Clinicopathologic profiles of canine ocular melanosis: A comparative study between cairn terriers and non-cairn terriers

OBJECTIVES

To identify canine breeds at risk for ocular melanosis and to compare the clinical and histologic features between affected Cairn Terriers (CTs) and non-Cairn Terriers (NCTs).

DESIGN

Relative risk (RR) analysis and retrospective cohort study of dogs histologically diagnosed with ocular melanosis.

PROCEDURES

The COPLOW archive was searched for globe submissions diagnosed with ocular melanosis. Six hundred fifty globes were included, and RR analysis was performed to identify at-risk NCT breeds. A cohort of 360 CT and NCT globes diagnosed from 2013 to 2023 were included in the retrospective cohort study. Clinical data were collected from submission forms, medical records, and follow-up surveys. One hundred fifty-seven submissions underwent masked histologic review. Immunohistochemical staining for CD204 was performed to determine the predominance of melanophages in affected uvea from five NCTs.

RESULTS

At-risk NCT breeds included the Boxer, Labrador Retriever, and French Bulldog. Glaucoma was the reported reason for enucleation in 79.4% of submissions. At enucleation, clinical features less prevalent in NCTs than CTs included pigmentary abnormalities in the contralateral eye (33.7% vs. 63.1%, p = .0008) and abnormal episcleral/scleral pigmentation in the enucleated globe (25.4% vs. 53.6%, p = .0008). Histologic involvement of the episclera was also less frequent in NCTs than in CTs (39.7% vs. 76.9%, p = .008). Concurrent melanocytic neoplasms arising in melanosis were more common in NCTs (24.4%) than CTs (3.9%). Melanophages were not predominant in any samples evaluated immunohistochemically.

CONCLUSIONS

Several popular NCT breeds carry risk for ocular melanosis, and some clinicopathologic disease features may differ from those described in CTs.

Development of Crystalline Corneal Opacities (Steroid Keratopathy) in Dogs After Treatment With Ophthalmic Corticosteroids

PURPOSE

To retrospectively evaluate and describe the relationship between the use of topical corticosteroids and the development of crystalline corneal opacities (steroid keratopathy) in a colony of research Beagles and Beagle-derived dogs.

METHODS

Medical records of 73 purpose-bred Beagles and Beagle-derived dogs were reviewed from June 2012 to May 2021. All dogs were treated with topical ophthalmic corticosteroids for at least 21 days. In addition to regular ophthalmic examination, some dogs also had a systemic lipid profile (n = 6) performed to work up further and characterize the crystalline corneal opacities. Globes of 3 dogs were examined histopathologically.

RESULTS

Axial stromal crystalline corneal opacities were appreciated in 25 eyes of 14 dogs after a median of 141 days after initiating treatment (35-396 days). Multiple corticosteroids were used, including neomycin-polymyxin b-dexamethasone 0.1% ophthalmic ointment, prednisolone acetate 1% ophthalmic suspension, and difluprednate 0.05% ophthalmic emulsion (Durezol). Resolution of corneal opacity was documented in 4 of 25 eyes when ophthalmic corticosteroids were discontinued after a median of 406.5 days (271-416 days). Histopathologic examination revealed a dense band of acellular material, poorly staining with periodic acid-Schiff, subtending the corneal epithelium, and being surrounded by spindle cells.

CONCLUSIONS

This case series documents the onset of steroid keratopathy in Beagles and Beagle-derived dogs after treatment with ophthalmic corticosteroids. Clinical resolution of steroid keratopathy lesions may be possible after discontinuation of ophthalmic corticosteroids.

Tumor-like lymphoplasmacytic conjunctivitis in the third eyelid in a dog

This report aims to describe a case of tumor-like lymphoplasmacytic conjunctivitis in a 7-year-old spayed-female Pomeranian. On complete ophthalmic examination, a mass with papillary projections was noted on the bulbar surface of the right third eyelid. Debulking of the mass was performed while preserving as much of the third eyelid as possible. On the histopathological examination, the mass was diagnosed as lymphoplasmacytic conjunctivitis with mild epithelial hyperplasia. Although a slight regrowth of the mass was noted 3 weeks after surgery, intralesional injection of triamcinolone acetonide led to its disappearance. There was no further recurrence after 5 months.

Clinical description with magnetic resonance appearance of a high-grade undefined optic nerve glioma with intracranial extension

A 4-year-old mixed-breed dog was presented for hyphema and glaucoma of the right eye. Enucleation of the right globe was carried out, and histopathology examination revealed an optic nerve glioma with incomplete surgical margins. At 8 wk after surgery, the dog had depressed mentation and a diminished pupillary light reflex of the left eye. Magnetic resonance imaging revealed an irregular, heterogeneously T2 hyperintense/T1 isointense mass in the region of the optic chiasm. Compression of the rostral thalamus was present, with effacement of the pituitary gland and involvement of the right orbit. The dog was euthanized 4.5 mo after initial presentation. An undefined glioma of the right optic nerve with extension to the diencephalon was diagnosed on necropsy. Key clinical message: Although rare, intraocular glioma is a differential diagnosis for hyphema, glaucoma, and retinal detachment. Magnetic resonance imaging should be considered in cases of intraocular neoplasia, notably in those with incomplete surgical margins of the optic nerve.

Report of a self-resolving corneal viral papilloma in a dog

A 10-month-old male castrated beagle dog, without prior history of ocular disease, was referred for a corneal mass of the right eye. A non-painful raised mass with frond-like projections originated from the dorsotemporal paraxial cornea of the right eye. In addition, a plaque-like conjunctival lesion and several raised, smooth masses of the eyelid were noted around the right eye. An incisional biopsy of the corneal mass and an excisional biopsy of the conjunctival mass were performed. Histopathology confirmed the clinical diagnosis of viral papilloma. Conservative management with monitoring was elected, and the lesion self-resolved 3 mo after initial appearance. Key clinical message: This case suggests that monitoring is appropriate for corneal lesions definitively diagnosed as viral papillomas, as they may be self-limiting.

P15.04.B Serial18F-fluciclovine PET-CT and multiparametric MRI during chemoradiation for glioblastoma - an exploratory clinical study with pre-clinical correlation

Background

Positron emission tomography (PET) using anti-1-amino-3-18fluorine-fluorocyclobutane-1-carboxylic acid (18F-fluciclovine) shows preferential glioma cell uptake with low activity in normal brain. Dynamic contrast-enhanced (DCE) MRI may also be used to investigate regions of glioma that do not show gadolinium-enhancement on post-contrast T1-weighted MR sequences (Gd-T1) and may reflect tumour infiltration beyond the Gd-T1 enhancing margin. There is a paucity of data on how 18F-fluciclovine uptake correlates with Gd-T1 and DCE-MRI activity, how it correlates with tumour biology and whether significant changes in uptake occur during treatment. The aims of this pilot study were: 1 To compare 18F-fluciclovine PET, DCE-MRI and Gd-T1 in patients undergoing chemoradiotherapy for glioblastoma (GBM) 2 To investigate correlation between 18F-fluciclovine uptake, MRI findings, and tumour biology in a pre-clinical glioma model.

Material and Methods

18F-fluciclovine-PET-CT and MRI including DCE-MRI were acquired before, during and after adjuvant chemoradiotherapy (60 Gy in 30 fractions with temozolomide) in GBM patients. DCE-MRI and Gd-T1 volumes were manually contoured, and PET volumes defined using semi-automatic thresholding. Gd-T1 was subtracted from PET and DCE-MRI volumes to identify areas beyond the Gd-T1 volume boundary and similarity of the PET and DCE-MRI volumes outside the Gd-T1 volume boundary were measured using the Dice similarity coefficient (DSC). CT-2A tumour cells were stereotactically injected into the right striatum of 8 to 10-week-old C57BL6J mice and they underwent MRI and 18F-fluciclovine PET-CT. Post-mortem mice brains underwent immunohistochemistry staining for ASCT2 (amino acid transporter), nestin (stemness) and Ki-67 (proliferation) to assess for biologically active tumour.

Results

6 patients were recruited (GBM 1-6). For GBM 1-3: PET volumes were greater than DCE-MRI, in turn greater than Gd-T1. For GBM 4-6, Gd-T1 volumes were similar to DCE-MRI and both were greater than PET volumes. GBM 1-3 had lower overall survival than GBM 4-6: median 249 vs. 903 days. 18F-fluciclovine uptake and Gd uptake (on DCE-MRI) was seen beyond the margins of the standard Gd-T1 volume. Comparing these regions beyond the Gd-T1 margins, the PET and DCE-MRI had low DSC, suggesting distinct areas of fluciclovine and DCE-MRI uptake. Pre-clinical PET-CT demonstrated tumour-specific 18F-fluciclovine uptake which corresponded to biologically active tumour based on immunostaining for Ki-67, nestin and ASCT2.

Conclusion

Results from this joint pre-clinical and clinical pilot study suggest volumes of 18F-fluciclovine-PET activity beyond that depicted by MRI-DCE and Gd-T1 are associated with a poorer prognosis in patients undergoing chemoradiotherapy for GBM. The pre-clinical model confirmed 18F-fluciclovine uptake reflected biologically active tumour.

What Is Your Diagnosis?

In collaboration with the American College of Veterinary Radiology.

Clinical and pathologic evaluation of chorioretinal lesions in wild owl species

OBJECTIVE

Investigate histopathology and spectral-domain optical coherence tomography (OCT) imaging of wild owls with chorioretinitis and identify any potential correlation with an infectious etiology.

MATERIALS AND METHODS

Ophthalmic examination and retinal OCT imaging were performed on fifteen great horned (Strix varia) and barred (Bubo virginianus) owls (30 eyes) with chorioretinitis and five owls with normal eyes (10 eyes). Testing to investigate the presence of potential infectious diseases included a complete blood count, biochemistry, protein electrophoresis, West Nile virus (WNV) plaque reduction neutralization test, Toxoplasma gondii modified direct agglutination test, WNV RT-PCR, and Avian Influenza RT-PCR. A necropsy was performed on all owls, including ocular histopathology.

RESULTS

Fundus lesions included retinal detachment (7/15 owls), depigmented lesions (12/15), pigment clumping (8/15), and retinal tear (4/15). All birds were negative for WNV and Avian Influenza on RT-PCR. Of the owls with chorioretinitis, 3/15 were seropositive for WNV and 7/15 for T. gondii. Optical coherence tomography of 25/30 affected eyes revealed outer retinal lesions (19/25 eyes), retinal detachment (16/25), and retinal tears (3/25). Histopathological examination revealed outer nuclear layer atrophy (19/30 eyes), retinal detachment (18/30), retinal tears (7/30), suprachoroidal hemorrhage (12/30), scleral rupture (3/30), and ossicle fracture (3/30).

CONCLUSIONS

Although 20% of birds were seropositive for WNV and 46.6% for T. gondii, histopathologic findings supported that the posterior segment lesions in the study group were likely due to blunt ocular trauma rather than an infectious etiology. The results of OCT imaging and histopathology documented retinal changes most consistent with blunt ocular trauma.

Pemphigus foliaceus in two pet Nigerian Dwarf goats

Two male Nigerian Dwarf pet goats from a group of three living in rural southern Wisconsin, USA, presented at the same time with an eight-month history of pruritus and marked crusting on head, axillae and inguinal regions. Parasite investigations were negative, and there was no response to antiparasitic treatment. Fungal and bacterial cultures did not reveal a cause. Histopathology was consistent with a diagnosis of pemphigus foliaceus, and goats were treated with immunosuppressive doses of injectable dexamethasone sodium phosphate. After six weeks of treatment, clinical remission was achieved, and immunosuppressive therapy was continued. Three months later, goat 2 developed presumptive viral pneumonia; necropsy reported presumptive caprine arthritis encephalitis virus. One year into treatment, goat 1 developed similar clinical signs and was euthanased. In goats, pemphigus foliaceus is rare and can be treated using glucocorticoids, but as in other species, chronic immunosuppression increases susceptibility to infections.

Canine ocular and periocular snakebites requiring enucleation: A report of 19 cases

PURPOSE

To describe the clinical and histopathologic features secondary to ocular and periocular snakebites in dogs requiring enucleation.

METHODS

Retrospective review of patients with recorded snakebite envenomation from the archives of the Comparative Ocular Pathology Laboratory of Wisconsin (COPLOW) and Texas A&M Veterinary Medical Teaching Hospital (1997-2017). The cases included in this study required witnessed snakebites to the dog by the owner, clinical signs supportive of periocular or ocular envenomation, and/or histopathologic lesions compatible with snakebites. Two groups were established: ocular bites (OB) and periocular bites (PB).

RESULTS

Nineteen cases were included in the study (OB = 16/19; PB = 3/19). Dogs affected were typically older (median 8 years; range 1-18), and both sexes were equally represented. Left eyes (14/19) were more likely to sustain snake-induced trauma compared to right eyes (5/19). Fifteen breeds were identified, with terriers (9/19) commonly represented. Snakes bites occurred in six US states, with the majority of cases from Texas (7/19), California (5/19), and Arizona (4/19). Common clinical signs included facial edema, corneal ulceration, keratomalacia, uveitis, hyphema, and secondary glaucoma. All eyes demonstrated vision loss prior to enucleation. Histologically, the ocular and periocular tissues contained extensive necrosis associated with envenomation. Retinal detachment, lens capsule rupture, and intraocular hemorrhage/inflammation were commonly found.

CONCLUSIONS

Snakebite envenomation is a largely necrotizing disease process that can result in profound infiltrative and destructive ocular changes presumed to be related to the proteolytic factors and necrotoxins in venom. Ocular alterations secondary to snakebites may be irreversible regardless of supportive therapy instituted.

Microphthalmia With Multiple Anterior Segment Defects in Portuguese Water Dogs

Portuguese Water Dog breeders and veterinary ophthalmologists recognize microphthalmia with multiple congenital ocular anomalies. Fifteen Portuguese Water Dog puppies (<8 weeks of age; 8 females, 7 males) and 1 adult (5 years old; castrated male) with microphthalmia were examined. The 2 most common abnormalities were microphthalmia (31/32 eyes; 97%) and lens abnormality (congenital cataract or aphakia; 32/32 eyes; 100%). Other common histologic lesions included lack of both a ciliary cleft and trabecular meshwork (15/32 eyes; 47%) and abnormal relationship of anterior segment structures (15/32 eyes; 47%). Many of the observed lesions were similar to those described in various types of anterior segment dysgenesis in humans. Our findings define the histologic lesions in affected Portuguese Water Dogs and suggest a genetic defect that causes anterior segment malformation early in development.

Uveal schwannoma in a brown-eyed dog

An eleven-year-old, female spayed Boxer dog was diagnosed with a uveal schwannoma (formerly known as the spindle cell tumor of the blue-eyed dog or SCTBED) despite having a uniformly brown iris. The patient presented to emergency for ocular discomfort, and the right globe was subsequently enucleated due to glaucoma and submitted for histopathology. Upon histopathologic evaluation, a uveal schwannoma was diagnosed and confirmed with immunohistochemical staining. Complete metastatic evaluation 1 and 6 months after initial presentation did not reveal evidence of metastasis, and the dog remains systemically healthy. This case represents a unique variant of uveal schwannoma and is relevant because although the vast majority of these tumors occur in blue-eyed dogs, clinicians should not completely rule out this tumor as a differential based on the iris color.

Bone Disease in the Common Marmoset: Radiographic and Histological Findings

The common marmoset (Callithrix jacchus) is a New World primate that is used in biomedical research due to its small size and relative ease of handling compared with larger primates. Although bone disease in common marmosets is well recognized, there are very few detailed descriptions in the literature that cover the range of lesions seen in these animals. For all animals used to model human disease, it is important to be aware of background lesions that may affect the interpretation of study findings. This retrospective study details bone diseases encountered in marmoset breeding colonies at 2 different institutions. Affected marmosets at Johns Hopkins University had lesions compatible with diagnoses of rickets, fibrous osteodystrophy and osteopenia. Affected marmosets at the Wisconsin National Primate Research Center exhibited severe lesions of osteoclastic bone resorption and remodeling that had an unusual distribution and were not easily categorized into a known disease entity. The purpose of this report is to document these naturally occurring skeletal lesions of common marmosets and suggest an approach to evaluating skeletal disease in prospective studies of these animals that will allow the most accurate diagnoses.

Fusarium solani species complex associated with carapace lesions and branchitis in captive American horseshoe crabs Limulus polyphemus

Captive American horseshoe crabs Limulus polyphemus housed at the National Aquarium presented with a variety of shell and gill lesions over a 3 yr period. Carapace lesions were located on both the dorsal and ventral prosoma and opisthosoma and included multifocal circular areas of tan discoloration, ulcerations, and/or pitting lesions, extending from superficial to full thickness. Gill lesions involved both the book gill cover (operculum) and individual book gill leaflets and included multifocal circular areas of tan discoloration, tan to off-white opaque proliferative lesions, and/or areas of black discoloration. Histopathology revealed fungal hyphae, with variable morphology throughout the thickened and irregular cuticle of the carapace and occasionally penetrating into subcuticular tissues, with associated amebocytic inflammation. Book gill leaflets were infiltrated by fungal hyphae and contained necrotic debris and amebocytes. Thirty-eight of 39 animals (97%) evaluated via histopathological examination had intralesional fungal hyphae. Fungal cultures of carapace and gill lesions were attempted in 26 tissue samples from 15 individuals and were positive in 13 samples (50%), with 10 cultures (77%) yielding identification to genus. Fusarium sp. was identified in 8 of the 10 cultures (80%) via culture morphology. The Fusarium solani species complex was confirmed in 6 of these 8 (75%) via polymerase chain reaction amplification of 2 different ribosomal-specific sequences of isolated fungal DNA. Ante-mortem systemic and topical treatments were performed on some affected individuals, but no appreciable change in lesions was observed. Mycotic dermatitis and branchitis are serious health issues for captive American horseshoe crabs.

Serum albumin and body weight as biomarkers for the antemortem identification of bone and gastrointestinal disease in the common marmoset

The increasing use of the common marmoset (Callithrix jacchus) in research makes it important to diagnose spontaneous disease that may confound experimental studies. Bone disease and gastrointestinal disease are two major causes of morbidity and mortality in captive marmosets, but currently no effective antemortem tests are available to identify affected animals prior to the terminal stage of disease. In this study we propose that bone disease and gastrointestinal disease are associated disease entities in marmosets and aim to establish the efficacy of several economical antemortem tests in identifying and predicting disease. Tissues from marmosets were examined to define affected animals and unaffected controls. Complete blood count, serum chemistry values, body weight, quantitative radiographs, and tissue-specific biochemical markers were evaluated as candidate biomarkers for disease. Bone and gastrointestinal disease were associated, with marmosets being over seven times more likely to have either concurrent bone and gastrointestinal disease or neither disease as opposed to lesions in only one organ system. When used in tandem, serum albumin <3.5 g/dL and body weight <325 g identified 100% of the marmosets affected with concurrent bone and gastrointestinal disease. Progressive body weight loss of 0.05% of peak body weight per day predicted which marmosets would develop disease prior to the terminal stage. Bone tissue-specific tests, such as quantitative analysis of radiographs and serum parathyroid hormone levels, were effective for distinguishing between marmosets with bone disease and those without. These results provide an avenue for making informed decisions regarding the removal of affected marmosets from studies in a timely manner, preserving the integrity of research results.

Prolonged blockade of VEGF receptors does not damage retinal photoreceptors or ganglion cells

It has recently been reported that relatively short-term inhibition of vascular endothelial growth factor (VEGF) signaling can cause photoreceptor cell death, a potentially clinically important finding since VEGF blockade has become an important modality of treatment of ocular neovascularization and macular edema. However, in a set of studies in which we achieved extended and complete blockage of VEGF-induced vascular leakage through retinal expression of a VEGF binding protein, we did not observe any toxicity to retinal neurons. To follow-up on these apparently discrepant findings, we designed a set of experiments with the kinase inhibitor SU4312, which blocks phosphorylation of VEGF receptors, to look directly for evidence of VEGF inhibition-related retinal toxicity. Using transgenic mice with sustained expression of VEGF in photoreceptors, we determined that periocular injection of 3 microg of SU4312 every 5 days markedly suppressed subretinal neovascularization, indicating effective blockade of VEGF signaling. Wild-type mice given periocular injections of 5 microg of SU4312 every 5 days for up to 12 weeks showed normal scotopic and photopic electroretinograms (ERGs), no TUNEL stained cells in the retina, and no reduction in outer nuclear layer thickness. Incubation of cultured ganglion cells or retinal cultures containing photoreceptors with high doses of SU4312 did not reduce cell viability. These data suggest that blocking VEGF signaling in the retina for up to 12 weeks does not damage photoreceptors nor alter ERG function and should reassure patients who are receiving frequent injections of VEGF antagonists for choroidal and retinal vascular diseases.

Electroretinographic features of the retinopathy, globe enlarged (rge) chick phenotype

PURPOSE

The purpose of the study was to characterize the electroretinographic features of the autosomal recessive retinopathy, globe enlarged (rge) phenotype, in chickens (Gallus gallus).

METHODS

Dark-adapted, light-adapted intensity series and light-adapted 30 Hz flicker responses were recorded from rge and age matched normal control chicks from one to 270 days of age. Retinal sections from rge and control retinas were examined in 7 and 270-day-old chicks.

RESULTS

Electroretinogram (ERG) thresholds of rge birds were raised, the intensity response plots were shifted toward brighter intensities, and retinal sensitivity was reduced. The leading slope of the dark- and light-adapted a-waves was more shallow than normal, suggesting altered photoreceptor responses. The inner retinal components to the ERG were also abnormal; there was a marked lack of oscillatory potentials and an abnormally smooth and broad shape to the b-wave. Additionally, the b-wave was supernormal in response to brighter stimuli in the earlier stages of the disease. There was a progressive deterioration in ERG amplitudes with age that mirrored a slowly progressive thinning of the photoreceptor layer.

CONCLUSIONS

The rge chicken has unusual ERG changes from an early age with altered waveforms and initially they develop a supernormal b-wave. This is followed by a progressive reduction of ERG amplitudes with age. The changes suggest that both photoreceptor and inner retinal responses are abnormal. Additional studies are needed to further elucidate the origin of the abnormal ERG components in the rge chick.

Detailed histopathologic characterization of the retinopathy, globe enlarged (rge) chick phenotype

PURPOSE

The purpose of this study was to characterize the morphological abnormalities in the retinas of chicks (Gallus gallus) suffering from the autosomal recessive disease, retinopathy, globe enlarged (rge/rge).

METHODS

rge/rge affected and age matched control retinas were examined from hatch up to 730 days of age. Thickness of retinal layers at six retinal regions was measured from plastic embedded sections. Morphological features were examined on semi-thin sections by light microscopy and on ultra-thin sections by transmission electron microscopy. Immunohistochemistry was performed using a panel of several different antibodies. Additionally, comparative counting of rod outer segments, rows of cells in the inner nuclear layer, and ganglion cells per unit length was performed.

RESULTS

The earliest changes observed in rge/rge retinas were disorganization of the outer plexiform layer and abnormal location of the endoplasmic reticulum of the photoreceptors. In rge/rge retinas, cone pedicles were larger, irregular in shape, and usually contained multivesicular bodies. In addition, synaptic ribbons of the cone pedicles and rod spherules in rge/rge retinas were less numerous compared to controls. Large glycogen deposits progressively accumulated in the perinuclear cytoplasm associated with the abnormally located endoplasmic reticuli in accessory cones and rods. Total retinal thickness progressively decreased with age in rge/rge birds. This was accompanied by a decrease in the number of cells in the inner nuclear layer and a decrease in the number of rod outer segments (OSs). Several changes were detected in the rge/rge retinas using immunohistochemistry, including mislocalized opsin immunoreactivity of rod photoreceptors, a decrease in number and disorganization of opsin positive rod OSs (especially in the peripheral regions), a decrease in number of tyrosine hydroxylase positive neurites in the distal inner plexiform layer, and activation of macroglial and microglial cells.

CONCLUSIONS

As we previously reported, the rge/rge chick has vision loss that is not the result of photoreceptor loss and is unusual in that electroretinographic responses, although abnormal, are maintained until well after vision loss has developed. The phenotype is associated with a developmental disruption of both rod and cone photoreceptor synaptic terminals that progresses with age. It is possible that these changes may be indicative of abnormal circuitry within the outer plexiform layer, and that they underlie the progressive loss of vision in rge/rge birds. Other early changes suggesting photoreceptor abnormality are dilation of photoreceptor cell bodies, abnormal positioning of endoplasmic reticulum in the perinuclear region that is associated with abnormal glycogen deposition, and mislocalization of opsin immunoreactivity in rods. The rge/rge birds develop globe enlargement after the morphological and electroretinographic abnormalities. Globe enlargement in chicks can be induced by a number of different environmental factors. It is possible that abnormal signaling of photoreceptors to inner retinal cells could induce excessive ocular growth in the rge/rge birds. Many of the morphological changes such as retinal thinning seen in older rge/rge birds may be partly the result of the considerable globe enlargement that occurs later in the disease process. Molecular genetic studies to identify the causal gene mutation should help explain the morphological features of the rge/rge phenotype and clarify their association with vision loss and electroretinographic abnormalities.

Transcriptional regulation of the Bacillus subtilis bscR-CYP102A3 operon by the BscR repressor and differential induction of cytochrome CYP102A3 expression by oleic acid and palmitate

The adjacent yrhI and yrhJ genes were identified by the Bacillus subtilis genome sequencing project. We now report that yrhJ (renamed CYP102A3) encodes a cytochrome P450 and that yrhI (renamed bscR) encodes a repressor that negatively regulates the transcription of the bscR-CYP102A3 operon. The transcriptional initiation site of bscR has been mapped by primer extension analysis. An 18-bp perfect palindromic sequence centered 65.5 bp downstream from the transcriptional initiation site of bscR has been identified as the binding site for BscR by gel mobility shift assays. Base substitutions in the 18-bp inverted repeat resulted in derepression of the bscR-xylE transcriptional fusion in vivo. bscR-xylE fusion studies and Northern blot analysis revealed that oleic acid and palmitate could induce the expression of the bscR-CYP102A3 operon to a considerable extent. However, only oleic acid was capable of preventing the binding of BscR to its operator DNA in vitro, suggesting that the induction of CYP102A3 expression by oleic acid and palmitate in B. subtilis might be mediated through different mechanisms.

Negative regulation of expression of the Bacillus megaterium bmlP1 gene by the bmlP1 3' flanking region

We report that the expression of the Bacillus megaterium bmlP1 gene is subject to negative regulation by the bmlP1 3' flanking region. This repression occurred both in B. megaterium and in Escherichia coli. When the bmlP1 promoter was replaced with a heterologous promoter or when the orientation of the bmlP1 3' flanking region was reversed, the inhibitory effect was still observed. However, the bmlP1 3' flanking region was unable to exert repression on a heterologous gene when fused downstream in either orientation, and it was incapable of acting in trans. Dot blot and Northern blot analyses revealed that the repression occurred at the RNA level. Deletion analysis showed that the regulatory site responsible for the repression is located within a 116-bp region immediately following the bmlP1 gene. Possible mechanisms for this repression are discussed.

The basal-level expression of the cytochrome P450(BM-1) gene is negatively affected by the bm1P1 gene of Bacillus megaterium

Evidence against the Bm1P1 protein as a positive transcription factor for barbiturate-mediated induction of cytochrome P450(BM-1) in Bacillus megaterium has been provided in our previous report. In the present study, we show that the basal-level expression of the P450(BM-1) promoter-xylE transcriptional fusion is significantly reduced when the bm1P1 gene is present on the same plasmid. Moreover, disruption of the chromosomal bm1P1 gene results in enhanced expression of the P450(BM-1) promoter-xylE fusion on a multicopy plasmid. By using a binary vector system, we found that expression of the P450(BM-1) promoter-xylE fusion from a high-copy plasmid is substantially repressed by expression of bm1P1 from a low-copy plasmid. Taken together, these results suggest that the basal-level expression of P450(BM-1) is negatively affected by bm1P1. Possible mechanisms for this control are discussed.

Cloning, expression, and catabolite repression of a gene encoding beta-galactosidase of Bacillus megaterium ATCC 14581

A gene encoding beta-galactosidase, designated mbgA, was isolated from Bacillus megaterium ATCC 14581. Chromosomal beta-galactosidase production could be dramatically induced by lactose but not by isopropyl-beta-D-thiogalactopyranoside (IPTG) and was subject to catabolite repression by glucose. Disruption of mbgA in the B. megaterium chromosome resulted in loss of lactose-inducible beta-galactosidase production. A 27-bp inverted repeat was found to overlap the mbgA promoter sequence. Two partially overlapping catabolite-responsive elements (CREs) were identified within the inverted repeat. Base substitutions within CRE-I and/or CRE-II caused partial relief from catabolite repression. The results suggest that the 27-bp inverted repeat may serve as a target for a catabolite repressor(s).

Evidence against the Bm1P1 protein as a positive transcription factor for barbiturate-mediated induction of cytochrome P450BM-1 in bacillus megaterium

The Bm1P1 protein was previously proposed to act as a positive transcription factor involved in barbiturate-mediated induction of cytochrome P450BM-1 in Bacillus megaterium. We now report that the bm1P1 gene encodes a protein of 217 amino acids, rather than the 98 amino acids as reported previously. In vitro gel shift assays indicate that the Bm1P1 protein did not interact with probes comprising the regulatory regions of the P450BM-1 gene. Moreover, disruption of the bm1P1 gene did not markedly affect barbiturate induction of P450BM-1 expression. A multicopy plasmid harboring only the P450BM-1 promoter region could increase expression of the chromosome-encoded P450BM-1. The level of expression is comparable with that shown by a multicopy plasmid harboring the P450BM-1 promoter region along with the bm1P1 gene. These results strongly suggest that the Bm1P1 protein is unlikely to act as a positive regulator for barbiturate induction of P450BM-1 expression. Finally, deletion of the Barbie box did not markedly diminish the effect of pentobarbital on expression of a reporter gene transcriptionally fused to the P450BM-1 promoter. This suggests that the Barbie box is unlikely to be a key element in barbiturate-mediated induction of P450BM-1.

Repetitive elements in the third intron of murine apolipoprotein A-I gene

Genomic DNAs containing the gene encoding apolipoprotein A-I (apoA-I) from four strains of mice and three strains of rats have been sequenced. Some peculiar repetitive sequences were found in the third intron of apoA-I of the murine species. The striking features include regular tandem repeats of C(A)4 and C(A)6 in mice and long A-tracts in rats. Not completely identical but very similar motifs were found in mice or rats belonging to the same species while repetitive elements from different species show some variation from their species-specific consensus sequences. These repetitive motifs are very similar to the sequences flanking human Alu and rodent B1 repetitive elements, although no evidence for the existence of Alu or B1 was found near the peculiar repetitive DNA sequences in apoA-I gene.

Iron and salicylate induction of cytochrome P450BM-1 in Bacillus megaterium

The effects of iron and salicylate on the expression of cytochrome P450s in Bacillus megaterium were investigated in this report. Immunoblot analysis showed that the addition of 4 mM ferric iron or 10 mM salicylate to the culture medium resulted in a significant increase in the P450BM-1 level, while the same condition had little effect on P450BM-3 expression. Substantial induction of chloramphenicol acetyltransferase (CAT) activity by iron and salicylate in B. megaterium cells bearing a P450BM-1 promoter-cat transcriptional fusion vector suggests that the induction of P450BM-1 by iron and salicylate occurs at the transcriptional level. Unexpectedly, in contrast to the bm1P1-dependent induction of P450BM-1 by pentobarbital, disruption of bm1P1 gene did not affect induction of P450BM-1 by iron and salicylate. This result suggests that the induction of P450BM-1 by iron and salicylate occurs by a bm1P1-independent mechanism. To our knowledge, this is the first example of an iron-regulated cytochrome P450 gene in prokaryotes.

Changes in plasma levels of lipids and lipoprotein composition in patients with Kawasaki disease

Studies on the response of plasma lipids and lipoproteins to Kawasaki disease are scarce so far. The purpose of this study was to investigate the changes in plasma levels of lipids and apolipoproteins as well as the composition of different lipoproteins in patients during the acute and convalescence phases of Kawasaki disease. The results showed that during the acute phase, the concentrations of plasma high density lipoprotein (HDL)-cholesterol, apolipoprotein A-I (apoA-I) and A-II (apoA-II) were significantly reduced. While the reduction of HDL-cholesterol was mainly related to the lowering of esterified and unesterified cholesterols in HDL2 during the acute stage of Kawasaki disease, most of which recovered during the subsequent convalescence phase. The plasma concentration of triglycerides was 46% higher in patients during the acute phase of Kawasaki disease than in the control subjects, which may be ascribed to the increase of triglycerides in very low density lipoprotein (VLDL), low density lipoprotein (LDL) and HDL2. The variables studied above did not appear to be independent parameters. The level of plasma apoA-I showed a stronger negative association with triglyceride concentration (r = -0.22) than apoA-II (r = -0.11) and HDL-cholesterol (r = -0.07). Furthermore, the levels of cholesterol, apoA-I and apoA-II in HDL2, but not in HDL3, were inversely correlated with the levels of triglyceride. We conclude that the temporary changes of lipid levels associated with Kawasaki disease results predominantly from alterations of lipoprotein composition.

A 53-base-pair inverted repeat negatively regulates expression of the adjacent and divergently oriented cytochrome P450(BM-1) gene and its regulatory gene, bm1P1, in Bacillus megaterium

To study the role of the cis-acting element(s) in controlling the expression of the cytochrome P450(BM-1) gene and its upstream regulatory gene, bm1P1, in Bacillus megaterium, various deletion derivatives were constructed. A 53-bp inverted repeat located midway between the P450(BM-1) gene and bm1P1 gene was found in vivo to negatively regulate the expression of both genes, the regulation of which may occur at the transcriptional level. The promoter of the P450(BM-1), gene was also identified and found to be similar to those recognized by the sigmaA RNA polymerase of Bacillus subtilis. Possible mechanisms by which the 53-bp inverted repeat regulates the gene expression are discussed.

Purification and characterization of 6xHis-tagged Bm3R1 repressor of Bacillus megaterium

The bm3R1 gene-encoded repressor controls the expression of cytochrome P450BM-3 gene as well as its own expression in Bacillus megaterium. We have developed an efficient system for overexpression and purification of Bm3R1 protein by nickel ion affinity chromatography. Adding six histidine residues at either N-terminus or C-terminus of Bm3R1 repressor caused no loss of its operator DNA binding ability. We have investigated the interaction between Bm3R1(His)6 and its operator DNA by equilibrium and kinetic methods. The results showed that the apparent dissociation constant is around 1.8 x 10(-9) M and the half-life of Bm3R1(His)6-operator complex is about 50 minutes. We have also found by gel filtration chromatography that Bm3R1(His)6 may exist in low oligomeric state(s) in solution, which is competent for binding to its operator DNA.

Inhibition by barbiturates of the binding of Bm3R1 repressor to its operator site on the barbiturate-inducible cytochrome P450BM-3 gene of Bacillus megaterium

In our previous publication (Shaw, G.-C., and Fulco, A. J. (1992) J. Biol. Chem. 267, 5515-5526), we reported that Bm3R1, a protein encoded in an open reading frame just upstream from the cytochrome P450BM-3 gene, is a repressor critically involved in the barbiturate-inducible expression of this gene in Bacillus megaterium. We now describe the purification of the Bm3R1 protein from an overproducing Escherichia coli strain harboring a bm3R1 gene-carrying plasmid and report the effect of barbiturate inducers on the interaction of Bm3R1 with a fragment of B. megaterium DNA containing the bicistronic operator and promoter sequences. Gel filtration analysis revealed that, under our experimental conditions, most of the Bm3R1 protein exists in highly aggregated forms. Gel mobility shift assays showed that Bm3R1 protein bound specifically to a segment of DNA containing the promoter-operator region of the bm3R1 gene while DNase I footprinting experiments established that Bm3R1 protected a region of DNA that covers and flanks the palindromic operator sequence. The interaction between Bm3R1 repressor and its operator, in vitro, was strongly inhibited by the addition of 2 mM pentobarbital or 2 mM methohexital (strong in vivo inducers of P450BM-3) but not by the same concentration of phenobarbital (a relatively weak inducer) or by mephobarbital (a non-inducer). A detailed comparison of pentobarbital and methohexital at concentrations lower than 2 mM indicated that methohexital was 5-10 times more effective as an inhibitor of Bm3R1 binding in vitro, as compared with its 7-fold greater inducer potency in vivo. The observation that the in vitro inhibition effects of barbiturates on the interaction of Bm3R1 repressor and its operator correlate strongly with their in vivo potency as inducers of cytochrome P450BM-3 suggests a mechanism for the induction process. It seems plausible that the barbiturate inducers might bear a conformational resemblance to and mimic the mode of action of an as yet unidentified endogenous inducer(s) in B. megaterium that functions by releasing the binding of Bm3R1 repressor from its operator site.

Barbiturate-mediated regulation of expression of the cytochrome P450BM-3 gene of Bacillus megaterium by Bm3R1 protein

In a previous publication (Wen, L.-P., Ruettinger, R. T., and Fulco, A.J. (1989) J. Biol. Chem. 264, 10996-11003), we reported that about 1 kilobase of 5' flanking sequence was required for barbiturate-inducible expression of the cytochrome P450BM-3 gene in Bacillus megaterium. We have now found, by analysis of various deletion and frameshift derivatives of this region, that an open reading frame immediately upstream of the B. megaterium cytochrome P450BM-3 structural gene encodes a protein, designated Bm3R1, which negatively controls the expression of the P450BM-3 gene at the transcriptional level. A helix-turn-helix DNA binding motif was found near the N-terminal portion of Bm3R1 protein. The 5' terminus of the bm3R1 transcript generated in vivo was determined by nuclease S1 mapping and primer extension analysis to be 44 base pairs upstream of the translation initiation sequence GTG of bm3R1. A putative promoter sequence with a high degree of similarity to the -35 and -10 consensus sequence recognized by the Bacillus subtilis sigma-43 factor was located at an appropriate distance from the transcription start site. A B. megaterium mutant which highly constitutively produced P450BM-3 protein was isolated and complementation of this cytochrome P450BM-3-constitutive mutant by a DNA fragment containing the wild-type bm3R1 gene indicated that the mutation in this locus was trans-dominant. Sequence analysis of the bm3R1 gene and its upstream region from this mutant, after amplification by the polymerase chain reaction, identified a single base change that resulted in a glycine to glutamate substitution in the beta-turn region of the DNA binding motif. By placing the bm3R1 gene under the control of a tac promoter and changing the translation initiation sequence from GTG to ATG, we succeeded in overproducing the Bm3R1 protein in Escherichia coli. A 20-bp perfect palindromic putative operator site, located between the presumed promoter sequences and the bm3R1 structural gene, was defined both by in vivo titration of Bm3R1 repressor and by gel mobility shift assays using the cell-free extracts containing the overproduced wild-type or mutant Bm3R1 protein. The barbiturate effect in mediating the induction of cytochrome P450BM-3 appears to be indirect but probably involves, in part, the release of inhibition by Bm3R1 repressor protein by interfering with its binding to the palindromic putative operator sequence and perhaps to other sites on the regulatory region of the gene encoding cytochrome P450BM-3.

Studies on outbreak of viral hepatitis at Calcutta with special reference to serological investigations

Sixty cases of acute viral hepatitis were studied from clinical, biochemical and in particular serological point of view. Majority of the patients had significant pre-icteric and icteric phase with moderate elevations of bilirubin, SGOT and SGPT and marginal elevations of serum alkaline phosphatase. Cholestatic features were observed only in 6.7% of cases. All subjects improved and there was no death in this series. Serological marker studies revealed hepatitis A in 8 (13.3%) cases and hepatitis B in 3 (5.0%) cases. Rest 49 cases were possibly due to non-A, non-B hepatitis. As there was no evidence of parenteral transmission, it was concluded that this epidemic was water borne from contaminated municipal water supply.