乳腺癌的二级预防

在我国乳腺癌的发病率有逐渐增加的趋势，而且它对我国中年妇女的威胁最大。乳腺癌二级预防已被公认是降低死亡率的有效途径。综合应用宣教、自检、体检、Ｘ线摄影、近红外线摄影、超声检查、针吸活检、手术活检等方法对年龄在３０～６０岁的城市妇女定期进行分层筛检、监检可以使乳腺癌患者早期被发现，降低乳腺癌死亡率。     

Longitudinal relationship between incisal tooth wear and periodontal condition

The purpose of the study was to examine the relationship between the longitudinal development of incisal tooth wear and periodontal conditions in 51 persons. Stone casts obtained at the ages of 15 and 27 yr were used to assess incisal wear according to a graded scale, the Incisal wear Index (Iwl). The wear increase after 12 yr, ΔIwI, was related to the various health index scores at the age of 15 yr, including the Plaque Index (PII) and Gingival Index (GI) systems. The chi-square tests showed a statistically significant association between AIwI and periodontal condition in 15-yr-olds. Thus, relatively low P1I and GI values were accompanied by relatively high AIwI values. It was concluded that in 15-yr-olds, P1I and GI levels are clinical predictors of future wear (ΔIwI) of maxillary and mandibular central incisors. Pocket depth (PD) was a less valuable clinical predictor of such wear.     

Prediction of severe postoperative complications in patients admitted to neuroanaesthesia

The purpose of this study was to identify factors which will predict the risk of severe postoperative complications in individual patients in a neurosurgical unit. Eleven risk factors were investigated in 363 neurosurgical patients, of whom 40 (11%) developed postoperative complications requiring mechanical ventilation for more than 24 h in an intensive care unit, 16 were found to be severely disabled or in a vegetative state at follow-up 1 month after admission, and 28 patients died. By applying stepwise, logistic regression analysis to the patient's data, we were able to select two significant risk variables, i.e. the Glasgow Coma Scale (GCS) 8 or less preoperatively and emergency anaesthesia. The presence of GCS 8 or less on the consciousness scale was associated with postoperative complications in approximately 40% of the cases. Emergency patients with severe neurological damage had the greatest risk of postoperative complications (93%). Fatal outcome for patients with postoperative complications was seen in 40% of the cases.     

Structure and conformation of linear peptides XII. Structure of tryptophanyl-glycyl-glycine dihydrate

The crystal structure of a tripeptide, tryptophanyl-glycyl-glycine dihydrate (C₁₅H₁₈N₄O₄·2H₂O, molecular weight = 354) has been determined. The crystals are orthorhombic, space group P2₁2₁2₁ with a= 7.875 (1) A,b= 9.009(1), c= 24.307(1) and Z = 4. The final R-index is 0.058 for 1488 reflections ((sin θ/λ≤ 0.6 A^?1) with I < 2σ(I). The molecule exists as a zwitterion, with terminal NH⁺₃ and COO^? groups. The peptide units are trans and nearly perpendicular to the plane of the carboxyl group. The backbone torsion angles are: ψ₁= 132.7°, ω₁= 174.2°, φ₂ 88.2°, ψ= 8.6°, ω₂ - 179.8°, φ= - 85.2°, ψ₃₁, = - 178.1°, ψ₃₂ 5.0°. For the sidechain of tryptophan, χ₁= - 171.6°, χ₂ 101.0°.     

Structure and conformation of peptides involving prolyl residue III. L-Prolyl-L-isoleucine monohydrate

The dipeptide, L-prolyl-L-isoleucine monohydrate (C₁₁ H₂₀N₂O₃· H₂O, molecular weight 246.3) crystallizes in the monoclinic space group P2₁, with a = 6.601(3)Å, b = 5.413(3) Å, c = 19.128(6) Å, β= 98.1(1)°, Z = 2, Do = 1.20g·cm^-3 and Dc = 1.208g·cm^-3. The structure was solved by MULTAN–80 and refined to a final R-factor of 0.081 for 594 reflections measured on a Enraf Nonius CAD-4 diffractometer. The peptide linkage exists in the trans conformation. The pyrrolidine ring is disordered with two alternate envelope conformations for the C^γ atom. The values of the sidechain torsion angles are: χ₁₁=– 63.6(17)°, χ₁₂= 171.1(16)° and χ₂=– 59.6(21)° for isoleucine (C-terminal). The crystal structure is stabilized by a three-dimensional network of N—H ? O, O—H ? O and C—H ? O hydrogen bonds. The dipeptide exists in the extended Conformation.     

Short utterance recognition using a network with minimum training

A feedforward network is used to recognize short, digitized, isolated utterances. A high, multispeaker recognition rate is achieved with a small vocabulary with a single training utterance. This approach makes use of the pattern recognition property of the network architecture to classify different temporal patterns in the multidimensional feature space. The network recognizes the utterances without the need of segmentation, phoneme identification, or time alignment. We train the network with four words spoken by one single speaker. The network is then able to recognize 20 tokens spoken by 5 other speakers. We repeat the above training and testing procedure using a different speaker's utterances for training each time. The overall accuracy is 97.5%. We compare this approach to the traditional dynamic programming (DP) approach, and find that DP with slope constraints of 0 and 1 achieve 98.5% and 85% accuracies respectively. Finally we validate out statistics by training and testing the network of a four-word subset of the Texas Instruments (Tl) isolated word database. The accuracy with this vocabulary exceeds 96%. By doubling the size of the training set, the accuracy is raised to 98%. Using a suitable threshold, we are able to raise the accuracy of one network from 87% to 98.5%. Thresholding applied to all networks would then raise the overall accuracy to well over 99%.

This technique is especially promising because of the low overhead and computational requirements, which make it suitable for a low cost, portable, command recognition type of application.     

The universal algorithm of maturation for secretory and excretory protein precursors.

During maturation, most proteins undergo different posttranslational modifications. In most simple cases, signal peptidases remove the signal or leader peptide from the precursors of the secretory proteins during their translocation across the ER membrane. For biologically active proteins, such as enzymes, regulatory and defense proteins, toxins, etc., additional maturation-regulating mechanisms were shown to proceed with limited proteolysis of inactive precursors by specific enzymes. A number of specific enzymes from different cell types selectively cleave proproteins at specific processing sites. In this work, we analyzed the sequences of protein precursors synthesized in the excretory glands of different animals and identified new, non-traditional processing sites. They differ from the motifs previously identified in secreted proteins' precursors and enabled us to reconstruct the sequence of events leading to the conversion of protein precursors into the final products (mature proteins). We also found that in animals, the maturation mechanism of secretory and excretory proteins and the set of enzymes involved are species specific. The processing sites identified in protein precursors in this study are useful for a more detailed genome analysis and more accurate mature protein sequence prediction.     

Complete structure of eclosion hormone of Manduca sexta

The locations of the three disulfide bonds of eclosion hormone (EH) isolated from Manduca sexta were assigned by sequence analysis of thermolysin fragments and by comparison of a key heterodimeric fragment to regiospecifically synthesized parallel and antiparallel isomers. We elucidated the complete structure of Manduca EH as a 62-residue peptide which has three disulfide bonds between Cys¹⁴-Cys³⁸, Cys¹⁸-Cys³⁴, and Cys²¹-Cys⁴⁹.