Excitation Gap in the Normal State of Underdoped Bi2Sr2CaCu2O8+delta

Angle-resolved photoemission experiments reveal evidence of an energy gap in the normal state excitation spectrum of the cuprate superconductor Bi2Sr2CaCu2O8+delta. This gap exists only in underdoped samples and closes around the doping level at which the superconducting transition temperature Tc is a maximum. The momentum dependence and magnitude of the gap closely resemble those of the dx2-y2 gap observed in the superconducting state. This observation is consistent with results from several other experimental techniques, which also indicate the presence of a gap in the normal state. Some possible theoretical explanations for this effect are reviewed.

[Quality of health services in Africa : example of dystocia prenatal screening in Nioki (Zaire)]

Childbirth, though a common yet highly valued social event in Africa, is a major risk for the mother and child. During these last few decades, extension of health services has gained attention and their accessibility has improved. However, these health services remain inefficient because of their poor quality, especially for prenatal screening. This study with 59 cases and 177 controls was carried out in a rural district of Zaire. The objectives were to first assess the quality of the diagnosis of high risk pregnancy (HRP) and secondly to identify the main risk factors associated with complicated deliveries. The diagnosis of HRP has a low sensitivity (53%) yet a high specificity (95%). The diagnosis is based on postpartum hemorrhage and maternal height but does not consider primiparity or previous complicated deliveries. By improving the use of currently available information, a higher sensitivity (72%, could be obtained, identifying close to 3 out of 4 HRPs, but with a lower specificity (67%). The current diagnosis is conservative, partly because health personnel are reluctant to refer pregnant women, who could deliver normally, to the district hospital. Predictive criteria of complicated pregnancy are: primiparity, maternal height, previous difficult childbirth (dystocia), previous postpartum hemorrhage and lack of prenatal care. Prenatal screening should be a major component of safe motherhood programs. Our results show that in developing countries where emphasis is mainly put on the accessibility of health services, the quality of these services should become a priority. Quality is linked to efficiency, yet good quality gives a better image of services and improves compliance of the women.

Controversies in counseling for mitochondrial conditions

A healthy woman sought preconceptional genetic counseling regarding a family history of a mitochondrial myopathy in her brother and retinitis pigmentosa (RP) in her two maternal aunts. Several questions were raised: (1) What is the likelihood of a familial mitochondrial condition? (2) What molecular tests or prenatal screening can we offer? (3) How would these tests help assess the likelihood of a familial mitochondrial condition? A mitochondrial mutation previously identified in the brother consisted of a heteroplasmic 2.9 kb deletion. We detected this deletion in the peripheral blood of the brother by PCR amplification of the deletion breakpoint, but not in his mother, the consultand, nor in one of the two aunts affected with RP. Although the molecular analysis was encouraging to the consultand, a familial mitochondrial disorder could not be eliminated with certainty. The pros and cons of prenatal testing for mitochondrial disorders are discussed in general, and as specifically related to this family.

Mitochondrial mutation associated with nonsyndromic deafness

PURPOSE

The first mutation associated with nonsyndromic deafness has recently been identified in pedigrees with susceptibility to aminoglycoside ototoxicity and in a large Arab-Israeli pedigree. The mutation is maternally transmitted, and is a nucleotide substitution in the mitochondrial 12S ribosomal RNA gene. A different sequence change, in the mitochondrial tRNA(Ser)(UCN)/COI gene, has been proposed as a candidate mutation in a Scottish nonsyndromic deafness pedigree. We have now identified a family in New Zealand with maternally inherited nonsyndromic sensorineural deafness, and the purpose of the current study is to identify the molecular basis of deafness in this family.

MATERIALS AND METHODS

A family tree was established by history and chart review, and audiological and clinical data were obtained. Blood was sampled from 10 family members, and lymphoblastoid cell lines were established for 4 of them. The DNA of these individuals was extracted, and the mitochondrial genome was analyzed by Southern blot analysis for gross rearrangements. Subsequently, the entire coding sequence of the mitochondrial genome was sequenced, compared to the normal sequence, and all sequence variations were analyzed by allele-specific oligonucleotide hybridization or restriction enzyme analysis.

RESULTS

Several candidate mutations were identified, one of them being the nucleotide 7445 A-->G mutation in the mitochondrial tRNAser(UCN)/COI gene. This mutation was heteroplasmic and identical to the one previously identified in the Scottish pedigree.

CONCLUSIONS

The finding of the same heteroplasmic mutation in two independent pedigrees with the same phenotype and transmission pattern, establishes this sequence change as the most likely determinant of the deafness phenotype in these families. This implies that nonsyndromic deafness can be caused by mutations in generalized cell processes, such as oxidative phosphorylation, rather than in hearing specific molecules.

Susceptibility mutations in the mitochondrial small ribosomal RNA gene in aminoglycoside induced deafness

Aminoglycoside induced deafness has been linked recently to a predisposing homoplasmic mutation in the 3' end of the small ribosomal RNA (rRNA) gene of the human mitochondria (1555 A-->G) that makes the mitochondrial rRNA structurally more similar to its bacterial counterpart. This mitochondrial DNA mutation was consistently found in families in which the susceptibility to develop ototoxic deafness was inherited through the maternal lineage. However, the 1555 A-->G mutation was rarely found in sporadic patients in China, where a significant proportion of the population has been exposed to aminoglycosides. To further characterize the mutations predisposing to aminoglycoside ototoxicity, we analysed the 12S rRNA gene in 35 Chinese sporadic patients without the 1555 A-->G mutation. Using single stranded conformational polymorphism (SSCP) analysis, heteroduplex (HD) analysis, sequencing, and allele specific oligonucleotide hybridization, we found three out of 35 sporadic patients with unique sequence changes in the 12S rRNA gene. Two of the patients had homoplasmic mutations. One patient displayed localized heteroplasmy around nt 961, with an absence of the thymidine at this position and different populations of mitochondrial DNA with varying numbers of inserted cytosines. The description of these putative susceptibility mutations, in particular the heteroplasmic mutation around nt 961, provides further support for the important role of the mitochondrial 12S rRNA in genetic predisposition to aminoglycoside induced ototoxic deafness.

Quality, cost and utilization of health services in developing countries. A longitudinal study in Zaïre

Many developing countries, particularly in Africa, have recently introduced payment schedules based on the selling of essential drugs. This is one of the main elements of the Bamako Initiative according to which the income generated would ensure a reliable supply of drugs and would improve other aspects of the quality of the services offered. Thus, quality improvements would compensate for the financial barrier and as a result the utilization of public health services would be increased or at least maintained. These hypotheses have proven to be partially valid, since there have been cases where the utilization of health services has increased and others where it has decreased; these inconclusive results have fuelled criticisms concerning the inequitable nature of these measures. This longitudinal study in a rural community of Zaïre shows that the utilization of health services had diminished by close to 40% over 5 yr (1987-1991) and that 18-32% of this decrease is explained by cost. The regular supply of drugs and the improvement in the technical quality of the services--technical qualification of the staff, allocation of microscopes, and renovation of the infrastructures--was not enough to compensate for the additional financial barriers created by the increased cost of services. However, on a local level, the interpersonal qualities displayed by some of the nurses sometimes helped to compensate for the negative effects of the costs, and even to increase the level of utilization of some health centres. The quality of public services has often been neglected in developing countries. While some attention is given to technical qualities, the interpersonal components of the quality of the services are generally ignored or underestimated by planners and they are the very components which are most resistant to change. It will be a major challenge for health systems to address this issue of quality of care in order to minimize the negative impact of the introduction of user payment schemes. Therefore, now is the time to place quality next to coverage in planners' agendas.

The role of universities and the ethics of their interventions in international health

Even though exchange has always been a part of the University essence, we are now witnessing an important movement towards internationalization, which cannot be indissoluble from the phenomenon of the globalization of culture and exchanges. In the international health field, universities, either in the South or North, have traditionally played an important role which is ever expanding, due to the broadening of the concept of international health. In Canada, academic centers of international health have developed rapidly over the last decade, along with a network linking all universities that are active in the field. The development of this type of center at the University of Montreal is described in this paper. The lessons learned there lead us to insist on the importance of the attachment of international cooperation development programs to the teaching assignments and research programs of universities, and to pay particular attention to research in order to strive for excellence. It is also important to pay attention to the freedom of thought and action which is a fundamental value among university members. Among the universities involved in international health, some have gone adrift: be it the opportunism of some or the inappropriate use of university expertise by international cooperation agencies of others. Universities, in their undertakings, must respect, in addition to their own traditional ethic, the one of development.

Transesophageal echocardiography for the diagnosis and management of nonobstructive thrombosis of mechanical mitral valve prosthesis

BACKGROUND

Diagnosis of a mechanical mitral valve prosthesis thrombosis is currently made with transthoracic Doppler echocardiography and occasionally with fluoroscopy. However, identifying a thrombus on a valve prosthesis may be difficult, especially if the thrombus is nonobstructive. To prospectively define the role of transesophageal echocardiography for identification of nonobstructive thrombi, we studied a series of patients in whom the prosthetic valve was considered to function normally on clinical examination and transthoracic echocardiography.

METHODS AND RESULTS

One hundred fourteen consecutive patients with mechanical mitral valve prosthesis were investigated by both transthoracic echocardiography and transesophageal echocardiography. These examinations were performed for recent systemic emboli (15 patients), fever of unknown etiology (11 patients), routine postoperative evaluation (56 patients), and other reasons (32 patients). Based on transthoracic echo diagnosis, all prostheses were considered normal. Yet, in 20 patients transesophageal echocardiography revealed the presence of a 2- to 15-mm-long mobile thrombus localized on the atrial surface of the prosthesis. When compared with the remaining 94 patients with no visible thrombi, there was no significant difference between the two groups in terms of incidence of atrial fibrillation (65% versus 52%), left atrial size (48 +/- 9 versus 51 +/- 13 mm), left ventricular end-diastolic diameter (49 +/- 10 versus 51 +/- 13 mm) and fractional shortening (28 +/- 9% versus 31 +/- 10%), presence of spontaneous contrast to the left atrium (40% versus 41%), transprosthetic mean pressure gradient (4.0 +/- 1.4 versus 3.9 +/- 1.5 mm Hg), or the type of prosthesis used. After we discovered a nonobstructive thrombosis, patients were treated with heparin (n = 9) or oral anticoagulation (n = 11). The presence of a localized thrombus was confirmed in 3 patients who were operated on. In the present study, evolution appeared to depend on thrombus size: of 14 patients exhibiting a small (< 5 mm) thrombus, 10 had an uneventful course, whereas 5 of 6 patients with a large (> or = 5 mm) thrombus developed complications or died.

CONCLUSIONS

Transesophageal echocardiography appears to be a reliable method to diagnose thrombi on a mechanical mitral valve prosthesis, even when transthoracic Doppler echocardiographic parameters appear to be normal. Transesophageal echo assessment of thrombus size may be helpful in deciding whether a patient with mitral prosthesis should be treated by anticoagulation, thrombolysis, or valve rereplacement.

[Contribution of transesophageal echocardiography to the diagnosis of pulmonary embolism]

Between September 1992 and August 1993 transoesophageal echocardiography was undertaken in 30 patients with clinical and scintigraphic signs of pulmonary embolism. The diagnosis was confirmed by pulmonary angiography (1 patient had failure of venous puncture; 1 patient refused the investigation). The aim of this study was to assess the tolerance and to determine the diagnostic value of transoesophageal echocardiography in patients with suspected pulmonary embolism (PE). Two groups of patients were identified: Group 1: presence of thrombus in the pulmonary artery on transoesophageal echocardiography and group 2: absence of visible thrombus. The produce was well tolerated in all patients. In 21 cases (group 1) 21 thrombi were observed in the right pulmonary artery and 4 thrombi in the left pulmonary artery. The appearances were those of a mobile venous thrombosis in 20 cases (91%) and of clearcut amputation of the proximal segment of the right pulmonary artery in 1 case. No thrombus was detected in 9 patients (group 2). In group 1, the first clinical signs occurred 12 +/- 12 days and the latest signs 2 +/- 3 days before the investigation. One patient had a history of chronic bronchitis. Two patients had a history of PE but with no sign of chronic post-embolic cor pulmonale. Twenty patients underwent pulmonary angiography. Miller's index was 71 +/- 9% and obstruction of proximal pulmonary arteries was observed in 20 patients. In group 2, the PE was confirmed at angiography in 8 cases. The first clinical signs dated from 27 +/- 54 days and the latest signs were observed 6 +/- 4 days before investigation.(ABSTRACT TRUNCATED AT 250 WORDS)

Stimulation of ileal calcium absorption by sorbitol, L-xylose, or creatine via a decrease in luminal sodium concentration: relation with concomitant changes in enterocyte energy metabolism

Ligated ileal loops, 30 cm in length, of 4-month-old male Wistar rats were instilled with 3 ml of a 10 mM CaCl2 solution (added with 0.25 muCi 45Ca) in the absence (control) or presence of 100mM sorbitol, L-xylose, or creatine. Ileal calcium (Ca) transport, measured by plasma 45Ca appearance, was found to be similar 30 minutes after fluid instillation in all four instances. However, thereafter, 45Ca appearance in plasma did not increase further in control animals whereas it increased twice as much during the subsequent 30 minutes in the presence of sorbitol, L-xylose, or creatine. However, when loops of similar length were instilled with only 1.0 ml of such solutions, the sorbitol effect was already observed during the first 30 minutes. The stimulation of ileal Ca absorption induced by the presence of sorbitol appeared to be due to a cellular effect, associated with a decreased flux across the paracellular pathway, as indicated by 3H-mannitol absorption. The presence of sorbitol in instilled ileal solution induced a significant decrease in luminal Na, K, bicarbonate, and Cl concentrations at each time point studied (30, 60, 120, or 240 minutes after instillation). Thirty minutes after instillation, no difference in soluble Ca concentration was observed between control and experimental rats. After 60 minutes, Ca concentration was dramatically decreased in control rats but it remained nearly constant in experimental animals. Thus, the presence of substances enhancing ileal Ca transport favored the maintenance of soluble Ca in ileal solution during longer time periods than their absence. In the ileal enterocyte, these substances induced a twofold increase of ATP content compared with controls.(ABSTRACT TRUNCATED AT 250 WORDS)

Natural instability of Agrobacterium vitis Ti plasmid due to unusual duplication of a 2.3-kb DNA fragment

The octopine/cucumopine (o/c) Ti plasmids of Agrobacterium vitis carry two T regions, TA and TB. The TA region resembles the octopine TL region. The TB region contains the auxin synthesis genes TB-iaaM and TB-iaaH and the cucumopine synthesis gene cus. Within the group of o/c isolates, strains 2608 and 2641 are closely related. However, 2641 lacks the TB region. The restriction maps of pTi2608 and pTi2641 were established and showed that the TB deletion resulted from intramolecular recombination between two directly repeated sequences separated by 66 kb in pTi2608. The 2,294-bp repeated sequence lacks inverted repeats and does not duplicate its target site, indicating that it is not a classical bacterial insertion sequence (IS element). It was therefore called an RSAv element (repeated sequence of A. vitis). The RSAv element carries two open reading frames: ORF234 is homologous to the traR gene of the A. tumefaciens nopaline Ti plasmid pTiC58; ORF488 is homologous to the sucrose phosphorylase gene of Leuconostoc mesenteroides and the glucosyl transferase A gene of Streptococcus mutans. The RSAv repeat starts precisely at the start codon of ORF488 and ends two base pairs 3' of the stop codon of ORF234. The structural organization of the RSAv element suggests that the amplification event did not result from a random amplification process. A study of the distribution of the two RSAv copies (RSAv-1 and RSAv-2) in pTi2608 and other o/c isolates indicates that the ancestor o/c Ti plasmid contained only RSAv-1 and that this sequence was duplicated at one point during the divergent evolution of the o/c Ti plasmids.(ABSTRACT TRUNCATED AT 250 WORDS)

[Osteomalacia of renal origin disclosing Gougerot-Sjögren syndrome]

Latent renal tubular diseases are common in Sjögren's syndrome but rarely complicated by osteomalacia. The authors report a 28 years old woman's case where osteomalacia reveal the disease. In the other hand, pseudo-lymphoma is suspected from radiographic features. According to several studies, the authors review different types of renal diseases and describe different physiopathological hypotheses about bone involvement and pseudo-lymphomas.

[Role of ultrasonographic tests in the diagnosis of moderate to severe pulmonary embolism]

Between November 1991 and June 1992, 50 patients suspected of pulmonary embolism (SP > 20%) underwent Doppler echocardiography, venous Doppler ultrasonography and pulmonary angiography. Pulmonary embolism was confirmed by pulmonary angiography in all patients but 3 (2 pts: mean pulmonary pressure > 50 mmHg and 1 pt: mobile thrombus between the infundibulum and the main pulmonary artery). Two groups were identified on the basis of Miller's index: Group 1: "non-massive" pulmonary embolism, Miller < 60% (n = 18); Group 2: "massive" pulmonary embolism, Miller > or = 60% (n = 29). The patient with thrombus in the main pulmonary artery and the two with high pulmonary pressures were included in Group 2. Venous Doppler ultrasonography was performed in 96% (n = 48) of patients, including 90% within the first 24 hours. No distinction could be drawn between the two groups on the basis of venous Doppler ultrasonography findings. A majority of patients had thrombosis of main collecting vessels (Group 1 = 75%, Group 2 = 78%) and 10% of patients had no venous thrombosis of the lower limbs. Doppler echocardiography was performed in all patients, including 94% (n = 47) within the first 24 hours. Dilatation of the left ventricle as well as analysis of septal contraction was evaluable in all patients except one of Group 2, because of poor technical quality and of artificial pacing. A RV/LV ratio > 0.60 was found in 97% (30/31) of patients of Group 2 as compared with 39% (7/18) in Group 1.(ABSTRACT TRUNCATED AT 250 WORDS)

Identical mitochondrial DNA deletion in mother with progressive external ophthalmoplegia and son with Pearson marrow-pancreas syndrome

We describe a family in which the mother has progressive external ophthalmoplegia with the common 4977 base pair deletion, and her son has a syndrome similar to the Pearson marrow-pancreas syndrome with the identical deletion. This case extends the clinical phenotype of the Pearson syndrome and raises the possibility that developmentally regulated tissue-specific nuclear factors are responsible for the differential phenotypic expression of these two mitochondrial disorders.

Colocalization of centromeric and replicative functions on autonomously replicating sequences isolated from the yeast Yarrowia lipolytica

Two sequences (ARS18 and ARS68) displaying autonomous replication activity were previously cloned in the yeast Yarrowia lipolytica. The smallest fragment (1-1.3 kb) required for extrachromosomal replication of a plasmid is significantly larger in Y. lipolytica than in Saccharomyces cerevisiae. Neither autonomously replicating sequence (ARS) is homologous with known ARS or centromere (CEN) consensus sequences. They share short regions of sequence similarity with each other. These ARS fragments also contain Y. lipolytica centromeres: (i) integration of marker genes at the ARS loci results in a CEN-linked segregation of the markers, (ii) an ARS on a plasmid largely maintains sister chromatid attachment in meiosis I, and (iii) integration of these sequences at the LEU2 locus leads to chromosome breakage. Deletions performed on ARS18 show that CEN and ARS functions can be physically separated, but both are needed to establish a replicating plasmid.

Chromosomal polymorphism of the yeast Yarrowia lipolytica and related species: electrophoretic karyotyping and hybridization with cloned genes

Significant differences in electrophoretic karyotyping patterns were found among 27 strains of Y. lipolytica. Twenty-one of these strains were classified into four groups of similar karyotypes while six strains showed unique karyotypes. Chromosomal DNAs of different strains were hybridized with cloned genes of Y. lipolytica (URA3, LEU2, ARS18 and ARS68), which revealed four different bands in most strains. We conclude that the haploid chromosome number of Y. lipolytica is at least four, and possibly five or six. Electrophoretic karyotyping and hybridization with cloned genes of Y. lipolytica provided evidence of a large divergence between Y. lipolytica and related species of Saccharomycopsis, Endomycopsella and Endomyces.

[A new cause of torsades de pointes: combination of terfenadine and troleandomycin]

The authors report a case of wave-burst arrhythmia which occurred during combined treatment with terfenadine and troleandomycin. After the treatment had been stopped and the QT interval returned to normal, terfenadine treatment was reintroduced with no major change in repolarization. However, as soon as troleandomycin was associated, there was a significant and progressive prolongation of QT. Normal repolarization was restored again with troleandomycin alone. These findings suggest drug interaction between terfenadine and troleandomycin. Although it is not possible to carry out serum assays of terfenadine, one possible physiopathological hypothesis would be an overdose of terfenadine. Terfenadine undergoes hepatic oxidative metabolism involving the cytochrome P450 pathway and troleandomycin inhibits cytochrome P450. In the literature, a case has already been described of wave-burst arrhythmia related to terfenadine overdose when associated with a cytochrome P450 inhibitor.

IS870 requires a 5'-CTAG-3' target sequence to generate the stop codon for its large ORF1

The TB regions of the Agrobacterium vitis octopine/cucumopine Ti plasmids constitute a family of related structures. All contain a bacterial insertion element downstream of the TB-iaaM gene, IS870.1. Whereas 43 isolates with octopine/cucumopine Ti plasmids carry only one IS870 copy, strain Ag57 carries a second copy (IS870.2) 3.9 kb to the right of IS870.1 and part of the same TB region. Two other octopine/cucumopine strains carry an IS870 copy on their chromosome (IS870.3). A study of the unmodified insertion sites of IS870.2 and IS870.3, cloned from closely related strains, enabled us to delimit the IS870 elements. IS870 has a size of 1,152 bp and is terminated by inverted repeats. It contains a large open reading frame without a stop codon. However, a stop codon is generated by insertion into the target sequence 5'-CTAG-3'. IS870 is related to five other insertion sequence elements. For two of these, the stop codon of the largest open reading frame is also created by insertion into a CTAG target site.