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Biomedical subjects

G Striker

Publications and source records attributed to G Striker.

At least 19 recordsLinked to original sources
PubMed2006

PPARalpha agonist fenofibrate improves diabetic nephropathy in db/db mice.

Peroxisome proliferator-activated receptor alpha (PPARalpha) is a member of the ligand-activated nuclear receptor superfamily, and plays an important role in lipid metabolism and glucose homeostasis. The purpose of this study is to determine whether the activation of PPARalpha by fenofbrate would improve diabetes and its renal complications in type II diabetes mellitus. Male C57 BLKS db/db mice and db/m controls at 8 weeks of age were divided to receive either a regular diet chow (db/db, n=8; db/m, n=6) or a diet containing fenofibrate (db/db, n=8; db/m, n=7). Mice were followed for 8 weeks. Fenofibrate treatment dramatically reduced fasting blood glucose (P<0.001) and HbA1c levels (P<0.001), and was associated with decreased food intake (P<0.01) and slightly reduced body weight. Fenofibrate also ameliorated insulin resistance (P<0.001) and reduced plasma insulin levels (P<0.05) in db/db mice. Hypertrophy of pancreatic islets was decreased and insulin content markedly increased (P<0.05) in fenofibrate-treated diabetic animals. In addition, fenofibrate treatment significantly reduced urinary albumin excretion (P<0.001). This was accompanied by dramatically reduced glomerular hypertrophy and mesangial matrix expansion. Furthermore, the addition of fenofibrate to cultured mesangial cells, which possess functional active PPARalpha, decreased type I collagen production. Taken together, the PPARalpha agonist fenofibrate dramatically improves hyperglycemia, insulin resistance, albuminuria, and glomerular lesions in db/db mice. The activation of PPARalpha by fenofibrate in mesangial cells may partially contribute to its renal protection. Thus, fenofibrate may serve as a therapeutic agent for type II diabetes and diabetic nephropathy.

Albuminuria↗
PubMed2001

Glomerular mRNAs in human type 1 diabetes: biochemical evidence for microalbuminuria as a manifestation of diabetic nephropathy.

BACKGROUND: In patients with type 1 diabetes, some consider microalbuminuria to be a predictor of diabetic nephropathy while others believe it is an early feature of diabetic nephropathy. METHODS: Levels of mRNAs that are of pathogenetic relevance in diabetic nephropathy were compared in glomeruli isolated from microalbuminuric and overtly proteinuric subjects and in control normoalbuminuric diabetic subjects and living renal transplant donors. RESULTS: In subjects with microalbuminuria and overt proteinuria, glomerular mRNAs were virtually identical and approximately twofold higher for connective tissue growth factor (CTGF; P < 0.01) and collagen alpha2(IV) (P < 0.03) compared to living renal donors and normoalbuminuric patients. Glomerular glyceraldehyde-3-phosphate dehydrogenase (GAPDH) levels were not significantly different among the groups (P = 0.4). Weak but statistically significant correlations were noted between CTGF mRNA and albuminuria (assessed by rank), fractional mesangial surface area, and a composite renal biopsy index. Glomerular CTGF mRNA correlated inversely with creatinine clearance. Glomerular collagen alpha2(IV) mRNA levels correlated with albuminuria (by rank) and less strongly with fractional mesangial area. CONCLUSION: To our knowledge, these data provide the first biochemical evidence demonstrating that the glomeruli of microalbuminuric patients and those with overt proteinuria do not differ significantly. The data support the concept that microalbuminuria is not "predictive" of diabetic nephropathy, but rather is an earlier point in the spectrum of diabetic nephropathy.

Adult↗
PubMed2000

Glomerular type IV collagen in patients with diabetic nephropathy with and without additional glomerular disease.

BACKGROUND: Type IV collagen is a constituent of mesangial matrix and is increased in amount in many forms of glomerular injury. METHODS: We performed renal biopsies in patients who (1) were donating a kidney to a relative (LRD, N = 6), (2) had diabetic glomerulopathy with or without nephrosclerosis (DM, N = 6), or (3) had diabetic glomerulopathy with a superimposed glomerular lesion (DM+, N = 5). Glomerular collagen alpha2(IV) and control glyceraldehyde-3-phosphate dehydrogenase (GAPDH) mRNAs were measured, and the former correlated with clinical and morphological data to assess its usefulness in reflecting glomerular injury. RESULTS: Collagen alpha2(IV) mRNA levels were lowest in LRD (2.9 +/- 0.6 attomol/glomerulus), higher in DM (5.9 +/- 1.6, P = 0.05), and highest in DM+ (12.7 +/- 2.8 attm/glomerulus, P < 0.05 vs. LRD and vs. DM). Control GAPDH mRNA levels were not significantly different (P > 0.05). Levels of proteinuria, serum creatinine, and glomerular size did not correlate with collagen alpha2(IV) mRNA levels. The fractional mesangial area and the fractional mesangial area occupied by type IV collagen were higher in both diabetic groups than in LRD (P < 10-6), but the intensity of type IV collagen staining in the diabetic patients was significantly less than that seen in the LRD (P < 0.01). In DM+ patients, extramesangial type IV collagen was present. Fractional mesangial area and glomerular collagen alpha2(IV) mRNA levels correlated (r = 0.45, P < 0.05). CONCLUSION: These data are consistent with a view of diabetic nephropathy as a lesion of increased alpha2 type IV collagen transcription, increased total amount of collagen present, but decreased mesangial density relative to other matrix molecules. These data further demonstrate that glomerular injury superimposed on diabetic nephropathy contributes to additional structural damage by inducing increased synthesis of type IV collagen at extramesangial sites.

Adult↗
PubMed1999

DNA bending due to specific p53 and p53 core domain-DNA interactions visualized by electron microscopy.

We have used transmission electron microscopy to analyze the specificity and the extent of DNA bending upon binding of full-length wild-type human tumor suppressor protein p53 (p53) and the p53 core domain (p53CD) encoding amino acid residues 94-312, to linear double-stranded DNA bearing the consensus sequence 5'-AGACATGCCTAGACATGCCT-3' (p53CON). Both proteins interacted with high specificity and efficiency with the recognition sequence in the presence of 50 mM KCl at low temperature ( approximately 4 degrees C) while the p53CD also exhibits a strong and specific interaction at physiological temperature. Specific complex formation did not result in an apparent reduction of the DNA contour length. The interaction of p53 and the p53CD with p53CON induced a noticeable salt-dependent bending of the DNA axis. According to quantitative analysis with folded Gaussian distributions, the bending induced by p53 varied from approximately 40 degrees to 48 degrees upon decreasing of the KCl concentration from 50 mM to approximately 1 mM in the mounting buffer used for adsorption of the complexes to the carbon film surface. The p53CD bent DNA by 35-37 degrees for all salt concentrations used in the mounting buffer. The bending angle of the p53/DNA complex under low salt conditions showed a somewhat broader distribution (sigma approximately 39 degrees ) than at high salt concentration (sigma approximately 31 degrees ) or for p53CD (sigma approximately 24-27 degrees ). Together, these results demonstrate that the p53CD has a dominant role in complex formation and that the complexes formed both by p53 and p53CD under moderate salt conditions are similar. However, the dependence of the bending parameters on ambient conditions suggest that the segments flanking the p53CD contribute to complex formation as well. The problems associated with the analysis of bending angles in electron microscopy experiments are discussed.

Base Sequence↗
PubMed1999

Mesangial cells from diabetic NOD mice constitutively express increased density of atrial natriuretic peptide C receptors.

BACKGROUND: Experimental evidence shows that natriuretic peptides (NPs) play a pathophysiological role in the glomerular hemodynamic abnormalities that occur in diabetes mellitus. METHODS: In this study, the cGMP response to NPs and the different subtypes of NP receptors were examined in mesangial cells derived from a genetic model of diabetes, the nonobese diabetic (NOD) mouse. Multiple mesangial cell lines were derived from diabetic (D-NOD) and nondiabetic (ND-NOD) adult mice and were studied at different passages. RESULTS: cGMP accumulation after stimulation by atrial NP (ANP) or C-type NP (CNP) was markedly inhibited in D-NOD cells irrespective of the glucose concentration (6 or 20 mM) in the culture medium. In contrast, NP receptor density measured from [125I]-ANP saturation binding curves was 7.5 times greater in D-NOD than in ND-NOD cells. No change in KD (200 pM in both cell lines) was observed. Competitive inhibition studies showed that 4-23 C-ANP, which is specific of clearance receptors (NPR-C), displaced 90% of the maximum fraction bound, suggesting the predominance of NPR-C in both cell lines. Further identification was obtained from RNase protection assay and reverse transcription-polymerase chain reaction, which also demonstrated the higher expression of NPR-C mRNA in D-NOD cells. In contrast, NPR-A mRNA was not modified. Increased expression of NPR-C in D-NOD cells was associated with an increase of ANP internalization rate at 37 degrees C, indicating that these receptors were functional. CONCLUSIONS: These studies demonstrate that the constitutive overexpression of NPR-C in D-NOD mesangial cells is associated with a decreased response of cGMP to ANP or CNP treatment. This could be due to the lesser availability of the peptides for binding to NPR-A or NPR-B or to an inhibitory effect on NP-dependent guanylate cyclase activity via the activation of NPR-C.

Animals↗
PubMed1998

Continuous wave two-photon scanning near-field optical microscopy.

We have implemented continuous-wave two-photon excitation of near-UV absorbing fluorophores in a scanning near-field optical microscope (SNOM). The 647-nm emission of an Ar-Kr mixed gas laser was used to excite the UV-absorbing DNA dyes DAPI, the bisbenzimidazole Hoechst 33342, and ethidium bromide in a shared aperture SNOM with uncoated fiber tips. Polytene chromosomes of Drosophila melanogaster and the nuclei of 3T3 Balb/c cells labeled with these dyes were readily imaged. The fluorescence intensity showed the expected nonlinear (second order) dependence on the excitation power in the range of 8-180 mW. We measured the fluorescence intensity as a function of the tip-sample displacement in the direction normal to the sample surface in the single- and two-photon excitation modes (SPE, TPE). The fluorescence intensity decayed faster in TPE than in SPE.

3T3 Cells↗
PubMed1997

Assessment of structure and function in progressive renal disease.

The incidence and prevalence rates of end-stage renal disease (ESRD) in the United States continue to increase. In 1995, the incidence rate was 262 per million population, with a point prevalence rate of 975 per million population. The exact number of individuals with abnormal renal function but not yet at end stage is difficult to assess. Crude estimates suggest that approximately 0.4% of the U.S. population has serum creatinine values greater than 2.0 mg/dl. In some sub-populations, such as African Americans, the estimate is + as high as 1.0%. The rate of progression, likewise, is difficult to assess. In general, renal manifestations of certain systemic diseases such as diabetes mellitus and systemic lupus erythematosus, and those with significant proteinuria (usually greater that 3.0 g/24 hr) seem to have a more rapid progressive course to end stage. If intervention is expected to be successful in halting or slowing down progression, accurate assessment of the early manifestations of renal disease, structure, and function need to be established. Currently accepted methods of assessment of renal disease include measurement of renal function such as serum creatinine and glomerular filtration rate, measurement of proteinuria, assessment of tubular function, glomerular sieving and permselectivity, radiologic imaging techniques, and evaluation of histo-morphometry. Interventions that have been shown to slow progression include control of hypertension, and treatment modalities that reduce proteinuria, such as, the use of angiotensin converting enzyme inhibitors. Further clinical and basic science studies are needed to accurately define the important predictors of progression, and interventions that are effective in slowing or halting progression.

Animals↗
PubMed1994

The effects of dietary protein restriction and blood-pressure control on the progression of chronic renal disease. Modification of Diet in Renal Disease Study Group.

BACKGROUND: Restricting protein intake and controlling hypertension delay the progression of renal disease in animals. We tested these interventions in 840 patients with various chronic renal diseases. METHODS: In study 1, 585 patients with glomerular filtration rates of 25 to 55 ml per minute per 1.73 m2 of body-surface area were randomly assigned to a usual-protein diet or a low-protein diet (1.3 or 0.58 g of protein per kilogram of body weight per day) and to a usual- or a low-blood-pressure group (mean arterial pressure, 107 or 92 mm Hg). In study 2, 255 patients with glomerular filtration rates of 13 to 24 ml per minute per 1.73 m2 were randomly assigned to the low-protein diet (0.58 g per kilogram per day) or a very-low-protein diet (0.28 g per kilogram per day) with a keto acid-amino acid supplement, and a usual- or a low-blood-pressure group (same values as those in study 1). An 18-to-45-month follow-up was planned, with monthly evaluations of the patients. RESULTS: The mean follow-up was 2.2 years. In study 1, the projected mean decline in the glomerular filtration rate at three years did not differ significantly between the diet groups or between the blood-pressure groups. As compared with the usual-protein group and the usual-blood-pressure group, the low-protein group and the low-blood-pressure group had a more rapid decline in the glomerular filtration rate during the first four months after randomization and a slower decline thereafter. In study 2, the very-low-protein group had a marginally slower decline in the glomerular filtration rate than did the low-protein group (P = 0.07). There was no delay in the time to the occurrence of end-stage renal disease or death. In both studies, patients in the low-blood-pressure group who had more pronounced proteinuria at base line had a significantly slower rate of decline in the glomerular filtration rate. CONCLUSIONS: Among patients with moderate renal insufficiency, the slower decline in renal function that started four months after the introduction of a low-protein diet suggests a small benefit of this dietary intervention. Among patients with more severe renal insufficiency, a very-low-protein diet, as compared with a low-protein diet, did not significantly slow the progression of renal disease.

Blood Pressure↗
PubMed1994

p53 protein and vimentin in invasive ductal NOS breast carcinoma--relationship with survival and sites of metastases.

p53 protein and vimentin status were available from immunocytochemical studies of 253 formalin-fixed paraffin-embedded invasive ductal not otherwise specified (NOS) carcinomas from patients for whom follow-up data was also on file. For the 127 node-negative patients, multivariate analysis showed a highly significant correlation between p53 and vimentin (P < 0.001), a strong correlation between vimentin and probability of survival to 90 months but only a weak association between p53 and survival to 90 months. p53 also never entered trees of prognostic indicators derived using stepwise regression with Kaplan-Meier statistics for node-negative and node-positive subgroups, while vimentin status dominated the node-negative trunk. In addition, p53 and vimentin status were analysed versus the site of the first distant metastasis for node-negative and node-positive patients. Analysis by p53 status showed no significant effect on visceral metastases. In contrast, vimentin-positive primaries metastasised twice (and in node-negative patients, 3.5 times) as often to lung, liver and brain as did the vimentin-negative primaries. Both p53-positive and vimentin-positive tumours showed a significantly lower tendency to metastasise to the bone than did their negative counterparts.

Adult↗
PubMed1992

Cathepsin D in invasive ductal NOS breast carcinoma as defined by immunohistochemistry. No correlation with survival at 5 years.

Cathepsin D expression was assessed by immunohistochemistry in 59 node-negative and 77 node-positive infiltrative ductal not otherwise specified (NOS) breast carcinomas and compared with overall survival at 90 months. Cancer cells in 60% (81/136) of the tumors expressed cathepsin D. In the stroma of 33% (18 of 55) cathepsin D negative tumors, numerous strongly cathepsin D positive, benign macrophage-like cells were found. Multivariate analysis showed no significant correlation of cathepsin D expression and overall survival for all patients for node-negative and node-positive patients and for patients with vimentin-positive and -negative tumors. However, in node-negative but not in node-positive patients, a trend for better survival for patients with cathepsin-positive vimentin-negative tumors and worse survival for those with cathepsin-positive vimentin-positive tumors was noted. Due to the low number of patients in these subgroups, neither trend reached significance. Cathepsin D expression was independent of patient age, size, and histologic grade of tumor, and vimentin expression. However, in the node-positive group, negative correlation of cathepsin D and vimentin expression was found. We suggest that prognostic significance of cathepsin D in infiltrative ductal NOS breast carcinomas may be associated with the pathway of its synthesis rather than with its mere presence in tumor cells.

Breast Neoplasms↗
PubMed1991

Evolution of mouse B1 repeats: 7SL RNA folding pattern conserved.

In a recent report mouse B1 genomic repeats were divided into six families representing different waves of fixation of B1 variants, consistent with the retroposition model of human Alu elements. These data are used to examine the distribution of nucleotide substitutions in individual genomic repeats with respect to family consensus sequences and to compare the minimal energy structures of the corresponding B1 RNAs. By an enzymatic approach the predicted structure of B1 RNAs is experimentally confirmed using as a model sequence an RNA of a young B1 family member transcribed in vitro by T7 RNA polymerase. B1 RNA preserves folding domains of the Alu fragment of 7SL RNA, its progenitor molecule. Our results reveal similarities among 7SL-like retroposons, human Alu, and rodent B1 repeats, and relate the evolutionary conservation of B1 family consensus sequences to selection at the RNA level.

Animals↗
PubMed1990

Vimentin expression appears to be associated with poor prognosis in node-negative ductal NOS breast carcinomas.

Vimentin expression in tumors from 83 node-negative and 112 node-positive patients with infiltrative ductal not otherwise specified (NOS) breast carcinomas has been compared with 5-year survival. For node-negative, but not for node-positive patients, there was a significant inverse relation between vimentin expression and survival. Five-year survival of node-negative patients with vimentin-positive tumors was significantly worse compared with vimentin-negative tumors (P less than 0.0001). In the node-negative group, only 36% of patients with vimentin-positive tumors but 82% of patients with vimentin-negative tumors survived 5 years. Tumors of all eight node-negative patients with ductal NOS cancer who died in the first 27 months expressed vimentin. Multivariate analysis of the node-negative group showed a strong correlation of vimentin expression and overall survival, but weak and not significant correlation between histologic grade or size and overall survival at 5 years. Thus vimentin expression seems to be a strong indicator of poor prognosis in node-negative ductal NOS breast carcinomas.

Biopsy↗
PubMed1989

Sequence conservation in Alu evolution.

A statistical analysis of a set of genomic human Alu elements is based on a published alignment and a recent classification of these sequences. After separation of the Alu sequences into families, the consensus sequences of these families are determined, using the correct weighting of the unidirectional decay of CG-dinucleotides. For, the tenfold greater mutation rate at CG's requires separate consideration of an independent clock at every stage of analysis. The distributions of the substitutions with respect to the new consensus sequences, taking the CG and the non-CG-nucleotide positions separately, lie far closer to the expected distributions than the total diversity. Computer analysis of the folding of RNAs derived from these sequences indicates that RNA secondary structure is conserved among Alu families, suggesting its importance for Alu proliferation and/or function. The folding pattern, further substantiated by a number of compensatory mutations, includes secondary structure domains which are homologous to those observed in 7SL RNA and a defined region of interaction between the two Alu subunits. These results are consistent with a model in which a small number of conserved Alu master genes give rise via retroposition to the numerous copies of Alu pseudogenes, that then diversify by random substitution. The master genes appeared at different periods during evolution giving rise to different families of Alu sequences.

Base Composition↗
PubMed1989

Kidney disease of diabetes mellitus: NIDDK initiatives for the comprehensive study of its natural history, pathogenesis, and prevention.

Kidney disease of diabetes mellitus (KDDM) is the most common single cause of end-stage renal disease in the United States and western Europe. Diabetic patients have increased morbidity and mortality and are more likely to develop renal failure than the general US population. In addition, the 5-year survival of patients with KDDM who are receiving dialytic therapy is less than one-half that of patients without diabetes mellitus. The National Institute of Diabetes and Digestive and Kidney Diseases, in collaboration with public, private, and academic groups, has developed an implementation plan to enhance understanding of the underlying mechanisms in KDDM and to develop strategies to prevent the onset and the progression of KDDM.

Clinical Trials as Topic↗
PubMed1989

The three conformations of the anticodon loop of yeast tRNA(Phe).

The complex conformational states of the anticodon loop of yeast tRNA(Phe) which we had previously studied with relaxation experiments by monitoring fluorescence of the naturally occurring Wye base, are analyzed using time and polarization resolved fluorescence measurements at varying counterion concentrations. Synchrotron radiation served as excitation for these experiments, which were analyzed using modulating functions and global methods. Three conformations of the anticodon loop are detected, all three occurring in a wide range of counterion concentrations with and without Mg2+, each being identified by its typical lifetime. The fluorescence changes brought about by varying the ion concentrations, previously monitored by steady state fluorimetry and relaxation methods, are changes in the population of these three conformational states, in the sense of an allosteric model, where the effectors are the three ions Mg2+, Na+ and H+. The population of the highly fluorescent M conformer (8ns), most affine to magnesium, is thus enhanced by that ligand, while the total fluorescence decreases as lower pH favors the H+-affine H conformer (0.6ns). Na+-binding of the N conformer (4ns) is responsible for complex fluorescence changes. By iterative simulation of this allosteric model the equilibrium and binding constants are determined. In turn, using these constants to simulate equilibrium fluorescence titrations reproduces the published results.

Anticodon↗
PubMed1989

Basement membrane heparan sulfate proteoglycan is the main proteoglycan synthesized by glomerular epithelial cells in culture.

The production and distribution of basement membrane-type heparan sulfate proteoglycans (BM HSPG) were investigated in a mouse glomerular epithelial cell line. Confluent cell monolayers were radiolabeled with [35S]sulfate or [35S]cysteine. Proteoglycans were isolated from the medium and cell layers by ion exchange chromatography and their nature determined by enzyme digestion (chondroitinase ABC) or degradative treatment (nitrous acid). It was found that more than 80% of the proteoglycans in both the cell layer and medium were heparan sulfate proteoglycans (HSPG) based on their susceptibility to nitrous acid degradation. More than half of the HSPG in the cell layer could be precipitated with an antiserum that specifically recognizes BM HSPG; only 10% of those released into the medium were precipitated with this antiserum. When immunoprecipitates of [35S] sulfate-labeled proteoglycans were analyzed by SDS-PAGE, the mature proteoglycans ran as a broad band at the top of the gel. When immunoprecipitates of [35S]cysteine-labeled proteoglycans were similarly analyzed, a 250 kd precursor core protein band was seen in addition to the mature proteoglycan. When BM HSPG were localized by immunofluorescence and immunoelectron microscopy (immunoperoxidase), they were found intracellularly in biosynthetic compartments (ER and Golgi cisternae) and extracellularly in deposits of basement membrane-like matrix located beneath and between the cells. These results indicate that l) BM HSPG are the predominant type of proteoglycans made by glomerular epithelial cells in culture; 2) these HSPG are assembled into a loosely organized matrix that is deposited beneath and between the cells; and 3) this cell type produces a higher proportion of BM HSPG than other cultured epithelial cells studied previously.

Animals↗