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Biomedical subjects

R G Smith

Publications and source records attributed to R G Smith.

At least 307 records · Page 17Linked to original sources
PubMed1987

Carbonic Anhydrase-Dependent Inorganic Carbon Uptake by the Red Macroalga, Chondrus crispus.

The rate of photosynthetic carbon uptake of Chondrus crispus Stack-house plants, at various CO(2) concentrations and pretreated with carbonic anhydrase (CA) inhibitors, was determined using an air-suspension, differential infra-red gas analyzer technique. It was found that the CA inhibitors, acetazolamide, dextran-bound acetazolamide (DBI, which does not permeate cell membranes), and subtilisin (a protease that attacks the cell surface) inhibit photosynthetic carbon uptake in C. crispus. Inhibition was greatest at low CO(2) concentrations, and decreased at CO(2) saturation. Acetazolamide inhibited carbon uptake to a greater extent than DBI. The data support the conclusion that C. crispus plants utilize HCO(3) (-) for photosynthesis, and that both cell-surface and internal CA are involved in the photosynthetic uptake of inorganic carbon.

Journal Article↗
PubMed1987

Long term amantadine treatment. The danger of withdrawal.

Three elderly Parkinsonian patients on long term amantadine therapy (mean nine years) are presented. In each case abrupt withdrawal of amantadine resulted in rapid deterioration in the patient's condition which was corrected by reintroduction of amantadine.

Aged↗
PubMed1987

Monoclonal antibody recognizing a human neuroblastoma-associated antigen.

The derivation of an IgG1k monoclonal antibody (HSAN 1.2) recognizing a cell membrane determinant on human neuroblastoma cells is reported. The determinant was found on all 17 cultured human neuroblastoma cells that were tested, but the density of the antigen varied widely on different cell lines. The antibody also bound to fresh and cultured Wilm's tumor cells, retinoblastoma cells, and one of two Ewing's sarcoma cell lines tested, it did not bind to mouse neuroblastoma cells, normal fibroblasts, blood, or bone marrow. Tumor cells that did not stain with HSAN 1.2 included glioma, medulloblastoma, melanoma, rhabdomyosarcoma, mesenchymoma, leukemia, and lymphoma cells. The distribution of the HSAN 1.2 antigen in normal tissues was confined to brain and newborn kidney. As few as 0.1% tumor cells in bone marrow aspirates were detectable by fluorescein-conjugated HSAN 1.2 antibody and flow cytometry. This antibody should be useful for the discrimination of neuroblastoma from other pediatric malignancies, for the detection of tumor cells in metastatic sites such as bone marrow, and for selective removal of neuroblastoma cells from marrow harvested for autologous transplantation.

Antibodies, Monoclonal↗
PubMed1987

Characterization of a leukemia-derived transforming growth factor.

A novel transforming growth factor activity has been identified in the serum-free medium derived from cultures of SMS-SB cells, a human pre-B acute lymphoblastic leukemia cell line. This activity (leukemia-derived transforming growth factor) was biochemically distinct from known fibroblast mitogens such as epidermal growth factor, transforming growth factor alpha, transforming growth factor beta, platelet-derived growth factor, and the endothelial cell growth factor/fibroblast growth factor family of mitogens. Leukemia-derived transforming growth factor was heterogeneous on heparin affinity chromatography, fractionating into three peaks of activity. Although these peaks differed in dose-response characteristics in agar colony and mitogenic assays, each activity was similarly inactivated by heat, acid treatment, and sulfhydryl reduction. Each of the heparin derivatives also behaved similarly on gel filtration and diethylaminoethyl chromatography. Leukemia-derived transforming growth factor was not mitogenic for normal or leukemic lymphocytes or granulocyte/macrophage progenitors. Therefore, a direct or autocrine function for this activity seems unlikely.

Animals↗
PubMed1987

Functional tests of spermatozoa. Sperm penetration assay.

Optimization of each step in the standard protocol of the sperm penetration assay has increased the sensitivity of the traditional assay, and this increased sensitivity has allowed us to avoid the production of false-positive results. Development and use of routine quality control methods now enable us to compare different samples from a given individual and monitor with confidence biological variation and response to medical or surgical treatment. Although our test is extremely predictive of how well a patient's specimen may do as a result of normal intercourse, artificial insemination, and human in-vitro fertilization, it must be stressed that the sperm penetration assay and the sperm capacitation index reported by our laboratory only measure the ability of a sperm to capacitate and fuse with zona-free hamster ovum. How well spermatozoa disperse the cumulus and bind to and penetrate the human zona pellucida is not measured by this test. This would be reflected by an apparent "false-positive" outcome in the sperm penetration assay. However, our data from 138 patients suggest that this occurs only on rare occasions (in 2 of the 138). The test can be used only as a supplement to a conventional semen analysis because other factors, such as motile concentration and motility characteristics, clearly are also of importance particularly in vivo. The results obtained by our laboratory using the optimized assay described herein demonstrate that this test can play an important role in the evaluation of an infertile man.

Animals↗
PubMed1986

Receptor interconversion model of hormone action. I. ATP-mediated conversion of estrogen receptors from a high to lower affinity state and its relationship to antiestrogen action.

We have previously reported that the estrogen receptor exists in three distinct states in the oviduct of the estrogen-treated chick. Since two of these forms bind estrogen and possess a number of similar properties, the intrinsic relationship between these two receptor forms has been investigated. We now show that a quantitative conversion of the high affinity (Rx) to the lower affinity (Ry) state can be induced by mild heating (30 degrees C) in the presence of estradiol and ATP, or the synthetic analogue alpha,beta-methylene adenosine triphosphate and the divalent cation Mg2+. Other nucleotides, including ADP, GTP, CTP, cAMP, and cGMP, as well as the nonhydrolyzable analogues beta,gamma-methylene adenosine triphosphate and alpha,beta-methylene adenosine diphosphate are ineffective. The conversion occurs only partially in the absence of estradiol but completely in its presence. The process is not inhibited by the protease inhibitors phenylmethylsulfonyl fluoride and alpha 2-macroglobulin, and when conversion is induced by low concentrations of ATP (1 mM), a time dependent reequilibration back to Rx occurs. These observations and the fact that the pure hormone-binding peptides Rx and Ry have similar molecular weights on sodium dodecyl sulfate-polyacrylamide gels (66,000) confirm that proteolysis is not involved in the conversion. Moreover their physical properties suggest that Rx and Ry exist in alternate conformations, with Ry being favored as a result of an ATP-mediated event involving the gamma-phosphoryl moiety. The biological relevance of the receptor conversion is suggested by studies with the antiestrogen hydroxytamoxifen. This antiestrogen binds to Rx with higher affinity than either estradiol or diethylstilbestrol but with low affinity to Ry. Hydroxytamoxifen also inhibits the conversion of Rx to Ry. Since this antiestrogen is a complete antagonist in the chick oviduct and prevents estradiol-induced stimulation of ovalbumin gene transcription, it is speculated that Rx to Ry conversion is crucial for ovalbumin gene activation and that Rx may act as a transcriptional repressor. Furthermore, since Rx and Ry both bind to nuclei and DNA, it is proposed that the presence of Ry is a better predictor of ovalbumin gene activation than DNA binding alone.

Animals↗
PubMed1986

Receptor interconversion model of hormone action. II. Nucleotide-mediated conversion of estrogen receptors from nonsteroid binding to the lower affinity binding state.

Two steroid binding states of an estrogen receptor each with different equilibrium constants (Kd values) Rx (Kd = 0.06 nM) and Ry (Kd = 0.8 nM) have been identified and characterized in the hen and estrogen-stimulated chick oviduct. A third nonestrogen binding form of the receptor, designated Rnb, is now described which exists in short-term estrogen withdrawn chick oviduct cytosol. A model is presented in which the receptor can be interconverted between the three states. The interconversion is monitored by Scatchard analysis, sucrose density gradient analysis, and affinity labeling using [3H]tamoxifen aziridine followed by receptor purification with estrogen receptor monoclonal antibody affinity chromatography and sodium dodecyl sulfate-gel electrophoresis. The results are consistent with each state existing in different conformations having a common molecular weight of approximately 66,000. This paper defines the conditions and nucleotide requirements for the Rnb to Ry conversion. The conversion to the steroid binding form is induced by ATP, ADP, and GTP. Cyclic nucleotides are ineffective. There is a specific requirement for Mg2+; neither Ca2+ nor Mn2+ will substitute. Nonhydrolyzable nucleotide analogues were tested for their relative efficiency to convert Rnb to Ry. Conversion occurred with alpha,beta-methylene adenosine triphosphate, but beta,gamma-methylene adenosine triphosphate and alpha,beta-methylene adenosine diphosphate were inert. Thus, activation of Rnb to form Ry appears to be catalyzed by an event requiring the loss of the terminal phosphoryl moiety from either ATP or ADP. Receptor derived from conversion of Rnb to Ry has the same physical properties as native Ry. Activation of Rnb is to Ry specifically; no increase in the Rx form of estrogen receptor was ever observed. The accompanying paper similarly describes the Rx to Ry conversion. Since these data also explain observations made with glucocorticoid and with epidermal growth factor receptors, it is speculated that the receptor interconversion model may have general application to hormone action.

Adenine Nucleotides↗
PubMed1986

Molecular analysis of the t(2;14) translocation of childhood chronic lymphocytic leukemia.

Two rare cases of chronic lymphocytic leukemia (CLL) in children have been studied; both are associated with a previously undescribed chromosomal translocation [t(2;14) (p13;q32)]. In one patient the translocation was reciprocal and the breakpoint on chromosome 14 occurred just 5' of the C gamma 2 region on the productive immunoglobulin heavy-chain allele. The breakpoint on chromosome 2 does not involve the K locus but lies within an uncharacterized region that coincides with the position of a constitutive fragile site that occurs within normal lymphocytes. Data on the second patient are consistent with these findings and suggest that these cases represent a rare but distinct subgroup of CLL's with a specific cytogenetic change.

Alleles↗
PubMed1986

Characterization of a second estrogen receptor species in chick oviduct.

Scatchard analysis of estradiol binding to chick oviduct cytosol is consistent with the existence of two high-affinity estrogen receptors which bind this ligand with equilibrium dissociation constants (Kd) of 0.06 and 0.8 mM. While the higher affinity receptor has been characterized and purified [Smith, R. G., & Schwartz, R.J. (1979) Biochem. J. 184, 331-343], the properties of the lower affinity receptor have not previously been defined; thus, its existence has been questioned. We now report the separation of the two receptors by low-capacity affinity chromatography, by sucrose density gradient centrifugation, and the partial separation by diethylaminoethyl ion-exchange chromatography. The former utilizes differences in estrogen binding kinetics associated with each receptor; the rate of dissociation (k-1) of [3H]estradiol from each receptor is identical (k-1 = 7.7 X 10(-5) s-1) while rates of association (k1) reflect the 10-fold differences in Kd. The lower affinity receptor has a k1 = 1.63 X 10(5) M-1 s-1, and the higher affinity receptor has a k1 = 1.33 X 10(6) M-1 s-1. The lower affinity receptor sediments at 3.5 S on sucrose density gradients compared to 4.2 S for the high-affinity form; it has high specificity for estrogen and is tissue specific, and its nuclear occupancy is associated with increases in ovalbumin gene transcription; thus, this macromolecule meets the criteria of an estrogen receptor. Augmentation of this receptor is possible by treatment of the cytosol with ATP/Mg2+, illustrating the existence of a non-steroid binding species.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1986

Rat Sertoli cells secrete a growth factor that blocks epidermal growth factor (EGF) binding to its receptor.

The conditioned medium from Sertoli cells contains a potent mitogen(s) that can markedly stimulate the proliferation of 4 different cell lines of endoderm or mesoderm origin in the presence or absence of serum. With A431 cells, conditioned medium produced in a dose-dependent manner up to a 5.2-fold increase in cell number after 5 days in culture. Addition of follicle-stimulating hormone (FSH), testosterone, retinol, and insulin to the Sertoli cells increased the secretion of the mitogenic activity. The ability of Sertoli cell conditioned medium (SCCM) to displace 125I-labeled epidermal growth factor (125I-EGF) from formalin-fixed A431 cells was also examined. The SCCM from Sertoli cells incubated with insulin contained 1.42 ng eq of EGF/ml; testosterone, retinol, and FSH (in the presence of insulin) further increased the secretion of this EGF competing activity to 2.09, 2.56, and 3.22 ng eq/ml, respectively. The amount of EGF competing activity was positively correlated with mitogenic activity. Separation of SCCM by gel filtration on Bio-Gel P-10 produced three major peaks of EGF-competing activity at apparent Mr = 1800-2100, 3800-4200, and 8000-9500. Chromatographing SCCM (in the presence of protease inhibitors) on size exclusion high performance liquid chromatography revealed two peaks of EGF competing activity at Mr about 8000 and 2000 coincident with and proportional to peaks of mitogenic activity. This activity was heat-sensitive and resistant to reducing agents, and addition of an equivalent amount of EGF as that present in SCCM produced an inhibition in growth of the A431 cells compared to a 3-fold stimulation with SCCM. Thus, the Sertoli cells secrete a potent mitogen that is distinct from EGF and alpha TGF. This factor that we have termed Sertoli cell-secreted growth factor is hormonally regulated by FSH, testosterone, and retinol and may play an important role in controlling spermatogenesis.

Animals↗
PubMed1986

Steroid regulation of receptor concentration and oncogene expression.

The DDT1MF-2 cell line was derived from an estrogen/androgen-induced tumor of the hamster ductus deferens. This cell line contains receptors for both androgens and glucocorticoids and its proliferation is differentially sensitive to these classes of steroids. Androgens stimulate cell growth dramatically and augment intracellular androgen receptors, whereas glucocorticoids inhibit growth and prevent androgen receptor augmentation. Androgen receptor augmentation occurs by an androgen-dependent increase in receptor half-life and an increase in the rate of synthesis. Glucocorticoids, in the presence of androgens, reduce both the half-life and the rate of synthesis of androgen receptors. For comparison purposes, a glucocorticoid-resistant mutant (DDT1MF-2-GR) of this cell line has been developed. Unlike the wild type, in this variant glucocorticoids neither arrest cell growth nor inhibit androgen receptor augmentation. Glucocorticoids block growth of the wild type in the G1-phase of the cell cycle. This event can be overcome either by addition of exogenous platelet-derived growth factor (PDGF) or by the addition of concentrated conditioned medium from nonglucocorticoid-treated cells, however, androgen receptor augmentation remains inhibited. The reduced production of PDGF-like growth factors in the presence of glucocorticoids appears to be the result of a decrease in production of mature mRNA with homology to v-sis (the viral oncogene coding for PDGF-like proteins). The level of regulation appears to be posttranscriptional and does not occur in the DDT1MF-2-GR cells. Thus glucocorticoids regulate the autocrine growth of the DDT1MF-2 cells by a mechanism that can be uncoupled from the regulation of androgen receptor augmentation.

Androgens↗
PubMed1986

Delta-9-tetrahydrocannabinol stimulates ABP secretion from rat Sertoli cells in vitro.

The effect of delta-9-tetrahydrocannabinol (THC) on rat Sertoli cell function was investigated. THC significantly increased ABP secretion by 1.5- to 2.1-fold but did not consistently enhance the stimulation of ABP induced by FSH, testosterone or dibutyryl cyclic AMP. ABP was measured by steady-state polyacrylamide gel electrophoresis, DEAE Bio-Gel and immunoassay; all three methods gave similar results. The minimal concentration of THC that stimulated ABP was 10 ng/ml; maximal stimulation was observed with 100-200 ng/ml. This effect was specific since THC did not affect gamma glutamyl transpeptidase activity or the secretion of plasminogen activator, lactate and transferrin. This observation that THC affects ABP secretion specifically is the first report of any differential effect of a drug on Sertoli cell secretion.

Androgen-Binding Protein↗
PubMed1986

Chronic granulocytic leukemia: the devastating consequences of genetic instability.

Recent advances in the pathogenesis and treatment of chronic granulocytic leukemia (CGL) are reviewed. Three major phases of CGL are recognizable: the presymptomatic phase, the chronic phase, and the metamorphosis. The molecular dissection of the Philadelphia chromosome has revealed that this translocation activates the c-abl oncogene by fusion with another gene called bcr whose function is as yet unknown. Although almost all patients with CGL still succumb within 10 years of diagnosis, alpha-interferon and allogeneic bone marrow transplantation represent promising newer therapeutic developments. In particular, marrow transplantation appears to have curative potential in CGL.

Animals↗
PubMed1986

Thromboembolic complications of the Jarvik-7 total artificial heart: case report.

The Jarvik-7 total artificial heart (TAH) has now been implanted in seven patients, with four (57%) suffering cerebral embolic events. Functional recovery in two patients was impaired by subsequent intracranial hemorrhage from anticoagulant therapy. The findings of a Jarvik-7 TAH explanted following a cerebral embolus are reported here. Thrombotic deposition was seen in the inner crevice formed between the two components of the aortic quick connector. In addition, deposition was seen around all four valves in the crevice formed between the valve ring and the plastic valve housing. On the atrioventricular valves, the deposition in this crevice was most severe on the outflow surface adjacent to the minor flow orifice. On the pulmonic valve, deposition was seen around the entire circumference of both the inflow and the outflow crevices. No thrombi were seen on the diaphragm, the diaphragm-housing junction, or the housing of the left ventricle. Hypercoagulability of the patient's blood gradually developed during implant, reaching a maximum on the evening before the clinical embolus. Increasing resistance to heparin was also demonstrated by in vitro testing.

Adult↗
PubMed1986

Characterization of human neuroblastoma cell lines established before and after therapy.

Six new cell lines have been established from human neuroblastomas. Cell line SMS-KAN, from primary tumor before therapy, and line SMS-KANR, from bone marrow after chemotherapy and radiotherapy, were established from the same patient. Cell lines SMS-KCN (from primary tumor before any therapy) and SMS-KCNR (from bone marrow after chemotherapy) were established from another patient. Two other lines (SMS-MSN and SMS-SAN) were established from different patients before any therapy was given. Cell lines established from recurrent disease after chemotherapy (SMS-KANR and SMS-KCNR) had significantly shorter doubling times and increased plating efficiencies compared to those of cell lines derived from the same patient before chemotherapy (SMS-KAN and SMS-KCN). All cell lines contained tyrosine hydroxylase, aromatic L-amino acid decarboxylase, and dopamine-beta-hydroxylase. Measurable amounts of choline acetyltransferase were also detected in SMS-KAN and SMS-KANR. Karyotype analysis showed all cell lines except SMS-MSN to be pseudodiploid with modal numbers of 46 and deletions of the short arm of chromosome 1; SMS-MSN had a modal number of 57-58 chromosomes. All cell lines had double-minute chromosomes, except SMS-KANR, which had abnormally banding regions. These new cell lines provide in vitro models of neuroblastoma suitable for the study of differences in neuroblastoma cell populations before chemotherapy as compared to the cell populations that proliferate after therapy.

Catecholamines↗