A reappraisal of sterol biosynthesis and metabolism in aphids

Aphids of Schizaphis graminum (Rondani) (biotype C) reared on its host-plant, Sorghum bicolor (L.) Moench, sequestered campesterol, stigmasterol and sitosterol. Aphids reared for 72 hr on holidic diets supplemented with [4-¹⁴C]-sitosterol contained both [¹⁴C]-sitosterol and [¹⁴C]-cholesterol, indicating that these aphids are capable of dealkylation at C-24. When aphids were reared on artificial diets containing [2-¹⁴C]-mevalonic acid, no detectable amounts of radioactively labelled desmethyl sterols, nor metabolic intermediates in sterol synthesis (i.e. squalene, 2,3-oxidosqualene, 4,4-dimethyl and 4-monomethyl sterols) were found to accumulate in their tissues. The relevance of these findings to previous research suggesting the ability of aphids, via their symbiotes, to synthesize sterols is discussed.     

Growth of Chikungunya Virus in Baby Hamster Kidney Cell (BHK-21-Clone 13) Suspension Cultures

This report describes the methods used to obtain high titers of chikungunya virus with suspension cultures of BHK-21-clone 13 cells. The cells were grown at 37 C to a cell concentration of 10(6) to 2 x 10(6) per ml. After maximum cell growth, the cells were inoculated with chikungunya virus at a multiplicity of 1 to 2 50% suckling mouse intracerebral lethal doses (SMICLD(50)) per cell in the spent Eagle's minimum essential medium for suspension cultures (MEMS), or the cell cultures were centrifuged at 200 x g and resuspended in either fresh MEMS or medium 199 prior to inoculation. The medium used had no effect on virus titer. The inoculated cultures were incubated at 34 C until the cell viability dropped to 30%, which usually occurred 28 to 30 hr postinoculation. After these procedures, chikungunya virus titers of log(10) 10.3 to 11.8 SMICLD(50) per ml were obtained.     

Growth and lipolysis of rat adipose tissue: effect of age, body weight, and food intake

The purpose of the present work was to study age- and weight-controlled rats to determine which is the primary factor in reducing the lipolytic response of free fat cells and which has the greater effect on the ratio of fat cells to nonfat cells in adipose tissue. The method for estimating fat cell and nonfat cell numbers is based on the analysis of adipose tissue and fat cell DNA and lipid. In adequately fed rats, epididymal adipocyte hyperplasia is complete between 9 and 14 wk of age. Chronic underfeeding delays, but does not eliminate, normal fat cell hyperplasia and is accompanied by a net loss in the nonfat cell population. During 9-14 wk of age, rat epididymal adipose tissue enlarges mainly through adipocyte hypertrophy. Total fat cells from the epididymal adipose tissue of control rats represent only 20-23% of the total cell population. Chronic underfeeding increases the percentage of fat cells in the fat pad from 23 to 28%. Noradrenaline-stimulated lipolysis is proportional to fat cell numbers but is inhibited when fat cell lipid increases to over 80% of fat pad wet weight. Rat age is apparently not primarily responsible for the decreased noradrenaline-stimulated lipolysis in fat cells of 350-g rats in vitro.     

Dissociation by Chelating Agents and Substructure of the Thermophilic Bacteriophage TP84

The thermophilic bacteriophage TP84 is dissociated into its head, tail, and released deoxyribonucleic acid (DNA) by chelating agents such as ethylenediaminetetraacetic acid (EDTA) and phosphate. The phage is more sensitive to EDTA than to phosphate, and dialysis against either agent causes more effective dissociation than standing in their presence. The tail possesses a knobbed structure which is inserted into the head of the intact phage and to which the DNA appears to be attached. The method of dissociating TP84 described in this paper provides a source of undamaged structural components and intact strands of DNA for subsequent investigations. A possible mechanism of chelate inactivation is discussed.     

Transformation in Bacillus amyloliquefaciens

The methodology and some of the requirements for the deoxyribonucleic acid-mediated transformation of an arginine auxotroph of Bacillus amyloliquefaciens to prototrophy are described.     

Primitive erythropoiesis in early chick embryogenesis. II. Correlation between hemoglobin synthesis and the mitotic history

Primitive erythroblasts in the circulating blood of the chick embryo continue to divide while synthesizing hemoglobin (Hb). Hb measurements on successive generations of erythroblasts show that there is a progressive increase in the Hb content of both interphase and metaphase cells. Furthermore, for any given embryo the Hb content of metaphase cells is always significantly greater than that of interphase cells. The distribution of Hb values for metaphase cells suggests that there are six Hb classes corresponding to the number of cell cycles in the proliferative phase. The location of erythroblasts in the cell cycle was determined by combining Feulgen cytophotometry with thymidine radioautography on the same cells. Measurements of the Hb content for erythroblasts in different compartments of the cell cycle (G1, S, G2, and M) show a progressive increase through the cycle. Thus, the amount of Hb per cell is a function of the number of cell divisions since the initiation of Hb synthesis and, to a lesser degree, the stage of the cell cycle. Earlier generations of erythroblasts synthesize Hb at a faster rate than the terminal generation. Several models have been proposed to explain these findings.     

CYTOPLASMIC FILAMENTS IN DEVELOPING AND ADULT VERTEBRATE SMOOTH MUSCLE

An extensive study of adult and developing smooth muscle has revealed the widespread occurrence of a distinct filament with an average diameter of about 100 A (termed the 100 A filament). Unlike that of myofilaments, their appearance in longitudinal section is uniform, but in transverse section they have a round profile, occasionally exhibiting a less electron-opaque core. The 100 A filaments are almost invariably preserved under a variety of fixation procedures, whereas myofilaments, particularly the thicker filaments, are preserved inconsistently. The 100 A filaments appear to be randomly oriented throughout the cytoplasm, either singly or in small groups, although they are sometimes concentrated in the juxtanuclear region of the smooth muscle cells. The intimate association of 100 A filaments with dark bodies, in both developing and adult smooth muscle cells, may indicate that these filaments either play a role in dark body formation or, at least, constitute a part of the dark body. The 100 A filaments are conspicuous in developing smooth muscle cells and occasionally form networks or clusters; they appear to decrease in relative number as maturation proceeds, but considerable numbers are still present in adult tissue.     

The enzymic and non-enzymic degradation of colneleic acid, an unsaturated fatty acid ether intermediate in the lipoxygenase pathway of linoleic acid oxidation in potato (Solanum tuberosum) tubers

Colneleic acid is an unsaturated ether fatty acid derived from linoleic acid via a lipoxygenase-mediated enzyme pathway. It is degraded (a) by an enzyme in potato tubers which is heat-labile and non-dialysable and (b) by a model system containing catalytic amounts of Fe(2+) ions. Both enzyme- and Fe(2+)-catalysed systems have similar properties with respect to pH optima (pH5.0-5.5), oxygen requirement (0.6-0.7 mol of O(2) consumed/mol of ether degraded), inhibitors and reaction products. An unstable product breaks down to C(8) and C(9) carbonyl fragments. Both systems are inhibited by low concentrations of antioxidants (e.g. 5mum-butylated hydroxytoluene) and some chelating agents (e.g. 5mum-diethyldithio-carbamate). The model system is strongly inhibited by metal ions, particularly Cu(2+) and Fe(3+), at 20mum. Hydrogen peroxide and haemoproteins do not substitute for the enzyme or Fe(2+) ions but the non-haem iron protein, ferredoxin, does catalyse the degradation.     

Arginine metabolism in insects. Role of arginase in proline formation during silkmoth development

1. Ornithine delta-transaminase (l-ornithine-2-oxo acid aminotransferase, EC 2.6.1.13) and Delta(1)-pyrroline-5-carboxylate reductase [l-proline-NAD(P) 5-oxidoreductase, EC 1.5.1.2] were demonstrated in fat-body and flight-muscle tissues of the silkmoth Hyalophora gloveri. Arginase (l-arginine ureohydrolase, EC 3.5.3.1) is also present in these tissues. 2. Arginase, ornithine transaminase and pyrroline-carboxylate reductase are generally considered to make up the catabolic pathway for the conversion of arginine into proline. The conversion of l-[U-(14)C]arginine into [(14)C]proline by intact fat-body tissue was used to show that the enzymes in insect fat body also function in this capacity. 3. Of the three enzymes of the catabolic pathway, only arginase increased during adult development and the increase coincided with the emergence of the winged adult moth. Since proline appears to be a major substrate utilized in insect flight metabolism, the increase in arginase activity at this stage suggests a major role for arginase in proline formation.