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  • Springer  (18)
  • Society of Economic Geologists (SEG)
  • 1990-1994  (9)
  • 1980-1984  (9)
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  • 1
    Electronic Resource
    Electronic Resource
    Components of phototaxis of the nematode Mermis nigrescens (1990)
    Springer
    Journal of comparative physiology 167 (1990), S. 245-255 
    Details
    ISSN: 1432-1351
    Keywords: Undulatory locomotion ; Scanning motion ; Directed turn ; Orientation ; Phototaxis ; Klinotaxis ; Photomovement ; Nematode
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary The gravid females of Mermis are positively phototaxic at the time of their migration to egglaying sites in vegetation on which their grasshopper hosts feed. On a horizontal felt surface, segments of the path traced by the tail are oriented approximately towards a source of monochromatic light in the 350–540 nm region, but are not oriented at longer wavelengths and in the dark. The components of this phototaxis include locomotion by the posterior 4/5 of the body, orientational bending of the neck region while the anterior is held above the substrate, and a scanning motion (bending) of the head region (anterior 2 mm). Like other nematodes and snakes, propulsion is associated with posteriorly propagated body waves, but unlike other animals known, the waves tend to lie perpendicular to a felt surface, and unlike other nematodes, contact with the surface is on the female's ventral surface. The body waves are initiated by the motion of the anterior 1/5 (15 mm) of the body, the average orientation of which determines the path of the following 4/5. During phototaxis, the anterior tip is swung both sideways and vertically about the direction towards the light source. The tip motion is a result of a scanning motion of the head and a slower orientational bending of the neck. The base of the head appears to be actively directed towards the source by the bending of the neck. This behavior can resolve two light sources positioned 120° apart but not 90° apart. The scanning motion of the head is independent of neck orientation and appears to enhance the probability of discovering the direction of a new source. Discovery is followed by a directed turn of the base of the head towards the source which is initiated by the bending of the neck. Locomotion of the body follows the path of the anterior through the turn and phototaxis is thus initiated.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00188117
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  • 2
    Electronic Resource
    Electronic Resource
    Intragenomic DNA sequence homologies in the chicken and other members of the classAves: DNA re-association under reduced stringency conditions (1980)
    Springer
    Journal of molecular evolution 15 (1980), S. 291-307 
    Details
    ISSN: 1432-1432
    Keywords: Avian genome evolution ; Intragenomic DNA sequence homology Reduced-stringency DNA reassociation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary We have investigated the intragenomic DNA sequence homologies of twelve species of birds representing five orders, and emphasizing Galliformes. This study differs in two important ways from the classical approaches taken in constructing and evaluating phylogenies based on DNA sequence similarities. Comparisons are made on the basis of sequence homologieswithin genomes of related birds, rather than between genomes. DNA is reassociated at 50°C in 0.5M phosphate buffer; these conditions allow formation and detection of duplexes containing more mismatch than would normally be permitted using more stringent conditions, affording an opportunity to observe more ancient sequence homologies. Thermal stability profiles of DNA duplexes formed under these conditions are the basis of comparison; three general patterns were observed. This approach emphasizes differences in sequence composition between genomes while the more traditional method of intergenomic tracer DNA hybridization at higher stringency emphasizes sequence similarities. No correlation was found between taxonomic position and intragenomic sequence composition, either within or between lineages. The thermal stability profiles of DNA duplexes formed within avian genomes did not reflect the biological similarities inferred from morphology, karyotype, and studies of interspecific hybridization. While all of the differences observed could have occurred over geological time, it was surprising that the genomes of the domestic chicken and the Red Jungle Fowl (Gallus gallus) differ in their sequence compositions. It appears that amplification/reduction events and/or positional changes occur rather often during evolution of a lineage.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01733136
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  • 3
    Electronic Resource
    Electronic Resource
    Scanning motion, ocellar morphology and orientation mechanisms in the phototaxis of the nematode Mermis nigrescens (1990)
    Springer
    Journal of comparative physiology 167 (1990), S. 257-268 
    Details
    ISSN: 1432-1351
    Keywords: Scanning motion ; Shadowing ; Ocellus ; Mechanism ; Orientation ; Phototaxis ; Klinotaxis ; Photomovement ; Transverse phototaxis ; Nematode
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary The putative ocellus of Mermis females consists of a hollow cylinder of dense hemoglobin pigmentation located in the anterior tip. The exact location of the photoreceptive nerve endings, however, is unknown. During phototaxis a continual bending or scanning motion of the head (anterior 2 mm) causes the orientation of the tip to swing about the direction of the source. By turning off (shuttering) the light source whenever the tip orientation was to one side of the source direction, the average orientation of the base of the head, and eventually the body orientation, was caused to be biased about 28° to the opposite side. Because the shuttering was synchronized with the scanning motion, the scanning motion must be involved in the maintenance of orientation to light. The direction of the bias rules out a two-signal comparison mechanism of orientation and demonstrates that a deviation of the tip from the source direction must decrease, rather than increase, the illumination of the photoreceptors. These findings, and the ocellar morphology, require that the photoreceptors be located inside the hollow tube of pigmentation where they can be shadowed by the pigment during deviations of the tip. Focusing by the curved anterior end should cause a similar modulation of the illumination at this location. The occasional episodes of transverse phototaxis can be explained by the leakiness of the pigment walls to transverse illumination. Analysis of the motion of the anterior in the presence and absence of shuttering indicates that the orientation of the base of the head, due to the motion of the neck, is controlled by the signals generated during one or more cycles of the scanning motion of the head. The orientation may be regulated by the phase relationship between the photoreceptor signal and putative proprioceptive signals that indicate the bending in the head.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00188118
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  • 4
    Electronic Resource
    Electronic Resource
    Contribution of collagen and mineral to the elastic anisotropy of bone (1994)
    Springer
    Calcified tissue international 55 (1994), S. 381-386 
    Details
    ISSN: 1432-0827
    Keywords: Acoustic microscopy ; Bone ; Collagen fiber ; Elastic anisotropy ; Mineral crystal
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine , Physics
    Notes: Abstract It has long been thought that collagen fibers within the bone matrix are deposited in an aligned pattern that channels mineral growth. If this model of bone structure is correct, both organic and inorganic phases of bone should have similar elastic anisotropy. Using an acoustic microscope, we measured longitudinal and transverse acoustic velocities of cortical specimens taken from 10 dog femurs before and after removal of either the mineral (using 10% EDTA) or collagen phases (using 7% sodium hypochlorite) and calculated longitudinal (CL) and transverse (CT) elastic coefficients. The anisotropy ratio (CL/CT) decreased significantly after demineralization (1.61 before versus 1.06 after, P〈0.0001, paired t-test). However, there was no significant change after decollagenization (1.51 before versus 1.48 after, P=0.617, paired t-test). We conclude that the orientation of mineral crystals is the primary determinant of bone anisotropy, and the collagen matrix within osteonal bone has little directional orientation.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00299319
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  • 5
    Electronic Resource
    Electronic Resource
    Remodeling and the repair of fatigue damage (1993)
    Springer
    Calcified tissue international 53 (1993), S. S75 
    Details
    ISSN: 1432-0827
    Keywords: Microdamage ; Remodeling ; Fatigue ; Osteoporosis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine , Physics
    Notes: Summary This paper reviews the direct and indirect evidence for and against the idea that bone remodeling repairs fatigue damage. It defines experiments that should be performed to determine whether the accumulation and repair of fatigue damage is relevant to the pathogenesis of osteoporotic fracture. The experimental evidence favors the hypothesis that microdamage evokes local remodeling. The data suggest that the balance between the microdamage burden and bone repair is nearly constant. The indirect evidence comes from clinical observations that show positive relationships between depressed bone formation rate or prolonged remodeling period with bone fracture. More compelling indirect evidence comes from studies in which bone remodeling was pharmaceutically depressed, and fracture incidence rose in direct proportion. Data on microdamage accumulation were not collected in these studies. Conversely, some experimental evidence disputes a direct relationship between fatigue microdamage and repair. In these studies, increased amounts of bone microdamage in hyperadrenocortical dogs, and in irradiated dogs, could not be demonstrated even though bone fragility increased without associated osteopenia. Finally, the indirect evidence that argues that microdamage does not initiate repair is based on inference and does not provide an adequate test of the hypothesis. In balance, the current body of evidence favors the contention that bone remodeling repairs fatigue damage and thereby prevents fracture. Future studies should verify that microdamage accumulates when bone fracture occurs in conjunction with depressed remodeling activation frequency.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01673407
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  • 6
    Electronic Resource
    Electronic Resource
    Lead exposure from conventional and cottage lead smelting in Jamaica (1991)
    Springer
    Archives of environmental contamination and toxicology 21 (1991), S. 65-71 
    Details
    ISSN: 1432-0703
    Source: Springer Online Journal Archives 1860-2000
    Topics: Energy, Environment Protection, Nuclear Power Engineering , Medicine
    Notes: Abstract A survey was conducted to determine the distribution and determinants of environmental and blood lead levels near a conventional and several cottage lead smelters and to assess the relationship between environmental and blood lead levels in a tropical, developing-country setting. Fifty-eight households were studied in the Red Pond community, the site of the established smelter and several backyard smelters, and 21 households were studied in the adjacent, upwind Ebony Vale community in Saint Catherine Parish, Jamaica. Households were investigated, using questionnaires, soil and housedust lead measurements, and blood lead (PbB) measurements from 372 residents. Soil lead levels in Red Pond exceeded 500 parts per million (ppm) at 24% of households (maximum-18,600 ppm), compared to 0% in Ebony Vale (maximum 150 ppm). Geometric mean PbB in Red Pond, where 44% of children 〈6 years of age had PbB levels ≥ 25 micrograms per deciliter (μg/dL), was more than twice that Ebony Vale in all age groups (p 〈 0.0005). Within Red Pond, proximity to backyard smelters and to the conventional smelter were independent predictors of soil lead (p 〈 0.05). Soil lead was the strongest predictor of PbB among Red Pond subjects under 12 years of age. The blood lead-soil lead relationship in children differed from that reported in developed countries; blood lead levels were higher than expected for the household-specific soil lead levels that were observed. These data indicate that cottage lead smelters, like conventional ones, are a hazard for nearby residents and that children exposed to lead contamination in tropical, developing countries may be at higher risk for developing elevated blood lead levels than similarly-exposed children in developed countries.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01055558
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  • 7
    Electronic Resource
    Electronic Resource
    Ovarian development in 46,XY gonadal dysgenesis (1982)
    Springer
    Human genetics 〈Berlin〉 60 (1982), S. 196-199 
    Details
    ISSN: 1432-1203
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary In human the XY ovary is degenerative, there being scant evidence of persistence of that organ beyond the perinatal period. Here we describe indications of functional ovarian tissue in a 17-year-old female with male karyotype, H-Y+ cellular phenotype, and some signs of the Turner syndrome. Her gonads were removed after the onset of secondary amenorrhea. Histological examination revealed a degenerative right ovary devoid of germ cells and follicles, and a left streak gonad. There was no trace of testicular development in either side.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00569712
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  • 8
    Electronic Resource
    Electronic Resource
    Sequence, identification and characterization of cDNAs encoding two different members of the 18 kDa heat shock family of Zea mays L. (1991)
    Springer
    Plant molecular biology 16 (1991), S. 699-711 
    Details
    ISSN: 1573-5028
    Keywords: heat shock ; heat shock cDNAs ; maize ; small heat shock proteins
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Heat-shocked maize seedlings (cv. Oh43) synthesize a characteristic set of heat-shock proteins (hsps) which include an 18 kDa family containing at least six major isoelectric variants. A cDNA library was constructed from poly(A)+ RNAs isolated from the radicles of heat-shocked maize seedlings and screened with a DNA fragment from the theoretical open reading frame of a putative Black Mexican Sweet maize hsp 18 genomic clone. Two clones, cMHSP18-3 and cMHSP18-9, were isolated, and the RNA transcripts generated from them were translated into proteins which immunoreact with antibodies directed against the maize 18 kDa hsps and exhibit the same electrophoretic characteristics as two different members of the 18 kDa hsp family. Nucleotide sequence analyses of the cDNAs in these clones reveal that their 5′ and 3′ untranslated regions exhibit 33–34% identity and that their protein encoding regions share 93% identity. The deduced amino acid sequences of these clones show 90% identity, and the apparent molecular masses and isoelectric points of these proteins agree with those established for two different 18 kDa hsps, numbered 3 and 6. This report substantiates that at least two of the 18 kDa hsps in maize are products of different but related genes. Moreover, it establishes that transcripts for these proteins accumulate during heat shock and that both their nucleotide and deduced amino acid sequences share extensive similarities with the class VI small hsps in soybean and with transcripts expressed during meiosis in Lilium.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00023434
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  • 9
    Electronic Resource
    Electronic Resource
    Enzootic Aspergillosis in wild Red Vented Cockatoos in the Philippines (1981)
    Springer
    Mycopathologia 73 (1981), S. 21-23 
    Details
    ISSN: 1573-0832
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract Philippine Red Vented Cockatoos were being trapped in the wild and dispersed directly to private homes, aviarys, pet stores and for export to the United States of America. Except for non-aggressive behaviour and tiring easily the subjects showed clinically nothing peculiar. Numerous cases of Aspergillosis with no clinical signs prior to death were being reported at the United States Air Force Base, Clark Field, Angeles City, Philippines. In all cases stress was a predisposing factor to death; such as enclosure in a small bird cage. Those birds in aviarys that were kept free-flying remained clinically normal, with no deaths recorded. Systematiç examination to determine the causative source of infection was carried out and revealed natural infection in the wild state as the cause of disease in caged Red Vented Cockatoos in the Philippines. Examination on three other species of Philippine Pstitticine birds revealed only the Red Vented Cockatoo to be infected or a latent carrier in the wild state.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00443008
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  • 10
    Electronic Resource
    Electronic Resource
    Solar Maximum Mission (1980)
    Springer
    Solar physics 65 (1980), S. 5-14 
    Details
    ISSN: 1573-093X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract The scientific objective of the Solar Maximum Mission is to understand the physics of solar flares. A description is provided for the SMM spacecraft, the scientific planning activity, the observing vprogram and the guest investigator program associated with the mission.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00151380
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