Knowledge, attitude, and practice of blood donation: A cross-sectional survey in Khulna city, Bangladesh

Background

There is evidence that the worldwide need for safe blood is not being met, particularly in poor nations like Bangladesh, where there is a scarcity of voluntary blood donors. This research intends to evaluate the public's knowledge, attitude, and practice of voluntary blood donation and the socio-demographic factors associated with blood donation in Khulna city, Bangladesh.

Materials and methods

720 interviews were taken using a structural questionnaire with Khulna city residents implementing the convenience sampling technique. After pre-processing and removing missing values, 697 records were left for further analysis. To investigate the association of sociodemographic factors such as age, gender, education, occupation, marital status, permanent address, and smoking status with knowledge, attitude, and practice of blood donation, the binary logistic regression model was used.

Results

According to this research, 478 (68.58%), 654 (93.83%), and 451 (64.71%) respondents were knowledgeable, had a favorable attitude, and practiced VBD, respectively. The study level higher secondary (AOR = 2.2; CI: 1.16-4.18), honors or degree (AOR = 2.37; CI: 1.3-4.3), and masters or above (AOR = 3.27; CI: 1.69-6.35) were associated with the knowledge. The favorable attitude was connected with being male (AOR = 2.24; CI: 1.23-4.06), learning about VBD through online social media (AOR = 2.61; CI: 1.13-6.05), and having knowledge of VBD (AOR = 3.05; CI: 1.82-5.12). Age between 26 and 35 years (AOR = 2.83; CI: 1.43-5.57) and older than 45 years (AOR = 3.74; CI: 1.34-10.4), being a man (AOR = 3.6; CI: 2.25-5.78), being a smoker (AOR = 1.87; CI: 1.17-2.98), knowing about VBD (AOR = 2.31; CI: 1.55-3.42), and having a positive attitude (AOR = 3.78; CI: 2.11-6.77) were significant factors for practicing blood donation.

Conclusion

This research demonstrates poor blood donation practices and limited knowledge of blood donation among Khulna city residents. The awareness of the residents should be prolonged for voluntary blood donation by the health bureau, the government, and non-governmental organizations.

Association of Serum Vitamin D (25OHD) Level with Acute Exacerbation of Chronic Obstructive Pulmonary Disease

Acute exacerbations of COPD is characterized by a change in the patients baseline dyspnoea, cough and/or sputum that is beyond normal day to day differences and guides to a change in standard medications in a patient with COPD. Vitamin D influences the innate & adaptive immune system, and exerts pleiotropic antimicrobial and anti-inflammatory responses. Vitamin D deficiency is frequent among COPD patients but its contributory role in disease exacerbations is widely debated. This study was aimed to assess relationship between reduced serum vitamin D (25-OHD) level with COPD severity and acute exacerbation. This observational cross-sectional study was carried out in the department of Respiratory Medicine, NIDCH, Mohakhali, Dhaka, Bangladesh from October 2016 to September 2017. Consecutive 80 hospital admitted patients with acute exacerbation of chronic obstructive pulmonary disease diagnosed on the basis of clinical history & pulmonary function tests and 78 age & sex matched controls were investigated for serum vitamin D (25-OHD) level. Among the COPD patients, 37% had Vitamin D deficiency (<20ng/ml) and 28.75% had Vitamin D insufficiency (20-29ng/ml). Mean vitamin D (25-OHD) level of COPD patients (25.82±10.62ngm/ml) was found to be significantly lower than healthy controls (32.57±11.32ngm/ml). Vitamin D deficiency was found, by Pearson correlation test, to be significantly associated with severity of COPD. Multivariate analysis showed that age (in years), FEV1 (percent predicted), frequent exacerbators (≥2 in the last year), and smoking (>40 pack year) were significantly associated with Vitamin D deficiency. Acute exacerbation of chronic obstructive pulmonary disease patients was found to have vitamin D deficiency and vitamin D deficiency was significantly associated with severity of COPD. Vitamin D deficiency was also associated with frequent disease exacerbation.

Heat treatment effects on electrochemical corrosion parameters of high-Pd alloys

This research determined the effect oxidation, as that occurs during porcelain firing, has upon the corrosion parameters of Pd-based ceramic alloys and how it may relate to Pd allergy. The 20 h open circuit potential (OCP), 20 h corrosion rate (Icorr), and anodic polarization (E-i) curves of 11 commercial Pd alloys were measured in a phosphate buffered saline solution. The alloys were divided into the following four groups based upon composition: PdGa(Ag), PdCu, PdAg, and AuPd and tested in both as-cast and oxidized conditions. In both the as-cast and oxidized conditions, the OCP of Ag-containing Pd alloys is significantly lower than non Ag-containing high-Pd alloys. The OCP of all alloys increased after oxidation. With regard to corrosion rate, the Ag-containing alloys showed a decrease in Icorr with oxidation. In contrast, three of the four non Ag-containing high-Pd (>or=74 wt%) alloys exhibited a higher Icorr. A comparison of the anodic polarization curves showed only the alloys containing larger amounts (>or=16 wt%) of Ag displayed a notable difference between as-cast and oxidized states. Oxidation as required during porcelain-fused-to-metal device preparation alters the electrochemical characteristics of the alloys studied. This alteration may be of importance with regard to their potential for Pd allergy.

Characterization of adsorbed silane on fillers used in dental composite restoratives and its effect on composite properties

The purpose was to study the effect of silane treatment of fillers on viscosity, flexural strength, and hydrolytic degradation of experimental dental composite resins fabricated with these fillers. The fillers consisted of a mixture of barium glass and amorphous silica. The resin was mainly based on ethoxylated bisphenol A dimethacrylate and polycarbonate dimethacrylate. The adsorption of silane on the filler surface was characterized by FTIR. There was significant correlation between the adsorbed silane on filler surface and the silane concentration in silane/methanol solution used for filler treatment. The silane concentration varied from 0.75 to 14% by weight. An increase in silane concentration led to a decrease in viscosities of the corresponding composite resins. The flexural strengths of composites with silanated fillers were greater than that of composites with unsilanated fillers: however, no significant difference was found between the flexural strengths of various silanated groups. The resistance to hydrolytic degradation of different composites increased when the fillers were treated with silane and was the highest at 1.1% silane.

Physicochemical basis of the biologic properties of mineral trioxide aggregate

This study characterized the interactions of mineral trioxide aggregate with a synthetic tissue fluid composed of a neutral phosphate buffer saline solution and root canal dentin in extracted human teeth using inductively coupled plasma-atomic emission spectroscopy, scanning electron microscopy, energy dispersive X-ray analysis, and X-ray diffraction. Mineral trioxide aggregate exposed to synthetic tissue fluid at 37 degrees C released its metallic constituents and produced precipitates with a composition and structure similar to that of hydroxyapatite [Ca10(PO4)6(OH)2-HA]. Endodontically prepared teeth filled with mineral trioxide aggregate and stored in synthetic tissue fluid at 37 degrees C for 2 months produced at the dentin wall an adherent interfacial layer that resembled hydroxyapatite in composition. The authors conclude that Ca, the dominant ion released from mineral trioxide aggregate, reacts with phosphates in synthetic tissue fluid, yielding hydroxyapatite. The dentin-mineral trioxide aggregate interfacial layer results from a similar reaction. The sealing ability, biocompatibility, and dentinogenic activity of mineral trioxide aggregate is attributed to these physicochemical reactions.

A study of hepatobiliary function in chronic heroin smokers

The controversy over the relationship between heroin addiction and hepatocellular dysfunction was examined by assay of serum activities of aspartate and alanine aminotransferases, total protein, albumin and globulin in 48 chronic heroin smokers and 33 controls. Biliary secretion in the addicts was compared to controls by assay of serum bilirubin and its conjugated and unconjugated fractions. Serum aminotransferases, total protein, albumin and globulin did not differ significantly between the addict and the control groups (p < 0.05), whereas total bilirubin and its conjugated fraction were significantly higher in the addicts (p < 0.02). The results indicate that chronic abuse of heroin by smoking affects biliary secretion but exercises little influence over hepatocellular function.

Oviductal sperm storage structure and their changes during the seasonal (dissociated) reproductive cycle in the soft-shelled turtle Lissemys punctata punctata

The oviduct of the Indian fresh water soft-shelled turtle Lissemys punctata punctata was examined throughout the year under light and scanning electron microscopes to determine the location, histomorphological characteristics, and function of sperm storage structure, as well as their changes at different phases of the seasonal reproductive cycle. Sperm storage structures in the form of tubules were observed in the wall of isthmus throughout the year. These tubules developed either by folding or fusion of the oviductal mucosal folds and were lined by both ciliated and nonciliated epithelial cells. The height and secretory activities of the epithelia were markedly high during the breeding phase (August to September) but low in the nonbreeding phase (October to June). A few short tubules lined by cuboidal epithelium appear in the wall of infundibulum only during the breeding phase. Following mating (May), inseminated sperm were stored within the tubules of isthmus up to the pre-ovulatory stage (August). Thereafter, sperm associated with PAS-positive materials secreted from the epithelium (referred to as a carrier matrix) moved forward to the infundibulum and were stored within the storage tubules of the infundibulum for a short time. Subsequently, sperm evacuated the storage tubules and entered the oviductal lumen to fertilize the subsequently ovulated eggs during or prior to ovulation. The isthmus-tubules become shorter and narrower in the regressive phase (October to November) and remained so until the early preparatory phase (April). Sperm release might have been stimulated by estrogen secreted from the ovarian follicles of pre-ovulatory turtles. Stored sperm not utilized for fertilization remained viable not less than six months in the present turtle species.

Internal corrosion in dental composite wear

The internal corrosion of dental resin composites is associated with water-sorption and leads to (1) interfacial debonding, (2) filler dissolution, (3) matrix cracking, and (4) subsurface damage. The last factor creates a condition for "corrosive-wear" in which the damaged layer is worn with ease exposing a new surface and perpetuating the cycle of corrosion and wear. Central to the simulation of in vivo corrosive-wear is the recreation of the subsurface damage layer. To produce this layer in water, artificial saliva, and in media of low pH is time-consuming, because the degradation process in these environments is extremely slow. In laboratory wear tests using aqueous environments, the contact time of resin composites with water is too short to cause significant internal degradation. Thus, data obtained from such tests represent abrasive and not corrosive-wear, and do not correlate well with in vivo wear data. In considering this limitation of the above media for accelerated wear tests, an alkaline medium has been used in this study to simulate corrosive-wear of eleven commercial composites. The procedure consists of exposing each material to 0.1 N NaOH at 60 degrees C for 2 weeks followed by abrasion in a tooth brushing machine. The medium choice is based on the rationale that in vivo degradation arises from reaction with the OH(-), and this reaction can be enhanced by raising the pH and the temperature of the medium. The warm NaOH solution satisfies both these conditions. Parameters examined to evaluate the resistance of each composite to corrosion and wear were (1) mass loss, (2) Si-loss, (3) degradation depth, and (4) wear depth, respectively. A highly significant correlation has been observed among various corrosion and wear parameters. SEM examination indicated degradation to be associated with interfacial separation, filler dissolution, matrix cracking, and subsurface damage. These features are characteristics of in vivo worn composite restorations. Time is of utmost importance in laboratory evaluation of restorative materials. The ability of NaOH to meet this expediency and to mimic the in vivo degradation process makes it a useful medium for corrosive-wear studies of dental composites.

Dealloying and electroformation in high-Pd dental alloys

OBJECTIVE

The corrosion of high-Pd dental alloys, depending on their composition, is postulated to be associated with dealloying and electroformation. The aim of this study was to obtain additional information to support these postulations.

METHODS

The corrosion characteristics of two commercial high-Pd alloys, Naturelle (79Pd-10Cu-2Au-9Ga wt%) and Rx 91 (54Pd-37Ag-9Sn), and their elemental components were evaluated in a phosphated buffer saline (PBS) solution. Indium, a common element in high-Pd alloys, was also included. The corrosion characteristics measured for each material were the 24 h open circuit potential (OCP) and the potentiodynamic anodic polarization curve. Additionally, the surface composition of the two alloys, before and after immersion corrosion in PBS for 2 months, was analyzed by X-ray photo electron spectroscopy (XPS).

RESULTS

Of the pure metals, Ga had the most electroactive OCP followed in order by In, Sn, Cu, Ag, Au, and Pd. The anodic polarization data showed all base metals to be unstable in PBS. The electroformation of AgCl was evidenced in the polarization curve of pure Ag. Both electrochemical characteristics of the PdCu-based alloy were very similar to that of pure Pd. The PdAg-based alloy displayed corrosion behavior resembling that of Ag. XPS data showed that the corrosion of the PdCu-based alloy was associated with a decrease in surface content of Cu and Ga but an increase in Pd and Au. The PdAg-based alloy surface during corrosion showed a decrease in Sn, an increase in Ag, and an unaltered Pd content. The behavior of the PdCu-based alloy is attributed to the operation of a galvanic interaction that causes dissolution of base metals and surface enrichment with primarily Pd. Dealloying, Ag-enrichment, and AgCl formation are thought to have contributed to the observed behavior of the PdAg-based alloy. These mechanisms are consistent with data from published ion release studies.

SIGNIFICANCE

The allergenic potential of any Pd alloy is dependent on its propensity to develop a Pd-rich surface and thus release Pd+2 ions. The present study, though limited, has shown that electrochemical characteristics, namely OCP and polarization curves, can be used to identify such alloys. Further studies are warranted to evaluate the widespread applicability of these characteristics in distinguishing between Pd alloys that are biologically safe and those that are not.

Electrochemical characteristics of high-Pd alloys in relation to Pd-allergy

OBJECTIVE

The aim of this study was to determine whether the Pd-Cu-based dental ceramic alloys possess any electrochemical characteristics distinguishable from that of other Pd-containing alloys. Of all Pd-containing alloys, this particular alloy group has been linked to frequent incidence of allergy and hypersensitivity reactions. Electrochemical corrosion may instigate these reactions.

METHODS

Four groups of alloys, Pd-Cu, Pd-Ga-(with and without Ag), Pd-Ag, and Au-Pd, were evaluated by traditional corrosion measurement techniques in a phosphated buffer saline solution at 20 degrees C. The electrochemical characteristics measured were: (1) 20 h open circuit potential (OCP); (2) 20 h corrosion rate (Icorr); and (3) anodic polarization (E-i) curves.

RESULTS

The OCP values (232 +/- 25 mV) of the Ag-free Pd-Ga and Pd-Cu-based alloys were higher than and distinctly different from that (144 +/- 52 mV) of the Ag-containing alloys. The Icorr values of different alloys, despite varied compositions, were indistinguishable from one another. The E-i curves of all alloys were essentially similar, with the Ag-containing (> 5 wt%) alloys showing a subtle difference in their anodic slope within 100 mV above their corrosion potentials.

SIGNIFICANCE

The OCP values of Pd-Cu alloys and the Ag-free Pd-Ga alloy are comparable to that reported for pure Pd (239 +/- 21 mV), which indicates that during corrosion these alloys undergo dealloying and consequent Pd-enrichment on their surface. Such a condition is conducive to the release of allergenic Pd++ ions and offers a plausible explanation for the frequent incidence of hypersensitivity reactions associated with the Pd-Cu alloys. The OCP values in other alloys are attributed to dealloying followed by surface enrichment with Ag and/or Au and the possible formation of an insoluble AgCl surface film on the respective alloy surfaces. These events have the potential to suppress or prevent Pd++ ion release. Alloys showing these characteristics have seldom been linked to allergic reactions.

Degree of conversion in denture base materials for varied polymerization techniques

New processing techniques for denture base acrylic resins have been introduced which have not comparatively quantified the residual monomer content. While proper processing keeps the residual monomer in a tolerable range for most patients, tissue irritation and reaction due to potentially higher residual monomer in these alternative techniques could be a clinical concern. Decreased degree of conversion may influence physical properties as well as biocompatibility. This investigation evaluated the residual monomer content of acrylic resins cured by three different polymerization modes. Materials (polymerization system) evaluated were: Lucitone 199 (conventional process), Accelar 20 (rapid boil-out), and Acron MC (microwave). Fourier transform infrared spectrometry (FTIR) was employed to determine the degree of conversion. All curing methods produced similar results (Lucitone 199 = 92.7% (0.21), Acron MC = 92.6% (0.57), Accelar 20 = 90.9% (0-73). Conversion for Accelar 20 (rapid boil-out technique), though statistically different (P < 0.05, ANOVA) from the other two materials and polymerization techniques, was only slightly less. It is unlikely that the rapid boil-out technique would induce more adverse tissue responses than the other techniques included in this study.

Long-term corrosion of a Ga-containing restorative material

OBJECTIVE

The aim was to simulate and characterize the long-term corrosion of a Ga-containing alloy (Galloy, SDI).

METHODS

To induce corrosion, cylindrical specimens, 8 x 4 mm, of the material were subject to potentiostatic polarization at -0.1 V (SCE) in a phosphated buffered saline (PBS) solution at 20 degrees C for d. The current-time transients during polarization were recorded and the corresponding anodic charge, Q, was calculated. Parallel potentiostatic corrosion tests in a Cl-free PBS solution were also conducted to demonstrate the significance of the Cl- ion in corrosion. In addition, potentiodynamic anodic polarization tests were performed to characterize the overall corrosion behavior of the alloy in both electrolytes. The external and internal corroded layers, formed during potentiostatic corrosion in PBS, were measured by optical microscopy. SEM and EDXA were used to characterize the morphology and composition of the potentiostatically polarized surfaces.

RESULTS

Galloy was passive in Cl-free PBS. The Cl- ion in PBS destroyed passivity and initiated a "dissolution-precipitation" type reaction during potentiostatic corrosion. The latter led to circumferential internal corrosion and growth of a layer of external corrosion products. The thickness of the internal and external corrosion layers was 0.77 +/- 0.07 and 0.86 +/- 0.37 mm, respectively. The Q value (89.3 +/- 13.7 C/cm2) in PBS was about two orders of magnitude higher than that (0.66 +/- 0.24 C/cm2) in Cl-free PBS. The corrosion products contained Sn, Ga, In, Cu, O and Cl.

SIGNIFICANCE

Massive internal and external corrosion in a Cl-containing medium as in saliva, accumulation of corrosion products at the cavity wall, and the consequent stress build-up contribute to post-operative pain, tooth straining, marginal breakdown and fractured teeth reported with the clinical use of Galloy.

Effect of Pd or Au addition on age-hardening in AgMn-based alloys

OBJECTIVE

The objective of this research was to characterize the age-hardening behavior of AgMn alloys modified with Au or Pd. These alloys are being studied as possible alternatives to Type III dental alloys.

METHODS

The age-hardening reactions in Ag-37 at % Mn alloys with 5 at% Au or Pd were investigated by optical microscopy, electrical resistivity, X-ray diffraction and hardness tests.

RESULTS

Optical microscopy showed no grain boundary precipitates formed after overaging. The maximum hardness reached by aging in all alloys is about 260 (Hv) and identical to that of traditional AgPdCu dental alloys. The precipitation reactions were retarded with the addition of 5 at% Au or Pd. X-ray diffraction studies suggest a fine precipitate, alpha-Mn, is dispersed within the grain interior. The activation energy for the precipitation reaction is 114 kJ/mol for the AgMn and AgMnAu alloys. This value is about one-half of the activation energy for volume diffusion of manganese in AgMn alloys.

SIGNIFICANCE

The age-hardenable AgMn-based alloys modified with Au or Pd can achieve hardness values comparable to those of traditional AgPdCu alloys. Provided the in vivo corrosion resistance of these alloys is adequate, they show promise as a Cu-free alternative material for cast restorations.

Metal-matrix interface in reinforced glass ionomers

OBJECTIVE

In reinforced materials, interfacial bonding is critical for efficient transfer of stress from the matrix to the reinforcement. The goal of this study was to characterize the physical and chemical nature of this interface in three metal-reinforced glass ionomers. Two of them were commercial, ESPE-Ketac Silver (KS) and GC-Miracle Mix (MM), and the third, EX, was experimental.

METHODS

The techniques of scanning electron microscopy (SEM) and infrared spectroscopy (IR) were used to accomplish the stated goal. SEM analysis utilized polished sections of set cylindrical specimens of each material prepared from their respective powder and liquid components. The glass and the liquid in EX were the same as in MM. The reinforcing agent in EX, 50% by weight, was an Ag-base spherical alloy similar in composition to that in MM. For EX, the alloy was oxidized to promote its bonding to the matrix. The specimens for IR study were prepared as follows. The metallic powders of each material were mixed with the corresponding liquid in excess, stored at 37 degrees C for 1 h, washed with warm water (60 degrees C), filtered and dried. The untreated metallic powders served as controls for IR analysis.

RESULTS

SEM revealed a distinct halo shaped internal reaction layer surrounding each alloy particle in EX. A similar layer was not seen in MM and KS. The alloy-matrix interface was continuous and gap-free in EX. In contrast, gaps separating matrix from respective reinforcements were conspicuous features in MM and KS. The IR spectrum of the liquid treated EX alloy powder showed absorbency bands characteristic of unreacted carboxyl groups and carboxylate salts. These bands were absent in the IR spectra of all other powders--treated and untreated.

SIGNIFICANCE

The absence of interfacial bonding in MM and KS demonstrated in this study provides a reason why these two materials, in spite of metal addition, have not proved to be any stronger or more durable than their metal-free counterparts. A means of creating interfacial bonding presented here could be useful in the design of improved reinforced glass ionomer materials.

Corrosion of three experimental AgMn-based casting alloys

OBJECTIVE

Alloys based on AgMn are being evaluated in our laboratory for their possible use as an alternative to Type III dental alloys. They respond to heat treatment and develop hardness values comparable to that of Type III alloys. The objective of the present research was to evaluate their corrosion characteristics.

METHODS

The three experimental silver-based alloys of the following composition (at%): (1) 63Ag37Mn, (2) 60Ag35Mn5Au and (3) 60Ag35Mn5Pd, were tested in their peak-hardened condition. Following 0.5 h open-circuit potential (OCP) measurement of each alloy in a phosphated buffer saline (PBS) solution, its current-potential profile was generated by the cyclic voltammetry technique within -1300 and +200 mV (SCE) at 1 mV s-1. In a separate test, the OCP of each alloy was monitored over a 24 h period.

RESULTS

Each of the three alloys showed ennoblement of their OCP over time due to dissolution of Mn and consequent enrichment with Ag (Au or Pd). At 24 h, the two ternary alloys were the most noble followed by the binary alloy. With respect to the cyclic voltammetry, oxidation of Ag was noted during forward scans at around 0 mV. The reverse scan was associated with a reduction current peak between -37 and -128 mV. The values for this peak, which is a measure of Ag oxidation, were highest (11.5 mA cm-2) for the binary alloy followed by the Au- (2.9 mA cm-2) and Pd-containing (0.04 mA cm-2) alloys, respectively. This indicates that, for equivalent concentration, Pd is more effective in reducing Ag corrosion than Au.

SIGNIFICANCE

Alloys based on the AgMn system are as hard as Type III dental alloys. Information on the corrosion characteristics of the AgMn-based alloys presented here is of value in further development of this alloy system.

Haematological changes in buprenorphine-treated mice

Studies were carried out in adult male Swiss mice to determine whether different haematological parameters like total counts of red and white blood cells, differential counts of white blood cells, haematocrit value and blood haemoglobin level were affected by the synthetic opioid analgesic, buprenorphine, which has currently been known to be abused in several countries by the heroin addicts as a cheap substitute for heroin. The mice were daily given an intraperitoneal injection of buprenorphine (300 micrograms/kg) for 60 consecutive days. A severe leucopenia accompanied by decreases in lymphocyte and monocyte counts, an increase in neutrophil count, a decrease in haematocrit value, a rossette-like adherence of red blood cells to a few neutrophils and platelet satellitism were observed at the advanced stages of treatment. The abnormalities, however, reverted to normal within 45 days following withdrawal of the drug. The necessity of periodic monitoring of the blood picture in human abusers of the drug is suggested.

Melatonin action on thyroid activity in the soft-shelled turtle, Lissemys punctata punctata

Adult female turtles (Lissemys punctata punctata) were treated with pineal indoleamine melatonin (100 micrograms/100 g) or the antithyroid agent, methylthiouracil (100 micrograms/100 g) or melatonin together with methylthiouracil (100 micrograms of each drug/100 g) for 12 days. Melatonin alone inhibited thyroid activity as evidenced by reduction in the gland weight, follicular epithelial cell height, thyroid peroxidase, and plasma thyroxine levels. Methylthiouracil caused hyperplasia of the gland, although it inhibited thyroid activity and reduced thyroid peroxidase and plasma thyroxine levels. Melatonin together with methylthiouracil produced changes similar to those obtained with melatonin alone. The results indicate that melatonin probably exerts inhibitory effects influences on both thyrotropin release from the pituitary and the activity of the thyroid itself in turtles.

Cytotoxicity of anthrax lethal factor microinjected into macrophage cells through Sendai virus envelopes

Lethal toxin (LT) secreted by Bacillus anthracis consists of two proteins, protective antigen (PA) and lethal factor (LF). LT causes lysis of macrophages and derived cell lines at low concentrations. PA binds to the cell surface receptors and mediates translocation of LF into cytosol of mammalian cells. Internalization of LF into cytosol by osmotic lysis of pinocytic vesicles requires high concentration of LF for cell lysis. To examine the possible cell lysis by LF at low concentration, we introduced LF directly into cytosol of J774A.1 cells through reconstituted Sendai virus envelopes. The introduction of LF lysed J774A.1 cells in a concentration dependent manner. Internalization of PA alone through virosome had no toxic effect on J774A.1 cells. In the process of cytotoxicity LF was not cleaved by cellular proteases. Unlike many protein toxins, golgi was not involved in the expression of lethal toxin activity. These results indicate that LF is the toxic component of anthrax lethal toxin and prior proteolytic processing or trafficking through golgi is not required for its activity.

Influence of dentinal adhesives and a prefabricated post on fracture resistance of silver amalgam cores

PURPOSE

Failures of silver amalgam cores for endodontically treated teeth have been attributed to the use of posts. The use of adhesive agents has been reported to improve the strength of silver amalgam restorations. The purpose of this study was to test the effects of two adhesive agents on the fracture resistance of silver amalgam cores with and without a post.

MATERIAL AND METHODS

Sixty mandibular molars were restored with the use of silver amalgam, with or without one of the adhesive agents and/or a tapered prefabricated post. A universal testing machine, with a constant load rate of 0.5 mm/minute, was used to determine the force in kilograms at failure.

RESULTS

The use of either adhesive agent with silver amalgam significantly increased the force at failure, and neither adhesive agent was significantly better than the other. Silver amalgam with a post and without an adhesive agent had the least resistance to fracture.

CONCLUSIONS

The results indicated that endodontically treated mandibular molars restored with silver amalgam are more resistant to fracture when an adhesive agent is used.

Photothermal effects on ovarian growth and function in the soft-shelled turtle Lissemys punctata punctata

Investigations were carried out to find out the role of higher and lower ambient temperatures together with short and long photoperiods on ovarian growth and secretion of steroids (estradiol-17 beta and progesterone) in the adult female soft-shelled turtle Lissemys punctata punctata during the preparatory, recrudescent, and quiescent phases of its seasonal reproductive cycle. In each phase, females were treated with 3 degrees C higher and 3 degrees C lower than the mean highest and lowest ambient temperatures in association with short and long photoperiods for short-term (4 week) and long-term (8 weeks or more) durations. Short-term high-temperature treatment significantly stimulated ovarian growth and secretion of estradiol-17 beta during the preparatory phase. Eight-week treatment failed to exercise further stimulation over 4-week treatment, whereas 10-week treatment caused regressive changes of ovary (atresia of follicles). Both short- and long-term high-temperature treatments caused degeneration of ovarian follicles during the recrudescent phase. Low-temperature treatment slowed down ovarian growth and secretion in both the preparatory and recrudescent phases. In the quiescent phase, low- as well as high-temperature treatments exercised little influence over the refractory ovarian growth and secretion. Photoperiod appeared to have no effect on female reproduction in any phase. Thus, high temperature is suggested to have a triggering role on ovarian growth and secretion of estrogen at the early preparatory phase, but once the ovarian function sets in, high temperature seems to have a regressive rather than stimulatory effect on ovarian growth and function.

Polyamines exert regulatory control on mycobacterial transcription: a study using RNA polymerase from Mycobacterium phlei

We have used purified RNA polymerase from Mycobacterium phlei to study the role of polyamines in mycobacterial transcription. Both initiation and elongation phases of the process were affected biphasically by polyamines. Interaction of polyamines with DNA template plays an important role in transcription modulation. Our studies emphasize that polyamines can exert a regulatory control on mycobacterial transcription.

In vitro torque-deformation characteristics of orthodontic polycarbonate brackets

The purpose of this study was to investigate the torque-deformation characteristics of the following four types of polycarbonate brackets: (1) pure polycarbonate, PPC (anterior Miura, RMO, Denver, Colo.), (2) ceramic reinforced polycarbonate, CRPC (Silkon bracket, American, Sheboygan, Wis.), (3) metal slot reinforced polycarbonate, MRPC (Plastic bracket, Tella Tech, Miami, Fla.), and (4) metal slot and ceramic reinforced polycarbonate, MCRPC (Spirit, Ormco, Glendora, Calif.). A stainless steel bracket, (Mini Diamond, Ormco, Glendora, Calif.), was used as a control. Ten brackets of each type were tested. Each bracket was bonded to a porcelain tooth and engaged in a torquemeter. The tooth-bracket assembly was made stationary by embedding it in die stone. Torsion was applied to the bracket at 4 degrees per minute and the resultant torque (grams.centimeters) and deformation (degree) were measured. For optimum labiolingual tooth movement for a maxillary incisor at 175 grams . centimeters, the amount of angular deflection necessary for the different polycarbonate brackets was the following: (a) 15 degrees for MRPC, (b) 17 degrees for MRPC, (c) 24 degrees for CRPC, and (d) > 30 degrees for PPC. The amount of deformation at this deflection was the least for MRCP followed by MCRPC, CRCP, and PPC. When compared with the stainless steel bracket, all polycarbonate brackets showed significantly (p < 0.0001) higher deformation and lower torque. Within the polycarbonate group, there was a significant difference (p < 0.0001) between each bracket for both measurements. The MRPC produced the highest torque and lowest deformation values followed by the MCRPC, CRCP, and PPC. It appears that only the metal slot reinforced brackets are clinically capable of torquing teeth sufficiently.

Microstructural characterization of a foil crown system

In this study, the microstructural nature of the Renaissance crown system has been characterized in an effort to understand its reported properties and performance. Intergranular cavitation was characteristic of the foil surface. The brazed area joining various pleats was porous and exhibited an equiaxial grain structure. Particles of the interfacial alloy sintered with each other and bonded to the foil. Flow of porcelain into intergranular grooves of the foil and within the porous interfacial alloy network was observed. Tags that formed as a result contributed to the micromechanical retention of porcelain on the foil. No evidence of foil-porcelain chemical bonding was found, nor was there any indication of substantial interlayer diffusion.

An in vitro study of the effect endodontic access preparation and amalgam restoration have upon incisor crown retention

Endodontic access preparation leads to a significant reduction in crown retention. This study sought to determine whether this retention can be regained after access. Eighteen extracted human maxillary incisors had PFM crowns fabricated. Crowns were cemented, retention measured, recemented, access preparations cut, and retention once again measured. Then, crowns were recemented and accesses restored with dental amalgam and new retention measured. This format allowed each crown to be used as a control of itself. For crowns cemented with zinc phosphate cement and restored with amalgam, a 126% increase over original retention was measured. For crowns cemented with polycarboxylate cement and restored with amalgam, a 237% increase over original retention was measured. For crowns cemented with polycarboxylate cement and restored with amalgam, a 237% increase over original retention was measured. These results suggest that recementing crowns secondary to endodontic access and restoring the access with amalgam regains and even surpasses the original retention.

Fluoride release from glass-ionomer cements in de-ionized water and artificial saliva

Most of the data reported on the release of fluorides from glass-ionomer cements are based upon measurements made in de-ionized water. De-ionized water does not represent the complex chemistry of the oral environment. In this study, an artificial saliva solution was used, and the data on the fluoride ions released into it from four glass-ionomer cements were compared with those obtained in de-ionized water. The glass-ionomer cements used were: Ketac-Fil (ESPE), Ketac-Silver (ESPE), Fuji-II (GC), and Miracle Mix (GC). Ten disc samples (2 cm x 0.1 cm) of each cement were prepared. Each was individually suspended in either de-ionized water or artificial saliva (five samples in each medium) and stored for 24 h at 37 degrees C, then transferred to fresh media for a total of 60 days. Collected media were buffered with TISAB, and fluoride was measured by a specific electrode. Artificial saliva was prepared according to Fusayama et al. (1963). The data obtained showed that: (1) glass-ionomer cements released more fluoride in de-ionized water than in artificial saliva; (2) Ketac-Fil released 20% more fluoride in saliva than did Fuji-II, the latter releasing 49% more fluoride than Ketac-Fil in de-ionized water; and (3) conventional glass ionomers released more fluoride than did meta-reinforced ones in both media.

Microscopic examination of embrittled pin-retained base metal casting

Differential thermal analysis, optical microscopy, scanning electron microscopy, and energy dispersive radiographic analysis were used to examine and analyze two failed platinum-palladium-gold pin-retained nickel-chromium castings. The microstructure and chemical composition of the pin-casting interface were different from those of the pin and the cast alloy. Porosity was also observed at the interface. The observations with these samples suggest that the pin melted during casting. The embrittlement and failure of plantium-palladium-gold pins cast with nickel-chromium alloy have been attributed to this melting phenomenon. Further study is necessary to determine whether these observations are valid for a large number of samples.

An in vitro study of the effect endodontic access preparation has upon the retention of porcelain fused to metal crowns of maxillary central incisors

Endodontic therapy often requires cutting access preparations through existing restorations. The purpose of this study was to determine whether endodontic access preparation affected the retention of porcelain fused to metal crowns of maxillary central incisors. Retentive forces required to displace porcelain fused to metal crowns of maxillary central incisors were measured using an Instron constant displacement rate testing machine. Using a paired t test analysis, a significant difference was found between crown retention before and after endodontic access preparation.

Mechanism of improved corrosion resistance of Zn-containing dental amalgams

The aim of this study was to determine the mechanism of improved corrosion resistance of Zn-containing dental amalgams. Two Zn-containing conventional amalgams, their Zn-free counterparts, and three experimental amalgams (SnHg, ZnHg, and SnZnHg) were evaluated by the potentiodynamic polarization technique in 1% NaCl solution. The main difference between the two types of amalgams was found in their respective breakdown potentials at which passivity was destroyed. The breakdown potential of Zn-containing amalgams was about 200 mV more positive than that of the Zn-free amalgams. The improved stability of the Zn-containing amalgams has been attributed to the formation of a previously reported Zn stannate passive film which, according to the polarization data, is more resistant to the aggressive chloride ion than tin hydroxide that forms on Zn-free amalgams. The formation of Zn stannate was not found to affect the oxygen reduction reaction, the major cathodic reaction involved in the corrosion of dental amalgams.

The microstructural basis of creep of gamma 1 in dental amalgam

A previous study has shown that the addition of small amounts of tin to gamma 1 leads to the formation of a SnHg intergranular precipitate. The purpose of this study was to determine the effect of this precipitate on the creep of gamma 1. Two groups of samples were investigated. Group I included a series of gamma 1 samples with 0, 1, 2, and 3 wt% Sn fabricated by a sintering technique at 55 degrees C and 125 mN/m2 for 72 h. Group II contained the same samples as in Group I that were further annealed at 60 degrees C for 2000 h. Annealing was carried out to allow gamma 1 grain growth and equilibrium distribution of Sn at grain boundaries. Creep tests were conducted according to the American Dental Association Specification 1. The microstructures of all samples were characterized by scanning electron microscopy. The creep of gamma 1 was found to be controlled by the intergranular precipitate when the Sn concentration was above 1%. For a specific concentration of Sn, i.e. the intergranular precipitate, creep was dependent on the distribution of Sn and not on the gamma 1 grain size. The more nearly continuous precipitates found in annealed samples favoured higher creep.

Solid solubility of tin in silver-mercury gamma 1 in dental amalgams

The solid solubility of Sn in gamma 1 has been studied by examining a series of gamma 1 samples containing 0.25-2.0 wt% Sn by scanning electron microscopy and energy-dispersive X-ray analysis. It has been observed that the addition of Sn to gamma 1 leads to the formation of mainly an intergranular Sn-Hg compound. On the basis of this observation it has been concluded that the solubility of Sn in gamma 1 is virtually nil.

Heat treatment, microstructure and corrosion of a low-gold casting alloy

The aim of this study was to understand the relationship between heat treatment, microstructure and corrosion of a low-gold casting alloy. Potentiostatic and potentiodynamic polarization techniques were used to evaluate the chloride corrosion resistance of the alloy in the following conditions: (A) as cast, (B) bench cooled, (C) homogenized, (D) homogenized and aged for 2 h, and (E) homogenized and aged for 4 h. The microstructure of each sample, before and after corrosion, was examined by optical and/or scanning electron microscopy. In general, heterogeneous structures containing dendritic segregations and precipitates were found to be more prone to corrosion than the single phase solid solution structure produced by homogenization. On the basis of the potentiodynamic polarization data, the samples were ranked as follows: C greater than D greater than B greater than A greater than E, C being the most corrosion resistant structure.

Role of gallium in alloy-porcelain bonding

With scanning electron micrographs and semiquantitative x-ray analysis, the role of gallium in alloy-porcelain bonding was studied. The insight gained from this study should be of interest to both dentists and laboratory technicians making ceramometal restorations.

Study of ascorbate status in murine and human leukaemias

Since mice can synthesize ascorbic acid but man cannot, the ascorbate status in murine and human leukaemia was compared. The decline in plasma ascorbate concentration in both cases indicates that vitamin C deficiency occurs in malignancy. Analysis of tissue ascorbate values in mice also indicated that an enhanced rate of utilization of this vitamin occurs during malignancy, as does an increased rate of excretion, and both events may be responsible for vitamin C deficiency. The hepatic ascorbate values suggest an endeavour by the animals to compensate for the loss through increased synthesis and storage of the vitamin, at least in the early stages of the disease.

The in vivo corrosion of Dispersalloy

The in vivo corrosion of Dispersalloy amalgam restorations was characterized by scanning electron microscopy and energy dispersive X-ray analysis. It was observed that the corrosion of CuSn resulted in pitting on the restoration surface. Corrosion of Sn-rich grain boundaries led to intergranular separation of gamma 1 grains. The tin released through corrosion reacted with Ca, P, Cl and O forming various insoluble complexes on the external surface, at the tooth-amalgam interface, and within the interior of the restoration. The demineralization of the amalgam-adjacent margin has been attributed to corrosion.

Relationship between creep, gamma 2, and marginal fracture of dental amalgams

The effect of gamma 1 and gamma 2 on the creep deformation of dental amalgams has been investigated. It has been shown that the creep of a conventional amalgam is not dependent on gamma 1 as was previously reported. Rather it is strongly influenced by gamma 2 and its volume fraction. It has been speculated that Sn-rich grain boundaries also enhance creep by facilitating grain boundary sliding. The reported correlation between creep and marginal fracture has been explained in terms of this dependence of creep on corrosion-prone Sn-rich microstructural constituents of amalgams.

The effects of undernutrition of suckled pigs on subsequent growth and body composition after nutritional rehabilitation

The effect of nutritional restriction and rehabilitation imposed between 5 and 35 d and 35 and 166 d of age, respectively, on body and tissue growth were investigated in 96 Yorkshire pigs from 12 litters. One-half of the pigs were allowed to suckle continuously until weaning (fully fed, FF); the remainder were removed from the sow for 16 h of each 24 h period (1600 to 0800 h), during which time they received only water (restricted feeding, RF). All pigs were fed ad libitum from 35 d of age. Although significantly lower body and tissue (liver, kidney and gastrocnemius muscle) weights were observed in the RF pigs at 35 and 70 d of age, by 166 d, because of compensatory growth between 35 and 166 d, the difference in body and muscle weights between the two groups of pigs (RF and FF) was reduced to 5%, but the difference in kidney and liver weight remained as high as 15 and 9%, respectively. Total DNA, RNA and protein in the tissues examined were also lower in the RF pigs at 35 and 70 d of age, but increased after ad libitum feeding to more than 90% of the corresponding value in the FF pigs by the time they reached 166 d of age. The results of these measurements and the comparison of the protein: DNA ratios of the tissues indicated that growth retardation in the RF pigs was associated with reduced cell proliferation in liver and kidney and nuclear proliferation in muscle rather than any decrease in cell (or fiber) volume. Percentage of fat was lower while percentage of protein was higher (on a dry matter basis) in the RF pigs than in the FF pigs at 35 d of age. No significant difference in fat and protein content in the carcasses between the RF and FF pigs at 70 or 166 d of age or 90 kg body weight was noted. The carcass of intact males had more protein and less fat than that of females.

The chloride corrosion behaviour of four orthodontic wires

Potentiodynamic cyclic polarization of four orthodontic alloys (wires), namely Permachrome, Elgiloy, a beta-titanium alloy and Nitinol in a 1% NaCl solution within -500 mV and +300 mV (SCE) indicated the first three alloys to be passive whereas breakdown of passivity was observed on Nitinol. The SEM examination of the pre- and post-polarized alloy surfaces provided evidence which was consistent with the electrochemical measurements, in that the first three alloys exhibited no appreciable corrosion damage whereas pitting corrosion was observed on Nitinol. The results obtained from X-ray analysis of the pitted surface indicated that this pitting could be due to selective dissolution of nickel from Nitinol.

In vitro corrosion and in vivo marginal fracture of dental amalgams

The relationship between in vitro corrosion and in vivo marginal fracture of dental amalgams has been studied. The potentiodynamic cyclic polarization technique has been used to determine the in vitro corrosion index. The marginal fracture data have been obtained from previous clinical studies reported by three independent research groups. A linear regression analysis has been employed to determine the degree of correlation between in vitro and in vivo data. Depending on the method of corrosion index measurement and the source of clinical data, correlation coefficients (r) ranging from 0.82 to 0.94 (p less than .01) have been obtained.

Effect of long-term immersion corrosion on the flexural properties of nitinol

This study suggests that sporadic failure of nitinol orthodontic wire is due to the presence of surface defects generated during manufacturing and not to the effects of corrosion. The flexural properties were evaluated for both control and corroded samples of nitinol wires and were not found to be statistically different. Fractured surfaces of control as well as corroded samples following bending were examined by scanning electron microscopy to determine the mode of failure.

The tooth-amalgam interaction

The interaction between tooth and amalgam during in vitro corrosion of dental amalgams has been studied in this investigation. Extracted teeth have been restored with five commercial amalgams, one of which was gamma 2 -free and the others contained the gamma 2-phase. The restored teeth were immersed in a 1% NaC1 solution for 9 months. Post corrosion restorations have been examined by optical microscopy, scanning electron microscopy, and X-ray microanalysis. The results are: (1) gamma 2-containing amalgam surfaces were covered with Ca-Sn-P-rich corrosion products of various morphology which occasionally contained relatively low concentrations of C1 and/or Zn; (2) the corrosion products on the gamma 2-free amalgam surface indicated relatively high concentrations of Hg in addition to Ca, p, Sn, Cu, and Zn. These results agree with the past observations that corrosion of amalgam restorations is not an isolated process. Rather it may involve reactions of the restoration and the surrounding oral environment including tooth and oral fluids in which interactions of Sn, Zn, Hg, Ca and P take place.

Strengthening mechanism of bonded alumina crowns

The results of this study suggest that the strengthening of aluminous porcelain with Sn-plated Pt is an effect of (1) a chemical interaction involving diffusion and dissolution of Sn-oxide in the glass phase of the porcelain and (2) a better wetting of te Sn-plated substrate by the porcelain. This conclusion supports and confirms the earlier hypothesis of McLean and Sced.

The chloride corrosion behavior of silver-base casting alloys

The chloride corrosion behavior of five silver-palladium dental casting alloys was investigated in a 1% NaCl solution through the use of electrochemical hysteresis technique. The corrosion mechanism has been interpreted in terms of the microstructure of these alloys and their possible electrochemical reactions.