含锰固氮酶组分Ⅰ蛋白的纯化和特性

棕色固氮菌（Azotobacter vinelandii Lipmann)突变种UW3能在无Mo的无氨培养基中固氮生长,低浓度的Mn对UW3突变种生长有促进作用,从在Mn中生长的UW3菌体中分离得到的部分纯固氮酶组分Ⅰ蛋白含量有Mn和Fe原子（Fe/Mo/Mn为10．41：0．19：1．00）并有OP MoFe蛋白一半的还原乙炔和质子的活性。这种蛋白的吸收光谱和圆二色谱与MoFe蛋白存在明显的差异,含Mn蛋白的亚基分子量都与MoFe蛋白的α亚基相近。初步结果表明,这种含Mn蛋白可胡是一种固氮酶组分Ⅰ蛋白。     

Immunolocalization of band 3 protein in normal and cystic fibrosis skin

Current evidence indicates that the defect in cystic fibrosis (CF) involves chloride transport in various epithelial cells. The sweat gland, one site of altered chloride transport in CF, was examined immunocytochemically for localization of a chloride-channel membrane protein, designated band 3 protein. Immunoreactivity was observed in sweat duct cell membranes of both normal and CF samples, whereas secretory coil regions were entirely unreactive. No difference was observed in the pattern or intensity of immunoreactivity between the two groups at the light microscopic (LM) level of resolution.     

The structure and evolution of the spider monkey delta-globin gene

We have isolated the delta-globin gene of the New-World spider monkey, Ateles geoffroyi, and compared its nucleotide sequence with those of other primate delta- and beta-globin genes. Among primate delta-globin genes, the rate of nonsynonymous substitutions is much less than the rate of synonymous substitutions. This suggests that primate delta- globin genes may remain under evolutionary conservation, perhaps because hemoglobin A2 has an as yet unknown physiological importance.      

Differences between ATP-mediated cytotoxicity and cell-mediated cytotoxicity.

There has been considerable recent interest in the possible role of extracellular ATP in cell-mediated cytotoxicity. To investigate the similarities and differences between ATP-mediated lysis and CTL-mediated lysis, we studied in detail the ATP-mediated lysis of EL-4 cells, which are highly susceptible to lysis by extracellular ATP. ATP-mediated lysis was time and concentration dependent; most lysis occurred within 4 to 6 h of incubation. The kinetics of ATP- and cell-mediated lysis were similar. However, in contrast to CTL-mediated lysis, ATP-mediated lysis of EL-4 cells did not appear to be accompanied by characteristic chromosomal degradation (apoptosis). In order to compare these cytotoxic processes in greater detail, ATP-resistant clones were derived by growing EL-4 cells continuously in the presence of high concentrations of ATP. These cloned EL-4 lines showed marked resistance to ATP-mediated cytotoxicity across a wide range of concentrations but were as susceptible as the parent EL-4 cells to cell-mediated cytotoxicity by an alloreactive effector population from a MLC. Thus, there appear to be a number of differences between ATP-mediated and cell-mediated cytotoxicity in this system; most notable is the identification of cell lines that are resistant to ATP but susceptible to CTL-mediated lysis.     

Phosphorylated retinoblastoma protein complexes with pp32 and inhibits pp32-mediated apoptosis

The retinoblastoma gene product (Rb) is a tumor suppressor that affects apoptosis paradoxically. Most sporadic cancers inactivate Rb by preferentially targeting the pathway that regulates Rb phosphorylation, resulting in resistance to apoptosis; this contrasts with Rb inactivation by mutation, which is associated with high rates of apoptosis. How phosphorylated Rb protects cells from apoptosis is not well understood, but there is evidence that Rb may sequester a pro-apoptotic nuclear factor. pp32 (ANP32A) is a pro-apoptotic nuclear phosphoprotein, the expression of which is commonly increased in cancer. We report that hyperphosphorylated Rb interacts with pp32 but not with the closely related proteins pp32r1 and pp32r2. We further demonstrate that pp32-Rb interaction inhibits the apoptotic activity of pp32 and stimulates proliferation. These results suggest a mechanism whereby cancer cells gain both a proliferative and survival advantage when Rb is inactivated by hyperphosphorylation.     

Meiotic Recombination in Human Oocytes

Studies of human trisomies indicate a remarkable relationship between abnormal meiotic recombination and subsequent nondisjunction at maternal meiosis I or II. Specifically, failure to recombine or recombination events located either too near to or too far from the centromere have been linked to the origin of human trisomies. It should be possible to identify these abnormal crossover configurations by using immunofluorescence methodology to directly examine the meiotic recombination process in the human female. Accordingly, we initiated studies of crossover-associated proteins (e.g., MLH1) in human fetal oocytes to analyze their number and distribution on nondisjunction-prone human chromosomes and, more generally, to characterize genome-wide levels of recombination in the human female. Our analyses indicate that the number of MLH1 foci is lower than predicted from genetic linkage analysis, but its localization pattern conforms to that expected for a crossover-associated protein. In studies of individual chromosomes, our observations provide evidence for the presence of “vulnerable” crossover configurations in the fetal oocyte, consistent with the idea that these are subsequently translated into nondisjunctional events in the adult oocyte.     

Skin cancer after X-ray treatment for scalp ringworm

Some 2,224 children given X-ray therapy for tinea capitis (ringworm of the scalp) have been followed for up to 50 years to determine cancer incidence, along with a control group of 1,380 tinea capitis patients given only topical medications. The study found a relative risk (RR) of 3.6 (95% confidence interval, 2.3-5.9) for basal cell skin cancer (BCC) of the head and neck among irradiated Caucasians (124 irradiated cases and 21 control cases), in response to a scalp dose of about 4.8 Gy. No melanomas of the head and neck have been seen, and only a few squamous cell carcinomas. About 40% of irradiated cases have had multiple BCCs, for a total of 328 BCCs. Although 25% of both the irradiated and control groups are African-American, only 3 skin cancers have been seen among them, all in the irradiated group, indicating the importance of susceptibility to UV radiation as a cofactor. Light complexion, severe sunburning and North European ancestry were predictive of BCC risk in the irradiated group, but chronic sun exposure was not. Children irradiated at young ages had the highest BCC risk. The RR for BCC risk is approximately constant with time since exposure, suggesting that risk will probably last for a lifetime.     

Using dynamic pupillometry as a simple screening tool to detect autonomic neuropathy in patients with diabetes: a pilot study

Background  

Autonomic neuropathy is a common and serious complication of diabetes. Early detection is essential to enable appropriate interventional therapy and management. Dynamic pupillometry has been proposed as a simpler and more sensitive tool to detect subclinical autonomic dysfunction. The aim of this study was to investigate pupil responsiveness in diabetic subjects with and without cardiovascular autonomic neuropathy (CAN) using dynamic pupillometry in two sets of experiments.