The life cycle ofAmblyomma parvum Aragao, 1908 (Acari: Ixodidae) under laboratory conditions

A colony ofAmblyomma parvum was started with engorged females collected from cattle in the Province of Salta (25°01 S, 63°56 W), Argentina. The progeny of those ticks were fed on rabbits and the non-parasitic stages maintained at 27±1°C, 83–86% RH in darkness. The life cycle (prefeeding period not evaluated) had a mean duration of 99.6 days. The mean time (days) for the different phases of the cycle were as follows: feeding period of females, 8.0; pre-oviposition period, 5.7; oviposition period, 17.5; minimum incubation period of the eggs, 31.8; feeding period of larvae, 3.2; premoult period to nymphs, 10.9; feeding period of nymphs, 4.7; premoult period to adults, 17.8. The oviposition pattern was typical of an ixodid tick, including a linear relationship between weights of engorged females and the number of eggs laid (r=0.8659). The males increased 18% in weight after feeding on hosts (P<0.01). The mean recovery rates of larvae, nymphs and females were 28.2%, 95.3% and 90.7%, respectively. The nymphs moulting to females were heavier (6.8±0.69 mg) than those moulting to males (3.2±0.29 mg) (P<0.01). A comparison of biological values ofA. parvum with American and non-AmericanAmblyomma species is presented.     

Nonuniform size distribution of nascent globin peptides, evidence for pause localization sites, and a cotranslational protein-folding model

Examination of nascent globin peptides accumulatingin vitro during globin synthesis in rabbit reticulocyte lysates was carried out. A view was supported that nonrandom distribution of codons with different usage frequencies in mRNA may determine the messenger's translation kinetics. Regions of reduced translation of - and -globin polypeptide chains were localized, and the cotranslational protein-folding model suggested previously was substantiated. An active conjunction of synthesis and folding of proteins was proposed as one of the main destinations of a translation nonuniformity.     

Pathogenesis of barley leaves by Helminthosporium teres I: Green island formation and the possible involvement of cytokinins

Infection sites/green islands were formed in host leaf tissue infected with drops of H. teres. They exhibited higher cytokinin-like activity, sugar and starch than their surrounding tissue and tissue under water drops. The cytokinin-like activity at the infection sites increased from 24 to 72 h of incubation. However, the cytokinin-like activity of the tissue surrounding the infection drops and the tissue under water drops fell from 24 to 72 h incubation. The culture filtrate extracts of the fungus also produced cytokinin-like activity which increased from 1 to 10 days incubation. Application of this culture filtrate extract evoked green island formation. Application of kinetin to host leaves duplicated the green island effect. Thin-layer chromatographic fractions of the tissue extracts and the culture filtrate extracts revealed that a major portion of cytokinin-like activity corresponded to zeatin and zeatin riboside. The presence of zeatin and zeatin riboside (both in tissue and culture filtrate extracts) was confirmed by high performance liquid chromatography. Increases in the amounts of cytokinin-like substances, particularly zeatin and zeatin riboside, attributed to pathogen influence are suggested to be involved in infection and pathogenicity of H. teres.     

The relative importance of local phase and local amplitude in patchwise image reconstruction

Natural images were subjected to patchwise Fourier analysis, and the local amplitude and phase spectra were swapped between different images. When the patches were large relative to the image size, the appearance of the reconstructed image was similar to that of the image from which the phase information had been derived, in agreement with previous reports of phase-dominance in the global Fourier Transform. However, when the patch size was made sufficiently small, the appearance of reconstructed images was dominated by amplitude rather than phase. This was not simply due to the DC component of the amplitude spectrum. Prior low-pass filtering of the images enhanced the dominance of amplitude information in the patchwise transform. We conclude that patchwise-reconstructed images contain two quite distinct kinds of information for the human observer. The first is the positional information (local sign) of the patches themselves; the second is the textural information within patches, which is dominated by amplitude rather than phase. The reason why the global Fourier Transform is dominated by phase is that in the absence of any other information about local sign, phase is necessary to reconstruct localised features such as edges.     

Wide distribution of a 36-megadalton plasmid among clinical and environmental Spanish isolates ofLegionella pneumophila serogroup 1

With the eventual goal of characterizingLegionella pneumophila serogroup 1 plasmids at the molecular level, we have analyzed the plasmid contents of 78 clinical and environmental Spanish isolates. After selection of a suitable alkaline lysis method, we detected plasmids with approximate molecular weights of 25, 36, 40, 61, 80, 85, 90, and 95 megadalton (MDal). Several factors (i.e., wide temporal and geographic distribution, high frequency in both clinical and environmental isolates, and apparent high copy number after subculturing) make the 36 MDal type IA plasmid an appropriate plasmid for further molecular studies.     

Protein phosphorylation in the facultative chemolithotrophThiobacillus novellus

The phosphorylation of at least five proteins with M_r of about 160,000; 93,000; 85,000; 45,000; and 29,000 respectively was demonstrated in crude extracts from the facultative chemolithotrophThiobacillus novellus. The incorporation of [-³²P]phosphate from ATP into these proteins was dependent on the presence of magnesium ion. The phosphorylation reactions were found to be reversible and required 12.5 mM NaF for maximal activity, indicating the action of phosphatases. In addition, 3,5-cAMP had little effect on protein kinase activity, whereas Ca²⁺ alone was weakly stimulatory. This activation was enhanced by the addition of 3,5-cAMP. Ca²⁺ with calmodulin had a strong stimulatory effect on phosphate incorporation into the proteins. A highly purified preparation containing only the 160, 93, and 85 kDa proteins phosphorylated histone, whereas the uptake of³²P by the three proteins was inhibited. Rabbit muscle phosphorylase b prevented incorporation of radiolabel only into the 160 and 93 kDa proteins.     

Regulation of assimilatory nitrate reductase in the cyanobacteriumAnabaena doliolum

The assimilatory nitrate reductase (NR) from the cyanobacteriumAnabaena doliolum was membrane bound and solubilized by sonication. The Km value of the enzyme was 870 µM for nitrate with dithionite-reduced methyl viologen (MV) as electron donor. The pH optimum was 10.5 in the MV assay. Nitrate acted as an inducer and ammonium as repressor of the enzyme synthesis. In the presence ofl-methionine-d,l-sulfoximine (MSX) or azaserine, inhibitors of the glutamine synthetase-glutamate synthase (GS-GOGAT) pathway, ammonium did not exhibit any inhibitory effect on the enzyme. The photosynthetic nature of NR was shown with PS II inhibitor, 3-(3,4-dichlorophenyl)-1,1-dimethylurea (DCMU). This enzyme fromA. doliolum has been shown to be a light-driven process, requiring de novo protein synthesis. It was inhibited by chlorate, the structural analog of nitrate;p-chloromercuribenzoate, a thiol reagent; sodium tungstate; and certain cations.     

Purification and characterization of an extracellular chitobiase fromTrichoderma harzianum

Chitobiase (EC 3.2.1.29), from the culture filtrate ofTrichoderma harzianum, was purified in sequential steps by ammonium sulfate precipitation, ion exchange chromatography, and gel filtration. The physical and biochemical properties of the enzyme have been determined. The native enzyme has a molecular weight of 118 kDa when determined by gel filtration, and 64 kDa by SDS-PAGE. The enzyme catalyzed the hydrolysis of N,N-diacetylchitobiose andp-nitrophenyl--N-acetyl glucosamine with apparent Km of 575 µM and 235 µM, respectively. The pH optimum for the enzyme was pH 5.5, and maximum activity was obtained at 50°C. Glucosamine and N-acetylglyucosamine strongly inhibited the enzyme.     

Age at menopause of Tamang women tea-labourers of Jalpaiguri district,West Bengal,India

The Tamang women tea-labouren of Jalpaiguri district show no significant difference in age at menopause among their three «migration status» groups, viz., MO, M1 and M2+. The mean age at menopause is 47.3±4.26 and the median age is 47.68 years. A significant difference occurs between the observed mean age at menopause and 45 years, which is generally taken to be the menopausal age by convention. These Tamang women seem to be similar to other hill women in respect of age at menopause.