Hindered diffusion of high molecular weight compounds in brain extracellular microenvironment measured with integrative optical imaging

This paper describes the theory of an integrative optical imaging system and its application to the analysis of the diffusion of 3-, 10-, 40-, and 70-kDa fluorescent dextran molecules in agarose gel and brain extracellular microenvironment. The method uses a precisely defined source of fluorescent molecules pressure ejected from a micropipette, and a detailed theory of the intensity contributions from out-of-focus molecules in a three-dimensional medium to a two-dimensional image. Dextrans tagged with either tetramethylrhodamine or Texas Red were ejected into 0.3% agarose gel or rat cortical slices maintained in a perfused chamber at 34 degrees C and imaged using a compound epifluorescent microscope with a 10 x water-immersion objective. About 20 images were taken at 2-10-s intervals, recorded with a cooled CCD camera, then transferred to a 486 PC for quantitative analysis. The diffusion coefficient in agarose gel, D, and the apparent diffusion coefficient, D*, in brain tissue were determined by fitting an integral expression relating the measured two-dimensional image intensity to the theoretical three-dimensional dextran concentration. The measurements in dilute agarose gel provided a reference value of D and validated the method. Values of the tortuosity, lambda = (D/D*)1/2, for the 3- and 10-kDa dextrans were 1.70 and 1.63, respectively, which were consistent with previous values derived from tetramethylammonium measurements in cortex. Tortuosities for the 40- and 70-kDa dextrans had significantly larger values of 2.16 and 2.25, respectively. This suggests that the extracellular space may have local constrictions that hinder the diffusion of molecules above a critical size that lies in the range of many neurotrophic compounds.

Long-term effects on pancreatic function of feeding a HC formula to rats during the preweaning period

We have investigated pancreatic changes associated with hyperinsulinemia and an insulin secretory response to an oral glucose load in a new rat model for obesity. Male Sprague-Dawley pups were reared on a high-carbohydrate (HC) or high-fat (HF) formula by gastrostomy during the suckling period and were weaned onto a stock diet. These animals remained either nutritionally unchallenged or challenged with a high-sucrose diet during the postweaning period. The HC formula-fed animals showed increased insulin concentrations in the plasma and pancreas and also showed impaired insulin secretory response compared with mother-fed control or HF animals in adult life. Immunocytochemical and morphometric studies revealed that hyperinsulinemia in the HC animals during the preweaning period and also in adult life was associated with hypertrophy of beta-cells in the pancreas. The results show that consumption of a HC formula during the suckling period influences pancreatic islet morphology resulting in hyperinsulinemia which eventually leads to the development of obesity later in adult life.

Transport of sugars, including sucrose, by the msm transport system of Streptococcus mutans

The range of substrates transported by the sugar-binding protein-dependent msm (multiple sugar metabolism) system of S. mutans was investigated. By determining the ability of unlabeled sugar to compete with radiolabeled melibiose transport, we have demonstrated that the transported sugars included a number of carbohydrates structurally related to raffinose. A model accommodating these results has been devised which accounts for the sugars transported by the msm transport system. Competition with radiolabeled melibiose transport indicated sucrose to be an msm substrate. This was confirmed by examination of uptake of radiolabeled sucrose in scrAB mutants lacking the sucrose-specific phosphotransferase system.

T- and B-cell functions and epitope expression in nonhuman primates immunized with simian immunodeficiency virus antigen by the rectal route

Transmission of human immunodeficiency virus (HIV) in North America and Europe occurs most commonly through the rectal mucosa during homosexual intercourse. The simian immunodeficiency virus (SIV) macaque model has been used to investigate rectal immunization. The vaccine used was a recombinant SIV gag p27 expressed as hybrid Ty virus-like particles (Ty-VLP). Sequential ororectal (OR) mucosal immunization was compared with i.m. immunization. Whereas both routes of immunization induced serum IgA and IgG p27 antibodies, only OR immunization induced rectal secretory IgA antibodies. Specific CD4+ T-cell proliferative responses to stimulation with p27 were found after i.m. immunization only in the blood and spleen, but after OR immunization they were found in the internal iliac and inferior mesenteric lymph nodes in addition to the blood and spleen. T-cell epitope mapping of the proliferative responses of short-term cell lines (STCLs) grown from peripheral blood or lymphoid cells revealed a major epitope within the polypeptide 121-150 after either route of immunization. Two minor T-cell epitopes were found within peptide 41-80 in STCLs from splenic and circulating cells. B-cell epitope mapping of serum or biliary IgA and IgG antibodies revealed two overlapping or adjacent immunodominant epitopes to the T-cell epitopes within the polypeptides 121-170 and 51-90. The results suggest that rectal augmented by oral immunization with a recombinant particulate antigen in nonhuman primates elicits secretory IgA and to a lesser extent IgG responses in the draining lymph nodes and the rectal mucosa, whereas systemic immunization targets predominantly splenic and circulating T- and B-cell responses. These findings may have important implications in the strategy of designing vaccines in prevention of homosexual transmission of HIV infection.

Sterilization of human teeth: its effect on permeability and bond strength

Extracted human teeth were randomly divided into three groups. Group 1 teeth were untreated and served as controls. Group 2 teeth were sterilized in a steam autoclave. Group 3 teeth were sterilized by exposure to ethylene oxide gas. Crown segments were then prepared from these teeth by resection of the roots at the CEJ and the occlusal enamel to expose a flat occlusal plane of dentin. The permeability of the dentin was determined to be similar in all three groups. The shear bond strength of Prisma Universal Bond 3 and C&B Metabond was also similar in all groups indicating that sterilization of teeth does not alter dentin permeability or bond strength.

Transformation efficiency of EMS-induced mutants of Streptococcus mutans of altered cell shape

Some Streptococcus mutans strains change shape from bacillary to coccal or ellipsoid form in response to the ratio of bicarbonate to potassium or of borate to potassium in growth media. So that insight into determinants of shape of these streptococci could be gained, and future genetic studies facilitated, the shapes of a series of transformable and nontransformable strains of S. mutans were studied and attempts made to isolate a mutant of augmented transformability. Several strains were mutagenized by ethylmethane sulfonate and mutants with altered colonial and cellular morphologies isolated. Cell shapes were studied by Gram stain and Nomarski interference microscopy, and by scanning and transmission electron microscopy. Diverse shape-altered mutants were isolated from seven transformable and two nontransformable strains of S. mutans. Among these, length-to-width ratios ranged from > 10 to about 0.25. Regulation of timing of cell division, septum formation, or septum completion events may have been altered in these mutants. While most mutants substantially or completely lost transformability, mutant LT11 had transformation efficiency of 1.3 x 10(-4) to 2.3 x 10(-3), more than two to three orders of magnitude greater than its parental UA159 and the well-known transformable strain GS5(HK), respectively. There was no evidence of production of competence factor by LT11. Competence of LT11 was maintained for at least six months upon storage at -70 degrees C, facilitating its use for genetic studies. While the morphologies of several shape-altered mutants were no longer responsive to changes of the bicarbonate/potassium, unlike those of their parentals, the morphology of LT11 persisted in its response to this condition.(ABSTRACT TRUNCATED AT 250 WORDS)

Effects of oxalate on dentin bonding

The purpose of this study was to determine how much topical treatment of dentin with potassium oxalate would interfere with subsequently placed dentin bonding resins. The results indicated that oxalate lowered the bond strengths of Superbond, All Bond and Scotchbond 2, but that normal bond strengths could be obtained for Superbond and All Bond after pumicing the oxalate-treated dentin.

[Long-term follow up of dacryorhinostomy in 14 cases with fibroendoscopy]

The orifice of anastomosis and the lower aperture of the nasolacrimal duct in 14 cases (16 eyes) after dacryorhinostomy were followed up with the fibroendoscope. It was found that the size of the office and positioning of the bony window were key factors for a successful operation. Postsurgical management was advised to continue for at least 3 months or preferably 6 months. Deviation of the nasal septum toward the affected side was not regarded as contraindication for the operation, and the authors recommended fibroendoscopy in the diagnosis and postsurgical examination of lacrimal passage diseases.

Identification of several rod loci and cloning of the rodD locus of Streptococcus mutans

Previous work has shown that Streptococcus mutans is normally a short rod or a sphere, depending on its environment. This paper describes two distinct genetic approaches used to identify multiple loci and isolate one locus, rodD, controlling S. mutans rod shape. The first method involved isolation of a group of rod- mutants caused by transposon Tn916 insertion, and analysis of the inactivated genes by Southern hybridization. The second method involved mutagenesis via a shotgun insertion-duplication technique, isolation of a rod- mutant, and cloning the intact rod locus, employing an integration shuttle plasmid, pVA891. These approaches have led to the identification of multiple rod loci involved in determining the rod shape of S. mutans, and also cloning of one rod locus, rodD. The cloning strategy may also be useful for cloning other streptococcal genes which cannot be detected by their expression in Escherichia coli.

Structure of the bovine transducin gamma subunit gene and analysis of promoter function in transgenic mice

Transducin, the major photoreceptor guanine nucleotide-binding protein (G protein), is composed of three polypeptides: alpha, beta and gamma subunits. The transducin gamma subunit (T gamma) is expressed preferentially in photoreceptors. To study the control mechanisms for photoreceptor-specific expression of the T gamma gene, clones of the bovine T gamma gene were isolated from a bacteriophage genomic library, and the structure of the gene, including a portion of its 5'-flanking region, was characterized. The gene consists of three exons and two introns. The first intron is 91 base pairs (bp) long and is located in the region corresponding to the 5'-untranslated sequence of the T gamma mRNA. The second intron is 5.3 kilobases (kb) long and splits the protein-coding region centrally. A bovine Alu-type repetitive sequence and putative Ret-1 and AP-1 binding site sequences are located in the 5'-flanking region. To investigate promoter function, 1.4 kb of DNA from the 5'-flanking region was joined to the prokaryotic chloramphenicol acetyltransferase (CAT) gene, and the chimeric bovine T gamma gene was used to generate a line of transgenic mice. CAT activity was readily detected in the retinas of the transgenic mice, but was absent in brain, heart, kidney, liver, lung, spleen and other tissues. These results suggest that the 1.4 kb 5'-flanking region of the bovine T gamma gene contains conserved sequence elements that direct tissue-specific expression. Human T gamma cDNA clones were characterized, and a short homologous region of the human T gamma gene promotor was obtained by polymerase chain reaction (PCR) amplification for comparison with the bovine promoter.

Cloning and expression of the multiple sugar metabolism (msm) operon of Streptococcus mutans in heterologous streptococcal hosts

The multiple sugar metabolism (msm) operon of Streptococcus mutans is responsible for the uptake and metabolism of a variety of sugars. In order to further characterize the substrate specificities of the transport system, a 12-kb region of DNA containing the entire msm operon was cloned, via a novel two-step integration strategy, into the chromosomes of two heterologous streptococcal strains, Streptococcus gordonii Challis and Streptococcus anginosus Is57, as well as the chromosome of a natural isolate of S. mutans with a deletion of the msm region. These strains are unable to transport or ferment melibiose, raffinose, or isomaltosaccharides, but the newly constructed recombinants gained the ability to ferment all of these sugars. The S. gordonii Challis construct containing msm was shown to transport radiolabelled melibiose, raffinose, isomaltotriose, and isomaltotetraose, and the transport function was also subjected to induction by raffinose, an inducer of the msm operon in S. mutans. The results confirm the role of the msm operon in the transport and metabolism of melibiose, raffinose, and isomaltosaccharides.

MsmE, a lipoprotein involved in sugar transport in Streptococcus mutans

Metabolic labelling by [14C]palmitic acid showed that growth of Streptococcus mutans LT11 in raffinose, an inducer of the msm operon, resulted in increased production of a 45-kDa lipoprotein corresponding to MsmE, which is believed to be a sugar-binding protein. MsmE was also labelled when an msmE clone was expressed in Escherichia coli. The presence of a lipid anchor on MsmE provides a likely explanation of how the sugar-binding protein component of the msm binding protein-dependent multiple sugar transport system is retained at the cell surface.

Bond strengths to superficial, intermediate and deep dentin in vivo with four dentin bonding systems

The shear bond strength of four dentin bonding systems which remove or modify the smear layer were measured in vivo in dog canine and molar teeth as a function of dentin depth. Dentin bond strengths were higher with cuspid teeth compared to molar teeth. Most bonding systems gave higher bonds to superficial dentin and progressively lower bond strengths deeper dentin. The highest bond strengths were obtained with Clearfil Liner Bond, followed by Superbond C&B, Scotchbond 2 and Tenure. The former two bonding systems achieved shear bond strengths to cuspids that were > 10 MPa regardless of dentin depth while the latter two systems produced bond strengths < 10 MPa. In molars, the same ranking of bonding systems was noted but the value that separated the high from the low bonds was 5 MPa.

Induction of mucosal and systemic immunity to a recombinant simian immunodeficiency viral protein

Heterosexual transmission through the cervico-vaginal mucosa is the principal route of human immunodeficiency virus (HIV) infection in Africa and is increasing in the United States and Europe. Vaginal immunization with simian immunodeficiency virus (SIV) had not yet been studied in nonhuman primates. Immune responses in macaques were investigated by stimulation of the genital and gut-associated lymphoid tissue with a recombinant, particulate SIV antigen. Vaginal, followed by oral, administration of the vaccine elicited three types of immunity: (i) gag protein p27-specific, secretory immunoglobulin A (IgA) and immunoglobulin G (IgG) in the vaginal fluid, (ii) specific CD4+ T cell proliferation and helper function in B cell p27-specific IgA synthesis in the genital lymph nodes, and (iii) specific serum IgA and IgG, with CD4+ T cell proliferative and helper functions in the circulating blood.

Comparison and characterization of retinal pericytes and retinal pigment epithelial cells on subcellular IP3-sensitive Ca2+ pools

A comparative study of inositol 1,4,5-trisphosphate (IP3)-induced Ca2+ mobilization in bovine retinal capillary pericytes (BRCP) and bovine retinal pigment epithelial cells (BRPE) was carried out. Both cells were permeabilized with saponin. The two cell types had similar basal levels of [Ca2+]i (130 nM for BRCP, 132 nM for BRPE) and responded to IP3 in a dose-dependent manner. However, when stimulated by various concentrations of IP3 (1-10 microM), the increase in [Ca2+]i of BRCP was always two- to threefold higher than that in BRPE. Subcellular-fractionation studies showed that a single population of IP3 binding site with a high affinity and high specificity of IP3 mainly localized to plasma membrane in these two cell types. Although the dissociation constant of specific [32P]-IP3 binding sites (Kd 1.9-2.8 nM) was similar, the profile of maximal binding capacity (Bmax) of each fraction was markedly different. In comparison, plasma membrane fractions of BRCP were with Bmax of 165 fmol/mg protein versus 90 fmol/mg protein for BRPE membranes. The ATP-dependent Ca2+ uptake and IP3-dependent Ca2+ release were observed in the both plasma membrane fractions. With quantitative correlation, the membrane fraction (2 mg) of BRCP released 0.2 nmol Ca2+ whereas BRPE only released 0.07 nmol Ca2+ with the same dose of IP3 (5 microM). The selectively higher density of IP3 binding sites in coupling to the larger Ca(2+)-release in the membrane of BRCP suggests that the quantity of Ca2+ mobilized is determined by the spatially preferential distribution of membrane-associated IP3 binding sites. These findings may provide an explanation for the differences observed between BRCP and BRPE in IP3-induced DNA replication.

Novel streptococcal-integration shuttle vectors for gene cloning and inactivation

Seven new streptococcal integration shuttle vectors have been constructed which contain different antibiotic-resistance-encoding genes capable of expression in both Streptococcus sp. and Escherichia coli. These plasmids can replicate in E. coli, but not in streptococci because of the absence of a streptococcal origin of replication. The size, antibiotic resistance, and number of unique restriction sites available for cloning for each plasmid are as follows: pSF141 (7.6 kb, CmR and KmR, 7 sites), pSF143 (5.7 kb, TcR, 6 sites), pSF148 (7.3 kb, CmR and SpR, 7 sites), pDL285 (3.4 kb, KmR, 3 sites), pDL286 (3.1 kb, SpR, 4 sites), pSF151 (3.5 kb, KmR, 10 sites), pSF152 (3.2 kb, SpR, 9 sites). If these plasmids carry a fragment of streptococcal DNA they can specifically integrate into the chromosome via Campbell-like, homologous recombination. Therefore, they should be useful for gene inactivation, cloning, chromosomal walking, or linkage analysis in streptococci. The availability of these integration plasmids resistant to different antibiotics, along with the previously described plasmid, pVA891 (ErR), should also allow the construction of mutants possessing multiple insertionally inactivated genes useful for a variety of genetic studies.

Rapid and sensitive anion-exchange high-performance liquid chromatographic determination of radiolabeled inositol phosphates and inositol trisphosphate isomers in cellular systems

A rapid and sensitive high-performance liquid chromatographic method for the determination of multiple inositol phosphates and inositol trisphosphate isomers was developed. The separation of inositol phosphates was optimized by controlling the ionic strength with stepped gradient programs and the pH of mobile phase. Six inositol phosphates were determined within 22 min or the six compounds plus an inositol trisphosphate isomer within 24 min using a single anion-exchange column containing the quaternary ammonium functional group. This technique was successfully applied to the determination of inositol phosphatide turnover by AlF4-stimulation in a small amount (5.10(5)-1.10(6) cells) of cultured retinal capillary pericytes. Because of its efficiency, accuracy and applicability to the separation of inositol phosphates from biological samples, this method may be useful in signal transduction studies in cellular systems.

Differential binding of (+) and (-) gossypol to plasma protein and their entry into rat testis

Concentrations of (+) and (-) gossypol were measured by high performance liquid chromatography after they were incubated with plasma proteins in vitro. The concentration of (-) gossypol decreased more than the concentration of (+) gossypol. A similar decrease in free gossypol concentrations in the blood plasma of rats was observed after intravenous infusion of gossypol enantiomers. The concentration of (-) gossypol was also found to be lower than the concentration of (+) gossypol at the blood-testis barrier. The biological effect of (-) gossypol probably results from its stereospecific binding to extra- and intracellular proteins in vivo and inhibition of the biological activity of some proteins.

A binding protein-dependent transport system in Streptococcus mutans responsible for multiple sugar metabolism

An 11-kilobase gene region of Streptococcus mutans has been identified which contains eight contiguous genes involved with the uptake and metabolism of multiple sugars (the msm system). Sequence analysis of this region indicates that several of these genes specify proteins with strong homology to components of periplasmic binding protein-dependent transport systems of Gram-negative bacteria. Additionally, this operon is controlled by a regulatory gene (msmR) that acts as a positive effector. The proteins specified by the structural genes of the msm operon include alpha-galactosidase (aga), a "periplasmic-like" sugar-binding protein (msmE), two membrane proteins (msmF, msmG), sucrose phosphorylase (gtfA), an ATP-binding protein (msmK), and dextran glucosidase (dexB). Insertional inactivation of each of these genes along with uptake data indicate that this system is responsible for the uptake of melibiose, raffinose, and isomaltotriose and the metabolism of melibiose, sucrose, and isomaltosaccharides.

Relationship between bond strength and microleakage measured in the same Class I restorations

Microleakage measurements were made by use of a pressurized fluid method in Class I restorations prepared in extracted human teeth just prior to measuring the tensile bond strengths of the same restorations. The restorative materials included dentin bonding systems that are applied to smear layers as well as those which remove the smear layer. A light-cured glass-ionomer cement was also included. The results demonstrated that there was an inverse relationship between dentin bond strength and microleakage in some materials and that the bond strengths made to three-dimensional Class I cavities were much lower than those made to flat dentin surfaces. Measurement of microleakage by fluid filtration had no apparent effect on bond strength.

Effect of endodontic procedures on root dentin permeability

The purpose of this study was to quantitate the sequential effects of endodontic procedures on the permeability of human root dentin in vitro. Forty single-rooted teeth were used. Both the crown and the apical 2 mm of the root were removed. The hydraulic conductance of the root before and after various endodontic procedures was measured using a fluid filtration method. Measurements were also made of dentin thickness, intracanal diameter changes, and changes in intracanal surface area. The results showed that instrumentation by K files alone or in combination with Gates Glidden drills did not alter radicular dentin permeability when the cementum remained intact. After removing the cementum, the creation of a smear layer and smear plugs on the canal surface tended to offset the expected increase in dentin permeability created by increasing the intracanal surface area and decreasing root dentin thickness. EDTA treatment inside the instrumented canal to remove the smear layer did not increase permeability significantly. The use of K files followed by Gates Glidden drills tended to remove more cervical dentin, increased the intracanal surface area, and increased the hydraulic conductance of root dentin more than the use of K files alone.

Effects of high-speed cutting on dentin permeability and bonding

The effects of high-speed cutting by use of a diamond bur with or without water coolant or sanding by 80-grit SiC paper on dentin permeability, before and after surface treatment, and dentin bonding of adhesive resins were compared. Three different bonding systems were used: Scotchbond DC, which requires no removal of smear layers, and two others, Clearfil Photobond and Superbond C&B, both of which remove smear layers (phosphoric acid gel or 10% citric acid containing 3% ferric chloride, respectively). Creation of smear layers by bur cutting or sanding reduced dentin permeability to levels that were only 1-3% of the maximum permeability values. Scotchbond DC gave low but consistent bond strengths (3.7-6.1 MPa) to dentin covered with smear layers. Clearfil PHotobond also produced consistent bond strengths (8.6-9.4 MPa). The increase in the permeability of dentin after phosphoric acid treatment was higher when the SiC paper was used (146%) than when the high-speed bur was used (87-90%). The smear layer and smear plugs produced by the diamond bur were more resistant to 10-3 treatment than were the SiC-created smear layers. The bond strengths of Superbond showed the highest bond strengths to the conditioned dentin when the high-speed cutting was used with water coolant (16.3 MPa), compared with the other two groups (12.2-12.5 MPa).

Measurement of dentin permeability and wetness by use of the Periotron device

The ability of the Periotron device to measure changes in dentin permeability and wetness was evaluated by use of extracted human teeth in vitro. Pulpal pressures were varied from zero to 40 cm H2O for simulation of different pulpal tissue pressures. Non-physiologic pulpal pressures of 703 cm H2O were used for comparison of dentin permeability measurements made with the Periotron device with those made using micropipettes. Measurements made with the Periotron device correlated well with methods used previously for measurement of dentin permeability. The shear bond strength of Scotchbond 2/Silux was measured 24 h after being bonded to dentin held at zero pulpal pressure. There was an inverse correlation between the shear bond strengths of Scotchbond 2/Silux and Periotron values, suggesting that increased wetness decreases the bond strength of that system. The Periotron device offers a new, simple, convenient measure of dentin surface wetness which may be useful in dentin bonding studies.

Comparison of Gluma bond strength to primary vs. permanent teeth

The purpose of this study was to measure the shear bond strength of Gluma/Lumifor (Gluma and Lumifor--Columbus Dental, St. Louis, MO) to the occlusal dentin of primary first and second molars, permanent first and second molars and premolars. The data were examined for differences using a one-way analysis of variance and Duncan's Multiple Range test. The shear bond strength, (kc/cm2, x +/- SEM) to primary molars was 85.6 +/- 13.7, to permanent molars was 110.1 +/- 9.3, and to premolars was 124.0 +/- 9.3. Gluma/Lumifor provides moderately good bonding to dentin. The bond strengths of Gluma/Lumifor to primary molars was statistically significantly lower than to permanent teeth.

Reduced absolute rate of myo-inositol biosynthesis of cultured bovine retinal capillary pericytes in high glucose

De novo biosynthesis of myo-inositol (MI) by permeabilized cultured bovine retinal capillary pericytes (BRCP) and feline retinal pigment epithelial cells (FRPE), grown in different concentrations of glucose, were studied. After incubation with a physiological concentration of [14C]glucose 6-phosphate (G6P), the radioactive G6P derivatives were quantitated by a single HPLC column. Based on the determined specific activity of [14C]G6P, activities of inositol 1-phosphate synthase (MI synthase) were calculated. The activity of MI synthase was reduced 48% by growing BRCP in a high-glucose medium (20 mM) in comparison with that in the normal medium (glucose 5 mM). In contrast, the de novo MI biosynthesis by FRPE was not changed with increasing concentrations of glucose in the medium. As compared with MI uptake previously studied, the synthesized MI contributes a substantial proportion of cellular MI pool in BRCP. Therefore, in BRCP growing in high glucose the reduced MI biosynthesis aggravates the low MI content resulting from the inhibited MI uptake, and thus leads to altered inositol phospholipid metabolism.

Dentin permeability: effects of crown preparation

Sequential crown reductions of extracted human teeth were made to evaluate both regional differences in dentin permeability and the effects of tooth reduction. Two different methods of tooth reduction were used. In group 1, tooth reduction was nonuniform but was done in a manner similar to conventional crown preparations. Maximum, total crown permeability was measured using a pressurized fluid filtration technique after removing the smear layer. Regional reductions in permeability were accomplished by creating smear layers on mesial, distal, buccal, lingual, and occlusal surfaces sequentially. Between each step, changes in dentin permeability were measured. In group 2, tooth reductions were uniform and regional permeability was reduced by localized application of potassium oxalate. Both methods demonstrated increased permeability of dentin as the prepared surfaces approached the pulp chamber. Generally, the mesial surfaces were more permeable than the distal surfaces. The occlusal and lingual surfaces were the least permeable regions.

Biochemical and genetic analysis of Streptococcus mutans alpha-galactosidase

The aga gene coding for alpha-galactosidase in Streptococcus mutans was detected in a recombinant gene library constructed in phage lambda. The gene was subcloned into plasmid vectors and shown to specify a novel protein of Mr 80,000. Characterization of alpha-galactosidase from S. mutans and from recombinant Escherichia coli expressing aga indicated that the enzyme functions as a tetramer. The amino acid composition of the alpha-galactosidase, deduced from nucleotide sequencing of aga, gave a predicted Mr of 82,022 and revealed regions of homology to alpha-galactosidases encoded by the E. coli Raf plasmids and by Bacillus stearothermophilus. Inactivation of the aga gene in S. mutans resulted in loss of all alpha-galactosidase activity and abolished the ability to ferment melibiose; alpha-glucosidase activity was also lost, due to an indirect effect on the dexB gene.

Pulpal pressure and bond strengths of SuperBond and Gluma

The effects of storage under a simulated pulpal pressure on the shear bond strength of SuperBond and Gluma were evaluated using extracted, unerupted human teeth. Also evaluated was the effect of dentin position both vertically (i.e., superficial versus deep) and horizontally (center versus pulp horns) in the presence or absence of a pulpal pressure. Thirty-two cm of H2O pressure had no effect on the 24 hour shear bond strength of SuperBond C & B. There was also no significant difference in the bond strength of SuperBond to superficial versus deep dentin or central dentin versus dentin directly over pulp horns. The bond strengths of SuperBond ranged from 16.3-19.1 MPa. Gluma bonds were less than half as strong as those obtained with SuperBond C & B. Although there was no effect of dentin position on Gluma bond strength, in the presence of a pulpal pressure, the strength of the bonds fell in deep dentin especially over pulp horns. This testing protocol may prove of value in screening new dentin bonding systems.

Epinephrine permeation across dentin in vitro

The permeation of epinephrine across human dentin discs was studied in vitro. Permeation was measured across dentin of two different thicknesses, with and without the presence of smear layers. Epinephrine was readily detected at the earliest measured time (10 min) and reached peak concentrations between 30 and 50 min. Epinephrine flux (concentration multiplied by the volume of the effluent per min) increased with decreasing thickness of the discs and increased significantly with the removal of the smear layer. The T 1/2 (half-time in min necessary to reach steady-state diffusion of epinephrine) decreased as dentin thickness was reduced and fell further in the absence of the smear layer. This study suggests that the permeation of epinephrine across dentin is inversely related to dentin thickness and retarded by the presence of a smear layer. Also, the topical use of 1 mg/ml epinephrine produced therapeutically useful drug concentrations, but the rate of permeation was relatively slow.

Shear bond strength of Scotchbond in vivo

The shear bond strengths of Scotchbond, HEMA/Scotchbond, and Scotchbond 2 were measured in vivo in dog canine and molar enamel and dentin. Dentin bond strengths were compared in superficial, middle, and deep dentin. The acid-etched enamel bond strengths of the three bonding systems ranged from 10 to 11 MPa and were not statistically different. Scotchbond/Silux bonds to superficial and middle cuspid and molar dentin were 3 MPa and were not statistically different. HEMA-treated dentin did not consistently improve Scotchbond strengths to either tooth type at any dentin depth. Deep dentin from either tooth type yielded significantly lower bond strengths. Scotchbond 2/Silux shear bond strengths were significantly higher (6-8 MPa) in superficial and middle cuspid dentin but were not different from Scotchbond bonds made to deep cuspid dentin or to any depth of molar dentin. The observation that molar bond strengths are lower than those made to cuspid dentin indicates that there are important substrate differences between teeth as well as within dentin as a function of depth. The dog model may be useful for the screening of new dentin bonding systems prior to clinical trials.

Fluid and protein flux across the pulpodentine complex of the dog in vivo

Dentinal fluid volume and protein concentrations were measured from cavities prepared in the dentine of dog molars. Fluid was collected under spontaneous conditions, during the application of negative pressures, and during a recovery period. The data allowed the calculation of dentine permeability as hydraulic conductances, fluid flux, protein flux, reflection coefficients and pulpal tissue pressures. In general, the protein concentration of dentinal fluid was about one-fifth that of plasma during spontaneous conditions and it fell when fluid flux was increased by the application of external negative pressures. The collection and analysis of dentinal fluid looks promising as a non-invasive method of assessing the state of the underlying pulp.

Bond strengths of luting cements to potassium oxalate-treated dentin

Potassium oxalate is gaining popularity as a dentin treatment to prevent the development of dentin sensitivity. Because treated dentin surfaces are covered with calcium oxalate crystals, the bond strength of cements to oxalate-treated dentin required investigation. This study determined the tensile bond strengths of glass-ionomer, polycarboxylate, and zinc phosphate cements used to cement castings to dentin treated with either water or potassium oxalate. The results indicate that oxalate-treated dentin did not affect the bond strength of glass-ionomer or polycarboxylate cements, but produced a large decrease in the bond strength of zinc phosphate cement.

Evaporative water loss from human dentine in vitro

The rate of spontaneous evaporation of water from dentine was measured in extracted human teeth in vitro. Spontaneous water loss was the same with or without a smear layer. When air was blown on the dentine, the rate of evaporation increased significantly. After removal of the smear layer, the air blast-induced evaporative loss was twice as great as before its removal. Thus, with a smear layer present, evaporation is the major route by which fluid is lost from dentine rather than by filtration of dentinal fluid. After smear layer removal, fluid filtration sometimes may exceed the spontaneous rate of fluid evaporation.

Correlation among dentin depth, permeability, and bond strength of adhesive resins

Correlations among dentin permeability, dentin depth, and dentin bonding of Scotchbond, Clearfil New Bond, and Superbond C&B were studied in bovine incisor crown segments. Since the dentin surface was prepared on deeper dentin, the permeability of the dentin increased both in the presence of, and especially after removal of, the smear layer. In general, the deeper the dentin, the lower the bond strengths of Scotchbond, Clearfil New Bond, and Superbond C&B. The higher the dentin permeability, the lower the bond strength of Superbond C&B, but there was no simple relationship in the case of either Scotchbond or Clearfil New Bond. The bond strength of Superbond C&B was much higher than those of Scotchbond or Clearfil New Bond at any depth of dentin. Superbond C&B should be considered as both an enamel- and dentin-bonding agent.

Dentin permeability and bond strengths after various surface treatments

Numerous reports suggest that removal of the smear layer increases the bond strengths of some dentin adhesives while lowering the bond strengths of others. Smear layer removal also increases dentin permeability and wetness. The purpose of this study was to compare the permeability and shear bond strengths of occlusal vs. buccal dentin before and after removal of the smear layer with 6% citric acid and before and after substitution of the smear layer by topical oxalate treatment. Shear bond strengths of Scotchbond/Silux to smear layers were higher than those to acid-etched dentin. Oxalate treatment of acid-etched dentin increased bond strengths to levels that were higher than smear layer controls. Removal of the smear layer increased dentin permeability. This result was completely reversed by oxalate treatment.

The entry of gossypol across the blood-testis barrier in rats

This paper presents the experimental data about how different formulations of gossypol enter the blood-testis barrier following intravenous administration in acute experiments on rats. It was found that gossypol encapsulated by liposomes crossed the blood-testis barrier more readily than free gossypol, without affecting its pharmacokinetic pattern in the circulating blood, suggesting that liposomes may be useful as drug carriers and may facilitate the entry of encapsulated gossypol into the seminiferous tubule from the blood.

Dentin perfusion effects on the shear bond strengths of bonding agents to dentin

The effect of pulpal pressure on the shear bond strength of Scotchbond and Gluma was evaluated in the presence and absence of smear layers. There was no statistically significant difference in bond strength for either Scotchbond or Gluma on dentin with a smear layer in the presence or absence of 32 cm of hydrostatic pulpal pressure. When no pulpal pressure was present and the smear layer was removed, the bond strength of Scotchbond fell while that of Gluma nearly doubled. When 32 cm of pulp pressure was applied, the bond strength of Scotchbond/Silux fell 86% and that of Gluma fell 75% in 24 hours.

The relationship between dentin bond strengths and dentin permeability

The relationship between dentin permeability and the shear bond strength of Scotchbond/Silux was investigated. In the presence of a smear layer, there was no correlation between dentin permeability and dentin bond strengths. After removal of the smear layer with acids, there was an inverse relationship between dentin permeability and dentin bond strength. The bond strengths were high when dentin permeability was low and decreased as dentin permeability increased. Creation of smear layers with abrasive paper or dental burs reduced permeability by 80-85%. When Scotchbond/Silux bonds were made to such smear layers and then broken, the permeability of the dentin remained low. If the smear layer was removed by acid-etching prior to bonding, the permeability increased. When these bonds were broken, the permeability of the dentin remained elevated.

The permeability of dentine from bovine incisors in vitro

The permeability of coronal dentine was investigated by measuring the hydraulic conductance of dentine discs. Reductions in dentine thickness from the enamel side of disc resulted in a greater increase in permeability than reductions from the pulpal side. Scanning electron microscopy revealed fewer dentinal tubules with smaller diameters in superficial dentine than in deep dentine. The permeability of coronal incisor bovine dentine is six to eight times less than that of unerupted coronal human third molar dentine but similar to that of human root dentine.

Factors influencing cell shape in the mutans group of streptococci

Electron and light microscopic and growth studies of representatives of the diverse species of mutans streptococci revealed the cells to be either bacillary or coccoid in shape. Some strains changed from bacillary to coccoid if the HCO3-/K+ ratio of the media was increased and from coccoid to bacillary if the ratio was decreased. Doubling times of rods and cocci were the same despite an HCO3-/K+ ratio change between 0.008 and 2.84. For strain 10449S, no tested anions or cations substituted for HCO3- or K+ to produce this effect, except for B4O7(2-). Strain 10449S grown at a high B4O7(2-)/K+ ratio became ellipsoid, and this phenomenon was associated with slower doubling times. Up to three incomplete septa could be observed in one rod, but no more than one incomplete septum could be observed in either ellipsoid or spherical cells. Interseptal distances were greatest in rods, shorter in spheres, and shortest in ellipses. All of the above differences were statistically significant (P less than 0.001).

Comparison of in vivo vs. in vitro bonding of composite resin to the dentin of canine teeth

Dogs were utilized in a study to compare the bond strengths of dentin bonding agents made to dentin in vivo and then again in vitro in the same teeth 30 min, one day, one week, and one month post-extraction. No statistically significant differences were observed between bonds made in vivo and those made in vitro at any time period. Contamination of the dentin surfaces with blood or saliva lowered the bond strengths, but these could be restored to control values by re-surfacing of the dentin with a bur.