Search PubMed⌕ Search

Biomedical subjects

R Stephens

Publications and source records attributed to R Stephens.

At least 109 records · Page 6Linked to original sources
PubMed1985

Gastrin release from dispersed gastrinoma cells: effects of calcium and calcium ionophore (A23187).

Dispersed single-cell suspensions of human gastrinoma tissue were incubated for 15, 60, and 120 min in a calcium-containing medium, (0.1, 2, 10 mM) in calcium-free medium and in calcium-free medium containing the calcium ionophore A23187 (0.01, 1, and 100 micrograms/ml). Supernatant and pellet (intracellular) gastrin levels were determined by radioimmunoassay. Supernatant gastrin levels remained stable over 120 min in calcium chloride or calcium gluconate containing medium, while intracellular pellet gastrin approximately tripled during the same incubation period. Total gastrin (supernatant plus pellet) approximately doubled during the 2-hr incubation in calcium. However, calcium (0.1, 2, or 10 mM) failed to produce a dose-dependent rise in supernatant, pellet, or total gastrin when compared to calcium-free incubates. Contrary to the expected gastrin response to calcium, supernatant and pellet gastrin levels were higher in incubates in calcium-free medium than in calcium-containing incubates. A23187 (0.01 or 1 mcg/ml) in a calcium-free medium decrease supernatant gastrin while high dose ionophore (100 mcg/ml) increased supernatant gastrin. All doses of ionophore stimulated pellet and total gastrin levels. Thus, it appears that the clinical augmentation of gastrin levels, seen with calcium challenge in vivo may not be solely due to changes in serum calcium.

Adult↗
PubMed1985

Psoralens increase the concentration of cyclic AMP in human cells in vitro.

8-Methoxypsoralen (8-MOP) and 4,5',8-trimethylpsoralen (TMP) were assessed for their effects on cyclic AMP (cAMP) accumulation in normal human fibroblasts, epithelial cells, and mononuclear leukocytes in vitro. In the absence of ultraviolet A radiation, 8-MOP and TMP caused an increase in the concentration of cAMP, but not cyclic GMP, in all of these cells. The effect was seen within 1 min and was sustained over control levels for at least 6 h. At 15 min, the highest dose of 8-MOP or TMP increased the cAMP concentration of fibroblasts by 52% and 69%, respectively. In mononuclear leukocytes, 8-MOP led to a 142% increase in cAMP after 20 min. Several analogs of 8-MOP and TMP had no effect on the cyclic nucleotide system of the cells. The pattern of the time-dependent increase in cAMP indicated that the effect was probably due to an inhibition of phosphodiesterase, rather than an activation of adenylyl cyclase. These results demonstrate that clinically effective psoralens, in the absence of UV radiation, can alter the cAMP concentration of human fibroblasts, epithelial cells, and mononuclear leukocytes in vitro.

Cyclic AMP↗
PubMed1984

Culture-independent diagnosis of Chlamydia trachomatis using monoclonal antibodies.

To simplify the diagnosis of chlamydial genital infection, we used a fluorescein-conjugated monoclonal antibody in immunofluorescence tests on smears prepared from urethral or cervical secretions obtained directly from patients. This direct test, requiring less than 30 minutes to perform, was based on the detection of extracellular chlamydial elementary bodies. A comparison of the direct test with cultures stained with iodine on specimens from 926 patients demonstrated a sensitivity of 93 per cent and a specificity of 96 per cent. The direct test provides a rapid, simple, and sensitive method for the diagnosis of chlamydial infection, which can be performed in laboratories that do not have tissue-culture capability.

Antibodies, Monoclonal↗
PubMed1984

Diabetogenic effect of pentamidine. In vitro and in vivo studies in a patient with malignant insulinoma.

Pentamidine can cause hypoglycemia followed by hyperglycemia. The mechanism of this biphasic response is not known but has been reported to be similar to that of streptozotocin and N-3-pyridyl-N-p- nitrourea (Vacor). Pentamidine (4 mg/kg per day for 12 days) was used in a patient with malignant insulinoma after several unsuccessful debulking procedures and chlorozotocin therapy. Mean glucose and immunoreactive insulin levels (+/- SEM) before and after therapy were 80 +/- 40 mg/dl versus 70 +/- 50 mg/dl and 216 +/- 12 microU/ml versus 198 +/- 22 microU/ml, respectively. These were not significantly different. The patient's five-month-old malignant insulinoma monolayer cell culture was incubated with pentamidine (60 micrograms/ml) in the presence or absence of supplemented stimulatory medium consisting of glucose (300 mg/dl) and theophylline (20 micrograms/ml). Chloroquine (60 micrograms/ml) was added to inhibit lysosomal degradation of immunoreactive insulin. Aliquots of media for immunoreactive insulin determination were obtained at 30 minutes, 20 hours, 72 hours, and three weeks. The cells were examined by high-power light microscopy at each time interval. At 30 minutes, pentamidine alone caused passive release of immunoreactive insulin, 23 percent higher than control (p less than 0.01). Stimulatory medium increased immunoreactive insulin 45 percent greater than control (p less than 0.01). Pentamidine plus stimulatory medium had no additive effect on immunoreactive insulin released within 30 minutes. At the end of 20 hours, immunoreactive insulin was no different with pentamidine and/or stimulatory medium. However, the addition of chloroquine increased immunoreactive insulin by 35 percent above the medium with pentamidine and stimulatory medium (p less than 0.01). At 72 hours, pentamidine suppressed immunoreactive insulin by 100 percent in all the media, irrespective of the presence or absence of stimulatory medium and/or chloroquine. At the end of three weeks, there was 50 percent suppression of immunoreactive insulin in the control medium, but pentamidine again completely suppressed immunoreactive insulin. High-power microscopy demonstrated intact cells in the control medium, whereas no cell structure could be detected in the media containing pentamidine at three weeks. In summary, pentamidine had no acute in vivo effect in a patient with malignant insulinoma. However, when used in an in vitro monolayer system, pentamidine caused (1) acute immunoreactive insulin release followed by inhibition of immunoreactive insulin secretion and (2) cytolysis of human malignant insulinoma cells in vitro.

Adenoma, Islet Cell↗
PubMed1984

High-dose methotrexate with leucovorin rescue plus vincristine in advanced sarcoma: a Southwest Oncology Group study.

Twenty-six evaluable patients with advanced soft tissue and bony sarcomas refractory to chemotherapy were treated with vincristine plus high-dose methotrexate and leucovorin rescue. A 14% response rate was observed among 14 patients presenting with refractory soft tissue sarcomas. No responses were observed among 12 patients with bony sarcoma. Toxic reaction with nausea, vomiting, nephrotoxicity, and myelosuppression was manageable. While this study did demonstrate activity of this regimen in doxorubicin-refractory patients, the duration of the responses was relatively brief. Thus, the clinical utility of such a regimen is questionable.

Antineoplastic Combined Chemotherapy Protocols↗
PubMed1983

Hunter's disease in a girl: association with X:5 chromosomal translocation disrupting the Hunter gene.

We describe a 3 year old girl with the typical clinical features of the X linked recessive condition, Hunter's disease. The diagnosis was confirmed by the pattern of urinary excretion of glycosaminoglycans and the absence of iduronate sulphatase activity in her fibroblasts. She also had an apparently balanced reciprocal chromosomal translocation 46XX,t(X:5) with the X breakpoint being between q26 and q27. Pedigree analysis, and the normal iduronate sulphatase activity in the mother's fibroblasts, serum, and hair roots indicate that the affected child represents a new mutation. Since the parents' karyotypes are normal, it seems that the translocation disrupted the iduronate sulphatase gene itself, thus mapping this to Xq26-27 for the first time. The severe clinical features, not expected in a girl, may be explained by non-random X inactivation.

Child, Preschool↗
PubMed1982

Combination chemotherapy, radiotherapy, and BCG immunotherapy in limited small-cell carcinoma of the lung: a Southwest Oncology Group Study.

From November 1976 to March 1979 the Southwest Oncology Group treated 298 patients with limited (disease confined to the chest and encompassed by one radiotherapy port) small-cell carcinoma of the lung with combination chemotherapy and radiotherapy with or without BCG immunotherapy. Two induction chemotherapy programs were utilized: (1) cyclophosphamide, vincristine, methotrexate, fluorouracil; or (2) cyclophosphamide, doxorubicin, and vincristine. Patients received 4500 rads of radiation therapy to the bulk primary tumor and 3000 rads to whole brain followed by maintenance chemotherapy. One-half of all the patients were randomized to receive one vial (5 x 10(8)) of high viability Pasteur BCG by scarification technique given on days 8 and 15 of each 21--28 day treatment cycle. Increased granulocytopenia accompanied the addition of BCG immunotherapy. Patients receiving BCG achieved a response rate of 49% vs. those patients not receiving BCG of 44% (P = 0.579). Median response duration was 40 weeks for the BCG arms and 38 weeks for the arms without BCG; survival was no different, 42 weeks for the BCG arms vs. 50 weeks for the arms without BCG. In patients who responded to therapy and survived longer than one year, those who continued to receive BCG therapy demonstrated a slight, yet significant, survival benefit over those patients not receiving BCG (93 weeks vs. 81 weeks, P = 0.03). It appears that BCG immunotherapy has no beneficial effect on response rate, duration of response, or survival in programs using chemotherapy and radiotherapy for control of limited small-cell carcinoma of the lung except in this small group of long-term survivors.

Antineoplastic Agents↗
PubMed1982

Plasminogen activator released as inactive proenzyme from murine cells transformed by sarcoma virus.

We have previously reported the purification of a plasminogen-activating serine protease with an approximate Mr of 48 000 from sarcoma-virus-transformed murine cells. We now report that under serum-free conditions the enzyme is released from the cells in an inactive form. After affinity chromatography with 4-aminobenzamidine-cellulose, ion-exchange chromatography and gel filtration, the proenzyme could be obtained from culture fluid as a pure, homogeneous protein as evaluated by polyacrylamide gel electrophoresis with sodium dodecylsulphate. Proenzyme was quantitatively converted to active enzyme by incubation with catalytic amounts of plasmin. Analysis by polyacrylamide gel electrophoresis with sodium dodecylsulphate under reducing and non-reducing conditions showed that the inactive form consisted of a single polypeptide chain with an Mr of approximately 48 000, while the active form consisted of two chains with Mr values of approximately 18 000 and 29 000 , held together by one or more disulphide bridges. The active-site reagent diisopropylfluorophosphate in radiolabelled form was incorporated into the 29 000-Mr chain of the active enzyme, but not into the inactive form. These findings provide conclusive evidence for the existence of an inactive proenzyme to this plasminogen activator and thus demonstrate and additional step in a cascade-like reaction leading to extracellular proteolysis. Regulatory as well as methodological implications of this findings are discussed.

Animals↗
PubMed1982

DNA sequence relationship of the baboon endogenous virus genome to the genomes of other type C and type D retroviruses.

Baboon endogenous virus (BaEV) is a type C retrovirus present in multiple proviral copies in the DNA of baboons. Although interspecies antigenic determinants present on reverse transcriptase and gag proteins are shared among all mammalian type C viruses, no nucleic acid homology between BaEV and other type C viruses (except RD-114) has been found in conventional liquid hybridization experiments. In this study, we used restriction fragments of cloned BaEV DNA immobilized on nitrocellulose to test for relatedness with [(32)P]cDNA's of various type C and type D viruses. We detected the following distant relationships previously found only through immunological and protein sequencing techniques: (i) eight type C viral cDNA's (the endogenous virus of rhesus monkeys, feline leukemia virus, simian sarcoma virus, gibbon ape leukemia virus, Rauscher murine leukemia virus, BALB-2, NZB, and RD-114) and two type D viral cDNA's (Mason-Pfizer monkey virus and squirrel monkey retrovirus) were able to hybridize with cloned BaEV DNA; (ii) the eight type C probes hybridized to restriction fragments spanning most of the BaEV genome, but only RD-114 hybridized to fragments within the 1.9 kilobases at the 3' end of the genome; (iii) the two type D probes hybridized primarily to fragments within the 1.9 kilobases at the 3' terminus and weakly or not at all elsewhere; and (iv) [(32)P]cDNA's of several other oncornaviruses (mouse mammary tumor virus, equine infectious anemia virus, bovine leukemia virus, and reticuloendotheliosis virus) exhibited no homology with BaEV DNA. DNA sequence analysis has allowed us to orient the BaEV restriction map with the genetic map at both ends of the genome. Homologies between retroviral cDNA's and BaEV clone restriction fragments could thus be related to specific BaEV genes. Whereas type C cDNA's hybridized to fragments from gag, pol, and the pol-env junction, squirrel monkey retrovirus cDNA hybridized only to a fragment coding for the p15E portion of env. Mason-Pfizer monkey virus cDNA also hybridized within the p15E region, but exhibited homology to the 3' half of gp70 as well. These results are discussed relative to previously reported antigenic relatedness of retroviral proteins. The data suggest that BaEV represents an important link in oncornavirus evolution.

Base Sequence↗
PubMed1982

Metachromatic leucodystrophy: review of 38 cases.

Clinical and laboratory features of 38 children suffering from metachromatic leucodystrophy (MLD) are reported. Twenty-four children with the late infantile form of MLD presented between ages 6 and 25 (mean 17) months with a delay or deterioration in walking, followed by a general loss of abilities. There was severe handicap by age 3 years and death occurred between 5 months and 8 years after presentation. Neurological signs at the time of diagnosis were varied. Motor nerve conduction velocity was slowed in the 18 children tested. The disease became evident at a later age in 14 children. One boy presented at 13 years, while in the remainder there appeared to be two clinical patterns of the disease which could be termed (1) early juvenile or intermediate and (2) juvenile MLD. In 7 children with early juvenile or intermediate MLD a gait disorder developed between ages 4 and 6 (mean 5) years. This was accompanied in 4 children, and followed between 8 and 26 months later in the remaining 3, by loss of other abilities. Neurological signs were varied. Motor nerve conduction velocity was slowed in 2 of the 5 patients tested. Six children with juvenile MLD presented between ages 6 and 10 years with educational or behavioural difficulties. Motor disorders arose from 6 months to 4 years later. Neurological signs at the time of diagnosis, although mixed, were predominantly extrapyramidal and motor nerve conduction velocity was slowed in 2 of the 3 children tested. In the early juvenile form of MLD, progression of the disease was slower than in the late infantile form and death occurred between 31/2 and 18 years after presentation. Only one-third of patients had fits and these tended to be a late feature.

Child↗
PubMed1981

Exposure to lead.

Explore the source record for details and available documents.

Air Pollutants↗
PubMed1981

Antenatal diagnosis of Niemann-Pick disease in a twin pregnancy.

An Ashkenazi Jewish woman had a child with Niemann-Pick disease in her first marriage. She subsequently remarried a man who was also heterozygous for the condition and conceived twins. Prenatal diagnostic tests were performed and one twin was shown to be homozygous and the other heterozygous for Niemann-Pick disease. The problems of prenatal diagnosis and counselling in twin pregnancies are discussed.

Diseases in Twins↗
PubMed1980

Combination chemotherapy, radiotherapy, and BCG immunotherapy in extensive (metastatic) small cell carcinoma of the lung. A Southwest Oncology Group study.

From November 1976 to November 1978, the Southwest Oncology Group treated 254 patients with extensive (metastatic) small cell carcinoma of the lung with combination chemotherapy and radiotherapy with and without BCG immunotherapy. Patients receiving BCG achieved a response rate of 50% versus those patients not receiving BCG of 46% (P = .704). Response duration was 20 weeks for the BCG arms and 23 weeks for the no-BCG arms; survival was 28 weeks for the BCG arms versus 29 weeks for the no-BCG arms. An adverse effect in patients surviving more than one year was detected; those continuing to receive BCG had significantly shorter survival, 60 weeks versus 85 weeks (P = .019). Toxicities of the programs were not affected by the addition of BCG immunotherapy. It appears that BCG immunotherapy has no beneficial effect on response rate or duration of response in programs using chemotherapy and radiotherapy for control of metastatic small cell carcinoma of the lung. In addition, because of the adverse effect on long-term survival, we do not recommend the addition of BCG immunotherapy as a treatment modality in this tumor type.

Antineoplastic Agents↗