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L A Perkins

Publications and source records attributed to L A Perkins.

34 records · Page 2Linked to original sources
PubMed1992

Analysis of concentration-response relationships by seemingly unrelated nonlinear regression (SUNR) technique.

In performing statistical evaluation of concentration-response relationship in pharmacological studies, all the commercially available statistical packages assume each data point is an independent measure of the drug response, and do not account for the dependence between the multiple measurements taken from the same subject (tissue, animal, or sample). Seemingly unrelated nonlinear regression (SUNR) is a statistical technique that takes into account both within-and between-subject variance. This technique has been implemented in an SAS-based interactive program called SUNR. The statistical analyses are based upon the original work by Gallant (Gallant, 1975, J Econometrics 3:35-50; Gallant and Goebel, 1976, JASA 71:961-967), which has been further developed by Muller and Helms (1984) (Presented at ASA meeting in Washington, D.C.) To test this program, we have analyzed both simulated and actual data with SUNR, comparing our results to those of several popular statistical programs. All the programs yielded essentially the same estimates for the EC50, minimum and maximum response in both the simulated and experimental data sets. However, our results differed markedly from the commercial packages in the estimates of standard errors associated with the estimated maxima. When analyzing simulated data, which were far less noisy than the experimental data, differences between the analyses were minimal. However, in the analyses of experimental data, the standard errors calculated by the commercial programs appear to significantly underestimate the standard error. Using SUNR, however, the 95% confidence limits on the maxima are markedly wider, and, importantly, always cover the observed actual data range.

Animals↗
PubMed1992

Genetic and developmental analysis of polytene section 17 of the X chromosome of Drosophila melanogaster.

Polytene section 17 of the X chromosome of Drosophila melanogaster, previously known to contain six putative lethal complementation groups important in oogenesis and embryogenesis, has here been further characterized genetically and developmentally. We constructed fcl+Y, a duplication of this region, which allowed us to conduct mutagenesis screens specific for the region and to perform complementation analyses (previously not possible). We recovered 67 new lethal mutations which defined 15 complementation groups within Df(1)N19 which deletes most of polytene section 17. The zygotic lethal phenotypes of these and preexisting mutations within polytene section 17 were examined, and their maternal requirements were analysed in homozygous germline clones using the dominant female sterile technique. We present evidence that an additional gene, which produces two developmentally regulated transcripts, is located in this region and is involved in embryogenesis, although no mutations in this gene were identified. In this interval of 37 to 43 polytene chromosome bands we have defined 17 genes, 12 (71%) of which are of significance to oogenesis or embryogenesis.

Amino Acid Sequence↗
PubMed1992

Agonist action of indole derivatives at 5-HT1-like, 5-HT3, and 5HT4 receptors in vitro.

1. The potency of indole analogues has been studied, in vitro, at 5-hydroxytryptamine4 (5-HT4) receptors mediating contractions of guinea-pig ileum and relaxation of rat oesophagus. These have been compared to other 5-HT receptors in canine saphenous vein (5-HT1-like), rabbit aorta (5-HT2), and guinea-pig ileum (5-HT3). 2. At receptors mediating 5-HT4 responses in ileum and oesophagus, the rank orders of potency were similar. These rank orders differed from those observed at 5-HT1-like, 5-HT2, and 5-HT3 receptors. In particular, 5-hydroxy N,N, dimethyltryptamine but not 5-methoxy N,N, dimethyltryptamine acted as agonists at 5-HT4 receptors. At 5-HT1-like, 5-HT2 and 5-HT3 receptors these compounds were both active. 3. The 5-HT receptors mediating contractions of canine cephalic vein exhibited a rank order profile similar to that observed at receptors mediating contractions of canine saphenous vein, suggesting stimulation of a 5-HT1-like receptor. 4. The rank order of potency of the substituted indoles differed at 5-HT receptors mediating responses in canine saphenous vein, rabbit aorta and guinea-pig ileum (determined in the presence of 5-methoxytryptamine to desensitize 5-HT4 receptors), suggesting the presence of three distinct receptors. Indeed, at 5-HT3 receptors in the ileum, only three agonists (5-HT, 2-methyl-5-HT and 5-hydroxy N,N, dimethyltryptamine) elicited a response, while all remaining compounds were inactive. 5. It is concluded that rank orders of indole potency can prove useful in the delineation of 5-HT subtypes and together with differential antagonist affinities support the existence of four 5-HT receptor subtypes.

Animals↗
PubMed1990

Putative protein kinase product of the Drosophila segment-polarity gene zeste-white3.

The metameric pattern of the Drosophila embryo is regulated by a combination of maternal and zygotic genes. The segment-polarity class of genes are required for the correct patterning within each segmental unit. Mutations in any one of these genes results in deletions and duplications of parts of each segment. The segment-polarity genes act coordinately by means of local cellular interactions to assign and maintain an identity for each cell in the segment, and to establish segment boundaries. Here we describe the molecular characterization of a novel segment-polarity gene, zeste-white3 (zw3). Embryos derived from germ lines that are homozygous for zw3 mutations (zw3 embryos) have phenotypes similar to embryos that are mutant for the segment-polarity gene naked (nkd). These embryos lack most of the ventral denticles, which are differentiated structures derived from the most anterior region of each segment. We have isolated the zw3 gene and compared the structure of one maternal and one zygotic transcript encoded by the gene. The zw3 gene is unique among the segment-polarity genes so far characterized, in that it encodes proteins that have homology to serine-threonine protein kinases. This indicates that zw3 may play a part in a signal transduction pathway involved in the establishment of cell identity within each embryonic segment.

Amino Acid Sequence↗
PubMed1990

5-Methoxytryptamine and 2-methyl-5-hydroxytryptamine-induced desensitization as a discriminative tool for the 5-HT3 and putative 5-HT4 receptors in guinea pig ileum.

Agonist-induced desensitization has been utilized to discriminate and independently "isolate" the neuronal excitatory receptors to 5-hydroxytryptamine (5-HT) in the guinea pig ileum (5-HT3 and putative 5-HT4 receptors). Electrically stimulated longitudinal muscle myenteric plexus preparations, and non-stimulated segments of whole ileum were used. Exposure to 5-methoxytryptamine (10 mumol/l) inhibited completely responses to 5-HT at the putative 5-HT4 receptor without affecting 5-HT3-mediated responses. Conversely, exposure to 2-methyl-5-HT (10 mumol/l) inhibited completely responses to 5-HT at the 5-HT3 receptor without affecting putative 5-HT4-mediated responses. The inhibition with 5-methoxytryptamine and 2-methyl-5-HT, either alone or in combination, appeared selective as responses to KCl, DMPP, carbachol, histamine, and substance P were unaffected or only very slightly modified. Furthermore, the pA2 values for ICS 205-930 at the putative 5-HT4 (pA2 = 6.2 to 6.5) and 5-HT3 (pA2 = 7.6 to 8.1) receptors (estimated in the presence of 2-methyl-5-HT and 5-methoxytryptamine, respectively) were consistent with those estimated in the absence of desensitization. 5-Methoxytryptamine, but not 2-methyl-5-HT, suppressed completely but reversibly the concentration-effect curve to renzapride, suggesting that responses to this agent are mediated exclusively via agonism at the putative 5-HT4 receptor. It is concluded that 5-methoxytryptamine and 2-methyl-5-HT can be utilized as selective probes to discriminate the putative 5-HT4 receptor from the 5-HT3 receptor in guinea pig ileum. This finding is of importance as no selective antagonist exists for the putative 5-HT4 receptor.(ABSTRACT TRUNCATED AT 250 WORDS)

5-Methoxytryptamine↗
PubMed1990

Drosophila homolog of the mammalian jun oncogene is expressed during embryonic development and activates transcription in mammalian cells.

By means of low-stringency cross-species hybridization to Southern DNA blots, human c-jun sequences were used to identify a unique Drosophila melanogaster locus (Djun). The predicted DJun protein is highly homologous to members of the mammalian Jun family in both the DNA binding and leucine zipper regions. Djun was mapped by in situ hybridization to position 46E of the second chromosome. It encodes a 1.7-kilobase transcript constitutively expressed at all developmental stages. Functionally, Djun in cooperation with mouse c-fos can trans-activate activator protein 1 DNA binding site when introduced into mammalian cells. Taken together, these data suggest that Djun, much like its mammalian homolog, may activate transcription of genes involved in regulation of cell growth, differentiation, and development. Furthermore, the identification of Djun allows one to exploit the genetics of Drosophila to identify genes in signal transduction pathways involving Djun and thus c-jun.

Amino Acid Sequence↗
PubMed1990

Molecular and developmental characterization of the heat shock cognate 4 gene of Drosophila melanogaster.

The Drosophila heat shock cognate gene 4 (hsc4), a member of the hsp70 gene family, encodes an abundant protein, hsc70, that is more similar to the constitutively expressed human protein than the Drosophila heat-inducible hsp70. Developmental expression revealed that hsc4 transcripts are enriched in cells active in endocytosis and those undergoing rapid growth and changes in shape.

Amino Acid Sequence↗
PubMed1989

A Drosophila gene expressed in the embryonic CNS shares one conserved domain with the mammalian GAP-43.

By cross hybridization with the mammalian growth-related protein, GAP-43, we have isolated several Drosophila cDNAs and genomic sequences. These sequences correspond to a single copy gene that encodes two developmentally regulated transcripts 2.4 and 2.0 kb in length. The predicted protein sequence from the cDNAs contains a stretch of 20 amino acids closely related to the mammalian GAP-43 protein. These residues are also highly conserved in a cDNA isolated from the nematode C. elegans. Prior to dorsal closure, expression of the Drosophila gene is observed in non-neuronal tissues, especially in the mesectoderm and presumptive epidermis, both in a metameric pattern. After dorsal closure, expression becomes restricted to sets of cells that are segmentally reiterated along the periphery of the nervous system. These cells appear to include at least one specific set of glia that may establish scaffolding for the development of the longitudinal neuropile.

Amino Acid Sequence↗
PubMed1988

Alternative RNA products from the Ultrabithorax domain of the bithorax complex.

The homeotic gene, Ultrabithorax (Ubx) is involved in specifying the identities of several segments in the fly Drosophila melanogaster. The structures of over 60 independent Ubx cDNAs have been examined. There are two major species of transcripts, 3.2 and 4.3 kb in length, which are produced by alternate sites of polyadenylation. Differential splicing gives rise to at least five variant Ubx proteins. The variant forms share common 5' and 3' exons but differ in their small internal 'micro' exons. Additional variation is generated by two separate splice donor sites at the end of the common 5' exon, situated 27 bp apart. Northern hybridization and S1 nuclease protection studies of RNA from various developmental stages and tissue types reveal that the alternate splicing and the choice of polyadenylation site are each differentially regulated in both a temporal and a tissue specific manner. Additional transcripts were found just downstream of the Ubx transcription unit, which may be products of the lethal left of bithorax gene (llb).

Animals↗
PubMed1986

Mutant sensory cilia in the nematode Caenorhabditis elegans.

Eight classes of chemosensory neurons in C. elegans fill with fluorescein when living animals are placed in a dye solution. Fluorescein enters the neurons through their exposed sensory cilia. Mutations in 14 genes prevent dye uptake and disrupt chemosensory behaviors. Each of these genes affects the ultrastructure of the chemosensory cilia or their accessory cells. In each case, the cilia are shorter or less exposed than normal, suggesting that dye contact is the principal factor under selection. Ten genes affect many or all of the sensory cilia in the head. The daf-19 (m86) mutation eliminates all cilia, leaving only occasional centrioles in the dendrites. The cilia in che-13 (e1805), osm-1 (p808), osm-5 (p813), and osm-6 (p811) mutants have normal transition zones and severely shortened axonemes. Doublet-microtubules, attached to the membrane by Y links, assemble ectopically proximal to the cilia in these mutants. The amphid cilia in che-11 (e1810) are irregular in diameter and contain dark ground material in the middle of the axonemes. Certain mechanocilia are also affected. The amphid cilia in che-10 (e1809) apparently degenerate, leaving dendrites with bulb-shaped endings filled with dark ground material. The mechanocilia lack striated rootlets. Cilia defects have also been found in che-2, che-3, and daf-10 mutants. The osm-3 (p802) mutation specifically eliminates the distal segment of the amphid cilia. Mutations in three genes affect sensillar support cells. The che-12 (e1812) mutation eliminates matrix material normally secreted by the amphid sheath cell. The che-14 (e1960) mutation disrupts the joining of the amphid sheath and socket cells to form the receptor channel. A similar defect has been observed in daf-6 mutants. Four additional genes affect specific classes of ciliated sensory neurons. The mec-1 and mec-8 (e398) mutations disrupt the fasciculation of the amphid cilia. The cat-6 (e1861) mutation disrupts the tubular bodies of the CEP mechanocilia. A cryophilic thermotaxis mutant, ttx-1 (p767), lacks fingers on the AFD dendrite, suggesting this neuron is thermosensory.

Animals↗
PubMed1985

Axonal guidance mutants of Caenorhabditis elegans identified by filling sensory neurons with fluorescein dyes.

Eight pairs of chemosensory neurons in Caenorhabditis elegans take up fluorescein dyes entering through the chemosensory organs. These are amphid neurons ADF, ASH, ASI, ASJ, ASK, and ADL and phasmid neurons PHA and PHB. When filled with dye, the processes and cell bodies of these neurons can be examined in live animals by fluorescence microscopy. Using this technique, we have identified five genes, unc-33, unc-44, unc-51, unc-76, and unc-106, that affect the growth of the amphid and phasmid axons. These genes were found to affect the axons of the mechanosensory PDE neurons as well. The unc-33 mutation specifically affects neuronal microtubules. Sensory dendrites in this mutant have a superabundance of microtubules. Moreover, many of these microtubules are abnormal in diameter, and some form hooks or multiple tubules.

Animals↗
PubMed1975

Endoribonuclease from bovine adrenal cortex cytosol.

An endoribonuclease which digests a variety of synthetic homoribopolymers and poly(A)-rich mRNA has been identified and purified greater than 500-fold with respect to specific activity from bovine adrenal cortex cytosol. Enzymatic digestion of synthetic poly(riboadenylic acid) was stimulated by Mn-2+ and Mg-2+ and the enzyme exhibited broad pH and salt optima. Poly(cytidylic acid) and poly(uridylic acid), but not poly(guanylic acid), served as substrates for the enzyme preparation; double-stranded RNA, DNA, and DNA-RNA hybrids were not digested by the enzyme. Digestion generated oligonucleotides with 3-hydroxyl and 5'-monophosphoester termini. On isoelectric focusing, the enzymatic activity banded at pH 8.3 plus or minus 0.2. An initial preferential cleavage of the poly(A) tract of poly(A)-rich RNA is suggested by the rapid appearance of a 4-6S digestion product highly enriched for adenylic acid; however, progressive digestion of the RNA occurs with additional incubation.

Adrenal Cortex↗
PubMedDate not supplied

Topographic correspondence of contrast echocardiographic perfusion mapping and myocardial infarct extent after varying durations of coronary occlusion.

After acute coronary occlusion, the extent of dysfunction exceeds the extent of infarction by a variable amount. Contrast echocardiography has been shown to be a good predictor of the extent of acute infarction after permanent occlusion. We used hydrogen peroxide contrast echocardiography to study the temporal and topographic relationship between contrast enhancement and tissue viability during acute myocardial infarction in 32 dogs undergoing 1, 2, 3, or 4 hours of circumflex occlusion before reperfusion. To account for changes in collateral blood flow, contrast studies were performed by aortic root injection immediately before reperfusion. The area, circumference, and transmural extent of the region at risk in vivo by contrast echocardiography were statistically unchanged regardless of the duration of occlusion before reperfusion. Echo contrast defect analysis of the risk region predicted the area, circumference, and transmural extent of infarcts reperfused at 2 or more hours (r = 0.81, 0.84, 0.71, respectively). For the 1-hour occlusion group, contrast defect analysis predicted the circumference at risk but markedly overestimated the area and transmural extent of infarction. These data indicate that the circumferential extent of infarction can be identified by contrast echo and is fixed by 1 hour of occlusion. Infarction progression transmurally within the circumferential boundaries had nearly reached the transmural contrast extent by 2 hours of occlusion in this model. Assuming the development of a similar high contrast agent safe for human injection, aortic root contrast echocardiography could be useful to predict myocardium at risk of infarction early after occlusion. Late after occlusion it could be of value to predict the presence of still viable myocardial layers within the dysfunctional infarct region.

Animals↗
PubMedDate not supplied

The molecular genetics of tail development in Drosophila melanogaster.

The formation of the telson in the Drosophila embryo, which encompasses all structures posterior to abdominal segment 7, is under the control of the "terminal class" genes. These maternally expressed genes are organized in a signal transduction pathway which implicates cell-cell interactions between the germ cell derivatives (the nurse cells and oocyte) and the surrounding follicle cell epithelium. Activation of this localized signal transduction pathway at the termini of the embryo is believed to specify the domains of activation and repression of a set of zygotic genes whose interactions specify the various cell states required for the proper formation of tail structures.

Animals↗