Seasonal mammals use the photoperiodic variation in the nocturnal production of the pineal hormone melatonin to synchronize their reproductive activity with seasons. In rodents, the (SD) short day profile of melatonin secretion has long been proven to inhibit reproductive activity. Lately, we demonstrated that melatonin regulates the expression of the hypothalamic peptides kisspeptins (Kp) and ...

A Syrian hamster embryo, aged 11 days and 4 h post-coitus, had a developing quadricuspid aortic valve. The septation of the cardiac outflow tract was confined to the distal part of the conotruncus. There was a conspicuous recess in the anlage that normally gives rise to the left aortic valve cushion. Globular endothelial cells arranged in several layers were present at the luminal side of the r...

The effect of mating behavior on the expression of Fos protein was analyzed within the chemosensory pathways of the male Syrian hamster brain. Following a single mating test, the number of Fos-immunoreactive (Fos-ir) neurons increased within the amygdala, bed nucleus of the stria terminalis and medial preoptic area. The mating-induced pattern of Fos expression within these brain regions shows a...

Proteins solubilized from the chemically transformed, highly tumorigenic Syrian hamster cell line, BP6T, and the untransformed parental embryo cells, have been analyzed by two-dimensional gel electrophoresis. Differences in seven major polypeptides have been identified in cytoplasmic and nuclear cell fractions from these two related cell types. The tumorigenic cells have lost the ability to syn...

The present paper records the availability of a new transplantable melanotic tumor in the Syrian golden hamster. A previous report (1) described the induction of multiple pigmented tumors in the Syrian golden hamster following the application to the skin of a single dose of the carcinogen 9,10dimethyl-l,2-benzanthracene. These tumors were sharply demarcated and located in the dermis and subcuta...

The present paper records the availability of a new transplantable melanotic tumor in the Syrian golden hamster. A previous report (1) described the induction of multiple pigmented tumors in the Syrian golden hamster following the application to the skin of a single dose of the carcinogen 9,10dimethyl-l,2-benzanthracene. These tumors were sharply demarcated and located in the dermis and subcuta...

The structurally modified polyene antibiotic nystatin methyl ester (NME) has been utilized as a half-selection agent for isolating interspecific mouse--Syrian hamster hybrids. By using HAT media supplmented with NME we have isolated hybrid clones from polyethylene glycol-fused cultures of biochemically defective mouse (A9 or B82) and genetically normal Syrian hamster (KHK/C13) cells. Unfused pa...

The golden hamster's (Mesocricetus auratus) performance on radial maze tasks has not been studied a lot. Here we report the results of a spatial memory task that involved eight food stations equidistant from the center of a circular platform. Each of six male hamsters depleted the food stations along successive choices. After each choice and a 5-s retention delay, the hamster was brought back t...

Chromatin from two Syrian hamster tissues: the Kirkman-Robbins hepatoma and the liver, has been separated into soluble (S) and insoluble (P) fractions. Both fractions contain the complete set of five main histones but differ in respect of HI subfractions. The hepatoma chromatin is known to contain an unusual HI subfraction, HI slow [12, 13], probably identical with a similar subfration present ...

Chromatin from two Syrian hamster tissues: the Kirkman-Robbins hepatoma and the liver, has been separated into soluble (S) and insoluble (P) fractions. Both fractions contain the complete set of five main histones but differ in respect of H1 subfractions. The hepatoma chromatin is known to contain an unusual H1 subfraction, H1 slow [12, 13], probably identical with a similar subfraction present...