Expression of Kidney Injury Molecule-1 in Healthy and Diseased Feline Kidney Tissue.

Sensitive markers to detect acute kidney injury (AKI) in cats are lacking. Kidney injury molecule-1 (KIM-1) is a promising marker of acute tubular injury in humans, and sequence and structure of feline KIM-1 have been determined. KIM-1 is shed into urine of cats with natural AKI. The objectives of this study were to characterize temporal and cellular expression of KIM-1 in kidneys from cats without and with experimental and natural AKI using histopathology and immunohistochemistry. Tissue sections from 8 cats without kidney disease, 3 to 4 cats with experimentally induced AKI on each day 1, 3, 6, and 12 after unilateral ischemia/reperfusion, and 9 cats with natural AKI were assessed. In sections from cats without kidney disease, patterns of periodic acid-Schiff and aquaporin-1 staining allowed identification of 3 distinct segments of the proximal tubule. KIM-1 staining was absent in segments 1 (S1) and S2, and faint in S3. Injury of S3 in cats with experimental and natural AKI was characterized by cell loss and necrosis, and remaining intact cells had cytoplasmic blebs and reduced brush borders. In experimental AKI, intensity of KIM-1 expression increased in proportion to the severity of injury and was consistently present in S3 but only transiently in other segments. Vimentin was absent in proximal tubules of healthy cats but expressed in injured S3. These findings indicate that S3 is the proximal tubular segment most susceptible to ischemic injury and that KIM-1 is a sensitive tissue indicator of AKI in cats.

Characterization of kidney injury molecule-1 in cats.

BACKGROUND: Kidney disease (KD) is common in older cats and presumed to arise from subclinical kidney injuries throughout life. Sensitive markers for detecting kidney injury are lacking. Kidney injury molecule 1 (KIM-1) is a useful biomarker of kidney injury in humans and rodents. HYPOTHESIS/OBJECTIVES: Feline KIM-1 is conserved across species, expressed in kidney, and shed into urine of cats with acute kidney injury (AKI). The objectives were to characterize the feline KIM-1 gene and protein, assess available immunoassays for detecting KIM-1 in urine of cats, and identify KIM-1 expression in kidney sections. ANIMALS: Samples from 36 hospitalized and 7 clinically healthy cats were evaluated. Hospitalized cats were divided into 2 groups based on absence (n = 20) or presence (n = 16) of historical KD. METHODS: Feline KIM-1 genomic and complementary DNA sequences were amplified, sequenced and analyzed to determine the presence of isoforms, exon-intron organization and similarity with orthologous sequences. Presence in urine was evaluated by immunoassay and expression in kidney by immunohistochemistry. RESULTS: Three expressed feline KIM-1 transcript variants comprising 894, 810, and 705 bp were identified in renal tissue. KIM-1 immunoassays yielded positive results in urine of cats with conditions associated with AKI, but not chronic KD. Immunohistochemistry of kidney sections identified KIM-1 in proximal tubular cells of cats with positive urine immunoassay results. CONCLUSIONS AND CLINICAL IMPORTANCE: Kidney injury molecule 1 was expressed in specific segments of the nephron and detected in urine of cats at risk of AKI. Urine KIM-1 immunoassay may be a useful indicator of tubular injury.

Medial septal modulation of hippocampal theta cell discharges.

The effect of small electrolytic lesions in various areas of the septum on the behavioral correlates and firing repertoires of hippocampal theta cells, was investigated in the freely moving rabbit. Lesions localized to the medial septum were found to abolish both slow wave theta and the rhythmic firing of CA1 and dentate layer theta cells, in both the type 1 theta (movement) and type 2 theta (sensory processing) behavior conditions. Small lesions of the diagonal band, lateral septum and fimbria/fornix regions only affected rhythmicity to the extent that they also involved the medial septal region. The same medial septal lesions that abolished rhythmicity were also shown to reduce the mean discharge rate of theta cells occurring during the type 1 movement condition by approximately 50%, while the discharge rate occurring during the type 2 sensory processing condition did not change significantly. Behavioral changes were also only observed for lesions involving the medial septum. The importance of afferent input from the medial septum in the generation of hippocampal theta cell rhythmicity was discussed.