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Biomedical subjects

A J Cook

Publications and source records attributed to A J Cook.

At least 37 records · Page 2Linked to original sources
PubMed1989

Mental and physical health of elderly people: five-year follow-up of a total population.

The change in mental and physical functioning over 5 years for 594 survivors of a community survey of the elderly is described. An increase in cognitive impairment, physical disability and incontinence over the period was found with increasing age. Women in the two oldest age groups had a significantly greater increase in physical disability than men. An annual incidence of cognitive impairment of 1.4% was found and the implications of this are discussed.

Aged↗
PubMed1986

Prolonged C-fibre mediated facilitation of the flexion reflex in the rat is not due to changes in afferent terminal or motoneurone excitability.

A standard suprathreshold mechanical stimulus applied to the hindpaw of decerebrate-spinal rats produces a discharge in hamstring flexor alpha-motoneurones which is stable for hours, provided no tissue injury is produced. Tissue injury results, however, in a decrease of threshold and an increase in the responsiveness of the reflex. This reflex hypersensitivity can be mimicked by brief (20 s) low frequency (1 Hz) conditioning stimuli to muscle or cutaneous nerves, if C-fibres are recruited. The prolonged post-conditioning facilitation of the flexion reflex by C-afferent volleys is now shown to be independent of changes in the excitability of the test afferent terminals in the dorsal horn and of the motoneurones. The hypersensitivity is therefore due to changes in the interneurones that link cutaneous nociceptive afferents with flexor motoneurones.

Animals↗
PubMed1986

Evaluation of the nitrosamine hypothesis of gastric carcinogenesis in precancerous conditions.

A 24 hour gastric aspiration study was carried out on nine Polya gastrectomy, eight pernicious anaemia, and nine matched control subjects. Intragastric pH, bacteria, nitrite, and N-nitroso compounds were assessed half hourly whilst ambulant and hourly when in bed. Both total and nitrate reducing bacterial counts were positively related to pH (chi 2 = 279.3; p less than 0.001), as was nitrite concentration (F = 19.1; p less than 0.0001). By contrast, total (F = 40.6; p less than 0.0001) and stable (F = 257.4; p less than 0.0001) N-nitroso compound concentrations were negatively related to pH. Clear differences in these gastric juice factors were not apparent between matched control and either pernicious anaemia, or Polya gastrectomy because the Polya gastrectomy and matched control groups were heterogeneous for gastric acidity. Thus, although eight of eight pernicious anaemia subjects were hypoacidic (defined as intragastric pH greater than 4 for greater than 50% of both daytime and night time periods), only five of nine Polya gastrectomy and two of nine matched control subjects were hypoacidic. When subjects were rearranged into hypoacidic (n = 15) and acidic (n = 11) groups, bacterial counts (p less than 0.01) and nitrite concentrations (p less than 0.01) were higher, whereas N-nitroso compounds tended to be lower (NS) in the hypoacidic group. These data suggest that, although hypoacidity predisposes to bacterial overgrowth and nitrite generation, it does not enhance nitrosation. Instead, this is maximal at low pH, suggesting chemical rather than bacterial nitrosation, contrary to the nitrosamine hypothesis of gastric carcinogenesis.

Aged↗
PubMed1985

Use of the computerized tomographic scan in the diagnosis and treatment of abscesses.

Over a 5 year period, 89 patients underwent one or more computerized tomographic scans to locate an abscess during 92 hospitalizations. The scans were a most sensitive (93 percent), specific (98 percent), and accurate (96 percent) means of abscess detection. Thirty-nine patients had positive scans. Sixteen patients were treated directly by open surgical methods, 1 of whom required percutaneous drainage in the postoperative period for incomplete drainage. An additional 23 patients underwent attempted percutaneous abscess drainage. In 17 patients, drainage was successful. Five patients underwent percutaneous drainage and later required laparotomy, two of whom underwent unavoidable surgical procedures and three surgery for incomplete drainage. Overall, percutaneous abscess drainage was successful in 83 percent. Of 11 deaths, 8 occurred in the group with computerized tomographic scans negative for abscess. Three of these were false-negative scans. Three deaths occurred in the group with scans positive for abscess. All were of patients with hepatic abscesses treated by open surgical drainage, one after failed percutaneous drainage. Twelve patients had multiple organ failure, and 8 of these patients died, for a mortality of 67 percent. The computerized tomographic scan is the diagnostic procedure of choice in the diagnosis of abscesses. In selected patients, percutaneous abscess drainage is also a successful means of abscess treatment and avoids the complications of a laparotomy. The onset of multiple organ failure in the surgical patient should alert the diagnostician to the possibility of a septic focus. The role of early laparotomy in these patients is uncertain. We recommend early use of the computerized tomographic scan in the septic surgical patient. Prompt diagnosis and treatment of abscesses, whether by open or percutaneous routes, may avert the development of multiple organ failure and reduce morbidity and mortality.

Abscess↗
PubMed1985

Cutaneous receptive field and morphological properties of hamstring flexor alpha-motoneurones in the rat.

Intracellular recordings have been made from twenty antidromically identified posterior biceps femoris/semitendinosus (p.b.s.t.) hamstring flexor alpha-motoneurones in the decerebrate-spinal rat. The hamstring motoneurones had either low or no spontaneous background activity. In nineteen of the twenty cells high-frequency phasic responses could be elicited by stimulation of the ipsilateral hind paw with firm pressure or pinch. There was no response to light touch or brush. Contralateral cutaneous mechanoreceptive fields with higher thresholds and weaker responses were present in 70% of the motoneurones. Noxious heating of the ipsilateral hind paw produced excitatory responses in six of eight cells tested and two of these cells also responded to heating of the contralateral hind paw. Stimulation of the ipsilateral sural nerve at graded strengths that successively activated A beta, A delta and C afferents produced excitatory post-synaptic potentials (e.p.s.p.s) at progressively longer latencies in the motoneurones. The C-fibre induced e.p.s.p. lasted up to 200 ms. Horseradish peroxidase was injected into ten motoneurones and in seven cases full reconstructions of dendritic field, cell body and axon could be made. In agreement with previous reports from studies in the cat, the dendritic fields of rat motoneurones are very extensive in the rostrocaudal, mediolateral and dorsoventral planes. The general pattern of dendritic branching for each motoneurone in this functionally homogeneous population was uniformly organized. Three major spatial orientations were always present: a rostrocaudally restricted series of dendrites emerging from the cell body and directed dorsolaterally towards the dorsolateral funiculus with branches in the lateral dorsal horn, a laterally, and a ventromedially directed series of branches arranged obliquely in the ventral horn, both of which were distributed rostrocaudally for equal distances from the cell body. Many of these dendritic branches terminated within the lateral and ventral white columns. Although the sizes of the rat flexor motoneurones' somas (51 +/- 4.9 micron, S.E., n = 10) were similar to those of cat lumbosacral alpha-motoneurones, the tip-to-tip rostrocaudal extent of their dendritic fields (1130 +/- 34 micron, S.E., n = 7) was half that reported in the cat. These results are discussed in terms of the organization of the cutaneous flexor withdrawal reflex in the rat.

Action Potentials↗
PubMed1983

Twenty-four-hour continuous electrocardiography during exercise and free activity in 80 apparently healthy runners.

To determine the incidence of arrhythmias and conduction disturbances in trained athletes and the level of physical training at which they occur, 24-hour ambulatory electrocardiographic recordings were obtained in 80 healthy runners during both exercise and free activity. Subjects were grouped according to the number of miles per week (mpw) they had regularly run during the previous 3 months: Group I--0 to less than or equal to 5 mpw (less than or equal to 8 km); Group II--greater than 5 to less than or equal to 15 mpw (greater than 8 to less than or equal to 24 km); Group III--greater than 15 to less than or equal to 30 mpw (greater than 24 to less than or equal to 48 km); and Group IV--greater than 30 mpw (greater than 48 km). Ectopic ventricular complexes occurred in 41 of 80 subjects (50%) and ectopic supraventricular complexes occurred in 33 (41%). There were 2 episodes of paired ventricular ectopic activity and a 5-beat run of ventricular tachycardia with exercise. The study revealed no significant differences in the occurrence of arrhythmias or conduction disturbances in the different groups, although the 2 episodes of paired ventricular ectopic activity and 5-beat run of ventricular tachycardia are of concern.

Activities of Daily Living↗
PubMed1983

When is arthrography indicated in Legg-Calvé-Perthes disease?

We evaluated plain radiographs and arthrograms of twenty-one children with active Legg-Calvé-Perthes disease in order to determine the value of the arthrography. We found that when epiphyseal protrusion was shown by the arthrograms it could be seen on the plain radiographs as well in all patients. Also, an acetabulum-head index of less than 90 or an acetabulum-head quotient of less than 92 as determined on plain radiographs correlated well with a diagnosis of protrusion. Thus, an arthrogram is not necessary to make the diagnosis of protrusion in most patients. The arthrogram is more useful in delineating changes in the articular surface for prognoses concerning arthritis and in tailoring the treatment to the individual patient.

Child↗
PubMed1980

Practical considerations in the use of computed tomography in the measurement of femoral anteversion.

A new technique is presented for measuring femoral anteversion by computed tomography, which has advantages over earlier techniques. Computed tomography allows the visual portrayal of the cervical axis to be superimposed on the diacondylar axis for direct goniometric measurement of the anteversion angle. In addition to being accurate, the procedure requires no complicated positioning framework and can be done in a brief span of time. Clinical experience with 111 hips in 56 patients has produced accurate data, particularly with regard to congenital dislocation of the hip and Legg-Calvé-Perthes disease.

Femur↗
PubMed1978

BCG treatment of transplanted rat tumours of spontaneous origin.

Six transplanted rat tumours (three mammary carcinomas and three fibrosarcomas), all of spontaneous origin and of limited immunogenicity, have been examined for susceptibility to immunotherapy with BCG (Glaxo). Growth of limited numbers of cells from five tumours was suppressed when cells were injected subcutaneously in admixture with BCG organisms. There was no clear correlation between the immunogenicity of tumour lines and their susceptibility to regionally applied BCG. Active specific immunotherapy, using vaccines of viable or radiation-attenuated tumour cells in admixture with BCG, was reproducibly successful with only one tumour, the mammary carcinoma Sp4, this being the most immunogenic of the tumours examined. These studies indicate that naturally arising tumours are less susceptible to BCG-mediated suppression than carcinogen-induced tumours widely used for experimental immunotherapy, but indicate that local application of BCG may give the best therapeutic response.

Animals↗
PubMedDate not supplied

Investigation of risk factors for porcine Taenia solium cysticercosis: a multiple regression analysis of a cross-sectional study in the Yucatan Peninsula, Mexico.

A cross-sectional survey for seropositivity to cysticercosis of pigs in the Yucatan Peninsula, Mexico, was carried out in 1996 together with a standardized questionnaire on predetermined individual pig and household risk factors for porcine infection. Serum samples from 697 pigs were analysed by immunoblot for antibodies to Taenia solium cysticercosis and questionnaires from 227 households in 18 villages were collected. All the data were analysed using multivariate analytical techniques taking household clustering into account. The overall porcine seroprevalence in the area was found to be 29%. The most important risk factors for seropositivity in pigs were presence versus absence of a toilet (adjusted odds ratio [adj. OR] 2.37, P = 0.005), crowded households (adj. OR 1.75, P = 0.034) and both corralling (adj. OR 2.14, P = 0.017) and letting pigs loose (adj. OR 2.32, P = 0.035) versus tying them up. There was evidence of clustering at household level and that possible risk factors at municipal or village level may also interact with higher risk management practices such as allowing pigs to run loose.

Animal Husbandry↗
PubMedDate not supplied

Dynamic receptive field plasticity in rat spinal cord dorsal horn following C-primary afferent input.

The central terminals of cutaneous primary afferent neurons are spatially ordered in the dorsal horn in a highly organized fashion such that a point-to-point map represents the body surface. This afferent terminal somatotopic map correlates with the map of the receptive fields of the cells on which they terminate. The location, size and modality of the cutaneous receptive fields of dorsal horn neurons necessarily depend upon the anatomical presence of afferent nerve fibres which deliver information from the periphery, directly or indirectly, to the cells. However the receptive field size and modality of a cell do not depend only on anatomical connections. Excitatory and inhibitory interneurons, descending influences and facilitations or depressions of synaptic contacts can alter receptive field properties. Here we show that prolonged and substantial cutaneous receptive field changes can be produced by brief inputs from peripheral unmyelinated afferent fibres.

Afferent Pathways↗