Live cell imaging reveals distinct roles in cell cycle regulation for Nek2A and Nek2B

Two splice variants of Nek2 kinase, a member of the NIMA-related family, have been identified as Nek2A and Nek2B. Nek2A regulates centrosome disjunction, spindle formation checkpoint signaling, and faithful chromosome segregation. A specific role for Nek2B has not yet been identified. Here, we have examined the distinct roles of Nek2A and Nek2B using timelapse video microscopy to follow the fate of cells progressing through the cell cycle in the absence of either Nek2A or Nek2B. We show that the down-regulation of Nek2B leads to a mitotic delay in the majority of cells. Upon exiting mitosis, cells exhibit mitotic defects such as the formation of multinucleated cells. Such phenotypes are not observed in cells that exit mitosis in the absence of Nek2A. These observations suggest that Nek2B may be required for the execution of mitotic exit.     

Characterization and regulation of the latent transforming growth factor-β complex secreted by vascular pericytes

Transforming growth factor-β (TGF-β) stimulates the accumulation of extracellular matrix in renal and hepatic disease. Kidney glomerular mesangial cells (GMC) and liver fat-storing cells (FSC) produce latent or inactive TGF-β. In this study, we characterized the latent TGF-β complexes secreted by these cells. Human FSC produce a single latent TGF-β complex, predominantly of the TGF-β1 isoform, whereas GMC secrete multiple complexes of latent TGF-β, containing β1 and β2 isoforms. At least four forms were identified in GMC using ion exchange chromatography, including a peak not previously described in other cell types which eluted at 0.12 M NaCl, and predominantly of the β2 isoform. Both cell types secrete the latent TGF-β1 binding protein of 190 kDa, as part of a high molecular weight TGF-β complex. Epidermal growth factor stimulates the secretion of latent TGF-β and latent TGF-β binding protein in both cell types. Secretion of the latent TGF-β in both cell types was found to be associated with secretion of decorin. This study shows that vascular pericytes from the kidney and the liver have distinctly different profiles of latent TGF-β complexes, with GMC secreting a unique form of latent TGF-β2. The regulatory effect of epidermal growth factor and platelet-derived growth factor has potential implication for the pathophysiology of liver regeneration and chronic liver and kidney diseases. © 1996 Wiley-Liss, Inc.     

Facial correlates of sociosexuality

Previous studies have documented variation in sexual behaviour between individuals leading to the notion of ‘restricted’ individuals (i.e., people who prefer long-term relationships) and ‘unrestricted’ individuals (i.e., people who are open to short-term relationships). This distinction is often referred to as sociosexual orientation. Observers have been previously found to distinguish sociosexuality from video footage of individuals, although the specific cues used have not been identified. Here we assessed the ability of observers to judge sexual strategy based specifically on cues in both facial composites and real faces. We also assessed how observers' perceptions of the masculinity/femininity and attractiveness of faces relate to the sociosexual orientation of the pictured individuals. Observers were generally able to identify restricted vs. unrestricted individuals from cues in both composites and real faces. Unrestricted sociosexuality was generally associated with greater attractiveness in female composites and real female faces and greater masculinity in male composites. Although male observers did not generally associate sociosexuality with male attractiveness, female observers generally preferred more restricted males' faces (i.e., those with relatively strong preferences for long-term relationships). Collectively, our results support previous findings that androgenisation in men is related to less restricted sexual behaviour and suggest that women are averse to unrestricted men.     

A missense mutation in rpoD results in an A-signalling defect in Myxococcus xanthus

The Myxococcus xanthus asg genes ( asgA, asgB , and asgC ) are necessary for production of extracellular A-signal, which is thought to function as a cell-density signal. Previous analyses of the asgA and asgB genes suggest that they perform regulatory functions. In this work, we localized asgC to a region that contains genes homologous to rpsU, dnaG , and rpoD of the Escherichia coli macromolecular synthesis (MMS) operon. Surprisingly, asgC767 was found to be a mutant allele of rpoD , the gene encoding the major sigma factor of M. xanthus . The mutation in asgC767 results in a glutamate to lysine substitution at amino acid 598, which lies within conserved region 3.1 of the major sigma factors. Previous studies have shown that the asg mutants share a number of growth and developmental phenotypes. We found that A-signal restores developmental expression of an A-signal-dependent gene (Ω4521) in the asgC767 ( rpoDEK598 ) mutant background in a manner similar to that seen in the asgA and asgB mutants. Because the asg mutants have very similar phenotypes and the asg genes encode proteins that appear to have regulatory functions, we hypothesize that the asg gene products function together in a regulatory pathway that is required for extracellular A-signal production.     

Two new species ofOdilia (Nematoda: Heligmonellidae) from Australian rodents,with comments onO. bainae Beveridge & Durette-Desset, 1992

Odilia tasmaniensis n. sp.,O. praeputialis n. sp. andO. bainae Beveridge & Durette-Desset, 1992 from the small intestine of Australian murids are described and illustrated. The two new species are distinguished from the other eight species in the genus, namelyO. mackerrasae (Mawson, 1961),O. brachybursa (Mawson, 1961),O. emanuelae (Mawson, 1961),O. melomyos (Mawson, 1961),O. polyrhabdote (Mawson, 1961),O. uromyos (Mawson, 1961),O. mawsonae (Durette-Desset, 1969) andO. bainae Beveridge & Durette-Desset, 1992.O. tasmaniensis n. sp. fromRattus lutreolus is characterised by the longitudinal cuticular ridges being continuous, the presence of 18 ridges in cross-section in the middle region of the body, the joined distal ends of the spicules forming a curved bluntly rounded tip, a short genital cone with a single ventral papilla and a pair of laterally curving dorsal raylets and the posterior end of the female tapering sharply.O. praeputialis n. sp. fromZyzomys woodwardi is characterised by continuous longitudinal cuticular ridges, the presence of 22–35 ridges in cross-section in the middle of the body, the sharply pointed joined distal tips of the spicules, a complex genital cone with a flat membraneous proconus, a ventral papilla projecting from an extension of the body wall, a pair of short straight dorsal raylets and the presence of a praepuce on the posterior end of the female.O. bainae is characterised by the longitudinal cuticular ridges being continuous, the presence of 17–22 ridges in cross-section in the middle region of the body, the joined distal ends of the spicules surrounded in an oval transparent cap, a long genital cone with a single ventral papilla and a pair of laterally curving dorsal raylets, and the absence of a praepuce on the posterior end of the female.Rattus lutreolus and the pseudomyine rodentsPseudomys higginsi andMastacomys fuscus are new host records for this species.     

Factors regulating fruit and seed production in the desert annual Lesquerella gordonii

Summary This study examines the pattern of reproduction and factors that limit the maternal reproductive output in the self-incompatible annual, Lesquerella gordonii. Greenhouse experiments showed that fruits do not abscise and they mature if they contain at least one fertilized (outcrossed) ovule. Field studies showed that flowering increased to a peak and then fell off rapidly, while seed production/fruit decreased through the season. Pollen addition did not increase the number of fruit or seeds per fruit, suggesting that fruit and seed production are not pollinator limited. Addition of water increased fruit and seed production by extending the life of the plant, by increasing the number of stalks which flowered, and by increasing the number of seeds per fruit. This indicates that fruit and seed production are resource limited. Fruits are relatively inexpensive as compared to seeds as over 93% of the water in fruits is contained in the seeds. Fifty-three percent of the plants were lost to herbivory as were 64.6% of the fruits on the remaining plants, indicating that herbivory also limited fruit and seed production. It is hypothesized that high fruit set coupled with variable seed set in L. gordonii is an adaptive response to unpredictable, variable resource levels, and high herbivory risk.     

Detection of mutation in transgenic CHO cells using green fluorescent protein as a reporter

A novel approach was developed for rapidly estimating the frequency of specific mutations in genetically engineered Chinese hamster ovary (CHO) cells. We designed double-transgenic CHO cell lines that contain a transgene consisting of the sequence coding for green fluorescent protein under the control of a tetracycline (Tet) responsive promoter and a second transgene coding for the constitutively expressed Tet repressor. Cultures of these CHO cells were treated with gamma-radiation, N-methyl-N-nitrosourea or methyl methanesulfonate, and the fluorescence of individual cells from both control and treated cultures was measured by flow cytometry. The treatments increased the number of highly fluorescent cells, those with presumed mutations in the Tet-repressor gene. Mutant cells from gamma-radiation-exposed cultures were isolated by fluorescence-activated cell sorting, cultured, and individual clones expanded. A PCR-based analysis indicated that the highly fluorescent expanded cells had lost the transgene coding for the Tet repressor, suggesting that the system mainly detects large genetic alterations. A similar approach may be useful for making high-throughput in vivo models for mutation detection.