Stathmin Regulates Centrosomal Nucleation of Microtubules and Tubulin Dimer/Polymer Partitioning

Stathmin is a microtubule-destabilizing protein ubiquitously expressed in vertebrates and highly expressed in many cancers. In several cell types, stathmin regulates the partitioning of tubulin between unassembled and polymer forms, but the mechanism responsible for partitioning has not been determined. We examined stathmin function in two cell systems: mouse embryonic fibroblasts (MEFs) isolated from embryos +/+, +/−, and −/− for the stathmin gene and porcine kidney epithelial (LLCPK) cells expressing stathmin-cyan fluorescent protein (CFP) or injected with stathmin protein. In MEFs, the relative amount of stathmin corresponded to genotype, where cells heterozygous for stathmin expressed half as much stathmin mRNA and protein as wild-type cells. Reduction or loss of stathmin resulted in increased microtubule polymer but little change to microtubule dynamics at the cell periphery. Increased stathmin level in LLCPK cells, sufficient to reduce microtubule density, but allowing microtubules to remain at the cell periphery, also did not have a major impact on microtubule dynamics. In contrast, stathmin level had a significant effect on microtubule nucleation rate from centrosomes, where lower stathmin levels increased nucleation and higher stathmin levels reduced nucleation. The stathmin-dependent regulation of nucleation is only active in interphase; overexpression of stathmin-CFP did not impact metaphase microtubule nucleation rate in LLCPK cells and the number of astral microtubules was similar in stathmin +/+ and −/− MEFs. These data support a model in which stathmin functions in interphase to control the partitioning of tubulins between dimer and polymer pools by setting the number of microtubules per cell.     

The effect of randomly altering the time and location of feeding on the behaviour of captive coyotes (Canis latrans)

Captive carnivores appear highly susceptible to the negative effects of predictable feeding routines. Current research and reviews suggest feeding unpredictably may increase species typical behaviour, but positive results have been limited to a few species. Our objectives were to determine whether randomly altering the time and location of feeding increased species typical behaviour, or affected the temporal distribution of captive coyote (Canis latrans) behaviour. We assigned 12 coyotes individually to either a predictable or an unpredictable (in time and location) feeding condition and measured behaviours in the morning and evening. Overall, mean time spent foraging, travelling, resting or standing was similar in both conditions, but coyotes in the unpredictable condition marked (118 vs. 42; P = 0.01, one-tailed) and howled (81 vs. 24; P = 0.05, one-tailed) significantly more than coyotes in the predictable condition. There were also significant temporal differences (a.m. vs. p.m.) in behaviour between conditions. Specifically, coyotes fed predictably foraged (P = 0.03) and travelled (P = 0.03) more in the morning and rested (P = 0.03) more in the evening, whereas coyotes fed unpredictably howled (62 vs. 19; P = 0.03) and stood (P = 0.05) more in the morning and foraged (P = 0.03) more in the evening. Optimum predictability for captive carnivores should be based on species-specific captive study results and relevant ecological data. Our results suggest coyote feeding regimes may be improved by including unpredictable elements nested within a predictable framework to mirror seasonal fluctuations in resources and increase species-specific behaviour in captivity.     

The roles of calcium signaling and ERK1/2 phosphorylation in a Pax6 +/- mouse model of epithelial wound-healing delay

Background  

Congenital aniridia caused by heterozygousity at the PAX6 locus is associated with ocular surface disease including keratopathy. It is not clear whether the keratopathy is a direct result of reduced PAX6 gene dosage in the cornea itself, or due to recurrent corneal trauma secondary to defects such as dry eye caused by loss of PAX6 in other tissues. We investigated the hypothesis that reducing Pax6 gene dosage leads to corneal wound-healing defects. and assayed the immediate molecular responses to wounding in wild-type and mutant corneal epithelial cells.     

The importance of ecological and behavioural data in studies of hybridisation among marine fishes

Natural hybridisation is a widespread phenomenon, particularly well documented in terrestrial and freshwater ecosystems, where it has been ascribed substantial evolutionary and adaptive relevance. Hybridisation has received comparatively less attention in marine systems, though there has been a recent surge of reported marine hybrids, particularly among corals and fishes. This review summarises the current knowledge of hybridisation in marine fishes, with a focus on ecological and behavioural factors that may play a role in hybridisation processes. Rarity of one or both parental species within the hybrid zone, overlap in habitat use, dietary overlap and the breakdown in assortative mating appear to have a role in facilitating hybridisation. Despite this, most of the recent literature on marine fish hybridisation has a strong genetic focus, with little or no quantitative information about the ecological and behavioural factors that initiate or facilitate hybridisation. Future studies should attempt to gather ecological and behavioural data from hybrid zones, thus teasing out which processes are most relevant to overcoming pre-zygotic barriers to reproductive isolation. Not only will this advance our understanding of the adaptive and evolutionary relevance of hybridisation in marine fishes, but it will also provide unique insights into the maintenance of reproductive isolation and the process of speciation in the marine environment.     

Body concentration of caesium-137 in patients from Western Isles of Scotland.

OBJECTIVES--To compare caesium-137 concentrations in patients from the Western Isles Health Board, Glasgow area, and other parts of the Scottish mainland, and to investigate the source of 137Cs in patients from the Western Isles. DESIGN--Study of hypertensive patients having electrolyte concentrations measured, including 137Cs. Interview by questionnaire of island subjects about intake of foods likely to contain radiocaesium and the source of these foods. Measurement of 137Cs and 134Cs in food, urine, and vegetation. SETTING--Scottish mainland and Western Isles, 1979-86. All measurements before Chernobyl nuclear accident. PATIENTS--413 consecutive patients referred to the blood pressure unit for investigation of hypertension. 60 from the Western Isles, including 44 from North Uist; 32 from North Uist participated in the dietary analysis. MAIN OUTCOME MEASURES--Concentration of radiocaesium in the body, urine, food, and vegetation. Islanders'' consumption of local produce. RESULTS--Patients from the Western Isles had five times higher body concentrations of 137Cs (median 2.54 (interquartile range 1.25-3.73)) Bq/gK) than did patients from around Glasgow (0.47 (0.26-0.66) Bq/gK) and other parts of the Scottish mainland (0.42 (0.24-0.71) Bq/gK). Islanders often consumed local milk and mutton, but ate local fish rarely. 137Cs and 134Cs were present in coastal (21.6 Bq/kg 137Cs, 0.25 Bq/kg 134Cs) and moorland (135.9, 0.65 Bq/kg) grasses and in islanders'' urine (2.01, 0.013 Bq/l). Lower concentrations (0.336, 0.004 Bq/l), were found in the urine of Glasgow controls (p less than 0.001 for both isotopes). CONCLUSIONS--Islanders have excess body 137Cs concentrations, most of which probably comes from local milk and lamb. The radioactivity is not above the recommended safety limit. The presence of 134Cs suggests that nuclear reprocessing is the source of some of the radiocaesium.