Effect of temperature and sperm supply on the reproductive potential ofTetranychus evansi (Acari: Tetranychidae)

The biology ofTetranychus evansi Baker and Pritchard was studied at five different temperatures on excised leaves ofSolanum douglasii Dunal. The theoretical lower threshold temperature of development was ca. 13°C. The combined immature stages required ca. 148 day-degrees for completion. Progressively later initiation of mating resulted in higher peak proportions of females produced, up to an 8-day period between emergence and mating at 30°C. The proportion of male offspring always increased towards the end of the oviposition period, apparently because of sperm depletion. The calculated intrinsic rate of increase was highest (0.432) at 35°C, the highest temperature tested. At that same temperature, daily oviposition rate and net reproductive rate were maximum (9.5 and 111.77, respectively), and mean generation time and doubling time were minimum (10.92 and 1.6 days, respectively).     

Bounding fluid viscosity and translational diffusion in a fluid lipid bilayer

Fluorescence recovery after photobleaching was used to investigate the translational diffusion of a fluorescent derivative of a membrane-spanning lipid in L phase multibilayers of 1-palmitoyl-2-oleoylphosphatidylcholine prepared in water and in glycerol. The translational diffusion coefficient in hydrated bilayers (D _w) ranged between 2 and 5x10^–8 cm²/s and in glycerinated bilayers (D _g) the range was between 3 and 24×10^–10 cm²/s between 10° and 40°C. These results are discussed in terms of models for diffusion in membranes.     

Regulation of the amylase secretion by the yeast Filobasidium capsuligenum and a 2-deoxy-d-glucose resistant mutant

Summary The regulation of extracellular amylase production by the basidiomycetous yeast Filobasidium capsuligenum CCY 64-5-1 was characterized using growing and resting cells. A basal level of amylolytic activity was produced with various carbon sources including glucose. Amylase secretion was repressed by glucose and, more severely, by 2-deoxy-d-glucose, whereas compounds with -1,4-linked glucose, such as methyl glucoside, maltose, -cyclodextrin and soluble starch, served as inducers. Repression was not relieved by exogenously added cAMP. The effects of several metabolic inhibitors on amylase secretion were studied. Following UV-mutagenesis a mutant strain (FC-5) capable of growing in a 2-deoxy-d-glucose supplemented corn starch medium was selected for further characterization. This strain produced more amylase, had acquired an increased resistance against repression by glucose, and retained a growth rate comparable to the wild type. FC-5 was also characterized by a reduced glucokinase activity and an increased hexokinase activity.     

Chromosomal aberrations induced in human cultured cells by liposome-encapsulated deoxyribonuclease I

Experiments of incorporation of a nucleolytic enzyme into human cells cultured in vitro have been carried out with the aim of inducing structural chromosome variations. Human heteroploid cells, either as asynchronous populations or enriched in mitoses, and PHA-stimulated lymphocytes were used as recipients. We found that all these cells when exposed to pancreatic DNAase I encapsulated in liposomes, either of multilamellar (MLV) or of small unilamellar (SUV) type, show an incidence of chromosome damage higher than that induced by the enzyme free in the incubation buffer. Our results indicate that liposomes are suitable vehicles for the transfer of an exogenous nuclease into human cultured cells. The enzyme remains functionally active and interacts with nuclear DNA, giving rise to chromosome lesions.     

Specific Inhibition of Lignification in Bryonia dioica: Effects on Thigmomorphogenesis

Rubbing-induced lignification in Bryonia dioica internodes is significantly impaired by N(o-hydroxyphenyl) and N(o-aminophenyl) sulfinamoyl tertiobutyl acetate, specific inhibitors of cinnamyl alcohol dehydrogenase, an enzyme which is strictly associated with lignin monomer synthesis. Along with the reduction of lignification, these inhibitors counteract the inhibition of elongation due to rubbing. These results indicate that lignification participates in the thigmomorphogenetic growth response of Bryonia dioica internodes. In a general way, the data point to the causal role of lignification in the limitation of plant growth.     

Biphasic fluence-response curves for phytochrome-mediated kalanchoë seed germination : sensitization by gibberellic Acid

The fluence-response curves for the effect of two red pulses separated by 24 hours on the germination of Kalanchoe blossfeldiana Poelln. cv Vesuv seeds, incubated on gibberellic acid (GA₃) are biphasic for suboptimal concentrations. The response in the low fluence range corresponds with a classical red/far-red reversible phytochrome mediated reaction. GA₃ induces an additional response in the very low fluence range, which is also phytochrome mediated. The sensitivity to phytochrome-far-red absorbing form (Pfr), however, is increased about 20,000-fold, so that even far-red fluences become saturating. Both in the very low and low fluence response range, the maximal responses induced by saturating fluences are modulated by the GA₃ concentration. GA₃ having no direct influence on the phytochrome phototransformations, alters the Pfr requirement and determines the responding seed population fraction in the very low and low fluence range. The effet of GA₃ appears to be on the transduction chain of the phytochrome signal.     

Different Characteristics of the Two Glutamate Synthases in the Green Leaves of Lycopersicon esculentum

The two glutamate synthases, NAD(P)H- and ferredoxin-dependent, from the green leaves of tomato plants (Lycopersicon esculentum L. cv Hellfrucht frühstamm) differed in their chemical properties and catalytic behavior. Gel filtration of NAD(P)H enzyme gave an apparent molecular size of 158 kilodalton, whereas the ferredoxin enzyme molecular size was 141 kilodalton. Arrhenius plots of the activities of the two enzymes showed that the NAD(P)H enzyme had two activation energies; 109.6 and 70.5 kilojoule per mole; the transition temperature was 22°C. The ferredoxin enzyme however, had only one activation energy; 56.1 kilojoule per mole. The respective catalytic activity pH optima for the NAD(P)H- dependent and the ferredoxin dependent enzymes were around 7.3 and 7.8. In experiments to evaluate the effects of modulators aspartate enhanced the NAD(P)H-linked activity, with a K_a value of 0.25 millimolar, but strongly inhibited that of the ferredoxin-dependent glutamate synthase with a K_i of 0.1 millimolar. 3-Phosphoserine was another inhibitor of the ferredoxin dependent enzyme with a K_i value of 4.9 millimolar. 3-Phosphoglyceric acid was a potent inhibitor of the ferredoxin-dependent form, but hardly affected the NAD(P)H-dependent enzyme. The results are discussed and interpreted to propose different specific functions that these activities may have within the leaf tissue cell.     

Relative biological effectiveness (RBE) of neutrons produced by 50 MeV deuterons and by 34, 45, 65 and 75 MeV protons

RBE of p(34) + Be, p(45) + Be, p(65), + Be, p(75) + Be and d(50) + Be neutron beams produced at the cyclotron "Cyclone" of Louvain-la-Neuve were measured. The biological criterion was the regeneration of the crypts of the intestinal mucosa (50 regenerated crypts per circumference) after abdominal irradiation in mice. Taking the p(65) + Be neutrons as reference, RBE values were found equal to 1.12, 1.07, 1.00 (Ref.), 0.96 and 1.02 respectively. These results are consistent with those published for cell lethality in vitro. However, the RBE variation is smaller than this previously obtained in the laboratory for growth inhibition in Vicia faba.     

Trichodorus persicus n. sp. (Nematoda: Trichodoridae) from Iran

Trichodorus persicus n. sp. is described from the Caspian region of Iran, where it was found in woodland and orchard soil. Males of the new species usually have two ventral cervical papillae anterior to the excretory pore but posterior to the base of the onchiostyle; there are three ventromedian preanal supplements, the posterior one lying near the heads of the retracted spicules; the spicules are 51–61 m long with faint transverse striations distally. Females have two pairs of lateral body pores, large rounded sclerotized thickenings at the vulva and the vagina tapers inwards in lateral view.