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991.
JB Jennings 《Canadian Metallurgical Quarterly》1997,27(6):679-691
Symbiosis is a dominant trait in the Platyhelminthes. The Neodermata (Aspidogastrea, Monogenea, Digenea, Udonellidea, Cestoda) are wholly parasitic and even the predominantly free-living Turbellaria have almost 200 species from 35 families living in permanent associations with other animals. In the simplest turbellarian symbioses, ectosymbiotes such as the Temnocephalida, some other Rhabdocoela and a few Tricladida live on the body surfaces or in the branchial chambers of their mainly arthropodan or chelonian hosts. They feed on the same types of prey as their free-living relatives but supplement their diet by opportunistic commensalism. Their digestive physiology and food reserves are the same as in free-living species. The entosymbiotic Umagillidae, Graffillidae, Pterastericolidae, Fecamplidae and Acholadidae live in internal body cavities or body wall derivatives of echinoderms, molluscs or arthropods and show increasing metabolic dependence on their hosts. Patterns of digestive physiology and food storage generally differ markedly from those of ectosymbiotic and free-living species. Some umagillids, in echinoids, feed as entozoic predators on co-symbiotic protozoa, supplemented by opportunistic ingestion of the hosts' ingesta, gut cells or coelomocytes. Others, in holothurians, feed mainly on gut cells, which also provide some digestive enzymes, and to a lesser extent on host ingesta and co-symbiotes. Graffillids, in molluscs, lack endogenous digestive enzymes and rely entirely on those taken in with host ingesta and gut tissues. Pterastericolids, in asteroids, similarly utilise gut tissues both as food and enzyme sources. The climax to metabolic dependence occurs in the Fecamplidae and Acholadidae. The former, in crustacean haemocoels and myzostomid tissues, lack conventional alimentary systems and absorb soluble nutrients through the epidermis. In the latter the only known species lives in the tube feet of its asteroid host, lacks a normal endodermal gut, but has a modified epidermis performing both digestive and absorptive functions. Most of these entosymbiotes show a shift from the lipid storage characteristic of free-living and ectosymbiotic species to the glycogen storage predominating in the Neodermata. In both groups this emphasis on carbohydrate metabolism is often independent of the PO2 of their environment. Both groups also show high fecundity and it is suggested that there is a direct relationship between this and glycogen storage. High fecundity, while clearly of adaptive value in entosymbiotes, is arguably primarily related to the assured food supply conferred by the entosymbiotic habit and thus can be viewed as a consequence of the latter rather than a prerequisite for it. Some entosymbiotic Turbellaria have evolved physiologically active haemoglobins, allowing them to abstract oxygen preferentially from host tissues; some have also evolved facultative glycolytic mechanisms comparable to those of the Cestoda. All these adaptations to ecto- and entosymbiotic life in the Turbellaria exemplify possible pathways to wholly parasitic lifestyles, with total metabolic dependence on the hosts, which may have been followed during the evolution of the Neodermata. 相似文献
992.
FH Hausheer ND Jones P Seetharamulu UC Singh JB Deeter LW Hertel JS Kroin 《Canadian Metallurgical Quarterly》1996,20(4):459-467
Thirty-seven of 41 consecutive patients with recurrent anterior instability of the shoulder were retrospectively observed for a mean of 5.6 years (range, 4 to 10) after an arthroscopic stabilization procedure had been performed. The operative technique involved the use of transglenoid sutures to repair the capsule and labrum. According to the criteria established by Rowe, 27 patients (74%) had good or excellent results, and 3 patients (7%) were graded as fair. Seven patients (19%) developed recurrent instability after the procedure and had failed results. Failure rates were equal in patients with a history of recurrent dislocation and those with recurrent subluxation. Absence of a Bankart lesion at operation was associated with postoperative instability (P = 0.03). The presence or size of humeral head defects did not influence the result. Eight of 12 athletes who engaged in sports requiring repetitive overhead shoulder motion returned to full activity, and none of the 12 developed instability after operation. Four of the 13 patients who participated in contact sports or recreational skiing developed postoperative instability (P = 0.21). All failures occurred within 2 years of the procedure. 相似文献
993.
994.
FW Jansen K Kapiteyn T Trimbos-Kemper J Hermans JB Trimbos 《Canadian Metallurgical Quarterly》1997,104(5):595-600
Extrahepatic obstruction of the portal vein is a well known cause of portal hypertension in childhood, that causes severe morbidity. We evaluated 34 children (24 boys, 10 girls, age 4.5 months to 12 years, mean 5.5 +/- 3.8 years) with this diagnosis, to define the clinical picture, laboratory changes, diagnostic tools and therapeutic modalities. Gastrointestinal bleeding was the commonest mode of presentation (64.7%), with the second being splenomegaly. The cause of the obstruction could be determined in 38.2% (13/34) of the subjects. At the beginning of the study the main diagnostic procedure was splenoportography although in more recent years pulsed duplex Doppler ultrasonography has been used. The follow up period was median of 5 years (range 1-11 years). The mean number of bleeding episodes was 4.7 +/- 5.9 (range 1-26), while nine patients never bled. There was no mortality. Ten patients underwent surgery, while sclerotherapy was performed on 10. Twenty-one patients received beta-blocker drugs. No difference was found among these therapeutic modalities. It is well established that the major risk for children with extrahepatic portal vein obstruction is gastrointestinal bleeding which is tolerated quite well. Surgery should be indicated only in children where bleeding cannot be controlled by medical means including sclerotherapy. 相似文献
995.
JB Meijer van Putten 《Canadian Metallurgical Quarterly》1997,141(28):1405-1406
996.
In this study we established cultures of astrocytes from the forebrain of the adult rat. The homeostatic regulatory mechanisms of the aerobic and anaerobic pathways of energy metabolism in these cells showed that adult astrocytes express many of the regulatory properties previously demonstrated in neonatal astrocytes. Changes in mitochondrial respiration and ATP production were readily evident upon incubation with the relevant substrates. Inhibition of mitochondrial respiration led to a compensatory increase in anaerobic glycolysis as evidenced by an increased release of lactate. We assessed the role of cytosolic calcium in the regulation of the mitochondrial energy metabolism. Increases in cytosolic calcium concentration in response to ATP or stimulation of mechanical receptors were followed by depolarizations of the mitochondrial membrane potential, whose magnitude reflected the amplitude of the cytosolic calcium response. The changes in mitochondrial membrane potential were largely dependent on the presence of external calcium. These results provide the first evidence of a signalling mechanism in astrocytes by which changes in cytosolic calcium mediate changes in respiration, possibly through mitochondrial calcium uptake and subsequent activation of several mitochondrial dehydrogenases. This signalling pathway would thus ensure that energy demands due to changes in cytosolic calcium concentrations are met by increases in energy production through increases in mitochondrial oxidative phosphorylation. 相似文献
997.
BJ Conlon M Walsh D McShane N Corcoran M Moriarty JB Healy I Fraser TP O''Dwyer 《Canadian Metallurgical Quarterly》1997,22(4):327-331
In a unilateral ureteral obstruction model, a progressive accumulation of hyaluronan (HA) was observed in the renal papilla during the first 11 days of obstruction, after which the amount of HA decreased until the last day of observation, i.e. day 22. The initial accumulation of HA in the obstructed kidney probably reflects the attempts of the kidney to maintain osmotic balance. Consequently, when filtration ceases, HA synthesis decreases and the concentration of HA falls. In the papilla of the contralateral kidney, that had not been exposed to any mechanical damage, the HA content was found to vary in a similar way to that in the obstructed kidney. The explanation for this could be that the mesenchymal cells within the papilla increase their production of HA in order to meet the requirements of increased function necessary to also shoulder the function of the damaged kidney. In short similar variations in the HA content of the renal papilla was observed in both healthy and obstructed kidneys in a unilateral ureteral obstruction model. 相似文献
998.
999.
JB Sindambiwe M Calomme S Geerts L Pieters AJ Vlietinck DA Vanden Berghe 《Canadian Metallurgical Quarterly》1998,61(5):585-590
PURPOSE: This article presents a review that used three ADA studies on the distribution of dentists to determine whether the number of private practice prosthodontists in the mid 1990s has kept pace with the population in the various regions and states. RESULTS: Findings indicate that between 1987 and 1991 there was a marked national increase in numbers of prosthodontists followed by a marked decrease during the first half of the 1990s. There continued to be major differences, however, in practitioner-to-population ratios in different geographic areas. Since the mid 1980s, there has been a general increase in the number of graduates from prosthetic programs, but an increasing percentage of these graduates were foreign trained dentists. CONCLUSION: There continues to be a need to determine the adequacy of the number and distribution of prosthodontists. 相似文献
1000.
RK Pope KN Pestonjamasp KP Smith JD Wulfkuhle CP Strassel JB Lawrence EJ Luna 《Canadian Metallurgical Quarterly》1998,52(3):342-351
The specific aim of this study was to determine the response of alveolar bone after it was augmented vertically using distraction osteogenesis and subsequently loaded with implant restorations. Four dogs each had four implants placed horizontally into an edentulous mandibular quadrant and, after integration, a distraction osteogenesis device was fabricated in the laboratory. An osteotomy was made to allow the crest of the alveolar ridge to be distracted vertically. After 10 mm of vertical distraction, the device was stabilized with light cured resin. Following bone fill confirmation of the distraction gap at 10 weeks, two implants were placed into the ridges, one in distracted bone and one in nondistracted bone. After 4 months for implant integration, freestanding prostheses were fabricated. Crestal bone levels were evaluated throughout the period of function. Animals were sacrificed after 1 year of loading, for histologic evaluation of the bone. The vertical ridge augmentation averaged 8.85 +/- 1.05 mm after 10 weeks of healing following distraction, without change over 1 year of implant loading. Histologic examination showed that bone had formed between the distracted segments, creating an augmented ridge. The average thickness of the labial cortex in the distraction gap was significantly thinner than the lingual cortex in distracted bone and the lingual and labial nondistracted cortical bone. The presence of the dental implant did not significantly affect cortical bone thickness. Serial sections showed that implants remained integrated and functional without soft tissue inflammation. Dental implants placed into alveolar ridges augmented with the technique of distraction osteogenesis maintained bone and were functional for the length of this study. 相似文献