Regulation of carbonic-anhydrase activity, inorganic-carbon uptake and photosynthetic biomass yield inChlamydomonas reinhardtii.

The regulation of carbonic anhydrase by environmental conditions was determined forChlamydomonas reinhardtii. The depression of carbonic anhydrase in air-grown cells was pH-dependent. Growth of cells on air at acid pH, corresponding to 10 μm CO2 in solution, resulted in complete repression of carbonic-anhydrase activity.

Genetic effects of methylmethanesulphonate during meiosis in Saccharomyces cerevisiae.

Enhanced mutagenic action after methylmethanesulphonate (MMS) treatment was found in pre-replicative meiotic yeast cells of the strain D7. The level of gene conversion after MMS treatment rose above the spontaneous level during the period of commitment to meiotic recombination, but at later times into meiosis became indistinguishable from the full meiotic level. In contrast reciprocal recombination detected between ade 2 and the centromere of chromosome XV after MMS treatment remained above the spontaneous level up to commitment to meiotic cell division with relatively high levels through meiotic prophase I.

EFFECTS OF NITROGEN DEPRIVATION ON RATES OF UPTAKE OF NITROGENOUS COMPOUNDS BY THE DIATOM, PHAEODACTYLUM TRICORNUTUM BOHLIN.

A culture of Phaeodactylum tricornutum was suspended in nitrogen-free growth medium under conditions which favoured photosynthesis. Nitrogen deprivation was continued for 60 h and, over this period, samples were removed for measurement of rates of uptake of arginine, guanine, nitrate, nitrite, lysine, methylammonium and urea. In another experiment, the effect of nitrogen deprivation on the ability to take up methylammonium and ammonium was compared.

The effect of Michler's ketone on cell division, chromosome number and structure in cultured Chinese hamster cells.

The industrial chemical Michler's ketone (MK) has been examined for its ability to induce abnormalities of mitotic cell division and the production of chromosomal aberrations and aneuploidy. MK was shown to produce aberrant cell division stages in cultured mammalian cells probably by interference with centrosome replication leading to the production of monopolar spindles during metaphase, and multipolar telophase spindles, in the first division after exposure. Cells in the second division after exposure to MK showed increased levels of chromosome aneuploidy which is presumed to result from aberrant cell division.

An illustration of simple sequence analysis with reference to the agonistic behaviour of four strains of laboratory mouse.

Many authors have assumed that the functions of behavioural elements may be deduced from the sequence in which they occur. This study explains from basic principles a simple procedure, based of the X(2) test, for analysing behavioural sequences. The formation of groups of "similar" elements (cluster analysis) and their interpretation is discussed with reference to the agonistic behaviour of individually-housed male mice from four different strains.

Hypothalamic levels of LHRF in male mice of differing social status and from individual housing.

Swiss male mice were individually-housed or maintained in groups of 8 from weaning until 80 days of age. At this time, the grouped mice were allocated to new groups of 5-6 previously unfamiliar individuals. Identified dominants were then caged with two clearly submissive males for 1 week.

Citrate-synthase mRNA in relation to enzyme synthesis in division-synchronized Euglena cultures.

The regulation of citrate-synthase (EC 4.1.3.

Influences of alcohol on the social responses of male resident mice to anosmic female intruders.

The effects of acutely administered ethanol (0, 0.5, 1.0 or 2.

Naloxone does not affect tube restraint-induced target biting by male Swiss mice.

Opioid peptides have been implicated in the mediation of intermale conflict. The effect of naloxone upon tube restraint-induced target biting was investigated since a high correlation between bite scores and intermale aggression has been claimed. No significant modification of target biting behaviour by naloxone was produced, in mice either naive or habituated to the apparatus (high and low baselines of responding respectively) suggesting no involvement of opioid peptides in this paradigm.

Ethological analyses of the effects of naloxone and the opiate antagonist ICI 154, 129 on social interactions in male house mice.

The influences of the mu blocker naloxone and the novel opioid delta receptor antagonist ICI, 154, 129 on videotaped encounters between individually-housed, male Swiss mice and anosmic male 'standard opponents' were assessed using a variety of ethological analyses. The effects of drugs were studied on individual elements and on the times allocated by subjects to broad categories of behaviour. Neither of the drugs significantly altered times allocated to broad categories of behaviour.

Glycollate-pathway enzymes in mitochondria from phototrophic, organotrophic and mixotrophic cells of Euglena.

Glycollate dehydrogenase and NADFH-glyoxylate reductase are constitutive enzymes in Percoll-purified mitochondria from phototrophic, mixotrophic and organotrophic cells of Euglena gracilis Klebs strain z Pringsheim. Glycollate oxidation by isolated mitochondria is stimulated four-fold by the addition of glutamate but rates of glycine oxidation are low in mitochondria from all cell types, the ratio of malate to glycine oxidation always being greater than 4:1. Measurement of the rate of NADPH oxidation in intact mitochondria and mitoplasts showed that the outer mitochondrial membrane is impermeable to NADPH and in the absence of NADPH-dehydrogenase activity the oxidation of NADPH by mitoplasts is dependent on the presence of glyoxylate for NADPH-glyoxylate-reductase activity.

Aspartate aminotransferase allozyme variation in a germplasm collection of the domesticated lentil (Lens culinaris).

Variation at a polymorphic Aspartate aminotransferase locus was assayed in a sample of 298 accessions from the ICARDA germplasm collection of the domesticated lentil (Lens culinaris). Two alleles Aat-1 (F) and Aat-1 (S) were detected with global frequencies of 0.51 and 0.

A Head-Space Method for Measuring Activity Coefficients, Partition Coefficients, and Solubilities of Hydrocarbons in Saline Solutions.

An apparatus is described which measures the equilibrium distribution of a hydrocarbon between a gas and aqueous phase. Soluble hydrocarbons are extracted from an aqueous salt solution by very small bubbles of hydrogen generated electrolytically from a gold electrode located at the bottom of a cylindrical cell. The partition coefficient is determined from the volume of the aqueous solution and the solute concentration in the head-space after a measured volume of hydrogen has bubbled through the cell.

Hypothalamic levels of thyrotropin-releasing hormone (TRH) in male albino mice of different social status.

Hypothalamic levels of TRH were contrasted in identified dominant and submissive (housed together for 4 days) Swiss male mice and undisturbed 'isolated' counterparts. Both dominants and submissives had significantly higher titres of this hormone than the 'isolates', suggesting that the experience of fighting relatively elevates the concentration of this factor in both winners and losers. It seems likely that titres of TRH are modified by fighting experience and these factors may alter subsequent behaviour but more investigation is needed on this topic.

Sensitivity to ethidium bromide during meiosis in Saccharomyces cerevisiae.

Ethidium bromide was found to inhibit nuclear and mitochondrial DNA synthesis during meiosis which resulted in the inhibition of meiotic gene conversion and sporulation and was also lethal. Protection from the effects of ethidium bromide on meiotic gene conversion and survival was found to coincide with DNA synthesis, but it is possible that protection from sporulation inhibition occurs only later in meiosis.

The regulation of synthesis of mitochondrial enzymes in regreening and division-synchronized Euglena cultures.

The effect of light and carbon nutrition on the synthesis of citrate synthase (EC 4.1.3.

Studies on tube restraint-induced attack on a metal target by laboratory mice.

This study examines factors influencing the attack on a metal target by laboratory 'TO' strain mice confined within a narrow perspex tube and contrasts this form of behaviour with attack seen in less equivocal forms of 'aggression test'. The effects of sex, housing condition, reproductive experience, density, anosmia and castration (in the male) were systematically examined. This 'model' of 'aggression' shows few parallels with social conflict, parental defense and electroshock-induced forms of attack as none of the above manipulations influenced the level of target biting in this situation.

The systemic response of male mice to differential housing: A path-analytical approach.

Path analysis was used to examine the effects of grouping/individual housing, duration of differential housing (13 days or 10 weeks), and the age at which differential housing was initiated (at weaning or 4 months) on the physiology of male TT strain mice. Variables studied included body and relative ventral prostate, left testis and left adrenal gland weights, and plasma corticosterone level and (Na+) /(K+) ratio. Compared with grouped counterparts, individual housing produced lower adrenal weights and plasma corticosterone levels, but higher prostate weights.

Measurements of the Octanol/Water Partition Coefficient by Chromatographic Methods.

A theoretical relationship is developed to provide a quantitative definition of hydrophobicity using established theoretical and semi-empirical relationships. A method of predicting partition coefficients of relatively water-insoluble third components between water and an immiscible second component is devised and tested. Comparison with experimental data for four classes of compounds in the water/-octanol system at 25 °C shows excellent agreement, indicating that values for substances for which direct determination is experimentally precluded can be calculated with confidence.

Ammonium generation by nitrogen-starved cultures of Chlamydomonas reinhardii.

Ammonium (NH 4 (+) ) assimilation by Chlamydomonas reinhardii was inhibited when cultures were incubated with methionine sulphoximine (MSO). Methionine sulphoximine inhibited glutamine synthetase acitvity in vitro in extracts from wild-type (2192) and mutant (CC419) cultures. Mutant cultures were insensitive to MSO inhibition in vivo.

Irregular segregation at the Pr locus controlling plastid inheritance in Pelargonium: gametophytic lethal or incompatibility system?

Two distinct segregation patterns are recognized after G X W plastid crosses in Pelargonium. Type I parents produce offspring in which maternal zygotes are frequent, biparental intermediate, and paternal zygotes rare (MZ>BPZ>PZ), as defined by the presence or absence of green or white plastids in the young embryos into which the zygotes develop. Type II parents produce offspring in which maternal and paternal zygotes are frequent with biparental zygotes the least frequent class (MZ>BPZ View Article and Find Full Text PDF

The effect of the type of opponent in tests of murine aggression.

The interactions between isolated resident mice and anosmic, juvenile, submissive and dominant intruders were studied; the responses of intruder mice to being attacked and the distribution of bites on these subjects were investigated. Anosmic, juvenile and (trained) submissive intruders did not attack residents; they did, however, show differences both in thir responses to being attacked and their ability to avoid bites to particular regions of their body surface. These differences are likely to make it difficult to extrapolate between tests that employ different types of intruder.

The effect of social isolation of the rat on open field activity and emergence.

It has been suggested that naive isolated rats show more "fear responses" than group-housed controls. However, in contrast to previous studies, dark conditions and low noise levels were used to evaluate the latency to emerge from a small chamber into an open field and the subsequent ambulation and rearing behaviour of isolated and group-housed rats. The prediction that these conditions would be conducive to the rapid development of hyperactivity in isolates was confirmed, but there were no significant differences in emergence latency.

Attempts to determine the status of electroshock-induced attack in male laboratory mice.

An attempt was made using a combination of simple experimental manipulations and videotape recorder (VTR) analysis of bite targets employed to determine whether electroshock-induced attack on anosmic opponents in laboratory mice was an offensive or a defensive behaviour. VTR analysis suggested that ventral surface biting was more evident in this form of attack than in social conflict. Individually- and group-housed males showed similar levels of fighting on exposure to electroshock, but dominant males from pairs showed greater attack than their subordinate partners.