Significance of magnetic resonance signal enhancement in evaluation of myocardial infarction in cats

RATIONALE AND OBJECTIVES

To correlate magnetic resonance (MR) signal enhancement with pathophysiologic changes occurring during ischemia and reperfusion in evaluation of myocardial infarction in cats.

METHODS

Seven cats were subjected to 150 minutes of occlusion of the left anterior descending coronary artery followed by 90 minutes of reperfusion. Gadolinium (Gd) diethylenetriaminepentaacetic acid-polylysine (molecular weight [mw] = 40 to 50 kd, DP230) contrast-enhanced MR images were acquired with coinjection of poly-L-lysine-fluorescein isothiocyanate (mW = 40 to 50 kd, DP219) as a fluorescent tracer molecule of the contrast agent. Signal intensities on the MR images and fluorescence activities on the resected cardiac specimens were measured. Pathologic examinations by electron and light microscopes and 2,3,5-triphenyltetrazolium chloride histochemical staining were performed on the specimens.

RESULTS

Magnetic resonance signal intensity was lower in the center (3.49 +/- 0.36) than in the periphery (4.71 +/- 0.89) of the enhanced area. Fluorescence activities were absent in the normal myocardium; they were scant as nonspecific discrete dots in the center and numerous as specific interstitial distribution in the periphery of the ischemic myocardium. Electron and light microscopic examinations showed severely damaged ultrastructures of the center and moderately distorted ultrastructures of the periphery.

CONCLUSIONS

The center of the MR signal-enhanced area is the infarct center with severe ultrastructural damages, which also might be an area of little or absent of blood reflow. Conversely, the peripheral-enhanced area is the infarct periphery with moderate myocardial damages.

Isolation and characterization of the chicken trypsinogen gene family

Based on genomic Southern hybridizations and cDNA sequence analyses, the chicken trypsinogen gene family can be divided into two multi-member subfamilies, a six-member trypsinogen I subfamily which encodes the cationic trypsin isoenzymes and a three-member trypsinogen II subfamily which encodes the anionic trypsin isoenzymes. The chicken cDNA and genomic clones containing these two subfamilies were isolated and characterized by DNA sequence analysis. The results indicated that the chicken trypsinogen genes encoded a signal peptide of 15 to 16 amino acid residues, an activation peptide of 9 to 10 residues and a trypsin of 223 amino acid residues. The chicken trypsinogens contain all the common catalytic and structural features for trypsins, including the catalytic triad His, Asp and Ser and the six disulphide bonds. The trypsinogen I and II subfamilies share approximately 70% sequence identity at the nucleotide and amino acid level. The sequence comparison among chicken trypsinogen subfamily members and trypsin sequences from other species suggested that the chicken trypsinogen genes may have evolved in coincidental or concerted fashion.

Molecular electronics of a single photosystem I reaction center: studies with scanning tunneling microscopy and spectroscopy

Thylakoids and photosystem I (PSI) reaction centers were imaged by scanning tunneling microscopy. The thylakoids were isolated from spinach chloroplasts, and PSI reaction centers were extracted from thylakoid membranes. Because thylakoids are relatively thick nonconductors, they were sputter-coated with Pd/Au before imaging. PSI photosynthetic centers and chemically platinized PSI were investigated without sputter-coating. They were mounted on flat gold substrates that had been treated with mercaptoacetic acid to help bind the proteins. With tunneling spectroscopy, the PSI centers displayed a semiconductor-like response with a band gap of 1.8 eV. Lightly platinized (platinized for 1 hr) centers displayed diode-like conduction that resulted in dramatic contrast changes between images taken with opposite bias voltages. The electronic properties of this system were stable under long-term storage.

Changing the inhibitory specificity and function of Cucurbita maxima trypsin inhibitor-V by site-directed mutagenesis

Cucurbita maxima trypsin inhibitor-V (CMTI-V) is also a specific inhibitor of human blood coagulation factor beta-factor XIIa. A recombinant version of CMTI-V has allowed probing of roles of individual amino acid residues including the reactive site residue, lysine (P1), by site-directed mutagenesis. The K44R showed at least a 5-fold increase in inhibitory activity toward human beta-factor XIIa, while there was no change toward bovine trypsin. This result demonstrates that beta-factor-XIIa prefers an arginine residue over lysine residue, while trypsin is non-specific to lysine or arginine in its binding pocket. On the other hand, the specificity of CMTI-V could be changed from trypsin to chymotrypsin inhibition by mutation of the P1 residue to either leucine or methionine (K44L or K44M).

Identification and characterization of a human cDNA homologous to yeast SKI2

A monoclonal antibody, 170A1, which recognizes a nucleolar peptide of molecular weight 90,000, was raised. The protein was conserved among various vertebrates. To characterize the antigen, we screened a human fetal liver expression library using the monoclonal antibody as a probe. Molecular analyses of immunopositive clones suggested the presence of a novel cDNA. It appeared to be a single-copy gene and encoded about 4- and 5-kb mRNAs. The gene appeared to be expressed in every cell tested so far. Its deduced amino acid sequence revealed an overall homology to recently described yeast SKI2. The SKI2 gene of Saccharomyces cerevisiae encoded a nucleolar protein that is involved in the antiviral system. We report here the partial human cDNA sequence and the localization of the corresponding gene on chromosome 6p21.

Adhered platelet morphology in diabetes mellitus

We compared the morphology of platelets obtained from diabetic patients in various stages of retinopathy and nephropathy with those of control patients. The platelets were collected on to polyethylene films, processed and observed under scanning electron microscopy. Different platelet morphologies were observed within the diabetic group, correlating with the severity of complications, whereas platelets appeared normal in the control group. After more extensive follow-up and comparative studies, these preliminary observations could provide another diagnostic tool for detecting and evaluating severe complications associated with diabetes.

Comparative evaluation of bipolar atrial electrogram amplitude during everyday activities: atrial active fixation versus two types of single pass VDD/R leads

Endocardial P wave amplitude (PWA) is an important determinant of the atrial sensing capabilities of an atrial-based pacing system. Although changes in PWA during physical activities are known to occur in DDD/R pacing, there is little information on the P wave stability in single pass lead VDD/R pacemakers using floating P wave sensing. We investigated the variation of PWA during daily life activities using telemetry recorded atrial electrograms in 21 patients with DDDR pacemakers (Relay or Elite) and 29 patients with single lead VDD/R pacemakers (Unity or Thera). Physical activities resulted in marked individual variability of PWA but, as a group, there was no significant difference between PWA during sitting, standing, lying down, and coughing in both DDDR and VDD/R pacing. In the Elite II pacemaker, walking at 2 miles per hour resulted in significant reduction of PWA (11.6% compared with sitting, P < 0.05). The most consistent reduction in PWA occurred in the relaxation phase of the Valsalva maneuver (VM), with all pacemakers showing a reduction in PWA (mean reduction in PWA compared with sitting in DDDR and VDD/R were 16.6% and 12.8%, respectively). Two patients with DDDR pacemakers (Relay) and three patients with VDD/R pacemakers (1 Unity and 2 Thera) had atrial sensing failure during VM or walking. In conclusion, large variation in PWA occurs during daily life activities. The extent of variation is dependent on the patients, types of atrial lead, and the maneuvers performed. A twice sensing threshold may be insufficient to ensure adequate atrial sensing during these activities.(ABSTRACT TRUNCATED AT 250 WORDS)

Tissue-isolated human tumor xenografts in athymic nude mice

An ex vivo perfused solid tumor preparation provides control over the physiological, biochemical, and pharmacological composition of the arterial input and easy access to the venous output. This is advantageous for studies of transport and metabolism in solid tumors. Here we present a tissue-isolated tumor preparation adapted to the nude mouse, allowing ex vivo perfusion of human tumor xenografts. Previously, such preparations have only been developed in rats, to study primarily rodent tumors. In the present study this new tumor preparation is physiologically characterized in comparison with subcutaneously transplanted tumors in nude mice using the human colon adenocarcinoma LS174T.

Quantitative comparison of rate response and oxygen uptake kinetics between different sensor modes in multisensor rate adaptive pacing

Although multisensor pacing may mitigate the inadequacy of rate adaptation in a single sensor system, the clinical role of multisensor driven rate adaptive pacing remains unclear. The cardiopulmonary performance of six patients (mean age 63.5 +/- 10 years) who had undergone the implant of combined QT and activity VVIR (Topaz) pacemakers was assessed during submaximal and maximal treadmill exercise with the rate response sensor randomly programmed to either single sensor mode, QT and activity (ACT), or dual sensor mode, with equal contribution of QT and ACT (QT = ACT). The rate of response, the proportionality, oxygen kinetics, and maximal exercise performance of the various sensor modes during exercise were measured and compared. The ACT sensor mode "overpaced" and the QT and QT = ACT sensor modes "underpaced" during the first three quartiles of exercise (P < 0.05). The ACT sensor mode also gave the fastest rate of response with the shortest delay (13 +/- 1.5 sec vs 145 +/- 58 sec and 41 +/- 17 sec, P < 0.05), time to 50% rate response (39 +/- 2.7 sec vs 275 +/- 48 sec and 203 +/- 40 sec, P < 0.05), and time to 90% of rate response (107 +/- 21 sec vs 375 +/- 34 sec and 347 +/- 34 sec, P < 0.05) and a smaller oxygen debt (0.87 +/- 0.16 L vs 1.10 +/- 0.2 L and 1.07 +/- 0.18 L, P < 0.05) compared to the QT and QT = ACT sensor modes, respectively. These differences were most significant at low exercise workloads. Thus, different sensor combinations result in different rate response profiles and oxygen delivery, especially during low level exercise.(ABSTRACT TRUNCATED AT 250 WORDS)

Effect of hemodilution and resuscitation on tumor interstitial fluid pressure, blood flow, and oxygenation

Hemodilution due to hemorrhage may increase tumor blood flow (TBF) by lowering blood viscosity and decrease tumor interstitial fluid pressure (TIFP) by moving fluid from the interstitium to the vascular compartment and by lowering microvascular pressure (MVP), mainly due to the decrease in systemic pressure. To test this hypothesis, we measured mean arterial blood pressure (MABP), TIFP, hematocrit, relative TBF (RBC flux), and intratumor pO2 during hemorrhage and volume restitution in severe combined immunodeficient mice, bearing LS174T human colon adenocarcinoma xenografts. MABP and TIFP significantly decreased after 0.2 ml of blood (approximately 12% of blood volume) was withdrawn. MABP decreased from 87.5 +/- 3.9 mmHg (mean +/- standard error) to 59.8 +/- 4.8 mmHg (n = 5, P = 0.01) within 2.5 min after the withdrawal of blood and then returned to control value within 10 min. TIFP gradually decreased from 18.7 +/- 2.3 mmHg to 11.3 +/- 0.9 mmHg after 1 hr (n = 8, P = 0.01), while RBC flux increased by a factor of 1.99 +/- 0.38 (n = 5, P = 0.02). The systemic hematocrit decreased from 51.2 to 45.9% (n = 7, P = 0.02). Tumor oxygenation did not significantly improve (median pO2 for control, 28 mmHg, and median pO2 after blood withdrawal, 32 mmHg; P = 0.14). When 0.2 ml blood was withdrawn and replaced (within 2.5 min) with the same volume of normal saline, MABP significantly decreased from 86.4 +/- 2.4 mmHg to 65.6 +/- 4.6 mmHg (n = 11) at 1 hr post-treatment (P = 0.001). TIFP decreased, but not significantly, from 24.2 +/- 2.9 mmHg to 20.4 +/- 2.4 mmHg (P = 0.35). Blood withdrawals in excess of 0.3 ml significantly decreased MABP and TIFP without recovery during 1 hr of observation. Volume restitution with hyperoncotic/hyperosmotic 6.0% Dextran 70 and 7.5% saline had effects attributable to a direct transmission of systemic pressure to the tumor microcirculation and to a lowering of tumor venous resistance. These effects appear to be common to saline blood restitution and volume top-load with Dextran 70. In conclusion, mild hemorrhage (withdrawal of approximately 12% of blood volume) can significantly lower TIFP without a reduction in TBF and pO2.

Mechanism of apical and basolateral Na(+)-independent Cl-/base exchange in the rabbit superficial proximal straight tubule

The present study was undertaken to determine the magnitude and mechanism of base transport via the apical and basolateral Na(+)-independent Cl-/base exchangers in rabbit isolated perfused superficial S2 proximal tubules. The results demonstrate that there is an apical Na(+)-independent Cl-/base exchanger on both membranes. HCO3- fails to stimulate apical Cl-/base exchange in contrast to the basolateral exchanger. Inhibition of endogenous HCO3- production does not alter the rate of apical Cl-/base exchange in Hepes-buffered solutions. Both exchangers are inhibited by H2DIDS and furosemide; however, the basolateral anion exchanger is more sensitive to these inhibitors. The results indicate that the apical and basolateral Cl-/base exchangers differ in their transport properties and are able to transport base equivalents in the absence of formate. The formate concentration in rabbit arterial serum is approximately 6 microM and in vitro tubule formate production is < 0.6 pmol/min per mm. Formate in the micromolar range stimulates Jv in a dose-dependent manner in the absence of a transepithelial Na+ and Cl- gradient and without a measurable effect on Cl(-)-induced equivalent base flux. Apical formic acid recycling cannot be an important component of any cell model, which accounts for formic acid stimulation of transcellular NaCl transport in the rabbit superficial S2 proximal tubule. We propose that transcellular NaCl transport in this nephron segment is mediated by an apical Na+/H+ exchanger in parallel with a Cl-/OH- exchanger and that the secreted H+ and OH- ions form H2O in the tubule lumen.

Enhancement of antigen-induced T-cell proliferation by soluble CD26/dipeptidyl peptidase IV

The addition of a soluble recombinant CD26 (sCD26) enhanced proliferation of peripheral blood lymphocytes induced by the recall antigen tetanus toxoid. sCD26 itself did not provide a mitogenic signal and did not augment the proliferative response of T cells to other mitogenic stimuli such as phytohemagglutinin and anti-CD3. Dipeptidyl peptidase IV-negative sCD26 did not have this enhancement effect, implying a requirement for enzyme activity. It was found that there exists a large variation in the levels of human plasma sCD26/dipeptidyl peptidase IV in vivo which may regulate T-cell activity. Peripheral blood lymphocytes from individuals whose plasma sCD26 was high and responded strongly to tetanus toxoid stimulation were insensitive to the enhancing effects of exogenously added sCD26. This suggests that plasma sCD26 had modulated the responsiveness of T cells of these individuals in vivo and that the endogenous plasma sCD26 regulates immune responses by allowing antigen-specific T cells to exert a maximal response to their specific antigen.

Endodermal sinus tumor: immunophenotypic expression of a carcinoma

A series of five endodermal sinus tumors was studied for their cytoskeletal and other phenotypic markers. They included 2 ovarian, 2 testicular, and 1 inguinal tumors. The cytoskeletal expression was also studied by gel electrophoresis and immunoblotting. Every tumor was diffusely and strongly immunostained for cytokeratin. By SDS-PAGE and immunoblotting, cytokeratins 8 & 18 were detected. Vimentin was focally coexpressed in 4 cases. The stroma was diffusely immunostained for vimentin. None of them expressed desmin, neurofilament, or glial filament protein. Desmoplakin was expressed only in one ovarian tumor. Alpha-fetoprotein and S-100 protein were also diffusely positive among the neoplastic cells; intracytoplasmic globules were especially strongly immunostained. These findings suggest that endodermal sinus tumors represent a group of pure malignant epithelial neoplasms, and may be regarded as primitive carcinomas.

In vitro MR imaging of the resected stomach with a 4.7-T superconducting magnet

PURPOSE

To study the effects of formalin fixation, signal intensity characteristics of the stomach-wall layers, and findings suggestive of cancerous invasion to the stomach wall in vitro with magnetic resonance (MR) imaging in humans.

MATERIALS AND METHODS

MR images of nine specimens of stomach cancer and 29 normal specimens were obtained at 4.7 T; 26 of the normal specimens were fixed in 10% formalin for 2 hours to 187 days before imaging. The field gradient was 10 G/cm; the spatial resolution, 0.1 mm.

RESULTS

The mucosal, submucosal, and proper-muscle layers were clearly identifiable. The submucosa of the fresh specimens had the lowest signal intensity of all specimens on both T1- and T2-weighted images (P < .01). No statistical correlation existed between signal intensity and duration of fixation. Tumor invasion was detected in seven of eight specimens with mucosal invasion, all eight specimens with submucosal invasion, and three of six specimens with muscle invasion.

CONCLUSION

In vitro MR imaging enabled differentiation of all three layers of the stomach wall, detection of the cancer, and measurement of the depth of invasion.

Catalytic antibodies: perusing combinatorial libraries

Combinatorial libraries are a promising alternative for isolating catalytic antibodies produced by the immune system in response to the transition-state analog of a given reaction. Large, diverse panels of antibodies with high affinity for the transition-state analog can be isolated using screening or selection approaches. Furthermore, we have estimated that nucleotide sequences that bear close similarity to the sequence for a known catalytic antibody occur in combination at frequencies sufficient for their detection in such libraries.

Changes in tumour blood flow, oxygenation and interstitial fluid pressure induced by pentoxifylline

Pentoxifylline (PTX) has been shown to increase radiation damage to tumours and to decrease late radiation-induced injury to normal tissues. This tumour radiation sensitisation results from increased oxygen supply via improved tumour perfusion. We propose that the improved perfusion results from decreased viscous resistance and/or geometric resistance. The decreased flow resistance may be accompanied by a reduction in microvascular pressure (MVP). Since MVP is approximately equal to the interstitial fluid pressure (IFP), PTX should lead to a decrease in IFP. To test this hypothesis, we measured PO2, laser Doppler flow (RBC flux) and IFP in FSaII murine tumours at two doses (PTX at 25 and 100 mg per kg body weight) which sensitise this tumour to X-irradiation. We found that 25 mg kg-1 PTX was ineffective, but 100 mg kg-1 PTX was effective in increasing the PO2 of this tumour. PTX at 100 mg kg-1 (i.p.) increased median PO2 from 5 to 7 mmHg (P < 0.05) within 2 h, and decreased the fraction of PO2 values < 5 mmHg from 65% to 45% (P < 0.05). In support of our hypothesis, we found that with this dose of PTX, RBC flux in the tumour centre increased significantly (n = 6, P < 0.05) prior to an approximately 40% decrease (n = 13, P < 0.05) in tumour interstitial fluid pressure (TIFP), without changes in mean arterial blood pressure (MABP). In conclusion, a single i.p. administration of PTX at 100 mg kg-1 can increase oxygen availability in the tumour due to ameliorate hypoxia in tumour microregions. Second, PTX can lower the elevated TIFP without lowering the MABP.

Thymic epithelial cells of severe combined immunodeficiency (SCID) mice

To characterize thymic epithelial cells of SCID (severe combined immunodeficiency) mice in comparison with those of Balb C mice, we did an immunohistochemical study using cortical and medullary epithelial cell specific monoclonal antibodies (MoAbs), Th-3 and Th-4, as well as gel electrophoresis and immunoblotting. The thymi of SCID mice were composed of epithelial cells and a few lymphocytes. Most epithelial cells were immunostained diffusely with Th-3, which indicated that they might be "cortical-type" epithelial cells. There were a few clusters of stellate cells with dendritic processes which were negative with Th-3 but stained strongly with Th-4. Cortical type epithelial cells and most of the Th-4 reacting cells were strongly immunostained with cytokeratin antibody MNF116. By immunoblotting, cytokeratin polypeptides No. 10 and 18 were detected in both SCID and Balb C mice; however, the relative amounts of each cytokeratin polypeptides were different. With immunohistochemical and immunoblotting results, we conclude; 1) Th-3 and Th-4 are reliable markers for cortical and medullary thymic epithelial cells in SCID mice; 2) disorganization of cells thymic structure is mostly due to maldevelopment of medullary epithelial and T lymphocytes; and 3) the composition of cytokeratin subfamilies of SCID mice thymi may represent a phenotypic marker of the maldevelopment of medullary epithelial cells.

Extrafollicular reticulum cells in pathologic lymph nodes

Extrafollicular reticulum cells in lymph nodes are heterogeneous. They express cytokeratins, desmin, and/or vimentin as their intermediate filament profile. Using those markers, we undertook an immunohistochemical study of human lymph nodes under various pathologic conditions. Samples included 15 simple reactive lymph nodes, 7 follicular hyperplasia, 1 necrotizing lymphadenitis, 4 tuberculous lymphadenitis, 13 malignant lymphoma (9 non-Hodgkin's and 4 Hodgkin's lymphomas), and 11 metastatic adenocarcinoma. In lymph nodes with follicular hyperplasia, cytokeratin and/or desmin expressing reticulum cells displayed a characteristic dendritic meshwork in the subcapsular, perisinusoidal, and paracortical regions. In other forms reactive lymph nodes, they were similarly distributed but were less prominent. By SDS-PAGE and immunoblotting, cytokeratin polypeptides were identified. In necrotizing lymphadenitis, they were increased and the pattern of distribution was disturbed. In tuberculous lymphadenitis, they were also increased and located at nongranulomatous as well as in perigranulomatous areas. In lymphomas the reticular meshwork was entirely obliterated. Cytokeratin or desmin expressing reticulum cells were rarely seen within tumors. The reticular meshwork was also obliterated in metastatic carcinoma. However, the meshwork was maintained in uninvolved areas. In conclusion, extrafollicular reticulum cells displayed characteristic patterns of distribution under various pathologic conditions, and may be implicated in the pathogenesis of those pathologic conditions in human lymph nodes.

Isolation of LUMINIDEPENDENS: a gene involved in the control of flowering time in Arabidopsis

Plants have evolved the ability to regulate flowering in response to environmental signals such as temperature and photoperiod. The physiology and genetics of floral induction have been studied extensively, but the molecular mechanisms that underlie this process are poorly understood. To study this process, we isolated a gene, LUMINIDEPENDENS (LD), that is involved in the timing of flowering in Arabidopsis. Mutations in this gene render Arabidopsis late flowering and appear to affect light perception. The late-flowering phenotype of the ld mutation was partially suppressed by vernalization. Genomic and cDNA clones of the LD gene were characterized. The predicted amino acid sequence of the LD protein contains 953 residues and includes two putative bipartite nuclear localization signals and a glutamine-rich region.

Jarcho-Levin syndrome--a report of an autopsy case with cytogenetic analysis

Jarcho-Levin syndrome (JLS) is a condition manifested by malformations of vertebral bodes and related ribs. There are two major subtypes spondylocostal dysostosis and spondylothoracic dysostosis, with different survival rates, associated malformations, and inheritance patterns. We have experienced an autopsy case of a premature female fetus with multiple congenital anomalies. She was 30 weeks of gestational age, born as the second baby of twins and expired shortly after birth. A post-mortem examination revealed multiple abnormalities including cervicothoracic hemivertebrae, a diminished number of right-sided ribs, and pulmonary hypoplasia with left diaphragmatic hernia. In addition, there were anomalous rotation of the foregut, unfused pancreas and anomalous drainage of the superior vena cava. Chromosomal analysis showed 46, XX, del(4)(q ter).

Reticular network of the human thymus

To investigate the development of the reticular network of the thymus with aging and under pathologic conditions, we performed reticulin stains on the following samples; 5 fetal thymi (22 to 33 weeks of gestational age) and 35 postnatal thymi (less than 1 month to 33 years of age). The latter included 1 hyperplastic thymus, 4 pathologically involuted thymi and 1 physiologically involuted thymus as well as 29 normal thymi. Reticulin fibers were invariably seen along the capsule and interlobular septae of all the thymi. In fetal thymi, reticulin fibers circumscribed only cortical blood vessels and Hassall's corpuscles. Postnatal thymi from the children aged less than 1 month showed discontinuous reticulin fibers along the blood vessels of the corticomedullary junction. With aging, the amount of reticulin fibers increased and formed a "fibroreticular network(FRN)" from the branching point of the interlobular septae along the corticomedullary junction. It completely circumscribed the outer medulla in fully developed thymi. In the hyperplastic thymus, the reticular network retained its original structure. Both pathologically and physiologically involuted thymi revealed irregularly collapsed reticulin fibers. These findings suggest that the reticular network of the thymus consists of FRNs as well as capsule and interlobular septae and matures with aging before involution.

Expression of alpha-smooth muscle actin in liver diseases

To evaluate the distribution of alpha-smooth muscle actin (alpha-SMA) positive cells in various liver diseases, we undertook an immunohistochemical study of liver diseases including chronic persistent hepatitis, chronic active hepatitis, liver cirrhosis, intrahepatic cholelithiasis and hepatocellular carcinoma. As a control, fetal livers (gestational age: 22-26 weeks) showed alpha-SMA positive cells along the blood vessels of the portal area, terminal hepatic venules and at perisinusoidal spaces. Perisinusoidal alpha-SMA positive cells were bipolar shaped and had round nuclei. In chronic persistent hepatitis, a few alpha-SMA positive cells were admixed with the inflammatory infiltrates mostly along the intact limiting plate. They were also detected multifocally in a linear pattern along the dilated sinusoid. In chronic active hepatitis, very strong alpha-SMA staining was detected at the site of piecemeal necrosis and adjacent lobules. A-SMA expression was decreased in some cases after interferon treatment. In cases of transplanted liver biopsies, expression of intralobular alpha-SMA was diffusely increased but showed no correlation with degree of acute rejection. Cirrhotic livers revealed strong alpha-SMA positivity in fibrous septae as well as in the perisinusoidal space of intact hepatocytes at the leading edge of fibrosis. Interlobular bile ducts were concentrically circumscribed by alpha-SMA positive cells in cases of intrahepatic cholelithiasis. In trabecular type hepatocellular carcinomas, most sinusoidal lining cells were positive for alpha-SMA. Most intralobular alpha-SMA positive cells represent, if not all, perisinusoidal cells (PSCs) which are involved in intralobular fibrogenesis in various liver diseases.(ABSTRACT TRUNCATED AT 250 WORDS)