In situ hybridization and cytochemistry: localization of mRNA at stained neuromuscular junctions with 33P-labeled probes

We modified the Karnovsky and Roots method of staining sites of acetylcholinesterase (AChE) activity at neuromuscular junctions (NMJs) to survive the lengthy, multiple steps of in situ hybridization and autoradiography. When the original method of Karnovsky and Roots is used to identify the muscle endplates, the stain does not survive the in situ hybridization procedures and association of mRNA to specific endplates can be inferred only indirectly. The successful modification involves secondary staining with diaminobenzidine (DAB) and H2O2 using the Karnovsky-Roots staining reaction product as a catalyst. Mounted longitudinal cryosections of mouse sternocleidomastoid muscle were fixed and stained in one step on the slide with paraformaldehyde plus the Karnovsky-Roots stain, followed by DAB-H2O2 secondary staining. The tissues were then processed for in situ hybridization and probed for the acetylcholine receptor (AChR) epsilon-subunit mRNA, known to be localized at the NMJ. The probe was labeled with 33P, which is ideal for in situ hybridization. By this procedure, the endplate stain was retained even after the hybridization and autoradiographic procedures, and the developed grains due to radiolabeling of the AChR epsilon-subunit mRNA were localized at readily identified endplates.

Single-chain antibody variable region-targeted interleukin-2 stimulates T cell killing of human colorectal carcinoma cells

Recombinant DNA techniques were used to clone, construct and express the bifunctional molecule FV/IL-2. The FV/IL-2 is a single-chain 37 kDa fusion protein expressed in Escherichia coli under control of the strong T7 bacteriophage promoter in the expression vector pT7-7-FV-IL-2. The fused gene fragment FV-IL-2 contains a single-chain anti-TAG72 FV gene fragment and the human recombinant cDNA fragment of the IL-2 molecule. The renatured soluble form of FV/IL-2 was purified from E. coli inclusion bodies using hydroxylapatite chromatography. The yield of this fusion protein was estimated at 2.0 mg/L. Our data showed that the FV/IL-2 molecule retained the TAG72 antigen-binding specificity and the IL-2 activity as measured in the standard T cell proliferation as well as cytotoxicity assays. Therefore, it may prove to be useful in targeting the biological effect of IL-2 to tumour cells and stimulating its immune destruction.

Mouse muscle epsilon- and gamma-containing acetylcholine receptors expressed in Xenopus laevis oocytes do not differ in their degradation half-lives

Mouse acetylcholine receptors (AChRs) consisting of either the embryonic form (2 alpha, 1 beta, 1 delta and 1 gamma) or the adult form (2 alpha, 1 beta, 1 delta and 1 epsilon) were expressed in Xenopus laevis oocytes. As expected, the single channel conductance was approximately 52 pS and the exponential decay time constants were 2.2 and 8.2 ms for the gamma-AChR and respectively 65 pS and 0.6 and 2.8 ms for the epsilon-AChR. No difference was seen in the degradation rate between the gamma- and epsilon-containing AChRs, both having a half-life of about 5 days.

Excitation-contraction coupling in single guinea-pig ventricular myocytes exposed to hydrogen peroxide

1. The effects of hydrogen peroxide (H2O2), an in vitro free radical generating system, on excitation-contraction (E-C) coupling were studied in isolated adult guinea-pig ventricular myocytes using Ca(2+)-sensitive dyes and the patch-clamp technique. 2. In paced myocytes loaded with indo-1 AM, 1 mM H2O2 briefly increased, then decreased the amplitude of intracellular Ca2+ ([Ca2+]i) transients and cell contractions. Diastolic [Ca2+]i increased in association with cell shortening. Automaticity also developed, followed shortly by inexcitability. In contrast, paced myocytes exposed to the metabolic inhibitors carbonyl cyanide-p-trifluoromethoxyphenylhydrazone (FCCP) and 2-deoxyglucose (DG), rapidly became inexcitable and exhibited marked diastolic shortening prior to increases in diastolic [Ca2+]i. 3. In patch-clamped myocytes loaded with fura-2, H2O2 reduced the amplitude of the Ca2+ current (ICa), the [Ca2+]i transient, and active cell shortening. H2O2 prolonged the relaxation phase of the [Ca2+]i transient, and activated an outward membrane current consistent with the ATP-sensitive K+ current (IK,ATP), but did not change the voltage dependence of ICa, the peak [Ca2+]i transient or active cell shortening. These responses were qualitatively similar to patch-clamped myocytes exposed to FCCP and DG. 4. Following exposure to H2O2, ICa elicited smaller [Ca2+]i transients than under control conditions. This was consistent with the observation that H2O2 reduced sarcoplasmic reticulum (SR) stores of Ca2+ by 42%, when assessed by observing the [Ca2+]i transients elicited by rapid extracellular application of 5 mM caffeine. In contrast FCCP-DG tended to increase SR Ca2+ stores. 5. Despite the decrease in the caffeine-induced Ca2+i release after H2O2, there was an increase in the Na(+)-Ca2+ exchange current associated with the caffeine-induced [Ca2+]i transient. 6. We conclude, therefore, that as with metabolic inhibitors, H2O2 interferes with E-C coupling in guinea-pig myocytes by impairing ICa and activating IK,ATP. However, unlike metabolic inhibitors, H2O2 stimulates Na(+)-Ca2+ exchange and depletes SR Ca2+ stores. Furthermore, diastolic [Ca2+]i becomes elevated while the myocyte is still excitable. These observations suggest that free radicals have primary effects on cardiac E-C coupling independent of their depressant effects on metabolism.

Mutations in the ras proto-oncogenes in patients with myelodysplastic syndromes

Activation of the N- and K-ras proto-oncogenes is the most common molecular abnormality in myelodysplastic syndromes (MDS) and acute myeloid leukemia (AML). In retrospective studies, approximately 3-36% of MDS patients were reported to harbor a mutated ras proto-oncogene, with some series suggesting the presence of ras-mutations are associated with progressive disease and a poor prognosis. Since hematopoietic growth factors such as granulocyte colony-stimulating factor (G-CSF) are currently used for therapy in MDS but may stimulate the proliferation of leukemic cells, we assessed the frequency and significance of ras mutations in 27 MDS patients, 15 of whom underwent G-CSF therapy. Patients were analyzed for the presence of mutations in codons 12, 13, and 61 of the N- and K-ras proto-oncogenes. Only three patients (11%, two refractory anemia with excess of blasts (RAEB), one RAEB in transformation (RAEB-T)) harbored activated ras oncogenes with the mutations localized in N-ras codons 12 and 61. Patients were followed for periods of up to 4 years or until death supervened. Patients exhibiting ras mutations were no more likely to develop AML compared to ras-negative patients (1/3 vs. 10/24) or to have decreased survival (p = 0.64). These data indicate that, in this group of MDS patients, ras mutations do not appear to correlate with a poor prognosis, and do not adversely interact with exogenously administered G-CSF.

Secreted collagen induced by ascorbic acid in L5 cloned muscle cultures does not affect acetylcholine receptor expression

Previous studies have shown that ascorbic acid increases both the total surface acetylcholine receptor (AChR) expression and the mRNA for the alpha-subunit of this receptor in myotubes of cloned L5 muscle cultures. Since ascorbic acid increases collagen synthesis in fibroblasts, we studied the effect of ascorbic acid on collagen secretion in L5 muscle cells and investigated the possibility that the effects of ascorbic acid on collagen and AChR are related. We report that L5 muscle cells secrete collagen types I, III, and V, with collagen type I being the most abundant species, and that accumulation of secreted collagens increased in the medium approximately two- to ninefold within 3 h of ascorbic acid treatment. The increase in surface AChRs, on the other hand, developed more slowly, and was detected only about 20-24 h after ascorbic acid treatment. A short (5 h) treatment with ascorbic acid is, however, sufficient to trigger an increase in AChRs 24 h later. Since ascorbic acid caused a rapid increase in collagen secretion, whereas the effect on total surface AChRs occurs more slowly, we tested the possibility that an increase in secreted collagen might be necessary for the increase in AChRs. However, when the L5 cultures were treated with bacterial collagenase, the ascorbic acid-induced increase in secreted collagen was abolished but its inductive effect on AChRs was unchanged. The increase in secreted collagen is therefore not necessary for the increase in AChRs to occur.

[Extraction and homogeny of larvicidal toxin in Bacillus sphaericus strain C3-41]

Spore-crystal toxin and spore-wall protein of Bacillus sphaericus C3-41 were extracted respectively from spore-crystal complex. When subjected to SDS-PAGE, spore-crystal toxin might give two toxic protein bands (43 and 40 kilodaltons), but spore-wall protein had only a protein band (MW 104 kD), which was degraded into toxic 43 and 40 kD proteins by using NaOH. The LC50 values of spore-wall protein and spore-crystal toxin purified by Sephadex G-75 were 267 and 10 ng/ml respectively against the third instar larvae of Culex quinquefasciatus at 48 hours. The results of immunodiffusion showed that sodium hydroxide-solubilized spore-crystal toxins from spore-crystal complex of strain 2362, 1593, Bs-10 (H5a5b) and 2297 (H25) revealed cross reactions with 43 and 40 kD antiserum of strain C3-41, but those of strain K (H1), SS II-1, 1404 (H2) and 2315. (H26) without cross reaction with the same antiserum.

Differences in antigen-binding affinity caused by a single amino acid substitution in the variable region of the heavy chain

Site-directed mutagenesis has been used to examine the importance of histidine-99 in the VH CDR3 region of a mouse/human chimeric anti-TAG72 antibody, cB72.3-1-3. The expression vectors mpSV2neo-EP1-V-m4-10C gamma 1, containing seven different mutant VH region fragments (Vm4-10) in association with the immunoglobulin enhancer (E), promoter (P1) and human genomic C gamma 1 region fragments, were transfected into a heavy chain loss mutant cell line B72.3 Mut(K), respectively. Mutant chimeric antibodies cB72.3m4-10 were purified from the transfectant supernates, and their binding affinities for the TAG72 antigen relative to that of the original cB72.3-1-3 antibody were compared. Substitution of histidine-99 by glutamine resulted in a higher affinity antibody (cB72.3m4) whereas substitution by isoleucine resulted in a lower affinity antibody (cB72.3m9). The binding affinity of these mutant antibodies varied nearly eight-fold. It was concluded that the residue at position 99 in the VH CDR3 region is in a 'contact' position in the B72.3/TAG72 antibody-combining site. The polar side-chains of glutamine and asparagine or the ionized side-chains of histidine, arginine or glutamic acid contribute to higher binding affinity, whereas the hydrophobic side-chains of isoleucine, leucine or phenylalanine resulted in a lower binding affinity for the TAG72 antigen.

Recombinant bifunctional molecule FV/IFN-gamma possesses the anti-tumor FV as well as the gamma interferon activities

Recombinant DNA techniques were used to clone, construct and express the bifunctional molecule FV/IFN-gamma. The FV/IFN-gamma is a single-chain 42KD fusion protein expressed in E. coli under control of the strong T7 bacteriophage promoter in the expression vector pT7-7-FV-IFN-gamma. The fused gene fragment FV-IFN-gamma containing a single-chain anti-TAG72 FV gene fragment as well as the human recombinant cDNA fragment of IFN-gamma molecule. The renatured soluble form of FV/IFN-gamma was purified from E. coli inclusion bodies using HTPT chromatography. The yield of this fusion protein was estimated at 10mg/L. Our data showed that the FV/IFN-gamma molecule retained the TAG72 antigen-binding specificity and the IFN-gamma activity as measured in ELISA, Western blotting and up-regulation of CEA expression by IFN-gamma. Therefore, it may prove to be useful in targeting the biological effect of IFN-gamma to tumor cells and stimulating its immune destruction.

Glucose alone does not completely hydrate bacteriorhodopsin in glucose-embedded purple membrane

Glucose embedding is a simple and highly effective method for preparing biological macromolecules for high-resolution electron microscopy. The investigation of conditions that can trap the M-state intermediate in the bacteriorhodopsin (bR) photocycle has revealed, however, that when glucose-embedded bR is prepared at ambient humidity, it does not fully retain the capability to execute a proper photocycle. However, 'native' photocycle properties are returned after glucose-embedded samples are equilibrated at 81% relative humidity. Equilibration at relative humidities significantly higher than 81% causes glucose to dissolve in its own water of hydration, resulting in samples that may be too thick to be suitable for electron microscopy. The results obtained with bR indicate that caution should be taken with other biological specimens, and it cannot be assumed that glucose-embedded biological macromolecules retain completely their native, hydrated structure, even when high-resolution electron diffraction patterns are obtained. Equilibration of such samples at high humidity may generally be a worthwhile precaution when using the glucose-embedding technique.

The tyrosine residue at position 97 in the VH CDR3 region of a mouse/human chimeric anti-colorectal carcinoma antibody contributes hydrogen bonding to the TAG72 antigen

One amino acid, tyrosine at position 96 and 97 in the VH CDR3 region of a mouse/human chimeric anti-TAG72 antibody cB72.3m4 was substituted by the phenylalanine residue and by a number of amino acids from different amino acid groups by the site-directed mutagenesis technique. The expression vector mpSV2neo-EP1-Vm11-16C1 containing mutant VH region fragments (Vm11-16) as well as the immunoglobulin enhances (E), promoter (P1) and the human genomic C1 region fragments, were transfected into a heavy-chain-loss mutant cell line B72.3Mut(K), respectively. Mutant chimeric cB72.3m11-16 antibodies were purified from the transfectant supernates and compared based upon their binding affinity for the TAG72 antigen relative to that of the original cB72.3m4 antibody. The data showed that a single amino acid substitution of tyrosine by phenylalanine and a number of amino acids including serine, asparagine, histidine and arginine at position 97 in the VH CDR3 region all resulted in approximate 18-fold lower binding affinity, whereas the substitution of tyrosine by phenylalanine at position 96 in the VH CDR3 region did not affect the binding affinity of the cB72.3m4 antibody. This suggests that the tyrosine residue at position 97 in the VH CDR3 region is in a contact position in the B72.3/TAG72 antibody/antigen interaction, and that the terminal hydroxyl group of the position 97 tyrosine side-chain contributes hydrogen bonding to the TAG72 antigen, whereas the position 96 tyrosine side-chain does not.

Renal extracellular matrix accumulation in acute puromycin aminonucleoside nephrosis in rats

Progressive renal fibrosis is considered to be the final common pathway leading to chronic renal insufficiency. In this study, the authors examined some of the cellular and molecular mechanisms regulating the renal accumulation of extracellular matrix (ECM) proteins using rats with puromycin amino-nucleoside (PAN) nephrosis as an acute model system. Puromycin aminonucleoside rats developed reversible nephrotic syndrome accompanied by an interstitial infiltrate of monocytes. The number of interstitial fibroblasts expressing ST4 antigen did not increase. During the first 4 days, steady-state mRNA levels for all genes examined remained at or below control levels. At 1 week, nephrotic syndrome and interstitial inflammation were established, and a period of renal cell proliferation occurred, identified by increased histone mRNA levels and localized by tritiated thymine autoradiography to tubular epithelial cells and occasional interstitial cells. Transforming growth factor-beta (TGF-beta) steady-state mRNA levels were increased eightfold, but returned to control levels by 3 weeks. At week 1, there was a 10- to 20-fold increase in kidney steady-state mRNA levels for genes encoding interstitial matrix proteins collagen I and fibronectin and basement membrane collagen IV. By in situ hybridization, alpha 1(I) procollagen mRNA was localized to interstitial cells. Immunofluorescence microscopy demonstrated focal accumulation of ECM proteins in the tubulointerstitial compartment at 2 and 3 weeks, but by 6 weeks, kidney immunohistology was normal again. Steady-state mRNA levels for the matrix degrading metalloproteinase stromelysin remained at control values, whereas the levels for interstitial collagenase were normal at week 1 and increased twofold to threefold at 2 and 3 weeks. Steady-state mRNA levels for the tissue inhibitor of metalloproteinases (TIMP) increased fivefold at 1 week and returned to baseline values over the next 2 weeks. The results of this study suggest that tubulointerstitial ECM accumulation occurs in rats with acute PAN nephrosis because of the activation of genes encoding several matrix proteins and inhibition of matrix degradation mediated by TIMP. These events are reversed during the phase of recovery from nephrotic syndrome. Increased mRNA levels for TGF-beta, possibly originating from inflammatory interstitial monocytes, are likely to be one of the mediators of the molecular events observed.

ras oncogene activation and occupational exposures in acute myeloid leukemia

BACKGROUND

Epidemiologic studies of acute myeloid leukemias (AMLs) show small increases in risk of disease associated with certain occupations and chemical exposures.

PURPOSE

This study was designed to determine whether the presence of mutationally activated ras oncogenes in AML are associated with occupational and chemical exposures.

METHODS

We interviewed 62 patients with newly diagnosed AML (or their next-of-kin), all of whom were enrolled in a national multicenter clinical trial, and 630 healthy control subjects. DNA extracted from patients' pretreatment bone marrow samples was amplified by using the polymerase chain reaction and probed with allele-specific oligonucleotides for activating point mutations at the 12th, 13th, and 61st codons of three protooncogenes: H-ras (also known as HRAS), K-ras (also known as KRAS2), and N-ras (also known as NRAS).

RESULTS

Patients with ras mutation-positive AML had a higher frequency (six of 10 patients) of working 5 or more years in an a priori high-risk occupation than did patients with ras mutation-negative AML (eight of 52; odds ratio [OR] = 6.8; 95% confidence interval [CI] = 1.3-36). Patients with ras mutation-positive AML were more likely than patients with ras mutation-negative AML to have breathed chemical vapor on the job (OR = 9.1; 95% CI = 1.3-64) or to have had skin contact with chemicals (OR = 6.9; 95% CI = 1.3-37). When ras-positive patients were compared with healthy control subjects, the ORs for occupation and occupational exposures remained elevated, while patients with ras mutation-negative AML showed no increased risk when compared with control subjects.

CONCLUSION

Activation of ras proto-oncogenes may identify an etiologic subgroup of AML caused by occupation and chemical exposure.

IMPLICATION

Disease etiology may be better understood if epidemiologic measures of exposure are integrated with molecular assays of the genetic defects responsible for cancer initiation and promotion.

Characterization of the conformational change in the M1 and M2 substates of bacteriorhodopsin by the combined use of visible and infrared spectroscopy

A combination of visible and Fourier transform infrared (FTIR) spectroscopies is used to characterize the formation of the M1 and M2 substates of the bacteriorhodopsin photocycle in glucose-embedded, hydrated thin films. Difference FTIR bands in the amide I region verify the previously reported existence of a significant peptide backbone conformational change in the transition from M1 to M2. The visible absorption spectra demonstrate that contamination of the M-intermediate samples by L, N, or other non-M species should contribute negligibly to the observed changes in the amide I region, and this conclusion is supported by comparison of specific carboxyl group peaks with corresponding bands in published L and N FTIR difference spectra. Based upon spectroscopic results, an extension of the C-T Model (Fodor, S., Ames, J., Gebhard, R., van den Berg, E., Stoeckenius, W., Lugtenberg, J., and Mathies, R. (1988) Biochemistry 27, 7097-7101) is presented. The results of this work suggest that protein structural changes should be clearly visible in M-bR, difference Fourier density maps and that these structural changes may in turn elucidate how bacteriorhodopsin actively pumps ions across the purple membrane of Halobacterium halobium.

Alterations of the p53 gene in nasopharyngeal carcinoma

Nasopharyngeal carcinoma (NPC) is a malignancy which is consistently associated with the Epstein-Barr virus (EBV). The structure of the EBV genome in NPC suggests that NPC is a clonal proliferation of epithelial cells which emerges after EBV infection. The disease develops with high incidence in specific populations in discrete geographic locations, implicating possible genetic or environmental cofactors. Mutations of the p53 gene are among the most frequent genetic changes found in a large variety of human tumors. Mutations in p53 have been shown to abrogate the suppressor function of wild-type p53 and thus contribute to the transformed phenotype. To determine if mutation in p53 participates in the development of the malignant clone in NPC, the structure and sequence of p53 in 42 primary, metastatic, and nude mouse-passaged NPC specimens was analyzed. A high frequency (6 of 9) of mutations was detected in the nude mouse-passaged tumors, while only 2 of 15 metastatic and 0 of the 18 primary tumors harbored mutant p53. The p53 mutations included single-point mutations and more extensive changes such as frame shifts, deletion, duplication, or complete loss of coding sequences. These data indicate that alterations of the p53 gene are unlikely to be involved in the initial genetic events leading to the clonal outgrowth in NPC. However, although it is a rare NPC which can be established in nude mice, this growth advantage appears to be conferred on tumors bearing a mutant p53.

B region variant of the estrogen receptor gene

Images

The HER2 (c-erbB-2) oncogene is frequently amplified in in situ carcinomas of the breast

Amplification and overexpression of the HER2 (c-erbB-2) oncogene was assessed in paraffin-embedded specimens from 27 in situ carcinomas of the breast and from 122 stage II breast cancers. Gene amplification detected in these archival tissues by differential polymerase chain reaction (PCR) was found in 48% of in situ carcinomas and in 21% of stage II lesions (chi 2 = 7.62, p less than or equal to 0.01). In addition, the level of gene amplification correlated with the level of HER2 oncoprotein expression as measured by immunohistochemistry for both in situ cancers (p less than or equal to 0.025) and stage II cancers (p less than or equal to 0.0005). This high incidence of HER2 gene amplification with accompanying overexpression in non-invasive breast tumors suggests that perturbations of the HER2 oncogene are among the earliest and most common genetic lesions in human breast cancer.

Analysis of gene amplification in archival tissue by differential polymerase chain reaction

Oncogene amplification is found in many human tumors, and its detection may have important prognostic value. However, analysis of gene amplification may be hampered by inadequate tissue or poor DNA quality. We have previously described a polymerase chain reaction (PCR)-based procedure called differential PCR that can detect variations in gene dosage using miniscule amounts of tumor DNA [Frye, R.A., Benz, C.C. & Liu, E. (1989). Oncogene, 4, 1153-1157]. We now report the optimization of this technique for the analysis of oncogene amplification in paraffin-embedded archival tissues. We find that differential PCR is able to detect amplification of the HER2 (c-erbB-2) and the epidermal growth factor receptor (EGFR) genes and can be used to arrive at a semiquantitative estimate of gene dosage. Furthermore, our approach can determine gene amplification in samples in which the DNA is significantly degraded. Using differential PCR on paraffin-embedded tissues from cases previously investigated by standard DNA extraction and dot-blot procedures, good correlation between the two methods was found. Approaches are described to overcome technical problems posed by factors that affect the differential PCR, including the method of DNA extraction and extreme fragmentation of the DNA (less than 200 base pairs). Furthermore, the resulting analytical algorithm reported herein has proved effective in detecting oncogene amplification in archival breast cancer specimens from standard pathology laboratories. Thus, differential PCR will be particularly helpful in the analysis of tumor specimens that are archived, small in size or rare in occurrence.

Production of hybrid bispecific antibody recognizing human colorectal carcinoma and CD3 antigen

The present study reports on the use of gene transfer by vector DNA in the generation of hybrid hybridoma, the quadroma secreting the hybrid bispecific antibody. A quadroma B72.3neo/OKT3gpt was simply derived from the fusion of two hybridoma cell lines, B72.3 and OKT3, tagged with vector DNA mpSV2neo and mpSV2gpt, respectively, and selected in the media containing both G418 and mycophenolic acid. The hybrid bispecific antibody B72.3/OKT3 was purified from the quadroma ascites by the use of hydroxylapatite column on high-pressure liquid chromatography. This bispecific antibody contained one binding site for the TAG72 antigen on OVCAR3 tumor cells and the other binding site for the CD3 molecule on human T cells. It was able to target human T lymphocytes to significantly lyse the human ovarian cancer cells and may therefore be useful in immunotherapy of cancer.

Pathogenesis of interstitial fibrosis in chronic purine aminonucleoside nephrosis

A cellular and molecular approach was used to gain new insight into the pathogenesis of interstitial fibrosis in chronic purine aminonucleoside nephrosis (PAN) nephrosis. Thirty experimental rats (PAN rats) were given 15 mg/100 g body wt of i.p. PAN at time 0, followed by 4.3 mg/100 g body wt i.p. on days 20, 27 and 34; 25 control rats received i.p. saline at the same time intervals. All rats had a right unilateral nephrectomy within the first four days. Groups of control and PAN rats were killed at 21, 37, 52, 72 and 91 days. Renal sections were studied by immunofluorescence to quantitate interstitial macrophages, T lymphocytes and fibroblasts, and to characterize the deposition of the extracellular matrix (ECM) proteins (collagens I, III and IV, fibronectin and laminin) and the tissue inhibitor of the metalloproteinases (TIMP). Steady state concentrations of mRNA from the whole kidney for these ECM proteins, the metalloproteinases, TIMP, and transforming growth factor beta (TGF-beta 1) were quantitated by Northern blot analysis. Significant increases in the number of interstitial macrophages and T lymphocytes were found in the PAN rat groups compared to that in controls. All ECM proteins examined were quantitatively increased in the tubulo-interstitium of PAN rats. The pattern of distribution of some ECM proteins was also modified in experimental animals. TIMP was increased in the interstitium of PAN rats; at later times, TIMP was most prominent in sclerotic regions of the glomeruli and in tubular protein droplets. Northern blot analysis revealed increased steady-state mRNA levels for components of each of the ECM proteins, no change for the metalloproteinases--stromelysin or collagenase--and a marked increase for TIMP and TGF-beta 1 in PAN animals. The results of this study suggest that the diffuse interstitial fibrosis found in chronic PAN nephrosis results from both increased production of ECM proteins and decreased matrix degradation.

Effects of lysophosphatidylcholine on electrophysiological properties and excitation-contraction coupling in isolated guinea pig ventricular myocytes

Lysophosphoglyceride accumulation in ischemic myocardium has been implicated as a cause of arrhythmias. We examined the effects of lysophosphatidylcholine (LPC) in isolated guinea pig ventricular myocytes. In paced myocytes loaded with the Ca2+ indicator Indo-1-AM and studied at room temperature, 20 microM LPC caused an initial positive inotropic effect followed by spontaneous automaticity, a decline in active cell shortening, and progressive diastolic shortening (contracture) leading to cell death. These changes were accompanied by a progressive increase in cytosolic [Ca2+]i. In patch-clamped myocytes dialyzed internally with high EGTA concentrations, LPC caused membrane depolarization, shortening of the action potential duration, and abnormal automaticity as seen in multicellular preparations. Voltage clamp experiments revealed the appearance of a nonselective leak conductance without significant changes in the delayed rectifier K+ current, inward rectifier K+ current, L-type Ca2+ current, and T-type Ca2+ current. Pretreatment with 20 mM caffeine and [Ca2+]o-free solution did not prevent the leak current. In patch clamped myocytes loaded with 0.1 mM Fura-2 salt, the [Ca2+]i transient induced by either voltage clamps or brief caffeine exposure remained normal until the nonselective leak current developed. The Na(+)-Ca2+ exchange current elicited during caffeine-induced [Ca2+]i transients also did not appear to be altered by LPC. Qualitatively similar results were obtained in myocytes studied at 35 degrees C. The membrane detergent saponin (0.005% wt/wt) mimicked all of the effects of LPC. We conclude that under these experimental conditions the effects of LPC are most compatible with a detergent action causing membrane leakiness with resultant depolarization, [Ca2+]i overload, and contracture.

Amiloride improves hemodynamics in patients with chronic congestive heart failure treated with chronic digoxin and diuretics

Potassium-sparing diuretics have been reported to decrease the positive inotropic effect of digoxin. We studied the hemodynamic effects of amiloride in patients taking digoxin for chronic heart failure. Eleven men with a history of congestive heart failure were studied in a double blind, cross-over, placebo controlled trial with the patients on digoxin alternating placebo with amiloride. After 7 days on the trial drug, a Swan-Ganz catheter was placed in the pulmonary artery and measurements made at rest and with increasing degrees of supine bicycle exercise. Right-sided and pulmonary artery wedge pressures and systemic arterial pressures, as well as cardiac outputs, were measured. After a 7 day washout period, placebo (P) and Amiloride (A) were switched and after 7 days on the therapy, a second hemodynamic study at rest and varying degrees of supine bicycle exercise was repeated. At rest there were no significant differences in the right-sided, pulmonary arterial wedge pressure or cardiac outputs between the patients on Amiloride (A) versus placebo (P). During exercise there were significant differences between (P) and (A) at the 50 watt-second stage of exercise.(ABSTRACT TRUNCATED AT 250 WORDS)

Erythrocyte vesiculation in paroxysmal nocturnal hemoglobinuria

Red blood cells from patients with paroxysmal nocturnal hemoglobinuria (PNH) were found to be liable to vesiculate, as demonstrated by both DMPC liposome- and CaCl2-induced vesiculation and measured in terms of acetylcholinesterase activity and 3H-inositol radioactivity in the supernatant. Membrane proteins released from the cells during vesiculation included several constituents with molecular weights identical to those of some complement regulating factors (e.g. DAF) which play an essential role in complement-mediated hemolysis. Red blood cells from both normal and PNH patients showed decreased deformability after vesiculation. Liability to vesiculate and the consequential loss of certain essential membrane proteins and decreased deformability might be a factor contributing to the mechanism of hemolysis in PNH.