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Biomedical subjects

D Lorenzo

Publications and source records attributed to D Lorenzo.

At least 19 recordsLinked to original sources
PubMed2005

Renal transplantation from non-heart-beating donors: a single-center 10-year experience.

BACKGROUND: Reluctance to accept non-heart-beating donors (NHBD) as a source of kidneys, is due to medical, ethical, and logistical reasons. Evidence suggest that the short-term graft survival is similar to that of kidneys obtained from heart-beating donors (HBD). However, few studies, with long-term follow-up are available. We conducted a single-center study of kidneys obtained from NHBD, in a 14-year period. METHODS: We studied 100 patients transplanted with kidneys between 1989 and 2004, using NHBD, supported by heart compression and mechanical ventilation (n = 24), intravascular in situ cooling (n = 59), or cardiorespiratory resuscitation plus manual abdominal counterpulsation without cooling (n = 17), the last technique being used from 1998. The median follow-up was 51 +/- 51 months (range, 1 to 170). The outcomes of these procedures were compared to those of 1025 transplantations of kidneys from HBD performed during the same period. RESULTS: The characteristics of the recipients did not differ significantly between the two groups. Kidneys from NHBD showed a significantly higher rate of delayed graft function (DGF; 84% vs 26%; (P < .001), furthermore, the primary nonfunction (PNF) incidence was significantly higher with NHBD vs HBD (16% vs 10%; P < .001). The incidence of acute rejection episodes (ARE) within 3 months and at 1 year did not differ between the groups of donors; however, more NHBD kidneys were lost from ARE. The short-term (3-month and 1 year) and long-term (5 and 10 years) renal function, determined by the serum creatinine levels, and patient and graft survival were not different for kidneys obtained from NHBD. CONCLUSIONS: The incidences of PNF and DGF were significantly higher with NHBD, which produced poorer renal function at the time of hospital discharge. One-, 5-, and 10-year graft survivals and renal function did not differ between NHBD and HBD grafts. In our series, PNF was the main barrier to the use of NHBD.

Adult↗
PubMed2004

[Comparison of 4 techniques for internal saphenous nerve block].

OBJECTIVE: To assess the efficacy of 4 techniques for internal saphenous nerve block with 10 mL of 1.5% mepivacaine. METHODS: Eighty ASA I-II patients scheduled for foot (hallux valgus) surgery with combined sciatic and saphenous nerve blocks were randomized to receive the saphenous nerve block by one of the following techniques: a paravenous approach (n = 20), a transsartorial approach (n = 20), a femoral nerve approach in the inguinal region using a nerve stimulator (n = 20), and by subcutaneous infiltration between the tibial tuberosity and the internal gastrocnemius muscle (n = 20). A pressure cuff was placed 10 cm below the knee of all patients. Success was assessed by pin prick inside the ankle 30 minutes after initiation of the block. Tolerance of the pressure cuff and discomfort during performance of the technique were also assessed. RESULTS: The 4 groups were similar as to distribution of males and females and mean weight, age, and height. Blocking the saphenous nerve by way of the femoral nerve in the inguinal region was the most effective approach (success in 95% of patients), significantly better than the other 3 techniques (P < 0.05). The paravenous approach was successful in 60% of cases, the transsartorial approach in 50%, and the subcutaneous infiltration technique in 45%. The pressure cuff was well tolerated by all patients (100%) in whom the femoral nerve approach was used. The cuff was tolerated by 70% in the paravenous approach group, by 65% in the transsartorial approach group, and by 60% in the subcutaneous infiltration group. Patients reported more discomfort during initiation of the blockade in the paravenous approach and subcutaneous infiltration groups than in the femoral nerve or transsartorial approach groups (P < 0.05). CONCLUSION: The femoral nerve approach in the inguinal region, with nerve stimulator, to block the internal saphenous nerve led to a larger number of successful blocks than did the paravenous or transsartorial approaches, or the technique of subcutaneous infiltration between the tibial tuberosity and internal gastrocnemius muscle.

Aged↗
PubMed2003

[Prognostic markers determining the start of dialysis].

BACKGROUND: It is widely known that renal disease progresses towards the terminal stage regardless of the cause. The aim of this study is to identify prognostic factors in the progression that determine the start of dialysis. METHODS: From january 1998 until december 1999, 76 patients diagnosed with renal failure were monitored, 52 of whom started dialysis treatments. Clinical and analytical variables were studied. An actuarial analysis was carried out following the methodology of Kaplan-Meier to determine the likelihood of the need for dialysis and the Cox proportional risk analysis was also used. RESULTS: The patients enrolled in this study were between 20 and 78 years of age. 49 (64.5%) of the subjects were men and 27 (35.5%) were women. The most prevalent pathology was nephroangiosclerosis (26.3%), followed by diabetes (25.0%). During the monitoring program, 68.4% of the patients began dialysis treatments (table I). Systolic blood pressure, haemoglobin and the total proteins were univariately identified as prognostic variables. 89.47% and 71.58% of the patients with a systolic blood pressure reading of under 140 mmHg had not begun dialysis after 12 and 24 months respectively. 87.02% and 53.63% of the patients with a systolic blood pressure reading of over 140 mmHg had not begun dialysis after 12 and 24 months respectively (p = 0.025) (fig. 1). With a haemoglobin level higher than 10 gr/dl after 12 months 92.7% had not started dialysis, dropping to 72.33% after 24 months. With a haemoglobin level of under 10 g/dl 78.6% and 37.59% had not started dialysis after 12 and 24 months respectively (p = 0.0008) (fig. 2). Taking into account the mean values of different variables in the two year period prior to starting or not starting dialysis, it was found that haemoglobin significantly affected the risk of the need to start dialysis treatments [RR = 0.729; 95% CI = (0.554;0.959)], while systolic blood pressure was on the borderline of statistical significance (table IV). CONCLUSIONS: Haemoglobin levels significantly affect the risk of the need to start dialysis treatments, while other variables were identified as possible prognostic factors.

Adult↗
PubMed2001

Asaricin, the main component of Ocotea opifera Mart. essential oil.

Investigation of the volatile fraction from the stem bark of Ocotea opifera Mart. led to the isolation and characterization of asaricin, a phenolic derivative with antifungal and insecticidal activity, as the main component, which is described for the first time for the genus Ocotea. The structure has been established by a study of its mono- and bidimensional NMR spectra and mass spectrometry.

Allylbenzene Derivatives↗
PubMed2000

Uruguayan essential oil. 12. Composition of Nova and Satsuma mandarin oils.

The composition of the laboratory-prepared essential oils from Uruguayan Nova and Satsuma mandarins has been studied. The volatile fraction was analyzed by HRGC and HRGC/MS (quadrupole); 79 and 73 components were identified in Nova and Satsuma mandarin oils, respectively. The linear retention indices were calculated for almost all identified components on two different stationary phases. The enantiomeric distribution of beta-pinene, sabinene, limonene, linalool, and alpha-terpineol was studied by multidimensional gaschromatography (MDGC). Polymethoxylated flavones, present in the nonvolatile residue, were analyzed by normal-phase HPLC.

Chromatography, Gas↗
PubMed2000

Achyrocline satureioides essential oils from southern Brazil and Uruguay.

The essential oils of the aerial parts of Achyrocline satureioides (D.C.) Lam., a regional medicinal plant, from different collection locations in the South of Brazil and Uruguay were examined by GC and GC-MS. Monoterpene and sesquiterpene hydrocarbons were the main fractions of both the oils from Brazil and Uruguay. The oxygenated monoterpenes and sequiterpenes were at much lower percentage in both samples. The Uruguayan samples have 1,8-cineole which is not present in the Brazilian samples and has not been reported in other samples from Brazil. The results indicated a high biodiversity of the native populations of A. satureioides.

Asteraceae↗
PubMed1999

Origin and propagation of spontaneous electrographic sharp waves in the in vitro turtle brain: a model of neuronal synchronization.

OBJECTIVES: Neuronal synchronization is a basic feature in the generation of epileptiform discharges. Spontaneous large sharp waves (LSWs) can be recorded in the turtle brain in vitro, indicating the synchronous activation of large neuronal populations. The aim of this study was to analyze the spatial and temporal distribution of LSWs within the brain; the participation of glutamate in LSWs generation was also investigated. METHODS: Extracellular field potentials were recorded in vivo (n = 4) and in vitro (n = 36). LSWs were recorded from cerebral cortex, optic tectum, and thalamus. RESULTS: LSWs were recorded from cerebral cortex, optic tectum and thalamus. No LSWs were observed in cerebellum and brain stem. In some experiments, LSWs could be recorded only from medial cortex. Latency studies demonstrated that, within each hemisphere, medial cortex led the generation of LSWs; in addition, isolated medial cortex could sustain LSWs. Intracortical laminar field potentials in medial cortex indicated that LSWs generate mainly in the molecular layer, probably at pyramidal cell dendrites. Pharmacological experiments demonstrated that NMDA and non-NMDA glutamate receptors are involved in LWSs generation. CONCLUSIONS: These results suggest that turtle medial cortex is the pacemaker area for LSWs generation and it can be a useful model to study cellular and circuital mechanisms of neuronal synchronization.

Animals↗
PubMed1995

N-type Ca2+ channels mediate transmitter release at the electromotoneuron-electrocyte synapses of the weakly electric fish Gymnotus carapo.

The effects of omega-conotoxin-GVIA (omega-CgTX) on synaptic transmission were studied in the electromotoneuron-electrocyte synapses of the electric organ (EO) of the weakly electric fish Gymnotus carapo. omega-CgTX selectively and irreversibly blocked excitatory postsynaptic potentials (EPSPs) in a dose dependent-manner. The toxin had no effect on: (a) resting postsynaptic membrane potential and conductance; (b) postsynaptic action potentials elicited by depolarizing transmembrane current pulses; (c) the action potential conduction in the presynaptic fiber; (d) acetylcholine (ACh)-induced postsynaptic responses. Nifedipine - a selective dihydropyridine antagonist of the L-type voltage-dependent Ca2+ channels (VDCCs) - did not affect synaptic transmission. Transmission was also undisturbed by the peptide omega-Agatoxin (omega-Aga-IVA), the low molecular weight polyamine, funnel-web toxin (FTX) - both included in the venom of the spider Agelenopsis aperta - and its synthetic analog sFTX, all selective blockers of P-type VDCCs. Since omega-CgTX irreversibly blocks the N-type VDCCs, we conclude that presynaptic N-type VDCCs mediate transmitter release at electromotoneuron terminals. The VDCCs involved in fish peripheral electromotoneuron-electrocyte presynaptic transmitter release are therefore similar to those in amphibian, reptilian and avian peripheral synapses, but differ from mammalian and invertebrate motoneuron terminals.

Animals↗
PubMed1986

Effects of "partial axotomy" upon synaptic function.

A lesion limited to the dorsal columns, at the level of L3-L4, was carried out in chronic cats. This operation produced a "partial axotomy" type of lesion on the ascending branches of Ia hind limb afferents. Two to six months after this operation, intracellular studies on L7-S1 motoneurons were carried out. Similar studies were done in normal animals. The peak amplitude and the rate of rise (dV/dt) of heteronymous EPSP's were studied during control conditions (sampling at 1 Hz) and during the post-tetanic potentiation produced by a 500 Hz tetanus (for 3 s). The analysis of these synaptic potentials makes us conclude that: The amplitude of the enlarged EPSP's, observed during PTP, seems to be linearly dependent on their amplitude during control (i.e., pre-tetanus) conditions. Judging by their amplitude, there is no difference between potentiated EPSP's of operated and normal animals. There is also a linear relationship between the rate of rise of EPSP's and their peak amplitude. The slope of this relationship becomes steeper after "partial axotomy", i.e., for a given EPSP amplitude, the dV/dt of its rising part is steeper in operated cats. This steeper slope is also present in EPSP's studied during PTP. The sharper rate of rise of EPSP's, induced by the "partial axotomy" of Ia fibers, would be the mechanism behind the larger monosynaptic reflex previously observed in these operated cats.

Afferent Pathways↗
PubMed1983

Complex pathogenesis of hyperoxaluria after jejunoileal bypass surgery. Oxalogenic substances in diet contribute to urinary oxalate.

Balance studies and oxalate loading tests were carried out in order to define the pathogenesis of hyperoxaluria in 8 patients with jejunoileal bypass surgery for severe obesity; two healthy volunteers were also studied. In the bypass patients, urinary oxalate was markedly elevated (118 +/- 43 mg/day, mean +/- SD) when they were on a high oxalate diet (252 mg/day). Hyperabsorption of dietary oxalate was confirmed by the markedly increased urinary recovery of [14C]oxalate given in a test meal. In addition, the oxalate radioactivity was excreted in urine far more slowly than in healthy volunteers, suggesting that the colon was a major site of oxalate absorption. Elevated urinary oxalate excretion persisted, averaging 38 +/- 12 mg/day, despite ingestion of a very low oxalate diet (approximately 6 mg/day), suggesting that the diet contained "oxalogenic" substances other than preformed dietary oxalate which also contributed to dietary oxalate in these patients. Urinary oxalate decreased in 7 of 8 patients, however, when protein-rich foods were removed from the diet, suggesting that at least one dietary factor was digestive products of protein or creatinine. These results confirm the current view that in patients with hyperoxaluria secondary to jejunoileal bypass, the majority of urinary oxalate derives from dietary oxalate that is absorbed from the colon. Tissue or bacterial production of oxalate or an oxalate precursor from dietary constituents associated with protein, however, also appears to contribute to urinary oxalate. The results provide an explanation for the reported difficulty of eliminating secondary hyperoxaluria by restriction of dietary oxalate alone.

Adult↗