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  • Ultrastructure  (15)
  • bioavailability  (12)
  • Springer  (27)
  • 1980-1984  (27)
  • 1955-1959
  • 1983  (12)
  • 1981  (15)
Collection
Keywords
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  • Springer  (27)
Years
  • 1980-1984  (27)
  • 1955-1959
Year
  • 1
    Electronic Resource
    Electronic Resource
    Ultrastructure of the sperms ofPlumbago zeylanica (1981)
    Springer
    Protoplasma 107 (1981), S. 85-107 
    Details
    ISSN: 1615-6102
    Keywords: Male cytoplasmic inheritance ; Plumbago ; Pollen grain ; Pollen tube ; Sperm ; Ultrastructure
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Male gametes ofPlumbago zeylanica were examined in pollen grains and tubes using light and electron microscopy of chemically and physically fixed tissues, and Nomarski interference microscopy of isolated, living sperm cells. Male gametes are elongate, spindleshaped cells containing a nucleus, mitochondria, ER, ribosomes, vesicles, dictyosomes, probable microfilaments, and a variable number of plastids. In mature pollen grains ofP. zeylanica, the two sperm cells are directly linked; they share a transverse cell wall with plasmodesmata and are enclosed together by the inner vegetative cell plasma membrane. One of these two sperms is also associated with the vegetative nucleus as a consistent feature of pollen grain organization. The basis of this association appears to be a long, narrow projection of the sperm cell (averaging 〈 1 μm wide and about 30 μm long) which wraps around the periphery of the vegetative nucleus and occupies embayments of that nucleus. This association is maintained throughout pollen tube growth but becomes less extensive near the completion of tube growth and is severed following tube discharge. The consistent occurrence of the sperm-vegetative nucleus association in pollen grains, tubes and isolated pollen cytoplasm suggests that the two structures may be directly connected, but attempts to visualize this type of connection were unsuccessful. Possibly, the entwining nature and extent of complementary interfaces between vegetative nucleus and sperm may have a role in stabilizing their association. Functionally, the two sperms and vegetative nucleus appear to travel as a linked unit within the pollen tube, possibly increasing the effectiveness of gamete delivery and helping to ensure nearly simultaneous transmission of sperms into the receptive megagametophyte.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01275610
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  • 2
    Electronic Resource
    Electronic Resource
    Evaluation of medigoxin in outpatients (1981)
    Springer
    European journal of clinical pharmacology 19 (1981), S. 251-258 
    Details
    ISSN: 1432-1041
    Keywords: medigoxin ; digoxin ; dissolution rate ; proportionality ; bioavailability ; prediction
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary We compared our ability to predict the dose of medigoxin and of digoxin required to achieve a fixed serum concentration (the dose requirement) in 33 outpatients. Preliminary work supported the assumptions that the steady state glycoside concentration achieved was proportional to the daily dose given to an individual, and that the bioavailability of the different tablet presentations was similar for either glycoside. We were not able to predict the dose requirement from patient characteristics with any more certainty for medigoxin than for digoxin. Not only the between-patient variability in dose requirement, but also the within-patient variability, was similar for the two glycosides. However the digoxin used had a dissolution rate of over 90% in 1 h. When comparing medigoxin with digoxin of lower, or more variable dissolution rate, medigoxin may be preferable.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00562801
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  • 3
    Electronic Resource
    Electronic Resource
    Bioavailability and diurnal variation in absorption of sustained release theophylline in asthmatic children (1983)
    Springer
    European journal of clinical pharmacology 25 (1983), S. 667-672 
    Details
    ISSN: 1432-1041
    Keywords: theophylline ; asthma ; children ; sustained-release ; diurnal ; absorption ; bioavailability
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary The absolute oral bioavailability of a sustained release theophylline tablet (Nuelin-SR250), given 12 hourly was determined in 14 asthmatic children aged 5 to 13 years. In 4 of the patients, mean bioavailability of the fourth dose was 38.9±8.4% and that of the sixth dose was 67.9±25.9% (p〈0.05) in the other ten patients. This suggests steady-state had not been achieved after four doses. In the initial study with 9 patients, a significant diurnal variation in predose plasma theophylline concentrations was observed, as the mean morning predose concentrations were 2.9 fold greater than the mean evening predose concentrations (p〈0.005). Dual peak plasma concentrations occurred in 5 out of the 9 patients. The mechanism of this diurnal variation was investigated in a further 5 asthmatic children (10.8 years ±1.6). Morning and night steady-state plasma theophylline concentrations during a continuous intravenous infusion of aminophylline were not different (14.9±5.3 mg/l vs. 15.6±5.9 mg/l), demonstrating that there was no diurnal variation in the plasma clearance of theophylline. The diurnal variation in predose concentrations with Neulin-SR250 was confirmed with the morning concentrations again being 2.6 fold greater than those in the evening. However, bioavailability was not significantly different for day (09.00–21.00) and night (21.00–09.00) dosing intervals after doses 6 and 7 respectively of Nuelin-SR250. The plasma concentration versus time profiles suggested that the diurnal variation in predose concentrations was due to slower absorption of the evening dose.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00542356
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  • 4
    Electronic Resource
    Electronic Resource
    The effects of nitrogen limitation on the ultrastructure of the cyanobacterium Agmenellum quadruplicatum (1981)
    Springer
    Archives of microbiology 130 (1981), S. 204-212 
    Details
    ISSN: 1432-072X
    Keywords: Agmenellum quadruplicatum ; Nitrogen starvation ; Ultrastructure ; PATO poststain ; Cyanobacteria
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The effects of nitrogen limitation on the ultrastructure of the unicellular cyanobacterium, Agmenellum quadruplicatum, were studied by thin sectioning transmission electron microscopy. Nitrogen became limiting for growth 14–15 h after transfer to nitrogen-limiting medium, but cultures retained full viability for at least 45 h. The c-phycocyanin: chlorophyll a ratio and cellular nitrogen content of the culture dropped rapidly after 14–15 h, as a progressive deterioration of major cell structures took place. Phycobilisomes were degraded first, followed by ribosomes and, then, thylakoid membranes. These structures were virtually depleted from the cells within 26 h. Intracellular polysaccharide accumulated in place of the normal cell structures throughout this period. Nitrogen limitation did not affect polyphosphate bodies, carboxysomes, lipid granules, the cell envelope, or the extra-cellular glycocalyx. All of the ultrastructural changes resulting from nitrogen limitation were reversed upon addition of nitrate to a starved culture. Most cell structures were restored within 3 h, and restoration was complete within 9 h.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00459520
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  • 5
    Electronic Resource
    Electronic Resource
    Stomatal pore and cuticle formation inFunaria (1983)
    Springer
    Protoplasma 116 (1983), S. 1-13 
    Details
    ISSN: 1615-6102
    Keywords: Cuticle ; Peristomatal transpiration ; Stomata ; Ultrastructure ; Funaria
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Cuticle and pore development in the guard cells ofFunaria were investigated with the electron microscope. Pore cuticle formation is simultaneous with the creation of the pore itself. The morphology of the pore cuticle is unlike that of any cuticle described in the literature. It has many lamellae which are penetrated by electron dense fibrils. Three different cuticular morphologies exist from the pore to the subsidiary cell walls. The cuticles on the pore and outer walls contain fibrils that sometimes reach to the surface. The subsidiary cell cuticle lacks fibrils altogether. It is hypothesized that (1) cuticularization of the middle lamella contributes to ventral wall separation and (2) differences in extent of cuticular fibrils are related to greater water loss from stomata than from subsidiary cells (peristomatal transpiration).
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01294225
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  • 6
    Electronic Resource
    Electronic Resource
    Topography, ultrastructure and phagocytic capacity of avian lymph nodes (1983)
    Springer
    Cell & tissue research 228 (1983), S. 389-403 
    Details
    ISSN: 1432-0878
    Keywords: Lymph node, avian ; Ultrastructure ; Macrophages ; Phagocytic capacity
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary The structure of the avian lymph node (ALN) is characterized by a thin capsule, thin lymphoreticular cords, and an absence of trabeculae. It is not possible to subdivide the ALN into cortex, paracortex and medulla, or to subdivide the system of sinuses into marginal, trabecular and medullary divisions. The lymphoreticular cords contain avian germinal centers (AGC) with B-lymphocytes and the area of T-lymphocytes. Postcapillary venules are responsible for the recirculation of lymphocytes. Sinus reticular cells do not exist in the ALN, but free macrophages are present. The phagocytic capacity of the macrophages was determined by injection of vital dyes (India ink, Berlin blue) and inoculation with Candida cells. Macrophages filled with markers migrate from the lymph sinuses into the lymphoreticular cords and further into the AGC. The mobility of the macrophages is remarkably lower after phagocytosis of Candida cells.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00204887
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  • 7
    Electronic Resource
    Electronic Resource
    Ultrastructure of differentiating preameloblasts from tooth germs of the permanent dentition ofMacaca mulatta andMacaca arctoides (1981)
    Springer
    Calcified tissue international 33 (1981), S. 603-618 
    Details
    ISSN: 1432-0827
    Keywords: Preameloblasts ; Tooth germs ; Monkey ; Enamel ; Ultrastructure
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine , Physics
    Notes: Summary Cytodifferentiation of inner enamel epithelium and the adjacent connective tissue from the tip of the cervical loop to the initiation of enamel elaboration in twoMacaca species was examined. Ten- to twelve-month-old specimens were fixed by perfusion and the permanent tooth buds were prepared for transmission electron microscopy. At the cervical loop proper, inner enamel epithelium cells have lobed nuclei, a paucity of cytoplasm, and wide extracellular spaces; the basal lamina facing the dental papilla is straight. With increasing distance from the tip of the cervical loop, the following changes occur gradually: (a) preameloblasts elongate from 15 to 45 µm, and their organelles, particularly mitochondria and profiles of rough endoplasmic reticulum, become more numerous; (b) extracellular spaces decrease between preameloblasts starting at the basal (infranuclear) end; (c) the basement membrane becomes convoluted and associated with aperiodic fibers; (d) preodontoblast projections penetrate the aperiodic fibers; (e) collagen fibers subjacent to the basement membrane increase in density, with particularly thick fibers paralleling the aperiodic fibers. These modifications occur within three-fourths of the distance from the tip of the cervical loop to the mineralization front. The condensation of preodontoblasts is followed immediately by predentin synthesis. Concomitantly, the basement membrane breaks down and the aperiodic fibers are engulfed by preameloblasts. Preameloblast projections penetrate junctional predentin, contact mineralized dentin, and enamel synthesis ensues. At this stage the ameloblast is 45 µm long, the nucleus is central or basal, the Golgi apparatus has migrated apically, but the Tomes' process has not yet formed. The results indicate that odontogenesis inMacaca monkeys more closely resembles human odontogenesis than does that in the murine rodents.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02409498
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  • 8
    Electronic Resource
    Electronic Resource
    Pharmacokinetics of triamterene after i.v. administration to man: Determination of bioavailability (1983)
    Springer
    European journal of clinical pharmacology 25 (1983), S. 237-241 
    Details
    ISSN: 1432-1041
    Keywords: triamterene ; bioavailability ; pharmacokinetics ; metabolism ; hydroxy triamterene sulphate ; urinary excretion ; i.v. administration ; first-pass-effect
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary With a new formulation, which made intravenous infusion of triamterene (TA) possible, plasma levels and urinary excretion rates of TA and its main metabolite (OH-TA-ester) were measured in a randomized, cross-over trial in 6 healthy volunteers given triamterene 10 mg i.v. and 50 mg p.o. TA and OH-TA-ester were determined by densitometric measurement of native fluorescence after thin layer chromatography. Distribution volumes of the central compartment of TA and OH-TA-ester were 1.49 l/kg and 0.11 l/kg, respectively. Terminal half-lives were 255 min for TA and 188 min for OH-TA-ester after i.v. administration. For TA total plasma clearance was 4.5 l/min and renal plasma clearance 0.22 l/kg. The formation of OH-TA-ester was very rapid and the concentration of the metabolite exceeded that of TA at all times. After i.v. administration the urinary recovery of TA and OH-TA-ester was 4.4% and 50.9%, respectively. The bioavailability of TA was 52%, corresponding to absorption of 83%. TA is partly eliminated by a first-pass-effect. The main metabolite of TA is OH-TA-ester, which is pharmacologically active.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00543797
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  • 9
    Electronic Resource
    Electronic Resource
    Effect of dose on bioavailability of oral digoxin (1981)
    Springer
    European journal of clinical pharmacology 19 (1981), S. 53-55 
    Details
    ISSN: 1432-1041
    Keywords: digoxin ; bioavailability ; dose-dependency ; urinary excretion ; healthy volunteers
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary Nine healthy volunteers received single 0.25, 0.5, 1.0, 1.5, and 2.0 mg doses of oral digoxin tablets in random sequence on five occasions separated by at least 4 weeks. Urinary excretion of immunoassayable digoxin was determined from 8 consecutive 24 h urine samples collected after each dose. Mean values of cumulative urinary excretion of digoxin at the 5 doses were: 40.9, 35.6, 36.4, 34.1, and 33.5% of the dose (F=0.64; d. f.=4.32; N. S.). Mean values of urinary excretion half-life were: 2.48, 2.03, 2.20, 2.07, and 1.87 days (F=2.87; d. f.=4.32;p=0.05). Thus, the bioavailability of orally administered digoxin tablets in healthy volunteers is dose-independent over an 8-fold range of doses.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00558384
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  • 10
    Electronic Resource
    Electronic Resource
    Bioavailability of ketoprofen in man with and without concomitant administration of aluminium phosphate (1981)
    Springer
    European journal of clinical pharmacology 19 (1981), S. 305-307 
    Details
    ISSN: 1432-1041
    Keywords: ketoprofen ; aluminium phosphate ; bioavailability ; antacid ; pharmacokinetics ; interaction study
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary The purpose of this study was to determine whether a concomitant single dose of antacid (aluminium phosphate), or multiple doses of this antacid, administered prior to and with ketoprofen would alter the bioavailability of this non steroidal anti-inflammatory agent. The possible effects of aluminium phosphate were evaluated following administration of ketoprofen alone (Phase I), co-administration of antacid and ketoprofen (Phase II), and antacid for four days before administration of ketoprofen with co-administration on the day of the study (Phase III). There were no significant differences between treatment means for peak plasma concentration, time to peak plasma concentration, and area under the plasma concentration-time curve. The observed differences were due only to individual effects. The results indicate a lack of interaction between ketoprofen and the antacid aluminium phosphate (Phosphalugel)
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00562809
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