Proximate mechanisms driving circadian control of neuroendocrine function: Lessons from the young and old

Circadian rhythms impact a variety of behavioral and physiological functions contributing to longevity and successful reproduction. In their natural environments, individuals of a species are faced with a multitude of challenges and the coordination of internal processes and behavior with external pressures has been hypothesized to be an important target of natural selection. Several lines of evidence from cyanobacteria, Drosophila, and plants provide strong support for an important role of the circadian clock in survival and reproductive success. Similarly in mammals, disruptions in circadian function markedly impact reproduction and lifespan. The present review discusses research outlining the proximate and ultimate mechanisms responsible for the central and peripheral control of the reproductive axis. Because precise temporal coordination of the endocrine system is particularly crucial for reproduction by females, the present overview focuses on the role of circadian timing in this sex.     

exma: an X-linked insertional mutation that disrupts forebrain and eye development

Formation of the neural tube plays a primary role in establishing the body plan of the vertebrate embryo. Here we describe the phenotype and physical mapping of a highly penetrant X-linked male-lethal murine mutation, exma (exencephaly, microphthalmia/anophthalmia), that specifically disrupts development of the rostral neural tube and eye. The mutation arose from the random insertion of a transgene into the mouse X Chromosome (Chr). Eighty-three percent of transgenic male embryos display an open, disorganized forebrain and lack optic vesicles. No transgenic males survive beyond birth. Hemizygous females show a variable phenotype, including reduced viability and occasional exencephaly and/or microphthalmia. Altered or reduced expression patterns of Otx2, Pax6, Six3, and Mrx, known markers of early forebrain and eye development, confirmed the highly disorganized structure of the forebrain and lack of eye development in affected exma male embryos. Physical mapping of the transgene by FISH localized a single insertion site to the interval between Dmd and Zfx on the X Chr. A 1-Mb contig of BAC clones was assembled by using sequences flanking the transgene and revealed that the insertion lies close to Pola1 and Arx, a gene encoding a highly conserved homeobox protein known to be expressed in the developing forebrain of the mouse. Data from Southern blots of normal and transgenic DNA demonstrated that a large segment of DNA encompassing Arx and including part of Pola1 was duplicated as a result of the transgene insertion. From the physical mapping results, we propose a model of the gross rearrangements that accompanied transgene integration and discuss its implications for evaluating candidate genes for exma.     

Katanin contributes to interspecies spindle length scaling in Xenopus

Bipolar spindles must separate chromosomes by the appropriate distance during cell division, but mechanisms determining spindle length are poorly understood. Based on a 2D model of meiotic spindle assembly, we predicted that higher localized microtubule (MT) depolymerization rates could generate the shorter spindles observed in egg extracts of X. tropicalis compared to X. laevis. We found that katanin-dependent MT severing was increased in X. tropicalis, which, unlike X. laevis, lacks an inhibitory phosphorylation site in the katanin p60 catalytic subunit. Katanin inhibition lengthened spindles in both species. In X. tropicalis, k-fiber MT bundles that connect to chromosomes at their kinetochores extended through spindle poles, disrupting them. In both X. tropicalis extracts and the spindle simulation, a balance between k-fiber number and MT depolymerization is required to maintain spindle morphology. Thus, mechanisms have evolved in different species to scale spindle size and coordinate regulation of multiple MT populations in order to generate a robust steady-state structure.     

Scleroblast cultures from the gorgonianLeptogorgia virgulata (Lamarck) (Coelenterata: Gorgonacea)

Summary Scleroblasts were separated from fragmented tissue of growing tips ofLeptogorgia virgulata and cultured using a modification of the technique of Rannou. Replacement of fetal bovine serum with horse serum seemed to increase scleroblast viability. Cell adhesion occurred from 14 to 43 d. Cultured scleroblasts demonstrated cell aggregation, spicule formation, and extrusion of spicules into the external medium. Cells showing spicules in the process of being extruded appeared on the average after 24 d of culture. Variability among cultures was marked with respect to both division and spicule formation. Healthy cultures were maintained for more than 4 mo. This work was supported by National Science Foundation grants PCM8201389 and DCB8502698. This is contribution No. 674 of Belle W. Baruch Institute for Marine Biology and Coastal Research, University of South Carolina.     

Original cervical cytology and follow-up biopsy results in positive high risk human papillomavirus DNA tests with high-level resuls

OBJECTIVE: To ascertain Pap test and biopsy results of specimens with high level of human papillomavirus (HPv) DNA and compare atypical squamous cells of undetermined signiqicance (ASC-US) populations with HPV DNA. STUDY DESIGN: Positive HPV tests with relative light unit (RLU) values > or =1000 were identified and original Pap test and follow-up biopsy results recorded. Pap test and biopsy results for ASC-US were compared to positive results with RLU <1000. RESULTS: From 1892 total HPV-positive tests, 156 specimens with high RLU were identified; 145 had biopsies. The interpretations of the corresponding Pap tests were as follows: negative for intraepithelial lesion and malignancy, 3; ASC-US, 87; ASC, cannot exclude high grade squamous intraepithelial lesion, 5; low grade squamous intraepithelial lesion, 40 and high grade squamous intraepithelial lesion, 10. Biopsies showed 60 negative, 58 cervical intraepithelial neoplasia (CIN) 1 and 27 CIN 2+. In the highly positive ASCUS group, biopsy showed higher percentage of CIN 1 (33% vs. 16%) compared to the low-positive group. CONCLUSION: Compared to low-positive results, high-positive results showed more abnormal Pap tests. CIN 1 was a more likely result for high-positive ASCUS. More transient infections may account for these findings. The results do not argue for different management schemes between the categories.