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N M Bass

Publications and source records attributed to N M Bass.

At least 55 records · Page 3Linked to original sources
PubMed1994

Immunological identity of rat liver cytosolic heme-binding protein with purified and recombinant liver fatty acid binding protein by western blots of two-dimensional gels.

We examined the degree of similarity between rat liver cytosolic heme-binding protein (HBP) and rat liver fatty acid binding protein (L-FABP) purified from rat liver cytosol and recombinant L-FABP (rL-FABP). We compared 1) HBP, 2) L-FABP, and 3) rL-FABP prepared in three different laboratories and probed them with three different antisera also from different laboratories on Western blots. The objective was to determine whether the isoform pattern of the recombinant would resemble those of the purified rat liver proteins and whether heme is bound by the isoforms. To investigate the similarities, we compared the immunoreactivity of purified HBP, L-FABP, and rL-FABP by probing Western blots of 2-D gels with polyclonal antibodies raised against each of these proteins. All of the antibodies react with the same isoelectric species for each of the proteins. In addition, [55Fe]-heme binds equally well to the 2 major HBP isoforms.

Animals↗
PubMed1994

Evidence for a novel keratinocyte fatty acid uptake mechanism with preference for linoleic acid: comparison of oleic and linoleic acid uptake by cultured human keratinocytes, fibroblasts and a human hepatoma cell line.

Keratinocytes require the essential fatty acid (FA), linoleic acid (LA), for the synthesis of stratum corneum membrane lipids. A plasma membrane-FA binding protein (PM-FABP), is postulated to mediate cellular FA-uptake in hepatocytes and several other tissues, but the mechanism whereby exogenous FA are taken up by keratinocytes has not been investigated. This study examines the uptake of LA and oleic acid (non-essential) in cultured human keratinocytes, in comparison to dermal fibroblasts and the human hepatoma cell line, HepG2. As previously reported for hepatocytes, FA-uptake in keratinocytes was curvilinear, with an initial (30 s) rapid cellular influx. The initial uptake component was temperature dependent, exhibited saturable kinetics and was significantly inhibited by pretreatment with trypsin. In contrast, fibroblast FA-uptake lacked an initial rapid uptake component, was relatively temperature insensitive, and was not inhibited by trypsin. Keratinocytes differed from both hepatocytes and fibroblasts by more rapid uptake of LA in comparison to oleic acid during the initial influx phase. Moreover, FA-uptake in keratinocytes was not inhibited by preincubation with a anti-rat liver PM-FABP antibody. These data provide evidence for a PM-FA transporter in keratinocytes that is distinct from the hepatic PM-FABP. The apparent preference of the putative keratinocyte FA transporter for LA may function to ensure epidermal capture of sufficient LA for barrier lipid synthesis.

Adult↗
PubMed1993

Regulation of pathways of extramitochondrial fatty acid oxidation and liver fatty acid-binding protein by long-chain monocarboxylic fatty acids in hepatocytes. Effect of inhibition of carnitine palmitoyltransferase I.

The regulation of the extramitochondrial fatty acid oxidation pathways located in the peroxisomes and the endoplasmic reticulum is not fully understood. Although both long-chain dicarboxylic fatty acids, which are poorly metabolized in hepatocytes, and non-beta-oxidizable fatty acid analogs induce peroxisomal beta-oxidation and liver fatty acid-binding protein (L-FABP) by a pretranslational mechanism, monocarboxylic long-chain fatty acids, which are rapidly esterified and oxidized, do not. To establish whether impaired utilization and, hence, sustained intracellular levels of monocarboxylic long-chain fatty acids increase their efficacy as inducers, the effect of oleic acid on cytochrome P-450 4A1, peroxisomal beta-oxidation, and L-FABP during inhibition of mitochondrial beta-oxidation was determined. In primary hepatocyte cultures, oleic acid had no inducing effect, but in the presence of 2-tetradecylglycidic acid (TDGA), an inhibitor of carnitine palmitoyltransferase I, it induced P-450 4A1, peroxisomal beta-oxidation, and L-FABP pretranslationally. An increase in peroxisomal beta-oxidation was also noted in the presence of etomoxir, another inhibitor of carnitine palmitoyltransferase I. Exposure of hepatocytes to TDGA for 1 h led to an expected decrease in incorporation of radiolabel from [1-14C]oleate into CO2 and water-soluble products. In contrast, long-term exposure to TDGA increased incorporation of [1-14C]oleate into oxidation products, most likely due to an adaptive induction of peroxisomal beta-oxidation. Both acute and long-term exposure of hepatocytes to TDGA decreased incorporation of oleic acid into triglycerides, an effect that may have contributed to the intracellular accumulation of fatty acids. These results provide support for a mechanism by which long-chain fatty acids or specific metabolites, including long-chain acyl-CoA esters and long-chain dicarboxylic acids, act as signals in the induction of P-450 4A1, peroxisomal beta-oxidation, and L-FABP under conditions in which long-chain fatty acids accumulate due to impaired entry into the mitochondrial beta-oxidation pathway.

Acyl-CoA Oxidase↗
PubMed1993

Induction of peroxisomal fatty acid beta-oxidation and liver fatty acid-binding protein by peroxisome proliferators. Mediation via the cytochrome P-450IVA1 omega-hydroxylase pathway.

Both the enzymes of peroxisomal fatty acid beta-oxidation and the liver fatty acid-binding protein (L-FABP) are induced in the liver by peroxisome proliferators, such as clofibrate (CF), as well as high fat diets. One proposed mechanism for this induction is that it represents an adaptive response to altered intracellular fatty acid fluxes, mediated by dicarboxylic fatty acids formed via the cytochrome P-450IVA1 omega-oxidation pathway. The studies presented in this paper were designed to investigate the role of the products of P-450IVA1 omega-oxidation in the regulation of peroxisomal beta-oxidation and L-FABP. In primary hepatocyte cultures exposed to CF, the increase in P-450IVA1 activity preceded the induction of peroxisomal beta-oxidation and L-FABP. The CF-mediated increases in peroxisomal beta-oxidation and L-FABP, but not P-450IVA1, could be significantly inhibited pretranslationally by concurrent exposure of cultured hepatocytes to inactivators of cytochromes P-450, such as 1-aminobenzotriazole and 10-undecynoic acid. Hexadecanedioic acid, a 16-carbon dicarboxylic fatty acid, that is poorly metabolized in hepatocytes, induced peroxisomal beta-oxidation and L-FABP, but not P-450IVA1, via a pretranslational mechanism that was not inhibited by 1-aminobenzotriazole. Long-chain monocarboxylic acids were without such inducing effect. In further studies, non-beta-oxidizable dicarboxylic acid analogs were found to display greater potency as inducers of peroxisomal beta-oxidation when compared to hexadecanedioic acid. The inducing effects of the dicarboxylic acid analogs were also independent of the P-450 omega-oxidation pathway. The results of these studies suggest that the regulation of peroxisomal beta-oxidation enzymes and L-FABP is mediated, to a significant extent, by poorly metabolized long-chain dicarboxylic acids formed via the P-450IVA1 pathway.

Animals↗
PubMed1993

High-affinity fatty acid-binding activity in epidermis and cultured keratinocytes is attributable to high-molecular-weight and not low-molecular-weight fatty acid-binding proteins.

Fatty acid-binding proteins (FABPs) are abundant low-molecular-weight cytosolic proteins in tissues involved in fatty acid (FA) metabolism. Because epidermis is also an active lipogenic tissue, we examined cytosols from murine and porcine epidermis and cultured human keratinocytes and fibroblasts for FABPs. High-affinity FA-binding activity was present in both epidermis and differentiated keratinocytes, whereas no high-affinity FA-binding activity was found in cultured human fibroblasts or undifferentiated keratinocytes. By column chromatography, a single binding peak was identified in the high (90-100 kDa)-molecular-weight range and no binding activity was evident in the low (14-15 kDa)-molecular-weight range, where conventional FABPs elute. Moreover, rabbit anti-rat heart FABP, anti-rat intestine FABP, and anti-rat liver FABP antisera did not identify proteins in the 14-15-kDa range in murine epidermal cytosol by Western immunoblots, whereas the anti-rat-heart antibody recognized a protein of approximately 32 kDa. Isoelectric focusing of differentiated keratinocyte cytosol demonstrated a single FA-binding peak having a pI of approximately 4.0. Analysis of this binding peak by SDS-PAGE revealed peptides of approximately 66 and 38 kDa. These findings suggest the possibility that the FA-binding protein in keratinocyte cytosol normally exists as a heterodimer. Western immunoblots of both differentiated keratinocyte cytosol and keratinocyte-conditional media stained with a rabbit anti-human serum albumin antibody identified a protein of approximately 67 kDa, but the electrofocused fraction did not react with this antibody. Thus, epidermis and differentiated keratinocytes possess high-affinity cytosolic FA-binding activity that cannot be ascribed either to conventional low-molecular-weight FABPs or to albumin.

Binding, Competitive↗
PubMed1993

Fatty-acid metabolism and the pathogenesis of hepatocellular carcinoma: review and hypothesis.

Despite increasing understanding of the genetic control of cell growth and the identification of several involved chemical and infectious factors, the pathogenesis of clinical and experimental hepatocellular carcinoma remains unknown. Available evidence is consistent with the possibility that selected changes in the hepatocellular metabolism of long-chain fatty acids may contribute significantly to this, process. Specifically, studies of the peroxisome proliferators, a diverse group of xenobiotics that includes the fibrate class of hypolipidemic drugs, suggest that increased fatty acid oxidation by way of extramitochondrial pathways (i.e., omega-oxidation in the smooth endoplasmic reticulum and beta-oxidation in the peroxisomes) results in a corresponding increase in the generation of hydrogen peroxide and, thus, oxidative stress. This in turn leads to alterations in gene expression and in DNA itself. We also review evidence supporting a potentially decisive influence of particular aspects of hepatocellular fatty acid metabolism in determining the activity of the extramitochondrial pathways. Moreover, certain intermediates of extramitochondrial fatty acid oxidation (e.g., the long-chain dicarboxylic fatty acids) impair mitochondrial function and are implicated as modulators of gene expression through their interaction with the peroxisome proliferator-activated receptor. Finally, the occurrence of hepatic tumors in type I glycogen storage disease (glucose-6-phosphatase deficiency) may exemplify this general mechanism, which may also contribute to nonneoplastic liver injury and to tumorigenesis in other tissues.

Animals↗
PubMed1992

The primary structure of fatty-acid-binding protein from nurse shark liver. Structural and evolutionary relationship to the mammalian fatty-acid-binding protein family.

The primary structure of a fatty-acid-binding protein (FABP) isolated from the liver of the nurse shark (Ginglymostoma cirratum) was determined by high-performance tandem mass spectrometry (employing multichannel array detection) and Edman degradation. Shark liver FABP consists of 132 amino acids with an acetylated N-terminal valine. The chemical molecular mass of the intact protein determined by electrospray ionization mass spectrometry (Mr = 15124 +/- 2.5) was in good agreement with that calculated from the amino acid sequence (Mr = 15121.3). The amino acid sequence of shark liver FABP displays significantly greater similarity to the FABP expressed in mammalian heart, peripheral nerve myelin and adipose tissue (61-53% sequence similarity) than to the FABP expressed in mammalian liver (22% similarity). Phylogenetic trees derived from the comparison of the shark liver FABP amino acid sequence with the members of the mammalian fatty-acid/retinoid-binding protein gene family indicate the initial divergence of an ancestral gene into two major subfamilies: one comprising the genes for mammalian liver FABP and gastrotropin, the other comprising the genes for mammalian cellular retinol-binding proteins I and II, cellular retinoic-acid-binding protein myelin P2 protein, adipocyte FABP, heart FABP and shark liver FABP, the latter having diverged from the ancestral gene that ultimately gave rise to the present day mammalian heart-FABP, adipocyte FABP and myelin P2 protein sequences. The sequence for intestinal FABP from the rat could be assigned to either subfamily, depending on the approach used for phylogenetic tree construction, but clearly diverged at a relatively early evolutionary time point. Indeed, sequences proximately ancestral or closely related to mammalian intestinal FABP, liver FABP, gastrotropin and the retinoid-binding group of proteins appear to have arisen prior to the divergence of shark liver FABP and should therefore also be present in elasmobranchs. The presence in shark liver of an FABP which differs substantially in primary structure from mammalian liver FABP, while being closely related to the FABP expressed in mammalian heart muscle, peripheral nerve myelin and adipocytes, opens a further dimension regarding the question of the existence of structure-dependent and tissue-specific specialization of FABP function in lipid metabolism.

Amino Acid Sequence↗
PubMed1992

Mechanism-based probes of the topology and function of fatty acid hydroxylases.

The use of three mechanism-based probes to investigate the topology and function of fatty acid hydroxylases is discussed. 1) The observation of protein rather than heme alkylation in the reaction of cytochrome P4504A1 with 10-undecynoic acid supports the argument that the enzyme circumvents the inherent preference for omega-1 hydroxylation by restricting access to the ferryl oxygen. 2) The regiochemistry of the ferricyanide-mediated iron-to-nitrogen shift of the cytochrome P450102 (P450BM-3) phenyl-iron complex indicates that the active site of this bacterial fatty acid hydroxylase is open primarily above pyrrole ring A of the prosthetic heme group, 3) Inhibition of clofibrate-mediated peroxisome proliferation in cultured rat hepatocytes by inactivation of cytochrome P4504A1 indicates that omega-hydroxylation of fatty acids provides a signal for peroxisome proliferation.

Animals↗
PubMed1992

Intracranial pressure monitoring and liver transplantation for fulminant hepatic failure.

Cerebral edema and intracranial hypertension, commonly present in fulminant hepatic failure, may lead to brainstem herniation and limit the survival of comatose patients awaiting liver transplantation before a donor organ becomes available. Also, they are likely responsible for postoperative neurological morbidity and mortality. Although intracranial pressure monitoring has been proposed to aid clinical decision making in this setting, its use in the prevention of brainstem herniation preoperatively, in the selection of patients for liver transplantation who have the potential for neurological recovery and in the maintenance of cerebral perfusion during liver transplantation has not been examined in detail. To address these issues, we established a protocol for intracranial pressure monitoring in comatose patients with fulminant hepatic failure as part of their preoperative and intraoperative management. Twenty adults and three children underwent intracranial pressure monitoring. Ten patients required preoperative medical therapy with mannitol, barbiturates or both for a rise in intracranial pressure above 25 mm Hg. Four patients had a sustained lowering of intracranial pressure, three of whom survived hospitalization. Six patients had intracranial hypertension refractory to medical management, were removed from a waiting list for a donor organ and died with brainstem herniation. Of the remaining 17 patients, 3 died of other causes while awaiting a donor organ, 2 recovered spontaneously without neurological sequelae and 12 underwent liver transplantation. All but one patient undergoing liver transplantation had transient intraoperative intracranial hypertension develop, requiring medical treatment. The 12 patients who had transplants recovered neurologically and were discharged from the hospital.(ABSTRACT TRUNCATED AT 250 WORDS)

Hepatic Encephalopathy↗
PubMed1991

In situ binding of fatty acids to the liver fatty acid binding protein: analysis using 3-[125I]iodo-4-azido-N-hexadecylsalicylamide.

A photoactivatable radioiodinated fatty acid analogue, 3-[125I]iodo-4-azido-N-hexadecylsalicylamide (125I-AHS) has been synthesized and used to investigate the involvement of cellular lipid carriers in hepatic fatty acid utilization. Photoactivation of Hep G2 internalized 125I-AHS revealed that several cellular proteins were crosslinked with the radiolabeled fatty acid analogue. Three predominant proteins in the membrane fraction of the cell with molecular masses 17, 50 and 127 kDa were crosslinked with the lipid analogue, as determined using autoradiography after SDS-PAGE. Three other proteins in the soluble fraction of the cell, with molecular masses 14, 24 and 35 kDa, were also labeled in situ. In contrast to the other labeled proteins, the fatty acid analogue accumulated on the cytoplasmic 14 kDa protein in a time and temperature dependent fashion. The in situ-labeled 14 kDa protein was identified from primary rat hepatocytes as the liver fatty acid binding protein by partial purification and its ability to be immunoprecipitated with immunospecific L-FABP antiserum. Collectively the results indicate that fatty acids traverse the plasma membrane and are bound cytoplasmically by the liver fatty acid binding protein, as well as other proteins in the cell. This represents the first demonstration in intact hepatocytes that the liver fatty acid binding protein participates in the process of intracellular fatty acid trafficking, and supports a model in which cytoplasmic lipid carriers solubilize fatty acids as a step in their metabolic utilization.

Affinity Labels↗
PubMed1991

A methylsulfonyl metabolite of a polychlorinated biphenyl can serve as a ligand for liver fatty acid binding protein in rat intestinal mucosa.

When a 100,000 x g supernatant from rat intestinal mucosa was incubated with 4,4'-bis([3H]methylsulfonyl)-2,2',5,5'-tetrachlorobiphenyl, [(CT3SO2)2TCB] a (CT3SO2)2TCB-protein complex was formed. The (CT3SO2)2TCB-protein complex was isolated and purified using gel filtration and ion-exchange chromatography. The protein portion of this complex was characterized to be liver fatty acid binding protein (L-FABP) by SDS-polyacrylamide gel electrophoresis and immunoblot analysis. No cross reactivity was observed in the immunoblot analysis between the purified protein and anti-heart or anti-intestinal fatty acid binding protein. (CT3SO2)2TCB was extractable from L-FABP and therefore not covalently bound to L-FABP.

Animals↗
PubMed1991

Isolation and characterization of fatty acid binding protein in the liver of the nurse shark, Ginglymostoma cirratum.

1. A 14.5 kDa fatty acid binding protein was isolated from the liver of the nurse shark, Ginglymostoma cirratum. 2. Purified shark liver FABP (pI = 5.4) bound oleic acid at a single site with an affinity similar to that of mammalian FABP. 3. The apparent size, pI and amino acid composition of shark liver FABP indicate a close structural relationship between this protein and mammalian heart FABP.

Animals↗
PubMed1991

The aesthetic analysis of the face.

An analysis of the facial soft tissues is presented which permits aesthetic considerations of facial harmony and balance to be measured, and assessed quantitatively. The assessment is carried out in a practical and straight-forward manner, avoiding the measurement of angles. The visually determined Aesthetic Horizontal Line is used as the reference line, with more reliability than the Natural Head Position and more relevance to the soft tissues than Frankfort Horizontal. The analysis accurately predicts the correct position of the mandible so that the extent of orthopaedic or surgical correction necessary can be evaluated. The ideal position and angulation of the maxillary incisors are determined and established as treatment goals, to give optimal exposure of the dentition in expressive behaviour. Comparison of before and after treatment cephalograms permits quantitative assessment of aesthetic change.

Adolescent↗