Characterization of Gypsy Moth (Lymantria dispar) Nuclear Polyhedrosis Virus

Characterization of the proteins and nucleic acid of the gypsy moth nuclear polyhedrosis virus isolated in Ithaca, N.Y. (LdNPV-IT) is presented. A total of 29 viral structural proteins were identified by sodium dodecyl sulfate-polyacrylamide gel electrophoresis when the virus was isolated in the absence of alkaline protease activity. Fourteen surface envelope viral proteins were identified by lactoperoxidase iodination. Eleven proteins were associated with nucleocapsids prepared by Nonidet P-40 detergent treatment. Distinct alterations of viral proteins were documented when virions were purified in the presence of occlusion body-associated alkaline protease(s). Restriction enzyme digests of viral DNA indicated that this isolate was composed of a large number of genetic variants. On the basis of the major molar fragments resulting from EcoRI, BamHI, BglII, and HindIII digests, the molecular weight of the LdNPV genome was approximately 88 × 10⁶.     

A unique and essential role for insulin in the phenotypic expression of rat mammary epithelial cells unrelated to its function in cell maintenance

Mammary explants from pregnant rats can be induced in regard to casein synthesis and alpha-lactalbumin activity when cultured in the presence of hydrocortisone, prolactin and levels of insulin approaching physiological concentrations. No detectable induction occurs in the absence of insulin. Although epidermal growth factor and multiplication stimulating activity, in the presence of hydrocortisone, can maintain the initial level of NADH-cytochrome c reductase as well as insulin, neither can substitute effectively for insulin in the induction of the milk proteins. Proinsulin, nerve growth factor, platelet-derived growth factor and fibroblast growth factor are also ineffective substitutes for insulin in this regard. Whereas prolonged tissue exposure to multiplication stimulating activity, hydrocortisone and prolactin does not result in induction of alpha-lactalbumin activity, subsequent addition of insulin leads to prompt response. The results suggest that the ability of insulin to function as a unique, essential factor in the induction of rat milk proteins is independent of its cell-maintenance activity. Thus, in addition to its well established functions in metabolic processes, insulin appears to play a vital role in certain developmental processes.     

EFFECT OF COPPER ON GROWTH,SILICIC ACID UPTAKE AND SOLUBLE POOLS OF SILICIC ACID IN THE MARINE DIATOM,THALASSIOSIRA WEISFLOGII (BACILLARIOPHYCEAE)1

The toxicity of Cu to Thalassiosira weissflogii (Grunow) was investigated, focusing on the internal soluble pool of silicic acid. Silicic acid uptake and growth rates were found to be functions of both the cupric ion activity and the concentration of silicic acid in the growth medium. The soluble pool of Si per cell depended on the balance between the uptake rate and the division rate. The soluble pool in non-dividing cultures reflected simply the uptake rate (and inhibition by copper of the uptake rate), but in dividing cultures the soluble pools had complex patterns with time depending on uptake rates and timing of division. Intracellular soluble pools of silicic acid are a good indicator for the relative inhibition of uptake and growth processes.     

From creation to evlution: Sir William Dawson and the idea of design in the nineteenth century

Journal of the History of Biology -     

Tryptophan feeding adversely influences pregnancy

Additional tryptophan during pregnancy reduces embryo and neonate survival in the golden hamster, $\text{Mesocricetus auratus}$.Relatively small doses of exogenous serotonin have been reported to cause abortions in several vertebrate species (1, 2, 3, 4, 5). Smaller doses reduce litter sizes, increase still births and neonate abnormalities, and otherwise influence pregnancy adversely. These effects are produced by serotonin throughout pregnancy, beginning at implantation (6).The availability of tryptophan is probably the most important rate limiting factor in serotonin synthesis (7). Inasmuch as tryptophan is an essential amino acid and is not synthesized by the body, the diet is the sole source; studies have shown that increases (8) or decreases (9) in dietary tryptophan lead to concomitant changes in serotonin content. Because tryptophan is employed in humans to promote sleep (10, 11, 12) and to decrease appetite (13) we felt it might be important to test whether increased amounts of diet tryptophan can adversely influence pregnancy.     

The Influence of Specific Phospholipids on the Interaction of Hexokinase with the Outer Mitochondrial Membrane

Repeated washing of a brain mitochondrial fraction results in a progressive decrease in the proportion of mitochondrially bound hexokinase that can be solubilized during a subsequent incubation with glucose-6-phosphate (glucose-6-P). Phospholipids removed during the washing procedure can be added back to washed mitochondria, resulting in enhancement of the solubilization by glucose-6-P. Column and thin-layer chromatographic methods have been used to isolate and identify active phospholipids. Additional studies were performed with purified lipids obtained commercially. Both lysophospholipids and acidic phospholipids were active in enhancing solubilization of hexokinase by glucose-6-P. Phospho-inositides, particularly diphosphoinositide, were quite effective, raising the possibility that the actively metabolized phosphoinositides may be involved in regulation of hexokinase binding in vivo.     

Study of Glial Fibrillary Acidic Protein in a Human Glioma Cell Line Grown in Culture and as a Solid Tumor

Abstract: A continuous human glioma cell line grown in culture and as a solid tumor was analyzed for glial fibrillary acidic (GFA) protein. This material provided a rich source for GFA protein that could also be manipulated and controlled. Immunoperoxidase staining at the light and electron microscopic levels revealed that the cell culture and tumor specimens were strongly positive for GFA protein. When aqueous soluble fractions of the cell culture and tumor were separated by sodium dodecyl sulfate (SDS)-polyacrylamide gel electrophoresis, electroblotted onto nitrocellulose and stained immunochemically, they contained exclusively low molecular weight (41–43 K-dalton) GFA peptides. SDS (0.15%)-soluble fractions contained either low molecular weight only (culture) or a mixture of peptides ranging from 41 to 49K daltons. SDS (1%) extracts of either cell culture or tumor contained only 49K dalton GFA protein. Two-dimensional gel separation revealed that the GFA protein extracted from either the culture or tumor with 1% SDS resolved to two or three spots at pH 5.8. Low molecular weight GFA peptides (<49K daltons) in aqueous and 0.15% SDS-soluble extracts became increasingly more acidic with decreasing molecular weight. The extremely rapid degradation seen suggests that this cell line may be a valuable system for further study of intermediate filament protein turnover.     

Postnatal Changes in Cathepsin D in Rat Neural Tissue

Cathepsin D, an aspartyl endopeptidase, was analyzed in cortex from forebrain and cerebellum, spinal cord, and optic and sciatic nerves, and in the liver of rats from 1 to 120 days of age. Cathepsin D was quantitated in tissue extracts by measurement of enzyme specific activity on a substrate of [methyl-¹⁴C]-methylated hemoglobin and by radioimmunoassay. Immunocytochemistry was used to ascertain the identity of the mixed cell types that contributed to the cathepsin D detected. As quantitated by radioimmunoassay, immunoreactive cathepsin D varied between 0.2 and 1 ng/μg of total protein. Maximum activity occurred at approximately the 15th postnatal day; the least amount of immunoreactive cathepsin D was found at 30 or 60 days of age. A subsequent increase of varying magnitude occurred at postnatal day 120. There was good correspondence between immunoreactive enzyme and enzyme specific activity, which ranged from 1 to 4 ng/μg of total protein, and the activities determined by the two methods provided similar, but not identical, developmental profiles. Cathepsin D was demonstrated by immunocytochemistry to be present in most neurons, in all choroid plexus epithelium, and in certain oligodendrocytes from the first postnatal day. Cathepsin D was present in oligodendrocytes in cord lateral funiculi and optic nerve by the first postnatal day, and by the sixth postnatal day many oligodendrocytes were abundantly stained. In contrast, oligodendrocytes in the corpus callosum and in the cerebellar white matter did not contain demonstrable cathepsin D until postnatal days 10 and 15, respectively. These results indicate a role for cathepsin D during the postnatal development of rat CNS and suggest that this proteinase may be involved in the steps of myelination.     

The Identity of Hexokinase Activities from Mitochondrial and Cytoplasmic Fractions of Rat Brain Homogenates

Cytoplasmic hexokinase (ATP: D-hexose 6-phosphotransferase, EC 2.7.1.1) was purified from the soluble fraction of a rat brain homogenate by a procedure that included a unique affinity elution of the enzyme from Blue Dextran-Sepharose. The purified enzyme was examined with respect to properties in which the impure cytoplasmic enzyme has been reported to differ from the solubilized mitochondrial enzyme. These included the ability to bind to mitochondria, inhibition by quercetin, effect of pH on activity, and kinetics. In all regards the purified mitochondrial and cytoplasmic enzymes appeared identical. In addition, comparative peptide maps after partial proteolysis showed no detectable differences. These results do not support the view that there exist distinct mitochondrial and cytoplasmic forms of hexokinase, the latter being permanently relegated to a cytoplasmic location and unable to participate in a dynamic equilibrium with the mitochondrially-bound enzyme. Alternatives are proposed to explain previous results that had been interpreted as indirect evidence for the existence of a distinct cytoplasmic hexokinase.