Biomedical subjects

Nora Rozengurt

Publications and source records attributed to Nora Rozengurt.

17 recordsLinked to original sources

PubMed2006

Genetic background controls tumor development in PTEN-deficient mice.

PTEN is one of the most frequently mutated tumor suppressor genes in human cancers. Germ line mutations of PTEN have been detected in three rare autosomal-dominant disorders. However, identical mutations in the PTEN gene may lead to different symptoms that have traditionally been described as different disorders, such as Cowden disease, Lhermitte-Duclos disease, and Bannayan-Zonana syndromes. This lack of genotype-phenotype correlation prompted us to directly test the possible effects of genetic background or modifier genes on PTEN-controlled tumorigenesis using genetically engineered mouse models. In this study, we generated two animal models in which either exon 5 (Pten(Delta5)) or promoter to exon 3 (Pten(-)) of the murine Pten gene were deleted and compared phenotypes associated with individual mutations on two genetic backgrounds. We found that the onset and spectrum of tumor formation depend significantly on the genetic background but less on the type of mutation generated. Our results suggest that PTEN plays a critical role in cancer development, and genetic background may influence the onset, the spectrum, and the progression of tumorigenesis caused by Pten mutation.

Alleles↗

PubMed2006

Colocalization of the alpha-subunit of gustducin with PYY and GLP-1 in L cells of human colon.

In view of the importance of molecular sensing in the function of the gastrointestinal (GI) tract, we assessed whether signal transduction proteins that mediate taste signaling are expressed in cells of the human gut. Here, we demonstrated that the alpha-subunit of the taste-specific G protein gustducin (Galpha(gust)) is expressed prominently in cells of the human colon that also contain chromogranin A, an established marker of endocrine cells. Double-labeling immunofluorescence and staining of serial sections demonstrated that Galpha(gust) localized to enteroendocrine L cells that express peptide YY and glucagon-like peptide-1 in the human colonic mucosa. We also found expression of transcripts encoding human type 2 receptor (hT2R) family members, hT1R3, and Galpha(gust) in the human colon and in the human intestinal endocrine cell lines (HuTu-80 and NCI-H716 cells). Stimulation of HuTu-80 or NCI-H716 cells with the bitter-tasting compound phenylthiocarbamide, which binds hT2R38, induced a rapid increase in the intracellular Ca2+ concentration in these cells. The identification of Galpha(gust) and chemosensory receptors that perceive chemical components of ingested substances, including drugs and toxins, in open enteroendocrine L cells has important implications for understanding molecular sensing in the human GI tract and for developing novel therapeutic compounds that modify the function of these receptors in the gut.

Calcium↗

PubMed2005

Cardiac manifestations in the mouse model of mucopolysaccharidosis I.

Mucopolysaccharidosis I (MPS I, alpha-l-iduronidase deficiency disease) is a heritable lysosomal storage disorder involving multiple organs, including the heart. Malfunction of the heart is also a major manifestation in the mouse model of MPS I, progressing in severity from 6 to 10 months (of a 1 year life span). In comparisons of MPS I with wild-type mice, the heart was found enlarged, with thickened septal and posterior walls, primarily because of infiltration of the muscle by storage-laden cells. Heart valves were enlarged and misshapen, and contained large numbers of highly vacuolated interstitial cells. The thickened aortic wall contained vacuolated smooth muscle cells and interrupted elastic fibers. Hemodynamic measurements and echocardiography revealed reduced left ventricular function as well as mitral and aortic regurgitation. But despite these abnormalities, free-roaming MPS I mice implanted with radio telemetry devices showed surprisingly normal heart rate and blood pressure, though their electrocardiograms were abnormal. An incidental finding of the telemetry studies was a disturbed circadian rhythm in the MPS I mice. Restoration of enzyme activity in the heart of one mouse, by transplantation of retrovirally modified bone marrow, resulted in normalization of left ventricular function as well as loss of storage vacuoles in myocytes and endothelial cells, though not in valvular interstitial cells. This study demonstrates the usefulness of the mouse model for in-depth studies of the cardiovascular component of MPS I.

Animals↗

PubMed2005

Monitoring antiproliferative responses to kinase inhibitor therapy in mice with 3'-deoxy-3'-18F-fluorothymidine PET.

UNLABELLED: The aim of this study was to evaluate, whether PET with (18)F-FDG and 3'-deoxy-3'-(18)F-fluorothymidine ((18)F-FLT) may be used to monitor noninvasively the antiproliferative effects of tyrosine kinase inhibitors. METHODS: Using a high-resolution small animal scanner, we measured the effect of the ErbB-selective kinase inhibitor PKI-166 on the (18)F-FDG and (18)F-FLT uptake of ErbB1-overexpressing A431 xenograft tumors. RESULTS: Treatment with PKI-166 markedly lowered tumor (18)F-FLT uptake within 48 h of drug exposure; within 1 wk (18)F-FLT uptake decreased by 79%. (18)F-FLT uptake by the xenografts significantly correlated with the tumor proliferation index as determined by proliferating cell nuclear antigen staining (r = 0.71). Changes in (18)F-FLT uptake did not reflect inhibition of ErbB kinase activity itself but, rather, the effects of kinase inhibition on tumor cell proliferation. Tumor (18)F-FDG uptake generally paralleled the changes seen for (18)F-FLT. However, the baseline signal was significantly lower than that for (18)F-FLT. CONCLUSION: These results indicate that (18)F-FLT PET provides noninvasive, quantitative, and repeatable measurements of tumor cell proliferation during treatment with ErbB kinase inhibitors and provide a rationale for the use this technology in clinical trials of kinase inhibitors.

Animals↗

PubMed2004

Uropathic observations in mice expressing a constitutively active point mutation in the 5-HT3A receptor subunit.

Mutant mice with a hypersensitive serotonin (5-HT)3A receptor were generated through targeted exon replacement. A valine to serine mutation (V13'S) in the channel-lining M2 domain of the 5-HT3A receptor subunit rendered the 5-HT3 receptor 70-fold more sensitive to serotonin and produced constitutive activity when combined with the 5-HT3B subunit. Mice homozygous for the mutant allele (5-HT3Avs/vs) had decreased levels of 5-HT3A mRNA. Measurements on sympathetic ganglion cells in these mice showed that whole-cell serotonin responses were reduced, and that the remaining 5-HT3 receptors were hypersensitive. Male 5-HT3Avs/vs mice died at 2-3 months of age, and heterozygous (5-HT3Avs/+) males and homozygous mutant females died at 4-6 months of age from an obstructive uropathy. Both male and female 5-HT3A mutant mice had urinary bladder mucosal and smooth muscle hyperplasia and hypertrophy, whereas male mutant mice had additional prostatic smooth muscle and urethral hyperplasia. 5-HT3A mutant mice had marked voiding dysfunction characterized by a loss of micturition contractions with overflow incontinence. Detrusor strips from 5-HT3Avs/vs mice failed to contract to neurogenic stimulation, despite overall normal responses to a cholinergic agonist, suggestive of altered neuronal signaling in mutant mouse bladders. Consistent with this hypothesis, decreased nerve fiber immunoreactivity was observed in the urinary bladders of 5-HT3Avs/vs compared with 5-HT3A wild-type (5-HT3A+/+) mice. These data suggest that persistent activation of the hypersensitive and constitutively active 5-HT3A receptor in vivo may lead to excitotoxic neuronal cell death and functional changes in the urinary bladder, resulting in bladder hyperdistension, urinary retention, and overflow incontinence.

Animals↗

PubMed2004

Classification of proliferative pulmonary lesions of the mouse: recommendations of the mouse models of human cancers consortium.

Rapid advances in generating new mouse genetic models for lung neoplasia provide a continuous challenge for pathologists and investigators. Frequently, phenotypes of new models either have no precedents or are arbitrarily attributed according to incongruent human and mouse classifications. Thus, comparative characterization and validation of novel models can be difficult. To address these issues, a series of discussions was initiated by a panel of human, veterinary, and experimental pathologists during the Mouse Models of Human Cancers Consortium (NIH/National Cancer Institute) workshop on mouse models of lung cancer held in Boston on June 20-22, 2001. The panel performed a comparative evaluation of 78 cases of mouse and human lung proliferative lesions, and recommended development of a new practical classification scheme that would (a) allow easier comparison between human and mouse lung neoplasms, (b) accommodate newly emerging mouse neoplasms, and (c) address the interpretation of benign and preinvasive lesions of the mouse lung. Subsequent discussions with additional experts in pulmonary pathology resulted in the current proposal of a new classification. It is anticipated that this classification, as well as the complementary digital atlas of virtual histological slides, will help investigators and pathologists in their characterization of new mouse models, as well as stimulate further research aimed at a better understanding of proliferative lesions of the lung.

Animals↗

PubMed2004

Prostate pathology of genetically engineered mice: definitions and classification. The consensus report from the Bar Harbor meeting of the Mouse Models of Human Cancer Consortium Prostate Pathology Committee.

The Pathological Classification of Prostate Lesions in Genetically Engineered Mice (GEM) is the result of a directive from the National Cancer Institute Mouse Models of Human Cancer Consortium Prostate Steering Committee to provide a hierarchical taxonomy of disorders of the mouse prostate to facilitate classification of existing and newly created mouse models and the translation to human prostate pathology. The proposed Bar Harbor Classification system is the culmination of three meetings and workshops attended by various members of the Prostate Pathology Committee of the Mouse Models of Human Cancer Consortium. A 2-day Pathology Workshop was held at The Jackson Laboratory in Bar Harbor, Maine, in October 2001, in which study sets of 93 slides from 22 GEM models were provided to individual panel members. The comparison of mouse and human prostate anatomy and disease demonstrates significant differences and considerable similarities that bear on the interpretation of the origin and natural history of their diseases. The recommended classification of mouse prostate pathology is hierarchical, and includes developmental, inflammatory, benign proliferative, and neoplastic disorders. Among the neoplastic disorders, preinvasive, microinvasive, and poorly differentiated neoplasms received the most attention. Specific criteria were recommended and will be discussed. Transitions between neoplastic states were of particular concern. Preinvasive neoplasias of the mouse prostate were recognized as focal, atypical, and progressive lesions. These lesions were designated as mouse prostatic intraepithelial neoplasia (mPIN). Some atypical lesions were identified in mouse models without evidence of progression to malignancy. The panel recommended that mPIN lesions not be given histological grades, but that mPIN be further classified as to the absence or presence of documented associated progression to invasive carcinoma. Criteria for recognizing microinvasion, for classification of invasive gland-forming adenocarcinomas, and for characterizing poorly differentiated tumors, including neuroendocrine carcinomas, were developed and are discussed. The uniform application of defined terminology is essential for correlating results between different laboratories and models. It is recommended that investigators use the Bar Harbor Classification system when characterizing new GEM models or when conducting experimental interventions that may alter the phenotype or natural history of lesion progression in existing models.

Animals↗

PubMed2004

Retrovirally transduced bone marrow has a therapeutic effect on brain in the mouse model of mucopolysaccharidosis IIIB.

Mucopolysaccharidosis IIIB (MPS IIIB) is a lysosomal storage disorder caused by mutations in NAGLU, the gene encoding alpha-N-acetylglucosaminidase. The disease is characterized by profound mental retardation and eventual neurodegeneration, but relatively mild somatic manifestations. There is no available therapy. We have used a mouse knockout model of the disease to test therapy by genetically modified bone marrow. Bone marrow from Naglu -/- male mice was transduced with human NAGLU cDNA in an MND-MFG vector, and transplanted into 6- to 8-week-old lethally irradiated female -/- mice. Sham-treated mice received bone marrow transduced with eGFP cDNA in an MND vector. alpha-N-Acetylglucosaminidase activity in plasma and leukocytes, measured 3 and 6 months after transplantation, varied from marginal to nearly 30 times wild-type. A low level of alpha-N-acetylglucosaminidase activity, as little as provided by transplantation of unmodified Naglu +/+ bone marrow, could normalize biochemical defects (glycosaminoglycan storage and beta-hexosaminidase elevation) in liver and spleen, but a very high level was required for an effect on kidney. Effects on the brain were best seen by examination of cellular morphology using light and electron microcopy. Mice that expressed very high levels of alpha-N-acetylglucosaminidase in blood had an increased number of normal-appearing neurons in the cortex and other parts of the brain, while microglia with engorged lysosomes had almost completely disappeared. Immunohistochemistry showed a marked decrease of staining for subunit c of mitochondrial ATP synthase and for Lamp1, markers of neuronal and microglial pathology, respectively, as well as a decrease in staining for glial fibrillary acid protein, a marker of activated astrocytes. These results show that genetically modified cells of hematopoietic origin can reduce the pathologic manifestations of MPS IIIB in the Naglu -/- mouse brain.

Acetylglucosaminidase↗

PubMed2003

Time course of inner ear degeneration and deafness in mice lacking the Kir4.1 potassium channel subunit.

The Kir4.1 gene (KCNJ10) encodes an inwardly rectifying K(+) channel subunit abundantly expressed in the CNS. Its expression in the mammalian inner ear has been suggested but its function in vivo in the inner ear is unknown. Because diverse human hereditary deafness syndromes are associated with mutations in K(+) channels, we examined auditory function and inner ear structure in mice with a genetically inactivated Kir4.1 K(+) channel subunit. Startle response experiments suggest that Kir4.1-/- mice are profoundly deaf, whereas Kir4.1+/- mice react like wild-type mice to acoustic stimuli. In Kir4.1-/- mice, the Reissner membrane is collapsed, the tectorial membrane is swollen, and type I hair cells and spiral ganglion neurons as well as their central processes degenerate over the first postnatal weeks. In the vestibular ganglia, neuronal cell death with apoptotic features is also observed. Immunostaining reveals that Kir4.1 is strongly expressed in stria vascularis of wild-type but not Kir4.1-/- mice. Within the spiral ganglion, Kir4.1 labeling was detected on satellite cells surrounding spiral ganglion neurons and axons. We conclude that Kir4.1 is crucial for normal development of the cochlea and hearing, via two distinct aspects of extracellular K(+) homeostasis: (1). in stria vascularis, Kir4.1 helps to generate the cochlear endolymph; and (2). in spiral and vestibular ganglia, Kir4.1 in surrounding glial cells helps to support the spiral and vestibular ganglion neurons and their projecting axons.

Animals↗

PubMed2003

Treatment of the mouse model of mucopolysaccharidosis I with retrovirally transduced bone marrow.

Mucopolysaccharidosis I is a lysosomal storage disorder caused by mutations in the IDUA gene, resulting in deficiency of alpha-L-iduronidase and accumulation of glycosaminoglycans. Bone marrow transplantation has been the only available therapy, soon to be joined by enzyme replacement. We have tested retroviral gene therapy in a knockout mouse model of the disease. Bone marrow from Idua-/- male donor mice was transduced with human IDUA cDNA in an MND vector and transplanted into 6-8-week-old, lethally irradiated female Idua-/- mice. Sham-treated mice received Idua-/- bone marrow that was either unmodified or transduced with eGFP. Unmodified Idua+/+ (wild type) bone marrow was transplanted for comparison. Recipient mice were sacrificed 2-6 months after transplantation. Three biochemical parameters were used to gauge therapeutic success: appearance of alpha-L-iduronidase activity, reduction of beta-hexosaminidase activity and reduction of soluble glycosaminoglycan accumulation. Transplantation of unmodified +/+ bone marrow was effective in reducing storage in liver and spleen, but not in kidney or brain. The level of alpha-L-iduronidase activity achieved by transplantation of IDUA-transduced bone marrow varied greatly between experiments. But even modest activity resulted in correction of pathology of kidney, bladder epithelium, fibrocartilage, choroid plexus, and thalamus, as seen by light microscopy, while electron microscopy showed the presence of some normal neurons in the cortex. The partial correction of brain pathology is attributed to migration of donor hematopoietic cells, demonstrated by the presence of the Y chromosome and of normal microglia in the brain of mice receiving IDUA cDNA.

Animals↗

PubMed2003

PTEN tumor suppressor regulates p53 protein levels and activity through phosphatase-dependent and -independent mechanisms.

We show in this study that PTEN regulates p53 protein levels and transcriptional activity through both phosphatase-dependent and -independent mechanisms. The onset of tumor development in p53(+/-);Pten(+/-) mice is similar to p53(-/-) animals, and p53 protein levels are dramatically reduced in Pten(-/-) cells and tissues. Reintroducing wild-type or phosphatase-dead PTEN mutants leads to a significant increase in p53 stability. PTEN also physically associates with endogenous p53. Finally, PTEN regulates the transcriptional activity of p53 by modulating its DNA binding activity. This study provides a novel mechanism by which the loss of PTEN can functionally control "two" hits in the course of tumor development by concurrently modulating p53 activity.

Animals↗

PubMed2003

Prostate-specific deletion of the murine Pten tumor suppressor gene leads to metastatic prostate cancer.

The murine Pten prostate cancer model described in this study recapitulates the disease progression seen in humans: initiation of prostate cancer with prostatic intraepithelial neoplasia (PIN), followed by progression to invasive adenocarcinoma, and subsequent metastasis with defined kinetics. Furthermore, while Pten null prostate cancers regress after androgen ablation, they are capable of proliferating in the absence of androgen. Global assessment of molecular changes caused by homozygous Pten deletion identified key genes known to be relevant to human prostate cancer, including those "signature" genes associated with human cancer metastasis. This murine prostate cancer model provides a unique tool for both exploring the molecular mechanism underlying prostate cancer and for development of new targeted therapies.

Animals↗

PubMed2003

Mitigation of neutrophil infiltration in a rat model of early Staphylococcus aureus endophthalmitis.

PURPOSE: Infectious endophthalmitis is characterized by neutrophil migration into the eye. The purpose of this study was to determine whether systemic neutrophil depletion mitigates the ocular influx of neutrophils during the early phases of experimental endophthalmitis. METHODS: Endophthalmitis was induced in rats by intravitreal injection of Staphylococcus aureus. Animals received a single systemic dose of an anti-neutrophil-depleting antibody (dAb) or normal rabbit serum (NRS) 6 or 12 hours after intravitreal injection. Inflammation was graded both in vivo and by histopathology. Myeloperoxidase (MPO) was used as a biomarker of neutrophil infiltration. Bacterial clearance was evaluated by determining the amount of viable bacteria recovered from ocular specimens. RESULTS: Rats that received dAb 6 hours after bacterial injection exhibited significantly lower clinical scores, MPO activity, fewer vitreous exudates, and higher vitreous bacterial counts at 24 hours (P < 0.05). As the neutrophil population returned in this group, measured by the number in the peripheral blood, increasing intraocular inflammation was observed. Rats receiving dAb 12 hours after vitreous injection also demonstrated significantly lower clinical scores, MPO activity and less vitreous exudates at the 24-hour time point (P < 0.05). No significant differences from the control were detected at any of the subsequent time points, except in bacterial counts and MPO activity. CONCLUSIONS: Depletion of neutrophils early in the inflammatory response delayed the onset of severe ocular inflammation but also prevented adequate bacterial clearance. These results confirm the important role of neutrophils in ocular host defense during the early stages of experimental endophthalmitis.

Animals↗

PubMed2002

Expression of bitter taste receptors of the T2R family in the gastrointestinal tract and enteroendocrine STC-1 cells.

Although a role for the gastric and intestinal mucosa in molecular sensing has been known for decades, the initial molecular recognition events that sense the chemical composition of the luminal contents has remained elusive. Here we identified putative taste receptor gene transcripts in the gastrointestinal tract. Our results, using reverse transcriptase-PCR, demonstrate the presence of transcripts corresponding to multiple members of the T2R family of bitter taste receptors in the antral and fundic gastric mucosa as well as in the lining of the duodenum. In addition, cDNA clones of T2R receptors were detected in a rat gastric endocrine cell cDNA library, suggesting that these receptors are expressed, at least partly, in enteroendocrine cells. Accordingly, expression of multiple T2R receptors also was found in STC-1 cells, an enteroendocrine cell line. The expression of alpha subunits of G proteins implicated in intracellular taste signal transduction, namely Galpha(gust), and Galpha(t)-(2), also was demonstrated in the gastrointestinal mucosa as well as in STC-1 cells, as revealed by reverse transcriptase-PCR and DNA sequencing, immunohistochemistry, and Western blotting. Furthermore, addition of compounds widely used in bitter taste signaling (e.g., denatonium, phenylthiocarbamide, 6-n-propil-2-thiouracil, and cycloheximide) to STC-1 cells promoted a rapid increase in intracellular Ca(2+) concentration. These results demonstrate the expression of bitter taste receptors of the T2R family in the mouse and rat gastrointestinal tract.

Animals↗

PubMed2002

Mouse model for human arginase deficiency.

Deficiency of liver arginase (AI) causes hyperargininemia (OMIM 207800), a disorder characterized by progressive mental impairment, growth retardation, and spasticity and punctuated by sometimes fatal episodes of hyperammonemia. We constructed a knockout mouse strain carrying a nonfunctional AI gene by homologous recombination. Arginase AI knockout mice completely lacked liver arginase (AI) activity, exhibited severe symptoms of hyperammonemia, and died between postnatal days 10 and 14. During hyperammonemic crisis, plasma ammonia levels of these mice increased >10-fold compared to those for normal animals. Livers of AI-deficient animals showed hepatocyte abnormalities, including cell swelling and inclusions. Plasma amino acid analysis showed the mean arginine level in knockouts to be approximately fourfold greater than that for the wild type and threefold greater than that for heterozygotes; the mean proline level was approximately one-third and the ornithine level was one-half of the proline and ornithine levels, respectively, for wild-type or heterozygote mice--understandable biochemical consequences of arginase deficiency. Glutamic acid, citrulline, and histidine levels were about 1.5-fold higher than those seen in the phenotypically normal animals. Concentrations of the branched-chain amino acids valine, isoleucine, and leucine were 0.4 to 0.5 times the concentrations seen in phenotypically normal animals. In summary, the AI-deficient mouse duplicates several pathobiological aspects of the human condition and should prove to be a useful model for further study of the disease mechanism(s) and to explore treatment options, such as pharmaceutical administration of sodium phenylbutyrate and/or ornithine and development of gene therapy protocols.

Animals↗

PubMed2002

Conditional loss of PTEN leads to precocious development and neoplasia in the mammary gland.

PTEN tumor suppressor is frequently mutated in human cancers, including breast cancers. Female patients with inherited PTEN mutations suffer from virginal hypertrophy of the breast with high risk of malignant transformation. However, the exact mechanisms of PTEN in controlling mammary gland development and tumorigenesis are unclear. In this study, we generated mice with a mammary-specific deletion of the Pten gene. Mutant mammary tissue displayed precocious lobulo-alveolar development, excessive ductal branching, delayed involution and severely reduced apoptosis. Pten null mammary epithelial cells were disregulated and hyperproliferative. Mutant females developed mammary tumors early in life. Similar phenotypes were observed in Pten-null mammary epithelia that had been transplanted into wild-type stroma, suggesting that PTEN plays an essential and cell-autonomous role in controlling the proliferation, differentiation and apoptosis of mammary epithelial cells.

Animals↗

PubMed2002

Outbreak of hind limb paralysis in young CFW Swiss Webster mice.

An outbreak of paralysis among 16- to 20-week-old CFW Swiss Webster sentinel mice developed in one of our barrier facilities. Two months after arrival and over a period of four weeks, six of 400 mice purchased from an approved vendor, developed progressive hind limb paralysis without other clinical signs of disease. On the basis of the histopathologic changes and negative serologic test results, lymphoblastic lymphoma causing compression of the spinal cord was diagnosed. There were two leading features to this outbreak: its unusual epidemiologic presentation, and the localization of the lesions principally in the lumbar muscles. A presumptive diagnosis of retroviral infection with Abelson's murine leukemia virus (A-MuLV) was established on the basis of histopathologic and immunohistochemical findings. Little is known about retroviral status in many commercial colonies, and few users report presence of spontaneous lymphomas. This report points out complications derived from commercially available animals that carry endogenous retroviruses. It also emphasizes the need of diagnosing and reporting clusters of hind limb paralysis or lymphomas in mice to assess the prevalence and relevance of retroviral infections in commercial colonies.

Abelson murine leukemia virus↗