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Biomedical subjects

M Davidson

Publications and source records attributed to M Davidson.

At least 19 recordsLinked to original sources
PubMed2006

Recombinant tissue plasminogen activator injected into the vitreous cavity may penetrate the retinal veins of a porcine model of vascular occlusion.

AIM: To determine if recombinant tissue plasminogen activator (rtPA) injected into the vitreous cavity can penetrate the retinal vessels of porcine eyes with or without vascular occlusion. METHODS: Eight eyes (group I) of four pigs underwent clamping of the optic nerve flush with the globe for 90 minutes. One hour after reperfusion, one eye of each pig was injected with 75 microg of rtPA, and the fellow eye was injected with balanced salt solution (BSS). Eyes were processed for immunohistochemistry. Four additional eyes (group II) of two pigs were subjected to the same injections, but without optic nerve clamping. RESULTS: After reperfusion, the clinical picture was similar to that of a central retinal vein occlusion. Immunoperoxidase staining showed rtPA only in the retinal veins but not the retinal arteries in all eyes injected with rtPA in both groups I and II. Those eyes also showed intense rtPA staining at the level of the internal limiting membrane (ILM). No staining was seen at the level of the ILM or inside the retinal vessels in the BSS injected eyes. Immunofluorescence staining showed intense staining at the level of the ILM, but not inside the retinal vessels in the rtPA-injected eyes. CONCLUSIONS: rtPA may penetrate the retinal veins, but not the arteries of porcine eyes with and without vascular occlusion. The ILM may play a part in preventing rtPA penetration.

Animals↗
PubMed2006

Prevalence and persistence of antibodies to herpes viruses, Chlamydia pneumoniae and Helicobacter pylori in Alaskan Eskimos: the GOCADAN Study.

The prevalence and persistence of antibodies against cytomegalovirus (CMV), herpes simplex virus types 1 (HSV1) and 2 (HSV2), Helicobacter pylori and Chlamydia pneumoniae were determined in Alaskan Eskimos. The study included 610 individuals (mean age 43 +/- 15 years; 45% males) participating in the Genetics of Coronary Artery Disease in Alaska Natives (GOCADAN) study. Archived serum samples and those collected during the GOCADAN study were analysed for antibodies against the above pathogens by ELISA. The current prevalence of antibody seropositivity was 94% to CMV, 90% to HSV1, 38% to HSV2, 80% to H. pylori, and 42% to C. pneumoniae. The persistence of antibodies (in both archived and current samples) against CMV, HSV1 and H. pylori was high (83%, 84% and 67%, respectively) compared with those against HSV2 (26%) and C. pneumoniae (29%). Moreover, the seroconversion rates to these organisms were low. Most individuals acquired CMV, HSV1 and H. pylori antibodies by the age of 24 years (94%, 90% and 72%, respectively), and >50% carried HSV2 and C. pneumoniae antibodies by the age of 45 years. There were gender differences in antibody seropositivity rates. Over 70% of individuals had antibodies to at least three of the five pathogens tested. The study demonstrated the high prevalence and lifelong persistence of multiple antibodies, suggesting chronic infections among Alaskan Eskimos.

Adolescent↗
PubMed2005

Detection, identification and mapping of iron anomalies in brain tissue using X-ray absorption spectroscopy.

This work describes a novel method for the detection, identification and mapping of anomalous iron compounds in mammalian brain tissue using X-ray absorption spectroscopy. We have located and identified individual iron anomalies in an avian tissue model associated with ferritin, biogenic magnetite and haemoglobin with a pixel resolution of less than 5 microm. This technique represents a breakthrough in the study of both intra- and extra-cellular iron compounds in brain tissue. The potential for high-resolution iron mapping using microfocused X-ray beams has direct application to investigations of the location and structural form of iron compounds associated with human neurodegenerative disorders--a problem which has vexed researchers for 50 years.

Absorptiometry, Photon↗
PubMed2005

In situ characterization and mapping of iron compounds in Alzheimer's disease tissue.

There is a well-established link between iron overload in the brain and pathology associated with neurodegeneration in a variety of disorders such as Alzheimer's (AD), Parkinson's (PD) and Huntington's (HD) diseases [1]. This association was first discovered in AD by Goodman in 1953 [2], where, in addition to abnormally high concentrations of iron in autopsy brain tissue, iron has also been shown to accumulate at sites of brain pathology such as senile plaques [3]. However, since this discovery, progress in understanding the origin, role and nature of iron compounds associated with neurodegeneration has been slow. Here we report, for the first time, the location and characterisation of iron compounds in human AD brain tissue sections. Iron fluorescence was mapped over a frontal-lobe tissue section from an Alzheimer's patient, and anomalous iron concentrations were identified using synchrotron X-ray absorption techniques at 5 mum spatial resolution. Concentrations of ferritin and magnetite, a magnetic iron oxide potentially indicating disrupted brain-iron metabolism, were evident. These results demonstrate a practical means of correlating iron compounds and disease pathology in-situ and have clear implications for disease pathogenesis and potential therapies.

Alzheimer Disease↗
PubMed2004

Diabetes mellitus in midlife and the risk of dementia three decades later.

OBJECTIVE: To examine the association between diabetes in midlife (1963-1968) and dementia more than three decades later (1999-2001). METHODS: The authors characterized dementia using standard methods for 1,892 participants among 2,606 survivors of 10,059 participants in the Israeli Ischemic Heart Disease study, a longitudinal investigation of the incidence of and risk factors for cardiovascular disease among Jewish male civil servants in Israel. Face to face interviews were conducted with the 652 subjects identified as possibly demented by the Modified Telephone Interview for Cognitive Status. Logistic regression analysis was performed to assess the association of diabetes with dementia controlling for sociodemographic and cardiovascular variables compared to those with no cognitive impairment. RESULTS: Of 1,892 assessed subjects (mean age 82 at assessment), 309 (16.3%) had dementia. Diabetic subjects had significantly more dementia than non-diabetic subjects (chi2 = 7.54, df = 1, p = 0.006, OR 2.83 [95% CI = 1.40 to 5.71]). Those who survived to the time of this study were younger and healthier than those who died. CONCLUSIONS: Evidence for diabetes as a risk factor for dementia was found, similar to other epidemiologic studies. In contrast to the earlier studies, however, the authors linked diabetes in midlife to dementia more than three decades later in the very old survivors of a large male cohort.

Adult↗
PubMed2004

Microdistributions of prospective BNCT-compound CuTCPH in tissue sections with a heavy ion microbeam.

Microdistributions of the prospective BNCT-compound CuTCPH, a carborane-containing tetraphenylporphyrin with one Cu atom in its molecular structure, have been obtained in tissue sections of different organs of tumor-bearing and normal Syrian hamsters injected with the boron compound by employing a heavy ion microbeam. High resolution X-ray spectroscopy following micro-PIXE (Particle Induced X-ray Emission with micrometer-sized beams) with a focused (16)O ion beam was used. Focusing was performed with a heavy-ion scanning high-precision magnetic quadrupole triplet microprobe. Squamous Cell Carcinomas were induced on the right Cheek Pouch of Syrian Hamsters (HCP), sampled, cryo-sectioned and freeze-dried. Two-dimensional maps of elemental concentration were obtained by scanning the beam over the samples. Very non-uniform Cu concentrations were found in all sections.

Animals↗
PubMed2004

Cognitive performance of male adolescents is lower than controls across psychiatric disorders: a population-based study.

OBJECTIVE: Psychiatric patients, as well as humans or experimental animals with brain lesions, often concurrently manifest behavioral deviations and subtle cognitive impairments. This study tested the hypothesis that as a group, adolescents suffering from psychiatric disorders score worse on cognitive tests compared with controls. METHOD: As part of the assessment for eligibility to serve in the military, the entire, unselected population of 16-17-year old male Israelis undergo cognitive testing and screening for psychopathology by the Draft Board. We retrieved the cognitive test scores of 19 075 adolescents who were assigned any psychiatric diagnosis, and compared them with the scores of 243 507 adolescents without psychiatric diagnoses. RESULTS: Mean test scores of cases were significantly poorer then controls for all diagnostic groups, except for eating disorders. Effect sizes ranged from 0.3 to 1.6. CONCLUSION: As group, adolescent males with psychiatric disorders manifest at least subtle impairments in cognitive functioning.

Adolescent↗
PubMed2003

Percutaneous endoscopic gastrostomy (PEG) in patients with ALS and bulbar dysfunction.

OBJECTIVE: To compare characteristics of ALS patients with and without percutaneous endoscopic gastrostomy (PEG). METHODS: Using the ALS Patient Care Database, data from patients with and without PEG with ALS Functional Rating Scale-bulbar subscale (ALSFRSb) scores < or = 5 were analyzed; follow-up data were also collected. RESULTS: PEG use was markedly increased with declining ALSFRSb scores. Demographics did not differ, but ALSFRS composite scores and bulbar and arm subscale scores were lower (P<0.0001). PEG patients used significantly more assistive devices, multidisciplinary care, home care nurses and aides, had more frequent physician and emergency department visits and hospital admissions (P<0.0001), and had lower health status based on the mini-SIP scale (P=0.0047). PEG use varied greatly between ALS centers. In the follow-up study, positive impact of PEG was noted in 79 % of PEG patients but in only 37.5% of patients who received PEG later, based on a small number of patients. PEG use showed no survival benefit. CONCLUSION: Patients did not receive PEG until bulbar function was severely reduced and overall ALS had markedly progressed. PEG may have been performed too late to demonstrate survival benefits. Aggressive proactive nutritional management appears essential in patients with ALS. To determine whether PEG provides benefits, it must be performed at earlier stages of the disease and prospectively studied.

Amyotrophic Lateral Sclerosis↗
PubMed2003

The current status of sports medicine training in United States internal medicine residency programmes.

OBJECTIVE: To determine the general status of sports medicine training in internal medicine residency programmes in the United States. METHODS: A cross sectional survey of the programme directors and chief residents of each of the 407 accredited internal medicine programmes listed in the 1999-2000 Graduate Medical Education Directory. RESULTS: The questionnaire was returned by 231 of 404 (57%) programme directors and 233 of 404 (58%) chief residents. A chief and director of the same programme (paired responses) replied from 144 of 404 (36%) programmes surveyed. A formal sports medicine curriculum was reported by 22.1% of programme directors. Programmes with a formal curriculum were 2.9 times more likely to offer any of the sports medicine educational experiences (p<0.0001; Cochran-Mantel-Haenszel). Programmes with block rotations were more likely to include all of the educational experiences surveyed than those without (p<0.002 for each; chi(2) test). A total of 162 programmes included sports medicine as part of other rotations. Most programmes only included sports medicine as part of other rotations: 44.6% (103/231) of all programmes and 63.6% (103/162) of programmes with sports medicine as part of other rotations. Some 29.9% (69/231) of directors reported having an elective, and 3.9% (9/231) reported a required rotation. Almost a quarter (21.7%; 50/231) of directors reported that their residents received no clinical experience in sports medicine. CONCLUSIONS: Little attention is given to the subject of sports medicine when internal medicine residency curricula are developed in the United States. Thus only a small percentage of American internal medicine residency programmes provide significant training in sports medicine.

Clinical Competence↗
PubMed2003

Low energy proton irradiation effects on alveolar macrophages from young and aged rats.

A prospective study was undertaken to assess the radiotoxicity of accelerated particles in pulmonary alveolar macrophages (AM). We evaluated the effects of a single dose (10-75 Gy) of an external low-energy (20 MeV) proton beam on cultured AM oxidative metabolism and phagocytic function. Macrophages are the first line of defense against invading pathogens and are known to generate superoxide anion (O2), nitric oxide (NO), and mediators of antimicrobial and antitumoral defense mechanisms. We obtained AM by bronchoalveolar lavage from young (1-2 month old) and aged (9-12 month old) male Wistar rats. Cell viability, phagocytosis, O2 and NO production in control and proton-irradiated cultured AM were evaluated The effect of proton irradiation on cell viability was dose-dependent The higher doses induced a dramatic decrease in viability in the aged population. Phagocytosis increased 1.3-1.4 fold inboth populations irrespective of the dose delivered. Generation of O2 was always higher in the aged population for all the doses assayed and showed no significant variation from the control values. In the young population a clear increase was observed with doses of 25 and 50 Gy. NO production in AM from young animals rose in a dose-dependent manner. Conversely, proton irradiation did not affect NO production in macrophages from aged animals. The results of this study demonstrate that AM isolated from young and aged rats are functionally different and show a distinct behavior when exposed to proton irradiation. These findings suggest that age may condition response and must be taken into account when accelerated particle-radiotherapy protocols are considered as a valid therapeutic option for the treatment of cancer. To the best of our knowledge, this is the first report comparing sham-irradiated and proton-irradiated young and aged AM.

Aging↗
PubMed2001

Comparison of the efficacy of atorvastatin versus cerivastatin in primary hypercholesterolemia.

This 6-week Prospective, Randomized, Open-label Blinded End point (PROBE) study conducted at 12 sites in the United States compared the efficacy and safety of atorvastatin with cerivastatin. In all, 215 hypercholesterolemic patients (low-density lipoprotein [LDL] cholesterol > or = 160 mg/dl [4.14 mmol/L]; triglycerides < or = 400 mg/dl [4.52 mmol/L]) were randomized to receive either atorvastatin 10 mg once daily (n = 108) or cerivastatin 0.3 mg once daily (n = 107). Efficacy was assessed by measuring changes from baseline in LDL cholesterol, total cholesterol, high-density lipoprotein cholesterol, apolipoprotein B, and triglycerides. Atorvastatin produced significantly greater (p < 0.0001) reductions from baseline to week 6 in LDL cholesterol (37.7% vs 30.2%), total cholesterol (27.5% vs 22.2%), and apolipoprotein B (28.6% vs 21.2%), and a significantly greater (p < 0.05) increase from baseline to week 6 in high-density lipoprotein cholesterol (6.8% vs 4.3%) than cerivastatin. Atorvastatin treatment was also associated with a greater percent decrease from baseline to week 6 in triglycerides, with a trend toward statistical significance (p = 0.0982). The percentage of patients that achieved the National Cholesterol Education Program LDL cholesterol goal was greater for those receiving atorvastatin (73%) than for those receiving cerivastatin (66%). The proportion of patients experiencing drug-attributable adverse events, which were mostly mild to moderate and related to the digestive system, was significantly less (p < 0.05) with atorvastatin (5%) than with cerivastatin (14%) treatment. In conclusion, atorvastatin (10 mg/day) is more effective at lowering LDL cholesterol in hypercholesterolemic patients than cerivastatin (0.3 mg/day). Both atorvastatin and cerivastatin are well tolerated, with safety profiles similar to other members of the statin class.

Administration, Oral↗
PubMed2001

Risperidone versus haloperidol in long-term hospitalized chronic patients in a double blind randomized trial: a post hoc analysis.

BACKGROUND: Patients who remain in hospital for an extended time pose a special therapeutic challenge. OBJECTIVES: The goal of this study was to examine whether the acute response of long-term hospitalized schizophrenic patients differs between haloperidol and risperidone based on a post hoc, sub-analysis of data from a large double blind pivotal trial. METHOD: Data on chronic schizophrenic patients who had been hospitalized for at least 60 days (median 351 days) prior to entering this 8-week randomized double blind controlled trial were examined. This included 75 patients treated with 4 mg of risperidone and 69 treated with 10mg of haloperidol. Changes in symptoms were assessed with the Positive and Negative Syndrome Scale for Schizophrenia (PANSS) and the Clinical Global Impression (CGI). Data were analyzed using analysis of variance. RESULTS: The analyses revealed that patients receiving risperidone improved significantly more than those treated with haloperidol. CONCLUSIONS: Results suggest that the most often prescribed dose of risperidone, 4 mg, might be more effective for long-stay chronic schizophrenic patients than haloperidol 10mg.

Adult↗
PubMed2001

Microfluidic device for combinatorial fusion of liposomes and cells.

We describe an electrofusion-based technique for combinatorial synthesis of individual liposomes. A prototype device with containers for liposomes of different compositions and a fusion container was constructed. The sample containers had fluid contact with the fusion container through microchannels. Optical trapping was used to transport individual liposomes and cells through the microchannels into the fusion container. In the fusion container, selected pairs of liposomes were fused together using microelectrodes. A large number of combinatorially synthesized liposomes with complex compositions and reaction systems can be obtained from small sets of precursor liposomes. The order of different reaction steps can be specified and defined by the fusion sequence. This device could also facilitate single cell-cell electrofusions (hybridoma production). This is exemplified by fusion of transported red blood cells.

Cells↗