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991.
Hideyo Suzuki Kuo-Hsiung Lee Mitsumasa Haruna Toshiyuki Iida Kazuo Ito Huan-Chang Huang 《Phytochemistry》1982,21(7):1824-1825
A new lignan, (+)-aretigenin has been isolated from the roots of Wikstroemia indica (Nan-Ling-Jao-Hua) and identified as 8(R) 8′(S)-4′-hydroxy-3, 4,3′-trimethoxylignan-olid (9, 9′) on the basis of spectral evidence as well as a direct comparison with its enantiomer, (?)-arctigenin. 相似文献
992.
Summary Organic components leaked fromSorghum bicolor seedlings (‘root exudates’) were examined by recovering14C labelled compounds from root solutions of seedlings inoculated withAzospirillum brasilense, Azotobacter vinelandii orKlebsiella pneumoniae nif-. Up to 3.5% of the total14C recovered from shoots, roots, and nutrient solutions was found in the root solutions. Inoculation with Azospirillum and
Azotobacter increased the amounts of14C and decreased the amounts of carbohydrates in the root solutions. When sucrose was added as a carbon source for the bacteria,
the increase of14C in the solutions did not occur. Quantities of14C found in the root solutions were proportional to amounts of mineral nitrogen supplied to the plants. Bacterial growth also
was proportional to nitrogen levels. When sorghum plants were grown in soil and labelled with14CO2, about 15% of the total14C recovered within 48 hours exposure was found in soil leachates. 相似文献
993.
994.
Charles R. Kleeman Jack W. Coburn Arnold S. Brickman David B. N. Lee Robert G. Narins Richard M. Ehrlich 《The Western journal of medicine》1980,132(4):313-332
The prevalence of kidney stones has steadily risen during this century; passage of a calculus and a positive family history increase the probability of recurrence. Findings from recent studies on the cause of renal calculi have stressed crystallization and crystal aggregation of stone minerals from supersaturated urine, rather than excessive organic matrix. Absence of normal urine inhibitors of calcium salts is also stressed. Formation of calcium oxalate stones is the major problem. Therapy with decreased calcium and oxalate intake, thiazides, phosphate salts and allopurinol in various combinations has substantially decreased the prevalence of recurrent stones. The rationale for the use of allopurinol is that uric acid salts enhance the tendency for calcium oxalate to crystallize from supersaturated urine. The hypercalciuria seen in 30 percent to 40 percent of patients with oxalate stones is usually caused by intestinal hyperabsorption of calcium. Although patients with uric acid calculi constitute only a small fraction of those in whom stones form, they represent a group in whom good medical therapy, based on sound physiologic principles, has proved extremely successful. Renal tubular syndromes lead to nephrocalcinosis and lithiasis through hypercalciuria, alkaline urine and hypocitraturia, the latter an inhibitor of calcium salt precipitation. Recent advances in surgical techniques are discussed, including the rationale for removing staghorn calculi. The ileal ureter and coagulum pyelolithotomy deserve special emphasis. 相似文献
995.
In simulated diurnal experiments withChlorella pyrenoidosa andPseudomonas fluorescens, bacterial growth was virtually confined to the daylight period and occurred at the expense of glycolate, the predominant extracellular product of the alga. Both glycolate levels and14C-DOC excretion rates were much lower in mixed algal-bacterial than in axenicChlorella cultures.This close coupling of bacterial growth to algal photosynthesis and extracellular release was also observed in Jack's Lake, but not in Lake Erie. Experimental enrichment with lake water particulates >30m suppressed the daytime growth of bacteria in Jack's Lake, but increased it dramatically in Lake Erie. Daylight doubling times for bacteria in lakewater ranged from 2 to 19 days. In mixed culture withChlorella, Pseudomonas had a doubling time of about 2 hours in the light. 相似文献
996.
Summary The susceptibility of cellulose to enzymatic hydrolysis can be significantly affected through pretreatment by means of gamma-ray radiation. Experiments were carried out to investigate the effects of this radiation on enzymatic hydrolysis and on the two major structural features of cellulose that most influence hydrolysis, namely, specific surface area and crystallinity.D. H. Beardmore is currently with Phillips Petroleum Company, Bartlesville, OK 74004, U.S.A. 相似文献
997.
C.Y. Lee Margaret Mcpherson Vojtech Licko J. Ramachandran 《Archives of biochemistry and biophysics》1980,201(2):411-419
The biological properties of the naturally occurring pituitary peptide αh7–38-adrenocorticotropin (ACTH) have been investigated. αh7–38-ACTH is devoid of steroidogenic activity but inhibits competitively ACTH-induced steroidogenesis in vitro as well as in vivo. The long-term actions of ACTH on normal and tumor adrenal cells in culture are also antagonized by αh7–38-ACTH. The apparent Ki for the inhibition of cyclic AMP production by αh7–38-ACTH (301 ± 62 nm) was significantly higher than the apparent Ki for the inhibition of corticosterone synthesis (21.6 ± 6.8 nm). Analysis of the inhibition of ACTH-induced steroidogenesis and cyclic AMP production in normal rat adrenocortical cells indicates that two separate receptors may be involved in mediating these responses. 相似文献
998.
999.
Strategies for the uses of lanthanide NMR shift probes in the determination of protein structure in solutio. Application to the EF calcium binding site of carp parvalbumin. 下载免费PDF全文
The homologous sequences observed for many calcium binding proteins such as parvalbumin, troponin C, the myosin light chains, and calmodulin has lead to the hypothesis that these proteins have homologous structures at the level of their calcium binding sites. This paper discusses the development of a nuclear magnetic resonance (NMR) technique which will enable us to test this structural hypothesis in solution. The technique involves the substitution of a paramagnetic lanthanide ion for the calcium ion which results in lanthanide induced shifts and broadening in the 1H NMR spectrum of the protein. These shifts are sensitive monitors of the precise geometrical orientation of each proton nucleus relative to the metal. The values of several parameters in the equation relating the NMR shifts to the structure are however known as priori. We have attempted to determine these parameters, the orientation and principal elements of the magnetic susceptibility tensor of the protein bound metal, by studying the lanthanide induced shifts for the protein parvalbumin whose structure has been determined by x-ray crystallographic techniques. The interaction of the lanthanide ytterbium with parvalbumin results in high resolution NMR spectra exhibiting a series of resonances with shifts spread over the range 32 to -19 ppm. The orientation and principal elements of the ytterbium magnetic susceptibility tensor have been determined using three assigned NMR resonances, the His-26 C2 and C4 protons and the amino terminal acetyl protons, and seven methyl groups; all with known geometry relative to the EF calcium binding site. The elucidation of these parameters has allowed us to compare the observed spectrum of the nuclei surrounding the EF calcium binding site of parvalbumin with that calculated from the x-ray structure. A significant number of the calculated shifts are larger than any of the observed shifts. We feel that a refinement of the x-ray based proton coordinates will be possible utilizing the geometric information contained in the lanthanide shifted NMR spectrum. 相似文献
1000.
The effect of increased temperature during transportation of clinical dermatophyte specimens was investigated. Recovery rates from untransported specimens cultured at dermatologists' offices and from duplicate transported specimens were compared. During the months of hot weather specimens could be exposed intermittently to temperatures as high as 60°C during transportation from Tucson area clinics to the University laboratory. The rates of recovery from known positive specimens were found not to be significantly different at these places regardless whether specimens were transported during the hot months or cooler months of the year.In a controlled experimental approach to the effect of this elevated temperature on clinical specimens weighed amounts of skin scales collected from guinea pigs artificially infected withTrichophyton mentagrophytes were exposed to 60 °C for up to four hours and then digested with 0.5% (1 300) trypsin for one hour. Analysis of plate counts done from the digestion mixture showed no significant difference between counts obtained from specimens exposed to elevated temperature and unexposed controls. 相似文献