A Primitive Growth Factor, NME7AB , Is Sufficient to Induce Stable Naïve State Human Pluripotency; Reprogramming in This Novel Growth Factor Confers Superior Differentiation.

Scientists have generated human stem cells that in some respects mimic mouse naïve cells, but their dependence on the addition of several extrinsic agents, and their propensity to develop abnormal karyotype calls into question their resemblance to a naturally occurring "naïve" state in humans. Here, we report that a recombinant, truncated human NME7, referred to as NME7AB here, induces a stable naïve-like state in human embryonic stem cells and induced pluripotent stem cells without the use of inhibitors, transgenes, leukemia inhibitory factor (LIF), fibroblast growth factor 2 (FGF2), feeder cells, or their conditioned media. Evidence of a naïve state includes reactivation of the second X chromosome in female source cells, increased expression of naïve markers and decreased expression of primed state markers, ability to be clonally expanded and increased differentiation potential. RNA-seq analysis shows vast differences between the parent FGF2 grown, primed state cells, and NME7AB converted cells, but similarities to altered gene expression patterns reported by others generating naïve-like stem cells via the use of biochemical inhibitors. Experiments presented here, in combination with our previous work, suggest a mechanistic model of how human stem cells regulate self-replication: an early naïve state driven by NME7, which cannot itself limit self-replication and a later naïve state regulated by NME1, which limits self-replication when its multimerization state shifts from the active dimer to the inactive hexamer.

Dynamics of cylindrically converging precursor plasma flow in wire-array Z -pinch experiments.

This paper summarizes the present understanding of the processes leading to precursor column formation in cylindrical wire arrays on the 1 MA MAGPIE generator at Imperial College London. Direct experimental measurements of the diameter variation during the collapse and formation phase of the precursor column are presented, along with soft x-ray emission, and quantitative radiography. In addition, data from twisted cylindrical arrays are presented which give additional information on the behavior of coronal plasma generated in wire array z pinches. Three stages in precursor column formation are identifiable from the data: broad initial density profile, rapid contraction to small diameter, and slow expansion after formation. The correlation of emission to column diameter variation indicates the contraction phase is a nonlinear collapse resulting from the increasing on-axis density and radiative cooling rate. The variation in the minimum diameter is measured for several array materials, and data show good agreement with a pressure balance model. Comparison of column expansion rates to analytical models allows an estimate of column temperature variation, and estimates of the current in the column are also made. Formation data are in good agreement with both fluid and kinetic modeling, but highlight the need to include collisionless flow in the early time behavior.

Study of three-dimensional structure in wire-array z pinches by controlled seeding of axial modulations in wire radius.

Three-dimensional perturbations have been seeded in wire-array z pinches by etching 15 microm diameter aluminum wires to introduce 20% modulations in radius with a controlled axial wavelength. These perturbations seed additional three-dimensional imploding structures that are studied experimentally and with magnetohydrodynamics calculations, highlighting the role of current path nonuniformity in perturbation-induced magnetic bubble formation.

Laser irradiation of bone: III. Long-term healing following treatment by CO2 and Nd:YAG lasers.

BACKGROUND: Relative few reports exist concerning healing of laser created osteotomies over an extended period of time. The purpose of this study was to evaluate long-term healing, from 21 to 63 days, of osteotomy defects in the rat tibia created with the Nd:YAG and CO2 in the presence of a surface cooling spray of air/water. METHODS: The experimental model consisted of 15 large Sprague-Dawley rats. Six treatment modalities were randomly distributed among 6 tibial recipient sites: 1) a negative control (no treatment); 2) a positive control (bur osteotomy); 3) CO2 laser at 5 W (860 J/cm2); 4) CO2 laser at 6 W (1,032 J/cm2); 5) Nd:YAG laser at 5 W (714 J/cm2); and 6) Nd:YAG laser at 7 W (1,000 J/cm2). All laser irradiation was delivered in the presence of a surface coolant consisting of air (15 psi) and sterile water. Five animals were sacrificed at each of 3 time intervals: 21, 35, and 63 days post-treatment. Multiple histologic sections from each treatment site were examined by light microscopy using hematoxylin and eosin Goldner's trichrome stains, and polarized light and evaluated for presence of a char layer, heat induced cracking, heat related alterations in cells or tissue matrix, and osseous regeneration. RESULTS: Healing was severely delayed in all laser treated sites compared to positive control sites. Of the laser treated sites, those irradiated by CO2 laser at 5 W (780 J/cm2) exhibited the greater amount of bone regeneration. At best, however, only a small percentage of sections from any of the laser treated specimens showed evidence of bone regeneration within the ablation defect regardless of the post-treatment time interval. CONCLUSIONS: Under the conditions of this study, the osseous healing response was severely delayed by CO2 and Nd:YAG laser irradiation of bone, even in the presence of a surface cooling spray of air/water.

Composite grafting and hyperbaric oxygen therapy in pediatric nasal tip reconstruction after avulsive dog-bite injury.

It is estimated that more than four million people are bitten by dogs in the United States each year. The majority of such injuries are minor, and their treatment does not usually require surgical consultation. However, the authors report a case in which a Rottweiler inflicted a mutilating nasal tip/alar rim avulsion on a 5-year-old boy. They report their experience with immediate reconstruction of the nasal defect using a large ipsilateral auricular cartilage composite graft (crus helix). Adjunctive hyperbaric oxygen therapy (without sedation or anesthesia) was used to maximize the stimulus for graft revascularization. Reconstructive goals were achieved while avoiding the need for a central facial donor site defect.

PCR monitoring for tetracycline resistance genes in subgingival plaque following site-specific periodontal therapy. A preliminary report.

BACKGROUND: The selection of antibiotic resistance genes during antibiotic therapy is a critical problem complicated by the transmission of resistance genes to previously sensitive strains via conjugative plasmids and transposons and by the transfer of resistance genes between gram-positive and gram-negative bacteria. The purpose of this investigation was to monitor the presence of selected tetracycline resistance genes in subgingival plaque during site specific tetracycline fiber therapy in 10 patients with adult periodontitis. METHOD: The polymerase chain reaction (PCR) was used in separate tests for the presence of 3 tetracycline resistance genes (tetM, tetO and tetQ) in DNA purified from subgingival plaque samples. Samples were collected at baseline, i.e., immediately prior to treatment, and at 2 weeks, and 1, 3, and 6 months post-fiber placement. The baseline and 6-month samples were also subjected to DNA hybridization tests for the presence of 8 putative periodontal pathogenic bacteria. RESULTS: PCR analysis for the tetM resistance gene showed little or no change in 5 patients and a decrease in detectability in the remaining 5 patients over the 6 months following tetracycline fiber placement. The results for tetO and tetQ were variable showing either no change in detectability from baseline through the 6-month sampling interval or a slight increase in detectability over time in 4 of the 10 patients. DNA hybridization analysis showed reductions to unmeasurable levels of the putative periodontal pathogenic bacteria in all but 2 of the 10 patients. CONCLUSIONS: These results complement earlier studies of tet resistance and demonstrate the efficacy of PCR monitoring for the appearance of specific resistance genes during and after antibiotic therapy.

Relationship between a self-reported health questionnaire and laboratory tests at initial office visits.

BACKGROUND: Dental patients routinely complete a medical questionnaire and have an oral interview during their initial visit, but may have undiagnosed systemic problems which can affect their dental treatment. METHODS: Thirty-nine consecutive patients referred for a periodontal evaluation completed a medical questionnaire and an oral interview. They were referred to a hospital laboratory for an urinalysis, complete blood count, and a standard blood chemistry panel. RESULTS: The self-reported medical history responses were compared with the laboratory data and several abnormalities were noted. Abnormal levels were found with cholesterol, (26/39 patients, 67%); triglycerides, (13/39, 33%); glucose, (6/39, 15%); eosinophils, (18/39, 46%); and monocytes, (10/39, 26%). Smokers (17/39, 44%) had a higher number of abnormal levels or percentages of cholesterol, triglycerides, basophils, lymphocytes, eosinophils, and monocytes. Gender differences were seen in elevated triglyceride levels, abnormal aspartate aminotransferase (AST) and alanine aminotransferase (ALT), and self-reported cardiovascular disease. CONCLUSIONS: This study demonstrated that many patients are unaware of their current medical status and a significant number had undiagnosed abnormalities.

The use of biodegradable polylactic acid barrier materials in the treatment of grade II periodontal furcation defects in humans--Part II: A multicenter investigative surgical study.

This study evaluated whether differences in design of 3-dimensional polylactic acid barriers (EPi-Guide and Guidor) would influence hard tissue results in the treatment of Grade II furcations in humans. A multicenter study was conducted, using 40 patients with moderate to advanced bilateral chronic adult periodontitis of the mandibular first or second molars. After flap access, debridement, and root preparation, surgical bone level measurements were taken and membranes were placed on a random basis. Surgical reentry occurred at 1 year. Data collected from all 3 investigative centers were pooled and analyzed using an analysis of variance appropriate for a counterbalancing design. Both barrier materials resulted in significant gains of attachment level and defect reduction. The composite reduction in the vertical component of the osseous defects was greater in the sites treated with Epi-Guide as compared to those treated with Guidor; the difference between barriers reached statistical significance (P = 0.02).

In vivo comparison of synthetic osseous graft materials. A preliminary study.

The purpose of this study was to compare the in vivo osseous healing response of 4 commercially-available synthetic bone grafting materials; hydroxylapatite (HA), calcium sulfate (CaSO4) plus autogenous bone, or a bioactive glass ceramic: with particle size of 300-360 microm (BG1) or 90 to 710 microm (BG2). 4 osteotomy sites were prepared in each tibia of 10 adult male rabbits. One unfilled osteotomy site served as negative control (NC) and another site filled with autogenous bone was the positive control (PC). All animals received BG1 in 2 sites and BG2 in 2 sites. 5 animals received HA and five CaSO4 plus autogenous bone in the remaining 2 sites. Animals were sacrificed at 28 days post-surgery, histologic sections obtained and the % surface area of new bone formation for each material was determined by computerized image analysis. All graft sites showed evidence of bone formation, i.e., (NC) 41.95%; (PC) 50.41%; (BG1) 41.82%; (BG2) 40.36%; (HA) 41.83% and (CaSO4) 58.83%. Statistical analysis using an ANOVA with repeated measures on the materials common to all animals (excluding HA and CaSO4 groups) showed significant differences between materials in surface area of bone, with positive controls better than negative controls, and BG1 and BG2 not significantly different from the negative control. These results indicate that synthetic graft materials can support new bone formation in surgically prepared defects. The utility of a rabbit model for studying physiologic osseous turnover and healing is questioned for studies of slowly resorbing synthetic graft materials.

Laser irradiation of bone: II. Healing response following treatment by CO2 and Nd:YAG lasers.

BACKGROUND: Currently, the most commonly used lasers for dental procedures are the Nd:YAG and CO2. Studies comparing healing of osteotomy defects prepared with rotary burs to those created by laser irradiation have reported conflicting results. The purpose of this study was to evaluate and compare the histologic healing of bone in rat tibial osteotomy defects created either by a dental bur, CO2 laser with and without removal of the char layer, and Nd:YAG laser with char layer removed and with and without use of an air/water surface cooling spray. METHODS: Tibial osteotomy defects were created in 4 groups of 6 rats each using the following: 1) #6 round bur with simultaneous saline irrigation; 2) CO2 laser with char layer intact; 3) CO2 laser with char layer removed; 4) Nd:YAG laser with air/water surface cooling, and char layer intact; 5) Nd:YAG laser with air/water surface cooling, and char layer removed; and 6) Nd:YAG laser without air/water surface cooling, and char layer removed. Both laser types were used at energy densities typically utilized for oral soft tissue surgery. RESULTS: Progressive healing from day 0 through day 21 post-treatment was observed in all treatment groups. However, compared to controls treated by rotary dental bur, those specimens treated by laser, regardless of laser type, energy density, or other parameters, exhibited a delay in healing that appeared to be related to the presence of residual char in the osseous defect. Specimens treated with the Nd:YAG laser using an air/water surface coolant exhibited a decreased thickness and continuity of the char layer and yielded the only specimens with new bone formation at the surface of the laser ablation defect. In addition, the normal pattern of bone remodeling in the rat tibia appeared to have been altered by laser irradiation. CONCLUSIONS: In this animal model, laser-induced osteotomy defects, when compared to those prepared by rotary bur, exhibited a delayed healing response that appeared to be related to the presence of residual char in the osseous defect.

Use of biodegradable polylactic acid barrier materials in the treatment of grade II periodontal furcation defects in humans--Part I: A multicenter investigative clinical study.

This study evaluated two bioresorbable polylactic acid barriers (Epi-Guide and Guidor) to determine if design differences were of therapeutic significance in the treatment of Grade II furcation defects in humans. Forty patients with bilaterally matched, Grade II furcation defects in maxillary or mandibular first or second molars were treated in a multicenter study. Comprehensive initial periodontal therapy, followed by defect debridement and root preparation, preceded randomized membrane placement. Data collected from all three investigative centers were pooled and analyzed using an analysis of variance appropriate for a counterbalancing design. Both barrier types produced measurable improvements of clinical probing values. Barrier exposure scores taken through the eighth week postoperative revealed that Epi-Guide was less likely to become exposed than Guidor. The findings of this study, which was conducted over a 12-month period, demonstrated that Epi-Guide and Guidor were comparable as measured by clinical probing determinations.

Laser irradiation of bone. I. An in vitro study concerning the effects of the CO2 laser on oral mucosa and subjacent bone.

The purpose of this study was twofold: first, to evaluate the histologic effects of CO2 laser irradiation on biopsies of porcine oral mucosa and underlying bone under conditions that simulate the applications of the laser during gingival surgery; and second, to evaluate the histologic effects on cortical bone following irradiation with increasing energy densities. Specimens consisting of mucosa and underlying bone were subjected to multiple passes of the laser beam in the same line of incision at energy densities ranging from 240 to 1,032 J/cm2. A second group of specimens consisting only of cortical bone was irradiated by a single pass of the laser at energy densities ranging from 40 to 2,062 J/cm2. In both groups the mean depth of ablation, width of surface damage, and widths of the zones of thermal necrosis and thermal damage were determined. Results showed a direct correlation between increasing energy density and/or number of energy beam passes and increasing depths of ablation and widths of surface damage. Further, more than three passes at 1,032 J/cm2 penetrated the mucosal layer to involve underlying bone. The mean depth of ablation for bone specimens following a single pass of the energy beam ranged from 0.02 mm at 160 J/cm2 to a maximum of 0.75 mm at 2,062 J/cm2. Using those energy densities most common to oral soft tissue surgery, the mean depth of ablation in bone specimens ranged from 0.17 mm at 240 J/cm2 to 0.28 mm at 640 J/cm2 to 0.35 mm at 1,032 J/cm2. All specimens regardless of tissue composition, energy density, or number of energy beam passes exhibited a distinct layer of residual carbonized tissue, a zone of thermal necrosis characterized by tissue coagulation, and a zone of tissue exhibiting thermal damage.

Histologic evaluation of soft tissue attachment to CO2 laser-treated root surfaces: an in vivo study.

There is little support in the dental literature to justify the use of lasers for periodontal root therapy. To the contrary, there are several in vitro studies suggesting potentially adverse effects when lasers are applied to root surfaces. The purpose of this study was to evaluate, in vivo, soft tissue attachment to root surfaces following CO2 laser irradiation. Using a four-quadrant design with one quadrant serving as an untreated control, the remaining quadrants in each of two dogs were treated by (1) scaling and root planing, (2) laser only, and (3) laser followed by scaling and root planing. Prior to the assigned treatments, the roots of three teeth in each quadrant (including the control) were exposed by flap reflection and ostectomy. After root therapy the flaps were repositioned and allowed to heal for 28 days. Clinical attachment levels were determined prior to surgery, at 28 days, and by histologic measurement. Results indicate that specimens treated with laser only lost attachment compared to controls and other treatment groups. Furthermore, there was no histologic evidence of soft tissue attachment to a laser-treated surface that featured a residual char layer.

Gingival overgrowth with valproic acid: a case report.

A case of a nine-year-old epileptic girl with severe gingival overgrowth who had been taking valproic acid since two months of age is presented. A review of the literature and possible mechanisms for drug-induced gingival overgrowth is outlined.

Determination of energy density threshold for laser ablation of bacteria. An in vitro study.

The Nd:YAG and CO2 lasers have been shown to be bactericidal at relative low energy densities. However, at energy densities exceeding 120 J/cm2 (CO2) and 200 J/cm2 (Nd:YAG), laser irradiation also causes irreparable root surface damage. The purpose of this study was to determine, in vitro, the energy density threshold at which microbial ablation could be achieved while inflicting the least amount of damage to the root surfaces of human teeth. Pairs of Escherichia coli colonies cultured on broth agar were treated with a CO2 laser using a pulsed waveform at approximate energy densities ranging from 3 to 110 J/cm2. One of each colony-pair was then examined by scanning electron microscopy (SEM) and the other subcultured for viable microbes. Roots of extracted teeth were lightly scaled and treated by CO2 laser, again with pulsed beam using approximate energy densities of 3 to 110 J/cm2: and examined by SEM. Regardless of the level of energy density, residual bacteria could be subcultured from all laser treated microbial colonies. The inability of the laser to completely obliterate microbial colonies was likely due to: depth of energy penetration, difficulty in precisely overlapping beam focal spots, irregular beam profile, and presence of microbes at the periphery of the beam focal spot. The threshold energy density for bacterial obliteration was determined to be 11 J/cm2 and that for root damage was 41 J/cm2. Root damage was evident by charring, crater formation, melt-down and resolidification surface mineral, and increasing surface porosity. The results of this in vitro study indicate that when used at an energy density between 11 and 41 J/cm2 the CO2 laser may destroy microbial colonies without inflicting undue damage to the tooth root surface.

Treatment of root fracture by CO2 and Nd:YAG lasers: an in vitro study.

The purpose of this in vitro study was to use scanning electron microscopy and polarized light microscopy to evaluate the feasibility of using either the CO2 laser or an Nd:YAG laser in combination with air/water surface cooling to effect fusion of fractured tooth roots. The experimental unit consisted of 81 single-rooted teeth, each with an induced root fracture. Fifty-six teeth that had been reapproximated in dental stone and 25 teeth that had been reapproximated with C-clamps were assigned to untreated control groups or groups for treatment using CO2 and Nd:YAG lasers. Laser treatment consisted of multiple passes along the line of fracture, which was inspected using a dissecting microscope after each pass until a visual indication of fusion or irreparable damage resulted. Scanning electron microscopy evaluation of the treated lines revealed heat-induced fissures and cracks, areas of cementum meltdown and resolidification, crater formation, and separation of cementum from underlying dentin. In no instance-regardless of reapproximation technique, laser type, energy, and other parameters-did the treatment effect fusion of the fractured root halves.

Histologic evaluation of porcine skin incisions produced by CO2 laser, electrosurgery, and scalpel.

The purpose of this study was to histologically compare the healing of porcine skin incisions made by CO2 laser, electrosurgery, and conventional scalpel. Incisions were made on the dorsal thorax of two microswine at staggered time intervals allowing the harvest of specimens at 0, 4, 7, 14, and 21 days postsurgery at the time of sacrifice. Each of the following histologic zones were identified and measured for both laser and electrosurgery incisions: (1) zone of tissue ablation. (2) zone of thermal necrosis, and (3) width of surface damage. The depth of cut and width of surface opening was measured for the scalpel incision. Furthermore, for each specimen, the presence and character of inflammatory cell infiltrate was noted, as well as the relative times at which bridging of the incision by connective tissue and coverage of the wound by an intact epithelial layer had occurred. Results showed that in this wound-healing model, the scalpel incisions produced more defined borders, healed more rapidly, and resulted in less collateral tissue damage than those produced by CO2 laser or electrosurgery. It was also noted that to create a wound 1.29 mm in depth required at least five passes of the laser beam within the same line of incision using 206.4 J/cm2 (6 W, continuous mode).

Biostimulation of wound healing by low-energy laser irradiation. A review.

This paper reviews studies on the basic principles of biostimulation of wound healing by various low-energy lasers. It looks at the mechanism of action of biostimulation as well as the laser's effect on cell proliferation, collagen synthesis, and would healing.

Migration of human gingival fibroblasts over guided tissue regeneration barrier materials.

The purpose of this investigation was to determine the ability of human gingival fibroblasts, in vitro, to migrate along a chemotactic gradient over 3 different guided tissue regeneration barrier materials; i.e., polytetrafluoroethylene, polylactic acid, and sterile calcium sulfate. Forty petri dishes were divided into 4 equal groups. In each group of 10 dishes, a different barrier material served as the fibroblast substrate with the polystyrene floor of one group of Petri dishes serving as the control. The under agarose technique of measuring cell migration was employed using platelet derived growth factor-BB homodimer as the chemoattractant and Hanks balanced salt solution to test random migration. In addition, fibroblasts were directly cultured on triplicate sets of barrier materials and the control surface for 24 hours and examined by scanning electron microscopy. Comparative analysis of the fibroblast migration data showed the mean migration distance (adjusted for random migration) for controls to be significantly greater than any of the three barrier materials. Further, mean migration distance over calcium sulfate was significantly greater when compared to that of the polylactic acid barrier group. All other comparisons between groups were not statistically significant. Scanning electron microscopic examination fibroblasts cultured directly on barrier membranes and compared to controls indicated that the calcium sulfate substrate appeared to facilitate cell attachment and spreading whereas cells on polytetrafluoroethylene and polylactic acid barriers exhibited a morphology not conducive to migration or, in many cases, cell health. Based on these limited in vitro results and, given the 3 barrier materials considered, it would appear that calcium sulfate offers the greater potential for guided tissue regeneration in surgical sites where primary wound closure cannot be obtained.

Morphologic changes following in vitro CO2 laser treatment of calculus-ladened root surfaces.

BACKGROUND AND OBJECTIVE: The purpose of this study was to compare morphologic changes following C02 laser or manual curette treatment of calculus-ladened tooth root surfaces. STUDY DESIGN/MATERIALS AND METHODS: Laser treatment consisted of repeated single passes with a 6 Watt focused beam at 20 pulses per second, a pulse length of 0.01 second, and a manufacturer's laser efficiency rating of 86% (i.e., the amount of total power delivered through the aperture). The rate of beam passage over the target surface was controlled at 4 mm/second using an 0.8 mm diameter tip. The calculated energy density was 240 J/cm2 for each pass of the beam. Scaled and root planed surfaces were treated with a standardized force of 600 grams using new curettes. Specimens were evaluated by scanning electron microscopy. RESULTS: Laser-induced surface changes included charring, meltdown and resolidification of calculus mineral, and ablation of microbial plaque. Laser-treated specimens also exhibited residual calculus and microbial plaque deposits in areas directly adjacent to the beam path. Scaled and root planed surfaces featured smooth and/or scale like smear layers and islands of residual calculus and microbial plaque. CONCLUSIONS: The rough surface topography resulting from laser treatment and residual calculus and microbial plaque deposits indicates that C02 laser treatment of exposed root surfaces is, at best, an adjunct to traditional methods of therapy.