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Biomedical subjects

L Perry

Publications and source records attributed to L Perry.

At least 19 recordsLinked to original sources
PubMed1992

Mechanical properties of the human lumbar anterior longitudinal ligament.

A new technique incorporating a motion analysis system and a materials testing machine was used to investigate regional differences in the tensile mechanical properties of the lumbar spine anterior longitudinal ligament (ALL). Bone-ALL-bone specimens were prepared from young human cadaveric motion segments with no disc or bony pathology. Each specimen was distracted until failure at a constant crosshead displacement rate of 2.5 mm s-1 (approximately 1.0% strain per second). Strains were evaluated from digitized video recordings of markers attached to the ALL at 12 sites along its length and width, including the ligament substance and insertions. The 'overall' strain in the ligament was calculated from the outermost pairs of markers along the ligament length. The average tensile strength, the 'overall' tensile modulus and the 'overall' strain of the ALL at failure were 27.4 MPa (S.D. 5.9), 759 MPa (S.D. 336) and 4.95% (S.D. 1.51), respectively. Large and significant variations in the strains were present along the width and length of the ALL. Peak substance strains were over twofold greater than peak strains at the ligament insertion sites, whereas across the ligament width, peak strains in the outer portion of the ligament were over 40% greater than in the central region. Failure consistently occurred in the ligament mid-substance and ultimate strains at the ligament failure site averaged 12.1% (S.D. 2.3). These results indicate that the strains are highly nonuniform in the normal ALL.

Adult↗
PubMed1992

The biomechanical and histopathologic effects of surface texturing with silicone and polyurethane in tissue implantation and expansion.

There has been considerable interest in determining the effect of morphologic alterations of prosthetic surfaces on capsule response in breast surgery. The purpose of this study was to provide a precise, three-dimensional evaluation of soft-tissue response to surface modifications in both implantation and expansion. Expandable 100-cc prostheses were designed with one of three surfaces: textured silicone (Biocell), standard smooth silicone, or polyurethane (Natural-Y, Meme). A new submuscular implantation site in the rabbit was developed. Each animal randomly received a smooth-surface device on one side and either a textured silicone or polyurethane device on the other. In one group of animals, the prostheses were expanded monthly. Capsular response was evaluated monthly in vivo using standardized techniques as well as biomechanical methods for up to 6 months in the expander group (n = 7 to 16) and 8 months in the implant group (n = 7 to 15). Analysis of biomechanical and histologic data revealed that prosthetic surface morphology can specifically alter capsular response. Polyurethane was the only effective surface in preventing capsular contracture in implantation. In expansion, both textured silicone and polyurethane surfaces resulted in significantly less capsular contracture and less resistance to expansion than comparable smooth-surfaced controls. Statistical comparisons reveal that the biomechanical methods utilized in this study provide the most precise and objective method of defining overall soft-tissue contracture around implanted biomaterials.

Animals↗
PubMed1992

Role and specificity of T-cell subsets in spontaneous recovery from Friend virus-induced leukemia in mice.

Spontaneous recovery from Friend virus complex-induced leukemic splenomegaly in H-2Db/b mice correlated with the appearance of Friend virus complex-specific cytotoxic T lymphocytes (CTL) detectable directly in spleen cell populations. By testing CTL on target cells containing expression vectors encoding individual retroviral structural proteins, the main viral protein recognized was shown to be the Friend murine leukemia helper virus envelope glycoprotein. In vivo depletion of CD8-positive T cells drastically reduced the incidence of recovery, providing direct evidence for the role of CD8-positive CTL in the spontaneous recovery process. In vivo depletion of CD4-positive cells had little effect on the early stages of recovery but did cause a marked reduction in the final incidence of recovery at 60 to 90 days. Thus, CD8-positive cells were required for the initiation of the recovery process, whereas CD4-positive cells appeared to be required for maintenance of the recovered status.

Animals↗
PubMed1991

Development of hypoparathyroidism after excision of laryngeal rhabdomyosarcoma in a dog.

An uncommon neoplasm of the larynx, rhabdomyosarcoma, was diagnosed in a 6-year-old 14-kg neutered female Spitz. In addition to the progressive onset of expected clinical signs of the tumor (exercise intolerance, respiratory stridor, inability to bark), the dog experienced hyperthermic crisis. Laryngectomy was successful in eradicating the local neoplastic tissue; however, unusual postoperative complications developed and included acute complications of pharyngotracheal fistula and hypoparathyroidism, and long-term complications of periodic collapse of the tracheal stoma and intolerance to heat. Probable causes and successful management of these complications are described. At 22 months after laryngectomy, the dog was admitted for a solitary hepatic metastasis. While hospitalized, the dog died of apparent asphyxiation attributable to stoma collapse.

Animals↗
PubMed1991

Coxsackie virus B4 infection of the mouse pancreas: I. Detection of virus-specific RNA in the pancreas by in situ hybridisation.

The pathology of Coxsackie virus B4 (CVB4) infection in a murine model was investigated by in situ hybridisation using a biotinylated cDNA probe derived from CVB4. During the acute phase of infection virus RNA sequences were detected in the exocrine pancreas of 60% of mice infected with a pancreotropic variant of CVB4. A positive hybridisation signal was observed in other organs in some animals including the heart and liver of 1 mouse 28 days after infection. The cellular distribution of virus RNA sequences corresponded well with the histological findings in most tissues. Possible causes for failure of hybridisation in some infected pancreases are discussed in conjunction with potential application of the technique in human pancreas biopsy samples.

Animals↗
PubMed1991

Technique for quantification of LTB4-induced changes in peripheral granulocyte counts in vivo in the rabbit.

A method to quantify leukotriene B4-(LTB4)-induced changes in peripheral granulocyte counts in the rabbit is described. Rabbits were surgically prepared with vascular access ports cannulating the right external jugular vein. This preparation made possible rapid, accurate, and repeated sampling of venous blood. Intravenous infusion of LTB4 (0.5-2 micrograms/mL) into the left marginal ear vein was found reproducibly to cause an initial, rapid (1-5 min) leukopenia (64%-100% reduction) followed by an extended (20-30 min) leukocytosis (121%-178% increase). Saline infusion for 30 min resulted in no changes in peripheral granulocyte number. The method described was sensitive and reproducible enough to allow evaluation of the LTB4 receptor antagonist, LY223982 (10 mg/kg, i.v.), which was shown to block both the leukopenia and the leukocytosis induced by LTB4 infusion.

Animals↗
PubMed1991

Lack of modulation of the adrenocortical response to ACTH by an opioid peptide.

Eight normal male subjects received 1 mg dexamethasone at 23.00 h and 0.5 mg on wakening followed by a physiological intravenous dose of synthetic ACTH1-24 250 ng, with and without the administration of a stable met-enkephalin analogue (guanyl-DAMME, 100 micrograms) 10 minutes prior to the ACTH. The opioid analogue caused no change in the peak, incremental, or incremental area under the curve responses of plasma cortisol to the ACTH. This study does not support a role for opioid peptides in the acute modulation of the adreno-cortical response to ACTH.

Adrenal Cortex↗
PubMed1991

Short and long-term responses to metyrapone in the medical management of 91 patients with Cushing's syndrome.

OBJECTIVE: To analyse the clinical and biochemical effects of metyrapone in the treatment of Cushing's syndrome. DESIGN: An evaluation of the standard clinical practice at one institution. PATIENTS: Ninety-one patients with Cushing's syndrome: 57 pituitary-dependent Cushing's disease, 10 adrenocortical adenomas, six adrenocortical carcinomas and 18 ectopic ACTH syndrome. MEASUREMENTS: The acute response to metyrapone was assessed by measuring cortisol, 11-desoxycortisol and ACTH at 0, 1, 2, 3, 4 hours after a test dose of 750 mg of metyrapone. The longer-term effect of metyrapone was judged by measuring serum cortisol at 0900, 1200, 1500, 1800, 2100 and sometimes 2400 h and calculating a mean. RESULTS: A test dose of 750 mg of metyrapone decreased serum cortisol levels within 2 hours in all groups of patients and this effect was sustained at 4 hours. At the same time, serum 11-desoxycortisol levels increased in all patients, while plasma ACTH increased in patients with pituitary Cushing's disease and the ectopic ACTH-syndrome. Fifty-three patients with Cushing's disease were followed on short-term metyrapone therapy (1 to 16 weeks) before other more definitive therapy. Their mean cortisol levels (median 654 nmol/l, range 408-2240) dropped to the target range of less than 400 nmol/l in 40 patients (75%) on a median metyrapone dose of 2250 mg/day (range 750-6000). Metyrapone was given long term in 24 patients with Cushing's disease who had been given pituitary irradiation, for a median of 27 months (range 3-140) with adequate control of hypercortisolaemia in 20 (83%). In 10 patients with adrenocortical adenomas and six with adrenocortical carcinomas, metyrapone in a median dose of 1750 mg/day (range 750-6000) reduced their mean cortisol levels (median 847 nmol/l, range 408-2000) to less than 400 nmol/l in 13 patients (81%). In 18 patients with the ectopic ACTH-syndrome the 'mean cortisol levels', obtained from five or six samples on the test day (median 1023 nmol/l, range 823-6354) were reduced to less than 400 nmol/l in 13 patients (70%), on a median dose of 4000 mg/day (range 1000-6000). Reduction of cortisol levels was clearly associated with clinical and biochemical improvement. The medication was well tolerated. Transient hypoadrenalism and hirsutism were unusual but were the most common side-effects. CONCLUSIONS: In our experience metyrapone remains a most useful agent for controlling cortisol levels in the management of Cushing's syndrome of all types.

ACTH Syndrome, Ectopic↗
PubMed1991

The effects on anterior pituitary hormone secretion of salmon calcitonin in healthy volunteers.

The reports of the effect of calcitonin on pituitary function are confusing and often refer to uncontrolled studies. We have now carried out a double-blind placebo-controlled trial of intravenous and subcutaneous salmon calcitonin on anterior pituitary function in 17 healthy volunteers. Visual analogue scores for the nausea and vomiting seen after salmon calcitonin correlated with the rise in ACTH and, secondarily, cortisol. Calcitonin had no effect on growth hormone, prolactin, thyrotrophin, luteinizing hormone or follicle stimulating hormone. It is concluded that the stimulation of ACTH secretion following a single dose of salmon calcitonin is probably the result of the stress of nausea rather than a direct effect on the pituitary.

Adrenocorticotropic Hormone↗
PubMed1990

Fecal proteolytic activity in clinically normal cats and in a cat with exocrine pancreatic insufficiency.

Fecal proteolytic activity determined in single samples collected on each of 3 consecutive days from each of 20 clinically normal cats ranged from 19 to 363 azocasein units (ACU)/g of feces when determined colorimetrically, using azocasein substrate, and ranged from undetectable (in 1 sample from 1 cat) to 21 mm of gel-clearing when determined using radial enzyme diffusion in agar gels containing a casein substrate. Corresponding mean 3-day values for each cat ranged from 29 to 207 ACU/g and from 5 to 16 mm, respectively. Studies of proteolytic activity remaining after treatment of fecal extracts with a specific trypsin inhibitor indicated that trypsin accounted for 0 to 77% of proteolytic activity. In a cat with exocrine pancreatic insufficiency, fecal proteolytic activity was 0, 0, and 3 ACU/g in a sample of feces collected from each of 3 consecutive days and was undetectable by use of radial enzyme diffusion. Assay of fecal proteolytic activity by use of either azocasein hydrolysis or radial enzyme diffusion allows evaluation of pancreatic function in cats, provided that several samples of feces are tested.

Animals↗
PubMed1990

4-hydroxyandrostenedione--further clinical and extended endocrine observations.

4-Hydroxyandrostenedione (4-OHA) was administered (250 mg intramuscularly 2-weekly) in a phase 2 clinical trial to 20 postmenopausal patients with advanced breast cancer, who had failed other endocrine therapy. Seven out of 18 assessable patients (39%) responded with minimal toxicity. Endocrine studies demonstrated that the drug produced significant initial falls in oestradiol and oestrone levels, but that these levels rose toward pretreatment levels as the study progressed. Sex hormone binding globulin (SHBG) levels gradually fell during the study suggesting that the drug has a minor degree of androgenic activity albeit of no clinical significance. There was a transient reduction of adrenal steroid levels, which remained however within the normal range. There were no symptoms of adrenal insufficiency.

Aged↗
PubMed1990

The effects of submaximal endurance exercise upon LH pulsatility.

The acute effects of submaximal endurance exercise (three consecutive 20-min runs on a treadmill at 50, 60 and 70% of the subjects' maximum oxygen uptake) upon the pulsatile release of LH were compared with those accompanying leisurely strolling for a similar period in seven normally menstruating young women. All trials were conducted during the early to mid-luteal phase, as determined by body temperature patterns, ultrasonic scans of the ovaries, detection of the LH surge in first morning urine specimens, and serial measurements of plasma progesterone. Blood was sampled every 10 min via an indwelling cannula for 8 h before and 12 h after exercise and serum LH measured by radioimmunoassay. LH pulsations were analysed by a time series method. Following cannulation, mean LH levels declined but then rose to reach a maximum 2 h before the beginning of the exercise bout. LH concentrations remained virtually unchanged during exercise itself, and exhibited a declining trend throughout the post-exercise period. The findings in the two groups were similar in all respects, except that in the control study the rate of LH pulsatility was significantly diminished (P less than 0.05) during the first 2 h of sampling as compared with the subsequent 2-h period. The approximate half-life of LH varied from 27 to 57 min, with a mean of 41 min.

Adult↗
PubMed1990

New initiatives in a district AIDS counselling unit, 1988-89.

This paper describes the workload of the AIDS Counselling Unit in Hampstead District Health Authority during its second year of service. Between April 1988 and March 1989, the average number of patients seen each month by the Unit doubled. It is anticipated that the caseload in the district will continue to increase, both among those with human immunodeficiency virus (HIV) infection and those without. New initiatives were developed within the district during the year. These included a new inpatient facility for patients with the acquired immunodeficiency syndrome (AIDS), the appointment of a designated HIV/AIDS consultant, and counselling services for people attending the antenatal clinic as well as those entering drug trials. Appropriate counselling services will need to be established in other health districts to meet local demand.

Acquired Immunodeficiency Syndrome↗
PubMed1989

Human IgM monoclonal proteins that bind 3-fucosyllactosamine, asialo-GM1, and GM1.

Analysis of monoclonal human Ig that occur in association with lymphoproliferative diseases has provided valuable information about antibody structure and idiotypes. We analyzed 940 human sera that contained monoclonal IgM proteins for their ability to bind to four carbohydrate epitopes. Ten sera bound asialo-GM1, five of these sera also bound GM1, 10 bound to 3-fucosyllactosamine (3-FL), and one each bound to levan and galactan. Although the antibody activity in each serum was associated with a single L chain isotype, both kappa and lambda isotypes were represented among the proteins that bound to asialo-GM1 and to 3-FL. Some antibodies against asialo-GM1 were highly specific for this compound, whereas others cross-reacted with the structurally related gangliosides GM1 and GD1b. The antibodies to asialo-GM1 also varied considerably in their ability to lyse liposomes that contain asialo GM1. An association of IgM mAb against gangliosides with peripheral neuropathies has been reported recently, but only one of five patients whose antibodies reacted with GM1 ganglioside had a neuropathy. The antibodies that bound 3-FL exhibited narrower specificity, and less than 10% cross reactivity was noted with structurally related carbohydrates. The frequency of monoclonal proteins that bound 3-FL and asialo-GM1, approximately 1:100 sera for each specificity, was surprisingly high in view of the fact that both of these epitopes are expressed in human tissues. We suggest that these antibodies may be poly-specific and/or that the subset of B lymphocytes that synthesizes these anti-carbohydrate antibodies undergoes malignant transformation more frequently than other B lymphocytes.

Antibodies, Monoclonal↗
PubMed1989

Differential effect of high-dose naloxone on the plasma adrenaline response to the cold-pressor test.

1. Although the opiate antagonist naloxone has been shown to affect sympathoadrenomedullary function in some studies, this has not been a uniform finding in all investigations, using different doses of naloxone. We have therefore investigated the actions of saline placebo and increasing bolus doses of intravenous naloxone (25, 100 and 250 micrograms/kg) on the plasma noradrenaline, adrenaline, adrenocorticotrophin (ACTH) and cortisol responses to a cold-pressor test in six males and two females in a double-blind randomized study. 2. Basal levels of adrenaline did not differ on any of the study occasions: the cold-pressor stimulus produced a significant rise in mean plasma adrenaline to a peak of 0.16 nmol/l, with a peak incremental rise of 0.08 nmol/l. In the presence of the two higher doses of naloxone, the incremental rise in the mean adrenaline level was significantly enhanced, reaching 0.30 nmol/l at 100 micrograms of naloxone/kg and 0.29 nmol/l at 250 micrograms of naloxone/kg, with no significant enhancement observed at the lowest dose of naloxone. The rise in plasma noradrenaline, systolic and diastolic blood pressure and pulse rate during the cold-pressor test was not consistently altered by any dose of naloxone, but there was a significant trend for the degree of discomfort to increase with the dose of naloxone. 3. Neither plasma ACTH nor serum cortisol rose in response to the cold-pressor stimulus.(ABSTRACT TRUNCATED AT 250 WORDS)

Adrenocorticotropic Hormone↗
PubMed1989

Paradoxical interventions in counselling for people with an intractable AIDS-worry.

This article has two main objectives. Firstly, consideration is given to the context in which certain individuals become convinced that they have been infected with the Human Immunodeficiency Virus (HIV), despite repeated negative HIV antibody tests and reassurance. Secondly, it is to describe an intervention which is designed to escalate anxiety in individuals with an intractable AIDS-worry, in order to release them from their rigid and distressing beliefs. A case study is presented to illustrate this.

Acquired Immunodeficiency Syndrome↗