Contractile properties of isolated porcine ventricular myocytes

OBJECTIVE

The aim was to examine the structure, function, and inotropic responsiveness of isolated porcine myocytes.

METHODS

Left ventricular myocytes were harvested from six pigs with normal echocardiographic and pressure indices of left ventricular function: fractional shortening 30 (SEM 2)%, peak+dP/dt 1225(110) mm Hg.s-1, end diastolic pressure 7(2) mm Hg, and cardiac output 2.8(0.5) litres.min-1. Indices of myocyte contractility were examined using a computer assisted video edge detection system which included the percent and velocity of myocyte shortening. Myocyte contractions were recorded by alternating field stimulation at 1 Hz and measurements performed in the presence of 2-10 mM extracellular Ca2+. Contractile properties of isolated porcine myocytes were examined unattached (n = 20) or following attachment to a basement membrane substrate (n = 63).

RESULTS

Left ventricular myocytes were successfully obtained from all pigs with a 68% average yield of viable myocytes. Isolated myocyte length was 128(6) microns with an average profile surface area of 2226(51) microns 2 (coefficients of variation of 25% and 35% respectively). Electron microscopic examination showed normal cytoarchitecture with 62(4)% myofibrils by volume. Baseline extent and velocity of shortening for unattached myocytes was 6.2% and 77(10) microns.s-1 respectively. Baseline extent and velocity of shortening for myocytes adherent to a basement substrate were 4.9(0.4)% and 64(7) microns.s-1. These indices of myocyte contractile function increased from baseline values for both the unattached and attached cells with increased extracellular Ca2+.

CONCLUSIONS

Isolated porcine left ventricular myocytes retain normal cytoarchitecture and composition, respond to field stimulation, and are responsive to extracellular Ca2+. Myocytes adherent to a basement membrane substrate were capable of contracting against this resistive load.

Transmission of dengue virus-induced helper signal to B cell via macrophages

The helper T cells (TH) generated in dengue type 2 virus (DV) infection of mice produce a soluble helper cytokine (HF) which enhances the clonal expansion of DV-specific IgM antibody plaque forming cells (PFC). The present study was undertaken to investigate the mechanism of transmission of the helper signal from TH and HF to B cells. It was observed that TH could transmit the helper signal to B cells by direct cell to cell contact, but HF could not do so without the presence of live macrophages (M phi). HF was adsorbed by both heat killed and live M phi but the former could not transmit it to B cells. Both the polypeptide chains of HF bind to M phi. HF remains on the surface of M phi and can be retrieved completely by contact with B cells for 40 min. The helper signal from TH or HF-adsorbed M phi could not be transmitted to B cells when they were separated from each other by a cell impermeable membrane. The enhancement of PFC count is greater when the signal is transmitted by HF-adsorbed M phi as compared to that by TH alone. Thus, even with lower frequency of TH a significant number of B cells may be triggered with the help of HF and M phi. The findings thus show that the DV-specific helper signal could be transmitted only by a close physical contact of the plasma membranes of the signal presenting cells (TH or HF-adsorbed M phi) and B cells.

Induction of lepromin positivity by a candidate anti-leprosy vaccine Mycobacterium w in lepromin negative healthy contacts of multibacillary leprosy patients

In a hospital based study, 362 household contacts of multibacillary leprosy patients were screened for evidence of leprosy and 54 (14.9%) were found to be having leprosy. The remaining 308 apparently healthy contacts were lepromin tested and 109 (35.4%) were observed to be negative to Mitsuda lepromin. M.w vaccine was administered intradermally to 95 of these 109 lepromin negative contacts. Sixty eight of them could be retested for lepromin A reactivity. Fifty six (82.35%) manifested lepromin conversion. The twelve subjects who did not show lepromin conversion, received a second dose of the vaccine, and eleven subsequently became lepromin positive. The overall lepromin conversion rate was thus 98.5% (67 out of 68). Follow-up of these contacts upto a period of 30 months did not demonstrate reversion of lepromin positivity back to negativity status. No untoward effects of vaccination were observed except for local ulceration at the site of vaccine administration.

Do human leukocyte antigens have a role to play in differential manifestation of multibacillary leprosy: a study on multibacillary leprosy patients from north India

118 multibacillary leprosy patients with differential manifestations were studied for the antigens they expressed at MHC loci to investigate the role of human leukocyte antigens in the differential response to the same causative agent. While the lepromatous leprosy (LL) patients showed a significant increase of Bw60, DR2, DRw8 and DQw1, borderline lepromatous (BL) patients had Bw52, DR9 and DQw7 significantly more often as compared to the normal controls. A comparison of LL, BL and mid-borderline (BB) patients showed a significantly higher frequency of Bw60 in LL patients as compared to the BL. However, Bw52, Bw53, DR9 and DQw7 were found significantly more often in the BL patients as compared to the LL patients but the difference failed to reach significance after pc. A comparison of HLA antigens in BB patients with those of either the LL or BL patients did not show any significant differences.

hsp70 synthesis in Schwann cells in response to heat shock and infection with Mycobacterium leprae

Induction of heat shock protein synthesis was monitored in murine and monkey Schwann cells exposed to elevated temperatures. Synthesis of the stress-inducible 70-kDa heat shock protein (hsp70) was detected in both murine and primate Schwann cells by metabolic labelling and by immunoblotting with a specific monoclonal antibody. hsp70 synthesis was also induced in Schwann cells after infection with Mycobacterium leprae and was detected from 24 h to 1 week postinfection. These results are discussed with respect to the possible role of heat shock proteins in immunopathological events associated with the clinical manifestations of leprosy.

Relation between ventricular and myocyte function with tachycardia-induced cardiomyopathy

Chronic supraventricular tachycardia (SVT) causes left ventricular (LV) dilatation and dysfunction. Changes in myocyte function and structure may be important factors in the development of SVT cardiomyopathy. Accordingly, LV function and isolated myocyte structure and function were examined in six pigs with pacing-induced SVT cardiomyopathy (3 weeks at 240 beats per minute) and six control pigs. LV function was examined by simultaneous echocardiography and catheterization, and isolated myocyte function was studied using computer-assisted video microscopy. Indexes of isolated myocyte contractile performance were examined in the unloaded, unattached state (31 control and 24 SVT cells) and after attachment to a basement membrane substrate (65 control and 45 SVT cells). LV fractional shortening and peak +dP/dt significantly decreased in SVT cells compared with control cells (12 +/- 2% versus 28 +/- 2%, and 842 +/- 61 versus 1,216 +/- 119 mm Hg/sec, respectively; p less than 0.05). Isolated myocyte percent shortening and normalized peak velocity of shortening of SVT myocytes adherent to a basement membrane were significantly lower than attached control myocytes (1.2 +/- 0.2% versus 4.3 +/- 0.3%, and 15 +/- 2 versus 37 +/- 5% resting cell length/sec, respectively; p less than 0.05). Similarly, in the unattached state, the extent and velocity of shortening of SVT myocytes were reduced by over 50% from control values. Contractile properties of attached and unattached cardiocytes were also examined in the presence of 2-8 mM extracellular Ca2+. For both attached and unattached SVT myocytes, responsiveness to increases in extracellular Ca2+ were significantly blunted from control values. Ultrastructural examination of SVT myocytes revealed that the percent volume of myofibrils within isolated myocytes was reduced from control values (46 +/- 7% versus 65 +/- 2%, p less than 0.05). In summary, SVT cardiomyopathy is probably due to a primary defect in isolated myocyte contractile performance. The reduced contractile function of SVT cardiomyopathic myocytes was associated with abnormalities in cytoarchitecture and Ca2+ responsiveness.

Ultrastructural study of mouse dorsal root ganglion cultures infected long term with M. leprae

Ultrastructural changes in the mouse dorsal root ganglion cultures infected long-term with viable M.leprae were studied. Subtle cytomorphological changes and loss of neurites noted in the long-term infected cultures were correlated to early events in the nerve damage.

Characterization of the dengue virus-induced helper cytokine

Dengue type 2 virus (DV) induces a subpopulation of T lymphocytes of mouse spleen to secrete a soluble helper cytokine (HF) which enhances the DV-specific IgM antibody plaque forming cells (PFC). The present study undertaken to purify and characterize HF shows that it can be purified by low pressure liquid chromatography (LPLC) using Sephacryl S-200 column. HF consisted of two subunits, having a M(r) of 65-68 kDa on SDS-PAGE, and both had similar activity. The isoelectric point of HF was 6.5. HF-specific antisera (HFAS) raised in mice neutralized the activity of HF in mice, reacted with it in a Western blot assay, and bound HF in an immunosorbent column. HF bound to DV-antigen in an immunosorbent column and enhanced only the DV-specific PFC. HF had no effect on PFC against heterologous antigens such as Japanese encephalitis virus, Coxsackie B4 virus or sheep red blood cells. HF generated in mice of H-2k haplotype, enhanced DV-specific PFC in the same strain of mice but had no effect on that in the H-2d or H-2q haplotype strains of mice. Thus, DV-induced HF with a M(r) of 65-68 kDa, antigen-specificity and genetic-restriction differs from most of the similarly acting cytokines but appears similar to the cell-free form of T cell receptor alpha beta dimer.

Serum tumor necrosis factor and interleukin 1 in leprosy and during lepra reactions

Tumor necrosis factor--alpha (TNF), one of the mediators of septic shock, has a role in the immunopathological complications of several infections. However, its role in leprosy is yet unclear. In this study, serum TNF and IL-1 levels in 64 patients spread over the spectrum of leprosy [lepromatous leprosy (LL), 30; borderline lepromatous, 12; borderline borderline, 8; and borderline tuberculoid-tuberculoid leprosy, 14] were measured at the time of admission. Elevated levels of TNF ranging from 15 to 4500 pg/ml were detected in lepromatous leprosy cases (399 +/- 189) and low levels ranging from 15 to 160 pg/ml were detected in the tuberculoid form of leprosy. Patients undergoing type 1 and type 2 lepra reactions also exhibited high TNF levels of 15-2100 pg/ml. Of the 14 clinically healthy individuals studied, 3 showed TNF levels of 15, 50, and 58 pg/ml. Interleukin 1-beta (IL-1) levels were found to be significantly higher in LL cases (70-5000 pg/ml) (328 +/- 184) in comparison to other groups or normal controls (9 +/- 3). The coefficient of correlation between TNF and IL-1 levels was statistically significant in LL and reaction cases (r = 0.96, P less than 0.001). These patients were followed up as outpatients for a period of 1 year. It was observed that 4 out of 8 patients with TNF levels greater than 100 pg/ml went into lepra reactions between 2 and 6 months after entry into the study, whereas only 5 out of 56 with less than 100 pg/ml went into mild lepra reactions (chi 2 = 9.7, P less than 0.01). Determination of TNF and IL-1 levels thus seems to have a prognostic significance in terms of lepra reaction in patients.

The effects of valvular regurgitation on thermodilution ejection fraction measurements

Through the use of thermodilution principles and rapid response thermistors, it is now possible to measure right ventricular ejection fractions serially in patients. However, to our knowledge, the extent to which tricuspid regurgitation affects the accuracy of thermodilution ejection fraction measurements has not been quantified. The purpose of this study was to compare actual and thermodilution ejection fraction measurements in an in vitro model of tricuspid regurgitation over a wide range of ejection fractions. Stepwise perforation of the inlet valve resulted in regurgitant fractions ranging from 4 to 40 percent. At each increment of inlet valve regurgitation, triplicate sets of thermodilution (EFthermo) ejection fraction measurements were obtained and compared with actual ejection fractions (EFactual). The mean difference between EFactual and EFthermo significantly increased with 8 percent regurgitation and significantly increased with greater increments of inlet valve regurgitation. EFthermo consistently underestimated EFactual over the entire range of regurgitant values. Linear regression analysis revealed a significant correlation between EFactual and EFthermo for all degrees of regurgitation; however, the correlation coefficient significantly declined from control valves with 13 percent regurgitation and declined further with 33 percent regurgitation. Qualitative classification of the inlet valve regurgitation into mild, moderate, and severe regurgitation was performed using pulsed Doppler echocardiography. Mild inlet valve regurgitation resulted in a significantly increased difference between EFactual and EFthermo from control values. A significant increase in the difference between EFactual and EFthermo was observed with both moderate and severe regurgitation. In summary, thermodilution underestimated actual ejection fraction in a direct linear relationship to the degree of inlet valve regurgitation. Thus, in the presence of tricuspid regurgitation, this method may still be useful in serially measuring changes in right ventricular ejection fraction.

Myocardial Na+,K(+)-ATPase in tachycardia induced cardiomyopathy

Na+,K(+)-ATPase is a major determinant of myocyte homeostasis and excitation-contraction. Cardiac glycosides such as digitalis and ouabain increase the inotropic state of the heart through the inhibition of Na+,K(+)-ATPase. While cardiac glycosides are commonly used in the setting of congestive heart failure, optimal therapy would depend upon an intact Na+,K(+)-ATPase system. Changes in Na+,K(+)-ATPase activity and glycoside receptor density with the development of cardiomyopathy have not been well defined. Accordingly, left ventricular (LV) function and Na+,K(+)-ATPase activity and glycoside binding were examined in 7 pigs with dilated cardiomyopathy and in 7 controls. Dilated cardiomyopathy was produced by pacing induced supraventricular tachycardia (SVT) for 3 weeks at 240 bpm. Left ventricular function was examined by simultaneous echocardiography and catheterization. Left ventricular fractional shortening significantly decreased with SVT (34 +/- 2 vs. 10 +/- 2%, P less than 0.05) and LV diastolic dimension and pressure significantly increased (3.8 +/- 0.3 vs. 5.1 +/- 0.4 cm, and 8 +/- 2 vs. 27 +/- 2 mmHg, respectively, P less than 0.05) as compared to controls. Na+,K(+)-ATPase activity was assayed as potassium dependent p-nitrophenol-phosphatase activity. Glycoside receptor density (Bmax) and affinity (KD) was determined using [3H]-ouabain binding assays. Na+,K(+)-ATPase activity, Bmax, and KD all significantly fell from control values with SVT induced cardiomyopathy (0.64 +/- 0.06 vs. 0.45 +/- 0.12 micrograms pNP/mg/h, 5.5 +/- 0.4 vs. 1.9 +/- 0.4 pmol/mg, and 15 +/- 3 vs. 9 +/- 3 nM, respectively, P less than 0.05). The distribution of Na+,K(+)-ATPase in LV sections taken from control and SVT hearts were examined using immunohistochemical techniques. A patchy distribution of Na+,K(+)-ATPase along the sarcolemma in SVT sections was observed as opposed to a more uniform distribution in control myocytes. There was no observable change in the relative content and distribution of the Na+,K(+)-ATPase isoforms alpha 2 and alpha 3 in the SVT sections as compared to controls. In an additional set of experiments, changes in LV as well as isolated myocyte responsiveness to ouabain were examined. Left ventricular fractional shortening and peak dP/dt were measured following administration of 20-60 micrograms/Kg of ouabain in control (n = 3) and SVT (n = 3) pigs. In the control group, 40 micrograms/Kg caused a 25% in LV fractional shortening and a 60% increase in peak dP/dt from baseline. Cumulative doses of 60 micrograms/Kg in the control pigs resulted in over a 75% increase in peak dP/dt from baseline values.(ABSTRACT TRUNCATED AT 400 WORDS)

Histopathological monitoring of an immunotherapeutic trial with Mycobacterium w

Immunotherapeutic trials with Mycobacterium w (M. w.) on multibacillary patients are in progress at two large hospitals in New Delhi. A total of 380 patients so far have been inducted into the trial. The histopathological profile of the initial 87 patients (52 in the vaccine group, 35 in the control group) who have now completed 2 years of treatment are presented in this report. The vaccine group received multidrug therapy (MDT) and eight intradermal injections of M. w. every 3 months; the control group had MDT with starch injections as a placebo. Skin biopsies were taken at induction and thereafter at every 6 months. The results show a significantly higher proportion of biopsies with histopathological upgrading and/or clearance of dermal granuloma among the vaccinated cases. The number of patients becoming bacteriologically negative was higher in the vaccine group. There was no increase in the degree of neural inflammation in the biopsies showing upgrading. The lepromin site biopsy in patients who converted to positivity after vaccination showed epithelioid cell granulomas as did the biopsies from the nodules developing at the vaccination sites. The histopathological observations confirm the additional immunotherapeutic effect of M. w. used along with standard MDT therapy.

In vitro characterization of T cells from Mycobacterium w-vaccinated mice

Tuberculosis caused by the intracellular bacterial pathogen Mycobacterium tuberculosis still represents a major health problem, and its effective control would best be accomplished by active vaccination. Although vaccination with M. bovis BCG has proven highly effective in certain parts of the world, in several developing countries it has been found to confer only marginal protection. Hence, novel vaccination strategies are warranted. Mycobacterium w is a saprophytic cultivable mycobacterium which shares several antigens with M. tuberculosis. In the murine system, vaccination with killed M. w was found to protect against subsequent tuberculosis. In order to characterize the responsible immune mechanisms more precisely, mice were vaccinated with killed M. w and T cells restimulated in vitro with mycobacterial antigens. These T cells produced interleukin 2 and gamma interferon but no detectable interleukin 4 and interleukin 5. Killed M. w induced significantly stronger T-cell responses than killed M. tuberculosis, and both vaccination regimes were markedly improved by administration in a mild adjuvant, i.e., the Ribi adjuvant containing trehalose dimycolate, monophosphoryl lipid A, and mycobacterial cell wall skeleton. Our data suggest that M. w-induced immunity against M. tuberculosis rests primarily on TH1 cells, which are thought to be of major relevance for acquired antituberculosis resistance. Our study therefore provides a further step toward the identification of a novel tuberculosis vaccine.

Association of HLA antigens with differential responsiveness to Mycobacterium w vaccine in multibacillary leprosy patients

Leprosy patients undergoing phase II trials in two hospitals of New Delhi, India, were HLA typed to see the association of HLA with differential responsiveness to Mycobacterium w vaccine. The vaccine comprises an atypical, nonpathogenic mycobacterium, Mycobacterium w, which has cross-reactive antigens with M. leprae. Multibacillary patients who are lepromin negative are vaccinated at an interval of 3 months. Considerable improvement is evident in the patients in terms of a decline in bacterial indices and histopathological and immunological upgrading. But all the patients do not respond to the vaccine in the same manner; some are slow responders, while others are good responders. HLA-A28 and DQw3 (DQw8 + 9) were found to be associated with slow responsiveness, while DQw1 and DQw7 were found to be associated with a more rapid responsiveness to the M. w vaccine. However, these associations were not significant after P correction for the number of antigens tested for each locus except for HLA-DQw3 (DQw8 and DQw9) and DQw7. DQw7, a new defined split of HLA-DQw3, seems to be associated with the responsiveness to M. w vaccine.

Dengue virus-induced helper cytokine has two polypeptide chains which bear different determinants

Dengue type 2 virus (DV) induces generation of a T cell helper cytokine (HF) in mouse spleen which enhances the antigen-specific antibody plaque forming cell count in syngeneic mice. The present study was undertaken to investigate the molecular structure of HF. It was observed that the activity of HF was abrogated by treatment with reducing agents such as glutathione, ouabain or dithiothreitol (DTT) which cleave disulphide bonds, separating the polypeptide chains. The two polypeptide chains could be purified by high performance liquid chromatography of DTT treated HF. The individual chains had no helper activity, but it could be restored by mixing the two. One chain of the HF bonded to the DV-antigen coupled immunosorbent column and the other to the anti-I-Ak antibody coupled column. Thus, DV-induced HF is a disulphide bonded double chain structure, one chain having antigen and the other having I-A determinants; the presence of both chains is essential for helper activity.

A rapid latex agglutination test for detection of antibodies in tuberculosis and Hansen's disease

Antigens of Mycobacterium w, a saprophytic fast growing organism having antigenic epitopes cross-reactive with Mycobacterium leprae and Mycobacterium tuberculosis, were coated on to latex beads (0.33 micron Zn size), and the reactivity tested with sera of tuberculosis and Hansen's disease (HD) patients. Seventy nine percent of lepromatous leprosy (LL) and eighty five percent of pulmonary tuberculosis (TB) patients sera showed an agglutination reaction easily read by naked eye. Specificity of the test was further checked by testing sera of non-mycobacterial infection cases and all of them were found negative. Among apparently healthy controls, 4.3% were found positive from non-endemic and 8.8% from endemic area. The sensitivity of the assay is further enhanced from 78.7% to 90.4% and 85.7% to 91.6% in both LL HD and pulmonary tuberculosis respectively, by using immune complexes extracted from the patients sera. Potential of these antigen coated beads to detect the two major human mycobacterial disease, LL HD and pulmonary TB was also put evidence in a double blind study on coded sera samples obtained from various hospitals in India. The antigen coated beads are stable for upto 6 months at 4 degrees C. The latex slide agglutination test reported here, is simple, rapid, easy to perform and can be used even in rural areas of developing countries.

Immunological upgrading with combined immunotherapy and chemotherapy in a lepromatous leprosy patient: a case report

Immunotherapy with Mycobacterium w was given, in addition to standard multidrug therapy (MDT) to a lepromatous leprosy (LL) patient with a bacteriological index (BI) of 6. After 15 months of treatment this patient attained bacteriological negativity and clinical inactivity. Histopathologically the patient upgraded to borderline-tuberculoid at 12 months, and at 15 months showed features of nonspecific infiltration in the dermis. The rapid immunological upgrading seen in the patient is highlighted in this paper.

T-cell responses to fractionated antigens of Mycobacterium w, a candidate anti-leprosy vaccine, in leprosy patients

Mycobacterium w, an atypical cultivable mycobacterium, is undergoing phase III clinical trials as a vaccine against leprosy in India. It has brought about lepromin conversion and histopathological upgradation in a significant number of patients studied so far. It is important to identify antigens of M. w that trigger T-cell responses in leprosy patients vaccinated with this organism. In the present study the peripheral T-cell repertoire of 12 M. w-vaccinated leprosy patients, 10 unimmunized leprosy patients, 8 tuberculoid and 5 healthy contacts was analysed with fractionated antigens of M. w. The lepromatous leprosy patients who are in general anergic to antigens of M. leprae did not respond to antigens of M. w. However, peripheral blood mononuclear cells obtained from leprosy patients who had been vaccinated with M. w responded to many antigens. These responses were frequently directed against low molecular weight entities of 14-45 kDa. T cells from tuberculoid leprosy patients and healthy contacts also responded predominantly to a number of low molecular weight antigens of M. w. The study also identified an immunodominant 28-31 kDa antigenic fraction carrying T- as well as B-cell activating determinants.

Radiolabeling of Mycobacterium leprae lipids within schwannoma cells, a potential drug screening system

This study describes a novel method which could be developed into a test system of evaluating the efficacy of antileprosy drugs. The method estimates incorporation of [14C]acetate into lipids of Mycobacterium leprae maintained within the 33B Schwannoma cell line. Schwannoma cell-resident M. leprae cells incorporated significant levels of radiolabel within their lipids during 12 days of incubation in vitro. This incorporation was markedly reduced by 5 micrograms of rifampin per ml (decrease, 81.62%); this decrease was observed within 24 h of addition of the drug. Dapsone also reduced the radiolabel incorporation into the lipids, but to a lesser extent (decrease, 27.58%). This system was also able to differentiate between rifampin-sensitive and -resistant strains of mycobacteria. It is suggested that since the effect of bacteriostatic (dapsone) and bactericidal (rifampin) drugs could be detected by using this technique, it may prove useful in screening novel drugs acting against M. leprae.

In vitro validation of a right ventricular thermodilution ejection fraction system

Right ventricular ejection fraction (RVEF) is used clinically as an index of right ventricular (RV) pump function. Clinical measurements of RVEF are complicated by the need for complex imaging equipment to compute RV volumes. Recently, the use of thermodilution (TD) methods have been suggested as a simplified means to measure RVEF (RVEFTD) in patients using rapid response thermistors. Validation, however, by comparison of RVEFTD and other methods in vivo, is difficult. Accordingly, thermodilution derived EF measurements (EFTD) were compared to known values using an in vitro system, with known ejection fractions (EF) set from 17-78% and stroke rates varying independently from 50-100 strokes/min. EFTD was computed by fitting the downslope of the TD curve to a monoexponential function and computing the time constant of thermal decay. A significant correlation existed between EFTD and actual EF over the entire study (r = 0.96, p less than 0.001). Bias analysis showed that the points were within a 95% confidence interval of +/- 12%. Multivariate analysis showed that stroke rate did not significantly affect TD measurements (r = 0.03, p greater than 0.7). This study demonstrates that TD accurately predicts EF using an in vitro system and appears to be independent of stroke rate. Thus, TD methods may provide an accurate, simple and reliable means to serially measure RVEF in the clinical setting.