Genetic control of male fertility in Arabidopsis thaliana: structural analyses of postmeiotic developmental mutants

Seven new male-sterile mutants (ms7-ms13) of Arabidopsis thaliana (L.) Heynh. (ecotype columbia) are described that show a postmeiotic defect of microspore development. In ms9 mutants, microspores recently released from the tetrad appear irregular in shape and are often without exines. The earliest evidence of abnormality in ms12 mutants is degeneration of microspores that lack normal exine sculpturing, suggesting that the MS12 product is important in the formation of pollen exine. Teratomes (abnormally enlarged microsporocytes) are also occasionally present and each has a poorly developed exine. In ms7 mutant plants, the tapetal cytoplasm disintegrates at the late vacuolate microspore stage, apparently causing the degeneration of microspores and pollen grains. With ms8 mutants, the exine of the microspores appears similar to that of the wild type. However, intine development appears impaired and pollen grains rupture prior to maturity. In ms11 mutants, the first detectable abnormality appears at the mid to late vacuolate stage. The absence of fluorescence in the microspores and tapetal cells after staining with 4',6-diamidino-2-phenylindole (DAPI) and the occasional presence of teratomes indicate degradation of DNA. Viable pollen from ms10 mutant plants is dehisced from anthers but appears to have surface abnormalities affecting interaction with the stigma. Pollen only germinates in high-humidity conditions or during in-vitro germination experiments. Mutant plants also have bright-green stems, suggesting that ms10 belongs to the eceriferum (cer) class of mutants. However, ms10 and cer6 are non-allelic. The ms13 mutant has a similar phenotype to ms10, suggesting is also an eceriferum mutation. Each of these seven mutants had a greater number of flowers than congenic male-fertile plants. The non-allelic nature of these mutants and their different developmental end-points indicate that seven different genes important for the later stages of pollen development have been identified.     

Dietary deficiency of cystine and methionine in rats alters thiol homeostasis required for cyanide detoxification

Nutritional status is an important factor in modulating the metabolic fate of xenobiotics. Sulfur amino acid (SAA) deficiency has been proposed as a risk factor for human neurological diseases among protein-poor populations subsisting on the cyanophoric plant cassava. Female Sprague-Dawley rats were used to develop and define a model of SAA deficiency for use in future studies examining cassava-related neurotoxicity. Rats were kept in metabolic cages for 7-21 d and fed a balanced diet (BD) of known composition or a comparable diet selectively deficient in methionine and cystine (SAA-free diet). Animals fed the SAA-free diet failed to thrive, lost body weight, excreted porphyrinic materials, and showed a steep and persistent reduction of urinary inorganic sulfate. In contrast, animals on the BD gained body weight and maintained baseline output of urinary inorganic sulfate. Urinary thiocyanate excretion did not differ between groups, but plasma thiocyanate concentrations reached double that in SAA-deficient rats. Increased plasma thiocyanate suggests mobilization of sulfur amino acids from endogenous sources. Liver glutathione and blood cyanide concentrations were similar in animals on the BD and the SAA-deficient diet. In summary, a diet free of methionine and cystine results in increased retention of inorganic sulfur as thiocyanate and a near absence of inorganic sulfur excretion in urine.     

A review of methods and instruments for assessing externalizing disorders: theoretical and practical considerations in rendering a diagnosis

This review addresses the most current and widely used methods of assessing childhood and adolescent externalizing disorders. Interviews, rating scales, and self-report instruments are described, and their strengths and weaknesses are discussed. Direct observational techniques in naturalistic and analogue settings are also reviewed. Throughout the article, commentary is offered regarding the psychometric adequacy and clinical validity of these instruments. It is suggested that, although the instruments presently used to assist in diagnosing externalizing disorders generally possess adequate reliability and representational validity, evidence of elaborative validity is lacking. Clinicians and researchers are encouraged to adopt a broader conceptualization of the diagnostic process, to question existing standards for establishing validity, and to consider alternative means of demonstrating diagnostic utility.     

Aging and mitochondria

Aging is a complex physiological phenomenon and several different theories have been elaborated about its origin. Among such theories, the 'mitochondrial theory of aging', which has gained a large support, indicates the accumulation of somatic mutations of mitochondrial DNA leading to the decline of mitochondrial functionality as one of the driving forces for the process itself. In this review data on rat and man from our laboratory and from recent literature have been thoroughly examined and compared in order to provide the 'state-of-the-art' on the role of mitochondria in aging. Alterations of structure and expression of mitochondrial genome with aging, to find out the eventual relevant changes of mitochondrial biogenesis, have been studied in rat whereas the relationship between cytochrome c oxidase activity and 'common deletion' has been studied in man. Results on the effect of acetyl-L-carnitine on the mitochondrial functionality are also reported.     

Non-C282Y familial iron overload: evidence for locus heterogeneity in haemochromatosis

Haemochromatosis (HC) is an autosomal recessive disease with progressive iron overload leading to midlife onset of clinical complications. The causal gene (HFE) maps to 6p, in close linkage with the HLA class I genes. An HFE candidate gene recently identified has two missense mutations (C282Y and H63D) associated with the disease. Here we document the phenotypic and genetic analysis of a nuclear family comprising two sibs with symptomatic and massive iron overload before the age of 25. The disease seemed to be recessively transmitted and fitted the agreed criteria for haemochromatosis, but was neither associated with the C282Y and H63D mutations nor linked with HLA markers. Our data strongly support locus heterogeneity in haemochromatosis by showing evidence that the gene responsible for juvenile haemochromatosis (JH) does not map to 6p. In the absence of clear cut phenotypic distinction from typical haemochromatosis, patients below 30 years of age and C282Y negative should be considered as putative juvenile cases. This has practical implications in genetic counselling and family management.     

The effect of ionic strength on liposome-buffer and 1-octanol-buffer distribution coefficients

BACKGROUND: To evaluate the safety and effectiveness of tepid perfusion and isothermic blood cardioplegia in coronary surgery. METHODS: We studied 200 patients undergoing myocardial revascularization: 100 procedures were performed with moderate systemic hypothermia (28 degrees C) and cold crystalloid cardioplegia (4 degrees C); the other 100 patients received tepid systemic perfusion (TP) (34 degrees C) and intermittent blood cardioplegia at the same temperature according to the minicardioplegia technique (Group 2). The two groups were comparable with regards to age, extent of disease, preoperative left ventricular function and extra-corporeal circulation (ECC) time. RESULTS: In the tepid group we observed a higher incidence of spontaneous resumption of cardiac rhythm at cross-clamp removal compared to the hypothermic group (93% vs 34%; p<0.001). No difference was found in cardiac index at specified intervals, myocardial enzymes, inotrope requirements, arrhythmias, need for vasopressors and postoperative blood loss. Fluid balance at the end of ECC was significantly lower in the tepid group (343+/-635 ml vs 883+/-925 ml; p<0.001). Hospital mortality and morbidity were the same in the two groups. CONCLUSIONS: Our data suggest that TP and isothermic blood cardioplegia represent a simple, safe and effective method of systemic and myocardial protection which may be an alternative to traditional hypothermia.     

Helicobacter pylori cagA status, vacA genotypes and ulcer disease

The in vitro sensitivity of P. falciparum drug-resistant isolates was evaluated in the region of Bobo-Dioulasso during the 1995 and 1996 rainy seasons. Two routinely used antimalarials (chloroquine and quinine) and two new antimalarials (mefloquine and halofantrine) were assessed using 24-hour in vitro cultures with tritiated hypoxanthine and a parasite density > or = 4,000/microl of blood. The proportion of chloroquine-resistant isolates was 20% in 1995 and 19% in 1996, whilst in 1996, the proportion of isolates resistant to halofantrine was greater than in 1995 (9.6% versus 1%). No significant differences were seen in the mean IC50 values in relation to the susceptibility of chloroquine-resistant or chloroquine-sensitive isolates to mefloquine and halofantrine. In the case of quinine, the mean IC50 values were significantly higher in chloroquine-resistant isolates than in chloroquine-sensitive ones. A significant positive correlation was found between the following IC50 values: chloroquine versus quinine, quinine versus mefloquine and mefloquine versus halofantrine.     

IL-10 regulates thrombus-induced vein wall inflammation and thrombosis

Vein wall inflammation associated with venous thrombosis is mediated by an imbalance in proinflammatory as compared with antiinflammatory molecules. We hypothesize that IL-10 is an important antiinflammatory cytokine that influences vein wall inflammation and thrombus propagation during venous thrombosis. To test this hypothesis a model of inferior vena caval thrombosis was used. Studies were performed at sacrifice 2 days after thrombus induction and included leukocyte morphometrics, myeloperoxidase activity, vein wall permeability, thrombus weight, and IL-10 ELISA analysis from the vein wall. IL-10 was elevated in the vein wall during venous thrombosis. Neutralization of IL-10 increased inflammation, while supplementation with rIL-10 demonstrated a dose- and time-dependent decrease in inflammation. Interestingly, a low 2.5-microg rIL-10 dose given at time of initiation of thrombosis most significantly decreased inflammation. Thrombus weight was importantly diminished by reconstitution of IL-10. These studies support an important role for IL-10 in the regulation of thrombus-associated inflammation and thrombosis and suggest that IL-10 could be used as a therapeutic agent in the treatment of venous thrombosis.