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D A Kendall

Publications and source records attributed to D A Kendall.

At least 127 records · Page 7Linked to original sources
PubMed1990

Differential effects of elevated calcium ion concentrations on inositol phospholipid responses in mouse and rat cerebral cortical slices.

Inositol phospholipid turnover in cerebral cortical slices from mouse and rat was assessed using a [3H]inositol pre-labelling technique followed by anion exchange chromatography to isolate [3H]inositol phosphates ([3H]InsP chi). In both mouse and rat cerebral cortical slices, elevating the CaCl2 concentration of the Krebs medium from 1.3 to 4 mM did not significantly enhance the accumulation of [3H]InsP chi in the absence of any stimulus, or in the presence of glutamate (3 mM), depolarizing concentrations of KCl (25 mM), 5-hydroxytryptamine (0.3 mM), the calcium ionophore A23187 (33 microM) or carbachol (1 mM). However, the accumulations of [3H]InsP chi induced by histamine (1 mM) or noradrenaline (0.1 mM) were significantly increased by between 95 and 178% in cerebral cortical slices from both species by the elevation of extracellular calcium. Analysis of the individual inositol phosphates revealed that elevated ambient calcium enhanced the histamine-generated accumulations of [3H]InsP2, [3H]InsP3 and [3H]InsP4 by up to two-fold, while only the [3H]InsP3 response to carbachol was significantly increased. Under the same conditions, histamine, but not carbachol, selectively increased the accumulation of [3H]PtdInsP2 by up to 50%. The [3H]InsP chi responses to histamine and noradrenaline in combination with the calcium ionophore A23187 were greater-than-additive, inferring an enhancement of the receptor response by raised intracellular calcium. However, the combination of A23187 with glutamate or KCl resulted in significantly less-than-additive [3H]InsP chi responses. The [3H]InsP chi response to carbachol or 5-hydroxytryptamine was not significantly altered in the presence of A23187. Taken together, these results indicate heterogeneity between the mechanisms of inositol phospholipid turnover induced by these various stimuli in mammalian cerebral cortical slices.

Animals↗
PubMed1990

Polymeric sequences reveal a functional interrelationship between hydrophobicity and length of signal peptides.

We have examined the hydrophobicity component of signal peptide function using polymeric sequences in combination with cassette mutagenesis. Using homopolymeric units of either isoleucine, leucine, valine or alanine to replace the natural core segment of the Escherichia coli alkaline phosphatase signal peptide, the hydrophobicity requirements for export and processing were delineated. The transport properties of these mutants demonstrated that the net hydrophobicity determines the total extent of precursor processing, while a high mean hydrophobicity/residue is critical for complete, rapid processing and translocation. Moreover, alkaline phosphatase was converted from a periplasmic to an active membrane-anchored protein via a signal containing 20 leucine residues. This application of polymeric sequences allows systematic comparisons to be made, unambiguously revealing the hydrophobicity requirements governing specific steps in the transport process.

Alkaline Phosphatase↗
PubMed1990

A comparative analysis of single- and multiple-residue substitutions in the alkaline phosphatase signal peptide.

The alkaline phosphatase signal peptide participates in transport of the enzyme to the periplasmic space of Escherichia coli. The signal sequence, like that of other signal peptides, is composed of a polar amino-terminal segment, a central region rich in hydrophobic residues and a carboxy-terminal region recognized by signal peptidase. We have previously shown that an alkaline phosphatase signal peptide mutant containing a polyleucine core region functions efficiently in transport of the enzyme [D. A. Kendall, S. C. Bock, and E. T. Kaiser (1986) Nature 321, 706-708]. In this study, some of the amino acid changes involved in the polyleucine sequence are examined individually. A Phe to Leu substitution as the sole change results in impaired transport properties in contrast to when it is combined with three other amino acid changes in the polyleucine-containing sequence. A mutant with a Pro to Leu substitution in the hydrophobic core region is comparable to wild type while the same type of substitution (Pro to Leu) in the carboxy-terminal segment results in substantial accumulation of the mutant precursor. Finally, introduction of a basic residue into the hydrophobic segment (Leu to Arg substitution) results in a complete export block. These results exemplify the spectrum of properties produced by individual residue changes and suggest there is some interplay between hydrophobicity and conformation for signal peptide function.

Alkaline Phosphatase↗
PubMed1990

The influence of adrenalectomy on alpha-adrenoceptor responses in rat cerebral cortex slices.

Experiments were undertaken to examine the effect of depletion of adrenal steroids on neurotransmitter-stimulated cAMP accumulation in rat cerebral cortex slices. Long-term depletion due to bilateral adrenalectomy (ADX) and short term depletion due to the steroid synthesis inhibitor metopirone (MET) caused a significant increase in alpha 1-adrenoceptor-mediated potentiation of beta-adrenoceptor-stimulated cAMP accumulation. The effect of MET was prevented by corticosterone treatment. This effect of ADX was selective in that there was no change in alpha 1-adrenoceptor-mediated inositol phosphate accumulation. In addition, ADX had no effect on potentiation of isoprenaline-stimulated cAMP by either the GABAB agonist baclofen or the phorbol ester, 4 beta-phorbol dibutyrate. However, 2-chloroadenosine-stimulated cAMP accumulation was significantly reduced in ADX rats.

Adrenal Glands↗
PubMed1990

Discriminatory effects of forskolin and EGTA on the indirect cyclic AMP responses to histamine, noradrenaline, 5-hydroxytryptamine, and glutamate in guinea-pig cerebral cortical slices.

The effects of forskolin (1 microM) and EGTA (5 mM) on indirect cyclic AMP responses in slices of guinea-pig cerebral cortex were examined. Forskolin had little effect on the direct 2-chloroadenosine-stimulated cyclic AMP response. However, it completely abolished the glutamate-induced augmentation of this response. In contrast, forskolin had very little effect on the indirect cyclic AMP responses to noradrenaline, 5-hydroxytryptamine, and histamine. Conversely, rapid removal of extracellular calcium with EGTA 2 min before addition of the indirectly acting agent markedly reduced the augmentation responses produced by these latter agonists, but had little effect on the glutamate augmentation. When EGTA was added once a steady level of cyclic AMP had been achieved with the indirect agents, it was without effect on any of the responses. Thus, calcium appears to have a role in the early, but not the later, stages of the noradrenaline, 5-hydroxytryptamine, and histamine responses. A role for protein kinase C in the glutamate augmentation response was suggested, because forskolin inhibited the augmentation of the 2-chloroadenosine response produced by phorbol esters (which mimic the actions of diacylglycerol in activating protein kinase C). We conclude that there is more than one mechanism by which the augmentation of cyclic AMP responses can occur.

Animals↗
PubMed1990

Is the adenosine receptor modulation of histamine-induced accumulation of inositol phosphates in cerebral cortical slices mediated by effects on calcium ion fluxes?

In this report, we show that under conditions designed to provide an initially uniform incorporation of [3H]inositol into mouse and guinea pig cerebral cortical slices prior to agonist stimulation, the accumulation of 3H-inositol phosphates (3H-InsPx, x = 1-4) induced by histamine in mouse and guinea pig cerebral cortical slices increased in a quasilinear manner with increasing added calcium. Raising the ambient calcium ion concentration failed to reduce the adenosine receptor-mediated inhibition of the histamine-induced 3H-InsPx response in mouse cerebral cortical slices. Similarly, the potentiation of the histamine response by adenosine receptor activation in guinea pig cerebral cortical slices was unaffected by lowering the added calcium ion concentration. The presence of the calcium ionophore A23187 (33 microM) produced 3H-InsPx responses in both mouse and guinea pig cerebral cortical slices, which were not affected by the presence of the stable adenosine analogue 2-chloroadenosine. A23187 also potentiated the accumulation of 3HInsPx induced by histamine in both species. Both the inhibitory and potentiatory modulations of the histamine response by 2-chloroadenosine in mouse and guinea pig, respectively, were still apparent in the presence of A23187. These results indicate that the histamine-induced 3H-InsPx accumulations in both mouse and guinea pig cerebral cortical slices are sensitive to variations in calcium ion concentrations. However, the adenosine receptor modulations of the histamine responses are relatively insensitive to fluctuations in either extra- or intracellular calcium ion concentrations, and thus cannot be mediated by effects on calcium ion movements.

2-Chloroadenosine↗
PubMed1990

Excitatory amino acid-induced formation of inositol phosphates in guinea-pig cerebral cortical slices: involvement of ionotropic or metabotropic receptors?

In cerebral cortical slices from the guinea-pig, quinoxalinedione derivatives antagonised the generation of 3H-inositol phosphates evoked by the excitatory amino acids quisqualate and DL-alpha-amino-3-hydroxy-5-methyl-4-isoxalone propionic acid but were without effect on the trans-DL-1-amino-1,3-cyclopentanedicarboxylic acid and L-glutamate responses. Omission of calcium from the medium reduced the accumulation of 3H-inositol phosphates induced by incubation with trans-DL-1-amino-1,3-cyclopentanedicarboxylic acid (incubation for 45 min) by greater than 50%, whereas the responses to L-glutamate and the two other amino acid analogues were reduced by approximately 20%. Generation of inositol 1,4,5-trisphosphate over a 30-s period by treatment with quisqualate, trans-DL-1-amino-1,3-cyclopentane-dicarboxylic acid, KCl, and carbachol was abolished in the presence of nominally calcium-free medium. L-Glutamate induced a large, rapid increase in inositol 1,4,5-trisphosphate mass (more than three-fold), which was, however, unaffected by omission of calcium from the medium. These results indicate that of the excitatory amino acids tested, only L-glutamate may be classed as a metabotropic receptor agonist in guinea-pig cerebral cortical slices with respect to generation of inositol phosphates. The other agents appear to stimulate accumulation of inositol phosphates, at least in part through some mechanism requiring the presence of extracellular Ca2+, presumably Ca2+ entry.

Amino Acids↗
PubMed1990

The glycine antagonist 7-chlorokynurenic acid blocks the effects of N-methyl-D-aspartate on agonist-stimulated phosphoinositide hydrolysis in guinea-pig brain slices.

Despite having no effect on basal phosphoinositide hydrolysis. N-methyl-D-aspartate (NMDA) inhibited carbachol-stimulated accumulation of 3H-inositol phosphates and enhanced that due to noradrenaline in guinea-pig cerebral cortex slices. The glycine antagonist 7-chlorokynurenic acid inhibited the effects of NMDA and this inhibition was reversed by glycine. The action of 7-chlorokynurenic acid was not mimicked by strychnine or HA 966 (1-hydroxy-3-aminopyrrolid-2-one). L-Glutamate also inhibited carbachol-stimulated accumulation of 3H-inositol phosphates, but this inhibition was not blocked by 7-chlorokynurenic acid. The data are consistent with glycine maintaining tonic control over NMDA receptor activity in guinea-pig brain.

Animals↗
PubMed1990

Niguldipine discriminates between alpha 1-adrenoceptor-mediated second messenger responses in rat cerebral cortex slices.

The effect of both isomers of niguldipine, a highly selective alpha 1-adrenoceptor antagonist and dihydropyridine calcium channel blocker, on noradrenaline-stimulated inositol phosphate (IP) accumulation and adenosine 3':5'-cyclic monophosphate (cyclic AMP) potentiation was examined. Both isomers inhibited noradrenaline-stimulated IP accumulation. (+)-Niguldipine was 100 fold more potent than (-)-niguldipine. Potentiation of beta-adrenoceptor-stimulated cyclic AMP by noradrenaline was only partially inhibited by both isomers. The dihydropyridine, israpidine, did not inhibit either second messenger response. This study provides further evidence that the alpha 1-adrenoceptors mediating IP accumulation and cyclic AMP potentiation are different.

Animals↗
PubMed1990

Inositol phospholipid hydrolysis in human brain; adenosine inhibition of the response to histamine.

1. Inositol phospholipid hydrolysis was examined in human cerebral cortex slices by a [3H]-inositol prelabelling assay. 2. Enhancement of [3H]-inositol phosphates accumulation was observed in the presence of carbachol, noradrenaline, histamine, 5-hydroxytryptamine (5-HT) and depolarizing concentrations of KCl. 3. Despite having no effect alone, adenosine (and its analogue 2-chloroadenosine) selectively inhibited the direct response to histamine. 4. The inhibition due to adenosine was antagonized by theophylline, but not by 8-cyclopropyltheophylline.

2-Chloroadenosine↗
PubMed1990

The effects of acute and chronic lithium treatment on pilocarpine-stimulated phosphoinositide hydrolysis in mouse brain in vivo.

1. Measurements were made of the in vivo formation of inositol phosphates in the brains of C57/B1/601a mice treated acutely or chronically with lithium chloride (LiCl). 2. A single injection of LiCl (10 mEquiv kg-1, s.c.) 18 h before death increased the accumulation of [3H]-inositol phosphates ([3H]-Ins P's) in the brains of mice injected i.c.v. with [3H]-myo-inositol 24 h previously. 3. Pilocarpine (200 mg kg-1, i.p.) injected 15 min before death further enhanced the formation of [3H]-Ins P's in the brains of LiCl-treated, but not saline-treated, mice. The enhancement due to pilocarpine was abolished by injection of atropine sulphate (10 mg kg-1, i.p.) 10 min earlier. 4. Chronic (14 days) LiCl feeding produced an accumulation of [3H]-Ins P's significantly less than that due to a single injection of LiCl, but the response to pilocarpine was markedly greater in mice chronically fed with LiCl when compared with mice acutely injected with LiCl. 5. Mass measurements of endogenous inositol 1,4,5 triphosphate revealed increases due to pilocarpine and chronic LiCl feeding alone. A combination of the two treatments produced levels greater than either alone. 6. These results demonstrate that LiCl treatment enhances both basal and pilocarpine-stimulated inositol phospholipid hydrolysis in vivo and this might be relevant to its therapeutic effects.

Animals↗
PubMed1990

Lithium amplifies inhibitions of inositol phospholipid hydrolysis in mammalian brain slices.

1. We have examined the effects of lithium chloride (LiCl) on inhibitions of inositol phospholipid hydrolysis in guinea-pig and rat brain slices by assessing the accumulation of [3H]-inositol phosphates ([3H]-InsP), in vitro. 2. In guinea-pig and rat cerebral cortex slices the accumulation of total [3H]-inositol phosphates due to the cholinoceptor agonist carbachol was inhibited by the excitatory amino acid L-glutamate, but only when LiCl was present. 3. The effects of LiCl were time and concentration-dependent. Significant inhibitions of the carbachol response by glutamate (in the presence of LiCl) being evident only after 20-30 min of stimulation at LiCl concentrations above 1.2 mM. 4. N-methyl-D-aspartate (NMDA), in the absence of LiCl, enhanced the response to carbachol at low concentrations of the amino acid and inhibited the response at higher concentrations. In the presence of 5 mM LiCl, only the inhibitory phase was observed. 5. In rat cerebral cortex slices, aluminium fluoride inhibited [3H]-InsP accumulation in the presence of carbachol, noradrenaline and a depolarising concentration of KCl and these inhibitions were more marked when LiCl was present. The response to histamine was unaffected. 6. The data presented provide evidence that LiCl amplifies inhibitions of inositol phospholipid hydrolysis due to receptor and non-receptor mediated stimuli, although the mechanism underlying the effect is, as yet, obscure.

Aluminum↗
PubMed1989

Signal peptide subsegments are not always functionally interchangeable. M13 procoat hydrophobic core fails to transport alkaline phosphatase in Escherichia coli.

Bacterial signal peptides display little amino acid sequence homology despite their shared role in mediating protein transport. This heterogeneity may exist to permit the establishment of signal peptide conformations that are appropriate for transport of particular proteins. In this paper we explore how signal peptides are composed of structural units that may interact with each other and with the mature protein to effect transport. Using a new application of cassette mutagenesis, we have replaced the hydrophobic core of the Escherichia coli alkaline phosphatase signal peptide with cores from the signals of maltose-binding protein, OmpA, and M13 major coat protein. The core regions from maltose-binding protein and OmpA effectively replaced the alkaline phosphatase core; the resultant hybrid signals performed as well as wild type in periplasmic transport and processing of alkaline phosphatase. However, the core region from M13 major coat protein generated a transport-incompetent hybrid signal peptide. Elimination of a proline-containing portion of the M13 major coat protein core did not improve transport effectiveness. However, restoration of the procoat cleavage region and the negatively charged amino terminus of the mature protein did ameliorate the transport defect. These results suggest that at least in the case of these procoat-derived signal peptide mutants, there is a requirement for complementarity among the hydrophobic core, cleavage region, and part of the mature protein in order for efficient protein transport to occur.

Alkaline Phosphatase↗
PubMed1989

Inositol phospholipid hydrolysis and potentiation of cyclic AMP formation by noradrenaline in rat cerebral cortex slices are not mediated by the same alpha-adrenoceptor subtypes.

A pharmacological study was undertaken to determine whether the noradrenaline-stimulated breakdown of inositol phospholipids and the potentiation of isoprenaline-stimulated cyclic AMP by noradrenaline in rat cerebral cortex slices are mediated by the same alpha-receptor subtype. The rank order of potency of a range of alpha 1 and alpha 2 antagonists suggests that both responses may involve an alpha 1 receptor, but there were several differences between the pharmacological profiles for the two systems. Although in both cases, all selective alpha 1 antagonists were more potent than alpha 2 antagonists, the rank orders and the absolute potencies differed for the two responses. The inhibition of the inositol phosphate response was characterised by a high alpha 1/alpha 2 antagonist ratio, and in most cases, Hill slopes of inhibition were consistent with the involvement of a single receptor site. Inhibition of the cyclic AMP response had a much lower alpha 1/alpha 2 antagonist ratio and generally exhibited Hill slopes less than one. Evidence has been provided suggesting that adenosine is involved in the potentiation of cyclic AMP and that other, as yet unidentified, factors may also be involved. Even in the absence of an adenosine component, the results presented support the suggestion that the potentiation due to noradrenaline is mediated by a receptor whose identity does not easily fit with the currently accepted classification of alpha adrenoceptors.

Adenosine↗
PubMed1989

Effects of lithium on inositol phospholipid hydrolysis and inhibition of dopamine D1 receptor-mediated cyclic AMP formation by carbachol in rat brain slices.

The in vitro and ex vivo effects of lithium on muscarinic cholinergic inositol phospholipid hydrolysis and muscarinic cholinergic inhibition of dopamine D1-receptor-stimulated cyclic AMP formation were examined in rat brain slices. Following chronic lithium feeding, carbachol-stimulated inositol phosphate accumulation was reduced ex vivo in slices of cerebral cortex but not in striatal slices. Lithium (1 mM) in vitro had no direct effect on dopamine D1-receptor-stimulated cyclic AMP formation, but enhanced the inhibitory effect of carbachol on the D1 response, in striatal slices, and this was not significantly altered by prior lithium feeding. Lithium therefore has effects on two discrete muscarinic responses in rat brain which are apparently maintained after chronic exposure to the ion and might be relevant to its antimanic actions.

Animals↗
PubMed1989

No role for phospholipase A2 and protein kinase C in the potentiation by alpha-adrenoceptors of beta-adrenoceptor-mediated cyclic AMP formation in rat brain.

This study was undertaken to examine the role of phospholipase A2 and protein kinase C in the potentiation of beta-adrenoceptor-mediated cyclic AMP formation by alpha-adrenoceptors in rat cerebral cortical slices. Inhibition of arachidonic acid metabolism by a range of cyclooxygenase and lipoxygenase inhibitors had no effect on the potentiation of isoprenaline-stimulated cyclic AMP. Conversely, stimulation of leukotriene formation had no effect on the response to isoprenaline. The phospholipase A2 activator, melittin, stimulated cyclic AMP and potentiated the effect of isoprenaline, but these responses were not influenced by cyclooxygenase or lipoxygenase inhibitors. Indomethacin was also ineffective against the potentiation of vasoactive intestinal peptide-stimulated cyclic AMP by noradrenaline. Phorbol ester potentiated the cyclic AMP response to isoprenaline, and this potentiation was antagonized by three different putative protein kinase C inhibitors. However, the same inhibitors did not affect the alpha-adrenoceptor-stimulated enhancement of the response to isoprenaline. We have found no evidence, therefore, to support the suggestion that arachidonic acid and its metabolites and/or protein kinase C mediate the alpha-adrenoceptor modulation of beta-adrenoceptor function.

Animals↗
PubMed1989

Differences in the adenosine receptors modulating inositol phosphates and cyclic AMP accumulation in mammalian cerebral cortex.

1. 2-Chloroadenosine stimulated adenosine 3':5'-cyclic monophosphate (cyclic AMP) accumulation and potentiated (guinea-pig) or inhibited (mouse) the histamine H1-receptor-stimulated hydrolysis of inositol phospholipids in slices of guinea-pig and mouse cerebral cortex. 2. Two xanthine-based adenosine receptor antagonists were identified which were one order of magnitude more potent at the adenosine receptor mediating augmentation of the histamine-stimulated inositol phospholipid hydrolysis than at the receptor linked to cyclic AMP formation in guinea-pig cerebral cortical slices. 3. These compounds, 8-cyclopentyl-1,3-dipropylxanthine (DPCPX) and 7-benzyl-3-(2-methylpropyl)xanthine (BMPX) retained their selectivity under near-identical incubation conditions in both assays. 4. These compounds also showed similar affinities and selectivity for the adenosine receptor mediating inhibition of histamine-stimulated inositol phospholipid hydrolysis in mouse cerebral cortical slices. 5. Inclusion of agents which give rise to, or mimic, high levels of cyclic AMP (forskolin (1 microM), 8-bromo-cyclic AMP (1 mM) and vasoactive intestinal polypeptide (1 microM] in the incubation medium failed to mimic the action of 2-chloroadenosine on inositol phospholipid turnover in cerebral cortical slices from either species. 6. These data suggest that the adenosine receptor modulating the hydrolysis of inositol phospholipid in mouse and guinea-pig cerebral cortical slices is different from the adenosine receptor linked to cyclic AMP formation, and, furthermore, that the modulation of inositol phospholipid metabolism in either species is not mediated via alterations in cyclic AMP levels.

1-Methyl-3-isobutylxanthine↗