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Biomedical subjects

A Geyer

Publications and source records attributed to A Geyer.

At least 19 recordsLinked to original sources
PubMed1992

Further characterisation of human rotaviruses isolated from asymptomatically infected neonates in South Africa.

Stool specimens were collected from healthy neonates at Ga-Rankuwa Hospital in the winters of 1984 and 1986 and tested for the presence of rotavirus infection. Asymptomatic excretion was found to occur in 25% of the newborn babies analysed. Gel electrophoresis of the rotavirus RNA genome revealed that a genomically stable strain of rotavirus was endemic in the ward at the time intervals examined. Hybridisation analysis of the VP4 and VP7 rotavirus genes, which encode the outer capsid neutralization proteins of the virus, was conducted. These results showed the presence of a serotype 4 rotavirus strain with an M37-like VP4 gene allele, which remained conserved in the nursery over the time period examined. Partial nucleotide sequences were obtained for a variable region of the VP7 gene and for the hyperdivergent region of the VP4 gene from 8 of these viruses and showed that remarkable conservation of these regions in the genes of the viruses occurred over time.

Base Sequence↗
PubMed1992

Unusual thionation of a cyclic hexapeptide. Conformational changes and dynamics.

One carbonyl oxygen of the cyclic hexapeptide cyclo(-Gly1-Pro2-Phe3-Val4-Phe5-Phe6-) (A) can be selectively exchanged with sulphur using Yokoyama's reagent. Surprisingly it was not the C=] of Gly1 but that of Phe5 which was substituted and cyclo(-Gly1-Pro2-Phe3-Val4-Phe5 psi [CS-NH]Phe6-) (B) was obtained. Thionation results in a conformational change of the peptide backbone although the C=O of Phe5 and the corresponding C=S are not involved in internal hydrogen bonds. Two isomers in slow exchange, containing a cis Gly1-Pro2 bond in a beta VIa-turn (minor) and a trans Gly-Pro bond in a beta II'-turn (major), were analyzed by restrained molecular dynamics in vacuo and in DMSO as well as using time dependent distance constraints. It is impossible to fit all experimental data to a static structure of each isomer. Interpreting the conflicting NOEs, local segment flexibility is found. MD simulations lead to a dynamic model for each structure with evidence of an equilibrium between a beta I- and beta II-turn about the Val4-Phe5 amide bond in both the cis and trans isomers. Additionally proton relaxation rates in the rotating frame (R1 rho) were measured to verify the assumption of this fast beta I/beta II equilibrium within each isomer. Significant contributions to R1 rho-rates from intramolecular motions were found for both isomers. Therefore it is possible to distinguish between at least four conformers interconverting on different time scales based on NMR data and MD refinement. This work shows that thionation is a useful modification of peptides for conformation-activity investigations.

Amino Acid Sequence↗
PubMed1990

[Occlusive therapy of psoriasis--comparison of clinical effectiveness of short-term and prolonged use].

In an open clinical trial on stationary psoriatic plaques, we compared the effects of shortime occlusive (SO) dressing (24h) and prolonged occlusion (PO: 5-28 days). IN SO, Weinstein's index decreased from 7.3 +/- 1.7 to 3.3 +/- 1.8 (n = 21), in PO from 6.5 +/- 1.1 to 3.7 +/- 1.7 (n = 15). The results were even better in cases with optimal PO dressing (decrease from 6.8 +/- 1.4 to 2.5 +/- 0.9). The most important side effects were itching and exsudation with ensuing smell. In only one of the cases did the side effects cause a drop-out after 5 days. Regarding stationary psoriatic plaques on the extensor sides of the lower legs and forearms. We recommend continuous occlusive dressing for 8-10 days--either as an alternative mode of therapy, or as an intermediate regimen.

Adolescent↗
PubMed1989

[The effect of endogenous and exogenous factors on psoriasis vulgaris. A clinical study].

Using computerized data collected from 390 patients we investigated the impact of "endogeneous" factors (infections, menarche, menopause, gravidity, hormonal contraception, stress, nutrition, alcohol consumption, drugs) and "exogenous" factors (seasons, climate, sun exposition, Koebner phenomenon) on the course of psoriasis. We recommend certain rules of behaviour based up on our data and the reviewed literature. It is of importance to inform patients about their skin disease and positive as well as negative modifications of its course by endo- und exogenous factors. This is the only way to enable patients for an active selfcare.

Adult↗
PubMed1988

Enteropathogens isolated from children with gastro-enteritis at Ga-Rankuwa Hospital, South Africa.

A prospective 3-year study for enteric pathogens associated with diarrhoea in children was undertaken at Ga-Rankuwa Hospital, South Africa. Rotavirus was the most commonly isolated pathogen (24%), showing a marked seasonal distribution, with an autumn peak in activity. Enterotoxigenic and enteropathogenic Escherichia coli were frequently identified, and Salmonella, Shigella and Campylobacter were also isolated. Cryptosporidium and Giardia lamblia were the most frequently seen parasites. Rotavirus, E. coli, Salmonella and Campylobacter occurred predominantly in children less than 1 year old, whilst Shigella and the parasites were prevalent at all ages.

Animals↗
PubMed1987

[Measurement of pressure and force as a basis of the postoperative evaluation of abdominal wall function].

By quantifying profiles of pressure and effects of forces in the operating area of inguinal hernia operations we found coughing to be the extreme burden for the abdominal wall and Bassini suture. The described technique of measuring the forces exercised in the suture spot by using an expanding wire can be used in principle such as the measurement of pressure in the rectum, for similar cases of general care in surgery.

Abdominal Muscles↗
PubMed1985

[Malfunction of equipment by the addition of a bacterial filter in the expiratory branch of the respiratory circuit].

The addition of a continuous Flow System to the circuit of a volume cycled respirator results in an additional IMV option and shows excellent performance for this purpose. The insertion of a bacterial filter into this modified circuit resulted in a dangerous increase of airway pressures after 54 "running hours" for that filter. Test series revealed an insufficient air transmission through the filter, caused by the water vapour-saturated inspiratory gas mixture, which is necessary in long term ventilation. Furthermore it was demonstrated that wet bacterial filters cause malfunction of SIMV systems due to interference with the demand valve responsible for proper air supply. The routine use of a bacterial filter placed in the expiratory branch results in higher risks in an already risky artificial ventilation system and use-nonuse relationships seem to be questionable.

Adult↗
PubMed1979

[Assessment of the cardiac output by impedance cardiography (differential rheography) to give optimum continuous positive pressure ventilation (author's transl)].

It is very important to know the cardiac output in artificial positive pressure ventilation for the determination of the exact dosage of dopamine and the endexpiratory pressure. Invasive monitoring of the cardiac output is not suitable for routine bedside use. In our study we looked into the question of whether the dosage of dopamine in continuous positive pressure ventilation could be controlled by impedance determination. Differential rheography, as described by Kaindl, Polzer, and Schuhfried, was used in the study. Relative changes in cardiac output after dopamine administration are shown with sufficient accuracy using the above-mentioned method.

Cardiac Output↗
PubMed1979

[The alveolar-arterial oxygen quotient. standard norms, clinical findings (author's transl)].

From the practical standpoint of view the A-aDO2 proved to be a good parameter for evaluation of global gas exchange. The endexspiratory oxygen pressure, recorded by mass spectrometry, is set equal to the alveolar oxygen pressure. Therefore it is possible for clinical use to have an on line monitoring of PETO2--PaO2. It is necessary to specify the pressure difference in dependence of the inspiratory oxygen pressure since the alveolo-arterial oxygen pressure difference increases with increasing inspiratory oxygen pressure concentration. For practical clinical purposes we come out with the relative ratio of the difference adjusted to the alveolar oxygen pressure. The alveolar-arterial oxygen quotient also called "quotient": formula: (see text) has proved to be a clinical suitable figure. For this quotient are no standard norms reported in the literature. This study was set up to evaluate the quotient in 9 healthy volunteers. The standard norms, found in our study, can basically used for practical clinical purposes. This quotient is demonstrated to be practicable in intensive care medicine (obstructive pulmonary disease, acute pulmonary failure, positive pressure ventilation).

Adult↗
PubMed1979

[Loss of resistance in axillary plexus blockade].

The results of the "loss of resistance" method for identification of the perivascular space are demonstrated. The axillary plexus with its accompanying structures is embeded in the perivascular space. 20 pressure readings were performed with a special transducer. A statistically significant pressure loss was demonstrated after passing the vascular and nerve sheath. The distinct pressure differences during the tissue penetration are recognized with the finger guiding the syringe, similar to the technique used for peridural anaesthesia. We thus believe that we can offer an exact method for blocking the axillary plexus with maximum safety which does not rely on the cooperation of the patient.

Axilla↗
PubMed1978

An automatic counter for autoradiographed cells in Petri dishes.

A simple automatic counting device for cells on Petri dishes is described. The device is tested up to 1 x 10(4) cells (0.01 m)-2 and counts linearly without coincidence error. The counting time for each dish is c. 3-4 min including the time required to place the dish in the apparatus.

Autoradiography↗
PubMed1977

[Control of respiratory therapy by means of rheography (author's transl)].

Rheography measures changes in electrical conductivity. In measurements taken at the thorax it was appeared that the changes in conductivity caused by breathing are superimposed by the changes caused by circulatory factors and exceed them in amplitude quite far. This makes the expansion of rheography for electrical respiration control possible. The changes in electrical conductivity are explained by inspiration into the alveoles, by the increase in the distance of the electrodes on thoracic expansion, and by the change in the intrathoracic blood volume. When using respiratory therapy the physiotherapist must pay great attention how the patient reacts to respiratory therapy and whether he is adapted correctly to the mechanical respiratory support devices. The method of "rheospirography" was tested as to whether it allows an objective, direct evaluation of the interplay between respiratory therapy and patient. The method appears to be able to control respiratory therapeutic measures as it allows an evaluation of the respiratory type, the regional ventilation, and the adaption of the patient to the device.

Adult↗
PubMed1977

The kinetics of contact inhibition in mammalian cells.

To elucidate the process of contact inhibition in mammalian cells, we investigated the kinetics of growth arrest in [3H]thymidine labelled embryonic chinese hamster (Cricetulus griseus L.) cells after the addition of various concentrations of unlabelled cells. It was observed that after the contact inhibition concentration had been reached, the cells grew undisturbed for one more generation. In the following 24 hr the concentration fell back to the level at the beginning of the experiment and stayed there.

Animals↗
PubMed1977

[Classical conditioning of agonistic behavior in the Syrian golden hamster (Mesocricetus auratus Waterhouse)].

Nine different reactions of unconditioned agonistic behavior of golden hamsters (Mesocricetus auratus Waterhouse) which could be elicited by an air blow (UCS) were classically conditioned at a sound of a xylophone (tone g), a previously neutral stimulus. Tone g (CS) was paired with UCS for a different number of trials/day. In all animals exposed to over 20 pairings/day components of the agonistic behavior were brought under the control of CS, but it was not possible to predict which one of the agonistic reactions would appear. Most of the animals generalized and also showed conditioned reactions (CR) when presenting tone c' instead of tone g. When utilizing a differential conditioning procedure the animals learned to discriminate between the different tones. Extinction of CR at tone g was reached after an individually different number of trials.

Acoustic Stimulation↗
PubMed1977

[Rheographic monitoring of lung ventilation (author's transl)].

Electrical conductivity changes are measured with rheography. Changes of conductivity on the thorax caused by respiration, superimpose and exceed those caused by different circulatory conditions. Therefore rheography was adapted for monitoring of respiration. Changes in electric conductivity can be explained by the inflow of air to the alveoli, by increase of the distance between electrode, and by changes of the intrathoracic blood volume. Rheography developed by Polzer and Schuhfried was tested in the intensive care unit and the respiration therapy department. It was shown that this method is suitable for control of respiration, for demonstrating regional differences of pulmonary ventilation, for checking of respiration therapy and for monitoring the ventilated patient.

Asthma↗
PubMed1976

An automatic apparatus for continuous suspension culture with a concentrating device.

A chemostat in which mammalian cells can be raised in continuous suspension culture is described. It is constructed from commercially available parts. This apparatus has the advantage over earlier models in that the medium can be pumped off free of cells, thus suddenly increasing the cell concentration in the culture. The apparatus has been successfully used in studies on contact inhibition.

Automation↗
PubMed1976

[Measurement of bronchopulmonary elastance and airway resistance: comparison between common methods and automatic continuous measurement by the system AUPREM (author's transl)].

The system AUPREM is a new measurement device, which allows continuous measurement of the mechanical properties of the lung and bronchial system. Pulmonary elastance and airway resistance can be measured continuously even in extremly debilitated or unconscious patients. Transpulmonary pressure change, airflow and tidal volume are used as input. From these values airway resistance and pulmonary elastance are calculated. Comparative measurements in a group of healthy subjects and in a group of patients with pathological resistance and elastance values revealed that there was no significant correlation between the system AUPREM and the commonly used methods bodyplethysmography and elastance measurement by oesophageal balloon. However, the differences are in a low order of magnitude.

Airway Resistance↗