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.

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.

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.

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.

Refined carbohydrates affect blood pressure and retinal vasculature in spontaneously hypertensive and Wistar-Kyoto rats.

Spontaneously hypertensive (SHR) and Wistar-Kyoto (WKY) rats received diets differing in amount and source of carbohydrates (CHO). When the CHO was in excess and the source was refined sugar or starch rather than natural ingredients, blood pressure (BP) rose, more so in SHR. This BP increase was observed whether sucrose, glucose, fructose or starch was the principal CHO. Increased urinary excretion of norepinephrine, dopamine and epinephrine also occurred. After only 2-3 months retinal capillary basement membrane damage was demonstrated in SHR and WKY rats ingesting large amounts of sucrose. No similar changes occurred on a high-starch diet. The damage consisted of thickening of capillary basement membranes, loss of homogeneity, and debris inclusions. These results suggest: that high dietary ingestion of CHO in the form of refined CHO augments BP in SHR and WKY rats via increased catecholamine production and/or release, and that the temporally foreshortened experimental period offered by the SHR/WKY model may be valuable in the study of diet-induced retinopathies.

Early sucrose-induced retinal vascular lesions in spontaneously hypertensive rats (SHR) and Wistar Kyoto rats (WKY).

Retinal capillary basement membrane damage was demonstrated over a relatively short time period (two to three months) by feeding a diet containing high amounts of sucrose to spontaneously hypertensive rats (SHR) and their normotensive controls, Wistar Kyoto rats (WKY). Similar changes did not occur in SHR and WKY on a high starch diet. The early damage to the capillaries consisted of thickening of capillary basement membranes, loss of homogeneity, and inclusions containing debris. Previous studies on sucrose-induced eye lesions have reported chronic pathological changes only after prolonged periods of heavy sucrose ingestion, usually exceeding one year. Accordingly, the temporally foreshortened experimental pathogenesis offered by the SHR/WKY model allowed us to examine early changes in sucrose-induced vascular eye lesions.

Protein A-coated glass beads. Universal support medium for high-performance immunoaffinity chromatography.

High-performance immunoaffinity chromatography (HPIC) is a technique for the fast isolation and quantitation of both antibodies and antigens. Protein A-coated glass beads provide a stable general immobilization support for most immunoglobulin G (IgG) antibodies. In conjunction with the modern expanding repertoire of monoclonal antibodies, HPIC can be applied to the quantitation and isolation of any biological material, in an active form.

Isolation and quantitation of serum IgE levels by high-performance immunoaffinity chromatography.

High-performance immunoaffinity chromatography on monoclonal antibodies coupled to protein A-coated glass beads is a method for the rapid isolation and quantitation of immunoglobulin E (IgE) from the serum of both adult and pediatric patients. The technique is as sensitive as most immunoassays but takes less than an hour to perform. In addition to measuring total IgE in both plasma and serum, the technique provides biologically active, affinity-isolated IgE, which can be used for other clinical and research studies.

High-performance affinity chromatography: a rapid technique for the isolation and quantitation of IgG from cerebral spinal fluid.

Standard techniques for the quantitative measurement of IgG in cerebral spinal fluid take up to 24 hs. This often delays diagnosis and treatment, critical in newborn infants. A high-performance affinity chromatography (HPAC) column, containing immobilized anti-IgG antibody, produced the same or better results in 1 h. The HPAC system gave a 98% correlation with the standard techniques at the normal-abnormal IgG level, but was more accurate at the extremely low IgG level.

Centrioles, primary cilia and calcium in the growth of Balb/c 3T3 cells.

In every mammalian cell the interphase centriole forms a primary cilium during some part of the cell cycle. Many sensory receptors are modifications of primary cilia, but a sensory role for primary cilia in mammalian cells has not been proven. Nevertheless, we have found that both growth factors and calcium ionophore (A23187) induce calcium fluxes and shortening of the primary cilium. This evidence raises the question of whether the primary cilium is involved in calcium fluxes that are necessary for growth stimulation in mammalian cells.

Acute lymphoblastic leukemia--hand mirror variant--viral immune interrelationship as demonstrated by ultrastructural studies.

Acute lymphoblastic leukemia--hand mirror variant--was extensively restudied in a 22-year-old white female who survived for 22 months without therapy. Immune complexes to the baboon endogenous virus (BaEV) were found in the bone marrow plasma of the relapse specimen in 1977, but not in the bone marrow plasma from the terminal state in 1979. Immunoperoxidase-tagged IgM antibody prepared from the patient's bone marrow plasma revealed BaEV antigen on the tip of the uropod of the HMC at the time immune complexes were found in the marrow. Absence of immune complexes in the marrow. Absence of immune complexes in the bone marrow in the terminal state suggested a failure of the patient's immune surveillance system and/or possible immune suppression by chemotherapy.

Langerhans cells in dermoid cysts: transmission electron microscopic, cytochemical and immunofluorescent observations.

Langerhans cells were detected in squamous, stratified epithelia lining human dermoid cysts. Their presence was assayed by ATPase staining and reactivity with heteroantisera against "Ia-like" antigens. Transmission electron microscopic studies demonstrated variations in the numbers of cells showing Birbeck granules in epithelia with different degrees of keratinization. Indeterminate cells (i.e. lacking granules), were more frequent in epithelia showing combined mucous and keratinizing differentiation. Membrane-coating-granules and keratohyalin granules were present in epithelia containing Langerhans cells with clearly identifiable Birbeck granules. Interepithelial mast cells were observed in epithelia with mucous differentiation. A relationship between Langerhans cells and keratinization was suggested. Such non-immune functions are compatible with the known macrophage characteristics of the cell.