The usefulness of rabbit serum as a culture medium for postimplantation rat embryos was examined. Rat embryos at day 9.5 of gestation were cultured in a mixture of rat and rabbit sera at various ratios (v/v) for 48 h. In 100% rat serum, a usual medium, rat embryos grew well. On the contrary, rat embryos died with little growth in 100% rabbit serum. In 75% rabbit and 25% rat sera, rat embryos grew but were morphologically abnormal. In 50% rabbit and 50% rat serum, however, rat embryos grew well showing no morphological abnormalities, as in 100% rat serum. It was concluded from these results that rabbit serum could be used at a proportion up to 50% as a medium for postimplantation rat embryo culture in a mixed form with rat serum. The rat embryo culture using rabbit serum as a medium would be useful in developmental toxicity studies, especially those involving species differences and toxicokinetics.

Animals↗

PubMedDate not supplied

Effect of dietary environment on the development of impaired glucose tolerance and pancreatic hormone secretion in neonatal streptozocin-treated (NSZ) rats.

The effects of four different diets, a balanced (BD), a high protein (HP), a high fat (HF), and a high carbohydrate (HC) diet on glucose tolerance and pancreatic hormone secretion were compared during the ten-week period immediately after weaning in rats having glucose intolerance induced by streptozocin in the neonatal period (NSZ). Feeding HF or HC produced decrease in calorie intake and a delay in body weight increase. All NSZ rats showed glucose intolerance as adults; the HF rats showed a further deterioration of glucose tolerance and a decreased insulinogenic index after oral glucose loading. Plasma insulin levels of HC rats were lowest. The glucose-induced insulin and somatostatin secretion from the isolated perfused pancreas was almost identical in all four groups. The arginine-induced insulin and glucagon secretion was decreased in HF and HC rats, compared to both HP and BD rats, but somatostatin secretion was not. These results indicate that a high fat or high carbohydrate dietary environment is an important factor in the development of glucose intolerance and in the impairment of pancreatic hormone responsiveness to stimulation.

Animals↗

PubMedDate not supplied

Presenilin 1 cleavage is a universal event in human organs.

A panel of antibodies raised against various regions of human presenilin 1(PS1)--the amino-terminal domain, the domain between the transmembrane domains 1 and 2, the cleavage-site, loop domains, or carboxyl-terminal domain--was prepared to analyze PS1 in human tissues. We observed the predominance of two fragments (28-kDa NH2 and 18-kDa COOH fragments) in various tissues, including cerebral cortices. In addition to these two fragments, we found a previously unidentified amino-terminal fragment of PS1 with Mr 14 kDa in the lungs, spleen, pancreas, and testes. Using a sensitive ELISA for PS1, we measured the amount of PS1 species in tissues and found high contents of PS1 fragment in the testes. Our data show that common and unique processing pathways of PS1 occur in a tissue-dependent manner. It is likely that cleavage at the loop structure of PS1 to produce a functional form is a common event in human organs.

Alzheimer Disease↗