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Biomedical subjects

M Barra

Publications and source records attributed to M Barra.

At least 19 recordsLinked to original sources
PubMed2005

Photosynthetic O2 formation tracked by time-resolved x-ray experiments.

Plants and cyanobacteria produce atmospheric dioxygen from water, powered by sunlight and catalyzed by a manganese complex in photosystem II. A classic S-cycle model for oxygen evolution involves five states, but only four have been identified. The missing S4 state is particularly important because it is directly involved in dioxygen formation. Now progress comes from an x-ray technique that can monitor redox and structural changes in metal centers in real time with 10-microsecond resolution. We show that in the O2-formation step, an intermediate is formed--the enigmatic S4 state. Its creation is identified with a deprotonation process rather than the expected electron-transfer mechanism. Subsequent electron transfer would give an additional S4' state, thus extending the fundamental S-state cycle of dioxygen formation.

Chemical Phenomena↗
PubMed2001

Fetal myocardial hypertrophy in an experimental model of gestational diabetes.

INTRODUCTION: The frequent occurrence of prenatal hypertrophy of the muscular ventricular septum has been widely reported in fetuses of diabetic mothers. OBJECTIVES: This experimental study was carried out to test the hypothesis that the weight of the heart, the ratio of the cardiac weight to that of the body, the thickness of the muscular ventricular septum, and the myocytic profile within the ventricular septum are all increased in fetuses of diabetic rats in comparison to fetuses of normal rats. METHODS: Diabetes was induced in 5 pregnant Wistar rats, bearing 30 fetuses, on the eighth day after conception, by intraperitoneal injection of 50 mg/kg of streptozotocin. Five normal pregnant Wistar rats, bearing 20 fetuses, made up the control group. Morphometric data were obtained by a computer-assisted method applied to the measurements of the thickness of the ventricular septum, and myocytic nuclear area. Statistical analysis utilized Student's t-test and Kruskal-Wallis test. RESULTS: The mean thickness of the septum was 675.56 microm (+/-159) in the control fetuses, and 904.39 microm (+/-262) in the fetuses carried by diabetic mothers (p < 0.001). The cardiac weight was 0.016 g (+/-0.004) in the control group, and 0.023 g (+/-0.005) in the group of diabetic fetuses (p < 0.001). The ratio of cardiac to body weight was 0.294% (+/-0.079) in the control group, and 0.514% (+/-0.073) in the diabetic group (p < 0.001). The myocytic nuclear area was 14.70 microm2 in the control group, and 21.43 microm2 in the diabetic group (p < 0.001). CONCLUSIONS: The presence of cellular and morphologic cardiac hypertrophy in fetuses of diabetic rats was demonstrated by the significant difference between the two groups for each analyzed feature.

Animals↗
PubMed2000

Kinetic studies on the thermal cis-trans isomerization of 1, 3-diphenyltriazene in aqueous solution. Effects Of acids and bases

The thermal cis-to-trans isomerization of 1,3-diphenyltriazene (DPT) has been investigated in buffered aqueous solutions by means of laser-flash photolysis techniques. The cis-to-trans isomerization process is found to be catalyzed by general acids and general bases as a result of acid/base-promoted 1,3-prototropic rearrangements. Acid catalysis is attributed to rate-limiting proton transfer to the nitrogen-nitrogen double bond of cis-DPT, whereas base catalysis is attributed to rate-limiting base-promoted ionization of the amino nitrogen of cis-DPT leading to the isomerization. In addition, a process ascribed to the interconversion of cis rotamers through hindered rotation around the nitrogen-nitrogen single bond is also observed; at high pH this process becomes rate-limiting.

Journal Article↗
PubMed1998

[Emergency surgery in inflammatory bowel disease. Experience in 26 cases].

BACKGROUND: The emergency surgical treatment of inflammatory chronic bowel diseases is closely related to the classification of patients according to their symptoms and clinical conditions, as well as possible surgical options. In our study, an actual set of criteria is proposed for the classification of the degree of seriousness of symptoms, related to patient conditions, and applicable surgical strategies. METHODS: Retrospectively evaluation of the outcome of the disease has been performed over 26 patients undergoing emergency treatment in our Hospital, and with at least 5 years of follow-up. Fourteen patients were affected by ulcerative rectocolitis and 11 underwent subtotal colectomy with ileostomy; the remaining 12 were affected by Crohn's disease and were treated with colic or ileal local resection. RESULTS: Among 11 operated patients with RCU, 6 toxic megacolon, 4 severe colitis and one perforation (postoperative death) have been diagnosed. Recanalization was possible in 8 patients. On the other hand proctectomy was necessary in the remaining 3 patients as final operation. In MC patients 6 occlusions, 4 severe colitis, one multiple perineal fistulization and one perforation of occult right colon tumor have been diagnosed. We performed 5 right colectomy, 4 jejuno-ileal resections, one Hartmann's operation, one colostomy in emergency and one multiple bypass. Because of recurrence, one right colectomy needed following total colectomy and two jejuno-ileal resections needed right colectomy soon after. Three jejuno-ileal resections were performed with a conservative purpose in patients treated by right colectomy. CONCLUSIONS: It has resulted that in ulcerative rectocolitis total colectomy actually permits an adequate control of the disease, as well as a satisfactory therapy of the rectal stump, with subsequent recanalization in the majority of cases, whereas in Crohn's disease the frequency of recidive is higher and it seems more advisable to opt for a radical resection treatment (chiefly right colectomy), but with a conservative purpose.

Adolescent↗
PubMed1996

[Balanced beta--alpha-blocker treatment with carvedilol in mild-moderate arterial hypertension].

The search for the ideal antihypertensive drug is ongoing. Carvedilol is a new beta-adrenoceptor antagonist which also causes peripheral vasodilation primarily via alpha 1-adrenergic blockade. Twenty patients with mild to moderate essential hypertension and previous intolerance and side effects to other antihypertensive drugs were studied. After initial baseline assessment, patients received 25 mg carvedilol orally q.d. The treatment lasted 60 days. In our study carvedilol was well tolerated and no important side effect was recorded. Blood pressure decreased significantly to normal values, without orthostatic blood pressure decreases. Heart rate decreased significantly too, but no significant bradycardia was induced. No negative effects on serum lipids and no clinical evidence of increase in peripheral resistance were observed. Ventricular arrhythmia on Holter monitoring were significantly reduced after treatment with carvedilol.

Adrenergic alpha-Antagonists↗
PubMed1995

[Our experience with the surgical treatment of carcinoma of the colon].

The Authors analyze a series of 441 patients affected by carcinoma of the colon operated on between June 1980 and November 1993. The incidence of the different stages of the disease according to Dukes resulted comparable to that reported in the literature as well as the incidence of morbidity and mortality. Recostruction was performed in all cases with mechanical sutures (T-L for the right colon and L-T for the left colon) and without protection enterostomy. Long-term results evaluated by actuarial methods were influenced by the stage of the disease, and not by sex or duration of symptoms. The need of early diagnosis as well as oncologically correct surgical technique is furthermore confirmed. The importance of clinical trials on adjuvant chemotherapy is emphasized in order to improve survival in patients operated for stage B and C colon cancer.

Adult↗
PubMed1994

[The therapy of the liver metastases of colorectal carcinoma].

The treatment of liver metastases should be addressed in a multidisciplinary way, considering the manifold therapeutic options available, for each of which corresponds a particular indication. The best results are obtainable with resective surgery in cases in which there is a partial involvement of the liver (25-50%) and a variable intra-hepatic distribution (monolobar), situations that correspond to Gennari stages I and II. In the authors' experience, the extent of the liver resection does not influence possible survival and oncologically correct resections should be carried out such as segmentectomies, pluri-segmentectomies or wedge resection in compliance with the principle of removing at least 1.5 cm of healthy perineoplastic tissue. The authors reserve major hepatectomies to special situations: voluminous metastases, diffuse involvement of a single lobe, topographic localisation contraindicating segmentary resection.

Carcinoma↗
PubMed1990

[Theoretical and practical aspects of globular sedimentation velocity].

The following methods used to determine globular sedimentation rate (VSG) were reviewed: Westergren and Wintrobe techniques, Chattas micromethod, Sibora and Sediplast systems and z percentage sedimentation. Also included are the VSG phases and those factors which determine the aggregation of the red corpuscles whether they be plasmatic, globular or extrinsic.

Blood Sedimentation↗
PubMed1990

[Modified erythrocyte sedimentation rate. Study in pre-school and school children].

The Westergren inclined technique can be used to determine the globular sedimentation rate (GSR) at 10 and 15 minutes which are equivalent to the first and second hours respectively of the classic method. The present study compares GSR correlations using both methods, on a sample of 64 healthy children, included according to predetermined study selection criteria. The sample included 38 preschoolers (59.37%) and 26 school children (48.63%); with an age range between 4.14 +/- 0.48 years and 8.68 +/- 0.62 years (mean +/- 2 EE) respectively. The hematocrit range was between 38.75 +/- 0.56 Vol%; no erythrocyte alterations were observed. A significant positive correlation was observed in the GSR determinations between 1 hour-10 min and 2 hours-15 min, which were r1 = 0.9049 (P less than 0.001) and r2 = 0.9404 (P less than 0.001). No significant difference (P greater than 0.05) was noted on the basis of sex (34 males, 30 females). The determinations taken with the Westergren inclined method proved superior to the classic method, but the technique requires the inclusion of normal values of the former. The conclusion is that the inclined method can be used and interpreted by the clinician in the same way as the classic Westergren method. It permits a time saving, which in large hospital practices implies an important economic factor.

Adolescent↗
PubMed1989

Ventricular and dual chamber pacing for treatment of carotid sinus syndrome.

Thirty-nine consecutive patients with recurrent syncope and either cardioinhibitory or mixed type carotid sinus syndrome were studied to determine the efficacy of ventricular (VVI) pacing in 16, and dual chamber (DDD/DVI) in 23 patients. Only those patients affected by the isolated vasodepressor form were excluded. Follow-up lasted 12 +/- 5 months. Symptoms were totally eliminated in 67% of patients and ameliorated with persistence of minor symptoms in 33%. All patients underwent an initial 2-month follow-up in the VVI mode. Evaluation of the 19 patients who remained symptomatic and the 20 who became asymptomatic with VVI pacing demonstrated that factors observed prior to pacemaker implant were related to failure of the VVI mode. These included symptomatic pacemaker effect (42% vs 0%), mixed carotid sinus syndrome (95% vs 65%), orthostatic hypotension (47% vs 15%), or ventriculoatrial conduction (68% vs 38%). In the 23 patients with dual chamber pacing, random 2 month comparisons were performed between VVI and DVI/DDD pacing. The dual chamber mode was preferred by 14 patients, none preferred the VVI mode and nine noted no difference. Comparison of the two groups found that the factors linked to DVI/DDD preference were symptomatic pacemaker effect (50% vs 0%), ventriculoatrial conduction (78% vs 44%), or orthostatic hypotension (50% vs 11%). VVI pacing is efficacious in a high proportion of patients affected by cardioinhibitory or mixed carotid sinus syndrome. The identification of causes of VVI pacing failure allows determination of those who will benefit from VVI pacing and those who should have DVI/DDD. VVI pacing is suggested for the cardioinhibitory type with no symptomatic pacemaker effect and for the mixed type with no symptomatic pacemaker effect or orthostatic hypotension or ventriculoatrial conduction. Dual chamber pacing should be used in all other instances.

Aged↗
PubMed1988

Natural and unnatural history of patients with severe carotid sinus hypersensitivity: a preliminary study.

Natural history of patients with symptomatic severe carotid sinus hypersensitivity is not clearly known. In order to evaluate the effectiveness of pacing therapy in these patients we performed a randomized treatment/no-treatment prospective study in 35 patients. They were randomly assigned to two groups: 19 patients received no therapy, 16 patients received a VVI (#11) or DDD (#5) pacemaker implant. During the 8.4 +/- 4.3 month follow-up period patients receiving no therapy had recurrence of syncope in 9 cases (47%) and minor symptoms in 13 (68%); at the 16th month, actuarial curve showed absence of syncope in 36% of patients and of any symptoms in 30%. During the 7.2 +/- 4.1 month follow-up period, the patients receiving the pacemaker implant had no recurrence of syncope, minor symptoms in three (19%); at the 16th month, actuarial curve showed absence of syncope in 100% of patients and of any symptoms in 78%. During follow-up, 12 patients in no-treatment group received a pacemaker implant because of the recurrence of severe symptoms; successively they had a strong reduction of symptoms. In conclusion, this study definitively demonstrates that patients with severe symptomatic carotid sinus hypersensitivity had a high rate of recurrence of spontaneous symptoms and that in these patients cardiac pacing is a useful therapy.

Aged↗
PubMed1988

Is DDD superior to VVI pacing in mixed carotid sinus syndrome? An acute and medium-term study.

The aim of this study was to evaluate the importance of atrial synchronism for pacing therapy of patients with mixed carotid sinus syndrome. In 23 patients (21 m, two f; mean age 69 +/- 8 years) affected by symptomatic mixed carotid sinus syndrome we performed: (1) Research of ventriculo-atrial conduction, orthostatic hypotension and pacemaker effect; and (2) Carotid sinus massage in the standing position during VVI and DVI temporary pacing. Next, all patients received a permanent DDD pacemaker and entered a 2 month two period single-blind, randomized, cross-over study on DVI/DDD versus VVI mode. During the DVI/DDD period, no syncope occurred in any patients, minor symptoms persisted in 11 (48%) of them; during VVI period syncopes recurred in three patients, symptoms requiring the withdrawal of VVI pacing and premature DVI/DDD reprogramming in eight patients, minor symptoms in 17 (74%). A comparison between 14 patients, who preferred DVI/DDD period (Group A), and the remaining nine patients who noted no preference between DVI/DDD and VVI period (Group B) was performed on the basis of the preimplant evaluation. Group A patients had a greater pacemaker effect (-34 +/- 16 mmHg vs -16 +/- 14 mmHg) and a higher prevalence of symptomatic pacemaker effect (50% vs 0%), of ventriculo-atrial conduction (78% vs 44%) and of orthostatic hypotension (50% vs 11%), while the entity of the systolic pressure fall caused by carotid sinus massage was similar in the two groups either during VVI mode (Group A -51 +/- 16 mmHg vs Group B -56 +/- 27 mmHg) or DVI mode (Group A -38 +/- 17 mmHg vs Group B -45 +/- 17 mmHg).(ABSTRACT TRUNCATED AT 250 WORDS)

Aged↗
PubMed1988

[Comparison of permanent cardiac pacing and cardiac pacing on demand in mixed carotid sinus syndrome. Acute- and medium-term follow-up study].

The aim of the study was to evaluate the importance of atrial synchronism for pacing therapy of patients with mixed carotid sinus syndrome. On 23 patients (21 m, 2 f; mean age 69 +/- 8 years) affected by symptomatic mixed carotid sinus syndrome we performed: 1) the study of ventriculo-atrial conduction, 2) the evaluation of pacemaker effect and 3) the carotid sinus massage in standing position during VVI and DVI temporary pacing. All patients received a permanent DVI pacemaker and then underwent a two-month period single-blind, randomized, cross-over study on DVI vs VVI mode. During DVI period, no syncope occurred in any patients, minor symptoms persisted in 11 (48%) of them; during VVI period syncopes recurred in 3 patients, symptoms requiring the withdrawal of VVI pacing and premature DVI reprogramming in 8, minor symptoms were observed in 17 (74%). A comparison between 14 patients who preferred DVI period (Group A) and the remaining 9 patients who had no preference for DVI and VVI period (Group B) revealed that Group A patients had a greater pacemaker effect (-34 +/- 16 mmHg vs -16 +/- 14 mmHg; p less than 0.02) and a higher prevalence of ventriculo-atrial conduction (78% vs 44%; p = 0.1), while the entity of the systolic pressure fall caused by carotid sinus massage was similar in the two groups both during VVI mode (Group A -51 +/- 16 mmHg vs Group B -56 +/- 27 mmHg) and DVI mode (Group A -38 +/- 17 mmHg vs Group B -45 +/- 17 mmHg).(ABSTRACT TRUNCATED AT 250 WORDS)

Aged↗