Identification of cation-binding sites on actin that drive polymerization and modulate bending stiffness.

The assembly of actin monomers into filaments and networks plays vital roles throughout eukaryotic biology, including intracellular transport, cell motility, cell division, determining cellular shape, and providing cells with mechanical strength. The regulation of actin assembly and modulation of filament mechanical properties are critical for proper actin function. It is well established that physiological salt concentrations promote actin assembly and alter the overall bending mechanics of assembled filaments and networks. However, the molecular origins of these salt-dependent effects, particularly if they involve nonspecific ionic strength effects or specific ion-binding interactions, are unknown. Here, we demonstrate that specific cation binding at two discrete sites situated between adjacent subunits along the long-pitch helix drive actin polymerization and determine the filament bending rigidity. We classify the two sites as "polymerization" and "stiffness" sites based on the effects that mutations at the sites have on salt-dependent filament assembly and bending mechanics, respectively. These results establish the existence and location of the cation-binding sites that confer salt dependence to the assembly and mechanics of actin filaments.

Otodental syndrome: a case presentation in a 6-year old child.

BACKGROUND: Otodental syndrome is a rare condition characterised by globodontia, and sensorineural high frequency hearing loss. To date, only 20 cases of otodental syndrome have been reported. CASE REPORT: A 6 year-old girl presented with a chief complaint of delay in the eruption of primary canines. Following clinical, radiographic and audiologic evaluations, the patient was diagnosed with otodental syndrome. CONCLUSION: Globodontia is a diagnostic feature of the otodental syndrome, which often provides the path to discovery of the associated hearing loss. Missing teeth, arch-size discrepancies, chewing problems and teething disturbances are the other major complications.

Development of a hardened THz energy meter for use on the kilojoule-scale, short-pulse OMEGA EP laser.

A highly adaptable and robust terahertz (THz) energy meter is designed and implemented to detect energetic THz pulses from high-intensity (>1018 W/cm2) laser-plasma interactions on the OMEGA EP. THz radiation from the laser driven target is detected by a shielded pyrometer. A second identical pyrometer is used for background subtraction. The detector can be configured to detect THz pulses in the 1 mm to 30 µm (0.3- to 10-THz) range and pulse energies from joules to microjoules via changes in filtration, aperture size, and position. Additional polarization selective filtration can also be used to determine the THz pulse polarization. The design incorporates significant radiation and electromagnetic pulse shielding to survive and operate within the OMEGA EP radiation environment. We describe the design, operational principle, calibration, and testing of the THz energy meter. The pyrometers were calibrated using a benchtop laser and show linear sensitivity to up to 1000 nJ of absorbed energy. The initial results from four OMEGA EP THz experiments detected up to ∼15µJ at the detector, which can correspond to hundreds of mJ depending on THz emission and reflection models.

Cofilin-linked changes in actin filament flexibility promote severing.

The actin regulatory protein, cofilin, increases the bending and twisting elasticity of actin filaments and severs them. It has been proposed that filaments partially decorated with cofilin accumulate stress from thermally driven shape fluctuations at bare (stiff) and decorated (compliant) boundaries, thereby promoting severing. This mechanics-based severing model predicts that changes in actin filament compliance due to cofilin binding affect severing activity. Here, we test this prediction by evaluating how the severing activities of vertebrate and yeast cofilactin scale with the flexural rigidities determined from analysis of shape fluctuations. Yeast actin filaments are more compliant in bending than vertebrate actin filaments. Severing activities of cofilactin isoforms correlate with changes in filament flexibility. Vertebrate cofilin binds but does not increase the yeast actin filament flexibility, and does not sever them. Imaging of filament thermal fluctuations reveals that severing events are associated with local bending and fragmentation when deformations attain a critical angle. The critical severing angle at boundaries between bare and cofilin-decorated segments is smaller than in bare or fully decorated filaments. These measurements support a cofilin-severing mechanism in which mechanical asymmetry promotes local stress accumulation and fragmentation at boundaries of bare and cofilin-decorated segments, analogous to failure of some nonprotein materials.

Ameloblastic fibro-odontoma: a clinicopathologic study of 12 cases.

OBJECTIVE: The ameloblastic fibro-odontoma (AFO) is an uncommon odontogenic tumor occurring in childhood with limited reported data on recurrence. The purpose of this AFO study was to review its clinicopathologic features, investigate treatment modalities and establish a recurrence rate. STUDY DESIGN: The clinicopathologic features of 12 new cases of AFO were analyzed and compared with those of 208 cases from the literature, with special emphasis on the clinical behavior, treatment, and recurrence rate. RESULTS: The average age was 9.4 (+/- 6.7) years with a male-to-female ratio of 1.6:1. The mandible was the site of occurrence in 59.5%. The tumor most often presented radiographically as a unilocular mixed density lesion associated with the crown of an impacted tooth. Displacement of teeth, delayed eruption and bony expansion were commonplace. There were 5 recurrences among 68 cases with adequate follow-up for a recurrence rate of 7.4%. All recurrences were attributed to incomplete removal at the time of the initial surgery. CONCLUSIONS: The AFO is a childhood tumor most often affecting the posterior jaws and frequently causing bony expansion with profound affects on the dentition. Conservative surgical removal with extraction of the associated teeth is recommended. The established recurrence rate is less than 10%.

Origin of twist-bend coupling in actin filaments.

Actin filaments are semiflexible polymers that display large-scale conformational twisting and bending motions. Modulation of filament bending and twisting dynamics has been linked to regulatory actin-binding protein function, filament assembly and fragmentation, and overall cell motility. The relationship between actin filament bending and twisting dynamics has not been evaluated. The numerical and analytical experiments presented here reveal that actin filaments have a strong intrinsic twist-bend coupling that obligates the reciprocal interconversion of bending energy and twisting stress. We developed a mesoscopic model of actin filaments that captures key documented features, including the subunit dimensions, interaction energies, helicity, and geometrical constraints coming from the double-stranded structure. The filament bending and torsional rigidities predicted by the model are comparable to experimental values, demonstrating the capacity of the model to assess the mechanical properties of actin filaments, including the coupling between twisting and bending motions. The predicted actin filament twist-bend coupling is strong, with a persistence length of 0.15-0.4 µm depending on the actin-bound nucleotide. Twist-bend coupling is an emergent property that introduces local asymmetry to actin filaments and contributes to their overall elasticity. Up to 60% of the filament subunit elastic free energy originates from twist-bend coupling, with the largest contributions resulting under relatively small deformations. A comparison of filaments with different architectures indicates that twist-bend coupling in actin filaments originates from their double protofilament and helical structure.

Outcome measures in spinal cord injury: recent assessments and recommendations for future directions.

STUDY DESIGN: Review by the spinal cord outcomes partnership endeavor (SCOPE), which is a broad-based international consortium of scientists and clinical researchers representing academic institutions, industry, government agencies, not-for-profit organizations and foundations. OBJECTIVES: Assessment of current and evolving tools for evaluating human spinal cord injury (SCI) outcomes for both clinical diagnosis and clinical research studies. METHODS: a framework for the appraisal of evidence of metric properties was used to examine outcome tools or tests for accuracy, sensitivity, reliability and validity for human SCI. RESULTS: Imaging, neurological, functional, autonomic, sexual health, bladder/bowel, pain and psychosocial tools were evaluated. Several specific tools for human SCI studies have or are being developed to allow the more accurate determination for a clinically meaningful benefit (improvement in functional outcome or quality of life) being achieved as a result of a therapeutic intervention. CONCLUSION: Significant progress has been made, but further validation studies are required to identify the most appropriate tools for specific targets in a human SCI study or clinical trial.

First measurements of remaining shell areal density on the OMEGA laser using the Diagnostic for Areal Density (DAD).

A glass Cherenkov detector, called the Diagnostic for Areal Density (DAD), has been built and implemented at the OMEGA laser facility for measuring fusion gammas above 430 keV, from which remaining shell ⟨ρR⟩ abl can be determined. A proof-of-principle experiment is discussed, where signals from a surrogate gas Cherenkov detector are compared with reported values from the wedge range filter and charged particle spectrometer and found to correlate strongly. The design of the more compact port-based DAD diagnostic and results from the commissioning shots are then presented. Once absolutely calibrated, the DAD will be capable of reporting remaining shell ⟨ρR⟩ abl for plastic and glass capsules within minutes of a shot and with potentially higher precision than existing techniques.

Shifting the optimal stiffness for cell migration.

Cell migration, which is central to many biological processes including wound healing and cancer progression, is sensitive to environmental stiffness, and many cell types exhibit a stiffness optimum, at which migration is maximal. Here we present a cell migration simulator that predicts a stiffness optimum that can be shifted by altering the number of active molecular motors and clutches. This prediction is verified experimentally by comparing cell traction and F-actin retrograde flow for two cell types with differing amounts of active motors and clutches: embryonic chick forebrain neurons (ECFNs; optimum ∼1 kPa) and U251 glioma cells (optimum ∼100 kPa). In addition, the model predicts, and experiments confirm, that the stiffness optimum of U251 glioma cell migration, morphology and F-actin retrograde flow rate can be shifted to lower stiffness by simultaneous drug inhibition of myosin II motors and integrin-mediated adhesions.

Postoperative acute respiratory distress syndrome development in the thoracic surgery patient.

Acute respiratory distress syndrome (ARDS) in the thoracic surgery patient is a dreaded complication that occurs in 4% to 5% of pneumonectomies. This peculiar syndrome is indistinct from other forms of ARDS yet is associated with an exceedingly higher mortality rate. Current management parallels ARDS treatment of other etiologies.

A picosecond beam-timing system for the OMEGA laser.

A timing system is demonstrated for the OMEGA Laser System that guarantees all 60 beams will arrive on target simultaneously with a root mean square variability of 4 ps. The system relies on placing a scattering sphere at the target position to couple the ultraviolet light from each beam into a single photodetector.

Perioperative management of special populations: the geriatric patient.

Americans over age 65 represent the fastest growing segment of the United States population. As a result, the demographic landscape of America is changing. Knowledge of aged physiology is necessary to construct a risk-benefit analysis tailored for each patient to improve perioperative outcomes and lower the morbidity and mortality rates among the elderly. Benefit estimates should account for a patient's life expectancy and quality of life before and after surgery. With aging, baseline functions of almost every organ system undergo progressive decline resulting in a decreased physiologic reserve and ability to compensate for stress. Pain control, postoperative cognitive dysfunction, end-of-life issues, and realistic expectations after surgery are paramount issues throughout the perioperative period.

Fluosol and oxygen breathing as an adjuvant to radiation therapy in the treatment of locally advanced non-small cell carcinoma of the lung: results of a phase I/II study.

Fluosol, a perfluorcarbon emulsion, has the ability to carry oxygen in solution. In conjunction with oxygen breathing and radiation, Fluosol has been shown in animal models to enhance local tumor control. In September 1985, a Phase I/II Study was instituted to evaluate the effect of this adjuvant therapy with radiation in non small cell carcinoma of the luing. Fifty patients were enrolled in the study which was closed for accrual in November 1987. Five patients were withdrawn prior to the institution of radiation: one patient diagnosed with bone metastasis and four patients withdrawn due to mild to moderate reactions to Fluosol. Of the 49 patients administered Fluosol, 34 mild to moderate adverse reactions were noted in 22 patients to either the test dose/infusion (16 reactions including withdrawn patients) or post infusion (18). Flushing, dyspnea and hypertension (test dose/infusion) and chills and/or fever (postinfusion) were the typical symptoms. Transient elevation of blood chemistries (SGOT, SGPT, alkaline phosphatase, BUN) were noted in some patients. Six patients had transient depression of WBC counts (toxicity scores of 1 or 2) and two patients had transient depression of platelets (toxicity score of 1). None of these altered treatment. Forty-five patients received Fluosol of which 34 completed the planned therapy. Six patients were diangosed with metastatic disease during therapy and three patients died of their disease during treatment. One patient was withdrawn due to ineligibility and one patient withdrawn due to moderate reactions to Fluosol during the 3rd and 4th infusions. The total dose of Fluosol was escalated from 42 mL/Kg to 49 mL/Kg in 5, 6, or 7 weekly infusions. Patients breathed 100% oxygen for a minimum of one-half hr prior to and during radiation treatment. Radiation therapy was administered at a daily fraction of 165 to 200 cGy per fraction to a total dose of 5940 to 6800 cGy. Seventeen of 34 patients (50%) achieved a complete response to treatment and 11 patients (32%) had a partial response. Thirteen patients remain alive (range of 12 to 20 months) including 10 of 17 complete responders, 2 of 11 partial responders, and 1 treated with chemotherapy postradiation. The median absolute survival time of the patients completing therapy was 15.5 months and the 12 and 18 month absolute survival rates were 81% and 74%, respectively. The 45 patients starting protocol therapy had a median absolute survival of 9.2 months with a 12-month and 18-month survival of 45% and 35%, respectively.(ABSTRACT TRUNCATED AT 400 WORDS)

Intranuclear inclusions correlate with the ultrastructural detection of herpes-type virions in oral hairy leukoplakia.

Hairy leukoplakia (HL) is an Epstein-Barr virus-associated lesion of the oral mucosa that occurs in persons infected with human immunodeficiency virus. Ultrastructural studies have demonstrated herpes-type virions in 63-100% of cases of HL. In this investigation, incisional biopsy specimens from 52 consecutive patients with oral lesions clinically suspicious for HL were analyzed by light and electron microscopy to determine which light microscopic features correlated best with the presence of herpes-type virions ultrastructurally. The predominant histopathologic features consisted of irregular hyperparakeratosis, acanthosis, koilocytoid cells, and an absence of significant inflammation. Candidal organisms and bacterial colonies were variable findings. Intranuclear inclusions, identical to Cowdry type A inclusions seen in other herpesvirus infections, were observed in 46 cases and demonstrated the best correlation with the presence of virions ultrastructurally (p less than 0.0001). Koilocytoid cells also had a statistically significant correlation with the presence of virions (p less than 0.001). We conclude that Cowdry type A inclusions are present in many cases of HL and that their presence, when combined with the other clinical and histologic findings in these lesions, is the most specific light microscopic feature of HL.

Ultrastructural detection of herpes-type virions by negative staining in oral hairy leukoplakia.

Hairy leukoplakia (HL) is a newly recognized virus-associated lesion of oral mucosa that occurs in persons infected with human immunodeficiency virus. Studies have demonstrated Epstein-Barr virus within epithelial cells of HL. The authors examined 12 cases of HL by transmission electron microscopy to compare the use of a negative staining technique versus routine plastic embedment for the detection of viruses. Herpes-type virions were identified by both methods in 11 cases. One case had negative results for viruses by both methods. Negative staining is a simple and rapid technique that compares favorably with plastic embedment in the detection of herpes-type virions in HL.

Radiation sterilization of surgical instruments with a consideration of metal shielding on sterilization efficiency.

The feasibility of the use of radiation for sterilization of surgical instruments was evaluated. Two aspects were considered: radiation biology of relevant microorganisms, that is, bacterial spores and viruses, and shielding and radiation protection by the metal of the instruments. After proper cleaning and hot water machine washing, surgical instruments carry few, if any contaminants; however, subsequent handling increases the contamination load. Although large instruments may attenuate as much as 30% of the incident radiation, spores dried on the metal are sensitized to irradiation by some 40%. A dose of 25 kGy (2.5 Mrad) is adequate to inactivate a potential contamination load of approximately 10(7) bacterial spores or approximately 10(4) viruses. Therefore, 25 kGy will provide a high sterility assurance level, and can be recommended with a considerable degree of confidence for hospital-based sterilization of surgical instruments.

Fibrolipoma of the gingiva. A case report.

A case of gingival fibrolipoma is described. The lesion presented as a tumor-like mass with a broad base arising from the attached gingiva adjacent to the mandibular left first bicuspid. Microscopic evaluation of the lesion revealed an admixture of mature adipose tissue and fibrous connective tissue. Fibrolipomas are an infrequent variant of lipomas. A review of the literature indicates that a gingival location for such lesions is rare.

Subacute necrotizing sialadenitis: report of 7 cases and a review of the literature.

Subacute necrotizing sialadenitis (SANS) is a nonspecific inflammatory condition of unknown etiology affecting oral minor salivary glands. The lesion is most often characterized by a localized palatal swelling, accompanied by an abrupt onset of pain. In this report, we describe the clinical, microscopic, and ultrastructural features of 7 new cases of SANS and combine them with those of 15 cases previously published in the English language medical literature. Patient ages ranged from 15 to 45 years, with a mean age of 21.9 years. A male to female ratio of 3.4 to 1 was observed, but probably reflects a male sampling bias because 14 of the 22 cases occurred in a military population. Seventeen cases occurred on the hard palate, 4 on the soft palate, and 1 on the tonsillar pillar. The lesions were nonulcerated swellings ranging in size from 0.3 to 2.5 cm in diameter. All lesions except one were painful, and most had been present for a week or less at the time of diagnosis. Histopathologic features included diffuse involvement of minor salivary glands by lymphocytes, histiocytes, neutrophils, and variably by eosinophils. Loss of acinar cells, early acinar cell necrosis, and atrophy of ductal cells were also observed. Although possible viral particles have been reported ultrastructurally in some cases of SANS, none were observed in our study. SANS appears to be a self-limiting process with most cases resolving 2 to 3 weeks after biopsy. SANS has been questioned as an entity by some investigators who prefer to include it within the spectrum of necrotizing sialometaplasia. However, we believe there is justification for the separation of these 2 entities based on clinical and histopathologic parameters. Although the specific etiology of SANS remains unknown, it most likely represents an infectious process or perhaps an immune response to an unknown allergen.

Oncocytoid artifact of the parotid gland: a newly reported artifact.

Electrocautery can induce significant alterations in the connective tissues and epithelium of specimens removed for diagnostic or therapeutic purposes. When electrocautery is used during parotid surgery, it can cause an oncocytoid artifact. The alterations described in this article are enlarged, tightly packed serous acinar cells with coarse to granular eosinophilic cytoplasm, distinct cell borders, and round basal nuclei that on cursory microscopic examination resemble oncocytes with respect to morphology. These changes are seen in conjunction with other, more recognized changes secondary to electrocautery and are believed to occur as a consequence of the electrothermal discharge. On the basis of our findings, this artifact is common is parotid surgical specimens and was misdiagnosed as benign oncocytic lesions in 5 cases.

Ductal papillomas of salivary gland origin: A report of 19 cases and a review of the literature.

The term ductal papilloma is used to identify a group of 3 rare benign papillary salivary gland tumors known as inverted ductal papilloma, sialadenoma papilliferum, and intraductal papilloma. They represent adenomas with unique papillary features and arise from the salivary gland duct system. We describe the clinical and microscopic features of 19 new cases of ductal papillomas and combine them with 116 cases previously published in the English-language medical literature. These 19 cases were composed of 13 inverted ductal papillomas, 3 sialadenoma papilliferums, and 3 intraductal papillomas. Collectively, these 19 ductal papillomas occurred most commonly in the sixth to eighth decade of life, with an average patient age of 54 years. Men predominated 1.37:1. The sialadenoma papilliferums presented as papillary lesions clinically with all 3 misinterpreted as squamous papillomas by the surgeons. The inverted ductal papillomas and intraductal papillomas appeared as submucosal nodules. The lip and the palate were the most common locations for inverted ductal papilloma and sialadenoma papilliferum, respectively. The sites for the 3 intraductal papillomas were the parotid papilla of the Stensen's duct, the upper lip, and the buccal mucosa. With light microscopy, inverted ductal papillomas appeared to arise from the excretory ducts near the mucosal surface, whereas intraductal papillomas appeared to arise from the excretory ducts at a deeper level. Sialadenoma papilliferum had a more complex histology, with a biphasic growth pattern of exophytic papillary and endophytic components. All 19 cases were treated by surgical excision. Follow-up information was available in only 2 cases, both inverted ductal papillomas. Neither case recurred during a 20-year period. Sialadenoma papilliferum, with a literature-derived recurrence rate of 10% to 15%, seems to assert a more significant biological behavior than inverted ductal papilloma and intraductal papilloma. Our findings justify the separation of these 3 entities based on clinical and histologic parameters. They are tumors of adulthood and, in addition, have in common their relationship to the excretory duct system, their anatomical distribution, and their general behavior.