Adaptation to CO(2) Level and Changes in the Phosphorylation of Thylakoid Proteins during the Cell Cycle of Chlamydomonas reinhardtii

The photosynthetic performance of synchronously grown Chlamydomonas reinhardtii alternated rhythmically during the cell cycle. The activity of the “CO₂ concentrating mechanism” including the ability to accumulate CO₂ internally and the activity of carbonic anhydrase peaked after 6 to 9 hours of light and reached minimum after 6 to 9 hours of dark. Consequently, the apparent photosynthetic affinity to extracellular CO₂ alternated rhythmically. At the end of the dark period the cells behaved as if they were adapted to high CO₂ even though they were continuously aerated with air. Results from experiments in which the light or dark periods were extended bear on the interaction between the internal (cell cycle or biological clock) and the external (light) signal. The observed rhythmical alterations in photosynthetic V_max may result from changes in PSII activity. The latter may be partly explained by the capacity for phosphorylation of thylakoid proteins, which reached maximum after 9 hours of light and decreased toward the dark period.     

A Numerical Simulation of the One-Locus, Multiple-Allele Fertility Model

Numerical simulations were performed to determine the equilibrium behavior of the one-locus fertility model in which fitness is considered as a property of a pair of mating diploids. A series of patterns of "fertility matrices" were considered for a single locus with two to six alleles. From these simulations, 19 different statistics were collected that characterize, at equilibrium, the heterozygosity, the mean fitness and the fate of populations begun at the allele-frequency centroid. For more than one-half of the trajectories produced by random fertility matrices, there was a decrease in the mean fitness at some time on the way to equilibrium. The mean number of alleles maintained at equilibrium increased only slightly with matrix dimension. Despite the potential for fertility models to display multiple stable equilibria, random fertility models maintain fewer distinct stable points than do random one-locus viability models. Pleiotropic models were also considered with fertility and viability selection operating sequentially within each generation. Most of the equilibrium statistics (with the exception of mean fertility) for the pleiotropic model were intermediate between the corresponding random viability and fertility models.     

Mechanismen der pathologischen Pigmentbleichung bei Pflanzen

Viele pathologische Pigmentbleichungen sind oxidative Prozesse. In einer Reihe von Simulationsversuchen und Modellreaktionen wurden die Grundbedingungen für die Auslösung dieser Prozesse studiert und mit ?in vivo” Meßdaten verglichen. Bei den verwendeten oxidativen Bedingungen, unter denen Pigmente gebleicht werden, handelt es sich um chemische, enzymkatalysierte und lichtabhängige Oxidationen, wobei der Singulettsauerstoff, neben weiteren reaktiven Sauerstoffspezies eine herausragende Rolle spielt. Ausgelöst werden solche Pigmentbleichungen unabhängig davon, ob der ?aktivierte Sauerstoff” außerhalb oder innerhalb der Thylakoidmembranen erzeugt wird, wobei jedoch die zugrunde liegenden Mechanismen unterschiedlich sind. Parallel zur Pigmentbleichung wird grundsätzlich eine Oxidation von Lipiden gemessen; wird primär eine Lipidperoxidation induziert, so ist die Pigmentbleichung als Kooxidation von Lipiden zu sehen. Mit Hilfe der empfindlichen HPLC-Technik wurden Kinetiken der Bleichraten von Chlorophyll a, Chlorophyll b, β-Karotin, Neoxanthin, Violaxanthin und Lutein gemessen. Die schnellsten Bleichungsraten werden unter Bedingungen erzielt, die einen stark limitierten Elektronenfluß hervorrufen. Die erzielten Ergebnisse erlauben den Vergleich mit ?in vivo” Beobachtungen. Es können Rückschlüsse über die basalen Mechanismen der virus- bzw. pilzbedingten Vergilbung von Zuckerrüben sowie der Vergilbung von Fichtennadeln gezogen werden.     

Influences of exercise intensity, age, and medication on resting systolic blood pressure of SHR populations

The influence of exercise training on the resting caudal arterial blood pressures (RBP) of hypertensive rats is unclear despite numerous investigations by different investigators. To determine whether RBP values were influenced by the intensity and the initial age of the animal at the time of training, several studies were undertaken that involved more than 100 rats. When male and female rats were endurance trained for 24 wk at an O2 consumption in excess of 75% of their maximum (Vo2 max), RBP results from nontrained (NT) or trained (T) animals were not significantly different even though at several time periods the T animals had higher resting pressures. However, when exercising rats at an intensity level representing 40-60% of their Vo2 max, the T groups had consistently lower RBP than their NT controls during the majority of the experimental time periods. In addition exercising young (2-3 wk old) hypertensive-prone rats at a moderate intensity was associated with lower RBP within 4-6 wk after the initiation of training; however, exercise training could not normalize RBP. Reduced dosages (85% of normal) of antihypertensive medication, when combined with moderate training, was also associated with lower and "normal" RBP in male but not female rats. We conclude that moderate exercise at an early age when combined with subnormal dosages of antihypertensive medication holds promise for the normalization of RBP in male hypertensive rats of a genetic origin.     

Genetic polymorphism of human plasminogen.

Using isoelectric focusing (IEF) in polyacrylamide gel of neuraminidase-treated serum or plasma samples and immunofixation or caseinolytic overlay after urokinase activation of gels, a common genetic polymorphism in human plasminogen has been delineated. Two alleles PLGN*A and PLGN*B, were observed with gene frequencies in whites of .69 and .30; in Orientals of .96 and .03; and in blacks of .80 and .18. Several rare alleles were also found. The distribution of phenotypes fits the Hardy-Weinberg equilibrium. Inheritance is autosomal codominant and fits the expectations of Mendelian inheritance. There is fetal synthesis, but no transplacental passage of plasminogen in either direction.     

Mouse (C57BL/KsJ) liver phosphofructokinase. Allosteric kinetics and age-related changes in the genetically diabetic state

The regulatory kinetic properties of phosphofructokinase partially purified from the livers of C57BL/KsJ mice were studied. The fructose 6-phosphate saturation curves were highly pH dependent. At a fixed MgATP concentration (1 mM), allosteric kinetics was observed in the range of pH studied (7.3 to 8.3) and the S0.5 values for fructose 6-phosphate decreased by about 0.2 to 0.3 mM for each 0.1-unit increment in pH. Allosteric effects on the sigmoidal response to fructose 6-phosphate: activation by AMP, NH4+, and glucose 1,6-bisphosphate, inhibition by MgATP2-, and synergistic inhibition between ATP and citrate, were all present at pH 8.0 to 8.2. Comparative kinetic studies with liver phosphofructokinase isolated from both the normal (C57BL/KsJ) and the genetically diabetic (C57BL/KsJ-db) mice of 9 to 10 and 15 to 16 weeks of age showed that the enzyme from the livers of diabetic mice exhibited decreased activity at subsaturating concentrations of fructose 6-phosphate. However, phosphofructokinase isolated from the livers of normal and genetically diabetic mice of 4 to 5 weeks of age showed no difference in kinetic properties. Thus, there appears to be a correlation between the change in properties of liver phosphofructokinase and the expression of hyperglycemia and obesity in the genetically diabetic mice. The decreased activity of liver phosphofructokinase in the older diabetic animals may well be one of the causes of the increased blood glucose levels. The results are also discussed in a general context with regard to the possible role of phosphofructokinase in the regulation of hepatic gluconeogenesis.     

Linkage relationships among five enzyme-coding gene loci in the copepod Tigriopus californicus: A genetic confirmation of achiasmatic meiosis

Linkage relationships among five polymorphic enzyme-coding gene loci in the marine copepod Tigriopus californicus have been determined using electrophoretic analysis of progeny from laboratory matings. Phosphoglucose isomerase (PGI; EC 5.3.1.9) was found to be tightly linked to glutamate-pyruvate transaminase (GPT; EC 2.6.1.2), with only one recombinant observed in 364 progeny; glutamate-oxaloacetate transaminase (GOT; EC 2.6.1.1) is linked to the PGI-GPT pair, with a recombination fraction of approximately 0.20 in male double heterozygotes. Phosphoglucomutase (PGM; EC 2.7.5.1) and an esterase (EST; EC 3.1.1.1) are not linked to the PGI, GPT, GOT grouping, which has been designated linkage group I. Reciprocal crosses have revealed that no recombination occurs in female T. californicus; this observation confirms a previous report that meiosis in female Tigriopus is achiasmatic.     

Preparation and Properties of Antibodies to GD3 and GM1 Gangliosides

Abstract: Gangliosides G_D3 and G_M1 were coupled to proteins by their car-boxyl groups and antisera were raised against the complexes. Anti-ganglioside antibodies were isolated by affinity chromatography on ganglioside-amino-propyl silica gel columns and the specificity of the antibodies was determined by a quantitative microcomplement fixation assay. Antibodies to G_D3 were highly specific and did not crossreact with G_M3, lactosyl ceramide, or other glycolipids. Purified antibodies to G_M1, in contrast, crossreacted with asialo-G_M1, G_D1b and to a lesser extent, G_M2 and asialo-G_M2. A derivative of G_M1, containing a C-7 sialic acid residue produced by periodate oxidation, reacted with the anti-G_M1 antibodies almost as readily as with G_M1. The specificities of anti-G_M1 antibodies elicited by the covalent ganglioside-protein complexes were similar to those produced by immunization with noncovalent complexes of G_M1 and methylated bovine serum albumin. The ganglioside-protein complexes described here should be useful for preparing antibodies to polysialo-gangliosides that contain neuraminidase-sensitive linkages.     

Oxygen utilization by Lactobacillus plantarum

Cell-free extracts of Lactobacillus plantarum contain non-proteinaceous compounds which mimic superoxide dismutase activity. Using the test system in which O ₂ ^– is generated by xanthine oxidase, superoxide dismutase activity is found in cell-free extracts, where proteins are removed by precipitation. This activity is strongly decreased after dialysis of cell-free extracts. Superoxide dismutase activity was also investigated by means of pulse radiolysis. Cell-free extracts of Escherichia coli were also investigated as a comparison, which were known to contain superoxide dismutase. With cell-free extracts of both L. plantarum and E. coli the decay of O ₂ ^– was markedly increased. However, the type of reaction of the O ₂ ^– decay was of first order in the presence of E. coli extracts due to superoxide dismutase(s), and of second order in the presence of L. plantarum extracts, indicating that O ₂ ^– elimination is not an enzymic reaction. Mn²⁺ phosphate(s) might be responsible for the observed elimination of O ₂ ^– . The production of O ₂ ^– is not detectable during NADH-, lactate- or pyruvate oxidase reactions in L. plantarum extracts.