Search PubMed⌕ Search

Biomedical subjects

B D Nelson

Publications and source records attributed to B D Nelson.

At least 19 recordsLinked to original sources
PubMed1996

Sp1 activates and inhibits transcription from separate elements in the proximal promoter of the human adenine nucleotide translocase 2 (ANT2) gene.

Expression of the adenine nucleotide translocator 2 (ANT2) gene is growth regulated. We report a feature of the ANT2 promoter that involves a novel regulatory function for the Sp1 transfactor. We show that expression from the ANT2 proximal promoter is modulated through three Sp1 elements, two of which activate and one of which partially inhibits transcription. The inhibitor site, box C, is juxtaposed to transcription start (nucleotides -7 to -2). Sp1 bound to box C decreases transcription initiation. This was demonstrated by introducing mutations in box C which (a) increased chloramphenicol acetyltransferase expression in the transient transfection assay and (b) inhibited binding of both purified Sp1 and Sp1 in crude nuclear extracts. The activating elements (A and B boxes) are located at adjacent sites in the distal region of the proximal promoter. Mutation of either box inhibits transfection by 90%, indicating that they act in a synergistic manner. Supershift experiments with crude nuclear extracts showed that only Sp1 was bound to the three GC boxes. The finding that Sp1 acts as an activator/inhibitor within the same promoter region was verified in NIH3T3, HeLa, JEG3, and COS-1, indicating that this dual effect of Sp1 is widely preserved. These data suggest a unique role for Sp1 and raise the possibility that growth activation of the ANT2 gene is regulated by the interaction of Sp1 on the A, B, and C boxes.

3T3 Cells↗
PubMed1996

Thyromimetic action of the peroxisome proliferators clofibrate, perfluorooctanoic acid, and acetylsalicylic acid includes changes in mRNA levels for certain genes involved in mitochondrial biogenesis.

The effects of three peroxisome proliferators on the mRNA levels for some mitochondrial inner-membrane proteins in rat liver were investigated. Clofibrate, perfluorooctanoic acid, and acetylsalicylic acid all increased the mRNA levels for the mitochondrial-encoded respiratory-chain components cytochrome c oxidase subunit I and NADH dehydrogenase subunit I. Mitochondrial 16S rRNA was also induced by clofibrate. The mRNA levels for the nuclear-encoded mitochondrial inner-membrane proteins adenine nucleotide translocator and cytochrome c1 were selectively induced by the different peroxisome proliferators. Malic enzyme, which is induced by thyroid hormone, was also induced by the three peroxisome proliferators tested. These effects are in some ways similar to those obtained with thyroid hormone.

Animals↗
PubMed1995

The role of thyroid hormone and promoter diversity in the regulation of nuclear encoded mitochondrial proteins.

Thyroid hormone regulates the in vivo expression of a selected set of rat nuclear genes encoding mitochondrial inner membrane proteins. Certain mRNAs, such as that for cytochrome c1, are increased as much as 20-50-fold, while others, such as core protein 1 of Complex III and the F1-ATPase beta-subunit do not respond. The promoter region of human cytochrome c1 also supports thyroid hormone induction of a reporter gene in transient transfection experiments. Thus, thyroid hormone regulates only selected genes, even for subunits within the same complex and in widely varying species. By contrast, growth activation of quiescent NIH3T3 cells, a second paradigm used for stimulating mitochondrial biogenesis, does not increase cytochrome c1 mRNA but does increase F1-ATPase beta-subunit mRNA. These findings suggest that nuclear OXPHOS genes are not necessarily expressed in a coordinated manner, and that multiple regulatory circuits might exist which are linked to different physiological stimuli. Analysis of the promoters of several OXPHOS genes reveals a great diversity and heterogeneity of transfactor binding elements. No single regulatory feature exists which could account for a coordinated expression of all OXPHOS genes. The potential diversity for regulating expression of nuclear OXPHOS genes raises the possibility for the existence of disease states linked to regulatory defects.

3T3 Cells↗
PubMed1994

Mitogen activation of human peripheral T lymphocytes induces the formation of new cyclic AMP response element-binding protein nuclear complexes.

A large body of evidence indicates that experimental agents which raise cellular cAMP levels inhibit T cell growth and division. By contrast, many studies have reported that mitogen activation of T cells increases cAMP levels, implying a positive physiological role for cAMP in the activation process. In the present study we demonstrate that mitogen activation of human peripheral T lymphocytes induces nuclear factors that form complexes with cyclic AMP response element-binding protein (CREB). Four complexes are identified by the electrophoretic mobility shift assay, two of which are induced by mitogen activation. All four complexes contain CREB and are bound to the cAMP response element (CRE) core sequence (TGACGTCA), as indicated by antibody and oligonucleotide competition experiments. Binding of the four complexes to CRE is prevented by dephosphorylation of nuclear extracts and is restored by rephosphorylation with cAMP-dependent protein kinase or endogenous kinases. Similar complexes are detected in nuclear extracts of Jurkat cells. Mitogen induction of the electrophoretic mobility shift assay complexes is not accounted for by protein phosphorylation or by induction of CREB. Rather, the data indicate that mitogen increases the levels of a nuclear factor(s) that dimerizes with CREB. Induction of new CREB complexes implies a physiological role for cAMP in mitogen activation of T lymphocytes.

Animals↗
PubMed1994

Interactions between brain mitochondria and cytoskeleton: evidence for specialized outer membrane domains involved in the association of cytoskeleton-associated proteins to mitochondria in situ and in vitro.

The surface distribution of several proteins (porin, hexokinase, and two proteins associated with microtubules or actin filaments) on the outer membrane of brain mitochondria was analyzed by immunogold labelling of purified mitochondria in vitro. The results suggest the existence of specialized domains for the distribution of porin in the outer mitochondrial membrane. Similarities between the distribution of porin and the distribution of microtubule-associated proteins bound in vitro to mitochondria suggested that mitochondria and microtubules interact by binding microtubule-associated proteins to porin-containing domains of the outer membrane. This hypothesis was supported by biochemical studies on outer mitochondrial proteins involved in in vitro binding of cytoskeleton elements. In vitro interactions between mitochondria and microtubules or neurofilaments were analyzed by electron microscopy. These studies revealed cross-bridging between the outer membrane of mitochondria and the two cytoskeleton elements. Cross-bridging was influenced by ATP hydrolysis and by several proteins associated with the surface of mitochondria or with microtubules. In addition, unidentified proteins which were recognized by antibodies to all intermediate filaments subunits were associated either with the mitochondrial surface or with microtubules. This data suggest the participation of additional cytoplasmic proteins in the interactions between cytoskeleton elements and mitochondria.

Animals↗
PubMed1993

The effects of cAMP on the expression of glycolytic isozymes in activated peripheral human T lymphocytes.

Forskolin, an activator of adenylate cyclase, inhibits mitogen induction of glycolytic isozymes in human peripheral T cells. Inhibition of lactate dehydrogenase isozyme activity is correlated with lowered mRNA levels, suggesting a transcriptional block in the presence of increased cAMP. Forskolin added with the mitogen, or 12-24 h after the mitogen, strongly inhibits isozyme expression and DNA synthesis, and causes cells to accumulate in the G0 or early G1 phase of the cell cycle. The data suggest that DNA synthesis and isozyme expression are both inhibited by a cAMP-sensitive step(s) in the early activation or progression phase.

Cell Cycle↗
PubMed1993

Decision support for concurrent utilization review using a HELP-embedded expert system.

Utilization Review is the process of evaluating the efficiency of medical care, based on examination of the patient record. At LDS Hospital, the electronic patient record is in an advanced state. This paper describes the development and knowledge base verification of ASSURE (Automated Support System for Utilization Review), an application within the HELP hospital information system. ASSURE applies the Appropriateness Evaluation Protocol (AEP) Day of Care criteria to the electronic patient record, concurrent with the patient's stay. In blinded trials, an experienced Utilization Manager agreed with 92% of ASSURE's decisions on single AEP criteria for 560 acute care patients. Agreement was statistically significant, with kappa = 0.84, P < 0.0001.

Computer Systems↗
PubMed1992

Transcript levels for nuclear-encoded mammalian mitochondrial respiratory-chain components are regulated by thyroid hormone in an uncoordinated fashion.

Thyroid hormone is one of the few known physiological regulators of mammalian mitochondrial biogenesis. Although it exerts a global effect on biogenesis, it does so by regulating the expression of a limited number of unidentified mitochondrial proteins. We have investigated these hormone-regulated proteins in rat liver. Hormone injection induced a 30-fold increase in the levels of cytochrome-c1 mRNA after 3 d. In addition, the mRNA for the growth-activated adenine-nucleotide translocator, ANT2, was increased 13-fold and that for the ATPase N,N'-dicyclohexylcarbodiimide-binding protein increased 4-5-fold. Mitochondrial transcripts of cytochrome-oxidase subunit I also increased. No changes were found in the mRNA levels for the F1-ATPase beta-subunit or cytochrome oxidase IV. A single low dose of triiodothyronine induces rapid increases in cytochrome-c1 and ANT2 mRNA species which parallel changes in the activity of the hormone-responsive malic enzyme, but are earlier than other mitochondrial biogenetic events. These data strengthen the view that thyroid hormone regulates synthesis of specific components within each respiratory-chain complex and that these products apparently play key roles in inner-membrane biogenesis and assembly. The significance of ANT2 induction is also discussed with respect to the rapid respiratory response induced by thyroid hormone.

Adenosine Triphosphatases↗
PubMed1992

Differential regulation of the transcript levels of some nuclear-encoded and mitochondrial-encoded respiratory-chain components in response to growth activation.

Biogenesis of mammalian mitochondria requires the participation of both nuclear and mitochondrial genes. In order to study the expression and coordination of these two sets of genes, serum-deprived, quiescent NIH 3T3 cells were activated by serum addition. The steady-state levels of the transcripts for two growth-response genes (the mitochondrial adenine-nucleotide translocator and non-mitochondrial beta-actin), one nuclear-encoded respiratory-chain component (F1-ATPase beta-subunit) and the mitochondrial-encoded subunit I of cytochrome oxidase decreased significantly in quiescent cells and were rapidly restored with similar kinetics after addition of serum. The transcripts for two additional nuclear-encoded mitochondrial genes (cytochrome c1 and cytochrome oxidase subunit IV) did not respond to serum deprivation or growth activation. These results imply that mitochondrial biogenesis is at least partially regulated through growth-dependent mechanisms. Furthermore, the expression of nuclear genes encoding mitochondrial respiratory-chain components does not appear to be tightly coordinated, suggesting the existence of multiple control circuits.

3T3 Cells↗
PubMed1992

Regulation of the expression of lactate dehydrogenase isozymes in human lymphocytes.

Mitogen activation of human peripheral lymphocytes leads to a switch in the isozymes of LDH; resting cells contain low activities of only the B4 and B3A forms, whereas activated cells contain high activities of the A4 and A3B forms. B4 LDH is not altered in activated cells. In this study we show that the appearance of the A subunits occurs concomitantly with a several fold increase in the steady state levels of LDH-A mRNA. Responses in LDH-A mRNA are observed within 12 hrs of activation, and are, thus, associated with the G0/G1 transition or with early G1 (Marjanovic et al. Exp. Cell Res. (1991) 193: 425-431). Maximal expression of LDH-A mRNA requires both phorbol ester and concanavalin A, implying a complex regulatory pathway involving cascade systems activated through both the antigen receptor (TR) and protein kinase C.

Blotting, Northern↗
PubMed1991

Hexokinase bound to rat brain mitochondria uses externally added ATP more efficiently than internally generated ATP.

The rates of glucose phosphorylation by bound hexokinase were investigated in mitochondria isolated from rat brain. Initial rates obtained either with ATP generated from oxidative phosphorylation or with ATP added externally were compared. Our results show that the external ATP supports a 2-3-fold higher hexokinase activity than does ATP generated by oxidative phosphorylation under Stage 3 conditions. ATP formed by mitochondrial creatine kinase in the presence of creatine phosphate also supports higher initial rates of glucose phosphorylation than does oxidative phosphorylation. The data suggest that concentrations of ATP present in the cytosol of normal tissue will probably maintain higher rates of glucose phosphorylation than ATP being exported directly from the mitochondrial matrix at maximal State 3 rates.

Adenosine Triphosphate↗
PubMed1991

ADP is a substrate for the AAUAAA-directed poly(A) addition reaction catalyzed by HeLa cell nuclear extracts.

The specific poly(A) addition reaction catalyzed by crude nuclear extracts from HeLa cells can use ADP as efficiently as ATP as the donor of AMP residues. Both the ADP- and ATP-supported reactions require an intact upstream polyadenylation signal sequence element (AAUAAA). The mutated signal sequence (AACAAA) supports neither reaction. The ADP-supported poly(A) addition reaction can be resolved by glycerol gradient centrifugation of the crude nuclear extract into two components which are active when recombined but are inactive individually. The ATP-supported poly(A) addition is reconstituted by recombining the same gradient fractions, but the activity is lower than that supported by ADP, suggesting that an ATP-specific factor has been removed. A 150 mM KCl fraction DEAE-Sepharose of the nuclear extract, also devoid of the ATP-supported poly(A) addition reaction, retains a normal ADP-supported reaction. Together, these data show that ADP is a substrate for polyadenylation, and suggest that different factors might be required to induce ADP- or ATP-specificity in the poly(A) addition reaction.

Adenosine Diphosphate↗
PubMed1991

Expression of glycolytic isoenzymes in activated human peripheral lymphocytes: cell cycle analysis using flow cytometry.

Human peripheral lymphocytes activated with concanavalin A and phorbol myristate ester exhibit an increase in glycolysis on a time-course similar to that for DNA synthesis. Elevated glycolysis is accompanied by increased specific activities of the glycolytic enzymes. Increased enzyme activities are accounted for by the appearance of specific isoenzyme forms (muscle forms) normally expressed in rapidly growing tumor cells or in growth-stimulated cells. In the present study we analyzed the expression of the glycolytic isoenzymes during cell cycle progression of activated human lymphocytes using two-parameter (DNA and protein) flow cytometry. Time-course studies and analysis of subpopulations prepared by elutriation centrifugation showed that the inducible isoenzymes are expressed at low levels or not at all in G0 cells. They are expressed first during the G0 to G1 transition or in early G1. However, expression increases throughout G1, reaching a maximum in S-phase. Thus, induction of glycolytic isoenzymes provides an excellent marker of T-cell activation and progression toward DNA synthesis.

Cell Cycle↗
PubMed1991

Primary biliary cirrhosis (PBC): characterization of a monoclonal antibody (PBC-MoAb) having specificity identical with disease-associated autoantibodies.

We have raised a monoclonal antibody (PBC-MoAb) directed against mitochondria which resembles patent anti-mitochondrial autoantibodies (AMA) (M2 type) in several respects. The reaction pattern of PBC-MoAb was characterized by western blot experiments, immunoaffinity purification and enzyme inhibition studies. PBC-MoAb reacts specifically with an epitope on the E2 subunit of pyruvate dehydrogenase (dihydrolipoamide acyltransferase) which is essential for enzymatic activity. This was shown as follows: (1) PBC-MoAb, like PBC-AMA, completely inhibited PDH enzyme activity and reacted weakly with OGDH; (2) PBC-MoAb bound strongly to the E2 subunit in western blots, with weaker binding to a doublet of about 56 kDa; and (3) in immunosorbent experiments, PBC-MoAb absorbed most (greater than 95%) of the AMA reactive material found in solubilized mitochondria. The present data together with earlier findings that the majority of PBC patient autoantibodies bind to epitopes defined by the PBC-MoAb, makes this antibody a valuable tool for characterizing the major PBC-associated epitope on PDH-E2 and localizing this epitope in liver tissue.

Animals↗
PubMed1990

Expression of a new set of glycolytic isozymes in activated human peripheral lymphocytes.

The combination of phorbol 12-myristate 13-acetate (PMA) and concanavalin A induces the expression of a new set of glycolytic isozymes in human peripheral lymphocytes. The induced isozyme for each enzyme tested (hexokinase, phosphofructokinase, enolase, pyruvate kinase and lactate dehydrogenase) is usually the muscle form, which is often associated with rapidly dividing tumor cells. Increases in a specific isozyme can account for the 2-5-fold increase in specific activities of the enzyme induced by Con A plus PMA. Increased specific activities and the appearance of the new isozyme forms both occur relatively late, and are probably associated with the G1 or S phase of the cell cycle.

Cells, Cultured↗
PubMed1990

Thyroid hormone regulation of mitochondrial function. Comments on the mechanism of signal transduction.

Thyroid hormone exerts two types of effect on mitochondria. The first of these is a rapid activation of respiration which takes place within minutes after hormone injection, and is preserved in isolated mitochondria. The second response occurs after 1 to several days of injection and leads to mitochondrial biogenesis and increases in mitochondria mass. The hormone signal for these two responses involves either triiodothyronine (T3)-responsive nuclear genes or a direct action of T3 at mitochondria binding sites.

Animals↗
PubMed1990

Symptomatic lower extremity deep venous thrombosis: accuracy, limitations, and role of color duplex flow imaging in diagnosis.

Color duplex flow imaging (CDFI) permits pain- and risk-free direct imaging of the deep venous system of the lower extremities. To prospectively ascertain the accuracy and limitations of this technique, CDFI was performed in 75 lower limbs of 69 consecutive patients referred for venographic evaluation of clinically suspected lower extremity deep venous thrombosis (DVT). The CDFI study was obtained within 24 hours of the contrast venogram. Both studies were interpreted without knowledge of the patient's clinical findings or the results of the other test. Contrast venography was regarded as the standard for diagnosis of DVT. Accuracy was 99% for detection of DVT above the knee and 81% below the knee. Sonographic evaluation of the calf veins was technically adequate in 60% of limbs; accuracy was 98% in this group. In the 40% of limbs with technically limited CDFI studies of the calf, accuracy decreased to 57%. Although small nonocclusive thrombi occurred infrequently in this series of symptomatic patients, CDFI missed three of four such thrombi. It is concluded that CDFI, when not technically compromised, is sufficiently accurate to definitively diagnose symptomatic lower extremity DVT.

Adult↗