Fluid shear stress stimulates mitogen-activated protein kinase in endothelial cells

Local alterations in the hemodynamic environment regulate endothelial cell function, but the signal-transduction mechanisms involved in this process remain unclear. Because mitogen-activated protein (MAP) kinases have been shown to be activated by physical forces, we measured the phosphorylation and enzyme activity of MAP kinase to identify the signal events involved in the endothelial cell response to fluid shear stress. Flow at physiological shear stress (3.5 to 117 dynes/cm2) activated 42-kD and 44-kD MAP kinases present in cultured bovine aortic endothelial cells, with maximal effect at 12 dynes/cm2. Activation of a G protein was necessary, as demonstrated by complete inhibition by the nonhydrolyzable GDP analog GDP-beta S. Activation of protein kinase C (PKC) was required, as shown by inhibiting PKC with staurosporine or downregulating PKC with phorbol 12,13-dibutyrate. Both Ca(2+)-dependent and -independent PKC activity, measured by translocation and substrate phosphorylation, increased in response to flow. However, MAP kinase activation was not dependent on Ca2+ mobilization, since Ca2+ chelation had no inhibitory effect. On the basis of these findings, it is proposed that flow activates two signal-transduction pathways in endothelial cells. One pathway is Ca2+ dependent and involves activation of phospholipase C and increases in intracellular Ca2+. A new pathway, described in the present study, is Ca2+ independent and involves a G protein and increases in PKC and MAP kinase activity.

Protein kinases as mediators of fluid shear stress stimulated signal transduction in endothelial cells: a hypothesis for calcium-dependent and calcium-independent events activated by flow

Fluid shear stress regulates endothelial cell function, but the signal transduction mechanisms involved in mechanotransduction remain unclear. Recent findings demonstrate that several intracellular kinases are activated by mechanical forces. In particular, members of the mitogen-activated protein (MAP) kinase family are stimulated by hyperosmolarity, stretch, and stress such as heat shock. We propose a model for mechanotransduction in endothelial cells involving calcium-dependent and calcium-independent protein kinase pathways. The calcium-dependent pathway involves activation of phospholipase C, hydrolysis of phosphatidylinositol 4,5-bisphosphate (PIP2), increases in intracellular calcium and stimulation of kinases such as calcium-calmodulin and C kinases (PKC). The calcium-independent pathway involves activation of a small GTP-binding protein and stimulation of calcium-independent PKC and MAP kinases. The calcium-dependent pathway mediates the rapid, transient response to fluid shear stress including activation of nitric oxide synthase (NOS) and ion transport. In contrast, the calcium-independent pathway mediates a slower response including the sustained activation of NOS and changes in cell morphology and gene expression. We propose that focal adhesion complexes link the calcium-dependent and calcium-independent pathways by regulating activity of phosphatidylinositol 4-phosphate (PIP) 5-kinase (which regulates PIP2 levels) and p125 focal adhesion kinase (FAK, which phosphorylates paxillin and interacts with cytoskeletal proteins). This model predicts that dynamic interactions between integrin molecules present in focal adhesion complexes and membrane events involved in mechanotransduction will be integrated by calcium-dependent and calcium-independent kinases to generate intracellular signals involved in the endothelial cell response to flow.

Association of basonuclin with ability of keratinocytes to multiply and with absence of terminal differentiation

Basonuclin is a protein possessing three pairs of zinc fingers and a nuclear localization signal. Expression of the gene is largely confined to keratinocytes of stratified squamous epithelia and hair follicles. In the epidermis and in stratified epidermal cultures, basonuclin is present in the nuclei of cells in or close to the basal layer but not in the nuclei of cells in more superficial layers. The Ki-67 protein, a nuclear marker for any stage of the multiplication cycle is present in only a subclass of basonuclin-containing cells. In cultured keratinocytes, the disappearance of basonuclin mRNA is associated with loss of colony-forming ability and the appearance of mRNA for involucrin, a protein characteristic of terminal differentiation. In hair follicles, the largest reservoir of basonuclin-containing cells is the outer root sheath, which contains precursors of differentiated cells of the hair shaft and of the epidermis. Basonuclin is not a cell cycle marker but is likely instead to be a regulatory molecular whose presence in the keratinocyte is linked to the maintenance of proliferative capacity and prevention of terminal differentiation.

Basonuclin: a keratinocyte protein with multiple paired zinc fingers

A cDNA clone has been prepared from mRNA of cultured human keratinocytes. The sequence of the cDNA reveals that in the C-terminal two-thirds of the corresponding protein (basonuclin), there are three separated pairs of adjacent zinc fingers. The amino acid sequence of each pair is homologous to that of the single pair of zinc fingers of the Drosophila transcription factor encoded by disco. Near the C-terminal end of basonuclin and on the surface of a putative alpha-helix, there is a stripe of serine residues similar to that of the transcription factor PRDII-BF1. Basonuclin possesses a sequence of six amino acids quite similar to one present in the myogenic family of proteins, including Myf5; this sequence is located in the omega loop of the myogenic proteins but within a zinc finger of the keratinocyte protein. As basonuclin is present mainly in the nuclei of the basal cell layer, its regulatory function is likely to be exerted prior to the process of terminal differentiation.

Olfactory memory in unmedicated schizophrenics

Previous studies have indicated that schizophrenic patients have olfactory deficits. The question as to whether olfactory deficits are due to chronic effects of medication has not been addressed. This is the first paper to report that never-medicated schizophrenic patients also have olfactory deficits. Twenty four normal subjects and twenty unmedicated schizophrenic patients were examined with two tests of olfactory function: the University of Pennsylvania Smell Identification Test (UPSIT) and a match-to-sample olfactory memory test. Results indicated that schizophrenics did poorly on both the UPSIT and the olfactory match-to-sample memory test relative to sex and age-matched controls. ANCOVA showed that the deficit in performance on the olfactory match-to-sample test was still present even when the variance due to the UPSIT was taken out of the analysis. Deficits in olfactory identification and olfactory memory are consistent with the concept that schizophrenics have dysfunctional limbic systems.

Remodeling of the involucrin gene during primate evolution

The protein involucrin is a product of terminal differentiation in the epidermal cell and related cell types. By comparing the nucleotide sequence of the involucrin gene of the lemur with that of the human, it is clear that the gene has undergone unusual evolution in the primates. The coding region of the gene contains an ancestral segment, most of which is common to the lemur and the human, and a species-specific segment of repeats derived from the ancestral segment. Instead of the modern segment of repeats found in the human gene, the lemur gene possesses repeats derived from another sequence at a different location in the ancestral segment. The two kinds of segments of repeats probably represent alternative ways of creating a repeat structure in the involucrin molecule. The modern segment of repeats must have been created after divergence of the higher primates from the prosimians.

Elastic fibers in the aortic valve spongiosa: a fresh perspective on its structure and role in overall tissue function

This study characterizes the elastic fiber structure within the aortic valve spongiosa, the middle layer of the tri-laminate leaflet. The layer is rich in glycosaminoglycans and proteoglycans, through which it resists compression and lubricates shear between the outer layers. Elastin in this layer forms a fine, interweaving structure, yet it is unclear how this particular structure, which uses elasticity to preload the leaflet, assists spongiosa function. In this study, immunohistochemistry (IHC) and scanning electron microscopy (SEM) are used to characterize spongiosa elastin, as well as investigate regional differences in structure. IHC for elastin highlights an intermediate structure which varies in thickness and density between regions. In particular, the spongiosa elastin is thicker in the hinge and coaptation region than in the belly. SEM of NaOH-digested leaflets shows a rectilinear pattern of elastic fibers in the hinge and coaptation region, as opposed to a radially oriented stripe pattern in the belly. In conclusion, elastic fibers in the spongiosa connect the two outer layers and vary regionally in structure, while possibly playing a role in responding to regionally specific loading patterns.

Function of basonuclin in increasing transcription of the ribosomal RNA genes during mouse oogenesis

Active protein synthesis during early oogenesis requires accelerated transcription of ribosomal RNA genes (rDNAs). In response to this demand, rDNAs are amplified more than 1000-fold early in Xenopus oogenesis. Here, we report evidence that rDNA is not amplified in mouse oocytes, but these cells may instead employ the zinc-finger protein basonuclin, a putative rDNA transcription factor, to enhance rRNA synthesis. This conclusion is based on observations that basonuclin is localized in the nucleolus in the mouse oocyte early in its growth phase, when rRNA transcription is highly active; and that the binding sites of basonuclin zinc fingers on the human and mouse rDNA promoters are homologous. In a co-transfection assay, basonuclin can elevate transcription from an rDNA promoter, and its zinc-finger domain can inhibit RNA polymerase I transcription, as detected by a run-on assay, in growing mouse oocytes.

Doppler ultrasound, laser Doppler, and perfusion fluorometry in bowel ischemia

Improved accuracy and objectivity in the evaluation of intestinal viability has been reported by some investigators using Doppler ultrasound, and more recently laser Doppler velocimetry and perfusion fluorometry. To compare the sensitivity and clinical applicability of these techniques, intestinal viability was evaluated by each method in nine 15- to 50-cm loops of small bowel prepared by division of the mesenteric vasculature in five anesthetized dogs. The sensitivity of Doppler ultrasound was 86%, of laser Doppler flow velocity 85%, of laser Doppler index 94%, and of perfusion fluorometry 95%. Though the sensitivity of Doppler ultrasound is significantly less than that of laser Doppler and perfusion fluorometry, this is not unexpected since the latter two techniques are more quantitative than Doppler ultrasound. Clinically, Doppler ultrasound compares favorably with laser Doppler and perfusion fluorometry, and its low cost and simplicity suggest its adjunctive use in the operative setting.

A role for decorin in controlling proliferation, adhesion, and migration of murine embryonic fibroblasts

The proteoglycan decorin putatively inhibits cell adhesion and cell migration on various extracellular matrix substrates through interactions with beta(1) integrins. This study, therefore, examined the adhesive, migration, and proliferative characteristics of decorin knockout (Dcn(-/-)) murine embryonic fibroblasts compared to wild-type controls on collagen-coated, fibronectin-coated, and uncoated tissue culture plates. The Dcn(-/-) cells showed significantly greater proliferation than wild-type controls on all substrates. The Dcn(-/-) cells also showed significantly greater adhesion to both collagen and fibronectin; both cell types showed greater adhesion to collagen. The addition of exogenous decorin had a differential effect on adhesion to collagen between cell types, but not on fibronectin. For collagen, blocking either alpha(2) or beta(1) integrin subunits significantly reduced adhesion for Dcn(-/-) cells; whereas for fibronectin, blocking either the alpha(5) or beta(1) integrin subunits reduced adhesion for both cell types. Decorin and the alpha(5)beta(1) integrin may have lesser roles in adhesion to fibronectin than previously presumed. Finally, compared to wild-type cells, Dcn(-/-) cells showed greater migration on both uncoated and collagen substrates. This study demonstrates that decorin affects the biology of various integrins that participate in cell proliferation, adhesion, and migration on various substrates.

Translocation of the zinc finger protein basonuclin from the mouse germ cell nucleus to the midpiece of the spermatozoon during spermiogenesis

Basonuclin was first described as a human keratinocyte zinc finger protein present in the nuclei of proliferative basal keratinocytes in the epidermis. It disappears from keratinocytes that have lost their proliferative ability and have entered terminal differentiation. We now report that basonuclin is present also in the germ cells of the mouse testis and ovary. Immunocytochemical staining detected basonuclin in the nuclei of spermatogonia and spermatocytes at various developmental stages. During spermiogenesis, it relocated from the nucleus to the midpiece of the flagellum of the spermatozoa. In the ovary, basonuclin was found mainly in the nuclei of developing oocytes. The dual presence of basonuclin in differentiated spermatozoa and oocytes suggests that it may play a role in their differentiation and the early development of an embryo.

Risk factors for exposure of glaucoma drainage devices: a retrospective observational study

OBJECTIVES

The purpose of this study was to identify risk factors for exposure of glaucoma drainage devices (GDD).

SETTING

This retrospective, observational study was conducted in the eye clinic of an academic medical centre.

PARTICIPANTS

Participants included 1073 consecutive adults who underwent GDD surgery between 1 January 2005 and 1 January 2011. Participants were included if chart review indicated GDD surgery during the study period and excluded if at least 12 months of clinical follow-up was not available in the medical record.

PRIMARY OUTCOME MEASURE

The primary outcome measure was exposure of the GDD occurring at least 1 month after implant surgery. The characteristics of participants who experienced exposure of the implant were compared to the characteristics of participants who did not experience exposure.

RESULTS

Of the 1073 participants having undergone GDD surgery, 67 experienced exposure of the device. Neither the type of GDD, type of patch graft (eye bank sclera, Tutoplast sclera and Tutoplast pericardium), surgeon, location of GDD, number of GDD previously implanted into the eye, nor history of diabetes or uveitis were associated with likelihood of exposure. Women were more likely than men to experience exposure of the GDD (OR 2.004 (95% CI1.170 to 3.431)) in both univariable (p=0.011) and multivariable (p=0.013) analyses. In survival analysis, exposure of the GDD occurred earlier for women than for men (58 vs 61 months; p=0.024).White race (vs black) was also associated with increased risk of GDD exposure (OR 1.693 (95% CI 1.011 to 2.833)) in univariable (p=0.044) and multivariable (p=0.046) analyses.

CONCLUSIONS

Women are two times more likely to experience GDD exposure than men, independent of age. White race is also a risk factor for exposure.

OPTN is a host intrinsic restriction factor against neuroinvasive HSV-1 infection

Fast-replicating neurotropic herpesviruses exemplified by herpes simplex virus-1 (HSV-1) naturally infect the central nervous system (CNS). However, most individuals intrinsically suppress the virus during a primary infection and preclude it from significantly damaging the CNS. Optineurin (OPTN) is a conserved autophagy receptor with little understanding of its role in neurotropic viral infections. We show that OPTN selectively targets HSV-1 tegument protein, VP16, and the fusion glycoprotein, gB, to degradation by autophagy. OPTN-deficient mice challenged with HSV-1 show significant cognitive decline and susceptibility to lethal CNS infection. OPTN deficiency unveils severe consequences for recruitment of adaptive immunity and suppression of neuronal necroptosis. Ocular HSV-1 infection is lethal without OPTN and is rescued using a necroptosis inhibitor. These results place OPTN at the crux of neuronal survival from potentially lethal CNS viral infections.

Basonuclin is associated with the ribosomal RNA genes on human keratinocyte mitotic chromosomes

Basonuclin is a zinc finger protein mainly expressed in keratinocytes of the basal layer of epidermis and the outer root sheath of hair follicles. It is also found in abundance in the germ cells of testis and ovary. In cultured keratinocytes, basonuclin is associated with chromatin in all phases of the cell cycle, including mitosis. By immunocytochemical methods, we demonstrate here that in mitosis basonuclin is associated with the short arms of the acrocentric chromosomes and with other loci on many metaphase chromosomes of human keratinocytes. Using the evolutionarily highly conserved N-terminal pair of zinc fingers in an electrophoresis mobility shift assay, we demonstrate that the DNA target sequences of basonuclin on the acrocentric chromosomes are likely to be within the promoter region of the 45S rRNA gene transcription unit. DNase I footprinting shows that basonuclin zinc fingers interact with the upstream control element of this promoter, which is necessary for the high level of transcription of the rRNA genes. This result suggests that basonuclin may be a tissue-specific transcription factor for the ribosomal RNA genes.

Body machine interface: remapping motor skills after spinal cord injury

The goal of a body-machine interface (BMI) is to map the residual motor skills of the users into efficient patterns of control. The interface is subject to two processes of learning: while users practice controlling the assistive device, the interface modifies itself based on the user's residual abilities and preferences. In this study, we combined virtual reality and movement capture technologies to investigate the reorganization of movements that occurs when individuals with spinal cord injury (SCI) are allowed to use a broad spectrum of body motions to perform different tasks. Subjects, over multiple sessions, used their upper body movements to engage in exercises that required different operational functions such as controlling a keyboard for playing a videogame, driving a simulated wheelchair in a virtual reality (VR) environment, and piloting a cursor on a screen for reaching targets. In particular, we investigated the possibility of reducing the dimensionality of the control signals by finding repeatable and stable correlations of movement signals, established both by the presence of biomechanical constraints and by learned patterns of coordination. The outcomes of these investigations will provide guidance for further studies of efficient remapping of motor coordination for the control of assistive devices and are a basis for a new training paradigm in which the burden of learning is significantly removed from the impaired subjects and shifted to the devices.

Basonuclin in murine corneal and lens epithelia correlates with cellular maturation and proliferative ability

Basonuclin is a zinc finger protein with highly restricted tissue distribution. It has been found in abundance only in keratinocytes of stratified epithelia and the germ cells of the testis and ovary. We studied the expression pattern of basonuclin in relation to cellular proliferation and differentiation in murine corneal and lens epithelia, two self-renewing tissues in the eye which contain cells that proliferate throughout life. Mouse corneal and lens epithelial cells at various stages of development were labeled with BrdU for 90 min to detect cells in S phase and to establish proliferative rates. Whole eyes of mouse or rat were processed for frozen sections and cellular basonuclin was detected by either a rabbit antimouse- or a rabbit anti-human-basonuclin antibody. Basonuclin was expressed in virtually all cells in the basal layer of corneal epithelium and in the pre-equatorial lens epithelium, the respective proliferative compartments of adult corneal and lens epithelia. Basonuclin expression in corneal epithelium began at post-natal life day 4, first in a few cells and then spread to virtually all basal cells at day 20. Basonuclin was consistently absent in limbal epithelium. Lens basonuclin, which was detected earlier than that of the cornea, was confined to the pre-equatorial epithelium and was absent in equatorial cells that expressed p57KIP2, an early differentiation marker for these cells. An important distinction between corneal and lens basonuclin is that the former is predominantly nuclear whereas the latter cytoplasmic.

Basonuclin, a zinc finger protein associated with epithelial expansion and proliferation

Basonuclin is a zinc finger protein first described as a keratinoycte specific protein present in various stratified squamous epithelia found in epidermis, esophagis, cornea and virgina. Recent studies showed that its distribution also includes the germ cells of testis and ovary. The presence of basonuclin appeared always related to the cellular proliferative ability not just cell division, for it was found both in dividing and quiescent cells. Basonuclin disappeared when a cell became post-mitotic. This review examines the latest findings about the distribution, molecular and cellular biology of basonuclin and discusses its possible role in cell proliferation.

Retinal thinning in amyotrophic lateral sclerosis patients without ophthalmic disease

IMPORTANCE

Amyotrophic lateral sclerosis (ALS) is a fatal, rapidly progressive neurodegenerative disease that primarily affects motor neurons. Recently, three causative genes have been implicated in both ALS and glaucoma. However, it is still uncertain whether patients with ALS have neurodegeneration in their retinas. If so, retinal thickness measurements might be a useful biomarker for ALS progression. Previous work in this area has been inconclusive, as it has not taken into account the effect of ophthalmic diseases on retinal thinning.

OBJECTIVE

To determine whether there are differences in retinal neurons in ALS patients utilizing spectral-domain optical coherence tomography (SD-OCT). We tested the hypothesis that ALS patients exhibit retinal neurodegeneration that is not associated with ophthalmic diseases.

DESIGN, SETTINGS AND PARTICIPANTS

Observational, comparative, cross-sectional study performed on patients recruited from the Duke University Medical Center ALS clinic. Patients underwent a comprehensive ophthalmologic examination to rule out ocular pathology. 21 patients met inclusion criteria. Two eyes with ocular pathology were excluded, leading to a total of 40 eyes of 21 patients included in the study. Retinal neurodegeneration was assessed by retinal nerve fiber layer (RNFL) thickness measurement using SD-OCT (Spectralis; Heidelberg Engineering).

MAIN OUTCOMES AND MEASURES

ALS disease severity, determined through the ALS Functional Rating Scale (ALSFRS-R); mean and six sector RNFL thickness values compared to age-adjusted values in the normative database provided by Heidelberg Engineering; RNFL thickness correlation with ALSFRS-R, ALSFRS-R progression rate, forced vital capacity (FVC), and visual acuity.

RESULTS

ALSFRS-R mean score was 30+/-10. Mean RNFL thickness in ALS patients was 88.95 +/- 10.8 microns, significantly thinner than values in the normative database (95.81 +/- 0.8). These RNFL thickness values did not demonstrate correlation to ALSFRS-R score, ALSFRS-R progression rate, FVC, intraocular pressure, or visual acuity.

CONCLUSIONS

Using SD-OCT, our study shows that ALS patients without ocular pathology exhibit thinned retinal layers. Future studies are warranted to clarify the clinical relationship between retinal thinning and motor neuron loss in ALS.

CDDO-Me, Sulforaphane and tBHQ attenuate the RANKL-induced osteoclast differentiation via activating the NRF2-mediated antioxidant response

Metabolic bone diseases are global public health concerns and are primarily caused by uncontrolled osteoclast (OC) formation and activation. During OC differentiation, intracellular reactive oxygen species (ROS) stimulated by receptor activator of nuclear factor kappa-B ligand (RANKL) can serve as the signaling molecules to promote osteoclastic genes expression. Nuclear factor erythroid-2 related factor 2 (NRF2), a master mediator of cellular antioxidant response, also plays a critical role in OC differentiation through the regulation of redox homeostasis. In this study, we investigated the effects of three NRF2 inducers on osteoclastogenesis, including Bardoxolone methyl (CDDO-Me), Sulforaphane (SFN), and tert-butylhydroquinone (tBHQ). By treating RAW cells with three compounds, we found that NRF2 was activated and its downstream antioxidant genes were upregulated, and the RANKL-induced intracellular ROS production and osteoclastogenesis were impaired. Additionally, the expression of nuclear factor of activated T cells c1 (NFATC1), C-FOS and tumor necrosis factor alpha (TNFα) were inhibited after acute exposures (6 h) to the three compounds. Furthermore, suppressed the expression of osteoclast differentiation-associated genes, tartrate-resistant acid phosphatase (TRAP), cathepsin K (CTSK), matrix metalloproteinase-9 (MMP-9) and dendritic cell-specific transmembrane protein (DC-STAMP) were observed after prolonged exposures (5 days) to the compounds. Taken together, these results suggest that CDDO-Me, SFN and tBHQ attenuate RANKL-induced osteoclastogenesis via activation of NRF2-mediated antioxidant response. Among these compounds, relatively low concentrations of CDDO-Me showed stronger active and inhibitory effects on antioxidant response and osteoclastogenesis, respectively.

Effects of surface treatments on bond strength of glass-infiltrated ceramic

The purpose of this study was to evaluate the effects of various surface treatments on the bond strength at the In-Ceram/resin composite interface. Ninety-eight In-Ceram specimens were divided into seven groups and exposed to various surface treatments as follows: (A) control (B) saliva contamination (C) saliva contamination plus aluminum oxide sandblasting (D) glove powder contamination (E) glove powder contamination plus aluminum oxide sandblasting (F) rough aluminum oxide sandblasting and (G) excess glass infiltration. A resin composite cylinder was cemented to each In-Ceram specimen with Panavia 21 resin luting cement. Half of the cemented specimens in each group were stored in water for 24 h, and the other half were stored in water for 2 weeks and then were thermo-cycled for 2000 cycles. Shear bond strengths (SBS) of seven specimens in each subgroup were determined and analysed using analysis of variance (ANOVA) and Tukey HSD test as well as Student's t-test. Scanning electronic microscopy was used to identify the type of bond failure. Shear bond strength was significantly decreased by saliva and glove powder contaminations (P < 0.05). Sandblasting treatment did not improve the saliva-contaminated specimens. However, the glove powder plus sandblasting group showed no significant difference in SBS compared with the control group. There was no significant difference in SBS between the excess glass-infiltrating group and the control group. The SBS was significantly decreased by rough aluminum oxide sandblasting (P < 0.05). The SBS values of groups without thermocycling were significantly greater than those of groups with thermocycling (P < 0.05). There were no significant differences among SBS values of the seven groups with thermocycling. Combined cohesive and adhesive bond failures were seen in every group. Various surface treatments or contaminants may significantly influence the bond strength of In-Ceram restorative in clinical use.

The human basonuclin gene

The human gene for basonuclin, a zinc-finger protein of keratinocytes, has been cloned, sequenced and assigned to chromosome 15. The transcription unit spans nearly 29 kb of sequence. The coding region is distributed over five exons, and the three pairs of zinc fingers are encoded by the last two. The 5' flanking sequence and first exon are unusually rich in G+C and in CpG dinucleotides. This region contains numerous target sites for the transcription factor Sp1.

DNA cloning without restriction enzyme and ligase

One common problem in using the traditional DNA cloning procedure is that suitable natural restriction sites are often unavailable for a given task. Creating new restriction sites is often time consuming. Here, I describe a simple technique of producing "customized cohesive ends" by a combination of PCR primer design and lambda exonuclease digestion. These complementary cohesive ends can form hybrids to link two sequences. Because the overhangs created by lambda exonuclease are slightly longer than the complementary sequence, after hybrid formation, a stretch of single-strand gap remains, which then is repaired by Klenow (3'-->5' exo-) enzyme. The repair process also stabilizes the linkage. Because of the independence from natural or artificial restriction sites, this method allows rapid and precise insertion of one DNA fragment into another at virtually any position. It also simplifies the planning of a cloning strategy, increases recombinant frequency and is suitable for automation.

Cardiac receptor physiology and its application to clinical imaging: present and future

Both gamma imaging and positron emission tomography (PET) imaging of cell surface receptors have become possible through the development of agonists and antagonists with high specific radioactivity and high specificity for the receptors. An understanding of the physiology of the cardiac receptor system is essential to comprehending receptor imaging. The complexity of the physiologic information developed over the past decade has been compounded by the concomitant discovery of additional receptor subtypes. The following is a review of a select group of cardiac receptors and their regulation-namely, adrenergic, muscarinic-cholinergic, adenosine, and angiotensin I and II receptors. The role of imaging regional receptor localization and function in providing new insights into cardiac pathology and therapeutic avenues is explored.

Roles of autophagy in orthodontic tooth movement

INTRODUCTION

Orthodontic tooth movement (OTM) relies on efficient remodeling of alveolar bone. While a well-controlled inflammatory response is essential during OTM, the mechanism regulating inflammation is unknown. Autophagy, a conserved catabolic pathway, has been shown to protect cells from excess inflammation in disease states. We hypothesize that autophagy plays a role in regulating inflammation during OTM.

METHODS

A split-mouth design was used to force load molars in adult male mice, carrying a GFP-LC3 transgene for in vivo detection of autophagy. Confocal microscopy, Western blot, and quantitative polymerase chain reaction analyses were used to evaluate autophagy activation in tissues of loaded and control molars at time points after force application. Rapamycin, a Food and Drug Administration-approved immunosuppressant, was injected to evaluate induction of autophagy.

RESULTS

Autophagy activity increases shortly after loading, primarily on the compression side of the tooth, and is closely associated with inflammatory cytokine expression and osteoclast recruitment. Daily administration of rapamycin, an autophagy activator, led to reduced tooth movement and osteoclast recruitment, suggesting that autophagy downregulates the inflammatory response and bone turnover during OTM.

CONCLUSIONS

This is the first demonstration that shows that autophagy is induced by orthodontic loading and plays a role during OTM, likely via negative regulation of inflammatory response and bone turnover. Exploring roles of autophagy in OTM holds great promise, as aberrant autophagy is associated with periodontal disease and its related systemic inflammatory disorders.