Up-regulation of p75 neurotrophin receptor (p75NTR) is associated with apoptosis in chronic pancreatitis

Activation of apoptosis in chronic pancreatitis has been demonstrated. The low-affinity neurotrophin receptor p75 (p75NTR) mediates apoptosis in many cell types in vivo and in vitro. The aim of this study was to examine whether p75NTR is involved in the apoptotic process in chronic pancreatitis. The quantity and localization of the receptor was evaluated using northern blot analysis, in situ hybridization, immunohistochemistry, and western blot analysis. Apoptosis was determined by TUNEL assay. By northern blot analysis, p75NTR mRNA levels were increased 40-fold in chronic pancreatitis compared with normal pancreas (P < 0.01). in situ hybridization revealed weak p75NTR mRNA expression in some ductal cells in the normal pancreas. In contrast in chronic pancreatitis moderate p75NTR expression was present in acinar cells next to fibrosis, ductal cells, and cells of ductular structures as well as in some islet cells. Immunostaining of p75NTR in normal pancreas and chronic pancreatitis tissue samples showed a similar intensity and distribution pattern as found by in situ hybridization. Higher p75NTR protein levels could be confirmed by western blot analysis, which revealed an 8.6-fold increase of p75NTR in chronic pancreatitis. TUNEL staining showed, in chronic pancreatitis samples, positivity in some acinar cells next to fibrosis, some ductal cells, and cells of ductular structures. Also some islet cells were positive by TUNEL staining. The presence of p75NTR immunoreactivity was positively correlated (P < 0.05) with the apoptotic index in the exocrine and endocrine pancreas. In conclusion, p75NTR, the low-affinity receptor of neurotrophins which mediates apoptosis, is up-regulated in CP and is involved in the apoptotic process of the exocrine and endocrine pancreas.     

Reduced arsenic clearance and increased toxicity in aquaglyceroporin-9-null mice

Expressed in liver, aquaglyceroporin-9 (AQP9) is permeated by glycerol, arsenite, and other small, neutral solutes. To evaluate a possible protective role, AQP9-null mice were evaluated for in vivo arsenic toxicity. After injection with NaAsO₂, AQP9-null mice suffer reduced survival rates (LD₅₀, 12 mg/kg) compared with WT mice (LD₅₀, 15 mg/kg). The highest tissue level of arsenic is in heart, with AQP9-null mice accumulating 10–20 times more arsenic than WT mice. Within hours after NaAsO₂ injection, AQP9-null mice sustain profound bradycardia, despite normal serum electrolytes. Increased arsenic levels are also present in liver, lung, spleen, and testis of AQP9-null mice. Arsenic levels in the feces and urine of AQP9-null mice are only ≈10% of the WT levels, and reduced clearance of multiple arsenic species by the AQP9-null mice suggests that AQP9 is involved in the export of multiple forms of arsenic. Immunohistochemical staining of liver sections revealed that AQP9 is most abundant in basolateral membrane of hepatocytes adjacent to the sinusoids. AQP9 is not detected in heart or kidney by PCR or immunohistochemistry. We propose that AQP9 provides a route for excretion of arsenic by the liver, thereby providing partial protection of the whole animal from arsenic toxicity.Evolutionary exposure to environmental arsenic has led to selection of organisms ranging from microbes to mammals with mechanisms for coping with arsenic toxicity. Humans may be inadvertently exposed to arsenic from water contaminated from geological sources or industrial pollution. Up to 57 million people in Bangladesh presently drink groundwater with arsenic concentrations above the World Health Organization acceptable standard (1). In clinical medicine, arsenic trioxide is used in tandem with all-trans-retinoic acid to treat acute promyelocytic leukemia (2, 3), and drugs containing arsenic and antimony are used to treat parasitic infections, African sleeping sickness, and leishmaniasis (4).Transport proteins are critical in the response to arsenic toxicity, because uptake and export are two key features in the cellular drug response. Members of the ATP-binding cassette transporter family export certain drugs, and some cell lines resistant to arsenic have increased expression of multidrug-resistance proteins (MRPs) (5–7). MRP1-null mice exhibit increased sensitivity to sodium arsenite (8). Multidrug-resistance gene MDR1a/1b double-null mice are even more sensitive and accumulate arsenic in their organs after exposure (9).Several lines of evidence indicate that aquaglyceroporins are involved in arsenite uptake by mammalian cells. A member of the aquaporin gene family, yeast glycerol transporter (Fps1p), was shown to facilitate arsenite [As(III)] and antimonite [Sb(III)] uptake by eukaryotic cells (10). The mammalian aquaglyceroporins AQP3, AQP7, and AQP9 were shown to transport arsenite and antimonite (7, 11). Studies of multiple cultured cell lines revealed increased AQP3 or AQP9 expression, resulting in increased arsenic accumulation and toxicity (7, 12–15). A human lung adenocarcinoma cell line resistant to arsenic was found to have decreased levels of AQP3 (7). When AQP3 expression was reduced further, arsenite uptake declined still further, and cellular resistance to arsenic toxicity increased (7).Known to transport a range of small, neutral solutes (16), including arsenite, antimonite, and methylarsonous acid [MAs(III)] (11, 17), AQP9 is expressed in liver, testes, brain, and leukocytes (16, 18, 19), some tissues being sensitive to arsenite. In vivo studies may be complicated by conversion of arsenite to other forms by oxidation, reduction (20), methylation (21, 22), and glutathionylation (20, 23). Despite plentiful evidence that aquaglyceroporins are involved in arsenite transport, arsenic toxicity has not been reported in AQP9-null mice.Here, we describe arsenic toxicity studies of AQP9-null mice compared with WT mice. We determined that AQP9-null mice suffer reduced survival after injection with sodium arsenite (NaAsO₂). Increased accumulation of arsenic was observed in multiple organs of AQP9-null mice, with highest levels of arsenic in heart, accompanied by profound bradycardia. Excretion of arsenic in urine and feces of AQP9-null mice is greatly reduced. Although AQP9 is known to facilitate uptake of arsenite by single cells in culture (12–15), our studies cause us to propose that AQP9 also facilitates in vivo arsenic excretion by the liver, thereby providing partial protection against arsenic toxicity.     

Neurotrophin p75 receptor (p75NTR) promotes endothelial cell apoptosis and inhibits angiogenesis: implications for diabetes-induced impaired neovascularization in ischemic limb muscles

Diabetes impairs endothelial function and reparative neovascularization. The p75 receptor of neurotrophins (p75(NTR)), which is scarcely present in healthy endothelial cells (ECs), becomes strongly expressed by capillary ECs after induction of peripheral ischemia in type-1 diabetic mice. Here, we show that gene transfer-induced p75(NTR) expression impairs the survival, proliferation, migration, and adhesion capacities of cultured ECs and endothelial progenitor cells (EPCs) and inhibits angiogenesis in vitro. Moreover, intramuscular p75(NTR) gene delivery impairs neovascularization and blood flow recovery in a mouse model of limb ischemia. These disturbed functions are associated with suppression of signaling mechanisms implicated in EC survival and angiogenesis. In fact, p75(NTR) depresses the VEGF-A/Akt/eNOS/NO pathway and additionally reduces the mRNA levels of ITGB1 [beta (1) integrin], BIRC5 (survivin), PTTG1 (securin) and VEZF1. Diabetic mice, which typically show impaired postischemic muscular neovascularization and blood perfusion recovery, have these defects corrected by intramuscular gene transfer of a dominant negative mutant form of p75(NTR). Collectively, our data newly demonstrate the antiangiogenic action of p75(NTR) and open new avenues for the therapeutic use of p75(NTR) inhibition to combat diabetes-induced microvascular liabilities.     

急性髓细胞白血病患者NGF及p75NTR测定的临床意义

目的探讨急性髓细胞白血病（AML）患者神经生长因子（NGF）及其低亲和性NGF受体（p75NTR）表达及临床意义。方法运用ELISA测定24例AML患者血清NGF水平,流式细胞术测定骨髓白血病细胞群p75NTR的表达水平;同时选择15例健康者作为对照组。结果①AML患者血清NGF水平与对照组比较明显升高（P〈0.05）,骨髓白血病细胞群表面p75NTR表达水平较对照组明显降低（P〈0.05）。②AML完全缓解（CR）者化疗前p75NTR较未缓解（NR）者明显高表达（P〈0.05）,NGF变化不明显（P〉0.05）。NR者化疗后NGF和p75NTR表达水平与对照组比较差异均有统计学意义（P均〈0.05）,且p75NTR较CR者明显低表达（P〈0.05）。③AML患者NGF以及p75NTR高表达和低表达3年总体生存率比较差异无统计学意义（P〉0.05）。结论 AML患者血清NGF高水平以及骨髓白血病细胞群p75NTR低表达可能参与AML发生发展,且可能是判断近期疗效的有效指标。     

p75NTR介导神经细胞凋亡对老龄鼠学习记忆的影响及补肾方药的作用

目的观察左归丸及熟地黄对衰老大鼠学习记忆能力以及与凋亡相关的脑源性神经生长因子前体(pro BDNF)、p75NTR、sortilin、caspase-3、bcl-2及bax蛋白表达的影响。方法以大剂量D-半乳糖腹腔注射复制大鼠衰老模型,随机分为衰老模型组、衰老左归组、衰老熟大组和衰老熟小组,另设青年对照组。采用Morris水迷宫法观察大鼠空间学习记忆能力、透射电镜检测大鼠海马神经细胞凋亡情况、Western印迹法观察海马组织pro BDNF、p75NTR、sortilin、caspase-3、bcl-2及bax蛋白表达变化。结果与青年对照组比较,衰老大鼠空间学习记忆能力明显降低(P0.05);神经细胞存在凋亡,海马组织pro BDNF、caspase-3、bax蛋白表达显著增加(P0.05),p75NTR及sortilin蛋白表达有升高的趋势,bcl-2蛋白表达明显减少(P0.05)。左归丸及熟地黄对上述指标的异常变化存在一定的调节作用。结论左归丸及熟地黄可能是通过调节凋亡相关分子的表达,从而改善衰老大鼠空间学习记忆能力,延缓衰老。     

Tumor necrosis factor alpha (TNFalpha) and its soluble receptor p75 (sTNF-R p75) in familial combined hyperlipidemia (FCHL)

BACKGROUND AND AIM: Familial combined hyperlipidemia (FCHL) is a genetic disorder of lipid metabolism associated with insulin resistance and abnormalities in fatty acid metabolism whose underlying mechanisms are largely unknown. Perturbations in the TNFalpha/TNF-R pathway may play a role in these abnormalities. METHODS AND RESULTS: We determined plasma levels of TNFalpha and sTNF-R p75 in 85 FCHL patients (TC 245+/-45 mg/dl; TG 260+/-148 mg/dl; apoB 148+/-37 mg/dl) and in 29 age- and sex-matched normolipemic relatives (NL) (TC 187+/-22.8 mg/dl; TG 115+/-37 mg/dl; apoB 106+/-16 mg/dl). Thirty-four normolipemic subjects (TC 180+/-34 mg/dl; TG 107+/-42 mg/dl; apoB 95+/-22 mg/dl) were also included as unrelated controls (NC). Plasma free fatty acids (NEFA) were also measured and insulin sensitivity was evaluated by HOMA. Levels of sTNF-R p75 were significantly reduced in FCHL compared to NL (2.30+/-0.55 ng/ml vs. 2.64+/-0.88 ng/ml, p<0.05) but not compared to NC (2.35+/-0.68 ng/ml). HOMA values were comparable in all groups and did not show any relation with plasma levels of sTNF-R p75. Logistic analysis demonstrated that a low concentration of sTNF-R p75 was an independent predictor of the affected status within FCHL families, but this role was no longer evident when FCHL patients were compared to NC. In FCHL, age (p<0.001) was positively, and TG (p=0.029) and HDL-C (p=0.025) were negatively correlated with plasma concentrations of sTNF-R p75. In the other groups, age (in NL) and non-HDL-C (in NC) were significantly correlated with sTNF-R p75. CONCLUSIONS: Although our data do not support a causative role of TNFalpha/TNF-R alterations in FCHL, they confirm that variation in TNF-R shedding may influence lipid phenotypic expression in FCHL families.     

High nerve growth factor receptor (p75NTR) expression is a favourable prognostic factor in paediatric B cell precursor-acute lymphoblastic leukaemia

Nerve growth factor (NGF) plays a pivotal role in cellular survival/death decisions with the low affinity receptor p75NTR predominately transmitting anti-proliferative signals. In spite of its established role in B-cell function and identification as a prognostically favourable marker in a number of malignancies, little is known about the expression pattern and prognostic significance of p75NTR in B cell precursor-acute lymphoblastic leukaemia (BCP-ALL). p75NTR expression was prospectively studied on primary ALL-blasts in a cohort of paediatric patients with common ALL (n = 86) and preB-ALL (n = 34) treated within the Co-operative study group for childhood acute lymphoblastic leukaemia (CoALL) protocol, CoALL06-97. Flow cytometric analysis showed that almost half of the patients expressed no or negligible amounts of p75NTR (<10%). The median expression in patients expressing p75NTR beyond that threshold was 49% (range 11-100%). In patients classified as low-risk at diagnosis, p75NTR expression was significantly higher than in high-risk patients (P = 0.001). Of note, p75NTR expression was lower in the 21 patients who subsequently developed relapse compared with those remaining in remission (P = 0.038). Accordingly, relapse-free survival was significantly better in patients expressing high surface p75NTR (P = 0.041). Thus, in this prospective analysis, high p75NTR expression was a strong prognostic marker that identified a group of paediatric ALL patients with favourable outcome.     

The neurotrophin receptor p75NTR modulates long-term depression and regulates the expression of AMPA receptor subunits in the hippocampus

Neurotrophins are involved in the modulation of synaptic transmission, including the induction of long-term potentiation (LTP) through the receptor TrkB. Because previous studies have revealed a bidirectional mode of neurotrophin action by virtue of signaling through either the neurotrophin receptor p75NTR or the Trk receptors, we tested the hypothesis that p75NTR is important for longterm depression (LTD) to occur. Although LTP was found to be unaffected in hippocampal slices of two different strains of mice carrying mutations of the p75NTR gene, hippocampal LTD was impaired in both p75NTR-deficient mouse strains. Furthermore, the expression levels of two (RS)-alpha-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA) receptor subunits, GluR2 and GluR3, but not GluR1 or GluR4, were found to be significantly altered in the hippocampus of p75NTR-deficient mice. These results implicate p75NTR in activity-dependent synaptic plasticity and extend the concept of functional antagonism of the neurotrophin signaling system.     

The simple truth is seldom true and never simple: dual role for p75(NTR) in transdifferentation and cell death of hepatic stellate cells

Differentiation of hepatic stellate cells (HSCs) to extracellular matrix- and growth factor-producing cells supports liver regeneration through promotion of hepatocyte proliferation. We show that the neurotrophin receptor p75(NTR), a tumor necrosis factor receptor superfamily member expressed in HSCs after fibrotic and cirrhotic liver injury in humans, is a regulator of liver repair. In mice, depletion of p75(NTR) exacerbated liver pathology and inhibited hepatocyte proliferation in vivo. p75 (NTR-/-) HSCs failed to differentiate to myofibroblasts and did not support hepatocyte proliferation. Moreover, inhibition of p75(NTR) signaling to the small guanosine triphosphatase Rho resulted in impaired HSC differentiation. Our results identify signaling from p75(NTR) to Rho as a mechanism for the regulation of HSC differentiation to regeneration-promoting cells that support hepatocyte proliferation in the diseased liver.     

糖尿病患者甲襞微循环病变及其与颈动脉内-中膜厚度的相关性

目的探讨2型糖尿病患者微血管病变特征及其与大血管病变的相关性。方法将78例2型糖尿病患者设为试验组与40例正常对照组进行对比,分别进行甲襞微循环检测,分析2型糖尿病患者微血管病变特征;采用中位数法将糖尿病人按甲襞微循环总分(NFM)分为积分≤中位数(NFM≤median)和积分中位数(NFMmedian)两部分,分析其与颈动脉内-中膜厚度及斑块形成的相关性。结果试验组甲襞微循环的交叉、畸形、渗出、出血、红细胞聚集五项积分高于对照组;NFMmedian患者颈动脉内-中膜增厚出现频次高于NFM≤median患者(P0.05);NFMmedian患者颈动脉斑块出现频次高于NFM≤median患者(P0.05)。结论 2型糖尿病患者微循环病变主要表现为交叉、畸形、红细胞聚集、袢周渗出、出血;糖尿病患者微血管与大血管病变密切相关。     

高血压患者颈动脉粥样硬化病变与脑梗死关系的初步探讨

目的 初步探讨高血压及高血压伴糖尿病（DM）患者颈动脉病变与脑梗死的关系。方法 应用彩色多谱勒显像仪对48例非老年高血压患者、79例老年血压患者、37例老年高血压伴DM患者进行颈动脉检测,观察颈动脉病变与脑梗死及血脂、血凝的关系。结果 老年高血压组颈动脉斑块的检出率（63．3％）显著高于非老年高血压组（22．9％,P＜0．01）,老年高血压伴DM组与老年高血压组比较差异无显著性。老年高血压组中,颈动脉内膜增厚组脑梗死发生率（66．7％）较颈动脉正常组（25．0％）增高（P＜0．05）,与斑块组（36．0％）比较差异无显著性;老年高血压伴DM组中内膜增（66．7％）及斑块组（46．4％）脑梗死发生率均较颈动脉正常组（0．0％）高（P＜0．05）。老年高血压组及老年高血压伴DM组高血压病史与颈动脉病变呈正相关,血脂及纤维蛋白原（FIB）与颈动脉斑块呈正相关。结论 颈动脉超声对脑梗死的预测有一定的实用参考价值,应积极控制脑梗死的危险因素。     

Insulin resistance and increased pancreatic beta-cell proliferation in mice expressing a mutant insulin receptor (P1195L)

Several mutations of the tyrosine kinase domain of insulin receptor (IR) have been clinically reported to lead insulin resistance and insulin hypersecretion in humans. However, it has not been completely clarified how insulin resistance and pancreatic beta-cell function affect each other under the expression of mutant IR. We investigated the response of pancreatic beta-cells in mice carrying a mutation (P1195L) in the tyrosine kinase domain of IR beta-subunit. Homozygous (Ir(P1195L/P1195L)) mice showed severe ketoacidosis and died within 2 days after birth, and heterozygous (Ir(P1195L/wt)) mice showed normal levels of plasma glucose, but high levels of plasma insulin in the fasted state and after glucose loading, and a reduced response of plasma glucose lowering effect to exogenously administered insulin compared with wild type (Ir(wt/wt)) mice. There were no differences in the insulin receptor substrate (IRS)-2 expression and its phosphorylation levels in the liver between Ir(P1195L/wt) and Ir(wt/wt) mice, both before and after insulin injection. This result may indicate that IRS-2 signaling is not changed in Ir(P1195L/wt) mice. The beta-cell mass increased due to the increased numbers of beta-cells in Ir(P1195L/wt) mice. More proliferative beta-cells were observed in Ir(P1195L/wt) mice, but the number of apoptotic beta-cells was almost the same as that in Ir(wt/wt) mice, even after streptozotocin treatment. These data suggest that, in Ir(P1195L/wt) mice, normal levels of plasma glucose were maintained due to high levels of plasma insulin resulting from increased numbers of beta-cells, which in turn was due to increased beta-cell proliferation rather than decreased beta-cell apoptosis.     

Reduced apurinic/apyrimidinic endonuclease 1 activity and increased DNA damage in mitochondria are related to enhanced apoptosis and inflammation in the brain of senescence- accelerated P8 mice (SAMP8)

The senescence- accelerated mouse prone 8 (SAMP8) is a well- characterized animal model of senescence that shows early age- related neurodegeneration with impairment in learning and memory skills when compared with control senescence- resistant mice (SAMR1). In the current study, we investigated whether such impairment could be partly due to changes in mitochondrial DNA (mtDNA) repair capacity and mitochondrial DNA damage in the brain of SAMP8 mice. Besides we studied whether these potential changes were related to modifications in two major processes likely involved in aging and neurodegeneration: apoptosis and inflammation. We observed that the specific activity of one of the main mtDNA repair enzymes, the mitochondrial APE1, showed an age- related reduction in SAMP8 animals, while in SAMR1 mice mitochondrial APE1 increased with age. The reduction in mtAPE1 activity in SAMP8 animals was associated with increased levels of the DNA oxidative damage marker 8oxodG in mtDNA. Our results also indicate that these changes were related to a premature increase in apoptotic events and inflammation in the brain of SAMP8 mice when compared to SAMR1 counterparts. We suggest that the premature neurodegenerative phenotype observed in SAMP8 animals might be due, at least in part, to changes in the processing of mtDNA oxidative damage, which would lead to enhancement of apoptotic and inflammatory processes.     

Expression and externalization of annexin 1 in the adrenal gland: structure and function of the adrenal gland in annexin 1-null mutant mice

Annexin 1 (ANXA1) is a member of the annexin family of phospholipid- and calcium-binding proteins with a well demonstrated role in early delayed (30 min to 3 h) inhibitory feedback of glucocorticoids in the hypothalamus and pituitary gland. This study used adrenal gland tissue from ANXA1-null transgenic mice, in which a beta-galactosidase (beta-Gal) reporter gene was controlled by the ANXA1 promoter, and wild-type control mice to explore the potential role of ANXA1 in adrenal function. RT-PCR and Western blotting revealed strong expression of ANXA1 mRNA and protein in the adrenal gland. Immunofluorescence labeling of ANXA1 in wild-type and beta-Gal expression in ANXA1-null adrenals localized intense staining in the outer perimeter cell layers. Immunogold electron microscopy identified cytoplasmic and nuclear ANXA1 labeling in outer cortical cells and capsular cells. Exposure of adrenal segments in vitro to dexamethasone (0.1 mum, 3 h) caused an increase in the amount of ANXA1 in the intracellular compartment and attached to the surface of the cells. The N-terminal peptide ANXA1(Ac2-26) inhibited corticosterone release. Corticosterone release was significantly greater from ANXA1-null adrenal cells compared with wild type in response to ACTH (10 pm to 5 nm). In contrast, basal and ACTH-stimulated aldosterone release from ANXA1-null adrenal cells was not different from wild type. Morphometry studies demonstrated that ANXA1 null adrenal glands were smaller than wild-type, and the cortical/medullary area ratio was significantly reduced. These results suggest ANXA1 is a regulator of adrenocortical size and corticosterone secretion.     

Reduced expression of the Caenorhabditis elegans p53 ortholog cep-1 results in increased longevity

Hyperactivation of mammalian p53 has been shown to result in segmental progeria and decreased survivorship. Repression of the p53 homolog in Drosophila melanogaster has also been shown to increase survival. We show that RNA interference (RNAi) or genetic knockout of the Caenorhabditis elegans p53 ortholog, cep-1, leads to increased life span, which is dependent upon functional daf-16. Furthermore, one other DNA damage-responsive C. elegans mutant, hus-1(op241), exhibits a life-span increase. The cep-1(gk138) knockout mutant does not show increased resistance to heat, oxidative, or ultraviolet stress; nor to bacterial pathogenicity. cep-1 RNAi does not extend the life span of a sir-2.1(geIn3) overexpressing strain. cep-1 RNAi does not alter dauer formation propensity or nuclear-localization of DAF-16::GFP, even under heat stress; nor does it change nuclear-persistence and/or retention of DAF-16::GFP. This study clarifies the inverse relationship between cep-1 expression and C. elegans life span, and, by extrapolation, that between p53 expression and mammalian life span.     

The development and potential of acoustic radiation force impulse (ARFI) imaging for carotid artery plaque characterization

Stroke is the third leading cause of death and long-term disability in the USA. Currently, surgical intervention decisions in asymptomatic patients are based upon the degree of carotid artery stenosis. While there is a clear benefit of endarterectomy for patients with severe (> 70%) stenosis, in those with high/moderate (50-69%) stenosis the evidence is less clear. Evidence suggests ischemic stroke is associated less with calcified and fibrous plaques than with those containing softer tissue, especially when accompanied by a thin fibrous cap. A reliable mechanism for the identification of individuals with atherosclerotic plaques which confer the highest risk for stroke is fundamental to the selection of patients for vascular interventions. Acoustic radiation force impulse (ARFI) imaging is a new ultrasonic-based imaging method that characterizes the mechanical properties of tissue by measuring displacement resulting from the application of acoustic radiation force. These displacements provide information about the local stiffness of tissue and can differentiate between soft and hard areas. Because arterial walls, soft tissue, atheromas, and calcifications have a wide range in their stiffness properties, they represent excellent candidates for ARFI imaging. We present information from early phantom experiments and excised human limb studies to in vivo carotid artery scans and provide evidence for the ability of ARFI to provide high-quality images which highlight mechanical differences in tissue stiffness not readily apparent in matched B-mode images. This allows ARFI to identify soft from hard plaques and differentiate characteristics associated with plaque vulnerability or stability.     

p53-dependent apoptosis in the inhibition of spermatogonial differentiation in juvenile spermatogonial depletion (Utp14bjsd) mice

In adult male mice homozygous for the juvenile spermatogonial depletion (Utp14b jsd) mutation in the Utp14b gene, type A spermatogonia proliferate, but in the presence of testosterone and at scrotal temperatures, these spermatogonia undergo apoptosis just before differentiation. In an attempt to delineate this apoptotic pathway in jsd mice and specifically address the roles of p53- and Fas ligand (FasL) /Fas receptor-mediated apoptosis, we produced jsd mice deficient in p53, Fas, or FasL. Already at the age of 5 wk, less degeneration of spermatogenesis was observed in p53-null-jsd mice than jsd single mutants, and in 8- or 12-wk-old mice, the percentage of seminiferous tubules showing differentiated germ cells [tubule differentiation index (TDI)] was 26-29% in the p53-null-jsd mice, compared with 2-4% in jsd mutants with normal p53. The TDI in jsd mice heterozygous for p53 showed an intermediate TDI of 8-13%. The increase in the differentiated tubules in double-mutant and p53 heterozygous jsd mice was mostly attributable to intermediate and type B spermatogonia; few spermatocytes were present. Terminal deoxynucleotidyl transferase-mediated deoxyuridine triphosphate nick end labeling staining showed that most of these differentiated spermatogonia still underwent apoptosis, thereby blocking further continuation of spermatogenesis. In contrast, the percentage of tubules that were differentiated was not significantly altered in either adult Fas null-jsd mice or adult FasL defective gld-jsd double mutant mice as compared with jsd single mutants. Furthermore, caspase-9, but not caspase-8 was immunochemically localized in the adult jsd mice spermatogonia undergoing apoptosis. The results show that p53, but not FasL or Fas, is involved in the apoptosis of type A spermatogonia before/during differentiation in jsd mice that involves the intrinsic pathway of apoptosis. However, apoptosis in the later stages must be a p53-independent process.