Dispersions of alkyl-capped silicon nanocrystals in aqueous media: photoluminescence and ageing.

Alkyl-capped silicon nanocrystals can be dispersed in aqueous media by shaking or stirring their solutions in organic solvents (DMSO, ether, THF) with excess water. THF is the most straightforward choice with which to prepare stable aqueous dispersions, because the nanocrystals are very soluble in THF and it is also miscible with water. As little as 0.01% v/v tetrahydrofuran is sufficient. DMSO and ether were the preferred choices for subsequent staining of live cells because THF shows some acute toxicity even when very dilute. The luminescence intensity of the aqueous dispersions is linear in particle concentration and independent of pH over the range 5-9. The sols retain their photoluminescence and are stable against flocculation for at least 6 months.

Deep data science to prevent and treat growth faltering in Maya children.

The Maya people are descended from the indigenous inhabitants of southern Mexico, Guatemala and adjacent regions of Central America. In Guatemala, 50% of infants and children are stunted (very low height-for-age), and some rural Maya regions have >70% children stunted. A large, longitudinal, intergenerational database was created to (1) provide deep data to prevent and treat somatic growth faltering and impaired neurocognitive development, (2) detect key dependencies and predictive relations between highly complex, time-varying, and interacting biological and cultural variables and (3) identify targeted multifactorial intervention strategies for field testing and validation. Contributions to this database included data from the Universidad del Valle de Guatemala Longitudinal Study of Child and Adolescent Development, child growth and intergenerational studies among the Maya in Mexico and studies about Maya migrants in the United States.

The distinctiveness of ATP:citrate lyase from Aspergillus nidulans.

ATP:citrate lyase (ACL), an important enzyme in lipid synthesis, has been purified from Aspergillus nidulans to a specific activity of 19.6 micromol min(-1) mg(-1), almost twice that of any other purified ACL and shown to be distinct from any previously purified ACL. The enzyme is a 371+/-31 kDa hexamer of 3 alpha, 3 beta proteins, unlike the 4 alpha tetramer found in rats or yeasts. The molecular weights of the alpha and beta protein subunits were determined by SDS-PAGE to be 70 and 55 kDa. ACL in A. nidulans (unlike Aspergillus niger) appears to be regulated by the carbon source present in the media. In crude extracts, it was found at high activity (88 micromol min(-1) mg protein(-1)) in glucose-grown cells but only at low activity (10 micromol min(-1) mg protein(-1)) in acetate-grown cells.

Placental cord drainage after spontaneous vaginal delivery as part of the management of the third stage of labour.

BACKGROUND: Cord drainage in the third stage of labour involves unclamping the previously clamped and separated umbilical cord and allowing the blood from the placenta to drain freely into an appropriate receptacle. Currently there are no systematic reviews of the effects of placental cord drainage on the management of the third stage of labour. OBJECTIVES: The objective of this review was to assess the specific effects of placental cord drainage on the third stage of labour, with or without the prophylactic use of oxytocics. SEARCH STRATEGY: We searched the Cochrane Pregnancy and Childbirth Group Trials register (July 2005), CINAHL (1982 to December 2004) and the National Research Register (December 2004). SELECTION CRITERIA: Randomised trials involving placental cord drainage as a variable within the package of interventions as part of the management of the third stage of labour. DATA COLLECTION AND ANALYSIS: Two review authors independently assessed the quality of trials and extracted data. MAIN RESULTS: Two studies met our inclusion criteria in terms of quality and relevance. Cord drainage could impact the third stage of labour as the results show a statistically significant reduction in the length of third stage of labour (one trial, n = 147, weighted mean difference (minutes) -5.46, 95% confidence interval (CI) -8.02 to -2.90). In the incidence of retained placenta at 30 minutes after birth (one trial, n = 477, relative risk 0.28, 95% CI 0.10 to 0.73) a significant difference was found, but this should be interpreted with caution due to potential intervention bias. AUTHORS' CONCLUSIONS: It is difficult to draw conclusions from such a small number of studies, especially where the review outcomes were presented in a variety of formats. However, there does appear to be some potential benefit from the use of placental cord drainage in terms of reducing the length of the third stage of labour. More research is required to investigate the impact of cord drainage on the management of the third stage of labour.

Identification and disruption of the gene encoding the K(+)-activated acetaldehyde dehydrogenase of Saccharomyces cerevisiae.

The identity of the gene encoding the mitochondrial K(+)-activated acetaldehyde dehydrogenase (K(+)-ACDH) of Saccharomyces cerevisiae has been confirmed. The gene is situated on the right arm of chromosome XV, bears the systematic name YOR374w and the deduced product shows significant homology to other members of the S. cerevisiae aldehyde dehydrogenase (ALDH) family. YOR374w has now been assigned the gene name ALD7. The N-terminal amino acid sequences of K(+)-ACDHs purified from several diverse strains of S. cerevisiae were determined, and found to have 81-100% identity in alignments with the product of ALD7. Haploid mutants containing a deletion of ALD7 were constructed and, in these strains, the K(+)-ACDH was not detectable under any growth conditions examined. The activity of the Mg(2+)-activated acetaldehyde dehydrogenase (Mg(2+)-ACDH), encoded by ALD6, remained at wild-type levels in the mutants. Growth on glucose was not affected in the mutants lacking ALD7 (in contrast to the behaviour of ald6 mutants), whereas growth on ethanol was severely impaired. This observation, together with previous work by our group, shows that both the Mg(2+)- and K(+)-ACDHs are required for growth on ethanol, whilst only the former plays a role during growth on glucose.

Application of chest high-resolution computer tomography in young children with cystic fibrosis.

SUMMARY. High-resolution computed tomography (HRCT) of the chest permits early detection of lung disease; two relevant scoring systems (Bhalla and Nathanson) have been developed to describe CF lung disease. Comparisons between the two scoring systems have not been made, and it is not known which system is more appropriate for young children, i.e., the age group where other objective markers are scarce. We reviewed the clinical findings, pulmonary function data, and HRCT of 16 children aged less than 12 years. The Bhalla scoring system had a better correlation with FEV(1) (r = -0.65, P = 0.012) than the Nathanson score (r = 0.53, P = 0.05). All children had bronchiectasis, including 5 with normal pulmonary function tests. The lower lobes were universally involved, and 5 children did not have any upper lobe disease. Four of these 5 children were aged less than 7 years. We conclude that the Bhalla scoring system is more applicable to young children than is the Nathanson system. Also, in this group of young children with CF, lower lobes are more commonly involved than upper lobes, which is in contrast to the classical teaching that CF lung disease begins in the upper lobes.

Conformational changes and activation of yeast aldehyde dehydrogenase by various agents.

Activity assays are characterised by a slow activation phase lasting 1-2 min which arises from the conversion of the low activity/inactive form of the isolated yeast aldehyde dehydrogenase into a high activity form upon binding NADP(+). When Mg(2+) is present as an activator, the binding of coenzyme is relatively strong and activation is effectively complete when the steady-state rates are measured. Lineweaver-Burk plots with 1/[NADP(+)] as variable are linear. In the absence of Mg(2+), coenzyme binding is relatively weak and the conversion of inactive to active enzyme is not complete when steady-state rates are measured. The balance of equilibrium is now finely balanced and the degree of activation depends on the NADP(+) concentration. Under these conditions, rate versus [NADP(+)] plots are sigmoid, characterised by a Hill coefficient of 1.8 because the active (as opposed to the total) enzyme concentration is different in assays with different [NADP(+)]. Kinetic studies indicate that the activation process involves two steps, but the data do not allow discrimination between alternative mechanisms. Gel filtration and sedimentation equilibrium centrifugation indicate that the activation process does not involve enzyme association-dissociation. Activation of the enzyme can also be achieved by replacing Mg(2+) by small amounts of protamine sulphate, poly-L-lysine or poly-L-arginine. The mechanism for these activations is unknown, but presumably involves the binding of the enzyme to these positively charged molecules.

The activity of yeast ADH I and ADH II with long-chain alcohols and diols.

The activities of yeast ADH I and ADH II towards long chain alcohols and diols were studied using rather unusual conditions (1.0 M Tris pH 8.75, approximately 0.3 mg/ml enzyme and [S]<<

Knee tumours--duration and nature of symptoms prior to investigation.

The incidence of most musculoskeletal neoplasms is highest around the knee. Royal College of Radiologists Guidelines for diagnostic imaging state that plain radiographs are not routinely indicated for knee pain without restriction of movement or symptoms of locking. The notes of 19 patients with knee tumours presenting over a 5 year period were analysed. Irrespective of age or the grade of malignancy the majority of patients had symptoms for around 6 months prior to the initial radiograph. Only four patients had symptoms which would have merited radiological investigation under the present Guidelines. Even in these patients the symptoms prior to either pathological fracture or locking would not have come under the Guidelines. There is a case for regarding persistent, unilateral knee pain for longer than 6 weeks as an indication for imaging.

Multifocal skeletal tuberculosis: bone scan appearances.

Bone scans are not generally required in the investigation of tuberculosis. The most common reason for the request is bone pain, which may precede the diagnosis of tuberculosis. The finding of multifocal areas of increased uptake on a bone scan may be due to a number of causes, the most common of which is metastatic bone disease. Therefore, there is a risk that those caused by tuberculosis may be misdiagnosed. We report six such bone scans occurring over 5 years which were found to be due to skeletal tuberculosis. Five patients were of Asian descent, four of whom had had bone biopsies confirming the presence of mycobacterium tuberculosis. The sixth patient, a Caucasian, had a bone biopsy which isolated mycobacterium bovis. Although skeletal tuberculosis is generally secondary to a primary pulmonary focus, all six patients had a normal chest X-ray.

Potential independent factors of variability of biological status and reproductive history of Yucatecan women.

In this paper, we report the results of the application of principal component analysis (PCA) in a study of the human ecology of rural-to-urban migrantion in Yucatan, Mexico. Socioeconomic, reproductive and anthropometric data from 216 women 32 years of age or older, were obtained in 1989-1990. Seventeen socioeconomic, demographic and environmental properties of the families of such women, plus migrant status, were employed in a PCA, which yielded five independent factors, explaining 57.1% of the total variance of such properties. These factors were employed to made a multiple regression analysis on 19 anthropometric and 21 reproductive traits, age adjusted. According to the multiple regression of women's biological status to independent factors, we found that in better living conditions (Factor 3), women are heavier, taller, with more body surface and subcutaneous fat in the trunk and in the upper extremity, than in worse living conditions. Better educational level of wife and husband (Factor 2) is associated with lower number of pregnancies and alive born children, as well as less reproductive losses. Women living in families with higher income (Factor 4), have a younger age at the first pregnancy, older age at the last pregnancy, greater number of pregnancies, alive born children and alive offspring at the interview, and they experience less reproductive losses in relation to the number of pregnancies. This fact suggests that for the families in this sample, big families are a strategy to cope with poverty and uncertainty in employment and income. Our results are discussed against the reports in the literature.

Studies on the mechanism of sheep liver cytosolic aldehyde dehydrogenase. The effect of pH on the aldehyde binding reactions and a re-examination of the problem of the site of proton release in the mechanism.

Initial-rate measurements and stopped-flow spectrophotometric experiments over a wide range of pH implicate an enzyme group of pKa approximately 6.6 affecting the aldehyde binding reactions. It is possible, though not proved, that the group involved is the cysteine residue involved in catalysis. Stopped-flow fluorescence studies show that a group of pKa greater than 8.5 facilitates hydrolysis of the NADH-containing acyl-enzyme species. The identity of this group is quite unknown. Studies with 4-nitrobenzaldehyde show that this substrate gives marked substrate inhibition at quite low (less than 20 microM) concentrations. The mechanism of catalysis seems to be the same as for propionaldehyde oxidation. It is argued that proton release occurs with both substrates on hydrolysis of the NADH-containing acyl-enzyme and not before hydride transfer, as has been previously suggested [Bennett, Buckley & Blackwell (1982) Biochemistry 21, 4407-4413].

Studies on the mechanism of sheep liver cytosolic aldehyde dehydrogenase.

The dissociation of the aldehyde dehydrogenase X NADH complex was studied by displacement with NAD+. The association reaction of enzyme and NADH was also studied. These processes are biphasic, as shown by McGibbon, Buckley & Blackwell [(1977) Biochem. J. 165, 455-462], but the details of the dissociation reaction are significantly different from those given by those authors. Spectral and kinetic experiments provide evidence for the formation of abortive complexes of the type enzyme X NADH X aldehyde. Kinetic studies at different wavelengths with transcinnamaldehyde as substrate provide evidence for the formation of an enzyme X NADH X cinnamoyl complex. Hydrolysis of the thioester relieves a severe quenching effect on the fluorescence of enzyme-bound NADH.