Optimal conditions for the study of growth control in BALB/c 3T3 fibroblasts

The effect of a Fibroblast Growth Factor (FGF) on the initiation of DNA synthesis in sparse populations of BALB/c 3T3 cells maintained quiescent in the presence of various serum concentrations has been investigated. The initiation of DNA synthesis, as measured by ³H-thymidine incorporation, is greatest in cultures maintained quiescent in the presence of 0.8% serum. Under these conditions, the cells are on the border between quiescence and growth. The minimal effective dose of FGF needed to increase DNA synthesis is 0.01 ng/ml and plateau values are obtained between 2.5 and 5 ng/ml. At plateau concentrations, FGF is 65% as effective as saturating concentrations of serum in the stimulation of DNA synthesis. When dexamethasone and insulin are present, FGF was 82% as effective. In contrast, cultures maintained in the presence of lower serum concentrations (0.2% and 0.4%) are much less responsive to the FGF. This can be attributed to the lack of supplemental factors which make the cells maximally responsive to growth stimulation and to degenerative changes that take place in the cells. Insulin and the glucocorticoid, dexamethasone, potentiated the response to FGF and delayed the degeneration of cells maintained in low serum.     

Ultrastructure of the grasshopper proximal femoral chordotonal organ

Summary Calpasoma dactyloptera, a tentacled form of minute, freshwater coelenterate, has been investigated by light and electron microscopy and time-lapse cinematography. Each tentacle consists of a protrusion from a single ectodermal epithelial cell termed a tentaculocyte. hin tentaculocyte vesicles which represent invaginations of the plasma membrane. A cnidocil protrudes into the external medium. The bottom of each nematocyte is elongated as a stalk which extends to the tentacle base, coursing through tubular membrane lined channels within the tentaculocyte. A network of fibers and microtubules, originating in the cnidocil, extends to the base of the nematocyte stalk.Supported by PHS Research Career Development Award 1-K04-GM42595 and NSF Research Grant GB 29284.     

Frequency of chromosomal abnormalities in embryos from superovulated merino ewes

Chromosomal analysis was carried out on 48 Day 2-7 embryos collected from superovulated Merino ewes. Three embryos had abnormal chromosome complements (1 X 1N, 1 X 1N/2N, 1 X 3N), yielding an incidence of 6.25% abnormal embryos. It is concluded that superovulation does not cause an increase in the incidence of chromosomal abnormalities in embryos of Merino sheep.     

Tritium labeling of thermolysin, elastase, and ribonuclease by exposure to tritium gas at low pressure

The bacterial metalloendoprotease thermolysin, bovine pancreatic ribonuclease, and porcine pancreatic elastase have been tritiated by exposure to subcurie amounts of tritium gas at pressures below 50 mTorr for periods of 1 to 6 h. Thermolysin, ribonuclease, and elastase have been purified to specific radioactivities of 15, 5, and 1 Ci/mol, respectively. Amino acid analyses of the tritiated enzymes revealed higher relative specific radioactivities for His, Pro, and Phe in all three proteins while Val and Ile were among the residues with the lowest relative specific radioactivities. The recovery of enzyme activity was always greater than 95% and the formation of tritiated decomposition products was not observed. This lowpressure gas exposure process requires less tritium gas and less time than the original method of Wilzbach to achieve equal or higher levels of tritium incorporation. In addition, the enzymes were completely active and did not show the presence of highly radioactive byproducts which have been observed in earlier studies of the Wilzbach labeling of proteins.     

Sexual selection and population divergence III: Interspecific and intraspecific variation in mating signals

A major challenge for studying the role of sexual selection in divergence and speciation is understanding the relative influence of different sexually selected signals on those processes in both intra‐ and interspecific contexts. Different signals may be more or less susceptible to co‐option for species identification depending on the balance of sexual and ecological selection acting upon them. To examine this, we tested three predictions to explain geographic variation in long‐ versus short‐range sexual signals across a 3,500 + km transect of two related Australian field cricket species (Teleogryllus spp.): (a) selection for species recognition, (b) environmental adaptation and (c) stochastic divergence. We measured male calling song and male and female cuticular hydrocarbons (CHCs) in offspring derived from wild populations, reared under common garden conditions. Song clearly differentiated the species, and no hybrids were observed suggesting that hybridization is rare or absent. Spatial variation in song was not predicted by geography, genetics or climatic factors in either species. In contrast, CHC divergence was strongly associated with an environmental gradient supporting the idea that the climatic environment selects more directly upon these chemical signals. In light of recently advocated models of diversification via ecological selection on secondary sexual traits, the different environmental associations we found for song and CHCs suggest that the impact of ecological selection on population divergence, and how that influences speciation, might be different for acoustic versus chemical signals.     

Functional analysis of RPS27 mutations and expression in melanoma

Next‐generation sequencing has enabled genetic and genomic characterization of melanoma to an unprecedent depth. However, the high mutational background plus the limited depth of coverage of whole‐genome sequencing performed on cutaneous melanoma samples make the identification of novel driver mutations difficult. We sought to explore the somatic mutation portfolio in exonic and gene regulatory regions in human melanoma samples, for which we performed targeted sequencing of tumors and matched germline DNA samples from 89 melanoma patients, identifying known and novel recurrent mutations. Two recurrent mutations found in the RPS27 promoter associated with decreased RPS27 mRNA levels in vitro. Data mining and IHC analyses revealed a bimodal pattern of RPS27 expression in melanoma, with RPS27‐low patients displaying worse prognosis. In vitro characterization of RPS27‐high and RPS27‐low melanoma cell lines, as well as loss‐of‐function experiments, demonstrated that high RPS27 status provides increased proliferative and invasive capacities, while low RPS27 confers survival advantage in low attachment and resistance to therapy. Additionally, we demonstrate that 10 other cancer types harbor bimodal RPS27 expression, and in those, similarly to melanoma, RPS27‐low expression associates with worse clinical outcomes. RPS27 promoter mutation could thus represent a mechanism of gene expression modulation in melanoma patients, which may have prognostic and predictive implications.     

Long‐term persistence of wildlife populations in a pastoral area

Facilitating coexistence between people and wildlife is a major conservation challenge in East Africa. Some conservation models aim to balance the needs of people and wildlife, but the effectiveness of these models is rarely assessed. Using a case‐study approach, we assessed the ecological performance of a pastoral area in northern Tanzania (Manyara Ranch) and established a long‐term wildlife population monitoring program (carried out intermittently from 2003 to 2008 and regularly from 2011 to 2019) embedded in a distance sampling framework. By comparing density estimates of the road transect‐based long‐term monitoring to estimates derived from systematically distributed transects, we found that the bias associated with nonrandom placement of transects was nonsignificant. Overall, cattle and sheep and goat reached the greatest densities and several wildlife species occurred at densities similar (zebra, wildebeest, waterbuck, Kirk's dik‐dik) or possibly even greater (giraffe, eland, lesser kudu, Grant's gazelle, Thomson's gazelle) than in adjacent national parks in the same ecosystem. Generalized linear mixed models suggested that most wildlife species (8 out of 14) reached greatest densities during the dry season, that wildlife population densities either remained constant or increased over the 17‐year period, and that herbivorous livestock species remained constant, while domestic dog population decreased over time. Cross‐species correlations did not provide evidence for interference competition between grazing or mixed livestock species and wildlife species but indicate possible negative relationships between domestic dog and warthog populations. Overall, wildlife and livestock populations in Manyara Ranch appear to coexist over the 17‐year span. Most likely, this is facilitated by existing connectivity to adjacent protected areas, effective anti‐poaching efforts, spatio‐temporal grazing restrictions, favorable environmental conditions of the ranch, and spatial heterogeneity of surface water and habitats. This long‐term case study illustrates the potential of rangelands to simultaneously support wildlife conservation and human livelihood goals if livestock grazing is restricted in space, time, and numbers.