Attachment as a factor in the protection of Enterobacter cloacae from chlorination.

Enterobacter cloacae attached to drinking water distribution particles was subjected to chlorination. Attachment resulted in the protection of these organisms from disinfection. This effect was found to be dependent upon both the level of chlorine in the system and attachment time. The results obtained in this study indicate that attached organisms may play an important role in coliform outbreaks.     

Size of the directing moiety at carbon 5 of cytosine and the activity of human DNA(cytosine-5) methyltransferase

M13 DNAs in which carbon 5 of each deoxycytidine residue in one strand is replaced with a bulky group are very good substrates for human DNA (cytosine-5) methyltransferase. Rate enhancements of up to 35 fold are obtained depending on the size of the moiety at C-5. The enzyme appears optimally suited to sense a methyl group in one strand at this position. Alkaline density gradient analyses of the distribution of methyl groups applied to 5-BrdCyd or 5-IdCyd substituted DNA reveal that these groups serve to direct the enzyme to methylate the unsubstituted strand.     

Purification and characterization of hen oviduct microsomal signal peptidase

Hen oviduct signal peptidase requires only two proteins for proteolysis of fully synthesized secretory precursor proteins in vitro: one with a molecular mass of 19 kilodaltons (kDa) and one which is a glycoprotein whose mass varies from 22 to 24 kDa depending on the extent of glycosylation. Purified signal peptidase has been analyzed both as part of an active catalytic unit and after electroelution of the individual proteins out of a preparative polyacrylamide gel. The multiple forms of the glycoprotein component of signal peptidase bind to concanavalin A and are shown to be derived from the same polypeptide backbone. Removal of their oligosaccharides by digestion with N-glycanase converts these proteins to a single 19.5-kDa polypeptide. The glycoproteins all exhibit very similar profiles following individual digestion with trypsin and separation of the resulting peptides by reverse-phase high-performance liquid chromatography. In addition, sequence analysis of selected peptides from corresponding regions in chromatograms representing each form of the glycoprotein reveals the same amino acid sequences. The 19-kDa signal peptidase protein does not bind concanavalin A, has a distinct tryptic peptide map from that of the glycoprotein, and appears to share no amino acid sequences in common with the glycoprotein. Its copurification on a concanavalin A-Sepharose column indicates that it must interact directly with the glycoprotein subunit.     

Major histocompatibility (B) complex and sex effects on the phytohaemagglutinin wattle response

The influence of the major histocompatibility (B) complex and sex on the phytohaemagglutinin (PHA) wattle response was studied in 136 segregants (B2/B2, B2/B5 and B5/B5) of a fourth generation cross between inbred lines 6(1) and 15(1). At 6 weeks of age, chickens were injected with 100 micrograms purified PHA-P. Wattle thickness measurements were taken 4, 24, 48, 72 and 96 h after injection. Analysis of variance showed that 4 h after injection, males had a significantly higher response than females but the sex-genotype interaction was also significant. Females had higher responses than males 24 and 48 h after injection as a consequence of more rapid development and earlier resolution of the reaction in males. B2/B2 chickens had significantly lower responses than B5/B5 chickens 72 and 96 h after injection, signifying a faster late resolution phase in the B2/B2 genotype. The developmental and early resolution phases of the PHA wattle response were influenced by sex while the late resolution phase was influenced by B genotype.     

Human DNA (cytosine-5)methyltransferase selectively methylates duplex DNA containing mispairs.

The presence of the C.C mispair in a defined duplex oligodeoxynucleotide enhanced its capacity to serve as a substrate for highly purified human DNA methyltransferase. Analysis of tritiated reaction products showed that the C.C mispair acted as a "methylation acceptor" in that it was itself rapidly methylated. The m5C.G base pair also enhanced the capacity of the oligodeoxynucleotide to serve as a substrate for the enzyme. However, this complementary base pair was found to act as a "methylation director". That is, the presence of the m5C in one strand induced the enzyme to rapidly methylate at the cytosine residue on the opposite strand in an adjacent C.G base pair.     

Allometric Root/Shoot Relationships and Predicted Water Uptake for Desert Succulents

Root morphology, shoot morphology, and water uptake for Agavedeserti and Ferocactus acanthodes of various sizes were studiedusing allometric relationships (y = ax^b) and a previously developedwater uptake model. Shoot surface area increased with shootvolume with an exponent b of 0.75 for both species. Root lengthand the ground area explored by the roots increased with shootsurface area with b's of 0.72 for A. deserti and 0.92 for F.acanthodes. Various sized individuals had about the same ratioof root length to explored ground area, with higher values occurringfor A. deserti. Predicted water uptake averaged over the exploredground area was approximately constant over a 10⁴-fold rangein shoot surface area, suggesting that shoot size confers nointraspecific competitive advantage for water uptake. For theroot lengths per explored ground area observed in the field,water uptake was predicted to be 85 per cent of maximal; wateruptake could be increased by the production of more rain roots.When differences in shoot volume were accounted for by allometry,small plants had relatively less shoot surface area and relativelymore root length per shoot volume than did large plants, whichmay be important for the water relations of seedling establishment. Agave deserti, Ferocactus acanthodes, allometry, desert succulents, root distribution, root length, seedling growth, seedling establishment, shoot surface area, shoot volume, water uptake     

Book Review

International Journal of Primatology -     

Differential expression of guinea pig class II major histocompatibility complex antigens on vascular endothelial cells in vitro and in experimental allergic encephalomyelitis

Previous studies have shown that vascular endothelial cells do not normally express major histocompatibility complex (MHC) Class II antigens either in vivo or in vitro. In this investigation it was found that endothelial in the central nervous system (CNS) of normal guinea pigs constitutively express MHC Class II antigens recognized by the monoclonal antibodies HLA-DR, 27E7, and MSgp8. This phenotype is retained when these CNS-derived endothelial cells are propagated in tissue culture. Furthermore, examination of CNS tissue taken from animals in the acute phase of chronic relapsing experimental allergic encephalomyelitis shows that additional epitopes of the MHC Class II antigen, detected by the monoclonal antibodies CI.13.1 and 22C4, are present during the diseased state. This study not only demonstrates constitutive expression of certain MHC Class II determinants by guinea pig endothelial cells, but also shows that other Class II determinants can be differentially expressed in certain disease states.