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91.
Studies on the Formation of 6-Hydroxydopamine in Mouse Brain After Administration of 2,4,5-Trihydroxyphenylalanine (6-HydroxyDOPA) 总被引:1,自引:1,他引:0
2,4,5-Trihydroxyphenylalanine (6-OH-DOPA) destroys central and peripheral noradrenergic neurons, while sparing dopaminergic neurons. Previous studies indicate that 6-OH-DOPA toxicity is mediated by the formation of 6-hydroxydopamine. However, levels of 6-hydroxydopamine in brain following peripheral administration of 6-OH-DOPA have not been documented. In the current study, 6-OH-DOPA and 6-hydroxydopamine were measured in brain by HPLC with electrochemical detection after intraperitoneal injection of 6-OH-DOPA. When mice were injected with 100 mg 6-OH-DOPA/kg, 6-hydroxydopamine levels in the striatum were highest (1.9 microgram/g) at 15 min and fell slowly to 24% of the peak value at 4 h. Experiments with reserpine indicated that the relatively stability of 6-hydroxydopamine was largely dependent upon storage in synaptic vesicles. Reserpine (10 mg/kg) lowered striatal 6-hydroxydopamine levels to 21.6% of control (non-reserpine-treated) values at 1 h, and to 8.9% of control values at 4 h. Levels of 6-hydroxydopamine in the striatum at 1 h were increased 113% by pargyline (100 mg/kg), 145% by alpha-methyldopahydrazine (carbidopa; 25 mg/kg), and 261% by pargyline and carbidopa together. Levels of dopamine in the striatum were unchanged at 2.5 h after 200 mg 6-OH-DOPA/kg (with pargyline and 50 mg carbidopa/kg), whereas levels of norepinephrine in the frontal cortex fell by 77%. At the same time, 6-hydroxydopamine levels were 8.8-fold higher in the striatum (5.54 micrograms/g) than in the cortex (0.63 micrograms/g).(ABSTRACT TRUNCATED AT 250 WORDS) 相似文献
92.
Micrococcus luteus produced 29 μM riboflavin during growth on 6.5 mM pyridine but not during growth on other substrates. On the basis of the results of radiolabelling studies, riboflavin was not directly synthesized from pyridine. Pyridine may interfere with riboflavin biosynthesis or elicit a general stress response in M. luteus. 相似文献
93.
94.
The cumulative effect of wetlands on stream water quality and quantity. A landscape approach 总被引:7,自引:0,他引:7
A method was developed to evaluate the cumulative effect of wetland mosaics in the landscape on stream water quality and quantity in the nine-county region surrounding Minneapolis—St. Paul, Minnesota. A Geographic Information System (GIS) was used to record and measure 33 watershed variables derived from historical aerial photos. These watershed variables were then reduced to eight principal components which explained 86% of the variance. Relationships between stream water quality variables and the three wetland-related principal components were explored through stepwise multiple regression analysis. The proximity of wetlands to the sampling station was related to principal component two, which was associated with decreased annual concentrations of inorganic suspended solids, fecal coliform, nitrates, specific conductivity, flow-weighted NH4 flow-weighted total P, and a decreased proportion of phosphorus in dissolved form(p < 0.05). Wetland extent was related to decreased specific conductivity, chloride, and lead concentrations. The wetland-related principal components were also associated with the seasonal export of organic matter, organic nitrogen, and orthophosphate. Relationships between water quality and wetlands components were different for time-weighted averages as compared to flow-weighted averages. This suggests that wetlands were more effective in removing suspended solids, total phosphorus, and ammonia during high flow periods but were more effective in removing nitrates during low flow periods. 相似文献
95.
Roger A. Hoffman Peter Habeeb Gerald R. Buzzell 《Journal of comparative physiology. B, Biochemical, systemic, and environmental physiology》1990,160(3):269-275
Summary Long-term increased or decreased circulating levels of thyroid hormones significantly modify porphyrin concentrations and morphology in the Harderian glands of male and female hamsters. Administration of T3 reduced porphyrin concentrations in females; this treatment or decreasing thyroid hormone levels with KClO4 suppressed the post-castration rise of porphyrins in males. Hypophysectomy led to increased porphyrins in the Harderian glands of males; this rise was suppressed in hypophysectomized males by T3 or T4. In females, hypophysectomy reduced porphyrins which were further reduced by daily administration of T3 or T4. These modifications in the normal females were identical in castrated males. Mitotic activity in the Harderian glands of females was stimulated by KClO4 and by hypophysectomy with or without exogenous T3. In males, castration increased mitotic activity which was suppressed by T3 and exacerbated by KClO4. Increased mitotic activity seemingly follows loss of tissue mass. The data show that thyroid hormones act directly on the Harderian glands rather than indirectly through modification of TSH synthesis/release. Female type glands in males are a consequence of loss of gonadal androgens by castration, or by suppression or loss of thyroid hormones by hypophysectomy or by treatment with KClO4. However, male type glands in females are the result of androgen treatment, and/or increased levels of thyroid hormones via reduced ambient temperatures or of photic input. We conclude that regulation of the Harderian gland appears to be different in the two sexes.Abbreviations
T
3
Triiodothyronine
-
T
4
Thyroxine
-
TSH
Thyroid Stimulating Hormone
-
KClO
4
Potassium Perchlorate
-
h
hours
-
ml
milliliter
-
mg
milligram
-
g
gram
-
male
-
female
-
castrated male
- AP
hypophysectomized
-
CON
Control
-
ALA
delta aminole-vulenic acid
-
HG
Harderian Gland 相似文献
96.
Serum-free culture of enriched mouse anterior and ventral prostatic epithelial cells in collagen gel
Timothy Turner Howard A. Bern Peter Young Gerald R. Cunha 《In vitro cellular & developmental biology. Plant》1990,26(7):722-730
Summary Sustained growth of mouse ventral and anterior prostatic epithelial cells embedded within collagen gel matrix was achieved
in a serum-free medium composed of Dulbecco's modified Eagle's medium and Ham's F12 medium, 1∶1 (vol/vol), supplemented with
bovine serum albumin fraction V, epidermal growth factor, transferrin, cholera toxin, prolactin, 5α-dihydrotestosterone, cortisol,
putrescine, fibroblast growth factor, and a trace element mixture. Three-dimensional growth of prostatic epithelial cells
occurred inside the collagen gel matrix. This serum-free medium allowed cell growth greater than sevenfold over 10 d in culture.
Tissue recombination and cell culture techniques were integrated to demonstrate that cultured cells retained prostatic characteristics.
Following 10 d of culture, epithelial colonies from mouse ventral and anterior prostatic epithelial cell cultures were isolated
and combined with rat fetal urogenital sinus mesenchyme and grown for 4 wk under the renal capsule of intact athymic male
mice. These tissue recombinants showed distinctive prostatic histologic characteristic (alveoli and ducts lined with cuboidal
or columnar epithelium surrounded by stroma). When histologic sections of recombinants were stained with the Hoechst 33258,
epithelial cells of mouse origin were distinguishable from stromal cells of rat origin.
Aided by grants CA-05388 and CA-09041 from the National Institutes of Health, Bethesda, MD, and by M. A. R. C. fellowship
GM08730 to T. T. 相似文献
97.
Quinones may be toxic by a number of mechanisms. including arylation and oxidative stress caused by redox cycling. Using isolated hepatocytes, we have studied the cytotoxicity of four quinones. with differing abilities to arylate cellular nucleophiles and redox cycle. in relation to their effects on cellular pyridine nucleotides. High concentrations of menadione (redox cycles and arylates). 2-hydroxy-1,4-naphthoquinone (neither arylates nor redox cycles via a one electron reduction) 2.3-dimethoxy-1.4-naphthoquinone (a pure redox cycler) and p-benzoquinone (a pure arylator) caused an initial decrease in NAD+ and loss of viability, which was not prevented by 3-aminobenzamide. an inhibitor of poly(ADP-ribose)polymerase. In contrast. 3-aminobenzamide inhibited the loss of NAD' and viability caused by dimethyl sulphate so implicating poly(ADP-ribose)polymerase in its toxicity but not that of the quinones. Non-toxic concentrations of menadione. 2.3-dimethoxy-1.4-naphthoquinone and 2-hydroxy-1.4-naphthoquinone all caused markedly similar changes in cellular pyridine nucleotides. An initial decrease in NAD+ was accompanied by a small. transient increase in NADP+ and followed by a larger. prolonged increase in NADPH and total NADP+ + NADPH. Nucleotide changes were not observed with non-toxic concentrations of p-benzoquinone. Our findings suggest that a primary event in the response of the cell to redox cycling quinones is to bring about an interconversion of pyridine nucleotides. in an attempt to combat the effects of oxidative stress 相似文献
98.
Identification of consensus patterns in unaligned DNA sequences known to be functionally related 总被引:16,自引:0,他引:16
Hertz Gerald Z.; Hartzell George W. III; Stormo Gary D. 《Bioinformatics (Oxford, England)》1990,6(2):81-92
We have developed a method for identifying consensus patternsin a set of unaligned DNA sequences known to bind a common proteinor to have some other common biochemical function. The methodis based on a tnatrix representation of binding site patterns.Each row of the matrix represents one of the four possible bases,each column represents one of the positions of the binding siteand each element is determined by the frequency the indicatedbase occurs at the indicated position. The goal of the methodis to find the most significant matrix-i.e. the one with thelowest probability of occurring by chance-out of all the matricesthat can be formed from the set of related sequences. The reliabilityof the method improves with the number of sequences, while thetime required increases only linearly with the number of sequences.To test this method, we analysed 11 DNA sequences containingpromoters regulated by the Escherichia coli LexA protein. Thematrices we' found were consistent with the known consensussequence, and could distinguish the generally accepted LexAbinding sites from other DNA sequences.
Received on November 6, 1989; accepted on December 20, 1989 相似文献
99.
Kwan-Fu Rex Sheu Noel Y. Calingasan Gerald A. Dienel Harriet Baker Eun-Hee Jung Kwang-Soo Kim †Francesco Paoletti Gary E. Gibson 《Journal of neurochemistry》1996,67(2):684-691
Abstract: Thiamine deficiency impairs oxidative metabolism and causes metabolic encephalopathy. An early reduction in transketolase (TK) activity may be an important pathogenic event. To assess the role of TK, we have delineated the regional/cellular distribution of TK protein and mRNA in adult rat brain in pyrithiamine-induced thiamine deficiency. TK activity declined in both vulnerable and spared regions. Immunoblots showed a parallel reduction of TK protein. With a few exceptions, immunocytochemistry indicated an overall decline of TK immunoreactivity and the decrease was not specific to vulnerable areas. In contrast to the pronounced, general decline of TK protein, in situ hybridization revealed a regional decrease of 0–25% of TK mRNA in thiamine deficiency. Northern blots indicated a similar level of TK mRNA in whole brain in thiamine deficiency. These results show that the decline of TK activity results from a proportional decrease of TK protein, and the deficiency may be due to an instability of TK protein or an inhibition of TK mRNA translation. The lack of correlation of the distribution, and the absence of specific alteration, of TK in affected regions suggest that the reduced TK may not be linked directly to selective vulnerability in thiamine deficiency. 相似文献
100.
Eberhard Fuchs Jan-Christian Wasmuth Gabriele Flügge Gerald Huether Raphael Troost Jürgen Beyer 《Cellular and molecular neurobiology》1996,16(1):21-37
Summary 1. Corticotropin-releasing factor (CRF) is thought to be involved in the regulation of the diurnal activity of the hypothalamus-pituitary-adrenal
(HPA) axis and to act as a neurotransmitter in the brain. To date it is unknown whether the binding sites of the central CRF
system are subject to diurnal variations.
2. We measured the number of CRF binding sites over the course of a complete 24-hr light-dark cycle in the pituitary, amygdala,
bed nucleus of the stria terminalis (BNST), cingulate cortex, visceral cortex, paraventricular nucleus of the hypothalamus,
hippocampus, and locus ceruleus of rats byin vitro receptor autoradiography with iodinated ovine CRF. A 24-hr time course was also established for plasma CRF and corticosterone.
3. The diurnal pattern of plasma CRF does not correlate with the pattern of plasma corticosterone. Within the brain, CRF binding
in the basolateral nucleus of the amygdala showed a U-shaped curve with maximum levels in the morning and a wide hallow between
1500 and 0100. A biphasic profile with a small depression in the afternoon and a more pronounced depression in the second
half of the activity period is characteristic for the other brain areas and the pituitary. The profile for the pituitary correlates
with those for the BNST and the area of the locus ceruleus. Furthermore, the diurnal pattern of CRF binding sites in the BNST
correlates with that of the hippocampus, and the daytime pattern of the visceral cortex is similar to that of both the hippocampus
and the BNST.
4. Since the CRF-binding profiles in the brain and the pituitary clearly differ from the profiles of both plasma CRF and corticosterone,
one may assume that the diurnal pattern of central CRF binding sites is not directly coupled to the activity of the HPA axis. 相似文献