A cell adhesion protein from the crayfish Pacifastacus leniusculus, a serine proteinase homologue similar to Drosophila masquerade

A cDNA encoding a protein resembling masquerade, a serine proteinase homologue expressed during embryogenesis, larval, and pupal development in Drosophila melanogaster, was identified in hemocytes of the adult freshwater crayfish, Pacifastacus leniusculus. The crayfish protein is similar to Drosophila masquerade in the following aspects: (a) overall sequence of the serine proteinase domain, such as the position of three putative disulfide bridges, glycine in the place of the catalytic serine residue, and the presence of a substrate-lining pocket typical for trypsins; (b) the presence of several copies of a disulfide-knotted motif in the putative propeptide. This masquerade-like protein is cleaved into a 27-kDa fragment, which could be detected by immunoblot analysis using an affinity-purified antibody against a synthetic peptide in the C-terminal domain of the protein. The 27-kDa protein could be immunoaffinity-purified from hemocyte lysate supernatant and exhibited cell adhesion activity in vitro, indicating that the C-terminal domain of the crayfish masquerade-like protein mediates cell adhesion.

In vivo and in vitro natural frequency analysis of periodontal conditions: an innovative method

BACKGROUND

When measuring periodontal disease, various types of equipment for making objective measurements of tooth mobility have been proposed. However, these devices and methodology are insufficient in terms of reliability. An innovative method using vibrational theories to assess the periodontal attachment level of natural teeth is presented in this study.

METHODS

Modal testing technique, a non-destructive and time-saving method, was used for non-invasive and quantitative measurement of the natural frequencies of the upper central incisor in vivo and in vitro. A finite element model was established, and modal testing experiments were simulated to assess the relationship between bone level and teeth.

RESULTS

The first dominant natural frequency of healthy human upper central incisors ranges from 710 Hz to 3,360 Hz, with an average of 1,701+/-679 Hz. Both in vitro experiment and finite element simulation showed that lowering of the attachment level causes a significant decrease in the natural frequencies, and a strong relationship (r = -0.99, P <0.01) was observed between the frequency and the bone level height.

CONCLUSIONS

Our results suggested that natural frequency is an important parameter for assessing the periodontal condition and that the modal testing technique is a useful supplemental method for assessing the attachment conditions of the periodontium.

Synthesis and characterization of stereospecific 1-propargyl-2-(dimethoxymethyl)-1-cyclohexanols

Stereochemical isomers with hydroxy groups were synthesized by reacting 2-(dimethoxymethyl)cyclohexanone with propargylmagnesium bromide. The stereo chemical structures were identified by NMR spectral interpretation and the geometry optimization. To assist the NMR interpretation, geometry optimization based on semi-empirical AM1 and PM3 methods was applied. Throughout this study, the structures of the two isomers were all determined and 1H and 13C NMR spectra were fully assigned. It was proven that the less polar isomer is an axial alcohol and the more polar one is an equatorial alcohol.

Osseous metaplasia with functioning bone marrow in hydroxyapatite orbital implants

BACKGROUND

Bone formation within the hydroxyapatite implant has been reported in explanted spheres in humans. Bone-specific differentiation was observed to occur earlier in the pores of spherical hydroxyapatite implants enhanced with osteogenin within the rabbit socket. We observed previously unreported bone marrow formation in a coralline hydroxyapatite implant placed into the rabbit orbit after evisceration.

METHODS

One eye of each of 10 New Zealand white rabbits weighing between 2 and 3 kg was eviscerated and implanted with hydroxyapatite spheres. The explanted hydroxyapatite spheres 20 weeks after surgery were examined under the microscope.

RESULTS

Histopathologic examination of the excised implants showed the presence of trabeculae of mature bone with fatty marrow and hematopoietic elements. Scattered throughout the fatty tissue were bone marrow elements consisting of precursors of the granulocytic and erythroid series and also megakaryocytes.

CONCLUSION

The osseous metaplasia with functioning bone marrow was incidentally observed in the coralline hydroxyapatite implant without the addition of any osteogenesis-inducing agents.

Identification of rice blast fungal elicitor-responsive genes by differential display analysis

In order to study molecular interactions that occur between rice and rice blast fungus upon infection, we isolated fungal elicitor-responsive genes from rice (Oryza sativa cv. Milyang 117) suspension-cultured cells treated with fungal elicitor prepared from the rice blast fungus (Magnaporthe grisea) employing a method that combined mRNA differential display and cDNA library screening. Data base searches with the isolated cDNA clones revealed that the OsERG1 and OsERG2 cDNAs share significant similarities with the mammalian Ca2+-dependent lipid binding (C2) domains. The OsCPX1 cDNA is highly homologous to peroxidases. The OsHin1 cDNA exhibits homology to the tobacco hin1 gene, whose expression is induced by avirulent pathogens. The OsLPL1 and OsMEK1 cDNAs share homologies with lysophospholipases and serine/threonine mitogen-activated protein (MAP) kinase kinases, respectively. The OsWRKY1 and OsEREBP1 cDNAs are homologous to transcription factors, such as the WRKY protein family and the AP2/EREBP family, respectively. Transcripts of the OsERG1, OsHin1, and OsMEK1 genes were specifically elevated only in response to the avirulent race KJ301 of the rice blast fungus. Our study yielded a number of elicitor-responsive genes that will not only provide molecular probes, but also contribute to our understanding of host defense mechanisms against the rice blast fungus.

NMR structure of activated CheY

The CheY protein is the response regulator in bacterial chemotaxis. Phosphorylation of a conserved aspartyl residue induces structural changes that convert the protein from an inactive to an active state. The short half-life of the aspartyl-phosphate has precluded detailed structural analysis of the active protein. Persistent activation of Escherichia coli CheY was achieved by complexation with beryllofluoride (BeF(3)(-)) and the structure determined by NMR spectroscopy to a backbone r.m.s.d. of 0.58(+/-0.08) A. Formation of a hydrogen bond between the Thr87 OH group and an active site acceptor, presumably Asp57.BeF(3)(-), stabilizes a coupled rearrangement of highly conserved residues, Thr87 and Tyr106, along with displacement of beta4 and H4, to yield the active state. The coupled rearrangement may be a more general mechanism for activation of receiver domains.

Application of a mid-infrared fiber bundle in remote measurement of gas concentrations in a chemical vapor deposition chamber

A fiber bundle has been designed for measurement of gas concentrations in a chemical vapor deposition (CVD) chamber. The bundle is broadband, covering the spectrum range from 500 to 6000 cm(-1). Using this bundle, we have designed Fourier Transform infrared (FTIR) sampling configurations with reduced beam divergence (from 0.4 to 0.1 rad) and focal spot diameters (from 12 to 4 mm). The FTIR spectrum of tetraethoxysilane vapors in a CVD chamber was determined with the bundle and modified SAM connectors. An ellipsoid reflector was designed that yielded improved signal-to-noise ratios (SNR's) in the fiber-based spectra by a factor of 2. The incorporation of this reflector in spectrometers by use of the fiber bundle has the potential to reduce the sampling times for spectra while retaining acceptable SNR's.

Degradation of repaired denture base materials in simulated oral fluid

This in vitro study evaluates the degradation of repaired denture bases upon immersion in a simulated oral fluid. Denture base materials (Luciton 199), after being repaired by Repair Material and Triad, using three different joint surface designs (butt, round and 45 degrees bevel), were immersed onto 99.5 vol.% ethanol/water solution (with similar solubility parameter) for various amounts of time (0-72 h). The flexural loads of the six combination of groups were measured by the three-point bending tests using a universal testing machine. Acoustic emission (AE) during sample fracturing were processed using the MISTRA 2001 system. The fracture pattern and surface details of the interface were examined with a scanning electronic microscope (SEM). Data were analysed using three-way ANOVA and Tukey LSD tests. SEM micrographs of the fracture interface were used to differentiate the fracture mode. The flexural loads (2.72 +/- 0.51 Kgf) of the round joint specimens were significantly higher (P< 0.05) than those (butt: 1.66 +/- 0.38 Kgf, 45 degrees bevel: 1.93 +/- 0.41 Kgf) of the other two designs. This corresponds to the microscopic examination in which more cohesive failure mode was found for the round joint group after storage. The flexural loads (2.54 +/- 0.39 Kgf) of the specimens repaired with Triad were significantly higher (P < 0.05) than those (1.59 +/- 0.40 Kgf) of specimens repaired with Repair Material. Significant progressive reduction of the flexural load and/or AE signals of the specimens was noted in proportion to the length of time of the immersion in the simulated oral fluid. Mechanical strength of a denture base repaired with a round joint design and light-cured material is significantly higher after immersion in simulated oral fluid.

Cloning, overexpression and purification of Bacillus subtilis elongation factor Tu in Escherichia coli

To establish the overexpression and one-step purification system of Bacillus subtilis elongation factor-Tu (EF-Tu), the EF-Tu gene was amplified with or without own ribosome binding site (rbs) by PCR and the only PCR product without rbs was subcloned successfully. For the expression of the EF-Tu gene cloned after PCR amplification, a constitutive expression system and inducible expression system with His6 tag at N-terminus or C-terminus, or glutathione-S-transferase (GST) fusion system were examined in E. coli and B. subtilis. Except GST fusion system in E. coli, however, all other trials were unsuccessful at the step of plasmid construction for the EF-Tu expression. The GST/EF-Tu fusion proteins were highly expressed by IPTG induction and obtained as both soluble and insoluble form. From the soluble GST/EF-Tu fusion protein, EF-Tu was obtained to near homogeneity by one-step purification with glutathione-sepharose affinity column chromatography followed by factor Xa treatment. The purified EF-Tu showed high GDP binding activity. These results indicate that the GST/EF-Tu fusion system is favorable to overexpression and purification of B. subtilis EF-Tu.

Transfer RNA identity change in anticodon variants of E. coli tRNA(Phe) in vivo

The anticodon sequence is a major recognition element for most aminoacyl-tRNA synthetases. We investigated the in vivo effects of changing the anticodon on the aminoacylation specificity in the example of E. coli tRNA(Phe). Constructing different anticodon mutants of E. coli tRNA(Phe) by site-directed mutagenesis, we isolated 22 anticodon mutant tRNA(Phe); the anticodons corresponded to 16 amino acids and an opal stop codon. To examine whether the mutant tRNAs had changed their amino acid acceptor specificity in vivo, we tested the viability of E. coli strains containing these tRNA(Phe) genes in a medium which permitted tRNA induction. Fourteen mutant tRNA genes did not affect host viability. However, eight mutant tRNA genes were toxic to the host and prevented growth, presumably because the anticodon mutants led to translational errors. Many mutant tRNAs which did not affect host viability were not aminoacylated in vivo. Three mutant tRNAs containing anticodon sequences corresponding to lysine (UUU), methionine (CAU) and threonine (UGU) were charged with the amino acid corresponding to their anticodon, but not with phenylalanine. These three tRNAs and tRNA(Phe) are located in the same cluster in a sequence similarity dendrogram of total E. coli tRNAs. The results support the idea that such tRNAs arising from in vivo evolution are derived by anticodon change from the same ancestor tRNA.

Secretory production of human leptin in Escherichia coli

Human leptin is a 16 kDa (146 amino acids) protein secreted from adipocytes and influences body weight homeostasis. In this study, human leptin was produced and secreted efficiently in Escherichia coli using a novel Bacillus sp. endoxylanase signal peptide. The endoxylanase signal sequence consisted of 28 amino acids (84 bp) was fused to the leptin structural gene. The fused gene was expressed using an inducible promoter (T7 or Trc) by adding 1 mM IPTG. Using T7 promoter in E. coli BL21(DE3), most of protein produced was in a premature form. Using the Trc promoter, which is weaker than T7, leptin was efficiently produced and secreted as a mature form (40% of total proteins) at 37 degrees C. However, most of leptin (about 90%) formed the inclusion bodies in the periplasmic space of E. coli. At 30 degrees C, ca. 90% of leptin was produced in a soluble form, but the total amount of leptin produced was 40% less than that obtained at 37 degrees C. When the periplasmic oxidoreductase of E. coli, DsbA, was co-expressed, 69% of the secreted leptin (26% of total proteins) was produced as soluble form at 37 degrees C without the decrease of the amount of leptin produced.

Observation of a hybrid spin resonance

A new type of spin depolarization resonance has been observed at the Brookhaven Alternating Gradient Synchrotron (AGS). This spin resonance is identified as a strong closed-orbit sideband around the dominant intrinsic spin resonance. The strength of the resonance was proportional to the 9th harmonic component of the horizontal closed orbit and proportional to the vertical betatron oscillation amplitude. This "hybrid" spin resonance cannot be overcome by the partial snake at the AGS, but it can be corrected by the harmonic orbit correctors.

Serogroups of the beer spoilage bacterium Megasphaera cerevisiae correlate with the molecular weight of the major EDTA-extractable surface protein

Megasphaera cerevisiae is a Gram-negative obligate anaerobe that causes turbidity and off-flavour and aroma in beer. Seven isolates of M. cerevisiae were obtained worldwide, and their extractable surface antigens were focused upon to determine if there is more than one serogroup of this bacterium. Sodium dodecyl sulphate polyacrylamide gel electrophoresis of ethylenediaminetetraacetic acid (EDTA) bacterial extracts revealed a predominant protein with apparent molecular weights of 46,000, 45,000, and 43,000 for three, two, and two isolates, respectively. When mouse anti-serum generated against any of the EDTA extracts was reacted with denatured bacterial proteins in immunoblots, all bacterial isolates exhibited extensive cross-reactivity involving three antigens, one being the major EDTA-extractable protein. In contrast, when the sera were tested for surface reactivity with intact bacteria, three cross-reactivity groups were observed, with the groups individually comprised of bacteria having the same size major EDTA-extractable surface protein. When BALB/c mice immunized with a bacterium from each of the three serogroups were used for monoclonal antibody (Mab) hybridoma production, bacterial surface-reactive Mabs were obtained whose reactivities parallel the three polyclonal antibody-defined serogroups. Through combining these surface-reactive Mabs, it will be possible to rapidly detect and identify beer contamination by M. cerevisiae belonging to any serogroup.

Correction of axillary burn scar contracture with the thoracodorsal perforator-based cutaneous island flap

Axillary scar contracture is observed frequently after severe burn insult and is usually accompanied by injuries to the adjacent area. Although many therapeutic methods, including skin grafting, Z-plasties, local flaps, island flaps, and free flaps, have been established, each technique has its own advantages and disadvantages in specific situations. The decision regarding which technique to use can only be made after consideration is given to the merits of the individual case. We applied thoracodorsal perforator-based cutaneous flaps to 5 patients with axillary burn scar contractures and damaged adjacent tissues. In 1 patient both axillae were involved. Elevated flaps as large as 11 x 27 cm in size were used. All flaps survived completely even when raised in scar tissue. The donor sites were closed primarily except one, which needed a skin graft. Three patients obtained satisfactory release with more than 160 deg shoulder abduction. In 2 patients, release was incomplete with only 110 deg shoulder abduction, but neither one required a second release. The range of motion in terms of shoulder abduction was improved preoperatively (30-90 deg) to postoperatively (110-170 deg). The thoracodorsal perforator-based cutaneous flap presents a very useful reconstructive method for the treatment of axillary defects.

Mucociliary transport pathway on laryngotracheal tract and stented glottis in guinea pigs

We investigated the laryngotracheal mucociliary transport pathway of guinea pigs in vivo and immediately postmortem. Only intraperitoneal anesthesia was used during the procedure to avoid the disturbance of mucociliary function. Resin particles were used as the marking substance. A microcolpohysteroscope was placed at different levels in the laryngotracheal region for observing the marking particles and recording the transport pattern. The tracheal mucociliary transport flow primarily moved along the posterior wall and both lateral walls in a zigzag trace. Upon reaching the subglottis, the resin particles stayed underneath the vocal cords, and a whirlpool phenomenon developed. The majority of the particles were shifted and directed onto the posterior glottic area. With a short delay, some resin particles crossed over the free edge of the vocal cords and turned posteriorly along the medial upper cordal margin. No mucociliary transport could be observed on the entire upper surface of the true vocal cords, which is covered by squamous epithelium. Occasionally, a few resin particles in the vicinity of the epiglottic root traveled along the aryepiglottic folds toward the posterior commissure. All streams of mucociliary transport finally joined together in the interarytenoid area. After leaving the glottis, the resin particles traveled to the hypopharynx and entered the esophagus through the motion of deglutition. The pattern of mucociliary clearance in the laryngotracheal region was not delayed by stenting.

Production of poly(3-hydroxybutyrate-co-3-hydroxyhexanoate) by high-cell-density cultivation of Aeromonas hydrophila

The newly screened Aeromonas hydrophila produces copolymer consisting of 3-hydroxybutyrate (3HB) and 3-hydroxyhexanoate (3HHx). The characteristics of cell growth and polymer accumulation were examined using various carbon sources. P(3HB-co-3HHx) was produced from lauric acid and oleic acid only. P(3HB-co-3HHx) content can be increased by limitation of phosphorus. A maximal P(3HB-co-3HHx) content of 28.8 wt% could be obtained in flask culture. By applying the optimally designed nutrient feeding strategy, cell dry weight, P(3HB-co-3HHx) content, and 3HHx fraction obtained over the course of 43 h were 95.7 g/L, 45.2 wt%, and 17 mol%, respectively, resulting in a productivity of 1.01 g polyhydroxyalkanoate (PHA)/L. h.

A lipopolysaccharide- and beta-1,3-glucan-binding protein from hemocytes of the freshwater crayfish Pacifastacus leniusculus. Purification, characterization, and cDNA cloning

A lipopolysaccharide- and beta-1,3-glucan-binding protein (LGBP) was isolated and characterized from blood cells (hemocytes) of the freshwater crayfish Pacifastacus leniusculus. The LGBP was purified by chromatography on Blue-Sepharose and phenyl-Sepharose, followed by Sephacryl S-200. The LGBP has a molecular mass of 36 kDa and 40 kDa on 10% SDS-polyacrylamide gel electrophoresis under reducing and nonreducing conditions, respectively. The calculated mass of LGBP is 39,492 Da, which corresponds to the native size of LGBP; the estimated pI of the mature LGBP is 5.80. LGBP has binding activity to lipopolysaccharides as well as to beta-1,3-glucans such as laminarin and curdlan, but peptidoglycan could not bind to LGBP. Cloning and sequencing of LGBP showed significant homology with several putative Gram-negative bacteria-binding proteins and beta-1, 3-glucanases. Interestingly, LGBP also has a structure and functions similar to those of the coelomic cytolytic factor-1, a lipopolysaccharide- and glucan-binding protein from the earthworm Eisenia foetida. To evaluate the involvement of LGBP in the prophenoloxidase (proPO) activating system, a polyclonal antibody against LGBP was made and used for the inhibition of phenoloxidase (PO) activity triggered by the beta-1,3-glucan laminarin in the hemocyte lysate of crayfish. The PO activity was blocked completely by the anti-LGBP antibody. Moreover, the PO activity could be recovered by the addition of purified LGBP. These results suggest that the 36-kDa LGBP plays a role in the activation of the proPO activating system in crayfish and thus seems to play an important role in the innate immune system of crayfish.

Variations in geographical distribution of foreign and domestically trained physicians in the United States: 'safety nets' or 'surplus exacerbation'?

In the United States, a debate has existed for decades about whether foreign-trained physicians (known in the US as 'international medical graduates' or 'IMGs') and US medical graduates (USMGs) have been differentially distributed such that IMGs were more likely to be found in locales characterized as high in need or medical underservice. This 'safety net' hypothesis has been countered by the IMG 'surplus exacerbation' argument that IMGs have simply swelled an already abundant supply of physicians without any disproportionate service to areas in need. Through an analysis of the American Medical Association Physician Masterfile and the Area Resource File, we classified post-resident IMGs and USMGs into low and high need counties in each of the US states, compared the percentage distributions, and determined whether IMGs were found disproportionately in high need or underserved counties. Using four measures (infant mortality rate, socio-economic status, proportion non-white population, and rural county designation), we show that there were consistently more states having IMG disproportions than USMG disproportions. The magnitude of the differences was greater for IMGs than for USMGs, and there was a correlation between IMG disproportions and low doctor/100,000 population ratios. These findings are shown to exist simultaneously with two empirical facts: first, not all IMGs were located in high new or underserved counties; second, IMGs were more likely than USMGs to be located in states with a large number of physicians. The juxtaposition of an IMG presence in 'safety net' locales and of IMGs' contribution to a physician abundance is discussed within the context of the current debate about a US physician 'surplus' and initiatives to reduce the number of IMGs in residency training.

Retentive and compressive strengths of modified zinc oxide-eugenol cements

OBJECTIVES

This investigation sought to improve the handling and physical properties of a commonly used temporary zinc oxide-eugenol cement by changing the base/accelerator (B/A) ratio or combining it with a petroleum jelly or fluoride varnish.

METHODS

Twelve modifications of a temporary cement were evaluated in terms of retentive strength, compressive strength at 24 h, film thickness and by scanning electron microscopy.

RESULTS

Decreasing the B/A mixing ratio increased the retentive and compressive strengths, but reduced the film thickness of the cement. By increasing the percentage of incorporated petroleum jelly or fluoride varnish in the cement, there was a progressive decrease in the retentive and compressive strengths and in film thickness.

CONCLUSIONS

Modifications of a zinc oxide-eugenol temporary cement to change the B/A ratio or to incorporate additives resulted in variations in physical properties. All modified forms of the cement had a film thickness less than 25 microns and a compressive strength below 35 MPa. With a wide range of retentive strength, modified forms of zinc oxide-eugenol cement may be found to have diverse clinical applications.

Lymphocytic hypophysitis in a patient with systemic lupus erythematosus

A case of lymphocytic hypophysitis in a patient with systemic lupus erythematosus is described. A 20-year-old woman was admitted to our hospital with generalized myalgia and facial rash in May 1998. The patient had a medical history, physical examination, and laboratory findings compatible with systemic lupus erythematosus (SLE). Headache and nausea had developed 3 months previously and worsened over the following months. Hormonal investigation showed hypopituitarism except for prolactin. A magnetic resonance image of the brain showed a mass lesion in the pituitary fossa. A trans-sphenoidal surgical procedure was performed which revealed a dark-yellowish hematoma. Microscopic examination showed diffuse infiltration of lymphocytes and plasma cells with fibrosis in the anterior pituitary. Post-operatively the patient's headaches and nausea resolved. This indicates that lymphocytic hypophysitis may be associated with SLE.

Acute histological effects of interstitial hyperthermia on normal rat brain

Histological changes in the brains of Fischer rats at different times after interstitial heating with various thermal doses were studied. The brains, subjected to sham-heating, and heating at 39 and 40 degrees C for 30 min showed mild capillary congestion and minimal vacuolation at 4, 24 and 72 h. In the brains heated to 41, 42 and 43 degrees C for 30 min, there was local vascular congestion, petechiae, vacuolation and cellular shrinkage with nuclear pyknosis at 4 h; enhanced congestion and petechiae, acute cellular necrosis, infiltration of polymorphonuclear leukocytes and marked vacuolation at the margin at 24h; total coagulative necrosis of all parenchymal and vascular elements, early liquefaction necrosis and vascular hyperplasia at the margin at 72 h; enhanced vascular hyperplasia at the margin at 120 h and 168 h. The threshold thermal dose for the histopathological damage in the rat brain was heating at 41 degrees C for 30 min.

Reappraisal of the role of the bilioenteric conduit in the pathogenesis of postoperative cholangitis

The incidence of postoperative cholangitis has changed very little despite progressive improvement in the treatment of biliary atresia. The role of the bilioenteric conduit in its pathogenesis is still uncertain. A retrospective study of 39 patients undergoing either a conventional Kasai operation (group 1, n = 20) or with placement of an antireflux valve (group 2, n = 10) or lengthening (group 3, n = 9) of the jejunal conduit from 40 to 60 cm was performed to compare the incidence of cholangitis. Postoperative cholangitis developed in 18 of the 39 patients (46%). The incidence was 10/20 (50%) in group 1, 5/10 (50%) in group 2, and 3/9 (33%) in group 3 (P = 0.679). An animal experiment was conducted concomitantly to compare quantitative bacterial cultures of the bilioenteric anastomosis and the liver before and 1 week after Roux-en-Y hepaticojejunostomy (HPJ) in piglets without (group A, 25 cm) and with (group B, 50 cm) lengthening of the jejunal conduit in a porcine model of extrahepatic biliary obstruction. The growth of bacteria in both the bilioenteric anastomosis and the liver was not affected by lengthening the jejunal conduit from 25 to 50 cm (P = 0.612 and 0. 057, respectively), despite a geometric increase in bacterial concentrations in both groups after HPJ. It is concluded that neither bacterial growth in the liver nor cholangitis following bile-duct reconstruction was affected by valving or lengthening the bilioenteric conduit.

Ultrastructural changes in microvessel with age in the hippocampus of senescence-accelerated mouse (SAM)-P/10

Microvessels in the hippocampus of aged SAM-P/10 (14 months old) showed the following ultrastructural changes compared with those of young-mature controls (3 months old): (1) the majority of capillaries had lost the smooth contours typical of young cases; (2) the luminal surface of capillaries showed irregularity; (3) the endothelial cytoplasm was thicker; (4) vesicles appeared more frequently in the endothelium; (5) interendothelial tight junctions and basement membranes, however, seemed to show no significant abnormalities; (6) pericytes, especially those of arterioles and venules, contained many enlarged cytoplasmic inclusions with honeycomb-like vacuoles; (7) the area of glial perivascular end feet was greater. These morphological findings raise the possibility of impaired blood-brain barrier function and microhemodynamic disturbances in aged SAM-P/10 hippocampus.

Genetically engineered transgenic plants with the domain 1 sequence of tobacco mosaic virus 126 kDa protein gene are completely resistant to viral infection

In many plant RNA viruses, Domains 1, 2 and 3 are conserved in replicase proteins. In order to examine the interference of viral replication by the Domain 1 sequence, we generated transgenic plants transformed with DNA corresponding to the Domain 1 sequence of the TMV 126 kDa protein. This DNA sequence includes the TMV RNA from nucleotides 1 to 2,149, which comprises both the 5'-untranslated and methyl transferase region. The transgenic plants obtained showed complete resistance to TMV infection. The presence of the Domain 1 sequence in the plants completely prevented local necrosis in Nicotiana tabacum cv. Xanthi nc, and any systemic development of symptoms in Nicotiana tabacum Xanthi upon TMV inoculation. Most transgenic plants sustained the conferred resistance even under TMV inoculum concentrations up to as high as 1,000 microg/ml. To detect any accumulation of TMV coat protein or viral RNA in infected transgenic plants, immunochemical tests and Northern blot analyses were carried out. Neither viral RNA or coat protein was detectable in the systemic leaves of the completely resistant transgenic plants, whereas they were accumulated in large quantities in all of the control plants. Because of the conservation of Domain 1 in many plant RNA viruses, the acquisition of resistance to virus infection using the Domain 1 sequence appears to be a very effective strategy for breeding of viral resistant plants.

Beryllofluoride mimics phosphorylation of NtrC and other bacterial response regulators

Two-component systems, sensor kinase-response regulator pairs, dominate bacterial signal transduction. Regulation is exerted by phosphorylation of an Asp in receiver domains of response regulators. Lability of the acyl phosphate linkage has limited structure determination for the active, phosphorylated forms of receiver domains. As assessed by both functional and structural criteria, beryllofluoride yields an excellent analogue of aspartyl phosphate in response regulator NtrC, a bacterial enhancer-binding protein. Beryllofluoride also appears to activate the chemotaxis, sporulation, osmosensing, and nitrate/nitrite response regulators CheY, Spo0F, OmpR, and NarL, respectively. NMR spectroscopic studies indicate that beryllofluoride will facilitate both biochemical and structural characterization of the active forms of receiver domains.