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Biomedical subjects

D L Bull

Publications and source records attributed to D L Bull.

At least 19 recordsLinked to original sources
PubMed2001

Developing public health management training capacity in Nicaragua.

The Cooperative for Assistance and Relief Everywhere (CARE) and Centers for Disease Control and Prevention (CDC) Health Initiative in Nicaragua is distinctive in its focus on developing a cadre of in-country trainers whose aim is to equip frontline public health managers with widely applicable tools and techniques to assist them in identifying and solving implementation problems. Since 1999, 137 trainees--37% more than originally planned--have demonstrated competence by completing and presenting applied management projects. Nineteen professors from the preventive medicine faculty at the Autonomous University of Nicaragua also have been trained. The country office now has a cadre of seasoned trainers who can meet the ongoing management training needs of CARE staff and their counterparts in the Ministry of Health and in other nongovernmental organizations.

Administrative Personnel↗
PubMed1999

Don't ask questions: a psychotherapeutic strategy for treatment of involuntary clients.

This article puts forth the proposition that asking questions is detrimental to successful therapy with unwilling clients. The utility of three commonly used approaches is examined by asking. Does continuing questioning impede therapy with involuntary clients? Are therapists asking questions primarily as a means of coping personally with sullen and silent, or angry and abrasive client behavior? Is it correct to assume that asking "why" is a particularly poor therapy intervention because it brings therapists and clients into a futile search for causation of behaviors? It is recommended that statements, instead of questions, should be introduced as the preferred therapeutic modality with reluctant and unwilling clients.

Adaptation, Psychological↗
PubMed1998

Effects of exposure to cypermethrin on saxitoxin binding in susceptible and pyrethroid-resistant houseflies.

Saxitoxin (STX) binding was measured in susceptible (SBO) and pyrethroid-resistant (KDR) female houseflies having only target site insensitivity as a resistance mechanism. In KDR flies, there was a quantitative decrease in STX binding capacity (Bmax) relative to SBO flies coupled with an increase in binding affinity (Kd). Treatment of SBO flies with sublethal doses of cypermethrin resulted in a large decrease in the number of STX binding sites and an increase in STX binding affinity. In KDR flies, identical treatments had the opposite effects. Treatment of both strains with higher doses of cypermethrin resulted in smaller decreases in Bmax values coupled with decreases in binding affinities. The results show that physiological changes in STX binding occur upon exposure to extremely low doses of cypermethrin. The data suggest that the kdr resistant gene may be expressed as changes in STX binding kinetics and that measurements of STX binding in pyrethroid-treated insects may be a useful approach for studying pyrethroid's mode of action and resistance.

Animals↗
PubMed1996

Operational problems of an iron supplementation programme for pregnant women: an assessment of UNRWA experience.

Assessed is a large-scale iron supplementation programme for the 70 000 pregnant refugee women cared for by the United Nations Relief and Works Agency for Palestine Refugees in the Near East (UNRWA). For this purpose, a retrospective survey of 1267 antenatal records was conducted in health centres located in the West Bank, Gaza, Syrian Arab Republic, Jordan, and Lebanon. The following operational problems were identified: late entry to antenatal care; high drop-out rate from antenatal care; low compliance in follow-up haemoglobin examinations; and misdirected continued testing of women who were not anaemic at registration. Routine iron supplementation of all pregnant women should be considered only in those countries where severe anaemia is prevalent and should always be coupled with additional interventions that are effective at improving iron deficiency anaemia in a given population. In most countries attention should be directed towards changing dietary habits to enhance the availability of local foodstuffs that are rich in iron. One initial haemoglobin test may help in focusing on the relatively few initially anaemic subjects who need further attention. Repeated testing during pregnancy is unwarranted.

Adult↗
PubMed1991

Interactions of carbaryl with susceptible and multiresistant house flies (Diptera: Muscidae).

The in vivo and in vitro fate of [14C]carbaryl was compared in adult male and female house flies from an insecticide-susceptible (S) strain and a resistant (R) strain with multiple resistance to different classes of insecticides. Cuticular penetration of topically applied carbaryl (0.01 microgram/insect) was very rapid and rates were essentially the same among males and females of both strains. Rates of penetration were dramatically reduced as the concentration of applied carbaryl was increased over a range of 0.01-5.0 micrograms/insect. In vivo and in vitro tests demonstrated that the R strain had an enhanced capability for the metabolic degradation of carbaryl. In evaluations of topical toxicity and in vitro metabolic degradation, coadministration of the metabolic synergists piperonyl butoxide (a microsomal oxidase inhibitor) and S,S,S-tributyl phosphorothioate (DEF, an esterase inhibitor) with carbaryl provided conclusive evidence that microsomal oxidases were the major factor in enhanced metabolism and that hydrolytic enzymes had only a minor effect. Studies of the in vitro inhibition of acetylcholinesterase (AChE) activity by carbaryl demonstrated that there was no difference between males and females of a given strain and that the R strain AChE was considerably less sensitive to inhibition. These tests also indicated that homogenates of brains from the R strain contained more than one form of AChE with different sensitivities to the inhibitor. This information and results of toxicity tests with other insecticides suggest that the R strain is not homozygous in its resistance to carbaryl.

Animals↗
PubMed1990

Hydrolysis of sphingomyelin and phosphatidylcholine by midgut homogenates of the stable fly.

Qualitative and quantitative analyses were made to characterize the enzymatic degradation of sphingomyelin and phosphatidylcholine by midgut homogenates of the adult stable fly, Stomoxys calcitrans (L.). The results indicated that sphingomyelin was hydrolyzed by an enzyme with sphingomyelinase-like properties, and that phosphatidylcholine was hydrolyzed by an enzyme with properties similar to phospholipase C. The optimum pH for the sphingomyelinase was 7.6, and the rate of hydrolysis of sphingomyelin at that pH was linear from 1 to 4 nmol of substrate and 5 to 25 micrograms of enzyme preparation. Dialysis of the homogenates against Tris-HCl and imidazole buffers resulted in a decrease of sphingomyelinase activity by 59% and 98%, respectively, and the original activity was not restored with the addition of Ca++, Mg++, or Mn++.

Animals↗
PubMed1990

Plasmid-associated sensitivity of Bacillus thuringiensis to UV light.

Spores and vegetative cells of Bacillus thuringiensis were more sensitive to UV light than were spores or cells of plasmid-cured B. thuringiensis strains or of the closely related Bacillus cereus. Introduction of B. thuringiensis plasmids into B. cereus by cell mating increased the UV sensitivity of the cells and spores. Protoxins encoded by one or more B. thuringiensis plasmids were not involved in spore sensitivity, since a B. thuringiensis strain conditional for protoxin accumulation was equally sensitive at the permissive and nonpermissive temperatures. In addition, introduction of either a cloned protoxin gene, the cloning vector, or another plasmid not containing a protoxin gene into a plasmid-cured strain of B. thuringiensis all increased the UV sensitivity of the spores. Although the variety of small, acid-soluble proteins was the same in the spores of all strains examined, the quantity of dipicolinic acid was about twice as high in the plasmid-containing strains, and this may account for the differences in UV sensitivity of the spores. The cells of some strains harboring only B. thuringiensis plasmids were much more sensitive than cells of any of the other strains, and the differences were much greater than observed with spores.

Bacillus cereus↗
PubMed1989

Pharmacodynamics of malathion and carbaryl in susceptible and multiresistant German cockroaches (Dictyoptera: Blattellidae).

Studies with malathion and carbaryl were done to compare toxicity; absorption, metabolism, internal accumulation, and excretion; and in vivo inhibition of acetylcholinesterase (AChE) after topical applications to adult male susceptible (S, Orlando normal) or multiresistant (R, HRDC) German cockroaches, Blattella germanica (L.). Compared with the S strain, R cockroaches were highly resistant to malathion (about 33-fold) and only moderately resistant or tolerant to carbaryl (about 5-fold). Tests with topically applied 14C-labeled malathion and carbaryl indicated that both compounds penetrated rapidly and radioactive products were readily excreted. Rates of absorption or excretion in S and R strains did not differ significantly. Both insecticides were extensively metabolized; each yielded the same array and similar concentrations of metabolites in insects from either strain. In contrast, metabolic detoxification of malathion and carbaryl was significantly greater in R cockroaches when the insects were treated by injection. Strains did not differ significantly in the in vitro inhibition of brain AChE by either malaoxon or carbaryl. However, dramatic differences were observed between strains in the in vivo inhibition of AChE during a 6-h test period after topical treatment with malathion, and moderate but significant differences occurred between strains in the in vivo inhibition of AChE by carbaryl. These data suggest that the strong resistance to malathion and moderate resistance or tolerance to carbaryl in R cockroaches is probably a result of enhanced capability for metabolic detoxification.

Animals↗
PubMed1986

Fate of [14C]xanthotoxin (8-methoxypsoralen) in a goat and in bovine ruminal fluid.

A lactating Nubian goat was treated with [14C]xanthotoxin, a photosensitizing psoralen that occurs naturally in some phototoxic range plants, as a single oral dose equivalent to 10.0 mg of xanthotoxin/kg of body weight. The radiochemical was rapidly absorbed, metabolized, and excreted. Although expired air was not monitored for the presence of volatile radiocarbon, the data indicated that greater than 50% of the administered [14C]xanthotoxin was metabolized by cleavage of the O-[14C]methyl moiety, with subsequent loss of the label as, presumably, [14C]CO2. Studies with bovine ruminal fluid in vitro indicated that cleavage of the O-methyl moiety of xanthotoxin could occur rapidly in the rumen. In the goat, nonmetabolized xanthotoxin was not excreted in urine, and of several metabolites in urine extracts, 3 were identified as resulting from opening of the furan or lactone ring. Only about 2% of the dose was recovered in the feces, and this consisted mainly of unmetabolized xanthotoxin. Although appreciable amounts of radiocarbon were secreted into milk, this radiocarbon was not in the form of xanthotoxin or any identifiable metabolites. The radiocarbon in milk likely resulted from the biosynthetic incorporation of [14C]CO2 into normal milk components.

Animals↗
PubMed1977

Movement and persistence of aldicarb in certain soils.

When the rate of movement and the persistence of aldicarb in 4 types of soils were investigated in laboratory and field studies some leaching was detected in coarse sand; however, leaching was quite limited in clay loam and muck soils. These data indicated that aldicarb degraded quite rapidly in the selected soils and most of the applied radioactivity volatilized from these soil columns as 14CO2. The evolution of 14CO2 from the treated soil suggested severe degradation of the aldicarb molecule and consequently provided indirect evidence against the accumulation of significant quantities of toxic metabolites in the soil types evaluated. Under field conditions this toxicant appeared to have a half-life of about 7 days in loam soil.

Aldicarb↗