Abundance of Lutzomyia ovallesi but not Lu. gomezi (Diptera: Psychodidae) correlated with cutaneous leishmaniasis incidence in north-central Venezuela

In north-central Venezuela Lutzomyia gomezi and Lu. ovallesi are the main endophilic/anthropophilic species of phlebotomine sandflies implicated as vectors of cutaneous leishmaniasis (CL). Lutzomyia ovallesi has been found infected with Leishmania braziliensis (1.2%) and less often with Le. mexicana (0.07%), while Le. braziliensis infections have also been found in Lu. gomezi (0.47%). We investigated population densities of these sandflies using two sampling methods with four series of collections between January 1991 and March 1995 at El Ingenio, Miranda State. All-night outdoor collections from a Shannon trap were correlated with indoor collections from CDC light–traps by linear regression, which proved to be statistically significant for both species. Estimated numbers of female sandflies per house per night were found to be proportional to monthly precipitation (i.e. rainfall), with a lag time of seven months for Lu. ovallesi and of six months for Lu. gomezi . Predominance of Lu. ovallesi over Lu. gomezi ( c. 10 :1 ) was observed throughout the year, with the number of infected females estimated as 0.043 ± 0.047 Lu. ovallesi and 0.0085 ± 0.0124 Lu. gomezi per CDC trap per house per night (ratio ∼ 5:1). The mean rate of new CL cases per house per year and sandfly abundance were correlated by linear regression, showing a statistically significant relationship for Lu. ovallesi but not for Lu. gomezi . The negative intercept indicated that, on average, the CDC trap density exceeds 800 Lu. ovallesi females/house/year before new CL cases occur at El Ingenio.     

Proline Accumulation as a Symptom of Drought Stress in Maize: A Tissue Differentiation Requirement

Ibarra-Caballero, J., Villanueva-Verduzco, C., Molina-Galan,J. and Sanchez-de-Jimenez, E. 1988. Proline accumulation asa symptom of drought stress in maize: a tissue differentiationrequirement.—J. exp. Bot. 39: 889–897. Seedlings and callus tissue of maize (Zea mays L.) were testedfor proline accumulation under drought stress. A variety froma tropical humid region, a semi-desertic variety and its improvedpopulation selected for drought stress resistance, were usedfor this study. Proline accumulation was found in green leaves of maize seedlingsunder drought stress; no correlation was found between prolineaccumulation in leaves and the variety or population tested.White tissue, callus and leaves of etiolated seedlings did notshow this response to drought stress, nor did green callus ordetached leaves (green or etiolated), even when stress causeda loss of water from leaves similar to that observed when wholeseedlings were drought-stressed. Addition of abscisic acid togreen or white tissue did not result in proline accumulation.The above data indicate that proline accumulation caused bydrought stress does not seem to be an indication of droughtstress resistance, but rather a symptom of it. For this accumulationto take place it seems that fully organized chloroplasts arerequired as well as the systemic development of the plant. Key words: Proline, maize, drought-stress     

Evolutionary conservation of the chromosomal configuration and regulation of amylase genes among eight species of the Drosophila melanogaster species subgroup

Nuclear DNA was extracted from each of the eight species comprising the Drosophila melanogaster species subgroup. Southern hybridization of this DNA by using a molecular probe specific for the alpha-amylase coding region showed that the duplicated structure of the amylase locus, first found in D. melanogaster, is conserved among all species of the melanogaster subgroup. Evidence is also presented for the concerted evolution of the duplicated genes within each species. In addition, it is shown that the glucose repression of amylase gene expression, which has been extensively studied in D. melanogaster, is not confined to this species but occurs in all eight members of the species subgroup. Thus, both the duplicated gene structure and the glucose repression of Drosophila amylase gene activity are stable over extended periods of evolutionary time.      

Cochlodinium heterolobatum n.sp.: Structure and Some Cytophysiological Aspects*

SYNOPSIS. Structure and morphogenesis, and cytochemical data on Cochlodinium heterolobatum, a new species of unarmored dinoflagellate, were derived from living and fixed material from culture. C. heterolobatum is characterized by the torsion of the girdle which descends in a left-hand spiral 1.8 turns; the sulcus having a torsion of 0.8 turn; a sulcus loop in the epicone; a tongue-shaped lobe in the right hypocone; nucleus in the epicone; and a stigma in the left epicone. Trichocysts and behavior of the nucleus during typical and atypical divisions are described in cells from cultures of different ages. A small form with the specific characters was found. Intracellular bacteria were seen and their growth followed in individuals from cultures of different ages. A possible relationship between those bacteria and the accumulation of metabolites inside old cells is discussed.     

Growth of Phytomonas serpens in a Defined Medium; Nutritional Requirements

ABSTRACT. Three strains of Phytomonas serpens two from tomatoes, Lycopersicon esculentum one from the insect Phtia picta (Hemiptera, Coreidae), were cultivated in a chemically defined medium developed from a defined medium for cultivating insect flagellates. Besides organic growth factors required by other insect trypanosomatids this flagellate requires, serine and inositol. Glutamine stimulates growth, and, surprisingly, does not require heme.     

Membrane Skeletal Proteins and Their Integral Membrane Protein Anchors are Targets for Tyrosine and Threonine Kinases in Euglena

ABSTRACT. Proteins of the membrane skeleton of Euglena gracilis were extensively phosphorylated in vivo and in vitro after incubation with [³²P]-orthophosphate or γ-[³²P] ATP. Endogenous protein threonine/serine activity phosphorylated the major membrane skeletal proteins (articulins) and the putative integral membrane protein (IP39) anchor for articulins. The latter was also the major target for endogenous protein tyrosine kinase activity. A cytoplasmic domain of IP39 was specifically phosphorylated, and removal of this domain with papain eliminated the radiolabeled phosphoamino acids and eliminated or radically shifted the PI of the multiple isoforms of IP39. In gel kinase assays IP39 autophosphorylated and a 25 kDa protein which does not autophosphorylate was identified as a threonine/serine (casein) kinase. Plasma membranes from the membrane skeletal protein complex contained threonine/serine (casein) kinase activity, and cross-linking experiments suggested that IP39 was the likely source for this membrane activity. pH optima, cation requirements and heparin sensitivity of the detergent solubilized membrane activity were determined. Together these results suggest that protein kinases may be important modulators of protein assembly and function of the membrane skeleton of these protistan cells.     

Sequence variation in the outer-surface-protein genes of Borrelia burgdorferi

Borrelia burgdorferi is a spirochete pathogen transmitted among warm- blooded hosts by ixodid ticks. Frequency-dependent selection for variant outer-surface proteins might be expected to arise in this species, since rare variants are more likely to avoid immune surveillance in previously infected hosts. We sequenced the OspA and OspB genes of nine North American strains and compared them with nine strains previously described. For each gene, the mean number of synonymous substitutions per synonymous site and the mean number of nonsynonymous substitutions per nonsynonymous site show only a twofold excess of silent mutations. Synonymous rates vary widely along the OspB protein. Some regions show a significant excess of silent substitutions, while divergence in other regions is constrained by biased base composition or selection. The presence, in antigenically important regions of the protein, of significant variation among strains, as well as evidence for recombination among strains, should be considered in attempts to develop vaccines against this disease.