Evaluation of the establishment of Aphidius ervi Haliday (Hymenoptera: Braconidae) in lucerne aphid populations in New South Wales

The aphid parasitoid Aphidius ervi was released in the major lucerne-growing areas of New South Wales (NSW), Australia, between 1978 and 1981. With the collaboration of district agronomists of the New South Wales Department of Agriculture, five State-wide surveys were conducted in 1982–1983 to determine the success of the release program. In each survey, the distribution of the parasitoid was checked in relation to populations of the aphids Acyrthosiphon kondoi Shinji and Acyrthosiphon pisum (Harris) (Hemiptera: Aphididae). The surveys confirmed the successful dispersal and establishment of A. ervi in the major lucerne-growing areas of NSW. They demonstrated its ability to survive and recover rapidly after a severe and widespread drought.     

Demonstration of prolactin messenger RNA after amplification in the brain in rats]

By means of immunocytochemistry, a central neuronal network containing a prolactin-like substance has been described in the rat. In order to demonstrate the synthesis of this peptide in these cells, we examined the presence of prolactin messenger RNA (PRL mRNA) in several brain samples including the pituitary gland. Amplification of the PRL mRNA was performed by the polymerase chain reaction technique, followed by southern blotting and hybridization with a specific oligonucleotide. Results showed the presence of the expected cDNA (468 bp) in the hypothalamus. Another cDNA with a lower molecular weight was also observed.     

Enhancer of Polycomb is a suppressor of position-effect variegation in Drosophila melanogaster.

Polycomb group (PcG) genes of Drosophila are negative regulators of homeotic gene expression required for maintenance of determination. Sequence similarity between Polycomb and Su(var)205 led to the suggestion that PcG genes and modifiers of position-effect variegation (PEV) might function analogously in the establishment of chromatin structure. If PcG proteins participate directly in the same process that leads to PEV, PcG mutations should suppress PEV. We show that mutations in E(Pc), an unusual member of the PcG, suppress PEV of four variegating rearrangements: In(l)wm4, B(SV), T(2;3)Sb(V) and In(2R)bw(VDe2). Using reversion of a Pelement insertion, deficiency mapping, and recombination mapping as criteria, homeotic effects and suppression of PEV associated with E(Pc) co-map. Asx is an enhancer of PEV, whereas nine other PcG loci do not affect PEV. These results support the conclusion that there are fewer similarities between PcG genes and modifiers of PEV than previously supposed. However, E(Pc) appears to be an important link between the two groups. We discuss why Asx might act as an enhancer of PEV.     

Effects of dietary copper on human autonomic cardiovascular function

Heart rate and blood pressure responses during supine rest, orthostasis, and sustained handgrip exercise at 30% maximal voluntary contraction were determined in eight healthy women aged 18-36 years who consumed diets varying in copper and ascorbic acid content. Copper retention and plasma copper concentration were not affected by diet. Enzymatic, but not immunoreactive, ceruloplasmin was lower (p less than 0.05) after the low copper and high ascorbic acid diet periods. Diet had no effect on resting supine heart rates, orthostatic responses in heart rate and blood pressure, or standing resting blood pressure. Systolic and diastolic blood pressures were increased significantly (p less than 0.05) during the handgrip test at the end of the low copper and ascorbic acid supplementation periods. Also, the ratio of enzymatic to immunoreactive ceruloplasmin decreased significantly during these dietary treatments. The mean arterial blood pressure at the end of the handgrip test was negatively (p less than 0.0004) correlated with the ceruloplasmin ratios. These findings indicate a functional alteration in human blood pressure regulation during mild copper depletion.     

Truncated variants of apolipoprotein B cause hypobetalipoproteinaemia.

Familial hypobetalipoproteinaemia is a rare autosomal dominant disorder in which levels of apo-B-containing plasma lipoproteins are approximately half-normal in heterozygotes and virtually absent in homozygotes. Here we describe mutations of the apo-B gene that cause two different truncated variants of apo-B in unrelated individuals with hypobetalipoproteinaemia. One variant, apo-B(His1795----Met-Trp-Leu-Val-Thr-Term) is predicted to be 1799 amino acids long and arises from deletion of a single nucleotide (G) from leucine codon 1794. This protein was found at low levels in very low density and low density lipoprotein fractions in the blood. The second, shorter variant, apo-B(Arg1306----Term), is caused by mutation of a CpG dinucleotide in arginine codon 1306 converting it to a stop codon and predicting a protein of 1305 residues. The product of this allele could not be detected in the circulation. The differences in size and behaviour of these two variants compared to apo-B100 or apo-B48 point to domains that may be important for the assembly, secretion or stability of apo-B-containing lipoproteins.     

Statistical inference from single channel records: two-state Markov model with limited time resolution

Though stochastic models are widely used to describe single ion channel behaviour, statistical inference based on them has received little consideration. This paper describes techniques of statistical inference, in particular likelihood methods, suitable for Markov models incorporating limited time resolution by means of a discrete detection limit. To simplify the analysis, attention is restricted to two-state models, although the methods have more general applicability. Non-uniqueness of the mean open-time and mean closed-time estimators obtained by moment methods based on single exponential approximations to the apparent open-time and apparent closed-time distributions has been reported. The present study clarifies and extends this previous work by proving that, for such approximations, the likelihood equations as well as the moment equations (usually) have multiple solutions. Such non-uniqueness corresponds to non-identifiability of the statistical model for the apparent quantities. By contrast, higher-order approximations yield theoretically identifiable models. Likelihood-based estimation procedures are developed for both single exponential and bi-exponential approximations. The methods and results are illustrated by numerical examples based on literature and simulated data, with consideration given to empirical distributions and model control, likelihood plots, and point estimation and confidence regions.     

A two-site immunoradiometric assay of proatrial natriuretic factor. Application to tissue extracts

A "two-site" immunoradiometric assay (IRMA) was developed to specifically measure ANF (1-126), the precursor of ANF. This assay is based on the simultaneous use of antibodies against two different antigenic determinants: murine monoclonal antibody (2H2), which recognizes positions 101 through 103 of ANF, is linked to Immunobeads and employed to extract any ANF C-terminal; a second antibody, which is directed against positions 11 through 37, is radioiodinated and allows binding to any C-terminal-2H2-Immunobead material which bears the N-terminal antigenic site. A curvilinear relationship was obtained between radioactivity and the amount of proANF (1.5 to 400 fmol) added. Optimisation of IRMA was determined by the amount of 2H2-Immunobeads and labeled antibody used, incubation time as well as possible interference by both ANF (99-126) and ANF (1-98). Tissue extracts were used to validate the assay. proANF was detected in decreasing amounts in heart atria, heart ventricles, lungs, kidneys and adrenal glands. Its presence was further confirmed by reverse-phase HPLC followed by radioimmunoassay. IRMA is a simple and rapid method for the direct measurement of proANF in tissue extracts and chromatographic fractions. The presence of proANF in tissues strongly suggests local synthesis.