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  • 1
    Electronic Resource
    Electronic Resource
    In vitro analysis of fetal fibroblast collagenolytic activity (1997)
    Oxford, UK : Blackwell Science
    Wound repair and regeneration 5 (1997), S. 0 
    Details
    ISSN: 1524-475X
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Tissue repair in the rabbit fetus is remarkably rapid and occurs without significant inflammation or excessive collagen deposition. The objective of this study was to compare the ability of rabbit fetal and adult fibroblasts to express the matrix metalloproteinases which are thought to be critical to scar tissue remodeling. In vitro, both fetal and adult rabbit fibroblasts express procollagenase messenger RNA in a constitutive manner. Mechanical disruption of fetal fibroblast monolayers caused a twofold increase in procollagenase mRNA. In contrast, the adult rabbit fibroblast procollagenase mRNA remained unchanged. The mRNA data correlated well with enzyme protein levels. Quantitation by immunoprecipitation showed a 2.3-fold increase in fetal fibroblast procollagenase protein after mechanical injury, whereas the level in adult rabbit fibroblasts remained unchanged. However, it was noted that the constitutive levels of procollagenase mRNA and protein were higher in adult fibroblasts. Analysis of enzyme activity, by means of a fluorogenic substrate, showed that adult fibroblasts had 2.2 times more collagenase activity compared with fetal cells. After mechanical injury, the fetal fibroblast collagenase activity increased 1.3-fold compared with 1.7-fold in the adult fibroblasts. In contrast, fetal fibroblast gelatinase activity was 1.25 times greater than in adult cells and increased 1.4-fold after mechanical injury, whereas the adult profile remained unchanged. Immunolocalization studies indicated that 1 hour after mechanical injury, procollagenase was produced primarily by fibroblasts along the mechanical injury ridge. By 4 hours after injury, the ridge cells began to migrate out into the open area and procollagenase was noted in adjacent cells of both adult and fetal origin. By 12 and 18 hours, all cells throughout the monolayer were expressing procollagenase. These findings show that in vitro fetal fibroblasts actually had lower levels of procollagenase, but higher levels of gelatinase compared with adult fibroblasts. The increased gelatinase expression may explain why fetal wounds do not have excessive collagen accumulation and heal without a visible scar.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1046/j.1524-475X.1997.50207.x
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  • 2
    Electronic Resource
    Electronic Resource
    Optimization and validation of an ischemic wound model (2005)
    Malden, USA : Blackwell Science Inc
    Wound repair and regeneration 13 (2005), S. 0 
    Details
    ISSN: 1524-475X
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Localized tissue ischemia is a key factor in the development and poor prognosis of chronic wounds. Currently, there are no standardized animal models that provide sufficient tissue to evaluate the effect of modalities that may induce angiogenesis, and in vitro models of angiogenesis do not mimic the complexity of the ischemic wound bed. Therefore, we set out to develop a reproducible ischemic model for use in wound-healing studies. Male Sprague–Dawley rats underwent creation of dorsal bipedicle skin flaps with centrally located excisional wounds. Oxygen tension, wound-breaking strength, wound area, lactate, and wound vascular endothelial growth factor (VEGF) were compared in flaps measuring 2.5 and 2.0 × 11 cm with and without an underlying silicone sheet. We found that the center of the 2.0 cm flap with silicone remains in the critically ischemic range up to 14 days without tissue necrosis (33±4 vs. 49±6 mmHg in controls). Wound healing and breaking strength were significantly impaired and tissue lactate from the center of this flap was 2.9 times greater than tissue from either nonischemic controls and 2.5 cm flap (0.23±0.05 mg/dL/mg sample vs. 0.09±0.02 and 0.08±0.02, respectively). Vascular endothelial growth factor was 2 times greater than the nonischemic control. This ischemic wound model is relatively inexpensive, easy to perform, reproducible, and reliable. The excisional wounds provide sufficient tissue for biochemical and histologic analysis, and are amenable to the evaluation of topical and systemic therapies that may induce angiogenesis or improve wound healing.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1524-475X.2005.00080.x
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  • 3
    Electronic Resource
    Electronic Resource
    Comparison of the polyvinyl alcohol sponge and expanded polytetrafluoroethylene subcutaneous implants as models to evaluate wound healing potential in human beings (1995)
    Oxford, UK : Blackwell Science
    Wound repair and regeneration 3 (1995), S. 0 
    Details
    ISSN: 1524-475X
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Our current understanding of the complex processes involved in wound healing is based mainly on studies of animal models. Although this information has been useful, it may not totally reflect the response found in human beings. For example, human beings have a tendency to either “overheal,” as seen in keloids and hypertrophic scar formation, or have deficient healing, as seen in chronic ulcer formation. No animal models are available to analyze these human clinical pathologic conditions. Therefore the objective of this study was to analyze the wound healing response in a large population (n = 40) of normal healthy human beings as a first step to begin studies of abnormal human wound healing. Simultaneously, a comparison was made between the polyvinyl alcohol implant and the expanded polytetrafluoroethylene implant model. Under sterile conditions with the use of local anesthesia, two preweighed polyvinyl alcohol implants and two standard 6 cm expanded polytetrafluoroethylene implants were placed subcutaneously in the upper arm of each subject. High-performance liquid chromatography was used to quantitate isoleucine and hydroxy-l-proline in acid hydrolysates of each implant. Isoleucine was used as an indicator of protein content in the tissue sample, whereas hydroxyproline reflected collagen content. No infectious or hemorrhagic complications were found in the 40 volunteers included in the study. No significant difference was found in isoleucine or hydroxy-l-proline content between postoperative day 7 polyvinyl alcohol implants and day 14 polyvinyl alcohol implants. In contrast, both isoleucine and hydroxy-l-proline content were significantly increased in day 14 expanded polytetrafluoroethylene implants compared with day 7 implants (p 〈 0.005 and p 〈 0.001, respectively). In addition, the ratio of hydroxy-l-proline to isoleucine was significantly increased in day 14 expanded polytetrafluoroethylene implants compared with day 7 expanded polytetrafluoroethylene and both day 7 and day 14 polyvinyl alcohol implants (p 〈 0.001). This observation suggests that by 14 days implantation of expanded polytetrafluoroethylene stimulated an increased deposition of collagen. No significant differences were found in the hydroxy-l-proline to isoleucine ratios among day 7 expanded polytetrafluoroethylene, day 7 polyvinyl alcohol, and day 14 polyvinyl alcohol implants. Histologic analyses correlated with the biochemical findings. These results suggest that expanded polytetrafluoroethylene may be the preferred implant for studies designed to examine pathologic processes associated with retarded wound healing. In contrast, the polyvinyl alcohol implant may be better suited for studies where a low background response is required. Moreover, the extreme variability in normal healthy volunteers seen in this study correlates clinically with the finding that, among the normal adult human population, there is a heterogeneous wound healing response.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1046/j.1524-475X.1995.30309.x
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  • 4
    Electronic Resource
    Electronic Resource
    X-irradiation effects on growth and metamorphosis of gastropod larvae (Crepidula fornicata): A model for environmental radiation teratogenesis (1986)
    Springer
    Archives of environmental contamination and toxicology 15 (1986), S. 227-234 
    Details
    ISSN: 1432-0703
    Source: Springer Online Journal Archives 1860-2000
    Topics: Energy, Environment Protection, Nuclear Power Engineering , Medicine
    Notes: Abstract Little information is available on the effects of x-irradiation on the development of multicellular marine organisms. Larvae of the marine gastropodCrepidula fornicata were irradiated at 200 rad/min, 250 kVp x-rays, to doses between 500 and 20,000 rad in a single fraction. During the weeks following exposure, changes in shell length and biomass, incidence of metamorphosis to the juvenile stage of development, and mortality were measured. The results over a 20-day period demonstrated a dose-dependent decrease in growth rate of larval shells following doses above 2,000 rad (control at day 20=850±110 μm length, 820±11 μm for 500 rad, 750±30 μm for 2,000 rad, 710±30 μm for 5,000 rad, 620±30 μm for 10,000 rad, and 580±15 μm for 20,000 rad). Shell length-specific biomass was significantly decreased for doses above 10,000 rad. A significant increase in larval mortality was detected with doses above 2,000 rad. The cumulative percent of larval metamorphosis was decreased by exposures to 5,000 rad and was detectable as early as 18 days after irradiation; however, metamorphosis of larvae after 5,000 rad occurred faster by day 21 while other groups metamorphosis required 34–35 days for completion.Crepidula fornicata may provide a very sensitive and convenient system in which to study teratogenic effects of x-irradiation on multicellular organisms.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01059971
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  • 5
    Electronic Resource
    Electronic Resource
    Natural Disasters and Primate Populations: The Effects of a 2-Year Drought on a Naturally Occurring Population of Ring-Tailed Lemurs (Lemur catta) in Southwestern Madagascar (1999)
    Springer
    International journal of primatology 20 (1999), S. 69-84 
    Details
    ISSN: 1573-8604
    Keywords: drought ; ring-tailed lemurs ; environmental effects ; mortality
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract We examine demographic patterns from a long-term study (1987–1996) of the population of ring-tailed lemurs in the Beza-Mahafaly Special Reserve, in southwestern Madagascar. In particular, we focus on the effects that a severe drought in 1991 and 1992 had on the population. The population of adult animals peaked in 1991 but decreased rapidly during the subsequent drought and immediate postdrought years. In the 1992 birth season (and second year of the drought) infant mortality reached 80%, and 20.8% of all adult females in the reserve died. The following year, adult female mortality reached a high of 29.9%. Juvenile mortality in 3 intensively studied groups was 57% during the second year of the drought. We compare these data with infant, juvenile, and adult female mortality in non-drought years. We are not able to calculate adult male mortality, as they often emigrate from the reserve to the adjacent forest; however, in the same 3 intensively studied groups, 89% of the males disappeared during the 2 immediate postdrought years. By 1996, the population had begun to recover after the decline that correlated with the drought conditions. Annual reproduction, high birth rates (.80–.86 annually), early sexual maturity, and dietary adaptability may be contributing factors to the recovery. Effects of and recovery from this type of natural disaster in the Beza Mahafaly ring-tailed lemur population parallel responses of some species of macaques and baboons with respect to the adaptability of edge species.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1020584200807
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  • 6
    Electronic Resource
    Electronic Resource
    The social development of free-ranging infantLemur catta at Berenty reserve, Madagascar (1990)
    Springer
    International journal of primatology 11 (1990), S. 297-318 
    Details
    ISSN: 1573-8604
    Keywords: Lemur catta ; infants ; social development ; sex differences ; rank differences
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The social development of 11 free-ranging infantLemur catta was examined over the first 16 weeks of the infants' lives. By 16 weeks, infants still occasionally suckled and were carried dorsally, but on the whole, they were independent of their mothers. Sex or mother's rank was not found to affect frequency or type of play behavior. Mother's rank had no effect on frequency of maternal rejections, from the nipple or from riding, but female infants were rejected slightly more frequently than males were. Mothers tended to reject infants more severely and more frequently from dorsal riding than from the nipple. Sex and rank differences were not found with respect to behaviors determined as measures of independence; however, lower-ranking infants engaged in significantly more “dependent” behaviors than higher-ranking young did. It may be necessary for the infant of a low-ranking mother to maintain closer proximity to its mother for a longer period of time during infancy because such infants may be subject to abuse by higher-ranking group members and, furthermore, may not be as readily rescued in a stressful or dangerous situation as a higher-ranking infant. Sex was not found to be a factor in terms of measures of dependence. The lack of sex differences in developmental behaviors in this species may be related to female dominance, as well as to the fact that, as adults, both sexes engage in aggressive territorial behavirs.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02193002
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  • 7
    Electronic Resource
    Electronic Resource
    Why Be Vigilant? The Case of the Alpha Animal (1997)
    Springer
    International journal of primatology 18 (1997), S. 401-414 
    Details
    ISSN: 1573-8604
    Keywords: vigilance behavior ; white-faced capuchins ; ring-tailed lemurs ; alpha individual
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract We compared patterns of vigilance behavior in a male- and a female-dominant species—white-faced capuchins and ring-tailed lemurs—and used the results to test four hypotheses to explain vigilance behavior in primates. Adult male white-faced capuchins spent significantly more time vigilant than females did, and much male vigilance appeared to be directed toward males from other social groups. This finding supports the protection of paternity hypothesis. No sex difference existed in vigilance behavior among the ring-tailed lemurs, and subjects of both sexes exhibited more vigilance toward predators/potential predators than toward extragroup conspecifics, which supports the predator detection hypothesis. A trade-off argument, suggesting that females tolerate males in a group in return for greater male vigilance, does not apply to ring-tailed lemurs in our study. In both the male-dominant capuchins and the female-dominant ring-tailed lemurs, the alpha subject in the majority of the study groups was significantly more vigilant than other group members were. In white-faced capuchins, the alpha male mates more often than subordinate males do; therefore, the greater degree of vigilance exhibited by the alpha male may correspond to the protection of his reproductive investment. In ring-tailed lemurs, there can be more than one matriline in a group. Thus, the greater amount of vigilance behavior exhibited by the alpha female may be related to protection of her matriline, which could ultimately lead to greater inclusive fitness. Alpha subjects in our study groups exhibited certain behaviors more frequently or exclusively. Accordingly, there may be a constellation of behaviors characteristic of alpha animals.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1026338501110
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  • 8
    Electronic Resource
    Electronic Resource
    Intermale affiliative behavior in ringtailed lemurs (Lemur catta) at the Beza-Mahafaly reserve, Madagascar (1997)
    Springer
    Primates 38 (1997), S. 15-30 
    Details
    ISSN: 0032-8332
    Keywords: Ringtailed lemurs ; Affiliative behavior ; Adult males
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Intermale affiliative behavior was studied in three groups of naturally occurring ringtailed lemurs over a one-year period. The adult males in the sample exhibited affiliative behavior with all other males in their social groups; but affiliative behavior between some male-male dyads occurred markedly more often than between others. These dyads are called “preferred partnerships.” The formation of preferred partnerships did not appear to be influenced by male dominance rank or age-class. Furthermore, these partnerships were of a short-term nature, and none persisted throughout the entire study period. The following factors may explain the absence of rank or age effects, and the brevity of preferred partnerships: (1) frequent fluctuation in the male dominance hierarchy in each study group; (2) the fact that higher-ranking males may not offer specific benefits to lower-ranking males; and (3) the fact that male dispersal affected the male membership of each group over the 12-month study period. The focal males engaged in significantly more affiliative behavior during the lactation period compared with the other reproductive seasons. Migration partners may offer each other predator protection during the transfer process, and although males that transfer together do not engage in alliance or coalition behavior towards resident males, males transferring in pairs or threesomes are in a better position to spot and defend themselves against attack by resident males. Migration partners also provide social contact for each other while in the process of immigration.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02385919
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