AT-1.1: A thymus-specific alloantigen of chickens

A thymocyte-specific alloantigen, designated AT (avian thymus) –1.1, has been detected in Cornell C strain (CS) and Obese strain (OS) chickens, the latter being a strain derived from CS which develops a spontaneous form of autoimmune thyroiditis (SAT). Antisera specific for this antigen were developed first in a turkey immunized with thymocytes from an OS chicken and, later, in AT-1.1-negative CS chickens immunized with AT-1.1-positive thymocytes. AT-1.1 was detected in 50–70% of cells in a thymus cell suspension, but was not seen on peripheral blood lymphocytes, erythrocytes, or cells from bursa, spleen, kidney, liver, or brain. It was present on thymocytes of chickens at all ages tested, from 1 day to 6 months of age. AT-1.1 was not detected in six chicken lymphoid tumor cell lines tested, and birds expressing it were found to be negative for the presence of Marek's disease viral antigens. Pedigree studies on 287 (OS × CS)F₂ chickens demonstrated that AT-1.1 is expressed in a dominant or codominant manner, and the gene coding for this antigen was not linked to the B (major histocompatibility) complex. The genetics and tissue distributions of AT-1.1 indicate that it differs from thymus cell surface antigens, avian or mammalian, previously described.     

Photobilirubin II

An improved preparation of photobilirubin II in ammoniacal methanol is described. Evidence is presented which distinguishes between the two structures proposed earlier for photobilirubin II in favour of the cycloheptadienyl structure. Nuclear-Overhauser-enhancement measurements with bilirubin IX alpha and photobilirubin II in dimethyl sulphoxide are complicated by the occurrence of negative and zero effects. The partition coefficient of photobilirubin II between chloroform and phosphate buffer (pH 7.4) is 0.67.     

Combined effect of growth medium,age of cells and phase of sporulation on heat resistance and recovery of Hansenula anomala

Effects of two growth media, age of cells and phase of sporulation on heat resistance of Hansenula anomala were determined. Cells were grown on two solid media, McClary's acetate and V8 juice agars, at 21 ° C for 16 days. Heat resistance of cells was determined in 0.06 M potassium phosphate buffer at 48 ° C. Heat-stressed cells were plated on four recovery media: yeast extract-malt extract-peptone-glucose (YMPG), pH 7.0; YMPG, pH 3.5; YMPG containing 6% NaCl, pH 7.0; and YMPG containing 20% sucrose, pH 7.0. The composition of sporulation medium influenced the extent of sporulation and the relative heat resistance of sporulating cells. One-day-old cells were the most sensitive to heat. The heat resistance of cells was generally increased as the incubation time was extended to 16 days. Heat treatment caused a greater increase in sensitivity to NaCl than to sucrose or acid pH in recovery media. Young cells were more sensitive to NaCl than were older cells.     

Nitrogenase — hydrogenase relationships in Rhizobium japonicum

The conditions necessary for coordinate derepression of nitrogenase and O₂-dependent hydrogenase activities in free-living cultures of Rhizobium japonicum were studied. Carbon sources were screened for their ability to support nitrogenase, and then hydrogenase activities. There was a positive correlation between the level of nitrogenase and corresponding hydrogenase activities among the various carbon substrates. The carbon substrate -ketoglutarate was able to support the highest levels of both nitrogenase and hydrogenase activities. When cells were incubated in -ketoglutarate-containing medium, without added H₂ but in the presence of acetylene (to block H₂ evolution from nitrogenase) significant hydrogenase activity was still observed. Complete inhibition of nitrogenase-dependent H₂ evolution by acetylene was verified by the use of a Hup^- mutant. Hydrogen is therefore not required to induce hydrogenase. The presence of 10% acetylene inhibited derepression of hydrogenase. Constitutive (Hup^c) mutants were isolated which contained up to 9 times the level of hydrogenase acitivity than the wild type in nitrogenase induction medium. These mutants did not have greater nitrogenase activities than the wild type.This is contribution number 1254 from the Department of Biology and the McCollum-Pratt Institute Abbreviations: -Ketoglutarate-containing medium (LOKG) and pre-adaptation medium (SRM) as described in Materials and methods     

Morphometric integration in the rat (Rattus sp.) scapula

Morphometric integration was analysed in 19 anatomical measures taken on the scapula and humerus in a population of 519 rats. As hypothesized, genetic integration was the highest, the average phenotypic genetic, and environmental correlations being 0·53, 0·67 and 0·42, and the index of integration 0·56, 0·69 and 0·48. Phenotypic and genetic correlation matrices were most similar (correlation =+0.79), genetic and environmental matrices least similar (correlation =+0.49). The first unrotated vector produced from principal components analysis explained a high percentage of the total variation (from 50% in the environmental to 70% in the genetic solution), and was highly heritable in all cases. Rotated vectors defined two length, one width, and one height grouping in the phenotypic solution, these being explained largely in terms of muscle assemblages. The four vectors produced in the genetic solution were similar to those from the phenotypic ones, but were more functionally interpretable. The five vectors produced from the environmental correlations paralleled those from the phenotypic correlations with regard to the length, but not the width measures. The general concordance among appropriate vectors from all three solutions was reasonably high. Twelve of the 13 vectors, as well as several hypothetical ones. exhibited moderate to high heritabilities.     

Coordinate regulation of protein synthesis and messenger RNA content during growth arrest of suspension Chinese hamster ovary cells

We have found Chinese Hamster Ovary cells, cultured in suspension, are subject to growth control by serum. When suspended in medium containing 0.5% serum the cells become reversibly arrested in the beginning of the G₁ phase of the cell cycle and can be maintained in this viable, nonproliferating state for several days. This system was used to examine the regulation of protein synthesis with growth rate. In particular, the experiments addressed the question whether mRNA content is the principal controlling factor determining the rate of protein synthesis. The rate of leucine incorporation in resting cells in low serum is 2- to 2.5-fold lower than that of cells growing in 10% serum. The steady-state number of cytoplasmic poly A (+) RNA molecules shows a proportional decrease, consistent with it being a determining factor controlling the rate of protein synthesis. Furthermore, the rate of production of poly A (+) and poly A (?) RNA appears to be regulated coordinately. Regulation of the rate of initiation of translation would result in fewer ribosomes bound per active message and/or a lower proportion of total mRNA's being active. Our measurements indicate that the fraction of cytoplasmic poly A (+) mRNA in polyribosomes and the relative degree of loading of each active poly A(+) mRNA with ribosomes is the same in resting and growing cells. Thus these cells resemble 3T6 and translational control does not appear to be an important part of the change in protein synthetic rate with the state of growth.     

Comparison of various ultraviolet sources for fluorescent detection of ethidium bromide-DNA complexes in polyacrylamide gels

Ultraviolet sources with output wavelengths of 254, 300, and 366 nm were compared for detection of ethidium bromide-DNA complexes in acrylamide gels. The 254- and 300-nm sources were both much more sensitive than the 366-nm source. The 254-nm source produced a great deal of photodamage, photonicking and photodimerization, and photobleaching, while the longer wavelength sources cause little damage or bleaching. The 300-nm source is clearly the most suitable source, providing high sensitivity and a relatively low amount of photodamage and photobleaching.     

Temporal patterning of feeding by hummingbirds

For five species of hummingbirds in the laboratory, time between meals was related to energy intake on the first meal and rate of energy expenditure between meals. Field observations gave similar results. Average meal sizes were similar at one intake rate independent of food caloric density; females averaged longer bouts than males. When rate of intake was approximately halved, meal duration approximately doubled and volume intake remained similar. We postulate that feeding is initiated when crop contents reach a lower threshold and that feeding is terminated after ingestion of an optimal volume determined by the added weight of the meal.