Involvement of CYP2E1 and carboxylesterase enzymes in vinyl carbamate metabolism in human lung microsomes

Previous studies have shown that CYP2E1 and carboxylesterase enzymes contributed to vinyl carbamate (VC) metabolism in murine lung. Moreover, these studies have implicated CYP2E1 and the carboxylesterases in bioactivation and detoxication, respectively. Here we have tested the hypothesis that CYP2E1 and carboxylesterase enzymes are involved also in VC metabolism in human lung. Demethylation of N-nitrosodimethylamine (NDMA) is an enzyme activity associated with CYP2E1, and was used as a catalytic marker for this P450 in human lung microsomes. NDMA demethylase activity in lung microsomes from 10 patients ranged from 36.9 +/- 1.0 to 82.4 +/- 2.4 pmol/mg protein/min. Significant decreases (40-65%) in demethylase activity were detected in lung microsomes incubated with VC and NADPH, compared with the controls in which incubations were performed with only VC or only NADPH. Preincubation with the CYP2E1 inhibitor diallyl sulfone also significantly decreased demethylase activity, and abrogated the VC-induced effect. Similarly, preincubation of lung microsomes with a human CYP2E1 inhibitory monoclonal antibody ameliorated the VC-induced reduction in demethylase activity. Microsomal carboxylesterase activity in lung microsomes from 10 patients ranged from 19.02 +/- 2.28 to 48.18 +/- 4.34 nmol/mg protein/min, and was significantly decreased (25-45%) in microsomes incubated with phenylmethylsulfonyl fluoride, an inhibitor of the carboxylesterase enzyme. Preincubation of lung microsomes with phenylmethylsulfonyl fluoride and subsequent incubation with VC and NADPH exacerbated the reduction (60-80%) in demethylase activity evoked by reaction with VC and NADPH. These results are consistent with a role for the CYP2E1 enzyme and microsomal carboxylesterases in VC metabolism.

Elevated anti-parasitic activity in peripheral blood monocytes and neutrophils of cattle infected with Babesia bovis

The innate immune response to bovine Babesia bovis infection in vivo has not previously been established. We used assays measuring phagocytosis and oxidative burst to investigate the immune response because they are indicative of the innate antimicrobial capacity of monocytes and neutrophils. Monocyte and neutrophil phagocytosis is thought to be non-specific in nature and so the phagocytosis of either opsonised Zymosan or Escherichia coli was used to indicate the non-specific phagocytic capacity of monocytes and neutrophils ex vivo. The kinetics of both phagocytic and oxidative burst activity in monocytes and neutrophils were followed twice weekly from pre-inoculation (day 0) through to 31 days after inoculation. Peripheral blood monocytes were found to display a pronounced oxidative burst, but a suppressed capacity to phagocytose during a primary infection. On the other hand, neutrophils exhibited an increased phagocytic capacity and reduced oxidative activity during a primary infection. These findings identified considerable antimicrobial activity evident in peripheral blood monocytes and neutrophils from cattle exposed to B. bovis as a primary exposure. This elevated antimicrobial activity was coincident with the time that parasite numbers peaked in the circulation and occurred prior to parasite clearance. These results suggest that peripheral blood monocytes and neutrophils are active mediators in the innate immune response to a primary B. bovis.

Opposition of rapid baroreceptor resetting by prostanoids in rabbits

Arterial baroreceptors reset rapidly within minutes during acute hypertension; baroreceptor pressure threshold (Pth) is increased and the pressure-baroreceptor activity relation is shifted to the right. The purpose of the present study was to determine if prostacyclin (PGI2) or other prostanoids, released during acute hypertension modulate the magnitude of baroreceptor resetting. Baroreceptor activity was recorded from the vascularly-isolated carotid sinus during distension of the sinus with slow pressure ramp in rabbits anesthetized with chloralose. Pressure-activity curves were generated after holding carotid sinus pressure for 10-15 min from 30 to 100 mmHg. In control, the elevation of holding pressure increased Pth from 44+/- to 65+/-5 mmHg (p < 0.05, n = 12). In the presence of PGI2 (20 microM), Pth averaged 43+/-4 and 45+/-3 mmHg (n = 12) after holding pressure at 30 and 100 mmHg, respectively. In the control group before exposing the carotid sinus to indomethacin, an elevation of holding pressure increased Pth from 49+/-2 to 71+/-3 mmHg (p < 0.05, n = 12). After inhibition of the endogenous formation of prostanoids with indomethacin (20 microM), Pth increased by a significantly greater extent from 61+/-2 to 90+/-3 mmHg (p < 0.05, n = 12) with the increase in holding pressure. The slope of the pressure-activity curve (baroreceptor gain) was not influenced by the change in holding pressure. It was increased significantly by PGI2, while decreased by indomethacin. Neither the change in holding pressure nor PGI2 affected the circumferential wall strain of carotid sinus over a wide range of pressure alteration. The results suggest that PGI2 or other prostanoids released during acute hypertension sensitizes baroreceptors and provides a negative feedback mechanism that opposes and limits the magnitude of rapid baroreceptor resetting.

Putative salivary allergens of the cat flea, Ctenocephalides felis felis

The cat flea, Ctenocephalides felis felis, is the major initiator of flea bite hypersensitivity in dogs. Previous analyses of whole extracts of the flea and flea salivary secretions have failed to identify the allergens responsible. We dissected >2000 salivary glands from adult female fleas, extracted them into buffered saline containing protease inhibitors and fractionated the extract using gel permeation HPLC. Dogs were classified as hypersensitive to fleas (flea-feeding positive, FF+) or insensitive (flea-feeding negative, FF-) using a provocative test with live fleas. The allergenicity of the components of the salivary gland extract was tested by intradermal injection of samples of the column eluates. Dogs were also injected intradermally with a sample of whole salivary gland extract, and with histamine as a positive control. Negative control injections consisted of eluate from the column collected prior to fractions containing any protein. The skin of FF- dogs either did not respond or had a minimal response (a bleb approximately 2 mm larger than the injection blebs at the negative control injection sites) to all fractions and to the whole extract; histamine control injections produced positive responses (defined as wheals 5 mm greater than the blebs at the negative control injection sites) in all dogs. The skin of three of the nine FF+ dogs reacted positively to injection of a fraction containing protein/s with apparent MW 40k. Five other FF+ dogs reacted positively to the fractions containing proteins with apparent MW 12-8k. A single dog responded with very large, red wheals to injection of both the approximately MW 40k and MW12-8k fractions. These findings suggest that proteins with apparent MW 40k and MW 12k-8k are important in flea bite hypersensitivity. This work also supports a previous finding that mice which had been exposed to flea bites had antibodies to proteins with approximately MW 40k that were detected in salivary secretions of the flea.

Detection and measurement of canine alpha-macroglobulins by enzyme immuno-assay

The alpha-macroglobulins are broad-specificity protease inhibitors important in the regulation and clearance from circulation of biologically active proteases. Inappropriate protease activation may be a feature of canine acute pancreatitis and the ability of the animal to clear these proteases may be important in determining survival. An enzyme immunoassay for the detection and measurement of canine alpha-macroglobulins in plasma samples was developed. A reference range for the canine alpha-macroglobulins of 1.20-2.72 mg ml-1 was established from a panel of canine plasma samples, and the stability of the alpha-macroglobulins in plasma samples stored at 4 degrees C was investigated. Changes in the level of the alpha-macroglobulins during disease states involving increased endogenous protease activity can now be investigated using a rapid, repeatable and quantifiable assay.

Anti-immunoglobulin antisera used in an ELISA to detect antibodies in barramundi Lates calcarifer to Cryptocaryon irritans

Immunoglobulins (Ig) in serum from barramundi vaccinated with bovine serum albumin (BSA) were purified by ammonium sulphate precipitation and affinity chromatography using BSA as the ligand. The BSA-binding activity of eluted putative Ig fractions was assessed by enzyme-linked immunosorbent assay (ELISA) before being pooled and characterised by sodium dodecyl sulphate polyacrylamide gel electrophoresis (SDS-PAGE). Double affinity purification did not improve the purity of the Ig preparation compared to single affinity purification. Barramundi Ig were injected into sheep to produce anti-Ig antisera which were assessed in an indirect ELISA as the secondary antibody to detect serum Ig in barramundi vaccinated with Cryptocaryon irritans theronts. Affinity-purified Ig induced a more specific reagent for use as secondary antibody in ELISA than did normal whole-barramundi sera. The heavy (H) chain of barramundi Ig had an apparent molecular weight of 70 kDa while that of the light (L) chain was 27 kDa in SDS-PAGE studies. Under non-reducing conditions 2 putative populations of Ig were identified, at 768 and 210 kDa. The N-terminal sequence of the barramundi Ig H chain showed 78% homology with channel catfish Ictalurus punctatus Ig H chain sequence.

Inactivation of cytochrome P-450 (CYP2E1) and carboxylesterase (hydrolase A) enzymes by vinyl carbamate in murine pulmonary microsomes

We tested the hypothesis that vinyl carbamate (VC) is metabolized in vitro by cytochrome P-450 and carboxylesterase enzymes in murine lung. Incubations with VC and an NADPH-generating system produced a 50% decrease in N-nitrosodimethylamine (NDMA) demethylation and a corresponding loss in the amounts of immunodetectable CYP2E1. Preincubation of microsomes with a CYP2E1 inhibitory antibody or the CYP2E1-selective inhibitor diallyl sulfone (DASO2) inhibited demethylase activity; no alterations were detected upon subsequent exposure to VC. Carboxylesterase-mediated hydrolysis of p-nitrophenyl acetate was reduced by 22% in microsomes incubated with VC. Decreased carboxylesterase activity also was detected in microsomes incubated with phenylmethylsulfonyl fluoride (PMSF), an inhibitor of hydrolase A, a carboxylesterase isozyme. No change in enzyme activity was detected when microsomes were subsequently incubated with VC. The loss in carboxylesterase activity correlated with decreased immunodetectable hydrolase A in microsomes incubated with VC, PMSF, or PMSF and VC. The reduction in VC-induced NDMA demethylase activity was increased to 85% of the control in microsomes previously incubated with PMSF, and this corresponded with a marked decrease in CYP2E1 immunoreactivity in the immunoblots. Covalent binding of VC to proteins was detected in microsomes incubated with VC and an NADPH-generating system. Binding was inhibited in microsomes preincubated with either an inhibitory CYP2E1 antibody or DASO2. In contrast, binding levels were augmented in microsomes preincubated with PMSF. These data supported VC metabolism by CYP2E1 and hydrolase A in murine lung microsomes and is consistent with involvement of CYP2E1 and hydrolase A in the activation and detoxication of VC, respectively.

Sustained-release delivery systems and their application for endoparasite control in animals

A solid formulation of a potent anthelmintic macrocyclic lactone, moxidectin, was administered using a non-degradable delivery device to discharge the agent into the subcutaneous tissues of sheep. In vivo release was monitored in sheep indirectly using faecal egg counts. Using a dose of 0.2 mg moxidectin/kg body weight when applied in the form of a solid pellet, protection of sheep against Haemonchus contortus challenge was conferred to a level greater than that of sheep which received Cydectin, the commercial liquid injectable form delivered at the same dosage. The anthelmintic efficacy of the solid formulation was assessed at four dosage levels in sheep and it was demonstrated that the dosage of anthelmintic agent could be reduced to 1/6 of the present recommended injectable dose. When two pellets containing the recommended dose of moxidectin were loaded into a non-degradable delivery device, the period of H. contortus control was extended from 42 to 183 days. Antibody levels of sheep receiving repeated infections of H. contortus L3 larvae and treated with moxidectin-loaded devices were reduced significantly compared to the levels observed in sheep treated with Cydectin (p < 0.0005). This implies that the group treated with the moxidectin-loaded devices was exposed to a reduced antigenic load compared to sheep treated with placebo devices, and sheep treated with Cydectin. The antibody levels generated in the sheep treated with placebo devices were no different to those treated with Cydectin. Application of this sustained release device may allow the control of nematode diseases in livestock throughout an entire season with a single administration.

Isozyme-selective metabolism of ethyl carbamate by cytochrome P450 (CYP2E1) and carboxylesterase (hydrolase A) enzymes in murine liver microsomes

Cytochrome P450 and carboxylesterase enzymes have been implicated in the metabolism of the carcinogen ethyl carbamate (EC). In this study, we have used a murine liver microsomal system to investigate the relative contributions of P450 and carboxylesterase isozymes to hepatic metabolism of EC. N-Nitrosodimethylamine (NDMA) demethylation and p-nitrophenyl acetate (PNA) hydrolysis were used as catalytic markers of CYP2E1 and carboxylesterase enzymes, respectively. Incubation of liver microsomes with EC (1 mM) produced slight but significant decreases in NDMA demethylation and PNA hydrolysis activities. Incubation of microsomes with paraoxon (PAX), a general carboxylesterase inhibitor, or phenylmethylsulfonyl fluoride (PMSF), a specific inhibitor of hydrolase A, produced decreases of 85 and 45%, respectively, in carboxylesterase activities; neither of the inhibitors elicited alterations in levels of NDMA demethylation. Reaction of microsomes with either PAX or PMSF and then with EC exacerbated the reduction (285%) of NDMA demethylation, and this loss corresponded to decreases in immunodetectable CYP2E1 content. The reduction in PNA hydrolysis activity induced by PAX, PMSF, or EC correlated with decreased immunodetectable hydrolase A in liver microsomes; however, reaction with PAX and not PMSF or EC resulted in loss of immunoreactivity for hydrolase B. These data correlated with levels of covalent binding of [ethyl-14C]EC to liver microsomes, which were significantly elevated in incubations conducted with PAX or PMSF. Antibody inhibition of the CYP2E1 enzyme significantly reduced levels of binding to microsomal proteins, compared with control levels. These results are consistent with the premise that EC is metabolized by CYP2E1 and hydrolase A in liver microsomes of mice.

Metabolism of ethyl carbamate by pulmonary cytochrome P450 and carboxylesterase isozymes: involvement of CYP2E1 and hydrolase A

The lung is highly susceptible to ethyl carbamate (EC)-induced tumorigenesis. Our goal in this study was to investigate the in vitro isozyme-selective metabolism of EC in lung microsomes by cytochrome P450 and carboxylesterase enzymes. Our results showed that incubations with EC produced significant reduction in p-nitrophenol (PNP) hydroxylation and N-nitrosodimethylamine (NDMA) demethylation; there were no alterations in 7-pentoxyresorufin- and 7-ethoxyresorufin O-dealkylase activities. Reaction of microsomes with an inhibitory CYP2E1 antibody and subsequent reaction with EC abolished the EC-induced diminution in NDMA demethylase activity. Carboxylesterase activity, as assessed by hydrolysis of p-nitrophenyl acetate, was significantly decreased in microsomes incubated with EC. Reactions with EC in conjunction with the carboxylesterase inhibitors, paraoxon (PAX) or phenylmethylsulfonyl fluoride (PMSF), abolished the EC-induced decrease in carboxylesterase activity; PAX is a broad-spectrum carboxylesterase inhibitor, whereas PMSF is a specific inhibitor of hydrolase A, a carboxylesterase isozyme. Incubations of EC in combination with either PAX or PMSF exacerbated the EC-induced reduction in PNP hydroxylase and NDMA demethylase activities. Alterations in immunodetectable CYP2E1 protein levels were not apparent in microsomes incubated with EC alone, but the amounts were decreased in reactions with EC in conjunction with either PAX or PMSF. Immunoblotting with antibodies for the carboxylesterase isozymes, hydrolase A and B, revealed loss of immunodetectable hydrolase A in microsomes incubated with EC, PAX, or PMSF. However, immunodetectable hydrolase B was only decreased in microsomes reacted with PAX but not with PMSF or EC. These findings correlated with our covalent binding data, which showed that levels of binding of [14C-ethyl]EC to lung microsomes were significantly higher in incubations conducted in conjunction with PAX or PMSF, compared with control levels. Antibody inhibition of the CYP2E1 enzyme significantly reduced the extent of binding. Our results demonstrated that EC metabolism in lung microsomes, as estimated from magnitudes of covalent binding, is mediated by the P450 isozyme CYP2E1 and the carboxylesterase isozyme hydrolase A.

Characterization of cytokine profiles and double-positive lymphocyte subpopulations in normal bovine lungs

OBJECTIVE

To characterize cytokine profiles and lymphocyte subpopulations in lung parenchyma and bronchoalveolar lavage (BAL) fluid from normal bovine lungs.

ANIMALS

Eight 12- to 18-month-old cattle.

PROCEDURE

Cell populations in BAL fluid and collagenase-digested lung parenchyma were analyzed by flow cytometry and monoclonal antibodies. Proportions of total cell populations were determined, using Giemsa-stained cytospots. Distribution of lymphocytes within the lung parenchyma was analyzed by immunohistochemistry, and cytokine mRNA species in the parenchyma were characterized by use of reverse transcriptase-polymerase chain reaction analysis.

RESULTS

Cytokine profiles indicated high amounts of mRNA for interleukins 6 and 10 and transforming growth factor beta. In the BAL fluid and lung parenchyma, macrophages were the predominant cell type, although the proportion was lower in the parenchyma. Lymphocytes made up approximately 3% of both cell populations. Common to both lung compartments was the predominance of CD2+ and gamma delta T cells over B lymphocytes. There were more CD8+ T cells than CD4+ T cells in both compartments. The gamma delta cells made up approximately 9% of the lymphocyte populations. Two-color flow cytometry revealed CD8+ gamma delta T cell and CD8+CD5- populations that were unique to BAL fluid. In the BAL fluid and parenchyma, most CD4+ and CD8+ T cells expressed high amounts of CD44, a characteristic of memory T cells. The gamma delta T cells were CD44(10), as were B cells in the lung parenchyma. The B cells from BAL fluid expressed high amounts of CD44. Immunohistologic analysis of lung tissue revealed bronchus-associated lymphoid tissue structures with distinctive germinal center organization of B cells encompassed by CD4+ T cells.

CONCLUSIONS

Results provided normal values for comparison with those of other species and with the bovine respiratory tract response to disease.

Differential formation of 1,1-dichloroethylene-metabolites in the lungs of adult and weanling male and female mice: correlation with severities of bronchiolar cytotoxicity

The bronchiolar Clara cell cytotoxicant, 1,1-dichloroethylene (DCE), is selectively metabolized by CYP2E1 to metabolites including 2,2-dichloroacetaldehyde and DCE-epoxide. We have performed comparative studies in the lungs of adult and weanling male and female mice to determine their relative capacities to metabolize DCE. Levels of activities of p-nitrophenol hydroxylase, N-nitrosodimethylamine demethylase and NADPH-cytochrome P450 reductase were all significantly higher in adult female mice than in either adult male or weanling mice of both sexes. The quantities of 2,2-dichloroacetaldehyde (identified as its hydrolysis product, acetal) and the DCE-epoxide (identified as the GSH conjugates, 2-(S-glutathionyl) acetyl glutathione [B] and 2-S-glutathionyl acetate [C]) formed were significantly higher in lung microsomes from adult female mice than in those from either adult male or weanling mice of both sexes. Also, the metabolite levels formed in weanling mice were significantly higher than in adult male mice. The amounts of DCE-metabolites produced correlated with the relative severities of DCE-induced bronchiolar damage. The severities of bronchiolar injury were in the rank order adult female > weanling male and female > adult male mice, and coincided with the rank order of DCE-epoxide formation in these experimental groups of mice. In comparison with adult male and weanling male and female mice, adult female mice expressed highest levels of activities of CYP2E1-selective and reductase enzymes, formed most of the DCE-epoxide and were most susceptible to DCE-induced pneumotoxicity. These findings demonstrated sex-related differences in expression of activating enzymes and DCE metabolism in lung, and only in the adult female vs. female weanling mice were there age-related effects in regard to formation of both DCE-metabolites and cytotoxicity.

Purification of hydrophobic integral membrane proteins from Mycoplasma hyopneumoniae by reversed-phase high-performance liquid chromatography

A general and practical approach for isolating, fractionating and purifying large quantities of outer membrane hydrophobic proteins is described as applied to membrane proteins of Mycoplasma hyopneumoniae. Outer membrane proteins were extracted with Triton X-114 detergent and were precipitated from the detergent phase with 90% ethanol. Precipitated proteins were dissolved in 65% formic acid and separated by RP-HPLC using a formic acid-acetonitrile gradient. A M(r) 48 000 protein was obtained in high yield and at greater than 90% purity by optimisation of parameters for RP-HPLC. The combination of Triton X-114 extraction followed by high resolution RP-HPLC is a novel and rapid procedure for the isolation and purification of hydrophobic proteins. Proteins purified by this approach were suitable for subsequent characterisation by direct sequencing of the amino terminus as well as generation of peptides by digestion with cyanogen bromide.

Protection from 1,1-dichloroethylene-induced Clara cell injury by diallyl sulfone, a derivative of garlic

Bronchiolar Clara cell damage ensues after treatment of mice with 1,1-dichloroethylene (DCE). The cytotoxicity is mediated by CYP2E1, a cytochrome P450 isozyme that is highly localized in the Clara cells. Bioactivation of DCE produces the primary metabolites 2,2-dichloroacetaldehyde, which hydrolyzes to the acetal, and DCE epoxide, which reacts with glutathione to form the conjugates 2-(S-glutathionyl) acetyl glutathione [B] and 2-S-glutathionyl acetate [C]. In this study, we investigated the potential of diallyl sulfone (DASO2) to inhibit CYP2E1, to suppress the bioactivation of DCE to reactive intermediates and to abrogate DCE-induced Clara cell cytotoxicity. Our results showed that treatment of mice with DASO2 (100 mg/kg p.o.) produced decreases in CYP2E1-dependent p-nitrophenol hydroxylation that were apparent at 1 h. Enzyme activity plummeted to about 20% of the control by 2 h and remained at this low level from 3 to 8 h. Recovery of activity was evident at 16 h and returned to the control level by 24 h. Immunoreactivity of the CYP2E1 protein was decreased in immunoblots of lung microsomes from DASO2-treated mice. Treatment with DASO2 did not cause any structural alterations in lung tissue; in contrast, treatment with DCE (75 mg/kg) produced Clara cell damage. This lesion was not manifested in mice treated with DASO2 in conjunction with DCE. The lack of cytotoxicity observed in vivo correlated with a reduction of about 45% in the levels of both the acetal and the DCE epoxide-derived conjugates [B] and [C] in vitro. These results demonstrated that DASO2 significantly inhibited the CYP2E1 enzyme, decreased the production of DCE metabolites and protected Clara cells from DCE-induced cytotoxicity.

Predictors of mortality in severe malaria: a two year experience in a non-endemic area

Management of severe malaria is an increasing problem worldwide. This paper reviews the pathophysiology and management documenting two years' experience of admissions of severe malaria to an ICU in a non-endemic area. Clinical and laboratory features of severe malaria were analysed for predictors of mortality Twenty-eight patients had clinical or laboratory features compatible with the WHO criteria for severe malaria and, despite treatment with intravenous quinine and supportive ICU care, mortality was 28.5% (8/28). The three pregnant patients died with 100% foetal mortality and the four paediatric patients survived. Of the non-survivors, 8/8 developed ARDS (defined by worst ALI score > 2.5), 7/8 developed shock requiring inotropic support and 7/8 developed acute renal failure requiring CVVHD. Admission haemoglobin, platelet count, parasite count, and lowest Glasgow Coma Score in the first 24 hours were shown not to be predictors of mortality.

Pulmonary CYP2E1 bioactivates 1,1-dichloroethylene in male and female mice

Pulmonary cytotoxicity induced by 1,1-dichloroethylene (DCE) has been linked to the generation of reactive intermediates through a cytochrome P450-dependent pathway. In the present studies, our objectives were to investigate and compare cytochrome P450 isozyme-selective bioactivation of DCE in vitro in the lungs of male and female mice. Our results showed that CYP2E1-dependent p-nitrophenol hydroxylation was significantly higher in microsomes from female (0.45 +/- 0.01 nmol/mg protein/min) than from male (0.38 +/- 0.02 nmol/mg protein/min) mice. Lung microsomes from male mice incubated in the presence of an NADPH-generating system and increasing amounts of DCE (5-20 mM) exhibited corresponding decreases in p-nitrophenol hydroxylase activity (19%-50%); however, greater decreases (26%-70%) were observed in lung microsomes from female mice incubated under the same conditions. In contrast, alterations in CYP2B1-dependent 7-pentoxyresorufin O-dealkylation and CYP1A1-dependent 7-ethoxyresorufin O-dealkylation were not detected in any microsomal preparation incubated with DCE. Reaction with an anti-CYP2E1 antibody abolished the inhibition of p-nitrophenol hydroxylation by DCE. Protein immunoblotting revealed significant decreases in the intensity of the bands of microsomal samples incubated previously with DCE; in contrast, alterations in heme content were not evoked by reaction with DCE. Our results have demonstrated that CYP2E1, and not CYP2B1 or CYP1A1, mediated the bioactivation of DCE. Furthermore, this bioactivation occurred to a greater extent in lung microsomes from female than from male mice, which suggests that females may be at slightly greater risk for DCE-induced pneumotoxicity.

Antigens identified by monoclonal antibodies in tissue sections of Boophilus microplus

A panel of monoclonal antibodies (mAbs) raised against midgut antigens of Boophilus microplus were used to probe various stages and organs of the tick. One of the monoclonal antibodies in this panel (QU13) has previously been shown to recognize protective antigens. Of the 18 mAbs tested, all except two (QU5 and QU12) reacted with sections of adult midgut and Malpighian tubules using an avidin-biotin alkaline phosphatase method for immunostaining. MAbs QU1, QU2, QU3, QU4, QU12, QU13, and QU18 reacted specifically with the lumenal surfaces of type III acini of the salivary gland. These seven mAbs also stained the midgut in larval sections indicating that the antigens recognized were not stage specific. However, none of the seven mAbs tested recognised antigens in either the adult ovary or the developing egg. Antigens which were immunogold labelled by mAbs QU1, QU4, QU11, QU13, and QU15 in electron microscopy were located either on or near the surface of the microvilli of digestive cells from the midgut of the adult tick. We conclude that common antigens are present on the lumenal surfaces of the adult midgut, type III acini of the salivary gland, and the Malpighian tubules and that these antigens are also located in the larval gut.

Anti-idiotypic antibodies as surrogate antigens for vaccinating against the cattle tick, Boophilus microplus

QU13, a monoclonal antibody (mAb) raised against midgut (GM) antigens from Boophilus microplus and shown to recognise antigens which protect cattle from tick challenge was used to immunise cattle and rabbits to produce anti-idiotypic antibodies (AIA). Polyclonal antisera against mAb QU13 were produced in rabbits and cattle. AIA were purified from these antisera by affinity chromatography procedures. These purified AIA were found to block mAb QU13 binding to GM in enzyme-linked immunosorbent assay (ELISA). AIA purified from bovine antiserum elicited an immune response in cattle to antigens extracted by detergent from the midgut of B. microplus (TXGM) after the fourth vaccination (P = 0.06) compared with the bovine immunoglobulin (Ig) control. The mean antibody level in the group of experimental cattle vaccinated with AIA purified from rabbit antisera was significantly higher (P < 0.03) than that of bovine Ig control cattle after the fourth vaccination and an anamnestic response (P < 0.11) occurred in the rabbit AIA vaccinated group of cattle when a single booster dose of 300 micrograms of TXGM was given after the first tick challenge. The positive control group of cattle vaccinated with TXGM were significantly protected (P < 0.05) against tick infestation after the booster dose of 300 micrograms of TXGM. The AIA vaccinated groups of cattle were not protected against challenge with 20,000 larval ticks either before or after the booster injection of 300 micrograms of TXGM.

In vitro biotransformation of 1,1-dichloroethylene by hepatic cytochrome P-450 2E1 in mice

1,1-Dichloroethylene (DCE) is hepatotoxic in mice and its cytotoxic effects are associated with cytochrome P-450 (P450)-dependent formation of metabolite(s) that bind covalently to tissue macromolecules. Our goal was to investigate effects of DCE on P450 in liver microsomes. Specific objectives were to examine 1) inactivation of P450 by DCE and to determine if during this inactivation the heme and/or apoprotein moieties are destroyed and 2) isozyme-selective biotransformation of DCE by P450. Our results showed significant reduction of P450 content in reactions containing DCE and microsomes from untreated (30%) or phenobarbital-treated (20%) mice. Maximal reduction (50%) of P450 was evoked by DCE in reactions catalyzed by microsomes from acetone-treated mice. Alterations in heme levels were not detected in any microsomal preparation incubated in the presence of DCE. Significant inhibition of p-nitro-phenol hydroxylation was found in microsomes incubated previously with DCE and was most pronounced in acetone-treated mice, as compared to control and phenobarbital-treated mice. DCE did not cause inhibition of 7-pentoxyresorufin-O-dealkylation in any microsomal preparation. Immunoinhibition with an anti-2E1 antibody abolished the observed inhibition of p-nitrophenol hydroxylation. Densitometric scanning of protein immunoblots using an anti-2E1 antibody revealed a 40% decrease in microsomes reacted with DCE, whereas no change was observed in immunoblots prepared with an anti-2B antibody. These results showed that 1) biotransformation of DCE is catalyzed by the 2E1 and not by the 2B enzyme and 2) DCE inactivates P450 by destruction of the apoprotein rather than the heme moieties.

Mesenteric panniculitis presenting as a multilocular cystic mesenteric mass: CT and MR evaluation

Mesenteric panniculitis is a non-neoplastic, inflammatory process affecting the adipose tissue of the mesentery in adults with slight male predilection. Typical computed tomography (CT) or magnetic resonance imaging (MRI) findings are of either diffuse mesenteric infiltration or nodular mesenteric masses. We encountered a case of mesenteric panniculitis in a 26-year-old woman with the left upper quadrant pain and fullness, in which CT and MRI disclosed a large, ill-defined, multilocular cystic mesenteric mass. After surgery, the diagnosis of mesenteric panniculitis was made. The cystic components were dilated lymphatics due to lymphatic and venous obstruction by the mesenteric panniculitis.

Immune responses of cattle to biochemically modified antigens from the midgut of the cattle tick, Boophilus microplus

Treatment of membrane antigens of the midgut (GM) of the cattle tick, Boophilus microplus with sodium metaperiodate (periodate), pronase and lipase significantly inhibited the reactivity of the GM with antibodies in the sera of 57 cattle vaccinated with GM. Treatment of GM with periodate only removed the correlation between antibody reactivity of sera and protection against infestation with ticks. A monoclonal antibody (MoAb QU13), which recognises protective antigens solubilized from GM (Lee + Opdebeeck 1991), did not react with GM treated with periodate. Cattle vaccinated with GM extracts were significantly protected against infestation with cattle ticks (P less than 0.05), whereas cattle vaccinated with either GM extracts treated with periodate or with antigens precipitated from GM extracts with MoAb QU13 and also treated with periodate, were not protected against infestation. These studies provide preliminary evidence that protective antigens in the tick midgut membrane either are carbohydrate or are dependent on carbohydrate for their specificity.

CPAP, effective respiratory support in patients with AIDS-related Pneumocystis carinii pneumonia

Human Immunodeficiency Virus (HIV) related Pneumocystis carinii pneumonia (PCP) associated with severe respiratory failure is an increasingly common problem in major centres and is associated with a high mortality in previous and recent studies. Early in the epidemic, alternatives to invasive intensive care treatment were utilized in our institution and found to be successful. When respiratory failure developed, mask CPAP was used instead of intubation and ventilation. A retrospective review of 175 cases of HIV infected patients with confirmed first presentation PCP was undertaken. Treatment with our protocol resulted in an overall hospital mortality of 9%. Those patients who did not require supplemental oxygen or respiratory support had no in-hospital mortality. The group who required supplemental oxygen had a mortality of 10%. If respiratory failure supervened (severe respiratory distress, PaO2 less than 50 mmHg, SaO2 less than 90% on mask oxygen), CPAP was introduced. The mortality in this group was 22%. Only two patients were admitted to the intensive care unit for respiratory support after failure of CPAP. Both patients were intubated and received intermittent positive pressure ventilation (IPPV). Both patients died.