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X-ray diffraction measurements of natural talc plus water at combined pressures and temperatures of 0-15 GPa and 23-400 °C reveal the presence of a structural change that could be interpreted as a new high-pressure phase at 4.0 (±0.5) GPa, and raise the possibility that the newly inferred phase transition takes place in cold subducting slabs as a precursor to appearance of the 10 Å phase of talc. [ABSTRACT FROM AUTHOR]

Examines equation of state measurements of chlorite, pyrophyllite and talc. Room temperature compressibility of chlorite; Thermal expansivity of chlorite; Implications of data for phase stabilities in the earth.

Assesses the prevalence of Staphylococcus aureus carriage in consecutive newly referred children with atopic eczema, in their topical preparations and in their parents/carers. Intensity of eczema and extent of skin involvement; Relationship between the previous use of anti-staphylococcal antibiotics and the presence or absence of S. aureus.

The b subunit dimer of the Escherichia coli ATP synthase, along with the delta subunit, is thought to act as a stator to hold the alpha(3)beta(3) hexamer stationary relative to the a subunit as the gammaepsilonc(9-12) complex rotates. Despite their essential nature, the contacts between b and the alpha, beta, and a subunits remain largely undefined. We have introduced cysteine residues individually at various positions within the wild type membrane-bound b subunit, or within b(24-156), a truncated, soluble version consisting only of the hydrophilic C-terminal domain. The introduced cysteine residues were modified with a photoactivatable cross-linking agent, and cross-linking to subunits of the F(1) sector or to complete F(1)F(0) was attempted. Cross-linking in both the full-length and truncated forms of b was obtained at positions 92 (to alpha and beta), and 109 and 110 (to alpha only). Mass spectrometric analysis of peptide fragments derived from the b(24-156)A92C cross-link revealed that cross-linking took place within the region of alpha between Ile-464 and Met-483. This result indicates that the b dimer interacts with the alpha subunit near a non-catalytic alpha/beta interface. A cysteine residue introduced in place of the highly conserved arginine at position 36 of the b subunit could be cross-linked to the a subunit of F(0) in membrane-bound ATP synthase, implying that at least 10 residues of the polar domain of b are adjacent to residues of a. Sites of cross-linking between b(24-156)A92C and beta as well as b(24-156)I109C and alpha are proposed based on the mass spectrometric data, and these sites are discussed in terms of the structure of b and its interactions with the rest of the complex.

Superoxide anion (O2-) plays a key role in the endogenous suppression of endothelium-derived nitric oxide (NO) bioactivity and has been implicated in the development of hypertension. In previous studies, we found that O2- is produced predominantly in the adventitia of isolated rabbit aorta and acts as a barrier to NO. In the present studies, we characterize the enzyme responsible for O2- production in the adventitia and show that this enzyme is a constitutively active NADPH oxidase with similar composition as the phagocyte NADPH oxidase. Constitutive O2--generating activity was localized to aortic adventitial fibroblasts and was enhanced by the potent vasoconstrictor angiotensin II. Immunohistochemistry of aortic sections demonstrated the presence of p22(phox), gp91(phox), p47(phox), and p67(phox) localized exclusively in rabbit aortic adventitia, coincident with the site of staining for O2- production. Furthermore, immunodepletion of p67(phox) from adventitial fibroblast particulates resulted in the loss of NADPH oxidase activity, which could be restored by the addition of recombinant p67(phox). Further study into the regulation of this adventitial source of O2- is important in elucidating the mechanisms regulating the bioactivity of NO and may contribute to our understanding of the pathogenesis of hypertension.

Prenatal correction of certain cardiac lesions with a poor prognosis may have advantages over postnatal repair. For this to be done, safe and effective support of the fetal circulation must be devised. Studies involving fetal cardiac bypass have demonstrated progressive fetal hypoxemia, hypercapnia, and acidosis, indicating placental dysfunction. We performed fetal cardiac bypass in 18 fetal lambs (126 to 140 days' gestation) to assess the effect of flow rate on fetal oxygenation and metabolism and function of the placenta as an in vivo oxygenator. Fetal cardiac bypass was done for a 30-minute study period at normothermia in all fetuses. During the study period the fetal aorta was cross-clamped and cold cardioplegia was administered to the heart so there was no fetal cardiac contribution to systemic output. Nine fetuses underwent studies at low flow rates (109 +/- 20 mL.kg-1.min-1) and 9 at higher flow rates (324 +/- 93 mL.kg-1.min-1). At the lower flow rate, mean aortic pressure, arterial pH, and oxygen tension decreased whereas carbon dioxide tension and lactate levels increased when compared with prebypass levels. At the higher flow rate mean aortic pressure, pH, oxygen tension, carbon dioxide tension, and lactate levels remained similar to prebypass levels during the 30-minute study period. When the animals were weaned from the bypass circuit after studies at high flow rates, arterial oxygen tension and pH decreased whereas carbon dioxide tension increased to levels similar to those in the low-flow group.(ABSTRACT TRUNCATED AT 250 WORDS)

The past few years have seen a tremendous renaissance in biological optical microscopy, mainly as a result of the application of digital image processing and video imaging techniques. We review recent developments in microscopy that are permitting unprecedented views of biological structure and function.

The standard treatment of innominate artery compression of the trachea has been innominate artery suspension, but the syndrome can recur when this technique is used. From October 1985 until March 1991, 29 infants and children were treated for this syndrome by innominate artery reimplantation. In all patients severe anterior vascular compression of the trachea was demonstrated preoperatively by bronchoscopy and in 17 the diagnosis was confirmed by magnetic resonance imaging scanning. Indications for operation included apneic episodes in 17 (58.6%), severe stridor in seven (24.1%), recurrent bronchopulmonary infections in four (13.8%), and exercise-induced stridor in one (3.4%). Through a median sternotomy, the innominate artery was reimplanted more proximally on the ascending aorta and to the right of the trachea. In this new position, the innominate artery no longer crosses the trachea anteriorly, and the anatomic cause of tracheal obstruction is completely eliminated. There were no early or late deaths, and 27 of the 29 patients (93%) had complete resolution of symptoms. Partial resolution of symptoms was seen in two patients (7%). Reimplantation of the innominate artery offers a unique method by which the anatomic cause of tracheal compression is eliminated. It is a safe and effective means of treating symptomatic compression of the trachea by the innominate artery.

A new instrument has been developed for the electrophoretic separation of large DNA molecules that can independently regulate the voltage of each of 24 electrodes and allow the magnitude, orientation, homogeneity, and duration of the electric field to be precisely controlled. Each parameter can be varied at any time during the electrophoretic process. Thus distinct sets of conditions can be combined to optimize the separation of various fragment sizes in a single run. Independent control of electrode voltage allows all of the fields to be generated with electrodes arranged in a closed contour, independent of a particular geometry. This device increases both the resolution in any size range and the speed of separation, especially for DNA molecules larger than 3 megabases.

Quantitative measurement of DNA migration in gel electrophoresis requires precisely controlled homogeneous electric fields. A new electrophoresis system has allowed us to explore several parameters governing DNA migration during homogeneous field pulsed field gel (PFG) electrophoresis. Migration was measured at different switch times, temperatures, agarose concentrations, and voltage gradients. Conditions which increase DNA velocities permit separation over a wider size range, but reduce resolution. We have also varied the angle between the alternating electric fields. Reorientation angles between 105 degrees and 165 degrees give equivalent resolution, despite significant differences in DNA velocity. Separation of DNA fragments from 50 to greater than 7000 kilobases (Kb) can easily be optimized for speed and resolution based on conditions we describe.