20-Hydroxyeicosatetraenoic acid is a potent dilator of mouse basilar artery: role of cyclooxygenase

20-Hydroxyeicosatetraenoic acid (20-HETE), an arachidonic acid (AA) metabolite synthesized by cytochrome P-450 omega-oxidases, is reported to produce vasoconstriction in the cerebral circulation. However, we find that like 14,15-epoxyeicosatrienoic acid (14,15-EET), 20-HETE produces dilation of mouse basilar artery preconstricted with U-46619 in vitro. Indomethacin inhibited the vasodilation produced by 20-HETE but not by 14,15-EET, suggesting a cyclooxygenase (COX)-dependent mechanism. Metabolic studies indicated several mechanisms that may play a role in this process. Mouse brain endothelial cells (MBEC) converted 20-HETE to 20-OH-PGE(2), which was as potent as PGE(2) in dilating the basilar artery. 20-HETE also stimulated AA release and PGE(2) and 6-keto-PGF(1alpha) production in MBEC. Furthermore, the basilar artery converted 20-HETE to 20-COOH-AA, which also produced COX-dependent dilation of the basilar artery. 20-COOH-AA increased AA release and PGE(2) and 6-keto-PGF(1alpha) production by the MBEC, but to a lesser extent than 20-HETE. Whereas the conversion of 20-HETE to 20-OH-PGE(2) and production of endogenous prostaglandins probably are primarily responsible for vasodilation, the production of 20-COOH-AA also may contribute to this process.

Developments in medical law in the United Kingdom in 2005 and 2006

This article highlights and summarises the key developments in medical law in the jurisdictions of the United Kingdom in 2005 and to April 2006. Topics are mental health and mental capacity, data protection, freedom of information and the impact on health data, the Human Tissue Act, genetic research databanks, Human Fertilisation and Embryology Act--Review of the legislation, consultations and related case law, developments in embryo and embryonic stem cell research, clinical trials and human subject research, medical futility, and physician assisted dying.

Comparative RNA expression analyses from small-scale, single-donor platelet samples

BACKGROUND

Comparisons of platelet RNAs could provide crucial information on platelet function, thrombopoiesis and the etiology of megakaryocyte (MK) or platelet disorders.

OBJECTIVES

We developed a method for stringent purification of platelets from small blood samples from single donors. Purity of the platelet preparations was verified by an RT-PCR assay. We tested three methods to identify the differences in RNA between platelet sources.

METHODS

Differential hybridization to cDNA macro-arrays and suppressive-subtractive hybridization PCR (SSH-PCR) were used to compare RNAs from normal platelets to those from a Bernard-Soulier syndrome (BSS) patient. Affymetrix GeneChip U133 plus 2.0 arrays were used to compare male and female platelet RNAs.

RESULTS

Macroarrays identified approximately 7500 platelet transcripts, but failed to identify differentially expressed transcripts with confidence. SSH-PCR produced libraries almost exclusively of mitochondrial-derived transcripts, but included nuclear-encoded genes that could not be confirmed by immunoblotting of normal and BSS platelet lysates. The Affymetrix platform gave reproducible profiles from our small-scale purified platelet preparations, whereas a partially purified platelet preparation produced a drastically skewed transcript profile. The microarray analysis identified the heparanase precursor transcript as overexpressed in female platelets, and we observed variable yet consistently higher levels of heparanase protein in female platelets compared with male platelets in four independent donor pairs.

CONCLUSIONS

This demonstrates for the first time that differential platelet transcript levels can identify changes in expression level of platelet proteins. Combined with our small-scale platelet preparation method, this establishes a system to compare platelets from the limited clinical sources to help elucidate molecular bases for platelet or megakaryocyte pathologies.

14,15-Dihydroxyeicosatrienoic acid activates peroxisome proliferator-activated receptor-alpha

Epoxyeicosatrienoic acids (EETs), lipid mediators synthesized from arachidonic acid by cytochrome P-450 epoxygenases, are converted by soluble epoxide hydrolase (SEH) to the corresponding dihydroxyeicosatrienoic acids (DHETs). Originally considered as inactive degradation products of EETs, DHETs have biological activity in some systems. Here we examined the capacity of EETs and DHETs to activate peroxisome proliferator-activated receptor-alpha (PPARalpha). We find that among the EET and DHET regioisomers, 14,15-DHET is the most potent PPARalpha activator in a COS-7 cell expression system. Incubation with 10 microM 14,15-DHET produced a 12-fold increase in PPARalpha-mediated luciferase activity, an increase similar to that produced by the PPARalpha agonist Wy-14643 (20 microM). Although 10 microM 14,15-EET produced a threefold increase in luciferase activity, this was abrogated by the SEH inhibitor dicyclohexylurea. 14-Hexyloxytetradec-5(Z)-enoic acid, a 14,15-EET analog that cannot be converted to a DHET, did not activate PPARalpha. However, PPARalpha was activated by 2-(14,15-epoxyeicosatrienoyl)glycerol, which was hydrolyzed and the released 14,15-EET converted to 14,15-DHET. COS-7 cells incorporated 14,15-[3H]DHET from the medium, and the cells also retained a small amount of the DHET formed during incubation with 14,15-[3H]EET. Binding studies indicated that 14,15-[3H]DHET binds to the ligand binding domain of PPARalpha with a Kd of 1.4 microM. Furthermore, 14,15-DHET increased the expression of carnitine palmitoyltransferase 1A, a PPARalpha-responsive gene, in transfected HepG2 cells. These findings suggest that 14,15-DHET, produced from 14,15-EET by the action of SEH, may function as an endogenous activator of PPARalpha.

Human coronary endothelial cells convert 14,15-EET to a biologically active chain-shortened epoxide

Cytochrome P-450 epoxygenase-derived epoxyeicosatrienoic acids (EETs) play an important role in the regulation of vascular reactivity and function. Conversion to the corresponding dihydroxyeicosatrienoic acids (DHETs) by soluble epoxide hydrolases is thought to be the major pathway of EET metabolism in mammalian vascular cells. However, when human coronary artery endothelial cells (HCEC) were incubated with (3)H-labeled 14,15-EET, chain-shortened epoxy fatty acids, rather than DHET, were the most abundant metabolites. After 4 h of incubation, 23% of the total radioactivity remaining in the medium was converted to 10,11-epoxy-hexadecadienoic acid (16:2), a product formed from 14,15-EET by two cycles of beta-oxidation, whereas only 15% was present as 14,15-DHET. Although abundantly present in the medium, 10,11-epoxy-16:2 was not detected in the cell lipids. Exogenously applied (3)H-labeled 10,11-epoxy-16:2 was neither metabolized nor retained in the cells, suggesting that 10,11-epoxy-16:2 is a major product of 14,15-EET metabolism in HCEC. 10,11-Epoxy-16:2 produced potent dilation in coronary microvessels. 10,11-Epoxy-16:2 also potently inhibited tumor necrosis factor-alpha-induced production of IL-8, a proinflammatory cytokine, by HCEC. These findings implicate beta-oxidation as a major pathway of 14,15-EET metabolism in HCEC and provide the first evidence that EET-derived chain-shortened epoxy fatty acids are biologically active.

Inactivation of sarcoplasmic reticulum Ca(2+)-atpase in low-frequency stimulated rat muscle

Continuous low-frequency stimulation (CLFS) by implanted electrodes for 12-24 h led to a significant (approximately 30%) decrease in the activity of sarcoplasmic reticulum Ca(2+)-ATPase in fast-twitch extensor digitorum longus (EDL) and tibialis anterior (TA) muscles of intact rats. The decline in catalytic activity after 24 h of CLFS was accompanied by an approximately twofold increase in dinitrophenylhydrazine-reactive carbonyl groups of the enzyme. It also correlated with an immunochemically determined 30% decrease in Ca2(+)-ATPase protein. Recovery studies after 12 h of CLFS revealed a relatively slow (48-72 h) re-establishment of normal catalytic activity. These findings suggest that the 30% decline of Ca(2+)-ATPase activity in low-frequency stimulated rat muscle led to an irreversible modification by protein oxidation. The decrease in Ca(2+)-ATPase protein most likely resulted from the degradation of inactive Ca(2+)-ATPase molecules. The relatively slow recovery of Ca(2+)-ATPase activity suggests that de novo synthesis of the enzyme may be necessary to re-attain normal activity.

Pathways of epoxyeicosatrienoic acid metabolism in endothelial cells. Implications for the vascular effects of soluble epoxide hydrolase inhibition

Epoxyeicosatrienoic acids (EETs) are products of cytochrome P-450 epoxygenase that possess important vasodilating and anti-inflammatory properties. EETs are converted to the corresponding dihydroxyeicosatrienoic acid (DHET) by soluble epoxide hydrolase (sEH) in mammalian tissues, and inhibition of sEH has been proposed as a novel approach for the treatment of hypertension. We observed that sEH is present in porcine coronary endothelial cells (PCEC), and we found that low concentrations of N,N'-dicyclohexylurea (DCU), a selective sEH inhibitor, have profound effects on EET metabolism in PCEC cultures. Treatment with 3 microM DCU reduced cellular conversion of 14,15-EET to 14,15-DHET by 3-fold after 4 h of incubation, with a concomitant increase in the formation of the novel beta-oxidation products 10,11-epoxy-16:2 and 8,9-epoxy-14:1. DCU also markedly enhanced the incorporation of 14,15-EET and its metabolites into PCEC lipids. The most abundant product in DCU-treated cells was 16,17-epoxy-22:3, the elongation product of 14,15-EET. Another novel metabolite, 14,15-epoxy-20:2, was present in DCU-treated cells. DCU also caused a 4-fold increase in release of 14,15-EET when the cells were stimulated with a calcium ionophore. Furthermore, DCU decreased the conversion of [3H]11,12-EET to 11,12-DHET, increased 11,12-EET retention in PCEC lipids, and produced an accumulation of the partial beta-oxidation product 7,8-epoxy-16:2 in the medium. These findings suggest that in addition to being metabolized by sEH, EETs are substrates for beta-oxidation and chain elongation in endothelial cells and that there is considerable interaction among the three pathways. The modulation of EET metabolism by DCU provides novel insight into the mechanisms by which pharmacological or molecular inhibition of sEH effectively treats hypertension.

Low-frequency stimulation of fast muscle affects the abundance of Ca(2+)-ATPase but not its oligomeric status

After chronic, low-frequency stimulation, a rapid decline in Ca(2+) pump activity is observed during the early stages of skeletal muscle transformation. However, this variation in enzymatic activity does not coincide with a drastic reduction in the amount of sarcoplasmic reticulum Ca(2+)-ATPases. To investigate whether changes in subunit interactions within Ca(2+) pump complexes contribute to this phenomena, we performed a chemical cross-linking analysis of 4 days continuously, and 4 days discontinuously, electrostimulated fast muscle fibers. The abundance of the slow and fast Ca(2+)-ATPase isoforms sarco(endo)plasmic reticulum Ca(2+)- ATPase types 1 and 2 was affected during the fast-to-slow transition process, demonstrating that, even after short-term stimulation, distinct changes in the isoform expression pattern of muscle proteins occur. However, the oligomeric status of both ion pump species did not change. Hence, chemical modifications of critical enzyme domains must be responsible for the rapid stimulation-induced activity changes, not variations in protein-protein interactions within Ca(2+)-ATPase units. Oligomerization appears to be of central importance to the proper physiological functioning of the Ca(2+)-ATPase and does not undergo changes during skeletal muscle conditioning.

Selection and implementation for coagulation instruments/reagents in a multiple hospital/clinic network

Selection, standardization, and implementation of instrumentation and reagents throughout a health care facility network can often be a difficult process. However, in today's ever-changing health care setting, it is often mandated. The Veteran's Integrated Systems Network 16 (VISN 16) was faced with such a task early in 1999, with the targeted area being its coagulation laboratories. The plan outlined in this paper was drafted to help facilitate the selection, standardization and implementation of coagulation systems for 17 health care facilities that make up the VISN 16 network. The VISN, encompassing 170,000 square miles, has 10 tertiary care hospitals, six of which have close relationships with affiliate universities. There are 299,733 patients enrolled in this health delivery system. The facilities range from large institutions performing both tertiary and outpatient care to small outpatient clinics. Because of the plan's detailed, comprehensive content, which included analyses of a large number of performance parameters as well as cost-efficiency, the selection process was carried out using a checklist that could be helpful to other organizations selecting equipment and reagents for coagulation studies. An implementation process was devised, resulting in coagulation standardization across the Integrated Health Network.

Paramecium calmodulin mutants defective in ion channel regulation can bind calcium and undergo calcium-induced conformational switching

Calmodulin (CaM) is an essential eukaryotic protein that binds calcium ions cooperatively at four EF-hand binding sites to regulate signal transduction pathways. Interactions between the apo domains of vertebrate CaM reduce the calcium affinities of sites I and II below their intrinsic values, allowing sequential opening of the two hydrophobic clefts in CaM. Viable domain-specific mutants of Parameciumcalmodulin (PCaM) differentially affect ion channels and provide a unique opportunity to dissect the roles of the two highly homologous half-molecule domains. Calcium binding induced an increase in the level of ordered secondary structure and a decrease in Stokes radius in these mutants; such changes were identical in direction to those of wild type CaM, but the magnitude depended on the mutation. Calcium titrations monitored by changes in the intrinsic fluorescence of Y138 in site IV showed that the affinities of sites III and IV of wild type PCaM were (i) higher than those of the same sites in rat CaM, (ii) equivalent to those of the same sites in PCaM mutants altered between sites I and II, and (iii) higher than those of PCaM mutants modified in sites III and IV. Thus, calcium saturation drove all mutants to undergo conformational switching in the same direction but not to the same extent as wild type PCaM. The disruption of the allosteric mechanism that is manifest as faulty channel regulation may be explained by altered properties of switching among the 14 possible partially saturated species of PCaM rather than by an inability to adopt two end-state conformations or target interactions similar to those of the wild type protein.

Comparative analysis of the isoform expression pattern of Ca(2+)-regulatory membrane proteins in fast-twitch, slow-twitch, cardiac, neonatal and chronic low-frequency stimulated muscle fibers

Although all muscle cells generate contractile forces by means of organized filament systems, isoform expression patterns of contractile and regulatory proteins in heart are not identical compared to developing, conditioned or mature skeletal muscles. In order to determine biochemical parameters that may reflect functional variations in the Ca(2+)-regulatory membrane systems of different muscle types, we performed a comparative immunoblot analysis of key membrane proteins involved in ion homeostasis. Cardiac isoforms of the alpha(1)-dihydropyridine receptor, Ca(2+)-ATPase and calsequestrin are also present in skeletal muscle and are up-regulated in chronic low-frequency stimulated fast muscle. In contrast, the cardiac RyR2 isoform of the Ca(2+)-release channel was not found in slow muscle but was detectable in neonatal skeletal muscle. Up-regulation of RyR2 in conditioned muscle was probably due to degeneration-regeneration processes. Fiber type-specific differences were also detected in the abundance of auxiliary subunits of the dihydropyridine receptor, the ryanodine receptor and the Ca(2+)-ATPase, as well as triad markers and various Ca(2+)-binding and ion-regulatory proteins. Hence, the variation in innervation of different types of muscle appears to have a profound influence on the levels and pattern of isoform expression of Ca(2+)-regulatory membrane proteins reflecting differences in the regulation of Ca(2+)-homeostasis. However, independent of the muscle cell type, key Ca(2+)-regulatory proteins exist as oligomeric complexes under native conditions.

Survival of Salmonella species in river water

The survival of four Salmonella strains in river water microcosms was monitored by culturing techniques, direct counts, whole-cell hybridization, scanning electron microscopy, and resuscitation techniques via the direct viable count method and flow cytometry. Plate counts of bacteria resuspended in filtered and untreated river water decreased several orders of magnitude within the first week of incubation, while they did not decrease as rapidly in autoclaved water. In situ hybridization studies suggested a rapid decrease in ribosomal content, as determined by the drastic decrease in the number of detectable cells after 72 h. In contrast, direct counts remained relatively constant during 45 days in all microcosoms. Although the culturable counts of two bacterial strains in filtered water after 31 days represented approximately 0.001% of the total counts, direct viable counts and resuscitation studies with a dilution series suggested that the number of viable bacteria was at least four orders of magnitude higher. Additionally, notable changes in forward scatter and in nucleic acid content were observed only after 4 h of nutrient amendments by flow cytometry. However, cells from the resuscitation experiments did not grow on solid media unless cell-free supernatant from viable cultures was added during the resuscitation period. The results in this study suggest the presence of a not immediately culturable status in Salmonella.

Oligomerization of the sarcoplasmic reticulum Ca2+-ATPase SERCA2 in cardiac muscle

The slow/cardiac isoform of the sarcoplasmic reticulum Ca2+-ATPase plays an important role in cardiac muscle Ca2+-homeostasis. To determine the native configuration of the SERCA2 ion pump, a chemical cross-linking analysis of heart microsomes was performed. Using one- and two-dimensional immunoblotting following incubation with the hydrophilic probe bis-sulfosuccinimidyl suberate or the hydrophobic crosslinker dithiobis-succinimidyl-propionate, we demonstrate here that SERCA2 forms high-molecular-mass aggregates. In contrast to the Na+/Ca2+-exchanger, Ca2+-ATPase clusters can be stabilized by hydrophilic 1.2 nm crosslinkers and are sensitive to chemical reduction. Hence, the native form of this important Ca2+-regulatory membrane protein involved in cardiac muscle relaxation appears not to exist as a monomeric ion pump unit. Protein-protein interactions might play an important role in the physiological functioning of this Ca2+-ATPase isoform, as has previously been shown for skeletal muscle Ca2+-pumps, Ca2+-binding proteins and Ca2+-channels.

The Uniformed Services University of the Health Sciences, F. Edward Hébert School of Medicine: status of the Federal Medical School after 25 years

In its first 25 years, the Uniformed Services University of the Health Sciences (USUHS) has become a quality institution of medical education that provides a steady flow of career physicians for the military. It compares favorably with U.S. medical school averages in all aspects of undergraduate medical education: faculty, teaching facilities, matriculants, curriculum, student performance, and cost. USUHS provides excellent medical education and adds unique preparation for uniformed public service. It also provides military-specific graduate education, graduate medical education, continuing health education, medical research, clinical services, consultation, public service, and ties with international military, medical, and research institutions.

L-Dopa and dopamine-producing gene cassettes for gene therapy approaches to Parkinson's disease

As an aid in the development of vector systems for use in gene therapy paradigms of central nervous system disorders such as Parkinson's disease, we have developed L-Dopa or dopamine-producing gene cassettes. Specifically, a human tyrosine hydroxylase cDNA (HTH-2) was rendered constitutively active by truncation of the N-terminal regulatory domain (tHTH). In addition, a bicistronic construct capable of directing the production of dopamine was created by inserting an internal ribosome entry site downstream of tHTH followed by the coding sequences of aromatic amino acid decarboxylase. All three constructs generated immunoreactive peptides of the predicted size, were enzymatically active, and produced L-Dopa (HTH-2, tHTH) or dopamine (bicistronic construct) following transient transfection of COS-7 cells. These constructs, in conjunction with viral or nonviral expression systems, may be efficacious in gene therapy approaches to Parkinson's disease.

Dynamic changes in striatal dopamine D2 and D3 receptor protein and mRNA in response to 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) denervation in baboons

Loss of nigrostriatal neurons leads to striatal dopamine deficiency and subsequent development of parkinsonism. The effects of this denervation on D2-like receptors in striatum remain unclear. Most studies have demonstrated increases in striatal dopamine D2-like receptors in response to 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP)-mediated denervation, but others have found either decreases or no change in binding. To clarify the response to denervation, we have investigated the time-dependent changes in dopamine D2, D3, and D4 receptor protein and mRNA levels in unilaterally MPTP-lesioned baboons. MPTP (0.4 mg/kg) was infused into one internal carotid artery, producing a contralateral hemi-parkinsonian syndrome. After MPTP treatment, the animals were maintained for 17-480 d and then euthanized. MPTP decreased ipsilateral dopamine content by >90%, which did not change with time. Ipsilateral D2-like receptor binding in caudate and putamen initially decreased then increased two- to sevenfold over the first 100 d and returned to near baseline levels by 480 d. Relative levels of D2 mRNA were essentially unchanged over this period. D4 mRNA was not detected. In contrast, D3 mRNA increased sixfold by 2 weeks and then decreased. At the peak period of increase in binding sites, all D2-like receptors were in a micromolar affinity agonist-binding state, implying an increase in uncoupled D2 but not D3 receptor protein. Taken together, these data suggest that MPTP-induced changes in D2-like dopamine receptors are complex and include translational or post-translational mechanisms.

The human aromatic L-amino acid decarboxylase gene can be alternatively spliced to generate unique protein isoforms

Aromatic L-amino acid decarboxylase (AADC) is expressed in a wide variety of tissues, including those where it is known to convert L-DOPA and 5-hydroxytryptophan to dopamine and serotonin, respectively. AADC has been cloned from many species and shown to undergo alternative splicing within its 5' untranslated region. Here, we report that the human AADC gene can undergo additional alternative splicing of exon 3, generating two different protein isoforms (termed AADC480 and AADC442). Both transcripts are widely expressed, with AADC442 predominating in many neuronal and nonneuronal tissues. When homogenates were prepared from COS-7 cells transfected with expression vectors containing either cDNA, AADC480 catalyzed the decarboxylation of both L-DOPA and 5-hydroxytryptophan. AADC442 was inactive in either assay. These findings suggested that AADC442 may have a different function in non-monoamine-expressing tissues. Taken together, these results suggest that the human AADC gene undergoes complex processing, leading to the formation of both tissue-specific transcripts as well as unique protein isoforms.

The effect of spinal immobilization on healthy volunteers

STUDY OBJECTIVE

To determine the effects of standard spinal immobilization on a group of healthy volunteers with respect to induced pain and discomfort.

DESIGN

Prospective study.

SETTING

University teaching hospital.

TYPE OF PARTICIPANTS

Twenty-one healthy volunteers with no history of back disease.

INTERVENTIONS

Subjects were placed in standard backboard immobilization for a 30-minute period. Number and severity of immediate and delayed symptoms were determined.

MEASUREMENTS AND MAIN RESULTS

One hundred percent of subjects developed pain within the immediate observation period. Occipital headache and sacral, lumbar, and mandibular pain were the most frequent symptoms. Fifty-five percent of subjects graded their symptoms as moderate to severe. Twenty-nine percent of subjects developed additional symptoms over the next 48 hours.

CONCLUSION

Standard spinal immobilization may be a cause of pain in an otherwise healthy subject.

Photoreceptors of mouse retinas possess D4 receptors coupled to adenylate cyclase

In the mouse, the light-sensitive pool of cAMP can be eliminated in the dark by application of the dopamine D2-like receptor agonists LY 171555 (quinpirole), (+)-N0437 (2-[N-(n-propyl)-N-2-(thienylethylamino)-5-hydroxytetralin]) , or (+)-3-PPP [3-(3-hydroxyphenyl)-N-propylpiperidine hydrochloride]. The rank-order affinity of the ability of the D2-like antagonists to block the action of LY 171555 matched that of the rat D4 receptor. Reverse transcription of retina mRNA followed by DNA amplification using D4-specific nucleotides demonstrates the presence of D4 mRNA in retina. In situ hybridization studies using D4-specific digoxygenin-labeled oligonucleotides or 35S-labeled UTP RNA probes demonstrate the presence of D4 mRNA in the photoreceptor cell layer and in the inner nuclear and ganglion cell layers. The modulation by D4 ligands of the dark level of light-sensitive cAMP in photoreceptors demonstrates the physiological coupling of the D4 receptor subtype.

The rat dopamine D4 receptor: sequence, gene structure, and demonstration of expression in the cardiovascular system

Dopamine receptors have been implicated in a variety of neurological and neuropsychiatric disorders. Here we describe the use of the polymerase chain reaction and low stringency library screening to isolate a rat genomic clone encoding a novel dopamine receptor. Sequence data and pharmacological analysis reveal this clone to be the rat analog of the human D4 receptor, which exhibits a high affinity for the antipsychotic drug clozapine. The mRNA for this receptor shows a restricted pattern of expression in the central nervous system. Significant levels of expression were found in the hypothalamus, thalamus, olfactory bulb, and frontal cortex. However, 20-fold higher levels of D4 mRNA expression were observed in the cardiovascular system. Thus, this receptor appears to mediate dopamine function in the cardiovascular system as well as the central nervous system.