Identification of the regions conferring calmodulin-like properties to troponin C

The structural and functional correlations between troponin C (TnC) and calmodulin (CaM) were investigated by mutagenizing a synthetic cDNA coding rabbit skeletal muscle TnC. Compared with TnC, calmodulin lacks the N-terminal alpha-helical arm (N-helix), and its central helix is shorter due to the absence of 88KGK90 residues. Deleting both regions concomitantly (delta Nt delta KGK) elicited CaM-like regulation as tested (i) by smooth muscle contractility (maximal tension = 80 +/- 5% Po of control) and (ii) by the activation of phosphodiesterase (Vmax = 75 +/- 2% of control). The Ca(2+)-binding capacity of the mutant and the effect of the mutant on maximally Ca(2+)-activated tension of skinned rabbit psoas muscle fibers were both conserved. Furthermore, in the linker region of the central helix, replacing the TnC-characteristic 85EDAKGK90 successive residues with CaM-specific DTD residues generated a highly effective CaM mimic (Vmax = 96 +/- 2%) whether or not the N-helix was also retained. Apparent KD values (i.e. concentrations for half-maximal response) for the successful mutants were similar to each other but about 200-fold higher than that for CaM. A part of the alpha-helical linker region in CaM may unfold and bend to promote multiplicity of target interaction using all four hands (Ikura, M., Clore, G. M., Gronenborn, A. M., Zhu, G., Klee, C. B., and Bax, A. (1992) Science 256, 632-638; Meador, W. E., Means, A. R., and Quiocho, F. A. (1992) Science 257, 1251-1255). In contrast, our results suggest that the TnC central helix evolved to be less pliable by the combined influences of 85EDAKGK90 residues and the alpha-helical extension in N terminus, thereby keeping the N-terminal hands well separated from their C-terminal counterparts.

Use of gene fusions of the structural gene sdaA to purify L-serine deaminase 1 from Escherichia coli K-12

The purification by affinity chromatography of beta-galactosidase from strains carrying sdaA/lacZ gene fusions results in the copurification of L-serine deaminase 1. We conclude that sdaA is the structural gene for the latter enzyme. The purified L-serine deaminase 1 obtained after collagenase treatment of an sdaA-collagen-lacZ fusion differs from the native enzyme by the addition of several amino acids at the C-terminal. Like the enzyme in crude extracts, this purified enzyme is catalytically inactive, and is activated by incubation with iron and dithiothreitol.

The mechanism of Ca(2+)-coordination in the EF-hand of TnC, by cassette mutagenesis

Genetic engineering of TnC and skinned fiber physiology on rabbit psoas muscle are combined to study the mechanisms of Ca(2+)-binding in the EF-hand in TnC. Of the six coordinating positions (X,Y,Z,-Y,-X & -Z) for Ca(2+)-binding in the loop, the X position is invariably occupied by an aspartate, and the -Z position by a glutamate. X-ray analysis has indicated that both oxygen atoms of the beta-carboxylate in aspartate (in X) are extensively hydrogen bonded to other residues in the loop. When this aspartate in site II was replaced by a glutamate (gamma-carboxylate), Ca(2+)-binding was annihilated, and the mutant was unable to regulate force development in the fiber. Similarly, glutamate for aspartate exchange in the -Z position of site I also inactivated the site as well as its function in skinned fiber. Mutations in the Y position indicated that a glutamate was unacceptable in place of aspartate but that an asparagine was acceptable. The Ca(2+)-sensitivity with asparagine was also similar to that of the wild type. The study indicates a powerful approach for defining the physicochemical principles governing Ca-coordination and sensitivity in Ca-binding proteins. Furthermore, by comparison with findings on chemically synthesized peptides, the results show that behavior of the EF-hand in TnC is modified by quaternary structure of the molecule.

Immunogenicity of a synthetic oligopeptide corresponding to antigenically common T-helper and B-cell neutralizing epitopes of the major outer membrane protein of Chlamydia trachomatis

Sexually transmitted diseases (STDs) caused by Chlamydia trachomatis are an important public health problem and a vaccine to prevent or control these diseases is badly needed. The major outer membrane protein (MOMP) is the principal candidate antigen for the development of subunit vaccine against chlamydial STDs. The immunogenicity of a synthetic oligopeptide, termed A8-VDIV, corresponding to MOMP sequences containing both C. trachomatis species common T-helper (A8) and B-cell (VDIV) epitopes was studied in mice and non-human primates. Six of eight H-2 congenic mouse strains immunized with peptide A8-VDIV produced high-titre IgG antibodies against the VDIV B-cell portion of the oligopeptide. Fine mapping of the anti-peptide antibodies by pepscan ELISA showed that each of the responding mouse strains made antibodies reactive with a species-common septmeric neutralizing epitope 298LNPTIAG304 contained in the VDIV sequence. The mouse anti-peptide antibodies reacted with intact C. trachomatis elementary bodies (EBs) by ELISA and neutralized chlamydial infectivity for cultured eukaryotic cells with sub-species specificity. Three cynomolgus monkeys were immunized with peptide A8-VDIV and their IgG antibody responses were similarly studied. All three monkeys produced IgG antibodies which reacted with the VDIV peptide and which recognized the species-common LNPTIAG neutralizing site within the VDIV sequence. Monkey anti-peptide antibodies bound to intact C. trachomatis EBs and were neutralizing in vitro.(ABSTRACT TRUNCATED AT 250 WORDS)

Identification of the transcriptional unit, structural organization, and promoter sequence of the human sex-determining region Y (SRY) gene, using a reverse genetic approach

Using a simple strategy involving cosmid-mediated gene transfer, cDNA library construction, and molecular characterization techniques, we have determined the transcriptional unit, structural organization, and promoter sequence of the human sex-determining region Y (SRY) gene, the putative testis-determining factor (TDF) gene on the human Y chromosome. By this approach, a recombinant cosmid harboring the human SRY sequence was isolated and transfected to appropriate tissue-cultured cells. Recombinant cDNA clones were isolated from a cDNA library constructed from poly (A) + RNA of the transfected cells. Comparative studies between the respective cDNAs and the genomic cosmid have provided information regarding the organization of the SRY gene and its mRNAs. The results indicate that the human SRY gene is an intronless gene, produces transcripts of 1.1 kb, and possesses promoter activities in the transfected cells at approximately 310 bp of its upstream sequences.

Functional delineation of the Ca(2+)-deficient EF-hand in cardiac muscle, with genetically engineered cardiac-skeletal chimeric troponin C

Cardiac and fast skeletal isoforms of TnC each comprise four putative EF-hand (helix-loop-helix) motifs as potential Ca(2+)-binding sites (sites 1-4), except that site 1 in cardiac TnC is deficient in Ca2+ coordination. In skeletal TnC, the N-terminal sites 1 and 2 are both essential for the trigger mechanism of the contraction switch. However, the mechanism in cardiac muscle is unsettled; it is obscure whether the cardiac site 1 is functionally inert due to calcium deficiency and consequently site 2 is the lone trigger site, or whether sites 1 and 2 perform interactively despite the impairment. These possibilities were addressed by mutagenizing site 1 in skeletal TnC to mimic the cardiac response. In one mutant (STnC-1), two selected Ca(2+)-ligands were abolished. In another (C1/S chimera), 41 N-terminal residues from cardiac TnC were spliced to STnC. The Ca(2+)-binding capacities as well as skinned fiber responses were measured. The STnC-1 derivative failed to switch on contraction. In contrast, the chimeric construct expressed close to full contractile potential in myocardium (74 +/- 3% Po; Po = maximal tension) and also the manifest cardiac phenotype. By devising supplemental chimeric constructs, cardiac-type N-terminal overhang together with cardiac-type EF-hand for site 1 both were found essential for the phenotype. We conclude that cardiac TnC site 1 is actively engaged in the trigger mechanism and in fact dominates the phenotype despite the inability to chelate Ca2+. The N-terminal overhang also participates in this mechanism, which is a novel finding. The conclusion that a non-chelating site functions interactively with a proximal site in cardiac TnC may have wider significance, inasmuch as similar pairings of disparate EF-hands are of common occurrence.

Repression of liver-specific hepatitis B virus enhancer 2 activity by adenovirus E1A proteins

Two regions of the hepatitis B virus (HBV) genome have been shown to display properties of a transcriptional enhancer. Enhancer 1 is active in most hepatoma lines examined as well as in some non-hepatocyte-derived cell lines. In contrast, enhancer 2 activity is strictly liver specific. In this study, we show that adenovirus E1A expression in the highly differentiated human hepatoma line Huh6 strongly inhibits HBV enhancer 2-stimulated transcription while having no effect on HBV enhancer 1 activity. A sequence motif in HBV enhancer 2 which is essential for its enhancer function is the target for E1A-mediated repression. The repression of HBV enhancer 2 activity is mediated through the N-terminal region of the E1A proteins known to bind a 300-kDa cellular protein. Our results suggest that HBV enhancer function may be modulated by a cellular mechanism similar to E1A-mediated transcriptional repression.

Demonstration of a stage-specific expression of the ZFY protein in fetal mouse testis using anti-peptide antibodies

The zinc finger Y (Zfy) gene is located on the Y chromosome of all placental mammals. Although it is phylogenetically conserved and is expressed in mouse fetal testis, it is not the sex determining Y (Tdy) gene. To address the possible function of the Zfy gene in mice, the distribution of Zfy protein in fetal mice was investigated by immunocytochemical staining using several specific antisera against synthetic peptides of the mouse Zfy protein. Analysis of various fetal tissues at different embryonic stages demonstrated a specific staining only in fetal testis. In particular, reactive protein was initially observed in male fetal gonads at day 11.5 postcoitum (p.c.). The immuno-staining intensified in fetal testes at day 12 and 12.5 p.c., decreased drastically in those at day 13 and 14 p.c. and became undetectable in those at day 15 p.c. and beyond. The reactive molecules were distributed mostly within the seminiferous tubules of the embryonic testis. The present observations confirm the previous findings with RT-PCR analysis and indicate that Zfy or Zfy-like protein is expressed in stage-specific manner during early testis differentiation. Its location in the seminiferous tubules suggests a possible role in early germ cell development.

Determination of residue specificity in the EF-hand of troponin C for Ca2+ coordination, by genetic engineering

Utilizing protein engineering of troponin C (TnC), combined with the physiology of skinned fibers, the present study sought to delineate the mechanisms for metal ion coordination and sensitivity in the sites (EF-hands) that execute the Ca2+ switch for contraction. A total TnC-encoding gene comprising multiple target sequences for restriction enzymes was synthesized, furnishing a pliant molecular handle to manipulate sites I and II in the NH2 terminus of the protein. Of the six positions (X, Y, Z, -Y, -X, and -Z) essential for metal ion chelation in a typical EF-hand, invariably the X position has aspartate, and -Z position has glutamate. In the X position of site II, mutation of aspartate for either glutamate (gamma-carboxylate) or asparagine (same side chain length as aspartate) yielded functionally inactive proteins with concomitantly diminished Ca2+ binding capacity. Similarly, in -Z position (site I), neither aspartate nor glutamine were compatible in exchange for the conserved glutamate. In contrast, for the Y coordinate of site II, a preference for asparagine comparable to that for wild-type aspartate was detected, but glutamate was impermissible. Evidently, physicochemical and steric factors both are critical in governing the mechanism for metal ion chelation in TnC in a physiological milieu. Furthermore, the findings manifest that the quaternary structure of hydrated TnC restrains the EF-hands during on-off operation of the Ca2+ switch.

Wounding acts as a tumor promoter in chickens inoculated with avian sarcoma virus 17

Avian sarcoma virus 17 (ASV17) is an acutely transforming retrovirus which carries the oncogene v-jun. The virus induces fibrosarcomas in chickens at the site of inoculation. Here we describe wound-related tumor formation in 77% of chickens inoculated with ASV17 in one wing and wounded by metal clip insertion in the opposite wing. Tumors from both wound-related and inoculation-related sites were histologically diagnosed as fibrosarcomas. Tissues cultured from both tumor sites produced infectious virus in culture and expressed high levels of the v-Jun oncoprotein detectable by immunofluorescent staining. By varying the time of wounding relative to virus inoculation we defined the early stages of wound healing (2-7 days postinoculation) as favoring wound-related tumor formation. Three other acutely transforming retroviruses containing oncogenes coding for nonreceptor protein tyrosine kinases (v-src, v-yes, and v-fps), inoculated in the same manner, induced wound-related tumors in all cases. We conclude that in chickens, ASV17 collaborates with wound healing to promote tumorigenesis by a process which may relate either to a biochemical function of Jun or to a more general, shared characteristic of transforming retroviruses.

Isolation of a phylogenetically conserved and testis-specific gene using a monoclonal antibody against the serological H-Y antigen

Several cDNA clones of a gene termed male-enhanced antigen-2 (Mea-2), have been isolated from a mouse testicular expression cDNA library using a monoclonal histocompatability Y (H-Ys) antibody which detects specific protein(s) present in the mouse testis but not the ovary. The Mea-2 gene is phylogenetically conserved among various mammalian species examined, and is expressed at high levels in adult mouse testis. The expression pattern of Mea-2 is very similar to that of another gene, the male-enhanced antigen-1 (Mea-1), previously isolated using a polyclonal H-Ys antibody. Northern blotting and RT-PCR analyses demonstrated that Mea-2 is also expressed in other adult and fetal mouse organs at low levels. The testis-enhanced expression of this gene is associated with germ cell development at mid- to late-meiotic stages of spermatogenesis. Analysis of an intersubspecies mouse backcross has assigned this gene to chromosome 5, between the loci Gus and Hnf-1.

Regulation of hepatitis B virus gene expression by its two enhancers

Hepatitis B virus (HBV) infection causes acute and chronic hepatitis and is closely associated with the development of hepatocellular carcinoma. The principal site of HBV infection is liver, and HBV actively replicates in hepatocytes. Two regions of the HBV genome have been shown previously to display properties of a transcriptional enhancer. In this study, we show that either of the two HBV enhancers can activate all three major HBV promoters in several human hepatoma lines, and the cooperative action of the two enhancers ultimately affects overall activity of the three promoters. In addition, our data suggest that HBV gene expression may be differentially regulated by its enhancers. HBV infection causes chronic liver inflammation and hepatocyte regeneration. It has been proposed that progressive accumulation of mutations during the regenerative hyperplasia may lead to alterations in the differentiation state of hepatocytes. Thus, the development of two differentially regulated enhancers may reflect a strategy of HBV to replicate efficiently in less differentiated hepatocytes during hepatocyte regeneration or hepatocarcinogenesis.

Immunogenicity of a chimeric peptide corresponding to T helper and B cell epitopes of the Chlamydia trachomatis major outer membrane protein

The immunogenicity of a chimeric T/B cell peptide corresponding to antigenically characterized epitopes of the Chlamydia trachomatis major outer membrane protein (MOMP) was studied in mice to further define its potential use in the development of a subunit vaccine in preventing blinding trachoma in humans. The chimeric peptide, designated A8-VDI, corresponds to a conserved MOMP T helper (Th) cell epitope(s) (A8, residues 106-130) and serovar A VDI (residues 66-80), which contains the serovar-specific neutralizing epitope 71VAGLEK76. Mice immunized with peptide A8-VDI produced high-titered polyclonal IgG antibodies which recognized the VAGLEK-neutralizing epitope. Peptide A8-VDI primed A/J mice to produce high-titered serum-neutralizing antibodies in response to a secondary immunization with intact chlamydial elementary bodies (EBs). Peptide A8-VDI, but not peptide VDI alone, was immunogenic in six different inbred strains of mice disparate at H-2, indicating that the Th cell epitope(s) contained in the A8 portion of the chimera was recognized in the context of multiple major histocompatibility complex (MHC) haplotypes. An unexpected finding of this work was that different inbred strains of mice immunized with the chimeric peptide produced antibodies of differing fine specificities to the VDI portion of the chimera. Some mouse strains produced anti-VDI antibodies that did not recognize the VAGLEK-neutralizing epitope. The ability of mice to respond to the VAGLEK-neutralizing site was not dependent on MHC haplotype since mouse strains of the same H-2 haplotype produced anti-VDI antibodies of differing fine specificity.

Expression of Fc gamma RIII on HeLa 229 cells: possible effect on in vitro neutralization of Chlamydia trachomatis

The neutralizing activities of a murine immunoglobulin G3 (IgG3) monoclonal antibody specific for the major outer membrane protein of Chlamydia trachomatis and its monovalent Fab fragments were studied by using Syrian hamster kidney (HaK) cells and human epithelial (HeLa 229) cells. The intact IgG3 antibody was neutralizing for HaK cells but was nonneutralizing for HeLa cells. In contrast, monovalent Fab antibody fragments neutralized chlamydial infectivity for both HaK and HeLa cells. Immunofluorescence analysis of HeLa 229 cells with a panel of monoclonal antibodies specific to human Fc gamma receptors revealed the expression of cell surface Fc gamma RIII. We propose that Fc gamma RIII may obscure the chlamydia-neutralizing activity of certain IgG isotypes by facilitating the Fc gamma R-mediated entry of chlamydiae into HeLa 229 cells. These findings may help explain the inconsistencies that are commonly observed in results when HeLa 229 cells are used in chlamydia neutralization assays.

In vitro neutralization of Chlamydia trachomatis by monovalent Fab antibody specific to the major outer membrane protein

Monovalent Fab antibodies to serovar- and subspecies-specific epitopes of the major outer membrane protein (MOMP) of Chlamydia trachomatis neutralized infectivity for hamster kidney cells by preventing chlamydial attachment. These findings exclude the aggregation of chlamydiae as a mechanism of anti-MOMP neutralization and provide additional evidence in support of the MOMP as a chlamydial adhesin.

Interaction of the envelope glycoprotein of human immunodeficiency virus with C1q and fibronectin under conditions present in human saliva

Human saliva has been shown to reduce the infectivity of human immunodeficiency virus (HIV) particles in vitro. The factors in human saliva involved in this inhibition of HIV infectivity are unknown, although the salivary sediment of normal individuals has the major HIV neutralizing activity. Interestingly, the first complement component (C1) has been detected on the surface of the salivary sediment in the whole saliva of normal individuals. At the relatively low ionic strength of saliva, we determined that purified human C1q bound with high affinity to the envelope glycoprotein of HIV. Normally, the interaction of the C1q globular heads with immune complexes causes C1 activation. However, direct interactions between C1 and rgp120 (or rgp160) did not lead to C1 fixation, as determined by hemolytic studies with rate-limiting levels of C1, nor did rgp120 cause C1 activation as determined by activated C1s-mediated C4 conversion in normal human serum. Using ELISA, it was observed that intact C1, with the C1r2C1s2 tetramer associated with the collagen-like stem of C1q, did not bind to immobilized rgp120, whereas free C1q did bind. In addition, digestion of the C1q stem portion with collagenase completely eliminated its binding to rgp120. These findings suggest that the collagen-like stem region of C1q, rather than the globular heads, may participate in the binding to the envelope glycoprotein of HIV. Fibronectin, which is present in submandibular saliva, appeared to bind to rgp120 and to enhance the interaction of C1q with rgp120. It is conceivable that C1q and fibronectin, in binding and sequestering HIV particles (i.e. to the salivary sediment), may play an important role in the reduction of HIV transmission via saliva. Further studies will be needed to test the latter speculation.

A novel L-serine deaminase activity in Escherichia coli K-12

We demonstrate here that Escherichia coli K-12 synthesizes two different L-serine deaminases (L-SD) catalyzing the nonoxidative deamination of L-serine to pyruvate, one coded for by the previously described sdaA gene and a second, hitherto undescribed enzyme which we call L-SD2. A strain carrying a null mutation in sdaA made no detectable L-SD in minimal medium, but had activity in Luria broth. We describe a mutation, sdaX, which affects the regulation of L-SD2 and permits its expression in minimal medium, and an insertion mutation, sdaB, which abolishes L-SD2 activity completely. Both mutations lie near 60.5 min on the E. coli genetic map. The two L-SD enzymes have similar enzyme parameters, and both require posttranslational activation.

The Chlamydia trachomatis hyp operon is homologous to the groE stress response operon of Escherichia coli

The Chlamydia trachomatis serovar A hyp operon was cloned, sequenced, and expressed in Escherichia coli. Two cotranscribed open reading frames, hypA and hypB, encoded polypeptides of 17 and 57 kilodaltons, respectively. The deduced amino acid sequences of serovar A HypA and HypB proteins were (respectively) 85 and 94% identical with HypA and HypB proteins of Chlamydia psittaci GPIC, and HypB was greater than 50% identical to 60-kilodalton stress response proteins from other procaryotes and eucaryotes. The sequence should be useful in defining the antigenic structure of the Chlamydia trachomatis HypB protein, a necessary step toward understanding the relationship between the immune response to this protein and the pathogenesis of human chlamydial diseases.

Identification and characterization of T helper cell epitopes of the major outer membrane protein of Chlamydia trachomatis

Chlamydia trachomatis serovars A, B, and C are the causative agents of trachoma, the world's leading cause of preventable blindness. Immunoprophylaxis is a possible approach to control trachoma. The chlamydial major outer membrane protein (MOMP) is thought to play an important role in the development of protective immunity against chlamydial infection, and is therefore considered to be a promising candidate antigen in the development of a trachoma vaccine. Much effort has been focused on the molecular characterization of B cell sites of the MOMP that elicit neutralizing antibodies. Neutralizing sites have been identified as linear epitopes that reside within variable domains (VDs) of the protein whose primary sequences vary among different serovars. No information exists on MOMP T helper (Th) cell antigenic determinants, which are likely critical components for the development of a successful chlamydial vaccine. We used overlapping synthetic peptides (25 mers) representing the entire primary sequence of serovar A MOMP in T cell proliferation assays to identify T cell antigenic determinants of this molecule. Eight synthetic peptides (A-2, A-3, A-7, A-8, A-11, A-22, A-23, and A-24) stimulated proliferative responses of splenic T cells isolated from MOMP-immunized A/J mice. To ascertain if these peptides functioned as Th cell antigens, we determined their ability to prime A/J mice in vivo to produce an anamnestic IgG response specific to the MOMP. Mice primed with synthetic peptides A-8 (106-130) or A-23 (331-355) produced IgG antibodies reactive with the native MOMP and with the synthetic peptides corresponding to surface-accessible serovar-specific epitopes located in VD I and serogroup-specific epitopes located in VD IV of the protein. We synthesized the A-8 and A-23 peptides with the VD I sequence as colinear chimeric peptides. Immunization of mice with the T/B cell peptides produced high titered antibodies against the VD I sequence, and these antibodies reacted with the native MOMP and intact chlamydiae. The MOMP sequences containing these Th cell epitopes are conserved among the MOMP genes of different C. trachomatis serovars, indicating that they are common Th cell antigenic sites. Thus, the Th cell epitopes contained within these peptides, in combination with different trachoma serovar-specific B cell neutralizing determinants, may be useful in the development of a synthetic or recombinant trivalent trachoma vaccine.

Chlamydia trachomatis-host cell interactions: role of the chlamydial major outer membrane protein as an adhesin

The major outer membrane protein (MOMP) of Chlamydia trachomatis is characterized by four symmetrically spaced variable domains (VDs I to IV) whose sequences vary among serotypes. The surface-exposed portions of these VDs contain contiguous sequences that are both serotyping determinants and in vivo target sites for neutralizing antibodies. Previous studies using surface proteolysis of C. trachomatis B implicated VDs II and IV of the MOMP of this serotype in the attachment of chlamydiae to host cells. In this study, we used monoclonal antibodies (MAbs) specific to antigenic determinants located in VDs II and IV of the MOMP of serotype B to further investigate the role of the MOMP in the attachment of chlamydiae to host cells. MABs specific to serotype- and subspecies-specific epitopes located in exposed VDs II and IV, respectively, neutralized chlamydial infectivity for hamster kidney cells by blocking chlamydial attachment. We radioiodinated these MAbs and used them to determine the number and topology of the surface-exposed VDs II and IV epitopes on chlamydial elementary bodies. VDs II and IV each comprised approximately 2.86 x 10(4) negatively charged sites and were in proximity on the chlamydial cell surface. These studies suggest that the MAbs blocked chlamydial attachment by inhibiting electrostatic interactions with host cells. We examined the effects of thermal inactivation on both chlamydial attachment and conformation of the MOMP. Heat-inactivated chlamydiae failed to attach to host cells and exhibited a conformational change in an inaccessible invariant hydrophobic nonapeptide sequence located within VD IV of the MOMPs of C. trachomatis serotypes. These findings suggest that in addition to electrostatic interactions, a common hydrophobic component of the MOMP also contributes to the binding of chlamydiae to host cells. Thus, we propose that the MOMP functions as a chlamydial adhesin by promoting nonspecific (electrostatic and hydrophobic) interactions with host cells. Surface-accessible negatively charged VDs appear to be important in electrostatic binding, while the invariant region of VD IV may provide a subsurface hydrophobic depression which further promotes binding of chlamydiae to host cells through hydrophobic interactions.

[Evaluation of prosthetic valvular regurgitation by color Doppler echocardiography]

Prosthetic valvular regurgitation was evaluated by color Doppler echocardiography in 107 patients with prostheses. Regurgitant jets were detected in 37 (35%) prostheses, 76% of them were transvalvular and 24% of them were perivalvular. The ratio of bioprostheses with increased intensity and transvalvular regurgitant jets increased parallel to the duration after replacement. Of those bioprostheses replaced more than 6 years, 23% developed regurgitation with a higher degree. Transvalvular regurgitation was detected in 25% of St. Jude Medical prostheses recently replaced, but the degree was low.

Modulation of bullous pemphigoid antigens by gamma interferon in cultured human keratinocytes

We report the effects of human recombinant gamma interferon (gamma-IFN) on the expression of bullous pemphigoid (BP) antigens by human cultured keratinocytes. Secondary epidermal cell cultures were grown on 3T3 mouse fibroblasts; when confluent, some cultures were maintained in control medium while others were exposed to various concentrations of gamma-IFN (100, 200, 400 U/ml) for 14 days. The expression of BP antigens was analyzed by indirect immunofluorescence on epithelial sheets and immunoblotting of Tris, SDS, beta-mercaptoethanol culture extracts using different BP sera. Our results show that gamma-IFN alters the expression of BP antigens in a way varying according to the skin donor: we observed results ranging from complete loss and decreased expression to unchanged reactivity patterns. Thus, gamma-IFN modifies BP antigen expression; this behavior has been previously shown for other adhesion molecules such as fibronectin and thrombospondin. However, the observed variability of the expression of BP antigens according to the skin donor suggests an unexpected variability in keratinocyte sensitivity to gamma interferon, which remains to be explored both in vitro and in vivo.

Comparative expression of bullous pemphigoid antigens in normal human epidermis and cultured keratinocytes

A heterogeneity of the bullous pemphigoid (BP) antigen initially described as a 220- to 240-kDa polypeptide doublet expressed in normal human skin was recently demonstrated. The aim of our study was to compare the heterogeneity of BP antigen by the immunoblotting technique in extracts of both human epidermis and keratinocyte cultures. Extracts of epidermal tissues obtained from plastic surgery skin samples and secondary keratinocyte cultures were analyzed for their immunologic content defined by 30 BP sera. Twenty-six out of 30 tested sera showed similar binding reactivities with one or several polypeptide bands in both extracts. These sera defined seven antigens of molecular weights ranging from 240 to 97 kDa. Three groups of sera reacting with three, two, or only one antigen could be distinguished in which 180, 200, and 220 kDa polypeptides represented the major BP antigens both in vivo and in vitro. The binding reactivity of most immunofluorescent negative sera demonstrated the sensitivity of the immunoblotting technique to evidence the heterogeneity of BP antigens and antibodies. Keratinocyte cultures represent a reproducible substrate for such analysis and offer a standardization attempt in comparative investigations in BP.

Immunohistochemical study of normal skin of HIV-1-infected patients shows no evidence of infection of epidermal Langerhans cells by HIV

Langerhans cells (LC) are dendritic epidermal antigen-presenting cells expressing the surface molecule CD4, which renders them theoretical cellular targets for direct infection by the human immunodeficiency virus (HIV). To date, somewhat conflicting results have been reported concerning the in vivo infection of LC by HIV as well as the numerical alteration of these cells in the course of HIV infection. In the present work we studied clinically normal skin of a group of 44 HIV-1-seropositive patients classified according to the Centers for Disease Control (CDC) stages II (n = 14), III (n = 9), and IV (n = 21). Monoclonal antibodies (MAb) to HIV p18, p24, and gp120 and to HLA-DR and CD1a antigens (specific for LC) were applied on frozen skin sections using an amplification biotin-streptavidin-fluorescein technique. The MAb to HIV p18 cross-reacted with a cytoplasmic antigen of epidermal basal keratinocytes also present on HIV-seronegative skin specimens. No other reactivity was observed with any of the three anti-HIV MAb. The quantitative study showed that no significant correlations could be established between the number of LC (evaluated independently by HLA-DR and CD1a antigens) and the number of peripheral blood CD4+ve lymphocytes or the CDC disease stage. These results cast some doubt on the previously reported in vivo infection and numerical decrease in LC in HIV infection. The precise involvement of LC in HIV infection awaits further investigation.

Distribution of an estrogen receptor-related protein (P29) in normal skin and in cultured human keratinocytes

A monoclonal antibody, ERD5, which recognizes a 29Kd phosphoprotein associated with human estrogen receptor of myometrium was used to study the expression of this protein in normal skin and in cultured human keratinocytes. By indirect immunofluorescence, both in vivo and in vitro keratinocytes showed a variable cytoplasmic staining which increased with cell differentiation. SDS gel electrophoresis of soluble extracts of cultured keratinocytes and normal epidermis showed that P29 was a minor protein. Immunoblot analysis demonstrated that ERD5 strongly reacted only with a 29Kd polypeptide band without any cross-reactivity. These data suggest that keratinocytes might be estrogen sensitive like other cells in which P29 has already been located. The exact role of this protein in the keratinocyte differentiation process and its relationship with estrogen receptors remain to be elucidated.

Bullous pemphigoid and cicatricial pemphigoid: immunoblotting detection of involved autoantigens

Bullous pemphigoid (BP) and cicatricial pemphigoid (CP) are subepidermal bullous autoimmune diseases which have distinct clinical features but identical immunological status. In order to determine whether these diseases could be dissociated on the basis of qualitative differences in serum antibodies to basement membrane zone (BMZ) antigens, the reactivity of sera from 7 CP and 29 BP patients with proteins extracted from normal human epidermal sheets (containing most of the lamina lucida components) was analysed using immunoblotting and compared to that of 10 normal sera. 20 out of the 29 BP sera contained antibodies recognizing one or several protein(s) of 240, 200, 180 and 165 kD molecular weight (MW). Antibodies in 4 out 7 CP sera specifically reacted with one or two polypeptides of 240 and 120 kD MW. These data confirm the heterogeneity of BP antigens and show the presence in CP of a novel 120 kD MW polypeptide which is found only in CP but not in BP. Taken together these findings demonstrate that in BP and CP, autoantibodies are directed to both common and specific BMZ antigens, their physiopathological significance need to be understood.

A comparison of the distributions of eight peptides in spinal cord from normal controls and cases of motor neurone disease with special reference to Onuf's nucleus

The distributions of 8 peptides were studied in the 4 major segmental levels (cervical, thoracic, lumbar, sacral) of the spinal cord in 52 neurologically normal cases. Similar regions from 36 cases of motor neurone disease (MND) were compared using the same procedures to determine possible changes in the distribution of peptides in areas associated with sensory, motor and autonomic function. In normal spinal cords, calcitonin gene-related peptide (CGRP)-, the C-flanking peptide of neuropeptide Y (CPON)-, enkephalin-, galanin-, neurokinin-like-, somatostatin- and vasoactive intestinal polypeptide (VIP)-immunoreactive fibres were abundant in the dorsal horn. Numerous somatostatin-immunoreactive cell bodies were also present. In the ventral horn, immunoreactive fibres were less abundant. Most motoneurones were closely apposed by fibres immunoreactive for enkephalin, neurokinin, somatostatin and thyrotrophin-releasing hormone (TRH). A subpopulation of motoneurones, most notable in lumbar segments, displayed CGRP immunoreactivity. In common with autonomic nuclei, Onuf's nucleus, which is thought to innervate perineal striated muscle and external urethral and anal sphincters, was densely innervated with CPON-, enkephalin-, and in particular somatostatin-immunoreactive fibres, thus suggesting Onuf's nucleus may have an autonomic component. In the diseased cords, there was a reduction in the area of the ventral horn and numbers of motoneurones as revealed by conventional histological staining and immunostaining of neurofilament triplet proteins. No changes in the distribution of peptides was noted in the dorsal horn or autonomic nuclei. By contrast, in the ventral horn, neurokinin-, enkephalin-, somatostatin- and TRH-immunoreactive fibres, which are normally found associated with motoneurones, were absent. Therefore, not only are motoneurones lost in MND, but also the fibres which innervate them. CGRP-immunoreactive motoneurones were not observed, a finding consistent with the proposed role of this peptide as a muscle-trophic factor. In contrast to the large motoneurone groups in the ventral horn, the neuronal integrity of Onuf's nucleus and the peptides associated with it were spared. These data further imply that Onuf's nucleus is not a typical motor nucleus and it is not purely somatic. The coincident loss of peptide immunoreactivity and motoneurones from the large motor nuclei and sparing of Onuf's nucleus and its peptide-containing constituents in the diseased state suggests that peptides contribute to maintenance of neural integrity.

Differential effect of trypsin on infectivity of Chlamydia trachomatis: loss of infectivity requires cleavage of major outer membrane protein variable domains II and IV

The initial interaction of chlamydiae with host cells is not well understood. Chlamydial cell surface components that function in attachment are key virulence factors, and their identification is critical for understanding the pathogenic strategies of this very successful parasite. We used trypsin proteolysis of chlamydiae to define surface components that function in chlamydia-host cell interactions. We found that trypsin had a differential effect on the infectivity of Chlamydia trachomatis serovars B and L2 for HeLa 229 cells. Trypsin treatment resulted in a significant loss of attachment and infectivity of serovar B but had no effect on the infectivity of serovar L2. Fluorograms of chlamydiae metabolically labeled with 14C-amino acids and treated with trypsin showed that the major outer membrane protein (MOMP) of both serovars was cleaved. Evidence for two trypsin cleavage sites was found for the serovar B MOMP. One cleavage site was located between lysine 145 and valine 146 in variable domain (VD) II of the protein. The second site was located between lysine 309 and threonine 310 in VD IV. In contrast, the serovar L2 MOMP was cleaved only at lysine 309 in VD IV. These results suggest a functional role for MOMP in chlamydial attachment and implicate VDs II and IV of MOMP in this interaction.

Mapping antigenic domains expressed by Chlamydia trachomatis major outer membrane protein genes

Chlamydia trachomatis is an obligate prokaryotic intracellular pathogen of humans that infects mucosal epithelial cells. Exposed domains of its major outer membrane protein (MOMP) are both serotyping and protective antigenic determinants. To identify these domains, we have cloned and epitope-mapped the genes of serovars A, C (C serogroup) and L2, B (B serogroup) with a panel of monoclonal antibodies (mAbs). Predominantly conserved regions of the genes of both serogroups are interspersed with four short variable domains (I-IV). Recombinant phage clones expressing specific MOMP antigenic determinants revealed that protective serotype-specific recognized epitopes in variable domains I and II. Protective subspecies and serogroup-specific mAbs recognized overlapping determinants in variable domain IV near the C terminus. A nonprotective species-specific mAb mapped to an invariant peptide of nine residues contained within variable domain IV. In the intact chlamydial organism of serovar B, variable domains II and IV were susceptible to proteolytic digestion, whereas both N and C termini were protected. These results suggest an arrangement of MOMP in the outer membrane in which three of the four variable domains are exposed to the outside and in which both N and C termini are presumably oriented toward the periplasmic space. This molecular analysis of MOMP antigenic determinants and their surface topology on intact chlamydiae will be useful toward the development of a recombinant subunit or synthetic chlamydial vaccine.

Retrograde tracing shows that CGRP-immunoreactive nerves of rat trachea and lung originate from vagal and dorsal root ganglia

The origins of sensory innervation of the lower respiratory tract are thought to be principally the nodose and jugular ganglia of the vagus nerve. It has been suggested and partially demonstrated that there is also a component arising from dorsal root ganglia, but the segmental levels involved are not known precisely. We have therefore investigated the origins of sensory nerves within the rat respiratory tract, particularly those containing calcitonin gene-related peptide (CGRP), using the technique of retrograde axonal tracing combined with immunohistochemistry. Injections of True blue were made into extra-thoracic trachea (n = 4 rats) and percutaneously into the right and left lung (n = 4 each). Retrogradely labelled neuronal perikarya were detected in vagal and dorsal root ganglia, and sympathetic chain ganglia. CGRP-immunoreactive cells were seen only in vagal and dorsal root ganglia. Tracheal innervation arose bilaterally in the vagal sensory ganglia but those on the right side represented the principal source; the majority of CGRP-containing neurons occurred in the jugular ganglion. A very small component of labelling occurred in spinal ganglia at levels C2-C6. The sensory innervation of the lungs was seen to arise predominantly from the ipsilateral dorsal root ganglia (45% of cells CGRP-immunoreactive) at levels T1-T6. In contrast to the trachea, the contribution of vagal sensory neurones to the lungs appeared to be less than that of the spinal ganglia. These results show that the sensory innervation of the rat lungs has a major origin in the dorsal root ganglia, in which almost half of the involved neurons contain CGRP, and confirm that most CGRP-immunoreactive nerves in the trachea arise in the right jugular ganglion.

Transplantation of anastomosed vascular allomentum and split thickness autogenous skin grafting for repair of deep electrical burns of the wrist

The use of allomentum to replace automentum or skin flaps in treating 3 patients with severe electrical burns of the wrist is discussed, as are the specific advantages and disadvantages, and the prospects for clinical use of the technique.

High tension electrical burns of upper arms treated by segmental excision of necrosed humerus. An introduction of a new surgical method

This paper describes treating high-tension electrical burns of the upper arms by segmental excision of the necrosed humerus. This is a new surgical method of treating local electrical burns. The authors use modification of traditional surgical method, shorten the course of treatment, and preserve the injured limb. However, this surgical method should not be used to treat all high-tension electrical burns of the upper arm, and should be used only under certain conditions. Therefore, it is important to grasp the operative indications.

Studies on the ultrastructure of envelope of elementary bodies of Chlamydia trachomatis

Electron microscopy of purified Chlamydia trachomatis treated by various physical and chemical means shows that the envelope of the elementary bodies (EB) consists of the outer cell wall layer, the inner cell wall layer, and the inner membrane. The outer cell wall layer is mainly made up of granular subunits arranged in a hexagonal pattern and may be called the "mural structural protein layer". It forms together with the inner cell wall layer the rigid cell wall. The inner or protoplasmic membrane is not easily shown in the young EB. In the negatively stained specimen, a frail and easily removable superficial layer is seen adhering to the "mural structural protein layer". But in ultra-thin sections this superficial layer is not shown separately. There are fold-like grooves which are special structures probably related to reproduction. There are seen some EB's in binary fission, and a number of bodies very big in size yet having morphological characteristics of the EB's, which are in various processes of multiplication, such as binary fission, budding, and "multicentered germination". These observations give a challenge to the current opinion that only the initial bodies have the power of reproduction.