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Biomedical subjects

J Ross

Publications and source records attributed to J Ross.

At least 181 records · Page 10Linked to original sources
PubMed1997

Visual performance and patient preference: a comparison of anti-reflection coated and uncoated spectacle lenses.

BACKGROUND: Anti-reflection (AR) coatings of spectacle lenses are designed to reduce the reflected images often found in uncoated lenses. This study examined the visual impact of a specific AR coating. METHODS: First, using a survey, it was determined if patients were aware of the AR coating and, if given an identical pair of lenses without the AR coating, which lenses were preferred and why. Second, in the laboratory, changes in visual performance were evaluated when an anti-reflection coating was applied to a lens. RESULTS: Verbal reports were obtained from 18 patients on both types of lenses. All patients were aware the AR coating reduced unwanted reflections, and many reported reductions in visual problems associated with glare. Within the laboratory, 28 patients were tested on a battery of clinical vision tests. Under normal room illumination, visual acuity, grating-contrast sensitivity, and letter-contrast sensitivity were identical for both coated or uncoated lenses. In a second experiment, the effects of AR coating on contrast sensitivity were examined when subjects viewed a dimly illuminated target while their eye and face were brightly illuminated. Under these conditions, significantly better (a factor of two) contrast sensitivity was observed with AR-coated lenses. CONCLUSIONS: On the basis of these findings, it is proposed that drivers should wear AR-coated spectacle lenses at night.

Adult↗
PubMed1997

Expression of pro- and anti-apoptosis gene products in brains from paediatric patients with HIV-1 encephalitis.

We have previously demonstrated the presence of DNA fragmentation in neurons, macrophages and microglia consistent with apoptosis, but not in reactive astrocytes in brain tissue from paediatric patients with HIV-1 encephalitis (HIVE). To further understand the underlying mechanism(s) for these findings as they relate to gene-directed neural cell death, we studied the in-situ expression of the Bcl-2 family of proteins, including the pro-apoptosis gene product Bax, the anti-apoptosis gene product Bcl-2, and Bcl-x. We demonstrate significantly elevated numbers of Bax-positive microglia and macrophages immunoreactive in basal ganglia and cerebral cortex of children who had HIVE, in comparison to HIV-1 infected children without encephalitis or children who were seronegative for HIV-1. In contrast, patients with HIVE, but not HIV-1 without encephalitis, or seronegative controls, had increased expression of Bcl-2 and Bcl-x in reactive astrocytes in cortex and basal ganglia. In vitro studies using Western blot analysis demonstrated an up-regulation in the levels of Bax, and phosphorylated (i.e. inactive) Bcl-2 in HIV-1 infected macrophages, and in LPS-activated macrophages, relative to levels in virus-negative unstimulated macrophages. These results suggest that productive HIV-1 infection, or cellular activation, renders macrophages more vulnerable to apoptosis. Taken together, these findings suggest that brain-resident macrophages and microglia in patients with HIV-1 encephalitis are more prone to undergo apoptosis and that astrocytes in contrast may be resistant to apoptosis. This may represent a mechanism to limit microglial activation and the spread of productive HIV-1 infection in the CNS of children with HIV-1 encephalitis.

Adolescent↗
PubMed1997

Transitions between routes of benzodiazepine administration among heroin users in Sydney.

A sample of 312 heroin users were interviewed regarding their benzodiazepine use. The majority (94%) had used benzodiazepines, 72% in the 6 months prior to interview. Benzodiazepine injecting was common, with 28% of the sample having injected these drugs, 13% in the 6 months preceding interview. Current benzodiazepine injectors showed greater polydrug use, injection-related HIV risk-taking behaviour, criminal involvement, psychological distress and injection-related health problems, as well as poorer general health, and an increased risk of having overdosed, than other users of benzodiazepines. Of those subjects who had injected benzodiazepines, 55% were no longer current benzodiazepine injectors. Concern for general health emerged as the most common reason for having made a transition away from injecting, and for being likely to make such a transition.

Administration, Oral↗
PubMed1997

Management of unstable coronary syndromes in patients with previous coronary artery bypass grafts following coronary angiography.

OBJECTIVE: To characterize patients who had undergone previous coronary artery bypass grafting (CABG) and who were admitted for coronary angiography for unstable coronary syndromes, to determine the long-term therapy selected for these patients and to assess the outcomes of the intervention. DESIGN: Descriptive retrospective study. SETTING: A university-affiliated tertiary care institution. PATIENTS: A total of 129 patients with 1 previous CABG who underwent coronary angiography for myocardial infarction or unstable angina in 1991. OUTCOME MEASURES: Information regarding initial CABG, indications for cardiac angiography, cardiovascular risk factors, ultimate treatment selected and outcomes at 1 year were abstracted from patients' charts, and outcomes at 1 year were also determined by a patient survey. RESULTS: Seventy-six patients (59%) were given drug therapy, 28 patients (22%) were treated with angioplasty, and 25 (19%) underwent repeat surgery. During their index admissions, of patients given drug therapy, 4 (5.3%) died from myocardial infarction (MI) and 42 (55%) were discharged without complications; of those undergoing angioplasty, all except 2 were treated successfully (major procedural complications included nonfatal MI in 1 patient [4%] and nonfatal ventricular arrhythmia in 1 patient [4%], as well, reocclusion of the lesions occurred before discharge in 2 patients [7%]); of those undergoing repeat surgery, almost all patients (96%) were discharged, except 1 who died from MI during the postoperative period (there were no procedural complications, but early complications included nonfatal MI in 2 patients [8%], angina in 2 [8%] and nonfatal arrhythmias in 11 [44%]). Eighty-seven patients (67%) were available for follow-up at 1 year. Of the patients given drug therapy, 3 (6.4%) had died, 14 (30%) had recurrent anginal episodes and 5 (11%) required either angioplasty or CABG. Of the patients who initially received angioplasty, 15 (63%) had recurrent angina but none died, 12 (50%) underwent repeat angioplasty and 2 (8.3%) required repeat CABG. No patients who received repeat surgery died or required further surgery or angioplasty. Three of these patients (19%) had recurrent angina within the first year. Patients in this category also enjoyed a greater degree of symptomatic improvement of coronary artery disease. CONCLUSIONS: Patients who had a previous CABG and subsequently presented with MI were more likely to be given conservative drug therapy than those who presented with unstable angina. At 1-year follow-up, recurrent angina occurred more often in the patients treated by angioplasty, less often in patients given drug therapy and least in those who underwent repeat bypass grafting. Restenosis remained a problem, and about 50% of patients treated with angioplasty (without intracoronary stenting) required a second angioplasty within the first year. Patients who were candidates for repeat CABG enjoyed greater symptomatic improvement within the first year.

Angina, Unstable↗
PubMed1996

Neural mechanisms of the octave illusion: electrophysiological evidence for central origin.

The octave illusion is experienced when two simultaneous tones, separated by one octave and presented to the opposite ears, are continuously reversed between the two ears. Subjects consistently report a sequence of alternating single tones: the high tone in the right ear and the low in the left. We wished to determine whether such a complex tone sequence is encoded as it is presented or as it is perceived. This was accomplished by making the tone sequence infrequently correspond to how it is perceived, and recording event-related potentials (ERPs) to these perceptually equivalent but physically different events. The illusion-mimicking tones elicited the mismatch negativity (MMN), a change-specific ERP component with origin in the auditory cortex. This indicates that the stimuli giving rise to the octave illusion are encoded according to their physical rather than perceptual properties. Consequently, the generator of the octave illusion is located beyond the level of the auditory cortex.

Acoustic Stimulation↗
PubMed1996

Prevalence and correlates of the injection of methadone syrup in Sydney, Australia.

A sample of 312 heroin users was interviewed on their injection of methadone syrup. Methadone injecting was widespread, with 52% of subjects having injected methadone syrup, 29% in the preceding six months. Males and females were equally likely to report methadone injecting. Forty per cent of current methadone injectors reported weekly or more frequent methadone injecting over the preceding six months. A history of methadone injecting was associated with abscesses and infections in injection sites, having been diagnosed with a venous thrombosis and a history of heroin overdose. Current methadone injectors were in poorer general health, had more injection-related symptoms, higher levels of psychological distress, were more likely to have recently passed on used injecting equipment and to have recently committed criminal acts. Implications for the reduction in the prevalence of methadone injecting and associated harm are discussed.

Adolescent↗
PubMed1996

Elevated blood pressure and enhanced myocardial contractility in mice with severe IGF-1 deficiency.

To circumvent the embryonic lethality of a complete deficiency in insulin-like growth factor 1 (IGF-1), we generated mice homozygous for a site-specific insertional event that created a mutant IGF-1 allele (igf1m). These mice have IGF-1 levels 30% of wild type yet survive to adulthood, thereby allowing physiological analysis of the phenotype. Miniaturized catheterization technology revealed elevated conscious blood pressure in IGF-1(m/m) mice, and measurements of left ventricular contractility were increased. Adenylyl cyclase activity was enhanced in IGF-1(m/m) hearts, without an increase in beta-adrenergic receptor density, suggesting that crosstalk between IGF-1 and beta-adrenergic signaling pathways may mediate the increased contractility. The hypertrophic response of the left ventricular myocardium in response to aortic constriction, however, was preserved in IGF-1(m/m) mice. We conclude that chronic alterations in IGF-1 levels can selectively modulate blood pressure and left ventricular function, while not affecting adaptive myocardial hypertrophy in vivo.

Adenylyl Cyclases↗
PubMed1996

Essential role of beta-adrenergic receptor kinase 1 in cardiac development and function.

The beta-adrenergic receptor kinase 1 (beta ARK1) is a member of the G protein-coupled receptor kinase (GRK) family that mediates the agonist-dependent phosphorylation and desensitization of G protein-coupled receptors. We have cloned and disrupted the beta ARK1 gene in mice by homologous recombination. No homozygote beta ARK1-/- embryos survive beyond gestational day 15.5. Prior to gestational day 15.5, beta ARK1-/- embryos display pronounced hypoplasia of the ventricular myocardium essentially identical to the "thin myocardium syndrome" observed upon gene inactivation of several transcription factors (RXR alpha, N-myc, TEF-1, WT-1). Lethality in beta ARK1-/- embryos is likely due to heart failure as they exhibit a > 70% decrease in cardiac ejection fraction determined by direct in utero intravital microscopy. These results along with the virtual absence of endogenous GRK activity in beta ARK1-/- embryos demonstrate that beta ARK1 appears to be the predominant GRK in early embryogenesis and that it plays a fundamental role in cardiac development.

Animals↗
PubMed1996

Regional deficits of myocardial blood flow and function in left ventricular pacing-induced heart failure.

BACKGROUND: Pacing-induced congestive hear, failure has become a preferred model for the study of the pathogenesis of dilated cardiomyopathy. However, little is known regarding regional myocardial blood flow and function during the development of heart failure in this model. METHODS AND RESULTS: To determine whether regional differences in myocardial blood flow are associated with regional dysfunction in ventricular pacing-induced heart failure, regional myocardial blood flow (radioactive microspheres) and regional wall thickening (transthoracic echocardiography) were measured in pigs studied at weekly intervals during the progression of heart failure induced by rapid pacing from the lateral wall of the left ventricle (220 +/- 9 bpm for 26 +/- 4 days). Echocardiography and hemodynamic measurements with the pacemaker off showed progressive, severe global left ventricular dysfunction. During pacing over the 3- to 4-week period, a progressive decrease in systolic wall thickening in the lateral wall occurred compared with the interventricular septum (IVS; P = .001); at 21 to 28 days, the difference was 50% (lateral wall, 14 +/- 6%; IVS, 28 +/- 6%; P = .0001). A difference in subendocardial blood flow per beat between the left ventricular lateral wall (the site of stimulation) and the IVS was found immediately on the initiation of pacing (IVS, 0.009 +/- 0.002 mL.min-1.g-1.beat-1; lateral wall, 0.005 +/- 0.001 mL.min-1.g-1.beat-1; P = .001), a difference that was sustained during pacing throughout the study. Subendocardial blood flow per beat was normal in both regions with the pacemaker off throughout the study. CONCLUSIONS: These data indicate that regional myocardial ischemia is associated with the development of contractile dysfunction of the paced wall during prolonged rapid left ventricular pacing and that regional stunning contributes to persistent global left ventricular dysfunction when pacing is discontinued.

Adenosine Diphosphate↗
PubMed1996

Transthoracic echocardiography in models of cardiac disease in the mouse.

BACKGROUND: Transthoracic echocardiography (M-mode and Doppler) offers a noninvasive approach for in vivo evaluation of the mouse heart. The present study examines its usefulness for assessing the morphological/functional phenotype of the left ventricle (LV) in several transgenic and surgical murine models of cardiac disease. METHODS AND RESULTS: Observations were made in 83 intact, anesthetized mice. In mice with a surgical arteriovenous fistula, volume overload and LV dilation were detected. In normal mice, echocardiographic indexes of increased contractility (dobutamine) were confirmed by LV dP/dtmax. In transgenic mice with overexpression of the beta 2-adrenergic receptor, heart rate and mean velocity of circumferential fiber shortening were increased, indicating enhanced contractility. In colony screening of transgenic mice overexpressing the H-ras gene, 45% had increased LV wall thickness (> 0.9 mm), and those showing a striking increase were selected for breeding. In mice with LV hypertrophy (aortic constriction) and normal mice, the actual LV mass determined by echocardiography correlated well (r = .93), and 95% confidence limits were determined. The maximum intraobserver and interobserver coefficients of variation for M-mode data were 0.03 +/- 0.29 mm (+/- 2 SD), < 10% for LV internal dimensions but 27% to 30% for wall thickness. CONCLUSIONS: These studies provide the first application of transthoracic echocardiography for morphological/functional characterization of the cardiac phenotype in transgenic and surgical murine models, including (1) high reliability for detecting LV chamber dilation and function; (2) reliability (and its limits) for determining abnormal LV wall thickness and LV mass; (3) identification of marked, sometimes asymmetrical, hypertrophy in a transgenic model of hypertrophic cardiomyopathy; and (4) usefulness for transgenic colony screening to identify markedly abnormal phenotypes.

Anesthesia↗
PubMed1996

Cardiovascular effects of insulin-like growth factor-1 and growth hormone in chronic left ventricular failure in the rat.

BACKGROUND: Insulin-like growth factor-1 (IGF-1) appears to have favorable cardiac effects associated with left ventricular remodeling early after myocardial infarction in the rat. The present study was designed to determine whether IGF-1 combined with growth hormone would be beneficial later as well, when infarct healing and cardiac remodeling have occurred. METHODS AND RESULTS: Four weeks after coronary occlusion, 36 rats were randomized to IGF-1 (3 mg.kg-1.d-1) plus growth hormone (0.1 mg BID) or to placebo for 4 weeks. Treated rats had significant increases in body weight (22%), while the ratio of heart weight to body weight was unchanged. Under anesthesia, cardiac output (fluorescent microspheres) increased 46%, and systemic vascular resistance decreased by 21% (P < .001) in the treated group; a significant (22%) increase of the cardiac index was limited to treated rats with large myocardial infarctions. Small increases in the reduced left ventricular ejection fractions and left ventricular dP/dt(max) values with treatment were not significant. Treated rats showed a borderline (16%) increase in left ventricular end-diastolic volume (angiography), whereas the ratio of left ventricular end-diastolic volume to body weight was reduced in the treated group. CONCLUSIONS: IGF-1 plus growth hormone administered to rats with left ventricular failure starting 1 month after MI was associated with substantial body growth, decreased systemic vascular resistance, and increased cardiac output. The failing heart also underwent treatment-induced increases in left and right ventricular weights in proportion to body growth, but left ventricular remodeling was minor, and a decrease in the ratio of left ventricular end-diastolic volume to body weight reflected relatively less chamber dilation compared with controls. A significant interaction between size of the myocardial infarction and treatment was observed for several variables, and IGF-1 and growth hormone increased the cardia index (P < .035) in rats with a large myocardial infarction.

Animals↗
PubMed1996

Natural killer cells and cancer.

BACKGROUND: Natural cytotoxicity, mediated by natural killer (NK) cells and cell with lymphokine-activated killer (LAK) activity, is believed to play an important role in host anti-cancer mechanisms. METHODS: The authors critically review recent publications on the role of natural cytotoxicity in patients with cancer. RESULTS: In patients with cancer, several studies have noted variations in the numbers and activity of NK and cells with LAK activity in different body compartments. NK cell activity in the peripheral blood lymphocytes (PBLs) is higher than that found in lymph nodes and within tumors, and this appears to be due to the presence of suppressor factors. The natural cytotoxicity of PBLs in patients with different types of cancers varies. However, there appears to be a trend for natural cytotoxicity to be reduced in certain cancer patients, possibly related to tumor volume or dissemination. Anti-cancer treatments (e.g., surgery, hormonal modulation, radiotherapy and chemotherapy) can also result in suppression of natural cytotoxicity, although the long-term effect on response to treatment and development of metastases is at present unknown. CONCLUSIONS: NK and LAK cells, through the use of immune biologic modifiers, have been demonstrated to have a therapeutic role in the treatment of human cancers. Further studies are required to determine the optimal dosages and combinations of chemotherapeutic agents, the timing of surgery, and the adjuvant use of immune biologic response modifiers. An increasing awareness and understanding of this field, may allow for the future development of anti-cancer therapies.

Cytotoxicity, Immunologic↗
PubMed1996

The effect of an educational intervention on the perceived risk of breast cancer.

OBJECTIVE: To appraise women's perceived risk of developing breast cancer and the effects of a physician's educational intervention on this perception. DESIGN: Longitudinal before-and-after study involving four measures of participants risk of developing breast cancer. Eligible women provided the data needed to calculate an objective estimate of their individual risk of developing breast cancer before age 80 using the Gail formula. They also provided a subjective estimate of their individual perceived risk. Then, each participant met with a general internal medicine physician who provided personalized information and education. Immediately after education, and again several months later, we reassessed each woman's perceived risk. SETTING: Physicians office. PARTICIPANTS: A convenience sample of 59 women participating in the Tamoxifen Breast Cancer Prevention Trial. Twenty-nine women returned for the follow-up risk assessment. MEASUREMENTS AND MAIN RESULTS: The median calculated risk of breast cancer before age 80 (by the Gail formula) was 15%, but the median perceived risk before educational intervention was 50%. The perceived risk after educational intervention fell to 25%. At late follow-up, the median perceived risk remained at 25%. The difference between the preeducational perceptions and the calculated estimates was significant (1) < .0001). After educational intervention, perceived risk measures shifted closer to the calculated value, but still remained significantly higher (p <.0001). CONCLUSIONS: Women often substantially overestimate their chances of getting breast cancer. Educational intervention by a physician, including explanation of an individual's calculated risk, can reduce this error. The effect of education appears to persist at least for several months.

Adult↗
PubMed1996

Perceived contrast following adaptation to gratings of different orientations.

Using a contrast matching procedure, we measured the perceived contrast of vertical test gratings after adapting to other gratings of either vertical or horizontal orientation. The results show that both parallel and orthogonal adapting gratings reduce perceived contrast and do so proportionally more at low test contrasts than at high. The results are consistent with a single mechanism model proposed by Ross and Speed [(1991). Proceedings of the Royal Society (Series B), 246, 61-69] that assumes that adaptation to gratings repositions contrast-response transducer functions. They are not consistent with the notion of two different forms of adaptation, subtractive for parallel and multiplicative for orthogonal adaptors as proposed by Snowden and Hammett [(1992). Nature, 355, 248-250]. Nowhere is the reduction in perceived contrast by an orthogonal grating greater than that by a parallel grating of the same contrast. A direct comparison using two orthogonal adaptors confirms the greater potency of parallel adaptors, but also reveals interactions between the adaptors.

Adaptation, Ocular↗