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Biomedical subjects

D A White

Publications and source records attributed to D A White.

At least 73 records · Page 4Linked to original sources
PubMed1996

Pulmonary disease.

This article has presented the reader with an overview of the pulmonary disorders that develop during the course of HIV disease with special emphasis on the more commonly encountered entities. This information is intended to prepare the clinician to recognize the hallmark characteristics of the various diseases as well as atypical features. Despite the advances in basic understanding of the clinicopathologic consequences of infection with HIV, a cure has not been realized. There has, however, been success in controlling some of the major pulmonary problems that adversely affect both the quality and the length of life for persons with AIDS. For most complications of HIV infection, prognosis ultimately depends not only on treatment of the specific problem, but also controlling the relentless process of progressive immunosuppression. Continued research into treatment or prevention of HIV infection itself is needed, but at present prevention, rapid diagnosis, and treatment of recognized problems remain an intermediary goal.

AIDS-Related Opportunistic Infections↗
PubMed1996

Pulmonary complications of HIV-associated malignancies.

Approximately 25% of patients infected with HIV will develop malignancies, most commonly Kaposi's sarcoma and non-Hodgin's lymphoma. These tumors can involve the lung, causing significant morbidity and mortality. This article discusses the clinical presentation, diagnosis, and treatment of the pulmonary complications of the malignancies associated with HIV infection.

Humans↗
PubMed1996

Leaf water relations of Eucalyptus globulus ssp. globulus and E. nitens: seasonal, drought and species effects.

In August 1990, a 2-ha plantation was established in an area where rainfall (about 515 mm year(-1)) was insufficient to meet evaporative demand. On nine occasions between September 1991 and April 1993, pressure-volume curves were constructed for irrigated and rainfed Eucalyptus globulus ssp. globulus Labill. and E. nitens (Deane and Maiden) Maiden trees. During the experiment, rainfed trees experienced six periods when predawn water potential was significantly lower than that of irrigated trees. In early spring of 1991 and 1992, osmotic potentials at full turgor and turgor loss point in the irrigated E. nitens were significantly lower than at other times of the year, probably because of winter hardening. Water stress reduced osmotic potential and increased bulk elastic modulus in E. nitens, whereas the reverse occurred in E. globulus. However, treatment differences with respect to changes in osmotic and elastic properties were commonly overshadowed by interspecific differences. These were most apparent at the end of the sixth period of water stress when osmotic potentials at full and zero turgor were significantly higher and bulk elastic modulus and relative water content at turgor loss point were significantly lower in E. globulus than in E. nitens. We conclude that the drought-tolerance responses of E. globulus make it a more suitable species than E. nitens for establishment on sites where moderate water stress is experienced.

Journal Article↗
PubMed1996

Variation of sapflow velocity in Eucalyptus globulus with position in sapwood and use of a correction coefficient.

Sapflow sensors were used to investigate variation in sapflow velocity at different positions in the sapwood of three-year-old Eucalyptus globulus ssp. globulus Labill. trees. Sapflow velocity was measured at 5-mm intervals across the sapwood by moving two probe sets simultaneously on two opposite radii. Another probe set placed in a fixed position at right angles to the first two sets acted as a control. A sapflow velocity ratio was defined as the velocity given by each moving sensor divided by that given by the static sensor. Correlation between observations of sapflow velocity at different positions exceeded 95%, and the ratio of velocity between any pair of sensors was constant. We observed radial variation in sapflow velocity across the sapwood with the lowest velocities at the center of the tree. Variation due to sensor position was high implying the need for large numbers of sensors for accurate estimates of sap flux. To overcome this need, we used a correction coefficient, namely a simple weighted average of the sapflow ratios with depth in the sapwood, for each fixed sensor. We recommend the use of three probe sets to estimate the correction coefficient. Subsequently, two probe sets can be placed at two fixed positions for routine measurements of sap flux.

Journal Article↗
PubMed1996

Respiratory infections in HIV-negative immunocompromised patients.

The number of immunosuppressed patients is increasing, with many being managed by community physicians. Encouraging success in vaccinating some patients with Hodgkin's disease against encapsulated organisms has been reported. The significance of and management of tuberculosis in solid organ transplants is being defined. Fungal infection remains a problem, but pathogenesis and treatment are being clarified. The overall incidence of Pneumocystis carinii pneumonia is low, but it is being seen in patients without malignant disease, especially those with Wegener's granulomatosis. Many authors have tried to establish risk factors that will allow development of clear indications for prophylaxis in these patients. New approaches to cytomegalovirus infection are discussed as well as the role of community-acquired viruses in causing disease in the immunosuppressed population.

Community-Acquired Infections↗
PubMed1996

Increased expression of genes for platelet-derived growth factor in circulating mononuclear cells of hypercholesterolemic patients.

Platelet-derived growth factor (PDGF) is implicated in the accumulation of smooth muscle cells in atherosclerotic lesions following monocyte migration through the vascular endothelium. We show here a 15- to 20-fold increase in expression of PDGF-A and -B genes (as measured by a quantitative reverse transcription-polymerase chain reaction assay of mRNA concentration) in circulating monocytes of hypercholesterolemic and hyperlipidemic patients compared with normocholesterolemic individuals. Strong positive correlations between PDGF-A and -B mRNA concentrations indicate that the two genes are coordinately regulated in mononuclear cells in both normal and hypercholesterolemic individuals. PDGF gene expression in patients correlates with concentrations of plasma total cholesterol and low-density lipoprotein cholesterol, a proven risk factor for atherosclerosis. Activation of monocyte PDGF expression may be an important component of the atherosclerotic risk associated with raised cholesterol levels and may represent an essential step in the early stages of atherogenesis. However, the marked increases in PDGF mRNA levels in patients with modest hypercholesterolemia compared with normal subjects suggest that other factors are involved. The relationship of monocyte PDGF expression to other atherosclerotic risk factors and to the different stages of atherosclerosis needs to be carefully evaluated.

Adolescent↗
PubMed1996

Laterality differences in quantitative and qualitative Hooper performance.

The Hooper Visual Organization Test (HVOT) is a measure of visuospatial processing commonly employed in neuropsychological assessment. Despite the well-documented relationship between visuospatial abilities and right hemisphere function, the literature has not supported a right hemisphere association with HVOT performance. The current study was conducted to examine laterality differences in HVOT performance. Sixty-seven geriatric stroke patients (44 right CVAs, 23 left CVAs) were administered the HVOT and the Mini-Mental State Exam (MMS). Results revealed significant differences between CVA groups for total score, with right CVA patients performing more poorly. Qualitative error analyses revealed highest frequencies for part responses and don't know/no response errors. Between-group differences were seen for part and unformed/unassociated errors (higher right CVA rates), and language-based errors (higher left CVA rates). Findings are consistent with theories of brain lateralization and suggest that whereas HVOT performance predominantly involves right hemisphere functions, left hemisphere dysfunction may also lead to impaired performance, and the two can be discriminated by qualitative analysis of errors.

Journal Article↗
PubMed1995

Modulation of hepatic apolipoprotein B, 3-hydroxy-3-methylglutaryl-CoA reductase and low-density lipoprotein receptor mRNA and plasma lipoprotein concentrations by defined dietary fats. Comparison of trimyristin, tripalmitin, tristearin and triolein.

Different dietary fatty acids exert specific effects on plasma lipids but the mechanism by which this occurs is unknown. Hamsters were fed on low-cholesterol diets containing triacylglycerols enriched in specific saturated fatty acids, and effects on plasma lipids and the expression of genes involved in hepatic lipoprotein metabolism were measured. Trimyristin and tripalmitin caused significant rises in low-density lipoprotein (LDL) cholesterol which were accompanied by significant reductions in hepatic LDL receptor mRNA levels. Tripalmitin also increased hepatic expression of the apolipoprotein B gene, implying an increased production of LDL via very-low-density lipoprotein (VLDL) and decreased removal of LDL in animals fed this fat. Hepatic levels of 3-hydroxy-3-methylglutaryl-CoA reductase mRNA did not vary significantly between the groups. Compared with triolein, tristearin had little effect on hepatic gene expression or total plasma cholesterol. However, it caused a marked decrease in VLDL cholesterol and a rise in LDL cholesterol such that overall it appeared to be neutral. Lipid analysis suggested a rapid desaturation of much of the dietary stearate. The differential changes in plasma lipids and hepatic mRNA levels induced by specific dietary fats suggests a role for fatty acids or a metabolite thereof in the regulation of the expression of genes involved in lipoprotein metabolism.

Adipose Tissue↗
PubMed1995

Regulation of hamster hepatic microsomal triglyceride transfer protein mRNA levels by dietary fats.

The effect of dietary fat on hepatic microsomal triglyceride transfer protein(MTP) large subunit mRNA levels in the hamster was examined. Increasing the dietary fat concentration from 11.7 energy % to 46.8 energy % caused a 60% increase in hepatic MTP mRNA; this increase was shown to be dose-dependent (r = 0.688 p = 0.0023). MTP mRNA levels correlated significantly with several plasma lipoprotein cholesterol parameters. No significant relationship was observed between MTP mRNA and either plasma or VLDL triglyceride. The nature of the dietary fatty acids also influenced MTP mRNA levels, with trimyristin and tripalmitin enriched diets significantly elevating MTP mRNA relative to diets enriched in triolein and trilinolein.

Animals↗
PubMed1995

Folstein vs modified Mini-Mental State Examination in geriatric stroke. Stability, validity, and screening utility.

OBJECTIVE: Two studies were conducted with the Folstein Mini-Mental State Examination (MMS) and the Modified Mini-Mental State Examination (3MS) to examine whether the expanded version is a more useful screening tool in stroke populations. DESIGN: Clinical utility of screening tests (MMS and 3MS) was evaluated in reference to neuropsychological performance and functional outcome in rehabilitation. SETTING: Medical rehabilitation unit of university-affiliated hospital. PATIENTS: Two groups (n = 77, and n = 70) of patients who were admitted consecutively. MAIN OUTCOME MEASURES: Neuropsychological performance and functional outcome (functional independence measure). RESULTS: The reliability, stability, and validity of the 3MS were established in the stroke population. Classification accuracy did not differ between the MMS and 3MS, although the 3MS had higher sensitivity. In detecting cognitive impairment when compared with the extended neuropsychological battery, both instruments were adequate in patients with left-sided cerebrovascular accidents and were ineffective in patients with right-sided cerebrovascular accidents. The 3MS correlated with some cognitive domains missed by the MMS, thus adding useful clinical information. Finally, the 3MS was a significantly better predictor of functional outcome than the MMS. CONCLUSIONS: The 3MS was found to be a reliable, valid, and stable cognitive screening instrument in the stroke population. Classification accuracy indicates that both screening instruments are not strong in their ability to detect cognitive impairment in patients with stroke, especially in right-sided cerebrovascular accidents. The 3MS does have some advantages over the MMS; the expanded version of the screen not only provides additional cognitive information but also allows for better predicting of functional outcome.

Aged↗
PubMed1995

The relationship between systolic pressure and stroke volume describes myocardial contractility.

OBJECTIVE: To develop a method of measuring end-systolic elastance from information obtained outside the ventricle and thereby simplify its transduction. DESIGN: Prospective, within-animal comparative analysis. SETTING: University-based laboratory study. PARTICIPANTS: Six mixed-breed dogs. INTERVENTIONS: Instrumentation included minor axis sonomicrometry, ascending aortic flow probe, aortic and ventricular pressure transducers, and constricting cuffs on the vena cavae and aorta. MEASUREMENTS AND MAIN RESULTS: Elastance was determined from the equation PES = EES (VED - VES), where VED - VES is stroke volume and PES is end-systolic arterial pressure. EES was derived from both preload and afterload manipulation. Cardiac performance indices were calculated automatically by computer under conditions of varying load and inotropy. This extraventricular method of elastance calculation was compared by linear regression and analysis of variance to preload recruitable stroke work, traditional EES determination (using ventricular dimension instead of volume), and LVdP/dt at 50 mmHg. EES measured from the aortic sites correlated well with the other contractility indicators (p < 0.003 in all cases) and demonstrated more sensitivity and stability under loading manipulation than traditional EES. A strong relationship between the change in stroke volume and end-systolic ventricular diameter during acute aortic constriction (r = 0.924, p < 0.0001) was observed, and the mean r value for the individual outflow elastance measurements was 0.97 +/- 0.02. CONCLUSIONS: In this study, measurement of EES from the ventricular outflow tract during progressive aortic constriction produced results more consistent and descriptive than EES by traditional techniques and has the potential for obtaining elastance measurements from possibly less invasive techniques.

Analysis of Variance↗
PubMed1995

Working memory following improvements in articulation rate in children with cerebral palsy.

It has been postulated that rehearsal rate is the primary determinant of working memory capacity for verbal material (Baddeley et al., 1975). A previous study of normal control children and children with spastic diplegic cerebral palsy (SDCP) suggested that covert rather than overt rehearsal rate determines working memory capacity (White et al., 1994). In the current study, a subset of SDCP children who received a surgical treatment to relieve spasticity were retested on measures of articulation rate and memory span. A subset of control children from the original study were also retested. The SDCP group showed improvements in articulation rate at follow-up, though memory span did not change and was again equivalent to that of controls. These findings indicate that increases in articulation rate are not necessarily accompanied by improvements in memory span, and provide additional evidence that working memory capacity may be determined by covert rather than overt articulatory rehearsal.

Articulation Disorders↗
PubMed1995

The HNRC 500--neuropsychology of HIV infection at different disease stages. HIV Neurobehavioral Research Center.

The present study examined neuropsychological (NP) functioning and associated medical, neurological, brain magnetic resonance imaging (MRI), and psychiatric findings in 389 nondemented males infected with Human Immunodeficiency Virus-Type 1 (HIV-1), and in 111 uninfected controls. Using a comprehensive NP test battery, we found increased rates of impairment at each successive stage of HIV infection. HIV-related NP impairment was generally mild, especially in the medically asymptomatic stage of infection, and most often affected attention, speed of information processing, and learning efficiency; this pattern is consistent with earliest involvement of subcortical or frontostriatal brain systems. NP impairment could not be explained on the bases of mood disturbance, recreational drug or alcohol use, or constitutional symptoms; by contrast, impairment in HIV-infected subjects was related to central brain atrophy on MRI, as well as to evidence of cellular immune activation and neurological abnormalities linked to the central nervous system.

AIDS Dementia Complex↗
PubMed1995

Neuropsychological studies of asymptomatic human immunodeficiency virus-type-1 infected individuals. The HNRC Group. HIV Neurobehavioral Research Center.

The current review was conducted to address the ongoing debate regarding the presence or absence of neuropsychological impairment in asymptomatic HIV-Type 1 (HIV-1) seropositive individuals. Results were summarized from 57 studies that compared the performances of seropositive asymptomatic and seronegative individuals. Overall, the differences observed between median rates of impairment for asymptomatic (35%) and seronegative (12%) groups provided the clearest indication of deficits in asymptomatics. In addition, five variables were examined as possible contributors to inconsistencies found in the literature: mode of infection, test battery type, test battery size, sample size, and method of data analysis. Of these variables, only mode of infection and test battery size appeared to substantially influence the outcome of the studies reviewed with regard to identifying neuropsychological impairment in asymptomatics.

AIDS Dementia Complex↗
PubMed1995

Is a telephone helpline of value to the workplace smoker?

This paper reports the findings of the evaluation of a national smokers' helpline which was set up by British Telecom (BT) for its employees. The helpline formed part of a new comprehensive smoking policy for all BT staff. Over 1000 employees, more than 3.0% of all smokers, phoned the helpline during the first three months of its operation. Two-thirds of callers tried to quit smoking after calling the helpline, and a quarter were still successful three months later. One in six callers reduced the number of cigarettes that they smoked on working days. While the helpline and other cessation support services were evaluated positively by callers, it appears that helplines only appeal to a small minority of smokers. However, they do seem to be an effective mechanism for a nationwide company to identify those smokers who want support, and a useful means of centralizing the administration of support services. They are potentially a cost-effective option for larger employers.

Adolescent↗
PubMed1995

Syndrome of acute dyspnea related to combined mitomycin plus vinca alkaloid chemotherapy.

We report the incidence, clinical features, and course of acute dyspnea following combination chemotherapy using mitomycin and vindesine or vinblastine. The courses of 387 patients with advanced non-small cell lung cancer receiving combined mitomycin and vinca alkaloid chemotherapy were analyzed. Of these patients, 25 experienced acute respiratory distress. Factors contributing to the dyspnea are reported. The syndrome is characterized by the sudden onset of dyspnea without other respiratory symptoms. Acute shortness of breath always occurred on a day when a vinca alkaloid was administered. The median number of previous doses of vinca alkaloid at the time of the event was 10 and the median number of prior mitomycin doses was 3. Rechallenge with the drug in two cases led to recurrence. The incidence was 4% in a group of 378 patients on four protocols for non-small cell lung cancer. Radiographs of 87% of patients showed new focal or diffuse interstitial infiltrates. Arterial blood gases demonstrated low PO2 and increase in A-a gradient. Pulmonary function tests revealed severely impaired diffusing capacity. Substantial improvement occurred over 24 hours. Approximately 60% of the patients experienced chronic respiratory impairment that only partially responded to corticosteroid therapy. No other causes for this syndrome were identified. A syndrome of acute dyspnea occurred in 4% of patients treated with mitomycin and vinca alkaloid therapy. The syndrome has a distinctive presentation, which can lead to chronic pulmonary insufficiency. Clinicians caring for patients receiving combined therapy with mitomycin and a vinca alkaloid should be aware of this type of acute pulmonary toxicity. Further studies are necessary to clarify its etiology.

Acute Disease↗
PubMed1995

Diffuse idiopathic pulmonary neuroendocrine cell proliferation presenting as interstitial lung disease.

Pulmonary neuroendocrine cell (PNEC) hyperplasia typically occurs as an adaptive response in persons living at high altitudes and as a reactive response in the setting of lung injury. However, previous studies suggest that PNEC hyperplasia can occur in the absence of preexisting lung disease and may even give rise to airway disease through the development of pulmonary tumorlets and airway fibrosis and perhaps the release of paracrine secretions. We describe a patient with diffuse PNEC proliferation of a probable hyperplastic nature developing in the absence of a chronic pulmonary disorder who presented clinically with an interstitial lung process. Open lung biopsy displayed a florid intraepithelial population of PNEC diffusely involving the distal airways and alveoli with desquamation and filling of alveolar spaces by nests of PNEC. The presence of alveolar thickening was attributable to the intraepithelial proliferation of PNEC associated with interstitial fibrosis and accounted for mild reductions in the pulmonary diffusing capacity. The neuroendocrine differentiation of this proliferation was evident by light microscopic and ultrastructural examination. The absence of airway fibrosis and pulmonary tumorlets was in agreement with the lack of clinical airway disease in this case. The intraepithelial growth and absence of parenchymal invasion in this lesion favor a diffuse, florid PNEC hyperplasia with mild dysplastic features over a pulmonary neuroendocrine neoplasm.

Aged↗