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Biomedical subjects

J Leavitt

Publications and source records attributed to J Leavitt.

At least 55 records · Page 3Linked to original sources
PubMed1984

Neoplastic human fibroblast proteins are related to epidermal growth factor precursor.

We report the amino acid composition of two polypeptides, p788 and p789. These polypeptides are reliable markers for neoplastic transformation in human fibroblasts. Their compositions are unusually rich in cysteine and serine. Because the recently reported amino acid sequence of mouse epidermal growth factor precursor (prepro-EGF) is also rich in those two amino acids and because the role of p788 and p789 as markers for neoplastic transformation is consistent with the fact that epidermal growth factor has been shown to play some role in transformation, we investigated the hypothesis that p788 and p789 are related to prepro-EGF. We compared the amino acid composition of p788 with that of all possible interior domains of prepro-EGF of appropriate length. We found that the composition of p788 is remarkably similar to that of residues 630-880 of prepro-EGF. The similarity is sufficiently strong to support the conclusion that it reflects amino acid sequence homology.

Amino Acid Sequence↗
PubMed1984

Limitations of the brief form of the Halstead Category Test.

This study attempted to cross-validate a short form of the Category Test (subtests 1-4) first used by Calsyn, O'Leary, and Chaney (1980). One hundred and sixty-eight subjects were assigned to one of six neurological categories, and Category Test scores predicted (via regression analysis) from performance on the short form were compared with actual scores obtained from the original long form. While there was a high correlation (r = .91) between the two sets of scores, a large number of normal subjects were misclassified as brain-damaged. Additionally, subjects with focal right lesions could not be differentiated from normals either on the basis of error scores predicted from short form performance or the absolute number of errors made on subtests 1-4. These results suggested that shortening the Category Test may limit its applicability with certain populations.

Adult↗
PubMed1984

Molecular cloning and characterization of mutant and wild-type human beta-actin genes.

There are more than 20 beta-actin-specific sequences in the human genome, many of which are pseudogenes. To facilitate the isolation of potentially functional beta-actin genes, we used the new method of B. Seed (Nucleic Acids Res. 11:2427-2446, 1983) for selecting genomic clones by homologous recombination. A derivative of the pi VX miniplasmid, pi AN7 beta 1, was constructed by insertion of the 600-base-pair 3' untranslated region of the beta-actin mRNA expressed in human fibroblasts. Five clones containing beta-actin sequences were selected from an amplified human fetal gene library by homologous recombination between library phage and the miniplasmid. One of these clones contained a complete beta-actin gene with a coding sequence identical to that determined for the mRNA of human fibroblasts. A DNA fragment consisting of mostly intervening sequences from this gene was then used to identify 13 independent recombinant copies of the analogous gene from two specially constructed gene libraries, each containing one of the two types of mutant beta-actin genes found in a line of neoplastic human fibroblasts. The amino acid and nucleotide sequences encoded by the unmutated gene predict that a guanine-to-adenine transition is responsible for the glycine-to-aspartic acid mutation at codon 244 and would also result in the loss of a HaeIII site. Detection of this HaeIII polymorphism among the fibroblast-derived clones verified the identity of the beta-actin gene expressed in human fibroblasts.

Actins↗
PubMed1984

Identification of polypeptides on two-dimensional electrophoresis gels by amino acid composition.

We present a method that can, in principle, provide tentative identification of a substantial proportion of the polypeptides resolvable on a given two-dimensional electrophoresis gel. Computerized microdensitometry of autoradiograms from 20 gels labeled in turn with each of the 20 common amino acids provides the data for simultaneously measuring the amino acid composition of all polypeptides of interest on the gel. These compositions are then compared with computer data bases of known protein compositions. Similarity between a known and an unknown polypeptide with comparable molecular mass indicates a potential identification, which can then be confirmed with conventional techniques. We illustrate this technique by applying it to the identification of proteins in a transformed human cell line (HuT-14).

Amino Acids↗
PubMed1983

A randomized prospective study of vindesine versus doxorubicin and cyclophosphamide in the treatment of epidermoid lung cancer.

A randomized prospective study was conducted comparing vindesine (VDS) with doxorubicin and cyclophosphamide (D/C) in the treatment of advanced squamous cell carcinoma of the lung. No patient had a complete response. Seven of 28 (25%) patients had partial response (PR) to VDS while one of 19 (5%) had a PR to D/C (P less than 0.08). Adding PR plus minor response (MR), ten of 28 (36%) patients responded to VDS while two of 19 (11%) responded to D/C (P less than 0.05). Median survival was improved among patients showing PR and MR over those not responding (P less than 0.05). This study concludes, VDS is an active agent in the treatment of squamous cell carcinoma of the lung and should be considered for combination chemotherapy and adjuvant trials. VDS toxicity appears acceptable with six weekly doses of 3 mg/m2. The benefit of a maintenance schedule could not be demonstrated.

Adult↗
PubMed1983

Tumorigenic potential of human fibroblasts as a function of ability to express a novel form of influenza A nucleocapsid protein.

Influenza A virus released by infected diploid human fibroblasts contains nearly equal amounts of two electrophoretic forms of the viral nucleocapsid protein NP (NP1 and NP2). Pulse-chase labeling and tryptic fingerprinting of NP1 and NP2 have suggested that NP1 is converted to NP2 late in the lytic cycle as a consequence of a post-translational proteolytic event. Within normal fibroblasts only one cellular form of NP (NP1) is detectable indicating that synthesis of NP2 is associated only with the release of virus from these normal cells. Four neoplastic substrains derived from the normal fibroblast strain exhibit varying degrees of neoplastic character in vitro and tumorigenic potential in athymic mice. This family of human fibroblast strains can be divided into three orders of tumorigenic potential: (i) normal and non-tumorigenic; (ii) neoplastic but rarely tumorigenic; and (iii) neoplastic and always tumorigenic. In contrast to the parental non-tumorigenic cell type which exhibits no cellular NP2, the two classes of neoplastic fibroblasts exhibit NP2 at abundance levels which appear to reflect the two elevated degrees of tumorigenic potential. Thus, assessment of influenza A gene expression may have detected a novel cellular protease which is incrementally elevated along with tumorigenic potential of this human fibroblast family.

Capsid↗
PubMed1983

Skin tags: a cutaneous marker for colonic polyps.

The relation between adenomatous colonic polyps and the development of adenocarcinoma of the colon is well established. An association between skin tags and colonic polyps in patients with acromegaly has also been reported. To ascertain if skin tags are a cutaneous marker for colonic polyps independent of the presence of acromegaly, 100 men referred for colonoscopy were studied. Forty-six patients had colonic polyps and 37 also had skin tags; the correlation was highly significant (p less than 0.005). The sensitivity and specificity of the presence of skin tags serving as a cutaneous marker for adenomatous colonic polyps were both greater than 75%. Thus, at least in this population, skin tags may serve as a means for identifying patients at increased risk for having colonic polyps.

Colonic Neoplasms↗
PubMed1982

Changes in gene expression accompanying chemically-induced malignant transformation of human fibroblasts.

The modulation of gene expression accompanying neoplastic transformation has been assessed by computerized microdensitometry or autoradiographic patterns of [35S]methionine labeled polypeptides separated by two-dimensional polyacrylamide gel electrophoresis. Nearly 1000 polypeptide species of parent diploid human fibroblasts (KD strain) and clonally-derived malignant fibroblasts (HUT-14 strain) were compared. HUT-14 fibroblasts express a mutation in one of the two functional beta-actin genes and possess properties that distinguish them as neoplastic cells. Of the 700 more abundant polypeptides measured, 13 were lost and 14 were gained following this neoplastic transformation. It is estimated that less than or equal to 2% of the genes expressing abundant polypeptides were either activated or shut off, but at least 32% were modulated quantitatively as a consequence of this neoplastic transformation. Classes of "highly variable" and "marginally variable" polypeptides were assigned. Among the "highly variable" polypeptides, two related species barely detectable in KD parental cells were synthesized at a 25-31-fold higher rate in the transformed cells, and the cell-associated and extracellular matrix forms of fibronectin were each diminished by greater than 90%. Principles emerging from this study may form a basis for interpretation of the role of individual genes in the expression of neoplastic characteristics of HUT-14 cells.

Autoradiography↗
PubMed1982

Actin mutations in a human fibroblast model for carcinogenesis.

We assessed the modulation of gene expression accompanying neoplastic transformation by computerized microdensitometry of autoradiographic patterns of [35S]-methionine-labeled polypeptides separated by two-dimensional polyacrylamide gel electrophoresis. Nearly 1000 polypeptide species of parent diploid human fibroblasts (KD strain) and clonally-derived malignant fibroblasts (HUT-14 strain) were compared. We found that the neoplastic HUT-14 fibroblasts express a mutation in one of the two functional beta-actin genes. In addition, of the 700 more-abundant polypeptides measured, 13 were lost and 14 new ones gained after this neoplastic transformation. We estimate that although 2% of fewer of the genes expressing abundant polypeptides were either activated or shut off, at least 32% were modulated quantitatively. A substrain of HUT-14--HUT-14T--shows increased tumorigenicity, producing larger, faster-growing fibrosarcomas in the nude mouse than does the present parent HUT-14 strain, and with fewer inoculated cells. This increase in tumorigenicity is accompanied by three subsequent changes in the mutant beta-actin polypeptide expression. A more variant mutant actin species is synthesized in HUT-14T, which differs from the original mutant polypeptide by (i) one additional negative net charge, (ii) a short half-life in the cell, (iii) a greatly diminished ability to incorporate into the detergent-resistant cytoskeleton, (iv) a decrease in affinity for deoxyribonuclease I (EC 3.1.21.1), and (v) a faster rate of synthesis. Our results suggest that a second-site mutation in the mutant beta-actin of HUT-14 was selected for during a subcloning step in the presence of 6-thioguanine before derivation of the HUT-14T substrain. This apparent mutation and two subsequent defective beta-actin expressions are accompanied by incremental increases of malignant potential.

Actins↗
PubMed1982

Vindesine (VDS) monochemotherapy for non-small cell lung cancer: a report of 45 cases.

Fifty-three patients with non-small cell lung cancer were treated with vindesine. Of the 45 evaluable patients, 11 (24%) had a partial response. Responses were all evident within 6 weeks. Median duration of response was 8 weeks from documentation. Median survival was not improved significantly among responders (P less than 0.10, two-tailed test of significance). The most frequent toxic effect was leukopenia. The most troublesome toxic effect was peripheral neuropathy, with patients greater than 60 years old experiencing this more frequently.

Adenocarcinoma↗
PubMed1981

Mutated beta-actin gene: coexpression with an unmutated allele in a chemically transformed human fibroblast cell line.

By in vitro translation, we have identified the mRNA species that codes for a novel actin polypeptide (Ax-actin) in the chemically transformed human fibroblast line HuT-14. The relatedness of the coding sequences of the Ax- and beta-actin genes is indicated by our finding that pcDd actin ITL-I DNA, a recombinant plasmid DNA that contains a DNA sequence complementary to actin mRNA of Dictyostelium discoideum, hybridizes both the Ax-actin mRNA and the beta-actin mRNA but not the gamma-actin mRNA. In contrast, pcHa-1 DNA, a recombinant plasmid constructed by cloning a DNA sequence complementary to human actin mRNA from HuT-14 cells into pBR322, hybridized to all three mRNA species. In addition, no difference was observed between Ax- and beta-actin mRNAs when their molecular size was determined either by sucrose density gradient sedimentation or by methyl mercury agarose gel electrophoresis. Southern blot transfer of radioactive pcDd actin DNA to restriction endonuclease-digested Hut-14 DNA produced only a single hybrid band (a 6-kilobase fragment); the pcHa-1 DNA probe detected one additional band (a 3-kilobase fragment). These results suggest that HuT-14 cells contain only one copy per haploid genome for Ax- or beta-actin. When considered together with recent determination of the entire amino acid sequences of Ax- and beta-actin, our findings indicate that Ax-actin is the product of a mutated beta-actin gene and are evidence for the occurrence of a mutation in a chemically transformed cell.

Actins↗
PubMed1980

Dissimilar modes of expression of beta- and gamma-actin in normal and leukemic human T lymphocytes.

Actin polypeptides are the most abundant protein components of replicating normal human T lymphocytes, comprising 16% of the total cellular protein. Unlike other replicating cell types which synthesize equal proportions of beta- and gamma-actin polypeptides, T cells synthesize beta-actin as the predominant species. By contrast, leukemic T cells (the Molt-4 cell line) synthesize nearly equal proportions of beta- and gamma-actin. In addition, novel forms of beta-actin in normal T cells and of beta- and gamma-actin in Molt-4 cells appear to be present, perhaps resulting from a post-translational modification process. Otherwise, both divergent T cell types express a relatively common spectrum of polypeptide species, thereby suggesting that regulation of actin biosynthesis may be involved in the neoplastic transformation process.

Actins↗
PubMed1980

Expression of a variant form of actin and additional polypeptide changes following chemical-induced in vitro neoplastic transformation of human fibroblasts.

Malignant human fibroblasts, transformed in vitro by a single chemical treatment, and the untransformed parental cells have been compared by two-dimensional gel electrophoresis of their proteins. One transformed cell line, HUT-14, exhibits an abundance of a new polypeptide, A' (pI 5.2; molecular weight 44,000), amounting to approximately 3% of the cellular protein. There are at least 23 additional differences in polypeptides out of greater than 1000 electrophoretically distinguishable species. The A' polypeptide has been identified as a variant form of actin by immunoprecipitation with anti-actin antibody and comparison of its tryptic peptide patterns with those produced by beta- and gamma-actin polypeptides also found in HUT-14 cells. A' is distinguishable from the normal forms of actin (alpha, beta, and gamma polypeptides) in that it is more acidic and migrates at a slower rate in sodium dodecyl sulfate gels. Synthesis of A' may occur as a result of a somatic mutation affecting one of the normal actin genes. The electrophoretic behavior of A' in two-dimensional gels is compatible with several mutation models.

Actins↗
PubMed1980

Coexpression of a mutant beta-actin and the two normal beta- and gamma-cytoplasmic actins in a stably transformed human cell line.

HUT 14 is a cloned transformed cell line derived from normal diploid human KD fibroblasts. HUT 14 cells have an altered actin phenotype. In addition to the two nonmuscle actins beta and gamma, also present in the parent KD cells, they show the stable expression of a novel actin species (Ax-actin). Amino acid sequence analysis has been used to identify the three actins of HUT 14 cells. beta- and gamma-actins are identified as normal mammalian nonmuscle actins whereas Ax-actin is characterized as a beta-actin mutant revealing a single amino acid substitution at position 244. The results obtained are compatible with a simple mutational event involving a point mutation in one of the two beta-nonmuscle actin genes assumed to be present in proliferating human diploid fibroblasts. Certain emerging principles of nonmuscle actin gene expression in higher vertebrates are discussed.

Actins↗
PubMed1980

Pancreatic exocrine function.

Stimulation of the pancreatic secretion of water, electrolytes, and enzymes is under neurohumoral control sensitive to the ingestion and digestion of food. Hormones interact to maximize physiologic responses to a meal and to autoregulate pancreatic secretion. Clinical manifestations of pancreatic exocrine insufficiency may result from obstruction to pancreatic flow through the major duct or to destructive disease of the exocrine cells; this insufficiency is a consequence of reduced volume, electrolytes, and enzyme output.

Animals↗