TBX5 transcription factor regulates cell proliferation during cardiogenesis.

Mutations in human TBX5, a member of the T-box transcription factor gene family, cause congenital cardiac septation defects and isomerism in autosomal dominant Holt-Oram syndrome. To determine the cellular function of TBX5 in cardiogenesis, we overexpressed wild-type and mutant human TBX5 isoforms in vitro and in vivo. TBX5 inhibited cell proliferation of D17 canine osteosarcoma cells and MEQC quail cardiomyocyte-like cells in vitro. Mutagenesis of the 5' end of the T-box but not the 3' end of the T-box abolished this effect. Overexpression of TBX5 in embryonic chick hearts showed that TBX5 inhibits myocardial growth and trabeculation. TBX5 effects in vivo were abolished by Gly80Arg missense mutation of the 5' end of the T-box. PCNA analysis in transgenic chick hearts revealed that TBX5 overexpression does suppress embryonic cardiomyocyte proliferation in vivo. Inhibitory effects of TBX5 on cardiomyocyte proliferation include a noncell autonomous process in vitro and in vivo. TBX5 inhibited proliferation of both nontransgenic cells cocultured with transgenic cells in vitro and nontransgenic cardiomyocytes in transgenic chick hearts with mosaic expression of TBX5 in vivo. Immunohistochemical studies of human embryonic tissues, including hearts, also demonstrated that TBX5 expression is inversely related to cellular proliferation. We propose that TBX5 can act as a cellular arrest signal during vertebrate cardiogenesis and thereby participate in modulation of cardiac growth and development.

Identification and localization of TBX5 transcription factor during human cardiac morphogenesis.

Mutations in the TBX5 transcription factor gene cause human cardiac malformation in Holt-Oram syndrome. To identify and localize TBX5 during cardiac morphogenesis, we performed immunohistochemical studies of TBX5 protein cardiac expression during human embryogenesis. Specific antibody to human TBX5 was generated in rabbits with a TBX5 synthetic peptide and affinity purification of antiserum. Anti-TBX5 was used in immunohistochemical analyses of human cardiac tissue. In embryonic and adult heart, TBX5 is expressed throughout the epicardium and in cardiomyocyte nuclei in myocardium of all four cardiac chambers. Endocardial expression of TBX5 is only present in left ventricle. Asymmetric left-sided transmyocardial gradients of TBX5 protein expression were observed in embryonic but not adult hearts. Human cardiac expression of TBX5 protein correlates with the cardiac manifestations of Holt-Oram syndrome. TBX5 transmyocardial protein gradients may contribute to normal patterning of the human heart during embryogenesis.

A t(2;19)(p13;p13.2) in a giant invasive cardiac lipoma from a patient with multiple lipomatosis.

Cardiac lipomas occur infrequently but account for a significant portion of rare cardiac tumors. Common cutaneous lipomas have previously been associated with rearrangements of chromosome band 12q15, which often disrupt the high-mobility-group protein gene HMGIC. In this report, we describe the cytogenetic analysis of an unusual giant cardiac lipoma that exhibited myocardial invasion in a patient with a history of multiple lipomatosis (cutaneous lipoma, lipomatous gynecomastia, lipomatous hypertrophy of the interatrial septum, and dyslipidemia). Cytogenetic studies of cells derived from the cardiac lipoma demonstrated no abnormalities of chromosome 12, but did reveal a t(2;19)(p13;p13.2). A liposarcoma-derived oncogene (p115-RhoGEF) previously mapped to chromosome 19 and the low-density lipoprotein receptor gene (LDLR) previously mapped to chromosome band 19p13 were evaluated to determine whether they were disrupted by this translocation. Fluorescence in situ hybridization analyses assigned p115-RhoGEF to chromosome 19 in bands q13.2-q13.3 and mapped the LDLR to chromosome arm 19p in segment 13.2, but centromeric to the t(2;19) breakpoint. Thus, these genes are unlikely to be involved in the t(2;19)(p13;p13.2). Further studies of the regions of chromosomes 2 and 19 perturbed by the translocation in this unusual infiltrating cardiac lipoma will identify gene(s) that participate in adipocyte growth and differentiation and may provide insight into syndromes of multiple lipomatosis.

Mice transgenic for monocyte-tropic HIV type 1 produce infectious virus and display plasma viremia: a new in vivo system for studying the postintegration phase of HIV replication.

To generate an in vivo system for investigating the postintegration phase of HIV-1 replication, mouse lines transgenic for a full-length infectious proviral clone of a monocyte-tropic HIV-1 isolate, HIV-1JR-CSF, were constructed. Leukocytes from two independent JR-CSF transgenic mouse lines produced HIV-1 that infected human PBMCs. Plasma viremia was detected in these mice at levels (mean, >60,000 HIV RNA copies/ml) comparable to those reported for HIV-1-infected individuals. The levels of HIV RNA in these mice increased several-fold after either treatment with the superantigen Staphylococcus enterotoxin B or infection with Mycobacterium tuberculosis. Thus, a provirus encoding a monocyte-tropic HIV-1 strain under the control of its LTR expressed as a transgene in mice can proceed through the postintegration replication phase and produce infectious virus. In addition, the presence of plasma viremia that can be monitored by measuring plasma HIV-1 RNA levels permits these mice to be used to study the impact of different interventions on modulating in vivo HIV-1 production. Therefore, these mice provide a novel manipulable system to investigate the in vivo regulation of HIV-1 production by factors that activate the immune system. Furthermore, this murine system should be useful in delineating the role of human-specific factors in modulating HIV-1 replication and investigating the in vivo therapeutic efficacy of agents that target the postintegration stages of HIV-1 replication.

Molecular genetic diagnosis of the familial myxoma syndrome (Carney complex).

We describe an individual in whom molecular genetic testing provided a diagnosis of the Carney complex, an autosomal dominant syndrome comprising cutaneous and cardiac myxomas, spotty pigmentation of the skin, and endocrinopathy. Recently, we localized the Carney complex disease gene to chromosome region 17q2. Our patient was a member of a family segregating the Carney complex, but was not, himself, initially thought to be affected. Haplotype analysis based on genotyping studies with 17q2 microsatellites predicted that this individual was, in fact, affected by Carney complex and was at risk for development of myxomas. Further clinical evaluation and re-review of prior pathologic studies, then, confirmed the DNA-based diagnosis. This report highlights the difficulty in establishing a diagnosis of Carney complex based on clinical and pathologic findings alone, and we suggest that molecular genetic analyses provide an important diagnostic method for this familial myxoma syndrome.

Immunoproliferative small intestinal disease: case report and literature review.

Immunoproliferative small intestinal disease (IPSID) is a subtype of lymphoma of mucosa-associated lymphoid tissue. Notable for a high production of alpha-heavy chains, it is designated alpha-heavy-chain disease. IPSID is a debilitating disease that has a predilection for impoverished populations of developing countries. It has been documented primarily in subjects of Middle Eastern countries and thus was previously referred to as Mediterranean lymphoma. We report the case of a 42-year-old man from Senegal who presented with chronic diarrhea, dehydration, and weight loss. The endoscopic, pathologic, and serologic findings before, during, and after treatment with fludarabine phosphate are presented. We review the literature concerning current concepts on the etiology, pathogenesis, and management of IPSID.

Instructional review improves performance of anesthesia apparatus checkout procedures.

Checkout recommendations for anesthesia apparatus are promoted as a means of improving patient safety. We sought to determine residents' performance of institutional checkout procedures and the degree of their improvement after instructional video review. Twenty-nine residents performing a list of pre-use checkout procedures were videotaped (VT1) prior to randomization into a Control or Test group. The Control group had a second videotaping (VT2), whereas the Test group received instructional review of VT1 prior to VT2. Control and Test subjects then had instructional review of all tapes. A blinded investigator scored all tapes without interacting with any subject. Control and Test video scores were compared at VT1 and VT2 using analysis of variance. Differences were sought between the clinical anesthesia (CA) 1-, 2-, and 3-yr residents. Percent "perfect," "partial," or "no" completion of each criterion was calculated to determine performance and improvement. A low-performance rate of 69% (20.6/30) occurred in VT1, significantly improving to 81% (24.2/30) in the Test group after intervention (P < 0.0021) with significant reductions in criteria that were totally missed. Anesthesia apparatus checkout procedures are improved after intensive training sessions, although high rates of completion are not achieved. This performance deficit may have implications for the ability of physicians to detect anesthesia machine faults.

IL-12 increases resistance of BALB/c mice to Mycobacterium tuberculosis infection.

IL-12, a cytokine produced by macrophages and B cells, has recently been found to exert pleiotropic effects on the immune system. When BALB/c mice, a strain highly susceptible to virulent Mycobacterium tuberculosis infection, were given IL-12 at the initiation of infection with M. tuberculosis, their mean survival time doubled from 58 to 112 days. IL-12-treated mice had diminished bacterial burdens, whereas treatment with exogenous IFN-gamma had no effect on survival or bacterial burden. IL-12 treatment also delayed lung pathology in BALB/c mice. In contrast with the findings in the BALB/c model, IL-12 did not increase survival of M. tuberculosis-infected gko mice, transgenic mice in which the IFN-gamma gene has been disrupted, indicating that IL-12 does not induce protection against tuberculosis in mice in the absence of IFN-gamma.

Tumor necrosis factor-alpha is required in the protective immune response against Mycobacterium tuberculosis in mice.

Understanding the immunological mechanisms of protection and pathogenesis in tuberculosis remains problematic. We have examined the extent to which tumor necrosis factor-alpha (TNF alpha) contributes to this disease using murine models in which the action of TNF alpha is inhibited. TNF alpha was neutralized in vivo by monoclonal antibody; in addition, a mouse strain with a disruption in the gene for the 55 kDa TNF receptor was used. The data from both models established that TNF alpha and the 55 kDa TNF receptor are essential for protection against tuberculosis in mice, and for reactive nitrogen production by macrophages early in infection. Granulomas were formed in equal numbers in control and experimental mice, but necrosis was observed only in mice deficient in TNF alpha or TNF receptor. TNF alpha and the 55 kDa TNF receptor are necessary conditions for protection against murine M. tuberculosis infection, but are not solely responsible for the tissue damage observed.

Divergent effects of chronic HIV-1 infection on human thymocyte maturation in SCID-hu mice.

We have recently developed a modified SCID-hu mouse model in which the implanted human thymus and liver (hu-thy/liv) and human peripheral T cells become infected with HIV-1 after i.p. inoculation. By using this model, we evaluated the effect of HIV-1 infection on thymic maturation and observed that different HIV-1 strains had divergent effects of thymic maturation. Although minimal effects on continued thymopoiesis in the hu-thy/liv implant were observed after chronic infection with two primary patient isolates, HIV-1(28) and HIV-1(59), and with HIV-1ADA, HIV-1Ba-L, HIV-1JR-CSF, HIV-1JR-FL, and HIV-1SF162, significant thymocyte depletion was detected after infection with HIV-1IIIB and HIV-1RF. Thus, the effect of HIV-1 infection on thymocyte maturation may depend upon the strain of HIV-1 infecting the thymus. Despite the minimal effects on thymopoiesis observed in the hu-thy/liv implanted in SCID-hu mice 6 mo after infection with HIV-1(28), significant changes were seen in the human T cell population circulating in the peripheral blood of these mice. These changes ranged from an inversion of the CD4/CD8 ratio of peripheral human T cells in some SCID-hu mice to the almost complete depletion of peripheral human T cells observed in other SCID-hu mice. Because these effects were associated with the detection of HIV-1 infection of the peripheral human T cells, these modified SCID-hu mice should prove to be a valuable model for investigating the effects of chronic HIV-1 infection on the peripheral human T cell population.

The concurrent maturation of mouse and human thymocytes in human fetal thymus implanted in NIH-beige-nude-xid mice is associated with the reconstitution of the murine immune system.

To determine whether the human thymus provides an environment for the maturation of murine T cells, human fetal thymus and liver (hu-thy/liv) were implanted into congenitally athymic NIH-beige-nude-xid (BNX) mice or C.B-17 scid/scid (SCID) mice. 3 mo after implantation, in contrast to the hu-thy/liv implant in SCID mice, which was populated only with human CD4/CD8 single- and double-positive thymocytes, the hu-thy/liv implant in BNX mice contained a chimeric population of human and mouse CD4/CD8 single- and double-positive thymocytes. Immunohistochemical staining of the hu-thy/liv implant in BNX mice indicated that the population of double-positive mouse thymocytes was localized to discrete areas of the human fetal thymus. Quantitative improvements in mouse T cell and immunoglobulin (Ig) G parameters were observed after grafting of the human fetal thymus and liver tissue into BNX mice. In addition, in contrast to the nonimplanted BNX mice, the implanted BNX mice were capable of mounting a keyhole limpet hemocyanin-specific IgG response and their peripheral T cells were responsive to stimulation with mitogens and antibodies directed to the T cell receptor. Furthermore, after in vivo priming, T cells present in lymph nodes of the implanted BNX mice were capable of mounting an antigen-induced in vitro T cell-dependent proliferative response. Thus, concurrent with the continued maturation of human T cells, murine T cells differentiated within the human fetal thymus implanted in the BNX mice and mediated the phenotypic and functional reconstitution of the murine immune system. Mice with a reconstituted immune system that contain a human thymic implant that is infectible with human immunodeficiency virus (HIV) should prove useful in the investigation of T cell maturation in the thymus and in the evaluation of potential HIV vaccines.

Major histocompatibility complex class I-restricted T cells are required for resistance to Mycobacterium tuberculosis infection.

Mice with a targeted disruption in the beta 2-microglobulin (beta 2m) gene, which lack major histocompatibility complex class I molecules and consequently fail to develop functional CD8 T cells, provided a useful model for assessing the role of class I-restricted T cells in resistance to infection with virulent Mycobacterium tuberculosis. Of mutant beta 2m-/-mice infected with virulent 10(6) M. tuberculosis, 70% were dead or moribund after 6 weeks, while all control mice expressing the beta 2m gene remained alive for > 20 weeks. Granuloma formation occurred in mutant and control mice, but far greater numbers of tubercle bacilli were present in the lungs of mutant mice than in controls, and caseating necrosis was seen only in beta 2m-/-lungs. In contrast, no differences were seen in the course of infection of mutant and control mice with an avirulent vaccine strain, bacille Calmette-Guérin (BCG). Immunization with BCG vaccine prolonged survival of beta 2m-/-mice after challenge with M. tuberculosis for 4 weeks but did not protect them from death. These data indicate that functional CD8 T cells, and possibly T cells bearing gamma delta antigen receptor, are a necessary component of a protective immune response to M. tuberculosis in mice.

M-cholinergic receptors in mice B-lymphocytes in the process of immune response.

With the help of the radioactive blocker of M-cholinergic receptors 3H-Quinuclidinil benzylate their quantity was determined on B-lymphocytes of CBA mice spleen. On the 3rd and 4th day after immunization with ovalbumin the number of M-cholinergic receptors became somewhat higher. The specific antigen decreased the expression of M-cholinergic receptors on B-lymphocytes most of all on the 4th day after immunization, and did not have any effect on this indicator in control animals. This testifies to the possibility of steric interaction between the antigen binding immunoglobulin and M-cholinergic receptors on B-lymphocytes during the immune reaction.

A method for preparing and handling cross-sections from early chick embryos for scanning electron microscopy.

A method is described for processing multiple cross-sections from early chick embryos for scanning electron microscopy. Embryos are cut through the desired regions. Sections are affixed to a coverslip with Duco cement and critical point dried by Freon 13 or liquid CO2. This method provides a reliable means for preparing multiple cross-sections from single embryos and eliminates the need for direct handling of brittle tissues after drying.

Scanning electron microscopy of primordial germ cells in early chick embryos.

Primordial germ cells (PGCs) of the early chick embryo were examined using scanning electron microscopy. Temporal changes in the form and distribution of surface projections were found to be correlated with migratory phases of PGCs. Non-migrating PGCs were spherical to ovoid with relatively smooth surfaces. Their transition to the migratory phase was first evidenced by a burst of membrane activity. Migrating PGCs became somewhat flattened against the underlying hypoblast (which serves as the substratum for their migration) and exhibited blebs and lamellar processes. The lamellar processes were most prominent at the leading edges of actively migrating PGCs. Overall results of the present study indicates that PGCs found in the germinal crescent area of early chick embryos actively migrate on the dorsal surface of the hypoblast towards posterior embryonic regions.