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The effect of microgravity on cellulose synthesis using the model system of Acetobacter xylinum was the subject of recent investigations using The National Aeronautics and Space Administration's Reduced Gravity Laboratory, a modified KC-135 aircraft designed to produce 20 sec of microgravity during the top of a parabolic dive. Approximately 40 parabolas were executed per mission, and a period of 2 x g was integral to the pullout phase of each parabola. Cellulose biosynthesis was initiated on agar surfaces, liquid growth medium, and buffered glucose during parabolic flight and terminated with 2.0% sodium azide or 50.0% ethanol. While careful ground and in-flight controls indicated normal, compact ribbons of microbial cellulose, data from five different flights consistently showed that during progression into the parabola regime, the cellulose ribbons became splayed. This observation suggests that some element of the parabola (the 20 sec microgravity phase, the 20 sec 2 x g phase, or a combination of both) was responsible for this effect. Presumably the cellulose I alpha crystalline polymorph normally is produced under strain, and the microgravity/hypergravity combination may relieve this stress to produce splayed ribbons. An in-flight video microscopy analysis of bacterial motions during a parabolic series demonstrated that the bacteria continue to synthesize cellulose during all phases of the parabolic series. Thus, the splaying may be a reflection of a more subtle alteration such as reduction of intermicrofibrillar hydrogen bonding. Long-term microgravity exposures during spaceflight will be necessary to fully understand the cellulose alterations from the short-term microgravity experiments.

To study the effect of immunosuppression on the development of murine cytomegalovirus (MCMV) retinitis, BALB/c mice were immunosuppressed with methylprednisolone (a corticosteroid) and/or with antibodies against CD4+ and CD8+ T cells and inoculated with low-dose MCMV (5 x 10(2) plaque-forming units) by the supraciliary route. Nonimmunosuppressed mice inoculated with low-dose MCMV by the supraciliary route did not develop necrotizing retinitis. By contrast, 78-100% of immunosuppressed mice developed retinitis after inoculation of low-dose MCMV. To study the effect of depletion of individual T cell subsets, mice were depleted of either CD4+ or CD8+ T cells and inoculated with low-dose MCMV by the supraciliary route. The frequency of retinitis in CD4-depleted mice (30%) was not significantly different from that of nonimmunosuppressed control mice (0%). The frequency of retinitis in the CD8-depleted group (80%) was similar to that observed in mice immunosuppressed with corticosteroid alone (90.9%), with antibodies to both T cell subsets (100%), or with steroid and both T cell subset antibodies (100%). These results support the conclusion that the CD8+ T cell subset is responsible for control of ocular MCMV infection. Furthermore, these results suggest that the CD8+ T cell subset may be important in preventing ocular CMV infection in immunosuppressed patients.

The finding that codons for hydrophobic and hydrophilic amino acids are generally complemented by codons for hydrophilic and hydrophobic amino acids respectively has led to a novel observation. The antisense peptides coded for by the complementary DNA strand of biologically active peptides are able to bind their active sense counterparts with high specificity. Sense-antisense relationships have been observed in several peptide species as well as in receptor-ligand interactions. The idea that sense-antisense interactions are biologically relevant and indeed feasible among complex molecules prompts the examination of virus-host cell interactions. We propose such a sense-antisense interaction exists between the HIV glycoprotein gp120 and the intracellular domain of the HIV receptor CD4. This interaction is at a site which may be occupied by the proto oncogene product p56lck.

Immune-privileged sites, such as the the internal compartments of the eye, and perhaps the brain, are physiological adaptations that act to modify systemic immune responses such that effector mechanisms that invoke locally destructive inflammation are suppressed. In the case of the eye, the parenchymal cells of the iris and ciliary body create an intraocular microenvironment that alters both the induction and expression of immunity to antigens placed within the eye. The immunosuppressive properties of the intraocular microenvironment are mediated by cytokines, especially transforming growth factor-beta (TGF beta). This cytokine has been demonstrated to endow intraocular antigen-presenting cells with the capacity to induce an atypical or deviant form of immunity to intraocular antigens which is selectively deficient in T cells that mediate delayed hypersensitivity. Moreover, TGF beta, along with other intraocular factors, can impair the intraocular expression of pre-existing cell-mediated immunity by inhibiting antigen-driven activation of primed T cells. The strategies employed by the eye to engender specialized immune responses appropriate to its physiological functions are discussed in terms of other privileged sites such as the brain.

This report postulates that the activity of cellular proliferation along the surface of the retina during proliferative vitreoretinopathy (PVR) is reflected in the aggregate effect of proliferation-inducing growth factors in the vitreous. A method for quantifying the "net" proliferation-inducing capacity of an individual vitreous sample was developed and this assay was used to evaluate the vitreous proliferative activity in a model for experimental PVR. Vitreous was aspirated sequentially after onset of fibroblast-induced PVR in a rabbit model. A simple bioassay for the "aggregate" stimulating activity was developed and each sample was assigned a quantitative value in terms of "proliferation units" (PU). Experimental eyes demonstrated a wide range of stimulating activity (0-1765 PU), but control eyes showed uniformly low levels of activity (0-337 PU). Experimental eyes that ultimately developed retinal detachment displayed higher levels of proliferative activity than did those eyes destined to remain attached. The differences were statistically different by day 3, prior to the onset of clinical retinal changes. We conclude that quantification of vitreous proliferation-stimulating activity is possible and that this method might be useful for screening eyes at high risk for the development of recurrent retinal detachment from PVR.

Resistance of the anterior chamber (AC) of mouse eyes to expression of cell-mediated immunity can be overcome by pre-treating the eye with a dose of recombinant rat gamma-interferon (gamma IFN) that is of itself noninflammatory. To study the mechanism of this form of intraocular inflammation, cells of the tissues surrounding the AC (iris, ciliary body, cornea) were studied in vivo for alterations in phenotype and in vitro regarding their effects on antigen-driven T cell activation. The results indicate that gamma IFN: (1) induced class II major histocompatibility complex (MHC) expression on resident bone marrow-derived cells of iris and ciliary body (I/CB), but not the cornea; (2) led to recruitment of bone marrow-derived cells into the I/CB stroma; and (3) failed to induce class II MHC expression on ocular epithelial cells. Cell suspensions prepared from gamma IFN-treated I/CB superficially resembled normal I/CB cells in that neither were able to activate allogeneic T cells and both were able to suppress antigen-driven T cell activation in vitro. However, unlike cells from normal eyes, I/CB cells from gamma IFN-treated eyes suppressed T cell activation primarily through the secretion of prostaglandins. These results indicate that the ability of gamma IFN-treated eyes to display immunogenic inflammation probably does not result merely from the restoration of conventional antigen presenting cells to this environment, but appears to correlate with a critical change in the molecular mediators of immunosuppression. The findings are discussed in terms of the possibility that the eye may be able to respond to abrogation of its primary immunosuppressive microenvironment by erecting a secondary microenvironment that also is capable of suppressing immunogenic inflammation with a different set of antiinflammatory mediators.

The normal aqueous humor contains a variety of soluble immunosuppressive factors, including transforming growth factor-beta, alpha-melanocyte stimulating hormone, and vasoactive intestinal peptide. These factors are largely the secretory products of parenchymal cells of the iris and ciliary body. TGF beta has recently been shown to alter the functional capacity of intraocular antigen presenting cells, such that they are capable of inducing Anterior Chamber Associated Immune Deviation (ACAID). This deviant systemic immune response is characterized by an impaired capacity to mount an effective cell-mediated immune attack directed at antigens that are placed in, or arise within, the eye. A second property of immunosuppressive factors in aqueous humor is to suppress directly the expression of delayed hypersensitivity in the anterior chamber. In fact, even when the intraocular microenvironment is disturbed by local instillation of gamma-interferon, making it possible for limited expression of cell-mediated immunity in the eye, the microenvironment of the anterior chamber remains profoundly immunosuppressive. In this latter instance, prostaglandins replace TGF beta as the major molecular mediators of suppression in the aqueous humor. In the aggregate, factors present in the normal (or perturbed) intraocular microenvironment have the capacity to modify both the afferent and efferent limbs of the systemic immune response, and this accounts for the longstanding observation that the anterior chamber is an immunologically privileged site. Since evidence suggests that the eye can mobilize more than one molecular mechanism in its effort to limit the sight-destroying potential of immunogenic inflammation, we believe that elucidation of intraocular cytokines and factors that create and maintain an immunosuppressive microenvironment will contribute to a better understanding of the pathogenesis of the acute and chronic uveitides, especially those of autoimmune and infectious etiology.

Cellular proliferation is an important component in the pathogenesis of complex retinal detachments caused by proliferative vitreoretinopathy (PVR). We used flow cytometry to measure the proliferation of cells recovered from the vitreous cavity in an experimental model of tractional retinal detachment induced by homologous fibroblast injection. Two distinct populations of cells were detected. One population comprised smaller, dense cells representing mostly leukocytes. A second population of larger cells contained not only the injected fibroblasts but also high concentrations of host-derived cells with significant proliferative activity, whose number increased for 3 days following injection. Flow cytometry was useful for analysis of the recovered cells for concentration, morphologic features and proliferation. This technique may be applicable in the identification of patients at high risk for the development of PVR.

Cell suspensions prepared enzymatically from an ocular choroidal melanoma were cultured in vitro in an effort to generate (1) melanoma tumor cell lines and (2) tumor-infiltrating lymphocytes cytotoxic for ocular melanoma cells. Even though histologic study of the tumor did not show "significant" infiltrating bone marrow-derived cells, lymphocytes were generated readily in cultures to which interleukin-2 was added. Phenotypic analysis of the cultured lymphocytes indicated that T-cells, natural killer (NK) cells, and lymphokine-activated killer (LAK) cells were present. Moreover, functional studies of the cultured lymphocytes revealed NK activity, LAK activity, and most importantly, tumor antigen-specific cytotoxic T-cell activity. It was concluded that it is possible to obtain tumor cell lines and tumor-infiltrating lymphocytes from ocular tumors, both of which would be required if cellular immunotherapy of ocular tumors is contemplated. In addition, these results indicate that ocular melanomas can express unique tumor-specific antigens and that the immune system of a patient with such an ocular tumor can perceive these tumor antigens because antigen-specific precursor cytotoxic T-cells were present in the tumor-containing eye at the time of enucleation. The theoretic and therapeutic implications of these findings are discussed.

The anterior chamber of the eye is an immunologically privileged site. Over the past 15 years, numerous laboratories documented that the privileged status of this unique site is mediated by multifactorial immunoregulatory processes. Among the participating factors is the aqueous humor that circulates in the anterior chamber and is in contact with most of the tissues in the anterior segment of the eye. Recently, it was found that normal aqueous humor is a powerful inhibitor of antigen-driven T lymphocyte activation, but it spares other important functional properties of T cells. The spectrum of immune inhibitory properties resembles some of the activities of transforming growth factor-beta (TGF-beta), a polypeptide cytokine. Because of this similarity, the authors tried to determine if TGF-beta is present in aqueous humor and whether this cytokine could account for the lymphocyte inhibitory activity of this biologic fluid. They found TGF-beta in aqueous humor by dot-blot analysis. Using the CCL-64 mink lung epithelial cell bioassay for this compound, TGF-beta bioactivity was shown in aqueous humor from several different species, including human. In rabbit and human aqueous humor, most of the biologic activity was due to TGF-beta 2 (80-90%). Dose-response curves generated by using purified porcine TGF-beta showed that aqueous humor contained sufficient concentrations of TGF-beta to account for the observed inhibition in several assays for T cell activation and proliferation. Partial purification of the lymphocyte inhibitor in rabbit aqueous humor by size exclusion in high-performance liquid chromatography demonstrated that several lymphocyte inhibitory fractions contained TGF-beta bioactivity. Finally, neutralizing antisera to TGF-beta 2 were able to reverse most of the lymphocyte inhibitory activity of aqueous humor. It was concluded that TGF-beta was present in high concentration in normal aqueous humor and that this cytokine contributed to the immunosuppressive properties of aqueous humor.

Cytomegalovirus (CMV) retinitis is the most frequent infectious ocular complication of the acquired immune deficiency syndrome (AIDS). Currently, there are few animal models to study the virologic and immunologic factors which contribute to the pathogenesis of CMV retinitis. In these experiments, 1-2 X 10(4) PFU of murine cytomegalovirus (MCMV) was inoculated into the supraciliary space of BALB/c mice. Within three days of inoculation, moderate iridocyclitis was observed which progressed to necrosis of the ciliary body by day 14. Approximately 60% of the mice developed typical retinitis characterized by virus-infected cytomegalic cells in the retina and retinal pigment epithelium, focal retinal infiltrates, transition zones between uninvolved and involved retina, and optic neuritis. The remaining animals exhibited atypical retinitis characterized by non-specific retinal inflammation in the absence of obvious viral infection. This murine model of CMV retinitis shares some features with retinitis observed in AIDS patients with CMV retinitis and may be useful to evaluate the efficacy of immunologic and/or pharmacologic treatment strategies for CMV retinitis.

Immunologic privilege of the anterior chamber has been associated with the capacity to induce a unique form of deviant systemic immunity after anterior chamber (AC) immunization. However, the capacity of privilege to suppress expression of immunity in the AC has not been examined. We studied the ability of the AC to sustain immunogenic inflammation after direct antigen challenge (delayed hypersensitivity-DH) in C57BL/6 mice primed to M tuberculosis (MT) antigens. Compared to subcutaneous and subconjunctival sites where primed mice demonstrated vigorous and significant DH, the anterior chambers of these mice failed to develop signs of inflammation unless toxic doses of antigen were injected. In an attempt to promote intraocular DH, the AC's of MT-primed mice were pre-treated with subinflammatory intracameral injections of IFN-gamma, a cytokine that antagonizes TGF-beta, recruits antigen presenting cells (APC) from the blood and activates resident APC precursors. It was observed that AC injection of IFN-gamma, followed 3 days later by AC challenge with 200 ng of MT, resulted in severe intraocular inflammation only in primed (but not naive) mice. We conclude that the normal mouse AC resists DH unless its immunosuppressive microenvironment is abolished, as in these experiments by IFN-gamma. We propose that impaired expression of cell-mediated immunity is an important component of immune privilege of the AC.

One of the barriers to using belief networks for medical information retrieval is the computational cost of reasoning as the networks become large. Stochastic simulation algorithms allow one to compute approximations of probability values in a reasonable amount of time. We previously examined the performance of five stochastic simulation algorithms applied to four simple belief networks networks and found that the Self-Importance algorithm performed well. In this paper, we examine how the same five algorithms perform when applied to a belief network derived from the cardiovascular subtree of the Medical Subject Headings (MeSH). Both the Likelihood Weighting and Self-Importance algorithms perform well when applied to the MeSH-derived network, suggesting that stochastic simulation algorithms may provide reasonable performance in medical information retrieval settings.

Frozen storage of semen and embryos is now a well established part of the breeding of many eutherian mammals but it has not been applied to marsupials. This paper reports the first successful technique for the frozen preservation of marsupial spermatozoa. Semen was collected by electroejaculation under anaesthesia from a pool of five brushtail possums. The ejaculated semen was diluted 1:1 with Krebs Henseleit Ringer, centrifuged at 800 g for 5 min, resuspended in the test cryoprotectant media at 1, 2 and 5 x 10(6) spermatozoa mL-1 and 7, 10.5, 14 and 17.5% glycerol and then drawn up into 0.25 mL plastic straws. The spermatozoa were rapidly frozen in the vapour phase, 6 cm above liquid nitrogen, for 30 min before the straws were plunged into the liquid. Sperm motility was assessed blind for coded straws by phase-contrast microscopy on a warmed stage (35 degrees C), before freezing and after rapid thawing in a water bath at 37 degrees C (10 s). The highest recovery of both percentage motility (around 50-60%) and progressive motility (around 0.5-1 unit lower than prefreeze) occurred when spermatozoa were frozen and thawed in the presence of 17.5% glycerol. Recovery of motility was greater at the higher sperm concentrations (2 and 5 x 10(6) mL-1). There was no evidence of acrosomal damage or loss after freezing and thawing in high concentrations of glycerol. The only defect detected in spermatozoa subjected to the protocol was a variable tendency to bending of the neck region. This ranged from heads inclined at a slight angle to the tail through to complete flexure.(ABSTRACT TRUNCATED AT 250 WORDS)

WALT (Washington University's Approach to Lots of Text), is a prototype interface designed to support information retrieval research. The WALT interface serves as a "front end" to a wide array of retrieval engines including those based on Boolean retrieval, latent semantic indexing, term frequency--inverse document frequency, and Bayesian inference techniques. The WALT interface is composed of seven distinct components: a document examination component known as the Document Browsing Area; four navigation components called the Book Shelf, the Book Spine, the Table of Contents, and the Path Clipboard; a term-based information retrieval component called Control Panel; and a relevance feedback component known as the Reader Feedback Panel. WALT's most unique feature may be it's use of "book shelf" and "book spine" metaphors both to facilitate navigation and to provide a histogram-based display showing documents deemed appropriate for answering user queries.

Regulation of T cell-dependent immune responses is mediated in part by bone marrow-derived antigen presenting cells (APC) that (a) process and present antigens which engage the T cell receptor and (b) secrete cytokines that influence the threshold of T cell activation. The anterior chamber of the eye is lined by the corneal endothelium (which rests on a stroma and epithelium that is devoid of class II MHC + APC) and iris/ciliary body (which contain significant numbers of bone marrow-derived cells, one third of which are class II MHC +). When tested in vitro, these potential APCs fail to present antigens in a form that activates T cells. Moreover, iris/ciliary body cells actually suppress activation of T cells exposed to antigens on conventional APC. In addition, aqueous humor under normal circumstances contains factors (one of which is TGFB) that are potent inhibitors of antigen-driven T cell activation, but spare other aspects of T cell function. Evidence suggests that the bone marrow-derived cells in iris/ciliary body are the source of this factor. Thus, the anterior chamber contains powerful forces that can prevent induction and can suppress expression of T cell mediated immunity. It is proposed that these forces are responsible for immunologic privilege and anterior chamber associated immune deviation, and for suppressing pathologic proliferation and inflammation in the anterior segment of the eye.

Identification and analysis of antigen-activated lymphocytes from sites of ocular inflammation is important to understanding of the role of infiltrating immune effectors in ocular inflammatory disease. Unfortunately, few assays can distinguish activated lymphocytes from the antigen-irrelevant lymphocytes that randomly migrate to sites of inflammation. The authors describe a method that allows the quantitative recovery and identification of activated lymphocytes from mouse eyes. Recovered subconjunctival lymphocytes were simultaneously stained for specific cell-surface markers (with fluorescein-labeled antibodies) and for DNA content (with propidium iodide), then analyzed by flow cytometry. For any subpopulation of lymphocytes, the relative percentage and absolute number of cells in each phase of the cell cycle was determined. The activated subset of T and B cells was quantitated by determining the number of proliferating cells (ie, the number of cells in the S + G2 + M phases of the cell cycle). Using this method, T cell proliferation was found to be a specific component of the subconjunctival immunogenic inflammatory response induced by a local graft-versus-host reaction and by subconjunctival delayed hypersensitivity reactions. In addition, proliferating T cells could be distinguished from nonproliferating B cells produced by the subconjunctival inoculation of a T cell tumor.

Surgical treatment of pressure ulcers using the myocutaneous flap procedure is a relatively new approach for patients with spinal injuries. First, the pressure ulcers are treated conservatively; however, if they become large or infected, surgery is considered. We have performed approximately 1,500 of these surgeries in the past five years. Only 5% of the cases have developed complications. The primary complication experienced was small wound dehiscence, which we attributed to mechanical interference with wound healing. We attribute the overall success of these surgeries to the rigid protocol and interdisciplinary approach to management.

We reviewed the clinical findings, color photographs, and fluorescein angiograms of 147 patients (154 involved eyes) who participated in the Branch Vein Occlusion Study through the Bascom Palmer Eye Institute for the presence of macroaneurysms within or adjacent to the zone of branch vein occlusion. Four distinct categories of macroaneurysms included arterial, venous, capillary, and collateral-associated types. We identified 59 lesions among 25 of the 154 (16.2%) affected eyes. Intraretinal lipid exudation and hemorrhage were commonly observed around the lesions, but these complications usually did not affect visual acuity. Macroaneurysms were associated with capillary nonperfusion on fluorescein angiography. Retinal neovascularization occurred in eight of 25 eyes (32%) with macroaneurysms.

The immune response to antigens within the anterior chamber is deviant (anterior chamber associated immune deviation - ACAID) in that delayed hypersensitivity is deficient, whereas other immune effector modalities are intact. Experimental evidence indicates that the eye itself is critical to the induction of ACAID. We have examined the antigen processing and presenting potential of cells within the anterior segment of the eye, and have analyzed the potential immunoregulatory properties of these cells, their secretory products, and the aqueous humor itself. Evidence indicates that bone marrow-derived cells within the stroma of the iris and ciliary body inhibit antigen-driven T lymphocyte activation, although they themselves lack the capacity to present antigens to T lymphocytes. The mechanism is in part through secretion of immunosuppressive cytokines. Since aqueous humor contains similar cytokines, it is inferred that these molecules are constitutively secreted. We have determined that a major inhibitory molecule within normal aqueous humor is transforming growth factor-beta (TGFB), which inhibits antigen processing and presentation, and suppresses both T lymphocyte activation and certain aspects of non-specific inflammation. These effects also turn out to be properties of normal aqueous humor. These findings support the hypothesis that local features of the eye modify intraocular antigens such that an ACAID-inducing signal is produced. Experimental evidence suggests that these same properties may play a major role in suppressing efferent immune responses in the eye.

A single intraperitoneal dose of endotoxin (lipopolysaccharide or LPS) induces an acute inflammatory response in the uveal tract of rats. This inflammation is characterized by a breakdown of the blood/aqueous barrier within 3 hr after the LPS and the subsequent development of clinical disease and a cellular infiltrate. Early change in vascular permeability, clinical, and pathological changes were dose dependent with the two highest doses (100 micrograms or 500 micrograms) producing more severe pathology. Clinical and histopathologic abnormalities peaked at 24 hr and were resolving by 48 hr. Although clinical and histologic changes correlated well, the degree of breakdown of the blood/aqueous barrier at 3 hr failed to predict the extent of the cellular exudate measured by either clinical or histologic criteria. In addition, pharmacologic suppression of the early vascular permeability changes with indomethacin, cyproheptadine, or both agents failed to protect the animals consistently from subsequently developing significant clinical disease or cellular infiltrates on histopathology. LPS-induced uveitis in the rat provides a simple, reproducible model for ocular inflammation without requiring direct eye manipulation. The mediators responsible for the early vascular permeability in this model appear to be distinct from the mediators primarily responsible for the subsequent cellular exudate.

Bacterial endotoxin (lipopolysaccharide; LPS) is known to alter systemic vascular permeability, but this effect is difficult to monitor and quantitate in vivo. The ocular vessels of the rabbit are particularly sensitive to LPS. Using a slit lamp equipped with a fluorophotometer, we have adapted a method to quantitate endotoxin-induced ocular vascular permeability by measuring the accumulation of fluorescein isothiocyanate-conjugated albumin into the anterior chamber of the eye. After intravenous administration of Salmonella typhimurim LPS, the anterior chamber fluorescence and blood fluorescence were measured at intervals of 15 min and 1 h, respectively, over 4 h. In controls, maximal fluorescence in the anterior chamber was 3.1 +/- 0.8% of blood fluorescence. Doses of LPS as low as 0.25 mug/kg produced an ocular/serum fluorescence ratio of 17.6 +/- 4.9. A dose of 2.5 mug of LPS per kg tended to produce a higher ratio (68.0 +/- 7.1) than a larger dose of 50 mug/kg (30.5 +/- 16.6). Permeability changes began within 30 min after LPS, and the rate of dye accumulation varied over time, with maximal leakage usually occurring 90 min after LPS, but occasionally occurring much later. Repeated doses produced tolerance. By conjugating albumin to rhodamine and utilizing a second filter with the slit lamp to measure accumulation of this dye, we demonstrated the persistence of marked permeability during a period when intraocular fluorescein isothiocyanate and albumin levels were relatively constant. This methodology indicates that extremely low doses of LPS induce ocular permeability changes and that neither the time course nor the dose response of this effect is linear. Ocular fluorophotometry is a sensitive, noninvasive technique to study the dynamics and pharmacology of LPS-induced permeability changes.

BALB/c mice inoculated with herpes simplex virus type 1 in one anterior chamber develop retinitis with subsequent retinal necrosis in the contralateral eye. The clinical features of this disease were characterized with indirect ophthalmoscopy and fundus photography. Three phases of the disease were delineated: (1) acute retinitis; (2) retinal necrosis; and (3) resolution; the clinical findings in each phase were correlated with the microscopic features. In addition, we compared the virus titers from individual animals with and without clinical evidence of retinitis to demonstrate that retinal inflammation correlated with the titer of virus in the uninoculated eye. This animal model is useful for the analysis of the clinical, virologic and immunologic manifestations of herpetic retinitis.

Platelet counting by means of the Coulter Thrombocounter, using the Thrombofuge method for specimen preparation has been evaluated in order to determine the cause of discrepancies in results obtained in interlaboratory quality assessment surveys. The method was assessed for accuracy, precision, drift and carry-over. When the method was used, as in routine practice, some discrepancies occurred; an important source of error was identified as being due to the level of sedimented plasma layer from which samples are removed. When the method was performed strictly in accordance with the manufacturer's instructions results were generally satisfactory and comparable to those obtained with the whole blood reference method, although, even with this standardized technique, the Thrombo-fuge tended to give higher platelet counts than the reference method with counts above 200 X 10(9)/l. This discrepancy to be independent of PCV, MCV or other identifiable factors.

Platelet volume was measured in 30 healthy controls and 87 diabetic patients, the latter subdivided according to the absence, presence and severity of retinopathy, to investigate if platelet size is related to microangiopathy. The platelet volume of the whole diabetic population was increased (p less than 0.05) due to a higher percentage of large elements (p less than 0.05). The patients with various degrees of retinopathy had similar increases (p less than 0.05) in their platelet size, while those without complications occupied an intermediate position between normal controls and retinopathy patients. It is concluded that: (i) increased platelet size accompanies diabetic retinopathy, irrespective of its severity, and (ii) patients without this complication form a heterogeneous group, some of which already have alterations of platelet volume. The role of these abnormalities in the development and progression of diabetic microangiopathy remains to be established.

Following uniocular anterior chamber (a.c.) inoculation of HSV-1 into BALB/c mice, the architecture of the uninoculated eye is destroyed by a pan-retinal inflammatory process within 10 days. BALB/c inoculated with HSV-1 via the a.c. route also develop anterior chamber associated immune deviation (ACAID), one characteristic of which is impairment of virus-specific delayed hypersensitivity (DH) responsiveness. To determine whether other strains of mice develop ACAID and contralateral retinitis, DBA/2 and C57BL/6 mice were inoculated with HSV-1 (KOS strain) via the a.c. route. At intervals after inoculation, animals were examined clinically for evidence of retinitis in the uninoculated eye and were either (1) sacrificed for virus recovery studies or (2) ear-challenged for DH assays. Seven of 15 DBA/2 mice had clinical evidence of retinitis in the uninoculated eye by day 10 post-inoculation (p.i.). At this time, the average titer of virus in the uninoculated eyes was 3.37 log10 PFU/ml. Animals of this strain also had significantly impaired HSV-1 virus-specific DH responses consistent with ACAID. No (0/12) C57BL/6 developed contralateral retinitis; at day 10 p.i., the average virus titer in the uninoculated eyes of C57BL/6 mice was 1.10 log10 PFU/ml. Following a.c. inoculation of HSV-1, C57BL/6 mice developed vigorous DH responses comparable to those of subcutaneously immunized, DH-positive animals. The results of these experiments suggest that different strains of mice vary in their susceptibility to HSV-1 retinitis and that the development of retinitis is linked to the amount of virus in the uninoculated eye.(ABSTRACT TRUNCATED AT 250 WORDS)

A series of 600 pseudophakic retinal detachments in 578 patients undergoing surgical repair between 1974 and 1984 was reviewed. Patients with previous retinal surgery of less than six months follow-up were excluded. The series included 395 iris-fixated (IF) lenses, 130 anterior chamber (AC) lenses, and 75 posterior chamber (PC) lenses. The overall success rate for retinal detachment was 88% but was significantly better in the PC lens group and significantly worse in the AC lens group. Forty-one percent of all cases achieved 20/40 visual acuity or better, although the AC lens group did worse (28%), while the PC lens group did significantly better (48%). Risk factors that were predictive of failure also were identified. Many of these factors occurred more frequently in the AC lens group and probably are related to the overall worse outcome in eyes with AC lens implants. The implications of these results for retinal and cataract surgeons are discussed.

Patients with aplastic anaemia have a relatively specific immune defect--leucopenia with neutropenia. We have carried out a retrospective analysis of infective episodes in 11 patients with aplastic anaemia. 5723 follow-up days accrued and 29 infective episodes were documented. Overall the number of infective episodes was significantly associated with the mean white cell and monocyte counts (r = 0.59, 0.02 less than P less than 0.05) but not with length of follow-up, presentation values of white cell, neutrophil and monocyte counts, or mean neutrophil count. The patients appeared to divide clinically into two groups, those at low risk (seven patients) and those high risk (four patients) of infection. Patients in the high risk group had significantly more infections (P = 0.01) and significantly lower monocyte counts (0.02 less than P less than 0.05) than patients in the low risk group. These results are in contrast to similar studies in patients with chemotherapy-induced neutropenia; in our patients the overall rate and severity of infection was low, Gram negative infections were uncommon and monocytopenia appeared to be of greater importance than neutropenia in determining susceptibility to infection.

The development of the trophic level concept(1) is described and the causes of its failure as a predictive model in ecology are examined. A defence(2) of and modifications to the trophic level concept are reviewed. A trend towards taxonomic food web analysis is identified leading to models that are independent of the trophic level approach., (Copyright © 1987. Published by Elsevier Ltd.)

When engineers function in a biomechanics clinic team, collecting information for the definition and solution of problems, and developing solutions in a logical pattern, then establishment of criteria by which to judge actions and results at various stages are essential. In our procedures, we make the most general statement we can which will indicate the goal we have for the patient or the type of patient being considered. Based on this, we proceed with a breakdown of the goal into increasingly explicit statements keeping the objective in focus. Eventually, with the criteria we need in order to decide "yes or no" to any aspect of the solution developing, we consider the constraints. These we see as imposed by the life-requirements of the patient, the effects of the physical environment, the limitations imposed by the social environment, and the limits of available technology including the skills of the designers, the manufacturing capabilities and the distribution system with which the designers must cope. When a "checklist" of requirements and limits has been established, the "critical eye" watches over the rehabilitation engineer as he in effect watches over himself!

In 16 diabetic patients with microangiopathy, survival of 111In-labelled autologous platelets, mean platelet volume, megathrombocyte index, spontaneous and ADP-induced platelet aggregation, platelet retention, beta-thromboglobulin, von Willebrand factor and factor VIII-related antigen were measured; the splenic uptake of radioactive label was quantitated in six patients. Compared with normal subjects, increased platelet aggregation (p less than 0.01), von Willebrand factor (p less than 0.02) and factor VIII-related antigen (p less than 0.02) were observed. Platelet survival was shortened in two patients. It correlated inversely with the splenic radioactivity uptake (r = -0.95; p less than 0.01), suggesting that platelets ended their life in the spleen, not in the microcirculation. No significant relationships were found between the various tests performed, nor between these and the severity of microangiopathy or other clinical data. In spite of the evidence for altered platelet function in patients with diabetic microangiopathy, currently available tests are not specific enough to clarify the nature of these changes or their possible pathogenic significance.

Herpes simplex virus type 1 (HSV-1) inoculated intracamerally into one anterior chamber of a BALB/c mouse produces retinitis in the uninoculated contralateral eye within 7 to 10 days while the retina of the inoculated eye is spared. In sharp contrast, animals receiving HSV type 2 (HSV-2) by the anterior chamber route develop a dramatic retinitis in the inoculated eye by day 7 postinoculation while the retina of the contralateral eye remains uninvolved. Histopathologic examination of retinal destruction in the HSV-2-infected ipsilateral eye revealed features which were distinct from those observed in the contralateral eye of HSV-1-infected animals. Whereas HSV-1 produced a rapid, explosive, retinitis which led to destruction of all cell layers of the contralateral retina, HSV-2 induced a retinitis in the ipsilateral eye that was more gradual in onset. Ipsilateral HSV-2 retinitis was characterized initially by disruption of the ganglion and inner nuclear layers which progressed by day 10 to 14 to complete replacement of the retina by a fibrocellular scar. These changes were dominated by a vigorous mononuclear cell infiltrate, a feature not observed in the HSV-1-infected contralateral retinitis. These results suggest that experimental retinitides produced by HSV-1 and HSV-2 are of diverse pathogenesis.

Injection of the KOS strain of herpes simplex virus type 1 into the anterior chamber of one eye of a BALB/c mouse produces bilateral retinal inflammation which progresses in the contralateral eye to total retinal necrosis by day 10 post-inoculation. Although both immune and direct viral cytopathic effects have been proposed as causes of the initial infiltration, the precise mechanism(s) of the contralateral retinal necrosis remains uncertain. In this study, histopathological examination of the uninoculated eyes of HSV-1 injected BALB/c mice revealed the presence of vitreous traction against the internal limiting membrane of the retina which was associated with separation of the nerve fiber layer from the underlying ganglion cell layer. This separation resulted in avulsion of Mueller cell footplates and retinal vessels, hemorrhage into the schisis cavity and disruption of the underlying retinal architecture. The schisis began focally on day 8 or 9 post-inoculation, and the entire retina of most animals was involved by day 10 or 11. These results suggest that retinal schisis involving separation of the nerve fiber layer from the ganglion cell layer contributes to necrosis of the retina in the uninoculated contralateral eye.

Adaptive histogram equalization (AHE) is a method for adaptive contrast enhancement of digital images. It is an automatic, reproducible method for the simultaneous viewing of contrast within a digital image with a large dynamic range. Recent experiments have shown that in specific cases, there is no significant difference in the ability of AHE and linear intensity windowing to display gray-scale contrast. More recently, a variant of AHE which limits the allowed contrast enhancement of the image has been proposed. This contrast-limited adaptive histogram equalization (CLAHE) produces images in which the noise content of an image is not excessively enhanced, but in which sufficient contrast is provided for the visualization of structures within the image. Images processed with CLAHE have a more natural appearance and facilitate the comparison of different areas of an image. However, the reduced contrast enhancement of CLAHE may hinder the ability of an observer to detect the presence of some significant gray-scale contrast. In this report, a psychophysical observer experiment was performed to determine if there is a significant difference in the ability of AHE and CLAHE to depict gray-scale contrast. Observers were presented with computed tomography (CT) images of the chest processed with AHE and CLAHE. Subtle artificial lesions were introduced into some images. The observers were asked to rate their confidence regarding the presence of the lesions; this rating-scale data was analyzed using receiver operating characteristic (ROC) curve techniques. These ROC curves were compared for significant differences in the observers' performances. In this report, no difference was found in the abilities of AHE and CLAHE to depict contrast information.

A reference method has been defined for platelet counting by counting chamber haemocytometry, and a procedure has been developed, using platelet rich plasma (PRP) and a Coulter ZBI counter which provides a reliable, rapid and relatively simple method for platelet counting which is closely comparable to the reference method and can thus be used both as a secondary reference method and a routine method. The optimal method for obtaining PRP from EDTA blood was by augmented sedimentation with Boyum's methyl cellulose-metrizoate mixture at sp. gr. 1.08. This was shown to yield a platelet suspension which reflects closely the platelet content of the original blood. Calibration of electronic counters for platelet counting requires material which is stable and which parallels natural human platelets in size, distribution and other physical characteristics. A suspension of glutaraldehyde-fixed human platelets in glycerol appears to be suitable as a reference preparation. Its method of production is described.

Development of the eyelids and cornea in repeated epilation (Er/Er) mice is characterized by fusion of the tarsal conjunctiva to the epithelia of the bulbar conjunctiva and cornea. We investigated the ultrastructural features of this malformation and tested for abnormal expression of filaggrin by immunofluorescence. Heterozygous (Er/+) breeding stock were mated and 13,14,15, and 19-day-old embryos were studied by light and electron microscopy. Fusion occurred in all Er/Er specimens and was associated with abnormal migration of surface ectodermal cells onto the cornea. Immunofluorescence studies with antimouse filaggrin antibody on day 13 and day 15 revealed the presence of filaggrin precursors in the fused epithelia of mutants, but not in normal corneal or conjunctival epithelia. The results suggest defective regulation of the synthesis of cellular proteins and altered cell surface properties in the Er/Er ocular epithelia.

The function ex vivo of autologous platelets, labelled with 111In, was evaluated at various times following injection by comparing the retention on foreign surfaces of radioactivity with the retention of total platelets (represented almost entirely by unlabelled and therefore unmanipulated platelets) after the application of fresh un-anticoagulated whole blood to (a) filter paper and (b) glass bead columns. Relative retentions were similar for the two materials, with labelled platelet retention being about 80% that of native platelet retention. Prior to injection, when labelled platelets were returned to an excess of freshly drawn whole blood, retention of radioactivity was greater than that of native platelets with a ratio significantly greater than that seen with labelled platelets tested ex vivo. Filter paper retention provides a simple technique which may be useful for the evaluation of labelled platelet function as a function of platelet age and also, with further standardisation, as an inexpensive rapid test of unlabelled platelet function.