Crystal structure analysis of sea lamprey hemoglobin at 2 Å resolution

The crystal structure of the predominant hemoglobin component of blood from the sea lamprey, Petromyzon marinus, has been determined by X-ray diffraction analysis. Crystals for this analysis were grown from cyanide methemoglobin V as crystal type D₂. These crystals are in space group P2₁2₁2₁ and have unit cell dimensions of $\text{a = 44.57}\text{A}\text{?}\text{, b = 96.62}\text{A}\text{?}\text{and}\text{c = 31.34}\text{A}\text{?}$. Isomorphous heavyatom derivatives were prepared by soaking crystals in solutions of Hg(CN)₂, K₂Hg(CNS)₄ and KAu(CN)₂. Diffracted intensities to as far as 2 Å spacings were measured on a diffractometer. Phases were found by means of the isomorphous replacements and anomalous scattering, with supplementary information provided by the tangent formula. An atomic model was fitted to the final electron density map in a Richards optical comparator. The lamprey hemoglobin molecule is generally similar in structure to other globins, but differs in many details. Each molecule is in contact with ten neighboring molecules in the crystal lattice. The nature of the binding of the heavy atoms to lamprey hemoglobin has been interpreted.     

Initiation of Vaccinia Virus Infection in Actinomycin D-pretreated Cells

The early steps in vaccinia virus infection were studied in HeLa cells which had been treated with actinomycin D (1 μg/ml) and then incubated for several hours in fresh medium prior to infection. Initiation of infection occurred in such cells even though the synthesis of cellular ribonucleic acid and deoxyribonucleic acid (DNA) was severely depressed. Thymidine kinase was synthesized in amounts that exceeded those found in untreated, infected cells. The breakdown of viral “cores” to liberate viral DNA and the synthesis of viral specific DNA-polymerase also occurred but were somewhat delayed. A deoxyribonuclease resembling an exonuclease was made by the infected, pretreated cells. The time course for these events suggested that the genetic code for synthesis of thymidine kinase can be expressed before “cores” are broken down, but the DNA-polymerase can be synthesized only after liberation of the viral DNA. The amount of viral specific DNA-polymerase which was made after infection was proportional to the total number of virus synthesizing sites even beyond the point where all the cells were infected with one infectious particle. A similar relationship was observed for the amount of thymidine kinase formed and for the rate of viral DNA synthesis from ³H-thymidine.     

Base composition of deoxyribonucleic acid isolated from mycobacteria

Guanine plus cytosine values of deoxyribonucleic acid derived from 30 cultures representing 14 mycobacterial species or varieties are presented. These data provide impressive reasons for maintaining the separation between the genera Corynebacterium and Mycobacterium; no conclusions can be arrived at from these data with respect to the Nocardia-Mycobacterium relationship. A bimodal clustering, in terms of guanine plus cytosine composition, is apparent within the genus Mycobacterium. In general, all members of any single phenetic species appear to fit into one or another of these clusters. The phenetic separation of species is, in some cases, confirmed by separation in terms of guanine plus cytosine values. The bimodal separation of guanine plus cytosine values within the genus Mycobacterium does not correspond to a division of the species into slow and rapid growers; it thus provides no justification for splitting Mycobacterium into two genera, composed of slow and rapid growers. This is not to say that such a split would not be useful, only that these data do not contribute to such a decision. Any further attempts to correlate phenetic classification with properties of mycobacterial deoxyribonucleic acid will require more specific techniques, such as molecular hybridization.     

BRANCHED PISTILLATE INFLORESCENCES IN JUGLANS AND CARYA

Manning , Wayne E. (Bucknell U., Lewisburg, Pa.) Branched pistillate inflorescences in Juglans and Carya. Amer. Jour. Bot. 49(9): 975–977. Illus. 1962.—One or 2 clusters of abortive pistillate flowers or of short, slender branches of abortive perfect flowers are occasionally found at the base of the terminal pistillate spike in certain species of Juglans and Carya. These make the pistillate inflorescence a branched one, essentially a small panicle. These flower clusters and special branches are considered to be due to the retention of a primitive condition, probably a pre-juglandaceous one.     

Autolysis and Secondary Growth of Mycobacterium tuberculosis in Submerged Culture

Mycobacterium tuberculosis has been found to exhibit autolysis and spontaneous secondary growth in modified Sauton medium. The phenomenon is a function of high glycerol concentration of the medium and limitation of air in test tubes. It is not a function of depletion of nutrients and is probably not a manifestation of lysogeny or spheroplast formation. The cycle of growth, autolysis, and secondary growth is related to development of lethal conditions during a period of severe oxygen limitation followed by a metabolic change associated with slower depletion of glycerol.     

DEVELOPMENTAL STUDIES OF ERYTHROCLADIA ROSENVINGE IN CULTURE

Erythrocladia subintegra has been cultured for over 3 years. The life history includes reproduction by monospores, a long period of ameboid motility by monospores, their germination and growth into monostromatic disk-shaped plantlets composed of adherent, often dichotomously branched filaments. Plants become centrally polystromatic with age and produce monospores. Variations in plant size and shape, cell size and shape, spore size, shape, and motility are discussed. Variations in plants of E. subintegra grown on different substrates have been studied and discussed in relation to other species in the genus.     

CULTURE AND DEVELOPMENTAL MORPHOLOGY OF COMPSOPOGON COERULEUS

Compsopogon coeruleus has been grown in culture for 4 years. The life-history consists of reproduction by monospores and their germination and growth into erect filamentous (corticated or uncorticated) thalli. Plastids are parietal sheets in young cells but undergo characteristic divisions to form discoid segments in older cells. The chromosome number has been determined as 7 ± 1. Sporangia have been studied and their derivation compared to the sporangial types of Drew-Baker. Variations in cell walls, basal systems, spore germination and young plantlets are discussed.     

The density of the cell sap and endoplasm of Nitellopsis and Chara

We measured the densities of the cell sap, endoplasm and cell wall of Nitellopsis obtusa and Chara corallina using interference microscopy, refractometry, immersion refractometry, equilibrium sedimentation and chemical microanalysis techniques. These values are important for the determination of many rheological properties of the cytoplasm as well as for understanding buoyancy regulation, dispersal mechanisms and how cells respond to gravity. The average densities of the cell sap, endoplasm and cell wall are 1,006.9, 1,016.7 and 1,371 kg m-3 for Nitellopsis and 1,005.0, 1,013.9, and 1,355.3 kg m-3 for Chara.     

Early growth and bone mineralization of the iguanid lizard,Sceloporus occidentalis in captivity: Is vitamin D3 supplementation or ultraviolet B irradiation necessary?

The insectivorous, heliophilic iguanid lizard, Sceloporus occidentalis, was used in this study. Eight groups of field-collected juveniles were subjected to different doses of ultraviolet-B radiation or were fed crickets maintained on different diets with varying amounts of vitamin D₃ and other nutrients. The crickets fed to all groups were dusted with calcium carbonate powder. Snout-vent lengths and body masses were significantly greater within each group at the end of 10 weeks; however, there were no significant among-group differences in growth. There were no differences among treatment groups regarding plasma calcium concentration or bone calcium, phosphorus or magnesium concentrations. However, compared to length-matched field controls, individuals from treatment groups had significantly greater body masses, greater bone calcium concentrations, and lower bone magnesium concentrations. Lizards exposed to ultraviolet radiation exhibited lower plasma phosphorus concentrations relative to several other treatment groups and field controls. In the field sample, bone calcium concentration was positively correlated with body size while bone magnesium and phosphorus concentrations were negatively correlated with body size.