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Biomedical subjects

E A Jackson

Publications and source records attributed to E A Jackson.

At least 37 records · Page 2Linked to original sources
PubMed1995

In vitro assessment of infant pulmonary function equipment.

Commercially available automated pulmonary monitors are used increasingly in neonatal intensive care units. However, detailed information regarding the static and dynamic accuracy of these monitors is rarely available. Collaboration between scientists, clinicians, and manufacturers is essential to establish improved technical standards and protocols for testing of equipment and for the development of more reliable neonatal pulmonary monitors. The aim of this study was to develop a protocol for the in vitro assessment of commercial infant pulmonary function equipment which could be applied within the laboratory to provide rapid feedback to the manufacturer. A recently released neonatal pulmonary monitor, the Bicore CP100 (software version 3.3), was selected for the development of this protocol. The deadspace and resistance of the measuring device were determined. The flow and airway pressure measuring systems were evaluated alone and connected to a tracheal tube for both static accuracy and frequency response. The pressure-volume relationship of the esophageal balloon was determined and its static accuracy and frequency response were assessed. The algorithms for on-line calculations were checked and their correct application confirmed by examination of an ASCII data print out. Finally, the pulmonary monitor was tested during intermittent positive pressure ventilation of a neonatal lung model of known compliance and resistance.

Algorithms↗
PubMed1995

Comparison of single-breath and plethysmographic measurements of resistance in infancy.

Single-breath technique (SBT) measurements of total respiratory resistance (Rrs) were compared with plethysmographic measurements of airway resistance (Raw) in healthy infants < or = 13 wk of age (Group 1; n = 49) and > 13 wk of age (Group 2; n = 37) and in infants > 13 wk of age with prior wheeze (Group 3; n = 49). A significantly higher percentage of Rrs (19%) than of Raw (2%) measurements were technically unsatisfactory, alinearity of the flow-volume curve accounting for 54% of Rrs failures. Although both Rrs and Raw were significantly higher in Group 3 infants, between-subject variability was wide in all groups. Rrs was significantly higher than initial expiratory (IE) Raw in all groups. Mean difference Rrs-IE Raw (95% CI) values were 1.98 (1.51, 2.48), 1.29 (0.96, 1.62), and 1.97 (1.56, 2.38) kPa.L-1.s for Groups 1, 2, and 3, respectively. Significant but smaller differences were seen for end-expiratory (EE) Raw in Groups 1 and 2 but not in Group 3. Mean difference Rrs-EE Raw (95% CI) values were 0.68 (0.11, 1.26), 0.55 (0.19, 0.92), and 0.31 (-0.06, 0.69) kPa.L-1.s for Groups 1, 2, and 3, respectively. Despite wide between-subject variability in Rrs and a relatively high failure rate, the SBT is simple to use, and it may be applicable to epidemiologic studies. However, clinical applications in individual infants may be limited by failure to detect the dynamic changes in resistance throughout the breath evident from plethysmographic studies.

Airway Resistance↗
PubMed1994

The relationship between tPTEF:tE and specific airway conductance in infancy.

This study examines the association between the time taken to achieve peak tidal expiratory flow as a proportion of total expiratory time (tPTEF:tE) and specific airways conductance (SGaw) in healthy infants and those with prior physician diagnosed, associated, lower respiratory illness with wheezing (prior LRI) during the first year of life. We compared tPTEF:tE and SGaw, the latter estimated during both initial inspiration (ll) and end-expiration (EE), in 168 infants (94 males), measured on 220 occasions. Mean (range) tPTEF:tE was 0.321 (0.150-0.522) in 73 healthy infants aged less than 3 months (mean, 7.8 weeks), in whom mean (range) EE SGaw and plethysmographic thoracic gas volume at functional residual capacity (FRCpleth) were 2.47 s-1 kPa-1 (0.6-5.8) and 141 mL (87-204), respectively. Both tPTEF:tE and EE SGaw were significantly lower in older infants with prior LRI (n = 79; mean age, 50.0 weeks) compared to a similarly aged group of healthy infants (n = 68; mean age, 48.5 weeks), the mean difference [95% confidence intervals (CI)] being -0.039 (-0.013, -0.064) and -0.48 s-1 kPa-1 (-0.24, -0.72), respectively. A significant but weak association between tPTEF:tE and EE SGaw was found among infants above 3 months of age, irrespective of prior wheezing status. However, this relationship was not significant in healthy younger infants, in whom a significant but weak association with FRCpleth was found. Further work is needed to elucidate the factors influencing tidal expiratory flow patterns in infancy.

Age Factors↗
PubMed1994

Analysis of tidal breathing parameters in infancy: how variable is TPTEF:TE?

During recent years there has been increasing interest in the measurement of tidal breathing parameters, such as the time to reach peak tidal expiratory flow as a proportion of total expiratory time (TPTEF:TE), and their application to population-based studies of the determinants of early respiratory morbidity. However, little is known about factors influencing the within and between-subject variability of these parameters. This study examines the influence of sedation on TPTEF:TE, estimates the optimal number of breaths and breath epochs required to measure TPTEF:TE, and assesses short-term repeatability of this parameter during the first year of life, taking account of age-related differences. Measurements were made in 266 healthy infants and young children (1 d to 19 mo old). Mean (SD) TPTEF:TE fell from 0.49 (0.11) in the first 2 wk of life to 0.34 (0.09) by 5 to 8 wk, remaining similar thereafter. Sedation with triclofos sodium (75 mg/kg) had no significant effect on TPTEF:TE, which was 0.33 (0.10) in 23 unsedated 6-wk-old infants and 0.32 (0.08) in 49 sedated infants of similar age and weight (95% CI for the difference: -0.05, 0.04). At least 10 breaths in each of two separate epochs from each infant were required to provide a representative estimate of TPTEF:TE. The mean (SD) difference between repeat measurements made 5 to 108 min apart was 0.02 (0.08) in 34 infants younger than 6 wk of age (95% limits of agreement: -0.15, 0.18) and -0.01 (0.04) (95% limits of agreement -0.09, 0.08) in 30 infants 6 wk and older.(ABSTRACT TRUNCATED AT 250 WORDS)

Age Factors↗
PubMed1993

Age-related effects of 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine treatment of common marmosets.

The effect of treatment with 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) on juvenile (6-8 months), young adult (2-4 years) and aged (8-10 years) common marmosets were compared. Juvenile marmosets were more resistant to the actions of MPTP and required a greater cumulative dose over a longer period to induce the same degree of motor disability observed in older animals. Young adult and aged marmosets showed an equivalent motor recovery in the 4-5 weeks following cessation of MPTP treatment, but juvenile animals were less able to compensate for the motor impairments. Losses of putamen [3H]dopamine uptake and caudate nucleus dopamine content were equivalent in young adult and aged animals. However, juvenile animals showed a more marked degree of dopamine depletion and reduction in [3H]dopamine uptake. Histological analysis showed cell loss in the substantia nigra to be most prominent in juvenile animals although it was evident in all groups. No loss of cells in the locus coeruleus was apparent in any of the groups studied, and no intraneuronal eosinophilic inclusions were seen. Greater nigral cell loss and dopamine depletion were required in juvenile animals to impair motor function. The degree of behavioural recovery was less in juvenile animals than in young adult and aged marmosets. The extent of behavioural recovery appeared linked to the severity of cell loss and was not reduced in old age.

3,4-Dihydroxyphenylacetic Acid↗
PubMed1993

Factors affecting gay and bisexual men's decisions and intentions to seek HIV testing.

OBJECTIVES: This paper describes the relationships of sociodemographic, attitudinal, and behavioral variables to (1) decision to be tested, (2) expressed intention to be tested, and (3) reasons for not being tested for the human immunodeficiency virus (HIV) antibody. METHODS: A sample of 1295 men completed an anonymous questionnaire in gay-identified venues. Factor analysis was used to group reasons for not being tested and logistic and multiple linear regression were used to model the dependent variables. RESULTS: Fifty-three percent of the respondents had been tested, of whom 26% tested positive. Metropolitan residence and anal intercourse most strongly correlated with previous test-seeking. Previous test experience correlated most strongly with intention to be tested. Reasons for not being tested fell into three groups: (1) desire for anonymity, (2) self-perceived health, and (3) no benefit and denial. The odds were lower for gay men than bisexuals and men who did not participate in anal intercourse to express a desire for anonymity. CONCLUSIONS: Public health agencies should be prepared to individualize testing policies and education to deal with specific concerns and fears. Improving access to the test by removing some of the current psychological and physical barriers will enhance its medical and public health value.

AIDS Serodiagnosis↗
PubMed1992

HIV, substance use and related behaviour of gay and bisexual men: an examination of the talking sex project cohort.

This paper reports on the substance use of 612 gay and bisexual men who participated in an HIV risk reduction project. Use/non-use, level of substance use, and reported frequency of use prior to sexual activity were examined in relation to number of sexual partners, sexual activities, HIV antibody test seeking behaviour and known HIV status. The use of substances among the study cohort appear to be higher than in a comparable heterosexual male group. An association was found between substance use, and both number of sexual partners and sexual activities. However, no significant difference was found in substance use between men participating in protected versus unprotected anal sex. Similarly, no significant difference was found in the reported frequency of substance use prior to sex by those participating in protected and unprotected anal intercourse. Greater drug use was reported among those who were known to be HIV antibody positive. These findings raise issues for further research. The high use of alcohol and drugs by gay and bisexual men may pose significant health risks for this group of men.

AIDS Serodiagnosis↗
PubMed1991

The effect of triclofos sodium sedation on respiratory rate, oxygen saturation, and heart rate in infants and young children.

Chloral hydrate is frequently used to sedate infants for lung function testing. While no effect on respiratory function has been demonstrated, a recent study has reported a fall in oxygen saturation (SaO2) following sedation in wheezy infants. This study was designed to assess the effects of the closely related but less gastrically irritant drug triclofos sodium on respiratory rate (RR), heart rate (HR), and SaO2 in infants without cardiopulmonary disease. Paired measurements using respiratory inductance plethysmography and pulse oximetry were obtained in 10 infants (4-19 months of age) during natural and sedated sleep. Following sedation with triclofos, mean RR rose by 1.9 breaths min-1 (95% confidence intervals [Cl] of the mean difference: 0.13-3.7 min-1). Mean heart rate rose by 5.5 beats min-1 (95% Cl: -0.9-11.9 min-1). Mean SaO2 fell by 0.68% (95% Cl -1.8-0.45%). None of these changes are considered to be of clinical importance, and only the change in RR reached statistical significance at the 5% level.

Procedural Sedation↗
PubMed1990

1-Methyl-4-(2'-methylphenyl)-1,2,3,6-tetrahydropyridine (2'-methyl-MPTP) is less neurotoxic than MPTP in the common marmoset.

Four adult marmosets were treated with increasing doses of 1-methyl-4-(2'-methylphenyl)-1,2,3,6-tetrahydropyridine (2'-methyl-MPTP) in the range 0.23-4.3 mg/kg i.p. to give a cumulative dose of 11.0-11.6 mg/kg over a 6-10 day period. After 4 days of treatment, and as the dosage was gradually increased, the animals exhibited mild motor deficits. These abnormalities slowly declined over the following 1-6 week period. In contrast, similar treatment of common marmosets with 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) (1-4 mg/kg i.p.) for 3-5 days in a cumulative dose of 6.9-9.2 mg/kg produced gross impairment of motor function which persisted throughout the 5 weeks period of observation. Administration of 2'-methyl-MPTP for 6-10 days caused some decrease in dopamine and 3,4-dihydroxyphenylacetic acid (DOPAC), but not homovanillic acid (HVA) content in the caudate nucleus in animals 5-6 weeks after the start of treatment. There was a small decrease in [3H]dopamine uptake into putamen synaptosomes. This contrasted with the marked decreases in all these parameters observed after MPTP treatment of common marmosets. Histological examination of the substantia nigra from the four animals treated with 2'-methyl-MPTP did not show degeneration or loss of dopamine-containing cell bodies in the zona compacta. In contrast, MPTP caused severe destruction of these pigmented nigral neurones. In the common marmoset 2'-methyl-MPTP does not appear to show the same neurotoxic action as MPTP itself. This contrasts with findings in the mouse where 2'-methyl-MPTP is more toxic to dopamine-containing cells of substantia nigra than MPTP.

1-Methyl-4-phenyl-1,2,3,6-tetrahydropyridine↗
PubMed1990

cDNA cloning and expression of a Talaromyces emersonii beta-glucosidase determinant in Escherichia coli.

Intact mRNA has been isolated from the thermophilic fungus Talaromyces emersonii following growth on lactose-containing media and this has been used as template to produce cDNA. This cDNA has been cloned into the Escherichia coli expression system, pUC18 and this DNA was used to transform E. coli. A 2.1 kb fragment was isolated and shown to encode functional beta-glucosidase activity in E. coli. When the fragment was sub-cloned into a leaky strain of E. coli K-12, beta-glucosidase activity was detected in culture supernatants. The fragment was characterised further using restriction enzyme analysis and was also used as a probe in Northern and Southern blotting analyses of T. emersonii mRNA and genomic DNA, respectively. Results obtained from these analyses verified that the cloned insert DNA was of T. emersonii origin.

Blotting, Northern↗
PubMed1990

Sterility of insulin in prefilled disposable syringes.

The sterility of insulin in prefilled syringes that had been prepared by visiting nurses in patients' homes and stored in their refrigerators for one month was studied. Twenty elderly diabetic patients requiring weekly home-nursing visits were enrolled in the study. At the initial study visit, a nurse filled 15 syringes with the type and amount of insulin being used by the patient. Seven syringes constituted the patient's supply for the coming week; the remaining eight syringes were appropriately labeled and placed in a separate part of the refrigerator. Upon returning to replenish the patient's insulin supply during each of the following four weeks, the nurse removed two of the stored syringes for subsequent culturing. The culture medium used was appropriate for bacteria that are usual skin flora and therefore are most likely to cause touch contamination during the syringe-filling process. Control-positive cultures were prepared by intentionally contaminating two vials of 0.9% sodium chloride injection and two vials of NPH insulin with Staph. aureus and Staph. epidermidis. Insulin from 159 syringes was tested, and no bacterial growth was detected by daily readings of cultures for one week. Of the contaminated control syringes, those containing sodium chloride injection produced positive cultures at each of the study weeks; the contaminated insulin samples, although positive at week 0, had become negative by week 3, confirming the bactericidal activity of one or more of the components of this insulin product. Prefilled insulin syringes that are prepared by nurses using good aseptic technique and are stored in the patient's refrigerator appear to remain sterile for up to one month after preparation.

Aged↗
PubMed1989

Behavioural and morphological changes following treatment with GM-1 ganglioside of rats with an electrolytic lesion of the substantia nigra.

The effects of daily treatment with GM-1 ganglioside (30 mg/kg i.p.) or saline (1 ml/kg i.p.) in rats with discrete unilateral electrolytic lesions of the dorsal substantia nigra were investigated. Treatment with GM-1 ganglioside, beginning 3 days prior to surgery and continuing for 33 days post-operatively, caused reductions in the total ipsilateral turns and peak turning rates induced by apomorphine (0.75 mg/kg s.c.) between 7 and 31 days post-operatively, without altering the time course of the effect of apomorphine. No effects of GM-1 on lesion-induced changes in synaptosomal uptake of [3H]dopamine, dopamine, serotonin in the striatum or corresponding levels of metabolites were found. Treatment with GM-1 ganglioside had no effect on the rostrocaudal extent of the electrolytic lesion, but caused morphological changes at the site of the lesion, including a reduction in the density of glial cells. Treatment with GM-1 ganglioside resulted in a relative preservation of cell bodies, staining immunocytochemically for tyrosine hydroxylase, in the substantia nigra pars compacta (expressed as a percentage of the intact side), when compared with saline-treated rats. The results showed that GM-1 ganglioside promoted a partial functional recovery from apomorphine-induced circling, which may be due in part to a reduction in the extent of damage at the lesion site.

Animals↗
PubMed1989

Treatment with a selective MAO B inhibitor prevents loss of dopamine in the nucleus accumbens of MPTP-treated common marmosets.

Administration of 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) to common marmosets induced motor deficits, associated with a marked decrease in the uptake of [3H]dopamine into synaptosomes in the putamen and a reduction in the content of dopamine in both caudate nucleus and nucleus accumbens. Histological analysis showed a marked loss of dopamine-containing cells in the zona compacta of the substantia nigra and less loss in the ventral tegmental area. Treatment of animals with the selective monoamine oxidase (MAO) B inhibitor, MDL 72145 (0.5 or 2.0 mg/kg) prior to, during and following administration of MPTP partially protected animals from the motor abnormalities induced by administration of MPTP alone. Both doses inhibited the onset of akinesia but only the large dose of MDL 72145 prevented the occurrence of other motor abnormalities. Moreover, while MDL 72145 (2.0 mg/kg) prevented the loss in uptake of [3H]dopamine into synaptosomes of the putamen, this was only partly prevented using the smaller dose. Similarly, while MDL 72145 (2.0 mg/kg) prevented loss of dopamine in the caudate, only partial protection was afforded by the smaller dose. However, in the nucleus accumbens, both doses of MDL 72145 prevented the depletion of dopamine, occurring in this region. Histological examination of the substantia nigra showed little or no cell loss in animals receiving the larger dose of MDL 72145 but a moderate cell loss in animals receiving the smaller dose. No damage was observed in the ventral tegmental area of animals treated with MDL 72145 (2.0 mg/kg) and only mild cell loss in those receiving the smaller dose.(ABSTRACT TRUNCATED AT 250 WORDS)

1-Methyl-4-phenyl-1,2,3,6-tetrahydropyridine↗
PubMed1989

Splenic phagocytic function in children with sickle cell anemia receiving long-term hypertransfusion therapy.

To determine the effects of blood transfusions on splenic function in older patients with sickle cell anemia, we investigated splenic function in 12 patients who had had cerebrovascular accidents and who were being treated at two collaborating centers using different transfusion protocols. Splenic function was assessed by radionuclide scan and pocked erythrocyte count. Patients were 6 to 18 years of age and had been receiving transfusions for 7 months to 10 years (median 4.2 years). Of the 12 children, five had normal or increased splenic size and function (normal scan and normal or minimally elevated pocked erythrocyte count). All were receiving intensive transfusion therapy, with the aim of maintaining the hemoglobin S level at less than 20%. The other seven patients had abnormal splenic function (absent radionuclide uptake and elevated pocked erythrocyte count); each was receiving less intensive transfusion therapy, with the pretransfusion hemoglobin S level usually at 30% to 40%. No patient developed bacterial septicemia while receiving hypertransfusion therapy. We conclude that splenic function during a long-term transfusion program is variable, depending in part on the "intensity" of transfusion therapy. Apparent splenic involution and fibrosis may be a reversible event in some patients.

Adolescent↗
PubMed1988

Issues with antihypertensive therapy: safety perspectives.

The benefits of treating hypertension have been documented by several long-term studies that have shown a decreased incidence of morbidity and mortality associated with stroke, left ventricular failure, and renal insufficiency. With the large number of antihypertensive drugs currently available, several safety factors need to be considered when initially choosing a regimen so as not to adversely influence the potential benefits of blood pressure control. Antihypertensive agents should be chosen based on their hemodynamic profile, the absence of adverse metabolic effects and subjective side effects, and the presence of beneficial effects on the patients' quality of life. Thiazide diuretics and beta-blocking agents have often been recommended as initial therapy in patients with mild to moderate hypertension. However, thiazide diuretics may be less desirable in certain patients because of their effects on lipids, potassium, and glucose tolerance; beta-blocking agents are not ideal for some patients because of their effects on lipids, exercise tolerance, and overall quality of life. The angiotensin-converting enzyme inhibitors, selective alpha 1-blocking agents, and calcium channel blocking agents may be more appropriate for initial therapy of hypertension in many patients.

Antihypertensive Agents↗