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41.
42.
Protein synthesis by microsomal particles from regenerating rat liver 总被引:12,自引:12,他引:0
1. Washed microsome particles from regenerating liver were shown to incorporate [(14)C]leucine into protein more actively than similar preparations from normal liver. 2. The total incorporation in the preparations from regenerating liver increased linearly with the amount of protein incubated, whereas this was not so with preparations from normal liver. 3. The greater activity of regenerating-liver microsomes appeared to be associated with the bound polysomes. 4. The size distribution of polysomes obtained after removal of membrane with deoxycholate was the same in normal and regenerating liver. 5. In general the activity of polysome preparations from normal and regenerating liver was similar. 6. It is concluded that the greater activity of the particles in the microsome fraction from regenerating liver is to be attributed to the ribosomes bound to membrane and that their activity is controlled by factors present in the membrane. 相似文献
43.
A red strain ofA. pisum produced more alatae, was more fecund, and reproduced more rapidly but did not live as long as a green strain; it was also disturbed more easily, responding only to moist, not dry, currents of air, and it was less active in finding the new growth on bean plants.
Populations-masstäbe, flügelbildung und verhalten bei roten und grünenAcyrthosiphon pisum (Harris) (Homoptera: Aphididae)
Zusammenfassung Ein roter Stamm vonAcyrthosiphon pisum, der in Südengland gesammelt worden war, wurde mit dem grünen Stamm der Insektizid-Abteilung in Rothamsted verglichen. Die Lebensdauer des roten Stammes war nicht so groß wie die des grünen, aber er produzierte an jungenVicia faba-Pflanzen schneller und mehr Larven als der grüne. Er wurde auch sehr viel leichter gestört. Bei der Prüfung mit einem standardisierten Luftstrom ließen sich die roten Erbsenläuse viel leichter als die grünen von der Pflanze herabfallen. Diese Reaktion konnte nur mit feuchter, nicht aber mit trockener Luft hervorgerufen werden. Wenn sich die Läuse unbeeinflußt auf der Bohnenpflanze verteilen konnten, fanden sich die roten weniger häufig am jungen Zuwachs und die grünen wanderten häufiger von den Pflanzen ab. Der rote Stamm brachte mehr Geflügelte hervor als der grüne. Alle diese Unterschiede waren statistisch signifikant. Es wird vermutet, daß die Unterschiede in der Flügelbildung und der Schreckreaktion eine gemeinsame Ursache in den Schwellenwerten der Berührungsempfindlichkeit besitzen.相似文献
44.
Marshall E. Landay Robert W. Wheat Norman F. Conant Edwin P. Lowe 《Mycopathologia》1967,33(3-4):225-232
Summary The results of this study indicated that antigens prepared from the three morphological phases ofCoccidioides immitis differed in their complement fixing activity with anti-Histoplasma capsulatum pooled serum. Spherule antigens were serologically less active in tests with the anti-H. capsulatum pooled serum than antigens prepared from arthrospores and from mycelium.Antigenic determinants which are common toC. immitis andH. capsulatum appeared to be located on the intact arthrospore cellular surface but not on the surface of spherule cells.Part of a dissertation submitted to the Graduate School of Duke University in partial fulfillment of requirements for the Ph. D. degree.This work was supported by contract with the Department of the Army, Fort Detrick, Frederick, Maryland.In conducting the research reported herein, the investigators adhered to Guide for Laboratory Animal Facilities and Care established by the Committee on the Guide for Laboratory Animal Facilities and Care of the Institute of Laboratory Animal Resources, NAS-NRC. 相似文献
45.
Papain-catalysed hydrolysis of some hippuric esters. A new mechanism for papain-catalysed hydrolyses 总被引:6,自引:6,他引:0
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1. The Michaelis–Menten parameters for the papain-catalysed hydrolysis of a number of alkyl, aryl and alkyl-thiol esters of hippuric acid have been determined. 2. For all the aryl esters and most of the alkyl esters studied, the catalytic constant, k0, is 2–3sec.−1 and most probably represents deacylation of the common intermediate, hippuryl-papain. 3. Two alkyl esters and hippurylamide, however, have catalytic rate constants, k0, less than 2–3sec.−1. It is possible to interpret all the available kinetic data in terms of a three-step mechanism in which an enzyme–substrate complex is first formed, followed by acylation of the enzyme through an essential thiol group, followed by deacylation of the acyl-enzyme. 4. The logarithm of the ratio of the Michaelis–Menten parameters, which reflect the acylation rate constant, for four aryl esters of hippuric acid studied give a linear Hammett plot against the substituent constant, σ. Arguments are presented that indicate acid as well as nucleophilic catalysis in the acylation process and that the most likely proton donor is an imidazolium ion. 5. It is suggested that this imidazolium ion is part of the same histidine residue that has been tentatively implicated in the deacylation process (Lowe & Williams, 1965b). 6. A new mechanism is proposed for the papain-catalysed hydrolysis of N-acyl-α-amino acid derivatives. 相似文献
46.
H Werner M Adamo W L Lowe C T Roberts D LeRoith 《Molecular endocrinology (Baltimore, Md.)》1989,3(2):273-279
The developmental regulation of rat brain-derived/Hep G2 glucose transporter gene expression was studied by means of Northern blot hybridization, using a rat brain glucose transporter cDNA probe, in order to directly quantify steady state glucose transporter mRNA levels. The results obtained showed different tissue-specific patterns of glucose transporter mRNA levels during ontogenesis; while in brain there was a sustained increase in the levels of the message from 20 days embryogenesis until 50 days postnatal, other organs such as heart, lung, liver, and muscle expressed maximal levels of the glucose transporter mRNA in 20-day fetuses and 1-day neonates, decreasing subsequently to very low levels. The relative expression of the glucose transporter mRNA in the different tissues, at both fetal and adult stages, was analyzed using a solution hybridization-RNase protection assay. This approach revealed that, while the heart expresses the highest levels of glucose transporter mRNA at 20 days of fetal life, the brain shows the highest levels at the adult stage. These results indicate a tissue-specific ontogenic pattern of glucose transporter gene expression, suggesting a developmental role for this glucose transporter gene product. 相似文献
47.
Expression of insulin-like growth factor-I and its receptor by SV40-transformed rat granulosa cells 总被引:2,自引:0,他引:2
M Zilberstein J Y Chou W L Lowe Z Shen-Orr C T Roberts D LeRoith K J Catt 《Molecular endocrinology (Baltimore, Md.)》1989,3(9):1488-1497
Cellular proliferation is a dominant aspect of ovarian follicular development in the rat, and insulin-like growth factor I (IGF-I) has been proposed as a mediator of cellular growth and differentiation in the ovary. An SV40-transformed rat granulosa cell line (RGA-41S) has been established as a model for studies on dividing cells of granulosa origin. Granulosa cells from the ovaries of immature diethylstilbestrol-treated rats were infected with the tsA255 mutant of SV40, followed by cloning in serum-free medium to select transformed cell lines which were serum independent. At the permissive temperature (33 C), RGA-41S cells exhibited a transformed phenotype and rapidly formed high density multilayers of compact cells that readily overgrew nontransformed cells. At the nonpermissive temperature (40 C) cell replication declined and division ceased after 4 days. Furthermore, at 40 C the cells grew as a monolayer and assumed a tetrahedral shape with a high cytoplasm-to-nucleus ratio, and displayed reduced ability to overgrow nontransformed cells. The transformed ovarian cells did not express detectable gonadotropin receptors and steroidogenic activity but retained their epithelial phenotype as demonstrated by cytokeratin staining of the cytoskeleton, the presence of microvilli, and the formation of tight junctions between cells. In support of the proposed autocrine-paracrine actions of IGF-I in the ovary, assay of conditioned serum-free culture medium revealed secretion of IGF-I-immunoreactive material by RGA-41S cells. HPLC-purified IGF-I immunoreactivity from these cells eluted with the same retention time as recombinant human IGF-I. When hybridized with a 32P-labeled rat IGF-I cDNA probe, poly(A)+ mRNA prepared from RGA-41S cells grown at both temperatures showed the typical three size classes of IGF-I mRNA on Northern blots (7.5, 1.7, and 0.8-1.2 kilobase kb), although the levels were somewhat higher at 33 C. The presence of IGF-I receptors in transformed cells was demonstrated by specific 125I-IGF-I binding to intact cells. Scatchard analysis indicated a single class of high affinity receptors at a density of 10(5) binding sites per cell and a dissociation constant (Kd) = 0.52 x 10(-9) M. Furthermore, hybridization of a 32P-labeled IGF-I receptor probe to Northern blots of poly(A+) RNA prepared from cells grown at 33 C and 40 C revealed an 11-kilobase rat IGF-I receptor mRNA. Physiological concentrations of IGF-I increased [3H]aminoisobutyric acid uptake by RGA-41S cells grown at either temperature, attesting to the retention of responsiveness to IGF-I in these transformed granulosa cells.(ABSTRACT TRUNCATED AT 400 WORDS) 相似文献
48.
49.
A. W. Procter† E. H. F. Wjong‡ G. C Stratmann S. L. Lowe D. M. Bowen 《Journal of neurochemistry》1989,53(3):698-704
The novel N-methyl-D-aspartate receptor channel ligand (+)-[3H]5-methyl-10,11-dihydro-5H-dibenzo[a,d]-cyclohepten-5, 10-imine maleate ([3H]MK-801) has been utilized to label this receptor in human brain tissue. Characteristics of [3H]MK-801 binding to well-washed membranes from 17 control subjects and 16 patients with Alzheimer's disease were determined in frontal, parietal, and temporal cerebral cortex and cerebellar cortex. In control tissue the pharmacological specificity of the binding of this substance is entirely consistent with the profile previously reported for rat brain. Binding could be stimulated by the addition of glutamic acid to the incubation medium; addition of glycine produced further enhancement which was not prevented by strychnine. The specificity of the effects of these and other amino acids on the binding was the same as in the rat. In Alzheimer's disease significantly less binding was observed in the frontal cortex under glutamate- and glycine-stimulated conditions. This appears to be associated with a reduced affinity of the site whereas the pharmacological specificity of the site remained unchanged. The effect did not appear to be due to differences in mode of death between Alzheimer's disease and control subjects and is unlikely to be related to factors for which the groups were matched. In contrast, binding was not altered in the absence of added amino acids and presence of glutamate alone. These results imply that in the cerebral cortex the agonist site and a site in the cation channel of the receptor are not selectively altered, but that their coupling to a strychnine-insensitive glycine recognition site is impaired. 相似文献
50.
Pleomorphic adenoma is the most common neoplasm of the parotid gland, generally presenting as a slowly enlarging, firm, well-circumscribed, painless nodule. Occasional cases have presented after a short period of rapid growth or have been associated with pain. The vast majority of these tumors are solid, but rare examples have been associated with cystic degeneration or hemorrhage. Spontaneous and tumor-associated infarction of the parotid has been reported, but these examples have been limited to infarctions of Warthin's tumors and postoperative infarctions of salivary glands. We present the case of a 48-year-old male with a one-year history of a painful, enlarging, left parotid mass associated with paresthesia of the tongue. Computed tomographic examination of the parotid demonstrated a left superficial lobe mass with a rim of enhancement and low attenuation center. Fine needle aspiration yielded necrotic debris and atypical squamous elements that were thought to be compatible with carcinoma. A superficial parotidectomy with intraoperative frozen section revealed a pleomorphic adenoma with extensive central necrosis. To our knowledge, this represents the first reported case of an infarcted pleomorphic adenoma and illustrates the potential for misinterpretation of these cytologic and radiologic findings as indicative of malignancy. 相似文献