Biomedical subjects

M Perret

Publications and source records attributed to M Perret.

At least 19 recordsLinked to original sources

PubMed2005

Social inhibition of seasonal fattening in wild and captive gray mouse lemurs.

Due to their differential reproductive investment, males and females often exhibit high differences in energy management. The main hypothesis tested in this study is that short photoperiod-induced fattening in the small primate Microcebus murinus is strongly affected by social cues. Short photoperiod-induced changes in body mass, lean mass and thyroid hormone T4 plasma levels measurements were investigated in wild and captive animals. Individual housing showed that both males and females are able to fatten. Fattening was associated with a slight increase of lean mass that reached a plateau after 3 weeks. In contrast, social grouping led to an inhibition of fattening, even when direct interactions were prevented. This social inhibition was mainly observed in males, especially when housed with females, suggesting that their low weight gain in the wild is due to female dominance. Accordingly, wild and captive animals of both sexes exhibited a decrease in T4 plasma levels, revealing a decrease in energy expenditure. Moreover, testis recrudescence observed after 20 weeks of short photoperiod exposure did not lead to any inhibition of fattening, indicating that males take advantage of female hibernation late in the dry season to fatten and use their fat reserves for the mating competition. Therefore, seasonal fattening may be used by females to prepare for hibernation and by males to prepare for the mating competition.

Analysis of Variance↗

PubMed2005

Relationship between urinary estrogen levels before conception and sex ratio at birth in a primate, the gray mouse lemur.

BACKGROUND: In primates, including humans, bias of sex ratio at birth has been reported to depend on maternal condition at conception. In a Malagasy primate, the gray mouse lemur, male-biased sex ratio at birth occurred in captive parous females. The male bias was previously demonstrated to be pre-conceptual and independent of the female's nutritional state. It was hypothesized to be related to changes in hormonal state at ovulation. METHODS AND RESULTS: The relationship between urinary estradiol (E2) levels during the follicular phase until estrus and litter production (number and sex of newborns) was assessed in 91 females mated under controlled conditions. Changes in E2 levels prior to ovulation followed the typical primate pattern characterized by a gradual rise during the 10 days preceding the sharp increase at estrus. A clear decline in E2 levels occurred with ageing. Direction of the sex ratio bias was unrelated to E2 levels at ovulation time but was significantly dependent on E2 levels during the follicular phase. Reduced E2 levels prior to estrus led to male-biased litters. CONCLUSION: This study suggests that hormonal stimulation during the follicular phase plays a role in shifting sex ratio at conception through changes in the local environment of the ova. This hypothesis deserves testing by assessing estrogen levels throughout the follicular phase in other primate species including humans.

Age Factors↗

PubMed2005

Shortened seasonal photoperiodic cycles accelerate aging of the diurnal and circadian locomotor activity rhythms in a primate.

The gray mouse lemur (Microcebus murinus), a prosimian primate, exhibits seasonal rhythms strictly controlled by photoperiodic variations. Previous studies indicated that longevity can be altered by long-term acceleration of seasonal rhythms, providing a model for assessing various aspects of aging. To assess the effect of aging and accelerated aging on the circadian system of this primate, we compared the circadian rhythm of the locomotor activity in adult mouse lemurs (2-4.5 years, n = 9), aged mouse lemurs (5-9 years, n = 10), and adult mouse lemurs that had been exposed from birth to a shortened seasonal photoperiodic cycle (2-4.5 years, n = 7). Compared to adult animals, aged mouse lemurs showed a significant increase in intradaily variability and an advanced activity onset. Aging was characterized by a decrease in amplitude, with both a decrease in nocturnal activity and an increase in daytime activity. When maintained in constant dim red light, aged animals exhibited a shortening of the free-running period (22.8 +/- 0.1 h) compared to adult animals (23.5 +/- 0.1 h). A 3- to 5-year exposure to an accelerated seasonal photoperiodic rhythm ("annual" duration of 5 months) in accelerated mouse lemurs produced disturbances of the locomotor activity rhythm that resembled those of aged mouse lemurs, whether animals were studied in entrained or in free-running conditions. The present study demonstrated a weakened and fragmented locomotor activity rhythm during normal aging in this primate. Increasing the number of expressed seasonal cycles accelerated aging of parameters related to circadian rhythmicity in adult animals.

Aging↗

PubMed2004

Factors affecting the daily rhythm of body temperature of captive mouse lemurs (Microcebus murinus).

Microcebus murinus, a small nocturnal Malagasy primate, exhibits adaptive energy-saving strategies such as daily hypothermia and gregarious patterns during diurnal rest. To determine whether ambient temperature (T(a)), food restriction and nest sharing can modify the daily body temperature (T(b)) rhythm, T(b) was recorded by telemetry during winter in six males exposed to different ambient temperatures (T(a) = 25, 20, 15 degrees C) and/or to a total food restriction for 3 days depending on social condition (isolated versus pair-grouped). At 25 degrees C, the daily rhythm of T(b) was characterized by high T(b) values during the night and lower values during the day. Exposure to cold significantly decreased minimal T(b) values and lengthened the daily hypothermia. Under food restriction, minimal T(b) values were also markedly lowered. The combination of food restriction and cold induced further increases in duration and depth of torpor bouts, minimal T(b) reaching a level just above T(a). Although it influenced daily hypothermia less than environmental factors, nest sharing modified effects of cold and food restriction previously observed by lengthening duration of torpor but without increasing its depth. In response to external conditions, mouse lemurs may thus adjust their energy expenditures through daily modifications of both the duration and the depth of torpor.

Adaptation, Physiological↗

PubMed2004

Changes in olfactory inputs modify the energy balance response to short days in male gray mouse lemurs.

The role of olfaction/olfactory cues on photoperiodic responses was assessed in Malagasy primate, the gray mouse lemur. When exposed to short photoperiod (SP), this primate demonstrates rapid changes in energy balance as adaptive anticipatory response for winter survival. To follow early changes induced by SP exposure, body mass, food intake, resting metabolism (RMR) and free thyroxin levels in plasma (T4) were measured in males abruptly transferred to SP: six intact males (controls), eight males that underwent bilateral olfactory removal (BOX) and eight males exposed to male urinary cues (U-exposed). To assess the effect of SP exposure, two other groups were maintained for 6 weeks under LP: six controls and six BOX males. Whereas all studied parameters remained constant in controls and BOX males maintained under LP, exposure to SP led to different responses according to groups. In controls, SP exposure led to a regular increase in body mass and after 4 weeks under SP, plasma T4 levels, food consumption and RMR significantly decreased. Even if BOX males demonstrated hyperphagic patterns regardless of the photoperiod, an increase in body mass was also induced by SP exposure but without changes in RMR or food intake that were body mass-dependent. In U-exposed males, body mass gain was significantly reduced while food intake and RMR remained high. In both BOX and U-exposed males, SP exposure led to a transient but high increase in T4 levels compared to controls. These results suggest that olfaction/olfactory cues may delay the SP-mediated changes in energy balance.

Adaptation, Physiological↗

PubMed2003

Daily hypothermia in captive grey mouse lemurs (Microcebus murinus): effects of photoperiod and food restriction.

The grey mouse lemur (Microcebus murinus) is a small nocturnal primate exhibiting daily torpor. In constant ambient temperature (22-24 degrees C), body temperature (Tb) and locomotor activity were monitored by telemetry in animals exposed to short (SP: 10 h light/day) or long (LP: 14 light/day) photoperiods. They were first fed ad libitum for 8 days and then subjected to 80% restricted feeding for 8 more days. During ad libitum feeding, locomotor activity was significantly lower in SP-exposed animals than in LP-exposed animals. Whatever the photoperiod, animals entered daily hypothermia within the first hours following the light onset. Depth of daily hypothermia increased irregularly under SP exposure, whereas minimal daily Tb was constantly above 35 degrees C under LP exposure. After the transfer from long photoperiod to short photoperiod corresponding to the induction of seasonal fattening, locomotor activity and depth of controlled daily hypothermia did not change significantly. In contrast, food restriction led to a significant increase in locomotor activity and in frequency of daily torpor (Tb<33 degrees C) and body temperature reached minimum values averaging 25 degrees C. However, SP-exposed animals exhibited lower minimal daily Tb and higher torpor duration than LP exposed animals. Therefore, daily torpor appears as a rapid response to food restriction occurring whatever the photoperiod, although enhanced by short photoperiod.

Animals↗

PubMed2002

Brown fat and nonshivering thermogenesis in the gray mouse lemur (Microcebus murinus).

The gray mouse lemur Microcebus murinus is a rare example of a primate exhibiting daily torpor. In captive animals, we examined the metabolic rate during arousal from torpor and showed that this process involved nonshivering thermogenesis (NST). Under thermoneutrality (28 degrees C), warming-up from daily torpor (body temperature <33 degrees C) involved a rapid (<5 min) increase of O(2) consumption that was proportional to the depth of torpor (n = 8). The injection of a beta-adrenergic agonist (isoproterenol) known to elicit NST induced a dose-dependent increase in metabolic rate (n = 8). Moreover, maximum thermogenesis was increased by cold exposure. For the first time in this species, anatomic and histological examination using an antibody against uncoupling protein (UCP) specifically demonstrated the presence of brown fat. With the use of Western blotting with the same antibody, we showed a likely increase in UCP expression after cold exposure, suggesting that NST is also used to survive low ambient temperatures in this tropical species.

Adipose Tissue, Brown↗

PubMed2002

Characterization of low- and very-low-density hepatitis C virus RNA-containing particles.

The presence of hepatitis C virus (HCV) RNA-containing particles in the low-density fractions of plasma has been associated with high infectivity. However, the nature of circulating HCV particles and their association with immunoglobulins or lipoproteins as well as the characterization of cell entry have all been subject to conflicting reports. For a better analysis of HCV RNA-containing particles, we quantified HCV RNA in the low-density fractions of plasma corresponding to the very-low-density lipoprotein (VLDL), intermediate-density lipoprotein, and low-density lipoprotein (LDL) fractions from untreated chronically HCV-infected patients. HCV RNA was always found in at least one of these fractions and represented 8 to 95% of the total plasma HCV RNA. Surprisingly, immunoglobulins G and M were also found in the low-density fractions and could be used to purify the HCV RNA-containing particles (lipo-viro-particles [LVP]). Purified LVP were rich in triglycerides; contained at least apolipoprotein B, HCV RNA, and core protein; and appeared as large spherical particles with a diameter of more than 100 nm and with internal structures. Delipidation of these particles resulted in capsid-like structures recognized by anti-HCV core protein antibody. Purified LVP efficiently bind and enter hepatocyte cell lines, while serum or whole-density fractions do not. Binding of these particles was competed out by VLDL and LDL from noninfected donors and was blocked by anti-apolipoprotein B and E antibodies, whereas upregulation of the LDL receptor increased their internalization. These results suggest that the infectivity of LVP is mediated by endogenous proteins rather than by viral components providing a mechanism of escape from the humoral immune response.

Hepacivirus↗

PubMed2002

Quantitative assessment of testicular germ cell production and kinematic and morphometric parameters of ejaculated spermatozoa in the grey mouse lemur, Microcebus murinus.

Germ cell production and organization of the testicular epithelium in a prosimian species, the grey mouse lemur, Microcebus murinus, was investigated to extend knowledge of comparative primate spermatogenesis. In addition, semen samples collected from adult male lemurs (body weight 53-92 g; n = 16) by rectal probe electroejaculation were evaluated using computer-assisted morphometric and kinematic analysis of spermatozoa. Epididymidal spermatozoa were collected from six animals after hemicastration; the testes were weighed and prepared for stereological analysis and flow cytometry. The relative testis mass (as a percentage of body weight) ranged between 1.17 and 5.6%. Twelve stages of testicular seminiferous epithelium as described for macaques were applied and only a single stage was observed in most of the seminiferous tubule cross-sections. On average (mean SD), a single testis contained 1870 +/- 829 x 10(6) germ cells and 35 +/- 12 x 10(6) Sertoli cells. Germ cell ratios (preleptotene:type B spermatogonia = 2, round spermatid:pachytene = 3; elongated spermatid:round spermatids = 1) indicated high spermatogenic efficacy. Sperm head dimensions and tail lengths of the ejaculated and epididymidal spermatozoa were similar. Percentages of defects (neck/mid-piece and tail) were low ( 10%) and similar for ejaculated and epididymidal spermatozoa. Spermatozoa were highly motile, characterized by extensive lateral head displacement, but relatively low progressive motility. In conclusion, the grey mouse lemur has unusually large testes with a highly efficient spermatogenic process and large sperm output. These features, together with the high proportion of morphologically normal and highly motile spermatozoa in the ejaculates, indicate that Microcebus murinus is a species in which sperm competition after ejaculation is likely to occur. The predominantly single spermatogenic stage system seems to be an ancestral feature among primates.

Animals↗

PubMed2001

Comparative distribution of mRNA encoding the growth hormone secretagogue-receptor (GHS-R) in Microcebus murinus (Primate, lemurian) and rat forebrain and pituitary.

The forebrain and pituitary sites of synthesis of growth hormone secretagogue-receptor mRNA were identified in four adult lemurs (Microcebus murinus) by in situ hybridisation performed with a radiolabeled cRNA probe transcribed from human Growth Hormone Secretagogue-Receptor cDNA. The cRNA sense and antisense probes were hybridised to cryostat sections containing structures extending from the rostral hypothalamus to its caudal limit as defined by the mammillary bodies. The pituitary gland and areas adjacent to the hypothalamus were also analyzed. For comparative purposes, sections from five adult rats containing these structures were hybridised with the same probes. The results point to a widespread distribution of Growth Hormone Secretagogue-Receptor mRNA in the hypothalamus, hippocampal formation, and cerebellar cortex of both lemurs and rats. As in the rat, specific hybridisation was particularly dense in the arcuate nucleus. Significant species differences were observed in the periventricular nucleus, the ventromedial nucleus, the lateral hypothalamic area, and the pituitary gland. In contrast to the rat, the lemur exhibited marked labelling in the infundibular nucleus, the periventricular nucleus and the pars tuberalis of the pituitary gland, whereas no labeling was detectable in the ventromedial nucleus and the lateral hypothalamic area. These results are discussed in terms of difference between the control of growth hormone secretion, feeding behaviour and seasonal rhythmicity among murine species and primates.

Animals↗

PubMed2001

Artificially accelerated aging by shortened photoperiod alters early gene expression (Fos) in the suprachiasmatic nucleus and sulfatoxymelatonin excretion in a small primate, Microcebus murinus.

In mammals, a number of anatomical and functional changes occur in the circadian timing system with aging. In certain species, aging can be modified by various factors which induce a number of pathological changes. In a small primate, the gray mouse lemur (Microcebus murinus), long-term acceleration of seasonal rhythms by exposing the animals to a shortened photoperiodic regime (up to 2.5 times the natural photoperiodic regime) alters longevity, based on survival curves and morphological changes. This provides a model for challenging the idea that modifications of the circadian pacemaker are related to chronological (years) versus biological (photoperiodic cycles) age. To assess the effect of aging and accelerated aging on the circadian pacemaker of this primate, we measured body weight variations, the daily rhythm in urine 6-sulfatoxymelatonin and the light-induced expression of the immediate early gene (Fos) in the suprachiasmatic nucleus of mouse lemurs that had been exposed to different photoperiodic cycles. Urine samples were collected throughout the day and urine 6-sulfatoxymelatonin levels were measured by radioimmunoassay. Light-induced Fos expression in the suprachiasmatic nucleus was studied by exposing the animals to a 15-min monochromatic pulse of light (500 nm) at saturating or sub-saturating levels of irradiance (10(11) or 10(14) photons/cm(2)/s) during the dark phase. The classical pattern of 6-sulfatoxymelatonin excretion was significantly altered in aged mouse lemurs which failed to show a nocturnal peak. Fos expression following exposure to low levels of irradiance was reduced by 88% in the suprachiasmatic nucleus of aged mouse lemurs. Exposure to higher irradiance levels showed similar results, with a reduction of 66% in Fos expression in the aged animals. Animals subjected to artificially accelerated aging demonstrated the same alterations in melatonin production and Fos response to light as animals that had been maintained in a routine photoperiodic cycle. Our data indicate that there are dramatic changes in melatonin production and in the cellular response to photic input in the suprachiasmatic nucleus of aged mouse lemurs, and that these alterations depend on the number of expressed seasonal cycles rather than on a fixed chronological age. These results provide new insights into the mechanisms underlying artificial accelerated aging at the level of the molecular mechanisms of the biological clock.

Aging↗

PubMed2001

Regulation of cell cycle progression by Swe1p and Hog1p following hypertonic stress.

Exposure of yeast cells to an increase in external osmolarity induces a temporary growth arrest. Recovery from this stress is mediated by the accumulation of intracellular glycerol and the transcription of several stress response genes. Increased external osmolarity causes a transient accumulation of 1N and 2N cells and a concomitant depletion of S phase cells. Hypertonic stress triggers a cell cycle delay in G2 phase cells that appears distinct from the morphogenesis checkpoint, which operates in early S phase cells. Hypertonic stress causes a decrease in CLB2 mRNA, phosphorylation of Cdc28p, and inhibition of Clb2p-Cdc28p kinase activity, whereas Clb2 protein levels are unaffected. Like the morphogenesis checkpoint, the osmotic stress-induced G2 delay is dependent upon the kinase Swe1p, but is not tightly correlated with inhibition of Clb2p-Cdc28p kinase activity. Thus, deletion of SWE1 does not prevent the hypertonic stress-induced inhibition of Clb2p-Cdc28p kinase activity. Mutation of the Swe1p phosphorylation site on Cdc28p (Y19) does not fully eliminate the Swe1p-dependent cell cycle delay, suggesting that Swe1p may have functions independent of Cdc28p phosphorylation. Conversely, deletion of the mitogen-activated protein kinase HOG1 does prevent Clb2p-Cdc28p inhibition by hypertonic stress, but does not block Cdc28p phosphorylation or alleviate the cell cycle delay. However, Hog1p does contribute to proper nuclear segregation after hypertonic stress in cells that lack Swe1p. These results suggest a hypertonic stress-induced cell cycle delay in G2 phase that is mediated in a novel way by Swe1p in cooperation with Hog1p.

CDC28 Protein Kinase, S cerevisiae↗

PubMed2001

Daily hypothermia and torpor in a tropical primate: synchronization by 24-h light-dark cycle.

To study the temporal organization of daily hypothermia and torpor in a nocturnal Malagasy primate, the gray mouse lemur, body temperature (T(b)) and locomotor activity were recorded using telemetry on 39 males held in 24-h light-dark cycles of different photoperiods. Under free-running condition, the circadian T(b) and locomotor activity rhythms had a period shorter than 24 h. Circadian daily hypothermia started by a rapid drop in T(b) (0.24 degrees C/10 min) at the end of subjective night (13 h 25 +/- 20 min) and was characterized by minimal T(b) values 3 h 20 +/- 5 min later. Spontaneous arousal from daily hypothermia occurred at a fixed time (6 h 05 +/- 15 min, n = 7) after the beginning of subjective day. In animals exposed to 24-h light-dark cycles with night duration varying from 10 to 14 h, locomotor activity was strictly restricted to dark time, but the temporal organization of daily hypothermia was not modified, although changes in amplitude of T(b) rhythm were observed. Daily hypothermia was directly induced by light and lasted 5 h 10 +/- 10 min, with minimal T(b) values 3 h 30 +/- 30 min (n = 28) after lights on, on condition that nighttime did not exceed the duration of subjective night. However, in animals exposed to 24-h light-dark cycles with night duration varying from 10 to 5 h, the limit of induction of daily hypothermia by light was ~9 h after the beginning of night. Finally, under short days (14:10-h light-dark cycle), long bouts (6 h 50 +/- 40 min) of actual torpor (minimum T(b) 27.6 +/- 0.9 degrees C) were observed and would involve mechanisms depending on physiological changes induced by short day exposure.

Animals↗

PubMed2001

WAKs: cell wall-associated kinases linking the cytoplasm to the extracellular matrix.

There are only a few proteins identified at the cell surface that could directly regulate plant cell wall functions. The cell wall-associated kinases (WAKs) of angiosperms physically link the plasma membrane to the carbohydrate matrix and are unique in that they have the potential to directly signal cellular events through their cytoplasmic kinase domain. In Arabidopsis there are five WAKs and each has a cytoplasmic serine/threonine protein kinase domain, spans the plasma membrane, and extends a domain into the cell wall. The WAK extracellular domain is variable among the five isoforms, and collectively the family is expressed in most vegetative tissues. WAK1 and WAK2 are the most ubiquitously and abundantly expressed of the five tandemly arrayed genes, and their messages are present in vegetative meristems, junctions of organ types, and areas of cell expansion. They are also induced by pathogen infection and wounding. Recent experiments demonstrate that antisense WAK expression leads to a reduction in WAK protein levels and the loss of cell expansion. A large amount of WAK is covalently linked to pectin, and most WAK that is bound to pectin is also phosphorylated. In addition, one WAK isoform binds to a secreted glycine-rich protein (GRP). The data support a model where WAK is bound to GRP as a phosphorylated kinase, and also binds to pectin. How WAKs are involved in signaling from the pectin extracellular matrix in coordination with GRPs will be key to our understanding of the cell wall's role in cell growth.

Arabidopsis↗

PubMed2001

[Arterial hypertension management in general practice in France according to global risk factors].

OBJECTIVE: The absolute benefit of antihypertensive medications increases with the level of cardiovascular risk. Moreover in high risk groups, it has been demonstrated that tight blood pressure (BP) control conferred a substantial reduction in the risk of cardiovascular events compared to less tight BP control. Taking into accounts these data, the WHO guidelines recommend to achieve normal BP in high risk subjects. The aim of the study was to assess BP control in a large population of hypertensives (HT) after stratification by cardiovascular risk. METHODS: 15,514 HT defined as office BP > or = 140/90 or the presence of antihypertensive treatment were recruited in France by 3,152 general practitioners. Cardiovascular risk factors and office BP were recorded. Controlled hypertension was defined as a BP < 140/90 mmHg. In patients free of cardiovascular disease, 10-year cardiovascular risks were calculated on the basis of the equations derived from the Framingham Study. RESULTS: 10-year risks were available in 13,560 HT. Those in the highest quartile had greater body mass index (BMI) and the highest concentration of diabetics and current smokers (upper quartile versus lower quartile: BMI: 28.15 vs 26.51 kg/m2; diabetics: 45% vs 3%; current smoking 32% vs 12%; p < .001). [table: see text] Increasing quartiles of risk were associated with the prevalence of uncontrolled hypertension and at a lesser extent with the use of combination therapy. Subjects in the upper quartile had more frequent calcium-blockers, ACE inhibitors and diuretics use and a less frequent betablocker use. CONCLUSION: In general practice, 85% of hypertensives at highest risk are uncontrolled whereas half of them are under monotherapy. An antihypertensive strategy based on global risk may improve BP control in high risk patients.

Adult↗

PubMed2001

[Influence of cardiovascular risk factors on prescribing of antihypertensives].

OBJECTIVE: The World Health Organization Guidelines on the management of Hypertension recommends to take care of cardiovascular risk factors for selecting drug treatment. The aim of the study was to analyze relationship between cardiovascular risk factors and use of antihypertensive drugs in general practice in France. METHODS: This was a national cross sectional epidemiological survey performed by 3,152 general practitioners between September 1999 and May 2000. Each investigator had to include 5 consecutive hypertensives (HT) (BP > or = 140/90 or presence of antihypertensive treatment). Cardiovascular risk factors, antihypertensive treatments and office BP were recorded. A stepwise logistic regression analysis was performed for each class of antihypertensive treatment in order to determine risk factors associated with prescription. Significant threshold was fixed at 0.05. Results are expressed in the form of odds ratios (OR). RESULTS: 14,551 treated hypertensives (mean age 60 +/- 10 years, male 56%) were analyzed. Sixteen per cent of patients were diabetics, 17% current smokers and the mean value of cholesterol was 2.29 +/- 0.37 g/L. ACE inhibitors, diuretics, beta-blockers (BB), dihydropyridines, angiotensin II antagonists (AAII), non DHP calcium antagonists (CA) were prescribed in respectively 47%, 35%, 28%, 18%, 14% and 12% of patients. The main risk factors associated with each kind of prescription was diabetes for ACE (OR = 1.36), coronary artery disease for BB, DHP and non-DHP CA (OR = 2.53; 1.51; 1.4 respectively) and BMI for AAII (OR = 1.03). OR > 1 indicates that risk factors was positively linked to prescription. Age had minor influence on selecting drug treatment. Conversely to BB and AAII, the use of ACE and non-DHP CA increases with presence of diabetes and cholesterol increase. CONCLUSION: In general practice, presence of cardiovascular risk factors influences mildly management of hypertension. Conversely to BB, ACE are more prescribed in HT with metabolic disorders.

Adult↗

PubMed1999

Oxidation of arsenite to arsenate by a bacterium isolated from an aquatic environment.

Arsenic is ubiquitous in the biosphere and frequently reported to be an environmental pollutant. Global cycling of arsenic is affected by microorganisms. This paper describes a new bacterial strain which is able to efficiently oxidize arsenite (As[III]) into arsenate (As[V]) in liquid medium. The rate of the transformation depends on the cell density. Arsenic species were separated by high performance liquid chromatography (HPLC) and quantified by inductively coupled plasma-atomic emission spectrometry (ICP-AES). The strain also exhibits high minimum inhibitory concentrations (MICs) for As[III] (6.65 mM (500 mg L-1)) and other heavy metals, such as cadmium (1.42 mM (160 mg L-1)) or lead (1.20 mM (250 mg L-1)). Partial identification of the strain revealed a chemoorganotrophic, Gram-negative and motile rod. The results presented here demonstrate that this strain could represent a good candidate for arsenic remediation in heavily polluted sites.

Arsenates↗

PubMed1998

Predictive factors for late toxicity after endobronchial brachytherapy: a multivariate analysis.

PURPOSE: To determine the predictive factors associated with hemoptysis and radiation bronchitis after endobronchial brachytherapy by univariate and multivariate analyses METHODS AND MATERIALS: One hundred forty-nine patients underwent endobronchial brachytherapy and were divided into three therapeutic groups: group 1: patients treated with palliative intent (n=47); group 2: patients treated with curative intent (small endobronchial tumors without mediastinal or general dissemination: n=73); group 3: patients also receiving external irradiation (n=29). One hundred twelve patients had previously received external irradiation. Brachytherapy was delivered with a dose per fraction ranging from 4 to 7 Gy and a prescription point between 0.5 and 1.5 cm, usually 1 cm from the source center. Two to six fractions were delivered according to the therapeutic group and clinical situation. The influence of the following variables on the incidence of hemoptysis or radiation bronchitis was studied: age, sex, Karnofsky score, therapeutic group, histologic type, endoscopic tumor length, dose per fraction, total brachytherapy dose, total external beam irradiation dose, total dose (brachytherapy dose plus external irradiation dose), volumes of the 100% and 200% isodoses, and volumes of the 7 and 14 Gy isodoses. RESULTS: We observed 11 hemoptyses (7.4%), 10 were lethal. All but one occurred in patients with progressive disease. Two clinical factors were significantly associated with hemoptysis by univariate analysis: palliative group (p=0.009) and endobronchial tumor length (p=0.004). No technical factors seem to be implicated in the occurrence of hemoptysis. Only endobronchial tumor length remained in the multivariate model (p=0.02). Radiation bronchitis was observed in 13 cases (8.7%). By univariate analysis, a good Karnofsky score (p=0.02), curative treatment (p=0.02), and tumor location on trachea and main stem bronchus (p=0.002) were significantly associated with this complication. Two technical factors were also incriminated: the total dose (p=0.04) and the 100% isodose volume (p=0.02). By multivariate analysis, only the tumor location retained statistical significance (p=0.009). CONCLUSION: Hemoptysis is most likely due to disease progression, with the bleeding being facilitated by brachytherapy. Some rare cases could be a direct complication of brachytherapy itself, particularly when tumors are located in the upper lobes. In contrast, radiation bronchitis occurred more frequently in patients with controlled disease, and was significantly influenced by tumor location and technical factors (dose and volumes treated). Technical improvements should increase the therapeutic ratio.

Analysis of Variance↗