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Biomedical subjects

G Smith

Publications and source records attributed to G Smith.

At least 307 records · Page 17Linked to original sources
PubMed1997

Density-dependent seasonal dynamics of blacklegged tick (Acari:Ixodidae) nymphs.

The midsummer seasonal decline in abundance of unfed Ixodes scapularis Say nymphs on experimental plots in New Jersey was density-dependent. Nymph density was manipulated on 9 plots (10 by 10 m each) in Morristown. National Historical Park, NJ, in early June 1994. Subsequent rates of decline were directly proportional to initial density (linear regression, R2 = 0.83). A 6-fold manipulation of density caused more than a 10-fold increase in per-capita disappearance rate. Absence of density-dependent mortality in simultaneous field cage experiments implicated dispersal at rates higher than reported previously, positive-density-dependent host finding success, or predation, possibly in the form of host grooming. Each of these possibilities has important implications for the role of unfed nymphs in the regulation of I. scapularis populations.

Animals↗
PubMed1997

Physostigmine reversal of scopolamine-induced hypofrontality.

The muscarinic receptor antagonist scopolamine produces a transient memory deficit in healthy humans. This deficit has been offered as a model of the cholinergic deficit of Alzheimer's disease (AD). However, we have previously shown that scopolamine produces a deficit of cortical perfusion maximal in the frontal lobe, dissimilar to the parietal cortex deficit characteristic of AD. The current experiment was aimed at replicating and extending this observation by critically testing the central cholinergic origin of both cognitive and perfusion deficits. Nine healthy subjects participated in regional cerebral blood flow (rCBF) measurements at baseline, after scopolamine (7.2 micrograms/kg i.v.), and after both physostigmine (22 micrograms/kg i.v.) and neostigmine (7 or 11 micrograms/kg i.v.). rCBF was quantified by the xenon 133 inhalation method. As expected, scopolamine reduced cortical perfusion, mainly in the frontal cortex, and produced a memory deficit. Physostigmine, but not neostigmine, reversed all three variables partially or completely. These results support the hypothesis that all three consequences of scopolamine, namely, reduction of mean flow, frontal deficit, and memory impairment, are cholinergically mediated. Furthermore, because neostigmine poorly crosses the blood-brain barrier, these findings confirm that the effect is centrally mediated and cannot be explained by peripheral effects. However, they also confirm the frontal cortex locus of action for both scopolamine and its reversal by physostigmine and therefore suggest a major dissimilarity to the characteristic rCBF appearance of AD. This study extends our previous preliminary findings with tacrine and strengthens the suggestion that only nicotinic receptors are associated with the characteristic parietal deficit of AD.

Acetylcholine↗
PubMed1997

Changes in equivalent and gradient refractive index of the crystalline lens with accommodation.

The ocular dimensions and refraction of the eye were measured for accommodation stimulus levels of 0.0, 1.5, 3.5, 5.5, and 8.0 D for 11 subjects aged 18 to 28 years, mean 21.2 +/- 2.62 years using keratometry, autorefraction, A-Scan ultrasonography, and video phakometry techniques. The subjects had refractive errors in the range + 0.50 to -4.25 D, mean -1.88 +/- 1.64 D. With the maximum level of accommodation the anterior chamber depth decreased by 0.23 +/- 0.09 mm, the lens thickness increased by 0.28 +/- 0.09 mm, and no significant differences were recorded in axial length or vitreous chamber depth. The radius of curvature of the anterior surface of the crystalline lens decreased from 11.54 +/- 1.27 to 6.59 +/- 0.97 mm and the posterior surface from -6.67 +/- 0.97 to -5.30 +/- 0.4 mm. We determined the equivalent refractive index to be 1.4277 +/- 0.0011, with no significant differences at different levels of accommodation. When the crystalline lens was modeled as a gradient refractive index (GRIN) structure with elliptical iso-indicial lines, the mean surface refractive index of the lens was 1.3859 +/- 0.0009 for an assumed central refractive index of 1.406. The power of the anterior surface of the lens increased from 4.38 +/- 0.49 to 7.59 +/- 0.34 D, the posterior surface increased from 7.67 +/- 1.28 to 9.32 +/- 0.64 D, and the GRIN power increased from 9.70 +/- 1.31 to 13.74 +/- 0.77 D for the maximum accommodative stimulus of 8.00 D. On the basis of the model used, a substantial part of the increase in power of the crystalline lens with accommodation resulted from the change in refractive index distribution within the lens.

Accommodation, Ocular↗
PubMed1997

Marek's disease virus EcoRI-Q gene (meq) and a small RNA antisense to ICP4 are abundantly expressed in CD4+ cells and cells carrying a novel lymphoid marker, AV37, in Marek's disease lymphomas.

Mature lymphomas produced in Rhode Island Red (RIR) chickens infected with the RB1B strain of Marek's disease virus (MDV) were examined for the presence of viral DNA and RNA and expression of viral antigens. In situ hybridization showed that all tumours examined contained viral DNA in areas of lymphoid infiltration. In 3/5 tumours, there was a correlation between the number and distribution of cells expressing the Marek's disease EcoRI-Q gene (meq) and those that carried the lymphoid cell marker AV37. Expression of the MDV-specific phosphoprotein pp38 was infrequent in lymphomas but abundant in a splenic tumour which also expressed the viral glycoprotein gB. Northern blot analysis of lymphocyte fractions purified by immunoaffinity showed that CD4+ and AV37+ fractions from lymphomas expressed meq and the small RNA antisense to ICP4 (SAR). The results are consistent with the notion that transformed cells are CD4+ cells, carrying the AV37 marker and expressing meq and SAR.

Animals↗
PubMed1997

Provision of physiotherapy services at the sixth All Africa Games.

The provision of physiotherapy services to guest nations by the host nation, Zimbabwe, at the sixth All Africa Games is examined. There was a high rate of pre-existing injury. Ice, the Cryocuff, and ultrasound were the most frequently used tools, and should be made available to physiotherapists at all multisport events. It is recommended that collection of epidemiological data be standardised to allow comparison between events.

Africa↗
PubMed1997

Latex allergy: epidemiological study of 1351 hospital workers.

OBJECTIVE: To determine the prevalence of latex sensitisation among a large group of healthcare workers, study the occupational and non-occupational factors associated with latex allergy, and characterise latex exposure in air and by gloves. METHODS: All 2062 employees of a general hospital in Hamilton, Ontario, Canada who regularly used latex gloves were invited to participate in a cross sectional survey, representing the baseline phase of a prospective cohort morbidity study. Attempts were made to recruit employees who were diagnosed with latex allergy before the survey. Glove extracts were assayed for antigenic protein, and area and personal air samples were obtained on two occasions (summer and winter) to estimate exposure to airborne latex protein. A questionnaire on medical and occupational information was administered by an interviewer. Skin prick tests were performed with latex reagents, three common inhalants, and six foods. RESULTS: The mean (SD) latex protein concentrations were 324 (227) micrograms/g in powdered surgical gloves and 198 (104) micrograms/g in powdered examination gloves. Personal latex aeroallergen concentrations ranged from 5 to 616 ng/m3. There was a total of 1351 (66%) participants. The prevalence of positive latex skin tests was 12.1% (95% confidence interval (95% CI) 10.3% to 13.9%). This prevalence did not vary by sex, age, hospital, or smoking status but subjects who were latex positive were significantly more likely to be atopic (P < 0.01). Participants who were latex positive were also significantly more likely to have positive skin tests to one or more foods (Mantel-Haenszel odds ratio (OR) adjusted for atopy 12.1, 95% CI 7.6 to 19.6, P < 10(-9)). Work related symptoms were more often reported among latex positive people, and included hives (OR 6.3, 95% CI 3.2 to 12.5), eye symptoms (OR 1.9, 95% CI 1.2 to 2.8), and wheezy or whistling chest (OR 4.7, 95% CI 2.8 to 7.9). The prevalence of latex sensitivity was highest among laboratory workers (16.9%), and nurses and physicians (13.3%). When the glove consumption per healthcare worker for each department was grouped into tertiles, the prevalence of latex skin test positivity was greater in the higher tertiles of glove use for sterile (surgical) gloves (P < 0.005) but not for examination gloves. CONCLUSIONS: In this large, cross sectional study of healthcare workers, the prevalence of latex sensitisation was 12.1% (9.5% among all those eligible), and there were significant associations with atopy, positive skin tests to certain foods, work related symptoms, and departmental use of gloves per healthcare worker. This cohort is being followed up prospectively and will be retested to determine the incidence of development of latex sensitivity.

Adult↗
PubMed1997

Decreasing disruptive behavior by adolescent boys in residential care by increasing their positive to negative interactional ratios.

An intervention for disruptive boys in residential care involving increases in positive to negative interactional ratios is described. The target of the intervention was daily problem behavior. Results from a pooled time series analysis of the data revealed a significant decrease in behavior problems (one problem per boy per day) during the intervention for the boys as a group. Results from comparisons of mean behavior problems during baseline and intervention revealed decreases for five of the six boys. Results from a multiple baseline across boys revealed experimental control for three of the six. The results are discussed in terms of response contingent reinforcement and systemic behavior analyses. The benefits of combined group and single subject data analyses are also discussed.

Adolescent↗
PubMed1997

Equivalent power of the crystalline lens of the human eye: comparison of methods of calculation.

We present four methods, with different levels of sophistication and precision, for calculating the refractive power of the ocular lens from its optical structure. The first method uses finite ray tracing but simulates a paraxial ray by using small ray heights. The second method involves a recursive paraxial ray-tracing procedure. The other two methods do not depend on any ray-tracing procedure but use much simpler, approximate equations. In the third method the ray height is assumed not to change within the lens, and in the fourth method the ray path is assumed to be parabolic. The fourth method, but not the third method, can separately calculate the power of the surfaces and the gradient-index lens bulk, which are then used in the three-lens equation to calculate the power of the lens as a whole.

Humans↗
PubMed1997

Improved respiratory function and analgesia control after endovascular AAA repair.

PURPOSE: Endovascular abdominal aortic aneurysm (AAA) repair has been proposed as a minimally invasive alternative to conventional surgery and may offer significant advantages in respiratory function and analgesic requirements due to the absence of an abdominal incision. METHODS: Respiratory function and analgesic requirements were quantified in 22 age-matched patients undergoing aneurysm repair under general anesthesia. Twelve patients underwent endovascular aneurysm repair, while 10 AAA patients had conventional surgery. One endovascular patient required conversion to conventional repair. RESULTS: The endovascular group required postoperative artificial ventilation for a shorter time (6 versus 21 hours, p < 0.05) and had lower PCA (patient-controlled analgesia) morphine consumption (41 versus 133 mg, p < 0.05) than the conventional group. The endovascular group also had significantly better forced expiratory volume and forced vital capacity at both 3 and 5 days when expressed as percentages of the preoperative values (p < 0.05). CONCLUSIONS: Endovascular AAA repair attenuates respiratory dysfunction associated with conventional surgery and reduces perioperative analgesia requirements.

Aged↗
PubMed1997

Controlled gene gun delivery and expression of DNA within the cornea.

Selective delivery of genes to ocular tissues in vivo has been a long sought after goal for potential gene therapy of ocular disease. The gene gun was considered for this purpose because of its ability to focally transfer DNA to cells through gold microparticles coated with DNA. Through experimentation, we optimized a technique that allows focal delivery and expression of a plasmid encoding green fluorescent protein in the corneal epithelium 100% of the time. Though the corneal epithelium has a delicate structure, this introduction was not associated with any corneal or ocular damage and did not produce any apparent ocular irritation. These findings demonstrate the utility of gene gun delivery of DNA to selected ocular tissues for potential experimental and therapeutic purposes.

Animals↗
PubMed1997

A comparison of the cytology of endomyocardial biopsy washings from heart transplants with biopsy histologic study and peripheral blood lymphocyte counts.

Cytospin preparations of endomyocardial biopsy washings were examined on 117 occasions from 13 heart transplant recipients and categorized according to the pattern of cell types observed. Twenty-nine percent of samples were acellular, a further 10% too bloodstained for analysis, and 61% were cellular. Eight lymphocytic samples were found and in all cases there was at least grade 1B rejection (four grade 1B, three grade 2, and one grade 3A) on histologic study. However, histologic study showed at least 1B rejection in 48% of cases when cytospins showed mixed inflammatory cells, 33% of cases when cytospins were histiocytic and in 35% when cytospins were bloodstained or acellular. Furthermore 16 of these rejection episodes with nonlymphocytic cytospins were grade 2. Although the recovery of a lymphocytic cytospin was specific for rejection, the sensitivity of the test was poor. Even when the sample is adequate, this method of biopsy washings will predict only one third of cases of significant acute rejection (grade 2 or worse). The large proportion of unsuitable samples also severely limits the utility of endomyocardial biopsy washings for the diagnosis of rejection. Histiocytic cytospins were seen in 63% of samples when previous biopsy sites were reported on histologic study and also in all three samples when histologic study showed ischemic injury. A mixed inflammatory cell pattern was seen to a lesser extent (31% of samples) in relation to previous biopsy sites. High peripheral blood lymphocyte counts were found when endomyocardial biopsy washings were lymphocytic or mixed inflammatory and also when histologic study showed endocardial lymphocytic infiltration (Quilty effect).

Biopsy↗
PubMed1997

Simultaneous hemodynamic and echocardiographic changes during abdominal gas insufflation.

The purpose of this study was to investigate cardiovascular changes during CO2 pneumoperitoneum. We performed simultaneous hemodynamic recordings and transesophageal echocardiographic measurements of possible alterations in cardiac dimensions. Seven patients scheduled for elective laparoscopic cholecystectomy were investigated. With an intraabdominal pressure of 15 mm Hg, mean arterial pressure increased from 75 to 93 mm Hg (p < 0.05). Despite the increase in pulmonary capillary wedge pressure (PCWP) from 10 (9.5-12) to 17 (16-19.9) mm Hg (p < 0.05), left ventricular end-diastolic area index (EDAI) did not change significantly. The cardiac index remained unchanged. Thus abdominal gas insufflation substantially alters the PCWP/EDAI relation. During pneumoperitoneum, left ventricular filling pressure, estimated by PCWP, cannot be used as an indicator of left ventricular dilation.

Adult↗
PubMed1997

Accelerating response in geriatric depression: a pilot study combining sleep deprivation and paroxetine.

Elderly depressed patients often require an average of 12 weeks of pharmacotherapy before attaining remission. The delay between treatment initiation and remission may decrease compliance and prolongs suffering; hence, interventions that decrease the time to onset of antidepressant activity are needed. Our objective was to evaluate, in an open trial, the use of one night of total sleep deprivation combined with paroxetine to accelerate antidepressant response in elderly patients. Thirteen elderly patients with major depression were sleep-deprived for one night and started paroxetine on the night of recovery sleep. Patients were followed for twelve weeks, and clinical improvement was rated using the 17-item Hamilton Depression Rating Scale and a version of the Hamilton modified for sleep deprivation studies. 8/13 (62%) patients experienced significant improvement of depressive symptoms by 2 weeks. Within 12 weeks 11/13 (85%) patients responded to the combination of sleep deprivation and paroxetine. Median response time was 2 weeks. Clinical response at 12 weeks was correlated with changes in Sleep Deprivation Depression Rating Scale Scores between baseline and recovery sleep. In an open trial, the combined use of total sleep deprivation and paroxetine appears to be an effective method for speeding the onset of clinical antidepressant activity in geriatric depression and for improving early recognition of non-response.

Aged↗
PubMed1996

Quantitative estimation of epidermal growth factor receptor and c-erbB-2 in human breast cancer.

Epidermal growth factor receptor (EGFR) expression by human breast cancer has been shown to predict poor patient outcome, as has amplification of the c-erbB-2 proto-oncogene. We have developed a quantitative immunohistochemical method for measuring protein levels of both receptors and have applied this to a series of 123 breast primaries. We find EGFR expression is substantially lower than normal in nearly all breast cancers (97%). Quantification of p185erbB-2 indicates overexpression in 91% of the tumors. Two separate tumor populations are apparent with levels of c-erbB-2 expression ranging from 0.33 to 19 and 45 to 480 times normal, respectively. Within the lower population, p185erbB-2 expression is inversely related to EGFR expression (rank correlation, P < 0.0005). Using fluorescent in situ hybridization we show that tumors in the latter population have c-erbB-2 amplification and that amplification is restricted to this group. Our findings indicate that significant overexpression of p185erbB-2 occurs in the absence of amplification; these lower levels of expression may have functional significance. Fifty-three patients underwent in vivo bromodeoxyuridine labeling, allowing flow cytometric analysis of tumor cell cycle kinetics. EGFR expression correlates directly to the labeling index (P = 0.011) and indirectly to potential doubling time (P = 0.010), but not to the duration of the S-phase (P = 0.502). Conversely, p185erbB-2 expression does not relate to indices of proliferation. Our results have important implications for the use of both receptor types as therapeutic targets.

Adolescent↗
PubMed1996

Interleukin-1 beta-converting enzyme-like protease cleaves DNA-dependent protein kinase in cytotoxic T cell killing.

Cytotoxic T cells (CTL) represent the major defense mechanism against the spread of virus infection. It is believed that the pore-forming protein, perforin, facilitates the entry of a series of serine proteases (particularly granzyme B) into the target cell which ultimately leads to DNA fragmentation and apoptosis. We demonstrate here that during CTL-mediated cytolysis the catalytic subunit of DNA-dependent protein kinase (DNA-PKcs), an enzyme implicated in the repair of double strand breaks in DNA, is specifically cleaved by an interleukin (IL)-1 beta-converting enzyme (ICE)-like protease. A serine protease inhibitor, 3,4-dichloroisocoumarin (DCl), which is known to block granzyme B activity, inhibited CTL-induced apoptosis and prevented the degradation of DNA-PKcs in cells but failed to prevent the degradation of purified DNA-PKcs by CTL extracts. However, Tyr-Val-Ala-Asp-CH2Cl (YVAD-CMK) and other cysteine protease inhibitors prevented the degradation of purified DNA-PKcs by CTL extracts. Furthermore, incubation of DNA-PKcs with granzyme B did not produce the same cleavage pattern observed in cells undergoing apoptosis and when this substrate was incubated with either CTL extracts or the ICE-like protease, CPP32. Sequence analysis revealed that the cleavage site in DNA-PKcs during CTL killing was the same as that when this substrate was exposed to CPP32. This study demonstrates for the first time that the cleavage of DNA-PKcs in this intact cell system is exclusively due to an ICE-like protease.

Amino Acid Sequence↗