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  • 1
    ISSN: 1573-6903
    Schlagwort(e): Glutamate ; vitamin E ; oxidative stress ; synaptosomes ; aging
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Notizen: Abstract We examined the influence of aging upon the uptake of glutamate by synaptosomes, and the oxidation of Synaptosomal vitamin E. Synaptosomes isolated from the cerebral hemispheres of Fischer 344 rats, 4 and 24 months old, were suspended at 37°C in buffer (pH 7.4) simulating extracellular fluid containing 10 mM glucose. The Km for the high affinity uptake of tritium labeled glutamate was ∼10 μM. The uptake of glutamate was lower in synaptosomes from older animals than those from younger animals for periods of up to 20 minutes. Upon incubation with a mixture of ferrous iron and ascorbate, more of the alpha tocopherol in synaptosomes derived from older rats was oxidized than in those derived from younger ones. Older animals may be more susceptible to excitotoxicity because: a) Synaptosomal reuptake of glutamate is less efficient and b) oxidative stress induced by various agents including glutamate may be higher in synaptosomes from the older animal.
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
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  • 2
    Digitale Medien
    Digitale Medien
    Springer
    Journal of insect behavior 9 (1996), S. 755-769 
    ISSN: 1572-8889
    Schlagwort(e): fecundity ; oviposition ; behavior ; egg masses ; eggs ; aging ; population density ; adult longevity
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Abstract Age-related oviposition patterns ofOstrinia nubilalis were studied at three population densities in the laboratory by releasing newly eclosed adults in wire-screened cages and analyzing their oviposition throughout the adult stage with digital analysis. Oviposition sequences of individual females depositing egg masses were documented on the third and seventh nights after eclosion with a video camcorder. During a sequence, a female produced an egg in an average time of 15 or 26 s on the third and seventh nights, respectively, and completed depositing an egg mass the size of 20–39 eggs in an average time of 316 and 525 s, respectively. Females were not easily disturbed during egg mass deposition and pulsated their abdomen before deposition of each egg. Females produced few egg masses the first night after eclosion. Oviposition increased on nights 2 and 3 but declined steadily thereafter as females matured. Females older than 6 nights produced fewer egg masses; the proportion of egg masses with fewer than 20 eggs increased gradually. By the end of the adults' lifetime, nearly 100% of the egg masses had fewer than 20 eggs. The data are fundamental to our research to define the role of phytochemicals in modifying oviposition behavior of the European corn borer.
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
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  • 3
    ISSN: 1573-2568
    Schlagwort(e): aging ; gastric secretion ; gastrin ; rats
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Notizen: Abstract The purpose of this study was to characterize the effects of aging on gastric acid secretion and on serum and antral concentrations of gastrin in rats. Young and old Fischer 344 rats were prepared with gastric fistulas. Twenty-four hours after surgery, graded doses of human synthetic gastrin-17 (SHG-17) (2, 5, 10, 20, and 40 μg/kg) were given intravenously in random order. Gastric secretions were collected for gastric acid measurement before and at 15-min intervals after each dose of gastrin. In a separate study, blood was collected and the stomachs were removed for antral gastrin extraction from fed young and old rats. Serum and antral gastrin was measured by radioimmunoassay. The basal and gastrin-stimulated acid secretions were significantly decreased in aged rats compared to the young rats. The basal acid output was 0.4±0.2 μeq/15 min in the aged rats and 1.5±0.5 μeq/15 min in the young. The maximal acid output stimulated by gastrin was 11.1±1.8 μeq/15 min in the aged rats and 24.2±2.8 μeq/15 min in the young. Both serum and antral concentrations of gastrin were significantly decreased in aged rats. Serum gastrin concentration was 114.8±7.4 pg/ml in the aged rats and 192.0±14.4 pg/ml in the young. Antral gastrin concentration was 3.9±0.5 μg/g tissue in the aged rats, which was significantly less than the concentration in the young (6.5±0.4 μg/g tissue). Antral gastrin content did not change with aging. Gastric acid secretion in aged rats is significantly decreased compared to the young in both the basal condition and in response to fixed doses of exogenous gastrin. Diminished concentrations of circulating gastrin may well be responsible, at least in part, for the diminished acid secretion in the aged rats.
    Materialart: Digitale Medien
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  • 4
    Digitale Medien
    Digitale Medien
    Springer
    Digestive diseases and sciences 38 (1993), S. 410-416 
    ISSN: 1573-2568
    Schlagwort(e): aging ; enterectomy ; disaccharidase ; proliferation ; differentiation
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Notizen: Abstract Two groups of male Fisher 344 rats (young: 4 months old; aged: 25 months old) underwent either 70% distal small bowel resection or sham operation (small bowel transection). Rats from each treatment group of each age were sacrificed on the 10th (N=15: young rats;N=13: aged rats) or 20th (N=15: young;N=13: aged) postoperative day (POD), and the duodenal mucosa was weighed and assayed for DNA, RNA, and protein contents, as well as for specific activities of the disaccharidase, sucrase, maltase, and lactase. Compared to the sham operation, distal small bowel resection significantly increased DNA by 48%, RNA by 122%, and protein by 75% in young rats and DNA by 40%, RNA by 92%, and protein by 71% in aged rats on the 20th POD. Both young and aged rats showed similar adaptive hyperplasia on the 10th POD. On the 20th POD after distal small bowel resection, specific activities of all tested enzymes were significantly increased in young rats (sucrase +86%, maltase +110% and lactase +64%), but showed no significant changes in aged rats. These findings suggest that the duodenum of aged rats may have sufficient proliferative potential to respond to distal small bowel resection, but that the mechanisms governing return of function in response to distal small bowel resection are inhibited in aged rats, compared to those mechanisms in the young.
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
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  • 5
    ISSN: 0362-2525
    Schlagwort(e): Life and Medical Sciences ; Cell & Developmental Biology
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Biologie , Medizin
    Zusätzliches Material: 8 Ill.
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
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  • 6
    Digitale Medien
    Digitale Medien
    New York, NY : Wiley-Blackwell
    Journal of Morphology 133 (1971), S. 273-280 
    ISSN: 0362-2525
    Schlagwort(e): Life and Medical Sciences ; Cell & Developmental Biology
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Biologie , Medizin
    Notizen: The cloacal sacs of Leptotyphlops dulcis are nonglandular, posterior evaginations of the cloaca. The median cloacal gland is tubuloalveolar. Similar unpaired cloacal glands as well as paired sacs are noted in certain colubrid snakes. Terminology applied to these cloacal derivatives is discussed, and a standardization of names is provided.
    Zusätzliches Material: 5 Ill.
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
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  • 7
    Digitale Medien
    Digitale Medien
    New York, NY : Wiley-Blackwell
    Journal of Morphology 212 (1992), S. 257-267 
    ISSN: 0362-2525
    Schlagwort(e): Life and Medical Sciences ; Cell & Developmental Biology
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Biologie , Medizin
    Notizen: The ontogeny of various middle-ear structures was examined in 11 groups of chicks between 10 days embryonic and adult. Measurements of the tympanic membrane surface area and height, columella length, and that of the columella footplate, annular ligament, and oval window area were obtained using video micrographs and computer digitization techniques. The oval window matures first at 53 days post-hatching, whereas the columella achieves adult size at 74 days. The tympanic membrane surface area is the last middle-ear variable studied to reach adult size (79 days post-hatch). The columella increases its length from 0.63 mm (10 days embryonic) to 2.73 mm in the adult. The tympanic membrane area expands by 280% whereas the columellar footplate area increases by 11x. As a result, the pressure amplification of the middle ear due to the tympanic membrane/columellar footplate area ratio improves by over 400%. These data further contribute to our understanding of the functional development of the middle ear. © 1992 Wiley-Liss, Inc.
    Zusätzliches Material: 9 Ill.
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
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  • 8
    Digitale Medien
    Digitale Medien
    New York, NY : Wiley-Blackwell
    Journal of Morphology 176 (1983), S. 249-259 
    ISSN: 0362-2525
    Schlagwort(e): Life and Medical Sciences ; Cell & Developmental Biology
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Biologie , Medizin
    Notizen: The development of middle-ear structures in the mouse was examined in nine groups of pups between 1 and 45 days of age. The area of the tympanic membrane (pars tensa and pars flaccida), the length of the lever arms of the malleus and incus, the surface area of the oval window, and the volume of the bulla all showed systematic changes during neonatal life. The area of the oval window reached maturity first and the lever arms achieved 90% of their adult size on day 11. The tympanic membrane achieved the same criterion on day 18. These data help us further to understand the processes that contribute to the functional ontogeny of the middle ear.
    Zusätzliches Material: 9 Ill.
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
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  • 9
    Digitale Medien
    Digitale Medien
    New York, NY : Wiley-Blackwell
    Journal of Morphology 226 (1995), S. 47-77 
    ISSN: 0362-2525
    Schlagwort(e): Life and Medical Sciences ; Cell & Developmental Biology
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Biologie , Medizin
    Notizen: Intratendinous ossification (tenostosis; Tendo ossificans) is a distinct structural form feature of the avian musculoskeletal system with different definitions in terms of morphogenesis, resultant morphology, and functional role(s). Interpretation of these structural elements and their pattern(s) among avian taxa at different systematic levels is reviewed with regard to age-related changes in tendon, form features in avian phylogeny, and adaptive features in biomechanics and kinematics of locomotion. Specific examples of patterns in the musculoskeletal elements of the head and hyolingual system, axial (vertebral) system, and the limbs in several avian taxa are given. A series of questions is formulated as a prospectus for further study. © 1995 Wiley-Liss, Inc.
    Zusätzliches Material: 11 Ill.
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
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  • 10
    Digitale Medien
    Digitale Medien
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Cellular Physiology 88 (1976), S. 277-286 
    ISSN: 0021-9541
    Schlagwort(e): Life and Medical Sciences ; Cell & Developmental Biology
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Biologie , Medizin
    Notizen: The effect of serum on the growth properties of non-transformed Balb 3T3 A31 and SV40-transformed Balb 3T3 A31 was studied. The concentration of serum in the growth medium of non-transformed cells had little effect on the initial population doubling time, but did regulate the cell density at which the population became quiescent in G1. The doubling time of transformed cells, however, was increased significantly as the concentration of serum was decreased below 4%. This effect on the growth of transformed cells was seen at serum concentrations so low that non-transformed cells did not complete one population doubling. Flow microfluorometric analysis of these populations indicated that the primary effect of different serum concentrations on the non-transformed cells was to modulate the average residence time in G1; whereas, all the cell cycle phases of the transformed cells were affected by serum. At saturation densities, the non-transformed cells became quiescent in G1, but the transformed cells still traversed the cell cycle and their saturation density appeared to be a balance between cell production and cell death occurring primarily in the G1 phase of the cell cycle.
    Zusätzliches Material: 5 Ill.
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
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