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Biomedical subjects

J Ross

Publications and source records attributed to J Ross.

At least 253 records · Page 14Linked to original sources
PubMed1995

Will young children comply and follow instructions to successfully wear soft contact lenses?

We fit eighty-five children between the ages of 11 years and 13 years, 11 months with soft contact lenses to study safety of soft contact lens wear in children. We report the results at 6 months of a 3 year longitudinal study. Contact lens care compliance, a critical factor in successful lens wear, was evaluated using a questionnaire. The questionnaire was completed by 74 subjects at dispensing and at 1-week and 6-months post-dipensing visits. Subjects found contact lens removal to be the easiest and lens insertion the most difficult procedures. After 6 months, 85% of the children correctly identified the purpose of lens care solutions, 90% knew that daily cleaning was necessary, 96% understood lens disinfection, and 99% expressed confidence in their ability to care for their lenses.

Adolescent↗
PubMed1994

Purification of a human polyribosome-associated 3' to 5' exoribonuclease.

In cells and cell-free extracts, the early steps in histone mRNA decay occur at the 3' terminus and appear to be catalyzed by a polysome-associated 3' to 5' exoribonuclease. We describe the purification of a polysomal 3' to 5' exoribonuclease that is magnesium-dependent, active at pH 7-8 in salt concentrations below 200 mM, and resistant to the inhibitor of the RNase A family of RNases. The purified enzyme is inactive with 3'-phosphorylated RNA substrates and with DNA but can degrade duplex RNA in the absence of added ATP. The enzyme migrates at approximately 37 kDa by native state gel filtration and at 33 kDa in a SDS-polyacrylamide gel. It degrades poly(A) but not a complex of poly(A) with poly(A) binding protein, and it accelerates histone mRNA decay in high salt-washed (enzyme-depleted) polysomes. Similarities between the purified exoribonuclease and the activity that degrades histone mRNA in vitro suggest that the enzyme might be a mammalian messenger ribonuclease.

Exoribonucleases↗
PubMed1994

Can we talk? Inpatient discussions about advance directives in a community hospital. Attending physicians' attitudes, their inpatients' wishes, and reported experience.

BACKGROUND: The attitudes of hospitalized patients and their attending physicians about advance directives have not been well studied. We compared these attitudes and explored relationships between them and the frequency of actual directives and directive discussions during hospitalization. METHODS: We conducted scripted interviews with 258 (94.5%) of 273 patients admitted consecutively to the acute medical service of a community teaching hospital in Rochester, NY, and contemporaneously surveyed their attending physicians (n = 68) regarding attitudes about advance directives. Primary outcome measures were patients' willingness to discuss directives, actual physician-patient directive discussions, and patients' preferences for life-sustaining treatments. Also measured were physicians' indications for directive discussions, their reasons not to discuss directives, and their knowledge and attitudes about life-sustaining treatments. RESULTS: Eighty-one percent (172/212) of competent interviewed patients either did (100) or wanted to (72) discuss advance directives in hospital. Forty-one percent of patients chose to forgo cardiopulmonary resuscitation; 24% to 41% refused other life-sustaining interventions (intensive care unit admission, mechanical ventilation, cardioversion, vasopressors). Overall, 90% (246/273) of all patients met at least one of three criteria reported by their physicians as indications for advance directive discussions: age at least 75 years, critical or potentially fatal illness, and patients' desire to discuss directives. Multiple logistic regression revealed that these same variables predicted patients' willingness to discuss cardiopulmonary resuscitation, their preferences to receive or forgo cardiopulmonary resuscitation, and the frequency of physician-patient discussions about these issues. CONCLUSIONS: Most medical inpatients in a community hospital want to, are able to, and meet their own physicians' indications to discuss advance directives. Hospitalization presents an unrealized opportunity for physicians and patients to initiate these discussions.

Adolescent↗
PubMed1994

Selective suppression of the magnocellular visual pathway during saccadic eye movements.

Visual scientists have long sought to explain why the world remains stable during saccades, the ballistic eye-movements that continually displace the retinal image at fast but resolvable velocities. An early suggestion was that vision may be actively suppressed during saccades, but experimental support has been variable. Here we present evidence that saccadic suppression does occur, but that it is selective for patterns modulated in luminance at low spatial frequencies. Patterns of higher spatial frequency, and equiluminant patterns (modulated only in colour) at all spatial frequencies were not suppressed during saccades, but actually enhanced. The selectivity of the suppression suggests that it is confined to the colour-blind magnocellular stream (which provides the dominant input to motion centres and areas involved with attention), where it could dull the otherwise disturbing sense of fast low-spatial-frequency image motion. Masking studies suggest that the suppression precedes the site of contrast masking and may therefore occur early in visual processing, possibly as early as the lateral geniculate nucleus.

Color Perception↗
PubMed1994

Molecular and physiological alterations in murine ventricular dysfunction.

The present study reports the development and characterization of a murine model of right ventricular dysfunction following graded constriction in the pulmonary artery via microsurgical approaches. To analyze in vivo ventricular function, a technique of x-ray contrast microangiography was developed to allow the quantitative analysis of ventricular volumes and of ejection fraction in normal and pressure-overloaded right ventricle. Severe, chronic pulmonary arterial banding for 14 days resulted in right ventricular dilatation and dysfunction, associated with right atrial enlargement, and angiographic evidence of tricuspid regurgitation. These effects were dependent on the extent of hemodynamic overload, since more moderate pulmonary arterial constriction resulted in hypertrophy with maintenance of right ventricular function. With severe pulmonary artery constriction, the murine right ventricle displays a failing heart phenotype including chamber dilation with reduced function that resembles right ventricular dysfunction in man during chronic pulmonary arterial hypertension. Northern and immunoblot analyses demonstrate a marked down-regulation of phospholamban mRNA and its corresponding protein with both levels of constriction, while a less pronounced but significant depression of sarcoplasmic reticulum Ca(2+)-ATPase protein was observed with severe overload, suggesting that this pattern is an early genetic marker of ventricular dysfunction. By coupling mouse genetics with this murine model and the ability to assess cardiac function in vivo, one should be able to test the role of the down-regulation of phospholamban and other defined alterations in the cardiac muscle gene program in the onset of the failing heart phenotype.

Adenosine Triphosphatases↗
PubMed1994

Long term acid suppressing treatment in general practice.

OBJECTIVE: To determine the current practice in selected general practices for prescribing long term (> 6 months) treatment to suppress gastric acid secretion. SETTING: Seven general practices in the Harrow area that always or usually refer to Northwick Park Hospital. SUBJECTS: 60,148 patients on lists of the general practices. DESIGN: Identification of patients receiving long term treatment through repeat prescribing data, followed by a manual and computer survey of patients' notes for indications and investigations. Patient compliance and views on treatment were sought by a postal questionnaire. MAIN OUTCOME MEASURES: Indications for treatment, treatment given, investigations undertaken before and during treatment. RESULTS: 492 patients (0.82% of the population) were taking long term acid suppressing treatment. The most common diagnosis was duodenal ulcer disease (183 (37%) of all patients); oesophageal disease (118 (24%)) was also common. 93 patients (19%) were treated for abdominal pain where no diagnosis had been reached or who had only a diagnosis of gastritis on endoscopy. Ranitidine was prescribed in 394 (80%) patients. 298 (74%) patients found treatment helpful, but 108 (27%) had a poor understanding of their diagnosis. 317 patients (78%) took their drug as prescribed. 37 patients were also taking prescribed non-steroidal anti-inflammatory drugs and an additional 43 patients took regular aspirin or ibuprofen without prescription. CONCLUSIONS: Long term acid suppressing treatment is common, and a substantial number of patients are taking these drugs long term without a diagnosis having been reached. It is hoped that protocols for investigation and treatment will improve these figures. Patients need to be better informed about their disease and the possible adverse effects of taking non-steroidal anti-inflammatory drugs in acid related upper gastrointestinal disease.

Abdominal Pain↗
PubMed1994

Purification and properties of a protein that binds to the C-terminal coding region of human c-myc mRNA.

The short half-life of c-myc mRNA is influenced by sequences in the 3'-untranslated region and the C-terminal part of the coding region. In cell-free extracts, a polysomal protein binds to RNA corresponding to the coding region stability determinant. This and other observations suggest that the protein is bound to polysome-associated c-myc mRNA and protects the mRNA from a ribosome-associated endoribonuclease (Bernstein, P.L., Herrick, D.J., Prokipcak, R.D., and Ross, J. (1992) Genes & Dev. 6, 642-654). Here, we describe a four-step purification of the binding protein: solubilization from ribosomes, ammonium sulfate precipitation, RNA affinity chromatography, and reverse-phase high performance liquid chromatography. The 70-kDa protein can be renatured from solutions containing sodium dodecyl sulfate or organic solvents, greatly facilitating its purification. Protein binding to c-myc coding region RNA is blocked by diamide and N-ethylmaleimide, indicating a requirement for sulfhydryl groups. The protein also binds to N-myc coding region RNA but with approximately 5-fold lower affinity than to the comparable c-myc region. Excess c-myc competitor RNA induces 8-fold destabilization of c-myc mRNA in cell-free mRNA decay extracts. In contrast, N-myc coding region competitor RNA has no effect on c-myc mRNA half-life. Therefore, the protein we have purified probably affects c-myc mRNA metabolism with high specificity.

Binding Sites↗
PubMed1994

Pattern recognition, chaos, and multiplicity in neural networks of excitable systems.

We study a neural network composed of excitable FitzHugh neurons that interact by diffusive type connections. Patterns of neural activity may be stored by a Hebbian rule. The stored patterns are recalled and given by the transient activity of the neurons after the network has been perturbed by related patterns and relaxes back to its steady state. Periodic perturbations of the network are repeated requests for computations and result in simple periodic, complex periodic, and chaotic responses and corresponding computational performances.

Models, Theoretical↗
PubMed1994

Large scale production and semi-purification of kedarcidin in a 1000-L fermentor.

Actinomycete strain ATCC 53650 was grown in a 1000-L fermentor containing 680 L of medium and the production of kedarcidin was monitored by HPLC. The titers of kedarcidin in the fermentor cultures were 0.49-0.53 mg ml-1. A quick and efficient purification method involving the use of anion exchange resin DE23 (batch adsorption-desorption) and an ultrafiltration system yielded high recovery (65% yield) of kedarcidin from the fermentor culture. Over 200 grams of lyophilized kedarcidin of 70% purity was recovered from each of two 1000-L fermentor cultures using this process.

Actinomycetaceae↗
PubMed1994

Illusory brightness step in the Chevreul illusion.

It is well known that a staircase luminance profile is not seen veridically, but appears as the scallopy-like Chevreul illusion. We have shown that adding thin lines (either light or dark) to the centre of each step creates an illusory brightness change at the point of the line. The regions between the added lines and the edges seem to be uniform, with a clear change in brightness at the point where the line was added. The conditions under which the illusion occurred were measured systematically, both by contrast matching and by annulment. One model that can readily account for the illusion is the local-energy model of feature detection (Morrone & Burr, 1988 Proceedings of the Royal Society of London B, 235, 221-245). Adding the bar to the step creates a peak in local energy at all scales. At the higher scales, the phase of the energy is near zero, the signal for a line; but at the lower scales the phase is near pi/2, the signal for an edge. We propose that the edge signal of the lower scales causes the brightness illusion and that this brightness difference is structured by the feature defined sharply by the higher scales (even though that feature is not an edge). As well as predicting the existence of the illusion, simulations with the energy model predicted quantitatively the apparent contrast of the illusion as a function of stimulus contrast, bar-position and high-pass filter frequency.

Contrast Sensitivity↗
PubMed1994

Computational functions in biochemical reaction networks.

In prior work we demonstrated the implementation of logic gates, sequential computers (universal Turing machines), and parallel computers by means of the kinetics of chemical reaction mechanisms. In the present article we develop this subject further by first investigating the computational properties of several enzymatic (single and multiple) reaction mechanisms: we show their steady states are analogous to either Boolean or fuzzy logic gates. Nearly perfect digital function is obtained only in the regime in which the enzymes are saturated with their substrates. With these enzymatic gates, we construct combinational chemical networks that execute a given truth-table. The dynamic range of a network's output is strongly affected by "input/output matching" conditions among the internal gate elements. We find a simple mechanism, similar to the interconversion of fructose-6-phosphate between its two bisphosphate forms (fructose-1,6-bisphosphate and fructose-2,6-bisphosphate), that functions analogously to an AND gate. When the simple model is supplanted with one in which the enzyme rate laws are derived from experimental data, the steady state of the mechanism functions as an asymmetric fuzzy aggregation operator with properties akin to a fuzzy AND gate. The qualitative behavior of the mechanism does not change when situated within a large model of glycolysis/gluconeogenesis and the TCA cycle. The mechanism, in this case, switches the pathway's mode from glycolysis to gluconeogenesis in response to chemical signals of low blood glucose (cAMP) and abundant fuel for the TCA cycle (acetyl coenzyme A).

Biochemistry↗
PubMed1994

Morphological transformation and DNA adduct formation by dibenz[a,h]anthracene and its metabolites in C3H10T1/2CL8 cells.

The major routes of metabolic activation of dibenz[a,h]-anthracene (DBA) have been studied in transformable C3H10T1/2CL8 (C3H10T1/2) mouse embryo fibroblasts in culture. The morphological transforming activities of three potential intermediates formed by metabolism of DBA by C3H10T1/2 cells, trans-3,4-dihydroxy-3,4-dihydro-DBA-(DBA-3,4-diol), trans-dihydroxy-3,4-dihydro-DBA-anti-1,2-oxide (DBA-3,4-diol-1,2-oxide) and DBA-5,6-oxide were determined. DBA-3,4-diol-1,2-oxide was a strong morphological transforming agent giving a mean of 73% dishes with Type II or III foci and 1.63 Type II and III foci per dish at 0.5 microgram/ml. DBA-3,4-diol produced a mean of 42% dishes with Type II or III foci and 0.81 Type II and III foci per dish at 2.5 micrograms/ml. DBA gave a mean of 24% dishes with Type II or III foci and 0.29 Type II and III foci per dish at 2.5 micrograms/ml. DBA-5,6-oxide was found to be inactive. DNA adducts of DBA, DBA-3,4-diol, DBA-3,4-diol-1,2-oxide, DBA-1,4/2,3-tetrol and DBA-5,6-oxide in C3H10T1/2 cells were analyzed by 32P-postlabeling method. DBA gave 11 adducts, nine of which were observed in the DNA of cells treated with DBA-3,4-diol and seven from cells treated with DBA-3,4-diol-1,2-oxide. Two of these adducts that appear in each of the treatment groups have been identified as the product of the interaction of DBA-3,4-diol-1,2-oxide with 2'-deoxyguanosine. Furthermore, there is evidence for DBA-DNA adducts in cells treated with DBA, DBA-3,4-diol and DBA-3,4-diol-1,2-oxide arising from metabolism to (+,-)-trans,trans-3,4,10,11-tetrahydroxy-3,4,10,11-tetrahydro-DBA (DBA-3,4,10,11-bis-diol). These results are based on co-migration of C3H10T1/2 DNA adducts with skin DNA adducts formed after topical treatment of mice with DBA-3,4,10,11-bis-diol. In C3H10T1/2 cells, DBA is metabolically activated through DBA-3,4-diol, which is further activated via the DBA-3,4-diol-1,2-oxide and DBA-3,4,10,11-bis-diol pathways. No evidence is provided for the metabolism of DBA by the K-region pathway.

Animals↗
PubMed1994

In vivo assessment of left ventricular remodelling after myocardial infarction by digital video contrast angiography in the rat.

OBJECTIVE: The aim was to develop a digital video contrast angiographic method for assessing global left ventricular function and volume in vivo in the rat and then to apply it to a study of ventricular remodelling after coronary occlusion, with and without reperfusion. METHODS: Digital contrast angiography was performed on 29 rats, including the following groups: sham operated (n = 11), non-transmural myocardial infarction produced by reperfusion (n = 8), and transmural infarction produced by permanent occlusion (n = 10). Under anaesthesia three weeks later, biplane fluoroscopic images were acquired following venous contrast injection. Levophase images were digitised, and left ventricular end diastolic and end systolic volumes and ejection fractions were obtained using an area-length method. Left ventricular ejection fraction data also were calculated by videodensitometry from video density curves. RESULTS: Compared to the sham operated group, the reperfused group showed a significant decrease in left ventricular ejection fraction, at 53(SD 7) v 70(5)% (p < 0.01), and an increase in end diastolic volume. The permanent occlusion group showed a further decrease in the ejection fraction [40(8)%] and a further significant increase in end diastolic volume compared to the reperfused group (p < 0.01). Left ventricular ejection fraction correlated inversely with percent infarct size (r = 0.882) and showed a positive correlation with the spared epicardial area (r = 0.721). Most haemodynamic variables, including maximum left ventricular dP/dt, failed to discriminate between the groups. The methods showed reasonable accuracy when tested in vitro using contrast filled balloons. In vivo, the left ventricular ejection fraction calculated by densitometry showed adequate interobserver variability (2 SD +/- 8.5 percentage points), but the area-length method showed somewhat more scatter. CONCLUSIONS: Digital video contrast angiography is a feasible method for the assessing global left ventricular function in the rat and should be useful in other small animal models. Significant differences in left ventricular volumes and ejection fractions were detected between reperfused and permanent occlusion groups, whereas haemodynamic variables showed non-significant trends. Reperfusion after 45 min of occlusion caused sparing of the epicardium, prevented unfavourable remodelling, and improved the ejection fraction compared to permanent occlusion.

Angiography, Digital Subtraction↗
PubMed1994

Risk factors for injury during basic military training. Is there a social element to injury pathogenesis?

A retrospective case-control study into the risk factors for injury during basic military training was conducted at the Recruit Training Unit, Royal Australian Air Force Base Edinburgh, South Australia. Case subjects were recruits suffering a musculoskeletal injury during the course, severe enough to result in backcoursing (being delayed and joining a later course) and usually requiring the loss of 5 days of training. Control subjects were 629 recruits selected randomly from recruits who were not case subjects from the same period of Jan 1, 1985 to Dec 31, 1990. Two hundred thirty-eight cases were identified (2.7% of the recruit population), of which 123 were overuse-type injuries and 115 acute-type injuries. Most injuries occurred in the first 2 weeks of training. Bivariate and logistic regression analysis of possible risk factors for injury was conducted, both for all case subjects and for the subgroup of case subjects with overuse injuries. Statistically significant associations were identified for female gender, body mass index > 26.9, winter training, a history of lower limb injury, and the presence of a lower limb deformity. All these associations were stronger for overuse injury, and preenlistment physical activity was also significantly associated with overuse injury. No significant association was found for height, weight, age, smoking, or gender makeup of courses. Most striking was a large rise in overuse injury incidence in women over the period of study, from 0.2% in 1985 to 8.8% in 1990. Reasons for this increase may include "social pathogenesis."

Adult↗
PubMed1994

Transitions between routes of administration of regular amphetamine users.

A sample of 301 regular amphetamine users was interviewed regarding transitions between routes of administration of amphetamines. Use of amphetamines by injecting was widespread, with two-thirds (67%) of subjects having injected the drug during the preceding 6 months. Needle-sharing was common, with 41% of injectors having shared a needle in the month preceding interview. A transition to regular amphetamine injecting from other routes of administration was reported by 40% of subjects, with males being twice as likely to report such a transition. The median number of such transitions was one. The main reasons given by subjects for the transition to injecting were liking the "rush" from injecting, and seeing it as a more economical and a healthier way to use. A small proportion of subjects (9%) reported a transition away from injecting amphetamines, with a median of one such transition. The most common reason given for abandoning injecting was concern about vascular damage. Interventions to encourage safer use of amphetamines need to address the misconceptions that injecting is more economical and more healthy, and to emphasize the vascular problems associated with injecting.

Adolescent↗