Trypanosoma cruzi: Nucleotide and vitamin requirements of growing epimastigotes

Using a defined culture medium it was shown that Trypanosoma cruzi epimastigotes (strains Y, Ma, and F1) do not require exogeneous nucleotides for continuous cultivation. Biochemical determinations carried out on parasites grown in the presence or absence of exogenous nucleotides revealed no differences in intracellular nucleotide concentrations. This suggests that T. cruzi epimastigotes have the capacity for de novo nucleotide synthesis. Choline and folic acid were necessary only for high yields of T. cruzi, suggesting that epimastigotes can partially satisfy their vitamin requirements.     

Walking performance and aerobic and anaerobic metabolism of Carcinus maenas (L.) in sea water at 15°C

Walking performance of the shore crab Carcinus maenas (L.) in sea water at 15 °C was assessed. In large crabs there was an inverse relationship between fatigue time and speed; crabs ran for $\text{\$}\text{?}$10 min at 3.2 m·min^?1 and for only 2 min at 14 m·min^?1. There were linear relationships between oxygen consumption and walking speeds for small and large animals walking at up to 4 m·min^?1 Estimates of maximum oxygen consumption were proportional to W^0.13 whereas inactive consumption is proportional to W^0.44 this resulted in aerobic scope (i.e. the difference between inactive and maximal rates of oxygen consumption) remaining almost constant across a weight range of animals whereas the aerobic expansibility (maximal rates/inactive rates) declined from 7- to 4-fold with increasing size. After a 12-h period without handling (settled animals) the animals could immediately become active and reach maximal rates of oxygen consumption similar to those of animals handled 1 h before the experiment. The aerobic expansibility of these settled animals could range from 21 to 8 times their inactive rates of oxygen consumption in small and large animals respectively. After 10 min of exercise oxygen consumption and whole body lactate levels returned to pre-exercise values within 5 to 25 min. The net oxygen debts range from 16 to 64% of the net oxygen consumption increase during exercise in small and large animals respectively.Calculations of the energy gained from lactate accumulation indicated that the net aerobic energy production during walking was supplemented from 4 to 71 % by anaerobic metabolism in small and large animals respectively. With increasing animal size the decline in aerobic expansibility was offset by an increased capacity for lactate production so that the overall maximum energy production during sustained activity remained almost constant at around seven times the inactive rate. The cost of transport (the net increase in oxygen consumption per g per m) falls with increased walking speed and increased animal size.     

Caloric requirements of human populations: A model

Currently available models used for predicting human caloric requirements do not reflect the great variability in activity patterns observed among populations, and are insensitive to important anthropometric, demographic, and environmental variables. They are thus inadequate for application to many populations and problems of anthropological interest. We present a model for determining caloric requirements which more accurately accommodates the effects of variation in activity and in anthropometries on individual needs, and which predicts population requirements based on individual needs and demographic parameters. The model is tested on four populations (the Andean community of Nuñoa, Peru, the Dobe !Kung of Botswana, and two New Guinean villages) and is found to provide consistently better estimates of caloric requirements than are generated by the Food and Agriculture/World Health Organization's model. This model should be useful to anthropologists and human ecologists concerned with problems involving human energy consumption, such as the efficiency of subsistence strategies, optimum family composition, or certain consequences of increased labor migration or technological change.This research was supported by a grant from the Research Foundation of the State University of New York. Funds for computer time and materials were provided by the State University of New York at Binghamton and The Pennsylvania State University.     

Carbon-nitrogen requirements for the expression of nitrogenase activity in cultured Parasponia-Rhizobium strain ANU 289

Nutritional factors controlling derepression of nitrogenase activity in Parasponia-Rhizobium strain ANU 289 were studied in stationary and agitated liquid cultures. Altering type and/or concentrations of the constituents of the derepression medium in respect of carbon and nitrogen sources influenced both derepression kinetics as well as the maximal level of activity. Hexose sugars and disaccharides stimulated nitrogenase activity three to six-fold compared to pentose sugars. Activity was also modulated by combining sugars with some organic acids such as succinate, fumarate and pyruvate but not with others (e.g. -ketoglutarate, malate, malonate). Of the range of nitrogen sources tested, either casamino acids (at 0.05%, but not at 0.1%), glutamate, proline or to a lesser extent histidine (each at 5 mM N) supported significant derepression of nitrogenase activity. Notably glutamine, urea, alanine, ammonium sulfate, nitrate, nitrite (each at 5 mM N) and yeast extract (0.05%) failed to derepress or support nitrogenase activity. Ammonium (5 mM) abolished established nitrogenase activity of rapidly agitated cultures within 15 h after addition. This inhibitory effect was alleviated by the addition of methionine sulfoximime (10 mM). Thus, in view of strong glutamine effects, ammonium repression appears to be mediated by glutamine and not by ammonium itself.Abbreviations HEPES [4-(2-hydroxyethyl)-1-piperazine-ethane; sulfonic acid] - MOPS [3-(N-morpholino) propane sulphonic acid] - MSX Methionine sulfoximine     

Improved growth conditions for hyphomicrobium sp. B-522 and two additional strains

Growth yields and rates of 3 hyphomicrobia were improved by varying components of or adding compounds to medium 337. Methanol (0.5% v/v), and similarly methylamine·HCl (3.38g/l), were optimal among 22 C-sources tested; increasing the methylamine·HCl concentration to 5.07g/l gave higher Hyphomicrobium B-522 yields but also prolonged lag periods. Ten C-sources (organic acids, alcohols) stimulated growth slightly but significantly, even in subcultures. Sugar compounds were not utilized. Strains B-522 and ZV-580 were stimulated by l-lysine and gluconate, while NQ-521 gr was stimulated by aspartate.N-Sources tested were inorganic (3), organic (3), or complex (3). (NH₄)₂SO₄ (0.5g/l) was optimal for strains ZV-580 and NQ-521 gr, but Hyphomicrobium B-522 grew best with urea-N. With NH ₄ ⁺ , strain B-522 grew as homogeneous suspension, all other N-sources caused clumping and pellicle formation. Inorganic requirements (PO ₄ ^3- , Mg, Ca, Fe, Mn, Mo) of strains B-522 and ZV-580 were optimized. Addition of Ni, Co, or Zn had no effect; metals 44 or Cu, resulted in growth inhibition.Vitamin B₁₂ stimulated Hyphomicrobium B-522; 2.5g/l B₁₂ decreased the doubling time from 9.3–10.8h to 5.4–5.8h. All combined single improvements resulted in a protein increase of 557% (B-522), 141% (NQ-521 gr), or 109% (ZV-580), respectively.     

Isothermic variation of the specific growth rate of Saccharomyces cerevisiae in batch culture

The specific growth rate () of a respiration-deficient mutant of Saccharomyces cerevisiae growing under defined experimental conditions in batch culture (mineral medium plus glucose and vitamins at 25°C) varied from experiment to experiment over a wide range (0.10–0.24 h^-1) and showed a normal distribution. Neither the age of the culture, the history of the inoculum, nor experimental error accounted wholy for the variability of . The variation was positively correlated with the specific rate of glucose transfer and negatively with the specific rate of production of non-fermentative CO₂. The yield decreased with implying higher maintenance requirements in batch culture (4.7 mmoles g^-1 h^-1) than in continuous culture (0.8 mmoles g^-1 h^-1). It was concluded that the strain is capable of establishing any one of several steady states of growth under the same experimental conditions, each steady state displaying some buildin inertia with respect to change. The variations of the specific rates of glucose transfer and non-fermentative CO₂ production, and of the yield appeared to be consequences rather than causes of the variation of . The ultimate causes of the variation of remained unidentified.Part of a doctoral thesis submitted by J. Martinez-Peinado to the University of Navarra Spain     

Noninvasive techniques for measuring body elemental composition

In the past 20 yr, in vivo analysis of body elements by neutron activation has become an important tool in medical research. In particular, it provides a much needed means to make quantitative assessments of body composition of human beings in vivo. The data are useful both for basic physiological understanding and for diagnosis and management of a variety of diseases and disorders. This paper traces the development of the in vivo neutron activation technique from basic systems to the present state of the art facilities. A scan of some of the numerous clinical applications that have been made with this technique reveals the broad potentialities of in vivo neutron activation. The paper also considers alternative routes of future development and raises some of the questions now faced in making the technique more widely available to both medical practitioners and medical investigtors. In vivo neutron activation has opened a new era of both clinical diagnosis and therapy evaluation, and investigation into the modeling of body composition. The techniques are new, but it is already clear that considerable strides can be made in increasing accuracy and precision, increasing the number of elements susceptible to measurement, and reducing the dose required for the measurement.     

Effects of excessive ammonium deposition on the nutritional status and condition of pine needles

In the southeastern part of the Netherlands many Scots pine ( Pinus sylvestris L.) trees show signs of yellowing. To investigate whether there is a relation between this phenomenon and the high ammonium deposition, needle and soil samples were analyzed. Soil samples from the discoloured forests contained more extractable nitrogen than samples from healthy stands, whereas differences in pH values were small. Needles from yellow trees had higher levels of total nitrogen than needles from green trees as well as severe imbalances of Mg, K⁺ and P relative to N. The amount of leaf pigments was substantially lower in needles of the diseased trees, but they contained much higher quantities of free arginine, which accounted for a major part of total nitrogen. This may be an indication of a severe nitrogen overload. The linkage between this excessive nitrogen nutrition and the observed process of yellowing is discussed.     

Natural diets and self-selection: Heliothis zea larvae and maize

Although the first two instars tend to eat the silks, last instar larvae of the corn earworm, Heliothis zea (Boddie) (Lepidoptera: Noctuidae), prefer to feed on the kernels rather than on the other components of the maize ear. They feed preferentially on the germ of the kernel, but when offered whole kernels also eat some of the endosperm. Larvae that eat cut portions of the kernels that include all of the germ and some endosperm utilize their food for growth more efficiently than do larvae that eat portions of the kernel that include only endosperm. Adults that ate germ portions or endosperm portions of the kernel as larvae do not differ significantly in longevity, number of days on which they oviposit, number of eggs laid per day or the percentage of the eggs that hatched. We suggest that the larvae use self-selection to increase their intake of germ, thus increasing utilization efficiency and decreasing the amount of food that they must eat. When they feed on plants (other than maize) with small fruits, this probably increases their ability to compete for food when it is scarce and minimizes exposure to predation by decreasing the number of foraging trips and the distance that they must travel in search of food.

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Résumé Bien que les deux premiers stades larvaires d'H. zea (Lepid.: Noctuidae) tendent à consommer les soies, les trois derniers stades préfèrent les grains aux autres parties de l'épi de maïs. La chenille du dernier stade consomme de préférence le germe du grain, mais quand on lui offre l'ensemble du grain, elle consomme aussi une partie de l'albumen. Les chenilles qui coupent des morceaux du grain comprenant la totalité du germe et une fraction d'albumen ont une alimentation permettant une croissance plus efficace que les chenilles qui consomment des portions de grain ne contenant que de l'albumen. Ainsi, les chenilles qui mangent des fractions de germe ont besoin de consommer moins, pour atteindre le même poids que les chenilles qui consomment des morceaux d'albumen. Les longévités, les nombres de jours de ponte, les fécondités quotidiennes et les fertilités des oeufs sont les mêmes pour les papillons provenant des chenilles ayant consomme des morceaux de germe ou des morceaux d'albumien. L'albumen seul est un aliment suboptimal, et H. zea pourrait théoriquement améliorer ultérieurement son régime en mangeant plus de germes. Nous estimons que ceci ne serait pas rentable puisque la durée des stades devrait être prolongée et que la manutention et les rejets d'albumen devraient être accrus. H. zea se serait adapté à une solution de compromis pour l'optimalisation du régime alimentaire. Il réduit le temps de récolte et perd en efficacité en consommant de l'albumin suboptimal; mais il regagne autant que possible en efficacité en mangenat le germe de pratiquement tous les grains attaqués. Cette augmentation de l'efficacité diminue la quantité d'aliments qui doit être ingéré, et fournit un potentiel adaptatif quand les chenilles consomment des plantes (autres que le maïs) avec des petits fruits. L'exposition à la prédation est réduite, puisque la distance parcourue pour la recherche des fruits est diminuée.