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  • 1
    Electronic Resource
    Electronic Resource
    Longitudinal Overgrowth of Bone After Osteotomy in Young Rats: Influence of Bone Stability (1997)
    Springer
    Calcified tissue international 60 (1997), S. 391 -393 
    Details
    ISSN: 1432-0827
    Keywords: Key words: Bone growth — Fractures — Osteotomy.
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine , Physics
    Notes: Abstract. One hundred and five 5-week-old male rats were used to study the influence of the stability of an osteotomy on longitudinal overgrowth of the bone. In 45 rats (Group 1) a transverse diaphyseal osteotomy of the right tibia was made; the left tibia was left untreated. In the second 45 rats (Group 2) the right tibia was osteotomized after applying an external fixator; the left tibia underwent a sham operation without osteotomy. Fifteen further rats (Group 3) were used as a nonoperated control group. After being measured at different periods up to 20 weeks, the osteotomized tibiae of the Group 1 (unstable) were 16–25% longer than those of their nontreated limbs (P 〈 0.001). The osteotomized tibiae of the Group 2 (stable) were 6–11% longer than those of the sham-operated opposite limbs (P 〈 0.001). The osteotomized and unstable tibiae were 9–17% longer than the osteotomized and stable tibiae (P 〈 0.001) throughout the whole study. Although several factors have been considered to be responsible for longitudinal bone overgrowth after fracture in young animals, this work suggests that bone's stability plays a decisive role in the final outcome.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s002239900249
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  • 2
    Electronic Resource
    Electronic Resource
    Influence of Skeletal Site of Origin and Donor Age on Osteoblastic Cell Growth and Differentiation (1999)
    Springer
    Calcified tissue international 64 (1999), S. 280-286 
    Details
    ISSN: 1432-0827
    Keywords: Key words: Human osteoblastic cells — Skeletal site — Aging.
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine , Physics
    Notes: Abstract. Bone loss with aging may be due, at least in part, to inadequate bone formation. Moreover, the process of bone aging is known to follow a different pattern throughout the skeleton. In this study, we examined the cell proliferation rate (area under the cell growth curve, AUC) and the secretion of C-terminal type I procollagen (PICP), alkaline phosphatase (ALP), and osteocalcin (OC) in primary cultures of osteoblastic cells from human trabecular bone. Osteoblastic cells were obtained for 168 donors (100 women and 68 men). Ninety-eight bone samples were obtained from subjects undergoing knee arthroplastia, 52 aged 50–70 years (64 ± 5) and 46 over age 70 (73 ± 2). Another 70 bone samples were obtained from subjects undergoing hip arthroplastia; 51 were 50–70 years old (64 ± 4) and 19 were over 70 (75 ± 5). Osteoblastic cells from the older donors had a lower proliferation rate and OC secretion than those from younger subjects. However, ALP secretion was higher in the former subjects, whereas PICP secretion was unchanged. Osteoblastic cells from hip had a lower proliferation rate than those from knee. PICP secretion was also lower and ALP secretion was higher in the former cells. In age-matched cell cultures, osteoblastic cells from the knee had higher proliferation rate and PICP secretion than osteoblastic cells from the hip. However, ALP secretion was lower in knee osteoblastic cells than those from hip only in the younger group. With aging, ALP secretion was found to increase in knee osteoblactic cells, whereas OC secretion decreased in osteoblastic cell cultures from the hip. Our findings suggest that bone loss with aging may be accounted for, at least in part, by a decreased osteoblastic cell proliferation and an increased osteoblastic maturation. In addition, our data indicate that these changes with aging do not occur similarly at different skeletal sites.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s002239900619
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  • 3
    Electronic Resource
    Electronic Resource
    Collision avoidance and resolution multiple access (CARMA) (1998)
    Springer
    Cluster computing 1 (1998), S. 197-212 
    Details
    ISSN: 1573-7543
    Source: Springer Online Journal Archives 1860-2000
    Topics: Computer Science
    Notes: Abstract The collision avoidance and resolution multiple access (CARMA) protocol is presented and analyzed. CARMA uses a collision avoidance handshake in which the sender and receiver exchange a request to send (RTS) and a clear to send (CTS) before the sender transmits any data. CARMA is based on carrier sensing, together with collision resolution based on a deterministic tree-splitting algorithm. For analytical purposes, an upper bound is derived for the average number of steps required to resolve collisions of RTSs using the tree-splitting algorithm. This bound is then applied to the computation of the average channel utilization in a fully connected network with a large number of stations. Under light-load conditions, CARMA achieves the same average throughput as multiple access protocols based on RTS/CTS exchange and carrier sensing. It is also shown that, as the arrival rate of RTSs increases, the throughput achieved by CARMA is close to the maximum throughput that any protocol based on collision avoidance (i.e., RTS/CTS exchange) can achieve if the control packets used to acquire the floor are much smaller than the data packet trains sent by the stations. Simulation results validate the simplifying approximations made in the analytical model. Our analysis results indicate that collision resolution makes floor acquisition multiple access much more effective.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1019089616850
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  • 4
    Electronic Resource
    Electronic Resource
    Enzymatic characterisation of high-palmitic acid sunflower (Helianthus annuus L.) mutants (1999)
    Springer
    Planta 207 (1999), S. 533-538 
    Details
    ISSN: 1432-2048
    Keywords: Key words: Acyl-acyl carrier protein thioesterase ; Fatty acid synthetase II ; Helianthus (seed) ; β-keto-acyl-acyl carrier protein synthetase II ; Mutant fatty acid ; Palmitic acid
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract. Two high-palmitic acid sunflower (Helianthus annuus L.) mutants, CAS-5 and CAS-12, have been biochemically characterised. The enzymatic activities found to be responsible for the mutant characteristics are β-keto-acyl-acyl carrier protein synthetase II (KASII; EC 2.3.1.41) and acyl-acyl carrier protein thioesterase (EC 3.1.2.14). Our data suggest that the high-palmitic acid phenotype observed in both mutant lines is due to the combined effect of a lower KASII activity and a higher thioesterase activity with respect to palmitoyl-acyl carrier protein (16:0-ACP). The level of the latter enzyme appeared to be insufficient to hydrolyse the produced 16:0-ACP completely. As a consequence of this, three new fatty acids appear: palmitoleic acid (16:1 Δ9), asclepic acid (18:1 Δ11), and palmitolinoleic acid (16:2 Δ9 Δ12). These fatty acids should be synthesised from palmitoyl-ACP or a derivative by the action of the stearoyl-ACP desaturase, fatty acid synthetase II and oleoyl-phosphatidylcholine desaturase, respectively.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s004250050514
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  • 5
    Electronic Resource
    Electronic Resource
    Oleate desaturation and acyl turnover in sunflower (Helianthus annuus L.) seed lipids during rapid temperature adaptation (1998)
    Springer
    Planta 205 (1998), S. 595-600 
    Details
    ISSN: 1432-2048
    Keywords: Key words:Helianthus (seed) ; Microsome ; Oil body ; Oleate desaturase ; Temperature adaptation ; Triacylglycerol
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract. In-vivo experiments with developing sunflower (Helianthus annuus L.) seeds demonstrated that oleate desaturase activity was stimulated by low temperature (10 °C), repressed by high temperature (30 °C) and rapidly restored by returning the seeds to low temperature. Within time periods of 2–4 h, in which the de-novo fatty acid synthesis was negligible, the percentages of oleate (18:1) and linoleate (18:2) were modified in the seed lipids as a consequence of temperature adaptation. When the seeds were transferred to low temperature, the 18:2 content increased in all lipids from both microsomal membranes and oil bodies. After shifting to high temperature, the overall 18:2 content remained constant, but the 18:2 content decreased in diacylglycerols, phosphatidylcholine (PC) and other polar lipids of the two fractions and also in triacylglycerols (TAGs) of the microsomes but increased in TAGs of the oil bodies. The results indicate that the mechanism for the rapid adaptation of sunflower seeds to temperature changes involves (i) the synthesis or activation of oleate desaturase at low temperature and the reversible inhibition of this enzyme at high temperature and (ii) the exchange of 18:1 and 18:2 between TAGs and PC. Under both low and high temperature, 18:1 is transferred from reserve TAGs to PC and 18:2 is transferred from PC to reserve TAGs. At low temperature, 18:1 is desaturated to 18:2 thus allowing the enrichment of membrane lipids with 18:2, the excess being stored in reserve TAGs. At high temperature, however, and provided that oleate desaturase is repressed, the membrane lipids become enriched in 18:1 and the oil-body TAGs become enriched in 18:2.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s004250050361
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  • 6
    Electronic Resource
    Electronic Resource
    Inheritance of high palmitic acid content in the seed oil of sunflower mutant CAS-5 (1999)
    Springer
    Theoretical and applied genetics 98 (1999), S. 496-501 
    Details
    ISSN: 1432-2242
    Keywords: Key words Helianthus annuus ; Sunflower mutant ; Palmitic acid ; Inheritance ; Fatty acid composition
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract  Sunflower genotypes with increased levels of palmitic acid (C16 : 0) in the seed oil could be useful for food and industrial applications. The objective of the present study was to determine the inheritance of the high C16 : 0 content in the sunflower mutant line CAS-5 (〉25% of the total oil fatty acids). This mutant was reciprocally crossed with the lines HA-89 (5.7% C16 : 0) and BSD-2-691 (5.4% C16 : 0), the latter being the parental line from which CAS-5 was isolated. No maternal effect for the C16 : 0 content was observed from the analysis of F1 seeds in any of the crosses. The inheritance study of the C16 : 0 content in F1, F2 and BC1F1 seeds from the crosses of CAS-5 with its parental line BSD-2-691 indicated that the segregation fitted a model of two alleles at one locus with partial dominance for the low content. The analysis of the fatty acid composition in the F2 populations from the crosses with HA-89 revealed a segregation fitting a ratio 19 : 38 : 7 for low (〈7.5%), middle (7.5–15%), and high (〉25%) C16 : 0 content, respectively. This segregation was explained on the basis of three loci (P1, P2, P3) each having two alleles showing partial dominance for low content. The genotypes with a high C16 : 0 content were homozygous for the recessive allele p1 and for at least one of the other two recessive alleles, p2 or p3. This model was further confirmed with the analysis of the F3 and the BC1F1 generations. It was concluded that both the recessive alleles p2 and p3 were already present in the BSD-2-691 line, the allele p1 being the result of a mutation from P1. This genetic study will facilitate breeding strategies associated with the incorporation of the high C16 : 0 trait into agronomically acceptable sunflower hybrids.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s001220051097
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  • 7
    Electronic Resource
    Electronic Resource
    Genetic control of high stearic acid content in the seed oil of the sunflower mutant CAS-3 (1999)
    Springer
    Theoretical and applied genetics 99 (1999), S. 663-669 
    Details
    ISSN: 1432-2242
    Keywords: Key words Helianthus annuus ; Sunflower mutant ; Stearic acid ; Oil quality ; Genetic control
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract  A sunflower mutant, CAS-3, with about 25% stearic acid (C18:0) in the seed oil was recently isolated after a chemical-mutagen treatment of RDF-1-532 seeds (8% C18:0). To study the inheritance of the high C18:0 content, CAS-3 was reciprocally crossed to RDF-1–532 and HA-89 (5% C18:0). Significant reciprocal-cross differences were found in one of the two crosses, indicating possible maternal effects. In the CAS-3 and RDF-1–532 crosses, the segregation patterns of the F1, BC1, and F2 populations fitted a one-locus (designated Es1) model with two alleles (Es1, es1) and with partial dominance of low over high C18:0 content. Segregation patterns in the CAS-3 and HA-89 crosses indicated the presence of a second independent locus (designated Es2) with two alleles (Es2, es2), also with partial dominance of low over high C18:0 content. From these results, the proposed genotypes (C18:0 content) of each parent were as follows: CAS-3 (25.0% C18:0) =es1es1es2es2; RDF-1–532 (8.0% C18:0) =Es1Es1es2es2; and HA-89 (4.6% C18:0) =Es1Es1Es2Es2. The relationship between the proposed genotypes and their C18:0 content indicates that the Es1 locus has a greater effect on the C18:0 content than the Es2 locus. Apparently, the mutagenic treatment caused a mutation of Es1 to es1 in RDF-1–532.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s001220051282
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  • 8
    Electronic Resource
    Electronic Resource
    Collision avoidance and resolution multiple access with transmission queues (1999)
    Springer
    Wireless networks 5 (1999), S. 95-109 
    Details
    ISSN: 1572-8196
    Source: Springer Online Journal Archives 1860-2000
    Topics: Electrical Engineering, Measurement and Control Technology , Computer Science
    Notes: Abstract We introduce a stable multiple access protocol for broadcast channels shared by bursty stations, which we call CARMA-NTQ (for collision avoidance and resolution multiple access with non-persistence and transmission queues). Like previous efficient MAC protocols based on tree-splitting algorithms (e.g., DQRAP), CARMA-NTQ maintains a distributed queue for the transmission of data packets and a stack for the transmission of control packets used in collision resolution. However, CARMA-NTQ does not require the mini-slots commonly used in protocols based on collision resolution. CARMA-NTQ dynamically divides the channel into cycles of variable length; each cycle consists of a contention period and a queue-transmission period. The queue-transmission period is a variable-length train of packets, which are transmitted by stations that have been added to the distributed transmission queue by successfully completing a collision-resolution round in a previous contention period. During the contention period, stations with packets to send compete for the right to be added to the data-transmission queue using a deterministic first-success tree-splitting algorithm, so that a new station is added to the transmission queue. A lower bound is derived for the average throughput achieved with CARMA-NTQ as a function of the size of the transmission queue and the number of queue-addition requests that need to be resolved. This bound is based on the upper bound on the average number of collision resolution steps needed to resolve a given number of queue-add requests.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1019178423020
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  • 9
    Electronic Resource
    Electronic Resource
    A sedimentary facies model for perennial and meromictic saline lakes: Holocene Medicine Lake Basin, South Dakota, USA (1995)
    Springer
    Journal of paleolimnology 14 (1995), S. 123-149 
    Details
    ISSN: 1573-0417
    Keywords: sedimentology ; saline lake ; meromixis ; Northern Great Plains ; Holocene
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Geosciences
    Notes: Abstract Medicine lake is a small (about 1 km2), shallow (up to 10 m deep), saline (50–170 g l−1) and meromictic lake formed after the retreat of the Wisconsin ice in the north American Great Plains. Based on a detailed sedimentological analysis of cores, we describe and interpret 13 sedimentary subfacies grouped in 9 associations which characterize the following lacustrine subenvironments: clastic littoral (freshwater and saline), springs, microbial mats, bench slope, and pelagial (oxic, alternating oxic-anoxic, anoxic and hypersaline, and organic-dominated). Lateral distribution and vertical evolution of subfacies in our model are controlled by climate fluctuations, climate-related limnological parameters (lake level, TDS and brine composition, and redox conditions), and autocyclic processes (progressive infilling of the basin and higher sedimentation rate in the pclagial realm). Microbial and chemical processes govern deposition in this system, and meromixis plays a decisive role in lake dynamics. Phototropic bacterial plate communites at the chemocline dominated as pelagial organic producers during stable meromictic periods, whereas benthic microbial communities developed during mixed water periods. Water stratification during the Holocene was mainly controlled by three parameters: 1) basin morphometry, 2) lake level, and 3) differences in TDS values between mixolimnion and monimolimnion waters. Sedimentary facies analyses is a powerful descriptive and interpretative tool that greatly contributes to deciphering the high resolution paleoenvironmental information archived in lake sequences. Depositional and paleoenvironmental models provide a dynamic framework for integrating paleolimnological data and other proxy paleorecords. Medicine lake serves as a facies model for shallow, perennial hypersaline, meromictic lakes in modern and ancient lacustrine basins. The sediment sequence from Medicine lake cores is consistent with the general paleoclimatic evolution of the northern Great Plains since the retreat of ice sheets. Our study reveals a plethora of rapid fluctuations in the water cycle both during the middle and the late Holocene. These augment prior paleoclimate reconstructions based on diatom studies of the lower Holocene freshwater to saline transition and on pollen profiles which show little variability during the subsequent long prairie grass episode.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00735478
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  • 10
    Electronic Resource
    Electronic Resource
    Limnogeology of Laguna Miscanti: evidence for mid to late Holocene moisture changes in the Atacama Altiplano (Northern Chile) (1996)
    Springer
    Journal of paleolimnology 16 (1996), S. 1-21 
    Details
    ISSN: 1573-0417
    Keywords: Atacama ; Holocene ; limnogeology ; South America ; paleoclimatology ; lake sediments
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Geosciences
    Notes: Abstract Sedimentological, mineralogical and geochemical analyses of sediment cores from 9 m-deep, saline Laguna Miscanti, Chile (23 ° 44′S, 67 °46′W, 4140 m a.s.l.) together with high-resolution seismic profiles provide a mid to late Holocene time series of regional environmental change in the Atacama Altiplano constrained by 210Pb and conventional 14C dating. The mid Holocene was the most arid interval since the last glacial maximum, as documented by subaerial exposure and formation of hardgrounds on a playa surface. Extremely low lake levels during the mid Holocene appear consistent with lower effective moisture recorded at other sites along the Altiplano and in the Amazon Basin. Termination of this arid period represented a major shift in the regional environmental dynamics and inaugurated modern atmospheric conditions. The cores show a progressive upward increase in effective moisture interrupted by numerous century-scale drier periods of various intensities and durations that characterize a fluctuating late Holocene climate. In spite of chronological uncertainties, the major environmental changes seem to correlate with the available paleorecords from the region providing a coherent account of effective moisture variability in the tropical highlands of South America.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00173268
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