Polyosides (encapsulated bacteria)

The polysaccharide capsule which surrounds bacterial species such as Haemophilus influenzae, Streptococcus pneumoniae, Neisseria meningitidis and Salmonella typhi is a potent virulence factor by protecting the bacteria from phagocytosis. The host responds with antibody production and specific antibodies plus complement binding to the capsule facilitate opsonization of the micro-organism, which is phagocytized and eliminated. Purified capsular polysaccharides elicit T-independent antibody responses without a memory function, but are often poorly immunogenic in infants where much of the invasive H. influenzae type b (Hib) and pneumococcal infections is seen. Therefore purified polysaccharides have found limited use as vaccines. However, covalent linkage of the capsular polysaccharide, or fractions thereof, to immunogenic carrier proteins creates glycoconjugates which are T-dependent antigens and which elicit antibodies also in infants and which prime for boosting either with the glycoconjugate or the capsular polysaccharide. In the last decade Hib glycoconjugate vaccines have been successfully introduced and in countries with very high immunization coverage the disease has been virtually eliminated and a decline of over 95% has been seen in countries with slightly lower vaccine rates. World-wide use of Hib glycoconjugate vaccines offers the possibility of elimination of invasive Hib disease. Pneumococcal (11 serotypes with coverage of approximately 85% of invasive disease), meningococcal (A, C, W 135, Y but not B) and S. typhi glycoconjugates are in advanced development and offer the prospect of being as successful as the Hib glycoconjugates.     

Thermal unfolding of G-actin monitored with the DNase I-inhibition assay stabilities of actin isoforms.

Actin is one of the proteins that rely on chaperonins for proper folding. This paper shows that the thermal unfolding of G-actin, as studied by CD and ultraviolet difference spectrometry, coincides with a loss in DNase I-inhibiting activity of the protein. Thus, the DNase I inhibition assay should be useful for systematic studies of actin unfolding and refolding. Using this assay, we have investigated how the thermal stability of actin is affected by either Ca2 + or Mg2 + at the high affinity divalent cation binding site, by the concentration of excess nucleotide, and by the nucleotide in different states of phosphorylation (ATP, ADP.Pi, ADP. Vi, ADP.AlF4, ADP.BeFx, and ADP). Actin isoforms from different species were also compared, and the effect of profilin on the thermal stability of actin was studied. We conclude that the thermal unfolding of G-actin is a three-state process, in which an equilibrium exists between native actin with bound nucleotide and an intermediate free of nucleotide. Actins in the Mg-form were less stable than the Ca-forms, and the stability of the different isoforms decreased in the following order: rabbit skeletal muscle alpha-actin = bovine cytoplasmic gamma-actin > yeast actin > cytoplasmic beta-actin. The activation energies for the thermal unfolding reactions were in the range 200-290 kJ.mol- 1, depending on the bound ligands. Generally, the stability of the actin depended on the degree with which the nucleotide contributed to the connectivity between the two domains of the protein.     

Design, synthesis and SAR of potent statine-based BACE-1 inhibitors: exploration of P1 phenoxy and benzyloxy residues

Several BACE-1 inhibitors with low nanomolar level activities, encompassing a statine-based core structure with phenyloxymethyl- and benzyloxymethyl residues in the P1 position, are presented. The novel P1 modification introduced to allow the facile exploration of the S1 binding pocket of BACE-1, delivered highly promising inhibitors.     

Morphological and Molecular Resolution of a Putative Cryptic Species Complex: a Case Study of Notoacmea Fascicularis (Menke, 1851) (Gastropoda: Patellogastropoda)

Evidence that Notoacmea fascicularis (Menke, 1851) is a complexof at least two distinct taxa of species rank is ambiguous.A discriminant function analysis of conchological data showsa weak geographic effect, while radular morphology clearly delineatestwo sympatric groups with rare intermediates. Lastly, moleculardata (mt cytochrome c oxidase subunit I) suggests a single speciesand a geographic effect. We consider N. fascicularis to be a singletaxon, variable for radular lateral tooth morphology. In thepast these two different radular morphologies would be indicativeof generic rank. Our knowledge of the intraspecific variability ofmost gastropod characters is poor, and this makes specific identificationsor groupings based on single character systems such as the radulaprecarious. Adequate sampling and evaluation of population-levelcharacter states (conchological, anatomical and molecular) isneeded to identify as well as falsify cryptic species complexes. (Received 28 August 1997; accepted 6 May 1998)     

Cytosolic persistence of mouse brain CYP1A1 in chronic heme deficiency

Previous work has demonstrated that the function of extrahepatic cytochrome P450 CYP1A1 is dependent on the availability of heme. CYP1A1 is involved in the activation of polyaromatic hydrocarbons. In the present study we used a transgenic mouse model with chronic impairment of heme synthesis - female porphobilinogen deaminase-deficient (PBGD-/-) mice - to investigate the effects of limited heme in untreated and beta-naphthoflavone (beta-NF)-treated animals on the function of CYP1A1 in brain. The heme content of PBGD-/- mice was diminished in the liver and brain compared to wild types. In the liver, partial heme deficiency led to less potent induction of CYP1A1 mRNA after beta-NF treatment. In the brain, CYP1A1 protein was detected not only at the endoplasmic reticulum (ER), but also in the cytosol of PBGD-/- mice. Furthermore, 7-deethylation of ethoxyresorufin, an indicator of CYP1A1 metabolic activity, could be restored by heme in cytosol of PBGD-/- mouse brain. Independent of the genotype, we found only one cyp1a1 gene product, indicating that the cytosolic appearance of CYP1A1 most likely did not originate from mutant alleles. We conclude that heme deficiency in the brain leads to incomplete heme saturation of CYP1A1, which causes its improper incorporation into the ER membrane and persistence in the cytosol. It is suggested that diseases caused by relative heme deficiency, such as hepatic porphyrias, may lead to impaired hemoprotein function in brain.     

Activation in isolation: exposure of the actin-binding site in the C-terminal half of gelsolin does not require actin

Gelsolin requires activation to carry out its severing and capping activities on F-actin. Here, we present the structure of the isolated C-terminal half of gelsolin (G4-G6) at 2.0 A resolution in the presence of Ca(2+) ions. This structure completes a triptych of the states of activation of G4-G6 that illuminates its role in the function of gelsolin. Activated G4-G6 displays an open conformation, with the actin-binding site on G4 fully exposed and all three type-2 Ca(2+) sites occupied. Neither actin nor the type-l Ca(2+), which normally is sandwiched between actin and G4, is required to achieve this conformation.     

Effects of central vasotocin and mesotocin manipulations on social behavior in male and female zebra finches

Male and female zebra finches (Taeniopygia guttata; total n = 40) were fitted with chronic guide cannulae directed at the lateral ventricle and were tested for aggression, affiliation, and partner preference following infusions of mesotocin (MT), vasotocin (VT), their antagonists, and vehicle control. Aggressive behavior was tested in a mate competition paradigm and tests of intersexual affiliation and partner preference were conducted following 1 day of cohabitation with an opposite-sex individual. These tests also provided data on male courtship singing. The results demonstrate a modest dose-dependent facilitation of aggression by VT, but not MT, in both male and female finches. However, only males were sensitive to infusions of a vasopressin antagonist, suggesting that endogenous VT is more important for behavioral modulation in males. Peptide effects were specific to aggression, as no treatments influenced intersexual affiliation, partner preference, or male courtship singing. Thus, in contrast to rodents, partner preference is not readily induced by VT or MT in this species. However, the potential necessity of endogenous VT and MT for natural pair-bond formation remains to be tested.