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Biomedical subjects

A Hoek

Publications and source records attributed to A Hoek.

At least 19 recordsLinked to original sources
PubMed2002

High volume continuous venovenous haemofiltration (HV-CVVH) in an equine endotoxaemic shock model.

Equine acute abdominal disease is often associated with shock. Important aspects in the onset of this complication include hypovolaemia, the translocation of endotoxins from the gut and the subsequent activation of the cytokine network. The clinical efficacy of high volume continuous venovenous haemofiltration (HV-CVVH) and the clearance of cytokines were therefore investigated in an equine endotoxaemic model. Ten male Shetland ponies received a slow infusion of LPS (2 microg/kg bwt) under general anaesthesia. The treatment group (n = 5) received HV-CVVH (2 ml/kg bwt/min) using a 75 kD polymethylmethacrylate (PMMA filter). Haemodynamic, blood variable and cytokine (TNF, IL-1 and IL-6) measurements were performed every 30 min for a 6 h period. The ponies showed a typical reaction in mean pulmonary arterial pressure, blood chemical and haematological markers after LPS challenge. No significant differences were found between the treatment group and the control group. Only a slight increase in cardiac index and no marked decrease in mean arterial pressure were seen. A clear cytokine response was found in all ponies, though substantially different in magnitude between individuals. The clearance of cytokines from the blood increased in time, but did not lead to significant decrease in serum levels. In this study, HV-CVVH with a PMMA filter did not prove to have a significant beneficial effect on the course of experimental endotoxaemia in horses. However, in a more severe model, better efficacy might be obtained. Testing additional filters might lead to a more suitable therapy for horses.

Animals↗
PubMed2001

The flock-to-flock force of infection for scrapie in Britain.

A postal survey of British sheep farmers provided information on the proportion of farms that experienced their first case of scrapie in each year between 1962 and 1998. We found no evidence of a large increase in the proportion of scrapie-affected farms prior to, during or following the epidemic of BSE in British cattle. After correcting for between-farm heterogeneity in the probability of acquiring scrapie, we estimated the yearly between-flock force of infection since 1962. The current force of infection is estimated at approximately 0.0045 per farm per year and combined with a simple model of scrapie spread provides an estimate of the average duration of a scrapie outbreak on an individual farm. Considering all farms, the average outbreak lasts for five years, but if only those farms that have cases in animals born on the farm are considered, it lasts 15 years. We use these parameter estimates to compare the proportion of farms with scrapie in time periods of different lengths. In the survey, 2.7% of farms had a case in 1998. The 5.3% of farms reporting having a case between 1993 and 1997 is consistent with the hypothesis that the scrapie force of infection remained constant over this period.

Animals↗
PubMed2001

The prevalence of parasite infestation and house dust mite sensitization in Gabonese schoolchildren.

BACKGROUND: Allergic diseases seem less prevalent in communities in less developed parts of the world, where parasite infections are highly prevalent. Altogether not much is known about the association between chronic infections with tissue and blood-dwelling parasites and atopy. METHODS: In an area in Gabon endemic for blood and tissue parasites, 520 schoolchildren were parasitologically examined and skin prick-tested for a set of common environmental aeroallergens. Levels of allergen-specific IgE and polyclonal IgE were measured. RESULTS: In schoolchildren schistosome and filarial infections increased with age, whereas malaria was more prevalent in younger children. In contrast to allergen sensitization that increased with age, skin test reactivity tended to decline. The number of children with mite-specific IgE antibodies (47%) by far exceeded the number responding to skin prick testing (11%). Mite sensitization was found to be the highest in children infected with schistosomes and/or filariae whereas skin test reactivity was lowest. The multiple logistic regression showed that the risk of a positive skin test was 8-fold higher with increasing levels of mite-specific IgE but was reduced by 72% when infected with blood stage helminths. CONCLUSIONS: Chronic blood and tissue parasite infections that are often capable of modulating immune responses in the host are negatively associated with skin test reactivity in a sensitized population.

Adolescent↗
PubMed2000

Descriptive epidemiology of scrapie in Great Britain: results of a postal survey.

In 1998, a questionnaire was sent to 11,554 British sheep farmers to determine how many believed that scrapie cases had occurred in their flock; 61.4 per cent of them responded anonymously. The results indicated that 14.9 per cent of farmers with more than 30 breeding ewes thought that they had ever experienced scrapie in their flock and 2.7 per cent thought that they had had cases in the past 12 months. A comparison of these results with the number of farmers reporting suspect scrapie cases to MAFF, in accordance with the statutory requirement, suggests that only 13 per cent of farmers who suspect that they may have cases of scrapie are currently reporting them. Scrapie occurred in all regions of the country but there was an apparent regional variation. Larger farms and those with purebred sheep appeared to be at greater risk of having cases. Other differences between affected and unaffected farms included lambing practices and sheep purchasing policy. On the majority of farms the first case occurred in a purchased animal. The survey also revealed a need for the provision of further information about scrapie to farmers.

Animals↗
PubMed2000

Predictive value of basal follicle-stimulating hormone concentrations in a general subfertility population.

OBJECTIVE: To assess the predictive value of elevated basal FSH concentrations during the initial subfertility workup with respect to fecundity in a general subfertility population with ovulatory menstrual cycles. DESIGN: Nested case-control study. SETTING: Fertility center of a university hospital. PATIENT(S): Fifty subfertile women with basal FSH levels >10.0 IU/L and 50 age-matched controls. INTERVENTION(S): Long-term follow-up (3-7 years). MAIN OUTCOME MEASURE(S): Pregnancies, deliveries, and time to pregnancy. RESULT(S): Patients with elevated basal FSH levels and controls were comparable with regard to basic characteristics, clinical diagnoses, and subfertility treatment. Long-term follow-up showed that 52% of the women with elevated basal FSH concentrations became pregnant (positive predictive value 48%) versus 62% of the controls, and 42% versus 46% eventually delivered a child, respectively. The mean time to pregnancy was 3.0 years in the elevated-FSH group and 3.4 years in controls. Most of the pregnancies in both groups occurred after spontaneous conceptions. CONCLUSION(S): The results of this study suggest that screening for elevated basal FSH concentrations is of no additional value in a general subfertility population with ovulatory menstrual cycles.

Biomarkers↗
PubMed2000

Incipient ovarian failure and premature ovarian failure show the same immunological profile.

PROBLEM: Incipient ovarian failure (IOF) is characterized by regular menstrual cycles, infertility and a raised early-follicular FSH in women under 40. IOF might be a precursor or a mitigated form of premature ovarian failure (POF). Disturbances in the immune system may play a role in ovarian failure. METHOD OF STUDY: Autoantibodies and lymphocyte subsets were determined in 63 POF patients, 50 IOF patients, and 27 controls. RESULTS: The prevalence of autoantibodies did not differ between the groups. There was a statistically significant difference in lymphocyte subsets between the control group and the POF group, with the IOF group taking an intermediate position. We found a decrease in percentage of T-suppressor cells with a rise in T-helper/T-suppressor cell ratio, a decrease in natural killer cells, and an increase in B lymphocytes and HLA-DR positive T cells. CONCLUSIONS: These data support the concept that IOF is a mitigated form of POF. The question remains whether these changes are the cause or the consequence of the ovarian failure.

Adult↗
PubMed1999

Scrapie transmission in Britain: a recipe for a mathematical model.

Responses to an anonymous postal survey concerning scrapie are analysed. Risk factors associated with farms that have had scrapie are identified as size, geographical region, lambing practices and holding of certain breeds. Further analysis of farms that have scrapie only in bought-in animals reveals that such farms tend to breed a smaller proportion of their replacement animals than farms without scrapie. Farms that have had scrapie in home-bred animals have attributes associated with breeding many animals: large numbers of rams bought, few ewes bought, and many animals that are home-bred. The demography of British sheep farms as described by size, breeds, purchasing behaviour, age structure and proportion of animals that are home-bred is summarized. British farms with scrapie reveal certain special features: they have more sheep that are found dead, more elderly ewes and more cases of scab.

Animals↗
PubMed1999

Heat-shock protein-specific T-cell responses in various stages of bovine paratuberculosis.

Bovine paratuberculosis is characterized by a chronic inflammation of the small intestine, caused by infection with Mycobacterium avium ssp. paratuberculosis. Research regarding diagnostic as well as immunopathogenic aspects of paratuberculosis are hampered by the lack of specific antigens. The aim of the present study was to evaluate the potential of mycobacterial heat-shock proteins, as specific antigens, to measure cell-mediated immune responses during various stages of the disease. In a cross-sectional study, peripheral blood mononuclear cells of 179 cows in different stages of M. avium ssp. paratuberculosis infection, vaccinated against paratuberculosis or noninfected, were used to evaluate lymphoproliferative responses to mycobacterial heat-shock protein of 70 kD (HSP70) and 65 kD (HSP65). In addition, lymphoproliferative responses were measured using purified protein derivate (PPD) preparations from M. avium ssp. paratuberculosis, M. avium and M. bovis as antigens. Responses to HSP70 were higher in the vaccinated animals and in asymptomatic animals that shed the organism in their faeces. Compared with these animals, responses were lower in cows with clinical signs of paratuberculosis. Mycobacterial HSP65 induced less prominent responses compared with HSP70, but showed a similar pattern with regard to the stages of disease. Vaccinated and shedding animals also showed the highest responses to PPD derived from M. avium ssp. paratuberculosis (PPD-P). Observations with short-term cell lines raised to PPD-P and to HSP70 indicated that the similarity between those two antigens was not due to the presence of HSP70 in PPD-P. In conclusion, our study indicated that, as for PPD antigens the mycobacterial heat-shock protein-specific cell-mediated immune responses decrease when comparing the asymptomatic stage to the clinical stage in bovine paratuberculosis. Furthermore, this study shows that HSP70, being a well-defined antigen in comparison with PPD antigens, can be used to monitor cell-mediated immune responses in studies regarding the immunopathogenesis of bovine paratuberculosis.

Animals↗
PubMed1998

The immune response of cattle, persistently infected with noncytopathic BVDV, after superinfection with antigenically semi-homologous cytopathic BVDV.

Cattle persistently infected (PI) with noncytopathic (ncp) bovine virus diarrhea virus (BVDV) are at risk for developing fatal mucosal disease (MD), which is considered to occur after superinfection with antigenically homologous cytopathic (cp) BVDV. In this study, we intranasally inoculated four PI-animals, that were PI with 2 ncp BVDV strains with 10(5) TCID50 antigenically closely related cp BVDV. Two PI-animals were inoculated with 10(5) TCID50 ncp BVDV and one PI-animal, with virus free cell culture medium. Two out of four PI-animals that were inoculated with cp BVDV, developed MD and were euthanized at day 17 and at day 24 after infection. Postmortem, both animals showed typical lesions of MD and cp BVDV was isolated. The other two PI-animals that were inoculated with cp BVDV did not develop MD and were euthanized at day 51. They showed ulcerations in the gastrointestinal tract, cp BVDV was isolated and neutralizing antibodies were detected. From the three PI-animals, that were inoculated with ncp BVDV or cell culture medium, cp BVDV was also isolated. Cross neutralization tests were performed and no antigenic differences could be detected between the cp strains isolated from the PI-animals. Lymphocyte subsets of these PI-animals were determined by flow cytometric analysis. Before superinfection, the percentages of gamma delta subsets were much higher in the PI-animals that did not develop MD than in nonviremic control animals and in the PI-animals that died of MD. From this study we conclude that the presence of antigenically closely related cp BVDV in PI-animals does not necessarily lead to the development of MD and that besides the antigenic relatedness between the persisting ncp BVDV and cp BVDV other factors, for instance the number of circulating gamma delta cells, might determine whether or not PI-animals develop MD.

Animals↗
PubMed1997

Impaired specific immunoreactivity in cows with hepatic lipidosis.

In this study, hepatic lipidosis in cows was experimentally induced by offering an energy surplus during the dry period. Liver triacylglycerol (TAG) was 16% in the experimental group. In the control group fed the same diet in restricted quantities, liver TAG was about 7%. The animals of both groups were vaccinated with tetanus vaccine at Day 3 after parturition. It was demonstrated that the cows with high liver TAG percentages had lower humoral and cellular (P < 0.05) immunological responses compared with the animals with low liver TAG levels at Day 14 after vaccination. The results obtained in the high TAG group support the notion that the frequent occurrence of aspecific infections in cows with hepatic lipidosis may be due to impaired immunoreactivity.

Animals↗
PubMed1997

Antigen-specific immune responses in cattle with inherited beta2-integrin deficiency.

The significance of beta2-integrins for the generation of antigen-specific immune responses in vivo was studied employing the bovine model of beta2-integrin deficiency. To that end four cattle with bovine leukocyte adhesion deficiency (BLAD) and healthy age-matched controls were immunized with tetanus toxoid (TT) and rabies virus (RV) vaccines three times in monthly intervals. In addition, two animals with BLAD and three controls received a fourth vaccination 8 months after the start of the study. Proliferative responses of peripheral blood mononuclear cells (PBMC) to the antigens TT and RV as well as specific serum immunoglobulin G (IgG) titers were determined in intervals for up to 10 months after primary vaccination. Proliferative responses of PBMC to TT and RV were substantially lower in cattle with BLAD than in controls, although PBMC from cattle with BLAD were shown to have the capacity to proliferate in the response to the mitogen concanavalin A. Occurrence of antigen-specific IgG titers was delayed and they were considerably lower in cattle with BLAD compared to controls. Finally, treatment of TT- and RV-stimulated PBMC from an immunized control with different concentrations of the anti-CD18 monoclonal antibody R15.7 resulted in a dose-dependent inhibition of lymphocyte proliferation to almost 100%. The results of the present study show that beta2-integrin deficiency leads to delayedand severely impaired immune responsiveness in vivo. The observations that antibody production, although considerably delayed and impaired, does occur and that apparently class-switching takes place in BLAD indicate T-cell reactivity in vivo.

Animals↗
PubMed1997

Premature ovarian failure and ovarian autoimmunity.

Premature ovarian failure (POF) is defined as a syndrome characterized by menopause before the age of 40 yr. The patients suffer from anovulation and hypoestrogenism. Approximately 1% of women will experience menopause before the age of 40 yr. POF is a heterogeneous disorder with a multicausal pathogenesis involving chromosomal, genetic, enzymatic, infectious, and iatrogenic causes. There remains, however, a group of POF patients without a known etiology, the so-called "idiopathic" form. An autoimmune etiology is hypothesized for the POF cases with a concomitant Addison's disease and/or oöphoritis. It is concluded in this review that POF in association with adrenal autoimmunity and/or Addison's disease (2-10% of the idiopathic POF patients) is indeed an autoimmune disease. The following evidence warrants this view: 1) The presence of autoantibodies to steroid-producing cells in these patients; 2) The characterization of shared autoantigens between adrenal and ovarian steroid-producing cells; 3) The histological picture of the ovaries of such cases (lymphoplasmacellular infiltrate around steroid-producing cells); 4) The existence of various autoimmune animal models for this syndrome, which underlines the autoimmune nature of the disease. There is some circumstantial evidence for an autoimmune pathogenesis in idiopathic POF patients in the absence of adrenal autoimmunity or Addison's disease. Arguments in support of this are: 1) The presence of cellular immune abnormalities in this POF patient group reminiscent of endocrine autoimmune diseases such as IDDM, Graves' disease, and Addison's disease; 2) The more than normal association with IDDM and myasthenia gravis. Data on the presence of various ovarian autoantibodies and anti-receptor antibodies in these patients are, however, inconclusive and need further evaluation. A strong argument against an autoimmune pathogenesis of POF in these patients is the nearly absent histological confirmation (the presence of an oöphoritis) in these cases (< 3%). However, in animal models using ZP immunization, similar follicular depletion and fibrosis (as in the POF women) can be detected. Accepting the concept that POF is a heterogenous disorder in which some of the idiopathic forms are based on an abnormal self-recognition by the immune system will lead to new approaches in the treatment of infertility of these patients. There are already a few reports on a successful ovulation-inducing treatment of selected POF patients (those with other autoimmune phenomena) with immunomodulating therapies, such as high dosages of corticosteroids (288-292).

Addison Disease↗
PubMed1997

Dendritic cells and macrophages in the pituitary and the gonads. Evidence for their role in the fine regulation of the reproductive endocrine response.

Blood monocytes are able to mature into macrophages as well as into dendritic cells. Dendritic cells and macrophages have mainly been studied for their function in the immune response, e.g. in the presentation of antigens to lymphocytes and in the phagocytosis/degradation of unwanted material. The cells are also, however, important producers of a variety of signalling molecules and hormones and are thus involved in other physiological functions such as wound healing, the regulation of the microcirculation and the regulation of the function and growth of endocrine cells. This review summarizes the existing evidence for a regulatory role of dendritic cells and macrophages in the function and growth of hormone-producing cells of the pituitary-gonadal axis. It focuses on the presence, localization and phenotype of dendritic cells and macrophages in the anterior pituitary and the gonads, the endocrine regulatory role of cytokines produced by these cells and the existence of putative feedback mechanisms between endocrine cells of the pituitary-gonadal axis and dendritic cells and macrophages. The recognition of a 'floating endocrine-regulatory force' of monocyte-derived cells that also plays a role in the initiation of immune responses has implications for our understanding of the pathogenesis of gonadal and pituitary autoimmune reactions.

Animals↗
PubMed1996

Identification of monoclonal antibodies with specificity to alpha- or beta-chains of beta 2-integrins using peripheral blood leucocytes of normal and bovine leucocyte adhesion deficient (BLAD) cattle.

The reactivity of monoclonal antibodies entered in the panels of the Third Workshop on Ruminant Leucocyte Antigens with lymphocytes and monocytes of normal and beta 2-integrin deficient (Bovine Leucocyte Adhesion Deficiency: BLAD) animals was determined by flow cytometry to investigate potential specificities to alpha- or beta-chains of beta 2-integrins. From the 13 monoclonal antibodies that were entered as having specificity for CD11/CD18 antigens, ten were confirmed correct, but three had reactivity with cells from BLAD animals. We conclude that our approach provides an easy way to reliably identify the majority of beta 2-integrin specific monoclonal antibodies.

Animals↗