Radial changes of extracellular potential amplitude and integral characteristics and the inverse problem in electroneurography

The possibility of solving the inverse problem in electroneurography, i.e. of estimating the main parameters specifying the activated fibre's functional state, using the amplitude and integral characteristics of the surface potentials generated by infinite homogeneous fibres, has been analysed. An analytical expression has been found for the amplitude of the negative phase A_nph of the single fibre extracellular action potential (SFEAP) as a function of the wavelength b, the fibre-electrode distance y and a scale factor A_o proportional to the intracellular action potential amplitude V_m, to the square of the fibre radius a and to the ratio of the axoplasm conductivity τ_a and volume conductor conductivity τ_e. For a large fibre-electrode distance, typical of surface recordings, an analytical expression of the integral of the negative phase I_nph of the SFEAP as a function of A_o, b, y and the propagation velocity v was also found. Simple methods are proposed for estimating v, the location of the electrical centre of the activated fibres' territory and the product of the number of activated fibres N, duration T_in of the intracellular action, potential and of the factor A_o. The estimation errors due to the temporal and spatial dispersion of the activated fibres were analysed as a function of the fibre-electrode distance and the territory shape.     

Preparation and characterization of the monoclonal antibodies against Japanese encephalitis virus.

Six mouse monoclonal antibodies (MoAbs) against Japanese encephalitis virus (JEV) were prepared and analyzed with indirect immunofluorescence assay (IFA), enzyme linked immunosorbent assay (ELISA), haemagglutination inhibition test (HI), neutralization test (NT), antibody dependent cell mediated cytotoxicity (ADCC) assay, antigenic site specific analysis and relative affinity measurement. These MoAbs could be divided into three classes by indirect immunofluorescence cross reactivity among four flaviviruses, 2H4, 2F2, and nG2 were type specific; 2D2 and mC3 were subgroup specific; and mG9 was family specific. 2H4 and 2F2 had higher neutralization activity, 2D2 and mC3 had the function of inducing ADCC effect, mG9 had higher titer in HI. The six MoAbs recognized five antigenic sites on JEV envelope glycoprotein, 2H4 and 2F2 recognized the same or very similar antigenic site and their relative affinity was ranked as: nG2 > 2H4 > 2D2 > mG9 > 2F2 > mC3.     

Ubiquitin: its potential significance in murine AA amyloidogenesis.

Amyloid enhancing factor (AEF), which has recently been shown to have identity with ubiquitin (Ub), is believed to play a causative role in experimentally induced AA amyloidosis in mice. We have examined the profile of Ub in activated leukocytes and splenic reticulo-endothelial (RE) cells and its relationship with serum amyloid A protein (SAA) and AA amyloid deposits in an alveolar hydatid cyst (AHC)-infected mouse model of AA amyloidosis. Two monospecific antibodies, anti-ubiquitin (RABU) and anti-mouse AA amyloid, were used as immunological probes to localize Ub, SAA, and AA amyloid. In response to AHC infection, the dull and diffuse Ub immunoreactivity in normal mouse leukocytes and RE cells promptly changed to a discrete granular pattern suggesting an increase in the intracellular concentration of Ub and the formation of Ub-protein conjugates. This corresponded to an elevation in SAA levels, SAA uptake by RABU-positive phagocytic cells, co-localization of Ub-SAA immunoreactive splenocytes in the perifollicular areas, and deposition of Ub-bound AA amyloid in the splenic and hepatic tissues. These results suggest that Ub-loaded monocytoid cells may play an important role in the physiological processing of the sequestered SAA into AA amyloid. Aspects of AA amyloidogenesis are discussed in relation to other experimental models in which stress-induced Ub-protein conjugate formation and its transport to lysosomal vesicles have been studied.     

Malignant fibrous histiocytoma of the heart.

We describe a 54-year-old man with a recurrent malignant fibrous histiocytoma in the left atrium. During the patient's first hospitalization, the tumor clinically presented as a typical atrial myxoma and was removed by routine procedure. Histologically, it was diagnosed as sarcoma, probably rhabdomyosarcoma. Nine months later the patient was readmitted because of recurrence. This time, the tumor, along with interatrial septum and a part of the anterior atrial wall, was excised by means of cardiac explantation and reimplantation. On light microscopic, immunohistochemical, and electron microscopic examination, the tumor was classified as a storiform-pleomorphic type of malignant fibrous histiocytoma. No other therapeutic procedures were performed, and 11 months after the second surgery the patient died of massive hemorrhage from a duodenal ulcer. A recurrent tumor in the left atrium and several distant metastases were found at autopsy.     

Detection of HCV RNA in saliva, urine, seminal fluid, and ascites.

Approximately half of the patients with type C hepatitis do not have a history of parenteral exposure. The route of nonparenteral infection remains unknown. To evaluate the possible role of body fluids, the existence of hepatitis C virus (HCV) RNA in saliva, urine, seminal fluid, and ascites was examined by "nested" polymerase chain reaction (PCR). Amplification of the HCV 5' noncoding sequences was carried out. The amplified product was confirmed by Southern blot hybridization and restriction endonuclease digestion. Among 34 patients with chronic liver disease who were positive for anti-HCV and serum HCV RNA, the prevalence of HCV RNA in body fluids was 100% (7/7) in ascites, 48% (15/31) in saliva, 24% (4/17) in seminal fluid, and 7% (2/29) in urine. The body fluids collected from 3 healthy subjects and 5 patients with chronic liver disease who were positive for anti-HCV but negative for serum HCV RNA were all negative for HCV RNA. Hence, the potential infectivity of body fluids in patients testing negative for serum HCV RNA can probably be discounted. Conversely, the presence of HCV RNA in saliva and seminal fluid of patients positive for serum HCV RNA suggests sexual and household contact as likely modes of nonparenteral transmission of type C hepatitis. Furthermore, the high prevalence of HCV RNA in ascites and saliva may have important implications in medical and dental practice.     

Inhibition of abnormal T cell development and autoimmunity in gld mice by transgenic T cell receptor beta chain.

Mice homozygous for the gld (generalized lymphoproliferative disease) mutation developed systemic autoimmune disease and severe lymphadenopathy due to an age-related accumulation in the peripheral lymphoid organs of polyclonal T cells bearing a unique phenotype (CD4-CD8-TCR alpha beta+B220+). These T cells overexpress T cell receptor (TcR) alpha beta chain RNA, proto-oncogenes c-myb and fyn, and proliferate poorly in response to TcR-mediated stimulation. The origin of these T cells is poorly understood. To study the influence of a functionally rearranged TcR beta chain on the T cell developmental abnormality of the gld mutation and autoimmunity, we have backcrossed TcR V beta 8.1-transgenic mice to C3H-gld/gld to homozygosity (transgenic gld mice). In transgenic gld mice, lymphadenopathy was markedly inhibited and the accumulation of CD4-CD8- T cells did not occur, although the remaining T cells overexpressed c-myb and proliferated poorly in response to TcR occupancy. These features indicate that the pattern of proto-oncogene expression and abnormal function persist in phenotypically normal T cells in transgenic gld mice, and that these characteristics can be dissociated from the accumulation of CD4-CD8- T cells. The hypergammaglobulinemia and anti-double-stranded DNA (anti-dsDNA) antibody production was partially improved in transgenic gld mice, supporting the critical role of T cells in abnormal B cell activation described in autoimmunity-prone mice. To investigate further the mechanisms underlying the inhibition of CD4-CD8- T cell accumulation in transgenic gld mice, the fetal ontogeny of T cells in transgenic mice was compared with that of non-transgenic mice. In transgenic thymus, development of TcR alpha beta+ cells was accelerated as detected by earlier expression of CD4, CD8 and TcR in fetal thymus. In contrast, the number of TcR gamma delta+ cells was reduced. We suggest that altered T cell development in transgenic mice directly or indirectly inhibits the accumulation of abnormal T cells in gld mice.     

Nuclear translocation of monoclonal antibody directed against cell-surface carbohydrate Y determinant.

Monoclonal antibody (MAb) Br 15-6A directed against the carbohydrate Y determinant expressed on tumor cells was found to be internalized and translocated to the nucleus of SK Br 5 breast carcinoma and SW 1116 and SW 707 colorectal carcinoma cells. Intracellular localization of MAb Br 15-6A was determined by cell fraction and by indirect immunofluorescence staining. Internalization of MAb Br 15-6A seems to be mediated by a specific cell surface protein of M(r) 108,000 in colorectal carcinoma cells and M(r) 92,000-96,000 in breast carcinoma cells. The MAb Br 15-6A precipitates an 88,000 M(r) chromatin protein and appears to be bound specifically to two EcoRI-digested and two HincII-chromatin fragments. Another MAb against the Y determinant (MAb Br 55.2) recognizes the same antigens as MAb Br 15-6A, but is not internalized.     

Cytogenetic findings in a breast stromal sarcoma. Application of fluorescence in situ hybridization to characterize the breakpoint regions in an 11;19 translocation.

Cytogenetic analysis of a stromal breast sarcoma revealed a complex karyotype that included a reciprocal 11;19 translocation, along with multiple numerical changes, deletions, and other unbalanced structural rearrangements. Karyotypic abnormalities have not been reported previously in this rare neoplasm that arises from mesenchymal breast tissue, and the t(11;19) is of interest because various types of sarcoma are characterized by specific reciprocal translocations. Because of the pericentric nature of the breakpoints on chromosomes 11 and 19 in the t(11;19), classical cytogenetic banding could not reveal the centromeric origin of the translocation derivatives. Using nonisotopic in situ hybridization with chromosome 11 and 19 alpha-satellite probes, the centromere of each derivative chromosome was determined, and the rearrangement was interpreted as a balanced translocation, t(11;19)(q12 or q13.1;p12 or p13.1). This abnormality has not been described previously in any breast tumor.     

Performance characteristics of transmission imaging using a uniform sheet source with parallel-hole collimation.

Transmission imaging is receiving increasing attention in SPECT due to the need to compensate for nonuniform attenuation in cardiac-chest SPECT. The quality of a transmission image has an important effect on the measured attenuation distribution. To improve image quality, knowledge of the performance characteristics of a transmission imaging system is essential. The characteristics, spatial resolution, detection efficiency, photon flux, and exposure to the object, of a transmission imaging system consisting of a gamma camera and a uniform sheet source have been studied. The results demonstrate that spatial resolution of a transmission imaging system can be improved by use of a high-resolution source collimator at the price of a moderate decrease in detection efficiency, in comparison to the uncollimated case. Also, the source collimator significantly reduces the photon flux and exposure to the object. This investigation suggests that a high-resolution collimator be used with an intense sheet source to improve spatial resolution and reduce statistical noise with low exposure to the patient. This research further suggests that the amount of source activity is determined by the requirement of image quality, detection geometry, and allowed absorbed dose to the patient.     

Calcium signalling by the high affinity macrophage Fc gamma receptor requires the cytosolic domain.

Hematopoietic cells express multiple receptors which bind the Fc domain of IgG. We utilized transfection of COS-1 cells, a cell line which lacks endogenous Fc receptors, to study the expression and function of Fc gamma RI, the high affinity Fc gamma receptor in the absence of other Fc gamma receptors. Fc gamma RI was efficiently expressed in transiently transfected COS-1 cells as measured by flow cytometry and the binding of IgG sensitized RBCs (EA). In addition, analysis at the single cell level demonstrated that individually transfected COS-1 cells release cytosolic free Ca2+ [(Ca2+)i] upon activation with anti-Fc gamma RI antibody. The calcium response required Fc gamma RI cross-linking. COS-1 cells transfected with mutant Fc gamma RI lacking the cytosolic domain expressed Fc gamma receptors and bound EA as well as wild type receptors, but failed to induce an increase in [Ca2+]i. These data indicate that Fc gamma RI in the absence of other Fc gamma receptors mediates a calcium signal and that the cytoplasmic domain of Fc gamma RI contains the elements required for calcium dependent signal transduction.