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Biomedical subjects

J Turner

Publications and source records attributed to J Turner.

At least 253 records · Page 14Linked to original sources
PubMed1991

Voluntary activation of human quadriceps during and after isokinetic exercise.

The extent of voluntary activation in fresh and fatigued quadriceps muscles was investigated during isometric and isokinetic voluntary contractions at 20 and 150 degrees/s in 23 normal human subjects. The muscles were fatigued by a total of 4 min of maximal knee extension at an angular velocity of 85 degrees/s. Voluntary activation was determined by the superimposition of tetanic electrical stimulation at 100 Hz for 250 ms, initiated at a constant knee angle. The relationship between voluntary and stimulated force was similar to that found with the established twitch superimposition technique used on isometric contractions. In fresh muscle all the subjects showed full voluntary activation during isometric contractions. Some activation failure was seen in five subjects at 20 degrees/s [2.0 +/- 0.9 degrees (SE)] and in two subjects at 150 degrees/s (0.7 +/- 0.5). After fatigue all subjects showed some activation failure at 0 and 20 degrees/s (36.4 +/- 3.1 and 28.8 +/- 4.1 degrees, respectively), but only two showed any at 150 degrees/s (1.4 +/- 5.7). We conclude that brief high-intensity dynamic exercise can cause a considerable failure of voluntary activation. This failure was most marked during isometric and the lower-velocity isokinetic contractions. Thus a failure of voluntary activation may have greater functional significance than previous studies of isometric contractions have indicated.

Adult↗
PubMed1991

Helicobacter pylori-associated gastritis is rare in AIDS: antibiotic effect or a consequence of immunodeficiency?

Helicobacter pylori is the principal cause of type B histologic gastritis. AIDS is associated with increased susceptibility to Gram-negative enteric infections. Using a retrospective study design, we have determined the prevalence of H. pylori-associated histologic gastritis (based on gastric histopathology) in 201 patients with AIDS. These data were compared with H. pylori prevalence rates (based on serology) from healthy HIV-negative, age-matched Australian controls (n = 785) and a cohort (n = 137) of HIV-negative, dyspeptic patients undergoing panendoscopy and antral biopsy, at a community endoscopy center. Twenty-five of 201 (12.5%) patients with AIDS had histologic gastritis and, of these, six (25%) had H. pylori. The 3% (six of 201) H. pylori prevalence rate in the AIDS patients was significantly less than age-matched HIV-negative controls (22%) p = 0.001 and endoscopy center controls (59%) p = 0.009. The explanation for this unexpectedly low prevalence of H. pylori is not possible from these data. It may be a consequence of antimicrobial therapy. Other potential explanations may include specific HIV-related host factors, including hypochlorhydria or an inadequate mucosal inflammatory response, which may impair successful colonization of H. pylori.

Acquired Immunodeficiency Syndrome↗
PubMed1991

Cerebellopontine angle lipomatous hamartoma of nerve: case report.

Cerebellopontine angle lipoma has been previously described in 21 patients and is frequently unresectable. An intracanalicular lipomatous hamartoma in a 60-year-old male is presented. MRI enabled a correct preoperative diagnosis to be made. Complete surgical excision, without major neurologic deficit was achieved. A review of the literature reveals that the tumor is frequently infiltrative, especially when vascular elements are prominent. The histologic characteristics and the hamartomatous nature of the lesion are discussed.

Audiometry, Evoked Response↗
PubMed1991

An acute pulmonary syndrome possibly representing acute graft-versus-host disease involving the lung interstitium.

An acute pulmonary syndrome possibly representing acute graft-versus-host disease (GVHD) involving lung interstitium occurred in a patient given an allogeneic bone marrow transplant for haematological malignancy. He presented at day 34 with acute GVHD of skin and bowel, and this was associated with cough, dyspnoea and an asymmetrical change on chest X-ray. Lung biopsy demonstrated an interstitial and peribronchial lymphocytic infiltrate and acute bronchial epithelial degeneration. He responded symptomatically to high dose intravenous methylprednisolone. The radiological change resolved completely. This case, thought to represent GVHD involving lung interstitium, emphasizes the need for tissue procurement in the management of non-bacterial lung disease after marrow transplantation.

Acute Disease↗
PubMed1990

Flow and image cytometric DNA analysis in rhabdomyosarcoma.

Rhabdomyosarcoma is the most common malignant soft-tissue tumor in childhood, with an overall 3-year disease-free survival of 73%. DNA content is known to correlate with prognosis and therapy response in many cancers. To determine the role of DNA content in rhabdomyosarcoma, 23 tumor samples were studied retrospectively: 18 primary tumors and 5 post-chemotherapy recurrences or specimens obtained at second-look surgeries. The DNA analysis was performed on disaggregated paraffin-embedded tissue nuclei by flow and image cytometry and correlated with the histology and clinical history. Of the primary tumors 4 were diploid, 4 polyploid, and 10 aneuploid (9 with a single aneuploid G0G1 peak and 1 multiploid) by flow cytometry. The concordance rate between flow and image cytometry was 19 of 23 (83%); one case did not have flow cytometry available. Most embryonal rhabdomyosarcomas were aneuploid (10 of 12; 83%), and they had a high incidence of recurrence in Stages III and IV (4 of 12; 33%). Although aneuploidy in pediatric cancers may predict a therapeutic response and good prognosis, this was not supported by our findings in rhabdomyosarcoma. The tumor DNA content correlated with the clinical stage but not with the patient's clinical course or tumor histopathological type. DNA content did not appear to be as important a prognostic tool as tumor stage.

Adolescent↗
PubMed1990

Absence of coronary or aortic atherosclerosis in rats having dietary lipid modified vulnerability to cardiac arrhythmias.

Laboratory studies have shown that saturated fats in the diet increase vulnerability to ventricular fibrillation and other cardiac arrhythmias while polyunsaturates, especially the n-3 fatty acids of fish oils, are antiarrhythmic. Similarly, dietary saturated fat has been implicated in the development of coronary atherosclerosis while polyunsaturated fatty acids are reported to provide protection. In the present study, dietary fat supplements known to influence arrhythmic vulnerability after long term feeding in the rat were tested for their propensity to induce or prevent changes in the aorta or coronary vasculature. It was found that dietary supplementation for 15 months with saturated fat (from sheep fat) or n-6 (sunflower seed oil) or n-3 (fish oil) polyunsaturated fatty acids made no difference to the development of vascular changes in coronary arteries or aorta of the rat despite some significant differences in plasma triglyceride and cholesterol levels. The vascular lesions observed were minimal even in non-supplemented age-matched reference animals. They consisted of focal intimal thickening and slight mucopolysaccharide accumulation with no evidence of progression to fibrotic lesions or calcium accumulation and there were no fatty deposits observed. It is concluded that significant atherosclerosis-induced chronic myocardial ischaemia in no way contributes to dietary lipid modulation of arrhythmic vulnerability in the rat.

Animals↗
PubMed1990

Induction of micronuclei in cultured murine splenocytes exposed to elevated levels of ferrous ions, hydrogen peroxide and ultraviolet irradiation.

The frequency of micronuclei in cultured mouse splenocytes increased positively and in a dose-related manner to exposure to ferrous ions and ultraviolet irradiation, but not to hydrogen peroxide. Combined treatments, especially when ferrous ions were present with hydrogen peroxide or with ultraviolet irradiation, led to a synergistic enhancement in micronucleus frequency. The results indicate that a significant level of chromosome damage is associated with exposure to ultraviolet light and to general cellular pro-oxidative stress, and indicate that under these conditions the micronucleus assay can provide an effective in vitro model for the study of genotoxicity in relation to oxygen-derived free radicals.

Animals↗
PubMed1990

Evaluation of the teratogenic potential of the dopamine agonist bromocriptine in rats.

Single subcutaneous injections of bromocryptine (BCR; 2 mg/kg) to rats on days 5, 7 or 10 of gestation caused a lowering of the serum prolactin (PRL) concentration and, on days up to and including day 8 of gestation, abortion of entire litters. Coincident with the end of the PRL-dependent phase of gestation (approximately day 9), BCR was no longer abortifacient, allowing higher doses of the drug to be administered from this time without the risk of abortion. Treatment at 50 or 100 mg/kg from day 10 to 16 of pregnancy, despite affecting the dams (increased water consumption), had no adverse effects on pregnancy or fetal development.

Abnormalities, Drug-Induced↗
PubMed1990

Serum levels of CA 125 during the first trimester of normal outcome, ectopic and anembryonic pregnancies.

Single serum samples were obtained during the first trimester of pregnancies with a retrospectively normal outcome (n = 150), ectopic pregnancies (n = 38) and anembryonic pregnancies (n = 78). Serial samples during the first trimester were also obtained from 43 women achieving pregnancy following successful treatment for infertility and with a retrospectively defined normal outcome. Significant variation in serum CA 125 levels in relation to gestational age was observed in pregnancies with a normal outcome (P less than 0.0001). Peak serum CA 125 levels were observed at 6-7 weeks, the mean level at this gestation being 40.1 U/ml (range 31.7-50.7 U/ml) in the normal conception/normal outcome group and 36.5 U/ml (range 25.6-52.0 U/ml) in the assisted conception/normal outcome group. A rise and fall in serum CA 125 levels during the first trimester was observed in 42 of 43 assisted conceptions monitored serially, with peak levels ranging from 7 to 1398 U/ml (median 48.8 U/ml) occurring at 28-61 days (median 45 days) gestation. Mean serum CA 125 levels were higher in the anembryonic pregnancy group at 4-5 and 6-7 weeks gestation than in both normal pregnancy outcome groups (P less than 0.01).

Antigens, Tumor-Associated, Carbohydrate↗
PubMed1990

A risk of malignancy index incorporating CA 125, ultrasound and menopausal status for the accurate preoperative diagnosis of ovarian cancer.

Age, ultrasound score, menopausal status, a clinical impression score and serum CA 125 level were assessed to see how they could best distinguish between patients with benign (n = 101) and malignant (n = 42) pelvic masses. Each criteria used alone provided statistically significant discrimination. The most useful individual criteria were a serum CA 125 level of 30 U/ml (sensitivity 81%, specificity 75%) and an ultrasound score of 2 (sensitivity 71%, specificity 83%). Three criteria could be combined in a risk of malignancy index (RMI) which is simply calculated using the product of the serum CA 125 level (U/ml), the ultrasound scan result (expressed as a score of 0, 1 or 3) and the menopausal status (1 if premenopausal and 3 if postmenopausal). This index was statistically virtually as effective a discriminant between cancer and benign lesions as more formal methods. Using an RMI cut-off level of 200, the sensitivity was 85% and the specificity was 97%. Patients with an RMI score of greater than 200 had, on average, 42 times the background risk of cancer and those with a lower value 0.15 times the background risk.

Adult↗
PubMed1990

Plasma tumor necrosis factor in patients with septic shock. Mortality rate, incidence of adult respiratory distress syndrome, and effects of methylprednisolone administration.

We assayed serial plasma samples from 86 patients, who were enrolled in a prospective randomized trial of the effects of methylprednisolone (MPSS) in septic shock, for the presence of cytokine tumor necrosis factor (TNF) using an enzyme-linked immunosorbent assay. TNF was present in the plasma of 27 of the 74 patients with septic shock, but in only 1 of the 12 patients with shock due to other causes. TNF was detected with equal frequency in patients with shock from gram-negative or from gram-positive bacillary sepsis. TNF levels were highest on the initial sample and decreased significantly over the subsequent 24 h in both the patients treated with MPSS and in those given placebo. Patients with detectable TNF had a higher incidence and severity of the adult respiratory distress syndrome and a higher mortality rate than did patients without detectable TNF.

Humans↗
PubMed1990

Elevated von Willebrand factor antigen is an early plasma predictor of acute lung injury in nonpulmonary sepsis syndrome.

In this prospective study of 45 patients, we tested the hypothesis that markedly elevated levels of plasma von Willebrand antigen (vWf-Ag) a marker of endothelial cell injury, might predict the development of acute lung injury in patients with nonpulmonary sepsis syndrome. Acute lung injury was quantified on a four-point scoring system. At the time of entry into the study, none of the 45 patients had evidence of lung injury. Subsequently, 15 patients developed lung injury and 30 patients did not develop lung injury. The mean plasma vWf-Ag level was markedly elevated in the 15 patients who developed lung injury compared with the 30 patients who did not develop lung injury (588 +/- 204 vs. 338 +/- 196, percentage of control, P less than 0.01). Furthermore, a plasma vWf-Ag level greater than or equal to 450 was 87% sensitive and 77% specific for predicting the development of acute lung injury in the setting of nonpulmonary sepsis. In addition, the combination of a plasma vWf-Ag greater than 450 and nonpulmonary organ failure at the time of entry into the study had a positive predictive value of 80% for acute lung injury. Also, a plasma vWf-Ag level greater than 450 had a positive predictive value of 80% for identifying nonsurvivors. Thus, in patients with nonpulmonary sepsis, an elevated level of plasma vWf-Ag is a useful, early biochemical marker of endothelial injury and it has both predictive and prognostic value.

Acute Disease↗
PubMed1990

Balint's syndrome in Alzheimer's disease: visuospatial functions.

A subgroup of patients with Alzheimer's disease (AD) developed Balint's syndrome, an uncommon and incompletely understood disorder of visuospatial processing. We characterized the visuospatial features of three AD patients with Balint's syndrome and compared them to three comparably demented AD patients without this syndrome. On visuospatial tasks, the Balint patients were unable to integrate visual stimuli over space. On contrast sensitivity testing, the Balint patients had significantly decreased contrast sensitivities for low spatial frequency gratings (0.5, 1.0 and 2.0 cpd) alternated at 7.5 Hz. Furthermore, the Balint patients had left visual field attentional deficits and normal hemifield P100 visual evoked potentials. In AD, Balint's syndrome involved decreased sensitivity to low spatial frequencies necessary for global visuospatial analysis, a disturbance suggesting damage to the magnocellular visual system in the occipitoparietal association cortex and, possibly, in the optic nerves.

Aged↗
PubMed1989

Neuropeptide degradation by large vessel and microvessel-derived endothelial cells in vitro: cell surface catabolism of thyrotropin releasing hormone (TRH).

Cell surface ectopeptidase activity of purified, cultured large vessel and microvessel-derived endothelial cells (EC) was studied. Degradation of thyrotropin releasing hormone (TRH), and production of cyclo-His-Pro was significantly increased (P less than 0.001) in large vessel EC compared with microcapillary EC. Since the rate of catabolism in the microvascular capillary bed is 5 times less than that in the large vessel wall, peptide concentrations are likely maintained longer in close proximity to their site of biosynthesis, where they are presumably most active.

Aminopeptidases↗