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Biomedical subjects

S Chaffee

Publications and source records attributed to S Chaffee.

35 records · Page 2Linked to original sources
PubMed1989

Basis for resistance to 3-deazaaristeromycin, an inhibitor of S-adenosylhomocysteine hydrolase, in human B-lymphoblasts.

Clones resistant to 3-deazaaristeromycin, a potent inhibitor of S-adenosylhomocysteine hydrolase, were selected from a nucleoside kinase-deficient derivative of the WIL-2 human B-lymphoblastoid cell line. The resistant clones took up 3-deazaaristeromycin and showed no alteration in the level of S-adenosylhomocysteine hydrolase activity or in the sensitivity of the enzyme to inhibition by 3-deazaaristeromycin. However, they displayed markedly elevated S-adenosylmethionine content during growth in 3-deazaaristeromycin and, following prolonged selection, enhanced export of S-adenosylhomocysteine. As a result they maintained a high ratio of S-adenosylmethionine to S-adenosylhomocysteine and thus were resistant to the inhibition of S-adenosylmethionine turnover and transmethylation caused by 3-deazaaristeromycin. Expanded S-adenosylmethionine pools declined over several weeks of nonselective growth, suggesting a metabolic adaptation rather than a mutational mechanism. No alterations in S-adenosylmethionine synthetase activity were found in the 3-deazaaristeromycin-resistant clones. S-Adenosylhomocysteine export appeared to be carrier-mediated and largely unidirectional. The resistant clones showed a 5-fold increased rate of S-adenosylhomocysteine export compared with parental cells, but a similar Km for intracellular S-adenosylhomocysteine, estimated to be approximately 1 mM. Our results highlight the opposing effects of S-adenosylmethionine and S-adenosylhomocysteine on transmethylation and suggest that the ability to elevate S-adenosylmethionine pools and to export S-adenosylhomocysteine may provide for homeostatic control of transmethylation in lymphoid cells when S-adenosylhomocysteine hydrolase activity is limited.

Adenosine↗
PubMed1988

Phenotypic variation in the response to the human immunodeficiency virus among derivatives of the CEM T and WIL-2 B cell lines.

Derivatives of the CEM T and WIL-2 B cell lines showed striking diversity in their responses to the HTLV-IIIB strain of the human immunodeficiency virus (HIV). Several stable phenotypic patterns could be defined, based on whether cells were permissive (P+, P-) for virus production, were sensitive or insensitive to cytopathic effects after infection by free virus (C+, C-), and whether they underwent fusion on contact with virus-infected cells (F+, F-). Although expression of CD4 was essential for infection by HTLV-IIIB, very low levels were sufficient for productive infection of WIL-2 derivatives. Conversely, some CEM T cell lines that expressed ample CD4, and which were able to bind virus gp120 and undergo fusion, did not support productive infection by free virus. One nonpermissive, CD4+ derivative of CEM could bind gp120 but failed to undergo fusion, suggesting an alteration in some membrane protein other than CD4 that is essential for virus entry and HIV-induced cell fusion. The AA2 derivative of the WIL-2 cell line is also described, which is remarkably permissive for HIV replication and exquisitely sensitive to virus cytopathic effect. The panel of related cell lines with different host-virus phenotypes could be useful for more precisely defining steps in the infectious cycle of HIV, and for identifying host cell genes and gene products that determine the outcome of HIV infection.

Antigens, Surface↗
PubMed1988

Childhood hepatic mesenchymoma: successful treatment with surgery and multiple-agent chemotherapy.

Malignant undifferentiated sarcoma (mesenchymoma) of the liver is a rare tumor of childhood, with fewer than 100 cases reported in the literature. The overall prognosis for patients with this malignancy is poor. In this report, two children with hepatic mesenchymoma underwent surgical excision followed by 2 years of adjuvant chemotherapy. Rotating cycles of cisplatinum, vincristine/doxorubicin, vincristine/cyclophosphamide, and vincristine/actinomycin D were given with minimal toxicity. Both patients are alive, with no evidence of disease at least 5 years from diagnosis. Previous reports of treatment are reviewed.

Adolescent↗
PubMed1987

Efficacy of intravenous gamma globulin in autoimmune-mediated pediatric blood dyscrasias.

Sixteen pediatric patients diagnosed with a variety of autoimmune-mediated hematocytopenias were treated with one to 50 courses of intravenous gamma globulin (IVIG), pH 4.25, over the course of one to 30 months. Thirteen patients had immune thrombocytopenic purpura (ITP), two had autoimmune neutropenia, and one had autoimmune hemolytic anemia. In one patient, chronic ITP was associated with systemic lupus erythematosis, and in a second patient, acute ITP was the presenting manifestation of infection with human immunodeficiency virus. Initial therapy consisted of 400 mg/kg/dose daily for five days for the first seven patients treated, and 1,000 mg/kg/dose daily for two days for the remaining nine patients. In 15 of 16 patients, there was a response to IVIG therapy. In nine of 16 patients, maintenance IVIG therapy for two to more than 30 months was required. Minimal toxicity was experienced in four of 210 separate infusions. Data are presented to support the use of IVIG in the management of childhood autoimmune disorders.

Adolescent↗
PubMed1987

Treatment of platelet alloimmunization with intravenous immunoglobulin. Two case reports and review of the literature.

Two pediatric patients with severe aplastic anemia, elevated antiplatelet antibody levels, refractoriness to human lymphocyte antigen-matched platelet transfusions, and sustained bleeding problems were treated with intravenous immunoglobulin (IVIG), pH 4.25, for three to over nine months. Improved responses to platelet infusions and improved hemostasis were demonstrated in both patients. A review of the published literature analyzing the role of IVIG in the treatment of platelet alloimmunization is presented.

Anemia, Aplastic↗
PubMed1987

Treatment of lymphohistiocytic erythrophagocytosis with VP-16 and aziridinylbenzoquinone.

Lymphohistiocytic erythrophagocytosis (LE) is a usually fatal disease characterized by fever, organomegaly, hyperlipidemia, central nervous system involvement, and cellular immunodeficiency. Treatment with corticosteroids, cytotoxic chemotherapy, and blood exchange is unsuccessful. We have treated two children with the epipodophyllotoxin VP-16 and with intrathecal chemotherapy. Each patient had an initial complete response, and one remains in remission 36 months after therapy began. Aziridinylbenzoquinone (AZQ) therapy induced a complete response in a patient who relapsed during VP-16 therapy. A combination of VP-16 and intrathecal chemotherapy appears to be the most effective therapy for LE, and further evaluation of the role of AZQ is indicated.

Antineoplastic Combined Chemotherapy Protocols↗
PubMed1987

Management of human immunodeficiency virus-associated thrombocytopenia with intravenous gamma globulin.

A 17-month-old boy in whom immune-mediated thrombocytopenia (ITP) was the presenting manifestation of infection with human immunodeficiency virus (HIV) is being successfully managed with intermittent high-dose intravenous gamma globulin (IVIG) allowing maintenance of hemostatic platelet counts while avoiding the immunosuppression associated with other therapeutic modalities used to treat ITP. He continues to demonstrate marked responsiveness to IVIG, and has been maintained on weekly or bimonthly infusions for 12 months. The serendipitous documentation of HIV infection prior to IVIG therapy for immune-mediated thrombocytopenia in this child documents the importance of HIV testing prior to IVIG therapy to prevent erroneous assignment of IVIG as the vehicle responsible for transmission of HIV infection. This case history also documents the importance of HIV testing in the diagnostic evaluation of immune-mediated thrombocytopenias.

Acquired Immunodeficiency Syndrome↗
PubMed1987

Bacterial endocarditis in a child with a Broviac catheter.

Broviac and Hickman catheters facilitate the care of children with cancer but provide a source of potential infection. We describe a child with a Broviac catheter who developed left-sided bacterial endocarditis in whom right-to-left atrial shunting was documented following catheter flushing. Following removal of the catheter and administration of prolonged intravenous antibiotics, recovery was complete and cardiac function returned to normal.

Antineoplastic Combined Chemotherapy Protocols↗
PubMed1986

Treatment of trilateral retinoblastoma with vincristine and cyclophosphamide.

Current therapy for patients with trilateral retinoblastoma, consisting primarily of surgical intervention and radiotherapy, has resulted in no long-term survivors. The use of adjuvant chemotherapy has not improved this outcome. After observing a tumor response to cyclophosphamide in a patient with suprasellar retinoblastoma, we treated a subsequent patient with trilateral retinoblastoma with both vincristine and cyclophosphamide. Objective tumor regression resulted. Although the tumor ultimately progressed in both patients, these findings suggest that vincristine and cyclophosphamide are active in patients with intracranial (trilateral) retinoblastoma.

Cyclophosphamide↗
PubMed1986

Severe Mycoplasma pneumonia in three sisters with sickle cell disease.

Mycoplasma pneumoniae, which usually causes mild infections in normal children, has been shown to cause isolated cases of severe pneumonia in children with sickle cell disease. We recently observed an outbreak of Mycoplasma pneumonia in three sisters with homozygous sickle cell disease. Two of them required hospitalization, and one progressed to respiratory failure requiring prolonged ventilatory assistance. All eventually recovered without long-term pulmonary complications. Familial outbreaks are not uncommon in Mycoplasma infection, but they have not been described previously in siblings with sickle cell disease. It is assumed that local or systemic host defense abnormalities predispose patients with sickling syndromes to more severe courses of Mycoplasma infections.

Anemia, Sickle Cell↗