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Biomedical subjects

M T Zenzes

Publications and source records attributed to M T Zenzes.

At least 19 recordsLinked to original sources
PubMed1992

Chromosome status of untransferred (spare) embryos and probability of pregnancy after in-vitro fertilisation.

Many spontaneous abortions are associated with chromosomal abnormality of the fetus. In in-vitro fertilisation (IVF) the chromosome status of untransferred ("spare") embryos and subsequent fate (pregnancy or not) of the transferred sibling embryos might be related. Since the spare and transferred embryos of a patient's cycle genetically are full siblings, the inherited chromosomal abnormalities in spare embryos have a 50% probability of also appearing in transferred embryos. We have tested whether chromosome analysis of spare embryos has predictive power for transferred embryos. 48 couples with a total of 437 embryos were selected because their spare embryos (1-4 per couple; 76 total) were successfully analysed for chromosome status. 16 patients became pregnant. These women produced a higher proportion of chromosomally normal spare embryos (9/24; 37.5%) than those who did not achieve pregnancy (1/52; 1.9%). The proportion of patients who had only normal embryos was significantly higher (p = 0.012) in the pregnant group than in the non-pregnant group, and the proportion of patients who had only abnormal embryos was significantly higher (p = 0.001) in the non-pregnant group. Patients with preclinical and clinical pregnancy losses had only chromosomally abnormal spare embryos; by contrast, 50% of spare embryos from patients with ectopic pregnancies were normal. The proportion of spare embryos that were normal (13%, 10/76), was similar to the livebirth rate of 11% per transferred embryo (19 infants from 171 transferred embryos). These results suggest that chromosome analysis of spare embryos may have predictive value for their transferred sibling embryos. We conclude that improving detection of chromosomally normal embryos for transfer should improve the success rate in IVF.

Chromosome Aberrations↗
PubMed1992

Cytogenetics of human oocytes, zygotes, and embryos after in vitro fertilization.

Chromosome errors, inherited or arising de novo during gametogenesis and transmitted at fertilization to the conceptus, may be a major cause of embryonic mortality. The in vitro fertilization and embryo transfer (IVF/ET) procedure provides extra material--oocytes, zygotes, and embryos--to investigate the contribution of chromosomal abnormality to implantation failure. This paper reviews the results of cytogenetic studies on such material. Estimates from a total of 1120 oocytes from 11 studies give an overall proportion of chromosomal abnormality of 35%. Single and multiple nullisomies and disomies are found, involving nonrandom chromosome gain or loss. Hypohaploid complements are more frequent than hyperhaploid complements. The higher rate of chromosome loss of hypohaploid karyotypes was found to be largely artifactual. The estimated overall frequency of aneuploidy is 13%. In embryos the level of chromosomal abnormality is 23%-40%. Errors of fertilization are responsible for a substantial number of triploid embryos, many of which develop into mosaics. Factors extrinsic to the conceptus, such as infertility, advanced maternal age, and ovarian hyperstimulation, may increase the level of chromosomal abnormality. More refined methods for accurately recognizing and selecting chromosomally normal embryos for transfer are needed to improve the success rate of this reproductive technology.

Adult↗
PubMed1992

Evidence for maternal predisposition to chromosome aneuploidy in multiple oocytes of some in vitro fertilization patients.

OBJECTIVES: To assess the rate of chromosome aneuploidy (e.g., extra or missing chromosomes) in oocytes remaining unfertilized in our in vitro fertilization (IVF) program. To determine whether two parameters of the IVF technique, advanced maternal age and hormonal follicle stimulation, affect this rate. DESIGN: Data on oocyte retrieval, fertilization, and aneuploidy rates are analyzed to test for possible relations with maternal age and two hormonal stimulation regimens. SETTING: Patients of our IVF program from 119 stimulated cycles over 8 months. PATIENTS, PARTICIPANTS: In vitro fertilization patients selected for having oocytes (1 to 18) remaining unfertilized after insemination in vitro. RESULTS: Advanced maternal age decreases both the number of retrieved oocytes and the fertilization rate, but hormonal treatments have no effect. Aneuploidy (rate 27%), involving group G most frequently, appears associated with advanced age. Patients who were previously parous produced significantly reduced numbers of aneuploid oocytes compared with the nonparous group. A significant excess (P = 0.01) of patients had multiple oocytes all alike (all haploid or all aneuploid), showing correlation among multiple oocytes of a patient in chromosome status. CONCLUSIONS: Maternal age affects reproductive performance and is related to specific chromosomal aneuploidy. Women who were previously parous are more likely to produce normal oocytes than nonparous women; oocyte normality therefore may improve the chance for a future successive pregnancy. Nonrandomness in chromosome abnormality of some patients' multiple oocytes is evidence for maternal predisposition to meiotic nondisjunction. Consequently, these patients are at risk for failed IVF cycles.

Adult↗
PubMed1990

Abnormalities of sperm chromosome condensation in the cytoplasm of immature human oocytes.

This study analysed data from 27 couples in an IVF-ET programme. The maternal age range was 28-43 years. Statistical analyses on 182 oocytes showed no maternal age effect on the number of oocytes, their stage of maturation or their fertilization rate. There was also no effect of age of either partner or of seminal parameters on the fertilization rate. In contrast, occurrence of diploid oocytes was confined to three of the older women. The proportion of failures of fertilization was significantly higher in immature oocytes. These failures, which included 18 uncleaved, multipronuclear or fragmented zygotes, were related to disturbances of oocyte maturation. Four (out of five) oocytes re-inseminated with fresh semen produced polyspermy. One zygote showed marked asynchrony in the development of the two pronuclei. In eight zygotes the paternal complements had an allocyclic pattern of chromosome condensation between and within chromosomes or chromosome regions. In two other zygotes the paternal complement showed one chromosome prematurely condensed. This single-chromatid chromosome would be lost in the following cleavage division, suggesting that aneuploidy due to 'anaphase lag' is not a rare event during embryo cleavage.

Adult↗
PubMed1987

Sperm from some infertile men may consist of several populations.

In the hamster ovum penetration (HOP) test, when ova have equal penetrability and sperm have equal penetrating ability, the distribution of zona-free hamster ova classified by number of penetrating human sperm is expected to follow the Poisson distribution (PD). This study reports tests for PD in HOP tests on 9 infertile patients and 11 normal controls. The data, presented in detail, show the expected PD in the control group. In contrast, 3 patients had HOP tests with definite non-PDs, whereas 5 patients have clearcut PDs. The cause of non-PD is unknown, but could result from differences among motile sperm in penetrating ability.

Adult↗
PubMed1987

Confirmation of an abnormal (non-Poisson) distribution of sperm from some infertile men in the hamster-ovum test.

The present study was carried out to investigate an earlier report that stated that some men of infertile couples (patients), but not normal donors, have an abnormal (non-Poison) distribution of penetrating sperm among ova in the hamster-ovum test. Semen samples from 60 men, 24 proven fathers and 36 patients, were analyzed for agreement with the theoretical Poisson distribution (PD). Most of the fathers (23 of 24) fit PD well, but 10 of the patients did not. The overall (group) fit of fathers is good, but that of the patients is poor. Patients, but not fathers, are heterogeneous in their agreement with PD; about 25% fit poorly whereas more than 50% fit well. The 25% fitting poorly may often be those patients who are truly infertile (even when their wives are actually fertile).

Adult↗
PubMed1987

Testicular function in eight patients with seminoma after unilateral orchidectomy and radiotherapy.

Testicular function was monitored in eight patients with low stage seminoma who were treated with radiotherapy following unilateral orchidectomy. The absorbed gonadal radiation dose ranged from 15 to 157.5 rad. At 10-24 months after radiotherapy, serum hormone levels, sperm analysis, sperm penetration into zona-free hamster ova (HOP-test) and lymphocyte chromosome abnormalities were evaluated. Two patients were azoospermic with elevated serum levels of LH and FSH. The remaining six patients had slightly decreased (n = 3) or normal (n = 3) seminal parameters. Their HOP rates were within the normal range. A low incidence of polyspermy (i.e. only one penetrating sperm per ovum) was found in the patients, suggesting low penetrability of motile sperm. A highly significant correlation was found between sperm count or sperm penetrability and time post-irradiation. The results indicate that restitution of testicular function is time-dependent.

Adult↗
PubMed1986

[Clinical aspects of 7 pregnancies following in vitro fertilization and embryo transfer (IVF/ET)].

Between September 1, 1983 and June 15, 1984 69 patients were treated by in-vitro fertilization as part of a clinical research project. The scientific questions were aimed at optimizing the principal methodological aspects of the new technique. One hundred and sixty-nine follicle punctures were performed under laparoscopic or ultrasonographic control. A total of 207 preovulatory oocytes were obtained, 57 of which were transferred to the uterus as cleaving embryos following in-vitro fertilization. Seven clinical pregnancies were diagnosed. Two resulted in spontaneous abortion in the fifth and sixth week of gestation, the remaining five as three single and two twin births. The infrastructure of reproduction medicine has been broadened successfully within a short time. Considering the results of current clinical and experimental research, the efficiency of the methods used is likely to be improved.

Abortion, Spontaneous↗
PubMed1986

Time course of human sperm transformation in the cytoplasm of zona-free hamster ova.

The time required for nuclear transformation of human spermatozoa in the cytoplasm of zona-free hamster ova was determined using semen samples from four individuals. Zona-free ova were incubated with capacitated spermatozoa for either 3 h or for 4-8 h. After the first hour of insemination, up to 85 ova were fixed at 1-h intervals. Assessments of sperm transformation were carried out on Giemsa-stained preparations of ova. Considerable variation between individuals was found in the maximal time of sperm decondensation, ranging from 2 to 7 h. Decondensing sperm heads developed into pronuclei within 3-5 h. At and subsequent to pronuclear formation, the incidence of decondensing sperm heads was considerably reduced in both insemination times. This variability in sperm transformation is relevant in clinical evaluations of the functional capacity of spermatozoa.

Adult↗
PubMed1985

Cytologic investigation of human in vitro fertilization failures.

A cytogenetic study of unsuccessfully fertilized oocytes was done for information on the frequency and type of chromosomal abnormalities leading to preimplantation loss. Of 72 oocytes, 44 were assessed as mature, 19 as intermediate, and 9 as immature. The mean fertilization rate was 68%. This rate was significantly lower in immature oocytes than in mature ones (22% versus 79%). Immature oocytes completed maturation in vitro up to metaphase II of meiosis. Intermediate oocytes became fertilizable, however, a significant proportion showed morphologic abnormalities after fertilization. Thus, eggs with three pronuclei were hypotriploid or had three prophasic chromosome sets, together with polyspermy and with first polar body chromosomes. Eggs with developmental arrest showed marked asynchrony in pronuclear morphogenesis. One had a chromosome complement of 24,XX. It is concluded that insemination prior to completion of maturation leads to abnormal development.

Adult↗
PubMed1979

Pattern of activity of nucleolus organizers during spermatogenesis in mammals as analyzed by silver-staining.

Silver-staining in the nuclei and chromosomes of spermatogenesis of four species of mammals (Man, Mus musculus, Rattus norvegicus, and Cavia cobaya) was investigated qualitatively and quantitatively. These species show a very similar pattern of activity of the nucleolus organizer regions (NORs) during the various stages of spermatogenesis. Silver precipitates are detectable in growing spermatogonia and up until the pachytene stage of meiotic prophase. During the meiotic metaphases I and II and during interkinesis silver-stainability disappears completely. A resumpton of silver-stainability occurs in round spermatids indicating a postmeiotic reactivation of NORs. This process does not persist beyond the early elongation phase. The quantitative determination of the silver-covered areas in relation to the total nuclear areas reveals minor differences between the species investigated with regard to the times and extents of maximum activation. The known localizations of the NORs in the karyotypes of the species investigated was confirmed using metaphase-preparations derived from somatic tissues.

Animals↗
PubMed1978

Studies on H-Y antigen in different cell fractions of the testis during pubescence: immature germ cells are H-Y antigen negative.

Various cell types of the rat testis during pubescence, including germ, Sertoli, and Leydig cells, were partially enriched. The fractions were tested for the presence, binding, and secretion of H-Y antigen. The main results are: Immature germ cells are H-Y antigen-negative until the late diploid stages, and late primary spermatocytes or spermatids become positive; the somatic cells of the gonad are positive at all ages examined (18 days old to adulthood). Secretion of H-Y antigen is restricted to the Sertoli cell fraction. Binding of externally supplied antigen takes place on Leydig cells; the Sertoli cell surface will be saturated because of active secretion; there is no binding to germ cells. Thus, immature germ cells seem to be the only H-Y antigen-negative cells of the male organism, and the Sertoli cells seem to be the only ones to secrete H-Y antigen.

Age Factors↗
PubMed1978

Appearance of hCG-receptor after conversion of newborn ovarian cells into testicular structures by H-Y antigen in vitro.

In a previous report (Zenzes et al., 1978b) it was shown that dissociated ovarian cells of newborn rats in vitro, if exposed to H-Y antigen, reorganize into testicular structures. The current study was designed to see whether this morphological conversion also results in a functional conversion. The LH/hCG receptor was used as a parameter characteristic for the newborn testis, but not for the newborn ovary. In the converted ovary, the LH/hCG receptor becomes detectable a few hours after onset of the culture and remains continuously present afterward. The appearance of this receptor may be due to a hormone-like action of H-Y antigen.

Animals↗
PubMed1978

The testis as a secretory organ for H-Y antigen.

After cultivation of dissociated rat testicular tissues, H-Y antigen is detectable in the medium; this is not the case if nongonadal male tissues are incubated. Release of H-Y antigen by testis cells is inhibited by the addition of cycloheximide. All tissues still type H-Y positive after culture. It is assumed that the testis actively secretes H-Y antigen. This assumption is supported by the finding that the amount of H-Y antigen in the epididymal fluid increases with the age of the animals.

Animals↗
PubMed1978

Organization in vitro of ovarian cells into testicular structures.

While it has been shown previously (Zenzes et al., 1978; Ohno et al., 1978) that when dissociated testicular cells are exposed to anti H-Y antiserum in vitro they are prevented from reorganizing into testicular structures, forming ovarian follicular structures instead, the most conclusive evidence for the action of H-Y antigen would be the conversion of ovarian cells into testicular organization. Testing for H-Y antigen of the medium collected from cultivated testicular cells revealed a positive reaction. Dissociated ovarian cells of newborn rats cultivated in this medium reorganize into testicular structures. It is concluded that H-Y antigen is responsible for this histomorphologic change.

Animals↗
PubMed1978

Binding studies of H-Y antigen in rat tissues: indications for a gonad-specific receptor.

The binding capacity for H-Y antigen was studied in various rat tissues of both sexes. In nongonadal tissues (liver, kidney, brain, epidermis) binding could not be demonstrated. In contrast, the gonads are able to bind exogenously supplied H-Y antigen. In the ovary, the binding capacity remains unchanged in newborn and adult animals, while in the testis, this capacity decreases with age. A receptor like that of a proteohormone is assumed to exist in the gonads but not in other tissues. In nongonadal tissues, H-Y antigen apparently is present only if the cell itself synthesizes the antigen. The H-Y antigen receptor of the gonads is not sex-specific. Thus, the primary sex differentiation depends on whether H-Y antigen is synthesized in the organism.

Animals↗
PubMed1978

Studies on the function of H-Y antigen: dissociation and reorganization experiments on rat gonadal tissue.

On circumstantial evidence, H-Y antigen is assumed to be responsible for the differentiation of the undetermined gonadal anlage into a testis. A direct approach to test the function of H-Y antigen is provided by Moscona-type experiments. Applying a modified technique of in vitro reassociation of cell suspensions, we obtained the following results: (1) dissociated newborn rat gonads, both testis and ovary, reorganize into histotypic structures; (2) under exposure to anti-H-Y antiserum, testicular cells reassociate into ovarian follicular-like organization; (3) anti-H-1 antiserum by itself does not prevent the testicular cells from forming tubular structures. It is concluded that H-Y antigen acts as a differentiation between preferably or exclusively on the cell elements participating in the formation of the seminiferous cords.

Animals↗