Maternal aging and chromosomal abnormalities: new data drawn from in vitro unfertilized human oocytes

The effect of maternal age on the incidence of chromosomal abnormalities was investigated on a large sample of 3,042 in vitro unfertilized human oocytes II obtained from 792 women aged 19-46 years and participating in an in vitro fertilization program for various indications. The chromosomal analysis combined a gradual fixation of oocytes and an adapted R-banding technique. A total of 1,397 interpretable karyotypes were obtained. Various types of numerical aberration were observed, involving conventional chromosome nondisjunction (3.5%), single-chromatid nondisjunction (5.9%), complex (0.8%) or extreme aneuploidy (0.5%), diploidy (5.4%), and set of single chromatids (3.8%). No significant difference was found in the mean age of women according to the various types of chromosomal abnormalities. A positive relationship was found between maternal age and the global rate of aneuploidy, in agreement with the findings of epidemiological studies. The incidence of both whole-chromosome nondisjunction and precocious chromatid separation were correlated to maternal aging but the most significant correlation was found between maternal aging and single-chromatid nondisjunction. The rate of diploidy was also correlated to a slight extent to maternal aging, whereas no correlation was found between maternal age and the rate of single-chromatid sets. These data reveal that single-chromatid malsegregation is an essential factor in the age-dependent occurrence of nondisjunction in human oocytes. Disturbance in sister-chromatid cohesion might be a causal mechanism predisposing to premature chromatid separation and subsequently to nondisjunction in female meiosis.     

Enzymatic Browning and Biochemical Alterations in Black Spots of Pineapple [Ananas comosus (L.) Merr.]

Penicillium funiculosum Thom. was consistently isolated from pineapple-infected fruitlet (black spots). Polyphenol oxidase, peroxidase, and laccase activities were determined in extracts from contiguous and infected fruitlets. Healthy fruitlets showed a rather high level of polyphenol oxidase (optimum pH 7.0), and this activity was tremendously increased (×10) in contiguous infected fruitlets. Furthermore, infected fruitlets also exhibited laccase activity (optimum pH 4.0), while peroxidase was rather constant in both fruitlets. Browning reactions were attributed to qualitative and quantitative modifications of the enzymatic equipment (polyphenol oxidase and laccase) (p<0.0001). In infected fruiltets, sucrose and L-malic acid were present at significantly lower amounts than in healthy ones, likely owing to fungal metabolism (p<0.0001), whereas cell wall material was three times higher, which could be viewed as a defense mechanism to limit expansion of the mycelium. RID= ID= <E5>Correspondence to: </E5>S. Avallone; <E5>email:</E5> avallone&commat;siarc.cnearc.fr Received: 3 September 2002 / Accepted: 25 September 2002     

Enzymatic browning and biochemical alterations in black spots of pineapple [Ananas comosus (L.) Merr.

Penicillium funiculosum Thom. was consistently isolated from pineapple-infected fruitlet (black spots). Polyphenol oxidase, peroxidase, and laccase activities were determined in extracts from contiguous and infected fruitlets. Healthy fruitlets showed a rather high level of polyphenol oxidase (optimum pH 7.0), and this activity was tremendously increased (X 10) in contiguous infected fruitlets. Furthermore, infected fruitlets also exhibited laccase activity (optimum pH 4.0), while peroxidase was rather constant in both fruitlets. Browning reactions were attributed to qualitative and quantitative modifications of the enzymatic equipment (polyphenol oxidase and laccase) (p < 0.0001). In infected fruiltets, sucrose and L-malic acid were present at significantly lower amounts than in healthy ones, likely owing to fungal metabolism (p < 0.0001), whereas cell wall material was three times higher, which could be viewed as a defense mechanism to limit expansion of the mycelium.     

Modulation of guinea pig intrinsic cardiac neurons by prostaglandins

Activation of cardiac mast cells has been shown to alter parasympathetic neuronal function via the activation of histamine receptors. The present study examined the ability of prostaglandins to alter the activity of guinea pig intracardiac neurons. Intracellular voltage recordings from whole mounts of the cardiac plexus showed that antigen-mediated mast cell degranulation produces an attenuation of the afterhyperpolarization (AHP), which was prevented by the phospholipase A2 inhibitor 5,8,11,14-eicosatetraynoic acid. Exogenous application of either PGD2 or PGE2 produced a biphasic change in the membrane potential and an inhibition of both AHP amplitude and duration. Examination of prostanoid receptors using bath perfusions (1 microM PGE2 and PGD2), specific agonists (BW245C, sulprostone, and butaprost), and antagonists (AH6809 and SC19220) found evidence for both the PGE2-specific EP2 and EP3 receptors, but not for EP1 or the PGD2-specific prostanoid (DP) receptors. Sulprostone was able to mimic the PGE2 responses in some cells, but not in all PGE2-sensitive cells. Butaprost was able to mimic the PG-induced hyperpolarization in some cells, but did not alter the AHP. Inhibition of specific potassium channels with either TEA, charybdotoxin, or apamin showed that neither TEA nor charybdotoxin could prevent the PGE2-induced AHP attenuation. Apamin alone inhibited AHP duration, with PGs having no further effect in these cells. These results demonstrate that guinea pig intracardiac neurons can be modulated by PG, most likely through either EP2, EP3, or potentially EP4 receptors, and this response is due, at least in part, to a reduction in small-conductance KCa currents.     

Cardiac effects of burn injury complicated by aspiration pneumonia-induced sepsis

Early fluid resuscitation, antimicrobials, early excision, and grafting have improved survival in the early postburn period; however, a significant incidence of pneumonia-related sepsis occurs after burn injury, often progressing to multiple organ failure. Recent studies have suggested that this initial injury (burn injury) primes the subject, producing an exaggerated response to a second insult, such as pneumonia-related sepsis. We developed an experimental animal model that included a third-degree burn over 40% of the total body surface area, followed by sepsis (intratracheal administration of Streptococcus pneumoniae, 4 x 106 colony-forming unit), which was produced either 48 or 72 h after burn injury in adult male rats. Hearts harvested after either burn alone, sepsis alone, or burn plus sepsis were used to assess either contractile function (Langendorff) or cardiomyocyte secretion of tumor necrosis factor-alpha, interleukin (IL)-1beta, IL-6, and IL-10 (ELISA). Experimental groups included the following: 1). sham (sham burn and no sepsis); 2). burn injury alone studied either 24, 48, or 72 h postburn; 3). pneumonia-related sepsis in the absence of burn injury; and 4). pneumonia-induced sepsis studied either 48 or 72 h after an initial burn injury. Burn injury alone (24 h) or sepsis alone produced myocardial contractile defects and increases in pro- and anti-inflammatory cytokine secretion by cardiomyocytes. Sepsis that occurred 48 h postburn exacerbated the cardiac contractile defects seen with either burn alone or sepsis alone. Sepsis that occurred 72 h postburn produced contractile defects resembling those seen in either burn alone or sepsis alone. In conclusion, our data suggest that burn injury primes the subject such that a second insult early in the postburn period produces significantly greater cardiac abnormalities than those seen with either burn alone or sepsis alone.     

Diverging patterns of mitochondrial and nuclear DNA diversity in subarctic black spruce: imprint of a founder effect associated with postglacial colonization

High-latitude ecotonal populations at the species margins may exhibit altered patterns of genetic diversity, resulting from more or less recent founder events and from bottleneck effects in response to climate oscillations. Patterns of genetic diversity were investigated in nine populations of the conifer black spruce (Picea mariana [Mill.] BSP.) in northwestern Québec, Canada, using seed-dispersed mitochondrial (mt) DNA and nuclear (nc) DNA. mtDNA diversity (mitotypes) was assessed at three loci, and ncDNA diversity was estimated for nine expressed sequence tag polymorphism (ESTP) loci. Sampling included populations from the boreal forest and the southern and northern subzones of the subarctic forest-tundra, a fire-born ecotone. For ncDNA, populations from all three vegetation zones were highly diverse with little population differentiation (thetaN = 0.014); even the northernmost populations showed no loss of rare alleles. Patterns of mitotype diversity were strikingly different: within-population diversity and population differentiation were high for boreal forest populations [expected heterozygosity per locus (HE) = 0.58 and thetaM = 0.529], but all subarctic populations were fixed for a single mitotype (HE = 0). This lack of variation suggests a founder event caused by long-distance seed establishment during postglacial colonization, consistent with palaeoecological data. The estimated movement of seeds alone (effective number of migrants per generation, NmM < 2) was much restricted compared to that estimated from nuclear variants, which including pollen movement (NmN > 17). This could account for the conservation of a founder imprint in the mtDNA of subarctic black spruce. After reduction, presumably in the early Holocene, the diversity in ncDNA would have been replenished rapidly by pollen-mediated gene flow, and maintained subsequently through vegetative layering during the current cooler period covering the last 3000 years.     

What is the nature of the replicative niche of a stealthy bug named Brucella?

Brucella spp. are facultatively intracellular bacteria that persist and multiply in the macrophages of their mammalian hosts. The so-called phagosome to which they have adapted is their natural living niche. Characterization of this niche would facilitate an understanding of the true relationship between the host cell and the intracellular bacteria. This Opinion analyses and discusses the characteristic properties and genesis of this vacuole during phagocytosis as deduced from the virulence factors necessary for intracellular multiplication of the pathogen. We conclude that the replicative niche of Brucella spp.--the 'brucellosome'--differs from all other cellular organelles, and that it isolates the pathogen from certain cytoplasmic nutrients. Adaptation to the stress conditions encountered and the use of anaerobic respiration enable brucellae to replicate in the compartment they create.     

New nitrogen mustards structurally related to (L)-carnitine

Enantiopure nitrogen mustards which mimic (L)-carnitine framework are prepared by a multi-step synthesis from the (R)-di-tert-butyl malate and their antitumor properties evaluated.