Design, synthesis and characterisation of a peptide with oxaloacetate decarboxylase activity

The synthesis of Oxaldie-3, a synthetic 31-residue peptide with oxaloacetate decarboxylase activity, is described. Biophysical characterisation by gel filtration, CD and NMR spectroscopy indicated that the peptide adopted a folded structure in solution. Oxaldie-3 was an efficient catalyst at concentrations as low as 2 microM, 100-fold lower than the previously described Oxaldie-2, which relied on aggregating alpha-helices for activity. Oxaldie-3 speeded decarboxylation by more than three orders of magnitude relative to simple amines.

Psychological resources, positive illusions, and health

Psychological beliefs such as optimism, personal control, and a sense of meaning are known to be protective of mental health. Are they protective of physical health as well? The authors present a program of research that has tested the implications of cognitive adaptation theory and research on positive illusions for the relation of positive beliefs to disease progression among men infected with HIV. The investigations have revealed that even unrealistically optimistic beliefs about the future may be health protective. The ability to find meaning in the experience is also associated with a less rapid course of illness. Taken together, the research suggests that psychological beliefs such as meaning, control, and optimism act as resources, which may not only preserve mental health in the context of traumatic or life-threatening events but be protective of physical health as well.

The association between asthma and dental caries in children and adolescents: A population-based case-control study

This study explored the potential association between childhood asthma and caries using oral examination and health interview data from the Third National Health and Nutrition Examination Survey 1988-1994 (NHANES III). We fitted GEE Poisson regression models with adjustment for parents' income, gender, race, exposure to potentially xerostomic drugs, and the presence of pit and fissure sealants. There was no association between the use of drugs commonly used by asthmatics (antihistamines, corticosteroids, and antiasthmatic inhalers) and df/DMF scores. Asthmatic children 4-10 years of age at all severity levels had similar dfs scores to the controls, however, severely asthmatic children 4-10 years of age had significantly lower DMFS (p = 0.010) and DMFT (0.049) scores than controls. Similarly, severely asthmatic children 11-16 years of age had significantly lower DMFT scores than controls (p = 0.024) and DMFS scores approaching statistical significance (p = 0.053). While our analysis adjusted for covariates, potential confounders such as fluoride intake from water, diet, use of topical fluorides, and dose of antiasthmatic medication could not be addressed. Our results indicate that any association between asthma and dental caries may occur primarily in younger children with no evidence of an association between asthma and dental caries as children mature.

Simulation of low temperature anaerobic digestion of dairy and swine manure

The data reported by L.M. Safley, P.W. Westerman [Bioresource Technology 47 (2) (1994) 165-171] from the laboratory digestion of dairy and swine manure at psychrophilic temperatures (i.e., 10-23 degrees C) have been used to determine the response of the latest comprehensive dynamic mathematical model of methanogenesis [D.T. Hill, S.A. Cobb, Transactions of the ASAE 39 (2) (1996) 565-573] in this low temperature range. Extensive performance data from digesters using animal waste in this temperature range have been lacking, thus allowing limited validation of the comprehensive model. The results of the comprehensive model simulations were compared with the actual data reported by Safley and Westerman (loc. cit.) and with their empirical regression models. Results indicate that the comprehensive model is as accurate as Safley and Westerman's models for three of the four cases reported, but shows a great dissimilarity for the fourth case.

A new medication for treatment of dry mouth in Sjögren's syndrome

Traditionally, treatment of dry mouth in SS is focused on palliative measures (using salivary substitutes). However, due to the dynamic nature of the oral cavity, the salivary substitute is removed from the mouth during swallowing. Therefore, the duration of effect of salivary substitutes is short. Another drawback is that salivary substitutes do not provide the protective roles of saliva. Effective treatment of dry mouth requires increasing salivary output. Gustatory stimulation of the salivary glands with sugar free gum and sugar free candies may be effective in inducing salivary output, however, they impose significant inconvenience on the patient which can compromise compliance. Pharmacological stimulants provide an alternative effective measure and improve compliance. Both Salagen and Evoxac are FDA approved salivary stimulants. They are effective, and safe given awareness of their indications, contraindications, potential adverse effects, and patient's tolerance.

Association of Bartonella species and Coxiella burnetii infection with coronary artery disease

Coronary artery disease is an inflammatory condition associated with several infections. We prospectively evaluated 155 consecutive patients undergoing coronary angiography for evidence of Bartonella species and Coxiella burnetii infection. All Bartonella cultures were found to be negative. Multivariable logistic regression analysis that controlled for potential confounding factors revealed no association between coronary artery disease and seropositivity to Bartonella henselae (odds ratio [OR], 0.852; 95% confidence interval [CI], 0.293-2.476), Bartonella quintana (OR, 0.425; 95% CI, 0.127-1.479), C. burnetii phase 1 (OR, undefined), and C. burnetii phase 2 (OR, 0.731; 95% CI, 0.199-2.680). The geometric mean titer (GMT) for C. burnetii phase 1 assay was slightly higher in persons with coronary artery disease than in those without such disease (P<.02). B. henselae, B. quintana, and C. burnetii seropositivity was not strongly associated with coronary artery disease. On the basis of GMTs, C. burnetii infection may have a modest association with coronary artery disease.

Kinetic analysis of 125I-iodorotenone as a deposited myocardial flow tracer: comparison with 99mTc-sestamibi

The goal of this investigation was to assess the accuracy of 7'-Z-[125I]iodorotenone (125I-iodorotenone) as a new deposited myocardial flow tracer and compare the results with those for 99mTc-sestamibi.

METHODS

The kinetics of these two flow tracers were evaluated in 25 isolated, erythrocyte- and albumin-perfused rabbit hearts over a flow range relevant to patients. The two flow tracers and a vascular reference tracer (131I-albumin) were introduced simultaneously as a compact bolus through a port just above the aortic cannula in the absence of tracer recirculation. Myocardial extraction, retention, washout, and uptake parameters were computed from the venous outflow curves using the multiple-indicator dilution technique and spectral analysis.

RESULTS

The extraction of 125I-iodorotenone was much higher than the extraction of 99mTc-sestamibi (0.84 +/- 0.05 vs. 0.48 +/- 0.10, respectively, P < 0.001). 125I-iodorotenone extraction was also less affected by flow than was 99mTc-sestamibi (P < 0.001). Net retention of 125I-iodorotenone was significantly greater than 99mTc-sestamibi net retention at 1 min (0.77 +/- 0.08 vs. 0.41 +/- 0.11, respectively, P < 0.001) and 26 min (0.46 +/- 0.13 vs. 0.27 +/- 0.11, respectively, P < 0.001) after tracer injection. Flow had less effect on 125I-iodorotenone net retention than on 99mTc-sestamibi net retention 1 min after tracer injection (P < 0.04). However, at 26 min, flow had an equivalent effect on the retention of both flow tracers (P < 0.4). The relationship between 125I-iodorotenone and 99mTc-sestamibi washout was complex and depended on elapsed time after isotope introduction and perfusion rate. Reflecting the favorable extraction and retention characteristics of 125I-iodorotenone, both its maximum myocardial uptake and its 26-min uptake were more closely related to flow than were those of 99mTc-sestamibi (P < 0.001 for both comparisons).

CONCLUSION

The extraction and retention of 125I-iodorotenone were greater than those of 99mTc-sestamibi, making 125I-iodorotenone the superior flow tracer in the isolated rabbit heart.

Small-scale spatial and temporal variance in the concentration of heavy metals in aquatic sediments: a review and some new concepts

Uncertainty associated with data derived by the analyses of heavy metals in aquatic sediment is due to variance produced in the laboratory (precision), plus 'natural', small-scale spatial variance, (or field variance) at the sampling site. Precision is easily determined and is usually reported in contaminant studies, but field variance is poorly understood and seldom documented. It is important to have an understanding of the field variance because if small-scale spatial variance in the concentration of heavy metals is excessive, regional trends may be limited value. Similarly, if temporal change is large, the results of single synoptic surveys may be questionable and the ability to demonstrate anthropogenic contributions over time will be difficult. However, it is evident from the literature that the information needed to address problems of spatial and temporal variance in the field is beyond the resources of most researchers. Analytical precision of about 5% relative standard deviation (RSD) for heavy metal analysis is typical of a well-managed laboratory. Many studies of small-scale spatial variability made during the current investigation indicate that field variance is related to ambient energy and to the type of sedimentological environment. Total variance (analytical plus field variance) is approximately 10% RSD (mean for a suite of nine trace elements) for depositional parts of estuaries and the marine environment, but increases to about 20-35% RSD for the more dynamic parts of the estuarine environment and the fluvial system. Repeated sampling over periods of up to 7 years undertaken during the present study, indicate a similar order of magnitude for temporal variability in these sedimentological environments. A proposed scheme to provide information on field variance is to undertake small-scale spatial and temporal studies in discrete sedimentological environments in the study area after sediment sampling and characterisation has been completed. The comparatively large proportion of total variance associated with small-scale spatial and temporal variability in the field questions the often excessive cost and effort made in attempting minor reductions in analytical precision in contaminant investigations.

Serotonin transporter inhibitors: synthesis and binding potency of 2'-methyl- and 3'-methyl-6-nitroquipazine

Racemic 2'-methyl- and 3'-methyl-6-nitroquipazine ligands were selected as targets, synthesized and evaluated at the serotonin transporter employing an in vitro competitive inhibition assay with [3H]paroxetine and rat cortical membrane. The 2'-methyl-6-nitroquipazine was found to be 50 times more potent than the 3'-methyl-substituted counterpart and of comparable potency to the known high affinity agent 5-iodo-6-nitroquipazine.

Structure of a fusion peptide analogue at the air-water interface, determined from surface activity, infrared spectroscopy and scanning force microscopy

We have investigated a point mutant of the HIV-1 fusion peptide in a compressed monolayer at the air-water interface. A variety of surface sensitive techniques were applied to study structural features under conditions mimicking the hydrophobic/hydrophilic environment of a biomembrane. Possible partitioning into the aqueous bulk phase and molecular areas were examined by surface activity based mass conservation plots. This shows that the peptide is practically fully accumulated in the interface. Secondary structure and orientation was analyzed by means of polarized infrared reflectivity. Brewster angle microscopy and scanning force microscopy contributed nanostructural images. At low surface pressures the molecules form anti-parallel beta-sheets lying flat on the interface. Upon a moderate increase of the lateral pressure a flat beta-turn structure appears with inter- and intramolecular H-bonds. We also observed aggregates forming fingerprint-like structures with a diameter of approximately double the hydrophobic length of a beta-turn conformation. Beyond approximately 18 mN m(-1) the beta-turns straighten up. The lowest measured tilt angle was 45 degrees at 36 mN m(-1).

Biobehavioral responses to stress in females: tend-and-befriend, not fight-or-flight

The human stress response has been characterized, both physiologically and behaviorally, as "fight-or-flight." Although fight-or-flight may characterize the primary physiological responses to stress for both males and females, we propose that, behaviorally, females' responses are more marked by a pattern of "tend-and-befriend." Tending involves nurturant activities designed to protect the self and offspring that promote safety and reduce distress; befriending is the creation and maintenance of social networks that may aid in this process. The biobehavioral mechanism that underlies the tend-and-befriend pattern appears to draw on the attachment-caregiving system, and neuroendocrine evidence from animal and human studies suggests that oxytocin, in conjunction with female reproductive hormones and endogenous opioid peptide mechanisms, may be at its core. This previously unexplored stress regulatory system has manifold implications for the study of stress.

Biobehavioral responses to stress in females: tend-and-befriend, not fight-or-flight

The human stress response has been characterized, both physiologically and behaviorally, as "fight-or-flight." Although fight-or-flight may characterize the primary physiological responses to stress for both males and females, we propose that, behaviorally, females' responses are more marked by a pattern of "tend-and-befriend." Tending involves nurturant activities designed to protect the self and offspring that promote safety and reduce distress; befriending is the creation and maintenance of social networks that may aid in this process. The biobehavioral mechanism that underlies the tend-and-befriend pattern appears to draw on the attachment-caregiving system, and neuroendocrine evidence from animal and human studies suggests that oxytocin, in conjunction with female reproductive hormones and endogenous opioid peptide mechanisms, may be at its core. This previously unexplored stress regulatory system has manifold implications for the study of stress.

Psychosocial resources and the SES-health relationship

Psychosocial resources, which include optimism, coping style, a sense of mastery or personal control, and social support, influence the relationship between SES and health. To varying degrees, these resources appear to be differentially distributed by social class and related to health outcomes. Such resources may partially mediate the impact of SES on health. For example, environments that undermine personal control may have an impact on chronic arousal and the corresponding development of disease, such as CHD. Psychosocial resources may also moderate the impact of SES on health. For example, a large number of positive social relationships and a few conflictual ones may buffer individuals against the adverse effects of SES-related stress. These psychosocial resources are moderately intercorrelated, and so a research strategy that explores their coherence as a psychosocial profile that promotes resilience to stress is tenable and merits empirical examination. The erosion of these resources as one moves lower on the SES scale and specific factors that contribute to such erosion are discussed.

Psychological resources, positive illusions, and health

Psychological beliefs such as optimism, personal control, and a sense of meaning are known to be protective of mental health. Are they protective of physical health as well? The authors present a program of research that has tested the implications of cognitive adaptation theory and research on positive illusions for the relation of positive beliefs to disease progression among men infected with HIV. The investigations have revealed that even unrealistically optimistic beliefs about the future may be health protective. The ability to find meaning in the experience is also associated with a less rapid course of illness. Taken together, the research suggests that psychological beliefs such as meaning, control, and optimism act as resources, which may not only preserve mental health in the context of traumatic or life-threatening events but be protective of physical health as well.

Negative HIV-specific expectancies and AIDS-related bereavement as predictors of symptom onset in asymptomatic HIV-positive gay men

This study examined negative HIV-related expectancies, AIDS-related bereavement, and the interaction of expectancies and bereavement as predictors of the onset of significant HIV-related symptoms among previously asymptomatic HIV-positive gay men. From a longitudinal psychobiological investigation, 72 men were selected who had been HIV-positive and asymptomatic from study entry (approximately 3 years). Participants were followed for an additional 2 1/2 to 3 1/2 years after psychosocial assessment, with symptom status assessed every 6 months. The interaction of negative HIV-specific expectancies and bereavement was a significant predictor of symptom onset. Negative HIV-specific expectancies predicted the subsequent development of symptoms among bereaved men, controlling for immunological status, use of zidovudine, high-risk sexual behavior, substance use, and depression.

Negative HIV-specific expectancies and AIDS-related bereavement as predictors of symptom onset in asymptomatic HIV-positive gay men

This study examined negative HIV-related expectancies, AIDS-related bereavement, and the interaction of expectancies and bereavement as predictors of the onset of significant HIV-related symptoms among previously asymptomatic HIV-positive gay men. From a longitudinal psychobiological investigation, 72 men were selected who had been HIV-positive and asymptomatic from study entry (approximately 3 years). Participants were followed for an additional 2 1/2 to 3 1/2 years after psychosocial assessment, with symptom status assessed every 6 months. The interaction of negative HIV-specific expectancies and bereavement was a significant predictor of symptom onset. Negative HIV-specific expectancies predicted the subsequent development of symptoms among bereaved men, controlling for immunological status, use of zidovudine, high-risk sexual behavior, substance use, and depression.

Polymorphism and interactions of a viral fusion peptide in a compressed lipid monolayer

With a view toward possible new insights into viral fusion mechanisms, we have investigated the HIV-1 gp41 fusion peptide in a monomolecular film of the biomembrane lipid palmitoyloleoylphosphatidylcholine. Its surface activity at an air/water interface was measured under equilibrium conditions, using the conventional Langmuir trough technique. Through a novel thermodynamic analysis, the partial molecular area of the peptide in the lipid moiety could be determined as a function of the lateral pressure and the interfacial peptide/lipid ratio. This indicates an orientation of the peptide backbone parallel to the lipid hydrocarbon tails. The molecular area decreases significantly upon monolayer compression, suggesting a conformational transition from a somewhat compact configuration to a more extended, presumably beta-strand structure when a lipid packing density is approached that is generally believed to mimic the physical state of a biological membrane. Up to a lateral pressure of approximately 15 mN/m, practically all peptide inserts into the lipid monolayer. At higher compression a distinct partitioning into the aqueous subphase is observed. Under these conditions the data also reflect a strong aggregation of the lipid-associated peptide. Beyond a critical peptide/lipid ratio, the peptide's area requirement was found to become substantially enhanced, possibly because of the formation of water-filled pores.

Preemptive pharmacologic intervention in radiation-induced salivary dysfunction

Xerostomia ("dry mouth") is a symptom of several diseases. It also occurs as a side effect of certain therapeutic interventions, most frequently pharmacotherapy. The most severe and irreversible forms of salivary dysfunction result from damage to or loss of salivary acinar cells. One of the severest forms of iatrogenic salivary gland destruction results from the therapeutic doses of irradiation given to treat head and neck cancer or to purge the bone marrow before transplantation. Xerostomia encompasses a wide range of involvement, from an inconvenience when mild, to a debilitating condition when severe. Reports of the symptom of dry mouth by patients do not always correlate with the degree of diminished salivary flow. However, a significant loss of stimulated flow makes it difficult to process solid food into a bolus that can be swallowed. If sustained, nutritional deficiencies may result. Saliva also facilitates formation of speech patterns. Its loss hinders speaking and communicating, possibly causing the patient to withdraw from social interaction. Together these conditions can impair the physiological and psychological well-being of the patient. Thousands of individuals undergo radiation therapy for head and neck cancer in the United States each year. Increasing numbers are receiving total body radiation before transplantation of bone marrow. Although the salivary gland is not one of the more actively dividing organs in the body, nevertheless it ranks as one of the most radiosensitive. The mechanism of this sensitivity is not understood. This article reviews human and animal pathophysiology of radiation-induced salivary damage. We also discuss animal studies that have employed various strategies to modify and clarify this process. Finally, we describe encouraging results from early clinical trials suggesting that protection of salivary glands during therapeutic irradiation may be possible.

Dielectric Spectroscopic and Molecular Simulation Evidence for Aggregation of Surfactant-stabilized Calcium Carbonate Nanocolloids in Organic Media

Dielectric spectroscopy carried out on overbased phenate micelle particles of nominal diameter approximately 2 nm containing calcium carbonate cores in hydrophobic liquids indicates that the micelles are strongly aggregated. Mean cluster sizes in excess of approximately 10(3) individual micelles are typically found in toluene. The level of association is a little higher in dodecane which is chemically closer to engine oil, the usual solvent for these systems. The mean aggregate size increases dramatically with concentration above an effective solids volume fraction of approximately 0.1 on treating the micelles as spheres. Aggregate size also depends on the level of overbasing, with lower levels of overbasing giving more micelles in the cluster. Molecular dynamics simulations of individual micelle particles reveal them to have large dipole moments originating mainly from the amorphous carbonate cores. Dipoles of magnitude approximately 20D are typical for a range of different surfactant types used in the model. The magnitude of the dipole depends somewhat on the chemical composition of the stabilizing surfactant shell. Monte Carlo simulations of two phenate nanocolloids taking into account all atom and charge pair interactions show these particles to have a strong short-range coulombic attraction of typically -25kBT at T = 298 K in the favored "side-by-side" relative arrangement. This attraction could be responsible for the strong level of association inferred from the dielectric spectroscopy experiments. Copyright 1999 Academic Press.