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We present combined in situ thermal cleaning and intentional doping strategies near the substrate regrowth interface to produce high-quality AlGaN/GaN high electron mobility transistors on semi-insulating (0001) GaN templates with low interfacial impurity concentrations and low buffer leakage. By exposing the GaN templates to an optimized thermal dissociation step in the plasma-assisted molecular beam epitaxy environment, oxygen, carbon, and, to lesser extent, Si impurities were effectively removed from the regrowth interface under preservation of good interface quality. Residual Si was further compensated by C-doped GaN via CBr4 to yield highly resistive GaN buffer layers. Improved N-rich growth conditions at high growth temperatures were then utilized for subsequent growth of the AlGaN/GaN device structure, yielding smooth surface morphologies and low residual oxygen concentration with large insensitivity to the (Al+Ga)N flux ratio. Room temperature electron mobilities of the two-dimensional electron gas at the AlGaN/GaN interface exceeded >1750 cm2/V s and the dc drain current reached ∼1.1 A/mm at a +1 V bias, demonstrating the effectiveness of the applied methods. [ABSTRACT FROM AUTHOR]

In this paper, we outline the forward problem of metrical variation due to the Casimir effect in transitioning superconducting shells. We consider a massless scalar quantum field inside a hollow superconducting sphere and a cylinder. Metric equations are developed describing the evolution of the scale factors after the superconducting shells transition to the normal state. [ABSTRACT FROM AUTHOR]

Intraoperative MR imaging techniques have the potential to greatly improve the stereotactic methods used for functional neurosurgery. No longer are neurosurgeons and patients always constrained by uncomfortable head frames and conventional stereotaxy. Accuracy and complication avoidance are improved by intraoperative imaging. Safety of operative machinery and equipment in an MR imaging operative suite is attainable, even with deep brain stimulating electrodes in depth electrodes for epilepsy. Although cost-effectiveness remains to be determined (see article by Kucharczyk et al in this issue), the minor inconveniences of operating within an iMRI environment seem to be significantly outweighed by the benefits.

Objective: Intracranial aneurysm rupture during placement of Guglielmi detachable coils has been reported, but the management and consequences of this event have not been extensively described. We present our experience with this feared complication and report possible neuroradiological and neurosurgical interventions to improve outcomes., Methods: We retrospectively reviewed the records for 701 patients with 734 intracranial aneurysms that were treated with endovascular coiling, during a 6-year period, in the metropolitan Minneapolis-St. Paul (Minnesota) area. This analysis revealed 10 cases of perforation during coiling. The management and outcomes were recorded, and the pertinent literature was reviewed., Results: All 10 cases involved previously ruptured aneurysms. This complication occurred sporadically and was not observed in the first 100 cases. Perforation occurred during microcatheterization of the aneurysm in two cases and during coil deposition in eight cases. Seven of the perforated aneurysms were located in the anterior circulation and three in the posterior circulation. Six of the 10 patients made good or fair recoveries; all three patients with posterior circulation lesions died immediately after rehemorrhage. Elevated intracranial pressure (ICP) was noted for all five patients with intraventricular catheters in place. Bilateral pupil dilation and profound hemodynamic changes were noted for eight patients. Coiling was rapidly completed, and total or nearly total occlusion was achieved in all cases. Emergency ventriculostomy was performed to rapidly reduce increased ICP for two patients, both of whom made good recoveries. Hemodynamic and angiographic factors after perforation, such as prolonged systemic hypertension, persistent dye extravasation after deployment of the first Guglielmi detachable coil, and persistent prolongation of contrast dye transit time (suggesting ongoing ICP elevation), were correlated with poor outcomes., Conclusion: Previously ruptured aneurysms seem to be more susceptible to endovascular treatment-related perforation than are unruptured lesions. Worse prognoses are associated with iatrogenic rupture during coiling of posterior circulation lesions, compared with those in the anterior circulation. When perforation is recognized, the definitive treatment seems to be reversal of anticoagulation therapy and completion of Guglielmi detachable coil embolization. Immediate neurosurgical intervention is limited in these cases and focuses on decreasing ICP via emergency ventriculostomy. However, these measures may be life-saving, and neurosurgical assistance must be readily available during treatment of these cases.

Canine transmissible venereal tumor (CTVT) grows progressively (P-phase) in the host and then spontaneously regresses (R-phase). The mechanisms behind the transition from the P-to R-phases are not well understood. In this study, in order to determine the proliferation characteristics of CTVT, we evaluated telomerase activity and enumerated nuclear organizing regions (AgNOR) and proliferating cell nuclear antigen (PCNA). It was found that CTVT cells from the P-and R-phases were both positive for telomerase activity, although it was lower in the R-phase. Evaluations of telomerase activity should take into account the stage of mitosis. Although, in the majority of cases, telomerase activity can be used to differentiate between benign and malignant tumors in dogs, other factors or markers should also be used to obtain accurate diagnoses. The PCNA-positive rate and the number and area of AgNOR per cell increased much more in the P-phase than the R-phase. However, the AgNOR values were always higher. Thus, the AgNOR count can be used to distinguish the P-and R-phases of CTVT. In addition, mitotic figures were much higher in number in the P-phase as compared to the R-phase. We believe that, during spontaneous regression of CTVT cells, slow tumor cell proliferation must contribute to the decrease in tumor size. However, shortening of tumor cell telomeres is not directly involved in this process. Other factors, such as expression of MHC antigens on CTVT cells, humoral immunity, cytokines released by the inflammatory cells and, especially, tumor infiltrating lymphocytes may contribute to CTVT regression.

High-field strength iMRI guidance is an effective tool for brain tumor resection. Although its use lengthens the average time for a craniotomy, the reward is a more extensive tumor excision compared with conventional neurosurgery without an increased risk to the patient (Table 4). Although intraoperative patient transfer into and out of the magnet is cumbersome, the possibility for complete resection, especially for a low-grade glioma, makes the effort worthwhile. The cost and technical support required for this system presently limits its use to only a few sites worldwide. As with any technology, further refinements will make this system less expensive and more attainable. Practical consideration aside, high-field strength iMRI is presently [table: see text] the most effective tool available for brain tumor resection. Because of its novelty, future studies are necessary to determine if this technology lowers the incidence of and extends the duration to tumor recurrence as the preliminary data in children suggests. These are the ultimate measures of efficacy for any brain tumor treatment. Based on the rapid advancement of technology, will today's high-field strength interventional magnet become tomorrow's low-field system? Very high-field strength designs may improve diagnostic capabilities through higher resolution, but their interventional applications may be hindered by increased sensitivity for clinically insignificant abnormalities and decreased specificity for clinically relevant lesions. As new technology is developed, clinicians must continue to explore and refine the existing high-field strength iMRI to make it cost-effective and widely applicable.

Objective and Importance: Except for its role in shunt infections, Propionibacterium acnes has been of little interest to neurosurgeons. The rarity and indolent nature of focal intracranial infections by P. acnes limit their recognition. Three cases of serious intracranial infection due to this organism are described. CLINCAL PRESENTATION: Three patients with histories of immunosuppression and neurosurgical procedures developed nonspecific, delayed presentations (5 wk to 5 yr after surgery) of intracranial infections. In two patients, radiological investigations showed enhancing lesions that were later found to be brain abscesses. A subdural empyema was found in the third patient., Intervention: All three patients underwent surgical drainage of the purulent collections. P. acnes was isolated in each case, and each patient was treated with a 6-week course of intravenous penicillin. All three patients made good recoveries, and subsequent imaging showed no recurrence of the infectious collections., Conclusion: P. acnes is an indolent organism that may rarely cause severe intracranial infections. This organism should be suspected when an intracranial purulent collection is discovered in a patient with a history of neurosurgical procedures. Immunosuppressed patients may be susceptible to this otherwise benign organism. Surgical drainage and treatment with intravenous penicillin should be considered standard therapy.

To replace the complex and time-consuming procedure of limb transplantation, we developed a new osteomyocutaneous model that excluded the function but retained all the tissue components of the limb. Ten vascularized grafts from five donor hindlimbs were contralaterally transplanted to 10 syngeneic recipients' inguinal region. The graft of this model is composed of complete tibia and fibula and partial muscle and skin of the crus. The operative time was 145.3 +/- 9.1 minutes with the harvesting time of 49.7 +/- 5.8 minutes and the warm ischemia time of 65.4 +/- 6.0 minutes. The transplantation procedure of this model takes significantly less time and is less stressful to the animals than the previous whole limb transplantation model. This model is suitable for the studies of limb or composite tissue transplantation if functional recovery is not the main concern., (Copyright 2001 Wiley-Liss, Inc.)

Background: Quantifying silver stained nucleolar organizer regions (AgNORs) and proliferation cell nuclear antigens (PCNA) are useful techniques to measure proliferative activity of tumor cells; however, the nonspecific deposition of stains and overlappings of AgNOR and PCNA counts between grades of tumors hamper their applications., Materials and Methods: Fifty-two surgical specimens from dogs, including mast cell tumors, perianal gland tumors and hyperplasias, fibromas, fibrosarcomas, and normal tissues were studied. The 3 microns dewaxed sections of formalin-fixed tissues were stained to detect AgNORs by a modified inverted incubation technique in a newly developed silver staining device. Data were collected and analyzed using a high-resolution digital microscope camera and image analysis software. Sequential sections were also stained for PCNA using an immunohistochemical method., Results: The improved system for quantifying AgNOR provided more accurate and non-overlapping mean AgNOR counts, which enable us to distinguish benign states from malignant changes. The mean AgNOR cut-off points that discriminated grade II or III mast cell tumors from grade I, perianal gland carcinomas from adenomas (or hyperplasia), fibrosarcomas from non-fibrosarcoma tissues, were 6.0, 14.1, 9.4, and 8.8 respectively. The mean AgNOR areas, relative AgNOR areas, and PCNA positive rates of some malignant and non-malignant tissues (benign tumor and normal tissues) were significantly different (P < 0.05)., Conclusions: This improved system is a sensitive and rather precise method for quantifying the AgNOR and PCNA. It provides a valuable objective measurement for differentiating benign and malignant tumors.

The purpose of this study was to conduct a randomized clinical trial to assess whether a self-management group intervention can improve mood, self-efficacy, and activity in people with central vision loss due to age-related macular degeneration (AMD). Ninety-two elderly patients with AMD (average age = 79) from a university ophthalmology clinic were randomly assigned to the self-management intervention (n = 44) or to a wait-list (n = 48). All patients were legally blind in at least one eye. The intervention consisted of 6 weekly 2-hour group sessions providing education about the disease, group discussion, and behavioral and cognitive skills training to address barriers to independence. All participants eventually completed the intervention allowing pre-post comparisons for all patients. The battery of measures included the Profile of Mood States (POMS); Quality of Well-Being Scale; and assessments of self-efficacy, participation in activities, and use of vision aids. Participants' initial psychological distress was high (mean total POMS = 59.72) and similar to distress experienced by other serious chronic illness populations (e.g. cancer, bone marrow transplant). Analysis of covariance testing the primary hypothesis revealed that intervention participants experienced significantly (p = .04) reduced psychological distress (pre mean = 61.45; post mean = 51.14) in comparison with wait-list controls (pre mean = 57.72; post mean = 62.32). Intervention participants also experienced improved (p = .02) self-efficacy (pre mean = 70.16; post mean = 77.27) in comparison with controls (pre mean = 67.71; post mean = 69.07). Further, intervention participants increased their use of vision aids (p < .001; pre mean = 3.37, post mean = 6.69). This study demonstrates that a relatively brief behavioral intervention can substantially reduce psychological distress and increase self-efficacy in elderly adults experiencing vision loss due to macular degeneration. Self-management intervention appears to improve mood, self-efficacy, and use of vision aids, further enhancing the lives of poorly sighted individuals with AMD.

Investigators from eight laboratories analyzed the reactivity of 22 monoclonal antibodies (mAb) against porcine myeloid cells. Based on binding data, clustering analysis and inhibition studies, workshop mAb 74-22-15 (003) and 6F3 (007) were assigned a swine workshop cluster number 3 (SWC3). These mAb recognized macrophages and neutrophils; neutrophils; a monocyte/macrophage-specific mAb was not identified by this workshop.

We purified porcine whey lactoferrin by affinity chromatography on a heparin-Sepharose column, followed by high-performance liquid chromatography. Molecular mass of purified lactoferrin (PLF) is 78,000 daltons. The iron-binding activity of PLF had a UV/visible-light absorption spectrum indistinguishable from that of human and bovine lactoferrins (absorbance ratio [465 nm/280 nm] approx 0.046). The growth ratio of WIL-2 cells in PLF-supplemented medium is 70% of that in serum-containing medium. The aforementioned characteristics are similar to those of human and bovine lactoferrins. Immunoblot analysis, using polyclonal antibody raised in rabbits against porcine whey lactoferrin, revealed high specificity for PLF, and low cross-reactivity with commercial human and bovine lactoferrins.

Morphologic structures of the lymphoid tissues associated with the mucosa of the respiratory tract in swine aged 11 to 13 weeks were studied by dissecting, light, and transmission electron microscopy. Tissues along the respiratory tract were collected for further examination. Light microscopic examination showed that the lymphoid tissues were associated with bronchi (8.38%), bronchioles (81.63%), and respiratory bronchioles (9.98%). The lymphoid tissues were identified at different levels of the airways and were designated intrapulmonary airway mucosa-associated lymphoid tissues. Anatomically, the lymphoid tissues were found mostly in the bronchiolar bifurcations, with an arteriole frequently nearby. Histologically, the lymphoid tissues contained a single dome-shaped lymphoid follicle, which bulged out from the mucosal surface into the airway, where it was covered along the mucosal side by a layer of specialized epithelium. Ultrastructurally, the mucosal surface of the specialized epithelial cells was equipped with microfolds or cytoplasmic projections instead of cilia. The cytoplasm was elongated, and therefore much thinner than that of ordinary epithelial cells. Many lymphocytes were found scattered in the mucosal epithelium between or beneath the specialized epithelial cells. This structure was similar to that seen in the Peyer's patches of the small intestine in swine and other animals.

Pathologic and viral investigations were done on 13 fetal placentas and 23 aborted fetuses associated with naturally occurring pseudorabies in swine. Of the 13 fetal placentas examined, 7 (53.8%) had various degrees of necrotizing placentitis. The lesions were characterized by coagulative necrosis of the chorionic fossae and by intranuclear inclusions in degenerating trophoblasts and occasionally in mesenchymal cells. In addition, a mild inflammatory cell reaction was observed in the mesenchyma. Numerous viral particles, ultrastructurally indistinguishable from herpesvirus, were observed by electron microscopy in the affected chorionic membrane. Large aggregates of herpesvirus virions were demonstrated in the nucleus and cytoplasm of degenerated trophoblasts and mesenchymal cells. Of the 23 aborted fetuses examined, 22 (95.6%) had typical coagulative necrosis in the liver, spleen, adrenal glands, and visceral lymph nodes. Inclusions similar to those in the chorionic placenta were observed in the parenchymal cells of those organs, on the margins of necrotic areas. Pseudorabies virus was isolated from various organs of the aborted fetuses, but virus isolation from the placentas was not attempted. In a survey of 52 affected sows, sera from 49 (94.2%) neutralized the isolated virus. The findings indicated that the placental lesions caused by the virus were primary. The study also indicated the merit of routine examination of aborted fetal placentas and fetuses for diagnosis of pseudorabies.

The small intestine is a tissue which maintains contact with the external environment constantly. It receives antigenic stimulation and is attacked by various microorganisms at day and day base. The animals are then in danger without an efficient immune system of the gastrointestinal tract. The evidence described by this paper in the areas of morphology, position, structure, physiological phenomenon and immunologic functions, indicates strongly that IEL is a group of cells with important immunologic activities. In the last decade, technology to purify IEL has been improved, thereby enhancing immunologic research on this cell dramatically. Results disclose that immunologic activities such as ADCC, SCMC, NK, NC and CC are present in the IEL population. The surface maker studies on IEL in addition to the discovery of GML subpopulation further prove the immunologic importance of IEL. It is therefore believed at the present time that IEL is a combination of cells gathered at the intestinal mucosa in order to fulfill various local immunologic activities.

From March to June 1982, three cases of avian cryptosporidiosis were encountered in chickens, ducklings, and canaries. The bursa of Fabricius of chickens and ducklings were the main target organs and the agents were found to attach the microvillus border of the plical epithelium. In canaries, the parasites adhered to the microvillus border of mucosal epithelium of the proventriculus. Diagnoses were based on the microscopic pathology, the morphology of the parasites, and the type of attachment to epithelium. This represents the first authenticated evidence of cryptosporidial infection in Taiwan.

The peroxidase-antiperoxidase (PAP) staining technique was used for the detection of transmissible gastroenteritis virus (TGEV) in small intestines of TGEV-infected 8-week-old pigs and in infected McClurkin pig testicle cells by means of light microscopy. The specific-positive reaction was characterized by the presence of many brown granules of various sizes in the cytoplasm of infected cells. Nonspecific granules caused by endogenous peroxidases in the cytoplasm of eosinophils stained by PAP were darker, larger, more round, and more uniform in size than were specific granules. Acetone fixation was superior to fixation with periodate-lysine-paraformaldehyde or 10% formalin. Our results indicate that the PAP staining technique is a sensitive, specific technique for detection of TGEV in the small intestines of pigs.

Two day old piglets were inoculated intravenously with 1 ml of swine vesicular disease virus UK-G 27-72 isolate. Using infectivity tests, immunofluorescent staining and gross and histopathological examination, pathogenesis of the infection was studied in tissue specimens collected daily from one through seven days postinoculation. Swine vesicular disease virus had a strong affinity for the epithelia of the tongue, snout, coronary band and lips, the myocardium and the lymphoid elements of the tonsil and the brain stem. The virus had the greatest affinity for the epithelium of the tongue. However, there was no evidence that the tongue was the initial replication site for swine vesicular disease virus. Prickle cells in the stratum spinosum appear to be the primary targets for the virus. The necrotic foci in the stratum spinosum appeared first, followed the next day by reticular degeneration and multilocular intraepidermal vesicular formation. In the digestive tract and most of the other visceral organs the short duration and sudden drop of the virus titres and the negative fluorescence and pathological findings suggest that these are not important sites for the replication of swine vesicular disease virus in this experiment. The virus was recovered from most of the central nervous tissue specimens. Although the piglets had significant central nervous system lesions, signs of impaired central nervous system function were not detected. However, subtle nervous signs could have been obscured by difficulties in locomotion resulting from severe lesions of the feet.

A subpopulation of purified, interepithelial lymphocytes from porcine small intestinal mucosa contained cytoplasmic granules. Toluidine blue staining revealed metachromatic granules in 13.64% (606/4,450) cells. The cells had scant organelles, a single large nucleus with obvious invagination of the nuclear membrane, and prominent chromatin. Each cell contained 1 to 10 cytoplasmic membrane-bound granules, 0.6 to 1.5 micron in diameter. These findings indicated that the granular mucosal lymphocytes are related morphologically to mucosal mast cells. The presence of serotonin in the granules, confirmed by the serotonin releasing test, provided functional evidence that granular mucosal lymphocytes are related to mucosal mast cells.

Fifteen conventional 8-week-old pigs were used to compare the morphology and function of Peyer's patches (PP) in different parts of the small intestine with special emphasis on the dome epithelium (DE). The comparisons were done by morphological observation through light and electron microscopy, and by the ability of the DE complex to phagocytize horseradish peroxidase (HRP). Dome epithelium of the PP in the jejunum was more superficially located in the mucosa in comparison with the ileum. The DE's of the ileum were much smaller, with an area of 3.7 micron2/DE, than that of the jejunum (18.4 micron2/DE). The number of DE areas/5 cm2 in the ileum was more than in the jejunum. However, the total surface area of DE/5 cm2 of PP, was larger in the jejunum (180.5 micron2) than in the ileum (55.6 micron2). Brown discoloration of diaminobenzidine-hydrogenperoxide (DAB+H2O2)-treated PP specimens, after HRP inoculation, intensified with post-inoculation time from 20 s to 5 min. The brown pigment first appeared on the surface of microvilli and infiltrated into the dome. No morphological differences were observed between the jejunum and the ileum in 1 micron thick Epon-embedded specimens. Intramucosally, brown pigment was almost always found in DE areas. The pigmented areas were more numerous in the jejunum but the color intensity showed no obvious difference. By transmission electron microscopy, the electron dense materials (which were interpreted as the products of HRP and DAB+H2O2) were found between the microvilli of membraneous (M) cells, in the intercellular spaces of the DE, and in a form similar to intracytoplasmic vesicles in the cytoplasm of M-cell and DE complex lymphocytes. Our results confirmed that DE of PP had much stronger phagocytic activity than did the ordinary villous epithelium. This evidence indicates that the DE complex of PP in the swine intestine is immunologically important.

Large numbers of viral particles resembling rotavirus were detected with negative stained electron microscopy in bacteria free fecal filtrate obtained from 10-day old diarrheal suckling piglets of a conventional pig farm in Taiwan. The clinical signs of vomiting and diarrhea were reproduced in colostrum deprived piglets artificially infected with the fecal filtrates. Rotavirus particles persisted in the fecal samples after two in vivo serial passages, and was not seen in the uninfected control animal. The Cytoplasm of infected jejunal and ileal enterocyte fluoresced when standard anti-porcine rotavirus conjugate was applied in an direct immunofluorescent staining test. In the experimentally infected piglets, moderate villous atrophy of the small intestine was the main microscopic lesion observed. The virus was identified by the above evidence to be rotavirus.

A 2.5-month-old, 30 kg Duroc pig died 10 days after showing clinical signs of dyspnoea and diarrhoea. Acute necrotizing and fibrinous pleuropneumonia with locally extensive lesions was found. Chromobacterium violaceum was isolated from pneumonic lung tissues and intratracheal inoculation of a pure culture into two SPF pigs reproduced lesions similar to those found in the natural infection.

The responses of the interepithelial lymphocytes (IEL) and aggregated lymph nodules (ALN; Peyer's patches) of the small intestines of 8-week-old pigs to transmissible gastroenteritis virus (TGEV) infection were characterized at 12, 18, and 24 hours after pigs were inoculated. There was no significant difference in numbers of IEL between control and TGEV-infected pigs at 12 and 18 hours. However, in pigs examined at 24 hours, there was a significant decrease in the number of IEL in the duodenum and cranial portion of the jejunum and an increase of IEL numbers in the nuclear level of the intestinal epithelium. Number and distribution were unchanged in the middle portion of the jejunum and the ileum. Microscopic changes in TGEV-infected pigs included microulceration of the dome epithelium (DE) over the ALN, especially in the cranial portion of the intestine, and villous atrophy in the entire length of the small intestine. Generally, TGEV was found by means of peroxidase-antiperoxidase staining in areas where microscopic lesions occurred. Electron microscopy revealed that M cells and ordinary microvillus-covered epithelial cells in the DE embraced one or more lymphocytes, and formed a specialized cell complex or DE complex. Most of the lymphocytes in the DE complex possessed many organelles indicative of an active cell state. The TGEV was found between microvilli, in the cytoplasmic vesicles of M cells and microvillus-covered epithelial cells in the DE, and in the cytoplasm of macrophages and lymphocytes and some degenerated cells of unidentified origin in the domes of the ALN. The virus was also commonly found in cytoplasmic vesicles of macrophages and degenerated cells in the intestinal lumen near the base of the dome of the ALN.