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Biomedical subjects

H Janssen

Publications and source records attributed to H Janssen.

84 records · Page 5Linked to original sources
PubMed1980

Analysis of secondary modifications of mouse mammary tumor virus proteins by two-dimensional gel electrophoresis.

The structural proteins of mouse mammary tumor virus (MMTV) were analyzed by two-dimensional electrophoresis on isoelectric focusing and sodium dodecyl sulfate gels. Many of the viral proteins displayed heterogeneity in charge due to variable contents of carbohydrates (in particular, sialic acid) and phosphate residues. Neuraminidase treatment of the virions influenced the isoelectric pattern of the envelope glycoproteins. The glycoproteins of an MMTV variant which was attenuated by replication in feline kidney cells had different isoelectric points. This suggested that the acquisition of an altered carbohydrate configuration had changed the host range of the virus. The major MMTV structural core protein, p27, consisted of two species, which had identical iodinated tryptic peptide compositions but differed in phosphate contents. Another MMTV phosphoprotein, p21, was separated into four different phosphorylated species. Phosphorylation of p21 could be performed in vitro by the MMTV virion-associated protein kinase. This enzyme also has a high affinity for MMTV p30 as a substrate. Possible functions of this enzyme are discussed.

Electrophoresis, Polyacrylamide Gel↗
PubMed1976

Studies on digitalis. VI. The effect of heparin on serum protein binding of digitoxin and digoxin.

The aim of the present study was to investigate the nature of the previously reported changes in the serum protein binding of digitoxin and digoxin in uremic patients under treatment with hemodialysis. Kinetic studies on protein binding during hemodialysis showed that the free fraction of digitoxin rose from 2.6% to 6.9% after 5 min of hemodialysis and remained elevated during the dialyzing period. Free digoxin rose from hemodialysis and remained elevated during the dialyzing period. Free digoxin rose from 78.3% to 87.1% during the same period. In vitro hemodialysis experiments showed that such changes occurred only in vivo. Injection of heparin (5,000 IU) to control subjects produced similar kinetic changes in the protein binding of digitoxin and digoxin. Free fatty acids changed in the same way. These results indicate that the heparin-induced release of free fatty acids causes displacement of digitoxin and digoxin from their albumin-binding sites. Patients on hemodialysis have lower serum levels of digitoxin and cardioactive metabolites (mean, 8.9 ng/ml) than control patients (mean, 16.7 ng/ml) (p less than 0.005) on similar doses (mean, 0.085 mg/day). They should be maintained on the same digotoxin doses as uremic and control patients, but serum digitoxin levels should be adjusted to 10 to 15 ng/ml in hemodialysis patients compared to 15 to 25 ng/ml in uremic patients and in patients with normal renal function.

Blood Proteins↗
PubMed1976

Cardiovascular effects of cerebroventricular ouabain perfusion in the adult dog.

Cerebroventricular perfusion with artificial cerebrospinal fluid containing 10(-5) M ouabain was performed in adult dogs in order to describe the time course of the cardiovascular effect of intraventricular ouabain and to evaluate treatments to eliminate the cardiovascular effect. The central effect of ouabain caused a 56% increase in blood pressure above control values and a 35% increase in heart rate with various cardiac arrhythmias. Both alpha- and beta-adrenergic blocking drugs given intravenously.altered the pressure and rate effects ou ouabain, whereas vagotomy attenuated the effect.

Adrenergic alpha-Antagonists↗
PubMedDate not supplied

Production of Co-60 sources for high-accuracy efficiency calibrations of gamma-ray spectrometers.

Activity determination by gamma-ray spectrometry is a valuable aid which is widely used where radioactive sources are applied. For the construction of an efficiency curve vs. energy in a standard geometry, the accuracy is limited not only by the uncertainty of peak area determination and the knowledge of the relevant emission probabilities but also by the uncertainties of the activity values applied to efficiency calibration with standard sources. Recently, a method to determine a relative efficiency function using selected radionuclides with gamma cascades of well known emission probabilities has been developed which yields very accurate efficiency values. Such a curve has to be converted into an absolute efficiency curve by calibration of the detector system with at least one source of very well known activity. Especially for this purpose, a set of Co-60 gamma-ray spectrometer sources was produced at the PTB. The activity values (10-45 kBq) were measured by the 4pi beta-gamma coincidence technique with a standard uncertainty of less than 0.1%. Production and measurement of these sources are described in the present paper. Special care was taken to include all contributions to the standard uncertainty of the activity value when establishing the uncertainty budget for the activity of each of these sources. The activity ratio of two of these sources, as obtained by the absolute measurements, was checked by independent gamma-ray counting at two other laboratories, where the precision achieved was less than 0.2%. The procedure described is considered to be a step towards more accurately determined efficiency functions in gamma-ray spectrometry.

Journal Article↗
PubMedDate not supplied

Standardization and decay data of 237Np.

This paper reports contributions from participants in the EUROMET project (No. 416) which was entitled "237Np research into problems relating to purification, characterization and standardization". Primary standardizations were made by the defined low solid angle, coincidence, 4pi alpha, 2pi alpha and liquid scintillation counting methods. Secondary standardizations were made with calibrated gamma-ray spectrometers. Absolute X-ray, gamma-ray and alpha-particle emission probabilities were also determined. The results for the successful conclusion of both primary and secondary standardization are presented together with the values for alpha-particle and gamma-ray emission probabilities determined in this exercise. Several significant inconsistencies remain with the gamma-ray emission probabilities, and these are highlighted.

Journal Article↗
PubMedDate not supplied

Semen analysis in the Usher syndrome type 2A.

Semen analysis in patients with Usher syndrome suggested that defective connecting cilia axonemes may be involved in the irreversible, progressive loss of photoreceptors in Usher's syndrome. In the framework of clinical genetic research into Usher syndrome, a pilot study was set up to test these findings. The semen of 6 Usher 2A patients was analysed. The fertility status of the study group of Usher 2A patients was evaluated, including semen analysis, supplemented by electron microscopic examination of the spermatozoa. Except for a significantly increased pH value, no abnormalities were found in the functional semen analysis, whereas electron microscopy revealed microtubular tail abnormalities. The latter finding was of little relevance, however, in view of the normal motility of the spermatozoa observed in these patients. There were no fertility problems in our group of Usher 2A patients, nor have any been mentioned in Usher patients in general. Earlier study findings were not supported by our data.

Adult↗
PubMedDate not supplied

Gender differences in attrition from orthopaedic surgery residency.

We conducted a national survey of orthopaedic surgery residency program directors regarding resident attrition. Female residents had a statistically higher attrition rate than male residents (p < 0.001). The female early withdrawal residents left voluntarily and for personal reasons more often than their male counterparts. These tendencies, however, were not statistically significant. We feel that more in-depth counseling of female medical students and increased mentoring for women in orthopaedic residency could help prevent this attrition.

Career Choice↗