Variance-component estimation from human sibship data

The large-sample relative efficiencies of the analysis-of-variance (ANOVA) estimators of variance components and the intraclass correlation coefficient rho are investigated for the unbalanced single classification in the context of family studies. The efficiency of an analysis based on the method of unweighted group means is also investigated. From a Monte Carlo study which generates the group sizes from typical family-size distributions it is found that the relative efficiency of the ANOVA estimators of the between-group variance component exceeds 95% for values of .2 less than or equal to rho less than or equal to .4, but can fall below 60% for values of rho that are very close to zero. For the estimation of the between-group variance component the method of unweighted means tends to be preferable to the ANOVA method only if rho greater than .5.     

Studies of adaptation of carabid beetles (Coleoptera,carabidae) to feeding on the Colorado potato beetle, <Emphasis Type="Italic">Leptinotarsa decemlineata</Emphasis> say (Coleoptera,chrysomelidae) in Agrocenoses of potato and other crops

In 1979–2008, serological investigation of carabid beetles as predators of the Colorado potato beetle was carried out in the fields of potato and other Solanaceae crops in nine regions of Russia, Moldova, and Ukraine. The fraction of carabid beetles feeding on the pest in the potato, tomato, and egg-plant fields grows with the duration of the pest presence in the region and is proportional to its population density.     

Pathways and control of connexin oligomerization

Connexins form gap junction channels that link neighboring cells into an intercellular communication network. Many cells that express multiple connexins produce heteromeric channels containing at least two connexins, which provides a means to fine tune gap junctional communication. Formation of channels by multiple connexins is controlled at two levels: by inherent structural compatibilities that enable connexins to hetero-oligomerize and by cellular mechanisms that restrict the formation of heteromers by otherwise compatible connexins. Here, I discuss roles for secretory compartments beyond the endoplasmic reticulum in connexin oligomerization and evidence that suggests that membrane microdomains help regulate connexin trafficking and assembly.     

Tobacco transformants expressing the <Emphasis Type="Italic">Medicago truncatula</Emphasis> ornithine aminotransferase cDNA

The Medicago truncatula ornithine aminotransferase cDNA was cloned under the potent constitutive 35S RNA promoter of the cauliflower mosaic virus and transferred into the genome of tobacco Nicotiana tabacum SR1 plants. Transformed tobacco plants grew better in salinity stress, but did not differ in proline content under normal or stress conditions from control plants. It was assumed that the role of ornithine aminotransferase in the molecular mechanisms of stress resistance is not associated with additional proline synthesis.     

Regulation of Connexin43 Oligomerization is Saturable

We have used connexin constructs containing a C-terminal di-lysine-based endoplasmic reticulum (ER) retention/retrieval signal (HKKSL) transfected into HeLa cells to study early events in connexin oligomerization. Using this approach, we found that Cx43-HKKSL stably expressed at moderate levels by HeLa cells was retained in the ER and prevented from oligomerization. However, Cx43-HKKSL stably overexpressed by HeLa cells escaped from the ER and localized to a perinuclear region of the cell that included the Golgi apparatus. Overexpressed Cx43-HKKSL oligomerized into hexamers and also formed Triton X-100 insoluble, intracellular complexes that resembled gap junctions. Thus, the ability of HeLa cells to inhibit Cx43 oligomerization was saturable. HeLa cells stably overexpressing Cx43-HKKSL may provide a useful model system to evaluate pharmacologic agents and/or cDNAs encoding chaperones with the potential to regulate initial steps in Cx43 oligomerization.     

Relatedness of the flagellins from methanogens

Purified flagellar filaments isolated from six methanogens were composed of multiple flagellins. Two flagellins were present in Methanococcus deltae (M _r =34000 and 32000), Methanoculleus marisnigri (M _r =31000 and 25500) and Methanococcus jannaschii (M _r =31000 and 27500), three in Methanothermus fervidus (M _r =34000, 25000 and 24000) and four or more in both Methanococcus vanniellii and Methanococcus maripaludis (M _r ranging from 27500 to 32000). The flagellins of M. fervidus and M. deltae reacted positively with glycoprotein-specific stains. The flagellins of M. deltae, M. maripaludis and M. vannielii were closely related to those of M. voltae based on cross-reactivity with antisera raised against M. voltae flagellins and homology with flagellin-specific oligonucleotide probes to the N-terminus and leader peptide of M. voltae flagellins. Similarities appear to exist among the flagellins of M. fervidus, M. marisnigri and Halobacterium halobium based on cross-reactivity with antisera produced against the flagella of Methanospirillum hungatei JF1. The N-termini of the flagellins from the mesophilic Methanococcus spp. and M. marisnigri show homology with the N-termini of other archaebacterial flagellins. These N-termini may undergo a modification involving removal of a leader peptide.     

Physiological adaptations involved in alkane assimilation at a low temperature by Rhodococcus sp. strain Q15.

We examined physiological adaptations which allow the psychrotroph Rhodococcus sp. strain Q15 to assimilate alkanes at a low temperature (alkanes are contaminants which are generally insoluble and/or solid at low temperatures). During growth at 5 degrees C on hexadecane or diesel fuel, strain Q15 produced a cell surface-associated biosurfactant(s) and, compared to glucose-acetate-grown cells, exhibited increased cell surface hydrophobicity. A transmission electron microscopy examination of strain Q15 grown at 5 degrees C revealed the presence of intracellular electron-transparent inclusions and flocs of cells connected by an extracellular polymeric substance (EPS) when cells were grown on a hydrocarbon and morphological differences between the EPS of glucose-acetate-grown and diesel fuel-grown cells. A lectin binding analysis performed by using confocal scanning laser microscopy (CSLM) showed that the EPS contained a complex mixture of glycoconjugates, depending on both the growth temperature and the carbon source. Two glycoconjugates [beta-D-Gal-(1-3)-D-GlcNAc and alpha-L-fucose] were detected only on the surfaces of cells grown on diesel fuel at 5 degrees C. Using scanning electron microscopy, we observed strain Q15 cells on the surfaces of octacosane crystals, and using CSLM, we observed strain Q15 cells covering the surfaces of diesel fuel microdroplets; these findings indicate that this organism assimilates both solid and liquid alkane substrates at a low temperature by adhering to the alkane phase. Membrane fatty acid analysis demonstrated that strain Q15 adapted to growth at a low temperature by decreasing the degree of saturation of membrane lipid fatty acids, but it did so to a lesser extent when it was grown on hydrocarbons at 5 degrees C; these findings suggest that strain Q15 modulates membrane fluidity in response to the counteracting influences of low temperature and hydrocarbon toxicity.     

Identification of rab20 as a potential regulator of connexin 43 trafficking

Connexin oligomerization and trafficking are regulated processes. To identify proteins that control connexin 43 (Cx43), a screen was designed using HeLa cells expressing a Cx43 construct with di-lysine endoplasmic reticulum (ER)-retention/retrieval motif, Cx43-HKKSL. At moderate levels of expression, Cx43-HKKSL is retained in the ER as monomers; however, Cx43-HKKSL stably overexpressed by HeLa cells localizes to the perinuclear region and oligomerizes. HeLa/Cx43-HKKSL overexpressors were transiently transfected with pooled clones from a human kidney cDNA library and used immunofluorescence microscopy to identify cDNAs that enabled overexpressed Cx43-HKKSL to convert from a perinuclear to ER localization pattern. Using this approach, a small molecular weight GTPase, rab20, was identified as a candidate protein with the ability to regulate Cx43 trafficking. Enhanced green fluorescent protein (EGFP)-tagged rab20 showed a predominantly perinuclear and ER localization pattern and caused wild-type Cx43 to be retained inside the cell. By contrast, mutant EGFP-rab20T19N, which lacks the ability to bind GTP, had no effect on Cx43. These results suggest Cx43 is transported through an intracellular compartment regulated by rab20 along the secretory pathway.