Verification of the protein in the outer membrane of Bdellovibrio bacteriovorus as the OmpF protein of its Escherichia coli prey.

Two research groups showed that several Bdellovibrio strains incorporated into their outer membranes intact OmpF porin proteins derived from their Escherichia coli prey. These results could not be reproduced by another group using Bdellovibrio bacteriovorus 109J. They showed that a major protein appearing in the Bdellovibrio Triton X-100-insoluble outer membrane was coded for by the bdellovibrios. We reconciled these results by examining the strain used by this group and by reviving a freeze-dried culture of strain 109J which had been stored for almost 9 years. B. bacteriovorus 109J failed to acquire substantial amounts of the OmpF protein from E. coli ML35, and a protein coded for by the bdellovibrios was expressed in its place. However, B. bacteriovorus 109J incorporated the OmpF protein from rough K-12 strains of E. coli, and the revived 9-year-old culture of B. bacteriovorus 109J incorporated more of the OmpF protein from the smooth E. coli ML35 than did its contemporary counterpart. The protein isolated from the outer membrane of the bdellovibrios was identified as the OmpF protein of E. coli by its protease peptide profile on sodium dodecyl sulfate-polyacrylamide gel electrophoresis and by Western blot analysis. This confirmed that bdellovibrios relocalize outer membrane proteins from their prey, but relocalization may be an unstable trait which can be influenced by the prey.     

Integration of New Endogenous Mouse Mammary Tumor Virus Proviral DNA at Common Sites in the DNA of Mammary Tumors of C3Hf Mice and Hypomethylation of the Endogenous Mouse Mammary Tumor Virus Proviral DNA in C3Hf Mammary Tumors and Spleens

To understand the molecular mechanisms by which the endogenous murine mammary tumor virus (MuMTV) proviruses are expressed and produce late-occurring mammary tumors in C3Hf mice, we analyzed, by the use of restriction enzymes and the Southern transfer procedure, genomic DNA from normal organs of mammary tumor-bearing and tumor-free mice and from 12 late-occurring C3Hf mammary tumors. We found, by using the restriction enzymes EcoRI and HindIII, that in addition to the preexisting endogenous MuMTV proviruses, new MuMTV-specific proviral DNA was integrated into new sites in the host genome in all 12 of the tumors that we examined. PstI digests of C3Hf tumor DNA revealed that the new proviral DNA found in C3Hf tumors was of endogenous origin. Moreover, the respective sizes of at least one of the new DNA fragments generated by EcoRI or HindIII digestion were the same in at least 50% of the C3Hf tumors analyzed, suggesting that the integration site of this new proviral DNA could be at the same location in the host genome of these tumors. Our results may imply that mammary tumorigenesis in C3Hf mice results from activation of cellular oncogenes by an MuMTV proviral DNA promoter. Specific hypomethylation of MuMTV proviral DNA was detected in the mammary tumors and spleens of C3Hf tumor-bearing mice. Our results indicated that most, if not all, of the hypomethylated MuMTV proviral DNA sequences were derived from the endogenous MuMTV provirus located at the MTV-1 locus, a locus responsible for the production of MuMTV antigens and increased incidence of mammary carcinoma in C3Hf mice. In spleens of non-tumor-bearing mice of ages 3, 6, 9, and 12 months, there was progressive hypomethylation of proviral DNA with increasing age, suggesting a possible correlation between demethylation of MuMTV proviral DNA in the spleens of C3Hf mice and the expression of endogenous MuMTV.     

Atomic structure and specificity of bacterial periplasmic receptors for active transport and chemotaxis: variation of common themes

Crystallographic structure refinement at very high resolutions of a dozen periplasmic receptors has revealed that, though they have different sizes (26 to 60kDa) and little sequence homology, they have high tertiary structure similarity. They consist of two distinct globular domains bisected by a cleft or groove wherein the ligand binds and is buried by a hinge-bending motion between the two domains. Structural analysis also reveals how hydrogen-bonding interactions can be tailored to a wide spectrum of specificity, ranging from the stringent specificity for phosphate and sulphate to the more loose specificity for peptides.     

Comparative efficacy of two controlled-release gypsy moth mating disruption formulations

The effects of aerial applications of the gypsy moth sex pheromone, disparlure, on mating disruption and suppression of growth of populations of the gypsy moth, Lymantria dispar (L.), were investigated. Two formulations of disparlure, plastic laminate flakes applied in a single application and polymethacrylate beads applied in two applications, were compared in two separate tests conducted in 1993 and 1994. The beads were applied in two applications spaced 2 weeks apart because preliminary tests had indicated that they released pheromone too rapidly to maintain adequate emission rates throughout the period of male flight. In 1993, the flakes were applied at a rate of 50 g a.i./ha, and the beads were applied at a rate of 15 g a.i./ha for each application. In 1994, the flakes were applied at a rate of 75 g a.i./ha and the beads were applied at rates of 32.5 and 42.5 g a.i./ha for the two applications. Beads with larger average particle size were used in 1994 to prolong disparlure release. The treatments applied in 1993 resulted in >97% reduction in mating and >82% suppression of population growth in the following year. Because of a 1995 collapse of gypsy moth populations in the vicinity of the tests, reliable population growth data were not available for the treatments applied in 1994, but significant mating disruption did occur under both treatments. Based on measurements of residual disparlure after field aging, the flakes released 32 and 48% of their disparlure content during the 6 weeks of male moth flight in 1993 and 1994, respectively. The smaller beads used in 1993 released 75% of their disparlure content, and the larger beads used in 1994 released 52% of their disparlure content, during the 6 weeks of male flight. The biological efficacy data suggest that the bead and flake formulations, as applied in these tests, have similar effects on gypsy moth mating disruption and subsequent population growth. Based on the observed release rates from both 1993 and 1994, a single application of the beads would provide emission rates equal to or greater than those provided by the flakes when applied at an equal dose.     

Effect of anterior chamber paracentesis on decreased retinal circulation due to retrobulbar hematoma in dogs

An experimental canine model for blindness following blepharoplasty was developed to demonstrate occlusion of retinal circulation resulting from simulated retrobulbar hematoma. Seven mongrel dogs were studied, monitoring retinal vascular patterns by funduscopic examination and intraocular pressure by pneumotonometry. Anterior chamber paracentesis was performed in five dogs 10 minutes after injecting blood retrobulbarly, with an immediate decrease in pressure and return of retinal blood flow. In two dogs without paracentesis, increased pressure and blindness persisted. Anterior chamber paracentesis has been shown to reduce intraocular pressure from hematoma of the retro-orbital area in dogs. Although controversial, anterior chamber paracentesis may represent a useful temporizing adjunct in the treatment of increased intraocular pressure and impaired vision from hematoma following blepharoplasty.     

The Human Homolog of Insect-Derived Growth Factor, CECR1, Is a Candidate Gene for Features of Cat Eye Syndrome

Cat eye syndrome (CES) is a developmental disorder with multiple organ involvement, associated with the duplication of a 2-Mb region of 22q11.2. Using exon trapping and genomic sequence analysis, we have isolated and characterized a gene, CECR1, that maps to this critical region. The protein encoded by CECR1 is similar to previously identified novel growth factors: IDGF from Sarcophaga peregrina (flesh fly) and MDGF from Aplysia californica (sea hare). The CECR1 gene is alternatively spliced and expressed in numerous tissues, with most abundant expression in human adult heart, lung, lymphoblasts, and placenta as well as fetal lung, liver, and kidney. In situ hybridization of a human embryo shows specific expression in the outflow tract and atrium of the developing heart, the VII/VIII cranial nerve ganglion, and the notochord. The location of this gene in the CES critical region and its embryonic expression suggest that the overexpression of CECR1 may be responsible for at least some features of CES, particularly the heart defects.