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.     

Spring and summer hosts for Pieris rapae in Southern Spain with special attention to Capparis spinosa

The suitability of different host plants for Pieris rapae L. in the South of the Iberian Peninsula, was studied in relation to host plant phenology, female behaviour, and larval development. Capparis spinosa is the only host plant available during the dry season of the year in the area studied. D. virgata, R. raphanistrum, H. incana and S. alba being suitable spring hosts. Comparative studies on mortality, larval development and larval growth between C. spinosa and the spring hosts revealed no significant differences.

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Résumé L'adéquation de différentes plantes comme hôtes de P. rapae a été examinée en fonction de la phénologie des végétaux, du comportement de la femelle et du développement larvaire dans le sud de la péninsule ibérique. Pendant la saison sèche, C. spinosa est la seule plant convenable dans la zone étudiée. Diplotaxis virgata, Raphanus raphanistrum, Hirschfeldia incana et Sinapis alba sont des hôtes printaniers convenables. La mortalité, le développement et la croissance larvaires ne sont pas différentes sur C. spinosa et sur les hôtes de printemps.

     

Sequential study of the synaptonemal complex in rat (Rattus norvegicus) oocytes by light and electron microscopy

The progression of first meiotic prophase and synaptonemal complex (SC) formation in female rats, Rattus norvegicus S.D., is described through the analysis of the different stages of the first meiotic prophase, and confirms the high synchrony of the process in this species. Leptotene is a stage of very short duration and since pairing of the homologues begins very early, only a leptotene-zygotene stage can be distinguished. The progression of pairing during zygotene is asynchronous. The morphology of the SCs is similar to that described in other species. During diplotene and before desintegration of the lateral elements, desynapsis takes place.In some oocytes a double or even multiple nature of lateral elements was seen. Associations between SCs and nucleoli or nucleolar filaments are frequent. The presence of fragmented SCs can be interpreted as a technical artifact.     

Targets for calcium channel blockers in mammalian skeletal muscle and their respective functions in excitation-contraction coupling

The L-type Ca2+ channel is blocked by 1,4-dihydropyridines (DHP), by phenylalkylamines, by diphenylbutylpiperidines or by benzolactams. We first show with mouse muscle cells in culture that all these L-type Ca2+ channel blockers block contraction. However, voltage-clamp analysis associated to contraction measurements also clearly show that Ca2+ influx through L-type Ca2+ channels is not required for contraction. Therefore, there is a need for a voltage-sensor which would be responsible for the excitation-contraction (E-C) coupling. We are showing here that the voltage-sensor involved in E-C coupling and the L-type Ca2+ channel have a similar pharmacology. Some of the blockers used are more active on the voltage sensor, others on the L-type Ca2+ channel.     

Searching for autolysin functions. Characterization of a pneumococcal mutant deleted in the lytA gene

The first mutant of Streptococcus pneumoniae showing a complete deletion in the lytA gene coding for the N-acetylmuramyl-L-alanine amidase has been isolated and characterized. This amidase was previously the only autolysin detected in this species. This mutant shows a normal growth rate and can be transformed using either chromosomal or plasmid DNA. The most remarkable biological consequences of the absence of the amidase are the formation of small chains (six to eight cells) and the absence of lysis in the stationary phase of growth. In addition, this mutant exhibits a tolerant response against the beta-lactam antibiotics.     

Identification of epsilon-N-mono-, epsilon-N-di-, and epsilon-N-trimethyllysine by high-performance liquid chromatography.

Dansyl derivatives of epsilon-N-mono-, epsilon-N-di-, and epsilon-N-trimethyllysine were resolved from other amino acids in proteins by the use of high-performance liquid chromatography. The system was tested with amino acid standard combinations as well as with acid-hydrolyzed proteins known to contain methylated residues. In all cases the methylated lysines were well resolved.     

Comparative biological activities of ANF (Arg 101-Tyr 126) and the synthetic form of circulating ANF (Ser 99-Tyr 126)

The biological activities of ANF (Arg 101-Tyr 126) and of the circulating form, ANF (Ser 99-Tyr 126), were compared in the following assays: precontracted rabbit aortic strip and chick rectum, rat natriuresis, inhibition of aldosterone secretion and receptor affinity in bovine and rat adrenal zona glomerulosa cells, and receptor affinity in rabbit aorta and rat mesenteric artery cells. The results demonstrate that both peptides share the same biological activities. It is concluded that the addition of two amino acids to the N-terminal of ANF (Arg 101-Tyr 126) does not modify its biological characteristics, validating thus previous research employing this peptide.     

A protein kinase copurified with chick oviduct progesterone receptor

A magnesium-dependent protein kinase activity was copurified with both the molybdate-stabilized 8S form of the chick oviduct progesterone receptor (PR) and its B subunit. In each case, purification was performed by hormonal affinity chromatography followed by ion-exchange chromatography. The Km(app) values of the phosphorylation reaction for [gamma-32P]ATP and calf thymus histones were approximately 1.3 X 10(-5) M and approximately 1.6 X 10(-5) M, respectively, and only phosphorylated serine residues were found in protein substrates, including PR B subunit. Physicochemical parameters of the enzyme [pI approximately 5.3, Stokes radius approximately 7.2 nm, sedimentation coefficient (S20,w) approximately 5.6 S, and Mr approximately 200,000] were compared to those of purified forms of PR (B subunit, pI approximately 5.3, Stokes radius approximately 6.1 nm, and Mr approximately 110,000; 8S form, Stokes radius approximately 7.7 nm and Mr approximately 240,000). The results suggest that most of the protein kinase activity copurified with both oligomeric and monomeric forms of PR belongs to an enzyme distinct from currently known receptor components. Its physiological significance remains unknown.     

Partial characterization and solubilization of receptors for atrial natriuretic factor in rat glomeruli

Specific receptors for atrial natriuretic factor (ANF) have been identified and solubilized in glomeruli from rat kidney. Radioiodinated synthetic ANF (Arg 101-Tyr 126) bound to a single class of high affinity (Kd 27 +/- 24 pM) sites with a density of 390 +/- 230 fmole/mg protein. The binding was time- and temperature-dependent, saturable and reversible. The ANF-receptor complex was not affected by angiotensin II, ACTH or vasopressin. Solubilization with 10 mM 3-[(3-cholamidopropyl)-dimethylammonio]- 1-propane sulfonate (CHAPS) slightly increased the affinity for ANF (Kd 5.0 +/- 3.3 pM) without affecting the density (250 +/- 110 fmole/mg protein). Similar results were found with 1% Triton X-100. ANF-related peptides interact generally in the same way with non-solubilized and solubilized receptors, indicating a fully preserved specificity of the receptors.     

Identification of a biologically active circulating form of rat atrial natriuretic factor

An atrial natriuretic peptide has been isolated from plasma of morphine treated rats by means of glass beads extraction, immunoaffinity chromatography, and reverse phase HPLC. 1.3 micrograms of immunoreactive material was obtained. The biological activity of this material was found comparable to that of ANF (Arg 101 - Tyr 126) on the inhibition of basal aldosterone secretion by rat adrenal zona glomerulosa cells and the displacement curve of iodinated ANF from ANF receptors in a mesenteric artery preparation. Gas phase amino acid sequencing indicated that it is related to ANF (Ser 99 - Tyr 126). These results suggest that the maturation of ANF may require a tryptic-like cleavage after a single Arg residue.