LAVH confusion reigns--the return of the Jabberwocky.
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Adult↗
Biomedical subjects
R L Levine
Publications and source records attributed to R L Levine.
Extracranial intravascular vasodilatory response to acetazolamide and magnetic resonance angiography.
Cerebral vasodilatory testing provides an important measure of both the hemodynamic significance of arterial occlusive disease and the adequacy of collateral pathways. This study measured the extracranial intravascular volume flow rate response to acetazolamide using phase-contrast magnetic resonance angiography. From 10 patients with unilateral carotid transient ischemic attacks (TIAs), a total of 18 extracranial carotid arteries (10 symptomatic, 8 asymptomatic, 2 occluded) and 19 extracranial vertebral arteries were studied. Patients were free of large-vessel intracranial stenoses, evident areas of ischemic infarction, evident areas of nonspecific white matter change, and hemodynamic or low-flow induction of TIA symptomatology. Asymptomatic carotid volume flow rates rose from 151 +/- 19 (standard error of mean) to 220 +/- 26 ml/min while symptomatic flow rates rose from 106 +/- 22 to 145 +/- 25 ml/min. Dominant vertebral volume flow rates rose from 128 +/- 23 to 160 +/- 22 ml/min while nondominant rates rose from 40 +/- 12 to 61 +/- 15 ml/min. Carotid volume flow rates were inversely proportional to percent stenosis for both baseline (r = 0.51, p < 0.02) and acetazolamide (r = 0.81, p < 0.001) data. Baseline-plus-acetazolamide volume flow rate techniques safely measure intravascular vasodilatory responses. Intracranial measurement techniques are being developed to further study cerebrovascular reserve using phase-contrast magnetic resonance angiography.
Acetazolamide↗
Nonspecific esterase activity in astrocytes of the goldfish brain.
We examined the distribution of nonspecific esterase (NSE) activity in the brain of the goldfish, Carassius auritus, and found that the enzyme is expressed at high levels in cells that appeared to be radial astrocytes. Several instances in which neurons expressed NSE activity were also seen. To confirm the identity of the radial profiles as astrocytes, similar sections were labeled with antiserum against goldfish glial fibrillary acidic protein (GFAP). The concordance between the NSE and the anti-GFAP data in both the visual system and the telencephalon was essentially complete, confirming that the NSE reaction was labeling astrocytes in these structures. The two methods also gave similar results in both the cerebellum and the vagal lobes, although the concordance between them in these instances was somewhat less complete. Both the NSE reaction and immunohistochemistry with anti-GFAP serum revealed labeled nonradial cells lying free in the cerebellar molecular layer. We suggest that these cells may represent free astrocytes, a cell type that has not previously been reported in morphological studies of the teleostean brain. On the basis of our observations, we suggest that the NSE reaction may be a useful adjunct in morphological studies of teleost astroglia. Finally, we propose that the expression of NSE activity in goldfish astrocytes may he related to their ability to internalize neural debris during Wallerian degeneration.
Animals↗
Determination of 2-oxohistidine by amino acid analysis.
Oxidative modification of proteins has been implicated in aging, ischemia reperfusion, carcinogenesis, and other phenomena. Oxidation of the C-2 position of the imidazole ring of histidine converts the residue to 2-oxohistidine, a novel amino acid which may serve as a marker of oxidative modification of proteins (K. Uchida and S. Kawakishi, J. Biol. Chem. 269, 2405-2410, 1994). It has been identified in oxidatively modified proteins by electrochemical detection during reverse-phase high-pressure liquid chromatography, by mass spectrometry, and as the phenylthiohydantoin after Edman degradation, but not by amino acid analysis of protein hydrolysates. We now describe procedures for stabilizing 2-oxohistidine which allow its quantification by routine methods of amino acid analysis. These include classical ion exchange chromatography with postcolumn derivatization by o-phthaldialdehyde, reverse-phase chromatography with precolumn derivatization by o-phthaldialdehyde, and reverse-phase chromatography with precolumn derivatization by 6-aminoquinolyl-N-hydroxysuccinimidyl carbamate. Using these techniques, a previously unidentified amino acid which appears during the oxidative inactivation of glutamine synthetase was shown to be 2-oxohistidine. One picomole of 2-oxohistidine was readily detected in a protein hydrolysate containing 1700 pmol total amino acids.
Amino Acids↗
Inhibition of the human immunodeficiency virus-1 protease and human immunodeficiency virus-1 replication by bathocuproine disulfonic acid Cu1+.
The protease encoded by the human immunodeficiency virus-1 (HIV-1) is essential for processing viral polyproteins which contain the enzymes and structural proteins required for the infectious virus. It was previously found that cupric chloride, in the presence of dithiothreitol or ascorbic acid, could inhibit the HIV-1 protease. It was suggested that a Cu1+ chelate was the moiety responsible for inhibition of the protease. This hypothesis has now been investigated directly by utilizing the stable Cu1+ chelate, bathocuproine disulfonic acid Cu1+ (BCDS-Cu1+). BCDS-Cu1+ inhibited the HIV-1 wild type protease as well as a mutant HIV-1 protease lacking cysteines. BCDS-Cu1+ was a competitive inhibitor of the mutant HIV-1 protease with an apparent Ki of 1 microM. Replication of HIV-1 in human lymphocytes and the cytotoxic effect of HIV-1 in CEM cells was inhibited by micromolar BCDS-Cu1+. Inhibition of the protease and of HIV replication by BCDS-Cu1+ was dependent on the presence of Cu1+ as BCDS alone was ineffective. EDTA blocked the inhibition of the protease by Cu1+ but was unable to block inhibition of the protease by BCDS-Cu1+, indicating that the Cu1+ complex was the inhibitory agent. The apparent IC50 for BCDS-Cu1+ on the inhibition of replication by primary isolates of HIV-1 was 5 microM. However, BCDS-Cu1+ did not affect polyprotein processing in an H9 cell line chronically infected with HIV-1, indicating that BCDS-Cu1+ acts by yet another mechanism to block HIV infection. Other possible targets for BCDS-Cu1+ include inhibition of viral adsorption and/or inhibition of the HIV-1 integrase.
Antiviral Agents↗
Carbonic anhydrase III. Oxidative modification in vivo and loss of phosphatase activity during aging.
Oxidative modification of DNA, lipids, and proteins occurs as a consequence of reaction with free radicals and activated oxygen. Oxidative modification of total cellular proteins has been described under many pathologic and experimental conditions, but no specific proteins have been identified as in vivo targets for oxidative modification. Utilizing an immunochemical method for detection of oxidatively modified proteins, we identified a protein in rat liver that was highly oxidized. It was purified to homogeneity and identified as carbonic anhydrase, isozyme III. Its characteristics match those previously described for a protein that was lost during aging of the rat, senescence marker protein-1. Carbonic anhydrase III was purified from rats aged 2, 10, and 18 months, and the proteins were characterized. All three preparations were highly oxidatively modified as assessed by their carbonyl content. The enzyme has three known catalytic activities, and the specific activities for carbon dioxide hydration and for ester hydrolysis decreased during aging by approximately 30%. However, the third activity, that of a phosphatase, was virtually lost during aging. While the physiologic role of carbonic anhydrase III is unknown, we suggest that it functions in an oxidizing environment, which leads to its own oxidative modification.
Aging↗
Aging of the liver: proteolysis of oxidatively modified glutamine synthetase.
During aging cells accumulate altered forms of proteins, notably oxidatively modified proteins. The multicatalytic protease selectively degrades oxidized proteins, suggesting that the age-related accumulation of oxidized proteins might be a consequence of decreased activity of this protease. The protease activity of liver homogenates was assayed with an improved fluorimetric method, using oxidatively modified glutamine synthetase as substrate. Application of this assay to extracts from liver of Fischer 344 rats from both Japan and the United States demonstrated a marked preference for the oxidized substrates, as expected. Extracts from animals ages 8 to 26 months maintain both total proteolytic activity and the ability to distinguish between native and oxidized substrates. Oxidatively modified hepatocyte extracts were also employed as substrate, and older animals again maintained proteolytic activity. The multicatalytic protease was purified from liver of young and old rats, and the specific activity of the preparations were comparable when assayed with oxidatively modified glutamine synthetase. We conclude that the intrinsic neutral or alkaline proteolytic activity of rat liver is maintained during aging.
Aging↗
Magnetic field effects on spatial discrimination and melatonin levels in mice.
Previous research has demonstrated a decrement in spatial discrimination learning following exposure to a .30 Tesla magnetic field. It had been suggested that those findings might be the result of an interaction between the magnetic field and physiological ferromagnetic material (magnetite). In the present study, mice were exposed for 100 min to a 2.0 Tesla field and both their left-right discrimination learning ability and serum melatonin levels were compared with a control group. Results indicated a significant interference with spatial discrimination learning following exposure, but no significant differences in serum melatonin levels. These findings appeared to rule out magnetically induced melatonin fatigue as an explanation of the decrement in spatial learning, as opposed to other possibilities such as magnetic effects on brain magnetite. However, additional controls are suggested for future research.
Animals↗
Oxidative modification of fibrinogen inhibits thrombin-catalyzed clot formation.
Plasma fibrinogen plays a central role in controlling hemostasis. In an earlier report, we found that fibrinogen is oxidized when whole plasma is treated with a metal-catalyzed oxidation system. These studies show that oxidative modification of purified human fibrinogen leads to an exposure-dependent loss of thrombin-induced clot formation. Inhibition of clotting occurred when either metal-catalyzed oxidation or gamma-irradiation was employed to generate oxidizing radicals. Both systems caused covalent modification of fibrinogen, assessed by measuring incorporation of protein carbonyls. Thrombin-catalyzed fibrinopeptide release was normal in irradiated fibrinogen and was only slightly diminished in protein exposed to metal-catalyzed oxidation, indicating that the inhibition of clotting activity was due to impaired fibrin monomer polymerization. Thus, oxidative modification of normal fibrinogen causes dysfibrinogenemia and constitutes a novel mechanism for inhibition of thrombosis.
Ascorbic Acid↗
Use of end-tidal carbon dioxide to predict outcome in prehospital cardiac arrest.
STUDY OBJECTIVE: End-tidal CO2 (ETCO2) measurement can be used to predict death in prehospital cardiac arrest patients with pulseless electrical activity (PEA). DESIGN: A prospective, observational study. SETTING: An urban and rural emergency medical services system in northwestern Washington state. PARTICIPANTS: Ninety consecutive victims of prehospital cardiac arrest with PEA. INTERVENTIONS: Patients were intubated in the field and treated using standard advanced cardiac life support protocols with online medical control. In addition, all patients were evaluated using mainstream ETCO2 monitoring. In this study, a hypothetical decision was made to cease resuscitative efforts based on an ETCO2 level of 10 mm Hg or less after 20 minutes of advanced cardiac life support. RESULTS: The study included 90 patients (61 were men) with a mean age of 67.6 +/- 13.6 years (range, 27 to 95 years). The initial ETCO2 averaged 11.7 +/- 6.6 mm Hg in nonsurvivors (range, 5 to 50 mm Hg) and 10.9 +/- 4.9 mm Hg in survivors (range, 5 to 24 mm Hg) (P > .672 [NS]). After 20 minutes of advanced cardiac life support, ETCO2 averaged 3.9 +/- 2.8 mm Hg (range, 0 to 12 mm Hg) in patients in whom the theoretical decision was made to cease field resuscitation. In contrast, survivors' ETCO2, just before restoration of circulation, averaged 31 +/- 5.3 mm Hg (range, 16 to 35 mm Hg) (P < .0001). Using an ETCO2 of 10 mm Hg or less as a theoretical threshold to predict death in the field successfully discriminated between the 16 survivors to hospital admission (those that achieved return of spontaneous circulation) and 75 prehospital deaths. Of the 16 survivors to hospital admission, 9 died in the hospital, and 7 were discharged from the hospital alive. In 13 of the 16 survivors, the first evidence of return of spontaneous circulation, before a palpable pulse or blood pressure, was a rising ETCO2. The logistic-regression parameters for the model are 4.4391 + ETCO2*-0.3624 (P < .0001). Sensitivity was 97.3%; specificity 100%; positive predictive value 100%; and negative predictive value 88.9%. CONCLUSION: This study suggests that a low ETCO2 (10 mm Hg or less) can be used to predict irreversible death in patients with pulseless electrical activity undergoing prehospital advanced cardiac life support. If future studies validate this model, use of ETCO2 may allow for triage decisions in the field.
Adult↗
Laparoscopic suturing and ligation techniques.
The laparoscopic literature addressing operative techniques and use of suturing and knot tying is reviewed. Many operations that have traditionally been performed by laparotomy, may now be primarily accomplished by laparoscopy. Increasing improvements in laparoscopic instruments and techniques permit more surgical procedures to be performed on an ambulatory basis, therefore setting a new trend in gynecologic surgery. The evolution of endoscopic procedures will require laparoscopic surgeons to master suturing techniques which will improve their level of comfort and performance. This review of suturing and knot tying procedures may be helpful to both the established surgeons and the beginners as it gives a comprehensive review of laparoscopic suturing and knot tying techniques.
Equipment Design↗
Comparison of the effect of intermittent administration and continuous infusion of famotidine on gastric pH in critically ill patients: results of a prospective, randomized, crossover study.
OBJECTIVES: To compare the effects of intermittent intravenous administration and continuous intravenous infusion of famotidine on gastric pH in critically ill patients. DESIGN: A prospective, randomized, crossover study of continuous infusion and bolus administration of famotidine in critically ill patients. SETTING: A 14-bed medical intensive care unit (ICU) of a 500-bed county hospital. PATIENTS: Medical ICU patients requiring stress ulcer prophylaxis. INTERVENTIONS: Patients were randomized to receive an equivalent dose of famotidine by continuous infusion or intravenous bolus for 24 hrs, and then were crossed over to the other arm of the study. MEASUREMENTS AND MAIN RESULTS: Critically ill patients who met the inclusion criteria were randomly assigned to receive famotidine 20 mg i.v. over 10 mins, every 12 hrs or a continuous infusion of 1.7 mg/hr for 24 hrs. After a 16-hr washout period, patients crossed over to the other arm of the study. Gastric pH was monitored continuously for 24 hrs. A total of 710 gastric pH measurements were obtained for each phase of the study. The mean area under the pH-time curve for a 24-hr period was higher for continuous infusion than bolus administration (p = .05). Continuous infusion of famotidine maintained a gastric pH of > or = 4 over a longer time period than bolus administration (20.8 hrs vs. 12.6 hrs, respectively; p < .01). Onset of therapeutic gastric pH for continuous infusion was slightly delayed as compared with bolus administration. CONCLUSIONS: Continuous infusion of famotidine is more effective than an equivalent dose given by intermittent bolus in maintaining the appropriate gastric pH necessary for prevention of stress ulceration. Delayed onset of effect may warrant a priming dose when famotidine is given by continuous infusion.
Adult↗
Basilar artery dolichoectasia. Review of the literature and six patients studied with magnetic resonance angiography.
Six patients for whom computed tomography revealed a curvilinear calcific mass anterior to their brainstem were evaluated and magnetic resonance imaging and magnetic resonance angiography were performed on each. Magnetic resonance studies confirmed the suspicion of basilar artery dolichoectasia, and demonstrated a partial thrombus in the basilar artery in 1 patient. The patients' clinical features were combined with those of basilar artery dolichoectasia patients reported in the literature (n = 122) who had case histories sufficiently detailed enough to determine each person's mode of clinical presentation. Basilar artery dolichoectasia patients were more often men (95/128, 74%) and had a mean age of 59 +/- 11 years. Of the 128 patients studied, there were cranial nerve compressive signs in 74 (58%), especially facial spasm (29/74, 39%) and trigeminal neuralgia (20/74, 27%); vertebral basilar insufficiency or vertebral basilar stroke or both in 61 (48%); hydrocephalus in 40 (31%); compressive brainstem symptoms and signs that progressed clinically in 31 (24%); and arterial hypertension in 31 (24%). Magnetic resonance imaging and magnetic resonance angiography safely diagnose this interesting arterial abnormality. The modes of clinical presentation of this disorder are reviewed.
Aged↗
Recognition, assessment, and treatment of anxiety in the critical care patient.
A multidisciplinary group of experts involved in the treatment of critically ill patients participated in a workshop conference designed to develop practice recommendations for the recognition, assessment, and treatment of anxiety in the critical care environment. Anxiety was identified as a ubiquitous problem in critical care that may interfere with healing and recovery. The faculty agreed that clinicians should be familiar with the signs and symptoms of anxiety and should be able to determine when interventions are necessary. Whenever possible, nonpharmacologic methods for anxiolysis should be incorporated into intensive care protocols. Intensive care personnel should be trained in those interventions that require specialized expertise, and they should become familiar with the drugs available for the treatment of anxiety. Protocols for determining the best agents to be used in a given setting and their most appropriate method of administration should be established. Pharmacologic and nonpharmacologic treatments are not mutually exclusive but should be complementary. Finally, procedures for obtaining psychiatric consultation, when necessary, should be in place.
Adaptation, Psychological↗
Reactivity of cysteine-67 of the human immunodeficiency virus-1 protease: studies on a peptide spanning residues 59 to 75.
The protease encoded by the human immunodeficiency virus-1 (HIV-1) is essential for the processing of viral polyproteins into mature viral proteins. The 99-residue protease from HIV-1 contains two generally conserved cysteine residues, one of which (Cys-67) is located on the solvent-exposed surface. It was shown previously that Cys-67 of the native enzyme reacted with 5,5'-dithiobis-(2-nitrobenzoic acid) (DTNB, Ellman's reagent) at pH 6.2, causing a reversible inactivation of the protease. However, there was no reaction when the protein was denatured in 6 M guanidine hydrochloride, implying that the native conformation rendered Cys-67 more reactive. To investigate the structural basis of the lowered pKa in the native protein, we synthesized a 17-residue peptide matching the sequence of residues 59-75. The reactivity of this synthetic peptide with DTNB mimicked that of the protease, being more reactive in the absence of 6 M guanidine hydrochloride than in its presence. It was possible that His-69 or Lys-70 could facilitate ionization of the SH group of Cys-67, which is required for reaction with DTNB. Apparently both residues are important, because increased reactivity of the native peptide was eliminated when either His-69 or Lys-70 were changed to Ala. Replacement of His-69 by Glu reversed the reactivity, so that the native peptide was less reactive than that denatured in guanidine hydrochloride. Thus, the reactivity of Cys-67 is modulated by the charges on residues 69 and 70 in the protein. The presence of His-69 and Lys-70 renders the native protease especially susceptible to oxidation and disulfide formation. The resulting reversible inactivation of the protease may be important in the normal regulation of the viral life cycle, a suggestion supported by the strong conservation of the residues in this region.
Amino Acid Sequence↗
Oxidative dissociation of human alpha 2-macroglobulin tetramers into dysfunctional dimers.
Human alpha 2-macroglobulin is a broad-spectrum, homotetrameric antiproteinase that can maximally bind up to two proteinase molecules in a ternary complex. Proteinases cleave the inhibitor within a peptide stretch termed the bait region and induce the emergence of internal thiol esters whose nucleophilic scission precede a major conformational change which entraps enzymes within molecular cages. In a previous study, leukocyte-generated hypohalous acids and N-haloamines were identified as the first examples of physiologically relevant inactivators of the antiproteolytic activity of alpha 2-macroglobulin (Reddy, V. Y., Pizzo, S. V., and Weiss, S. J. (1989) J. Biol. Chem. 264, 13801-13809), but the mechanisms whereby the oxidants damaged the inhibitor remained undefined. We now demonstrate that N-chloramines (RNCl) destroy the antiproteolytic activity of alpha 2-macroglobulin in an unusual biphasic process that results in the formation of inactive alpha 2-macroglobulin half-molecules. In the first phase, 8 eq of RNCl reacted with each alpha 2-macroglobulin subunit to generate a partially oxidized antiproteinase containing 8 methionyl sulfoxide residues/monomer. Structure-function analyses demonstrated that the oxidized inhibitor retained its homotetrameric structure as well as its ability to entrap proteinases. In marked contrast, the oxidation of an additional 6 methionyl residues and a single tryptophanyl residue fractured the alpha 2 M homotetramer across its non-covalent axis into two pairs of disulfide-linked dimers. Despite the fact that the oxidized dimers displayed normal bait regions whose cleavage by proteinases initiated thiol ester scission, all antiproteolytic activity was lost. Furthermore, the oxidized dimers were unable to undergo the critical conformational changes normally associated with bait region cleavage or thiol ester scission. Together, these results demonstrate that chlorinated oxidants destroy the antiproteolytic activity of alpha 2-macroglobulin by attacking a subset of methionyl and tryptophanyl residues whose oxidation mediates the dissociation of the native homotetramer into conformationally locked dimers.
Amino Acid Sequence↗
Axonal transport of proteoglycans in regenerating goldfish optic nerve.
Labeling of goldfish optic nerve and tectum proteoglycans (PGs) was quantified following intraocular injection of 35SO4 and [3H]proline or [3H]glucosamine. Both intact animals and animals which had survived for periods of 10 to 119 days after an optic nerve crush lesion were examined. Regenerating retinal ganglion cell (RGC) axons reached the rostral pole of the tectum by 10 days postcrush and by 21 days had densely innervated the optic synaptic laminae. If the contralateral tectum had been removed, the regenerating RGC axons innervated the remaining ipsilateral tectum with a delay of approximately 14 days. There was a biphasic increase in the synthesis and transport of PGs during optic fiber regeneration which was not affected by the removal of the tectum. More highly sulfated PGs were preferentially off-loaded from the orthograde transport pool proximally in the optic nerve, both in the unoperated animals and during regeneration. These PGs also had longer and/or more glycosaminoglycan (GAG) chains than those off-loaded distally, in the tectum. During early regeneration, the synthesis and transport of chondroitin sulfate PGs (CSPGs) increased more than those of heparan sulfate PGs, and during the period of optic fiber invasion of the synaptic laminae, the PGs retained in the nerve had a higher content of CSPGs than those transported into the tectum. Removal of the contralateral tectum at the time of nerve crush resulted in a decrease in the size and/or numbers of GAGs and overall sulfation of PGs in the nerve by 21 days postoperatively.(ABSTRACT TRUNCATED AT 250 WORDS)
Animals↗
Magnetic field effects on spatial discrimination learning in mice.
A magnetic sense has been demonstrated in several species, including mice. It has been suggested that the basis of this sense, and its role in navigation, rests on the existence of ferromagnetic materials in the brain. Several researchers have shown changes in navigation during exposure to relatively weak magnetic fields, which presumably interact with magnetite in the brain. In this study, mice were exposed to the powerful magnetic field of an MRI scanner and their left-right discrimination learning was compared with a control group. Results indicate a significant decrement in such learning ability immediately after exposure. Suggestions for future research are presented.
Animals↗