Multi-layer core/shell microgels with internal complexity and their nanocomposites

In this study, we show that core/shell (CS) microgels with multiple layers can be created via a one-pot precipitation polymerization, in which monomers are added to the reaction flask multiple times once most of the previous monomer has been consumed. The complex internal structures of the microgels were examined using a combination of scattering and microscopy techniques.

The compression of deformed microgels at an air/water interface

The compression of deformed hydrogel microspheres (microgels) at air/water interfaces was investigated using a Langmuir-Blodgett trough with simultaneous in situ visualization of the process using a fluorescent microscope. The relationship between the structure of the microgel arrays and the compression behavior was clarified using microgels with different degrees of crosslinking.

Durable gelfoams stabilized by compressible nanocomposite microgels

Compressible nanocomposite microgels can stabilize the air/water interfaces of gas bubbles for several months, which affords durable gelfoams.

Non-close-packed arrangement of soft elastomer microspheres on solid substrates

Unlike rigid microparticles, soft and deformable elastomer (rubber) microspheres were found to exhibit a non-close-packed arrangement on solid substrates after the evaporation of water from their dispersions. The microscopic observation revealed that individual microspheres are ordered in regular intervals at the air/water interface of a sessile droplet and remain fixed on the substrate without being affected by the capillary forces during evaporation due to their deformability. Moreover, using the Langmuir-Blodgett method, thin films of non-close-packed structures could be successfully generated over large areas. Our findings may potentially help to control the arranged structures of elastomer microspheres, which can be expected to improve the nano-science and technology for the precise control for e.g. surface patterning.

Nanostructure and thermoresponsiveness of poly(N-isopropyl methacrylamide)-based hydrogel microspheres prepared via aqueous free radical precipitation polymerization

Thermoresponsive hydrogel microspheres (microgels) are smart materials that quickly respond to external stimuli, and their thermoresponsiveness can be tuned by varying the constituent chemical species. Although uniformly sized microgels can be prepared via aqueous free radical precipitation polymerization, the nanostructure of the obtained microgels is complex and remains unclear so far. In the present study, the nanostructure and thermoresponsiveness of poly(N-isopropyl methacrylamide) (pNIPMAm)-based microgels, which have a volume-transition temperature of ∼43 °C, were evaluated mainly using temperature-controllable high-speed atomic force microscopy. These observations, which are characterized by high spatio-temporal resolution, revealed that the pNIPMAm microgels have a peculiar heterogeneous structure, for example a core-shell and non-thermoresponsive nanostructure in the core region, that originates from the precipitation polymerization process. Furthermore, it was found that the adsorption concentration of the microgels on the substrate is one of the keys for controlling their thermoresponsiveness. These findings can be expected to advance the design of new materials such as thermoresponsive nanosheets and stimuli-responsive coatings.

Nanostructures, Thermoresponsiveness, and Assembly Mechanism of Hydrogel Microspheres during Aqueous Free-Radical Precipitation Polymerization

Although techniques to produce uniformly sized hydrogel microspheres (microgels) by aqueous free-radical precipitation polymerization are well established, the details of the polymerization process remain mysterious. In the present study, the structural evolution and thermoresponsiveness of the developing microgels during the polymerization were evaluated by temperature-controlled high-speed atomic force microscopy. This analysis clarified that the swelling properties of the precursor microgels formed in the early stages of the polymerization are quite low due to the high incorporation of cross-linkers and that non-thermoresponsive deca-nanosized spherical domains are already present in the precursor microgels. Furthermore, we succeeded in tracking the formation of nuclei and their growth process, which has never been fully understood, in aqueous solution by real-time observations. These findings will help us to design functional microgels with the desired nanostructures via precipitation polymerization.

Two-step yielding behavior of densely packed microgel mixtures with chemically dissimilar surfaces and largely different sizes

Steady-state flow and elastic behavior is investigated for the moderately concentrated binary suspensions of soft microgels (pastes) with chemically dissimilar surfaces, and various degrees of size- and stiffness disparities. The pastes of poly(N-isopropyl acrylamide) (N) and poly(N-isopropyl methacrylamide) (NM) microgels with different values of yield strain γc (γNc > γNMc) are employed as the components. For the single microgel pastes (φ ≈ 1 where φ is apparent volume fraction), the values of γc are governed by the chemical species of constituent polymer in microgel surface whereas γc is insensitive to cross-link density and particle size. We demonstrate that the binary N/NM pastes with large size disparity (RN/NM = DN/DNM < 0.26 where D is the microgel diameter) at low φN (φN: weight fraction of small N microgels) exhibit the peculiarities in several rheological aspects, i.e., the two-step yielding in steady-state flow, and their values of γc and equilibrium shear modulus (G0) being equivalent to those of the single large NM microgel paste. These peculiarities are attributed to the characteristic packing resulting from large size disparity in which all or almost of the small N microgels tend to be accommodated in the gap between the large NM microgels even in moderately concentrated state. This characteristic packing substantially masks the contribution of the small N microgels at low φN, explaining the φN-independent G0 and γc as well as the first yielding governed solely by the large NM microgels. The second yielding results from the emerged contribution of the small N microgels expelled out from the gap by the positional rearrangements after the first yielding. The binary homo-N/N pastes with the similarly large size disparity at low φsmall also exhibit the φsmall-independent values of G0, but they show one-step yielding, indicating that the two-step yielding requires not only sufficiently large size disparity but also chemical dissimilarity (different values of γc) between the two components.

Hydrophobic Monomers Recognize Microenvironments in Hydrogel Microspheres during Free-Radical-Seeded Emulsion Polymerization

The three-dimensional structure of nanocomposite microgels was precisely determined by cryo-electron micrography. Several nanocomposite microgels that differ with respect to their nanocomposite structure, which were obtained from seeded emulsion polymerization in the presence of microgels, were used as model nanocomposite materials for cryo-electron micrography. The obtained three-dimensional segmentation images of these nanocomposite microgels provide important insights into the interactions between the hydrophobic monomers and the microgels, that is, hydrophobic styrene monomers recognize molecular-scale differences in polarity within the microgels during the emulsion polymerization. This result led to the formation of unprecedented multi-layered nanocomposite microgels, which promise substantial potential in colloidal applications.

The Belousov-Zhabotinsky Reaction in Thermoresponsive Core-Shell Hydrogel Microspheres with a Tris(2,2'-bipyridyl)ruthenium Catalyst in the Core

The Belousov-Zhabotinsky (BZ) reaction shows temporal or spatiotemporal structures such as redox oscillation of the catalyst, [ruthenium(II)tris(2,2'-bipyridine)][PF₆]₂ ([Ru(bpy)₃][PF₆]₂). In this study, autonomously oscillating hydrogel microspheres (microgels) were investigated, which show swelling/deswelling oscillation induced by the redox oscillation of the BZ reaction inside the gel. Despite the periodically and autonomously induced oscillation that does not require an external stimulus, it has not been possible to perform any manipulation of the oscillatory behavior over time. The results of the present study show that it is possible to reversibly switch the microgel oscillations from an "on" active state of the BZ reaction to an "off" inactive state by changing the temperature in combination with thermoresponsive microgels. To realize on-demand switching, the construction of double-shell structures is crucial; the thermoresponsive first shell allows the microgels to modulate the diffusion of the substrates or intermediates in the BZ reaction, while the second shell maintains colloidal stability under high temperatures and high ion concentrations. The functionalized double-shell microgels were prepared via multistep seeded precipitation polymerization. The oscillatory switching behavior of the BZ reaction was observed directly and evaluated by ultraviolet-visible (UV-vis) spectroscopy. The central concept of this study, i.e., "on-off switching" can be expected to benefit the development of advanced bioinspired materials.

Effect of Charge Groups Immobilized in Hydrogel Microspheres during the Evaporation of Aqueous Sessile Droplets

In contrast to conventional dispersions of solid microspheres, dilute dispersions containing soft hydrogel microspheres (microgels) exhibit unique drying behavior due to their selective adsorption at the air/water interface of sessile droplets. So far, the impact of the size, chemical composition, and softness (degree of cross-linking) of microgels has been investigated. In the present study, we present the impact of charged groups introduced in the microgels on the adsorption and assembly behavior of these microgels at the air/water interface using a series of microgels with different amounts and distribution of charged groups. A series of experiments under different conditions (pH value and ionic strength) afforded information that clarified the adsorption, interpenetration, and deformation behavior of such charged microgels at the air/water interface. The results indicate that the adsorption and the deformation of charged microgels at the air/water interface are suppressed by the presence of charged groups. Moreover, charged microgels adsorbed at the interface are more dynamic and not highly entangled with each other; i.e., even though the more dynamic charged microgels are arranged at the interface, these arranged structures are disrupted upon transferring onto the solid substrates. Our findings of this study can be expected to promote the further development of applications, e.g., foams and emulsions stabilized by microgels, that crucially requires an in-depth understanding of the adsorption behavior of charged microgels at the air/water interface such as coatings.

Concentration dependence of the dynamics of microgel suspensions investigated by dynamic light scattering

The dynamics of colloidal gel particle suspensions, i.e., microgel suspensions, has been investigated by dynamic light scattering (DLS) over a wide concentration range from the (I) dilute (φ < φcp) to the (II) intermediate (φ ≈ φcp) and (III) high concentration regions (φ ≫ φcp), where φ and φcp are the volume fraction of the gel particles in the suspension and the random close packing fraction, φcp ≈ 0.64, respectively. The time-intensity correlation function exhibited a distinct change with increasing φ, i.e., from ergodic behaviour (region I and II) to nonergodic behaviour (region III). A mode transition from translational (region I) to cooperative diffusion (the so-called gel mode) (region II) was also observed due to the soft and deformable nature of the microgels. Different from the dynamics of hard colloidal glass suspensions, the gel mode remained even at φ ≫ φcp. By using the ensemble-averaged time-correlation function, IE, we quantify the relationship between φ and their dynamics, and show that the soft microgels are deswollen in the densely packed state.

Protein uptake into individual hydrogel microspheres visualized by high-speed atomic force microscopy

The moment of protein uptake into hydrogel microspheres (microgels) was directly monitored at the nanoscale by high-speed atomic force microscopy, and suitable design of microgels to suppress the aggregation in the presence of proteins was found.

Self-Organization of Soft Hydrogel Microspheres during the Evaporation of Aqueous Droplets

The unique drying behavior of aqueous droplets that contain soft hydrogel microspheres (microgels) upon evaporation was systematically investigated. Compared to the ring-shaped deposits that are obtained from drying solid microsphere dispersions, we have previously reported that uniformly ordered thin films are obtained from drying ∼1.2 μm-sized poly( N-isopropyl acrylamide) microgel dispersions. In the present study, we thoroughly investigated several hitherto unexplored aspects of this self-organization, such as the effect of the size, chemical structure, and "softness" of the microgels (or rigid microspheres). For the macro- and microscopic observation of the drying behavior of various microsphere dispersions, an optical microscope and a digital camera were employed. The results suggested that the convection in the aqueous droplets plays an important role for the transportation of the microgels to the air/water interface, where the softness and surface activity of the microgels strongly affects the adsorption of the microgels. On the basis of these discoveries, a design concept for the rapid formation of uniform thin films of soft microgels was proposed.

The deformation of hydrogel microspheres at the air/water interface

The deformation of soft hydrogel microspheres (microgels) adsorbed at the air/water interface was investigated for the first time using large poly(N-isopropyl acrylamide)-based microgels synthesized by a modified aqueous precipitation polymerization method.

Endocardial Invasion of Lung Cancer Undiagnosable before Autopsy

A 59-year-old male patient presented with left chest discomfort on admission. His medical history included encephalitis in childhood and his smoking history was 20 cigarettes per day for 40 years. A physical examination showed an anemic and edematous face with weak respiratory sounds in the left lung. The patient had elevated calcium levels and decreased hemoglobin and potassium. His parathyroid hormone-related protein level was elevated. Thoracic radiography showed cardiomegaly and computed tomography revealed a left lung mass with invasion of the heart and pleural effusion. Magnetic resonance imaging showed endocardial invasion of the tumor mass. Gallium-68 imaging revealed positive accumulation in the region surrounding the heart. No diagnoses were possible upon frequent cytology of his sputum and pleural effusion. The patient died from congestive heart failure with anoxia 38 days after admission. An autopsy revealed tumoral mass occlusion in the left main bronchus and tumoral invasion of the left atrium, left ventricle, and aorta.

Spontaneous remission of epstein-barr virus-positive diffuse large B-cell lymphoma of the elderly

A 94-year-old female patient presented with anorexia and left axillar lymphadenopathy on admission. Her past history was angina pectoris at 83 years of age and total gastrectomy due to gastric cancer at 87 years. The family history revealed that her son had had a malignant lymphoma, the histopathological diagnosis of which was diffuse large B-cell lymphoma. A physical examination showed both cervical, axillar, and inguinal lymphadenopathy without tenderness. She had elevated lactate dehydrogenase, ferritin, and soluble interleukin-2 receptor (sIL-2R). Whole-body computed tomography confirmed the cervical, axillary, and inguinal lymphadenopathy. Gallium-68 imaging revealed positive accumulation in these superficial lymph nodes. A right inguinal lymph node biopsy showed features of Epstein-Barr virus-associated lymphoproliferative disorder. Immunohistological studies on this lymph node biopsy showed CD20-positive large cells, CD3-positive small cells, and CD30-partly-positive large cells. In situ hybridization showed Epstein-Barr virus-positive, LMP-partly-positive, and EBNA2-negative cells. She refused chemotherapy as her son had died from hematemesis during chemotherapy. She received intravenous hyperalimentation for 1 month after admission. No palpable lymph nodes were identified by physical examination or computed tomography 3 months after admission, and regression of lactate dehydrogenase, ferritin, and sIL-2R was observed. She recovered from anorexia and was discharged. She died from pneumonia 10 months later after initial symptoms of anorexia. The autopsy showed no superficial lymphadenopathy.

Heterogeneity of Brunsting-Perry type pemphigoid: a case showing blister formation at the lamina lucida, immune deposition beneath the lamina densa and autoantibodies against the 290-kD polypeptide along the lamina densa

An otherwise healthy 31-year-old man presented with multiple, vesicular, subepidermal blistering on the head, face, chest and oral cavity, leaving shallow scar formation, typical of Brunsting-Perry type pemphigoid. Direct immunofluorescence showed linear deposition of immunoglobulin (Ig)G and C3 along the basement membrane zone (BMZ), and indirect showed anti-BMZ autoantibodies (IgG, >40×) reacting with the dermal side under the salt-split study. Immunofluorescence staining for type IV collagen and laminins, as well as routine electron microscopy, demonstrated that the cleavage level of the blister was intra-lamina lucida. The immunoperoxidase method applied to lesional skin demonstrated IgG deposits along the lamina densa. The post-embedding immunogold method demonstrated that the autoantibodies against BMZ reacted with the lamina densa and the dermis just beneath it. Immunoblot studies demonstrated that the autoantibodies reacted with the 290-kD polypeptide (suggesting type VII collagen) when dermal extract was used as the substrate. The patient was treated with combination therapy consisting of 30 mg prednisolone, 900 mg nicotinamide and 750 mg tetracycline, and the number of newly forming blisters decreased. We concluded that Brunsting-Perry type pemphigoid, a rare autoimmune blistering disease, includes cases showing characteristics of epidermolysis bullosa acquisita as well as bullous pemphigoid. This case showed discrepancy between the blistering level (intra-lamina lucida) and location of antigen (lamina densa and sub-lamina densa areas).

Myeloperoxidase-antineutrophil cytoplasmic antibody-negative microscopic polyangiitis with pulmonary haemorrhage and IgA nephropathy

AIM

To report a case of a patient with myeloperoxidase-antineutrophil cytoplasmic antibody (ANCA)-negative microscopic polyangiitis (MPA) and IgA nephropathy associated with severe pulmonary haemorrhage.

CASE REPORT

A 59-year-old man presented with ANCA-negative systemic vasculitis accompanied by purpura, nephritis and pulmonary haemorrhage. A skin biopsy specimen revealed pandermal leucocytoclastic vasculitis without IgA deposition and a kidney biopsy showed mesangial nephritis with IgA deposition. Considering these findings, the patient was diagnosed as having MPA with IgA nephropathy.

DISCUSSION

In most cases, MPA presents with rapidly progressive necrotizing glomerulonephritis and sometimes lung haemorrhage, while IgA nephropathy is less common among MPA cases. As recent research suggested that in MPA immunoglobulin deposition in the kidney may be an exacerbating factor for renal dysfunction and poor prognosis, close observation is required in these cases.

[Intractable pneumothorax secondary to pulmonary metastasis of angiosarcoma]

A 68-year-old male suffered from right pneumothorax and was admitted to our hospital. He had a previous history of angiosarcoma of the scalp, and had received local resection and chemoradiotherapy. Chest computed tomography (CT) on admission revealed right pneumothorax and bilateral multiple thin-walled cavities of the lung. We performed partial resection of right lung. Histopathological examination showed a small metastatic lesion around the thin-walled cavities of the lung. Four months after the 1st lung resection, he suffered left pneumothorax. We performed partial resection of the left lung. Ten days after the 2nd lung resection, left pneumothorax recurred. Nine days later, he also developed right pneumothorax. We performed the 3rd operation for right lung. Thoracoscopy demonstrated multiple bullas in right lung and it showed impossibility for radical surgery. Although surgical resection for pneumothorax secondary to metastatic lung cancer is usually efficient, it is very hard to manage the pneumothorax of metastatic angiosarcoma.

Influence of avilamycin administration and its subsequent withdrawal on emergence and disappearance of antimicrobial resistance in enterococci in the intestine of broiler chickens

AIMS

To investigate the influence of avilamycin (AVM) administration and its subsequent withdrawal on the emergence and disappearance of AVM-resistant enterococci in the intestine of broiler chickens.

METHODS AND RESULTS

Five chicks each of C, L and H groups were given the basal diet, the basal diet supplemented with 5 g AVM/ton and the basal diet supplemented with 50 g AVM/ton, respectively. The AVM-resistant Enterococcus faecalis population did not emerge during 30 days of the AVM administration period, whereas the AVM-resistant Enterococcus faecium with a minimum inhibitory concentration of >512 microg ml(-1) in the faeces of chicks of the L and H groups emerged on 3 and 1 days after the AVM administration, respectively. Thereafter, the AVM-resistant Ent. faecium population density in both L and H groups maintained high levels during the AVM administration period. Twenty days after the AVM withdrawal, the AVM-resistant Ent. faecium population disappeared from the intestines of both four of five chicks of L group and three of five chicks of H group. The AVM-resistant Ent. faecium population density in one chick from each of the groups, L and H, did not change before and after the AVM removal.

CONCLUSIONS

The AVM-resistant Ent. faecium emerged during the AVM administration, and disappeared from the intestine of most chicks after the AVM withdrawal. However, the AVM-resistant Ent. faecium persisted in some chicks 20 days after AVM withdrawal.

SIGNIFICANCE AND IMPACT OF THE STUDY

Our results suggest that introducing an AVM withdrawal period could minimize the risk of AVM-resistant Ent. faecium becoming carcass contaminants, and that prudent antibiotic use alone is not sufficient to stem emergence of the AVM-resistant Ent. faecium.

Predicting recurrence following curative surgery in stage I non-small cell lung cancer patients using an angiogenesis-associated factor

There are still difficulties in determining the risk of recurrence to decide whether to perform selective adjuvant treatment for stage I non-small cell lung cancer. This study reviewed 122 stage I patients who underwent curative surgery to assess the usefulness of an angiogenesis-associated factor as a predictor of recurrence. By immunohistochemical examination, we collected information about tumor-induced vascular endothelial growth factor (VEGF)-A and -C expression at the primary site. During the median follow-up period of 120 months, the overall 10-year survival rate was 53.5%. The 10-year survival rates according to VEGF-A/C expression were as follows: VEGF-A high/VEGF-C high group, 26.0%; VEGF-A high/VEGF-C low group, 42.7%; VEGF-A low/VEGF-C high group, 73.1%; VEGF-A low/VEGF-C low group, 65.1%. The VEGF-A high/VEGF-C high group showed the worst outcome. The diagnostic values of the marker combination for predicting recurrence were as follows: sensitivity, 71.4%; specificity, 63.8%; and accuracy, 65.6%. When stratified by T factor, preferable high values for both negative predictive value and specificity were obtained in patients with stage IA disease. In order to select the patients eligible for selective adjuvant therapy at early stages, especially in stage IA disease, simultaneous assessment of tumor-induced VEGF-A/C warrants further study.

A subgroup of intrahepatic cholangiocarcinoma with an infiltrating replacement growth pattern and a resemblance to reactive proliferating bile ductules: 'bile ductular carcinoma'

AIMS

The histogenesis and biological behaviour of peripheral intrahepatic cholangiocarcinoma (peripheral CC) remain unclarified. The aim of this study was to examine the growth pattern of peripheral CC (24 cases) in comparison with hepatocellular carcinoma (HCC, 27 cases) and metastatic colorectal adenocarcinoma (MCA, 24 cases).

METHODS AND RESULTS

Tumour/surrounding liver borders were classified as: (i) fibrous encapsulation, (ii) compressive growth, and (iii) infiltrating replacement. Nineteen of 24 peripheral CCs showed (iii), whereas 23 of 27 HCCs showed (i) and 17 of 24 MCAs showed (ii). In (iii), carcinoma cells infiltrated the surrounding liver without compression, and hepatic supporting vascular structures such as portal tracts were secondarily incorporated into the tumour. In (i) and (ii), the surrounding liver was compressed and no or few portal tracts were incorporated within the tumour. Fifteen of 24 peripheral CCs were composed of carcinoma cells resembling reactive bile ductules and these cells were positive for neural cell adhesion molecule (NCAM), a marker of proliferating bile ductules. The remaining nine peripheral CCs were composed of ordinary adenocarcinoma and negative for NCAM.

CONCLUSIONS

A subgroup of peripheral CCs with an infiltrating replacement growth pattern resembles reactive bile ductules and expresses NCAM. 'Bile ductular carcinoma' may be a better term for this subgroup.

[Surgical results of non-small cell lung cancer invading parietal pleura and chest wall]

This retrospective analysis was undertaken to review our results of treatment of lung cancers with invasion of non-apical and non-vertebral chest wall structures. In summary of our experience, although relatively good prognosis can be expected in N0M0 patients with the histological type of adenocarcinoma by initial operation, distant relapse remains a major problem of the disease. Furthermore, our results are in agreement with the idea that postoperative adjuvant therapy is of little value in patients with complete resection. To ameliorate surgical outcomes, induction treatment should be considered and preoperative staging assessment needs to be strictly done for proper selection of patients with this locally advanced disease. The indication of initial operation needs to be cautiously determined for patients with this disease.

Solid serous cystadenoma of the pancreas: MR imaging with pathologic correlation

We report a case of solid type serous cystadenoma of the pancreas. Computed tomographic and magnetic resonance (MR) images showed a hypervascular solid tumor that was difficult to differentiate from endocrine tumor of the pancreas. However, the tumor showed marked hyperintensity similar to that of hepatic cyst on MR cholangiopancreatography, indicating not a solid but rather a cystic nature. MR cholangiopancreatography (heavily T2-weighted image) is quite useful for clearly differentiating solid from cystic tumors.

Inclusive double-pomeron exchange at the fermilab tevatron p p collider

We report results from a study of events with a double-Pomeron exchange topology produced in p p collisions at sqrt[s]=1800 GeV. The events are characterized by a leading antiproton and a large rapidity gap on the outgoing proton side. We find that the differential production cross section agrees in shape with predictions based on Regge theory and factorization, and that the ratio of double-Pomeron exchange to single diffractive production rates is relatively unsuppressed as compared to the O(10) suppression factor previously measured in single diffractive production.

The results of therapy for bilateral multiple primary lung cancers: 30 years experience in a single centre

AIMS

This study reviews our 30 years experience in the clinical assessment and surgical management of bilateral multiple primary lung cancer (BMPLC).

METHODS

Between January 1973 and December 2001, 1906 patients with primary lung cancer underwent surgical resection in Kanazawa University Hospital. Thirty-seven patients (1.9%) who had developed a BMPLC using the criteria of Martini and Antakli.

RESULTS

Eighteen patients had synchronous lesions, and 18 patients had metachronous lesions. One patient had synchronous and metachronous lesions. Overall 10-year survival was 56%. The actuarial 5-year survival for bilateral synchronous cancers was 69%, median survival (MST) 90 months (range 8-153 months), and 10-year survival was 47%. The actuarial 5-year survival for second metachronous cancers was 51%, with an MST of 114 months (range 6-192 months).

CONCLUSION

Aggressive surgical therapy is effective in patients with a bilateral MPLC if they satisfy the usual criteria of operability. The surgical methods that preserve healthy lung tissue such as sleeve resection and limited resection must be selected in compliance with cancer characters.

Search for Kaluza-Klein graviton emission in pp collisions at square root[s] = 1.8 TeV using the missing energy signature

We report on a search for direct Kaluza-Klein graviton production in a data sample of 84 pb(-1) of ppmacr; collisions at sqrt[s]=1.8 TeV, recorded by the Collider Detector at Fermilab. We investigate the final state of large missing transverse energy and one or two high energy jets. We compare the data with the predictions from a (3+1+n)-dimensional Kaluza-Klein scenario in which gravity becomes strong at the TeV scale. At 95% confidence level (C.L.) for n=2, 4, and 6 we exclude an effective Planck scale below 1.0, 0.77, and 0.71 TeV, respectively.

Search for pair production of scalar top quarks in R-parity violating decay modes in pp collisions at square root of s=1.8 TeV

We present the results of a search for pair production of scalar top quarks (t(1)) in an R-parity violating supersymmetry scenario in 106 pb(-1) of pp collisions at square root of s=1.8 TeV collected by the Collider Detector at Fermilab. In this mode each t(1) decays into a tau lepton and a b quark. We search for events with two tau's, one decaying leptonically (e or mu) and one decaying hadronically, and two jets. No candidate events pass our final selection criteria. We set a 95% confidence level lower limit on the t(1) mass at 122 GeV/c(2) for Br(t(1)-->tau b)=1.

Polymorphous low-grade adenocarcinoma of the major salivary glands: report of three cases in an unusual location

AIMS

Polymorphous low-grade adenocarcinoma (PLGA) is the second most common type of malignant neoplasm in minor salivary glands. Its origin in major salivary glands is considered exceedingly rare. Herein, we present three cases of de novo PLGA arising in major salivary glands.

METHODS AND RESULTS

Three cases of PLGA were identified in a large series of primary tumours of major salivary glands. We investigated their clinicopathological profiles, including immunohistochemical features. The three patients (two men and one woman) were 51, 65, and 79 years old. The tumours were 20-30 mm large; two were in the parotid gland and one in the submandibular gland. Histologically, all the tumours had a polymorphous architectural pattern showing predominantly solid, tubular, and cribriform features and invasive growth. Papillary areas were observed focally in two tumours and an 'Indian-file' array in one. The tumour cells had a bland cytological appearance and low mitotic count. Two tumours showed perineural invasion. No preexisting pleomorphic adenoma component was identified. In all cases, tumour cells were positive for epithelial markers, S100 protein, and vimentin but negative for alpha-smooth muscle actin, muscle-specific actin, and glial fibrillary acidic protein. Proliferative activities assessed with the Ki67 labelling index were 4.3%, 7.1%, and 7.6%; no p53 overexpression was observed. Two patients had local recurrence, but none had metastasis or died of tumour.

CONCLUSIONS

PLGAs arising in major salivary glands and those in minor salivary glands have similar clinicopathological and immunohistochemical characteristics. It is important to recognize that PLGA can occur ab initio in the major salivary glands, although it is extremely rare.

Search for lepton flavor violating decays of a heavy neutral particle in p(-)p collisions at sqrt[s]=1.8 TeV

We report on a search for a high mass, narrow width particle that decays directly to emu, etau, or microtau. We use approximately 110 pb(-1) of data collected with the Collider Detector at Fermilab from 1992 to 1995. No evidence of lepton flavor violating decays is found. Limits are set on the production and decay of sneutrinos with R-parity violating interactions.

Central pseudorapidity gaps in events with a leading antiproton at the fermilab tevatron pp collider

We report a measurement of the fraction of events with a large pseudorapidity gap deltaeta within the pseudorapidity region available to the proton dissociation products X in p+p-->p+X. For a final state p of fractional momentum loss xi(p) and 4-momentum transfer squared t(p) within 0.06<xi(p)<0.09 and |t(p)|<1.0 [0.2] GeV2 at sqrt[s]=1800 [630] GeV, the fraction of events with deltaeta>3 is found to be 0.246+/-0.001 (stat)+/-0.042 (syst) [0.184+/-0.001 (stat)+/-0.043 (syst)]. Our results are compared with gap fractions measured in minimum bias pp collisions and with theoretical expectations.

A comparative histological and morphometric study of vascular changes in idiopathic portal hypertension and alcoholic fibrosis/cirrhosis

AIM

To examine the pathological changes of hepatic arteries in idiopathic portal hypertension (IPH) which is characterized by the obliteration of the intrahepatic portal vein branches and presinusoidal portal hypertension.

METHODS AND RESULTS

Liver specimens (biopsied or surgically resected) from 20 patients with IPH, 20 patients with alcoholic fibrosis/cirrhosis (AF/C) and 20 histologically normal livers were used. The vascular lumina of arterial and venous vessels in portal tracts were morphometrically evaluated by an image analysis system. The ratio of portal venous luminal area to portal tract area (portal venous index) of IPH and that of AF/C were significantly reduced compared with normal liver. The portal venous index for IPH was significantly lower than that for AF/C. The ratio of hepatic arterial luminal area to portal tract area for AF/C was significantly higher than that in normal liver; however, that for IPH was similar to normal. The peribiliary vascular plexus was increased in AF/C but not in IPH. In AF/C, the number of mast cells and macrophages known to be the source of angiogenic substances was significantly increased in the portal tract compared with normal liver, while in IPH it was not increased.

CONCLUSIONS

In AF/C, a reduction in portal venous lumen was associated with an increase of hepatic arterial lumen and of angiogenesis-related cells in portal tracts. However, such compensatory arterial changes were not evident in IPH, and this compensatory failure may be a feature of IPH.

Search for the supersymmetric partner of the top quark in dilepton events from pp collisions at square root of s=1.8 TeV

We have searched for pair production of the supersymmetric partner of the top quark (stop) in 107 pb(-1) of pp collisions at square root of s=1.8 TeV collected by the Collider Detector at Fermilab (CDF). Each stop is assumed to decay into a lepton, bottom quark, and supersymmetric neutrino. Such a scenario would give rise to events with two leptons, two hadronic jets, and a substantial imbalance of transverse energy. No evidence of such a stop signal has been found. We exclude stop masses in the region (80</=m(t)</=135 GeV/c(2)) in the mass plane of stop versus sneutrino.

Search for associated production of Upsilon and vector boson in pp collisions at sqrt[s]=1.8 TeV

We present a search for associated production of the Upsilon(1S) and a vector boson in 83 pb(-1) of ppmacr; collisions at sqrt[s]=1.8 TeV collected by the CDF experiment in 1994-1995. We find no evidence of the searched signal in the data, and set upper limits to the production cross sections.

Endosonographic evaluation of c-kit-positive gastrointestinal stromal tumor

BACKGROUND

Endosonographic features of c-kit-positive gastrointestinal stromal tumors (GISTs) were compared with those of leiomyomas and schwannomas.

METHODS

Twenty-four patients with gastric mesenchymal tumors who underwent endoscopic ultrasonography (EUS) and surgical treatment were enrolled. GISTs were defined as c-kit (CD117)-positive tumors, leiomyomas as desmin-positive and c-kit-negative tumors, and schwannomas as S-100-positive and c-kit-negative tumors. Invasion to adjacent organs or more than 20 mitotic counts per 50 high power fields indicated malignancy.

RESULTS

There were 19 GISTs, three leiomyomas, and two schwannomas. All five malignant tumors were GISTs. A marginal halo was found in 12 of 19 GISTs and in both of the schwannomas, but not in any of the three leiomyomas. The echogenicities of GISTs were low but higher than that of the normal proper muscle layer, whereas those of leiomyomas and schwannomas were usually low. Lobulation of the tumor surface was documented only in GISTs, particularly in malignant ones. The tumor doubling time of a malignant GIST was 9.3 months, and that of six benign GISTs was 18.7 months (range = 10.7-28.0 months).

CONCLUSION

Marginal halo and relatively higher echogenicity on EUS might suggest GIST. Marginal lobulation and a short doubling time may be signs of a malignant GIST.