Sequence Tag Site and Host Range Assays Demonstrate that Radapholus similis and R. citraphilus are not Reproductively Isolated

Males of citrus-parasitic Radopholus citrophilus (FL1) were mated with non-citrus-parasitic R. similis (FL5) females. Progeny inherited a 2.4-kb sequence tag site (DK#1) and the ability to reproduce in citrus from the paternal parent (FLl); both traits were absent in the maternal line (FL5). The hybrid progeny produced offspring in roots of citrus seedlings over an 8-month period and therefore were considered reproductively viable. Genomic DNA hybridization studies indicated that one or more copies of DK#1 were present in R. citrophilus FL1. It is not likely that DK#1 represents a citrus parasitism gene because it was amplified from some burrowing nematode isolates that did not parasitize citrus and because DK#1 contains no open reading frames. Inability to reliably test individual nematodes for their ability to parasitize citrus was a constraint to obtaining F2 data required for definitive genetic characterization of citrus parasitism in burrowing nematodes, and alternate approaches will be required. Although the physical relationship of DK#1 and the citrus parasitism locus remains undefined, results of controlled mating studies using these parameters as genetic markers enabled us to identify hybrid F₁ progeny. Therefore, R. similis and R. citrophilus are not sibling species since gene flow between the two does not appear to be restricted via geographic isolation (sympatric in Florida) or by genetics.     

Cell stress and implications of the heat-shock response in skin

Heat-shock proteins (HSPs), or so-called stress proteins may play an important role in cutaneous pathophysiology. HSPs are a group of highly conserved molecules that are expressed by all cells when subjected to heat or other forms of physical or chemical stress. The physiological roles of stress proteins are varied and are important in stress and nonstress conditions. They bind to other cellular proteins and participate in protein folding pathways during stress and also during the synthesis of new polypeptides. HSPs are also essential for thermotolerance and for prevention and repair of damage caused in DNA after ultraviolet exposure. Although HSPs are expressed in the skin in both epidermis and dermis, HSPs may influence many other cellular processes in the inflammatory and immune skin response. Many authors have speculated on a link between HSPs and human skin disease characterized by inflammation and proliferation.Abbreviations HSP heat-shock protein - IL-1 interleukin-1     

Philopatry in the alpine grasshopper, Podisma pedestris: a novel experimental and analytical method

Abstract.

• 1 Local dispersal and philopatric behaviour of the alpine grasshopper, Podisma pedestris, were studied at two sites in the Alpes Maritimes using a new mark—release—resight technique featuring marking in situ, and multiple resighting without handling. The time-consuming nature of the design was justified by the quantity and quality of the data yielded.
• 2 Philopatry is defined independently of any concept of home range as a phenomenon by which movements over longer periods are less than would be expected by extrapolation of measures over shorter periods.
• 3 By this definition, the grasshoppers are shown to exhibit philopatry. Nymphs comprise two heterogenous classes of those which move little and those which move considerable distances.
• 4 Daily dispersal estimates were obtained from movements of 1055 nymphs and adults at one site, and of 593 adults at another.
• 5 Differences are demonstrated in daily dispersal distances for age, sex and site combinations.
• 6 Some differences in microhabitat preference were observed.
• 7 The findings are compared with previous measurements of dispersal in this species, and the merits of the new technique are discussed.

     

RAD51 homologues in Xenopus laevis: two distinct genes are highly expressed in ovary and testis

The RAD51 gene is a eukaryotic counterpart of the Escherichia coli recA gene which is involved in genetic recombination. Two distinct Xenopus laevis RAD51 cDNA clones (XRAD51.1 and XRAD51.2) were isolated from an oocyte cDNA library using the human RAD51 cDNA (HsRAD51) as a probe. Sequence analysis revealed that 98.2% of the amino-acid residues were identical between XRAD51.1 and XRAD51.2, and that both were 95% identical to HsRAD51. Both of the XRAD51 genes were expressed at a higher level in ovary and testis than in other somatic tissues, suggesting their involvement in meiotic recombination. The expression of XRAD51.1 was about eightfold in excess of that of XRAD51.2 in all of the tissues examined. Analysis of the rates of synonymous substitution in the coding sequences of the two XRAD51 suggests that these two genes diverged about 50 million years ago. The structural similarities of the XRAD51 proteins to RecA in E. coli and Rad51 in yeasts or vertebrates are discussed.     

高邮杂交鲫（鲫♀×白鲫）及其亲本血清生化组成的比较研究

本文对高邮杂交鲫（鲫♀×白鲫♂）及其亲本血清生化组成的定量分析。结果表明,在测定的血清总蛋白、白蛋白、胆固醇、尿素氮、葡萄糖、乳酸脱氢酶、ａ－羟丁酸脱氢酶、ａ－淀粉酶和谷草转氨酶等九个生化指标中,大部分指标高邮杂交鲫与母本无显著差异,而与父本则有极显著差异。这从代谢方面论证了高邮杂交鲫是一个偏向于母本的杂交种。     

Properties of thermolysin immobilized in polymer matrix by radiation polymerization

Thermolysin (Bacillus thermoproteolyticus neutral proteinase, EC 3.4.24.4) has been immobilized by radiation polymerization of hydrophilic and hydrophobic monomers, and its properties, such as enzyme activity, thermal stability and durability, have been studied. The activity of the immobilized enzymes increased with an increase in the hydrophilicity of the polymer matrix and with a decrease in monomer concentration. Immobilization with hydrophilic monomers increased the thermal stability of the enzymes, but the thermal stability of the enzymes immobilized with hydrophobic monomers was comparable with that of native enzymes. The durability of the immobilized enzymes was examined by continuous hydrolysis of casein; enzymes immobilized with a high concentration (90%) of hydrophilic monomers appeared to be stabilized and could be used for long times.     

Fluorescence studies using synchrotron radiation on normal and differentiated cells labeled with parinaric acids

Changes in membrane properties during the differentiation process in K562 cells have been investigated. A decrease of lectin-induced agglutination has been detected. The agglutination assay revealed to be an early and sensitive test to monitor the induced differentiation of the K562 cells. Naturally occurring fluorescent fatty acids (cis- and trans-parinaric acids) and the recently developed multifrequency phase and modulation technique were used to study cell membrane properties. Changes in fluorescence lifetime and polarization are clearly associated with cell differentiation, suggesting the involvement of the cellular plasma membrane in the differentiation process.     

Hybrid recombinant human leukocyte interferon inhibits differentiation in murine B-16 melanoma cells

We have investigated the effects of recombinant human leukocyte interferons (IFN-alpha A and IFN-alpha D) and various hybrid recombinant human leukocyte interferons on differentiation in B-16 mouse melanoma cells. Inhibition of both spontaneous and melanocyte hormone stimulated differentiation was observed with one hybrid construct, IFN-alpha A/D (Bgl) consisting of amino acids 1 to 62 from IFN-alpha A and amino acids 64 to 166 from IFN-alpha D. In contrast, the parental human interferons, IFN-alpha A and IFN-alpha D, when used alone or in combination, as well as other hybrid human leukocyte interferons, did not cause significant inhibition of melanogenesis in B-16 mouse cells. The tumor promoter 12-O-tetradecanoylphorbol-13-acetate (TPA) also inhibited B-16 differentiation and the combination of TPA with IFN-alpha A/D (Bgl) or mouse L-cell interferon was synergistic in delaying melanogenesis. These studies indicate that the IFN-alpha A/D (Bgl) hybrid that exhibits antiviral activity on mouse cells can also inhibit differentiation of murine cells.     

Inhibition of parathormone-stimulated bone resorption by type I interferon

The effect of Type I interferon on bone resorption was studied by measuring its effect on parathormone-stimulated calcium release from neonatal murine calvaria in vitro. A pure human recombinant leukocyte interferon hybrid of the A and D subtypes was used, which has high antiviral activity on mouse cells. Calcium release was inhibited in a dose dependent fashion with 50% inhibition at about 10(-10) M or 600 U/ml, and the inhibition was reversible. The presence of interferon was required before or during the activation phase of the resorptive response, when the formation of osteoclasts from precursor cells would occur. When added to actively resorbing bone it had no effect. The data suggest that Type I interferon can inhibit the parathormone-regulated development of active osteoclasts, possibly by inhibiting osteoclast precursor differentiation.     

Radiation inactivation of membrane proteins: Molecular weight estimates in situ and after Triton X-100 solubilization

Target size analysis by radiation inactivation is widely used for molecular weight determination of membrane enzymes and receptors in situ without the need for prior solubilization or purification. However, since most molecular weight data available in the literature on membrane proteins involve the use of detergents for solubilization, the target sizes of membrane proteins in situ and after solubilization by detergent treatment have been compared. Using data from the literature and personal results, three different types of behavior of membrane proteins in presence of detergents were found: (i) uncoupling of subunits (electric eel acetylcholinesterase, placental steroid sulfatase, and human nonspecific β-glucosidase); (ii) coupling of protein molecules (mouse liver neuraminidase, and rat liver insulin receptor regulatory component); and (iii) no major change in quaternary structure (rat liver insulin receptor, kidney γ-glutamyltransferase, asialoglycoprotein receptor, insulin degrading enzyme, and human leucocyte neuraminidase). For all these proteins, there is a statistically significant increase in target size of about 24% over the value obtained in situ without detergent. A relatively large body of literature data involving a variety of membrane proteins, membrane types, and irradiation conditions (electron accelerators or ⁶⁰Co sources, and proteins irradiated in lyophilized form or frozen solution) was examined, and it was concluded that target sizes of membrane proteins, irradiated in the presence of Triton X-100, should be diminished by a factor of about 24% to obtain the molecular weight value.