Biosynthesis of cyanogenic glucosides: in vitro analysis of the glucosylation step

The last step in the biosynthesis of cyanogenic glucosides, the glucosylation of the cyanohydrin intermediate, has been investigated in detail using Triglochin maritima seedlings. The glucosyltransferase activity is not associated with membranes and appears to be a "soluble" enzyme. The cyanohydrin intermediate, which is formed by hydroxylation of 4-hydroxyphenylacetonitrile by a membrane-bound enzyme, is free to equilibrate in the presence of the glucosyltransferase and UDPG, because it can be trapped very efficiently. This indicates that this intermediate is not channeled (unlike some of the other intermediates), although it is probably the most labile of all of them. The glucosyltransferase of T. maritima responsible for the glucosylation of the cyanohydrin was separated from another glucosyltransferase, which used 4-hydroxybenzylalcohol as a substrate, and purified over 200-fold. It catalyzed the glucose transfer from UDPG to only 4-hydroxymandelonitrile and 3,4-dihydroxymandelonitrile, giving rise to the respective cyanogenic glucosides. Although the activities with these two substrates behaved differently in certain respects (e.g., extent of inactivation during purification and difference in activation by higher salt concentrations), most of the data acquired favor the view that only one enzyme in T. maritima is responsible for the glucosylation of both substrates.     

Involvement of the neurointermediate lobe of the pituitary gland in the secretion of prolactin and luteinizing hormone in the rat

The relationship between prolactin (PRL) secretion and the neurointermediate lobe (NIL) of the pituitary gland was investigated. Plasma PRL concentrations in rats bearing anterior pituitaries autografted with or without the NIL to the renal capsule were elevated to equal extents at 1 through 6 weeks after surgery (p > 0.10). PRL levels in ovariectomized rats in which the NIL had been removed surgically (NIL-X) or only visualized (NIL-C) were 3–7 ng/ml 4, 7, and 28 days after surgery (p > 0.10); however, they were slightly higher in NIL-X $\text{vs.}$ NIL-C rats 14 days after surgery (p < 0.05). Plasma luteinizing hormone (LH) concentrations in NIL-C rats increased by 36% from 2 to 4 weeks after surgery (p < 0.05); this increase was not detected in NIL-X rats. PRL and LH surges were induced by estradiol implants in ovariectomized NIL-X and NIL-C rats; the profiles of the PRL surges were superimposable, although the magnitude of the LH surge was only 50% that in NIL-C rats (p < 0.05). These results cast doubt on the importance of the NIL in the regulation of PRL secretion either $\text{via}$ secreting hypophysiotropic hormones or $\text{via}$ conducting anterior pituitary hormones directly to the median eminence. However, the NIL may have a physiologically important role in the regulation of LH secretion.     

Triplet state properties of the methylmercury(II)-tyrosine complex

CH₃Hg(II)OH forms complexes at pH 8 with tyrosine and with tyrosine ethyl ester (TEE) that are detected by ultraviolet difference absorption spectra. With K_f defined by CH₃HgOH + HB

CH₃HgB + H₂O, we find log K_f = 3.61 (tyrosine) and 3.36 (TEE). A heavy-atom effect is observed in frozen glasses of the complexes; this indicates a close interaction between Hg and the chromophore. No UV difference spectrum or heavy-atom effect is observed with N-acetyl tyrosine ethyl ester, indicating that complexing at the phenol O does not occur, and suggesting that binding occurs at the amine N. Zero field optically detected magnetic resonance (ODMR) measurements of the CH₃Hg(II)-tyrosine triplet state give (D, E) = (0.129, 0.047) or (0.134, 0.041) cm^?1 depending upon assignment of transitions. D of tyrosine is relatively unaffected, but E is reduced by CH₃Hg(II) complexing. Low-temperature kinetic measurements show that the shortest lived sublevel of the complex is T_z, where z lies along the phenol long axis in tyrosine. A dominant 11.6-msec component in the 77 K decay of the phosphorescence is consistent with the individual sublevel lifetimes obtained by ODMR.     

Passive cable properties of hippocampal CA3 pyramidal neurons

The passive electrical cable properties of CA3 pyramidal neurons from guinea pig hippocampal slices were investigated by applying current steps and recording the voltage transients from 25 CA3 neurons, using a single intracellular microelectrode and a 3-kHz time-share system. Two independent methods were used for estimating the equivalent electrotonic length of the dendrites, L, and the dendritic to somatic conductance ratio, . The first method is similar to that used by Gorman and Mirolli (1972) and gave an average L of 0.96; the average was 2.44. The second method is derived here for the first time and assumes a finite-length cable with lumped soma. It is an exact solution for L and , using the slopes and intercepts of the first two peeled exponentials. The average L was 0.94; the average was 1.51. The results, using both methods, are in close agreement. The average membrane time constant for all 25 CA3 neurons was 23.6 ms, suggesting a large (23,600 cm²) average membrane resistivity. It is concluded that CA3 neurons are electronically short.This work was supported by Grants NS 11535 and NS 15772 from the National Institute of Neurological and Communicative Disorders and Stroke, National Institutes of Health, U.S. Public Health Service.     

Classical Conditioning-Induced Changes in Low-Molecular-Weight GTP-Binding Proteins in Rabbit Hippocampus

Classical conditioning of Hermissenda, involving paired light-rotation events, results in a 30-35% decrease in the levels of a 20-kDa G protein (cp20). To test whether a similar protein exists in vertebrates, rabbits were trained to associate a tone with periorbital electrical stimulation and G proteins were analyzed by photoaffinity labeling with [alpha-32P]GTP-azidoanilide. A 20-kDa G protein similar to cp20 decreased by 36% in the hippocampus of rabbits subjected to paired tone and electrical stimulation, but not in unpaired controls. Learning-specific decreases were also found in the amount of ras protein.     

Naltrexone partially inhibits the estrogen-induced increase in prolactin secretion and anterior pituitary weight

The effects of naltrexone, a specific opiate antagonist, on stimulation by estradiol benzoate (EB) of prolactin (PRL) release and anterior pituitary (AP) weight, were studied in gonadectomized female and male Sprague-Dawley rats. One week after castration, rats were injected for 10 days once daily with 2 μg EB alone, or together with twice daily injections of 2 mg naltrexone/kg body weight (BW). Blood was collected for radioimmunoassay of PRL by orbital sinus puncture on days 0 and 6, and by decapitation on day 11, at which time the AP was quickly removed, weighed and assayed for PRL.Serum PRL concentrations and AP weights were significantly increased by EB administration. These effects of EB were partially but significantly inhibited by naltrexone. These results suggest that endegenous opiates may be involved in the estrogen-induced rise in serum PRL and increase in pituatary weight.     

Crenation and cupping of the red cell: A new theoretical approach. Part II. Cupping

Typical, axisymmetrical cup shaped cells have been carefully measured and the shapes analyzed mathematically. The results show that the strain energy of a cup shaped cell is always higher than that of a biconcave cell except when the two layers of the membrane involved in resistance to bending are free to slide over one another. This is true whether intrinsic curvature of the membrane is positive, negative or zero. If the two layers can slide over one another, the cup shape becomes the lower energy form. Shear resistance, if appreciable, must cause the cup cell to buckle. Photomicrographs of cup shaped cells show buckled configurations characteristic of those of a partly deflated thin-walled rubber ball, which is a similar object having a low ratio of bending/shear strength.In light of these findings, the cup shape of the red cell can no longer be considered as evidence of intrinsic membrane curvature of opposite sign to that of the crenated cell, but appears to indicate a phase change either in the hydrophobic interior of the bimolecular membrane or in some equivalent interface.     

胰腺癌患者血清CEA、CA242、CA199水平变化及联合诊断的ROC曲线分析

目的:探讨胰腺癌患者血清癌胚抗原(CEA)、糖类抗原242(CA242)、糖类抗原199(CA199)水平变化,并分析上述指标对胰腺癌的联合诊断价值,为胰腺癌的临床诊断提供参考。方法:选择2014年2月至2018年2月我院收治的186例胰腺癌患者(胰腺癌组)、89例胰腺炎患者(胰腺炎组)作为研究对象,并取同期来我院检查的268例健康人作为对照组。比较三组受试者的血清CEA、CA242、CA199水平变化,对比分析血清CEA、CA242、CA199的单一以及联合诊断的准确度、特异度以及灵敏度,并绘制ROC曲线以分析上述指标的诊断价值。结果:三组受试者血清CEA、CA242、CA199水平差异具有统计学意义(P<0.05)。且胰腺炎组和胰腺癌组的血清CEA、CA242、CA199水平明显高于对照组,胰腺癌组患者的血清CEA、CA242、CA199水平明显高于胰腺炎组,差异均有统计学意义(P<0.05)。ROC曲线结果显示,CEA诊断价值最大,CA199诊断价值最小。CEA是胰腺癌单项肿瘤标志物中敏感度最高的,为85.48%;特异度最高的为CA242(96.72%);三项肿瘤标志物联合诊断的准确度增加至92.27%,敏感度增加至95.16%,特异度相比略有下降。结论:与单一肿瘤标记物诊断胰腺癌相比,CEA、CA242、CA199联合诊断的敏感度和准确度均明显升高,可以明显改善胰腺癌的漏诊率,提高患者的生存率,具有较好的临床应用价值。     

Genomic and signalling pathway characterization of the NZM panel of melanoma cell lines: A valuable model for studying the impact of genetic diversity in melanoma

Melanoma is a disease associated with a very high mutation burden and thus the possibility of a diverse range of oncogenic mechanisms that allow it to evade therapeutic interventions and the immune system. Here, we describe the characterization of a panel of 102 cell lines from metastatic melanomas (the NZM lines), including using whole‐exome and RNA sequencing to analyse genetic variants and gene expression changes in a subset of this panel. Lines possessing all major melanoma genotypes were identified, and hierarchical clustering of gene expression profiles revealed four broad subgroups of cell lines. Immunogenotyping identified a range of HLA haplotypes as well as expression of neoantigens and cancer–testis antigens in the lines. Together, these characteristics make the NZM panel a valuable resource for cell‐based, immunological and xenograft studies to better understand the diversity of melanoma biology and the responses of melanoma to therapeutic interventions.