In vivo growth hormone (GH) response to human GH-releasing factor (GRF) or somatostatin (SRIF) in foetal pigs.

The short-term effect of hypothalamic GRF and SRIF on the pituitary release of GH at different stages of gestation has been studied. In the present experiment eighteen gilts were used, six at each of 66, 88 and 110 days of gestation. Ventral laparotomy was performed under general anaesthesia and a section of uterus was exteriorized. Blood samples were obtained from the umbilical vein of three foetuses per gilt just prior to the injection of each foetus with either saline, 5 micrograms/kg of hGRF (1-44)NH2 or 50 micrograms/kg of SRIF into the umbilical vein. Additional blood samples were obtained 15, 30, 45 and 60 min post-injection. Serum samples were radioimmuno-assayed for GH (porcine). There was a treatment by gestational age interaction (P less than 0.01) on mean GH concentrations, area under the GH curve and GH peaks. While treatments had no effect (P greater than 0.1) on GH variables at 66 days of gestation, the area under the GH curve was slightly increased by GRF (P = 0.14) at day 88 and all GH variables were significantly increased (P less than 0.01)) by GRF at 110 days of gestation. There was a quadratic effect of time post-injection on GH concentrations at 88 (P less than 0.05) and 110 (P less than 0.001) days of gestation. There was no effect of SRIF injection (P greater than 0.1) on GH concentrations at any gestational age. In conclusion, the foetal pituitary responsiveness to GRF develops with foetal age and is maximal at the end of gestation, whereas there is no short-term response to a bolus of SRIF at any stage of gestation.     

Electromyography of the gluteal muscles in Hylobates,Pongo, and pan: Implications for the evolution of hominid bipedality

The gluteal musculature of primates has been a focus of great research interest among those who study human evolution. Most current theorists agree that gluteus superficialis (= maximus) need not have changed its action in the step from pongid to hominid, but dispute has arisen over a purported change in action and role of the gluteus medius. To clarify the functions of gluteus medius, gluteus superficialis, and tensor fasciae femoris during ape locomotion, we conducted a telemetered electromyographic study of these muscles in two gibbons, one orangutan, and four chimpanzees as they walked bipedally on the ground and on a horizontal tree trunk, walked quadrupedally on the same substrates, and climbed a vertical tree trunk. The results indicate that the gluteus medius of apes is not, as has been previously suggested, primarily an extensor of the thigh; its action is chiefly that of medial rotation. The role of the gluteus medius during bipedality is the same in apes and humans–to provide side-to-side balance of the trunk at the hip. The change in the hominid lateral balance mechanism can be viewed as primarily osteological, allowing preservation of the same muscle function with an extended thigh. As a result, the stride length is increased and there occurs a diminution of the demands placed on other muscles to maintain anteroposterior balance at the hip and knee. Our data also support the view that vertical climbing may be specifically preadaptive to bipedalism. One may picture the earliest hominid as part biped, when on the ground traveling between scattered food trees, and part climber, when moving from the ground to food.     

Carbon dioxide exchange characteristics of C4 Hawaiian Euphorbia species native to diverse habitats

Summary The characteristics of the photosynthetic apparatus of 11 Hawaiian Euphorbia species, all of which possess C₄ photosynthesis but range from arid habitat, drought-deciduous shrubs to mesic or wet forest evergreen trees and shrubs, were investigated under uniform greenhouse conditions. Nine species exhibited CO₂ response curves typical of C₄ plants, but differed markedly in photosynthetic capacity. Light-saturated CO₂ uptake rates ranged from 48 to 52 mol m^-2 s^-1 in arid habitat species to 18 to 20 mol m^-2 s^-1 in mesic and wet forest species. Two possessed unusual CO₂ response curves in which photosynthesis was not saturated above intercellular CO₂ pressures [p(CO₂)] of 10 to 15 Pa, as typically occurs in C₄ plants.Both leaf (g₁) and mesophyll (g_m) conductances to CO₂ varied widely between species. At an atmospheric p(CO₂) of 32 Pa, g₁ regulated intercellular p(CO₂) at 12–15 Pa in most species, which supported nearly maximum CO₂ uptake rates, but did not result in excessive transpiration. Intercellular p(CO₂) was higher in the two species with unusual CO₂ response curves. This was especially apparent in E. remyi, which is native to a bog habitat. The regulation of g₁ and intercellular p(CO₂) yielded high photosynthetic water use efficiencies (P/E) in the species with typical CO₂ response curves, whereas P/E was much lower in E. remyi.Photosynthetic capacity was closely related to leaf nitrogen content, whereas correlations with leaf morphological characteristics and leaf cell surface area were not significant. Thus, differences in photosynthetic capacity may be determined primarily by investment in the biochemical components of the photosynthetic apparatus rather than by differences in diffusion limitations. The lower photosynthetic capacities in the wet habitat species may reflect the lower light availability. However, other factors, such as reduced nutrient availability, may also be important.     

Enzymes of amide and ureide biogenesis in developing soybean nodules

Amide and ureide biogenic enzymes were measured in the plant fraction of soybean (Glycine max) nodules during the period 11 to 23 days after inoculation with Rhizobium japonicum (USDA 3I1b142). Enzymes involved in the initial assimilation of ammonia, i.e. glutamine synthetase, glutamate synthase, and aspartate aminotransferase, showed substantial increases in their specific activities over the time course. These increases paralleled the induction of nitrogenase activity in the bacteroid and leghemoglobin synthesis in the plant fraction. The specific activity of asparagine synthetase, however, showed a rapid decline after an initial increase in specific activity. Following the initial increases in the ammonia assimilatory enzymes, there was an increase in the activity of 5-phosphoribosylpyrophosphate amidotransferase, the enzyme which catalyzes the first committed step of de novo purine biosynthesis. This was followed by a dramatic increase in the purine oxidative enzymes, xanthine dehydrogenase and uricase. Smaller increases were observed in the activities of enzymes associated with the supply of metabolites to the purine biosynthetic pathway: phosphoglycerate dehydrogenase, serine hydroxymethylase, and methylene tetrahydrofolate dehydrogenase.     

Catabolism of adenine nucleotides in adenosine deaminase deficient erythrocytes

$\text{In vitro}$ incubation studies using fluoride and iodoacetate as glycolytic inhibitors have been carried out on red cells of the two subjects with adenosine deaminase deficiency. For comparison, similar studies have also been carried out on red cells from a normal subject and from a child with severe combined immunodeficiency with normal adenosine deaminase activity. The adenosine formed in the adenosine deaminase deficient red cells is a measure of adenosine 5′-phosphate breakdown initiated by 5′-nucleotidase, whereas inosine 5′-phosphate, inosine and hypoxanthine formation is a measure of adenosine 5′-phosphate breakdown initiated by adenylate deaminase. With fluoride as inhibitor, nearly all of the adenosine 5′-phosphate breakdown proceeded by way of adenylate deaminase, while with iodoacetate as inhibitor, 20–30% of the adenosine 5′-phosphate breakdown was initiated by 5′-nucleotidase acting on adenosine 5′-phosphate. In addition, significant amounts of adenine were produced in adenosine deaminase deficient red cells in the presence of the glycolytic inhibitors. Possible explanations for the findings noted in this study are discussed and related to recent studies on the properties of the pertinent purine nucleotide catabolic enzymes.     

Preliminary observations on the feeding behavior ofPan paniscus in the lomako forest of central Zaïre

The feeding behavior and ecology ofPan paniscus was studied over a seven-month period in Equateur, Republic of Zaïre, during 1974–1975. Additional data were gathered during four weeks in 1979.Pan paniscus was found to be primarily frugivorous but bonobo foods also consist of leaves, flowers, pith, invertebrates and small mammals.     

Pyruvate dehydrogenase complex from germinating castor bean endosperm

Subcellular organelles from castor bean (Ricinus communis) endosperm were isolated on discontinuous sucrose gradients from germinating seeds which were 1 to 7 days postimbibition. Marker enzyme activities of the organelles were measured (fumarase, catalase, and triose phosphate isomerase) and the homogeneity of the organelle fractions was examined by electron microscopy. Pyruvate dehydrogenase complex activity was measured only in the mitochondrial fraction and attempts to activate or release the enzyme from the proplastid were not successful. A pathway is proposed for the most efficient use of endosperm carbon for de novo fatty acid biosynthesis that does not require the presence of the pyruvate dehydrogenase complex in the proplastid to provide acetyl-coenzymeA.     

Allantoic Acid Synthesis in Soybean Root Nodule Cytosol via Xanthine Dehydrogenase

Allantoin and allantoic acid are the major forms of nitrogen transported from soybean nodules to other parts of the plant. Neither the pathway or the site of ureide synthesis has been demonstrated in root nodules.     

Piroxicam, a structurally novel anti-inflammatory compound. Mode of prostaglandin synthesis inhibition

Piroxicam is a potent inhibitor of prostaglandin biosynthesis. Experiments utilizing cell culture and microsomes derived from various sources have demonstrated that piroxicam is a selective inhibitor of the cyclooxygenase step of arachidonic acid metabolism. Little blocking activity is observed at the phospholipase, thromboxane or prostacyclin synthetase, and arachidonic acid lipoxygenase steps.     

Synthesis of a precursor to the B subunit of heat-labile enterotoxin in Escherichia coli.

Escherichia coli K-12 minicells were employed to investigate the biosynthesis of plasmid-encoded, heat-labile enterotoxin of E. coli. Two polypeptide species related to the B subunit of the toxin were expressed in the minicells. One of these polypeptides (molecular weight, 11,500) was immunoprecipitated by antiserum to cholera toxin. Because the B subunits of heat-labile enterotoxin and cholera toxin have common antigenic sites, we concluded that this species was the mature B subunit. The larger polypeptide (molecular weight, 13,000) is likely to be a precursor of the B subunit because it could be chased into the mature form. This conversion was inhibited by compounds which dissipate proton motive force, suggesting that processing requires energy.