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J Ross

Publications and source records attributed to J Ross.

At least 343 records · Page 19Linked to original sources
PubMed1991

Analysis of herpes simplex virus-induced mRNA destabilizing activity using an in vitro mRNA decay system.

Most host mRNAs are degraded soon after infection of cells with herpes simplex virus type 1 (HSV-1). This early shutoff or early destabilization response is induced by a virion component, the virion host shutoff (vhs) protein. HSV-1 mutants, vhs1 and vhs-delta Sma, which produce defective or inactive vhs protein, fail to induce early shutoff. We have used an in vitro mRNA decay system to analyze the destabilization process. Polysomes from uninfected human erythroleukemia cells, used as a source of target mRNAs, were mixed with polysomes or with post-polysomal supernatant (S130) from HSV-1- or mock-infected murine erythroleukemia cells. Normally stable gamma-globin mRNA was destabilized by approximately 15-fold with S130 from wild-type virus-infected cells but was not destabilized with S130 from mock-infected cells or from cells infected with either of the two HSV mutants. The virus-induced destabilizing activity had no significant effect on the in vitro half-lives of two normally unstable mRNAs, histone and c-myc. No destabilizing activity was detected in polysomes from infected cells. We conclude that a virus-induced destabilizer activity can function in vitro, is located in the S130 of infected cells, and accelerates the decay rates of some, but not all, polysome-associated host mRNAs.

Amino Acid Sequence↗
PubMed1991

Influence of right bundle branch block on short- and long-term survival after acute anterior myocardial infarction.

The impact of right bundle branch block on long-term prognosis after anterior wall myocardial infarction is unclear. In 932 patients with Q wave anterior infarction, the short- and long-term prognostic significance of the presence of right bundle branch block was analyzed. Compared with 754 patients without block, 178 patients with right bundle branch block after myocardial infarction showed an increased incidence of left ventricular failure (72% versus 52%, p less than 0.001) and increased in-hospital (32% versus 8%, p less than 0.001) and 1 year after hospital discharge (17% versus 7%, p less than 0.001) cardiac mortality rates. The presence of right bundle branch block was an independent predictor of increased in-hospital and 1-year mortality when entered in a multivariate analysis. However, the absence of left ventricular failure identified a subgroup of patients with right bundle branch block with low in-hospital (4%) and 1 year postdischarge (5%) cardiac mortality rates comparable with those of patients with neither failure nor right bundle branch block (1.7% and 4.8%, respectively). In the presence of left ventricular failure, patients with associated right bundle branch block had higher in-hospital (43% versus 14%, p less than 0.01) and 1 year postdischarge (24% versus 9%, p less than 0.01) cardiac mortality rates than those of patients with failure but no right bundle branch block. Thus, the presence of right bundle branch block after anterior myocardial infarction is an independent marker of poor prognosis.(ABSTRACT TRUNCATED AT 250 WORDS)

Bundle-Branch Block↗
PubMed1991

Hypertrophic cardiomyopathy: prognosis with medical or surgical therapy.

Over the past 30 years, knowledge of the natural history and effects of therapy in patients with hypertrophic cardiomyopathy has expanded greatly, but progress has been hampered by its variable patterns of expression. Many but not all patients show symptomatic improvement with medical treatment. Chronic beta blockage does not appear to affect long-term survival, whereas results with calcium channel blockade by verapamil have been encouraging; however, they await confirmation, and verapamil may be hazardous in some patients with severe left ventricular (LV) outflow tract obstruction and elevated LV end-diastolic pressure. Reported beneficial effects of amiodarone on survival also require further study. Surgical therapy has become the treatment of choice for medically refractory patients with proven outflow tract obstruction. In several centers, the operative risk is low, and long-term follow-up demonstrates prolonged symptomatic relief. It is hoped that work currently underway will provide more definitive information on the long-term effects of the role of calcium channel blockers, antiarrhythmic medications, and the long-term effects of surgical therapy on survival of patients with this disorder.

Adrenergic beta-Antagonists↗
PubMed1991

Variable threshold as a model for selective attention, (de)sensitization, and anesthesia in associative neural networks.

We study the influence of a variable neuronal threshold on fixed points and convergence rates of an associative neural network in the presence of noise. We allow a random distribution in the activity levels of the patterns stored, and a modification to the standard Hebbian learning rule is proposed for this purpose. There is a threshold at which the retrieval ability, including the average final overlap and the convergence rate, is optimized for patterns with a particular activity level at a given noise level. This type of selective attention to one class of patterns with a certain activity level may be obtained at the cost of reducing the retrieval ability of the network for patterns with different activity levels. The effects of a constant threshold independent of noise, time, and pattern are discussed. For high-(low-) activity patterns, the average final overlap is shown to be increased at high noise levels and decreased at low noise levels by a negative (positive) constant threshold, whereas a positive (negative) threshold always reduces the final average overlap. When the magnitude of the constant threshold exceeds a critical value, there is no retrieval. Rates of convergence towards the stored pattern with negative (positive) thresholds are greater than those with positive (negative) thresholds. These results are related to (de)sensitization and anesthesia. For certain threshold values and patterns with certain activity levels, hysteresis appears in the plot of the average final overlap versus the noise level, even for first order interactions. We make the analogy between the pattern-dependent neuronal threshold proposed in the present paper and the "task-related" modulation in neuronal excitability determined by cognitive factors, such as the attentional state of a higher animal. A constant threshold is associated with overall changes in neuronal excitability caused, e.g., by various drugs and physical injuries. Neurophysiological evidence of a dynamically variable neuronal threshold, such as accommodation and potentiation, is presented.

Anesthesia↗
PubMed1991

Dynamic changes in left ventricular outflow tract flow velocities after amyl nitrite inhalation in hypertrophic cardiomyopathy.

Doppler echocardiography was performed in 21 patients with hypertrophic cardiomyopathy (HC), in nine patients with no evidence of left ventricular (LV) hypertrophy by two-dimensional echocardiography, and in five patients with systemic hypertension and concentric LV hypertrophy. The LV outflow tract (LVOT) peak velocity was recorded by continuous wave Doppler technique at rest and after amyl nitrite inhalation. The LVOT pressure gradient was calculated by the modified Bernoulli equation. A significant increase in heart rate and a drop in systolic blood pressure were observed in all patients after amyl nitrite inhalation; no adverse effects were encountered. The peak LVOT velocity and pressure gradient increased significantly after provocation in all patients, but the increase was much more pronounced in patients with HC (peak LVOT velocity increased from 2.2 +/- 0.8 to 4.3 +/- 1.0 m/sec and peak gradient increased from 22 +/- 17 to 78 +/- 36 mm Hg). The Doppler spectral signal in patients with HC demonstrated a characteristic contour, with peak velocity occurring in late systole. However, the observed increase in LVOT peak velocity was not statistically different between treated (with beta-blockers and calcium blockers) and untreated patients with HC. We conclude that LVOT peak velocity and pressure gradients in patients with HC can be readily assessed by Doppler echocardiography both at rest and after amyl nitrite inhalation. The dynamic changes in LVOT velocity induced by this provocation have certain characteristic features in obstructive HC but appear to be independent of the medical regimen used, at least in the dosages tested in our study.

Administration, Inhalation↗
PubMed1991

Factors associated with recurrent myocardial infarction within one year after acute myocardial infarction.

In a large population of patients (n = 3666) who were discharged from the hospital after acute myocardial infarction and followed up for 1 year, factors associated with recurrent nonfatal (n = 171) or fatal (n = 74) infarction were identified. Also, the effects of combining various end points (recurrent nonfatal or fatal infarction and other cardiac death) in multivariate analyses, a practice common in many small studies that evaluate the predictive-value of various treatments or special tests, was examined. In univariate analyses, patients with nonfatal recurrent infarction did not differ with respect to age or gender from infarct-free survivors, but they more often had a history of previous myocardial infarction, congestive heart failure, angina pectoris, and diabetes; more severe pulmonary congestion was present on chest x-ray during the admission, and a non-Q wave index infarction was more frequent. Patients with either a fatal or nonfatal recurrent infarction had more angina pectoris during follow-up (55% to 60%) compared with 27% in event-free survivors and 31% in patients who died of other cardiac causes in whom this factor could be assessed before death. In multivariate analyses, historical and clinical prognostic factors were ranked differently for fatal or nonfatal reinfarction and other cardiac causes of death; angina pectoris at follow-up was highly related to recurrent infarction (fatal or nonfatal), along with a history of diabetes, and a non-Q wave index infarction. These factors were not independently related to other causes of cardiac death.(ABSTRACT TRUNCATED AT 250 WORDS)

California↗
PubMed1991

The impact of injury severity and prehospital procedures on scene time in victims of major trauma.

STUDY OBJECTIVE: To evaluate the relationship among injury severity, prehospital procedures, and time spent at the scene by paramedics for victims of major trauma. DESIGN: Retrospective study of 98 consecutive patients with an Injury Severity Score of more than 15 who were brought to a trauma center by fire department paramedics. SETTING: A medium-sized metropolitan emergency medical services (EMS) system and a Level I trauma center. RESULTS: There were 66 male and 32 female patients with a mean age of 34 years. Thirty-two patients (32.6%) died. Blunt and penetrating trauma accounted for 68.4% and 31.6% of cases, respectively. Thirty-three patients (33.7%) had successful advanced airway procedures, and 81 (82.7%) had at least one IV line started in the field. Analysis of scene time, prehospital procedures, and injury severity parameters revealed that more procedures were performed in the field on the more severely injured cases; that despite this, there was a trend toward shorter scene time for more severely injured patients; and that there was a mean scene time of 8.1 minutes. This is the shortest scene time reported to date for prehospital trauma care in an EMS system. CONCLUSION: Extremely short scene times can be attained without foregoing potentially life-saving advanced life support interventions in an urban EMS system with strong medical control. In such a system, the most severely injured victims may spend less time at the scene although more procedures are performed on them.

Adolescent↗
PubMed1991

DNA adducts in rat lung, liver and peripheral blood lymphocytes produced by i.p. administration of benzo[a]pyrene metabolites and derivatives.

DNA adducts produced in vivo in rat lung, liver and peripheral blood lymphocytes following the i.p. administration of several synthetic benzo[a]pyrene (B[a]P) metabolites and ring-substituted derivatives have been analyzed by the nuclease P1 version of the 32P-postlabeling assay. These include 1-, 2-, 3-, 4-, 5-, 6-, 7-, 8-, 9-, 10-, 11- and 12-hydroxy-B[a]P, (+/-)-B[a]P-trans-4,5-dihydrodiol, (+/-)-B[a]P-trans-7,8-dihydrodiol, (+/-)-B[a]P-trans-9,10-dihydrodiol and B[a]P-7,8-dione. Among the monohydroxy derivatives, only 2-, 9- and 12-hydroxy-B[a]P produced detectable adducts. The only disubstituted derivative studied that produced adducts was the trans-7,8-dihydrodiol. The resulting DNA adducts were compared to those produced in each tissue by administration of B[a]P. 9-Hydroxy-B[a]P and B[a]P-trans-7,8-dihydrodiol each lead to the formation of major B[a]P adducts seen in lung and liver respectively. None of the adducts derived from either 2-hydroxy-B[a]P or 12-hydroxy-B[a]P were observed following administration of B[a]P alone.

7,8-Dihydro-7,8-dihydroxybenzo(a)pyrene 9,10-oxide↗
PubMed1991

Validity and reliability of a domain-referenced test of clinical competence for foreign medical graduates.

The authors determined the reliability and validity of domain-referenced scores obtained from a multiple-station clinical skills examination administered at the University of Toronto to a group of foreign medical graduates in early 1990. Issues associated with the identification of essential checklist items and the setting of minimum passing scores (cutting scores) for each station and for the total test were addressed. In addition, they examined the consistency of classification of candidates and the perceived appropriateness of the number of candidates classified "competent." The findings provide evidence of the validity of standard-setting procedures based on both the performance of criterion groups and the judgment of "experts."

Clinical Competence↗
PubMed1991

Evidence that the fate of class II-disparate corneal grafts is determined by the timing of class II expression.

While the immune privilege nature of the eye affords significant protection to corneal grafts, immunologic rejection is the leading cause of graft failure. Class II antigens are normally absent or expressed at very low levels in normal cornea. The role that class II antigens play in causing graft rejection is particularly interesting. Class II molecules are present on many cells of the immune system, and therefore are important in modulating and mediating immune reactions. The absence of class II bearing cells in the cornea leads to the interesting issue of whether or not those antigens can induce immune rejection of a corneal graft. In the current study we have made use of a pair of congenic rat strains that differ only at class II loci to determine the impact of these antigens on corneal graft survival. Central corneal grafts were not rejected. Recipients preimmunized with skin grafts rejected 100% of the class II disparate corneas with a median survival time (MST) of 15.5 days. When class II disparate Langerhans-cell-containing (LC+) corneas were grafted, the corneas were not rejected, but they immunized the recipients as evidenced by the rejection of a second corneal graft on the contralateral eye. Immunofluorescent stains demonstrated transient expression of class II antigens on graft epithelium after transplantation. This temporary appearance of class II provides a target for rejection in the preimmunized animals but is of insufficient duration to both prime naive animals and provide a target for antigraft effectors.

Animals↗
PubMed1991

Acceptance of H-Y-disparate corneal grafts despite concomitant immunization of the recipient.

Male-specific, H-Y antigen is a widely utilized antigen system for analyzing the role of non-MHC transplantation antigens in graft rejection. In this study, we examined the role of H-Y antigen in corneal graft rejection. Orthotopic corneal grafts from male LBNF1 rats were transplanted to syngeneic female LBNF1 recipients. The male corneal grafts survived beyond 100 days on naive female recipients. In other experiments, hosts bearing clear male corneal grafts and systemically immunized with subcutaneous inoculations of male splenocytes followed by full-thickness male skin grafts failed to reject their corneal grafts, even though the male skin grafts were swiftly rejected. The inability of female hosts to reject existing male corneal grafts suggested that the cornea failed to express H-Y transplantation antigen. Further experiments, however, revealed that male-specific antigen was expressed on corneal grafts. Hosts bearing clear male grafts in the left eye rejected subsequent male skin grafts and promptly rejected male corneal grafts transplanted to the contralateral eye. Interestingly, the original male corneal grafts remained clear during the rejection of both the skin graft and the second corneal graft. The results indicate that corneal grafts representing minor histocompatibility disparities enjoy immunologic privilege in the naive host, even if the host is subsequently immunized systemically.

Animals↗