Biomedical subjects
A L Smith
Publications and source records attributed to A L Smith.
Role of dendritic cells in induction of tolerance and immunity in vivo.
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A study of the factors affecting the metabolic clearance of quinine in malaria.
OBJECTIVE: To assess the factors that contribute to impaired quinine clearance in acute falciparum malaria. PATIENTS: Sixteen adult Thai patients with severe or moderately severe falciparum malaria were studied, and 12 were re-studied during convalescence. METHODS: The clearance of quinine, dihydroquinine (an impurity comprising up to 10% of commercial quinine formulations), antipyrine (a measure of hepatic mixed-function oxidase activity), indocyanine green (ICG) (a measure of liver blood flow), and iothalamate (a measure of glomerular filtration rate) were measured simultaneously, and the relationship of these values to the biotransformation of quinine to the active metabolite 3-hydroxyquinine was assessed. RESULTS: During acute malaria infection, the systemic clearance of quinine, antipyrine and ICG and the biotransformation of quinine to 3-hydroxyquinine were all reduced significantly when compared with values during convalescence. Iothalamate clearance was not affected significantly and did not correlate with the clearance of any of the other compounds. The clearance of total and free quinine correlated significantly with antipyrine clearance (rs = 0.70, P = 0.005 and rs = 0.67, P = 0.013, respectively), but not with ICG clearance (rs = 0.39 and 0.43 respectively, P > 0.15). In a multiple regression model, antipyrine clearance and plasma protein binding accounted for 71% of the variance in total quinine clearance in acute malaria. The pharmacokinetic properties of dihydroquinine were generally similar to those of quinine, although dihydroquinine clearance was less affected by acute malaria. The mean ratio of quinine to 3-hydroxyquinine area under the plasma concentration-time curve (AUC) values in acute malaria was 12.03 compared with 6.92 during convalescence P = 0.01. The mean plasma protein binding of 3-hydroxyquinine was 46%, which was significantly lower than that of quinine (90.5%) or dihydroquinine (90.5%). CONCLUSION: The reduction in quinine clearance in acute malaria results predominantly from a disease-induced dysfunction in hepatic mixed-function oxidase activity (principally CYP 3A) which impairs the conversion of quinine to its major metabolite, 3-hydroxyquinine. The metabolite contributes approximately 5% of the antimalarial activity of the parent compound in malaria, but up to 10% during convalescence.
Safety of repeated intermittent courses of aerosolized recombinant human deoxyribonuclease in patients with cystic fibrosis.
OBJECTIVES: To determine the effect of repeated doses of aerosolized recombinant human deoxyribonuclease (rhDNase) on the development of anti-rhDNase antibodies, acute allergic reactions, and pulmonary function in patients with cystic fibrosis. DESIGN: A multicenter, open-label study in which 184 patients received 10 mg aerosolized rhDNase twice a day for 14 days followed by a 14-day washout period for a total of 6 treatment cycles. Serial determinations of anti-rhDNase antibodies and pulmonary functions were performed. RESULTS: Detectable anti-rhDNase antibodies developed in 16 (8.7%) patients. These patients had no changes in their symptoms from the time they entered the trial. Antibodies detected were all of the IgG isotype. Increases in both forced expired volume in 1 second and forced vital capacity were noted from the beginning to the end of each cycle of treatment returning to baseline during the off-treatment period of each cycle. Seropositivity to rhDNase was not associated with allergic reactions and had no relationship on improvement in pulmonary function. CONCLUSIONS: Development of anti-rhDNase antibodies occurred in a small number of patients and was not associated with side effects. Intermittent administration of rhDNase for 24 weeks to patients with cystic fibrosis was well tolerated and was not associated with anaphylaxis in any patient. Pulmonary function improved significantly during the 14-day cycles while rhDNase was administered and returned to baseline when rhDNase was discontinued.
Immunologic and autoradiographic localisation of the Na+, K(+)-ATPase in articular cartilage: upregulation in response to changes in extracellular Na+ concentration.
The maintenance of a relatively low intracellular Na+:K+ ratio is essential for the functioning of a wide range of cellular processes, and is achieved principally by the activity of the membrane-bound Na+, K(+)-ATPase. Chondrocytes, the cells of articular cartilage, exist in an ionic environment where the free extracellular [Na+] is higher (250-400 mM) than that of most other tissues (approximately 140 mM) owing to the fixed negative charges on glycosaminoglycans in the extracellular matrix. This can increase further during static joint loading when fluid expression occurs. To determine aspects of how chondrocytes regulate their ionic composition, in this study, the in situ distribution, pattern of isoform expression and density of the Na+, K(+)-ATPase within cartilage has been investigated. The density of the Na+, K(+)-ATPase was found to be high in the mid-zone, but lower in the surface and deep zones. Immunofluorescence microscopy using monoclonal antibodies to the catalytic alpha subunits of the Na+, K(+)-ATPase revealed the expression of isoforms alpha 1 and alpha 3. Alterations to the extracellular [Na+] (from 80-220 mM, or 120-220 mM) significantly elevated Na+, K(+)-ATPase density of in situ chondrocytes. The results indicate that the Na+, K(+)-ATPase is abundantly expressed in articular chondrocytes and its density is sensitive to the extracellular [Na+]. The expression of the alpha 3 isoform is surprising for a non-neuronal cell, and may indicate a physiological adaptation to the unusually high extracellular [Na+] to which chondrocytes are exposed in the extracellular matrix of cartilage.
Neonatal protein-losing enteropathy caused by intestinal lymphatic hypoplasia in siblings.
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A first-generation whole genome-radiation hybrid map spanning the mouse genome.
We have assembled a first-generation anchor map of the mouse genome using a panel of 94 whole-genome-radiation hybrids (WG-RHs) and 271 sequence-tagged sites (STSs). This is the first genome-wide RH anchor map of a model organism. All of the STSs have been previously localized on the genetic map and are located 8.8 Mb apart on average. This mouse WG-RH panel, known as T31, has an average retention frequency of 27.6% and an estimated potential resolution of 145 kb, making it a powerful resource for efficient large-scale expressed sequence tag mapping. [All of the mapping data for the maps presented here have been deposited at the Research Genetics, Inc., web site and can be freely accessed and downloaded at http://www.resgen.com/.]
Xanthogranulomatous pyelonephritis--a rare case of fistula between colon and kidney.
We report the case of a 63 year old lady with xanthogranulomatous pyelonephritis. The treatment of choice is nephrectomy. At operation a fistula between large bowel and kidney was found requiring bowel resection. This is a rare complication of xanthogranulomatous pyelonephritis.
Base of the fifth metatarsal fractures, an unusual presentation.
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Sterile abscess formation following plague vaccination.
As part of the immunisation programme of servicemen on OP Granby, deployed in the Gulf, plague vaccine was recommended as a prophylaxis. Out of a total of 524 vaccinations at our location, one sterile abscess formation was noted. The case report is described.
A comparison of peak sputum tobramycin concentration in patients with cystic fibrosis using jet and ultrasonic nebulizer systems. Aerosolized Tobramycin Study Group.
STUDY OBJECTIVE: To determine whether adequate concentrations of a new formulation of tobramycin could be delivered to the lower respiratory tract of patients with cystic fibrosis (CF) using a jet nebulizer delivery system. DESIGN: A multicenter, open-label, randomized, crossover study. SETTING: Ten tertiary care, university-affiliated, teaching hospitals in the United States. PATIENTS AND CONTROL SUBJECTS: Sixty-eight patients recruited from 10 CF Foundation centers and who were at least 8 years of age, had a diagnosis of CF, and expectorated daily sputum. No control subjects enrolled. INTERVENTIONS: Each patient received one administration of aerosolized tobramycin from each of the three nebulizer systems in random order. Each administration was separated by a minimum of 48 h. The two jet nebulizer systems tested were the Sidestream (Medic-Aid; Sussex, UK), and the Pari LC (Pari Respiratory Equipment; Richmond, Va), with a DeVilbiss Pulmoaide compressor (DeVilbiss Health Care; Somerset, Pa), both administering 300 mg tobramycin in 5 mL of 1/4 normal saline solution (NS). Patients were also administered 600 mg tobramycin in 30 mL of 1/2 NS with the UltraNeb 99/100 (DeVilbiss). MEASUREMENTS: Sputum and serum tobramycin concentration and pulmonary function were monitored. An adequate peak sputum tobramycin concentration was defined as > 128 microg/g sputum at any of three time points (10, 60, or 120 min) after completion of treatments. RESULTS: The peak tobramycin concentrations in expectorated sputum were 687+/-663 microg/g (mean+/-SD) with the Pari LC and 489+/-402 microg/g with the Sidestream. Adequate peak sputum tobramycin concentration was achieved in 93% of the patients with the Sidestream, and in 87% of the patients with the Pari LC. Peak sputum concentrations were found to be substantially higher when patients received tobramycin administered with the UltraNeb 99/100, 1,498+/-1,331 microg/g with 30% of patients having levels exceeding 2,000 microg/g. Serum tobramycin concentrations were < or = 4 microg/mL for all patients following administration with each nebulizer. CONCLUSIONS: Adequately high sputum tobramycin concentrations were documented in sputum in > 85% of patients following the administration of 300 mg/5 mL formulation of tobramycin aerosolized by the two jet nebulizer delivery systems, Sidestream and Pari LC. The single tobramycin administration delivered by these two systems is well-tolerated.
The role of T cells in the regulation of B cell tolerance.
The study of conventional models of B cell tolerance has suggested that self-tolerance is imposed on B cells at an early stage in their development due to a peculiar sensitivity of immature B cells to tolerance induction. While this concept accounts for some aspects of central B cell tolerance, it is inconsistent with recent reports of tolerance induction in mature splenic B cells from immunoglobulin transgenic mice. We present an alternative model, the hierarchical model (Aust. N. Z. J. Med. 25, 761-767, 1995), in which regulation of naive B cell reactivity is a function of antigen signal strength and availability of T cell help, but is independent of B cell maturation stage. In turn, the development of tolerance or memory in the T cell compartment is dependent on a combination of antigen-MHC recognition by T cells and antigen-nonspecific signalling by antigen-presenting cells. Using a transgenic model of T-B collaboration, we have shown that both immature and mature self-reactive B cells can be rescued and induced to secrete auto-antibody if the B cell determinant is linked to a carrier protein bearing a foreign T cell determinant.
T-cell alpha beta + and gamma delta + deficient mice display abnormal but distinct phenotypes toward a natural, widespread infection of the intestinal epithelium.
Vertebrate immune systems contain T cells bearing either alpha beta or gamma delta T-cell antigen receptors (TCRs). alpha beta T cells perform all well-characterized T-cell effector functions, while the biological functions of gamma delta + cells remain unclear. Of particular interest is the role of gamma delta + cells during epithelial infections, since gamma delta + cells are commonly abundant within epithelia. Eimeria spp. are intracellular protozoa that infect epithelia of most vertebrates, causing coccidiosis. This study shows that in response to Eimeria vermiformis, mice lacking alpha beta T cells display defects in protective immunity, while mice lacking gamma delta + cells display exaggerated intestinal damage, apparently due to a failure to regulate the consequences of the alpha beta T cell response. An immuno-downregulatory role during infection, and during autoimmune disease, may be a general one for gamma delta + cells.
Haemophilus influenzae pili are composite structures assembled via the HifB chaperone.
Haemophilus influenzae is a Gram-negative bacterium that represents a common cause of human disease. Disease due to this organism begins with colonization of the upper respiratory mucosa, a process facilitated by adhesive fibers called pili. In the present study, we investigated the structure and assembly of H. influenzae pili. Examination of pili by electron microscopy using quick-freeze, deep-etch and immunogold techniques revealed the presence of two distinct subassemblies, including a flexible two-stranded helical rod comprised of HifA and a short, thin, distal tip structure containing HifD. Genetic and biochemical studies demonstrated that the biogenesis of H. influenzae pili is dependent on a periplasmic chaperone called HifB, which belongs to the PapD family of immunoglobulin-like chaperones. HifB bound directly to HifA and HifD, forming HifB-HifA and HifB-HifD complexes, which were purified from periplasmic extracts by ion-exchange chromatography. Continued investigation of the biogenesis of H. influenzae pili should provide general insights into organelle development and may suggest novel strategies for disease prevention.
Gamma delta T cell help of B cells is induced by repeated parasitic infection, in the absence of other T cells.
BACKGROUND: gamma delta T cells, like alpha beta T cells, are components of all well-studied vertebrate immune systems. Yet, the contribution of gamma delta T cells to immune responses is poorly characterized. In particular, it has not been resolved whether gamma delta cells, independent of any other T cells, can help B cells produce immunoglobulin and form germinal centers, anatomical foci of specialized T cell-B cell collaboration. RESULTS: TCR beta-/- mice, which lack all T cells except gamma delta T cells, routinely displayed higher levels of antibody than fully T cell-deficient mice. Repeated parasitic infection of TCR beta-/- mice, but not of T cell-deficient mice, increased antibody levels and induced germinal centers that contained B cells and monoclonal gamma delta cells in close juxtaposition. However, antibody specificities were more commonly against self than against the challenging pathogen. gamma delta T cell-B cell help was not induced by repeated inoculation of TCR beta-/- mice with mycobacterial antigens. CONCLUSIONS: In the absence of any other T cells, gamma delta T cell-B cell collaboration can be significantly enhanced by repeated infection. However, the lack of obvious enrichment for antibodies against the challenging pathogen distinguishes gamma delta T cell help from alpha beta T cell help induced under analogous circumstances. The increased production of generalized antibodies may be particularly relevant to the development of autoimmunity, which commonly occurs in patients suffering from alpha beta T cell deficiencies, such as AIDS.
The enediyne antibiotics.
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Mouse parvovirus infection potentiates rejection of tumor allografts and modulates T cell effector functions.
Lymphocytotropic mouse parvoviruses can perturb immune responses. For example the recently identified mouse parvovirus designated MPV-1 persistently infects lymphoid tissues and interferes with the ability of cloned T cells to proliferate. As a consequence of these findings the present studies were undertaken to characterize further the immunomodulatory effects of MPV-1 on T cell-mediated immune responses in vivo and in vitro. To evaluate the effect of MPV-1 on CD8+ T cell-mediated responses sarcoma I (SaI) cells, devoid of class II major histocompatibility (MHC) antigens, were administered to MPV-1-infected adult BALB/c mice. MPV-1 infection accelerated tumor allograft rejection. Immunofluorescence staining and in situ hybridization studies of tumors suggested that direct infection of the tumor cells was not responsible for accelerated rejection. Furthermore, compared with uninfected mice, T cells from infected mice that had rejected SaI tumors had a diminished cytolytic capacity. Taken together these results suggest that MPV-1 may induce "bystander help." To examine the in vivo effect of MPV-1 on CD4+ T cell mediated responses adult mice were primed with ovalbumin (OVA) and infected with MPV-1. Spleen and popliteal lymph node cells from OVA-primed mice 3 or 7 days after MPV-1 inoculation had reduced proliferation responses, whereas the proliferative capacity of mesenteric lymph node cells from these mice was increased. Similarly, MPV-1 reduced cytokine-induced proliferation of allospecific CD8+ cloned L3 T cells and OVA-reactive CD4+ T cells without effecting cell viability. Since parvoviruses are widespread among laboratory rodents, these findings emphasize the importance of identifying and excluding parvovirus infections in mice used for transplantation studies and in cultures of mouse T lymphocytes.
Growth characteristics and protein profiles of prototype and wild-type rat coronavirus isolates grown in a cloned subline of mouse fibroblasts (L2p.176 cells).
Rat coronaviruses (RCVs) infect laboratory rats and confound biomedical research results. In vitro systems developed so far have limited the growth in knowledge about RCVs by not permitting generation of plaque-cloned virus stocks, reliable isolation of RCVs from rat tissues, or growth of high titered stocks of all isolates. Due to the fact that less than 20% of L2(Percy) cells were becoming infected, sublines were produced and selected for maximal growth of RCVs. Screening of 238 cell sublines yielded L2p.176 cells which were highly susceptible to all RCVs tested; however, susceptibility declined after 30 passages in vitro. Low-passaged L2p.176 cells were used to isolate virus from natural outbreaks and to propagate individual RCV plaques into high titered stocks. Proteins from six RCV isolates were immunoblotted using polyclonal rat and mouse antibodies to sialodacryoadenitis virus and polyclonal monospecific rabbit and goat antibodies against the peplomer (S) and nucleocapsid (N) proteins of mouse hepatitis virus (MHV). Proteins of two prototype, one Japanese and three wild type RCVs were examined and found to be similar to those of MHV, although the exact sizes and ratios of protein forms were unique for most RCV isolates. This study reports the development of a continuous cell line which reliably supports RCVs opening an opportunity for further in vivo studies of the biology of these agents. As a first step in the characterization of RCVs, we have shown that RCV proteins are very similar to those of MHV.