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Biomedical subjects

J K Peterson

Publications and source records attributed to J K Peterson.

At least 19 recordsLinked to original sources
PubMed2004

Using genetic technologies for promoting canine health and temperament.

The entire canine genome is scheduled to be sequenced by researchers at the Whitehead Institute/MIH Center for Genome Research by the end of 2004. Thus, new genetic technologies are likely to be developed that can soon predict certain aspects of health and temperament in dogs. The C. familiaris is similar in size to that of humans and other mammals, with an estimated 2.8 billion base pairs. Although, the boxer was chosen as the first breed to sequence, it will have application for all dog breeds. Once the entire genome is sequenced, genetic markers for specific diseases and temperaments may be developed, which can guide breeders to make informed decisions concerning breeding management. Such a technology may be useful for guide and service dog organizations that have breeding colonies. It is important that the human-animal bond be preserved for as long as possible, both for pet owners and also for those disabled individuals who depend upon a dog for independence and mobility. Because genetic diseases may not manifest in carriers, and some genetic diseases do not manifest until after a dog is older and has already produced other animals with the same defect, genetic markers to identify some of the over 400 genetic diseases could be very useful in promoting canine health.

Animals↗
PubMed2004

Integrating pharmacology and in vivo cancer models in preclinical and clinical drug development.

Historically, cancer drug development has been a roller coaster. Numerous agents have shown exciting activity in preclinical models and yet have had minimal activity clinically. These disappointments have led to reasonable scepticism about the true value of both syngeneic and xenograft rodent tumour models in accurately identifying agents that will have important clinical utility. Whereas the development of newer techniques, including transgenic mouse models of cancer, offers the potential to develop more predictive models, the role of such mice in cancer drug development is not yet validated. To advance in our understanding of predictive model systems it may be wise to analyse both the successes and the failures of conventional models in order to understand some of their limitations and perhaps to avoid making the same mistakes in the future. Here we review the value and limitations of xenograft models, and the role of integrating preclinical pharmacology in developing new treatments for solid tumours of childhood.

Animals↗
PubMed2001

Zonal expression of endothelial nitric oxide synthase in sheep and rhesus adrenal cortex.

There is mounting evidence that nitric oxide (NO) may inhibit adrenal steroidogenesis by binding to the heme group of P450 enzymes, particularly the rate-limiting steps cholesterol side-change cleavage P450, aldosterone synthase P450, and 17 alpha-hydroxylase/C(17/20)-lyase P450. Using immunohistochemistry, nitrotyrosine was detectable throughout the ovine adrenal cortex, and endothelial NO synthase (eNOS) was further identified in zona glomerulosa (ZG) and at a higher level throughout the zona fasciculata, increasing toward the medulla. Caveolin-1, 90-kDa heat shock protein, ERK-1/2, and Akt, all known and proposed regulators of eNOS activity, were detected throughout the ovine adrenal cortex. Western immunoblotting confirmed the identity of these proteins as well as the absence of neuronal NOS, inducible NOS, caveolin-2, and caveolin-3. Through dual immunostaining we further identified for the first time a zona intermedia without strong staining for 17 alpha-hydroxylase/C(17/20)-lyase P450 or angiotensin II type 1 receptor, but positive for eNOS. Rhesus adrenals also stained positively for eNOS, but staining was seen only in the ZG and zona reticularis. We conclude that eNOS may play a role in controlling zone-specific aldosterone synthase vs. 11 beta-hydroxylase activities of the single CYP11B gene in sheep. In the rhesus monkey, NO may modulate ZG aldosterone synthase, but it is not needed for control of the distinct 11 beta-hydroxylase in the zona fasciculata. In the zona reticularis, however, eNOS may control C(19) steroid production at the level of 17 alpha-hydroxylase vs. 17,20-lyase activity otherwise unopposed by 3beta-hydroxysteroid dehydrogenase.

Adrenal Cortex↗
PubMed2001

Effect of nitrogen on resistance of sweet potato to sweetpotato weevil (Coleoptera: Curculionidae) and on storage root chemistry.

The effects of nitrogen fertilizer on sweet potato, Ipomoea batatas (L.) Poir., resistance to the sweetpotato weevil, Cylas formicarius elegantulus (Summers), was studied. Adult weevil feeding and oviposition preference, larval survival, and pupal weight were used as measures of sweet potato resistance. Sweet potato resin glycosides and caffeic acid concentrations in the periderm tissue of storage roots also were measured. Sweet potato genotypes (Beauregard, Excel, W-244, W-250, and Sumor) with varying levels of resistance to sweetpotato weevil were grown in the field under three nitrogen regimes (0, 45, and 135 kg N/ha). Harvested storage roots were evaluated in the laboratory for feeding and oviposition activity of sweetpotato weevil female adults under no-choice and choice test conditions. Larval survival rate and pupal weight were determined by rearing the insects individually on storage root sections. Nitrogen level had a significant effect on the number of eggs deposited, but not on the number of feeding punctures. Sweetpotato weevils laid fewer eggs on plants with the highest level of nitrogen. Nitrogen levels did not significantly affect larval survival and pupal weight. Genotype had a significant effect on feeding, oviposition, and larval survival. Beauregard had higher levels of feeding, oviposition, and larval survival compared with the other genotypes. No interaction effects between nitrogen and genotype were significant. Resin glycosides and caffeic acid concentrations were significantly different among genotypes and between years. Nitrogen levels significantly affected the concentrations of caffeic acid in 1997.

Animals↗
PubMed2001

Methoprene and 20-OH-ecdysone affect male production in Daphnia pulex.

Exposure of Daphnia pulex to the insecticide and juvenile hormone-mimic methoprene resulted in a decrease in the incidence of all-male broods and an increase in the incidence of all-female broods compared with controls. These effects were observed at nominal concentrations of 10 and 100 microg/L, within the upper range of concentrations at which methoprene is applied in the environment. Because methoprene has been found to bind to the mammalian retinoid X receptor, we also tested the effects of retinoic acid on Daphnia reproduction. Neither 9-cis-retinoic acid nor all-trans-retinoic acid had any observable effect. Because juvenile hormone and ecdysteroids interact in many insect systems, we also exposed Daphnia to 20-OH-ecdysone. Exposure to the crustacean hormone 20-OH-ecdysone at levels of 1 and 10 microg/L resulted in an increase in all-male broods and a decrease in all-female broods, but 100 microg/L 20-OH-ecdysone resulted in a decrease in all-male broods and an increase in all-female broods. Our results suggest that juvenile hormone and ecdysteroids might play a role in the Daphnia sex determination system.

Alitretinoin↗
PubMed2000

Sublethal effects of resin glycosides from the periderm of sweetpotato storage roots on Plutella xylostella (Lepidoptera: Plutellidae).

Resin glycoside material extracted from the periderm tissue of storage roots from sweetpotato, Ipomoea batatas (L.) Lam., was bioassayed for effects on survival, development, and fecundity of the diamondback moth, Plutella xylostella (L.). The resin glycoside was incorporated into an artificial diet and fed to P. xylostella larvae. First instars were placed individually into snap-top centrifuge vials containing artificial diet with one of six concentrations of resin glycoside material (0.00, 0.25, 0.50, 1.00, 1.50, and 2.00 mg/ml). Each replication consisted of 10 individuals per concentration, and the experiment was repeated 13 times. Vials were incubated at 25 degrees C and a photoperiod of 14:10 (L:D) h in a growth chamber. After 6 d, surviving larvae were weighted and their sex determined, then returned to their vials. Later, surviving pupae were weighed and incubated at 25 degrees C until moths emerged. Females were fed, mated with males from the laboratory colony, and allowed to lay eggs on aluminum foil strips. Lifetime fecundity (eggs/female) was measured. There were highly significant negative correlations between resin glycoside levels and survival, and between glycoside levels and larval weight after 6 d of feeding. For larvae that lived at least 6 d, there was no additional mortality that could be attributed to the resin glycoside material. However, there was a significant positive correlation between glycoside dosages and developmental time of larvae (measured as days until pupation). Lifetime fecundity also was negatively affected at sublethal doses. Resin glycosides may contribute to the resistance in sweetpotato breeding lines to soil insect pests.

Animals↗
PubMed1980

Effects of supervised daily dental plaque removal by children after 3 years.

The benefits of a school-based plaque removal program are presented. Children in grades 5-8 were inclined in a study which was designed to determine the effect on oral hygiene, gingival inflammation and dental caries of removing dental plaque through supervised daily flossing and toothbrushing in school. A fluoride-free dentifrice was used. Controls did not receive instruction in plaque removal procedures nor did they engage in plaque removal activities at school. For three school years the students in the treatment group practiced daily plaque removal, supervised by trained personnel. All participants were examined initially for plaque (PHP), gingival inflammation (DHC) and dental caries (DMFS). Girls in the treatment group showed a significant reduction (28%) in mean plaque scores and, for girls and boys, the mean changes in gingivitis scores were significantly reduced (40% and 17%, respectively). Adjusted mean incremental DMF surface scores were 13% lower in the treatment group than in the control group. The difference between groups was not statistically significant and was accounted for entirely by the findings in mesial and distal surfaces (26%). This difference approached statistical significance (P=0.07).

Adolescent↗
PubMed1980

Influence of alkaline pH on the effectiveness of sodium fluoride dentifrices.

Two similar sodium fluoride dentifrices, one neutral and one alkaline, were compared to a placebo for clinical effectiveness in reducing caries. The neutral dentifrice contained 35% less soluble fluoride than the alkaline dentifrice. Both fluoride dentifrices were significantly effective but were not different from each other.

Child↗
PubMed1980

Effect on dental caries of a stannous fluoride-calcium pyrophosphate dentrifice in an adult population: one-year results.

The first year of a two-year double-blind clinical trial of the anticaries effectiveness of a stannous fluoride-calcium pyrophosphate (SnF2-CPP) dentifrice as compared to a placebo control dentifrice involved 1,337 adult subjects, 18 to 78 years of age. Adult subjects were examined for dental caries at a baseline examination and after one year of ad lib dentifrice usage by an experienced clinical examiner using a visual-tactile examination and a radiographic evaluation. Results of the study after one year indicate a significant (P < 0.05) 33.3% difference in new caries formation with use of the SnF2-CPP dentifrice as compared to the placebo control based on the DMFS score.

Adolescent↗
PubMed1977

Effects of supervised daily dental plaque removal by children: II. 24 months' results.

After two school years of a supervised daily plaque-removal program in school, children in the treatment group showed a significant reduction in plaque and gingival inflammation scores compared with children in the control group. However, differences between groups in terms of plaque and gingivitis scores virtually disappeared during the summer vacation. The increment of dental caries was lower in the treatment group than in the control group, but the reduction, which averaged about 20 percent, was not statistically significant either for teeth or for surfaces. Although the 24-month findings of the present study indicate some degree of success in reducing plaque and gingivitis and a marginal effect in reducing the incidence of dental caries among children who engaged in daily, supervised plaque-removal in school, obvious drawbacks limit the value of this regimen.

Adolescent↗
PubMed1976

Effects of supervised daily dental plaque removal by children: first-year results.

In September 1973, a three-year school-based study was initiated in East Hampton, Connecticut, a rural nonfluoridated community. The purpose of the study is to determine the effect on dental decay, gingival inflammation and oral hygiene of removing dental plaque through supervised daily toothbrushing and flossing in school during a three-year period. To establish baseline data, three indexes were used: the DHC Index to evaluate gingivitis; the DMF Surface Index to quantify dental caries and the PHP Index to measure dental plaque. The examinations for dental caries, including radiographs, are scheduled annually in September, whereas the plaque and gingival examinations are done biannually, in September and June. After the baseline examinations the 481 children were blocked according to grade and sex and then were randomly assigned to either a treatment group or to a control group. In November, the treatment group was provided 10 sessions of instruction in plaque removal. For the remainder of the year (six months) they practiced daily plaque removal, supervised by a dental hygienist and a nurse. The control group was not instructed in oral hygiene procedures. In the treatment group, mean plaque and gingival scores at the June (first follow-up) examination were 14 percent and 29 percent lower, respectively, than at baseline. No change was seen in the control group. At the second follow-up examination in September (after summer vacation), the same indexes were nearly at baseline levels in the treatment group. There was no treatment effect on dental caries increments after one year of study. Considering the nature of the treatment regimen and the few treatments during the first year of the study, it is not surprising that there were no caries-preventive benefits demonstrated among children in the treatment group after one year. The total number of the plaque removal sessions will be greater during the second year of the study. Therefore, the possibility of detecting a caries preventive effect at the twenty-four month examinations, should one exist, will be enhanced.

Adolescent↗