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Biomedical subjects

R Watson

Publications and source records attributed to R Watson.

At least 55 records · Page 3Linked to original sources
PubMed2001

Kinetics of fetal cellular and cell-free DNA in the maternal circulation during and after pregnancy: implications for noninvasive prenatal diagnosis.

BACKGROUND: Fetal genetic material is detectable in the maternal circulation and has been used for noninvasive prenatal diagnosis. However, few data are available concerning its quantity and natural history during gestation. STUDY DESIGN AND METHODS: This study prospectively characterized the kinetics of cellular and cell-free fetal DNA in the circulation of 25 healthy women during and after uncomplicated pregnancy. Real-time kinetic PCR was used to quantitate human Y-chromosome sequences, and liquid oligomer hybridization with (32)P-labeled probes was used to verify the identity of amplified products. RESULTS: In all male pregnancies, but no female pregnancies, low-level fetal Y-chromosome DNA was detected in both cellular and cell-free compartments beginning at 7 to 16 weeks but increasing steadily after 24 weeks and reaching a peak at parturition. The fetal DNA decreased rapidly after birth. CONCLUSION: Fetal genetic material can be detected throughout pregnancy, and its quantity is a function of gestational age and of whether the plasma or cellular compartment is examined. Both the absolute quantity of fetal DNA and its ratio to total DNA (maternal + fetal) are greater in the plasma than in the cellular compartment. Fetal DNA is cleared rapidly from both compartments after parturition, which suggests that turnover is dynamic. Because they provide prospective and quantitative data concerning fetal DNA levels, these observations and kinetic PCR methods may have implications for noninvasive prenatal diagnosis. Further studies will be needed to determine the immunologic implications of fetal-maternal DNA exchange and cellular microchimerism.

Adult↗
PubMed2001

Putting portfolios in their place.

This paper discusses the use of portfolios in nursing education and sets this in an international context. It argues that the assessment of clinical competence in the practice setting is inherently problematic, as recognized in certain recent policy documents, and evaluates the role that portfolios can play. A number of theoretical approaches to the definition and use of portfolios are discussed, and particular attention is paid to their reliability and validity as assessment tools. The paper concludes by arguing that there is a need for further research into the credibility, reliability and validity of this approach to the assessment of nurses' competence.

Clinical Competence↗
PubMed2001

Direct measurement of sodium and potassium in the transpiration stream of salt-excluding and non-excluding varieties of wheat.

The xylem-feeding insect Philaenus spumarius was used to analyse sodium and potassium fluxes in the xylem of intact, transpiring wheat plants. Two cultivars were compared: the salt-excluding (Chinese Spring) and the non-excluding (Langdon). Chinese Spring accumulated much less sodium in its leaves than the salt-sensitive Langdon. After 7 d in 150 mol m(-3) NaCl, the sodium concentration in the leaf sap of Langdon reached over 600 mol m(-3). This was some three-fold greater than that in Chinese Spring. Similar findings have previously been reported from these cultivars. The reduced ion accumulation was specific to sodium; accumulation of K(+) was unaffected by NaCl in Chinese Spring, such that it developed a much lower leaf Na(+)/K(+) ratio than Langdon. The spittlebug, P. spumarius was used to sample xylem sap from both cultivars. This approach showed that the leaf xylem sap of Chinese Spring had much lower levels of sodium than that of Langdon. In the 150 mol m(-3) NaCl treatment, sodium levels in the leaf xylem reached only 2-3 mol m(-3) in Chinese Spring, compared with 8-10 mol m(-3) in Langdon. Transpiration rates were found to be similar in the two varieties. The lower leaf xylem content alone was thus sufficient to account for the reduced accumulation of sodium in leaves of Chinese Spring. The mechanisms by which xylem sodium might be lowered are discussed and it is concluded that sodium is probably excluded from the xylem in the root of Chinese Spring.

Animals↗
PubMed2001

Nerve blocks versus subcutaneous infiltration for stereotactic frame placement.

In this unblinded, randomized controlled trial, we compared supraorbital and greater occipital nerve blocks with subcutaneous infiltration for anesthesia during the placement of a stereotactic head-frame. Twenty consecutive patients scheduled for functional surgery to treat Parkinson's disease were studied. Each patient received supraorbital and greater occipital nerve blocks on one side of the head and subcutaneous infiltration on the other, thereby acting as their own control. Pain was assessed by visual analog scale pain scores (scale: 0-100) for both local anesthetic injection and stereotactic pin placement. Supplementary subcutaneous infiltration was also recorded. Results are presented as mean +/- SD. Nerve blocks were significantly less painful than subcutaneous infiltration of local anesthetic at both the frontal (34 +/- 24 vs 49 +/- 25) and occipital (34 +/- 21 vs 49 +/- 23) sites. Neither technique was superior in preventing pain associated with pin placement, at either the frontal site (48 +/- 27 vs 46 +/- 24) or occipital site (33 +/- 27 vs 32 +/- 24). Supraorbital nerve blocks required significantly more supplementation than either greater occipital nerve blocks or subcutaneous infiltration. Visual analog scale pain scores were greater at local anesthetic injection and pin placement than at any subsequent time. We conclude that supraorbital and greater occipital nerve blocks are an alternative to subcutaneous infiltration for the placement of a stereotactic frame.

Administration, Cutaneous↗
PubMed2001

The contact lens and myopia progression (CLAMP) study: design and baseline data.

BACKGROUND: Although previous contact lens myopia control studies indicate that rigid contact lenses slow the progression of myopia in children, they have all suffered from limitations that challenge the significance of their results. The Contact Lens and Myopia Progression (CLAMP) Study addresses the limitations of previous studies and attempts to correct them by implementing alternative Study designs. The CLAMP study also measures all the ocular components to examine the potential mechanism of treatment effect. METHODS: Eligible children were fitted with rigid gas-permeable contact lenses and enrolled in a run-in period to determine whether they were able to adapt to rigid contact lens wear. Subjects who successfully completed the run-in period were randomly assigned to wear rigid contact lenses or soft contact lenses for the remainder of the 3-year study. The primary outcome measure will be the 3-year change in cycloplegic autorefraction; the secondary outcome measures will include the 3-year change in axial length, peripheral autorefraction, crystalline lens curvatures, corneal curvature and thickness, accommodation, and intraocular pressure, which are being measured annually. RESULTS: We examined 148 eligible subjects who participated in the run-in period. Of the 148 eligible subjects, 116 (78.4%) were able to adapt to rigid contact lens wear and were enrolled in the CLAMP Study. The mean age of the participants at the baseline visit was 10.5 years, and 59.5% were girls. At the randomization visit, the mean (+/-SD) spherical equivalent refractive error in the right eye was -2.09 +/- 0.89 D, the mean central curvature of the right cornea by videokeratography was 44.5 +/- 1.3 D, and the mean axial length of the right eye was 24.13 +/- 0.71 mm. CONCLUSIONS: Four of five children aged 8- to 11-years-old were able to adapt to rigid gas-permeable contact lens wear. The CLAMP Study aims to further clarify the effect of rigid gas-permeable contact lenses on myopia progression in children.

Astigmatism↗
PubMed2000

Isolation and characterization of the human A-myb promoter: regulation by NF-Y and Sp1.

The A-myb transcription factor shows a restricted tissue distribution and is cell cycle regulated. Furthermore its deregulation has profound effects on the growth and/or differentiation of the cells in which it is normally expressed. We have therefore characterized its promoter. A 12 kb genomic clone was isolated that comprises the first exon, part of the first intron as well as upstream regulatory sequences. Multiple transcription start sites have been identified which operate in both B lymphocytes and epithelial cells and the upsteam region was shown to have promoter, activity. The boundaries of the minimal promoter region (-183-14), of a positive upstream (-538-183) and a negative downstream regulatory region (NRE) (+83+374) have been defined. The NRE is promoter- and orientation-independent but position specific. The A-myb minimal promoter is GC-rich, does not contain any TATA box but has a functional CCAAT box. The CCAAT box and minimal promoter is highly conserved in the corresponding murine sequence. The CCAAT box efficiently binds the NF-Y complex and its mutation decreases basal promoter activity by 50%. Two Sp1 binding sites are present upstream from the CCAAT box which can bind Spl and contribute to A-myb promoter activity by 70 and 30%, respectively. The two Sp1 sites and CCAAT box together contribute to over 80% of A-myb basal promoter activity and are therefore the major regulatory elements. Finally, we show that the promoter is cell cycle regulated and that the SP1 and CCAAT elements are required for S phase induction.

Animals↗