Cryptic species within Anopheles longipalpis from southern Africa and phylogenetic comparison with members of the An. funestus group.

House-resting Anopheles mosquitoes are targeted for vector control interventions; however, without proper species identification, the importance of these Anopheles to malaria transmission is unknown. Anopheles longipalpis, a non-vector species, has been found in significant numbers resting indoors in houses in southern Zambia, potentially impacting on the utilization of scarce resources for vector control. The identification of An. longipalpis is currently based on classical morphology using minor characteristics in the adult stage and major ones in the larval stage. The close similarity to the major malaria vector An. funestus led to investigations into the development of a molecular assay for identification of An. longipalpis. Molecular analysis of An. longipalpis from South Africa and Zambia revealed marked differences in size and nucleotide sequence in the second internal transcribed spacer (ITS2) region of ribosomal DNA between these two populations, leading to the conclusion that more than one species was being analysed. Phylogenetic analysis showed the Zambian samples aligned with An. funestus, An. vaneedeni and An. parensis, whereas the South African sample aligned with An. leesoni, a species that is considered to be more closely related to the Asian An. minimus subgroup than to the African An. funestus subgroup. Species-specific primers were designed to be used in a multiplex PCR assay to distinguish between these two cryptic species and members of the An. funestus subgroup for which there is already a multiplex PCR assay.

Feeding and indoor resting behaviour of the mosquito Anopheles longipalpis in an area of hyperendemic malaria transmission in southern Zambia.

Anopheles longipalpis (Theobald) (Diptera: Culicidae) is a predominantly zoophilic mosquito that has not been implicated in malaria transmission. However, this species was collected indoors with An. funestus s.l. in southern Zambia, where transmission of Plasmodium falciparum is hyperendemic, and we initially misidentified it morphologically and molecularly as An. funestus s.l. The indoor resting density and blood-feeding behaviour of An. longipalpis were investigated during the 2004-05 and 2005-06 transmission seasons in Mufwafwi village in southern Zambia. Numbers of endophilic An. longipalpis increased towards the end of the rainy season. Although specimens were collected during human landing catches, the feeding behaviour of An. longipalpis was significantly biased towards cattle (88.7%), with other bloodmeals originating from dogs, goats and chickens. None of the 177 specimens of An. longipalpis were infected with P. falciparum. These data are consistent with existing reports that An. longipalpis is not involved in malaria transmission. However, more extensive sampling is necessary. Importantly, the correct identification of An. longipalpis is crucial for malaria control programmes in areas where An. funestus s.l and An. longipalpis exist sympatrically so that scarce resources are not wasted on the control of a non-vector.

The new chemicals process at the Environmental Protection Agency (EPA): structure-activity relationships for hazard identification and risk assessment.

Section 5 of the Toxic Substances Control Act (TSCA) does not require any toxicity testing as a prerequisite for submission of a Premanufacturing Notice (PMN) for a new chemical. In order to compensate for the lack of actual test data, a process involving structure-activity relationships (SAR) for assessing hazard potential was constructed. The hazard assessment is then coupled with an estimation of potential exposure to determine potential risk. This process involves the use of multiple interdisciplinary teams that work within a 90-day time frame to complete approximately 2000 risk assessments per year.

Molecular biology in the diagnosis and epidemiology of tuberculosis.

Tuberculosis is the predominant infectious cause of mortality today, killing 3 million people annually. The cornerstones of diagnosis rest on microscopy of specimens using auramine and Ziehl-Neelsen stains followed by culture on Lowenstein-Jensen or alternative media. The long generation time of Mycobacterium tuberculosis means 2-8 weeks usually elapse before a result is available to the clinician. This has stimulated research into the use of molecular diagnostic techniques. This article reviews the use and limitations of DNA hybridization, restriction fragment length polymorphism, pulsed-field gel electrophoresis and the polymerase chain reaction in the diagnosis and epidemiology of tuberculosis. The applicability of molecular biology to determine drug resistance is also addressed.

The in-vitro bactericidal activities of combinations of antimicrobial agents against clinical isolates of Mycobacterium avium-intracellulare.

The in-vitro activities of five antimicrobial agents (rifabutin, clarithromycin, ethambutol, ciprofloxacin and amikacin), alone and in combination, were evaluated against 21 strains of Mycobacterium avium-intracellulare isolated from patients with AIDS. The combined activities of these agents were studied on solid medium by a full chequerboard method. Synergy was demonstrated most frequently (28-71% of isolates) with those combinations that included ethambutol. In killing curve experiments where double and triple combinations of agents were tested against two of the strains, 99% kill was achieved in seven days at concentrations well below those that are attainable in serum. However, an additive rather than a synergic effect was seen in most instances. Although ciprofloxacin alone had the greatest bactericidal activity against these two strains, its activity was antagonized in the presence of rifabutin; this antagonism became inapparent when a third agent was added. Demonstration of bactericidal activity in broth culture may be more relevant than the results of susceptibility testing on solid medium when choosing antimicrobial therapy for patients with this infection.

Household formation by the young in the United States.

"A model of household formation by the young is specified and estimated. It was found that the headship rate for the young in the United States depends on income, the cost of housing, the number of families receiving AFDC payments, the age at first marriage for females and for males, and the percentage of males enrolled in college. Household formation by the young is much more sensitive to changes in income and the price of housing than household formation by the entire adult population. The estimated results are used to examine the change in the headship rate from 1961 to 1979 and from 1979 to 1987."

Reversible dissociation of a carbamoyl phosphate synthase-aspartate transcarbamoylase-dihydroorotase complex from ovarian eggs of Rana catesbeiana: effect of uridine triphosphate and other modifiers.

Glutamine-dependent carbanoyl phosphate synthase [ATP6carbamate phosphotransgerase (dephosphorylating), EC 2.7.2.9], aspartate transcarbamoylase (carbamoylphosphate: L-aspartate carbamoyltransferase, EC 2.1.3.2) and dihydroorotase (L-5,6-dihydroorotate amidohydrolase, EC 3.5.2.3), are copurified as a high-molicular-weight complex from extracts of unfertilized eggs of Rana catesbeiana. UTP is required to maintain the integrity of the complex during the last two purification steps. Removal of the nucleotide results in dissociation of the complex. Based on sedimentation behavior in glycerol gradients, the dissociated carbamoyl phosphate synthase has an apparent molecular weight of 260,000 +/- 20,000 and that of dihydroorotase is estimated at 280,000 +/- 20,000. Aspartate transcarbamoylase is broadly distributed over the gradient. The addition of ATP, 5-phosphoribosyl-1-pyrophosphate, Mg++, or inorganic phosphate to the dossociated complex results in the appearance of a peak of aspartate transcarbamoylase activity with an apparent molecular weight of 110,000 +/- 10,000. Icubation of a mixture of the dissociated enzymes with UTP and Mg++ leads to their reassociation into the high-molecular-weight complex.