Nutritional copper deficiency does not affect sponge granuloma formation in the rat

Sponge granuloma formation was compared in copper-deficient and copper-sufficient rats following feeding of respective diets for 20, 40, or 60 d. Body weight, total blood hemoglobin, and activities of ceruloplasmin and Cu, Zn-superoxide dismutase in plasma were monitored to ascertain copper deficiency. Mean granuloma weights (mg +/- SEM) in copper-deficient and copper-sufficient groups of rats, respectively, were as follows: 37 +/- 2 and 38 +/- 2 after 20 d, 22 +/- 2 and 23 +/- 2 after 40 d, and 19 +/- 1 and 21 +/- 1 after 60 d on respective diets. Thus, nutritional copper deficiency did not have an effect on sponge granuloma formation in the rat.     

Control of sporulation in yeast: SAD1-a mating-type specific, unstable alteration that uncouples sporulation from mating-type control

Summary Normally, in order to sporulate, a diploid yeast cell must be heterozygous (MAT a/MAT) at the mating-type locus. In a new mutant, this requirement is circumvented by SAD1. This alteration is mating-type specific; it allows sporulation of MAT/ MAT. MAT/mat a-1, and MAT/mat-2 diploid cells, but not MAT a/MAT a or MAT a/0 (monosomic) strains. Other than acquiring the ability to sporulate, SAD1 cells behave as wild-type MAT/MAT strains; they exhibit medial budding, normal mating factor production and response and mate with normal mating efficiencies and kinetics. The segregation of SAD1 is often bizarre; for example, MAT/MAT strains which were constructed to be heterozygous SAD1/+ often segregate 4 SAD1:0+progeny and strains which were constructed to be homozygous SAD1/ SAD1 sometimes segregated 1 SAD1:3+progeny. The genetic analyses of SAD1 suggest that it is dominant and is located 30 cM from MAT on chromosome III.     

PURIFICATION AND CHARACTERIZATION OF OX BRAIN NAD+ -DEPENDENT ISOCITRATE DEHYDROGENASE

Abstract— The NAD⁺ -dependent isocitrate dehydrogenase from ox brain has been purified about 130-fold by a method involving affinity chromatography on an NAD⁺ -derivative of agarose. The enzyme preparation is not homogeneous but it is free from contaminating enzyme activities that could interfere with kinetic studies. The kinetic properties of the enzyme did not appear to have been altered by the purification procedure involved. The initial velocity of the reaction showed a sigmoid dependence on the concentration of isocitrate, and ADP behaved as an allosteric activator. The kinetics with NAD⁺ as the substrate were hyperbolic. The molecular weight of the purified enzyme was found to be 285,000 ± 25,000.     

Mutations Affecting Sexual Conjugation and Related Processes in SACCHAROMYCES CEREVISIAE. II. Genetic Analysis of Nonmating Mutants

Rare diploids formed by sterile mutants have been studied by tetrad analysis. Sixteen classes of mutants representing at least five distinct genetic loci have been defined. One group of mutations, isolated only in alpha, maps at the mating-type locus, while none of the others shows any linkage to mating type. Some of the mutations are nonspecific for mating type, while others act only on a or alpha. In addition, mutations were found that prevent sporulation when heterozygous in diploids. These appear to be mutations of the mating-type alleles.     

Morphogenesis of bone ornamentation in extant and extinct crocodilians

Summary Histological study of bone in the skull and osteoscutes of extant and extinct Crocodylia reveals that the skeletal ornamentation of crocodiles is caused by a process of differential, superficial resorption of bone. A partial reconstruction follows the resorption, and several resorption-reconstruction cycles are necessary to suit pit dimensions to overall bone growth. Bone ornamentation is a dynamic structure during ontogeny: the shape and the location of a given pit or groove vary in accordance with the instantaneous regional trends of skeletal growth. This supports the contention that bone oranmentation can be used as a reliable indicator of regional bone growth trends.     

Cyclic AMP-stimulated protein kinase activity in rabbit peripheral myelin

Cyclic AMP-sensitive protein kinase activity has been found in suspensions of purified rabbit peripheral myelin. The enzyme phosphorylated the P₀, Y, X, P₁, and P₂ myelin proteins. Kinase activity, which was maximal at physiological pH, 2.5 mM Mg²⁺, and 2 M cAMP, was stimulated three-fold over basal levels by cyclic AMP. Addition of calcium or EGTA had no effect on the enzyme activity in the presence or absence of cyclic AMP. Cyclic GMP also did not stimulated endogenous or exogenous protein phosphorylation. Theophylline, an inhibitor of 3,5-cyclic nucleotide phosphodiesterase activity, increased protein kinase activity in the presence of cyclic AMP. These data show that PNS myelin proteins can be phosphorylated in situ by a protein kinase system whose activity is stimulated selectively by cyclic AMP.     

The Ion Permeability Induced in Thin Lipid Membranes by the Polyene Antibiotics Nystatin and Amphotericin B

Characteristics of nystatin and amphotericin B action on thin (<100 A) lipid membranes are: (a) micromolar amounts increase membrane conductance from 10^-8 to over 10^-2 Ω^-1 cm^-2; (b) such membranes are (non-ideally) anion selective and discriminate among anions on the basis of size; (c) membrane sterol is required for action; (d) antibiotic presence on both sides of membrane strongly favors action; (e) conductance is proportional to a large power of antibiotic concentration; (f) conductance decreases ~10⁴ times for a 10°C temperature rise; (g) kinetics of antibiotic action are also very temperature sensitive; (h) ion selectivity is pH independent between 3 and 10, but (i) activity is reversibly lost at high pH; (j) methyl ester derivatives are fully active; N-acetyl and N-succinyl derivatives are inactive; (k) current-voltage characteristic is nonlinear when membrane separates nonidentical salt solutions. These characteristics are contrasted with those of valinomycin. Observations (a)–(g) suggest that aggregates of polyene and sterol from opposite sides of the membrane interact to create aqueous pores; these pores are not static, but break up (melt) and reform continuously. Mechanism of anion selectivity is obscure. Observations (h)–(j) suggest—NH₃⁺ is important for activity; it is probably not responsible for selectivity, particularly since four polyene antibiotics, each containing two—NH₃⁺ groups, induce ideal cation selectivity. Possibly the many hydroxyl groups in nystatin and amphotericin B are responsible for anion selectivity. The effects of polyene antibiotics on thin lipid membranes are consistent with their action on biological membranes.