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Biomedical subjects

J Downs

Publications and source records attributed to J Downs.

At least 19 recordsLinked to original sources
PubMed2006

Development of a video-based evaluation tool in Rett syndrome.

This paper describes the development of a video-based evaluation tool for use in Rett syndrome (RTT). Components include a parent-report checklist, and video filming and coding protocols that contain items on eating, drinking, communication, hand function and movements, personal care and mobility. Ninety-seven of the 169 families who initially agreed to participate returned a videotape within 8 months of the first request. Subjects whose videos were returned had a similar age profile to those who did not provide a video but were more likely to have classical than atypical RTT. Evidence of the content and social validity and inter-rater reliability on 11 videos is provided. Video may provide detailed, objective assessment of function and behaviour in RTT.

Adolescent↗
PubMed1996

Application of the fuzzy ARTMAP neural network model to medical pattern classification tasks.

This paper presents research into the application of the fuzzy ARTMAP neural network model to medical pattern classification tasks. A number of domains, both diagnostic and prognostic, are considered. Each such domain highlights a particularly useful aspect of the model. The first coronary care patient prognosis, demonstrates the ARTMAP voting strategy involving 'pooled' decision-making using a number of networks, each of which has learned a slightly different mapping of input features to pattern classes. The second domain, breast cancer diagnosis, demonstrates the model's symbolic rule extraction capabilities which support the validation and explanation of a network's predictions. The final domain, diagnosis of acute myocardial infarction, demonstrates a novel category pruning technique allowing the performance of a trained network to be altered so as to favour predictions of one class over another (e.g. trading sensitivity for specificity or vice versa). It also introduces a 'cascaded' variant of the voting strategy intended to allow identification of a subset of cases which the network has a very high certainty of classifying correctly.

Artificial Intelligence↗
PubMed1992

Consistency of results from the Vettest 8008 clinical biochemistry analyser.

Findings are presented on the precision of a clinical biochemistry analyser designed specifically for veterinary use. Twenty biochemical analytes have been examined in detail for variation within and between runs. The results indicate that the analyser can provide high precision for all the analytes with the possible exception of calcium, and suggest that the instrument can be used with confidence in the practice laboratory to aid diagnosis and to monitor biochemical changes in animals receiving treatment.

Animals↗
PubMed1991

Servo-controlled indenter for determining the transverse stiffness of ventricular muscle.

Regional ventricular wall stress is a critical determinant of cardiac function. There are, however, no validated methods for accurately estimating this stress. We have shown in the isolated ventricular septum that, during steady-state indentations, the transverse stiffness (the ratio of indentation stress [pressure acting on indenter face] to indentation strain [amount of indentation/nonindented thickness]) can be used as an estimate of the in-plane wall stress. Because of the long acquisition time for those transverse stiffness determinations, it was not possible to follow changes in wall stress over a single contraction. We recently developed a dynamic indentation system that can determine transverse stiffness in as little as 10 ms, allowing estimation of wall stress over a single contraction cycle. The apparatus consists of an indentation probe coupled to a linear motor. This indentation system was tested on two beating canine ventricular septa that were mounted in a biaxial system the could apply strains in the plane of the septa and measure the resulting in-plane stresses. The probe indented the septa with peak displacements of 0.1-0.5 mm at frequencies of 20 and 50 Hz. The transverse stiffness was calculated as the slope of the relation between the indentation stress and indentation strain during each high-frequency indentation. Consistent with earlier studies, the transverse stiffness was related to the inplane stress. In contrast to earlier studies, however, these dynamic transverse stiffness determinations could be made during a single contraction. Thus, dynamic transverse stiffness determinations allow estimation of wall stress in the isolated septa by minimal surface contact, and may lead to methods for estimating wall stress in the intact heart.

Animals↗
PubMed1990

An improved video-based computer tracking system for soft biomaterials testing.

We present an improved video-based computer system for on-line tracking of small markers moving in a plane. The system consists of a CCD camera, a video monitor, a dedicated 80386/20 microcomputer, a video frame grabber, and custom software. Up to four markers can be tracked at the 30-Hz video frame rate using a two-step, correlation-based search procedure. We discuss the requisite hardware and software requirements and illustrate how this tracking system can be used to collect strain data during biaxial stretching tests on planar soft tissues. Operating at 30 Hz, this system is an improvement over those previously reported, which are either slower or yield less information.

Algorithms↗
PubMed1989

Effect of linoleic acid infusion on blood pressure in normotensive and hypertensive rats.

High dietary intake of linoleic acid lowers arterial pressure, and, in vitro, linoleic acid inhibits the enzymatic activity of renin. The purpose of the present study was 1) to evaluate the effect of intravenous infusion of linoleic acid on blood pressure in normotensive and hypertensive Sprague-Dawley rats and 2) to determine whether the hypotensive response to linoleic acid infusion is caused by inhibition of circulating renin. Blood pressure was decreased (P less than 0.01) by linoleic acid infusion in normotensive sodium chloride-deprived animals and in animals with two-kidney, one-clip hypertension. In contrast, linoleic acid infusion did not affect blood pressure in normotensive rats on a "normal" or high sodium chloride intake, in rats with deoxycorticosterone acetate (DOCA)-salt hypertension, and in anephric rats. In sodium chloride-deprived rats, the reduction of blood pressure by linoleic acid infusion was associated with increased plasma renin activity (P less than 0.05); serum angiotensin-converting enzyme activity was unchanged. The in vitro enzymatic activity of exogenous renin in plasma of anephric rats was not affected by linoleic acid infusion. In two-kidney, one-clip hypertensive animals, pretreatment with indomethacin did not alter the hypotensive response to linoleic acid. Thus, although linoleic acid infusion lowered blood pressure in high renin but not in low renin states, the reduction of blood pressure was not related to inhibition of circulating renin or to alterations of endogenous prostaglandin biosynthesis.

Animals↗
PubMed1985

Continuous positive airway pressure by face mask in acute cardiogenic pulmonary edema.

The therapeutic efficacy of continuous positive airway pressure (CPAP) administered by face mask was studied in 40 patients with acute cardiogenic pulmonary edema and respiratory failure. Arterial blood gas values and pH, systemic arterial pressure, heart rate and respiratory rate were measured during administration of 30% oxygen with a high-flow face mask apparatus at ambient airway pressure. Twenty patients were then randomly chosen to continue ambient airway pressure breathing and 20 received 10 cm H2O of CPAP. The measurements were repeated 10, 60 and 180 minutes after therapy was initiated. During the first 10 minutes of CPAP treatment, arterial blood oxygen partial pressure increased 8 +/- 9 mm Hg (mean +/- 1 standard deviation), (p less than 0.01) and respiratory rate decreased 5 +/- 5 breaths/min (p less than 0.001). Systolic arterial pressure decreased 12 +/- 21 mm Hg (p less than 0.05), and heart rate by 10 +/- 11 beats/min (p less than 0.001). A decrease in respiratory rate by 2 +/- 5 breaths/min (p less than 0.05) was the only change that occurred in the control group. The improvement in arterial blood oxygenation persisted throughout the investigation period (p less than 0.05). Thirteen patients (65%) in the control group and 7 patients (35%) in the CPAP group met our criteria for treatment failure during the study (p = 0.068). Thus, CPAP administered by face mask improves gas exchange, decreases respiratory work, unloads circulatory stress, and may reduce the need for ventilator treatment in acute cardiogenic pulmonary edema.

Acute Disease↗
PubMed1985

Affective disorders in referred children and younger siblings of manic-depressives. Mode of onset and prospective course.

We studied 68 referred juvenile offspring or siblings of adult bipolar patients. Mean age at onset of affective and related disturbances was 15.9 years (range, 6 to 24 years). Although four of the ten prepubertal children had hypomanic features, full-blown manic psychosis did not appear before puberty. In the sample at large, 12 were classified as dysthymic and ten as cyclothymic. Eleven additional subjects with polysubstance abuse, who at onset did not meet criteria for affective disorder, were reclassified as having either a dysthymic or a cyclothymic disorder during follow-up. Of the remaining patients--24 depressive, eight manic, and three mixed state--71% experienced recurrences; mood-incongruent features, present in four cases at onset, recurred in only one patient during subsequent episodes. Overall, half the sample evidenced signs of bipolarity during a mean prospective follow-up period of three years.

Acute Disease↗
PubMed1985

A new histologic approach to the differentiation of enchondroma and chondrosarcoma of the bones. A clinicopathologic analysis of 51 cases.

Fifty-one cases of central, hyalin cartilage tumors of the long and flat bones were analyzed. Although Grade 2 and 3 chondrosarcomas could be diagnosed on the basis of cytologic features alone, low-grade chondrosarcoma could not be adequately differentiated from pure, benign enchondroma(s) by cytology alone. The tumors can be distinguished by a new histologic approach based on tissue patterns. The crucial enchondroma patterns consist of multiple nodules of hyalin cartilage separated by normal marrow in conjunction with partial to complete encompassing plates of lamellar bone that conform to the irregular shapes of the cartilage nodules. The chondrosarcomatous patterns consist of a single confluent mass of cartilage, which commonly permeates the marrow, "trapping" host lamellar bone on all sides, and which forms bands of fibrosis between the confluent peripheral cartilage lobules. Other less common patterns included cartilagenous infiltration of the Haversian systems or marrow fat and/or the development of a soft tissue mass. A central secondary chondrosarcoma is defined as one that shows the combination of both the enchondromatous and chondrosarcomatous patterns. All 18 of the pure enchondromas diagnosed by the methods proposed in this article behaved with strict benignity (i.e., without evidence of recurrence or metastasis with an average follow-up period of 7.2 years). The 33 primary and secondary chondrosarcomas diagnosed using the described patterns behaved with the predicted frequency of recurrence, metastasis, and patient demise.

Adolescent↗
PubMed1983

Evaluation of an ethylene oxide sterilizer.

Ethylene oxide gas can be used under controlled conditions to sterilize heat and moisture sensitive articles, particularly those which cannot be steam sterilized or immersed in disinfectants. The ethylene oxide process is essentially one of sterilization and all micro-organisms, including bacterial spores, are destroyed.

Equipment and Supplies, Hospital↗
PubMed1982

In vitro activity of MK-0366 against clinical urinary pathogens including gentamicin-resistant Pseudomonas aeruginosa.

MK-0366, a new derivative of nalidixic acid, was tested against 250 urinary pathogens including Escherichia coli, Serratia marcescens, and Pseudomonas aeruginosa. This new agent was more active than any of the other antibiotics tested, which included carbenicillin, ampicillin, cephalexin, tetracycline, trimethoprim, trimethoprim-sulfamethoxazole, and nalidixic acid. Gentamicin-resistant P. aeruginosa were highly sensitive to MK-0366, with a 90% minimal inhibitory concentration of 0.8 microgram/ml. Serratia strains were the most resistant organisms, with a 90% minimal inhibitory concentration of 3.1 micrograms/ml. These results suggest that clinical trials should be designed to investigate the clinical usefulness of this new drug in urinary infections.

Anti-Bacterial Agents↗
PubMed1978

Isolation of subunits from trypsin-cleaved sarcoplasmic reticulum Ca2+ transport adenosine triphosphatase.

Controlled tryptic digestion of purified rat skeletal muscle sarcoplasmic reticulum (Ca2+ + Mg2+)-adenosine triphosphate yields two products designated Fragments 3a and 3b with molecular weights of 65,000 and 56,000 respectively. The isolation of these products in high yield should facilitate exploration of the molecular characteristics of this adenosine triphosphatase. A simple, rapid method for accomplishing this isolation was developed which provides a high yield and utilizes mild conditions. The fragments obtained by this method were used to determine the phospholipid and sulfhydryl contents of Fragments 3a and 3b. In addition, information was obtained on the orientation of these adenosine triphosphatase components in the enzyme lipoprotein complex.

Adenosine Triphosphatases↗