Apoptosis of late-stage erythroblasts in megaloblastic anemia: association with DNA damage and macrocyte production

An in vitro model of folate-deficient erythropoiesis has been developed using proerythroblasts isolated from the spleens of Friend virus-infected mice fed an amino acid-based, folate-free diet. Control proerythroblasts were obtained from Friend virus-infected mice fed the same diet plus 2 mg folic acid/kg diet. Our previous studies showed that, after 20 to 32 hours of culture in folate-deficient medium with 4 U/mL of erythropoietin, the folate-deficient proerythroblasts underwent apoptosis, whereas control erythroblasts survived and differentiated into reticulocytes over a period of 48 hours. The addition of folic acid or thymidine to the folate-deficient medium prevented the apoptosis of the folate-deficient erythroblasts, thereby implicating decreased thymidylate synthesis as the main cause of apoptosis in the folate-deficient erythroblasts. In the study reported here, we examined intracellular folate levels, uracil misincorporation into DNA, p53 and p21 proteins, and reticulocyte formation in erythroblasts cultured in folate-deficient or control medium. In all experiments, the folate-deficient erythroblasts cultured in folate-deficient medium gave results that varied significantly from folate-deficient erythroblasts cultured in control medium or control erythroblasts cultured in either folate-deficient or control media. Folate-deficient erythroblasts cultured in folate-deficient medium had marked decreases in all coenzyme forms of folate that persisted throughout culture, increased uracil misincorporation into DNA, persistent accumulations of p53 and p21, and decreased reticulocyte production but increased size of individual reticulocytes. A model of folate-deficient erythropoiesis based on apoptosis of late stage erythroblasts is presented. This model provides explanations for the clinical findings in megaloblastic anemia.     

中国陆相烃源岩氮同位素组成与有机质聚集

氮作为重要的生命元素与有机质聚集之间具有成因联系,但尚未形成系统性、规律性认识。以中国广泛发育的二叠系—古近系陆(湖)相烃源岩为例,对此进行了探讨。结果表明,根据氮同位素(δ¹⁵N)组成,结合盐度和蒸发性碱类矿物特征,可将中国陆相烃源岩分为3组：近中性组1(δ¹⁵N平均值为4.0‰±1.5‰)、近中性组2(δ¹⁵N平均值为7.1‰±1.6‰)和碱性组(δ¹⁵N平均值为18.4‰±3.3‰)。在δ¹⁵N < 10‰的近中性组中,烃源岩的δ¹⁵N与有机质丰度、类型、生烃能力和页岩油潜力呈正相关,原因在于较高的δ¹⁵N值指征了生烃母质组成的变化。在δ¹⁵N>10‰的碱性组中,有机质类型都较好,页岩油潜力都较高,但烃源岩的δ¹⁵N与有机质聚集的响应关系不如中性组,反映有机质聚集受非δ¹⁵N其他综合因素的影响与控制。据此建立了基于δ¹⁵N划分出的3类湖相烃源岩的有机质聚集模式(< 5‰、5‰~10‰、>10‰)。δ¹⁵N具有示踪有机质聚集和烃源岩质量的潜力,以湖相烃源岩为例,低δ¹⁵N型(δ¹⁵N < 5‰)质量差,中—高δ¹⁵N型(δ¹⁵N>5‰)质量好。从氮同位素组成和氮循环这一新角度探讨了烃源岩有机质聚集,丰富了氮的生物地球化学与烃源岩地球化学研究。     

Activation of the genetically defined m1 muscarinic receptor potentiates N-methyl-D-aspartate (NMDA) receptor currents in hippocampal pyramidal cells

Evidence suggests that cholinergic input to the hippocampus plays an important role in learning and memory and that degeneration of cholinergic terminals in the hippocampus may contribute to the memory loss associated with Alzheimer's disease. One of the more prominent effects of cholinergic agonists on hippocampal physiology is the potentiation of N-methyl-D-aspartate (NMDA)-receptor currents by muscarinic agonists. Here, we employ traditional pharmacological reagents as well as m1-toxin, an m1 antagonist with unprecedented selectivity, to demonstrate that this potentiation of NMDA-receptor currents in hippocampal CA1 pyramidal cells is mediated by the genetically defined m1 muscarinic receptor. Furthermore, we demonstrate the colocalization of the m1 muscarinic receptor and the NR1a NMDA receptor subunit at the electron microscopic level, indicating a spatial relationship that would allow for physiological interactions between these two receptors. This work demonstrates that the m1-muscarinic receptor gene product modulates excitatory synaptic transmission, and it has important implications in the study of learning and memory as well as the design of drugs to treat neurodegenerative diseases such as Alzheimer's.     

Transcutaneous electrical nerve stimulation and temporary S3 neuromodulation in idiopathic detrusor instability

PURPOSE: We studied the effects of electrical stimulation on idiopathic detrusor instability. MATERIALS AND METHODS: Between January 1993 and December 1994, 30 men and 41 women (mean age plus or minus standard deviation 48 +/- 16 years) underwent transcutaneous electrical nerve stimulation (TENS) of the S2-S3 dermatomes, and 13 men and 22 women (mean age 48 +/- 12 years) underwent S3 neuromodulation. Subjective assessment was performed using a diary and symptom score of 0 to 14. Objective outcome was analyzed with urodynamic studies. RESULTS: Mean duration of TENS was 3 +/- 1 weeks (range 2 to 4). Although there were no major complications 31% of the patients reported local skin irritation. The overall urinary symptom scores improved from 10 +/- 2 (range 5 to 14) before the study to 7 +/- 3 (range 1 to 14) during stimulation. Urodynamic analysis revealed significant (p < 0.05) improvements in total bladder capacity and voided volume, and decreases in the number and frequency of unstable contractions. Mean duration of S3 neuromodulation was 6 +/- 1 days (range 4 to 8 days). Four procedures failed due to electrode displacement in 3 cases and procedure intolerance in 1. Hemorrhage from the puncture site occurred in 1 patient. Overall urinary symptom scores were 10 +/- 3 (range 5 to 14) before the study and 5 +/- 2 (range 2 to 10) during stimulation. Although symptomatic relief was more pronounced with S3 neuromodulation, no statistically significant differences were found regarding urinary symptoms compared to TENS. CONCLUSIONS: In patients with severe detrusor instability refractory to conservative treatments the use of TENS and S3 neuromodulation produced significant changes in urodynamic parameters and presenting symptoms. Our results appear to justify evaluation with neuromodulatory techniques before definitive surgical intervention in these patients.