Differential effects of maternal hypoxia or nutrient restriction on carotid and femoral vascular function in neonatal rats

In response to reduced oxygen or nutrient supply, the fetus may redistribute cardiac output to conserve brain and heart growth, at the expense of the peripheral tissues; however, it is not known whether alterations in vascular function are maintained after birth or whether reduced fetal oxygen versus nutrient supply produces distinct effects. Using a pressure myograph, we examined isolated carotid and femoral artery responses to phenylephrine and endothelin-1 in neonatal rats, after either reduced maternal oxygen or global nutrient restriction during late gestation. Timed-pregnant Sprague-Dawley rats were randomly assigned to control (n = 10), hypoxia (12% O2, n = 9), or nutrient restriction (NR, 40% of control diet, n = 7) protocol and treated from day 15-21 of pregnancy. Pups were collected 3-12 h after birth. Neonatal weights (P < 0.001) and relative liver weights (P < 0.001) were lower in hypoxia and nutrient restriction treatments compared with control, while relative heart weights were greater in the hypoxia than in the control or nutrient restriction groups (P < 0.01). Constriction to phenylephrine was reduced in carotid arteries from the hypoxia and nutrient restriction groups compared with control (P < 0.001), while the femoral artery response was greater in hypoxia-treated neonates compared with control or nutrient-restricted neonates (P < 0.01). Only the hypoxia reduced carotid responses to endothelin-1, while no differences were observed in the endothelin-1 responses in femoral arteries. Maternal hypoxia and maternal nutrient restriction produced distinct effects on heart growth and neonatal vascular function, suggesting that regional changes in cardiovascular function after poor fetal growth are dependent on the nature of the insult in utero.     

Nutrient control of brain neurotransmitter synthesis and function

Dietary fluctuations in nutrient availability are factors in the regulation of brain function. Until recently the prevailing view was that brain biochemistry and function were influenced by diet only when biochemical and clinical evidence of nutrient deficiency was present. It is now clear, however, that the brain is sensitive and responsive to diet composition. Preliminary data show that variation in vitamin and mineral nutrient intakes over ranges that are considered to maintain normal nutritional status may impact on brain biochemistry, owing to their many coenzyme roles. Furthermore, the synthesis of at least five brain neurotransmitters, namely serotonin, the catecholamines, acetylcholine, histamine, and glycine responds to dietary fluctuations in availability of their nutrient precursors, tryptophan, tyrosine, choline, histidine, and threonine, respectively. Not only are these biochemical events altered by normal variations in diet composition, but considerable evidence now exists to show that the brain uses this information to regulate many functions. Future studies can be expected to continue to elucidate the links between diet, brain neurotransmission, and brain function, and to exploit the application of these links in understanding the function of the brain under normal and disease conditions.     

Two-Tiered Control of Epithelial Growth and Autophagy by the Insulin Receptor and the Ret-Like Receptor,Stitcher

Body size in Drosophila larvae, like in other animals, is controlled by nutrition. Nutrient restriction leads to catabolic responses in the majority of tissues, but the Drosophila mitotic imaginal discs continue growing. The nature of these differential control mechanisms that spare distinct tissues from starvation are poorly understood. Here, we reveal that the Ret-like receptor tyrosine kinase (RTK), Stitcher (Stit), is required for cell growth and proliferation through the PI3K-I/TORC1 pathway in the Drosophila wing disc. Both Stit and insulin receptor (InR) signaling activate PI3K-I and drive cellular proliferation and tissue growth. However, whereas optimal growth requires signaling from both InR and Stit, catabolic changes manifested by autophagy only occur when both signaling pathways are compromised. The combined activities of Stit and InR in ectodermal epithelial tissues provide an RTK-mediated, two-tiered reaction threshold to varying nutritional conditions that promote epithelial organ growth even at low levels of InR signaling.     

Causal relations among cell cycle processes in Tetrahymena pyriformis. An analysis employing temperature-sensitive mutants

Utilization of temperature-sensitive mutants of Tetrahymena pyriformis affected in cell division or developmental pathway selection has permitted elucidation of causal dependencies interrelating micronuclear and macronuclear replication and division, oral development, and cytokinesis. In those mutants in which cell division is specifically blocked at restrictive temperatures, micronuclear division proceeds with somewhat accelerated periodicity but maintains normal coupling to predivision oral development. Macronuclear division is almost totally suppressed in an early acting mutant (mola) that prevents formation of the fission zone, and is variably affected in other mutants (such as mo3) that allow the fission zone to form but arrest constriction. However, macronuclear DNA synthesis can proceed for about four cycles in the nondividing mutant cells. A second class of mutants (psm) undergoes a switch of developmental pathway such that cells fail to enter division but instead repeatedly carry out an unusual type of oral replacement while growing in nutrient medium at the restrictive temperature. Under these circumstances no nuclei divide, yet macronuclear DNA accumulation continues. These results suggest that (a) macronuclear division is stringently affected by restriction of cell division, (b) micronuclear division and replication can continue in cells that are undergoing the type of oral development that is characteristic of division cycles, and (c) macronuclear DNA synthesis can continue in growing cells regardless of their developmental status. The observed relationships among events are consistent with the further suggestion that the cell cycle in this organism may consist of separate clusters of events. with a varying degree of coupling among clusters. A minimal model of the Tetrahymena cell cycle that takes these phenomena into account is suggested.     

Stem galls drain nutrients and decrease shoot performance in Diplusodon orbicularis (Lythraceae)

Insect galls are important nutrient sinks in the plant, ultimately affecting its reproductive success. We assessed the influence of a stem galler on the survival of plant shoots and whether these are able to concentrate nutrients in the gall’s tissues; thus testing the nutrient sink hypothesis. We measured gall sizes and nutrient concentrations in a Brazilian Cerrado plant, Diplusodon orbicularis, and its Cecidomyiidae stem galler. Galls grew larger on thicker shoots. Also, these shoots suffered smaller mortality from gall attack, while thinner shoots were commonly associated with the death of the shoot distal to the gall. Apical shoots suffered higher mortality, while basal shoots suffered lower mortality and were proportionally less attacked. Galled tissues were more nutrient rich than non-galled tissues. The nutrients P, Ca, and Mg were more concentrated inside the galls when compared to tissues in non-galled stems. Gallers also seem to be able to reduce toxic Al concentration in the plant tissues, as Al occurred in smaller concentrations inside the galls than out of them. Although stem gallers feed on tissues of low nutritional value, these are in a favourable position to intercept flowing nutrients and water. The death of small galled shoots possibly is due to the lack of essential nutrients and energy drained, or water restriction in them.     

Influence of dietary restriction on accumulation of heat-labile enzyme molecules in the liver and brain of mice

The influence of dietary restriction on alterations of two aminoacyl-tRNA synthetases was investigated in mouse tissues. Mice were fed a restricted diet (first 80% and then 60% of the ad libitum intake) from 23.5 months of age for 70 days. Before dietary restriction, about 35 and 25% of these enzymes in the brain and liver, respectively, were heat-labile. Dietary restriction resulted in a decrease in the percentage of heat-labile enzyme in both tissues: After 40 and 70 days of dietary restriction the percentage of heat-labile enzyme decreased to about 20 and 10%, respectively, in the brain and to undetectable or very low levels in the liver. These results suggest an interesting possibility that prolongation of the life span by dietary restriction is due to reduction in the level of altered enzyme molecules whose accumulation may be detrimental to cellular functions.     

Bacterial endophyte communities of two wheatgrass varieties following propagation in different growing media

Bacterial endophyte communities of two wheatgrass varieties currently being used in the revegetation of military training ranges were studied. Culturable and direct 16S rDNA PCR amplification techniques were used to describe bacterial communities present in Siberian and slender wheatgrass seeds, leaf tissues, and root tissues following propagation in either sand or a peat-based growing mix. Our hypothesis was that the resulting plant endophytic communities would be distinct, showing not only the presence of endophytes originating from the seed but also the characteristics of growth in the two different growing media. Both culture and culture-independent assays showed the likely translocation of Actinobacteria, Firmicutes, and Gammaproteobacteria from seed to mature plant tissues as well as subsequent colonization by exogenous organisms. Statistical analysis of 16S terminal restriction fragment profiles identified growing media as having a greater significant effect on the formation of the endpoint endophytic communities than either plant tissue or wheatgrass variety. In silico digests of the ribosomal database produced putative identifications indicating an increase in overall species diversity and increased relative abundances of Firmicutes and Cyanobacteria following propagation in sand and Betaproteobacteria following propagation in the peat-based growing mix. Results indicated a substantial translocation of endophytes from seed to mature plant tissues for both growing media and that growing medium was a dominant determinant of the final taxonomy of the endpoint plant endophytic communities.     

The effect of medium composition on the acetone-butanol fermentation in continuous culture

The effects of growing Clostridium acetobutylicum NCIB 8052 in a chemostat under conditions of glucose, NH(4) (+), PO(4) (3-), Mg(2+), and Fe(2+) limitation were examined. It was noted that limitation of any major nutrient resulted in the same fermentation pattern. Conditions where minor nutrient levels were reduced appeared to stimulate solvent production. Under conditions of Mg(2+) restriction, a productive solventogenic culture was produced, with a yield of total solvents on glucose of 35.5%.     

Protein malnutrition after weaning disrupts peripheral clock and daily insulin secretion in mice

Changes in nutritional state may alter circadian rhythms through alterations in expression of clock genes. Protein deficiency has a profound effect on body metabolism, but the effect of this nutrient restriction after weaning on biological clock has not been explored. Thus, this study aims to investigate whether the protein restriction affects the daily oscillation in the behavior and metabolic rhythms, as well as expression of clock genes in peripheral tissues. Male C57BL/6 J mice, after weaning, were fed a normal-protein (NP) diet or a low-protein (LP) diet for 8 weeks. Mice fed an LP diet did not show difference in locomotor activity and energy expenditure, but the food intake was increased, with parallel increased expression of the orexigenic neuropeptide Npy and disruption of the anorexigenic Pomc oscillatory pattern in the hypothalamus. LP mice showed disruption in the daily rhythmic patterns of plasma glucose, triglycerides and insulin. Also, the rhythmic expression of clock genes in peripheral tissues and pancreatic islets was altered in LP mice. In pancreatic islets, the disruption of clock genes was followed by impairment of daily glucose-stimulated insulin secretion and the expression of genes involved in exocytosis. Pharmacological activation of REV-ERBα could not restore the insulin secretion in LP mice. The present study demonstrates that protein restriction, leading to development of malnutrition, alters the peripheral clock and metabolic outputs, suggesting that this nutrient provides important entraining cues to regulate the daily fluctuation of biological clock.     

Relationships among Rhizosphere Oxygen Deficiency,Root Restriction,Photosynthesis, and Growth in Baldcypress (Taxodium Distichum L.) Seedlings

Seedlings of baldcypress (Taxodium distichum L.) grown in sealed containers containing nutrient solution were subjected to root-zone oxygen deficiency, physical restriction, and the combined stresses in a greenhouse. After six weeks of treatments (Phase I), half of the plants were harvested. The remaining half were allowed to continue (Phase II) under various treatments except plants that had restricted roots were freed thus allowing free expansion of roots into the nutrient solution. Oxygen deficiency and root physical restriction inhibited plant gas exchange parameters. Net photosynthetic rate (PN) was significantly higher in aerated unrestricted root (AUR) plants than in aerated root restricted (AR) plants and in anaerobic root unrestricted (FUR) plants than in anaerobic root restricted (FR) plants. After Phase I, FUR plants' shoot and root biomasses were 57.0 and 30.6 % lower than those of AUR plants, and AUR plants showed 3.3 and 3.8 times greater shoot and root biomasses than the AR plants, respectively. During Phase II, PN recovered rapidly in plants under aerated conditions, but not in plants under anaerobic conditions. The removal of physical root restriction under both aerated and anaerobic conditions resulted in rapid shoot and root growth in seedlings. Hence, root restriction or root-zone anaerobiosis, reductions in plant gas exchange, and biomass production in baldcypress were closely interrelated. In addition, root release from restriction was related to the regain of photosynthetic activity and biomass growth. The results support the previously proposed source-sink feed-back inhibition of photosynthesis in plants subjected to root-zone oxygen deficiency or physical restriction.     

Studies on the application of iron to some glasshouse vegetables grown in soilless culture

Summary The application of iron to some glasshouse crops in soilless culture was studied in the course of an investigation. The growing systems consisted of nutrient film technique and rockwool. The test crops were tomatoes, cucumbers and sweet peppers.Various iron chelates were compared in a range of concentrations in a nutrient film system as well as in a rockwool system. The results showed that higher iron levels in the nutrient solution are required in the nutrient film technique than in the rockwool system. The level of the iron content in the nutrient solution had a significant effect on the structure of the root system. Crop analyses showed that on the whole no clear relationship could be found between the iron content of the plant tissues and iron chlorosis in the crop. Only in a few instances could a relationship be established and them only by averaging the results of a series of samplings.     

Biodiversity and the productivity and stability of ecosystems

Attempts to unveil the relationships between the taxonomic diversity, productivity and stability of ecosystems continue to generate inconclusive, contradictory and controversial conclusions. New insights from recent studies support the hypothesis that species diversity enhances productivity and stability in some ecosystems, but not in others. Appreciation is growing for the ways that particular ecosystem features, such as environmental variability and nutrient stress, can influence biotic interactions. Alternatives to the diversity-stability hypothesis have been proposed, and experimental approaches are starting to evolve to test these hypotheses and to elucidate the mechanisms underlying the functional role of species diversity.     

Regulation of SIRT1 protein levels by nutrient availability

The mammalian NAD+ dependent deacetylase, SIRT1, was shown to be a key protein in regulating glucose homeostasis, and was implicated in the response to calorie restriction. We show here that levels of SIRT1 increased in response to nutrient deprivation in cultured cells, and in multiple tissues of mice after fasting. The increase in SIRT1 levels was due to stabilization of SIRT1 protein, and not an increase in SIRT1 mRNA. In addition, p53 negatively regulated SIRT1 levels under normal growth conditions and is also required for the elevation of SIRT1 under limited nutrient conditions. These results have important implications on the relationship between sirtuins, nutrient availability and aging.     

Nutrient restriction induces failure of reproductive function and molecular changes in hypothalamus–pituitary–gonadal axis in postpubertal gilts

People on a diet to lose weight may be at risk of reproductive failure. To investigate the effects of nutrient restriction on reproductive function and the underlying mechanism, changes of reproductive traits, hormone secretions and gene expressions in hypothalamus–pituitary–gonadal axis were examined in postpubertal gilts at anestrus induced by nutrient restriction. Gilts having experienced two estrus cycles were fed a normal (CON, 2.86 kg/d) or nutrient restricted (NR, 1 kg/d) food regimens to expect anestrus. NR gilts experienced another three estrus cycles, but did not express estrus symptoms at the anticipated fourth estrus. Blood samples were collected at 5 days’ interval for consecutive three times for measurement of hormone concentrations at the 23th day of the fourth estrus cycle. Individual progesterone concentrations of NR gilts from three consecutive blood samples were below 1.0 ng/mL versus 2.0 ng/mL in CON gilts, which was considered anestrus. NR gilts had impaired development of reproductive tract characterized by absence of large follicles (diameter ≥ 6 mm), decreased number of corepus lutea and atrophy of uterus and ovary tissues. Circulating concentrations of IGF-I, kisspeptin, estradiol, progesterone and leptin were significantly lower in NR gilts than that in CON gilts. Nutrient restriction down-regulated gene expressions of kiss-1, G-protein coupled protein 54, gonadotropin-releasing hormone, estrogen receptor α, progesterone receptor, leptin receptor, follicle-stimulating hormone and luteinizing hormone and insulin-like growth factor I in hypothalamus–pituitary–gonadal axis of gilts. Collectively, nutrient restriction resulted in impairment of reproductive function and changes of hormone secretions and gene expressions in hypothalamus–pituitary–gonadal axis, which shed light on the underlying mechanism by which nutrient restriction influenced reproductive function.     

ARRESTED GROWTH OF CHINESE HAMSTER OVARY (CHO) CELL COLONIES ON AGAR

Chinese hamster ovary (CHO) cells plated on agar form two classes of colonies; those which increase continuously in diameter and those which become arrested in outward growth. All colonies continue to increase in mass and thickness as demonstrated by computer-assisted analysis of time sequence photographs of several thousand colonies and by examination of histological sections. Colonies which shift from a monolayer to a mounded morphology at fairly large colony diameter (?1 mm) continue to increase in diameter. Colonies in which mounding occurs at smaller colony diameter (?1 mm) cease to increase in diameter but continue to increase in thickness, as demonstrated by histological examination and by computer-assisted analysis. Rapid cell division occurs at the edge of all colony classes, as shown by the distribution of mitotic figures. In arrested colonies these dividing cells must move toward the colony core to compensate for dying cells. Necrotic cells are found as a discrete zone at the air-colony interface in all cases for CHO cell colonies growing on agar. As such, necrosis is probably due to limitations in nutrient diffusion upward from the agar rather than oxygen diffusion downward.     

Early nutritional stress impairs development of a song-control brain region in both male and female juvenile song sparrows (Melospiza melodia) at the onset of song learning

Birdsong is a sexually selected trait and is often viewed as an indicator of male quality. The developmental stress hypothesis proposes a model by which song could be an indicator; the time during early development, when birds learn complex songs and/or local variants of song, is of rapid development and nutritional stress. Birds that cope best with this stress may better learn to produce the most effective songs. The developmental stress hypothesis predicts that early food restriction should impair development of song-control brain regions at the onset of song learning. We examined the effect of food restriction on song-control brain regions in fledgling (both sexes, 23-26 days old) song sparrows (Melospiza melodia). Food restriction selectively reduced HVC volume in both sexes. In addition, sex differences were evident in all three song-control regions. This study lends further support to a growing body of literature documenting a variety of behavioural, physiological and neural detriments in several songbird species resulting from early developmental stress.     

Tissue specificity and organisation of CpG methylation in calf satellite DNA I.

Examination of bovine satellite DNA I methylation within CpG dinucleotides has been made by restriction analysis. It is shown that variations in the methylation patterns occur between different tissues (brain, liver, thymus and sperm) . Some of the 8 Hpa II sites present per repeat are clearly undermethylated in sperm as compared to other tissues. Methylation is considered therefore, as a highly specific event. It is also shown that there is a spatial specificity in the methylation pattern of the 3 Hha I sites in all tissues. These results are discussed in the light of methylation and satellite DNA functions.