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排序方式: 共有491条查询结果,搜索用时 15 毫秒
481.
AGING LIVE ANTARCTIC FUR SEALS AND SOUTHERN ELEPHANT SEALS 总被引:1,自引:0,他引:1
This study describes a method for extracting post-canine or incisor teeth from live antarctic fur seals ( Arctocephalus gazella ) and southern elephant seals ( Mirounga leonina ) respectively and their use to determine age in a field situation. Dental elevators were used to loosen the teeth from the alveolus and periodental ligament. Most teeth were removed within l-2 min and a total of 214 and 81 teeth were collected by this method from antarctic fur seals and southern elephant seals respectively. No seal recaptured at intervals up to a year after a tooth was extracted showed signs of infection or distress related to removal of the tooth. Teeth were thin-sectioned for the purpose of aging. In both species cementum growth layer groups were a more satisfactory indicator of age than dentinal growth layer groups. Estimates of age from cementum growth layers were confirmed for Antarctic fur seals using seals which had been tagged as pups up to 16 yr before sampling. 相似文献
482.
Three hominid molars were recovered from a depth of 7.0-7.1 meters in the Mumba Shelter at Lake Eyasi, northern Tanzania. Geological context of the finds and archaeological data indicate that people with a Middle Stone Age technology were using the Mumba locality intermittently whenever retreat of lake waters allowed access to the site. Uranium series dates suggest an age on the order of 130,000 years bp for the teeth and stone tools. Based on morphological analyses, the dental remains probably belonged to one individual and appear to be the crowns of two upper permanent M2s and one lower permanent M2. Crown areas are very small, even in comparison to the variation exhibited by recent African populations. Crown patterns have no archaic features. These teeth are smaller than any verifiable archaic Homo sapiens examples; thus, they may represent early anatomically modern Homo sapiens. 相似文献
483.
L P?llmann 《Chronobiology international》1984,1(2):151-157
The course of swelling after maxillo-facial surgery was investigated by measuring the distance from the tragus to the pogonium. The post-surgical swelling does not diminish continuously, but decreases in a circaseptan periodic mode. The reactive periodicity is preferentially induced not by the injury, but by the surgical treatment. Identical surgical treatment induces a lower level of swelling under local anaesthesia. In contrast to 'biologicaľ remedies, 'chemicaľ antiphlogistic agents, derived from antirheumatic drugs, reduce the extension of swelling, but they also flatten out the increase of swelling around day 7 after surgery. 相似文献
484.
Manish Arora Sheena W. Y. Chan Brendan J. Kennedy Ashwini Sharma Dante Crisante D. Murray Walker 《Journal of trace elements in medicine and biology》2004,18(2):135-139
Lead remains one of the most hazardous metals in our environment. The concentrations of lead in coronal dentine and enamel have previously been reported but limited information is available regarding lead levels in radicular dentine and cementum. This study reports the distribution of lead in 26 roots of 16 human maxillary primary teeth from seven individuals. In addition, calcium and phosphorous concentrations were also measured to detect any variations in the degree of mineralization in different regions of the roots. The mean lead concentration in these roots was 1.67 +/- 1.43 microg/g, which is comparable to other studies. In all cases there were higher lead concentrations in the apices of non-resorbed roots of primary maxillary teeth relative to middle and cervical regions. The findings reported here are of potential significance during the process of physiological root resorption whence periapical tissue may be exposed to higher levels of lead. 相似文献
485.
J. Michael Plavcan 《American journal of physical anthropology》1993,92(2):201-216
While studies of canine dimorphism in primates are common, only a few have examined canine tooth size independently within each sex. Recently, Greenfield and Washburn (Am. J. Phys. Anthropol. 84:17–34, 1991) proposed that there are two types of male canines which reflect different allometric scaling patterns of canine crown height against canine occlusal dimensions. They also suggest that proportional canine shape, measured as canine crown height (or projection) relative to the occlusal dimensions, provides an estimate of the canine's function as a weapon, though they provide no test of this hypothesis. This analysis critically examines the claim that there are two types of male canines among anthropoids. It then tests the hypothesis that relative male canine size (measured against body weight) and proportional canine shape are related to estimates of intermale competition, diet, and substrate (used as a surrogate measure of predation pressure). While there is strong taxonomic variation in canine size and shape among male anthropoids, no evidence is found for two discrete canine types. Rather, within families and subfamilies, canine dimensions scale isometrically against body weight and against each other, with a continuum of canine shapes among different taxa. While variation in male canine size is associated with intermale competition and substrate, even when taxonomic variation is controlled, variation in proportional canine shape is not. Neither canine size nor shape are generally associated with variation in diet. © 1993 Wiley-Liss, Inc. 相似文献
486.
A method is presented for histological examination of undecalcified ground sections of tooth roots affected with periodontal disease. The roots were placed in Karnovsky's fixative overnight, postfixed in 2% buffered osmic acid, and dehydrated in an ascending series of ethanol. The specimens were then infiltrated with propylene-oxide and Epon-Araldite resin, embedded in Epon-Araldite, and sections were prepared using a cutting and grinding system. The resulting ground sections were 8-12 μm thick. The sections were allowed to air dry at room temperature. When thoroughly dried, a coverglass was applied using resinous mounting medium DPX. The specimens were examined by phase-contrast microscopy. The method is useful for simultaneous examination of mineralized dental tissue and bacterial morphotypes covering the root surface of teeth involved with periodontal disease. 相似文献
487.
Tansley Review No. 22 What becomes of the transpiration stream? 总被引:2,自引:0,他引:2
M. J. CANNY 《The New phytologist》1990,114(3):341-368
488.
489.
Robert Rapp 《Biotechnic & histochemistry》1992,67(4):235-240
An inexpensive laboratory apparatus designed to section undecalcified teeth and bone has been constructed. It consists of an electric motor with a mandrel bearing a carborundum sectioning disk centered within a Plexiglas enclosure. A coolant flows from a reservoir positioned in the upper portion of the Plexiglas enclosure to prevent desiccation or burning of the tissues. Undecalcified tissue can be cut into a series of thin, 0.5-1 mm slices to facilitate studies of pulpal enzymes, tooth morphology and design of dental cavity preparations. 相似文献
490.
Lara R. Gawenis Paulette Spencer Laura S. Hillman Matthew C. Harline J. Steven Morris Lane L. Clarke 《Biological trace element research》2001,83(1):69-81
Although abnormal hard tissue mineralization is a recognized complication of cystic fibrosis (CF), the pathogenesis leading
from the defective cystic fibrosis transmembrane conductance regulator (CFTR) protein is poorly understood. We hypothesized
that CFTR plays a direct role in the mineralization of bone and teeth and tested the hypothesis using CF mouse models [CFTR(−)
mice]. In vivo measurements by dual-emission X-ray absorpitometry (DEXA) indicated that bone mineral density (BMD) was reduced
in CF mice as compared to gender-matched littermates. However, no change was evident after correction of BMD for the covariant
of body weight. The latter finding was confirmed in isolated femurs and nasal bones by standard dry-ashing and instrumental
neutron activation analysis (INAA). INAA of the continuously growing hypsodont incisor teeth from CFTR(−) mice revealed reduced
Ca and normal P in the enamel layer—a finding consistent with changes in the deciduous teeth of CF children. Interestingly,
enamel fluoride was increased in the CFTR(−) incisors and may associate with abnormal enamel crystallite formation. The iron
content of the incisor enamel was reduced, explaining the loss of yellow pigmentation in CFTR(−) incisors. In contrast to
the incisors, the mineral content of the slow-growing brachydont molar teeth was not different between CFTR(−) and CFTR(+)
mice. It was concluded that CFTR does not play a direct role in the mineralization of bones or brachydont teeth in mice. Functional
CFTR is apparently required for normal mineralization of the hypsodont incisors. However, multiple changes in the mineral
composition of the CF incisors suggest an indirect role for CFTR, perhaps by maintaining a normal salivary environment for
continuous tooth eruption.
Preliminary reports published in Pediatric Pulmonology, 14, 253A (1997) and 15, 253A (1998). 相似文献