A test for preference of association in a color polymorphic poeciliid fish: laboratory study

Synopsis The ecological and evolutionary forces maintaining genetic polymorphism within populations is of continuing interest to evolutionary biologists. Male pygmy swordtails,Xiphophorus pygmaeus, are polymorphic at a Y-linked locus controlling body color. Fish with the + and cp alleles have blue bodies; those with the con allele have bright gold bodies. Male and female fish were tested in the laboratory to determine if there were any preferences for association with groups of male fish based on color. Single test fish were presented with two groups of males of different phenotypes, and times in which the test fish spent in proximity to each group were recorded. Males of different phenotypes showed no differences in preference, nor did phenotype of the males in the groups affect the behavior of the test fish. Females also showed no preference for males of a particular phenotype. Finally, female test fish showed no preference for groups containing a male with the rare phenotype compared to a group containing all males of the same phenotype.     

Random location of nucleosomes on genes for 5 S rRNA.

The location of nucleosomes on genes for 5 S rRNA in rat liver was determined by the preparation of nucleosome core DNA fragments, hybridization with 5 S rRNA, RNase digestion, and gel electrophoresis. The resulting size distribution of RNA fragments was essentially the same as that found when the experiment was carried out with random DNA fragments.     

Ploidy Effects in Isogenic Populations of Alfalfa : II. Photosynthesis, Chloroplast Number, Ribulose-1,5-Bisphosphate Carboxylase, Chlorophyll, and DNA in Protoplasts

Photosynthetically-active protoplasts isolated from isogenic sets of diploid-tetraploid and tetraploid-octoploid alfalfa (Medicago sativa L.) leaves were used to investigate the consequences of polyploidization on several aspects related to photosynthesis at the cellular level. Protoplasts from the tetraploid population contained twice the amount of DNA, ribulose-1,5-bisphosphate carboxylase (RuBPCase), chlorophyll (Chl), and chloroplasts per cell compared to protoplasts from the diploid population. Although protoplasts from the octoploid population contained nearly twice the number of chloroplasts and amount of Chl per cell as tetraploid protoplasts, the amount of DNA and RuBPCase per octoploid cell was only 50% higher than in protoplasts from the tetraploid population. The rate of CO₂-dependent O₂ evolution in protoplasts nearly doubled with an increase in ploidy from the diploid to tetraploid level, but increased only 67% with an increase in ploidy from the tetraploid to octoploid level. Whereas leaves and protoplasts had similar increases in RuBPCase, DNA, and Chl with increase in ploidy level, it was concluded that increased cell volume rather than increased cell number per leaf is responsible for the increase in leaf size with ploidy.     

A convenient plate assay for the quantitation of hyaluronidase in hymenoptera venoms

A simple plate assay for hyaluronidase activity in biological samples is described. Hyaluronic acid is incorporated into agarose gels and the enzyme is allowed to diffuse from punched wells. The undigested hyaluronic acid is then precipitated with cetylpyridinium chloride and the diameters of the clear circles are proportional to the logarithm of the enzyme concentration applied to the well. The assay was utilized to examine commercially available hymenoptera venoms, manufactured for use in allergy diagnosis and treatment, for their content of hyaluronidase as a measure of lot-to-lot consistency. The assay permits the analyses of a large number of samples with good reproducibility, without the need for any special instrumentation. Based on the quantity of purified hyaluronidase reported in honey bee venom (T. P. King, A. K. Sobotka, L. Kochoumian, and L. M. Lichtenstein, 1976, Arch. Biochem. Biophys.172, 661–671) we estimate that the assay should detect 70 ng/ml of purified honey bee venom hyaluronidase.     

Regulation of the biosynthesis of aminoacyl-transfer ribonucleic acid synthetases and of transfer ribonucleic acid in Escherichia coli. V. Mutants with increased levels of valyl-transfer ribonucleic acid synthetase.

Spontaneous revertants of a temperature-sensitive Escherichia coli strain harboring a thermolabile valyl-transfer ribonucleic acid (tRNA) synthetase were selected for growth at 40 degrees C. Of these, a large number still contain the thermolabile valyl-tRNA synthetase. Three of these revertants contained an increased level of the thermolabile enzyme. The genetic locus, valX, responsible for the enzyme overproduction, is adjacent to the structural gene, valS, of valyl-tRNA synthetase. Determination (by radioimmunoassay) of the turnover rates of valyl-tRNA synthetase showed that the increased level of valyl-tRNA synthetase is due to new enzyme synthesis rather than decreased rates of protein degradation.     

Photoreduction of sulfur dioxide by spinach leaves and isolated spinach chloroplasts

Labeled sulfur dioxide was found to be extensively absorbed by spinach (Spinacea oleracea L.) leaves. Labeled sulfides detected in leaf blades following fumigations with sulfur dioxide in light indicated that photoreduction of sulfur dioxide had occurred. Measurable proportions of this labeled sulfur was localized within the chloroplast fraction. Suspensions of isolated chloroplasts supplied with labeled sulfur dioxide contained labeled sulfides following a 30-minute illumination period in water-cooled reaction vessels. With reference to recent studies of the chloroplast sulfur reduction pathway, probable points of entry for sulfur dioxide and the subsequent release of hydrogen sulfide are discussed.     

Microbiological quality of frozen breaded fish and shellfish products.

A survey was made of the microbiological quality of seven frozen, breaded, precooked fish and shellfish products and of frozen, breaded, uncooked shrimp at the retail level. Geometric mean aerobic plate counts per gram (and number of units examined) were as follows: fish sticks, 8,300 (1,539); fish cakes, 5,600 (1,378); crab cakes, 4,900 (1,226); scallops, 1,700 (1,392); clams, 450 (1,384); haddock, 15,000 (1,306); fish in fish and chips dinner, 7,200 (1,485); and uncooked shrimp, 220,000 (1,462). Geometric mean coliform, Escherichia coli, and Staphylococcus aureus counts for all eight products ranged from 1 to 10/g.     

Interaction of water with poly-alpha-amino acids. I. Relationships between conformation and relaxation processes.

The relaxation behaviour of the sodium salt of poly (L -glutamic acid) in the solid state has been examined by means of dynamic mechanical spectroscopy. Bound water was found to exert a profound influence on the relaxation behaviour and on a bulk property, the rigidity. Certain features of the loss spectrum have been identified with the hydration-dependent β-to-α conformational transition. Thus two side-chain relaxations are observed below ambient temperature, one associated with the β from (β₁^β) and a second at a lower temperature associated with the α form (β₁^α). The greater rigidity of the α form below the relaxation temperature and the larger rigidity drop accompanying the β₁^α can be explained in terms of the structural differences of the two conformations.