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Biomedical subjects

G Davidson

Publications and source records attributed to G Davidson.

124 records · Page 7Linked to original sources
PubMed1970

Field attempt to assess the mating competitiveness of sterile males produced by crossing 2 member species of the Anopheles gambiae complex.

In laboratory experiments sterile males produced by crossing member species of the Anopheles gambiae complex competed very successfully with normal males for normal females and the latter when mated with sterile males laid sterile eggs.A field trial was arranged in a small isolated village near Bobo-Dioulasso, Upper Volta; the trial took place at the end of the rainy season against a declining population of species A. Sterile males were produced from the cross between species B males and An. melas females; this cross yielded an F(1) generation mainly composed of sterile males with a sporadic occurrence of a sometimes significant proportion of females which were reproductively normal.The F(1) generation was reared to pupae and these were released into existing breeding places and later from artificial containers.Some 300 000 pupae were so released over a period of 2 months and adult collections were made periodically from inside houses and from outside shelters after releases started. Of the males caught, 75% proved to be sterile while nearly 6% of normal-looking ovipositions failed to hatch. However 2.5% of them proved to be from hybrid females and not from species A females. In control villages, 1.35% of normal-looking ovipositions did not hatch.It was concluded from this field trial that the sterile males were not mating on any significant scale with the natural species A females. This could have been due to a number of factors but the most important is considered to be an ethological one-a mating barrier preventing mating between introduced sterile males and natural females. This is strongly expressed under natural conditions but not operative in the limited confines of a cage. The use of a cross between two species against a third species may well have enhanced this barrier.

Animals↗
PubMed1970

Cytotaxonomy.

Explore the source record for details and available documents.

Animals↗
PubMed1969

The potential use of sterile hybrid males for the eradication of member species of the Anopheles gambiae complex.

The eradication of certain insect pests of medical importance has already been achieved in some countries by inundation of the natural populations with sterilized insects.The crossing of member species of the Anopheles gambiae complex results in the production of vigorous competitive males which are sterile. Crosses between the males of the freshwater species, provisionally called species A and B, and the females of the saltwater species A. melas and A. merus result in F(1) generations almost entirely composed of males, which again are sterile.This paper reports the results of cage experiments in which adult sterile males from these latter crosses were added to normal males and females in varying proportions and larval seeding experiments in which larvae known to produce virtually nothing but sterile males were added to normal larvae in varying proportions, reared together and the adults allowed to emerge together and mate.Both series of experiments resulted in a significant reduction in the fecundity of the females and, in the adult series, strong evidence of superior mating ability of the sterile males was given.The potentiality of this method of species eradication is discussed in relation to present difficulties experienced in the control or eradication of A. gambiae-transmitted malaria.

Animals↗
PubMed1967

Further chromatographic studies of the systematic relationship within the Anopheles gambiae complex; studies of laboratory strains.

As serious consideration is given to initiating malaria eradication programmes in tropical Africa, it becomes essential to be able to distinguish between the various species comprising the Anopheles gambiae complex. At the present time, A and B species cannot be separated by conventional taxonomic methods.The chromatographic method used in the thorough statistical study reported is capable of differentiating between species of the A. gambiae complex. Whereas 9 of the 10 strains studied could be distinguished from one another, 8 of the strains fell into three species-groups. The results indicate that by this technique it may be possible to discern subtle species relationships not yet established by conventional taxonomy.

Anopheles↗
PubMed1966

A chromatographic study of the systematic relationship within the Anopheles gambiae complex.

In the planning of malaria eradication programmes for Africa, it is necessary to be able to characterize and distinguish between various species of the Anopheles gambiae complex in order to proceed on a sound and economic basis. However, at present there are no reliable taxonomic methods for separating the sibling species which comprise Groups A and B.The study reported was undertaken to investigate the possibility of differentiating morphologically indistinguishable members of this complex on the basis of chromatographic patterns of fluorescing components obtained from extracts of adult mosquitos. The results indicate that this biochemical taxonomic method can be used to characterize and differentiate A. gambiae species that are indistinguishable by conventional taxonomy.

Animals↗
PubMedDate not supplied

Using continuous quality improvement to increase preventive services in clinical practice--going beyond guidelines.

BACKGROUND: Even the most uniformly accepted prevention guidelines do not by themselves lead to implementation or to adequate rates of preventive services in medical practice. Although much has been learned about the office systems that seem to be needed for major change in a busy clinical practice, there are still no examples of a model for developing, implementing, and sustaining those office systems in a nonacademic practice. METHODS: IMPROVE, the first large randomized controlled trial of CQI (continuous quality improvement) in any industry, is providing a scientific test of the hypothesis that HMO sponsorship of a CQI-based intervention can lead to sustained organizational change, implementation and maintenance of office systems, and improved rates of adult preventive services in contracted private primary care clinics. The 22 clinics assigned to the intervention arm of the study are receiving training, consultation, networking, and reinforcement for internal multidisciplinary teams as they work through a structured process to understand and improve their clinic's process for providing preventive services. Rates and quality of eight preventive services in these clinics are being compared over time with those in 22 matched comparison clinics. RESULTS: The 44 clinics needed for the trial have been recruited and randomized, and baseline comparisons show no significant differences between the two groups. Nine months into the trial, 21 of 22 intervention clinics have completed training and are pursuing a systematic improvement process for preventive services. CONCLUSIONS: With external training and consultation, many private primary care clinics will voluntarily engage in a lengthy multidisciplinary team effort to use CQI techniques to study and systematically improve their entire process for providing preventive services.

Adult↗
PubMedDate not supplied

A preliminary study of the analysis of Cannabis by supercritical fluid chromatography with atmospheric pressure chemical ionisation mass spectroscopic detection.

A rapid method is described for the analysis of Cannabis products by supercritical fluid chromatography (SFC) coupled to atmospheric pressure chemical ionization-mass spectroscopic (APCI-MS) detection. The method had a shorter analysis time than GC-MS methods, without the need for derivatization prior to analysis. It was also faster than HPLC methods, with better resolution and definitive identification. Linearity of detector response to cannabidiol, delta 8-tetrahydrocannabinol, delta 9-tetrahydrocannabinol and cannabinol was established, the detection limits for mass on column being 0.55 ng, 1.20 ng, 0.69 ng and 2.10 ng respectively. The technique offers a means by which Cannabis products can be definitively identified in a single chromatographic run. Application to casework samples is described.

Cannabinoids↗
PubMedDate not supplied

A retrospective review of a service to provide comprehensive dental care under general anesthesia.

Day-stay general anesthesia is indicated for a number of dental reasons, not least for those patients who are unable to accept routine dental care. Since 1979, the Dental Hospital of the University of Newcastle upon Tyne, UK, has provided a weekly day-stay service for the dental care of such patients. Reviews of this service were undertaken in 1983 and again in 1993. The latter study investigated the provision of care for 265 patients and compared this with that for the 96 patients reviewed in the earlier study. This paper presents the results of the review and underlines the need for a very aggressive approach to preventive dental care for patients treated by this modality.

Adolescent↗
PubMedDate not supplied

Uncovering the missing Medicaid cases and assessing their bias for estimates of the uninsured.

General population surveys of health insurance coverage are thought to undercount Medicaid enrollment, which may bias estimates of the uninsured. This article describes the results of an experiment undertaken in conjunction with a general population survey in Minnesota. Responses to health insurance questions by a known sample of public program enrollees are analyzed to determine possible reasons for the undercount and the amount of bias introduced in estimates of uninsured people. While public program enrollees often misreport the type of coverage they have, the impact on estimates of those without insurance is negligible. Restrictions to generalizing the finding beyond this study are discussed.

Bias↗
PubMedDate not supplied

Characterization of varietal differences in essential oil components of hops (Humulus lupulus) by SFC-FTIR spectroscopy.

A supercritical fluid chromatographic method combined with Fourier-transform infrared spectroscopy detection (SFC-FTIR) was developed for determination of varietal differences in essential oil constituents in hops (Humulus lupulus). Infrared spectra (IR) of the major constituents of essential oil of hops were taken as films deposited on AgCl discs and compared with those obtained after chromatographic separation in the IR flow-cell with supercritical carbon dioxide (scCO2). Spectra from AgCl discs were comparable to those in scCO2, but in scCO2 most of the bands appeared approximately 8-10 cm-1 to higher wave numbers. Open-tubular SFC-FTIR analysis of the essential oil of 4 different hop varieties was performed. The SFC-FTIR chromatograms showed differences in the location and relative intensity of the peaks depending on the variety, which was further confirmed by consideration of their FTIR spectra.

Edible Grain↗
PubMedDate not supplied

Failure of a continuous quality improvement intervention to increase the delivery of preventive services. A randomized trial.

CONTEXT: Although there has been enormous interest in continuous quality improvement (CQI) as a measure to improve health care, this enthusiasm is based largely on its apparent success in business rather than formal evaluations in health care. OBJECTIVE: To determine whether a managed care organization can increase delivery of eight clinical preventive services by using CQI. DESIGN: Primary care clinics were randomly assigned to improve delivery of preventive services with CQI (intervention group) or to provide usual care (control group). INTERVENTION: Through leadership support, training, consulting, and networking, each intervention clinic was assisted to use CQI multidisciplinary teams to develop and implement systems for delivery of preventive services. SETTING: 44 primary care clinics in greater Minneapolis-St. Paul. PATIENTS: Patients 19 years of age and older completed surveys at baseline (n = 6830) and at follow-up (n = 6431). Medical chart audits were completed on 4777 patients at baseline and 4546 patients at follow-up. MAIN OUTCOME MEASURES: The proportion of patients who were up-to-date (according to chart audit) and the proportion of patients who were offered a service if not up-to-date (according to patient report) for 8 preventive services. RESULTS: Compared with the control group, based on the proportion of patients who were up-to-date, use of only one preventive service--pneumococcal vaccine--increased significantly in the intervention group (17.2% absolute increase from baseline to follow-up compared with a 0.3% absolute increase in the control group, P = 0.003). Similarly, based on patient report of being offered a service if not up-to-date, delivery of only one preventive service--cholesterol testing--significantly increased in the intervention group compared with the control group (4.6% increase vs. 0.4% absolute decrease in the control group; P = 0.006). CONCLUSION: In this trial, CQI methods did not result in clinically important increases in preventive service delivery rates.

Adult↗