Tribo-electrochemical characterization of metallic biomaterials for total joint replacement.

Knee and hip joint replacement implants involve a sliding contact between the femoral component and the tibial or acetabular component immersed in body fluids, thus making the metallic parts susceptible to tribocorrosion. Micro-motions occur at points of fixation leading to debris and ion release by fretting corrosion. ß-Titanium alloys are potential biomaterials for joint prostheses due to their biocompatibility and compatibility with the mechanical properties of bone. The biotribocorrosion behavior of Ti-29Nb-13Ta-4.6Zr was studied in Hank's balanced salt solution at open circuit potential and at an applied potential in the passive region. Reciprocating sliding tribocorrosion tests were carried out against technical grade ultra high molecular weight polyethylene, while fretting corrosion tests were carried out against alumina. The wear of the alloy is insignificant when sliding against polyethylene. However, depassivation does take place, but the tested alloy showed an ability to recover its passive state during sliding. The abrasivity of the alloy depends on the electrochemical conditions of the contact, while the wear of polyethylene proceeds through third body formation and material transfer. Under fretting corrosion conditions recovery of the passive state was also achieved. In a fretting contact wear of the alloy proceeds through plastic deformation of the bulk material and wear resistance depends on the electrochemical conditions.

Study on tobacco use and awareness among marginalized children.

BACKGROUND: The current study entailed a survey of children from the lower socioeconomic strata of rural and urban regions of the states of Maharashtra and Assam who are vulnerable to tobacco usage. More than 1700 children were checked for precancerous lesions and 1004 were surveyed for tobacco habits and awareness. AIMS: The objective of the survey was to determine and report on all the variant factors affecting the use of tobacco among the underprivileged children population. The aim of the clinical check-up was to detect precancerous lesions in the tobacco-using children at an early treatable stage. MATERIALS AND METHODS: Awareness lectures and ENT camps were conducted at 12 organizations/community centers. A cross-section of children were interviewed to understand tobacco use among them. All the children were screened for precancerous lesions. Children with suspicious oral lesions were sent for further evaluation at a nearby diagnostic cancer facility. The survey was conducted by trained social workers. RESULTS: The percentage of tobacco users in urban Mumbai was quite low at 4.8% compared with rural Kasara (36%) and Assam (76%); and 74.6% of the children were aware that tobacco use was dangerous and harmful to health. The average age of initiation was 9 years. Out of the 1004 children surveyed, 253 were tobacco users and 79% were males. Of the 1700 children screened, 23.5% presented with precancerous oral lesions. CONCLUSION: This study addresses the tobacco habits of a typical sample of marginalized children in India and the need for effective interventions aiming at reducing the burden of tobacco-related cancers by controlling at the point of initiation.

Severe muscle weakness due to hyperkalemia.

Hyperkalemia is a commonly encountered electrolyte disturbance in patients with renal insufficiency. It develops very rapidly when potassium is supplemented while a patient is on a potassium-sparing diuretic. Most often it remains asymptomatic and manifests in the form of electrocardiographic changes. Muscle weakness and paralysis although described is seldom observed in clinical practice. We report one such case.

Distribution of substance P positive cells and nerve fibers in the rat thymus.

The immune and nervous systems communicate through an array of signalling molecules which includes substance P. This work investigates the anatomical relationship between substance P nerve fibers, receptors, and substance P positive cells in the thymus. Thymuses from rats were frozen or paraformaldehyde fixed. In vitro autoradiography was used to map the distribution of SP receptors. Immunostaining was used to localize SP positive cells and nerve fibers by transmitted light and confocal microscopy. SP receptors exhibited a broader distribution than previously reported, being present throughout the organ with a preferential concentration in the cortico-medullary zone. While SP fibers were frequently associated with the blood vasculature, they were also present throughout the organ independent of blood vessels and were most prominent in the cortico-medullary zone. SP positive cells followed a similar pattern of distribution as the SP fibers and were present as single cells or aggregates of SP positive cells. Confocal microscopy revealed close spatial contact between the SP positive nerve fibers and the SP positive thymic cells. The close spatial relationship between the SP positive thymic cells and SP positive nerve fibers supports the concept of a structural-functional unit between SP nerve fibers and their potential receptor-bearing target cells in the thymus.

Developmental expression of calcium-binding protein-containing neurons in neocortical transplants.

The present study examined the development of calcium binding protein-containing neurons in a timed series of fetal neocortical transplants. The immunoexpression of parvalbumin and calbindin, which are subpopulations of GABAergic neurons, have been widely studied in normal development and in disease and injury states. Because of their purported resistance to oxidative injury by their ability to buffer Ca++ influx, these neurons have been particularly studied following ischemia. Because it is likely that oxidative stress is associated with the grafting procedure, we sought to determine if these neurons displayed enhanced survival characteristics. Normally, parvalbumin and calbindin represent about 5-10% of cortical neurons. Within 2-4 wk after grafting the expression of both proteins increased markedly in that a relatively larger number of neurons (27% for parvalbumin) were immunopositive. This increase was transitory, however, and by 4 mo and beyond, confocal microscopic data showed a reduction of over 50% of parvalbumin (+) neurons and processes. Calbindin (+) processes showed a qualitative change in that they were smaller with less terminal branching. Electron microscopy confirmed a substantial reduction in parvalbumin synaptic contacts. Interestingly, in older grafts, remaining parvalbumin neurons were those that were strongly NSE (+) suggesting a link between normal metabolism and Ca++ buffering in grafted neurons. It is possible that in early grafts certain neuronal populations transiently upregulated calcium binding proteins as a defensive mechanism against Ca++ influx associated with oxidative stress. Over time, however, following physiological normalization within grafts, the calcium binding protein (+) neurons are diminished, possibly due to lack of appropriate afferent input to the interneuronal pool.

Surface changes of the erythrocytes membrane in alcoholics--a study of lectin binding.

Erythrocytes from 30 alcoholic patients as well as age and sex matched healthy control were examined, for hemagglutination titre, against, a purified galactose specific lectin from the latex of Pedilanthus tithymalodies. Mean hemagglutinin titre was significantly elevated (P < 0.001) in alcoholics as compared to controls. The results indicate that alcohol abuse is associated with adoptive cell surface changes on erythrocytes, measurable by its lectin binding capacity.

Approach to aerosol therapy in management of asthma at primary care level.

Present day management of bronchial asthma focuses on use of inhaled drugs. To find out the acceptability of aerosol therapy at primary care level, a questionnaire survey was conducted on practical acceptance of aerosol therapy in management of asthma. Seven clinically relevant questions were asked regarding management modalities followed in bronchial asthma. Amongst the group of general practitioners (n = 60) studied, it was found that in treatment of chronic stable asthma inhaled steroids are used by only 50% and inhaled bronchodilators by 86.7%, whereas 93.3% use oral bronchodilators and 60% use oral steroids to treat the same. During exacerbation injectable bronchodilators are preferred to inhaled drugs. Poor compliance to aerosol therapy was reported by 33.3%. Reasons for non-compliance are discussed, important ones are cost and technique. Spacer was reported to be useful by 20% and lung functions are carried out occasionally by only 5% of practitioners.

The effect of low temperatures on enzyme activity.

The stability of two enzymes from extreme thermophiles (glutamate dehydrogenase from Thermococcales strain AN1 and beta-glucosidase from Caldocellum saccharolyticum expressed in Escherichia coli) has been exploited to allow measurement of activity over a 175 degrees C temperature range, from +90 degrees C to -85 degrees C for the glutamate dehydrogenase and from +90 degrees C to -70 degrees C for the beta-glucosidase. The Arrhenius plots of these enzymes, and those for two mesophilic enzymes (glutamate dehydrogenase from bovine liver and beta-galactosidase from Escherichia coli), exhibit no downward deflection corresponding to the glass transition, found by biophysical measurements of several non-enzymic mesophilic proteins at about -65 degrees C and reflecting a sharp decrease in protein flexibility as the overall motion of groups of atoms ceases.

Immunocytochemical expression of the blood-brain barrier glucose transporter (GLUT-1) in neural transplants and brain wounds.

The present study examined the immunocytochemical expression of the blood-brain barrier glucose transporter (GLUT-1) in a series of fetal neocortical transplants, autonomic tissue transplants, and stab wounds to the rat brain. GLUT-1 is one of a family of different glucose transporters and is found exclusively on barrier-type endothelial cells. In the brain it is responsible for the regulated facilitative diffusion of glucose across the blood-brain barrier. This investigation is the first to determine if this important molecule is altered during the process of angiogenesis that occurs following neural transplantation procedures or direct brain injury. Beginning in late fetal brain, e.g., E18 and continuing into maturity, GLUT-1 was strongly and exclusively expressed on normal cerebral vessels. In solid fetal central nervous system (CNS) transplants up to around 3 weeks postoperative, GLUT-1 was only weakly expressed, particularly as exemplified by colloidal gold immunostaining when compared with the host. At later times examined, up to 15 months postoperative, GLUT-1 immunoexpression was comparable with the normal adjacent brain. In autonomic tissue transplants, where the vessels do not have a blood-brain barrier, as expected, GLUT-1 was not expressed. In stab wounds, at 1 week there was extensive gliosis, and the injured vessels appeared fragmented and collapsed but still expressed GLUT-1, although to a somewhat lesser extent than normal brain. Between 3 and 6 weeks, GLUT-1 was expressed on tortuous vessels and in apparently fibrillar processes in the wound vicinity with a similar pattern to astrocyte (GFAP) reactivity. These results suggest the occurrence of a down-regulation of GLUT-1 in early transplants, perhaps related to reduced glycolytic activity or transient ischemia, or possibly due to the utilization of alternative energy sources. That GLUT-1 expression was not entirely lost in stab wounds to the mature brain suggests that the protein may be more labile in fetal or perinatal brain than in the adult and may not be affected by direct injury. Coupled with previous transplantation studies that have shown reduced neuronal glycolysis and potential barrier alterations, the reduction of GLUT-1 activity within nearly the identical time frame could indicate a relatively early critical period in cellular metabolism following transplantation of CNS tissue.

Immunocytochemical distribution of the brain glucose transporter (GLUT 1) in experimental gliosis.

The present study has examined the immunocytochemical expression of the blood-brain barrier glucose transporter GLUT 1 as compared with GFAP in models of experimental gliosis. In neocortical grafts, gliosis was prominent at the graft-host interface mostly associated with blood vessels. Consecutive sections examined for anti-GLUT 1 showed that the protein was distributed in nearly an identical pattern to the anti-GFAP, staining fibrillar processes and all vessels and also appeared extracellularly. In stab wounds, GLUT 1 immunoexpression was similar to GFAP reactivity and stained injured vessels and glial-like processes that were reminiscent of astrocytic end-feet. Normal glial cells and processes in unaffected neuropil, however, were never stained. This report suggests that GLUT 1 protein may be upregulated in non-endothelial components, such as reactive astroglia or possibly microglia, that are associated with injured or angiogenic vessels.

[Evaluation of 3 diagnostic methods in premature rupture of membranes: diamine-oxidase assay, alpha-fetoprotein assay, colorimetric method evaluating the pH]. / Evaluation de trois méthodes diagnostiques dans la rupture prématurée des membranes: dosage de la diamine-oxydase, dosage de l'alpha-foeto-protéine, méthode colorimétrique évaluant le pH.

The authors set out to assess the three diagnostic methods available which can detect early breaking of the membranes: radio-enzymatic assay of diamine-oxidase (DAO), radioenzymatic assay of alpha-fetoprotein (AFP), colorimetric method for determining pH (Amnicator). Between June 1991 and March 1992, 114 samples of vaginal secretions were taken from 104 pregnant patients being followed up at Maternity Unit A, Bordeaux (France). The results of the assays were expressed in quantitative terms (microU/ml for DAO and ng/ml for AFP); ROC (Receiver Operating Characteristic) curves were used to determine the positivity threshold in terms of the sensitivity and specificity (20 microU/ml for DAO and 15 ng/ml for AFP). The sensitivity of the pH test was 97.5%, which was significantly better than that of DAO (90.2%) and even that of AFP (82.9%). However, there was no difference between the specificities of the pH, DAO and AFP tests (93.3%, 96.6% and 93.5% respectively). The data were compared with those in the literature. The problems in collecting the vaginal secretions probably accounts for the better results of the colorimetric test. This is a reliable, fast and easily reproducible test; these qualities make it the preferred test in EBM, and it can be completed using a radioenzymatic method (DAO) or immunoradiometric test (AFP).

Endothelial cell compatibility testing of three different Pellethanes.

There is a need for viable small diameter vascular grafts, the luminal surface of which could be seeded by endothelial cells (ECs) to prevent thrombosis. In order to select candidates for EC seeding before implantation, the in vitro cytocompatibility of three different Pellethanes (polyetherurethanes) using human ECs was investigated. The methodology included two stages depending on either direct contact between cells and materials or contact between cells and material extracts, obtained under standardized conditions. By the latter method, we observed a cytotoxic effect on cell growth with 2363-55 D Pellethane extract at a 50% (v/v) concentration in the nutrient medium, likely provoked by leachables and correlated with the lowest levels of tPA, PAI1, and vWF antigens in the supernatants. By the former method, we studied EC attachment and growth. Morphology was studied by classical means and completed by scintigraphy and microautoradiography after 111Indium-labeling of the EC monolayer. Differentiation was determined by the release of vWF antigen and measurement of vWF activity (multimeric organization) after human thrombin stimulation. Despite an inhibition of proliferation for both 55 D and 75 D types (compared to the control), a functional monolayer of ECs was obtained on 75 D. Pellethane 75 D could be the best support for in vitro endothelization.

Ex vivo leucocyte adhesion and protein adsorption on TiN.

Titanium nitride (TiN) is regarded as a potential biomaterial for blood-contact applications. Its in vitro haemocompatibility has been evaluated already and gave promising results. The purpose of this study was to continue studying its 'biological' behaviour through an ex vivo evaluation. The material was a physical vapour deposition elaborated TiN coating and the phenomena observed were leucocyte adhesion and albumin and fibrinogen adsorption. These ex vivo results were compared with in vitro results obtained previously. Two reference medical grade silicone elastomer and three TiN arterio-arterial extra-corporeal circuits were tested. No leucocyte was retained by TiN, as in in vitro experiments; the ex vivo fibrinogen adsorbed quantity was higher and albumin adsorption was about the same in in vitro and in ex vivo situations. TiN can be considered as a suitable blood-contacting material.

Hemocompatibility of diamond-like carbon coating.

The new prosthetic heart valve that has been designed by FII Company and Pr. Baudet involves a new "composite" material: titanium alloy T16A14V coated with Diamond-like Carbon. The purpose of this study was to evaluate the in vitro hemocompatibility of this new material in terms of protein adsorption and platelet retention. The static protein adsorption test gave interesting results, particularly for the albumin assay (237%) compared to the results obtained with a silicone elastomer chosen as a reference; the fibrinogen quantity, adsorbed on the surface of the material was slightly higher than that adsorbed on the silicone surface. Platelets adhere quite twice as much as they do on the reference surface. Such investigations showed good hemocompatibility results and should initiate further studies.

Brain angiogenesis: variations in vascular basement membrane glycoprotein immunoreactivity.

Changes in the distribution and quantity of laminin and fibronectin within the basement membranes of developing or regenerating CNS blood vessels were investigated using two immunocytochemical techniques. Three models of angiogenesis were studied: normal pre- and postnatal development, wound healing, and vascularization of fetal neocortical transplants placed in the adult rat brain. Although all brain vessels were stained in enzymatically pretreated immunoreacted paraffin sections, those associated with wound and transplant sites were the most intensely reactive with both antisera during the first postoperative week. When 40-microns vibratome sections of normal adult brains were immunoprocessed, only the meninges and vessels of the circumventricular organs were stained. The remainder of the brain vasculature was immunoreactive only if sections were enzymatically treated prior to immunoprocessing. In contrast, the nascent vasculature in developing brain and the regenerating vessels at wound and transplant sites were reactive to both antisera without enzymatic pretreatment of the sections. This immunoreactivity decreased by 11 days postnatal in normal animals and 4 weeks postoperative in experimental animals, coinciding with the period of astrocytic contact and complete vascular basement membrane formation in both cases. The variations in staining pattern and intensity may be reflections of differences in the quantity of laminin and fibronectin within the basement membranes of proliferating and/or non-blood-brain barrier vasculature. However, the results of the different experimental protocols suggest that immature vascular basement membranes may have a molecular configuration that does not require an enzymatic unmasking step to react with the antisera. Alternatively, the looseness of the surrounding neuropil inherent in developing and injured CNS could allow the antisera greater access to basement membrane antigens.

Biocompatibility of carbon-carbon materials: blood tolerability.

Carbon-carbon composites are well known in the field of aerospace technology. Such composites have been proposed to be used as biomaterials, particularly in contact with blood. To evaluate their haemocompatibility, samples were tested in vivo and in vitro, using radiotracers. In vivo study showed the accumulation of platelets on the exposed surface material with any surface morphology, whereas platelet concentration in blood remained constant. In vitro study allowed us to distinguish, among entrapped platelets, active adhering platelets from those mechanically retained and it appeared that the bulk structure of materials influenced the adhesion mechanism of platelets.