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Biomedical subjects

H Guzman

Publications and source records attributed to H Guzman.

9 recordsLinked to original sources
PubMed1992

Trans-beta-farnesene as a feeding stimulant for the sand fly Lutzomyia longipalpis (Diptera: Psychodidae).

The aphid alarm pheromone, trans-beta-farnesene (TBF), was found to stimulate feeding in both male and female Lutzomyia longipalpis Lutz & Neiva. Four other structurally related compounds (farnesol; 808 farnesene; trans, trans-farnesyl acetate; farnesyl methyl ether) were slightly less stimulating to these insects. The effect of TBF varied with sand fly age and the concentration of the chemical used. In contrast, TBF did not stimulate feeding in either sex of four other sand fly species (L. shannoni Dyar, Phlebotomus papatasi (Scopoli), P. argentipes Annandale & Brunetti, P. perniciosus Newstead). TBF might be useful in enhancing L. longipalpis field collections or in developing a poison bait for the control of this species.

Animals↗
PubMed1992

Ultrastructural aspects of replication of the New Jersey serotype of vesicular stomatitis virus in a suspected sand fly vector, Lutzomyia shannoni (Diptera: Psychodidae).

Transmission electron microscopy was used to examine replication of the New Jersey serotype of vesicular stomatitis virus (VSNJ) (Rhabdoviridae: Vesiculovirus) in Lutzomyia shannoni (Diptera: Psychodidae), a recently implicated sand fly vector. Following ingestion of an infectious blood meal, female sand flies were fixed and examined at approximately 12-hr intervals for six days. The New Jersey serotype of vesicular stomatitis virus was first detected in the abdominal midgut after 34 hr of incubation. Virus next appeared in fat body and the thoracic midgut at 48 hr, while salivary glands first contained visible virus in apical cavities 5-6 days after infection. Flight muscles and nervous tissue occasionally contained small numbers of VSNJ virions, while virus was never detected in the ovaries or malphigian tubules. The midgut and fat body appeared to be major sites of VSNJ virus replication. In all tissues examined, virus matured primarily by budding from the plasma membrane. Virions were occasionally observed within vacuoles, along with nucleocapsids. In the midgut, budding occurred exclusively from the basolateral plasma membrane, while maturation in salivary gland cells involved apical budding. Accumulation of virions adjacent to basal laminae surrounding several tissues suggested that this structure physically impedes virus dissemination within the sandfly. The paucity of virus budding 120-144 hr after infection suggested that the VSNJ virus infection was modulated in Lu. shannoni.

Animals↗
PubMed1992

Simulation of arbovirus overwintering: survival of Toscana virus (Bunyaviridae:Phlebovirus) in its natural sand fly vector Phlebotomus perniciosus.

A series of experiments were done to study the effect of simulated summer and winter temperatures on the development of Phlebotomus perniciosus (Diptera:Psychodidae) and on the survival of Toscana virus in transovarially infected insects. Sand flies maintained at 28 degrees C developed relatively fast, with adults emerging from 40 to 55 days after initial oviposition. Similar results were obtained with insects reared at 25 degrees C. In contrast, sand flies maintained at 15 degrees C developed slowly up to the fourth larval instar; at that point, further development ceased and the insects entered diapause. Diapause could be terminated by increasing the ambient temperature to 25 degrees C. The ambient temperatures at which the immature forms were reared (15 degrees C, 25 degrees C, and 28 degrees C) had no effect on the subsequent F1 adult filial infection rates with Toscana virus (49.1%, 47.5%, and 46.5%, respectively). The results of these experiments provide a model of how Toscana virus survives the winter in endemic areas by maintenance in diapausing P. perniciosus larvae. In another experiment, venereal transmission of Toscana virus was shown from transovarially infected males to non-infected virgin females. This is the first demonstration of sexual transmission of a phlebovirus by sand flies. If venereal transmission occurs in nature, it would provide an alternative method of virus amplification in the vector population, in the absence of viremic vertebrates.

Animals↗
PubMed1991

Effect of ivermectin on the ovarian development of Aedes aegypti (Diptera: Culicidae).

The effect of ivermectin (0.1 microgram/ml) on blood digestion, ovarian development, and ovipositional attributes of Aedes aegypti was studied using standard morphological and histological techniques. Uncoordinated movements and paralysis were observed in most ivermectin-treated females within 1 h after ingestion of blood containing the chemical. Eight days after the blood meal, 23.5% of the treated females had died, whereas no mortality occurred in controls. Formation of the peritrophic membrane and digestion of the blood meal were delayed in the surviving treated mosquitoes. The most striking effect of ivermectin on Ae. aegypti at this dosage was on ovarian development. Changes observed among ivermectin-treated mosquitoes included: blood digestion without development of ovarian follicles; degeneration of primary follicles and formation of ovarian dilatations within 24 h after ingestion of the chemical; significant reduction in the rate of vitellogenesis and follicle development; decreased egg production; reduced egg hatching; abnormal egg size and shape; and increased percentages of unhatched embryonated and sterile eggs. Although the precise action of ivermectin on Ae. aegypti is unknown, our studies indicate that the chemical directly or indirectly affects at least three major organ systems (nervous, digestive, and reproductive).

Aedes↗
PubMed1991

Characterization of Leishmania colombiensis sp. n (Kinetoplastida: Trypanosomatidae), a new parasite infecting humans, animals, and phlebotomine sand flies in Colombia and Panama.

Characterization of Leishmania colombiensis sp.n. is presented, which on the basis of biological and molecular criteria, appears to be a new member of the L. braziliensis complex. A total of nine isolates of the new parasite were made in Colombia and Panama between 1980 and 1986: two from human cases of cutaneous leishmaniasis, six from phlebotomine sand flies, and one from a sloth. Although most closely related to L. lainsoni, L. colombiensis sp.n. is clearly distinguishable from other members of the genus by its reactivity with monoclonal antibodies, isoenzyme electrophoresis, and restriction endonuclease fragment patterns of kinetoplast DNA (k-DNA).

Adult↗
PubMed1990

Mortality and infertility in adult mosquitoes after the ingestion of blood containing ivermectin.

Mosquitoes of 3 species (Aedes aegypti, Ae. albopictus, and Culex quinquefasciatus) were fed on human blood containing various concentrations of ivermectin. Three effects (death, decreased egg production, and reduced egg hatching) were observed in the insects, depending upon the concentration of ivermectin ingested. The LD50 of ivermectin in human blood for the 3 mosquito species was estimated to be 126, 208, and 698 ng/ml, respectively. Mosquitoes dying after ingestion of ivermectin developed signs of acute toxicity including paralysis, lethargy, incoordination, and difficulty in movement. Death usually occurred within 48-72 hr. With sublethal blood concentrations of the chemical, mosquitoes survived, but there was a marked reduction in both the number and viability of their eggs. This infertility was only temporary, however, as subsequent refeeding of the insects on uncontaminated blood resulted in the production of normal numbers of fertile eggs. Blood levels of ivermectin which made 50% of the eggs infertile in Ae. aegypti and Ae. albopictus were calculated 3.4 and 4.3 ng/ml, respectively. These latter concentrations of the chemical are within the range found in blood of humans and domestic animals receiving ivermectin for treatment of parasitic infections. This finding suggests that the widespread use of ivermectin in veterinary and human medicine may have an unrecognized effect on mosquito populations.

Aedes↗
PubMed1990

[Results of treatment of porphyria cutanea tarda with bloodletting and chloroquine].

In 59 patients showing clear clinical and biochemical signs of porphyria cutanea tarda (PCT), we tested 3 different modes of therapy: 20 patients received combined treatment with repeated bleeding and chloroquine, 24 patients were exclusively treated with oral chloroquine in low doses, and 15 patients underwent repeated phlebotomy only. On an average, the time necessary for remission amounted to 3.5, 10.2, and 12.5 months, respectively. So the combined therapy proved the quickest. In patients with the acquired form of PCT, the pattern of urinary porphyrin normalized; those suffering from hereditary PCT retained the typically high uro/copro ratio. The values of the plasma porphyrin count and the plasma porphyrin index (PPI), which had been greatly enhanced before, went down to normal after therapy.

Administration, Oral↗
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[Resin combinations].

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Acrylic Resins↗