Biomedical subjects
G Green
Publications and source records attributed to G Green.
Social support and HIV.
This paper reviews research about the relationship between social support and health for people with HIV. Current studies linking social support and HIV are described and the major findings summarized in order to identify gaps in the literature. It is argued that, to date, research in this area has focused primarily upon gay white men in the USA at a symptomatic stage of the illness. There are few studies which have considered the impact of social position on the relationship between social support and health, and few which have included HIV-negative controls. Whilst there is evidence of a link between social support and the psychological well-being of people with HIV, research is still in its infancy. Much information is required about which particular aspects of social support and health are associated, how this association changes over time according to the stage of the disease, and with the socio-economic and cultural characteristics of those with HIV.
Nausea: the most important factor determining length of stay after ambulatory anaesthesia. A comparative study of isoflurane and/or propofol techniques.
Speed of recovery and length of stay in hospital were studied in 95 ambulatory patients undergoing laparoscopy or arthroscopy. The patients were divided into three groups regarding maintenance of anaesthesia. Group A (n = 32) received isoflurane 0.7% end-tidally, group B (n = 31) propofol infusion for 25 min and thereafter isoflurane, and group C (n = 32) received an infusion of propofol throughout the procedure. Recovery was assessed by a combination of the Maddox-Wing, the Choice Reaction Time test and p-deletion. The awakening period was somewhat shorter in group A, but psychomotor recovery was somewhat slower compared to groups B and C. The length of stay in hospital depended on whether the patient was nauseated or not. In group A, 44% suffered from nausea requiring medical intervention compared to 13% and 19% in groups B and C, respectively. The stay in hospital was 235 +/- 90 min (mean +/- standard deviation) in group A compared to 184 +/- 56 min and 197 +/- 55 min in groups B and C, respectively. The non-nauseated patients in group A had a stay in hospital of 188 +/- 55 min compared to 184 +/- 52 and 184 +/- 37 in the non-nauseated patients in groups B and C, respectively. In total, the nauseated patients (n = 24) stayed 267 +/- 95 min compared to 185 +/- 47 min for the non-nauseated patients (n = 71), P < 0.001. We found nausea to be the most important factor determining length of stay after ambulatory anaesthesia.(ABSTRACT TRUNCATED AT 250 WORDS)
Endocrine responses and conception rates in fallow deer (Dama dama) following oestrous synchronization and cervical insemination with fresh or frozen-thawed spermatozoa.
In Expt 1, 59 mature fallow deer does were allocated to six treatments (n = 9-10 per treatment). Does assigned to treatments 1, 2 and 3 each received an i.m. injection of 500 micrograms cloprostenol on day 13 of a luteal cycle. Does in treatments 2 and 3 received 50 or 100 iu pregnant mares' serum gonadotrophin (PMSG), respectively, at the time of prostaglandin administration. Does assigned to treatments 4, 5 and 6 each received single intravaginal controlled internal drug release (CIDR) devices for 14 days. Does in treatments 5 and 6 received 50 or 100 iu PMSG, respectively, at the time of CIDR device withdrawal. Incidence of oestrus was higher following treatment with CIDR devices than with prostaglandin (29 of 30 versus 12 of 29, P < 0.001). PMSG induced earlier onset of oestrus (34.6 +/- 0.9 h versus 44.7 +/- 2.4 h, P < 0.01) and reduced the range in the time to onset of oestrus (from 22 to 8 h for prostaglandin-treated does and from 36 to 14 h for progesterone-treated does). The number of LH surges was higher following treatment with CIDR devices than with prostaglandin (10 of 12 versus 3 of 12, P < 0.01). The overall mean peak LH concentration and time to LH peak were 30.2 +/- 3.4 ng ml-1 and 45.2 +/- 2.2 h after prostaglandin administration or CIDR device withdrawal. The overall median time of ovulation was 26 h after the onset of oestrus.(ABSTRACT TRUNCATED AT 250 WORDS)
Auditory successive conditional discrimination and auditory stimulus equivalence classes.
This paper describes an experimental demonstration of stimulus equivalence classes consisting entirely of auditory stimuli. Stimuli were digitized arbitrary syllables (e.g., "cug," "vek") presented via microcomputer. Training and testing were conducted with a two-choice auditory successive conditional discrimination procedure. On each trial, auditory samples and comparisons were presented successively. As each comparison was presented, a response location (a rectangle) appeared on the computer screen. After all stimuli for a trial were presented, subjects selected one of the response locations. Six subjects acquired the conditional discrimination baseline, 4 subjects demonstrated the formation of three-member auditory equivalence classes resulting from sample-S+ relations, and 1 subject demonstrated equivalence classes resulting from sample-S- relations. Four subjects received additional training and subsequently demonstrated expansion of the three-member classes to four members each.
Ethnicity and polycystic ovary syndrome are associated with independent and additive decreases in insulin action in Caribbean-Hispanic women.
This study was conducted to determine the impact of polycystic ovary syndrome and ethnicity on insulin action. Thirteen Caribbean-Hispanic and 10 non-Hispanic white polycystic ovary syndrome women were compared with 5 Caribbean-Hispanic and 8 non-Hispanic white normal women matched for age, weight, and body composition. All subjects underwent a 2-h 75 g oral glucose tolerance test and euglycemic glucose clamp study with a 40 mU.m-2 x min-1 insulin dose. Hepatic glucose production was determined basally and throughout the euglycemic clamp study. Polycystic ovary syndrome was associated with significant increases in fasting insulin levels (P < 0.05) and in 2-h postglucose-load glucose and insulin levels (P < 0.001). Ethnicity was not associated with any changes in these parameters. Polycystic ovary syndrome but not ethnicity was also associated with hepatic insulin resistance, because significant (P < 0.05) residual hepatic glucose production occurred during the euglycemic clamp in the polycystic ovary syndrome women. However, significant independent effects existed for both polycystic ovary syndrome (P < 0.01) and ethnicity (P < 0.05) that resulted in decreased insulin-mediated glucose disposal. Similarly, significant independent effects of polycystic ovary syndrome (P < 0.005) and ethnicity (P < 0.05) occurred, resulting in increased steady-state insulin levels during the euglycemic clamp. This appeared to be, in part, secondary to a decrease in the metabolic clearance rate of insulin associated with ethnicity (P < 0.05). We conclude that polycystic ovary syndrome and ethnicity result in independent and additive decreases in insulin sensitivity in Caribbean-Hispanic women.(ABSTRACT TRUNCATED AT 250 WORDS)
Differential effects of oral glucose-mediated versus intravenous hyperinsulinemia on circulating androgen levels in women.
OBJECTIVE: To determine whether transient endogenous or continuous exogenous hyperinsulinemia produced different changes in circulating gonadal steroid levels because insulin is a putative regulator of gonadal steroid secretion in polycystic ovarian syndrome (PCOS). DESIGN: An oral glucose tolerance test (OGTT) and a 2-hour euglycemic clamp (+100 microU/mL [718 pmol/L] steady-state insulin levels) were performed in obese patients with PCOS (n = 7) in nonobese patients with PCOS (n = 5), and in age- and weight-matched ovulating normal women (obese normal n = 7, nonobese normal n = 6). RESULTS: Despite increased insulin levels, the levels of T and androstenedione (A) decreased in three of the four groups during the OGTT (nonobese normal women showed a slight increase in T during the OGTT). In contrast, the continuous 2-hour insulin infusion resulted in increased androgen levels. When all four groups were pooled, the difference in the changes in A levels between the two tests was significant, and the difference in T levels between the two tests approached significance. CONCLUSIONS: Transient physiological hyperinsulinemia produced by an oral glucose load was associated with a decrease rather than an increase in circulating androgen levels. The effects on circulating androgen levels of oral glucose-mediated increases in insulin levels were significantly different from those of a continuous intravenous insulin infusion. Sustained hyperinsulinemia produced by exogenous insulin infusion appeared to be required to increase androgen levels in women; transient physiological increases in insulin levels after an oral glucose load were insufficient to produce hyperandrogenism. Postmeal hyperinsulinemia does not contribute to hyperandrogenism in women.
Using stimulus equivalence procedures to teach name-face matching to adults with brain injuries.
On pretests, 3 men with brain injuries matched dictated names of three therapists to written names, but did not match dictated or written names to photos, produce correct names in response to photos, locate offices given written names, or name therapists on sight. Match-to-sample training established conditional relations between dictated names and photos. Posttests showed the emergence of untrained conditional relations involving photos and written names, indicating development of three classes of equivalent stimuli (each containing a dictated name, photo, and written name). For 1 participant, conditional relations involving photos of office nameplates were also examined, but did not emerge pre- or posttraining. Two participants produced names orally when given photos and sorted written names and faces together after training; the 3rd participant was unavailable for these posttests. After training, 1 participant located and named all three therapists in their offices.
The nonequivalence of behavioral and mathematical equivalence.
Sidman and his colleagues derived behavioral tests for stimulus equivalence from the axiom in logic and mathematics that defines a relation of equivalence. The analogy has generated abundant research in which match-to-sample methods have been used almost exclusively to study interesting and complex stimulus control phenomena. It has also stimulated considerable discussion regarding interpretation of the analogy and speculation as to its validity and generality. This article reexamines the Sidman stimulus equivalence analogy in the context of a broader consideration of the mathematical axiom than was included in the original presentation of the analogy and some of the data that have accumulated in the interim. We propose that (a) mathematical and behavioral examples of equivalence relations differ substantially, (b) terminology is being used in ways that can lead to erroneous conclusions about the nature of the stimulus control that develops in stimulus equivalence experiments, and (c) complete analyses of equivalence and other types of stimulus-stimulus relations require more than a simple invocation of the analogy. Implications of our analysis for resolving current issues and prompting new research are discussed.
Evidence for distinctive and intrinsic defects in insulin action in polycystic ovary syndrome.
Women with PCO have a unique but poorly characterized disorder of insulin action. Obese (n = 16) and nonobese (n = 14) PCO women and age- and weight-matched normal, nondiabetic ovulatory women (obese, n = 15; nonobese, n = 17) had insulin action determined in vivo with sequential multiple insulin dose euglycemic clamps and in isolated abdominal adipocytes to clarify the mechanisms of insulin resistance. PCO resulted in significant increases in the ED50 insulin for glucose utilization in vivo (P less than 0.001) and in adipocytes (P less than 0.01), without significant changes in adipocyte insulin-binding sites. PCO also resulted in significant decreases in maximal insulin-stimulated rates of glucose utilization in vivo (P less than 0.01) and in adipocytes (P less than 0.01). Obesity resulted in smaller decreases in insulin sensitivity than PCO (ED50 insulin, P less than 0.001 in vivo and P less than 0.05 in adipocytes), but greater decreases in insulin responsiveness (Vmax, P less than 0.001 in vivo and in adipocytes). The ED50 insulin for suppression of HGP was increased only in obese PCO women (P less than 0.001), and the interactions between PCO and obesity on this parameter were statistically significant. No significant correlations between androgen or estrogen levels and adipocyte insulin binding or action were found. Because insulin binding was not changed, we conclude that the major lesion causing insulin resistance in PCO is a striking decrease in insulin sensitivity secondary to a defect in the insulin receptor and/or postreceptor signal transduction. PCO also is associated with modest but significant decreases in glucose transport. These defects in insulin action appear to represent intrinsic abnormalities that are independent of obesity, metabolic derangements, body fat topography, and sex hormone levels. Conversely, changes in hepatic insulin sensitivity appear to be acquired with obesity.
Chronic high-dosage androgen administration to ovulatory women does not alter adrenocortical steroidogenesis.
OBJECTIVE: To evaluate the role of chronic long-term exogenous androgen administration to normal ovulatory women on adrenal steroidogenesis. DESIGN: Prospective study of four consecutive female-to-male transsexuals before and during chronic testosterone (T) therapy. SETTING: Clinical Research Center of the Mount Sinai Medical Center. PATIENTS: Four female-to-male transsexuals were studied before and during 6 to 12 months of chronic T enanthate therapy for desired virilization. All four subjects were ovulatory before treatment. Adrenocorticotropic hormone (ACTH) testing was performed before, and 6 and 12 months of androgen therapy and various adrenal androgens as well as precursor:product pairs were evaluated as an index of specific adrenocortical biosynthetic defects. RESULTS: Baseline and 1 hour after 0.25 mg ACTH intravenously, adrenal androgen levels as well as adrenal precursor/product pairs demonstrated no difference before and during chronic T treatment. Studies included determinations of plasma 17-hydroxypregnenolone, 17-hydroxyprogesterone, dehydroepiandrosterone, androstenedione, 11-deoxycortisol, and cortisol. CONCLUSION: It is concluded that chronic hypertestosteronemia does not alter adrenal steroidogenesis.
Cultured vascular endothelial cells secrete a protein factor(s) that promotes the contraction of collagen lattices made with fibroblasts.
Conditioned media collected from arterial endothelial cells contain protein factor(s) that promotes the contraction of collagen lattices made with skin fibroblasts. Based on the lattice contraction-promoting activity, a protein with an apparent molecular weight of 22 kDa was identified. This 22-kDa protein stimulated lattice contraction in both serum-containing and serum-free media. When assayed at a 30% equivalent of the conditioned medium, the contraction-promoting activity of the purified factor was about 50 to 60% of that elicited by the unfractionated conditioned medium. Some contraction-promoting activity was also present in certain subfractions of the conditioned medium generated during the separation of the 22-kDa protein. Taken together, the results indicate that the lattice contraction-promoting activity in the endothelial cell-conditioned medium is probably aided by multiple active principles. The biochemical and biological characteristics indicated that the 22-kDa protein is not a transforming growth factor-beta-related factor nor a fibroblast growth promoter.
Like parent like child? Associations between drinking and smoking behaviour of parents and their children.
This paper examines the association between the smoking and drinking behaviours of parents and their adolescent children, and the effect of gender and social class upon this association. It is based on data collected from a cohort of young people and their parents, resident in the west of Scotland. Both social class and parental smoking behaviour were independently associated with young people's smoking, with young people from lower social class households or whose parents smoked being most likely to smoke. Social class and gender were independently associated with young people's drinking, with males and young people from non-manual households being most likely to drink. Parental drinking behaviour was associated positively with young people's drinking only in non-manual classes and among daughters. We conclude that it is important to take social class and gender into account since it may influence whether or not there is an association between the behaviour of young people and that of their parents, and it may influence young people's behaviour in addition to influences from parental behaviour.
Effect of acute hypoxia on respiration and brain stem blood flow in the piglet.
Changes in local brain stem perfusion that alter extracellular fluid Pco2 and/or [H+] near central chemoreceptors may contribute to the decrease in respiration observed during hypoxia after peripheral chemoreceptor denervation and to the delayed decrease observed during hypoxia in the newborn. In this study, we measured the changes in respiration and brain stem blood flow (BBF) during 2-4 min of hypoxic hypoxia in both intact and denervated piglets and calculated the changes in brain stem Pco2 and [H+] that would be expected to occur as a result of the changes in BBF. All animals were anesthetized, spontaneously breathing, and between 2 and 7 days of age. Respiratory and other variables were measured before and during hypoxia in all animals, and BBF (microspheres) was measured in a subgroup of intact and denervated animals at 0, 30, and 260 s and at 0 and 80 s, respectively. During hypoxia, minute ventilation increased and then decreased (biphasic response) in the intact animals but decreased only in the denervated animals. BBF increased in a near linear fashion, and calculated brain stem extracellular fluid Pco2 and [H+] decreased over the first 80 s both before and after denervation. We speculate that a rapid increase in BBF during acute hypoxia decreases brain stem extracellular fluid Pco2 and [H+], which, in turn, negatively modulate the increase in respiratory drive produced by peripheral chemoreceptor input to the central respiratory generator.
Acanthosis Nigricans, insulin action, and hyperandrogenism: clinical, histological, and biochemical findings.
Acanthosis nigricans (AN) is a frequent clinical finding in hyperandrogenic women. Its presence has been used to subgroup such women. We performed this study in order to determine the actual histological prevalence of AN and its relationship to sex hormone levels and insulin action. Insulin-mediated glucose disposal was determined by the euglycemic clamp technique, and neck or axillary skin biopsies were graded blind for the presence and severity of AN in lean and obese women with the polycystic ovary syndrome (PCO) and in age- and weight-matched normal ovulatory controls. AN was present on clinical examination in 11 of 13 obese PCO, 3 of 6 lean PCO, 4 of 14 obese normal, and 0 of 4 lean normal women. AN was present on histological examination in 13 of 13 obese PCO, 5 of 6 lean PCO, 13 of 14 obese normal, and 1 of 4 lean normal women. The severity of histological AN was most highly correlated with insulin-mediated glucose disposal (r = -0.61; P less than 0.001) rather than fasting (r = 0.46; P less than 0.05) or glucose-stimulated insulin levels (r = 0.48; P less than 0.01). The only sex steroid correlated with histological AN was dehydroepiandrosterone sulfate (r = 0.46; P less than 0.01). We conclude that 1) clinical skin examination was very insensitive for detecting AN; 2) the best biochemical correlate of histological AN was decreased insulin action, rather than insulin or androgen levels per se; and 3) AN is a very common epiphenomenon of insulin resistance, and its clinical presence should not be used as a criterion for stratifying hyperandrogenic women.
The role of instructions in the transfer of ordinal functions through equivalence classes.
In two experiments, adult subjects completed match-to-sample training and testing to establish four equivalence classes of four figures each. Then the subjects were taught one three-position sequence consisting of one stimulus from Class 1, one from Class 2, and one from Class 3. Inclusion of Class 4 stimuli in sequences was never reinforced, but two different stimuli from Class 4 appeared as distractors on each sequence trial. Tests assessed whether subjects would produce novel three-position sequences composed of members of Classes 1 through 3 that had not been used in sequence training. Three subjects in Experiment 1 received instructions about the match-to-sample and sequencing tasks, in addition to training contingencies. All 3 demonstrated equivalence class formation after match-to-sample training. After they were taught one sequence with one member of Classes 1 through 3, none of these subjects produced untrained sequences with other equivalence class members reliably. One additional sequence was trained directly; thereafter 1 subject showed some evidence of transfer of the trained ordinal functions across the remaining members of the equivalence classes, but the other 2 did not. Following a review of equivalence class training and testing and a review of the original sequence training, all 3 subjects produced most of the predicted, untrained sequences on tests. Experiment 2 replicated Experiment 1 with 2 adults but omitted all instructions except the minimal ones necessary to initiate responding. Unlike the subjects in Experiment 1, both of these subjects demonstrated virtually complete transfer of ordinal functions through the equivalence classes after direct training on just one sequence composed of one member of Classes 1 through 3.
Development and crossmodal transfer of contextual control of emergent stimulus relations.
Six normally capable adults first learned three conditional relations in each of two prospective equivalence classes via match-to-sample training with figures as conditional (sample) and discriminative (comparison) stimuli. Then one trained conditional relation in each prospective class was brought under the control of contextual stimuli, two dictated nonsense syllables. Test performances indicated the emergence of untrained conditional relations, and therefore two equivalence classes, that were conditional on the contextual stimuli. These tests involved untrained combinations of contextual stimuli and stimuli in conditional relations, suggesting that the contextual stimuli functioned independently to control conditional relations rather than forming compound stimuli with samples and comparisons in training. Next, two novel figures were made equivalent to each of the original dictated contextual stimuli by match-to-sample training and testing. On subsequent tests, all subjects demonstrated transfer of conditional control of untrained conditional relations from the original auditory contextual stimuli to equivalent visual stimuli. These outcomes further supported the conclusion that the contextual stimuli exerted true conditional control over conditional relations in the equivalence classes and were not merely elements of compound stimuli.
Nursing education: crisis or opportunity.
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