PubMed Health⌕ Search

Biomedical subjects

T Higgins

Publications and source records attributed to T Higgins.

At least 37 records · Page 2Linked to original sources
PubMed1996

[D-Arg1,D-Trp5,7,9,Leu11]Substance P coordinately and reversibly inhibits bombesin- and vasopressin-induced signal transduction pathways in Swiss 3T3 cells.

The novel substance P (SP) analogue, [D-Arg1,D-Trp5,7,9,Leu11]SP like [D-Arg1,D-Phe5,D-Trp7,9,Leu11]SP inhibited DNA synthesis induced by bombesin, vasopressin, and bradykinin, but did not interfere with the mitogenic response induced by other growth factors or pharmacological agents in Swiss 3T3 cells. [D-Arg1,D-Trp5, 7,9,Leu11]SP reversibly inhibited bombesin-induced DNA synthesis, causing a 6-fold greater rightward shift in the bombesin dose response than [D-Arg1,D-Phe5,D-Trp7,9,Leu11]SP at identical concentrations (10 microM). We found that the new, more potent, SP analogue coordinately and reversibly inhibited bombesin-induced Ca2+ mobilization and protein kinase C (PKC) and mitogen-activated protein (MAP) kinase activation. The dose-response curves for bombesin-induced Ca2+ mobilization and MAP kinase activation were similarly displaced (51- and 40-fold, respectively) by [D-Arg1, D-Trp5,7,9,Leu11]SP. In addition, [D-Arg1,D-Trp5,7,9,Leu11]SP reversibly inhibited bombesin-induced tyrosine phosphorylation of Mr 110,000-130,000 and 70,000-80,000 bands as well as p125 focal adhesion kinase. [D-Arg1,D-Trp5,7,9,Leu11]SP also reversibly and coordinately inhibited vasopressin-induced Ca2+ mobilization, PKC stimulation, MAP kinase activation, tyrosine phosphorylation, and DNA synthesis in Swiss 3T3 cells. Surprisingly, deletion of the terminal Leu of [D-Arg1,D-Phe5,D-Trp7,9,Leu11]SP to yield [D-Arg1, D-Phe5,D-Trp7,9]SP1-10 resulted in a selective loss of inhibitory activity of this analogue against bombesin- but not vasopressin-stimulated DNA synthesis, Ca2+ mobilization, and MAP kinase activation. Collectively, these results suggest that SP analogues act at the receptor level to coordinately and reversibly antagonize bombesin- or vasopressin-induced signal transduction in Swiss 3T3 cells.

3T3 Cells↗
PubMed1996

Metabolism of the broad-spectrum neuropeptide growth factor antagonist: [D-Arg1, D-Phe5, D-Trp7,9, Leu11]-substance P.

Broad-spectrum neuropeptide growth factor antagonists, such as [D-Arg1, D-Phe5, D-Trp7,9, Leu11]substance P (antagonist D) and [Arg6, D-Trp7,9, NmePhe8]substance P(6-11) (antagonist G), are currently being investigated as possible anti-tumour agents. These compounds are hoped to be effective against neuropeptide-driven cancers such as small-cell lung cancer. Antagonist D possesses a broader antagonistic spectrum than antagonist G and hence may be of greater therapeutic use. The in vitro metabolism of antagonist D has been characterised and the structures of two major metabolites have been elucidated by amino acid analysis and mass spectrometry. Metabolism was confined to the C-terminus where serine carboxypeptidase action produced [deamidated]-antagonist D (metabolite 1) and [des-Leu11]-antagonist D (metabolite 2) as the major metabolites. Biological characterisation of the metabolites demonstrated that these relatively minor changes in structure resulted in a loss of antagonist activity. These results provide some of the first structure-activity information on the factors that determine which neuropeptides these compounds inhibit and on the relative potency of that inhibition.

Amino Acid Sequence↗
PubMed1995

Metabolism of the anticancer peptide H-Arg-D-Trp-NmePhe-D-Trp-Leu-Met-NH2.

H-Arg-D-Trp-NmePhe-D-Trp-Leu-Met-NH2 (Antagonist G) will be the first broad-spectrum neuropeptide antagonist to enter a phase I clinical trial. Its in vitro and in vivo metabolism has been extensively characterized. The major metabolites were identified and their structures elucidated by mass spectroscopy and amino acid analysis. Metabolism occurred almost exclusively at the C-terminus and was arrested by phenylmethylsulfonylfluoride, a known serine-protease inhibitor. Biological characterization of the metabolites demonstrated that the degradation of Antagonist G produces metabolites that retain neuropeptide antagonist properties.

3T3 Cells↗
PubMed1995

The effect of intermittent steroid therapy on anti-sperm antibody levels.

Sperm-bound antisperm antibody levels were measured in 10 males in subfertile partnerships who were treated with high dose intermittent prednisolone therapy over a period up to 9 months. Antibody levels fell in all patients during therapy, although a transient rise occurred after 2-4 months. There were low treatment complication rates. Four pregnancies occurred during the treatment of the 10 patients. There was no correlation between pregnancy and change in antibody.

Adult↗
PubMed1994

Preferential inhibition of platelet-derived growth factor-stimulated DNA synthesis and protein tyrosine phosphorylation by nordihydroguaiaretic acid.

Nordihydroguaiaretic acid (NDGA), a reportedly specific lipoxygenase inhibitor, was found to selectively inhibit platelet-derived growth factor (PDGF)-stimulated DNA synthesis in Swiss 3T3 cells. Maximal inhibition of PDGF-induced [3H]thymidine incorporation (96%) was observed using 4 microM NDGA (IC50 = 1.5 microM). No effect of NDGA was observed upon DNA synthesis stimulated with either fetal bovine serum, bombesin, or epidermal growth factor (EGF) in the presence of insulin, or with the potent mitogen Pasteurella multocida toxin. The selective inhibition of PDGF-stimulated DNA synthesis by NDGA was also observed in diploid murine cells, rat, and human fibroblasts. Furthermore, 4 microM NDGA also inhibited PDGF-stimulated anchorage-independent colony growth of rat-1 cells by 76%. Using Swiss 3T3 cells, we found that PDGF-stimulated arachidonic acid mobilization and prostaglandin E2 production was abolished by NDGA in a dose-dependent manner. Inhibition of PDGF-stimulated arachidonic acid mobilization by NDGA could not, however, explain its potent inhibitory effect upon PDGF-stimulated DNA synthesis. Our results showed that NDGA also selectively inhibited PDGF receptor tyrosine phosphorylation in a dose-dependent manner in intact cells. Protein tyrosine phosphorylation stimulated by EGF or bombesin was not altered by NDGA treatment. Crucially, NDGA inhibited in vitro the tyrosine kinase activity of anti-phosphotyrosine and anti-PDGF receptor immunoprecipitates prepared from cultures stimulated with PDGF. This inhibition of receptor tyrosine phosphorylation in a cell-free system confirmed that NDGA acts directly at the level of the PDGF receptor tyrosine kinase domain. These results suggest that the potent and selective inhibitory effect of NDGA on PDGF-stimulated DNA synthesis results from its inhibitory action on tyrosine phosphorylation.

3T3 Cells↗
PubMed1991

Stimulation by xanthine oxidase of 3T3 Swiss fibroblasts and human lymphocytes.

Xanthine oxidase stimulates [3H]thymidine incorporation by 3T3 cells even in the absence of any added xanthine, but in the presence of, and synergistically with, insulin or various other growth-stimulating factors. Optimal stimulation was obtained with 2-3 mU enzyme/ml and higher concentrations were toxic. Xanthine oxidase also stimulated human peripheral blood lymphocytes in the presence of phytohemagglutinin and xanthine.

Animals↗
PubMed1991

Mastoparan, a novel mitogen for Swiss 3T3 cells, stimulates pertussis toxin-sensitive arachidonic acid release without inositol phosphate accumulation.

Mastoparan, a basic tetradecapeptide isolated from wasp venom, is a novel mitogen for Swiss 3T3 cells. This peptide induced DNA synthesis in synergy with insulin in a concentration-dependent manner; half-maximum and maximum responses were achieved at 14 and 17 microM, respectively. Mastoparan also stimulated DNA synthesis in the presence of other growth promoting factors including bombesin, insulin-like growth factor-1, and platelet-derived growth factor. The synergistic mitogenic stimulation by mastoparan can be dissociated from activation of phospholipase C. Mastoparan did not stimulate phosphoinositide breakdown, Ca2+ mobilization or protein kinase C-mediated phosphorylation of a major cellular substrate or transmodulation of the epidermal growth factor receptor. In contrast, mastoparan stimulated arachidonic acid release, prostaglandin E2 production, and enhanced cAMP accumulation in the presence of forskolin. These responses were inhibited by prior treatment with pertussis toxin. Hence, mastoparan stimulates arachidonic acid release via a pertussis toxin-sensitive G protein in Swiss 3T3 cells. Arachidonic acid, like mastoparan, stimulated DNA synthesis in the presence of insulin. The ability of mastoparan to stimulate mitogenesis was reduced by pertussis toxin treatment. These results demonstrate, for the first time, that mastoparan stimulates reinitiation of DNA synthesis in Swiss 3T3 cells and indicate that this peptide may be a useful probe to elucidate signal transduction mechanisms in mitogenesis.

1-Methyl-3-isobutylxanthine↗
PubMed1990

Sequence analysis of the potent mitogenic toxin of Pasteurella multocida.

Pasteurella multocida toxin is a potent mitogen for cultured Swiss 3T3 cells where it causes an accumulation of inositol phosphates and activation of protein kinase C. The gene sequence described here coded for a 146 kDa protein. The ORF was preceded by a ribosome binding site and followed by a stem loop. There was no evidence for a signal sequence. The gene had a low G + C base ratio which differs from the rest of the Pasteurella genome. There was no significant homology with other known proteins, although a motif found in certain bacterial toxins which are ADP-ribosyl transferases is present. A recombinant expressing only part of the PMT gene was not mitogenic.

Amino Acid Sequence↗
PubMed1990

Fibroblast growth factor stimulates protein kinase C in quiescent 3T3 cells without Ca2+ mobilization or inositol phosphate accumulation.

To elucidate the transmembrane signalling processes initiated by fibroblast growth factor (FGF), we have studied the effect of recombinant basic FGF (bFGF) on various early events associated with mitogenesis in Swiss 3T3 fibroblasts. bFGF, at mitogenic concentrations, neither induced Ca2+ mobilization from intracellular stores nor increased the accumulation of inositol phosphates. In contrast, bFGF stimulated the phosphorylation of the Mr 80,000 (80K) cellular protein which is a major substrate of protein kinase C. This effect was potentiated by the diacylglycerol kinase inhibitor R59022. Two-dimensional polyacrylamide gel electrophoresis and phosphopeptide mapping showed that the 80K phosphoproteins generated in response to bFGF, bombesin, and phorbol 12,13-dibutyrate were indistinguishable. Down-regulation of protein kinase C prevented bFGF stimulation of 80K phosphorylation. Other protein kinase C-dependent early events such as transmodulation of the epidermal growth factor receptor, cytoplasmic alkalinization, inhibition of vasopressin induced increase in cytosolic [Ca2+], and enhancement of cAMP accumulation in response to forskolin were also induced by bFGF. Similar results were obtained when bFGF was added to quiescent cultures of tertiary mouse embryo fibroblasts. We conclude that bFGF stimulates protein kinase C through a signal transduction pathway distinct from inositol phospholipid turnover and Ca2+ mobilization.

Animals↗
PubMed1990

Training for an agricultural discrimination task.

Skeleton weed, centaurea juncea, is a declared weed in Western Australia because it competes with grain crops for nutrients and moisture. When it is found during harvesting, mechanised teams search and eradicate it. In an earlier report of field trials (Hartley et al, 1989) it was reported that search teams' detection rate was poor and since search teams had usually never seen skeleton weeds, visual discrimination learning was to be expected and observed during searches. The present study investigated the nature of this discrimination learning in a laboratory by developing a training programme of colour photographic slides of weeds in stubble. Subjects receiving specific training with feedback on their performance compared with those receiving pseudo-training showed a significant improvement in detections. Subsequently the benefit of the programme was validated in a field trial.

Journal Article↗
PubMed1990

Bombesin stimulation of c-fos expression and mitogenesis in Swiss 3T3 cells: the role of prostaglandin E2-mediated cyclic AMP accumulation.

Bombesin is a potent mitogen for Swiss 3T3 cells and can stimulate DNA synthesis in the absence of any other growth factor. This effect is mediated by multiple synergistic signaling pathways, including an accumulation of intracellular cyclic AMP (cAMP) and an increase in c-fos mRNA expression. The cyclooxygenase inhibitor indomethacin abolished prostaglandin E2 release and substantially depressed cAMP levels induced by bombesin (EC50 congruent to 10 nM). In contrast, indomethacin at 1 microM did not affect 80K phosphorylation or Ca2+ mobilization by bombesin, indicating that cAMP synthesis can occur through a phospholipase C-independent pathway. Indomethacin caused a 30 to 35% decrease in c-fos induction and DNA synthesis in cells treated with bombesin (EC50 congruent to 40 nM). Significantly, the inhibitory effect of indomethacin was reversed in the presence of forskolin, a direct activator of adenylate cyclase. We conclude that cAMP plays a regulatory role in c-fos induction and mitogenesis in Swiss 3T3 cells treated with bombesin.

Animals↗
PubMed1990

Pasteurella multocida toxin: potent mitogen for cultured fibroblasts.

Native Pasteurella multocida toxin (PMT) is shown to be an extremely potent mitogen for Swiss 3T3 fibroblasts. Half-maximal stimulation of DNA synthesis was obtained at concentrations of 1 and 2 pM for recombinant PMT (rPMT) and PMT, respectively. The degree of rPMT-induced DNA synthesis was comparable to that elicited by 10% fetal bovine serum and, moreover, was observed in the complete absence of other factors. Cell proliferation was also enhanced by rPMT. The toxin was also a potent mitogen for BALB/c and NIH 3T3 cells, 3T6 cells, and tertiary mouse embryo or human fibroblasts. The mitogenic activity of rPMT was heat-labile. A polyclonal antiserum to PMT inhibited DNA synthesis when added early, but not late, during treatment of the Swiss 3T3 cells with rPMT. A similar time-dependent action of methylamine was also observed. Furthermore, transient exposure of the cells to rPMT at 37 degrees C, but not at 4 degrees C, resulted in a stimulation of DNA synthesis. Thus, toxin action may require cell entry and processing via an acidic compartment. The toxin, at mitogenic concentrations, caused a large increase in the production of inositol phosphates. In contrast, rPMT did not increase the intracellular concentration of cyclic AMP in Swiss 3T3 cells. The basis of rPMT action may afford a unique insight into molecular signaling events involved in the control of cell proliferation.

Animals↗
PubMed1990

The incidence of periodontopathic microorganisms in young children.

Thirty-six children in 4 cohorts of 0-1 week, 1-6 months, 1-2 years and 2-2 1/2 years of age were examined for the presence of black-pigmented Bacteroides species and some other bacteria suspected of being involved in the subsequent development of periodontal destruction. None of the sought-after bacteria were detected in the first week of life. Bacteroides intermedius and Bacteroides melaninogenicus were detected as early as 1 month after birth. Both of these bacteria were detected in 16-37% of children in the different cohorts. Bacteroides denticola was detected in one child. Other black-pigmented species including Bacteroides gingivalis and Bacteroides loescheii were not detected. Eikenella corrodens was detected in 62% of children under 6 months. Capnocytophaga spp. were detected in 12% and Fusobacterium nucleatum in 25% of children in this age group. With increasing age there was a trend towards an increase in the number of children with F. nucleatum but other bacteria were detected in similar numbers of children throughout the 3 older cohorts. Actinobacillus actinomycetemcomitans was not detected at any age.

Age Factors↗