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Biomedical subjects

K A Williams

Publications and source records attributed to K A Williams.

At least 37 records · Page 2Linked to original sources
PubMed2000

Anti-rat ICAM-1 antibody does not influence the course of experimental melanin-induced uveitis.

PURPOSE: Experimental melanin-induced uveitis (EMIU) is a T cell-mediated rat model of acute anterior uveitis. We investigated the possibility of preventing the inflammation with monoclonal antibody directed against rat intercellular adhesion molecule 1 (ICAM-1). METHODS: To induce EMIU, Lewis rats were immunized with bovine ocular melanin extract (250-500 microg). Each day from day 6 post-immunization, rats were injected intraperitoneally with anti-ICAM-1 monoclonal antibody (IA29) or normal mouse serum, and examined with a slit-lamp biomicroscope. On the first day of clinical inflammation, intravital microscopy of iris vasculature was performed on each animal following intraperitoneal injection of rhodamine 6G. At the peak of clinical inflammation, rats were killed, and eyes were examined histologically. Binding potency of IA29 was tested by flow cytometry using concanavalin A-stimulated rat T cells. Immunohistochemical staining was used to detect IA29 on rat uveal vascular endothelium. RESULTS: The ability of IA29 to bind T cell blasts was present to a 1:2000 dilution, and IA29 was readily detectable on uveal vascular endothelium following systemic administration. However, there was no significant difference (p > 0.05) in incidence, time of onset, or severity or histological appearance of EMIU for the rats treated with IA29 when compared with the control rats. Intravital microscopy revealed sticking of leukocytes in the iris vasculature in both groups. CONCLUSIONS: We were unable to demonstrate an inhibitory effect of anti-rat ICAM-1 antibody on the outcome of EMIU. Our observations may reflect a redundancy in the adhesion molecule profile responsible for this uveitis.

Animals↗
PubMed2000

Apoptosis is a prominent feature of acute anterior uveitis in the Fischer 344 rat.

AIMS: To examine the hypothesis that apoptosis of infiltrating cells contributes to spontaneous resolution of uveitis in clinically relevant rodent models. METHODS: Experimental melanin induced uveitis (EMIU) was induced in Fischer 344 rats by immunisation with 250 microg bovine ocular melanin. Endotoxin induced uveitis (EIU) was induced by injection of 200 microg Escherichia coli lipopolysaccharide. Formalin fixed, paraffin embedded ocular cross sections were stained by terminal deoxynucleotidyl transferase mediated deoxyuridine triphosphate biotin nick end labelling (TUNEL) to identify apoptotic cells. Indirect immunoperoxidase staining of paraformaldehyde lysine periodate fixed tissue cross sections was used to demonstrate expression of inducible nitric oxide synthase (iNOS). RESULTS: TUNEL positive mononuclear cells were observed in the anterior uvea during both EMIU and EIU at all selected time points. However, whereas the majority of mononuclear cells appeared apoptotic from the outset of disease, neutrophils were notably TUNEL negative at all time points examined. Many infiltrating neutrophils expressed iNOS. CONCLUSION: Apoptosis occurs early in the course of rat EMIU and EIU, and may contribute to resolution of these diseases. In general, infiltrating mononuclear cells die rapidly, while neutrophils survive, producing inducible nitric oxide synthase which may contribute to disease pathogenesis.

Acute Disease↗
PubMed1999

Projection structure of NhaA, a secondary transporter from Escherichia coli, at 4.0 A resolution.

Electron cryomicroscopy of frozen-hydrated two-dimensional crystals of NhaA, a Na+/H+ antiporter from Escherichia coli predicted to have 12 transmembrane alpha-helices, has facilitated the calculation of a projection map of NhaA at 4.0 A resolution. NhaA was homologously expressed in E.coli with a His6 tag, solubilized in dodecyl maltoside and purified in a single step using Ni2+ affinity chromatography. Two-dimensional crystals were obtained after reconstitution of purified protein with E.coli lipids. The projection map reveals that this secondary transporter has a highly asymmetric structure in projection. NhaA exhibits overall dimensions of approximately 38x48 A with a ring-shaped density feature probably corresponding to a bundle of tilted helices, adjacent to an elongated region of density containing several peaks indicative of transmembrane helices. Two crystal forms with p22121 symmetry show tightly packed dimers of NhaA which differ in the interactions between adjacent dimers. This work provides the first direct glimpse into the structure of a secondary transporter.

Bacterial Proteins↗
PubMed1999

Increased stress right ventricular activity on dual isotope perfusion SPECT: a sign of multivessel and/or left main coronary artery disease.

OBJECTIVES: This study sought to determine the anatomic and physiologic correlates of increased right ventricular (RV) activity on exercise single-photon emission computed tomography (SPECT) perfusion imaging in patients with coronary artery disease (CAD). BACKGROUND: Because SPECT perfusion imaging delineates relative myocardial blood flow, patients with global left ventricular (LV) hypoperfusion but normal RV perfusion may have increased relative RV tracer uptake as an indicator of multivessel CAD. METHODS: Rest thallium-201 and exercise 99mTc-sestamibi or 99mTc-tetrofosmin SPECT perfusion images were analyzed for peak RV and LV activity (RV:LV index) in 315 patients, including 240 patients with documented CAD, 39 patients with no significant CAD on arteriography, and a "normalcy" group of 36 patients with a low pre- and posttest probability of CAD. RESULTS: Resting RV:LV perfusion index ranged from 0.32 to 0.34 in each group, increasing to 0.36 with exercise in control and normalcy groups. CAD patients with the highest exercise RV:LV were those with severe left main CAD (or "left main equivalent"), with a lesser degree of proximal right CAD (0.51, n = 14, p < 0.001 vs. other groups). An exercise RV:LV >0.42 with a exercise:rest ratio >1.2 was present in 93% patients with this pattern of CAD, but was absent in 97% of the normalcy group, 92% of patients without significant angiographic CAD, and 100% of patients with proximal right CAD tighter than stenoses in the left system. CONCLUSIONS: Increased RV:LV activity exercise may occur in patients with acute RV strain, but is otherwise an indicator of exercise-induced RV:LV perfusion imbalance associated with severe CAD, particularly high-grade left main with less severe proximal right CAD.

Coronary Circulation↗
PubMed1999

Analysis of macromolecular structure and dynamics by electron cryo-microscopy.

Electron cryo-microscopy has yielded a wealth of detailed new information on structures of biological macromolecules ranging from alphabeta-tubulin at 3.7 A resolution to hepatitis B virus at 7.4 A resolution, as well as a number of membrane proteins at 6-8 A resolution. Much of this progress was made possible by recent advances in instrumentation and image processing techniques.

Animals↗
PubMed1999

Experimental melanin-induced uveitis in the Fischer 344 rat is inhibited by anti-CD4 monoclonal antibody, but not by mannose-6-phosphate.

Experimental melanin-induced uveitis (EMIU) is a rodent model of acute anterior uveitis which was described in 1993. We investigated strain susceptibility, and age and gender characteristics of the model, undertook histological and immunohistochemical studies to investigate underlying cellular mechanisms, and examined several treatment options. Rats were immunized with bovine ocular melanin (250 microg), and disease was followed by slit lamp examination. Lewis, Fischer 344 and Porton rats were found to be susceptible to EMIU, whereas Wistar-Furth, DA, and Hooded Wistar strains were resistant. EMIU was neither age- nor gender-dependent. In Fischer 344 rats, EMIU was characterized clinically by florid anterior segment inflammation. Histopathological findings included infiltration of ciliary body and iris with mononuclear cells and neutrophils. Both CD4+ and CD8+ T lymphocytes were prominent. Rats were then treated with intraperitoneal injections of anti-CD4, anti-CD8 or irrelevant isotype-matched MoAb on days -3, 0, 3, 6 and 9 with respect to melanin immunization. Incidence of uveitis was significantly reduced in rats treated with a non-depleting cocktail of anti-CD4 MoAbs (P = 0.007), whereas a depleting anti-CD8 antibody had no effect on the disease. Mannose-6-phosphate inhibits lymphocyte migration in some models of T cell-mediated inflammation. This simple sugar was administered to additional rats via intraperitoneal osmotic pumps for 14 days following disease induction, but did not influence the uveitis. We conclude that EMIU is controlled by CD4+ T cells, and disease may be abrogated by treatment with anti-CD4 MoAbs.

Animals↗
PubMed1999

A new model of orthotopic penetrating corneal transplantation in the sheep: graft survival, phenotypes of graft-infiltrating cells and local cytokine production.

BACKGROUND: Orthotopic penetrating keratoplasty in the sheep was developed as an outbred preclinical model to allow correlation of the cellular infiltrate during graft rejection with local production of cytokine mRNA. METHODS: Penetrating corneal autografts and allografts were performed in Merino sheep. Graft outcome was followed at the slit-lamp. Corneal infiltrates were examined by immunoperoxidase staining on postmortem specimens. Cytokine mRNA was detected by polymerase chain reaction. RESULTS: Corneal autografts survived indefinitely. Allografts became vascularized and underwent rejection at a median of 20 days postgraft. Both endothelial and epithelial rejection lines were observed. Immunohistochemical staining of rejecting grafts showed up-regulation of major histocompatibility complex class I molecules on corneal graft epithelium, damaged or absent graft endothelium and a marked, predominantly mononuclear cell infiltrate. CD4-positive T cells were observed in the graft within 2 days of the onset of rejection, followed several days later by CD8-positive T cells. Messenger RNA transcripts for interleukin (IL)-2, tumour necrosis factor (TNF)-alpha and IL-10 (but not for interferon (IFN)-gamma or IL-4) were found in autografted corneas. Proportionately, more allografts than autografts contained transcripts for IL-2 and TNF-alpha, and IFN-gamma was detected in three of four allografts. CONCLUSIONS: Corneal graft rejection in the sheep is macroscopically and histologically similar to human corneal graft rejection. Allografts become infiltrated by both CD4- and CD8-positive T cells and local production of pro-inflammatory cytokines occurs during graft rejection.

Animals↗
PubMed1998

Basic pathogenic mechanisms operating in experimental models of acute anterior uveitis.

Acute anterior uveitis is a recurrent inflammatory disease of the eye that occurs commonly, is distressing for the patient, and may have potentially blinding sequelae. The pathogenesis of the disease is poorly understood, and anti-inflammatory treatment is consequently non-specific and may be associated with significant complications. Animal models are a possible key to a better understanding of this disease. In one model, rats and mice develop a relatively short-lived anterior uveal inflammation almost immediately after systemic injection of bacterial endotoxin. Accumulating evidence suggests that cytokine production by resident uveal macrophages initiates endotoxin-induced uveitis which is characterized by an infiltration of neutrophils and mononuclear cells. A second model displays features in keeping with a delayed-type hypersensitivity immune response. Experimental melanin-induced uveitis is an acute recurrent uveitis with delayed onset but extended duration, observed when rats are immunized with bovine ocular melanin. Both animal models have clinical features in common with acute anterior uveitis, although experimental melanin-induced uveitis appears to mimic the human disease more closely. Novel treatment options to target implicated inflammatory cells and molecules are currently under consideration.

Acute Disease↗
PubMed1998

Uveal mast cells are not required for rodent uveitis.

Uveal mast cells have previously been considered to be vital mediators of experimental uveitis. We extended the study of these cells to experimental melanin-induced uveitis (EMIU), a recently described clinically relevant model, and re-examined their role in endotoxin-induced uveitis (EIU) using genetically mast cell-depleted mice on a single background. EMIU was induced in Fischer 344 rats by immunisation with bovine ocular melanin (250 microgram. Animals were killed immediately, and on days 1 and 3 of clinical disease. Numbers of uveal mast cells and the percentage of degranulated cells were counted in whole-mount preparations. There was no significant change in either measure across the selected time points. To induce EIU, normal and mast cell-depleted DBA/2 mice were injected with Escherichia coli lipopolysaccharide (400 microgram). Cells infiltrating the eye 24 h after injection were quantified in 5 micrometer ocular cross-sections. Disease was not significantly reduced in the mast cell-depleted mutants. We conclude that uveal mast cells are not required for the development of EMIU or, in contrast to earlier work, EIU.

Animals↗
PubMed1998

Mice deficient in tumor necrosis factor receptors p55 and p75, interleukin-4, or inducible nitric oxide synthase are susceptible to endotoxin-induced uveitis.

PURPOSE: To investigate the roles of tumor necrosis factor-alpha (TNF-alpha), interleukin-4 (IL-4), and inducible nitric oxide synthase (iNOS) in endotoxin-induced uveitis (EIU) using gene knock-out mice. METHODS: Mice (C57BL/6 x 129) either of normal phenotype or deficient in the genes encoding one or both tumor necrosis factor receptors (TNFR p55 and TNFR p75), IL-4, or iNOS were given footpad injections of 400 micrograms Escherichia coli lipopolysaccharide. Animals were killed 24 hours later, and infiltrating cells were counted on 5-micron ocular cross-sections through the optic nerve. RESULTS: All abnormal mouse phenotypes were susceptible to EIU. Yet, TNFR p55 and IL-4 gene knock-out mice experienced less ocular inflammation than control animals (P = 0.021 and 0.007, respectively), whereas disease was not reduced for iNOS-deficient mice. Mice deficient in TNFR p55 and TNFR p75 experienced milder EIU than mice lacking TNFR p75 alone (P = 0.046). CONCLUSIONS: Mice deficient in TNFR p55 and TNFR p75, IL-4, or iNOS retain the susceptibility to EIU, but TNF-alpha and IL-4 influence the influx of inflammatory cells to the eye during this disease.

Acute Disease↗
PubMed1998

First-pass radionuclide angiographic analysis with two regions of interest to improve left ventricular ejection fraction accuracy.

UNLABELLED: First-pass radionuclide angiographic (FPRNA) analysis, using the standard, single-fixed region of interest (ROI) drawn at end-diastole, often underestimates the left ventricular ejection fraction (LVEF) as determined by other standard techniques. This study examined the hypothesis that correction for the anatomic motion of the aortic valve plane toward the apex during systole, which results in improper inclusion of aortic counts within the single-fixed ROI, using a two-ROI method to compensate for this motion would eliminate this underestimation. METHODS: In 70 patients who underwent FPRNA and planar gated equilibrium radionuclide angiography (GERNA) on the same day, Fourier transform phase and amplitude images were used to generate functional maps of the aorta and the left ventricle on the FPRNA representative cycle. The region of low amplitude between the aorta and left ventricle, which corresponds to the degree of aortic valve plane motion, was used to guide the manual placement of two ROIs. The first was over the left ventricle at the end-diastole including the aortic valve plane area, and the second was a smaller end-systolic ROI drawn over the first ROI, excluding the valve plane area. RESULTS: Both the fixed- and dual-ROI FPRNA methods had excellent correlation with GERNA (r = 0.92 and 0.91, respectively). The mean FPRNA LVEF using a fixed ROI (45% +/- 14%) was significantly lower than GERNA (51% +/- 15%, p < 0.001), but the mean LVEF calculated from the dual-ROI (51% +/- 14%) was essentially identical to those obtained with GERNA. The method of manual placement of the two ROIs had extremely high levels of inter- and intraobserver reproducibility (r = 0.98 and 0.99, respectively). CONCLUSION: Despite good correlation, the standard, fixed-ROI method of FPRNA analysis systematically underestimates the LVEFs of GERNA. This problem can be eliminated by taking into account valve plane motion during the cardiac cycle by using Fourier-guided, dual-ROI analysis on FPRNA. These differences in methods and results should be considered when substituting or comparing LVEFs derived from these techniques.

Female↗
PubMed1997

Rethinking immunological privilege: implications for corneal and limbal stem cell transplantation.

Immunological privilege operates within the normal eye by multiple passive and active mechanisms, including antigen sequestration, maintenance of an immunosuppressive local environment and induction of apoptotic death in infiltrating cells of the immune system. Ocular privilege might have developed to protect the eye from the collateral damage associated with an inflammatory response to invading pathogens. Nevertheless, corneal grafts do undergo irreversible immunological rejection and, furthermore, corneal graft rejection is very similar at a histological level to the rejection processes that operate in vascularized organ grafts. Ocular privilege is thus relative. The question arises as to how corneal grafts are rejected in the face of so many mechanisms designed to prevent immune responses from operating inside the eye--a question that is still essentially unanswered.

Animals↗
PubMed1997

Relationships among oocyte-cumulus morphology, follicular atresia, initial chromatin configuration, and oocyte meiotic competence in the horse.

Horse oocytes with expanded (EX) cumuli appear to have greater meiotic competence than do horse oocytes with compact (CP) cumuli but are thought to come from atretic follicles. We evaluated the relationships among cumulus expansion, follicle viability, initial chromatin configuration, and meiotic competence of horse oocytes. Follicle walls were sectioned for histological examination, and the follicles were scraped to obtain the oocytes. Half of the oocytes were evaluated immediately and half were matured for 24 h in vitro. Cumulus expansion was significantly associated with follicle atresia. Initially, significantly more EX than CP oocytes had chromatin condensed into one mass within the germinal vesicle (CC configuration; 61% vs. 32%). After culture, significantly more EX than CP oocytes had matured (74% vs. 30%). The proportion of oocytes with the CC configuration was lowest in viable follicles and increased in follicles with slight to moderate atresia. The maturation rate of oocytes from viable follicles was significantly lower than for oocytes from follicles with slight or moderate atresia. The CC chromatin configuration appears to be associated with meiotic competence in horse oocytes. The association of follicle atresia with increased meiotic competence suggests that acquisition of meiotic competence is related to a loss of suppressive activity by the degenerating follicle.

Animals↗
PubMed1997

Influence of advanced recipient and donor age on the outcome of corneal transplantation. Australian Corneal Graft Registry.

AIMS: The aims of this study were to examine the influence of advanced recipient and donor age on the long term outcome of corneal transplantation. METHODS: Records of 1036 penetrating corneal grafts in recipients aged > or = 80 years at surgery (defined as the elderly subset) and 8092 donor corneas used for transplantation were obtained from the Australian Corneal Graft Register database, Kaplan-Meier graft survival plots were compared using log rank statistics. RESULTS: Elderly recipients constituted 15% of the recipient pool. The major indication for corneal transplantation in the elderly was bullous keratopathy. Graft survival fell with increasing recipient age (p < 0.00001); the major cause of graft failure was rejection (33%). The desired outcome in 51% of cases was to improve vision and in 42% of cases to relieve pain; 23% of elderly recipients achieved a Snellen acuity of 6/18 or better in the grafted eye and 66% recorded improved acuity after transplantation. Elderly recipients suffered more complications and comorbidities in the grafted eye than did younger recipients. Donor age (stratified in 10 year intervals) did not influence corneal graft survival significantly (p = 0.10). CONCLUSIONS: Elderly graft recipients fared less well after corneal transplantation than did younger recipients, but outcomes in terms of long term graft survival and visual rehabilitation were still good. Donor age did not affect graft survival.

Age Factors↗