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Biomedical subjects

G Verheyen

Publications and source records attributed to G Verheyen.

At least 73 records · Page 4Linked to original sources
PubMed1993

Effect of freezing method, thawing temperature and post-thaw dilution/washing on motility (CASA) and morphology characteristics of high-quality human sperm.

Sixteen semen samples, 12 donor and four patient samples of high initial quality, were processed to compare the effect of two freezing methods, two thawing temperatures and the effect of dilution and washing on sperm motility and morphology characteristics. Sperm samples were divided in two equal parts and frozen either by fast vapour freezing or by slow computer-controlled freezing. For each freezing method, half of the straws were thawed at room temperature (22 degrees C), the other half were thawed at 37 degrees C. From each freeze-thawing treatment, one straw was evaluated immediately post-thawing; another straw was washed to remove the cryoprotectant solution. In this way, each semen sample was subjected to eight freeze-thawing treatments. No effect of the freezing method and thawing temperature was observed on motility characteristics evaluated by computer-assisted semen analysis, nor on light-microscopical morphology parameters. Post-thaw dilution and washing, however, exerted a deleterious effect on sperm motility, by reducing percentage motility by 50% compared to unwashed thawed specimens. Linearity and percentage of morphologically normal spermatozoa were obviously impaired, while percentage of abnormal tails and beat cross frequency increased significantly. In general, freeze-thawing was most successful when rapid vapour freezing was followed by 37 degrees C thawing, and when slower computer-controlled freezing was combined with 22 degrees C thawing, causing significant interactions between the freezing method and the thawing temperature. For semen samples of high initial quality, vapour and computer-controlled freezing were equally effective in terms of recovery of morphologically normal, motile spermatozoa.

Cryopreservation↗
PubMed1993

An auto-controlled study in in-vitro fertilization reveals the benefit of Percoll centrifugation to swim-up in the preparation of poor-quality semen.

The efficiency of spermatozoa prepared by swim-up or by Percoll centrifugation was assessed in an in-vitro fertilization programme on 71 semen samples of a well-defined quality [total number of type A (WHO criteria) motile spermatozoa]: category I (n = 21) with > 100 x 10(6), II (n = 31) with 15-100 x 10(6), III (n = 11) with 5-15 x 10(6) and IV (n = 8) with < 5 x 10(6) type A motile spermatozoa. Oocytes were inseminated 4 h after oocyte retrieval, alternately with spermatozoa derived from swim-up and Percoll preparation. Both selection procedures resulted in a significantly higher (P < 0.001) percentage motility as compared to fresh semen. For low-quality samples (III and IV), however, swim-up was more effective in selecting highly motile (P = 0.004) and morphologically normal spermatozoa (P < 0.05). For high-quality samples, this difference might have been masked by introducing a swim-up step to remove Percoll particles. Regardless of the initial sperm quality, the mean fertilization rate was significantly higher (P = 0.003) when Percoll-treated spermatozoa were used for insemination (51.3 versus 37.8%). For semen of groups I and II, no difference in fertilization capacity was observed according to the sperm preparation method. Despite the lower percentage motility and normal morphology for the Percoll compared to the swim-up treatment in groups III and IV, fertilizing capacity was significantly (P < 0.001) in favour of this selection method (65.3 versus 26.5% in group III, 47.6 versus 11.6% in group IV).(ABSTRACT TRUNCATED AT 250 WORDS)

Centrifugation↗
PubMed1993

Loa loa microfilariae aspirated during oocyte retrieval.

Loa loa is a filarial parasite which is mainly confined to West and Central Africa. Although considered as mildly pathogenic for people living in endemic areas, its appearance in other places might be a cause for concern. We report here the unusual finding of Loa loa microfilariae in the follicular aspirate of a 35-year-old black women during oocyte retrieval for in-vitro fertilization. Most likely these microfilariae were aspirated, along with follicular fluid, from the small blood vessels around the ovarian follicles, which are frequently lacerated during ovarian puncture. Despite the spectacular microscopic view of vigorous moving worms trapped on the cumulus cells, the presence of Loa loa microfilariae does not seem to prevent fertilization and cleavage completely.

Adult↗
PubMed1991

Thyrotropin-releasing hormone (TRH) is not thyrotropic but somatotropic in fed and starved adult chickens.

Adult fed and starved Warren chickens, 2 yr of age, and approaching the end of the second laying year, were injected iv with 1 of the following products: 10 micrograms of thyrotropin releasing hormone (TRH); 100 micrograms of bovine thyrotropin (bTSH); 100 micrograms of ovine growth hormone (oGH); saline. The influence on plasma concentrations of thyroxine (T4), triiodothyronine (T3) or chicken GH (cGH) were followed. Prior to injection, it was clear from the control values that starvation for 3 d decreased plasma levels of T3 and increased cGH, whereas 7 d of fasting increased T4 and cGH. The plasma levels of cGH were elevated greater than 10-fold at 15 min following the TRH challenge in food-deprived chickens compared to a less than 4-fold increase in normal fed hens. This increase was followed by a rise in T3 after 1 h, which was also more pronounced in the starved animals, whereas T4 decreased or remained unaffected. Increases in T4 can, however, be obtained with 100 micrograms TSH in normal fed (2-fold) or starved animals (greater than 3-fold). Following injection of 100 micrograms oGH, a significant increase in T3 levels was observed which in fed animals was already present at 30 min, but the higher levels persisted for 1 and 2 h in fed and starved hens. At the same time, a decrease in T4 was observed in both groups of GH-treated chickens. It is concluded that TRH at the dose used is not thyrotropic but has a somatotropic effect and is responsible for the peripheral conversion of T4 into T3.

Animals↗
PubMed1990

Accumulation of zinc in egg yolk, ovarian follicles and organs after forced resting by high dietary zinc.

1. Eighteen Warren SSL hens of 71 weeks of age were forced-moulted by ad libitum feeding of a high-zinc diet (10,000 ppm zinc for 2 days followed by 5,000 ppm zinc-supplement diet for 4 days). From the start of the treatment, eggs were collected and 3 hens were slaughtered on days 0, 2, 3, 4, 5 and 6 of the study. 2. Zinc analyses were carried out on the different components of the eggs and on liver, pancreas, kidney, different yolky follicles of the ovary and various segments of the oviduct. 3. Seven-, six- and threefold increases in zinc concentration were found in pancreas, liver and kidney, respectively. 4. The shell gland and isthmus, but not the magnum, also showed slight but significant increases in Zn content. 5. Zinc accumulation was also high and almost identical in ovarian follicles F1 to F4 but slightly less in F5 and F6 follicles. 6. In the egg, a significant increase in zinc concentration was only observed in the yolk.

Animals↗
PubMed1988

Changes in progesterone metabolism in the chicken hypothalamus during induced egg laying stop and molting.

In the present study, we have established and validated a radioenzyme assay which permits us to quantify progesterone metabolism in the chicken brain. Progesterone metabolism was then studied in five brain areas obtained by microdissection from the telencephalon (part of the lobus paraolfactorius immediately rostral to the preoptic area), the preoptic area, and the hypothalamus. Three metabolites of progesterone were produced in large amounts in these brain regions and were quantified in this study: 5 beta-pregnane-3,20-dione (5 beta-DHP) as well as its metabolite 3 alpha-hydroxy-5 beta-pregnane-20-one (5 beta,3 alpha-ol) and 5 alpha-pregnane-3,20-dione (5 alpha-DHP). The unmetabolized progesterone was also recovered and quantified. The 5 beta-reduction of progesterone (production of 5 beta-DHP and 5 beta,3 alpha-ol) was very active but its 5 alpha-reduction (production of 5 alpha-DHP) was almost absent in the lobus paraolfactorius. An opposite pattern of metabolism was found in the preoptic area and the hypothalamus (higher 5 alpha- but lower 5 beta-reductase activity). The changes in progesterone metabolism in these brain areas were then studied in groups of hens submitted to induced egg laying stop and molting. A significant decrease in progesterone 5 alpha-reduction was found in the median hypothalamus of hens during the period of molt. Simultaneously, the experimental procedures induced significant decreases in the production of 5 beta-DHP by the lobus paraolfactorius, anterior, and medial hypothalamus but induced a significant increase in the production of this metabolite in the preoptic area. These changes are likely to be involved in the control of reproductive functions including sexual behavior and secretion of luteinizing hormone-releasing hormone, and a number of possible causal mechanisms are presented. These should now be tested experimentally especially in view of the very limited information which is now available on the biological effects of the metabolites of progesterone.

3-Hydroxysteroid Dehydrogenases↗
PubMed1988

Effect of temperature during induced moulting on plumage renewal and subsequent production.

1. Four groups of 18 cages each containing 4 brown laying hybrids aged 79 weeks were formed by two levels of restriction of a moulting diet (lasting for 29 d) being applied at two moulting temperatures (11 degrees C and 29 degrees C, lasting for 56 d). 2. Low temperature-low feeding resulted in greatly retarded growth of remiges, but the final extent was similar in all 4 groups, and reached 4 to 5 new primaries (median value). Body-plumage of hens moulted at 11 degrees C was 25% heavier than of hens moulted at 29 degrees C. 3. Second year production variables (rate of laying, egg mass, efficiency of food utilisation) were greatly influenced by moulting temperature (low moulting temperature performing better), but not by feeding rate. 4. The persistence of the improved food utilisation is related to energetic consequences of improved plumage renewal during moulting at the lower temperature, which can be seen as an acclimatization effect.

Animals↗
PubMed1987

The influence of methimazole on the thyrotrophic and peripheral activity of thyrotrophin and thyrotrophin-releasing hormone in the chick embryo and growing chicken.

Plasma concentrations of thyroxine (T4) and triiodothyronine (T3) were profoundly depressed both in chick embryos and growing chickens after methimazole (MMI) treatment. There was no response of T4 and T3 levels to TRH or TSH injections in the MMI group, either in embryos or growing chickens. Peroxidase activity measured in the thyroid gland was significantly higher in embryos and growing chickens treated with MMI. However, neither TRH nor TSH affected this activity 2 hr after injection in either control or the MMI-treated group. Hepatic 5'-monodeiodinase activity was significantly stimulated in the MMI-treated groups of embryos and growing chickens but only when additional sulphydryl groups (DTT) were provided. In embryos, monodeiodination activity 2 hr after TSH injection was not significantly different from control values for either DTT-stimulated or unstimulated conditions within the control and MMI-infused groups. However, in both control and MMI-treated embryos monodeiodination activity significantly increased 2 hr after TRH injection. In the growing chickens, monodeiodination activity 2 hr after TRH or TSH injection was not significantly different from control values in either stimulated or unstimulated conditions of each group.

Animals↗
PubMed1987

Growth hormone stimulates the peripheral conversion of thyroxine into triiodothyronine by increasing the liver 5'-monodeiodinase activity in the fasted and normal fed chicken.

Normal fed and 2 days fasted Warren chickens were injected intravenously with 100 micrograms of ovine growth hormone (GH) and ovine prolactin and plasma concentrations of thyroid hormones were assayed prior and up to 2 h after injection. Fasting alone decreases T3, but increases T4. An injection of GH resulted in increases of plasma T3 concentrations in two fasting experiments by 40% (after 3/4 h) and 104% (after 1 h). In normal fed animals no increase is observed in the first experiment, whereas a 35% increase occurs in the second one. An injection of 100 micrograms prolactin does not influence T3 in normal fed or fasting animals. Both GH and prolactin, however, may decrease plasma concentrations of T4. In a separate experiment 50 micrograms and 200 micrograms of GH raised the decreased T3 levels after fasting by 39% and 60% respectively 1 h after injection and by 24 and 61% respectively in normal fed chicken, whereas prolactin was ineffective in this regard. Using Hisex chickens, the influence of an injection of 100 micrograms GH on plasma concentrations of thyroid hormones could be confirmed. At the same time GH increases the liver 5'-monodeiodinase activity by 330% after 1 h and by 147% after 2 h. The peroxidase activity is not influenced in normal fed chickens, but GH decreases this activity in food deprived animals after 1 h and 2 h. It is concluded that ovine GH, but not prolactin, stimulates the peripheral conversion of T4 into T3 in both normal fed and food deprived chicken and that this effect is dose dependent.

Animals↗
PubMed1987

Effect of exogenous LH on plasma concentrations of progesterone and oestradiol in relation to the cessation of egg laying induced by different moulting methods.

Artificially induced cessation of egg laying caused regression of the reproductive tract in hens, as well as changes in circulating concentrations of sex steroids. Hens were bled at several stages during and after artificial moult induced by fasting or overfeeding a diet low in calcium or high in zinc. Hens received a single injection of 200 i.u. of horse LH at Day 0, 7, 21, 35 and 77 (Exp. 1) or Day 0, 8, 23, 35 and 71 (Exp. 2) after start of the treatment to induce moult. Blood samples were taken before and 20, 40 and 60 min (Exp. 1) or 15, 30 and 45 min (Exp. 2) after LH injection. Hens which were fasted or given the diet high in zinc had low plasma progesterone concentrations and the response to LH was reduced or delayed. In hens fed low calcium the reduction in plasma progesterone was less pronounced and the responsiveness to LH was more or less maintained. Conversely, there was no response of oestradiol to LH in laying hens. However, oestradiol concentrations increased in moulting hens after LH injection, due to the high oestradiol secretion from the small white follicles, since all yolky follicles were atretic.

Animals↗
PubMedDate not supplied

A battery of DNA effect biomarkers to evaluate environmental exposure of Flemish adolescents.

The present paper deals with the evaluation of a battery of genotoxicity biomarkers in healthy Flemish adolescents and their relation with common pollutants occurring in their life environment. DNA damage as reflected by the comet assay appeared to be most sensitive to ozone (partial r(2) = 0.102, p < 0.00001), and to a lesser extent to ortho-cresol (partial r(2) = 0.055; p = 0.001) and 1-hydroxy-pyrene (1-OH-pyrene, partial r(2) = 0.031; p = 0.013). 8-hydroxy-deoxyguanosine (8-OHdG) was only related to ortho-cresol (r(2) = 0.069; p < 0.007). Interestingly, the comet assay results and urinary 8-OHdG concentrations were positively correlated with a Pearson r = 0.21 (p = 0.003, N = 200). Logistic regression models revealed significant relations between chromatid breaks and 1-OH-pyrene (relative risk (RR): 1.58; p = 0.008), and t,t-muconic acid (RR: 1.71; p = 0.014). There was no correlation between micronucleus formation or occurrence of chromosomal or chromatid breaks on the one hand and comet or 8-OHdG results on the other hand. Thus, in this study the comet assay on whole blood samples and urine 8-OHdG measurements especially appeared sensitive biomarkers for assessing the genetic effects of environmental pollutants to which adolescents may be exposed.

8-Hydroxy-2'-Deoxyguanosine↗
PubMedDate not supplied

Comparison of different hypo-osmotic swelling solutions to select viable immotile spermatozoa for potential use in intracytoplasmic sperm injection.

The hypo-osmotic swelling test, originally developed as a diagnostic sperm test, is used to discriminate viable from non-viable spermatozoa for intracytoplasmic sperm injection (ICSI) in cases of complete asthenozoospermia. In the present study, three hypo-osmotic solutions were compared, i.e. (A) Jeyendran solution containing sodium citrate and fructose; (B) a mixture of 50% culture medium and 50% milli-Q water; and (C) milli-Q water. While both the percentage of swelling and vitality assessed by eosin Y remained unchanged after 5-30 min of sperm exposure to solutions A and B, incubation in water for only 5 min was in itself detrimental. Ten frozen-thawed donor samples and 10 asthenozoospermic patient samples were exposed to the three solutions for given periods of time. Percentages of swelling and the results of the eosin Y test were well correlated for solutions B and C, but only weakly correlated for solution A. Percentage viability was further assessed by eosin Y and motility of spermatozoa after 2 h and 24 h exposure to the three solutions was compared with unexposed control spermatozoa. While a significant decrease in both parameters was observed for all three solutions in comparison with the control, sperm quality was significantly higher after exposure to solution B than after exposure to solutions A and C. It may be concluded that solution B (composed of 50% culture medium and 50% water) is to be preferred for the selection of viable immotile spermatozoa for ICSI.

Cell Survival↗
PubMedDate not supplied

[Mesotherapy in abarticular rheumatism].

Mesotherapy is a method of treatment in which subcutaneous infiltrations are given loco dolenti at short intervals of time. In this way a mixture of readily available drugs is administered. There are many indications for mesotherapy, although most applications are found in the field of the osteo-articular affections. As yet there is no scientific explanation for the effect of this therapy. Studies on this subject are currently being performed.

Humans↗