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Biomedical subjects

L C Racusen

Publications and source records attributed to L C Racusen.

At least 37 records · Page 2Linked to original sources
PubMed1998

Vitamin E ameliorates enhanced renal lipid peroxidation and accumulation of F2-isoprostanes in aging kidneys.

Aging results in progressive glomerular sclerosis and reductions in glomerular filtration rate (GFR). Oxidative stress may be an important mechanism for the aging process, but to date the role of oxidative stress on renal aging has not been determined. The present study was performed to determine whether age-related alterations in renal hemodynamics and morphology were associated with oxidative stress and whether this could be attenuated by chronic administration of vitamin E. Rats, aged 13 mo, were given either control diet containing vitamin E 50 IU/kg (n = 6) or a high-vitamin E diet (5,000 IU/kg; n = 6) for 9 mo. Another group of rats (3-4 mo old; n = 7) served as young controls. Aging was accompanied by a 60% reduction in GFR, a threefold increase in renal F2 isoprostanes, newly discovered vasoconstrictive F2-like prostaglandins generated by free radical-mediated lipid peroxidation. Renal aging was also associated with an increase in oxidant-sensitive heme oxygenase, advanced glycosylation end products (AGEs), and the AGE receptor, RAGE. AGE-RAGE interaction has been shown to induce oxidative stress. With high-vitamin E diet, GFR was increased by 50%, F2 isoprostanes were suppressed, and expression of heme oxygenase and RAGE was attenuated. There was also a tendency for glomerular sclerosis to be attenuated. These data demonstrate that age-related decline in renal function is accompanied by oxidative stress and that administration of antioxidants, such as vitamin E, could attenuate the decline in renal function.

Aging↗
PubMed1997

Evaluation of pancreas transplant needle biopsy: reproducibility and revision of histologic grading system.

BACKGROUND: Tissue samples for the diagnosis of pancreatic allograft rejection are now obtained routinely through the application of the percutaneous needle biopsy technique. The availability of biopsy material (89% adequate for diagnosis in our setting) presents a challenge for pathologists who are asked to provide a fast and accurate diagnosis of rejection and its severity, while at the same time being able to differentiate rejection from other causes of graft dysfunction. METHODS: To differentiate rejection from other pathologic processes, 26 histologic features were assessed in 92 biopsies performed for confirmation of clinical diagnosis of rejection and the results were compared with 31 protocol biopsies, 12 allograft pancreatectomies with non-rejection pathology, and 30 native pancreas resections with various disease processes. RESULTS: Based on these comparisons, a constellation of findings relating to the vascular, septal, and acinar inflammation was identified for the diagnosis of rejection. Application of these features led us to revise our scheme for grading rejection (ranging from 0-normal to V-severe rejection) to include the categories of "inflammation of undetermined significance" and "minimal rejection." The scheme was used by five pathologist to grade 20 biopsies independently of any clinical data and the interobserver level of agreement was highly significant (kappa=0.83, P<0.0001). This grading scheme was applied blindly to all (183) biopsies from 77 patients with 6-52 months of follow-up. The correlation of the highest degree of rejection on each patient and ultimate graft loss (0% for grades 0-I, 11.5% for grade II, 17.3% for grade III, 37.5% for grade IV, and 100% for grade V) was highly statistically significant (P<0.002). The fraction of grafts lost due to pure immunologic causes increased proportionally to the grade of rejection (0, 50, 66, and 100% for grades II, III, IV, and V, respectively). CONCLUSIONS: This study provides strong support for the proposed pancreas rejection grading scheme and confirms its potential for practical use.

Adult↗
PubMed1997

Cell lines with extended in vitro growth potential from human renal proximal tubule: characterization, response to inducers, and comparison with established cell lines.

Few model systems exist for the study of injury to human renal proximal tubule epithelium. Optimized differentiated human renal epithelial cell lines with extended in vitro growth potential would provide an alternative model system to primary culture or other available non-human mammalian kidney cell lines. For this purpose, human renal tubule epithelial cells were isolated from normal kidney cortex and exposed in culture to a hybrid immortalizing virus, adenovirus 12-SV40. Cell lines were developed by limiting dilution, and three selected cell lines were screened for growth pattern, production of immortalizing virus, tumorigenicity, and ploidy. Cell lines were also monitored for response to inducer agents and matrix factors and were screened for expression of biochemical properties and differentiation markers of renal epithelium. All three are nonproducers of the immortalizing virus and are nontumorigenic. They grow in monolayer, have intermediate growth kinetics, and express markers of renal proximal tubular epithelium by immunohistochemistry. They also express biochemical properties comparable to other widely used proximal tubular cell lines including LLC-RK1, OK, and HK-2 and comparable to human tubular cells in stable culture. Growth medium containing low levels of fetal calf serum, or epidermal growth factor combined with parathyroid hormone, produced optimal growth characteristics, brush border enzyme expression, biochemical properties, and glucose transport in a selected cell line. The addition of dimethyl sulfoxide allows maintenance in morphologically intact monolayers for prolonged periods. These cell lines should be useful model systems for the study of human renal proximal tubular injury or disease.

Adenosine Triphosphate↗
PubMed1997

Adhesion molecules and rejection of renal allografts.

Despite an increasing amount of immunohistochemical and molecular biology data relating to the pathogenesis of kidney transplant rejection, the pathological diagnosis of this condition still rests on routine light microscopy. The detection of changes in expression and distribution of adhesion molecules in renal allograft biopsies may open a new era of increased accuracy of rejection diagnosis. Of the various adhesion molecule reactivities, peritubular capillary VCAM-1 staining appears to be the most specific finding for chronic rejection. This same staining reaction is seen in acute rejection, but may have less specificity in that setting.

Animals↗
PubMed1997

Long-term dietary supplementation with L-arginine prevents age-related reduction in renal function.

Aging is associated with loss of nephron function and reductions in serum L-arginine and excretion of nitric oxide (NO) metabolites. The present study was performed to determine if long-term dietary treatment with L-arginine, the NO synthase substrate, could prevent age-related renal injury. Studies were performed in four groups of rats, aged 12-13 mo, for 8 mo: group 1 received L-arginine (2% in 2.5% corn syrup, n = 5); group 2 received sodium nitrite, an NO donor (0.1%, in 2.5% syrup, n = 7); group 3 was an untreated control group (n = 7); group 4 was treated with 2.5% corn syrup (n = 5). Urinary protein increased and urinary nitrate/nitrite decreased with age in controls, but, during L-arginine treatment, urinary protein decreased and nitrate/nitrite increased. Two weeks after L-arginine was stopped, urinary protein had increased and nitrate/nitrite had decreased to the same level as in controls. L-Arginine treatment increased glomerular filtration rate (GFR) by 50% compared with untreated controls. In contrast, nitrite had no effect on GFR. Morphologically, L-arginine protected against aging injury by reducing the number of sclerotic glomeruli. In summary, we found that L-arginine prevented the age-related glomerular injury and reduction in GFR. The mechanism of protection, however, may be independent of NO.

Aging↗
PubMed1997

Pathology of acute renal failure: structure/function correlations.

Acute renal failure can be fully understood only in the context of an understanding of the morphological changes that underlie or reflect functional changes occurring in the kidney. This review emphasizes morphological findings in the most common form of acute renal failure, so-called acute tubular necrosis. Morphological findings in acute renal failure are discussed, with particular attention to changes in tubular cells with sublethal injury, and changes of apoptotic cell death. It is emphasized that pathogenic mechanisms and morphological changes are complex and interdependent, and in some cases evanescent, making correlation of a single morphological finding to functional end points difficult, especially in the setting of clinical renal injury. It is the constellation of morphological findings that should be assessed to establish the most meaningful correlation with function.

Acute Kidney Injury↗
PubMed1996

Improvement of lesion quantitation for the Banff schema for renal allograft rejection.

The Banff Working Formulation provides objective criteria for diagnosis and grading of acute rejection in renal allografts and should be a reliable tool in the hands of most pathologists. However, as with any such schema, improvement and refinement are both possible and desirable. Agreement should be enhanced by more careful definitions of morphologic criteria, a process which is already underway. In addition, immunostaining, even nonspecific staining for common leukocyte antigen, would be useful in particular for identifying and quantitating glomerular and tubulitis. More specific immunostains, eg, for effector cell populations, cytokines, and/or adhesion molecules will doubtless also be validated by ongoing and future studies, and be incorporated into this rejection assessment schema.

Basement Membrane↗
PubMed1995

Renal proximal tubular epithelium from patients with nephropathic cystinosis: immortalized cell lines as in vitro model systems.

The renal proximal tubule is a major site of injury in a variety of congenital/metabolic diseases including nephropathic cystinosis, the most commonly known cause of renal Fanconi's syndrome. In this lysosomal storage disease there are defects in proximal tubule function within the first few months of life. While culture of renal tubular cells from the urine of these patients is possible, development of immortalized cell lines would insure large numbers of homogeneous cells for studies of renal epithelial cell morphology and pathophysiology in this disease. To develop immortalized cells, cystinotic and normal proximal tubular cells in culture were exposed to an immortalizing vector, containing pZiptsU19 with the temperature sensitive SV40 T-antigen allele tsA58U19 and a neomycin resistance gene, and neomycin-resistant tubular cells were selected for propagation. Ten clones from cystinotic patients have been developed and characterized. All clones express T-antigen at permissive temperature (33 degrees C). Immortalized cells have an epithelial morphology and grow to form confluent monolayers; doubling times vary from 31 to 86 hours. Cystinotic clones are keratin, MDR P-glycoprotein, and alpha-95 kD brush-border associated protein positive but Tamm-Horsfall protein negative by immunocytochemistry, as are normal proximal tubule cells immortalized with this vector. This is consistent with a proximal tubule origin of the cystinotic clones. The cystine content of the cystinotic cells is 70 to 160 times that of normal renal proximal tubular cells in culture, with most of the cystine sequestered in cell lysosomes, confirming that these cell lines express the storage defect.(ABSTRACT TRUNCATED AT 250 WORDS)

Cell Fractionation↗
PubMed1995

The histopathology of acute renal failure.

The morphologic and immunohistologic features in acute renal failure (ARF) are discussed in this article. The focus is on tubular epithelial cell injury, the central pathologic finding in the majority of cases of ARF. Tubular damage may be due to sublethal or lethal cell injury. Cell necrosis, including classic coagulative necrosis and apoptosis, manifestations of sublethal injury, and tubular cell exfoliation are described in detail. Pathologic findings in native kidneys are described.

Acute Kidney Injury↗
PubMed1994

Glomerular metalloprotease activity in streptozotocin- treated rats and in spontaneously diabetic rats (BB/DP).

Differences in the type and extent of diabetic glomerular injury occur in rats made diabetic with streptozotocin (STZ) and in a spontaneously diabetic rat model of the BB/Wor strain. The diabetes prone (BB/DP) rat develops no mesangial matrix expansion with diabetes, whereas the STZ-treated Sprague Dawley rat does. The present study was performed to determine if glomerular metalloprotease activities were decreased in these two rat models of diabetes. Rats were studied at 8 weeks following the onset of hyperglycemia. All diabetic rats were maintained moderately hyperglycemic (plasma glucose = 350 mg/dL) with daily injection of insulin. Glomerular preparations were made and metalloprotease activities were assayed by hydrolysis of gelatin. Metalloprotease activities were decreased by 40-50% in STZ-treated Sprague Dawley rats, but not in BB/DP rats or diabetes resistant rats (BD/DR--the control for the BB/DP) made diabetic by STZ-injection. These data suggest that the decrease in glomerular metalloprotease activity may contribute to mesangial matrix expansion in the diabetic Sprague Dawley rats.

Analysis of Variance↗
PubMed1994

Cell shape changes and detachment in cell culture: models of renal injury.

Loss of tubular cell adhesion may be important in the pathophysiology of injury to renal tubular cell epithelium. In-vitro model systems have been utilized to examine altered cell adhesion in response to hypoxic/anoxic and oxidant-induced cell injury. Alterations in cell cytoskeleton and cell surface adhesion molecules, including L-CAM and integrins, have been demonstrated in these systems, and are probably important in the pathogenesis of altered structure and function in response to injury in renal tubular epithelium.

Animals↗
PubMed1994

New approaches to renal biopsy assessment in acute renal failure: extrapolation from renal transplantation.

Although frequently considered synonymous with acute tubular necrosis, acute renal failure may be brought about by primary disease in any of the four histologic components of the kidney: glomerular, tubular, interstitial, or vascular. It is reasonable to ask whether our current classification system of renal pathology and descriptive approach to renal biopsy interpretation in this setting is optimal. Assessment of renal transplant biopsies performed in the setting of acute dysfunction is becoming much more quantitative, therapy-oriented, pathogenesis-based, and standardized. It would be highly beneficial to the field if similar changes occurred in the approach to native kidney biopsies in acute renal failure. Tighter linkage should be established between promising new developments in the research laboratory and the clinical practice of renal pathology with creation of therapy-oriented classifications which employ standardized quantitative lesion assessment. In a field largely limited to traditional empirical therapies, new pathogenesis-oriented therapeutic approaches to native kidney acute renal failure and allied conditions should be developed based on the products of enlightened renal pathology research.

Acute Kidney Injury↗
PubMed1994

Alterations in human proximal tubule cell attachment in response to hypoxia: role of microfilaments.

Detachment of viable renal proximal tubular cells is seen in clinical and experimental acute tubular necrosis and may contribute to the acute renal dysfunction seen in acute tubular necrosis. Mechanisms of detachment of tubular cells are unknown but must involve changes in tubular cell adhesion. To begin to define mechanisms of altered cell adhesion, cultured human proximal tubular cells were made hypoxic by nitrogen gassing. Cells were monitored (blinded) for cell retraction and rounding over 90 minutes of N2. Hypoxia caused gradual alterations in cell shape, with 37.9% +/- 5.2% retracted-rounded cells by 90 minutes; control monolayers showed no significant change. Fluorescence confocal microscope imaging revealed that hypoxia caused displacement of actin filaments to basal margins of the retracted cells and produced a perinuclear aggregation of short filaments. Phalloidin (10(-6) mol/L), which stabilizes microfilaments and is able to penetrate these hypoxic cells, decreased the percentage of cells showing morphologic changes with hypoxia to < 5% by 90 minutes (p < 0.01). Viability, as assessed by Trypan blue dye exclusion, was well maintained (90% to 98% at 90 minutes) and did not correlate with shape changes. In separate experiments, cytochalasin (10(-6) mol/L)--which depolymerizes microfilaments--but not nocodazole--which disrupts microtubules--produced cell shape change in non-hypoxic monolayers. Disruption of microfilaments appears to play a role in loss of cell-to-cell and cell-to-substrate adhesion and loss of epithelial integrity in hypoxic injury to the renal tubule. These in vitro observations may be relevant to renal proximal tubular cell detachment in in vivo renal injury.

Actin Cytoskeleton↗
PubMed1993

Morphology of ischemic acute renal failure, normal function, and cyclosporine toxicity in cyclosporine-treated renal allograft recipients.

To characterize morphologic changes in the early post-transplant period in cyclosporine-treated renal allograft recipients, we examined biopsies from three groups of cyclosporine-treated patients: normal function (N = 9), ischemic acute renal failure or "acute tubular necrosis" (N = 12), and cyclosporine toxicity (N = 7). Groups were compared with each other and with previously studied groups of azathioprine-treated patients and native kidney patients. The interstitial infiltrate commonly observed in normally functioning azathioprine-treated grafts was not observed in normally functioning cyclosporine-treated grafts, but two of nine such grafts had a significant venulitis, a change also seen in three of the patients with cyclosporine nephrotoxicity. "Acute tubular necrosis" (ATN) in cyclosporine-treated graft recipients was characterized by focal necrosis of complete tubular cross sections, a finding normally rare in other types of ATN, and by shedding into the tubular lumen of tubular cells with non-pyknotic nuclei, a finding supporting our previous observation of detachment of viable tubular cells in ATN but not in the normal kidney. Hyaline arteriolar thickening was the only morphologic finding on biopsy which distinguished patients with cyclosporine nephrotoxicity from other groups. In summary, the morphologic changes observed in cyclosporine-treated renal allograft recipients with ATN or normal function are quite different from those observed in azathioprine-treated patients. Cyclosporine appears to enhance the tubular injury observed in ATN. Hyaline arteriolar thickening is the main distinguishing feature of cyclosporine nephrotoxicity.

Adult↗