IR spectroscopic study of the structure and phase behavior of long-chain diacylphosphatidylcholines in the gel state.

Fully hydrated dispersions of simple linear saturated diacylphosphatidylcholines with even-numbered acyl chains of lengths from 18 to 24 carbons can exist in a low-temperature, highly ordered, orthorhombic phase (G(o)) that differs from the L beta phase (Gd) normally found for shorter chains. The temperature behavior of these dispersions has been studied by infrared spectroscopy. Chain packing in the G(o) phase was found to be nearly identical to that of the orthorhombic phase of crystalline n-alkanes. With increasing temperature, the G(o) phase undergoes a transition to Gd at approximately 45 degrees C below Tm. This transition occurs at a higher temperature and becomes sharper with increasing chain length. Chain packing in the Gd phase was found to be disordered in a way that can be expressed in terms of a distribution of subcell setting angles. The Gd phase converts to a phase (Gh) with hexagonal-like chain packing at temperatures below Tm. The results support and extend those of a recent x-ray diffraction study of the 24-carbon diacyclphosphatidylcholine gel.     

Cyclic variations in sensitivity to X-irradiation during meiosis in Saccharomyces cerevisiae

Cyclic variation in mutation induction and lethality was found following X-irradiation during meiosis in Saccharomyces cerevisiae. An enhanced mutagenic response was found in meiotic G1 phase cells in comparison to cells later in meiosis, similar to the response shown during mitosis, but meiotic G1 phase cells appeared more resistant to the lethal effects of X-irradiation than mitotic G1 phase cells. Resistance to the lethal effects of X-rays was found during meiotic DNA synthesis in the strain SK1, which may indicate the operation of a sister-chromatid exchange repair mechanism. A difference was found between gene conversion which appeared to be at a maximum by the end of meiotic DNA synthesis and reciprocal recombination, which could be induced up to prophase I.     

Circadian Modulation of Cold-Induced Thermogenesis in the Golden Hamster

The relationship between the circadian and homeostatic control of body temperature was studied in golden hamsters maintained under a 14:10 LD cycle. Telemetric records of body temperature showed that body temperature oscillates daily with a low phase during the light section of the LD cycle and a high phase during the dark section. The low phase of the temperature rhythm was found to start two hours after lights on and to last about 8 hours. The high phase was found to start immediately after lights off and to last about 8 hours also. Metabolic heat production was measured by indirect calorimetry during the high phase and the low phase of the body temperature rhythm. Heat production in a thermoneutral environment was higher during the high phase of the body temperature rhythm than during the low phase, but cold-induced thermogenesis was greater during the low phase than during the high phase. This finding suggests that the autonomic thermoregulatory system is more responsive to cold stress during the low phase than during the high phase. Consequently, the daily oscillation of body temperature cannot be explained by an elevation of the thermoregulatory set point during the high phase of the rhythm. The homeostatic and circadian control of body temperature seem to be exerted separately from each other.     

Circadian Modulation of Cold-Induced Thermogenesis in the Golden Hamster

The relationship between the circadian and homeostatic control of body temperature was studied in golden hamsters maintained under a 14:10 LD cycle. Telemetric records of body temperature showed that body temperature oscillates daily with a low phase during the light section of the LD cycle and a high phase during the dark section. The low phase of the temperature rhythm was found to start two hours after lights on and to last about 8 hours. The high phase was found to start immediately after lights off and to last about 8 hours also. Metabolic heat production was measured by indirect calorimetry during the high phase and the low phase of the body temperature rhythm. Heat production in a thermoneutral environment was higher during the high phase of the body temperature rhythm than during the low phase, but cold-induced thermogenesis was greater during the low phase than during the high phase. This finding suggests that the autonomic thermoregulatory system is more responsive to cold stress during the low phase than during the high phase. Consequently, the daily oscillation of body temperature cannot be explained by an elevation of the thermoregulatory set point during the high phase of the rhythm. The homeostatic and circadian control of body temperature seem to be exerted separately from each other.     

Fungal melanin inhibitor and related compounds from Penicillium decumbens

In Silene vulgaris (M.) G. cell culture three growth phases were distinguished, namely, a lag phase, an exponential phase and a stationary phase. Pectin termed silenan and an acidic arabinogalactan were isolated as cell wall polysaccharides of S. vulgaris callus at the different growth phases during culture. Production of silenan as the galacturonan (or rhamnogalacturonan) core was observed at the beginning of the exponential phase and at the stationary phase of the callus growth. Arabinogalactan, containing the galacturonic acid residues, is formed at the exponential phase followed by attachment to the core of silenan in the middle of the exponential phase. The arabinogalactan constituent of silenan appeared to be destroyed gradually at the stationary growth phase. The monosaccharide compositions of silenan and arabinogalactan were determined at various phases of the callus growth. Silenan was found to be formed in maximum amounts at the exponential phase of the cell growth. Insignificant alterations of the yields of acidic arabinogalactan were found during culture while total productivity per litre of medium and rate of production per day of arabinogalactan were found to be maximal at the exponential phase of growth.     

HPD在胃癌细胞各时相中的转运分布和损伤部位的关系

本文探讨了HPD衍生物加红光对人胃低分化腺癌MGC 80-3细胞不同周期的生物学效应。我们观察到HPD的转运与分布决定于细胞周期。G_1期在30分至60分钟内HPD从膜转运至胞质;S、G_2期则直接进入胞质的不同部位;而M期在核部位弥散分布。同步化细胞经HPD加红光处理后,引起细胞大量光敏杀伤,S与G_1期较明显,而M期光敏性最小。我们还观察到:不同周期细胞HPD的分布和HPD的光敏损伤部位密切相关。核仁对HPD的选择性结合也很明显。     

Physiological behaviour of Saccharomyces cerevisiae in aerated fed-batch fermentation for high level production of bioethanol

Saccharomyces cerevisiae was able to produce 20% (v/v) of ethanol in 45 h in a fully aerated fed-batch process recently developed in our laboratory. A notable feature of this process was a production phase uncoupled to growth, the extent of which was critical for high-level ethanol production. As the level of production was found to be highly variable, we investigated on this high variability by means of a detailed physiological analysis of yeast cells in two fed-batch fermentations showing the most extreme behaviour. We found a massive leakage of intracellular metabolites into the growth medium which correlated with the drop of cell viability. The loss of viability was also found to be proportional to the reduction of plasma membrane phospholipids. Finally, the fed-batch processes with the longest uncoupling phase were characterized by induction of storage carbohydrates at the onset of this phase, whereas this metabolic event was not seen in processes with a short uncoupling phase. Taken together, our results suggested that reproducible high-level bioethanol production in aerated fed-batch processes may be linked to the ability of yeast cells to impede ethanol toxicity by triggering a metabolic remodelling reminiscent to that of cells entering a quiescent GO/G1 state.     

固相小柱对沙苑子总黄酮萃取方法的研究

目的:以沙苑子总黄酮为研究对象,考察固相萃取小柱的洗脱条件,确定固相萃取沙苑子总黄酮的实验方法。方法:以不同浓度的甲醇对不同填料的固相小柱进行洗脱,将洗脱液在岛津VP-ODS(150 mm×4.6 mm,5μm)柱上进行高效液相色谱分析。通过比较不同浓度及体积甲醇的萃取效率,确定沙苑子苷在固相萃取小柱上的洗脱条件。结果:用正相氨基小柱以50%甲醇洗脱效果好,回收率可达100%。结论:经试验,正相氨基小柱对沙苑子苷的萃取回收率约为100%,适用于沙苑子总黄酮中沙苑子苷的分析。     

Deactivation ofCandida rugosa lipase

Summary Deactivation ofCandida rugosa lipase was found to be complex. Hydrophobic interaction induced by iso-octane influenced the initial phase of deactivation, and increased the turn-over rate of the intermediate in the transition phase. After urea-treatment the structure of the last phase was not further influenced by thermal treatment, whereas that of initial phase was more sensitive to temperature change. Charge interaction was important in maintaining the structure during the deactivation, and especially anion charge might be a major factor.     

The bactericidal activity of a methyl and propyl parabens combination: isothermal and non-isothermal studies.

The effect of temperature on the kill rate of Escherichia coli by methyl and propyl parabens was studied. The kill kinetics was first order. It was shown that the Arrhenius equation provided a good model for describing the relationship between the first order rate constant and the temperature. The activation energy was found to be 274 kJ/mol for exponential phase cells and 168 kJ/mol for stationary phase cells. Exponential phase cells were much more susceptible to the lethal effects of the parabens than were the stationary phase cells. For example, at 34 degrees C stationary phase cells, in chemically defined media, had a kill rate constant of 0.072/h while the corresponding value for exponential phase cells was 0.238/h. In water the rate of kill for exponential phase cells was even faster giving a rate constant of 5.25/h at 34 degrees C. Non-isothermal kinetic testing was not found to be useful for modelling bacterial kill kinetics because we could not achieve the precision required in bacterial enumeration.     

Effects of hydrostatic pressure on bilayer phase behavior and dynamics of dilauroylphosphatidylcholine.

Deuterium nuclear magnetic resonance spectroscopy was used to study the thermotropic phase behavior of dilauroylphosphatidylcholine (DLPC) bilayers at pressures up to 221 MPa. Pressure was found to separate the liquid crystal to gel transition from the gel to ordered crystalline phase transition. The jump in chain order observed on cooling through the transition into the gel phase was found to be small and thus consistent with the trend in longer chain saturated diacyl phosphatidylcholines. On cooling, DLPC was observed to enter an unusual state above the transition into the gel phase. This unusual state displayed fluid-like conformational order but short transverse relaxation times. It was found to be much better pronounced and to span a broader temperature range at elevated pressure than at lower pressures. Transverse relaxation measurements of deuterons on the chain alpha-carbons revealed a substantial slowing of molecular motions within the temperature range of the unusual fluid phase. The observation of such a phase at high pressure appears to be consistent with recent reports of an unusual fluid phase, Lx, in DLPC at ambient pressure.     

Tyrosine aminotransferase sensitivity to bromodeoxyuridine during restricted intervals of S phase in hepatoma cells

Synchronized hepatoma tissue culture (HTC) cells, accumulated at the G1/S boundary with aminopterin, were released into S phase with either thymidine or 5-bromodeoxyuridine (BUdR). Tyrosine aminotransferase (TAT) activity was found to be unaffected by BUdR over the initial 3 h of S phase, but then to rapidly decline to a new basal level of 40% of control by 9 h. There was no corresponding response in the activities of alcohol dehydrogenase, malate dehydrogenase, acid phosphatase, and alkaline phosphatase, or in the rate of protein and RNA synthesis. If BUdR incorporation was restricted to limited periods of S phase, TAT was found to be maximally suppressed by incorporation into the initial 40% of the DNA. Incorporation of the analogue into the latter 60% of DNA synthesized during S phase had no effect on TAT. This is the first report that the effect of BUdR on TAT in HTC cells is associated with incorporation of the analog into DNA synthesized during a specific interval of S phase.     

Lipid phase separation induced by a hydrophobic protein in phosphatidylserine--phosphatidylcholine vesicles

Differential scanning calorimetry (DSC) was used to detect phase separation induced by hydrophobic myelin protein, lipophilin, in a mixture of phosphatidylserine (PS) and dipalmitoylphosphatidylcholine (DPPC). Preferential binding of PS to the boundary layer of lipophilin causes a decrease in the PS content of the remaining lamellar phase with a resultant shift in the phase-transition temperature to a higher temperature. The phase diagram for this mixture in the presence and absence of lipophilin is presented. From the phase diagram, it can be estimated that for an equimolar mixture of PS and DPPC, the boundary layer contains only PS, although for higher DPPC contents, some DPPC can also be found in the boundary layer. In the case where partial phase separation in induced in this mixture by Ca2+ alone, lipophilin increases the phase separation indicating that it also binds PS preferentially in the presence of Ca2+. Preferential binding of two other acidic lipids, phosphatidic acid and phosphatidyl-glycerol, to the boundary layer was also found, including a mixture where the acidic lipid was the higher melting component in the mixture.     

The bactericidal activity of a methyl and propyl parabens combination: isothermal and non-isothermal studies

D. GILLILAND, A. LI WAN PO AND E. SCOTT. 1992. The effect of temperature on the kill rate of Escherichia coli by methyl and propyl parabens was studied. The kill kinetics was first order. It was shown that the Arrhenius equation provided a good model for describing the relationship between the first order rate constant and the temperature. The activation energy was found to be 274 kJ/mol for exponential phase cells and 168 kJ/mol for stationary phase cells. Exponential phase cells were much more susceptible to the lethal effects of the parabens than were the stationary phase cells. For example, at 34°C stationary phase cells, in chemically defined media, had a kill rate constant of 0.072/h while the corresponding value for exponential phase cells was 0.238/h. In water the rate of kill for exponential phase cells was even faster giving a rate constant of 5.25/h at 34°C. Non-isothermal kinetic testing was not found to be useful for modelling bacterial kill kinetics because we could not achieve the precision required in bacterial enumeration.     

Extracellular lysine production from hydrocarbons byArthrobacter globiformis

A bacterium isolated from Burdwan (India) soil was found to accumulatel-lysine in the growth medium and was identified asArthrobacter globiformis. The strain grew and accumulated lysine in a purely synthetic medium. Supplementation of the synthetic medium stimulated growth but did not improve the yield. The entire fermentation period could be divided into a growth phase and a production phase, which could be prolonged by adjustment of pH to the neutral range. Among the different hydrocarbon and nitrogen sources tested SR gas oil at 4 % and ammonium sulphate at 0.4 %, respectively, were found most to be suitable. Different vitamins and antibiotics stimulated growth and lysine yield; inoculum of 7 % (V/V) of the medium was found to be optimal. The yield of lysine under optimal conditions was 3.4 g per litre medium. Lysine was isolated in crystalline form from the fermented broth by IEC and found to be a purel-isomer.     

Induction of stolon settlement in the scyphopolyps ofAurelia aurita (Cnidaria,Scyphozoa, Semaeostomeae) by glycolipids of marine bacteria

The settlement of pedal stolons of scyphopolyps ofAurelia aurita Lamarck could be induced by addition of a species of bacteria from the family Micrococcaceae. After treatment of the bacteria with several organic solvents a crude lipid extract free of bacteria could be obtained which was shown to be effective in inducing stolon settlement. Crude lipids extracted from the late logarithmic growth phase had an optimal effect on stolon attachment, in contrast to previously published experiments showing that all logarithmic phases of bacteria had the same level of effectiveness. After separation of the crude lipid extracts by thin layer chromatography and subsequent bioassay of the reeluated substances, acylgalactosidyldiglyceride and monogalactosidyldiglyceride were identified as the effective substances. Monogalactosidyldiglyceride was only found in bacteria from the medium logarithmic growth phase, whereas the former was found at all stages. The effectiveness of acylgalactosidyldiglyceride was independent of the growth phase of the extracted bacteria.     

Production of valine by a Bacillus sp.

A bacterium isolated from Burdwan (India) soil was found to accumulate L-valine in the growth medium and identified to be a strain of Bacillus subtilis. The strain is able to grow and accumulate valine in a purely synthetic medium, but supplementation of the synthetic medium with either Casamino acids or yeast extract or with both, significantly improves the yield. The entire fermentation period can be divided into a growth phase and a production phase, which can be prolonged by adjustment of pH to the neutral range. Among the different carbon and nitrogen sources tested glucose at 8.5% and L-glutamic acid at 0.8%, respectively, were found most suitable. Cane sugar molasses tested as a substitute for glucose significantly stimulated growth but valine production was less. Different vitamins tested stimulated growth and valine yield and an inoculum level of 10% (v/v) of the medium was found to be optimal. The yield of valine under optimal conditions was found to be 4.53 g per litre of the medium. Valine has been isolated in crystalline form from the fermented broth by ion exchange resin chromatography and found to be a pure sample of the L-isomer.     

Role of extracellular virus on the maintenance of the persistent infection induced in Aedes albopictus (mosquito) cells by Sindbis virus.

Sindbis virus infection of cultured mosquito cells was found to have no effect on the growth of these cells; instead, a persistent infection of the culture followed an initial acute phase of rapid virus synthesis. Nearly all of the cells in the acute stage of infection were found to actively release virus in an infectious-center assay and to contain significant amounts of virus antigen as determined by immunofluorescence. Cells in the persistent phase of infection released few virions into the media, and only a small percentage of the cultured cells could be demonstrated to contain detectable amounts of virus antigen by immunofluorescence assay. In spite of the fact that nearly 100% of the cells in the persistent phase of infection were found to be virus negative by the two assays described above, the culture as a whole totally excluded the expression of superinfecting virus, as did cells in the acute phase, suggesting that most of the persistently infected cells did, indeed, contain virus information. Prevention of reinfection of the cells in the persistent phase by eliminating extracellular virus resulted in a curing of the culture such that it responded to infection by added virus much as would an uninfected culture.     

Cyclic variations in the immunoglobulins of human vaginal fluid

In order to study the cyclic variations in the immunoglobulins of the human vaginal fluid, vaginal secretions were obtained from 12 volunteers during the follicular phase (Days 7-12 of cycle) and from 12 during the luteal phase (Days 18-25 of cycle). At follicular phase, immunoglobulin G was present in all samples, and immunoglobulin A similar to serum immunoglobulin A was found occasionally. At luteal phase, immunoglobulin G apparently occurred at a greater concentration, and another immunoglobulin A, different from the serum type, was found. No immunoglobulin M was detected in any sample. It is postulated that the cyclic variations in immunoglobulins of human vaginal fluid, which occur under normal conditions could be 1) related to the plasma cells found in the vaginal mucosa and 2) mediated by the ovarian hormones.     

Immunogenic complexes of the soluble surface antigens of Sh. sonnei]

The comparative study of the immunogenic properties of Sh. sonnei (phases I and II) soluble surface antigens obtained by the modified method of aqueous-saline extraction and Sh. sonnei (phase I) antigen obtained by Boivin's method was made with the use of the keratoconjunctival test in guinea pigs. The protective activity of a high molecular fraction obtained by the fractionation of phase I soluble surface antigens in Sepharose 4B was studied. Boivin's antigen, when used for immunization in optimum doses, was found to have pronounced protective properties, whereas phase II soluble surface antigens showed no protective activity. A high molecular fraction obtained from phase I soluble surface antigen was found to be the most immunogenic. Protective activity was largely connected with protein antigen. The question whether protein antigen was an independent protective antigen or whether it constituted a part of a complex which determined the protective activity of a high molecular fraction remained unsolved.