白藜芦醇对脂多糖诱导的巨噬细胞极化改变的影响

目的：探讨白藜芦醇对脂多糖（LPS）诱导的小鼠巨噬细胞系RAW264．7细胞极化表型改变的影响。方法体外培养的RAW264．7小鼠巨噬细胞在六孔板孵育12 h ,分为磷酸盐缓冲液（PBS）对照组、LPS（100 ng／mL）组、LPS（100 ng／mL）＋白藜芦醇（30μmol／L）组,LPS＋白藜芦醇组在加入LPS前预先加入白藜芦醇孵育12 h;上述细胞在LPS刺激12 h后分别收集细胞和培养上清液;实时定量PCR（RT‐qPCR）检测经典的炎症活化型巨噬细胞（M1）型相关基因iNOS、TNF‐αmRNA表达,以及替代活化巨噬细胞（M2）型相关基因IL‐10、PPARγ和Arg‐1 mRNA表达,Western blot检测细胞iNOS、Arg‐1蛋白表达,ELISA检测培养上清液中炎性因子IL‐12 p40、IL‐10和 TNF‐α的水平。结果 RT‐qPCR检测结果显示,与LPS组相比,M1型相关基因iNOS、TNF‐αmRNA较LPS＋白藜芦醇组显著上升（P＜0．05）,而M2型相关基因IL‐10、PPARγ、Arg‐1 mRNA表达显著下调（P＜0．05）。Western blot检测发现,LPS组iNOS蛋白水平显著高于LPS＋白藜芦醇组（P＜0．05）,而Arg‐1蛋白水平显著低于LPS＋白藜芦醇组（P＜0．05）。ELISA检测发现,LPS组培养上清液中炎性因子IL‐12 p40、TNF‐α水平显著高于LPS＋白藜芦醇组（P＜0．05）,而IL‐10和水平显著低于LPS＋白藜芦醇组（P＜0．05）。结论白藜芦醇可能促进了LPS刺激的RAW264．7巨噬细胞向M2型极化改变。     

巴马汀对LPS诱导的RAW264．7巨噬细胞NO分泌及iNOS表达的影响

目的：观察巴马汀对脂多糖（LPS）诱导的RAW264．7小鼠巨噬细胞一氧化氮（NO）的分泌及诱导型一氧化氮合酶（iNOS）表达的作用。方法：采用LPS诱导RAW264．7巨噬细胞建立细胞炎症反应模型,加入不同浓度的巴马汀,采用Griess法测定NO的分泌量;采用Westernblot法检测iNOS蛋白的表达。结果：巴马汀能明显抑制LPS诱导的RAW264．7巨噬细胞NO的分泌,以及iNOS蛋白的表达,并呈现出浓度依赖性。结论：巴马汀可通过抑制LPS诱导的RAW264．7巨噬细胞NO的分泌及iNOS的表达,从而发挥抗炎作用。     

NLRP3、IL-33在LPS诱导的巨噬细胞中的表达及格列本脲对其表达的影响

目的研究NLRP3、IL．33在脂多糖（LPS）诱导的RAW264．7巨噬细胞炎症模型中的表达及格列本脲对其表达的影响。方法培养RAW264．7巨噬细胞,将其分为空白对照（A）组、NLRP3抑制剂格列本脲预处理＋LPS（B）组,LPS模型（C）组;B、C组采用LPS刺激RAW264．7巨噬细胞建立炎症模型,B组在LPS刺激前30rain给予格列本脲处理．空白对照组只给予培养基培养。采用蛋白免疫印迹法（Western．Mot）检测细胞中NLRP3蛋白的表达;酶联免疫吸附试验（EUSA）检测细胞培养上清中1L．33的含量;四氮唑盐（MYr）法测定各组细胞的增殖能力。结果C组中NLRP3蛋白表达均高于A组、B组（均P〈0．05）,B组NLRP3蛋白表达高于A组（P〈O．05）。C组IL-33含量比A、B组高（P〈0．05）,A组和B组之间差异无统计学意义。M1T试验中C组细胞增殖率高于A组、B组（P〈0．05）,而A、B组差异无统计学意义。结论NLRP3、IL．33在LPS诱导RAW264．7的巨噬细胞中表达升高,而格列本脲干预后可抑制NLRP3的表达及IL-33的分泌。     

槐定碱对小鼠巨噬细胞TLR4及JNK/c-jun mRNA表达的影响

目的观察槐定碱预处理对LPS刺激RAW 264.7巨噬细胞表达TLR4、JNK和c-jun mRNA及分泌TNF-α的影响,探讨槐定碱抗内毒素机制。方法培养RAW 264.7巨噬细胞,实验分为4组：空白对照组、槐定碱对照组、LPS组、槐定碱预处理组,用RT-PCR技术检测RAW 264.7细胞TLR4、JNK和c-jun的mR-NA表达量,放免法检测细胞培养液TNF-α分泌量。结果槐定碱对RAW 264.7巨噬细胞TLR4、JNK、c-jun的mRNA及细胞培养液中TNF-α基础表达无影响,但对经LPS激活的巨噬细胞的TLR4、JNK mRNA表达有显著抑制作用（均P〈0.01）,c-jun mRNA表达亦降低,但与LPS模型组比较差异尚无统计学意义。槐定碱预处理组细胞液中TNF-α含量显著低于LPS模型组（P〈0.01）。结论槐定碱抗内毒素机制与其抑制LPS引起的TLR4、JNK的mRNA高表达,并减少TNF-α分泌有关。     

槐定碱对小鼠巨噬细胞TLR4及JNK/c-jun mRNA表达的影响

目的观察槐定碱预处理对LPS刺激RAW 264.7巨噬细胞表达TLR4、JNK和c-jun mRNA及分泌TNF-α的影响,探讨槐定碱抗内毒素机制。方法培养RAW 264.7巨噬细胞,实验分为4组:空白对照组、槐定碱对照组、LPS组、槐定碱预处理组,用RT-PCR技术检测RAW 264.7细胞TLR4、JNK和c-jun的mR-NA表达量,放免法检测细胞培养液TNF-α分泌量。结果槐定碱对RAW 264.7巨噬细胞TLR4、JNK、c-jun的mRNA及细胞培养液中TNF-α基础表达无影响,但对经LPS激活的巨噬细胞的TLR4、JNK mRNA表达有显著抑制作用(均P<0.01),c-jun mRNA表达亦降低,但与LPS模型组比较差异尚无统计学意义。槐定碱预处理组细胞液中TNF-α含量显著低于LPS模型组(P<0.01)。结论槐定碱抗内毒素机制与其抑制LPS引起的TLR4、JNK的mRNA高表达,并减少TNF-α分泌有关。     

抑制 Toll样受体4表达对巨噬细胞极性转化的影响

目的：通过观察CLI－095对巨噬细胞表型的影响,探讨Toll样受体4（ TLR4）在巨噬细胞极性转化中的作用。方法以体外培养的小鼠骨髓来源巨噬细胞为研究对象,按数字表法随机分为3组,对照组（常规培养小鼠源性骨髓巨噬细胞48 h,不给予任何药物处理）、模型组（常规培养细胞24 h,换液后加入终浓度为1．0×105 U／L的γ干扰素和5 mg／L脂多糖干预24 h）、处理组（先给予1 mg／L的CLI－095孵育细胞24 h,换液后加入终浓度为1．0×105 U／L的γ干扰素和5 mg／L脂多糖干预24 h）。应用实时荧光定量聚合酶链反应检测TLR4 mRNA的表达;应用流式细胞术检测膜分子CD16／32、CD206的表达;用酶联免疫吸附法检测白细胞介素－10（IL－10）和IL－12的分泌。结果模型组较对照组CD16／32、IL－12明显升高,CD206明显降低,符合M1型巨噬细胞特性。处理组与模型组比较,TLR4 mRNA表达降低,提示TLR4受到抑制,CD16／32和IL－12表达下降,CD206和IL－10明显上升,差异有统计学意义（P＜0．05）,符合M2型巨噬细胞极性特点。结论 TLR4在巨噬细胞极性转化中起着重要的作用,抑制TLR4表达可诱导炎症性巨噬细胞向抗炎性M2型转化。     

Fractalkine 通过激活 Wnt/β-catenin 信号通路抑制脂多糖诱导的巨噬细胞M1型极化

目的 研究Fractalkine（CX3CL1,FKN）对脂多糖（LPS）诱导的RAW264.7巨噬细胞免疫应答的作用机制。方法 体外培养RAW264.7细胞,使用慢病毒技术构建过表达FKN的稳定细胞珠。细胞分为8组：（1）空白对照组;（2）LPS组,细胞给予脂多糖（1 μg/mL,12 h）;（3）ICG-001组,细胞给与Wnt/β-catenin信号通路抑制剂ICG-001（10 μmol/mL,48 h）;（4）过表达FKN组;（5）ICG-001+LPS组,细胞给与ICG-001（10 μmol/mL预处理36 h）后,加入脂多糖（1 μg/mL,12 h）;（6）过表达FKN+LPS组,过表达 FKN细胞给与脂多糖（1 μg/mL,12 h）;（7）过表达FKN+ICG-001组,过表达FKN细胞给予ICG-001（10 μmol/mL,48 h）;（8）过表达 FKN+ICG-001+LPS 组,过表达 FKN 细胞给与 ICG-001（10 μmol/mL 预处理 36 h）后,加入脂多糖（1 μg/mL,12 h）;应用 CCK-8细胞增殖实验检测ICG-001作用于巨噬细胞中的安全浓度;应用酶联免疫吸附（ELISA）实验检测巨噬细胞上清液中M1型极化因子TNF-α和IL-6的含量;应用蛋白质免疫印记（WB）实验检测巨噬细胞中FKN、Wnt/β-catenin通路关键因子Wnt-4和β-catenin、M1型极化因子iNOS、TNF-α和IL-6的蛋白表达水平;应用免疫荧光（IF）实验检测巨噬细胞中M1型极化因子IL-6蛋白的定位。结果 过表达FKN的RAW264.7细胞中FKN的蛋白水平较空白对照组明显升高（P<0.01）。CCK-8实验显示ICG-001作用于RAW264.7细胞48 h的IC50为10 μmol/mL。与LPS组相比,ICG-001+LPS组上清液中TNF-α和IL-6的分泌量以及细胞内TNF-α、IL-6和iNOS蛋白含量均升高（P<0.05）,而细胞内FKN、Wnt-4和β-catenin蛋白含量均显著降低（P<0.01）;EXFKN+LPS组上清液中TNF-α和IL-6的分泌量以及细胞内TNF-α、IL-6和iNOS蛋白含量均显著降低（P<0.01）,而细胞内FKN、Wnt-4和β-catenin蛋白含量均显著升高（P<0.01）。与LPS组相比,ICG-001+LPS组中IL-6在细胞质中的定位增强,而EXFKN+LPS组中IL-6在细胞质中的定位受到抑制。结论 过表达FKN通过激活Wnt/β-catenin信号通路抑制脂多糖诱导的巨噬细胞M1型极化。     

冠心平含药血清对LPS诱导的RAW264.7巨噬细胞极化的影响

目的?探讨冠心平（GXP）含药血清对LPS诱导的RAW264.7巨噬细胞极化的调控作用。方法?RAW264.7巨噬细胞分为对照组、模型组、GXP低、中、高剂量组,100?ng/mL LPS刺激12?h诱导M1型极化模型,不同浓度GXP含药血清进行干预。ELISA法检测巨噬细胞上清肿瘤坏死因子-α（TNF-α）、转化生长因子-β1（TGF-β1）含量;流式细胞术检测M1、M2型巨噬细胞特征性表面标记分子CD86、CD206表达水平;qPCR法检测巨噬细胞CD86、CD206 mRNA表达情况。结果?冠心平高剂量显著减少巨噬细胞TNF-α分泌（P<0.01）,各剂量减少TGF-β1分泌（P<0.01）;冠心平低、高剂量显著降低M1型巨噬细胞特征性分子CD86表达（P<0.05）,显著升高M2型巨噬细胞特征性分子CD206表达（P<0.01）;同时冠心平CD206 mRNA表达显著增加（P<0.05）。结论?冠心平含药血清能够抑制LPS诱导的巨噬细胞M1型极化而促进M2型极化,这或许是冠心平治疗动脉粥样硬化的潜在机制之一。      

谷氨酰胺对RAW264.7细胞HSP 72表达和TNF-α释放的影响

目的探讨不同条件下谷氨酰胺（Gln）对小鼠腹腔巨噬细胞株RAW264．7热休克蛋白（HSP）72表达和肿瘤坏死因子（TNF）-α释放的影响。方法将RAW264．7细胞与含Gin（0、0．5和8mmol／L）的培养液分别进行下列处理：①共同培养165min后,加入脂多糖（LPS）刺激0、1、4、12和24h;②共同培养的同时行热应激预处理45min,370C培养2h后加入LPS刺激4h;③共同培养的同时行DON预处理,165min后加入LPS刺激4h;④两者与含LPS的培养液共同培养1h,改用含0．5mmol／L Gln和LPS的培养液继续培养4h。ELISA法检测细胞上清液TNF-α的浓度,Western blotting检测细胞HSP 72蛋白表达。结果①LPS刺激后4h,RAW264．7细胞均有HSP 72表达,经8mmol／L Gln培养者较经0和0．5mmol／L Gln培养者HSP 72表达显著增加（P〈0．01）,而24h时三者HSP 72表达差异无统计学意义（P〉0．05）;Gln促进TNF-α释放,与Gln呈时间和浓度依赖关系。②热应激显著促进Gln诱导的HSP72表达（P〈0．01）,抑制Gln诱导的TNF—α释放,但TNF—α释放仍随Gln浓度增加而增加。③DON预处理不影响HSP 72的表达,但显著抑制TNF—α释放（P〈0．01）。④短时间不同浓度Gln处理,与0．5和8mmol／L Gln共同培养者较与0mmol／L Gln共同培养者HSP72表达显著增加（P〈0．01）;TNF—α的释放随Gln浓度增加有升高趋势,但三者间差异无统计学意义（P〉0．05）。结论Gln可诱导RAW264．7细胞表达HSP 72,但并不足以抑制其TNF—α释放。除诱导HSP 72表达外,Gln在脓毒症时调节机体炎症反应还可能存在其他机制。     

黄芪苷对脂多糖诱导巨噬细胞一氧化氮和一氧化氮合酶表达的影响

[摘要] 目的：研究黄芪苷对小鼠巨噬细胞一氧化氮（NO）生成和诱导型一氧化氮合酶（iNOS）表达的影响。方法：体外培养小鼠巨噬细胞RAW264.7,取生长良好的细胞分别加入LPS（终浓度1μg/ml）和不同浓度黄芪苷（终浓度10,50,100μM）进行干预,并设空白对照组。取培养24h细胞上清,用Griess法检测NO生成量;取培养8h和24h细胞,分别提取细胞总RNA和蛋白,用RT-PCR法和Western Blot法检测iNOS基因和蛋白水平表达情况。结果：与空白对照组相比,LPS明显促进了RAW264.7细胞iNOS表达和NO的生成;加入黄芪苷可抑制 LPS诱导的RAW264.7细胞iNOS mRNA和蛋白表达,减少NO的生成,与LPS组有显著性差别。结论：黄芪苷可明显降低LPS诱导的巨噬细胞iNOS表达和NO生成,这可能是其抗动脉粥样硬化斑块形成的作用机制之一。     

Value of D-Dimers in patients with acute aortic dissection

Objective: To evaluatel the value of D-dimers in patients with acute aortic dissection (AAD). Methods: This study consisted of 16 patients with AAD and 27 non-AAD patients. Serum D-dimets were measured by Sta-Liatest D-DI immunoturbidimetric assay. Results: D-dimer level was higher (P ＜ 0.001) in patients with AAD(7.91 ± 5.52 μg/ml) than that in non- AAD group(1.57±1.24 μg/ml). D-dimer was positive (＞0.4 μg/ml) in all patients with AAD and in 10 control group patients (37%). Among patients with acute AAD, D-dimers tended to be higher in Stanford A than in Stanford B (8.67 ± 4.31 μg/ml vs. 3.24±1.27 μg/ml, P ＜0.01). D-dimer values tended to be higher in more extended disease(3.84 ± 1.65 μg/ml, 8.57 ± 3.58 μg/ml and 11.87 ± 5.69 μg/ml in thoracic aorta, thoracic and abdominal aorta, thoracic and abdominal aorta and iliacal arteries, respectively, P ＜ 0.05 for both 8.57 ± 3.58 and 11.87 ± 5.69 vs. 3.84 ± 1.65 ). Including the control group into the analysis, we found a sensitivity of 100%, a negative predictive value of 100%, and a specificity of 66% and a positive predictive value of 64% for D-dimer in diagnosis of AAD in our patients with suspected AAD. Conclusion: D-dimer was elevated in patients with AAD. A negative D-dimer test result could be useful in excluding AAD.     

Research of combined liver-kidney transplantation model in rats

Objective： To set up a simple and reliable rat model of combined liver-kidney transplantation. Methods： SD rats served as both donors and recipients. 4℃ sodium lactate Ringer＇s was infused from portal veins to donated livers,and from abdominal aorta to donated kidneys, respectively. Anastomosis of the portal vein and the inferior vena cava （IVC） inferior to the right kidney between the graft and the recipient was performed by a double cuff method, then the superior hepatic vena cava with suture. A patch of donated renal artery was anastomosed to the recipient abdominal aorta. The urethra and bile duct were reconstructed with a simple inside bracket. Results： Among 65 cases of combined liver-kidney transplantation, the success rate in the late 40 cases was 77.5%. The function of the grafted liver and kidney remained normal. Conclusion： This rat model of combined liver-kidney transplantation can be established in common laboratory conditions with high success rate and meet the needs of renal transplantation experiment.     

Development on Adjustable Calibration Marker for Shock Wave Focus

Shock wave lithotripsy （SWL） is a treatment of choice for upper urinary stones. However, this procedure is inappropriate for obese patients because the focus is often unable to reach the target owing to the limited focal distance in shock wave source. Although treating such patients in a blast path may increase the application length of shock wave source, it＇s difficult to find this path on the lithotripter monitor. For this reason, we invented an adjustable calibration marker in order to set an effective focus in the shock wave hath.     

Study on the TCM Pathogenesis of Angiopathic Complications of Type II Diabetes

Excess production of reactive oxygen species(ROS)of mitochondrion mediated by hyperglycemia is the common pathogenesis of angiopathic complications of diabetes.TCM holds that the damp from the dysfunction of spleen.kidney and liver is the causative factor of complications of diabetes.This is similar to the mechanism of Ros resulting in angiopathic complications of diabetes.When the angiopathic complications of type II diabetes mellitus(T2DM)are difierentiated as caused by turbid damp in TCM can be explained as ROS.Since the obstruction of pathogenic damp in channels and collaterals is said to be the main pathogenesis,the treating principle should be dissolving the damp to remove the obstruction.     

Leptin, Ghrelin and TNF-α before and after Hypo-caloric Traditional Chinese Diet and Auricular Acupuncture

INTRODUCTION Obesity is a complex emergent problem, which can be possibly solved not only by the diet but also by the life style and promotion of a constant physical exercise. 1, 2 No doubt careful attentions must be given to the nutritional condition of obese people, the dietary habits, the somatic build (i.e. distribution of fat mass) and the organic functions linked to formation of the fat mass. All the parameters should be constantly monitored before, during and after a diet treatment. 3, 4, 5     

BLOOD PRESSURE CHANGE WITH AGE IN SALT-SENSITIVE TEENAGERS

Objective To observe blood pressure change with age in salt-sensitive teenagers whose salt sensitivity were determined by repeated testing.Methods Salt sensitivity was determined through intravenous infusion of normal saline combined with volume-depletion by oral diuretic furosemide in 55 teenagers. After five years, salt sensitivity was re-examined and subject blood pressure was followed up. Blood pressure changes in salt-sensitive teenagers were compared to that of non-salt sensitive teenagers over five years.Results After 5 years, the repetition rate of salt sensitivity determined by intravenous saline loading is 92.7%. In teenagers with salt sensitivity on the baseline, both the systolic blood pressure increments and increment rates were much higher than non-salt sensitive teenagers (12.7±12.1 mmHg vs. 2.8±5.2 mmHg, P＜ 0.01; 12.2%± 12.0% vs. 2.5% ±4.4%, P＜ 0.001,respectively). There was a similar trend for diastolic blood pressure (8.4 ± 6.4 mmHg vs. 3.7 ± 6.4 mmHg, P = 0.052; 13.2% ±10.6 % vs. 6.8%± 10.1%, P = 0.053, respectively).Conclusions Salt sensitivity determined by intravenous saline loading showed good reproducibility. Blood pressure increments with age were much higher in salt-sensitive teenagers than non-salt sensitive teenagers, especially in terms of systolic blood pressure.     

Relationship between Dysglycemia and Carotid Atherosclerosis in Tibetan Population

People with dysglycemia are at high risk for atherosclerotic diseases. This study aims at investigating the atherosclerotic vascular damage in dysglycemia and its metabolic origin in Tibetan population.     

APPLICATION OF LORNOXICAM TO PATIENT-CONTROLLED ANALGESIA IN PATIENTS UNDERGOING ABDOMINAL SURGERIES

FOR anesthesiologis s ,treatingpostoperativepainhas alwaysbeen a problem.Althoughopioidshave been provedtobe effective,theirsideeffectscouldnotbeignored.With thedevelopmentofscienceand pharmacology,many drugs with aspectsof satisfactoryanalgesicefficacyand couldbe welltoleratedby patientshave been developed.And lornoxicamisone of them, which isa non-steroidalanti-inflammatorydrug (NSAID ), with analgesic, anti-infl-ammatory,andantipyreticproperties.Itseliminationhalf-time(3 to 5 hours) isle…     

CLINICAL SIGNIFICANCE OF SERUM CYTOKINES IL-1β,sIL-2R,IL-6,TNF-α,AND IFN-v IN ACUTE CORONARY SYNDROME

Objectives To explore serum cytokines levels (including IL-1 β, sIL-2R, IL-6, TNF-α, and IFN-v) and their significance in patients with acute coronary syndrome (ACS) and the subsequent follow-ups, with attempt to estimate the role of various serum inflammatory markers in the diagnosis and assessment of ACS.Methods The study population include 40 patients with acute myocardial infarction (AMI), 40 patients with unstable angina pectoris (UAP), and 40 controls. Among the 80 patients, 60 patients attended a follow up 4 months later. Serum inflammatory markers including IL-1 β, sIL-2R, IL-6, TNF-α, and IFN-v were measured by enzyme linked immunosorbent assay.Results Serum IL- 1 β, sIL-2R, IL-6, TNF-α were significantly higher in AMI group or UAP group compared to the control group and became significantly lower 4 months later in the follow-up patients. Serum levels of IFN-v shows no significant difference between AMI group or UAP group and controls, also showing no significant change when measured in follow up patients. There was no correlation between serum creatine kinase-MB isoenzyme levels and serum inflammatory markers either in UAP or AMI group. Furthermore, when divided into two subgroups using Wagner's QRS scoring system in the AMI group, there is no difference of each serum inflammatory marker between ≤ 6 scores group and ＞ 6 scores group.Conclusion Serum levels of certain inflammatory markers may have some diagnostic value for ACS, and can be a useful marker reflecting disease stability.     

Possible Spread of adenovirus type 3 from poultry to humans ：indirect evidence from an outbreak in China

Objective:To explore the epidemiology and etiology for an outbreak of acute respiratory tract infection that occurred in one county of Jiangsu Province, China 2004. Methods: Only cases meeting the case definition were included in the study. We reviewed the medical records of the cases who were admitted to the local hospitals, interviewed cases by a standard questionnaire, and then described the epidemiotogic features and analyzed risk factors by means of a case-control study. We collected pharyngeal swab specimens and sent them to different laboratories for isolation and culture. The laboratory used different detection methods such as DIP, PCR, electron microscope examination and microneutralization assay, to identify and then type the positive specimens. Results:A total of 871 cases were reported during the period from April 18 to July 4,2004. The distribution of onset times presented two peaks, one in late May and another in middle June. The epidemic occurred mainly in the elementary and junior high schools in ten townships of one county, and the mean age of the cases was 12 years (range 7 months to 18 years). The course of the disease was acute, and was characterized by fever accompanied with sore throat and tonsillitis. The WBC count of cases was normal or elevated. The mean duration of illness was 5 days (range 2 to 12 days). No fatalities from illness were reported. A case-control study indicated that the possible risk factors were close contact with a case and/or poultry before onset and sharing of towels among members of the family. The typical CPE was observed through inoculating pharyngeal swab specimens into the HEP-2 cell cultures in different laboratories. An infection of adenovirus type 3 was verified by detecting positive specimens in different methods. Conclusion:This investigation demonstrated that the acute respiratory infection in cases was caused by adenovirus type 3. Cases occurred in over 70 schools in ten townships in 2004, and the route of transmission was possibly close contact with cases or droplet transmission.