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It is possible that dietary conditions can result in the production of abnormal bone protein. For example, a heavily maize-dependent diet could be deficient in one or more essential amino acids necessary to normal human biochemistry and consequently necessary for normal bone protein synthesis. Amino acid analysis of bone tissues, thus, could provide a useful diagnostic tool in paleopathology. To test this potential we have compared the amino acid analyses of bone samples from a prehistoric Southwest Indian child exhibiting porotic hyperostosis with samples taken from (1) two children's skeletons lacking bone lesions but from the same area and time, (2) a modern child who died from accidental causes, and (3) adult human compact bone. Analytical results of the nonpathological prehistoric specimens were virtually identical to that of the modern infant, indicating remarkable preservation of bone protein. The pathological bone sample differed from the three control specimens by having as much as 25% less of those amino acids containing hydroxyl group and acidic side chains. We interpret the amino acid profile for the diseased child as indicating the presence of a greater proportion of helical protein (or less noncollagenous protein) as well as a lowered degree of hydroxylation of proline and lysine. One explanation for our data is that protein biosynthesis is altered in the child exhibiting porotic hyperostosis, and either some proteins important in the early phases of mineralization are not produced in sufficient quantity, or some necessary enzyme cofactors (e.g., dietary ferrous ions) are missing. We conclude that our data are compatible with, but do not prove, the hypothesis that the porotic hyperostosis exhibited by the Southwest Indian child is the result of iron deficiency anemia. 相似文献
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M Camacho Ochoa T A Jackson C S Aaron R A Lahti G M Strain P F Von Voigtlander 《Life sciences》1992,51(14):1135-1143
A morphometric study of kainic acid- (KA) induced lesions was designed for the study of the interaction of the diamines U-5449A and U-50488H with excitatory amino acids, and the dose-response relationship thereof. IC50S determined for binding at the kappa receptor and other opioid receptors demonstrated the lack of kappa activity of U-54494A, a structurally related analog of U-50488H. Both opiate kappa receptor related anticonvulsant diamines were tested for their ability to protect the mouse hippocampus from the cytopathological changes induced by KA in neurons and glia. The damage observed with i.c.v. KA in mouse was restricted to neurons of the CA3 pyramidal region and glia of the hippocampus. It involved massive cell loss and shrunken neurons with dark cytoplasm and nuclei. Groups treated with combinations of KA and U-54494A or U-50488H showed scarce damage, but patches of necrotic changes were still observed. Control animals treated with saline (i.c.v.) and U-54494A (s.c.) or U-50488H (s.c.) did not suffer any noticeable alterations of the polymorphic layers of the hippocampal formation. Image analysis of the CA3 area of the hippocampus was used to quantitate the vacuolization induced by KA lesions in the control and treated groups. By this method, both U-54494A and U-50488H were shown to protect this area in a dose-related fashion as evidenced by reduced vacuolization. The anticonvulsant properties of these compounds may result in the antagonism of the excitotoxic lesions. More specifically, the ability of these diamines to block depolarization-induced influxes of Ca++ may protect the CA3 cells from the cytotoxic effects of persistent depolarization. 相似文献
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RNA helicases melt regions of duplex RNA in a process that requires energy derived from the hydrolysis of nucleoside triphosphates. The process of protein synthesis in prokaryotes and eukaryotes involves one proven RNA helicase (elF-4A) and several putative RNA helicases. Of these, one group of helicases is thought to unwind secondary structure in the 5′ non-coding region of mRNAs to facilitate ribosome binding. A second group is implicated in ribosome assembly, in particular in ribosomal RNA maturation. 相似文献
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Bruno Von Berzins 《Hydrobiologia》1954,6(3-4):309-320
Ohne Zusammenfassung 相似文献
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A total of 62,811 cases of the acquired immunodeficiency syndrome (AIDS) have been reported to the World Health Organization from throughout the world. Extensive epidemiologic studies have shown that human immunodeficiency virus (HIV) infections are transmitted by three routes: sexual, parenteral and perinatal. Three geographic patterns of transmission have been defined. In pattern I, transmission occurs predominantly among homosexual and bisexual men and urban intravenous drug abusers; transmission via blood products has been controlled; the male:female sex ratio is 10:1 or more; population HIV seroprevalence is low, and perinatal transmission is uncommon (for instance, United States, western Europe). In pattern II, transmission is predominantly heterosexual and perinatal; transmission via blood products exists but is being reduced; unsterile needles and other skin-piercing instruments cause some parenteral transmission (magnitude not known); the male:female sex ratio is 1:1, and population seroprevalence often exceeds 1% (central Africa, Haiti). In pattern III, AIDS cases are just being documented and are generally due to sexual exposure abroad or imported blood products (Middle East, Asia). 相似文献
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The method of tight-seal whole-cell recording was used to study the amino-acid specificity of the Na+/alanine cotransporter in pancreatic acinar cells. Single cells or small clusters of electrically coupled cells were obtained by enzymatic dissociation of mouse pancreas. Inward currents were measured under 'zero-trans' conditions, i.e., at finite concentrations of Na+ and amino acid at the extracellular side and vanishing concentrations at the cytoplasmic side. The cotransporter, which corresponds to 'system A', as previously defined in the literature, was found to exhibit a wide tolerance to neutral amino acids (L-cysteine, L-serine, L-alanine, glycine, L-phenylalanine). Competition experiments with 2-methylaminoisobutyric acid (MeAIB) indicate that for glycine a second electrogenic transport system exists in pancreatic acinar cells. 相似文献
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Von H. Zwölfer J. Herbst 《Journal of Zoological Systematics and Evolutionary Research》1988,26(5):320-340
Preadaptation, host shifts and parallel cladogenesis in the evolution of phytophagous insects In this contribution we investigate the possibilities to apply concepts developed for the evolution of animal parasites to insect-plant systems. We compare host parasite systems in animals with plant-herbivore systems and list similarities and differences. The terms preadaptation, predisposition, expansion and contraction of host ranges, and parallel cladogenesis are discussed. We enumerate general preadaptations for the evolution of herbivory in insects and preadaptations for shifts between herbivory and entomophagy. Examples are given for expansions of host ranges based on phytochemical or structural characters of host plants. Cases of parallel cladogenesis in herbivoreparasitoid systems and plant-herbivore systems are compiled from the literature. An analysis of the insect fauna of the “thistles” (Cynaroideae) in the Palearctic and Nearctic demonstrates the importance of the evolutionary history of the plant taxa and of the existence of preadapted pools of herbivores for the evolution of guilds of specialized herbivores. The members of the Curculionid taxon Cleoninae provide examples for multiple colonizations and radiations of herbivores on the Cynaroideae. The taxonomic and biological relationships of the weevil genera Rhinocyllus, Bangasternus and Larinus which exploit the flower heads of Cynaroideae, can be interpreted as result of a basic parallel cladogenesis between herbivore and host. A gelelectrophoretic analysis of Larinus spp. supports this hypothesis. 相似文献