Congruent evolution between whiteflies (Homoptera: Aleyrodidae) and their bacterial endosymbionts based on respective 18S and 16S rDNAs

Whiteflies (family Aleyrodidae) possess heritable eubacterial endosymbionts sustained in specialized organ-like structures called mycetomes. Comparisons of distances between the ash whitefly,Siphoninus phillyreae, and two biotypes (A and B) of the sweetpotato whitefly,Bemisia tabaci, based on sequence analysis of genes for 18S rRNAs (rDNAs), were equivalent to the distances represented by the 16S rDNAs of their respective endosymbionts. This finding indicates that evolutionary divergence in whitefly hosts and their endosymbionts is congruent. The nucleotide sequences of the 18S rDNAs and endosymbiont 16S rDNAs indicate the two biotypes ofB. tabaci are the same species.     

Use of the polymerase chain reaction and 16S rRNA sequences for the rapid detection of Brochothrix spp. in foods

Oligonucleotide primers were designed against rRNA sequences to give a DNA-based PCR assay for the rapid identification/detection of Brochothrix spp. The PCR products could be confirmed by hybridization to an internal oligonucleotide probe. The method successfully and sensitively detected/identified these organisms in pure cultures but was of limited value as a detection method because the detection sensitivity, in relation to conventional plate counts, varied and the assay sensitivity was reduced in the presence of staphylococci. Furthermore, sensitivity was also lost when the assay was applied directly to meat samples. However, a separation step using a lectin (from Agaricus bisporus ) immobilized on magnetic beads prior to the PCR assay, allowed the direct detection of low numbers (> 10 cfu g^-1) of Brochothrix in meat samples within a working day.     

Inherited prion disease (PrP lysine 200) in Britain: two case reports.

OBJECTIVE--To identify cases of inherited prion diseases in Britain and to assess their phenotypic features. DESIGN--Screening study of patients suspected clinically to have Creutzfeldt-Jakob disease and other neurodegenerative diseases by prion protein gene analysis. SETTING--Biochemical research department. SUBJECTS--Patients suspected to have Creutzfeldt-Jakob disease and other neurodegenerative diseases. RESULTS--Two patients with symptoms characteristic of sporadic Creutzfeldt-Jakob disease were found to have inherited prion protein disease (PrP lysine 200), with a mutation at codon 200 of the prion protein gene. Both were homozygous at codon 129 of the gene. One patient was a man aged 58 of British descent while the other was of Libyan Jewish origin. CONCLUSION--Two foci of inherited prion disease are known, among Libyan Jews and in Slovakia. A separate British focus of the disease may also exist. Heterozygosity at codon 129 may lead to reduced penetrance of the mutation.     

Protein-free models for the proton-coupled reduction of haemoproteins

Reduction of the bis-pilocarpate-haemin complex at pH greater than or equal to 10 involves the simultaneous uptake of an electron by the Fe(III) ion and a proton by the pendant alkoxide group of an axial ligand. This provides a protein-free model for reactions such as the proton-coupled reduction of cytochromes which involve cooperative Coulombic interaction between two non-bonded sites.     

Interrelationships of dietary protein level,aflatoxin B1 metabolism,and hepatic microsomal epoxide hydrase activity

In a continuation of studies on protein intake and aflatoxin B₁ (AFB₁) metabolism, weanling rats were fed semipurified diets containing either 20% casein or 5% casein for two weeks to determine the effect of dietary protein level on hepatic microsomal epoxide hydrase activity and AFB₁ metabolism in an effort to evaluate the role of protein intake on the formation and degradation of the reactive metabolite of AFB₁. Styrene oxide was used as substrate for epoxide hydrase since the hypothetical AFB₁ 2,3-epoxide (AFB-epox) cannot be synthesized because of its lability. Two groups of animals were fed 20% casein diets; one was fed ad libitum and the second was pair fed to the 5% casein group in order to control the effects of total feed intake. The depression of epoxide hydrase activities caused by the 5% casein diets was approximately equivalent to that previously seen with hepatic microsomal mixed function oxidase (MFO) activities with the identical protocol. Similarly, the metabolism of AFB₁ to AFQ₁ and AFM₁ was depressed by the 5% casein diets, with an increase in the production of chromatographically more polar material. The relationship of the MFO and epoxide hydrase activities to AFB₁ metabolism and formation of macromolecular adducts is discussed.     

The effect of premature and delayed birth on the development of UDP-glucuronosyltransferase activities towards bilirubin, morphine and testosterone in the rat.

In the rat, UDP-glucuronosyltransferase activities towards bilirubin, morphine and testosterone increase markedly after normal or premature birth. This rapid development is superimposed upon a much slower maturation of activity which occurs in utero during the last 2 days of normal gestation and gestation when birth is delayed. Development of all three activities is similar under these different conditions, suggesting a common developmenpal regulatory mechanism.     

Analysis of structural similarities between brain Thy-1 antigen and immunoglobulin domains. Evidence for an evolutionary relationship and a hypothesis for its functional significance.

The Thy-1 membrane glycoprotein from rat brain is shown to have structural and sequence homologies with immunoglobulin (Ig) domains on the basis of the following evidence. 1. The two disulphide bonds of Thy-1 are both consistent with the Ig-fold. 2. The molecule contains extensive beta-structure as shown by the c.d. spectrum. 3. Secondary structure prediction locates beta-strands along the sequence in a manner consistent with the Ig-fold. 4. On the basis of rules derived from known beta-sheet structures, a three-dimensional structure with the Ig-fold is predicted as favourable for Thy-1. 5. Sequences in the proposed beta-strands of Thy-1 and known beta-strands of Ig domains show significant sequence homology. This homology is statistically more significant than for the comparison of proposed beta-strand sequences of beta 2-microglobulin with Ig domains. An hypothesis is presented for the possible functional significance of an evolutionary relationship between Thy-1 and Ig. It is suggested that both Thy-1 and Ig evolved from primitive molecules, with an Ig fold, which mediated cell--cell interactions. The present-day role of Thy-1 may be similar to that of the primitive domain.