In most in-vitro fertilization (IVF)/intracytoplasmic sperm injection (ICSI) programmes approximately one ongoing pregnancy in three is multiple. The need to characterize embryos with optimal ...implantation potential is obvious. We retrospectively examined all of 23 double transfers resulting in ongoing twins, occurring between January 1, 1996 and May 19, 1997. Characteristics of these top quality embryos were absence of multinucleated blastomeres, four or five blastomeres on day 2, seven or more cells on day 3, and ≤20% anucleated fragments. In a subsequent series of 400 IVF/ICSI cycles (out of which 372 were selected for embryo transfer) from May 20, 1997 to July 31, 1998, only women <38 years of age had multiple pregnancies: after 221 transfers of two embryos, 45/116 (39%) were multiple, and after 77 transfers of >2 embryos, 11/31 (35%) were multiple. We applied our top quality criteria to the 221 double transfers: 106 transfers with two top embryos resulted in 65 (63%) ongoing pregnancies with 37 (57%) twins, 65 transfers with one top embryo in 38 (58%) ongoing pregnancies with eight (21%) twins. In the group without top embryos, 12/52 (23%) ongoing singletons occurred, with no twins. The corresponding ongoing implantation rates were 49, 35 and 12%. This analysis suggests that single embryo transfer with an acceptable pregnancy rate might be considered if a top quality embryo is available.
A prospective randomized study comparing single embryo transfer with double embryo transfer after in-vitro fertilization or intracytoplasmic sperm injection (IVF/ICSI) was carried out. First, top ...quality embryo characteristics were delineated by retrospectively analysing embryos resulting in ongoing twins after double embryo transfer. A top quality embryo was characterized by the presence of 4 or 5 blastomeres at day 2 and at least 7 blastomeres on day 3 after insemination, the absence of multinucleated blastomeres and <20% cellular fragments on day 2 and day 3 after fertilization. Using these criteria, a prospective study was conducted in women <34 years of age, who started their first IVF/ICSI cycle. Of 194 eligible patients, 110 agreed to participate of whom 53 produced at least two top quality embryos and were prospectively randomized. In all, 26 single embryo transfers resulted in 17 conceptions, 14 clinical and 10 ongoing pregnancies implantation rate (IR) = 42.3%; ongoing pregnancy rate (OPR) = 38.5% with one monozygotic twin; 27 double embryo transfers resulted in 20 ongoing conceptions with six (30%) twins (IR = 48.1%; OPR = 74%). We conclude that by using single embryo transfer and strict embryo criteria, an OPR similar to that in normal fertile couples can be achieved after IVF/ICSI, while limiting the dizygotic twin pregnancy rate to its natural incidence of <1% of all ongoing pregnancies.
Three cases of cervical pregnancy are described: the incidence, the diagnostic approach and different therapeutic managements used for this rare type of ectopic pregnancy are discussed. The last case ...shows that hysterectomy can be avoided by early diagnosis and by an adequate tamponing technique to control haemorrhage. For this purpose, a three-way Dufour catheter was successfully used to rinse the uterus with heated saline, allowing evacuation of intrauterine blood after curettage and to tampon the cervix.
Models for asymmetric [2+2] cycloadditions Houge, C; Frisque-Hesbain, A. M; Mockel, A ...
Journal of the American Chemical Society,
05/1982, Letnik:
104, Številka:
10
Journal Article
The chemical reactivity of a series of cephalosporins is examined as a function of the substituents at positions 3 and 7. In most cases, the nature of the C7 side chain has a minor influence on the ...beta-lactam reactivity. But in the case of amino-containing C7 substituents, when intramolecular nucleophilic attack may occur, the reactivity may be greatly increased. The spectroscopic and structural characteristics of the beta-lactam linkage do not correlate with the chemical reactivity of studied compounds. The hydrolysis rates are linked neither with the IR frequency or 13C NMR chemical shift of the carbonyl beta-lactam nor with the geometry of the beta-lactam ring. However, a relationship is confirmed between the beta-lactam ring opening rate and the polarity of the C3-C4 double bond, reflected in the different 13C NMR chemical shifts of those atoms. The results are an experimental verification of the theoretical calculations of Boyd et al. on cephalosporin model compounds, which foresee that a C3 substituent could favor the opening of the beta-lactam cycle by stabilizing a transition state involved in alkaline hydrolysis.
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