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Biomedical subjects

J Ross

Publications and source records attributed to J Ross.

At least 307 records · Page 17Linked to original sources
PubMed1993

A review of lower limb overuse injuries during basic military training. Part 1: Types of overuse injuries.

Lower limb injuries present the greatest source of medical problems during basic military training. These main overuse lower limb injuries, anterior compartment syndrome, stress fractures, Achilles tendinitis, plantar fasciitis, shin splints, and chondromalacia patellae, are reviewed with respect to current knowledge of rates, diagnosis, and treatment. Part 2 shall review possible etiological factors involved in the causation of these injuries.

Adolescent↗
PubMed1992

Low-dose (7.5 mg) oral methotrexate for chronic progressive multiple sclerosis. Design of a randomized, placebo-controlled trial with sample size benefits from a composite outcome variable including preliminary data on toxicity.

OBJECTIVE: To present a detailed description of (1) the study design of this ongoing trial, (2) advantages of using a composite outcome variable instead of multiple individual outcome measures, (3) treatment group characteristics at baseline, and (4) observed short-term methotrexate (MTX) toxicity. DESIGN: Randomized, double-masked, placebo-controlled intervention study. SETTING: Referral-based outpatient multidisciplinary multiple sclerosis (MS) clinic. PATIENTS: Participation offered to all clinically definite chronic progressive multiple sclerosis (CPMS) patients attending clinic ages 21 to 60, disease duration > 1 year, Expanded Disability Status Scale (EDSS) score 3.0 to 6.5 (ambulatory with moderate disability). Patients first stratified by EDSS 3.0 to 5.5 and 6.0 to 6.5, then randomized to MTX or placebo treatment. INTERVENTION: Weekly oral low-dose (7.5 mg) MTX or identical-appearing placebo for 2 years followed by a 1-year observation period. MAIN OUTCOME MEASURES: Sample size calculations undertaken prior to enrolling patients based upon a composite outcome variable consisting of designated change in any of the following functional measures: (1) EDSS, (2) Ambulation Index (AI), (3) Box and Block Test (BBT), and (4) 9-Hole Peg Test (9HPT). RESULTS: (1) Treatment group characteristics were comparable at baseline, (2) no patient has been withdrawn for adverse effects or lost to follow-up, (3) no significant short-term MTX toxicity has been observed. CONCLUSIONS: (1) The use of a composite outcome measure in the design of MS clinical trials is a promising alternative to multiple individual outcome measures that are relatively insensitive to detecting clinical change, (2) low-dose oral weekly MTX does not appear to be associated with significant short-term toxicity in CPMS. Conclusions regarding therapeutic efficacy of MTX in MS must await completion of this clinical trial.

Adult↗
PubMed1992

Chemical implementation of finite-state machines.

With methods developed in a prior article on the chemical kinetic implementation of a McCulloch-Pitts neuron, connections among neurons, logic gates, and a clocking mechanism, we construct examples of clocked finite-state machines. These machines include a binary decoder, a binary adder, and a stack memory. An example of the operation of the binary adder is given, and the chemical concentrations corresponding to the state of each chemical neuron are followed in time. Using these methods, we can, in principle, construct a universal Turing machine, and these chemical networks inherit the halting problem

Journal Article↗
PubMed1992

Chemical implementation and thermodynamics of collective neural networks.

The chemical implementation of a neuron and connections among neurons described in prior work is used to construct collective neural networks. With stated approximations, these chemical networks are reduced to networks of the Hopfield type. Chemical networks approaching a stationary or equilibrium state provide a Liapunov function with the same extremal properties as Hopfield's energy function. Numerical comparisons of chemical and Hopfield networks with small numbers (2-16) of neurons show agreement on the results of given computations.

Catalysis↗
PubMed1992

Improved processes for the production and isolation of dynemicin A and large-scale fermentation in a 10,000-liter fermentor.

Supplementing the culture of Micromonospora chersina sp. nov. No. M956-1 with NaI (0.5 mg/l) enhanced the production of dynemicin A by 35-fold in shake flask culture. Homogeneous dynemicin A was obtained from the whole broth extract by Dicalite chromatography, Sephadex LH-20 chromatography and vacuum liquid chromatography. Gram quantities of dynemicin A were obtained from the fermentation of M. chersina sp. nov. No. M956-1 in a 10,000-liter fermentor.

Anthraquinones↗
PubMed1992

Spatial frequency tuning of facilitation by masks.

The spatial frequency tuning of facilitation by masks is derived for a 2 c/deg test grating, counterphased at 8.8 Hz, from the contrasts at which masks of different spatial frequencies facilitate maximally. This tuning function has a bandwidth at half height of roughly 1.5 octaves, much broader than has been estimated previously from tuning functions determined at a constant contrast for each mask. We show also that best facilitation more than doubles sensitivity for tests of 4 c/deg and below, and that the magnitude of the facilitation effect declines at higher spatial frequencies.

Contrast Sensitivity↗
PubMed1992

Self-administered mixture of Entonox and isoflurane in labour.

Entonox (50% nitrous oxide premixed in oxygen) was compared with a mixture of Entonox and approximately 0.25% isoflurane (Entonox-isoflurane) for pain relief in the first stage of labour in 39 mothers. An Oxford Miniature Vaporizer was incorporated as the draw-over vaporizer for adding isoflurane to Entonox. The mixture was self-administered via the Entonox on-demand valve. The two mixtures were given in random sequence for five consecutive contractions of labour to each patient. Linear analogue pain relief scores were significantly higher (P=0.001) with Entonox-isoflurane. Fourteen patients continued using Entonox-isoflurane until delivery. No adverse effect from prolonged use was noted. Entonox-isoflurane is considered worthy of further investigation.

Journal Article↗
PubMed1992

Dysphagia as a major symptom of tetanus.

Dysphagia is a common symptom presenting to ENT departments. Two cases of tetanus with dysphagia as a major symptom are discussed, together with a review of previously reported cases. Although tetanus is a rare disease in the United Kingdom, the possibility of this diagnosis should be borne in mind in patients presenting with progressive dysphagia, especially if there are other head and neck symptoms present.

Barium Sulfate↗
PubMed1992

The role of value orientations in curricular decision making: a rationale for teachers' goals and expectations.

This research examined the role of value orientations in curricular decision making from the perspective of high school physical education teachers and students. Educational value orientations served as the theoretical base for the research. Teachers who exhibited one of two paired orientations, disciplinary mastery/learning process (DM/LP) or ecological integration/social reconstruction (EI/SR), were interviewed to examine the extent to which their value orientations influenced their stated (a) goals for student learning, and (b) expectations for academic performance and behavior. Students were also interviewed to investigate the extent to which they acknowledged these goals and expectations. Data were analyzed using constant comparison. Results suggested that goals and expectations of DM/LP and EI/SR teachers were distinctly different and that comments from students in the EI/SR teachers' classes did not reflect their teachers' goals and expectations. Dynamical system theory was used to conceptualize value orientations as attractors within the educational ecosystem. Teachers working from weak EI/SR value attractors may be limited by learner, instructional, and contextual constraints.

Curriculum↗
PubMed1992

The effect of postural drainage positioning on ventilation homogeneity in healthy subjects.

Body position is known to have significant effects on oxygen transport. These effects, however, are seldom considered during postural drainage (PD). The purpose of this study was to examine the effect of modified PD positions on ventilation homogeneity (the evenness of the distribution of ventilation), which is a key component of oxygen transport. The single-breath nitrogen washout test was used to obtain an index of ventilation homogeneity (slope of phase 3 [SBN2/L%]). Seventeen healthy individuals, ranging from 22 to 40 years of age ( mean = 28.4, SD = 5.6), performed the single-breath nitrogen test while sitting, lying supine with the bed tipped head down, right side lying, and right side lying with the bed tipped head down. Within-subject one-way analyses of variance and Tukey's post hoc analyses were used to compare differences in SBN2/L% across the four positions. The distribution of ventilation was significantly less homogeneous in the side-lying positions compared with the supine and sitting positions. Although these results reflect a position-induced change in pleural pressure gradient, they also reflect the effect of gravity-independent, intraregional changes on ventilation distribution. Thus, modified PD positioning has a significant effect on ventilation homogeneity, which may predispose a patient to arterial desaturation. Given the complexity of the factors involved, patients considered for PD positioning should be monitored for arterial saturation.

Adult↗
PubMed1992

Control of c-myc mRNA half-life in vitro by a protein capable of binding to a coding region stability determinant.

Polysome-associated c-myc mRNA is degraded relatively rapidly in cells and in an in vitro mRNA decay system containing extracts from cultured mammalian cells. Using this system, a competition/screening assay was devised to search for factors that bind to specific regions of polysome-associated c-myc mRNA and thereby alter its half-life. mRNA stability was first assayed in reactions containing exogenous competitor RNAs corresponding to portions of c-myc mRNA itself. The addition of a 182-nucleotide sense strand fragment from the carboxy-terminal portion of the c-myc-coding region destabilized c-myc mRNA by at least eightfold. This RNA fragment had no effect on the stability of other mRNAs tested. Moreover, c-myc mRNA was not destabilized in reactions containing unrelated competitor RNAs or sense strand RNA from the c-myc 5' region. Polysome-associated globin mRNA containing the c-myc-coding region segment in-frame was also destabilized in vitro by the 182-nucleotide RNA. As determined by UV-cross-linking experiments, the 182-nucleotide RNA fragment was recognized by and bound to an approximately 75-kD polysome-associated protein. On the basis of these data plus Northern blotting analyses of c-myc mRNA decay products, we suggest that the approximately 75-kD protein is normally bound to a c-myc-coding region determinant and protects that region of the mRNA from endonuclease attack. Possible links between the protective protein, translation, ribosome pausing, and c-myc mRNA turnover are discussed.

Base Sequence↗