Effects of Illumination on the Circadian Motor Rhythm of the Chelipeds of Crayfish

The effects of different illumination conditions on the main parameters of the circadian motor rhythms of the two chelipeds of the crayfish, Procambarus digueti , were compared. Under either constant darkness (DD) or constant light (LL) the phase relationship between the two circadian rhythms was more stable than under entrained conditions (LD cycles). These results suggest that the oscillators responsible for these rhythms differ in their sensitivity to light. The role of paired organs in the internal temporal order of the crayfish is discussed.     

The larval development of lateral musculature in gilthead sea bream Sparus aurata and sea bass Dicentrarchus labrax

Fibre-type differentiation of the lateral musculature has been studied in Sparus aurata (L.) and Dicentrarchus labrax (L.) during larval development. Histochemical and ultrastructural techniques show two presumptive muscle layers and two germinative zones of presumptive myoblasts. At hatching, myotomal muscle consists of a monolayer of thin undifferentiated cells near the skin (first germinative zone) overlying another mono-layer of small diameter fibres extending hypaxially and epaxially away from the transverse septum. Below this, there is a much thicker, deep layer of fibres, generally large in diameter and polygonal in shape. The presumptive myoblasts are located between these two layers of fibres in the second germinative zone. Initially, the superficial and deep muscle fibres show high and low myosin ATPase activity, respectively. Both layers grow by generating new fibres from the two mentioned germinative zones. At the end of larval life, the superficial layer changes its histochemical profile from high to low myosin ATPase activity and, at the same time, intermediate or pink muscle fibres can be observed by oxidative activity (the NADH-TR reaction). Morphometric analysis shows a significant increase in mean fibre diameter during successive ages, as shown by the Student's t-test (hypertrophic growth). Skewness and kurtosis values of fibre diameters point to the generation of a new fibre population from the germinative zones (hyperplastic growth).     

Changes in the intracellular concentrations of the adenosine phosphates and nicotinamide adenine dinucleotides ofSaccharomyces cerevisiae during batch fermentation

Significant changes in the intracellular concentrations of adenosine phosphates and nicotinamide adenine dinucleotides were observed during fermentation of grape must by three different strains ofSaccharomyces cerevisiae: S. cerevisiae var.cerevisiae, a typical fermentative yeast strain and two flor-veil-forming strains,S. cerevisiae var.bayanus andS. cerevisiae var.capensis. The intracellular concentration of ATP was always higher inS. cerevisiae var.cerevisiae than in the flor-veil-forming strains. NAD⁺ and NADP⁺ concentrations decreased at faster rates in the flor-veil-forming yeasts than in the other yeast but NADH concentration was the same in all yeasts for the first 10 days of fermentation. NADPH concentration was always lower inS. cerevisiae var.cerevisiae than in the other yeasts and this yeast also showed higher rates of growth and fermentation during the early stages of the fermentation and the presence of non-viable cells at the end of fermentation. In contrast, the flor-veil-forming strains maintained growth and fermentation capabilities for a relatively long time and viable cells were present throughout the entire fermentation process (31 days).The authors are with the Department of Microbiology, Faculty of Sciences, University of Cordoba, Avda. San Alberto Magno s/n, 14004-Córdoba, Spain     

Inactivation by ammonia of the photosynthetic reduction of nitrate in Nostoc muscorum particles.

Ammonia, as well as other uncouplers of photophosphorylation, strongly inhibit the photosynthetic reduction of nitrate by particles of the blue-green alga Nostoc muscorum. The enzyme responsible for nitrate reduction, nitrate reductase, can be reversibly inactivated by reduction in a ferredoxin-dependent reaction. Nitrate protects against this inactivation, and molecular oxygen restores the original activity.     

Spiral growth in the radially-expanding piloboloid mutants ofPhycomyces blakesleeanus

The growth zone of the sporangiophore of a piloboloid mutant,pil, ofPhycomyces expands radially at an increased rate until the growth zone becomes nearly spherical, in sharp contrast to that of the wild-type sporangiophore which exhibits longitudinal elongation only and is conical. The rotation of thepil sporangiophore reverses its direction from clockwise (CW) to counterclockwise (CCW) during the period of increased radial expansion, and the CCW rotation continues as long as does the radial expansion. The direction of rotation and the time of reversal are correlated with the relative rates of cell-wall expansion in the longitudinal and transverse directions. The CCW rotation of the sporangiophore of this mutant can be explained by the behavior of the microfibrils, as previously proposed to explain the rotation of the wild-type sporangiophore.Abbreviations CW clockwise - CCW counterclockwise — both as viewed from above     

Effect of propranolol on glycerol induced acute renal failure in rats

The effect produced by propranolol, administered for a prolonged period of time and in large doses, on renal function in rats has been studied, as well as the modifications induced by this treatment in an experimental model of acute renal failure, and the effects of a single dose of propranolol given 1 hour before provoking failure. Propranolol, administered chronically, causes sodium and water retention and increases creatinine clearance. Acute renal failure induced by glycerol in rats treated for 7 days with propranolol is less severe than the one produced in untreated animals. In this ARF model, a single dose of propranolol does not seem to have a protective effect.     

Effect of temperature on the kinetics of electron transfer from the tetraheme cytochrome to the primary donor in Rhodopseudomonas viridis.

The kinetics of electron transfer from the third highest potential heme (c-552, Em = +20 mV) to the primary donor (P-960) have been measured by flash absorption spectroscopy in isolated reaction centers of Rhodopseudomonas viridis between 300 K and 7 K. The data are analyzed on the basis of three exponential components with a very fast phase (t1/2 = 120 ns) dominating at high temperature and a very slow one (t1/2 = 1.2 ms) at low temperature. This multiphasic behavior is interpreted in terms of the existence of three states with a temperature-dependent population and a very limited effect of the temperature on the kinetics for each state.     

Cortisol influence on some typical parameters of protein malnutrition in rats (author's transl)

A daily v.s. dose of cortisol administered to rats, induces certain metabolic modifications, which after using the "pair-fed" system have been proven to be at least partially independent of the ingesta decrease originated by cortisol. Both cortisol treatment and experimental proteic malnutrition, originate a decrease in corporal weight, a lessening of the gamma-globulins plasmatic fraction, and an elimination increase in total nitrogen, protein, creatine and creatinine in urine. Cortisol treatment determines an increase in blood red cells number, as well as an increase in total serum proteins, especially albumin, without provoking a lessening in the beta-globulins fraction, as happens in cases of proteic malnutrition.     

A.C. cable theory and its implications on the measurements of the membrane electric parameters

The solution to the a.c. cable equations for a leaky non-inductive coaxial cable is presented. It is shown that the exact solution can be expressed in terms of a simple Ohm's law formulation modified by multiplicative factors. A numerical analysis of these factors shows that the formulation reduces to a simple Ohm's law for the case of infinite impedance terminations, if the voltage is recorded at a distance 0·421/λ from the centre of a midpoint current injection, 1 is the half-length of the cell and A the space constant. The same result applies to the case of external current injection if the voltage is recorded at a distance of 0·581/λ from the centre of the cell segment of length 21. This thus allows an easy and accurate computation of the membrane resistance and capacitance. It is also shown that the accuracy obtained in these computations can be estimated quantitatively. The actual values of the accuracy obtained in a.c. studies of Nitella translucens are presented.     

Pharmacological reactivity in cricetus aureus uterus (author's transl)]

The motility of the isolated Cricetus auratus uterus was studied and compared to that of other species. Oxitocyn, epinephrine, norepinephrine, histamine, 5-hydroxy-tryptamine and acetylcholine were used as spasmogen agents. There was not contractil response with epinephrine or nor-epinephrine. Histamine reduced basal tonus. There was contraction with acetylcholine, oxytocin and 5-hydroxy-tryptamine. Cricetus auratus uterus appeared more sensitive when the contraction was registered by the isometric method. No taquifilaxy was produced by 5-hydroxy-tryptamine, as opposed to such effect in rat uterus. The Cricetus auratus uterus has, therefore, shown similar reactivity to that of rat, but different from rabbit and guinea-pig.