PubMed Health⌕ Search

Biomedical subjects

C Lauritzen

Publications and source records attributed to C Lauritzen.

At least 19 recordsLinked to original sources
PubMed1992

Numerical chromosome anomalies after fertilization of freeze-thawed mouse oocytes.

The chromosome complement of first cleavage stage mouse embryos was analyzed to investigate the effect of slow freezing-fast thawing cryopreservation on chromosome numbers by comparing these numbers with those found fresh after fertilization of control oocytes. Fewer frozen-thawed (34.1%) than control oocytes (75.0%) cleaved to the 2-cell stage after in vitro fertilization. The incidence of hyperploidy was significantly increased by freezing (4.5% vs. 0% in controls). Polyploidy was not significantly affected (17.0% for freeze-thaw embryos vs. 26.2% for controls).

Aneuploidy↗
PubMed1992

Effects of N-terminal extension peptides on the structure and stability of bovine pancreatic trypsin inhibitor studied by 1H n.m.r.

Four N-terminal extended species of the wild-type bovine pancreatic trypsin inhibitor (WT-BPTI), Arg-BPTI (1-BPTI), Met-Glu-Ala-Glu-BPTI (4-BPTI), Ser-Ile-Glu-Gly-Arg-BPTI (5-BPTI) and Gly-Ser-Ile-Glu-Gly-Arg-BPTI (6-BPTI) have been studied by 1H n.m.r. The overall structure of the protein is largely unaffected by the addition of extension peptides. pH titration effects on the C-terminal Ala 58 H beta chemical shift indicate that the structure of 1-BPTI at neutral pH is very similar to that of the WT protein, with a salt bridge between the main chain terminal charges. A salt bridge interaction is prevented by addition of the longer extension peptides. Temperature stabilities are measured by high temperature hydrogen isotope exchange and by microcalorimetry. The stability of 1-BPTI is equal to that of WT-BPTI. A slight decrease in stability is observed for longer extensions, following the order WT-BPTI = 1-BPTI < 5-BPTI = 6-BPTI < 4-BPTI. Small changes in chemical shift are observed for 30 invariant resonances in 4-, 5- and 6-BPTI and for a subset of this group in 1-BPTI. These protons are distributed over about half of the BPTI molecule. The size of the chemical shift changes for many resonances follow the same ranking as the temperature stability. The chemical shift effects are attributed to charge and dielectric effects from extension peptides that probably share a common orientation on the surface of BPTI.

Amino Acid Sequence↗
PubMed1992

Role of frequency and amplitude of repetitive HCG stimulations for sustained progesterone secretion from the bovine corpus luteum in vitro.

This investigation aimed at evaluating a role for frequencies and amplitudes of repeated HCG stimulations for the optimal maintenance of progesterone (P4) secretion from the bovine corpus luteum in vitro. Slices (100-120 mg) of midluteal bovine corpora lutea were perifused with medium M199 (0.05% BSA, pH 7.2, 38.5 degrees C) and the perifusion effluent collected at 15 minute intervals for 20-29 hours. Unstimulated P4 release (n = 5) was distinctly pulsatile (by Pulsar pulse algorithm), with pulses occurring every 90 +/- 6 minutes (mean +/- SEM) and pulse amplitudes of 14.4 +/- 1.1 ng. Conversely, no pulses were detected in two control perifusions. Unstimulated P4 release increased during the first 5 perifusion hours (from 39.3 +/- 4.6 to 50.3 +/- 5.6 ng/15 min, p less than 0.01), but then appeared to decline (to 29.3 +/- 1.3 ng/15 min, p less than 0.05) towards the end of the perifusion periods. Hourly pulses of HCG (6.7 mM) did not change the P4 pulse amplitudes (16.6 +/- 2.0 ng), the pulse periodicities (105 +/- 15 min) and overall release rates (34.7 +/- 5.7 ng/15 min), nor did they prevent the decline in P4 secretion towards the end of perifusions (n = 5). In contrast, 2-hourly HCG stimulations maintained stable P4 release rates throughout the perifusion periods (34.7 +/- 6.8 ng/15 min), with P4 pulses of similar amplitudes (14.7 +/- 1.7 ng), but of lower periodicities (135 +/- 2 min, p less than 0.05) than during unstimulated conditions (n = 5).(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1992

[Promoting pregnancy following partial zona dissection of the oocyte within the scope of in vitro fertilization].

Partial dissection of the zona pellucida (PZD) is one of several micromanipulatory methods for the treatment of male subfertility. PZD involves the mechanical introduction of a small hole in the zona pellucida of the oocyte prior to insemination. Thus, fusion with the oolemma and fertilization of the oocyte is facilitated for spermatozoa with impaired quality that otherwise would not be able to penetrate the zona. We have established this technique at our clinic and report on the first pregnancy achieved by PZD of the oocyte during our IVF programme.

Adult↗
PubMed1992

[Cytogenetics of unfertilized or uncleaved oocytes within the scope of in vitro fertilization. Relations to hormone content of follicular fluid].

Constituents of the follicular fluid (FF) have been suspected to influence fertilizability and cytogenetic constitution of human oocytes. Therefore, we analysed the FF concentrations of 17 beta-estradiol (E2), progesterone (P), testosterone (T), and prolactin (PRL) of 114 oocytes recovered for in vitro fertilisation (IVF). 46 of these oocytes were fertilised and transferred to the maternal uterus. Among the unfertilized gametes, 27 were not analysable. 30 were normal haploid, and 11 were classified as abnormal. There was no significant difference between fertilised and unfertilized oocytes for FF concentrations of E2, P, T, and PRL and for the E2/P ratios. Similarly, we detected no significant difference between normal and abnormal oocytes for these parameters.

Chromosome Aberrations↗
PubMed1992

[New perspectives of in vitro kallikrein treatment. II. Study of the hamster ovum penetration test in relation to the kallikrein-kinin system].

A significant enhancement of the fertilizing capacity of human spermatozoa by Kallikrein has recently been described in a former study. To assess the therapeutic possibilities it would be of great interest to know more about the biochemical effect of Kallikrein on the fertilizing capacity of human spermatozoa. This fact made the authors investigate 64 semen samples in which the binding score and the fertilizing capacity were determined after application of Kallikrein in a HOP-test (hamsterovum-penetration-test) and compared to the control. Furthermore these results were compared to the varying concentrations of the components of the Kallikrein-Kinin-system. An application of Kallikrein in the swim-up preparation resulted in a higher motility in patients with asthenozoospermia, whereas the patients belonging to the group of oligoasthenozoospermia showed a lower progressive motility compared to the control. The binding score (number of affixed spermatozoa) showed nearly the results in both preparations. On the other hand the fertilizing capacity in the Kallikrein preparation was significantly higher. A possible connection with the concentrations of the components of seminal plasma has not been found, yet, but regarding all results a direct enzymatic effect of Kallikrein on fertilizing potential can be assumed.

Animals↗
PubMed1992

[Type and incidence of cytogenetic abnormalities in unfertilized or uncleaved human oocytes within the scope of in vitro fertilization].

Human oocytes remaining unfertilized or uncleaved during in vitro fertilization (IVF) yield valuable information on the kind and frequency of numerical and structural chromosome aberrations after their fixation. This enables us to assess the maternal contribution to perturbations in the course of fertilization and early embryonic development. Therefore, 566 unfertilized or uncleaved oocytes from our IVF programme were processed for cytogenetic examination. 223 gametes were not analyzable. 260 oocytes were completely karyotyped and chromosome counts could be established for 83 cells. 243 eggs had the normal haploid chromosome complement whereas 100 cells (29.2%) were abnormal. In detail, we found the following aberrations: hypohaploidy = 10.2%, hyperhaploidy = 4.7%, diploidy = 9.0%, tetraploidy = 1.2%, structural anomalies = 2.6%, prematurely condensed sperm chromosomes = 3.2%. Six cells had to be considered in two of these categories. Our results and comparisons with other publications imply that the total rate of anomaies in human oocytes from stimulated cycles amounts to 20 to 30%. This high frequency might be one of the limiting factors for the success rate of IVF.

Adult↗
PubMed1991

How do androgens affect episodic gonadotrophin secretion in postmenopausal women?

In the absence of any significant ovarian oestrogen secretion, as in post-menopausal women, the hypothalamic-pituitary axis may still be influenced by the androgens which continue to be produced. The episodic secretion of luteinizing hormone (LH) and follicle-stimulating hormone (FSH) by postmenopausal women was accordingly assessed following short-term androgen antagonism induced by flutamide, a specific androgen receptor blocker. Blood samples were collected at 10-min intervals for 10 h in nine women before and during flutamide administration (750 mg/day for 6 days) for the determination of gonadotrophin and sex hormone concentrations by radioimmunoassay. On both occasions, 25 micrograms of gonadotrophin-releasing-hormone (GnRH) was injected intravenously 8 h after initiation of the blood collections. Flutamide administration decreased (P less than 0.01 or less) androgen concentrations (testosterone, androstenedione and dehydroepiandrosterone sulphate) in relation to baseline values, but did not alter oestrogen (oestrone and oestradiol) or sex-hormone-binding globulin levels. The LH and FSH pulse characteristics (frequency, amplitude, interpulse interval and transverse mean levels) determined by a cluster algorithm in the gonadotrophin secretory profiles did not differ before and during androgen blockade. By contrast, androgen antagonism increased LH (P less than 0.01) and tended to enhance FSH (P = 0.10) FSH release in response to GnRH stimulation. Hence, short-term androgen receptor blockade with flutamide did not greatly affect episodic gonadotrophin secretion. However, the combined evidence of the enhanced gonadotrophin release observed in response to GnRH stimulation and the unchanged gonadotrophin secretion during androgen antagonism suggests that alterations in the magnitude, but not the frequency, of hypothalamic GnRH release had occurred. Even in the presence of substantial serum androgen concentrations, the gonadotrophin pulse rhythm in hypogonadal women constitutes the maximal-rate GnRH-LH release pattern.

Androgens↗
PubMed1991

[Pregnancy after direct oocyte-sperm transfer (DOST)--a simple alternative to in vitro fertilization (IVF)].

We report on the first pregnancies achieved at our clinic following direct oocyte-sperm-transfer (DOST). Immediately after follicular aspiration, oocytes together with spermatozoa prepared by the swim-up-technique are transferred to the uterus in a manner similar to the embryo transfer following IVF. Our study population consists of 9 patients with bilateral tubal occlusion, accompanied by a male factor in three cases. Up to now, we have achieved four pregnancies, including one twin pregnancy, all occurring, when a male factor was absent. The method described appears promising in terms of efficiency, reduction in the costs and technical procedures during treatment of human infertility.

Embryo Transfer↗
PubMed1991

[Cytogenetic analysis of sperm chromosomes in couples with habitual abortion].

Genetic factors, especially numerical chromosome anomalies, play an important role in embryonic loss. Since somatic cell analysis cannot assess the risk of errors arising de novo during germ cell maturation, we investigated, whether the male gametes from couples with habitual abortion (group HA) carry a higher rate of anomalies, than those from donors without reproductive dysfunction (group K). Chromosomes were demonstrated after fusion of sperm with zona-free golden hamster ova. Our results indicate no significant difference between the two groups for the total rates of aneuploidy (HA: 3.6%, K: 2.0%) and structural anomalies (HA: 15.3%, K: 7.0%). However, the levels of chromosome breaks and acentric fragments were significantly higher in the abortion group (5.8% and 8.1%, respectively, vs. 2.4% each in group K). The implications of this fact remain to be investigated.

Abortion, Habitual↗
PubMed1991

The impact of ovarian laser surgery on the gonadotrophin secretion in women with polycystic ovarian disease.

To evaluate the effects of ovarian surgery on the deranged episodic gonadotrophin release of women with the polycystic ovarian disease (PCOD), we studied 11 patients with the clinical and endocrinological features of PCOD before and after laparoscopic laser coagulations of ovarian surfaces and cysts. During both occasions, blood was collected at 15-min intervals for 8 h to determine LH and FSH secretory profiles and additionally for 3 h during GnRH injections (25 micrograms twice within 2 h) to assess pituitary responsiveness. Serum testosterone, androstendione and oestrogen (oestrone, oestradiol) levels were markedly reduced (P less than 0.05 or less) after surgery. Mean LH concentrations declined (P less than 0.001), while FSH levels increased (P less than 0.01) following laser treatments. The LH pulse frequencies (by Cluster analysis) did not change after ovarian surgery, but the LH pulse amplitudes were markedly reduced (P less than 0.01). Lower (P less than 0.05 or less) LH concentrations were attained in response to GnRH challenges, and the stimulated FSH release also tended to decrease after laser treatments. Thus, ovarian surgery in PCOD women resulted in reduced serum sex steroid concentrations and in divergent effects on serum LH and FSH levels. The attenuated pituitary LH responsiveness after ovarian surgery suggests action of sex steroids primarily at the pituitary site, while the increase in FSH concentrations may be attributed to other factors selectively modulating FSH release.

Adult↗
PubMed1991

Gonadotropin secretion during aging in postmenopausal women.

Although chronological aging is known to result in reduced gonadotropin secretion in women, the precise mechanisms to account for this neuroendocrine manifestation are yet obscure. To evaluate the extent to which the pituitary and/or hypothalamus are involved in the process of aging, we aimed at characterizing the unstimulated and GnRH-stimulated gonadotropin secretion in postmenopausal women (PMW) of different ages. Accordingly, 9 younger PMW (mean age: 53.8 years) in their first and 9 older PMW (mean age: 80.3 years) in their 4th decade of life after natural onset of menopause were studied. In both groups, blood was collected at 10-min intervals for 10 h, while GnRH (25 micrograms i.v.) was administered 8 h after initiation of blood samplings. Compared to younger PMW, basal serum concentrations of dehydroepiandrosterone-sulfate were lower (p less than 0.05) in older PMW, while estrogen (estradiol, estrone), androgen (testosterone, androstendione) and sex hormone binding globulin levels were similar. Lower (p less than 0.01) mean LH levels composed of attenuated (p less than 0.05) LH pulse amplitudes and pulse frequencies (as determined by the cluster pulse algorithm) were found in the 8-hour LH secretory profiles of older PMW. Furthermore, the FSH secretion of older PMW was characterized by lower (p less than 0.01) mean FSH levels with lower (p less than 0.05) FSH pulse amplitudes, but not pulse frequencies. The absolute peak concentrations attained and the total amount of LH and FSH released in response to GnRH stimulations were blunted (p less than 0.001) in older PMW.(ABSTRACT TRUNCATED AT 250 WORDS)

Aging↗
PubMed1991

Autonomous progesterone secretion from the bovine corpus luteum in vitro.

While the regulation of progesterone secretion from the corpus luteum by LH has been convincingly demonstrated, the secretory patterns in the absence of any pituitary LH inputs are yet unclear. Consequently, we investigated the progesterone secretion by an in vitro perifusion system to characterize spontaneous progesterone release from the isolated bovine corpus luteum. Slices (120 mg) of midluteal corpora lutea were placed in perifusion chambers and continuously perifused by Medium-199 for 160-320 min. Progesterone was determined by radioimmunoassay in the effluent fractions collected at 2-min intervals. The spontaneous progesterone release from all bovine corpora lutea was pulsatile. Pulses were observed at mean (+/- SEM) intervals of 17.7 +/- 1.5 min with amplitudes of 6.7 +/- 0.5 ng and release rates of 29.5 +/- 2.4 ng.ml-1.(2 min)-1 (N = 5). Addition of 6.7 nmol/l hCG to the perifusion medium appeared to increase the pulse amplitudes and release rates (195 +/- 25% over unstimulated conditions), but did not change the pulse frequencies (N = 3). Perifusions with calcium-free medium containing 50 mumol/l verapamil and 20 mmol/l EGTA tended to suppress the pulse frequencies and amplitudes of this spontaneous progesterone release, whereas addition of hCG reversed this decrease again (N = 3). When prostaglandin activity was inhibited by 100 mumol/l indomethacin added to the perifusion medium, both pulse frequencies and amplitudes of this progesterone release were enhanced (N = 4). During perifusions with 100 mumol/l of the anti-progesterone ZK 96.734, both the pulse frequencies and amplitudes increased (N = 4). These studies demonstrate an episodic progesterone release from the bovine corpus luteum perifused in vitro.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗