Scanning electron microscopic study of the oesophageal mucous layer in the eel, Anguilla anguilla L.

The structure of the mucous layer covering the oesophageal epithelium was analysed by scanning electron microscopy in the eel, Anguilla anguilla . Different fixation procedures were used to conserve the mucus in situ. The mucous layer changes progressively down the oesophagus from a thick dense layer to a very thin fibrous network. The possible roles of these mucous structures in ion absorption are discussed.     

Glutathione S-transferase in human organs

Glutathione S-transferase (GSH-T) distribution has been investigated in human tissues. The relative contribution of each species to total enzyme activity of the various tissues has been compared. "Cationic" (pI greater than 7.5) "neutral" (pI 6-6.5) and "anionic" (pI less than 5.4) species of GSH-T were separated by isoelectric focusing. "Cationic" GSH-Ts (ligandin) quantitated by radioimmunoassay were present in all tissues studied. Highest concentrations were in liver, kidney, duodenum, testis and adrenal. "Neutral" and "anionic" GSH-Ts were not present in every tissue or in every specimen of some tissues studied. Marked inter-organ and inter-individual variation in the relative concentration of the 3 GSH-T species may explain individual and organ susceptibility to drugs and toxins and underlines the need for future studies to examine individual enzymes rather than total activity.     

Production of Alanine by Fusarium moniliforme

Fusarium moniliforme grown in a chemically defined medium in submerged culture accumulated amino acids extracellularly. Alanine and glutamic acid were present in greatest amounts, with traces of glycine, lysine, threonine, and valine detectable. Increasing the glucose and urea concentrations of the medium increased yields of alanine. Further increases in alanine production occurred with elevated levels of mineral salts in the medium, whereas the addition of a vitamin mixture proved to be inhibitory. Chemical changes resulting from the growth of F. moniliforme in the final fermentation medium disclosed maximal alanine production, mycelial weight, and glucose consumption after 72 hr of incubation at 28.5 C. Total soluble nitrogen, by contrast, was minimal at the same time period. The pH remained in the alkaline range throughout the fermentation.     

Post-albumin, a foetal-specific rat plasma protein: Purification, physicochemical and immunological studies

1. The foetal-specific post-albumin of rat plasma was purified by electrophoresis on a Pevicon block. 2. The sedimentation coefficient, diffusion coefficient and molecular weight were determined for this protein and found to be similar to those of adult rat plasma albumin. 3. Foetal post-albumin and adult albumin were compared immunologically and shown, with rabbit antisera, to share no antigenic determinants, suggesting different genetic control of the production of each. 4. It is suggested that the disappearance of post-albumin in the newborn animal may result from the disappearance of haemopoietic tissue from the rat liver with advancing age.     

Oxygen radical mechanisms of brain injury following ischemia and reperfusion.

This review addresses current understanding of oxygen radical mechanisms as they relate to the brain during ischemia and reperfusion. The mechanism for radical production remains speculative in large part because of the difficulty of measuring radical species in vivo. Breakdown of lipid membranes during ischemia leads to accumulation of free fatty acids. Decreased energy stores during ischemia result in the accumulation of adenine nucleotides. During reperfusion, metabolism of free fatty acids via the cyclooxygenase pathway and metabolism of adenine nucleotides via the xanthine oxidase pathway are the most likely sources of oxygen radicals. Although leukocytes have been found to accumulate in some models of ischemia and reperfusion, their mechanistic role remains in question. Therapeutic strategies aimed at decreasing brain injury have included administration of radical scavengers at the time of reperfusion. Efficacy of traditional oxygen radical scavengers such as superoxide dismutase and catalase may be limited by their inability to cross the blood-brain barrier. Lipid-soluble antioxidants appear more efficacious because of their ability to cross the blood-brain barrier and because of their presence in membrane structures where peroxidative reactions can be halted.     

Angiogenic activity of maternal and fetal placental tissues of ewes throughout gestation

In Study 1, explants of caruncular and intercaruncular endometrium and fetal membrane were collected from ewes (5-6/day) on Days 11-13, 16-18 and 21-23 after mating and Days 10-12 after oestrus, and incubated for 24 h. Explant-conditioned media were evaluated for their effects on endothelial cell proliferation. Both caruncular and intercaruncular endometrium secreted factor(s) which stimulated endothelial cell proliferation, and which appeared to be greater than 100 x 10(3) Mr and heat-labile. In Study 2, conditioned media from explant incubations of caruncular and intercaruncular endometrium, cotyledon and intercotyledonary fetal membrane obtained from ewes (6-7/day) on Days 40, 65, 90, 115 and 140 after mating were evaluated for their effects on endothelial cell proliferation. Caruncular and intercaruncular endometrium and intercotyledonary fetal membrane secreted factor(s) which inhibited endothelial cell proliferation. Media from cotyledonary explants tended to stimulate endothelial cell proliferation on Day 115. Conditioned media from cotyledonary explants obtained from 3 additional ewes at Day 120 of gestation stimulated endothelial cell proliferation, and this activity also appeared to be greater than 100 x 10(3) Mr. Placental angiogenesis in ewes therefore appears to be modulated by both maternal and fetal placental tissues via stimulatory and inhibitory factors.     

Interaction of a potential vacuolar targeting receptor with amino- and carboxyl-terminal targeting determinants.

A protein of 80 kD from developing pea (Pisum sativum) cotyledons has previously been shown to exhibit characteristics of a vacuolar targeting receptor by means of its affinity for the amino-terminal vacuolar targeting sequence of proaleurain from barley (Hordeum vulgare). In this report we show that the same protein also binds to the amino-terminal targeting peptide of prosporamin from sweet potato (Ipomoea batatas) and to the carboxyl-terminal targeting determinant of pro-2S albumin from Brazil nut (Bertholletia excelsa). The receptor protein does not bind to the carboxyl-terminal propeptide (representing the targeting sequence) of barley lectin. The binding of the 80-kD protein to the sporamin determinant involves a motif (NPIR) that has been shown to be crucial for vacuolar targeting in vivo. The binding to the carboxyl-terminal targeting determinant of pro-2S albumin appears to involve the carboxyl-terminal propeptide and the adjacent five amino acids of the mature protein. The 80-kD protein does not bind to peptide sequences that have been shown to be incompetent in directing vacuolar targeting.     

Influence of simulated microgravity on the exercise performance of Fischer 344 rats

Measurements from mission specialists after space flights or from subjects subjected to head down tilt experiments have demonstrated a decrease in exercise performance. Similar decreases have been reported for rats that have participated in simulated microgravity studies using the head down-tail suspended method of Morey-Holton (HDS). Because it is unclear whether older animal populations would exhibit similar responses, we undertook a HDS study with Fischer 344 male rats.