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Biomedical subjects

S M Davis

Publications and source records attributed to S M Davis.

At least 55 records · Page 3Linked to original sources
PubMed2000

Comparison of DSM-III-R chronic major depression and major depression superimposed on dysthymia (double depression): validity of the distinction.

The nosology of chronic depression has become increasingly complex since the publication of the revised third edition of the Diagnostic and Statistical Manual of Mental Disorders (DSM-III-R; American Psychiatric Association, 1987), but there are few data available to evaluate the validity of the distinctions between the subtypes of chronic depression. The validity of the distinction between DSM-III-R chronic major depression (CMD) and major depression superimposed on dysthymia (double depression, DD) was examined. Participants were 635 patients with chronic depression in a 12-week trial of antidepressant medications. Patients with CMD, DD, and a 3rd group with a chronic major depressive episode superimposed on dysthymia (DD/CMD) were compared on demographic and clinical characteristics, family history, and response to treatment. Few differences were evident, although the depression of patients with DD/CMD tended to be more severe.

Adult↗
PubMed1999

Absent middle cerebral artery flow predicts the presence and evolution of the ischemic penumbra.

OBJECTIVES: In acute ischemic stroke the pattern of a perfusion-imaging (PI) lesion larger than the diffusion-weighted imaging (DWI) lesion may be a marker of the ischemic penumbra. We hypothesized that acute middle cerebral artery (MCA) occlusion would predict the presence of presumed "penumbral" patterns (PI > DWI), ischemic core evolution, and stroke outcome. METHODS: Echoplanar PI, DWI, and magnetic resonance angiography (MRA) were performed in 26 patients with MCA territory stroke. Imaging and clinical studies (Canadian Neurological Scale, Barthel Index, and Rankin Scale) were performed within 24 hours of onset and repeated at days 4 and 90. RESULTS: MCA flow was absent in 9 of 26 patients. This was associated with larger acute PI and DWI lesions, greater PI/DWI mismatch, early DWI lesion expansion, larger final infarct size, worse clinical outcome (p < 0.01) and provided independent prognostic information (multiple linear regression analysis, p < 0.05). Acute penumbral patterns were present in 14 of 26 patients. Most of these patients (9 of 14) had no MCA flow, whereas all nonpenumbral patients (PI < or = DWI lesion) had MCA flow (p < 0.001). Penumbral-pattern patients with absent MCA flow had greater DWI lesion expansion (p < 0.05) and worse clinical outcome (Rankin Scale score, p < 0.05). CONCLUSIONS: Absent MCA flow on MRA predicts the presence of a presumed penumbral pattern on acute PI and DWI and worse stroke outcome. Combined MRA, PI, and DWI can identify individual patients at risk of ischemic core progression and the potential to respond to thrombolytic therapy beyond 3 hours.

Adult↗
PubMed1999

Preventive health care among rural American Indians in New Mexico.

BACKGROUND: Incidence of and mortality from cardiovascular disease, cancer, diabetes, and other chronic diseases are rapidly increasing among American Indians; however, the utilization of preventive services for these conditions is not well characterized in these ethnic groups. METHODS: We interviewed 1,273 American Indian adults in New Mexico, ages 18 years and older, by telephone regarding routine health checks, including blood pressure, blood cholesterol, mammograms, clinical breast exams, Pap smears, influenza and pneumonia vaccinations, and diabetes using items from the CDC Behavioral Risk Factor Surveillance System. RESULTS: We found that utilization of preventive service was surprisingly high among rural American Indians. Routine health checks and blood pressure checks within the past year were reported by more than 70% of the population. Blood cholesterol checks (41.1%) and pneumonia vaccinations (30.7%) were less commonly reported. Utilization of cancer screening for the most common women's cancers was also high. Most women reported ever having a Pap smear test (88.3%), a clinical breast examination (79.5%), and a mammogram (75.6%). The prevalence of diagnosed diabetes (8.8% overall and 26.4% for ages 50 years and older) greatly exceeds the nationwide prevalence. CONCLUSIONS: The utilization of preventive services delivered by a unique governmental partnership is high among American Indians in New Mexico and, except for cholesterol screening, is comparable with rates for the U.S. population. Because cardiovascular disease is on the rise, more attention to preventive services in this arena is warranted. The high and increasing prevalence of diagnosed diabetes suggests that aggressive diabetes screening and interventions are needed.

Adult↗
PubMed1999

Practicing participatory research in American Indian communities.

The purpose of this article is to explore the historical issues that affect research in American Indian communities and examine the implications of these issues as they relate to culturally sensitive, respectful, and appropriate research with this population. Methods include review and analysis of the literature and examination of our collective experience and that of our colleagues. Recommendations are given for conducting culturally sensitive, participatory research. We conclude that research efforts must build on the establishment of partnerships between investigators and American Indian communities to ensure accurate findings and analyses and to implement culturally relevant benefits.

Asian People↗
PubMed1999

Multisite formative assessment for the Pathways study to prevent obesity in American Indian schoolchildren.

We describe the formative assessment process, using an approach based on social learning theory, for the development of a school-based obesity-prevention intervention into which cultural perspectives are integrated. The feasibility phase of the Pathways study was conducted in multiple settings in 6 American Indian nations. The Pathways formative assessment collected both qualitative and quantitative data. The qualitative data identified key social and environmental issues and enabled local people to express their own needs and views. The quantitative, structured data permitted comparison across sites. Both types of data were integrated by using a conceptual and procedural model. The formative assessment results were used to identify and rank the behavioral risk factors that were to become the focus of the Pathways intervention and to provide guidance on developing common intervention strategies that would be culturally appropriate and acceptable to all sites.

Asian People↗
PubMed1999

Pathways: a culturally appropriate obesity-prevention program for American Indian schoolchildren.

Pathways, a culturally appropriate obesity prevention study for third-, fourth-, and fifth-grade American Indian schoolchildren includes an intervention that promotes increased physical activity and healthful eating behaviors. The Pathways intervention, developed through a collaboration of universities and American Indian nations, schools, and families, focuses on individual, behavioral, and environmental factors and merges constructs from social learning theory with American Indian customs and practices. We describe the Pathways program developed during 3 y of feasibility testing in American Indian schools, with special emphasis on the activities developed for the third grade; review the theoretical and cultural underpinnings of the program; outline the construction process of the intervention; detail the curriculum and physical education components of the intervention; and summarize the formative assessment and the school food service and family components of the intervention.

Asian People↗
PubMed1999

Pathways family intervention for third-grade American Indian children.

The goal of the feasibility phase of the Pathways family intervention was to work with families of third-grade American Indian children to reinforce health behaviors being promoted by the curriculum, food service, and physical activity components of this school-based obesity prevention intervention. Family behaviors regarding food choices and physical activity were identified and ranked according to priority by using formative assessment and a literature review of school-based programs that included a family component. The family intervention involved 3 primary strategies designed to create an informed home environment supportive of behavioral change: 1) giving the children "family packs" containing worksheets, interactive assignments, healthful snacks, and low-fat tips and recipes to take home to share with their families; 2) implementing family events at the school to provide a fun atmosphere in which health education concepts could be introduced and reinforced; and 3) forming school-based family advisory councils composed of family members and community volunteers who provided feedback on Pathways strategies, helped negotiate barriers, and explored ideas for continued family participation. For strategy 2, a kick-off Family Fun Night provided a series of learning booths that presented the healthful behaviors taught by Pathways. At an end-of-year Family Celebration, a healthy meal was served, students demonstrated newly learned Pathways activities, and certificates were presented in recognition of completion of the Pathways curriculum. Based on evaluation forms and attendance rosters, strategies 1 and 2 were more easily implemented and better received than strategy 3. Implications for developing family involvement strategies for intervention programs are discussed.

Adult↗
PubMed1999

Process evaluation in a multisite, primary obesity-prevention trial in American Indian schoolchildren.

We describe the development, implementation, and use of the process evaluation component of a multisite, primary obesity prevention trial for American Indian schoolchildren. We describe the development and pilot testing of the instruments, provide some examples of the criteria for instrument selection, and provide examples of how process evaluation results were used to document and refine intervention components. The theoretical and applied framework of the process evaluation was based on diffusion theory, social learning theory, and the desire for triangulation of multiple modes of data collection. The primary objectives of the process evaluation were to systematically document the training process, content, and implementation of 4 components of the intervention. The process evaluation was developed and implemented collaboratively so that it met the needs of both the evaluators and those who would be implementing the intervention components. Process evaluation results revealed that observation and structured interviews provided the most informative data; however, these methods were the most expensive and time consuming and required the highest level of skill to undertake. Although the literature is full of idealism regarding the uses of process evaluation for formative and summative purposes, in reality, many persons are sensitive to having their work evaluated in such an in-depth, context-based manner as is described. For this reason, use of structured, quantitative, highly objective tools may be more effective than qualitative methods, which appear to be more dependent on the skills and biases of the researcher and the context in which they are used.

Asian People↗
PubMed1999

Cervicocerebral artery dissections.

OBJECTIVE: To determine the aetiology, frequency, presentation, and outcome of blunt cervicocerebral arterial dissection presentations. PATIENTS AND METHODS: Cases were retrospectively identified through the stroke registers at Royal Melbourne Hospital (a tertiary teaching hospital) and Geelong Hospital (a regional referral centre). Medical notes were then reviewed. RESULTS: A total of 18 cases were identified, with ages ranging from 28 to 53 years. Fifty five per cent of the injuries sustained were to the internal carotid artery and 45% to the vertebral artery. The majority of the injuries were either spontaneous or associated with trivial forces. Other causes included motor vehicle accidents, falls, and cervical manipulations. Fifty five per cent of patients complained of significant neck pain before presentation. Most patients had delayed presentations, with only 39% presenting on the day of the incident. Seventy eight per cent presented with a neurological deficit. Initial computed tomography was normal in 71% of patients. The majority of patients were managed with anticoagulation, and had minimal functional deficit on discharge. Other treatment modalities included surgery (one patient) and thrombolysis (two patients). One patient was managed conservatively. CONCLUSIONS: The incidence of blunt cervicocerebral arterial dissection is unknown; however it is an uncommon diagnosis. The most common presentation is that of a delayed neurological event. Initial brain computed tomography is usually normal. Minimal adverse outcomes at discharge were noted in patients treated with anticoagulation only.

Adult↗
PubMed1999

Antiviral effect of gingyo-san, a traditional Chinese herbal medicine, on influenza A2 virus infection in mice.

Gingyo-san is a crude drug containing extracts from 7 medicinal plants and fermented soybeans in a specific ratio. It has been used clinically in China as a therapeutic agent for the common cold. In the present study, we examined the antiviral effect of this agent on influenza virus infection in mice. Gingyo-san and its components were administered orally to mice 1 day before, then 1 and 4 days after the inhalation of a mouse-adopted strain of influenza A2 (H2N2) virus. After infection with a 10 LD50 of the virus, 100% of mice treated with 10 mg/kg of the agent survived as compared with a 0% survival of control mice treated with saline. Also, the mean survival days were increased and consolidation scores were decreased in treated mice as compared with those of control mice. Two components contained in the agent, extracts from Glycyrrhizae radix and Arctii fructus, expressed antiviral activities in mice infected with influenza virus. However, in vitro growth of influenza virus in MDCK cells or viability of the virus was not affected by these extracts or Gingyo-san. From these results Gingyo-san was shown to be an antiviral agent in mice infected with a lethal amount of a mouse-adopted strain of influenza A2 virus.

Animals↗
PubMed1999

Pathophysiological topography of acute ischemia by combined diffusion-weighted and perfusion MRI.

BACKGROUND AND PURPOSE: Combined echoplanar MRI diffusion-weighted imaging (DWI), perfusion imaging (PI), and magnetic resonance angiography (MRA) can be used to visualize acute brain ischemia and predict lesion evolution and functional outcome. The appearance of a larger lesion by PI than by DWI quantitatively defines a mismatch of potential clinical importance. Qualitative lesion variations exist in the topographic concordance of this mismatch. We examined both the topographic heterogeneity and relative frequency of mismatched patterns in acute stroke using these MRI techniques. METHODS: Acute DWI, PI, and MRA studies of 34 prospectively recruited patients with supratentorial ischemic lesions scanned within 24 hours of stroke onset (range 2.5 to 23.3 hours, 12 patients <6 hours) were analyzed. RESULTS: Ischemic lesions were predominantly in the middle cerebral artery (MCA) territory (94%), with DWI lesions most commonly affecting the insular region. Mismatched patterns with PI lesion larger than DWI lesion occurred in 21 patients (62% overall), in all 4 patients imaged within 3 hours, and in 44% of patients imaged after 18 hours. A patient with a large PI but no DWI lesion and severe clinical deficit at 2.5 hours after stroke onset recovered completely. Regional variations in DWI and PI lesion loci were found, inferring site of proximal MCA occlusion, embolic pathogenesis, and regional arterial reperfusion. CONCLUSIONS: Analysis of the topographic concordance of PI and DWI lesions in acute stroke reveals regional PI lesions without concomitant DWI lesions, which do not necessarily progress to infarction but may suggest stroke pathogenesis and site of current arterial occlusion. Location of DWI lesions may suggest an earlier site of arterial occlusion and regions of maximal perfusion deficit.

Aged↗
PubMed1999

Identification of major ischemic change. Diffusion-weighted imaging versus computed tomography.

BACKGROUND AND PURPOSE: Thrombolytic therapy is not recommended in patients with CT changes of recent major infarction, which has been defined as reduced attenuation or cerebral edema involving >33% of the middle cerebral artery territory (European Cooperative Acute Stroke Study [ECASS] criteria). Diffusion-weighted imaging (DWI) is more sensitive than CT in detecting acute ischemia, and the combination of DWI, MR perfusion imaging, and MR angiography provides additional information from a single examination. We sought to determine whether DWI could identify the presence and extent of major ischemia as well as CT in hyperacute stroke patients. METHODS: Seventeen suspected hemispheric stroke patients were studied with both CT and DWI within 6 hours of symptom onset. None received thrombolytic therapy. The scans were examined separately by 2 neuroradiologists in a blinded fashion for ischemic change and cerebral edema, graded as normal, <33%, or >33% of the MCA territory. Final diagnosis of stroke was determined with the use of standard clinical criteria and T2-weighted imaging at day 90. RESULTS: Sixteen of 17 patients had a final diagnosis of stroke. Acute ischemic changes were seen in all 16 on DWI (100% sensitivity) and in 12 of 16 on CT (75% sensitivity). DWI identified all 6 patients with major ischemia on CT, with excellent agreement between the 2 imaging techniques (kappa=0.88). One patient eligible for thrombolysis on the ECASS CT criteria had major ischemia on DWI. CONCLUSIONS: DWI is more sensitive than CT in the identification of acute ischemia and can visualize major ischemia more easily than CT.

Adult↗
PubMed1999

Serial study of apparent diffusion coefficient and anisotropy in patients with acute stroke.

BACKGROUND AND PURPOSE: We sought to characterize the evolution of apparent diffusion coefficient (ADC) and apparent diffusion anisotropy (ADA) in acute stroke and to evaluate their roles in predicting stroke evolution and outcome. METHODS: We studied 26 stroke patients acutely (<24 hours), subacutely (3 to 5 days), and at outcome (3 months). Ratios of the ADC and ADA within a region of infarction and the normal contralateral region were evaluated and compared with the Canadian Neurological Scale, Barthel Index, and Rankin Scale. RESULTS: Heterogeneity in ADC and ADA evolution was observed not only between patients but also within individual lesions. Three patterns of ADA evolution were observed: (1) elevated ADA acutely and subacutely; (2) elevated ADA acutely and reduced ADA subacutely; and (3) reduced ADA acutely and subacutely. At outcome, reduced ADA with elevated ADC was observed generally. We identified 3 phases of diffusion abnormalities: (1) reduced ADC and elevated ADA; (2) reduced ADC and reduced ADA; and (3) elevated ADC and reduced ADA. The ADA ratios within 12 hours correlated with the acute Canadian Neurological Scale (r=0.46, P=0.06), subacute Canadian Neurological Scale (r=0.55, P=0.02), outcome Barthel Index (r=0.62, P=0.01), and Rankin Scale (r=-0.77, P<0.0005) scores. CONCLUSIONS: Combined ADC and ADA provide differential patterns of stroke evolution. Early ADA changes reflect cellular alterations in acute ischemia and may provide a potential marker to predict stroke outcome.

Acute Disease↗
PubMed1999

Nimodipine and perfusion changes after stroke.

BACKGROUND AND PURPOSE: Meta-analysis of previous trials of oral nimodipine in acute stroke has suggested a benefit when commenced within 12 hours of onset. We sought to study the effect of oral nimodipine on reperfusion after acute stroke and the relation between reperfusion and outcome. METHODS: Fifty patients with acute middle cerebral artery territory cortical infarction were blindly randomized within 12 hours of onset to either oral nimodipine (30 mg every 6 hours) or placebo. Treatment was continued for 2 weeks. Cerebral blood flow was assessed with the use of 99mTc-hexamethylpropyleneamine oxime single-photon emission CT before therapy, 24 hours later, and at 3 months. Hypoperfusion was measured by a validated volumetric technique. Neurological impairment and functional outcome were assessed with the Canadian Neurological Scale and Barthel Index, respectively. Tissue loss was measured with CT at 3 months. Four patients were excluded from analysis for technical reasons. RESULTS: Twenty-three patients received nimodipine, and 23 received placebo. In the nimodipine group, there was early reperfusion that was not maintained at outcome (P=0.01). In the placebo group, mean infarct hypoperfusion volumes showed no overall change. Nonnutritional reperfusion in nimodipine-treated patients was associated with adverse neurological (P=0.05) and functional outcome (P=0.06). There was, however, no difference in clinical outcome between the 2 groups. CONCLUSIONS: Oral nimodipine administered within 12 hours enhanced acute reperfusion, but this was largely nonnutritional. Larger studies using a shorter treatment delay are required to evaluate the clinical efficacy of nimodipine in acute ischemic stroke.

Acute Disease↗
PubMed1999

Ischemic stroke risk and passive exposure to spouses' cigarette smoking. Melbourne Stroke Risk Factor Study (MERFS) Group.

OBJECTIVES: This study investigated the association between ischemic stroke risk and passive exposure to cigarette smoking. METHODS: Risk factors among 452 hospitalized cases of first-episode ischemic stroke were compared with 452 age- and sex-matched "neighbor-hood" controls. RESULTS: The risk of stroke was twice as high for subjects whose spouses smoked as for those whose spouses did not smoke (95% confidence interval = 1.3, 3.1), after adjustment for the subject's own smoking, heart disease, hypertension, diabetes, and education level. These results were confirmed when analysis was limited to those who never smoked. CONCLUSIONS: These findings provide evidence that spousal smoking may be a significant risk factor for ischemic stroke.

Aged↗
PubMed1999

Limiting neurological damage after stroke: a review of pharmacological treatment options.

Acute ischaemic stroke is a leading cause of death and a major cause of long term disability worldwide. Effective treatments for limiting the neurological damage after stroke have proven elusive. An improved understanding of the complicated cascade of cellular events following the onset of cerebral ischaemia has led to exploration of a number of avenues for early intervention. Reperfusion of the ischaemic territory using thrombolytic drugs has shown promise in clinical trials as a method for achieving tissue salvage. Antithrombotic and antiplatelet agents have not demonstrated efficacy as acute therapies, although the early use of aspirin (acetylsalicylic acid) appears to produce a reduction in early stroke recurrence. A wide variety of drugs which interfere at various points in the ischaemic cascade, so-called 'neuroprotective agents', have also been studied, but with mixed success. Of these, antagonists of voltage-gated calcium channels, antagonists at the N-methyl-D-aspartate (NMDA) receptor and scavengers of free radicals have been most extensively studied. Despite proving effective in animal models of cerebral ischaemia, these drugs have largely failed to fulfil their promise in clinical trials. While individual compounds have proven ineffective, combinations of drugs with different mechanisms of action may yet provide the best treatment for acute ischaemic stroke.

Cerebrovascular Disorders↗
PubMed1999

Association of cytochrome b5 with 16-androstene steroid synthesis in the testis and accumulation in the fat of male pigs.

The 16-androstene steroids, one of the principal causes of boar taint, are synthesized in the testis by the andien-beta synthase enzyme system. This system has been shown in vitro to involve both cytochrome P450c17 and cytochrome b5. The objective of this work was to investigate the relationship between the levels of cytochrome b5 in the testis, in vitro steroidogenesis, and the accumulation of 16-androstene steroids in the fat of pubertal boars. We found that the in vitro rate of 16-androstene steroidogenesis in testis microsomes was correlated with 16-androstene steroid concentrations in fat (r = .66, P < .01). Western blots were used to determine the amounts of cytochrome b5 and cytochrome P450c17 protein in testis, and two immunoreactive cytochrome b5 proteins of approximately 12 and 16 kDa were found. Levels of cytochrome P450c17 or the high molecular weight cytochrome b5 in testis were not significantly correlated to levels of 16-androstene steroids in fat. However, levels of total cytochrome b5 immunoreactive protein and levels of the low molecular weight immunoreactive cytochrome b5 were correlated to fat 16-androstene steroid concentrations (r = .59, P < .001; r = .72, P = .0001, respectively). Levels of the low molecular weight immunoreactive cytochrome b5 were also correlated to 16-androstene steroid synthesis rates in vitro (r = .62, P < .05). These results indicate that increased levels of a low molecular weight immunoreactive cytochrome b5 protein, and not of cytochrome P450c17, are related to increased testicular 16-androstene steroid production and accumulation in fat. These results support the hypothesis that selection for reduced levels of this low molecular weight immunoreactive cytochrome b5 protein in the testis may result in decreased levels of 16-androstene steroids in fat and reduced boar taint in uncastrated male pigs.

Adipose Tissue↗