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Biomedical subjects

T Byrne

Publications and source records attributed to T Byrne.

At least 19 recordsLinked to original sources
PubMed2005

Inherited chondrodysplasia in Texel sheep.

CASE HISTORY: A skeletal disease characterised by dwarfism, limb deformity and sometimes sudden death occurred over a period of 5 years in lambs born on a commercial sheep farm in Southland. The disease showed variable expression and occurred in crossbred sheep. A genetic aetiology was supported by the birth of affected lambs over two seasons in a flock of putative carrier and affected sheep transported to Massey University. CLINICAL FINDINGS: Affected lambs appeared normal at birth but showed evidence of dwarfism, wide-based stance and exercise intolerance as early as 1 week of age. Most died within the first 3 months of life, often after developing bilateral varus deformity of the forelimbs. Some severely-affected lambs died suddenly of respiratory embarrassment, probably due to tracheal collapse. Mildly-affected individuals had a short, blocky stature and some survived to breeding age. PATHOLOGICAL FINDINGS: Gross and microscopic lesions of variable severity were present in the tracheal, articular, epiphyseal and physeal cartilages. In severe cases, articular cartilage in major joints was eroded from weight-bearing surfaces. The trachea was flaccid, abnormally kinked, and had thickened cartilaginous rings and a narrow lumen. Affected sheep that survived to breeding age eventually developed severe degenerative joint disease. Histologically, chondrocytes were disorganised, surrounded by concentric rings of abnormal fibrillar material, and the matrix often contained focal to coalescing areas of chondrolysis. DIAGNOSIS: Inherited chondrodysplasia of Texel sheep. CLINICAL RELEVANCE AND CONCLUSIONS: This chondrodysplasia differs from those previously described in sheep and is considered to be a newly-recognised, recessively-inherited genetic disease of the Texel breed. A defect in the synthesis of glycosaminoglycans in cartilage matrix is suspected. This disease of sheep may provide a suitable model for studying various forms of therapy for human chondrodysplasias.

Animals↗
PubMed2001

Utility of paired BACTEC MYCO/F LYTIC blood culture vials for detection of bacteremia, mycobacteremia, and fungemia.

In previous bloodstream infection studies in Malawi, we inoculated blood from a single venesection into a single BACTEC MYCO/F LYTIC (MFL) vial. Inoculation of one vial, however, would be expected to reduce the sensitivity of bloodstream pathogen detection with MFL vials. To ascertain the degree of this loss of sensitivity, blood was drawn from each of 228 febrile, adult inpatients in Malawi and 5 ml of each blood sample was inoculated into each of two MFL vials. Of 228 paired vials, 51 (22%) were both positive, 172 (75%) were both negative, and 5 (3%) had discordant results. Bloodstream infection would have been detected in 11 (92%) of 12 patients with mycobacteremia and 38 (92%) of 41 patients with bacteremia had only one MFL vial been inoculated. Our study shows that a second MFL vial does not significantly increase diagnostic sensitivity.

Bacteremia↗
PubMed2000

Effects of cocaine and morphine under mixed-ratio schedules of food delivery: support for a behavioral momentum analysis.

Previous studies have shown that ratio size influenced the development of tolerance under simple and multiple schedules, but not under progressive-ratio (PR) schedules. PR schedules share certain features with mixed-ratio (MR) schedules, and pilot data suggested that ratio size fails to modulate tolerance to cocaine or morphine under MR schedules. The present study examined more comprehensively the pre- and postchronic effects of cocaine and (in separate birds) morphine under MR schedules with fixed-ratio (FR) 5 and FR 95, FR 25 and FR 75, and FR 50 and FR 50 components. Acute doses of cocaine and morphine initially were given in an ascending series (beginning with 0.56 mg/kg) until responding was reduced to near-zero levels. Chronic (daily) dosing with a dose that reduced, but did not eliminate, responding then occurred until response rates stabilized. Finally, postchronic dose-response determinations were conducted. Both cocaine and morphine reduced response rates at all FR values. Tolerance was consistently observed to the effects of morphine, but not to those of cocaine. With both drugs the degree of tolerance observed did not vary as a function of FR value. These findings, like those obtained under PR schedules, indicate that ratio size does not always modulate drug tolerance. A behavioral momentum analysis of drug action appears to account for whether or not ratio size modulates tolerance, and such an analysis is provided.

Animals↗
PubMed2000

MDMA and learning: effects of acute and neurotoxic exposure in the rat.

In two experiments, the effects of MDMA on the acquisition of lever-press responding of rats were examined under procedures in which water delivery was delayed by 0, 10, or 20 s relative to the response that produced it. In the first study, experimentally naive, water-deprived rats received an intraperitoneal injection of MDMA (0, 1.0, 3.2, or 5.6 mg/kg) prior to one 8-h experimental session. Response acquisition was observed under all conditions at all drug doses. MDMA increased the total number of responses emitted and the total number of water deliveries earned in dose-dependent fashion, but only when reinforcement was immediate. Under conditions of delay, MDMA had no effect on either measure. Under all reinforcement conditions, higher doses of MDMA typically produced an initial reduction in lever pressing, and in that sense interfered with learning. In the second study, rats received an MDMA injection regimen previously shown to be neurotoxic. Control rats received saline solution according to the same injection schedule. Two weeks after completing the regimen, rats were water deprived and exposed to behavioral procedures as described for the first experiment. Although MDMA significantly reduced 5-HT and 5-HIAA levels in the striatum and prefrontal cortex, mean performance of rats exposed to MDMA did not differ from that of rats exposed to vehicle. Twenty-five percent of the rats exposed to MDMA and delayed reinforcement did fail to acquire responding, which suggests that further study of the effects of neurotoxic doses of MDMA on initial response acquisition is warranted.

Animals↗
PubMed2000

Student perceptions of methylphenidate abuse at a public liberal arts college.

With the ever-increasing diagnosis of attention deficit hyperactivity disorder, methylphenidate has become readily accessible in the college environment. Several properties of methylphenidate indicate abuse liability. A survey regarding the recreational use of methylphenidate was distributed to the student body at a public, liberal arts college. More than 16% of the students reported they had tried methylphenidate recreationally, and 12.7% reported they had taken the drug intranasally. Use of the drug was more common among traditional students than among nontraditional students. Among traditional-age students, reports of methylphenidate use were roughly equivalent to reports of cocaine and amphetamine use. Environmental conditions characteristic of college student life may influence the recreational use of the drug.

Adult↗
PubMed2000

Comparison of BACTEC MYCO/F LYTIC and WAMPOLE ISOLATOR 10 (lysis-centrifugation) systems for detection of bacteremia, mycobacteremia, and fungemia in a developing country.

In less-developed countries, studies of bloodstream infections (BSI) have been hindered because of the difficulty and costs of culturing blood for bacteria, mycobacteria, and fungi. During two study periods (study period I [1997] and study period II [1998]), we cultured blood from patients in Malawi by using the BACTEC MYCO/F LYTIC (MFL), ISOLATOR 10 (Isolator), Septi-Chek AFB (SC-AFB), and Septi-Chek bacterial (SC-B) systems. During study period I, blood was inoculated at 5 ml into an MFL bottle, 10 ml into an Isolator tube for lysis and centrifugation, and 10 ml into an SC-B bottle. Next, 0.5-ml aliquots of Isolator concentrate were inoculated into an SC-AFB bottle and onto Middlebrook 7H11 agar slants, chocolate agar slants, and Inhibitory Mold Agar (IMA) slants. During study period II, the SC-B and chocolate agar cultures were discontinued. MFL growth was detected by fluorescence caused by shining UV light (lambda = 365 nm) onto the indicator on the bottom of the bottle. During study period I, 251 blood cultures yielded 44 bacterial isolates. For bacteremia, the MFL was similar to the Isolator concentrate on chocolate agar (34 of 44 versus 27 of 44; P, not significant [NS]), but more sensitive than the SC-B bottle (34 of 44 versus 24 of 44; P = 0.05). For both study periods combined, 486 blood cultures yielded 37 mycobacterial and 13 fungal isolates. For mycobacteremia, the sensitivities of the MFL and Isolator concentrate in the SC-AFB bottle were similar (30 of 37 versus 29 of 37; P, NS); the MFL bottle was more sensitive than the concentrate on Middlebrook agar (30 of 37 versus 15 of 37; P = 0.002). For fungemia, the MFL bottle was as sensitive as the SC-B bottle or Isolator concentrate on chocolate agar or IMA slants. We conclude that the MFL bottle, inoculated with just 5 ml of blood and examined under UV light, provides a sensitive and uncomplicated method for comprehensive detection of BSI in less-developed countries.

Adult↗
PubMed1998

Response acquisition with delayed reinforcement: a comparison of two-lever procedures.

Groups of 8 experimentally naive rats were exposed during 8-hr sessions to resetting delay procedures in which responses on one lever (the reinforcement lever) produced water after a delay of 8, 16, 32, or 64 s. For rats in one condition, responses on a second (no-consequences) lever had no programmed consequences. For rats in another condition, responses on a second (cancellation) lever during a delay initiated by a response on the reinforcement lever prevented delivery of the scheduled reinforcer; responses on the cancellation lever at other times had no programmed consequences. Under both conditions and at all delays, most subjects emitted more responses on the reinforcement lever than did control rats that never received water emitted on either lever. At 8-s delays, both conditions engendered substantially more responding on the reinforcement lever than on the other lever, and performance closely resembled that of immediate-reinforcement controls. At delays of 16 and 32 s, however, there was clear differential responding on the two levers under the cancellation condition but not under the other condition. When the delay was 64 s, differential responding on the two levers did not occur consistently under either condition. These findings provide strong evidence that the behavior of rats is sensitive to consequences delayed by 8, 16, and 32 s, but only equivocal evidence of such sensitivity to consequences delayed 64 s. They also indicate that acquisition depends, in part, on the measure of performance used to index it.

Animals↗
PubMed1997

Urine glycosaminoglycan concentrations in mucopolysaccharidosis VI-affected cats following bone marrow transplantation or leukocyte infusion.

Urinary glycosaminoglycan (GAG) concentrations were determined in nineteen normal cats (eleven kittens and eight adult cats), eighteen mucopolysaccharidosis VI (MPS VI)-affected untreated cats (ten kittens and eight adult cats), thirteen cats MPS VI-affected cats following bone marrow transplants (BMT), and two MPS VI-affected cats following intravenous infusion of leukocytes from normal cats. Mucopolysaccharidosis VI-affected cats treated with BMT had a precipitous decrease in urinary GAG by day 7 post-BMT, then a transient increase just prior to engraftment, followed by a sustained decrease to within, or near, the range of urinary GAG concentration established for normal cats. The pre-engraftment changes in urinary GAG excretion were reproduced by leukocyte infusion. After infusion of comparable members of normal peripheral blood leukocytes, a significant decrease in urinary GAG concentrations, specifically dermatan sulfate (DS), was seen with a nadir at day 5 post-infusion, followed by a return by day 9 to pre-infusion values. Post-engraftment, a continued low urinary GAG concentration with a specific decrease in DS can be utilized to document successful autologous engraftment in MPS VI-affected cats.

Animals↗
PubMed1997

Effects of chlorpromazine on rats' acquisition of lever-press responding with immediate and delayed reinforcement.

The effects of chlorpromazine (0, 2, 6, and 10 mg/kg) on the acquisition of lever-press responding by rats were examined under conditions where reinforcement (water delivery) was immediate or delayed. Under the immediate reinforcement condition, water-deprived rats were exposed during 8-h sessions to a fixed-ratio 1 (FR 1) schedule of water delivery without prior autoshaping or hand shaping. Under the delayed reinforcement condition, similar rats were exposed to a tandem FR 1 fixed-time 8-s schedule of water delivery. A different squad of eight rats was exposed to each delay condition and drug dose. For all subjects, responses on one lever produced water and responses on a second lever had no programmed consequences. Regardless of whether reinforcement was immediate or delayed, chlorpromazine reduced in dose-dependent fashion the mean number of operative-lever responses emitted, which suggests that the drug interfered with learning. At all chlorpromazine doses except 10 mg/kg, substantially more operative-lever than inoperative-lever responding occurred, indicating that the operant response was acquired. Chlorpromazine at 2 and 6 mg/kg disrupted the acquisition of stimulus control by the operative lever when reinforcement was delayed, but not when it was immediate. At 10 mg/kg, most subjects did not acquire lever-pressing regardless of whether they were exposed to the immediate or delayed reinforcement procedure. Procedures similar to those used in the present study appear to provide a reasonable assay for examining how drugs affect the initial behavioral effects of immediate and delayed reinforcement, and may merit further investigation.

Animals↗
PubMed1997

Screening for neuroblastoma is ineffective in reducing the incidence of unfavourable advanced stage disease in older children.

Neuroblastoma exhibits many characteristics which would suggest that preclinical detection may improve outcome. The Quebec Neuroblastoma Screening Project was initiated to determine whether mass screening could reduce mortality in a large cohort of infants. All 476,603 children born in the province of Quebec during a 5-year period of time (1 May 1989 to 30 April 1994) were eligible for determinations of urinary catecholamine metabolites at 3 weeks and 6 months of age. Children with positive screening were referred to one of four paediatric cancer centres in Quebec for uniform evaluation and treatment. Standardised incidence ratios (SIRs) were calculated for neuroblastoma in Quebec and two comparable population-based controls during the same period of time using similar ascertainment procedures. Compliance with screening in Quebec was 91% at 3 weeks (n = 425,816) and 74% at 6 months (n = 349,706). Up to 31 July 1995 with a follow-up of the birth cohort of 15-75 months, 118 cases of neuroblastoma were diagnosed, 43 detected preclinically by screening, 20 detected clinically prior to screening at 3 weeks of age and 55 detected clinically after 3 weeks of age having normal screens (n = 52) or never screened (n = 3). Based on data from concurrent control populations, 54.5 cases of neuroblastoma would have been expected in Quebec during the study period for an SIR of 2.17 (95% CI 1.79-2.57, P < 0.0001). For the two control groups, the overall SIR was 1.00 (NS). SIRs for Quebec by age at diagnosis in yearly intervals show a marked increased incidence under 1 year of age (SIR = 2.85, 95% CI 2.26-3.50), with no reduction in incidence in subsequent years. We conclude that screening for neuroblastoma markedly increases the incidence in infants without decreasing the incidence of unfavourable advanced stage disease in older children. It is unlikely that screening for neuroblastoma in infants will reduce the mortality of this disease.

Canada↗
PubMed1997

Spontaneous neurological improvement in anti-Hu associated encephalomyelitis.

Symptoms of anti-Hu associated paraneoplastic encephalomyelitis (PEM) and sensory neuropathy (PSN) are usually severe and irreversible. Two patients are reported whose symptoms improved spontaneously, and in one of them they resolved after resection of an inflammatory lesion of the lung. Spontaneous neurological improvement, although rare, should be considered in the evaluation of therapies for PEM/PSN.

Aged↗
PubMed1996

A phase III randomized prospective trial of external beam radiotherapy, mitomycin C, carmustine, and 6-mercaptopurine for the treatment of adults with anaplastic glioma of the brain. CNS Cancer Consortium.

PURPOSE: This study was designed to evaluate strategies to overcome the resistance of anaplastic gliomas of the brain to external beam radiotherapy (ERT) plus carmustine (BCNU). Patients were > or = 15 years of age, had a histologic diagnosis of malignant glioma, and a Karnofsky performance status (KPS) > or = 60%. METHODS AND MATERIALS: In Randomization 1, patients were assigned to receive either ERT alone (61.2 Gy) or ERT plus mitomycin C (Mito, IV 12.5 mg/m(2)) during the first and fourth week of ERT. After this treatment, patients went on to Randomization 2, where they were assigned to receive either BCNU (i.v. 200 mg/m(2)) given at 6-week intervals or 6-mercaptopurine (6- MP, 750 mg/m(2) IV daily for 3 days every six weeks), with BCNU given on the third day of the 6-MP treatment. Three hundred twenty-seven patients underwent Randomization 1. One hundred sixty-four received ERT alone, and 163 received ERT + Mito [average 52.7 years; 63% male; 69% glioblastoma multiforme (GBM); 66% had a resection; 56% KPS > or = 90%]. Step-wise analysis of survival from Randomization 1 or 2 indicates that survival was significantly diminished by: (a) age > or = 45 years (b) KPS < 90%; (c) GBM/gliosarcoma histology; (d) stereotactic biopsy as opposed to open biopsy or resection. Median survival from Randomization 1 in both arms (ERT + Mito) was 10.8 months. Median survival from Randomization 2 was 9.3 months for BCNU/6MP vs. 11.4 months for the BCNU group (p = 0.35). Carmustine/6-MP showed a possible survival benefit for histologies other than GBM/GS. Two hundred and thirty-three patients underwent Randomization 2. The proportion of patients in the ERT group who terminated study prior to Randomization 2 was significantly less in the ERT group than in the ERT + Mito group (20 vs. 37%, p < 0.001). CONCLUSIONS: (a) The addition of Mito to ERT had no impact on survival; (b) patients treated with ERT + Mito were at greater risk of terminating therapy prior to Randomization 2; (c) there was not a significant survival benefit to the addition of 6-MP to BCNU.

Adult↗
PubMed1996

Differences between respondents and nonrespondents in a multicenter community-based study vary by gender ethnicity. The Atherosclerosis Risk in Communities (ARIC) Study Investigators.

This study provides data on differences between respondents and nonrespondents by gender and ethnicity in a multicenter community-based study that is rarely collected and that may be useful for estimating bias in prevalence estimates in other studies. Demographic, general health, and cardiovascular risk factors were examined in black and white respondents and nonrespondents to the Atherosclerosis Risk in Communities (ARIC) Study, a prospective study investigating cardiovascular risk factors in approximately 16,000 adults that was initiated in 1986 in four U.S. communities. In one of the communities (Jackson, MS) black participants were recruited exclusively; in another (Forsyth County, NC) 12% of the eligible sample were black, whereas the samples in Washington County, MD and the northwestern suburbs of Minneapolis, MN were almost all white. Demographic and health characteristics were collected during a home interview. Subjects who subsequently agreed to complete a clinical examination were defined as respondents, while eligible participants who only took part in the home interview were considered to be nonrespondents. Approximately 75% of age-eligible individuals (45-64 years) in each community completed the home interview. In three of the communities 86-88% of those who took part in the home interview also completed the clinic examination, whereas only 65% did so in Jackson. Among white participants, response rates were similar in men and women and between communities. Among black participants, the response rates were considerably lower, particularly in men. White male respondents reported a higher socioeconomic status, better general health and a lower prevalence of cardiovascular disease and associated risk factors than white male nonrespondents. The difference between white respondents and nonrespondents were greater for men than women despite similar response rates. Among black participants, respondent/nonrespondent difference were usually of smaller magnitude or absent, particularly in women. General health status and recent hospitalization rates were almost identical in black respondents and nonrespondents. Low response rates can bias estimates of prevalence in community-based studies although differences between respondents and nonrespondents tend to exaggerate real differences between respondents and the eligible population sampled. For example, among white males 25% of respondents and 44% of nonrespondents were current smokers, yet the estimated community prevalence of smoking was 31%. In conclusion, difference observed between respondents and nonrespondents were in the expected direction, but were greater for men than women and for whites than blacks.

Bias↗
PubMed1996

Case study: anorexia nervosa and autistic disorder in an adolescent girl.

The development of anorexia nervosa in a high-functioning, early adolescent, autistic female is described. This case raises the issue of co-occurrence of childhood-onset disorders sharing the phenomena of obsessions and compulsions. The role of dysregulation of the serotonergic neurotransmitter system as a common underlying mechanism in these disorders is suggested. Psychoactive agents affecting the serotonin system and in particular the atypical neuroleptic risperidone may be of value in these disorders. There is added benefit to the combined use of biological and behavioral therapies.

Adolescent↗
PubMed1996

Variations in the natural history and survival of patients with supratentorial low-grade astrocytomas.

Data from 55 consecutive patients with low-grade astrocytomas treated between 1982 and 1990 were analyzed to determine specific outcome factors, including time to recurrence, incidence of anaplastic transformation, and survival. Gender, type of symptoms, contrast enhancement, and timing of radiation therapy were not significant in determining outcome. Patients who had symptoms for > 2 years and underwent gross-total resection of the tumor, with age as a continuous variable, were associated with significantly longer time to recurrence and survival. Within the population of patients with low-grade astrocytomas, patients with chronic epilepsy clearly had the best prognoses. There were no tumor recurrences or deaths in 27 patients with chronic epilepsy, regardless of the extent of surgery and without the use of radiotherapy. Ten-year survival was 100% for 31 patients who underwent gross-total tumor resection, regardless of the length of preoperative symptoms. Immediate postoperative radiotherapy did not prolong the time to recurrence, reduce the incidence of transition to more malignant tumors at recurrence, or increase the length of survival when compared with delayed radiotherapy. Because recurrence with a high-grade lesion caused 92% of the mortality in our series, the benefit in patients who underwent aggressive surgery seems to result from a significant decrease in the risk of recurrence when compared with patients who underwent anything less than gross-total resection. Our data also suggest that variability in the natural history of low-grade astrocytomas has a strong influence in determining survival and that tumors associated with chronic epilepsy are much less likely to become more malignant over time.

Adult↗
PubMed1996

Effects of D-amphetamine on response acquisition with immediate and delayed reinforcement.

The present study examined in 8-hour sessions the effects of d-amphetamine (1.0, 5.6, and 10 mg/kg) on the acquisition of lever-press responding in rats that were exposed to procedures in which water delivery was delayed by 0, 8, or 16 seconds relative to the response that produced it. Both nonresetting- and resetting-delay conditions were studied. Although neither shaping nor autoshaping occurred, substantial levels of operative-lever responding developed under all conditions in which responses produced water. The lowest dose (1.0 mg/kg) of d-amphetamine either had no effect on or increased operative-lever pressing, whereas higher doses typically produced an initial reduction in lever pressing. Nonetheless, overall rates of operative-lever pressing at these doses were as high as, or higher than, those observed with vehicle. Thus, response acquisition was observed under all reinforcement procedures at all drug doses. In the absence of the drug, most responding occurred on the operative lever when reinforcement was immediate. Such differential responding also developed under both nonresetting- and resetting-delay procedures when the delay was 8 seconds, but not when it was 16 seconds. d-Amphetamine did not affect the development of differential responding under any procedure. Thus, consistent with d-amphetamine's effects under repeated acquisition procedures, the drug had no detrimental effect on learning until doses that produced general behavioral disruption were administered.

Amphetamines↗
PubMed1996

A comparison of two column agglutination technologies for routine antibody screening using the indirect antiglobulin technique.

Two commercial column agglutination technologies were compared for routine antibody screening using the indirect antiglobulin technique with 1000 heparinised blood samples from a general hospital. The I.D. microtyping system (Diamed) utilises a Sephadex gel, and the Biovue system (Ortho Diagnostics) consists of a column containing minute glass beads. Both systems have antihuman globulin incorporated into them resulting in agglutinates being trapped and allowing free red cells to pass through to the base. The purpose of this study was to compare the two technologies with the minimum amount of variables possible. The spin tube antiglobulin technique was not included in this study as this technology has not been used in this laboratory since January 1991. The systems compared well, despite different serological problems.

Blood Grouping and Crossmatching↗