洛沙坦对蛋白激酶C在慢性缺氧大鼠模型肺动脉胶原表达作用的影响

目的　观察洛沙坦对蛋白激酶C(PKC)在慢性缺氧大鼠模型肺动脉胶原表达作用的影响。方法　将二级SD大鼠分为 3组 :A组 (正常对照组 )大鼠室内常规饲养。B组 (单纯缺氧 4周组 )大鼠置于常压低氧舱中 ,舱内充入氮气 ,使氧浓度维持在 (1 0 0± 0 5) % ,每天 8h ,每周 6d ,连续 4周 ;大鼠每天缺氧前用 2ml蒸馏水灌胃。C组 (洛沙坦干预组 )缺氧条件同B组 ,大鼠每天缺氧前用洛沙坦 (洛沙坦 50mg/kg溶于 2ml蒸馏水 )灌胃。采用透射电镜、放射活性测定法、免疫组化、原位杂交等方法观察 3组大鼠肺细小动脉超微结构、肺组织PKC活性、肺动脉管壁PKC免疫组化及Ⅰ、Ⅲ型胶原和Ⅰ、Ⅲ型前胶原基因表达的变化。结果　 (1 )B组大鼠平均肺动脉压、右心室重量比显著高于A组(P <0 0 1 ) ,C组显著低于B组 (P <0 0 1 )。 (2 )光镜下可见B组大鼠肺血管管壁厚度占血管外经的百分比、管壁面积占管总面积的百分比显著高于A组 (P <0 0 1 ) ,C组显著低于B组 (P <0 0 1 )。电镜下可见B组大鼠肺动脉胶原纤维较A组明显为多 ,C组较B组明显为少。 (3)B组大鼠肺组织细胞PKC总活性、胞膜PKC活性、胞质PKC活性及胞膜PKC活性占PKC总活性的百分比显著高于A组(P <0 0 1 ) ,C组上述指标均显著低于B组 (P <0 0 1 )。 (4)免疫组化显示 ,B     

洛沙坦对大鼠糖尿病模型肾脏转化生长因子βⅠ型、Ⅱ型受体表达的影响

目的　观察洛沙坦对大鼠糖尿病模型肾脏转化生长因子 βⅠ型受体 (TGFβRⅠ )、Ⅱ型受体 (TGFβRⅡ )表达的影响。 方法　 30只大鼠按体重随机分为 3组 ,每组 10只。A组 :健康对照组 ;B组 :糖尿病模型组 ,尾静脉注射链脲佐菌素 5 0mg/kg体重制成糖尿病模型 ;(3)C组 :洛沙坦治疗组 ,按B组方法建立大鼠糖尿病模型后第 2天给予洛沙坦 10mg·kg体重 -1·d-1灌胃。 8周后半定量逆转录 聚合酶链反应检测 3组肾皮质TGFβRⅠ、TGFβRⅡ和纤维连接蛋白 (FN)mRNA的表达。免疫组化测 3组肾皮质TGFβRⅠ、TGFβRⅡ和FN蛋白的表达。生化法测血糖、尿素氮和肌酐水平。放射免疫法测血胰岛素和血管紧张素Ⅱ。磺基水杨酸法测 2 4h尿蛋白。结果　B组大鼠平均肾小球体积、肾重 /体重增加 ,2 4h尿蛋白、血尿素氮和肌酐水平上升 (P <0 0 5 ) ;肾皮质TGFβRⅠ、TGFβRⅡ、FNmRNA和蛋白表达显著增加 (P <0 0 5 )。C组大鼠平均肾小球体积、肾重 /体重减少 ,2 4h尿蛋白、血尿素氮和肌酐水平下降 (P <0 0 5 ) ;肾皮质TGFβRⅠ、TGFβRⅡ、FNmRNA和蛋白表达显著降低 (P <0 0 5 )。 结论　洛沙坦下调大鼠糖尿病模型肾脏TGFβRⅠ、TGFβRⅡ的表达 ,抑制肾脏细胞肥大 ,减少细胞外基质成分的合成。     

洛沙坦降低糖尿病大鼠肾组织膜3型基质金属蛋白酶mRNA的表达

目的　研究洛沙坦对糖尿病大鼠肾组织膜 3型基质金属蛋白酶 (MT3 MMP)mRNA表达的影响。方法　雄性Wistar大鼠分为 3组 ,A组 (11只 )为正常对照组 ,B组 (11只 )为糖尿病未干预组 ,C组 (9只 )为糖尿病大鼠洛沙坦 (血管紧张素Ⅱ 1型受体阻断剂 )干预组。以链脲佐菌素 (STZ)制备糖尿病大鼠模型。大鼠饲养 18周后取出肾脏检测MT3 MMPmRNA表达、电镜检测大鼠肾小球基底膜厚度及系膜基质密度 (系膜基质面积 /系膜面积 ) ;收集 2 4h尿测定尿白蛋白排泄量 (UAE)。mRNA表达采用RT PCR ,以 β actin作为内对照。UAE测定采用大鼠白蛋白特异的酶免疫分析试剂盒。结果　肾组织MT3 MMPmRNA表达在B组大鼠 (1.37± 0 .96 )显著高于A组 (0 .75± 0 .34,P <0 .0 5 )和C组 (0 .75± 0 .30 ,P <0 .0 5 ) ,而后两组比较差异无显著性。UAE、肾小球基底膜厚度及系膜基质密度在B组大鼠均显著高于A组和C组 (P <0 .0 5 )。结论　STZ糖尿病大鼠肾组织MT3 MMPmRNA表达明显增加 ,洛沙坦处理能延缓糖尿病肾病的发生 ,与此同时降低MT3 MMPmRNA表达。提示MT3 MMP与糖尿病肾病发病可能有一定关系。     

阻断肾素-血管紧张素系统对糖尿病大鼠肾脏蛋白激酶CβⅡ亚型的影响

目的　研究链脲佐菌素诱导的糖尿病大鼠肾组织蛋白激酶C(PKC) βⅡ亚型的表达和转位 ,以及阻断肾素 血管紧张素系统 (RAS)对其的影响。方法　糖尿病模型大鼠随机分为伊贝沙坦组 (4 0mg·kg-1·d-1)、福辛普利组 (4 0mg·kg-1·d-1)、两药合用组 (各 2 0mg·kg-1·d-1)、糖尿病对照组。另设正常对照组。给药 4周末检测各组血糖、胰岛素水平 ,采用免疫组化法检测肾组织中PKCβⅡ的表达 ,Western印迹法检测肾皮质、髓质PKCβⅡ的表达和胞膜转位情况。结果　糖尿病对照组肾皮质总的和胞膜部分的PKCβⅡ表达量均明显降低 ,分别为正常对照组的 66.0 %和 5 0 .0 % (均P <0 .0 5 ) ,而各治疗组均可部分地纠正这种异常。肾髓质各组间PKCβⅡ的总量及胞膜、胞浆部分的量差异无显著性。结论　早期糖尿病大鼠肾脏中PKCβⅡ的表达存在着量和转位的异常 ,而阻断RAS可部分纠正这种变化 ,提示RAS可通过影响PKC转导途径的异常而参与糖尿病肾病的发生发展机制。     

洛沙坦对糖尿病大鼠肾脏转化生长因子-β1及其Ⅱ型受体表达的影响及机制

目的　探讨血管紧张素Ⅱ(AngⅡ)受体拮抗剂洛沙坦对糖尿病 (DM )大鼠肾脏的保护作用及其作用机制。　方法　大鼠随机分为正常对照组 (C组 )、糖尿病组 (DM组 )和DM洛沙坦治疗组 (DL组 ) ,每组 10只。观察 8周后用半定量RT PCR检测各组肾皮质转化生长因子 βⅡ型受体 (TβRⅡ)和纤维连接蛋白 (FN)mRNA的表达。用免疫组化检测各组肾皮质转化生长因子 β1(TGF β1)、TβRⅡ和FNmRNA的表达。检测血糖 (BG )、尿素氮 (BUN )、肌酐 (Cr)、血胰岛素 (Ins)、AngⅡ、尿白蛋白排泄率(UAER)。　结果　DM组 8周出现平均肾小球体积、肾重 /体重增加 ,UAER、血BUN和Cr水平上升(P <0 .0 5)。DM组肾皮质TβRⅡ和FNmRNA的表达明显增加 ,TGF β1、TβRⅡ和FNmRNA的表达也显著增加 (P <0 .0 5)。洛沙坦治疗 8周后 ,DL组平均肾小球体积、肾重 /体重减少 ,UAER、血BUN和Cr水平下降 (P <0 .0 5)。肾皮质TβRⅡ和FNmRNA的表达降低 ,TGF β1、TβRⅡ和FNmRNA的表达也降低 (P <0 .0 5)。　结论　洛沙坦对DM大鼠肾脏具有保护作用。其机制可能为洛沙坦下调TGF β系统的表达 ,后者抑制肾细胞肥大、减少细胞外基质 (ECM)成分的合成     

蛋白激酶C对慢性低氧大鼠肺动脉胶原表达的调控及灯盏花素的干预作用

目的　探讨蛋白激酶C(PKC)对慢性低氧大鼠肺动脉胶原表达的调控作用及灯盏花素的影响。方法　将二级Sprague Dawley(SD)大鼠分为 :对照组 (A) ,低氧组 (B) ,低氧 +灯盏花素组 (C) ,低氧时间为 4周。采用透射电镜、放射活性测定法、免疫组化、原位杂交等方法综合进行评价。结果(1)B组肺动脉平均压 (mPAP)、右心室重量比 (RV/LV +S)显著高于A组 (P <0 0 1) ,C组mPAP、RV/LV +S显著低于B组 (P <0 0 1) ;(2 )电镜显示B组肺动脉胶原纤维较A组明显为多 ,C组较B组明显为少 ;(3)B组肺组织PKC总活性 (PKCt)、胞膜PKC活性 (PKCm)、胞浆PKC活性 (PKCc)及PKCm占PKCt的百分比显著高于A组 (P <0 0 1) ,C组PKCt、PKCm、PKCc及PKCm占PKCt的百分比显著低于B组 (P <0 0 5 ) ;(4)免疫组化显示B组肺细小动脉 (直径 10 0～ 2 0 0 μm)PKC含量 (平均吸光度A值 )显著高于A组 (P <0 0 1) ,C组较B组显著为低 (P <0 0 1) ;(5 )免疫组化和原位杂交显示B组肺细小动脉 (直径约 10 0～ 2 0 0 μm)Ⅰ型胶原及Ⅰ型前胶原mRNA平均A值较A组明显为高 (P <0 0 1) ,C组较B组为低 (P <0 0 1) ,Ⅲ型胶原及Ⅲ型前胶原mRNA平均A值各组间差异无显著性 (P >0 0 5 ) ;(6 )肺组织PKC活性和肺动脉管壁PKC的表达与肺动脉管壁Ⅰ型胶原mRNA和蛋白     

抑制核因子-κB活性降低糖尿病大鼠肾组织血管紧张素Ⅱ及其1型受体的水平

目的　观察抑制核因子 κB(NF κB)活性对实验性糖尿病大鼠肾组织血管紧张素 (Ang)Ⅱ水平及其 1型受体 (AT1R)mRNA表达的作用。方法　雄性Wistar大鼠分为 3组 :A组为正常对照组 (11只 ) ,B组为糖尿病大鼠未干预组 (11只 ) ,C组为吡咯烷二硫基甲酸酯 (NF κB活性抑制剂 )干预组 (9只 )。以链脲佐菌素制备糖尿病模型。在实验的第 18周末取出肾脏检测NF κB活性、AngⅠ与AngⅡ水平及AT1RmRNA表达。NF κB活性检测采用电泳迁移率变动分析。AngⅠ和AngⅡ水平以放免法检测。mRNA检测采用RT PCR法。结果　B组大鼠肾组织NF κB活性 (1.85± 0 .5 4× 10 6)显著高于A组 (0 .0 7± 0 .11× 10 6,P <0 .0 1)和C组 (0 .2 5± 0 .2 5× 10 6,P <0 .0 1)。肾组织肾素活性在 3个观察组间差异无显著性。B组大鼠肾组织AngⅠ (2 .5 7± 1.94)pg/mg显著高于A组〔(1.2 9± 0 .47)pg/mg组织 ,P <0 .0 1〕和C组〔(1.15± 0 .3 1)pg/mg组织 ,P <0 .0 1〕。肾组织AngⅡ水平B组大鼠 (12 1.9± 2 1.9)pg/mg组织与A组大鼠 (10 1.9± 2 0 .3 )pg/mg组织比较差异无显著性 ,C组大鼠 (75 .4± 2 7.5 )pg/mg组织显著低于B组 (P <0 .0 1)。AT1RmRNA表达在B组大鼠 (0 .62± 0 .17)显著低于A组 (1.13± 0 .82 ,P <0 .0 1) ,C组 (0 .2 0± 0     

肿瘤坏死因子-α对大鼠离体灌注肾血管收缩的影响

目的观察肿瘤坏死因子(TNF)-α对肾血管收缩的影响及机制。方法 56只大鼠制备离体灌注肾模型,随机分为8组(n=7):A1组:Kreb液灌流;A2组:Kreb液+TNF-α灌流;B1组:Kreb液+Verapamil灌流;B2组:Kreb液+Verapamil+TNF-α灌流;C1组:无钙Kreb液灌流;C2组:无钙Kreb液+TNF-α灌流;D1组:无钙Kreb液+2-APB灌流;D2组:无钙Kreb液+2-APB+TNF-α灌流。各组均在刺激期加内皮素(ET)。灌流结束后,计算肾脏水肿率,HE染色观察肾小球及肾小管形态、结构。结果各组基础灌注压比较无显著差异(P0.05)。A1、A2、B1、B2、C1、C2组ET刺激后,肾灌注压较基础压均明显升高(P0.05);A2、B2、C2组灌注压升高值分别显著高于A1、B1、C1组(P0.01)。D1、D2组ET刺激后,肾灌注压均略升高,但与基础灌注压比较无显著差异(P0.05);两组灌注压升高值比较无显著性差异(P0.05)。8组肾脏的水肿率均低于30%,灌流后肾脏标本切片均未发现明显的器质性损伤,与灌流前相符。结论 TNF-α可能通过上调1,4,5-三磷酸肌醇受体(IP3R)增强ET引起的肾血管收缩。     

2型糖尿病大鼠肾脏血红素加氧酶-1、Nrf-2表达及Hemin、Znpp的干预效果

目的观察模拟2型糖尿病大鼠肾脏血红素加氧酶(HO)-1表达及Hemin、Znpp干预效果。方法实验分为:(A)正常组,(B)糖尿病组,(C)糖尿病+氯高铁血红素组,(D)糖尿病+锌原卟啉组,观察干预后大鼠血清HO-1活性、含量、肾脏HO-1、Nrf-2的表达,超氧化物歧化酶(SOD)、丙二醛(MDA)水平。结果 B组HO-1活性和含量肾脏表达低于A组(P0.05),D组较B组下降更明显,C组结果升高但未达到A组水平。结论糖尿病大鼠HO-1变化可能通过影响Nrf-2的表达引起SOD、MDA改变发挥抗氧化应激作用。     

安体舒通抗肝纤维化作用实验性研究

目的　研究和评估安体舒通对实验性大鼠肝纤维化的防治作用 ,探讨其抗肝纤维化作用的可能机制。结果　将雄性Wistar大鼠 80只随机分为正常对照组 (A组 ,16只 ) ,肝纤维化模型组Ⅰ (B组 ,5 4只 ) ,安体舒通治疗组Ⅰ (C组 ,10只 ) ,采用CCl4 复合因素造模 ,治疗组于造模同时予安体舒通每日 10 0mg·kg-1·mL-1灌胃 ,6周末造模成功处死C组大鼠 ,同时随机处死A组及B组大鼠各 8只 ;对B组剩下大鼠行二次随机分组 ,分为模型对照组Ⅱ (D组 ,12只 ) ,安体舒通治疗组Ⅱ (E组 ,10只 ) ,E组于第 7周开始给予安体舒通治疗 ,10周末处死大鼠。检测大鼠肝功能 ,血清透明质酸 (HA) ,层粘蛋白 (LN) ,Ⅲ型前胶原 (PCⅢ ) ,Ⅳ型胶原 (CIV) ;免疫组化法检测肝组织基质金属蛋白酶组织抑制因子 (TIMP -1)的表达。结果　C组与B组比较 ,血清ALT、AST、HA、LN、CIV、PCⅢ均显著降低 (P <0 .0 1) ,TIMP -1活性明显降低 (0 .34± 0 .0 5vs 0 .45± 0 .0 5 ,P <0 .0 1) .E组与D组相较 ,TIMP -1活性亦有明显降低(0 .31± 0 .0 7vs 0 .42± 0 .0 6,P <0 .0 1)。结论　安体舒通对肝纤维化有一定预防作用 ,并可能通过抑制TIMP -1活性表达而促进肝细胞外基质降解     

The immunoneuroendocrine role of melatonin

Abstract: A tight, physiological link between the pineal gland and the immune system is emerging from a series of experimental studies. This link might reflect the evolutionary connection between self-recognition and reproduction. Pinealectomy or other experimental methods which inhibit melatonin synthesis and secretion induce a state of immunodepression which is counteracted by melatonin. In general, melatonin seems to have an immunoenhancing effect that is particularly apparent in immunodepressive states. The negative effect of acute stress or immunosuppressive pharmacological treatments on various immune parameters are counteracted by melatonin. It seems important to note that one of the main targets of melatonin is the thymus, i.e., the central organ of the immune system. The clinical use of melatonin as an immunotherapeutic agent seems promising in primary and secondary immunodeficiencies as well as in cancer immunotherapy. The immunoenhancing action of melatonin seems to be mediated by T-helper cell-derived opioid peptides as well as by lymphokines and, perhaps, by pituitary hormones. Melatonin-induced-immuno-opioids (MHO) and lymphokines imply the presence of specific binding sites or melatonin receptors on cells of the immune system. On the other hand, lymphokines such as -γ-interferon and interleukin-2 as well as thymic hormones can modulate the synthesis of melatonin in the pineal gland. The pineal gland might thus be viewed as the crux of a sophisticated immunoneuroendocrine network which functions as an unconscious, diffuse sensory organ.     

Changes in connexin43, the gap junction protein of astrocytes, during development of the rat pineal gland

Abstract: The abundance of gap junctions between rat pineal astrocytes formed by connexin43 (Cx43) was studied during development. Levels and distribution of Cx43 were measured by immunoblotting and indirect immunofluorescence, respectively. The amount of Cx43 in cells located within the gland was low until about the 7th postnatal day and increased to adult values between the 14th and 21st days postpartum. Although astrocytes, recognized by their vimentin immunoreactivity, were scarce before birth, they were abundant by the 7th postnatal day suggesting that the low levels of Cx43 found at this age corresponded to a low expression of this protein. Localization of the immunoreactivity to Cx43 and vimentin showed a close correlation, indicating that mature or immature pineal astrocytes form gap junctions made of Cx43. Since Cx43 levels attained their adult values at about the time the innervation and the functional state of the gland reached maturity (2–3 weeks after birth), it is proposed that astrocyte gap junctions are involved in the function of the adult rat pineal gland.     

Response of rat pineal melatonin to calcium, magnesium, and lithium is circadian stage dependent

Abstract: Herein we documented the response of pineal melatonin production to electrolytes known to be effective on pineal function in view of a possible circadian stage dependence. We studied the release of melatonin by perifused rat pineal glands at 2 different circadian stages corresponding to the middle of the light and dark periods, i.e., respectively, 7 and 19 HALO (Hours After Light Onset, L:D = 12:12). The initial efflux rates were, as expected, much higher in the perifusates of glands removed from rats sacrificed during the dark phase than of those removed during the light phase. After 3 hr of perifusion, melatonin release reached similar levels which were found constant up to the 8th hr of perifusion, whatever the circadian stage. Perifusion of the glands with physiological concentrations for the rat of calcium (5.2 mmol/1) and magnesium (1.34 mmol/1) resulted in a stimulatory effect on the pineal glands removed from rats sacrificed in the middle of the dark period (19 HALO), whereas no effects were observed on the pineal glands removed from rats sacrificed during the light (7 HALO). Lithium (0.28 and 0.55 mmol/1) was ineffective on melatonin release in pineal glands removed 7 and 19 HALO. Our results show differences in the initial efflux rates of melatonin and in the response of perifused pineal glands to calcium and magnesium according to the circadian stage.     

Conservative management of perforated duodenal diverticulum： A case report and review of the literature

Duodenal diverticula are a relatively common condition. They are asymptomatic, unless they become complicated, with perforation being the rarest but most severe complication. Surgical treatment is the most frequently performed approach. We report the case of a patient with a perforated duodenal diverticulum, which was diagnosed early and treated conservatively with antibiotics and percutaneous drainage of secondary retroperitoneal abscesses. We suggest this method could be an acceptable option for the management of similar cases, provided that the patient is in good general condition and without septic signs.     

Presence of immunoreactive growth hormone and prolactin in the ovine pineal gland

Abstract: The use of antisera raised against bovine growth hormone (GH) and ovine prolactin (PRL) enabled the detection of related immunoreactive (ir) sequences of proteins in ovine pineal tissue. The isolation of PRL-like ir-material was accomplished using a 0.25 M ammonium sulphate (pH 5.5) extraction followed by ethanol precipitation, whereas the resulting 2.0 M ammonium sulphate (pH 7.0) precipitate contained a GH-like immunoreactivity. Gel chromatography of the GH-like immunoreactivity (Sephadex G-100) indicated the presence of several GH-like fragments ranging in the M_r range of 7,000 to 55,000. Analyses of the PRL-like ir-material found in pineal tissue on HPLC using a TSK 545-DEAE column led to the resolution into a single peak of immunoreactivity. A single peak of activity was also observed following chromatofocusing and hydrophobic interaction chromatography of the ir-peak from the TSK 545-DEAE column. The PRL-like ir-material inhibited the binding of [¹²⁵I]ovine PRL-S14 to anti-ovine PRL antibodies without showing an affinity for binding to anti-rat PRL or anti-bovine GH antibodies. Scatchard analysis of the binding of pineal PRL-like ir-material and pituitary ovine PRL-S14 to liver membranes from day-20 pregnant rats revealed similar affinity constants (K_a of 4.7 ± 0.2 × 10⁹ M^-1). In addition, the replication of Nb 2 Node rat lymphoma cells was stimulated by pineal PRL-like ir-material, an effect known to be specific for lactogenic hormones. The pineal PRL-like immunoreactivity appeared on sodium dodecyl sulfate polyacrylamide gels as a single major band of M_r 24,000. The functional status of PRL-and GH-like ir-material in the ovine pineal remains to be determined, but evidence is presented that the overall protein synthesis rate of the rat pineal responded to circulating concentrations of PRL.     

Microbiology of human immunodeficiency virus anorectal disease

PURPOSE: Individuals who are seropositive for the human immunodeficiency virus are at high risk for opportunistic infection and anorectal disorders. Little prospective information is available regarding anorectal pathogens in these patients. METHODS: One hundred sixty-three HIV-seropositive patients presented to the colorectal clinic between 1989 and 1992. Forty-seven (29 percent) patients were thought to have an infectious process and were prospectively studied using a standardized multiculture protocol. RESULTS: Mean age was 33 (range, 19–59) years. All were male; high-risk behavior accounted for 87 percent of HIV transmissions. Presenting complaints included anorectal pain (79 percent), pus per anum (28 percent), and blood per anum (26 percent). Examination revealed perianal tenderness (60 percent), condyloma (38 percent), perianal ulcers (38 percent), and anal fissures (34 percent). Sixty-six sets of cultures were performed; 28 patients had one set, 15 had two sets, and 4 had three sets. Thirty-two of these 47 patients (68 percent) had positive cultures including herpes (50 percent), cytomegalovirus (25 percent),Neisseria gonorrhoeae (16 percent), chlamydia (16 percent), acidfast bacilli (2 percent), and others (9 percent). Six of 32 patients with positive cultures had more than one organism cultured. Sixteen (50 percent) patients with positive cultures were treated medically, 8 (25 percent) were treated surgically and 8 (25 percent) were treated with both modalities. Sixty-one procedures were performed on 17 patients for condylomata. Eighteen patients had 20 procedures for abscesses, 50 percent of whom had positive cultures for other than common bowel flora; all improved. Fourteen patients underwent 33 procedures for perianal fistulas.Mycobacterium fortuitum was cultured from one patient who required 13 procedures for abscesses and fistulas. Forty-five (96 percent) patients were followed for an average of 12.5 months ±2.9 SEM (range, 1–94 months). Symptoms were improved or resolved in 22 of 32 (69 percent) patients with positive cultures and in 11 of 13 (84 percent) with negative cultures. CONCLUSIONS: Specific pathogens may often be identified in human immunodeficiency virus-seropositive patients with anorectal disorders if aggressively sought. Although patients without specific pathogens identified may be expected to improve with planned empiric treatment, positive identification allows more directed therapy.