Showing papers by "University of Dundee published in 1978"
TL;DR: The finding that the ‘modulator’ could substitute for troponin-C in restoring calcium sensitivity to actomyosin ATPase in reconstituted systems was substantiated by the determination of the amino acid sequence of the “calcium-dependent modulator” from bovine brain and rat testis.
579 citations
TL;DR: In this paper, the authors proposed a natural scheme of layering in which a surface layer, the active layer, is distinguished from the inert layer, and suggested that the upper layer be termed the acrotelm and the lower layer the catotelm.
Abstract: Summary
Two recent North American soil classification schemes embodying criteria for distinguishing layers in mire soils are criticised as being artificial and unrelated to function. In these soils, the most important functional processes are hydrological. The two-layer hypothesis of K. E. Ivanov, involving a set of hydrological differences and associated biological characteristics, is accordingly advocated as a basis for a natural scheme of layering, in which a surface layer, the ‘active layer’, is distinguished from the ‘inert layer’ below. Since both expressions are deemed inadmissible, it is suggested that the upper layer be termed the acrotelm and the lower layer the catotelm. A two-layered mire soil should be termed diplotelmic and one without an acrotelm, haplotelmic. Basic definitions for all 4 terms are provided. Possible applications to eroded or reclaimed mires are briefly discussed.
407 citations
TL;DR: The levels of the 32000-Mr protein in the inner membrane of guinea-pig brown-adipose-tissue mitochondria correlate with the degree of thermogenic adaptation of the animal.
Abstract: Brown-adipose-tissue mitochondria possess an energy-dissipating ion uniport which is inhibited by purine nucleotides. The regulatory nucleotides bind to a high-affinity site on the outer face of the inner membrane which is independent of the adenine nucleotide translocator. A direct correlation between affinity for the regulatory site and ability to inhibit the ion uniport is demonstrated for a number of nucleotide analogues. 8-Azido-adenosine 5'-triphosphate, a photoaffinity label, also competes with GDP for the binding site and induces respiratory control. 8-Azido-adenosine [gamma-32P]triphosphate was prepared and covalently bound to hamster brown-adipose-tissue mitochondria by near-ultraviolet irradiation. Two major radioactive bands were identified of apparent molecular weight 30000 and 32000, representing 6% and 10% of the inner membrane protein respectively. Selective labelling enabled the 30000-Mr protein to be identified as the carboxyatractylate binding component of the adenine-nucleotide translocator and the 32000-Mr protein to be identified as the regulatory site of the energy-dissipating ion uniport. The levels of the 32000-Mr protein in the inner membrane of guinea-pig brown-adipose-tissue mitochondria correlate with the degree of thermogenic adaptation of the animal.
391 citations
TL;DR: A steady-state cycling of Ca(2%) through independent influx and efflux pathways provides a model which is kinetically and thermodynamically consistent with the present observations, and which predicts an extremely precise regulation of pCa(2+) (0) by liver mitochondria in vivo.
Abstract: The mechanism whereby rat liver mitochondria regulate the extramitochondrial concentration of free Ca2+ was investigated. At 30°C and pH7.0, mitochondria can maintain a steady-state pCa2+0 (the negative logarithm of the free extramitochondrial Ca2+ concentration) of 6.1 (0.8μm). This represents a true steady state, as slight displacements in pCa2+0 away from 6.1 result in net Ca2+ uptake or efflux in order to restore pCa2+0 to its original value. In the absence of added permeant weak acid, the steady-state pCa2+0 is virtually independent of the Ca2+ accumulated in the matrix until 60nmol of Ca2+/mg of protein has been taken up. The steady-state pCa2+0 is also independent of the membrane potential, as long as the latter parameter is above a critical value. When the membrane potential is below this value, pCa2+0 is variable and appears to be governed by thermodynamic equilibration of Ca2+ across a Ca2+ uniport. Permeant weak acids increase, and N-ethylmaleimide decreases, the capacity of mitochondria to buffer pCa2+0 in the region of 6 (1μm-free Ca2+) while accumulating Ca2+. Permeant acids delay the build-up of the transmembrane pH gradient as Ca2+ is accumulated, and consequently delay the fall in membrane potential to values insufficient to maintain a pCa2+0 of 6. The steady-state pCa2+0 is affected by temperature, incubation pH and Mg2+. The activity of the Ca2+ uniport, rather than that of the respiratory chain, is rate-limiting when pCa2+0 is greater than 5.3 (free Ca2+ less than 5μm). When the Ca2+ electrochemical gradient is in excess, the activity of the uniport decreases by 2-fold for every 0.12 increase in pCa2+0 (fall in free Ca2+). At pCa2+0 6.1, the activity of the Ca2+ uniport is kinetically limited to 5nmol of Ca2+/min per mg of protein, even when the Ca2+ electrochemical gradient is large. A steady-state cycling of Ca2+ through independent influx and efflux pathways provides a model which is kinetically and thermodynamically consistent with the present observations, and which predicts an extremely precise regulation of pCa2+0 by liver mitochondria in vivo.
343 citations
TL;DR: The role of cyclic-AMP-dependent protein kinase in the regulation of glycogen metabolism in mammalian skeletal muscle is discussed, which determines the time at which dephosphorylation of the β subunit and inactivation of the enzyme can become rapid through phosphorylations of the α subunit.
Abstract: Publisher Summary This chapter discusses the role of cyclic-AMP-dependent protein kinase in the regulation of glycogen metabolism in mammalian skeletal muscle. When assayed at optimal ATP-Mg-concentrations and in the presence of saturating amounts of Ca2+, purified phosphorylase kinase has a very low activity at physiological pH (6.8) relative to the activity at pH 8.2. Phosphorylation of α subunit of phosphorylase kinase controls the rate of dephosphorylation of the β subunit catalyzed by phosphorylase kinase phosphatase. The conversion of phosphorylase kinase a to phosphorylase b correlates with dephosphorylation of the β subunit, and the rate of dephosphorylation of the enzyme in the absence of divalent cations is determined by the extent of phosphorylation of the α subunit. Phosphorylation of the α subunit alters the conformation of phosphorylase kinase in such a way that it facilitates the action of phosphorylase kinase phosphatase on the β subunit. Cyclic-AMP-dependent protein kinase plays two roles: (1) it activates the enzyme through phosphorylation of the β subunit and (2) it determines the time at which dephosphorylation of the β subunit and inactivation of the enzyme can become rapid through phosphorylation of the α subunit.
334 citations
TL;DR: This review surveys briefly the responses of seeds held at different hydration levels, from normal germination in a free water supply to seed activation without germination under slight moisture stress, seed deterioration at greater moisture stress and the damage that can be caused to seeds in very dry conditions, as well as the responses to subsequent dehydration.
Abstract: Current interest in seed hydration treatments for the improvement of level, rate and uniformity of germination or field emergence has revealed how little is known of the physiology of germination control under water stress. This review surveys briefly the responses of seeds held at different hydration levels, from normal germination in a free water supply to seed activation without germination under slight moisture stress, seed deterioration at greater moisture stress and the damage that can be caused to seeds in very dry conditions, as well as the responses to subsequent dehydration. Inhibition of germination, though not of seed activation, at certain levels of water stress is likened to various forms of dormancy, and the mechanism governing the initiation of cell elongation is suggested as the possible key to control over germination. Several lines of evidence on cell membrane integrity and action, and their responses to external factors, point to the role that the membrane may play in cell elongation (and hence germination) control, and membrane integrity may also be associated with the transition between seed deterioration at one hydration level and seed activation and repair at slightly higher hydration levels. Seed activation without germination is also considered in an ecological context.
305 citations
TL;DR: The purified protein was in a state approaching homogeneity as judged by the criteria of polyacrylamide-gel electrophoresis and ultracentrifugal analysis, and amino acid composition suggest than inhibitor-1 may possess little ordered structure.
Abstract: Inhibitor-1 is a protein which inhibits phosphorylase phosphatase only when it has been phosphorvlated by cyclic-AMP-dependent protein kinase [Huang, F. L. and Glinsmann. W. H. (1976) Eur. J. Biochem. 70, 419–426].
Inhibitor-1 was purified by a heat treatment at 90°C, precipitation with ammonium sulphate, chromatography on DEAE-cellulose, gel filtration on Sephadex G-100, and finally recromatography of the phosp0horylated protein on DEAE-cellulose. The protein was purified 4000-fold and 1.5 mg per 1000 g muscle was obtained in seveven days corresponding to an overall yield of 15–20%. The purified protein was in a state approaching homogeneity as judged by the criteria of polyacrylamide-gel electrophoresis and ultracentrifugal analysis. The concentration of inhibitor-1 in vivo was calculated to be 1.5 μMM, which is at least as high as the concentrationof phosphorylase phosphatase.
The amino acid composition of inhibitor-1 showed several unusual features. Glutamic acid and proline accounted for nearly one third of the residues, tyrosine, tryptophan and cysteine were absent, and the content of aromatic amino acids was very low.
The molecular weight measured by sedimentation equilibraium centrifugation was 19 200 and by amino acid analysis was 20 800. These values were lower than the mol. wt of 26000 determined empirically by gel electrophoresis in the presence of sodium dodecyl sulphate, and much lower than the apparent molecular weitht of 60000 estimated by filtraation on Sephadex G-100. The gel filtration behaviour, stability to heating at 100°C and amino acid composition suggest than inhibitor-1 may possess little ordered structure.
The phosphorylated form of inhibitor-1contained close to one molecule of covalently bound phosphate per mole of protein, which is consistent with previous finding of a unique decapeptide sequence at the site of phosphorylation, Ile-Arg-Arg-Arg-Arg-Pro-Thr(p-Pro-Ala-Thr-[Cohen, P., Rylatt, D. B. and Nimmo, G. A. (1977) FEEBS Lett. 76, 182–186].
The phosphorylated form of inhibitor-1 inhibited phosphorylase activity (0.02 U) by 50% at a concentration of only 7.0 nM in the standard assay, but the phosphorylated decapeptide was 1000–2000 times less effective as an inhibitor.
279 citations
TL;DR: A method is described for the preparation of ;free' and ;synaptosomal' brain mitochondria from fractions of guinea-pig cerebral cortex respectively depleted and enriched in synaptosomes, which shows a hyperbolic dependency on free Ca(2+) concentration.
Abstract: A method is described for the preparation of ;free' and ;synaptosomal' brain mitochondria from fractions of guinea-pig cerebral cortex respectively depleted and enriched in synaptosomes. Both preparations of mitochondria have a low membrane H(+) conductance, a high capacity to phosphorylate ADP, and a capacity to accumulate Ca(2+) at rates limited by the activity of the respiratory chain. Ca(2+) transport by ;free' brain mitochondria is compared with that of heart mitochondria. The Ca(2+) conductance of ;free' brain mitochondria was at least 20 times that for rat heart mitochondria. Ca(2+) uptake by brain mitochondria increased the pH gradient and decreased membrane potential, whereas little change occurred during the much slower uptake by heart mitochondria. In the presence of ionophore A23187, dissipative Ca(2+) cycling decreased the H(+) electrochemical potential gradient of brain mitochondria from 190 to 60mV, but caused only a slight decrease with heart mitochondria, although the ionophore lowered the pH gradient and increased membrane potential. The Ca(2+) conductance of ;free' brain mitochondria is distinctive in showing a hyperbolic dependency on free Ca(2+) concentration. In the presence of Ruthenium Red, a rapid Na(+)-dependent Ca(2+) efflux occurs. The H(+) electrochemical potential gradient is maintained during this efflux, and membrane potential increases, with both ;free' brain and heart mitochondria. The Na(+) requirement for Ca(2+) efflux appears not to be related to the high Na(+)/H(+) exchange activity but may represent a direct exchange of Na(+) for Ca(2+).
252 citations
TL;DR: Following-up over 18 months suggested that both early initiation and increased frequency of breast-feeding extended the nursing period, the former having the greater effect.
239 citations
TL;DR: Using a photo-affinity analogue of ATP, the nucleotide binding component is identified as a protein of 32,000 daltons that represents the molecular site of non-shivering thermogenesis in hamster brown adipose tissue mitochondria.
Abstract: The proton conductance of the inner membrane of hamster brown adipose tissue mitochondria can be regulated in vitro by exogenous purine nucleotides, which “bind to a component on the outer face of the inner membrane. This unique mechanism has been proposed to represent the molecular site of non-shivering thermogenesis in this tissue. Using a photo-affinity analogue of ATP, we have identified the nucleotide binding component as a protein of 32,000 daltons.
150 citations
TL;DR: Patterns of intraurban accessibility to primary medical care in four major Scottish cities are examined and results indicate that disparities in accessibility tend to compound many other patterns of socioeconomic disadvantage.
Abstract: Patterns of intraurban accessibility to primary medical care in four major Scottish cities are examined in the context of existing public policy and against the background of intraurban patterns of...
TL;DR: Inhibitor-1 from rabbit skeletal muscle was phosphorylated by protein kinase dependent on adenosine 3' :5'-monophosphate (cyclic AMP), but not by phosphorylase kinase or by glycogen synthetase Kinase-2, highlighting the potential importance of inhibitor-1 in the regulation of glycogen metabolism.
Abstract: Inhibitor-1 from rabbit skeletal muscle was phosphorylated by protein kinase dependent on adenosine 3' :5'-monophosphate (cyclic AMP), but not by phosphorylase kinase or by glycogen synthetase kinase-2. Protein phosphatase-III, isolated and stored in the presence of manganese ions to keep it stable, was in a form which catalysed a rapid dephosphorylation and inactivation of inhibitor-1. The kinetic constants for the dephosphorylation of inhibitor-1 [Km = 0.7 micron, V(rel) = 40] were comparable to those for the dephosphorylation of phosphorylase kinase [Km =1.1 micron, V (rel) = 62] and phosphorylase [Km = 5.0 micron, V (rel) = 100]. The dephosphorylation of inhibitor -1 was inhibited by inhibitor-2, indicating that it was catalysed by protein phosphatase-III, and not by another enzyme that might be contaminating the preparation. When protein phosphatase-III was diluted into buffers containing excess EDTA, it lost activity initially, but after 90 min, the activity reached a plateau that remained stable for at least 20h. The initial loss in activity varied with the substrate that was tested; it was 20-30% with phosphorylase a, 50-60% with phosphorylase kinase and greater than or equal to 95% with inhibitor-1. This form of protein phosphatase-III was inhibited by inhibitor-1 in a noncompetitive manner, and the Ki for inhibitor-1 was 1.6 +/- 0.3 nM. The phosphorylase phosphatase, phosphorylase kinase phosphatase and glycogen synthetase phosphatase activities of protein phosphatase-III were inhibited in an identical manner by inhibitor-1. This result emphasizes the potential importance of inhibitor-1 in the regulation of glycogen metabolism, since it can influence the state of phosphorylation of three different enzymes. The formation of the inactive complex between inhibitor-1 and protein phosphatase-III was reversed by incubation with trypsin (which destroyed inhibitor-1, but not protein phosphatase-III) or by dilution of the inactive complex. Kinetic studies, using the form of protein phosphatase-III which dephosphorylated inhibitor-1 very rapidly, demonstrated three unusual features of the system: (a) inhibitor-1 was still as powerful and inhibitor of the dephosphorylation of phosphorylase a and phosphorylase kinase a even under conditions where it was being rapidly dephosphorylated; (b) inhibitor-1 was not an inhibitor of its own dephosphorylation; (c) phosphorylase a did not effect the rate of dephosphorylation of inhibitor-1 even when it was present in a 50-fold molar excess over inhibitor-1. The result of these three properties is that inhibitor-1 is preferentially dephosphorylated by protein phosphatase-III even in the presence of a large excess of other phosphoprotein substrates. Inhibitor-1 was also dephosphorylated by protein phosphatase-II. The kinetic constants for the dephosphorylation of inhibitor-1 [Km = 2.8 micron, V (rel) = 200] and the alpha-subunit of phosphorylase kinase [Km = 3.7 micron, V (rel) = 100]were comparable...
Book•
01 Jan 1978TL;DR: In this article, a unified approach to multiparameter spectral theory of linear operators in Hilbert space is presented, which is applicable to both bounded and unbounded operators and has application in the study of multi-parameter spectral problems of ordinary differential operators.
Abstract: The object of this paper is to present a unified approach to multiparameter spectral theory of linear operators in Hilbert space. The theory is applicable to both bounded and unbounded operators and has application in the study of multiparameter spectral problems of ordinary differential operators. The main results include a Parseval equality and an eigenfunction expansion theorem.
TL;DR: Reduction in daylength and irradiance depressed the growth more in mycorrhizal than in uninfected maize plants, and in Rhizobium- and Glomus-infected alfalfa plants, a daylength of 16 h produced the highest carbon contents and C/N ratios.
Abstract: SUMMARY
Defoliation of maize and tomatoes reduced the mycorrhizal growth response and development of the endophyte, estimated as percentage infection, root pigmentation and spore production. More fresh and dry matter was produced in mycorrhizal grasses harvested on three separate occasions than from a single final harvest. The total yields from two harvests and the yield from a single harvest of alfalfa were similar although nodulated and mycorrhizal plants were larger at each harvest. In both grasses and alfalfa, periodic harvesting reduced the mycorrhizal infection by approximately 50%.
Reduction in daylength and irradiance depressed the growth more in mycorrhizal than in uninfected maize plants. In Rhizobium- and Glomus-infected alfalfa plants, a daylength of 16 h produced the highest carbon contents and C/N ratios. Plants exposed to short days produced more, smaller nodules and had higher nitrogen contents than plants given long days. Long days favoured the development of the mycorrhizal infection and these dually infected plants produced more dry matter, reduced acetylene faster and contained more nitrogen than nodulated only plants. The supply of photosynthate is probably an important factor controlling the development of the mycorrhiza.
TL;DR: In this paper, a series of model calculations based on the experimentally determined density of state distribution in glow-discharge a-Si is presented, where the net space charge in the barrier region is calculated as a function of energy for doped and undoped specimens.
Abstract: With the growing interest in the properties and application of amorphous (a-) Si it is relevant to look in some detail into the formation and electronic properties of the amorphous barrier and p-n junction. In the first part of this paper a series of model calculations based on the experimentally determined density of state distribution in glow-discharge a-Si is presented. The net space charge in the barrier region is calculated as a function of energy for doped and undoped specimens. A step-by-step solution of Poisson's equation then leads to the barrier profile showing that the a-barrier for undoped and weakly doped specimens differs basically from its crystalline counterpart. The analysis is then extended to the amorphous p-n junction. In the second part of the paper the differential barrier capacitance, C, is calculated and its dependence on applied potentials and on frequency investigated. It is found that C‒V plots should be critically dependent on the measuring frequency because the latter...
TL;DR: The results indicated that the magnitude of the tilt after-effect was not influenced by the colour of the inspection and test gratings, was not affected by binocular rivalry suppression, and was the same under various conditions of monocular and binocular inspection and testing.
TL;DR: Young and elderly subjects were given the hypnotic dichloralphenazone in a dose of 20 mg/kg nightly for two weeks and the extent of induction of liver microsomal drug metabolism was assessed, indicating that elderly patients show a reduced induction response.
Abstract: Young and elderly subjects were given the hypnotic dichloralphenazone (Welldorm) in a dose of 20 mg/kg nightly for two weeks and the extent of induction of liver microsomal drug metabolism was assessed from alteration in the plasma elimination of quinine and antipyrine (phenazone). With both indices, there was a significant increase in plasma drug clearance in young subjects following dichloralphenazone treatment but no significant alterations occured in the elderly group. These results indicate that, in addition to being less able to metabolize some drugs, elderly patients show a reduced induction response. They may therefore be less likely to become tolerant to those drugs which are inactivated by metabolism.
TL;DR: The combination of both drugs together more than doubled the FEV1 change in both groups of patients, and the addition of prednisolone to both drugs produced a marginal advantage only in those with asthma.
Abstract: Eleven patients with bronchial asthma and 10 with chronic bronchitis were treated over four consecutive 3-day periods, firstly with aerosols either of ipratropium bromide (40 microgram four times a day) or of salbutamol (200 microgram four times daily) by random allocation, then the alternate drug, next by both drugs together, and finally with prednisolone (10 mg three times daily) in addition to both drugs. The effects of these four treatment periods were assessed both clinically and by measuring ventilatory capacity, nitrogen slope and progressive exercise testing. Ipratropium bromide and salbutamol produced approximately equal improvements in both diseases, with salbutamol showing a marginal advantage in patients with asthma. The combination of both drugs together more than doubled the FEV1 change in both groups of patients. The addition of prednisolone to both drugs produced a marginal advantage only in those with asthma.
TL;DR: In this article, a rigorous and exact solution for the problem of the radiation of sound from a semi-infinite unflanged rigid duct with an internal acoustically absorbent lining was obtained by a modification of the normal Wiener-Hopf technique.
Abstract: A rigorous and exact solution is obtained for the problem of the radiation of sound from a semi-infinite unflanged rigid duct with an internal acoustically absorbent lining. The solution is obtained by a modification of the normal Wiener-Hopf technique. The solution is in terms of an infinite series of unknowns, which are determined from an infinite set of simultaneous equations. The infinite system converges rapidly enough to make the solution suitable for numerical computations. Some numerical results are given in graphical form for the propagation of the principal symmetric mode in the duct.
TL;DR: In this article, upwinded parabolic and cubic elements are derived on a uniform grid of size h for the finite element Galerkin method applied to the solution of the model conduction−convection problem.
Abstract: Upwinded parabolic and cubic elements are derived on a uniform grid of size h for the finite element Galerkin method applied to the solution of the model conduction−convection problem eu″ — Ku′ = 0, e, K > 0, subject to the boundary conditions u(0) = 1, u (1) = 0. Extension of the results to more complicated problems is indicated. Finally numerical results are given comparing some of the methods derived for a range of L(=Kh/2e), the grid Peclet number.
TL;DR: This giant amoeba is nutritionally versatile and can feed on bacteria, flagellates, blue green algae, diatoms and nematodes, and can attack and lyse spores of fungi.
Abstract: Feeding trials were carried out to assess the ability of a giant vampyrellid soil amoeba to attack and lyse spores of fungi. Of 24 species of fungi studies, 15 were perforated in the same manner as was reported for Cochliobolus sativus . This giant amoeba is nutritionally versatile and can feed on bacteria, flagellates, blue green algae, diatoms and nematodes. Seven other soil amoebae failed to lyse conidia of C. sativus .
TL;DR: The protein-glycogen particle preparation isolated from rabbit skeletal muscle extracts by mild acidification and differential centrifugation shows eight major protein-staining bands when examined by polyacrylamide gel electrophoresis, five of which have previously been identified as the glycogen debranching enzyme, the α and β subunits of phosphorylase kinase, glycogen phosphoryLase and glycogen synthase.
Abstract: The protein-glycogen particle preparation isolated from rabbit skeletal muscle extracts by mild acidification and differential centrifugation shows eight major protein-staining bands when examined by polyacrylamide gel electrophoresis, five of which have previously been identified as the glycogen debranching enzyme, the α and β subunits of phosphorylase kinase, glycogen phosphorylase and glycogen synthase [Taylor, C., Cox, A. J., Kernohan, J. C. & Cohen, P. (1975) Eur. J. Biochem. 51, 105–115].
The other three major proteins in this preparation have now been identified. Two of the proteins were identified as the heavy chain of myosin and actin respectively, based on their electrophoretic migration, their insolubility in buffers of low ionic strength, and their solubility in buffers containing 0.6 M KCl.
The third protein has been found to be calsequestrin, a major calcium-binding protein of the sarcoplasmic reticulum. This conclusion was based on the unusual chromatographic behaviour of the protein on DEAE-cellulose at pH 7.5, its electrophoretic mobility, amino acid composition, and immunological cross reactivity.
A simple method for the isolation of calsequestrin as a by-product of the purification of glycogen synthase has been developed, by which 70–80 mg of the protein were routinely isolated from 5000 g of muscle (6 rabbits) within five days. The protein was homogeneous by the criterion of polyacrylamide gel electrophoresis and sedimentation equilibrium centrifugation. The molecular weight determined by the latter technique was 41000 and the absorbance index A280 nm1%, was 11.7. The protein had a very low sedimentation coefficient of 1.97 S indicating that it is either very asymmetric or a largely unfolded protein, in the buffers used in these experiments, a conclusion supported by its abnormal gel filtration behaviour.
Since the three hitherto unidentified components of the protein-glycogen particle preparation are not enzymes of glycogen metabolism and merely constituents of particulate material (actomyosin and fragments of the sarcoplasmic reticulum) which have coprecipitated with the protein-glycogen complex, over 95% of the protein attached to glycogen is accounted for by just four enzymes.
TL;DR: It would appear that the pancreatic acinar cells at least possess receptor sites for ACh, CCK-PZ, bombesin, and secretin and there is now evidence for a marked direct action ofBombesin and bombes in-like peptides on acinar cell fluid and enzyme secretion.
Abstract: The pancreatic acinar cells secrete important digestive enzymes. The mechanism of enzyme extrusion is exocytosis.' The acinar cells also secrete f l ~ i d . ~ ~ Both secretory processes are under the control of the vagus nerve (neurotransmitter: acetylcholine, ACh)4s5 and the hormone cholecystokinin-pancreozymin (CCKPZ).3.436 Secretin which mainly acts on duct cells to cause secretion of bicarbonaterich f l ~ i d ~ . ~ , ~ ' only has a small effect on enzyme ~ e c r e t i o n . ~ . ~ There is now evidence for a marked direct action of bombesin and bombesin-like peptides on acinar cell fluid and enzyme secretion.l0.\" It would appear, therefore, that the acinar cells at least possess receptor sites for ACh, CCK-PZ, bombesin, and secretin. Activation of the ACh, CCK-PZ, or bombesin receptor sites causes marked mem brane potential and resistance changes, affects cellular Ca2+ metabolism, but does not change the cyclic-AMP concentration.\"-'\" In contrast, activation of secretin receptor sites markedly increases cyclic-AMP concentration, but has no effect on membrane electrophysiological properties or Ca2+ t r a n ~ p o r t . ' ~ . ' ~ '
TL;DR: Stimuli indicating the presence of food provoke an impressive increase in activity of most starved Nassarius and recently-fed whelks, however, often fail to respond to the same stimuli (Crisp, in preparation).
Abstract: Nassarius reticulatus, like most other members of the Nassariidae and Buccinidae, is a scavenger. It apparently relies on the rapid detection and location of a food supply which is intermittently and unpredictably available. The olfactory reactions of Nassarius species are well-adapted for finding dead or damaged animals (Copeland, 1918). Stimuli indicating the presence of food provoke an impressive increase in activity of most starved Nassarius (Dimon, 1905; Copeland, 1918). Recently-fed whelks, however, often fail to respond to the same stimuli (Crisp, in preparation).
TL;DR: It is shown that either 4,6,7,14, 6 or 8 H’ are transported out of the mitochondria per 2 epassing from succinate to oxygen down the respiratory chain, and the results obtained by different methods and research groups disagree.
Patent•
07 Aug 1978TL;DR: A flexible bulk container for carrying up to one ton of material in eg granular form The container includes a bag of woven fabric such as polypropylene where necessary for reasons of reinforcement, ie where lifting loops are attached, or adjacent seams, the warp of the fabric is of increased strength per unit width This is achieved by the use of higher tenacity warp threads, and/or a higher density of warp threads.
Abstract: A flexible bulk container for carrying up to one ton of material in eg granular form The container includes a bag of woven fabric such as polypropylene Where necessary for reasons of reinforcement, ie where lifting loops are attached, or adjacent seams, the warp of the fabric is of increased strength per unit width This is achieved by the use of higher tenacity warp threads, and/or a higher density of warp threads
TL;DR: In this paper, the best size of cylinder to achieve reasonable accuracy with a small demand for water supply is recommended, from which an equation to correct measured infiltration capacities for lateral seepage is derived and tested.