Biomedical subjects

D Burr

Publications and source records attributed to D Burr.

At least 19 recordsLinked to original sources

PubMed1998

A comparison of the effect of shoes on human tibial axial strains recorded during dynamic loading.

Percutaneous axial extensometers were mounted on the medial cortex of the midtibial diaphysis in seven male volunteers and the effect of three different shoes on in vivo peak-to-peak axial compression-tension strains measured during dynamic loading. Zohar shoes had lower axial strains and strain rates during treadmill walking than Nike Air Max running shoes or Israeli infantry boots. During running on a running track, there was no statistically significant difference between the axial strains or strain rates between the shoes tested. Shoe gear can modify tibial strains and strain rates that contribute to the development of tibial stress fractures.

Adult↗

PubMed1996

Suppression of the magnocellular pathway during saccades.

Saccades create two problems for the visual system: they cause fast (but resolvable) motion of the retinal image and a change in the relationship between retinal and external spatial co-ordinates. In this review, we examine the first of these problems, of why there is no distributing sense of motion during saccades. Recent evidence from a range of sources suggests that during saccades, the magnocellular pathway is selectively suppressed, while the parvocellular pathway is functionally unimpaired, or even enhanced. The suppression seems to occur early, possibly in the lateral geniculate nucleus, where the pathways are well separated. It is possible that the suppression shares similar mechanisms to those responsible for contrast gain control.

Animals↗

PubMed1996

The effect of shoe gear on human tibial strains recorded during dynamic loading: a pilot study.

The study was conducted to test the hypothesis that alterations in shoe gear can affect tibial strains in the human during dynamic loading. Rosette strain gauges were mounted on the medial border of the mid-diaphysis in two human subjects with a new strain gauge bonding technique using methyl methacrylate. Strain measurements were made at this site, the most frequent location for stress fractures in the Israeli Army during treadmill walking and free running while wearing various sport shoes (Rockport ProWalkers and New Balance NBX 900) and army boots (light Israeli infantry, double layered sole Israeli infantry, and Zohar infantry boots). Data were analyzed for only one of the subjects because strain gauge bonding was found to be inadequate at the time of surgical removal in the other subject. No single shoe lowered both the principal tibial compression and tensile strains, and the shear strains. The Zohar boot had the lowest principal compression strains during treadmill walking and mobile running, despite its relatively higher weight and sole durometry.

Biomechanical Phenomena↗

PubMed1995

Sounds right.

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Apoptosis↗

PubMed1994

On inconsistency of Breslow's estimator as an estimator of the hazard rate in the Cox model.

In the Cox proportional hazards model, Breslow's estimator of the cumulative hazard function is well known. This estimator is sometimes presented in such a way that it appears to offer a method of estimating the hazard rate function as well. We state and prove an asymptotic result for this estimator of the hazard rate, which shows that the estimator is inconsistent, and that it is asymptotically unbiased.

Biometry↗

PubMed1993

Enterotoxigenic Escherichia coli and other causes of infectious pediatric diarrheas in Jakarta, Indonesia.

A hospital stool survey of Indonesian children less than 5 years of age determined the prevalence of diarrhea caused by enterotoxigenic Escherichia coli (ETEC) and other bacterial enteropathogens, compared to non-diarrheic control patients. ETEC were the second most frequent cause of diarrhea, isolated from 16 of 194 (8.2%) of patient's stools compared to 2 of 97 (2.1%) of control stools. The highest prevalence was in infants 12 to 23 months of age (17.9%).

Age Factors↗

PubMed1992

Diagnosis of typhoid fever by detection of Salmonella typhi antigen in urine.

A monoclonal antibody specific for group D Salmonella antigen 9 was used in an indirect enzyme-linked immunosorbent assay (ELISA) for detecting the antigen in urine specimens collected from patients with clinical typhoid fever in Jakarta, Indonesia. The ELISA had a sensitivity of 95% in identifying patients in whom Salmonella typhi was isolated from hemocultures, 73% in patients in whom S. typhi was isolated from stool specimens, and 40% in patients in whom the organism was isolated from bone marrow cultures. Among patients in whom S. typhi was isolated from blood cultures, the ELISA had a sensitivity of 65% when a single urine specimen was examined and 95% when serially collected urine specimens were examined. A dot blot immunoassay performed on a nitrocellulose filter in parallel had a sensitivity of 85%, versus 83% for the plate ELISA in which S. typhi was isolated from blood, bone marrow, and/or stool specimens. Since S. typhi antigen is intermittently excreted in the urine of patients with typhoid fever, serially collected urine from patients with typhoid should be tested for antigen 9.

Antigens, Bacterial↗

PubMed1991

Osteoarthritic changes in canine articular cartilage, subchondral bone, and synovium fifty-four months after transection of the anterior cruciate ligament.

Anterior cruciate ligament transection (ACLT) in the dog results in osteophyte formation and in morphologic, metabolic, biochemical, and biomechanical changes in the articular cartilage of the unstable knee that mimic those of human osteoarthritis (OA). However, in dogs studied up to 2 years after ACLT, the changes have appeared to be self-limiting, which has led to the suggestion that this is a model of cartilage damage and repair, rather than of OA. To ascertain whether changes in articular cartilage and subchondral bone of dogs subjected to ACLT lead to progressive changes of OA, we studied 3 dogs for 54 months after ACLT. Arthrotomy was performed in the dogs to visualize and then transect the anterior cruciate ligament. When the dogs were killed, full-thickness ulceration of the articular cartilage was seen on the medial femoral condyle and tibial plateau of the unstable knee, while cartilage in other regions was thicker than that of the contralateral knee, consistent with hypertrophic cartilage repair. Synovial infiltration by mononuclear cells was not more severe than that seen in dogs killed at earlier intervals after ACLT, although gross fibrotic thickening of the capsule was apparent in each dog. Histomorphometric studies revealed a marked increase in subchondral bone volume and active bone formation. These findings show that the changes that develop in the canine knee joint after ACLT are progressive and are unambiguously those of OA.

Animals↗

PubMed1990

Rapid diagnosis of typhoid fever through identification of Salmonella typhi within 18 hours of specimen acquisition by culture of the mononuclear cell-platelet fraction of blood.

Detection of Salmonella typhi in blood by culture of the mononuclear cell-platelet layer was compared with other methods currently used for the diagnosis of typhoid fever. Colonies of S. typhi were present in all mononuclear cell-platelet layer-positive cultures within 18 h of plating and were identified within an additional 10 min by a coagglutination technique. In contrast, identification of all positive cultures by conventional blood culture required 3 days.

Agglutination Tests↗

PubMed1988

The effect of adenosine on respiratory chemosensitivity in the awake rat.

The effect of adenosine on respiration and respiratory chemosensitivity in awake animals was studied in rats, intact and chemodenervated, before and after intra-peritoneal injection of L-phenylisopropyladenosine (PIA). Respiration was measured by barometric plethysmography. The administration of PIA depressed respiration substantially, in a dose-related manner, the maximum effect occurring after 30-80 min; PIA also depressed body temperature but over a slower time course. In both intact and chemodenervated animals, the characteristic responses to hypoxia were maintained after the administration of PIA, but at depressed respiratory levels. There was no interaction between effects. Administration of PIA produced enhancement of the ventilatory response to hypercapnia, in both intact and peripherally chemodenervated animals. The results do not support the hypothesis that hypoxic effects on respiration are related to the accumulation of adenosine in brain tissues. Enhancement of the hypercapnic response represents evidence for disinhibition of the mechanism concerned.

Adenosine↗

PubMed1988

Alkaline phosphatase-conjugated oligonucleotide probes for enterotoxigenic Escherichia coli in travelers to South America and West Africa.

Several studies have demonstrated the usefulness of 32P-labeled recombinant DNA probes for identifying enterotoxigenic Escherichia coli (ETEC). The use of radioisotopes and X-ray development, however, severely handicaps the utility of DNA probes in most clinical laboratories. In this study, enzyme-labeled oligonucleotide probes for ETEC LT (heat-labile toxin) and ST (heat-stable toxin) genes were compared with the standard Y1 adrenal cell and suckling mouse assays for their ability to identify ETEC in a population of American adults experiencing acute episodes of diarrhea in South America and West Africa. The LT probe hybridized with 12% (64 of 529) of the E. coli colonies tested, whereas 11% (57 of 529) were positive by Y1 adrenal cell assay. DNA from 9% (47 of 529) of the E. coli colonies tested hybridized with the ST probe, whereas only 5% (28 of 529) produced ST as measured by the suckling mouse bioassay. For the patient samples tested, correlation between probe and bioassay for LT was 97%, or three discrepancies in 111 patients tested. Overall concordance of the ST probe and bioassay was 95%, or five discrepancies in 111 patients. Enzyme-labeled oligonucleotide probes represent a major advance in the diagnosis of ETEC-associated diarrheal disease and may be used in laboratories with minimal equipment.

Adult↗

PubMed1988

Selective association and transport of Campylobacter jejuni through M cells of rabbit Peyer's patches.

M cells in the Peyer's patches may facilitate transport of pathogens such as Campylobacter jejuni from the intestine. We evaluated this hypothesis by using electron microscopy to examine Peyer's patches in ligated adult rabbit ileal loops inoculated with 5-mL suspensions of 10(9) cfu/mL of Campylobacter jejuni. Peyer's patches taken at intervals from 15 min to 2 h after inoculation of loops in anaesthetized rabbits provided evidence that Campylobacter jejuni selectively adhered to M cells as opposed to absorptive epithelial cells and was transported, apparently intact, into the M cell follicle. Although intercellular organisms were seen within the follicle, many others were phagocytosed by lymphoid cells. The proximity of the lymphatic and blood circulatory systems to the M cell follicle makes this a probable route for systemic spread of Campylobacter jejuni.

Animals↗

PubMed1987

Comparison of the characteristics of children with multiple admissions to hospital for asthma with those with a single admission.

Hospital admission rates in children for asthma have increased strikingly and part of this increase is due to an increase in the readmission rate. The study compared the characteristics of European children with multiple admission to hospital for asthma with those having their first admission for asthma. The number and magnitude of the differences found were small. Differences found included asthma drug management in the 24 hours prior to the index admission and six months later and days lost from school. Twenty-four percent of study population were readmitted within six months. The number of parents who smoked and the number of pets in the home are of concern and the lack of difference between the multiple and single admission groups suggest our education efforts are ineffectual at altering parental behaviour.

Asthma↗

PubMed1981

Intra-cortical inhibition prevents simple cells from responding to textured visual patterns.

Evidence is presented that simple cells in the cat striate cortex (area 17) fail to respond to two dimensional random patterns but respond vigorously to one dimensional patterns with identical power at the preferred orientation of the cell. Further observations suggest that complex cells inhibit simple cells so as to permit them to respond selectively to one-dimensional stimuli. Implications for the role of this inhibition in visual analysis are discussed.

Animals↗

PubMed1980

Motion smear.

It is well known that the visual system summates signals over time, about 120 ms in daylight. Although this summation has the obvious advantage of enhancing visual sensitivity, it creates the potential problem of motion smear when viewing moving targets, whose images are also summated over time. Here I report some measurements which reveal that provided the moving target is exposed for long enough to elicit a clear sensation of motion, the amount of smear is far less than may be expected. This suggests that the visual mechanisms which signal motion are also responsible for signalling a clear unsmeared perception of the target in motion.

Form Perception↗

PubMed1979

Suprascapular entrapment neuropathy: a clinical, anatomical, and comparative study. Part 2: anatomical study.

Two hundred eleven adult scapulae were examined and quantitative data pertaining to the dimensions of the suprascapular notch were obtained. Six types of suprascapular notch were observed. Transitions tended to occur between Types II, III, and IV. A classification function was developed utilizing the measured values of the dimensions of the suprascapular notch, which might help in assigning the scapulae to these transitional types. Dissections of the suprascapular area were performed in 15 cadavers. Static and dynamic relationships of the suprascapular nerve to the suprascapular foramen were examined.

Adult↗

PubMed1979

Suprascapular entrapment neuropathy: a clinical, anatomical, and comparative study. Part 3: comparative study.

The suprascapular ligament seems to serve no defined function in the human. A comparative study was undertaken to elucidate its function. The suprascapular region was dissected in species representing seven existing primate families and six subprimate families. A striking dichotomy of pattern was observed. In the New World primates, the suprascapular ligament appeared to be continuous with the coracoclavicular ligament; the former merely served to increase the area of bony attachment of the coracoclavicular ligament. In the Old World monkeys and subprimate mammals, the suprascapular ligament was entirely absent. The human anatomy was comparable to that found in the New World primates. This dichotomy of pattern seems to be related to the function of the upper extremity in the different classes of mammals.

Animals↗

PubMedDate not supplied

Effect of cane use on tibial strain and strain rates.

The effect of cane ambulation on hip biomechanics has been well studied, but its effect on tibial strains and strain rates is not known. To test the hypothesis that cane use may lower tibial strain and strain rates during walking, percutaneous axial extensometers were mounted on the right medial cortex of the midtibial diaphysis in seven male volunteers. In vivo peak-to-peak axial tibial strains and strain rates were measured for ipsilateral and contralateral cane usage and compared with a no cane control. Cane-assisted ambulation was not found to significantly lower strain magnitudes; however, tibial strain rates were significantly lowered by both ipsilateral and contralateral cane usage. We conclude that either ipsilateral or contralateral cane usage may be beneficial when lowering tibial strain rate is desired, such as in the treatment of tibia stress fracture or osteoarthrosis of the knee.

Adult↗