Infertility: Avoidance of triplet pregnancies by elective transfer of two good quality embryos

Attempts to increase the probability of a successful pregnancyin in-vitro fertilization (IVF) treatment by increasing thenumber of embryos transferred automatically also increase theprobability of multiple pregnancies and their attendant risks.Even where the number of transferred embryos is limited to amaximum of three as in this and other centres, there is a highincidence of twins and triplets. The question therefore ariseswhether the number of transferred embryos should be furtherlimited to a maximum of two in cases where the prognosis isotherwise good. The only objection to this idea is a possiblelowering of pregnancy rate. The present study set out to investigatethis question. No significant lowering of pregnancy rate wasfound, so that limiting the number of transferred embryos totwo where the prognosis is otherwise good has now become standardpractice in our centre. A good IVF prognosis was defined bythe following criteria: first attempt for IVF, less than 37years old, and good embryo development. From 183 patients fulfillingthese criteria, 80 agreed to the transfer of two embryos (group1) and 103 opted for a triple transfer (group 2). Patient characteristicsand embryology results were similar in the two groups. In group1, 34 patients (42.5%) became pregnant and in group 2, 50 (48.5%).This difference is not significant. Similarly, twin pregnancyrates in both groups were high; eight twin pregnancies (23.5%)in group 1 and 12 (24%) in group 2. For the triplet pregnancyrate of 18% (nine triplet pregnancies) in group 2, there wasobviously no parallel in group 1. After thawing about half ofthe cryopreserved embryos and subsequently replacing them, preliminarycumulative pregnancy rates of 52.5% in group 1 and 53.4% ingroup 2 were obtained. Future results from cryopreservationshould provide relatively better outcomes for group 1 sinceall the patients in this group had at least one embryo frozenand fewer embryos replaced in the fresh cycle.     

Selective aflatoxin B1-induced sister chromatid exchanges and cytotoxicity in differentiating B and T lymphocytes in vivo

The purpose of this study was to assess the genotoxic and cytotoxic effects of the fungal metabolite aflatoxin B1 (AfB1) on the developing immune system of the chick embryo, a model in vivo system. Of particular interest was the assessment of AfB1 -mediated selective toxicity toward developing B lymphocytes as compared to T lymphocytes. In vivo bromodeoxyuridine (BrdU) labelling of DNA was used to detect the induction of sister chromatid exchanges (SCE) in lymphocytes and to assess the progression of these cells through successive cell cycles. Cytotoxicity was also assessed by studying the entrance and maintenance of cells in mitosis (mitotic index). Graded doses of AfB1 (1.09–17.4 μ/g embryo) were applied to chick embryos of 18 days of incubation (Dl). Embryos also received two doses of BrdU at 3 mg/200 μ (3 hr apart) to provide continuous labelling of B and T lymphocyte replicating DNA. B and T lymphocytes were harvested 20 hr post-AfB1/BrdU exposure from the bursa and thymus, respectively, and were processed for cytogenetic analyses. AfB1 induced dose-related increases in SCE in B lymphocytes; this induction was 6- to 8-fold that of controls at the higher doses tested, AfB1 -mediated induction of SCE in T cells was just 2-fold that of controls at the highest dose tested. AfB1 reduced the progression of B cells and to a lesser extent T ceels through successive rounds of replication. Furthermore, AfB1 dramatically reduced the mitotic index of B cells but not of T cells. These data indicate both selective genotoxicity and cytotoxicity of AfB1 toward B cells in the late stage embryo. © 1993 Wiley-Liss, Inc.     

胎儿骨临床应用的研究(附40例报告)

本文报告了6～9个月胎儿长骨的化学成分的测定结果及其组织特点并与成人作了比较。自1985～1987年共进行了胎儿骨移植40例,随访38例,经4～20个月(平均10.3个月)的临床观察,证实胎儿骨移植后“爬行替代”快,骨诱导能力强,排斥反应不明显,笔者认为这些特点与胎骨的形态结构及化学成分有关。胎儿骨的采取和贮存简便,应用方便,易于推广和普及。     

Single top quality embryo transfer as a model for prediction of early pregnancy outcome

BACKGROUND: Single embryo transfer (particularly of a top quality embryo) is an excellent model to correlate embryo quality in terms of morphological criteria to early pregnancy. We investigated whether this model could provide us with more information on what happens after implantation in the first trimester of pregnancy. METHODS: The outcome of 370 consecutive single top quality embryo transfers in patients younger than 38 years was analysed for pregnancy and first-trimester pregnancy loss (FTPL) before 13 weeks of gestation. Analysis was done on each cohort of embryos from which the transferred top quality embryo was selected. Serum HCG levels were measured on day 8 and day 12 after day 3 embryo transfer. The HCG index was calculated as the level of HCG on day 12/HCG on day 8. RESULTS: The pregnancy rate after single top quality embryo transfer was 51.9%. This was independent of the patients' age. FTPL, however, appeared to be age dependent: 15.4% for the whole group, 9% in patients younger than 30 years and 19% in patients above 30 years. The pregnancy rate was 50% in IVF cycles and 52% in ICSI cycles; FTPL was 19% in IVF cycles and 10% in ICSI cycles. Multiple regression analysis showed that these differences originated from age differences between both populations rather than from technique-related factors. An HCG level >or=45 IU/l on day 12 was predictive for ongoing pregnancy with 75.6% sensitivity and 100% specificity; an HCG index >or=3.5 similarly predicted ongoing pregnancy with 72.3% sensitivity and 100% specificity. CONCLUSIONS: These data show that embryo selection for transfer on day 3 can be used as an excellent tool for prediction of pregnancy but not for prediction of FTPL. The pregnancy rate of a single top quality embryo is not related to age, whereas FTPL is age dependent.     

人植入前胚胎细胞凋亡的细胞化学检测

目的建立原位末端标记法(TdT-m ed iated n ick end labeling,TUNEL)检测人植入前胚胎凋亡征象的方法。方法取试管婴儿助孕技术后异常受精的3原核胚胎,于2~10细胞期进行固定,采用TUNEL法检测3原核胚胎中的凋亡征象。结果在发育正常和发育停滞胚胎中,未检测到凋亡征象;在20%有碎片的胚胎中检测到TUNEL阳性信号。结论采用TUNEL法可以有效检测人植入前胚胎中的凋亡征象,细胞碎片的出现可能与凋亡有关。     

Scanning and transmission electron microscopy of venous sphincters in the rat lung

The rat pulmonary microvasculature was studied using scanning and transmission electron microscopy of vascular corrosion casts and tissue sections. Special emphasis was placed on small pulmonary venous vessels. The shape of vascular casts was analyzed and interpreted concerning the wall composition of corresponding vessels studied in tissue sections. On the casts of pulmonary venules and small pulmonary veins, narrow or wider annular constrictions were regularly observed. Within these constrictions, marks of circularly running grooves were seen as an additional structural detail, which obviously mimic impressions of single or grouped smooth muscle cells. The depth of the constrictions varies; it may be more or less pronounced, occasionally narrowing down the luminal diameter to approximately 50%. These constrictions are caused by muscular sphincters. In tissue sections of small pulmonary veins, sphincter regions were identified as abruptly appearing single or grouped true smooth muscle cells. Smooth muscle cells may be arranged side by side in a group or bundle or even staked in two or three layers. Between the sphincter regions, the venous wall consists merely of endothelium and an accompanying connective tissue layer. The smooth muscle cells of a sphincter are regularly positioned between endothelial layer and elastic lamina. The smooth muscle cells next to the endothelium form myoendothelial junctions. Autonomic nerves near the sphincters were never seen. The venous sphincters described are suggested to be effective devices involved in blood flow regulation. Blood-borne substances or local tissue hormones might govern sphincter function. © 1992 Wiley-Liss, Inc.     

Developmental aspects of children's behavior and safety while cycling

OBJECTIVE: To examine children's competence while cycling, as demonstrated in mistakes in performance and failure to comply with safety rules. METHODS: Children in three age groups (8, 10, and 12 years) participated in a realistic yet simulated traffic environment. RESULTS: The boys' cycling speed increased steadily with age, while that of the girls increased from 8 to 10 but decreased at age 12. Most children had adequate motor control by age 10, and the youngest compensated for their less developed skills by cycling slowly and braking early at junctions. Serious mistakes, often related to the children's age and gender, consisted of the children failing to stop at signals or stopping too late, especially at short stopping range. CONCLUSIONS: There are considerable individual differences in children's cycling competence that are related to biological factors, such as age and gender, and psychological factors, such as rule compliance and choice of cycling speed.     

Morphometric categorization of the human oocyte and early conceptus

Morphometrical procedures were used to quantitatively evaluate human oocytes and embryos in an IVF programme. The metaphase II oocyte was an irregular 3.5 x 10(6) microns 3 sphere of 1.05 coefficient of form. The ooplasmic volume of 1.4 x 10(6) microns 3 was reduced by 10% by fertilization. The zona pellucida behaved as a stable and almost spherical envelope of 1.8 x 10(6) microns 3 volume and 17 microns thickness. Through the first three cleavages, mean blastomere reduces 28.5% volume per division, evolving from an irregular spherical shape with 0.9 coefficient of form to an ellipsoid (0.8) at the 8-cell stage. The coefficient of diversity between sister blastomeres progressively moved from 1.4 to 1.6 during the first two (2n) cleavages. The coefficient of diversity also increased at 3-cell (2.2) and 6-cell (2.6) asynchronous divisions. Morphologically abnormal embryos showed some morphometrical differences. Embryos which successfully implanted and progressed to birth showed a higher coefficient of diversity between sister blastomeres.     

Extrinsic versus intrinsic cues in avian paraxial mesoderm patterning and differentiation.

Somitic and head mesoderm contribute to cartilage and bone and deliver the entire skeletal musculature. Studies on avian somite patterning and cell differentiation led to the view that these processes depend solely on cues from surrounding tissues. However, evidence is accumulating that some developmental decisions depend on information within the somitic tissue itself. Moreover, recent studies established that head and somitic mesoderm, though delivering the same tissue types, are set up to follow their own, distinct developmental programmes. With a particular focus on the chicken embryo, we review the current understanding of how extrinsic signalling, operating in a framework of intrinsically regulated constraints, controls paraxial mesoderm patterning and cell differentiation.