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J G Scott

Publications and source records attributed to J G Scott.

At least 37 records · Page 2Linked to original sources
PubMed1999

Cytochromes P450 and insecticide resistance.

The cytochrome P450-dependent monooxygenases (monooxygenases) are an extremely important metabolic system involved in the catabolism and anabolism of xenobiotics and endogenous compounds. Monooxygenase-mediated metabolism is a common mechanism by which insects become resistant to insecticides as evidenced by the numerous insect species and insecticides affected. This review begins by presenting background information about P450s, the role of monooxygenases in insects, and the different techniques that have been used to isolate individual insect P450s. Next, insecticide resistance is briefly described, and then historical information about monooxygenase-mediated insecticide resistance is reviewed. For any case of monooxygenase-mediated resistance, identification of the P450(s) involved, out of the dozens that are present in an insect, has proven very challenging. Therefore, the next section of the review focuses on the minimal criteria for establishing that a P450 is involved in resistance. This is followed by a comprehensive examination of the literature concerning the individual P450s that have been isolated from insecticide resistant strains. In each case, the history of the strain and the evidence for monooxygenase-mediated resistance are reviewed. The isolation and characterization of the P450(s) from the strain are then described, and the evidence of whether or not the isolated P450(s) is involved in resistance is summarized. The remainder of the review summarizes our current knowledge of the molecular basis of monooxygenase-mediated resistance and the implications for the future. The importance of these studies for development of effective insecticide resistance management strategies is discussed.

Animals↗
PubMed1999

Clinical utility of the Trail Making Test practice time.

The Trail Making Test (TMT) is one of the most frequently used measures in clinical neuropsychology. Data obtained from the TMT practice times were analyzed to determine their utility in predicting success and failure on the full version of the test and to allow establishment of criteria by which to judge administration or discontinuation of the full test. Results indicated that TMT practice times were useful in predicting successful completion of Part A and B of the TMT. Tables are provided which describe the classification accuracy of various TMT practice times. These tables allow clinicians to select a practice-time cutoff and then use the cutoff as a heuristic to assist in the decision to administer the remainder of that particular part of the TMT or discontinue the test. A 20-s cutoff resulted in optimal prediction of successful completion (< 180 s) of TMT Part A. A cutoff of 30 s optimally predicted successful completion (< 300 s) of TMT Part B.

Adult↗
PubMed1999

Review of magnet hospital research: findings and implications for professional nursing practice.

The label "magnet hospitals" originally was given to a group of U.S. hospitals that were able to successfully recruit and retain professional nurses during a national nursing shortage in the early 1980s. Studies of magnet hospitals illuminated the leadership characteristics and professional practice attributes of nurses within these organizations. Recent investigations within magnet hospitals document significant relationships between nursing and patient outcomes, including mortality and patient satisfaction. The purpose of this review is to: 1) synthesize the magnet hospital research that describes and evaluates the professional practice of nurses within these institutions and (2) identify areas for future research to advance professional nursing models within current hospital organizations.

Attitude of Health Personnel↗
PubMed1998

CYP6D1 protects thoracic ganglia of houseflies from the neurotoxic insecticide cypermethrin.

CYP6D1 is a housefly cytochrome P450 known to metabolize neurotoxic pyrethroid insecticides. To determine if the nervous system was capable of metabolizing pyrethroids, we examined CYP6D1-mediated in vitro metabolism in thoracic ganglia from pyrethroid-resistant (LPR) and -susceptible (CS) strains of housefly. SDS-PAGE/immunoblotting revealed that CYP6D1 was expressed in all tagmata and in thoracic ganglia of both strains, but in all cases the levels of CYP6D1 were higher in the LPR strain. Using a CYP6D1-specific antiserum, we found CYP6D1 to be the major, and possibly the only, P450 isozyme involved in cypermethrin metabolism in thoracic ganglia homogenates. Additionally, thoracic ganglia homogenates from LPR houseflies metabolize more cypermethrin than preparations from susceptible flies. This metabolism was inhibited by piperonyl butoxide and a CYP6D1-specific antibody. Our results indicate that thoracic ganglia of LPR houseflies are protected from the neurotoxin cypermethrin by virtue of the higher levels of CYP6D1 compared to the susceptible houseflies. This P450-mediated detoxification of an insecticide at the level of the target tissue helps to explain the high levels of resistance to pyrethroids in the LPR strain.

Animals↗
PubMed1998

Insect cytochromes P450: diversity, insecticide resistance and tolerance to plant toxins.

In the last decade, studies of individual insect P450s have blossomed. This new information has furthered our understanding of P450 diversity, insecticide resistance and tolerance to plant toxins. Insect P450s can be adult specific, larval specific or life stage independent. Similarly, insect P450s vary as to the tissues where they are expressed and in their response to inducers. Insect P450s can now be rapidly sequenced using degenerate PCR primers. Given the huge diversity represented by the Class Insecta, this technique will provide vast amounts of new information about insect P450s and the evolution of the P450 gene superfamily. CYP6D1 is responsible for monooxygenase-mediated resistance to pyrethroid insecticides in the house fly. CYP6D1 is ubiquitously expressed in adults with 10-fold higher levels found in the resistant strain compared to susceptible strains. CYP6D1 is on autosome 1 in house fly. The high level of expression found in the resistant strain is due to genes on autosomes 1 and 2. Whether or not the different CYP6D1 alleles found in resistant and susceptible strains have any role in resistance remains to be elucidated. The CYP6B gene subfamily is involved in the metabolism of host plant toxins (i.e. furanocoumarins). CYP6B gene transcripts in two Papilio (swallowtail) species have been shown to be induced by host plant toxins and in turn to metabolize these toxins. CYP6B P450s play a critical role in allowing Papilio to adapt to furanocoumarin-containing host plants. Similarities in structural and promoter regions of the CYP6B genes suggest that they are derived from a common ancestral gene. Although the P450 monooxygenases of insects are important for the metabolism of hormones and phermones, no individual P450 has yet been shown to metabolize an endogenous compound. Advances in this area are critical because they will provide important new information about insect physiology, biochemistry and development.

Animals↗
PubMed1998

Increased transcription of CYP6D1 causes cytochrome P450-mediated insecticide resistance in house fly.

Insecticide resistance is a major problem that continues to plague efforts to control pests of animals and crops. An important mechanism by which insects become resistant to insecticides is via increased detoxification mediated by the cytochrome P450 microsomal monooxygenases (monooxygenases). One of the fundamental gaps in our knowledge about this resistance mechanism is an understanding of how insects express high levels of the specific cytochrome P450(s) responsible for resistance. One such P450, CYP6D1, causes resistance to pyrethroid in the house fly and is expressed at 9-fold higher levels (mRNA and protein) in the Learn Pyrethroid Resistant (LPR) strain (compared to susceptible strains). The relative stability of CYP6D1 mRNA in resistant and susceptible strains was measured following inhibition of transcription with actinomycin D. The same time course of decrease in CYP6D1 mRNA abundance was detected in both strains indicating that the high level of expression of CYP6D1 in LPR is not due to increased stability of the mRNA. The comparative rates of transcription of CYP6D1 were measured using an in vitro run-on transcription assay. The relative amount of CYP6D1 transcript produced in this assay was 10-fold greater in the LPR strain compared to the susceptible strain. This demonstrates that increased transcription of CYP6D1 is an underlying cause of monooxygenase-mediated insecticide resistance. The increased rate of transcription of CYP6D1 in the resistant strain (LPR) is controlled by two factors: one on autosome 1 and another on autosome 2.

Animals↗
PubMed1997

Survival.

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Adult↗
PubMed1997

Clinical utility of Wechsler Memory Scale-Revised and predicted IQ discrepancies in closed head injury.

Comparisons between Wechsler Memory Scale-Revised (WMS-R) indexes and Wechsler Adult Intelligence Scale-Revised (WAIS-R) IQ scores have been proposed to identify severity of memory deficits. However, many neurologic conditions reduce both intellectual and memory functioning, and thus, examining differences between these scores may be of little value. Closed head injured subjects who completed the WMS-R were divided into either mild injury (MI, n = 41) or moderate/severe (SI, n = 41) injury groups based on trauma severity indicators and were matched on age and level of education. The Oklahoma Premorbid Intelligence Estimation (OPIE), a regression formula that takes into account demographic variables as well as IQ performance, was calculated for each subject. Discrepancy scores were calculated between predicted IQ scores and WAIS-R IQ and WMS-R indexes. SI head-injured subjects displayed significantly larger discrepancies (19 points) between OPIE scores and Delayed Recall Indexes from the WMS-R than the MI subjects (10 points). Significantly larger percentages of subjects in the SI group displayed significant (>SD) reductions in many of the WMS-R and WAIS-R scores from estimates than subjects in the MI group. Comparing current memory functioning to estimates of premorbid intellectual ability appears to be a sensitive indicator of presence and degree of intellectual and memory dysfunction in head trauma patients. Results also provide evidence that estimates of premorbid intellectual ability can serve as estimates of premorbid memory functioning.

Journal Article↗
PubMed1997

Functional expression of house fly (Musca domestica) cytochrome P450 CYP6D1 in yeast (Saccharomyces cerevisiae).

Cytochrome P450 CYP6D1 from the house fly is important in the detoxication of xenobiotics and in resistance to pyrethroid insecticides. In house fly microsomes CYP6D1 requires cytochrome b5 for the metabolism of some substrates, such as benzo[a]pyrene, but does not require cytochrome b5 for the metabolism of other substrates such as methoxyresorufin. To examine the molecular mechanisms involved in its metabolism of pyrethroids and other substrates, a system for the heterologous expression of CYP6D1 in the yeast Saccharomyces cerevisiae was developed. Heterologous CYP6D1 can be inducibly expressed by culture in media with galactose as the sole carbon source, and is successfully inserted into the yeast microsomes. CYP6D1 is enzymatically active, as measured by methoxyresorufin-O-demethylation, indicating that CYP6D1 is able to interact with yeast P450 reductase. However, CYP6D1 expression did not result in measurable benzo[a]pyrene hydroxylation, suggesting that CYP6D1 cannot interact with yeast cytochrome b5, or that there is insufficient cytochrome b5 in the yeast microsomes to support this CYP6D1-mediated activity. Some suggestions are made for improving the yeast microsomal oxidoreductase environment in order to optimize CYP6D1 function.

Animals↗
PubMed1997

Phenobarbital induction of CYP6D1 is due to a trans acting factor on autosome 2 in house flies, Musca domestica.

To improve our understanding of phenobarbital (PB) mediated induction of CYP6D1 we examined the genetic linkage of PB induction using PB responsive (aabys) and non-responsive (LPR) strains of house flies. PB induction was linked to autosome 2, indicating that CYP6D1 is trans regulated by this PB inducible element. Our results are discussed relative to a previous hypothesis that the same regulatory genes are responsible for both induction and monooxygenase-mediated insecticide resistance.

Animals↗
PubMed1997

Inheritance of CYP6D1-mediated pyrethroid resistance in house fly (Diptera: Muscidae).

The inheritance of cytochrome P450 monooxygenase-mediated (i.e., CYP6D1) resistance in the LPR strain of house fly, Musca domestica L., was investigated by comparing levels of monooxygenase-mediated permethrin resistance and CYP6D1 messenger RNA in 7 populations of house flies. Results indicate that monooxygenase-mediated resistance, and overexpression of CYP6D1 in the LPR strain are controlled by an incompletely recessive trans acting factor(s) on autosome 2 and a nearly completely dominant cis acting factor(s) on autosome 1. The polygenic nature of CYP6D1-mediated resistance and the relative dominance of the resistance factor(s) on autosome 1 suggests this type of resistance could develop relatively quickly.

Animals↗
PubMed1997

Cross-validation of predicted Wechsler Memory Scale-Revised scores in a normative sample of 25- to 34-year-old patients.

Equations for prorating Wechsler Memory Scale-Revised General Memory (GM) and Delayed Recall (DR) index scores ([Woodard and Axelrod, 1995]) were confirmed in the [Mittenberg et al. (1992)] normative WMS-R sample of 50 subjects between the ages of 25 and 34, and confirmed in a separate clinical sample of 30 patients with closed head injury who were age, education, and gender matched with 30 subjects from that normative sample. Predicted GM and DR index scores fell within 6 points of the obtained scores for 98% of the [Mittenberg et al. (1992)] sample and 93% to 100% of the matched head injury and normative samples, despite statistically significant differences between these groups in obtained GM, DR, and percent retention of LM I and II and VR I and II. Six points is well within the standard error of measurement of these index scores. These findings confirm the earlier cross-validation results reported by [Axelrod et al. (1996)] in a mixed sample of traumatic brain injury and other neurological insult, and suggest that this method of estimating weighted score sums for WMS-R General Memory and Delayed Recall indices may be safely used in normative samples of patients in this age range as well as neurologically compromised patients without significantly impacting index score accuracy.

Journal Article↗
PubMed1996

Adult specific expression and induction of cytochrome P450lpr in house flies.

Cytochrome P450lpr is a xenobiotic metabolizing P450 that is found in house flies (Musca domestica). To better understand the regulation of cytochrome P450lpr, the effects of 21 potential monooxygenase inducers were examined for their ability to induce total cytochromes P450 and cytochrome P450lpr levels in adult flies. Six compounds caused induction of total cytochromes P450 per mg protein in adult susceptible (CS) house flies: ethanol (1.6-fold), phenobarbital in food (1.5-fold) or water (1.5-fold), naphthalene (1.3-fold), DDT (1.3-fold), xanthotoxin (1.4-fold), and alpha-pinene (1.2-fold). Six compounds were found to be inducers of cytochrome P450lpr: piperonyl butoxide in food (1.9-fold), phenobarbital in food (1.4-fold) and water (3.4-fold), clofibrate (1.3-fold), xanthotoxin (1.3-fold), methohexital (1.3-fold), and isosafrole (1.3-fold). Comparison of our results with house fly P450 6A1 indicates that there are specific inducers for each of these individual P450s as well as compounds that induce both P450s. Total P450s were inducible by PB in CS house fly larvae, but not in LPR larvae. Immunoblotting revealed no detectable P450lpr in control or PB-treated larvae in either strain. Thus, although total P450s are inducible in the susceptible strain larvae, P450lpr does not appear to be normally present or inducible with PB in larvae of either strain. Northern blots of phenobarbital (in water) treated CS flies indicated that there was a 4.2-fold increase in the P450lpr (i.e., CYP6D1) mRNA levels over the untreated flies. In the multiresistant LPR strain there was no apparent induction of CYP6D1 mRNA by phenobarbital. Following phenobarbital induction, the level of CYP6D1 mRNA in the CS strain was about half of the level in the LPR strain.

Animals↗
PubMed1996

Genetic analysis of factors controlling high-level expression of cytochrome P450, CYP6D1, cytochrome b5, P450 reductase, and monooxygenase activities in LPR house flies, Musca domestica.

To understand better the biochemical genetics of cytochrome P450 monooxygenase-mediated insecticide resistance, we examined the microsomal monooxygenases in insecticide-susceptible (aabys) and pyrethroid-resistant (LPR) house fly strains, as well as 15 house fly lines derived from crosses of LPR and aabys. In comparison to the aabys strain, LPR had higher levels of total cytochromes P450, cytochrome b5, P450 reductase, CYP6D1, and three P450 monooxygenase activities: 7-ethoxycoumarin O-deethylase (ECOD), methoxyresorufin O-demethylase (MROD), and aromatic hydrocarbon hydroxylase (AHH). The elevated levels of cytochrome b5 were linked to factors on autosomes 1 and 2. This is similar to previous reports on monooxygenase-mediated resistance and is consistent with the idea that elevated cytochrome b5 levels are involved in monooxygenase-mediated resistance in the LPR strain. Linkage of the elevated P450 reductase is different from that of monooxygenase-mediated resistance. Strains having high levels of CYP6D1 (i.e., like LPR) had high levels of P450 reductase, while strains having intermediate levels of CYP6D1 also had high levels of reductase. Therefore, there is no clear evidence that the elevated P450 reductase in the LPR strain is required for the increased monooxygenase activity. Overexpression of total cytochromes P450, CYP6D1 (mRNA and protein), and CYP6D1-mediated monooxygenase activities (MROD and AHH) in LPR microsomes was linked to a combination of factors on autosomes 1 and 2. This demonstrates that increased expression of CYP6D1 in the LPR strain is both cis regulated by a factor(s) on autosome 1 and trans regulated by a factor(s) on autosome 2. The correlation between the overexpression of CYP6D1 mRNA and protein suggests that CYP6D1 expression is regulated transcriptionally. Monooxygenase-mediated resistance in LPR is controlled by factors on autosomes 1 and 2, which supports previous claims that CYP6D1 is responsible for monooxygenase-mediated resistance in the LPR strain.

Animals↗
PubMed1996

Purification and characterization of cytochrome b5 reductase from the house fly, Musca domestica.

NADH-cytochrome b5 reductase (b5R) from the house fly was purified through solubilization of microsomes with Triton X-100 followed by DEAE, carboxylmethyl and 5'-ADP affinity column chromatography. Yields of 9% with a 320-fold increase in NADH-ferricyanide reductase specific activity and 2% with a 76-fold increase in NADH-cytochrome b5R specific activity were obtained. Two forms of b5R, a major form with the apparent molecular mass of 31 kDa and a minor form of 33 kDa, were obtained. Both forms of purified b5R could reduce cytochrome b5 and both could use NADH or NADPH as an electron donor, although NADH was more efficient. Kinetics of the b5R activities were also studied. The 31-kDa b5R consists of integral of 291 amino acids with the NH2-terminal sequence of Thr-Ala-Arg-Leu-Arg-Thr-Leu-Ile-Asp-Ala. An antiserum developed against the 31-kDa b5R recognized both forms of b5R. Using this polyclonal antiserum as a probe, immunologically reactive proteins were found in microsomes from five species of Diptera, mouse and rat liver but not in spider mites nor insects from other orders.

Amino Acid Sequence↗
PubMed1996

Inhibitors of CYP6D1 in house fly microsomes.

CYP6D1 is a cytochrome P450 responsible for the metabolism of insecticides and other xenobiotics in the house fly (Musca domestica). Using a CYP6D1-specific monooxygenase activity and a non-CYP6D1-specific monooxygenase activity, 21 compounds were evaluated as inhibitors of CYP6D1 in house fly microsomes. CYP6D1 was strongly inhibited by xanthotoxin, chlorpyrifos, beta-naphthoflavone, piperonyl butoxide and 5-methoxypsoralen. The highest selectivity for inhibition of CYP6D1 was seen for 5-methoxypsoralen, xanthotoxin, beta-naphthoflavone, chlorpyrifos oxon, isosafrole and psoralen. The results clearly indicate that identification of isoform-selective inhibitors of P450s within an insect, and across species, is possible. In addition, psoralen and 5-methoxypsoralen stimulated ethoxycoumarin O-deethylation suggesting that these compounds were substrates for monooxygenases in house fly microsomes. Isosafrole was shown to be a potent synergist of pyrethroid insecticides in adult house flies.

Animals↗
PubMed1996

The role of intensive therapy and autologous blood and marrow transplantation for chemotherapy-sensitive relapsed and primary refractory non-Hodgkin's lymphoma: identification of major prognostic groups.

Patients with intermediate grade non-Hodgkin's lymphoma (NHL) who relapse or fail to achieve a complete remission after anthracycline-containing induction regimens have a poor outcome with conventional-dose salvage treatment. This outcome may be improved with intensive therapy and autologous transplantation (ABMT) but even in patients with proven chemotherapy-sensitive disease, relapse rates of up to 60% are observed. Reliable and powerful prognostic indicators are needed to identify appropriate patients for this expensive procedure and those subjects to whom alternative or additional treatment should be offered. We were interested in testing the hypothesis that tumour burden, and hence remission status immediately prior to transplant, is an important prognostic indicator of survival. We aggressively treated patients with conventional-dose salvage chemotherapy to maximum tumour response, and tested, by multivariate regression analysis, predictors of outcome post-transplant. We studied 81 consecutive patients with intermediate grade and immunoblastic NHL who achieved either a partial (PR) or complete remission (CR) following repetitive cycles of conventional-dose salvage therapy. Intensive therapy consisted of etoposide (60 mg/kg) and intravenous melphalan (160-180 mg/m2) with or without total body irradiation (TBI) followed by infusion of autologous unpurged bone marrow and/or blood cells. The predicted 4-year survival and progression-free survival (PFS) with a median follow-up of 37 months was 58% and 48% (95% confidence interval (CI) 37-55%), respectively. The only factor predictive of outcome was remission status at transplant (P=0.0001). The PFS at 4 years for the CR group was 61% (95% CI 53-75%). In contrast, only 25% (95% CI 11-40%) of patients undergoing autotransplant in PR were progression free at 4 years. We conclude that remission status at transplant after maximum tumour reduction is a powerful prognostic indicator.

Adult↗