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D C Spray

Publications and source records attributed to D C Spray.

At least 199 records · Page 11Linked to original sources
PubMed1974

Characteristics, specificity, and efferent control of frog cutaneous cold receptors.

1. Thermal stimulation of frog skin produces a discharge in afferents in the dorsocutaneous nerve. The characteristics of this response have been examined with regard to static and dynamic sensitivity to thermal stimuli and to mechanical sensitivity. Frog cutaneous receptors respond only to cooling, with no response to warming through the same thermal range.2. The static temperature at which these receptors are maximally active is about 24 degrees C for Rana pipiens and about 27 degrees C for R. catesbiana.3. The dynamic sensitivity of frog cutaneous receptors is linearly related to both stimulus slope and magnitude. Maximum dynamic sensitivity was between -90 and -120 impulses/ degrees C.sec.4. Antidromic occlusion experiments demonstrate relative insensitivity of these receptors to tonic mechanical stimulation. At high stimulus intensities, however, larger fibres are recruited into the response; this recruitment of action potentials of larger amplitude is a linear function of both stimulus slope and magnitude.5. Spike heights are linearly related to conduction velocities in the dorsocutaneous nerve; tonic mechanoreceptors have a mean spike height of 28.4+/-0.6 muV and conduction velocities about 6-8 m/sec, whereas these temperature sensitive receptors have spike heights 15.8+/-0.4 muV and conduction velocities about 3-4 m/sec.6. Maximum dynamic sensitivity skin is increased following stimulation of the first or second sympathetic ganglion. This increase is both marked and progressive, reaching a maximal enhancement of about 150-160% control at a stimulus rate of 5 stimuli/train, each train delivered once every 5 sec.7. Static sensitivity of the cold receptors is also increased following sympathetic stimulation. This increased sensitivity is shown by both increased discharge rate within the same thermal range and by decreased temperature of maximum static sensitivity.8. Sympathetic modulation of dynamic thermal sensitivity is mimicked by epinephrine and norepinephrine in doses of 10(-6)-10(-7) g/ml. Ephedrine, another adrenergic agonist, also mimics the enhancement of cold receptors by sympathetic stimulation.9. Larger fibres are recruited to account for the increased sensitivity of thermoreceptors following sympathetic stimulation and epinephrine application.10. Propranolol and phentolamine both block the enhancement of the response by sympathetic stimulation, but propranolol blocks the response of the receptor to thermal stimulation as well. Reserpine pre-treatment blocks the effect of sympathetic stimulation on the cold response.

Action Potentials↗
PubMedDate not supplied

Glycosaminoglycans and proteoglycans induce gap junction expression and restore transcription of tissue-specific mRNAs in primary liver cultures.

Normal rat hepatocytes maintained on tissue culture plastic and in serum-supplemented medium lose their gap junctions within 12 hr and expression of their tissue-specific functions within 24 to 72 hr. The gap junctions are lost via internalization and degradation, and the differentiated functions due to loss of synthesis and to rapid degradation of tissue-specific mRNAs. Near normal levels of tissue-specific mRNAs can be achieved by stabilization of the mRNAs but not by transcription (for most genes), if the cells are cultured in a serum-free, hormonally defined medium and on substrata of tissue culture plastic, fibronectin or laminin, or on various purified collagens. The hormonally defined medium also extends the life-span of the gap junctions to about 24 hr. Certain glycosaminoglycans, proteoglycans and anionic polysaccharides have proven to be potent inducers of gap junction expression and function, to increase abundance of tissue-specific mRNAs, and to lower abundance of common gene mRNAs, a level of gap junctions and a pattern of gene expression similar to that in vivo. Addition to the hormonally defined medium of 10 micrograms per ml of hyaluronates, dermatan sulfates, bovine lung heparan sulfate, chondroitin 4-sulfate or chondroitin 6-sulfate resulted in a weak response in induction of gap junctions (5 to 15% of the cells became dye and electrically coupled) and in gene expression. An intermediate response in gap junction expression (30 to 50% coupled cells) and in gene expression was observed with 50 to 100 micrograms per ml of heparins or hyaluronates.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMedDate not supplied

The Drosophila clock gene per affects intercellular junctional communication.

The per locus of Drosophila has been implicated in the control of behavioural rhythms. In fruitfly embryos and larvae per is expressed in salivary glands. Per mutations have striking effects on intercellular communication in salivary glands: gap junction channels are modulated so that their conductance varies inversely with the period of behavioural rhythms in the mutants. A similar effect on junctional communication in the nervous system may explain how per influences behavioural rhythms.

Animals↗
PubMedDate not supplied

The "patholog" of the genes expression profile, a new tool in defining, evaluating, and classifying genetic diseases.

The paper introduces the pre-Hilbert space of standard gene expression (SSGE) based on the normal variability in gene profiles, as revealed by the "spotting" microarray technique. In this space, every point represents a possible gene profile and every continuous curve a possible genetic evolution. The gene "patholog" is defined as the Euclidean distance separating the representative point of the gene profile from the unit, 0-centered hyperball. It is the most general quantification of the alteration in digital genes expression, suitable to define, evaluate, and classify the genetic diseases. Our mathematical model and the afferent computer package allow the researcher to identify the patterns of various genetic afflictions in the SSGE. A publicly available database will be opened where every interested experimentalist could introduce his/her results and process them according to our procedure.

Gene Expression↗
PubMedDate not supplied

New protocol in spotting microarray technique.

The "spotting" microarray technique, consisting in large sets of DNA sequences spotted on poly-L-lysine-coated glass microscope slides, has been developed to comparatively analyze genome-wide patterns of mRNA expression. It is now a valuable tool employed in order to quantitatively monitor gene expression profiles, as well as to analyze the alterations produced in case of genetic diseases, or induced by different treatments, abnormal nutrition and toxin. Our group improved the standard protocol as well as the results spreadsheet, adding new experiments and mathematical processing procedures in order to increase the accuracy of the data and get new information. In this contribution, we propose and verify two procedures to correct the spot ratios and a new protocol to get the normal variability of the digital gene expression.

Algorithms↗
PubMedDate not supplied

[Transcription regulation and coordination of some cell signaling genes in brain and heart of connexin 43 null mouse].

We performed a cDNA microarray study of the transcription regulation and coordination of four gene families whose products are involved in cell-cell and cell-matrix interaction (ADAM, integrin, MMP, TNF) within brain and hearts of wildtype (WT) and connexin43 null (KO) neonatal C57Bl/6j mice. The study revealed that both WT brain and heart exhibit significant correlations among the transcriptions of cell-signaling genes and that depletion of Cx43 regulates both their expression and coordination. Adam8 was identified as the command gene of the group in WT and Mmp2 in KO, while Tnsf6 plays the dominant role in both WT and KO heart. Our results suggest that the functional coordination of cell-signaling proteins may be related to the expression coordination of the corresponding genes presumably to ensure the efficiency of the functional pathways and that intercellular communication modulates cell-cell and cell-matrix interaction.

ADAM Proteins↗
PubMedDate not supplied

Control and variability of gene expression in mouse brain and in a neuroblastoma cell line.

We used cDNA microarrays to examine the extent to which the expression of individual genes varies in mouse brain and in cultured N2A neuroblastoma cells mRNA extracted from sixC57B1/6J neonatal mouse brains and from four distinct cultures of N2A neuroblastoma cells was cross-hybridized with ten AECOM cDNA microarray chips to determine the individual gene expression variability. A mathematical algorithm reduced the effect of potential sources of variability not associated to the biological material by about 80%. The interval estimates of the standard deviation of individual gene expressionwere determined through chi-square statistics. The newly introduced relative expression variability, defined as the quotient of the middle of the interval estimate of the standard deviation and the mean expression ratio (and its inverse, gene transcription control), was used to rank the most unstably and the most stably transcribed genes. In brains of different animals and in separate cultures of N2A cells, unique sets ofgenes exhibited exceptional stability or were highly variable. Possible implications for such tight or loose transcriptional control are discussed.

Animals↗
PubMedDate not supplied

Transcriptomic characterization of four classes of cell-cell/cell-matrix genes in brains and hearts of wild type and connexin43 null mice.

We have used a highly quantifiable cDNA microarray method to determine the stabilities and expression levels within gene families involved in cell-cell and cell-matrix interactions in neonatal mouse brain and heart. In addition, we have characterized the extent to which deletion of the gap junction protein connexin43 (Cx43) affects these characteristics. Our observations for individual genes revealed a range of differences and variabilities in transcription level among family members; calculation of the genomic patholog (a global measure of gene expression alteration) indicates that these cell interaction genes contribute disproportionately to the overall phenotype. We found significant transcriptomic differences between brain and heart, that deletion of Cx43 considerably decreased gene expression variability and that the average contribution to the pathology of the genes whose encoded proteins are involved in cell-cell or cell-matrix interaction in the Cx43-null mice was about twenty times higher than that of other genes. These findings indicate that gap junction gene expression influences the expression of other genes involved in intercellular and cell-substrate interaction and that expression of these genes is under strong regulatory pressure in the Cx43-null mouse, presumably representing a compensatory response to Cx43 deletion.

Animals↗