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Biomedical subjects

David Klein

Publications and source records attributed to David Klein.

14 recordsLinked to original sources
PubMed2006

Intensive care of the patient following open abdominal aortic surgery.

PURPOSE OF REVIEW: Abdominal aortic aneurysms still require open repair despite the advances that endovascular aneurysm repair has made in treating patients with significant operative risk. Older patients with significant comorbidities require open repair of their complex aneurysms when they fail to meet anatomic criteria for endovascular aneurysm repair. This review discusses the physiologic insult of abdominal aortic surgery. It aims to address which patients are the highest risk of postoperative morbidity, and advances in their intensive care unit management to reduce such morbidity. RECENT FINDINGS: Advanced age, chronic health dysfunction, emergency surgery, and multiple organ failure are independent predictors of postoperative mortality. Myocardial ischemia is the largest contributor to patient morbidity, with any rise in postoperative cardiac troponin I predicting increased in-hospital myocardial infarction and mortality. Highest-risk patients benefit most from optimizing perioperative cardiac status with beta-blockade. Perioperative treatment with fenoldopam may improve renal outcome. Tracheostomy to aid in weaning is associated with increased mortality but may improve outcome in patients with preoperative chronic obstructive pulmonary disease. SUMMARY: Demographic trends indicate that open aortic surgery will continue to be performed on older patients with complex aneurysms. Identifying patients at risk and optimizing their postoperative risk factors will improve outcomes.

Aortic Aneurysm, Abdominal↗
PubMed2006

Dissection of functional domains of the polar localization factor PodJ in Caulobacter crescentus.

The polar organelle development protein, PodJ, is important for proper establishment of polarity in Caulobacter crescentus. podJ null mutants are unable to form holdfast or pili, have reduced swarming motility, and have difficulty ejecting the flagellum during the swarmer to stalked cell transition. In this study, we create a series of truncation mutants to investigate functional domains of PodJ. We show that PodJ has a transmembrane domain between amino acids 600 and 670. We identify a periplasmic region important for pili production and a cytoplasmic region required for holdfast formation and swarming motility, and establish that PleC localization is not required for holdfast formation and motility in soft agar. Analysis of the mutants reveals that the last 54 amino acids of the protein negatively regulate processing of the full-length form of the protein, PodJ(L), to a shorter form, PodJ(S). Finally, we identify a cytoplasmic region of PodJ involved in targeting it to the flagellar pole, and a periplasmic region required for localization of PleC.

Bacterial Proteins↗
PubMed2005

Emerging technologies and corporate culture at Microsoft: a methodological note.

This article explores factors important in the study and examination of corporate culture and change. The particular focus is on the technological methods used to conduct a study of accessible technology and corporate culture at Microsoft Corporation. Reasons for particular approaches are explained. Advantages and challenges of emerging technologies that store and retrieve information in the study of corporate culture are reviewed.

Computers↗
PubMed2004

Prevalence of antibody to Bordetella pertussis antigens in serum specimens obtained from 1793 adolescents and adults.

Serum specimens were obtained from all subjects in the adolescent and adult acellular pertussis (aP) vaccine efficacy trial before and after immunization to study the prevalence of IgG and IgA antibody and geometric mean titers to 4 Bordetella pertussis antigens. Of 1793 adolescents and adult subjects who received aP vaccine, only 20%, 68%, 59%, and 39% had concentrations of IgG antibodies to pertussis toxin, filamentous hemagglutinin, pertactin, and fimbriae types 2 and 3, respectively, that were greater than or equal to the limit of quantitation of the enzyme-linked immunosorbent assay used in the analysis. There was minimal variation in antibody prevalence with respect to geographic area, age, sex, or race.

Adolescent↗
PubMed2004

Predictors for medical students entering a general surgery residency: National survey results.

BACKGROUND: The number of general surgery (GS) residency applicants had been decreasing before 2003. This national survey of fourth-year medical students elucidates factors related to the basic surgery clerkship that are associated with the decision to enter a GS residency. METHODS: A national sample of 2250 fourth-year medical students from all 4-year allopathic US medical schools was surveyed in spring 2002. Multivariate analyses were performed to identify mutable predictors for students entering GS. RESULTS: Data from 1531 fourth-year medical students from 121 different medical schools (response rate=68%) showed that 5.6% planned to enter GS. In multivariate analyses, the strongest predictor of entering GS was satisfaction with the quality of attending teaching (odds ratio 2.14, P <.01) in surgery clerkships. Several clerkship factors, such as frequency of call nights and total hours worked., were not as strongly associated with entering GS residency, Subsequent analyses showed that predictors of satisfaction with the quality of attending teaching included intraoperative activities (ie, suturing, cutting, and stapling), having attending-led rounds, and performing a history and physical with an attending. Significant negative predictors of satisfaction included observing or retracting only in surgery. CONCLUSIONS: In this national survey, factors are identified that are significantly associated with students entering a GS residency. Some of these mutable factors may increase the pool of GS residency applicants.

Adult↗
PubMed2004

NGFI-B (Nurr77/Nr4a1) orphan nuclear receptor in rat pinealocytes: circadian expression involves an adrenergic-cyclic AMP mechanism.

NGFI-B (Nur77/Nr4a1) is a member of a nuclear steroid receptor subgroup that includes the related factors Nurr1 (Nr4a2) and NOR-1 (Nr4a3). These proteins do not have recognized ligands and in fact function independently as orphan receptors with transcriptional regulatory activity. In the present study, expression of the NGFI-B gene in the rat pineal gland was found to exhibit a robust circadian rhythm, with elevated levels of NGFI-B mRNA occurring at night. The rhythm of NGFI-B mRNA is translated into a circadian rhythm of NGFI-B protein, which accumulates in the nucleus of pinealocytes. In addition, there is a parallel marked nocturnal increase in pineal DNA binding activity to a NGFI-B response element (NBRE, AAAGGTCA). Pharmacological studies indicate that NGFI-B mRNA and protein levels are elevated via activation of adrenergic receptors. NGFI-B protein levels are also elevated by dibutyryl cyclic AMP, as in other systems. In the pineal gland, regulation of NGFI-B expression also involves the AP-1 protein Fra-2, based on studies with a transgenic Fra-2 knockdown rat, in which pineal NGFI-B expression increases. This set of observations extends the number of pineal genes that are known to be regulated by Fra-2, and also provides the first indication that a member of the NGFI-B group of nuclear receptors is involved in controlling gene expression in the pineal gland.

Animals↗
PubMed2003

Rapid task-related plasticity of spectrotemporal receptive fields in primary auditory cortex.

We investigated the hypothesis that task performance can rapidly and adaptively reshape cortical receptive field properties in accord with specific task demands and salient sensory cues. We recorded neuronal responses in the primary auditory cortex of behaving ferrets that were trained to detect a target tone of any frequency. Cortical plasticity was quantified by measuring focal changes in each cell's spectrotemporal response field (STRF) in a series of passive and active behavioral conditions. STRF measurements were made simultaneously with task performance, providing multiple snapshots of the dynamic STRF during ongoing behavior. Attending to a specific target frequency during the detection task consistently induced localized facilitative changes in STRF shape, which were swift in onset. Such modulatory changes may enhance overall cortical responsiveness to the target tone and increase the likelihood of 'capturing' the attended target during the detection task. Some receptive field changes persisted for hours after the task was over and hence may contribute to long-term sensory memory.

Acoustic Stimulation↗
PubMed2003

Electronic doors to education: study of high school website accessibility in Iowa.

The Americans with Disabilities Act (ADA), and Sections 504 and 508 of the Rehabilitation Act, prohibit discrimination against people with disabilities in all aspects of daily life, including education, work, and access to places of public accommodations. Increasingly, these antidiscrimination laws are used by persons with disabilities to ensure equal access to e-commerce, and to private and public Internet websites. To help assess the impact of the anti-discrimination mandate for educational communities, this study examined 157 website home pages of Iowa public high schools (52% of high schools in Iowa) in terms of their electronic accessibility for persons with disabilities. We predicted that accessibility problems would limit students and others in obtaining information from the web pages as well as limiting ability to navigate to other web pages. Findings show that although many web pages examined included information in accessible formats, none of the home pages met World Wide Web Consortium (W3C) standards for accessibility. The most frequent accessibility problem was lack of alternative text (ALT tags) for graphics. Technical sophistication built into pages was found to reduce accessibility. Implications are discussed for schools and educational institutions, and for laws, policies, and procedures on website accessibility.

Persons with Disabilities↗
PubMed2003

Technology for independence: a community-based resource center.

Despite the prominence of the disability civil rights model--with its values of inclusion and empowerment--the majority of social and policy research conducted to date has not sufficiently included the perspective of persons with disabilities in the research process and as uniquely qualified researchers themselves. This article describes a new project, "Technology for Independence: A Community-Based Resource Center" (CBRC). Over a five-year period, the CBRC will attempt to enhance community and consumer-directed disability organizations to design, implement, and disseminate research that promotes access to and use of assistive technology (AT). The CBRC will use strategies such as leadership training, participatory action research, technical assistance, web-assisted training, and annual symposia. A primary goal of the CBRC is to increase the capacity of community organizations to conduct research on AT that is scientifically rigorous and relevant to disability services, policy, and law.

Activities of Daily Living↗
PubMed2003

Adherence to colorectal cancer screening in mammography-adherent older women.

Colorectal cancer (CRC) is the third leading cause of cancer mortality among women. Screening can prevent the development of CRC or diagnose early disease when it can effectively be cured, however existing screening methods are underutilized. In this study, we examined the utility of an updated Health Belief Model to explain CRC screening adherence. The present study included 280 older women seeking routine mammography at a large, urban breast diagnostic facility. Overall, 50% of women were adherent to CRC screening guidelines. Multiple regression indicated that self-efficacy, physician recommendation, perceived benefits of and perceived barriers to screening accounted for 40% of variance in CRC screening adherence. However, there was no evidence for two mediational models with perceived benefits and perceived barriers as the primary mechanisms driving adherence to CRC screening. These findings may inform both future theoretical investigations as well as clinical interventions designed to increase CRC screening behavior.

Aged↗
PubMed2003

Design for a brain revisited: the neuromorphic design and functionality of the interactive space 'Ada'.

While much is now known about the operation and organisation of the brain at the neuronal and microcircuit level, we are still some way from understanding it as a complete system from the lowest to the highest levels of description. One way to gain such an integrative understanding of neural systems is to construct them. We have built the largest neuromorphic system yet known, an interactive space called 'Ada' that is able to interact with many people simultaneously using a wide variety of sensory and behavioural modalities. 'She' received 553,700 visitors over 5 months during the Swiss Expo.02 in 2002. In this paper we present the broad motivations, design and technologies behind Ada, and discuss the construction and analysis of the system.

Behavior↗
PubMed1998

Convergence of Hamiltonian systems to billiards.

We examine in detail a physically natural and general scheme for gradually deforming a Hamiltonian to its corresponding billiard, as a certain parameter k varies from one to infinity. We apply this limiting process to a class of Hamiltonians with homogeneous potential-energy functions and further investigate the extent to which the limiting billiards inherit properties from the corresponding sequences of Hamiltonians. The results are mixed. Using theorems of Yoshida for the case of two degrees of freedom, we prove a general theorem establishing the "inheritability" of stability properties of certain orbits. This result follows naturally from the convergence of the traces of appropriate monodromy matrices to the billiard analog. However, in spite of the close analogy between the concepts of integrability for Hamiltonian systems and billiards, integrability properties of Hamiltonians in a sequence are not necessarily inherited by the limiting billiard, as we show by example. In addition to rigorous results, we include numerical examples of certain interesting cases, along with computer simulations. (c) 1998 American Institute of Physics.

Journal Article↗
PubMedDate not supplied

Technique for internal fixation of capitellum and lateral trochlea fractures.

Internal fixation for fractures of the humeral capitellum is a technically challenging procedure. Controversy exists regarding the optimal surgical approach and fixation technique. The benefit of stable fixation of the capitellum fragment is early mobilization. Our preferred technique involves anatomic reduction of the capitellar fragment and fixation with headless screws placed from anterior to posterior. When possible, the surgical exposure employed preserves the lateral ulnar collateral ligament (LUCL) and minimizes disruption of the soft tissues posterior to the capitellum.

Bone Screws↗