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51.
We consider the parallelization of two standard 2D reconstruction algorithms, filtered backprojection and direct Fourier reconstruction, using the data-parallel programming style. The algorithms are implemented on a Connection Machine CM-5 with 16 processors and a peak performance of 2 Gflop/s. 相似文献
52.
The low-resolution (2 nm) subunit symmetry of cucurbitin, the crystalline seed storage globulin of cucurbits, has been determined by X-ray diffraction. The wet crystals belong to the cubic space group F23 and there are 4 molecules per unit cell. The molecules therefore possess point-group symmetry 23 and contain 12 structural units which at this resolution are indistinguishable. On drying, the crystal lattice dimension shrinks from 13.6 nm to 12.4 nm with no apparent change in symmetry. Diffraction patterns of small crystals spun into a pellet, and sections of dry and wet native seed indicate that in situ the protein is organised in microcrystals of the same unit cell and symmetry. Edestin, the crystalline storage globulin from cannabis, and a crystalline globulin from tobacco seed both have the same crystal lattice as cucurbitin and, very likely, the same subunit symmetry. 相似文献
53.
Previous research has found differences in the speed and accuracy of responses involving concrete cognate nouns and non-cognate nouns in a range of written and "on-line" tasks using neurologically unimpaired, bilingual adults. The present study investigated whether cognateness affects verbal confrontation naming performance in balanced French/English bilinguals (N = 15 aphasic and 15 non-aphasic subjects). Subjects met selection criteria for equal proficiency, regular use, and early acquisition of both languages. Results of a picture naming test show that cognate pictures were more often correctly named in both languages than were non-cognates. Some error types and self-correction behaviors also varied with cognate status. There were similarities between the results of this study and those of previous studies of monolingual naming. Some error types and self-correction strategies appear to be unique to bilingual speakers. Theoretical questions and treatment applications arising from these findings are outlined. 相似文献
54.
PM Petersen NE Skakkebaek A Giwercman 《Canadian Metallurgical Quarterly》1998,106(1):24-34; discussion 34-6
This paper reviews current knowledge about the effect of testicular germ cell cancer (TGCC) on gonadal function and of cancer treatment on spermatogenesis and Leydig cell function. It is well documented that testicular cancer is associated with impaired spermatogenic function and some patients already have impairment of Leydig cell function before orchidectomy. The degree of spermatogenic dysfunction is higher than what can be explained by local tumour effect and by a general cancer effect, since patients with other malignant diseases have normal, or only slightly decreased, semen quality. Furthermore, sperm counts after orchidectomy are further reduced to less than half of the values in healthy men, even in patients cured from the cancer disease after orchidectomy alone. These observations are supported by histological investigations which have shown a high prevalence of abnormalities of spermatogenesis in the contralateral testis in patients with unilateral TGCC. The association between testicular cancer and poor gonadal function is very interesting both from a biological and from a therapeutic point of view. Firstly, the increase in incidence of testicular cancer has been suggested to be associated with a general decline in male reproductive health and it seems likely that the development of TGCC shares common aetiologic factors with development of other types of testicular dysfunction. This suggestion is supported by the observation that men with various types of gonadal dysfunction such as testicular dysgenesis, androgen insensitivity syndrome, and cryptorchidism have increased risk of testicular cancer. Secondly, the general cure rate in patients with testicular cancer exceeds 90% and the quality of life, including fertility aspects, is therefore important in the management of these patients. Spermatogenesis is already so severely impaired before treatment that fertility is lower than in healthy men. Moreover, radiotherapy and chemotherapy both induce dose-dependent impairment of spermatogenesis and recovery of spermatogenesis after treatment may be long lasting even more than five years in some patients. Sufficient androgen production is seen in the majority of the patients, but some patients suffer from testosterone deficiency. The effect of chemotherapy on Leydig cell function also seems to be dose-dependent. In conclusion there is no doubt that testicular cancer is associated with poor gonadal function even before treatment. Furthermore, the treatment of testicular cancer may have a serious impact on the gonadal function in these patients, most of whom are in the reproductive age. Moreover, the epidemiological and clinical data indicate a common aetiology between testicular germ cell cancer and other abnormalities in male reproductive health (such as infertility and cryptorchidism). These observations are in agreement with the suggestions of hormonal involvement in the aetiology of testicular cancer. Generally, men with TGCC need counselling about their reproductive function with respect to semen cryopreservation, chance of recovery of spermatogenesis, fertility, and the possible need for androgen replacement. 相似文献
55.
L Yu L Orlandi P Wang MS Orr AM Senderowicz EA Sausville R Silvestrini N Watanabe H Piwnica-Worms PM O'Connor 《Canadian Metallurgical Quarterly》1998,273(50):33455-33464
We have previously demonstrated that UCN-01, a potent protein kinase inhibitor currently in phase I clinical trials for cancer treatment, abrogates G2 arrest following DNA damage. Here we used murine FT210 cells, which contain temperature-sensitive Cdc2 mutations, to determine if UCN-01 abrogates G2 arrest through a Cdc2-dependent pathway. We report that UCN-01 cannot induce mitosis in DNA-damaged FT210 cells at the non-permissive temperature for Cdc2 function. Failure to abrogate G2 arrest was not due to UCN-01-inactivation at the elevated temperature because parental FM3A cells, which have wild-type Cdc2, were sensitive to UCN-01-induced G2 checkpoint abrogation. Having established that UCN-01 acted through Cdc2, we next assessed UCN-01's effect on the Cdc2-inhibitory kinase, Wee1Hu, and the Cdc2-activating phosphatase, Cdc25C. We found that Wee1Hu was indeed inactivated in UCN-01-treated cells, possibly just prior to Cdc2 activation and entry of DNA-damaged cells into mitosis. This inhibition appeared, however, to be a consequence of a further upstream action since in vitro studies revealed purified Wee1Hu was relatively resistant to UCN-01-inhibition. Consistent with such an upstream action, UCN-01 also promoted the hyperphosphorylation (activation) of Cdc25C in DNA-damaged cells. Our results suggest that UCN-01 abrogates G2 checkpoint function through inhibition of a kinase residing upstream of Cdc2, Wee1Hu, and Cdc25C, and that changes observed in these mitotic regulators are downstream consequences of UCN-01's actions. 相似文献
56.
Postcontrast MR angiography complements the standard spinal MR imaging study by improving detection and display of normal and abnormal intradural vessels, primarily veins. Detection of abnormal veins facilitates diagnosis of spinal vascular malformations and vascular tumors. The most useful application has been in screening for spinal dural arteriovenous fistula, in which MR angiography demonstrates the medullary vein into which the fistula drains, thus allowing noninvasive identification of the spinal level of the fistula. 相似文献
57.
EA Hassink AT Brugman-Boezeman LM Robbroeckx PN Rieu EM van Kuyk PM Wels C Festen 《Canadian Metallurgical Quarterly》1998,13(5-6):377-383
Parents play a crucial role in the life of a child suffering from an anorectal malformation (ARM), since their guidance contributes to the degree to which the child learns to cope with his or her disability. We investigated whether they experience stress in parenting such a child and also attempted to identify somatic or behavioral characteristics in the child that influence the stress of parenting. The parents of 109 children (69 males, 40 females; median age 5.9 years, range 1-18 years) with an ARM (58 low, 10 intermediate, 41 high) were studied. The Nijmegen Questionnaire on Child-rearing Situations (NQCS) was used to investigate the existing parenting situation. Behavioral characteristics of the children were studied by means of the Child Behaviour Checklist (CBCL) and the Teacher Report Form (TRF). In a semi-structured interview, we investigated how parents experienced the implications of the disability in everyday life with their child. Our study showed that as far as the perception of parenting stress is concerned, parents of children with an ARM do not differ from those with healthy primary-school children. Within the group of parents with ARM-afflicted children, the parents of older, incontinent children experienced relatively more stress, especially when the child concerned was male. With regard to the children's behavior, the parents and teachers under investigation did not report a higher than normal incidence of deviant behavior. However, when individual parents observed difficult behavior in their child, they found it harder to deal with than the incontinence for feces. Regarding the implications of the disorder for their everyday lives, parents were concerned and indicated a need for specific counselling. We conclude that having a child with a somatic affliction, in this case an ARM, does not automatically imply that the parents experience child-rearing problems. However, certain groups of parents are more at risk, i.e., parents with older, incontinent sons and parents with children exhibiting behavioral problems. In addition, our study shows that parents do have difficulties in coping with the implications of the disorder and express a need for support. We feel that patient care can be improved if aid is tailored to these specific problems. 相似文献
58.
JR Goss ME O''Malley L Zou SD Styren PM Kochanek ST DeKosky 《Canadian Metallurgical Quarterly》1998,149(2):301-309
A between-side comparison of GABAA receptor subunit expression levels in the globus pallidus and anterior-pole motor thalamic nuclei of rats with an ibotenate lesion of the striatum, and rats receiving a fetal striatal graft in the lesioned area was made by using immunocytochemistry with subunit-specific antibodies, at different times post-lesion or different times post-grafting. At 10 days post-lesion, there was already an increase in the labeling of the alpha 1- and beta 2/3-subunits in the globus pallidus, entopeduncular nucleus and ventrolateral nucleus ipsilateral to the lesion when compared with the contralateral side, while there were no significant changes at the level of the ventromedial nucleus. Labeling of the alpha 2-subunit showed a clear increase in the entopeduncular nucleus compared with the contralateral side at 10 days post-lesion. Similar changes were also observed for the different subunits studied at 30 and 120 days after lesioning. Rats with 20-day old transplants of fetal striatal neurons that were implanted in the ibotenate lesioned striatum at 10 days post-lesioning, continued to show changes in the expression of GABAA receptor subunits, albeit at a lower level than those of ibotenate lesioned rats at similar age post-lesion. However, when examining rats with 70-day old transplants, the ibotenate-lesion induced between-side changes were almost completely compensated. These findings suggest a correlation between the maturation of the grafts and their capability to function in reestablishing neuronal circuits as shown by the reduction of changes in GABAergic transmission induced by ibotenate lesions, as indicated by the reversal of changes in GABAA receptor subunit in several areas of the basal ganglia circuit. 相似文献
59.
Tumor cells that express a fusion gene comprised of Escherichia coli cytosine deaminase (CD) and herpes simplex virus type 1 thymidine kinase (TK) sequences exhibit activation of and subsequent killing by the normally innocuous prodrugs 5-fluorocytosine and ganciclovir (Rogulski et al., Hum. Gene Ther., 8: 73-85, 1997). To target localized expression of this therapeutic gene, we have constructed a recombinant adenovirus containing the CD-TK fusion gene under the control of a human inducible heat shock protein 70 promotional sequence. Strong expression of the fusion gene product was induced by heating at 41 degrees C for 1 h. Expression levels obtained were dependent on the multiplicity of infection used and the incubation time after heat shock. Heat-induced expression of the CD-TK protein significantly reduced the survival of PC-3 cells in the presence of both 5-fluorocytosine and ganciclovir. These studies represent a novel form of gene therapy for the transduction and regulation of a double suicide gene in tumor cells and may provide a unique application for hyperthermia in cancer therapy. 相似文献
60.
Cells that die by apoptosis need to be removed before lysis to preserve tissue integrity and function. Recent studies have identified components of the uptake machinery used by phagocytes, but much remains to be learnt, particularly about the recognition mechanisms and their coupling to the uptake machinery. 相似文献