Search PubMed⌕ Search

Biomedical subjects

D Mitchell

Publications and source records attributed to D Mitchell.

At least 397 records · Page 22Linked to original sources
PubMed1966

Some observations on the diagnosis and epidemiology of leptospirosis in swine.

The results of combined epidemiological, clinical, serological, bacteriological and histopathological studies following an outbreak of disease caused by L. pomona on a farm stocked with cattle, sheep, pigs, goats and horses maintained for experimental purposes, are reported.The incidence of infection was high in horses, cattle and pigs. A few low titres were seen in sheep. The goats were not infected. Apart from a single bovine abortion all the clinical symptoms observed occurred in pregnant sows. Seven of these aborted or gave birth to stillborn pigs within a six week period. Fifteen species of wildlife were trapped or shot on the farm during the year following the outbreak. L. pomona was isolated from four skunks and a porcupine. Epidemiological studies indicated that wildlife reservoir hosts were the primary source of infection for the domestic livestock. Leptospiruria and the serological response were studied in a group of eight infected sows. Microscopic agglutination titres of 10(2) or less could not be associated with leptospiruria and the duration of leptospiruria was found to range from a few weeks to over two years in individual sows. Direct dark-field examination of urine proved superior to guinea-pig inoculation as a method of detecting leptospiruria and it is suggested that the former technique could be adopted with advantage as a routine aid to diagnosis.

Agglutination Tests↗
PubMedDate not supplied

How to remain neutral: an experimental analysis of neutralization.

Many patients with obsessive-compulsive problems engage in neutralizing activity to reduce or "cancel out" the effects of the obsession. In many cases, neutralization is covert and therefore difficult to assess or manipulate experimentally. We hypothesize that neutralization resembles overt compulsions. In particular, it was predicted that: (i) neutralization reduces the anxiety evoked by unacceptable thoughts, and (ii) if neutralization is delayed, anxiety and the urge to neutralize will decay naturally. To test the hypothesis, 63 Ss prone to a cognitive bias known to be associated with obsessional complaints (thought-action fusion) were asked to write a sentence that would evoke anxiety. Measures of anxiety (and other variables of interest such as guilt, responsibility and the likelihood of harm) were taken. Subjects were then instructed to either immediately neutralize (n = 29) or delay for 20 min (n = 34), after which time anxiety and urge to neutralize were re-assessed. The Ss who had neutralized were then instructed to delay, and the Ss who had delayed were now instructed to neutralize, after which time the final assessments were taken. The results confirmed the predictions and supported the hypothesis that neutralization resembles overt compulsions. Of note, there were no differences between anxiety reduction after a 20-min delay, and after immediate neutralization. The problems involved in designing and conducting experiments on covert phenomena are discussed, and the clinical implications of the study are considered.

Adolescent↗
PubMedDate not supplied

An intra-articular bioabsorbable interference screw mimicking an acute meniscal tear 8 months after an anterior cruciate ligament reconstruction.

SUMMARY: Seven months after a quadrupled semitendinosus anterior cruciate ligament reconstruction, a 44-year-old active-duty soldier reported symptoms consistent with a medial meniscus tear. Preoperative magnetic resonance imaging showed an intra-articular bioabsorbable interference screw within his intercondylar notch. The screw was retrieved arthroscopically. The graft was intact and functional except for a small portion of the anterior fibers, which were debrided. The patient returned to full activities without complaints.

Absorbable Implants↗
PubMedDate not supplied

T-cell clones specific for myelin basic protein induce chronic relapsing paralysis and demyelination.

Experimental allergic encephalomyelitis (EAE) serves as a model for autoimmune diseases mediated by T lymphocytes. Following sensitization to rat, mouse or guinea pig myelin basic protein (MBP) in complete Freund's adjuvant, inbred mouse strains PL/J (H-2u), SJL/J (H-2s) and (PL/J X SJL/J)F1((PLSJ)F1) develop EAE. Whereas sensitization to the N-terminal 37 amino-acid peptide of rat or guinea pig MBP [MBP(1-37)] induces EAE in PL/J mice, immunization to the C-terminal peptide (89-169) leads to EAE in SJL/J mice. The immune response to MBP in (PLSJ)F1 mice is not co-dominant; sensitization to the N-terminal peptide induces EAE, while sensitization to the C-terminal peptide does not. We have generated MBP-specific T-cell clones restricted to class II (Ia) antigens of the major histocompatibility complex (MHC) from PL/J and (PLSJ)F1 mice following sensitization to rat MBP. Two such I-Au-restricted T-cell clones that proliferate in response to the encephalitogenic N-terminal MBP peptide and recognize a shared determinant with mouse (self) MBP cause paralysis in 100% of (PLSJ)F1 mice tested. Paralysis is induced even when recipients are injected with as few as 1 X 10(5) cloned T cells. Relapsing paralysis followed in two-thirds of the recipients after recovery from acute paralysis, whereas one-third developed chronic persistent paralysis, a form of EAE not usually seen. Histopathology revealed intense perivascular inflammation, demyelination and remyelination within the central nervous system of paralysed mice. The experimental disease induced with these clones shares important features with human demyelinating diseases such as multiple sclerosis. This is the first demonstration that T-cell clones that respond to a defined self-antigen can induce clinical and histological autoimmune disease.

Animals↗
PubMedDate not supplied

MR imaging of normal extrahepatic bile ducts.

Abdominal scans of 48 patients without evidence of biliary tree or pancreatic head pathology were retrospectively evaluated to determine how often the normal common bile duct (CBD) could be visualized, as well as to determine which projections and pulse sequences optimized its visualization. Axial sequences with long repetition time (TR) and for echo time (TE) intervals (2,000-2,500 and 60-80 ms, respectively) were the most useful, identifying the normal CBD in 15 of 30 diagnostic studies. Axial sequences using short TR/TE intervals (300-800 and 20-25 ms, respectively) were less informative, identifying the CBD in only eight of 30 studies. Coronal studies were not useful, identifying the CBD in only one of 10 long TR/TE pulse sequences.

Bile Ducts↗
PubMedDate not supplied

Tuberculosis in HIV seropositive individuals--a retrospective analysis.

A retrospective analysis of all culture-positive cases of Mycobacterium tuberculosis infection in HIV positive individuals, over a 5 year period, revealed 18 cases, drawn from a population of approximately 1500. The prevalence of culture proven M. tuberculosis over the 5 year period was therefore 1.2% and was strongly associated with either a concomitant, or a subsequent, AIDS diagnosis. Sixty-one per cent had pulmonary tuberculosis, 17% had both extra-pulmonary and pulmonary infection and 22% had extra-pulmonary infection alone. Although a wide range of radiological abnormalities was seen, segmental consolidation was the commonest, occurring in 57% of cases. Only 55% of the specimens were positive on initial stains for M. tuberculosis, with a mean duration of 4 weeks to become culture positive, emphasizing that early diagnosis rests on clinical suspicion.

Adult↗
PubMedDate not supplied

Congenital CNS primitive neuroectodermal tumor: case report and review of the literature.

A 30-week gestational age male fetus was found to have a congenital neoplasm involving the posterior cranial fossa, identified by fetal ultrasound examination in utero. Histological and immunohistochemical examination confirmed a diagnosis of primitive neuroectodermal tumor (PNET) of the posterior fossa, also referred to as medulloblastoma. Although PNETs have been well documented, there are relatively few reports of these occurring as congenital neoplasms. We present a case of an in utero, congenital PNET with a review of the literature and discussion of the criteria defining congenital tumors.

Adolescent↗
PubMedDate not supplied

Antinociceptive action of dopamine agonists in the nucleus raphe magnus of rats is mediated by D2 receptors.

We have shown previously that the dopamine agonist apomorphine is antinociceptive when injected into the nucleus raphe magnus of rats, presumably via stimulation of descending antinociceptive pathways. We have now extended the investigation to receptor-specific agonists. We measured nociception in conscious Sprague-Dawley rats, using the latency of the first flexor response following tail immersion in water at 49 degrees C, before and after injection of agonists into the nucleus raphe magnus through chronically implanted cannulae. The D2 agonist PPHT HCl produced an increase in latency, i.e. hypoalgesia, for 30 min after injection of doses of 10 and 20 nmol. The lowest dose of the D1 agonist SKF 38393 produced no change in latency, but a bimodal response was found at the higher two doses (20 and 200 nmol), with hypoalgesia at 15 min, followed by a sustained hyperalgesia. The dopamine autoreceptor agonist R (+)-3PPP produced a significant hypoalgesia at 10 and 20 nmol 15 min after injection, with no subsequent hyperalgesia. Our results are consistent with the hypothesis that the antinociceptive action of dopamine in the rat nucleus raphe magnus is mediated by the D2 receptor.

Analgesics↗
PubMedDate not supplied

In vitro low frequency electromagnetic field effect on fast axonal transport.

The objective of this study was to evaluate the effects of a low frequency electromagnetic field on fast axonal transport for future neuroprosthetic applications. Changes in speeds and densities of retrograde fast organelle transport in rat sciatic nerve preparations were measured in vitro upon exposure to 15 and 50 Hz pulsed magnetic fields with peak intensities of 4.4 and 8.8 mT. Maximum current density of the induced eddy current was calculated to be about 40 microA/cm2. Video enhanced differential interference contrast microscopy was used to record axons supporting active organelle transport. Strong effects were observed in myelinated axons (cessation of transport in up to 10 min). Such effects may eventually be used as part of a neuroprosthesis to noninvasively modify or couple to various parts of the nervous system.

Animals↗
PubMedDate not supplied

Papworth's progress.

Explore the source record for details and available documents.

Cardiac Surgical Procedures↗