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Biomedical subjects

G D Gray

Publications and source records attributed to G D Gray.

At least 19 recordsLinked to original sources
PubMed2004

Efficacy of benzimidazole anthelmintics in goats and sheep in the Philippines using a larval development assay.

The negative effects of nematodes in small ruminants can be reduced by use of dewormers but their effectiveness is increasingly limited by the emergence of anthelmintic resistance. The efficacy of benzimidazole (BZ) anthelmintics in the Philippines was estimated by an in vitro larval development assay using worm eggs recovered from faeces collected from goats and sheep. Two hundred and eighteen farms were selected to represent areas of the country with high goat and sheep populations and the full range of farm sizes, from smallholders with just a few animals to commercial and institutional farms with several hundred. Initial surveys of worm control advisers indicated that BZs have been in continuous widespread use for up to 20 years with little use of other chemical groups. A larval development assay (LDA: DrenchRite) was modified for use with BZs alone to allow up to five samples to be analysed on a single microtitre plate. The assay was validated by comparison with the faecal egg count reduction test (FECRT). The dominant nematode genera were Haemonchus and Trichostrongylus with small numbers of Oesophagostomum. The range of BZ efficacy estimated from the LDA results was 0-100% and the distribution of efficacy levels was continuous, with mean efficacy of 82 and 64% for goats and sheep, respectively. There were significant associations between efficacy and parameters measured to characterize the sampled farms: size of animal management group, FEC of sample, recent importation of stock and no access to common grazing were all correlated with decreased efficacy. Likewise, low efficacy was associated with reported frequency and number of years that BZ drenches had been used. The LDA was found to be highly suited to estimate efficacy in nematode populations from small farms where performance of a FECRT for even one chemical would be impractical. Using a larval development assay, we have demonstrated a wide efficacy range for BZs against nematodes from all sizes of goat and sheep farms in the tropics.

Animal Husbandry↗
PubMed2003

Enhancing immunity to nematode parasites in single-bearing Merino ewes through nutrition and genetic selection.

The effectiveness of protein supplementation and genetic selection to enhance the resistance of periparturient Merino ewes to infection from gastrointestinal parasites was tested in a replicated grazing experiment. One hundred and twenty ewes from lines selected for increased resistance (R) to Haemonchus contortus or at random (C) were subjected to one of the three supplement groups that provided 0 or 250 g per day cottonseed meal for 5 weeks prior to, or for 6 weeks after the start of lambing. Faecal egg counts (FEC) of R ewes were consistently lower than those of C ewes but both groups exhibited a periparturient rise in FEC. Supplementation during the pre-partum period reduced FEC and increased ewe body weight gain. The benefits of pre-partum supplementation in reducing FEC continued to be apparent up to 10 weeks after supplementation ceased. There was a strong suggestion that the benefits to parasite resistance from protein supplementation were greatest in C ewes. Wool growth rates (15%) and birth weights (5%) were greater for C ewes but differences between the lines for lamb body weight had disappeared by day 97. The greatest benefit to resistance from protein supplementation was observed when ewes were experiencing a loss of maternal body weight. Conversely, no benefits to resistance were observed when ewes had moderate (78-107 g per day) rates of maternal weight gain. These results suggest that increased resistance as a result of protein supplementation is dependent on the prevailing supply and demand for scarce nutrients such as metabolisable protein (MP). Both genetic selection and protein nutrition are effective strategies to enhance host resistance to nematode infection during the periparturient period.

Aging↗
PubMed1999

Workshop on irradiated larval vaccines.

The development of anthelmintic resistance in gastrointestinal parasites of sheep and goats has meant that there is an urgent need for non-chemical control of these parasites. In order to investigate a potential alternative method of control, a workshop on irradiated larval vaccines (ILV) was held in conjunction with the Second International Conference on Novel Approaches to the Control of Helminth Parasites of Livestock. The objectives of the workshop were to: (1) Review knowledge of irradiated helminth vaccines through the presentation of invited and contributed papers. (2) Identify opportunities for an ILV and in which host/parasite/production systems. (3) Determine what are the gaps in knowledge required to produce and apply an ILV. The workshop concluded that ILVs could be useful as research tools in the further definition of immune responses to parasites and in stimulating the immune response in young sheep and goats to facilitate the estimating of heritability of faecal egg counts. Although the workshop identified some problems associated with a live attenuated vaccine, an ILV could be a useful control measure in the production systems identified by the workshop. Before an ILV could be used on farms, additional research is required into the period of protection afforded by an ILV especially under field conditions. The efficacy of an ILV could be improved by interaction between host genotype and nutritional status and is deserving of further investigation.

Animals↗
PubMed1999

Long-term effects of short-term provision of protein-enriched diets on resistance to nematode infection, and live-weight gain and wool growth in sheep.

Weaner sheep that had been hand-fed on diets containing increasing concentrations of protein for a 9-week period (when uninfected, or infected with Haemonchus contortus) were studied during the next 69 weeks when put on to pasture as a single, unsupplemented flock. During the 9-week period, groups of 12 sheep (six infected, six uninfected) were offered one of five iso-energetic (9.0 MJ kg(-1)) diets containing 10, 13, 16, 19 or 22% crude protein. All sheep were treated with anthelmintic at the end of the 9 weeks and then put out to pasture for 69 weeks, where they were all subject to the same environmental variables including nematode larval challenge. During the grazing period, animals that had previously received the higher protein diets consistently had higher live-weight gain and wool production, higher antibody responses to both H. contortus and Trichostrongylus colubriformis antigenic challenge in vitro, and lower faecal nematode egg counts than did the lambs previously offered the lower protein diets. Faecal egg counts of the grazing sheep that had been artificially infected with H. contortus while being hand-fed were similar to those of the uninfected sheep and there was no interaction between previous infection and dietary protein concentration. We conclude that short periods of enhanced post-weaning nutrition can have long-term and perhaps life-long effects on production.

Animals↗
PubMed1999

The intramammary inflammatory response of genetically resistant Merino ewes infected with Haemonchus contortus.

The mammary glands of 103 pasture-reared non-lactating, non-pregnant Merino ewes were infused via the teat canal with antigens prepared from the nematode Haemonchus contortus, and the inflammatory response to infusion assessed by washing the gland of its contents after 24 h and 14 days. The ewes were of two genotypes: one with proven high levels of resistance to infection with the nematode H. contortus, the other random-bred animals with relative susceptibility to infection. On day 0 of a H. contortus infection, one gland of the subgroups of both genotypes was infused with the antigen preparation. At the same time, the other gland of the random-bred ewes was infused with sterile physiological saline. A third group of infected random-bred ewes was infused with only sterile physiological saline. Similar infusions were performed on other subgroups on days 12, 21 and 35 of infection, which was then terminated with anthelmintic. A fourth group of uninfected random-bred control ewes was given both infusions 35 days after the other groups were infected. Sheep of the resistant genotype had lower worm egg counts and smaller reductions in blood packed cell volumes from day 21 of infection. Infusion of antigen had no effect on the course of infection and no effect on the response of the other gland, which had been infused with saline alone. The dominant leukocyte response from the antigen-infused gland was eosinophilia. On all days of infusion, and after both 24 h and 14 days, eosinophil counts from the resistant genotype were higher than those from their random-bred counterparts. The sheep mammary gland provides a source of eosinophils whose number is related to host genotype and stage of infection and may provide a model for the investigation of cellular responses in mucosal immunity to nematode infections.

Animals↗
PubMed1998

Protein supplementation improves the performance of parasitised sheep fed a straw-based diet.

A study was made of the benefits of protein supplementation for parasitised and non-parasitised lambs. Sixty, 5-month-old crossbred wether lambs were placed in individual pens indoors for 9 weeks. Half of the animals were experimentally dosed with 1500 Haemonchus contortus larvae per head per week and were fed ad libitum and the other half were worm-free, pair-fed controls. Diets were formulated to be iso-energetic (9.0 MJ of calculated metabolisable energy per kg dry matter) with five levels of protein (10, 13, 16, 19 and 22% crude protein). These diets were based on oaten chaff, with barley, cotton-seed meal, urea and mineral mix (except for the 22% crude protein diet which did not contain barley). Dietary crude protein content increased live-weight gain, feed intake, rumen fluid ammonia-N, packed cell volume, eosinophil counts and antibody responses to H. contortus L3 antigen and decreased faecal worm egg counts significantly. Infection did not significantly affect packed cell volume of animals on diets with 16, 19 and 22% crude protein content. We conclude that extra dietary protein can prevent the adverse effects of H. contortus infection on animal production.

Ammonia↗
PubMed1998

Breeding for disease resistance in Merino sheep in Australia.

Breeding for disease resistance in Merino sheep in Australia has attracted considerable research and development attention. Increased labour costs, the reduced efficacy of common anthelmintics and insecticides, consumer demand for products which are free of chemicals and the poor prognosis of alternative long-term control strategies are all forcing sheep breeders to contemplate the best animal health options available, including selective breeding for resistance. The three major diseases which affect sheep production include gastrointestinal nematode parasites, flystrike (cutaneous myiasis) and footrot. Genetic improvement has been shown to be feasible in all these diseases, possibly with little adverse effect on genetic progress in other production traits. Programmes for resistance to internal parasites to be included in practical breeding programmes are now in progress. This paper deals with the incentives for focusing on the three major diseases in Merino sheep, the potential sources of genetic variation, and the means to exploit these sources of variation. The authors also highlight gains and benefits achieved in experimental selection flocks, and the difficulties and options available for commercial breeders.

Animals↗
PubMed1997

Transformed and immortalized cellular uptake of oligodeoxynucleoside phosphorothioates, 3'-alkylamino oligodeoxynucleotides, 2'-O-methyl oligoribonucleotides, oligodeoxynucleoside methylphosphonates, and peptide nucleic acids.

Direct quantitative comparisons of cellular uptake across a wide variety of analogs and cell types are necessary for the design of oligonucleotide diagnostic and therapeutic applications. This work reports quantitative cellular uptake and nuclear localization of [14C]oligodeoxynucleoside phosphorothioates (PS), 3'-alkylamino oligodeoxynucleoside phosphodiesters (PO-NH2), 2'-O-methyl oligoribonucleoside phosphodiesters (2OM), peptide nucleic acids (PNA), and oligodeoxynucleoside methylphosphonates (MP) in several transformed or immortalized cell lines. All analogs demonstrated active cellular uptake in that intracellular concentrations greatly exceeded the extracellular 1 microM concentration within 1-3 hr. However, by 9-24 hr, cellular accumulations of PS exceeded those of PO-NH2 and 2OM by 3- to 5-fold, PNA by 6- to 7-fold, and MP by 8- to 10-fold. Similar results were observed in two transformed cell lines, HL-60 leukocytes and H-ras transformed fibroblasts, using three different heterogeneous sequences. H-ras and IGF-1R transformed fibroblasts had a 2- to 5-fold higher uptake of all analogs than non-transformed immortalized fibroblasts. Nuclear levels of the PO-NH2, PS, and MP analogs were approximately 25% of total cellular uptake, while nuclear percentages of 2OM and PNA were less than 20%, suggesting some differences in nuclear localization among the analogs. These observations provide a direct quantitative comparison of cellular uptake as a function of oligonucleotide modification, and imply that transformation enhances cellular uptake. From the perspective of therapy and diagnosis, clear trade-offs were apparent between efficiency of uptake on the one hand, and nuclease resistance and hybridization strength on the other.

3T3 Cells↗
PubMed1997

The use of genetically resistant sheep to control nematode parasitism.

Research in the last 20 years has firmly established that it is possible to exploit genetic variation in resistance to the nematode parasites of sheep by selection. Selected sheep are more resistant to infection and commercial application of this research is under way in both Australia and in New Zealand. Not all the consequences of these breeding programs have been established, particularly long-term consequences for productivity and the interaction with other control measures, but the technology is available in the public domain with no commercial restrictions. Faecal worm egg count remains the most effective way of selecting sheep although many alternatives, such as DNA markers, host antibody and parasite antigen assays are being developed for use as selection criteria. Strategic nutritional supplementation is an immediate candidate for inclusion in worm control programs and although nematode vaccines remain elusive, it is likely that some will be field-tested in the next few years. For both of these approaches, nutritional and immunological, it is critical that the response of selected genotypes are assessed under commercial conditions and as components of worm control programs. There is evidence to support the possibility that selected sheep will be more responsive to vaccination while the long-term interaction between the effect of strategic nutritional supplements and resistant genotypes needs to be investigated.

Animal Nutritional Physiological Phenomena↗
PubMed1997

Rapid measurement of modified oligonucleotide levels in plasma samples with a fluorophore specific for single-stranded DNA.

Animal studies of therapeutic oligonucleotides require measurement of circulating levels of oligonucleotides by multistep, time-consuming methods. In contrast, addition of a single-stranded DNA binding fluorophore, OliGreen, to oligonucleotides in plasma samples allowed rapid quantitation. Dose-response curves were measured for five different oligonucleotide analogs added to plasma or serum. Phosphorothioate or 3'-amino phosphodiester oligodeoxynucleotides in calf serum reliably exhibited linear, dose-dependent fluorescence at 15-500 nM. The assay was equally sensitive in human and mouse plasma, with a heterogeneous variety of sequences. Oligonucleotides shorter than 10 nucleotides yielded substantially reduced fluorescence. In contrast, 2'-O-methyl oligoribonucleotides, DNA methylphosphonates, and peptide nucleic acids demonstrated little or no fluorescence with OliGreen. Following intravenous injection of a phosphorothioate pentadecamer into mice, fluorescence measurements of plasma phosphorothioate levels displayed a dose-dependent, biexponential decline over a 90 min period. Chronic infusion at 2.5 nmol/hour into mice yielded plasma oligonucleotide values equivalent to 0.1 microM, a value reflecting the contributions of intact and partially degraded strands. Tumor-bearing mouse plasma evidenced high fluorescence values in the absence of oligonucleotide administration, presumably because of elevated intrinsic plasma DNA fragments. Although limited in its ability to differentiate intact from partially degraded strands, OliGreen fluorescence provides a simple, rapid, and sensitive method for measuring circulating levels of phosphorothioate or phosphodiester oligonucleotides in healthy animals or humans.

Animals↗
PubMed1997

Receptors for the chemoattractants C5a and IL-8 are clustered on the surface of human neutrophils.

We have used high-resolution field emission scanning electron microscopy with backscatter electron imaging to detect immunogold-labeled C5a and interleukin-8 (IL-8) receptors on human blood neutrophils. The receptors were labeled with receptor-specific antibodies in combination with secondary antibody conjugated to immunogold. When neutrophils were isolated in a "nonactivated" state, both of these receptor populations were expressed primarily in clusters on nonprojecting domains of the cell membrane. When these cells were double labeled for C5a and IL-8 receptors, intermixing of these receptor species in a common cluster was not found. When neutrophils were isolated in an "activated" state, by mixing the blood with N-formylmethionyl-leucyl-phenylalanine, the cells were seen to be elongated and ruffled at their anterior pole, but the C5a receptors did not disperse or redistribute on the surface of the peptide-activated cells. Analysis of the distribution of human C5a receptors expressed by transfected mouse L-cell fibroblasts showed the C5a receptors to be clustered, but expressed on nonprojecting and projecting domains of the cell surface. These observations provide new information on the topographical expression of leukocyte receptors involved in directing cell migration.

Animals↗
PubMed1995

Incidence, source, and nature of complaints received in a large, urban emergency medical services system.

OBJECTIVE: To document the incidence, source, and reasons for all complaints received by a large municipal emergency medical services (EMS) program. METHODS: A retrospective review of all complaints received during three consecutive years (1990-1992) in a centralized EMS system serving a large municipality (population 2 million). All cases were categorized by year, source, and nature of the complaint. RESULTS: In the three study years, EMS responded to 416,892 incidents with nearly a half-million patient contacts. Concurrently, 371 complaints were received (incidence of 1.12 per thousand); 132 in 1990, 129 in 1991, and 110 in 1992. Most complaints involved either: 1) allegations of "rude or unprofessional conduct" (34%), 2) "didn't take patient to the hospital" (19%), or 3) "problems with medical treatment" (13%). Only 1.6% (n = 6) were response-time complaints. Other complaints included "lost/damaged property," "taken to the wrong hospital," "inappropriate billing," and "poor driving habits." The most common sources were patient's families (39%) and the patients themselves (30%). Only 7.8% were from health care providers. CONCLUSION: Reviews of complaints provide information regarding EMS system performance and reveal targets for quality improvement. For the EMS system examined, this study suggests a future training focus on interpersonal skills and heightened sensitivities, not only toward patients, but also toward bystanders and family members.

Consumer Behavior↗
PubMed1994

Antibody-containing cells in the abomasal mucosa of sheep with genetic resistance to Haemonchus contortus.

The frequency distribution of parasite-specific antibody-containing cells (ACC) and total immunoglobulin-containing cells (ICC) in the abomasal mucosa was examined in genetically resistant and random-bred sheep, following infection with Haemonchus contortus, to determine whether the two genotypes differed in the development of a local immune response. Immunofluorescence staining was used to detect ACC and ICC of IgA, IgG1, IgG2 and IgM classes. No ACC were found in the abomasum of any of the sheep before infection. ACC were first detected in the abomasal mucosa of both the resistant and susceptible sheep seven days after infection, reached a peak level on day 21 and then declined. At all observation times, the majority of ACC in both genotypes were of the IgA isotype, followed by IgG1 and IgM. The IgG2-ACC response was negligible compared with the IgA and IgG1 response. The comparison of genotypes showed that the resistant sheep had significantly more IgA-ACC on days 14, 21, 28 and 35, and significantly more IgG1-ACC than random-bred sheep on days 14, 21 and 28. The numbers of IgG2- and IgM-ACC did not differ between the genotypes. The abomasal mucosa of the resistant sheep was also found to have significantly more ICC than the mucosa of random-bred sheep; IgA-ICC predominated at all the observation times followed by IgG1 and IgM. These results suggest that IgA and IgG1 antibodies, produced locally in response to infection, may play a role in mediating genetic resistance to haemonchosis in sheep.

Abomasum↗
PubMed1993

Antisense DNA inhibition of tumor growth induced by c-Ha-ras oncogene in nude mice.

Antisense DNA has shown an ability to target specific oncogene transcripts and inhibit their expression in cells, but the degree to which sustained treatment can suppress total levels of an oncogenic product and alter tumorigenesis in vivo remains to be determined. In this study, NIH-3T3 cells transformed by the activated c-Ha-ras oncogene from T24 human bladder cancer cells were treated for 3 consecutive days in vitro with an antisense DNA pentadecamer complementary to a target in the 5'-flanking region of the c-Ha-ras RNA transcript. Following antisense DNA treatment, a portion of the cells was lysed for measurement of RAS p21 while the remaining cells were evaluated for tumorigeneity by injection s.c. into athymic nude mice at a dose of 5 x 10(5) cells/mouse. The 3 days of treatment with the anti-c-Ha-ras DNA reduced RAS p21 cellular levels by more than 90% while a nonspecific control DNA reduced p21 levels by approximately 20%. Tumor growth of cells treated with anti-c-Ha-ras DNA was significantly reduced for up to 14 days following the end of treatment and implantation into the mice whereas the nonspecific control DNA had no significant effect. These effects on tumor growth were evident in two different strains of nude mice and in both males and females. It is suggested that the pronounced decrease in RAS p21 levels produced by anti-c-Ha-ras DNA resulted in a reversal of the transformed phenotype, and it is this reversal which accounts for the prolonged inhibition of tumorigenesis following antisense DNA treatment.

3T3 Cells↗
PubMed1993

Host genes, parasites and parasitic infections.

Resistance to infection of mammalian hosts by parasites is under genetic control at many different levels: between species, between races, breeds and lines of single species and between individuals. These genetic effects have been described in many host-parasite systems. Here we review the interaction between three elements: host genes, parasites and the environment in which parasitic infections develop. Already livestock industries exploit genetic variation between breeds, particularly for the control of trypanosomiasis and tick infestation in cattle. In most populations, and to many diseases, resistance is heritable and selective breeding for resistance in commercial livestock species has been successful experimentally. Attempts at utilizing genetic variation are placed in the broad context of the coevolution of host and parasite, the limited knowledge we have of the mode of action of resistance genes and our ability to use genetic information to predict resistance to parasites.

Animals↗
PubMed1993

A search for associations between major histocompatibility complex restriction fragment length polymorphism bands and resistance to Haemonchus contortus infection in sheep.

Polymorphic bands were detected within the DQB and DRB regions of the ovine major histocompatibility complex by probing TaqI digested DNA from three large sheep half-sib families derived from a highly resistant ram. All animals were phenotypically assessed for Haemonchus contortus resistance by faecal egg counts and associations with RFLP bands and haplotypes were estimated using mixed model, best linear unbiased prediction statistical methods. Although the highly resistant sire was homozygous at the MHC, no significant associations were found between any band or haplotype and faecal egg count.

Animals↗
PubMed1993

Isotype-specific antibody responses to Haemonchus contortus in genetically resistant sheep.

The kinetics of anti-Haemonchus antibody responses in serum and faecal extracts of pasture-reared, genetically resistant and random-bred sheep infected with Haemonchus contortus were examined using an isotype-specific ELISA. Anti-Haemonchus antibodies of IgA, IgG1, IgG2 and IgM isotypes were detected in serum and faecal extracts of both resistant and random-bred sheep after challenge infection. Serum IgG1 and IgA levels in resistant sheep were significantly higher than in random-bred sheep between 10 and 31 days after infection. However, there were no differences in IgG2 and IgM antibody responses between the two genotypes. Faecal antibody responses to H. contortus showed a clear genetic effect with resistant sheep exhibiting higher IgA levels throughout infection and higher IgG1 levels between 24 and 31 days after infection. Furthermore, serum IgG1 and IgA, and faecal IgA responses were negatively correlated with faecal egg counts in both genotypes on 17, 24 and 31 days after infection. Together, these results are taken to indicate that anti-parasite IgA and IgG1 antibodies may play an important role in genetically determined resistance of sheep to haemonchosis.

Analysis of Variance↗