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Biomedical subjects

S Davidson

Publications and source records attributed to S Davidson.

At least 37 records · Page 2Linked to original sources
PubMed2000

Analysis of switching insurance plan type. Comparison of two statistical methods.

PURPOSE: To compare results of 2 statistical methods for identifying factors in claims data that are associated with switching insurance plans between managed care (MC) and indemnity (IN).METHODS: Using claims data from 2 insurance providers in a northeastern city, we analyzed patients aged 18+ with diabetes, asthma, or congestive heart failure (CHF) who were covered any time in 1993-1997 (N = 88,917). Stratifying by initial plan type, we examined predictors of switching from the initial plan type using logistic regression and survival analysis. Covariates included age, time in study (for logistic models), gender, diabetes (yes/no), CHF (yes/no), and asthma (yes/no). Survival analysis accounted for time to switch and allowed time-varying covariates.RESULTS: In logistic regression models, older individuals who were in IN were much less likely to switch into MC. Those in MC were more likely to switch to IN, with the greatest likelihood of switching in ages 60-69 (OR = 4.00, 95% CI = 3.32-4.83). Females were less likely to switch from IN to MC (OR = 0.92, 95% CI = 0.87-0.98), CHF patients were less likely to switch from IN to MC (OR = 0.75, 95% CI = 0.68-0.83), and diabetes patients were less likely to switch from MC to IN (OR = 0.77, 95% CI = 0.62-0.96). Hazard ratios calculated using Cox regression were similar to odds ratios for most covariates. However, some coefficients for diseases were significant in Cox models but not in the logistic models. Cox models took 45 times longer in CPU time than logistic regression models.CONCLUSIONS: Logistic regression was a good approximation to Cox regression in identifying many of the factors in switching insurance plan in these data, at a fraction of the computing time. However, Cox models allowed diseases to be time-varying, and so was more sensitive to identifying significant relationships with disease.

Journal Article↗
PubMed2000

Baryogenesis at low reheating temperatures

We note that the maximum temperature during reheating can be much greater than the reheating temperature T(r) at which the universe becomes radiation dominated. We show that the standard model anomalous (B+L)-violating processes can therefore be in thermal equilibrium for 1 GeV less, similarT(r)<<100 GeV. Electroweak baryogenesis could work and the traditional upper bound on the Higgs mass coming from the requirement of the preservation of the baryon asymmetry may be relaxed. Alternatively, the baryon asymmetry may be reprocessed by sphaleron transitions either from a (B-L) asymmetry generated by the Affleck-Dine mechanism or from a chiral asymmetry between e(R) and e(L) in a B-L = 0 universe.

Journal Article↗
PubMed2000

Cyclosporin A induces an atypical heat shock response.

Cyclosporin A is a widely used immunosuppressive drug having toxic side effects, in particular on kidneys and liver, as a result of its action on different molecular targets. Here we demonstrate that low doses of CsA are able to induce the expression of the heat shock protein HSP27 and its hyperphosphorylation. It also activates the two heat shock transcription factors, HSF1 and HSF2. Since these factors have been shown to be activated by proteasome inhibition, we tested the hypothesis that the inhibitory action of CsA on the proteasome might be responsible for the activation of HSFs and the subsequent expression of HSP27. The increase in multiubiquitinated proteins as well as the stabilization of p53 following CsA addition argues in favor of this hypothesis. The kidney BSC-1 cells are highly responsive to the addition of CsA: the possible link between HSP27 induction and hyperphosphorylation and nephrotoxicity is discussed.

Animals↗
PubMed2000

Molecular definition of a small amplification domain within 3q26 in tumors of cervix, ovary, and lung.

A common amplification target encompassing chromosome region 3q25 to q27 has been identified by comparative genomic hybridization analyses in tumors of the cervix, ovary, endometrium, lung, and head and neck. Because this segment spans at least 30 megabases, we undertook a molecular analysis of copy number to more precisely define the amplification domain. Our Southern blot and fluorescence in situ hybridization results with the use of 17 markers confirmed the presence of low-level 3q amplification events in cervical, ovarian, and variant SCLC tumors. Most of the tumor types studied appeared to have similar, broad amplification domains centered within 3q26.2, suggesting that the same target is being affected in all. The ovarian carcinoma cell line NIH:OVCAR3 had a highly restricted amplification domain spanned by four overlapping YAC clones, suggesting a small target. The region of highest amplification included the gene for the RNA component of telomerase (hTR), supporting it as a potential target. Although the importance of low-level amplification is unknown, the consistent and reproducible nature of this event in a variety of carcinomas suggests that 3q26.2 harbors an oncogene whose low-level amplification has a significant influence on tumor biology.

Blotting, Southern↗
PubMed2000

Cost comparison between three different general anaesthetic techniques for elective arthroscopy of the knee.

INTRODUCTION: We compared three anaesthetic techniques for elective knee arthroscopy with special reference to cost-effectiveness. METHOD: Seventy-five ASA I-II patients having elective arthroscopy of the knee joint were randomised to receive an anaesthetic technique based on propofol, fentanyl for induction followed by sevoflurane in oxygen:nitrous oxide (1:2 l/min) for maintenance of one of two intravenous techniques: propofol alfentanil or propofol-remifentanil infusions in combination with oxygen in air. RESULTS: All patients had an uncomplicated course. No differences were seen with regard to emergence, postoperative pain or emesis or time to discharge. The anaesthetic technique based on sevoflurane was associated with the lowest cost US$ 14.7 as compared to US$ 18 for the propfol/alfentanil and US$ 19.9 for the propofol/remifentanil technique, including both cost for wastage as well as premedication and other fixed drug costs. Looking only at the anaesthetic drugs consumed, the cost per minute was US$ 0.56 for sevoflurane/nitrous oxide as compared to US$ 0.68 and 0.63 per minute for the propofol/alfentanil and proprofol/remifentanil, respectively. When the cost for wastage was taken into account, the difference in mean anaesthetic drug cost was more pronounced: the sevoflurane anaesthetic technique US$ 0.58, the propofol/alfentanil US$ 0.74 and the propofol/remifentanil US$ 0.84 per minute respectively. CONCLUSION: From a cost-minimisation point of view, anaesthesia based on sevoflurane in oxygen:nitrous oxide is the technique of choice.

Adult↗
PubMed2000

Recurrent skin peeling following Kawasaki disease.

Long term follow up of 259 cases of Kawasaki disease led to the observation that 11% of children have episodes of recurrent peeling of the skin for several years after their recovery. These events were usually associated with an upper respiratory tract infection and were distinct from a recurrence of Kawasaki disease. Repeeling was significantly less frequent in children who had suffered coronary artery dilatation and was more frequently seen in those with nasal staphylococcal colonisation. The mechanism for this phenomenon is unclear, but it has been observed in a number of other conditions caused by infectious agents and their toxins. Paediatricians need to be aware of this phenomenon which is distinct from recurrence of Kawasaki disease.

Adolescent↗
PubMed2000

High-density hapten labeling and HRP conjugation of oligonucleotides for use as in situ hybridization probes to detect mRNA targets in cells and tissues.

Oligonucleotides that carry a detectable label can be used to probe for mRNA targets in in situ hybridization experiments. Oligonucleotide probes (OPs) have several advantages over cDNA probes and riboprobes. These include the easy synthesis of large quantities of probe, superior penetration of probe into cells and tissues, and the ability to design gene- or allele-specific probes. One significant disadvantage of OPs is poor sensitivity, in part due to the constraints of adding and subsequently detecting multiple labels per oligonucleotide. In this study, we compared OPs labeled with multiple detectable haptens (such as biotin, digoxigenin, or fluorescein) to those directly conjugated with horseradish peroxidase (HRP). We used branching phosphoramidites to add from two to 64 haptens per OP and show that in cells, 16-32 haptens per OP give the best detection sensitivity for mRNA targets. OPs were also made by directly conjugating the same oligonucleotide sequences to HRP. In general, the HRP-conjugated OPs were more sensitive than the multihapten versions of the same sequence. Both probe designs work well both on cells and on formaldehyde-fixed, paraffin-embedded tissues. We also show that a cocktail of OPs further increases sensitivity and that OPs can be designed to detect specific members of a gene family. This work demonstrates that multihapten-labeled and HRP-conjugated OPs are sensitive and specific and can make superior in situ hybridization probes for both research and diagnostic applications.

Biotin↗
PubMed2000

An operations model of psychosocial structure and function and of psychotherapy.

Currently, personality theory and clinical psychology have a fairly substantial tradition of promoting a strongly scientific basis for clinical work and theorizing. However, an appropriate foundation model has been difficult to identify and establish. A theory of human operations, here proposed, may provide such an elementary model. The theory is rooted in the organizational and industrial field known as operations, which is a highly systematic, precise, flexible, scientific approach to the understanding and management of human goal-seeking action in the broadest sense. The proposed model includes the classical humanistic, clinical, and decision theoretic notions of values, cognition, emotions, ego, behavior, objectives, outcomes, feedback, and defenses. These notions are placed within an overall operations frame of reference and developed in such a manner that they can be used to assess human clinical problems and to design therapeutic interventions. The strengths and limitations of the model are discussed.

Cognition↗
PubMed1999

Identification of differentially expressed mRNAs in human fetal liver across gestation.

Differential gene expression, with its precise start and stop times, is believed to be critical for the programmed development of new cells and tissues. Within the developing fetus, one tissue of particular interest is fetal liver. This organ undergoes rapid changes in the pathway toward liver development in utero since it is also the major site of hematopoiesis, until bone marrow hematopoiesis predominates. Believing that patterns would emerge from the bi-weekly large-scale inspection of expressed genes in the fetal liver, we employed differential display reverse transcription-polymerase chain reaction (DDRT-PCR) as ourprimary inspection tool. Using DDRT-PCR, we isolated cDNAs differentially expressed throughout fetal liver development and in adult liver. We displayed approximately 25 000 cDNAs from 10 and 24 week fetal liver and adult liver. From this initial screen, we determined that approximately 0.1-1% of the mRNA population undergoes expression changes. We extracted, purified and sequenced 25 differentially displayed cDNA bands. Fourteen cDNAs had similarities to known genes, while 11 cDNAs were not similar to any characterized gene. The differentially expressed cDNAs from known genes present in fetal liver include alpha-fetoprotein, stem cell factor, erythroid alpha-spectrin, 2,3-bisphosphoglycerate mutase, insulin-like growth factor-2, porphobilinogen deaminase and Mac30. The differentially expressed cDNAs present in adult liver but not in 10 week fetal liver were nicotinamide deaminase, human fibrinogen-related protein and alpha-acid glycoprotein. The majority of differentially expressed genes found during this effort appear to be turned on during organogenesis, however, some genes were found that are apparently turned off completely.

Adult↗
PubMed1999

Laser ablation of urethral hair.

BACKGROUND AND OBJECTIVE: Two separate cases involving laser ablation of hair follicles in the neourethra are described. STUDY DESIGN/MATERIALS AND METHODS: Urethral hair developed secondarily to free-flap urethroplasty for congenital urethral defects. In both cases, cystoscopic depilation with electrocautery fulguration was attempted on multiple occasions. RESULTS: No improvement was seen; therefore, laser ablation was employed. Both patients remain free of regrowth at greater than one year of follow-up.

Adult↗