Molecular cloning and functional expression of mannitol-1-phosphatase from the apicomplexan parasite Eimeria tenella

A metabolic pathway responsible for the biosynthesis and utilization of mannitol is present in the seven species of Eimeria that infect chickens, but is not in the avian host. Mannitol-1-phosphatase (M1Pase), a key enzyme for mannitol biosynthesis, is a highly substrate-specific phosphatase and, accordingly, represents an attractive chemotherapeutic target. Amino acid sequence of tryptic peptides obtained from biochemically purified Eimeria tenella M1Pase was used to synthesize degenerate oligonucleotide hybridization probes. Using these reagents, a partial genomic clone and full-length cDNA clones have been isolated and characterized. The deduced amino acid sequence of E. tenella M1Pase shows limited overall homology to members of the phosphohistidine family of phosphatases. This limited homology to other histidine phosphatases does, however, include several conserved residues that have been shown to be essential for their catalytic activity. Kinetic parameters of recombinant M1Pase expressed in bacteria are essentially identical to those of the biochemically purified preparation from E. tenella. Moreover, recombinant M1Pase is subject to active site-directed, hydroxylamine-reversible inhibition by the histidine-selective acylating reagent diethyl pyrocarbonate. These results indicate the presence of an essential histidine residue(s) at the M1Pase active site, as predicted for a histidine phosphatase.

Measurement of airborne flour exposure with a monoclonal antibody-based immunoassay

BACKGROUND

The development of simple and standardised methods to measure airborne levels of workplace biological allergens is an important step in reducing the incidence of occupational asthma. Such a method would be useful for measuring wheat flour allergens which cause asthma in bakers. Measurement of allergen per se rather than total dust enables exposure to be better defined.

METHODS

Monoclonal antibodies were produced, their specificity analysed by immunoblotting and then used to affinity-purify a putative flour allergen. The importance of this protein as an allergen was tested by RAST using sera from allergic bakers and it was identified by N-terminal sequencing. Suitable monoclonal antibodies were chosen to develop an enzyme-linked immunosorbent assay. Commercial baking flours and personal airborne dust samples were analysed using the immunoassay.

RESULTS

A sensitive and specific monoclonal antibody-based enzyme-linked immunosorbent assay was developed to measure a wheat alpha-amylase inhibitor. The wheat alpha-amylase inhibitor content of bulk wheat flours was 0.124% (95% confidence limits 0.083-0.164%) and airborne levels in bakeries had a geometric mean of 744 ng/m3 (95% confidence limits 371-1,496 ng/m3).

CONCLUSION

This assay is suitable for widespread use as the monoclonal antibodies and standards are well defined and potentially infinitely available. The assay therefore offers distinct advantages over those exposure assessment methods currently in use. Comparable results would be obtained by different investigators over a prolonged time period. The assessment of flour allergen exposure and the relationship with clinical response could then be investigated using a multi-centered approach.

Determination of protein loading in biodegradable polymer microspheres containing tetanus toxoid

Various methods to determine loading of vaccine in biodegradable polymer microspheres encapsulating tetanus toxoid were evaluated. The microspheres were composed of poly (D-lactic acid) (PLA) and poly (DL-lactic-co-glycolic acid) (PLGA). Dissolution of microspheres in organic solvents such as methylene chloride, chloroform, or dimethyl sulfoxide and extraction of vaccine antigen or total protein with phosphate buffered saline gave variable results which depended upon the characteristics of the microspheres, such as type of polymer, excipients used in the microspheres and formulation conditions. Microspheres made from low molecular weight PLGA polymer and showing a large burst release exhibited up to 25% extraction of antigen whereas microspheres made from PLA microspheres with low burst release showed < 1% extraction. Extraction of total protein with 0.1 N NaOH and 5% sodium dodecyl sulfate showed results similar to those obtained with organic solvent extraction method. Partial digestion of microspheres with 6 N HCl at 60 degrees C for 20 h resulted in approximately 30% loss in TT protein by micro-bicinchoninic acid (BCA) assay. The major problem with this method was strong reactions in the micro-BCA assay of stabilizers, particularly sugars (glucose, sucrose) used in the microsphere formulations. Complete digestion of microspheres with 6 N HCl at 110 degrees C for 20 h or with 13.5 N NaOH at 121 degrees C for 1 h and quantitation of amino acids by a modified ninhydrin assay showed reproducible results on the protein loading in the microspheres. However, this method was affected by the presence of stabilizers, such as gelatin, which contain amino acids. Further, sucrose concentrations higher than 10% caused interference in the ninhydrin assay on samples hydrolyzed with 6 N HCl. In contrast, hydrolysis with 13.5 N NaOH did not show any interference by sucrose. Stabilizers used outside the microspheres for lyophilization purposes may be removed by washing the microspheres before loading determination or by dialysis but stabilizers used inside the microspheres would still cause interference. For reliable determination of total protein in the microspheres containing vaccines, we suggest complete digestion of microspheres with acid or base followed by amino acid analysis by colorimeteric assays such as ninhydrin method or using amino acid analyzers. The method needs to be optimized for each type of formulation to eliminate interference by the excipients. Alternatively, total protein nitrogen in the microspheres may be determined by the Kjel-dahl method if no amino acids or other nitrogen containing stabilizer is used inside the microspheres.

Conversion from cyclosporin to tacrolimus in a patient with prolonged acute tubular necrosis

Acute tubular necrosis (ATN) is a common condition of following cadaveric renal transplantation with an incidence in many series of nearly 50%. The aetiology is uncertain; however, it would appear to be related to damage to the transplant kidney either prior to retrieval, During cold preservation or during re-warming of the kidney at the time of anastamotic construction. There is no specific therapy for ATN and treatment is comprised of an expectant policy with supportive dialysis and fluid restriction. Renal function improves in the majority of cases, though there may be delayed function for several weeks. We report a case of dialysis-dependent ATN that had persisted for 5 months following transplantation. Following conversion to tacrolimus there was immediate improvement in renal function, and after a month of tacrolimus therapy the patient was dialysis-independent.

Serum antibody concentrations of cytotoxin, exotoxin, A, lipopolysaccharide, protease, and elastase and survival of patients with Pseudomonas aeruginosa bacteremia

The relationship between survival and serum concentrations of antibody to cytotoxin, exotoxin A, lipopolysaccharide (LPS; IgM and IgG), protease, and elastase (determined by enzyme-linked immunosorbent assay) was studied in a group of 41 patients with Pseudomonas aeruginosa bacteremia. The lowest mean concentrations of antibody to cytotoxin (P < .05) and of IgG to LPS (P < .01) were noted in the patients who died within 48 hours of onset. The mean level of antibody to cytotoxin in patients who died 9-45 days or 5-22 months following onset was similar to that in controls, while in patients who survived > or = 24 months the level was higher than in controls (P < .01). The mean level of IgG to LPS was highest in patients who survived > or = 24 months. The mean concentrations of antibody to the other antigens (except IgM to LPS) were higher in patients than in controls (P < .01). No significant change occurred in any mean antibody concentrations over time. Administration of antipseudomonal antibodies, especially to cytotoxin and LPS, should be considered in the early stages of therapy for patients with P. aeruginosa bacteremia.

In vivo distribution of radioactivity in mice after injection of biodegradable polymer microspheres containing 14C-labeled tetanus toxoid

Radiolabeled tetanus toxoid (TT) was prepared by detoxifying chromatographically purified tetanus toxin with 14C-labeled formaldehyde. 14C-TT was encapsulated inside poly (D,L-lactide-co-glycolide, 50/50) microspheres (MS) of varying average size (approximately 10 microns and approximately 50 microns). Balb/c mice were injected subcutaneously with 5 Lf (approximately 15 micrograms) of 14C-TT, encapsulated in MS, mixed with blank MS without encapsulated antigen, as soluble antigen or adsorbed onto aluminum phosphate (AlPO4) and radioactivity was monitored at the site of injection, draining lymph nodes, blood, liver, spleen, and kidneys at various intervals. At one day, approximately 95% and 90% radioactivity disappeared from site of injection for soluble TT or blank MS mixed TT and AlPO4 adsorbed TT, respectively, whereas approximately 55% and 70% radioactivity disappeared from site of injection for MS of average size approximately 50 microns and approximately 10 microns, respectively. By 7 days, 99% of radioactivity disappeared from site of injection for soluble TT or blank MS mixed TT, whereas 2-3% radioactivity persisted at the site of injection for AlPO4 adsorbed TT for 4 weeks. In contrast, approximately 20% radioactivity stayed at the site of injection for MS injected mice up to 4 weeks. At all time points, large MS (approximately 50 microns) showed more radioactivity at the site of injection than small MS (approximately 10 microns). Other organs showing radioactivity were draining lymph nodes and kidneys. Small MS with encapsulated TT showed highest level of radioactivity in lymph nodes at 4 h. In kidneys, soluble and AlPO4 adsorbed TT showed a peak of radioactivity at 4 h whereas TT encapsulated in MS showed a peak of radioactivity at 7 days. These results indicate that AlPO4 did not act as a depot for TT at the site of injection, but TT encapsulated in MS did form a depot for approximately 1 month.

Diphtheria antitoxin levels in US blood and plasma donors

Plasma samples from 500 blood donors were titrated for diphtheria antitoxin (DAT) by the toxin neutralization (TN) test. Only 1.6% of donors had <0.01 IU/mL DAT, the minimum protective level against diphtheria; 15% had levels between 0.01 and <0.1 IU/mL, indicating basic protection, and 83.4% had levels > or =0.1 IU, indicating full protection. Three hundred fifty samples were studied by ELISA for diphtheria toxoid IgG antibodies to assess the utility of the assay as a quick, convenient method for evaluating diphtheria immunity. Although the correlation between TN and ELISA titers for the 350 samples was high (r = .80), there was no correlation (r = .07) for samples with antitoxin titers <0.1 IU/mL, the level of special interest for serosurveys for protection. Titration of 62 immune globulin samples (prepared from 1957 to 1994) showed that DAT levels in Massachusetts blood donors increased concurrently with increased use of tetanus-diphtheria vaccine in the state.

Cytomegalovirus involving gastrointestinal tract in renal transplant recipients

Infection due to cytomegalovirus (CMV) is a substantial cause of mortality and morbidity among renal transplant recipients but the prognosis of the disease has changed dramatically since the introduction of ganciclovir (GAN). During a period of 5 years we treated 54 patients who developed CMV disease. From this group of patients we identified 7 patients with primary gastrointestinal tract (GIT) CMV disease who received treatment with GAN. Tissue diagnosis was made by endoscopy of the upper GIT (6 patients) or sigmoidoscopy (one patient) and histological examination. All patients improved after treatment with GAN; three patients required additional treatment for recurrent CMV disease and recovered, and 1 patient relapsed without GIT involvement (P = 0.014). Recurrent CMV disease was more severe (mean score of 15 in relapse compared to 7 in the first episode). We believe relapse to be more common and the disease to be more severe in the presence of GIT involvement suggesting that a longer duration of treatment with GAN may be required in this clinical manifestation of CMV disease.

The bicyclams, a new class of potent human immunodeficiency virus inhibitors, block viral entry after binding

The bicyclams represent a new class of highly potent and selective HIV inhibitors. Time-of-addition experiments have previously shown that these compounds interfere with an early event in the viral replicative cycle. Additional experiments have now been carried out in order to investigate in more detail the mechanism of action of these promising compounds. As described in this paper, PCR experiments revealed that no viral DNA was formed following viral infection, thus confining the target(s) of action of the bicyclams to an early stage of HIV infection. An assay, using pseudotype virions containing the envelope of HIV-1 and the genome of a plaque-forming virus (Cocal Virus), pointed to viral entry as the main target of the bicyclams. HIV-1 strains resistant to two prototype bicyclams, JM2763 and SID791 (JM3100), were raised. Results obtained with SID791 with respect to syncytium formation induced by SID791-sensitive and -resistant HIV-1 strains and the cross-resistance observed for dextran sulfate, suggest inhibition of binding and/or fusion as a plausible target of SID791. Additional experiments enabled us to exclude SID791 and JM2763 as binding inhibitors and to conclude that bicyclams block the entry of cell-bound virus. Furthermore, a monoclonal antibody recognising the V3 loop of wild-type gp120 did not bind to this region in the two bicyclam-resistant strains. Our results point to gp120 as a possible target for the HIV-inhibitory effects of the bicyclams.

Characterization of the covalent binding of thiostrepton to a thiostrepton-induced protein from Streptomyces lividans

Thiostrepton is a highly modified multicyclic peptide antibiotic synthesized by diverse bacteria. Although best known as an inhibitor of protein synthesis, thiostrepton is also a potent activator of gene expression in Streptomyces lividans. In these studies, we characterize the nature of the interaction between thiostrepton and two proteins that it induces, TipAL and TipAS. In the absence of added cofactors, thiostrepton formed a complex with either TipAL or TipAS in aqueous solution. The TipA-thiostrepton complex was not dissociated by denaturants such as SDS, urea, or disulfide reducing agents. The mass of the TipAS-thiostrepton complex as determined by both sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) and mass spectrometry (MS) was equivalent to the sum of TipAS and thiostrepton. Thiostrepton also reacted spontaneously with free cysteine (but not with other amino acids tested) to generate stable compounds having masses equivalent to thiostrepton plus 3 to 4 cysteines. Blocking experiments indicated that complex formation required dehydroalanine residues on thiostrepton and cysteine residues on TipAS. When the TipAS-thiostrepton complex was digested with trypsin and analyzed by MS, the thiostrepton adduct was found bound only to the unique cysteine-containing TipAS peptide fragment. Amino acid analysis confirmed that the TipAS-thiostrepton complex contained lanthionine, the product of a reaction between dehydroalanine and cysteine. Together, these data document a covalent attachment of thiostrepton to TipA proteins mediated by bond formation between dehydroalanine of thiostrepton and cysteine of TipAS. Implications regarding the function of TipAS as a thiostrepton (electrophile)-sequestering protein and thiostrepton-mediated activation of TipAL as a model of irreversible transcriptional activation are discussed.

Adjuvant properties of non-phospholipid liposomes (Novasomes) in experimental animals for human vaccine antigens

Non-phospholipid liposomes composed of dioxyethylene cetyl ether, cholesterol and oleic acid were evaluated as adjuvants with human vaccine antigens, tetanus toxoid (TT) and diphtheria toxoid (DT), in mice and rabbits. Antigens encapsulated in or mixed with liposomes elicited antitoxin levels similar to those elicited by antigens given with Freund's adjuvant or adsorbed onto aluminum phosphate. All liposomal antigen preparations, antigen given with Freund's adjuvant or adsorbed onto aluminum phosphate, elicited significantly higher IgG antibodies and antitoxin levels than soluble antigens in mice after a single injection and in rabbits after each of three injections. TT encapsulated in liposomes elicited sustained anti-TT IgG antibody levels in mice after a single injection as compared to TT mixed with liposomes. TT mixed with or encapsulated within liposomes containing monophosphoryl lipid A/squalene or squalene alone, as well as aluminum phosphate adsorbed TT elicited greater primary responses in mice than TT mixed with or encapsulated within plain liposomes. Liposomal TT preparations produced a slightly higher anamnestic response in mice than aluminum phosphate adsorbed TT. Subclass analysis of anti-TT antibodies showed that the majority of the antibodies belong to IgG1 subclass. Liposomal TT preparations, particularly those with encapsulated monophosphoryl lipid A/squalene or squalene alone, consistently elicited higher levels of anti-TT IgG2a and IgG2b than aluminum phosphate adsorbed or soluble TT. None of the preparations elicited IgG3 or IgM antibodies. It appears that non-phospholipid liposomes are as potent adjuvants as the currently employed adjuvant for human vaccines (aluminum phosphate) or a benchmark adjuvant for experimental immunology (Freund's adjuvant), and may be able to modulate the immune response towards the Th1 type.

Alaska: Defining connectivity and access in an expansive state

The real challenge of Alaska's changing telecommunications landscape is approaching the opportunities in an orderly and logical manner. Given the exciting nature of the possibilities that new technology presents, it is all too easy to get wrapped up in what is new, instead of what is truly useful. For that reason, the main focus of the Telecommunications Information Council (TIC) in the near future will be developing and adopting a comprehensive technology plan for the state, and then examining where new technologies fit into that plan. The Knowles/Ulmer administration's first task in this effort was to reinvigorate the TIC and charge it with taking the lead in bringing Alaska back to the forefront of telecommunications technology. Our state has long had a reputation for leading the way in telecommunications. Our climate, geographic size, and location have always forced Alaskans to be innovators in technology. Supercomputers and satellites have operated in and above our state for many years, but much of that momentum was waning. That needed to change.

Poly(A) site selection in the HIV-1 provirus: inhibition of promoter-proximal polyadenylation by the downstream major splice donor site

In common with all retroviruses, the human immunodeficiency virus type 1 (HIV-1) contains duplicated long terminal repeat (LTR) sequences flanking the proviral genome. These LTRs contain identical poly(A) signals, which are both transcribed into RNA. Therefore, to allow efficient viral expression, a mechanism must exist to either restrict promoter-proximal poly(A) site use or enhance the activity of the promoter-distal poly(A) site. We have examined the use of both poly(A) sites using proviral clones. Mutation of the previously defined upstream activatory sequences of the 3' LTR poly(A) site decreases the efficiency of polyadenylation when placed in competition with an efficient downstream processing signal. However, in the absence of competition, these mutations have no effect on HIV-1 polyadenylation. In addition, the 5' LTR poly(A) site is inactive, whereas a heterologous poly(A) site positioned in its place is utilized efficiently. Furthermore, transcription initiating from the 3' LTR promoter utilizes the 3' LTR poly(A) signal efficiently. Therefore, the main determinant of the differential poly(A) site use appears to be neither proximity to a promoter element in the 5' LTR nor the presence of upstream activating sequences at the 3' LTR. Instead, we show that the major splice donor site that is immediately downstream of the 5' LTR inhibits cleavage and polyadenylation at the promoter-proximal site. The fact that this poly(A) site is active in a proviral clone when the major splice donor site is mutated suggests that the selective use of poly(A) signals in HIV-1 is mediated by a direct inhibition of the HIV-1 poly(A) site by downstream splicing events or factors involved in splicing.

Cytotoxic T lymphocyte lysis inhibited by viable HIV mutants

Immune evasion by the human immunodeficiency virus (HIV) is unexplained but may involve the mutation of viral antigens. When cytotoxic T lymphocytes engaged CD4-positive cells that were acutely infected with HIV bearing natural variant epitopes in reverse transcriptase, substantial inhibition of specific antiviral lysis was observed. Mutant viruses capable of these transactive effects could facilitate the persistence of a broad range of HIV variants in the face of an active and specific immune response.

Initial burn management in the primary care situation

Each year more than 150,000 people in Australia and New Zealand experience burning of sufficient severity for them to seek medical help, with 400 people dying annually. Primary care involves careful identification of burn healing potential and severity of injury. Major burns are best managed by regional Burn Units. The assessment, early management and burns unit transfer indications are addressed in this article.

Corn oil and beef tallow elicit different postprandial responses in triglycerides and cholesterol, but similar changes in constituents of high-density lipoprotein

OBJECTIVE

The study was designed to compare, in a homogeneous, normolipidemic population, the postprandial responses of plasma lipids, in particular, high-density lipoprotein (HDL) constituents, after administration of a polyunsaturated fat and a more saturated fat.

METHODOLOGY

Emulsions of 100 g corn oil (CO) and 100 g beef tallow (BT) were given in a crossover protocol to 12 male subjects (21-24 years). Plasma cholesterol (TC), triglycerides (TG), and HDL lipid and protein constituents were measured at 0, 2, 4, 7 and 10 hours.

RESULTS

A postprandial increase in TG at 2 hours after CO ingestion (96%) was twice that with BT (48%); TG returned to near fasting levels at 10 hours after ingestion of either fat. Areas under the TG response curves for CO and BT were 6.29 +/- 1.67 and 1.75 +/- 0.60 mmol x hour/L (mean +/- SE), respectively. TC and low-density lipoprotein cholesterol (LDL-C) levels were unchanged at 10 hours after CO ingestion, but they were increased 8.1% and 9.3%, respectively, with BT. Both fats increased HDL TG at 2-4 hours, and both similarly increased HDL free cholesterol, cholesterol ester, phospholipid, apolipoproteins A-I and A-II, and lipoprotein (A-I) levels at 7-10 hours. Changes in HDL were predominantly in HDL3.

CONCLUSIONS

The increase in LDL-C with BT at 10 hours suggests that levels may be abnormally elevated in "fasting" samples, dependent on the amount and type of fat in a prior meal. The increase in LDL-C is consistent with short-term regulation of hepatic LDL-receptor activity and/or LDL synthesis. Similar increases in HDL constituents at 7-10 hours after CO or BT, despite the difference in TG responses, suggests differences in the metabolism of chylomicrons and/or HDL due to the type of fat ingested.

Interleukin-10 inhibits initial reverse transcription of human immunodeficiency virus type 1 and mediates a virostatic latent state in primary blood-derived human macrophages in vitro

Interleukin-10 (IL-10), a product of T lymphocytes, B cells and macrophages, participates in Th-2 immune responses and modulates macrophage functions including possible interactions with pathogens. We have found that Chinese hamster ovary cell-derived human recombinant (hr) IL-10 inhibits human immunodeficiency virus type 1 strains Ada and Ba-L (HIV-1ADA and HIV-1Ba-L) replication in primary tissue culture-derived macrophages in a dose-dependent manner. Inhibition by IL-10 treatment (> 5 U/ml) was effective 72 h before or 24 h after infection and cytokine activity blocked by anti-hrIL-10 antibody (19F1), or lost after heat inactivation of IL-10. Viral production was measured by determining p24 and reverse transcriptase levels while reverse transcription kinetics for the long terminal repeat (LTR) and gag were assessed at timed intervals after infection and quantified by 32P end-labelling. IL-10 inhibited early steps of infection without modulating cell surface CD4+ levels. The onset of LTR reverse transcription was delayed by 4 to 8 h and the number of LTR transcripts was decreased by 77% at 24 h and by 87% 48 h after infection. IL-10 effects were reversible; after cytokine washout, cells treated before infection showed lower levels of virus compared with those treated after infection. IL-10 biological activity was confirmed in three virus-independent assays. These results demonstrate IL-10 decreases HIV-1 reverse transcription upon macrophage infection and subsequently mediates viral latency in vitro. Therefore, IL-10 may be involved in the effective control of HIV-1-infected macrophages in vivo.

Molecular determinants of the V3 loop of human immunodeficiency virus type 1 glycoprotein gp120 responsible for controlling cell tropism

We and others have identified the major determinant of cell tropism in human immunodeficiency virus type 1 (HIV-1) as the V3 loop of glycoprotein gp120. We have conducted a detailed study of two molecularly cloned isolates of HIV-1, HIVJR-CSF and HIVNL4-3, that differ in their tropism for immortalized CD4+ cell lines, by constructing a series of site-directed mutations within the V3 loop of HIVJR-CSF based on the sequence of HIVNL4-3. The phenotypes of these mutants fall into two classes, those which are viable and those which are not. A spontaneous mutant with significantly altered growth properties was also recovered and found to have an additional single amino acid change in the V3 loop sequence. The carboxy-terminal beta-strand part of the V3 loop is the major determinant of cell tropism. However, the results presented here indicate that the functional role of the V3 loop sequences can only be interpreted properly in the context of the original gp120 backbone from which they were derived. These findings show that over-simplistic interpretation of sequence data derived from unknown mixtures of HIV variants in infected persons may be highly misleading.

Inhibition of calcineurin by a novel FK-506-binding protein

FK-506, a potent immunosuppressive drug, acts during the commitment phase of T-lymphocyte activation to block a subset of calcium-associated events necessary for transcription of certain early lymphokine genes. The drug binds to an abundant, cytosolic 11.8-kDa protein termed the FK-506-binding protein (FKBP12). The FKBP12.FK-506 complex inhibits calcineurin, a calcium-dependent phosphatase that is a component of the signal transduction pathway leading to early lymphokine gene transcription. FKBP12 is one member of a growing gene family. Prior to this report, all other FKBP family members had been irrelevant to the mechanism of action of FK-506 because no other FKBP.FK-506 complexes were able to bind and inhibit calcineurin. Here, we report the purification and characterization of a novel FK-506-binding protein, FKBP12.6. Having 85% amino acid sequence identity to FKBP12, FKBP12.6 is, among the FKBPs, most closely related to FKBP12. When complexed with FK-506, FKBP12.6 binds to and inhibits calcineurin, making it only the second FKBP discovered thus far to do so. The ability to inhibit calcineurin establishes the potential relevance of FKBP12.6 to the immunosuppressive or toxic side effects of FK-506.

Determination of the kinetic parameters of Escherichia coli leader peptidase activity using a continuous assay: the pH dependence and time-dependent inhibition by beta-lactams are consistent with a novel serine protease mechanism

Bacterial leader peptidase (LPase) is a potential target for the development of novel anti-infective agents, but to data only peptides based upon natural macromolecular substrates have been reported as inhibitors. In this work is described a continuous assay for Escherichia coli LPase activity, based upon Ac-WSASALAKI-AMC (I) as the substrate, that can be monitored either spectrophotometrically or spectrofluorometrically. The LPase reaction is coupled to the liberation of AMC (aminomethylcoumarin) via a nonspecific leucine aminopeptidase. LPase and a short form of the enzyme (LPase-sf) lacking the membrane spanning domains displayed saturable kinetics toward I. The second-order rate constants were approximately 2 x 10(5) M-1 h-1 at pH 7.5 and were comparable to those reported in the literature for peptide substrates based upon natural cleavage sites in preproteins. LPase was inhibited by beta-lactams. [S-(R*,S*)]-4-[(1-(((1-(5-toluoyl)butyl)amino)carbonyl)-3,3-dimethyl-4- oxo-2-azetidinyl)oxyl]benzoic acid (L-684,-248, 588 microM) inhibited the LPase-catalyzed hydrolysis of 50 microM I and 125 microM Ac-WLVP-Nleu-LSFAAEGDDPA-NH2 by 30% and 88% over 1 and 4 h, respectively. The inhibition of LPase by L-684,248 and its C-4 diasteromer was time dependent and yielded second-order rate constants (kinact/Ki) of 12 and 7.7 M-1 min-1, respectively. The process was structurally specific as the C-3 diethyl substituted beta-lactam (C-4 S-isomer) was inactive. The latter data correlate with the LPase preference for alanine at the P1 position of peptide substrates [Kuo et al. (1993) Arch. Biochem. Biophys. 303, 274-280].(ABSTRACT TRUNCATED AT 250 WORDS)

Impact of child quality on earnings: the productivity-of-schooling hypothesis

"This paper investigates the relationship between average earnings, education (measured by years of schooling), and rates of return to education for major racial/ethnic groups in the United States. It considers the effect of including previously omitted 'productivity-of-schooling' (also referred to here as 'child quality') variables. An upward-sloping average education, rate-of-return-to-education profile exists for Hispanics, blacks, and whites. Productivity-of-schooling (i.e., child quality) measures--including family size, family composition, ability, and parental inputs--significantly affect earnings and rates of return to education."

A comparison of duplex Doppler ultrasonography and intrarenal manometry in the diagnosis of acute renal transplant rejection

Renal transplant rejection is frequently difficult to differentiate from other causes of renal dysfunction. This study examined the use of duplex Doppler ultrasound and intrarenal manometry in a consecutive series of 73 patients who underwent renal transplantation. Altogether 327 duplex scans were analyzed and, for each, a resistive index (RI) was calculated. A raised RI predicted rejection in patients with grafts that functioned immediately, but not in those that had delayed function. A rise in intrarenal pressure ( greater than or equal to 40 mmHg) indicated the presence of rejection in both groups. However, neither test had a sensitivity of more than 71% and this was not improved by combining the results of the two tests for each patient. Although both tests have a place in transplantation, renal biopsies may still be required to confirm rejection.

Use of recombinant DNA derived human relaxin to probe the structure of the native protein

This report describes the physical, chemical, and biological characterization of recombinant human relaxin (rhRlx) used as a probe to establish the disulfide pairing in native human relaxin. This strategy is necessary since native human relaxin is only available in the nanogram range. The relaxin molecule is composed of two nonidentical peptide chains, an A-chain 24 amino acids in length and a B-chain of 29 amino acids, linked by two disulfide bridges with an additional disulfide linkage in the A-chain. Native relaxin isolated from human corpora lutea was compared to rhRlx by reversed-phase chromatography, partial sequence analysis, mass spectroscopy, and bioassay. The potency of rhRlx was established by its ability to stimulate cAMP from primary human uterine endometrial cells. Native relaxin isolated from human corpora lutea was equipotent to chemically synthesized relaxin, which in turn was equipotent to rhRlx. A tryptic map was developed for rhRlx to confirm the complete amino acid sequence and assignment of the disulfide bonds. The three disulfide bonds (CysA10-CysA15, CysA11-CysB11, and CysA24-CysB23) were assigned by mass spectrometric analysis of the tryptic peptides and by comparison to chemically synthesized peptides disulfide linked in the two most probable configurations. In addition, the observed amino acid composition and sequence of rhRlx was in agreement with that predicted from the cDNA sequence with the exception that the A-chain amino terminal was pyroglutamic acid. The migration of rhRlx upon sodium dodecyl sulfate-polyacrylamide gel electrophoresis was consistent with a monomeric structure, and the identity of the band was demonstrated by immunoblotting.

Prevalence of specific IgE to storage mites (A. siro, L. destructor and T. longior) in an urban population and crossreactivity with the house dust mite (D. pteronyssinus)

The role of pyroglyphid mites in house dust allergy is well established and the major allergens from the common house dust mites (Dermatophagoides species) have been characterized. There is, however, relatively little progress in the understanding of the human IgE response to non-pyroglyphid storage mites, allergenic crossreactivity with other mite species and extent of environmental exposure. We studied 196 individuals from an urban environment who were not occupationally exposed to storage mites and found a 24% prevalence of specific IgE antibody to Dermatophagoides pteronyssinus and a 14% prevalence of RAST positivity to at least one of three storage mites, Acarus siro, Lepidoglyphus destructor and Tyrophagus longior. All individuals with a positive RAST to storage mites had specific IgE to D. pteronyssinus. RAST inhibition studies with the eight sera with greater than 2% RAST binding to both families of mites showed considerable crossreactivity between D. pteronyssinus and the storage mites A. siro and T. longior and limited crossreactivity between D. pteronyssinus and L. destructor. This suggests that at least some of the response to storage mites observed by direct RAST is a consequence of crossreactivity with the more abundant D. pteronyssinus.

World Transplant Games--Singapore, 1989

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Allergenic and antigenic relationship between three species of storage mite and the house dust mite, Dermatophagoides pteronyssinus

We have explored the antigenic and allergenic relationship between the house dust mite Dermatophagoides pteronyssinus and three species of storage mite, Glycyphagus destructor, Acarus siro, and Tyrophagus longior. Crossed immunoelectrophoresis demonstrated that all the mite extracts contained multiple antigens but that there was only limited cross-reactivity between the different species. Six sera were obtained from workers exposed to storage mites and with occupationally related lower respiratory tract symptoms. All workers had specific IgE to D. pteronyssinus and to one or more of the storage mites. The pattern of reactivity varied between the different sera, two responded primarily to D. pteronyssinus and A. siro and four sera to D. pteronyssinus and G. destructor. Only weak responses were observed to T. longior. RAST-inhibition and affinity-absorption experiments demonstrated that D. pteronyssinus had at least three groups of distinct allergenic determinants, determinants specific to D. pteronyssinus, determinants shared with A. siro, and determinants shared with G. destructor. Similarly, both A. siro and G. destructor have specific allergenic determinants and determinants shared with D. pteronyssinus. The findings demonstrate the complexity of the immunologic responses to the different mite species.

Effects of bilateral injection of GABA into the substantia nigra on spontaneous behavior and measures of analgesia

Bilateral injection of gamma-aminobutyric acid (GABA, 10-300 micrograms) into the substantia nigra (pars reticulata) of rats produced stereotyped sniffing and had an analgesic-like effect on the hot-plate but not on the tail-flick test. These effects of GABA (30 micrograms) were suppressed by simultaneous administration of a sub-convulsant dose of bicuculline methiodide (100 ng). Significant increases in locomotion occurred when GABA (300 micrograms) was injected along with the inhibitor of GABA-transaminase, d,l-gamma-vinyl-GABA (GVG; 5 micrograms) and the inhibitor of the uptake of GABA, 1-2,4-diaminobutyric acid (DABA; 5 micrograms). No other behavioral effects were observed following injection of GABA into the nigra, either alone or in combination with GVG and DABA. Bilateral injection of bicuculline (100-600 ng) into the nigra had strong convulsant actions. When injected simultaneously with bicuculline, GABA reduced bicuculline-induced seizures. These results are discussed in terms of their relevance to understanding the mechanisms that underlie the behavioral effects produced by injection of muscimol into the nigra.

Effect of dexamethasone on Fc gamma receptor expression in foetal and neonatal rat gut

When injected into 12-day-old suckling rats, dexamethasone caused a precocious disappearance of Fc gamma receptors from enterocytes of the proximal small intestine. However, dexamethasone appeared to be necessary for the maintenance or production of such receptors in foetal rat gut cultured in vitro.

Contractile function of isolated young and adult rat heart cells

The stimulated contractile function of aerobic isolated adult rat heart cells was assessed by laser light diffraction. Cells were maintained for up to 8 h by attachment to a cover slip and continuous perfusion in a chamber on the microscope stage. On stimulation such cells beat as though unattached. Cells showed a negative staircase which was reduced by increasing Ca or isoproterenol. Ryanodine caused a positive staircase on stimulation, which was enhanced by increasing Ca or isoproterenol or by using cells from younger rats. For beats of constant contraction duration, there was a linear relationship between the magnitude of cell shortening and the velocity of shortening, independent of the concentration of extracellular Ca. We conclude the following. 1) The beat characteristics of isolated cells are very similar to those of papillary muscle. 2) Attachment of cells need not alter their unloaded shortening characteristics. 3) Cells appear to contract against an internal load, to an extent determined by the degree of myofilament activation. 4) Cells from young rats require less extracellular Ca than those from adult rats for the same beat magnitude.

Ontogeny of the Fc gamma receptor in rat small intestine

The time course of Fc gamma receptor expression on isolated enterocytes of the small intestine of rat fetuses and sucklings has been studied. This was achieved principally using indicator sheep red blood cells (SRBC) sensitized with rabbit IgG in an erythrocyte-antibody rosette assay which detects receptors located mainly on the lateral and basal plasma membrane, and in a more limited way using binding of rabbit IgG to metabolically inhibited gut as detected by immunofluorescence and which detects receptors located on the apical brush border. From the time they were first detectable in the rosette assay (20-day-old fetuses) to the time they disappeared (22-day-old sucklings) such receptors were found always to be acid pH dependent and restricted to enterocytes from the proximal region. Acid pH, Fc-dependent binding of rabbit IgG to metabolically inhibited gut was first detectable at 21 days gestation and there were indications that receptors differentiate on enterocytes in a proximal to distal direction. This was also indicated by electron microscope studies using rabbit PAP injected into the duodenum of 21-day-old fetuses. Such studies also provided evidence for the receptor-mediated translocation of IgG across the duodenum of the fetal rat in a manner similar to that described for older sucklings.

Effect of drugs, hormones and electrical field stimulation on isolated muscle strips from human choledochoduodenal junction

The behaviour of in vitro strips from the human choledochoduodenal junction would appear to be related to the anatomical location of origin of the strip. Strips from the papillary region showed low tone and obvious spontaneous rhythmic contractions (0 X 5-6/min). Strips from the region of the inferior choledochal sphincter showed, in ten out of fifteen specimens, spontaneous myogenic tone and gave a relaxation or a biphasic response (relaxation followed by contraction) to electrical field stimulation (0 X 3 ms pulses at 10 Hz for 5 s). All strips from human choledochoduodenal junction are remarkably insensitive to a variety of gastrointestinal hormones and to opioid agents.

The treated histories of patients with Ta grade 1 transitional-cell carcinoma of the bladder

One hundred sixty patients with grade 1 transitional-cell carcinoma of the bladder were evaluated and treated at the Massachusetts General Hospital, Boston. The mean follow-up period was 57 months. There were 92 new patients and 68 patients who had a history of transitional-cell carcinoma. Fifty-three patients (33%) never had another transitional-cell carcinoma. Sixty-eight (43%) of the remaining 107 patients had recurrent Ta grade 1 transitional-cell carcinoma. In 32 patients (20%) disease progressed in grade, in seven patients (4%) invasive transitional-cell carcinoma developed, five patients underwent cystectomy, and one patient died of transitional-cell carcinoma. High-risk factors included positive results of cytologic studies after therapy and three or more recurrences. Multiple therapies were used, but it is impossible to determine if anything other than transurethral resection altered the course in these patients. The data suggest that patients with low-risk factors and Ta grade 1 tumors might be followed up with a quarterly cytologic examination and cystoscopy once or twice a year, unless a change in symptoms occurs.

Influence of tamoxifen and estradiol on the growth of human breast cancer cells in vitro

Cells obtained from freshly resected human breast cancer were grown in vitro utilizing the soft agar technique. The effects of adding an antiestrogen (tamoxifen, TAM) and 17 beta-estradiol alone or simultaneously on cell growth were assessed. The addition of TAM (10(-6) M) to the medium resulted in a significant decrease in cell growth in 26 of 36 (72%) estrogen receptor (ER)-positive tumors and in one of 5 ER-negative tumors (20%). The degree of inhibition caused by TAM was significantly higher in the ER-positive tumors that also contain the progesterone receptor (PgR) as compared to those that lacked that receptor (i.e., PgR negative) (46.2 +/- 2% versus 36.2 +/- 1.2% inhibition, P less than 0.01). The simultaneous addition of 17 beta-estradiol (10(-8) M) neutralized the inhibitory effect of TAM (10(-6) M) in the majority of tumors. With the presence of serum in the medium, the addition of 17 beta-estradiol alone resulted in an enhancement of cell growth in 6 of 17 tumors. However, because of the confounding effects of serum in the medium, we studied the individual effect of 17 beta-estradiol (10(-8) M) when added alone under serum-free conditions. Of 20 tumors studied, 17 beta-estradiol significantly enhanced cell growth in 12. There was a 67.8 +/- 12.6% increase in the number of colonies formed in these 12 responding tumors. One of these 12 responding tumors was ER negative as well as PgR negative, while the rest were all ER positive. These in vitro studies demonstrate that this approach can provide valuable information on endocrine mechanisms controlling the growth of human breast cancer.

Changes in specific B cells and the dissemination of the primed state in vivo following antigenic stimulation by different mucosal routes

Immunologic dogma holds that the adaptive and long-term potential of the antibody response is fashioned by antigen-dependent, selective clonal proliferation of specific B cells and the retention of some which may undergo a second round of antigen-stimulated clonal expansion with antibody production. Apparently, the short-term, immediate consequences of an antibody response depend on the mix of isotypes displayed in vivo upon exposure to antigen. This latter seems to be clearly regulated by T cells, but it is also likely that the isotype potential of a B cell population and its future possible display of isotypes is linked to the initial, antigen-dependent proliferative phase in the development of an antibody response. In vitro analysis at limiting dilutions of specific B cells primed in vivo has led to the operational definition of IgA-committed cells. These B cells increase in frequency following chronic or acute antigenic stimulation of gut mucosa and have the potential to proliferate again in the presence of antigen and TH(Ag) cells to produce exclusively IgA. A general relationship exists between mucosal or parenteral priming of B cells and their potentials to express IgA and/or IgE--both isotypes appear to be likely products of secondary B cells and frequently both can be expressed by the same clone activated by a second-round of T-dependent antigenic stimulation. Cross priming--exposure of GALT or BALT leading to secondary B cells in the opposite mucosal lymphoid tissue--suggests an inherent antagonism between development of allergic (IgE) and putative allergy blocking (IgA) potentials.(ABSTRACT TRUNCATED AT 250 WORDS)

Growth enhancement of N-nitrosomethylurea-induced rat mammary tumor cells in soft agar by estrogen or prolactin

Cells obtained from N-nitrosomethylurea-induced rat mammary tumors were grown in vitro using the soft-agar clonogenic assay technique. Their growth was studied in regular media containing serum as well as in media lacking serum, but to which insulin was added. Deletion of serum from the media resulted in a mean decrease of 49% in the number of colonies formed in vitro in 13 of 18 tumors and was without effect in the remaining 5 tumors. The addition of either 17 beta-estradiol (10(-8) M) or ovine prolactin (OPRL, 100 ng/ml) to the defined media resulted in an increase in the number of colonies formed in 12 of 18 tumors. The mean numbers of colonies per Petri dish in 17 beta-estradiol- and OPRL-treated Petri dishes were 95 +/- 5.4 (S.E.) and 92 +/- 6.2% of the values seen in serum-containing media. Simultaneous addition of both hormones to the defined media resulted in a significant increase in the number of colonies formed which was greater than that seen when either hormone was added separately. Of four tumors where neither hormone influenced colony formation, the addition of both 17 beta-estradiol and OPRL resulted in an increase in the number of colonies formed in three tumors. We conclude that the N-nitrosomethylurea-induced mammary tumors can be grown in soft agar using defined media and that their growth can be enhanced by either 17 beta-estradiol or OPRL. These hormones have a synergistic effect on the growth of some of these tumors in vitro. These data are consistent with the known in vivo effects of these hormones on the N-nitrosomethylurea-induced rat mammary tumors.

Cryptosporidiosis of the human small intestine: a light and electron microscopic study

Intestinal infection by the coccidian parasite Cryptosporidium is a well-recognized condition in immunocompromised hosts and in some normal persons. The authors studied a patient with acquired immunodeficiency syndrome and cryptosporidiosis of the small intestine. The parasite inhabits the microvillous brush border of the intestinal epithelium and must be carefully sought on light microscopic examination of intestinal biopsy specimens. Characteristic life cycle stages are observed on electron microscopy. The absence of significant light microscopic alterations of the villous architecture in this patient's biopsy specimen and in other cases suggests that other factors, such as toxin elaboration by cryptosporidia or other organisms, may be involved in the pathogenesis of diarrhea. Abnormal aggregation of lysosomes at the apices of intestinal epithelial cells may reflect ineffective host phagocytic mechanisms.