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Biomedical subjects

D D Colwell

Publications and source records attributed to D D Colwell.

At least 55 records · Page 3Linked to original sources
PubMed1994

Parasite infection attenuates nonopioid mediated predator-induced analgesia in mice.

Parasites have been shown to have a broad range of effects on host behavior, including alterations of host responses to predators. Response to the threat of predation consist of a number of defensive behaviors, including a reduction in pain sensitivity and the induction of analgesia. The present study examined the relationships between subclinical (i.e., nonpathological) infection with the naturally occurring, enteric, sporozoan (coccidian) parasite, Eimeria vermiformis, predator exposure, and nociceptive responses in male mice. Brief (30 s) exposure of nonparasitized mice to a predator (a cat) induced marked, relatively short-lived analgesia that was insensitive to naloxone and blocked by the serotonin-1A (5-HT1A) agonist, 8-OH-DPAT. In contrast, mice acutely infected for 6 days with E. vermiformis, failed to show a predator-induced analgesia. The parasitized mice did display a naloxone-sensitive hypoalgesia or analgesia. However, restraint-stressed mice, which displayed a naloxone-sensitive hypoalgesia similar in amplitude to that of the infected mice, still exhibited a nonopioid mediated, predator-induced analgesia. These observations indicate that parasite infection attenuates 5-HT1A-sensitive predator-induced analgesia and likely reduces the accompanying fear and anxiety related anticipatory defense reactions of the host to the predator.

Animals↗
PubMed1993

Multiple opioid system involvement in the mediation of parasitic-infection induced analgesia.

Although parasite modification of host behaviour is well established, little is known about the mechanisms underlying such effects. The present study examined the relationships between subclinical infection with the enteric sporozoan parasite, Eimeria vermiformis, nociceptive responses and endogenous opioid systems in male mice. Infected mice displayed significant analgesia which increased through the prepatent period [oocyst formation (pre-infective); days 1-7 post-infection (PI)], reached a maximum with the onset of patency (onset oocyst shedding and infectivity; days 7-8 PI) and declined during patency (oocyst shedding), with response latencies declining to basal levels with the cessation of oocyst production and infectivity (day 15 PI). The increasing nociception during the prepatent period (day 4 PI) was associated with kappa opioid mechanisms, being reduced by the kappa antagonist, nor-binaltorphimine, and insensitive to either the delta antagonist, ICI 174,864, or the general, predominantly mu antagonist, naloxone. Maximum analgesia (day 7 PI) associated with the onset of patency (infectivity) was sensitive to both the kappa and mu antagonists, but insensitive to the delta antagonist, while the declining analgesia during patency (day 10 PI) was reduced by the mu and delta antagonists, but was insensitive to the kappa antagonist. These results indicate that mu, delta and kappa opioid systems are involved in the mediation of subclinical parasitic infection-induced analgesia and likely other associated parasite-induced modifications of host behaviour.

Analgesia↗
PubMed1993

Neuropeptide FF (FLQPQRFamide) and IgG from neuropeptide FF antiserum affect spatial learning in mice.

There is evidence indicating that the mammalian octapeptide FLQPQRFamide (F8Fa or neuropeptide FF, NPFF) is an endogenous modulator ('anti-opioid') of opioid systems. There is also substantial evidence implicating opioid systems in the mediation of spatial learning and memory. In the present study determinations were made of the effects of NPFF and IgG from antiserum against NPFF on the spatial performance of male mice in a water maze task, whereby over one day in six blocks of four trials the animals had to acquire the location of a submerged hidden platform using distal visual cues. Pretraining intracerebroventricular (i.c.v.) injection of NPFF-IgG, impaired spatial acquisition and retention, while i.c.v. administration of 1.0 microgram of NPFF marginally improved, and 10 micrograms of NPFF significantly reduced spatial acquisition. These results suggest that NPFF may have a modulatory influence on spatial acquisition.

Amino Acid Sequence↗
PubMed1993

Evidence for involvement of endogenous opioid peptides in altered nociceptive responses of mice infected with Eimeria vermiformis.

Parasite modification of host behavior is a well established phenomenon; however, little is known about the modulatory mechanisms regulating such effects. This study examined the relationship between Eimeria vermiformis infection, nociceptive responses, and endogenous opioid peptide activity in male RML mice. Infected mice displayed increases in centrally mediated antinociceptive responses (i.e., analgesia, measured as the latency of a foot-lifting response to a 50 C surface) throughout the prepatent period. The level of analgesia declined following onset of patency on day 8 postinfection (PI). Opioids were implicated in the increased antinociceptive response of the infected mice as the response was blocked by administration of a prototypic opiate antagonist, naloxone (1.0 mg/kg), on day 7 PI when maximum levels of analgesia were noted. This indicates that the analgesia evident in the parasitized mice was associated with increased opioid activity. Analgesia is one of a variety of behaviors influenced by changes in opioid activity, thus these observations provide further support for the contention that other parasite-induced alterations in host behavior may, in part, be the result of alterations in the activity of opioid modulatory systems.

Animals↗
PubMed1992

Exposure to the scent of male mice infected with the protozoan parasite, Eimeria vermiformis, induces opioid- and nonopioid-mediated analgesia in female mice.

The present study examined the nociceptive responses of female mice exposed to the scent (soiled cage bedding) of male mice infected with the protozoan parasite, Eimeria vermiformis. A 30-min exposure to the odors of a parasitized male induced naloxone (1.0 mg/kg)-sensitive opioid-mediated analgesia in female mice, whereas a brief 1-min exposure to these odors resulted in a lower amplitude, relatively short, nonopioid analgesia that was insensitive to naloxone and blocked by the serotonin-1A (5-HT1A), agonist, 8-OH-DPAT. Exposure to the odors of nonparasitized males had no significant effects on the nociceptive responses of female mice. These results indicate that female mice are able to distinguish between the odors of parasitized and nonparasitized male mice, and that female mice display both opioid- and nonopioid-mediated aversive responses to the odor cues associated with the parasitized males. The implications of these findings for parasite-based mate choice are discussed.

8-Hydroxy-2-(di-n-propylamino)tetralin↗
PubMed1992

Evidence for activation of endogenous opioid systems in mice following short exposure to stable flies.

Biting flies influence both physiology and behaviour of domestic and wild animals. This study demonstrates that brief (30 min) exposure of male and female mice to stable flies leads to significant increases in nociceptive responses, indicative of the induction of analgesia. The biting fly-induced analgesia was mediated by endogenous opioid systems as it was blocked by the prototypic opiate antagonist naloxone. Exposure for 30 min to the bedding of biting fly-exposed mice also induced significant opioid mediated analgesic responses in mice. Exposure to either house flies or the bedding of house fly-exposed mice had no significant effects on nociception. These results indicate that brief exposure to either stable flies, or to olfactory cues associated with mice exposed to stable flies, activates endogenous opioid systems leading to the induction of analgesia and likely other opioid mediated behavioural and physiological stress responses. These results suggest the involvement of endogenous opioid systems in the mediation of the behavioural and physiological consequences of biting fly exposure in domestic and wild animals.

Animals↗
PubMed1991

Sex differences in opioid and non-opioid mediated predator-induced analgesia in mice.

The present study compared the nociceptive responses of male and female mice exposed to a predator, an ecologically relevant threatening stimulus. After 15 min of exposure to the presence of an experienced predatory cat, mice displayed a naloxone (1.0 mg/kg)-sensitive opioid mediated analgesic response, while after a brief 30-s exposure to the cat mice displayed a lower amplitude, relatively brief, non-opioid analgesia that was insensitive to naloxone and blocked by the serotonin-1A (5-HT1A) agonist, 8-hydroxy-2-(di-n-propylamino)tetralin. Male mice displayed a significantly greater opioid mediated predator-induced analgesia than females, whereas female mice showed a significantly greater non-opioid, 5-HT1A sensitive, analgesia than males. These results indicate that there are significant sex differences in both the opioid and non-opioid analgesic responses arising from exposure to a natural aversive stimulus.

8-Hydroxy-2-(di-n-propylamino)tetralin↗
PubMed1991

Mammalian immune responses to myiasis.

Myiasis is responsible for significant losses to the livestock industry worldwide. Control programs have been successful in reducing the number of infested animals. However, serious concerns regarding the use of pesticides have prompted research into alternative strategies for pest control. In this article, Bob Baron and Doug Colwell discuss progress made towards the understanding of the immune response to Hypoderma spp and other myiasis-producing arthropods. Prospects for vaccination are discussed.

Journal Article↗
PubMed1991

Enhanced resistance to cattle grub infestation (Hypoderma lineatum de Vill.) in calves immunized with purified hypodermin A, B and C plus monophosphoryl lipid A (MPL).

The influence of an antigen-specific cellular and humoral immune response, stimulated by immunization, on survival of a challenge infestation of Hypoderma lineatum was investigated. Calves immunized with a purified combination of hypodermin A, B and C plus monophosphoryl lipid A (MPL) developed a strong antigen-specific cellular immune response by completion of the immunization schedule which persisted to 12 weeks post-infestation. Responsiveness of peripheral blood lymphocytes to the mitogens concanavalin A and pokeweed was also elevated at 4 and 12 weeks post-infestation. Western blot analysis at the time of maximum grub counts demonstrated that immunized calves responded to hypodermin A, B and C while those receiving only MPL or infested controls responded only to hypodermin B and C. The antigen-specific antibody response as measured by ELISA at maximum grub count was significantly higher in vaccinated calves than in infested controls while the response in calves receiving only immunostimulator was also significantly elevated. Immunized (antigen plus MPL) calves produced 5.0 +/- 6.9 grubs per animal which successfully pupated while those receiving MPL alone produced 16.4 +/- 6.1 and infested controls produced 32.2 +/- 10.9 grubs per animal.

Animals↗
PubMed1991

Ultrastructure of the integument of first-instar Hypoderma lineatum and H. bovis (Diptera: Oestridae).

The ultrastructure of the integument of newly hatched, 60-d-old (in vitro-cultured) and 6-7-mo-old (recovered from the host) first-instar cattle grubs, Hypoderma lineatum (Villers) and H. bovis (L.), was studied. Changes in the cuticle during development of the first instar included increased thickness of the procuticle (0.8-1.4 to 7.5-7.9 microns) with an accompanying increase in number of lamellae (4-7 to 35-40), increased thickness of epicuticle (0.11-0.24 to 0.92 microns), and development of new epicuticle layers. The epithelial cells in newly hatched larvae also changed with age when compared with those in culture and those recovered from hosts. These changes included the appearance of dense plaques on the apical cell membrane and an increase in the folding of the basal cell membranes, with an accompanying increase in the amount of extracellular space. The basement membrane, separating epithelial cells from the hemocoel, also increased in thickness during the first instar. These changes reflect developments required to accommodate increased size but, in the case of the epithelial cells, suggest altered function. Ruthenium red staining on the cuticular surface of larvae cultured in vitro was indicative of the presence of negatively charged molecules, which may influence the host recognition and response capabilities.

Animals↗
PubMed1991

A model for estimating abundance of cattle grub (Diptera: Oestridae) from the proportion of uninfested cattle as determined by serology.

A model is presented for determining the abundance of cattle grubs in the backs of calves from the proportion of uninfested calves in a herd. The distribution of grubs in calves' backs was compared with the negative binomial, but no relationships were found among the distribution parameters, suggesting that the negative binomial is an inappropriate choice for the basis of a sampling model. The relationship between the mean number of grubs per animal (mean), variance (delta 2), and proportion of uninfested calves (p0) in a herd was determined and used as the basis for the sampling model. The relationship between p0 and p0e [determined using serology (ELISA)] was evaluated. The variance of estimates of mean grubs per animal based on the regression model and uncertainty due to using p0e as an estimate of p0 was examined. A test of the model indicated that p0e could be used to obtain a reliable estimate of mean grubs per animal and that the method would be applicable for monitoring grub populations, assessing chemical control programmes, and determining release rates of sterile insects for control.

Animals↗
PubMed1990

Exposure to mosquitoes, Aedes togoi (Theo.), induces and augments opioid-mediated analgesia in mice.

Mosquitoes and other biting flies are natural aversive stimuli commonly encountered by wild and domestic animals and by humans. We observed that male mice exposed for 30 min to a low density of female mosquitoes (Aedes togoi) displayed significant increases in nociceptive responses which were indicative of the induction of analgesia. This analgesia was blocked by the prototypic opiate antagonist naloxone (1.0 mg/kg). Exposure to a novel stimulus had no significant effect on nociception, whereas 30 min of restraint stress induced a naloxone-reversible analgesia qualitatively similar to that observed after exposure to mosquitoes. Confinement in a small chamber for 30 min also had a significant analgesic effect whose amplitude and duration were markedly potentiated by concurrent exposure to mosquitoes. These results show that exposure to mosquitoes, and likely other biting flies, both induces an opioid-mediated analgesia and augments the analgesic effects of other stressful stimuli.

Aedes↗
PubMed1990

Use of sterile insect releases in an IPM program for control of Hypoderma lineatum and H. bovis (Diptera: Oestridae): a pilot test.

A joint Canadian-U.S. pilot test study was conducted for 4 yr on about 3,800 km2 on the Montana-Alberta border to determine the effect of sterile male releases on Hypoderma lineatum (Villers) and H. bovis (L.) populations remaining after initial chemical treatments. Chemical treatments initially reduced populations, making sterile male releases more efficient. Insect material for release was obtained from yearling animals held in confinement, an expensive, labor-intensive method of production. Sterile males of H. lineatum were released in one-half of the study area and sterile males of H. bovis were released in the other half. The unsterilized species in each half served as a control. Although the number of sterile males released was limited (265-462 yr), each species was eliminated in its respective release area, whereas the control species was not.

Alberta↗
PubMed1990

Early detection of cattle grub (Hypoderma lineatum and H. bovis) (Diptera, Oestridae) using ELISA.

An enzyme-linked immunosorbent assay (ELISA) to detect cattle grub-infested animals in the autumn in Alberta has been developed. Antibody to Hypoderma lineatum de Vill. was detectable as early as 6 weeks post-infestation in artificially infested steers. Peak antibody concentrations preceded the peak in maximum 'apparent' grub numbers which occurred between 37 and 43 weeks after infestation. Natural infestations with H. lineatum and H. bovis L., ranging from one to ninety-two grubs per calf, were readily detected by November and the incidence of false positives in uninfested calves was only 5%. Low level (1-4 grubs) infestations of H. bovis only became detectable in February with peak antibody concentrations occurring at the end of April. Prevalence of cattle grub infestations in southern Alberta was shown to be 37% during this study.

Animals↗
PubMed1989

Scanning electron microscopy of the posterior spiracles of cattle grubs Hypoderma bovis and Hypoderma lineatum.

Posterior spiracles of newly hatched first instar larvae of Hypoderma bovis (L.) and H. lineatum (DeVill.) consist of two pairs of spiracular openings. Each pair is surrounded by a rima bearing three spines. Posterior spiracles of second instar larvae are composed of a pair of medial ecdysial scars bounded laterally by spiracular plates. H. bovis spiracular plates have twenty-nine to forty openings, each surrounded by a slightly raised rima. H. lineatum spiracular plates have eighteen to twenty-five openings. Spiracular openings lead to posterior felt chambers which are connected to a common anterior felt chamber filled with a meshlike network. In third instar H. bovis each medial ecdysial scar is surrounded by a strongly concave spiracular plate. Spiracular openings are surrounded by slightly raised rima. Most rimae bear a spine. Spiracular plates of H. lineatum are flat and rimae are without spines. Each spiracular opening leads to a posterior felt chamber, several of which are confluent with a larger anterior felt chamber. Anterior felt chambers open into the dorsal longitudinal tracheal trunk. Felt chambers in third instar larvae are also filled with a complex mesh.

Animals↗
PubMed1983

Development of Sarcocystis alceslatrans Dubey, 1980, in the small intestine of dogs.

Laboratory-reared dogs were fed moose musculature infected with Sarcocystis alceslatrans. These dogs shed sporocysts [15.6 X 11.4 microns (14.4 to 15.8 X 10.8 to 11.5)] 11 to 15 days after inoculation. The prepatent period was 10 to 14 days. Two cats and 1 coyote that also ate infected moose musculature did not pass sporocysts. Histologic examination of intestinal tissue from experimentally infected dogs revealed microgamonts, macrogametes, and oocysts. All stages were present in the lamina propria of the small intestine, usually in the luminal third of the villi. Infections were concentrated in the proximal half of the small intestine. Oocysts were first noticed in dogs killed 7 days after inoculation and a sequence of sporogonic development occurred in dogs killed on subsequent days. Ultrastructural observations were made on the oocyst and sporocyst walls during sporogony.

Animals↗
PubMed1981

Ultrastructure of the cyst wall and merozoites of Sarcocystis from moose (Alces alces) in Alberta, Canada.

Two distinct types of cysts of Sarcocystis from the musculature of moose (Alces alces) were compared by electron microscopy. The fusiform Type A cysts differed from the spherical Type B cysts in the appearance and thickness of the primary cyst wall, organization of cyst interior, and the presence of a secondary cyst wall around Type B. The respective merozoites also differed in size as well as in the number of rhoptries and diameter and arrangement of micronemes. Comparison of the ultrastructure of the moose sarcocysts with those described from other ungulates revealed substantial differences. It appears that two hitherto undescribed species of Sarcocystis are present in moose although cross-transmission and additional life cycle studies are necessary for a complete description.

Alberta↗