两株大肠杆菌对消毒剂及冷热抗力的试验比较

为比较两株大肠杆菌对消毒剂与冷热的抗力,进行了悬液抑菌抑菌、杀菌试验、结果,碘伏．醋酸氯已定同忆乙醇一样,对大肠杆菌8099株和ATCC11229株最小抑菌浓度或最小杀菌浓度均相近;在4℃放置1~7d,大肠杆菌8099株的存活率为95.40%-85.44%,ATCC11229株者为92．40%-79.74%,差异尤显著性(P＞0．05);经100℃作川1~5min,两株大肠杆菌的死亡率相同(均为99．99%~100%);以56℃作用5~30 min 或80℃作用1-10min,8099株死亡率分别为50．8%-99．68%与99.76%-99.99%,ATCC11229株死亡率分别为78．80%~99．96%与99.85%-100%,8099株死亡率均低于ATCC11229株。表明大肠杆菌8099株对湿热的抗力强于ATCC11229株.     

Hepatoma cells adapted to proliferate under normally lethal hyperthermic stress conditions show rapid decay of thermoresistance and heat shock protein synthesis when returned to 37°C

H35 hepatoma cultures were adapted to sustained growth at 41·3°C. In these variant cells the ‘basic’ levels of various heat shock proteins (hsps), especially those of hsp60, 70 and 100, are significantly raised. These cells exhibit a thermoresistance comparable with the induced thermotolerance in normal hepatoma cells heat shocked at 42·5°C for 30 min. However, this resistance of variant cells shows a rapid, exponential decay with a half-time of 2·2 h when the temperature is lowered to 37°C, with a concomitant decrease of the synthesis of hsp60 and 70. Heat shock experiments with variant cells grown at 41·3°C lead to increased thermoresistance and synthesis of hsps when further incubation was performed at the original temperature but not at 37·°C. In the latter case, only a 3-h delay in the onset of decay of thermoresistance is observed. However, when the variant cells were incubated at 37°C prior to heat stress normal induction of thermoresistance and hsp synthesis return inversely proportional to the progression of thermoresistance decay. Thermoresistant cells thus seem to be valuable tools in the study of the down-regulation of thermoresistance as well as of hsp synthesis.     

A Drosophila heat shock response represents an exception rather than a rule amongst Diptera species

Heat shock protein 70 (Hsp70) is the major player that underlies adaptive response to hyperthermia in all organisms studied to date. We investigated patterns of Hsp70 expression in larvae of dipteran species collected from natural populations of species belonging to four families from different evolutionary lineages of the order Diptera: Stratiomyidae, Tabanidae, Chironomidae and Ceratopogonidae. All investigated species showed a Hsp70 expression pattern that was different from the pattern in Drosophila. In contrast to Drosophila, all of the species in the families studied were characterized by high constitutive levels of Hsp70, which was more stable than that in Drosophila. When Stratiomyidae Hsp70 proteins were expressed in Drosophila cells, they became as short‐lived as the endogenous Hsp70. Interestingly, three species of Ceratopogonidae and a cold‐water species of Chironomidae exhibited high constitutive levels of Hsp70 mRNA and high basal levels of Hsp70. Furthermore, two species of Tabanidae were characterized by significant constitutive levels of Hsp70 and highly stable Hsp70 mRNA. In most cases, heat‐resistant species were characterized by a higher basal level of Hsp70 than more thermosensitive species. These data suggest that different trends were realized during the evolution of the molecular mechanisms underlying the regulation of the responses of Hsp70 genes to temperature fluctuations in the studied families.     

结肠肠管不同区域对热耐受性差异的研究

目的 :观察正常结肠肠管不同区域对热耐受性的差异。方法 :用腺体计数法来测定加热后结肠肠管不同区域的腺体数。结果 :在加热 43℃、30min时 ,肠管的左右侧和系膜对侧的腺体数与对照组比较差异非常显著 (P <0 .0 1)。而肠管系膜侧的腺体数加热到 44℃、30min时才与对照组有差异。另外 ,在 43℃和 44℃温度组 ,肠管左右侧和系膜对侧的腺体数丢失明显比系膜侧严重 (P <0 .0 1)。结论 :结肠左右侧和系膜对侧对热的耐受性明显比系膜侧差。对于这种差异 ,提示可能是结肠肠管不同区域的血供差异造成     

Association of genomic imbalances with drug resistance and thermoresistance in human gastric carcinoma cells

Therapy resistance is the major obstacle to advances in successful cancer treatment. To characterize chromosomal alterations associated with different types of acquired MDR and thermoresistance, we applied CGH to compare a unique panel of human gastric carcinoma cells consisting of the parental, drug-sensitive and thermosensitive cancer cell line EPG85-257P, the atypical MDR variant EPG85-257RNOV, the classical MDR subline EPG85-257RDB and their thermoresistant counterparts EPG85-257P-TR, EPG85-257RNOV-TR and EPG85-257RDB-TR. CGH with genomic DNA prepared from these cell lines as probes successfully identified genomic gains and/or losses in chromosomal regions encoding putative genes associated with drug resistance and/or thermoresistance. These genes included various members of the families of ABC transporters and molecular chaperones. The importance of these cell variant-specific genomic imbalances in the development of MDR and thermoresistance is discussed and remains to be elucidated.     

Comparative studies on thermoresistance of protein G-binding region and antigen determinant region of immunoglobulin G in acidic colostral whey

The kinetics of the denaturation of antigen determinant (AGD) region and protein G-binding (PGB) region of bovine immunoglobulin G (IgG) in acidic colostral whey were studied by single radial Immunodiffusion (SRID) and protein G affinity chromatography (PrGAC) during the same courses of heat treatment. The kinetic and thermodynamic parameters for heat-induced denaturation of AGD and PGB regions of IgG were determined over a temperature range of 69-81°C. The denaturation reactions of both AGD and PGB regions of IgG were best described with apparent reaction order of 1.2, the activation energy values of the denaturation reactions were 159.42 kJ/mol and 235.37 kJ/mol respectively. This work suggested that the AGD region was more heat-labile than the PGB region of IgG in acidic colostral whey, Moreover, the higher values of the constant for the AGD region meant that, once the unfolding of the region started, denaturation would occur more quickly than the PGB region on IgG molecule. All these factors contributed to the fact that generally the IgG contents in the products of bovine colostrum determined by PrGAC would be higher than those by SRID.     

Impact of BCRP/MXR, MRP1 and MDR1/P-Glycoprotein on thermoresistant variants of atypical and classical multidrug resistant cancer cells

The impact of the ABC transporters breast cancer resistance protein/mitoxantrone resistance associated transporter (BCRP/MXR), multidrug resistance-associated protein 1 (MRP1) and multidrug resistance gene-1/P-glycoprotein (MDR1/PGP) on the multidrug resistance (MDR) phenotype in chemoresistance and thermoresistance was investigated in the parental human gastric carcinoma cell line EPG85-257P, the atypical MDR subline EPG85-257RNOV, the classical MDR subline EPG85-257RDB and their thermoresistant counterparts EPG85-257P-TR, EPG85-257RNOV-TR and EPG85-257RDB-TR. Within the atypical MDR subline EPG85-257RNOV expression of BCRP/MXR and of MRP1 were clearly enhanced (vs. parental and classical MDR lines). MDR1/PGP expression was distinctly elevated in the classical MDR subline EPG85-257RDB (vs. parental and atypical MDR sublines). In all thermoresistant counterparts basal expression of BCRP/MXR, MRP1 and MDR1/PGP was increased relative to thermosensitive sublines. Although it could be shown that the overexpressed ABC transporters were functionally active, however, no decreased drug accumulations of doxorubicin, mitoxantrone and rhodamine 123 were observed. Thus, expression of BCRP/MXR, MRP1 and MDR1/PGP was found to be dependent on the appropriate type of chemoresistance; correlating with a classical or atypical MDR phenotype. Within the thermoresistant variants, however, the increase in ABC transporter expression did obviously not influence the MDR phenotype.