Lack of detectable genetic recombination on the X chromosome during the parthenogenetic production of female and male aphids

We used polymorphic microsatellite markers to look for recombination during parthenogenetic oogenesis between the X chromosomes of aphids of the tribe Macrosiphini. We examined the X chromosome because it comprises approximately 25 % of the genome and previous cytological observations of chromosome pairing and nucleolar organizer (NOR) heteromorphism suggest recombination, although the same is not true for autosomes. A total of 564 parthenogenetic females of Myzus clones with three distinct reproductive modes (cyclical parthenogenesis, obligate parthenogenesis and obligate parthenogenesis with male production) were genotyped at three informative X-linked loci. Also, parthenogenetically produced males from clones encompassing the full range of male-producing reproductive strategies were genotyped. These included 391 Myzus persicae males that were genotyped at three X-linked loci and 538 males from Sitobion clones that were genotyped at five informative X-linked loci. Our results show no departure from clonality in parthenogenetic generations of aphids of the tribe Macrosiphini: no recombinant genotypes were observed in parthenogenetically produced males or females.     

Growth and mineral nutrition of two Chlorococcalean algae

The effect of composition of the medium and pH on the growth of Pediastrum duplex Meyen and Dictyosphaerium pulchellum Wood was studied. Both species showed preference to alkaline conditions. The ammonium nitrate grown colonies of D. pulchellum lacked mucilage and showed a more compact form, resembling D. pulchellum var. minitum Deflandre. From this it appears that D. pulchellum var. minitum is a nutritional variant of the species and not a stable variety.     

Down-regulation of two non-homologous endogenous tomato genes with a single chimaeric sense gene construct

Tomatoes (Lycopersicon esculentum Mill cv. Ailsa Craig) were transformed with a gene construct having 244 bp of the 5 end of a polygalacturonase (PG) cDNA, coding for a 71 amino acid N-terminal extension to the mature protein, fused to 1320 bp of a pectinesterase (PE) cDNA encoding the full sequence of the mature PE protein. This chimaeric gene was inserted in a sense orientation between a CaMV 35S promoter and terminator for constitutive expression. In transformed tomato plants expression of the endogenous PG and PE genes in the fruit was inhibited; there was little or no observable PG and PE mRNA and a substantial reduction in the level of PG and PE enzyme activity. The transgene was expressed in the leaves of the transformed plants as demonstrated by the accumulation of mRNA, but no protein product could be identified. However, no transgene mRNA or protein were observed in the transgenic fruit.This paper represents the first report of the down-regulation of two non-homologous endogenous genes using a single gene construct. A sense gene construct was responsible for these effects. These findings are discussed in relation to possible mechanisms of action of co-suppression.     

A cadmium resistance plasmid, pXU5, in Staphylococcus aureus, strain ATCC25923

A 25.9-kb plasmid, pXU5, encoding high level cadmium resistance was isolated from Staphylococcus aureus strain ATCC25923. A labelled cadA probe from plasmid pI258 hybridised to a 2.3-kb EcoRI fragment of pXU5. pXU5 was incompatible with an S. aureus incompatibility group 1 plasmid.     

Evaluation of SQ 28,603, an inhibitor of neutral endopeptidase, in conscious monkeys.

The potent neutral endopeptidase inhibitor SQ 28,603 (N-(2-(mercaptomethyl)-1-oxo-3-phenylpropyl)-beta-alanine) significantly increased excretion of sodium from 4.9 +/- 2.3 to 14.3 +/- 2.1 muequiv./min and cyclic 3',5'-guanosine monophosphate from 118 +/- 13 to 179 +/- 18 pmol/min after intravenous administration of 300 mumol/kg (approximately 80 mg/kg) in conscious female cynomolgus monkeys. SQ 28,603 did not change blood pressure or plasma atrial natriuretic peptide concentrations in the normal monkeys. In contrast, 1-h infusions of 3, 10, or 30 pmol.kg-1.min-1 of human atrial natriuretic peptide lowered blood pressure by -3 +/- 4, -9 +/- 4, and -27 +/- 3 mmHg (1 mmHg = 133.322 Pa), increased cyclic guanosine monophosphate excretion from 78 +/- 11 to 90 +/- 6, 216 +/- 33, and 531 +/- 41 pmol/min, and raised plasma atrial natriuretic peptide from 7.2 +/- 0.7 to 21 +/- 4, 62 +/- 12, and 192 +/- 35 fmol/mL without affecting sodium excretion. In monkeys receiving 10 pmol.kg-1.min-1 of atrial natriuretic peptide, 300 mumol/kg of SQ 28,603 reduced mean arterial pressure by -13 +/- 5 mmHg and increased sodium excretion from 6.6 +/- 3.2 to 31.3 +/- 6.0 muequiv./min, cyclic guanosine monophosphate excretion from 342 +/- 68 to 1144 +/- 418 pmol/min, and plasma atrial natriuretic peptide from 124 +/- 8 to 262 +/- 52 fmol/mL. In conclusion, SQ 28,603 stimulated renal excretory function in conscious monkeys, presumably by preventing the degradation of atrial natriuretic peptide by neutral endopeptidase.     

Clonal propagation of Enset (Ensete superbum (Roxb.) Cheesman) through shoot tip cultures

Summary The morphogenetic potential of the shoot tip explants ofEnsete superbum (Roxb.) Cheesman, a wild relative of the cultivated bananas, was investigated and an effective clonal propagation method devised. Shoot tip explants grown in modified MS medium containing 1.5 mg l^–1 BAP and 1 mg l^–1 KIN developed corms which on transfer to medium containing 3 mg l^–1 IBA and 1.5 mg l^–1 BAP, regenerated a large number of shoots from the surface of the corm, the origin of which was traced to single hypodermal cells. Shoots were rooted on a half-strength MS medium salts containing 3 mg l^–1 IBA and 0.1 mg l^–1 BAP. The rooted plantlets were hardened and planted in the field where the plants looked normal.     

Detection of a high frequency RsaI polymorphism in the human pro alpha 2(I) collagen gene which is linked to an autosomal dominant form of osteogenesis imperfecta.

Screening of the pro alpha 2(I) collagen genes of Southern African populations for restriction fragment length polymorphisms (RFLPs) has revealed a locus polymorphic for the restriction enzyme RsaI. The frequency of the RFLP was 0.38 in Afrikaners, but much lower in indigenous Southern African populations, which suggests that it is of European origin. The polymorphism was used to study 19 affected and non-affected individuals in a four generation family with the autosomal dominant disorder, osteogenesis imperfecta (OI) type I. Co-inheritance of the loss of the RsaI site and the OI phenotype was observed with a lod score of 3.91 at a recombination fraction (theta) of zero, indicating strong linkage. This suggests that the defect in this family is caused by a structural mutation within or close to the pro alpha 2(I) collagen gene. The use of this high frequency RFLP together with other recently described polymorphisms at this locus will facilitate the analysis of the role of this gene in OI and other inherited disorders of connective tissue.     

Homozygosity mapping, to chromosome 11p, of the gene for familial persistent hyperinsulinemic hypoglycemia of infancy.

Familial persistent hyperinsulinemic hypoglycemia of infancy (PHHI) is a rare, autosomal recessive disease of unregulated insulin secretion, defined by elevations in serum insulin despite severe hypoglycemia. We used the homozygosity gene-mapping strategy to localize this disorder to the region of chromosome 11p between markers D11S1334 and D11S899 (maximum LOD score 5.02 [theta = 0] at marker D11S926) in five consanguineous families of Saudi Arabian origin. These results extend those of a recent report that also placed PHHI on chromosome 11p, between markers D11S926 and D11S928. Comparison of the boundaries of these two overlapping regions allows the PHHI locus to be assigned to the 4-cM region between the markers D11S926 and D11S899. Identification of this gene may allow a better understanding of other disorders of glucose homeostasis, by providing insight into the regulation of insulin release.     

Extension of Drosophila melanogaster life span with a GPCR peptide inhibitor

G protein-coupled receptors (GPCRs) mediate signaling from extracellular ligands to intracellular signal transduction proteins. Methuselah (Mth) is a class B (secretin-like) GPCR, a family typified by their large, ligand-binding, N-terminal extracellular domains. Downregulation of mth increases the life span of Drosophila melanogaster; inhibitors of Mth signaling should therefore enhance longevity. We used mRNA display selection to identify high-affinity (K(d) = 15 to 30 nM) peptide ligands that bind to the N-terminal ectodomain of Mth. The selected peptides are potent antagonists of Mth signaling, and structural studies suggest that they perturb the interface between the Mth ecto- and transmembrane domains. Flies constitutively expressing a Mth antagonist peptide have a robust life span extension, which suggests that the peptides inhibit Mth signaling in vivo. Our work thus provides new life span-extending ligands for a metazoan and a general approach for the design of modulators of this important class of GPCRs.     

Signal-to-signal neural networks for improved spike estimation from calcium imaging data

Spiking information of individual neurons is essential for functional and behavioral analysis in neuroscience research. Calcium imaging techniques are generally employed to obtain activities of neuronal populations. However, these techniques result in slowly-varying fluorescence signals with low temporal resolution. Estimating the temporal positions of the neuronal action potentials from these signals is a challenging problem. In the literature, several generative model-based and data-driven algorithms have been studied with varied levels of success. This article proposes a neural network-based signal-to-signal conversion approach, where it takes as input raw-fluorescence signal and learns to estimate the spike information in an end-to-end fashion. Theoretically, the proposed approach formulates the spike estimation as a single channel source separation problem with unknown mixing conditions. The source corresponding to the action potentials at a lower resolution is estimated at the output. Experimental studies on the spikefinder challenge dataset show that the proposed signal-to-signal conversion approach significantly outperforms state-of-the-art-methods in terms of Pearson’s correlation coefficient, Spearman’s rank correlation coefficient and yields comparable performance for the area under the receiver operating characteristics measure. We also show that the resulting system: (a) has low complexity with respect to existing supervised approaches and is reproducible; (b) is layer-wise interpretable, and (c) has the capability to generalize across different calcium indicators.