Jumping to conclusions in persistent pain using a somatosensory modification of the beads task

BACKGROUND

There is theoretical and empirical evidence that persistent pain occurs because of a distortion in top-down perceptual processes. 'Jumping to conclusions' (JTC) tasks, such as the beads task, purportedly capture these processes and have yet to be studied in people with chronic pain. However, the beads task uses visual stimuli, whereas tasks involving processing in the somatosensory domain seem at least more face valid in this population. This study uses a novel somatosensory adaptation of the beads task to explore whether a JTC reasoning style is more common in people with persistent pain compared controls.

METHODS

30 persistent pain patients and 30 age-, gender- and education-matched controls completed the visual beads JTC task and a novel somatosensory version of the JTC task that used tactile stimuli (vibrations to the fingertip).

FINDINGS

Patients with persistent pain showed a 'jumping to conclusions' reasoning style on both tasks compared to the control group and there was no significant difference in the effect sizes on the two tasks.

INTERPRETATION

This preliminarily study demonstrated that individuals with persistent pain show a JTC reasoning style to both visual and somatosensory stimuli. Future research should focus on establishing how or whether this bias directly influences the experience of persistent pain.

Development and preliminary evaluation of a new screening instrument for atypical odontalgia and persistent dentoalveolar pain disorder

AIM

To develop and preliminarily evaluate a new screening instrument for atypical odontalgia (AO) or persistent dentoalveolar pain disorder (PDAP). To evaluate the instrument's performance in detecting AO/PDAP amongst a heterogeneous group of orofacial pain conditions and pain-free controls and empirically compare its performance with an established neuropathic screening instrument (S-LANSS), which is the best available standard.

METHODS

The study design was cross-sectional; subjects recruited included a convenience sample of pain-free controls (n = 21) and four groups of orofacial pain conditions: AO/PDAP (n = 22); trigeminal neuralgia (n = 21); temporomandibular disorder (n = 41); and acute dental pain (n = 41). The instrument's internal reliability and factor structure were examined alongside its sensitivity and specificity and ROC-determined threshold score.

RESULTS

The 9 AO/PDAP-specific items were found to moderately correlate with the S-LANSS (r = 0.58; P < 0.01). The 14-items of the full instrument were examined using exploratory factor analysis and reduced to ten items in a two-factor structure that explained 96% of the variance. This 10-item final instrument had a ROC area of 0.77 (95% CI: 0.67; 0.88), sensitivity of 77% (95% CI: 55; 92%), and specificity of 69% (95% CI: 60; 77%) with an intentionally higher false-positive rate than false-negative rate. In contrast, the S-LANSS exhibited sensitivity of 32% (95% CI: 14;55%) and specificity of 78% (95% CI: 70;85%) with less optimal false-positive versus false-negative rates.

CONCLUSION

This preliminary study confirms the new screening instrument for AO/PDAP merits progression to field testing.

Multiple-therapy-resistant major depressive disorder: a clinically important concept

Many novel therapeutic options for depression exist that are either not mentioned in clinical guidelines or recommended only for use in highly specialist services. The challenge faced by clinicians is when it might be appropriate to consider such 'non-standard' interventions. This analysis proposes a framework to aid this decision.Declaration of interestIn the past 3 years R.H.M.W. has received support for research, expenses to attend conferences and fees for lecturing and consultancy work (including attending advisory boards) from various pharmaceutical companies including Astra Zeneca, Cyberonics, Eli Lilly, Janssen, LivaNova, Lundbeck, MyTomorrows, Otsuka, Pfizer, Roche, Servier, SPIMACO and Sunovion. D.M.B.C. has received fees from LivaNova for attending an advisory board. In the past 3 years A.J.C. has received fees for lecturing from Astra Zeneca and Lundbeck; fees for consulting from LivaNova, Janssen and Allergan; and research grant support from Lundbeck.In the past 3 years A.C. has received fees for lecturing from pharmaceutical companies namely Lundbeck and Sunovion. In the past 3 years A.L.M. has received support for attending seminars and fees for consultancy work (including advisory board) from Medtronic Inc and LivaNova. R.M. holds joint research grants with a number of digital companies that investigate devices for depression including Alpha-stim, Big White Wall, P1vital, Intel, Johnson and Johnson and Lundbeck through his mindTech and CLAHRC EM roles. M.S. is an associate at Blueriver Consulting providing intelligence to NHS organisations, pharmaceutical and devices companies. He has received honoraria for presentations and advisory boards with Lundbeck, Eli Lilly, URGO, AstraZeneca, Phillips and Sanofi and holds shares in Johnson and Johnson. In the past 3 years P.R.A.S. has received support for research, expenses to attend conferences and fees for lecturing and consultancy work (including attending an advisory board) from life sciences companies including Corcept Therapeutics, Indivior and LivaNova. In the past 3 years P.S.T. has received consultancy fees as an advisory board member from the following companies: Galen Limited, Sunovion Pharmaceuticals Europe Ltd, myTomorrows and LivaNova. A.H.Y. has undertaken paid lectures and advisory boards for all major pharmaceutical companies with drugs used in affective and related disorders and LivaNova. He has received funding for investigator initiated studies from AstraZeneca, Eli Lilly, Lundbeck and Wyeth.

A systematic review of the comorbidity between Temporomandibular Disorders and Chronic Fatigue Syndrome

The most common cause of chronic oro-facial pain is a group of disorders collectively termed temporomandibular disorders (TMDs). Chronic painful TMD is thought to be a 'central sensitivity syndrome' related to hypersensitivity of the nervous system, but the cause is unknown. A similar understanding is proposed for other unexplained conditions, including chronic fatigue syndrome (CFS). Exploring the comorbidity of the two conditions is a valuable first step in identifying potential common aetiological mechanisms or treatment targets.

METHOD

Systematic literature review. Studies were included if they recruited community or control samples and identified how many reported having both TMD and CFS, or if they recruited a sample of patients with either TMD or CFS and measured the presence of the other condition.

RESULTS

Six papers met inclusion criteria. In studies of patients with CFS (n = 3), 21-32% reported having TMD. In a sample of people with CFS and fibromyalgia, 50% reported having TMD. Studies in people with TMD (n = 3) reported 0-43% having CFS. Studies in samples recruited from oro-facial pain clinics (n = 2) reported a lower comorbidity with CFS (0-10%) than a study that recruited individuals from a TMD self-help organisation (43%).

CONCLUSION

The review highlights the limited standard of evidence addressing the comorbidity between oro-facial pain and CFS. There is a valuable signal that the potential overlap in these two conditions could be high; however, studies employing more rigorous methodology including standardised clinical assessments rather than self-report of prior diagnosis are needed.

High levels of exotic armored scales on imported avocados raise concerns regarding USDA-APHIS' phytosanitary risk assessment

Between 1914 and 2007, a quarantine protected California avocado, Persea americana Mill., groves from pests that might be introduced into the state along with fresh, imported avocados. Soon after Mexican avocados were first allowed entry on 1 February 2007, live specimens of several species of armored scales (Hemiptera: Diaspididae) not believed to be present in California were detected on 'Hass' avocados entering the state from Mexico. Initially, the California Department of Food and Agriculture (CDFA) prevented avocados infested with these scales from entering the state or required that they be fumigated with an approved treatment such as methyl bromide. After a Science Advisory Panel meeting in May 2007, U.S. Department of Agriculture-Animal and Plant Health Inspection Service (USDA-APHIS) reaffirmed its position that armored scales on shipments of fruit for consumption (including avocados) pose a "low risk" for pest establishment. In compliance with APHIS protocols, as of 18 July 2007, CDFA altered its policy to allow shipments of scale-infested avocados into the state without treatment. Here, we report on sampling Mexican avocados over an 8-mo period, September 2007-April 2008. An estimated 67 million Mexican Hass avocados entered California over this period. Based on samples from 140 trucks containing approximately 15.6% of this volume of fruit, we estimate that approximately 47.6 million live, sessile armored scales and an additional 20.1 million live eggs and crawlers were imported. We found eight probable species of armored scales in the samples, seven of these are not believed to occur in California; 89.3% of the live scales were Abgrallaspis aguacatae Evans, Watson and Miller, a recently described species. In contrast to the USDA-APHIS opinion, we believe the volume of shipments and levels of live scales they contain present a significant risk to California's US$300 million avocado industry and to other crops that might become infested by one or more of these exotic species.

A comparison of neurocognitive impairment in younger and older adults with major depression

BACKGROUND

Neurocognitive impairment is a well-recognized feature of depression that has been reported in younger and older adults. Similar deficits occur with ageing and it is unclear whether the greater deficits in late-life depression are an ageing-related phenomenon or due to a difference in the nature of late-life depression itself. We hypothesized that ageing alone would not fully explain the increased neurocognitive impairment in late-life depression but that differences in the illness explain the greater decrements in memory and executive function.

METHOD

Comparison of the neuropsychological performance of younger (<60 years) and older (60 years) adults with major depressive disorder (MDD) and healthy comparison subjects. Scores for each depression group were normalized against their respective age-matched control group and the primary comparisons were on four neurocognitive domains: (i) attention and executive function; (ii) verbal learning and memory; (iii) visuospatial learning and memory; and (iv) motor speed.

RESULTS

We recruited 75 subjects with MDD [<60 years (n=44), 60 years (n=31)] and 82 psychiatrically healthy comparison subjects [<60 years (n=42), 60 years (n=40)]. The late-life depression group had greater impairment in verbal learning and memory and motor speed but not in executive function. The two depressed groups did not differ in depression severity, global cognitive function, intelligence or education.

CONCLUSIONS

Late-life depression is associated with more severe impairment in verbal learning and memory and motor speed than depression in earlier adult life and this is not due to ageing alone.

Proteomic Analysis of the Genetic Premature Aging Disease Hutchinson Gilford Progeria Syndrome Reveals Differential Protein Expression and Glycosylation

Proteomics has revealed differential protein expression and glycosylation in membrane proteins from premature aging Hutchinson-Gilford progeria syndrome fibroblasts (progeria). Progeria is a rare autosomal dominant genetic disorder of premature aging characterized by marked growth retardation and specific, progressive, premature senescent changes of the skin and other tissues. Affected children live to an average age of 13 years. The 1q20-24 region of chromosome 1 which codes for one of these proteins, lamin A/C, has previously been implicated by Brown et al. (1990) who described identical twins with progeria, where cytogenetic analysis showed an inverted insertion in the long arm of the chromosome in 70% of cells. Luengo et al. (2002) similarly reported an interstitial deletion of chromosome 1q23, in a 9-year-old patient with a classic clinical picture of progeria.

Refining the mouse chromosomal location of Cdm, the major gene associated with susceptibility to cadmium-induced testicular necrosis

Cadmium (Cd++) is a widespread environmental pollutant and classifed as an IARC 'Category I' human carcinogen. Cd++ can also cause severe renal toxicity and may be involved clinically in cardiovascular disease and osteoporosis. Genetic differences in sensitivity to cadmium toxicity have been noted in humans, whereas, among inbred mouse strains, unequivocal genetic data exist. Resistance to cadmium-induced testicular damage was reported in 1973 to be associated with a single major recessive gene, named Cdm, which has now been localized to mouse chromosome (Chr) 3. Using polymorphic microsatellite markers and semiquantitative histological parameters, we have corroborated the original 1973 data concerning mendelian inheritance and have further refined the region containing the Cdm gene from more than 24 cM to 0.64 cM (estimated 40-80 genes). We phenotyped 26 recombinant inbred lines generated from C57BL/6J (B6, resistant) and DBA/2J (D2, sensitive) inbred mice, and determined that the Cdm gene maps between microsatellite markers D3Mit110 and D3Mit255. Although toxicity to numerous heavy metals is well known, virtually no molecular mechanisms have yet been uncovered either in humans or laboratory animals. Identification and characterization of the mouse Cdm gene should enhance our understanding of heavy metal toxicity by identifying and characterizing, for the first time, a major mammalian gene responsible for susceptibility to diseases caused by heavy metal toxicity.

Translocation (15;17)(q22;q21) as a secondary chromosomal abnormality in a case of acute monoblastic leukemia with tetrasomy 8

We describe a case of acute monoblastic leukemia (AML M5a), originally presenting as granulocytic sarcoma of the testis, showing unusual cytogenetic abnormalities. Tetrasomy 8 (primary) and t(15;17)(q22;q21) (secondary) were detected in bone marrow cells 6 months post-diagnosis, both by routine karyotype analysis and by fluorescence in situ hybridization (FISH) studies on metaphases and interphase nuclei. Retrospectively, the same abnormalities were identified in the primary testicular lesion using interphase FISH. However, reverse transcriptase polymerase chain reaction (RT-PCR) did not reveal the presence of a classic PML/RAR alpha fusion transcript. To the best of our knowledge, this is the first case to be reported in the literature of AML showing tetrasomy 8 in combination with secondary t(15;17).

Dioxin causes a sustained oxidative stress response in the mouse

Dioxin (2,3,7,8-tetrachlorodibenzo-p-dioxin; TCDD) is the prototype for environmental agonists of the aromatic hydrocarbon receptor (AHR) that are known to produce multiple adverse effects in laboratory animals as well as humans. Although not directly genotoxic, dioxin is known to increase transformation and mutations in mammalian cell culture and to cause an exaggerated oxidative stress response in the female rat. In humans and mice, however, dioxin-mediated oxidative stress appears to be more subtle, causing a response that has been poorly characterized. Using the female C57BL/6J inbred mouse, we show here that intraperitoneal treatment of 5 micrograms TCDD per kilogram on 3 consecutive days produces a striking, prolonged oxidative stress response: hepatic oxidized glutathione levels increase 2-fold within 1 week, and these effects persist for at least 8 weeks despite no further dioxin treatment. Urinary levels of 8-hydroxydeoxyguanosine--a product of DNA base oxidation and subsequent excision repair--remain elevated about 20-fold at 8 weeks after dioxin treatment, consistent with chronic and potentially promutagenic DNA base damage. These results demonstrate that dioxin exposure does produce a sustained oxidative stress response in the mouse.

The hereditary renal cell carcinoma 3;8 translocation fuses FHIT to a patched-related gene, TRC8

The 3;8 chromosomal translocation, t(3;8)(p14.2;q24.1), was described in a family with classical features of hereditary renal cell carcinoma. Previous studies demonstrated that the 3p14.2 breakpoint interrupts the fragile histidine triad gene (FHIT) in its 5' noncoding region. However, evidence that FHIT is causally related to renal or other malignancies is controversial. We now show that the 8q24.1 breakpoint region encodes a 664-aa multiple membrane spanning protein, TRC8, with similarity to the hereditary basal cell carcinoma/segment polarity gene, patched. This similarity involves two regions of patched, the putative sterol-sensing domain and the second extracellular loop that participates in the binding of sonic hedgehog. In the 3;8 translocation, TRC8 is fused to FHIT and is disrupted within the sterol-sensing domain. In contrast, the FHIT coding region is maintained and expressed. In a series of sporadic renal carcinomas, an acquired TRC8 mutation was identified. By analogy to patched, TRC8 might function as a signaling receptor and other pathway members, to be defined, are mutation candidates in malignant diseases involving the kidney and thyroid.

Docking and fusion in neurosecretion

A central issue in neurobiology concerns the mechanisms of membrane fusion that are essential for the rapid regulated delivery of neurotransmitters into the synapse. While many gene products are required for neurosecretion, recent research has focused on defining the core exocytotic machinery that is responsible for the docking of synaptic vesicles (SVs) and their fusion with the plasma membrane. N-ethylmaleimide-sensitive factor (NSF), soluble NSF attachment protein (SNAP) and SNAP receptor (SNARE) proteins are essential for fusion but may not be critical for SV docking. Current evidence suggests that NSF functions during an ATP-dependent step after docking but before fusion. NSF may function to liberate SNARE proteins from complexes so that the proteins on apposed membranes align in a parallel fashion to bring SVs into close contact with the plasma membrane for fusion.

Massive pulmonary edema and death after prostacyclin infusion in a patient with pulmonary veno-occlusive disease

Pulmonary veno-occlusive disease (PVOD) is a rare form of pulmonary hypertension associated with fibrotic occlusion of the smaller pulmonary veins. Although vasodilator therapy is effective in many patients with primary pulmonary hypertension, the role of vasodilators in PVOD is unclear because of concerns about precipitating pulmonary edema. Recently, however, there have been reports of successful therapy with oral vasodilators or intravenous administration of prostacyclin in patients with PVOD. In contrast, a patient with PVOD is described who developed acute pulmonary edema and respiratory failure during low-dose prostacyclin infusion, leading to death. This report suggests that vasodilators, especially prostacyclin, must be used with extreme caution in patients with known PVOD.

Human MDR 1 protein overexpression delays the apoptotic cascade in Chinese hamster ovary fibroblasts

Several laboratories have reported that overexpression of the multidrug resistance (MDR) protein is associated with intracellular alkalinization, and several investigators have reported that cells induced to undergo programmed cell death (apoptosis) acidify quite significantly. Because it is difficult to fully explain the resistance to apoptosis-inducing chemotherapeutic drugs that is exhibited by MDR tumor cells solely via altered drug transport alone [Hoffman et al. (1996) J. Gen. Physiol. 108, 295-313], we have investigated whether overexpression of the hu MDR 1 protein alters progression of the apoptotic cascade. LR73 fibroblasts induced to undergo apoptosis either via treatment with the chemotherapeutic drug colchicine or by serum withdrawal exhibit cellular volume changes, intracellular acidification, nuclear condensation, and chromosomal digestion ("ladder formation"), characteristic of apoptosis, in a temporally well-defined pattern. However, multidrug resistant LR73/20E or LR73/27 hu MDR 1 transfectants recently created in our laboratory without selection on chemotherapeutic drug are significantly delayed in the onset of apoptosis as defined by the above criteria, regardless of whether apoptosis is induced by colchicine treatment or by serum withdrawal. Thus, the delay cannot simply be due to the well-known ability of MDR protein overexpression to lower chemotherapeutic drug accumulation in MDR cells. LR73/27V500 "selectants", exhibiting similar levels of MDR protein overexpression but higher multidrug resistance due to selection with the chemotherapeutic drug vincristine, exhibit a slightly longer delay in the progression of apoptosis. Normal apoptotic cascade kinetics are partially restored by pre-treatment of the MDR cells with the MDR protein inhibitor verapamil. Untransfected LR73 cells not expressing MDR protein but elevated in pHi via manipulation of CO2/HCO3- as described [Hoffman et al. (1996) J. Gen. Physiol. 108, 295-313] are inhibited in DNA ladder formation, similar to LR73/hu MDR 1 transfectants. These results uncover an additional mechanism whereby MDR protein overexpression may promote the survival of tumor cells and further support the notion that in some systems intracellular acidification may be either causal or permissive for proper progression of the apoptotic cascade.

NSF is required for transport from early to late endosomes

Protein transport between early and late endosomes is a major membrane trafficking pathway in the cell followed by many proteins, including all down-regulated receptors. Yet, little is known at the molecular level about the mechanisms regulating membrane interactions in the endocytic pathway beyond early endosomes. In this study, we have used an in vitro transport assay to study the biochemical properties of endosome docking/fusion events. Our data demonstrate that N-ethylmaleimide (NEM) sensitive factor (NSF) and its soluble associated proteins (SNAPs) are required for transport from early to late endosomes, as well as at all other steps of endosomal membrane transport. We also find that these proteins are enriched on endosomal membranes. In addition, our studies suggest that besides NSF/SNAPs, another NEM-sensitive component may also be involved in docking/fusion at this late stage of the pathway. Finally, we find that, in contrast to Golgi membranes, NSF association to both early and late endosomal membranes occurs via an ATP-independent mechanism, indicating that the binding properties of endosomal and biosynthetic NSF are different. Our data thus show that NSF/SNAPs, perhaps together with another NEM-sensitive factor, are part of the basic molecular machinery which controls docking/fusion events during transport from early to late endosomes, along the lysosomal degradation pathway.

Effects of membrane potential versus pHi on the cellular retention of doxorubicin analyzed via a comparison between cystic fibrosis transmembrane conductance regulator (CFTR) and multidrug resistance (MDR) transfectants

Recently (Wei et al., Biophys J 69: 883-895, 1995), several 3T3/hu cystic fibrosis transmembrane conductance regulator (CFTR) transfectant clones were found to exhibit a low-level multidrug resistance (MDR) phenotype. This phenotype is similar, but not identical to that found for MDR transfectants not previously exposed to chemotherapeutic drugs. Both MDR and CFTR transfectants are depolarized (exhibit lower plasma membrane delta psi ), but the former have alkaline pHi whereas the latter are acidic. It has been proposed (Roepe et al., Biochemistry 32: 11042-11056, 1993) that both decreased delta psi and increased pHi contribute to altered cellular retention of chemotherapeutic drugs in MDR tumor cells, but the relative contribution of each to altered cellular drug accumulation, drug retention, and drug efflux has not been studied in detail. We therefore examined doxorubicin transport for hu CFTR and mu MDR 1 transfectants using sensitive continuous monitoring of fluorescence techniques. Both CFTR and MDR transfectants exhibited significantly reduced doxorubicin accumulation, relative to drug-sensitive control cells. Plots of the initial rate of accumulation versus doxorubicin concentration were linear for the control cells and the CFTR and MDR transfectants between 0.1 to 0.5 microM drug, but better fit by a quadratic between 0.1 to 1.5 microM drug. The slopes of these curves were proportional to measured delta psi. Low-level selection of either CFTR or MDR transfectants with chemotherapeutic drug did not decrease further the initial rate of drug accumulation or change delta psi. Accumulation experiments for control cells performed in the presence of various concentrations of K+ further suggests that the rate of accumulation is related to delta psi. By measuring the kinetics of doxorubicin release for CFTR and MDR transfectants preloaded with drug, we concluded that alkaline pHi perturbations are more important for determining relative intracellular binding efficiency. We also concluded, similar to the case previously made for MDR protein (Roepe, Biochemistry 31: 12555-12564, 1992) that CFTR overexpression does not enhance the rate of drug efflux. These data better define the role of lowered delta psi and elevated pHi in altering the cellular retention of doxorubicin in MDR tumor cells.

Acylation targets emdothelial nitric-oxide synthase to plasmalemmal caveolae

Endothelial nitric-oxide synthase (eNOS) generates the key signaling molecule nitric oxide in response to intralumenal hormonal and mechanical stimuli. We designed studies to determine whether eNOS is localized to plasmalemmal microdomains implicated in signal transduction called caveolae. Using immunoblot analysis, eNOS protein was detected in caveolar membrane fractions isolated from endothelial cell plasma membranes by a newly developed detergent-free method; eNOS protein was not found in noneaveolar plasma membrane. Similarly, NOS enzymatic activity was 9.4-fold enriched in caveolar membrane versus whole plasma membrane, whereas it was undetectable in non-caveolar plasma membrane. 51-86% of total NOS activity in postnuclear supernatant was recovered in plasma membrane, and 57-100% of activity in plasma membrane was recovered in caveolae. Immunoelectron microscopy showed that eNOS heavily decorated endothelial caveolae, whereas coated pits and smooth plasma membrane were devoid of gold particles. Furthermore, eNOS was targeted to caveolae in COS-7 cells transfected with wild-type eNOS cDNA. Studies with eNOS mutants revealed that both myristoylation and palmitoylation are required to target the enzyme to caveolae and that each acylation process enhances targeting by 10-fold. Thus, acylation targets eNOS to plasmalemmal caveolae. Localization to this microdomain is likely to optimize eNOS activation and the extracellular release of nitric oxide.

Toxicologic evaluation of a high-selenium hay diet in captive pronghorn antelope (Antilocapra americana)

Five captive-raised pronghorn antelope (Antilocapra americana) were fed an alfalfa-grass hay diet containing 15 ppm total dietary selenium (Se) for 164 days. Four additional captive-raised pronghorns fed a similar diet containing approximately 0.3 ppm total dietary Se served as controls. None of the pronghorns had clinical signs attributable to the high Se hay. Plasma Se increased more rapidly than blood Se concentrations, from baseline concentrations (< 0.15 g/ml) to > 0.40 g/ml within the first 50 days on the high selenium diet, but thereafter declined to approximately 0.30 microgram/ml. Mean primary antibody response to hen egg albumin was less in pronghorn on Se hay. No significant gross or histological lesions attributable to selenosis were found, nor was there any evidence of dystrophic hoof growth. The greatest Se tissue concentrations were found in liver and kidney (5.67 to 10.4 micrograms/g and 2.36 to 3.14 micrograms/g, respectively) from experimental animals; liver and kidney from the controls contained considerably less (< or = 0.52 microgram/g and < or = 0.61 microgram/g, respectively). Exposure of pronghorns for more than 5 mo to a diet containing 15 ppm Se caused significant increases in plasma, liver and kidney Se concentrations, in the absence of clinical disease or pathologic lesions due to selenosis. Based on these results, we propose that pronghorns are less susceptible to selenosis than previously reported and that diagnostic criteria for the disease should be modified.

Mutagenesis of palmitoylation sites in endothelial nitric oxide synthase identifies a novel motif for dual acylation and subcellular targeting

The endothelial nitric oxide synthase (ec-NOS) plays a key role in the transduction of signals from the bloodstream to the underlying smooth muscle. ecNOS undergoes a complex series of covalent modifications, including myristoylation and palmitoylation, which appear to play a role in ecNOS membrane association. Mutagenesis of the myristoylation site, which prevents both myristoylation and palmitoylation, blocks ecNOS targeting to cell membranes. Further, as described for some G-protein alpha subunits, both membrane association and palmitoylation of ecNOS are dynamically regulated: in response to agonists, the enzyme undergoes partial redistribution to the cell cytosol concomitant with depalmitoylation. To clarify the role of palmitoylation in determining ecNOS subcellular localization, we have constructed palmitoylation-deficient mutants of ecNOS. Serine was substituted for cysteine at two potential palmitoylation sites (Cys-15 and Cys-26) by site-directed mutagenesis. Immunoprecipitation of ecNOS mutants following cDNA transfection and biosynthetic labeling with [3H]palmitate revealed that mutagenesis of either cysteine residue attenuated palmitoylation, whereas replacement of both residues completely eliminated palmitoylation. Analysis of N-terminal deletion mutations of ecNOS demonstrated that the region containing these two cysteine residues is both necessary and sufficient for enzyme palmitoylation. The cysteines thus identified as the palmitoylation sites for ecNOS are separated by an unusual (Gly-Leu)5 sequence and appear to define a sequence motif for dual acylation. We analyzed the subcellular distribution of ecNOS mutants by differential ultracentrifugation and found that mutagenesis of the ecNOS palmitoylation sites markedly reduced membrane association of the enzyme. These results document that ecNOS palmitoylation is an important determinant for the subcellular distribution of ecNOS and identify a new motif for the reversible palmitoylation of signaling proteins.

Oligomerization of endothelial nitric oxide synthase. Evidence for a dominant negative effect of truncation mutants

Nitric oxide produced by the endothelial isoform of nitric oxide synthase (ecNOS) is a key determinant of vascular tone. In contrast to other nitric oxide synthase (NOS) isoforms, which have been characterized as soluble homodimeric enzymes, ecNOS is predominantly membrane-associated, a feature that has hindered direct biochemical analyses of its oligomeric structure. We investigated ecNOS oligomerization using co-immunoprecipitation experiments in transiently transfected COS-7 cells. When COS-7 cells co-transfected with constructs encoding wild-type ecNOS and an epitope-tagged myristoylation-deficient mutant were biosynthetically labeled with [3H]myristate, the antibody to the epitope tag specifically immunoprecipitated 3H-labeled ecNOS, reflecting enzyme oligomerization. In COS-7 cells transfected with cDNAs encoding epitope-tagged truncation mutants and untagged full-length ec-NOS, the wild-type enzyme could be immunoprecipitated by the antibody to the epitope tag. Co-immunoprecipitation of ecNOS with truncation mutants documented that both N- and C-terminal domains are involved in ecNOS oligomerization. When these truncation mutants are co-expressed with wild-type ecNOS, they exert a marked dominant negative effect on enzyme activity. Since NOS oligomerization itself may be subject to dynamic modulation, the regulation of ecNOS assembly may have implications for NO signaling in the vascular wall.

Language before and after temporal lobectomy: specificity of acute changes and relation to early risk factors

We evaluated language functions in 154 patients with left hemisphere speech dominance undergoing anterior temporal lobectomy (ATL). Measures of phonemic and semantic fluency, confrontation naming, repetition, comprehension, and reading were administered before and 3 weeks postoperatively. Patients were grouped by focus (left, LT; right, RT) and presence of early risk factors for development of seizures (ER, early risk, < or = 5 years; NER, no early risk): (LT-ER, n = 45; RT-ER, n = 49; LT-NER, n = 27; RT-NER, n = 33). Preoperatively, the LT group showed a selective naming deficit as compared with the RT group. Postoperatively only the LT-NER group showed significant overall decline in language. For this group, the change was attributable to a selective decline in naming as compared with other functions. These data indicate that there is a specific risk to naming after dominant ATL for adult temporal lobe epilepsy (TLE) patients with a left hemisphere focus and the absence of an early risk factor for the development of seizures.

Requirement for phosphoinositide 3-kinase in insulin-stimulated GLUT4 translocation in 3T3-L1 adipocytes

Insulin stimulates glucose transport in muscle and fat cells by inducing the redistribution of a specific glucose transporter, GLUT4, from intracellular vesicles to the cell surface. Phosphoinositide (PI) 3-kinase has been implicated as a key intermediate in insulin-stimulated glucose transport by studies that have examined the effects of wortmannin and LY294002, which are thought to be specific inhibitors of this enzyme. However, the specificity of these compounds for PI 3-kinase has recently been questioned. Epidermal growth factor, which activates mitogen-activated protein kinase in mouse 3T3-L1 adipocytes, has now been shown to have no effect on PI 3-kinase activity or GLUT4 translocation in these cells. Furthermore, microinjection of a dominant negative mutant of the 85-kDa subunit of PI 3-kinase, which lacks a binding site for the catalytic 110-kDa subunit, inhibited GLUT4 translocation induced by insulin in 3T3-L1 adipocytes; microinjection of the wild-type protein had no effect. These observations indicate that PI 3-kinase is necessary for insulin-induced GLUT4 translocation and glucose transport in adipocytes.

Agonist-modulated palmitoylation of endothelial nitric oxide synthase

The nitric oxide synthases (NOS) comprise a family of enzymes which differ in primary structure, biological roles, subcellular distribution, and post-translational modifications. The endothelial nitric oxide synthase (ec-NOS) is unique among the NOS isoforms in being modified by N-terminal myristoylation, which is necessary for its targeting to the endothelial cell membrane. The subcellular localization of the ecNOS, but not enzyme myristoylation, is dynamically regulated by agonists such as bradykinin, which promote ecNOS translocation from membrane to cytosol, as well as enhancing enzyme phosphorylation. Using transiently transfected endothelial cells, we now show that a myristoylation-deficient mutant ecNOS undergoes phosphorylation despite restriction to the cytosol, suggesting that phosphorylation may be a consequence rather than a cause of ecNOS translocation. We therefore explored whether other post-translational modifications might regulate ecNOS targeting and now report that ecNOS is reversibly palmitoylated. Biosynthetic labeling of endothelial cells with [3H]palmitic acid followed by immunoprecipitation of ecNOS revealed that the enzyme is palmitoylated; the label is released by hydroxylamine, consistent with formation of a fatty acyl thioester, and authentic palmitate can be recovered from labeled ecNOS following acid hydrolysis. Importantly, pulse-chase experiments in endothelial cells biosynthetically labeled with [3H]palmitate show that bradykinin treatment promotes ecNOS depalmitoylation. We conclude that ecNOS palmitoylation is dynamically regulated by bradykinin and propose that depalmitoylation of the enzyme may result in its cytosolic translocation and subsequent phosphorylation.

Evidence that p21ras mediates the neurotrophic effects of insulin and insulin-like growth factor I in chick forebrain neurons

Insulin and insulin-like growth factors (IGF-I and IGF-II) support the survival and differentiation of many types of neurons, including those from fetal chick forebrain. The mechanisms by which these peptides exert their neurotrophic actions are poorly understood. The aims of this study were to determine if insulin and IGF-I activate p21ras in fetal chick forebrain neurons and if activation of p21ras mediates the neurotrophic actions of these peptides. Activation of neuronal p21ras was examined by measuring the amount of GTP bound to p21ras before and after growth factor treatment. Insulin and IGF-I increased the ratio of GTP/GTP + GDP by 31 +/- 9.0% and 36 +/- 8.0%, respectively, p21Ras activation by insulin and IGF-I was maximal within 5 min. In the presence of insulin the response was sustained out to 180 min, whereas the response to IGF-I decreased significantly by 180 min. Both peptides stimulated p21ras at low concentrations with a maximal response obtained at 10 ng/ml for each peptide, idicating that insulin and IGF-I activate ras by interacting with their homologous receptor. Pretreatment of neurons with lovastatin (2 micrograms/ml), an inhibitor of ras isoprenylation, completely blocked the activation of p21ras by insulin and IGF-I. Lovastatin also blocked the ability of these growth factors to support the survival and differentiation of fetal chick neurons in culture. We conclude that insulin and IGF-I activate p21ras in fetal chick forebrain neurons by increasing the amount of GTP bound to p21ras. The activation of neuronal p21ras is necessary for insulin and IGF-I to promote survival and differentiation in these neurons.

Isolation and chromosomal localization of the human endothelial nitric oxide synthase (NOS3) gene

Nitric oxide (NO) is an important intercellular signaling molecule synthesized in diverse human tissues by proteins encoded by a family of NO synthase (NOS) genes. The similarity of sequence and cofactor binding sites has suggested that the NOS genes may also be related to cytochrome P450 reductase, as well as to plant and bacterial oxidoreductases. Endothelial NOS activity is a major determinant of vascular tone and blood pressure, and in several important (and sometimes hereditary) disease states, such as hypertension, diabetes, and atherosclerosis, the endothelial NO signaling system appears to be abnormal. To explore the relationship of the endothelial NOS gene to other similar genes, and to delineate the genetic factors involved in regulating endothelial NOS activity, we isolated the human gene encoding the endothelial NOS. Genomic clones containing the 5' end of this gene were identified in a human genomic library by applying a polymerase chain reaction (PCR)-based approach. Identification of the human gene for endothelial NOS (NOS3) was confirmed by nucleotide sequence analysis of the first coding exon, which was found to be identical to its cognate cDNA. The NOS3 gene spans at least 20 kb and appears to contain multiple introns. The transcription start site and promoter region of the NOS3 gene were identified by primer extension and ribonuclease protection assays. Sequencing of the putative promoter revealed consensus sequences for the shear stress-response element, as well as cytokine-responsive cis regulatory sequences, both possibly important to the roles played by NOS3 in the normal and the diseased cardiovascular system.(ABSTRACT TRUNCATED AT 250 WORDS)

Mitogen-activated protein kinase activation is not sufficient for stimulation of glucose transport or glycogen synthase in 3T3-L1 adipocytes

The role of mitogen-activated protein (MAP) kinase in the regulation of glucose metabolism has been investigated by comparing the effects of insulin and epidermal growth factor (EGF) on MAP kinase activation, glucose transport, and glycogen synthase in 3T3-L1 adipocytes. Insulin or EGF treatment for 5 min increased p42mapk and p44mapk activity to the same extent as determined by myelin basic protein kinase activity measurements and phosphotyrosine immunoblotting. The profiles of myelin basic protein kinase activity following MonoQ chromatography of extracts obtained from cells incubated with insulin or EGF were almost identical. Insulin increased glucose transport and GLUT4 translocation to the cell surface by 15- and 7-fold, respectively. EGF had no significant effect on these processes. Insulin increased the glycogen synthase ratio (-Glc-6-P/+Glc-6-P) by 7.5- and 3.5-fold in the presence and absence of glucose, respectively. EGF increased the ratios by only 2- and 1.3-fold, respectively. EGF did not appear to inhibit downstream of MAP kinase, because when adipocytes were incubated with insulin plus EGF, the stimulation of glucose transport and glycogen synthase was similar to that observed with insulin alone. These findings indicate that activation of the MAP kinase isoforms p42mapk and p44mapk is not sufficient for the activation of glucose transport and glycogen synthase in 3T3-L1 adipocytes.

Protein phosphatase-1 and -2a activities in cultured fetal chick neurons: differential regulation by insulin and insulin-like growth factor-I

In this study, we examined the developmental expression and regulation by insulin and insulin-like growth factor-I (IGF-I) of protein phosphatase-1 (PP-1) and protein phosphatase-2A (PP-2A) in cultured fetal chick neurons. Protein phosphatase activities were measured using 32P-labeled phosphorylase-a or 32P-labeled S6 kinase substrate peptide. In cell extracts from day 1-5 cultures, 40-45% of spontaneous protein phosphatase activity was due to PP-1. PP-2A accounted for the remaining 55-60% of enzyme activity. Spontaneous PP-1 activity increased by 100% in day 2 cultures and remained constant thereafter. PP-2A activity increased by 48% in day 2 cultures, with minimal increases in enzyme activity in later cultures. Under the assay conditions employed, at all times in culture a significant proportion (45-50%) of PP-1 was in an inactive form that could be reactivated by trypsin. PP-2A activity was not influenced by trypsin. Insulin stimulated neuronal PP-1 activity in day 4 and 5 cultures, but had no effect in earlier cultures. The activation of PP-1 by insulin was rapid, with a maximal effect (30-40% increase over basal levels) at 5 min with 10 ng/ml insulin. Insulin did not alter total (trypsin-released) PP-1 activity, the content of PP-1 catalytic subunit, or PP-2A activity at any time in culture. In contrast to insulin, IGF-I had no effect on PP-1 activity at any time in culture, but significantly increased PP-2A activity in day 5 cultures. Maximal stimulation of PP-2A activity by IGF-I was observed at 10 min, with an EC50 of 5 ng/ml. These results indicate that chick forebrain neurons contain both PP-1 and PP-2A activities and that neuronal PP-1 and PP-2A activities are differentially regulated by insulin and IGF-I. We conclude that although insulin and IGF-I share many steps in signal transduction, these growth factors have distinct actions on neuronal phosphatase activity that may impact on differences in their neurotropic actions.

Glucose transport in L6 myoblasts overexpressing GLUT1 and GLUT4

The roles of the glucose transporter isoforms, GLUT1 and GLUT4, in mediating insulin-stimulated glucose transport were investigated by stably overexpressing the transporters in L6 myoblasts. Levels of GLUT1 and GLUT4 in myoblasts from the cell lines having the highest content of these transporters were approximately 16- and 30-fold higher, respectively, than levels in nontransfected cells. The basal rate of 2-deoxy[3H]glucose uptake was severalfold higher in cells overexpressing GLUT1 than in the parent L6 myoblasts or in control cell lines that were generated by transfecting cells with expression vectors lacking transporter insert. The basal rate was not elevated in any of the lines expressing GLUT4. The net increase in 2-deoxy[3H]glucose uptake produced by insulin was larger in both the GLUT1 and GLUT4 cells than in the control cells. Insulin increased uptake in GLUT4 cells by as much as 6-fold; whereas, the fold increase over basal uptake produced by insulin in GLUT1 cells was comparable to that (2-fold) observed in the control myocytes. Thus, both GLUT1 and GLUT4 can mediate insulin-stimulated glucose transport in L6 myoblasts, although GLUT4 is needed to observe large percentage increases comparable to those observed in skeletal muscle fibers in vivo. In contrast to insulin, the protein phosphatase inhibitors, okadaic acid and calyculin A, inhibited glucose transport in cells expressing either GLUT1 or GLUT4. Calyculin A, which produced a half-maximum effect at 10 nM, was approximately 100 times more potent than okadaic acid in decreasing both basal and insulin-stimulated 2-deoxyglucose uptake. Inhibition of uptake by calyculin A was associated with a decrease in the cell surface concentration of both GLUT1 and GLUT4. These results indicate that increased protein phosphorylation can lead to inhibition of transport mediated by both GLUT1 and GLUT4.

Hippocampal regulation of the survival and morphological development of locus coeruleus neurons in dissociated cell culture

The influence of target structures on neural development, originally described for the peripheral nervous system, has more recently been investigated in the central nervous system. We sought to determine whether targets regulate the development of the locus coeruleus, with its diffuse and complex projections in marked contrast to the simpler neural circuits of the peripheral nervous systems. Dissociated locus coeruleus cells were grown alone or with the hippocampus in serum-free, chemically defined medium that minimized non-neuronal growth. Coculture with the hippocampus resulted in a significant increase in locus coeruleus tyrosine hydroxylase activity. Elevated tyrosine hydroxylase activity was accompanied by a commensurate increase in the number of tyrosine hydroxylase-immunoreactive cells, suggesting hippocampal enhancement of locus coeruleus survival. Furthermore, when hippocampal cells were added to locus coeruleus dissociates at zero time, or after two days, tyrosine hydroxylase-positive cell number was increased only by hippocampal cells added initially, suggesting that the target does indeed foster survival. The apparent target enhancement of locus coeruleus survival seems to be selective since total protein and total neuron number, estimated with neuron-specific enolase immunocytochemistry, were not affected by the hippocampus. Coculture with the hippocampus also increased the length and complexity of locus coeruleus cell processes. Neither the increase in tyrosine hydroxylase cell number nor the changes in morphology could be attributed to nonspecific effects of the increased cell density in cocultures. Our observations thus suggest that the target hippocampus influences the survival and neurite elaboration of afferent locus coeruleus neurons.

Insulin and insulin-like growth factor I induce c-fos expression in postmitotic neurons by a protein kinase C-dependent pathway

Recent studies indicate that insulin and insulin-like growth factors regulate development of the nervous system. The signal transduction pathways that mediate the neurotrophic responses to these peptides are largely unknown. The aims of this study were to examine the regulation of c-fos mRNA expression by insulin and insulin-like growth factor I (IGF-I) in postmitotic neurons derived from fetal chick forebrain and to investigate the role of protein kinase C (PKC) in c-fos induction by these growth factors. Cultured neurons were treated with growth factors or other known activators of c-fos gene expression, and then total cellular RNA was isolated and analyzed by Northern analysis using a full-length mouse c-fos cDNA probe. Fetal calf serum, insulin, IGF-I, 12-O-tetradecanoylphorbol (TPA), and cycloheximide induced a 2.2-kilobase c-fos transcript in neurons. Increased levels of c-fos mRNA were apparent as early as 15 min after the addition of insulin. Levels peaked after 60 min and then remained high up to 180 min. The onset of c-fos induction by IGF-I was similar to insulin; however, the response was more transient. Analyses of dose-response curves indicate that insulin and IGF-I stimulate c-fos expression by interacting with their own receptor type. The decay rate of c-fos mRNA was unaltered by insulin or IGF-I. Pretreatment of neurons with actinomycin D (2 microM) for 5 min prior to the addition of insulin completely blocked the induction of c-fos mRNA. TPA increased c-fos mRNA levels with similar kinetics to that of insulin and IGF-I; however, the attenuation phase more closely paralleled that of insulin. Two inhibitors of PKC, sphingosine and staurosporine, completely blocked the induction of c-fos mRNA by insulin, IGF-I, and TPA. These data indicate that insulin and IGF-I stimulate transcription of the c-fos gene in neurons by a PKC-mediated pathway. Increased AP-1 activity may mediate some of the neurotrophic responses to insulin and IGF-I.

Position of the vibroacoustic stimulator does not affect fetal response

OBJECTIVE

This study was designed to compare the fetal response to the vibroacoustic stimulation test when applied alternately over the fetal vertex or breech.

STUDY DESIGN

Two hundred five patients with a nonreactive nonstress test after 10 minutes were prospectively randomized to receive the vibroacoustic stimulation test over the fetal vertex (n = 115) or the fetal breech (n = 90). Fetal heart rate reactivity was evaluated. Two patient subsets were evaluated for fetal movement (n = 37) and the fetal startle response (n = 20) after the vibroacoustic stimulation test.

RESULTS

Virtually identical fetal heart rate responses and increases in fetal movement were observed after vibroacoustic stimulation over the fetal vertex or breech. The fetal startle response was uniformly observed in both groups.

CONCLUSION

Vibroacoustic stimulation over the fetal breech elicits an identical short-term fetal response compared with stimulation over the fetal vertex, potentially reducing the intensity of sound exposure at the fetal ear.

Insulin-regulated sorting of glucose transporters in 3T3-L1 adipocytes

Two glucose transporters (GLUT-4 and GLUT-1) move from within the cell to the plasma membrane (PM) when 3T3-L1 adipocytes are stimulated with insulin. To study the sorting of these two molecules, vesicles containing GLUT-4 and GLUT-1 were immunoadsorbed from basal and insulin-treated cells. Two different vesicle populations were isolated as follows: 1) a compartment that contained the majority of intracellular GLUT-4 and GLUT-1 and 2) a subpopulation of vesicles containing 43% of the intracellular GLUT-4 that was highly insulin regulatable and that contained relatively low levels of GLUT-1. After incubation at 19 degrees C, basal glucose transport was slightly increased, whereas insulin-dependent transport was blocked. Consistent with these observations, cell surface GLUT-1 levels were increased in the basal state, whereas insulin-dependent translocation of GLUT-4 to the PM was blocked at 19 degrees C. However, insulin-dependent sorting of GLUT-4 within the intracellular compartment was still evident at 19 degrees C. These data indicate that GLUT-1 and GLUT-4 are heterogeneously distributed throughout the same intracellular compartment in 3T3-L1 adipocytes. Furthermore, we have uncoupled two distinct steps in the insulin-dependent movement of GLUT-4 to the cell surface. These include movement of GLUT-4 out of its storage compartment and accumulation of GLUT-4 at the cell surface. Only the former step occurs in cells preincubated at 19 degrees C.

Translocation of the glucose transporter (GLUT4) to the cell surface in permeabilized 3T3-L1 adipocytes: effects of ATP insulin, and GTP gamma S and localization of GLUT4 to clathrin lattices

Insulin stimulates the movement of two glucose transporter isoforms (GLUT1 and GLUT4) to the plasma membrane (PM) in adipocytes. To study this process we have prepared highly purified PM fragments by gently sonicating 3T3-L1 adipocytes grown on glass coverslips. Using confocal laser immunofluorescence microscopy we observed increased PM labeling for GLUT1 (2.3-fold) and GLUT4 (eightfold) after insulin treatment in intact cells. EM immunolabeling of PM fragments indicated that in the nonstimulated state GLUT4 was mainly localized to flat clathrin lattices. Whereas GLUT4 labeling of clathrin lattices was only slightly increased after insulin treatment, labeling of uncoated PM regions was markedly increased with insulin. These data suggest that GLUT4 recycles from the cell surface both in the presence and absence of insulin. In streptolysin-O permeabilized adipocytes, insulin, and GTP gamma S increased PM levels of GLUT4 to a similar extent as observed with insulin in intact cells. In the absence of an exogenous ATP source the magnitude of these effects was considerably reduced. Removal of ATP per se caused a significant increase in cell surface levels of GLUT4 suggesting that ATP may be required for intracellular sequestration of these transporters. When insulin and GTP gamma S were added together, in the presence of ATP, PM GLUT4 levels were similar to levels observed when either insulin or GTP gamma S was added individually. Addition of GTP gamma S was able to overcome this ATP dependence of insulin-stimulated GLUT4 movement. GTP gamma S had no effect on constitutive secretion of adipsin in permeabilized cells. In addition, there was no effect of insulin or GTP gamma S on GLUT4 movement to the PM in noninsulin sensitive streptolysin-O-permeabilized 3T3-L1 fibroblasts overexpressing GLUT4. We conclude that the insulin-stimulated movement of GLUT4 to the cell surface in adipocytes may require ATP early in the insulin signaling pathway and a GTP-binding protein(s) at a later step(s). We propose that the association of GLUT4 with clathrin lattices may be important in maintaining the exclusive intracellular location of this transporter in the absence of insulin.

GLUT4 facilitates insulin stimulation and cAMP-mediated inhibition of glucose transport

The glucose transporter isoform GLUT4 is found only in cells that exhibit insulin-sensitive glucose transport. To investigate the function of this transporter, L6 myoblasts were stably transfected with GLUT4 cDNA. GLUT4 underwent insulin-dependent movement to the cell surface in myoblasts overexpressing the transporter. One cell line (243-6) expressed sufficient levels of the GLUT4 protein to study insulin-dependent glucose transport. Unlike wild-type L6 cells, 243-6 myoblasts exhibited two features that are characteristic of differentiated muscle fibers and adipocytes in vivo: a large insulin-stimulated component of glucose transport and inhibition of this stimulated component by cAMP. Relative to normal L6 cells, 243-6 cells responded to insulin or insulin-like growth factor 1 with a 5-fold larger increase in 2-deoxy[3H]glucose uptake. N6,O2'-Dibutyryladenosine 3',5'-cyclic monophosphate (Bt2cAMP) did not inhibit transport in normal L6 myoblasts, which express only GLUT1, but inhibited IGF-1/insulin-stimulated transport by 50% in 243-6 cells. The effect of cAMP was investigated further by using Chinese hamster ovary cells transiently expressing GLUT1 and GLUT4. Bt2cAMP inhibited glucose transport only in Chinese hamster ovary cells expressing GLUT4. These results indicate that cAMP-mediated inhibition of glucose transport is dependent on expression of the GLUT4 isozyme.

Immunocytochemical and biochemical studies of GLUT4 in rat skeletal muscle

In muscle and adipocytes, glucose transport is regulated by the translocation of insulin regulatable glucose transporters (GLUT4) between an intracellular compartment and the cell surface. In these studies we have characterized the cellular compartments containing GLUT4 in rat skeletal muscle. Immunocytochemical studies showed that in unstimulated muscle, GLUT4 was not present in surface membranes. Tubulo-vesicular structures clustered in the trans Golgi reticulum were enriched in GLUT4. GLUT4 underwent translocation to the sarcolemma in response to combined stimulation with insulin and exercise. Using immunoisolation, the intracellular GLUT4 vesicles (IRGTV) were purified 300-fold over the cell homogenate. IRGTV from unstimulated muscle were not enriched in markers specific for the sarcolemma, transverse tubules, sarcoplasmic reticulum or mitochondria; this was confirmed using gel filtration chromatography. Insulin resulted in a 40% decrease in GLUT4 levels in IRGTV confirming that this represents the intracellular compartment of GLUT4. GLUT4 is a major component of the IRGTV, constituting at least 5% of total vesicle protein. A subset of polypeptides are also markedly enriched in the muscle IRGTV. In conclusion, these data suggest that translocation of GLUT4 from intracellular tubulo-vesicular structures is the major mechanism by which insulin and exercise regulate muscle glucose transport.

Acute effect of anterior temporal lobectomy on musical processing

Patients with intractable epilepsy treated by anterior temporal lobectomy (Right, RT, n = 12; Left, LT, n = 9) and healthy controls (n = 12) with no musical training were prospectively evaluated with a standardized battery, including the Musical Aptitude Profile and the Seashore Tonal Memory Test. Before surgery, patients performed below controls (P less than 0.001), but there were no differences between RT and LT patients. After resection (2 weeks), RT patients showed a differential decline on tasks measuring perception of meter (P = 0.005) and tempo (P = 0.008) but not tonal processes. LT, and controls studied at the same time interval, showed no decline. The results support the role of the right hemisphere in specific aspects of musical processing.

Comparison of two short forms of the Wisconsin Card Sorting Test

Two short forms of the Wisconsin Card Sorting Test (WCST) were evaluated. The WCST-64 consists of one deck of 64 cards; derived measures are number of categories obtained and number of perseverative responses. The WCST-3 includes measures of the number of cards required to complete three categories and the number of perseverative responses. WCST protocols from 37 schizophrenics, 20 temporal lobe epileptics, 11 patients with probable SDAT, and 54 normal controls, were scored using the three methods. Pearson correlations between WCST and WCST-64 scores ranged from.70 to.91. while correlations between WCST and WCST-3 were somewhat lower (.36 to.82). The WCST-64 was superior to the WCST-3 in agreement with the full WCST. The WCST-3 tended to underestimate the number of perseverative responses on the full WCST. Although the use of a short form reduces reliability, the WCST-64 appears to be an acceptable alternative when administration of the full WCST is not possible.

Acute naming deficits following dominant temporal lobectomy: prediction by age at 1st risk for seizures

Age at 1st risk for seizures may predict anomia following dominant anterior temporal lobectomy. We assessed confrontation naming before and 2 to 3 weeks after surgery in 45 right-handed patients grouped by side of focus and presence or absence of early (less than or equal to 5 years) risk factors. After left lobectomy, 6 of 10 (60%) patients with no early risks demonstrated significant decline (greater than or equal to 25%) in naming, but none of the patients with early risks showed this decline. After right lobectomy, there was no change. Cerebral representation of naming may be atypical in patients with early risks.

Inhibition of thromboxane A synthesis in U937 cells by glucocorticoids. Lack of evidence for lipocortin 1 as the second messenger

The mechanism of inhibition of eicosanoid synthesis by glucocorticoids has been investigated using differentiated U937 cells as a model. These cells synthesize thromboxane A2 (TXA2) in response to a variety of agonists, and synthesis of TXA2 initiated by certain stimuli was inhibited by pretreatment of the cells with glucocorticoids. The inhibitory response was specific for glucocorticoid steroids and required receptor occupancy based on both the rate of onset of the inhibitory activity and the correlation between potency and receptor affinity of various analogs. The inhibitory response was also specific for the agonist used to initiate TXA2 synthesis. Both lipopolysaccharide- and zymosan-induced TXA2 synthesis were inhibited by increasing concentrations of dexamethasone (greater than 80%, IC50 10 nM), while synthesis initiated by addition of either exogenous arachidonic acid or the Ca2+ ionophore A23187 was unaffected over the same concentration range. The latter result indicates that the dexamethasone block is upstream from release of esterified arachidonic acid. Attempts to localize the block more accurately showed that although dexamethasone was not acting as a generalized inhibitor of transcription or translation, its ability to inhibit TXA2 synthesis was mimicked by the activity of actinomycin D and cycloheximide. The role of the purported phospholipase inhibitor protein lipocortin 1 in mediating the dexamethasone inhibition of TXA2 synthesis was studied by examining the effect of dexamethasone on lipocortin 1 metabolism. Under conditions which gave maximal inhibition of lipopolysaccharide- or zymosan-stimulated TXA2 synthesis, dexamethasone had no effect on the steady state level of lipocortin 1 mRNA or protein, indicating that lipocortin 1 induction by dexamethasone is not responsible for the observed inhibition. Furthermore, lipocortin 1 was not secreted from the cells under any conditions examined, and the intracellular form had a relatively long half-life (greater than 21 h). The lack of induction of lipocortin 1 by dexamethasone and the fact that it is not released from the cells are both inconsistent with the properties previously described for lipocortin-like activities and indicate that lipocortin 1 is not a glucocorticoid second messenger in this experimental model. Although the data are consistent with a mechanism involving inhibition of a factor that activates TXA2 synthesis, we cannot rule out a mechanism involving glucocorticoid induction of a phospholipase inhibitor protein distinct from lipocortin 1.

Reaction sequences for (Na+ + K+)-dependent ATPase hydrolytic activities: new quantitative kinetic models

To delineate better the reaction sequence of the (Na+ + K+)-ATPase and illuminate properties of the active site, kinetic data were fitted to specific quantitative models. For the (Na+ + K+)-ATPase reaction, double-reciprocal plots of velocity against ATP (in the millimolar range), with a series of fixed KCl concentrations, are nearly parallel, in accord with the ping pong kinetics of ATP binding at the low-affinity sites only after Pi release. However, contrary to requirements of usual formulations, Pi is not a competitor toward ATP. A new steady-state kinetic model accommodates these data quantitatively, requiring that under usual assay conditions most of the enzyme activity follows a sequence in which ATP adds after Pi release, but also requiring a minor alternative pathway with ATP adding after K+ binds but before Pi release. The fit to the data also reveals that Pi binds nearly as rapidly to E2 X K X ATP as to E2 X K, whereas ATP binds quite slowly to E2 X P X K: the site resembles a cul-de-sac with distal ATP and proximal Pi sites. For the K+-nitrophenyl phosphatase reaction also catalyzed by this enzyme, the apparent affinities for both substrate and Pi (as inhibitor) decrease with higher KCl concentrations, and both Pi and TNP-ATP appear to be competitive inhibitors toward substrate with 10 mM KCl but noncompetitive inhibitors with 1 mM KCl. These data are accommodated quantitatively by a steady-state model allowing cyclic hydrolytic activity without obligatory release of K+, and with exclusive binding of substrate vs. either Pi or TNP-ATP. The greater sensitivity of the phosphatase reaction to both Pi and arsenate is attributable to the weaker binding by the occluded-K+ enzyme form occurring in the (Na+ + K+)-ATPase reaction sequence. The steady-state models are consistent with cyclical interconversion of high- and low-affinity substrate sites accompanying E1/E2 transitions, with distortion to low-affinity sites altering not only affinity and route of access but also separating the adenine- and phosphate-binding regions, the latter serving in the E2 conformation as the active site for the phosphatase reaction.

Cation sites, spermine, and the reaction sequence of the (Na+ + K+)-dependent ATPase

Spermine, at 0.3 mM, inhibits the K+-nitrophenyl phosphatase activity of a dog kidney (Na+ + K+)-ATPase preparation, increasing the K0.5 for K+, reducing the Km for substrate, and affecting little the inhibition by Na+. These actions can be attributed, in a model of the phosphatase reaction, to parallel decreases in affinity for K+ and Na+ at their cytoplasmically accessible sites. In the (Na+ + K+)-ATPase reaction, spermine increases the K0.5 for Na+ and, to a lesser degree, the K0.5 for K+ as activators. With spermine, the double-reciprocal plots of velocity vs. ATP concentration (in the range 0.3-3 mM), at fixed levels of K+ (from 1 to 10 mM), remain parallel but are rotated clockwise and spread somewhat, reflecting stimulation at low ATP concentrations and inhibition at high ATP but low KCl concentrations. These actions can be attributed, in a steady-state ping-pong model of the ATPase reaction, solely to decreased rates of binding of Na+ and K+ to their sites, with major effects at the cytoplasmically accessible sites for Na+ (acceptance) and K+ (discharge), and with a lesser effect at the extracellularly accessible sites for K+ (acceptance). On these grounds, spermine is a highly specific and potentially valuable reagent for studying the reaction. Furthermore, the model for K+-ATP interactions not only supports a specific reaction sequence (K+ addition, Pi release, ATP addition, K+ release) but also argues against the availability of low-affinity substrate sites except during sharply restricted segments of the reaction sequence, thereby favoring proposals that the low-affinity substrate sites are transformed into high-affinity substrate sites with the E2 to E1 conformational change.

Effects of oligomycin and quercetin on the hydrolytic activities of the (Na+ +K+)-dependent ATPase

Quercetin inhibited a dog kidney (Na+ + K+)-ATPase preparation without affecting Km for ATP or K0.5 for cation activators, attributable to the slowly-reversible nature of its inhibition. Dimethyl sulfoxide, a selector of E2 enzyme conformations, blocked this inhibition, while the K+-phosphatase activity was at least as sensitive to quercetin as the (Na+ + K+)-ATPase activity, all consistent with quercetin favoring E1 conformations of the enzyme. Oligomycin, a rapidly-reversible inhibitor, decreased the Km for ATP and the K0.5 for cation activators, and its inhibition was also diminished by dimethyl sulfoxide. Although oligomycin did not inhibit the K+-phosphatase activity under standard assay conditions, a reaction presumably catalyzed by E2 conformations, its effects are nevertheless accommodated by a quantitative model for that reaction depicting oligomycin as favoring E1 conformations. The model also accounts quantitatively for effects of both dimethyl sulfoxide and oligomycin on Vmax, Km for substrate, and K0.5 for K+, as well as for stimulation of phosphatase activity by both these reagents at low K+ but high Na+ concentrations.

A model for the reaction pathways of the K+-dependent phosphatase activity of the (Na+ + K+)-dependent ATPase

(Na+ + K+)-dependent ATPase preparations from rat brain, dog kidney, and human red blood cells also catalyze a K+ -dependent phosphatase reaction. K+ activation and Na+ inhibition of this reaction are described quantitatively by a model featuring isomerization between E1 and E2 enzyme conformations with activity proportional to E2K concentration: (formula; see text) Differences between the three preparations in K0.5 for K+ activation can then be accounted for by differences in equilibria between E1K and E2K with dissociation constants identical. Similarly, reductions in K0.5 produced by dimethyl sulfoxide are attributable to shifts in equilibria toward E2 conformations. Na+ stimulation of K+ -dependent phosphatase activity of brain and red blood cell preparations, demonstrable with KCl under 1 mM, can be accounted for by including a supplementary pathway proportional to E1Na but dependent also on K+ activation through high-affinity sites. With inside-out red blood cell vesicles, K+ activation in the absence of Na+ is mediated through sites oriented toward the cytoplasm, while in the presence of Na+ high-affinity K+ -sites are oriented extracellularly, as are those of the (Na+ + K+)-dependent ATPase reaction. Dimethyl sulfoxide accentuated Na+ -stimulated K+ -dependent phosphatase activity in all three preparations, attributable to shifts from the E1P to E2P conformation, with the latter bearing the high-affinity, extracellularly oriented K+ -sites of the Na+ -stimulated pathway.