Testicular metamorphosis rates in European Starlings maintained under short daily photophases

Juvenile male European Starlings(Sturnus vulgaris) were maintained under discrete fixed daily photophases ranging from 1 to 11 h in duration. Treatment began on 20 December when all birds were reproductively quiescent, and continued until 14 June of the following year.In situ measurements of left testis widths at monthly intervals documented testicular width increases to levels associated with complete spermatogenesis in birds under all photoperiod regimens. Starlings maintained under the shortest and longest photoperiods required fewer days of treatment to achieve spermatogenic testes than did those under intermediate-length photoperiods. Data are consistent with the hypothesis that prolonged daily periods of darkness result in oscillations of a circadian timing system stimulating increased gonadotropin secretion and consequent testicular metamorphosis.     

Mutagen-induced fetal anomalies and death following treatment of females within hours after mating

In an earlier study (Generoso et al., 1987), it was observed that the mutagen, ethylene oxide (EtO), produced remarkable increases in the incidence of developmental abnormalities and death of fetuses when early zygotic stages were exposed. This is a major finding in experimental induction of embryopathy, implicating genetic damage to the zygotes as the likely cause. In the subsequent study reported here, 3 other mutagens--ethyl methanesulfonate (EMS), ethyl nitrosourea (ENU), and triethylene melamine (TEM), were studied for embryopathic effects following exposure of dictyate oocytes, prefertilization oviducal eggs and sperm, early pronuclear zygotes, zygotes undergoing pronuclear DNA synthesis, and two-cell embryos. All 4 mutagens produced developmental abnormalities among living fetuses following exposure of early pronuclear zygotes (the only stage studied for this endpoint in this report). With respect to stage specificity and gestational timing of death of conceptuses, EMS and EtO on one hand and ENU and TEM on the other, are very similar to one another. EMS, like EtO, produced a high incidence of midgestation and late fetal deaths only in prefertilization oviducal eggs and sperm and in early pronuclear eggs. In contrast, ENU and TEM produced high losses of conceptuses in all postmating stages studied but death occurred primarily prior to or around the time of implantation. Thus, the frequency of induction and the expression of embryopathy, which ranged from early embryonic preimplantation and late fetal deaths to subtle fetal anomalies, are dependent upon the stage exposed and the mutagen used.     

Increased incidence of developmental anomalies among descendants of carriers of methylenebisacrylamide-induced balanced reciprocal translocations

N,N'-Methylenebisacrylamide (MBA), a dimer of the monomeric acrylamide, was studied for induction of clastogenic effects in germ cells of male mice. It was found to be effective in inducing dominant-lethal mutations and heritable translocations in maturing sperm. The semisterile translocation carriers and their normal counterparts were used to determine the health impact of transmitted chromosomal rearrangements through anatomical analysis of their immediate descendants in utero. As expected, semisterility resulted primarily from embryonic death during the periimplantation stages presumably caused by sperm segregants with unbalanced chromosome complement fertilizing some of the eggs. Among conceptuses that survived to mid- and late-gestation stages, there was an increased incidence of developmental anomalies including fetal death and phenotypic defects. These anomalies are assumed to be caused by certain types of unbalanced segregants that are compatible with survival beyond the periimplantation period. This class of unbalanced segregants represent in humans a major health problem to the mother and her conceptus.     

The dilemma of negative analysis of variance estimators of intraclass correlation

Summary At least two common practices exist when a negative variance component estimate is obtained, either setting it to zero or not reporting the estimate. The consequences of these practices are investigated in the context of the intraclass correlation estimation in terms of bias, variance and mean squared error (MSE). For the one-way analysis of variance random effects model and its extension to the common correlation model, we compare five estimators: analysis of variance (ANOVA), concentrated ANOVA, truncated ANOVA and two maximum likelihood-like (ML) estimators. For the balanced case, the exact bias and MSE are calculated via numerical integration of the exact sample distributions, while a Monte Carlo simulation study is conducted for the unbalanced case. The results indicate that the ANOVA estimator performs well except for designs with family size n = 2. The two ML estimators are generally poor, and the concentrated and truncated ANOVA estimators have some advantages over the ANOVA in terms of MSE. However, the large biases may make the concentrated and truncated ANOVA estimators objectionable when intraclass correlation () is small. Bias should be a concern when a pooled estimate is obtained from the literature since <0.05 in many genetic studies.     

Electrospinning Bombyx mori silk with poly(ethylene oxide)

Electrospinning for the formation of nanoscale diameter fibers has been explored for high-performance filters and biomaterial scaffolds for vascular grafts or wound dressings. Fibers with nanoscale diameters provide benefits due to high surface area. In the present study we explore electrospinning for protein-based biomaterials to fabricate scaffolds and membranes from regenerated silkworm silk, Bombyx mori, solutions. To improve processability of the protein solution, poly(ethylene oxide) (PEO) with molecular weight of 900,000 was blended with the silk fibroin. A variety of compositions of the silk/PEO aqueous blends were successfully electrospun. The morphology of the fibers was characterized using high-resolution scanning electron microscopy. Fiber diameters were uniform and less than 800 nm. The composition was estimated by X-ray photoelectron spectroscopy to characterize silk/PEO surface content. Aqueous-based electrospining of silk and silk/PEO blends provides potentially useful options for the fabrication of biomaterial scaffolds based on this unique fibrous protein.     

Methylated DNA/RNA in Body Fluids as Biomarkers for Lung Cancer

DNA/RNA methylation plays an important role in lung cancer initiation and progression. Liquid biopsy makes use of cells, nucleotides and proteins released from tumor cells into body fluids to help with cancer diagnosis and prognosis. Methylation of circulating tumor DNA (ctDNA) has gained increasing attention as biomarkers for lung cancer. Here we briefly introduce the biological basis and detection method of ctDNA methylation, and review various applications of methylated DNA in body fluids in lung cancer screening, diagnosis, prognosis, monitoring and treatment prediction. We also discuss the emerging role of RNA methylation as biomarkers for cancer.     

Biologic and molecular characterization of two newly isolated ras-containing murine leukemia viruses.

A murine sarcoma virus (MSV) was recovered from an (NFS X NS.C58v-1) F1 mouse which developed splenic sarcoma and erythroleukemia 6 months after inoculation with a mink cell focus-inducing murine leukemia virus (MuLV) isolated from an NFS mouse infected with a wild mouse ecotropic MuLV. The MSV, designated NS.C58 MSV-1, induced foci of transformation in mouse and rat fibroblasts, and inoculation of mice of various strains 2 weeks of age or younger resulted in erythroleukemia and sarcomatous lesions in spleen, lymph node, and brain. The MSV provirus was molecularly cloned from a genomic library prepared from transformed non-producer rat cells. The 8.8-kilobase proviral DNA contained a 1.0-kilobase p21 ras coding segment which replaced most of the gp70-encoding portion of an MuLV, most likely the endogenous C58v-1 ecotropic virus. The ras oncogene is closely related to v-Ha-ras by hybridization, expression of p21 protein, and nucleotide sequence. It is nearly identical in sequence to v-bas, the only previously described transduced, activated mouse c-ras. At position 12 in the p21 coding region, arginine is substituted for the naturally occurring glycine present in c-ras. A second MSV isolate is described which is similar to NS.C58 MSV-1 except for a 100- to 200-base-pair deletion in the noncoding region of the ras-containing insert.