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Biomedical subjects

R Schmid

Publications and source records attributed to R Schmid.

At least 307 records · Page 17Linked to original sources
PubMed1980

[Changes in obstetric management over the past decade (author's transl)].

Over a observation period of 10 years (1969-1979) developments in perinatal control techniques, mostly started in the 1st Department of Obstetrics and Gynaecology, University of Vienna, at the beginning of that period, and their effect on the obstetric management are presented. In contrast to a trend of decreasing birth rate for the whole of Austria the annual numbers of deliveries in this hospital remained -after a temporary increase-unchanged. Subpartial cardiotocographic monitoring is presently applied in about 95% of all cases. The frequency of Caesarean sections has risen from below 4% to approximately 8% over the past years. Simultaneously, a shift was observed from vital to preventive fetal indications in Caesarean sections, with a parallel tendency to relatively fewer vaginal-operative deliveries. The uncorrected perinatal mortality rate has been lowered to 1.35%. This decrease is partly due to our efforts to select high-risk pregnancies in order to control them intensively. Thus, ultrasound examinations have been liberally put into practice, e.g. leading to an early diagnosis of multiple pregnancy. Use of tocolytic drugs, as well as surgical closure of the cervix together with intensive prenatal care of pregnant women with a high risk of prematurity have proved their worth as compared with control groups. Due to early and special interest in research and in monitoring of placental insufficiency, hormone determinations and measurements of placental perfusion by isotopes took a fixed place in monitoring of high-risk pregnancies early on during the observation period. Evaluation of fetal lung maturity by amniocentesis now enables us to make well-grounded decisions to stop tocolytic measures or to induce labour. In the latter field the local application of prostaglandins to the cervix by an adaptor has recently opened up new aspects. Attention has also been paid to the emotional aspect by new techniques of psychprophylactic preparation for childbirth and by a policy of rooming-in of mother and child.

Cesarean Section↗
PubMed1980

[Influence of duration of sterility on the course of pregnancy (author's transl)].

106 sterile patients who had become pregnant were divided into three groups depending on the duration of their sterility (3-5 years, 5-8 years, more than 8 years). Mostly within one year after treatment of sterility the women became pregnant independent on the duration of their sterility. Pregnant, former sterile patients showed a higher percentage of early and late abortions and of neonates with "low birth weight" (less than 2500 g) than a normal population, but there was not observed a relationship to the duration of sterility.

Abortion, Spontaneous↗
PubMed1980

Influence of otolithic stimulation by horizontal linear acceleration on optokinetic nystagmus and visual motion perception.

Several studies in the past have demonstrated the existence of an Otolith-Ocular Reflex (OOR) in man, although much less sensitive than canal ocular reflex. The present paper 1 confirms these previous results. Nystagmic eye movements (L-nystagmus) appear in the seated subject during horizontal acceleration along the interaural axis in the dark for an acceleration level (1 m/s2) about ten times the perception threshold with a sensitivity of about 0.035 rad/m. When sinusoidal linear acceleration is combined with optokinetic stimulation, the recorded nystagmus slow phase velocity exhibits strong periodic modulation related to subject motion. This marked effect of linear acceleration on the optokinetic nystagmus (OKN) appears at a level (0.1 m/s2) close to the acceleration perception threshold and has a 4-fold higher sensitivity than L-nystagmus. Modulation of OKN can reach a peak-to-peak amplitude as great as 20 degrees/s for a given optokinetic field size it increases with the velocity of the optokinetic stimulus, i.e. with the slow phase eye velocity. In parallel with changes in OKN slow phase velocity, linear acceleration induces a motion related decrease in the perceived velocity of the visual scene and modifications in self-motion perception. The results are interpreted in terms of a mathematical model of visual-vestibular interaction. They show that sensory interaction processes can magnify the contribution given to the control of eye movements by the otolithic system and provide a way of exploring its function at low levels of acceleration.

Acceleration↗
PubMed1980

A non-linear model for visual-vestibular interaction during body rotation in man.

A mathematical model for visual-vestibular interaction during body rotation in an illuminated visual surround is obtained by combining a previous model of the optokinetic reflex (OKR) with a simplified model of the vestibulo-ocular reflex (VOR). OKR is activated by the slip of the image of the external world on the retina, and represents a negative feedback loop around VOR. For large retinal slip velocities OKR behaves as a basically non-linear system. The validity of the model is proved via computer simulation by comparing predicted responses with the experimental results obtained in man by Koenig et al. (1978) in different situations of visual-vestibular interaction.

Eye Movements↗
PubMed1980

Mechanism of bilirubin diglucuronide formation in intact rats: bilirubin diglucuronide formation in vivo.

Although it is well established that bilirubin monoglucuronide is formed in the liver from bilirubin by a microsomal bilirubin uridine diphosphate (UDP)-glucuronosyltransferase, the subcellular site of conversion of monoglucuronide to diglucuronide and the molecular mechanism involved in diglucuronide synthesis have not been identified. Based on in vitro studies, it has been proposed that two fundamentally different enzyme systems may be involved in diglucuronide synthesis in rat liver: (a) a microsomal UDP-glucuronosyltransferase system requiring UDP-glucuronic acid as sugar donor or (b) a transglucuronidation mechanism that involves transfer of a glucuronosyl residue from one monoglucuronide molecule to another, catalyzed by a liver plasma membrane enzyme. To clarify the mechanism by which bilirubin monoglucuronide is converted in vivo to diglucuronide, three different experimental approaches were used. First, normal rats were injected with either equal amounts of bilirubin-IIIalpha [(14)C]monoglucuronide and unlabeled bilirubin-XIIIalpha monoglucuronide, or bilirubin-XIIIalpha [(14)C]monoglucuronide and unlabeled bilirubin-IIIalpha monoglucuronide. Analysis of radiolabeled diglucuronide excreted in bile showed that [(14)C]glucuronosyl residues were not transferred between monoglucuronide molecules. Second, in normal rats infused intravenously with dual-labeled [(3)H]bilirubin [(14)C]monoglucuronide, no transfer or exchange of the [(14)C]glucuronosyl group between injected and endogenously produced bilirubin monoglucuronide could be detected in the excreted bilirubin diglucuronide. Third, in homozygous Gunn rats, injected (14)C-labeled or unlabeled bilirubin mono- or diglucuronides were excreted in bile unchanged (except that diglucuronide was hydrolyzed to a minor degree). This indicates that Gunn rats, which lack bilirubin UDP-glucuronosyltransferase activity, are unable to convert injected monoglucuronide to diglucuronide. Collectively, these findings establish that a transglucuronidation mechanism is not operational in vivo and support the concept that bilirubin diglucuronide is formed by a microsomal UDP-glucuronosyltransferase system.

Animals↗
PubMed1980

Hemocyanins in spiders, XII. Dissociation and reassociation of Eurypelma hemocyanin.

The dissociation and reassembly of Eurypelma californicum hemocyanin was studied under various conditions of pH, ionic strength and protein, calcium and magnesium concentrations. The hemolymph concentrations of calcium and magnesium were determined to be ca. 4 and 0.9mM, respectively. Eurypelma hemocyanin does not dissociate upon dilution down to 0.04 mg/ml. At physiological pH, phosphate causes partial dissociation. Dissociation at alkaline pH requires two days for completion and is dependent on hemocyanin concentration. Reassociation, starting with the total dissociated subunits, yielded 37 S, 16 S and unreacted 5 S material. The yield of 37 S particles after one day was 75%, but rose slowly to 84% after two weeks. Raising the calcium concentration above 1mM resulted in an increase of 16 S particles (hexamers). High magnesium concentrations interfered with ordered reassembly. However, 37 S, native-like particles are readily formed in the absence of both calcium and magnesium. Reassociation is strongly favoured if ionic strength is increased. The significance of the 16 S reassociation product was studied by repeated dissociation and reassociation and analysis of subunit composition. It was found that the 37 S reassociate contained the whole set of subunits, their quantitative proportions being identical compared to native 37 S hemocyanin. In contrast, the 16 S material was lacking the dimeric subunit bc4 (= 4D). Evidently, this hexameric product arises by incorrect reassociation of monomeric subunits. P50 and nH values were recorded for the reassociated hemocyanins. The 37 S component had a higher affinity and lower cooperativity than native hemocyanin, possibly due to ageing of the subunits.

Animals↗
PubMed1980

Measurement of bilirubin and its monoconjugates and diconjugates in human serum by alkaline methanolysis and high-performance liquid chromatography.

No accurate methods are available for specific determination of unconjugated and conjugated bilirubin. Using a novel approach, we now have developed such an assay which permits direct individual measurement of bilirubin and its isomeric monoconjugates and diconjugates in serum. The monosugar and disugar conjugates are quantitatively converted to the corresponding methyl esters, which are readily extractable into chloroform. These monomethyl and dimethyl esters and unconjugated bilirubin are then separated by HPLC and detected spectrophotometrically in the effluent. Use of an internal standard and calibration of the method with crystalline reference bilirubin and bilirubin methyl esters permit direct measurement of the individual pigment fractions in the sample. The acuracy of this procedure was verified by a radioisotope dilution method. In sera of 22 healthy adults and six patients with Gilbert syndrome, only unconjugated bilirubin was detected. In 42 serum samples of jaundiced patients with hepatobiliary disease, unconjugated and all conjugated bilirubin fractions were increased, with the monoconjugates generally predominating. The total concentration of bilirubin and its carbohydrate conjugates, as determined by the new method, was considerably lower than the TB obtained with conventional diazo procedures. Contrariwise, both the new method and the diazo procedures gave comparable resuts when normal serum enriched with purified bilirubin glucuronides was assayed. Our findings thus indicate that unidentified, diazo-positive compounds distinct from bilirubin and its ester conjugates are present in pathlogical serum samples. The reported asssay is expectd to serve as a reference method for measurement of bilirubin and its carbohydrate conjugates in serum and to find general application in the study of bilirubin metabolism.

Biliary Tract Diseases↗
PubMed1979

[Hormonal and functional parameters in hyperprolactinaemia (author's transl)].

58 women with raised serum prolactin levels and normal hypophyseal-X-ray parameters were subdivided into three groups according to the serum prolactin level (16 to 40, 41 to 80, greater than 80 ng/ml). In addition to the determination of LH, FSH, oestradiol, progesterone and testosterone in the serum and thyroid diagnostic procedures the following hormonal tests were performed: 1. response to gestagen; 2. response to clomiphene; 3. Gn-RH-test for hypophyseal function; 4. ovarian response to administered gonadotropins (only in cases with prolactin levels greater than 80 ng/ml). The grade of menstrual cycle disorders depends on the severity of the observed hyperprolactinaemia. Slight disorders like luteal phase insufficiency, anovulatory cycle and oligomenorrhoea are associated with low- or medium-grade hyperprolactinaemia. Mainly secondary, but also primary amenorrhoea is found in cases with higher serum prolactin levels (greater than 80 ng/ml). In these cases the hypophyseal response to Gn-RH is frequently found (61%) to be negative and, moreover, the ovarian response to administered gonadotropins seems to be diminished. Increasing HPRL levels often appear to be associated with a negative response to the other above-mentioned tests.

Clomiphene↗
PubMed1979

A mathematical model of the optokinetic reflex.

The role of the optokinetic reflex (OKR) is that of cooperating with the vestibulo-ocular reflex (VOR) in the task of image stabilization on the retina during head rotations in a stationary visual surround. Since the dynamics of VOR was already well established, it has been possible to make a broad estimation of what the dynamics of OKR should be in order to obtain the performances observed in normal subjects. A mathematical model of OKR has been presented, and the experimental results obtained by Raphan et al. (1977) in the monkey and by Collins et al. (1970) in man were used to validate the model and to obtain a precise estimation of its parameters.

Animals↗