Intrinsic material property differences in bone tissue from patients suffering low-trauma osteoporotic fractures, compared to matched non-fracturing women

Osteoporotic (low-trauma) fractures are a significant public health problem. Over 50% of women over 50yrs. of age will suffer an osteoporotic fracture in their remaining lifetimes. While current therapies reduce skeletal fracture risk by maintaining or increasing bone density, additional information is needed that includes the intrinsic material strength properties of bone tissue to help develop better treatments, since measurements of bone density account for no more than ~50% of fracture risk. The hypothesis tested here is that postmenopausal women who have sustained osteoporotic fractures have reduced bone quality, as indicated with measures of intrinsic material properties compared to those who have not fractured. Transiliac biopsies (N=120) were collected from fracturing (N=60, Cases) and non-fracturing postmenopausal women (N=60, age- and BMD-matched Controls) to measure intrinsic material properties using the nano-indentation technique. Each biopsy specimen was embedded in epoxy resin and then ground, polished and used for the nano-indentation testing. After calibration, multiple indentations were made using quasi-static (hardness, modulus) and dynamic (storage and loss moduli) testing protocols. Multiple indentations allowed the median and variance to be computed for each type of measurement for each specimen. Cases were found to have significantly lower median values for cortical hardness and indentation modulus. In addition, cases showed significantly less within-specimen variability in cortical modulus, cortical hardness, cortical storage modulus and trabecular hardness, and more within-specimen variability in trabecular loss modulus. Multivariate modeling indicated the presence of significant independent mechanical effects of cortical loss modulus, along with variability of cortical storage modulus, cortical loss modulus, and trabecular hardness. These results suggest mechanical heterogeneity of bone tissue may contribute to fracture resistance. Although the magnitudes of differences in the intrinsic properties were not overwhelming, this is the first comprehensive study to investigate, and compare the intrinsic properties of bone tissue in fracturing and non-fracturing postmenopausal women.

Relationship of CD146 expression to activation of circulating T cells: exploratory studies in healthy donors and patients with connective tissue diseases

The endothelial cell adhesion molecule, CD146, is expressed on ≈ 2% of normal circulating T cells, correlating with T cell activation, endothelial interactions and T helper type 17 (Th17) effector functions. In this study, we have characterized CD146 expression in circulating T cells from healthy controls and patients with stable, well-controlled autoimmune connective tissue diseases (CTDs). In vitro, anti-CD3/anti-CD28 stimulation induced CD146 expression in both CD4 and CD8 T cells. In healthy controls and CTD patients, CD146 was associated with expression of recent and chronic activation markers (CD25(+), OX-40(+), CD69(+), CD27(-)) and was confined to CD45RO(+)/RA(-)/CD28(+) populations within the CD4 subset. Except for CD69, these markers were not associated with CD146 in the CD8 subset. Surprisingly, most CTD patients exhibited no T cell hyperactivation ex vivo. In five of five patients with secondary Sjögren's syndrome circulating T cells appeared activated despite therapy, and CD146 up-regulation, associated with activation markers, was observed both on CD4 and CD8 T cells. There was no association between CD146 and putative pro-atherogenic T cell subsets. In conclusion, the relationship of CD146 expression to T cell activation differs between T cell subsets in healthy subjects and correlates with systemic hyperactivity, where present, in patients with CTDs, as exemplified by the patients with secondary Sjögren's syndrome in this study.

Role of cyclin-dependent kinase inhibitors in the growth arrest at senescence in human prostate epithelial and uroepithelial cells

Cellular senescence has been proposed to be an in vitro and in vivo block that cells must overcome in order to immortalize and become tumorigenic. To characterize these pathways, we focused on changes in the cyclin-dependent kinase inhibitors and their binding partners that underlie the cell cycle arrest at senescence. As a model, we utilized normal human prostate epithelial cell (HPEC) and human uroepithelial cell (HUC) cultures. After 30-40 population doublings cells became growth-arrested in G0/1 with a threefold decrease in Cdk2-associated activity, a point defined as pre-senescence. Temporally following this growth arrest, the cells develop a senescence morphology and express senescence-associated beta-galactosidase (SA-beta-gal). Levels of p16(INK4a) and p57(KIP2) rise in HUCs during progressive passages, whereas only p16 increases in HPEC cultures. The induced expression of p57, similar to p16, produces a senescent-like phenotype. pRB, cyclin D, p19(INK4d) and p27(KIP1) decrease in both cell types. We find that p53, p21(CIP1) and p15(INK4b) are transiently elevated in HPECs and HUCs at the pre-senescent growth arrest, then return to low proliferating levels at terminal senescence. Analysis of p53, p21(CIP1), p15(INK4b), p16(INK4a), and p57(KIP2) reveals altered expression in immortalized, non-tumorigenic HPV16 E6 and E7 prostate lines and in tumorigenic prostate cancer cells. These results indicate: (i) the existence of a subset of growth inhibiting genes elevated at the onset of the senescence, (ii) a distinct class of genes involved in the maintenance of senescence, and (iii) the frequent inactivation of these pathways during immortalization.

Diabetes-related changes in cAMP response element-binding protein content enhance smooth muscle cell proliferation and migration

We hypothesized that diabetes and glucose-induced reactive oxygen species lead to depletion of cAMP response element-binding protein (CREB) content in the vasculature. In primary cultures of smooth muscle cells (SMC) high medium glucose decreased CREB function but increased SMC chemokinesis and entry into the cell cycle. These effects were blocked by pretreatment with the antioxidants. High glucose increased intracellular reactive oxygen species detected by CM-H(2)DCFA. SMC exposed to oxidative stress (H(2)O(2)) demonstrated a 3.5-fold increase in chemokinesis (p < 0.05) and accelerated entry into cell cycle, accompanied by a significant decrease in CREB content. Chronic oxidative challenge similar to the microenvironment in diabetes (glucose oxidase treatment) decreases CREB content (40-50%). Adenoviral-mediated expression of constitutively active CREB abolished the increase in chemokinesis and cell cycle progression induced by either high glucose or oxidative stress. Analysis of vessels from insulin resistant or diabetic animals indicates that CREB content is decreased in the vascular stroma. Treatment of insulin-resistant animals with the insulin sensitizer rosiglitazone restores vessel wall CREB content toward that observed in normal animals. In summary, high glucose and oxidative stress decrease SMC CREB content increase chemokinesis and entry into the cell cycle, which is blocked by antioxidants or restoration of CREB content. Thus, decreased vascular CREB content could be one of the molecular mechanisms leading to increased atherosclerosis in diabetes.

cAMP response element-binding protein content is a molecular determinant of smooth muscle cell proliferation and migration

We hypothesized that cAMP response element-binding protein (CREB) could function as a molecular determinant of smooth muscle cell fate. In arterial sections from the systemic and pulmonary circulation, CREB content was high in proliferation-resistant medial subpopulations of smooth muscle cells and low in proliferation-prone regions. In vessels from neonatal calves exposed to chronic hypoxia, CREB content was depleted and smooth muscle cell (SMC) proliferation was accelerated. Induction of quiescence by serum deprivation in culture led to increased CREB content. Highly proliferative SMC in culture were observed to have low CREB content. Exposure to proliferative stimuli such as hypoxia or platelet-derived growth factor decreased SMC CREB content. Assessment of CREB gene transcription by nuclear run-on analysis and transcription from a CREB promoter-luciferase construct indicate that CREB levels in SMC are in part controlled at the level of transcription. Overexpression of wild type or constitutively active CREB in primary cultures of SMC arrested cell cycle progression. Additionally, expression of constitutively active CREB decreased both proliferation and chemokinesis. Consistent with these functional properties, active CREB decreased the expression of multiple cell cycle regulatory genes, as well as genes encoding growth factors, growth factor receptors, and cytokines. Our data suggest a unique mode of cellular phenotype determination at the level of the nuclear content of CREB.

Gas chromatography-mass spectrometry method for the simultaneous determination of wood extractive compounds in quaking aspen

We have developed a rapid gas chromatography-mass spectrometry (GC-MS) method for the detailed compositional analysis of 70 underivatized wood extractive components present in quaking aspen (Populus tremuloides Michx.). Forty-four compounds were unequivocally identified by retention time and mass spectral comparison with standards. An additional 26 chromatographic peaks were assigned to broad chemical classes using retention time and mass spectra features. The results were compared to the respective tert.-butyldimethylsilyl derivatized wood extractives profile, and it was determined that derivatization was unnecessary for the GC-MS analysis of the target compounds.

A prospective human clinical trial of Endopore dental implants in restoring the partially edentulous maxilla using fixed prostheses

This is the first report of a group of 50 partially edentulous patients who received a total of 151 Endopore dental implants in the maxilla. A mean implant length of 8.7 mm was used, and 76.8% of implants were placed in the posterior maxilla. At re-entry, all implants appeared to be osseointegrated and were used to support fixed prostheses. Approximately half of the crowns (57%) in these prostheses were splinted to one another, while the remainder (43%) were not. At the time of this report, the mean functional time was 34.6 months and the cumulative survival rate was 97.3% (4 implants had failed). Analysis of carefully standardized sequential radiographs indicated no significant changes in mean crestal bone levels between baseline and any of the examination times (after 6 months, 1 year, and 2 years in function). There were no detectable correlations between crestal bone loss and the factors implant length (7, 9, or 12 mm); implant diameter (3.5, 4.1, or 5.0 mm); implant position anteriorly or posteriorly in the maxilla; or whether or not the implant-supported crowns were splinted.

Transoral, flexible endoscopic suturing for treatment of GERD: a multicenter trial

BACKGROUND

A totally transoral outpatient procedure for the treatment of GERD would be appealing.

METHODS

A multicenter trial was initiated that included 64 patients with GERD treated with an endoscopic suturing device. Inclusion criteria were 3 or more heartburn episodes per week while not taking medication, dependency on antisecretory medicine, and documented acid reflux by pH monitoring. Exclusion criteria were dysphagia, grade 3 or 4 esophagitis, obesity, and hiatus hernia greater than 2 cm in length. Patients underwent manometry, endoscopy, 24-hour pH monitoring, and symptom severity scoring before and after the procedure. Patients were randomized to a linear or circumferential plication configuration. Adverse procedural events were recorded.

RESULTS

Mean 6-month symptom score changes demonstrated procedural efficacy. Heartburn severity and frequency as well as regurgitation all improved (p > 0.0001 for each). Twenty-four-hour pH monitoring showed improvement in number of episodes below pH of 4 at 3 and 6 months (p < 0.0007 and 0.0002) and percentage of total time the pH was less than 4 at 6 months (p < 0.011). Plication configuration did not affect symptoms or pH monitoring results. One patient had a self-contained suture perforation that was successfully treated with antibiotics.

CONCLUSION

Endoscopic gastroplasty is safe. It is associated with reduced symptoms and medication use at 6 month follow-up in patients with uncomplicated GERD.

Adhesion of bonded orthodontic attachments to dental amalgam: In vitro study

Bonding orthodontic attachments to molars is difficult in the presence of extensive buccal amalgam restorations. The purposes of this study were (1) to examine different amalgam surface preparations, (2) to examine properties of adhesive cements to amalgam, (3) to determine the most shear-resistant bonding technique and (4) to discuss whether these shear bond strengths were of adequate magnitude to be of clinical acceptability. The sample consisted of 108 standardized amalgam cylinders divided into 9 groups of 12 based on surface treatment technique and resin type. SPEED brackets (Strite Industries, Cambridge, Ontario) were bonded to amalgam surfaces that were either polished, sandblasted with 50 microm aluminium oxide, or chemically corroded. Adhesives used were Phase II (Reliance Orthodontic Products Inc, Itasca, Ill), Panavia EX (J Morita USA Inc, Tustin, Calif), or C & B Metabond (Parkell, Farmingdale, NY). After thermocycling from 10 degrees C to 50 degrees C 10,000 times, all samples were tested for shear bond strength with the Universal Testing Machine (Instron Corporation, Canton, Mass). The results show significantly higher bond strengths for all of the resin systems when sandblasting of the amalgam surface is used (P <.0001). Only Panavia EX bonded strongly to polished samples, suggesting the presence of a chemical bond. Laboratory acceptable bond strengths to amalgam are possible. The surface characteristics of the amalgam appear to be more influential in the strength of the bond than does the nature of the resin.

Entrapment of the index flexor digitorum profundus tendon after fracture of both forearm bones in a child

Entrapment of the index FDP tendon in a radius fracture callus occurred after fracture of both forearm bones in a 4-year-old boy. Surgical release of the FDP tendon, three months after fracture, resulted in normal index finger motion. This clinical problem can be avoided by a detailed physical examination of children with forearm fractures, verifying full passive range-of-motion of the hand after cast immobilization. Prompt supervised active range-of-motion should be done to prevent adhesions at the fracture site.

Development and manufacture of prosthodontic components: do we need changes?

PURPOSE

Prosthodontic components for implant treatment have been developed with minimal reported scientific investigation. This paper aims to highlight a number of problems caused by this approach to the development and marketing of prosthodontic components and to suggest solutions.

CONCLUSION

Prosthodontic components must be developed with a scientific approach that involves both laboratory and clinical testing so as to optimize treatment outcomes in the future.

The Endopore implant-enhanced osseointegration with a sintered porous-surfaced design

The Endopore implant provides a novel method for reliable fixation of endosseous dental implants within the bone. Through the use of a porous-surfaced zone formed by sintering Ti alloy particles of the appropriate size and under appropriate processing conditions to a sold Ti alloy core of desired shape (tapered truncated cone), an implant is now available that can be placed using a relatively simple surgical procedure using either surgical burs or hand osteotomes. Of even greater value is the suitability of this implant design for treatment of cases that because of minimal bone height cannot be treated routinely using other currently-available implants. The high success rates experienced with significantly shorter implant lengths compared with other designs indicate the appropriateness of this system for difficult-to-treat cases. The Endopore system represents the next generation of endosseous dental implants characterized by uncomplicated and reliable treatment for a wider range of dentally-compromised patients. Its history is founded on extensive and fully-documented research at the human preclinical stage as well as human use experiences. The results during the past nine years have confirmed the high expectations that those early studies suggested.

Comparison of a rapid dipstick test and thick blood films for detecting parasites of plasmodium falciparum used under typical conditions at a semi-rural hospital in Cote d'Ivoire

This prospective study compares a rapid dipstick test (ParaSight-F) with thick blood films for the detection of parasites of P falciparum, under 'typical' conditions and constraints to be found in a semi-rural hospital in a tropical developing country in Africa. Eighty-two samples were tested using the two techniques and found to concur in 95.1% of cases. However, in four of the samples the results differed. The thick blood films of 60 samples were later re-read by a local reference laboratory. Of these 98.3% were in agreement with the reading performed at the hospital. Only one of the 60 slides differed. The rapid dipstick test proved to be both easy to use and free from many of the usual constraints such as a need for formally trained or experienced laboratory staff, laboratory equipment, and reliable water and electricity supplies. In an holoendemic area for P falciparum transmission, it would appear to be eminently suitable, in technical terms and ease of handling as well as on the basis of rapid results, for wider distribution within this region. Its main drawback remains financial.

Use of the Endopore dental implant to restore single teeth in the maxilla: protocol and early results

This report outlines the experimental, surgical, and prosthodontic protocols for a prospective clinical trial using the Endopore dental implant to replace single maxillary teeth. Twenty patients (10 male, 10 female) ranging in age from 30 to 60 years each received one implant (mean length 10.1 mm), which, after an initial healing period of 4 months, was restored with a single crown. Records collected included radiographs, Periotest mobility measurements, supragingival Plaque Index, and an assessment of peri-implant soft tissue health using pocket probing depths, sulcular bleeding following probing, and probing attachment levels. Radiographs were exposed at predetermined intervals following crown placement (1 and 6 months, and then yearly) in a standardized procedure using a specialized filmholder that attaches to each implant after removal of the crown. At the time of this preliminary report, all of the 20 implants placed had been uncovered and were in function; 16 of the implants had been in function for 6 months or more, 14 had passed 1 year of function, and 3 had passed the 2-year function point. There have been no failures to date.

Modifications to the National Dental Examining Board of Canada's certification process

Following a lengthy and intense consultation with stakeholders, and an analysis of the present certification process, the National Dental Examining Board of Canada (NDEB) and the 10 provincial licensing authorities recently approved major changes to the certification process for dental licensure in Canada. As of January 1997, graduates of dental programs accredited by the American Dental Association's Commission on Dental Accreditation (ADA Commission) must complete successfully the same examinations as graduates of programs accredited by the Commission on Dental Accreditation of Canada (CDAC) to be licensed to practice in Canada. In addition, NDEB's examination system for graduates of dental programs that are not accredited by CDAC or the ADA Commission (i.e. international programs) will be discontinued on December 31, 1999. As of January 1, 2000, graduates of non-accredited programs will be required to complete a CDAC accredited, university-based qualifying program to be eligible to participate in the same certification process as graduates of ADA Commission and CDAC accredited dental programs.

Systemic metal ion levels in dental implant patients

Metal ion release from metallic implants is known to occur, but its extent and implications are controversial. In spite of the rapidly growing use of such implants, little is known about metal ion release. Blood levels of titanium, aluminum, and vanadium were measured using an atomic absorption spectrophotometric technique preoperatively and at intervals over a 3-year period for 52 patients (17 men, 35 women), each of whom had three mandibular porous-surface endosseous dental implants. The results showed that there was no evidence of change from preoperative to long-term values for the three metals measured in the study. These findings are reassuring, but do not rule out local or remote accumulation of released ions, which was not measured in this study.

Isozyme-dependent sensitivity of adenylyl cyclases to P-site-mediated inhibition by adenine nucleosides and nucleoside 3'-polyphosphates

Recombinant adenylyl cyclase isozyme Types I, II, VI, VII, and three splice variants of Type VIII were compared for their sensitivity to P-site-mediated inhibition by several adenine nucleoside derivatives and by the family of recently synthesized adenine nucleoside 3'-polyphosphates (Désaubry, L., Shoshani, I., and Johnson, R. A. (1996) J. Biol. Chem. 271, 14028-14034). Inhibitory potencies were dependent on isozyme type, the mode of activation of the respective isozymes, and on P-site ligand. For the nucleoside derivatives potency typically followed the order 2',5'-dideoxyadenosine (2',5'-ddAdo) > beta-adenosine > 9-(cyclopentyl)-adenine (9-CP-Ade) >/= 9-(tetrahydrofuryl)-adenine (9-THF-Ade; SQ 22,536), with the exception of Type II adenylyl cyclase, which was essentially insensitive to inhibition by 9-CP-Ade. For the adenine nucleoside 3'-polyphosphates inhibitory potency followed the order Ado < 2'-dAdo < 2',5'-ddAdo and 3'-mono- < 3'-di- < 3'-triphosphate. Differences in potency of these ligands were noted between isozymes. The most potent ligand was 2',5'-dd-3'-ATP with IC50 values of 40-300 nM. The data demonstrate isozyme selectivity for some ligands, suggesting the possibility of isozyme-selective inhibitors to take advantage of differences in P-site domains among adenylyl cyclase isozymes. Differential expression of adenylyl cyclase isozymes may dictate the physiological sensitivity and hence importance of this regulatory mechanism in different cells or tissues.

Septic arthritis caused by chronic osteomyelitis

We have treated four cases of previously quiescent osteomyelitis which presented as septic arthritis in an adjacent joint. The osteomyelitic focus was in the bone proximal to the involved joints (zero to ten centimeters above the joint line). Based on the presenting history, physical findings, laboratory tests and cultures of joint fluids, the joint sepsis was low grade in all patients which led to delays in diagnosis and treatment. Aggressive surgical debridement of both bone and joint, followed by a prolonged course of antibiotics led to resolution in all patients. A high index of suspicion combined with adequate radiographs of the surrounding bones should lead to the appropriate diagnosis and treatment.

Simplifying the treatment of edentulism: a new type of implant

In this article, the authors describe the application of a new and unique root-form dental implant in a simplified approach to treating the completely edentulous mandible using an overdenture. The technique is supported by the results of a prospective clinical trial involving 52 patients that showed a three- to four-year success rate of 95 percent.

Contractile activity and passive stretch regulate tubulin mRNA and protein content in cardiac myocytes

Accumulation of tubulin protein and an increased array of microtubules have been associated with contractile dysfunction in cardiac myocytes after pressure overload in vivo. Experiments were performed to assess the ability of mechanical stimuli experienced by ventricular cardiac myocytes during the progression of hypertrophic and dilated pathology to increase beta-tubulin production in cultured neonatal rat cardiac myocytes. Results indicate that both contractile activity and load due to passive stretch increase beta-tubulin protein content in neonatal rat cardiac myocytes through accumulation of beta-tubulin mRNA, which occurs without increased beta-tubulin gene transcription. Western blot analysis demonstrated that contraction resulted in the accumulation of beta-tubulin in neonatal rat cardiac myocytes above increases observed in the content of total cellular protein. Northern blot analysis indicated that beta-tubulin mRNA content increased in response to both stretch and contraction. alpha-Adrenergic agonists that lead to pathophysiological growth in cardiac myocytes also stimulated an increase in beta-tubulin mRNA content. Treatment of contracting neonatal cardiac myocytes with angiotensin II (ANG II) further increased beta-tubulin mRNA content, whereas ANG II treatment in arrested neonatal cardiac myocytes failed to increase beta-tubulin mRNA. Nuclear run-on experiments indicate that contraction stimulates beta-tubulin mRNA accumulation without an increase in beta-tubulin gene transcription. These results imply that tubulin production in cultured cardiac myocytes can be regulated directly by mechanical forces. In mechanically challenged hearts, the accumulation of beta-tubulin and the development of contractile dysfunction may be directly related to the mechanical forces imposed on the myocardium during the onset and progression of cardiovascular disease.

Initial healing in the dog of submerged versus non-submerged porous-coated endosseous dental implants

It has previously been reported that porous-coated root form endosseous dental implants, became well integrated when used in the traditional 2-stage surgical approach. In this study, the placement of the implant in a 1-stage (non-submerged) technique was to be explored. Implants were placed in the mandibles of dogs, and 2 designs were used differing only in that one (experimental) had a 3-mm transgingival extension, permitting it to be exposed to the oral cavity from the outset. 12 (3 per animal) non-submerged implants were placed on 1 side of 4 beagle dogs and 12 control (submerged) implants were placed contralaterally. All implants were allowed to heal for 6 weeks, after which histological preparations were made. 2 of 12 non-submerged implants were lost due to post-operative complications; otherwise, all implants healed uneventfully. Histomorphometric analysis revealed bone-implant contact, as assessed by absolute bone contact (ABC) and contact length fraction (CLF), to be greater for the submerged design, suggesting that bone healing may be delayed with the non-submerged approach. As well, at this early stage of healing, for both implant designs, ABC and CLF were significantly greater on proximal than on buccal and lingual aspects.

Periodontal parameters around porous-coated dental implants after 3 to 4 years supporting overdentures

In this study, an assessment using modified periodontal indices was done on a group of 48 fully edentulous patients who had each been treated with 3 porous-coated (EndoPore) dental implants and a mandibular overdenture. Parameters assessed included plaque index (PI), sulcular bleeding index (SBI), pocket probing depth (PD), probing attachment level (PAL) and mobility (M) using a Periotest device. At the time of the assessment, all of the patients had passed 3 years of continuous function while 26 had passed 4 years. Approximately 50% of implant surfaces were plaque-free while 79% of surfaces showed no bleeding upon probing. There was no correlation between PI and SBI. The mean PD was 3.1 mm with 64% of sites < or = 3.5 mm. Mobility measurements taken with the Periotest device gave a mean PTV of (-4.35) with 96% of measurements (-0.5). No significant correlations were found between mobility and either PAL or implant length.

Desmin gene expression in cardiac myocytes is responsive to contractile activity and stretch

Experiments were performed to assess the ability of mechanical stimuli, experienced by ventricular cardiac myocytes during the progression of hypertrophic and dilated pathology, to increase the expression of desmin in cultured neonatal rat cardiac myocytes. Results indicate that both contractile activity and load due to passive stretch increase desmin content in neonatal rat cardiac myocytes through increased desmin gene transcription. Western blot analysis demonstrated that contraction induced a selective increase in desmin protein content in neonatal rat cardiac myocytes above increases observed in the content of total cellular protein. Northern blot analysis indicated that desmin mRNA content increased in response to contraction as well as to alpha-adrenergic stimulation. Desmin mRNA content also increased in cultured neonatal myocytes in response to stretch. Angiotensin II (ANG II) treatment of contracting neonatal cardiac myocytes further increased desmin mRNA content, whereas similar treatment in arrested neonatal cardiac myocytes further increased desmin mRNA content, whereas similar treatment in arrested neonatal cardiac myocytes failed to increase desmin mRNA. This contraction-dependent responsiveness to ANG II is not a function of increases in the density or relative subtype composition of ANG II receptors. Treatment of contracting neonatal rat cardiac myocytes with actinomycin D prevented increases in desmin mRNA content, suggesting regulation of transcription of the desmin gene by contraction. Nuclear run-on experiments indicate that contraction. Nuclear run-on experiments indicate that contraction increases transcription of the desmin gene in cardiac myocytes. These results are consistent with the modulation of desmin gene expression secondarily to changes in the mechanical environment that occur in cardiac tissue undergoing dilation or hypertrophy.

The natural history of the neglected felon

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A prospective clinical study in humans of an endosseous dental implant partially covered with a powder-sintered porous coating: 3- to 4-year results

A dental implant covered partially with a porous coating (EndoPore) developed at the University of Toronto was tested. This new implant is a tapered, truncated-cone endosseous root-form implant fabricated from Ti-6Al-4V. It utilizes a powder-sintered porous surface geometry over most of its length to promote three-dimensional bone ingrowth and implant stabilization. In this trial, three implants were placed in the anterior mandibles of 52 patients and were used subsequently as free-standing units to support an overdenture. Much shorter implants, shorter initial healing periods, and simpler surgical techniques than are customary with other implant designs were used. At the time of this report, all patients with implants had passed 3 years of function, and the cumulative implant success rate was 94.8%. Analysis of carefully standardized radiographs revealed a pattern of crestal bone loss similar to earlier published dog data. On a yearly basis, the mean bone loss was 0.43 mm in year 1, 0.17 mm in year 2, and 0.13 mm in year 3.

Type I and type VIII adenylyl cyclases constitute a family whose activation is coupled to cellular deformation through the action of calcium-calmodulin

In certain tissues and cells, increases in concentrations of the second messenger cAMP are seen in response to mechanical or deformational stimuli. Type I and type VIII adenylyl cyclases, representing members of a family of calcium-calmodulin-stimulated adenylyl cyclases, and type VII adenylyl cyclase were each stably expressed in human embryonal kidney (HEK) 293 cells. HEK 293 cells exogenously expressing either type I adenylyl cyclase or any one of three type VIII adenylyl cyclase splice variants respond to swelling with increases in cAMP, requiring the presence of calcium in the extracellular medium for such responsiveness. Type VII expressing HEK 293 cells failed to respond to swelling with increased cAMP but demonstrated potentiation of isoproterenol-stimulated activity. This is characteristic of the influence of protein kinase C on the activity of the type VII protein. The relative swelling responsiveness of HEK 293 cells expressing splice variants of the type VIII adenylyl cyclase is consistent with the relative EC50 values for calcium-calmodulin stimulation of these splice variants. This is consistent with the involvement of calmodulin and the requirement for increases in intracellular calcium in mediating swelling-induced acceleration of type VIII adenylyl cyclase activity.

Molecular cloning and characterization of the type VII isoform of mammalian adenylyl cyclase expressed widely in mouse tissues and in S49 mouse lymphoma cells

We have isolated a 5199-nucleotide cDNA from a mouse library containing an open reading frame encoding the 1099-amino acid type VII adenylyl cyclase protein. The type VII protein is most closely related in primary structure to an unpublished human adenylyl cyclase clone (GenBank accession no. D25538) and type II adenylyl cyclase. Northern blot analysis demonstrates that the type VII mRNA is most abundant in mouse heart, spleen, and lung. cAMP content rises rapidly in HEK 293 cells overexpressing type VII adenylyl cyclase following treatment with phorbol ester, peaking by 4 min, while cells expressing the type II adenylyl cyclase reach peak accumulation only after 20 min. Increases in intracellular calcium through treatment of type VII-293 cells with either ATP or A23187 alone failed to increase intracellular cAMP content. Phorbol ester treatment acted synergistically with beta-adrenergic stimulation to increase cAMP content in type VII-transformed cells. Pretreatment of type VII-transformed cells with pertussis toxin fails to prevent phorbol ester potentiation of isoproterenol stimulation. Thus the ability of phorbol ester to increase basal and isoproterenol-stimulated type VII activity appears to be a direct effect on this adenylyl cyclase isoform and not the result of modification of the inhibitory G protein, Gi.

Predictable crestal bone remodelling around two porous-coated titanium alloy dental implant designs. A radiographic study in dogs

We have previously suggested that altering the height of the porous-coat segment of a partially porous-coated TiAl6V4 endosseous dental implant would affect the degree of crestal bone loss occurring during implant function by changing the patterns of stress transfer. This conclusion arose from the analysis of data from several different experiments and lacked a direct intra-animal comparison. In the present study we have compared two implant designs varying only in the extent to which they were porous-coated. With one design (type A) the coronal 1.8 mm of the implant root had a machined surface while the remainder of its length was porous-coated with TiAl6V4 beads. The other design (type B) had all but the coronal-most 0.75 mm porous-coated. Two implants of each type were placed in each of 4 dogs and the sites allowed to heal for 4 weeks before re-entry and prosthesis attachment. Monthly the implant-supported bridges were removed and radiographs exposed of each implant using a special film holder connected separately to each implant. These radiographs were analyzed for crestal bone loss using both direct visual and computer-assisted techniques. The results showed that bone remodelled to the machined surface-to-porous coat junction for type B implants and achieved a steady state by 12 weeks of function, whereas a longer time was required to achieve this state with type A implants. Significantly more bone loss occurred with the type A design, and this difference was detectable as early as after the first month of function.

The structure and function of surfactant protein A. Hydroxyproline- and carbohydrate-deficient mutant proteins

Pulmonary surfactant protein A (SP-A) regulates the uptake and secretion of phospholipid by alveolar type II cells and is an important component of surfactant lipid aggregates. In an attempt to understand how specific structural domains of SP-A relate to the function of the protein, we used site-directed mutagenesis of the cDNA for SP-A and heterologous expression with baculovirus vectors. Synthesis of the wild type SP-A in insect cells resulted in a form of the protein in which proline residues were not hydroxylated and that is denoted SP-Ahyp. Three mutant SP-As with substitutions in the consensus sequences for glycosylation (SP-Ahyp,glc) to prevent N-linked oligosaccharide attachment at Asn1 and Asn187 were produced, individually and in tandem. The SP-Ahyp was glycosylated at both the Asn1 and Asn187 positions, demonstrated partial sulfhydryl-dependent oligomerization, and formed incomplete oligomers in solution. The SP-Ahyp and SP-Ahyp,glc bound to immobilized carbohydrate and to phospholipid liposomes and partially competed for occupancy of a plasma-membrane receptor for SP-A. The SP-Ahyp and the SP-Ahyp,glc were equally effective inhibitors of the secretion of surfactant lipids from isolated type II cells (IC50 = 0.5 microgram/ml) and aggregated phospholipid liposomes at 20 degrees C. All of the recombinant SP-As demonstrated markedly reduced aggregation of lipid at 37 degrees C. We conclude that the hydroxylation of proline residues is required for perfect oligomerization of SP-A and for thermal stability in the interaction with lipid. Furthermore, recombinant SP-A is able to inhibit the secretion of phospholipid from isolated type II cells and to aggregate lipid vesicles independent of the presence of N-linked carbohydrate or the site of glycosylation.

Analysis of metabolites in aqueous solutions by using laser Raman spectroscopy

Laser Raman scattering is conducted on aqueous solutions that contain organic chemicals that include glucose, lactate, ascorbate, pyruvate, and urea. At the concentrations of interest (below 1.0 wt. %), these various metabolites are found to scatter light independently of each other, and the scattering is linearly proportional to their concentrations. Through proper subtraction of water background scattering, the spectrum that is due to metabolite scattering is obtained and the composition of the solution can be determined by fitting its Raman spectrum with a linear sum of the known pure metabolite spectra. The spectrum of rabbit aqueous humor is presented and the potential application of this analytical method, such as noninvasive glucose monitoring, is discussed.

Molecular diversity in the adenylylcyclase family. Evidence for eight forms of the enzyme and cloning of type VI

The conservation of amino acid sequence among types I-IV adenylylcyclase has made it possible to apply the polymerase chain reaction to examine the extent of the molecular diversity within this family of enzymes. cDNA templates from rat heart, liver, kidney, guinea pig brain and testes, and mouse skeletal muscle were amplified with primers specific to adenylylcyclase sequences. Evidence was obtained for a total of eight distinct gene products divisible into five subfamilies. Five of the products correspond to regions from cloned forms of adenylylcyclase, while three are previously unidentified. As many as seven different adenylylcyclases are expressed in rat heart, liver, and kidney based on this analysis. Two newly identified polymerase chain reaction (PCR) products were utilized to screen a rat cDNA library from H35 Reuber hepatoma cells. A 6080-nucleotide cDNA contains an open reading frame encoding the 1166-amino acid type VI protein which has a predicted topography similar to that of other adenylylcyclases. The type VI message is abundantly expressed in rat heart, kidney, and brain. Human embryonal kidney cells stably expressing the cDNA showed an enhanced response to isoproterenol that could be inhibited by carbachol in intact cells. Increases in intracellular Ca2+ contribute to the inhibitory effect of carbachol.

Influence of dietary fat on the pharmacodynamics of propafenone in isolated, perfused rabbit hearts

BACKGROUND

The fatty acid composition of the phospholipids in sarcolemma may significantly influence cell membrane functions. We evaluated the effects of dietary fat on the pharmacodynamics of the antiarrhythmic drug propafenone in isolated, perfused rabbit hearts.

METHODS AND RESULTS

Three groups of weanling rabbits (n = 9 each group) were fed diets of 10% wt/wt lard, fish oil, or safflower oil for 40 days. Differences in electrophysiological variables were assessed at baseline and during propafenone perfusion. Myocardial concentration-effect relations were determined by plotting electrophysiological effects versus coronary sinus propafenone concentrations. The linoleic acid content of isolated sarcolemma was higher in the safflower group (33.4 +/- 11.4%) than in the lard (13.4 +/- 2.3%, p less than 0.01) and fish oil (8.5 +/- 1.4%, p less than 0.01) groups, whereas the omega-3 fatty acid content was higher in the fish oil group (p less than 0.01). During propafenone perfusion, greater changes in ventricular conduction time were observed in the lard group (22 +/- 11 msec) than in the safflower oil group (10 +/- 7 msec, p less than 0.05), whereas changes in ventricular conduction time in the fish oil group (16 +/- 7 msec) were intermediate between the lard and safflower oil groups. The slopes of the linear myocardial concentration-effect relations describing changes in QRS duration were steeper in the lard group (0.22 +/- 0.07 msec/micrograms/ml) than in the safflower oil group (0.13 +/- 0.04 msec/micrograms/ml, p less than 0.01) but not in the fish oil group (0.17 +/- 0.08 msec/microgram/ml, p = NS). Strength-interval curves were similar at baseline in all three groups. During propafenone perfusion, the threshold current was increased significantly at long coupling intervals (250-380 msec) in the lard group (1.8 +/- 1.0 mA) compared with the safflower oil group (0.8 +/- 0.6 mA, p less than 0.05) but not compared with the fish oil group (1.2 +/- 0.6 mA, p = NS).

CONCLUSIONS

Dietary fat significantly alters the fatty acid composition of the phospholipids in sarcolemma. Propafenone effects on ventricular conduction time and ventricular excitability are significantly influenced by the type of dietary fat.

The effect of partial coating with hydroxyapatite on bone remodeling in relation to porous-coated titanium-alloy dental implants in the dog

For inhibition of crestal bone resorption due to stress shielding and disuse atrophy, an hydroxyapatite (HA) plasma coating was added to the coronal portion of partially porous-coated endosseous dental implants. These implants, as well as control non-HA-coated implants were placed in healed mandibular premolar extraction sites in dogs for a 72-week period of function. Histological examination showed that both implant designs became securely fixed by bone ingrowth into the porous-coated apical region of the implants. The plasma-sprayed HA coating resulted in significantly greater bone height formation and maintenance next to the coronal portion of the implant compared with non-HA-coated implants of similar design. In addition, significant resorption of the 20-to-50-microns-thick plasma-sprayed HA coating occurred over the 18-month period of function.

Activation of adenylate cyclase during swelling of S49 cells in hypotonic medium is not involved in subsequent volume regulation

Experiments in S49 mouse lymphoma cells indicate that adenylate cyclase activity is increased following swelling in hypotonic medium through a mechanism independent of the G-proteins which are involved in hormonal regulation of the enzyme. An intact actin cytoskeleton is apparently required for stimulation of adenylate cyclase by mechanical forces. It was hypothesized that this increase in cAMP may be involved in triggering subsequent volume regulatory events. Manipulation of intracellular cAMP content and protein kinase A activity in S49 cells prior to swelling or during the regulatory volume decrease following swelling provided no evidence of a significant role for cAMP in regulating the extent of initial volume increase or the subsequent regulatory volume decrease. Treatment of S49 cells with 10-200 microM miconazole, previously shown to inhibit adenylate cyclase activity, attenuated the initial volume increase with medium dilution and accelerated the rate of regulatory decrease in a dose-dependent and time-dependent manner. However, incubation with 100 microM miconazole for 20 min, which completely inhibited swelling-induced increases in cAMP content, had no significant effect on either the initial volume expansion or the extent of regulatory volume decrease.

Function follows form: generation of intracellular signals by cell deformation

Cells are exposed during their lifetimes to an array of physical forces ranging from those generated by association with other cells and extracellular matrices to the constant forces placed on cells by gravity. Alterations in these forces, either with differentiation and development or changes in activity or behavior, result in modifications in the biochemistry and adaptation in structure and function of cells. Also, a variety of differentiated cells have unique shapes that relate to extremely specialized functions, with structure and function emerging concurrently. These observations lead to the concept that the forces perceived by cells may dictate their shape, and the combined effects of external physical stimuli and internal forces responsible for maintaining cell shape may stimulate alterations in cellular biochemistry. This review examines the state of our knowledge concerning the mechanisms through which physical forces are converted to biochemical signals (mechanotransduction), and speculates on the molecular structures that may be involved in mechanotransduction.

Dental implant design--effect on bone remodeling

Bone remodeling around three different endosseous dental implant designs placed in dog mandibles was studied using radiography during lengthy periods of function and by histology after animal sacrifice. The three designs investigated were (a) threaded (c.p. titanium), (b) fully porous-coated (titanium alloy), and (c) partially porous-coated (titanium alloy). The implants were kept in function for either 32 weeks (fully porous-coated) or 73 to 77 weeks (partially porous-coated and threaded). The studies indicated that some crestal bone loss occurred for both the threaded and partially porous-coated implants while no significant bone loss was seen with fully porous-coated implants in the absence of plaque-associated infection. It is suggested that these observed differences are a result of the different stress states that develop in bone surrounding the three designs underlying the importance of implant design on bone remodeling.

Mimosine reversibly arrests cell cycle progression at the G1-S phase border

It has previously been demonstrated that the compound mimosine inhibits cell cycle traverse in late G1 phase prior to the onset of DNA synthesis (Hoffman BD, Hanauske-Abel HM, Flint A, Lalande M: Cytometry 12:26-32, 1991; Lalande M: Exp Cell Res 186:332-339, 1990). These results were obtained by using flow cytometric analysis of DNA content to compare the effects of mimosine on cell cycle traverse with those of aphidicolin, an inhibitor of DNA polymerase alpha activity. We have now measured the incorporation of bromodeoxyuridine into lymphoblastoid cells by flow cytometry to determine precisely where the two inhibitors act relative to the initiation of DNA synthesis. It is demonstrated here that mimosine arrests cell cycle progression at the G1-S phase border. The onset of DNA replication occurs within 15 min of releasing the cells from the mimosine block. In contrast, treatment with aphidicolin results in the accumulation of cells in early S phase. These results indicate that mimosine is a suitable compound for affecting the synchronous release of cells from G1 into S phase and for analyzing the biochemical events associated with this cell cycle phase transition.

A histological comparison in the dog of porous-coated vs. threaded dental implants

The histological findings of an 18-month trial, in the dog of a partially porous-coated endosseous dental implant made of Ti-6Al-4V, with a truncated conical shape, are described and compared with those for a cylindrical, threaded, endosseous implant made of commercially pure Ti. Six beagle dogs each received two porous-coated implants on one side of the mandible and two threaded implants on the contralateral side. Each set of two implants supported a two-unit fixed bridge for an 18-month functional period. Methylmethacrylate sections of both the buccolingual and mesiodistal aspects of each implant were examined qualitatively and by computer-assisted morphometry. The morphometric measurements were used for determination of the length of implant surface in direct contact with bone on each aspect of each implant. The data were expressed both as an absolute length and as a fraction of the maximum length available for contact (contact length fraction or CLF). On the buccal and lingual aspects of the implants, both the absolute lengths and CLF were significantly smaller for the porous-coated design. For the mesial and distal aspects, the absolute lengths and CLF were less for the porous-coated design, but the differences were not significant. However, when the absolute contact length was related to the corresponding vertical bone height, significant differences were observed, the absolute contact length being greater for any given bone height for the porous-coated design. Taken together, the data suggest that shorter implants may be used with the porous-coated design.

Direct stimulation of adenylate cyclase by mechanical forces in S49 mouse lymphoma cells during hyposmotic swelling

S49 mouse lymphoma cells respond to swelling deformation with rapid increases in intracellular calcium and cAMP. Experiments demonstrate that these increases in calcium and cAMP concentrations are not coupled in a regulatory manner. Direct inhibition of adenylate cyclase in wild type cells with miconazole prevented swelling-induced accumulation of cAMP. No effect of swelling was observed on the activity of cAMP phosphodiesterase. Additionally, complete inhibition of cAMP phosphodiesterase did not prevent swelling-induced cAMP accumulation. Experiments involving cyc- mutants (lacking the Gs-alpha protein) and 2',5'-dideoxyadenosine indicate that increased adenylate cyclase activity with swelling is not mediated by Gs. No evidence was found for attenuation of Gi-mediated inhibition of adenylate cyclase activity following swelling. In addition, exposure to pertussis toxin or phorbol ester, which disrupts Gi inhibition of adenylate cyclase did not prevent cAMP accumulation following swelling. Disruption of the actin membrane skeleton resulted in a significant accumulation of cAMP which was not further increased by swelling. Disruption of the microtubular cytoskeleton also increased cAMP content in S49 cells which could be further increased by swelling. It is concluded that S49 cell-adenylate cyclase responds directly to mechanical forces transmitted through the actin membrane skeleton.

Accumulation of cAMP and calcium in S49 mouse lymphoma cells following hyposmotic swelling

Swelling of S49 "wild type" mouse lymphoma cells in hyposmolar medium was used to examine the effects of cellular deformation on cAMP metabolism. In S49 wild type mouse lymphoma cells incubated in a defined medium, progressive reductions in medium osmolarity of 5-50% resulted in proportionate expansion of cell volume. Increases in cell volume were accompanied by incremental increases in intracellular cAMP and calcium. These responses in S49 cells occurred rapidly, with increases in calcium concentration and cAMP content occurring within 1-2 min. Swelling of S49 cells in the absence of ions (hyposmolar versus normosmolar sorbitol) resulted in a significant accumulation of cAMP. Inclusion of papaverine or isobutyl methylxanthine amplified cAMP accumulation, and omission of calcium, sodium, or magnesium from the medium attenuated, but did not prevent accumulation of cAMP in S49 cells in response to swelling. Exposure to propranolol or nadolol attenuated the ability of swelling to increase cAMP concentration, while treatment with 2',5'-dideoxyadenosine or phentolamine had no effect on swelling-induced cAMP accumulation. It is concluded that cellular deformation of S49 wild type mouse lymphoma cells stimulates rapid accumulation of intracellular calcium and cAMP.