Nonlinear lattice dynamics as a basis for enhanced superconductivity in YBa2Cu3O6.5.

Terahertz-frequency optical pulses can resonantly drive selected vibrational modes in solids and deform their crystal structures. In complex oxides, this method has been used to melt electronic order, drive insulator-to-metal transitions and induce superconductivity. Strikingly, coherent interlayer transport strongly reminiscent of superconductivity can be transiently induced up to room temperature (300 kelvin) in YBa2Cu3O6+x (refs 9, 10). Here we report the crystal structure of this exotic non-equilibrium state, determined by femtosecond X-ray diffraction and ab initio density functional theory calculations. We find that nonlinear lattice excitation in normal-state YBa2Cu3O6+x at above the transition temperature of 52 kelvin causes a simultaneous increase and decrease in the Cu-O2 intra-bilayer and, respectively, inter-bilayer distances, accompanied by anisotropic changes in the in-plane O-Cu-O bond buckling. Density functional theory calculations indicate that these motions cause drastic changes in the electronic structure. Among these, the enhancement in the character of the in-plane electronic structure is likely to favour superconductivity.

Nonlinear Ultrafast Spin Scattering in the Skyrmion Phase of Cu_{2}OSeO_{3}.

Ultrafast x-ray scattering studies of the topological Skyrmion phase in Cu_{2}OSeO_{3} show the dynamics to be strongly dependent on the excitation energy and fluence. At high photon energies, where the electron-spin scattering cross section is relatively high, the excitation of the topological Skyrmion phase shows a nonlinear dependence on the excitation fluence, in contrast to the excitation of the conical phase which is linearly dependent on the excitation fluence. The excitation of the Skyrmion order parameter is nonlinear in the magnetic excitation resulting from scattering during electron-hole recombination, indicating different dominant scattering processes in the conical and Skyrmion phases.

The effect of antenatal lifestyle advice for women who are overweight or obese on secondary measures of neonatal body composition: the LIMIT randomised trial.

OBJECTIVE: To evaluate the effect of providing antenatal dietary and lifestyle advice on neonatal anthropometry, and to determine the inter-observer variability in obtaining anthropometric measurements. DESIGN: Randomised controlled trial. SETTING: Public maternity hospitals across metropolitan Adelaide, South Australia. POPULATION: Pregnant women with a singleton gestation between 10(+0) and 20(+0) weeks, and body mass index (BMI) ≥25 kg/m(2). METHODS: Women were randomised to either Lifestyle Advice (comprehensive dietary and lifestyle intervention over the course of pregnancy including dietary, exercise and behavioural strategies, delivered by a research dietician and research assistants) or continued Standard Care. Analyses were conducted using intention-to-treat principles. MAIN OUTCOME MEASURES: Secondary outcome measures for the trial included assessment of infant body composition using body circumference and skinfold thickness measurements (SFTM), percentage body fat, and bio-impedance analysis of fat-free mass. RESULTS: Anthropometric measurements were obtained from 970 neonates (488 Lifestyle Advice Group, and 482 Standard Care Group). In 394 of these neonates (215 Lifestyle Advice Group, and 179 Standard Care Group) bio-impedance analysis was also obtained. There were no statistically significant differences identified between those neonates born to women receiving Lifestyle Advice and those receiving Standard Care, in terms of body circumference measures, SFTM, percentage body fat, fat mass, or fat-free mass. The intra-class correlation coefficient for SFTM was moderate to excellent (0.55-0.88). CONCLUSIONS: Among neonates born to women who are overweight or obese, anthropometric measures of body composition were not modified by an antenatal dietary and lifestyle intervention.

Imaging Molecular Motion: Femtosecond X-Ray Scattering of an Electrocyclic Chemical Reaction.

Structural rearrangements within single molecules occur on ultrafast time scales. Many aspects of molecular dynamics, such as the energy flow through excited states, have been studied using spectroscopic techniques, yet the goal to watch molecules evolve their geometrical structure in real time remains challenging. By mapping nuclear motions using femtosecond x-ray pulses, we have created real-space representations of the evolving dynamics during a well-known chemical reaction and show a series of time-sorted structural snapshots produced by ultrafast time-resolved hard x-ray scattering. A computational analysis optimally matches the series of scattering patterns produced by the x rays to a multitude of potential reaction paths. In so doing, we have made a critical step toward the goal of viewing chemical reactions on femtosecond time scales, opening a new direction in studies of ultrafast chemical reactions in the gas phase.

Real-time manifestation of strongly coupled spin and charge order parameters in stripe-ordered La(1.75)Sr(0.25)NiO(4) nickelate crystals using time-resolved resonant x-ray diffraction.

We investigate the order parameter dynamics of the stripe-ordered nickelate, La(1.75)Sr(0.25)NiO(4), using time-resolved resonant x-ray diffraction. In spite of distinct spin and charge energy scales, the two order parameters' amplitude dynamics are found to be linked together due to strong coupling. Additionally, the vector nature of the spin sector introduces a longer reorientation time scale which is absent in the charge sector. These findings demonstrate that the correlation linking the symmetry-broken states does not unbind during the nonequilibrium process, and the time scales are not necessarily associated with the characteristic energy scales of individual degrees of freedom.

Hypnosis antenatal training for childbirth: a randomised controlled trial.

OBJECTIVE: To determine the use of pharmacologic analgesia during childbirth when antenatal hypnosis is added to standard care. DESIGN: Randomised controlled clinical trial, conducted from December 2005 to December 2010. SETTING: The largest tertiary referral centre for maternity care in South Australia. POPULATION: A cohort of 448 women at >34 weeks of gestation, with a singleton pregnancy and cephalic presentation, planning a vaginal birth. Exclusions were: the need for an interpreter; pre-existing pain; psychiatric illness; younger than 18 years; and previous experience of hypnosis for childbirth. METHODS: All participants received usual care. The group of women termed Hypnosis + CD (hypnotherapist guided) were offered three antenatal live hypnosis sessions plus each session's corresponding audio CD for further practise, as well as a final fourth CD to listen to during labour. The group of women termed CD only (nurse administered) were played the same antenatal hypnosis CDs as group 1, but did not receive live hypnosis training. The control group participants were given no additional intervention or CDs. MAIN OUTCOME MEASURE: Use of pharmacological analgesia during labour and childbirth. RESULTS: No difference in the use of pharmacological analgesia during labour and childbirth was found comparing hypnosis + CD with control (81.2 versus 76.2%; relative risk, RR 1.07; 95% confidence interval, 95% CI 0.95-1.20), or comparing CD only with control (76.9 versus 76.2%, RR 1.01, 95% CI 0.89-1.15). CONCLUSIONS: Antenatal group hypnosis using the Hypnosis Antenatal Training for Childbirth (HATCh) intervention in late pregnancy does not reduce the use of pharmacological analgesia during labour and childbirth.

Elective birth at 37 weeks of gestation versus standard care for women with an uncomplicated twin pregnancy at term: the Twins Timing of Birth Randomised Trial.

OBJECTIVE: To evaluate whether for women with an uncomplicated twin pregnancy, elective birth at 37 weeks of gestation was associated with reduced risk of death or serious outcomes for babies, without increasing harm. DESIGN: Randomised controlled trial. SETTING: Maternity hospitals across Australia, New Zealand and Italy. POPULATION: A total of 235 women with an uncomplicated twin pregnancy at 36(+6) weeks of gestation, with no contraindication to continuing their pregnancy. METHODS: Using a computer-generated, central telephone randomisation service, 235 women were randomised to Elective Birth (birth at 37 weeks; n=116) or Standard Care (continued expectant management, with birth planned from 38 weeks; n=119). Outcome assessors were masked to treatment allocation. MAIN OUTCOME MEASURE: A composite of serious adverse outcome for the infant. RESULTS: For women with an uncomplicated twin pregnancy, elective birth at 37 weeks of gestation was associated with a significant reduction in risk of serious adverse outcome for the infant (Elective Birth 11/232 [4.7%] versus Standard Care 29/238 [12.2%]; risk ratio [RR] 0.39; 95% CI 0.20-0.75; P=0.005), reflecting a reduction in birthweight less than the third centile using singleton gestational age-specific charts (Elective Birth 7/232 [3.0%] versus Standard Care 24/238 [10.1%]; RR 0.30; 95% CI 0.13-0.67; P=0.004). In a post hoc analysis using twin gestational age-specific charts, there was evidence of a trend towards a reduction in the primary composite of serious adverse infant outcome (Elective Birth Group 4/232 [1.7%] versus Standard Care Group 12/238 [5.0%]; RR 0.34; 95% CI 0.11 to 1.05; P=0.06). CONCLUSION: The findings of our study support recommendations for women with an uncomplicated twin pregnancy to birth at 37 weeks of gestation.

Antenatal interventions for overweight or obese pregnant women: a systematic review of randomised trials.

BACKGROUND: Overweight and obesity during pregnancy is an increasing health problem. OBJECTIVE: A systematic review to assess the benefits and harms of antenatal dietary or lifestyle interventions for pregnant women who are overweight or obese. SEARCH STRATEGY: The Cochrane Controlled Trials Register(CENTRAL) was searched (last search January 2010). Reference lists of retrieved studies were searched by hand. No date or language restrictions were used. SELECTION CRITERIA: Randomised controlled trials comparing antenatal dietary and/or lifestyle or other interventions with no treatment for overweight or obese women were considered.Studies were evaluated independently for appropriateness for inclusion and methodological quality. The primary outcome was large-for-gestational-age infants. DATA COLLECTION AND ANALYSIS: Nine randomised controlled trials were included involving 743 women who were overweight or obese during pregnancy. Seven trials compared a dietary intervention with standard antenatal care. MAIN RESULTS: There were no statistically significant differences identified between women who received an antenatal intervention and those who did not for the large-for-gestational-age infant outcome (three studies; 366 women; risk ratio 2.02; 95% CI 0.84,4.86) or mean gestational weight gain [four studies; 416 women;weighted mean difference )3.10 kg; 95% CI )8.32, 2.13 (random effects model)]. There were no statistically significant differences identified for other reported outcomes. AUTHOR'S CONCLUSIONS: The effect of providing an antenatal dietary intervention for overweight or obese pregnant women on maternal and infant health outcomes remains unclear.

Organelle assembly in yeast: characterization of yeast mutants defective in vacuolar biogenesis and protein sorting.

Yeast vacuole protein targeting (vpt) mutants exhibit defects in the sorting and processing of multiple vacuolar hydrolases. To evaluate the impact these vpt mutations have on the biogenesis and functioning of the lysosome-like vacuole, we have used light and electron microscopic techniques to analyze the vacuolar morphology in the mutants. These observations have permitted us to assign the vpt mutants to three distinct classes. The class A vpt mutants (26 complementation groups) contain 1-3 large vacuoles that are morphologically indistinguishable from those in the parental strain, suggesting that only a subset of the proteins destined for delivery to this compartment is mislocalized. One class A mutant (vpt13) is very sensitive to low pH and exhibits a defect in vacuole acidification. Consistent with a potential role for vacuolar pH in protein sorting, we found that bafilomycin A1, a specific inhibitor of the vacuolar ATPase, as well as the weak base ammonium acetate and the proton ionophore carbonyl cyanide m-chlorophenylhydrazone, collapse the pH gradient across the vacuolar membrane and cause the missorting and secretion of two vacuolar hydrolases in wild-type cells. Mutants in the three class B vpt complementation groups exhibit a fragmented vacuole morphology. In these mutants, no large normal vacuoles are observed. Instead, many (20-40) smaller vacuole-like organelles accumulate. The class C vpt mutants, which constitute four complementation groups, exhibit extreme defects in vacuole biogenesis. The mutants lack any organelle resembling a normal vacuole but accumulate other organelles including vesicles, multilamellar membrane structures, and Golgi-related structures. Heterozygous class C zygotes reassemble normal vacuoles rapidly, indicating that some of the accumulated aberrant structures may be intermediates in vacuole formation. These class C mutants also exhibit sensitivity to osmotic stress, suggesting an osmoregulatory role for the vacuole. The vpt mutants should provide insights into the normal physiological role of the vacuole, as well as allowing identification of components required for vacuole protein sorting and/or vacuole assembly.

Effect of cold compression on precipitation and conductivity of an Al-Li-Cu alloy.

Transmission electron microscopy has been used to investigate the effect of increasing the degree of deformation applied by cold compression on the ageing kinetics and electrical conductivity response of an Al-Li-Cu alloy containing Mg and Ag. When cold compressed greater than 3%, the increased dislocation density accelerates the widespread precipitation of the T(1) phase resulting in an enhanced age hardening response. The lengthening rate of T(1) precipitates is also reduced in this cold compressed condition owing to the reduced local solute supersaturation, a result of the widespread precipitation of T(1) plates. Cold compression by less than 3% does not increase the age hardening response, and the precipitation of GP zones/theta'' appears to be suppressed. Precipitation of the T(1) phase is also not significantly enhanced compared with that of the more than 3% cold compressed conditions. The anomalous decrease in electrical conductivity is associated with the nucleation and growth of the T(1) phase. Strain fields around T(1) precipitates combined with the increased volume fraction of T(1) are thought to be the cause of the anomalous conductivity behaviour.

Effects of short-term pH fluctuations on cadmium, nickel, lead, and zinc availability to ryegrass in a sewage sludge-amended field.

In this field experiment, sewage sludge was applied at 0, 5, 10, and 50tha(-1), and the availability of Cd, Ni, Pb, and Zn was assessed both by ryegrass uptake and by DTPA extractions. The aim was to investigate the role of important soil parameters, particularly pH, on heavy metal availability. It was found that metal uptake and extractability increased significantly in the 50tha(-1) treatment. In the 16th week of the experiment there was a significant, although temporary, increase in DTPA-extractable Cd, Ni, and Zn concentrations. Metal concentrations in ryegrass were also significantly elevated in week 20 compared to the subsequent cuttings. These fluctuations in both DTPA and ryegrass uptake occurred only at 50tha(-1) and were probably induced by a sudden pH decrease measured in the same treatment in week 16. This suggests that soils which have received high applications of sewage sludge may be prone to fluctuations in metal availability.

The role of intraoperative micro-Doppler ultrasound in verifying proper clip placement in intracranial aneurysm surgery.

We present the results of a retrospective study employing intraoperative micro-Doppler ultrasonography (MDU) in verifying proper clip placement during cerebral aneurysmal surgery. One hundred and thirty-four patients surgically treated for 147 intracranial aneurysms were studied. Thirteen patients harboring 17 aneurysms were surgically treated on an elective basis, while 121 patients with 130 aneurysms, presented with subarachnoid hemorrhage (SAH). Blood flow velocities of the parent and adjacent vessels as well as the aneurysmal sac were measured using a Conforma Micro-Doppler (Cook Vascular Inc., Leechburg, PA, USA). Pre- and post-operative cerebral angiography was obtained in all our patients. In 23 aneurysms (15.6%) there was decreased or absent flow in the parent vessel or in one of the adjacent vessels after clipping. In another 19 aneurysms (12.9%), MDU demonstrated flow through the aneurysmal dome even though the aneurysmal neck appeared to be totally obliterated. Presence of SAH, anatomic location and size of the aneurysm were associated with improper clip placement in a statistically significant fashion. The false positive rate for MDU was 2% while there were no false negative findings in our study. MDU appears to be a non-invasive, reliable alternative methodology to intra-operative angiography. This inexpensive method may lend itself to routine usage in aneurysm surgery.

A putative zinc finger protein, Saccharomyces cerevisiae Vps18p, affects late Golgi functions required for vacuolar protein sorting and efficient alpha-factor prohormone maturation.

Saccharomyces cerevisiae strains carrying vps18 mutations are defective in the sorting and transport of vacuolar enzymes. The precursor forms of these proteins are missorted and secreted from the mutant cells. Most vps18 mutants are temperature sensitive for growth and are defective in vacuole biogenesis; no structure resembling a normal vacuole is seen. A plasmid complementing the temperature-sensitive growth defect of strains carrying the vps18-4 allele was isolated from a centromere-based yeast genomic library. Integrative mapping experiments indicated that the 26-kb insert in this plasmid was derived from the VPS18 locus. A 4-kb minimal complementing fragment contains a single long open reading frame predicted to encode a 918-amino-acid hydrophilic protein. Comparison of the VPS18 sequence with the PEP3 sequence reported in the accompanying paper (R. A. Preston, H. F. Manolson, K. Becherer, E. Weidenhammer, D. Kirkpatrick, R. Wright, and E. W. Jones, Mol. Cell. Biol. 11:5801-5812, 1991) shows that the two genes are identical. Disruption of the VPS18/PEP3 gene (vps18 delta 1::TRP1) is not lethal but results in the same vacuolar protein sorting and growth defects exhibited by the original temperature-sensitive vps18 alleles. In addition, vps18 delta 1::TRP1 MAT alpha strains exhibit a defect in the Kex2p-dependent processing of the secreted pheromone alpha-factor. This finding suggests that vps18 mutations alter the function of a late Golgi compartment which contains Kex2p and in which vacuolar proteins are thought to be sorted from proteins destined for the cell surface. The Vps18p sequence contains a cysteine-rich, zinc finger-like motif at the COOH terminus. A mutant in which the first cysteine of this motif was changed to serine results in a temperature-conditional carboxypeptidase Y sorting defect shortly after a shift to nonpermissive conditions. We identified a similar cysteine-rich motif near the COOH terminus of another Vps protein, the Vps11/Pep5/End1 protein. Preston et al. (Mol. Cell. Biol. 11:5801-5812, 1991) present evidence that the Vps18/Pep3 protein colocalizes with the Vps11/Pep5 protein to the cytosolic face of the vacuolar membrane. Together with the similar phenotypes exhibited by both vps11 and vps18 mutants, this finding suggests that they may function at a common step during vacuolar protein sorting and that the integrity of their zinc finger motifs may be required for this function.

Protein sorting in Saccharomyces cerevisiae: isolation of mutants defective in the delivery and processing of multiple vacuolar hydrolases.

Using a selection for spontaneous mutants that mislocalize a vacuolar carboxypeptidase Y (CPY)-invertase fusion protein to the cell surface, we identified vacuolar protein targeting (vpt) mutants in 25 new vpt complementation groups. Additional alleles in each of the eight previously identified vpt complementation groups (vpt1 through vpt8) were also obtained. Representative alleles from each of the 33 vpt complementation groups (vpt1 through vpt33) were shown to exhibit defects in the sorting and processing of several native vacuolar proteins, including the soluble hydrolases CPY, proteinase A, and proteinase B. Of the 33 complementation groups, 19 were found to contain mutant alleles that led to extreme defects. In these mutants, CPY accumulated in its Golgi complex-modified precursor form which was secreted by the mutant cells. Normal protein secretion appeared to be unaffected in the vpt mutants. The lack of significant leakage of cytosolic markers from the vpt mutant cells indicated that the vacuolar protein-sorting defects associated with these mutants do not result from cell lysis. In addition, the observation that the precursor rather than the mature forms of CPY, proteinase A, proteinase B were secreted from the vpt mutants was consistent with the fact that mislocalization occurred at a stage after Golgi complex-specific modification, but before final vacuolar sorting of these enzymes. Vacuolar membrane protein sorting appeared to be unaffected in the majority of the vpt mutants. However, a subset of the vpt mutants (vpt11, vpt16, vpt18, and vpt33) was found to exhibit defects in the sorting of a vacuolar membrane marker enzyme, alpha-mannosidase. Up to 50% of the alpha-mannosidase enzyme activity was found to be mislocalized to the cell surface in these vpt mutants. Seven of the vpt complementation groups (vpt3, vpt11, vpt15, vpt16, vpt18, vpt29, and vpt33) contained alleles that led to a conditional lethal phenotype; the mutants were temperature sensitive for vegetative cell growth. This temperature-sensitive phenotype has been shown to be recessive and to cosegregate with the vacuolar protein-sorting defect in each case. Tetrad analysis showed that vpt3 mapped to the right arm of chromosome XV and that vpt15 mapped to the right arm of chromosome II. Intercrosses with other mutants that exhibited defects in vacuolar protein sorting or function (vpl, sec, pep, and end mutants) revealed several overlaps among these different sets of genes. Together, these data indicate that more than 50 gene products are involved, directly or indirectly, in the process of vacuolar protein sorting.

Spontaneous resolution of acute cranial subdural hematomas.

Acute cranial subdural hematoma (SDH) represents a common consequence of traumatic brain injury. The vast majority of acute SDHs larger than 10mm in thickness require immediate surgical evacuation. In rare occasions, however, spontaneous resolution may occur. In our current communication, we present four cases of spontaneous resolution of acute cranial SDH. Further more, the proposed theories explaining spontaneous resolution of acute SDH, as well as, clinical parameters and imaging characteristics that might predict such phenomenon, are also reviewed. The possibility of spontaneous resolution of an acute SDH, although remote, may impact the decision making process regarding the management of these patients under certain conditions.

The clinical application of non-invasive intracranial blood volume pulse wave monitoring.

An ultrasonic method was used to non-invasively measure intracranial blood volume (IBV) pulse waveforms. This technology has previously shown a strong association between invasively recorded ICP pulse waves and non-invasively recorded IBV pulse waves. The objective of the present study was to investigate the diagnostic value of non-invasively measured IBV pulse waves in the cases of different pathologies. A total of 75 patients were examined and these included cases of acute, chronic and stabilized hydrocephalus, spinal cord injury and terminal blood flow. These were compared to a control group of 53 healthy volunteers. The object of comparison was normalized and averaged IBV pulse waves. Pathological IBV pulse waveforms were compared with IBV pulse waveforms of the normal group using sub-wave values, the area under waveform curve and the Euclidean distance calculation. The non-invasively measured IBV pulse waveform is not significantly dependent on acoustic path, gender or age. A detectable change in IBV pulse waveform shape was observed in situations when disturbance in intracranial hydrodynamics was present, e.g. during hypoventilation tests, in cases of terminal blood flow and hydrocephaly, depicting the level of hydrocephalus activity and the patient's compensatory capabilities as well as the effect of treatment.

The effect of anaemia on hospital length of stay in lumbar decompression and fusion procedures.

Ways of reducing the length of hospital stay have received increased attention in recent years. Both preoperative and postoperative anaemia have been implicated as causative agents in increasing postoperative length of stay (LOS). In a retrospective study, 317 patients that underwent lumbar decompression and fusion surgery were assessed. Two separate block multivariate linear regression analyses were performed to evaluate the impact of preoperative anaemia, postoperative anaemia, and the degree of perioperative haemoglobin drop on LOS. Other anaemia related factors were also assessed. Preoperative anaemia, postoperative anaemia, and the amount of perioperative haemoglobin drop were all shown to prolong the length of hospitalisation and therefore to increase overall healthcare costs. Following strict anaemia corrective maneuvers could reasonably be expected to reduce expenditure.

Impact of restriction of placental and fetal growth on expression of 11beta-hydroxysteroid dehydrogenase type 1 and type 2 messenger ribonucleic acid in the liver, kidney, and adrenal of the sheep fetus.

We have investigated the effects of fetal growth restriction, induced by restriction of placental growth and function (PR), on 11beta-hydroxysteroid dehydrogenase type 1 (11betaHSD-1) and 11betaHSD-2 messenger RNA (mRNA) expression in fetal tissues in the sheep, using Northern blot analysis. Fetal liver, kidney, and adrenals were collected from normally grown fetuses at 90 days (n = 6), 125 days (n = 6), and 141-145 days (n = 7) and from PR fetuses at 141-145 days (n = 6). Expression of 11betaHSD-1 mRNA in the fetal liver increased significantly between 125 days (7.4+/-0.8) and 141-145 days gestation (27+/-5.3). There was also an approximately 2-fold increase in the ratio of 11betaHSD-1 mRNA/18S rRNA expression in the PR group (53.8+/-7.9) compared with that in control animals at 141-145 days gestation. There was a significant decrease in 11betaHSD-2 mRNA in fetal adrenals between 125 days (41.6+/-2.4) and 141-145 days (26.7+/-1.1) gestation, but there was no effect of PR on the expression of adrenal 11betaHSD-2 mRNA. 11betaHSD-2 mRNA expression in the fetal kidney increased between 90 days (16.8+/-1.7) and 141-145 days gestation (31.7+/-4.3), but there was no effect of PR on the levels of 11betaHSD-2 mRNA in the fetal kidney. In summary, 11betaHSD-2 mRNA is differentially regulated in the fetal adrenal and kidney in the sheep fetus during late gestation. There is also a specific increase in the expression of 11betaHSD-1 mRNA in the liver of growth-restricted fetuses in late gestation. This suggests that there is increased hepatic exposure to cortisol in the growth-restricted fetus, which may be important in the reprogramming of hepatic physiology that occurs after growth restriction in utero.

The autonomic control of heart rate and insulin resistance in young adults.

The pathophysiology of insulin resistance is unclear. A link between increased heart rate (HR) and insulin resistance suggests an association with sympathetic nervous system activity. To further evaluate this, we examined autonomic activity using spectral analysis of HR variability (HRV), which provides a measure of cardiac sympathovagal modulation, and related this to insulin sensitivity (Si) in 137 men and women (20 yr old). The HRV spectrum displays 2 major peaks: a high-frequency peak, reflecting vagal activity, and a low-frequency peak caused by vagal and sympathetic activity. The high-to-low ratio (HLratio) reflects sympathovagal balance. Si was measured, using the i.v. glucose tolerance test with minimal modeling, and HR data was derived from a 15-min supine electrocardiogram. Women were more insulin resistant than men (Si, 3.94 vs. 5.09 10(4) min(-1)/per pmol x L; P = 0.002), had higher HR (59 vs. 56 beats/min, P = 0.019), but had a higher HLratio (2.04 vs. 1.31, P = 0.001). In men (but not women), Si correlated with HR (r = -0.410, P = 0.001) and measures of HRV: HLratio (r = 0.291, P = 0.002) independently of body mass index. In conclusion, Si correlates with cardiac sympathovagal balance in men, but not women, suggesting gender differences in the autonomic modulation of insulin resistance.

The relationship between birth weight and blood pressure amplifies from childhood to adulthood.

OBJECTIVE: To investigate relationships between birth characteristics and blood pressure at age 20 years and to assess whether effects of birth weight on blood pressure are amplified from childhood to adulthood. DESIGN: A longitudinal study of 584 men and women from Adelaide, Australia, examined previously at 8 years and followed up at age 20 years. RESULTS: Birth weight was negatively associated with systolic pressure at age 20 years in men (regression coefficient 2.6 mmHg per kg; 95% confidence interval 0.7, 4.4) and women (regression coefficient 4.6 mmHg per kg; 95% confidence interval 2.9, 6.4), after adjustment for current weight There was an interaction with current size (P = 0.05 for men and P = 0.09 for women), such that effects were enhanced among individuals with relatively high weight or weight for height. Shortness at birth, thinness at birth, and low birth weight relative to placental weight were also associated with elevated systolic pressure at age 20 years. Effects of birth weight on blood pressure were stronger at age 20 than at age 8 years (P < 0.01 for men and P = 0.03 for women). This was not due simply to increased variability of blood pressure in adulthood. There were greater rises in blood pressure with age among individuals of relatively low birth weight. CONCLUSIONS: These findings are further evidence that poor fetal growth is associated with elevated blood pressure in later life. The results support the hypothesis that the relationship is amplified with increasing age.