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Biomedical subjects

G H Zeilmaker

Publications and source records attributed to G H Zeilmaker.

At least 55 records · Page 3Linked to original sources
PubMed1987

Monitoring of clomiphene citrate stimulation by means of plasma 17 beta-oestradiol determinations and ultrasonographic follicle measurements in in-vitro fertilization treatment cycles.

In 57 in-vitro fertilization (IVF) cycles stimulated with clomiphene citrate the relationship between plasma 17 beta-oestradiol (E2) and ultrasonographic measurements of follicle diameter was assessed. Under both monofollicular and multifollicular conditions a wide range in plasma E2 values was observed in the late follicular phase. No significant correlation could be established between the dimensions of the dominant preovulatory follicle and plasma E2 values, in mono-follicular or multi-follicular cycles. Pregnancies and conceptions occurred in cycles with both low and high circulating E2 levels. In pregnancy cycles a slight increase in plasma E2 values was found on the day following administration of human chorionic gonadotrophin (HCG). In conceptional cycles not leading to a clinical pregnancy, plasma E2 profiles varied considerably, whereas in cycles in which no oocytes were fertilized, plateauing or a distinct decrease occurred during this particular period. The present study suggests that the relative daily increase in plasma E2 values may be the most relevant aspect of plasma E2 monitoring.

Clomiphene↗
PubMed1987

High concentrations of immunoreactive renin, prorenin and enzymatically-active renin in human ovarian follicular fluid.

Prorenin (enzymatically inactive) and renin (active) were measured by radioimmunoassay, using monoclonal antibodies reacting either with both prorenin and renin or with renin alone, in pre-ovulatory follicular fluid (FF) from women in an in-vitro fertilization programme who were stimulated with human menopausal/human chorionic gonadotrophin. The concentration of prorenin in FF was 40 times higher than in plasma taken at the time of FF collection; renin in FF was 10 times higher. The plasma concentration of prorenin, but not of renin, in these women was higher than in non-stimulated women in the late follicular phase of the menstrual cycle. The concentration of reninsubstrate and angiotensin-converting enzyme in FF was 60% of that in plasma. Contamination of blood, which may occur at the time of FF collection, was less than 5%. Prorenin in FF was irreversibly converted into renin after adding trypsin or by endogenous serine protease, using procedures that also cause conversion of prorenin in plasma. These results support the hypothesis that the increased plasma level of prorenin in women whose ovulation is stimulated for the collection of oocytes has originated from the ovary and is under gonadotrophic control. This may also be true for the increase of plasma prorenin that has been observed in non-stimulated women during the luteal phase of the cycle and in early pregnancy.

Adult↗
PubMed1987

Cryopreservation of mouse, monkey and human islets of Langerhans for transplantation purposes.

Transplantation of islets of Langerhans is a possible future therapy for insulin-dependent diabetes mellitus. In contrast to total pancreas, isolated islets of Langerhans can be treated prior to transplantation to reduce their immunogenicity. Thus the success rate in allotransplantation of islets can be increased. The isolation of large amounts of islets from human pancreas is still a problem and islets from different donors have to be collected and stored by cryopreservation. In this paper we describe the methods used in our laboratory to isolate islets of Langerhans from rodent, monkey and human pancreas. The results are presented of successful cryopreservation of these islets. Firstly, by a more conventional freezing method using dimethylsulfoxide as cryoprotectant. Secondly, by vitrification using a mixture of cryoprotectants. The latter method has not been used previously for cryopreservation of islets. The integrity of the islets before and after freezing was tested in vitro and, for mice, in vivo.

Animals↗
PubMed1986

Ultrasonically guided percutaneous and laparoscopic oocyte aspiration: a comparative study.

Oocyte collection for in vitro fertilization was performed in 105 cycles (65 patients) by ultrasonically guided percutaneous puncture (63 cycles) or laparoscopy (42 cycles). During the ultrasonically guided approach an open or closed needle system was used. During both ultrasonically guided and laparoscopic follicle aspiration, all visible follicles were punctured. The mean number of punctured follicles per cycle was comparable for both techniques. Despite a significantly higher mean number of oocytes per cycle harvested during laparoscopy, the mean number of embryos per cycle was not essentially different with the two techniques. Also no difference could be established between the ultrasonically guided open and closed needle systems.

Embryo Transfer↗
PubMed1986

Volumetric behaviour and survival of mouse zygotes and embryos in hyperosmotic media.

Volume changes and survival of mouse zygotes and pre-implantation embryos were studied after their exposure to hyperosmotic media. Transfer of zygotes from culture medium to medium containing 1.5 M DMSO led to a rapid volume reduction to 60% of control values. After 10 min the volume was normal again, illustrating the rapid penetration of DMSO at room temperature. Re-transfer of zygotes equilibrated in 1.5 M DMSO to culture medium in one step doubled the volume. Twelve minutes later normal diameters were observed again. Volume changes were also recorded after transfer to media rendered hypertonic by the addition of NaCl or sucrose. A proportional decrease in volume was noticed up to 1500 mOsmol. A further increase in measured osmolarity up to 3100 mOsmol led only to limited further shrinkage of the zygotes (minimal volume observed was 27% of control volume). Addition of 1.5 M DMSO or 1.5 M propanediol had no influence on the final volume reaction to NaCl and sucrose. Exposure to media with a measured osmotic value of 3200 mOsmol (NaCl added) during 10 min did not prevent further development of the embryos to the hatched blastocyst stage. A solution of 4000 mOsmol proved lethal to nearly all embryos. Addition of 1.5 M DMSO to this medium did not have a protective effect against the osmotic stress at room temperature.

Animals↗
PubMed1986

Development and degeneration of retina in rds mutant mice: observations in chimaeras of heterozygous mutant and normal genotype.

In homozygous rds mutant mice the photoreceptor cells lack outer segment discs and slowly degenerate. In the heterozygotes the receptor cells develop abnormal outer segments and show altered disc shedding properties as revealed by the pigment epithelial phagosome content. The receptor cells also degenerate at a slower rate than in the homozygotes. The nature of the interaction resulting in dilution of the retinal lesion in the heterozygous retina was analysed in a series of chimaeras consisting of rds/+ and +/+ genotypes, which also differed in colour genes. In 64% of the chimaeras (18 out of 28) presence of both rds/+ and +/+ types of photoreceptors could be detected by electron microscopy. The relative proportion and patch size of the two components varied greatly between individuals but the location of the two types of photoreceptors was not related to the genotypes of the overlying pigment epithelial cells. Frequent occurrence of abnormally large phagosomes, resembling the rds/+ phenotype, was noted regularly in both rds/+ and +/+ types of pigment epithelial cells located above rds/+ types of receptors, but not in the cells of either genotype located above normal receptors. In the eyes examined at 12-18 months, localized and partial depletion of the perikaryal population in the outer nuclear layer was observed, and the location of such areas was also unrelated to the genotypes of the pigment epithelial cells. These findings confirm that the rds gene acts within the neural retina and possibly within the receptor cells and further show that the genetic interaction between the rds gene and its normal allele in the retina of the heterozygous mice takes place within the receptor cells.

Animals↗
PubMed1985

Effects of partial receptor cell loss on the electroretinogram of chimaeric mice.

A series of chimaeric mice were produced by aggregating morulae from rd/rd and normal (+/+) mice. In the retina of chimaeric mice, produced by aggregating morulae of these two genotypes, loss of rd/rd photoreceptor cells results in a patchy distribution of the surviving normal receptor cells. The number of remaining receptor cells vary between individual chimaeras. The inner retinal layers in the chimaeras, as well as in the two parental genotypes remain intact. Electroretinograms were recorded from 16 chimaeric mice, and various parameters were compared with the amount of visual cells present as estimated by the average thickness of the outer nuclear layer. The amplitudes of the a- and b-wave, showed a linear reduction with decreasing thickness of the outer nuclear layer thickness. However, threshold of the b-wave increased only when the thickness of the outer nuclear layer fell to about 25% of the normal thickness while the time-to-peak of the waves did not change appreciably among the chimaeric individuals. These results suggest that the changes in the electroretinogram of the chimaeric individuals are related to the amount of visual cells present in the retina.

Animals↗
PubMed1985

Prevalence of antibodies to Chlamydia trachomatis, Neisseria gonorrhoeae, and Mycoplasma hominis in infertile women.

A total of 57 infertile women, who had been referred for in vitro fertilisation or for diagnostic laparoscopy, were tested for the presence of antibodies to Chlamydia trachomatis, Neisseria gonorrhoeae, and Mycoplasma hominis. Four were excluded from the study. Of the remaining 53, 33 had laparoscopically obvious tubal disorders, such as adhesions, distal occlusions and strictures, and 20 did not. Antibodies to C trachomatis were found in 7/33 (21.2%) v 0/20, antibodies to N gonorrhoeae in 20/38 (60.6%) v 5/20 (25%), and antibodies to M hominis in 18/24 (75%) women with tubal disorders v 13/19 (68.4%) of those with no disorder. Antibodies to C trachomatis and N gonorrhoeae were significantly (p less than 0.05) more common in women with tubal disorders. The high prevalence of antibodies to N gonorrhoeae in infertile women without tubal disorders suggests that ciliated tubal epithelium is damaged after inflammation without this being laparoscopically visible. Our results confirm the important role of N gonorrhoeae and C trachomatis in the aetiology of infertility after tubal inflammation.

Adult↗
PubMed1984

Development and degeneration of retina in rds mutant mice: light and electron microscopic observations in experimental chimaeras.

Mice, homozygous for the rds gene, fail to develop the receptor outer segments and show a slow reduction of the outer nuclear layer. A series of 13 chimaeric mice was produced by combining morulae from albino rds/rds and pigmented normal (+/+) mice. At 3-4 weeks, variable stretches of visual cells without outer segments were observed together with stretches of visual cells with normal outer segments. The location of these areas was unrelated to the genotype of the overlying pigment epithelium. Phagosomes containing outer segment debris were present in albino pigment epithelial cells, located over normal outer segments, indicating normal functional properties of rds/rds pigment epithelial cells. At 9 months, regions with visual cell loss were observed underlying both types of pigment epithelial cells. Regions showing normal and intermediate thicknesses of the outer nuclear layer were seen more often than regions showing rds/rds type distribution. In another series of eight chimaeras, consisting of albino rds/rds and pigmented rd/rd genotypes, the eyes examined at 22 days showed more pronounced visual cell loss than in the rds----normal retinas at 9 months. Regions of the outer nuclear layer, containing a single row of cone perikarya, were similar to the rd/rd phenotype and differed from the phenotype of the double homozygous rd/rd rds/rds retina, which has a slower rate of degeneration than in rd/rd mice. Visual cell loss in these chimaeras at 9 months was similar to that in the rds/rds retina of the same age. The findings show that the expression of the rds gene, resulting in failure of outer segment development and eventual death of visual cells is unrelated to the genotype of the overlying pigment epithelial cells and suggest that the gene acts within the neural retina and possibly intracellularly in the visual cells.

Animals↗
PubMed1982

In vitro fertilizing capacity of human spermatozoa with the use of zona-free hamster ova: interassay variation and prognostic value.

The average fertilization percentage, with the use of zona-free hamster ova, of a donor group was 54% (range 11% to 100%). Nineteen sperm suspensions (24%) from a group of 79 infertile patients with semen abnormalities and 23 from a second group of 43 patients (54%) whose partner showed evidence of reproductive dysfunction, fertilized as well as spermatozoa from fertile donors. The interassay variation of the fertilization rates was found to be less than 20%. Spermatozoa from 10 patients with normal semen characteristics failed to penetrate. Six spontaneous conceptions were reported in the first group. Sperm from four of these patients had low fertilization percentages. This indicates that fertility prognosis cannot be made on the basis of a low in vitro fertilization percentage only. The fertilization rate negatively correlated with the duration of infertility. No positive assays were found after 6 years of infertility.

Animals↗
PubMed1982

Fertilization of hamster ova by human spermatozoa in relation to other semen parameters.

Different indices of the zona-free hamster ovum test system were interrelated. High correlations were found between the fertilization percentage and the average number of penetrated spermatozoa/ovum (r = 0.99) and between the fertilization percentage and the number of spermatozoa attached to the ova surfaces (r = 0.72). Fertilization percentages from 63 subfertile patients were correlated with different semen factors assessed by multiple exposure photography (MEP). Low correlations were found between sperm concentration and fertilization percentage (r = 0.29) and between fertilization percentage and motile sperm count (r = 0.33). Spermatozoa progressing with high average velocity had low fertilization rates compared to specimen with moderate average velocity. Effects of sperm washing on the in vitro fertilizing capacity were studied in a group of 40 subfertile men. The fertilization percentages of 8 specimens--with visual seminal plasma abnormalities--increased significantly when immediate dilution of semen was applied.

Animals↗