N. K. Ganguly

Decrease of myocardial infarct size with desferrioxamine: possible role of oxygen free radicals in its ameliorative effect

The ability of an iron chelator, desferrioxamine, to inhibit the infarct size in in vivo rat heart was assessed. Anaesthetised rats were subjected to coronary artery ligation (CAL) for 72 hr and infarct size was measured macroscopically using TTC staining. Systolic blood pressure and ECG were monitored. Desferrioxamine (10 mg/kg and 20 mg/kg i.v.) administered half an hour after CAL markedly reduced the infarct size. However, drug treatment did not alter the systolic blood pressure of animals. In addition, desferrioxamine in vitro and in vivo demonstrated an inhibition of rat PMN-evoked and luminol-enhanced chemiluminiscence. The capacity of desferrioxamine to impair the generation or to scavenge directly oxygen free radicals may be responsible for its beneficial effect on myocardial infarct size in rats.

Role of cardiac renin-angiotensin system in the development of pressure-overload left ventricular hypertrophy in rats with abdominal aortic constriction.

Possible involvement of cardiac renin-angiotensin system (RAS) in pressure overload induced left ventricular hypertrophy (LVH) was investigated. Rats were subjected to abdominal aortic constriction (AAC) and examined the effects of 4 weeks treatments with an angiotensin converting enzyme (ACE) inhibitor, captopril and a vasodilator, hydralazine on haemodynamics and ventricular RNA, DNA, protein and myosin isoform pattern in sham and hypertrophied rats. AAC increased the mean arterial pressure (MAP) and systolic blood pressure (SBP), and resulted in increased left ventricle/body weight ratio, LV thickness, RNA and protein content, however total DNA was not changed. The expression of fetal isogene, β-myosin heavy chain (β-MHC), was markedly enhanced where as u.-MHC was reduced. High-dose captopril (100 mg/kg p.o.,) significantly prevented the increase in haemodynamics, development of LVH, LV remodeling, increase in total protein, RNA and antithetical expression of myosin isoforms. Hydralazine (15 mg/kg p.o.,), did not modulate hypertrophic changes and low-dose captopril (1.5 mg/kg p.o.,) which has not produced any marked fall in MAP and SBP also modulated favourably the development of LVH and its biochemical markers. Thus, the prevention of the development of LVH and induction of β-MHC by non-hypotensive doses of captopril may be related to the blockade of intracardiac production of angiotensin II rather than circulating system. These results suggest that cardiac RAS may play an important role in pressure overload induced LVH.

Specific IgA response, T-cell subtype and cytokine profile in experimental intravaginal trichomoniasis.

Abstract. Trichomoniasis caused by Trichomonas vaginalis may lead to either a complete absence of symptoms or to severe inflammatory manifestations in infected women. Studies of the role of immune responses in the pathogenesis and varied symptomatology of this disease are lacking. Mice may prove useful as an experimental model for intravaginal trichomoniasis in developing an understanding of the role of local immune responses in the pathogenesis and varied symptomatology of this disease. The present study reports the levels of anti-Trichomonas IgA antibodies in serum and vaginal washes, and T-cell subtype and cytokine profile in vaginal cervical tissues of mice infected intravaginally with T. vaginalis isolates from 15 symptomatic and 15 asymptomatic women. It also correlates the responses with symptomatology of the patients. Successful intravaginal infection was established by inoculating T. vaginalis in BALB/c mice preinoculated with Lactobacillus acidophilus and pretreated with oestradiol. A significant increase in specific IgA antibody levels was detected with enzyme-linked immunosorbent assay in vaginal secretions and serum samples collected on the 7th post-infection day from animals infected with isolates from asymptomatic women when compared with mice infected with isolates from symptomatic women. T-cell subset analysis showed significant differences, with increased CD4+ T-cell count in animals infected with isolates from asymptomatic women compared with animals infected using isolates from symptomatic women. No difference in CD8+ T cells was observed between the two groups. Cytokine profile revealed significantly higher (P<0.001) production of γ-IFN and IL-2 in mice infected with asymptomatic isolates compared with animals infected with symptomatic isolates, using T. vaginalis crude antigen extract and nonspecific mitogen (ConA) as stimulants for vaginal cervical lymphocytes. However, no difference in IL-4 levels was observed in the two groups of animals. In contrast, significant increase in tumour necrosis factor (TNF-α) levels was observed in animals infected with asymptomatic isolates compared with those infected with isolates from symptomatic women and controls, thereby indicating that TNF-α may play an important role in the inflammatory response to trichomoniasis. The study further suggests that specific IgA antibodies might help to protect asymptomatic individuals from severe infection and T-lymphocytes may play an important function in the eradication of the parasite. The cytokine profile indicated the involvement of Th-1 like responses in mice infected with asymptomatic isolates, compared with those infected with symptomatic isolates.

Plasmodium falciparum induced perturbations of the erythrocyte antioxidant system

Erythrocyte antioxidants catalase, superoxide dismutase, reduced glutathione and glutathione peroxidase were studied in cells harbouring different growth stages of Plasmodium falciparum. Catalase and superoxide dismutase showed significant decrease during parasite maturation indicating hampered metabolism of hydrogen peroxide and superoxide anions. Glutathione peroxidase also exhibited a downward trend during the growth of P. falciparum, while there was a moderate accumulation of reduced glutathione. These findings suggest decreased utilization of the reduction potential in detoxification of reactive oxygen species. The fall in all three antioxidant enzymes studied was highly significant (P less than 0.001) in erythrocytes with mature stages of the parasite (trophozoites, schizonts). The increased vulnerability of erythrocytes to damage, which parallels the growth phases of the parasite emphasizes the need for early treatment of P. falciparum malaria to minimise red cell destruction and the resulting anaemia.

Cellular immune responses in human neurocysticercosis

Abstract Studies on the role of cell-mediated immune responses in human neurocysticercosis (NCC) are lacking. Various cell-mediated immune responses such as lymphocyte subpopulation, lymphocyte transformation to cysticercus antigens and cytokine profile were carried out in NCC patients. Lymphocyte transformation assays using larval antigens showed significantly higher 3H-thymidine uptake. Immunophenotyping analysis showed an insignificant increase in B cells and a decrease in total T cells. However, there was a significant decrease (Pu2009<u20090.05) in CD8+ T cells whereas there was no change in other cells like CD4+, HLA-DR+ and CD16+/CD56+. Cytokine profile revealed significantly higher (Pu2009<u20090.01) production of Th1 cytokines (γ-IFN and IL-2) using cysticercal antigens as stimulants for peripheral blood mononuclear cells, while there was no difference in IL-4 levels between NCC patients and healthy controls. The cytokine profile indicated the involvement of Th-1-like responses in NCC patients.

The alteration in signal transduction parameters induced by the excretory-secretory product from Giardia lamblia

The mechanism by which Giardia lamblia exerts its pathogenicity is likely to be multifactorial. A 58 kDa enterotoxin was purified and characterized from the excretory-secretory product (ESP) of the parasite (Kaur et al. 2001). In the present study an attempt has been made to elucidate the mechanism of action of the ESP, a potentially important enterotoxin. A 41 kDa glycoprotein was identified in the mouse enterocyte membrane fraction with which the ESP interacted in a GM1-specific manner. The GTPase activity was reduced in enterocytes stimulated with the ESP, resulting in an increase in the level of adenylate cyclase-dependent cyclic adenosine monophosphate (cAMP). The activity of protein kinase A (PKA) in the enterocytes was also upregulated after ESP treatment. Ultimately, a significant increase in intracellular Ca2+ concentration and decrease in cytosolic Cl- level were noticed in ESP-stimulated mouse enterocytes. Thus it is possible that the enterotoxic ESP could bind to the 41 kDa glycoprotein (receptor?) on the enterocytes and activate the G-protein-mediated signal transduction pathway resulting in alteration of electrolyte transport.

Detection of antigen B of Cysticercus cellulosae in cerebrospinal fluid for the diagnosis of human neurocysticercosis

Neurocysticercosis (NCC) is a major cause of morbidity and mortality in developed and developing countries. The diagnosis of this disease remains a problem. We report the detection of specific antigenic fraction (antigen B) ofCysticercus cellulosae by enzyme‐linked immunosorbent assay (ELISA) in various fractions of cerebrospinal fluid (CSF) obtained by high performance liquid chromatographic (HPLC) separation, for the diagnosis of human NCC. Forty patients attending or admitted to Nehru Hospital, Chandigarh were included in the study: 10 with suspected NCC, 20 with other neurological diseases and 10 undergoing surgery under spinal anaesthesia for non‐neurological conditions, who served as controls. CSF samples collected from all patients and controls were subjected to chromatographic separation on an HPLC system. Antigen B (AgB) was detected in separated fractions by an ELISA test and compared with the detection of antibody response in CSF samples by indirect haemagglutination (IHA) technique. Antigen B was detected in 9 out of 10 patients with suspected NCC based on clinical symptoms and radioimaging reports, but in none of the control subjects. However, antigen B was also detected in 9 out of 20 patients with other neurological disorders, mostly tubercular meningitis. Antibody response by IHA was found positive in only 2 of 10 cases clinically suspected of NCC. In conclusion, antigen B detection in CSF samples may be a useful adjunct to clinical suspicion and radiological reports for the diagnosis of NCC as there is no gold standard criteria to confirm this disease. However, the test needs to be evaluated on more patients in countries where tuberculosis and cysticercosis are endemic due to the high cross reactivity with samples from tubercular meningitis patients.

Mode of action of a potentially important excretory--secretory product from Giardia lamblia in mice enterocytes.

Giardia, a common enteric protozoan parasite is a well-recognized cause of diarrhoeal illness. The detailed mechanism of diarrhoea due to this infection is not well understood. A 58 kDa enterotoxin (ESP) was purified from the excretory-secretory product of the parasite. The present study was designed to investigate the mode of action of this enterotoxin of G. lamblia in mice enterocytes. An increase in cyclic adenosine monophosphate level, as well as intracellular Ca2+ concentration, was observed in the ESP-triggered enterocytes. The levels of phospholipase Cgamma1 and inositol triphosphate were found to be upregulated. The activity of protein kinase C (PKC) in the enterocytes was also enhanced following stimulation with the ESP. An increase in the level of reactive oxygen species in ESP-stimulated cells correlated well with the decline in the activity of antioxidant enzymes (superoxide dismutase and catalase). The significantly high levels of nitrite and citrulline indicated the generation of reactive nitrogen intermediates in the ESP-triggered enterocytes. Thus, ESP could induce cross-talk among the different signal transduction pathways in the enterocytes, which could together bring about a common secretory response.

Protective efficacy and immunogenicity of Escherichia coli K13 diphtheria toxoid conjugate against experimental ascending pyelonephritis

In the present study, protective efficacy of Escherichia coli capsular antigen, K13, was evaluated in a mouse model of pyelonephritis. Unconjugated capsular polysaccharide failed to provide any protection. However, coupling of K13 to diphtheria toxoid (DT) enhanced its immunogenicity and led to significant production of anticapsular antibodies in mice. Immunization of animals with K13–DT conjugate also caused significant improvement in cell-mediated immune response as indicated by an increase in lymphoblastogenic response and in the CD4+/CD8+ cell ratio of splenic lymphocytes. Significant decrease in bacterial load and renal severity scores were observed in K13–DT immunized animals. Suitability of K13–DT conjugate as an effective vaccine candidate against urinary tract infections caused by E. coli has been discussed.

Significance of Serum Endotoxin and Antiendotoxin Antibody Levels in Predicting the Severity of Acute Pancreatitis

Abstract.Abstract.Purpose: A close association between endotoxemia and acute pancreatitis has been reported, and attempts have been made to predict the severity of pancreatitis by estimating the levels of endotoxin. The present study was designed to correlate endotoxemia with the severity and complications of acute pancreatitis as graded by contrast-enhanced computed tomography and Blameys criteria.Methods: We examined 20 patients with acute pancreatitis, using Blameys criteria to assess the severity of pancreatitis. The endotoxin level was estimated by the Limulus Amoebocyte Lysate method and the antiendotoxin antibody level was assayed by the enzyme-linked immunoassay technique measuring combined levels of IgG and IgM.Results: Severe pancreatitis was confirmed in 9 of the 20 patients, 17 (85%) of whom were found to have endotoxemia. There was no correlation between the presence and level of endotoxemia and the severity of pancreatitis; however, antiendotoxin antibody titers were significantly lower in patients with severe disease (P < 0.05), those who suffered of major complications (P < 0.01), and those who died of the disease (P < 0.01).Conclusion: The findings of this study demonstrated that the presence of endotoxemia accompanied by a fall in antiendotoxin antibody titer predicts poor outcome in patients with acute pancreatitis.