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Biomedical subjects

David Brown

Publications and source records attributed to David Brown.

At least 19 recordsLinked to original sources
PubMed2007

Toric Implantable Collamer Lens for moderate to high myopic astigmatism.

PURPOSE: To assess the efficacy of the Toric Implantable Collamer Lens (ICL) to treat moderate to high myopic astigmatism. DESIGN: Prospective nonrandomized clinical trial. PARTICIPANTS: Two hundred ten eyes of 124 patients with between 2.38 and 19.5 diopters (D) of myopia (spherical equivalent [SE]) and 1 to 4 D of astigmatism participating in the United States Food and Drug Administration clinical trial of the Toric ICL. INTERVENTION: Implantation of the Toric ICL. MAIN OUTCOME MEASURES: Uncorrected visual acuity (UCVA), refraction, best spectacle-corrected visual acuity (BSCVA), adverse events, and postoperative complications. RESULTS: At 12 months postoperatively, the proportion of eyes with 20/20 or better UCVA (83.1%) was identical to the proportion of eyes with preoperative 20/20 or better BSCVA (83.1%); 76.5% had postoperative UCVA better than or equal to preoperative BSCVA. The mean manifest refractive cylinder dropped from 1.93 D (+/-0.84) at baseline to 0.51 D (+/-0.48) postoperatively, a 73.6% decrease in astigmatism. Although only 21.0% of eyes had 1-D refractive cylinder preoperatively (none less), 91.4% of cases had < or =1 D of cylinder postoperatively. Furthermore, 65.6% had < or =0.5 D and 40.9% had < or =0.25 D of refractive cylinder postoperatively. Mean manifest refraction SE (MRSE) improved from -9.36 D (+/-2.66) preoperatively to 0.05 D (+/-0.46) postoperatively. A total of 76.9% of eyes were predicted accurately to within +/-0.5 D, 97.3% to within +/-1.0 D, and 100% to within +/-2.0 D of predicted MRSE. Postoperatively, 37.6% of eyes had a BSCVA of 20/12.5 or better, compared with a preoperative level of 4.8%. Furthermore, BSCVA of 20/20 or better occurred in 96.8% postoperatively, compared with 83.1% preoperatively. Mean improvement in BSCVA was 0.88 lines; there were 3 cases (1.6%) that lost > or =2 lines of BSCVA after 12 months postoperatively, whereas 18.9% of cases improved by > or =2 lines. A total of 76.4% of cases gained > or =1 lines of BSCVA, whereas only 7.5% of cases lost the equivalent amount. Three ICL removals were performed without significant loss of BSCVA, and 1 clinically significant lens opacity was observed. CONCLUSION: The results support the efficacy and predictability of Toric ICL implantation to treat moderate to high myopic astigmatism. Important safety concerns were not identified.

Adult↗
PubMed2007

At-risk drinking and drug use among patients seeking care in an emergency department.

OBJECTIVE: This study reports the frequency of alcohol use and associated tobacco and drug use among emergency department (ED) patients, in order to increase physician awareness and treatment of women and men seeking care in ED settings. METHOD: All adults seen in the ED at the University Hospital in Lausanne, Switzerland, between 11 AM and 11 PM were screened by direct interview for at-risk drinking, tobacco use, drug use, and depression during an 18-month period. RESULTS: A total of 8,599 patients (4,006 women and 4,593 men) participated in the screening procedure and provided full data on the variables in our analysis. The mean age was 51.9 years for women and 45.0 years for men; 57.5% (n = 2,304) of women and 58.5% (n = 2,688) of men were being treated for trauma. Based on guidelines of the National Institute on Alcohol Abuse and Alcoholism, 13.1% (n = 523) of the women were at-risk drinkers, 57.3% (n = 2,301) were low-risk drinkers, and 29.6% (n = 1,182) were abstinent. Among men, 32.8% (n = 1,507) met criteria for at-risk drinking, 51.8% (n = 2,380) met criteria for low-risk drinking, and 15.4% (n = 706) were abstinent. Younger individuals (ages 18-30) had significantly higher rates of episodic heavy drinking episodes, whereas at-risk older patients were more likely to drink on a daily basis. A binary model found that women and men who drank at at-risk levels are more likely to use tobacco (odds ratio [OR] = 2.48, 95% confidence interval [CI]: 2.0-3.08) and illicit drugs (OR = 5.91, CI: 3.32- 10.54) compared with abstinent and low-risk drinkers. CONCLUSIONS: This study supports systematic alcohol screening of women and men seen in EDs and suggests that patterns of alcohol and drug use vary by age and gender.

Alcohol Drinking↗
PubMed2006

Isoniazid's bactericidal activity ceases because of the emergence of resistance, not depletion of Mycobacterium tuberculosis in the log phase of growth.

BACKGROUND: It is believed that the cessation of isoniazid's early bactericidal activity during the initial phase of antituberculosis therapy is due to the depletion of Mycobacterium tuberculosis in the exponential phase of growth. We examined the veracity of this cornerstone belief. METHODS: We used an in vitro infection model in which M. tuberculosis was exposed to isoniazid concentration-time profiles encountered in human patients. Experiments were performed to examine the time-related changes in the total bacterial population, the isoniazid-susceptible subpopulation, and the isoniazid-resistant subpopulation. RESULTS: The cessation of microbial kill occurred between days 3 and 4 of isoniazid therapy, as occurs in patients. There were multiple logs of organisms in the exponential phase of growth remaining at the time when bactericidal activity ceased. The isoniazid-susceptible subpopulation was replaced by an isoniazid-resistant subpopulation after 80 h of therapy. The size of the isoniazid-susceptible subpopulation continued to decrease after the total population had ceased to decrease, whereas the resistant subpopulation remained in the exponential phase of growth. Resistance was due to single point mutations in the catalase-peroxidase gene and to reserpine-inhibitable efflux pumps. CONCLUSIONS: The age-old hypothesis that isoniazid's microbial killing of M. tuberculosis during log-phase growth ceases because of the depletion of this bacillary population needs to be modified.

Antitubercular Agents↗
PubMed2006

Structure- and property-based design of factor Xa inhibitors: pyrrolidin-2-ones with acyclic alanyl amides as P4 motifs.

Structure-based drug design was exploited in the synthesis of 3-(6-chloronaphth-2-ylsulfonyl)aminopyrrolidin-2-one-based factor Xa (fXa) inhibitors, incorporating an alanylamide P4 group with acyclic tertiary amide termini. Optimized hydrophobic contacts of one amide substituent in P4 were complemented by hydrophobicity-modulating features in the second, producing potent fXa inhibitors including examples with excellent anticoagulant properties.

Alanine↗
PubMed2006

An introductory note to CHMP guidelines: choice of the non-inferiority margin and data monitoring committees.

The Committee on Medical Products for Human Use (CHMP) has recently issued two new guidance documents that are of particular note to statisticians. The purpose of this short note is to give a little background to the origins of these documents and a flavour of some of their most important features. The two guidelines are reproduced as the next two papers in the journal.

Clinical Trials Data Monitoring Committees↗
PubMed2006

Phenoxodiol, an experimental anticancer drug, shows potent antiangiogenic properties in addition to its antitumour effects.

Phenoxodiol (2H-1-benzopyran-7-0,1, 3-[4-hydroxyphenyl], PXD) is a synthetic analogue of the naturally-occurring plant isoflavone and anticancer agent, genistein. PXD directly induces mitotic arrest and apoptosis in most cancer cells and is currently undergoing clinical trials, as a chemotherapeutic in ovarian and prostate cancers. We show here that PXD also exhibits potent antiangiogenic properties. Thus, it inhibited endothelial cell proliferation, migration and capillary tube formation and inhibited expression of the matrix metalloproteinase MMP-2, a major matrix degrading enzyme. Importantly, we demonstrate that PXD is functional in vivo since it inhibited the extent of capillary tube invasion in an in vivo model of angiogenesis. We show that phenoxodiol inhibits hallmarks of endothelial cell activation, namely TNF or IL-1 induced E-selectin and VCAM-1 expression and IL-8 secretion. However, PXD had no effect on unstimulated endothelial cells. We also describe that PXD inhibits the lipid kinase sphingosine kinase, which recently has been implicated in endothelial cell activation and angiogenesis as well as oncogenesis. Thus, our results suggest that PXD may be an effective anticancer drug targeting the two drivers of tumour growth--the proliferation of the tumour cells themselves and the angiogenic and inflammatory stimulation of the vasculature.

Animals↗
PubMed2006

Design and synthesis of orally active pyrrolidin-2-one-based factor Xa inhibitors.

A series of novel, non-basic 3-(6-chloronaphth-2-ylsulfonyl)aminopyrrolidin-2-one-based factor Xa (fXa) inhibitors, incorporating an alanylamide P4 group, was designed and synthesised. Within this series, the N-2-(morpholin-4-yl)-2-oxoethyl derivative 24 was shown to be a potent, selective fXa inhibitor with good anticoagulant activity. Moreover, 24 possessed highly encouraging rat and dog pharmacokinetic profiles with excellent oral bioavailabilities in both species.

Administration, Oral↗
PubMed2006

Molecular mechanism of phenoxodiol-induced apoptosis in ovarian carcinoma cells.

BACKGROUND: Previously, it was demonstrated that phenoxodiol induces apoptosis in epithelial ovarian carcinoma (EOC) cells and that it is capable of sensitizing these cells to Fas-mediated apoptosis. The objectives of this study were to determine whether phenoxodiol can also act as chemosensitizer to chemotherapeutic agents and to characterize the molecular mechanism behind its sensitizing effect. METHODS: Ten EOC cell lines were used in this study. The effect of phenoxodiol on the inhibitory concentration 50% (IC50) of carboplatin, paclitaxel, and gemcitabine was determined by the CellTiter 96 Assay. The in vivo effect of combination treatments with phenoxodiol and the above-mentioned agents was determined in animal xenograft models. Apoptosis was measured using the Caspase-Glo Assay and the apoptotic cascade was characterized by Western blot analyses. RESULTS: The results showed that phenoxodiol is able to sensitize EOC cells to carboplatin, paclitaxel, and gemcitabine both in vitro and in vivo. In addition, it was demonstrated that phenoxodiol is capable of inducing apoptosis by: 1) the activation of the mitochondrial pathway through caspase-2 and Bid signaling, and 2) the proteasomal degradation of the anti-apoptotic protein XIAP. CONCLUSION: Understanding the components of the apoptotic pathway activated by phenoxodiol, which allows it to sensitize EOC cells to chemotherapeutic agents, will provide valuable information on the characteristic mode of action of a chemosensitizer. This will help in the identification of novel drugs and in the design of better strategies for combination therapy in patients with recurrent ovarian carcinoma.

Animals↗
PubMed2006

Extreme coronary guide catheter support: report of two cases of a novel telescopic guide catheter system.

Extra support of the guiding catheter is required in selected cases of percutaneous coronary intervention (PCI). We describe two successful cases of PCI of very calcified and tortuous right coronary arteries in which a novel telescopic guide system was devised. The system utilizes a long sheath that "armors" the guide catheter. The operator can adjust the support of the guiding system from soft up to extremely stiff.

Aged↗
PubMed2006

Transapical aortic valve implantation: an animal feasibility study.

BACKGROUND: Percutaneous aortic valve implantation has recently been performed in nonsurgical patients with severe aortic stenosis. Retrograde valve delivery has been problematic because of the size of the delivery system and concomitant peripheral vascular disease. We investigated a minimally invasive approach through the left ventricular apex for antegrade placement of a device-deliverable valve. METHODS: Transapical aortic valve implantation was performed using a 23-mm equine valve mounted on a stainless steel stent in 24 swine (weight range, 35 to 45 kg). A limited or full sternotomy approach was used to access the apex of the heart. The crimped valve was introduced through a sheath in the left ventricular apex. Fluoroscopy and echocardiography were used for guidance. Deployments were performed on the beating heart either with ventricular unloading using femoral extracorporeal circulation or rapid ventricular pacing. RESULTS: All valves were successfully delivered at the selected target site with acceptable visualization of the noncalcified aortic annulus. Valve migration occurred during eight deployments (two distal and six retrograde) secondary to persistent cardiac output, unfavorable annular anatomy, and dislodgement by the delivery catheter. Exact positioning of the nonmigrated valves at the aortic annulus was examined by necropsy of all animals at the end of the procedures. Paravalvular leak was noted in 14 of 18 (77.8%) valves remaining in situ. CONCLUSIONS: The transapical approach was used for the successful antegrade placement of a stented valve, obviating the technical problems associated with a large delivery system transiting the peripheral vascular system. Stent design contributing to paravalvular leak remains problematic.

Animals↗
PubMed2006

A link between translation of the hepatitis C virus polyprotein and polymerase function; possible consequences for hyperphosphorylation of NS5A.

Hyperphosphorylation of NS5A is thought to play a key role in controlling hepatitis C virus (HCV) RNA replication. Using a tetracycline-regulable baculovirus delivery system to introduce non-culture-adapted HCV replicons into HepG2 cells, we found that a point mutation in the active site of the viral polymerase, NS5B, led to an increase in NS5A hyperphosphorylation. Although replicon transcripts lacking elements downstream of NS5A also had altered NS5A hyperphosphorylation, this did not explain the changes resulting from polymerase inactivation. Instead, two additional findings may be related to the link between polymerase activity and NS5A hyperphosphorylation. Firstly, we found that disabling polymerase activity, either by targeted mutation of the polymerase active site or by use of a synthetic inhibitor, stimulated translation from the replicon transcript. Secondly, when the rate of translation of non-structural proteins from replicon transcripts was reduced by use of a defective encephalomyocarditis virus internal ribosome entry site, there was a substantial decrease in NS5A hyperphosphorylation, but this was not observed when non-structural protein expression was reduced by simply lowering replicon transcript levels using tetracycline. Therefore, one possibility is that the point mutation within the active site of NS5B causes an increase in NS5A hyperphosphorylation because of an increase in translation from each viral transcript. These findings represent the first demonstration that NS5A hyperphosphorylation can be modulated without use of kinase inhibitors or mutations within non-structural proteins and, as such, provide an insight into a possible means by which HCV replication is controlled during a natural infection.

Cell Line, Tumor↗
PubMed2006

Survey of select practice behaviors by primary care physicians on the use of opioids for chronic pain.

OBJECTIVE: To assess the use of opioids by primary care physicians for the treatment of chronic pain. METHODS: A written survey was completed by 248 primary care physicians. Outcomes of interest included type of opioids prescribed, common pain diagnoses treated, opioid prescribing concerns, treatment of patients with a history of substance use disorders and clinic-based protocols for pain management. RESULTS: The mean age of the physicians who completed the questionnaire was 41 years. The majority were between the ages of 30 and 49 years (68%) with an equal number of men and women. Seventy percent were family physicians, 28.7% internists and less than 2% were community physicians and geriatricians. Physician concerns regarding opioid therapy included prescription drug abuse (84.2%), addiction (74.9%), adverse effects (68%), tolerance (60.7%), and medication interaction (32%). The survey found that the majority of the physicians were comfortable in prescribing narcotics to patients with terminal cancer. However, they were less comfortable prescribing narcotics to patients with low back pain and persons with a current or past history of drug or alcohol abuse. Physician management practices suggested that urine toxicology tests were under-utilized with only 6.9% reporting obtaining this test before prescribing opioids and only 15.0% performing urine toxicology tests on patients already prescribed opioids. Logistic regression analysis revealed that whether or not physicians routinely conducted urine toxicology screens was significantly (p = 0.015) predicted by whether they had a system to track patients on opioids when prescribing narcotics. The primary limitation of the study is the reliance on physician self-report rather than objective measures of physician behavior. CONCLUSIONS: The survey suggests physicians are concerned about drug abuse, addiction, adverse effects, tolerance, and medication interaction. Their comfort level in prescribing opioids varies with the patient characteristics. Urine toxicology testing is underutilized in the primary care setting.

Adult↗
PubMed2006

Association between HSV-2 and HIV-1 viral load in semen, cervico-vaginal secretions and genital ulcers of Thai men and women.

We studied the association between herpes simplex virus type-2 (HSV-2) and HIV-1 viralload in plasma, semen, cervico-vaginal secretions and genital ulcers. Forty-seven (68%) men and 57 (80%) women were HSV-2 antibody positive, of whom 12 (26%, 95% confidence interval [CI] 20, 32) and five (8%, 95% CI 4, 12), respectively, had HSV-2 genital shedding detected by polymerase chain reaction. The mean HIV-1 seminal and cervico-vaginal viral loads did not differ significantly according to the presence of HSV-2 shedding. Eleven men and 15 women presented with genital ulcers; all ulcers were due to HSV-2. Ten men and nine women were followed up over six days: the mean (95% CI) HIV-1 log viral load copies/mL in the genital ulcers at baseline and final visits were 2.5 (2.3, 2.7) and 3.1 (2.0, 4.2) for men and 3.0 (2.6, 3.4) and 2.7 (2.3, 3.1) for women. These findings do not support the hypothesis that HSV-2 increases the HIV-1 viral load in genital secretions.

Adult↗
PubMed2006

Financial exploitation of older persons: challenges and opportunities to identify, prevent, and address it in the United States.

Financial exploitation is a recognized social problem of unknown, though likely increasing, magnitude. It can occur through numerous methods, including the misuse of powers of attorney and guardianship, illegal transfers of property, and outright fraud and theft. Financial crimes against older persons are difficult to address because they often go unreported. This paper provides a summary of findings from a study of financial exploitation of older persons. We review what is known about the nature and scope of financial exploitation of older persons and describe barriers to addressing the problem. We also identify gaps in knowledge, discuss current methods for addressing financial exploitation, and provide recommendations and suggested policy approaches for prevention and remediation.

Aged↗
PubMed2006

Target selection and pharma industry productivity: what can we learn from technology S-curve theory?

The number of new drug approvals per annum has been decreasing regularly over the past decade, and changes made 12 to 15 years ago to the research and development approach of the pharmaceutical industry may have contributed to this fall in productivity. In particular, the rapid switch at that time away from an 'observation-led' approach toward a 'hypothesis-led' approach to target selection may be a key contributing factor to this issue. The strengths and weaknesses of both approaches are analyzed herein, and it is suggested that unsolved weaknesses in both approaches are holding back the productivity of the pharmaceutical/biotechnology industry.

Animals↗