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Biomedical subjects

D E Walters

Publications and source records attributed to D E Walters.

At least 37 records · Page 2Linked to original sources
PubMed1995

The ecology of endoparasitic helminth infections of brown trout (Salmo trutta) and rainbow trout (Oncorhynchus mykiss) in Scotland.

Two hundred and forty brown trout (Salmo trutta) and 49 rainbow trout (Oncorhynchus mykiss), obtained from 21 locations in Central Scotland between October 1990 and August 1993, were examined for endoparasitic helminth infections. Crepidostomum farionis (Digenea) was the most widely distributed helminth species, followed by Eubothrium crassum (Cestoda), Diphyllobothrium dendriticum and D. ditremum (Cestoda), Neoechinorhynchus rutili (Acanthocephala), Echinorhynchus truttae (Acanthocephala), Eustrongylides sp. (Nematoda), Capillaria salvelini (Nematoda), Cyathocephalus truncatus (Cestoda), Raphidascaris acus (Nematoda) and Cystidicola farionis (Nematoda), in that order. The prevalences and intensities of each helminth infection were recorded. No evidence was found to indicate that even fish with the highest worm burdens (e.g. 339 plerocercoids of Diphyllobothrium spp.) were experiencing any obvious morbidity. An analysis of pairs of associations between species of helminths revealed a significantly positive association between N. rutili and C. farionis (P < 0.01). The results are discussed in terms of patterns in helminth communities in freshwater fish.

Acanthocephala↗
PubMed1994

Genetically evolved receptor models: a computational approach to construction of receptor models.

Given the three-dimensional structure of a receptor site, there are several methods available for designing ligands to occupy the site; frequently, the three-dimensional structure of interesting receptors is not known, however. The GERM program uses a genetic algorithm to produce atomic-level models of receptor sites, based on a small set of known structure-activity relationships. The evolved models show a high correlation between calculated intermolecular energies and bioactivities; they also give reasonable predictions of bioactivity for compounds which were not included in model generation. Such models may serve as starting points for computational or human ligand design efforts.

Aspartame↗
PubMed1994

Altered neurochemical and behavioral development of 10-day-old rats perinatally exposed to the kappa opioid agonist U-50,488H.

To determine the effects of chronic perinatal exposure to a kappa opioid agonist on the neurochemical and motor development of rat offspring, osmotic pumps containing trans-(+-)-3,4-dichloro-N-methyl-N-[2-(1-pyrrolidinyl)-cyclohexyl]- benzeneacetamide methane sulfonate (U-50,488H), 79 mg/ml, or vehicle were implanted into anesthetized pregnant female rats. On postnatal day 10, the nucleus accumbens (NAc) of male offspring were dissected and assayed for dopamine (DA) receptors. Male offspring from other litters were injected subcutaneously with the D2 agonist quinpirole, 0.05 mg/kg, the D1 agonist SKF 38393, 10 mg/kg, or 0.9% saline vehicle. Their locomotor activity was then monitored for 1 h. The binding of DA D1 and D2 receptors was significantly increased by 26% and 90%, respectively, in the NAc of 10-day-old offspring exposed to U-50,488H. There was a significant, 52%, decrease in the locomotor response to quinpirole by 10-day-old offspring exposed to U-50,488H. Exposure to U-50,488H had no significant effect on the locomotor response to SKF 38393 at this age. The results indicate that perinatal exposure to a kappa agonist alters the development of brain DA receptors and DA-mediated motor behavior. The data suggest that motor deficits observed in offspring exposed to opioids in utero may involve brain kappa opioid receptor mechanisms.

2,3,4,5-Tetrahydro-7,8-dihydroxy-1-phenyl-1H-3-ben↗
PubMed1994

Dopamine D2 autoreceptors in rats are behaviorally functional at 21 but not 10 days of age.

Previous studies used either racemic 3-(3-hydroxyphenyl)-N-n-propylpiperidine [(+/-)-3-PPP] or lower doses of the mixed dopamine (DA) D1/D2 agonist apomorphine (APO) to conclude that brain DA D2 autoreceptors are not behaviorally functional until 28 days of age. The purpose of this study was to provide behavioral evidence for functional D2 autoreceptors before 28 days of age using DA agonists with greater selectivity for D2 autoreceptors. The locomotor activity of 10-, 21-, 35-day-old and adult rats was monitored after injection of a D2 autoreceptor agonist. There were significant decreases in the locomotor activity of 21-, 35-day-old, and adult rats injected with (-)-3-PPP, SND 919, or PD 128483. Lower doses of APO significantly decreased the activity of adult and 35-day-old rats but not younger rats. The only significant effect on the locomotor activity of 10-day-old rats was an increase in activity after injection of APO, 0.01 mg/kg or higher, or B-HT 920, 0.01 mg/kg. The results suggest that brain DA D2 autoreceptors are behaviorally functional at 21, but not 10, days of age.

Aging↗
PubMed1994

The D2 autoreceptor agonists SND 919 and PD 128483 decrease stereotypy in developing rats.

Although stereotyped behavior in adult rats is partly regulated by dopamine (DA) D2 autoreceptors, previous attempts to demonstrate D2 autoreceptor regulation of stereotypy in developing rats have been unsuccessful. In the present study, two highly selective D2 autoreceptor agonists were used to demonstrate D2 autoreceptor regulation of spontaneous stereotyped behavior in developing rats. Both SND 919 and PD 128483 produced significant dose-dependent decreases in the stereotypy counts of 21-day-old, 35-day-old, and adult rats. There was a 51% decrease in the stereotypy counts of 21-day-old rats injected with SND 919, 0.05 mg/kg, compared to a 36% decrease in the counts of rats pretreated with haloperidol. Similarly, PD 128483 significantly decreased the stereotypy counts of 21-, 35-day-old, and adult rats in a dose-dependent fashion. There was a 58% decrease in the stereotypy counts of 21-day-old rats injected with PD 128483, 0.1 mg/kg, compared to a 17% decrease in counts when the rats were first treated with haloperidol. The effect of haloperidol plus PD 128483 was significantly different from the effect of PD 128483 alone. Injection of SND 919 or PD 128483 had no significant effects on the stereotypy counts of 10-day-old rats. The results suggest that DA D2 autoreceptor-mediated regulation of spontaneous stereotyped behavior is functional at 21, but not 10, days of age.

Aging↗
PubMed1994

Ovarian cancer and pregnancy: comment on a paper by Whittemore et al.

We must concede that we were not able, with the published aggregate figures, to correct for the nuisance variables mentioned in the report, nor were we able to examine the individual "Study" results to derive estimates of "Between Study" variation, and so assess the regularity and statistical importance of the patterns observed. The tentative inferences outlined in this note are made therefore on the assumption that the analysis of these aggregate figures provides a fair reflection of the complete data base. Certainly, our analyses are numerically consistent with those in the report by Whittemore et al. (1). Because of the inconsistencies discovered between portions of the data presented by Whittemore et al. (1), we believe that the nature of the association between ovarian cancer and certain features such as nulliparity and age at first pregnancy remains unclear and demands further investigation, possibly with the very data base used by Whittemore and her colleagues.

Age Factors↗
PubMed1994

Clinical pregnancy and male subfertility; the ESHRE multicentre trial on the treatment of male subfertility. European Society of Human Reproduction and Embryology.

Ovulation induction alone, and ovulation induction in conjunction with one of four assisted procreation methods [intra-uterine insemination (IUI), intra-peritoneal insemination (IPI), gamete intra-Fallopian transfer (GIFT) or in-vitro fertilization (IVF)] were tested as a treatment for male infertility in a prospective randomized trial. The trial when completed had generated data on 499 cycles from 346 patients. There was overwhelming evidence that some form of assisted procreation was beneficial, when compared to the spontaneous natural conception rate, which is generally assumed to be between 0.01 and 0.02 for male infertility. There was also firm evidence that IUI, GIFT or IVF (mean per cycle pregnancy rate 0.212) were superior to the remaining two treatments of IPI and ovulation induction alone (mean per cycle pregnancy rate 0.068). Duration of infertility and a diagnosis of endometriosis were the most important (adverse) pre-treatment factors detected.

Endometriosis↗
PubMed1992

Carboxylic acid replacement structure-activity relationships in suosan type sweeteners. A sweet taste antagonist. 1.

N-(4-Cyanophenyl)-N'-(2-carboxyethyl)urea (2), an analogue of suosan [1,N-(4-nitrophenyl)-N'-(2-carboxyethyl)urea], is a known high-potency sweetener derived from beta-alanine. Sulfonic and phosphonic acid analogues of 2 were prepared to develop structure-activity relationships through modification of the carboxylic acid region of this family of sweeteners. Neither of the carboxylic acid replacements resulted in sweet analogues. However, we found that N-(4-cyanophenyl)-N'-[(sodiosulfo)methyl]urea (7) is an antagonist of the sweet taste response. The bitter taste response to caffeine, quinine, and naringin was also antagonized. Antagonist 7 was found to inhibit the sweet taste perception of a variety of sweeteners. Antagonist 7 had no effect on the sour or salty taste response.

Aspartic Acid↗
PubMed1992

N,N'-disubstituted guanidine high-potency sweeteners.

The role and function of the aryl group in the highly potent trisubstituted guanidine sweeteners 7a-d was investigated. Four disubstituted guanidines, lacking the aryl group, were prepared. These guanidines contain a hydrophobic substituent on one nitrogen and a carboxymethyl group substituted on one of the other nitrogens. They were found to be tasteless or to have a significantly lower sweetness potency than the corresponding trisubstituted compounds. Possible rationales for the effects of structure on the sweet taste activity are discussed.

Anilides↗
PubMed1992

A possible genetic factor influencing protection from infection with Ascaris lumbricoides in Nigerian children.

An epidemiological study of Ascaris lumbricoides infections was carried out in primary school children aged 5-16 yr from Ile-Ife, Nigeria. Intensity of infection was assessed directly by means of counting worms passed during a 48-hr period after chemotherapy. Reinfection patterns of A. lumbricoides were assessed at 2 6-mo intervals and statistical evidence of predisposition to infection status was obtained. An investigation of 3 groups of children who were judged to be predisposed not to be infected, to be lightly infected, and to be heavily infected was undertaken. Assignment to the groups was based upon the mean worm burden plus 1 SD above the mean, measured at 2 6-mo intervals. The distribution of class I human leucocyte antigens among the 3 groups of children was described. None of the children who were predisposed to remain uninfected was found to possess the A30/31 antigens in contrast to those children who remained infected.

Adolescent↗
PubMed1991

High fecundity of amenorrhoeic women in embryo-transfer programmes.

There is uncertainty over whether the steady decline in human fertility with increasing maternal age is due to quality of the oocyte or of the endometrium. To clarify the issue age-related implantation and pregnancy rates in two embryo-transfer programmes were examined in relation to embryo quality and type of menstrual cycle. In both the UK and the US programmes rates were higher in previously amenorrhoeic (acyclic) women than in eugonadal women, irrespective of age and number of embryos replaced. Oocyte quality, as determined by age of oocyte donor, in-vitro growth of embryo, and proportion of defective embryos in culture, did not contribute to the difference, nor did type of cycle during therapy. If a uterus that has not been subjected to regular menstrual cycles is a favourable factor, a period of induced amenorrhoea might be beneficial for infertile women.

Amenorrhea↗