Proceedings of the Royal Society of London Series B-Containing Papers of Abiological Character最新文献

{"title":"Increased uptake of methylated low-density lipoprotein induced by noradrenaline in carotid arteries of anaesthetized rabbits.","authors":"S Shafi,&nbsp;N J Cusack,&nbsp;G V Born","doi":"10.1098/rspb.1989.0001","DOIUrl":"https://doi.org/10.1098/rspb.1989.0001","url":null,"abstract":"<p><p>Atherosclerosis is accelerated in hyperlipidaemias but, apart from the concentration of low-density lipoprotein (LDL) in the blood, very little is known about other influences on the disease process. We now provide evidence that in anaesthetized rabbits the atherogenic uptake of LDL by arterial walls is accelerated by noradrenaline at its physiological concentrations in rabbit and human blood. The principle of the experiments was to compare the uptake of intravenously injected, radioactively labelled LDL, methylated to prevent removal by high-affinity receptors, in the two carotid arteries of anaesthetized rabbits after infusing low concentrations of noradrenaline into one carotid and saline as control into the other, the volume rates of infusion being about 1% of the carotid blood flows. Human LDL, which behaves sufficiently like rabbit LDL for these purposes, was prepared, methylated and radio-iodinated by standard methods. At the end of the infusions, the arteries were excised and their radioactivities determined. Noradrenaline infused for 2 h to produce local blood concentrations of nominally 1, 10, 50 and 100 nM significantly increased the LDL radioactivities of the walls of the noradrenaline-infused carotids. Concentrations of nominally 100 nM also increased the LDL radioactivities of the walls of the saline-infused carotids; this was associated with significant increases in their blood noradrenaline concentrations. These results may contribute towards an explanation for the accelerated atherosclerosis and the increased incidence of its clinical manifestations in conditions associated with elevated blood noradrenaline concentrations, including the episodic increases associated with stress and cigarette smoking as well as the more persistent increases caused by phaeochromocytoma.</p>","PeriodicalId":54561,"journal":{"name":"Proceedings of the Royal Society of London Series B-Containing Papers of Abiological Character","volume":"235 1281","pages":"289-98"},"PeriodicalIF":0.0,"publicationDate":"1989-01-23","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1098/rspb.1989.0001","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"13708446","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Growth and elimination of nerve terminals at synaptic sites during polyneuronal innervation of muscle cells: a trophic hypothesis.","authors":"M R Bennett,&nbsp;J Robinson","doi":"10.1098/rspb.1989.0002","DOIUrl":"https://doi.org/10.1098/rspb.1989.0002","url":null,"abstract":"<p><p>This paper examines the possibility that the elimination of synapses from cells arises from a competition between the nerve terminals for trophic molecules made available by the cells. This idea is applied to the elimination of synapses that occurs during the polyneuronal innervation of muscle cells which accompanies both the development and reinnervation of muscles. In the proposed model, each motorneuron makes the same amount of receptor in its soma for a trophic molecule provided in limited quantities by each muscle cell; this receptor is then distributed to the collateral terminals of the motorneuron in concentrations proportional to the amount of receptor made in the soma by the motorneuron; the more collateral terminals initially possessed by a motorneuron the less will be their concentration of receptor. The receptors in the several collateral terminals on a muscle cell then compete for the trophic molecule provided by the muscle, and terminal growth is proportional to the number of receptor-trophic-molecule bonds formed. An autocatalytic effect has been introduced whereby the increase in size of a terminal accelerates the rate by which the trophic molecule is made available to that terminal for bonding with its receptors. In addition, the affinity between nerve terminal receptors and muscle molecules can be varied in the model. Finally, motorneuron cell death has been analysed as the elimination of neurons that have insufficient terminal area to take up a growth factor in amounts that will allow for the survival of the neuron.</p>","PeriodicalId":54561,"journal":{"name":"Proceedings of the Royal Society of London Series B-Containing Papers of Abiological Character","volume":"235 1281","pages":"299-320"},"PeriodicalIF":0.0,"publicationDate":"1989-01-23","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1098/rspb.1989.0002","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"13708447","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Restoration of fast muscle characteristics following cessation of chronic stimulation: physiological, histochemical and metabolic changes during slow-to-fast transformation.","authors":"J M Brown,&nbsp;J Henriksson,&nbsp;S Salmons","doi":"10.1098/rspb.1989.0003","DOIUrl":"https://doi.org/10.1098/rspb.1989.0003","url":null,"abstract":"<p><p>Implantable electronic stimulators were used to subject fast-twitch tibialis anterior and extensor digitorum longus muscles of adult rabbits to a chronically increased level of use. Stimulation was discontinued after 6 weeks and physiological, histochemical and biochemical properties of the muscles were examined at intervals over the ensuing 20 weeks. Previous work had shown that 6 weeks of stimulation was sufficient to bring about a substantial transformation of type in fast-twitch muscles, which then exhibited much of the character of muscles of the slow-twitch type. The present experiments showed that these stimulation-induced changes were completely reversible. The time-course of reversion was such that the muscles had recovered their original fast properties by about 12 weeks after the cessation of stimulation. The contractile characteristics and post-tetanic potentiation typical of fast muscle returned rapidly, in only 3-4 weeks, and over the same period the proportion of histochemical type 1 fibres declined from about 70% to control levels. Changes in fatigue-resistance, capillary density and enzyme activity followed a more prolonged time-course; in particular, the decline in the activity of enzymes of oxidative metabolism corresponded closely to that already established for the mitochondrial volume fraction. Reacquisition of fast properties was not accompanied by any changes in specific force-generating capacity. Observations from these experiments and from a related morphological study fit into a 'first-in, last-out' pattern for the response to stimulation and recovery. The slow-to-fast reversion that takes place during the recovery period provides a further opportunity for testing causal associations within the events underlying type transformation. It has important consequences for therapeutic applications that make use of the fatigue-resistant character of chronically stimulated muscle.</p>","PeriodicalId":54561,"journal":{"name":"Proceedings of the Royal Society of London Series B-Containing Papers of Abiological Character","volume":"235 1281","pages":"321-46"},"PeriodicalIF":0.0,"publicationDate":"1989-01-23","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1098/rspb.1989.0003","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"13708448","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Feature detection in human vision: a phase-dependent energy model.","authors":"M C Morrone,&nbsp;D C Burr","doi":"10.1098/rspb.1988.0073","DOIUrl":"https://doi.org/10.1098/rspb.1988.0073","url":null,"abstract":"<p><p>This paper presents a simple and biologically plausible model of how mammalian visual systems could detect and identify features in an image. We suggest that the points in a waveform that have unique perceptual significance as 'lines' and 'edges' are the points where the Fourier components of the waveform come into phase with each other. At these points 'local energy' is maximal. Local energy is defined as the square root of the sum of the squared response of sets of matched filters, of identical amplitude spectrum but differing in phase spectrum by 90 degrees: one filter type has an even-symmetric line-spread function, the other an odd-symmetric line-spread function. For a line the main contribution to the local energy peak is in the output of the even-symmetric filters, whereas for edges it is in the output of the odd-symmetric filters. If both filter types respond at the peak of local energy, both edges and lines are seen, either simultaneously or alternating in time. The model was tested with a series of images, and shown to predict well the position of perceived features and the organization of the images.</p>","PeriodicalId":54561,"journal":{"name":"Proceedings of the Royal Society of London Series B-Containing Papers of Abiological Character","volume":"235 1280","pages":"221-45"},"PeriodicalIF":0.0,"publicationDate":"1988-12-22","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1098/rspb.1988.0073","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"14042534","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Identification of molecules in leech extracellular matrix that promote neurite outgrowth.","authors":"L Masuda-Nakagawa,&nbsp;K Beck,&nbsp;M Chiquet","doi":"10.1098/rspb.1988.0074","DOIUrl":"https://doi.org/10.1098/rspb.1988.0074","url":null,"abstract":"<p><p>The molecular composition of the substrate is of critical importance for neurite extension by isolated identified leech nerve cells in culture. One substrate upon which rapid growth occurs in defined medium is a cell-free extract of extracellular matrix (ECM) that surrounds the leech central nervous system (CNS). Here we report the co-purification of neurite-promoting activity with a laminin-like molecule. High molecular mass proteins from leech ECM purified by gel filtration exhibited increased specific activity for promoting neurite outgrowth. The most active fractions contained three major polypeptide bands of ca. 340, 250 and 220 kDa. Electron microscopy of rotary-shadowed samples showed three macromolecules, one of which had a cross-shaped structure similar to vertebrate laminin. A second six-armed molecule resembled vertebrate tenascin and a third rod-like molecule resembled vertebrate collagen type IV. The most active fractions contained a protein of ca. 1 MDa on non-reducing gels with disulphide-linked subunits of ca. 220 and 340 kDa, with cross-shaped laminin-like molecules. We conclude that a laminin-like molecule represents a major neurite promoting component present in leech ECM. The experiments represent a first step in determining the location of leech laminin within the CNS and assessing its role in neurite outgrowth during development and regeneration.</p>","PeriodicalId":54561,"journal":{"name":"Proceedings of the Royal Society of London Series B-Containing Papers of Abiological Character","volume":"235 1280","pages":"247-57"},"PeriodicalIF":0.0,"publicationDate":"1988-12-22","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1098/rspb.1988.0074","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"14042535","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"A horizontal cell selectively contacts blue-sensitive cones in cyprinid fish retina: intracellular staining with horseradish peroxidase.","authors":"M B Djamgoz,&nbsp;J E Downing","doi":"10.1098/rspb.1988.0076","DOIUrl":"https://doi.org/10.1098/rspb.1988.0076","url":null,"abstract":"<p><p>A horizontal cell selectively contacting blue-sensitive cones has been intracellularly stained with horseradish peroxidase in the retina of a cyprinid fish, the roach. The light microscopical morphology of the cell belonged to the H3 category of horizontal cells found in cyprinid fish retinae. In response to spectral stimuli, the cell generated chromaticity-type S-potentials that were hyperpolarizing to blue and depolarizing to yellow-orange. A red-sensitive hyperpolarizing component was absent possibly because of suppression of the negative feedback pathway between luminosity-type (H1) horizontal cells and green-sensitive cones.</p>","PeriodicalId":54561,"journal":{"name":"Proceedings of the Royal Society of London Series B-Containing Papers of Abiological Character","volume":"235 1280","pages":"281-7"},"PeriodicalIF":0.0,"publicationDate":"1988-12-22","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1098/rspb.1988.0076","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"13615685","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Neurofibrillar long-range amacrine cells in mammalian retinae.","authors":"D I Vaney,&nbsp;L Peichl,&nbsp;B B Boycott","doi":"10.1098/rspb.1988.0072","DOIUrl":"https://doi.org/10.1098/rspb.1988.0072","url":null,"abstract":"<p><p>A distinct population of wide-field, unistratified amacrine cells are shown to be selectively stained by using neurofibrillar methods in rabbit and cat retinae. Their cell bodies may be located in the inner nuclear, inner plexiform or ganglion cell layers and they branch predominantly in stratum 2 of the inner plexiform layer. Characteristically, each cell has two or more long-range distal processes which extend for 2-3 mm beyond a more symmetrical, proximal dendritic field of 0.6-0.8 mm diameter. Although the neurofibrillar long-range amacrines account for less than 1 amacrine in 500, they achieve effective coverage of the retina by both the proximal and distal dendrites.</p>","PeriodicalId":54561,"journal":{"name":"Proceedings of the Royal Society of London Series B-Containing Papers of Abiological Character","volume":"235 1280","pages":"203-19"},"PeriodicalIF":0.0,"publicationDate":"1988-12-22","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1098/rspb.1988.0072","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"14042533","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Concomitant release of sialic acids and calcium by neuraminidase from rat aorta in situ.","authors":"C Ludlam,&nbsp;W Palinski,&nbsp;P Görög,&nbsp;G V Born","doi":"10.1098/rspb.1988.0068","DOIUrl":"https://doi.org/10.1098/rspb.1988.0068","url":null,"abstract":"<p><p>Male Wistar rats were heparinized and killed with pentobarbital. The upper and lower ends of the aortae were cannulated and the blood was washed out with saline until the washings contained calcium and sialic-acid-reacting material at minimal concentrations. The aortae were perfused with neuraminidase for 15 min. This caused the appearance of calcium as well as of sialic acids in the perfusate in total amounts of about 5.3 nmol and about 3.6 nmol per aorta respectively. The molar ratio of about 1.5 is sufficiently close to that determined for the association of calcium with sialic acids in vitro to suggest that their association is similar in vivo.</p>","PeriodicalId":54561,"journal":{"name":"Proceedings of the Royal Society of London Series B-Containing Papers of Abiological Character","volume":"235 1279","pages":"139-44"},"PeriodicalIF":0.0,"publicationDate":"1988-11-22","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1098/rspb.1988.0068","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"14043020","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"The Leeuwenhoek lecture, 1987. Towards an understanding of gene switching in Streptomyces, the basis of sporulation and antibiotic production.","authors":"D A Hopwood","doi":"10.1098/rspb.1988.0067","DOIUrl":"https://doi.org/10.1098/rspb.1988.0067","url":null,"abstract":"<p><p>Streptomycetes are soil bacteria that differ from the genetically well-known Escherichia coli in two striking characteristics. (1) Instead of consisting of an alternation of growth and fission of morphologically simple, undifferentiated rods, the streptomycete life cycle involves the formation of a system of elongated, branching hyphae which, after a period of vegetative growth, respond to specific signals by producing specialized spore-bearing structures. (2) The streptomycetes produce an unrivalled range of chemically diverse 'secondary metabolites', which we recognize as antibiotics, herbicides and pharmacologically active molecules, and which presumably play an important role in the streptomycete life cycle in nature. This 'physiological' differentiation is often temporally associated with the morphological differentiation of sporulation and there are common elements in the regulation of the two sets of processes. In the model system provided by Streptomyces coelicolor A3(2), the isolation of several whole clusters of linked antibiotic biosynthetic pathway genes, and some key regulatory genes involved in sporulation, has made it possible to study the basis for the switching on and off of particular sets of genes during morphological and 'physiological' differentiation. Genetic analysis clearly reveals a regulatory cascade operating at several levels in a 'physiological' branch of the differentiation control system. At the lowest level, within individual clusters of antibiotic biosynthesis genes are genes with a role as activators of the structural genes for the pathway enzymes, and also resistance genes. It is attractive to speculate that the latter play a dual role: protecting the organism from self-destruction by its own potentially lethal product, and forming an essential component of a regulatory circuit that activates the biosynthetic genes, thus ensuring that resistance is established before any antibiotic is made. A next higher level of regulation is revealed by the isolation of mutations in a gene (afsB) required for expression (probably at the level of transcription) of all five known secondary metabolic pathways in the organism. At a higher level still, the bldA gene, whose product seems to be a tRNA essential to translate the rare (in high [G + C] Streptomyces DNA) TTA leucine codon, controls or influences the whole gamut of morphological and 'physiological' differentiation, because bldA mutants fail to produce either secondary metabolites or aerial mycelium and spores, while growing normally in the vegetative phase.(ABSTRACT TRUNCATED AT 250 WORDS)</p>","PeriodicalId":54561,"journal":{"name":"Proceedings of the Royal Society of London Series B-Containing Papers of Abiological Character","volume":"235 1279","pages":"121-38"},"PeriodicalIF":0.0,"publicationDate":"1988-11-22","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1098/rspb.1988.0067","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"14043019","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"A structural approach to pathological crystallizations. Gout: the possible role of albumin in sodium urate crystallization.","authors":"D Perl-Treves,&nbsp;L Addadi","doi":"10.1098/rspb.1988.0069","DOIUrl":"https://doi.org/10.1098/rspb.1988.0069","url":null,"abstract":"<p><p>The interactions between sodium urate monohydrate (MSU) crystals and human serum albumin (HSA) were investigated in vitro in relation to the disease of gout. It was found that HSA accelerates (by up to ten times or even more) the nucleation of MSU crystals at a pH of more than 7.5, but only to a much lesser extent (1.2 times) at pH 7.0. Protein denaturation, as well as blocking exposed carboxylate groups on the protein, substantially reduced the nucleating effect. By use of immunofluorescence, immunogold labelling and crystal morphology studies, albumin was shown to interact preferentially with the (110) faces of MSU crystals. Taking these results into consideration, a mechanism is proposed whereby albumin stabilizes MSU crystal nuclei by interaction of structured carboxylate-containing protein domains with planes of the incipient crystal exposing sodium cation layers.</p>","PeriodicalId":54561,"journal":{"name":"Proceedings of the Royal Society of London Series B-Containing Papers of Abiological Character","volume":"235 1279","pages":"145-59"},"PeriodicalIF":0.0,"publicationDate":"1988-11-22","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1098/rspb.1988.0069","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"14043674","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}