The window for embryo transfer in oocyte donation cycles depends on the duration of progesterone therapy

In 192 oocyte donation cycles performed between January 1993 and July 1996, we examined the width of 'the window for embryo transfer' using standard hormonal replacement methods. All transfers were performed within 48 h of insemination. We varied the day of embryo transfer with regard to the initiation of progesterone therapy and, thus, the duration of endometrial exposure to progesterone and analysed the resulting pregnancy rates. Patients were divided into five groups (I-V) and embryo transfers were performed 2, 3, 4, 5 or 6 days following initiation of progesterone therapy. The number of pregnancies per transfer cycle achieved in groups I-V were 0 (0%), 3 (12%), 16 (40%), 29 (48.3%), and 10 (20.4%) respectively. The increased pregnancy rate in group III in comparison to group II is statistically significant (P < 0.03). Furthermore, the pregnancy rate in group IV (5 days of progesterone administration before embryo transfer) was significantly higher than in group V (6 days of progesterone administration before embryo transfer; P < 0.005). We also noted that, when embryos were transferred 4 or 5 days after initiation of progesterone therapy, the pregnancy rates were not significantly different between menopausal and cycling recipients (50% vs 43.7%). Our results indicate that the window for embryo transfer is dependent on duration of treatment with progesterone; it begins approximately 48 h after starting progesterone administration and lasts for approximately 4 days. The optimum period for transferring embryos at the 4- to 8-cell stage corresponds to cycle days 18 and 19. Transfers performed on the 17th and 20th days of the cycle can result in successful implantation, although the rates of implantation are highest when transfers are done on days 18 and 19.      

Patient-Related and Angiographic Predictors of Restenosis After Excimer Laser Coronary Angioplasty

Excimer laser coronary angioplasty (ELCA) is a useful technique for the treatment of selected complex coronary lesions. However, this technology has been limited by significant restenosis and, to date, predictors of restenosis after use of this device are not clearly defined. In order to determine predictors of restenosis after ELCA, 43 lesions presenting with restenosis (> 50% diameter stenosis) at angiographic follow-up were compared to 46 lesions without restenosis, based on patient-related, qualitative and quantitative angiographic parameters. Univariate analysis revealed 9 variables with at least a borderline (p < 0.15) significant relation to restenosis: (1) age (p = 0.0759), (2) proximal left anterior descending site (p = 0.074), (3) presence of a restenotic lesion (p = 0.104), (4) lesion length (p = 0.0034), (5) reference diameter of the treated vessel (p = 0.0076), (6) post laser minimal luminal diameter (MLD) (p = 0.1160), (7) post-procedural MLD (p = 0.0001), (8) post-procedural stenosis (p = 0.0250) and (9) total procedural gain (p = 0.0051). After entering stepwise logistic regression analysis, only 3 variables emerged as independent predictors of restenosis: treatment of a restenotic lesion (p = 0.0255), lesion length (p = 0.0291) and post-procedural MLD (p = 0.0007). Based on these data, we conclude that post-procedural MLD is the most important predictor of restenosis after ELCA. Lesion length and the treatment of restenotic lesions are also independently associated with an increased risk of restenosis after ELCA. Therefore, achieving the best possible luminal result at the time of the first intervention should be the goal of the procedure, especially when treating high restenosis risk lesions.     

The common 'thermolabile' variant of methylene tetrahydrofolate reductase is a major determinant of mild hyperhomocysteinaemia

Mild hyperhomocysteinaemia is a major risk factor for vascular disease and neural tube defects (NTDs), conferring an approximately three-fold relative risk for each condition. It has several possible causes: heterozygosity for rare loss of function mutations in the genes for 5,10-methylene tetrahydrofolate reductase (MTHFR) or cystathionine-&bgr;-synthase (CBS); dietary insufficiency of vitamin co-factors B6, B12 or folates; or homozygosity for a common 'thermolabile' mutation in the MTHFR gene which has also been associated with vascular disease and NTDs. We quantified the contribution of the thermolabile mutation to the hyperhomocysteinaemic phenotype in a working male population (625 individuals). Serum folate and vitamin B12 concentrations were also measured and their relationship with homocysteine status and MTHFR genotype assessed. The homozygous thermolabile genotype occurred in 48.4, 35.5, and 23.4% for the top 5, 10 and 20% of individuals repectively) ranked by plasma homocysteine levels, compared with a frequency of 11.5% in the study population as a whole establishing that the mutation is a major determinant of homocystein levels at the upper end of the range. Serum folate concentrations also varied with genotype, being lowest in thermolabile homozygotes. The MTHFR thermolabile genotype should be considered when population studies are designed to determine the effective homocysteine-lowering dose of dietary folate supplements, and when prophylactic doses of folate are recommended for individuals.      

New poly-imidazolium–triazole particles by CuAAC cross-linking of calix[4]arene bis-azide/alkyne amphiphiles – a prospective support for Pd in the Mizoroki–Heck reaction

A new imidazolium amphiphilic calix[4]arene with terminal acetylene fragments in the polar region was synthesized according to a two step scheme including regioselective chloromethylation of distal di-O-butyl calix[4]arene and subsequent interaction with 1-(hex-5-yn-1-yl)-1H-imidazole. The aggregation properties (CAC, the size and zeta potential of aggregates) of alkynyl calix[4]arene as well as of previously synthesized azidopropyl calix[4]arene and their 1 : 1 mixture were disclosed. Macrocycles with azide and alkyne fragments in the polar region were covalently cross-linked under CuAAC conditions in water. Successful cross-linking of molecules has been proven by IR spectroscopy and MALDI-TOF spectrometry. The obtained polymeric particles were studied both in solution and the solid state and the presence of submicron (∼200 nm) and micron (∼1–5 μm) particles with the prevalence of the latter was found. The average molecular weight of the polymer according to the static light scattering data was found to be 639 ± 44 kDa. The obtained polymeric imidazolium–triazole particles were tested as a support for Pd(OAc)₂ in the Mizoroki–Heck reaction carried out in both organic and water media. In both solvents (especially in water) the addition of imidazolium–triazole particles to Pd(OAc)₂ increased the conversion of 4-iodanisole. It was found that the ratio between the products (1,1 and 1,2-substituted ethylenes) changes drastically on going from DMF to water from 1 : 5 to 1 : 40 when using supported Pd(OAc)₂.

A new supramolecular approach to the formation of polytriazole–imidazolium particles, promising supports for catalysis, based on self-assembly of amphiphilic bis-azides and bis alkynes and their linkage using CuAAC is presented.