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Biomedical subjects

J Lafuente

Publications and source records attributed to J Lafuente.

At least 37 records · Page 2Linked to original sources
PubMed1999

On-line determination of the total lipolytic activity in a four-phase system using a lipase adsorption law.

Lipases have a very well known affinity for organic-aqueous interfaces. A previously developed on-line turbidimetric analyser can only analyse the lipase activity present in the aqueous phase of a culture broth. An adsorption law of Langmuir type has been derived to determine the lipolytic activity remaining in the organic-aqueous interface formed between oleic acid and culture broth in Candida rugosa lipase production fermentation. In the concentration range of oleic acid (0-8 g.l(-1)) and lipolytic activity (0-35 U.ml(-1)) tested, lipases were not adsorbed in a multilayer form and the Brunauer-Emmet-Teller (B.E.T.) law was not applicable. The Langmuir adsorption law has been shown to be the most suitable to describe the adsorption process involved. The methodology employed enables on-line determination of the total lipolytic activity produced by the microorganism, using the adsorption law determined. This finding, in combination with the on-line measurement of variables such as biomass, aqueous lipolytic activity, oleic acid concentration and specific growth rate, permits the development of control systems for ensuring improved throughput, quality and repeatability of the process.

Journal Article↗
PubMed1999

Value of a surgical high-dependency unit.

BACKGROUND: A minority of hospitals in the UK have a high-dependency unit (HDU). One reason for this is a lack of evidence supporting its benefit. This study sought to compare the outcomes of patients undergoing major abdominal surgery with regard to HDU utilization. METHODS: Data were collected prospectively from two groups of patients over 10 months. Patients in the no-HDU group underwent major abdominal surgery in a hospital without an HDU and returned to a general surgical ward. The other group was managed initially in an HDU. Data collected included Physiological and Operative Severity Score for enUmeration of Mortality and morbidity (POSSUM) scores, complications, deaths and length of stay. RESULTS: Physiological and operative scores as calculated on the RAJIS POSSUM software were similar in both groups. The HDU group comprised 121 patients. Sixty-four developed a complication whereas 58.81 were expected to, giving an observed : expected (O : E) ratio of 1.09. Sixteen deaths occurred and 14.54 were expected (O : E ratio 1.10). Some 50 per cent stayed in hospital longer than was predicted. The no-HDU group comprised 71 patients. Fifty-nine developed a complication compared with 33.82 expected (O : E ratio 1.74). Ten deaths occurred, whereas 8.88 were expected, giving an O : E ratio of 1.13. Some 63 per cent stayed longer than predicted. The O : E ratios for morbidity were significantly different (P < 0.0005). The complications that occurred more frequently in the absence of an HDU were chest infection, arrhythmias and hypotension. CONCLUSION: Postoperative management on an HDU was associated with fewer cardiorespiratory complications. There was no difference in mortality rate but there was a trend towards shorter hospital stay.

Adolescent↗
PubMed1998

Enhancement of Candida rugosa lipase production by using different control fed-batch operational strategies.

Simulation studies have predicted that maximum lipase activity is reached with fed-batch operation strategies. In this work, two different fed-batch operational strategies have been studied: constant substrate feeding rate and specific growth rate control. A constant substrate feeding rate strategy showed that maximum aqueous lipolytic activity (55 U/mL) was reached at low substrate feeding rates, whereas lipase tends to accumulate inside the cell at higher rates of substrate addition. In the second fed-batch strategy studied, a feedback control strategy has been developed based on the estimation of state variables (X and mu) from the measurement of indirect variables such as CER by means of mass spectrometry techniques. An on-off controller was then used to maintain the specific growth rate at the desired value by adjusting the substrate feeding rate. A constant specific growth rate strategy gave higher final levels of aqueous lipolytic activity (117 U/mL) at low specific growth rates. At higher specific growth rates the enzyme remained accumulated inside the cell, as was observed with a constant feeding fed-batch strategy. With a constant specific growth rate strategy, lipase production by Candida rugosa was enhanced 10-fold compared to a batch operation. Purification studies have demonstrated that lipolytic and esterasic specific activity ratios of Candida rugosa isoenzymes can be modified by using different operational conditions. These studies have also showed that the isoenzymes obtained in a controlled growth rate strategy are around three- to four-fold more active than those obtained in a constant feeding rate strategy.

Bioreactors↗
PubMed1998

Diagnostic imaging of lipoma arborescens.

OBJECTIVE: The imaging characteristics of lipoma arborescens using plain radiographs, computed tomography (CT), and magnetic resonance imaging (MRI) are described. DESIGN AND PATIENTS: Five patients with a diagnosis of lipoma arborescens are presented. Three had monoarticular involvement of the knee joint. In the remaining two patients both knees and both hips, respectively, were affected. All patients were examined using plain radiographs and MRI. CT was employed in two cases. RESULTS AND CONCLUSIONS: A conclusive diagnosis with exclusion of other synovial pathologies having similar clinical and radiological behavior can be achieved on the basis of the MRI characteristics of lipoma arborescens. The aetiology of lipoma arborescens remains unknown, but its association with previous pathology of the affected joints in all our patients supports the theory of a non-neoplastic reactive process involving the synovial membrane.

Adult↗
PubMed1998

Grading of subcutaneous soft tissue tumors by means of their relationship with the superficial fascia on MR imaging.

OBJECTIVE: To assess the diagnostic value of the relationship between subcutaneous tumors and the superficial fascia in the characterization of soft-tissue masses. DESIGN: MR studies of 64 soft tissue masses located in the subcutaneous space were reviewed. We established five grades of relationship between tumors and superficial fascia and analyzed the probability of the lesions in each group being malignant. Group 1 tumors did not contact the fascia; group 2 lesions contacted it slightly, with acute angles between the tumor and the fascia; group 3 lesions had wider contact with larger acute or right angles; group 4 tumors had even wider contact with obtuse angles with the fascia; and group 5 was composed of lesions that crossed the superficial fascia. RESULTS: The probability of a subcutaneous lesion that crosses the superficial fascia being malignant was 6.88 times greater than for lesions that did not cross the fascia. For lesions forming obtuse angles with the fascia the probability of malignancy was 6.3 times greater than that of tumors that did not present this sign. All histologically verified fascial infiltrations occurred in malignant lesions of groups 4 and 5. CONCLUSIONS: Malignant tumors of the subcutaneous compartment have a higher tendency to develop a close relationship with the fascia than benign lesions. Obtuse angles between superficial fascia and a subcutaneous mass or a lesion crossing the fascia strongly suggest malignancy.

Carcinoma, Squamous Cell↗
PubMed1998

Improving lipase production from Candida rugosa by a biochemical engineering approach.

It has been tested that the use of oleic acid as sole carbon source and as inducer of the production has an important effect in the lipase production by Candida rugosa under aerobic conditions. A simple structured mathematical model coupled with a methodology to estimate biomass, specific growth rate and substrate was developed and applied to the production of Candida rugosa lipase in batch, fed-batch and continuous operation to obtain a reproducible product. The best operation mode tested was a controlled specific growth rate fed-batch with a 10-fold increase in productivity related to batch operation. Downstream of the culture broth has demonstrated that the ratio between the different isoenzymes presented can be modulated by the selection of the operational strategy and this ratio is quite different comparing with commercial lipases. Thus, their catalytic properties in front of chiral reactions could be different.

Biotechnology↗
PubMed1998

Physiological control on the expression and secretion of Candida rugosa lipase.

The fungus Candida rugosa secretes an extracellular lipase whose production is induced by the addition of fatty acids to the culture broth. This lipase is indeed composed by several protein isoforms partly differing in their catalytic properties. Synthesis and secretion of lipase proteins by C. rugosa cells were studied in culture media containing either glucose or oleic acid as the carbon source. It was shown that, according to their regulation, lipase-encoding genes might be grouped in two classes, one of which is constitutively expressed and the other is induced by fatty acids. The synthesis of inducible enzymes is inhibited at the level of transcription by the addition of glucose and, conversely, oleic acid appears to hinder the synthesis of the constitutive lipase. Growth conditions supporting high level expression both in batch and in continuous culture give rise to the intracellular accumulation of enzyme, possibly due to the existence of a rate-limiting step in the transport of the newly synthesized protein. These results suggest the possibility to develop fermentation processes aimed at the control of the enzyme composition.

Biological Transport↗
PubMed1998

Buckling of cylinders may cause prolonged penile pain after prosthesis implantation: a case control study using magnetic resonance imaging of the penis.

PURPOSE: We identify risk factors associated with chronic postoperative penile pain after inflatable prosthesis insertion. MATERIALS AND METHODS: We performed a case control study to determine the incidence of prolonged penile pain in 65 men who underwent prosthesis insertion. The association of various potential risk factors, including diabetes mellitus, incision site, prosthesis type, patient age and history of pelvic surgery, was assessed. In addition, the penis was examined for physical findings, and penile magnetic resonance imaging (MRI) was done as an in situ evaluation of the anatomical position and functional status of the inflatable prosthesis. RESULTS: A total of 14 patients (21.5%) with prolonged pain were compared to the remaining 51 with no pain. All parameters evaluated were similar in both groups except for MRI findings. Of the 14 patients with pain 12 (85.7%) had buckling of the cylinders in the flaccid state compared to only 1 of the 51 controls (1.9%). Statistical analysis showed a highly significant association between buckling and penile pain (odds ratio 300, p <0.0001). Surgical correction of buckling resolved pain in 5 patients. CONCLUSIONS: Prolonged postoperative penile pain after prosthesis insertion is strongly associated with cylinder buckling. This buckling may be the consequence of an excessively long cylinder or an appropriate size cylinder that fails to reach the crural end. The method of accurately diagnosing these alterations is MRI of the penis.

Case-Control Studies↗
PubMed1997

Choroid plexus papillomas of the III ventricle in infants. Report of three cases.

The III ventricle is an uncommon location for choroid plexus papilloma at any age. We describe three new cases of choroid plexus papillomas of the III ventricle (CPPs). All children were boys under 4 months of age and all presented with increased intracranial pressure, hydrocephalus and macrocephaly. The three were examined by preoperative computed tomography (CT) and ultrasonography. Two of them were investigated with magnetic resonance imaging (MRI). The first case was treated with a right corticofrontal transventricular approach and subtotal resection, so that he required a second operation through a transcallosal approach. In the other two cases a transcallosal approach was used. Two children needed permanent ventriculo-peritoneal shunts. The average follow-up of 4.3 years has revealed no neurological deficits in any case. The timing of and the need for shunting are major considerations. Clinical and imaging follow-up (CT and/or ultrasonography) are very helpful in controlling postoperative hydrocephalus and subdural effusion, avoiding unnecessary shunting in many cases. The operative approaches, transcortical and transcallosal, are discussed.

Cerebral Ventricle Neoplasms↗
PubMed1996

Traumatic extradural hematomas of the posterior fossa in children.

The most favorable type of traumatic intracranial bleeding in childhood is the extradural hemorrage (EDH). The posterior fossa location is less frequent than the supratentorial site. In the period from January 1989 to January 1994 we treated 2,372 patients with craniocerebral trauma; 31 had extradural hematomas (1.3%); 3 of them were located in the posterior fossa (9.7%): 1 boy and 2 girls aged from 6 to 16 years. The traumatic mechanism was an occipital fall in all cases. Diagnosis was made by computed tomography scan (CT). Two of them had a rapidly deteriorating course. The three patients were operated on without mortality and there was no morbidity. The role of CT in the early detection of lesions and prompt surgical evacuation may reduce the mortality and morbidity from this lesion. The interaction between these factors is discussed.

Adolescent↗
PubMed1996

Myocardial revascularization in a hemophiliac.

The case of a mild hemophiliac who underwent a successful and uncomplicated myocardial revascularization is presented. The procedures was safely performed while the patient was receiving factor VIIIC.

Angina Pectoris↗
PubMed1995

Stability studies and effect of the initial oleic acid concentration on lipase production by Candida rugosa.

The production of lipase by Candida rugosa in batch cultures was studied. The initial concentration of the carbon source employed, oleic acid, had an important effect on the final lipolytic activity levels. The maximum lipase/substrate yield and specific productivity obtained correspond to an initial oleic acid concentration of 2 g/l. At higher concentrations, up to 8 g/l oleic acid, specific productivity decreased. Lipase production was not observed below 1 g/l oleic acid. Lipase inactivation in culture broth due to surface forces and shear stress at the gas/liquid interface was not observed. There was no shear stress denaturation at stirring rates of 250, 500 and 750 rpm. No temperature inactivation was detected up to 50 degrees C. Two different lipases with a similar molecular weight of 60 kDa were purified from culture broth.

Candida↗
PubMed1993

Uses of beta-galactosidase tag in on-line monitoring production of fusion proteins and gene expression in Escherichia coli.

A simple method for monitoring and quantifying automatically the production by fermentation of beta-galactosidase fusion proteins, making use of the remaining activity of the beta-galactosidase part, is considered. A hybrid protein carrying the major antigenic domain of foot-and-mouth disease virus C1 joined at the N-terminus of beta-galactosidase has been expressed in Escherichia coli. The yield of the chimeric protein has been monitored by flow injection analysis (FIA) during batch fermentations at laboratory scale, and a high correlation between values of product concentration from FIA and from immunological quantizations has been obtained. Because of the possibility of employing FIA in large-scale experiments, and the high sampling frequency, versatility, and reproducibility offered by this method, we propose FIA as a general, simple, quick, flexible, and reliable instrument for both monitoring the yield of recombinant proteins produced industrially, and performing basic research at laboratory scale.

Aphthovirus↗
PubMed1988

[Panencephalopathy of the Creutzfeldt-Jakob disease type].

Creutzfeldt-Jakob disease (CJD) occurring in later life has a duration of about one year. Gait disturbance, myoclonic jerks, dementia and akinetic mutism occur. Post-mortem examination of the brain shows nerve cell loss, gliosis and spongiform changes of the grey matter. Clinical and neuropathological features of a case of the panencephalopathic type of CJD, with additional extensive degeneration of the cerebral white matter, are described. The panencephalopathic type of CJD is characterized clinically by a longer duration and a biphasic course.

Adult↗