Risk factors and predictors of outcome in an Australian cohort with hepatitis C virus infection

OBJECTIVES

To define demographic and epidemiological features of an Australian population with chronic hepatitis C virus (HCV) infection and determine predictors of histological and clinical outcome.

DESIGN

Cohort study.

PATIENTS AND SETTING

342 consecutive HCV antibody-positive patients referred to the liver clinic of a major metropolitan general hospital.

OUTCOME MEASURES

Demographic data, serial alanine aminotransferase (ALT) levels, full blood count for all patients. Percutaneous liver biopsy in 152 patients (44%).

RESULTS

51% of patients had previously used injecting drugs, 15% had received a blood transfusion and 27% had no definite percutaneous risk factor (sporadic group). The injecting drug users (IDUs) were younger and more likely to have been born in Australia. The sporadic group were older and frequently were born in Mediterranean or Asian countries. A history of excessive alcohol use was common, particularly among IDUs (60%). Of 152 patients who had a liver biopsy, 49 had cirrhosis and 103 had chronic hepatitis. Some patients with a normal ALT level had marked necro-inflammatory activity. On univariate analysis, the presence of cirrhosis correlated with older age (P < 0.0001), lack of an identifiable risk factor (P < 0.001) and birth in a Mediterranean or Asian country (P < 0.0001). On multivariate analysis, the only significant predictor of cirrhosis was age (P < 0.001). Among patients with an identifiable percutaneous risk factor, cirrhosis was seen at a median time of 18 years after first exposure to risk, compared with 13 years in patients with chronic hepatitis (P < 0.01). Patients with clinical evidence of portal hypertension were, on average, 15 years older than those with histological cirrhosis only (P < 0.01).

CONCLUSIONS

Injecting drug use is the major risk factor for chronic HCV infection in Australia. In patients with an identifiable risk factor, the most significant factor associated with a biopsy finding of cirrhosis is the time since first exposure to HCV.

p53 protein immunoreactivity in cancers of the gallbladder, extrahepatic bile ducts and ampulla of Vater

Immunohistochemical expression of the p53 protein was investigated in carcinoma of the gallbladder (n = 13), common bile duct (n = 7) and ampulla of Vater (n = 9) using the polyclonal, CM1, and monoclonal, DO7, antibodies (Novocastra). This was compared with cases of chronic cholecystitis (n = 11) and preneoplastic lesions of the gallbladder (n = 4) and ampulla (n = 3). Nuclear immunostaining for p53 protein was found only in the poorly differentiated adenocarcinomas of the gallbladder (n = 9) and were associated with a shorter patient survival period (median: 18.6 mths). The moderately differentiated adenocarcinomas (n = 4) did not show p53 immunostaining and were associated with a longer median survival period (26 mths). The gallbladder dysplasias and adenoma also had no p53 protein immunoreactivity. The common bile duct carcinomas did not stain for p53. Focal p53 immunoreactivity was present in only one (11%) of the cases of ampullary carcinoma and in one (9%) of chronic cholecystitis. In summary, increased p53 immunostaining was associated with reduced patient survival and found more frequently in poorly differentiated adenocarcinoma of the gallbladder but not in the better differentiated carcinoma, chronic cholecystitis or preneoplastic lesions of the gallbladder. The differences in p53 immunohistological expression between gallbladder, common bile duct and ampullary carcinomas justify further investigation into the molecular mechanisms responsible for their development.

Patterns of asymmetry do not change over the course of idiopathic parkinsonism: implications for pathogenesis

We investigated the asymmetry of focal deficits of bradykinesia in a cross-sectional study of 198 patients with idiopathic parkinsonism. We have analyzed the difference in Unified Parkinson's Disease Rating Scale (UPDRS) scores between the more and less affected sides in these patients, whose duration of symptoms ranged from 1 to 15 years. There was no significant change in the asymmetry or focality over this period; the deficit for each side progressed faster initially and then approached the normal age-related linear rate of decline. Previous studies indicate that there is an inverse linear relation between the UPDRS bradykinesia score and the nigral dopaminergic cell count. We infer that the rate of death of nigral dopaminergic neurons is predetermined from the time of onset of pathogenesis. The simplest explanation is that a causal event kills some cells and damages others so that they undergo premature death. This sequence of changes could be implemented through environmental (toxic or viral) damage to the genome. Several diverse sources of evidence support this concept.

[Complications of massive blood transfusion after intrathoracic hemorrhage--a case report]

Acute hemorrhage leading to acute hypovolomic shock is a medical emergency carrying high mortality. It therefore requires prompt and effective treatment. We reported a case of lung tumor receiving lobectomy at our hospital. Repeated internal bleeding due to subclavian artery perforation occurred three times within three weeks after the surgery. During the period of resuscitation, the patient received emergently massive blood transfusion. Some complications of massive blood transfusion. Some complications of massive blood transfusion were noted later. A total of 89 units of whole blood, 34 units of fresh frozen plasma and 28 units of platelet was given.

Identification of 'molten globule'-like state in all beta-sheet protein

The cardiotoxin analogue III (CTX III), isolated from the Taiwan Cobra venom (Naja naja atra), is a sixty amino acid, all beta-sheet protein. The 2,2,2-trifluoro ethanol (TFE) induced unfolding of CTX III is studied under acidic conditions (pH 2.5). Using circular dichroism, 1-anilino-8-napthalene sulphonic acid binding and NMR experiments, it is shown that stable, partially structured state(s) ['molten globule'-like state] is formed between 50 and 80% TFE concentrations. The protein was found to exist in an unfolded state in 80% TFE containing 2M urea. The TFE induced unfolding process is shown to be completely reversible. In the 'molten globule' state of CTX III in 80% TFE, though portion(s) of the backbone of the protein assume helical conformation, most of the original beta-sheet secondary structural elements in the protein are intact. In our opinion, this is the first report of the identification of a 'molten globule'-like state in the unfolding pathway of an all beta-sheet monomeric protein.

Molecular dynamics simulations of chlorambucil/DNA adducts. A structural basis for the 5'-GNC interstrand DNA crosslink formed by nitrogen mustards

The alkylation of DNA by chlorambucil has been studied using a computational approach. Molecular dynamics simulations were performed on the fully solvated non-covalent complex, two monoadducts and a crosslinked diadduct of chlorambucil with the d(CGG3G2CGC).-d(GCG1CCCG) duplex, in which the N7 atoms of G1, G2 and G3 are potential alkylation sites. The results provide a structural basis for the preference of nitrogen mustards to crosslink DNA duplexes at a 5'-GNC site (a 1,3 crosslink, G1-G3) rather than at a 5'-GC sites (a 1,2 crosslink, G1-G2). In the non-covalent complex simulation the drug reoriented from a non-interstrand crosslinking location to a position favorable for G1-G3 diadduct formation. It proved possible to construct a G1-G3 diadduct from a structure from the non-covalent simulation, and continue the molecular dynamics calculation without further disruption of the DNA structure. A crosslinked diadduct developed with four BII conformations on the 3' side of each alkylated guanine and of their respective complementary cytosine. In the first monoadduct simulation the starting point was the same DNA conformation used in the crosslinked diadduct simulation with alkylation at G1. In this simulation the DNA deformation was reduced, with the helix returning to a more canonical form. A second monoadduct simulation was started from a canonical DNA conformation alkylated at G3. Here, no significant motion towards a potential crosslinking conformation occurred. Collectively, the results suggest that crosslink formation is dependent upon the drug orientation prior to alkylation and the required deformation of the DNA to permit 1,3 crosslinking can largely be achieved in the non-covalent complex.

A model to study cytokine profiles in primary and heterologously secondary Dengue-2 virus infections

Roles of cytokines in primary and secondary Dengue virus (DV) infections are not completely understood. In this study, we challenged mononuclear leukocytes (MNLs) obtained from non-immune and DV-1-infected donors with DV-2 in vitro to mimic primary and heterologously secondary DV-2 infections, respectively. We found that MNLs in response to DV-2 could release a large amount of interleukin-1 (IL-1 beta) and tumor necrosis factor alpha (TNF alpha). However, IL-1 beta and TNF alpha released by MNLs with primary or heterologously secondary exposure to DV-2 were not significantly different. In contrast, MNLs with heterologously secondary DV-2 infections produced significantly higher amount of interferon gamma (IFN gamma) than those with primary DV-2 infections. These results suggest that IFN gamma, but not TNF alpha or IL-1 beta, may in part participate in the pathogenesis of Dengue shock syndrome (DSS) frequently found in heterologously secondary DV-2 infections.

Properties of uracil phosphoribosyltransferase from Giardia intestinalis

Incorporation of pyrimidine ribonucleotides in Giardia intestinalis occurs via uracil phosphoribosyltransferase (UPRTase). The enzyme was purified over 1000-fold to apparent homogeneity from parasite extracts, using Fast Protein Liquid Chromatography, namely Mono Q anion exchange, Mono P chromatofocusing and Superose 12 chromatography. The specific activity of the purified enzyme was 3100 nmol min-1 mg protein-1. The enzyme was found to be a dimer of mol. wt. 76,000. Kinetic analysis, including initial velocity and product inhibition studies, indicated that it obeyed a rapid-random equilibrium mechanism. GTP and dGTP caused a dramatic increase in the activity of the enzyme, though there was no effect on the Michaelis constants. All other nucleotides tested were without effect or were inhibitory. The effect of GTP is similar to that observed for UPRTase from E. coli but not from other eukaryotes.

Neurophysin stimulates prolactin release from primary cultured rat pituitary cells

The neurohypophysial hormones, oxytocin and vasopressin, are present as non-covalently bound complexes with their designated neurophysin in the secretory granules of the posterior pituitary. The neurophysins are generally considered to be biologically inert carrier proteins for oxytocin and vasopressin. We have examined the actions of bovine neurophysin-I (bNP-I), bovine neurophysin-II (bNP-II), rat neurophysin (rat NP) and oxytocin on prolactin release using primary cultured rat pituitary cells. A dynamic perifusion system was chosen to test their stimulatory actions. The rat NP and bNP-II stimulated prolactin release. It is a new observation that rat NP and bNP-II stimulate prolactin release from primary cultured rat pituitary cells. The maximum sensitivities, the lowest concentration which stimulate prolactin release, of rat NP, bNP-II, bNP-I and oxytocin in primary cultured cells were 1 nmol/1, 1 nmol/l, 1000 nmol/1 and 1 nmol/1 respectively. The maximum sensitivities of rat NP and bNP-II were within the physiologically relevant concentrations.

Gas chromatographic determination of triclopyr in fruits and vegetables

This research was comprised of two parts: quantitative analyses, and confirmatory test. In the quantitative analyses, five classes of fruits and vegetables comprising 10 individual commodities were fortified with triclopyr herbicide at 0.4 and 0.8 ppm level. Triclopyr was extracted from the matrices and derivatized separately to 2-chloroethylene ester with 2-chloroethanol-BCl3 and methyl ester with diazomethane. The esters were then quantitated by GC-ECD and GC-NPD. The GC-ECD recoveries for 2-chloroethylene ester were 100.0% and 100.7% at 0.4 ppm and 0.8 ppm fortification levels, respectively, whereas methyl ester recovery was 103.9% at 0.4 ppm fortification level. Similarly, the GC-NPD recoveries for 2-chloroethylene ester were 99.0% and 97.9% at 0.4 ppm and 0.8 ppm fortification levels respectively, whereas methyl ester recovery was 102.0% at 0.4 ppm fortification level. In the confirmatory test, the 2-chloroethylene ester was introduced into a GC-ion trap. The EI mass spectrum was then interpreted based on the criteria of molecular ion, isotopes, base ion, characteristic ions and the nitrogen rule. Compared to existing methods, this method has reduced partition solvents to nearly one-tenth. In addition, this method proved to be simple, fast, safe and accurate.

Acute Q fever hepatitis in Taiwan

We report a case of a chronic hepatitis B carrier with an episode of acute hepatitis. The patient presented with a headache, arthralgias, jaundice and fever. While the laboratory tests mimicked chronic hepatitis B with an acute exacerbation, lipogranulomatous changes seen in the liver biopsy strongly suggested the presence of Q fever. Serology testing for Coxiella burneti proved positive and the patient responded to tetracycline therapy. While previously unreported in Taiwan, Q fever is important to consider in an atypical hepatitis presentation because it is a treatable condition.

Cellular responses during liver fluke infection in sheep and its evasion by the parasite

The cellular immune response in sheep to an acute and chronic primary and an acute secondary liver fluke infection were examined by immunohistology of liver tissue and flowcytometry of lymphocytes from the draining hepatic lymph nodes. Ten days after primary infection, portal tract areas surrounding migratory tunnels were infiltrated with CD4+ and CD8+ lymphocytes with fewer B cells and T19+ T cells. Micro abscesses were distributed sporadically in the liver parenchyma and young flukes could be easily observed in the liver tissue free from inflammatory cells. More intensive infiltration of the portal tract areas was observed during a secondary liver fluke infection characterized by a pronounced increase in eosinophils, B cells and CD4+ T cells. In addition, there was an increase in MHC class II+ fibroblastic-like cells surrounding the migratory tracts. In contrast to the primary infection, no young flukes were observed in the same tissue areas during the secondary infection. Chronic primary infections were characterized by perilobular fibrosis and a predominance of CD8+ and gamma delta-TCR+T19- T cells distributed within fibrotic strands. Distinct B cell follicles were observed in the fibrotic strands and near major bile ducts and necrotic patches. Pronounced lymphocyte infiltration could occasionally be observed surrounding liver fluke eggs lodged in liver tissue. A progressive increase in lymph node weight, cell number and CD4/CD8 ratio was observed in the acute and chronic primary infections. The role of the infiltrating cell populations and possible mechanism of immune evasion by the parasite are discussed.

Sick sinus syndrome with normal atropine response--a case report

A 76-year-old woman was admitted due to recurrent syncope. Sinus bradycardia and intermittent sinus pauses (up to 2.24 sec) were documented by 24 hour Holter electrocardiogram. Although intravenous atropine can increase the sinus rate up to 100 bpm, electrophysiologic study showed marked prolongation of sinus node recovery time both at the control state and after autonomic blockades. Sick sinus syndrome was diagnosed, even with a normal atropine test, and a permanent pacemaker resulted in resolution of the syncope.

Longitudinal fluorodopa positron emission tomographic studies of the evolution of idiopathic parkinsonism

Previous estimates of the rate of progression of the nigral pathology underlying idiopathic parkinsonism (IP) have been derived mainly from pathological studies that have an inherent selection bias. Fluorodopa positron emission tomography (PET) is a reliable tool for assessing nigrostriatal dopaminergic function in vivo. We performed fluorodopa PET on two occasions, 7 years apart, on 16 patients with IP (age at the time of the first scan, 51 +/- 14 yr [mean +/- SD]) and 10 normal controls (age, 54 +/- 16 yr). For the patients with IP, the average duration of symptoms from the time of diagnosis to the first scan was 4.5 years (range, 1-12 yr); their PET index (striatal-occipital)/occipital ratio, dropped by 1.7% per year, from 0.49 +/- 0.08 to 0.43 +/- 0.08 (p < 0.001). The normals' ratio decreased by 0.3% per year from 0.77 +/- 0.05 to 0.75 +/- 0.10 (p = 0.33). The ratios in the IP group progressed significantly faster than the controls (p = 0.036). The rate of decline in IP represents 7.8% per decade, expressed as a fraction of the normals' initial mean value at 54 years of age. These results also permit power analysis for the design of future studies assessing the effect of treatment on the underlying pathology in IP.

Treatment of renal artery stenosis after kidney transplantation by percutaneous transluminal angioplasty: report of two cases

Graft renal artery stenosis is one of the causes of hypertension after kidney transplantation. Surgical angioplasty was the treatment of choice before the development of percutaneous transluminal angioplasty (PTA) in the 1970s. Surgical repair was associated with some morbidity and graft loss while PTA was reported to have controversial results in the treatment of this disease. This is a report of two cases of graft renal artery stenosis occurring four and seven months after kidney transplantation that were treated with PTA. The immediate and short-term results of PTA were excellent, but the long-term effects require further follow-up.

Surgical correction of sinus venosus atrial septal defect associated with partial anomalous pulmonary venous connection to high superior vena cava--case report

A 63-year-old woman complained of general malaise and insomnia initially. Atrial septal defect was diagnosed by transthoracic echocardiography thereafter. She had not received complete cardiac studies until progressive dyspnea was noted half a year later. After a series of examinations, sinus venosus type atrial septal defect (ASD) associated with partial anomalous pulmonary venous connection to high superior vena cava (SVC) and persistent left SVC was documented. Surgical correction was performed later. The postoperative course was smooth and her condition improved gradually at 10-month follow-up.

Cavitation dynamics of mechanical heart valve prostheses

Nine different mechanical mitral heart valves were chosen in order to study cavitation dynamics in detail in an in vitro flow system simulating a single event of mitral valve closure. The transvalvular pressure (ventricular minus atrial pressure) rise rate averaged during the valve closing period was used as an index of the loading rate. A series of photographs in the vicinity of the inflow surface of the valve were attempted during the bubble appearance period using a stroboscopic visualization technique. The in vitro study revealed three sources of cavitation initiation in the design of the mechanical heart valves tested: stop (seat stop or seating lip), inflow strut, and clearance (gap formed between the occluder and the housing or between the two occluders in the closed position). Among these, the occluder stop design was the most critical to cavitation since all valves having the stop at the edge of the major orifice area showed a higher intensity of cavitation and threshold loading rates below the estimated normal physiological value. The analysis of bubble locations and dynamics led us to propose that the fluid squeezing effect between the occluder and the stop in the housing and the streamline contraction effect along the clearance are factors responsible for cavitation incipience.

nm23-H1 protein immunoreactivity in cancers of the gallbladder, extrahepatic bile ducts and ampulla of Vater

Immunohistochemical expression of the nm23-H1 protein was investigated in carcinoma of the gallbladder (n = 13), common bile duct (n = 5) and ampulla of Vater (n = 7) using the monoclonal antibody, NM 301 (Molecular Oncology Inc.). This was compared with cases of chronic cholecystitis (n = 11) and preneoplastic lesions of the gallbladder (n = 4) and ampulla (n = 3). Absent or weak nm23-H1 protein immunoreactivity was found in most (67%) of the poorly differentiated adenocarcinomas of the gallbladder and in half of the cases of moderately differentiated adenocarcinomas. The difference in nm23-H1 protein immunostaining between gallbladder carcinoma and chronic cholecystitis was statistically significant (p = 0.0022; X2 test). Significant correlation was found between prolonged patient survival periods and nm23-H1 immunoreactivity in gallbladder carcinomas (R = 0.687, p = 0.01, linear regression analysis; r = 0.652, p = 0.016, Spearman's rank test). Most of the gallbladder dysplasias and adenomas had no reduction in nm23-H1 protein immunoreactivity. All common bile duct carcinomas, most (67%) ampullary carcinomas in situ and some (43%) ampullary carcinomas had moderate to strong nm23-H1 immunostaining. In summary, low nm23-H1 protein immunoreactivity was found more frequently in gallbladder carcinomas than in chronic cholecystitis and was associated with reduced patient survival. The differences in nm23-H1 protein immunoreactivity in common bile duct and ampullary carcinomas suggest that these tumors have a different molecular origin to gallbladder cancers.

Rate-dependent properties of adenosine-induced negative dromotropism in humans

BACKGROUND

The antiarrhythmic effects of sodium channel and calcium channel blockers are known to be rate dependent. Little is known about the rate-dependent effect of adenosine on human atrioventricular (AV) nodal conduction. The purpose of this study was to determine whether the negative dromotropic effect of adenosine is dependent on heart rate.

METHODS AND RESULTS

Atrial pacing at 20-millisecond increments decreasing stepwise was performed, and the curves that relate the AH interval to the atrial pacing cycle length were analyzed. The change in AV nodal function was evaluated in three protocols: (1) In 8 group 1A and 6 group 1B patients, an intravenous infusion of adenosine at a dose of 140 and 320 micrograms.kg-1.min-1 was given, respectively; (2) a bolus injection of a fixed dose of adenosine was given to 12 group 2A patients without and 6 group 2B patients with propranolol (0.1 mg/kg) treatment; and (3) in 12 group 3 patients, the AV nodal function was evaluated after intravenous propranolol (0.05 mg/kg) and after subsequent intravenous aminophylline (loading dose, 5 mg/kg; maintenance dose, 0.9 mg.kg-1.h-1). No significant depression of AV nodal function could be demonstrated during intravenous infusion of adenosine. The bolus injection of adenosine could prolong the AH interval, which was dependent on heart rate and more significant at a shorter pacing cycle length. Intravenous propranolol significantly depressed the AV nodal conduction and shifted the curves of the AH interval versus the pacing cycle length to the right. Subsequent intravenous aminophylline shortened the AV nodal conduction time, however, in a rate-independent manner.

CONCLUSIONS

The negative dromotropic effects induced by intravenous bolus injection of adenosine became more pronounced at fast atrial pacing rates. These results indicate that adenosine causes rate-dependent prolongation of AV nodal conduction in humans.

Micellar electrokinetic chromatography with electroosmotic step gradient elution

The peak capacity, defined as the maximum number of resolvable peaks, is dependent on the range of the migration-time window in micellar electrokinetic chromatography (MEKC). By applying various radial electric potential gradients across the capillary wall, the direct control of the zeta potential and the electroosmotic flow in MEKC results in a significant increase in the migration-time window and a great enhancement of the separation resolution. The enhancement in the separation resolution is obtained at a large expense in analysis time. To optimize both the separation efficiency and the resolution in MEKC, the dynamic control of electroosmosis and the migration-time window during the separations is demonstrated with the use of neutral and charged phenylthiohydantoin-amino acids (PTH-amino acids) as a model system. A simple mathematic model which is capable of predicting migration times of analytes in electroosmotic step gradient elution MEKC is presented.

Genetic linkage studies in autosomal dominant parkinsonism: evaluation of seven candidate genes

Linkage studies were performed in three families (A, B, and C) with autosomal dominantly inherited parkinsonism affecting multiple members in three generations. Affected individuals exhibited the cardinal signs and symptoms of Parkinson's disease, with a mean age of onset of 51, 62, and 61 years in Families A, B, and C, respectively. Parkinsonian symptoms responded to L-dopa treatment, and an [18F]6-fluoro-L-dopa positron emission tomography scan in 1 affected member of Family B showed decreased striatal uptake typical of Parkinson's disease. Ancestors of all three families were traced to a small region in northern Germany and southern Denmark, suggesting the possibility of a common mutation. Linkage studies were performed with polymorphic markers associated with the following candidate genes: the genes for glutathione peroxidase (GPX1, 3q11), tyrosine hydroxylase (TH, 11p15.5), brain-derived neurotrophic factor (BDNF, 11p14), catalase (CAT, 11p13), amyloid precursor protein (APP, 21q21), copper-zinc superoxide dismutase (SOD1, 21q21), and debrisoquin 4-hydroxylase (CYP2D6, 22q13.1). Summed lod scores for all families excluded linkage to the genes GPX1, TH, APP, SOD1, and CYP2D6, as well as to the chromosomal region containing the genes CAT and BDNF. If families were analyzed individually, exclusion was possible for two (Family A), six (Family B), and five (Family C) of the seven candidate genes. There was strong evidence against linkage for the remaining loci in all families analyzed individually, except for TH, which was uninformative in Families A and B, and CYP2D6, which gave slightly positive pairwise lod scores in Family A. Our results indicate that the candidate genes investigated are not involved in the etiology of parkinsonism in these families.

Cryopreservation of blastomeres separated from two-cell mouse embryos by an ultrarapid freezing method

PURPOSE

To clarify the developmental capacity of frozen two-cell blastomeres, we investigated in vivo and in vitro viabilities of blastomeres that were frozen ultrarapidly after separation from two-cell mouse embryos. Two-cell embryos obtained from superovulated F1 hybrid females were denuded by treatment with 0.5% pronase solution and then induced to separate into two single blastomeres by gentle pipetting. The blastomeres were cryopreserved by an ultrarapid freezing method.

RESULTS

The preimplantation developmental rate of two-cell embryos frozen in 3.0 M DMSO was significantly higher than the rate of those frozen in 15 and 4.5 M DMSO (at least P < 0.05). The in vitro developmental rate of the ultrarapidly frozen-thawed blastomeres separated from two-cell embryos (75.0%) was similar to that of nonfrozen blastomeres (76.0%). When eight pairs of blastocysts that developed from frozen two-cell mouse blastomeres were transferred to pregnant ICR recipients on Day 3, four live singletons were born.

CONCLUSION

Thus, the results indicate that two-cell mouse blastomeres can be frozen by the ultrarapid freezing method.

The P1 reactive site methionine residue of ecotin is not crucial for its specificity on target proteases. A potent inhibitor of pancreatic serine proteases from Escherichia coli

The importance of the P1 reactive site for the specificity of ecotin on target proteases was examined by site-directed mutagenesis. The replacement of Met at the P1 site with Ile, Arg, Glu, or Tyr showed little or no effect on the ability of ecotin to inhibit trypsin. Similar results were obtained for chymotrypsin, except that its replacement with Glu caused about 40% reduction of the inhibitory activity of ecotin. On the other hand, the replacement of the Met residue with Arg, Tyr, or Glu dramatically reduced its ability to inhibit elastase, while that with Ile showed little or no effect. Nevertheless, elastase could be completely inhibited upon incubation with excess amounts of the mutant ecotin containing Arg, Glu, or Tyr. Moreover, all the mutant forms of ecotin could be cleaved at the mutated P1 site upon incubation with trypsin at pH 3.75. In addition, the replacement of a Cys residue in the disulfide bridge with Ser showed little or no effect on the ability of ecotin to inhibit trypsin, chymotrypsin, or elastase. However, the mutant ecotin containing Ser was more sensitive to inactivation by heating at 100 degrees C than the wild-type inhibitor. Furthermore, the wild-type ecotin whose disulfide bond had been reduced and alkylated was also more easily inactivated by heat treatment than the untreated control. These results strongly suggest that the P1 site of ecotin is not crucial for its specificity on target proteases and that the disulfide bridge in ecotin appears to play an important role in maintenance of its structural stability.