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Biomedical subjects

A Revel

Publications and source records attributed to A Revel.

At least 19 recordsLinked to original sources
PubMed2006

Cumulative sum (CUSUM) analysis in the assessment of trainee competence in fetal biometry measurement.

OBJECTIVE: To determine the value of cumulative sum (CUSUM) analysis in assessing trainee proficiency in fetal biometry measurement. METHODS: Three primary healthcare doctors with no prior ultrasound training were recruited. Each trainee measured the fetal biparietal diameter (BPD), head circumference (HC), abdominal circumference (AC) and femur length (FL) on 100 consecutive pregnant women. The supervisor repeated the measurements. The CUSUM for each set of trainee measurements was calculated at a set failure rate of 10%. The point at which the graph fell below two consecutive boundary lines indicated the number of examinations required to achieve competence. RESULTS: The CUSUM graphs showed that the rate of learning measurement skills varied among the three trainees. The graph for the CUSUM series for BPD and HC measurement for all trainees fell below two consecutive boundary lines and remained there, indicating competence. The CUSUM series for AC measurement for two of the trainees indicated that competence was achieved; however, for the third trainee, while the graph fell below two consecutive boundary lines, indicating competence, it rose again, crossing two consecutive boundary lines. This indicated a loss of competence and the need for further training. FL measurements for the same trainee never fell below two consecutive boundary lines, indicating failure to achieve competence; the other two achieved competence, but failed to maintain it. CONCLUSIONS: CUSUM is a useful tool for identifying points of competence and for quantifying the duration of ultrasound training required for each trainee. It provides an early indication of performance, and highlights difficulties in individual performance.

Abdomen↗
PubMed2005

Oocyte recovery, embryo development and ovarian function after cryopreservation and transplantation of whole sheep ovary.

BACKGROUND: Successful cryopreservation of a whole ovary may provide a solution for women with premature ovarian failure. The aim of this study was to evaluate the function of cryopreserved whole sheep ovaries both in vitro and in vivo. METHODS: Transplantation of frozen-thawed intact ovaries was performed on eight sheep by artery and vein anastomosis to the contralateral ovarian artery and vein. The remaining ovary was removed. Oocyte aspiration was performed 1 and 4 months post-transplantation. Serum progesterone levels were measured after 24 and 36 months. Magnetic resonance imaging (MRI) was carried out 12 months after transplantation. RESULTS: Progesterone activity was detected in three sheep from 24 to 36 months post-transplantation. Oocyte retrieval was successful in two sheep and parthenogenic activation has resulted in embryonic development up to the 8-cell stage. MRI revealed an intact ovary with small follicles and intact blood vessels. CONCLUSIONS: Whole ovaries, and the follicles and blood vessels they contain, are able to survive cryopreservation. In addition, MRI has shown that blood vessels were intact and that normal blood flow had resumed to the transplant. We conclude that immediate and long-term hormonal restoration and normal ovulation is possible after cryopreservation and transplantation of whole ovaries in sheep.

Animals↗
PubMed2005

Treatment of recurrent IVF failure and human leukocyte antigen similarity by intravenous immunoglobulin.

This study sought to assess the efficacy of intravenous immunoglobulin (IVIg) in improving pregnancy rates and outcome, in a select group of patients with repeated IVF failure and human leukocyte antigen (HLA) similarity. Couples suffering from recurrent IVF failure, defined as at least seven attempts at embryo transfer with no successful implantations, who were found to share at least three HLA loci, and a negative cross-match test, were included in the study. The treatment consisted of two 30 g IVIg doses: one before oocyte retrieval, and a second as soon as a fetal pulse was identified on ultrasound. Ten couples comprised the study group. In total, these couples had undergone 98 IVF cycles with no successful pregnancies prior to initiation of the study. Following a total of 18 IVIg courses, seven women conceived, two women twice. Up to date, five women have delivered at least one live fetus, at 27 weeks or later. One woman is currently in the early third trimester of a twin pregnancy, and one woman had a late abortion at 19 weeks. The results suggest that couples with recurrent IVF failure and HLA similarity, may benefit from IVIg treatment.

Adult↗
PubMed2005

A hierarchy of associations in hippocampo-cortical systems: cognitive maps and navigation strategies.

In this letter we describe a hippocampo-cortical model of spatial processing and navigation based on a cascade of increasingly complex associative processes that are also relevant for other hippocampal functions such as episodic memory. Associative learning of different types and the related pattern encoding-recognition take place at three successive levels: (1) an object location level, which computes the landmarks from merged multimodal sensory inputs in the parahippocampal cortices; (2) a subject location level, which computes place fields by combination of local views and movement-related information in the entorhinal cortex; and (3) a spatiotemporal level, which computes place transitions from contiguous place fields in the CA3-CA1 region, which form building blocks for learning temporospatial sequences. At the cell population level, superficial entorhinal place cells encode spatial, context-independent maps as landscapes of activity; populations of transition cells in the CA3-CA1 region encode context-dependent maps as sequences of transitions, which form graphs in prefrontal-parietal cortices. The model was tested on a robot moving in a real environment; these tests produced results that could help to interpret biological data. Two different goal-oriented navigation strategies were displayed depending on the type of map used by the system. Thanks to its multilevel, multimodal integration and behavioral implementation, the model suggests functional interpretations for largely unaccounted structural differences between hippocampo-cortical systems. Further, spatiotemporal information, a common denominator shared by several brain structures, could serve as a cognitive processing frame and a functional link, for example, during spatial navigation and episodic memory, as suggested by the applications of the model to other domains, temporal sequence learning and imitation in particular.

Action Potentials↗
PubMed2004

In vitro maturation and fertilization of oocytes from an intact ovary of a surgically treated patient with endometrial carcinoma: case report.

Polycystic ovary syndrome (PCOS) with prolonged anovulation had resulted in endometrial carcinoma in a 43-year-old woman. Since she and her husband did not share common biological children, they requested fertility preservation. Due to the woman's age, high dose progesterone and postponing surgery were both considered inappropriate. We therefore proposed oocyte retrieval from the ovaries removed by staging laparotomy followed by in vitro maturation and ICSI. Surrogacy could then enable a future pregnancy. Fourteen of 17 (82%) retrieved oocytes matured in vitro. Following ICSI, eight embryos (two at the pronuclear stage and six cleaved) were cryopreserved. To the best of our knowledge, this is the first report of oocyte aspiration, maturation and fertilization from an ovary removed by laparotomy.

Adult↗
PubMed2004

Twin delivery following 12 years of human embryo cryopreservation: case report.

It is uncertain how long IVF units can keep frozen embryos. Few data exist on success of embryo transfer for embryos that have been cryopreserved for many years. We report the delivery of healthy twins following the transfer of embryos cryopreserved for 12 years. To the best of our knowledge, this is the longest reported successful human embryo freezing.

Adult↗
PubMed2002

From view cells and place cells to cognitive map learning: processing stages of the hippocampal system.

The goal of this paper is to propose a model of the hippocampal system that reconciles the presence of neurons that look like "place cells" with the implication of the hippocampus (Hs) in other cognitive tasks (e.g., complex conditioning acquisition and memory tasks). In the proposed model, "place cells" or "view cells" are learned in the perirhinal and entorhinal cortex. The role of the Hs is not fundamentally dedicated to navigation or map building, the Hs is used to learn, store, and predict transitions between multimodal states. This transition prediction mechanism could be important for novelty detection but, above all, it is crucial to merge planning and sensory-motor functions in a single and coherent system. A neural architecture embedding this model has been successfully tested on an autonomous robot, during navigation and planning in an open environment.

Animals↗
PubMed2002

Simplified artificial endometrial preparation, using oral estradiol and novel vaginal progesterone tablets: a prospective randomized study.

There are various successful protocols for artificial endometrial preparation, comprising induction of endometrial proliferation with estrogens and secretory transformation with progestins. The aim of this prospective randomized study was to evaluate a simplified approach for endometrial preparation, comparing two constant doses of oral estradiol combined with a novel low-dose vaginal natural progesterone preparation (100 mg Endometrin tablets). Twenty-nine patients were enrolled in the study and divided randomly into two groups. Both groups received oral estradiol tablets from the beginning of menstruation, group A (15 patients) receiving 4 mg/day divided into two doses of 2 mg each, and group B (14 patients) receiving 6 mg/day divided into three doses. Serum estradiol and progesterone and sonographic thickness of the endometrium were measured on the 1st day of menstruation and on the 6th, 11th, 16th and 21st days of the artificial cycle. Following the first 12 days of estradiol priming, with an endometrial thickness of > or = 8 mm, Endometrin vaginal tablets 100 mg were added twice a day for 10 days. On the 21st cycle day, an endometrial biopsy was taken from all patients using Pipelle. In all 29 patients, appropriate changes in estradiol, progesterone and endometrial thickness were observed. Estradiol levels were significantly higher in the 6 mg/day group on days 6 and 11, but no significant difference was noted in serum progesterone level and endometrial thickess between groups. Histological evaluation of endometrial biopsies, on the 21st day, revealed adequate late-secretory endometrium in 14/15 (93.3%) patients of group A and in 13/14 (92.9%) patients of group B. In conclusion, our results demonstrate that an appropriate endometrial secretory transformation may be induced using an economical regimen of fixed low-dose oral estradiol (4 mg/day) and low-dose vaginal progesterone tablets (Endometrin 100 mg twice daily).

Administration, Intravaginal↗
PubMed2001

Dioxins in adipose tissue of non-occupationally exposed persons in France: correlation with individual food exposure.

We evaluated individual adipose tissue (subcutaneous lipomas) dioxin contamination in non-occupationally exposed persons living in France (adult patients undergoing a surgical ablation of benign lipomas), in relation to the corresponding individually evaluated mean daily dietary dioxin intake (DDDI). The diet survey (questionnaire) included information on consumption of meat, fish, milk and dairy products, from which the individual DDDI was calculated. Sixteen subjects participated in this study. DDDI ranged between 1.06 and 3.31 pg I-TEQ/kg body weight, bw (mean value: 2.05+/-0.72). Adipose tissue polychlorinated dibenzo-p-dioxins (PCDD)/polychlorinated dibenzofurans (PCDF) levels ranged between 18.5 and 76.9 pg I-TEQ/g lipids (mean value: 35.6+/-14.8). No relation was found between the DDDI and adipose tissue PCDD/PCDF concentrations. The mean DDDI in France does not fundamentally differ from those found in other industrialised countries, is within the range of 1-4 pg I-TEQ/kg/day recently suggested by WHO-ECEH/ICPS for the tolerable daily intake of dioxins. Adipose tissue PCDD/PCDFs levels are similar to levels in other European countries and USA without relation to sex or age, and can be considered representative European background concentrations. Globalisation of alimentary production leads to a similar food exposure in Western European countries, in spite of dioxins accidental selective contaminations that are epiphenomenon and thus do not have any impact in human dioxin background levels.

Adipose Tissue↗
PubMed2000

Ovarian cortex cryopreservation in pediatric and adolescent medicine

Background: Increased pediatric/adolescent cancer survivor rates have enhanced awareness of long-term effects of therapy, specifically gonadal failure. Ovarian cortex cryopreservation may hold the promise of fertility for those at risk for ovarian failure due to medical therapy. The object of this study was to determine if an ovarian cryopreservation program is feasible and to define suitable candidates.Method: A MEDLINE search supplemented by bibliographies. The review was limited to English articles on ovarian failure rates following radiation and/or chemotherapy and on ovarian cryopreservation. Investigators in the field were consulted to identify other sources.Results: Approximately one third of postpubertal females exposed to chemotherapy or radiotherapy develop ovarian failure. The risk is mostly significant for patients exposed to pelvic radiotherapy (up to 32% decrease in fertility) and alkylating agent based chemotherapy (infertility in 22%). A ninefold increase in premature ovarian failure results from exposure to combined pelvic radiotherapy and alkylator based chemotherapy. Practically all patients exposed to multiple agent chemotherapy combined with pelvic radiotherapy at doses used in preparation for bone marrow transplant will undergo irreversible loss of ovarian function. Currently human ovarian cortex can be cryopreserved, thawed and stimulated with gonadotrophins to produce follicles when transplanted into immunosuppressed mice, however there has yet to be any human pregnancies. The immunosupressed mouse model could also serve as a test to determine whether the tissue carries metastatic risk prior to reimplantation into the donor.Conclusion: Based on the literature we propose ovarian cortex cryopreservation and banking for postpubertal females prior to chemotherapy and/or radiation therapy that holds a high risk of ovarian failure. In the future this may provide oocytes for reproductive purposes. A protocol is currently under approval by the Hospital for Sick Children's ethics committee.

Journal Article↗
PubMed1999

A flexible protocol for artificial preparation of the endometrium without prior gonadotropin-releasing hormone agonist suppression in women with functioning ovaries undergoing frozen-thawed embryo transfer cycles.

OBJECTIVE: To present our experience with a flexible and convenient protocol for artificial endometrial preparation without prior GnRH agonist suppression in patients with functioning ovaries undergoing frozen ET. DESIGN: Case series. SETTING: An IVF unit in a university hospital. PATIENT(S): All patients who underwent IVF with embryo cryopreservation from December 1997 to June 1998 and requested transfer of their frozen-thawed embryos. INTERVENTION(S): Controlled endometrial preparation for ET entailed the use of a fixed dose of 6 mg/d of micronized E2 started on day 1 of the cycle, followed by concomitant administration of micronized P placed in the vagina. MAIN OUTCOME MEASURE(S): Hormonal and endometrial profiles throughout the cycle, pregnancy rate per ET, implantation rate, and pregnancy outcome. RESULT(S): Of 185 treatment cycles in 140 patients, 8 cycles (4.3%) were canceled. In another 2 cycles, no embryos were suitable for transfer. For the remaining 175 ET cycles, the calculated pregnancy rate and implantation rate were 21.7% and 9%, respectively. The proliferative phase could be extended up to 20 days but was a mean (+/-SD) of 15+/-1.9 days. CONCLUSION(S): For patients with functioning ovaries, controlled endometrial preparation for the transfer of frozen-thawed embryos can be done successfully by using oral E2 from day 1 of the cycle followed by P preparation. Prior suppression with GnRH agonist is not necessary.

Adult↗
PubMed1998

Comparison of cryopreservation outcome following intracytoplasmic sperm injection and conventional in vitro fertilization.

PURPOSE: Our purpose was to compare the success rate of transferring frozen-thawed embryos generated from either intracytoplasmic sperm injection (ICSI) or conventional in vitro fertilization (IVF). METHODS: A retrospective review of all frozen-thawed embryo transfer (ET) cycles between January 1995 and April 1997 was performed. There were 83 and 204 transfer cycles of frozen-thawed multicellular embryos generated from conventional IVF (group A) and ICSI (group B), respectively. The survival rate of frozen-thawed embryos and the outcome following ET in both groups were assessed. RESULTS: The groups did not differ in age (31.7 +/- 4.6 and 30.6 +/- 6.0; mean +/- SD) or number of embryos transferred (3.5 +/- 1.1 and 3.8 +/- 1.3 for groups A and B, respectively). An acceptable pregnancy rate per ET was achieved in both groups, but the rate was significantly higher (P = 0.04) for group A than group B, 32.5 and 20%, respectively. Group A included frozen embryos of a higher quality than those of group B, but the proportion of embryos surviving after thawing was significantly higher for group B than group A (92.5 and 85.6%, respectively; P = 0.0004). The abortion rate did not differ between the two groups: 22 and 26.8% for groups A and B, respectively. CONCLUSIONS: Although an overall high pregnancy rate was achieved following frozen-thawed ET, it was lower for cycles in which embryos had been generated from ICSI. This difference may be attributed to a lower prefreezing embryo quality in the ICSI group. Embryos originating from ICSI were not vulnerable to cryopreservation and, when implanted, resulted in a comparable abortion rate to thawed embryos of conventional IVF.

Abortion, Spontaneous↗
PubMed1998

Young low responders protected from untoward effects of reduced ovarian response.

OBJECTIVE(S): To correlate fertilization and clinical pregnancy rates (PRs) in low responders with their E2 levels (<500, 500-800, >800-1,000 pg/mL), age (20-30, 31-40, >40 years), number of follicles, and number of oocytes retrieved. DESIGN: A retrospective study. SETTING: The IVF unit of an academic hospital. PATIENT(S): One hundred forty-three women who failed to attain E2 levels of 1,000 pg/mL on the day of hCG administration. INTERVENTION(S): Controlled ovarian hyperstimulation, blood E2 and progesterone measurements, ultrasonographic scanning of ovarian follicles, oocyte retrieval after hCG administration, and ET. MAIN OUTCOME MEASURE: Clinical PR. RESULT(S): Although E2 levels, fertilization rates, age, and number of oocytes did not differ significantly between the three age groups, the PR achieved in the youngest group was approximately three times as high (19.3%) as that achieved in the two older groups. CONCLUSION: Young low responders represent a unique subset in that their age protects them from the deleterious effects of poor ovarian response.

Adult↗
PubMed1998

The pathogenesis of ovarian hyperstimulation syndrome: a continuing enigma.

PURPOSE: Our purpose was to review the available literature concerning the pathogenesis of ovarian hyperstimulation syndrome and, in light of the most recent information, to attempt to provide further insight on this iatrogenic complication associated with the induction of ovulation. METHODS: Published studies related to this topic were identified through a computerized bibliographic search. CONCLUSIONS: The exact mechanism for the development of ovarian hyperstimulation syndrome is still obscure. It is well established that the syndrome is associated with the process of ovulation induced by either luteinizing hormone or human chorionic gonadotropin. Following ovulation, one or more substances produced by the ovary are liberated in excess, increasing capillary permeability, resulting in the clinical features of the syndrome. It may well be that the syndrome is not triggered by a single mechanism but by the production and secretion of several substances acting in concert. These may include prostaglandins, cytokines, the ovarian reninangiotensin system, vascular endothelial growth factor, and nitric oxide.

Capillary Permeability↗
PubMed1996

Human follicular nitric oxide pathway: relationship to follicular size, oestradiol concentrations and ovarian blood flow.

Nitric oxide (NO) has been suggested to be involved in ovarian physiology. Our aim was to study follicular nitrite and nitrate (NO3/NO2) levels in women undergoing in-vitro fertilization (IVF), and to examine their relationship to follicular size, oestradiol concentrations, and ovarian artery and intra-ovarian blood flow as measured by Doppler ultrasound. A total of 15 patients from the IVF programme of Hadassah University Hospital, Mt Scopus, Israel, participated in the study. Detailed transvaginal ultrasonographic examination was performed before ovum collection, and ovarian artery and intra-ovarian blood flow were measured. While aspirating the follicles, the content of two to four of the follicles in each ovary was collected individually, the volume of follicular fluid measured, and NO3/NO2 concentrations were determined. A statistically significant positive correlation was found between follicular fluid NO3/NO2 concentrations and follicular volume (r = 0.76), as well as between NO3/NO2 concentrations and oestradiol concentrations (r = 0.63). A statistically significant negative correlation was found between follicular fluid NO3/NO2 concentrations and ovarian flow parameters as well as between NO3/NO2 concentrations in follicles containing 4-5 ml and ovarian artery pulsatility index.

Adult↗
PubMed1996

Characterization of intraperitoneal cytokines and nitrites in women with severe ovarian hyperstimulation syndrome.

OBJECTIVE: To assess the potential involvement of cytokines and nitrites in the hyperpermeability characterizing the ovarian hyperstimulation syndrome (OHSS). DESIGN: A controlled clinical study comparing peritoneal fluid (PF) from patients with severe OHSS and from non-OHSS controls. SETTING: Women hospitalized with severe OHSS in three tertiary medical centers. PATIENTS: Twelve patients with severe OHSS necessitating paracentesis and 20 non-OHSS controls. INTERVENTIONS: The criteria for ultrasound-guided paracentesis were tense ascites, hydrothorax, hemoconcentration, or oliguria. MAIN OUTCOME MEASURES: Interleukin (IL) 1 beta IL-1 receptor agonist, IL-2, IL-6, IL-8, and tumor necrosis factor alpha (TNF alpha) levels in PF were assayed by ELISA; nitrites were measured by the "Griess" reaction. Estradiol and P were determined by RIA. RESULTS: Ovarian hyperstimulation syndrome patients had significantly higher PF IL-6 (3,523 versus 30 pg/mL), TNF alpha (14 versus 4.2 pg/mL), and IL-8 (1,695 versus 900 pg/mL). In the serum, only IL-6 levels were significantly higher (375 versus 11 pg/mL). Conversely, nitrite levels were significantly lower in PF of OHSS patients (0.5 versus 34 nmol/mL). Interleukin 1 levels were higher and IL-1 receptor antagonist levels were lower in OHSS patients, suggesting potentially increased biologic potency of IL-1. CONCLUSION: These findings suggest that these substances could be involved in mediating the capillary hyperpermeability characterizing this syndrome.

Ascitic Fluid↗