Search PubMed⌕ Search

Biomedical subjects

D R Roberts

Publications and source records attributed to D R Roberts.

At least 73 records · Page 4Linked to original sources
PubMed1991

Behavioral response of Anopheles darlingi to DDT-sprayed house walls in Amazonia.

The behavioral response of Anopheles darlingi females to spraying of house walls with DDT was studied along the Ituxi River in Amazonas, Brazil, using a house sprayed with 2 g DDT per square meter of wall surface and an untreated house serving as a control. It was found that hardly any An. darlingi females entered, exited, or took blood meals inside the treated house after it was sprayed with DDT, and that specimens marked and released inside the house tended to depart immediately. This behavior appears to constitute true repellency rather than contact irritability. Since the typical house in the vicinity of the study site had only two walls, the persistence of malaria in the local area was probably due to home construction practices.

Animals↗
PubMed1991

Malaria transmission potential by Anopheles mosquitoes of Dajabon, Dominican Republic.

A field and laboratory study was conducted to determine some of the parameters relevant to malaria transmission by Anopheles mosquitoes in Dajabon Province, Dominican Republic. Although all 4 species occurring in the area, i.e., An. albimanus, An. crucians, An. grabhamii and An. vestitipennis, were included in the investigations, most of the work focused on the first and last named species because of their abundance. Gonotrophic cycles were determined to be 2.6 and 3.2 days for An. albimanus and An. vestitipennis, respectively. Mean parity rates for the 2 species were 37.3 and 20.7%, respectively, in outdoor samples. The human blood index, as determined by ELISA, was 0.08 for An. albimanus and 0.12 for An. vestitipennis. Only An. albimanus was confirmed positive for Plasmodium falciparum circumsporozoite protein, using ELISA. The vectorial capacity of An. albimanus was determined to be 0.019 and that of An. vestitipennis 0.005.

Animals↗
PubMed1991

[Response of Anopheles darlingi to spraying with DDT in Amazonas, Brazil].

To investigate the effectiveness of the malaria control program, the behavior of Anopheles darlingi females was studied following spraying of DDT on the walls of house-holds along the Ituxi river in the state of Amazonas, Brazil. The study was carried out on two four-walled dwellings, one of which was sprayed with 2 g of DDT per m2 of wall. Three methods were used to study the mosquitoes' activity before and immediately after the spraying, as well as at 2 and 12 months post-spraying. These methods were: capturing the mosquitoes in the act of resting on human baits, capturing them in traps as they entered or exited the dwellings, and liberating females tagged with fluorescent powder inside the house and then following them with ultraviolet light. Immediately after the spraying, the females stopped going in and out of the house and ceased biting inside the sprayed dwelling. In addition, the tagged females that had been set loose inside the house fled almost immediately. These phenomena were not observed in the unsprayed dwelling. The reaction of the A. darlingi to spraying is considered to indicate true repellency and not simply irritation from contact. Since the dwellings in the locality have only 2.2 walls on average, the persistence of malaria in the territory could be due to the type of household construction.

Animals↗
PubMed1991

Ventilation with isoflurane in the Triservice anaesthetic apparatus: a comparison with halothane and trichlorethylene.

Recovery from anaesthesia using the Triservice anaesthetic apparatus with either isoflurane alone or halothane and trichlorethylene, was assessed by measurement of reaction time. There was no statistically significant improvement in recovery between patients who received low concentrations of isoflurane and those who received halothane and trichlorethylene. The mean profiles of systolic pressure and heart rate were significantly greater in the isoflurane group (P less than 0.05) than in the halothane/trichlorethylene group. Cardiovascular stability was maintained into the recovery period. The benefits of low concentrations of isoflurane as sole agent in the Triservice anaesthetic apparatus and their extrapolation to a shocked casualty in a military setting are discussed.

Adult↗
PubMed1990

Gamma camera image acquisition, display, and processing with the personal microcomputer.

The authors evaluated the potential of a microcomputer for direct acquisition, display, and processing of gamma camera images. Boards for analog-to-digital conversion and image zooming were designed, constructed, and interfaced to the Macintosh II (Apple Computer, Cupertino, Calif). Software was written for processing of single, gated, and time series images. The system was connected to gamma cameras, and its performance was compared with that of dedicated nuclear medicine computers. Data could be acquired from gamma cameras at rates exceeding 200,000 counts per second, with spatial resolution exceeding intrinsic camera resolution. Clinical analysis could be rapidly performed. This system performed better than most dedicated nuclear medicine computers with respect to speed of data acquisition and spatial resolution of images while maintaining full compatibility with the standard image display, hard-copy, and networking formats. It could replace such dedicated systems in the near future as software is refined.

Gamma Cameras↗
PubMed1990

Occupational exposure of workers to 1,3-butadiene.

Researchers from the National Institute for Occupational Safety and Health (NIOSH) conducted an extent-of-exposure study of the 1,3-butadiene monomer, polymer, and end-user industries to determine the size of the exposed workforce, evaluate control technologies and personal protective equipment programs, and assess occupational exposure to 1,3-butadiene. A new analytical method was developed for 1,3-butadiene that increased the sensitivity and selectivity of the previous NIOSH method. The new method is sensitive to 0.2 microgram per 1,3-butadiene sample. Walk-through surveys were conducted in 11 monomer, 17 polymer, and 2 end-user plants. In-depth industrial hygiene surveys were conducted at 4 monomer, 5 polymer, and 2 end-user plants. Airborne exposure concentrations of 1,3-butadiene were determined using personal sampling for each job category. A total of 692 full shift and short-term personnel and 259 area air samples were examined for the presence of 1,3-butadiene. Sample results indicated that all worker exposures were well below the current OSHA PEL of 1000 ppm. Exposures ranged from less than 0.006 ppm to 374 ppm. The average exposure for all samples was less than 2 ppm. The present American Conference of Governmental Industrial Hygienists (ACGIH) threshold limit value for 1,3-butadiene is 10 ppm. To reduce the potential for occupational exposure, it is recommended that quality control sampling be conducted using a closed loop system. Also all process pumps should be retrofitted with dual mechanical seals, magnetic gauges should be used in loading and unloading rail cars, and engineering controls should be designed for safely voiding quality control cylinders.

Air Pollutants, Occupational↗
PubMed1990

Limnological and botanical characterization of larval habitats for two primary malarial vectors, Anopheles albimanus and Anopheles pseudopunctipennis, in coastal areas of Chiapas State, Mexico.

Field surveys of mosquito breeding sites on the Pacific coastal plain and foothill regions of southern Chiapas, Mexico, were carried out in the dry and wet seasons of 1988. At each site, selected environmental variables were measured or estimated, presence and percent cover of aquatic plants recorded, a water sample collected for subsequent analyses, and 10-30 dips made for mosquito larvae. Logistic regression and discriminant analyses revealed that the occurrence of Anopheles albimanus larvae in both the wet and dry seasons was positively associated with planktonic algae and negatively associated with altitude. In the dry season, An. albimanus larvae were largely restricted to the margins of permanent water bodies and were associated with the presence of floating plants, particularly Eichhornia crassipes. During the wet season An. albimanus larvae were positively associated with emergent plants, particularly seasonally flooded Cyperaceae, and phosphorus (PO4) concentrations, and were negatively associated with abundant filamentous algae, high levels of total suspended solids (TSS) and Salvinia. In the dry season, An. pseudopunctipennis larvae were positively associated with filamentous algae, altitude and the presence of Heteranthera if encountered in a riverine setting, and were negatively associated with water depth. During the wet season, flooding eliminated typical flood plain An. pseudopunctipennis habitats, and larvae were rarely encountered.

Altitude↗
PubMed1990

Prospects for standardized assays in vector biology.

The benefits of technological advances continue to accrue at an ever accelerating rate. In 1987 I presented a brief review of recent advances and applications of biotechnology to the study of arthropods and disease-vector relationships. Since 1987 progress has been made in practically all areas included in that earlier review and I want to give brief mention of just a few significant advances that have appeared in print since that time. An obvious spin-off of modern technology has been the production of continually improved tools to aid in species identification. This is true for the arthropods as well as for pathogenic organisms transmitted by arthropods. Consequently, we can now approach the problems presented by species complexes with an array of techniques, and we find that we are limited only by our access to the necessary reagents, grasp of the technology and funding. Likewise, in studies of arthropod-pathogen relationships, many new tools have been developed for detection of pathogens in the vectors and these tools are applicable to field and laboratory investigations into the many issues of vector competence.

Animals↗
PubMed1990

Host-seeking behavior and seasonal abundance of Culicoides paraensis (Diptera: Ceratopogonidae) in Brazil.

The ecology of Culicoides paraensis was studied with human bait collections at an agricultural research station near Belém and within 2 neighborhoods of Belém, Brazil, from 1977 to 1978. From collections conducted along transects that were centered on a house, we found most dense populations of host-seeking midges within and near the house. Host-seeking activity was least in areas fully exposed to sunlight compared to the levels of activity indoors and in shaded areas outside. Numbers of flies biting under shade trees and within the house increased during intervals of rain; concomitantly the levels of activity decreased in open areas. Seasonal population densities correlated with the pattern of rainfall, with a 2-month lag due to the long maturation time of immature C. paraensis. The effects of temperature and humidity on host-seeking activity are discussed.

Animals↗
PubMed1988

Application of biotechnology in the identification of filarial larva in mosquitoes.

Current methods for detecting and identifying filariae in mosquitoes are laborious and time consuming. With today's technology, we can reasonably expect development of rapid, sensitive and specific assays for detecting and identifying filariae in naturally infected mosquito populations. Progress in developing such assays is reviewed.

Animals↗
PubMed1988

Adaptation of biotechnology methods on the study of arthropods.

Biotechnological advances are rapidly being applied to the study of arthropods and arthropod-born diseases. Improved tools are available for species identification, study of species complexes, detection and identification of pathogens in vectors and detection and characterization of insecticide resistance. These techniques have their basis in hybridoma, DNA probe and biochemical assay technologies. Problem areas in assay development are discussed.

Animals↗
PubMed1987

The house-frequenting, host-seeking and resting behavior of Anopheles darlingi in southeastern Amazonas, Brazil.

Studies on the behavior of Anopheles darlingi were conducted at a site along the Ituxi River, Amazonas, Brazil. Patterns of host-seeking activity inside and outside a single-walled house both presented activity peaks at sunset and sunrise, but biting activity inside a four-walled house peaked after sunset then gradually decreased during the night. Major movements of females into and out of the four-walled house occurred at sunset and sunrise, respectively. Marked engorged and unengorged females released indoors were observed to preferentially rest on the ceiling. These behavior patterns were confirmed by replication and/or with more than one sampling technique or study method. Additional observations on exit sites, spatial distribution of resting females and physiological condition of exiting specimens were recorded.

Animals↗
PubMed1986

Relationships among drought resistance, transpiration rates, and abscisic acid levels in three northern conifers.

Water potentials, transpiration rates and abscisic acid (ABA) levels in shoots of black spruce (Picea mariana (Mill.) BSP), white spruce (Picea glauca (Moench) Voss) and jack pine (Pinus banksiana Lamb.) seedlings were monitored during periods of drought and recovery from drought. Abscisic acid contents of shoots increased during the period of drought as water potentials decreased. The increase in levels of ABA was closely associated with a decrease in rates of transpiration. In the spruces, the levels of ABA peaked and then fell while plant water potentials continued to decrease, whereas in jack pine, the level of ABA rose throughout the drought treatment. After rewatering, the levels of ABA in all three conifers fell concurrent with a rise in transpiration rates. At the end of the three-day recovery period, ABA levels and transpiration rates in the spruces were either at or near control levels, whereas the concentration of ABA in jack pine remained approximately twice the control level, and transpiration was only 60% of the control rate. A compound tentatively identified as phaseic acid followed trends similar to those for ABA.

Journal Article↗