Late immature mortality is the major influence on reproductive success of African black beetle, Heteronychus arator (Fabricius) (Coleoptera: Scarabaeidae), in a Mediterranean-climate region of Australia

In field and laboratory studies, mortality of African black beetle, Heteronychus arator, in the winter-rainfall, Mediterranean-type climate region of south-western Australia was higher in the late immature stages during summer than in the early immature stages that occur during spring, a contrast to summer-rainfall climatic regions. Greatest mortality occurred around the pupal stage in contrasting soil types, despite drying differences in summer and supplementary watering in some plots. Sampling of natural populations confirmed experimental results that mortality in late immature stages is the major factor limiting H. arator populations under a Mediterranean-type climate. Inter-generation increase in H. arator abundance was uncommon, explaining the consistent abundance typically observed between years in south-western Australia. Random dispersal of newly emerged adults in autumn was inferred to restore uniformity in adult abundance between areas of varying favourability for immature survival.     

Transplantation of insulin-secreting cells differentiated from human adipose tissue-derived stem cells into type 2 diabetes mice

Currently, there are limited ways to preserve or recover insulin secretory capacity in human pancreas. We evaluated the efficacy of cell therapy using insulin-secreting cells differentiated from human eyelid adipose tissue-derived stem cells (hEAs) into type 2 diabetes mice. After differentiating hEAs into insulin-secreting cells (hEA-ISCs) in vitro, cells were transplanted into a type 2 diabetes mouse model. Serum levels of glucose, insulin and c-peptide were measured, and changes of metabolism and inflammation were assessed in mice that received undifferentiated hEAs (UDC group), differentiated hEA-ISCs (DC group), or sham operation (sham group). Human gene expression and immunohistochemical analysis were done. DC group mice showed improved glucose level, and survival up to 60 days compared to those of UDC and sham group. Significantly increased levels of human insulin and c-peptide were detected in sera of DC mice. RT-PCR and immunohistochemical analysis showed human gene expression and the presence of human cells in kidneys of DC mice. When compared to sham mice, DC mice exhibited lower levels of IL-6, triglyceride and free fatty acids as the control mice. Transplantation of hEA-ISCs lowered blood glucose level in type 2 diabetes mice by increasing circulating insulin level, and ameliorating metabolic parameters including IL-6.     

Substrate Specificity, Substrate Channeling, and Allostery in BphJ: An Acylating Aldehyde Dehydrogenase Associated with the Pyruvate Aldolase BphI

BphJ, a nonphosphorylating acylating aldehyde dehydrogenase, catalyzes the conversion of aldehydes to form acyl-coenzyme A in the presence of NAD(+) and coenzyme A (CoA). The enzyme is structurally related to the nonacylating aldehyde dehydrogenases, aspartate-β-semialdehyde dehydrogenase and phosphorylating glyceraldehyde-3-phosphate dehydrogenase. Cys-131 was identified as the catalytic thiol in BphJ, and pH profiles together with site-specific mutagenesis data demonstrated that the catalytic thiol is not activated by an aspartate residue, as previously proposed. In contrast to the wild-type enzyme that had similar specificities for two- or three-carbon aldehydes, an I195A variant was observed to have a 20-fold higher catalytic efficiency for butyraldehyde and pentaldehyde compared to the catalytic efficiency of the wild type toward its natural substrate, acetaldehyde. BphJ forms a heterotetrameric complex with the class II aldolase BphI that channels aldehydes produced in the aldol cleavage reaction to the dehydrogenase via a molecular tunnel. Replacement of Ile-171 and Ile-195 with bulkier amino acid residues resulted in no more than a 35% reduction in acetaldehyde channeling efficiency, showing that these residues are not critical in gating the exit of the channel. Likewise, the replacement of Asn-170 in BphJ with alanine and aspartate did not substantially alter aldehyde channeling efficiencies. Levels of activation of BphI by BphJ N170A, N170D, and I171A were reduced by ≥3-fold in the presence of NADH and ≥4.5-fold when BphJ was undergoing turnover, indicating that allosteric activation of the aldolase has been compromised in these variants. The results demonstrate that the dehydrogenase coordinates the catalytic activity of BphI through allostery rather than through aldehyde channeling.     

Loss of ATRX leads to chromosome cohesion and congression defects

Alpha thalassemia/mental retardation X linked (ATRX) is a switch/sucrose nonfermenting-type ATPase localized at pericentromeric heterochromatin in mouse and human cells. Human ATRX mutations give rise to mental retardation syndromes characterized by developmental delay, facial dysmorphisms, cognitive deficits, and microcephaly and the loss of ATRX in the mouse brain leads to reduced cortical size. We find that ATRX is required for normal mitotic progression in human cultured cells and in neuroprogenitors. Using live cell imaging, we show that the transition from prometaphase to metaphase is prolonged in ATRX-depleted cells and is accompanied by defective sister chromatid cohesion and congression at the metaphase plate. We also demonstrate that loss of ATRX in the embryonic mouse brain induces mitotic defects in neuroprogenitors in vivo with evidence of abnormal chromosome congression and segregation. These findings reveal that ATRX contributes to chromosome dynamics during mitosis and provide a possible cellular explanation for reduced cortical size and abnormal brain development associated with ATRX deficiency.     

Immunolocalization of sperm protein 17 in human testis and ejaculated spermatozoa.

Sperm protein 17 (Sp17) is a highly conserved mammalian protein whose primary function is still poorly understood. Immunohistochemistry (IHC) in the human testis reveals the presence of Sp17 in some spermatocytes and abundantly in spermatids. All spermatogonia, Sertoli cells, and Leydig cells appear to be immunonegative for Sp17, whereas some interstitial cells are immunopositive. IHC recognized two distinct populations (immunopositive or not for Sp17) in the ejaculated spermatozoa. Although it will be necessary to clarify why some ejaculated spermatozoa do not contain Sp17, its distribution suggests that this protein may be associated with some phases of germinal cell differentiation.     

Molecular-genetic characterisation of a new nematode resistance gene in wheat

Bread wheat lines introgressed with Aegilops ventricosa chromosomes were evaluated for their resistance to the Australian cereal cyst nematode (CCN, Heterodera avenae) pathotype Ha13. Higher levels of resistance relative to the phenotype of the Cre1 CCN resistance gene in wheat were found in the donor Ae. ventricosa parental lines and chromosome-5N^v substitution or addition lines. The newly identified resistance to pathotype Ha13 on chromosome 5N^v, designated, Cre6, was shown to be independent of the Ae. ventricosa-derived Cre2 gene, effective against several European pathotypes. Another Ae. ventricosa derived gene, Cre5, showed partial resistance to pathotype Ha13. Inhibition of Ha13 female nematode reproduction was ranked in the order Cre6 >Cre1 >CreF≥Cre5. Cre6 was inherited as a single dominant locus. Gene sequences encoding nucleotide-binding sites and leucine-rich repeats (NBS-LRR) from the Cre3 CCN-pathotype Ha13 resistance locus were used as probes to isolate related sequences from one of the donor Ae. ventricosa parents. Related sequences from Ae. ventricosa (71–73% similarity at the amino-acid level to the Cre3-derived sequences) of chromosome 5N^v origin were identified and served as diagnostic molecular markers for the presence of 5N^v. CCN-susceptible plants, found as variants in some of the purported chromosome 5N^v lines, were also found to be missing the diagnostic 5N^v RFLP markers assayed by the NBS-LRR probe. An alloplasmic chromosome-5N^v addition line with Ae. ventricosa cytoplasm in the wheat cultivar, Moisson, background was particularly variable, with 43% CCN-susceptible plants and a corresponding loss of the diagnostic chromosome-5 molecular markers. Received: 26 June 2000 / Accepted: 15 July 2000     

The nematode-resistance gene,<Emphasis Type="Italic"> Mi-1</Emphasis>, is associated with an inverted chromosomal segment in susceptible compared to resistant tomato

The gene Mi-1 confers effective resistance in tomato (Lycopersicon esculentum) against root-knot nematodes and some isolates of potato aphid. This locus was introgressed from L. peruvianum into the corresponding region on chromosome 6 in tomato. In nematode-resistant tomato, Mi-1 and six homologs are grouped into two clusters separated by 300 kb. Analysis of BAC clones revealed that the Mi-1 locus from susceptible tomato carried the same number and distribution of Mi-1 homologs, as did the resistant locus. Molecular markers flanking the resistant and susceptible loci were in the same relative orientation, but markers between the two clusters were in an inverse orientation. The simplest explanation for these observations is that there is an inversion between the two clusters of homologs when comparing the Mi-1 loci from L. esculentum and L. peruvianum. Such an inversion may explain previous observations of severe recombination suppression in the region. Two Mi-1 homologs identified from the BAC library derived from susceptible tomato are not linked to the chromosome 6 locus, but map to chromosome 5 in regions known to contain resistance gene loci in other solanaceous species.Communicated by J.S. Heslop-Harrison