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C A Hansen

Publications and source records attributed to C A Hansen.

At least 55 records · Page 3Linked to original sources
PubMed1991

Mechanisms of receptor-mediated Ca2+ signaling in rat hepatocytes.

The Ca2+ signal observed in individual fura-2-loaded hepatocytes stimulated with the alpha 1-adrenergic agonist phenylephrine consisted of a variable latency period, a rapid biphasic increase in the cytosolic free Ca2+, followed by a period of maintained elevated cytosolic Ca2+ (plateau phase) that depended on the continued presence of both agonist and external Ca2+. Microinjection of guanosine-5'-O-(3-thiophosphate) elicited a Ca2+ transient with the same basic features. The Ca2+ transient resulting from microinjecting inositol 1,4,5-trisphosphate (Ins-1,4,5-P3) occurred with essentially no latency period and consisted of a rapid spike that decayed back to preinjection levels within 15 s. Microinjection of inositol 1,4,5-trisphosphorothioate (thio-IP3), a nonmetabolizable analog of Ins-1,4,5-P3, elicited a Ca2+ transient that was initially identical to that observed with Ins-1,4,5-P3, except that the cytosolic Ca2+ remained elevated. The maintained thio-IP3-induced Ca2+ increase was dependent on the presence of external Ca2+, suggesting an activation of Ca2+ influx. Reintroduction of external Ca2+ in the presence of 5 microM phenylephrine to Ca(2+)-depleted cells resulted in a 2-fold greater rate of rise in the cytosolic Ca2+ compared to the rate observed upon Ca2+ addition to cells Ca(2+)-depleted by preatement with thapsigargin. The rate of Ca2+ rise upon Ca2+ addition to cells microinjected with thio-IP3 was similar to that observed with phenylephrine. Coinjection of the cells with thio-IP3 plus heparin reduced the rate of Ca2+ rise upon Ca2+ addition to that observed in thapsigargin-treated cells. These data indicate that the mechanism responsible for receptor-mediated stimulation of Ca2+ entry into hepatocytes involves not only capacitative Ca2+ entry but also an additional component mediated directly by Ins-1,4,5-P3.

Animals↗
PubMed1991

A provisional removable partial denture for use during construction of an anterior splint bar prosthesis.

A technique for constructing a provisional removable partial denture before and during construction of an anterior splint bar prosthesis is described. The provisional prosthesis is easily adapted to fit the splint bar prosthesis after it is cemented in place. The technique assures that the patient will enjoy the benefits of a well-fitting and esthetic provisional restoration through all phases of construction of the splint bar and the final removable partial denture.

Denture Design↗
PubMed1990

Adherence of human neutrophils changes Ca2+ signaling during activation with opsonized particles.

Changes in the cytosolic free Ca2+ concentration ([Ca2+]i) upon activation of human neutrophils by opsonized particles (serum-treated zymosan; STZ) were evaluated by three different methods: (i) measurement of total fluorescence changes in indo-1 loaded neutrophils activated in suspension; (ii) measurement of fluorescence changes in individual indo-1 loaded neutrophils in a flow cytometer and (iii) measurement of fluorescence changes in individual fura-2 loaded neutrophils adherent to serum-coated coverslips. Our study shows that the opsonized particle-induced change in [Ca2+]i in neutrophils is altered during adherence of the cells to a serum-coated surface. These observations might be of importance for neutrophil function in vivo, since adherence is a prerequisite for diapedesis and chemotaxis.

Calcium↗
PubMed1990

Psychological impact of islet cell-antibody screening. Preliminary results.

The identification of at-risk individuals before the onset of insulin-dependent diabetes mellitus with islet cell-antibody (ICA) screening programs could have significant psychological sequelae. We initiated a descriptive study of ICA+ subjects and their family members in which reactions to study participation, anxiety, and coping responses are monitored. Described here are preliminary results from 18 ICA+ youngsters, 6 ICA+ adults, and their family members. ICA+ identification resulted in clinically significant anxiety that dissipated to normal levels over time for all participants. Both ICA+ subjects and family members coped with the news in similar ways, relying primarily on problem-focused and social-support coping strategies. Few blamed themselves for their own or their loved one's ICA+ status. There was some evidence that the ICA+ participants may minimize the potential impact of their at-risk status. Compared with family members, ICA+ subjects used more avoidance coping strategies, and few believed they would ever develop diabetes. In contrast, many family members believed their loved one would ultimately develop diabetes. Although the initial findings support the resiliency of this population, the long-term effects of ICA screening remain to be seen.

Adaptation, Psychological↗
PubMed1990

Adherence-health status relationships in childhood diabetes.

Used 24-hr recall interviews to assess adherence in a sample of seventy-eight 6- to 19-year-olds with insulin-dependent diabetes mellitus over a 3-month period. Thirteen adherence measures were quantified and grouped into six adherence factors (Injection, Exercise, Diet Type, Testing/Eating Frequency, Calories Consumed, and Concentrated Sweets). Prevailing glucose levels over a 2- to 3-month interval were indexed by glycosylated hemoglobin A1c (HA1c) and glycosylated serum protein (GSP) assays. Fasting triglycerides (TRIG) and total cholesterol (CHOL) assays were used to estimate lipid metabolism. Adolescents were generally less adherent than their young counterparts. Using hierarchical multiple-regression techniques, HA1c and GSP were not reliably predicted by most of the adherence factors; only Calories Consumed showed any predictive power. No significant regression equations emerged for CHOL. In contrast, TRIG was significantly associated with five of the six adherence factors; in all cases, adherence interacted with the patients' metabolic status (as defined by HA1c) at study entry, suggesting that adherence had different effects for youngsters in good versus poor diabetes control.

Adolescent↗
PubMed1989

Partial purification of inositol polyphosphate 1-phosphomonoesterase with characterization of its substrates and products by nuclear magnetic resonance spectroscopy.

A study of the enzyme activities that degrade Ins(1,3,4)P3 in rat brain showed that it was dephosphorylated primarily by a Mg2+-dependent inositol polyphosphate 1-phosphomonoesterase to Ins(3,4)P2 and then to Ins(3)P by a 4-phosphomonoesterase. A less active enzyme activity with the properties of a 4-phosphomonoesterase that converted Ins(1,3,4)P3 to Ins(1,3)P2 was also detected. The inositol polyphosphate 1-phosphomonoesterase was separated from the 4-phosphomonoesterase and the inositol monophosphate phosphomonoesterase by chromatography on phosphocellulose, DE-52 anion exchange and hydroxylapatite columns. Kinetic characterization of the partially purified inositol polyphosphate 1-phosphomonoesterase indicated that both Ins(1,3,4)P3 and Ins(1,4)P2 were substrates with apparent Km values of 0.9 microM and 0.7 microM, respectively. Either substrate was a competitive inhibitor of the other substrate and dephosphorylation of both substrates was directly inhibited by Li+ in an uncompetitive manner. These data strongly suggest that a single enzyme dephosphorylates both Ins(1,3,4)P3 and Ins(1,4)P2. The 4-phosphomonoesterase that dephosphorylated Ins(3,4)P2 to Ins(3)P was insensitive to Mg2+ and Li+ and was probably the same enzyme that degraded Ins(1,3,4)P3 to Ins(1,3)P2. The isomeric configurations of the major inositol polyphosphates formed from the degradation of Ins(1,3,4,5)P4 were determined using 1H- and 31P-NMR spectroscopy, and confirmation of the structures assigned to Ins(1,3,4,5)P4, Ins(1,3,4)P3 and Ins(3,4)P2 was obtained.

Animals↗
PubMed1989

Inositol tetrakisphosphate mobilizes calcium from cerebellum microsomes.

Ca2+ accumulated by rat cerebellum microsomes in the presence of MgATP was released by added inositol tetrakisphosphate [Ins(1,3,4,5)P4]. The concentrations of D-myo-inositol-1,4,5-trisphosphate [D-Ins(1,4,5)P3], D-Ins(1,3,4,5)P4, and DL-Ins(1,3,4,5)P4 required for half-maximal release were 0.15, 4.6, and 7.5 microM, respectively. Maximal concentrations of InsP4 released only 70% of the Ca2+ released by maximal concentrations of Ins(1,4,5)P3. Inositol pentakisphosphate and D-myo-inositol-1,3,4-trisphosphate were relatively inactive. Additional Ca2+ was released when Ins(1,4,5)P3 (or a nonhydrolyzable analog) was added after completion of InsP4-mediated Ca2+ release but not when this sequence of additions was reversed. This indicates that InsP4 releases Ca2+ from part of the InsP3-releasable compartment. No evidence for synergism between InsP4 and InsP3 was obtained and responses to suboptimal concentrations of both inositol phosphates were approximately additive. Heparin was a potent inhibitor of InsP4-mediated Ca2+ release. Inhibition by heparin was competitive with respect to InsP4 concentration and the Ki for heparin was 0.6 microgram/ml (approximately 100 nM), irrespective of whether InsP4 or InsP3 was used as an agonist. A 3-phosphatase capable of converting [3H]Ins(1,3,4,5)P3 to [3H]Ins(1,4,5)P3 could not be detected in cerebellum microsomes. Hence, we conclude that, in vitro, receptors capable of recognizing Ins(1,3,4,5)P4 can also be coupled directly to a Ca2+ release system.

Animals↗
PubMed1988

Characterization of inositol 1,3,4-trisphosphate phosphorylation in rat liver.

Liver homogenates phosphorylated Ins 1,3,4-P3 to an InsP4 isomer that was distinct from Ins 1,3,4,5-P4. This InsP4 isomer accumulated in vasopressin stimulated hepatocytes prelabeled with myo-[3H]inositol with a time course that lagged behind Ins 1,3,4-P3 formation. The Ins 1,3,4-P3 kinase responsible for its formation was partially purified from rat liver. The enzyme had a Km for Ins 1,3,4-P3 of 0.29 microM, a Km for ATP of 141 microM and was not affected by changes in free Ca2+ in the physiological range. The relationship of this new InsP4 isomer to the inositol phosphate signaling pathway is discussed.

Animals↗
PubMed1988

Purification of D-myo-inositol 1,4,5-trisphosphate 3-kinase from rat brain.

The ATP-dependent, calmodulin-sensitive 3-kinase responsible for the conversion of D-myo-inositol 1,4,5-trisphosphate to D-myo-inositol 1,3,4,5-tetrakisphosphate has been purified 2,700-fold from rat brain to a specific activity of 2.3 mumol/min/mg protein. A method of purification is described involving chromatography on phosphocellulose, Orange A dye ligand, calmodulin agarose, and hydroxylapatite columns. Neither the highly purified enzyme nor enzyme eluting from the phosphocellulose column were activated by Ca2+. However, enzyme in the 100,000 x g supernatant from rat brain was activated by Ca2+ over the range from 10(-7) to 10(-6) M and Ca2+ sensitivity of the purified enzyme was restored by the addition of calmodulin. The enzyme has a catalytic subunit Mr of 53,000 by sodium dodecyl sulfate-polyacrylamide gel electrophoresis. Size exclusion chromatography of the purified enzyme on a Superose 12 column gave a Mr value of 70,000, indicating that the purified enzyme was present as a monomer. In contrast, the 100,000 x g supernatant and the purified enzyme after addition of calmodulin and 10(-6) M Ca2+ chromatographed on size exclusion chromatography with a Mr of 150,000-160,000. These results imply that the native enzyme is a dimeric structure of two catalytic subunits plus calmodulin. The purified enzyme showed a Km of 0.21 +/- 0.08 microM for D-myo-inositol 1,4,5-trisphosphate and had a pH optimum of 8.5. Addition of calmodulin increased both the Km and the Vmax of the purified enzyme about 2-fold. The high affinity of the 3-kinase for D-myo-inositol 1,4,5-trisphosphate together with its activation by Ca2+/calmodulin suggests that this enzyme may exert an important regulatory role in inositol phosphate signaling by promoting the formation of additional inositol polyphosphate isomers.

Animals↗
PubMed1987

Purification and characterization of two types of soluble inositol phosphate 5-phosphomonoesterases from rat brain.

Two soluble forms of inositol phosphate 5-phosphomonoesterase have been partially purified and characterized from rat brain and are referred to as type 1 and type 2 according to their order of elution from DEAE-Sepharose. Together, these enzymes represent 26 +/- 3% (mean +/- S.E., n = 4) of the total inositol 1,4,5-triphosphate (Ins(1,4,5)P3) phosphatase activity assayed in crude brain homogenate and are present in approximately equal total activities in a 100,000 x g supernatant, with the remainder being membrane-bound. Both soluble enzymes require Mg2+ for activity, are moderately inhibited by Ca2+ in the micromolar range, and can be inhibited by millimolar concentrations of a variety of phosphorylated compounds. The type 1 enzyme has been purified to a specific activity of 1.06 mumol/min/mg protein. It elutes as a 60-kDa protein on Sephacryl S-200. On sodium dodecyl sulfate-polyacrylamide gel electrophoresis, the type 1 enzyme correlates with a pair of protein bands of 66 and 60 kDa. It has apparent Km values of 3 and 0.8 microM for Ins(1,4,5)P3 and inositol 1,3,4,5-tetrakisphosphate (Ins(1,3,4,5)P4), respectively, and hydrolyses Ins(1,4,5)P3 approximately 12 times faster than Ins(1,3,4,5)P4. The type 2 enzyme has been purified to a specific activity of 15.2 mumol/min/mg protein, elutes as a protein of 160 kDa on Sephacryl S-300, and migrates as a similarly sized subunit on sodium dodecyl sulfate-polyacrylamide gel electrophoresis. It has an apparent Km for Ins(1,4,5)P3 of 18 microM. Its apparent Km for Ins(1,3,4,5)P4, however, is greater than 150 microM, suggesting that this enzyme is primarily an Ins(1,4,5)P3 5-phosphomonoesterase. The relationship of these two enzymes to the inositol tris/tetrakisphosphate pathway is discussed.

Animals↗
PubMed1987

Inositol 1,3,4,5-tetrakisphosphate increases the duration of the inositol 1,4,5-trisphosphate-mediated Ca2+ transient.

The effect of Ins 1,3,4,5-P4 on the intracellular Ca2+ mobilization produced by Ins 1,4,5-P3 has been examined in permeabilized hepatocytes. Ins 1,3,4,5-P4 did not affect the magnitude of the Ins 1,4,5-P3-mediated Ca2+ release but did inhibit re-accumulation of the released Ca2+ back into intracellular stores. This effect was not mimicked by Ins 1,3,4-P3. In hepatocytes, the re-uptake phase of the response results from Ins 1,4,5-P3 hydrolysis. Measurements using labeled substrates indicate that Ins 1,3,4,5-P4 inhibits the hydrolysis of Ins 1,4,5-P3 and vice versa. Since the removal of the 5-phosphate on Ins 1,4,5-P3 and Ins 1,3,4,5-P4 is a common step in the disposal of both compounds, it is suggested that one of the biological effects of Ins 1,3,4,5-P4 may be to slow hydrolysis of Ins 1,4,5-P3 and thereby prolong the duration of a Ca2+ transient.

Calcium↗
PubMed1987

The segmented framework removable partial denture.

The segmented framework removable partial denture is made of two cast metal individual segments joined with a resin major connector. The small individual framework segments can be made to fit well and the design permits ready correction of the tissue surface of the major connector through relining or an altered cast procedure. The dentist is offered a valuable alternative treatment approach in selected patients.

Acrylic Resins↗
PubMed1987

Fracture of the thumb sesamoid bones.

Two cases of sesamoid fracture of the thumb are reported. The condition is presumably underdiagnosed because of incomplete ossification of the bone. If pain persists after immobilization, excision of the bone is curative.

Adolescent↗
PubMed1987

Mechanisms involved in receptor-mediated changes of intracellular Ca2+ in liver.

Interactions between the different signaling roles of myo-inositol 1,4,5-trisphosphate and 1,2-diacylglycerol, the products of agonist-stimulated phosphatidylinositol 4,5-bisphosphate breakdown, are assessed in isolated rat hepatocytes. Measurements of the kinetics of accumulation of individual [3H]inositol phosphates after the addition of different Ca2+-mobilizing agonists in general support the role of inositol 1,4,5-trisphosphate as the second messenger responsible for release of sequestered intracellular Ca2+. Various agonists, when added at maximal concentrations, however, produce qualitatively and quantitatively different responses, which reflect varying abilities of the agonists to activate phospholipase C. Qualitative differences are revealed by a pronounced biphasic pattern to the Ins(1,4,5)P3 accumulation after vasopressin and phenylephrine stimulation, which is indicative of negative feedback. It is suggested that this effect is mediated by a partial diacylglycerol activation of protein kinase C, which in vitro causes an activation of inositol phosphate 5-phosphatase and hence promotes removal of Ins(1,4,5)P3 to Ins(1,4)P2. An alternative mechanism proposed by Biden and Wollheim (1986) of a secondary Ca2+ activation of Ins(1,4,5)P3 3-kinase is considered less likely as a general mechanism, since highly purified kinase prepared from rat brain shows only an inhibition by Ca2+. Glucagon, 8-Br-cAMP, and EGF induce small increases of Ins(1,4,5)P3 in hepatocytes, together with slower and smaller increases of cytosolic free Ca2+ than those produced by vasopressin or phenylephrine, with Ca2+ being mobilized from the same intracellular pools with each of the agonists. The Ca2+-mobilizing effect of glucagon, therefore, may be entirely due to a cAMP-dependent process, although a direct receptor-mediated activation of phospholipase C, as suggested by Wakelam et al. (1986), remains a possibility. The EGF receptor appears to be coupled to phospholipase C, presumably via a G-protein. It is speculated that the mechanism by which cAMP increases Ins(1,4,5)P3 levels in hepatocytes could either be by phosphorylation and inhibition of inositol phosphate 5-phosphatase or by phosphorylation and facilitation of the coupling between the G-protein and phospholipase C. When protein kinase C is maximally activated by pretreatment of hepatocytes with PMA, the stimulatory effects of phenylephrine, glucagon, 8-Br-cAMP, and EGF on the accumulation of inositol phosphates and increase of cytosolic free Ca2+ are largely inhibited.(ABSTRACT TRUNCATED AT 400 WORDS)

Animals↗