A Comparative Study to Evaluate the Linear Dimensional Change and Compression Resistance of Four Elastomeric Interocclusal Recording Materials: An in vitro Study

The transfer of interocclusal data from the patient's mouth to articulators utilizing various types of recording media is necessary for the production of dental prostheses. Occlusal errors in the final prosthesis result from any discrepancies in these interocclusal records.

Materials and Methods

The purpose of this study was to assess the linear dimensional changes in the four elastomeric interocclusal recording materials as well as the material's resistance to compression during the cast mounting on the articulator.

Result

All four elastomeric materials showed decreasing stability over time and 2 mm thickness showed the highest compression resistance with minimal articulation error.

Conclusion

Dimensional stability depends on material and time factors, and compressive resistance decreases with increasing thickness.

Development and Characterization of Solid Dispersion System for Enhancing the Solubility and Dissolution Rate of Dietary Capsaicin

Background:

Capsaicin is a pungent component of chili peppers that suppresses the growth of various cancer cell lines including breast cancer. However, it shows extremely low oral bioavailability due to its poor water solubility.

Objective:

The objective of the present work was to improve the solubility and dissolution rate of capsaicin.

Methods:

Solid dispersions were prepared by the solvent evaporation method using different molar ratios of capsaicin and urea (1:1, 1:2, and 1:3). Differential Scanning Calorimetry (DSC) and X-Ray Diffraction (XRD) study were used to characterize the solid dispersion. Solid dispersions were evaluated for solubility, dissolution rate and in vitro cytotoxicity in breast cancer cell lines.

Results:

XRD and DSC studies exhibited the reduced crystallinity of a drug in solid dispersion. Phase solubility study shows that the drug solubility increased by increasing carrier concentration. In vitro release study of the solid dispersion showed the faster dissolution of a drug with increasing carrier concentration. Solid dispersion formulation effectively inhibited the growth of MCF-7 human breast cancer and MDA-MB-231 triple negative human breast cancer cells in an MTT assay that measures metabolic activity, but only slightly decreased cell viability when compared to capsaicin alone.

Conclusion:

The present study demonstrated that solid dispersion of capsaicin in PEG 6000 overcomes the problems related to the poor aqueous solubility of this drug and improving its dissolution rate.

An in vitro study to compare the influence of different all-ceramic systems on the polymerization of dual-cure resin cement

Aim:

The aim of the study is to compare the effect of composition of three different all-ceramic systems on the polymerization of dual-cure resin cement, using different curing cycles and evaluated immediately within 15 min and after 24 h.

Materials and Methods:

Resin cement disc samples were fabricated by polymerization through three different all-ceramic disc, namely: lithium disilicate discs – IPS e.max (Group B), leucitereinforced discs – IPS Empress (Group C), zirconia discs – Cercon (Group D), and without an intervening ceramic disc, as control (Group A). A total of 80 resin cement disc samples were fabricated for fur groups (n = 20). Each group further consisted of two subgroups (n = 10), t10 and t20 according to two different exposure times of 10 and 20 s, respectively. Each of the 80 resin disc samples was evaluated for their degree of polymerization achieved, by measuring the microhardness(Vickers hardness number) of the samples immediately within 15 min and after 24 h, giving us a total of 160 readings. Oneway analysis of variance test, ttest, and paired ttest were used for multiple group comparisons followed by Tukey's post hoc for groupwise comparison.

Results:

Direct activation of the resin cement samples of control (Group A) showed statistically significant higher mean microhardness values followed by Groups C then B and D, both immediately and after 24 h. The mean microhardness for immediate post-activation was always inferior to the 24 h post-activation test. For both 10 and 20 s curing cycle, there was a significant increase in the microhardness of the resin cement discs cured for 20 s through the different ceramics.

Conclusion:

Ceramic composition affected the polymerization of dual cured resin cement. Doubling the light irradiation time or curing cycle significantly increased mean microhardness value. Greater degree of conversion leading to an increase in hardness was observed when the resin cement discs were evaluated after 24 h.

Reverse Iontophoretic Extraction of Gabapentin: A Mechanistic Study

BACKGROUND

For the narrow therapeutic index anti-epileptic drugs, monitoring of plasma concentration is a necessity for avoiding complications related to fluctuation of plasma level.

OBJECTIVE

The work was aimed at extracting gabapentin by transdermal reverse iontophoresis to investigate its feasibility for noninvasive therapeutic drug monitoring.

METHODS

Gabapentin was delivered in phosphate buffer (pH 7.4) at a therapeutic concentration range of 2-10 µg/ml. The same media was also used in receiver compartment. Extractions were carried out under an electric field of 5 V (current intensity range 0.3 -0.5 mA/cm2), provided by a custom-made power source for a period of 4 h. Samples were withdrawn at hourly intervals and drug content was analyzed by HPLC.

RESULTS

Results indicated that gabapentin extraction occurred at both anode and cathode with cathodal extractions showing higher value at all concentrations. Extraction rates at both the chambers were affected by time, the first hour extraction was notably higher than the later hours. Highest extraction rate was noted at pH 5. Surprisingly, anodal extraction was found to show greater positive correlation with current intensity compared to cathodal extraction.

CONCLUSIONS

As gabapentin carried no net charge at pH 7.4, orientation mediated electromigration was suggested to be the cause.

Nano-encapsulation of Dietary Phytoconstituent Capsaicin on Emulsome: Evaluation of Anticancer Activity Through the Measurement of Liver Oxidative Stress in Rats

BACKGROUND

Excessive reactive species derived from oxygen and nitrogen leads to oxidative damage to tissue and organs. Capsaicin (CAP), a pungent component found in red pepper can prevent oxidative stress.

OBJECTIVE

The aim of the present work was to evaluate the protective effects of CAP loaded nano-emulsomes (EML) against the oxidative stress of rat livers induced through sodium fluoride (NaF).

METHOD

EML was prepared by thin film hydration method that is development of thin lipid film followed by hydration and sonication. EML was characterized by Fourier transform infrared (FT-IR) spectroscopy and X-ray diffraction (XRD) techniques. EML was evaluated for drug entrapment, in vitro drug release, and in vivo study.

RESULTS

In vitro drug release study of optimized formulation showed that 50% of CAP was released within 50.21 min while 85% CAP was released in 227.4 min. Single oral dose of free CAP and CAP loaded EML were given to rats 2 hour after NaF administration. Membrane of hepatic cells was damaged by NaF and it was judged by the estimation of lipid peroxidation, reactive oxygen species (ROS), and catalase activity. The administration of CAP loaded EML 2 hr after NAF consumption showed significant decrease in ROS level compared to free CAP. EML containing CAP was more effective in comparison to free CAP in controlling the lipid peroxidation that is thiobarbituric acid substance augmentation in liver by the treatment of NaF. The administration of CAP loaded EML showed significant increase in catalase activity compared to free CAP administration.

CONCLUSION

The results clearly demonstrated that CAP loaded EML may be accepted as an effective therapeutic formulation in preventing oxidative damage.

Protein S Thr103Asn mutation associated with type II deficiency reproduced in vitro and functionally characterised

Protein S functions as a cofactor to activated protein C (APC) in the degradation of FVa and FVIIIa. In protein S, the thrombin sensitive region (TSR) and the first EGF-like domain are important for expression of the APC cofactor activity. A naturally occurring Thr103Asn (T103N) mutation in the first EGF-like domain of protein S has been associated with functional (type II) protein S deficiency. To elucidate the functional consequences of the T103N mutation, recombinant protein S mutant was expressed in mammalian cells and functionally characterised. The expression level of protein S T103N from transiently transfected COS 1 cells was equal to that of wild type protein S. The mutant protein S and wild type protein S were also expressed in 293 cells after stable transfection, and the recombinant proteins purified. In APTT- and PT-based coagulation assays, the mutant protein demonstrated approximately 50% lower anticoagulant activity as compared to wild type protein S. The functional defect was further investigated in FVa- and FVIIIa-degradation assays. The functional defect of mutant protein S was attenuated at increasing concentrations of APC. The results demonstrate the region around residue 103 of protein S to be of functional importance, possibly through a direct interaction with APC.

Deficient APC-cofactor activity of protein S Heerlen in degradation of factor Va Leiden: a possible mechanism of synergism between thrombophilic risk factors

In protein S Heerlen, an S-to-P (single-letter amino acid codes) mutation at position 460 results in the loss of glycosylation of N458. This polymorphism has been found to be slightly more prevalent in thrombophilic populations than in normal controls, particularly in cohorts of patients having free protein S deficiency. This suggests that carriers of the Heerlen allele may have an increased risk of thrombosis. We have now characterized the expression in cell cultures of recombinant protein S Heerlen and investigated the anticoagulant functions of the purified recombinant protein in vitro. Protein S Heerlen was synthesized and secreted equally well as wild-type protein S by transiently transfected COS-1 cells. The recombinant protein S Heerlen interacted with conformation-dependent monoclonal antibodies and bound C4b-binding protein to the same extent as wild-type protein S. Protein S Heerlen displayed reduced anticoagulant activity as cofactor to activated protein C (APC) in plasma-based assays, as well as in a factor VIIIa-degradation system. In contrast, protein S Heerlen functioned equally well as an APC cofactor in the degradation of factor Va as wild-type protein S did. However, when recombinant activated factor V Leiden (FVa:Q506) was used as APC substrate, protein S Heerlen was found to be a poor APC cofactor as compared with wild-type protein S. These in vitro results suggest a possible mechanism of synergy between protein S Heerlen and factor V Leiden that might be involved in the pathogenesis of thrombosis in individuals carrying both genetic traits. (Blood. 2000;96:523-531)

In vitro characterisation of two naturally occurring mutations in the thrombin-sensitive region of anticoagulant protein S

The molecular consequences of two naturally occurring mutations in the thrombin-sensitive region of protein S were investigated using a combination of recombinant protein expression, functional analysis and molecular modelling. Both mutations (R49H and R70S) have been found in thrombosis patients diagnosed as having type I protein S deficiency. Molecular modelling analysis suggested the R49H substitution not to disrupt the structure of thrombin-sensitive region, whereas the R70S substitution could affect the 3D structure mildly. To elucidate the molecular consequences of these substitutions experimentally, site directed mutagenesis of protein S cDNA and expression in mammalian cells created the two mutants. The secretion profiles and functional anticoagulant activities of the protein S mutants were characterised. Secretion of the R49H mutant was similar to that of wild type protein S, whereas the R70S mutant showed moderately decreased expression. Neither of the mutants showed any major functional defects as cofactors to activated protein C (APC) in an APTT-based assay or in degradation of factor Va. However, both mutants demonstrated decreased activity in a factor VIIIa degradation assay, which in addition to APC and protein S also included factor V as synergistic APC cofactor. In conclusion, the R49H substitution did not produce a quantitative abnormality in vitro, raising doubts as to whether it caused the type I deficiency. In contrast, the experimental data obtained for the R70S mutant agrees well with the observed type I deficiency. Our study illustrates that in vitro experimental characterisation together with computer-based structural analysis are useful tools in the analysis of the relationship between naturally occurring mutations and clinical phenotypes.

Topological studies of the amino terminal modules of vitamin K-dependent protein S using monoclonal antibody epitope mapping and molecular modeling

Protein S is an important anticoagulant protein acting as cofactor to activated protein C (APC) in the degradation of membrane-bound factors Va and VIIIa. Binding of protein S to the membrane depends on the Gla-domain, whereas sites for APC-interaction are located in the thrombin-sensitive region (TSR) and the first EGF domain. The aims of the present investigation were to localize the sites on protein S which are involved in APC-cofactor function and to elucidate possible orientations of the TSR in relation to the membrane. For these purposes, we determined the epitope for a calcium-dependent monoclonal antibody (HPS67) against the TSR, which inhibits APC cofactor activity even though it does not impede protein S binding to the membrane. HPS67 did not recognize wild-type mouse protein S but gained reactivity against a recombinant mouse protein in which G49 and R52 were mutated to R and Q (found in human protein S), respectively, suggesting these two residues to be part of a surface exposed epitope for HPS67. This information helped in the validation and refinement of the structural model for the Gla-TSR-EGF1-modules of protein S. The X-ray structure of a Fab-fragment mimicking HPS67 was docked onto the protein S model. The observation that HPS67 did not inhibit phospholipid binding of protein S has implications for the possible orientation of protein S on the membrane surface. In the proposed model for membrane-bound protein S, there is no contact between the TSR and the membrane. Rather, the TSR is free to interact with membrane-bound APC.

A new direct, fast and quantitative enzyme-linked ligandsorbent assay for measurement of free protein S antigen

A new method to determine the concentration of free protein S in plasma is described. It is an enzyme-linked ligandsorbent assay (ELSA) which utilises the protein S binding capacity of the natural ligand C4b-binding protein (C4BP) to capture the free protein S from plasma samples. The use of C4BP as ligand in the assay is possible due to the high affinity (Kd = 0.1 nM) of the interaction between protein S and C4BP and to a slow rate of complex dissociation. A monoclonal antibody (HPS 54) was conjugated with horseradish peroxidase and used as target antibody. This antibody recognises a Ca2+ dependent epitope in the first EGF-like domain of protein S and does not interfere with C4BP binding sites of protein S. Addition of calcium in the assay helped prevent dissociation of the C4BP-protein S-HPS 54 complex. Three different experiments demonstrated the assay to be specific for free protein S. First, near-identical dose response curves were obtained with protein S in plasma and with purified protein S. Second, addition of purified C4BP to normal plasma resulted in loss of free protein S. Third, protein S depleted plasma gave zero values and around 80% of purified protein S added to protein S depleted plasma, and approximately 70% of protein S added to protein S deficient plasma samples, was recovered with the assay. The assay is fast (involves only a single incubation step of 30 min), sensitive and the range of measurement is 3% to 200% of free protein S when plasma dilution 1:20 represents 100%. Intra- and inter-assay coefficients of variation at two levels were 2.3-4.3% and 5.1-7.4%, respectively. In a large protein S deficient family, the assay showed 100% sensitivity and specificity for the causative mutation. Moreover, free protein S levels in anticoagulated protein S deficient patients were completely separated from those obtained in non-anticoagulated controls. The new assay for free protein S is suitable for automation and it provides a useful means for routine clinical purposes to detect protein S deficiencies.

Spectrum of clinical and laboratory characteristics of HIV infection in northern India

To define the impact of HIV infection in India, the clinical and laboratory profile and the correlation of CD4 count to the likely opportunistic infection in a cohort of 134 HIV positive patients in Northern India was analysed. Majority of the patients, 72% and 67.8% (children and adults respectively) were asymptomatic, having been detected during routine screening and maintained that status for a median follow-up period of 3 years. Among the symptomatic patients, oropharyngeal candidiasis was the most common opportunistic infection followed closely by tuberculosis (both pulmonary and extra pulmonary) around 3.6-4.0 years from probable HIV infection with a median CD4 of 420-578 per cmm. Infection with Cryptococcosis, Cryptosporidiosis and cytomegalovirus occurred only after a significant fall in CD4 to < 100/cmm usually around 8-10 years from probable HIV infection. Pneumocystis carinii pneumonia was the terminal event among the 12 deaths at a mean CD4 count of 6/cmm. Non specific constitutional symptoms like fever, prolonged diarrhoea and significant weight loss were frequent. In general, the clinical profile of Indian patients with HIV bears much resemblance to African countries owing perhaps to the similar background of poverty, malnutrition and endemic infection.

Sociodemographic characteristics of HIV infection in northern India

134 patients testing positive for HIV antibody during the period 1986-1993 were included in the present study. An in-depth analysis of the subjects revealed that the adult males seemed to have the highest propensity for HIV infection in this part of the country. Marital status had no bearing on incidence and route of seropositivity. This was not so in females. Extramarital heterosexual contact was the mode of HIV acquisition in adults in contrast to blood transfusion in children. Clinically, most of these patients were still asymptomatic. At presentation, oral Candidiasis was common. Pneumocystis carinii pneumonia (PCP) was the leading cause of death.

Profile of HLA-B27-related 'unclassifiable' seronegative spondyloarthropathy in females and its comparison with the profile in males

Unclassifiable seronegative spondyloarthropathy (SSA) syndrome is primarily considered to be an affliction of males. In this report from northern India, 25 HLA-B27 antigen positive females with this condition are described and compared with 39 HLA-B27-positive males with the same disease. All these patients presented with typical features of spondyloarthropathy such as predominantly lower limb synovitis, enthesopathy and inflammatory spinal pain. The onset was insidious in 56% of the females and in 64% of the males. The mean age of onset as also the mean duration of symptoms prior to diagnosis were significantly higher in females (26.2 vs 19.4 yr and 8 vs 2 yr, respectively). A mono- or oligo-arthritis was seen in 52% of the females and in 53% of the males, but the average number of joints involved was less in females (4.8 vs 7.7). Lower limb joints alone were involved in 56% of the females and 49% of the males, with the knees, ankles and hips being most commonly involved, often asymmetrically. The mean degree of symmetry was significantly lower in females (62 vs 76). Ninety-two per cent of females and 74% of males had inflammatory spinal pain. Radiographic sacroiliitis was demonstrable in 56% females and 74% males. It is concluded that 'unclassifiable' SSA syndrome is not infrequent in females but is diagnosed late. Fewer joints tend to be involved and there is greater tendency towards asymmetry in females.