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Biomedical subjects

Andrew White

Publications and source records attributed to Andrew White.

18 recordsLinked to original sources

The use of radiotelemetry to evaluate electrographic seizures in rats with kainate-induced epilepsy.

Temporal lobe epilepsy in humans is a chronic condition with a highly variable temporal evolution. Animal models of this disorder have been developed to recapitulate many of the characteristics seen in humans with temporal lobe epilepsy. These animal models generate chronic spontaneous electrographic and motor seizures with a progressive increase in frequency over many months. In order to understand the underlying cellular and molecular mechanisms driving epileptogenesis, a practical means for accurately assessing seizure progression over this extended time period must be devised. In this report, we describe the use of a three-channel radiotelemetry system to record spontaneous electrographic interictal "spikes" and seizure activity from the cortical surface and the two hippocampi. This approach has allowed continuous recording before, during, and several months after kainate-induced status epilepticus. The important advantages of this approach are the potential for long-term continuous electrographic recording with comparatively unrestricted behavior; the disadvantages include increased cost, surgical difficulty and lower frequency-response in the recordings.

Action Potentials↗

Delayed density-dependent season length alone can lead to rodent population cycles.

Studies of cyclic microtine populations (voles and lemmings) have suggested a relationship between the previous year's population density and the subsequent timing of the onset of reproduction by overwintered breeding females. No studies have explored the importance of this relationship in the generation of population cycles. Here we mathematically examine the implications of variation in reproductive season length caused by delayed density-dependent changes in its start date. We demonstrate that when reproductive season length is a function of past population densities, it is possible to get realistic population cycles without invoking any changes in birth rates or survival. When parameterized for field voles (Microtus agrestis) in Kielder Forest (northern England), our most realistic model predicts population cycles of similar periodicity to the Kielder populations. Our study highlights the potential importance of density-dependent reproductive timing in microtine population cycles and calls for investigations into the mechanism(s) underlying this phenomenon.

Animals↗

Cultivating systemic capacity: the Rhode Island tobacco control enhancement project.

This paper describes the Rhode Island Tobacco Control Enhancement Project (TCEP), a state-university-community technical assistance system. TCEP was developed under the auspices of the Rhode Island Department of Health's Tobacco Control program and was designed to build capacity among nine community-based organizations to mount comprehensive tobacco control interventions in five diverse communities within the state. This paper: (1) provides a description of community mobilization; (2) presents a logic model for planning and decision making used by state-university-community partners; (3) describes training, technical assistance services and implementation; and, (4) describes the evaluation and program improvement activities used to support on-going project development.

Comprehensive Health Care↗

Duration of illness is an important variable for untreated children with juvenile dermatomyositis.

OBJECTIVE: To evaluate the impact of duration of untreated symptoms in children with juvenile dermatomyositis (JDM) on clinical and laboratory status at diagnosis. STUDY DESIGN: We examined physical and laboratory data from the first physician visit for 166 untreated children with JDM. Disease activity scores (DASs) assessed skin and muscle involvement. Height and weight were compared with the National Health and Nutrition Examination Survey III dataset. Duration of untreated illness was designated as the time from first sign of rash or weakness to diagnostic visit. RESULTS: Boys and girls with untreated JDM were shorter and lighter than national norms (P > .0005 for both), and nonwhite children were weaker than white children (P > .0005). Older children had more dysphagia (P = .017) and arthritis (P > .001). Duration of untreated JDM was negatively associated with DAS weakness (P > .0005), unrelated to DAS skin, and positively associated with pathological calcifications (P = .006). With untreated disease > or = 4.7 months, serum levels of 4 muscle enzymes (aldolase, lactic dehydrogenase, creatine kinase, serum glutamic-oxaloacetic transaminase/aspartate aminotransferase) tended toward normal (P > .01 for each). CONCLUSIONS: Duration of untreated symptoms is an important variable and should be included in decisions concerning both diagnostic criteria and intensity of therapy for children with JDM.

Abdominal Pain↗

Intranasal ketorolac challenge for the diagnosis of aspirin-exacerbated respiratory disease.

BACKGROUND: Intranasal administration of aspirin-lysine has been used in Europe for the diagnosis of aspirin-exacerbated respiratory disease. It has a low adverse effect profile and is believed to be safer for asthmatic patients, particularly those with a low baseline forced expiratory volume in 1 second, in whom oral aspirin challenge would be contraindicated. Ketorolac, a nonsteroidal anti-inflammatory drug useful for severe pain, is available in the United States in parenteral form. OBJECTIVE: To determine whether ketorolac nasal challenge has acceptable specificity and sensitivity for diagnosing aspirin-exacerbated respiratory disease. METHODS: Twenty-nine patients with suspected aspirin-exacerbated respiratory disease were challenged with nasal ketorolac before oral challenge and desensitization with aspirin. Symptoms, objective changes in nasal examination findings, and peak nasal inspiratory flow values were recorded. Nasal lavage fluid for cysteinyl leukotriene analysis was collected. Ketorolac doses of 2.1, 5.2, or 7.8 mg were administered and compared with the results of oral aspirin challenge. RESULTS: Eighteen patients had a positive challenge reaction to oral aspirin. Ketorolac nasal inhalation had a sensitivity of 78% and a specificity of 64%. Patients in the reactor group had significantly higher levels of cysteinyl leukotrienes after ketorolac challenge than in the nonreactor group. Mild bronchospasm occurred in 3 patients, and 2 of these occurred at higher starting doses of ketorolac. CONCLUSIONS: Nasal ketorolac administration is a reasonably accurate and safe method for diagnosing aspirin-exacerbated respiratory disease.

Administration, Intranasal↗

Effect of leukotriene modifier drugs on the safety of oral aspirin challenges.

BACKGROUND: Aspirin-exacerbated respiratory disease can be diagnosed with oral aspirin challenges and treated with aspirin desensitization. OBJECTIVE: To evaluate whether controller medications, particularly leukotriene modifier drugs, taken during oral aspirin challenges can reduce the risk of severe asthmatic responses. METHODS: The medical records of 676 patients who had undergone oral aspirin challenges, followed by aspirin desensitization, were reviewed. Asthmatic responses were stratified based on severity of bronchospastic response or lack of response. The effect of pretreatment with controller medications on the outcome of oral aspirin challenges was measured. RESULTS: Leukotriene modifier drugs had the most significant effect in protecting the lower airways from severe reactions (P = .004). The protective effect of leukotriene modifier drugs was observed in patients already taking systemic corticosteroids, where the addition of leukotriene modifier drugs significantly shifted the response toward a milder asthmatic response (P < .001). CONCLUSION: Protection from significant aspirin-induced bronchospasm during oral aspirin challenge can be accomplished with leukotriene modifier drugs. The use of a combination of inhaled corticosteroids, long-acting beta-agonists, systemic corticosteroids, and leukotriene modifier drugs stabilized underlying airways in preparation for a reasonably safe and accurate oral aspirin challenge. However, only pretreatment with leukotriene modifier drugs enhanced the safety of oral aspirin challenge in patients with aspirin-exacerbated respiratory disease by significantly decreasing the degree of asthmatic responses. Therefore, outpatient oral aspirin challenges in most well-selected patients appear to be a reasonable decision.

Acetates↗

The evolution of parasites in response to tolerance in their hosts: the good, the bad, and apparent commensalism.

Tolerance to parasites reduces the harm that infection causes the host (virulence). Here we investigate the evolution of parasites in response to host tolerance. We show that parasites may evolve either higher or lower within-host growth rates depending on the nature of the tolerance mechanism. If tolerance reduces virulence by a constant factor, the parasite is always selected to increase its growth rate. Alternatively, if tolerance reduces virulence in a nonlinear manner such that it is less effective at reducing the damage caused by higher growth rates, this may select for faster or slower replicating parasites. If the host is able to completely tolerate pathogen damage up to a certain replication rate, this may result in apparent commensalism, whereby infection causes no apparent virulence but the original evolution of tolerance has been costly. Tolerance tends to increase disease prevalence and may therefore lead to more, rather than less, disease-induced mortality. If the parasite is selected, even a highly efficient tolerance mechanism may result in more individuals in total dying from disease. However, the evolution of tolerance often, although not always, reduces the individual risk of dying from infection.

Animals↗

Adaptive dynamics of Lotka-Volterra systems with trade-offs: the role of interspecific parameter dependence in branching.

We determine the adaptive dynamics of a general Lotka-Volterra system containing an intraspecific parameter dependency--in the form of an explicit functional trade-off between evolving parameters--and interspecific parameter dependencies--arising from modelling species interactions. We develop expressions for the fitness of a mutant strategy in a multi-species resident environment, the position of the singular strategy in such systems and the non-mixed second-order partial derivatives of the mutant fitness. These expressions can be used to determine the evolutionary behaviour of the system. The type of behaviour expected depends on the curvature of the trade-off function and can be interpreted in a biologically intuitive manner using the rate of acceleration/deceleration of the costs implicit in the trade-off function. We show that for evolutionary branching to occur we require that one (or both) of the traded-off parameters includes an interspecific parameter dependency and that the trade-off function has weakly accelerating costs. This could have important implications for understanding the type of mechanisms that cause speciation. The general theory is motivated by using adaptive dynamics to examine evolution in a predator-prey system. The applicability of the general theory as a tool for examining specific systems is highlighted by calculating the evolutionary behaviour in a three species (prey-predator-predator) system.

Algorithms↗

The geometric theory of adaptive evolution: trade-off and invasion plots.

The purpose of this paper is to take an entirely geometrical path to determine the evolutionary properties of ecological systems subject to trade-offs. In particular we classify evolutionary singularities in a geometrical fashion. To achieve this, we study trade-off and invasion plots (TIPs) which show graphically the outcome of evolution from the relationship between three curves. The first invasion boundary (curve) has one strain as resident and the other strain as putative invader and the second has the roles of the strains reversed. The parameter values for one strain are used as the origin with those of the second strain varying. The third curve represents the trade-off. All three curves pass through the origin or tip of the TIP. We show that at this point the invasion boundaries are tangential. At a singular TIP, in which the origin is an evolutionary singularity, the invasion boundaries and trade-off curve are all tangential. The curvature of the trade-off curve determines the region in which it enters the singular TIP. Each of these regions has particular evolutionary properties (EUS, CS, SPR and MI). Thus we determine by direct geometric argument conditions for each of these properties in terms of the relative curvatures of the trade-off curve and invasion boundaries. We show that these conditions are equivalent to the standard partial derivative conditions of adaptive dynamics. The significance of our results is that we can determine whether the singular strategy is an attractor, branching point, repellor, etc. simply by observing in which region the trade-off curve enters the singular TIP. In particular we find that, if and only if the TIP has a region of mutual invadability, is it possible for the singular strategy to be a branching point. We illustrate the theory with an example and point the way forward.

Adaptation, Physiological↗

Risk of ventricular proarrhythmia with selective opening of the myocardial sarcolemmal versus mitochondrial ATP-gated potassium channel.

Myocardial ATP-gated potassium channels (K-ATPs) are critical in the intracellular signaling cascade resulting in ischemic preconditioning (IP). Mitochondrial K-ATP channels seem to be responsible for IP, whereas the functions of K-ATP channels in the sarcolemmal membrane are less well understood. The proarrhythmic potential of specific versus nonspecific opening of K-ATP channels has not been investigated. In this study, Langendorff-perfused rabbit hearts were exposed to either pinacidil (1.25 microM), a nonselective K-ATP channel agonist, or selective mitochondrial or sarcolemmal K-ATP channel agonists or antagonists. The hearts were then subjected to 12 min of hypoxic perfusion and 40 min of reoxygenation. Hearts were monitored for the induction of ventricular fibrillation (VF). No heart subjected to hypoxia-reoxygenation without drug treatment developed VF (0 of 5). Pinacidil pretreatment induced VF (12 of 14; p = 0.004 versus control). Pinacidil's effect was blocked by HMR-1098 (1-[5-[2-(5-chloro-o-anisamide)ethyl]-2-methoxyphenyl]sulfonyl]-3-methylthiourea) (1 microM), a selective sarcolemmal K-ATP channel antagonist (1 of 7; p = 0.007 versus pinacidil; N.S. versus control). Hearts pretreated with 5-hydroxydecanoate (5-HD) (100 microM), a putatively selective mitochondrial K-ATP channel blocker developed VF in one of eight trials (N.S. versus control). 5-HD did not alter the effects of pinacidil (6 of 8; p < 0.05 versus control; N.S. versus pinacidil alone). Selective mitochondrial K-ATP channel activation with [(3R)-trans-4-((4-chlorophenyl)-N-(1H-imidazol-2-ylmethyl)dimethyl-2H-1-benzopyran-6-carbonitril monohydrochloride] (BMS-191095) (6 microM) resulted in zero of five hearts developing VF (N.S. versus control). Our data suggest that selective opening of the sarcolemmal K-ATP channel during hypoxia-reoxygenation induced VF, whereas opening of the mitochondrial channel was not associated with VF. The findings suggest that caution should be exercised when developing compounds aimed at inducing IP, and nonspecific opening of the K-ATP channel should be avoided.

Animals↗

Changes in bone architecture in the femoral head and neck in osteoarthritis.

This study analyses changes in the bony architecture of the femoral head and neck in osteoarthritis. Five osteoarthritic hips were obtained from female patients undergoing total hip replacement and were compared to non-arthritic control specimens from the dissecting room. Analysis was carried out on a coronal bony slice of the femoral head and on a transverse section of the upper femoral neck. The results indicated that in the region of the compressive trabeculae the intertrabecular areas were generally smaller in the osteoarthritic specimens and that the inferior part of the cortex of the femoral neck had thickened. Our data thus quantified changes consistent with the thickening of compressive trabeculae reported by others and with thickening of the region of the femoral neck on which they converge. We found less trabecular bone in non-weight-bearing regions of the lower femoral head and in the medulla of the upper neck in the osteoarthritic specimens consistent with loss of tensile trabeculae. Scanning electron microscopy suggested that bone resorption activity was higher in the subchondral and non-weight-bearing regions of the osteoarthritic femoral heads than in the controls.

Aged↗

Surgical adverse events, risk management, and malpractice outcome: morbidity and mortality review is not enough.

OBJECTIVE: To review all admissions (age > 13) to three surgical patient care centers at a single academic medical center between January 1, 1995, and December 6, 1999, for significant surgical adverse events. SUMMARY BACKGROUND DATA: Little data exist on the interrelationships between surgical adverse events, risk management, malpractice claims, and resulting indemnity payments to plaintiffs. The authors hypothesized that examination of this process would identify performance improvement opportunities overlooked by standard medical peer review; the risk of litigation would be constant across the three homogeneous patient care centers; and the risk management process would exceed the performance improvement process. METHODS: Data collected included patient demographics (age, gender, and employment status), hospital financials (hospital charges, costs, and financial class), and outcome. Outcome categories were medical (disability: <1 month, 1-6 months, permanent/death), legal (no legal action, settlement, summary judgment), financial (indemnity payments, legal fees, write-offs), and cause and effect analysis. Cause and effect analysis attempts to identify system failures contributing to adverse outcomes. This was determined by two independent analysts using the 17 Harvard criteria and subdividing these into subsystem causative factors. RESULTS: The study group consisted of 130 patients with surgical adverse events resulting in total liabilities of $8.2 million US dollars. The incidence of adverse events per 1,000 admissions across the three patient care centers was similar, but indemnity payments per 1,000 admissions varied (cardiothoracic = $30 US dollars, women's health = $90 US dollars, trauma = $520 US dollars). Patient demographics were not predictive of high-risk subgroups for adverse events or litigation. In terms of medical outcome, 51 patients had permanent disability or death, accounting for 98% of the indemnity payments. In terms of legal outcome, 103 patients received no indemnity payments, 15 patients received indemnity payments, four suits remain open, and in eight cases charges were written off ($0.121 million US dollars). To date, no cases have been adjudicated in court. Cause and effect analysis identified 390 system failures contributing to the adverse events (mean 3.0 failures per adverse event); there were 4.7 failures per adverse event in the 15 indemnity cases. Five categories of causes accounted for 75% of the failures (patient management, n = 104; communication, n = 89; administration, n = 33; documentation, n = 32; behavior, n = 23). The current medical review process would have identified 104 of 390 systems failures (37%). CONCLUSIONS: This study demonstrates no rational link between the tort system and the reduction of adverse events. Sixty-three percent of contributing causes to adverse events were undetected by current medical review processes. Adverse events occur at the interface between different systems or disciplines and result from multiple failures. Indemnity costs per hospital day vary dramatically by patient care center (range $3.60-97.60 US dollars a day). The regionalization of healthcare is in jeopardy from the burden of high indemnity payments.

Academic Medical Centers↗

The adaptive dynamics of Lotka-Volterra systems with trade-offs.

We analyse the adaptive dynamics of a generalised type of Lotka-Volterra model subject to an explicit trade-off between two parameters. A simple expression for the fitness of a mutant strategy in an environment determined by the established, resident strategy is obtained leading to general results for the position of the evolutionary singular strategy and the associated second-order partial derivatives of the mutant fitness with respect to the mutant and resident strategies. Combinations of these results can be used to determine the evolutionary behaviour of the system. The theory is motivated by an example of prey evolution in a predator-prey system in which results show that only (non-EUS) evolutionary repellor dynamics, where evolution is directed away from a singular strategy, or dynamics where the singular strategy is an evolutionary attractor, are possible. Moreover, the general theory can be used to show that these results are the only possibility for all Lotka-Volterra systems in which aside from the trade-offs all parameters are independent and in which the interaction terms are of quadratic order or less. The applicability of the theory is highlighted by examining the evolution of an intermediate predator in a tri-trophic model.

Adaptation, Biological↗

Antibodies to streptococcal inhibitor of complement function and M peptides in a post-streptococcal glomerulonephritis endemic region of Australia.

Post-streptococcal glomerulonephritis (PSGN) is an immune-mediated disease in which an immune complex containing a streptococcal antigen are deposited in affected glomeruli. Strains of only some M types are known to be associated with PSGN. A secretory protein called SIC inhibits complement function. Whereas all M1 and M57 strains express closely related SIC (CRS), all M12 and M55 strains express distantly related SIC (DRS) proteins. Strains belonging to these four M types are historically associated with PSGN. This study used ELISA to analyse 112 sera from individuals with a recorded history of PSGN and 86 sera from individuals who had no such recorded history, all from a PSGN endemic region in tropical Australia. Antibody reactions to CRS, DRS and peptides corresponding to the N-termini of M1, M5, M12, M49, M55 and M57 antigens were assessed. A large proportion of the population showed reactions to each of these antigens and there was no correlation between CRS seropositivity and antibodies to CRS-positive M types. Likewise there was no correlation between DRS seropositivity and antibodies to DRS-positive M types. Interestingly, in this community endemic for PSGN a significantly higher proportion of DRS seropositive subjects had a recorded history of PSGN than did DRS seronegative subjects. DRS may have a predictive value for PSGN diagnosis or a role in PSGN pathogenesis.

Adolescent↗

Diheteroarylmethanes. 6.(1) Probing the Electron-Withdrawing Rank of Heteroaryl Groups by Conformational Studies of Push-Pull Ethylenes. Isolation of NH-Enamine Tautomers of alpha,alpha-Diheteroarylacetaldehydes (Heteroaryl = 2-Benzoxazolyl, 2-Benzothiazolyl).

Enamines and enol ethers substituted in the beta position by the 2-benzoxazolyl and 2-benzothiazolyl group have been obtained by condensing dimethylformamide dimethyl acetal and ethyl orthoformate, respectively, with bis(2-benzoxazolyl)methane and bis(2-benzothiazolyl)methane. A dynamic NMR and semiempirical (PM3) investigation on rotational energy barriers has been carried out in order to rank the electron-withdrawing capacity of the heterocyclic rings. The NMR-based evaluation of the energy barriers corresponding to the rotation along the enaminic double bond has shown that the pi-electron-withdrawing power of benzothiazole is larger than that of benzoxazole, in full accord with previously obtained charge demand values based on (13)C and (15)N pi-charge/shift relationships. The NMR and the computational approaches have led to consistent results. The X-ray crystal structure of alpha,alpha-bis(2-benzothiazolyl)-beta-(dimethylamino)ethene shows that only one heteroaryl ring is coplanar with the enaminic double bond, while the second one is twisted by 73 degrees relative to such a plane. Moreover, in this case calculations closely reproduce the experimental results. In the calculated transition states corresponding to the rotational process along the enamine double bond, the two heteroaryl groups become coplanar and conjugation develops between the enaminic nitrogen electron pool and both heterocycles. The lower rotational barrier observed in the case of the 2-benzothiazolyl derivatives, with respect to the 2-benzoxazolyl derivatives, is therefore a direct consequence of the higher electron-withdrawing power of the former group. Furthermore, a stabilizing intramolecular nonbonded S.S interaction in the rotational transition state of the benzothiazolyl derivatives is evidenced by the calculations. An unprecedented isolation of the NH-enamine tautomer involving the benzoxazolyl and benzothiazolyl ring in alpha,alpha-diheteroacetaldehydes has been performed, confirming these heterocycles as strong electron-withdrawing substituents.

Journal Article↗