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P Munroe

Publications and source records attributed to P Munroe.

9 recordsLinked to original sources
PubMed2000

Focused ion beam in dental research.

Focused ion beam (FIB) has been available for over 10 yrs but until recently its usage has been confined to the semiconductor industry. It has been developed as an important tool in defect analysis, circuit modification and recently transmission electron microscope sample preparation. This paper introduces FIB and demonstrates its application in dental research. Its ion and electron imaging modes complement the SEM while its ability to prepare TEM samples from a wide range of material will allow the study of new types of adhesive interface. As an example, its use is described in the characterization of the interface of resin to a tribochemically treated surface of an experimental fiber-reinforced resin-based composite. As with all new techniques, the initial learning curve was difficult to manage. This new instrument offers opportunities to expand research in dental materials to areas not possible before.

Aluminum Oxide↗
PubMed1997

Progress in determining the genes for hypertension, insulin resistance, and dyslipidemia.

For the first time, we have techniques available that may enable us to determine cause and effect in common cardiovascular diseases. The observations presented herein require cautious interpretation until replicated. There are currently several large programs under way that seek to establish substantial family resources for investigation of the genetic basis of hypertension. When interpreting the results of genome screens, it will be necessary to consider that we may link genetic loci for coexistent features such as dyslipidemia and insulin resistance to hypertension. Therefore, careful phenotypic data will be necessary to dissect out the causes of hypertension.

Animals↗
PubMed1994

Linkage of the angiotensinogen gene to essential hypertension.

BACKGROUND: The renin-angiotensin system is a powerful pressor system with a major influence on salt and water homeostasis. Angiotensinogen (also called renin substrate) is a key component of this system; it is cleaved by renin to yield angiotensin I, which is then cleaved by angiotensin-converting enzyme to yield angiotensin II. The observation that plasma angiotensinogen levels correlate with blood pressure and track through families suggests that angiotensinogen may have a role in essential hypertension. We therefore investigated whether there is linkage between the angiotensinogen gene on chromosome 1q42-43 and essential hypertension. METHODS: Samples of DNA from 63 white European families in which two or more members had essential hypertension were tested for linkage of the angiotensinogen gene to this disorder. Affected cousins, nephews, nieces, and half-siblings were included when possible. To test for linkage, we used as a marker a dinucleotide-repeat sequence flanking this gene, and we employed the affected-pedigree-member method of linkage analysis. Two molecular variants of the angiotensinogen gene, one encoding threonine instead of methionine at position 235 (M235T) and the other encoding methionine rather than threonine at position 174 (T174M), were also tested for possible association with essential hypertension. RESULTS: We found significant linkage (t = 5.00, P < 0.001) and association (chi-square = 53.3, P < 0.001) of the angiotensinogen-gene locus to essential hypertension in the 63 multiplex families. This linkage was consistently maintained in the subgroup of subjects with diastolic pressure above 100 mm Hg and in the subgroups classified according to sex. It has been proposed previously that T174M and M235T are associated with essential hypertension. However, we found no association in our population between either polymorphism and this disorder. CONCLUSIONS: This study provides strong and consistent support for the linkage to essential hypertension of regions within or close to the angiotensinogen gene. Precisely how mutations in this region may result in hypertension remains to be determined.

Aged↗
PubMed1993

Deletion analysis maps ocular albinism proximal to the steroid sulphatase locus.

We describe a pedigree in which four male members are affected by a contiguous gene abnormality involving the short arm of the X chromosome (Xp22.32). Bivariate flow cytometry of lymphoblastoid cell lines from two of these individuals and a normal male showed a 6-7 megabase deletion in affected males, and high resolution chromosomal G-banding of an obligate heterozygote showed the deletion to reside in the Xp22.32 region. Affected members had X-linked ichthyosis due to steroid sulphatase deficiency, Kallmann's syndrome, but no ocular albinism. In two out of four affected individuals studied, there was unilateral renal agenesis. Deletion analysis using the Xp22.32 markers MIC2, DXS31, DXS 89, GMGX9, DXS278, DXS143, and DXS9 showed that the deletion extended from DXS31 to DXS143 (inclusive). The absence of ocular albinism in this pedigree shows conclusively that the X-linked ocular albinism gene resides proximal to the DXS143 locus. Further, the inconstant association of unilateral renal agenesis with X-linked Kallmann's syndrome, even when the latter is caused by a complete deletion of the gene, suggests that the absence of the X-linked Kallmann gene can be compensated in renal development.

Albinism, Ocular↗
PubMed1982

Filariasis in Amerindians of western Guyana with observations on transmission of Mansonella ozzardi by a Simulium species of the amazonicum group.

In order to conduct experimental infection studies of Mansonella ozzardi in local haematophagous Diptera, volunteers infected with this parasite were identified during a microfilaria survey in four Amerindian villages in the Pakaraima Mountains of western Guyana, near the Brazilian border. M. ozzardi microfilariae were detected in thick blood smears from 8-21% of persons examined. They were also found in skin snips from 8/73 persons all of whom were positive by blood smear examination. No Onchocerca volvulus microfilariae were detected. Dipetalonema perstans infections were found in three of the four villages but prevalence rates were only 1-8%. Manbaited catches of haematophagous Diptera made at the onset of the dry season in one of the villages yielded only three Simulium species. After flies were engorged on infected volunteers, M. ozzardi larvae developed to the infective stage in 6-7 days in the most abundant species, a member of the Simulium amazonicum group. Man-biting rates of up to 156 per 15-minute period were recorded for this species in midday collections along river banks near one of the villages. Developing filariae, including infective larvae of M. ozzardi, were also found in wild-caught flies. It was concluded that this Simulium species is a vector of M. ozzardi in the study area.

Adolescent↗
PubMed1976

Seroepidemiologic investigations of malaria in Guyana.

The results of longitudinal seroepidemiologic malaria surveys with the indirect haemagglutination test in four sectors in the interior of Guyana did not suggest recent malaria transmission. Indigenous malaria cases had not been detected in these sectors since 1968 but malaria surveillance here had been incomplete. The multi-stage cluster sampling method used proved to be efficient and permitted the survey of a large and sparsely populated area to be concentrated in relatively few localities. Observation of a group of 147 seropositive and seronegative persons after one year showed a four-fold or greater decline of antibody titres in five per cent of the cohort population and no such titre increases were seen, thus confirming the absence of recent malaria infections. Seropositivity rates were higher in persons with a history of malaria than in those without such a history. Collecting blood on filter paper facilitated obtaining material for serologic testing especially in the younger age group and no refusals were encountered. This advantage compensates for the slight loss in sensitivity when filter paper eluates are titrated instead of sera. The difference between the past infection probabilities of the age groups over and under 20 years old suggests that the disappearance of malaria from the interior was related more to the elimination of malaria transmission along the coast than to the specific malaria campaign in the interior.

Adolescent↗