Biomedical subjects

J W Nolten

Publications and source records attributed to J W Nolten.

3 recordsLinked to original sources

PubMed1978

Hypothalamic paraventricular unit activity during labour in the rat.

The spike activity of 191 antidromically identified paraventricular units was recorded during labour and the oestrous cycle of rats under urethane anaesthesia. Accelerated bursts of neuronal activity, as reported to occur during suckling, were not observed and changes in firing rate were not correlated with individual uterine contractions. There was, however, an increase in the magnitude of the mean spontaneous firing rate of antidromically identified neurosecretory cells during labour, as compared with all stages of the oestrous cycle. This increase was mainly caused by (1) a marked reduction (greater than 25%) in the percentage of totally silent cells and (2) an increase in the magnitude of the mean firing rate of the phasically firing units (1.58-3.44 spikes/s). It was concluded from these increases in spike activity that the tonic release of neurohypophysial hormones is stimulated during labour, and that this may contribute to the induction and course of labour.

Action Potentials↗

PubMed1976

Enzymic preparation of neurosecretosome- and pituicyte-enriched fractions from the rat neurohypophysis.

A microcellular dispersion procedure for the rat neurohypophysis was developed, comprising tissue softening and dissociation using a special sieving sytringe. In preparatory studies the influence of mesh width, and treatment with trypsin, pronase or collagenase-hyaluronidase was investigated using light and electron microscopy, as well as with microchemistry by means of protein and lactate dehydrogenase activity determinations. Trypsinization gave the best results. In the final adopted procedure, 3 incubated neurohypophyses were sequentially sieved through a 200- and a 50-mum mesh. The resulting 50-mul dispersion was found to contain numerous ultrastructurally well-preserved pinched-off axonal endings (neurosecretosomes), and pituicytes often revealing processes. On the basis of DNA and oxytocin assays 11% of the pituicytes and 28% of the axonal cytoplasm were recovered. Oxytocin immunofluorescence microscopy showed hormone within the neurosecretosomes, but often also in the cytoplasm of pituicytes. Microdensity gradient centrifugation was performed on neurohypophyseal disperions, in order to obtain fractions enriched for neurosecretosomes and pituicytes. Fractions were characterized by means of phase contrast, oxytocin immunofluorescence and electron microscopy, as well as by oxytocin and DNA assays as respective markers. With a 10:14:22% (w/v) Ficoll gradient, fractions were obtained for which the relative purification was by a factor of 4 on the basis of DNA/oxytocin ratios.

Animals↗

PubMed1976

Acid phosphatase activity in the rat neurohypophysis during increased levels of gonadothrophic hormones, in diabetes insipidus (Bratteboro strain) and after water loading.

The acid phos phatase activity of the rat neurohypophysis was measured during increased gonadotrophic hormone levels, in diabetes insipidus (DI) (Brattleboro strain) and after water loading, i.e. conditions that interfere with the function of the hypothalamo-neurohypophyseal system (HNS). In addition determination of tissue protein, lipid and DNA and of water metabolism were performed. Neurohypophyseal acid phosphatase activity expressed on a dry weight basis increased under all conditions. For gonadectomized females, Brattleboro rats and water loaded males an increased water metabolism was observed. The increased acid phosphatase activity is interpreted as being related to disposal of release residues during stimulation of the HNS (increased gonadotrophic hormone levels and DI) and to disposal of neurosecretory material during inhibition (water loading).

Acid Phosphatase↗