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Biomedical subjects

G Mason

Publications and source records attributed to G Mason.

At least 37 records · Page 2Linked to original sources
PubMed1999

Non-invasive RNA-based determination of fetal Rhesus D type: a prospective study based on 96 pregnancies.

OBJECTIVES: To develop a non-invasive method for determining fetal RhD status in order to provide improved care for women most at risk. DESIGN: A prospective study. METHODS: Fetal erythroblasts were enriched from the peripheral circulation of 96 RhD negative women with pregnancies at various stages in gestation using discontinuous density gradients. Amplification of RhD-specific mRNAs was carried out by reverse transcription-polymerase chain reaction assay. RNA, rather than DNA, was selected for amplification because it rarely contaminates samples, thus resulting in fewer false positives; moreover, its presence in multiple copies per cell should enhance the sensitivity of the assay, resulting in fewer false negatives. The study was prospective, relying on postnatal serological confirmation of RhD phenotype. RESULTS: The assay was 75% accurate at predicting fetal RhD status, comparing favourably with standard genomic DNA-based assays. However, we found that accuracy dropped from 85% (29/34) in the third trimester of pregnancy, to 82% (32/39) in the second and 48% (11/23) in the first trimester. Discordant data were due to false negatives in the majority (78%) of cases. CONCLUSIONS: We suggest that reverse transcription may be a useful and perhaps more sensitive alternative to standard genomic polymerase chain reaction in the majority of cases. However, under certain circumstances the absence or reduction of fetal erythroblasts or possibly RhD mRNA in some preparations may compromise the accuracy of the assay.

Biomarkers↗
PubMed1998

Determination of the aversion of farmed mink (Mustela vison) to carbon dioxide.

High concentrations of carbon dioxide are commonly used to kill mink before their pelts are removed. The aversiveness of this procedure was investigated by using a passive avoidance technique. Eight mink were trained to obtain a reward (a novel object) by entering a chamber which could be filled with carbon dioxide, as under commercial conditions (over 80 per cent by volume). In the absence of carbon dioxide, mink entered the chamber within a mean (sd) of 16 (2.1) seconds and spent 45 (12) per cent of the next 10 minutes interacting with the novel object. When there was carbon dioxide in the test chamber, the mink would not enter it and coughed and recoiled from the chamber's entrance instead. It was concluded that the mink detected and avoided high concentrations of carbon dioxide, and that if mink are to be killed humanely, less aversive techniques should be used.

Animal Husbandry↗
PubMed1998

Effectiveness of one-year participation in school-based volunteer-facilitated peer support groups.

This study evaluated the effectiveness of one-year participation in a program of volunteer-facilitated peer support groups conducted in a southeast Texas high school. One hundred eighteen students who experienced emotional distress or behavioral problems voluntarily participated in weekly groups facilitated by adult volunteers who were not mental health professionals. Seventy-six participants anonymously assessed the program using an instrument developed to evaluate the group experience. Results indicated that the program was highly accepted by the students even though two-thirds had initially felt uncomfortable in the groups. There was significant improvement in the interpersonal, internal, and school domains. Two-thirds of the alcohol and substance users reported reducing their intake or abstaining. The beneficial effects reported by a majority of the participants indicate that schools opting to implement this early intervention program can look forward to encouraging results within one year.

Adolescent↗
PubMed1997

A high incidence of melanoma found in patients with multiple dysplastic naevi by photographic surveillance.

OBJECTIVES: (1) To assess the incidence of melanoma in a cohort of patients with dysplastic melanocytic naevi (DMN) and the relationships between incident melanomas and preexisting naevi and between melanoma risk and numbers of DMN. (2) To examine the role of the patient versus the physician in detecting melanoma and the relative value of surveillance versus prophylactic excision. DESIGN: Prospective cohort study. PATIENTS AND SETTING: Two hundred and seventy-eight adults, each with five or more DMN, were followed up for a mean period of 42 months in a private dermatology practice. DMN were clinically diagnosed. RESULTS: Twenty new melanomas were detected in 16 patients, corresponding to an age-adjusted incidence of 1835/100000 person-years, 46 times the incidence in the general population. Eleven were detected because of changes evident in comparison with baseline photographs and nine were detected by patients or their partners. Thirteen of the 20 melanomas arose as new lesions and only three from DMN. Melanoma risk rose with increasing numbers of DMN. CONCLUSIONS: Increasing numbers of DMN are associated with increasing melanoma risk. Surveillance (baseline photography and follow-up) enabled early diagnosis of melanoma and was very much more cost-effective in preventing life-threatening melanoma than prophylactic excision of DMN.

Adolescent↗
PubMed1997

Counselling implications of chromosomal abnormalities other than trisomy 21 detected through a maternal serum screening programme.

OBJECTIVE: To identify counselling requirements, we reviewed the frequency and type of non-trisomy 21 chromosome abnormalities found at amniocentesis after maternal serum screening for Down's syndrome. DESIGN: The study involved a review of the cytogenetic results of amniocenteses performed because of a raised maternal serum screening risk. SETTING: The maternal serum screening and amniocenteses were performed at hospitals in the Yorkshire region. SAMPLE: 1715 amniocenteses were performed as a result of a raised maternal serum screening risk for the period 1990 to 1993. METHODS: The cytogenetic results were classified into the main categories of numerical and structural chromosomal abnormalities. MAIN OUTCOME MEASURES: The nature and frequency of abnormal cytogenetic results were identified in which parental samples were required in order to determine if the abnormal finding was de novo or familial and/or for which specialist genetic counselling was required. RESULTS: Sixty-nine pregnancies of 1715 amniocenteses were identified with a chromosomal abnormality (4.0%): 35 (2.0%) with trisomy 21 and 34 (2.0%) with another chromosomal abnormality. For 20 of these 34 abnormalities, parental karyotypes were required and in 29 of the 34 specialist genetic counselling was required. CONCLUSIONS: Women undergoing maternal serum screening and, in particular, those proceeding to amniocentesis, should be informed that there is an equal chance that a chromosomal abnormality other than trisomy 21 will be found at amniocentesis, the nature of which usually requires parental samples and specialist counselling.

Amniocentesis↗
PubMed1996

Quantification of Spatial Correlation in Porous Media and Its Effect on Mercury Porosimetry.

In many porous media the grains are packed in a disordered manner, rather than in regular lattices. Theoretical treatments of the properties of these media often assume that because there is no regular lattice, the pore space between grains is completely spatially disordered. Here we present an analysis of a real granular medium (a close packing of equal spheres) which shows that, contrary to the popular assumption, the pore space is spatially correlated. The origin of this pore space correlation is the strong spatial correlation of grain locations, which is a feature of all dense granular media. Our analysis relies on physically representative network models of the pore space constructed from knowledge of the grain locations. Simulated drainage experiments on these networks agree with mercury porosimetry experiments in simple sandstones, whereas simulations in uncorrelated but otherwise identical networks do not. Thus the spatial correlation inherent in the pore space of simple porous media significantly affects mercury porosimetry. Deriving pore size distributions from mercury porosimetry without considering spatial correlation can give misleading results. The likelihood of error is compounded if such pore size distributions are used to estimate transport coefficients such as permeability, diffusivity, and electrical conductivity.

Journal Article↗
PubMed1996

Altered thrombomodulin staining in blistering dermatoses.

The immunocytochemical distribution of thrombomodulin (TM) was examined in sections of skin from patients with blistering dermatoses occurring in the presence and absence of acantholysis. Skin sections were stained using polyclonal and monoclonal anti-human TM antibodies and were correlated with the staining pattern that resulted when using the monoclonal antibody 32-2B, which recognises the chief desmosomal adhesion molecule desmoglein I (DG I). Our study demonstrates a loss of TM staining in acantholytic dermatoses, occurring only in the region of actual disruption of the intercellular bridging between keratinocytes in the stratum spinosum. The thrombomodulin antigen expression paralleled the DG I expression. The strong correlation between the DG I and TM immunostaining pattern in both normal skin and acantholytic dermatoses supports the concept that TM has a role in mediating adhesion processes between keratinocytes.

Acantholysis↗
PubMed1996

Differentiation of growth retarded from normally grown fetuses and prediction of intrauterine growth retardation using Doppler ultrasound.

OBJECTIVE: To assess the hypothesis that infants exhibiting catch-up growth as an indicator of intrauterine growth retardation (IUGR) have a higher incidence of predelivery abnormal Doppler results. SETTING. Obstetric unit, St James's University Hospital, Leeds. PARTICIPANTS: One hundred and ninety-six women with singleton pregnancies at high risk of IUGR, delivered between October 1992 and August 1993. MAIN OUTCOME MEASURES: Postnatal catch-up growth during the first seven months. RESULTS: Forty-six of the 196 infants demonstrated catch-up growth and were therefore classified as growth retarded; 85% of this group had had abnormal Doppler results prior to delivery, compared with 14% of the normally grown group. However, there is considerable overlap in birthweight ratio distribution between the two groups. CONCLUSION: This study confirms the existence of a population of IUGR infants of average birthweight ratio. Doppler appears to distinguish IUGR (as defined by catch-up growth) from normal growth more successfully in infants with an average birthweight ratio than in infants with a low birthweight ratio and is a better predictor of IUGR than SGA.

Adult↗
PubMed1996

Imaging inflammatory diseases with neutrophil-specific technetium-99m-labeled monoclonal antibody anti-SSEA-1.

UNLABELLED: Imaging inflammatory diseases with a 99mTc-labeled neutrophil-specific agent that can be injected directly intravenously continues to be a challenge. METHODS: The antibody, anti-SSEA-1, chosen from studies of 10 neutrophil-specific MAbs, recognizes CD-15 antigens (5.1 x 10(5)/human PMN) with a high association constant (kd = 10(-11) M). One hundred micrograms of MAb labeled with 10-20 mCi 99mTc either by a direct or DTPA conjugation method were injected intravenously into 12 patients (9 men, 3 women, aged 19-48 yr) with clinical evidence of ongoing inflammatory processes. Vital signs of all patients were recorded before and up to 3 hr following administration of the MAb. HAMA was determined in two patients. Anterior and posterior spot views and whole-body images were obtained. All patients except one underwent biopsy, US or CT examinations and/or surgical procedures. Blood samples collected from five patients were analyzed. In nine patients, quantitative organ distribution was determined and radiation dosimetry was calculated. RESULTS: Labeling yields were 94.8% +/- 1.4% and 95.8% +/- 3.5%, respectively. All patients had unequivocally positive images within 3 hr of the MAb injection. Eleven of these were confirmed by other modalities. One patient recovered on antibiotics and was sent home without surgery or other procedures. The lack of radioactivity in the thyroid or gastrointestinal tract indicated that the in vivo stability of the agent was excellent. At 3 hr postinjection, bladder activity in six patients was 1.3% +/- 0.4% of the administered dose. At this time, splenic uptake (7.7% +/- 1.0% ad. dose) and red marrow uptake (14 +/- 1.8%) were lower than those of 111In-WBC. At 49.0% +/- 3.2% administrated dose, liver uptake was at the upper limit with 111In-WBC uptake. Renal uptake was only 2.4% +/- 0.03% administered dose. At 2 hr postinjection, 14% to 51% of the radioactivity was associated with PMN. Radioactivity with lymphocytes was 0.7% to 10.9%, 1.2% to 4.3% with platelets and 1.1% to 2.4% with RBC. No HAMA were detectable in either patient, and no adverse reaction was detectable in any patient. CONCLUSION: Results are highly encouaging and have prompted us to prepare a kit for instant preparation and to initiate clinical trials.

Abscess↗
PubMed1996

In search of effective programs to address students' emotional distress and behavioral problems part III: student assessment of school-based support groups.

Emotional distress and behavioral problems are common in high schools. This report describes the efficacy of an in-school program based on participation in volunteer-facilitated peer support groups in addressing these problems. Two hundred and fifty students who experienced such problems participated in weekly 50-minute peer support groups led by adult nonmental health professional volunteers. The students anonymously evaluated their progress and program acceptability using an instrument developed specifically to evaluate the group experience. Analysis of the evaluation of the 131 respondents documented the reliability of a proposed Self-Assessment Questionnaire which showed that participation led to improvement in school, interpersonal, and internal domains. The program was highly accepted and showed other signs of success: half of the alcohol and substance users reduced their intake, and 60% of those who considered dropping out of school continued their education. The results provide preliminary evidence that peer support groups show promise as an economical and well-accepted method for early recognition and management of emotional and behavioral problems in high schools. For some adolescents, these groups may be the only acceptable or available therapeutic modality.

Adolescent↗
PubMed1995

Clinical significance of fetal choroid plexus cysts.

Choroid plexus (CP) cysts are commonly detected on routine mid-trimester ultrasound scan. When associated anomalies are detected, the risk is sufficient to justify an invasive diagnostic test such as amniocentesis. However, the risk when no associated anomalies are detected is much less well defined. This information is required to determine the appropriate management in cases of apparently isolated CP cysts. We thought the only way to resolve the difficulties in counselling prospective parents was to conduct a prospective study in a large unselected population. A registry of fetal CP cysts detected over 3 years in the Yorkshire Region was compiled and we identified 524 CP cysts. These cases were then amalgamated and analysed with 1361 cases from prospective studies reported in the world English literature and a further 71 unpublished cases identified from a 2 year prospective series from Ninewells Hospital, Dundee. The risk of chromosomal abnormalities was 1 in 150 (95% CI 1 in 85, 1 in 261) when no fetal anatomic abnormalities, apart from the CP cysts themselves, were detected antenatally. The risk increased to approximately 1 in 3 if any other associated ultrasound abnormalities were detected antenatally. The risk did not appear to be related to whether or not cyst size diminished as gestation progresses, whether they were unilateral or bilateral, and whether they were small or large in size (60-80% < 10 mm). 76% of aneuploidic cases were trisomy 18 and 17% were trisomy 21. The risk of Down's syndrome in fetuses with CP cysts but no other anomalies detected antenatally is 1 in 880. The probability of a chromosomal abnormality is high when CP cysts are associated with any other antenatally detected anomaly, indicating a clear need to offering amniocentesis. The predictive value is much lower when no other anomalies are detected. In such cases, it is probably advisable to regard CP cysts as an indication for detailed ultrasound assessment, rather than invasive testing.

Brain Diseases↗