Systemic oxytocin increases glutamate efflux in the nucleus accumbens core of cocaine-experienced male and female rats but only increases dopamine efflux in males

Oxytocin attenuates cocaine-seeking when administered both systemically and directly into the nucleus accumbens core. This effect is blocked by intra-accumbens antagonism of mGlu2/3 and, together with our finding that intra-accumbens oxytocin increases glutamate concentrations in this brain region, indicates that pre-synaptic regulation of glutamate release by oxytocin influences cocaine relapse. However, mGlu2/3 receptors also regulate dopamine release in the nucleus accumbens. Here we aimed to determine whether systemic oxytocin increases glutamate and dopamine concentrations in the nucleus accumbens core of cocaine-experienced and cocaine-naïve male and female rats. A subset of rats self-administered cocaine (0.5 mg/kg/infusion) and then underwent extinction training for 2-3 weeks. Rats were implanted with microdialysis probes in the accumbens core and samples were collected for a baseline period, and following saline (1 mL/kg), and oxytocin (1 mg/kg, IP) injections. Locomotion was assessed during microdialysis. In cocaine-experienced rats, oxytocin increased glutamate concentrations in the accumbens core to the same extent in males and females but only increased dopamine concentrations in male rats. Oxytocin did not alter glutamate levels in cocaine-naïve rats. Oxytocin did not produce sedation. These results extend previous findings that systemic oxytocin increases nucleus accumbens dopamine in a sex-specific manner in cocaine-experienced rats. These data are the first to find that systemic oxytocin increases nucleus accumbens glutamate after cocaine experience, providing a mechanism of action by which oxytocin attenuates the reinstatement of cocaine seeking in both male and female rats.

Antenatal betamethasone and favourable outcomes in fetuses with 'poor prognosis' diaphragmatic hernia

Congenital diaphragmatic hernia (CDH) is a common abnormality affecting 1 in 2,000 gestations. The mortality exceeds 50% despite recent advances in postnatal treatment. The widespread antenatal use of glucocorticoids to induce lung maturation in fetuses at risk of premature delivery suggests a potential for a therapeutic effect in other fetuses with impaired lung development. The parents of three fetuses referred with CDH and features suggesting a poor postnatal prognosis (early diagnosis, liver herniation, and lung area-to-head circumference ratio <1.0, or associated abnormalities) elected to receive maternal betamethasone starting at 24 to 26 weeks' gestation rather than undergo a fetal tracheal plug. All three infants survived and were extubated within 10 days. The long-term use of antenatal steroids in the treatment of CDH may thus be of benefit and warrants further study.

Nurse-physician collaborative relationship on nurses' self-perceived job satisfaction in ambulatory care

The dynamic restructuring of the healthcare environment from a primary acute care focus to an ambulatory care focus has prompted a migration of nurses to the ambulatory care setting. The predication of nursing job satisfaction is a complex process that has received little attention in the ambulatory care setting. The purpose of this study was to determine if a relationship existed between the nurse-physician relationship and nurses' self-perceived job satisfaction in the ambulatory care setting. While study findings demonstrated there was no significant relationship between the nurse-physician relationship and nurses' self-perceived job satisfaction in the ambulatory care setting, it did confirm that registered nurses working in the ambulatory setting have a moderate level of job satisfaction. The lack of correlation between the nurse-physician relationship and job satisfaction may have been attributed to limitations such as a limited sample size and the nurses having a relationship with a smaller number of physicians in the ambulatory care setting. Recommendations to further understanding of the nurse-physician relationship included further descriptive studies of nurses working in the ambulatory care setting and further studies on job satisfaction of nurses.

The identification of alpha-ketoamides as potent inhibitors of hepatitis C virus NS3-4A proteinase

Peptides based upon the non-prime side residues of the NS4A-4B cleavage site of hepatitis C virus (HCV) NS3-4A proteinase containing an alpha-ketoamide moiety in place of the scissile amide bond are potent inhibitors of this enzyme.

The design and synthesis of potent inhibitors of hepatitis C virus NS3-4A proteinase

Hepatitis C virus (HCV) is the cause of the majority of transfusion-associated hepatitis and a significant proportion of community-acquired hepatitis worldwide. Infection by HCV frequently leads to persistent infections that result in a range of clinical conditions including an asymptomatic carrier state, severe chronic active hepatitis, cirrhosis and, in some cases, hepatocellular carcinoma. The HCV genome consists of a single-stranded, positive sense RNA containing an open reading frame of approximately 9060 nucleotides. This is translated into a single polyprotein of approximately 3020 amino acids (C-E1-E2-p7-NS2-NS3-NS4A-NS4B-NS5A-NS5B), which in turn is processed by a series of host and viral proteinases into at least 10 cleavage products. The N-terminal portion of the NS3 protein encodes a serine proteinase that is responsible for the cleavage at the NS3-4A, NS4A-4B, NS4B-5A and NS5A-5B junctions. The 54 amino acid NS4A protein is a cofactor that binds to the NS3 protein and enhances its proteolytic activity. This report describes the expression of a recombinant NS3-4A proteinase fusion protein in Escherichia coli and the in vitro characterization of the enzyme activity using synthetic peptide substrates. It then demonstrates how these results were employed to guide the design of potent inhibitors of this enzyme.

Self-reported abuse history and pain complaints among young adults

OBJECTIVE

Considerable evidence suggests that a self-reported history of physical and/or sexual abuse is more frequently reported among chronic pain populations and is associated with poorer adjustment to pain. However, previous research has typically included patients seeking treatment for pain, whereas few population-based studies have explored the association between abuse history and pain. This purpose of this study was to examine the association between self-reported history of sexual or physical abuse and recent pain complaints, health-related variables, and psychological disturbance among a nonclinical sample of young adults.

DESIGN

Subjects were 426 (275 female, 151 male) college students who completed a series of questionnaires assessing abuse history, recent pain, health care utilization, perceived health, and psychological variables.

RESULTS

Females reported a positive history of abuse (PHA) more frequently than males (43.5% vs. 23.8%), and females reported significantly higher rates for all types of abuse except physical abuse during childhood (p < 0.05). PHA subjects reported experiencing pain in more sites and pain of higher severity over the past month compared to subjects with a negative history of abuse (NHA) (p < 0.05). PHA subjects also reported more health care utilization and greater psychological disturbance, including depression, somatization, negative temperament, and higher levels of catastrophizing (p < 0.05). Interestingly, when somatization and depression scale scores were used as covariates, group differences in pain complaints and health care utilization became nonsignificant (p > 0.10).

CONCLUSION

These findings suggest that a self-reported history of physical or sexual abuse is associated with increased pain complaints, health care utilization, and psychological disturbance even among young adults from a nonclinical population. Moreover, the association between abuse and pain complaints appears to be moderated at least in part by the higher levels of somatization and depression observed in the PHA group.

Pregnancies complicated by retained placenta: sex ratio and relation to pre-eclampsia

Pre-eclampsia and placenta accreta have opposite histological features of placentation. This study set out to test the hypotheses that the sex ratios in these two pregnancy complications are opposite and that these conditions are mutually exclusive. A population-based database covering all deliveries in South Australia between 1986 and 1995 and the hospital-based obstetric database of the Adelaide Women's and Children's Hospital, covering 8549 births between 1993 and 1995, were used to ascertain the sex ratios in singleton pregnancies and the sex ratios in those pregnancies in which there was retained placenta, hypertension in pregnancy, or pre-eclampsia. The likelihood of independence of occurrence or mutual exclusivity of retained placenta and hypertension in pregnancy or pre-eclampsia were also examined. The male:female sex ratio in the South Australian population was 1.077. In pregnancies with hypertension in pregnancy it was 1.165 (P<0.001) and in pregnancies with retained placenta it was 0.883 (P<0.0001). There was a trend to an increased sex ratio in pre-eclamptic pregnancy (1.248 in primigravid and 1.092 in multigravid women) but there was insufficient power to detect significance (P=0.207 and 0.470, respectively). Neither hypertension in pregnancy nor pre-eclampsia were mutually exclusive of placenta accreta: hypertensive disorders of pregnancy and placenta accreta occurred independently of each other. Our findings suggest that sex-linked antigens are unlikely to influence maternofetal interactions consistently to give rise to one but not the other pregnancy complication.

Smearing of Vulcanized Rubber

The surface heating which occurs at the interface of rubber sliding under a load may be part of the mechanism of abrasion, especially under severe conditions. Removal of rubber by thermal degradation and a smearing process occurs if the rubber attains sufficiently high localized temperatures. A procedure, using a melting point bar, was developed for measuring the temperature at which smearing occurred for rubber vulcanizates. Smear points reproducible to about ±2° F were measured. The effect of compounding variables on the smear point was investigated. The most important variable in this category was the vulcanization system, probably inasmuch as it determined the type of cross-linking. The presence of free sulfur within the rubber also tended to increase the smear temperature. Highest smear points were obtained with mercaptobenzothiazole-tetramethylthiuram disulfide mixtures, and for a non-sulfur compound using p-quinone-dioxime as the curing agent. The highest smear point observed for natural rubber was 475° F, obtained with this system. GR-S tread compounds showed no smearing even at 560° F, which was as high as could be obtained with the apparatus used. The resistance to smearing of GR-S may be an important factor in explaining its superiority in road wear under severe conditions. Laboratory abrasion experiments were performed to illustrate the effect of smearing on the relative abrasion loss of GR-S and natural-rubber tread compounds.

Study of the Factors Affecting the Friction of Tread Compounds on Ice

The friction of tread compounds on ice is affected to a great extent by the methods and conditions of measurement. As velocity of sliding is increased from zero to about two centimeters per second, there is an increase in friction, after which there is a gradual decrease with further increase of velocity. Static friction depends on the length of time the sample is in stationary contact with the ice, and is of little practical significance. Of the test variables studied, temperature has the greatest influence. At the lowest temperatures used, −30 to −40° C, the coefficient was approximately double that usually observed slightly below the freezing point. Friction was also found to vary with pressure. An empirical equation of the form,k=C1−C2 log P, was found to fit results in many cases. Minor differences were noted, resulting from changes in sample shape and surface treatment. When testing conditions were held constant, it was found that several variables in the samples themselves affected the friction. The type of polymer used had a definite effect. Of about equal importance was hardness. In similar compounds the softer samples had higher coefficients of friction. The unusual frictional characteristics of rubber sliding on ice may be explained by taking into account the water layer formed between the sliding surfaces. The melting of ice to form this water layer takes place because of the heat generated by the work done against friction. The friction itself is believed to be caused by alternate welding and breaking of junctions between surface asperities. Although the process is initiated in part by pressure melting, that phenomenon has only minor importance after the motion is in progress.

Vibration Characteristics of Tread Stocks

Nonlinear vibration characteristics of tread compounds, as evidenced by a dependence of modulus and internal friction on amplitude, were studied in order to reach an understanding of these unexplained phenomena in terms of plausible structural alterations which may occur in the tread compounds because of vibration. This information is interesting both for a more exact description of the deformation processes in tread compounds, and because of the necessity of dealing with the effects in any dynamic testing procedure. Nonlinear vibration characteristics are readily observed for tread stocks of both Hevea and synthetic rubbers in the mechanical range of frequencies. Experiments were undertaken to study the extent to which these effects depend on temperature, compounding variables, and type of vibration. It may be shown that the nonlinearity is not due to temperature rise from vibration, although precise measurements are complicated by the temperature rise. The effects occur for stocks reinforced with fine silica pigment, Pliolite resin, and higher loadings of pigments generally considered to be nonreinforcing, as well as for those compounded with reinforcing blacks. The pigment loading necessary for the same degree of nonlinearity increases with the pigment size. The effects are observed in unvulcanized tread stocks and occur for vibrations in both shear, compression, and tension. Measurements of the nonlinearity for tread stocks over a range of temperatures suggest that the vibration elicits structural changes in the rubber analogous to those observed in the rheology of rubber solutions and raw rubber. The nature of these changes can be interpreted by the rheological criteria of structure developed for non-Newtonian systems. Such recognized mechanisms for structural viscosity as orientation, deformation, and breaking and reforming of bonds of the flow units are useful in explaining the phenomena observed. The effects appear to be of such magnitude that they should be taken into account in any exact study of the effect of modulus on tread wear and performance.

Low-Temperature Stiffening of Elastomers

The generally observed stiffening of elastomers at low temperatures may be supplemented by the occurrence of crystallization if the elastomers have sufficient regularity of molecular structure and other conditions are favorable. To study these effects, observations of the progressive stiffenings of elastomer compounds at low temperatures were made by measurements of the relative torsional modulus of test strips mounted in racks which were stored at low temperature. The periods of observation extended over 30 to 60 days with temperatures in the range from −59° to −18° C. A correlation was found between density changes due to crystallization as determined dilatometrically and torsional stiffness changes. Factors studied in addition to temperature included compounding variables such as cure and plasticizer content. Some data were obtained to show the acceleration of crystallization due to compressive stress. Progressive stiffening due to crystallization was observed for vulcanizates of Hevea, Neoprene Type GN, and Butyl rubber, as well as for an 85-15 butadiene-styrene redox-type copolymer. The results were interpreted in accordance with concepts of crystal nucleation and growth with necessary modifications due to the molecular structure of elastomers. Although the phenomenon of spontaneous crystallization of elastomers was found to be complicated by many factors, a useful degree of generality appears in some of the results.

Vulcanization at High Pressures

A technique was developed for vulcanizing cylinders of rubber 0.5 inch in diameter and up to 1 inch long at pressures as high as 150,000 pounds per square inch, using a small laboratory press (8-inch square platens). The specially designed mold was made of alloy steel according to general principles from the high pressure work of Bridgman. It was prestressed at 200,000 pounds per square inch. The temperature in the mold cavity was carefully calibrated with thermocouples to determine the equivalent length of cure of the test-specimens. Cylinders of GR-S tread stock were vulcanized for a range of cures at 1000, 20,000, 50,000, and 100,000 pounds per square inch. GR-S gum stock and Hevea gum and tread stocks were vulcanized for a range of cures at 100,000 pounds per square inch. Control specimens were cured in a regular type of mold, for which the pressure was not determined. All the volume compression during vulcanization is recovered when the pressure is released. This was determined by precise density measurements of the test-specimens. The electrical resistivity, dynamic modulus, internal friction, and resilience of the test-specimens were determined and the results are discussed.

Low Temperature Characteristics of Elastomers

The low temperature stiffening of elastomers frequently limits their usefulness. A new laboratory test for measuring their stiffness at low temperatures is described. Strips of the stocks to be tested are mounted around a cylindrical rack in a vertical, cylindrical insulated chamber. The temperature in the chamber is controlled by cooling the base externally with dry ice and by a moderate regulated flow of precooled air through dry ice in the bottom of the chamber. This system gives stable temperatures which are easily controlled. The chamber can be rotated to attach the samples in succession, by means of projecting top grips, to a suitably mounted torsion wire. The stiffness is measured by the angle of twist of the sample when the torsion head is rotated 180°. The relative modulus for any temperature is calculated as the ratio of the modulus at this temperature to that at 25° C. Plots of angle of twist against temperature show a rather sharp break at the low temperature end of the curve. This determines a somewhat subjective “freezing point”. Curves are given to illustrate the wide variety of low temperature stiffening characteristics for elastomers. In unplasticized stocks the chemical composition of the monomers is the dominating factor for these properties for various synthetic rubbers. The stiffness of elastomers which are capable of crystallization on stretching, such as Hevea, Neoprene, and Butyl rubber, depends not only on temperature but also on time of exposure. To study these effects, the foregoing apparatus was used in a cold room. A rather long induction period occurs, during which the stiffness is essentially constant. It then increases and eventually reaches a larger constant value. Several months may be required to complete these changes. x-Ray examination of Hevea and Butyl proved that the increased stiffness on long exposure is due to crystallization. No change was observed in the stiffness of GR-S in the period of 2.5 months at − 30° C. Reduction in the speed of retraction is a critical measure of the deterioration of high elasticity at low temperatures. It gives a wide differeniation at moderately low temperatures between Butyl rubber and Hevea or GR-S, whereas a slow modulus test does not.