Conformationally altered aortic myosin light chains

Aorta smooth myosin contains two types of light chain, LC20 and LC17, which fold together with the N-terminal region of each heavy chain to form the globular head region of myosin. We demonstrate an altered conformation of LC20 after its separation from heavy chain by high concentrations of urea, on the basis of the following evidende: 1) A polyclonal antibody against LC20 was not able to recognize this conformationally altered form; 2) Myosin reconstituted from heavy chains and urea-dissociated light chains exhibited extremely low ATPase activity. Circular dichroism unfolding profiles showed that light chains dissociated from heavy chains by SDS appeared to be more stable than those generated by urea dissociation.     

大鼠胰腺γ-氨基丁酸免疫组织化学定位

本文用ABC—GDN免疫组织化学方法,研究了γ-氨基丁酸(Gamma—Aminobutyric Acid,GABA)在大鼠胰腺的定位和分布,并用相邻切片法,观察它与胰岛素的共存关系。结果发现GABA免疫反应阳性细胞主要分布于胰腺内分泌部(胰岛)。在外分泌部亦有少许分布。大部分胰岛细胞呈GABA免疫反应阳性,集中位于胰岛的中央部。相邻连续切片免疫染色证实GABA与胰岛素共存于胰岛B细胞中。外分泌部胰腺GABA免疫反应阳性细胞,呈零散分布于腺泡和导管上皮间。本文为进一步探讨GABA在胰腺的生理作用提供了形态学依据。     

Mycobacteria glycolipids as potential pathogenicity effectors: alteration of model and natural membranes

Four mycobacterial wall glycolipids were tested for their effects on phospholipidic liposome organization and passive permeability and on oxidative phosphorylation of isolated mitochondria. From fluorescence polarization of diphenylhexatriene performed on liposomes it was concluded that the two trehalose derivatives (dimycoloyltrehalose and polyphthienoyltrehalose) rigidified the fluid state of liposomes, the triglycosyl phenolphthiocerol slightly fluidized the gel state, while the peptidoglycolipid ("apolar" mycoside C) just shifted the phase transition temperature upward. Dimycoloyltrehalose was without effect on liposome passive permeability, as estimated from dicarboxyfluorescein leak rates, and polyphthienoyltrehalose and triglycosyl phenolphthiocerol slightly decreased leaks, while mycoside C dramatically increased leaks. Activity of these lipids on mitochondrial oxidative phosphorylation was examined. The two trehalose derivatives have been tested previously: both had the same type of inhibitory activity, dimycoloyltrehalose being the most active. Triglycosyl phenolphthiocerol was inactive. Mycoside C was very active, with effects resembling those of classical uncouplers: this suggested that its activity on mitochondria was related to its effect on permeability. All these membrane alterations were called nonspecific because it is likely that they result from nonspecific lipid-lipid interactions, and not from recognition between specific molecular structures. Such nonspecific interactions could be at the origin of some of the effects of mycobacteria glycolipids on cells of the immune system observed in the last few years.     

Ecological studies on Indonesian lakes. Overturn and restratification of Ranu Lamongan

In July 1974 Ranu Lamongan overturned. The resulting deoxygenation of this small tropical crater lake killed some of its fishes. This paper describes the recovery of stratification of temperature and oxygen and follows short-term changes in the plankton during the three weeks after overturn. The lake is fringed with a floating mat of Eichhornia whose submerged roots support and shelter a rich community of invertebrates on which much of the fishery depends. Comparison of our findings with those of the German Sunda Expedition in 1928 show remarkably few changes in the lake or its biota during the 45-year interval, despite a marked increase in the human population and the introduction of four species of fishes.     

Testing hypotheses driving genetic structure in the cooperatively breeding Brown‐headed Nuthatch Sitta pusilla

Habitat fragmentation has often been implicated in the decline of many species. For habitat specialists and/or sedentary species, loss of habitat can result in population isolation and lead to negative genetic effects. However, factors other than fragmentation can often be important and also need to be considered when assessing the genetic structure of a species. We genotyped individuals from 13 populations of the cooperatively breeding Brown‐headed Nuthatch Sitta pusilla in Florida to test three alternative hypotheses regarding the effects that habitat fragmentation might have on genetic structure. A map of potential habitat developed from recent satellite imagery suggested that Brown‐headed Nuthatch populations in southern Florida occupied smaller and more isolated habitat patches (i.e. were more fragmented) than populations in northern Florida. We also genotyped individuals from a small, isolated Brown‐headed Nuthatch population on Grand Bahama Island. We found that populations associated with more fragmented habitat in southern Florida had lower allelic richness than populations in northern Florida (P = 0.02), although there were no differences in heterozygosity. Although pairwise estimates of F_ST were low overall, values among southern populations were generally higher than northern populations. Population assignment tests identified K = 3 clusters corresponding to a northern cluster, a southern cluster and a unique population in southeast Florida; using sampling localities as prior information revealed K = 7 clusters, with greater structure only among southern Florida populations. The Bahamas population showed moderate to high differentiation compared with Florida populations. Overall, our results suggest that fragmentation could affect gene flow in Brown‐headed Nuthatch populations and is likely to become more pronounced over time.     

Combined analysis of the association between p73 G4C14-to-A4T14 polymorphisms and cancer risk

P73 is a structural and functional homologue of p53, and plays an important role in regulating cell cycle and apoptosis. A potentially functional polymorphism (designated as p73 G4C14-to-A4T14) has been identified in a region in exon 2 of the p73 gene, which may theoretically form a stem-loop structure and thereby affect p73 expression. Several investigations have reported the correlation between p73 G4C14-to-A4T14 polymorphism and cancer risk. However, the results are inconclusive. To further assess the association between p73 polymorphism and cancer risk, we performed meta-analysis of the data sets obtained from 26 individual studies involving 8,148 cancer patients and 8,150 controls. The association between p73 G4C14-to-A4T14 polymorphism and cancer risk was determined by crude odd ratios (OR) with 95% CI (confidential interval). AT-allele carriers were found to have a significantly increased risk of cervical cancer (AT/GC vs. GC/GC, OR = 1.63, 95% CI = 1.14–2.33; AT/AT + AT/GC vs. GC/GC, OR = 1.49, 95% CI = 1.05–2.10), colorectal cancer (AT/AT vs. AT/GC + GC/GC, OR = 1.98, 95% CI = 1.25–3.12), head and neck cancer (AT/AT + AT/GC vs. GC/GC, OR = 1.44, 95% CI = 1.06–1.96) and other cancers (AT/AT vs. GC/GC, OR = 1.78, 95% CI = 1.24–2.57; AT/AT vs. AT/GC + GC/GC, OR = 1.80, 95% CI = 1.26–2.56). In the stratified analysis of ethnicity, a significantly elevated cancer risk was found in Caucasians (AT/AT + AT/GC vs. GC/GC, OR = 1.18, 95% CI = 1.08–1.30; allele AT vs. allele GC, OR = 1.15, 95% CI = 1.06–1.24). No significant association of p73 polymorphism with the cancer risk of smoking was detected by stratified analysis by smoking status. Together, our data suggest that the p73 G4C14-to-A4T14 may be a risk factor of cancer especially in Caucasians.     

Invasion of the African sharp-tooth catfish <Emphasis Type=Italic>Clarias gariepinus</Emphasis> (Burchell, 1822) in South China

We record here the invasion of the African sharp-tooth catfish Clarias gariepinus in the South China biodiversity hotspot, an area rich in endemic and endangered fish fauna. C. gariepinus was introduced into the natural systems as escapees from aquaculture ponds. These catfishes are very large, top predators, and thus have the potential to cause serious threats to the native fish fauna. The impact of C. gariepinus needs more investigation with emphasis on developing techniques for controlling its dispersal.