Laser welding in the dental laboratory: an alternative to soldering

Only recently has laser welding been applied to dental technology, primarily as an alternative to soldering. This article addresses how the laser is used for welding, the effect welding has on metals as the energy is converted into heat and reacts with the alloy's surface and the practicality of laser welding in the dental laboratory. A step-by-step procedure for accomplishing laser-welded connections in a fixed partial denture is included. A laser-welded clasp repair using wrought wire and the addition of custom cast parts welded to an existing removable partial denture framework on the master model are also shown.     

Antimyeloperoxidase-associated proliferative glomerulonephritis: an animal model

To develop an animal model for antimyeloperoxidase (MPO)-associated necrotizing crescentic glomerulonephritis (NCGN), we immunized Brown Norway rats with MPO and localized a neutrophil lysosomal enzyme extract, primarily consisting of MPO and elastinolytic enzymes, plus H2O2, the substrate of MPO, to the glomerular basement membrane (GBM). Upon immunization rats developed antibodies and positive skin tests to MPO. After unilateral perfusion of the left kidney with the lysosomal enzyme extract and H2O2, MPO and immunoglobulin (Ig)G localized transiently along the GMB. At the time of maximal inflammation, at 4 and 10 d after perfusion, MPO, IgG, and C3 could not be detected anymore. MPO-immunized rats perfused with the lysosomal enzyme extract and H2O2, in contrast to control-immunized and/or control-perfused rats, developed a proliferative GN characterized by intra- and extracapillary cell proliferation, ruptured Bowman's capsule, periglomerular granulomatous inflammation, and formation of giant cells. Monocytes, polymorphonuclear leukocytes (PMN), and to a far lesser extent T cells were found in the glomeruli. Interstitial infiltrates consisted of monocytes, PMN, and T cells. Granulomatous vasculitis of small vessels was found at 10 d after perfusion. The proliferative NCGN in this rat model closely resembles human anti-MPO-associated pauci-immune NCGN, and enables the study of the pathophysiology of anti-MPO-associated NCGN.     

Neurogenically mediated cystitis in rats: an animal model

PURPOSE: Pseudorabies virus (PRV) is a useful tool for mapping the control circuitry of the spinal cord. In the process of mapping CNS regulatory pathways for the lower urinary tract, a hemorrhagic change in the bladder was observed that was not overtly evident in other pelvic organs. The relationship between the appearance of hemorrhagic changes in the bladder and the evolution of PRV induced changes in the spinal cord was therefore explored. MATERIALS AND METHODS: Sprague-Dawley rats were injected with PRV into the ACD tail-muscle. Bladder and CNS fixation were achieved by transcardial perfusion with formaldehyde. Multi-level sections were obtained from T8 through S4. Fixed tissue was stained and evaluated by light microscopy. Immunohistochemical stains were carried out for PRV and iNOS on spinal cord tissue. We were therefore able to evaluate the relationship between the manifestation of the hemorrhagic cystitis, appearance of the PRV in the spinal cord and evidence of CNS inflammation. RESULTS: The evolution of hemorrhagic cystitis paralleled the evidence of inflammation in the thoraco-lumbar and sacral cord. These bladders contained 5 to 9 ml. of bloody urine (a normal rat bladder contains 1 to 2 ml.). On cystomanometry (CMG) the bladders were acontractile. No PRV could be cultured in the hemorrhagic bladders. The histological changes observed in the bladder represent true inflammation. CONCLUSION: There was no obvious explanation for these changes other than the associated inflammatory changes in the spinal cord. The findings are consistent with the hypothesis that a spinal cord stress, via an unknown metabolic pathway, can result in dramatic, neurogenically mediated changes in the bladder.     

Metachromatic leukodystrophy: molecular genetics and an animal model

Metachromatic leukodystrophy (MLD) is a lysosomal storage disorder caused by the deficiency of arylsulphatase A (ASA; EC 3.1.6.8). Deficiency of this enzyme causes intralysosomal storage of the sphingolipid cerebroside sulphate. This lipid is abundant in myelin and it may thus not be surprising that storage mainly affects oligodendrocytes. Patients suffer from a progressive demyelination causing various neurological symptoms. The disease is fatal and treatment is not available. The human ASA gene has been cloned and more than 40 mutations have been analysed that cause metachromatic leukodystrophy. Few of these alleles are frequent among patients, whereas most mutant alleles have only been found in single families. Since MLD has only been described in humans and no naturally occurring animal model has been described, ASA-deficient mice have been generated by homologous recombination. The ASA knockout mice are unable to degrade sulphatide and store the lipid intralysosomally. The pattern of lipid storage in neuronal and non-neuronal tissues resembles that described for patients. In the nervous system, lipid storage is found in oligodendrocytes, astrocytes and some neurons. Animals display an astrogliosis and a decreased average axonal diameter. Purkinje cells and Bergmann glia of the cerebellum are morphologically aberrant. Demyelination is seen in the acoustic ganglion and occurs between the ages of 6 and 12 months. The animals are deaf at this age and display various neuromotor abnormalities. However, compared to humans the mice have a surprisingly mild phenotype, since they have a normal life span and do not develop widespread demyelination. ASA-deficient mice have been transplanted with bone marrow, which was transduced with a retroviral vector expressing arylsulphatase A. The majority of transplanted animals display sustained expression of arylsulphatase A from the retroviral construct up to 5 months after transplantation. However, preliminary data suggest that this therapeutic approach does not reduce storage material.     

无头轧制技术及其潜在的经济效益

无头轧制工艺由于可消除传统轧制工艺中钢坯间的时间间隔、剔除轧件的切头去尾等工序，因而，近几年在国内外钢铁企业得到了应用。本文介绍了无头轧制的概念，比较了无头轧制工艺和传统轧制工艺的特点，分析了无头轧制工艺潜在的经济效益。     

Effects of cytokine application on glucocorticoid secretion in an animal model for systemic scleroderma

We previously reported on an altered immune-endocrine feedback loop via the hypothalamo-pituitary-adrenal (HPA) axis in Obese strain (OS) chickens afflicted with spontaneous autoimmune thyroiditis. These animals are deficient in plasma corticosterone increase after antigenic challenge or application of cytokine-containing conditioned medium of mitogen-stimulated spleen cells (CM). To investigate whether the impaired ability to respond to cytokines with glucocorticoid-increasing factor (GIF) activity, e.g. interleukin 1 (IL 1), is restricted to OS chickens as a model for an organ-specific autoimmune disease, we extended our experiments to another autoimmune-prone animal strain, the chickens of the University of California at Davis line 200 (UCD-200). These animals develop an inherited inflammatory fibrotic disease that closely resembles human progressive systemic sclerosis (scleroderma). Application of GIF-containing CM to UCD-200 chickens leads to a transient increase in glucocorticoid serum levels within 1-2 hours comparable to that of controls. But, while corticosterone levels in the latter returned to normal baseline levels after 4 hours, they were still elevated in autoimmune chickens. Although the peak of the glucocorticoid hormone serum concentrations was equal to that of controls, UCD-200 had to secrete twice as much adrenocorticotropic hormone to achieve this corticosterone serum level due to an apparent hyporesponsiveness of the adrenal gland to this secretagogue. The altered cytokine-induced glucocorticoid secretion is found in early as well as in chronic, sclerotic stages of the disease. Cellular alterations in the peripheral blood of UCD-200 chickens during the prolonged elevated corticosterone section, i.e. between 2-4 hours after CM application, are characterized by a significant decrease in the percentage of CD4+ and CD8+ cells. Furthermore, a significant increase in B cells up to 24 hours with a maximum after 1 hour was found. The proliferative response to the mitogen concanavalin A of peripheral mononuclear cells was inversely correlated to the serum corticosterone level, showing a permanent decrease of 80-90% after 1-4 hours in autoimmune animals. This functional alteration in UCD-200 was accompanied by an 80% decrease in serum interleukin 2 (sIL 2) activity 4 hours after CM application. Twenty-four hours later an eight-fold increase in sIL 2 rebound activity was found, indicating that the inhibitory effect of corticosterone in UCD-200 chickens is not long-lasting.     

Transcatheter liver lobar ablation: an experimental trial in an animal model

Complete embolization of tumor tissue together with surrounding liver sufficiently prevents collateral blood supply to the tumor, offering curative treatment for hepatic malignancies. The present experiment was designed to test the feasibility of hepatic lobar ablation by means of the transcatheter chemoembolization technique. Five groups of rats (n = 6) were treated with a mixture of iodized oil/ethanol in ratios of 5:1, 4:1, 3:1, 1:1, and 1:0, which was injected selectively into the right-lobe artery until saturation during open surgery. Another group (n = 6) was studied using in vivo microscopy to observe the distribution of the mixture in the liver and changes in hepatic microcirculation. Ethiodol/ethanol mixture entered the portal vein after injection into the hepatic artery creating dual, complete arterial and portal venous embolization. Lobar ablation effects were achieved in 2 weeks in the 5:1, 4:1, and 3:1 ratio groups, indicated by the lobe/liver weight measurements (p < 0.001 vs normal liver). Hepatic arterial administration of the Ethiodol/ethanol mixture creates dual hepatic arterial and portal venous embolization, achieving a lobar ablation effect.     

Periosteal migration in the growing mandible: an animal model

Migration of mandibular periosteum and attached musculature was tracked along the inferior border of the ramus in growing and nongrowing guinea pigs (Cavia porcellus) over a 6-week period. Particulate metallic growth-tracing implants were placed through the bony mandible and adjacent musculature at two anteroposterior locations and two bony reference markers were placed anteriorly. Quantification from weekly radiographs of growing animals showed marked posterior migration of the periosteum, whereas in nongrowing animals there was negligible periosteum movement. Significantly greater migration occurred in posterior (6.37 +/- 0.76 mm) implants relative to the anterior implants (3.45 +/- 0.86 mm, p < 0.001). The neutral zone, where little periosteal migration occurs, was calculated to be approximately at the anteroposterior center of the molar tooth row. Analysis of the orientation of the medial pterygoid muscle relative to the mandible showed that muscle fibers on average become more horizontal. Thus, the study found differential anteroposterior migration of the mandibular periosteum in growing animals and correlative changes in orientation of the medial pterygoid muscle.     

Building up of an animal model of conditioned immunosuppression and analysis of its possible mechanism

In the present study, camphor odor and intraperitoneal (ip) injection of cyclophosphamide (CY) were used as conditional and unconditional stimulus, respectively, in mice. Mice were exposed to camphor odor for 1 h in their cage in a closed area followed by an ip injection of CY (75 mg.kg-1). This association trial session was repeated once on the next day. Delayed type hypersensitivity response (DTH) was induced as follows: six days after the second association trial session the mice were sensitized by smearing dinitrochlorobenezene (DNCB) on their abdominal skin. The mice were challenged by smearing DNCB on the left ear 5 days after the antigen sensitization. The left and right ears were removed 24 h after the challenge and weighed, the weight ratio of left/right ears was calculated for identification of the response. The ratio was 1.30 +/- 0.113 (+/- s, P < 0.001), indicating that the challenged ear was heavier than the other and DTH was induced. In the unconditioned response (UCR) group, CY (75 mg.kg-1) was given 24 h prior to the challenge and the ratio was 1.09 +/- 0.024 (P < 0.001) indicating that DTH was suppressed by unconditional stimulus (CY). In the conditioned response (CR) group mice were reexposed to camphor odor 24 h prior to the challenge and normal saline was injected instead of CY. The ratio was 1.13 +/- 0.074 (P < 0.001), indicating that DTH was also suppressed by conditional stimulus (camphor odor). These results show that a conditioned immunosuppressive response was induced. In the experiment, many other groups, including unconditioned response group, CYE group and camphor control group, were described in more details in the text. In order to further analyse the mechanisms of the conditioned response, the blood from the mice in CR group was obtained 6 h after reexposure to camphor odor and the serum was injected to normal mice 6 h prior to the challenge. DTH was found to be suppressed significantly when compared with the mice injected with normal serum. The conditioned serum was dialyzed against a membrane with a 10,000 molecular weight cut off. The suppressive activity of the conditioned serum disappeared, suggesting that the molecular weight of the suppressive element in the serum was probably less than 10,000 kDa.     

alpha-Cell neogenesis in an animal model of IDDM

Currently there is debate regarding the capacity of pancreatic islets to regenerate in adult animals. Because pancreatic endocrine cells are thought to arise from duct cells, we examined the pancreatic ductal epithelium of the diabetic NOD mouse for evidence of islet neogenesis. We have evidence of duct proliferation as well as ductal cell differentiation, as suggested by bromodeoxyuridine-labeling and the presence of glucagon-containing cells within these ducts. In addition, the ductal epithelia in diabetic NOD mice expressed the neuroendocrine markers neuropeptide Y and tyrosine hydroxylase. These ducts also expressed the homeobox gene product, insulin promoter factor 1. Ductal cell proliferation and expression of these markers was not observed in transgenic NOD mice (NOD-E), which do not develop clinical or histopathological symptoms of IDDM. This suggests that the observed ductal cell proliferation and differentiation was a direct result of beta-cell destruction and insulin insufficiency in these adult diabetic mice, which further suggests that these events are recapitulating islet ontogeny observed during embryogenesis. It is possible that comparable processes occur in the human diabetic pancreas.     

Novelty seeking and drug use: Contribution of an animal model.

Although sensation seeking or novelty seeking is a reliable predictor of drug use in humans, individual differences in free-choice novelty seeking in animal models have generally failed to predict drug use. In the current article, hierarchical multiple regression analyses were used on data collected from a large sample of rats. Rats were screened on measures of inescapable and free-choice novelty tests and then were trained to lever press for sucrose or intravenous amphetamine. Although scores from the inescapable novelty test weakly predicted responding for amphetamine, the addition of free-choice novelty preference scores into the regression analyses significantly improved the predictive models. These results indicate that, similar to evidence in humans, individual differences in novelty seeking may be able to predict drug use in rats. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Different behaviour of radioiodinated human recombinant interleukin-1 and its receptor antagonist in an animal model of infection

Recently, we demonstrated that radiolabelled interleukin-1alpha (IL-1) specifically accumulates in focal infection in mice through interaction with its receptor. Unfortunately, systemic side-effects of IL-1 limit its clinical application. We investigated whether this problem could be circumvented by using the interleukin-1 receptor antagonist (IL-1ra), an equally sized protein that binds to the same receptors as IL-1 without induction of biological effects. Biodistribution of 125I-IL-1 and 125I-IL-1ra was determined in Swiss mice with Staphylococcus aureus-induced abscesses in the left calf muscle at 4, 12, 24 and 48 h after injection of either 0.4 MBq 125I-IL-1 or 0.4 MBq 125I-IL-1ra. In vitro, the proteins displayed similar binding characteristics. High-performance liquid chromatographic analysis revealed a tendency for IL-1ra to associate with serum proteins. Both proteins rapidly cleared from most organs. However, the abscess uptake of 125I-IL-1ra was significantly lower than that of 125I-IL-1 at all time points (48 h p.i.: 0.06+/-0. 01%ID/g vs 0.60+/-0.04%ID/g; P<0.02). The abscess-to-contralateral muscle ratios did not exceed 15.5+/-2.9 for 125I-IL-1ra, while the ratios for 125I-IL-1 reached 46.9+/-5.7 at 48 h p.i. Despite similar in vitro receptor binding, the abscess uptake of IL-1ra was much lower than that of IL-1. The interaction of IL-1ra with serum proteins in vivo may reduce its availability for receptor binding in the infection. Although on theoretical grounds IL-1ra is very interesting, these characteristics will prevent its development as a clinically useful radiopharmaceutical to image infection.     

Bovine hereditary cardiomyopathy: an animal model of human dilated cardiomyopathy

Bovine hereditary cardiomyopathy (bCMP) displays clinical characteristics of human idiopathic dilated cardiomyopathy (DCM). We studied isometric force of contraction in right ventricular trabeculae, plasma and tissue catecholamines, beta- and alpha 1-adrenoceptor density, Gi proteins and adenylyl cyclase activity in eight hearts with bCMP and eight control hearts (right and left atria and ventricles each). Results: Compared to control, the potency of isoprenaline in bCMP was eight-fold decreased, whereas the maximal positive inotropic effect of isoprenaline as well as the efficacy and potency of calcium were unchanged. Plasma noradrenaline was increased by 240%. Tissue noradrenaline and adrenaline were decreased by 36-63% and 58-69%, whereas dopamine was increased by 105-218%. beta-adrenoceptor density was drastically reduced by 90%, but binding affinity was unchanged. alpha-Adrenoceptor density and binding affinity were unchanged. Total PTX-substrates were increased in bCMP by 28-99%. Basal adenylyl cyclase activity was decreased by 36-47%. Similarly, stimulation by GTP, GMPPNP, isoprenaline, sodium fluoride, manganese or forskolin was attenuated by 26-62% (atria) and 45-66% (ventricles). In conclusion, we found marked activation of the sympatho-adrenergic system, downregulation of beta-adrenoceptors, upregulation of Gi proteins, global desensitization of adenylyl cyclase and selective subsensitivity to beta-adrenergic inotropic stimulation. These results closely resemble the characteristic alterations in the beta-adrenoceptor-G protein-adenylyl cyclase pathway in human heart failure, indicating that they are general features of heart failure. The similarity to human DCM, the inheritance and the availability of large tissue samples make bCMP a suitable model for human DCM.     

铸铁件激光再制造技术及其应用

铸铁件再制造包含缺陷挽救和铸件改性.在制造业中铸铁件使用量远大于铸钢件;在铸件实际生产中,铸铁件的缺陷远多于铸钢件;传统工艺未能充份发挥铸铁件性能.铸铁件激光再制造技术既有技术意义,更有市场意义.     

大气扩散模式及其应用

在进行环境质量评价时,一般都用大气扩散模式进行预测,本文分析了影响大气扩散的气象因子,讨论了高斯模式在其基本条件发生变化时的修正方法并在实际工作中进行应用。     

Characterization of an animal model of ventilator-acquired pneumonia

To develop an experimental model of ventilator-acquired pneumonia (VAP), we investigated whether healthy piglets could develop endogenously acquired pulmonary infection as a result of prolonged mechanical ventilation (MV). Thirty-three piglets underwent MV with anesthesia, analgesia, and paralysis produced by continuous infusion of midazolam, fentanyl, and pancuronium bromide. Ten animals received antibioprophylaxis with ceftriaxone (ATB group) and 23 received no antibiotics (control group). Eighteen control animals and 9 ceftriaxone-treated animals completed the 4-day study protocol. The presence of pneumonia on day 4 was ascertained by multiple pulmonary biopsy specimens, processed for microscopic examination and quantitative cultures. The anesthetic regimen provided satisfactory electrolyte balance and cardiovascular stability. Under these circumstances, 17 of 18 animals and 4 of 9 animals developed VAP in the control and the ATB groups, respectively. Lesions of different grades of severity were unevenly distributed through both lungs with a predominance and a higher severity in dependent lung segments. Noninfectious lesions frequently associated with VAP in humans were not observed. Pneumonia was usually polymicrobial with a predominance of Gram-negative organisms. Most of the causative organisms originated from the oropharynx. Histologic lesions and lung bacterial concentrations were less in the ATB group than in control animals. We then investigated the effects of intrabronchial challenge with bacterial pathogens in the absence of MV. Intrabronchial bacterial inoculation resulted in the development of pneumonia that spontaneously resolved even when using very highly titrated inocula. Therefore, MV seems to be the main predisposing factor in the development of pneumonia in this model. This model that resembles human VAP in its histologic, bacteriologic, and pathogenic aspects may be useful to further study pathogenesis, diagnosis, prevention, and therapy of VAP.     

Etiological role of cadmium in hypertension in an animal model

Dahl hypertension-resistant (R) and hypertension-sensitive (S) lines of rats were used to determine whether cadmium plays an etiological role in hypertension. In Study I, weanling (3-week-old) R and S rats of both sexes were given a low-salt (0.4% NaCl) diet and were divided into two groups. Rats in the cadmium group were injected with cadmium (2 mg/kg body weight, ip), whereas the controls received identical volumes of saline. Three weeks after the first injection, no elevations of systolic blood pressure were detected. A second dose of cadmium (1 mg/kg) produced hypertension in S females but not in S males or in R rats of either sex. Also, female S cadmium rats manifested significant (p less than 0.01) mild to moderate renal vascular changes. The concentrations of cadmium in hepatic and renal tissues of S cadmium rats were significantly higher (p less than 0.001) than in R rats. In Study II, weanling (3-week-old) female S rats on a high-salt (4% NaCl) diet were given cadmium (2 mg/kg body weight, ip) at week 3 followed by second and third injections of cadmium (1 mg/kg) at weeks 6 and 23. S controls received the same volumes of saline. Cadmium enhanced the rate and the degree of salt-induced hypertension development. Pathological lesions of periarteritis nodosa in the mesenteric arteries and renal vascular lesions occurred to the same extent in the cadmium and control groups. These data indicate that differences in genetic background influence the development of cadmium-induced hypertension in weanling rats, and that cadmium exacerbates the severity of salt-induced hypertension.     

连退机组焊机焊缝厚度预报模型及其影响因素

针对以往现场对焊接工艺的研究偏重于焊接电流、焊接热量的计算以及焊接原理的分析,而对焊缝厚度方面的研究则偏少,造成了焊缝质量控制不利的问题.在充分考虑了连退焊接机组的设备与工艺特点后,对焊缝厚度与搭接量、碾压轮压力、焊接电流、焊轮压力以及焊接速度等焊接工艺参数之间关系进行了分析,并建立了一套适合于连退焊接机组的焊缝厚度预...