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Biomedical subjects

J A Kant

Publications and source records attributed to J A Kant.

At least 37 records · Page 2Linked to original sources
PubMed1995

Molecular diagnosis of cystic fibrosis.

The clinical and pathologic features of patients with cystic fibrosis are summarized, and generalized genotype or phenotype correlations are discussed in this article. Incorporation of modern molecular biologic techniques into a rapid, cost-efficient, and specific diagnostic laboratory test is outlined. The protocol for the multiplex polymerase chain reaction detection of five common cystic fibrosis transmembrane conductance regulator (CFTR) mutations by ASO hybridization is detailed. Neonatal screening and issues involved in the genetic counseling of families at risk for cystic fibrosis are presented. Recommendations for molecular diagnostic testing in cystic fibrosis are made.

Base Sequence↗
PubMed1994

Biologic and therapeutic significance of MYB expression in human melanoma.

We investigated the therapeutic potential of employing antisense oligodeoxynucleotides to target the disruption of MYB, a gene which has been postulated to play a pathogenetic role in cutaneous melanoma. We found that MYB was expressed at low levels in several human melanoma cell lines. Also, growth of representative lines in vitro was inhibited in a dose- and sequence-dependent manner by targeting the MYB gene with unmodified or phosphorothioate-modified antisense oligodeoxynucleotides. Inhibition of cell growth correlated with specific decrease of MYB mRNA. In SCID mice bearing human melanoma tumors, infusion of MYB antisense transiently suppressed MYB gene expression but effected long-term growth suppression of transplanted tumor cells. Toxicity of the oligodeoxynucleotides was minimal in mice, even when targeted to the murine Myb gene. These results suggest that the MYB gene may play an important, though undefined, role in the growth of at least some human melanomas. Inhibition of MYB expression might be of use in the treatment of this disease.

Animals↗
PubMed1994

Plaque-associated neuronal proteins: a recurrent motif in neuritic amyloid deposits throughout diverse cortical areas of the Alzheimer's disease brain.

Diffuse and neuritic plaques are sites of accumulation of beta-amyloid peptides (A beta) in the brains of Alzheimer's disease (AD) patients. Although amyloid fibrils are formed from A beta, the contribution of other plaque-associated proteins and peptides to the pathogenesis of AD amyloidosis is unknown. To pursue this issue, we sought to identify proteins and peptides that were consistently associated with neuritic plaques in six different cortical areas of AD and control brains. We accomplished this by using quantitative, single and double label immunohistochemistry and a panel of antibodies to proteins or peptides that are known to be associated with neuritic plaques in the AD hippocampus. Our data showed that the molecular composition of neuritic plaques in association, limbic, sensory, and motor cortex was similar regardless of the type of cortex in which they were found or the apolipoprotein E genotype of the patient. Further, proteins and peptides associated with neuritic plaques in the cortical areas of the AD brain studied here were similar to those found in neuritic plaques of the AD hippocampus. Specifically, in addition to A beta 1-40 and A beta 1-42, these plaques contained immunoreactivity for other domains in A beta precursor proteins, neurofilament and tau proteins, as well as phosphotyrosine residues. We conclude that the recurrent association of a distinct group of neuronal and other proteins and peptides with neuritic plaques suggests that these plaque-associated components play a mechanistic role in the pathogenesis of amyloidosis in AD.

Aged↗
PubMed1994

Richter's syndrome associated with loss of response to transforming growth factor-beta.

A patient with chronic lymphocytic leukemia developed a large cell lymphoma apparently derived from the same neoplastic B-cell clone (Richter's syndrome). At the same time, mitogen-stimulated proliferation of the patient's circulating leukemic B-cells was no longer inhibited by the regulatory cytokine transforming growth factor-beta (TGF-beta), suggesting that such loss of inhibition might be contributing to the clinical and biological progression of the disease.

Aged↗
PubMed1993

Variability in the Michelin tire syndrome. A child with multiple anomalies, smooth muscle hamartoma, and familial paracentric inversion of chromosome 7q.

We describe a 2 1/2-year-old boy who has hirsutism and ringed creases of the extremities associated with an underlying smooth muscle hamartoma. Cutaneous findings in this child resemble those in other reports of the "Michelin tire syndrome." Histologic examination showed numerous well-demarcated fascicles of smooth muscle cells randomly distributed at all levels of the reticular dermis with haphazard orientation. These cells were immunoreactive with desmin, which confirmed their smooth muscle nature. In addition to the skin changes, this child has multiple unusual phenotypic anomalies, some of which have not previously been associated with the Michelin tire syndrome. These include distinctive facial dysmorphia, submucous cleft palate, lateral clefting of the mouth, genital, and dental anomalies. He also developed seizures at age 2 1/2 years and has moderate developmental delay. The patient and his mother have apparently identical paracentric inversions of the long arm of chromosome 7 (46,XY,inv(7)(q22q31.3) with no detectable loss or gain of either chromosomal material or DNA markers from the cystic fibrosis (CFTR) region. The relevance, if any, of the karyotypic abnormality to the phenotype in this child is discussed.

Abnormalities, Multiple↗
PubMed1992

In vivo treatment of human leukemia in a scid mouse model with c-myb antisense oligodeoxynucleotides.

The c-myb protooncogene encodes proteins that are critical for hematopoietic cell proliferation and development. Disrupting c-myb function might, therefore, prove an effective therapeutic strategy for controlling leukemic cell growth. Antisense oligodeoxynucleotides have been utilized for this purpose in vitro, but their in vivo efficacy has not been reported. We therefore established human leukemia-scid mouse chimeras with K562 cells and treated diseased animals with phosphorothioate-modified antisense oligodeoxynucleotides. K562 cells express the c-myb protooncogene, which served as the target for the antisense DNA. They also express the tumor-specific bcr-abl oncogene that was utilized to track the human cells in the mouse host. Once circulating leukemic blast cells had been detected, the survival of untreated control mice was 6 +/- 3 days (mean +/- SD). The survival of animals treated for 7 or 14 days with either sense or scrambled-sequence c-myb oligodeoxynucleotides was not statistically different from the control animals. In distinct contrast, animals treated for similar lengths of time with antisense c-myb oligodeoxynucleotides survived at least 3.5 times longer than the various control animals. In addition, animals receiving antisense c-myb DNA had significantly less disease at the two sites most frequently manifesting leukemic cell infiltration, the central nervous system and the ovary. These results suggest that phosphorothioate-modified antisense DNA may be efficacious for the treatment of human leukemia in vivo, and by analogy, for the treatment of other human neoplasias.

Animals↗
PubMed1992

CD28-stimulated IL-2 gene expression in Jurkat T cells occurs in part transcriptionally and is cyclosporine-A sensitive.

CD28 is a glycoprotein expressed as a homodimer on the surface of a major subset of human T cells. Previous studies have shown that proliferation of peripheral blood T cells involving the CD28 pathway is associated with cyclosporine A (CsA) resistant IL-2 gene expression. This pathway was shown to specifically regulate the stability of mRNA for several lymphokines including IL-2. We have investigated the expression of the IL-2 gene in the Jurkat cell line, J32 clone, induced by CD28 stimulation. Cross-linked anti-CD28 mAb alone was sufficient to induce the release of small amounts of IL-2 (256 U/ml). The CD28-mediated IL-2 release was enhanced with simultaneous engagement of CD28 and CD2 or CD28 and CD3 molecules. Hybrid constructs in which the human IL-2 gene 5' flanking region drives luciferase expression (pIL-2-Luc) were used to help delineate whether the CD28 pathway activates the IL-2 gene transcriptionally. Costimulation of cells with CD28 mAb and either PHA or CD2 mAb induced a 20- to 90-fold increase in the expression of pIL-2-Luc as well as IL-2 release. Costimulation with CD28 mAb plus PMA gave only five- to sevenfold increase in enhancer activity. In contrast, no enhancer activity was detected after stimulation with CD28 or CD2 mAb alone. Both IL-2 release and pIL-2-Luc activity were inhibited by CsA in J32 cells. The degree of CsA inhibition was concentration dependent and was similar in cells stimulated with either CD28 mAb or CD3 mAb. Maximum inhibition was achieved with 1 microgram/ml of CsA. Studies with internal deletion mutations of the IL-2 gene 5' flanking sequence revealed that as with stimulation through the TCR pathway, the CD28 pathway requires 5' flanking sequences located within 500 bp of the transcription start site. These results are the first direct evidence that the triggering of CD28 molecule is sufficient to induce IL-2 release in J32 cells. Furthermore these studies strongly indicate that IL-2 gene expression induced by CD28 stimulation occurs, in part, transcriptionally and is CsA sensitive in these cells.

Antigens, CD↗
PubMed1992

Frequent incidence of somatic mutations in translocated BCL2 oncogenes of non-Hodgkin's lymphomas.

The majority of non-Hodgkin's B-cell lymphomas contain a t(14;18) translocation that places the bc12 gene into juxtaposition with the transcriptically active Ig heavy-chain locus, thus deregulating the expression of this proto-oncogene. The bc12 gene product is a membrane-associated mitochondrial protein that regulates cell survival through unknown mechanisms. Although overproduction of the normal protein appears sufficient for conferring a selective growth or survival advantage to B cells, point mutations that alter the coding region of translocated bc12 genes have been described previously by others in a lymphoma cell line. However, it is not known whether somatic mutations that alter BCL2 proteins occur in vivo or whether they result from chemotherapy or arise through other mechanisms. For these reasons, we obtained DNA from the t(14;18)-containing tumors of five patients who had not undergone treatment for their disease, and used a polymerase chain reaction (PCR)-mismatch technique for rapid identification of point mutations in a portion of the bc12 open reading frame (ORF) corresponding to the first 131 aminoacids (aa) of the 239 aa p26 BCL2 protein. DNAs from two t(14;18)-containing cell lines were also analyzed. Point mutations in this region of the bc12 gene ORF were detected in three of five patients' tumors and in both cell lines. PCR-mismatch analysis of bc12 in cell lines and non-Hodgkin's lymphoma cases that lacked the t(14;18) translocation was negative, thus establishing the specificity of these results. DNA sequencing determined that these mutations are predicted to produce aa substitutions in the BCL2 proteins of two of the primary tumors and one of the cell lines. Interestingly, two of the patients contained an identical C----T transition that resulted in a nonconservative aa substitution (proline----serine) at position 59 of the BCL2 protein. Further analysis excluded the possibility that these mutations represented hereditary polymorphisms or PCR artifacts. A cluster of four point mutations within the translocation + bc12 allele of one patient had hallmarks of the somatic hypermutation mechanism that is associated with Ig genes and that contributes to antibody diversity. Because of the region of the bcl2 gene analyzed in these t(14;18) translocations is located nearly 300 kbp from the Ig heavy-chain locus, our data suggest that the Ig gene somatic hypermutation mechanism can act over extreme distances of DNA. It remains to be established whether these somatic mutations that alter BCL2 proteins influence the pathobiology of nonHodgkin's lymphomas.

Base Sequence↗
PubMed1992

Coincident Kaposi sarcoma and T-cell lymphoma in a patient with the Wiskott-Aldrich syndrome.

A 24 year old male with a history of eczema, recurrent mild infections, and thrombocytopenia consistent with the Wiskott-Aldrich syndrome (WAS) presented with a mediastinal mass, generalized lymphadenopathy, splenomegaly, and severe thrombocytopenia. Studies of immune function including immunoglobulin levels and T-cell subsets were normal. Furthermore, his T lymphocytes proliferated normally in response to phytohemagglutinin, concanavalin A, and the combination of neuraminidase/galactose oxidase. However, their proliferative responses to anti-CD43 antibody and periodate were diminished, consistent with the clinical diagnosis of WAS. An initial inguinal lymph node biopsy surprisingly revealed Kaposi sarcoma. However, following splenectomy to increase the platelet count, biopsy of the mediastinal mass revealed T-cell large cell lymphoma. Studies of biopsied tissue for the presence of Epstein-Barr virus and cytomegalovirus were negative, as were studies of blood, including the polymerase chain reaction, for the presence of the human immunodeficiency virus (HIV). This is the first report of Kaposi sarcoma arising in a patient with a congenital immunodeficiency syndrome. Although Kaposi sarcoma can arise in the face of the severe immunosuppression that follows allograft transplantation and in patients infected with HIV, we postulate that longevity in the face of mild immunosuppression was the major factor in the development of Kaposi sarcoma in this patient.

Adult↗
PubMed1992

Marrow fibrosis associated with a Philadelphia chromosome.

Three patients had marked marrow fibrosis and an apparent Philadelphia (Ph) chromosome. Hematologic, cytogenetic, and molecular studies demonstrated the heterogeneity of such cases, including the first example of clinically typical myelofibrosis (MF) associated with a bcr gene rearrangement characteristic of chronic myelogenous leukemia (CML).

Bone Marrow↗
PubMed1992

In situ hybridization for Epstein-Barr virus NotI repeats in posttransplant lymphoproliferative disorder.

Epstein-Barr Virus-associated posttransplant lymphoproliferative disorder (PTLD) is a serious complication of solid organ transplantation. In PTLD, B-cell expansions range from reactive hyperplasias to large cell lymphomas and are often associated with active Epstein-Barr virus (EBV) infection. The lymphoproliferations may infiltrate transplant allografts and therefore may need to be distinguished from acute cellular rejection (ACR). A total of 36 tissue specimens from 11 transplant patients (six kidney, two heart, three liver) with PTLD were studied for EBV content by automated in situ hybridization (ISH) on formalin-fixed or Bouin's-fixed, paraffin-embedded tissue using a synthetic 3' terminally biotin-labeled oligonucleotide DNA probe from the EBV NotI tandem repeat region. The NotI repeat is abundantly transcribed during productive EBV infection and may encode an EBV early antigen. EBV serologies from the 11 patients showed seven primary acute infections and one acute reactivation. Two serologic studies indicated infection of indeterminant onset, and serology was not performed on one patient. Histologically, seven patients presented with polymorphous infiltrates in transplant allograft biopsies, three of which progressed to disseminated monomorphous cell populations and death within 3 to 6 wk. Tissues examined by ISH from all 11 patients showed nuclear staining for EBV in the atypical lymphoid infiltrates (34/36 specimens). The nuclear signal ranged from a stippled pattern of positivity to homogeneous nuclear staining and was localized predominantly in follicular center cells and immunoblasts, although some smaller lymphocytes also contained the viral genome. ISHs performed on 31 allograft biopsies with ACR from 24 transplant patients (six kidney, five heart, 13 liver) without clinical evidence of PTLD and with serological evidence of past EBV infection were negative for the virus. Cell lines containing EBV in the productive state (EB3 and P3HR1) were positive with ISH for NotI, while a latently infected cell line (Raji) was negative. These data indicate that ISH with the NotI probe identifies amplified genome in EBV infections and is useful in discriminating the atypical infiltrate of EBV-associated PTLD from that seen in ACR.

Adolescent↗
PubMed1991

Identification of a zinc finger protein that inhibits IL-2 gene expression.

Transient activation of the interleukin-2 (IL-2) gene after antigen recognition by T lymphocytes is crucial for subsequent T cell proliferation and differentiation. Several IL-2 gene regulatory elements and binding factors necessary for activation of the IL-2 gene have been defined. However, little is known about negative regulation of IL-2 expression, which is likely to be important in the rapid shut-off of IL-2 transcription. A nucleotide sequence element (NRE-A) that negatively regulates IL-2 expression has been identified within the IL-2 gene. T cell nuclear extracts contained an NRE-A binding activity. A complementary DNA was isolated that encodes a zinc finger-containing protein that suppressed IL-2 gene expression. The observation of negative regulation of the immunoglobulin heavy chain gene enhancer by an element similar to NRE-A suggests that related proteins may regulate multiple immune response genes.

Amino Acid Sequence↗
PubMed1991

Two-temperature PCR and heteroduplex detection: application to rapid cystic fibrosis screening.

We describe a rapid two-temperature PCR protocol for amplification of genomic DNA applied to the region of the most common mutation (delta F508) of the cystic fibrosis gene. Amplification products are detected as homo- or heteroduplexes on polyacrylamide gels as previously described. Data using two-temperature PCR show complete concordance with allele-specific hybridization after classical three-temperature PCR in 105 normal, carrier and affected individuals. Clinical application is demonstrated in a family which was uninformative by traditional RFLP linkage analysis. Two-temperature PCR may offer advantages of speed and specificity over three-temperature PCR in many clinical and research applications.

Base Sequence↗
PubMed1991

Absence of t(14;18) major and minor breakpoints and of Bcl-2 protein overproduction in Reed-Sternberg cells of Hodgkin's disease.

The t(14;18) translocation, found in most human follicular non-Hodgkin's lymphomas (NHLs), juxtaposes the Bcl-2 oncogene at 18q21 with the immunoglobulin heavy chain locus at 14q32. As a result, the Bcl-2 protein is markedly overproduced. Most of the breakpoints on chromosome 18 cluster at one of two sites, the major breakpoint region (mbr) and the minor cluster region (mcr). Recently, others used the polymerase chain reaction (PCR) to detect the t(14;18) mbr in 32% of specimens diagnosed as Hodgkin's disease (HD). In an attempt to confirm and extend those observations the authors used PCR to assay for both the mbr and mcr in HD specimens diagnosed at their institution and examined the specimens for Bcl-2 overproduction. The authors subjected the DNAs from 28 well-characterized HD tumors of 26 patients to PCR analyses using primers specific for the t(14;18) mbr and mcr breakpoints. Based on various PCR controls, the authors ascertained that 26 of the 28 specimens contained amplifiable template DNA. Southern blotting of the amplification products showed that none of the 26 HD DNAs had detectable t(14;18) mbr or mcr breakpoints. By admixing small amounts of t(14;18)-bearing NHL DNA with HD DNA samples, the authors directly demonstrated that the sensitivity of the PCR assays was adequate for the molecular detection of t(14;18)-bearing cells at a frequency comparable to that of Reed-Sternberg cells and their variants in HD. Immunohistochemical studies employing a highly specific anti-Bcl-2 antiserum under conditions optimized to detect t(14;18)-mediated overexpression of the Bcl-2 gene showed that the Reed-Sternberg cells and variants in all 19 HD tumors examined were negative for Bcl-2 immunostaining. In conclusion, the PCR and immunohistochemical data provided evidence that the t(14;18) translocation was not involved in the pathogenesis of the HD cases.

Chromosomes, Human, Pair 18↗
PubMed1990

Clonal analysis of solitary follicular nodules in the thyroid.

Accumulated data using functional, morphologic, and histochemical analysis suggests that follicular proliferations in the thyroid include polyclonal and monoclonal patterns with encapsulated follicular adenomas most frequently monoclonal, and other nodules generally polyclonal. However, examples of polyclonal carcinomas or adenomas raise the possibility that histologically similar lesions may arise through different pathogenetic mechanisms. The authors have performed a clonal analysis of histologically benign and malignant thyroid nodules in seven women using HPRT (hypoxanthine phosphoribosyl transferase) and PGK (phosphoglycerate kinase) restriction fragment length polymorphisms (RFLPs) on the X chromosome. These RFLPs used in concert with methylation-sensitive restriction endonucleases HpaII and HhaI permit distinction of active and inactive X chromosomes. DNA from a multinodular goiter showed equal sensitivity of both X chromosome RFLP alleles to a methylation-sensitive restriction endonuclease, consistent with a polyclonal origin. In contrast, three solitary follicular nodules and three carcinomas displayed predominant sensitivity of a single RFLP allele, consistent with a monoclonal origin. Although further detailed studies will be necessary to understand polyclonal origins reported for some adenomas, our data from a limited number of samples supports a predominantly monoclonal origin, and possible neoplastic pathogenesis, for many solitary adenomatous nodules in the thyroid.

Adenoma↗