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Biomedical subjects

T Friedmann

Publications and source records attributed to T Friedmann.

180 records · Page 10Linked to original sources
PubMed1972

Gene therapy for human genetic disease?

In our view, gene therapy may ameliorate some human genetic diseases in the future. For this reason, we believe that research directed at the development of techniques for gene therapy should continue. For the foreseeable future, however, we oppose any further attempts at gene therapy in human patients because (i) our understanding of such basic processes as gene regulation and genetic recombination in human cells is inadequate; (ii) our understanding of the details of the relation between the molecular defect and the disease state is rudimentary for essentially all genetic diseases; and (iii) we have no information on the short-range and long-term side effects of gene therapy. We therefore propose that a sustained effort be made to formulate a complete set of ethicoscientific criteria to guide the development and clinical application of gene therapy techniques. Such an endeavor could go a long way toward ensuring that gene therapy is used in humans only in those instances where it will prove beneficial, and toward preventing its misuse through premature application. Two recent papers have provided new demonstrations of directed genetic modification of mammalian cells. Munyon et al. (44) restored the ability to synthesize the enzyme thymidine kinase to thymidine kinase-deficient mouse cells by infection with ultraviolet-irradiated herpes simplex virus. In their experiments the DNA from herpes simplex virus, which contains a gene coding for thymidine kinase, may have formed a hereditable association with the mouse cells. Merril et al. (45) reported that treatment of fibroblasts from patients with galactosemia with exogenous DNA caused increased activity of a missing enzyme, alpha-D-galactose-l-phosphate uridyltransferase. They also provided some evidence that the change persisted after subculturing the treated cells. If this latter report can be confirmed, the feasibility of directed genetic modification of human cells would be clearly demonstrated, considerably enhancing the technical prospects for gene therapy.

Animals↗
PubMed1972

Structural roles of polyoma virus proteins.

The superhelical, closed circular form of polyoma deoxyribonucleic acid (DNA) (Co 1) is bound in a 25S DNA-protein complex to the viral histone-like proteins after alkaline disruption of the virion. Nicked viral DNA or linear DNA are largely free of protein. Most of the viral protein disruption is in the form of capsomeres, sedimenting principally at 10S and 7S. Despite the relatively constant ratio of 10S to 7S material in many preparations, (1:5.5 to 1:6.0, respectively), the two classes of capsomeres are indistinguishable by electron microscopy and contain only P(2), P(3), and P(4) in molar ratios of approximately 5:1:1 or 6:1:1, respectively. Material with sedimentation rates of approximately 1 to 3S is enriched for P(5) and contains small amounts of P(2), P(3), and P(4). During the in vitro reassembly of DNA-free, shell-like particles from disrupted virus, proteins P(1), P(2), P(3), P(4), and P(7) are reincorporated efficiently, whereas P(5) and P(6) are not. The presence in empty reassembled particles of histone-like protein, expecially P(7), implies that at least this one of the minor protein components of the virion may participate in protein-protein interactions with other components of the capsid.

Autoradiography↗
PubMed1971

In vitro reassembly of shell-like particles from disrupted polyoma virus.

When purified polyoma virus is exposed to 0.01 M dithiothreitol in the presence of 0.2 M Na(2)CO(3)-NaHCO(3) (pH 10.6) at 0-4 degrees C, the capsids are rapidly disrupted to protein subunits of capsomere size, as judged by density gradient centrifugation, sedimentation equilibrium centrifugation, and electron microscopy. Hemagglutination activity and infectivity of disrupted virus are reduced to below detectable amounts. Removal of the disruption reagents by dialysis at 4 degrees C against 0.05 M Tris-0.14 M NaCl-1 mM EDTA and 0.1 mM 2-mercaptoethanol (pH 8.0) results in a time-dependent reappearance of up to 17% of the starting hemagglutination titer, under optimum conditions of ionic strength, pH, temperature, and virus protein concentration. The recovered hemagglutination activity is found in glycerol gradients associated with a 100S DNA-protein complex consisting mostly of linear aggregates of capsomeres. When the linear complex is treated with pancreatic DNase, the complex is converted into spherical particles, of approximately virus size, that sediment at 140 S (with aggregates at 180 S), as well as on the cushion of half-saturated CsCl at the bottom of the gradients. All reassembled particles are not infectious and have markedly reduced DNA to protein ratios.

Animals↗
PubMedDate not supplied

Primary structure of Torpedo californica acetylcholinesterase deduced from its cDNA sequence.

Acetylcholinesterase, an essential enzyme of the nervous system, rapidly terminates the action of acetylcholine released into the synapse. Acetylcholinesterase is also found (in lower abundance) in extrajunctional areas of muscle and nerve and on erythrocyte membranes. Hydrodynamic analyses of the native enzyme and characterization of its dissociated subunits have revealed multiple enzyme forms which can be divided into two classes: dimensionally asymmetric forms which are usually found within the synapse and contain a collagen-like structural subunit disulphide-linked to the catalytic subunits; and globular forms which appear to be widely distributed on the outer surface of cell membranes. Both forms have been characterized in the ray Torpedo californica and, although their catalytic behaviours seem to be identical, they differ slightly in amino-acid composition, peptide maps and reactivity with certain monoclonal antibodies. Here, we report the complete amino-acid sequence of an acetylcholinesterase inferred from the sequence of a complementary DNA clone. The 575-residue protein shows significant homology with the C-terminal portion of thyroglobulin.

Acetylcholinesterase↗
PubMedDate not supplied

Influence of spatial orientation of the C-6-OH group in ring C of morphine derivatives on opioid activity.

The effect of epimerization on agonist and antagonist activities of morphine and dihydromorphine, and those of their N-allyl, -propyl and -cyclopropylmethyl derivatives, were studied in rat tail flick, hot plate and mice hot plate and in isolated guinea-pig ileum assays, respectively. Using the rat tail flick, hot plate and mice hot plate tests, isomorphine and dihydroisomorphine were observed to produce dose-dependent, naloxone-reversible agonist (antinociceptive) actions, in a similar dose range as their parent molecules (relative potencies: 0.6-1.9). Also, these compounds produced agonist activities in isolated tissue preparations in a naloxone-reversible manner. While the N-substituted derivatives of isomorphine and dihydroisomorphine failed to produce antinociceptive activities in the rat tail flick test, they proved to be strong agonists in the guinea-pig ileum experiments, although the Ke values of naloxone were 5-6 times higher against these compounds than against their N-CH3 counterparts. Both the agonist and antagonist activities of the N-cyclopropylmethyl derivatives were found to be most potent in the guinea-pig ileum. The epimerization of morphine and dihydromorphine and their N-substituted derivatives evoked only slight changes in opioid activities in vitro. In vivo, merely the allyl substitution on nitrogen influenced the antagonist activities of epimer pairs. In contrast, substantial changes in opioid profile were observed when N-methyl was replaced by allyl-, propyl- or cyclopropylmethyl. Changes performed this way evoked, on the one hand, an enhancement of the affinities of compounds to mu-receptors, with simultaneous loss of intrinsic efficacy at these receptors, and, on the other hand, promoted the appearance of an agonist profile on a distinct (kappa) opioid receptor.

Analgesia↗
PubMedDate not supplied

Wild-type p53 suppresses the malignant phenotype in breast cancer cells containing mutant p53 alleles.

We have examined the effect of expression of a retrovirally mediated wild-type (wt) p53 allele on the neoplastic properties of five human breast cancer cell lines expressing mutant p53. After infection with the retroviral vector Lhp53RNL expressing both the neomycin phosphotransferase gene and the wt p53 gene, the ability of infected cells to form colonies in G418 selective medium was markedly reduced and their morphology demonstrated changes toward a flattened and enlarged phenotype. Employing a high multiplicity of infection (MOI) with Lhp53RNL without neoR selection, the replication of wt p53-reconstituted cells was greatly reduced. The ability of the genetically modified cells to produce colonies in semi-solid medium and to form tumors in recipient nude mice was also markedly suppressed. Restoration of wt p53 expression in human breast cancer cells expressing endogenous mt (mutant) p53 can suppress some aspects of the malignant phenotype by a trans-dominant mechanism.

Alleles↗