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Biomedical subjects

E Hofmann

Publications and source records attributed to E Hofmann.

At least 127 records · Page 7Linked to original sources
PubMed1990

A hysteretic cycle in glucose 6-phosphate metabolism observed in a cell-free yeast extract.

The dynamics of a partial glycolytic reaction sequence which converts glucose 6-phosphate to triose phosphates is described. The study was performed with cell-free extracts from baker's yeast harvested in the logarithmic and stationary growth phases. The experiments are based on a flow-through reactor supplied with the desalted cell-free extract as well as glucose 6-phosphate, ATP and phosphoenolpyruvate. In the reaction system the quasi-irreversible reactions catalyzed by 6-phosphofructo-1-kinase, pyruvate kinase, and fructose-1,6-bisphosphatase are involved. When substrate is supplied continuously, only stable stationary states can be observed. With transient perturbations of the substrate supply, multiple stationary states appear. Cyclic transitions between unique stable stationary states were induced by appropriate changes of the rate of substrate supply. A hysteretic cycle could then be demonstrated when, during reverse transitions, a parameter region of multistability was passed. The presence (in resting yeast) or absence (in growing yeast) of fructose-1,6-bisphosphatase did not significantly influence the dynamic capabilities of the investigated reaction sequence. The kinetic properties of the cell-free extracts fit mathematical models developed for in vitro systems reconstituted from purified enzymes.

Adenosine Triphosphate↗
PubMed1990

The "dense artery sign"--major cerebral artery thromboembolism demonstrated by computed tomography.

A 4 years review of high resolution thin slice (3-5 mm) computed tomography performed within 24 h after cerebral infarction revealed increased density in a major cerebral artery segment in 28 patients. Arteries affected were the vertebral and basilar artery in 6 and 8 patients, the sphenoid course of the middle cerebral artery in 13 cases and the extracranial internal carotid artery in 1 patient. In 35.7% of cases the so called "dense artery sign" provided earliest evidence of the ensuing infarction documented by CT controls in most patients. Angiography carried out in 8 patients, density calculations in the course of the affected vessel and resolution of the increased density on subsequent CT examinations suggest thrombembolism as the most likely etiology. In the clinical setting of acute stroke increased artery density encompassing the entire vessel diameter may serve as an early indicator of major cerebral artery occlusion and prompt angiographic investigation of a lesion potentially amenable to lysis.

Adult↗
PubMed1990

Verbal memory deterioration after unilateral infarct of the internal capsule in an adolescent.

After an infarction in the territory of the anterior perforating arteries, a 15-year-old, previously healthy, left-handed patient developed considerable verbal long term memory disturbances which could be followed up and tested for more than nine months. An extensive memory test battery was used to determine spared and impaired functions. The patient had remote memory disturbances with respect to personal events for the last 5 years and problems in all verbal task tested which required remembering items over time periods exceeding an hour. The patient was indistinguishable from control subjects on short-term memory tests and on a number of nonverbal learning and recognition tests. The crucial lesion for the observed deficits in the genu of the left internal capsule was assumed to have disrupted the anterior and inferior thalamic peduncles, fornix (column), stria terminalis, anterior commissure and the medial part of the globus pallidus. This infarct, therefore, most likely damaged traversing fibres which intercommunicate within the Papez circuit and the basolateral limbic circuit and which in part provide access to cortical memory representing areas.

Adolescent↗
PubMed1990

[Lumbosacral nerve root avulsion. Diagnosis using computed tomography, magnetic resonance tomography and myelography].

Root lesions in the lumbo-sacral region are rare, compared with injuries of the roots of the brachial plexus. They occur almost exclusively in association with serious injuries of the pelvis. The present case, without pelvic injury, is a rarity. The appearances on myelography and CT are well known, but the findings on MRI are also described and the value of this non-invasive procedure is discussed.

Adult↗
PubMed1990

Leg ulcers in a patient with spherocytosis: a clinicopathological report.

In a case of spherocytosis combined with ulcus cruris, Doppler sonography and phlebography revealed a chronic venous insufficiency, together with fibrinous precipitates in capillary and venous vessel walls. Some haemolysis and fragmentation of red cells in the biopsy was also observed. It is suggested that the haemodynamic alteration due to chronic venous insufficiency may have played the main role in the development of the ulcers, although the rheological disturbance caused by the spherocytosis may have had an aggravating effect. Circulatory disorders should be excluded, if skin ulcers are to be classified as haematological disorders.

Aged↗
PubMed1990

Regulation of the fructose 6-phosphate/fructose 2,6-bisphosphate cycle by enzyme phosphorylation and sn-glycerol 3-phosphate.

The regulation of the Fru-6-P/Fru-2,6-P2 cycle by the cooperation of allosteric and covalent mechanisms was investigated in a reconstituted enzyme system under in vitro conditions. Phosphorylation of the bifunctional enzyme exerts a much stronger effect than sn-glycerol 3-phosphate in lowering the quasi-stationary concentration of fructose 2,6-bisphosphate and in increasing the critical concentration of the fructose phosphates, respectively. However, sn-glycerol 3-phosphate is able to strongly amplify the decrease of the quasi-stationary concentration of fructose 2,6-bisphosphate due to phosphorylation. The experiments can be described by a mathematical model involving rate equations for the dephosphorylated and the phosphorylated PFD-2 and FBPase-2. The results are compared with data from the literature obtained under in vivo conditions.

Animals↗
PubMed1989

Effects of nifedipine on renal responses to human atrial natriuretic peptide in healthy subjects and normoglycemic patients with type 1 diabetes mellitus.

We examined renal responses to a pharmacological dosage of human atrial natriuretic peptide (hANP) and the potential interference of nifedipine administration with the effects of hANP on kidney function in healthy subjects and normoglycemic patients with type 1 diabetes mellitus. Ten healthy volunteers (age, 28 +/- 1 years) and ten patients (age, 33 +/- 2 years; diabetes duration; 14 +/- 3 years; HbAI 7.2% +/- 0.2%) were studied. According to a double-blind, randomized, placebo-controlled trial design, three experiments were performed in each subject using the double-dummy technique: placebo only, hANP only, and nifedipine + hANP. As i.v. bolus injection 100 micrograms hANP was given; nifedipine was applied buccally, at a dose of 10 mg 90 min before and at a dose of 5 mg together with hANP injection. At base-line and in the placebo only experiment, patients did not differ from controls. In the hANP only experiment, in both groups hANP resulted in increased urinary volume and both sodium and chloride excretion (P less than 0.05 vs placebo only experiment). In patients, hANP-induced increase in electrolyte excretion was greater than in controls (P less than 0.05). In the nifedipine + hANP experiment, hANP-induced changes in renal indexes were enhanced in controls (P less than 0.05 vs hANP only experiment) but not in patients. Thus, diuretic response to nifedipine + hANP in patients was decreased in comparison with controls (P less than 0.05). In patients, however, nifedipine administration decreased the hANP-induced increase in urinary albumin excretion (P less than 0.05 vs hANP only experiment). Creatinine clearance was uninfluenced throughout the experiments.(ABSTRACT TRUNCATED AT 250 WORDS)

Administration, Buccal↗
PubMed1989

MRI study of Baló's concentric sclerosis before and after immunosuppressive therapy.

An intra vitam diagnosis of Baló's concentric sclerosis in a 39-year-old male is described. To our knowledge this is the first reported case of ante-mortem diagnosis based solely on magnetic resonance imaging (MRI) findings. MRI showed features unique to this process. After high-dose intravenous therapy with prednisone, the clinical symptoms improved, and MRI showed marked changes of the concentric lesions.

Adult↗
PubMed1989

6-Phosphofructo-2-kinase and fructose-2,6-bisphosphatase from Saccharomyces cerevisiae.

In permeabilized yeast cells 6-phosphofructo-2-kinase and fructose-2,6-bisphosphatase are studied during growth. It is shown that in yeast at least two fructose 2,6-bisphosphate degrading enzyme activities occur, differing in pH profile and in their substrate affinities. The activities of 6-phosphofructo-2-kinase and of fructose-2,6-bisphosphatases drop in the exponential and the transition phase while the activity of the alkaline phosphatases steadily increases. In the stationary phase the activities of 6-phosphofructo-2-kinase and of the low Km fructose-2,6-bisphosphatase increase again. Yeast 6-phosphofructo-2-kinase and fructose-2,6-bisphosphatase were purified and separated from each other. The purified 6-phosphofructo-2-kinase was found to exhibit a very high specific activity (1.3 U/mg). The enzyme is efficiently inhibited by ATP. The ATP inhibition is most pronounced at low concentrations of magnesium and fructose-6-phosphate. Phosphoenolpyruvate and sn-glycerol 3-phosphate are inhibitors of the enzyme. The high-affinity yeast fructose-2,6-bisphosphatase releases inorganic phosphate from the 2-position of fructose 2,6-bisphosphate. It displays hyperbolic kinetics towards fructose 2,6-bisphosphate (Km = 0.3 microM) and is strongly inhibited by fructose 6-phosphate. The inhibition is counteracted by sn-glycerol 3-phosphate. The enzyme is shown to be inactivated by cAMP-dependent phosphorylation and reactivated by the action of protein phosphatase 2A.

Cell Membrane Permeability↗
PubMed1989

[The anatomy of the pterygopalatine fossa in CT].

The pterygopalatine fossa represents a central space in the depth of the facial skull. Acting as a mediator between neighbouring compartments it is traversed by numerous neurovascular structures. High resolution CT is possible not only to depict all those canals and openings but also the soft tissue contents of the fossa itself can be visualised by CT. This paper presents the radioanatomic prerequisites for assessment of the pterygopalatine fossa that may be affected by a variety of pathologic conditions.

Contrast Media↗
PubMed1989

Kinetics of 6-phosphofructo-2-kinase from Saccharomyces cerevisiae: inhibition of the enzyme by ATP.

6-Phosphofructo-2-kinase (PFK-2) was purified from yeast and separated from fructose-2,6-biphosphatase (FBPase-2). The purification procedure involved polyethylene glycol fractionation followed by chromatography on DEAE-Sephacel. PFK-2 and FBPase-2 were copurified in these steps. Separation of the two enzymes resulted from Sephacryl S-300 Blue chromatography. Then, PFK-2 was chromatographed on CM-Sephadex and eluted with a gradient of KCl. Finally, PFK-2 was rechromatographed at CM-Sephadex and specifically eluted with fructose 6-phosphate. PFK-2 (specific activity 1.3 U/mg) was purified about 25,000-fold. The enzyme is inhibited by ATP which is particularly pronounced at low concentrations of magnesium and fructose 6-phosphate. Phosphoenolpyruvate and sn-glycerol 3-phosphate are inhibitors of the enzyme.

Adenosine Diphosphate↗
PubMed1989

Influence of the placenta on fetal plasma insulin and neonatal hepatic enzyme induction in the rat.

In order to study the placental role in controlling glucose metabolism and neonatal induction of tyrosine aminotransferase in rat liver, a comparison was made between the artificially delivered-rat feto-placental unit and the newborn littermates. The immunoreactive serum insulin in the feto-placental unit remains as high as in utero for at least 1 h whereas in the newborn rat it decreases rapidly after delivery. From Caesarian section to 6 h later, in contrast to the newborn littermates, the feto-placental unit remains hyperglycaemic. Upon glucagon injection the feto-placental unit shows a delay in the increase of the hepatic tyrosine aminotransferase activity in comparison with the newborn rat.

Animals↗
PubMed1989

[Abnormalities of the bulbus venae jugularis: a cause for pulse synchronous tinnitus?].

Tinnitus synchronous with the pulse is usually caused by vascular processes. The best-known sources are vascular temporal bone tumours and arteriovenous malformations. Vascular tinnitus due to anomalies of the venous system is an entity of its own and may be associated with anomalies of the jugular foramen. The present investigation shows that a high jugular bulb facilitates the occurrence of pulsatile tinnitus, albeit not necessarily leading to a bruit. Imaging methods are necessary not only in the assessment of the jugular bulb but also in the diagnosis of intracranial hypertension, which can present by a typical venous tinnitus.

Humans↗
PubMed1989

Age-dependent effects of phorbol ester on adenylate cyclase stimulation by glucagon in liver of female rats.

The stimulation of adenylate cyclase by glucagon and isoproterenol in cell lysates of hepatocytes isolated from fetal and adult female rats were measured after pretreatment with 12-O-tetradecanoyl-phorbol-13-acetate (TPA). Glucagon stimulation of adenylate cyclase activation was found to decrease in the hepatocyte lysate of adult female rats. Application of guanyl-5'-yl-imidodiphosphate (GppNHp) and forskolin showed this effect to be localized on the receptor level. However, glucagon stimulation of glucose liberation from phorbol ester-treated hepatocytes from adult female rats was not influenced. Maximum effects of glucose liberation were observed at glucagon concentrations which did not stimulate adenylate cyclase. The results are in agreement with the proposed existence of a low and high affinity glucagon receptor coupled to two different transducing systems. It is concluded that TPA uncouples in the liver of adult female rats--most likely by phosphorylation--the low affinity receptor from the adenylate cyclase system, whereas the high affinity receptor and phospholipase C/inositol 1,4,5-trisphosphate (IP3)/diacylglycerol (DAG) signalling systems do not seem to be affected. Such TPA effects could not be found in the liver of fetal rats.

Adenylyl Cyclases↗