A kinetic hairpin transfer model for parvoviral DNA replication

The DNAs encapsidated by parvoviruses show distinctly different patterns with respect to the ratio of plus-to-minus strands and sequence heterogeneity at the ends. A kinetic model, based on differential rates of hairpin transfer at 3' termini, is described and shown to account for all known parvoviral DNA distributions.     

Variations among cell lines in the synthesis of sphingolipids in de novo and recycling pathways

There are several pathways for the incorporation of sugars into glycosphingolipids (GSL). Sugars can be added to ceramide that contains sphinganine (dihydrosphingosine) synthesized de novo (pathway 1), to ceramide synthesized from sphingoid bases produced by hydrolysis of sphingolipids (pathway 2), and into GSL recycling from the endosomal pathway through the Golgi (pathway 3). We reported previously the surprising observation that SW13 cells, a human adrenal carcinoma cell line, synthesize most of their GSL in pathway 2. We now present data on the synthesis of GSL in four additional cell lines. Approximately 90% of sugar incorporation took place in pathway 2, and 10% or less in pathway 1, in human foreskin fibroblasts and NB41A3 neuroblastoma cells. In contrast, approximately 50-90% of sugar incorporation took place in pathway 1 in C2C12 myoblasts. The C2C12 cells divide more rapidly and synthesize 10-14 times as much GSL as the other three cell lines. In C6 glioma cells, approximately 30% of sugar incorporation occurred in pathway 1 and 60% in pathway 2. There was no relation between the utilization of pathways for GSL and sphingomyelin synthesis in foreskin fibroblasts and C2C12 cells. In both cells pathways 1 and 2 each accounted for 50% of incorporation of choline into sphingomyelin. In five of the six cell lines that we have studied, most GSL synthesis takes place in pathway 2. We suggest that when the need for synthesis is relatively low, as in slowly dividing cells, GSL are synthesized predominantly from sphingoid bases salvaged from the hydrolytic pathway. When cells are dividing more rapidly, the need for increased synthesis is met by upregulating the de novo pathway.      

Exploring the multidimensionality of stature variation in the past through comparisons of archaeological and living populations

Adult stature variation is commonly attributed to differential stress-levels during development. However, due to selective mortality and heterogeneous frailty, a population's tall stature may be more indicative of high selective pressures than of positive life conditions. This article examines stature in a biocultural context and draws parallels between bioarchaeological and living populations to explore the multidimensionality of stature variation in the past. This study investigates: 1) stature differences between archaeological populations exposed to low or high stress (inferred from skeletal indicators); 2) similarities in growth retardation patterns between archaeological and living groups; and 3) the apportionment of variance in growth outcomes at the regional level in archaeological and living populations. Anatomical stature estimates were examined in relation to skeletal stress indicators (cribra orbitalia, porotic hyperostosis, linear enamel hypoplasia) in two medieval bioarchaeological populations. Stature and biocultural information were gathered for comparative living samples from South America. Results indicate 1) significant (P < 0.01) differences in stature between groups exposed to different levels of skeletal stress; 2) greater prevalence of stunting among living groups, with similar patterns in socially stratified archaeological and modern groups; and 3) a degree of regional variance in growth outcomes consistent with that observed for highly selected traits. The relationship between early stress and growth is confounded by several factors—including catch-up growth, cultural buffering, and social inequality. The interpretations of early life conditions based on the relationship between stress and stature should be advanced with caution. Am J Phys Anthropol 155:229–242, 2014. © 2014 Wiley Periodicals, Inc.     

Evidence that expression of asialo-GM1 may be associated with cell activation. Correlation of asialo-GM1 expression with increased total cellular RNA and protein content in normal thymocyte and spleen cell populations

The question of the biologic significance of asialo-GM1 (aGM1) expression by a limited number of cells including natural killer cells has been raised by the recent demonstrations that aGM1 is expressed by activated macrophages and activated T cells as well as the proliferating thymoblast and functionally mature subpopulations of thymus. The current report demonstrates that the expression of aGM1 on aGM1-negative lymphocytes can be induced by stimulation with mitogens under activating conditions. In addition, activation of the aGM1-negative tumor lines EL-4/F and P388D1/B1 under conditions that result in interleukin 2 or interleukin 1 production, respectively, also result in a significant increase in aGM1 expression by the tumor cell lines. Expression of aGM1 therefore appears to be associated with events occurring as a prelude to or during activation of effector function. Since the aGM1-negative cells do display sialylated versions of aGM1 which can be converted by neuraminidase treatment into serologically recognizable aGM1, it is suggested that the expression of aGM1 might reflect a change in the level of glycolipid sialylation rather than a change in membrane lipid composition per se. The small percentage of lymphocytes in normal, nonstimulated spleen and thymus populations which express significant levels of aGM1 were sorted and analyzed for total cellular protein and RNA. Increases in RNA synthesis and in total cellular protein and RNA above basal levels of resting lymphocytes are considered indicators of a G0----G1 transition. The aGM1-positive populations displayed a larger mean population size (as indicated both by higher forward light scatter and by higher total cellular protein content), and a higher mean population RNA content than the aGM1-negative populations. These data are discussed in the context of the hypothesis that the expression of aGM1 may be associated with early events in the activation of resting cells which prepare the cells for subsequent induction of effector function.     

Sexual responsiveness mediated by the corpora allata and its relationship to phonotaxis in the female cricket,Acheta domesticus L.

Summary FemaleAcheta domesticus can be clearly classified as sexually responsive or nonresponsive by their willingness to mount the courting male and assume the copulatory position. Females that were so classified as sexually responsive showed a definite phonotactic response to the calling song of the conspecific male. Immediate retesting of these females showed that a significant proportion exhibited very little movement in response to the sound. The females that did move in response to the calling song oriented phonotactically to the speaker also in the second trial. Females classified as nonresponsive did not react phonotactically to the calling song. The transition from the nonresponsive to the responsive state occurred within 24 h after transplanting the corpora allata from sexually responsive to nonresponsive females.We are greatly indebted to Professor Franz Huber for constructive discussion, critically reading the paper and for his interest in this work.     

Disc Plate Method of Microbiological Antibiotic Assay: II. Novel Procedure Offering Improved Accuracy 1

A detailed disc plate procedure is introduced for assay of antibiotics. The procedure is based on a previous study by the authors and deviates from conventional procedures in several respects: selected plastic petri dishes are employed; critical temperature control is simply provided at all stages of the test with refrigeration of the plates never used; all dilution is done with displacement microburettes; six pads (6.3 mm diameter) per dish are employed, all filled with the same unknown or reference solution; the sequence of all plates handled on 1 day is made a part of the protocol which allows accounting for the influence of the order of pouring and setting the plates; external reference plates are set at specified locations in the sequence; and, by averaging the diameters of all zones on a plate, most of the consequence of wedge shape of agar in plates, which is common and almost unavoidable, is removed. The present method is economical, uses simple facilities, and provides good accuracy of test results. Bacillus subtilis was most commonly employed, but other organisms may be employed in the present procedure.     

Hydroxyurea synchoronization of bovine fetal spleen cells.

Hydroxyurea (HU) was shown to be an effective synchronization agent for bovine fetal spleen (BFS) cells. Following exposure of cells to 2 mM HU for 32 h, DNA synthesis above background levels was not observed. BFS cells released from the HU block by washing began to synthesize DNA immediately. Within 2 h, 80–85% of the cells were in S phase, as determined by autoradiography, and the maximum rate of DNA synthesis occurred 2–4 h following removal of HU. The rapid induction of DNA synthesis in BFS cells and the high percentage of cells synthesizing DNA immediately after removal of HU demonstrate that HU produces a highly synchronized population of S phase BFS cells. Although RNA and protein synthesis were maintained at near normal rates early after cells were exposed to HU, the rates decreased to 40–50% of those observed in cells seeded in medium without HU by the time of release. These reduced rates of synthesis of RNA and protein in the absence of DNA synthesis may account for the low toxicity of HU for BFS cells.