Micro-computerized tomography assessment of fluorescence aided caries excavation (FACE) technology: comparison with three other caries removal techniques

BACKGROUND

The aim of this study was to determine the caries removal effectiveness (CRE) and minimal invasiveness potential (MIP) of four dentine caries removal methods.

METHODS

After carious molars were scanned using micro-computerized tomography (micro-CT), dentine caries were removed by fluorescence aided caries excavation (FACE) technology, laser induced fluorescence (LIF), chemomechanical excavation (CME), and conventional excavation (CE). Micro-CT was then repeated. CRE was determined based on the volume of residual caries/initial caries (RC/IC) and the mean mineral density (MD) at the cavity floor. MIP was determined by measuring the volume of the prepared cavity/initial cavity (PC/IC).

RESULTS

Among the four groups, the LIF group had the smallest RC/IC (0.08), the highest mean MD at the cavity floor (1.32 g/cm(3) ) and the highest MIP (4.47). The CME group had the highest RC/IC (0.24), the lowest mean MD (1.01 g/cm(3) ) and the lowest MIP (2.23). The CE group exhibited a more acceptable CRE (RC/IC = 0.13, mean MD = 1.21 g/cm(3) ) but had a higher MIP (3.95). Both the CRE and MIP parameters of FACE technology were the second most acceptable (RC/IC = 0.12, mean MD = 1.13 g/cm(3) , MIP = 3.20) and did not differ significantly from the most acceptable.

CONCLUSIONS

FACE is an effective caries removal technology for removing infected dentine without significantly increasing cavity size.

Identification of nitrogen-fixing Paenibacillus from different plant rhizospheres and a novel nifH gene detected in the P. stellifer

A total of 534 isolates were selectively obtained from different plant rhizospheres based on their growth on nitrogen-free medium and their resistance to 80 degrees C for 15 min. Of the 534 isolates, 23 isolates had nifH gene and exhibited nitrogenase activities. Based on 16S rDNA sequence, G + C content assay and DNA-DNA hybridization, by the 23 isolates, which were divided into four monophyletic clusters, all belonged to the Paenibacillus genus. NifH gene deduced amino acid alignment analysis revealed that cluster I, including 15 isolates, showed the highest NifH identity with Paenibacillus genus; while cluster II identified as P stellifer by DNA-DNA hybridization was consistent with four uncultured bacterial clones. This study suggested that the nitrogen-fixing Paenibacillus were distributed in various ecosystems and prevalent in different plant rhizospheres. It was the first demonstration that nitrogen fixation existed in P. jamilae and P. stellifer. In eight isolates identified as P. stellfer species, a novel nifH gene was detected in Paenibacillus.

Human PDE5A gene encodes three PDE5 isoforms from two alternate promoters

Sildenafil improves erectile function by inhibiting the cGMP-catalytic activity of phosphodiesterase type V (PDE5). We used rapid amplification of cDNA Ends-polymerase chain reaction (RACE-PCR) to isolate three PDE5 isoforms from human corpus cavernosum. Semiquantitative reverse transcription-polymerase chain reaction (RT-PCR) analysis on eight human cavernous tissue samples showed that all samples expressed the PDE5A1 at a lower level than the PDE5A2 isoform. Five samples expressed the PDE5A3 isoform at various levels while the other three did not. Analysis on non-penile tissues showed that all tissues expressed the A1 and A2 isoforms while only those that have substantial amounts of smooth muscle expressed the A3 isoform. Cloning and sequencing of the PDE5A gene showed that the isoform-specific 5'-ends of the PDE5 mRNAs are encoded from three alternative first exons arranged in the order of A1-A3-A2. Promoter activities were detected upstream from the A1-specific exon and in the intron preceding the A2-specific exon. The upstream PDE5A promoter is expected to direct the expression of all three PDE5 isoforms while the intronic PDE5A2 promoter only the A2 isoform. Both promoters were upregulated by increasing concentrations of either cAMP or cGMP. Several transcription factor AP2 and Sp1-binding sequences identified in the promoters are likely to be the mediators of cAMP/cGMP-responsiveness.

Age-related decrease of protein kinase G activation in vascular smooth muscle cells

Protein kinase G-I (PKG-I) activation is essential for vascular relaxation; however, its quantitative analysis in intact cells has been difficult. To overcome this difficulty, a monoclonal antibody, VASP-16C2, was recently developed that detects phosphorylated serine residue 239 of vasodilator-stimulated phosphoprotein (VASP), a substrate of PKG-I. In this study, we used this antibody to examine (i) possible functional differences between the alpha and beta isoforms of PKG-I, (ii) ability of cAMP to activate PKG-I, as compared to cGMP, the principal PKG-I-activating cyclic nucleotide, and (iii) time course and levels of PKG-I activation in vascular smooth muscle cells (VSMC) of young and old rats. We created COS-7 cell clones that overexpressed PKG-Ialpha or PKG-Ibeta, treated them with cAMP or cGMP, and analyzed their cell lysates for reactivity with VASP-16C2. The results showed that PKG-Ialpha phosphorylated VASP at a higher level than PKG-Ibeta, and cAMP was slightly weaker than cGMP in PKG-I activation. VSMC of young rats responded to cAMP or cGMP stimulation in a dose-dependent manner with increasing levels of PKG-I activation. The response was detected within 10 min and continued for at least 24 h. In contrast, VSMC of old rats showed no PKG-I activation during the first hour of cAMP or cGMP stimulation and, at 24 h these cells showed only low-level PKG-I activation. We propose that the reduced PKG-I activation may explain why vascular relaxation is decreased in older individuals.

Identification and regulation of human PDE5A gene promoter

PDE5A gene encodes type 5 phosphodiesterase (PDE5), the principal cGMP-catalyzing enzyme in the penis and the primary target of sildenafil (Viagra). We have isolated a 3.7-kb DNA fragment that contains the human PDE5A gene promoter. The DNA fragment contains a sequence of 234 nucleotides at its 3' end that corresponds to most of the untranslated region of the PDE5A1 mRNA. The remaining 3.5-kb upstream flanking sequence contains no apparent TATA box but has several sequences that resemble binding sequences for transcription factors such as androgen receptor (AR), AP1, AP2, AP4, Sp1, MyoD, Myc, and CArG. In search of promoter activities, we used a luciferase reporter system to examine 10 DNA fragments that cover various regions of the 3.7-kb fragment. We found that a full basal promoter activity was confined to a 139-bp region that includes 78 bp of the PDE5A1-specific first exon. A lesser basal promoter activity was still detectable in a 94-bp fragment that contains the same 78-bp PDE5A1-specific exon plus 16 bp of upstream sequence. Either the 139-bp or the 94-bp promoter fragment responded minimally to cAMP or cGMP (2 mM) stimulation. Longer fragments that contain either a 308-bp 5' extension (from the 138-bp fragment) or a 156-bp 3' extension (all exon sequence) responded at higher levels to cAMP and cGMP stimulation. The 5' and 3' extensions cooperated with each other to provide the highest level of responses to cAMP and cGMP stimulation. DNase I footprint analysis identified four AP2- and two Sp1-binding sites in the 5' extension and four Sp1-binding sites in the 3' extensions. Cyclic AMP and cGMP had similar stimulatory effects on the PDE5A promoter.

Regulation of human PDE5A2 intronic promoter by cAMP and cGMP: identification of a critical Sp1-binding site

PDE5A gene encodes type 5 phosphodiesterase (PDE5), the principal cGMP-catalyzing enzyme in the penis and the primary target of sildenafil (Viagra). We have previously reported the isolation of three alternatively spliced PDE5A isoforms in humans. We also reported the identification of three corresponding alternative first exons and an intronic promoter in the human PDE5A gene. The intronic promoter is situated upstream from the PDE5A2-specific first exon but downstream from the PDE5A1- and A3-specific first exons. In the current study we showed that the intronic promoter could be upregulated by either cAMP or cGMP. In order to identify possible regulatory elements in the promoter, we created deletion and base-substitution mutants targeting one AP2- and four Sp1-binding sequences. Loss of function of these mutants to bind to the respective transcription factors was verified by DNase I footprint analysis, and changes in promoter function were analyzed with a luciferase reporter system. Mutation of the AP2-binding sequence and deletion of the 3'-most Sp1-binding site (within the exon) had little effects on the basal or the cyclic nucleotide-inducible promoter functions. Mutation of the 5'-most Sp1-binding site had much more severe effects on the basal and the cyclic nucleotide-inducible promoter functions. Mutation of a neighboring site that contains two overlapping Sp1-binding sequences completely nullified the basal and cyclic nucleotide-inducible promoter activities. Thus, the PDE5A2 intronic promoter depends on the overlapping Sp1-binding site for basal and cyclic nucleotide-inducible functions.

Endogenous Zn(2+) is required for the induction of long-term potentiation at rat hippocampal mossy fiber-CA3 synapses

The functional role of the abundant Zn(2+) found in some hippocampal synapses has been an enigma. We show here, using N-[6-methoxy-8-quinolyl]-P-toluenesulfonamide (TSQ) staining, that chelatable-Zn(2+) can be removed from hippocampal synaptic boutons using dietary depletion or with Zn(2+) chelators. A chronic dietary deficiency of bouton Zn(2+) resulted in the impairment of long-term potentiation (LTP) at mossy fiber-CA3 synapses. The averaged normalized fEPSP slope 30 min after tetanus was 209 +/- 28% of baseline value in control (mean +/- SEM, n = 10), and 118 +/- 12% in Zn(2+)-deficient rats (mean +/- SEM, n = 12, P < 0.01). In the deficient rats with Zn(2+) supplements, mossy fiber LTP returned to normal levels. The acute depletion of bouton Zn(2+) in the hippocampal slice with membrane-permeable Zn(2+) chelators, dithizone, or diethyldithiocarbamic acid (DEDTC) blocked the induction of mossy fiber LTP. The mean amplitudes of EPSCs after tetanus were 194 +/- 22% of baseline value in control (n = 5), compared to 108 +/- 14% in dithizone (n = 6) and 101 +/- 12% in DEDTC (n = 5). The averaged value of LTP, at the associational commisural fiber-CA3 synapses, was 193 +/- 20% in the control (n = 6), compared to 182 +/- 21% (n = 6, P > 0.1) in the presence of dithizone. The blockade of mossy fiber LTP by dithizone was reversible after washout. In addition, normal LTP could be induced by tetanus if exogenous Zn(2+) was applied immediately following dithizone. Our results indicate that the endogenous Zn(2+) is specifically required for LTP induction at the mossy fiber input into CA3 neurons.

Magnetic resonance imaging in patients with central nervous system pathology: a comparison of OptiMARK (Gd-DTPA-BMEA) and Magnevist (Gd-DTPA)

RATIONALE AND OBJECTIVES

The objective of the two pivotal phase 3 studies was to evaluate the safety and efficacy of OptiMARK (Gd-DTPA-bis(methoxyethylamide) [Gd-DTPA-BMEA]) compared with Magnevist (Gd-DTPA) in magnetic resonance imaging of the central nervous system.

METHODS

Two multicenter, randomized, double-blind, parallel group studies were conducted in 395 patients with known or suspected central nervous system pathology. Subjects were randomized to receive a single 0.1 mmol/kg intravenous injection of either Gd-DTPA-BMEA or Gd-DTPA. The safety of Gd-DTPA-BMEA and Gd-DTPA was monitored for up to 72 hours after study drug administration. Precontrast and postcontrast administration magnetic resonance scans were acquired using identical imaging planes and techniques.

RESULTS

No deaths or unexpected adverse events were reported in either group. A comparison of adverse events by intensity and relation demonstrated no statistically significant differences between the two groups. Gd-DTPA-BMEA and Gd-DTPA were equivalent with respect to confidence in diagnosis, conspicuity, and border delineation.

CONCLUSIONS

Gd-DTPA-BMEA and Gd-DTPA demonstrated comparable efficacy profiles, and the safety profiles were considered similar.

Homologous acellular matrix graft for urethral reconstruction in the rabbit: histological and functional evaluation

OBJECTIVE

To evaluate urethral replacement by a free homologous graft of acellular urethral matrix in a rabbit model.

MATERIALS AND METHODS

In 30 male New Zealand rabbits, a 0.8 to 1.1 cm. segment of the urethra was resected, replaced with an acellular matrix graft of 1.0 to 1.5 cm. (mean 1.3 cm.), and placed on an 8F feeding tube. Additionally 4 animals underwent sham operation. At varying intervals before sacrifice (from 10 days to 8 months), the animals underwent urodynamic evaluation and retrograde urethrography (for which 4 untreated rabbits served as control). The grafted specimens were prepared for evaluation histologically and by reverse-transcription polymerase chain reaction (RT-PCR).

RESULTS

In all animals, the acellular matrix graft remained in its original position. Histological examination showed complete epithelialization and progressive vessel infiltration. At 3 months, smooth muscle bundles were first observed infiltrating the matrix at the end-to-end anastomosis; after 6 months, the smooth muscle bundles had grown into one-third of the matrix. Urodynamics did not detect any difference between the control and matrix-grafted animals in bladder volume, leak-point pressure and residual volume. RT-PCR detected an increase in IGF mRNA in the graft between week 3 and month 6 and in HB-EGF mRNA after day 10 through month 3. TGF-alpha mRNA was not detected; TGF-beta mRNA was unchanged from normal urethral tissue. By 8 months, the host and implant could not be differentiated by urethrography.

CONCLUSION

The acellular urethral matrix allows single-stage urethral reconstruction. All tissue components were seen in the grafted matrix after 3 months, with further improvement over time; however, the smooth muscle in the matrix was less than in normal rabbit urethra and was not well oriented. RT-PCR revealed the importance of time-dependent growth factor influences during regeneration.

Identification of three alternative first exons and an intronic promoter of human PDE5A gene

In the accompanying paper we present evidence for the existence of three PDE5A isoforms that differed only in the 5' end of the mRNAs. In this paper we present evidence that the three isoform-specific 5' ends were encoded by three alternative first exons that were arranged in the order of A1-A3-A2. Because the isoform-specific mRNAs could be transcribed from individual promoters, DNA fragments of the two intronic regions (A1-A3 and A3-A2) were tested for possible promoter activities. The intron between A1- and A3-specific exons did not exhibit any promoter activities even in smooth muscle cells that expressed the A3 isoform (see accompanying paper). In contrast, the intron between A3- and A2-specific exons had promoter activities in PDE5A2-expressing COS-7 and smooth muscle cells. This intronic promoter was bound by transcription factors AP-2 and Sp1, but not by AP-1, as shown by DNase I footprint analysis. However, the sequence bound by AP-2 (5'-GGGAAACGCTCGCGGGAGAGTTGG) is unusual in that it bears little resemblance to the consensus AP-2-binding sequence.

Expression of three isoforms of cGMP-binding cGMP-specific phosphodiesterase (PDE5) in human penile cavernosum

Inhibition of cGMP-specific phosphodiesterase type V (PDE5) has been shown to improve penile erection in patients with erectile dysfunction. We report here the cloning of three PDE5 isoforms from human penile tissues. Two of the isoforms were identical to PDE5A1 and PDE5A2, respectively, which had been isolated from nonpenile tissues. The third isoform was novel and hence called PDE5A3. The deduced amino acid sequence of PDE5A3 was the same as the C-terminal 823-residue sequence of PDE5A1 and PDE5A2. While PDE5A1 and A2 isoforms were expressed in all tissues examined, the A3 isoform was confined to tissues with a smooth muscle or cardiac muscle component. When expressed in COS-7 cells, PDE5A1, A2, and A3 isoforms had similar cGMP-catalytic activities with K(m) of 6.2, 5.75, and 6.06 microM, respectively. Their cGMP-catalytic activities were inhibited by zaprinast with IC(50) values of 3.2 microM, 1.3 microM, and 1.6 microM, respectively, and by sildenafil with IC(50) of 28, 14, and 13 nM, respectively.

Characterization of a polyepoxy compound fixed porcine heart valve bioprosthesis

Concerns with the currently available bioprostheses are calcification, long-term durability, and suboptimal hemodynamic performance. It is well known that these concerns are all more or less related to the cross-linking reagent, glutaraldehyde or formaldehyde, used in fixing bioprostheses. To address these concerns, we undertook the development of a porcine bioprosthesis fixed with a polyepoxy compound. In the development of this polyepoxy compound valve, it was found that the porcine leaflets fixed with polyepoxy compound were softer and more pliable than those fixed with glutaraldehyde. In this study, a special microtoming technique was developed to section the biological tissue so that the fixation uniformity in distinct layers of porcine aortic wall could be characterized. The fixation index and the denaturation temperature measurements in distinct layers of aortic walls showed that the cross-linking density was uniform throughout the entire aortic wall for the polyepoxy compound fixed porcine valve. It was also noted that the fixation index of the polyepoxy compound fixed aortic wall (91.5 +/- 0.5, n = 3) was not significantly different from that of its valvular leaflet (90.6 +/- 0.8, n = 3). Similarly, the denaturation temperature of the polyepoxy compound fixed aortic wall (80.4 +/- 0.9 degrees C, n = 5) was statistically comparable to that of its valvular leaflet (79.0 +/- 0.5 degrees C, n = 5). The results of this study indicated that polyepoxy compound can adequately fix the entire porcine aortic wall as well as its valvular leaflets.(ABSTRACT TRUNCATED AT 250 WORDS)

Analysis of neuronal nitric oxide synthase isoform expression and identification of human nNOS-mu

The neuronal form of nitric oxide synthase (nNOS) is responsible for the production of NO, which acts as a neurotransmitter for penile erection and urethra relaxation. An nNOS splice variant form, nNOS-mu, was first reported to be specifically expressed in skeletal muscle and heart in the rat, but later also identified in rat penile cavernosum. We report here an apparently universal expression of nNOS-mu mRNA in rat tissues, including brain, which was previously reported to be lacking nNOS-mu. Immunoblot analysis revealed that some commercially available nNOS antibodies had high levels of nonspecific activities, which could lead to the appearance of seemingly multiple forms of nNOS. Immunohistochemical analysis with these antibodies also produced nonspecific stainings. In humans, nNOS-mu; expression appeared to be confined to skeletal muscle and heart. Human penile tissues obtained from patients with erectile dysfunction did not express nNOS-mu. The human nNOS-mu-specific cDNA sequence was 89% homologous to its rat counterpart.

Anti-tumor immunity is involved in the thymidine kinase-mediated killing of tumors induced by activated Ki-ras(G12V)

We have established a syngeneic mouse tumor model to test the efficacy of the drug-sensitizing enzyme thymidine kinase from herpes simplex virus (HSVtk) in vivo. Activated mutant Ki-ras(G12V) is frequently found in human colon cancer and adenocarcinomas of the lung and pancreas. We have transformed BALB/c-3T3 cells by stable transfection of a plasmid directing the expression of the mutant Ki-ras cDNA. To transfer the HSVtk gene into tumor cells we used a Moloney murine leukemia virus (MoMLV)-based retroviral vector that carries the HSVtk gene. In this study we show that the activity of HSV-TK inhibits tumor growth in immune-compromised nude mice following GCV treatment for up to 50 days but is not sufficient to completely eliminate all tumor cells in these mice as evidenced by the occurrence of tumors between 40 and 50 days after tumor cell implantation. By contrast, immune-competent BALB/c mice develop a long-lasting antitumor immunity in response to HSVtk transduction and GCV treatment, indicating that the immune system is important for the long-term tumor suppression in vivo. In the presence of GCV co-culturing of tumor cells with HSVtk transfected cells leads to the efficient killing of HSVtk negative tumor cells. While this retroviral vector independent HSV-TK/GCV-mediated bystander effect is not sufficient to inhibit tumor formation in athymic animals it is very efficient in immune-competent syngeneic mice. Taken together the data indicate that the antitumor activity of HSV-TK is enhanced by an intact immune system.

UV-inactivated measles virus stimulates human and mice naive lymphocytes to proliferate in vitro

Ultra violet (UV) light-inactivated measles virus was used for the lymphocyte proliferation assay, where it caused consistently adult human peripheral blood monolymphocytes (PBML) proliferation which was not dependent on the measles virus complement fixation titre in the donor's sera. When the cord blood lymphocytes from newborn baby and spleen lymphocytes from unprimed Balb/c, C57bl and CBA mice were used in the proliferation assay, all the lymphocytes were stimulated by the UV-inactivated measles virus in a dose-dependent manner. These results suggest that: (1) lymphotropic measles virus can also activate lymphocytes in vitro, and (2) this activation appeared to be neither species- nor major histocompatibility complex (MHC)-restricted. These results may have important implications for measles vaccination and the understanding of the immunopathogenesis of measles virus infection.

Fixation of bioprosthetic tissues with monofunctional and multifunctional polyepoxy compounds

Collagen from a native tissue is fixed with a polyepoxy compound (PC) for use as a new biologic prosthetic material. Prior studies have shown that this biomaterial has comparable properties with collagen fixed with glutaraldehyde (GA), and thus has great promise for biomedical applications. A prior kinetic study indicated that the reaction between the functional groups of collagen and the multifunctional epoxy EX-313 is a 2.5th-order reaction. The purpose of this study was to understand the mechanism of the amino acid-PC reactions in a fixation process. Bovine arteries were fixed with a monofunctional PC (EX-131) and a multifunctional PC (EX-313) as a function of fixation time. A sequential fixation with a second fixative was used to identify the available remaining reactive sites from a prior fixation. The denaturation temperature (Td) was measured on each sample. Because the denaturation temperature is a direct indication of crosslinking of individual amino acids with the fixative, the increase in Td of a subsequent fixation may be indicative of the available remaining amino acids. The fixation index was measured on each sample to reflect the increase of fixation completion in a sequential fixation process. The fixation index and crosslink data also revealed that the reactive amino acids for EX-131 and EX-313 may not be exactly the same. The data in this study suggest that a monofunctional fixative can pre-react with the amino acids of collagen to effectively block further fixation of collagen with a second fixative. This amino acid masking may be associated with collagen branching. Collagen branching and its effect on denaturation temperature are described.

A newly developed porcine heart valve bioprosthesis fixed with an epoxy compound. An experimental evaluation

Concerns with currently available bioprostheses are calcification, long-term durability, and functional and hemodynamic performance. It has been well known that these concerns are all more or less related to the fixatives, glutaraldehyde or formaldehyde, used in preserving bioprostheses. To address these concerns, we undertook the development of a porcine bioprosthesis fixed with an epoxy compound. It was discovered that the porcine leaflets fixed with the epoxy compound appeared more natural than those preserved with glutaraldehyde. The performance of this newly developed epoxy compound bioprosthesis (three samples) was evaluated in a juvenile sheep model. The results were compared to those of its glutaraldehyde counterpart (three samples). Two-dimensional echocardiographic inspection of the valvular leaflet motion indicated that the epoxy compound leaflets were more pliable than their glutaraldehyde counterparts. In addition, the epoxy compound valve appeared to open more widely than the glutaraldehyde valve. Color Doppler flow mapping demonstrated that the blood flow distal to the epoxy compound valve was slightly broader than that observed distal to the glutaraldehyde valve. Moreover, at retrieval, less calcium and pannus ingrowth were observed in the epoxy compound valve than its glutaraldehyde counterpart. The results of this preliminary evaluation indicated that the performance of this newly developed epoxy compound valve was at least equivalent to its glutaraldehyde counterpart, if not better.