Search PubMed⌕ Search

Biomedical subjects

J Vallin

Publications and source records attributed to J Vallin.

At least 19 recordsLinked to original sources
PubMed2001

Cloning and characterization of three Xenopus slug promoters reveal direct regulation by Lef/beta-catenin signaling.

In amphibians and birds, one of the first steps of neural crest cell (NCC) determination is expression of the transcription factor Slug. This marker has been used to demonstrate that BMP and Wnt molecules play a major role in NCC induction. However, it is unknown whether Slug expression is directly or indirectly regulated by these signals. We report here the cloning and characterization of three Xenopus Slug promoters: that of the Xenopus tropicalis slug gene and those of two Xenopus laevis Slug pseudoalleles. Although the three genes encode proteins with almost identical amino acid sequences and are expressed with similar spatiotemporal patterns, their 5'-flanking regions are quite different. A striking difference is a deletion in the X. tropicalis gene located precisely at the transcription initiation site that results in the X. tropicalis promoter being inefficient in X. laevis. Additionally, we identified two regions common to the three promoters that are necessary and sufficient to drive specific expression in NCCs. Interestingly, one of the common regulatory regions presents a functional Lef/beta-catenin-binding site necessary for specific expression. As the Lef.beta-catenin complex is a downstream effector of Wnt signaling, these results suggest that Xenopus Slug is a direct target of NCC determination signals.

Alleles↗
PubMed2001

Where there are no data: what has happened to life expectancy in Georgia since 1990?

In recent years there has been a considerable increase in understanding of changes in mortality in Russia and some other former Soviet republics. However, the situation in the republics of the Caucasus remains poorly understood. Information on Georgia is especially fragmentary as a fifth of the country remains outside government control, there has been large scale migration since 1991, and the introduction of fees for vital registration has compromised the quality of official statistics. The aim of the study is to produce plausible estimates for life expectancy in Georgia for the period 1990-1998 and thus to assess whether Georgia has undergone changes similar to other former Soviet republics in the post-independence period. Four models were used to construct life tables. Model 1 used officially published statistics on deaths and population. Model 2 applied new estimates of population derived from household surveys to the observed deaths. Model 3 adjusted model 2 for under-registration at extremes of life, with parameter estimates derived from a survey of infant mortality and comparison of observed rates with Coale-Demeny standard life tables. Model 4 arose following inspection of death rates by cause that revealed implausible discontinuities in cancer mortality rates and involved applying the estimates of under-registration that this finding implied to model 3. The four models produce quite different estimates of life expectancy, differing by 7.8 y for men and 6.8 y for women by 1998. In any of the models, however, Georgia does not appear to have experienced the marked deterioration in life expectancy seen in Russia following the transition to independence. Importantly, Georgia had also not experienced a marked improvement in life expectancy during the 1985 Soviet anti-alcohol campaign, again unlike other Soviet republics.Official statistics substantially over-estimate life expectancy at birth in Georgia. Despite undergoing a civil war, life expectancy in Georgia has been less affected by the transition than has Russia and the overall trends in mortality since the mid 1980s suggest that this may be because alcohol has played a smaller role in these changes than it did in Russia.

Aged↗
PubMed2001

A hormone-dependent post-translationally regulated mutant for investigating type I cadherin function.

Type I cadherins are Ca2+-dependent cell adhesion molecules. Their function in early Xenopus laevis development has been extensively studied in recent years, by injecting synthetic mRNAs encoding dominant negative mutants with deletions of the extracellular domain into embryos. However, studies at post-gastrula stages have been hampered by the inabilityto progress through post-gastrula development in embryos expressing these mutant proteins. This problem has been partly overcome by injecting into a few targeted blastomeres in stage 6 N.F. embryos, but only restricted studies are possible with this technique. Several studies have made use of the hormone-binding domain (HBD), which is activated by hormones. In this study, we used this method to analyze the activity of dominant negative cadherins. We generated a mutant E-cadherin (AE-Cad, consisting of the cytoplasmic domain and transmembrane domain) fused to the hormone-binding domain of estradiol receptor (HBDER) and we validated this technique with functional analyses. The function of the mutant deltaE-HBDER was strictly dependent on hormone induction. This conditional mutant had the same effects and exerted the same dominant negative function as the corresponding constitutive mutant.

Animals↗
PubMed1999

Cancer mortality in Russia and Ukraine: validity, competing risks and cohort effects.

BACKGROUND: The dramatic increase in mortality in Russia and Ukraine in the late 1980s and 1990s has been due to increases in certain causes of death, particularly cardiovascular disease and accidents and violence. In contrast, there has been a slight fall in mortality from cancer. METHODS: This paper presents an analysis of trends and patterns in cancer mortality and examines four possible explanations for its recent fall: changes in data collection; cohort effects; competing mortality from other causes of death; and improvements in health care. RESULTS: All contribute to some extent to the observed changes, with each affecting predominantly different age groups. There is evidence of a significant underrecording of cancer deaths among the elderly especially in rural areas and of significant changes in coding practices in the early 1990s. Competing mortality from cardiovascular diseases and accidents can explain some reduction in male deaths from cancer in middle age. Birth cohort effects can explain some reduction among males after early middle age and among females at all ages. The impact of changes in health care are more difficult to identify with certainty but there is evidence of reduced deaths from childhood leukaemia. IMPLICATIONS: Recent changes in mortality in Russia are complex and their understanding will require a multidisciplinary approach embracing demography, epidemiology and health services research.

Adolescent↗
PubMed1998

Xenopus cadherin-11 is expressed in different populations of migrating neural crest cells.

We cloned the Xenopus homologue of cadherin-11 and studied its spatiotemporal expression pattern during early development. The messenger RNA is present from the mid-gastrulation through embryo development. It is expressed in different neural crest cell populations, during their migration and differentiation. This pattern, unexpected for an adhesion molecule, reinforces the idea of novel functions for type II cadherins.

Amino Acid Sequence↗
PubMed1997

Relax promotes ectopic neuronal differentiation in Xenopus embryos.

We previously isolated a novel rat cDNA encoding a basic helix-loop-helix transcription factor named Relax, whose expression in the developing central nervous system is strictly limited to discrete domains containing precursor cells. The timing of Relax expression coincides with neuronal differentiation. To investigate the involvement of Relax in neurogenesis we tested whether Relax activated neural genes in the ectoderm by injecting Relax RNA into Xenopus embryos. We demonstrate that ectopic Relax expression induces a persistent enlargement of the neural plate and converts presumptive epidermal cells into neurons. This indicates that Relax, when overexpressed in Xenopus embryos, has a neuronal fate-determination function. Analyses both of Relax overexpression in the frog and of the distribution of Relax in the rat neural tube strongly suggest that Relax is a neuronal fate-determination gene.

Animals↗
PubMed1996

Health crisis in Russia. I. Recent trends in life expectancy and causes of death from 1970 to 1993.

The authors analyze trends in life expectancy and causes of death in Russia from 1970 to 1993, with a focus on reasons for the recent declines in life expectancy. "Before discussing the trends themselves, we shall...look at the possible distortions that changes in data quality may have produced. However, even if it has been exaggerated to some degree, nobody contests the reality of the Soviet health crisis, and we shall attempt to derive some explanation by analysing the age and cause-of-death structures of mortality in Russia."

Cause of Death↗
PubMed1996

Health crisis in Russia. II. Changes in causes of death: a comparison with France and England and Wales (1970 to 1993).

"Trends in Russian mortality appear all the more negative in comparison with the very favourable trends in most Western countries, especially during the last two decades. To highlight the most damaging causes, we compare Russian cause-specific mortality trends with those observed in France and England and Wales, two countries for which we have reconstructed continuous time series of deaths by cause.... It was within the framework of...30 categories [of causes] that we calculated death rates by age group and standardized mortality rates by cause...."

Cause of Death↗
PubMed1996

[Twenty one years of hemodialysis in a patient with primary hyperoxaluria].

We report a male patient with primary hyperoxaluria from childhood who survived more than 21 years on conventional haemodialysis. Despite the severity of his bone disease, he was married and actively employed up until 2 years before his death. His condition really worsened a few months before his death. He presented with only renal and bone involvement and had hardly any cardiovascular complications, that was probably a reason for his prolonged survival. Such an evolution is very unusual and we speculate that the length of haemodialysis sessions in addition to the large surface of the membrane probably contributed to such an outcome. During the time period on HD, anemia was transiently controlled by recombinant erythropoietin despite oxalate involvement of the marrow. He was refused a liver-kidney transplant and died from malnourishment at 43 years of age. To our knowledge, such an outcome has not yet been reported. It shows that careful prolonged hemodialysis sessions should be helped in admet patients without severe cardiovascular involvement.

Adult↗
PubMed1995

[Causes of adult mortality in developing and developed countries with low mortality rates].

"In a certain number of developing countries, life expectancy levels now approach those of the developed world. But, though life expectancies at birth may be similar, the infant mortality rate in developing countries remains higher, but is compensated by a lower rate of mortality for adults. Is it to be expected that as infant mortality rates continue to decline, the developing countries will maintain their advantageous adult mortality rates and that life expectancy will forge ahead of the level achieved in developed countries?... To answer this question, recent trends in adult cause-specific mortality rates in four developing countries (Chile, Hong Kong, Mexico, and Costa Rica) were compared with those in three industrialized countries (France, Germany and Japan). The results were inconclusive. Whilst life expectancies in some of these countries may be expected to forge ahead (Chile, Hong Kong), in others the margin between their life expectancies and those of developed countries have already narrowed." (SUMMARY IN ENG)

Adult↗
PubMed1992

Mortality by cause in the USSR in 1970-1987: the reconstruction of time series.

"This paper is the first step in an exploration of Soviet cause-of-death statistics which became accessible after 1986. Its main aim is the reconstruction of consistent annual series for the period 1970-1987 in spite of changes in cause-of-death classification caused by the 1980 revision of the Soviet nosological system. In a second part, the series thus reconstructed are analysed to describe the main features of the evolution of mortality during these two decades, using first standardized mortality rates for several very important specific causes and, second, using a method of decomposition of life expectancy changes. For the first time, trends in causes of death are thus shown for the crucial period where life expectancy has grown again after two decades of regression." (SUMMARY IN FRE)

Cause of Death↗
PubMed1991

Reconstitution of annual life tables for nineteenth-century France.

"The nineteenth century was not one of runaway health progress, but it marked a deep transformation of mortality conditions [in France]. The reconstitution of mortality tables by single years of age and calendar years makes it possible to study this transformation in detail, and to distinguish between period fluctuations and structural changes. In the present article, we have given preference to graphic representation, and purposely limited the statistics.... We have also given preference to the period approach." Consideration is given to annual mortality trends, life expectancy, age-specific probability of dying, the war-related crisis years of 1813, 1871, and 1915, and differentials in mortality by sex. Data generally concern the period 1806-1898.

Age Factors↗
PubMed1990

Mortality and population ageing.

The authors examine the effects of mortality trends on age structure and how fertility and migration affect demograpnic aging. "Computations are done for both France and Italy on population ageing during the last 30 years as well as until the end of the official population projections around 2040. Though the ageing effect of fertility decline is usually emphasized, we can see here that the consequences of mortality changes are at least equally (and sometimes more) important. The case of the Italian projection is particularly fascinating. Even if the very low fertility level of 1.4 children per capita is maintained until the year 2040, more than half the increase in the proportion of the population aged 60 and over (from 21% to 43% for females) would be due to mortality change and slightly less to fertility change." (SUMMARY IN FRE)

Age Distribution↗
PubMed1990

When does a cohort's mortality differ from what we might expect?

The authors have developed a model to systematically analyze a matrix of mortality data. "Through its detailed description of the structure of the matrix, it offers the possibility of confirming certain hypotheses or of formulating new ones about the mortality experience of certain peculiar cohorts. The descriptive power of the method will be seen here in application to the French mortality experience over the period 1899-1981." This is a revised version of a paper originally presented at the 1988 Annual Meeting of the Population Association of America.

Cause of Death↗