Coupled partitioning of Au and As into pyrite controls formation of giant Au deposits.

The giant Carlin-type Au deposits (Nevada, USA) contain gold hosted in arsenic-rich iron sulfide (pyrite), but the processes controlling the sequestration of Au in these hydrothermal systems are poorly understood. Here, we present an experimental study investigating the distribution of Au and As between hydrothermal fluid and pyrite under conditions similar to those found in Carlin-type Au deposits. We find that Au from the fluid strongly partitions into a newly formed pyrite depending on the As concentration and that the coupled partitioning behavior of these two trace elements is key for Au precipitation. On the basis of our experimentally derived partition coefficients, we developed a mass balance model that shows that simple partitioning (and the underlying process of adsorption) is the major depositional process in these systems. Our findings help to explain why pyrite in Carlin-type gold deposits can scavenge Au from hydrothermal fluids so efficiently to form giant deposits.

Danazol: an effective option in acquired amegakaryocytic thrombocytopaenic purpura.

Acquired amegakaryocytic thrombocytopaenic purpura (AATP) is a rare haematological condition characterised by isolated thrombocytopaenia with normal other cell lines. It is often initially misdiagnosed as immune thrombocytopaenic purpura but has characteristic bone marrow findings of reduced megakaryocyte numbers. The optimal treatment of AATP is not clearly defined but revolves around immunosuppressive therapies. We report a case of successful treatment of AATP with danazol, an antioestrogenic medication. We also review the aetiologies and pathogenesis of the disorder and suggest that danazol should be considered as an effective alternative to potent immunosuppression in AATP.

Maternal recall bias, obstetric history and schizophrenia.

BACKGROUND: This study sought to clarify the role of obstetric complications (OCs) and maternal recall bias for patients with first episodes of schizophrenia and those at increased risk of the disorder. METHOD: Subjects at high risk of schizophrenia were compared with people with first-episode schizophrenia and with healthy volunteers. Consenting mothers of subjects were interviewed using a standardised questionnaire for the recall of OCs, and OCs were also measured from records collected at the time of pregnancy and delivery. RESULTS: High-risk subjects and first-episode patients had higher rates of OCs recalled by their mother than controls, but hospital records showed no differences in OCs between groups. The number of OCs recalled by mothers of the high-risk group was not related to whether the mother had schizophrenia or not, but was related to the maternally rated abnormal childhood behaviour as measured by the Child Behaviour Checklist. CONCLUSIONS: These results suggest that studies that rely on maternal recall alone are susceptible to bias. The excess of OCs recalled by the mother could be related to abnormal behaviour in their child rather than maternal illness, family history or psychotic symptoms.

The influence of chronic disease on resource utilization in common acute pediatric conditions. Financial concerns for children's hospitals.

OBJECTIVES: To estimate the resource utilization in hospitalizations for common pediatric conditions or procedures involving patients with chronic disease vs those with no chronic disease and to develop an economic model of hospital per-patient profit (or loss) when insurance contracts fail to account for the presence of chronic disease. SETTING AND DESIGN: A retrospective analysis of selected acute pediatric conditions found in the 1991 and 1992 MedisGroups National Comparative Data Base. PATIENTS: We studied 30379 pediatric admissions for common acute conditions, including concussion, croup, pneumonia, appendicitis, gastroenteritis, fractures, cellulitis, urinary tract infection, and viral illness. MAIN OUTCOME MEASURES: Hospital length of stay and total hospital charges. RESULTS: For patients without chronic disease, mean (geometric) length of stay was 2.53 vs. 3.05 days (P<.001) for patients with at least 1 chronic disease. For patients without chronic disease, mean (arithmetic) total hospital charge was S2614 vs. $3663 (P<.001) for patients with at least 1 chronic disease. Assuming 75% of patients with chronic disease are admitted to a children's hospital vs 25% to a general hospital, overall loss per patient at the children's hospital ranged between 1.5% and 2.9%, depending on assumptions regarding cost-to-charge ratios and the treatment of charge outliers. Pneumonia cases were associated with a 4.0% to 5.85% loss. CONCLUSIONS: Length of stay and charges are higher for everyday pediatric conditions or procedures when patients also have a chronic disease. If insurance contracts fail to account for chronic disease, then children's hospitals will realize significant financial losses, and over time this will lead to a decline in their financial viability, a reduction in quality, or a change in their mission.

Relationship between behavioral and physiological indicators of pain, critical care patients' self-reports of pain, and opioid administration.

OBJECTIVES: To examine the accuracy of inferences about critical care patients' pain based on physiological and behavioral indicators and to assess the relationship between registered nurse and patient pain scores and doses of opioids administered. DESIGN: Descriptive, comparative analysis. SETTING: Three intensive care units and two postanesthesia care units in two hospitals. SUBJECTS: Fourteen critical care nurses who conducted 114 pain assessments on 31 surgical patients. INTERVENTIONS: Nurses used a pain assessment and intervention notation algorithm that contained lists of behavioral and physiological indicators of pain to make inferences about a patient's pain intensity. Fourteen registered nurses completed up to five pain assessments on each patient over a 4-hr period. Following both the physiological and behavioral ratings, nurses rated the patients' pain intensity, using a 0 to 10 numeric rating scale, and they asked patients to provide a self-report of pain intensity, using a similar numeric rating scale. Nurses then administered an intravenous dose of an opioid from a sliding scale prescription. MEASUREMENTS AND MAIN RESULTS: Moderate-to-strong correlations were found between the number of behavioral indicators at times 1 through 5 and between the number of physiological indicators and nurses' ratings of the patients' pain intensity at times 1 through 4 (p < .05). Although nurses' pain ratings were consistently lower than patients' pain ratings across the five time points, these differences were not significant. The amount of opioid analgesic administered by the nurse correlated more frequently with nurses' pain ratings than with patients' self-reports of pain intensity. CONCLUSIONS: The use of a detailed, standardized pain assessment and intervention notation algorithm that incorporates behavioral and physiological indicators may assist healthcare professionals in making relatively accurate assessments of a patient's pain intensity. Further research is needed to determine the specific decision-making processes and criteria that healthcare professionals use to choose doses of analgesics to administer to critically ill patients.

Blockade of behavioral effects of bretazenil by flumazenil and ZK 93,426 in pigeons.

Benzodiazepine receptor partial agonists manifest full efficacy in preclinical tests of anxiolytic drug action but do not fully reproduce the discriminative stimulus effects of benzodiazepine receptor full agonists in pigeons. The partial agonist, bretazenil, binds to both diazepam-sensitive and diazepam-insensitive GABAA receptors. Previous studies have suggested a role for each of these receptor populations in some behavioral effects of bretazenil in pigeons. A possible role for these receptor subtypes in the behavioral effects of bretazenil was further investigated through drug interaction studies with the benzodiazepine receptor antagonists, flumazenil and ZK 93,426. Whereas flumazenil binds with high affinity to both receptor isoforms, ZK 93,426 binds preferentially to diazepam-sensitive binding sites. Bretazenil markedly increased punished responding of pigeons without significantly affecting nonpunished responding. In pigeons discriminating the full benzodiazepine receptor agonist, midazolam, from saline, bretazenil produced only 60-75% maximal effect. Flumazenil and ZK 93,426 neither increased punished responding nor substituted for midazolam, but dose-dependently blocked the effects of bretazenil on punished responding. Flumazenil also dose-dependently blocked the effects of bretazenil in midazolam-discriminating pigeons, whereas ZK 93,426 only attenuated this effect. These results indicate that bretazenil's actions as a partial agonist at diazepam-sensitive benzodiazepine receptors mediate increases in punished responding and substitution for the discriminative stimulus effects of midazolam in pigeons. The differences in the effects of flumazenil and ZK 93,426 on the discriminative stimulus effects of bretazenil suggest a potential contribution of diazepam-insensitive sites to this behavioral effect.

Clinical judgment and management of postoperative pain in critical care patients.

BACKGROUND: Acute pain is a significant problem in critical care patients. Although many barriers to successful assessment and management of pain in critical care patients have been noted, little is known about how critical care nurses make clinical judgments when assessing and managing patients' pain. OBJECTIVE: This qualitative analysis is part of a pilot study evaluating nurses' use of a pain assessment and intervention notation algorithm in patients in critical care areas who have limited communication abilities after abdominal or thoracic surgery. METHOD: Transcribed audiotapes of nurse participants' "thinking aloud" while using the pain assessment and intervention notation algorithm were analyzed by using interpretive phenomenology. The interpretive account is based on 31 tape recordings of 14 nurses caring for 41 patients (12 patients in the ICU and 29 patients in the postanesthesia care unit). FINDINGS: The two domains of clinical judgment found were (1) assessing the patient and (2) balancing interventions. CONCLUSIONS: Many nurses' reports showed that they accurately assessed their patients' needs for analgesics. Through testing of and learning from their patients' responses, nurses were able to give amounts of analgesics that diminished patients' postoperative pain. Additionally, nurses had to balance analgesic administration against the patients' hemodynamic and respiratory conditions, medical plan and prescriptions, and the desires of the patients and the patients' families.

Behavioral and biochemical characterization of benzodiazepine receptor partial agonists in pigeons.

The ability of benzodiazepine receptor partial agonists to exhibit full efficacy in preclinical anxiolytic tests, in conjunction with initial clinical results, has suggested the possibility of a reduced clinical side-effect profile compared to benzodiazepine receptor full agonists like diazepam. Because punished behavior of pigeons has been useful in detecting effects of novel anxiolytic drugs, effects of imidazobenzodiazepine and beta-carboline benzodiazepine receptor partial agonists and some related compounds were evaluated in this species. The abilities of these compounds to substitute for the discriminative stimulus effects of the full agonists midazolam also was determined. Intrinsic efficacy was assessed by the degree to which gamma-aminobutyric acid increased ligand potency to displace [(3)H]Ro15-1788 (flumazinil) from membranes of pigeon cerebrum, and ranged from full agonist-like efficacy (Ro 19-5470; 7-(3-cyclopropyl-1,2,4-oxodiazol-5-yl)-5,6-dihydro-5-methyl-4H- imidazo[1,5a]-thieno[3,2-f]diazin-4-one) to minimal gamma-aminobutyric acid potentiations close to that of the antagonist flumazenil (abecarnil and Ro 41-7812; 7-chloro-4,5-dihydro-3-(3-hydroxy-1-propynyl)-5-methyl-6H-imidazo[1,5-a] -[1,4 ]benzodiazepine-6-one). Punished responding was increased markedly by midazolam and by all partial agonists, except Ro 41-7812 and Ro 42-8773 (7-chloro-3-[3-(cyclopropylmethoxy)-1-propynyl]-4,5-dihyro-5 -methyl-6H-imidaz o[1,5-a][1,4]benzodiazepine-6-one), at doses that did not affect nonpunished responding. In contrast to the full substitution generally observed in mammals, all of the partial agonists produced incomplete substitution (40-70%) in the midazolam drug discrimination procedure in pigeons. A positive relationship was observed between the degree of substitution and intrinsic efficacy. The benzodiazepine antagonists, flumazenil and ZK 93,426 (ethyl-5-isopropoxy-4-methoxymethyl-beta-carboline-3-carboxylate), neither increased punished responding nor substituted for midazolam. The results of the present study suggest that benzodiazepine receptor partial agonists and related compounds may provide full anxiolytic activity at doses that do not fully reproduce the subjective effect profile of full agonists.

Effects of ibogaine on responding maintained by food, cocaine and heroin reinforcement in rats.

The effects of ibogaine (40 and 80 mg/kg, i.p.), an indole alkaloid proposed for the treatment of drug abuse, were determined in three different groups of rats responding under an FR10 schedule of food, cocaine or heroin reinforcement. Ibogaine (80 mg/kg, i.p.) given 60 min before the start of the session resulted in a 97% decrease in the number of ratios completed under the food reinforcement schedule and resulted in a decrease in responding the following day. Neither 40 mg/kg ibogaine given 60 min prior to the session nor 80 mg/kg given 24 h before the session suppressed responding maintained by cocaine infusions (0.33 mg/infusion). Pretreatment with 80 mg/kg ibogaine either 60 or 90 min prior to the session suppressed cocaine self-administration on the day it was administered and the longer pretreatment continued to suppress responding for 48 h. Responding maintained by heroin (18 micrograms/infusion) was the most sensitive to the effects of ibogaine. Both 40 and 80 mg/kg ibogaine resulted in an almost complete suppression of responding following a 60-min pretreatment period. Responding maintained by heroin returned to control levels the day following the administration of ibogaine.

A limits-oriented approach to evolutionary ecology.

Evolutionary ecology focuses on optimal traits to provide a mechanistic understanding of ecological patterns. For some issues, however, It might be a mismatch to marry optimality and ecology. Given that many ecological questions involve limits (to species distributions and abundances; to species diversity), it might be useful to focus on `limiting traits' rather than optimal traits; that is, to understand ecological limits it might be useful to identify the things that organisms do poorly, and to study constraints on the evolution of these limiting traits. While a limiting-traits approach has a long history in ecology, relatively few studies have fully applied the approach, and some ecological issues have only recently been examined from this view.

Monozygotic twinning: an evolutionary hypothesis.

Monozygotic twinning is rare within populations yet taxonomically widespread. We explore the evolution of monozygotic twinning by modeling an allele in a newly formed offspring that causes it to undergo mitosis and separation to form one or more clones (twins), potentially in conflict with the parents' best interest. The success of this twinning allele in our haploid models depends on the balance of the benefit of increased frequency in the clutch and the cost of reduced survival resulting from limited parental resources. The trait reaches high frequency in a broad range of plausible conditions but also fails to spread or is kept at low frequency in others when the survival cost is high (e.g., in small clutch sizes). Interestingly, there are two reasonable conditions that predict high frequency of the trait but low visibility: random parental abortion and selection for low penetrance. Thus our models suggest reasons why monozygotic twinning might be rare, or alternatively, be common yet appear rare. In addition, we discuss the implications for sex-linked twinning, dizygotic twinning, and twinning by gametes.

Anxiolytic and antidepressant mechanisms of 5-HT1A drugs in the pigeon: contributions from behavioral studies.

The discovery that compounds acting through 5-hydroxytryptamine (5-HT) receptor subtypes can produce anxiolytic and/or antidepressant therapeutic effects in humans has resulted in considerable interest in the role of the 5-HT receptor system in both anxiety and depressive disorders. Because many of the clinically efficacious 5-HT1A anxiolytic drugs are either ineffective or produce inconsistent results in traditional or standard types of preclinical punishment or conflict procedures with rodents and other nonhuman mammals, there is considerable need for alternative behavioral assays sensitive to and selective for these compounds. In contrast to data with nonhuman mammals, 5-HT1A drugs are quite effective in pigeons studied under a punishment procedure. This paper reviews the use of the pigeon conflict procedure as a method for the detection and analysis of potential anxiolytic drugs acting through 5-HT1A receptors. Additionally, recent studies, also with the pigeon, have indicated that, in contrast to the rat, it is possible to establish an antidepressant such as imipramine as a discriminative stimulus, and then to use this procedure to evaluate the neuropharmacological bases for the behavioral and, presumably, therapeutic actions of these drugs. Using the drug discrimination procedure, it has been possible to examine a number of selective compounds that substitute for imipramine, thereby clarifying specific substrates for the antidepressant activity of this and related drugs. The pigeon promises to be a useful species in the pharmacological analyses of novel anxiolytic drugs and provides new approaches to the analysis and understanding of traditional as well as the more recently introduced antidepressant drugs.

The Good Heart, Good Life survey: self-reported cardiovascular disease risk factors, health knowledge and attitudes among Greek-Australians in Sydney.

This survey aimed to assess the prevalence and knowledge of coronary risk factors and self-perceived coronary heart disease risk among Greek-Australians in the Marrickville area of inner Sydney. A random sample of 834 household addresses was selected from the 2,403 households having Greek-Australian surnames on the electoral roll. In each household, one individual aged 18 years or over was selected using a Kish grid, and a questionnaire was administered by a bilingual interviewer. Questions concerned knowledge of and self-reported risk factors for coronary heart disease, and ratings of perceived stress, social support and networks. There was a response rate of 81 per cent of actual Greek-Australian households, a total of 541 interviews (61 per cent women). Most of the sample (86 per cent) were born in Greece and 77 per cent of interviews were administered in Greek. The age-adjusted male prevalences of self-reported smoking, high blood pressure, high blood cholesterol and body mass index over 26 kg/m2 were 44 per cent, 5 per cent, 14 per cent and 58 per cent, respectively. The age-adjusted female prevalences of self-reported smoking, high blood pressure, high blood cholesterol and body mass index over 26 kg/m2 were 19 per cent, 8 per cent, 15 per cent and 40 per cent, respectively. Compared to the National Heart Foundation risk-factor prevalence survey, the prevalence of self-reported high blood pressure was lower, but obesity and, among males, smoking, were higher. Low levels of education and poor English-language skills among older Greek-Australians may be contributing to the problem.(ABSTRACT TRUNCATED AT 250 WORDS)

Asymptomatic gallstones revisited. Is there a role for laparoscopic cholecystectomy?

OBJECTIVE: To compare the mortality effects of prophylactic laparoscopic cholecystectomy with that of expectant management in persons with asymptomatic gallstones. DESIGN: Decision analytic models of the two clinical strategies using input data from a review of the published medical literature pertaining to the epidemiology, natural history, and treatment outcomes related to gallstone disease. PATIENTS: Cohorts of men and women aged 30 and 50 years with asymptomatic gallstones. INTERVENTION: Prophylactic laparoscopic cholecystectomy performed at the time of diagnosis of asymptomatic gallstones or expectant management, defined as therapeutic intervention delayed until gallstone symptoms or complications spontaneously develop. MAIN OUTCOME MEASURES: Gallstone-related deaths and gallstone-related life-years lost for each age and gender cohort, by strategy. Models were subjected to rigorous sensitivity analysis to test the robustness of the results to changes in individual input variables. Outcomes were calculated with and without discounting nonfinancial benefits. RESULTS: The prophylactic laparoscopic cholecystectomy strategy led to fewer gallstone-related deaths than the expectant management strategy, but all of the deaths in the prophylactic laparoscopic cholecystectomy group occurred earlier in life. In cohorts older than age 30 years, the expectant management strategy resulted in fewer undiscounted gallstone life-years lost than the prophylactic laparoscopic cholecystectomy strategy. Discounting favored expectant management further because life-years lost were delayed compared with prophylactic surgery. Sensitivity analysis demonstrated the superiority of expectant management over a wide range of input assumptions. CONCLUSIONS: Prophylactic laparoscopic cholecystectomy should not be routinely recommended for individuals with asymptomatic gallstones.

The psychiatric technician: trespasser or welcomed ally?

1. The increasing shortage of nurses, higher patient acuity levels, and greater demands placed on nursing to meet standards of care have contributed to the use of psychiatric technicians to alleviate the burden on nursing and ensure the delivery of quality patient care. 2. Psychiatric technicians provide care for a select group of patients under the supervision of the primary nurse. The patients assigned to psychiatric technicians require minimal direct nursing intervention. 3. Psychiatric technicians reported increased self-confidence and self-esteem; the nurses were able to perform more professional nursing activities, increasing their job satisfaction and promoting staff retention; and the patients received high-quality care.