Photoperiod affects the expression of neural cell adhesion molecule and polysialic acid in the hypothalamus of the Siberian hamster.

Immunohistochemical and immunoblot procedures were used to examine the effects of inhibitory short day (SD) photoperiod on the expression of neural cell adhesion molecule (NCAM) and its polysialylated form (PSA-NCAM) in the hypothalamus and preoptic area (POA) of the adult male Siberian hamster. In animals that had undergone SD-induced gonadal regression, immunoblot analyses revealed significant reductions in the content of immunoreactive PSA in anterior hypothalamic (AH) and mediobasal hypothalamic (MBH) regions. These changes were accompanied by increased contents of the 180 kDa NCAM isoform in the POA and AH, and decreased content in the MBH. The 140 kDa NCAM isoform also was elevated in the AH. Light microscopic analysis revealed a marked reduction in the density of NCAM-immunoreactive tanycyte-like processes in the MBH of animals exposed to SD. This effect was not blocked by castration, indicating that this may be a primay (sex steroid-independent) effect of altered photoperiod in the hypothalamus. Also, photoperiod-induced alterations in NCAM expression were not evident in non-responsive hamsters that maintained active testes under SD exposure. Collectively, these results are evidence that seasonal changes in photoperiod affect the expression of NCAM and PSA in the hypothalamus. Such changes could help promote plastic morphological rearrangements related to the regulation of seasonal reproductive and/or metabolic cycles.

[Soluble and membrane glycoproteins of the rat brain in radiation injury]. / Rastvorimye y membrannye glikoproteiny golovnogo mozga krys pri luchevom porazhenii.

The content of total protein, glycoproteins, and N-acetylneuraminic acid in different membrane fractions of rat brain tissues was studied 60 min and 24 h following X-irradiation with a dose of 0.31 C/kg. A slight increase in the amount of glycoproteins was noted upon electrophoresis due to the occurrence of low molecular weight carbohydrate-containing proteins. The derangement of the membrane glycoprotein structure is supposed to be one on the causes of radiation destruction of membranes.

On the interaction between 5-hydroxytryptamine and N-acetylneuraminic acid under aqueous conditions.

A complex designated 5-HT-NeuAc was formed between 5-hydroxytryptamine (5-HT) and N-acetylneuraminic acid (NeuAc) under aqueous conditions. Complex formation was encouraged by exposure to light (3000-3800 A; 1 A = 0.1 nm) and freeze-drying and the freeze-dried complex was isolated by gel filtration chromatography. Although stable to rechromatography on Bio-Gel P-2 if H2O was the eluent, 5-HT-NeuAc dissociated into the free components when placed in 0.1 M NaCl. Chemical analyses of the isolated complex showed that an equimolar amount of 5-HT and NeuAc was present and that all group functions were intact; these data suggested that the association between 5-HT and NeuAc was noncovalent. Spectrophotometric measurements demonstrated a small increase (approximately 12%) in extinction coefficient (275 nm) and a large increase (340- to 440-fold) in fluorescence emission (340 nm) compared with 5-HT alone. Data obtained from 1H nuclear magnetic resonance spectroscopy (250 MHz) of 5-HT and NeuAc standards compared closely to published reports. In comparison, measurements made with 5-HT-NeuAc showed that all 5-HT protons were slightly deshielded; of the NeuAc protons, slight deshielding of H8 and significant shielding of H3eq, H3ax, and H6 was observed. From these observations, a model describing the association between 5-HT and NeuAc is proposed.