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Biomedical subjects

J Ross

Publications and source records attributed to J Ross.

At least 325 records · Page 18Linked to original sources
PubMed1992

Cutaneous malignant melanoma and human immunodeficiency virus (HIV) infection: a report of three cases.

Cutaneous malignant melanoma was diagnosed in three patients suffering from human immunodeficiency virus (HIV) infection. Staging at presentation inversely correlated with absolute CD4 count. In addition, a notably sparse lymphocytic inflammatory response to the melanoma was observed in two cases. Established data on melanoma in non-HIV immunosuppressed patients suggests a poor prognosis for melanoma in HIV disease.

Adult↗
PubMed1992

Formant frequencies in Estonian folk singing.

Formant frequencies in an old Estonian folk song performed by two female voices were estimated for two back vowels /a/ and /u/, and for two front vowels /e/ and /i/. Comparison of these estimates with formant frequencies in spoken Estonian vowels indicates a trend of the vowels to be clustered into two sets of front and back ones in the F1/F2 plane. Similar clustering has previously been shown to occur in opera and choir singing, especially with increasing fundamental frequency. The clustering in the present song, however, may also be due to a tendency for a mid vowel to be realized as a higher-beginning diphthong, which is characteristic of the North-Estonian coastal dialect area where the singers come from. No evidence of a "singer's formant" was found.

Estonia↗
PubMed1992

A serovar analysis of heterosexual gonorrhoea in Edinburgh 1986-90.

OBJECTIVE: To analyse the frequency of different gonococcal serovars within Edinburgh, Scotland and to describe changes that occurred in the frequency of such serovars over time. METHODS: All heterosexual patients with a diagnosis of gonorrhoea confirmed on culture between January 1986 and December 1990 had their gonococcal strain serotyped. Temporal changes in the prevalence of gonorrhoea and the serovar of the isolates were analysed. RESULTS: Isolates of Neisseria gonorrhoeae from 1356 episodes of gonorrhoea were serotyped. Three serovars, Bajk (IB-3/IB-6), Bacejk (IB-1/IB-2) and Aedgkih (IA-1/IA-2), dominated, occurring in two-thirds of all infections. Over the study period Bajk (IB-3/IB-6) and Aedgkih (IA-1/IA-2) isolates declined in frequency in parallel with an overall fall in the prevalence of gonorrhoea but Bacejk (IB-1/IB-2) persisted at a lower but fairly constant level. Despite a fall in the number of gonococcal infections the variety of new serovars being isolated fluctuated. CONCLUSIONS: The ability of some serovars to persist while others decline in incidence may be partially related to antibiotic sensitivities but other factors such as an ability to evade the immune response and transfer of serovars from one population group to another may also be important.

Antigens, Bacterial↗
PubMed1992

Influence of the force-frequency relation on left ventricular function during exercise in conscious dogs.

BACKGROUND: The magnitude of the force-frequency effect on myocardial contractility in the conscious animal has been studied at rest, but it has not been assessed during exercise. METHODS AND RESULTS: The influence of heart rate (HR) changes were evaluated during treadmill exercise in eight preinstrumented, conscious dogs in which high-fidelity left ventricular (LV) pressure, LV volume (by sonomicrometry), and aortic pressure were measured. Under resting conditions, end-systolic pressure-volume relations were obtained using inferior vena caval occlusion. Dogs were run on a treadmill, and the intrinsic exercise HR was reduced by infusion of a specific bradycardic drug (UL-FS 49 0.5 mg/kg) during continuing exercise while HR was maintained at 240 beats per minute by atrial pacing. At 6 minutes of running at a fixed, paced HR when a stable drug effect had been achieved, no effects of UL-FS 49 on measures of LV contractility were detected compared with exercise before drug administration. HR was then reduced stepwise from 240 to 210, 180, or 150 beats per minute in a random manner, returning to 240 beats per minute between steps. Progressive reductions in measures of myocardial contractility occurred as the HR was slowed, and reduction of rate from 240 to 150 beats per minute reduced the LV maximum positive dP/dt by 31% and (dP/dt)DP40 by 21% despite increases in LV end-diastolic pressure. The entire end-systolic pressure-volume could not be determined during exercise, but beat-averaged end-systolic pressure-volume points during exercise were progressively shifted to the right and downward by slowing the exercise HR. Thus, a pronounced negative inotropic influence of slowing the heart was observed during exercise, and the rate of ventricular relaxation (tau) was also significantly prolonged. CONCLUSIONS: These findings indicate that force-frequency effects on the inotropic state of the intact LV are markedly enhanced by exercise.

Animals↗
PubMed1992

Enhancement of the force-frequency effect on myocardial contractility by adrenergic stimulation in conscious dogs.

BACKGROUND: The influence of changes in heart rate on myocardial contractility (the force-frequency effect) differs under various experimental conditions, including the anesthetized versus the conscious state. METHODS AND RESULTS: To assess the influence of beta-adrenergic stimulation on force-frequency effects on myocardial contraction and relaxation, seven instrumented conscious dogs were studied in which heart rate could be controlled by atrial pacing after the intrinsic rate was slowed with a bradycardiac agent (UL-FS 49 0.5-0.75 mg/kg). Left ventricular (LV) pressure was measured with a micromanometer under resting conditions and during dobutamine infusion at low, intermediate, and high doses (2.7, 5.4, and 10.7 micrograms/kg/min). At each dose, heart rate was progressively increased from 100 to 210 beats per minute. In the absence of dobutamine (control), no significant positive force-frequency effect was detected on LV dP/dtmax; this was probably due to the known effect of the observed decrease in preload to reduce LV dP/dtmax, thereby offsetting an effect of the force-frequency response to increased dP/dt. However, during dobutamine infusions, the force-frequency effect was observed to increase significantly in a dose-dependent manner with increases in heart rate. An increase in heart rate from 100 to 210 beats per minute increased LV dP/dtmax by 12.4 +/- 12.5% with low-dose, 22.7 +/- 13.1% with intermediate-dose, and 27.5 +/- 8.9% with high-dose dobutamine. Changes in preload and aortic pressure were within the same ranges under control conditions and at each of the three dobutamine doses. The time constant of LV pressure fall (tau) was significantly shorter with increases in heart rate during control, but only the highest dobutamine dose caused further significant shortening in tau with increased heart rate. CONCLUSIONS: These data indicate that there is a pronounced dose-dependent action of beta-adrenergic stimulation to enhance force-frequency-induced contractile responses in normal conscious dogs.

Adrenergic beta-Agonists↗
PubMed1992

Myocardial function and transmural blood flow during coronary venous retroperfusion in pigs.

BACKGROUND: The degree of recovery of regional myocardial contraction during coronary venous retroperfusion has not been well established, particularly in the absence of coronary collateral channels. Therefore, the maximal functional benefit attainable with coronary venous retroperfusion was assessed in pigs by means of using selective pump retroperfusion of the left anterior descending vein, with venting of the left anterior descending artery to zero pressure. METHODS AND RESULTS: In eight anesthetized open-chest pigs during selective left anterior descending venous retroperfusion over a range of retroperfusion flows, regional myocardial function (percent systolic wall thickening by sonomicrometry) increased progressively to an average of 62% of control values at a retroperfusion flow rate 200% of control arterial flow. Progressive thickening of the end-diastolic dimension of the anterior wall was observed with increasing retroperfusion flow (from 8.7 +/- 0.9 to 10.7 +/- 2.3 mm, p less than 0.001). Perfusion pressures within the left anterior descending vein increased linearly with increased retroperfusion flow rates (up to 132 +/- 57 mm Hg with retroperfusion flow 200% of control). A gradual increase of retrograde left anterior descending arterial outflow was observed with increasing retroperfusion flows; however, the absolute amount (maximum, 8.3 +/- 4.1 ml/min) was much too low to explain the extent of functional recovery. Transmural myocardial capillary blood flows in the anterior wall with retroperfusion flows of 100% and 200% of control arterial flow were 0.22 and 0.42 ml/min/g with corresponding subendocardial blood flows of 0.14 and 0.29 ml/min/g; ratios of endocardium to epicardium were 0.51 and 0.61, respectively. Thus, capillary blood flows during selective retroperfusion were relatively low despite considerable restoration of regional systolic wall thickening, and a significant difference was noted in the slopes of the relations between regional systolic wall thickening and myocardial blood flow during retroperfusion and anterograde arterial perfusion (p less than 0.05). With retrograde injection of silicone elastomer at different retroperfusion pressures (50, 75, and 100 mm Hg) in three pigs, capillaries were well visualized, and profuse intramyocardial venous anastomotic connections were seen at the highest retroperfusion pressure (100 mm Hg), whereas there was filling of small venules but little capillary filling at the lowest retroperfusion pressure (50 mm Hg). CONCLUSIONS: Considerable recovery of regional myocardial function with low regional capillary blood flows were observed during acute venous retroperfusion with high retroperfusion flows with arterial blood. These findings together with low levels of retrograde arterial outflow and visualization of retrograde capillary filling with a rich venous network provide evidence for possible oxygen delivery via the intramyocardial venous plexus.

Animals↗
PubMed1992

Myocardial cell hypertrophy after myocardial infarction with reperfusion in dogs.

BACKGROUND: The potential role of myocardial cell hypertrophy in the ischemic zone in the mechanism of late recovery of regional contractile function after myocardial infarction followed by reperfusion has not been examined. METHODS AND RESULTS: Eight chronically instrumented, conscious dogs were subjected to 90-120 minutes of circumflex coronary artery occlusion followed by reperfusion. The thickness and function of the anterior (AT) and posterior (PT) walls was measured by ultrasonic gauges at control, during occlusion, and after reperfusion. After 3 weeks, cross-sectional areas of surviving cells were determined from subepicardial (epi), midwall (mid), and subendocardial (endo) regions in six dogs and compared with those from six animals without infarction, including three sham-operated control dogs. PT systolic wall thickening showed dyskinesia during occlusion but recovered after reperfusion to 48% of control at 1 week and 67% at 3 weeks. End-diastolic thickness of the PT wall increased markedly after reperfusion, but AT and PT walls were only slightly thicker (p = NS) than in control dogs at 3 weeks. Cross-sectional areas of reperfused dogs in the infarct region averaged 279 (PTepi), 291 (PTmid), and 317 microns 2 (PTendo) and were significantly larger than in control animals (237 [PTepi], 241 [PTmid], and 233 microns 2 [PTendo]). PT cell areas were significantly larger than AT cells, ENDO cell areas were larger than EPI cells (both p < 0.05), and ENDO cells of the AT wall were larger than those of noninfarcted dogs (p < 0.05). CONCLUSIONS: In dogs with myocardial infarction followed by reperfusion, the cross-sectional areas of cells in the infarcted PT wall were larger than those in the noninfarcted AT wall, and within both the infarcted and noninfarcted zones, cell areas were larger in the endocardial than the epicardial region. In all regions of the infarcted wall and in the ENDO region of the noninfarcted wall, cell areas were generally larger than those of control dogs without infarction, and the control dogs showed no transmural differences in cell areas. The mechanisms responsible for this significant remodeling of the reperfused infarcted zone, which involves myocardial cellular hypertrophy, are unknown, but it is possible that hypertrophy of surviving regions of the infarcted wall played a role in the late recovery of regional function that accompanied this hypertrophic response.

Animals↗
PubMed1992

Myxomatosis: population dynamics of rabbits (Oryctolagus cuniculus Linnaeus, 1758) and ecological effects in the United Kingdom.

In 1953-1955, myxomatosis spread among rabbits (Oryctolagus cuniculus) in the United Kingdom, causing 99% mortality. Subsequently, there was a gradual increase in rabbit numbers. By 1955, the Ministry of Agriculture, Fisheries and Food (MAFF) had already found attenuated strains of myxoma virus. By 1970, genetic resistance had appeared. In the 1970s, mortality declined to 47-69% with only approximately 25% of rabbits infected, giving a field mortality of 12-19%. However, myxomatosis is persistent, generally showing a major prevalence peak in autumn and often a minor peak in spring. An eight-year MAFF experiment in which prevalence of the disease was artificially reduced indicates that myxomatosis remains a significant factor in population regulation. After rabbit numbers fell in the 1950s, important ecological changes took place: vegetation altered due to reduced grazing pressure, predators were affected by the reduction of a major prey species and these changes also affected many other animals. Currently, rabbit numbers have returned to approximately one-third of pre-myxomatosis levels and this is causing damage to farm and conservation habitats.

Animals↗
PubMed1992

Disappearance of Q waves following thrombolysis for acute myocardial infarction.

The development of Q waves on the surface electrocardiogram generally is considered indicative of myocardial infarction. Such Q waves are usually permanent, though may regress and disappear over months to years. Transient Q waves have been described during myocardial ischemia without evidence of infarction. More recently, Q waves have been noted to develop transiently during the acute phases of infarction, possibly representing stunned myocardium. In this case report, a patient with an evolving anterior myocardial infarction and new septal Q waves was treated with intravenous thrombolytic therapy. Three hours following treatment the patient was clinically improved, and the septal Q waves had been replaced by small but obvious R waves. Despite a large area of myocardium at risk of infarction on the initial electrocardiogram, the resultant infarction was enzymatically and echocardiographically small. Early Q waves in acutely evolving myocardial infarction may represent severely ischemic, rather than irreversibly damaged, myocardium which may still be salvaged with thrombolytic therapy.

Adult↗
PubMed1992

Identification of complex formation between two intracellular tyrosine kinase substrates: human c-Rel and the p105 precursor of p50 NF-kappa B.

Immune complexes of the product of the c-rel protooncogene and of p105, the p50 NF-kappa B precursor, isolated from human T-lymphoblastoid cell lines are comprised of multiple proteins. Only p105 and human c-Rel (hc-Rel) are common to complexes precipitated with antiserum directed against either p105 or hc-Rel. Both proteins are inducible by phytohemagglutinin (PHA) and phorbol 12-myristate 13-acetate (PMA) and their subcellular distribution is affected by this induction. We demonstrate that the Rel immune complex contains a protein with a molecular weight in the 40 kDa range (p40) which apparently is exclusively cytoplasmic. We were not able to detect p40 in the p105 immune complex, though hc-Rel is present. This indicates that hc-Rel exists in different multi-protein complexes and fits a model of functional regulation mediated by differential protein-protein interaction. We also demonstrate considerable isoform diversity of both hc-Rel and p105. We show that this heterogeneity is, in part, the result of phosphorylation. Furthermore, we demonstrate that p105 and hc-Rel are tyrosine kinase substrates. This finding indicates a role for both proteins in intracellular signal transduction pathways which are modulated by modification of their phosphorylation status.

Humans↗
PubMed1992

Discordance of airflow limitation and ventilatory inhomogeneity in asthma and cystic fibrosis.

Although it is known that both airflow rates and gas distribution are impaired in asthma and cystic fibrosis (CF), the concordance of the change in these defects between two points in time has not been studied. On two separate occasions, the FEV1, FVC and slope of Phase III (SBN2/L%) of the single breath nitrogen test were determined, as well as the concordance between the change in these indices in 14 healthy subjects, 14 subjects with asthma, and seven subjects with CF. The coefficient of variation within a test session averaged less than 5% for the FEV1 and less than 10% for the SBN2/L% within each group. The change in FEV1 correlated with the change in FVC in all three groups, but did not correlate with the change in SBN2/L% in any group. In seven of the 14 cases of asthma and six of the seven cases of CF (outliers), the differences in the indices (expressed as the change in percent predicted) were greater than the differences observed in the control group. In three of the asthmatic and four of the CF outliers, the changes were as predicted, that is, both tests returned toward normal, or both became more abnormal. In two of the asthmatic and CF outliers both the FEV1 and SBN2/L% increased, while both decreased in the other two asthmatic outliers. Although some of the same factors will affect both indices, a worsening of ventilation inhomogeneity, which will affect the SBN2/L%, could occur with an improvement in ventilatory flow rate. Alternatively, airflow limitation could worsen but be accompanied by an improvement in ventilation homogeneity.(ABSTRACT TRUNCATED AT 250 WORDS)

Adolescent↗
PubMed1991

Chemical implementation of neural networks and Turing machines.

We propose a reversible reaction mechanism with a single stationary state in which certain concentrations assume either high or low values dependent on the concentration of a catalyst. The properties of this mechanism are those of a McCulloch-Pitts neuron. We suggest a mechanism of interneuronal connections in which the stationary state of a chemical neuron is determined by the state of other neurons in a homogeneous chemical system and is thus a "hardware" chemical implementation of neural networks. Specific connections are determined for the construction of logic gates: AND, NOR, etc. Neural networks may be constructed in which the flow of time is continuous and computations are achieved by the attainment of a stationary state of the entire chemical reaction system, or in which the flow of time is discretized by an oscillatory reaction. In another article, we will give a chemical implementation of finite state machines and stack memories, with which in principle the construction of a universal Turing machine is possible.

Animals↗
PubMed1991

A plausible model for reversal of neoplastic transformations in plants based on multiple steady states.

We offer a plausible interpretation of some experiments on the reversal of neoplastic transformations in plants. We suggest that normal cells and tumorous cells represent multiple stable-steady states corresponding to a reaction feedback mechanism. The (autocatalytic) feedback loop is constructed from observations on the role played by myo-inositol: it increases the permeability of ions through the membrane and the biosynthetic pathway to myo-inositol is activated by ions. Provided that the permeabilities of nutrients (sugars and salts) are a product-enhanced function of myo-inositol, then we have a (oversimplified) model that can exhibit multiple stationary stable states, one or two depending on the exogenous nutrients and myo-inositol concentrations, and reversible and irreversible transitions from one of these states to the other are possible. From this model, straightforward simple experiments are suggested. We also propose that recent models dealing with the intracellular calcium regulation by hormones, where one key step requires the hydrolysis of inositol phospholipids, take into account free myo-inositol and endogenous hormone concentrations (e.g., auxins).

Calcium↗
PubMed1991

Morphological transformation and DNA adduct formation by benz[j]aceanthrylene and its metabolites in C3H10T1/2CL8 cells: evidence for both cyclopenta-ring and bay-region metabolic activation pathways.

Benz[j]aceanthrylene (B[j]A), a cyclopenta-fused polycyclic aromatic hydrocarbon related to 3-methylcholanthrene, has been studied to identify the major routes of metabolic activation in transformable C3H10T1/2CL8 (C3H10T1/2) mouse embryo fibroblasts in culture. Previous studies have reported that the major (55% of total) B[j]A metabolite formed by C3H10T1/2 cells was (+/-)-trans-9,10-dihydro-9,10-dihydroxy-B[j]A (B[j]A-9,10-diol), the dihydrodiol in the bay-region ring, with moderate amounts (14% of total) of (+/-)-trans-1,2-dihydro-1,2-dihydroxy-B[j]A (B[j]A-1,2-diol), the cyclopenta-ring dihydrodiol. The morphological transforming activities of three potential intermediates formed by metabolism of B[j]A by C3H10T1/2 cells, (+/-)-anti-trans-9,10-dihydro-9,10-dihydroxy-B[j]A-7,8-oxide (B[j]A-diol-epoxide), B[j]A-9,10-oxide, and B[j]A-1,2-oxide as well as the two B[j]A-dihydrodiols were examined. B[j]A, B[j]A-diol-epoxide, B[j]A-1,2-oxide, and B[j]A-9,10-diol were found to have moderate to strong activities with B[j]A-diol-epoxide the most active compared to B[j]A, while B[j]A-1,2-diol was inactive. B[j]A-9,10-oxide was found to be a weak transforming agent. At 0.5 microgram/ml, the following percentage of dishes with type II or III foci were observed: B[j]A, 59%; B[j]A-diol-epoxide, 75%; B[j]A-1,2-oxide, 25%; and B[j]A-9,10-diol, 17%. DNA adducts of B[j]A, B[j]A-9,10-diol, B[j]A-diol-epoxide, B[j]A-9,10-oxide, and B[j]A-1,2-oxide in C3H10T1/2 cells were isolated, separated, identified, and quantitated using the 32P-postlabeling method. B[j]A forms two major groups of adducts: one group of adducts is the result of the interaction of B[j]A-1,2-oxide with 2'-deoxyguanosine and 2'-deoxyadenosine; the second group of adducts is a result of the interaction of B[j]A-diol-epoxide with 2'-deoxyguanosine and 2'-deoxyadenosine. Qualitative and quantitative analysis of the postlabeling data suggests that B[j]A is metabolically activated by two distinct routes, the bay-region diol-epoxide route and the cyclopenta-ring oxide route, the former being the most significant.

Animals↗
PubMed1991

Contrast adaptation and contrast masking in human vision.

After a preliminary study of visual evoked potentials (VEPS) to a test grating seen in the presence of masks at different orientations, psychophysical data are presented showing the effects of adaptation and of masking on thresholds for detecting the same test grating. The test is a vertical grating of spatial frequency 2 cycles per degree; adapting and masking gratings differ from the test either in orientation or in spatial frequency. The effects of adaptation and masking are explained by a single mechanism model that assumes: (i) adaptation and masking both alter the contrast response (or transducer) function of the mechanism that detects the test; (ii) masks, but not adaptors, stimulate the mechanism that detects the test; and (iii) a test is detectable when it raises response level by a constant amount. The model incorporates two distinct tuning functions, a broad adaptive contrast function and a narrow effective contrast function. It accounts adequately for all the data, including the location and size of the facilitative dip found in some masking functions, the constant slopes of the threshold elevation segments of adaptation functions and the varying slopes of masking functions. It also predicts the sometimes surprising joint effects of adaptation followed by masking and of two masks operating simultaneously.

Adaptation, Ocular↗
PubMed1991

Segregation of atrial-specific and inducible expression of an atrial natriuretic factor transgene in an in vivo murine model of cardiac hypertrophy.

To study the mechanisms that activate expression of the atrial natriuretic factor (ANF) gene during pressure-induced hypertrophy, we have developed and characterized an in vivo murine model of myocardial cell hypertrophy. We employed microsurgical techniques to produce a stable 35- to 45-mmHg pressure gradient across the thoracic aorta of the mouse that is associated with rapid and transient expression of an immediate-early gene program (c-fos/c-jun/junB/Egr-1/nur-77), an increase in heart weight/body weight ratio, and up-regulation of the endogenous ANF gene. These responses that are identical to those in cultured cell and other in vivo models of hypertrophy. To determine whether tissue-specific and inducible expression of the ANF gene can be segregated, we used a transgenic mouse line in which 500 base pairs of the human ANF promoter region directs atrial-specific expression of the simian virus 40 large tumor antigen (T antigen), with no detectable expression in the ventricles. Thoracic aortic banding of these mice led to a 20-fold increase in the endogenous ANF mRNA in the ventricle but no detectable expression of the T-antigen marker gene. This result provides evidence that atrial-specific and inducible expression of the ANF gene can be segregated, suggesting that a distinct set of regulatory cis sequences may mediate the up-regulation of the ANF gene during in vivo pressure overload hypertrophy. This murine model demonstrates the utility of microsurgical techniques to study in vivo cardiac physiology in transgenic mice and should allow the application of genetic approaches to identify the mechanisms that activate ventricular expression of the ANF gene during in vivo hypertrophy.

Animals↗