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101.
102.
103.
The Escherichia coli LexA repressor-operator system works in mammalian cells. 总被引:4,自引:1,他引:3
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G M Smith K A Mileham S E Cooke S J Woolston H K George A D Charles W J Brammar 《The EMBO journal》1988,7(12):3975-3982
104.
A method is proposed for predicting the adjacency order in which strands pack in a -sheet in a protein, on the basis of its amino acid sequence alone. The method is based on the construction of a predicted contact map for the protein, in which the probability that various residue pairs are close to each other is computed from statistically determined average distances of residue pairs in globular proteins of known structure. Compact regions, i.e., portions of the sequence with many interresidue contacts, are determined on the map by using an objective search procedure. The proximity of strands in a -sheet is predicted from the density of contacts in compact regions associated with each pair of strands. The most probable -sheet structures are those with the highest density of contacts. The method has been tested by computing the probable strand arrangements in a five-strand -sheet in five proteins or protein domains, containing 62–138 residues. Of the theoretically possible 60 strand arrangements, the method selects two to eight arrangements as most probable; i.e., it leads to a large reduction in the number of possibilities. The native strand arrangement is among those predicted for three of the five proteins. For the other two, it would be included in the prediction by a slight relaxation of the cutoff criteria used to analyze the density of contacts. 相似文献
105.
A strain of Cryptococcus neoformans that was isolated from the cerebrospinal fluid of a human diagnosed as having acquired immunodeficiency syndrome (AIDS), and that produced cutaneous lesions in experimentally infected, normal mice is described. Although no unusual cutaneous manifestations were noted in the patient's records, this isolate of C. neoformans proved to be dermotropic when injected intravenously into CD-1 mice. The LD50 at 28 days post infection ranged from 3.6–7.5×105 cells per mouse, and in vitro growth rate studies demonstrated that this isolate grew well at 35 °C and at 37 °C, but did not grow at 40 °C and higher. This isolate was rhinotropic producing large granulomatous lesions in the nasal tissues. Other cutaneous tissues affected were the periocular tissues, ears, feet and tail, although the granulomas were nodular in structure and less necrotic than the nasal lesions. The brain, lungs, liver, kidneys and spleen also were culture positive for C. neoformans. Histopathologically, each affected tissue examined had large densities of yeast cells and a chronic, granulomatous host response. Animals surviving the infection appeared to develop a commensal-type relationship with the infective yeast. This is the first report of an isolate of C. neoformans from an AIDS patient that has caused cutaneous manifestations in an animal model. The model described in this report may be useful for elucidating pathogenic mechanisms of cryptococcosis, particularly cutaneous manifestations of the disease. 相似文献
106.
Prevalence of the 281 (Gly→Glu) mutation in hepatoerythropoietic porphyria and porphyria cutanea tarda 总被引:4,自引:0,他引:4
Hubert de Verneuil Joanna Hansen Christiane Picat Bernard Grandchamp James Kushner Andrew Roberts George Elder Yves Nordmann 《Human genetics》1988,78(1):101-102
Summary The prevalence of the 281 (GlyGlu) mutation in hepatoerythropoietic porphyria (HEP) was investigated by the use of hybridization with a synthetic oligonucleotide probe. The mutation was found in HEP-affected members of two unrelated families from Spain, but was absent in two other patients from Italy and Portugal who also had HEP. Moreover, this mutation was not detected in 13 unrelated cases of familial (type II) porphyria cutanea tarda. 相似文献
107.
George H. Renninger Leonard Kass Janice L. Pelletier Robert Schimmel 《Journal of comparative physiology. A, Neuroethology, sensory, neural, and behavioral physiology》1988,163(2):259-270
Efferent fibers from a central circadian clock innervate both photoreceptor cells and second-order neurons (eccentric cells) in the lateral compound eye ofLimulus, and release octopamine when activated. We have used intracellular microelectrodes to study the modulation of eccentric cell function by efferent optic-nerve activity, octopamine agonists, and a K+-channel blocker, TEA.
相似文献
1. | The dramatic increase in response to light observed in the eccentric cell during efferent activity originates in the photoreceptor cell; efferent activity causes only small changes in the encoding of photoreceptor responses as nerve impulses by the eccentric cell. In contrast, octopamine agonists and TEA produce large changes in the impulse encoder of the eccentric cell. |
2. | When lateral eyes are maintained in the dark, the rate of spontaneous impulse firing of eccentric cells increases in the presence of octopamine agonists, while spontaneous bump activity decreases. In contrast, endogenous efferent activity decreases both impulse rate and bump activity in the dark. |
3. | TEA reduces the effects of lateral inhibition between neighboring eccentric cells. |
4. | We suggest that the mechanisms for lateral inhibition and impulse generation are mediated by K+-channels that can be modulated by octopamine agonists. The distribution of efferent nerve terminals on the eccentric cells is such, however, that efferent optic-nerve activity can alter lateral inhibition, but is unlikely to produce large changes in the impulse encoder. |
108.
Geraldine E. Oliva George W. Rutherford Moses Grossman Janet Shalwitz Abigail English Frances Taylor David Werdegar 《The Western journal of medicine》1988,148(5):586-589
Although adolescents account for only 0.4% of reported cases of the acquired immunodeficiency syndrome (AIDS) in the United States, they are sexually active and, therefore, at risk of acquiring human immunodeficiency virus (HIV) infection. To address issues of HIV control in adolescents, we developed guidelines that emphasize education and medical care and deemphasize antibody testing. For adolescents known to be infected with HIV, we recommend no restrictions on access to educational or treatment programs except when their health providers recommend such restrictions to protect them from exposure to opportunistic infections. For adolescents of unknown antibody status with a possible previous exposure to HIV, we recommend that as long as the incidence of HIV infection and clinical AIDS remains low, there should be no restrictions on residential placements and no routine antibody testing. 相似文献
109.
Summary In the absence of an organic solvent, a buffer to enzyme weight ratio of 1 gives maximum selectivity to interesterification over hydrolysis in a lipase-catalyzed mixture of triacetin and tributyrin. Addition of hexane enhances interesterification as does a reversed micelle configuration. 相似文献
110.
Mark L. Paddock Scott H. Rongey Edward C. Abresch George Feher Melvin Y. Okamura 《Photosynthesis research》1988,17(1-2):75-96
Many herbicides that inhibit photosynthesis in plants also inhibit photosynthesis in bacteria. We have isolated three mutants of the photosynthetic bacterium Rhodobacter sphaeroides that were selected for increased resistance to the herbicide terbutryne. All three mutants also showed increased resistance to the known electron transfer inhibitor o-phenanthroline. The primary structures of the mutants were determined by recombinant DNA techniques. All mutations were located on the gene coding for the L-subunit resulting in these changes Ile229 Met, Ser223 Pro and Tyr222 Gly. The mutations of Ser223 is analogous to the mutation of Ser264 in the D1 subunit of photosystem II in green plants, strengthening the functional analogy between D1 and the bacterial L-subunit. The changed amino acids of the mutant strains form part of the binding pocket for the secondary quinone, Q
b
. This is consistent with the idea that the herbicides are competitive inhibitors for the Q
b
binding site. The reaction centers of the mutants were characterized with respect to electron transfer rates, inhibition constants of terbutryne and o-phenanthroline, and binding constants of the quinone UQ0 and the inhibitors. By correlating these results with the three-dimensional structure obtained from x-ray analysis by Allen et al. (1987a, 1987b), the likely positions of o-phenanthroline and terbutryne were deduced. These correspond to the positions deduced by Michel et al. (1986a) for Rhodopseudomonas viridis.Abbreviations ATP
adenosine 5-triphosphate
- Bchl
bacteriochlorophyll
- Bphe
bacteriopheophytin
- bp
basepair
- cyt c2+
reduced form of cytochrome c
- DEAE
diethylami-noethyl
- EDTA
ethylenediamine tetraacetic acid
- Fe2+
non-heme iron atom
- LDAO
lauryl dimethylamine oxide
- Pipes
piperazine-N,N-bis-2-ethane-sulfonic acid
- PSII
photosystem II
- RC
reaction center
- SDS
sodium dodecylsulfate
- Tris
tris(hydroxy-methyl)aminomethane
- UQ0
2,3-dimethoxy-5-methyl benzoquinone
- UQ10
ubiquinone 50 相似文献