Search PubMed⌕ Search

Biomedical subjects

J M Cunningham

Publications and source records attributed to J M Cunningham.

At least 145 records · Page 8Linked to original sources
PubMed1990

Human cells infected with retrovirus vectors acquire an endogenous murine provirus.

A 5.2-kilobase mouse RNA is expressed in human cells following infection with recombinant retroviruses propagated in mouse NIH 3T3 cells as psi-2 pseudotypes. This RNA is transcribed from a defective mink cell focus-forming provirus and copackaged into virions and integrated into human target cell DNA at a frequency comparable to that of the recombinant retrovirus genome.

Animals↗
PubMed1989

A putative murine ecotropic retrovirus receptor gene encodes a multiple membrane-spanning protein and confers susceptibility to virus infection.

Murine type C ecotropic retrovirus infection is initiated by virus envelope binding to a membrane receptor expressed on mouse cells. We have identified a cDNA clone that may encode for this receptor through a strategy combining gene transfer of mouse NIH 3T3 DNA into nonpermissive human EJ cells, selection of EJ clones that have acquired susceptibility to infection by retrovirus vectors containing drug resistance genes, and identification of the putative receptor cDNA clone through linkage to a mouse repetitive DNA sequence. Human EJ cells that express the cDNA acquire a million-fold increase in MuLV infectivity. The predicted 622 amino acid sequence of the putative receptor protein is extremely hydrophobic; 14 potential membrane-spanning domains have been identified. A computer-based search of sequence data banks did not identify a protein with significant similarity to the putative receptor. We conclude that a novel membrane protein determines susceptibility to ecotropic MuLV infection by binding and/or fusion with the virus envelope.

Amino Acid Sequence↗
PubMed1987

The regulated expression of erythropoietin by two human hepatoma cell lines.

The development of a cell culture system that produces erythropoietin (Epo) in a regulated manner has been the focus of much effort. We have screened multiple renal and hepatic cell lines (including MDCK, LLC-PK1, BHK, WRL 68, CLCL, A704, CRFK, A498, ACHN, TCMK-1, LLC-MK2, CaKi-2, HepG2, and Hep3B) for either constitutive or regulated expression of Epo. Only the human hepatoma cell lines, Hep3B and HepG2, made significant amounts of Epo as measured both by radioimmunoassay and in vitro bioassay (as much as 330 milliunits per 10(6) cells in 24 hr). The constitutive production of Epo increased dramatically as a function of cell density in both cell lines. At cell densities less than 3.3 X 10(5) cells per cm2, there was little constitutive release of Epo in the medium (less than 30 milliunits per 10(6) cells in 24 hr). With Hep3B cells grown at low cell densities, a mean 18-fold increase in Epo expression was seen in response to hypoxia and a 6-fold increase was observed in response to incubation in medium containing 50 microM cobalt(II) chloride. At similar low cell densities, Epo production in HepG2 cells could be enhanced an average of about 3-fold by stimulation with either hypoxia or cobalt(II) chloride. Upon such stimulation, both cell lines demonstrated markedly elevated levels of Epo mRNA. Hence, both Hep3B and HepG2 cell lines provide an excellent in vitro system in which to study the physiological regulation of Epo expression.

Carcinoma, Hepatocellular↗
PubMed1987

Neurite outgrowth on cryostat sections of innervated and denervated skeletal muscle.

To localize factors that guide axons reinnervating skeletal muscle, we cultured ciliary ganglion neurons on cryostat sections of innervated and denervated adult muscle. Neurons extended neurites on sections of muscle (and several other tissues), generally in close apposition to sectioned cell surfaces. Average neurite length was greater on sections of denervated than on sections of innervated muscle, supporting the existence of functionally important differences between innervated and denervated muscle fiber surfaces. Furthermore, outgrowth was greater on sections of denervated muscle cut from endplate-rich regions than on sections from endplate-free regions, suggesting that a neurite outgrowth-promoting factor is concentrated near synapses. Finally, 80% of the neurites that contacted original synaptic sites (which are known to be preferentially reinnervated by regenerating axons in vivo) terminated precisely at those contacts, thereby demonstrating a specific response to components concentrated at endplates. Together, these results support the hypothesis that denervated muscles use cell surface (membrane and matrix) molecules to inform regenerating axons of their state of innervation and proximity to synaptic sites.

Animals↗
PubMed1987

Autoimmune pathogenesis of paraneoplastic neurological syndromes.

"Remote effects" of cancer on the nervous system (paraneoplastic syndromes) are disorders of the nervous system of unknown cause that occur almost exclusively, or with greatly increased frequency, in patients with identifiable or occult cancer. There are several hypotheses concerning the pathogenesis of these rare disorders. One hypothesis is that the underlying tumor and portions of the nervous system share antigens and that an autoimmune response generated against the tumor causes the nervous system disorder. Evidence supporting this hypothesis includes the ability to transmit the Lambert-Eaton Syndrome (a paraneoplastic syndrome involving the neuromuscular junction) to experimental animals by infusing IgG from patients with the disorder, the presence of autoantibodies against Purkinje cell neurons in some patients with paraneoplastic cerebellar degeneration, and the presence of autoantibodies against many neurons in patients with sensory neuronopathy and encephalomyelitis. Other evidence supporting the hypothesis is presented in this review.

Antibodies, Monoclonal↗
PubMed1985

Acetylcholine receptors in small cell carcinomas.

The presence of muscarinic and nicotinic acetylcholine receptors (m- and nAChR, respectively) in small cell carcinomas (SCC) of the lung was assessed by measurement of specific binding of (-)[3H]quinuclidinyl benzilate ([3H]QNB) and 125I-alpha-bungarotoxin, respectively. Of five SCC studied, four were originally derived from patients with the Lambert-Eaton myasthenic syndrome, an autoimmune disease of neuromuscular transmission, and one was from a patient without evidence of neurological disease. There was no evidence of nAChR, but all tumors bound (-)[3H]QNB in a saturable and specific manner. Dissociation constants derived from saturation isotherms ranged between 35.4 and 181.7 fmol/mg protein (mean values for the five SCC). Competition studies revealed a pharmacological profile consistent with previous descriptions of mAChR. Competition by pirenzepine revealed only one class of binding sites, that with a relatively low affinity for pirenzepine. In the presence of the guanine nucleotide analogue 5'-guanylyl imidodiphosphate, a decrease in affinity of the mAChR of SCC for oxotremorine was observed, with an increase in the pseudo-Hill coefficient, but there was no change in the binding of atropine. The expression on SCC of mAChR, apparently of the M2 subclass, represents yet another neural differentiation marker of SCC. It is noteworthy that the expression of this marker is not restricted to patients with an autoimmune paraneoplastic syndrome involving cholinergic neurons.

Animals↗
PubMed1985

Stability of bombesin in serum, plasma, urine, and culture media.

Using a radioimmunoassay, we studied the stability of bombesin added to pooled human serum, plasma, urine, and two culture media (RPMI-1640 and M199). Bombesin was stable in serum for 5 h at 4 degrees C and 2 h at 21 degrees C. However, in plasma, about half was no longer detected by 5 h at 4 degrees C, and this decline was unaffected by added aprotinin. Bombesin was stable in urine for 24 h at 4 degrees C and for 2 h at 21 degrees C. When incubated in the culture media at 37 degrees C for 60 min, no loss was detected. Bombesin-like immunoreactivity was detectable in the serum of 22 mice bearing tumors established from biopsied small-cell lung carcinomas, two of 12 mice bearing tumors established from other malignancies and zero of nine control mice. In contrast, immunoreactivity to this analyte was detected in urine specimens from all mice except for one bearing a non-small-cell tumor. The concentrations detected in serum and urine were uncorrelated.

Animals↗
PubMed1983

The N-ras oncogene assigned to the short arm of human chromosome 1.

The human N-ras oncogene, isolated from the HL-60 promyelocytic leukemia cell line, is distantly related to viral oncogenes of Kirsten and Harvey sarcoma viruses. We have determined its chromosomal location by Southern blot analysis of DNAs from 37 human x rodent hybrid cell lines derived from 8 different human donors, some of whom carried balanced rearrangements of chromosome 1. The results indicate that the N-ras oncogene (RASN) is localized on the proximal part of the short arm of human chromosome 1, in region p3200 leads to cen.

Animals↗
PubMed1983

Characterization of a human colon/lung carcinoma oncogene.

DNA sequences capable of inducing oncogenic transformation of NIH3T3 mouse cells are found in a number of human tumour cell lines. When DNAs of these cell lines are applied to monolayer cultures of the mouse fibroblasts, foci of transformed cells are observed 2-3 weeks later. DNA from cells of such primary foci can be used in turn to induce foci in a second cycle of gene transfer. The human DNA sequences responsible for transformation have been called oncogenes, the best characterized of which is closely related to the Harvey murine sarcoma virus oncogene. Here we present a characterization of an oncogene which we found originally to be present in DNA of the SW480 colon carcinoma cell line. We indicate its structural outlines and demonstrate, in extension of reported results, its presence in an activated form in the genome of several types of human tumour cell lines as well as in biopsy tissue from an adenocarcinoma of the large bowel. We identify this tumour oncogene with c-Ki-ras2, one of two known members of the Kirsten ras family of human proto-oncogenes, extending a series of recent reports which have demonstrated homologies between human oncogenes and those of Harvey and Kirsten murine sarcoma viruses. The c-Ki-ras2 oncogene of several tumour cell lines is shown to be amplified.

Colonic Neoplasms↗
PubMed1983

Prevention of experimental allergic neuritis in the Lewis rat with bovine P2 protein.

Protective doses of bovine P2 protein (5, 15 or 50 micrograms) in incomplete Freund's adjuvant (IFA) were administered to Lewis rats and were followed 2, 4 or 10 weeks later by challenging doses of either 250 micrograms bovine P2 or 2.5 mg bovine PNS myelin in complete Freund's adjuvant (CFA). Protection from experimental allergic neuritis (EAN) could be achieved with a single dose of 5 micrograms of P2 in IFA. There was little difference between prophylactic 5 micrograms and 15 micrograms doses of P2. The degree of protection depended upon the interval between protective innoculation and challenge. Protection was partial at 2 weeks and maximal at 4 weeks at which time there was complete protection against P2-induced EAN and less complete protection from myelin-induced disease. Complete protection at 4 weeks from myelin-induced EAN was achieved with a 50 micrograms dose. Protection lasted for at least 10 weeks (the longest interval assessed) and was complete with respect to P2-induced EAN. Partial protection was observed in myelin-challenged animals after 10 weeks with the level of protection greater than that observed after 2 weeks.

Animals↗
PubMed1983

The HL-60 transforming sequence: a ras oncogene coexisting with altered myc genes in hematopoietic tumors.

The oncogene of the HL-60 human promyelocytic leukemia cell line has been passed serially through NIH/3T3 mouse fibroblasts. Oncogene-specific probes prepared from the resulting tertiary transfectants by molecular cloning have been used to show that loss of the transfected oncogene from NIH/3T3 cells correlates with reversion to nontransformed morphology. Analysis of cells transfected by the oncogenes of other tumors and tumor cell lines indicates that the transforming gene of the HL-60 leukemia cell line is closely related to oncogenes of a Burkitt's lymphoma, an acute myelogenous leukemia, an adenocarcinoma of the colon, a neuroblastoma, and two sarcomas. This oncogene is distantly related to the viral oncogenes of Kirsten and Harvey sarcoma viruses. It has been termed N-ras. The active N-ras oncogene coexists with altered versions of the myc oncogene in the HL-60 and AW Ramos human tumors. This suggests a multistep mechanism involving both ras and myc genes in the creation of these tumors.

Animals↗
PubMed1983

Experimental allergic neuritis. Humoral and cellular immune responses to the cyanogen bromide peptides of the P2 protein.

Lewis rats were immunized with P2 protein and peptides CN1, CN2 and CN3. In P2 immunized rats, antibody and cellular sensitivity to the P2 protein were seen prior to the appearance of clinical signs of EAN, during disease and during recovery. CN1 immunized rats had equal or more severe clinical and histological signs of EAN but lower antibody titers than P2 immunized animals. CN-1 elicited a greater blastogenic response in both P2 and CN-1 immunized animals. CN-2 and CN-3 immunized rats showed little clinical and histological evidence of EAN and no antibody. However, lymphocytes sensitive to the immunizing antigen and the P2 protein were present.

Animals↗