β-半乳糖苷酶的糖苷键作用特异性研究

研究了不同微生物来源乳糖酶的糖苷键键型作用特异性,研究表明米曲霉乳糖酶的水解优先顺序是β-1－6键＞β-1－4键＞β-1－3键,乳酸克鲁维酵母乳糖酶的水解顺序则是β-1－4键＞β-1－6键＞β-1－3键。并发现所实验所用的环状芽孢杆菌对β－1－4键表现出了高度的键专一性。乳糖水解合成低聚双糖的种类和有关动力学数据都表明不同酶源的乳糖酶在键特异性方面存在很大差异。     

多发性骨髓瘤骨髓细胞学特性与预后的关系

1目的　探求多发性骨髓瘤骨髓细胞学特性与预后的关系。 2方法　回顾性调查 ,两个样本均数的 t检验 ,多个样本均数的方差分析 ,二元线性回归分析。 3结果　成浆细胞型 MM与幼浆细胞型 MM比较 ,生存期差异显著 (P<0 .0 5 ) ,而各骨髓有核细胞增生程度间的 MM生存期则差异无显著性 (P>0 .0 5 ) ,瘤细胞比例的高低与生存期呈直线负相关。 4结论　幼浆细胞型 MM和瘤细胞比例高的 MM预后差     

耳穴特异性与生物分子活性的关系

目的　研究耳穴特异性与机体生物分子活性之间的关系。方法　通过 18例SLE患者和 17位健康者的同体双盲试验及统计和相关分析 ,并结合抗体基因结构与功能的研究。结果　证实耳穴电特性具有反应SLE病理变化的特异性 ;7项抗体指标 (含DNA、补体、类风湿因子、免疫球蛋白等 )与耳穴电特性存在不同程度的相关性。结论　耳穴特异性与机体生物分子活性存在密切的联系 ;耳穴反应病变的特异性可能源于机体内生物分子的活性 ,其中包括基因突变、基因表达及其调控。     

Can supplementary contrast-enhanced MRI of the breast avoid needle biopsies in suspicious microcalcifications seen on mammography? A systematic review and meta-analysis

PurposeTo analyze the rate of potentially avoidable needle biopsies in mammographically suspicious calcifications if supplementary Contrast-Enhanced MRI (CE-MRI) is negative.MethodsUsing predefined criteria, a systematic review was performed. Studies investigating the use of supplemental CE-MRI in the setting of mammographically suspicious calcifications undergoing stereotactic biopsy and published between 2000 and 2020 were eligible. Two reviewers extracted study characteristics and true positives (TP), false positives, true negatives and false negatives (FN). Specificity, in this setting equaling the number of avoidable biopsies and FN rates were calculated. The maximum pre-test probability at which post-test probabilities of a negative CE-MRI met with BI-RADS benchmarks was determined by a Fagan nomogram. Random-effects models, I²-statistics, Deek’s funnel plot testing and meta-regression were employed. P-values <0.05 were considered significant.ResultsThirteen studies investigating 1414 lesions with a cancer prevalence of 43.6% (range: 22.7–66.9%) were included. No publication bias was found (P = 0.91). CE-MRI performed better in pure microcalcification studies compared to those also including associate findings (P < 0.001). In the first group, the pooled rate of avoidable biopsies was 80.6% (95%-CI: 64.6–90.5%) while the overall and invasive cancer FN rates were 3.7% (95%-CI: 1.2–6.2%) and 1.6% (95%-CI 0–3.6%), respectively. Up to a pre-test probability of 22%, the post-test probability did not exceed 2%.ConclusionA negative supplementary CE-MRI could potentially avoid 80.6% of unnecessary stereotactic biopsies in BI-RADS 4 microcalcifications at a cost of 3.7% missed breast cancers, 1.6% invasive. BI-RADS benchmarks for downgrading mammographic calcifications would be met up to a pretest probability of 22%.     

Clonally restricted insulin autoantibodies in a cohort of 2200 healthy blood donors

Summary Serum samples of 2200 blood donors were screened for anti-insulin IgG by enzyme-linked immunosorbent assay. Specificity of detected antibodies was verified by competition with an excess of insulin and observation that saturated anti-insulin IgG were no longer measurable. The upper limit of measured signal in the population was defined as the mean plus three SD. In the direct assay, 32 sera were positive. Among these, 22 (1%) contained saturable insulin antibodies (true positive) and 10 were non-saturable and considered as non-insulin-specific. The positive blood donors were requested to answer a questionnaire and according to their answers, none had ever received insulin, was a first degree relative of a Type 1 (insulin-dependent) diabetic patient or had experienced a hypoglycaemic episode. None of the 22 true positive sera detected by enzyme-immunosorbent assay bound ¹²⁵-I-insulin to any significant extent. The nine sera yielding the highest signal were further characterized with regard to heavy and light chains as well as species specificity of ligand. Anti-insulin IgG from healthy blood donors contained only one heavy (1 2/9; 3 7/9) and one light ( 8/9; 1/9) chain. Three sera were human insulin specific; two were non-species-specific; the other four bound insulin in the order human = porcine > bovine. These results indicate that low affinity clonally restricted antibodies against insulin are present in unselected blood donors with a prevalence of 1%.     

Systematic Differences in Validity of Self-Reported Mammography Behavior: A Problem for Intergroup Comparisons?

Background. Prior studies of recall accuracy for screening mammogram behavior have examined relatively homogeneous groups. Data are limited on possible systematic group differences, so we evaluated women's recall accuracy in two separate care systems in one city.Methods. Women 50 to 70 years old with and without screening mammograms 10 to 14 months prior were identified from fiscal, clinic, and radiology records at a military care system (MCS) and a county-funded system (CFS) for indigents. Mammogram status was verified through radiology records. Women were excluded if mammograms were diagnostic, done for other than annual screening, or had abnormal results. Interview ers blinded to mammogram status surveyed randomly selected eligible women.Results. For 62 screened/31 unscreened MCS women and 78 screened/61 unscreened CFS women, specificity was similar, at 65 and 62%, respectively. In contrast, sensitivity varied significantly: 95% versus 79% (P = 0.011). Primary ethonocultural groups were Euro-American (MCS—60%) and Mexican American (CFS—85%). Although not different in specificity of recall (67% versus 61%), these major subgroups significantly differed in sensitivity (97% versus 80%, P = 0.017), proportion of true negatives due to never having a mammogram (35% versus 57%, P = 0.003), and proportion with ≥high school education (78% versus 19%, P < 0.00001).Conclusion. Systematic differences in recall validity may exist and compromise the accuracy of intergroup comparisons.     

Acetylcholine suppresses the spread of excitation in the visual cortex revealed by optical recording: possible differential effect depending on the source of input

Optical recording with a voltage-sensitive dye was performed in visual cortical slices of the rat to determine the effect of acetylcholine (ACh) on the spread of excitation. In the presence of ACh, the spread of excitation initiated by stimulation at the white matter/layer VI (WM/VI) was greatly suppressed throughout the cortex, with less suppression in the middle layers. By comparing the effect of ACh with that of 6-cyano-7-nitroquinoxaline-2,3-dione (CNQX), the fraction of the synaptic component that was sensitive to ACh was evaluated. ACh suppressed approximately 40-50% (maximum 55.8%, n = 11) of the initial synaptic component in the superficial and deep layers. In the middle, however, the effect was weakest and only approximately 20-30% (minimum 20.9%, n = 11) of the initial synaptic component was suppressed. On the basis of histological analysis, the region with the weakest ACh effect extended from upper V to lower II/III. To identify the site of ACh action in terms of pre- versus postsynaptic localization, exogenous glutamate was applied. Because ACh did not suppress the excitation induced by glutamate, the site of the ACh action was indicated to be presynaptic. When layer II/III was stimulated instead of WM/VI, the suppression was uniform throughout the cortex. A muscarinic receptor antagonist, atropine, blocked the suppression by ACh. In conclusion, our results indicate the following two points. First, ACh strongly suppresses intracortical connectivity through presynaptic muscarinic receptors. Secondly, in contrast to the intracortical connection, some group(s) of fibres, possibly thalamocortical afferents that arise from white matter and terminate in the middle cortical layers are suppressed much less by ACh. While ACh has been reported to have confusingly diverse effects, e.g. direct depolarization and hyperpolarization as well as synaptic facilitation and suppression, its effect on the propagation of excitation is very clear; suppression on intracortical connection, leaving thalamocortical inputs rather intact. We postulate that cholinergic innervation enables the afferent input to have a relatively dominant effect in the cortex.     

Validation of a predictive model for asthma admission in children: how accurate is it for predicting admissions?

We studied 364 index presentations to the Emergency Department of a children's hospital with a diagnosis of asthma. The admission rate for this group of children was about 31%. We developed a parsimonious multiple logistic regression model to predict asthma hospital admission based on asthma severity indicators. We then evaluated the model's predictive ability using two methods of cross-validation, using the same sample that was used for the predictive model, and using data from a split sample. The logistic regression model had a predictive accuracy of 90% (95% confidence interval 85–95%). The sensitivity and specificity were 86% and 88%, respectively. Cross-validation models confirmed that the predictive ability of the model was stable. In studies with limited sample sizes, it is possible to validate a model without setting aside a split sample for cross-validation.