The Relativistic Proton Spectrometer: A Review of Sensor Performance, Applications, and Science

The Relativistic Proton Spectrometer (RPS) on the Van Allen Probes spacecraft was a particle spectrometer designed to measure the flux, angular distribution, and energy spectrum of protons from ∼ 60 MeV to ∼ 2000 MeV . RPS provided new information about the inner Van Allen belt: a nearby region of space that had been relatively unexplored because of the difficulties of making charged particle measurements there and the associated hazards to satellite operations. We met the primary mission objective of providing accurate data for the AP9 radiation specification model at the high energies where there were little to no data prior to the Van Allen Probes mission. Along the way, we were able to demonstrate the long-term stability of parts of the Inner Belt by comparison with short-lived space science missions that operated decades prior to Van Allen Probes. The most significant surprises were the agreement between RPS and some of those historical measurements and the discovery of a trapped population of > 30 MeV leptons at the outer edge of the inner belt. This end-of-mission paper summarizes the instrument performance, calibration, data products, and specific science and engineering results, and includes suggestions for future investigations of intense radiation fields like those found within the inner belt.

Empirically Estimated Electron Lifetimes in the Earth's Radiation Belts: Van Allen Probe Observations

We use measurements from NASA's Van Allen Probes to calculate the decay time constants for electrons over a wide range of energies (30 keV to 4 MeV) and L values ( L = 1.3-6.0) in the Earth's radiation belts. Using an automated routine to identify flux decay events, we construct a large database of lifetimes for near-equatorially mirroring electrons over a 5-year interval. We provide the first accurate estimates of the long decay timescales in the inner zone ( ∼ 100 days), which are highly resolved in energy and free from proton contamination. In the slot region and outer zone, we compare our lifetime calculations with prior empirical estimates and find good quantitative agreement (lifetimes ∼ 1-20 days). The comparisons suggest that some prior estimates may overestimate electron lifetimes between L ≈ 2.5-4.5 due to instrumental effects and/or background contamination. Previously reported two-stage decays are explicitly demonstrated to be a consequence of using integral fluxes.

Szt2, a novel gene for seizure threshold in mice

In a chemical mutagenesis screen we identified Szt2 (seizure threshold 2) as a gene that confers low seizure threshold to mice and may also enhance epileptogenesis. The semidominant phenotype was mapped to Chromosome 4 and narrowed further to a critical interval of approximately 650 kb. A novel large (> 10 kb) transcript in the critical interval was found to have fourfold increased steady-state expression at the RNA level in Szt2 homozygous mutant brain. The corresponding 72 exon gene encodes a 378-kD protein with no significant or suggestive sequence similarities to any other protein. The mutant allele of Szt2 contains a splice donor mutation after exon 32, predicting transcriptional read-through, translational frameshift and premature stop. A second Szt2 allele, containing a gene-trap mutation in exon 21, also conferred a low seizure threshold and increased RNA expression, but unlike the original allele, some gene-trap homozygotes died embryonically. Szt2 is transcribed in many tissues, with the highest expression in brain, and it is also expressed during embryonic development. Szt2 is highly conserved in evolution, with a clear, single orthologue found in all land vertebrates and in many invertebrates. Interestingly, in mammals the Szt2 gene resides in a highly conserved head-to-head configuration with Med8 (which encodes a Mediator complex subunit), separated by only 91 nt. While the biological function of Szt2 remains unknown, its high conservation, unique structure and effect on seizure threshold suggest that it serves an important role in the central nervous system.

Mouse H6 Homeobox 1 (Hmx1) mutations cause cranial abnormalities and reduced body mass

BACKGROUND

The H6 homeobox genes Hmx1, Hmx2, and Hmx3 (also known as Nkx5-3; Nkx5-2 and Nkx5-1, respectively), compose a family within the NKL subclass of the ANTP class of homeobox genes. Hmx gene family expression is mostly limited to sensory organs, branchial (pharyngeal) arches, and the rostral part of the central nervous system. Targeted mutation of either Hmx2 or Hmx3 in mice disrupts the vestibular system. These tandemly duplicated genes have functional overlap as indicated by the loss of the entire vestibular system in double mutants. Mutants have not been described for Hmx1, the most divergent of the family.

RESULTS

Dumbo (dmbo) is a semi-lethal mouse mutation that was recovered in a forward genetic mutagenesis screen. Mutants exhibit enlarged ear pinnae with a distinctive ventrolateral shift. Here, we report on the basis of this phenotype and other abnormalities in the mutant, and identify the causative mutation as being an allele of Hmx1. Examination of dumbo skulls revealed only subtle changes in cranial bone morphology, namely hyperplasia of the gonial bone and irregularities along the caudal border of the squamous temporal bone. Other nearby otic structures were unaffected. The semilethality of dmbo/dmbo mice was found to be ~40%, occured perinatally, and was associated with exencephaly. Surviving mutants of both sexes exhibited reduced body mass from ~3 days postpartum onwards. Most dumbo adults were microphthalmic. Recombinant animals and specific deletion-bearing mice were used to map the dumbo mutation to a 1.8 Mb region on Chromosome 5. DNA sequencing of genes in this region revealed a nonsense mutation in the first exon of H6 Homeobox 1 (Hmx1; also Nkx5-3). An independent spontaneous allele called misplaced ears (mpe) was also identified, confirming Hmx1 as the responsible mutant gene.

CONCLUSION

The divergence of Hmx1 from its paralogs is reflected by different and diverse developmental roles exclusive of vestibular involvement. Additionally, these mutant Hmx1 alleles represent the first mouse models of a recently-discovered Oculo-Auricular syndrome caused by mutation of the orthologous human gene.

Corneal tattoo with tea infusion

Except in animal models of cataractogenesis, the literature on the effects of tea infusion on ocular tissue is scant. In our patient, prolonged exposure to tea infusion may have led to a hypesthetic cornea with secondary limbal stem cell loss. In turn, the eye developed keratinization and corneal neovascularization.

Surgical Feasibility Study of a Novel Polytetrafluoroethylene Graft Design for the Treatment of Peripheral Arterial Disease

Disturbed flow patterns, material mismatch, and surgical injury are often cited as being significant contributors to failure at the distal end of femoropopliteal bypass grafts. The objective of this research is to propose a novel bypass graft design concept which seeks to reduce the incidence of disturbed flow in the bypass junction and to establish the surgical feasibility of the proposed device. A preliminary evaluation of the hemodynamic benefit associated with the proposed device was made using computational fluid dynamics. A prototype of the device was then constructed from commercially available materials, and it was prepared for implantation into the aorta of a pig. The computational model of the proposed device showed that significant flow correction was occurring in the in vitro model due to the geometric configuration of the design. The magnitude of the peak wall shear stress in the recirculation region was noted to decrease by 78%. Surgical feasibility of the proposed device was verified by successful implantation into the aorta of the pig. The pig was sacrificed after 7 weeks, the graft and host artery were excised, and histological examination downstream from the distal junction showed that intimal hyperplasia had developed in the host artery. The proposed device is surgically feasible and may offer a significant hemodynamic advantage over current graft designs.

Emerging guidelines for use of NSAID therapy to optimize cataract surgery patient care

This analysis provides guidelines for the proper use of topical ophthalmic nonsteroidal anti-inflammatory drugs (NSAIDs), discusses their effect on inflammation, and their role in the prevention of cystoid macular edema (CME). A novel treatment strategy is presented for recommended topical ophthalmic NSAID dosing in patient populations based on risk factors for CME. The article reviews current topical ophthalmic NSAIDs, as well as a newest generation of pro-drug NSAIDs. In addition, combination therapy of NSAIDs and corticosteroids are discussed, along with a general review of therapeutic guidelines for dosing regimens, and benefits and risks of therapy. The goal of this analysis is to provide a suggested therapeutic regimen with topical NSAIDs to assist in achieving optimal clinical and functional outcomes.

Long-term survival of allogeneic donor cell-derived corneal epithelium in limbal deficient rabbits

PURPOSE

To investigate the capability of cultivated allogeneic epithelial stem cells to restore a functional ocular surface in a limbal deficient cornea; to verify the long term survival of epithelial allograft; and to examine the host immune response to heterologous cell transplant in a rabbit model.

METHODS

Limbal deficiency was established by performing limbectomy on rabbits (n = 100). Corneal epithelial stem cells were obtained from the limbus and replicated in vitro without a supporting layer. The cell (3 x 10(5)) suspension was then transplanted via topical application as eye drops. Animals were divided into allograft, autograft, and control groups. Females were used as recipients and males as donors for the allograft. Corneas were collected at 7, 14, 21, 40 days as well as 2, 3, 7 and 8 months after cell transplantation. Experimental corneas were evaluated by histology, immunofluorescence, immunohistochemistry and Y chromosome analysis.

RESULTS

A well-differentiated corneal epithelium was recognized at 14 to 40 days after cell transfer overlying an infiltrated corneal stroma. Corneal re-epitheliazation was confirmed in 31 of 36 allograft corneas. No significant immune rejection was noted. Stromal abnormality caused by previous limbal deficiency was mostly resolved three months after the regeneration of corneal epithelium.

CONCLUSIONS

Transplanted corneal epithelial stem cells were able to differentiate into normal corneal epithelium in vivo without the use of membrane scaffolding. This non-autologous donor cell-derived corneal epithelium survived up to 8 months without immunosuppression and was able to reverse the stromal scarring. Thus, cultivated epithelial stem cells have great potential as an alternative to multiple-surgical procedures in the treatment of limbal deficiency states.

The role of apoptosis in the pathogenesis of Fuchs endothelial dystrophy of the cornea

OBJECTIVE

To investigate the potential role of apoptosis in the pathogenesis of Fuchs endothelial dystrophy of the cornea.

METHODS

Twenty-one corneal buttons from patients with Fuchs dystrophy and 15 control corneas were studied. Apoptosis was assessed by the in situ end-labeling of double-stranded DNA breaks, and by immunohistochemical characterization of cellular markers associated with apoptosis (Fas, FasL, Bcl-2, and Bax). Expression of Bcl-2 and Bax mRNA in the corneal stroma and endothelium was separately analyzed by a semiquantitative reverse transcriptase polymerase chain reaction. Furthermore, cultivated keratocytes generated from diseased corneal buttons and donor rims were exposed to camptothecin, an apoptotic inducer, for 6 and 24 hours. They were then examined for protein and messenger RNA (mRNA) expression of apoptotic regulatory molecules.

RESULTS

DNA fragmentation was seen in the epithelium, stroma, and endothelium in 6 of 7 corneas with Fuchs dystrophy. A statistically significant difference was identified in the expression of Bax and its mRNA in the stroma, but not in the endothelium of Fuchs dystrophy corneas. Following exposure to camptothecin, keratocytes from patients with Fuchs dystrophy responded with an increased level of Bax and a low level of Bcl-2. This trend was distinctively different from the response of normal keratocytes.

CONCLUSIONS

The evidence in this study points to a disease-related disturbance in the regulation of apoptosis in Fuchs dystrophy. Our findings suggest that excessive apoptosis may be an important mechanism in the pathogenesis of Fuchs dystrophy.

In vitro susceptibilities of bacterial ocular isolates to fluoroquinolones

PURPOSE

To evaluate and compare the in vitro antimicrobial activity of levofloxacin versus ciprofloxacin and ofloxacin against ocular isolates from patients with bacterial conjunctivitis.

METHODS

The in vitro antimicrobial susceptibilities of ocular isolates to levofloxacin, ofloxacin, and ciprofloxacin were determined using both the agar disk diffusion and broth dilution methods.

RESULTS

Disk diffusion susceptibility testing disclosed that 99% (100 of 101 isolates) of gram-negative isolates and 98% (127 of 129 isolates) of gram-positive isolates were susceptible to levofloxacin; 96% (97 of 101 isolates) of gram-negative isolates and 78% (100 of 129 isolates) of gram-positive isolates were susceptible to ofloxacin; and 94% (95 of 101 isolates) of gram-negative isolates and 61% (79 of 129 isolates) of gram-positive isolates were susceptible to ciprofloxacin. Broth dilution testing disclosed that 99% (72 of 73 isolates) of gram-negative isolates and 98% (111 of 113 isolates) of gram-positive isolates were susceptible to levofloxacin; 96% (70 of 73 isolates) of gram-negative isolates and 92% (104 of 113 isolates) of gram-positive isolates were susceptible to ofloxacin; and 95% (69 of 73 isolates) of gram-negative isolates and 82% (93 of 113 isolates) of gram-positive isolates were susceptible to ciprofloxacin.

CONCLUSIONS

In this study, levofloxacin demonstrated superior in vitro activity against human bacterial conjunctival isolates compared with either ofloxacin or ciprofloxacin (levofloxacin > ofloxacin > ciprofloxacin).

The role of matrix metalloproteinases in ulcerative keratolysis associated with perioperative diclofenac use

OBJECTIVE

To investigate the role of matrix metalloproteinases (MMPs) in the pathogenesis of ulcerative keratolysis associated with topical use of generic diclofenac preoperatively and postoperatively. To characterize the inflammatory response of the cornea in this case of ulcerative keratolysis.

DESIGN

Case report with clinicopathologic correlation.

MAIN OUTCOME MEASURES

Corneal culture for microbial growth. Clinical and histopathologic examinations including routine histolopathologic, immunofluorescent, and immunohistochemical studies.

RESULTS

Microscopic examination of the corneal button disclosed fibrinous material with neutrophils and mononuclear inflammatory cells. The corneal epithelial basement membrane was irregularly thickened and patchy. Immunohistochemical staining detected weak staining of MMP-1 and a strong presence of MMP-8 in the epithelium. MMP-8 and 9 were also present in areas of leukocytic infiltration. MMP-2 appeared in a few stromal cells. Macrophages and leukocytes were the predominant infiltrating cells.

CONCLUSIONS

A nonspecific inflammatory response occurred in this case of ulcerative keratolysis. Corneal epithelial cells are capable of secreting MMP-1 and 8 and may participate in the stromal degradation and repair process of the ulcerative keratolysis associated with topical nonsteroidol antiinflammatory use.

Management of flap striae

There have been no comprehensive investigations of striae after LASIK. The ophthalmic literature has few reports, and no one consistent therapy has been recommended. Striae are relatively uncommon; nevertheless, refractive surgeons need a systematic approach in prevention and therapy for striae. Careful flap handling and positioning can prevent many striae. Early recognition is very important and makes treatment significantly more likely to eliminate or reduce the striae. If the striae are identified within 24 hours, lifting and refloating will likely result in resolution of the striae. If the striae are more imbedded and have been present longer, additional techniques, such as those discussed, are helpful. New techniques will likely be developed because of an increase in lamellar procedures and an increase in the occurrence of striae.

Molecular and functional mapping of the piebald deletion complex on mouse chromosome 14

The piebald deletion complex is a set of overlapping chromosomal deficiencies surrounding the endothelin receptor B locus collected during the Oak Ridge specific-locus-test mutagenesis screen. These chromosomal deletions represent an important resource for genetic studies to dissect the functional content of a genomic region, and several developmental defects have been associated with mice homozygous for distinct piebald deletion alleles. We have used molecular markers to order the breakpoints for 20 deletion alleles that span a 15.7-18-cM region of distal mouse chromosome 14. Large deletions covering as much as 11 cM have been identified that will be useful for regionally directed mutagenesis screens to reveal recessive mutations that disrupt development. Deletions identified as having breakpoints positioned within previously described critical regions have been used in complementation studies to further define the functional intervals associated with the developmental defects. This has focused our efforts to isolate genes required for newborn respiration and survival, skeletal patterning and morphogenesis, and central nervous system development.

Perioperative Microbiologic Profile of the Conjunctiva in Photorefractive Keratectomy

PURPOSE

Therapeutic soft contact lenses are used commonly as an adjunctive treatment after photorefractive keratectomy (PRK) to decrease postoperative pain caused by the movement of lids over the corneal epithelial defect and to facilitate epithelial healing. We assessed the microbiological profile of the conjunctiva of patients undergoing PRK for myopia, before and after the concurrent use of a therapeutic soft contact lens, and compared the effect on ocular bacterial colonization of prophylactic administration of topical tobramycin 0.3% versus ofloxacin 0.3%.

METHODS

Forty-three consecutive eyes from 37 patients underwent PRK for myopia or myopic astigmatism. Eyes were assigned randomly to prophylactic antibacterial treatment with either topical ofloxacin 0.3% or tobramycin 0.3%, applied prior to surgery and three times daily after surgery until therapeutic soft contact lens removal. Material from the conjunctival sac was obtained for bacteriologic cultures prior to surgery. Clinical evaluation of all eyes was conducted prospectively. Three days after PRK, the therapeutic soft contact lenses were removed and cultured. Cultures from the conjunctival sac were then repeated.

RESULTS

No statistically significant differences were observed in culture positivity between the two groups of eyes, in spite of some positive preoperative and postoperative cultures. Only one out of 43 eyes (assigned to the ofloxacin group) developed a peripheral corneal infiltrate. The corneal infiltrate healed completely without sequelae using antibiotic and corticosteroid therapy.

CONCLUSIONS

The use of therapeutic soft contact lenses after PRK with either topical tobramycin 0.3% or ofloxacin 0.3% were well tolerated. However, perioperative positive conjunctival cultures were relatively frequent and prophylactic antibiotics should be used in the setting of an epithelial defect and therapeutic soft contact lens following PRK.

Late traumatic dislocation of laser in situ keratomileusis corneal flaps

PURPOSE

To report the management and outcome of late-onset traumatic dislocation of laser in situ keratomileusis (LASIK) flaps.

DESIGN

Retrospective, observational case series.

PARTICIPANTS

Four patients with late-onset LASIK flap dislocation occurring after mechanical trauma at various intervals (10 days-2 months) after the procedure.

INTERVENTION

In all cases of postoperative traumatic LASIK flap dislocation, the flap was refloated with scraping and irrigation of the underlying stromal bed within 12 hours of the injury. A bandage contact lens was placed, and a regimen including topical antibiotics and corticosteroids was instituted in all cases.

MAIN OUTCOME MEASURES

Best spectacle-corrected visual acuity and complications associated with the surgery were monitored.

RESULTS

Postoperative follow-up ranged from 4 to 21 months. Nonprogressive epithelial ingrowth was noted in one patient and diffuse lamellar keratitis developed in another patient. All patients recovered pretrauma spectacle-corrected visual acuity.

CONCLUSIONS

Corneal LASIK flaps are prone to mechanical dislocation as late as 2 months after the procedure. Appropriate management results in recovery of optimal visual outcomes.

The role of apoptosis in the early corneal wound healing after excimer laser keratectomy in the rat

BACKGROUND

The potential role of apoptosis in corneal wound healing after excimer laser keratectomy was investigated in a rat model.

METHODS

Lewis rats underwent laser keratectomy using a 193-nm excimer laser. The central corneas were ablated in three depths: group A, epithelium; group B, superficial stroma; group C, deep stroma. Eyes were collected at 1, 12, 24, and 36 h and 1 week. Cellular markers associated with apoptosis--Fas, Fas ligand (FasL), Bcl-2, and Bax were examined by immunohistochemistry. Keratocyte depletion and endothelial changes were evaluated histologically. In situ end labeling of double-stranded DNA breaks was used to demonstrate apoptosis in corneal sections.

RESULTS

Keratocyte depletion was observed in 6 (50%) of 12 rats (total from groups A, B, and C) at 12 h, 11 (73%) of 15 at 24 h, 3 (20%) of 15 at 36 h, and 2 (15%) of 13 at 1 week after laser surgery. Corneal endothelial edema was observed in the ablation zone. Expression of Fas, FasL, Bcl-2, and Bax in corneal cells showed dynamics similar to that of keratocyte depletion and endothelial changes. There was less expression of apoptotic molecules in newly generated epithelial cells and more in endothelial cells of the stromal ablation groups.

CONCLUSIONS

Excimer laser keratectomy triggered apoptosis of corneal keratocytes and endothelial cells. More endothelial edema was observed in the stromal ablation than in the epithelial ablation group. The expression of apoptotic molecules coincided with the period of keratocyte depletion and regeneration and of endothelial recovery, suggesting that apoptosis is a dynamic part of corneal wound healing and remodeling after excimer laser keratectomy.

Loss of late primitive streak mesoderm and interruption of left-right morphogenesis in the Ednrb(s-1Acrg) mutant mouse

This study characterizes defects associated with abnormal mesoderm development in mouse embryos homozygous for the induced Ednrb(s-1Acrg) allele of the piebald deletion complex. The Ednrb(s-1Acrg) deletion results in recessive embryonic lethality and mutant embryos exhibit a truncated posterior body axis. The primitive streak and node become disfigured, consistent with evidence that cell migration is impaired in newly formed mesoderm. Additional defects related to mesoderm development include notochord degeneration, somite malformations, and abnormal vascular development. Arrested heart looping morphogenesis and a randomized direction of embryonic turning indicate that left-right development is also perturbed. The expression of nodal and leftb, Tgf-beta-related genes involved in a left-determinant signaling pathway, is variably lost in the left lateral plate mesoderm. Mutational analysis has demonstrated that Fgf8 and Brachyury (T) are required for normal mesoderm and left-right development and the asymmetric expression of nodal and leftb. Fgf8 expression in nascent mesoderm exiting the primitive streak is dramatically reduced in mutant embryos, and diminished T expression accompanies the progressive loss of paraxial, lateral, and primitive streak mesoderm. In contrast, axial mesoderm persists and T and nodal appear to be appropriately expressed in their specific domains in the node and notochord. We propose that this mutation disrupts a morphogenetic pathway, likely involving FGF signaling, important for the development of streak-derived posterior mesoderm and lateral morphogenesis.

Comparison of cerebrovascular effects of intravenous cocaine injection in fetal, newborn, and adult sheep

Cocaine may cause stroke, intracranial hemorrhage, seizures, and neurobehavioral abnormalities in fetuses, newborns, and adults, and there could be developmental and/or species differences in mechanisms for these cocaine-induced cerebrovascular effects. To evaluate developmental differences in responses to cocaine, we compared the cerebrovascular and metabolic responses to a 2 mg/kg iv cocaine dose in unanesthetized fetal (n = 8, previously reported, direct fetal injection), newborn (n = 6), and adult (n = 12) sheep. We measured cerebral blood flow, mean arterial blood pressure, and arterial and venous O(2) content, and we calculated cerebral O(2) consumption and cerebral vascular resistance at baseline and at 30 s and at 5, 15, and 60 min after cocaine injection. Cerebral blood flow increased 5 min after injection in the fetus and newborn, but not until 15 min in the adult. In the fetus, cocaine caused a transient cerebral vasoconstriction at 30 s; in all three groups, cocaine caused cerebral vasodilation, which was delayed in the adult. Cerebral metabolic O(2) consumption increased 5 min after injection in the fetus and newborn, but not until 15 min after injection in the adult. Arterial O(2) content decreased 5 min after injection in the fetus and 15 min after injection in the adult. We speculate that clinical differences in response to cocaine injection may be explained, in part, by these developmental differences in the cerebrovascular and metabolic responses to cocaine.

Herpes simplex virus DNA identification from aqueous fluid in Fuchs heterochromic iridocyclitis

PURPOSE

To report the presence of herpes simplex virus DNA in the aqueous humor of an eye with Fuchs heterochromic iridocyclitis.

METHODS

In an eye with a clinical diagnosis of Fuchs heterochromic iridocyclitis, samples of aqueous humor and anterior capsule of the lens were obtained during cataract surgery. Polymerase chain reaction was performed on the samples to detect the presence of viral DNA including herpes simplex virus, varicella-zoster virus, and cytomegalovirus. Serologic analysis was also performed for antiviral immunoglobulins.

RESULTS

Herpes simplex virus DNA was identified in the aqueous humor but not in the anterior capsule. Serum immunoglobulin G was positive for herpes simplex virus, varicella-zoster virus, and cytomegalovirus.

CONCLUSIONS

The presence of herpes simplex virus DNA in the aqueous humor of an eye with Fuchs heterochromic iridocyclitis suggests that herpes simplex virus infection may play a role in the pathogenesis of Fuchs heterochromic iridocyclitis.

Mechanisms of retention of pyrrolidinyl norephedrine on immobilized alpha(1)-acid glycoprotein

The HPLC separation of the R,S and S,R enantiomers of pyrrolidinyl norephedrine on immobilized alpha-1 glycoprotein (AGP) was investigated. Conditions for the separation were varied using a premixed mobile phase containing an ammonium phosphate buffer and an organic modifier. The influence of mobile phase pH, ionic strength, organic modifier composition, modifier type, and temperature on the chiral selectivity and retention were investigated. The presented data demonstrate that independent phenomena govern the enantioselectivity and retention. Retention is a function of both ion exchange equilibria and hydrophobic adsorption. Thermodynamic data derived from van't Hoff plots illustrates that while enantioselectivity is also enthalpically driven, the magnitude of the enthalpy term is governed by pH. Enantioselectivity has little dependence on ionic strength. Hydrophobic interactions appear to foster hydrogen bonding interactions; the two appear to be mutually responsible for chiral selectivity. The chiral selectivity decreases as the pH is decreased and increases with mobile phase buffer strength.

The subspecialty training, practice type, and geographical distribution of recently trained ophthalmologists: a study of male and female physicians

OBJECTIVE

To characterize the distribution of male and female ophthalmologists with regard to practice type, subspecialty training, rural-urban distribution, and regional distribution.

METHODS

Ophthalmology Matching Program files containing the records of residents who began their second year at accredited programs between 1986 and 1990 (inclusive), were compared to membership files of the American Academy of Ophthalmology. Practice locations for each individual were classified according to region, stage, and Rural-Urban Continuum County Code, as defined by the US Department of Agriculture.

RESULTS

This cohort comprised 2,494 individuals, 77.1% (1922) of whom were male and 22.9% (572) of whom were female. Group practice was most common (55.9% for women and 61.3% for men). More women were in salaried positions associated with health maintenance organizations (p = 0.006) and academic settings (p < 0.001) than were men. Notable differences in subspecialty choice were restricted to pediatric ophthalmology, chosen three times more frequently by women, and vitreoretinal diseases/surgery, chosen twice as often by men. Only 5.6% of women selected nonmetropolitan practice locales compared to approximately twice that percentage of men. The Middle Atlantic and New England regions attracted more women, while the South Atlantic attracted more men.

Acute unilateral corneal immunoprotein deposition in IgM monoclonal gammopathy

A healthy 43-year-old officer of a merchant ship at sea developed pain, redness, and photophobia in his right eye. During the next 2 weeks, he noted the presence of a band of opacity spreading from his temporal limbus toward his central cornea. His episcleral vessels were engorged in a distribution contiguous with the peripheral, sectorial, fleck-like corneal opacities. The opacity had progressed during topical and systemic antibiotic therapy, but halted with use of topical corticosteroids. Systemic evaluation showed mild IgM monoclonal gammopathy. Transmission electron microscopy of a corneal biopsy specimen revealed electron-dense fibrils identified as immunoprotein. To our knowledge, this is the first report of a case of acute unilateral deposition of corneal immunoprotein in a patient with monoclonal gammopathy. Clinicians should begin with a broad differential diagnosis when evaluating patients with corneal opacity.

Cytokines and apoptotic molecules in experimental melanin-protein induced uveitis (EMIU) and experimental autoimmune uveoretinitis (EAU)

The cytokine profile and occurrence of apoptosis during experimental melanin-protein induced uveitis (EMIU) were investigated and compared with that of experimental autoimmune uveoretinitis (EAU). EMIU or EAU was induced in Lewis rats. Eyes were collected at different time points after immunization. Cytokine mRNA expression was identified in the inflammatory cells in the uvea of EMIU rats; IL-2, IFN-gamma and IL-12 increased at the peak of the inflammation, and then tapered off as inflammation subsided. IL-4 and IL-10 increased at the peak of ocular inflammation, and persisted with inflammation resolved. Fas and FasL were expressed consistently in ocular resident cells of EMIU, but were elevated in EAU. In EAU, Bcl-2 expression showed a sharp peak in inflammatory cells but not in the resident cells. In EMIU, high levels of Bcl-2 were present and persisted in both ocular resident and inflammatory cells. Expression of Bax was relatively stable in both EAU and EMIU. Cellular DNA fragmentation was detected in the retinal glial cells of EAU and some inflammatory cells of EMIU. In EMIU, the dynamics of Th1 cytokines were consistent with the ocular inflammation, whereas persistent expression of Th2 cytokines was consistent with their known regulatory role. The continuous high expression of Bcl-2 and the high ratio of Bcl-2 to Bax in the eyes of EMIU may possibly contribute to prevention of ocular tissue damage, and of inflammatory cells from undergoing apoptosis, thus resulting in chronic recurrent inflammation.

Provision of anesthesia with single application of lidocaine 2% gel

PURPOSE

To compare the efficacy of a single application of lidocaine 2% gel with tetracaine 0.5% drops for topical anesthesia in clear corneal cataract surgery.

SETTING

The Wilmer Eye Institute, Johns Hopkins University School of Medicine, Baltimore, Maryland, USA.

METHODS

A preliminary toxicity study applied lidocaine 2% gel in the conjunctival fornices of rabbit eyes (n = 9). Biomicroscopic examination was performed and then enucleation at sequential intervals after the application. Intentional intracameral injection of lidocaine gel was performed (n = 3), followed by enucleation. Histopathological analysis was performed on all eyes. A randomized clinical trial comparing topical anesthesia in clear corneal cataract surgery was performed in 25 eyes of 25 patients (12 eyes randomly assigned to lidocaine gel, 13 eyes to tetracaine drops). Corneal sensation was measured with the Cochet-Bonnet aesthesiometer before application of the topical anesthesia, 5 minutes after application, and at the conclusion of surgery. Additional intraoperative local anesthesia and systemic sedation were recorded. Patients' subjective level of comfort was reported 20 minutes after surgery, and the surgeon's perception of patients' comfort was also noted.

RESULTS

In rabbits, lidocaine gel did not cause clinical or histopathological alteration of the ocular tissues. In the clinical study, median corneal sensitivity before application, after 5 minutes, and postoperatively was 6, 0, 0 (maximum sensitivity = 6), respectively, in the lidocaine gel group and 5, 0, 0, respectively, in the tetracaine drops group. Additional local anesthesia was administered in 17% and 31% of patients, respectively. Satisfactory comfort was reported by 58% in the lidocaine gel group and 62% in the tetracaine drops group.

CONCLUSIONS

A single application of lidocaine 2% gel was a safe and effective alternative to multiple topical anesthetic drops for clear corneal cataract surgery. Lidocaine 2% gel was similar to tetracaine drops in provision of corneal anesthesia and patient comfort, while causing no significant toxicity to the ocular surface.

Cytokine-induced calgranulin C expression in keratocytes

The authors have identified a corneal stromal protein (CO-Ag) that may be involved in the pathogenesis of Mooren's ulcer. The CO-Ag cDNA sequence is identical to that of human neutrophil calgranulin C (CaGC). This study sought to demonstrate expression of the CaGC gene in the human cornea and in corneal keratocytes after cytokine stimulation. In situ hybridization and immunohistochemistry were used to localize CaGC mRNA and protein in normal and diseased human corneas, including a specimen with Mooren's ulcer. Cultured bovine keratocytes were stimulated with IL-1 alpha or TNF-alpha, and reverse transcription polymerase chain reaction (RT-PCR) was performed to amplify CaGC cDNA from cytokine-stimulated keratocytes and unstimulated controls. Southern blotting verified the specificity of the RT-PCR amplification products. In situ hybridization detected human CaGC mRNA in the stroma of corneas with Fuchs' dystrophy, postinfection corneas, and a cornea with Mooren's ulcer. In cultured bovine keratocytes, peak levels of CaGC mRNA were reached 6 h after cytokine stimulation. Southern blots with an oligonucleotide probe specific for CaGC detected the RT-PCR products of expected sizes (273 bp) and confirmed that the amplified CO-Ag sequence was identical to that of CaGC. These studies are the first to demonstrate the presence of CaGC in the human cornea and the ability of stromal keratocytes to produce CaGC (CO-Ag). The up-regulation of CaGC gene expression by corneal keratocytes due to proinflammatory cytokines from trauma or inflammation may induce autoimmunity that ultimately results in Mooren's ulceration.

Propranolol blocks cocaine-induced cerebral vasodilation in newborn sheep

OBJECTIVE

The objective of this study was to test the hypothesis that cocaine-induced cerebral vasodilation in newborn sheep is mediated via beta-adrenergic receptor activation.

DESIGN

The cerebral effects of a single intravenous injection of cocaine (4 mg/kg) given 30 mins after pretreatment with propranolol (1 mg/kg) were studied and compared with the results from a previous study using an identical cocaine protocol without propranolol pretreatment.

SUBJECTS

Seven chronically catheterized, unanesthetized newborn sheep (6 +/- 1 days old).

MEASUREMENTS

Cerebral blood flow using radiolabeled microspheres, mean arterial blood pressure (MAP), heart rate, and cerebral arterial and venous oxygen content were measured at baseline, after administration of propranolol, and 0.5, 5, 15, and 60 mins after cocaine injection. Cerebrovascular resistance was calculated as the MAP divided by the cerebral blood flow.

MAIN RESULTS

Propranolol injection alone caused no systemic or cerebral physiologic changes other than an 11 +/- 2% (mean +/- SEM) decrease in heart rate, which was sustained after cocaine injection. In contrast to previous studies showing cerebral vasodilation (25% decrease in cerebrovascular resistance) and acute hypertension (57% increase in MAP) 30 secs after cocaine injection, there were no changes in cerebrovascular resistance after cocaine injection and after propranolol pretreatment and there was only a 23 +/- 7% increase in MAP 30 secs after injection, with a return to baseline by 15 mins. Cocaine and norepinephrine levels were similar to those previously reported in the newborn sheep after an injection of 4 mg/kg cocaine.

CONCLUSION

Propranolol blocks cocaine-induced cerebral vasodilation and blunts the acute hypertension in newborn sheep, suggesting that cocaine's cerebrovascular effects in the developing brain are mediated, at least in part, by beta-adrenergic receptor activation.

Determination of bis(tributyltin) oxide by GC--MS with on-line hydride derivatization: application to drug substance analysis

We report the determination of residual bis(tributyltin) oxide in a drug substance by GC-MS after extraction and on-line conversion to tributyltin hydride. Gas chromatography was performed using a 15 m x 0.25 mm i.d. DB-5 HT column with a temperature program from 100 to 160 degrees C at 15 degrees C min(-1). A mass range of 165-185 amu was monitored with the MS detector. Hydride generation is performed by placing a small amount of solid sodium borohydride in the injection port of a gas chromatograph and injecting samples and standards through this material. Conversion to tributyltin hydride is shown to be quantitative and linear for levels of bis(tributyltin) oxide between 1 and 100 ppm in the drug substance. The use of GC-MS provides sensitive and selective detection of tin containing species and the tin isotope pattern allows for confirmation of the presence of tin in chromatographic peaks. Recovery at 6 ppm was 89% with an injection precision of 6%. The limit of detection for bis(tributyltin) oxide in drug substance is 1 ppm.

Inflammatory response in the early stages of wound healing after excimer laser keratectomy

OBJECTIVE

To evaluate the inflammatory response and its potential role in the early stages of corneal wound healing after excimer laser keratectomy.

MATERIALS AND METHODS

Lewis rats underwent excimer keratectomy using a 193-nm excimer laser. The central corneas were ablated in 3 depths: group A, epithelium; group B, superficial stroma; or group C, deep stroma. Eyes were harvested 1, 12, 24, and 36 hours, and 1 week after the rats were killed. Immunohistochemistry was used to test frozen sections with monoclonal antibodies of various inflammatory cellular markers.

RESULTS

Reepithelialization was observed at 12 hours in group A, and at 24 hours in groups B and C. Regenerated epithelium covered the denuded corneal surface in groups B and C after 1 week. The expression of major histocompatibility complex II antigen was detected in infiltrating cells, corneal epithelial cells, and endothelial cells 1 hour after surgery. Only a few macrophages and Langerhans cells were in the limbus at baseline. Macrophages migrated from the limbus to the corneal ablation zone and increased 2-fold after 36 hours in all 3 groups compared with baseline. Occasional lymphocytic infiltration was identified after 25 to 36 hours.

CONCLUSION

Macrophages play an active role in the wound healing after laser keratectomy and may contribute to transient corneal haze.

Astigmatism Outcomes Following Spherical Photorefractive Keratectomy for Myopia

BACKGROUND

Our aim was to examine the change in astigmatism after spherical photorefractive keratectomy (PRK). These effects are essential to optimizing photoastigmatic refractive keratectomy (PARK) to correct astigmatism to within fractions of a diopter.

METHODS

We retrospectively reviewed 98 eyes of 178 patients with mild to moderate myopia and cylinder < or = 1.00 diopter (D) treated with spherical PRK (VISX 20/20 STAR excimer laser system); 31 eyes had epithelium removed mechanically with a blade and 67 eyes by a laser-scrape technique.

RESULTS

Refractive astigmatism was reduced by greater than 0.25 D in 27 eyes (28%); refractive astigmatism was induced by greater than 0.25 D in 31 eyes (32%); the average vector-corrected difference between an eye's astigmatism before and after surgery was 0.01 +/- 0.52 D (P = .85). Eyes with high topographic astigmatism but low refractive cylinder before PRK showed an average of 0.07 +/- -0.60 D change in refractive cylinder after PRK. Refractive astigmatism of more than 0.25 D was induced in 16 eyes (44%) that received manual removal of epithelium versus 15 eyes (24%) that received laser removal of epithelium (odds ratio 2.51, P < .01).

CONCLUSIONS

When using PRK for astigmatism correction, refractive cylinder before surgery rather than topographic astigmatism may be the most appropriate method for targeting the astigmatism correction, especially when the two values are discordant. An unpredictable mild increase or decrease in astigmatism may be expected.

Defensin gene expression in the cornea

PURPOSE

To determine whether defensin genes are expressed in human corneas and bovine corneal keratocytes.

METHODS

In situ hybridization and immunohistochemistry were used to localize defensin mRNA and protein in normal and diseased human corneas. Cultured bovine keratocytes were stimulated with IL-1alpha or TNFalpha to determine whether defensin mRNA production occurred. Reverse transcription polymerase chain reaction (RT-PCR) was performed to amplify defensin cDNA from cytokine-induced keratocytes, and Southern blots were used to verify the specificity of RT-PCR amplification products.

RESULTS

Defensin mRNA and protein were not detected in normal human corneal stroma, but were readily detectable in the corneal stroma in cases of rejected transplants and postinfectious keratitis. IL-1alpha was a potent inducer of defensin gene expression in keratocytes, which began 12 h after challenge and peaked at 18 to 24 h. TNFalpha weakly induced defensin mRNA in keratocytes at about 18 h. Southern blots of the RT-PCR products probed with an oligonucleotide complementary to internal sequences of defensin demonstrated the appropriately sized products (198 bp) specific for defensin.

CONCLUSIONS

This report demonstrates the presence of defensin in the human cornea and the capacity of corneal keratocytes to produce defensin mRNA in response to IL-1alpha and TNFalpha. Release of defensins by keratocytes in response to cytokines elaborated in corneal inflammation may contribute to the host defense response in microbial keratitis.

A combined marker and trephination instrument for penetrating keratoplasty

We have developed a new instrument for marking and trephination of the cornea for penetrating keratoplasty surgery. The instrument is an ergonomically designed combination of a corneal marker and a trephine.

Acridine orange staining for rapid diagnosis of Acanthamoeba keratitis

Acanthamoeba keratitis is uncommon, but one of the most severe infectious diseases of the cornea. Delayed diagnosis or misdiagnosis as bacterial or herpes simplex keratitis leads to extensive corneal inflammation and profound visual loss. Therefore, accurate and rapid diagnosis of Acanthamoeba keratitis is essential for successful treatment and good prognosis. We evaluated the usefulness of acridine orange staining from corneal scrapings and contact lens solutions for the rapid diagnosis of four consecutive cases of Acanthamoeba keratitis. Gram stain and culture on nonnutrient agar plates with Escherichia coli overlay were also made. Corneal scrapings stained with acridine orange revealed yellow-to-orange polygonal, cystic structures consistent with the appearance of Acanthamoeba among inflammatory cells and the corneal epithelial cells. The contact lens case solutions of two patients also showed numerous cysts with double wall. Some organisms from the third patient were identified as Acanthamoeba castellani and others as Acanthamoeba lugdunensis. Based on the acridine orange staining results in four cases of Acanthamoeba keratitis, this stain is recommended as a simple and reliable method for the rapid diagnosis of this disease.

Biochemical and functional antigenic mimicry by a polyclonal anti-idiotypic antibody for chlamydial exoglycolipid antigen

A vaccine developed by using a genus-specific antigen (Ag) of Chlamydia trachomatis would elicit a wide range of protection against various chlamydial infections. We have produced an anti-idiotypic antibody (Ab2) in guinea pigs which, in rabbits, mimics the immunogenicity of a genus-specific exoglycolipid Ag (GLXA) of C trachomatis. Furthermore, the Ab2 fulfills the functional criteria of an 'internal image' of the nominal Ag: it inhibits the binding of the idiotypic (Id) monoclonal Ab (mAb1) to GLXA, and it induces in rabbits anti-anti-Id antibody (Ab3) which recognizes both the affinity-purified nominal Ag GLXA and whole organisms. Moreover, Ab3 induced by immunization of rabbits with guinea pig Ab2 neutralizes infectious heterologous chlamydiae and prevents in vitro and in vivo infection. Taken together, these results demonstrate functional and biochemical mimicry of the Ab2 for the chlamydial GLXA and suggest that anti-idiotypic Ab to GLXA is a potential candidate vaccine against chlamydia-related diseases.

Effect of a non-steroidal anti-inflammatory drug on tissue levels of immunoreactive prostaglandin E2, immunoreactive leukotriene, and pain after periodontal surgery

The aim of this study was to measure tissue levels of immunoreactive prostaglandin E2 (iPGE2), immunoreactive leukotriene B4 (iLTB4), and pain after periodontal surgery and to evaluate the effect of the non-steroidal anti-inflammatory drug (NSAID), ibuprofen, on these levels. Two contralateral quadrants in each of nine patients were selected to undergo separate surgical procedures, one with ibuprofen (800 mg 1 hour presurgery and 400 mg postsurgery) and one with a placebo. Intra-operatively, a custom-made microdialysis probe, with a 3,000 dalton molecular weight cut-off, was inserted beneath the soft tissue flap and a dialysate collected every 20 minutes for 4 hours after surgery. Pain perception was measured at the same time intervals using two pain scales. Dialysate samples were assayed using two enzyme immunoassays. Mean tissue levels of iPGE2 in the placebo group increased from 74 nM at 40 minutes to a peak of 261 nM at 200 minutes. Mean tissue levels of iLTB4 in the placebo group fluctuated between 0.2 and 0.6 nM. Pain levels in this group increased continuously with time, peaking at 4 hours. Mean tissue levels of iPGE2 in the ibuprofen group were significantly suppressed, exhibiting more than a 95% reduction. This was accompanied by a significant reduction in pain. Ibuprofen had no detectable effect on tissue levels of iLTB4. These data indicate that iPGE2 and iLTB4 are present at relatively high concentrations in the periodontal tissues after surgery. Since these concentrations exceed the Kd values for binding to their respective receptors, PGE2 and LTB4 may be associated with the development of postsurgical pain and inflammation. These data also indicate that ibuprofen can successfully inhibit iPGE2 production in the periodontal tissues and in this way may help reduce postoperative pain and inflammation.

Complementation mapping of skeletal and central nervous system abnormalities in mice of the piebald deletion complex

The s15DttMb, s36Pub, s1Acrg and s24Pub piebald deletion alleles belong to a set of overlapping deficiencies on the distal portion of chromosome 14. Molecular analysis was used to define the extent of the deletions. Mice homozygous for the smallest deletion, s15DttMb, die shortly after delivery and display alterations in the central nervous system, including hydrocephalus and a dorsally restricted malformation of the spinal cord. These mice also display homeotic transformations of vertebrae in the midthoracic and lumbar regions. Homozygous s27Pub mice contain a point mutation in the piebald gene, survive to weaning, and display no central nervous system or skeletal defects, arguing that the s15DttMb phenotype results from the loss of genes in addition to piebald. A larger deletion, s36Pub, exhibits additional cartilage malformations and defects in the anterior axial and cranial skeleton. The skeletal defects in both s15DttMb and s36Pub mice resemble transformations associated with the targeted disruption of Hox genes and genes encoding the retinoic acid receptors, which play a role in the specification of segmental identity along the anteroposterior axis. Complementation analysis of the s15DttMb and s36Pub phenotypes, using two additional deletions, localized the gene(s) associated with each phenotype to a defined chromosomal region.

Comparative intravitreal antibiotic therapy for experimental Enterococcus faecalis endophthalmitis

OBJECTIVE

To evaluate the most effective intravitreal antibiotic treatment of vancomycin-sensitive and -resistant Enterococcus faecalis endophthalmitis.

DESIGN

Animal experiment.

SETTING

Seventy-eight New Zealand white rabbits received an intravitreal injection of 10(5) vancomycin-sensitive or -resistant E faecalis organisms in one eye. Infections were allowed to proceed 3 hours before dividing animals randomly into the following treatment groups (n = 6, each): the vancomycin-sensitive E faecalis model--(1) vancomycin (1 mg/0.1 mL), (2) combined vancomycin (1 mg/0.1 mL) and amikacin (0.4 mg/0.1 mL), (3) combined vancomycin (1 mg/0.1 mL) and gentamicin (0.1 mg/0.1 mL), (4) combined vancomycin (1 mg/0.1 mL) and ceftazidime (2 mg/0.1 mL), (5) combined ampicillin (5 mg/0.1 mL) and gentamicin (0.1 mg/0.1 mL), and (6) pristinamycin (1 mg/0.1 mL); and the vancomycin-resistant E faecalis model--(1)same as above, excluding group 4. Control groups received sterile balanced salt solution. Twenty-four hours following intravitreal treatment, vitreous humor was collected for quantitative bacteriological studies.

RESULTS

Intravitreal therapy with combined vancomycin and amikacin provided the most effective reduction of vancomycin-sensitive E faecalis organisms compared with combined vancomycin and gentamicin therapy (P =.10, Wilcoxon's rank sum test) or any other treatment group (P < .01, Wilcoxon's rank sum test). For vancomycin-resistant E faecalis endophthalmitis model, the combined ampicillin and gentamicin therapy was the most effective, followed by the combined vancomycin and amikacin therapy (P < .01, Wilcoxon's rank sum test).

CONCLUSIONS

Treatment with intravitreal vancomycin plus amikacin and with intravitreal ampicillin plus gentamicin provide an effective bactericidal therapy for severe experimental vancomycin-sensitive and -resistant E faecalis endophthalmitis, respectively.

The microbiologic effect of gas filtration

BACKGROUND

Air and expansile gases commonly are injected into the eye in both vitreoretinal surgery and anterior segment surgery. Although the halogenated gases are filtered routinely before injection, air often is not prepared in this manner. This study was designed to investigate the effect of filtration on the microbiology of gas mixtures.

METHODS

Two separate studies were conducted, one examining medical grade perfluoropropane gas (C3F8), and the other evaluating air collected from an ophthalmic operating room or emergency room. Aliquots of air or gas were collected through a 0.22-micron filter before and after filtration. The filter discs were cultured for bacterial and fungal organisms.

RESULTS

Of 514 samples collected, none grew either bacterial or fungal organisms. There was no difference with regard to recovered microbes between filtered and unfiltered air or C3F8, nor was there a difference between operating room air and emergency room air. Positive controls using aerosolized microorganisms yielded heavy growth.

CONCLUSION

Based on results obtained in this study and available information on the concentration of airborne microbes, the microbiologic effect of gas filtration is of little significance for volumes routinely injected in ophthalmic surgery.

Efficacy of ofloxacin vs cefazolin and tobramycin in the therapy for bacterial keratitis. Report from the Bacterial Keratitis Study Research Group

PURPOSE

To compare ofloxacin solution with a combination of fortified antibiotic cefazolin sodium and tobramycin sulfate solutions in the treatment of bacterial keratitis.

METHODS

Patients under care at any one of 28 participating clinical centers who had an eye with suspected bacterial keratitis were randomly allocated in a double-masked manner to treatment with 0.3% ofloxacin solution or a combination of the fortified antibiotics (1.5% tobramycin and 10.0% cefazolin solutions).

MAIN OUTCOME MEASURES

Time to healing defined as complete re-epithelization, accompanied by a nonprogressive stromal infiltrate for two consecutive visits. Secondary outcome measures included patient symptoms and signs of infection and adverse reactions to study medications. Only patients with a positive bacterial corneal culture were included in most analyses.

RESULTS

A positive bacterial corneal culture was obtained in 140 (56%) of the 248 enrolled patients. The time to healing was similar among the 73 patients receiving ofloxacin and the 67 patients receiving fortified antibiotics (P = .70). By 7 days after study entry, the keratitis in 37% of the ofloxacin group and 38% of the fortified antibiotics group had healed. By 28 days, keratitis in 89% of the ofloxacin group and 86% of the fortified antibiotics group had healed. Two patients receiving ofloxacin and one receiving fortified antibiotics discontinued study medication because of lack of efficacy. Patients receiving ofloxacin reported substantially less burning and stinging on instillation than the patients receiving fortified antibiotics (P < .001). Five of six patients among the 140 with positive bacterial cultures who had study medications discontinued because of ocular side effects were in the fortified antibiotics group; an additional three patients, all in the fortified antibiotics group, among the remaining 108 receiving study medications had ocular side effects.

CONCLUSIONS

The efficacy of ofloxacin solution in treating bacterial keratitis is equivalent to that of the fortified cefazolin and tobramycin solutions. The reduced frequency of ocular toxic effects and the relative ease of preparation of ofloxacin are additional considerations.

Murine model of ocular infection by a human biovar of Chlamydia trachomatis

PURPOSE

A human biovar of Chlamydia trachomatis was used to develop a murine model of ocular chlamydial infection. The inbred mouse model will allow detailed immunologic studies during ocular infection, and use of a human biovar for infection may aid in identification of appropriate vaccine strategies against chlamydial infections.

METHODS

BALB/c, C3H/HeN, and C57B1/6J mice (n = 5 to 10 mice/group) were topically infected in the conjunctiva with C serovar of C. trachomatis. The effects were tested of single and repeated infection with 5000 inclusion-forming units (IFU) in 5 microliters and different inoculum doses. Conjunctival surfaces of both eyes were swabbed for microbiologic signs (isolation culture or direct fluorescent antibody staining) of infection over 4 to 6 weeks. Conjunctivae were removed for histopathologic study, and lymphocytes from draining cervical lymph nodes and spleens were tested for chlamydia-specific proliferative responses. Serum was obtained from all mice and tested for anti-chlamydial antibodies.

RESULTS

BALB/c and C3H/HeN mice developed dose-dependent microbiologic, histopathologic, and immunologic evidence of ocular infection. Eyes of mice were culture-positive from day 7 through at least day 21, with the peak of infection at days 10 to 14 after infection. Histopathologically, the development of conjunctival subepithelial mononuclear infiltration, exudate, and loss of goblet cells occurred within 1 week. Dose-dependent lymphoproliferative responses to whole chlamydial elementary bodies were observed; anti-chlamydial antibody was detected by immunoblotting only in infected mice.

CONCLUSIONS

Several strains of inbred mice are susceptible to human chlamydial biovars and may provide a useful alternative disease model in which to study the immunopathogenesis of ocular chlamydial infection and test of vaccine candidates derived from clinically relevant human biovars.

Basic ocular pharmacotherapy

1. There are certain unique features of pharmacotherapy as it relates to the eye. One is that we have the ability to apply a drug directly to the surface of the eye in the form of eyedrops. This has important ramifications in terms of pharmacokinetics, the distribution of drug throughout the ocular tissues. 2. Ocular pharmacokinetics is the study of the distribution of a drug over time. One of the principles of pharmacotherapy is that we want to maximize the amount of drug that reaches the site of action in a sufficient concentration to cause a beneficial therapeutic effect. 3. Ophthalmic nurses play an important role in patient education, because they spend time talking to patients about the proper way to use drugs.

A chlamydial major outer membrane protein extract as a trachoma vaccine candidate

PURPOSE

As shown in infected humans and in animal models of chlamydial infection, the major outer membrane protein (MOMP) of Chlamydia trachomatis is immunogenically potent. The purpose of this investigation was to test in the cynomolgus monkey model of trachoma a new extract of MOMP as a candidate vaccine against ocular chlamydial infection.

METHOD

The nonionic detergent octyl-beta-D glucopyranoside (OGP) was used to extract MOMP from purified C. trachomatis (serovar C) elementary bodies. Protective immunization with OGP-MOMP by mucosal and systemic routes was compared in the cynomolgus monkey model of trachoma. All control and immunized monkeys were challenged by topical application of infectious C. trachomatis to the conjunctivae 35 days after the initiation of immunization.

RESULTS

Immunization with OGP-extracted MOMP successfully induced chlamydia-specific local and systemic immunity to MOMP and to whole organism before challenge and early clearance of infection by systemically immunized monkeys. Although ocular disease was not significantly reduced in either immunized group compared to control animals, the lowest clinical and microbiologic disease scores developed in two animals in the mucosal group with the highest immunoglobulin A tear antibody titers at day 0 to 14, whereas higher tear and serum immunoglobulin G correlated with reduced disease in the systemically immunized group.

CONCLUSIONS

These data demonstrate that despite evidence of vigorous MOMP-specific and other chlamydia-specific serologic and cell-mediated immunity, as well as anamnestic serologic responses to chlamydia, vaccination with OGP-MOMP was only partially protective against chlamydial ocular disease. The partial protection correlated best with tear immunoglobulin A responses after mucosal immunization and with local and systemic immunoglobulin G responses after peripheral immunization, suggesting that alternative chlamydial antigens may have to be considered in future vaccine development to induce more effective protective immunity and that evaluation of efficacy must be appropriate to route of immunization.

Fetal responses to acute fetal cocaine injection in sheep

Maternal cocaine injection causes fetal hypoxemia, hypertension, and increased cerebral blood flow (CBF) in sheep. To test the hypothesis that increased fetal CBF is not due solely to fetal hypoxemia, we injected cocaine directly into a fetal vein. A single dose of cocaine [1 (group 1; n = 7) or 2 (group 2; n = 8) mg/kg i.v.] was administered to chronically catheterized, unanesthetized, near-term fetal sheep. Fetal CBF (microspheres), arterial blood pressure (BP), O2 content, and cerebral O2 consumption (CMRo2) were measured at baseline, 30 s, and 2, 5, and 15 min after fetal cocaine injection. Fetal CBF increased 27 +/- 9% (SE) at 5 min in group 1 and returned to baseline by 15 min, whereas fetal CBF increased 57 +/- 8% at 5 min and remained elevated at 15 min in group 2. Fetal BP increased at 30 min in both groups and remained increased at 2 min in group 1 and at 5 min in group 2. Cerebrovascular resistance increased at 30 s in both groups and then decreased at 5 min only in group 2. Fetal hypoxemia was observed in group 2 5 min after cocaine injection (arterial PO2 decreased 24 +/- 5%), whereas no hypoxemia was noted in group 1. CMRO2 was unchanged in group 1 but increased in group 2 at 5 min (41 +/- 10%) and was associated with an increase in cerebral O2 extraction. Increases in myocardial and adrenal blood flows and reductions in both small and large intestinal blood flows were noted at 5 min in both groups.(ABSTRACT TRUNCATED AT 250 WORDS)