Studies of the ferredoxin from Thermus thermophilus

The soluble ferredoxin from Thermus thermophilus was examined by M?ssbauer and EPR spectroscopies and by reductive titrations. These studies demonstrate the presence of one 3Fe center, responsible for the characteristic g = 2.02 EPR signal in the oxidized protein, and one [4Fe-4S] center which is responsible for the rhombic EPR spectrum of the fully reduced protein. These assignments should replace those made by Ohnishi et al. (Ohnishi, T., Blum, H., Sato, S., Nakazawa, K., Hon-nami, K., and Oshima, T. (1980) J. Biol. Chem. 255, 345-348) prior to the discovery of the 3Fe clusters. The amino acid composition was determined and is discussed with reference to recent structural studies of 7Fe ferredoxins.     

Linkage Modification with Mixed Random Mating and Selfing: A Numerical Study

Although recombination cannot increase under conditions of random mating or complete selfing in regimes of constant selection, with mixed random mating and selfing, selection for increased recombination can occur. For some fitness regimes there may be selection for reduced recombination with both low and high degrees of selfing but selection for increased recombination with moderate degrees of selfing. With some fitness regimes there is a historical effect: depending on which equilibrium a population starts from, there may be selection for either increased or decreased recombination. In other cases the direction of selection may be determined by the present state of individuals within the population. If recombination is already fairly limited, there may be selection for further reduction. If recombination is already fairly frequent, there may be selection for increased recombination. For certain symmetric viability systems there may be an intermediate value of the recombination fraction between 0 and 0.5 toward which the population will evolve. Although it is not yet possible to classify precisely those fitness matrices that can exhibit selection for increased recombination, it does appear that selection for increased recombination can occur only if at least two of the double homozygotes are less fit than would be expected on the basis of a comparison of the fitnesses of the single and double heterozygotes on an additive scale.     

The periodate oxidation of bovine bone sialoprotein, and some observations on its structure

1. Bovine bone sialoprotein (mol.wt. 23000) contains N-acetylneuraminic acid and N-glycollylneuraminic acid, fucose, galactose, mannose, N-acetylgalactosamine and N-acetylglucosamine residues in the form of a very small number, perhaps one, of highly branched oligosaccharide structures linked covalently to peptide. 2. Periodate oxidation of the sialoprotein results in quantitative destruction only of the sialic acid and fucose residue consistent with the earlier findings of their positions as terminal groups. 3. Terminal sialic acid residues are attached to galactopyranose residues by 2,3-linkages, and to some N-acetylgalactosamine residues (at C-6). 4. Sequential Smith degradation indicates that N-acetylgalactosamine residues may be present as points of branching (linked in C-1, C-3 and C-6) and N-acetylglucosamine residues are located in the inner part of the structure, adjacent to the carbohydrate–peptide bond(s). 5. Mannose residues appear to be linked in the 1,3-positions.     

Feeding and the control of volume within the tests of regular sea-urchins

The rigid, fluid filled, echinoid test presents problems of internal volume control when the vital functions of the animal involve the introduction of material, from outside the test, into the internal fluid systems. The volume of food in the guts of echinoids can be shown to vary considerably in the short term, to an extent which demands considerable capabilities for internal volume compensation. This is achieved by adjusting the quantity of fluid held within the gut so that, although the volume of food may vary widely, the total volume of the gut remains constant within narrow limits. The volume of gut fluid varies inversely with the quantity of food, and ingestion of food through the mouth is compensated by ejection of an equal volume of fluid from the anus. Defaecation is compensated by intake of fluid into the gut. On starvation, the gut becomes completely fluid filled and free from food.
The food of regular urchins is habitually compacted into regularly sized subpherical pellets covered with a tough mucus coating. The formation of coated pellets takes place in the buccal cavity and pharynx. The pellets remain discrete throughout their passage along the gut. The mucus coating resists digestion and remains intact even after defaecation. The functional morphology of the buccal cavity and pharynx is described in detail.
It is suggested that the functional significance of the pellets is associated with the gut fluid, volume compensation mechanism, which requires free flow of fluid throughout the length of the gut. It is also suggested that the siphon may be implicated in volume control, where fine adjustment of gut volume can be achieved by balancing ejection of fluid from the anus with intake of water through the mouth, but that the water intake is by the siphonal route, thus avoiding the necessity of flushing and diluting the enzyme rich digestive stomach region.     

Novel Multi-Slit Large-Volume Air Sampler

Scientific investigators who are interested in the various facets of airborne transmission of disease in research laboratories and hospitals need a simple, continuous, high-volume sampling device that will recover a high percentage of viable microorganisms from the atmosphere. Such a device must sample a large quantity of air. It should effect direct transfer of the air into an all-purpose liquid medium in order to collect bacteria, viruses, rickettsia, and fungi, and it should be easy to use. A simple multi-slit impinger sampler that fulfills these requirements has been developed. It operates at an air-sampling rate of 500 liters/min, has a high collection efficiency, functions at a low pressure drop, and, in contrast to some earlier instruments, does not depend upon electrostatic precipitation at high voltages. When compared to the all-glass impinger, the multi-slit impinger sampler collected microbial aerosols of Serratia marcescens at 82% efficiency, and aerosols of Bacillus subtilis var. niger at 78% efficiency.     

STUDIES AT OYSTER BAY IN JAMAICA,WEST INDIES. IV. OBSERVATIONS ON THE MORPHOLOGY AND ASEXUAL CYCLE OF PYRODINIUM BAHAMENSE PLATE12

The morphology and asexual cycle of the luminescent armoured dinoflagellate, Pyrodinium bahamense Plate, were examined in situ and in vitro. Several previously unreported aspects of the cycle are described. Attempts to induce the formation of these alternate life stages by imposing new conditions were unsuccessful.     

Modification of the zona-free hamster ova bioassay of boar sperm fertility and correlation with in vivo fertility

These studies were designed to evaluate the ability of the zona-free hamster ova bioassay to detect differences in fertility of boar sperm. In the first study, sperm from two previously infertile boars were compared to sperm from seven previously fertile boars. The percentage of zona-free hamster ova penetrated by sperm from the previously infertile boars was significantly lower than the percentage of ova penetrated by sperm from previously fertile boars (18% of ova penetrated vs. 83%, P < .001). In the 14 ejaculates from the previously infertile boars that had ejaculate motilities of 50% or greater, the percentage of zona-free hamster ova penetrated continued to be lower than in ejaculates from the fertile boars. One of the two previously infertile boars consistently had a normal semen analysis. The only two observed manifestations of his reduced fertility were his zero conception rate and the limited ability of his sperm to penetrate zona-free hamster ova. In the second study, females were inseminated with equal numbers of sperm from two previously fertile males and the paternity of offspring determined at birth. The experiment was replicated with four combinations of six boars. A high correlation was observed between the percentage of offspring sired and the ability to penetrate zona-free hamster ova (R = .89). Neither morphology nor the ability of the sperm to undergo an acrosome reaction during in vitro incubation was correlated with fertility in the competitive mating situation. These results suggest the zona-free hamster ova bioassay can improve the in vitro fertility assessment of fresh boar semen.     

Pathogenesis of hemosiderosis in lemurs: Role of dietary iron,tannin, and ascorbic acid

Clinical disease associated with excess iron deposition (hemosiderosis) in the duodenum, liver, and spleen occurs in captive lemurs. In this report we review the occurrence of hemosiderosis and related disease in the Zoological Society of San Diego lemur collection; we then define and describe potential pathogenic factors with the goal of establishing rational husbandry methods to limit or prevent the disease. At the San Diego Zoo, all 49 lemurs necropsied since 1968 were hemosiderotic, the severity increasing with increasing age; liver and kidney disease were common. Our review of iron metabolism, current knowledge on the pathogenesis of hemosiderosis in humans, and the diets of captive and wild lemurs reveals several key dietary substances that may contribute to lemur hemosiderosis: iron, tannins, and ascorbic acid. In captivity, excess dietary iron (commercial monkey chow) and high levels of ascorbic acid (citrus fruits) lead to enhanced iron uptake and increased toxicity of stored iron due to free radical formation. In the wild, lemurs have an unusual preference for leaves, fruits, and bark high in tannin, a polyphenolic secondary plant compound that rapidly chelates iron, protein, and minerals in the gastrointestinal (GI) tract, preventing their absorption. These findings suggest that hemosiderosis in captive lemurs results from a diet high in iron, high in ascorbic acid, and lacking in tannin. Immediate correction of captive diets may limit hemosiderosis in lemurs in the future.