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Biomedical subjects

J McKenzie

Publications and source records attributed to J McKenzie.

At least 55 records · Page 3Linked to original sources
PubMed1992

Community work project in Gazankulu: a community-based training experience.

Speech Pathology and Audiology students at the University of the Witwatersrand participated in a field trip to learn about rural community work. In collaboration with rehabilitation workers at Tintswalo Hospital, Gazankulu, projects in pre-school language stimulation, aphasia assessment and intervention, and hearing screening were undertaken. Projects adhered to community work principles. These were successful in terms of both providing a service to the community and teaching students principles and practice of community work.

Audiology↗
PubMed1991

Immunocytochemical characterization of large granular lymphocytes in normal cervix and HPV associated disease.

A quantitative immunocytochemical study of large granular lymphocytes (LGLs) in the normal cervix and in human papillomavirus (HPV) associated disease was performed using a panel of monoclonal antibodies which included those for LGL surface markers CD56, CD16, and CD57. Only CD56-positive cells were found within the ectocervical epithelium and these cells increased in number in cervical intraepithelial neoplasia (CIN) in comparison with normal cervix. Examination of serial sections and double labelling suggests that these cells are CD3+, CD8+, CD56+, CD16+. The observed increase in number of this subset was not associated specifically with HPV infection but was related to CIN. Lymphocytes expressing all three LGL markers were found in the stroma and CD16(+)-positive cells clustered around endocervical glands with occasional cells extending into the endocervical epithelium. These results indicate that a small subset of LGLs which express T-cell markers is increased in number in CIN. Cells expressing classical NK markers are restricted to the stroma and are not found within the ectocervical epithelium.

Adult↗
PubMed1991

Second twin: quality of survival if born by breech extraction following internal podalic version.

The intrapartum management of the vertex-breech and vertex-transverse twin gestation is controversial. The fall in perinatal mortality rate to a low level has resulted in this parameter failing to be an adequate gauge of the safety of breech extraction and the answer lies in the quality of survival of the infants. Fifty-one twin pairs, collected over 12 years at the Mercy Hospital for Women, Melbourne, occurred where twin 2 was born by breech extraction following internal inversion and the control (twin 1) did not have this procedure performed. In 8 pairs either a stillbirth or neonatal death occurred; in one pair childhood death due to an accident (fire) occurred; in 4 pairs the parents refused entrance to the study as they perceived both twins to be similar; in 2 sets the assessment was incomplete; 11 sets were untraceable leaving 25 sets fully assessed as children ranging in age from 2 to 12 years. Growth, and psychological scores were not significantly different between twins 1 and 2 but 2 children had cerebral palsy and both were born by breech extraction following internal version at 29.2 and 30.1 weeks' gestation, respectively. Because of small numbers the results failed to achieve statistical significance and this study was unable to answer the question regarding the safety of breech extraction following internal version but did show that the majority of infants so born do well.

Apgar Score↗
PubMed1990

Orbital recurrence of retinoblastoma successfully treated by combined therapy.

Five children with an orbital recurrence of retinoblastoma have been successfully treated by a combination of excision biopsy of the tumour mass, radical orbital radiotherapy, and systemic chemotherapy. Nine previous children, consecutive with the five presented here, died from disseminated retinoblastoma after failure of earlier treatment programmes for orbital recurrence. An aggressive therapeutic approach is justified by this improvement in survival.

Antineoplastic Combined Chemotherapy Protocols↗
PubMed1989

GABA-immunoreactive neurons in the dorsal horn of the rat spinal cord.

An antiserum to GABA was used on semithin resin-embedded sections of rat dorsal horn. Immunoreactive neurons were evenly distributed throughout laminae I-III and constituted between 24 and 33% of the total neuronal population within three laminae. Fifty Golgi-stained cells in lamina II were tested with the antiserum. Most of the islet cells examined were immunoreactive, although some small islet cells were not. None of the 14 stalked cells tested was immunoreactive. These results provide further evidence that the stalked and islet cells of lamina II form two distinct functional classes and suggest that the islet cells function as inhibitory interneurons.

Animals↗
PubMed1989

Arachidonic acid affects membrane ionic conductances of GH3 pituitary cells.

Arachidonic acid (AA) stimulates prolactin release from pituitary cells, by mechanisms not yet understood. In this work, we analyzed the effects of AA on membrane ionic conductances in a clonal line of anterior pituitary cells (GH3/B6), finding time- and dose-dependent effects of AA on their membrane ionic conductances. The predominant response at concentrations between 100 nM and 10 microM was a prolongation of the action potential (AP) and an increase in the transient after-hyperpolarization potential. Voltage clamp studies showed that this was associated with a decrease in a voltage-dependent potassium current and an increase in a voltage-dependent calcium current. In some cells (30%) the effect of AP duration was less important, but spike firing was enhanced. For the highest concentrations used (1 and 10 microM) the effects described above were preceded by hyperpolarization of the cell membrane; in voltage clamp it was shown that this hyperpolarization resulted from the activation of a calcium-dependent potassium conductance suspected to be due to the release of intracellular calcium. The calcium store affected by AA was, at least in part, insensitive to vanadate and heparin. These data suggest that AA may enhance intracellular calcium concentration by increasing calcium entry during each voltage-dependent calcium AP, by increasing the spike frequency, or by releasing calcium from an intracellular compartment. The resulting rise in cytosolic free calcium concentration may be a key link in the process by which AA stimulates prolactin release in GH3/B6 pituitary cells.

Animals↗
PubMed1989

The assessment of chronic pancreatitis.

The stimulated pancreatic polypeptide (PP) response was compared to standard tests of pancreatic function in patients with proven chronic pancreatitis and control subjects. Although the median values of the PP test in patients were statistically significantly different from those of controls, much variability was seen in both groups. The PP response seems to correlate with pancreatic exocrine function and shows good agreement with the results of other tests of exocrine pancreatic function while avoiding many of the difficulties inherent in performing other tests. Although more studies are needed, the PP response provides a valuable test of pancreatic function.

Adult↗
PubMed1988

Measurement of choroidal melanomas: a comparison of methods.

The prognosis for death from metastatic choroidal melanoma following enucleation has been shown to be strongly correlated with a number of risk factors of which the most important are age of onset, aggressive cell types and tumour volume. The advantages of enucleation for the treatment of choroidal melanomas are put into question by the singular lack of a parallel increase in life expectancy following this treatment, and evidence that it may promote the development of metastatic disease. Alternative forms of treatment have been introduced including observation of small and asymptomatic tumours. We are using a computer-aided system for serial measurement and statistical analysis of area and volume of choroidal melanomas. A comparison of results using our method and the conventional method of estimating volume by the product of basal area and height for 51 measurements on 15 eyes over a 6-month period showed an overestimation of volume by conventional methods which could be corrected by applying a "shape constant" determined by linear regression. Calculation of tumour growth rates is also shape-dependent, and a slowing in growth rate or even a reduction in melanoma size is possible.

Choroid Neoplasms↗
PubMed1987

Low- and conventional-dose maintenance therapy with fluphenazine decanoate. Two-year outcome.

We evaluated the effectiveness and the side effects of what we defined as low (5-mg) and conventional (25-mg) doses of fluphenazine decanoate administered every two weeks in a double-blind comparison. Subjects were 66 patients who fulfilled DSM-III criteria for schizophrenic disorder. Evaluation of the survival with each dose revealed no significant difference at one year, but significantly better survival was seen with the 25-mg dose (64%) than the 5-mg dose (31%) at two years. There was no significant difference in survival when the clinician was permitted to make a dosage adjustment up to 10 mg in the low-dose group and 50 mg in the higher-dose group when the patient demonstrated evidence of a symptomatic exacerbation. Patients assigned to the higher dose appeared to feel more uncomfortable during the early months of the study, as indicated by significantly higher scores on subscales of the Hopkins Symptom Checklist-90R and higher side effect scores for retardation and akathisia. Implications for clinical practice are discussed.

Adult↗
PubMed1987

Chlorpropamide overdose in renal failure: management with charcoal hemoperfusion.

A potentially lethal chlorpropamide overdose in a patient with chronic renal failure on long-term hemodialysis was treated by two courses of charcoal hemoperfusion. Hemoperfusion shortened the half-life clearance of the drug from a mean value of 93.6 to 3.4 hours. Calculation of the fractional extraction indicated that hemoperfusion reduced the body burden of the drug by 24% and 19% (mean values) during the first and second hours of treatment, respectively. We conclude that charcoal hemoperfusion should be considered a definitive therapeutic option in such cases.

Adult↗
PubMed1986

Treatment of chronic knee effusions with 90yttrium-correlation of in vitro radiation and chemical effects with clinical results at three and six months.

Twenty seven knees, mainly of rheumatoid patients, received intra-articular 90Y for chronic effusions; 24% were effusion-free at 6 months. In vitro chemical, radiation (32P-induced), and combined effects of cold (non-radioactive) yttrium and 32P on synovial fluid mononuclear cells, failed to show any significant correlation with subjective and/or objective clinical effects at 3 or 6 months. If 90Y exerts its therapeutic effect via these cells, it probably does so other than by a direct effect on mononuclear cell viability.

Chronic Disease↗
PubMed1986

Sequential nonstress testing with use of each fetus as its own control.

The sequential nonstress tests of 126 high-risk fetuses were assessed for baseline fetal heart rate, acceleration frequency, amplitude, and duration and the observance of fetal heart rate decelerations. In 108 fetuses (563 tests) with normal perinatal outcomes, no significant trends in these parameters were found. In 18 fetuses (104 tests) with perinatal compromise, 16 had significantly declining acceleration frequencies, 15 had decreasing acceleration duration, four had rising mean baseline rates, and seven, in their last test before delivery, had repetitive late or severe variable decelerations. The last tests of 11 of these 18 fetuses met institutional criteria for reactivity. When the nonstress tests of compromised fetuses were viewed sequentially, acceleration frequency declined by an average of 59% and acceleration duration by an average of 40%. Sequential assessment of the nonstress test, when compared with the use of standard reactivity criteria, improved test sensitivity from 39% to 89% and negative predictive value from 91% to 98%. We conclude that sequential nonstress test assessment in individual fetuses may improve the diagnostic value of this modality and lead to earlier recognition of fetal compromise.

Female↗
PubMed1986

Industrial hygiene, chemical and biological assessments of exposures to a chlorinated phenolic sapstain control agent.

A two-year study of the occupational exposure of workers in a lumber mill to a wood preservative containing chlorophenol has been conducted. The methods were biological (urine) monitoring, industrial hygiene assessment and a questionnaire related to worker-perceived health effects. Approximately 40 workers exposed to the wood preservative and 40 unexposed controls working in other locations of the plant participated in the study. Evaluation of work conditions, assessment of urinary levels of tetra- and pentachlorophenol, and administration of a medical questionnaire were performed at a six-month intervals over a two-year period. Industrial hygiene ratings of exposures and adequacy of protection were evaluated in relation to the results of biological monitoring. Workers who came into contact with freshly treated and still wet wood had consistently higher urinary levels of tetrachlorophenol. Workers stationed adjacent to the spray applicator also had higher tetrachlorophenol levels. There was no statistically significant relationship between the subjective ratings by the industrial hygienist of exposure and adequacy of worker protection with the urinary levels of tetrachlorophenol. Nor was there a consistent pattern linking exposure ratings with adequacy of protection. The short half-life of tetrachlorophenol in the urine makes this a good indicator of only the most recent exposure. The differences in urinary levels between controls and exposed workers were large, with averages of 240.4 ppb for exposed workers and 14.6 for controls. Traditional industrial hygiene evaluation techniques, in conjunction with biological monitoring, proved to be the most effective method of assessing both exposure and work practices. Exposed workers reported a statistically significant increase of positive answers to known signs and symptoms of chlorophenol exposure compared with the controls. There was no statistically significant relationship between the number of these health problems reported and the mean urinary levels of tetra- or pentachlorophenol for the exposed group; however, for certain variables (heavy vs. light exposure, inadequate vs. adequate protection, greater than 100 ppb urinary tetrachlorophenol vs. less than 100 ppb), those with heavier exposure, inadequate protection or higher urinary tetrachlorophenol reported on the average more health problems over the two-year period. Firm statistical conclusions could not be drawn because of the small size of the study population.

Chlorophenols↗
PubMed1986

Percent acceleration time: a new method of fetal assessment.

The percent acceleration time (PAT) is a fetal heart rate parameter, which may be derived from the nonstress test (NST). It is based on measurement of the duration of individual movement-associated fetal heart rate accelerations (MAFAs), obtained during a nonstress test, and is calculated by the formula: (formula, see text) The authors studied 148 fetuses undergoing four or more serial nonstress tests who were delivered within one week of their last test. Percent acceleration time of fetuses with normal outcomes had a mean value of 15.5 +/- 10.0 (SD)%, correlated well with the frequency and amplitude of movement-associated fetal heart rate accelerations but was independent of gestational age and mean baseline fetal heart rate. No normal fetus had a percent acceleration time of less than 5% on its last nonstress test, while only one abnormal fetus had a percent acceleration time that exceeded the mean percent acceleration time of the normal group. All abnormal fetuses had a significant progressive decline in percent acceleration time (mean: 50.6%). Percent acceleration time values were more sensitive in identifying fetuses with perinatal compromise than were conventional criteria for nonstress test reactivity, and may provide a useful alternative to assessment of fetal status when other quantitative methods are unavailable (continuous ultrasound visualization) or less reliable (maternal perception, tokodynamometry, palpation).

Female↗
PubMed1985

Clinical sequelae of the extended nonstress test.

Two hundred eighty-one high-risk gravida women undergoing a collective total of 661 nonstress tests entered a protocol to determine whether extending initially nonreactive tests improved the positive predictive value of this test modality. Reactivity required the occurrence of at least three fetal heart rate accelerations (15 bpm, 15 seconds' duration), associated with fetal movement during a 30-minute episode. Tests failing these criteria were extended by sequential 30-minute increments until a reactive 30-minute window appeared or 90 minutes had elapsed. After 90 minutes, a nonreactive test was followed by a contraction stress test. Reactive tracings occurred in 266 patients (95%) and in all cases were evident by the end of 70 minutes. Corrected perinatal mortality and morbidity in this group were 0% and 5.6%, respectively. Nonreactive fetuses not only produced abnormal (positive or persistently equivocal) contraction stress tests in nearly all cases (93.3%) but had mortality and morbidity rates of 6.7% and 93.3%, respectively. Furthermore, in five of 15 instances, the contraction stress test was associated with profound fetal heart rate decelerations necessitating emergency delivery. We conclude that prolonged nonreactivity, in the absence of significant immaturity, congenital abnormalities, or pharmacologic agents, identifies significant fetal jeopardy. Expeditious termination of pregnancy should be considered and, under these circumstances, a subsequent contraction stress test may be relatively contraindicated.

Congenital Abnormalities↗
PubMed1985

Nonstress test: dimensions of normal reactivity.

Despite the widespread use of the nonstress test, there has been no consensus on the criteria for normal reactivity. The authors studied 495 nonstress tests of 230 normal term fetuses, using a standardized protocol. The frequency distribution of movement-associated fetal heart rate (FHR) accelerations exceeding 15 beats per minute and 15 seconds' duration was examined in windows, ranging from ten to 40 minutes. Mean, median, and modal frequencies of movement-associated FHR accelerations were determined in 1910, 1418, 895, and 473 windows of ten, 20, 30, and 40 minutes, respectively. No significant difference in movement-associated FHR acceleration frequency was observed for any sequential ten-minute window, but movement-associated FHR accelerations were absent in 19.5, 8.8, 5.2, and 5.0% of 10-, 20-, 30-, and 40-minute windows, respectively. The broad frequency distributions of movement-associated FHR accelerations, produced by normal fetuses, precludes discrete diagnostic cutoffs in short time windows, unless one is willing to accept significant negative predictive errors.

Female↗