Biomedical subjects

J Calamia

Publications and source records attributed to J Calamia.

6 recordsLinked to original sources

PubMed1999

Clinical effectiveness of a Class V flowable composite resin system.

This clinical study evaluated a Class V flowable composite resin restoration system and its ability to reduce dentin sensitivity. Twenty-one patients required Class V restorations because of erosion, abrasion, or decay at the cervical area. Each patient exhibited moderate or severe sensitivity and required replacement of tooth structure. The degree of sensitivity was determined by either tactile scraping of the tip of an explorer over the surface of the tooth or by an air blast from a syringe for 5 seconds. A total of 52 restorations were performed. According to phone conversations and questionnaires, 1 patient experienced continued sensitivity on 1 treated tooth for a duration of 1 week, but this sensitivity was gone at 1-month, 3-month, 6-month, and 1-year recalls. None of the other patients exhibited sensitivity at any phone checks or during recall visits.

Composite Resins↗

PubMed1999

A new approach to restorative dentistry: fabricating ceramic restorations using CEREC CAD/CAM.

Ceramic materials provide an alternative when choosing a tooth-colored restoration. Currently, posterior composite restorations can be used to achieve esthetic restorations; however, they have many disadvantages with regard to wear, polymerization shrinkage, discoloration, marginal leakage, and technique sensitivity. The use of CEREC CAD/CAM enables the dentist to place feldspathic porcelain (Vitablocs Mark II) and machinable glass ceramic (Dicor MGC) restorations in a single visit. When compared to composite materials, these materials closely approximate the physical properties of enamel in compressive and tensile strength and wear resistance. This study evaluated 50 CEREC CAD/CAM restorations after 4 years in service. Restorations ranged from Class I to 7/8s crown preparations.

Adult↗

PubMed1992

Membrane protein spanning segments as export signals.

Escherichia coli lac permease is a polytopic integral membrane protein with six translocated (periplasmic) domains. Individual N-terminal cytoplasmic regions and membrane-spanning segments adjacent to each of the periplasmic domains acted as export signals for an attached sensor protein (alkaline phosphatase). However, the export activity of one of the spanning segments was considerably lower than that of the others, and was limited by the presence of a positively charged residue (Arg302). These observations are compatible with models of membrane protein insertion in which hydrophilic domains are translocated independently. However, the results suggest that efficient translocation may sometimes require interaction between individual spanning segments.

Amino Acid Sequence↗

PubMed1990

lac permease of Escherichia coli: topology and sequence elements promoting membrane insertion.

The membrane topology of Escherichia coli lac permease was analyzed using a set of 36 lac permease-alkaline phosphatase (lacY-phoA) gene fusions. The level of enzymatic activity of alkaline phosphatase fused to a cytoplasmic membrane protein appears to reflect whether the fusion junction site normally faces the cytoplasm or periplasm. The alkaline phosphatase activities of cells expressing the lacY-phoA fusions distinguish between models previously proposed for the topology of lac permease and favor one with 12 transmembrane segments. This model is fully compatible with the results of earlier biochemical and immunological studies. The properties of fusions with junctions spanning two of the transmembrane segments at 2- or 3-amino acid intervals indicate that approximately half of the residues of either segment (9-11 amino acids) suffices to promote alkaline phosphatase translocation across the membrane. The additional transmembrane segment amino acids that are not required for this membrane insertion process may normally be needed in unfused lac permease after insertion for stable association with the membrane.

Alkaline Phosphatase↗

PubMed1986

Effect of osmolarity on cation fluxes in medullary thick ascending limb cells.

The effects of a hypertonic extracellular medium on furosemide-sensitive Na and K fluxes were studied in isolated cells from the rabbit medullary thick ascending limb of Henle's loop (mTALH). In the control incubation medium, the furosemide-sensitive 22Na uptake was 379.1 +/- 24.4 pmol . mg protein-1 . min-1 and the furosemide-sensitive 86Rb uptake was 30.5 +/- 16.9. The furosemide-sensitive 22Na flux was not stimulated by K gradients directed into the cells, and, conversely, the furosemide-sensitive 86Rb flux was not stimulated by Na gradients directed into the cells. These findings are consistent with a Na-Cl cotransport system. In the presence of 200 mM mannitol, the furosemide-sensitive 22Na and 86Rb fluxes were increased dramatically to 919.4 +/- 76.6 and 106.1 +/- 29.2 pmol . mg protein-1 . min-1, respectively. When the osmolarity of the incubation medium was increased, not only were the furosemide-sensitive fluxes increased but these fluxes became inter-dependent, i.e., removing Na or K prevented the increase in the furosemide-sensitive flux of the other cation. This finding is consistent with a Na-K-2Cl cotransport system in the mTALH cells. The data suggest that the Na-Cl and the Na-K-2Cl cotransport systems may be distinct functions of the same furosemide-sensitive cotransport system and that their expression may be regulated by changes in cell volume.

Animals↗

PubMed1985

Lack of potassium effect on Na-Cl cotransport in the medullary thick ascending limb.

The effect of potassium on sodium chloride uptake into rabbit renal medullary thick ascending limb of Henle's loop (mTALH) cells was studied to assess whether K participates in the Na-Cl cotransport system. Na uptake into the mTALH cells was inhibited 70% at 3 min by 1 mM furosemide. The total and furosemide-sensitive Na uptake was stimulated by Cl. Additionally, Cl uptake into the mTALH cells was stimulated by Na gradients and inhibited 42% at 3 min by 1 mM furosemide. Na uptake was studied in the presence of 0,5, or 140 mM external K gradients. Na uptake was similar in the absence and presence of K. Additionally, furosemide inhibited Na uptake as effectively in the absence or presence of K. Similar studies were conducted to study the effects of Na on 86Rb uptake. Na did not stimulate 86Rb uptake. The uptake of 86Rb was similar in the presence of 0,5, or 140 mM Na gradients. Furosemide had no significant inhibitory effect on 86Rb uptake. Barium (5 mM), an inhibitor of K conductance pathways, inhibited total 86Rb uptake by 19%. In the presence of 5 mM BaCl2, Na still did not have a stimulatory effect on 86Rb uptake. The results confirm the existence of a Na-Cl cotransport system in mTALH cells, but a direct effect of K on the NaCl cotransport system could not be demonstrated under the experimental conditions we used.

Animals↗