E versus k relations and many body effects in the model insulating copper oxide Sr2CuO2Cl2.
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Journal Article↗
Biomedical subjects
Z Shen
Publications and source records attributed to Z Shen.
Mediated, thin-layer cell, coulometric determination of redox-active iron on the surface of asbestos fibers.
Redox-active iron on the surface of asbestos fibers was detected and quantified using a thin-layer cell, coulometric method with soluble mediators to shuttle electrons between the mineral fibers and the solid electrode. The working and counter electrodes consisted of gold films on a glass slide with reference electrodes of silver. Asbestos fibers were entrapped in a thin-layer cell of 25 microns thickness. Hexaammineruthenium(II) or o-dianisidine (dication) was used as the reducing or oxidizing mediator, respectively. Hexaammineruthenium(III) undergoes a one-electron reduction, and protonated o-dianisidine undergoes a sequential two-electron oxidation. The measurement involved determination of the total charge for the oxidation or reduction of surface-immobilized Fe(II) or Fe(III) on the asbestos fibers. Analysis of the results showed that crocidolite and amosite have 4.3 +/- 0.7 and 3.3 +/- 0.7 nmol/mg of total redox-active iron that is accessible to the mediators, respectively. This corresponded to a surface coverage of accessible redox-active iron of approximately 4.3 x 10(-11) mol/cm2 for crocidolite and 9.5 x 10(-11) mol/cm2 for amosite. Furthermore, Fe(II) constituted 76% or 25% of the accessible redox-active iron on the surface of crocidolite or amosite, respectively. The method may be applied to other types of solid materials with redox-active species on their surfaces.
Asbestos, Amosite↗
The human and mouse homologs of the yeast RAD52 gene: cDNA cloning, sequence analysis, assignment to human chromosome 12p12.2-p13, and mRNA expression in mouse tissues.
The yeast Saccharomyces cerevisiae RAD52 gene is involved in DNA double-strand break repair and mitotic/meiotic recombination. The N-terminal amino acid sequence of yeast S. cerevisiae, Schizosaccharomyces pombe, and Kluyveromyces lactis and chicken is highly conserved. Using the technology of mixed oligonucleotide primed amplification of cDNA (MOPAC), two mouse RAD52 homologous cDNA fragments were amplified and sequenced. Subsequently, we have cloned the cDNA of the human and mouse homologs of yeast RAD52 gene by screening cDNA libraries using the identified mouse cDNA fragments. Sequence analysis of cDNA derived amino acid revealed a highly conserved N-terminus among human, mouse, chicken, and yeast RAD52 genes. The human RAD52 gene was assigned to chromosome 12p12.2-p13 by fluorescence in situ hybridization, R-banding, and DNA analysis of somatic cell hybrids. Unlike chicken RAD52 and mouse RAD51, no significant difference in mouse RAD52 mRNA level was found among mouse heart, brain, spleen, lung, liver, skeletal muscle, kidney, and testis. In addition to an approximately 1.9-kb RAD52 mRNA band that is present in all of the tested tissues, an extra mRNA species of approximately 0.85 kb was detectable in mouse testis.
Amino Acid Sequence↗
Visual estimation of ejection fraction by two-dimensional echocardiography: the learning curve.
Our purpose was to determine the learning curve of visual estimation of ejection fraction (EF) by echocardiography. Sixty consecutive patients, who had clinically indicated echocardiography and radionuclide ventriculography (RVG) within 1 month were selected. Five standard views were reviewed independently by a first-year cardiology fellow, a private cardiologist, and an experienced echocardiographer. Observers were given feedback of the RVG EFs immediately after estimating the EF on each study. To assess the effect of learning, the echocardiographic studies were divided into three groups of 20 and were read successively by each observer. A statistical comparison of the two methods was performed for each group. The correlation between the two techniques for the first group of studies was marginal. There was a significant improvement in the correlation with subsequent groups. The correlation did not change significantly with the last group of studies compared with the second group. In conclusion, visual estimation of EF by two-dimensional echocardiography can be learned, with a learning curve of approximately 20 studies if immediate feed-back is available.
Echocardiography↗
Automated grading of venous beading.
The degree of venous beading in ocular fundus images has been shown to be a more powerful predictor of conversion to proliferative diabetic retinopathy than any other type of retinal abnormality. Further, the degree of venous beading has been shown to be well correlated with disease progression. An algorithm for automated grading of venous beading in digitized ocular fundus images is described. Thresholding is used to extract a rough silhouette of the vein. Morphological closing is used to fill any holes in the silhouette arising from either the central light reflex or noise. The silhouette is then "thinned" to find vein centerlines. Each centerline is partitioned into fixed-length segments of 32 pixels. Vein diameters are measured as a function of distance along each segment with the aid of the local centerline orientations. The resulting diameter data are then interpolated and resampled to generate diameter data at constant sampling intervals. A fast Fourier transform is performed on the resulting data to determine the magnitude spectrum of vein segment diameter. A venous beading index is calculated from the distribution of vein diameter frequency components. Performance of the new algorithm is compared to the currently accepted clinical practice of manual grading in a pilot clinical study of 51 subjects. The algorithm is seen to perform well.
Algorithms↗
DIDS increases K+ secretion through an IsK channel in apical membrane of vestibular dark cell epithelium of gerbil.
Vestibular dark cell epithelium secretes K+ via IsK channels in the apical membrane. The previous observation that disulfonic stilbenes increased the equivalent short circuit current (Isc) suggested that these agents might be useful investigative tools in this tissue. The present experiments were conducted to determine if the increase in Isc was associated with an increase in K+ flux and if the effect was directly on the IsK channel or indirectly via a cytosolic intermediary. Measurements of transepithelial K+ flux with the K(+)-selective vibrating probe and of changes in net cellular solute flux by measurements of epithelial cell height showed that 4,4'-diisothiocyanatostilbene-2,2'-disulfonic acid (DIDS) increased K+ flux by a factor of 1.96 +/- 0.71 and caused net solute efflux. The apical membrane was partitioned with a macropatch pipette and DIDS was applied either to the membrane outside the pipette, inside the pipette or to the entire apical membrane. DIDS inside the pipette increased the current across the patch, the membrane conductance, the slowly-inactivating (IsK) component of the membrane current and shifted the reversal voltage toward the equilibrium potential for K+. DIDS outside the patch decreased the patch current and conductance, consistent with shunting of current away from the membrane patch. These findings strongly support the notion that DIDS increases K+ secretion through IsK channels in the apical membrane of vestibular dark cell epithelium by acting directly on the channels or on a tightly colocalized membrane component.
4,4'-Diisothiocyanostilbene-2,2'-Disulfonic Acid↗
Hypo-osmotic challenge stimulates transepithelial K+ secretion and activates apical IsK channel in vestibular dark cells.
Volume regulation of vestibular dark cells from the gerbilline inner ear in response to a hypo-osmotic challenge depends on the presence of cytosolic K+ and Cl-. The present study addresses the questions: (i) whether and by what mechanism K+ is released during volume regulation, (ii) whether the osmolarity of the basolateral medium has an effect on the steady-state rate of transepithelial K+ transport and (iii) whether there is cross-talk between the basolateral membrane responsible for K+ uptake and the apical membrane responsible for K+ release. K+ secretion (JK+,probe) and current density (Isc,probe) were measured with vibrating probes in the vicinity of the apical membrane and the transepithelial potential (Vt) and resistance (Rt) were measured in a micro-Ussing chamber. The equivalent short-circuit current (Isc) was calculated. The current (IIsK), conductance (gIsK) and inactivation time constant (tau IsK) of the IsK channel and the apparent reversal potential of the apical membrane (Vr) were obtained with the cell-attached macropatch technique. Vr was corrected (Vrc) for the membrane voltage (Vm) measured separately with microelectrodes. A hypo-osmotic challenge (294 to 154 mosM by removal of 150 mM mannitol) on the basolateral side of the epithelium increased JK+,probe and Isc,probe by a factor of 2.7 and 1.6. When this hypo-osmotic challenge was applied to both sides of the epithelium Vt and Isc increased from 5 to 14 mV and from 189 to 824 microA/cm2 whereas Rt decreased from 27 to 19 omega-cm2. With 3.6 mM K+ in the pipette IIsK was outwardly directed, tau IsK was 267 msec and the hypo-osmotic challenge caused IIsK and gIsK to increase from 14 to 37 pA and from 292 to 732 pS. Vrc hyperpolarized from -44 to -76 mV. With 150 mM K+ in the pipette IIsK was inwardly directed, tau IsK was 208 msec and the hypo-osmotic challenge caused IIsK and gIsK to increase in magnitude from 0 to -21 pA and from 107 to 1101 pS. Vrc remained unchanged (-2 vs. 1 mV). These data demonstrate that a hypo-osmotic challenge stimulates transepithelial K+ secretion and activates the apical IsK channel. The hypo-osmotically-induced increase in K+ secretion exceeded the estimated amount of K+ release necessary for the maintenance of constant cell volume, suggesting that the rate of basolateral K+ uptake was upregulated in the presence of the hypo-osmotic challenge and that cross-talk exists between the apical membrane and the basolateral membrane.
Animals↗
Suppressor cells and intrathymic inoculation of donor alloantigens in cardiac transplantation.
BACKGROUND: Donor-specific tolerance to a rat heterotopic cardiac allograft has been achieved by the pretransplantation intrathymic injection of donor splenocytes and a single intraperitoneal injection of antilymphocyte serum (ALS). Permanent tolerance is achieved without subsequent immunosuppression therapy. This study investigated the mechanisms responsible for maintenance of the tolerant state. METHODS: Tolerance was produced in Lewis rats by the administration of 1 mL of ALS intraperitoneally and 5 x 10(7) Lewis Brown Norway (LBN) splenocytes intrathymically 21 days before heterotopic transplantation using an LBN donor. RESULTS: In tolerant Lewis rats bearing LBN allografts for more than 100 days, rejection could not be produced by the intravenous injection of naive Lewis spleen cells (5 x 10(7) cells x 1 day, n = 5; 5 x 10(7) cells x 3 days, n = 5) or cells from Lewis rats sensitized to LBN tissues (5 x 10(7) cells x 3 days, n = 5). Naive Lewis recipients were pretreated with ALS and 6 days later with intravenous spleen cells (25 x 10(7), n = 5) or lymphoid cells (10 to 15 x 10(7), n = 5) from a tolerant animal bearing a viable LBN graft. When transplantation with an LBN donor was done the next day, significant prolongation of LBN allograft survival (mean survival time 32.8 days, p < 0.01; and 22.2 days, p < 0.01; respectively) was seen. Wistar-Furth allograft survival was not prolonged by treatment with ALS and intravenous spleen (n = 5) or lymph node (n = 5) cells from rats tolerant to LBN tissues (mean survival time 8.6 and 9.2 days, control 9 days; p = not significant). The administration of ALS alone (n = 5) did not prolong LBN graft survival (mean survival time 11.8 days). CONCLUSION: These data suggest that transferable suppressor cells specific for the donor strain are at least in part responsible for the maintenance of long-term allograft survival after intrathymic pretreatment with allogeneic cells.
Animals↗
Application of a sensitive HPLC-based fluorometric assay to determine the sialic acid content of human gonadotropin isoforms.
The human pituitary gonadotropins, follitropin (hFSH) and lutropin (hLH) are glycoproteins which are microheterogeneous in terms of their charge and molecular size, as well as their in vitro and in vivo bioactivities. The aim of this study was to determine the contribution of variations in sialic acid (N-acetyl neuraminic acid) content to the structural heterogeneity of these glycoproteins. Sialic acid (Neu5Ac) was released by partial acid hydrolysis (0.1 M TFA, 80 degrees C, 1 h) and derivatised with the fluorescent label DMB (1,2-diamino-4,5-methylenedioxybenzene) in conjunction with an internal standard (N-glycoyl-neuraminic acid). The derivatives were then separated by reversed-phase HPLC. This method allowed quantitation of the sialic acid content over a range of 5-100 pmol with between assay variation of < 6% for sialic acid released from approximately 100 ng (3 pmol) of hFSH or hLH. Comparison of the sialic acid contents of standard sialylated glycoproteins by either DMB-derivatisation or high-performance anion-exchange chromatography with pulsed amperometric detection yielded similar results, confirming the reliability of the fluorescence detection method. The sialic acid contents of 9 hFSH isoforms varied between 1.5-13.7 mol Neu5AC/mol FSH, whilst a range of 1.1-9.1 mol Neu5AC/mol LH was observed for 12 hLH isoforms. The sialic acid content of the hFSH isoforms was also observed to be related to the hormonal specific activity in a radioreceptor assay, confirming that alterations in the carbohydrate structure can influence the FSH-receptor interaction. In contrast, the sialic acid content of the hLH isoforms was found to be not related to specific activity at the receptor level.
Chromatography, High Pressure Liquid↗
Function of human Fc gamma RIIA and Fc gamma RIIIB.
Fc gamma RIIA (CD32), a conventional type I transmembrane protein, and Fc gamma RIIIB (CD16B), which has a glycan phosphatidylinositol (GPI) membrane anchor, are both expressed on human neutrophils. Although some details remain to be elucidated, signaling following crosslinking of Fc gamma RIIA requires the activation of tyrosine kinases of both Src-family kinases and Syk, resulting in tyrosine phosphorylation of Shc, phospholipase C gamma isozymes, and a [Ca2+]i transient. Ligation of neutrophil Fc gamma RIIIB triggers a [Ca2+]i transient, and degranulation, although probably not ADCC or an oxidative burst. However, the mechanism for signal transduction by Fc gamma RIIIB, which lacks a transmembrane domain, is not known. Fc gamma RIIA and Fc gamma RIIIB appear to synergize with each other, leading to suggestions that the GPI-anchored Fc gamma RIIIB utilizes the Fc gamma RIIA signaling apparatus. The relevance of proposed specialized membrane domains enriched in GPI-anchored proteins, sphingomyelin and glycolipids to the signaling properties of Fc gamma RIIIB likewise remains to be explored.
Gene Expression Regulation↗
Distribution and expression of cartilage oligomeric matrix protein and bone sialoprotein show marked changes during rat femoral head development.
Distribution and sites of synthesis of a cartilage extracellular matrix protein, cartilage oligomeric matrix protein (COMP), and of a bone extracellular matrix protein, bone sialoprotein (BSP), were studied in the femoral head of growing Wistar rats from day 14 to day 60 by immunocytochemistry and in situ hybridization. This period includes formation of the secondary ossification center and differentiation of articular cartilage. At early stages, immunoreactivity for COMP was pronounced throughout the cartilage. The localization of COMP was predominantly territorial in the center of the immature femoral head and in the growth plate at all ages studied. In the superficial parts, a shift from a uniform extracellular matrix staining at day 14 to an interterritorial localization at day 33 to day 60 was seen, apparently concurrent with formation of articular cartilage. COMP staining, representing cartilage remnants, also extended into the center of the trabecular bone in the primary spongiosa. In the secondary ossification center, the staining for COMP decreased at the onset of calcification. The protein was only synthesized by chondrocytes, as shown by in situ hybridization. The highest level of COMP mRNA was detected in chondrocytes in the central region of the growth plate. In the layer corresponding to the articular cartilage of the femoral head, mRNA levels for COMP were low from day 14 to day 33 but were increased on day 60. This shows substantial synthesis in the developing articular cartilage. Immunoreactivity for BSP was detected in bone trabeculae of primary spongiosa. In situ hybridization showed the highest levels of BSP mRNA in regions of newly formed bone. BSP mRNA was detected in hypertrophic chondrocytes in the secondary ossification center as early as day 18, well before the appearance of immunochemically detectable BSP. Interestingly, simultaneous expression of COMP and BSP mRNA was seen after day 18 in hypertrophic chondrocytes of the growth plate and later also in hypertrophic chondrocytes close to the mineralization zone of the articular cartilage.
Animals↗
Lack of neuronal nitric oxide synthase in nerve fibers of aganglionic intestine: a clue to Hirschsprung's disease.
The lack of nonadrenergic, noncholinergic (NANC) inhibitory innervation in aganglionic intestine is typical of Hirschsprung's disease. Several neuropeptides participating in the intestinal NANC innervation are greatly reduced in aganglionic intestine. However, these findings do not fully explain the pathophysiology of the disease. Recently, nitric oxide (NO) has been presented as a potent smooth muscle relaxant, and the enzyme responsible for its formation, nitric oxide synthase (NOS) has been demonstrated in neuronal elements in both the central and peripheral nervous system. In our study, nicotinamide adenine dinucleotide phosphate (NADPH)-diaphorase staining, a marker for NOS, and NOS immunohistochemistry revealed a dense innervation of the smooth muscle layers and the myenteric ganglia in ganglionic non afflicted intestine from patients with Hirschsprung's disease. By contrast, there was an almost complete lack of NOS-immunoreactive and NADPH-diaphorase-positive nerve fibers in the afflicted aganglionic bowel. NOS and vasoactive intestinal peptide were found to be partially colocalized in nerve fibers and neuronal cell bodies in the ganglionic but not in the aganglionic intestine. The lack of NO-producing nerve fibers in the aganglionic intestine probably contributes to the inability of the smooth muscle to relax, thereby causing lack of peristalsis in Hirschsprung's disease.
Amino Acid Oxidoreductases↗
Identification of widespread Helicobacter hepaticus infection in feces in commercial mouse colonies by culture and PCR assay.
The identification of a new murine pathogen, Helicobacter hepaticus, and its association with chronic active hepatitis and liver tumors prompted an evaluation of the prevalence of H. hepaticus in commercially available mice. Of the 28 different strains or stocks, totaling 160 mice from four major commercial vendors, cultured for H. hepaticus, 100% of mice from two outbred strains from one vendor were infected with H. hepaticus, whereas 9 of 13 inbred mouse strains from another vendor were infected. This high prevalence of H. hepaticus established a need for a rapid and reproducible, noninvasive assay for the screening of colony-maintained mice being used for biomedical research. The culturing of fecal material by using 0.45-microns-pore- size filtration for H. hepaticus consistently yielded reproducible results but required extended periods of time. (1 to 3 weeks) to obtain a definitive answer. Although it is rapid, the use of a direct PCR-based detection assay with fecal specimens is restricted by inhibitory agents. to circumvent these inhibitory agents and to augment our H. hepaticus culture technique, we have developed a novel PCR system in which the bacteria are isolated from fecal material in the presence of polyvinylpyropyrollidone and lysed by treatment with Chelex 100. The PCR is performed with Tth polymerase supplemented with a polymerase enhancer. By this PCR method, 24 H. hepaticus culture-positive and 30 H. hepaticus culture-negative fecal samples were correctly identified. Moreover, two samples which were PCR positive and culture negative initially were positive by both methods upon retesting of fresh material. Southern blot hybridizations and sequencing of PCR products showed them to be H. hepaticus specific. A comparison of results obtained under identical conditions indicated a 100-fold increase in sensitivity with Tth polymerase over Taq polymerase. This PCR method can be used as a noninvasive means of rapidly screening large numbers of colony mice for H. hepaticus.
Animals↗
Morphometric analysis of spinous cell in oral submucous fibrosis. Comparison with normal mucosa, leukoplakia and squamous cell carcinoma.
The morphometric analysis of the spinous cell in 16 specimens of oral submucous fibrosis (OSF) was made by using interactive image analysis system (IBAS-II). 19 parameters of the size and shape were chosen, and compared with normal mucosa, leukoplakia, dysplasia and carcinoma. The results indicated that the cell dimensions (area, perimeter, all kinds of diameter) and nuclear cytoplasmic ratio in OSF were between normal mucosa and dysplasia as well as carcinoma. The former showed a progressive decrease (P < 0.01), and the latter showed a progressive increase (P < 0.01). The dimensions of the nuclei did not show considerable differences among the groups (P < 0.05). A series of discriminant functions had been developed with stepwise discriminant analysis, the agreement ratio for OSF was 93.75%. The decrease of cell area and the increase of nuclear cytoplasmic ratio could reflect a malignant progress. The cell morphometric model could discriminate OSF well from other groups, suggesting that the change of the epithelium in OSF appearing in the spinous cell is specific itself.
Carcinoma, Squamous Cell↗
[Treatment of extensive deep burn of scalp with full-thickness necrosis of calvarial bone].
From 1990 to 1993 eight patients suffering from extensive deep burn of scalp with full-thickness necrosis of calvarial bone were treated. The intra-cranial damage following electrical injury or prolonged contact with heat source, and the extent of skull necrosis were delineated by CT and bone scanning. Primary coverage of the exposed calvarial bone using musculo-cutaneous flap or free skin flap was done, leaving the necrosed skull in situ to serve as a scaffold of "creeping substitution" for bone regeneration. Primary healing of the wound was achieved in four cases. Three cases required an average of 2.6 times of curettage or excision of the infected bone. None of the cases required a late reconstruction of the skull in this group.
Adolescent↗
[The expression of Cath-D, c-erbB-2 and EGFR in breast cancer and its correlation to lymphatic metastasis].
The expression of Cath-D c-erbB-2 and EGFR in breast cancer and its correlation of lymphatic metastases were studied in 277 cases by immunohistochemical technique. Positive staining of Cath-D was detected in 107 cases (38.62%), of which, 89 cases (83.17%) had documented metastasis in the lymph nodes. One hundred and seventy cases (61.38%) stained negative for Cath-D, of which 64 cases (37.64%) had detectable lymphatic metastases. There was a significant difference in the rate of the lymphatic metastases between the Cath-D positive and Cath-D negative groups (P < 0.0001). Fifty-six out of 107 Cath-D positive cases (52.34%) were c-erbB-2 positive as well. However, only 27 out of 170 Cath-D negative cases (15.88%) were c-erbB-2 positive. The positive rate of c-erbB-2 in Cath-D positive group was significantly different from that of Cath-D negative group (P < 0.0001). Among those 107 Cath-D positive cases, 49 cases (45.79%) were EGFR positive. Only 24 cases (14.12%) were EGFR positive among the 170 Cath-D negative cases. The positive rate of EGFR between these two groups was also significantly different (P < 0.0001). The results suggest that Cath-D status can be used as an indicator of the aggressiveness of the breast cancer. Breast cancer cases with a positive Cath-D staining are more likely to have lymphatic metastases and a poor prognosis. Therefore, alternative therapeutic strategies and close follow-ups are needed for these patients.
Adenocarcinoma↗
[A study of proliferative activity of soft tissue sarcomas].
Proliferative activity of soft tissue sarcomas (STS) in 31 cases was examined by histologic grading, mitotic count, DNA analysis by flow cytometry, and immunohistochemical procedures with monoclonal antibody Ki-67. Aneuploid was found in 12 of 16 cases (75.0%) with Grade 3, and in 4 of 15 cases (26.7%) with Grade 1,2 (P = 0.0121). Tumors with more than 100 Ki-67 positive cells per 10 high power fields (HPF) had a higher rate of aneuploid (81.3%) than those with less than 100 Ki-67 per 10 HPF (26.7%) (P = 0.0038). There was significant correlation between Grade and DNA index (DI) (r = 0.4901, P = 0.0051), Grade and Ki-67 (r = 0.4636, P = 0.0086), Ki-67 and DI (r = 0.6368, P = 0.0001). The results indicate that DI and reactivity of tumor cells to Ki-67 may reflect proliferative activity and be helpful for clinicians to judge the biological behaviour of tumors more accurately and objectively. Hence, supplementary to the grading of STS, DI and Ki-67 score could be useful as prognostic parameters for clinical invetigation of multimodality therapy for individual patients.
Adolescent↗
Highly efficient immobilization of phospholipase A2 and its biomedical applications.
A new method for the immobilization of phospholipase A2 (PLA2) has been developed to enhance the activity retention of immobilized PLA2. When PLA2 from the venom of Agkistrodon piscivorus piscivorus was pretreated with 4-nitro-3-octanoyl-oxybenzoic acid to acylate epsilon-amino groups of two lysines (Lys-7 and Lys-10) and the resulting acylated enzyme was covalently coupled onto carbonyldiimidazole-activated cross-linked agarose beads, the immobilized acylated enzyme showed high retention of activity toward various aggregated phospholipids. Toward densely packed phospholipid bilayers, such as large unilamellar vesicles of 1-palmitoyl-2-oleoyl-sn-glycero-3-phosphocholine, the immobilized acylated A. p. piscivorus PLA2 was 25-fold more active than the soluble A. p. piscivorus PLA2. The general applicability of our immobilization protocol was demonstrated by the high retention of activity achieved for the immobilized acylated PLA2 from the venom of Naja naja naja. In particular, full activity retention of the immobilized acylated A. p. piscivorus PLA2 toward phospholipids on the surface of human low density lipoproteins suggests its potential usefulness in a newly developed PLA2-based therapy for hypercholesterolemia.
Acylation↗