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Biomedical subjects

J Olivier

Publications and source records attributed to J Olivier.

At least 19 recordsLinked to original sources
PubMed2004

Pattern and process in Amazon tree turnover, 1976-2001.

Previous work has shown that tree turnover, tree biomass and large liana densities have increased in mature tropical forest plots in the late twentieth century. These results point to a concerted shift in forest ecological processes that may already be having significant impacts on terrestrial carbon stocks, fluxes and biodiversity. However, the findings have proved controversial, partly because a rather limited number of permanent plots have been monitored for rather short periods. The aim of this paper is to characterize regional-scale patterns of 'tree turnover' (the rate with which trees die and recruit into a population) by using improved datasets now available for Amazonia that span the past 25 years. Specifically, we assess whether concerted changes in turnover are occurring, and if so whether they are general throughout the Amazon or restricted to one region or environmental zone. In addition, we ask whether they are driven by changes in recruitment, mortality or both. We find that: (i) trees 10 cm or more in diameter recruit and die twice as fast on the richer soils of southern and western Amazonia than on the poorer soils of eastern and central Amazonia; (ii) turnover rates have increased throughout Amazonia over the past two decades; (iii) mortality and recruitment rates have both increased significantly in every region and environmental zone, with the exception of mortality in eastern Amazonia; (iv) recruitment rates have consistently exceeded mortality rates; (v) absolute increases in recruitment and mortality rates are greatest in western Amazonian sites; and (vi) mortality appears to be lagging recruitment at regional scales. These spatial patterns and temporal trends are not caused by obvious artefacts in the data or the analyses. The trends cannot be directly driven by a mortality driver (such as increased drought or fragmentation-related death) because the biomass in these forests has simultaneously increased. Our findings therefore indicate that long-acting and widespread environmental changes are stimulating the growth and productivity of Amazon forests.

Biodiversity↗
PubMed2004

The prediction of filter belt press dewatering efficiency for activated sludge by experimentation on filtration compression cells.

The filter belt press is commonly used to dewater activated sludge. However, little research has been done on this process and the prediction of its efficiency. Experimentation has been carried out in a filtration compression cell (FCC) and in a pilot scale filter belt press. It offers a way of determining filter belt press efficiency thanks to simple laboratory research. The pressure distribution around the pressing roller was measured inside the pilot scale filter belt press. It showed progressive increase (up to a certain maximum value: plateau), which was followed by a rapid decrease. The impact of the progressive increase of applied pressure onto the dry solid sludge content was observed in FCC. Similar dry solid contents were obtained from both the above laboratory devices when the application of the pressure is comparable (in time and increasing rate).

Compressive Strength↗
PubMed2001

Transcobalamin codon 259 polymorphism in HT-29 and Caco-2 cells and in Caucasians: relation to transcobalamin and homocysteine concentration in blood.

Transcobalamin (TC) is the plasma transporter that delivers vitamin B(12) to cells. We have already reported that HT-29 and Caco-2 cells secrete different TC variants. HT-29 secretes 2 TC isoproteins (codon 259-Pro/Arg [259-P/R]), exhibiting unequal concentrations (TC 259-P > TC 259-R), and Caco-2 cells only secrete the phenotype 259-R. We investigated the relation between phenotypic and genetic TC polymorphism in HT-29 cells transfected with Caco-2 TC complementary DNA and in 159 healthy Caucasians. We found that codon 259-R is buried and, thus, the genetic polymorphism provides no explanation why the TCs from HT-29 and Caco-2 cells have different isoelectric points in nondenaturing isoelectric focusing (IEF). The newly translated TC in HT-29 cells from the Caco-2 complementary DNA recombinant plasmid had the same isoelectric point as the TC constitutively expressed in HT-29 cells, suggesting that TC phenotypic variability involves a specific cell folding of the protein. The codon 259 polymorphism was found to have a biallelic distribution: homozygotes P = 34.6%, heterozygotes R/P = 47.8%, and homozygotes R = 17.6%. In heterozygous samples, the IEF showed that the TC 259-P/TC 259-R ratio = 1.6. The blood apo-TC concentration of 259-P homozygous Caucasians was significantly higher than that of homozygous 259-R (P <.0001) and heterozygous (P <.0006) Caucasians. The heterozygotes 259-R/P had homocysteine concentration significantly higher than the homozygotes 259-R and 259-P (P =.02 and P =.01, respectively). In conclusion, TC codon-259 polymorphism affects TC plasma concentration and may interfere in vitamin B(12) cellular availability and homocysteine metabolism.

Adult↗
PubMed2001

Pregnancy outcome in women with prosthetic heart valves.

The pregnancy outcome of 59 pregnancies in 38 women with prosthetic heart valves, managed at a tertiary referral centre from 1989-98 were reviewed. Ten women underwent valve replacement during pregnancy. The main outcome measures were major maternal complications and perinatal outcome. The maternal mortality rate for pregnancies following valve replacement surgery was 6.1%, with a 21% pregnancy loss before viability and a perinatal loss of 8%. Major morbidity in this group was as follows: haemorrhage 29.8%, cardiac failure 12.8%, thromboembolism 8.5%, infective endocarditis 6.4% and valve thrombosis 4.3%. No maternal mortality occurred among those who underwent valve replacement during pregnancy but their perinatal loss was 25%. We conclude that although maternal mortality and morbidity rates in women with prosthetic heart valves who became pregnant were high, the perinatal outcome was good except for women who underwent valve replacement during pregnancy who experienced a high perinatal loss rate.

Journal Article↗
PubMed2000

Resistance of tomato line Hawaii7996 to Ralstonia solanacearum Pss4 in Taiwan is controlled mainly by a major strain-specific locus.

Bacterial wilt caused by the soilborne bacterium Ralstonia solanacearum attacks hundreds of plant species, including many agriculturally important crops. Natural resistance to this disease has been found in some species and is usually inherited as a polygenic trait. In tomato, a model crop plant, genetic analysis previously revealed the involvement of several QTL (quantitative trait loci) controlling resistance and, in all of these studies with different strains of the pathogen, loci on chromosome 6 played the predominant role in controlling this trait. Using quantitative data collected from a greenhouse test F3 population, we identified a new locus on chromosome 12 that appears to be active specifically against a race 1 biovar 3 Pss4 bacterial strain endemic to Taiwan. Chromosome 6 still contributes significantly to the control of the resistance, and weaker associations of the trait to other regions of the genome are observed. These results are discussed in the context of current molecular knowledge about the strain specificity of disease resistance genes.

Chromosome Mapping↗
PubMed1999

Transcolonic retrograde ureteric catheterization assisted by 3-D computed tomography.

A 42-year-old woman had bladder exstrophy at birth, treated by ureterocolic anastomosis of her single kidney. She suffered recurrent hyperammonaemia, leading to comas, but refused an ileal conduit. During her most recent coma, it was decided to divert her urine to test whether this would reduce hyperammonaemia: this was accomplished by transcolonic retrograde catheterization of the ureter. This was only possible after computed tomography ureterography to show the ureterocolic anastomosis.

Adult↗
PubMed1999

Temporal and multiple quantitative trait loci analyses of resistance to bacterial wilt in tomato permit the resolution of linked loci.

Ralstonia solanacearum is a soil-borne bacterium that causes the serious disease known as bacterial wilt in many plant species. In tomato, several QTL controlling resistance have been found, but in different studies, markers spanning a large region of chromosome 6 showed strong association with the resistance. By using two different approaches to analyze the data from a field test F3 population, we show that at least two separate loci approximately 30 cM apart on this chromosome are most likely involved in the resistance. First, a temporal analysis of the progression of symptoms reveals a distal locus early in the development of the disease. As the disease progresses, the maximum LOD peak observed shifts toward the proximal end of the chromosome, obscuring the distal locus. Second, although classical interval mapping could only detect the presence of one locus, a statistical "two-QTL model" test, specifically adapted for the resolution of linked QTL, strongly supported the hypothesis for the presence of two loci. These results are discussed in the context of current molecular knowledge about disease resistance genes on chromosome 6 and observations made by tomato breeders during the production of bacterial wilt-resistant varieties.

Bacterial Infections↗
PubMed1996

Status spongiosis, optic neuropathy, and retinal degeneration in Helichrysum argyrosphaerum poisoning in sheep and a goat.

Lesions of natural Helichrysum argyrosphaerum poisoning were studied in eight sheep and one goat. Light microscopic examination revealed widespread, bilaterally symmetrical status spongiosis of the white matter of the brain consistently present in the subependymal area adjacent to the lateral ventricles, cerebellar peduncles, and brain stem in all animals. In three animals, the ultrastructural finding of intramyelinic vacuolation due to splitting of the myelin lamellae at the intraperiod lines indicated myelin edema. There was also mild distension of perivascular and extracellular spaces in the severely affected areas. Significant changes were absent in neurons, glial cells, axons, or blood vessel walls. Myelin edema associated with degeneration and loss of axons and myelin and astrocytic gliosis was present in the intraorbital and intracranial portions of the optic nerves. In the intracanalicular portions of the nerves in three animals that were studied, more chronic lesions consisting of fibrosis and atrophy of the nerve suggested that the optic neuropathy follows compression of the nerve in the optic canal as a result of myelin edema. The toxic principle of the plant also caused a degenerative retinopathy in five animals. The essential histopathologic change was degeneration and loss of the photoreceptor outer segments predominantly in the nontapetal retina. These retinal lesions were associated with hyperplasia and hypertrophy and with migration of the pigmented epithelium, focal retinal separation, and depletion and loss of the nuclear layers.

Animals↗
PubMed1995

Short-term relationships between winter temperatures and cardiac disease mortality in Cape Town.

The short-term relationship between winter temperatures and cardiac disease mortality in Cape Town was investigated for the period 1978-1985. The mortality data were stratified according to age (0-4 years, 5-59 years, 60 years and older), while the temperature data comprised daily maximum and minimum temperatures at Cape Town International Airport. The analyses identified a strong lagged relationship between extreme (high and low) temperatures and daily mortality, and it was established that large daily temperature variations were associated with above-average mortality rates.

Adolescent↗
PubMed1992

[Value of intravenous immunoglobulins. A case of Guillain-Barré syndrome].

A case of severe Guillain-Barré syndrome (GBS) was treated with high dose intravenous immunoglobulin (IVIG), 400 mg.kg-1.days-1, over three consecutive days. The treatment was repeated once. We observed a time-related response between immunoglobulins administration and clinical improvement. The pathologic lesions of the GBS suggest that this syndrome has an immunologic basis: a humoral factor is probably not the only immunological mechanism and cellular mechanisms are also likely to be of importance. Specific mechanisms might also be present in GBS, such as anti-idiotypic suppression of autoantibodies, and elimination of circulating immune complexes. Treatment with IVIG might have several therapeutic advantages over plasmapheresis: IVIG is easily infused without any delay, is easily available and has been used widely without serious complications.

Adult↗
PubMed1990

Postnatal development of lung alveoli: suppression by 13% O2 and a critical period.

We studied the effect of 13% O2 on the development of the lung's gas-exchange region. Rats, acclimatized to 13% O2, remained in 13% O2 while pregnant, and were kept with their pups in 13% O2 until the pups were killed or were placed in air at age 15 days; other rats were always in air. Pups kept in 13% O2, unlike air pups, did not decrease mean chord length (Lm) or increase surface-to-volume ratio (S/V) of gas-exchange air spaces between age 2 and 14 days or by age 40 days. Rats placed in air at age 15 days did not change Lm or S/V even in air. Rats kept in 13% O2, and rats placed in air at age 15 days had fewer alveolar attachments to bronchioles than air rats. Gas-exchange air volume (VA) in 13% O2 rats was equal to or greater than in air rats; VA/kg was larger in 13% O2 than air rats. We conclude that maintenance of rats in 13% O2 during gestation and during the period alveoli are formed by septation blocks septation in a seemingly irrevocable manner. We suggest diminished septation decreases radial traction on conducting airways leading to increased VA/kg.

Aging↗
PubMed1989

Brief perinatal hypoxia impairs postnatal development of the bronchiolar epithelium.

We placed pregnant rats in 10% O2 on the last day of gestation for less than or equal to 9 h plus 1-2 h (with their pups) after the onset of delivery. In the pups this brief perinatal hypoxia led to an altered cellular composition of the bronchiolar epithelium that persisted at least to age 30 days; it was characterized by a higher nuclear numerical density (Nvn) of Clara cells, a lower Nvn of ciliated cells, and a lower percentage and Nvn of Clara cells in mitoses compared with control rats. The perinatal hypoxia also led to a significantly lower volume and volume density of the secretory apparatus (rough endoplasmic reticulum and secretory granules) on day 7 in 10% O2-born rats. The data on the Nvn of Clara and ciliated cells and on Clara cell mitoses are consistent with the notion that exposure to 10% O2 impaired the differentiation of Clara cells into ciliated cells and this impairment persisted well beyond the period of exposure.

Aging↗
PubMed1989

Short-term perinatal 10% O2 alters postnatal development of lung alveoli.

We studied the effect of breathing 10% O2 for less than or equal to 9 h by rat dams during the last day of gestation and (with their pups) for 1-2 h immediately after birth on the development of the lung's gas exchange region in the pups. Our major finding is that this brief stress resulted in substantially altered lung development noted at age 7 days and still partially present at age 30 days. In particular, perinatal hypoxia slowed the postnatal increase of lung volume, delayed septation of the large gas exchange saccules, diminished the increase of the gas exchange surface area, but accelerated thinning of the wall of the gas exchange structures. The changes produced by briefly breathing 10% O2 had as great an effect on these aspects of lung development as the same prenatal exposure to 10% O2 plus continuous postnatal exposure to 10% O2 for 7 days. Breathing 10% O2 had a particularly strong effect on alveolar wall thinning, since 2 h of breathing 10% O2 immediately after birth, without prenatal hypoxia, accelerated thinning of the alveolar wall.

Aging↗