Strange quark contributions to parity-violating asymmetries in the backward angle G0 electron scattering experiment

We have measured parity-violating asymmetries in elastic electron-proton and quasielastic electron-deuteron scattering at Q2=0.22 and 0.63 GeV2. They are sensitive to strange quark contributions to currents in the nucleon and the nucleon axial-vector current. The results indicate strange quark contributions of approximately < 10% of the charge and magnetic nucleon form factors at these four-momentum transfers. We also present the first measurement of anapole moment effects in the axial-vector current at these four-momentum transfers.

New measurements of the European Muon Collaboration effect in very light nuclei

New Jefferson Lab data are presented on the nuclear dependence of the inclusive cross section from (2)H, (3)He, (4)He, (9)Be and (12)C for 0.3 < x < 0.9, Q(2) approximately 3-6 GeV(2). These data represent the first measurement of the EMC effect for (3)He at large x and a significant improvement for (4)He. The data do not support previous A-dependent or density-dependent fits to the EMC effect and suggest that the nuclear dependence of the quark distributions may depend on the local nuclear environment.

Development of an automated blood sampling system for use in humans

Many hormones are released in a pulsatile or burst-like pattern resulting in fluctuating blood levels that can undergo rapid modulation by physiological and pathological signals. To accurately measure these changes in hormone concentration requires frequent blood sampling, often over extended periods as the overall rhythmicity may vary over 24 hours. The aim of this study was to develop a computerized, automated blood sampling system which allows repeated stress-free blood sample collection from humans over an extended period under basal or test conditions. The system incorporates a peristaltic pump, fraction collector and standard infusion pump together with a custom built electronic control unit linked to a personal computer. Disposable tubing prevents cross-contamination between study participants. The computer programme is modifiable to adjust for the number of specimen tubes and volume of blood collected per sampling cycle. Patency of the collecting line is maintained with 0.9% saline, without the need for heparinization. To validate the system, 10-minute samples for cortisol were collected over 24 hours from five healthy volunteers, of whom two had additional concomitant ACTH sampling. Deconvolution analysis revealed an expected number of hormone secretory episodes and a non-pathological degree of orderliness within the data. There was high concordance between ACTH and cortisol secretory events. The ability of the system to allow multiple measurements and of the software program to link with other physiological monitoring equipment provides a powerful tool to study physiologic/pathophysiologic change in relation to blood hormone and other biomarker levels.

Microbial biodiversity of thermophilic communities in hot mineral soils of Tramway Ridge, Mount Erebus, Antarctica

Tramway Ridge, located near the summit of Mount Erebus in Antarctica, is probably the most remote geothermal soil habitat on Earth. Steam fumaroles maintain moist, hot soil environments creating extreme local physicochemical differentials. In this study a culture-independent approach combining automated rRNA intergenic spacer analysis (ARISA) and a 16S rRNA gene library was used to characterize soil microbial (Bacterial and Archaeal) diversity along intense physicochemical gradients. Statistical analysis of ARISA data showed a clear delineation between bacterial community structure at sites close to fumaroles and all other sites. Temperature and pH were identified as the primary drivers of this demarcation. A clone library constructed from a high-temperature site led to the identification of 18 novel bacterial operational taxonomic units (OTUs). All 16S rRNA gene sequences were deep branching and distantly (85-93%) related to other environmental clones. Five of the signatures branched with an unknown group between candidate division OP10 and Chloroflexi. Within this clade, sequence similarity was low, suggesting it contains several yet-to-be described bacterial groups. Five archaeal OTUs were obtained and exhibited high levels of sequence similarity (95-97%) with Crenarchaeota sourced from deep-subsurface environments on two distant continents. The novel bacterial assemblage coupled with the unique archaeal affinities reinvigorates the hypotheses that Tramway Ridge organisms are relics of archaic microbial lineages specifically adapted to survive in this harsh environment and that this site may provide a portal to the deep-subsurface biosphere.

Genetic background influences the behavioural and molecular consequences of neurokinin-1 receptor knockout

Genetic background affects animal phenotype and therefore is of particular relevance to studies using genetically manipulated mice. Strain differences in hypothalamic-pituitary-adrenocortical (HPA) axis activity may contribute to background-specificity of some mutations. Here, we analysed components of the HPA axis in mice lacking a functional neurokinin-1 receptor (NK1-/-) on two backgrounds: backcrossed C57BL/6 (B6) and mixed C57BL/6 x 129/sv (129B6). We hypothesized that HPA axis activity would vary between these strains, leading to differences in the NK1-/- phenotype. We compared levels of plasma corticosterone between the groups, and found 129B6 mice exhibited elevated levels of stress-induced corticosterone compared with B6 mice, regardless of genotype. Although the level of basal corticotrophin-releasing factor and stress-induced c-fos mRNAs did not differ between the genotypes of either strain, examination of glucocorticoid receptor immunoreactivity within the hippocampus revealed that NK1-/- mice on the 129B6 background had elevated expression compared with wild-type, whilst there was no difference between genotypes in the B6 strain. Similarly, hippocampal neurogenesis in NK1-/- mice was greater than in wild-type on the 129B6 strain, and did not differ between genotypes on the B6 background. Finally, novelty- and morphine-induced locomotion were assessed. NK1-/- mice on the 129B6 background exhibited hyperlocomotion in response to novelty and greater sensitivity to the locomotor-stimulating properties of morphine than wild-type. In contrast, in B6 mice, no differences were observed between genotypes for either locomotor behaviour. In summary, we find that HPA axis activity differs between the strains and that there are profoundly background-specific effects of the NK1 receptor mutation.

Measurement of nuclear transparency for the A(e,e'pi+) reaction

We have measured the nuclear transparency of the A(e,e'pi+) process in 2H, 12C, 27Al, 63Cu, and 197Au targets. These measurements were performed at the Jefferson Laboratory over a four momentum transfer squared range Q2=1.1 to 4.7 (GeV/c)2. The nuclear transparency was extracted as the super-ratio of (sigmaA/sigmaH) from data to a model of pion-electroproduction from nuclei without pi-N final-state interactions. The Q2 and atomic number dependence of the nuclear transparency both show deviations from traditional nuclear physics expectations and are consistent with calculations that include the quantum chromodynamical phenomenon of color transparency.

Effect of the glucocorticoid receptor antagonist Org 34850 on basal and stress-induced corticosterone secretion

The activity of the hypothalamic-pituitary-adrenal (HPA) axis is characterised both by an ultradian pulsatile pattern of glucocorticoid secretion and an endogenous diurnal rhythm. Glucocorticoid feedback plays a major role in regulating HPA axis activity and this mechanism occurs via two different receptors: mineralocorticoid (MR) and glucocorticoid receptors (GR). In the present study, the effects of both acute and subchronic treatment with the GR antagonist Org 34850 on basal and stress-induced HPA axis activity in male rats were evaluated. To investigate the effect of Org 34850 on basal diurnal corticosterone rhythm over the 24-h cycle, an automated blood sampling system collected samples every 10 min. Acute injection of Org 34850 (10 mg/kg, s.c.) did not affect basal or stress-induced corticosterone secretion, but was able to antagonise the inhibitory effect of the glucocorticoid agonist methylprednisolone on stress-induced corticosterone secretion. However, 5 days of treatment with Org 34850 (10 mg/kg, s.c., two times a day), compared to rats treated with vehicle (5% mulgofen in 0.9% saline, 1 ml/kg, s.c.), increased corticosterone secretion over the 24-h cycle and resulted in changes in the pulsatile pattern of hormone release, but had no significant effect on adrenocorticotrophic hormone secretion or on stress-induced corticosterone secretion. Subchronic treatment with Org 34850 did not alter GR mRNA expression in the hippocampus, paraventricular nucleus of the hypothalamus or anterior-pituitary, or MR mRNA expression in the hippocampus. Our data suggest that a prolonged blockade of GRs is required to increase basal HPA axis activity. The changes observed here with ORG 34850 are consistent with inhibition of GR-mediated negative feedback of the HPA axis. In light of the evidence showing an involvement of dysfunctional HPA axis in the pathophysiology of depression, Org 34850 could be a potential treatment for mood disorders.

PCR screening reveals unexpected antibiotic biosynthetic potential in Amycolatopsis sp. strain UM16

AIMS

To assess the antibiotic biosynthetic potential of Amycolatopsis sp. strain UM16 and eight other Amycolatopsis species.

METHODS AND RESULTS

Amycolatopsis genomic DNA was screened by PCR for the glycopeptide, Type-II (aromatic) polyketide and ansamycin biosynthetic gene clusters. Amycolatopsis sp. strain UM16, which exhibits weak antitubercular activity, was shown to have the glycopeptide oxyB gene and the Type-II (aromatic) polyketide-synthase KSalpha-KSbeta tandem gene pair, but not the AHBA synthase gene. The ristocetin (glycopeptide) producer, Amycolatopsis lurida NRRL 2430(T), was shown to have the oxyB gene and the Type-II polyketide-synthase KSalpha-KSbeta tandem gene pair. Amycolatopsis alba NRRL 18532(T) was shown to have the glycopeptide oxyB gene and the AHBA synthase gene. Phylogenetic analyses using Amycolatopsis oxyB and KSalpha-KSbeta gene sequences were conducted.

CONCLUSIONS

Amycolatopsis sp. strain UM16 appears to have the biosynthetic potential to produce glycopeptide and Type-II polyketide antibiotics, but not ansamycins. The potential to synthesize aromatic polyketides may be more widely distributed in Amycolatopsis than is currently recognized.

SIGNIFICANCE AND IMPACT OF THE STUDY

PCR screening is a very useful tool for rapidly identifying the biosynthetic potential of an antibiotic-producing actinomycete isolate. Advanced knowledge of the type of antibiotic(s) produced will allow appropriate methods to be selected for antibiotic purification.

Transverse beam spin asymmetries in forward-angle elastic electron-proton scattering

We have measured the beam-normal single-spin asymmetry in elastic scattering of transversely polarized 3 GeV electrons from unpolarized protons at Q2=0.15, 0.25 (GeV/c)2. The results are inconsistent with calculations solely using the elastic nucleon intermediate state and generally agree with calculations with significant inelastic hadronic intermediate state contributions. A(n) provides a direct probe of the imaginary component of the 2gamma exchange amplitude, the complete description of which is important in the interpretation of data from precision electron-scattering experiments.

First report of homoanatoxin-a and associated dog neurotoxicosis in New Zealand

In November 2005, at least five dogs died rapidly after contact with water from the Hutt River (lower North Island, New Zealand). Necropsy performed 24h later on one of the dogs (a 20-month-old Labrador) revealed few findings of interest, except for copious amounts of froth in the respiratory tract down to the bifurcation of the trachea and large quantities of algal material in the dog's stomach. Low and relatively stable flows in the Hutt River during spring had resulted in the proliferation of benthic cyanobacteria that formed large black/brown mats along the river edge. Samples from the Labrador's stomach contents and cyanobacterial mats were analysed microscopically and screened using chemical and biochemical assays for cyanotoxins: anatoxin-a, homoanatoxin-a, cylindrospermopsins, saxitoxins and microcystins. Liquid chromatography-mass spectrometry (LC-MS) confirmed the presence of the neurotoxic cyanotoxins anatoxin-a and homoanatoxin-a and their degradation products, dihydro-anatoxin-a and dihydro-homoanatoxin-a. This is the first report of homoanatoxin-a and associated degradation product in New Zealand. Based on morphology, the causative species was identified as Phormidium sp. Subsequent phylogenetic analysis of 16S rRNA gene sequences demonstrated that the causative organism was most similar to Phormidium autumnale. Further investigations led to the detection of homoanatoxin-a and anatoxin-a in cyanobacterial mats from four other rivers in the Wellington region (lower North Island, New Zealand). Access restrictions were placed on over 60% of river catchments in the western Wellington region, severely affecting recreational users.

New Zealand risk management approach for toxic cyanobacteria in drinking water

Cyanobacterial blooms are common seasonal phenomena occurring worldwide in fresh, estuarine and coastal waters, including those used for drinking-water supplies, recreation and stock watering. In New Zealand, the frequency of blooms and their geographic spread is likely to grow with increasing eutrophication and global climate change. The New Zealand Ministry of Health has recently developed national criteria for assessing and managing the risk of toxic cyanobacteria in drinking-water supplies. This paper investigates a cyanobacterial bloom incident in the summer 2002/03 in the Waikato River and hydro lakes, which are a major drinking-water supply for Hamilton City and many other smaller towns along the river. The procedures invoked by the Hamilton City Council and other authorities to deal with this bloom event are considered in terms of the best practice of the day and compared with the Drinking-Water Standards for New Zealand 2005. The presence of cyanobacteria has significant economic effects because of increases in water supply treatment costs or the need to use an alternative source, and there are also social effects from the disruption of recreational use of water bodies and loss of confidence in the quality of reticulated, treated water supplies. Notional evaluation of economic cost of monitoring regimes and control, based on the Waikato River cyanobacterial bloom incident, is also given. The multi-barrier and process-control risk management approach, reliant on good vertical communication systems between central and local government, is an advanced approach useful for any country that regularly experiences cyanobacterial problems.

Longitudinal-transverse separations of deep-inelastic structure functions at low Q2 for hydrogen and deuterium

We report on a study of the longitudinal to transverse cross section ratio, R=sigmaL/sigmaT, at low values of x and Q2, as determined from inclusive inelastic electron-hydrogen and electron-deuterium scattering data from Jefferson Laboratory Hall C spanning the four-momentum transfer range 0.06<Q2<2.8 GeV2. Even at the lowest values of Q2, R remains nearly constant and does not disappear with decreasing Q2, as might be expected. We find a nearly identical behavior for hydrogen and deuterium.

Production of anatoxin-a and a novel biosynthetic precursor by the cyanobacterium Aphanizomenon issatschenkoi

Cyanobacterial blooms in New Zealand surface water resources have been surveyed and, in response to strict new standards for drinking water, more intensive monitoring for cyanotoxins has been initiated. Aphanizomenon issatschenkoi was recently identified in a New Zealand lake and was found to produce the potent neurotoxin anatoxin-a (ATX). A strain of Aph. issatschenkoi (CAWBG02) was cultured for ATX production and a novel derivative of ATX was found to account for a high proportion of the toxin content in the Aph. issatschenkoi cells. Spectroscopic data (LC-UV, liquid chromatography with ultraviolet absorption detection; LC-MS/MS, liquid chromatography with tandem mass spectrometry; LC-HRMS, liquid chromatography with high resolution mass spectrometry) identified this derivative as 11-carboxyl anatoxin-a. Although precursors with a carboxyl group on C11 have been postulated in the biosynthetic pathway for ATX from amino acids and acetate, this is the first identification of a specific intermediate. The production of ATX and the intermediate by Aph. issatschenkoi was studied under different growth conditions. Concentrations of ATX and the intermediate increased in the aerated culture to 170 microg/L and 330 microg/L, respectively, at 21 days (18 x 10(9) cells/L). Cell concentrations did not markedly increase during subsequent growth to 37 days. ATX concentrations decreased, and 11-carboxyl ATX concentrations continued to increase during this period. Toxin production by Aph. issatschenkoi cells was maximal at 6 days of growth (0.08-0.09 pg/cell each; 2.3 x 10(8) cells/L). Other ATX analogues and metabolites were not detected in the cultures. Freeze-thawing of cultures resulted in complete conversion of the intermediate to ATX with a half-life of 5 min, and this conversion was inhibited by acidification, heating of the culture to 100 degrees C, or addition of methanol. The implications of the findings for mechanisms of biosynthesis of anatoxins by cyanobacteria and for monitoring of water bodies for cyanotoxins are discussed.

Onset of quark-hadron duality in pion electroproduction

A large data set of charged-pion (pi+/-) electroproduction from both hydrogen and deuterium targets has been obtained spanning the low-energy residual-mass region. These data conclusively show the onset of the quark-hadron duality phenomenon, as predicted for high-energy hadron electroproduction. We construct several ratios from these data to exhibit the relation of this phenomenon to the high-energy factorization ansatz of electron-quark scattering and subsequent quark-->pion production mechanisms.

Determination of the pion charge form factor at Q2=1.60 and 2.45 (GeV/c)2

The 1H(e,e'pi+)n cross section was measured at four-momentum transfers of Q2=1.60 and 2.45 GeV2 at an invariant mass of the photon nucleon system of W=2.22 GeV. The charged pion form factor (F(pi)) was extracted from the data by comparing the separated longitudinal pion electroproduction cross section to a Regge model prediction in which F(pi) is a free parameter. The results indicate that the pion form factor deviates from the charge-radius constrained monopole form at these values of Q2 by one sigma, but is still far from its perturbative quantum chromodynamics prediction.

Diurnal variation in the responsiveness of the hypothalamic-pituitary-adrenal axis of the male rat to noise stress

Basal activity of the rat hypothalamic-pituitary-adrenal (HPA) axis is highly dynamic and displays both circadian and ultradian rhythmicity in corticosterone secretion. This study investigated the relationship between basal corticosterone pulsatility and the corticosterone response to noise during the early light phase when there are no endogenous corticosterone pulses and during the early dark phase when there are hourly pulses of corticosterone. An automated blood sampling system was used to collect blood in conscious male rats at 5-min intervals before, during and after exposure to 10-min periods of white noise (104 dB). Behavioural responses to noise were also monitored during these periods. During the early light phase (morning), there was a consistent corticosteroid response to noise with corticosterone concentrations rising rapidly and reaching peak values 10-15 min after the noise had ceased, following which circulating concentrations declined at a rate comparable to the hormones half-life. A second noise stress, 80 min later, resulted in adaptation of the corticosterone response. During the early dark phase (evening), the corticosterone response to the noise was similar to that seen in the morning, although there was no adaptation to a second stimulus. During the evening, the inhibition of endogenous HPA activity after the sound was limited to 40 min following stress.

Changes in concentrations of microcystins in rainbow trout, freshwater mussels, and cyanobacteria in Lakes Rotoiti and Rotoehu

Microcystin concentrations in cyanobacteria and their accumulation in rainbow trout (Oncorhynchus mykiss) and freshwater mussels (Hyridella menziesi) in Lakes Rotoiti and Rotoehu (New Zealand) were investigated. Hatchery rainbow trout were added to an enclosure in Lake Rotoiti where concentrations of microcystins in the phytoplankton and cyanobacterial cell concentrations could be closely monitored. Rainbow trout that were free to roam in the entire area of each lake were also included in the study. Freshwater mussels were suspended subsurface in cages in the enclosure. Phytoplankton samples, rainbow trout liver and muscle tissue, and the tissues of mussels were analyzed for microcystins using the ADDA-ELISA method, and selected samples were analyzed using LC-MS. A maximum concentration of microcystins in the phytoplankton samples of 760 microg L(-1) was recorded in Te Weta Bay, Lake Rotoiti, in March 2004. ELISA results confirmed microcystin immunoreactivity in rainbow trout liver and muscle tissues and in freshwater mussels. The microcystin congeners LR, YR, RR, AR, FR, LA, and WR were detected by LC-MS in caged freshwater mussels in Lake Rotoiti but were not detected in either muscle or liver tissue of rainbow trout. The daily tolerable intake limit of microcystins for human consumption recommended by the World Health Organisation is 0.04 microg kg(-1) day(-1). Modeling was carried out for the human intake of microcystin compounds from rainbow trout muscle tissue, and the potential health risks were estimated, assuming the ADDA-ELISA was determining compounds of toxicity equivalent to microcystin-LR.

Strange-quark contributions to parity-violating asymmetries in the forward g0 electron-proton scattering experiment

We have measured parity-violating asymmetries in elastic electron-proton scattering over the range of momentum transfers 0.12 < or =Q2 < or =1.0 GeV2. These asymmetries, arising from interference of the electromagnetic and neutral weak interactions, are sensitive to strange-quark contributions to the currents of the proton. The measurements were made at Jefferson Laboratory using a toroidal spectrometer to detect the recoiling protons from a liquid hydrogen target. The results indicate nonzero, Q2 dependent, strange-quark contributions and provide new information beyond that obtained in previous experiments.

Organizational role for testosterone and estrogen on adult hypothalamic-pituitary-adrenal axis activity in the male rat

Organizational effects of testosterone during a critical period of neonatal life have major irreversible effects on adult sexual behavior. We have investigated whether perinatal androgen changes also affect another major sexually differentiated system, the hypothalamo-pituitary-adrenal axis. This was assessed in male rats who had been exposed to perinatal flutamide or 1,4,6-androstatriene-3,17-dione (ATD). Once the animals reached adulthood, an automated sampling system was used to collect blood from freely moving animals at 10-min intervals over 24 h, followed by a noise stress and then the administration of lipopolysaccharide (LPS). Perinatal flutamide- and ATD-treated rats not only had higher mean corticosterone levels and increased frequency and amplitude of corticosterone pulses over the 24 h compared with vehicle-injected controls, but they also showed markedly increased corticosterone responses to both noise and LPS. All parameters of increased hypothalamo-pituitary-adrenal activity resembled the normal physiological state of the intact adult female rather than that of the intact adult male rat. Furthermore, 3 h after LPS administration, both flutamide- and ATD-treated animals had markedly higher levels of corticotropin-releasing factor mRNA in the parvocellular paraventricular nucleus (PVN) and proopiomelanocortin mRNA in the adenohypophysis. Flutamide-treated rats also had a greater level of PVN arginine vasopressin mRNA. PVN glucocorticoid receptor mRNA levels were significantly lower in both the flutamide- and the ATD-treated male rats. These data highlight the importance of perinatal exposure to both testosterone and estrogen(s) on the development of a masculinized circadian corticosterone profile and stress-induced hypothalamo-pituitary-adrenal axis activity in the adult male rat.

Postnatal masculinization alters the HPA axis phenotype in the adult female rat

The ability of postnatal testosterone propionate (TP) to masculinize both behaviour and gonadal cyclicity in the female rat is well documented. We have investigated whether postnatal androgen also has an organizational effect on another sexually dimorphic neuroendocrine system--the hypothalamo-pituitary-adrenal (HPA) axis. Female rats were exposed to a single injection of testosterone propionate (TP) or oil within 24 h of birth. As adults, rats were either ovariectomized and given 17beta-oestradiol replacement (OVXE2) or sham ovariectomized with cholesterol implants (SHOVX). An automated sampling system collected blood from unanaesthetized adult female rats every 10 min over a 24-h period, during a mild psychological stress (noise) and following an immunological lipopolysaccharide stress (LPS). Neonatal TP-treated SHOVX rats had a significant reduction in the number, height, frequency and amplitude of corticosterone pulses over the basal 24-h period, compared to both the neonatal oil-treated and TP-treated OVXE2 animals. The corticosterone response to both noise and LPS was also significantly decreased for the TP-treated SHOVX females. Three hours post-LPS administration, TP females had significantly lower values of paraventricular nucleus (PVN) corticotrophin releasing hormone (CRH), arginine vasopressin (AVP) and anterior pituitary proopiomelanocortin (POMC) mRNAs and greater PVN glucocorticoid receptor (GR) mRNA expression compared to the oil-treated controls. E2 replacement in adult TP rats normalized all the mRNA levels, except for PVN GR mRNA which did fall towards the levels of the oil-control animals. A single injection of TP within 24 h of birth disrupts the development of the characteristic female pattern of corticosterone secretion and the normal female HPA response to stress, resulting in a pattern similar to that seen in males. These effects can be reversed by E2 treatment in the adult TP female rat.

Gonadal steroid replacement reverses gonadectomy-induced changes in the corticosterone pulse profile and stress-induced hypothalamic-pituitary-adrenal axis activity of male and female rats

We investigated the effects of gonadal hormone replacement on the pulsatile parameters underlying basal circadian corticosterone secretion in castrated male and ovariectomized female rats using an automated sampling system. Blood was collected from freely moving, unanaesthetized rats every 10 min over a 24-h period and sampling was continued during a noise stress and after lipopolysaccharide (LPS) administration. Castrated male rats had markedly higher corticosterone levels than intact controls. This was reflected by increased number and frequency of pulses in addition to an increase in the pulse height and amplitude under both basal circadian and stress conditions. Hormone replacement with either testosterone or dihydrotestosterone returned these corticosterone levels and circadian profile to those found in intact males, confirming an androgen-mediated effect. Ovariectomized females had significantly lower basal and stress-induced corticosterone levels with lower frequency and amplitude of corticosterone pulses than intact females. 17beta-oestradiol replacement returned basal levels, pulsatile measurements and stress-induced corticosterone levels to those found in intact females. Three hours post-LPS administration, castrated males demonstrated significantly higher values of parvocellular paraventricular nucleus (PVN) arginine vasopressin and corticotrophin-releasing factor and anterior pituitary pro-opiomelanocortin mRNA while ovariectomized females showed significantly lower levels of all three transcripts compared to intact controls. PVN glucocorticoid receptor mRNA levels 3 h post-LPS administration were significantly decreased in castrated males and significantly increased in ovariectomized female rats. Replacement of gonadal steroids resulted in a return to the levels found in intact controls after LPS. Gonadal steroid replacement is sufficient to reverse changes in the pulsatile characteristics of corticosterone release after gonadectomy. In addition, gonadal steroid replacement reverses stress-induced alterations in hypothalamic-pituitary-adrenal (HPA) activity. These data demonstrate a major contribution of gonadal steroids to the regulation of HPA axis activity and to the pulsatile characteristics of corticosterone release.

Correlated strength in the nuclear spectral function

We have carried out an (e,e'p) experiment at high momentum transfer and in parallel kinematics to measure the strength of the nuclear spectral function S(k,E) at high nucleon momenta k and large removal energies E. This strength is related to the presence of short-range and tensor correlations, and was known hitherto only indirectly and with considerable uncertainty from the lack of strength in the independent-particle region. This experiment locates by direct measurement the correlated strength predicted by theory.

Gonadectomy reverses the sexually diergic patterns of circadian and stress-induced hypothalamic-pituitary-adrenal axis activity in male and female rats

Enhanced corticosterone release by female compared to male rats under basal and stress conditions is well documented. The demonstration that gonadectomy enhances stress-induced corticosterone secretion in male rats, but reduces such levels in female rats, suggests a causal association between gonadal steroids and corticosterone release. The present study examined the corticosterone profile of sham gonadectomized and gonadectomized female and male rats under basal and stress conditions. An automated sampling system collected blood from each freely moving, unanaesthetized rat every 10 min (i) over a 24-h period; (ii) following noise stress; and (iii) following an immune-mediated stress (lipopolysaccharide, LPS). Plasma was analysed for corticosterone content using radioimmunoassay. Castration resulted in a significant increase in basal corticosterone release compared to the sham-castrated male rats. Pulsar analysis revealed a significant two-fold increase in the number of corticosterone pulses over 24 h. Corticosterone increases in response to noise stress and to LPS injection were enhanced following castration. Conversely, ovariectomy resulted in a two-fold reduction in the number of corticosterone pulses as well as the stress response compared to sham-ovariectomized female rats. Arginine vasopressin (AVP), corticotrophin-releasing hormone (CRH) and glucocorticoid receptor mRNAs in the paraventricular nucleus and pro-opiomelanocortin (POMC) mRNA in the anterior pituitary were analysed post-LPS administration by in situ hybridization. Significantly higher values were found for AVP, CRH and POMC mRNAs examined for sham females and castrated males compared to sham males and ovariectomized females. This study confirms previous reports concerning the influence of gonadal factors in regulating HPA axis activity and stress responsiveness. The present results extend these observations to the regulation of the dynamic pattern of corticosterone release under basal conditions and suggests that this alteration in pulsatility is important for the differences in stress responsiveness when comparing males and females.

Hypothalamic-pituitary-adrenal function

Basal hypothalamic-pituitary-adrenal (HPA) function is characterised by pulses of corticosterone secretion followed by a transient refractory period when the axis appears to be inhibited. In females pulses of corticosterone secretion occur approximately once per hour with variation in pulse amplitude underlying a diurnal rhythm. Males show smaller pulses of secretion which become widely spaced during the early light phase nadir. Pulsatility is altered by genetic programming, early life experiences and reproductive status. Activation of the HPA axis during adjuvant induced arthritis results in an increase in the pulse frequency. This is associated with a marked change in hypothalamic gene expression with a diminution of CRH mRNA and a marked increase of AVP mRNA which becomes the predominant HPA secretagogue.