Three predominant influences mark the evolution of human head form: big brain, erect bipedalism, modified oral apparatus. Confusing interplay between different adaptive requirements of each feature has made explanation of skull structure extremely difficult in the past. It now seems possible to isolate each influence in early fossil forms. A model of mammalian modes of feeding adaptation is proposed in the form of a “Natural Experiment” for tighter analysis of fossil forms. Two forms of australopithecines are recognized, “gracile” and “robust.” Both had closely similar brains, both had erect bipedalism, but each had different masticatory construction. Separation of the first two similar influences isolates the adaptive differences in oral mechanics. The gracile form had a projecting oral apparatus, distinct canine and zygomatic buttresses, moderate jaw-lever development, jaw joint not unlike most higher primates, large unusual anterior teeth, moderately sized posterior teeth. The robust form had a retruded, greatly deepened oral apparatus, “dished-in” face with fused canine and zygomatic buttresses, powerful jaw-lever development, distinctively different joint construction, remarkably small anterior teeth, enormous posterior teeth. Striking evidence for extraordinary jaw movements emerges from these features in the robust form. This is strongly supported by remarkably close parallels in Ursidae: grizzly bear and giant panda. 相似文献
Synopsis The body shape of the estuarine clupeidGilchristella aestuarius from the St. Lucia system is different from that of the same species in other estuaries. The morphology ofG. aestuarius is discussed in relation to long term food availability in the St. Lucia system. 相似文献
Synopsis Feeding chronology, daily ration, and the effects of temperature upon gastric evacuation were examined in the pipefish,Syngnathus fuscus, from field and laboratory data.S. fuscus displayed a pattern of diurnal feeding, characteristic of syngnathids. Daily ration calculations yielded estimates of 4.0 and 4.4% body weight per day, which are comparable to estimates for other teleosts. Evacuation rate was found to be temperature dependent. with more rapid evacuation with increasing temperature. In addition, evacuation rate was found to be positively correlated with gut content. Slowing of evacuation rate with decreasing gut content may allow for increased assimilation efficiency during periods of low food availability. Daily ration, although controlled by the temperature dependence of evacuation rate, may also be controlled by prey abundance; fish maximize food intake during periods of high prey availability, and maximize upon assimilation during periods of low prey availability.Contribution number 1035 of the Virginia Institute of Marine Science of the College of William and Mary. 相似文献
Injection of morphine or d-ala-2-met-5-enkephalinamide (DALA) into the paraventricular nucleus of the hypothalamus (PVN) produced a dose dependent increase in feeding in rats. DALA increased feeding within 45 minutes; morphine within 90 minutes. Naloxone injected into the PVN diminished the effect. DALA increased water intake only when food was available, suggesting the primary effect was on feeding. In summary, an enkephalin analogue induced feeding, and an opiate receptor blocker attenuated it; therefore the PVN may contain opiate receptors that facilitate feeding. 相似文献
A year-round study was conducted to examine feeding habits and food resources of the filter-feeding Trichoptera Arctopsyche grandis and Brachycentrus occidentalis along a regulated mountain stream gradient. There was a well defined longitudinal species replacement with A. grandis reaching maximum densities 2.3 kilometers below the impoundment, and concomitant with its decline downstream was an increase in B. occidentalis. At all sampling sites the < 75 µm organic seston fraction usually consisted primarily of diatoms (>70%, by areal estimate on microscope slides), whereas the 75–250 µm and > 250 µm seston fractions were predominantly composed of detritus (> 80 %). B. occidentalis larvae consumed primarily detritus and diatoms (> 70 % of the diet), while A. grandis ingested a variety of materials with animals, detritus and/or filamentous algae often constituting > 80% of the diet. Animal material was over-represented in the diets of both species when compared with amounts in the seston. Feeding habits provided partial explanations for the distinct longitudinal distribution patterns of filter-feeding Trichoptera observed in the regulated river. 相似文献
Extracellular levels of acetylcholine (ACh) were measured in the nucleus accumbens (NAC), striatum (STR), and hippocampus (HIPP) using microdialysis in 30-min intervals before, during, and after free-feeding in 20-h food-deprived rats. The effects on ACh in the NAC and STR were also observed in response to water intake in 20-h water-deprived animals. Neostigmine was used in the perfusate to improve ACh recovery. Basal ACh was sensitive to tetrodotoxin and low calcium, and therefore largely neuronal in origin. Feeding caused a 38% increase in extracellular ACh in the NAC and no change in the STR or HIPP. Dopamine was also increased in the NAC (48%) and to a lesser extent in the STR (21%) following feeding. Drinking caused 18-20% increases in ACh release in both the NAC and STR. In a separate experiment, ACh release in the NAC was monitored in 10-min intervals during free-feeding; ACh increased in the interval immediately following maximal food intake. These results suggest a site-specific increase in ACh release following feeding that cannot be solely attributed to the activation associated with this behavior. 相似文献
The utilization of gene technology and of new production technologies have made industrial enzymes with improved properties or better cost performance available. This has in turn opened important new areas of enzyme applications. The benefits to the customers are considerable: cost savings in the application process, improved product quality, and in most cases also a significantly reduced impact on the environment.
Gene technology offers several benefits to the enzyme industry. This technology enables the use of safe, well-documented host organisms easy to cultivate, the microbial production of enzymes of animal and plant origin, the realization of enhanced efficiency and high product purity, and also the production of enzymes with improved stability and activity.
Developments in production technology include advanced control methods, the use of expert systems, and the application of large-scale crystallization.
As case stories the development of a lipase and of a cellulase is described. The effect on environment of enzyme application and production is discussed. 相似文献
The central effect of cholecystokinin-octapeptide (CCK), SQ 19,844 or sincalide, on the intake of food and water and on colonic temperature (Tc) was investigated using the broiler cockerel. Four-week old chicks were maintained in a thermoneutral environment of 23-24 degrees C. After food was removed for a 24 hr interval, CCK was infused in a volume of 10.0 microliters into the lateral cerebral ventricle (ICV) in doses ranging from 10-150 ng. Although lower doses of CCK had no effect on food intake, 100 or 150 ng of CCK significantly reduced consumption of food in a dose-dependent manner; water drinking was significantly decreased by 100 ng of CCK. In addition, CCK at doses of 100 and 150 ng prevented the slow rise in Tc observed following infusions of control CSF. This latter effect appeared to be a result of feeding activity associated with caloric intake and the heat increment in the control birds rather than a specific thermoregulatory effect. Overall, our results suggest that CCK may comprise a part of the central mechanism underlying the neural control of short term satiety in an avian species similar to that proposed for the mammal. 相似文献