应用聚合酶链反应技术检测肝组织中的HBV－DNA

采用聚合酶链反应（ＰＣＲ）技术，对４２例肝活切组织石蜡切片中乙型肝炎病毒（ＨＢＶ）ＤＮＡ进行检测，并与乙肝表面抗原（ＨＢｓＡｇ）的免疫组织化学及血清学检测进行比较，ＨＢＶ－ＰＣＲ阳性率为７３．８％，高于组织及血清ＨＢｓＡｇ阳性率（分别为５９．５％和５０．０％）。３例病理形态呈肝炎改变，而血清ＨＢｓＡｇ（─）的肝组织中有２例检出ＨＢＶ－ＤＮＡ，提示ＰＣＲ的高度敏感性和准确性。８３．３％的门脉性肝硬变和８７．５％的肝细胞癌组织中ＨＢＶ－ＰＣＲ呈阳性，进一步证实了上述两病与ＨＢＶ的关系密切。我们还发现肝细胞淤胆患者ＨＢＶ感染率较高，ＨＢＶ－ＤＮＡ及组织ＨＢｓＡｇ阳性比例各为６／９和４／８。     

Alterations of pancreatic hepatocytes in rats exposed to carcinogens.

In this study, acute and chronic responses of pancreatic hepatocytes induced in F-344 rats by copper depletion-repletion protocol to certain hepatocarcinogens were examined. Administration of a single dose of tannic acid (subcutaneous), aflatoxin B1 (gavage), or lasiocarpine (intraperitoneally) caused characteristic nucleolar segregation in parenchymal cells of liver as well as in pancreatic hepatocytes. Chronic dietary administration of 2-acetylaminofluorene (0.025%) for 12 to 32 weeks led to the development of glutathione S-transferase-P-positive pancreatic hepatocytes in the pancreas. In addition, oval cell proliferation was observed in close association with pancreatic hepatocytes, but not in other areas of pancreas containing residual acinar cells. Oval cells in the pancreas and in the liver that developed in rats after chronic 2-acetylaminofluorene treatment and pancreatic duct cells stained positively with rat liver oval cell marker OV-6 antibodies by immunoperoxidase. These findings indicate that pancreatic hepatocytes respond to carcinogens in a fashion similar to parenchymal cells of liver.     

Reduction of FK-506 requirements by combination with polyethylene glycol superoxide dismutase in orthotopic rat liver transplantation

Reperfusion after ischemia results in endothelial cell injury and Kupffer cell activation. Inflammatory cytokines thus released can induce major histocompatibility complex antigens and increase the immunogenecity of the graft. An orthotopic rat liver allotransplant model was used to test the hypothesis that prevention of reperfusion injury by infusion of polyethylene glycol superoxide dismutase (PEG-SOD) would result in long-term allograft survival in the presence of subthreshold immunosuppressive dosages. ACI rats were used as donors, and Lewis strain rats as recipients. Orthotopic liver transplantation was initially performed to identify a subthreshold dose of the immunosuppressant FK-506, which would be unable to extend survival longer than control untreated rats with this strain combination. After testing three intramuscular FK-506 doses of 0.04, 0.08, and 0.16 mg/kg, it was observed that an FK-506 dose of 0.04 mg/kg/day for 14 days was unable to extend survival longer than in untreated recipients. This dose of FK-506 was used in combination with PEG-SOD at doses of 1000, 3000, 10,000, or 30,000 units. Recipient animals were treated intravenously with PEG-SOD as a loading dose to facilitate tissue penetration on day 1, and beginning on the day of transplantation, every 2 days for the duration of the study. Results of histologic studies and mean survival time were compared in untreated recipients and in rats treated with PEG-SOD plus 0.04 mg/kg/day FK-506. Mean survival time was increased significantly in these animals (p < 0.007) to 40.6 ± 25.6 days as compared with either untreated rats (10.0 ± 2.7 days) or rats treated with 0.04 mg/kg FK-506 alone (13.7 ± 4.2 days). Histologic examination demonstrated a significant reduction in the cellular infiltrate in rats treated with PEG-SOD plus FK-506, as compared with recipients treated with either agent alone or left untreated. Our results therefore suggest a potential approach to reducing immunosuppression in transplantation. (J ALLERGY CLIN IMMUNOL 1995;95:1276-81.)     

Effect of prenatal iron deficiency on myelination in rat pups.

In this study, a histopathologic examination of the brain from iron-deficient or iron-supplemented rat pups was carried out. Pups were obtained from female rats, which were fed an iron-deficient or iron-supplemented diet during both pregnancy and lactation. Immediately after anesthesia and the collection of blood, pups were fixed by intracardiac infusion of 2% glutaraldehyde. Brain and cervical spinal cord were fixed, embedded in paraffin, and cut at 6-mu thickness. Myelin was identified using Luxol fast blue stain. As compared with controls (hematocrit, 30.8%), 11-day-old iron-deficient pups (hematocrit, 11.9%) showed reduced myelination in the spinal cord. Although myelination increased somewhat in the iron-deficient 17-day-old pups (hematocrit, 8.5%), the amount of myelin in the spinal cord and white matter of cerebellar folds was reduced as compared with that of the corresponding controls. These observations show the importance of prenatal iron adequacy in myelinogenesis.     

Immediate breast reconstruction-impact on radiation management

Breast reconstruction is an option for women undergoing modified radical mastectomy due to a diagnosis of breast cancer. In certain patients, breast reconstruction is performed by insertion of a temporary tissue expander prior to the placement of permanent breast implants. Some of these patients, following mastectomy, may require chest wall irradiation to prevent loco regional relapse. The compatibility of radiation and tissue expanders placed in the chest wall is of major concern to the radiation oncologist. Clinically undetectable changes can occur in the tissue expander during the course of radiation therapy. This can lead to radiation treatment set-up changes, variation in tissue expansion resulting in unwanted cosmesis, and deviation from the prescribed radiation dose leading to over and/or under dosing of tumor burden. At Howard University hospital, a CT scan was utilized to evaluate the status of the temporary tissue expander during radiation treatment to enable us to prevent radiation treatment related complications resulting from dosimetric discrepancies. CT images of the tissue expander were obtained through the course of treatment. To avoid a 'geographic miss' the amount of fluid injected into the tissue expander was kept constant following patient's satisfaction with the size of the breast mound. The CT scans allowed better visualization of the prosthesis and its relation to the surrounding tumor bed. This technique ensured that anatomical changes occurring during radiation treatment, if any, were minimized. Repeated dosimetry evaluations showed no changes to the prescribed dose distribution. A CT of the reconstructed breast provides an important quality control. Further studies with greater number of patients are required for confirming this impact on radiation treatment.     

Expression of superoxide dismutase and catalase in rat brain as a function of age

Active oxygen species have been proposed to be involved in the aging process of the brain, therefore alterations of the levels of enzymes involved in the defence system against free radicals and other active species could substantially influence the aging process. In this study the enzyme activities of superoxide dismutase (Cu/Zn) and catalase as well as the relative levels of their mRNA were measured in the brain of Fischer F344 rats of various ages (5-37 months old). A gradual decrease in the activity of these enzymes (21-27%) was observed with increasing age. The alterations were paralleled by a decrease (39-40%) in the relative levels of these mRNA species. Thus the decrease in the activity of superoxide dismutase and catalase appears to be due to an age-dependent change in the expression of these genes.     

The Cbl family of ubiquitin ligases: critical negative regulators of tyrosine kinase signaling in the immune system

The Cbl family of proteins are evolutionarily conserved negative regulators of activated tyrosine kinase-coupled receptors. Antigen receptors are prominent targets of negative regulation by the Cbl family members, Cbl and Cbl-b, which proteins function as ubiquitin ligases. Cbl and Cbl-b contain substrate recognition domains that interact specifically with activated protein tyrosine kinases of the Src and Syk/ZAP-70 families. Cbl-mediated ubiquitination of these kinases leads to their degradation, resulting in attenuation of receptor signals. Cbl may also control activation-induced monoubiquitination of antigen receptors, thus facilitating their delivery to lysosomes for subsequent degradation. Finally, the interactions of Cbl proteins with downstream targets of tyrosine kinases, such as PI-3-kinase and Vav, could provide an additional mechanism to attenuate receptor signaling. By targeting multiple components of antigen receptor signaling for degradation, the Cbl protein family provides a critical mechanism to ensure an appropriate immune response. The hyperresponsiveness of Cbl(-/-) and Cbl-b(-/-) lymphocytes and the autoimmune phenotype of Cbl-b(-/-) mice lend strong support for this proposal. The ability to control early receptor signals through regulated protein degradation provides a novel paradigm of immunoregulation.