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M Olive

Publications and source records attributed to M Olive.

17 recordsLinked to original sources
PubMed1995

Extending dimerization interfaces: the bZIP basic region can form a coiled coil.

We appended a rationally designed acidic amphipathic protein sequence to the N-terminus of a leucine zipper. Circular dichroism data indicate that this engineered polypeptide sequence can 'zipper' up the basic region of a bZIP monomer into a heterodimeric coiled coil. This propagation of the leucine zipper dimerization interface into the basic region can proceed for up to four heptads and stabilizes the heterodimer complex 2.5 kcal/mol or > 100-fold. The acidic nature of the extension is the most critical component of the design, suggesting that the extension is acting as a DNA mimetic. The dimerization prevents the basic region in this heterodimeric coiled coil structure from binding to DNA. Gel-shift, fluorescence and transient transfection assays indicate that the acidic extension appended to a leucine zipper can inactivate the DNA-binding and transactivation properties of the bZIP protein C/EBP. The three bZIP basic regions examined in this study dimerize with similar stability with the acidic extension, suggesting that this N-terminal extension can be used to develop dominant-negatives to other bZIP transcription factors.

Amino Acid Sequence↗
PubMed1994

Cloning of the Xenopus laevis cdk2 promoter and functional analysis in oocytes and during early development.

CDK2 (cyclin-dependent kinase 2) is a serine/threonine kinase which is involved in regulating S-phase entry in higher eukaryotes. To investigate the transcriptional control of this gene, a 13-kb Xenopus laevis genomic clone containing the 5' flanking sequences was isolated. A 2.7-kb fragment containing the promoter region was sequenced and the transcription start point (tsp) was determined by primer extension. Several putative regulatory elements, such as the E2F-binding site, Y box and octamer-binding site, were localized in this region, but no TATA box was found. When fused to cat, a reporter gene encoding chloramphenicol acetyltransferase, the 5' flanking sequences were shown to function in oocytes and an enhancer activity was found in this region. During early embryogenesis, cdk2 promoter activity was tested and de novo transcription was detected at the mid-blastula transition.

Animals↗
PubMed1994

Parvalbumin immunocytochemistry and calcium deposition in muscle fiber necrosis and subsequent regeneration following intramuscular injection of metoclopramide.

We have studied the sequential change of parvalbumin immunocytochemistry and its correlation with intracellular Ca2+ deposition in an animal model of muscle fiber necrosis and regeneration induced by intramuscular injection of metoclopramide. Twenty-four hours after the drug's injection, extensive muscle fiber necrosis, together with dramatic loss of parvalbumin immunoreactivity and intracellular Ca2+ deposition, was observed. Muscle fiber regeneration began on day 4 after the injection and was complete by the end of the third week. Parvalbumin was not detected in the regenerating fibers, but gradually emerged during the second week as muscle fibers increased in size. It can be suggested that loss of parvalbumin in necrotic fibers is secondary to the loss in integrity of the sarcolemma. Alternatively, loss of parvalbumin in degenerating fibers may impair calcium buffering and act as a contributory factor in the necrotic process. The progressive appearance of parvalbumin immunoreactivity in regenerating fibers parallels that found in normal myogenesis.

Animals↗
PubMed1994

Promoter elements required for developmental expression of the maize Adh1 gene in transgenic rice.

To define the regions of the maize alcohol dehydrogenase 1 (Adh1) promoter that confer tissue-specific expression, a series of 5' promoter deletions and substitution mutations were linked to the Escherichia coli beta-glucuronidase A (uidA) reporter gene and introduced into rice plants. A region between -140 and -99 not only conferred anaerobically inducible expression in the roots of transgenic plants but was also required for expression in the root cap, embryo, and in endosperm under aerobic conditions. GC-rich (GC-1, GC-2, and GC-3) or GT-rich (GT-1 and GT-2) sequence motifs in this region were necessary for expression in these tissues, as they were in anaerobic expression. Expression in the root cap under aerobic conditions required all the GC- and GT-rich motifs. The GT-1, GC-1, GC-2, and GC-3 motifs, and to a lesser extent the GT-2 motif, were also required for anaerobic responsiveness in rice roots. All elements except the GC-3 motif were needed for endosperm-specific expression. The GC-2 motif and perhaps the GT-1 motif appeared to be the only elements required for high-level expression in the embryos of rice seeds. Promoter regions important for shoot-, embryo-, and pollen-specific expression were proximal to -99, and nucleotides required for shoot-specific expression occurred between positions -72 and -43. Pollen-specific expression required a sequence element outside the promoter region, between +54 and +106 of the untranslated leader, as well as a silencer element in the promoter between -72 and -43.

Alcohol Dehydrogenase↗
PubMed1994

Parvalbumin immunohistochemistry in denervated skeletal muscle.

Parvalbumin is a calcium-binding protein which, in muscle, is mainly found in type 2B fibres, whereas type 1 fibres lack parvalbumin immunoreactivity. Previous studies have shown that this pattern is highly dependent upon motor neuron innervation and is modified in denervated, cross-reinnervated or chronic low-frequency stimulated muscles. In the present study, we have examined the modifications of parvalbumin immunocytochemistry in the anterior tibialis muscle of the rat at different intervals following section of the sciatic nerve. During the first 2 weeks after denervation, no changes in parvalbumin immunoreactivity were seen, although a global reduction of fibre diameter was observed. Three weeks after denervation, small angulated, strongly parvalbumin-immunoreactive fibres appeared. From the second month onwards, the pattern of parvalbumin immunohistochemistry was characterized by areas composed of small, strongly immunoreactive fibres separated by less atrophic areas displaying a normal chequerboard distribution of parvalbumin immunoreactivity. The increase of parvalbumin-immunoreactivity in denervated and reinnervated muscle, as seen in our study, indicates that important changes in parvalbumin distribution occurs in muscle fibres after denervation. These changes are probably produced in an attempt to bind the free cytosolic calcium which accumulates in denervated fibres, and further reinforces the role of parvalbumin in calcium homeostasis during denervation and reinnervation.

Adenosine Triphosphatases↗
PubMed1991

Cellular growth response to epidermal growth factor in colon carcinoma cells with an amplified epidermal growth factor receptor derived from a familial adenomatous polyposis patient.

The receptor binding and cellular growth responses to exogenous epidermal growth factor (EGF) were studied using the DiFi cell line established from a familial adenomatous polyposis patient. The number of cell membrane EGF receptors on DiFi cells, as measured by competitive radioligand binding assays and Scatchard analysis of 125I-EGF binding isotherms, was calculated to be 4.8 x 10(6) receptors/cell. An acid prewash step performed prior to ligand binding assays did not reveal additional receptor numbers. A single, low-affinity receptor population was identified by Scatchard analysis, with an apparent Kd of 4.6 nM. This result was confirmed by radioligand binding studies performed in the presence and absence of the receptor-antagonist monoclonal antibody 528 IgG that binds predominantly to the low-affinity form of the EGF receptor. DiFi cells at 50-60% confluence, when exposed to 50 nM exogenous EGF, exhibited a rapid but partial (30%) reduction in their cell membrane-associated receptor, characteristic of sequestration. Exposure of DiFi cells to 50 nM EGF for longer periods of time (4 h) did not result in any further reduction in EGF-receptor number. The cellular growth response of DiFi cells to exogenous EGF was studied in monolayer cultures as well as in a soft agarose assay. Inhibition of soft agar colony formation was observed at exogenous EGF concentrations greater than 1.7 nM, and inhibition of monolayer growth occurred at EGF concentrations greater than 1 nM. In immune complex kinase assays, the DiFi receptor showed similar specific activity to that from the well-characterized A431 cell line. Additionally, phosphorylation of the receptor on tyrosine was qualitatively similar to that of A431 cells, further suggesting that the DiFi receptors identified by EGF-binding studies were biologically functional.

Adenomatous Polyposis Coli↗
PubMed1990

Establishment of a new human pancreatic adenocarcinoma cell line, MDAPanc-3.

A new cell line was established from a liver metastasis of a human pancreatic adenocarcinoma. The cell line, MDAPanc-3, which arose from a moderately differentiated adenocarcinoma, produces carbonic anhydrase II mRNA, but no detectable levels of insulin or alpha amylase mRNA. The stem line chromosome number was determined to be 43, with six marker chromosomes. Growth of MDAPanc-3 is stimulated by cholecystokinin (CCK) fragment 26-33. The cell line will be useful in further studies on the mechanism(s) by which CCK stimulates growth of certain human pancreatic adenocarcinomas and normal human pancreatic exocrine tissue.

Adenocarcinoma↗
PubMed1989

[Bone resorption in orthodontic tooth movement: an attempted schematization].

The osteoclast is the major cellular agent of bone resorption. Hormonal stimulation of bone resorption is indirect and depends on the osteoblastic function. Protease production is the final common pathway through which osteoblastic cells initiate osteoclastic resorption. Exposition of the mineralised matrix and contact with the osteoclasts always comes before resorption, regardless of the stimulating agent involved in the resorption process. In orthodontic conditions, production and activation of osteoclasts may be attained through different ways. Inflammation subsequent to tissue damage and bioelectric perturbations associated to alveolar bending can be considered as two major events which may lead to increase bone resorption and orthodontic tooth displacement. The precise transduction mechanism of an orthodontic force into cellular resorbing activity is still obscure.

Alveolar Process↗
PubMed1986

Differences in glycerolipid synthesis and insulin regulation in rat hepatocytes and adipocytes.

Glycerolipid synthesis was studied by determining radioactive incorporation from either [1-14C] acetate or [U-14C] palmitate. Glycerolipid synthesis in adipocytes, mainly from exogenous palmitate, was preferentially directed to the formation of triacylglycerols, whereas in hepatocytes triacylglycerols and phospholipids were synthesized at similar rates. Insulin stimulated glycerolipid synthesis from acetate in both types of cells, being triacylglycerols more significantly increased than phospholipids. The most relevant difference was the finding that in adipocytes insulin strongly stimulated the formation of diglycerides, apparently from phosphatidate, whereas in hepatocytes insulin only slightly increased diglyceride levels. A possible role of diacylglycerol in insulin action in adipocytes, but not in hepatocytes, is also discussed.

Acetates↗
PubMed1984

Lipid synthesis in isolated rat hepatocytes: activation by insulin and vanadate and inhibition by ouabain.

Lipid synthesis from [1-14C] acetate was stimulated by insulin in rat hepatocytes. Vanadate also enhanced lipid synthesis, although its effect was about 2-3 times higher than that of insulin, whereas ouabain significantly decreased hepatic lipid synthesis. The stimulatory effects of both insulin and vanadate were not dependent on extracellular Ca2+. Also, this stimulation was not mimicked by either ouabain or ouabain plus vanadate, even though they are expected to induce a non-specific increase of cytoplasmic Ca2+ concentration. These results suggest that insulin and vanadate stimulation of lipid synthesis may not be mediated by changes in Ca2+ fluxes through plasma membrane.

Acetates↗
PubMed1982

Effects of diazo-oxo-norleucine on cell kinetics and odontoblast differentiation in cultured embryonic mouse molars.

Diazo-oxo-norleucine (DON), an analogue of glutamine, prevented odontoblast differentiation in cultured tooth germs. Diazo-oxo-norleucine added after the onset of odontoblast differentiation, did not affect the secretion of predentine or the functional differentiation of ameloblasts. DON decreased explant volume and modified cell kinetics, decreasing mitotic index, labelling index and number of grains per nucleus; the 5 phase of the cell cycle was lengthened. These modifications of cell kinetics should be considered when interpreting the effects of DON on odontoblast differentiation.

Animals↗
PubMed1982

Facts and hypotheses concerning the control of odontoblast differentiation.

Numerous studies using amphibians have demonstrated that preodontoblasts emerging from the dental papilla are derived from cranial neural crest cells [4, 12, 46, 64]. However this has not been established for mammals. The history of odonotogenesis begins during the early stages of cranial-facial development when the maxillary and mandibular processes processes develop. Continuous epithelio-mesenchymal interactions condition the histogenesis and morphogenesis of the teeth [24-26, 43, 44, 49, 51, 58] as well as the terminal differentiation of odontoblasts and ameloblasts [23, 47, 52, 54, 59, 61, 67]. During recent years a considerable amount of experimental data relating to differentiation of odontoblasts has been published. We summarize these data and attempt to integrate them in deductive hypothesis concerning the control of odontoblast differentiation.

Adenylyl Cyclases↗