Cytogenetic study in spermatocytes of mice and Chinese hamsters after treatment with isoniazid (INH)

Summary Meiotic chromosomes of spermatocytes from INH-treated male mice and Chinese hamsters were analysed for chromosome aberrations in diakinesis-metaphase I and metaphase II. The experiments were performed in two laboratories while a third laboratory participated in the chromosome evaluation. No enhancement of chromosome aberrations could be observed after acute treatment of early primary spermatocytes or chronic treatment of spermatogonia with INH.     

Studies on the (pro) insulin biosynthesis of islets of Langerhans of sand rats (Psammomys obesus).

By feeding a regular laboratory chow, sand rats (Psammomys obesus) from our breeding colony gained different body weights, though they received approximately the same quantity of calories. Sand rats, reaching a body weight above 160 g (group B) showed significantly increased blood glucose values in contrast to the animals with a body weight under 160 g (group A). Isolated pancreatic islets of these two groups of sand rats were incubated with [3H]-leucine to study the incorporation of this amino acid into proinsulin and insulin. The incorporation into proteins of pancreatic islets of sand rats of group B was stimulated by 0.45 mg and 3.0 mg/ml glucose. In group A there was no further stimulation from 0.45 mg to 3.0 mg/ml glucose. Insulin secretion could be stimulated by glucose in both groups, but the stimulation was stronger in group B than in group A.     

The use of percoll gradients, elutriator rotor elution, and mithramycin staining for the isolation and identification of intraerythrocytic stages of plasmodium berghei

Intraerythrocytic parasites of Plasmodium vinckei and Plasmodium berghei were separated according to their developmental stages using discontinuous Percoll gradients. Contaminating nucleated blood cells such as leukocytes were removed by elutriation centrifugation. The stages were unequivocally identified in smears using a newly developed DNA-specific staining procedure with mithramycin and fluorescence microscopy. This stain can also be used to detect parasites in human blood of very low parasitemias. The combination of methods described has many possible applications in immunologic and biochemical parasite research.     

An efficient procedure for serial nucleic acid hybridizations by titration analysis.

A simplified and efficient procedure has been developed for performing hybridization reactions and analyses of the percentage of hybridization on glass plates. This method is as accurate as conventional methods, while considerably reducing the time and costs to perform the hybridization in titration hybridization experiments.     

An automatic method for determination of urinary 3-methylhistidine: normal values.

A system for automatic analysis of urinary 3-methylhistidine is described, applying ion-exchange chromatography and using an automatic sample injector, a motoric selector valve, and a diode programmer, which controls the analytical system. The method permits a sampling rate of 22 samples/day. 3-Methylhistidine was completely separated from histidine in 37 min whereas 1-methylhistidine was eluted together with ammonia. The 3-methylhistidine concentration was linear up to 150 nmol/ml and no appreciable sample interaction was found at automatic sequential runs. The error, in a single determination based on duplicate samples, was 4.61% and, in duplicated determinations, 3.26%. The mean urinary 3-methylhistidine output was 299.4 ± 23.8 μmol/day in 12 healthy females and 545.5 ± 35.2 μmol/day in 12 healthy males. The 3-methylhistidine excretion was significantly higher in males than in females, when expressed as the absolute daily output or as the estimated ratio to body weight, body surface area, or creatinine.     

Polarization of tryptophan fluorescence measurements in muscle

The degree of polarization of the intrinsic tryptophan fluorescence of glycerinated single muscle fibres or fibre bundles (rabbit psoas or dorsal longitudinal muscle of Lethocerus maximus) was measured:

1. With sufficiently high (15 mM) ATP concentration or when an ATP regenerating system was used no difference in the degree of polarization of a contracting and a relaxed muscle was detected, whereas a distinct difference was detected between the relaxed and the rigor state. In contrast a distinct difference between the relaxed and contracting state was obtained at low ATP concentrations (5 mM). This difference is interpreted to be caused by an ATP-free core (rigor core) in the centre of the fibre.
2. No change in the polarization degree was detected after a rapid release of the contracting muscle.
3. In rigor state no difference in the degree of polarization of the tryptophan fluorescence was observed in the presence or absence of AMPPNP (concentration 0.5 mM).

These findings and the lack of difference between the polarization degree of the contracting and the relaxed muscle is interpreted to indicate that the polarization degree of the tryptophan fluorescence is not sensitive to the orientation of the cross bridges, or that the cross bridges do not rotate.