Patent hepatic ciliated foregut remnant resulting in an umbilicobiliary sinus tract, with gallbladder agenesis, in an 8-wk-old male French Bulldog

Hepatic ciliated foregut remnants or cysts are congenital abnormalities resulting from retention of embryonic ciliated foregut within the liver. These structures are rarely reported in the human medical literature and have not been reported in the veterinary literature previously, to our knowledge. We describe here a case of an 8-wk-old male French Bulldog with a congenital patent hepatic ciliated foregut remnant resulting in an umbilicobiliary sinus tract. The dog also had concurrent gallbladder agenesis. The patient had yellow fluid discharging from the umbilicus, mimicking a patent urachus. Surgical exploration, removal, and histology provided a conclusive diagnosis of a hepatic foregut remnant and therapeutic resolution of the clinical signs. The histologic appearance of a hepatic foregut remnant is classical, namely a duct composed of 4 layers: an inner ciliated epithelial lining, loose connective tissue, smooth muscle, and a fibrous capsule.

Anaplastic Sarcoma and Sertoli Cell Tumor in a Central Bearded Dragon (Pogona vitticeps)

A five-year-old male central bearded dragon (Pogona vitticeps) was presented for investigation of blood in the voided urates. A small cutaneous mass was detected in the gular region, but clinical examination was otherwise unremarkable. Fecal parasitology was negative. Initially, further diagnostics were declined, and antimicrobial treatment was initiated. At re-examination one month later, the gular mass had increased in size and an additional mass was detected within the celomic cavity. Both masses were surgically excised and diagnosed by histopathology as a high-grade anaplastic sarcoma (gular mass), resembling a histiocytic sarcoma, and a Sertoli cell tumor (coelomic mass). Neither of these have been previously reported in the central bearded dragon. Twenty months post-surgery, the lizard remains well with no recurrence of clinical signs or evidence of tumor re-growth.

Odontoameloblastoma with extensive chondroid matrix deposition in a guinea pig

Odontoameloblastomas (previously incorporated within ameloblastic odontomas) are matrix-producing odontogenic mixed tumors and are closely related in histologic appearance to the 2 other types of matrix-producing odontogenic mixed tumors: odontomas and ameloblastic fibro-odontomas. The presence or absence of intralesional, induced non-neoplastic tissue must be accounted for in the diagnosis. Herein we describe a naturally occurring odontoameloblastoma with extensive chondroid cementum deposition in a guinea pig ( Cavia porcellus). Microscopically, the mass featured palisading neoplastic odontogenic epithelium closely apposed to ribbons and rings of a pink dental matrix (dentinoid), alongside extensive sheets and aggregates of chondroid cementum. The final diagnosis was an odontoameloblastoma given the abundance of odontogenic epithelium in association with dentinoid but a paucity of pulp ectomesenchyme. Chondroid cementum is an expected anatomical feature of cavies, and its presence within the odontoameloblastoma was interpreted as a response of the ectomesenchyme of the dental follicle to the described neoplasm. Our case illustrates the inductive capabilities of odontoameloblastomas while highlighting species-specific anatomy that has resulted in a histologic appearance unique to cavies and provides imaging and histologic data to aid diagnosis of these challenging lesions.

Physiological concentrations of estradiol attenuate endothelin 1-induced coronary vasoconstriction in vivo

BACKGROUND

Estrogens are cardioprotective hormones and are reported to have antianginal properties. We examined the effect of physiological concentrations of 17beta-estradiol on coronary reactivity in anesthetized female farm pigs.

METHODS AND RESULTS

Epicardial coronary cross-sectional area (CSA) was assessed by two-dimensional intravascular ultrasound, average coronary peak flow velocity (APV) by intravascular Doppler velocimetry, and coronary blood flow (CBF) was calculated. Dose-response curves to intracoronary endothelin-1 (ET-1, 1 pmol/L to 10 nmol/L), the selective ET(B) receptor agonist sarafotoxin (1 pmol/L to 10 nmol/L), and serotonin (0.1 nmol/L to 1 micromol/L) were assessed before and after a 10-minute infusion of intracoronary estradiol (1 nmol/L). Before estradiol administration, ET-1 induced significant dose-dependent decreases in CSA, APV, and CBF. Estradiol attenuated ET-1-induced epicardial vasoconstriction (P<.001) as well as ET-1-induced decreases in APV (P=.05) and CBF (P=.012). In an additional five pigs, vehicle (DMSO) had no effect on ET-1-induced coronary vasoconstriction. Before estradiol administration, sarafotoxin induced no net change in CSA but induced increases in APV and CBF, the extent of which did not change significantly after estradiol. Serotonin induced small decreases in CSA but increased APV and CBF. Estradiol did not influence serotonin-induced changes in CSA, APV, or CBF.

CONCLUSIONS

We conclude that estradiol attenuates ET-1-induced vasoconstriction, possibly through effects on the ET(A) receptor, because selective ET(B) receptor-induced stimulation with sarafotoxin remained unchanged. Such an effect on the ET(A) receptor may relate to the antianginal properties of estrogens.

Heme oxygenase-mediated resistance to oxygen toxicity in hamster fibroblasts

The role of heme oxygenase (HO)-1 was evaluated in the oxygen-resistant hamster fibroblast cell line, O2R95, which moderately overexpress HO when compared with the parental cell line, HA-1. To suppress HO-1 expression, O2R95 were transfected with HO-1 antisense oligonucleotide or treated with tin-mesoporphyrin (SnMP). To increase HO-1 expression, cells were transfected with HO-1 cDNA in a pRC/cytomegalovirus (CMV) vector. All cells were challenged with a 48-h exposure to 95% O2 (hyperoxia). When HO activity was suppressed, O2R95 cells had significantly decreased cell viability, increased susceptibility to lipid peroxidation, and increased protein oxidation in hyperoxia. In contrast, further overexpression of HO-1 did not improve resistance to oxygen toxicity. Antisense-transfected cells and SnMP-treated cells with lowered HO activity showed increased levels of cellular heme compared with controls. In the HO-1 cDNA-transfected O2R95 cells, cellular heme was lowered compared with controls; however, cellular redox active iron levels were increased. We conclude that HO mediates cytoprotection to oxygen toxicity within a narrow range of expression. We speculate that this protective effect may be mediated in part through increased metabolism of the pro-oxidant heme but that higher levels of HO activity obviate protection by increased redox active iron release.

Differences in basal and hyperoxia-associated HO expression in oxidant-resistant hamster fibroblasts

Heme oxygenase (HO) is the rate-limiting enzyme in the production of bilirubin from heme, and HO-1 is its inducible isoenzyme. In the metabolic pathway of HO a potential oxidant, heme, is degraded, a potential antioxidant, bilirubin, is generated, and a potent sequestering agent of redox active iron, ferritin, is thought to be coinduced. Therefore, the sum of the reactions of HO may be useful in antioxidant defense. To explore the role of HO in protection against oxidative stress, we examined HO-1 expression in Chinese hamster fibroblasts (HA-1) as well as stable hydrogen peroxide (H2O2)-resistant (OC-14) and 95% O2-resistant (O2R95) variant cell lines derived from HA-1, after exposure to 72 h of hyperoxia (95% O2-5% CO2). Total HO activity, HO-1 protein, and HO-1 mRNA steady-state levels were assessed before exposure and daily during exposure to hyperoxia. Controls were exposed to 95% air-5% CO2. Confluent monolayers of O2R95 and OC-14 cells had increased basal immunoreactive HO-1 protein levels relative to HA-1 cells when the cells were grown in normoxia, and O2R95 had higher total basal HO activity. When exposed to hyperoxia for up to 3 days, O2R95 cells, which were resistant to oxygen-induced killing, did not show induction of HO-1 mRNA or increased immunoreactive protein, whereas OC-14 and HA-1, which were relatively more sensitive than O2R95 to oxygen-related cytotoxicity, demonstrated significant increases in HO-1 expression during exposure to hyperoxia. Basal ferritin protein levels were highest in the O2R95 cells, intermediate in OC-14, and lowest in HA-1, but ferritin protein did not increase further, with hyperoxic exposure, in any of the cell lines. We conclude that increased constitutive HO-1 expression is associated with resistance to hyperoxia, whereas induction of HO-1 mRNA is an index of oxidative injury, since it only occurs after cells have sustained cytotoxic injury. We also conclude that increased ferritin expression does not necessarily accompany increased HO-1 expression in oxidant stress. We speculate that HO-1 plays a role in protection against hyperoxic damage.

Heterogeneity in the mitotic checkpoint control of BALB/3T3 cells and a correlation with gene amplification propensity

Chinese hamster ovary (and many rodent cell lines) transiently delay mitosis and progress into a second cell cycle without undergoing cytokinesis when treated with Colcemid, whereas HeLaS3 (and most human cell lines) arrest permanently in mitosis. We have discussed these differences and their consequences for cell survival under cell cycle-perturbing conditions within the context of mitotic checkpoint control (Schimke et al., Cold Spring Harbor Symp. Quant. Biol., 56: 417-425, 1991). Here, we report studies with mouse BALB/3T3 cell populations which, by the criterion of response to Colcemid, constitute a heterogeneous population with respect to mitotic checkpoint control. Clonal and subclonal populations retain population heterogeneity but with a bias for enrichment of cell populations that respond as do HeLaS3 cells. We have analyzed clones for their propensity for gene amplification as assessed by a stepwise increment selection protocol in methotrexate and report that there are significant differences in amplification propensities that correlate with differences in mitotic checkpoint control properties.

Alkyl- and aryl-substituted salicyl phosphates as detection reagents in enzyme-amplified fluorescence DNA hybridization assays on solid support

Nine salicyl phosphate esters with hydrophobic substituents (5-phenyl, 5-(2,4-difluorophenyl), 5-tert-octyl, 5-cumyl, 5-(4-tert-butylphenyl, 5-(1-adamantyl), 5-(n-dodecyl), 5-(1,1-diphenylethyl, and 5-trityl) were synthesized and found to be good substrates for calf intestinal alkaline phosphatase. The enzymatic hydrolysis produced the corresponding salicylates, which were strongly fluorescent when excited by ultraviolet light around 300 nm with maximum emission at 420-435 nm. The salicylates were less soluble and/or more adhesive than the nonfluorescent salicyl phosphate substrates, resulting in localization of fluorescence signal, which is a requirement for membrane-based assays. The salicyl phosphates bearing 8-14 carbon substitutents were found to be suitable detection reagents for dot-blot DNA hybridization assays on nylon membrane using a biotinylated probe, allowing the detection of 125 pg of target pBR322 plasmid DNA using a simple apparatus consisting of a transilluminator, a camera. and a 455-nm cutoff optical filter.

Time-resolved fluorescence detection of enzyme-amplified lanthanide luminescence for nucleic acid hybridization assays

A new nonisotopic detection method based on time-resolved fluorescence for nucleic acid hybridization assays with alkaline phosphatase labels has been developed: enzyme-amplified lanthanide luminescence (EALL). EALL combines the amplification of an enzyme label with the sensitivity and background elimination of time-resolved fluorescence detection of lanthanide ion luminescence. The detection system for alkaline phosphatase makes use of a phosphorylated salicylic acid derivative that, upon dephosphorylation, gives a product capable of forming a luminescent terbium chelate. We demonstrate DNA hybridization assays by using two substrates, one for membrane and one for solution-based formats. Using the substrate that produces a more adhesive product allows performance of dot-blot and Southern blot assays on nylon membranes; results can be recorded with a time-resolved photographic camera system, or with an ultraviolet transilluminator-based system. Less than 4 pg of target sequence can be detected in a dot-blot assay after incubation with substrate for 2-4 h. DNA microwell-plate hybridization assays with the more soluble substrate/product pair can be quantified with time-resolved fluorescence plate readers, giving a similar detection sensitivity. EALL is thus a practical time-resolved fluorescence-based alternative to other detection systems for DNA hybridization assays.

Time-resolved fluorescence detection of enzyme-amplified lanthanide luminescence for nucleic acid hybridization assays

A new nonisotopic detection method based on time-resolved fluorescence for nucleic acid hybridization assays with alkaline phosphatase labels has been developed: enzyme-amplified lanthanide luminescence (EALL). EALL combines the amplification of an enzyme label with the sensitivity and background elimination of time-resolved fluorescence detection of lanthanide ion luminescence. The detection system for alkaline phosphatase makes use of a phosphorylated salicylic acid derivative that, upon dephosphorylation, gives a product capable of forming a luminescent terbium chelate. We demonstrate DNA hybridization assays by using two substrates, one for membrane and one for solution-based formats. Using the substrate that produces a more adhesive product allows performance of dot-blot and Southern blot assays on nylon membranes; results can be recorded with a time-resolved photographic camera system, or with an ultraviolet transilluminator-based system. Less than 4 pg of target sequence can be detected in a dot-blot assay after incubation with substrate for 2-4 h. DNA microwell-plate hybridization assays with the more soluble substrate/product pair can be quantified with time-resolved fluorescence plate readers, giving a similar detection sensitivity. EALL is thus a practical time-resolved fluorescence-based alternative to other detection systems for DNA hybridization assays.