HMK sequences at opposite ends of the introduced gene, only full-length fusion protein becomes radiolabeled after purification. Avoiding the labeling of shorter fusion protein species, often observed in bacterial expression of foreign genes, is particularly important for a number of different purposes, including protein mobility shift analysis and protein footprinting technology.
Amino Acid Sequence↗
[Risk factors of listeriosis in Denmark 1989-1990].
Risk factors for listeriosis are foods and underlying diseases. A case-control-study of listeriosis patients' dietary habits showed that unpasteurized milk was a risk food for sporadic listeriosis. A blue-mould cheese was significantly more often eaten by patients ill with an epidemic phage type. Leukaemia, AIDS and renal transplantation were found to be associated with a more than 1000 times higher risk of acquiring listeriosis, compared with healthy persons. As a part of prophylaxis, persons with a high risk of listeriosis should be informed individually about food hygiene and risk foods.
Acquired Immunodeficiency Syndrome↗
[Parameters for risk assessment and risk prevention in pregnancy].
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Animals↗
[Cranial sinus thrombosis in puerperium].
Sinus venous thrombosis is a rare and severe disease, clinically characterised by headache, nausea, vomiting, focal deficits and epileptical seizures. We describe a case of sinus venous thrombosis 7 days post partum in a 21-year old woman. The pathogenesis symptoms, diagnosis and therapy are discussed. Advice for obstetric and gynaecological treatment after sinus venous thrombosis is given.
Adult↗
[Pulmonary adaptation of the newborn infant: in relation to respiratory distress syndrome].
At onset of respiration, important changes occur in the pulmonary circulation of the newborn. Pulmonary blood flow increases tenfold and pulmonary arterial pressure decreases quickly, thereby decreasing pulmonary vascular resistance to less than 5% of the prenatal values. Right-to-left shunting through the ductus arteriosus and the foramen ovale ceases concomitantly. About 100 ml of alveolar liquid are removed from the alveolar space by active and passive transport. Most of this fluid is drained by the pulmonary bloodstream. Both, disorders in the circulatory adjustments or a prolonged clearance of alveolar liquid, result in an interstitial oedema and hence can contribute to the development of respiratory failure in the newborn.
Adaptation, Physiological↗
Liquid movements in ventilated and perfused isolated lungs of fetal sheep at 0.87, 0.90, and 0.95 of term.
To study lung liquid movements, an isolated lung model, adapted from adult physiology, was developed to measure pulmonary weight changes after the onset of artificial ventilation of lungs from 16 fetal sheep at 0.87 (n = 5), 0.90 (n = 6), and 0.95 (n = 5) of gestation. The fetuses were delivered by Caesarean section. After tracheotomy and thoracotomy under general anaesthesia, a blocked air-free tracheal cannula and a pulmonary arterial catheter were inserted and secured to ensure in situ perfusion of the pulmonary circulation (Krebs-Henseleit buffer) without ventilation before the lungs were removed from the chest and mounted in a specially designed apparatus. Lung weight and pulmonary perfusion pressure were recorded continuously before, during and after the onset of ventilation. After 50 min of ventilation the perfusate was allowed to recirculate and samples were taken at 10-min intervals to determine the concentrations of sodium and the activity of lactate dehydrogenase (LDH) as a marker for cell destruction. In all lungs studied there was a significant removal of lung liquid after the onset of ventilation as assessed by lung weight loss. However, there was a positive correlation between lung weight loss and gestational age of the donor fetuses. These changes were accompanied by a rise in sodium concentrations in the perfusate, possibly suggesting that active sodium transport across the pulmonary epithelium facilitates alveolar liquid removal. As the experiments progressed the lungs regained weight while LDH concentrations increased, indicating that lung cell destruction causing pulmonary oedema may be involved. This pulmonary weight gain was inversely related to gestational age. It is concluded that in isolated ventilated and perfused lungs from fetal sheep, lung liquid removal is an age-related phenomenon that might involve an active sodium transport mechanism. It is further concluded that the development of pulmonary oedema during ventilation is also age related.
Animals↗
Circulatory responses to acute asphyxia in intact and chemodenervated fetal sheep near term.
The study concerned the role of the carotid sinus nerves in the effects of acute asphyxia on the fetal circulation. Fetal sheep (n = 12) were instrumented at approximately 130 days' gestation for placement of fetal vascular catheters and an occluder around the maternal descending aorta below the renal arteries. In 7 fetuses the carotid sinus nerves were cut. On the third post-operative day, asphyxia was produced by occluding the maternal aorta for 2 min and fetal blood flows were determined by the radio-labelled microsphere technique. In control, there were no differences between intact and denervated fetuses in blood gases, cardiovascular variables or blood flows, with the exception of lower blood flows to the cerebrum, caudate nucleus, kidney, skeletal muscle and scalp in the denervated group (P < 0.01). Fetal heart rate, cardiac output, stroke volume and the rate-pressure product were similar in asphyxia, with the exception that mean arterial pressure was lower in denervated fetuses after 2 min of asphyxia. Noradrenaline and adrenaline concentrations peaked at 2 min, then declined, the increase being smaller (P < 0.01) in denervated fetuses. Regional blood flows were similar in the two groups. Vascular resistance was lower in the placenta and abdominal aorta at 2 min in denervated fetuses. There were few differences in organ blood flows between intact and denervated fetuses, and the differences in flow in normoxia for the kidney, skeletal muscle and scalp (but not cerebrum, caudate nucleus and hippocampus) disappeared in asphyxia. This study confirms that section of the carotid sinus nerves has little effect on arterial blood pressure and fetal heart rate in normoxia but produces small differences in the responses to acute severe asphyxia, e.g. in arterial blood pressure and catecholamines, giving evidence for the operation of chemoreflexes. The lower blood flow to cerebrum, caudate nucleus, kidney, skeletal muscle and scalp in denervated fetuses in normoxia suggests a tonic vasodilatation, part of the drive for which comes from carotid chemo- or baroreceptors.
Animals↗
[Cerebral ischemia: ontogenetic differences in energy metabolism and protein biosynthesis].
OBJECTIVE: Are ontogenetic differences in the resistance of the brain towards ischemia reflected by differences in the postischemic disturbance of cerebral protein synthesis (PS) independently from energy metabolism (EM)? METHODS: We studied hippocampal slices from immature (E60) and mature (E60) fetal guinea pigs as well as from adult guinea pigs. Cerebral EM and PS were measured during and up to 24 h after ischemia. RESULTS: After in vitro ischemia there was no inhibition in cerebral PS in immature fetuses, a transient inhibition in mature fetuses, and a permanent inhibition in adults. During and after in vitro ischemia cerebral EM was hardly disturbed in immature fetuses. No differences in cerebral EM could be observed between mature fetuses and adults. CONCLUSION: Ontogenetic differences in the resistance of the brain towards ischemia are reflected by differences in the postischemic disturbance of cerebral PS. The differences between mature fetuses and adults are independent from cerebral EM.
Animals↗