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251.
Effects of Systemically Administered Lithium on Phosphoinositide Metabolism in Rat Brain, Kidney, and Testis 总被引:15,自引:4,他引:11
William R. Sherman Ling Y. Munsell Beverly G. Gish Michael P. Honchar 《Journal of neurochemistry》1985,44(3):798-807
A single subcutaneous dose of 10 mEq/kg LiCl gives rise to an increase in the cerebral cortex level of myo-inositol-1-P (I1P) that closely follows cortical lithium levels and, at maximum, is 40-fold above the control value. Kidney and testis show smaller increases in I1P level following LiCl administration. The I1P level is still sixfold greater than that of untreated rat cortex 72 h later. In cortex, parallel increases also occur in myo-inositol-4-P (I4P) and myo-inositol 1,2-cyclic-P (cI1,2P), whereas myo-inositol-5-P (I5P) remains unchanged. The cortical increases in I1P and I4P levels are partially reversed by administering 150 mg/kg of atropine 22 h after the LiCl, treatment that does not affect cI1,2P. When doses of LiCl from 2 to 17 mEq/kg are given, the cerebral cortex levels of I1P and myo-inositol, measured 24 h later, are found to reach a plateau at about 9 mEq/kg of LiCl, whereas cortical lithium levels continued to increase with greater LiCl doses. Levels of all three of the brain phosphoinositides are unchanged by the 10 mEq/kg LiCl dose, as is the uptake of 32Pi into these lipids. Chronic dietary administration of LiCl for 22 days showed that the effects of lithium on I1P and myo-inositol levels persist for that period. Over the course of the chronic administration of the lithium, levels of I1P, myo-inositol, and of lithium in cortex remained significantly correlated. We believe that these increases in inositol phosphates result from endogenous phosphoinositide metabolism in cerebral cortex and that lithium is capable of modulating that metabolism by reducing cellular myo-inositol levels. The size of the effect is a function of both lithium dose and the degree of stimulation of receptor-linked phosphoinositide metabolism. This property of lithium may explain part of its ability to moderate the symptoms of mania. Our chronic study suggests that prolonged administration of LiCl does not result in compensatory changes in myo-inositol-1-P synthase or myo-inositol-1-phosphatase. 相似文献
252.
Quinolinic Acid Phosphoribosyltransferase in Rat Brain 总被引:9,自引:7,他引:2
Because of the possible participation of quinolinic acid in brain function and/or dysfunction, the characteristics of its catabolic enzyme, quinolinic acid phosphoribosyltransferase (QPRTase; EC 2.4.2.19), were examined in rat brain tissue. For this purpose, a sensitive radiochemical assay method, based on the conversion of quinolinic acid to nicotinic acid mononucleotide (NAMN), was developed. For brain QPRTase, the Mg2+ dependency, substrate specificity, and optimal assay conditions were virtually identical to those of the liver enzyme. Kinetic analyses of brain QPRTase revealed a Km of 3.17 +/- 0.30 microM for quinolinic acid and Km = 65.13 +/- 13.74 microM for the cosubstrate phosphoribosylpyrophosphate. The respective Vmax values were: 0.91 +/- 0.08 pmol NAMN/h/mg tissue for quinolinic acid and 11.65 +/- 1.55 fmol NAMN/h/mg tissue for phosphoribosylpyrophosphate. All kinetic parameters measured for the brain enzyme were significantly different from those determined for liver QPRTase, indicating structural differences or distinct regulatory processes for the brain and liver enzymes. Phthalic acid was a potent competitive inhibitor of brain QPRTase. Examination of the regional distribution of QPRTase in the rat CNS and retina indicated a greater than 20-fold difference between the area displaying the highest activity (olfactory bulb) and those of only moderate activity (frontal cortex, striatum, retina, hippo-campus). Enzyme activity was present at the earliest age tested, 2 days, and tended to increase in older animals. Brain QPRTase activity was preferentially located in the nerve-ending (synaptosomal) fraction. Enzyme activity was stable over extensive periods of storage at -80 degrees C.(ABSTRACT TRUNCATED AT 250 WORDS) 相似文献
253.
Most previously published electromyographic (EMG) studies have indicated that the temporalis muscles in humans become almost
electrically quiet during incisai biting. These data have led various workers to conclude that these muscles may contribute
little to the incisai bite force. The feeding behavior and comparative anatomy of the incisors and temporalis muscles of certain
catarrhine primates, however, suggest that the temporalis muscle is an important and powerful contributor to the bite force
during incision. One purpose of this study is to analyze the EMG activity of the masseter and temporalis muscles in both humans
and macaques with the intention of focusing on the conflict between published EMG data on humans and inferences of muscle
function based on the comparative anatomy and behavior of catarrhine primates. The EMG data collected from humans in the present
study indicate that, in five of seven subjects, the masseter,anterior temporalis, and posterior temporalis muscles are very active during apple incision (i.e., relative to EMG activity
levels during apple and almond mastication). In the other two human subjects the EMG levels of these muscles are lower during
incision than during mastication, but in no instance are these muscles ever close to becoming electrically quiet. The EMG
data on macaques indicate that, in all six subjects, the masseter, anterior temporalis, and posterior temporalis muscles are
very active during incision. These data are in general agreement with inferences on muscle function that have been drawn from
the comparative anatomy and behavior of primates, but they do not agree with previous experimental data. The reason for this
disagreement is probably due to differences in the experimental procedure. In previous studies subjects simply bit isometrically
on their incisors and the resulting EMG pattern was compared to the pattern associated with powerful clenching in centric
occlusion. In the present study the subjects incised into actual food objects, and the resulting EMG pattern was compared
to the pattern associated with mastication of various foods. It is not surprising that these two procedures result in markedly
different EMG patterns, which in turn result in markedly different interpretations of jaw-muscle function. In an attempt to
explain the evolution of the postorbital septum in anthropoids, it has been suggested that the anterior temporalis is more
active than the masseter during incision (Cachel, 1979). The human and macaque EMG data do not support this hypothesis; during
incision, the two muscles show no consistent differences in humans and the masseter appears to be in fact more active than
the anterior temporalis in macaques. 相似文献
254.
William W. Dressler 《Culture, medicine and psychiatry》1985,9(3):257-286
The quantity of research on the effects of stress on disease has increased substantially in recent years, but little effort has been devoted to examining the effects of cultural influences in the stress process. A model is proposed in this paper in which cultural context exerts a modifying influence on the relationship between sociocultural stressors and psychosomatic symptoms, specifically in the context of modernization. In change situations involving increasing modernization there is increased differentiation in systems of social stratification within a community, due to increased potential for upward social mobility. The individuals who are upwardly mobile adopt a particular style of life, involving the acquisition of western consumer goods, as symbolic of their success. Lower class individuals strive to attain this same style of life as a claim to a higher status social identity, but their lower economic condition results in stressful incongruities and higher psychosomatic symptoms. Individuals who are successful in upward mobility are confronted by a different set of stressors that are primarily intrapsychic in nature. Events and circumstances perceived as threats to their self-identity are related to more psychosomatic symptoms. Thus, the meaning of specific stressors changes depending on the sociocultural context of the individual, and this meaning serves as a bridge between environmental circumstances and physiological outcomes. This model receives substantial empirical support in two field studies. Limitations of the model and implications for future research are discussed.Research in St. Lucia was supported by the Connecticut Research Foundation and the University of Connecticut Health Center. Research in the U.S. was supported by Research Grant MH 33943 from the Center for the Study of Minority Group Mental Health, National Institute of Mental Health. Drs. Arthur Kleinman, Lee Badger, H. B. M. Murphy, James Bindon, and Laurence Watkins kindly commented on previous drafts of this paper. Dr. Michael Murphy deserves a special note of gratitude for reading several drafts of the paper and for patiently sitting through several lengthy discussions of it. I alone am responsible for the errors and shortcomings. 相似文献
255.
Hector Lozoya-Saldana William O. Dawson T. Murashige 《Plant Cell, Tissue and Organ Culture》1985,(1):41-48
Although both ribavirin (1--ribofuranosyl-1,2,4-triazole-3carboxamide) and adenine arabinoside inhibited the multiplication of tobacco mosaic virus (TMV) in mechanically inoculated leaf tissues, neither chemical inhibited virus multiplication in unorganized tobacco callus after in vitro inoculation. The adenine deaminase inhibitor, pentostatin, did not increase the activity of adenine arabinoside in cultured cells. Several different developmental conditions and media did not increase the ability of either chemical to eradicate the virus from tobacco tissue cultures. However, the virus was eradicated from TMV-infected callus when grown in the presence of combinations of ribavirin and adenine arabinoside in shoot inducing medium. 相似文献
256.
Danielle J. Donnelly William E. Vidaver Kwai Y. Lee 《Plant Cell, Tissue and Organ Culture》1985,4(1):43-50
The leaf, petiole, stem and root anatomy of an aseptically cultured red raspberry clone (Rubus idaeus L.) was studied before and 5 weeks after transfer to soil under controlled environmental conditions. Tissues persistent from culture showed little or no change with time in soil; they grew minimally and slight secondary wall deposition occurred. New organs formed in successive weeks after transplantation showed a graded increase in potential size and development. Some features, such as collenchyma formation, rapidly returned to control levels; this was seen in new leaves expanding in the first week after transplantation. Other features, such as sclerenchyma formation, did not occur in leaves expanding during the first 2 weeks after transplantation, even when these were a month or more in age. Some sclerenchyma was seen in leaves expanding in the third week after transplantation, increasing in later-formed leaves. Increasing the light intensity of transplant accelerated the return to control-type organ size and appearance. During acclimatization transitional forms of leaves, petioles, stems and roots develop that ranged anatomically from culture-to control-type. This trend is analagous to the normal developmental sequence of organ formation as it affects the potential for development of successily formed organs. 相似文献
257.
Evidence is presented of the ability of H-2 class I antigens to function as teratocarcinoma transplantation (Gt) antigens. Coisogenic immunization against H-2 class I antigens expressed on transfected L cells is shown to induce resistance to embryonic carcinoma (EC) cell allografts. The Kb, Db, Dd, and, in appropriate recipients, Ld antigens can function as Gt antigens. The protocol presented may be useful for the molecular identification of other genes encoding histocompatibility antigens. 相似文献
258.
The effects of various metabolic inhibitors (dichlorophenyl dimethylurea, chloramphenicol, cycloheximide, carbonyl cyanide m-chlorophenyl hydrazone) on the accumulation of radiolabeled substrates (amino acids, glucose, bicarbonate, phosphate) by size-fractionated marine microbial plankton from the Sargasso Sea and the eastern Canadian arctic were studied in time-course fashion during experimental incubations either exposed to or shielded from ambient solar radiation. Picoplankton accounted for 65% of the organic substrates and phosphate accumulated by the assemblages. The rate of organic substrate accumulation was stimulated by solar radiation in some cases but inhibited in other cases. Presumably, stimulation and inhibition co-occur and the measured response is the net result arising from these counteracting tendencies. Approximately 40% of H14 CO3
– accumulation in the Sargasso Sea was associated with the picoplankton. The insensitivity of picoplankton14C-labeling to cycloheximide suggested active prokaryotic photosynthesis rather than heterotrophic assimilation of14C-labeled algal photosynthates as the route of labeling. The usefulness of some inhibitors was restricted in this study because of inconsistent correlations between the intended primary metabolic effect and the measured ecological response within the duration of the experiment. 相似文献
259.
Yeast communities in necroses of organpipe cactus (Stenocereus thurberi) were surveyed at 3 localities in Arizona. Quantitative analysis of random samples allows comparisons of the types and numbers of yeasts at 3 levels: within plants, between plants within a locality, and between localities. The analysis shows that the major source of variability is between plants. This pattern is identical with the pattern shown by agria cactus (Stenocereus gummosus) and is thought to be due to sampling different successional stages. No significant differences in estimates of the effective number of yeast species (ENS) in agria and organpipe samples were found. Comparisons of agria, organpipe, and prickly pear (Opuntia) cacti support the hypothesis that cactus chemistry is an important determinant of the yeast community structure which, in turn, is an important determinant of the diversity ofDrosophila species which utilize necrotic cacti as feeding and breeding substrates. 相似文献
260.
William Balée 《Human ecology: an interdisciplinary journal》1985,13(4):485-510
Several investigators cite population control, frequent settlement relocation, trekking, expansion of diet breadth, and food taboos as strategic responses to game depletion by indigenous populations living in interfluvial zones of lowland South America. The Ka'apor Indians of the interfluvial forest of northern Maranhão, Brazil, employ other means of optimizing hunting efficiency, partly based on ritual. Menstruating women, pubescent girls, and parents of newborns can consume meat only of the tortoise (Gochelone denticulata), the first prey species to be hunted out of an area. Tortoise capture requires, on average, one full day of hunting. This means that the full potential of hunting pressure does not materialize near the settlement. Meat productivity is unusually high even near old settlements. I argue that ritual tortoise hunting helps to regulate environmental utilization, to maintain a sustained yield of meat protein, and to expand the catchment area gradually. 相似文献