Biomedical subjects

J Reiczigel

Publications and source records attributed to J Reiczigel.

25 records · Page 2Linked to original sources

PubMed2000

Quantifying parasites in samples of hosts.

Whereas terminological recommendations require authors to use mean intensity or mean abundance to quantify parasites in a sample of hosts, awkward statistical limitations also force them to use either the median or the geometric mean of these measures when making comparisons across different samples. Here, we propose to reconsider this inconsistent practice by giving priority to biological realism in the interpretation of different statistical descriptors and choosing the statistical tools appropriate to our decisions. Prevalence, mean intensity, and indices of parasite distribution (such as median intensity) are suitable descriptors to quantify parasites in a sample of hosts. These measures have different biological interpretations and need different statistical methods to be compared between samples.

Animals↗

PubMed1999

Analysis of experimental data with repeated measurements.

Experimental data often consist of serial measurements on subjects after a treatment. Typical questions concerning such data are: (A) Do subjects really react to treatment or are the fluctuations just random? (B) What are the numerical characteristics of the response? (C) Is the response identical in all groups? Differences between the individuals in the dynamics of the reaction make it difficult to apply standard statistical procedures. This paper proposes to answer questions (A) and (B) at the individual level, then to give an answer to (C) on the basis of this information. This kind of analysis may be useful since it can separate subjects giving response from those that do not and can identify individual response patterns and compare treatments with respect to each numerical characteristic separately. To answer question (A), a permutation test is proposed and its power is evaluated by simulation.

Animals↗

PubMed1999

Circadian changes in blood ionized calcium, sodium, potassium, and chloride concentrations and pH in cattle.

OBJECTIVE: To explore diurnal variation in blood ionized calcium, sodium, potassium, and chloride concentrations and pH in pregnant dairy cows. ANIMALS: 14 dairy cows in their third or later pregnancy approximately 6 weeks before expected parturition. PROCEDURE: Throughout a 24-hour period, blood samples were taken at 2-hour intervals and analyzed for ionized calcium (iCa2+), potassium (K+), sodium (Na+), and chloride (Cl-) concentrations and pH. Paired t-tests were used to compare initial and final values. Circadian changes were tested by use of repeated-measures ANOVA. Additionally, a nonparametric analysis was performed for each animal to determine minimal and maximal values for the variables. RESULTS: Significant differences were not detected between initial and final values of any variable. Repeated-measures ANOVA indicated significant diurnal fluctuations in all variables. With the exception of Cl- concentration, nonparametric analysis of individual values also revealed significant changes over time. CONCLUSIONS AND CLINICAL RELEVANCE: The magnitude of daily fluctuations does not make it necessary to standardize time of sample collection for routine diagnostic examination of blood iCa2+, Na+, and Cl-concentrations and pH. However, it may be important to standardize time of sample collection in comparative studies in which more discrete differences may be identified.

Analysis of Variance↗

PubMed1998

Factors influencing ovarian activity and sexual behavior of postpartum mares under farm conditions.

Management of the postpartum period is one of the most important factors of stud farm medicine. In horses, owing to the long gestation period, the time from parturition to repeat conception needs be short to maintain an optimal yearly foaling interval. For this reason the features of postpartum ovarian activity and sexual behavior were studied under farm conditions. During 2 consecutive breeding seasons, 107 mares on 5 commercial horse farms were monitored after parturition by regular teasing, transrectal ultrasonography and blood sampling for progesterone. Foalings took place from January 1 to June 15. Body condition scoring was carried out within 5 d and at 60 to 65 d after parturition. The first ovulation occurred within 20 d after foaling in 84.1% (90/107) of the mares. The mean intervals from foaling to the first and second ovulations were 17.8 +/- 1.6 d (+/- SEM) and 40.9 +/- 2.7 d (+/- SEM), respectively. The mean intervals from parturition to the first and second ovulation (P < 0.001), the interovulatory interval (P < 0.01), the second follicular phase (P < 0.001), and the time until the first overt estrus (P < 0.01) were significantly longer in mares foaling before the vernal equinox. In the beginning of the breeding season the intervals from parturition to the first ovulation (P < 0.01), to the second ovulation (P < 0.01), and to the first overt estrus (P < 0.001) were significantly longer for primiparous mares than for multiparous animals. There was a tendency for an increased interovulatory interval and for a longer second follicular phase in mares with decreased body condition after parturition (P = 0.069, P = 0.089, respectively). Suckling and breed had no effect on postpartum ovarian activity. We concluded that under field conditions the resumption of cyclic ovarian activity and sexual behavior in mares after foaling are strongly affected by the season of parturition and parity. In some cases, body condition change and other factors may also play a role in influencing postpartum reproductive function.

Animals↗

PubMed1998

Host-mediated site segregation of ectoparasites: an individual-based simulation study.

Site segregation of coexisting ectoparasite species may result either from a direct interaction such as resource competition between them or from a host-mediated interaction. Here we present an individual-based model for the coevolution of 1 host and 2 parasite species to study this latter hypothesis. Parasite species are generalists at the start of the simulation and develop site specificities under the following assumptions. Parasite populations are not subject to resource limitations but are limited directly by host defense as predation. Hosts have 2 sites that need different defensive abilities to reduce their parasite burden. Parasites need to exhibit different evasive abilities to survive on different sites. Host grooming selects parasites for an increasing capability for evasion, whereas parasites select hosts for an increasing efficiency of grooming. Two trade-offs are incorporated into the model: one between host defensive abilities on the 2 sites, and another between parasite evasive abilities on the 2 sites. We conclude that, under these assumptions, the optimization of host defense and parasite evasion strategies may select ectoparasites for site segregation and this may stabilize the coexistence of parasite species.

Animals↗

PubMed1998

Progesterone determination in equine plasma using different immunoassays.

Several assay systems (3H radioimmunoassay (RIA) with and without extraction; microplate enzyme-linked immunoassay (ELISA); qualitative ELISA (tube test)] were used to measure plasma progesterone concentration in mare plasma. The direct RIA showed a close correlation (R = 0.94) with the extraction RIA. The direct RIA and the microplate ELISA were compared in two different studies. In the first study 1155 samples of postpartum mares were used for progesterone determination with both assays. The ELISA resulted in more elevated values both in oestrus and dioestrus (0.19+/-0.3 and 2.44+/-3.62 nmol/l for oestrus, n = 436, and 8.94+/-4.29 and 27.88+/-18.34 nmol/l for dioestrus, N = 719, for the RIA and ELISA, respectively, R = 0.71). The evaluation of individual progesterone profiles has revealed that the microplate ELISA detects the time of ovulation at the same time as it is determined by the RIA and clinical examination. The sensitivity and specificity were calculated for different progesterone threshold values. In the second study including 7 non-pregnant, cycling mares the progesterone concentration of 240 samples was determined by both assays. Basal values (Day 0) obtained with the ELISA were higher (1.57 nmol/l) than those of the RIA (0.2 nmol/l). Both curves reached the same maximum concentration (12.11 and 12.45 nmol/l) 5 days after ovulation. The correlation between the RIA and ELISA values was high (R = 0.90). The tube test was compared to the microplate ELISA as reference using 576 plasma samples of 34 non-pregnant, non-cycling mares included in an ovulation induction study. Of these samples 118 had higher and 458 had lower values than 3.18 nmol/l. In most cases the tube test was in complete agreement with the microplate ELISA. The sensitivity, specificity, + predictive and - predictive values for the tube test were 79.7%, 95.4%, 81.7% and 94.8%, respectively.

Animals↗

PubMed1997

Long term exposure to T-2 Fusarium mycotoxin fails to alter luteal function, follicular activity and embryo recovery in mares.

The effect of long term administration of T-2 toxin was studied in 6 Trotter mares during the summer and early autumn. After one complete oestrous cycle (Cycle 1) each mare was given 7 mg purified T-2 toxin per os daily (1 mg/ml in ethyl alcohol) beginning on Day 10 after ovulation in Cycle 2. Exposure to toxin was continued for 32-40 days, until Day 7 of Cycle 4. During this period all the animals remained in good physical condition, but skin lesions were observed around the mouth in 3 cases. Toxin administration had no effect on the length of the interovulatory interval or on the lengths of the luteal and follicular phases. It also had no effect on peripheral plasma progesterone profiles or follicular kinetics, including the growth rate and maximum size of ovulatory follicles and the maximum number, and time of first increase in number, of follicles larger than 1 and 2 cm. Uterine flushing was attempted in 5 mares and yielded 3 embryos (60%). These were of normal size and morphology and one was transferred nonsurgically to a recipient mare; a conceptus developed initially but it subsequently died and was resorbed. The results of the study allowed the conclusion that the administration of 7 mg/day T-2 toxin to mares in good body condition has no detrimental effect on ovarian activity, fertilisation or oviductal transport.

Animals↗