The capacity for growth stimulation by TGF beta 1 seen only in advanced colon cancers cannot be ascribed to mutations in APC, DCC, p53 or ras

Human colon cancer development is associated with the accumulation of mutations and deletions in the suppressor genes DCC, APC and p53 and mutations in the dominant oncogene K-ras, with loss of wild type alleles. In earlier studies we had observed that about half of the resected human colon cancers placed into primary culture were growth stimulated by TGF beta 1. This group included the more advanced cancers which were either poorly differentiated primary-site cancers or metastases. In contract, the more differentiated colon cancers were inhibited or unaffected by TGF beta 1, indicating that a switch in response to TGF beta 1 occurs during colon cancer progression. Different sublines of the HT29 colon carcinoma cell line model the resected cancers, responding to TGF beta 1 by proliferation, inhibition or no growth modulation. The current study shows that while the poorly differentiated, TGF beta 1-stimulated sublines are most tumorigenic, all the sublines have the same spectrum of mutations: truncating mutations in both APC (adenomatous polyposis coli) alleles, no activated ras genes, mutated and thus overexpressed p53, and very low expression of DCC compared to normal colon cells. Genes other than the four already implicated in colon carcinoma evolution are responsible for the mitogenic response to TGF beta 1 found in the more advanced cancers.

The effect of mutant beta 2-microglobulins on the conformation of HLA-B27 detected by antibody and by CTL

The arthritis-predisposing HLA-B27 consists of a heavy chain, a small peptide, and the monomorphic beta 2-microglobulin (beta 2-m). CTLs and a mAb, Ye-2, which recognize the complex with specificities both for the heavy chain and for the peptide, are available. The beta 2-m is in noncovalent association with the heavy chain at multiple points and is exchangeable with free beta 2-m outside of the complex. The purpose of our experiments was to test whether mutant beta 2-m capable of modulating HLA-B27 activity could be created. Eighteen recombinant mutants of the human beta 2-m were experimentally generated. In 14 of these, mutations were at or near residues that are either contact residues or interface residues with the heavy chain. Relative to the parent beta 2-m, two-thirds of the mutants showed reduced ability to exchange into HLA-B27 complexes. However, at least four of them induced more than 80% decrease in Ye-2 Ab reactivity. Two mutants were able to induce a minor decrease in susceptibility to lysis by four CTL clones. One of the CTL clones was autoreactive. Two of the CTL clones were specific for HLA-B27 cells experimentally infected with arthritis-causing Yersinia enterocolitica. These results indicate that certain beta 2-m residues play an indirect role in peptide presentation, although they are not directly associated with the peptide residues.

The effect of mutant beta 2-microglobulins on the conformation of HLA-B27 detected by antibody and by CTL

The arthritis-predisposing HLA-B27 consists of a heavy chain, a small peptide, and the monomorphic beta 2-microglobulin (beta 2-m). CTLs and a mAb, Ye-2, which recognize the complex with specificities both for the heavy chain and for the peptide, are available. The beta 2-m is in noncovalent association with the heavy chain at multiple points and is exchangeable with free beta 2-m outside of the complex. The purpose of our experiments was to test whether mutant beta 2-m capable of modulating HLA-B27 activity could be created. Eighteen recombinant mutants of the human beta 2-m were experimentally generated. In 14 of these, mutations were at or near residues that are either contact residues or interface residues with the heavy chain. Relative to the parent beta 2-m, two-thirds of the mutants showed reduced ability to exchange into HLA-B27 complexes. However, at least four of them induced more than 80% decrease in Ye-2 Ab reactivity. Two mutants were able to induce a minor decrease in susceptibility to lysis by four CTL clones. One of the CTL clones was autoreactive. Two of the CTL clones were specific for HLA-B27 cells experimentally infected with arthritis-causing Yersinia enterocolitica. These results indicate that certain beta 2-m residues play an indirect role in peptide presentation, although they are not directly associated with the peptide residues.

The role of nm23 in transforming growth factor beta 1-mediated adherence and growth arrest

nm23 has properties of a metastasis suppressor gene and also has been implicated in the control of response to transforming growth factor beta 1 (TGF beta 1) by studies in melanoma cells. In this report, we have examined the role of nm23 in two HT29 colon carcinoma sublines at different stages in tumor progression with different responses to TGF beta 1: the HD3 subline, which shows TGF beta 1-induced growth arrest and differentiation; and the more invasive and tumorigenic U9 subline, which induces tumors 7-fold as large as those induced by HD3 cells with one-half the latency. Analysis by semiquantitative reverse transcription-polymerase chain reaction showed that antisense phosphorothiolated oligonucleotides to the nm23 initiation site (nm23 AS oligos) decreased nm23 mRNA levels 2-8-fold in HD3 and U9 cells when normalized to beta-actin mRNA levels. However, a role for nm23 in TGF beta 1-mediated responses could only be found in HD3 cells. nm23 AS oligos inhibited the differentiation property of cell adherence over 90% in HD3 cells, and this loss of adherence could be partially blocked by concurrent treatment with TGF beta 1. In contrast, U9 cell adherence was not detectably altered by nm23 AS oligos, whether added in the presence or absence of TGF beta 1. The TGF beta 1-induced inhibition of HD3 cell proliferation was blocked by nm23 AS oligos, whereas the TGF beta 1-induced proliferation of U9 cells was unaffected by nm23 AS oligos.(ABSTRACT TRUNCATED AT 250 WORDS)

Colon carcinoma cells switch their response to transforming growth factor beta 1 with tumor progression

Transforming growth factor beta 1 (TGF-beta 1) switches from an inhibitor of tumor cell growth to a stimulator of growth and invasion during human colon carcinoma progression. We originally observed that metastatic colon carcinoma cells in primary culture responded to TGF-beta 1 by proliferation, whereas moderate to well-differentiated primary site colon carcinomas were growth inhibited by TGF-beta 1 (P. Schroy et al., Cancer Res., 50: 261-265, 1990). We then cloned several colon carcinoma cell lines which modeled these responses to TGF-beta 1 and expressed TGF-beta 1 (M. M. Hafez et al., Cell Growth & Differ., 1: 617-626, 1990; 3: 753-762, 1992). Two of these colon carcinoma cell lines, U9 and HD3, which activate approximately equal amounts of TGF-beta 1 and express equal amounts of TGF-beta receptors, are now used to compare the effects of TGF-beta 1 in modulating invasive behavior. The U9 cell line exhibits autocrine-positive growth regulation in vitro by TGF-beta 1, whereas the HD3 cell line shows the opposite response, autocrine-negative regulation. Blocking endogenous TGF-beta 1 with isotype-specific antibody inhibited U9 cell growth because autocrine TGF-beta 1 acts as a mitogen for U9 cells. In contrast, antibody to TGF-beta 1 stimulated HD3 cell proliferation because autocrine TGF-beta 1 inhibits growth of these cells. U9 cells were 13-fold more invasive in vitro through a collagen I layer than HD3 cells.(ABSTRACT TRUNCATED AT 250 WORDS)

Position-reading and the emergence of sense organ precursors in Drosophila

Genetic analysis of development in Drosophila melanogaster has advanced our understanding of "position reading", where the expression of particular genes informs a cell of its position in the developing animal. The first step in localization of fly sense organs is the local expression of a gene conferring neural competence on epidermal cells. The four genes of the achaete-scute (AS-C) complex play crucial roles in the localization of sense organs. The resolution of local expression of AS-C genes along one dimension is about 10%; accuracy is improved by the balancing local expression of AS-C antagonist genes such as extramacrochaete. Position reading seems to depend primarily on such patterns of gene expression, and not upon the compartmental identity of the cells. No evidence has been found for differing roles of the four AS-C genes in the generation of sense organ progenitor cells or in the specification of neuronal properties of innervating neurons. The formation of each sense organ may be a unique case where the different proneural and neurogenic gene products have varying importance, and fortuitous local effects acting on this complex combination of factors have come to be important. The fly may be evolving from a flexible regular pattern to an inflexible irregular pattern strongly dependent on local factors, turning the fly into a crystallized system. (Written by R. Wayne Davies.).

Testing the importance of each residue in a HLA-B27-binding peptide using monoclonal antibodies

When a peptide derived from histone 3.3 was incubated with mouse L cells transfected with HLA-B27, the cells became highly reactive with Ye-2, an anti-HLA-B27 mAb. The critical residues were analyzed by testing analogues in which each of the nine residues in the peptide was consecutively substituted by 19 other amino acids. The conclusions were separately verified using a different HLA-B27-positive cell line. The ability of some of these peptides to bind to HLA-B27 was also assayed by their ability to stabilize HLA-B27 in a mutant cell line which required HLA-B27-binding peptides to express HLA-B27 at 37 degrees C. These experiments showed that in P4, P5, P6, P7, P8, and P9, all 20 different amino acids could be substituted without eliminating the ability of the analogues to bind to HLA-B27. The residues which were responsible for the HLA-B27-peptide complex reacting with the Ye-2 antibody were P8 and P9. The latter might mediate its effect by altering either the surface conformation of the closely associated HLA-B27 heavy chain or the conformation of the peptide itself.

Testing the importance of each residue in a HLA-B27-binding peptide using monoclonal antibodies

When a peptide derived from histone 3.3 was incubated with mouse L cells transfected with HLA-B27, the cells became highly reactive with Ye-2, an anti-HLA-B27 mAb. The critical residues were analyzed by testing analogues in which each of the nine residues in the peptide was consecutively substituted by 19 other amino acids. The conclusions were separately verified using a different HLA-B27-positive cell line. The ability of some of these peptides to bind to HLA-B27 was also assayed by their ability to stabilize HLA-B27 in a mutant cell line which required HLA-B27-binding peptides to express HLA-B27 at 37 degrees C. These experiments showed that in P4, P5, P6, P7, P8, and P9, all 20 different amino acids could be substituted without eliminating the ability of the analogues to bind to HLA-B27. The residues which were responsible for the HLA-B27-peptide complex reacting with the Ye-2 antibody were P8 and P9. The latter might mediate its effect by altering either the surface conformation of the closely associated HLA-B27 heavy chain or the conformation of the peptide itself.

NURSETALK: the latest addition to the information highway

NURSETALK is an electronic bulletin board system (BBS) developed to provide information and meet the communication needs of three different nursing organizations in North Carolina. It was designed and conceptualized from a user perspective to promote functionality and acceptance.

Molecular cloning and structure of the human (GABATHG) GABA transporter gene

A cDNA molecule encoding the human GABA transporter was synthesized by means of polymerase chain reaction (PCR) technique and used as probe for selecting a human genomic DNA fragment encoding GABA transporter. A positive clone harboring the whole gene was obtained from a human lymphocyte genomic library through utilizing the genomic 'walking' technique. The clone, designated as pHGAT, harbours a DNA fragment of about 39 kb in length inserted into the BamHI site in cosmid pWE15. The gene covers about 25 kb in length and is constituted by four EcoRI restricted fragments which are 13.7 kb, 3.1 kb, 4.2 kb and 7.2 kb long, respectively. The genomic clone contains 15 introns, including two introns prior to the initiator methionine (i.e., the translation start site is in exon 3). Eleven exons encode the twelve transmembrane regions in the transporter protein. Thus as in the case for a number of other membrane proteins, there appears to be a strong tendency for the putative transmembrane domains to be encoded by separate exons. It is noted that the structure of the human GABA transporter gene reported here differs from the mouse gene which is contains 12 introns.

Can the stability of protein mutants be predicted by free energy calculations?

The use of free energy simulation techniques in the study of protein stability is critically evaluated. Results from two simulations of the thermostability mutation Asn218 to Ser218 in Subtilisin are presented. It is shown that components of the free energy change can be highly sensitive to the computational details of the simulation leading to the conclusion that free energy calculations cannot currently be used to reliably predict protein stability. The different factors that undermine the reliability are discussed.

Recombinant human G-CSF and retinoic acid in synergistically inducing granulocyte differentiation of human promyelocytic leukemic cells

The effects of recombinant human G-CSF (rhG-CSF) and retinoic acid (RA) were studied on the proliferation and differentiation of HL-60 cells and human acute myeloid leukemic cells. Synergistic effect on granulocyte differentiation was observed when HL-60 cells and primary acute promyelocytic leukemic cells were cocultured with RA plus rhG-CSF. rhG-CSF combined with RA increased more significantly the percentage of mature cells than RA alone and greatly increased NBT reduction activity (P < 0.001). These results suggested that proliferated effect of rhG-CSF on leukemic cells may be important for inducing differentiation of myeloid leukemic cells. But this effect might expose the patients to the risk of acute myeloblastic leukemia if G-CSF was used alone. However, RA could not only rule out the latter situation but retain former merit as well. The authors suggest that the combined use of G-CSF with RA is probably a new approach to the treatment of leukemia.

Effect of glycolipids on the phase behavior and dynamic properties of phospholipid liposomes

The glycolipids of Acholeplasma laidlawii AIH089 membranes were identified and purified. The effect of monoglucosyldiacylglycerol (MGDG) and diglucosyldiacylglycerol (DGDG) on the thermotropic behavior of multilamellar vesicles of dipalmitoylphosphatidylcholine (DPPC), dipalmitoylphosphatidylglycerol (DPPG) has been investigated by high sensitivity differential scanning calorimetry. The main transition peaks were broadened, the enthalpies were decreased. DGDG caused the decrease in the transition temperatures of DPPC, DPPG liposomes by 3.08 degrees C, 4.18 degrees C, respectively. MGDG did not cause the alteration of the transition temperature of DPPC liposomes but caused the decrease of the transition temperatures of DPPG liposomes by 2.20 degrees C. ESR experiments indicate that MGDG decreased the rotational correlation time of DPPC and DPPG liposomes.

Multiple transcripts encoded by the ilvGMEDA gene cluster of Escherichia coli K-12

We report here that, using Northern (RNA) blots, we identified two relatively stable transcripts of 4.6 and 1.1 kb that correspond to the products of the ilvEDA and ilvE genes and two relatively unstable transcripts of 6.7 and 3.6 kb that correspond to the products of the ilvGMEDA and ilvDA genes. The transcripts were identified by the use of eight probes derived from segments of the ilvGMEDA cluster. In addition, we used two strains with deletions of ilvG or ilvDA and observed the expected decrease in transcript size in Northern blots. Primer extension with reverse transcriptase generated a 169-nucleotide product corresponding to a 5' end within the ilvED intercistronic region, 37 nucleotides from the AUG codon of the ilvD gene. This primer extension product presumably indicates the 5' end of the ilvDA transcript that we detected in Northern blots. The stability of the transcripts was monitored, and RNase E was found to play a major role in ilv transcript degradation. Transcript levels varied in response to growth in the presence of the end product amino acids and in response to the presence of the polar frameshift site in ilvG. Although there have been speculations about the identities and numbers of transcripts derived from the ilvGMEDA cluster on the basis of the identification of some of the sites of transcription initiation and termination, this is the first report of the use of Northern blots to determine the actual sizes and distribution of mRNAs present in vivo.

[Role of enteric Klebsiella pneumonia infection and HLA-B27 in ankylosing spondylitis]

Klebsiella pneumonia (KP) infection and HLA-B 27 have been shown to be strongly associated with ankylosing spondylitis (AS). In the present study, faecal cultures were performed and showed faecal carriage rate of KP was much higher in patients with AS (10/30) and hospital volunteers (2/10) than in the non-hospital volunteers (0/20). An octadecapeptide encompassing the shared hexamer between HLA-B 27 and KP nitrogenase residue was synthesized and autoantibodies against this short peptide were detected in sera of patients with AS and Reiter's syndrome (RS) and other related disease and normal controls. The results showed that such autoantibodies were detected in 42.2% of AS and 30% of RS patients yielding positive rate much higher than those found in other control groups. It is concluded that enteric KP infection were strongly implicated in the pathogenesis of AS probably by the mechanism of molecular mimicry with HLA-B 27.

[Granulocyte differentiation of human promyelocytic leukemic cells induced by coordinate action of granulocyte colony stimulating factor and retinoic acid]

We analysed the effects of recombinant human G-CSF (rhG-CSF) and retinoic acid (RA) on proliferation and differentiation of HL-60 cells and human acute myeloid leukemic (AML) cells. A synergistic effect on granulocyte differentiation was observed when HL-60 cells and primary cultured acute promyelocyte leukemic cells were cocultured with 10(-8)mol/L RA plus 1:2000 or 1:1000 rhG-CSF. The rhG-CSF plus RA treated cells demonstrated significant increase in the percentage of mature cells. Morphological changes and nitroblue tetrazolium (NBT) reduction activity evidenced more increase than RA treatment alone (P less than 0.001). The results suggest that RA not only inhibits the proliferative action of G-CSF, but also retains and enhances the action of G-CSF to induce differentiation. Therefore, we believe that the combined use of G-CSF with RA may improve the treatment of leukemia.

The emergence of sense organs in the wing disc of Drosophila

We have examined the origin of a set of precisely located sense organs in the notum and wing of Drosophila, in transformant flies where lacZ is expressed in the progenitor cells of the sense organs (the sensory mother cells) and in their progeny. Here we describe the temporal pattern of appearance and divisions of the sensory mother cells that will form the eleven macrochaetes and the two trichoid sensilla of the notum, and five campaniform sensilla on the wing blade. The complete pattern of sensory mother cells develops in a strict sequence that extends over most of the third larval instar and the first 10 h after puparium formation. The delay between the onset of lacZ expression and the first differentiative division ranges from 30 h, in the case of the earliest mother cells, to 2 h for the latest mother cells. The first division shows a preferential orientation which is also specific for each sensory mother cell. Up to this stage, there is no marked difference between the three types of mechanosensory organs.

Antioxidant action of certain simple phenolic compounds derived from Chinese herbs

H2O2 and hydroxyl free radical active oxygen generation systems were utilized to define the antioxidant activities of simple phenolic compounds derived from Chinese herbs. Although the antioxidant activities of compounds differed when assessed in the two systems, all compounds tested were found to be effective at preventing red blood cell membrane lipid peroxidation, with the propyl and butyl esters of gallic acid being especially potent. No compound was able to prevent hemoglobin oxidation. All compounds but salicylic acid were found to interact dose-dependently with H2O2 and hydroxyl free radical as determined by a chemiluminescence method.

Sequence and transcriptional activity of the Escherichia coli K-12 chromosome region between rrnC and ilvGMEDA

We previously identified a protein related to the expression of the ilvGMEDA cluster of Escherichia coli K-12. It was observed that this ilv-related protein was produced at higher levels in UV irradiated cells infected with lambda dilvGMEDA phage with specific ilvG mutations (ValR), compared to phage carrying the wild-type(ValS) ilvG allele. The gene encoding this protein was further localized to a region between rrnC and ilvGMEDA by analyzing restriction fragment subsets in maxicells. We have now determined the nucleotide (nt) sequence of the 3.5-kb segment between rrnC and ilvGMEDA, and two open reading frames (ORFs) are present in the region expected to contain the ilv-related gene. These ORFs predicts Mrs of 18,751 (ORFI) and 20,085 (ORFII) Da, and both ORFs have a strong probability to encode proteins based on codon frequency analysis. Maxicell analysis revealed that a 1319-bp HindIII-SmaI fragment containing ORFI encodes the ilv-related peptide. We deleted a ClaI fragment that removed a portion of ORFI encoding the C-terminal region of the peptide, and maxicell analysis revealed a decrease in the size of the protein produced in accord with the prediction. RNA slot blots and Northern blots were used to characterize transcripts encoding ORFI. A transcript initiated 112 nt from the ilvGp2 promoter, but proceeding in the opposite direction, may encode the ORFI peptide.

Correction factor for strongly reflecting U-path RACs

An equation from the literature describing multiple reflections in a U-path surface-acoustic-wave (SAW) reflective array compressor (RAC) is simplified for RACs with a large time-bandwidth product, yielding a very convenient expression consisting of the relation for weakly reflecting RACs plus phase and amplitude correction factors. The quantitative effect of multiple reflections is immediately apparent, so that the designer has a better understanding of how various parameters affect the final performance. A down-chirp, which is more common in practical devices, is described. Empirical extensions to higher-order and variable weighing are deduced and verified numerically, while the possibility of variable chirp is discussed.

Medium-loss SAW filters with synthesized characteristics

Medium-loss surface acoustic wave (SAW) filters based on the in-line dot array structure are reported. This configuration is very amenable to device synthesis, potentially to specifications comparable to conventional high-loss designs. The design procedure fully allows for multiple reflections within the reflecting arrays and can handle chirps. The devices have achieved up to 0.2-dB RMS passband ripple and 32-dB rejection after direct coupling and multistrip coupler (MSC) reflection are removed. Passband loss (6-8 dB) could be reduced if transducer and MSC loss (3 dB) can be improved. The devices also have sharp cutoffs, and fairly uniform input and output impedances in the pass and transition bands. The reflectors chosen for the reflecting arrays are thin metal dots. The results of computation and experimental verification of dot reflectivity and velocity change for the particular size of dots and dot pattern used are given. The device design, and the measured results are discussed.

The power reflected in a SAW RAC

Considerations relating to the design of surface-acoustic-wave (SAW) reflective array pulse compressors (RACS), including the effect of array width on power reflected, the transmitted beam profile and the effect of randomized arrays, are discussed. Only a first-order analysis is used. Potential misunderstandings of these issues that could arise from the existing literature are clarified.

Phase correction of SAW ILRACs and RACs using Langmuir-Blodgett films

A novel method of adjusting surface-acoustic-wave (SAW) velocity in reflective array pulse compressors (RACs), including in-line devices (ILRACs) and hence correcting fabrication errors, is described. The velocity change is effected by depositing Langmuir-Blodgett films (LBFs) on the surface of the device. An accurate, stepped thickness profile can be created, enabling position-dependent velocity errors to be corrected. Experimental results for the velocity perturbation per LBF layer are first given together with data on temperature, humidity and age dependence. This is followed by the theory required to calculate the necessary thickness profile, including retrofitting to existing devices and allowing for the limitation to positive integer numbers of layers. Finally, experimental results are presented. In one device, simulated compressed pulse sidelobe levels are reduced by 19 dB.

Addendum to 'Possible design procedure for low-loss 180 degrees reflecting arrays in SAW devices' (Jan 88 57-60)

The original paper (ibid., vol.35, no.1, p.57-60, 1988) describes how multiple reflections can be allowed for in SAW reflecting arrays. Comments are now made on the error in frequency response due to truncation of the array to finite length, and on multiple transits between transducers via the array.

The scattering of surface acoustic waves by electrical effects in two-dimensional metal film structures

A theory is presented for the scattering of surface acoustic waves by electrical effects in thin metal films of arbitrary shape on the surface of a piezoelectric material. A Green's function approach is used, and an expression for the two-dimensional Green's function appropriate to the problem is given. General expressions are obtained for the far-field radiation pattern and for the response of an interdigital transducer to a single scatterer. Expressions for the reflection and velocity perturbation due to periodic arrays of scatterers are also presented. Good agreement is found when the theoretical predictions are compared with a wide range of experimental results on lithium niobate.

Correction factor for low-loss 180 degrees reflecting linear chirp arrays in SAW devices

Low-loss, 180 degrees -reflecting linear chirps with constant or slowly varying weighting and large time-bandwidth product are analyzed. Multiple reflections are fully taken into account, giving a universal correction factor as a function of array parameters. This should enable such chirps to be designed without making iterations. Surface acoustic-wave (SAW) device layouts making use of the 180 degrees arrays are suggested.

Possible design procedure for low-loss 180 degrees reflecting arrays in SAW devices

A procedure for designing highly reflecting arrays to specified responses in surface acoustic-wave (SAW) devices is proposed. Multiple reflections in the low-loss arrays are fully taken into account. The problem is made tractable by using a 180 degrees reflecting geometry rather than reflecting the SAW twice through 90 degrees.

B-lymphocyte activation mediated by anti-immunoglobulin antibody in the absence of protein kinase C

B-cell activation induced by crosslinking of surface immunoglobulin is known to stimulate hydrolysis of phosphatidylinositol to diacylglycerol and inositol trisphosphate. We now provide evidence that alternative pathways of activation may also be recruited during such activation. We utilized depletion of protein kinase C activity to determine whether this enzyme is required under all conditions for anti-immunoglobulin-stimulated B-cell activation. Although anti-immunoglobulin does not induce B-cell proliferation in protein kinase C-depleted cells, it stimulates an earlier event in B-cell activation as reflected by its ability to enhance the expression of major histocompatibility complex-encoded class II molecules. Furthermore, the ribonucleoside 8-mercaptoguanosine restores the ability of anti-immunoglobulin to induce B-cell proliferation in protein kinase C-depleted cells. This restoration is also demonstrated by an enhancement of synthesis of a nuclear protein that we find is increased during B-cell mitogenesis. These results indicate that B-cell activation stimulated by anti-immunoglobulin may recruit pathways in addition to the one dependent on protein kinase C.

Antiallergic activity profiles in vitro of RHC 3164 and related compounds. I. A lack of correlation between inhibition of cyclic nucleotide phosphodiesterases and antigen-induced release of histamine from rat mast cells

A series of 26 compounds belonging to the chemical class of (1,2,4)triazolo(4,3-a)-quinoxaline-1,4-diones have been investigated for their antiallergic activities in 3 in vitro models of anaphylaxis. Effects of these and other known antiallergic agents on cyclic nucleotide phosphodiesterases (cNUC-PDE) from purified rat mast cells have also been investigated. 18 compounds were potent (I50 less than or equal to 45 microM) inhibitors of antigen-induced release of histamine (AIR) from rat mast cells (RMC), 3 compounds inhibited anti-IgE-induced release of histamine from human basophils (I50 less than or equal to 25 microM) and none of the compounds significantly affected AIR from guinea pig lung slices. 13 of the compounds were more potent than theophylline as inhibitors of cyclic AMP-PDE and/or cyclic GMP-PDE from RMC. Parallel concentration-response curves for the inhibition of cyclic AMP-PDE and cyclic GMP-PDE indicated that these compounds probably interact with enzyme in the same manner. Paired regression analysis of the I50 values for inhibition of AIR and cNUC-PDE from RMC by these compounds revealed no statistically significant correlation between the inhibition of AIR and inhibition of cyclic AMP-PDE or cyclic GMP-PDE. We conclude: (1) some of these compounds are potent inhibitors of immunologic release of histamine from RMC with an in vitro activity profile similar to that of DSCG, and (2) inhibition of cyclic AMP or cyclic GMP hydrolysis by cNUD-PDE by these compounds, DSCG, and 6 known antiallergic agents is not the biochemical mechanism by which they inhibit AIR from RMC.

Antiallergic activity profiles in vitro of RHC 3164 and related compounds. II. Comparison of RHC 3164 with disodium cromoglycate

RHC 3164 has been investigated for its antiallergic activities in 3 in vitro models of anaphylaxis. RHC 3164 was 6 times more potent than DSCG as an inhibitor of antigen-induced release of histamine (AIR) from rat mast cells (RMC) and had an activity profile identical to that of DSCG in the following respects: loss of inhibitory activity with increasing preincubation time, tachyphylactic properties, cross-tachyphylaxis to DSCG, and inability to inhibit nonimmunologic release of histamine. Neither RHC 3164 nor DSCG had any effect on immunologic release of histamine from human basophils or guinea pig lung slices. We conclude that RHC 3164 is a potent inhibitor of immunologic release of histamine from RMC with a mechanism of action similar to that of DSCG.

Physiological and mutational protein variations in the ciliary membrane of Paramecium

The proteins in the ciliary membrane of wild-type and mutant Paramecium tetraurelia are examined with SDS and IEF gels. Over 80% of the proteins in the ciliary membrane belong to two groups: the immobilization antigen (I-Ag), which is a 220-280 kD surface protein, and a set of at least four integral proteins slightly over 40 kD (the 40 k), most of which focus near pH 4.0 (the acidic 40 k). Variations of the I-Ag in its apparent molecular weight appear spontaneously in different clones of the same strain and can be triggered by changing the culture temperatures. We discovered that the members of the acidic 40 k family also vary in their relative proportion. Furthermore, the variations in I-Ag and those in acidic 40 k are tightly coupled. The concerted changes suggest a co-regulation in the synthesis of these proteins. The ciliary membranes of 20 mutants of 11 complementation groups known for their behavioral and electrophysiological defects are examined. Coupled variations of I-Ag and acidic 40 k among clones, similar to those of the wild type, are seen. Besides the I-Ag and the acidic 40 k, this membrane has over 60 other species of proteins, most of which are invariant. Shifts in the isoelectric points of two of these minor proteins have been correlated with two different mutations, 'fast-2' and 'paranoiac A'. No electrophoretic shifts can be correlated with the 'pawn B' mutation as found by Merkel et al. [35].

Isolation and characterization of antigenic components of rat glomerular basement membrane

(1) A method was developed to separate normal rat glomerular basement membrane (GBM) into six components by collagenase digestion, urea extraction, and gel filtration.(2) Treatment of rat GBM with collagenase did not alter nephrotoxic antigenicity of the membrane. Further proteolytic digestion with pronase resulted in loss of ability to elicit nephrotoxic antibody. Rat GBM prepared by mild alkali treatment still retained nephrotoxic antigenicity.(3) Antibodies against isolated components, except two which were retained on Sephadex G-75, localized to GBM and induced proteinuria in rats. One of the components retained on Sephadex G-75 produced localizing, non-nephrotoxic antibodies, while the other produced no localizing antibodies. Multiple antigens and common antigenic determinants among membrane components were demonstrated by gel double diffusion.(4) A specific nephrotoxigenic antigen from rat GBM was characterized as a macromolecular glycoprotein containing 10.7% carbohydrate in the form of galactose, mannose, sialic acid, glucosamine, and galactosamine. On analytical ultracentrifugation in Tris buffer, it gave two peaks with sedimentation constants of 5.93 and 3.49 S, while in 8 M urea it appeared as a single symmetrical peak with lower sedimentation constant (1.33 S) suggesting the presence of aggregate forms of the glycoprotein.(5) Dog GBM and collagenase-solubilized components elicited antibodies which localized to rat GBM but failed to produce proteinuria. Antibody to tendon collagen also localized to rat GBM but had no nephrotoxic effect on normal rats. Antibody to collagen fragments obtained from collagenase digestion failed to localize on rat GBM but still cross-reacted with tendon collagen in gel diffusion.