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P Guerra

Publications and source records attributed to P Guerra.

At least 19 recordsLinked to original sources
PubMed1999

Hydration change during the aging of phosphorylated human butyrylcholinesterase: importance of residues aspartate-70 and glutamate-197 in the water network as probed by hydrostatic and osmotic pressures.

Wild-type human butyrylcholinesterase (BuChE) and Glu-197-->Asp and Asp-70-->Gly mutants (E197D and D70G respectively) were inhibited by di-isopropyl phosphorofluoridate under standard conditions of pH, temperature and pressure. The effect of hydrostatic and osmotic pressures on the aging process (dealkylation of an isopropyl chain) of phosphorylated enzymes [di-isopropylated (DIP)-BuChE] was investigated. Hydrostatic pressure markedly increased the rate of aging of wild-type enzyme. The average activation volume (DeltaV( not equal)) for the dealkylation reaction was -170 ml/mol for DIP wild-type BuChE. On the other hand, hydrostatic pressure had little effect on the aging of the DIP mutants (DeltaV( not equal)=-2.6 ml/mol for E197D and -2 ml/mol for D70G), suggesting that the transition state of the aging process was associated with an extended hydration and conformational change in wild-type BuChE, but not in the mutants. The rate of aging of wild-type and mutant enzymes decreased with osmotic pressure, allowing very large positive osmotic activation volumes (DeltaV not equal osm) to be estimated, thus probing the participation of water in the aging process. Molecular dynamics simulations performed on the active-site gorge of the wild-type DIP adduct showed that the isopropyl chain involved in aging was highly solvated, supporting the idea that water is important for stabilizing the transition state of the dealkylation reaction. Wild-type BuChE was inhibited by soman (pinacolyl methylphosphonofluoridate). Electrophoresis performed under high pressure [up to 2.5 kbar (1 bar=10(5) Pa)] showed that the soman-aged enzyme did not pass through a pressure-induced, molten-globule transition, unlike the native wild-type enzyme. Likewise, this transition was not seen for the native E197D and D70G mutants, indicating that these mutants are resistant to the penetration of water into their structure. The stability energetics of native and soman-aged wild-type BuChE were determined by differential scanning calorimetry. The pH-dependence of the midpoint transition temperature of endotherms indicated that the high difference in stabilization energy between aged and native BuChE (DeltaDeltaG=23.7 kJ/mol at pH 8.0) is mainly due to the salt bridge between protonated His-438 and PO(-), with pK(His-438)=8.3. A molecular dynamics simulation on the MIP adduct showed that there is no water molecule around the ion pair. The 'hydrostatic versus osmotic pressure' approach probed the importance of water in aging, and also revealed that Asp-70 and Glu-197 are the major residues controlling both the dynamics and the structural organization of the water/hydrogen-bond network in the active-site gorge of BuChE. In wild-type BuChE both residues function like valves, whereas in the mutant enzymes the water network is slack, and residues Gly-70 and Asp-197 function like check valves, i.e. forced penetration of water into the gorge is not easily achieved, thereby facilitating the release of water.

Alkylation↗
PubMed1999

Structural and hydration changes in the active site gorge of phosporhylated butyrylcholinesterase accompanying the aging process.

Wild-type (wt) butyrylcholinesterase (BuChE) and the E197D and D70G mutants were inhibited by diisopropylfluorophosphate (DFP) or soman under standard conditions of pH, temperature and pressure. The effect of hydrostatic and osmotic pressures on the aging process of DFP-phosphorylated enzymes (diisopropylphosphoryl-BuChE (DIP-BuChE)) was investigated. Hydrostatic pressure strongly increased the rate of aging of wt enzyme. The activation volumes (deltaV*) for the dealkylation reaction was -150 ml/mol for DIP-wtBuChE. On the other hand, pressure had little effect on the aging of the DIP-E197D mutant and no effect on the DIP-D70G mutant, indicating that the transition state of the aging reaction (dealkylation of an isoproxy chain) was associated with an extended conformation/hydration change in wtBuChE but not in mutants. The rate of aging decreased with osmotic pressure, supporting the idea that water is important for stabilizing the transition state. Molecular dynamics simulations were performed on the wtDIP adduct to relate the kinetic data to hydration changes in the enzyme active site gorge. The pH dependence of the melting temperature (Tm) of native and soman-wtBuChE, as determined by differential scanning calorimetry (DSC), indicated that the stabilization energy of aged BuChE is mainly due to the salt bridge between protonated H438 and PO-, with pK(H438) = 8.3. Electrophoresis under high pressure up to 2.5 kbar showed that aged wtBuChE did not undergo pressure-induced molten globule transition unlike the native enzyme. This transition was not seen for the mutant enzymes, indicating that mutants are resistant to the penetration of water into their structure. Our results support the conclusion that D70 and E197 are major residues for the water/H-bond network dynamics in the active site gorge of BuChE, both residues acting like valves. In mutant enzymes, mutated residues function like check valves: forced penetration of water in the gorge is difficult, release of water is facilitated.

Aging↗
PubMed1999

Technetium-99m-HMPAO-labeled leukocyte imaging in patients with seronegative spondyloarthropathies.

OBJECTIVE: Gut inflammation is frequent among patients with seronegative spondyloarthropathies (SSp). The purpose of this study was to evaluate the presence of positive abdominal findings in patients with SSp who did not have clinical symptoms or signs of inflammatory bowel disease (IBD). This represents a new indication for abdominal 99mTc-HMPAO-labeled leukocyte scintigraphy. METHODS: Eighty-six patients (59 with SSp and 27 controls) were prospectively imaged with 99mTc-HMPAO-labeled leukocytes. RESULTS: Leukocyte imaging was positive in 33 patients with SSp (56%), 27 of these patients scored between 2+ and 4+ (51%). Four (15%) control patients also had positive findings. CONCLUSION: These findings provide evidence linking SSp with intestinal inflammation. SSp may be an important new indication for 99mTc-HMPAO-labeled autologous leukocyte scintigraphy.

Adult↗
PubMed1998

Sleep bruxism is a disorder related to periodic arousals during sleep.

There is evidence that sleep bruxism is an arousal-related phenomenon. In non-REM sleep, transient arousals recur at 20- to 40-second intervals and are organized according to a cyclic alternating pattern. Polysomnographic recordings from six subjects (two females and four males) affected by sleep bruxism (patients) and six healthy age-and gender-matched volunteers without complaints about sleep (controls) were analyzed to: (1) compare the sleep structure of bruxers with that of non-complaining subjects; and (2) investigate the relations between bruxism episodes and transient arousals. Patients and controls showed no significant differences in conventional sleep variables, but bruxers showed a significantly higher number of the transient arousals characterized by EEG desynchronization. Bruxism episodes were equally distributed between non-REM and REM sleep, but were more frequent in stages 1 and 2 (p < 0.0001) than in slow-wave sleep. The great majority of bruxism episodes detected in non-REM sleep (88%) were associated with the cyclic alternating pattern and always occurred during a transient arousal. Heart rate during the bruxism episodes (69.3+/-18.2) was significantly higher (p < 0.0001) than that during the pre-bruxing period (58.1+/-15.9). Almost 80% of all bruxism episodes were associated with jerks at the anterior tibial muscles. The framework of the cyclic alternating pattern offers a unified interpretation for sleep bruxism and arousal-related phenomena.

Adult↗
PubMed1996

Evaluation of sex differences in the pharmacokinetics of ranitidine in humans.

A bioequivalence study of two oral formulations of 300 mg ranitidine was carried out in 16 healthy volunteers (8 men and 8 women), and the pharmacokinetics in both sexes were compared. There was bioequivalence of both formulations. The terminal half-life of ranitidine was 7% shorter and the oral apparent clearance 10.5% higher in women (1.44 L/h/kg) than in men (1.29 L/h/kg), although this difference did not reach statistical significance. No differences were observed in maximum concentration (Cmax) or the time of its occurrence (tmax). Sex, age, and weight did not correlate significantly with oral clearance. These results suggest that there are no sex differences in the pharmacokinetics of ranitidine, or that any differences would not be of clinical relevance. It also should be emphasized that bioequivalence trials also can be used to study other pharmacokinetic or pharmacodynamic characteristics of drugs without damaging the main endpoint of the study.

Adult↗
PubMed1995

Comparative bioavailability of a dispersible formulation of diclofenac and finding of double plasma peaks.

We carried out a comparative study of the bioavailability of a typical, enteric-coated diclofenac with regard to a new dispersible formulation whose faster dissolution results in an earlier onset of its analgesic effect. This randomized, crossover study was conducted in 12 healthy male volunteers, who received in fasting 100 mg of enteric-coated diclofenac (Dolotrén, FAES) and 100 mg of dispersible diclofenac (Dolotrén Dispersable, FAES), with one-week interval between both. Blood samples were taken at pre-established times during the 24 hours after dosing, and plasma concentrations of diclofenac were determined by HPLC. Possible adverse experiences were monitored with a check-list, and blood and urinalysis were performed for safety assessment. The dispersible formulation showed a relative extent of bioavailability between 78% and 99% (90% CI) for the AUC0-infinity, being the 90% CI for the Cmax 63%-129%. The time to Cmax (Tmax) was significantly shorter with the dispersible than with the enteric-coated formulation (95% CI for the difference = 1.5-4.25 hours) as the T0(lag) or time to measurable plasma concentrations (1.9-4.2 hours, 95% CI). A relevant feature in the study was the finding of a second peak at 2-2.5 hours post-dosing in 7 out of 11 profiles of subjects receiving the dispersible formulation. Both formulations were well tolerated in clinical and laboratory terms. In conclusion, the new dispersible formulation of diclofenac allows absorption to begin more rapidly and plasma peak is reached earlier, a fact that may be relevant to the analgesic treatment of acute pain.

Absorption↗
PubMed1995

Cyclosporin A increases somatomedin C insulin-like growth factor I levels in chronic rheumatic diseases.

OBJECTIVE: To determine whether anabolic hormones that affect the musculoskeletal system and active on the immune cells changed during cyclosporin A (CysA) therapy. METHODS: We carried out a randomized study of patients with rheumatic disease attending the outpatient clinic for rheumatic diseases. Twenty-four patients with chronic arthritis [20 with rheumatoid arthritis (RA) and 4 with psoriatic arthritis (PsA)] were divided into 2 groups (10 RA, 2 PsA) and randomly given CysA 5 mg/kg daily or hydroxychloroquine (OH-Chlor) 6 mg/kg daily in divided doses. RESULTS: A significant increase of insulin-like growth factor I (IGF-I) (somatomedin C) levels and of bone Gla protein was shown after 2 months in the CysA treated group, but not in the OH-Chlor group. A statistically significant correlation was observed between changes of IGF-I levels and of dehydroepiandrosterone sulphate (DHEAS). This finding was confirmed in a further series of 39 patients. No changes were seen in 25 OH-D, 1-25(OH)2-D3 or parathyroid hormone after CysA. CONCLUSION: The effects of CysA on IGF-I may explain some of the clinical, immunologic, and metabolic results during CysA treatment of rheumatic diseases.

Arthritis, Psoriatic↗
PubMed1994

Heme biosynthesis in uremic patients on CAPD or hemodialysis.

We have analyzed some parameters of porphyrin metabolism in 60 patients with end-stage renal failure, 20 of them on CAPD and the remaining on HD. In comparison with 56 control subjects, both groups of patients showed the three following findings: low erythrocyte aminolevulinate dehydrase activity, inhibition ability for the activity of this enzyme when their plasma was incubated in vitro with normal erythrocytes, and increased plasma porphyrin levels. Like anemia, these abnormalities were more remarkable in patients on HD who also exhibited increased erythrocyte protoporphyrin levels and compensatory porphobilinogen deaminase activities. Mean weekly porphyrin removal through dialysate was higher in CAPD (90.8 micrograms) than in HD patients (30.4 micrograms). Dialysate and plasma porphyrins were correlated in both circumstances (r = 0.714, P < 0.01 and r = 0.637, P < 0.05, respectively). The less pronounced porphyrin abnormalities found in CAPD patients with respect to HD patients may be due to the more efficient capability of peritoneal dialysis for removing from plasma protein-bound substances, as porphyrins and inhibitors of aminolevulinate dehydrase or other enzymes involved in erythropoiesis. Since no close relationship was found between these abnormalities of porphyrin metabolism and hematocrit values, the anemia of uremia cannot be merely considered as a direct consequence of altered heme biosynthetic pathway.

Adolescent↗
PubMed1994

The MAXM hematology autoanalyzer. An alternative?

The MAXM is a compact blood count and differential analyzer that appeals to both the space-limited, full-service laboratory and the large outpatient practice. The authors compared the performance of the Coulter MAXM to the larger Coulter STKS. Linearity and precision studies were comparable to the STKS. MAXM leukocyte differentials were closely correlated with STKS and manual readings, being excellent in the neutrophil, lymphocyte, and eosinophil categories but poorer on monocyte counts. Basophil counts did not correlate with STKS or manual counts. Analyzer suspect flagging was similar in both machines, with the MAXM exhibiting slightly reduced sensitivity and greater specificity. MAXM processing of a single sample requires twice the time. The MAXM functions well for a large office practice and as a backup for large medical laboratories but, because of its hands-on requirements and lack of speed, cannot replace the larger, more automated analyzers.

Autoanalysis↗
PubMed1994

Somatomedin C (insulin-like growth factor 1) levels decrease during acute changes of stress related hormones. Relevance for fibromyalgia.

OBJECTIVE: To determine the effects of stress hormones on insulin-like growth factor 1 (IGF-1). METHODS: Insulin induced hypoglycemia (< 3 mmol/l) and clonidine induced depression of noradrenergic tone were used to assess the acute effects of cortisol, human growth hormone (hGH), and norepinephrine (NE). RESULTS: Despite the increase of hGH during hypoglycemia, a statistically significant decrease of IGF-1 was observed along with the expected rise of cortisol and NE. To eliminate the role played by NE, NE tone was depressed by administering clonidine. A statistically significant decrease of IGF-1 was also observed. CONCLUSION: Acute cortisol release or a NE decrease induce low IGF-1 levels.

Clonidine↗
PubMed1992

Primary traumatic benign midbrain haematoma in hyperextension injuries of the head.

Primary traumatic brain stem injury occurring in isolation is not universally recognized as a distinct pathological entity which may follow a head injury. We describe two patients with clinical and radiological evidence of primary posttraumatic midbrain haemorrhage occurring in isolation associated with good recoveries. It is suggested that paramedian midbrain syndromes associated with midbrain haemorrhages should be recognized as a distinct, although unusual, complication of hyperextension injury to the head which may have a benign course.

Adult↗
PubMed1992

Sympathetic nervous system in high sodium one-kidney, figure-8 renal hypertension.

The contribution of the sympathetic nervous system and vasopressin to the maintenance of arterial pressure was investigated in high sodium-fed rats 4 weeks after the induction of one-kidney, figure-8 renal wrap hypertension. Arterial pressure was significantly greater in renal-wrapped rats than in sham-operated animals. The contribution of the sympathetic nervous system was assessed functionally by measuring the arterial pressure response to ganglionic blockade and estimating the apparent rate of release of norepinephrine. The contribution of vasopressin was assessed by administration of the vascular antagonist d(CH2)5Tyr(Me)-AVP. Whole-animal vascular responsiveness and cardiac baroreceptor reflex sensitivity were determined by graded intravenous bolus injections of angiotensin II, vasopressin, and phenylephrine. Hypertensive rats demonstrated an exaggerated reduction in arterial pressure to autonomic blockade before and after blockade of vascular vasopressin receptors. There was a significant 27% increase in the apparent rate of release of norepinephrine into the plasma. Administration of d(CH2)5Tyr(Me)-AVP did not affect arterial pressure when given alone. However, after ganglionic blockade, inhibition of the vasopressin system elicited similar falls in blood pressure in both normotensive and hypertensive rats. Arterial pressure dose-response effects of phenylephrine, angiotensin II, and vasopressin were similar between renal-wrapped and sham-operated animals; however, cardiac baroreceptor reflex sensitivity was suppressed in the hypertensive rats. These studies indicate that the maintenance of arterial pressure in chronic, high sodium renal-wrap hypertension is associated with an augmented sympathetic nervous system function.

Animals↗
PubMed1991

Treatment of advanced neuroblastoma with I-131 meta-iodobenzylguanidine.

From February 1986 to December 1988, 31 children with advanced pretreated neuroblastoma were treated with 131-I meta-Iodobenzylguanidine (131-MIBG). Thirteen children had been resistant to first-line therapy, three had suffered a local relapse, and fourteen had suffered a disseminated relapse without over bone marrow infiltration. One child was treated initially because of resistance to first-line therapy, and subsequently for a local relapse. A total of 72 courses of 131-MIBG was administered, with doses ranging from 2.8 to 6.0 GBq (median, 3.7 GBq). One child received five courses, two four courses, 13 three courses, four two courses, and 12 one course of 131-MIBG. The most common toxic effect was thrombocytopenia, with a platelet level of less than 50,000/cmm occurring after 19 of 60 evaluable courses. A leukocyte count less than 1000/cmm was seen only once. There were six major responses (two complete) lasting 4 to 9 months, and two minor responses lasting longer than 38 and 44 months. Responses were seen more commonly in children whose only lesion was a residual primary tumor and in children who had not been pretreated who experienced disseminated relapse. Further studies of the role of 131-I meta-Iodobenzylguanidine in treatment of neuroblastoma are needed.

3-Iodobenzylguanidine↗
PubMed1990

Therapeutic possibilities of 131I-MIBG in metastatic carcinoid tumors--preliminary report.

The poor results of traditional therapy in advanced carcinoid tumors and the well-proven uptake of 131I-MIBG shown by some of these tumors induced us to attempt a radiometabolic approach. We selected for the treatment 5 patients (3 men and 2 women) who showed progression of disease, a fairly good uptake of 131I-MIBG with severe related symptoms, and a poor response to traditional therapy. A cumulative radioactivity of 5.5-29.6 GBq was given. Acute side effects after 131I-MIBG administration or late radiation-induced damages were not observed. Symptoms increased during the first 2-4 weeks in 2 patients: in one of these relief was achieved with drugs. Results concerning objective remission of the disease were unsatisfactory. In contrast, definite improvement of symptoms was shown in 2 of 5 patients, resulting in a better quality of life.

3-Iodobenzylguanidine↗
PubMed1990

Effect of nifedipine in arterial vasculature of human placenta.

1. Nifedipine induced concentration-dependent relaxations in segments of human placental arteries precontracted with 40 mM K+. 2. Preincubation of segments with nifedipine induced concentration-dependent inhibition of contractions elicited by 40 mM K+ (IC50, 2.5 x 10(-9) M) and 10(-7) M 5-HT (5.9 x 10(-8) M). 3. The time-course of contractions elicited by K+ and 5-HT (responses not sustained) in the absence and in the presence of nifedipine was different. 4. Nifedipine inhibited Ca addition-evoked contractions in Ca-free medium containing 40 mM K+ or 10(-7) M 5-HT, mainly those obtained in depolarized segments. 5. These results indicate that these arteries are very sensitive to nifedipine and that the voltage-operated Ca channels are more affected by the Ca antagonist than receptor-operated ones.

Arteries↗
PubMed1990

Interference of diltiazem with serotonin- and potassium-induced contractions in human placental veins.

1. In segments of human placental veins precontracted with K+ (25, 40 or 75 mM), diltiazem produced concentration-dependent relaxations with similar EC50 values. 2. Diltiazem (20 min preincubations) also caused concentration-dependent inhibition of the contractions induced by K+ (40 or 75 mM) and 5-HT (serotonin, 3 x 10(-7) M). IC50 values were similar, in both cases. 3. The time-course of the vasocontractions induced by 75 mM K+ and 3 x 10(-7) M 5-HT in the absence and in the presence of diltiazem were different. The contractions caused by K+ were sustained and transient those elicited by 5-HT. 4. These data suggest that (1) this vasculature is sensitive to diltiazem, and (2) the Ca influx through voltage-operated Ca channels (activated by K+) and through receptor-operated Ca channels (activated by 5-HT) is very similar.

Diltiazem↗
PubMed1990

Effects of Ca2+ antagonists nifedipine and diltiazem on isolated human chorionic arteries and veins.

5-Hydroxytryptamine (5-HT) and K+ induced contractions in human chorionic arteries and veins. 5-HT-caused responses were blocked by ketanserin (10(-7) and 10(-6) M) and prazosin (10(-5) but not 10(-6) M). K(+)-induced contractions were practically abolished in a Ca2(+)-free medium, whereas those produced by 5-HT were reduced. The efficacy (EC50 values) of diltiazem to produce relaxation in arteries and veins contracted with 40 or 75 mM K+ was similar, but normally greater than that of nifedipine. The potency of nifedipine (IC50 values) to inhibit maximal K+ contractions was greater than to inhibit maximal 5-HT contractions; diltiazem showed an inverse order of potency, which was less than that of nifedipine. The time course of 10(-6) M 5-HT and 75 mM K+ contractions was different, as much in the absence as in the presence of both Ca2+ antagonists; 5-HT contractions were transient, but sustained those elicited by K+. K+ (75 mM) and 5-HT (10(-6) M) produced increases in 45Ca2+ uptake, which were reduced by the Ca2+ antagonists. These results indicate that (a) human chorionic arteries and veins are similarly sensitive to Ca2+ antagonists, (b) 5-HT-induced contractions were largely dependent on extracellular Ca2+ and mainly mediated by 5-HT2 receptors but not by alpha 1-adrenoceptors, and (c) nifedipine was more potent than diltiazem in inhibiting Ca2+ influx through potential- and receptor-dependent Ca2+ channels.

Arteries↗