Antigen contact sites in class I major histocompatibility complex-restricted, trinitrophenyl-specific T cell receptors

Cloned trinitrophenyl (TNP)-specific cytotoxic T cells (CTL) were obtained from mice transgenic for the beta chain of the antigen-specific receptor (TcR) of a Kb-restricted, TNP-specific CTL clone (BT7.4.1). The transgene-expressing CTL, specific for TNP/Kb were found to select for TcR alpha chains highly similar to that of the transgene donor clone BT7.4.1. In that way, two clones (II/7 and III/1) were identified whose TcR differed from the BT7.4.1 receptor only in their N alpha- and J alpha-sequences, i.e. within the third complementarity-determining regions of their alpha chains (CDR3 alpha). Moreover, the TcR of clones II/7 and III/1 had both rearranged the same J alpha element, thus differing from each other by only two amino acids in their V alpha/J alpha junctional regions. Functionally, however, clone III/1 exhibited unique cytolytic specificities for synthetic, Kb-binding TNP-peptides as well as for chemically TNP-modified allogeneic (H-2k) target cells. These findings demonstrate that (a) similar to "conventional" peptide antigens, synthetic hapten-peptide determinants are contacted by CDR3 alpha-determined amino acids of the TcR and (b) in contrast to current models, CDR alpha also appears to influence the major histocompatibility complex restriction specificity of a given TcR.

Increased frequency of 2,4,6-trinitrophenyl (TNP)-specific, H-2b-restricted cytotoxic T lymphocyte precursors in transgenic mice expressing a T cell receptor beta chain gene from an H-2b-restricted, TNP-specific cytolytic T cell clone

T cell antigen receptors (TcR) expressing V alpha 10/J alpha BBM142 genes in association with beta chains containing J beta 2.6 elements were found to be predominant among 2,4,6-trinitrophenyl (TNP)-specific, H-2b-restricted cytolytic T cell lines (CTL). To assess the relative contribution of the TcR beta chain to the TNP specificity as well as to the selection of the respective TcR alpha chain elements we generated transgenic mice expressing the TcR beta chain of the H-2b/TNP-specific CTL clone BT7.4.1. The TcR of this clone does not belong to the type predominant among H-2b/TNP-specific CTL, as it consists of an alpha chain encoded by a V alpha 8/J alpha DO gene rearrangement and a V beta 2/J beta 1.1-containing beta chain. In the transgenic mice almost all T cells exclusively express the transgenic V beta 2 gene, as a result of allelic exclusion. TNP-specific, H-2b-restricted precursors were found at 7- to 8-fold higher frequency in these mice as compared with non-transgenic littermates. In H-2b/d heterozygous transgenic mice, an increased frequency of TNP-specific precursors was found only in H-2b, but not in H-2d-restricted CTL. Analysis of H-2b/TNP-specific CTL lines derived from V beta 2-transgenic mice indicated a preferential association of the transgenic TcR beta chain with endogenous alpha chains encoded by V alpha 8 and J alpha BBM142 genes. This suggests that the hapten TNP is recognized like typical peptide antigens by combinatorial TcR alpha and beta contact sites.

Bronchial asthma due to Cannabis sativa seed

A 51-year-old man with asthmatic attacks due to Cannabis sativa seed inhalation was studied. Specific IgE against this seed was demonstrated by in vivo (skin and bronchial challenge tests) and in vitro methods (reverse enzyme immunoassay and histamine release from basophils), suggesting a Type I immunologic reaction.

Allelic exclusion of a T cell receptor-beta minilocus

A TCR-beta minilocus in germline configuration (beta M) has previously been shown to undergo rearrangement and expression in transgenic mice. To study allelic exclusion of TCR miniloci, several beta M transgenic mouse lines were generated and crossed with mice transgenic for a functionally rearranged TCR V beta 2 gene (beta R). PCR analysis of beta M beta R double transgenic mice revealed almost complete suppression of endogenous TCR V beta gene rearrangements, but blockage of minilocus V beta rearrangements was achieved with only one of five minilocus transgenic lines. This result cannot be explained by copy number or arrangement of the multiple miniloci integrated. It appears that the minilocus is not autonomously regulated which suggests that sequences flanking the integration sites influence accessibility of the minilocus for rearrangement and allelic exclusion. However, although productively rearranged genes were formed in double transgenic mice, surface expression of minilocus-encoded beta chains was not detected. This indicates that allelic exclusion may operate at a level after gene rearrangement.

Allelic exclusion in transgenic mice expressing a heavy chain disease-like human mu protein

Heavy chain diseases (HCD) are neoplastic proliferations of B cells which secrete truncated immunoglobulin heavy chains without associated light chains. These proteins are encoded by mutated genes which may also give rise to truncated membrane immunoglobulins. The neoplastic cells proliferate in vivo although they cannot bind any antigen, due to deletions in the variable domain of their antigen receptors. The reason for the clonal proliferation of HCD cells and the biological effects of the truncated membrane-bound chains are presently unknown. We wanted to determine whether the expression of HCD proteins would interfere with B cell development. To this end we made transgenic mice with a human mu gene, lacking the VDJ exon, that encodes a protein similar to that produced in two cases of HCD. Transgenic mice were also produced with a similar construct but encoding only the membrane-bound form of the truncated mu chain. Transgene encoded C mu proteins are expressed on the cell surface without associated light chains and are responsible for allelic exclusion of murine heavy chains.

Allelic exclusion of a T cell receptor-beta minilocus

A TCR-beta minilocus in germline configuration (beta M) has previously been shown to undergo rearrangement and expression in transgenic mice. To study allelic exclusion of TCR miniloci, several beta M transgenic mouse lines were generated and crossed with mice transgenic for a functionally rearranged TCR V beta 2 gene (beta R). PCR analysis of beta M beta R double transgenic mice revealed almost complete suppression of endogenous TCR V beta gene rearrangements, but blockage of minilocus V beta rearrangements was achieved with only one of five minilocus transgenic lines. This result cannot be explained by copy number or arrangement of the multiple miniloci integrated. It appears that the minilocus is not autonomously regulated which suggests that sequences flanking the integration sites influence accessibility of the minilocus for rearrangement and allelic exclusion. However, although productively rearranged genes were formed in double transgenic mice, surface expression of minilocus-encoded beta chains was not detected. This indicates that allelic exclusion may operate at a level after gene rearrangement.

Allelic exclusion at DNA rearrangement level is required to prevent coexpression of two distinct T cell receptor beta genes

In mice double transgenic for functionally rearranged T cell receptor (TCR) V beta 2 and V beta 8.2 genes we found that most T lymphocytes express both TCR beta chains simultaneously. These T cells show no abnormality in thymic selection in vivo and their TCRs are capable of transducing activation signals in vitro. These results indicate that multispecific T cells may appear in the periphery if allelic exclusion of TCR beta genes is not established at the level of gene rearrangement.

Analysis of the immune system with transgenic mice: B cell development and lymphokines

Over the last decade transgenic mice expressing genes relevant for the immune system have been generated. Transgenic expression of immunoglobulin heavy and/or light chain genes of different isotypes and different specificities have helped to better understand phenomena relevant to B cell development such as allelic exclusion of immunoglobulins and B cell tolerance. Transgenic mice expressing interleukin genes have also been used to study the ways of action of these important growth and differentiation factors in the context of the mouse immune system.

Molecular requirements for the mu-induced light chain gene rearrangement in pre-B cells

During B cell differentiation rearrangement of immunoglobulin (Ig) genes is partially regulated by the Ig proteins. Rearrangement of heavy (H) chain genes is inhibited, whilst that of light (L) chain genes is induced by the membrane form of the mu H chain. In order to analyse additional structural requirements of mu induced L chain gene rearrangement we transfected wild-type mu and mutant mu constructs lacking functional exons encoding the first or second constant domains into Abelson murine leukemia virus (AMuLV) transformed pre-B cells. All mu chains are expressed on the surface of the pre-B cell and all associate with omega and iota, two proteins forming a surrogate light chain, necessary for mu membrane expression. Nevertheless, only wild-type mu and not the mutant mu proteins promote L gene rearrangement. A heterodimer of proteins with Mr of 33 kd and 36 kd was found associated with wild-type but not with the mutant mu proteins. Continuous presence of mu is required for L chain gene recombination since loss of mu stopped and readdition of mu started L gene rearrangement. We propose that the protein complex composed of mu and the 33 kd/36 kd protein heterodimer is responsible for the activation of the L chain gene locus and its rearrangement.

The cellular basis for lack of antibody response to hepatitis B vaccine in humans

We had previously obtained evidence that among normal subjects the humoral antibody response to hepatitis B surface antigen (HBsAg) was bimodally distributed with about 14% of subjects producing less than 1,000 estimated radioimmunoassay RIA units. From the study of major histocompatibility complex (MHC) markers in the very poor responders who produced less than 36 estimated RIA units of antibody, it appeared that there was an excess of homozygotes for two extended haplotypes [HLA-B8, SC01, DR3] and [HLA-B44, FC31, DR7]. This finding suggested that a poor response was inherited as a recessive trait requiring nonresponse genes for HBsAg on both MHC haplotypes and was strengthened by finding a much lower antibody response among prospectively immunized homozygotes for [HLA-B8, SC01, DR3] compared with heterozygotes. In the present study, we have analyzed the cellular basis for nonresponse to this antigen by examining antigen-specific proliferation of T cells from responders and nonresponders in the presence and absence of autologous CD8+ (suppressor) cells. Peripheral blood cells from nonresponders to HBsAg failed to undergo a proliferative response to recombinant HBsAg in vitro, whereas cells from responders proliferated vigorously. This failure of cells from nonresponders to proliferate was not reversed in cell mixtures containing CD4+ and antigen-presenting cells devoid of CD8+ cells. There was no difference between responders and nonresponders with respect to the number of circulating T cells or their subsets, or the proliferative response to mitogens such as pokeweed or phytohemagglutinin or another antigen, tetanus toxoid. Our results indicate that our HBsAg nonresponding subjects have a very specific failure in antigen presentation or the stimulation of T helper cells, or both. Our evidence is against specific immune suppression as the basis for their nonresponsiveness. The failure of antigen presentation or T cell help is consistent with recessive inheritance of nonresponsiveness and suggests that response is dominantly inherited.

Development of lymphocytes in interleukin 7-transgenic mice

We have developed and established mouse transgenic lines in which the mouse interleukin 7 gene was targeted for expression in the lymphoid cell compartment. Northern blot analysis indicate that the transgene is expressed in bone marrow (BM), spleen and thymus, but not in kidney, liver, brain or heart. Both the frequency and absolute numbers of B cell precursors and mature B lymphocytes are increased in the BM and spleen of the transgenic mice. Although there is no expansion of the pro-T lymphocyte population in the BM, the number of all major subsets of thymocytes and peripheral T lymphocytes is increased in the majority of the transgenic mice analyzed. The B and T cell lymphocytes in the transgenic mice are functionally competent. In contrast, the number of granulocytes and macrophages in the BM of transgenic mice is similar to that in control non-transgenic littermates. Our results indicate that interleukin 7 plays an important role in vivo in the development of B and T lymphocytes.

Vasculitis as a paraneoplastic syndrome. Report of 11 cases and review of the literature

In a study of 222 patients with vasculitis, we identified 11 who had an associated neoplasia. Seven had hematological neoplasia and 4 had solid malignant tumors. In 4 patients vasculitis gave the first evidence of the neoplasia or of its recurrence. Nine of our patients had cutaneous vasculitis. The other 2 had vasculitis involving the intestine and resulted in acute abdomens. These 2 patients needed prednisone treatment for the vasculitis. Neoplasia should be considered in patients with vasculitis without an apparent cause.

Involvement of major histocompatibility complex class I antigens in T cell activation

During the last few years ample evidence has been collected indicating a regulatory role for major histocompatibility complex class I antigens (Ag) in T cell activation. However, due to differential effects (stimulatory and inhibitory) of anti-class I antibodies (Ab) observed under different conditions, no coherent scheme of the mechanism of action of these Ag has emerged. Here, we present evidence that the mode of action of anti-class I Ab depends upon the presence or absence of monocytes/macrophages (M phi) in the culture. The Ab inhibit Ag presentation by binding to M phi. Coating of tetanus toxin -pulsed M phi with anti-class I Ab is sufficient to suppress T cell activation. On the contrary, these Ab enhance lectin- as well as phorbol ester-induced T cell activation in the absence of M phi. Cross-linking of class I Ag on T cell surface mobilizes cytoplasmic Ca2+, and also enhances the CD3-induced Ca2+ flux inside the cells indicating a functional relationship between CD3 and class I Ag. Though surface modulation and immunoprecipitation experiments do not indicate any physical association between these two types of molecules on the T cell surface, capping studies show that cross-linking of class I Ag induces an association of these Ag with CD3. Binding of anti-CD3 Ab enhances the strength of association between CD3 and class I Ag, and the former co-caps completely with the latter. Based on these observations we propose that during antigen presentation M phi (or Ag-presenting cells) and T cells, besides interacting via peptide--class II Ag/CD3--T cell receptor complex formation, also interact through class I Ag. The latter interaction may stabilize the contact formation between T cells and Ag-presenting cell and support T cell activation.

Analysis of T-cell subpopulations in human IL-2R alpha transgenic mice: expansion of Thy1.2- thymocytes and depletion of double-positive T-cell precursors

Transgenic mice carrying the human IL-2R alpha/p55 gene under the control of the SV40 enhancer/promoter were used to study the relevance of IL-2R in T-cell development. Serological analysis of the mouse lines obtained indicated transient, regulated expression of the human p55 gene, mainly confined to the early thymus, but which was also detected in lower amounts in the spleen. These mice showed degenerated thymuses, with an increased number of Thy1.2- double-negative precursor cells; they also had specific depletion of double-positive thymocytes. Transgene expression led to an increased number of intermediate-affinity IL-2 receptors (possibly ascribed to deregulated expression of IL-2R beta/p75) in transgenic thymocytes older than 12 weeks. These results suggest the occurrence of strong linkage between the IL-2/IL-2R system elements and thymic differentiation/maturation; they lend support to the idea of functionality of IL-2R expressed transiently in early stages of T-cell development.

Regulation of immunoglobulin gene expression in trans by phorbol esters

Lipopolysaccharide-stimulated B cell cultures treated with phorbol-12,13-dibutyrate have been shown to down-regulate their steady state levels of microseconds RNA while the microns RNA remained constant. In contrast, the steady state levels of delta RNA was up-regulated by the same treatment. By using mice transgenic for a rearranged mu or delta gene, it could be shown that the down-regulatory effect acts in trans on a defined DNA stretch and is independent of isotype. Thus, the positive effect on endogenous delta RNA steady-state levels must be regulated at the level of RNA processing. In addition, a DNA construct containing 1.5 kb of a kappa promoter 5' of, and an IgH enhancer 3' of, a chloramphenicol acetyl transferase reporter gene could be down-regulated in trans by anti-mu- or phorbol-12,13-dibutyrate treatment, showing that transcriptional control of Ig promoter elements can readily be observed in non-transformed B lymphocytes.

Deforming arthropathy of the hands in systemic lupus erythematosus

Forty-one of 858 patients with systemic lupus erythematosus (SLE) developed clinical deformity of their hands. This deformity was clinically and radiologically different from that found in 40 patients with classical or definite rheumatoid arthritis (RA), and tended to appear early in the course of disease. Characteristics of this arthropathy included nonerosive carpal collapse; exceptional erosion of the styloid processes; Z deformity of the thumb; nonerosive ulnar deviation and subluxation of MCP joints; parametacarpophalangeal joint hook formation; scant and asymmetric joint erosions; and swan neck deformity of the fingers. Most of these changes seemed to be due to involvement of the ligaments rather than to the destructive effect of synovitis. Patients with SLE with deforming arthropathy had a higher frequency of rheumatoid factor positivity, sicca symptoms and antibodies to native DNA, whereas they had lower incidence of facial rash and photosensitivity than did those without. Other manifestations did not differ. We propose that most patients with SLE with deforming arthropathy belong to a subset of SLE rather than representing the coexistence of SLE and RA.

Expression of immunoglobulin delta chain causes allelic exclusion in transgenic mice

Rearrangement of the separated V, D and J segments of immunoglobulin heavy and light chain genes is an ordered and regulated process essential for the production and diversification of antibodies in mammals. Only one allele of the heavy and light chain gene locus is found functionally rearranged in normal B cells. The second allele is either non-functionally or incompletely rearranged, a phenomenon known as allelic exclusion. Recently, we and others have shown that expression of a rearranged mu gene introduced into the germline of mice leads to inhibition of rearrangement of endogenous heavy chain genes. It has been suggested that mu also exerts a positive influence on kappa light chain gene rearrangement. Here we show that a functionally rearranged delta gene is also able to prevent endogenous heavy chain gene rearrangement and could promote kappa light chain gene rearrangement.

Effects of L-canavanine on T cells may explain the induction of systemic lupus erythematosus by alfalfa

Alfalfa sprouts can induce systemic lupus erythematosus (SLE) in monkeys. This property of alfalfa sprouts has been attributed to their non-protein amino acid constituent, L-canavanine. Occurrence of autoimmune hemolytic anemia and exacerbation of SLE have been linked to ingestion of alfalfa tablets containing L-canavanine. In this report we show that L-canavanine has dose-related effects in vitro on human immunoregulatory cells, which could explain its lupus-inducing potential. These effects include: 1) diminution of the mitogenic response to both phytohemagglutinin and concanavalin A but not to pokeweed mitogen, as determined in both thymidine incorporation and cell cycle studies, and 2) abrogation of concanavalin A-induced suppressor cell function, which results in increased release of both IgG and DNA binding activity into supernatants by cells from normal subjects and SLE patients. These immunoregulatory effects of L-canavanine may explain the induction or exacerbation of SLE by alfalfa.

Different ways to modify monoclonal antibodies

In this paper we summarize experiments which were undertaken to create altered antibody molecules. Three different approaches were used. Established hybridoma lines were re-hybridized to mouse spleen cells to generate arrays of secondary hybridomas which express one particular heavy chain and one specificity together with a multitude of different light chains. In such hybrids the influence of light chains to the antibody combining site and the influence of affinity to antibody effector functions can be studied. Another way to obtain altered antibodies was the selection of cells producing less lytic IgM. With this technique we obtained (among many other variants) a series of mu-deletion products which were used to map the fine specificity of rat anti-mouse mu monoclonal antibodies. Both the anti-mu antibodies and the deletion variants were used to assign the Clq binding to the fourth C mu-domain demonstrating the power of mutant IgM in the structure-function analysis. In a third series of experiments we show the feasibility of generating new antibody combining sites by the methods of molecular genetics. The variable region gene of a heavy chain was placed in front of a kappa-constant region gene. The plasmid construct was transferred into mouse myeloma lines which stably express a variable heavy-constant light chain protein. Upon fusion with a light chain producing line, chimaeric light chain dimers with a functional antibody combining site were secreted. These experiments demonstrate that new series of man-made antibody molecules can be made in the future.

Plasmid transformation in Bacillus subtilis. Effects of the insertion of Bacillus subtilis rRNA genes into plasmids

Two HindIII generated DNA fragments of 3.0 and 2.3 Kb derived from rRNA genes of B. subtilis were cloned in E. coli with pBR322. The 3.0 Kb fragment could be subcloned in B. subtilis using pC194. However, only the multimeric, but not the monomeric derivatives of this hybrid plasmid were active in transformation of B. subtilis cells. The 2.3 Kb fragment could neither be subcloned in pC194 nor in pPL603, using both cell and protoplast transformation. We attribute the nonclonability of the 2.3 Kb fragment in B. subtilis to the presence of strong promoter activity in this fragment. Direct proof for the presence of a strong promoter, which is apparently responsible for the transcription of the rRNA gene, was obtained in experiments with B. subtilis and E. coli promoter search plasmids.

H Fluxes in Excised Samanea Motor Tissue : II. Rhythmic Properties

Homogeneous groups of cells were excised at regular intervals from opposing (extensor and flexor) motor tissue of Samanea saman (Jacq) Merrill maintained in white light for 34 hours. H(+) fluxes between the tissue and bathing solution were then monitored during 30 minutes of darkness. Flux rates in both cell types vary with circadian rhythms. Flexor cells secrete H(+) to the medium during two-thirds of the circadian cycle and take up H(+) during the remainder of the cycle, while extensor cells take up H(+) from the medium during the entire cycle.

H fluxes in excised samanea motor tissue : I. Promotion by light

Previous investigators revealed that white light-promoted leaflet opening in Samanea saman (Jacq) Merrill depends upon K(+) uptake by extensor cells and efflux from flexor cells of the pulvinus, while dark-promoted closure depends upon K(+) fluxes in the opposite directions. We now monitored H(+) fluxes during pulvinar movement to test a model proposing coupled H(+)/K(+) fluxes. H(+) fluxes were monitored by measuring changes in the pH of a weakly buffered solution (initial pH = 5.5) bathing excised strips of extensor or flexor tissue. White light at hour 3 of the usual dark period promoted pulvinar opening, H(+) efflux from extensor cells and uptake by flexor cells, while darkness at hours 2 to 4 of the usual light period promoted pulvinar closure, H(+) uptake by extensor cells and efflux from flexor cells. The following conditions altered H(+) fluxes during dark-promoted closure. (a) Light reversed the directions of the fluxes in both extensor and flexor cells. (b) Anoxia increased the rate of H(+) uptake by extensor cells and promoted H(+) uptake (rather than efflux) by flexor cells, consistent with an outwardly directed H(+) pump. KCN showed similar effects initially, but they were transient. (c) Increase in external pH from 5.5 to 6.7 promoted H(+) efflux (rather than uptake) by extensor cells and increased the rate of H(+) efflux from flexor cells, presumably by decreasing the rate of inward diffusion. (d) Change in external K(+) did not alter H(+) fluxes by extensor cells, but removal of external K(+) decreased the rate of H(+) efflux from flexor cells by 70%. These observations support a model for coupled H(+)/K(+) fluxes in pulvinar cells during light-and dark-promoted leaflet movements.

Aspirin or Coumadin as the drug of choice for valve replacement with porcine bioprosthesis

Eight hundred twenty-four patients who had cardiac valve replacement with a porcine bioprosthesis were given either Coumadin (sodium warfarin) or aspirin. No patient in sinus rhythm no matter what valve or valves were replaced had thromboembolism whether treated with Coumadin (124 patients) or aspirin (260 patients). One hundred fifty-one patients who had mitral valve replacement, were in atrial fibrillation, and were treated with Coumadin had seven embolic events (4.6%), while 135 similar patients treated with aspirin had five embolic events (3.7%). Fifty-one patients who had double-valve replacement, were in atrial fibrillation, and were treated with coumadin had three embolic episodes (5.9%), while 86 similar patients treated with aspirin had three embolic events (3.5%). No statistical difference was found in the incidence of thromboembolism between similar groups of patients whether treated with Coumadin or aspirin (p greater than 0.05). Hemorrhagic complications were higher and reached statistical significance (p less than 0.001) for the group treated with Coumadin. This study shows that aspirin prevents thromboembolic complications as well as Coumadin in patients having cardiac valve replacement with a bioprosthesis, and results in a lower rate of complications.

Early leaflet perforation as a cause of bioprosthetic dysfunction

Of 699 patients with 900 bioprostheses, who lived longer than six months, three cases of early perforation of bioprosthetic leaflets are reported. In two cases the cut ends of the suture used for valve insertion had perforated the bioprosthetic cusps from repeated trauma. Insertion of the sutures in the periphery of the sewing ring and cutting the sutures flush with the knots should avoid this complication. The third case showed massive collagen breakdown with destruction of most of the cusp tissue. A possible explanation for such a massive early tissue breakdown could be an inadequate collagen fixation by glutaraldehyde.

Brucella mellitensis endocarditis on a porcine heterograft bioprosthesis

A Brucella mellitensis endocarditis on a Hancock valve bioprosthesis is reported. The patient was successfully treated by a combination of valve replacement, wide surgical debridement of the aortic annulus and medical treatment with trimethoprim and sulfamethoxazole. To the best of our knowledge, this is the first case of Brucella endocarditis on a bioprosthesis.

Plasmid transformation in Bacillus subtilis. The significance of partial homology between plasmid and recipient cell DNAs

A series of hybrid plasmids consisting of pC194 or pUB112 and B. subtilis DNA were constructed. In contrast to plasmid pC194, purified monomeric forms of such plasmids were active in transformation, provided the recipient cells were recombination proficient. Similarly the monomers of pC194 derived plasmids, containing bacteriophage phi 105 DNA were able to transform phi 105 lysogenic but not nonlysogenic cells. From the results it is concluded that the presence of DNA/DNA homology between chromosomal DNA of the recipient cell and part of the hybrid plasmids used is a sufficient condition to endow monomeric plasmids with transforming activity.

Plasmid transformation in Bacillus subtilis. Alterations introduced into the recipient-homologous DNA of hybrid plasmids can be corrected in transformation

Various alterations (deletions, additions, inversions) were introduced into portions of pC194/B. subtilis or pC194/phi 105 hybrid plasmid molecules which are homologous to the DNA of recipients in transformation. These plasmids are stably maintained in transformations of recombination deficient cells. In transformations of recombination proficient cells, they can be corrected to those plasmid forms into which the alterations were originally introduced. This correction is most pronounced when transformations are performed with monomeric ccc forms of hybrid plasmids. It is suggested that correction is a consequence of mismatch repair occurring in the synapsis of homologous portions of plasmid and resident DNAs.

Quadricuspid aortic valve associated with fibromuscular subaortic stenosis and aortic regurgitation treated by conservative surgery

A case of subaortic fibromuscular stenosis associated with a quadricuspid aortic valve with severe aortic insufficiency is reported. Correction of the anomaly was by resection of the subaortic stenosis and aortic valvuloplasty was performed with excellent clinical and hemodynamic results.

Plasmid transformation in Bacillus subtilis: effects of insertion of Bacillus subtilis DNA into plasmid pC194

We have constructed a hybrid plasmid pBC1, which consists of plasmid pC194 with an insert of B. subtilis DNA as its HindIII restriction site. This plasmid is stably maintained in B. subtilis. In contrast with pC194, monomeric ccc forms of pBC1 are active in transformation. Transformations with these monomeric molecules of pBC1 have a stringent requirement for recombination proficiency, as defined by recE in the recipient cell. The extent of dependence of the transforming activity of oligomeric pBC1 DNA on the recombination proficiency of the recipient cell decreases with increasing oligomer size. A model of DNA processing during plasmid transformation of B. subtilis is presented.