Biomedical subjects

D D Colwell

Publications and source records attributed to D D Colwell.

At least 37 records · Page 2Linked to original sources

PubMed2000

Scanning electron microscopy of sarcophagid (Diptera) larvae recovered from a case of human cutaneous myiasis.

Scanning electron microscope observations were made on second instars of unindentified sarcophagid maggots recovered from the foot of a 2-mo-old child. The child had a 3-d history of irritation and swelling of the left foot, and larvae were present in the skin on the plantar surfaces. The lesions were not furuncular, but erythema and a serous exudate were evident and swelling of the infested toes was noted. Larvae were removed manually from the lesions and fixed in formalin. External features, examined by scanning electron microscopy (SEM), were typical for muscomorph larvae and shared features common to other sarcophagids. Details of the cephalic, thoracic, and terminal abdominal sensory structures and variation in the structure of spines from various body regions are described. Comparisons of SEM observations on the cephalic, thoracic, and posterior abdominal regions with other published information did not yield information that allowed the accurate identification of the larvae from this infestation.

Animals↗

PubMed1999

Parasites and behavior: an ethopharmacological analysis and biomedical implications.

Parasites and disease are increasingly recognized as agents of behavioral, ecological and evolutionary importance having a variety of influences on their hosts other than the more obvious pathological and immunological changes. Parasites can have significant behavioral effects even when parasitism is sub-clinical with these effects proposed to either benefit the parasite (parasite 'manipulation'), benefit the host, or to simply arise as side-effects of the infection (parasitic 'constraints'). However, until relatively recently little attention has been paid to the neuromodulatory substrates that mediate these behavioral changes. Ethopharmacology incorporates an evolutionary approach to the study of behavior with pharmacological analysis of neuromodulatory mechanisms. As such, this approach is appropriate for, and has been applied to, the analysis of the effects of ectoparasites (e.g. biting and blood-feeding flies) and endoparasites (e.g. protozoa, nematodes) on a number of behaviors (e.g. pain inhibition, learning and memory, responses to predators and anxiety, mate selection) in selected host-parasite systems. Ethopharmacology suggests a promising direction by which neuromodulatory mechanisms that underlie the effects of parasites on behavior, including that of humans, can be addressed.

Animals↗

PubMed1999

Scanning electron microscopy and comparative morphometrics of eggs from six bot fly species (Diptera: Oestridae).

Scanning electron microscope comparisons were made of the eggs of Cuterebra austeni Sabrosky, C. fontinella Coquillet, C. jellisoni Curran, C. lepusculi Townsend, C. ruficrus (Austen), and Alouattamyia baeri (Shannon & Greene). Larvae of these flies parasitize rodents, lagomorphs, and monkeys. Image analysis of the egg length (maximum projection) and width (minimum projection), egg area (in dorsal view), operculum area (in dorsal view), and operculum area as a percentage of egg area revealed differences among species. The chorion of these eggs is sculptured with a distinct pattern of "cells" covering the dorsal, lateral, and opercular surfaces. The chorion of A. baeri eggs was distinct with deeply sculpted, large, highly polymorphic "cells." C. jellisoni eggs also had large, highly polymorphic cells, but the sculpturing was not deep. The chorion of the 4 remaining species was quite similar. Image analysis of the chorionic sculpturing patterns revealed significant differences in the area, perimeter, maximum projection, minimum projection and aspect ratio of chorionic "cells" among the species examined. The chorionic "cell" parameters of A. baeri and C. jellisoni were different from 1 another and from the other species in all parameters. The "cell" parameters of C. lepusculi and C. ruficrus were similar. A combination of overall egg features in combination with cell features allow the eggs to be differentiated from one another. There was no strong association among structural features of the eggs and the habitat in which they were found. However, the deep sculpturing of the A. baeri eggs might help to prevent drowning in tropical rain forests.

Animals↗

PubMed1999

Learning to cope with biting flies: rapid NMDA-mediated acquisition of conditioned analgesia.

A 30-min exposure to intact biting flies (stable flies) induced an opioid-mediated analgesia in fly-naive male deer mice, whereas exposure to either altered biting flies whose biting mouthparts were removed or nonbiting house flies had no significant effects. However, mice that were previously exposed to intact stable flies for 30 min exhibited significant analgesia when exposed 24-168 hr later to stable flies whose biting parts were removed, but not to nonbiting house flies. Administration of the specific N-methyl-D-aspartate (NMDA) antagonist NPC 12626 to fly-naive mice before exposure to intact flies, although not significantly reducing the analgesic response, blocked the subsequent conditioned analgesia. Naloxone, which blocked the intact biting fly-induced analgesia, did not alter the acquisition of the conditioned analgesic response to the altered stable flies. This demonstrates an NMDA-mediated acquisition of conditioned analgesia to a natural aversive stimulus.

Adaptation, Physiological↗

PubMed1998

Parasitized female mice display reduced aversive responses to the odours of infected males.

The present study showed that parasites influence both the responses of uninfected females to males and the responses of female hosts to infected males. In female laboratory mice one of the consequences of exposure to the olfactory cues associated with an infected male was a reduction of the reactivity to a thermal surface, i.e. pain inhibition or analgaesia. Uninfected oestrous and non-oestrous female mice displayed marked analgaesic responses after exposure to the odours of males infected with either the enteric single-host nematode parasite, Heligmosomoides polygyrus, or the protozoan parasite, Eimeria vermiformis. The uninfected oestrous females distinguished between infected and physically stressed males, displaying a greater analgaesic response to the odours of infected males. These analgaesic responses and their anxiety/ fearfulness-associated behavioural correlates could elicit either a reduced interest in, or avoidance of, parasitized males by females. Oestrous female mice infected with H. polygyrus displayed a reduced analgaesic response to the odours of the infected males and differentially responded to the odours of males infected with either the same (H. polygyrus) or a different parasite (E. vermiformis). An exposure time of 1 min elicited minimal responses to the odours of males infected with the same parasite, H. polygyrus, and an attenuated, though significant, non-opioid peptide-mediated analgaesic response to males infected with E. vermiformis. An exposure time of 30 min elicited similar markedly reduced endogenous opioid peptide-mediated analgaesic responses to the odours of both of the categories of infected males. The responses to the odours of a stressed male were, however, unaffected by the parasitic infection. The reduced analgaesic responses of the parasitized females to the odours of infected males may involve either enhanced odour familiarity and responses to group odour templates and/or neuromodulatory shifts resulting in reduced fearfulness and potentially greater interest in the infected males.

Animals↗

PubMed1998

Analgesic responses of male mice exposed to the odors of parasitized females: effects of male sexual experience and infection status.

The present study shows that parasites influence both the responses of males to infected females and the responses of male hosts to females. Male mice exposed for 30 min to the odors of females infected with the nematode parasite Heligmosomoides polygyrus displayed a naloxone-sensitive, opioid-mediated analgesia, whereas males exposed for 1 min showed a shorter duration and lower amplitude naloxone-insensitive "nonopioid" analgesia that involved serotoninergic (5-HT) and excitatory amino acid (N-methyl-D-aspartate [NMDA] receptor) systems. The male mice distinguished between the odors of infected and physically stressed females, displaying greater analgesia after exposure to the odors of infected than stressed females. The analgesic responses to the odors of infected females were also affected by the males' prior sexual experience; sexually experienced males exhibited significantly greater analgesia than sexually naive males. In contrast, male mice infected with H. polygyrus failed to show a nonopioid analgesia after exposure to the odors of infected females and displayed a markedly lower level of opioid analgesia than uninfected mice. These results show that male mice can discriminate between the odors of parasitized and nonparasitized females and find the odors of parasitized estrous females aversive.

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

PubMed1998

Comparative scanning electron microscopy of third-instar Hypoderma spp. (Diptera: Oestridae).

Scanning electron microscope study of third-instar larvae of four species of Hypoderma revealed differences among species in the pattern of spination, spine morphology and morphology of the spiracular plates. These observations identify characters that enable the differentiation of Hypoderma actaeon and H. diana, parasitizing red deer (Cervus elaphus) in Europe, and provide additional characters for differentiating H. bovis and H. lineatum parasitizing cattle.

Animals↗

PubMed1998

Development of Alouattamyia baeri (Diptera: Oestridae) from howler monkeys (Primates: Cebidae) on Barro Colorado Island, Panama.

The fecundity and development of larval stages of the cuterebrid bot fly A. baeri were studied in an unusual host, remotely related to the primary host. Third-instar Alouattamyia baeri (Shannon & Greene) removed from howler monkeys, Alouatta palliata, were allowed to pupate and then were cultured under controlled conditions. Eclosion occurred after 37.9 +/- 0.4 (mean +/- SE) (male) and 38.2 +/- 0.4 (female) d at 26 degrees C. Five-day-old females were mated using a tethered flight technique and oviposited on ridged filter paper. The total egg complement was 1,399 +/- 243 (n = 2) eggs per female. Eggs were fully embryonated after incubation for 5 d at 26 degrees C. Eggs hatched when warmed in the palm of the hand. Hatching of eggs from an individual batch was asynchronous. Newly hatched larvae would not penetrate intact skin on a rabbit, Oryctolagus cuniculus L. Larvae placed near the nares or on the ocular conjunctiva migrated rapidly from view. Warbles containing larvae were first observed on infested rabbits 5 d after infestation. Development of larvae proceeded until day 39 after infestation, when nearly mature 3rd instars were observed. None of the larvae survived to pupate.

Alouatta↗

PubMed1998

Efficacy of eprinomectin against Hypoderma spp in cattle.

OBJECTIVE: To determine the efficacy of a topical formulation of eprinomectin against natural infestations of first (L1)-stage, and second and third (L2/L3)-stage larvae of Hypoderma spp. ANIMALS: 140 approximately 6- to 18-month-old cattle of various breeds. PROCEDURE: Cattle, selected from herds with high prevalence of Hypoderma infestation, were treated in 4 experiments: within each replicate, 1 animal received eprinomectin at a dosage of 500 micrograms/kg of body weight against first-stage larvae (L1). The second animal received the same treatment against second or third-stage larvae (L2/L3). The third animal served as an untreated control. In a fifth experiment, visible warbles were treated on half of the cattle. Remaining cattle served as vehicle-treated controls. In 1 experiment, warbles were examined from time of treatment until all lesions were resolved. In 4 experiments, emerging Hypoderma larvae were recovered, speciated, and enumerated, and viability was determined. RESULTS: Eprinomectin (500 micrograms/kg) efficacy was complete against L1. Hypoderma L2/L3 eradication approached 100% efficacy (1 live larva was recorded). Warbles in treated cattle resolved in a significantly shorter time than did those in controls. Adverse reactions related to treatment were not observed in any of the trials. CONCLUSIONS: Eprinomectin (500 micrograms/kg) applied topically was safe and highly efficacious for treatment of all larval stages of Hypoderma spp in these trials. CLINICAL RELEVANCE: Attributes of eprinomectin besides antiparasite efficacy allow treatment of all classes of cattle with no need for meat or milk withdrawal.

Administration, Topical↗

PubMed1997

Opioid and non-opioid NMDA-mediated predator-induced analgesia in mice and the effects of parasitic infection.

The present study examined the nociceptive responses (50 degrees C, hot-plate) of uninfected and subclinically parasitized male mice exposed to the odor of a predator, an ecologically relevant threatening stimulus. In uninfected mice a 15-min exposure to 2-propylthietane, the major component of weasel odor, induced a naloxone-reversible opioid analgesia. A 30-s exposure elicited a shorter duration and lower amplitude 'non-opioid' analgesia that was insensitive to naloxone, partially sensitive to either the serotonin-1A (5-HT1A) agonist, 8-OH-DPAT, or the GABAA antagonist, bicuculline, and blocked by the competitive N-methyl-D-aspartate (NMDA) antagonist, NPC 12626. In contrast, mice chronically (25 days) and subclinically infected with the murine nematode, Heligmosomoides polygyrus, failed to show a significant non-opioid analgesia and displayed a markedly lower level of opioid analgesia than uninfected mice. These results suggest that NMDA receptor mechanisms are potently associated with the expression of the analgesia arising from exposure to the naturally aversive stimulus of predator odor. These findings also demonstrate that parasites, and likely other subchronic infections, can have a significant impact on the display of opioid and non-opioid stress-induced analgesia arising from exposure to the ethologically relevant stimulus of predator odor.

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

PubMed1997

Influence of parasiticide treatment on kinetics of antigen specific antibody response in cattle infested with Hypoderma lineatum (Diptera:Oestridae).

The effect of parasiticide treatment on dynamics of antigen specific antibody responses to Hypoderma lineatum (De Villers) was investigated in naturally infested calves. Parasiticides were applied to cattle 1 month prior to, 1 week prior to, and coincident with the appearance of warbles in untreated calves from the same source herd. When cattle were treated approximately 1 month before warbles appeared in untreated control animals, antigen specific antibody levels increased for 25-34 days then declined to undetectable levels by approximately 75 days. Antigen specific antibody levels sharply declined in cattle treated 1 week prior to appearance of warbles in untreated controls. Treatment applied coincident with arrival of grubs on the back did not alter the antigen specific antibody profile, but reduced the relative magnitude of antigen specific antibodies present. Persistence of the antigen specific antibody following treatment will permit conduct of serological surveillance programmes.

Animals↗

PubMed1997

Stable fly, Stomoxys calcitrans, mouthpart removal influences stress and anticipatory responses in mice.

Biting fly attack induces a variety of stress and anxiety related changes in the physiology and behaviour of the target animals. Significant reductions in pain, or more appropriately, nociceptive sensitivity (latency of a foot-lifting response to an aversive thermal stimulus), are evident in laboratory mice after a 1 h exposure to stable flies, Stomoxys calcitrans. The role of the various components of biting fly attack in the development of this stress-induced reduction in pain sensitivity (analgesia) is, however, unclear. This study demonstrates that fly-naive mice do not exhibit a stress-induced analgesia when exposed to stable flies whose biting mouthparts have been removed. In contrast, mice that have been previously exposed to intact stable flies exhibit significant analgesia when exposed to flies that are incapable of biting. However, the level of analgesia induced is lower than that elicited by exposure to intact stable flies. Exposure to nonbiting house flies, Musca domestica, has no effect on nociceptive sensitivity. It appears that the actual bite of the stable fly is necessary for the induction of analgesia and probably other stress and anxiety associated responses in fly naive mice. However, mice rapidly learn to recognize biting flies and exhibit significant, possibly anticipatory analgesic responses to the mere presence of biting flies.

Animals↗

PubMed1996

Antibody immunoglobulin G (IgG) response to Alouattamyia baeri (Diptera:Cuterebridae) parasitism of howler monkeys, Alouatta palliata, in Panama.

Larval bot fly burdens and the presence of immunoglobulin G (IgG) antibodies to larval antigens of Alouattamyia baeri (Shannon & Greene) were determined in howler monkeys, Alouatta palliata authority, from Barro Colorado Island, Panama, during July and August of 1991 and 1992. Monkeys produced antibodies (IgG) to both 1st- and 3rd-instar proteins of the monkey bot as measured by an enzyme immunoassay. The response to 1st-instar antigen was correlated with number of bots for the 1991 data and for pooled data from 1991 and 1992. No correlation was observed for the response to 3rd instar antigen. First-instar extracts were composed of 9 major proteins as visualized by SDS-PAGE. Bands at 17, 25, and 32 kDa were positive in Western blots. Third-instar extracts contained at least 13 major bands, with those at 120 and 130 kDa reactive in immunoblots. The immune response to A. baeri may be involved in limiting larval bot numbers.

Alouatta↗

PubMed1995

Discrimination by female mice between the odours of parasitized and non-parasitized males.

The detection and avoidance of parasitized males has been proposed to be a component of female mate choice. We investigated whether or not female laboratory mice, Mus musculus domesticus, could discriminate between parasitized and non-parasitized males on the basis of odour. Female mice were given a choice between the urine and other odorous secretions of either a male mouse sub-clinically infected for five days with the naturally occurring, enteric, single host, protozoan parasite, Eimeria vermiformis, or an uninfected male. Females showed a marked preference for the odours of non-parasitized male mice over those of the parasitized males; as measured by number of investigations, time spent per investigation, and total investigation time of the odours in a choice situation. Female mice also displayed an overwhelming initial, or first choice, preference for the odours of the non-parasitized male mice over those of the parasitized males. These observations show that female mice can distinguish between the odours of parasitized and non-parasitized males, and discriminate against parasitized males on the basis of odour. We suggest that the detection and avoidance of infected males by female mice through odour cues may function to reduce parasite transmission and potentially serve as a component of female mate selection or choice.

Animals↗

PubMed1995

Reduced spatial learning in mice infected with the nematode, Heligmosomoides polygyrus.

Parasite modification of host behaviour influences a number of critical responses, but little is known about the effects on host spatial abilities. This study examined the effects of infection with the intestinal trichostrongylid nematode, Heligmosomoides polygyrus, on spatial water maze learning by male laboratory mice, Mus musculus. In this task individual mice had to learn the spatial location of a submerged hidden platform using extramaze visual cues. Determinations of spatial performance were made on day 19 post-infection with mice that had been administered either 50 or 200 infective larvae of H. polygyrus. The infected mice displayed over 1 day of testing (6 blocks of 4 trials) significantly poorer acquisition and retention of the water maze task than either sham-infected or control mice, with mice that had received 200 infective larvae displaying significantly poorer spatial performance than individuals receiving 50 larvae. The decrease in spatial learning occurred in the absence of either any symptoms of illness and malaise, or any evident motor, visual and motivational impairments. It is suggested that in this single host system the parasitic infection-induced decrease in spatial learning arises as a side-effect of the host's immunological and neuromodulatory responses and represents a fitness cost of response to infection.

Analysis of Variance↗

PubMed1995

Decreased predator avoidance in parasitized mice: neuromodulatory correlates.

Although parasites are reported to alter host responses to predators, little is known about the neurochemical mechanisms involved. Using an odour preference test, we examined the effects of an acute, subclinical infection with the naturally occurring, single host, enteric protozoan parasite, Eimeria vermiformis, on the responses of male laboratory mice, Mus musculus, to a predator. Uninfected mice avoided the odour of a predatory cat, spending a minimal amount of time in a Y-maze in the vicinity of the cat odour. In contrast, mice infected with E. vermiformis, spent a significantly greater amount of time in the proximity of the cat odour, showing a reduced avoidance of the cat odour and a reduction in predator-induced fear or anxiety. This was not related to augmented opioid activity and decreased pain sensitivity in the infected mice, as neither treatment with the exogenous opiate, morphine, nor restraint stress-induced augmentation of endogenous opioid activity, had any significant effects on the responses of uninfected mice to cat odour. The altered responses of the infected mice to the cat odour were reduced by peripheral administration of the gamma-aminobutyric A (GABAA) antagonists, bicuculline and picrotoxin, but were not significantly affected by either the benzodiazepine antagonist, Ro 15-1788, the opiate antagonist, naloxone, or the excitatory amino acid, N-methyl-D-aspartate (NMDA) antagonist, MK-801. These results indicate that infection with E. vermiformis in mice reduces the avoidance of predator odour through neurochemical systems associated with anxiety involving, at least in part, GABAA receptor mechanisms.

Animals↗

PubMed1995

Cuticular sensilla on newly hatched larvae of Gasterophilus intestinalis and Oestrus ovis.

Cuticular sensilla on newly hatched larvae of Gasterophilus intestinalis De Geer (Diptera: Gasterophilidae) and Oestrus ovis (L.) were studied by scanning electron microscopy. Two types of trichoid sensilla, two types of coeloconic sensilla and a pit sensillum were present on the thoracic and abdominal segments of G.intestinalis larvae. Sensilla on larvae of O.ovis were similar although only one type of trichoid sensillum was present. Total number of sensilla were higher for O.ovis than for G.intestinalis (248 v. 214). Variation in numbers of sensilla is consistent with the concept that increasing numbers of sensilla are associated with increasingly complex searching behaviour required to locate suitable habitats for development.

Animals↗

PubMed1995

Exposure to stable flies reduces spatial learning in mice: involvement of endogenous opioid systems.

Biting flies influence both the physiology and behaviour of domestic and wild animals. This study demonstrates that relatively brief (60 min) exposure to stable flies, Stomoxys calcitrans (L.), affects the spatial abilities of male mice. Stable fly exposure resulted in poorer subsequent performance in a water maze task in which individual mice had to learn the spatial location of a submerged hidden platform using extramaze visual cues. Determinations of spatial acquisition and retention were made with mice that had been previously exposed for 60 min to either stable flies or house flies, Musca domestica (L.). Mice exposed to stable flies displayed over one day of testing (six blocks or sets of four trials) significantly poorer acquisition and retention of the water maze task than either mice that had been exposed to house flies or fly-naive mice. This attenuation of spatial learning occurred in the absence of any evident sensorimotor or motivational impairments. The reduction in spatial abilities involved endogenous opioid systems, as the decreased performance resulting from stable fly exposure was blocked by pre-treatment with the prototypic opiate antagonist, naltrexone. These results indicate that relatively brief exposure to biting flies can lead to a decrease in spatial abilities which is associated with enhanced endogenous opioid activity. These results support the involvement of endogenous opioid systems in the mediation of the behavioural and physiological effects of biting fly exposure. They further suggest that decreases in spatial abilities and performance may be part of the behavioural consequences of biting fly exposure in domestic and wild animals.

Animals↗