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Biomedical subjects

J Ross

Publications and source records attributed to J Ross.

At least 199 records · Page 11Linked to original sources
PubMed1996

Suppression of the magnocellular pathway during saccades.

Saccades create two problems for the visual system: they cause fast (but resolvable) motion of the retinal image and a change in the relationship between retinal and external spatial co-ordinates. In this review, we examine the first of these problems, of why there is no distributing sense of motion during saccades. Recent evidence from a range of sources suggests that during saccades, the magnocellular pathway is selectively suppressed, while the parvocellular pathway is functionally unimpaired, or even enhanced. The suppression seems to occur early, possibly in the lateral geniculate nucleus, where the pathways are well separated. It is possible that the suppression shares similar mechanisms to those responsible for contrast gain control.

Animals↗
PubMed1996

Control of messenger RNA stability in higher eukaryotes.

The mRNA decay rate (half-life) is a major determinant of mRNA abundance in organisms from bacteria to mammals. mRNA levels can fluctuate many-fold following a change in mRNA half-life, without any change in transcription, and these fluctuations affect how a cell grows, differentiates and responds to its environment. The half-lives of many mRNAs vary tenfold or more in response to cytokines, hormones, starvation, hypoxia, or viral infection. Three major questions regarding mRNA stability are currently being addressed. What sequences in mRNAs determine half-lives? What enzymes degrade mRNAs? What (trans-acting) factors regulate mRNA stability and how do they function? This review focuses on RNA-binding or regulatory proteins and on candidate messenger ribonucleases (mRNases).

Animals↗
PubMed1996

The spectrum of ureteropelvic junction obstructions occurring in duplicated collecting systems.

The authors reviewed four cases of ureteropelvic junction obstruction (UPJ) in duplicated systems. Associated abnormalities included contralateral duplication, vesicoureteral reflux, and a case of ipsilateral upper pole ectopic ureter with a dysplastic upper pole moiety. Surgical management included dismembered pyeloplasty, ureteral reimplantation, end-to-side pyeloureterostomy to the upper-pole ureter, and upper-pole heminephrectomy with lower-pole dismembered pyeloplasty. UPJ obstructions occurring in duplicated systems often are associated with other anomalies.

Child, Preschool↗
PubMed1996

The role of hypertrophy and growth factors in heart failure.

The physiologic trophic factors growth hormone (GH) and insulin-like growth factor 1 (IGF-1) generally increase body weight and cardiac mass proportionately, and several studies suggest that both growth factors cause vasodilation and increased myocardial contractility. Established clinical benefits of ACE inhibitors can be explained, at least in part, by inhibition of cell hypertrophy, lowered systemic vascular resistance (SVR) and afterload, leading to reduction of progressive left-ventricular (LV) enlargement. An alternative approach would be to administer IGF-1 or GH to stimulate compensatory hypertrophy and reduce afterload by their vasodilator action, as well as through potential favorable effects on myocardial contractility. In our initial study in the rat myocardial infarction (MI) model, when IGF-1 was administered early (at 2 days) post-MI and continued for 2 weeks, body weight (BW) increased and LV weight/BW remained unchanged, the LV end-diastolic volume (EDV) and stroke volume increased (but not when normalized to BW), and the LV ejection fraction increased in rats with large infarctions. These findings suggested a beneficial rather than detrimental effect of such treatment, and we then studied the action of combined IGF-1 and GH starting after infarct healing at 4-weeks' post-MI. BW increased substantially and LVEDV/BW was lower in treated rats than in control rats, suggesting relatively less LV dilation with little remodeling in this setting; IGF-1/GH increased the cardiac output by 46%, systemic vascular resistance (SVR) fell and the cardiac index (CI) was significantly elevated in treated rats with a large MI. Recently, others have used the rat MI model to study the effects of 2-weeks' of GH started at 4-weeks' post-MI, as well as IGF/GH for 2-weeks in rats treated with an ACE inhibitor for 3-month's post-MI. In both studies, in conscious treated rats the BW increased, LV/BW was not different compared to the control rats, but the CI increased, SVR fell, and estimated LV dP/dtmax was significantly augmented. Preliminary data in our laboratory suggest that beneficial effects may also occur with GH administration in the setting of chronic angiotensin II receptor blockade (losartan) after MI in the rat. Thus, growth factor therapy appears to have favorable effects in heart failure early and late after MI in the rat. Additional cardiac hypertrophy occurs early after MI, but the later beneficial effects appear to relate primarily to systemic vasodilation, improved cardiac output, and enhanced myocardial contractility.

Angiotensin Receptor Antagonists↗
PubMed1996

Two techniques of laparoscopic Burch repair for stress incontinence: a prospective, randomized study.

STUDY OBJECTIVE: To determine if outpatient laparoscopic Burch procedure performed with mesh and staples is as effective as that done with the suture technique. DESIGN: Prospective, randomized study. SETTING: Community hospital. PATIENTS: Sixty-nine women with genuine stress incontinence (GSI) randomly assigned to either the suture group (group 1) or the mesh-staple group (group 2). INTERVENTIONS: Before surgery each patient had a complete history, physical and neurologic examinations, 24-hour urolog, urology questionnaire, urine culture and sensitivity, Q-Tip test, transperineal ultrasound, cough stress test, cystourethroscopy, and cystometrogram. Stress incontinence was diagnosed by positive Q-Tip, ultrasound, and cough stress tests and a negative cystometrogram for detrusor contraction. The laparoscopic Burch procedures were performed with either sutures for bladder neck elevation or with mesh and staples. Clinical and, if necessary, urodynamic studies were repeated at 6 weeks and 1 year postoperatively. MEASYRENEBTS AND MAIN RESULTS: The cure rate at 1 year was 91% in group 1 and 94% in group 2. Only objective cures by urologic testing are reported. The hypermobile urethra, as tested by transperineal ultrasound, was cured by both procedures. Of the 69 women, 68 were able to void spontaneously within 24 hours. CONCLUSIONS: Early results suggest that laparoscopic Burch colposuspension is effective in curing GSI. Both sutures and mesh with staples yield good outcomes.

Adult↗
PubMed1996

Psychological morbidity and route of administration among amphetamine users in Sydney, Australia.

A sample of 301 amphetamine users were interviewed about their experiences of psychological symptoms prior to, and subsequent to, their initiation of amphetamine use. Psychological morbidity was common, with 44% scoring greater than a conservative cut-off of 8 on the General Health Questionnaire. The most commonly reported symptoms subsequent to the onset of amphetamine use were depression (79%), anxiety (76%), paranoia (52%), hallucinations (46%) and violent behaviour (44%). All these symptoms increased in prevalence after the onset of amphetamine use. Route and frequency of amphetamine administration were significant independent predictors of overall psychological morbidity, while route of administration was related to the experience of hallucinations, violent behaviour and paranoia. The avoidance of injection as a route of administration and the use of amphetamines less than weekly are recommended as steps that users can take to reduce the psychological sequelae of amphetamine use.

Adult↗
PubMed1996

Overdose among heroin users in Sydney, Australia: II. responses to overdose.

A sample of 329 heroin users were interviewed about their experiences at other peoples' heroin overdoses. The overwhelming majority (86%) had witnessed a heroin overdose, on a median of six occasions. Heroin users were reluctant to seek medical attention, with an ambulance being called on only half (56%) of the most recent overdose occasions. At only 17% of most recent overdoses was calling an ambulance the first action taken. Males reported taking significantly longer than females to call an ambulance. Nearly half (44%) of subjects reported that there were factors that had delayed or stopped them seeking medical assistance, the most common impediment being a fear of police involvement. The importance of interventions to encourage help-seeking at overdoses are discussed.

Adolescent↗
PubMed1996

Benzodiazepine use among heroin users in Sydney: patterns of use, availability and procurement.

A sample of 210 heroin users who had used benzodiazepines during the preceding 6 months were interviewed about their benzodiazepine use. Forty-one percent of the sample reported having used benzodiazepines more than once a week during the 6 months preceding interview. Forty-eight percent had injected benzodiazepines, with 17% having done so during the preceding 6 months. Eleven percent of the sample reported having experienced convulsions when attempting detoxification from benzodiazepines. The majority of subjects (86%) indicated that benzodiazepines are easy or very easy to obtain. Only a third of the sample reported obtaining benzodiazepines exclusively through a doctor in the last 6 months. Over a half of the sample indicated that they had given or sold benzodiazepines to someone during that time. Diazepam was considered by subjects to be the easiest benzodiazepine to procure. Doctors should avoid the prescription of benzodiazepines to injecting drug users, particularly the more readily injectable drug temazepam. Given the widespread use of benzodiazepines by injection, research needs to examine the harm associated with the parenteral use of these drugs.

Journal Article↗
PubMed1996

Effects of vascular endothelial growth factor on hemodynamics and cardiac performance.

Vascular endothelial growth factor (VEGF), a major regulator of angiogenesis, has therapeutic benefit in animal models of coronary or limb ischemia. However, the hemodynamic effects of VEGF have not been investigated. We examined the effects of VEGF on hemodynamics and cardiac performance. Mean arterial pressure (MAP), heart rate (HR), cardiac output, stroke volume, left ventricular (LV) dP/dt, and hematocrit were measured before and after intravenous injection of VEGF in conscious, instrumented rats. VEGF caused a dose-dependent reduction in MAP and an associated increase in HR. VEGF (250 micrograms/kg) significantly decreased cardiac output and stroke volume without affecting the inotropic state of the left ventricle, as determined by dP/dt. VEGF significantly increased hematocrit. Furthermore, VEGF did not affect contractility or HR in the isolated rat heart in vitro. The data suggest that the VEGF-induced decrease in cardiac output is due to reduced stroke volume, which may be caused by a decrease in venous return rather than a direct effect on myocardial contractility. In addition, pretreatment with N omega-nitro-L-arginine methyl-ester (L-NAME), a nitric oxide (NO) synthase inhibitor, significantly attenuated the depressor and tachycardic responses to VEGF, suggesting that VEGF-induced hypotension may be mediated by NO.

Animals↗
PubMed1996

Ocular response to lens care systems in adolescent soft contact lens wearers.

The purpose of this 3-year prospective study is to compare high school-aged subjects, randomized into wearing soft contact lenses and spectacles, in terms of ocular health, refractive status, and self-esteem. This report focuses on ocular response to the lens care systems used through the first 18 months of the investigation. Eighty-four subjects were randomly fitted with either CibaSoft Visitint or CibaSoft-Standard Visitint contact lenses. Three lens care systems, Ciba Vision AOSept Disinfection/Neutralization Solutions (AOSept), Opti-Free Rinsing, Disinfection, and Storage Solution (Opti-Free), and ReNu Multi-Purpose Solution (ReNu), were randomly prescribed to the subjects wearing contact lenses. Limbal congestion, conjunctival hyperemia, corneal staining with fluorescein, corneal edema, and corneal neovascularization were graded at dispensing and at 6-, 12-, and 18-month visits. There were no significant differences among the groups at baseline. At 6 months statistically significant difference (p = 0.0131, Kruksal-Wallis) was found for fluorescein staining of the cornea among the systems. At 12 months significant differences were found for corneal edema (p = 0.0404, Kruksal-Wallis) and neovascularization (p = 0.0315, Kruksal-Wallis) among the systems. At 18 months generalized conjunctival hyperemia was significantly different (p = 0.0234, Kruksal-Wallis) among the systems along with greater limbal congestion (p = 0.0015, Kruksal-Wallis) and neovascularization (p = 0.0238, Kruksal-Wallis). In conclusion, the cornea, limbal vessels and the conjunctiva respond differently to the lens care systems used in this study. Overall, patients using AOSept showed less corneal staining and inflammatory response than patients using ReNu and Opti-Free.

Adolescent↗
PubMed1996

Variations in the fluorescence intensity of intact DAPI-stained bacteria and their implications for rapid bacterial quantification.

As current techniques for the quantification of bacteria are laborious and often imprecise, instrumental approaches such as sedimentation field-flow fractionation (SdFFF) are attractive. In this technique, fluorogenic dyes specific for nucleic acids are used to identify bacterial cells. Bacterial biomass can be quantified directly with SdFFF if the specific fluorescence of bacterial cells is constant. The effect of different growth conditions on the specific fluorescence of one strain each of Escherichia coli, Pseudomonas aeruginosa, Proteus mirabilis and Staphylococcus epidermidis stained with 4',6-diamidino-2-phenylindole was examined. Specific fluorescence varied over a 500-fold range, from 0.22 to 103 arbitrary fluorescence units per cell. Specific fluorescence was highest when cells were in log phase, and lowest when cells were in stationary phase. Specific fluorescence decreased when cells harvested in log phase were starved for 7 d in a carbon-free minimal medium, and increased rapidly (within 2 h) after cells were relieved from carbon limitation. Such variations in specific fluorescence must be considered when using gross fluorescence as a direct indicator of bacterial numbers in the SdFFF technique for quantifying bacterial biomass. Moreover, they have serious implications for the application of fluorescence techniques in other instrumental approaches for bacterial enumeration in environmental samples.

Bacteria↗
PubMed1996

The virion host shutoff protein of herpes simplex virus type 1: messenger ribonucleolytic activity in vitro.

Shortly after tissue culture cells are infected with herpes simplex virus (HSV) type 1 or 2, the rate of host protein synthesis decreases 5- to 10-fold and most host mRNAs are degraded. mRNA destabilization is triggered by the virion host shutoff (vhs) protein, a virus encoded, 58-kDa protein located in the virion tegument. To determine whether it can function as a messenger RNase (mRNase), the capacity of vhs protein to degrade RNA in vitro in absence of host cell components was assessed. Two sources of vhs protein were used in these assays: crude extract from virions or protein translated in a reticulocyte-free system. In each case, wild-type but not mutant vhs protein degraded various RNA substrates. Preincubation with anti-vhs antibody blocked RNase activity. These studies do not prove that vhs protein on its own is an mRNase but do demonstrate that the protein, either on its own or in conjunction with another factor(s), has the biochemical property of an mRNase, consistent with its role in infected cells.

Animals↗
PubMed1996

Pyrrolosporin A, a new antitumor antibiotic from Micromonospora sp. C39217-R109-7. I. Taxonomy of producing organism, fermentation and biological activity.

Strain C39217-R109-7 (ATCC 53791) is an actinomycete strain isolated from a soil sample collected at Puerto Viejo, Peru. It produces a new antitumor antibiotic, designated pyrrolosporin A. Taxonomic studies on its morphological, cultural and physiological characteristics identified this producing strain as Micromonospora sp. C39217-R109-7. Pyrrolosporin A shows antimicrobial activity against Gram-positive bacteria and it is weakly active against Gram-negative bacteria. Pyrrolosporin A prolongs the life span of mice inoculated with P388 leukemia cells.

Animals↗
PubMed1996

Effects of induced tolerance to bacterial lipopolysaccharide on myocardial infarct size in rats.

OBJECTIVES: Induced tolerance to bacterial lipopolysaccharide (LPS) by pretreatment with sublethal doses of LPS has been shown to reduce the inflammatory response of monocytes, circulating PMNs and PMN adhesion to endothelial cells in response to subsequent stimuli, and also to increase cellular and organ tolerance to stress by other mechanisms. Therefore, we undertook to determine whether or not LPS desensitization is associated with reduced myocardial infarct size at 3 days after reperfusion following coronary occlusion. METHODS: Rats were randomized to either daily intraperitoneal LPS injections to provide LPS tolerance, or to equal volumes of saline (controls). In both groups at day 7 nontransmural infarction was produced by a 45 min coronary occlusion followed by 3 days of reperfusion during which LPS injections were continued. Histologic infarct size was assessed as percent of the left ventricle and as a percent of the risk zone (determined by fluorescent microspheres). RESULTS: Myocardial infarct size as percent of the left ventricle and of the risk zone were significantly reduced in the LPS-tolerant group (n = 14) compared to control rats (n = 12), the latter being reduced by 37% (33.6 +/- 18.4 vs. 54.1 +/- 8.6% of the risk zone, P < 0.002). The percentages of activated circulating PMN after LPS desensitization and saline pretreatment were not different prior to coronary occlusion (at 7 days), but 3 days after coronary occlusion and reperfusion the percent of activated PMNs in the treated group was markedly reduced compared to controls (2.9 +/- 1.6 vs. 11.4 +/- 7.2%, respectively, P < 0.02). CONCLUSIONS: LPS desensitization in rats for 1 week prior to coronary occlusion inhibited activation of circulating PMNs 3 days after reperfusion following 45 min of coronary occlusion. LPS also is well-known to induce heat stress proteins and may affect other protective mechanisms. These actions are associated with a significant reduction in myocardial infarct size in LPS-tolerant animals compared to untreated controls.

Animals↗
PubMed1996

Overdose among heroin users in Sydney, Australia: I. Prevalence and correlates of non-fatal overdose.

A sample of 329 heroin users were interviewed regarding their personal experience of non-fatal heroin overdose. Experience of overdose was widespread, with two-thirds of subjects (68%) reporting having overdosed. The median number of life-time overdoses was three, with males and females equally likely to have overdosed. The majority (62%) of most recent heroin overdoses occurred in conjunction with the consumption of other central nervous system depressants (alcohol, benzodiazepines and other opioids). Logistic regression analyses indicated three independent factors associated with having overdosed: longer heroin using careers, greater heroin dependence and higher levels of alcohol consumption. Implications for the reduction in the prevalence and frequency of overdose are discussed.

Adolescent↗