Intramolecular i-Motif Structures of Telomeric DNA

Abstract The i-motif is an intercalated structure formed by association in a head to tail orientation of two parallel duplexes whose strands are held together by hemiprotonated C·C(+) pairs. The i-motif may be formed by a single strand containing four cytidine repeats, by association of two strands containing two cytidine repeats or by four strands containing a single cytidine stretch. The repeated C-rich sequences of centromeric and telomeric regions can potentially fold into an intramolecular i-motif. We have investigated by NMR spectroscopy the structure of d(CCCTA(2)CCCTA(2)CCCTA(2)CCCT), a fragment of the vertebrate telomere. It includes an i-motif core of six intercalated C·C(+) pairs. At one end (the "top"), the central TA(2) linker loops across one of the narrow grooves, and the core is extended by base stacking in the loop. At the bottom, where the two other TA(2) linkers loop across the wide grooves, the NMR spectra reveal motions in the microsecond to millisecond scale. The pseudo-symmetry of the structure, which results in degenerate spectra and poor resolution, was broken by appropriate substitution of T by U and of C by 5-methylcytidine (5mC). This allowed us to solve the structure of d(CCCTA(2)5mCCCTA(2)CCCUA(2)CCCT). The motion is restricted to a flip of A18 around the glycosidic bond. Returning to the pseudo-symmetrical sequence, we find that each of the bottom loops switches between the structures of the first and third loops of the non-symmetrical sequence. We also analyzed the effects of the loop sequence and of the length of the C-stretches on the topology and stability of the intramolecular i-motif structure.

Invited review: Role of livestock in human nutrition and health for poverty reduction in developing countries

Livestock keeping is critical for many of the poor in the developing world, often contributing to multiple livelihood objectives and offering pathways out of poverty. Livestock keeping also affects an indispensable asset of the poor, their human capital, through its impact on their own nutrition and health. This paper outlines the linkages between livestock keeping and the physical well-being of the poor, and examines a number of commonly held beliefs that misrepresent livestock development issues related to these linkages. These beliefs limit the scope of intervention programs to promote livestock and limit their potential contribution to poverty reduction. Recognition of the complexity of the role livestock play in household decision-making and of the opportunities foregone due to these misconceptions can enhance the ability of livestock to contribute to human well-being in the developing world.

The new 4DDome prosthesis: an original light and partially absorbable composite mesh for hernia repair

INTRODUCTION

The use of non-absorbable meshes for the repair of inguinal hernias has become standard; however, these meshes have been associated with complications including long-term postoperative pain. To this end, a new partially absorbable composite mesh has been developed, and the aim of this study was to investigate its efficacy in animal and human trials.

MATERIALS AND METHODS

Sixty male Wistar rats were used to evaluate the behavior of the newly designed composite mesh. Composite meshes were implanted in the extra-peritoneal plane for 2, 4 and 8 weeks and compared to a standard polypropylene mesh. Forty patients with symptomatic inguinal hernias were treated using a new 4DDome designed prosthesis. Follow-up was by clinical and ultrasound examination at 1, 6 and 12 months.

RESULTS

The animal study demonstrated that the inflammatory reaction associated with the new composite mesh was significantly lower than a standard polypropylene mesh, characterized by a lower macrophage infiltrate (P < 0.001). The mesh did not shrink over the 8-week period, unlike the polypropylene mesh (P < 0.05). The human study showed that there were three minor postoperative complications, no recurrences and the mesh was well tolerated. Follow-up with serial ultrasound showed that at 10 days and 1 month the dome was clearly visible in position; however, by 6 months it had flattened out, been partially absorbed and become incorporated into the repair.

CONCLUSION

These experimental and clinical studies have validated the concept of the new 4DDome composite mesh. It was well tolerated and was associated with good short-term results. The combination of the dome shape and the new composite mesh means that less polypropylene is required and represents a significant advance in anterior hernia repair.

Value of human papillomavirus testing after conization by loop electrosurgical excision for high-grade squamous intraepithelial lesions

OBJECTIVE

The aim of the study was to evaluate human papillomavirus (HPV) testing during the follow-up of patients after conization by loop electrosurgical excision for high-grade squamous intraepithelial lesion.

METHODS

A prospective study was conducted on 205 patients who underwent conization for high-grade squamous intraepithelial lesion (CIN 2 or 3). Loop electrosurgical excision procedure (LEEP) was used in all cases. High-risk HPV testing was realized by the Hybrid Capture II system before and 3 months after conization.

RESULTS

Of the 205 patients, 193 (94.1%) were positive for the HPV test before conization. Seventy-one were HPV positive after conization (34.6%). The margins were positive in 36.1%. Residual disease was observed in 27 cases (13.2%). Four patients (2%) developed a recurrence after a mean follow-up of 18.1 months (+/-12). There was no correlation between pretreatment HPV testing and the residual disease or recurrence. Patients with positive margins were significantly more likely to have residual disease than those with negative margins (P < 0.0001). Residual disease was more likely to occur when the posttreatment HPV test was positive (P < 10(-7)). All recurrences were observed in patients with a positive posttreatment HPV test (P < 0.05). Residual disease and recurrence were correctly predicted with a sensitivity of 81 and 100%, respectively, and a negative predictive value of 96 and 100%.

CONCLUSION

Posttreatment HPV testing could be useful in the follow-up of patients after conization. In case of negative posttreatment HPV testing, the frequency of follow-up could be reduced, particularly in those patients with free margins.

Management of female genital mutilation in Djibouti: the Peltier General hospital experience

Female genital mutilation (FGM) is still performed on 98% of Djiboutian women. Infibulation (FGM type 3) is the most widely used method of FGM in Djibouti. Even though this operation is mutilating, illegal and sometimes results in death, it is still practiced at approximately the same rate as in the past. Mass immigration of African women to Europe, Canada, Australia and the United States in the past decade has brought the problems of FGM to these countries. Female genital mutilation is a problem unfamiliar to most Western obstetrician-gynecologists. A tight infibulation can be a high risk for the mother and fetus if not handled by a skilled operator. It can lead to an unnecessary cesarean section as a result of the fear of handling infibulated women. Therefore, Western physicians need to be informed. The aim of this article was to share our experience of FGM. It will focus on FGM in Djibouti, its types, epidemiology and health consequences. It will present the management of obstetric and gynecologic complications and discuss medico-legal and health service measures to combat these dangerous and unnecessary practices

[Contribution of ovarian and uterine color Doppler in medically assisted reproduction techniques (ART)]

Along the menstrual cycle and during pregnancy, small blood vessels proliferate within the uterus and the ovulating ovary. Angiogenic factors such as VEGF are involved in this phenomenon. In the ovulating ovary, neo-angiogenesis spreads progressively inside the dominant follicle wall and plays a role in the maintenance of the corpus luteum, under the influence of LH (or HCG during pregnancy). In ART, the measure of the blood flow is interesting since it correlates to the number and quality of harvested oocytes. Follicle hypoxia may impair chromosomal organization and separation within the oocyte. This neo-angiogenesis is also important in endometrium, in particular for embryo implantation. Ultrasounds with Doppler allow to estimate the endometrial receptivity, especially in IVF cycles. It is assumed that chance for ongoing pregnancy is almost zero if: endometrial thickness is < 8 mm; uterine pulsatility index (PI) is > 3. Doppler ultrasounds are a useful and even mandatory complement to standard vaginal ultrasonoghraphy in ART. It can be viewed as an indicator of the endometrial and follicular "well-being".

[Cytological history of 148 women presenting with invasive cervical cancer]

OBJECTIVES

The aim of this study was to analyse the cytological history of women presenting with invasive cervical cancer.

MATERIAL AND METHODS

Retrospective study of 148 patients treated for invasive cervical cancer in three hospitals of the North Pas de Calais in France.

RESULTS

The average age of patients was 49 (26-86). Squamous carcinomas represented 81% of cases (120/148), adenocarcinomas 17% (25/148) and adenosquamous carcinomas 2% (3/148). 36.5% of patients (54/148) had never had a Pap smear. 34.5% (51/148) had had an occasional Pap smear (the last one dated of more than three years). 8.1% (12/148) were lost for follow up after a positive Pap smear. 3.4% (5/148) were treated for cervical dysplasia less than three years before the diagnosis of the cervical cancer. 17.5% (26/148) had had a Pap smear reported as negative less than three years before the diagnosis of the cervical cancer. In this last group, squamous carcinomas represented 57.7% of cases (15/26), adenocarcinomas 38.5% (10/26) and adenosquamous carcinomas 3.8% (1/26). 18 Pap smears of 26 reported as negative less than three years before the diagnosis of the cancer were reviewed. These Pap smears came from 11 patients presenting with squamous carcinoma and seven other presenting with adenocarcinoma. After review, 15 Pap smears were reported as false negatives and two as true negatives. The review was not possible in one case.

CONCLUSION

In this study, the failures of cervical cancer screening were essentially attributed to the lack or the insufficiency of screening and the existence of false negatives of the cytology.

Assessment of Fallopian tube patency by HyCoSy: comparison of a positive contrast agent with saline solution

OBJECTIVE

To compare the efficiency of air-filled albumin microspheres (Infoson) with saline solution in determining Fallopian tube patency during hysterosalpingo contrast sonography (HyCoSy).

METHODS

This was a prospective randomized multicenter study with a sequential design. Over a 10-month period, 23 patients (mean age, 33 years) referred for infertility were examined by HyCoSy (saline or Infoson) before conventional hysterosalpingography (Iopamiron 370), performed during the same session. Contrast agents were administered through a 5-F Ackrad balloon catheter inserted transcervically into the uterine cavity. HyCoSy was performed with a 7-MHz transvaginal probe using both B-mode and color Doppler, and tubal patency was demonstrated by the appearance of contrast agent in the peritoneal cavity near the ovaries. Data were registered for each patient during the examination and the results were monitored by sequential analysis.

RESULTS

Mean volumes of contrast injections were 35.3 mL of saline, 14.4 mL of Infoson, and 13.8 mL of Iopamiron 370. Infoson-enhanced HyCoSy provided a significantly larger (P = 0.006) number of correct diagnoses (20/22 Fallopian tubes) than did saline HyCoSy (12/24 Fallopian tubes), and the same number as that achieved by hysterosalpingography.

CONCLUSION

A positive ultrasound contrast agent appears to be more efficient than saline solution at determining Fallopian tube patency in infertile women by means of HyCoSy, and as efficient as an iodinated contrast agent in the same population explored by HSG. HyCoSy could be used to screen infertile women, thereby avoiding the use of iodinated contrast medium and exposure to ionizing radiation during conventional HSG in patients with patent Fallopian tubes.

[Diagnosis of endometrial cancer]

Endometrial cancer, a hormone-related disease with unopposal hyperestrogenemia as one of its major risk factor is usually diagnosed during post menopausal bleeding. Pathologic examination after endometrial biopsy or curettage is mandatory for the diagnosis before any treatment. The 2 first line procedures in the work up are transvaginal ultrasound with colour Doppler and hysteroscopy. Currently, there is not any cost-effective screening test for the early detection of endometrial cancer.

Clinical and radiographic features of multiple epiphyseal dysplasia not linked to the COMP or type IX collagen genes

Multiple epiphyseal dysplasia (MED) is a mild chondrodysplasia affecting the structural integrity of cartilage and causing early-onset osteoarthrosis in adulthood. The condition is genetically heterogeneous. Mutations in the COMP gene and in two genes (COL9A2; COL9A3), coding respectively for the alpha2(IX) and alpha3(IX) chains of type IX collagen, can cause the autosomal dominant forms of MED. Mutations in the DTDST gene have recently been identified in a recessive form of MED. However, for the majority of MED cases, the genetic defect still remains undetermined. We report a three-generation family with an autosomal dominant form of MED, characterised by normal stature, joint pain in childhood and early-onset osteoarthrosis, affecting mainly the hips and knees. Based on discordant inheritance among affected individuals linkage of the phenotype to the COMP, COL9A1, COL9A2, COL9A3 genes was excluded. Our study provides evidence that at least another locus, distinct from COL9A1, is involved in autosomal dominant MED.

Imino proton exchange and base-pair kinetics in RNA duplexes

Using NMR magnetization transfer from water and ammonia-catalyzed exchange of the imino proton, we have measured the base-pair lifetimes and the dissociation constants of six RNA duplexes: [r(CGCGAUCGCG)](2), [r(CGCGAAUUCGCG)](2), [r(CCUUUCGAAAGG)](2), [r(CGCACGUGCG)](2), [r(GGU(8)CC).r(GGA(8)CC)], and [poly(rA).poly(rU)], and we compare them with those of their DNA homologues. As predicted by a two-state (closed/open) model of the pair, the imino proton exchange times decrease linearly vs. the inverse of catalyst concentration. As in DNA duplexes, base pairs open one at a time, and the kinetics is in most cases insensitive to the nature of the adjacent residues. The lifetime of the r(G.C) pairs, 40 to 50 ms, is longer than that of the equivalent in the corresponding oligodeoxynucleotides, and the dissociation constants, about 10(-)(7), are slightly smaller. The r(A.U) opening and closing rates are much larger than those of the d(A.T) pairs, but the stabilities are comparable.

Structure of a C-rich strand fragment of the human centromeric satellite III: a pH-dependent intercalation topology

Repetitive DNA sequences may adopt unusual pairing arrangements. At acid to neutral pH, cytidine-rich DNA oligodeoxynucleotides can form the i-motif structure in which two parallel-stranded duplexes with C.C(+) pairs are intercalated head-to-tail. The i-motif may be formed by multimeric associations or by intra-molecular folding, depending on the number of cytidine tracts, the nucleotide sequences between them, and the experimental conditions. We have found that a natural fragment of the human centromeric satellite III, d(CCATTCCATTCCTTTCC), can form two monomeric i-motif structures that differ in their intercalation topology and that are favored at pH values higher (the eta-form) and lower (the lambda-form) than 4.6. The change in intercalation may be related to adenine protonation in the loops. We studied the uridine derivative methylated on the first cytidine base, d(5mCCATTCCAUTCCUTTCC), whose proton spectrum is better resolved. The intercalation topologies are (C7.C17)/(5mC1.C11)/(C6.C16)/(C2.C12) for form lambda and (5mC1.C11)/(C7.C17)/(C2.C12)/(C6.C16) for form eta. We have solved the structure of the eta-form, and we present a model for the lambda-form. The switch from eta to lambda involves disruption of the i-motif. In both forms, the central AUT linker crosses the wide groove, and the first and the third linkers loop across the minor grooves. The i-motif core is extended in the eta-form by the inter-loop reverse Watson-Crick A3.U13 pair, whose dissociation constant is around 10(-2) at 0 degrees C, and in the lambda-form by the interloop T5.T15 pair. In contrast, d(5mCCATTCCTTACCTTTCC) folds into a pH-independent structure that has the same intercalation topology as the lambda-form. The i-motif core is extended below by the interloop T5.T15 pair and closed on top by the T8.A10 pair.Thus, the C-rich strand of the human satellite III tandem repeats, like the G-rich strand, can fold into various compact structures. The relevance of these features to centromeric function remains unknown.

The RNA i-motif

Oligodeoxynucleotides with stretches of cytidine residues associate into a four-stranded structure, the i-motif, in which two head-to-tail, intercalated, parallel-stranded duplexes are held together by hemiprotonated C.C+ pairs. We have investigated the possibility of forming an i-motif structure with C-rich ribonucleic acids. The four C-rich RNAs studied, r(UC5), r(C5), r(C5U) and r(UC3), associate into multiple intercalated structures at acidic pH. r(UC5) forms two i-motif structures that differ by their intercalation topologies. We report on a structural study of the main form and we analyze the small conformational differences found by comparison with the DNA i-motif. The stacking topology of the main structure avoids one of the six 2'-OH/2'-OH repulsive contacts expected in a fully intercalated structure. The C3'-endo pucker of the RNA sugars and the orientation of the intercalated C.C+ pairs result in a modest widening of the narrow grooves at the steps where the hydroxyl groups are in close contact. The free energy of the RNA i-motif, on average -4 kJ mol(-1) per C.C+ pair, is half of the value found in DNA i-motif structures.

The i-motif in nucleic acids

Seven years after the discovery of the DNA i-motif, partial explanations for its occurrence have been uncovered, possibly involving CHellipsisO hydrogen bonds across the narrow grooves. Investigations of its biological significance have been encouraged by the demonstration and description of the intramolecular i-motif structure of human telomeric and centromeric sequences, by the recent observation of an intercalated RNA structure and by the discovery of proteins that associate with DNA sequences carrying cytosine repeats. The compatibility of the intercalation with peptide and phosphorothioate DNA analogs is favorable for possible pharmaceutical applications.

The solution structure and internal motions of a fragment of the cytidine-rich strand of the human telomere

We present the solution structure of d(CCCTA2CCCTA2CCCTA2CCCT), a fragment of the vertebrate telomere which folds intramolecularly. The four cytidine stretches form an i-motif which includes six intercalated C.C+ pairs and terminates with the cytidines at the 5' extremity of each stretch. Above, the second TA2 linker loops across one of the narrow grooves, while at the bottom, the first and third linkers loop across the wide grooves. At 30 degrees C, the spectra of the first and third linkers are quasi-degenerate. Severe broadening at lower temperature indicates that this results from motional averaging between at least two structures of each bottom loop, and makes it impossible to solve the configuration of the bottom loops directly, in contrast to the rest of the structure. We therefore turned to the modified sequence d(CCCTA(2)5MCCCTA2CCCUA2CCCT) in which the two base substitutions (underlined) break the quasi-symmetry between linkers 1 and 3. The three loops follow approximately the hairpin "second pattern" of Hilbers. In the first loop, T4 is in the syn orientation, whereas its analog in the third loop, U16, oriented anti, is in a central location, where it interacts with bases of both loops, thus contributing to their tight association. The only motion is a syn/anti flip of A18 in the third loop. Returning to the telomere fragment, we show that each of the bottom loops switches between the structures identified in the first and third loops of the modified structure. The motions are concerted, and the resulting configurations of the bottom loop cluster present a bulge to either right (T4 syn) or left (T16 syn).

Positive margins after conization and risk of persistent lesion

OBJECTIVE

The aim of this study was to investigate a method to reduce the frequency of uterine reoperation with no persistent lesion and to identify factors predictive of persistent or recurrent lesions.

MATERIALS AND METHODS

Of 505 conizations performed by the same surgeon, 71 had positive margins (average patient age = 35.7 +/- 7.7 years). The patients underwent either immediate reoperation or monitoring with a Pap smear and colposcopy.

RESULTS

Histologic assessment of the cervical cone after conization showed positive margins in 14.1% of cases [endocervical and exocervical margins affected in 50 of 505 (9.9%) and 21 of 505 (4.2%) cases, respectively]. Of 59 of these patients (83.1%) who underwent follow-up monitoring over an average of 35.2 months (range: 2.6-180. 8), 12 patients (average age: 40.8 +/- 6.4 years) underwent immediate hysterectomy and 47 (average age 34.0 +/- 7.4 years) benefited from monitoring first [secondary discovery of 19 persistent lesions within 6 months and 9 recurrences within 18 months on average (range: 8.8-48 months)]. Of the 9 patients with recurrent lesions, 7 underwent reintervention and 2 monitoring. Of the 19 patients with persistent lesions, 18 underwent reintervention and 1 monitoring. Normal histology was observed in 29.4% of patients undergoing secondary reoperation for an abnormal smear compared with 66.7% of patients undergoing immediate reoperation (P = 0.04). Severity of lesion and age of patients could not be used to predict the incidence of a persistent or recurring lesion. Seventy-nine percent of conizations had positive endocervical margins in patients with a recurring or persistent lesion compared with 48% in patients with normal follow-up (P = 0.03).

CONCLUSION

Cytology and colposcopy follow-up in cases of positive conization margins may help to establish justification for the choice of reoperation, thereby limiting morbidity following repeated surgery.

[Electroconization with loop diathermy. A retrospective series of 307 cases]

The electroconization with diathermic loop is a good procedure in the cervical dysplasia because there is a respect of the cervical tissue with a low cost, low complications, easy and quickly technic and a precise histological analysis of the histologic specimen. The indications are represented by high grade lesions, cyto-histologic discordance and endocervical squamo-columnar junction with a low grade lesion. The authors proposed a retrospective study about 307 cases of the electroconization with diathermic loop realised between January 1993 and June 1998.

[Detection of human papillomavirus DNA by molecular hybridization in tube: interest in cervical neoplasia]

The presence of human papillomavirus (HPV) DNA in 79 cervical specimens obtained from 70 patients was studied by using a molecular hybridization technique performed in tube. The results were compared to those of the cytological and histological studies. The molecular hybridization technique in tube (Hybrid Capture I) detects two groups of HPV types. One group is highly associated with the development of cancer (types 16, 18, 31, 33, 35, 45, 51, 52, 56) whereas the second group (types 6, 11, 42, 43, 44) is not. Among 42 patients with cervical lesions before any treatment, high risk DNA of HPV was found in 50% of those with low grade cytology and 90% with high grade cytology. In total, 32 out of the 42 patients (76%) who presented histological lesions, were actually infected by HPV. Samples were obtained before and after treatment from 9 patients. Seven out of 9 presented high grade cervical intraepithelial neoplasia (CIN) and 2 other patients had low grade CIN. HPV DNA was not detected in any of the patients after treatment. Detection of HPV DNA by molecular hybridization in tube is simple, sensitive, standardized, inexpensive and is well adapted to screening programs. It can be used in complement of the cytological diagnosis, in the surveillance of equivocal cytological abnormalities, and in the follow-up of treated patients.

[Why we prefer the thin layer technique to conventional Pap smears. A double-blind study of 473 specimens]

The study evaluated the feasibility of a thinlayer technique on a routine basis for cervical smears and compared 473 ThinPrep preparations to the matched conventional Papsmears. The interpretation was double-blind and performed according to the Bethesda system. A consensus was established in discordant cases. The technique was easily mastered by gynecologists and technicians. Main advantages of the thinlayer technique were: a low number (1%) of unsatisfactory samples; a constant quality; homogeneity of cell distribution; the disappearance of problems of interpretation due to fixation or smear artifacts, red cells, polymorphs; a more precise interpretation, a firmer diagnosis; less visual fatigue; a shorter time of interpretation; the possibility of preparing more slides and performing special techniques on the same specimen. Main disadvantages were a higher cost and a necessary period of learning for cytologists.

Determination of the residence time of water molecules hydrating B'- DNA and B-DNA, by one-dimensional zero-enhancement nuclear Overhauser effect spectroscopy

The residence time of water in the minor groove of the d(CGCGAATTCGCG) duplex has been determined by a recent measurement combining nuclear Overhauser enhancements (NOE, ROE) and 17O relaxation dispersion. The time is in the range of nanoseconds, so that it may be measured by a rather simple method proposed here, namely the choice of conditions such that the NOE between the observed DNA proton and a nearby water proton is zero. This condition is realized when the residence time of the water molecule is 0.178 times the nuclear magnetic resonance period (e.g. 0.297 ns at 600 MHz). It may be achieved by varying the magnetic field and/or the temperature. The zero-NOE measurement may be performed by one-dimensional NMR, and has therefore good sensitivity. We have developed excitation sequences which suppress two spurious contributions to the NOE: from neighboring exchangeable protons and from H3' protons whose chemical shift is close to that of water. The method is applied here to the comparison of residence times of water next to B-DNA and next to B'-DNA, the latter corresponding to better stacked, propeller-twisted base-pairs and a correspondingly narrower minor groove. In the minor groove of [d(CGCGAATTCGCG)]2, a B'-DNA duplex, the residence time of the water molecule next to H2 of adenine(6) (underlined), is 0.6 ns at 10 degreesC, in good agreement with the value obtained previously. The residence time is slightly but distinctly shorter for the water next to A5, suggesting non-cooperative departure of these two molecules which are presumed to be part of the hydration spine. Near A5 and A4 of [d(AAAAATTTTT)]2, another B'-DNA duplex, the residence times are approximately twice as long, but the activation enthalpies are about the same, ca. 38 kJ/mol. The residence time in the minor groove of the regular B-DNA sequence d(CGCGATCGCG) was 0.3 ns at 10 degreesC, shorter than in the case of the B'-DNA sequences by factors of 2 and 4, respectively. The temperature dependence is less, with an activation enthalpy of 27 kJ/mol. The major groove residence times are comparable for the three sequences, and a few times shorter than those of minor groove water. A value of 0.36 ns, or even more in case of rotation of water, is obtained around -8 degreesC. The most striking aspect of these results is the relatively small difference in the residence times of reputedly fast and slow-exchanging water molecules bound to DNA in biological conditions. This suggests that the spine of hydration is perhaps not a major stabilizer of the B'-DNA structure as compared with B-DNA.

[The mechanisms of endometriosis]

Endometriosis is characterised by the presence in abnormal situation of a tissue resembling the endometrium with glands and stroma. Several assumptions try to explain the development of this tissue. The oldest, the theory of the metaplasia, suggests that under various influences the coelomic tissues would be transformed into endometrium. Most often agreed, the theory known as the implantation theory, explains why the endometrial cells and fragment desquamated during menstrual period transported through the fallopian tubes into the peritoneal cavity (physiological phenomenon) could under certain conditions implant, proliferate and develop overcoming the local mechanisms of defence. The peritoneal cavity of the normal women have the capacity to prevent the evolution towards endometriosis. The reasons of an evolution towards the endometriosis and its symptoms (pain, sterility, adherences are probably numerous implying the immune system, the endometrium, the macrophages, the cells natural killer, the peritoneum the fallopian tubes. The failure to removes the peritoneal cavity of the fragments would induce an inflammatory local state with hyperactivation of the macrophages which secrete many molecules, of which some could lead the metaplasia of the peritoneum or the development of müllerian residues.

[Diagnosis of an ectopic pregnancy on a cesarean scar]

We report the diagnostic and therapeutic debate raised by an ectopic pregnancy on a cesarean scar. There were three phases. The first was to differentiate between an ongoing abortion and an ectopic pregnancy on a cesarean scar. The second was to determine whether the tissue was a mass of persistent trophoblasts or an invasive mole. Finally to determine the nature of a residual mass after chemotherapy and normalization of the beta CG level.

[Importance of the study of the expression of MIB-1 (Ki-67) for the diagnosis of endocervical glandular lesions]

The morphological criteria for the diagnosis of endocervical atypia and dysplasia are variably defined. Diagnosis is difficult. MIB-1 (Ki-67) cell proliferation-associated antigen was detected retrospectively by immunohistochemistry in 230 cervical cone specimens. The percentage of MIB-1 positive cells was 1 to 25% (median 2%) and limited to small hot spots in normal and subnormal glands (140 cases). It was 1 to 30% (median 4%) in endometrioid metaplasia and microglandular hyperplasia (55 cases); 30 to 60 (median 40%) and limited to 1-3 glands in atypia (24 cases); 45 to 60% (median 50%) and diffusely distributed in dysplasia (5 cases). In situ (3 cases) and invasive (3 cases) adenocarcinomas were characterized by a high% (> 60) of MIB-1 positive cells.

[Color echo-Doppler and endometrial receptivity in in vitro fertilization]

The chances of nidation after in vitro fertilization procedures are contingent upon the development potential of the transferred embryo(s), but they also depend on the receptivity of the endometrium and on the uterine vascular supply. It is generally accepted that the chances of pregnancy are practically nil: if the endometrium is less than 8 mm thick, and/or if the uterine pulsatility index (PI) is below 3. However, the predictive value of the Doppler evaluation alone is poor to the extent that other parameters require consideration, such as the aspect of the endometrium and/or the number of embryos transferred. This is why our group initiated a prospective study on 213 patients designed to validate a 10 point scale based on: -the PI of each uterine artery on the day of transfer; -the features of the protodiastolic notch (absent, moderate or clearcut); -the thickness of the endometrium; -the number of embryos transferred. Each parameter by itself had a poor predictive value: optimal values of endometrium thickness and pulsatility index (PI) predicted a 29% and 33% pregnancy rate, which is hardly higher than our overall pregnancy rate (24%). By contrast, a score that encompasses all these parameters increased predictive value, with a score > 9 the probability of pregnancy reach 53% and the one of multiple pregnancy 24%. Our results emphasize the usefulness of a score prior embryo transfer which should be used to adjust the number of embryos transferred. When the score is higher than 10 transferring 2 embryos will prevent the risk of multiple pregnancy. 3 embryos should be transferred when the score is between 7 and 10, and a bad score (< or = 6) should delay the transfer.

[Adenomyosis and fertility]

Adenomyosis is a frequent pathology of the uterus for women over 40. Difficult to diagnose, adenomyosis can be responsible of pelvic pain and menorrhagia. Association with infertility is a rare event and the responsibility of adenomyosis is difficult to prove. A medical treatment with LHRH agonist can be propose to improve fertility in case of patent adenomyosis.

An intramolecular i-motif: the solution structure and base-pair opening kinetics of d(5mCCT3CCT3ACCT3CC)

We present a high-definition structure of d(5mCCT3CCT3ACCT3CC), a DNA sequence which resembles a four-times repeat of the C-rich strand of telomeres and centromeres. The structure is monomeric. The CC stretches form four hemi-protonated C.C base-pairs, belonging to two parallel-stranded duplexes which intercalate head-to-tail into an i-motif core. The four grooves of the core are similar to those observed previously in i-motif tetramers, with P-P distances around 0.9 nm and 1.4 nm for the narrow and wide grooves, respectively. At 0 degrees C, the structure is formed even at pH 7, despite the required protonation of cytidine pairs, suggesting that it may be biologically relevant.The intercalation topology of the i-motif core is read off the pattern of inter-residue cross-peaks along each groove: between H1' protons across the narrow grooves, and between amino and H2' protons across the wide grooves. In the hemi-protonated C.C pairs, the imino proton is shared equally between the two bases, as shown by the equal intensities of the NOESY cross-peaks between the imino proton and the two cis amino protons of the pair. Short inter-sugar distances and the direction of CH1' bonds are consistent with CH1'...O4' hydrogen bonds across the narrow grooves, as suggested by Berger et al. (1996). Proc. Natl. Acad. Sci. USA, 93, 12116-12121. At one extremity of the i-motif core, the T3A linker loops across one of the two wide grooves. It extends the core by stacking of A11, which also forms a strongly propeller-twisted reverse-Hoogsteen pair with T8. At the other extremity, the two T3 linkers loop side by side across the two narrow grooves, extending the core by stacking of a T5.T16 pair which connects the two linkers. In this T.T pair between parallel strands, the hydrogen bonds are from imino proton to O4, and the base-pair lifetime is 6 ms at 0 degrees C. The structures of segments 1 to 7 and 12 to 18, which form the i-motif core and the T3 loops, are related by a 2-fold pseudo-symmetry: the geometries and environment are so similar that the NOESY spectra are barely resolved. These various interactions illustrate how linker sequences may affect the stability, intercalation topology and folding pattern of the intramolecular i-motif.

Internal motions of nucleic acid structures and the determination of base-pair lifetimes

Over the years, imino proton exchange measurements have provided a description of base-pair opening and of properties of internal motions of nucleic acids such as the individual opening of base pairs and the insensitivity of base-pair lifetimes to the nature and stability of neighboring pairs. A recent determination of base-pair lifetimes in d(CGCGATCGCG) conflicts with the original measurements and their interpretation. This question is analyzed in the present work. We emphasize the importance of high concentrations of exchange catalyst (eg 1 M NH3) for the accurate determination of base-pair lifetimes. These concentrations entail a high ionic strength, which can lead to aggregation, enhanced magnetic relaxation and underestimation of base-pair lifetimes if exchange is measured by its effect on the proton relaxation rate. Magnetization transfer which provides a more direct method for the measurement of proton exchange rates is therefore preferred. We show that the lack of measurements at high catalyst concentration is responsible for the discrepancy mentioned above. Measurements by the magnetization transfer method validate the original interpretation and inversion recovery experiments illustrate the effect of the ionic strength on the relaxation rate of the imino protons.

Solution structure and base pair opening kinetics of the i-motif dimer of d(5mCCTTTACC): a noncanonical structure with possible roles in chromosome stability

BACKGROUND

Repetitive cytosine-rich DNA sequences have been identified in telomeres and centromeres of eukaryotic chromosomes. These sequences play a role in maintaining chromosome stability during replication and may be involved in chromosome pairing during meiosis. The C-rich repeats can fold into an 'i-motif' structure, in which two parallel-stranded duplexes with hemiprotonated C.C+ pairs are intercalated. Previous NMR studies of naturally occurring repeats have produced poor NMR spectra. This led us to investigate oligonucleotides, based on natural sequences, to produce higher quality spectra and thus provide further information as to the structure and possible biological function of the i-motif.

RESULTS

NMR spectroscopy has shown that d(5mCCTTTACC) forms an i-motif dimer of symmetry-related and intercalated folded strands. The high-definition structure is computed on the basis of the build-up rates of 29 intraresidue and 35 interresidue nuclear Overhauser effect (NOE) connectivities. The i-motif core includes intercalated interstrand C.C+ pairs stacked in the order 2*.8/1.7*/1*.7/2.8* (where one strand is distinguished by an asterisk and the numbers relate to the base positions within the repeat). The TTTA sequences form two loops which span the two wide grooves on opposite sides of the i-motif core; the i-motif core is extended at both ends by the stacking of A6 onto C2.C8+. The lifetimes of pairs C2.C8+ and 5mC1.C7+ are 1 ms and 1 s, respectively, at 15 degrees C. Anomalous exchange properties of the T3 imino proton indicate hydrogen bonding to A6 N7 via a water bridge. The d(5mCCTTTTCC) deoxyoligonucleotide, in which position 6 is occupied by a thymidine instead of an adenine, also forms a symmetric i-motif dimer. However, in this structure the two TTTT loops are located on the same side of the i-motif core and the C.C+ pairs are formed by equivalent cytidines stacked in the order 8*.8/1.1*/7*.7/2.2*.

CONCLUSIONS

Oligodeoxynucleotides containing two C-rich repeats can fold and dimerize into an i-motif. The change of folding topology resulting from the substitution of a single nucleoside emphasizes the influence of the loop residues on the i-motif structure formed by two folded strands.

Structure and conversion kinetics of a bi-stable DNA i-motif: broken symmetry in the [d(5mCCTCC)]4 tetramer

At slightly acidic pH, protonation of C-rich oligomers results in the formation of a four-stranded structure composed of two parallel duplexes in a head to tail orientation with their hemi-protonated C.C+ pairs intercalated in a so-called i-motif. In all cases reported previously the duplexes are identical. The tetramer formed by the d(5mCCTCC) oligomer is different. The structure is computed on the basis of 55 inter-residue distances derived from NOESY cross-peaks measured at short mixing times. It consists of two intercalated non-equivalent symmetrical duplexes. The base stacking order is C5* C1 C4* C2 (T3*) T3 C2* C4 C1* C5, but the thymidine bases (T3*) of one duplex are looped out and lie in the wide grooves of the tetramer. The thymidine bases T3 stack as a symmetrical T.T pair between the sequentially adjacent C2.C2+ pair and the C2*.C2*+ pair of the other duplex. Numerous exchange cross-peaks provide evidence for duplex interconversion. The interconversion rate is 1.4 s-1 at 0 degree C and the activation energy is 94 kJ/mol. The opening of the T3.T3 pair, the closing of the T3*.T3 pair, and the opening of the C2*.C2*+ pair occur simultaneously with the duplex interconversion. This suggests that the concerted opening and closing of the thymidine bases drive the duplex interconversion. Opening of the C4.C4+ and C4*.C4*+ pairs, and dissociation of the tetramer are not part of the interconversion since they occur at much slower rates. Duplex interconversion within the [d(5mCCTCC)]4 tetramer provides the first structural and kinetics characterization of broken symmetry in a biopolymer. The tetramer formed by d(5mCCUCC) adopts a similar structure, but the rate of duplex interconversion is faster: 40 s-1 at 0 degree C. At 32 degrees C, interconversion is fast on the NMR time scale.

Inability of RNA to form the i-motif: implications for triplex formation

At slightly acidic or even neutral pH, oligodeoxyribonucleotides which include stretches of cytidines form a tetrameric structure involving C.C+ base pairs in a so-called i-motif. Such a structure, which is very stable at pH 6, is still detectable at neutral pH. This motif, whether intramolecular or intermolecular, was shown to act as an undesired, competing structure for triplex formation. Depending on the sequence and the experimental conditions, triple helix formation was inhibited or completely abolished. Thus, the sequence recognition repertoire of pyrimidine DNA third strands is more restricted than previously admitted; only T.A rich-oligopurine-oligopyrimidine sequences are amenable to triplex formation. On the other hand, cytosine-rich RNA oligoribonucleotides and their 2'-O-methyl derivatives were unable to form a stable autoassociated structure above pH 6. Concomitantly, they were shown to form a triplex with (C.G)-rich targets at pH 6. Thus, not only was the affinity for the duplex increased by DNA to RNA substitution, but the possibility of formation of an inactive form of the third strand was greatly reduced. Thus, i-motif formation is favored for cytosine-rich oligodeoxynucleotides, whereas triplex formation is favored for oligoribonucleotides. These properties make RNA pyrimidine oligonucleotides an attractive choice for triplex formation on a (C.G)-rich target, extending the practical sequence repertoire of pyrimidine triplexes to (C.G*C+)-rich sequences.

Acid-induced exchange of the imino proton in G.C pairs

Acid-induced catalysis of imino proton exchange in G.C pairs of DNA duplexes is surprisingly fast, being nearly as fast as for the isolated nucleoside, despite base-pair dissociation constants in the range of 10(-5) at neutral or basic pH. It is also observed in terminal G.C pairs of duplexes and in base pairs of drug-DNA complexes. We have measured imino proton exchange in deoxyguanosine and in the duplex (ATATAGATCTATAT) as a function of pH. We show that acid-induced exchange can be assigned to proton transfer from N7-protonated guanosine to cytidine in the open state of the pair. This is faster than transfer from neutral guanosine (the process of intrinsic catalysis previously characterized at neutral ph) due to the lower imino proton pK of the protonated form, 7.2 instead of 9.4. Other interpretations are excluded by a study of exchange catalysis by formiate and cytidine as exchange catalysts. The cross-over pH between the regimes of pH-independent and acid-induced exchange rates is more basic in the case of base pairs than in the mononucleoside, suggestive of an increase by one to two decades in the dissociation constant of the base pair upon N7 protonation of G. Acid-induced catalysis is much weaker in A.T base pairs, as expected in view of the low pK for protonation of thymidine.

Terminal base pairs of oligodeoxynucleotides: imino proton exchange and fraying

We have estimated the dissociation constant of the terminal base pairs of the B-DNA duplexes formed by 5'-d(CGCGATCGCG) and 5'-d(TAGCGCTA) by two methods, one based on the change in imino proton chemical shift with temperature and the other on the apparent pK shift of the imino proton, as monitored by the change in chemical shift of aromatic protons. These methods do not rely on imino proton exchange, whose rate was also measured. (1) The effect of ammonia on the imino proton exchange rate of the terminal pair of the 5'-d(CGCGATCGCG) duplex is 67 times less than on the isolated nucleoside. This provides an upper limit on the exchange rate from the closed pair. In fact, the effect is just as predicted from the dissociation constant, assuming that there is no exchange at all from the closed pair and that, as has been argued previously, external catalysts act on the open state as they do on the isolated nucleoside. The inhibition of catalyzed proton exchange in the closed pair, despite exposure of one face of the pair to solvent, is a new feature of the exchange process. It will allow determination of the dissociation constant of terminal pairs from the exchange rate. (2) Intrinsic catalysis of proton exchange is less efficient for the terminal pair than for an internal one. A possible explanation is that proton transfer across the water bridge responsible for intrinsic catalysis is slower, as expected if the open-state separation of the bases is larger in a terminal pair. This observation may lead to a direct method for the study of fraying. (3) At 0 degrees C, the dissociation constant of the second pair of the 5'-d(CGCGATCGCG) duplex is close to the square of the constant for the terminal pair, as predicted from a simple model of fraying. The enthalpy and entropy of opening of the terminal pairs may be compared with those of nearest neighbor interactions derived from calorimetry [Breslauer, K. J., et al. (1986) Proc. Natl. Acad. Sci. U.S.A. 83, 3746-3750].

Hydration and solution structure of nucleic acids

Of particular interest among the revelations from recent new DNA structures is the finding that both strands of the repeated DNA sequences found in telomeres and centromeres may adopt alternative conformations. High-definition NMR studies yielded information on the residence time of the water molecules interacting with nucleic acids. A better knowledge of the residence time of the hydration water may be useful in assessing its contribution to nucleic acid structure.

[Breast feeding: which contraceptive method?]

Contraception during breast feeding must take two points into account: the first physiological contraception due to anovulation which disappears at around the 9th week of lactation); the second pharmacological: any substance ingested by the mother during breast feeding is excreted in milk, chiefly by passive diffusion. All pharmacokinetic studies have shown that the transfer of progesterone or of estrogen when taking a contraceptive pill is extremely slight, being of the same order as that of natural hormones. When it is decided to use hormonal contraception, this should be started after the 6th week of lactation, when lipid profile has returned to normal and thromboembolic risk is identical to that of the population in general. As with all prescription during lactation, the drug should be taken as far as possible from the next feed. Barrier techniques (combining condoms and spermicides) are an elegant alternative to drug methods.

Solution structures of the i-motif tetramers of d(TCC), d(5methylCCT) and d(T5methylCC): novel NOE connections between amino protons and sugar protons

BACKGROUND

At slightly acid or even neutral pH, oligodeoxynucleotides that include a stretch of cytidines form a tetramer structure in which two parallel-stranded duplexes have their hemi-protonated C.C+ base pairs face-to-face and fully intercalated, in a so-called i-motif, first observed serendipitously in [d(TC5)]4.

RESULTS

A high-definition structure of [d(TCC)]4 was computed on the basis of inter-residue distances corresponding to 21 NOESY cross-peaks measured at short mixing times. A similarly defined structure of [d(5mCCT)]4 was also obtained. A small number of very characteristic (amino proton)-(sugar proton) cross-peaks entails the intercalation topology. The structure is generally similar to that of [d(TC5)]4. The sequence d(T5mCC) forms two tetramers in comparable proportions. The intercalation topologies are read off the two patterns of (amino proton)-(sugar proton) cross-peaks: one is the same as in the d(TCC) tetramer, the other has the intercalated strands shifted by one base, which avoids the steric hindrance between the methyl groups of the 5mC pairs of the two duplexes.

CONCLUSIONS

The structures obtained in this work and the procedures introduced to characterize them and to solve the problems linked to the symmetry of the structure provide tools for further exploring the conditions required for formation of the i-motif.

Intramolecular folding of a fragment of the cytosine-rich strand of telomeric DNA into an i-motif

In the recently discovered i-motif, four stretches of cytosine form two parallel-stranded duplexes whose C.C+ base pairs are fully intercalated. The i-motif may be recognized by characteristic Overhauser cross-peaks of the proton NMR spectrum, reflecting short H1'-H1' distances across the minor groove, and short internucleotide amino-proton-H2'/H2" across the major groove. We report the observation of such cross-peaks in the spectra of a fragment of the C-rich telomeric strand of vertebrates, d[CCCTAA]3CCC. The spectra also demonstrate that the cytosines are base-paired and that proton exchange is very slow, as reported previously for the i-motif. From UV absorbance and gel chromatography measurements, we assign these properties to an i-motif which includes all or nearly all the cytosines, and which is formed by intramolecular folding at slightly acid or neutral pH. A fragment of telomeric DNA of Tetrahymena, d[CCCCAA]3CCCC, has the same properties. Hence four consecutive C stretches of a C-rich telomeric strand can fold into an i-motif. Hypothetically, this could occur in vivo.

Acid multimers of oligodeoxycytidine strands: stoichiometry, base-pair characterization, and proton exchange properties

The structure recently proposed for the acid form of the oligonucleotide 5'-d(TC5) is a four-strand "tetrad" in which two parallel-stranded, base-paired duplexes are intimately associated, with their hemiprotonated C-C+ base pairs face-to-face and fully intercalated, in a so-called "i-motif" (Gehring et al., 1993). We use the amino and imino proton spectra to establish the structure and symmetry of the base pairs, properties which are a primary element in the resolution of the acid form describe above. The amino proton spectrum gives the best lower limit (8 x 10(4) s-1) on the rate of the imino proton jumping process which is responsible for the base-pair symmetry. The stoichiometry of the acid form of other deoxycytidine sequences is studied by gel filtration chromatography and in one case by an NMR equilibrium titration. In all cases, i.e., d(C12), d(T2C8T2), d(C4TC4), d(TC5), d(C5), d(C4), d(TC4), d(TC3T), and d(TC3), the acid form elutes as a tetramer. A single-strand component is also present in some cases. But no dimer is observed, except for some samples prepared by quenching from high temperatures. The characteristic H1'-H1' interresidue NOESY cross-peaks of the d(TC5) structure (Gehring et al., 1993) are also found in all the tetramers where they have been searched for, i.e., those of d(T2C8T2), d(C4TC4), d(TC3T), and d(TC3) (not shown), suggesting that these tetramers also are built on the i-motif and that such structures may be formed generally by strands containing a stretch of as little as three deoxycytidines. From the NMR titration of d(TC3), we derive a free energy of -7.6 kJ/mol per cytidine base pair for the formation of the tetramer from single strands. The free energy released by packing a base pair into the i-motif is comparable to that released in forming the base pair itself. Imino proton exchange is limited by base-pair opening, thanks to efficient intrinsic exchange catalysis: this explains the lack of effect of added catalysts. The base-pair lifetime is hundreds of times longer than in any DNA duplex, presumably due to the base-pair intercalation geometry. The variation of the lifetime along the sequence of the d(TC5) tetramer provides support for the recently proposed structure. The internal amino proton exchanges from the open state of the C-C+ pair, at a rate compatible with a pK of 9 appropriate for C+. But the external proton exchanges from the closed state, as with a pK of 17!(ABSTRACT TRUNCATED AT 400 WORDS)

A tetrameric DNA structure with protonated cytosine.cytosine base pairs

Oligomers containing tracts of cytidine form hemiprotonated base pairs at acid pH and have been considered to be double-stranded. We have solved the structure of the DNA oligomer 5'-d(TCCCCC) at acid pH and find that it is a four-stranded complex in which two base-paired parallel-stranded duplexes are intimately associated, with their base pairs fully intercalated. The relative orientation of the duplexes is antiparallel, so that each base pair is face-to-face with its neighbours. The NMR spectrum displays only six spin systems, showing that the structure is highly symmetrical on the NMR timescale; the four strands are equivalent. A model derived by energy minimization and constrained molecular dynamics shows excellent compatibility with the observed nuclear Overhauser effects (NOEs) particularly for the very unusual inter-residue sugar-sugar NOEs H1'-H1', H1'-H2" and H1'-H4'. These NOEs are probably diagnostic for such tetrameric structures.

Proton exchange in DNA-luzopeptin and DNA-echinomycin bisintercalation complexes: rates and processes of base-pair opening

Imino proton exchange studies are reported on the complexes formed by bisintercalation of luzopeptin around the two central A.T pairs of the d(CCCATGGG) and d(AGCATGCT) duplexes and of echinomycin around the two central C.G pairs of the d(AAACGTTT) and d(CCAAACGTTTGG) duplexes. The depsipeptide backbone of the drugs occupies the minor groove of the complexes at the bisintercalation site. The exchange time of the amide protons of the depsipeptide rings provides a lower estimate of the complex lifetime: 20 min at 15 degrees C for the echinomycin complexes and 4 days at 45 degrees C for the luzopeptin complexes. The exchange time of imino protons is always shorter than the complex lifetime. Hence, base pairs open even within the complexed oligomers. For the two base pairs sandwiched between the aromatic rings of the drug, the base-pair lifetime is strongly increased, and the dissociation constant is correspondingly reduced. Hence, the lifetime of the open state is unchanged. This suggests similar open states in the free duplex and in the complex. In contrast to the sandwiched base pairs, the base pairs flanking the intercalation site are not stabilized in the complex. Thus, the action of the bisintercalating drug may be compared to a vise clamping the inner base pairs. Analysis suggests that base-pair opening may require prior unwinding or bending of the DNA duplex.

Proton exchange and internal motions in two chromomycin dimer-DNA oligomer complexes

Previous structural studies on the complexes of the chromomycin (CHR) dimer with duplexes of d(A1-A2-G3-G4-C5-C6-T7-T8) and of d(A1-G2-G3-A4-T5-C6-C7-T8) in solution [one Mg(II) and two drugs per duplex] are extended to hydrogen exchange measurements. Exchange of the OH8 proton of chromomycin, measured by real time proton-deuterium exchange, is very slow and requires dissociation of the complex, whose lifetime is thus determined. The lifetimes and apparent dissociation constants of base pairs are deduced from the catalysis of imino proton exchange by ammonia. The four central base pairs, which interact with the CHR chromophores in the minor groove (Gao & Patel, 1990), may open within the complex, but the opening rate is less than in the free duplex by one to two orders of magnitude. The activation energy for base-pair opening and the differences between the lifetimes of adjacent pairs suggest that single base-pair opening is the predominant imino proton exchange pathway in all cases. In the symmetrical complex of chromomycin with the first duplex, the lifetimes of the central base pairs (G3.C6 and G4.C5) are in the same range (52 and 29 ms, respectively, at 38 degrees C). In the asymmetrical complex formed with the second duplex, the base-pair lifetimes in the G2-G3-A4-T5 segment that interacts with the chromophore moiety are strongly increased. That of G3.C6 is particularly long. Above 50 degrees C, exchange of the G3 imino proton is opening limited.(ABSTRACT TRUNCATED AT 250 WORDS)

[Obstetrical anesthesia of patients with disseminated lupus erythematosus]

The anaesthetic management of pregnant women who suffered from systemic lupus erythematosus (SLE) was reviewed retrospectively. During the ten-year period studied, there were nineteen pregnancies in eighteen women (mean age 27 years) who had either SLE or an isolated lupus type anticoagulant (LAF). Four pregnancies were stopped before the third trimester, two spontaneously, and the other two because of the mother's condition. Of the fifteen remaining pregnancies, eight children were born with a weight less than 2,500 g. One child, birth weight 750 g, died after three days. None of the fourteen living children had neonatal lupus. Six epidural and twelve general anaesthetics were carried out for four abortions, nine Caesarian sections, and five deliveries. Epidural anaesthesia was often contraindicated by neurological and haemostatic complications of the SLE: recent meningitis, thrombocytopaenia, prolonged bleeding, anticoagulant therapy. In fact, management of SLE patients required extensive preanaesthetic clinical and paraclinical assessment, as all the systems may be involved in this condition; moreover, it may worsen during pregnancy (seven times in this series). The most frequent complications were cardiovascular, renal, and haematological. Possible intubation difficulties must also be looked for. A LAF was associated with a great number of venous thromboses. An isolated LAF does not contraindicate epidural anaesthesia, as long as there is no associated haemostatic defect, such as a thrombocytopaenia. Furthermore, the patient should not have had prolonged episodes of unexplained bleeding, or require anticoagulants. In the present series, epidural anaesthesia was contraindicated in three of the four patients with LAF. Finally, prevention of thromboembolism, postoperative infection and adrenal failure (in those patients with long-term steroid therapy) must be carried out.

Processes of base-pair opening and proton exchange in Z-DNA

Using proton magnetic resonance, we have investigated imino and amino proton exchange in the Z form of the four oligomers d(Cbr8GCGCbr8G), d(CGm5CGCG), d(CG)6, and d(CG)12. In the latter two oligomers, all five exchangeable protons have been assigned. We find that proton acceptors such as NH3 or the basic form of Tris enhance imino proton exchange. The base-pair lifetime can then be obtained by extrapolation of the exchange time to infinite concentration of proton acceptor. For d(CG)6 and d(CG)12, the values are ca. 3.5 ms at 80 degrees C and ca. 130 ms at 35 degrees C. The latter value is about 65 times longer than in the same oligomers in the B form. The activation energy of base-pair opening, 80 kJ/mol, is the same in the Z and the B forms of d(CG)12. At 5 degrees C, the base-pair lifetime is about 3 s, much smaller than the time constant of the Z to B transition, to which it is therefore unrelated. The base-pair dissociation constant at 35 degrees C, 0.5 X 10(-6), is 5 times smaller than for the same oligomers in the B form. In the absence of added catalyst, at pH 7, the exchange time of the imino proton is 30 min at 5 degrees C. That of both cytidine amino protons, assigned by NOE, is about 50 min. The longest proton exchange time, ca. 330 min, is assigned unambiguously to the guanosine amino protons. Thus assigned and interpreted in terms of exchange chemistry rather than structural kinetics, the exchange times do not support earlier models of Z-DNA internal motions.

[Simple goiter and hypothyroidism during pregnancy. Diagnosis--monitoring--treatment]

37 cases of maternal hypothyroidism in 92,130 births (0.04%) were studied: post surgical (40%) or congenital (35%) hypothyroidism or after-effects of thyroiditis (11%) or of undetermined etiology (14%). The past history of these women, shows a sterility (11%) and spontaneous abortions (18%). Substitute hormonal therapy was usually well monitored, with almost always a stable thyroid function. These pregnancies progressed without any specific problems, the children's birth weight was normal and only one presented a hypothyroidism. 94 cases of goiters (0.10%) were reported including 1 out of 3 received an inhibiting hormonal therapy. Here also the pregnancies developed without problems and there was no difference with regards to the stability of the goiter and the development of the pregnancy between treated and non-treated women. The authors insist on strict monitoring of the treatment with assays of FT3, FT4, TSH and anti-thyroid antibodies, performed one or twice per trimester. The interest of thyroid hormones assays in the amniotic fluid or the blood cord may occur.