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Biomedical subjects

A Archibald

Publications and source records attributed to A Archibald.

18 recordsLinked to original sources
PubMed2006

Genetic diversity in European pigs utilizing amplified fragment length polymorphism markers.

The use of DNA markers to evaluate genetic diversity is an important component of the management of animal genetic resources. The Food and Agriculture Organisation of the United Nations (FAO) has published a list of recommended microsatellite markers for such studies; however, other markers are potential alternatives. This paper describes results obtained with a set of amplified fragment length polymorphism (AFLP) markers as part of a genetic diversity study of European pig breeds that also utilized microsatellite markers. Data from 148 AFLP markers genotyped across samples from 58 European and one Chinese breed were analysed. The results were compared with previous analyses of data from 50 microsatellite markers genotyped on the same animals. The AFLP markers had an average within-breed heterozygosity of 0.124 but there was wide variation, with individual markers being monomorphic in 3-98% of the populations. The biallelic and dominant nature of AFLP markers creates a challenge for their use in genetic diversity studies as each individual marker contains limited information and AFLPs only provide indirect estimates of the allelic frequencies that are needed to estimate genetic distances. Nonetheless, AFLP marker-based characterization of genetic distances was consistent with expectations based on breed and regional distributions and produced a similar pattern to that obtained with microsatellites. Thus, data from AFLP markers can be combined with microsatellite data for measuring genetic diversity.

Alleles↗
PubMed2003

Lymphoscintigraphic evaluation of chronic lower limb oedema.

Ultrasound, computed tomography (CT), magnetic resonance imaging (MRI), venography, lymphoscinti-graphy (LS) and contrast lymphography are frequently utilized in the evaluation of lower limb oedema but no clinical data from the Caribbean have been published on the role of LS despite its well-recognized clinical application. The successful clinical application of CT, colour doppler sonography and MRI in differentiating the various causes of lower limb oedema is well understood. Lymphoscintigraphy has found less acceptability especially in the Caribbean where nuclear imaging techniques are only now currently being developed. This paper describes the initial experience with this technique in 15 patients over a five-year period and discusses its value when lower limb lymphoedema is suspected. Scintigrams were analyzed for visualization of lymph vessels and lymph nodes, dilatation of lymphatic vessels, collaterals and dermal back flow. Lymphoscintigrams were classified as normal (n = 5) or consistent with lymphoedema (n = 10). Failure to visualize lymphatic vessels occurred in two cases of suspected primary lymphoedema. In the remaining eight cases of secondary lymphoedema, a positive study based on altered lymphatic flow and anatomy was recorded. An alternative explanation was offered in three out of five cases in which a normal lymphoscintigram was obtained.

Adult↗
PubMed2000

Porcine lung surfactant protein D: complementary DNA cloning, chromosomal localization, and tissue distribution.

Porcine organs and lung surfactant have medically important applications in both xenotransplantation and therapy. We have started to characterize porcine lung surfactant by cloning the cDNA of porcine surfactant protein D (SP-D). SP-D and SP-A are important mediators in innate immune defense for the lung and possibly other mucosal surfaces. Porcine SP-D will also be an important reagent for use in existing porcine animal models for human lung infections. The complete cDNA sequence of porcine SP-D, including the 5' and 3' untranslated regions, was determined from two overlapping bacteriophage clones and by PCR cloning. Three unique features were revealed from the porcine sequence in comparison to SP-D from other previously characterized species, making porcine SP-D an intriguing species addition to the SP-D/collectin family. The collagen region contains an extra cysteine residue, which may have important structural consequences. The other two differences, a potential glycosylation site and an insertion of three amino acids, lie in the loop regions of the carbohydrate recognition domain, close to the carbohydrate binding region and thus may have functional implications. These variations were ruled out as polymorphisms or mutations by confirming the sequence at the genomic level in four different pig breeds. Porcine SP-D was shown to localize primarily to the lung and with less abundance to the duodenum, jejunum, and ileum. The genes for SP-D and SP-A were also shown to colocalize to a region of porcine chromosome 14 that is syntenic with the human and murine collectin loci.

Amino Acid Sequence↗
PubMed2000

The role of quantitative single photon emission computerized tomography (SPECT) in the osseous integration process of dental implants.

OBJECTIVE: To evaluate the integration process of endosseous dental implants by using quantitative bone single photon emission computerized tomography (SPECT). METHODS: Five consecutive patients receiving titanium implants (Astra Tech, Mölndal, Sweden) in the normal edentulous jaw were evaluated by bone SPECT before loading and at regular intervals up to 5 months after loading. Osteoblastic activity at the implant site was compared with activity within the skull (reference) to calculate an osteoblastic activity index (AI). RESULTS: A time activity curve obtained by plotting AI against time over 5 months showed 3 distinct phases of osteoblastic activity: (1) a rise in osteoblastic activity, part of which may reflect postoperative changes, (2) maximum activity about 1 month after implant, and (3) a gradual falloff in the AI, which returned to pre-implant levels at about 4 months. CONCLUSIONS: We conclude that this method offers a simple, reproducible, objective, and physiologic approach to studying the osseous integration process that occurs after endosseous dental implants. In this small series of patients, this osseous integrative process appears to have become established approximately 4 months after loading. This method also has the capability of quantitating bone activity in absolute terms of microCi/gram (microcuries per gram) and can be useful when bone grafting and other surgical procedures are involved.

Dental Implantation, Endosseous↗
PubMed2000

The role of labelled red blood cell scintigraphy in the detection of acute gastrointestinal bleeding.

This paper describes the experience with 99m Technetium labelled red blood cell (99mTc RBC) scintigraphy in twenty-two patients presenting with acute gastrointestinal (GI) tract bleeding. Studies were positive in thirteen cases--eight from the lower GI tract and five from the upper. The data from surgical intervention were available in ten cases. Scintigraphy cannot diagnose the cause of GI bleeding, as it is a nonspecific study. Its usefulness lies in its ability to accurately diagnose the bleeding site, as was shown in this study where there was good surgical correlation. The simplicity, reproducibility and reliability of the technique, particularly when bleeding rates are low and intermittent, make it, in our view, the first line of investigation in any patient with suspected bleeding from the colon or upper GI tract if endoscopic evaluation is not possible in the latter. Its current under-utilisation in the Caribbean may be a reflection of the lack of nuclear imaging facilities.

Acute Disease↗
PubMed1999

Contrast material and gallbladder kinetics: implications for same day sonography after intravenous pyelography or CT scanning.

Sonographic examination of the gallbladder has allowed us to study the effects of various substances on this organ. A prospective study involving 77 patients was undertaken to evaluate the effects of intravenous or oral contrast agents on gallbladder volume changes in patients without known gallbladder disease. A mean volume after contraction of 24.8% was observed after administration of intravenous contrast agent (P < 0.01) and of 31.9% after oral administration (P < 0.01). This phenomenon of contraction of the gallbladder should therefore be recognized when sonographic or computed tomographic evaluation of the gallbladder is undertaken after imaging procedures that use radiographic contrast agents either intravenously or orally.

Administration, Oral↗
PubMed1999

Biotinidase deficiency: a treatable genetic disorder in the Saudi population.

Biotinidase deficiency is an autosomal recessive genetic disorder which is not uncommon in the Saudi population. Biotinidase is responsible for biotin recycling and biotin is an essential cofactor for activation of the carboxylase enzymes. Absence of biotinidase leads to infantile or early childhood encephalopathy, seizure disorder, dermatitis, alopecia, neural deafness and optic atrophy. The disease can be diagnosed by simple fluorometric enzyme assay. Treatment with biotin is both cheap and simple, resulting in rewarding clinical recovery and normalization of the biochemical, neuroradiological and neurophysiological parameters. If neglected, however, a patient may die of acute metabolic acidosis or may suffer from permanent neural deafness and optic atrophy, with mental and motor handicap. We describe the detection and treatment of 20 cases of biotinidase deficiency in our hospital and recommend the introduction of a neonatal screening programme for this disorder.

Amidohydrolases↗
PubMed1995

Myocardial perfusion scintigraphy using Tc99m labelled compounds: correlations with coronary angiography.

The increasing incidence of ischaemic heart disease with high mortality rate and the recent introduction of Tc99m labelled myocardial perfusion imaging agents, along with the advent of a Coronary Angiography programme in Trinidad and Tobago, prompted the comparison of the sensitivity and specificity of myocardial perfusion scintigraphy (MPS) with coronary angiography (CA). Using a standard one-day code-differential imaging protocol Single Photon Emission Computed Tomography (SPECT), images of the left ventricular myocardium of 30 patients were obtained at rest and following exercise: These images were analyzed for perfusion defects to assess each of the three main coronary arteries; the left anterior descending artery (LAD), the right coronary artery (RCA) and the left circumflex artery (LCx). The data were then correlated with the angiographic findings. MPS yielded an overall sensitivity of 97.5% and a specificity of 83.6% when compared to CA. Discordant data were obtained in the analysis of nine vascular territories with scintigraphy producing eight false positives and one false negative. The false positive cases were seen in two males and four females. Of the males, one was discovered to have intramyocardial tunnelling of the LAD artery and the other demonstrated differential perfusion between the LAD and LCx arteries. Of the females, one was classified as having Syndrome X and another demonstrated differential perfusion between the LAD and LCx arteries; the other two cases were attributed to breast attenuation. The one false negative was obtained in a patient who demonstrated good collateral circulation on angiography. MPS thus compares very well with CA in assessing the three main myocardial vascular territories.

Adult↗
PubMed1993

Characterization of 24 porcine (dA-dC)n-(dT-dG)n microsatellites: genotyping of unrelated animals from four breeds and linkage studies.

Twenty-four PCR primer pairs were designed for the detection of porcine microsatellites. Polymorphism was investigated in 76 unrelated animals from four different breeds: Duroc, Landrace, Hampshire, and Yorkshire. Compared with human microsatellites, a general lower heterozygosity was detected; however, for each microsatellite a significant variation between breeds in number of alleles and heterozygosity was seen. Mean heterozygosity was found to be significantly higher (P < 0.01%) in the Yorkshire breed than in the other three breeds. Linkage analyses with the CEPH linkage packet were performed in a backcross family comprising 45 animals, of which 43 had informative meioses. Ten of the microsatellites could be assigned to six different linkage groups, demonstrating that linkage mapping with microsatellites can be carried out with great efficiency in a relatively small number of animals. Four of the linkage groups represent Chromosomes (Chrs) 4, 6, 7, and 8 respectively, while two linkage groups are unassigned.

Alleles↗
PubMed1990

First trimester prenatal diagnosis of Tay-Sachs disease using the sulfated synthetic substrate for hexosaminidase A.

Uncultured and cultured embryonic trophoblastic tissue obtained by chorionic villus sampling (CVS) displays enzyme activity towards 4-methylumbelliferyl-2-acetamido-2-deoxy-beta-D-glucopyranosyl-6-sulfate (MUGS), a specific substrate for Hexosaminidase A (Hex A), the enzyme deficient in Tay-Sachs disease (TSD). Specific activity is comparable to that found in cultured amniocytes and fibroblasts. The enzyme activity has a pH optimum of 4.1 and an apparent Km of 6 x 10(-4) mol/L. Thirteen pregnancies in eight families at risk for TSD were monitored by CVS using MUGS as the Hex A substrate. Four fetuses were proven affected by enzyme analysis of fetal tissues and cultured fetal fibroblasts obtained at the time of termination of the pregnancies. Nine fetuses were judged to be unaffected. Eight babies were clinically normal while the other pregnancy is continuing. The use of MUGS as substrate for Hex A makes prenatal diagnosis by CVS of families at risk for TSD simple, direct and accurate.

Cells, Cultured↗
PubMed1981

Diagnosis of neural tube defects by estimation of amniotic fluid acetylcholinesterase.

Acetylcholinesterase (AChE) activity in amniotic fluid was assayed directly by a reaction rate method at 30 degrees C using acetylthiocholine iodide as substrate and ethopropazine as a safe 'pseudo' cholinesterase inhibitor. Fresh samples from 101 normal pregnancies of 14-24 weeks gestation had a mean AChE activity of 2.56 u/l (SD 1.10). Elevated levels of AChE were found in association with open spina bifida (5.5-20.4 u/l), anencephaly (10.2-19.5 u/l), exomphalos (2.7-15.6 u/l), intrauterine death (30.2-59.3 u/l) and Turner's syndrome (36.4 u/l) but not with closed spina bifida or rhesus isoimmunisation. When AChE activity was expressed as a percentage of the total cholinesterase activity ('percentage AChE'), there was a good correlation between AChE activity and 'percentage AChE' in normal pregnancies and the values associated with the 37 pregnancies affected by open neural tube defects (NTD) fell outside the 99.9 per cent confidence limits of the normal group. Qualitative differences in cholinesterase activity could be demonstrated between the groups with exomphalos and open NTD. It is suggested that the assay might be used satisfactorily to demonstrate the presence of open NTD in affected pregnancies.

Acetylcholinesterase↗