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R J Fallon

Publications and source records attributed to R J Fallon.

At least 37 records · Page 2Linked to original sources
PubMed1990

Staurosporine inhibits a tyrosine protein kinase in human hepatoma cell membranes.

Membranes from the human hepatoma cell line HepG2 mediate the phosphorylation on tyrosine of the asialoglycoprotein receptor. Manganese was the preferred divalent for phosphorylation although magnesium was effective at an 8-fold higher concentration. Calcium was ineffective at promoting phosphorylation and zinc was inhibitory. The protein kinase inhibitor staurosporine blocked asialoglycoprotein receptor phosphorylation on tyrosine in nanomolar concentrations (IC50 = 70 nM). In contrast another protein kinase C inhibitor, H7, was not inhibitory, suggesting that the effect of staurosporine was not mediated by protein kinase C inhibition. Concentrations of staurosporine that inhibit receptor phosphorylation by greater than 90% did not inhibit the phosphorylation of other protein substrates identified on SDS-polyacrylamide gels. These data suggest that staurosporine selectively and directly inhibits a membrane-associated tyrosine protein kinase.

1-(5-Isoquinolinesulfonyl)-2-Methylpiperazine↗
PubMed1990

Tyrosine phosphorylation of the asialoglycoprotein receptor.

The asialoglycoprotein (ASGP) receptor undergoes constitutive endocytosis through the coated pit/coated vesicle pathway in hepatocytes. Studies on HepG2 cells have shown that the receptor is phosphorylated at serine under control conditions and following protein kinase C stimulation. This study examined whether the ASGP receptor could also serve as a substrate for a tyrosine kinase in HepG2 cells. 32P labeling was performed in membrane preparations, in permeabilized cells at 4 degrees C, and in intact cells at 37 degrees C. The phosphorylated ASGP receptor was isolated by immunoprecipitation, hydrolyzed in 6 N HCl at 110 degrees C, and analyzed by two-dimensional high voltage electrophoresis. The receptor isolated from a membrane preparation incubated in vitro with [gamma-32P]ATP incorporated radiolabel predominantly (greater than 90%) into phosphotyrosine. ASGP receptor phosphorylation at both tyrosine and serine was detected in intact cells incubated with phosphatase inhibitors for 60 min at 37 degrees C. The presence of both phenylarsine oxide (20 microM) and sodium orthovanadate (200 microM) was required for tyrosine phosphorylation. Use of these inhibitors together resulted in a 16.4-fold increase in phosphorylation of the immunoprecipitated ASGP receptor, whereas phosphorylation of total HepG2 membrane proteins was not significantly augmented by this procedure. Selective proteolytic digestion of ASGP receptors in isolated vesicles demonstrated that the phosphorylation site identified in these studies is located at tyrosine 5 in the cytoplasmic tail.

Asialoglycoprotein Receptor↗
PubMed1990

A cumulative review of studies on travellers, their experience of illness and the implications of these findings.

A cumulative review of illness experienced by 13,816 travellers returning to Scotland since 1977, shows an overall attack rate of 36%. Alimentary complaints predominated; 18% of travellers had these alone and a further 10% had other symptoms as well as their gastro-intestinal disorder. Higher attack rates were noted in those taking package holidays. Inexperience of travel, smoking, more southerly travel and younger age (particularly those between 20- and 29-years-old) were other contributing factors. A similar pattern emerged from a I year study of hospital in-patients with travel related admissions. Serological studies of 470 travellers showed that 20% had incomplete immunity to poliomyelitis; 25% of those tested (312 travellers) had serological evidence of typhoid immunisation, I.9% (of 760 travellers) had antibodies to Legionella pneumophila, 64% (5II travellers tested) had antibodies to hepatitis A, 87% (288 tested) had adequate levels of tetanus antitoxin but only 40% of the 225 travellers tested had adequate levels of diphtheria antitoxin. Amongst a subgroup of 645 travellers the travel agent was the most frequently consulted source of pre-travel health advice. This carries particular significance for the dissemination of relevant advice in view of the inadequacies found from study of the health information in travel brochures. These findings, viewed against the perspective of the continuing growth in international travel, means that travellers, the medical profession, the travel trade, health educators, global health agencies and health authorities in those countries accepting and encouraging tourists, will be required to recognise the health implications of further tourism development if this problem of illness associated with travel is to be brought under control.

Adolescent↗
PubMed1990

Identification of a serpin-enzyme complex receptor on human hepatoma cells and human monocytes.

Formation of the covalently stabilized complex of alpha 1-antitrypsin (alpha 1-AT) with neutrophil elastase, the archetype of serine proteinase inhibitor serpin-enzyme complexes, is associated with structural rearrangement of the alpha 1-AT molecule and hydrolysis of a reactive-site peptide bond. An approximately 4-kDa carboxyl-terminal cleavage fragment is generated. alpha 1-AT-elastase complexes are biologically active, possessing chemotactic activity and mediating increases in expression of the alpha 1-AT gene in human monocytes and macrophages. This suggested that structural rearrangement of the alpha 1-AT molecule, during formation of a complex with elastase, exposes a domain that is recognized by a specific cell surface receptor or receptors. To test this hypothesis, the known three-dimensional structure of alpha 1-AT and comparisons of the primary structures of the serpins were used to select a potentially exteriorly exposed and highly conserved region in the complexed form of alpha 1-AT as a candidate ligand (carboxyl-terminal fragment, amino acids 359-374). We show here that synthetic peptides based on the sequence of this region bind specifically and saturably to human hepatoma cells and human monocytes (Kd = 4.0 X 10(-8) M, 4.5 X 10(5) plasma membrane receptors per cell) and mediate increases in synthesis of alpha 1-AT. Binding of peptide 105Y (Ser-Ile-Pro-Pro-Glu-Val-Lys-Phe-Asn-Lys-Pro-Phe-Val-Tyr-Leu-Ile) is blocked by alpha 1-AT-elastase complexes, antithrombin III (AT III)-thrombin complexes, alpha 1-antichymotrypsin (alpha 1-ACT)-cathepsin G complexes, and, to a lesser extent, complement component C1 inhibitor-C1s complexes, but not by the corresponding native proteins. Binding of peptide 105Y is also blocked by peptides with sequence corresponding to carboxy-terminal fragments of the serpins AT III and alpha 1-ACT, but not by peptides having the sequence of the extreme amino terminus of alpha 1-AT. The results also show that peptide 105Y inhibits binding of 125I-labeled alpha 1-AT-elastase complexes. Thus, these studies demonstrate an abundant, relatively high-affinity cell surface receptor which recognizes serpin-enzyme complexes (SEC receptor). This receptor is capable of modulating the production of at least one of the serpins, alpha 1-AT. Since the ligand specificity is similar to that previously described for in vivo clearance of serpin-enzyme complexes, the SEC receptor may also be involved in the clearance of certain serpin-enzyme complexes.

Amino Acid Sequence↗
PubMed1990

Microbiological investigations into an outbreak of Pontiac fever due to Legionella micdadei associated with use of a whirlpool.

In the investigation of a large outbreak of non-pneumonic legionellosis at a leisure complex in Lochgoilhead, Scotland all direct cultures of environmental samples were initially negative for legionellae. Legionellae readily infect appropriate protozoa under suitable conditions, and following immunofluorescence to select specimens for special study, Legionella micdadei was isolated from whirlpool water via co-cultivation with Acanthamoeba polyphaga. L micdadei was also isolated, along with host amoebae, from the whirlpool filter. The use of amoebae in the isolation of legionellae from environmental (and other) sources can be of great value, especially if specimens shown by indirect immunofluorescence to contain legionellae fail to yield legionellae on routine culture.

Acanthamoeba↗
PubMed1979

Tuberculous meningitis.

To evaluate modern treatment and identify important factors influencing the outcome of tuberculous meningitis, clinical and laboratory findings in 52 patients aged from 9 months to 68 years have been reviewed. Patients were classified by clinical criterions at admission and at the start of treatment. Delay in commencing treatment was associated with deterioration and consequently poorer prognosis, but some severely ill patients made a good recovery. Forty-four survivors (85%) recovered, and only two patients (4%) had severe residual disability; eight (15%) of the patients died. Treatment should commence as soon as possible on clinical grounds without necessarily waiting for demonstration of Mycobacterium tuberculosis, as the organism can often be demonstrated in CSF withdrawn after the start of drug therapy.

Adolescent↗
PubMed1979

Induction of human choriogonadotropin and follitropin in HeLa cell cultures by hyperosmolality.

The growth of cervical carcinoma cell (HeLa) cultures in a hyperosmolar environment stimulates increased production of the onco-developmental peptides human choriogonadotropin (hCG) and follitropin (FSH). This effect was observed in two sublines examined in this study, HeLa65 and HeLa71. hCG and FSH were measured by radioimmunoassay using antiserum against the beta-subunit of the hormone dimer, thus insuring immunochemical specificity, The amounts of hCG and FSH produced by HeLa65 and HeLa71 cells cultured in hyperosmolar medium were 2- to 50-fold higher than corresponding hormone levels in basal cultures. Synthesis of gonadotropins depended on concentration and duration of exposure to hyperosmolar medium. Levels of culture medium osmolality effective in inducing hormone production also inhibit the incorporation of 14C-thymidine into acid-insoluble macromolecules. Hyperosmolality thus stimulates the ectopic production of gonadotropic hormones while retarding cellular growth and nucleic acid synthesis.

Cell Division↗
PubMed1979

Cell cycle analysis of sodium butyrate and hydroxyurea, inducers of ectopic hormone production in HeLa cells.

Sodium butyrate and hydroxyurea, effective inhibitors of DNA synthesis in HeLa cells, cause these cells to produce increased levels of the ectopic glycopeptide hormones human chorionic gonadotropin (hCG), follicle stimulating hormone (FSH), and free alpha chains for these hormones. The objective of this study was an assessment of the role of modulation of cell cycle events in the action of these two chemical agents. A variety of experimental approaches was employed to obtain a clear view of the drugs' effects on cells located initially in all phases of the cell cycle. Cells in early G1, G2, or M phase at time of addition of either inhibitor were not arrested at early time points, but by 48 hours became collected at a location characteristic for each drug, near the G1-S phase boundary. Flow microfluorometry (FMF) and thymidine labeling index revealed that butyrate-treated cells arrested late in G1 phase very close to S phase, while hydroxyurea-blocked cells continued to early S phase. Both inhibitors prevented cells originally in S phase from reaching mitosis. S cells exposed to hydroxyurea were killed by 48 hours, but those growing in 5 mM butyrate progressed to the end of S or G2 phase where they became irreversibly arrested although not removed from the monolayer. Analysis of the cell cycle location and viability of each subpopulation resulting from 48 hour exposure to butyrate or hydroxyurea is important for the study of the function of each cellular subset. Treatment of HeLa cells with lower concentrations of butyrate (1 mM) resulted in slowed yet exponential growth. Fraction labeled mitosis (FLM) analysis shows that this is a result of prolongation of the G1 phase.

Butyrates↗
PubMed1979

Secretory proteins in the perfused human placenta.

A relatively simple perfusion technique of human placenta has been applied to the study of secretory proteins. Preferential secretion into the maternal circulation of human chorionic gonadotropin (HCG), human chorionic somatomammotropin (HCS), follicle-stimulating hormone (FSH), and placental alkaline phosphatase has been demonstrated, contrasting with the bidirectional secretion of progesterone. Evidence is presented for the net synthesis of HCS during perfusion. The technique offers advantages in the study of synthesis and secretion of placental materials.

Alkaline Phosphatase↗
PubMed1979

Scottish experience with the serologic diagnosis of Legionnaires' disease.

Four-hundred fifty-nine sera from 342 persons were examined at Ruchill Hospital, Glasgow, using an agar-grown heat-killed, ether-treated antigen derived from the Philadelphia 1 strain of the Legionnaires' disease bacterium. They were examined, in parallel, at the Center for Disease Control (CDC), Atlanta. Overall agreement (results agreeing +/- one twofold dilution) was reached with 90% of sera. Important differences were obtained with 10 (2.2%) sera. With three of these 10 sera the CDC alone obtained a significant titre (256) whereas with the other seven the Glasgow laboratory alone obtained a titre of 256. Altogether 28 persons (8.2%) with an agreed titre of 256 or higher were identified. However, some of these people had been ill 4 years before serum was obtained for examination. These persistent high titres make the serologic diagnosis of Legionnaires' disease difficult.

Antibodies, Bacterial↗