Occlusal pits and fissures continue to frustrate dentists battling to control decay. Several techniques being studied now offer hope of eventually eliminating caries in these areas.

Bisphenol A-Glycidyl Methacrylate↗

PubMed1992

[Clinical usefulness of measurement of creatine contents in human erythrocytes as an index of erythropoiesis].

The apparent half-life of erythrocytes in human blood have usually been measured using 51Cr or 32P-labeled erythrocytes. However, these methods are not suitable for routine methods for the determination of the half-life of erythrocytes because of requirement for both patient admission and complicated procedure. In 1967 Griffiths and Fitzpatrick suggested that creatine level in human packed erythrocytes reflected the mean-age of erythrocyte population. Fehr and Knob reported that erythrocyte creatine levels correlated closely with half-life of erythrocytes by means of 51Cr in severe and milder hemolytic anemias. In order to verify the clinical usefulness of measurement of creatine contents in human erythrocytes as an index of erythropoiesis, the number of reticulocytes counted by an automated reticulocyte counter (R-3000, Toa medical instruments) and creatine contents in erythrocytes measured by high performance liquid chromatography were compared. To evaluate the erythropoietic dynamics, we tried to determine the frequency distribution for individual erythrocyte cell age using erythrocyte creatine. The effect of erythrocyte life-span on hemoglobin A1c(HbA1c) was also appraised in normal blood sugar subjects. A significant increase (p less than 0.005) of erythrocyte creatine was found both in inactive autoimmune hemolytic anemia (AIHA) and in active AIHA. In severe AIHA, the frequency distribution of erythrocyte creatine shifted to the area of high level erythrocyte creatine, and showed a broad-pattern form corresponding to erythropoiesis. Negative correlation (r = -0.707, p less than 0.005) was revealed between erythrocyte creatine and HbA1c in normal blood sugar subjects.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗

PubMed1992

[A study on creatine uptake into human erythrocytes: relation to erythrocyte aging].

In order to assess the relation between creatine uptake into human erythrocytes and erythrocyte aging, actual influx of creatine into erythrocytes and creatine contents in erythrocytes were measured by using method of high performance liquid chromatography and isotopic estimation of 14C-creatine concentration. Actual influx of creatine into erythrocytes was showed rapidly, in spite of constant contents of erythrocyte creatine under the condition to be incubated at 37 degrees C for approximate 4 hours in isotonic saline containing high concentration of creatine. Km values of the creatine uptake into young erythrocytes were evidently smaller than that into old erythrocytes. On the other hand, no significant difference of Vmax values was observed to be dependent on erythrocyte aging.

Creatine↗

PubMed1991

Isolation of a candidate repressor/activator, NF-E1 (YY-1, delta), that binds to the immunoglobulin kappa 3' enhancer and the immunoglobulin heavy-chain mu E1 site.

We have determined that the developmental control of immunoglobulin kappa 3' enhancer (kappa E3') activity is the result of the combined influence of positive- and negative-acting elements. We show that a central core in the kappa E3' enhancer is active at the pre-B-cell stage but is repressed by flanking negative-acting elements. The negative-acting sequences repress enhancer activity in a position- and orientation-independent manner at the pre-B-cell stage. We have isolated a human cDNA clone encoding a zinc finger protein (NF-E1) that binds to the negative-acting segment of the kappa E3' enhancer. This protein also binds to the immunoglobulin heavy-chain enhancer mu E1 site. NF-E1 is encoded by the same gene as the YY-1 protein, which binds to the adeno-associated virus P5 promoter. NF-E1 is also the human homologue of the mouse delta protein, which binds to ribosomal protein gene promoters. The predicted amino acid sequence of this protein contains features characteristic of transcriptional activators as well as transcriptional repressors. Cotransfection studies with this cDNA indicate that it can repress basal promoter activity. The apparent dual function of this protein is discussed.

Amino Acid Sequence↗

PubMed1991

Regulation of acetyl-CoA carboxylase gene expression. Insulin induction of acetyl-CoA carboxylase and differentiation of 30A5 preadipocytes require prior cAMP action on the gene.

30A5 preadipocytes, derived from 10T1/2 mouse fibroblasts, can be induced to differentiate into adipocytes by hormone treatment. In this paper, we introduce a modified procedure to induce differentiation of 30A5 cells by pretreatment with cAMP for a brief period or by a "nutrition deprivation" pretreatment, followed by incubation in medium containing insulin. These procedures accelerate the differentiation of the preadipocytes, so that the cells are fully differentiated within 4 days instead of the 7-8 days normally required. This differentiation is accompanied by the early induction of acetyl-CoA carboxylase (ACC). ACC catalyzes the rate-limiting step in the biogenesis of long chain fatty acids. To analyze the relationship between cAMP and insulin action in the induction of ACC and cell differentiation, we identified the DNA sequences in promoter II of the ACC gene necessary for the action of insulin and cAMP. Chimeric genes between different fragments of the ACC promoter and the promoterless chloramphenicol transacetylase (CAT) gene were constructed, and stable clones containing these chimeric genes were obtained. By analyzing the CAT activities in these stable clones, we established that insulin action in inducing ACC and cell differentiation requires prior treatment of cells with cAMP and the presence of specific DNA regions in the ACC promoter for cAMP action. Stable clones containing a chimeric gene which consists of DNA sequences in promoter II that are required for insulin action, thymidine kinase promoter, and the CAT gene did not respond to insulin. However, when the DNA sequences required for cAMP action were placed in this chimeric gene, it responded to insulin upon prior treatment of 30A5 cells with cAMP. Thus, cAMP and insulin, whose physiological actions generally appear to be antagonistic, are synergistically interacting in the induction of ACC and the differentiation of 30A5 cells.

Acetyl-CoA Carboxylase↗

PubMed1991

The minimum surface fibrinogen concentration necessary for platelet activation on dimethyldichlorosilane-coated glass.

Albumin and fibrinogen were competitively adsorbed onto dimethyldichlorosilane-coated glass (DDS-glass) and platelet activation was examined as a function of the surface fibrinogen concentration. The weight ratio of albumin to fibrinogen in the adsorption solution was varied from 10 to 700. Platelet activation was quantitated by the area and circularity of spread platelets. When the DDS-glass was coated with albumin alone, platelets were only contact adherent and could not spread at all. After competitive adsorption of fibrinogen and albumin, however, platelets were able to spread on the surface. Platelet activation increased linearly as the surface fibrinogen concentration increased up to 0.02 micrograms/cm2. Platelets were able to activate fully if the surface fibrinogen concentration was 0.02 micrograms/cm2 or higher, even though the surface was dominated by albumin. It appears that platelets can activate fully as long as only a small fraction (2-15%) of the surface is covered with tightly bound fibrinogen.

Adsorption↗

PubMed1991

Correlation of secondary structure with biological activity for a leader peptide: circular dichroism-derived structure and in vitro biological activities of preproparathyroid hormone peptide and its analogs.

Leader or signal sequences are specialized domains within precursor proteins which serve an essential role in interacting with the cellular secretory apparatus to enable intracellular transport and secretion of proteins. Despite many differences in primary amino acid sequences, signal domains interact with a common set of intracellular components, presumably because the signal sequences share an overall conformational similarity. In a few instances, mutant signal peptides from prokaryotes have been studied and their structures correlated with function (export) in vivo. A series of analogs of the precursor-specific region of preproparathyroid hormone have been prepared which contain substitutions of either proline or a charged amino acid within the hydrophobic core. These synthetic "mutants" have previously been evaluated in several in vitro assays to determine their functionality with regard to protein secretion and suitability as substrates for signal peptidase. The secondary structural content of each peptide, as well as the native sequence and sulfur-free analog, was determined in aqueous and nonaqueous conditions by circular dichroism (CD) as a function of time. The structures obtained were correlated with in vitro bioactivities. Unlike the findings or previous CD studies, all the peptides examined here had low to undetectable alpha-helical content in both aqueous and nonaqueous buffers. The unsubstituted and sulfur-free analogs had high (80-85%) beta-structure in aqueous conditions which was reduced to approximately 30% in nonaqueous solvent. The proline- and charged-substituted peptides contained about half the beta-structure content (35-55%) in aqueous buffer; in nonaqueous solvent their structure was similar to the unsubstituted peptides. The structure-activity correlates found were as follows: a high degree of structure (aqueous conditions) correlated with interaction with signal recognition particle and substrate suitability for signal peptidase; a low degree of structure (nonaqueous environment) correlated with activity in the translocation assay.

Amino Acid Sequence↗

PubMed1991

"The first hospital among Christians": the Ospedale di Santa Maria Nuova in early sixteenth-century Florence.

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History, 15th Century↗

PubMed1991

Phoria, Hering's laws, and monocular perception of direction.

By recording eye movements while subjects fixated a stationary stimulus and reported on its apparent position, four experiments tested whether Hering's laws of visual direction describe monocular perception of egocentric direction. Experiments 1, 2, and 3 alternately covered each eye. Experiments 1 and 2 showed that the stimulus appeared to displace leftward when the left eye was occluded, and vice versa. The apparent displacement was correlated with lateral heterophoria in the occluded eye, and phoria was necessary for the illusory displacement. As a descriptive model, these results expand the range covered by Hering's laws, but they leave open several process models, including ones based on retinal image displacements without reference to extraretinal information. Experiment 4 eliminated retinal image displacements and found apparent target displacements that imply processing of extraretinal information.

Adult↗

PubMed1991

Calculation of solvation interaction energies for protein adsorption on polymer surfaces.

Of the interactions that govern protein adsorption on polymer surfaces, solvation interactions (repulsive hydration and attractive hydrophobic interactions) are thought to be among the most important. The solvation interactions in protein adsorption, however, have not been dealt with in theoretical calculation of the adsorption energy owing to the difficulties in modelling such interactions. We have evaluated the solvation interaction energies using the fragment constant method of calculating the partition coefficients of amino acids. The fundamental assumption of this approach is that the partition coefficients of amino acids between water and organic solvent phases are related to the free energies of transfer from bulk water to the polymer surface. The X-ray crystallographic protein structures of lysozyme, trypsin, immunoglobulin Fab, and hemoglobin from the Brookhaven Protein Data Bank were used. The model polymer surfaces were polystyrene, polypropylene, polyethylene, poly(hydroxyethyl methacrylate) [poly(HEMA)], and poly(vinyl alcohol). All possible adsorption orientations of the proteins were simulated to study the effect of protein orientation on the solvation interactions. Protein adsorption on either hydrophobic or hydrophilic polymer surfaces was examined by considering the sum of solvation and other interaction energies. The results showed that the contribution of the solvation interaction to the total protein adsorption energy was significant. The average solvation interaction energy ranged from -259.1 to -74.1 kJ/mol for the four proteins on the hydrophobic polymer surfaces, such as polystyrene, polypropylene, and polyethylene. On the other hand, the average solvation interaction energies on hydrophilic surfaces such as poly(HEMA) and poly(vinyl alcohol) were larger than zero. This indicates that repulsive hydration interactions are in effect for protein adsorption on hydrophilic polymer surfaces. The total interaction energies of the proteins with hydrophobic surfaces were always lower than those with more hydrophilic surfaces. This trend is in agreement with the experimental observations in the literature. This study suggests that consideration of the solvation interaction energies is necessary for accurate calculation of the protein adsorption energies.

Adsorption↗