Phospholipase resistance of the glycosyl-phosphatidylinositol membrane anchor on human alkaline phosphatase

Alkaline phosphatase (ALP) is attached to the cell surface in mammalian tissues via a glycosyl-phosphatidylinositol (GPI) anchor and can be released from the membrane by GPI-specific phospholipases. In a range of cultured human cell lines, however, the sensitivity of ALP to phospholipases was observed to be variable in magnitude (approximately 20-90%). The mechanism of phospholipase resistance was explored with phospholipases of different bond specificities. The results suggest that phospholipase resistance is the result of acylation of the inositol ring in the GPI anchor. The occurrence of phospholipase-resistant forms of ALP may have important implications for the in vivo release and disposition of plasma ALP.

Phospholipase Resistance of the Glycosyl-Phosphatidylinositol Membrane Anchor on Human Alkaline Phosphatase

Alkaline phosphatase (ALP) is attached to the cell surface in mammalian tissues via a glycosyl-phosphatidylinositol (GPI) anchor and can be released from the membrane by GPI-specific phospholipases. In a range of cultured human cell lines, however, the sensitivity of ALP to phospholipases was observed to be variable in magnitude (approximately 20-90%). The mechanism of phospholipase resistance was explored with phospholipases of different bond specificities. The results suggest that phospholipase resistance is the result of acylation of the inositol ring in the GPI anchor. The occurrence of phospholipase-resistant forms of ALP may have important implications for the in vivo release and disposition of plasma ALP.

CD48 is a counter-receptor for mouse CD2 and is involved in T cell activation

CD2 is an intercellular adhesion molecule that has been implicated in T cell activation and differentiation both in humans and mice. Although the ligand for human CD2 has been defined as LFA-3, that for murine CD2 has not been identified yet. To identify the ligand for mouse CD2, we generated a chimeric molecule consisting of the extracellular domain of mouse CD2 and human immunoglobulin (Ig)G1 Fc (mCD2Rg). A hamster monoclonal antibody (mAb), HM48-1, was established by screening mAbs that could block the binding of mCD2Rg to T cell lines at the ligand site. The putative mouse CD2 ligand recognized by this mAb was a glycosyl phosphatidylinositol-anchored glycoprotein with an apparent molecular mass of 45 kD, which were shared characteristics with human LFA-3. However, its expression was predominantly restricted to hematopoietic cells, unlike human LFA-3. Protein microsequencing analysis for the NH2-terminal 18 amino acid residues of the affinity-purified HM48-1 antigen revealed that it is almost identical with mouse CD48. This identity was further confirmed by the reactivity of HM48-1 with a soluble recombinant CD48 (sCD48) protein and the molecule recognized by a rat mAb raised against sCD48. A rat anti-CD48 mAb blocked the mCD2Rg binding as well as HM48-1. Moreover, sCD48 also inhibited the mCD2Rg binding to the cellular ligand. Finally, like anti-CD2 mAb, HM48-1 inhibited the phytohemagglutinin response and, when crosslinked, augmented the anti-CD3 response of splenic T cells. These results indicate that CD48 is a ligand for mouse CD2 and is involved in regulating T cell activation.

Rapid method for the determination of ketanserin in rat serum by high-performance liquid chromatography with fluorimetric detection

A simplified high-performance liquid chromatographic (HPLC) assay for the determination of ketanserin in rat serum is described. The chromatographic method allowed complete resolution of ketanserin from two of its metabolites. A protein precipitation extraction procedure was employed which allowed rapid sample preparation for injection into the HPLC system. Both intra- and inter-assay coefficients of variation at serum ketanserin concentration of 200 and 800 ng/ml were less than 6% and the accuracy was excellent. The assay has been applied for determining the elimination kinetics of ketanserin in the rat.

Microbial models of mammalian metabolism: production of 3'-hydroxywarfarin, a new metabolite of warfarin using Cunninghamella elegans

Warfarin, an anticoagulant and "metabolic probe" for cytochrome P-450 isozyme multiplicity, was metabolized by the fungus Cunninghamella elegans (ATCC 36112) to yield the previously unreported metabolite 3'-hydroxywarfarin. This metabolite was isolated from cell suspension cultures and characterized by analytical (HPLC) and spectral (EI-MS, PMR) comparisons with synthetic 3'-hydroxywarfarin.

Determination of betaxolol and its metabolites in blood and urine by high-performance liquid chromatography with fluorimetric detection

Analytical methods for the determination of betaxolol and two of its metabolites in blood and urine are described. Betaxolol, alpha-hydroxybetaxolol, and the acid metabolite were extracted, with over 65% efficiency, from biological samples by liquid-liquid extraction methods. Analysis was performed using reversed-phase high-performance liquid chromatography with fluorimetric detection. N,N-Dimethyloctylamine (0.005 M) was used to improve the chromatography of betaxolol and alpha-hydroxybetaxolol, while acetic acid (1%) was used for the acid metabolite. An excitation wavelength of 200 nm was found to produce the best detector response. Linear standard curves were obtained for all three compounds with detection limits (signal-to-noise ratio = 3) varying between 1 and 10 ng/ml. The coefficients of variation of the determination for all three compounds in blood and urine varied between 3.0 and 8.7%. The metabolism of betaxolol was studied in twelve healthy male subjects. The amounts (mean +/- S.D.) of betaxolol, alpha-hydroxybetaxolol and the acid metabolite renally excreted in the first 48 h after intravenous administration of 10 mg of betaxolol hydrochloride are 17.1 +/- 6.2, 0.4 +/- 0.1 and 14.5 +/- 3.7%, respectively, of the administered dose.

Structure, expression, and genetic linkage of the mouse BCM1 (OX45 or Blast-1) antigen. Evidence for genetic duplication giving rise to the BCM1 region on mouse chromosome 1 and the CD2/LFA3 region on mouse chromosome 3

The mouse BCM1 (OX45, Blast-1) antigen has been cDNA cloned and sequenced to provide data supporting the view that BCM1, LFA3, and CD2 constitute a subgroup within the Ig superfamily. Mouse BCM1 is widely expressed on leukocytes and is likely to be anchored to the cell surface by a glycosyl-phosphatidylinositol anchor, as is the case for rat and human BCM1 antigen. Genetic linkage studies by recombination and pulse field analysis showed the BCM1 locus (Bcm-1) to be on distal mouse chromosome 1 and to be linked within 1,600 kb to the locus for an ATPase alpha chain gene (Atpa-3). A similar relationship was established between the human BCM1 locus (BCM1) and ATP1A2, and other markers on chromosome 1q. Conservation of genomic organization within a segment of human chromosome 1q and mouse chromosome 1 was demonstrated. A similar situation is seen in the region of the CD2 and LFA3 genes between mouse chromosome 3 and human chromosome 1p. Furthermore, the CD2/LFA3 genes are linked within 580 kb to Atpa-1/ATP1A1 genes to provide a parallel situation to the linkage between Bcm-1/BCM1 and Atpa-3/ATP1A2 on chromosomes 1 (mouse) and 1q (human). Taken together, the data suggest duplication of a chromosome region including the precursors of the genes for BCM1, CD2, and LFA3, and the ATPase genes to give rise to the linkage groups now observed. The duplicated regions may have stayed together on chromosome 1 in the human (with the insertion of a centromere), while in the mouse, the genetic regions are proposed to have become dispersed in the formation of chromosomes 1 and 3. CD2 and LFA3 are more dissimilar in sequence than BCM1 and LFA3, and if the precursors of the CD2 and LFA3 loci formed before the proposed chromosome segment duplication, then a gene encoding a recognizer molecule for BCM1 may exist in linkage with Bcm-1/BCM1 on chromosome 1 (mouse) and 1q (human).

Microbial models of mammalian metabolism: stereoselective metabolism of warfarin in the fungus Cunninghamella elegans

Biotransformation stereoselectivity of warfarin was studied in the fungus Cunninghamella elegans (ATCC 36112) as a model of mammalian metabolism. This organism was previously shown to produce all known phenolic mammalian metabolites of warfarin, including 6-, 7-, 8-, and 4'-hydroxywarfarin, and the previously unreported 3'-hydroxywarfarin, as well as the diastereomeric warfarin alcohols, warfarin diketone, and aliphatic hydroxywarfarins. Using S-warfarin and R-warfarin as substrates, and an HPLC assay with fluorescence detection to analyze metabolite profiles, the biotransformation of warfarin was found to be highly substrate and product stereoselective. Both aromatic hydroxylation and ketone reduction were found to be stereoselective for R-warfarin. Ketone reduction with the warfarin enantiomers exhibited a high level of product stereoselectivity in that R-warfarin was predominantly reduced to its S-alcohol, while S-warfarin was reduced primarily to the corresponding R-alcohol.

Analysis of warfarin and its metabolites by reversed-phase ion-pair liquid chromatography with fluorescence detection

A high-performance liquid chromatographic method was developed for the determination of warfarin and its metabolites (diastereomeric warfarin alcohols and 6-, 7-, 8-, 4'- and 3'-hydroxywarfarin) in microbial cultures. Ion-pair chromatography with tetrabutylammonium ion as the counter ion allowed for the complete resolution of all compounds at pH 7.5 on a reversed-phase (C18) column, thus permitting direct fluorescence detection without the use of post-column pH switching techniques. Analysis of cell suspension cultures of the fungus Cunninghamella elegans (ATCC 36112) indicated that this organism metabolizes warfarin to all known mammalian metabolites, plus the previously unreported 3'-hydroxywarfarin. Detection limits for all compounds were in the low nanogram range.

Evaluation of a kinetic assay for angiotensin converting enzyme

We have verified the analytical reliability of a Sigma reagent kit, which is a modified method of Holmquist et al. (1) for the determination of angiotensin-converting enzyme (ACE) on the Abbott ABA-100 analyzer. The reaction was linear up to 160 U/L. Correlation with a radiometric method (Ventrex Laboratories) was good except for a negative constant bias and loss of linearity with the radiometric method at high levels. The reconstituted reagent was determined by atomic absorption spectroscopy to contain 5.6 mumol/L of zinc. An increase in zinc content up to 45.6 mumol/L had little or no effect on enzyme activities of preparations from three mammalian species: rabbit, guinea pig and human. Neither was ACE activity inhibited by preincubating each of two serum pools with any of four corticosteroids for up to 8 d. Enzyme activity in samples remained stable at 5 degrees C for 8 d.

Prevalence of hepatitis B markers in psychiatric in-patients in Singapore: a pilot study

The prevalence of hepatitis B infection among 71 patients in an adult psychiatric hospital was determined by testing for hepatitis B surface antigen (HBsAg), its antibody (anti-HBs) and antibody against hepatitis B core antigen (anti-HBc). The results showed 12.7 per cent positive for HBsAg, 63.4 per cent positive for anti-HBs and 69 per cent positive for anti-HBc. This assessment of the prevalence of hepatitis B in a group of adult long-term institutional patients may be used as a guide when hepatitis B vaccination is being considered for use in a psychiatric hospital. The need for a similar study on health care personnel working in the same institution is emphasized.

6-Methylmercaptopurine riboside resistance in human lymphocytes in the in vivo somatic cell mutation test

Additional drug-resistance markers are being investigated to broaden the in vivo somatic cell mutation test in human lymphocytes (PBL). The adenosine kinase (AK) locus was chosen for study because Gupta and Singh [Gupta RS, Singh B: Mutat Res 113:441-454, 1983] have demonstrated that in Chinese hamster ovary cells, mutants affected at this locus are obtained at a very high spontaneous frequency and that the response of this locus to different types of mutagens was comparable to that of the hypoxanthine-guanine phosphoribosyl transferase locus. The adenosine analog 6-methylmercaptopurine riboside (MeMPR) was used as the selective agent for obtaining AK-deficient mutants. Cultures of mitogen-stimulated PBL were set up in the presence (test) and absence (control) of the selective agent. Resistant cells capable of synthesizing DNA in the presence of MeMPR were labeled with tritiated thymidine and enumerated autoradiographically. The variant frequency (Vf) was calculated as the ratio of the number of labeled nuclei in the test relative to that in the control. Human PBL were found to be sensitive to MeMPR inhibition of DNA synthesis and exhibited a dose-dependent decrease in Vf with increasing concentrations of MeMPR. However, no leveling off of the dose-response curve was observed. Thus the background level of Vf was probably lower than the practical detection limit of the test (4.0 X 10(-7) with a 50-ml blood sample). It was concluded that, because of the autosomal recessive nature of the AK gene, the background Vf in human PBL is too low to allow a useful baseline to be established for the in vivo somatic mutation test.

Severe hepatic damage after acetaminophen use in psittacosis

A 63-year-old man with acute psittacosis had severe hepatic damage after ingesting about 10 g of acetaminophen over a 48 hour period. Transaminase levels showed striking elevation, with a serum glutamic-oxaloacetic transaminase level of over 15,000 IU/liter, and decreased rapidly, consistent with a toxic insult. No other etiologic agents were identified by history or serologic testing to explain this degree of damage. Liver histologic findings at autopsy showed severe central necrosis. Although psittacosis may infrequently cause a similar pattern of hepatic injury, disease of this severity has not been previously reported. It is postulated that acetaminophen may have accentuated hepatic disease produced by Chlamydia psittaci in this patient.

Are the pharmacological effects of L-prolyl-L-leucyl-glycinamide (PLG) mediated through specific receptor mechanisms?

In an attempt to delineate the mechanism subserving the demonstrated central effects of the tripeptide, L-prolyl-L-leucyl-glycinamide (PLG) in mammals including humans, we developed a radioligand binding assay to characterize the binding of 3H-PLG to rat brain membranes. Equilibrium binding studies indicated that PLG binds to rat striatum with high affinity (KD = 4.69 +/- 0.50 nM), saturability (Bmax = 9.20 +/- 0.30 fmoles mg-1 protein) and reversibility. Kinetic data yielded a KD = 1.42 +/- 0.21 nM for rat striatum. Regional distribution profile of specific 3H-PLG binding revealed that the striatum has the highest density of PLG binding sites, followed by the hypothalamus and the cerebral cortex. Analogues of PLG compete for specific PLG binding in rat striatum with potencies parallelling their in vivo activities in behavioural systems. Our results support the existence of a unique class of putative peptide receptor sites specific for PLG mediating a spectrum of pharmacological effects.

Seroreactivity to Mycoplasma pneumoniae and Legionella pneumophila: lack of a statistically significant relationship

We reviewed antibody titers to Mycoplasma pneumoniae and Legionella pneumophila serogroup I in sera from 1,060 cases of acute respiratory infection to determine whether there was an association in seroreactivity to these organisms. Of the 170 serum pairs with antibodies to L. pneumophila (35 seroconversions and 135 with presumptive titers), 32 (18.8%) demonstrated seroreactivity to M. pneumoniae (17 seroconversions and 15 with presumptive titers). This frequency was not significantly greater than the seroreactivity to M. pneumoniae observed in sera without antibodies to L. pneumophila (17.5%) (0.05 less than P less than 0.10), which included 111 seroconversions and 45 sera with presumptive titers.

The significance of western equine encephalomyelitis viral infections in Aedes trivittatus (Diptera: Culicidae) in Iowa. I. Variation in susceptibility of Aedes trivittatus to experimental infection with three strains of western equine encephalomyelitis virus

F1 pregnancy obtained from field-collected Aedes trivittatus were evaluated for susceptibility to infection with western equine encephalomyelitis (WEE) virus by intrathoracic inoculation and by oral imbibition of virus-blood suspensions through a membrane. Mosquitoes were uniformly susceptible to infection by intrathoracic inoculation of three strains of WEE virus, but minimum infective doses varied as much as 2,000 to 12,000-fold between strains by membrane feeding. Dose-response data obtained by membrane feeding also indicated that field strains of A. trivittatus were quite heterogeneous in their susceptibility to WEE virus since some individual mosquitoes could be infected by ingestion of low virus concentrations while others could not be infected by a 20,000-fold increase in virus concentration. Moreover, A. trivittatus showed a greater affinity for a WEE viral strain isolated from this species than for a WEE viral strain isolated from Culex tarsalis, even though the site, date of collection, and passage history of these isolates were identical. Field strains of A. trivittatus were relatively refractory to oral infection with WEE virus.

Legionnaires' disease in pneumonia patients in Iowa. A retrospective seroepidemiologic study, 1972-1977

The frequency of Legionnaires' disease among 586 cases of pneumonia that occurred in Iowa between fiscal years 1972 and 1977 was studied retrospectively on the basis of paired sera. The frequency of confirmed Legionnaires' disease was 4.1% and of presumptive Legionnaires' disease was 11.4%. Infections with the Legionnaires' disease (LD) bacterium were most frequent in the summer. Of the 22% of pneumonias for which a cause could be defined, Legionnaires' disease was third in frequency behind Mycoplasma pneumoniae and influenza A virus infections. Infections with the LD bacterium occurred in association with pneumonias in most age groups. The youngest patient with LD infection was a 5-year-old boy with pneumonia. The disease occurred 3.2 times more often in males than in females. In males, the frequency of confirmed and presumptive Legionnaires' disease increased steadily to plateau after the fourth decade at about 12% and 28%, respectively. In females the frequency of presumptive Legionnaires' disease was 7% to 16%, relatively evenly distributed over all age groups. Pneumonias associated with LD bacterium infection should be considered in the differential diagnosis of community-acquired pneumonias in most age groups.

Laboratory studies of transovarial transmission of trivittatus virus by Aedes trivittatus

Aedes trivittatus were experimentally exposed through a membrane to a concentration of trivittatus (TVT) virus in dog defibrinated blood of 10(3.4)-10(3.5) SMICLD 50/0.025 ml. Transovarial and transstadial transmission was demonstrated. Fifty-five percent of the infected mosquitoes tested transovarially transmitted TVT virus. TVT virus was isolated from 16% of the F1 generation progeny examined, including 19% of the larvae, 23% of adult females, and 10% of adult males.