TAG-1 can mediate homophilic binding, but neurite outgrowth on TAG-1 requires an L1-like molecule and beta 1 integrins

Subsets of axons in the embryonic nervous system transiently express the glycoprotein TAG-1, a member of the subfamily of immunoglobulin (Ig)-like proteins that contain both C2 class Ig and fibronectin type III domains. TAG-1 is attached to the cell surface by a glycosylphosphatidylinositol linkage and is secreted by neurons. In vitro studies have shown that substrate-bound TAG-1 promotes neurite outgrowth. We have examined the nature of axonal receptors that mediate the neurite-outgrowth promoting properties of TAG-1. Although TAG-1 can mediate homophilic binding, neurite outgrowth on a substrate of TAG-1 does not depend on the presence of TAG-1 on the axonal surface. Instead, neurite outgrowth on TAG-1 is inhibited by polyclonal antibodies directed against L1 and, independently, by polyclonal and monoclonal antibodies against beta 1-containing integrins. These results provide evidence that TAG-1 can interact with cell surfaces in both a homophilic and heterophilic manner and suggest that neurite extension on TAG-1 requires the function of both integrins and an L1-like molecule.     

Induction of superoxide dismutase isozymes by tumor necrosis factor-alpha and lipopolysaccharide in cultured normal and hyperplastic gingival fibroblasts

We studied 722 reexcision scars of benign and malignant lesions (except melanocytic lesions) excised over a 24-month period. The formalin-fixed, paraffin-embedded tissue sections were examined histologically and immunohistochemically. The histological features of melanocytic hyperplasia were present in 59 cases (8%), 56 from the sun-exposed skin of the face and neck and three from the trunk [p < 0.00001]. The most common sites were the nose and lower eyelids, but the forehead was also frequently involved. Of the 59 patients, 41 were women (p < 0.0001). Basal cell carcinoma was the most frequent original lesion in both sexes (80%). No melanocytic hyperplasia was found in 663 cases (298 on the trunk and extremities and 365 on the head and neck). We have seen this reaction pattern following reexcision of melanocytic lesions as well. Thus, interpreting reexcision margins when lentigo maligna or similar lesions are reexcised may be fraught with difficulty. It is important for pathologists and dermatopathologists to recognize this phenomenon because histologically the presence of increased numbers of large melanocytes could be misinterpreted as melanoma in situ.     

Diffusion of monomers from bonding resin-resin composite combinations through dentine in vitro

OBJECTIVES: Previous work has demonstrated diffusion of the monomer triethylene glycol dimethacrylate (TEGDMA) from resin composite through dentine in vitro. The objective of the present work was to examine monomer diffusion from bonding resins and resin composites used in combination. METHODS: Occlusal cavities were prepared in tooth crowns and restored with bonding resin-resin composite combinations. Aqueous samples from the 'pulpal chamber' of each tooth were removed at timed intervals for analysis by reversed phase-high performance liquid chromatography and mass spectrometry. RESULTS: Bonding resins contributed to monomer diffusion. A TEDGMA-containing bonding resin used in combination with a TEGDMA-containing resin composite hastened and increased TEGDMA diffusion through dentine. A 2-hydroxyethyl methacrylate (HEMA)-containing bonding resin used in combination with a TEGDMA-containing resin composite reduced TEGDMA diffusion only slightly compared with the resin composite alone and added substantial diffusion of HEMA. CONCLUSION: The bonding resins tested contributed to monomer passage to the pulp space and did not prevent movement of monomer from resin composites to the pulp.     

Symptomatic recurrent carotid stenosis and aneurysmal degeneration after endarterectomy

BACKGROUND: Aneurysmal degeneration of a carotid reconstruction was not recognized until the patient, who was known to have recurrent carotid artery stenosis, had a thromboembolic stroke. This sequelae of carotid endarterectomy is a serious complication, associated with a high morbidity and mortality rate. This review was conducted to establish the risk of transient ischemic attack and stroke for patients found to have recurrent carotid stenosis associated with aneurysmal degeneration of the carotid artery after endarterectomy. METHODS: A case is reported, and 100 literature references of aneurysmal degeneration of the carotid artery after endarterectomy were reviewed. RESULTS: False aneurysm from anastomotic disruption was the most common presentation identified in the cases reviewed. Nineteen of the patients had a significant neurologic event; however, three (50%) of six patients with aneurysm and recurrent carotid artery stenosis had a transient ischemic attack or stroke. CONCLUSIONS: The incidence of neurologic symptoms is markedly increased when recurrent carotid artery stenosis is associated with carotid aneurysm. During postoperative surveillance after endarterectomy, the identification of recurrent carotid artery stenosis requires evaluation for aneurysmal degeneration of the carotid artery with duplex scanning. These patients are at significant risk for transient ischemic attack and stroke. This rare complication merits operative repair.     

Cytotoxicity of polycyclic aromatic hydrocarbon o-quinones in rat and human hepatoma cells

A novel pathway of polycyclic aromatic hydrocarbon (PAH) metabolism involves the oxidation of non-K-region trans-dihydrodiols by dihydrodiol dehydrogenase (DD) to yield PAH o-quinones whose cytotoxicity and genotoxicity are unknown. The cytotoxicity of several PAH o-quinones derived from this reaction [naphthalene-1,2-dione (NPQ), benzo[a]pyrene-7,8-dione (BPQ), and 7,12-dimethylbenz[a]anthracene-3,4-dione (DMBAQ)] was examined in rat (H-4IIe) and human (Hep-G2) hepatoma cells which are known to express DD. 2-Methylnaphthalene-1,4-dione (menadione), a known cytotoxic p-quinone, was used as a positive control. Hepatoma cells (1 x 10(6) cells/mL) were exposed to PAH o-quinones (1-100 microM) for 0-4 h, and cell viability and survival were measured and related to O2.- production and changes in redox potential [GSSG/GSH and NAD(P)+/NAD(P)H]. Three different modes of cytotoxicity were observed: (1) NPQ (no bay region) and DMBAQ (methylated bay region) were as cytotoxic as menadione in reducing cell survival but had less effect on cell viability. These o-quinones adversely affected GSH levels and the redox state of the cell and caused an increase in the production of O2.- in cell suspensions. This cytotoxicity was not enhanced by dicoumarol (10 microM), a DT-diaphorase inhibitor, implying that this enzyme is unable to prevent these PAH o-quinones from entering one-electron redox-cycles. (2) BPQ (bay region only) was the least cytotoxic of the PAH o-quinones studied. BPQ decreased cell viability (< 40% at 20 microM) but did not adversely affect cell survival or the redox state of the cell.(ABSTRACT TRUNCATED AT 250 WORDS)     

Lactate clearance and survival following injury

Previous reports cite optimization of O2 delivery (DO2) to 660 mL/min/m2, O2 consumption (VO2) to 170 mL/min/m2, and cardiac index (CI) of 4.5 L/min as predicting survival. We prospectively evaluated 76 consecutive patients with multiple trauma admitted directly to the ICU from the operating room or emergency department. Patients had serum lactate levels and oxygen transport measured on ICU admission and at 8, 16, 24, 36, and 48 hours. Patients were analyzed with respect to survival (S) versus nonsurvival (NS), lactate clearance to normal (< or = 2 mmol/L) by 24 and 48 hours, hemodynamic optimization as defined above, as well as Injury Severity Score (ISS), ICU stay (LOS), and admission blood pressure. All patients achieved non-flow-dependent VO2. There was no difference in CI, DO2, VO2, or ISS when S was compared with NS. All 27 patients whose lactate level normalized in 24 hours survived. If lactate levels cleared to normal between 24 and 48 hours, the survival rate was 75%. Only 3 of the 22 patients who did not clear their lactate level to normal by 48 hours survived. Ten of the 25 nonsurvivors (40%) achieved the above arbitrary optimization criteria. Fifteen of the survivors never achieved any of these criteria. Optimization alone does not predict survival. However, the time needed to normalize serum lactate levels is an important prognostic factor for survival in severely injured patients.     

分子结构对增塑聚氯乙烯性能的影响

研究了聚合度、分子量分布和支化结构对增塑聚氯乙烯加工流变性能和物理力学性能的影响。结果表明，增塑ＰＶＣ的加工流变性能随聚合度的增加而恶化；拓宽分子量分布和引入支化结构均有利于加工流变性能的提高；增塑ＰＶＣ的拉伸强度随聚合度的增加而提高，而压缩永久变形却随之减小；分子量分布对物理力学性能的影响不大；支化ＰＶＣ的拉伸强度略有下降。     

ATM局域网仿真技术

本文介绍了ＡＴＭ局域网仿真技术并从ＡＴＭ仿真局网的组成、工作原理等方面介绍了这一技术的主要特点。     

Treatment of urinary tract infections

Urinary tract infections (UTIs) are common conditions in clinical practice. For uncomplicated UTIs, the causative organisms and their antimicrobial susceptibility profiles are generally predictable, and empiric short course (3 day) antibiotic therapy after an abbreviated laboratory workup is advocated. Acute pyelonephritis requires a 2 week antibiotic course, often with initial parenteral therapy. Women with frequent recurrences of UTIs may require intermittent self-treatment or continuous or postcoital antibiotic prophylaxis. Catheter-associated UTIs generally only require treatment if the patient shows signs of systemic infection. Treatment of asymptomatic bacteriuria is only recommended in certain circumstances. Careful consideration of the clinical circumstances, the patient's known or predicted urinary tract anatomy, and the antibiotic susceptibility of the bacterial pathogen(s) are critical factors in the choice of appropriate therapy for urinary tract infections.