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121.
Two new biological active cyclopentenones VM 4798-1a (1a) and VM 4798-1b (1b) were obtained as a 3:1 inseparable mixture from fermentations of Dasyscyphus sp. A47-98. The mixture of the two isomers showed cytotoxic and weak antibacterial and antifungal properties. VM 4898-1 (2-hydroxy-3,4-dimethyl-2-cyclopenten-1-one, 4), produced by another Dasyscyphus sp. showed no significant biological activity. The structures were elucidated by NMR techniques. 相似文献
122.
Electron microscopy was used to examine 72 cases of medulloblastoma to better characterize the ultrastructural spectrum of this tumor. Twenty-four cases showed prominent neural differentiation. Twenty-three cases showed minimal (21) or no (2) recognizable neural differentiation, and the remainder of the cases (25) showed intermediate differentiation. All 42 cases tested stained for neuron-specific enolase, 28 for synaptophysin, and 12 for neurofilament protein. All cases showed strong reactivity for glial fibrillary acidic protein (GFAP) within reactive astrocytes. Three cases showed reactivity for GFAP within tumor cells. Medulloblastoma exhibits a broad spectrum of neural differentiation, with nearly all cases showing at least some degree of this change, and it universally exhibits participation of reactive astrocytes which can create a potential for diagnostic confusion. 相似文献
123.
Dose-dependent localization of TCDD in isolated centrilobular and periportal hepatocytes 总被引:3,自引:1,他引:2
Santostefano MJ; Richardson VM; Walker NJ; Blanton J; Lindros KO; Lucier GW; Alcasey SK; Birnbaum LS 《Toxicological sciences》1999,52(1):9-19
Dose-response relationships for 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD)
suggest a differential sensitivity of liver cell types to the induction of
cytochrome P450 gene expression, and that the induction of hepatic protein
CYP1A2 causes sequestration of TCDD. In addition, immunolocalization of
hepatic CYP1A1/1B1/1A2 proteins is not uniform after exposure to TCDD. The
mechanism for the regio-specific induction of hepatic P450s by TCDD is
unknown, but may involve the differential distribution of participants in
the AhR-mediated pathway and/or regional P450 isozymes, as well as,
non-uniform distribution/sequestration of TCDD. Therefore, this study
examined the effects of TCDD in unfractionated, centrilobular and
periportal hepatocytes isolated from female Sprague-Dawley rats acutely
exposed (3 days) to a single oral dose of 0.01-10.0 microg [3H]TCDD/kg. A
dose- dependent increase in concentration of TCDD was accompanied by a
dose- dependent increase in CYP1A1, CYP1A2, and CYP1B1 mRNA expression and
associated enzymes in all liver-cell populations. Centrilobular hepatocytes
showed a 2.7- to 4.5-fold higher concentration of TCDD as compared to the
periportal hepatocytes at doses up to 0.3 microg TCDD/kg. Centrilobular
hepatocytes also exhibited an elevated MROD activity as compared to the
periportal hepatocytes at doses up to 0.3 microg TCDD/kg. Furthermore,
centrilobular hepatocytes showed an elevated concentration of induced
CYP1A2 and CYP1B1 mRNA as compared to periportal hepatocytes within the
0.01- and 0.3-microg TCDD/kg- treatment groups. This is the first study to
demonstrate that a dose- dependent difference in distribution of TCDD
exists between centrilobular and periportal cells that might be related to
regional differences in P450 induction.
相似文献
124.
Mooney LA; Bell DA; Santella RM; Van Bennekum AM; Ottman R; Paik M; Blaner WS; Lucier GW; Covey L; Young TL; Cooper TB; Glassman AH; Perera FP 《Carcinogenesis》1997,18(3):503-509
Prior epidemiological evidence suggests that genes controlling the
metabolism of carcinogens and antioxidant/nutritional status are associated
with lung cancer risk, possibly through their ability to modulate DNA
damage by carcinogens. We performed a cross-sectional analysis of 159 heavy
smokers from a cohort of subjects enrolled in a smoking cessation program.
A total of 159 blood samples were analyzed to determine the relative
contributions of genetic polymorphisms [CYP1A1 MspI and exon 7 and
glutathione S-transferase M1 (GSTM1)] and plasma micronutrients to
polycyclic aromatic hydrocarbon-DNA (PAH-DNA) adduct levels. DNA damage in
smokers was affected by genetic polymorphisms and nutritional status.
Smokers with the CYP1A1 exon 7 valine polymorphism had significantly higher
(2-fold, P < or = 0.03) levels of DNA damage than those without. In
parallel models, PAH-DNA adducts were inversely associated with plasma
levels of retinol (beta = -0.93, P = 0.01), beta-carotene (beta = -0.18, P
= 0.09), and alpha- tocopherol (beta = -0.28, P = 0.21) in 159 subjects.
The association between smoking-adjusted plasma beta-carotene levels and
DNA damage was only significant in those subjects lacking the GSTM1
detoxification gene (beta = -0.30, P = 0.05, n = 75). There was a
statistical interaction between beta-carotene and alpha-tocopherol; when
beta- carotene was low, alpha-tocopherol had a significant protective
effect (beta = -0.78, P = 0.04) on adducts, but not when beta-carotene was
high (beta = -0.16, P = 0.57). Plasma alpha-tocopherol was significantly
correlated with beta-carotene (r = 0.36, P = 0.0005) and less strongly with
retinol (r = 0.20, P = 0.0005). These results suggest that several
micronutrients may act in concert to protect against DNA damage and
highlight the importance of assessing overall antioxidant status. In
conclusion, a subset of smokers may be at increased risk of DNA damage and
possibly lung cancer due to the combined effect of low plasma
micronutrients and genetic susceptibility factors. The use of biological
markers to assess efficacy of interventions and to study mechanisms of
micronutrients is timely given the current debate regarding the use of
chemopreventive agents in high risk populations.
相似文献
125.
126.
Rhabdomyosarcoma is an often primitive tumor capable of diverse morphologic manifestations. The article describes three cases of childhood rhabdomyosarcoma in which a significant population of lipid-rich tumor cells was present. The lack of specificity and potentially confusing nature of this feature are discussed, and the ultrastructural diagnosis of rhabdomyosarcoma is briefly reviewed. 相似文献
127.
A young woman with a melanoma of the left forearm was found to have a right lung mass. This was initially interpreted as metastatic melanoma on the basis of clinical, radiographic, and light microscopic features, together with positive staining of tumor cells with antibody HMB-45. Electron microscopic examination performed for confirmation of the diagnosis revealed no evidence of melanocytic differentiation. Instead, there were features suggestive of the alternative diagnosis of sclerosing hemangioma (SH). This diagnosis was confirmed with additional immunocytochemical stains. To the authors' knowledge this is the first report of HMB-45 positivity in SH. This case illustrates a potentially disastrous diagnostic pitfall in interpreting lung tumors in patients with melanoma, and the vital role of electron microscopy in resolving conflicting and/or misleading immunocytochemical results. 相似文献
128.
In an ultrastructural study of 24 cases of histiocytosis X, we were able to demonstrate Langerhans cell granules in all of 18 cases from which tissue had been submitted primarily for electron microscopy and in 4 of 6 cases from which only tissue retrieved from paraffin blocks was available for examination. In a subsequent correlative study we were able to demonstrate Langerhans cell granules in deparaffinized material from 11 of 14 cases (79%) in which they were known to exist. The incidence of histiocytes displaying Langerhans cell granules (in a single plane of section) fell from a median of 48% in samples processed primarily for electron microscopy to 14% in those retrieved from paraffin blocks. Our data suggest that electron microscopy, even when applied to the study of suboptimally preserved material, is a highly sensitive technique for confirming a diagnosis of histiocytosis X. 相似文献
129.
Human sperm non-nuclear progesterone receptor expression is a novel marker for fertilization outcome 总被引:1,自引:0,他引:1
Jacob A; Hurley I; Mandel FS; Hershlag A; Cooper GW; Benoff S 《Molecular human reproduction》1998,4(6):533-542
In a prospective, blind study, we have examined the relationship among the
expression of human sperm surface progesterone receptors, the ability to
undergo a mannose-stimulated acrosome reaction and the rate of
fertilization in vitro. Individual aliquots of motile spermatozoa were
surface-labelled with progesterone and/or mannose-fluoresceinated ligands.
Spontaneous acrosome loss and the increase in acrosome reactions following
exposure of spermatozoa to mannose ligands were assessed using rhodaminated
Pisum sativum agglutinin. Progesterone fluoresceinated ligand binding was
observed to occur in two patterns: (i) a uniform distribution of labelling
over the acrosome cap (pattern II), and (ii) labelling limited to the
equatorial and postacrosomal regions of the human sperm head (pattern III).
A conversion of pattern II to pattern III binding was observed and was
associated with the acrosome reaction. Pattern III binding was highly
correlated with both fertilization potential and the ability to undergo a
mannose-stimulated acrosome reaction (P < 0.001). In contrast, normal
sperm mannose receptor expression was seen in five men whose abnormal
progesterone receptor expression/function and inability to acrosome react
after mannose treatment were correlated with their reduced fertility in
vitro. In conclusion, surface progesterone receptor aggregation enhances
the mannose ligand-stimulated acrosome reaction. Such detection of
defective sperm surface progesterone receptor expression/function may be
useful in the evaluation and management of male infertility.
相似文献
130.
Craig W. Zuppan Douglas A. Weeks Gail D. Wenger Ofelia A. Alvarez Gary W. Mierau 《Ultrastructural pathology》1997,21(5):453-456
Contamination of a biopsy or surgical specimen with spurious tissue is an uncommon but potentially disastrous event. In this regard, the case of a 5-year-old boy referred for treatment of an abdominal tumor is presented. Sections made from paraffin blocks brought by the family showed both neuroblastoma and a spindle cell sarcoma, initially suggesting the possibility of divergent or mixed differentiation. However, the resemblance of the spindle cell component to well-differentiated leiomyosarcoma rather than rhabdomyosarcoma raised the suspicion that a specimen contamination had occurred. Electron microscopy was instrumental in confirming the smooth muscle nature of the sarcomatous component, leading to a fluorescence in situ hybridization study, which established that this component was incompatible with the patient's gender. This case illustrates that even when the light microscopic differential has been compromised by specimen mishandling, electron microscopy can at times provide useful information regarding specimen identity, as well as assist in sorting out the correct diagnosis. 相似文献