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991.
James H. Resau Kosaku Sakamoto John R. Cottrell Eric A. Hudson Stephen J. Meltzer 《Cytotechnology》1991,7(3):137-149
Organ explant culture models offer several significant advantages for studies of patho-physiologic mechanisms like cell injury, secretion, differentiation and structure development. Organs or small explants/slices can be removed in vivo and maintained in vitro for extended periods of time if careful attention is paid to the media composition, substrate selection, and atmosphere. In the case of human tissues obtained from autopsy or surgery, additional attention must be paid to the postmortem interval, temperature, hydration, and cause of death. Explant organ culture has been effectively utilized to establish outgrowth cell cultures and characterize the histiotypic relationships between the various cell types within an organ or tissue.J. Resau is a visiting scientist at the NCI-LMO-DCE in Frederick, MD 21702, U.S.A.K. Sakamoto is a visiting scientist from the Department of Surgery, Gunma University School of Medicine, Maebashi, Japan 相似文献
992.
Edward W. Wilde John R. Benemann Joseph C. Weissman David M. Tillett 《Journal of applied phycology》1991,3(2):159-167
A process providing a beneficial use for waste heat and excess nutrients in the cooling waters of nuclear reactors and fossil-fueled power generating plants has been developed. The process involves the cultivation of selected strains of thermotolerant microalgae in heated discharge waters and the subsequent harvesting of the algal biomass for nutrient removal, recovery of energy and fertilizer, and extraction of high value products. The design of such a process is presented for a large cooling reservoir receiving a discharge of 1091?1 d?1 of secondary cooling water containing 100 μg 1?1 of available P and 400 μg 1?1 of available N. Based on this nutrient load, with a 1% P content in the algal biomass and a productivity of 10 g m?2 d ?1, a 100 ha region would be needed for the process. Hydraulic barriers (submerged plastic curtains) would isolate the 100 ha algal production area “cultivation zone” in the influent end of the reservoir to create a hydraulic and thermal environment conductive to the selective growth of filamentous, thermotolerant, nitrogen-fixing, blue-green algae. The algal culture would be inoculated into the thermal plume and harvested near the distal barrier of the cultivation zone with rotating, backwashed, fine mesh screens (“microstrainers”). A portion of the harvested biomass would be recycled to the inoculation site to maintain a dense culture. This process could mitigate both thermal and nutrient loadings on receiving bodies of water. 相似文献
993.
Olfactory bulb size was measured in 146 species of Carnivora in order to examine whether recently observed functional patterns for overall brain size were similar for component parts of the brain. Comparative measures were analysed in relation to various allometric characters (body, brain and skull size), phylogeny, behaviour and ecology. Olfactory bulbs are significantly and positively correlated with all allometric variables, but indices of skull size correlate slightly more closely than other variables. This probably relates to functional aspects of skull size, facial proportions, and anterior elements of the brain. Phylogenetic associations were examined by two comparative methods: the method of independent contrasts and phylogenetic autoregression. Both revealed similar phylogenetic correlation at generic and familial levels. Using calculated values from either method, relative olfactory bulb size only correlates with zonation among seven behavioural and ecological variables; aquatic otters have smaller bulb sizes than carnivores of other zonal types. This agrees with discussion about the diminution of olfactory communication in aquatic environments. Also, olfactory bulb size correlates with home range size, which is consistent with a recent model on the use of olfaction for foraging in designated home ranges. Generally, comparative differences in olfactory bulb size in carnivores do not associate with functional variables found in other comparative studies. Nevertheless, future analyses of specific brain components in mammals may be more useful than overall brain size for testing evolutionary hypotheses of mammalian brain size. 相似文献
994.
Summary The use of Cytophaga lysing enzymes was investigated for the liberation of poly--hydroxybutyrate (PHB) granules from the Gram-negative bacterium Alcaligenes eutrophus. Complete cell lysis was approached within a 60 minute period. Contrary to previous findings for the lysis of Gram-negative bacteria, prior removal of the outer membrane was not essential for enzymic lysis. The destabilisation of the outer membrane by the removal of divalent cations resulted in no significant improvement in the disruption process. 相似文献
995.
996.
Productivity and longevity decreased in a laboratory colony of the parasitoid wasp Microplitis croceipes (Cresson) (Hymenoptera: Braconidae). Using light microscopy, it was determined that the colony was free of microsporidia. However, samples of the colony examined for pathogens by electron microscopy revealed three types of viruses: a nonpathogenic polydnavirus which is produced by all female wasps; a nonoccluded baculovirus which is pathogenic to late-stage pupae and adults; and a picorna-like virus which is present in larvae, pupae, and adults. The nonoccluded baculovirus was eliminated from the laboratory colony of M. croceipes by selection of progeny from wasps which had oviposited within 2 to 3 days after emergence from the cocoons and which had lived for at least 14 days post-emergence. Upon death, the wasps were examined by negative stain electron microscopy and only progeny from baculovirus-free wasps were retained. Parasitoid colonies should be systematically examined for pathogenic viruses that may reduce their productivity and efficacy as biological control agents. In addition, exotic parasitoids and predators should be evaluated for viruses and other pathogens while in quarantine. 相似文献
997.
Summary Previous work has suggested that subcultivated human fetal heart muscle cell cultures contain immature cardiac muscle cells
capable only of limited differentiation after mitogen withdrawal. We studied several human fetal heart cultures (14–15 wk
gestation) at several passage levels using immunocytochemistry, autoradiography, and Northern blot analysis. Characteristics
in high-mitogen (growth) medium were compared with those after serum withdrawal. Cultured cells from one heart, expanded through
2 passages in growth medium, did not beat; however, 75% of cells did beat after subsequent culture for 24 days in low-serum
(differentiation) medium containing insulin. In confluent cultures after 1 passage, there was no detectable difference in
the number of cardiac myocytes present in growth medium compared with that 7 days after serum withdrawal. After 4 passages,
however, serum withdrawal increased the number of cells expressing immunoreactive sarcomeric myosin heavy chain by 100-fold;
expression of immunoreactive sarcomeric actin andα-cardiac actin mRNA also increased in the same cultures. Similar results were obtained in cultures kept in differentiation
medium for 20 days before passage and expansion in growth medium. Using isopycinc centrifugation, a high-density cell fraction
was isolated which contained no immunostained myocytes in growth medium but numerous myocytes after serum withdrawal. Combined
immunocytochemistry/autoradiography showed that myocytes synthesize DNA in growth medium and in serum-free medium containing
fibroblast growth factor, but not in serum-free medium alone. The results indicate that a) human fetal cardiac muscle cells
proliferate in vitro and can maintain a phenotype characteristic of fetal myocytes after multiple subcultivations followed
by serum withdrawal; b) after subcultivation in growth medium, some myocytes modulate their phenotype into one in which detectable
levels of cardiac contractile proteins are expressed only after mitogen withdrawal, and c) the phenotype attained after serum
withdrawal is in part dependent on passage level. Cultured human fetal myocardial cells my provide a useful experimental system
for the study of human cardiac muscle cell biology. 相似文献
998.
Charles D. Hébert Sumiyo Endo Kenneth S. Korach Jeff Boyd J. Carl Barrett John A. Mclachlan Retha R. Newbold 《In vitro cellular & developmental biology. Animal》1992,28(5):327-336
Neonatal treatment with estrogens is associated with development of uterine adenocarcinomas in CD-1 mice. Treatment with the
synthetic estrogen diethylstilbestrol (DES) on Days 1 to 5 after birth results in 90% incidence of these hormonedependent
lesions in 18-mo.-old mice. Three cell lines were established from these DES-associated tumors. Each of these cell lines exhibited
morphologic and ultrastructural characteristics of transformed epithelial cells, including an increased nuclear:ytoplasmic
ratio, enlarged and irregular nuclei with multiple nucleoli and areas of chromatin condensation, positive staining for cytokeratin,
desmosomes, and microvilli. After subcutaneous injection into nude mice, all three cell lines formed solid tumors within 4
wk. Although the primary uterine tumors and tumor transplants in nude mice had been shown to be estrogen-dependent and estrogen-receptor
positive, neither the monolayer growth nor the tumorigenicity of any of the three cell lines in this study was enhanced by
or dependent on estrogen. Estrogen receptor levels were low in early and intermediate passage cells. Allele-specific oligonucleotide
hybridization analysis of PCR-amplified cell line DNA revealed no point mutations in the 12th, 13th, or 61st codons of the
K-ras or H-ras protooncogenes. Southern analysis revealed no changes in genomic organization of the putative tumor suppressor
gene DCC, but demonstrated a three-to four-fold amplification of the c-myc gene in one cell line. Expression of c-myc RNA
was concomitantly increased in the same cell line. These three transformed cell lines represent the end point in the process
of hormone-associated tumorigenesis and as such should prove useful in investigating the molecular changes and the mechanisms
involved in hormonal carcinogenesis. 相似文献
1000.
John J. Shea 《Evolutionary anthropology》1992,1(4):143-150
Stone tools are the most durable and ubiquitous residue of prehistoric hominid activity. For this reason, archeologists attempt to learn as much as possible about hominid behavior from the analysis of lithic artifacts. Lithic microwear analysis reconstructs aspects of stone-tool use from patterned variation in the traces of microscopic wear on those tools. The analysis of lithic microwear traces has increased our understanding of how stone tools were used in contexts ranging from the early Pleistocene to the ethnographic present. 相似文献