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Biomedical subjects

E Keller

Publications and source records attributed to E Keller.

At least 325 records · Page 18Linked to original sources
PubMed1983

[Biosynthesis of phenylalanine and tyrosine in Streptomycetes].

The biosynthesis of phenylalanine and tyrosine from prephenic acid may proceed via phenylpyruvic acid or p-hydroxyphenylpyruvic acid or via arogenate. The enzymes necessary for these biosynthetic steps have been tested in a variety of Streptomycetes. Tyrosine is synthesized exclusively via arogenate, while phenylalanine is synthesized via phenylpyruvic acid. The feedback inhibition pattern of the corresponding enzymes has been determined. The organisms may be divided into four groups according to the properties of the phenylalanine and tyrosine biosynthetic enzymes and their regulation patterns.

Feedback↗
PubMed1982

Perceptual discrimination of vowels in aphasia.

In the present study 3 hypotheses were investigated: first, the notion that an aphasic impairment of vowel perception is not associated with particular aphasic syndromes or lesion sites, second, that it is a disorder comparable to a general impairment of perception in a normal speaker caused by some form of interference, and third, that perceptual phonemic discrimination is a separate process from the phonemic discriminative function necessary for speech production. The hypotheses were tested by means of a vowel discrimination test administered to 50 German-speaking aphasic patients (roughly equally divided between Broca's, mixed non-fluent, Wernicke's and mixed fluent groups); the same test, masked by white noise at -10 dB was also administered to 20 normal native speakers of German. Results were in support of all 3 hypotheses. First, aphasic patients' error patterns were similar across fluent and nonfluent groups and for all lesion sites. Second, the error distributions of aphasics with slight auditory impairment resembled those of normal subjects in the -10 dB white noise condition, while distributions of aphasics with severe auditory impairment were indicative of an added component of guessing behaviour. And third, the patients' performance on the discrimination task differed from that shown on a comparable repetition test. (It was argued that repetition involves a patient's expressive capacity in addition to his perceptual capacity). The differentiation of perceptual and expressive phonemic discrimination was further supported by an analysis of the speech errors occurring in the spontaneous (purely expressive) speech and in the repetition (expressive plus perceptual) tasks of 16 French Canadian and 5 English Canadian aphasics.

Adult↗
PubMed1982

Disposition and diuretic effect of furosemide in the nephrotic syndrome.

Plasma levels and diuretic response were determined in seven healthy subjects and six patients with severe nephrotic syndrome (NS) after 40 mg furosemide (Fu). Mean apparent volume of distribution and distribution volume at steady state of the groups did not differ. Total Fu clearance was higher in NS (251 +/- 54 ml/min) that in healthy subjects (174 +/- 32 ml/min) (P less than 0.01), a difference that correlated with the nonrenal clearance of 56 +/- 28 ml/min in healthy subjects and 154 +/- 45 ml/min in patients with NS (P less than 0.001). Normal beta-elimination half-life of 51 +/- 7.7 min was 37 +/- 6.2 min (P less than 0.001) in NS. Mean normal Fu protein binding pf 98.6 fell to 97.2%, with decreasing plasma albumin levels. After 40 mg IV Fu, sodium and volume excretion decreased in NS (P less than 0.001 and P less than 0.005). In patients Na+/Fu excretion rate ratios showed "tubular resistance" to Fu over the time when large amounts of Fu were excreted. The reduced diuretic response to Fu in NS is taken to be mainly a consequence of its impaired renal excretion.

Adult↗
PubMed1982

Arogenate (pretyrosine) pathway of tyrosine and phenylalanine biosynthesis in Pseudomonas aureofaciens ATCC 15926.

Assays of enzyme activities suggest that arogenate, the product of prephenate transamination, is an intermediate in the biosynthesis of both phenylalanine and tyrosine in Pseudomonas aureofaciens ATCC 15926. In addition to prephenate dehydratase and prephenate dehydrogenase, arogenate dehydratase and arogenate dehydrogenase activities were demonstrated. This pattern of aromatic amino acid biosynthesis in pseudomonads had previously been demonstrated only in P. aeruginosa. Arogenate dehydrogenase from P. aureofaciens differs from that in P. aeruginosa in its utilization of either NAD+ or NADP+ as cofactor and its inhibition by L-tyrosine. During ammonium sulphate fractionation, arogenate dehydratase co-precipitated with prephenate dehydratase I activity and not with prephenate dehydratase II. The pattern of regulation of the arogenate route to tyrosine in P. aureofaciens ATCC 15926 differed from that previously reported for strain ATCC 13986.

Amino Acids, Dicarboxylic↗
PubMed1982

[Problems of fresh rupture of the anterior cruciate ligament].

The importance of the anterior cruciate ligament as a part of the central pivot and the necessity of reconstruction in cases of fresh rupture is pointed out. In 400 arthroscopies of the knee joint we found 69 old ruptures of the anterior cruciate ligament. This number shows that a rupture of the anterior cruciate ligament is often not diagnosed early. In 28 fresh cases of knee joint trauma with haemarthrosis and without clinical or radiological instability arthroscopy was performed within 7 days after trauma. There was a fresh rupture of the anterior cruciate ligament in 20 cases. Haemarthrosis was the leading clinical sign in all cases of fresh ruptures.

Arthroscopy↗
PubMed1982

Effect of chronic ethanol treatment and withdrawal on mitochondrial redox activity in brain cortical slices.

The effect of chronic ethanol treatment on cytochrome a-a3 redox activity was studied in rat brain cortical slices. The slices were depolarized by electrical pulses and the level of reduced cytochrome a-a3 was directly measured within the slice by dual wavelength spectrometry. Cortical slices cut from the brains of rats withdrawn from ethanol demonstrated less reduction of cytochrome a-a3 following electrical depolarization compared both to controls and ethanol addicted rats. It is suggested that this effect of ethanol withdrawal on cytochrome a-a3 redox activity is due to a change in the regulation of mitochondrial activity.

Alcoholism↗
PubMed1982

[Activities of various enzymes in brown fat tissue of rabbits in the pre- and post-natal period].

Newborn rabbits have mainly brown or multilocular fat tissue. The activity of G-6-PDH shows a prenatal decrease. The G-6-PDH activity is clearly lower in postnatal as compared to the fetal period. This is due to the minor role of fatty acid synthesis with reduced fat storage during this time. The high capacity of glycolysis becomes apparent by the high activity of hexokinase and lactate dehydrogenase. The activity of both enzymes, however, shows only slight postnatal changes, so that HK and LDH in contrast to pyruvate kinase in the postnatal period apparently have no regulatory effect. The altogether high activity of the NADP specific isocitrate dehydrogenase indicates the high turnover rates in the Krebs cycle and suggests the adjustment of the metabolism to a high energy turnover.

Adipose Tissue, Brown↗
PubMed1982

[Carbohydrate metabolism in rabbit livers in the pre- and post-natal period].

Until the 25th day of gestation only traces of glycogen are present in the fetal liver of rabbits. Then, a steep rise can be observed until birth. The prenatal accumulation of glycogen protects the newborn against glucose deficiency after the sudden interruption of glucose supply after birth. Immediately after birth the blood glucose level falls in newborn rabbits. With insufficient gluconeogenesis stabilization during the first hours of postnatal life depends on the extent of the glucogen storage in the liver. The HK of the rabbit liver shows a higher activity during the fetal period as compared to the postnatal period. During postnatal life the relative proportion of the HK of the phosphorylation of glucose shows a consistent decrease; and in adult animals this function is nearly entirely taken over by the GK. In accordance with the occurrence of a GK activity the glycogen content shows a steep increase in the rabbit liver after the 9th day of life. The high PK activity of the fetal liver suggests a high glycolytic activity. The decrease in activity during the first days of life favours the overshooting gluconeogenesis of this phase and thus might contribute to the stabilization of the glucose blood level. The rise of activity at the 9th day of life shows a nearly synchronous behaviour in comparison with the development of the GK activity. Due to the change of food with introduction of solid nutrition rich in carbohydrates the PK shows a new rise after the 21st day of postnatal life. Whereas the activity of LDH of the fetal liver of rabbits is of the same magnitude as that of adult animals, there is a perinatal increase of activity with a peak at the 9th day of postnatal life. This step-up of activity is regarded as an adaptation phenomenon by de novo synthesis of enzyme protein.

Animals↗
PubMed1981

Disposition of hydrochlorothiazide (Hct) during phenytoin (Ph) treatment.

Plasma levels and urinary recovery of Hct were determined in seven healthy male volunteers. 75 mg Hct were administered as a tablet in a randomised fashion with or without phenytoin pretreatment (300 mg/d). Bioavailability of Hct showed considerable intra- and interindividual variation (32--87% and 42--77% respectively), but phenytoin did not influence the disposition parameters of the diuretic.

Adult↗
PubMed1981

Influence of hepatic cirrhosis and end-stage renal disease on pharmacokinetics and pharmacodynamics of furosemide.

After rapid intravenous injection of furosemide 40 mg (Fu), plasma levels were determined in 7 healthy volunteers, 8 patients with liver cirrhosis with ascites and 7 patients with end-stage renal disease (ESRD). The diuretic response was evaluated by measuring the urinary excretion of sodium and potassium and the urine volume. The mean elimination half life (t 1/2 beta) of Fu averaged 51 +/- 7.7 (+/- SD) min in healthy subjects, 52 +/- 7.7 min in cirrhosis and 200 +/- 57 min in ESRD. The non-renal clearance (Clnr) in healthy subjects (56 +/- 28 ml/min) corresponds to the total plasma clearance in functionally anephric patients (54 +/- 18 ml/min). In cirrhosis there was no significant change in the disposition parameters of Fu in comparison to the healthy volunteers, but there was a significant reduction in urine sodium and volume, whereas potassium excretion remained unchanged. Fu "excretion rate--response" curves showed diminished tubular sensitivity to Fu in cirrhosis.

Adult↗
PubMed1981

L-Proline inhibition of glutamate release.

The influence of 1 mM-L-proline on electrically stimulated release of endogenous glutamate from slices of rat frontal cortex was measured. One mM-L-proline approximates the in vitro concentration that inhibits glutamate-induced spreading depression. Also, this L-proline level has been reported to be present in brain after an intraperitoneal injection that induced amnesia in chicks. L-Proline but not D-proline exhibits an inhibitory effect on glutamate release, thus supporting the suggestion that this mechanism may play a role in memory retention and/or formation.

Animals↗
PubMed1981

[Fresh fibular rupture of the lateral capsular ligaments - diagnosis - treatment - results (author's transl)].

The frequent injuries of the lateral capsular ligaments of the ankle joint should be diagnosed and differentiated by an accurate case report and by physical and standardised radiological examination. Precise judgement and an adequate treatment are necessary to avoid recurrent subluxation of the ankle joint, a possible factor in the eventual development of post-traumatic arthrosis deformans. A primary suture should be preferred in all cases of fresh and severe instability, especially in young patients and in patients who are active in sports. After healing of the soft tissue and active functional treatment of the ankle joint, a plaster cast bearing the full weight of the patient is used for another four weeks. Follow-up examinations of 150 patients of a group of 552 patients, treated from 1971-1980, showed good results in 92.3% of the patients.

Adolescent↗
PubMed1981

[Results of a modified Watson-Jones graft used in the treatment of chronic fibular instability of the lateral ligaments (author's transl)].

Pathogenesis, signs and diagnosis of the chronic instability of the lateral ligaments of the upper ankle are described. The advantages and disadvantages of a modified Watson-Jones graft are discussed and are compared with other surgical procedures. From 1970 to 1980, 157 modified Watson-Jones grafts were performed at the Trade Association Accident Clinic in Tübingen. Follow-up examinations were possible in 100 patients. In none of the patients was it possible to demonstrate the same extent of pre-operative instability; the functional reduction of mobility appeared minimal. 39 of 54 athletes resumed full sports activities, and 89% of the patients stated they were satisfied with the results. The modified Watson-Jones graft, in spite of the well-known objections, is recommended as a satisfying method of treating chronic fibular instability.

Adolescent↗