K-ras is an essential gene in the mouse with partial functional overlap with N-ras

Mammalian ras genes are thought to be critical in the regulation of cellular proliferation and differentiation and are mutated in approximately 30% of all human tumors. However, N-ras and H-ras are nonessential for mouse development. To characterize the normal role of K-ras in growth and development, we have mutated it by gene targeting in the mouse. On an inbred genetic background, embryos homozygous for this mutation die between 12 and 14 days of gestation, with fetal liver defects and evidence of anemia. Thus, K-ras is the only member of the ras gene family essential for mouse embryogenesis. We have also investigated the effect of multiple mutations within the ras gene family. Most animals lacking N-ras function and heterozygous for the K-ras mutation exhibit abnormal hematopoietic development and die between days 10 and 12 of embryogenesis. Thus, partial functional overlap appears to occur within the ras gene family, but K-ras provides a unique and essential function.

Isoforms of rat liver fatty acid binding protein differ in structure and affinity for fatty acids and fatty acyl CoAs

Although native rat liver fatty acid binding protein (L-FABP) is composed of isoforms differing in isoelectric point, their comparative structure and function are unknown. These properties of apo- and holo-L-FABP isoforms were resolved by circular dichroism, time-resolved fluorescence spectroscopy, and binding/displacement of fluorescent ligands. Both apo-isoforms had similar hydrodynamic radii of 18.5 A, but apo-isoform I had a greater alpha-helical content and exhibited a longer Tyr lifetime, indicative of secondary and tertiary structural differences from isoform II. Isoforms I and II both had two fatty acid or fatty acyl CoA binding sites. Ligand binding decreased the isoform hydrodynamic radii by 3-4 A and increased Tyr rotational motions in a more restricted range. Fatty acyl CoAs were more effective than fatty acids in altering the isoform structures. Scatchard analysis showed that both isoforms bound cis- parinaric acid with high affinity (Kd values 41 and 60 nM, respectively) and bound trans-parinaric acid with 2- and 7-fold, respectively, higher affinity than for cis-parinaric acid. In contrast, isoform I had higher affinity for cis- and trans-parinaroyl CoAs (Kd values of 33 and 14 nM) than did isoform II (Kd values of 110 and 97 nM), thereby resulting in biphasic plots of parinaroyl-CoA binding to native L-FABP. Finally, displacement studies indicated that each isoform displayed distinct specificities for fatty acid/fatty acyl CoA chain length and unsaturation. Thus, rat L-FABP isoforms differ markedly in both structure and ligand binding function.

Molecular cloning, expression, and functional significance of a cytochrome P450 highly expressed in rat heart myocytes

A cDNA encoding a P450 monooxygenase was amplified from reverse transcribed rat heart and liver total RNA by polymerase chain reaction using primers based on the 5'- and 3'-end sequences of two rat pseudogenes, CYP2J3P1 and CYP2J3P2. Sequence analysis revealed that this 1,778-base pair cDNA contained an open reading frame and encoded a new 502 amino acid protein designated CYP2J3. Based on the deduced amino acid sequence, CYP2J3 was approximately 70% homologous to both human CYP2J2 and rabbit CYP2J1. Recombinant CYP2J3 protein was co-expressed with NADPH-cytochrome P450 oxidoreductase in Sf9 insect cells using a baculovirus expression system. Microsomal fractions of CYP2J3/NADPH-cytochrome P450 oxidoreductase-transfected cells metabolized arachidonic acid to 14,15-, 11,12-, and 8, 9-epoxyeicosatrienoic acids and 19-hydroxyeicosatetraenoic acid as the principal reaction products (catalytic turnover, 0.2 nmol of product/nmol of cytochrome P450/min at 37 degrees C). Immunoblotting of microsomal fractions prepared from rat tissues using a polyclonal antibody raised against recombinant CYP2J2 that cross-reacted with CYP2J3 but not with other known rat P450s demonstrated abundant expression of CYP2J3 protein in heart and liver. Immunohistochemical staining of formalin-fixed paraffin-embedded rat heart tissue sections using the anti-CYP2J2 IgG and avidin-biotin-peroxidase detection localized expression of CYP2J3 primarily to atrial and ventricular myocytes. In an isolated-perfused rat heart model, 20 min of global ischemia followed by 40 min of reflow resulted in recovery of only 44 +/- 6% of base-line contractile function. The addition of 5 microM 11, 12-epoxyeicosatrienoic acid to the perfusate prior to global ischemia resulted in a significant 1.6-fold improvement in recovery of cardiac contractility (69 +/- 5% of base line, p = 0.01 versus vehicle alone). Importantly, neither 14,15-epoxyeicosatrienoic acid nor 19-hydroxyeicosatetraenoic acid significantly improved functional recovery following global ischemia, demonstrating the specificity of the biological effect for the 11, 12-epoxyeicosatrienoic acid regioisomer. Based on these data, we conclude that (a) CYP2J3 is one of the predominant enzymes responsible for the oxidation of endogenous arachidonic acid pools in rat heart myocytes and (b) 11,12-epoxyeicosatrienoic acid may play an important functional role in the response of the heart to ischemia.

Inhibition of glucose transport in human red blood cells by adenosine antagonists

Previous studies have suggested that adenosine antagonists can interfere with normal glucose uptake in perfused rat heart. In the present studies, fluorine-19 nuclear magnetic resonance spectroscopy was used to study the effect of the adenosine antagonist, BW-A1433U, on the equilibrium exchange of fluorinated glucose analogs in human erythrocytes. Studies of the equilibrium exchange of both 2-fluoro-2-deoxy-D-glucose and 3-fluoro-3-deoxy-D-glucose with either one-dimensional magnetization transfer or two-dimensional exchange spectroscopy were performed, and significant inhibition was observed in all cases. From concentration-dependent studies, an inhibition constant for the equilibrium exchange measured at 37 degrees C of 24 microM was determined.

Sterol carrier protein-2 mediated cholesterol esterification in transfected L-cell fibroblasts

The relative function of the 15 and 13.2 kDa forms of SCP-2 in cholesterol trafficking and metabolism was assessed using L-cell fibroblasts permanently transfected with the cDNA encoding for either the mouse 15 kDa or 13.2 kDa SCP-2. Expression of the 15 kDa, but not the 13.2 kDa SCP-2 increased [3H]cholesteryl ester formation from medium derived cholesterol by 30% compared to control cells. In both SCP-2 expressing cell lines, sphingomyelinase treatment increased the initial rate of [3 H]cholesteryl ester formation from plasma membrane derived cholesterol more than 11-fold and elevated [3H]cholesteryl ester levels 1.5-fold compared to control cells. Expression of both proteins resulted in nearly a 1.5-fold increase in [3H]oleic acid esterification into cholesteryl esters, although [3H]oleic acid esterification into triacylglycerols was also increased in the 13.2 kDa SCP-2 expressing cells relative to control. In both transfected cell lines, the cholesteryl ester mass was increased nearly 2-fold compared to control cells, consistent with increased cholesteryl ester synthesis. Similarly, triacylglycerol levels were increased 1.3-fold in the 13.2 kDa SCP-2 expressing cells which is consistent with the increased [3H]oleic acid esterification into triacylglycerol. In the 15 kDa SCP-2 expressing cells, triacylglycerol levels were decreased 60%, but free cholesterol levels were increased 1.2-fold relative to control cells. Thus, only the 15 kDa expression product, containing the putative targeting sequence, specifically enhanced cholesteryl ester formation from either plasma membrane or medium-derived cholesterol. In contrast, the 13.2 kDa expression product, lacking the putative targeting sequence, stimulated an increase in [3H]oleic acid esterification into both cholesterol and triacylglycerol pools, suggesting a non-specific stimulation of fatty acid esterification.

The assessment of parenting using the parental bonding instrument: two or three factors?

BACKGROUND

The Parental Bonding Instrument (PBI) is a widely used measure of parenting, and is usually used to measure two parenting dimensions, care and over-protection. However, there is disagreement in the research literature about whether the PBI is best used as a two-factor or a three-factor measure.

METHOD

PBI scores from 583 US and 236 UK students were factor analysed to assess whether a three-factor solution was more satisfactory than a two-factor solution.

RESULTS

A three-factor (care, denial of psychological autonomy and encouragement of behavioural freedom) solution was found to be more satisfactory than a two-factor solution. Using the three-factor solution, group differences that were not apparent with the two-factor solution were identified and it was found that the parenting behaviours associated with depression could be more accurately identified.

CONCLUSION

The authors suggest that with modifications, the PBI could be used to measure three parenting variables (care, denial of psychological autonomy and encouragement of behavioural freedom), which would allow greater accuracy of prediction and a greater understanding of underlying processes.

The sterol carrier protein-2 fatty acid binding site: an NMR, circular dichroic, and fluorescence spectroscopic determination

The interaction and orientation of fatty acids with recombinant human sterol carrier protein-2 (SCP-2) were examined by nuclear magnetic resonance (NMR), circular dichroism (CD), and fluorescence techniques. 13C-NMR spectroscopy of stearic acid and oleic acid as well as fluorescence spectroscopy of cis-parinaric acid demonstrated that SCP-2 bound naturally occurring fatty acids with near 1:1 stoichiometry. Several findings indicated that the fatty acid was oriented in the binding site with its methyl end buried in the protein interior and its carboxylate exposed at the surface: the chemical shift of bound [18-13C]-stearate; dicarboxylic/monocarboxylic acid cis-parinaric acid displacement; complete ionization of the carboxylate group of SCP-2 bound [1-13C]stearate at neutral pH; lack of electrostatic interactions between 13C-fatty acids with SCP-2 cationic residues: pH titratability of the SCP-2 bound [1-13C]stearate carboxylate group. SCP-2 did not undergo global structural changes upon ligand binding or pH decrease as indicated by the absence of significant changes in NMR and only small alterations in time resolved fluorescence parameters. However, SCP-2 did undergo secondary structural changes detected by CD in the pH range 5-6. While these changes in secondary structure did not alter the fatty acid:SCP-2 binding stoichiometry, the affinity for fatty acid was increased severalfold at lower pH. In summary, 13C-NMR, CD, and fluorescence spectroscopy provided a detailed understanding of the interaction of fatty acids with SCP-2 and further showed for the first time the orientation of the fatty acid within the binding site. The pH-induced changes in SCP-2 secondary structure and ligand binding activity may be important to the mechanism whereby this protein interacts with membrane surfaces to enhance lipid binding/transfer.

The validity of screening for post-traumatic stress disorder and major depression among Vietnamese former political prisoners

The aim of this study was to investigate the validity of the Harvard Trauma Questionnaire (HTQ) and the depression sub-scale of the Hopkins Symptom Checklist-25 (HSCL-25) in screening for post-traumatic stress disorder (PTSD) and major depressive disorder (MDD) among Vietnamese former political prisoners (POWs). The study population included Vietnamese POWs (n = 51) who migrated to the Boston metropolitan area between January 1990 and July 1992 under the Special Released Re-education Center Detainees Resettlement Program. The criterion validity of the HTQ in assessing PTSD and of the depression sub-scale of the HSCL-25 in assessing MDD is supported by the results. Consideration of an appropriate cut-off score should include examination of the utility of a given screening instrument for PTSD or MDD within different settings, such as refugee camps vs. countries of third asylum.

A novel antibody-dependent cellular cytotoxicity epitope in gp120 is identified by two monoclonal antibodies isolated from a long-term survivor of human immunodeficiency virus type 1 infection

Two monoclonal antibodies (MAbs), 42F and 43F, were isolated some 14 months apart from a single long-term survivor of human immunodeficiency virus type 1 (HIV-1) infection. These MAbs were found to be indistinguishable in terms of their isotypes, specificities, affinities, and biological activities. Both 42F and 43F directed substantial antibody-dependent cellular cytotoxicity (ADCC) against cells infected with four divergent lab-adapted strains of HIV-1, but no neutralizing activity against these strains was detectable. The ability of MAbs 42F and 43F, as well as that of MAbs against two other gp120 epitopes, to direct ADCC against uninfected CD4+ cells to which recombinant gp120SF2 had been adsorbed (i.e., "innocent bystanders") was demonstrated to be less efficient by at least an order of magnitude than their ability to direct ADCC against HIV-1-infected cells. Flow cytometry analyses showed that 42F and 43F also bind to native primary isolate Envs from clades B and E expressed on cell surfaces. By direct binding and competition assays, it was demonstrated that the 42F/43F epitope lies in a domain of gp120 outside the previously described CD4-binding site and V3 loop ADCC epitope clusters. Immunoblot analysis revealed that the 42F/43F epitope is not dependent on disulfide bonds or N-linked glycans in gp120. Epitope mapping of 42F and 43F by binding to linear peptides demonstrated specificity of these MAbs for a sequence of 10 amino acids in the C5 domain comprising residues 491 to 500 (Los Alamos National Laboratory numbering for the HXB2 strain). Thus, 42F and 43F define a new ADCC epitope in gp120. Because of the relative conservation of this epitope and the fact that it appears to have been significantly immunogenic in the individual from which these MAbs were derived, it may prove to be a useful component of HIV vaccines. Furthermore, these MAbs may be used as tools to probe the potential importance of ADCC as an antiviral activity in HIV-1 infection.

Unsuccessful use of binaural amplification by an elderly person

An elderly person who preferred and performed better with monaural than with binaural amplification was extensively studied, both audiologically and neuropsychologically, in search of an explanation for the phenomenon. Particular emphasis was placed on the study of dichotic speech perception, both behaviorally and electrophysiologically. Results suggest that age-related changes in interhemispheric transfer of auditory input via corpus callosum may underlie the preference for monaural amplification. Implications for the evaluation of amplification potential in elderly persons are discussed.

Effects of alterations in calcium homeostasis on apoptosis during neoplastic progression

Our previous studies showed that early, stage I preneoplastic cells (sup+ I) are highly susceptible to apoptosis, whereas the later, stage II preneoplastic cells (sup- II) are relatively resistant. To examine possible mechanisms that might explain these differences in the regulation of apoptosis, Ca2+ homeostasis was analyzed and comparisons were made between these two Syrian hamster embryo cell lines. The Ca2+ indicator, fura-2, and fluorescent microscopy were used to measure intracellular free calcium concentrations, [Ca2+]i. The results indicated that the [Ca2+]i level in logarithmically growing sup+ I cells (approximately 100 nM) was considerably lower than that observed in sup- II cells (approximately 260 nM). Serum removal resulted in a reduction of [Ca2+]i in the sup+ I cells (approximately 82 nM), whereas the [Ca2+]i level in sup- II cells did not change. Endoplasmic reticulum (ER) calcium levels were determined by measuring thapsigargin-releasable Ca2+. Reduced ER calcium was consistently observed in cells induced to undergo apoptosis. Specifically, thapsigargin-releasable Ca2+ was greatly reduced in sup+ I cells (45 nM) as compared to sup- II cells (190 nNM) after 4 h in low serum. When sup- II cells were placed under conditions that resulted in apoptosis (thapsigargin or okadaic acid), decreased ER calcium was observed. To determine whether reduced ER calcium had a causative effect in apoptosis, ER calcium levels were exogenously increased in sup+ I cells by raising extracellular Ca2+ to 3 mM; ER calcium levels were maintained, and apoptosis was blocked. Studies were performed to determined whether the decrease in ER calcium could be attributed to reduced Ca2+ influx at the plasma membrane. To measure directly whether Ca2+ entry was decreased in sup+ I cells in 0.2% serum, Mn2+ uptake was used to monitor Ca2+ influx. The data show that in low serum, the rate of thapsigargin-induced Mn2+ entry in sup+ I cells was approximately 50% lower than that of sup- II cells, demonstrating that capacitative entry is reduced in sup+ I cells. In further support of this hypothesis, thapsigargin-treated sup+ I cells (0.2% serum) showed decreased Ca2+ entry upon raising extracellular Ca2+ from 0 to 2 mM. We report the novel finding that early preneoplastic cells, which exhibit a high propensity to undergo apoptosis, have decreased calcium entry at the plasma membrane, resulting in decreased ER calcium pools. This study provides new insight into mechanisms that can be involved in the regulation/dysregulation of apoptosis during neoplastic progression. Furthermore, the data imply that preneoplastic cells, which have developed a mechanism to maintain ER calcium, would be less susceptible to apoptosis and would thus have an increased potential for becoming transformed.

Fatty acid uptake in diabetic rat adipocytes

The effect of diabetic status and insulin on adipocyte plasma membrane properties and fatty acid uptake was examined. Studies with inhibitors and isolated adipocyte ghost plasma membranes indicated 9Z, 11E, 13E, 15Z-octatetraenoic acid (cis-parinaric acid) uptake was protein mediated. Cis-parinaric acid uptake was inhibited by trypsin treatment or incubation with phloretin, and competed with stearic acid. The initial rate, but not maximal uptake, of cis-parinaric acid uptake was enhanced two-fold in adipocytes from diabetic rats. Concomitantly, the structure and lipid composition of adipocyte ghost membranes was dramatically altered. However, the increased initial rate of cis-parinaric acid uptake in the diabetic adipocytes was not explained by membrane alterations or by a two-fold decrease in cytosolic adipocyte fatty acid binding protein (ALBP), unless ALBP stimulated fatty acid efflux. Thus, diabetic status dramatically altered adipocyte fatty acid uptake, plasma membrane structure, lipid composition, and cytosolic fatty acid binding protein.

The validity of posttraumatic stress disorder among Vietnamese refugees

The aim of this study was to examine the validity of posttraumatic stress disorder (PTSD) among Vietnamese refugees. The study population included 74 Vietnamese refugees who had resettled in the metropolitan Boston area. The previously validated Harvard Trauma Questionnaire was used to assess traumatic events and trauma-related symptoms. The number of traumatic events experienced was positively correlated with the severity of PTSD-related symptoms in this population. Internal consistency estimates and principal components analysis provided results that generally supported DSM-IV symptom dimensions of arousal, avoidance, and reexperiencing. However, the emergence of two separate dimensions of avoidance reflected the important contribution of depression to the traumatic response.

Effect of insulin on fatty acid uptake and esterification in L-cell fibroblasts

We examined the effects of insulin on fatty acid uptake in L-cell fibroblasts, using cis-parinaric acid to measure uptake rates in the absence of esterification and [3H]oleic acid to measure uptake rates in the presence of esterification. L-cells exhibited both high and low affinity insulin binding sites with Kd of 23 nM and 220 nM and a cellular density of 1.4 and 6.8 x 10(5) sites/cell, respectively. Insulin in the range 10(-9) to 10(-7) M significantly decreased both the initial rate and maximal extent of cis-parinaric acid uptake by 24 to 30%. Insulin also reduced [3H]oleic acid uptake up to 35%, depending on insulin concentration and decreased the amount of fatty acid esterified into the phospholipids and neutral lipids by 28 and 70%, respectively. In contrast, glucagon or epinephrine stimulated both the initial rate and extent of cis-parinaric acid uptake 18 and 25%, respectively. Because L-cells lack P-adrenergic receptors, the epinephrine effect was not the result of P-receptor stimulation. Hence, insulin altered not only fatty acid uptake, as determined by cis-parinaric and oleic acid uptake, but also altered the intracellular oleic acid esterification.

The effect of ionizing radiation on signal transduction: antibodies to EGF receptor sensitize A431 cells to radiation

What determines the degree of cell-resistance or sensitivity to ionizing radiation is not yet known. As a corollary to the ability of ceramide to induce apoptosis, some questions arise as to whether malignant cells escape apoptosis because of their inability to mount a ceramide response to inducers of apoptosis. To shed more light on the molecular mechanisms of tumor cell response to radiation, we tested whether exposure to ionizing radiation (of 200-1000 cGy) is associated with changes in ceramide levels in A431 tumor epithelial cells and whether the ability of ceramide to induce apoptosis is inhibited by protein kinase C (PKC) activation. Our studies demonstrate an immediate decrease in cellular levels of ceramide in response to radiation, while sphingosine levels increase. Under the same conditions the cellular 1,2-diacylglycerol (DAG) levels decrease as well, being accompanied by the translocation of PKC alpha from the membrane to the cytoplasm. Elevation of membrane PKC levels by 12-O-tetradecanoylphorbol 13-acetate (TPA) treatment had no effect on cell survival after irradiation, while treatment with EGF during and after irradiation augmented cell survival. Moreover, monoclonal antibodies to the EGF receptor (EGFR) sensitize cells to radiation by facilitating radiation-induced apoptosis. It is thus plausible that in human Squamous carcinoma cells, radiation activates predominantly the EGFR to induce resistance, while both sphingomyelin and PKC signal transduction pathways are deactivated and demonstrate no significant role in the modulation of the sensitivity or the resistance of A431 cells to ionizing radiation.

Intestinal fatty acid-binding protein expression stimulates fibroblast fatty acid esterification

The effect of intestinal fatty acid binding protein (I-FABP) expression on cell growth and cell lipid content is not known. Therefore, mouse L-cell fibroblasts were transfected with the cDNA encoding for I-FABP. The high expression clones expressed 0.35% of the total cytosolic proteins as I-FABP. Mock transfected L-cells did not differ from control L-cells in any properties tested. Neither the growth rate, maximal cell density, nor [3H]oleic acid uptake differed in I-FABP expressing as compared to control cells. In contrast, I-FABP expression increased triacylglycerol and cholesteryl ester mass (nmol/mg protein) by 63% and 25%, respectively. Phospholipid mass was unchanged in I-FABP expressing cells. The initial [3H]oleic acid esterification into triacylglycerols and cholesteryl esters was increased 3.9- and 2.5-fold in I-FABP expressing cells. Although, the initial [3H]oleic acid esterification into total phospholipids was unchanged, within the phospholipid fraction the initial [3H]oleic acid esterification into phosphatidylethanolamine was increased 70% and decreased 50% in phosphatidylcholine in I-FABP expressing cells. These observed differences suggest a distinct role for I-FABP in stimulating net formation, and not just turnover, of triacylglycerides and cholesteryl esters in transfected L-cell fibroblasts.

Recent advances in membrane cholesterol domain dynamics and intracellular cholesterol trafficking

Cholesterol is distributed nonrandomly in and between biological membranes. Despite over two decades' investigation of these phenomena, the origin, regulation, and function of membrane cholesterol asymmetry are not known. Likewise, although pathways of cellular cholesterol absorption/utilization as well as de novo synthesis have been investigated in depth, parallel progress in elucidating pathways of intracellular cholesterol trafficking and final deposition of cholesterol within membranes remains undefined. Understanding the nature and regulation of these processes is essential to resolving molecular mechanisms of cholesterol uptake, reverse cholesterol transport, steroidogenesis, and modulation of membrane function. Based on the fundamental observation that cholesterol is not distributed uniformly in the cell, three key concepts have contributed to recent advances in this field: First, cholesterol is asymmetrically distributed across the cell surface plasma membrane, wherein it translocates rapidly. Second, cholesterol is distributed within the plane of biomembrane bilayers into dynamic and static domains, with the latter predominating. The exact nature and physiological functions of such cholesterol domains or pools remain an enigma. Third, regulation of the size and kinetics of biomembrane cholesterol domains may be determining factors in intracellular cholesterol trafficking, targeting, and efflux. Contributions of both cytosolic carrier proteins and vesicular processes are recognized.