Biomedical subjects

L Yogev

Publications and source records attributed to L Yogev.

At least 55 records · Page 3Linked to original sources

PubMed1995

Female age does not affect the capacity of human zona pellucida to bind spermatozoa.

The purpose of this study was to evaluate the effect of female age on the capacity of the zona pellucida to bind spermatozoa. A total of 1008 unfertilized oocytes obtained from 210 women (aged 21-43 years) participating in the in-vitro fertilization programme were tested using a hemizona assay. Spermatozoa taken from a cryopreserved pool of fertile donor specimens served as a control in the hemizona assay, and were used to assess the ability of the zona pellucida to bind spermatozoa. The mean +/- SD number of spermatozoa attached to the hemizona was 107 +/- 42. The binding capacity of different oocytes from the same cohort varied substantially (coefficient of variation = 28%). Age was not found to be correlated with the number of spermatozoa bound to the zona pellucida (r = -0.02; P > 0.1). It was concluded that female age has no role in the ability of the human zona pellucida to bind spermatozoa.

Adult↗

PubMed1995

Pentoxifylline improves sperm binding to the zona pellucida in the hemizona assay.

OBJECTIVE: To evaluate the effect of pentoxifylline on sperm binding capacity to zona pellucida (ZP) using the hemizona assay (HZA). DESIGN: The fertility potential of 82 men was evaluated by routine semen analysis. Each ejaculate was incubated with or without pentoxifylline (3 mM) in Ham's F-10 medium (Flow Laboratories, Irvine, Scotland) before the HZA. The effect of the pentoxifylline treatment on sperm-binding capacity to ZP was assessed by the hemizona index. RESULTS: The mean hemizona indexes with medium or pentoxifylline treatment were 23% +/- 2.1% (mean +/- SE) and 41% +/- 3.4%, respectively. Taking into consideration a significant change of the hemizona index on rising above the intra-assay coefficient of variation (+/- 8%) after pentoxifylline treatment, 73.1% of specimens improved, 19.5% deteriorated, and 7.4% remained unchanged. Using a threshold hemizona index of 23% as a discriminator between fertile and infertile specimens, 43.5% of the "pentoxifylline-improved" samples ascended to the fertile zone (> 23%). No correlations were found between sperm variables in the raw semen and the effect of pentoxifylline on sperm binding capacity. CONCLUSION: Pentoxifylline may improve the binding capacity of human spermatozoa. However, this effect is confined to a selected group of patients and cannot be predicted by the basic sperm variables. Thus, to avoid uncertain or damaging effects of pentoxifylline while preparing sperm suspension for assisted reproductive techniques, it is recommended that its effect be tested by the HZA system before its use.

Female↗

PubMed1994

Blood luteinizing hormone and prolactin concentrations in response to naltrexone challenge: studies on rats with diabetes induced by different doses of streptozotocin.

Opiate system involvement in diabetes induced by three different doses of streptozotocin (STZ; 40, 50, and 60 mg/kg body weight [BW]) was studied by monitoring luteinizing hormone (LH) and prolactin (PRL) levels as a response to naltrexone (Nalt) administration. After four weeks of diabetes a marked decrease in BW, as well as severe hyperglycemia and increased blood urea nitrogen (BUN) levels were found. The rats, whose diabetes was induced by 50 mg/kg of STZ, exhibited the highest amount of blood glucose (P < 0.05, compared with the 40 mg/kg induced group) and BUN levels (P < 0.004 compared with the other two groups) and BW loss. The normal response to Nalt, which is expressed by elevation of plasma LH and decreased plasma PRL levels was observed only in the low-dose STZ (40 mg/kg BW) diabetes-induced group, while in the other two diabetic groups (50 and 60 mg/kg BW) there was no significant change in plasma LH and PRL as a result of the Nalt challenge. Presensitization of the endogenous opioid receptors by morphine in normoglycemic (control) and "low-dose diabetic" rats (40 mg/kg BW of STZ), presented a clear difference between the two. Morphine pretreatment inhibited LH response to Nalt in the low-dose, STZ-induced diabetic rats, while no effect of morphine pretreatment on LH response to Nalt could be recorded in the normoglycemic group. Thus it can be concluded that in STZ-induced diabetes, plasma glucose and BUN levels do not reflect the neuroendocrine injury observed when monitored by LH and PRL secretion in response to Nalt challenge. Supersensitization of the opioid receptors before the Nalt challenge may increase the ability to reveal neuroendocrine system impairment.

Animals↗

PubMed1994

The hemizona assay is of good prognostic value for the ability of sperm to fertilize oocytes in vitro.

OBJECTIVES: To assess the prognostic value of hemizona assay (HZA) in predicting the success of IVF. DESIGN: Samples from 133 patients, who were referred for semen evaluation, were tested by HZA. Thirty samples were tested twice to assess interassay variation. Seventy couples were also referred for IVF. Results of HZA were compared with standard parameters of sperm quality, fertilization rates, and pregnancies. RESULTS: The intra-assay and interassay coefficient of variation were 8% and 14%, respectively. Hemizona assay results had the highest correlation with sperm morphology (r = 0.60). Of all parameters evaluated, fertilization rates were best predicted by hemizona index (HZI) (r = 0.75). The assay was found to have high sensitivity and specificity rates, at a threshold HZI of 23%. CONCLUSIONS: The HZA is a valuable prognostic test for IVF. With a threshold HZI of 23%, it has a good predictive value for fertilization rates in IVF, and may thus be used for patient preselection before IVF.

Female↗

PubMed1994

The effect of egg yolk on the binding capacity of human spermatozoa to zona pellucida.

OBJECTIVE: To evaluate the effects of Tes and Tris (TEST)-yolk buffer (TYB) incubation on sperm function. DESIGN: Sperm samples obtained from 61 patients attending the infertility clinic were incubated in TYB and control medium. Binding to the zona pellucida (ZP), evaluated by the hemizona assay, membrane functional integrity evaluated by the hypoosmotic swelling test, and acrosome reaction and penetration through cervical mucus were assessed to ascertain the effect of TYB treatment. RESULTS: The only substantial effect of TYB treatment was enhanced sperm binding to the ZP. The mean number of sperm cells attached to the hemizonae with TYB or medium treatment, was 42 +/- 6.1 (+/- SE) and 31 +/- 5.8, respectively (n = 61). However, this improvement was most obvious in 12 patients whose sperm samples exhibited a marked increase in sperm binding capacity following TYB treatment compared to medium without TYB, 71 +/- 5.6 and 12 +/- 2.7, respectively. In the other sperm samples (n = 49), sperm binding capacity was similar following TYB and medium treatment (both 35 +/- 6.0). CONCLUSIONS: A 2-hour incubation of sperm samples with TYB-containing medium (at room temperature) enhances the binding capacity of human spermatozoa in approximately 20% of patients considered to have male factor infertility. The basis of this selective effect has yet to be studied further.

Egg Yolk↗

PubMed1994

Retrograde ejaculation.

Retrograde ejaculation is an uncommon cause of male infertility. It should be suspected in any case of azoospermia, and might be congenital, acquired or idiopathic in origin. When pharmacological attempts to restore anterograde ejaculation fail, it is suggested that spermatozoa should be recovered from post-ejaculation urine to be applied in one of the modern techniques of assisted reproduction. The successful recovery of viable spermatozoa from the urine is dependent upon careful regulation of pH and osmolarity of the urine at the time of ejaculation. Careful handling of the retrieved spermatozoa enables isolation of sperm cells with good quality for insemination of ovulated oocytes (in vivo) or retrieved oocytes (in vitro).

Ejaculation↗

PubMed1994

Serum prolactin response to ether stress in diabetic rats: opiate system contribution.

Diabetes in streptozotocin-treated rats is associated with alterations in various neuroendocrine systems, including endogenous opioids. These changes are suggested to be responsible for the significant reduction in serum prolactin (PRL) response to a brief restraint stress in diabetic male rats, as compared with normoglycemic controls. The present study examines serum PRL response to ether exposure in diabetic male rats. The animals' response to ether stress, which is known to be related to the opioid system, was examined twice in each rat: shortly after cannula insertion (Day 1), and seven days later. In order to evaluate the opiate system involvement, the experiment was repeated on Day 1 and 7 after surgery in a group of rats which were pretreated with naltrexone (Nalt), an opioid receptor antagonist. Opioid receptor sensitization was also performed by prior acute morphine administration on Day 7 after cannulation surgery. Following adaptation to the cannulation, no difference in serum PRL response to ether stress was found between diabetic and normoglycemic rats. However, on Day 1 after surgery, a significant difference was found between the diabetic and control groups: the normoglycemic (control) group exposed to ether responded to the surgical stress by augmented serum PRL levels. This response was not recorded in the diabetic rats. Opioid receptor blockade by Nalt administration 30 min before ether exposure eliminated this difference. Opioid receptor sensitization by morphine pretreatment facilitated PRL secretion in normoglycemic rats exposed to either, while no effect could be distinguished in the diabetic group. It is therefore concluded that the streptozotocin-induced diabetic rats do not differ from normoglycemic ones in their ability to respond to acute ether stress by itself. However, enhanced PRL secretion induced by ether exposure under additional surgical stress, or by presensitization of the opioid receptors by morphine, is prevented in diabetic rats, probably due to diminished opioid receptor response.

Animals↗

PubMed1993

[Hemizona assay for evaluating fertilizing capacity of human spermatozoa].

The hemizona assay (HZA), which tests the binding capacity of human spermatozoa to the zona pellucida, is described. This assay has very high sensitivity (86-100%) in predicting fertilizing capacity in the in vitro fertilization (IVF) system. It is recommended that it be carried out on semen samples before entering the IVF program. In addition, it can also help evaluate unexplained infertility and assess the quality of ova. The necessity for a control fertilized sample in each HZA might complicate the assay. To simplify the test, the use of sperm from the sperm bank was investigated. It was shown that fresh and frozen-thawed sperm have the same capacity to bind to the hemizonae. Thus, frozen donor semen preserved in the sperm bank can be used for controlling the HZA.

Cryopreservation↗

PubMed1993

Experimental uremia in male rats: effect on the reproductive tract and fertility.

Chronic renal failure was induced in 3-month-old male rats by 5/6 nephrectomy. Potency and fertility studies were performed after 3 months of chronic uremia. The mean serum testosterone at the end of the experiments was significantly lower: 0.96 +/- 0.14 ng/mL compared to a control group of sham-operated male rats, 2.86 +/- 0.59 ng/mL, p < .001. All the uremic male rats had normal accessory gland weights at the end of the study. Fertility and, in most animals, sexual behavior and mating were not different from the normal control group. It is concluded that in 5/6-nephrectomized uremic male rats, in spite of low testosterone level, fertility and reproductive system are maintained similar to normal control male rats.

Animals↗

PubMed1993

[New methods for predicting sperm fertilizing ability].

There is no reliable method for screening for the fertilizing ability of sperm. 3 new methods are presented: the freezing test (FT), hypoosmotic swelling test (HOST) and migration-sedimentation test (MST). The first 2, test the functional integrity and stability of the sperm membrane under certain osmotic conditions. The MST determines ability to separate high quality sperm. All tests were performed using either fresh semen of husbands, or thawed semen of donors used for fertilization in the IVF unit. Results of the FT were not correlated with the fertilizing ability of sperm in IVF, but HOST results with fresh, but not thawed semen, were correlated. Fertilization of oocytes in IVF was significantly better when HOST value of fresh semen was 45% or more. Motility and morphological normality of sperm separated by MST were better in ejaculates that fertilized ova under in vitro conditions, than in those that did not. Sperm separation by MST of 25% or more of motile sperm, or of more than 1.5 million motile sperm in the sample, indicated statistically significant ability for oocyte fertilization in an IVF system.

Cell Membrane↗

PubMed1992

The predictive fertilization value of the hypoosmotic swelling test (HOST) for fresh and cryopreserved sperm.

BACKGROUND: The hypoosmotic swelling test (HOST) was recommended as a predictive test for in vitro fertilization (IVF) outcome. These results, however, were controversial and the results for thawed semen were insufficient. The present study was conducted in order to clarify the predictive value of the HOST for IVF in fresh and thawed sperm. METHODS: The hypoosmotic swelling test was performed in three groups: husband's fresh semen "subfertile" group, donor's thawed semen group, and donor's fresh semen "fertile" group. RESULTS: No correlation was found between HOST values and sperm characteristics in fresh or thawed sperm. Fresh sperm HOST values correlated with IVF fertilizations. No such correlations were found when thawed sperm was used. HOST values were significantly higher in the fresh fertile donor group than in the fresh subfertile group (P less than 0.001). Following the freezing and thawing process, HOST values decreased dramatically. Nevertheless, the fertilization rate was still higher compared to that of the fresh subfertile group (P less than 0.001). There were significantly more IVF cycles with no fertilizations when HOST values were below 45%. CONCLUSION: The HOST has a predictive value for fertilization of oocytes in IVF cycles when fresh semen, but not thawed sperm, is used. The freezing-thawing process affects the outer membrane of the spermatozoon and changes its characteristics, leading to a decrease in HOST values. Sperm characteristics that play a role in the fertilization process are not expressed directly by HOST values.

Cell Membrane↗

PubMed1992

Improved fertilization rate in an in vitro fertilization program by egg yolk-treated sperm.

High fertilization and PRs have been achieved by using thawed donor sperm cryopreserved with medium containing EY. The aim of our study was to examine the possible effect of EY on the fertilizing capacity of fresh sperm in an IVF program. Preincubation of spermatozoa in EY for 2 hours at room temperature significantly improved fertilization (P less than 0.001) in couples who had low fertilization rates in previous cycles, whereas no effect was found concerning couples with high fertilization rates.

Egg Proteins↗

PubMed1992

Fresh and frozen-thawed human sperm bind in a similar pattern to the zona pellucida in the hemizona assay.

This study evaluated the impact of sperm cryopreservation on sperm quality. The HZA was used to test the binding capacity of fresh as opposed to frozen-thawed sperm from 12 donors. Fresh and frozen-thawed sperm motility was 47% +/- 1.5% and 24% +/- 3.8% (mean +/- SE), respectively. However, the number of sperm cells attached to the hemizonae was 75 +/- 12.0 and 74 +/- 11.9, respectively. We conclude that cryopreservation results in a reduced number of motile sperm cells but does not adversely affect the ability of rescued sperm cells to bind to the ZP. The study also supports the use of frozen-thawed rather than fresh donor sperm for control in the HZA procedure.

Cryopreservation↗

PubMed1992

Efficacy of varicocele embolization versus ligation of the left internal spermatic vein for improvement of sperm quality.

Efficacy of surgical varicocelectomy versus embolization of the spermatic vein was studied in 137 men diagnosed as suffering from left varicocele. The men were divided randomly into three groups according to the methods of treatment: A--embolization of the internal spermatic vein (51 men); B--Ivanissevich technique of high ligation of the spermatic veins (43 men); and C--Bernardi technique of high ligation (43 men). The groups were similar in terms of age, duration of infertility and possessed semen characterized as oligoteratoasthenozoospermia. The fertility of the female partners was evaluated carefully and they were found to be potentially fertile. Varicocele was diagnosed by at least two of the following methods: physical palpation during valsalva manoeuvre, venography, or scrotal scanning using the technetium pertechnetate radioactive method. Semen quality was assessed before treatment and at 3, 6 and 9 months post-treatment. Fecundity was followed-up for 18 months. The major results were: (i) Shrinkage of the varicocele was found in all three groups studied. The same rate of recurrence was recorded in the three groups (24%, 37% and 35% in groups A, B and C, respectively). (ii) Improvement of sperm quality was significant in groups A and B, with better results in group B. (iii) The pregnancy rate was significantly higher in group B, compared with A (38.2% vs. 20.6%; P less than 0.05). Thus, high ligation of the internal spermatic vein yields better results than low ligation or embolization as far as semen quality and pregnancy is concerned.

Embolization, Therapeutic↗

PubMed1992

Migration sedimentation technique as a predictive test for the fertilizing capacity of spermatozoa in an in-vitro fertilization programme.

The migration-sedimentation technique (MST) has been proposed as a means of separating high quality motile spermatozoa. The present study was conducted in order to evaluate whether sperm performance following separation by MST predicts their fertilizing capacity in an in-vitro fertilization (IVF) programme. Ninety semen specimens were analysed for use in an IVF-embryo transfer (ET) programme. Each specimens was divided into two parts: one was processed in the IVF programme and was used after sperm swim-up separation for insemination of human ova. The other aliquot (0.2 ml) was separated by MST, and the sperm then characterized by their concentration, motility, degree of motility and morphology. Sperm characteristics after separation by MST were then correlated with the results of the IVF-fertilization rates. In 79 of 90 IVF-ET cycles, at least one oocyte was fertilized. All post-MST sperm characteristics were significantly higher in cycles with fertilizations compared to IVF cycles without fertilization. A larger percentage of the total motile spermatozoa were recovered after MST in semen specimens with fertilization, compared to semen specimens without fertilization (39.9 +/- 3.6 and 20.6 +/- 6.6%, respectively; P < 0.05). This value was correlated with the percentage of fertilized oocytes (r = 0.24; P < 0.02). More IVF cycles with fertilizations were recorded in cases in which the recovery of motile sperm was > 25% (P < 0.005), or when more than 1.5 x 10(6) motile spermatozoa were recovered after MST (P < 0.0001). As sperm characteristics after MST correlated significantly with their fertilizing capacity, the MST test could be used in evaluation of the fertilizing capacity of spermatozoa.

Cell Separation↗

PubMed1991

The use of an electric freezer in human semen banking.

The use of an electric freezer for cryostorage of human semen is described. A simple method for semen freezing in liquid nitrogen after dilution with 7.5% glycerol was used. Thawing for quality analysis revealed only a small decrease (10%) in post-thaw sperm motility (59 +/- 1.4 vs. 53 +/- 1.8%; mean +/- SE, n = 12, P less than 10(-5)) and 14% in post-thaw sperm vitality (85.0 +/- 1.3 vs. 72.9 +/- 1.8%). After the freezing process, the samples, three of each donor, were cryopreserved in a regular electric freezer which maintained temperatures in the range of -85 degrees C (+/- 2 degrees C). The samples were stored for 1 week, 2 and 6 months, thawed and then assayed for motility and vitality. No effect of storage was found for a period up to 2 months. An additional decrease of 17.2% in sperm motility and 18% in sperm vitality were noted only after 6 months of preservation. The final motility and vitality rates of these sperm samples were 44 +/- 2.4 and 60 +/- 3.0%, respectively. According to these results, in cases of sperm storage for limited periods, it is recommended to cryopreserve human semen by the use of a combination of freezing in liquid nitrogen and storage of the samples in an electric freezer at -85 degrees C.

Analysis of Variance↗

PubMed1991

The efficiency of cryopreserved semen versus fresh semen for in vitro fertilization/embryo transfer.

The efficiency of cryopreserved donor semen versus fresh donor semen in an in vitro fertilization/embryo transfer programme was evaluated. Thirty-nine in vitro fertilization/embryo transfer cycles were performed using fresh donor semen (group A) and 74 cycles were carried out using cryopreserved semen (group B). All patients underwent a uniform controlled ovarian hyperstimulation using high doses of human menopausal gonadotropins. Oocytes were retrieved transvaginally under ultrasound imaging. Semen (fresh or frozen-thawed) were prepared for insemination by a washing technique. Each ovum was inseminated with 500,000-600,000 motile spermatozoa. No significant difference was noted between the two groups regarding female age, duration of infertility, and number of ova retrieved per aspiration. Even though the fertilization rate in group B was significantly lower than in group A (55.5 +/- 3.8 vs 70.4 +/- 3.5, P = 0.008), pregnancy rates per embryo transfer were similar--39.3 and 38.5%, respectively.

Adult↗

PubMed1991

Prerequisites for successful human sperm cryobanking: sperm quality and prefreezing holding time.

Frozen-thawed donor semen was used in artificial inseminations and in vitro fertilization programs. Semen accepted for donation was characterized (mean +/- SE) by sperm concentration of 150 +/- 18.6 x 10(6)/mL, normal morphology of 57% +/- 1.4%, good progressive motility at 1 hour of 57% +/- 1.0%, and post-thaw motility of 45% +/- 1.0%. Delay of the freezing process for greater than 1 hour after semen delivery caused a deleterious effect to the freezability of sperm. The average monthly fecundability for the 1st 6 months after inseminations was 13.6%. This value decreased dramatically to 2.6% from the 7th month onward. In 74 IVF/embryo transfer (ET) cycles, the fertilization rate was 55.3% +/- 3.8%, pregnancy rate (PR) per ET was 39.6%, and the PR per woman was 42.8%.

Cryopreservation↗