Light and electron microscopic features of eperythrozoon-like parasites in a North American opossum (Didelphis virginiana).

Epierythrocytic parasites associated with a severe anemic episode have not been previously reported in the opossum. A Wright-Giemsa-stained peripheral blood smear from an anemic North American opossum (Didelphis virginiana) revealed numerous organisms attached to red blood cells either singularly or in chains. Ring forms of the organism were common and could be found free in the plasma. Electron microscopy revealed that these organisms were attached to the intact plasma membrane in depressions on the surface of red blood cells. Delicate fibrils between the organism and adjacent membrane were observed. The organisms were round to oval with a diameter of 300-750 nm and were enclosed by a single limiting membrane. The light and electron microscopic features of these epierythrocytic organisms are similar to those reported for Eperythrozoon and Haemobartonella species.     

Early Tumor Response to Intraarterial or Intravenous Administration of Carboplatin to Treat Naturally Occurring Lower Urinary Tract Carcinoma in Dogs

Background

Survival times and tumor responses associated with malignant neoplasia of the lower urinary tract are poor despite the vast array of current treatments. Therefore, the evaluation of alternative treatments, such as intraarterial administration of chemotherapy (IAC) should be considered.

Objective

To describe a technique for superselective catheterization for IAC and to evaluate initial tumor response by ultrasonography after both IAC and intravenous administration of chemotherapy (IVC).

Animals

Client‐owned dogs with lower urinary tract neoplasia treated with either IVC (n = 15) or IAC (n = 11).

Methods

Retrospective study. An arterial approach via the carotid or femoral artery was utilized to obtain superselective access and administer chemotherapy in the IAC cases. Medical record review was performed, data were recorded, and recorded variables were evaluated statistically.

Results

Intraarterial chemotherapy was successfully administered in all cases. There was a significantly greater decrease in longest unidimensional measurement in the IAC group as compared to the IVC group (P = .013). The IAC group was also significantly more likely to have a tumor response as assessed by modified RECIST guidelines (P = .049). Dogs in the IAC group were significantly less likely to develop anemia (P = .001), lethargy (P = .010) and anorexia (P = .024).

Conclusion and Clinical Importance

This study demonstrated the feasibility and efficacy of performing IAC for lower urinary tract neoplasia. Further investigation is necessary as the follow‐up time was short and the impact on long‐term outcome and survival was not determined.     

Increasing wood production through old age in tall trees

How long forest trees can sustain wood production with increasing age remains an open question, primarily because whole-crown structure and growth cannot be readily measured from the ground or on felled trees. We climbed and directly measured crown structures and growth rates of 43 un-suppressed individuals (site trees) of the two tallest species – Eucalyptus regnans and Sequoia sempervirens – representing a wide range of tree sizes and ages. In both species, ground-level measurements of annual growth, including height, ring width, and basal area increment, exhibited the oft-reported trend of decreasing growth (or no change in growth) with age, yet wood production of the entire main trunk and whole crown both increased with size and age up to and including the largest and oldest trees we measured. The balance between structural metrics of whole-crown respiratory demands (cambium area, inner bark volume, sapwood volume, and heartwood deposition area) and photosynthetic capacity (leaf area and green bark area) was statistically independent of size but not age. After accounting for the effect of size, trees with lower potential respiratory demands grew more than trees with higher potential respiratory demands per unit photosynthetic area. The strongest determinant of tree energy balance was the ratio of aboveground cambium area to leaf area. Among the site trees we examined, over 85% of the variation in annual wood production was explained by variation in size, and the proportion of total aboveground wood production in appendages (branches, limbs, and reiterated trunks) increased linearly with size. With increasing age in both species, the proportion of annual wood production converted to heartwood increased in main trunks and appendages. The oldest tree we measured produced more heartwood in its main trunk over 651 years (351 m³) than contained in any tree we measured <1500 years old. The two tallest tree species achieve similar stature despite divergent growth dynamics and ecologies. At one extreme, E. regnans attains great size quickly but dies relatively young because trees are susceptible to fire and fungi. At the other extreme, S. sempervirens attains great size more slowly but has a long lifespan because trees resist fire and prioritize investment in decay-resistant heartwood. Increasing wood production as trees age is a mechanism underlying the maintenance of biomass accumulation during forest development and the carbon-sink capacity of old-growth forests.     

Radiographic features of suspected suture‐associated cystic calculi in dogs

This retrospective case series describes the radiographic features of suspected suture‐associated cystic calculi in six dogs with a history of at least one or multiple prior cystotomies. One of the dogs presented twice. Suspected suture‐associated cystic calculi were multifocal, short, predominantly linear mineral opacities localized in the center of the urinary bladder on abdominal radiographs. One patient (n = 1) presented with multifocal round, pin point, and linear radiopaque calculi. The calculi were all calcium oxalate in composition. On gross examination, the calculi had a hollow center. Six cystotomies used monofilament absorbable suture material (polydioxanone [n = 4] or poliglecaprone 25 [n = 1]) in prior cystotomies. Suture material in two of the cases was unknown. Suspected suture‐associated cystic calculi are a rare occurrence in veterinary medicine but should be considered in dogs that have a history of prior cystotomy, hollow core on gross analysis, and radiographic evidence of mineral opaque, predominantly linear, cystic calculi.     

α-Luminol prevents decreases in glutamate, glutathione, and glutamine synthetase in the retinas of glaucomatous DBA/2J mice

Objective  To test the hypothesis that in DBA/2J mice, oxidative stress decreases glutamine synthetase (GS) levels resulting in a loss of neuronal glutamate and that the antioxidant α-luminol (GVT®) decreases this stress and glutamate loss in some types of glaucoma.
Animals  DBA/2J mice were separated into two groups, of which one was not treated, and the other treated with GVT in the drinking water. At 7 months of age, retinas were examined from five untreated DBA/2J mice, seven GVT-treated mice, and five C57BL/6 mice (negative controls).
Methods  Serial 0.5 μm plastic sections were immunogold stained for glutamate, GS, and total glutathione, followed by image analysis for staining patterns and density.
Results  Focal decreases in glutamate immunostaining were common in the inner nuclear layer (INL) of DBA/2J retinas, but not in C57BL/6 or GVT-treated DBA/2J retinas. Decreases in glutathione and GS immunostaining were found in DBA/2J retinal regions where neuronal glutamate immunostaining was reduced. Retinas from GVT-treated DBA/2J had no significant decreases in INL levels of glutamate, glutathione, or GS.
Conclusions  Retinas of dogs with primary glaucoma are reported to have focal depletion of neuronal glutamate. In DBA/2J mice, similar changes occur prior to the development of clinical disease. In these focal glutamate-depleted regions, levels of glutathione and GS are also reduced, consistent with the hypothesis that oxidative stress contributes to retinal changes in glaucoma. The ability of GVT, an antioxidant, to inhibit retinal abnormalities in DBA/2J mice provides further support for this hypothesis.