Fracture and compaction of andesite in a volcanic edifice.

The failure mode of lava-dilatant or compactant-depends on the physical attributes of the lava, primarily the porosity and pore size, and the conditions under which it deforms. The failure mode for edifice host rock has attendant implications for the structural stability of the edifice and the efficiency of the sidewall outgassing of the volcanic conduit. In this contribution, we present a systematic experimental study on the failure mode of edifice-forming andesitic rocks (porosity from 7 to 25 %) from Volcán de Colima, Mexico. The experiments show that, at shallow depths (<1 km), both low- and high-porosity lavas dilate and fail by shear fracturing. However, deeper in the edifice (>1 km), while low-porosity (<10 %) lava remains dilatant, the failure of high-porosity lava is compactant and driven by cataclastic pore collapse. Although inelastic compaction is typically characterised by the absence of strain localisation, we observe compactive localisation features in our porous andesite lavas manifest as subplanar surfaces of collapsed pores. In terms of volcano stability, faulting in the upper edifice could destabilise the volcano, leading to an increased risk of flank or large-scale dome collapse, while compactant deformation deeper in the edifice may emerge as a viable mechanism driving volcano subsidence, spreading and destabilisation. The failure mode influences the evolution of rock physical properties: permeability measurements demonstrate that a throughgoing tensile fracture increases sample permeability (i.e. equivalent permeability) by about a factor of two, and that inelastic compaction to an axial strain of 4.5 % reduces sample permeability by an order of magnitude. The implication of these data is that sidewall outgassing may therefore be efficient in the shallow edifice, where rock can fracture, but may be impeded deeper in the edifice due to compaction. The explosive potential of a volcano may therefore be subject to increase over time if the progressive compaction and permeability reduction in the lower edifice cannot be offset by the formation of permeable fracture pathways in the upper edifice. The mode of failure of the edifice host rock is therefore likely to be an important factor controlling lateral outgassing and thus eruption style (effusive versus explosive) at stratovolcanoes.

Maternal and umbilical cord erythrocyte omega-3 and omega-6 fatty acids and haemorheology in singleton and twin pregnancies.

BACKGROUND: Being devoid of both nuclei and mitochondria, mature human erythrocytes provide an opportunity to study membrane structure and function outwith the restrictions of genetic control. With its unique rapid increase in vascularisation, pregnancy is considered the most opportune period in which to investigate blood rheology. METHODS: Maternal and fetal (cord) bloods were retained at delivery from 32 (25 singleton and seven twin) normal pregnancies at two maternity hospitals in the Glasgow area over a nine month period. Erythrocyte fatty acid compositions were assessed by mass spectroscopy, and corresponding membrane deformabilities measured by ultrafiltration through a membrane of 5 micro m diameter pore size, to mimic placental microcirculation. RESULTS: Significant direct correlations (Spearman rank) were found between erythrocyte membrane omega-3 docosahexaenoic acid concentrations and corresponding deformabilities in maternal and cord blood from both singleton and twin pregnancies, whereas greater omega-6 arachidonic acid content was associated with increased maternal membrane rigidity. Membrane concentrations of omega-3 fatty acids only correlated strongly both within and between maternal and cord bloods. Mean cord erythrocyte docosahexaenoic acid concentration was higher than maternal in singletons but lower in twins. When maternal erythrocyte concentrations exceeded about 7% (of total fatty acids), resistance to erythrocyte flow was virtually eliminated. CONCLUSIONS: It may be that a greater maternal intake of docosahexaenoic acid should be encouraged in some pregnancies for optimal tissue perfusion. Fetal demand for docosahexaenoic acid may not be entirely satisfied in multiple pregnancies.

Capacity building for health promotion and chronic disease prevention--Nova Scotia's experience.

The purpose of this paper is to report on the capacity building efforts that took place during the dissemination research phase of Heart Health Nova Scotia (HHNS). HHNS, a health promotion research team, is funded by Health Canada and the Nova Scotia Department of Health. It is located in Halifax, Nova Scotia, a province of 937,000 people situated on the east coast of Canada. It has been a member of the Canadian Heart Health Initiative since its inception in 1989. The first phase of the program, Demonstration, was successfully completed in December 1995 (Heart Health Nova Scotia, 1995). In 1996, HHNS entered its second phase, Dissemination Research, which was conducted between April 1996 and March 2001 in the Western Health Region of Nova Scotia. This was completed in collaboration with organizations, community groups, and government agencies who joined HHNS to form the Heart Health Partnership (HHP) (Heart Health Nova Scotia, 2001). The main aim of this phase of the initiative was to build and research organizational capacity for health promotion and chronic disease prevention.

Infant cerebellar gray and white matter fatty acids in relation to age and diet.

There is little evidence as to the fatty acid composition of the cerebellum in infancy and it remains uncertain whether milk diet can influence its composition. We therefore examined cerebellar gray and white matter of infants less than 6 month old who had died unexpectedly. The fatty acid content of 33 gray and 21 white matter specimens from infants born at term and 6 gray and 5 white matter specimens from preterm infants was assessed by gas chromatographic/mass spectrometric analysis. Infants were grouped according to whether they had received human or manufactured formula milk. Whereas cerebellar cortex docosahexaenoic acid (DHA, 22:6n-3) concentrations were significantly lower (P<0.01) in the formula-fed than breast-fed infants, no differences existed between the term (n = 10) and preterm (n = 5) Synthetic Milk Adapted [corrected] (SMA) formula-fed infants. Cerebellar white matter DHA concentrations were similarly lower (P<0.01) in the SMA formula-fed infants (n = 8) than in an age-matched breast-fed group. Low concentrations of cerebellar white matter lignoceric (24:0) and nervonic acid (24:1n-9) in two 7-wk-old preterm infants appeared to correlate with postgestational rather than chronological age. Dietary long-chain polyunsaturated fatty acids, particularly DHA, are probably essential for normal development of the infant cerebellum.

Infant growth and aorta total lipid fatty acids.

Abnormal fetal and infant growth have increasingly been correlated with adult onset cardiovascular disease. To date, there is little known about the lipid fatty acid profiles in infant cardiovascular tissue. Therefore, we analysed total lipid fatty acids from thoracic and abdominal aorta intima and media from 24 normally grown sudden infant death syndrome cases. Aorta from small for gestational age (n = 2), failure to thrive from birth (n = 3), and premature (n = 1) infants were also examined. Dihomo-gamma-linolenic acid (C20:3n-6) and oleic acid (C18:1n-9) concentrations were significantly lower in the thoracic than in the abdominal aorta. Similar dietary related differences were found in the subgroup (n = 15) of infants fed on formula milks. Both abdominal and thoracic intimal arachidonic (C20:4n-6) to dihomo-gamma-linolenic acid ratios were greater in the infants with retarded growth after birth than in their normally grown counterparts. Growth restriction in infancy might disrupt the normal accretion of vascular endothelial polyunsaturated fatty acids.

Coder gender and potential for hostility ratings.

This study examined the effects of coder gender on Potential for Hostility ratings. Six trained coders (3 men and 3 women) who were unaware of the coder gender effect hypothesis coded 30 male and 30 female undergraduates for Potential for Hostility. Although reliability estimates as calculated by Cronbach's alpha suggested that all coders were consistent, an analysis of variance revealed a significant main effect for coder gender, wherein female coders rated participants as displaying significantly less Potential for Hostility than did male coders. This significant difference was also meaningful, as coder gender accounted for 32% of the variance in Potential for Hostility scores. Thus, future Potential for Hostility investigations need to consider the gender of those coding, as this factor both significantly and substantially influences reported Potential for Hostility ratings.

Age- and dietary-related distributions of hepatic arachidonic and docosahexaenoic acid in early infancy.

A dietary-related deficiency of docosahexaenoic acid [C22:6(n-3)] in infant cerebral cortex has been identified. Absence or very low rates of hepatic synthesis from the essential fatty acid precursor, alpha-linolenic acid [C18:3(n-3)], in early life may have been a contributory factor. We have analyzed liver total lipid fatty acid compositions in 27 term (37-42 wk gestation) and 4 preterm (30-33 wk gestation) infants who died within the first 6 mo of life from sudden infant death syndrome. The infants were fed exclusively either human or formula milks. Formula-fed infants were subdivided into two groups, one receiving SMA milk with an alpha-linolenic acid content at 1.5% of total fatty acids and the other a composite group fed milks with low alpha-linolenic acid concentrations (< 0.1% to 0.4%). The hepatic content of arachidonic acid [C20:4(n-6)] and docosahexaenoic acid was generally lower in both formula-fed groups than in the human milk-fed group. The age-related distributions of docosahexaenoic acid showed that coincident minimum levels were present in both formula groups in the third month of life. This may indicate that the hepatic enzymes involved in the final stage (delta 4-desaturation) conversion of alpha-linolenic acid to docosahexaenoic acid could be inactive in the first months of life. Emphasis must be on provision of preformed dietary docosahexaenoic acid and possibly arachidonic acid as well as their essential fatty acid precursors, to both term and preterm infants for at least the first 16 wk of life.

Effect of diet on the fatty acid composition of the major phospholipids of infant cerebral cortex.

The fatty acid compositions of the major cerebral cortex phospholipids, phosphatidylcholine, phosphatidylethanolamine, and phosphatidylserine were measured in 16 term and one preterm 'cot death' infants fed exclusively either breast milk or one of two formulas. Docosahexaenoic acid (DHA; C22:6n-3) content in cerebral cortex phosphatidylethanolamine and phosphatidylserine of breast fed infants was greater than in both formula groups with significances varying between p < 0.1 and p < 0.001. Compensation for this deficiency in DHA in the formula fed infants was largely achieved by increased incorporation of docosapentaenoic acid (C22:5n-6) in the cerebral cortex of term infants and Mead (C20:3n-9) and dihomo Mead acids (C22:3n-9) in the preterm infant. As the phospholipids most affected are known to perform an important role in membrane function and are possibly integral to neurotransmission it is recommended that breast milk substitute infant formulas should contain n-3 and n-6 series polyunsaturated fatty acids in proportions similar to those of human milk.

Effect of diet on infant subcutaneous tissue triglyceride fatty acids.

Having demonstrated a deficiency in infant cerebral cortex docosahexaenoic acid of formula fed compared with breast milk fed infants, we sought to identify why the extensive subcutaneous tissue triglyceride fatty acid reserves in term new-born infants appeared to be ineffectual in its prevention. In addition to 24 term and six preterm infants who died from 'cot death', tissue was analysed from four perinatal surgical patients and in the former the results were correlated with dietary milk intake. The higher amounts (about 15% by weight) of unsaturated linoleic acid supplied in the formula milks were quantitatively incorporated into the subcutaneous tissue largely at the expense of the saturated palmitic acid possibly compromising adipocyte fluidity. The six preterm infants were in two formula fed groups and there was only one significant difference, namely a higher subcutaneous tissue concentration of alpha-linolenic acid in one of the preterm groups, distinguishing them from their term counterparts. This may imply that the enzymes involved in absorption and digestion of fatty acids are mature in the preterm infant. From birth the mean weight percentage of docosahexaenoic acid (0.4%) fell rapidly to undetectable levels (< 0.05%) in the formula fed group after about two months. It is therefore concluded that if breast feeding is not possible then a minimum daily requirement of 30 mg docosahexaenoic acid (approximately 0.2 g/100 g fatty acids) should be supplied in formulas designed for term infants to prevent the cerebral cortical deficiency of docosahexaenoic acid.

Infant cerebral cortex phospholipid fatty-acid composition and diet.

It has not been established whether nutrition in early infancy affects subsequent neurodevelopment and function. If there is an effect, it seems probable that the essential fatty acids and their metabolites, the major constituents of brain structure, will be the most susceptible to dietary influence. We determined the phospholipid fatty-acid composition of cerebral cortex grey matter obtained from 20 term and 2 preterm infants who had died of "cot deaths" and related results to the milk diet the infants had received. Tissues were analysed by gas chromatography. The mean weight percentage of docosahexaenoic acid was significantly greater (p less than 0.02) in 5 breast-milk-fed infants (9.7%) than in 5 age-comparable formula-milk-fed infants (7.6%). In these formula-fed babies, the overall percentage of long-chain polyunsaturated fatty acids was maintained by increased incorporation of the major n-6 series fatty acids. In 1 formula-fed preterm infant, in whom the lowest concentration of cortical docosahexaenoic acid was found, the compensatory effect was only partial with both n-9 series eicosatrienoic acid or Mead acid and docosatrienoic acid also detected in the phospholipid. Supplementation of formula milks for term infants with docosahexaenoic acid and those for preterm infants with both docosahexaenoic and arachidonic acid could prove beneficial to subsequent neurodevelopment.

Direct gas chromatographic assay of urinary medium-chain fatty acylcarnitines by their thermal decomposition.

We report a gas chromatographic assay for urinary medium-chain acylcarnitines which employs their property of thermal lability, and by circumventing the need for specialised mass spectroscopy is suitable for routine laboratory use. The method produces readily interpreted, uncomplicated chromatograms and has proved to be both sufficiently sensitive and specific to enable detection of octanoylcarnitine in a symptomatic individual with medium-chain CoA dehydrogenase deficiency and in two asymptomatic siblings following administration of a carnitine load.

A new sensitive microassay for the measurement of erythrocyte glycogen.

Conventional ethanol precipitation of sub-microgram amounts of glycogen leads to low yields (less than 50%). Quantitative recoveries of 90% were attained, however, when the isolation temperature was raised to 50 degrees C and ethanol was replaced by the less polar propan-2-ol. This improvement enabled development of an erythrocyte assay for glycogen which was both sensitive (0.1 microgram glycogen) and required only 1 ml of whole blood. 26 paediatric specimens were analysed and a reference range of values from undetected to 78 micrograms glycogen/g haemoglobin (Hb) was obtained.

Combined enzymatic assay of phosphatidylglycerol and phosphatidylcholine in amniotic fluid.

We present here a combined, quantitative enzymatic procedure for determining amniotic fluid phosphatidylglycerol and phosphatidylcholine and relate these findings to the assessment of fetal lung maturity. Under the assay conditions described phospholipase C specifically hydrolyses phosphatidylglycerol (PG) and phosphatidylcholine (PC) but not sphingomyelin, precluding the need for removal of sphingomyelin prior to analysis. Solvent extraction of the phospholipids from the amniotic fluid is, however, employed to avoid spurious elevation of PG and PC results by endogenous glycerol and choline. Of 45 amniocentesis fluids examined, 28 yielded detectable PG concentrations (greater than 0.5 mumol/l) and all but three of these exhibited PC concentrations in excess of 10 mumol/l. One case of respiratory distress occurred in an infant of 29 wk gestation with severe intrauterine growth retardation. Of the remaining 17 fluids in which PG was undetected enzymatically (less than or equal to 0.5 mumol/l), 14 also contained PC concentrations less than or equal to 10 mumol/l and all six cases of true respiratory distress syndrome came from within this sub-group. Strong correlations between the PC concentration and the lecithin:sphingomyelin ratio, r = 0.85 (p less than 0.001) and the PC and PG concentrations, r = 0.96 (p less than 0.001) were also found.

Dietary copper intake in artificially fed infants.

Plasma concentrations of copper and zinc and leucocyte concentrations of zinc were measured in mothers during later pregnancy, at delivery, and 8-10 weeks after birth, and plasma concentrations of copper and zinc were measured in their infants at delivery and 8-10 weeks after birth. The 145 infants were either breast fed or fed one of two milk formulas supplying copper at different concentrations. None of the infants achieved the minimum copper intakes recommended by the World Health Organisation (WHO). At 2 months of age there were no major differences in growth or health detected in infants fed the different copper intakes. Infant birth weight correlated well with the ratio of maternal venous plasma zinc:maternal leucocyte zinc at delivery. Maternal venous plasma copper and zinc concentrations at birth correlated with umbilical venous plasma copper and zinc concentrations. Infants fed the higher copper content formulas had a low mean plasma zinc concentration without a significant increase in the mean plasma copper concentration. The present WHO recommendations regarding minimum copper intakes for infants fed formulas cannot be achieved with currently available formulas and are probably wrong.