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Biomedical subjects

M Medina

Publications and source records attributed to M Medina.

At least 109 records · Page 6Linked to original sources
PubMed1997

Cholecystokinin-like systems in the chameleon brain.

Immunohistochemical techniques were used to determine the distribution of cholecystokinin-8 (CCK8) immunoreactivity in the brain of the chameleon. In the telencephalon, CCK8-immunopositive somata were sparse and observed principally in the olfactory tubercle at the ventromedial edge of the rostral telencephalon and in the medial septum. Immunopositive fibers were observed mainly in the medial septal region and the ventral telencephalon. In the diencephalon, numerous CCK8-reactive fibers were densely concentrated in the periventricular region, the dorsolateral hypothalamus and the external zone of the median eminence. In the thalamus, labelled fibers were restricted to the peri-rotundal nuclei and the lateral part of the habenula. Immunoreactive cell bodies were observed in the medial part of the dorsal lateral geniculate nucleus, in the periventricular, ventral and lateral regions of the hypothalamus. In the mesencephalon, the densest accumulations of immunopositive fibers were observed in the area pretectalis, the periventricular gray matter, the medial tegmentum and the isthmus. Labelled neurons were observed in the deep, and occasionally intermediate, tectal layers and in the laminar nucleus of the torus semicircularis. In the rhombencephalon, labelled fibers were observed at the highest density in the central gray matter and the locus coeruleus; labelled somata were observed only in the nucleus of the tractus solitarius.

Animals↗
PubMed1997

Acute brain swelling during removal of supratentorial cystic lesion caused by contralateral extradural hematoma: case report.

BACKGROUND: Protrusion of the cortex through a bone flap in the course of surgery is a very serious event and, if it persists, the procedure must be suspended, the cause sought, and the problem resolved. CASE DESCRIPTION: We report the case of a 13-year-old boy whose brain underwent sudden swelling during removal of a supratentorial cystic lesion. The operation was suspended at once and an emergency CT scan was performed. It revealed a large contralateral extradural hematoma, which was removed immediately. CONCLUSIONS: We considered the following possible mechanisms of the emergency: bleeding of bone at the site of the supposed piercing by the headrest pin and/or a vacuum mechanism consequent upon removal of the large cystic lesion. Our aims are to emphasize the importance of gauging the thickness of a child's skull before fixing the head in the headrest, especially when chronic intracranial hypertension is present, and the need to suspend the operation for CT scanning in the event of uncontrollable brain swelling.

Acute Disease↗
PubMed1997

Enrichment of glutamate-like immunoreactivity in the retinotectal terminals of the viper Vipera aspis: an electron microscope quantitative immunogold study.

A post-embedding immunogold study was carried out to estimate the immunoreactivity to glutamate in retinal terminals, P axon terminals and dendrites containing synaptic vesicles in the superficial layers of the optic tectum of Vipera. Retinal terminals, identified following either intraocular injection of tritiated proline, horseradish peroxidase (HRP) or short-term survivals after retinal ablation, were observed to be highly glutamate-immunoreactive. A detailed quantitative analysis showed that about 50% of glutamate immunoreactivity was localized over the synaptic vesicles, 35.8% over mitochondria and 14.2% over the axoplasmic matrix. The close association of immunoreactivity with the synaptic vesicles could indicate that Vipera retino-tectal terminals may use glutamate as their neurotransmitter. P axon terminals and dendrites containing synaptic vesicles, strongly gamma-aminobutyric (GABA)-immunoreactive, were shown to be also moderately glutamate-immunoreactive, but two to three times less than retinal terminals. Moreover, in P axon terminals, the glutamate immunoreactivity was denser over mitochondria than over synaptic vesicles, possibly reflecting the 'metabolic' pool of glutamate, which serves as a precursor in the formation of GABA.

Animals↗
PubMed1997

Combined effect of bacteriocin-producing lactic acid bacteria and lactoperoxidase system activation on Listeria monocytogenes in refrigerated raw milk.

The bactericidal activity of three bacteriocin-producing lactic acid bacteria alone and in combination with milk lactoperoxidase (LP) system activation against Listeria monocytogenes in refrigerated raw milk was studied. After 4 d at 4 degrees C, the population of L. monocytogenes in milk inoculated with bacteriocin-producing Lactococcus lactis subsp. lactis ATCC 11454, L. lactis subsp. lactis ESI 515 or Enterococcus faecalis INIA 4 was reduced by 0.21-0.24 log units. Activation of the LP system did not enhance inhibition at this temperature. After 4 d at 8 degrees C, L. monocytogenes levels in the non-activated LP system milk inoculated with L. lactis subsp. lactis ATCC 11454, L. lactis subsp. lactis ESI 515 or Ent. faecalis INIA 4 were reduced by 1.87, 1.54 and 1.11 log units compared to control milk, whereas in the activated LP system milk, this reduction was 1.99, 2.10 and 1.06, respectively. The higher nisin production by L. lactis subsp. lactis ESI 515 in milk with activated LP system than in non-activated LP system milk was responsible for the more pronounced decrease of L. monocytogenes counts in the former.

Animals↗
PubMed1997

Inhibition of Listeria monocytogenes by enterocin 4 during the manufacture and ripening of Manchego cheese.

The inhibitory effect of enterocin 4, a bacteriocin produced by Enterococcus faecalis INIA 4, on Listeria monocytogenes strains Ohio and Scott A during the manufacture and ripening of Manchego cheese was investigated. Raw ewe's milk was inoculated with ca 10(5) cfu ml-1 of L. monocytogenes and with 1% of a commercial lactic starter, 1% of an Ent. faecalis INIA 4 culture, or 1% of each culture. Manchego cheeses were manufactured according to usual procedures. Listeria monocytogenes Ohio counts decreased by 3 log units after 8 h and by 6 log units after 7 d in cheese made from milk inoculated with Ent. faecalis INIA 4 or with both cultures, whereas no inhibition was recorded after 60 d in cheese made from milk inoculated with commercial lactic starter. Listeria monocytogenes Scott A was not inhibited by enterocin 4 during cheese manufacture, but decreases of 1 log unit after 7 d and of 2 log units after 60 d were achieved in cheese made from milk inoculated with both commercial lactic starter and Ent. faecalis INIA 4.

Bacteriocins↗
PubMed1997

Idiopathic eosinophilic myositis associated with vasculitis and symmetrical polyneuropathy.

We present a 79-yr-old white woman admitted to the hospital with diffuse myalgias and muscle weakness associated with eosinophilia. Examination of a muscle biopsy section revealed eosinophilic myositis with vasculitis. This association is infrequent and we describe the first case report with symmetrical polyneuropathy. The treatment with prednisone (60 mg/day) led to a complete clinical-pathological recovery of the disease. We review the differential diagnosis and the aetiopathogenic mechanism.

Aged↗
PubMed1997

Symmetrical enchondromatosis of the hands and feet in two sisters.

We report two Portuguese sisters aged 9 and 12 years with symmetric well-circumscribed radiolucent cystic lesions on the long bone metaphysis of the hands and feet. The eldest also has soft tissue calcifications. They have no dysmorphic features and their growth is normal. Plasma values of parathyroid hormone (PTH), calcium, phosphorus, magnesium, and alkaline phosphatase are normal. Cerebral computed tomography (CT) scan shows no intracranial calcifications. A Raynaud phenomenon became evident during the last year in the eldest. The incisional biopsy of the left proximal metatarsial was performed through an area of typical radiographic appearance. The pathology specimen consisted of enchondroma tissue. The present cases are an extremely rare instance of this pathology, with symmetrical involvement of the hands and feet and a familial incidence.

Adolescent↗
PubMed1997

Effect of pH, temperature and culture medium composition on the production of an extracellular cysteine proteinase by Micrococcus sp. INIA 528.

Growth and proteinase production by Micrococcus sp. INIA 528 in a batch-operated laboratory fermentor were investigated, with trypticase soy broth as the basal medium for studies on optimum temperature, pH and medium composition. Maximum growth was recorded at 34 degrees C and pH 7.5, whereas optimum temperature and pH for proteinase production were 31 degrees C and pH 6.25. Maximum rate of enzyme production occurred during the late log and early stationary phases of growth. Addition of 5.0 g l-1 yeast extract, 1.0 g l-1 glucose, 1.0 g l-1 MgSO4 or 1.0 g l-1 K2HPO4 to basal medium resulted in a lower enzyme yield, but supplementation of basal medium with 2.5 g l-1 (NH4)2SO4 increased enzyme production by 45%. A high initial biomass added to fresh both supplemented with 2.5 g l-1 (NH4)2SO4 only increased enzyme activity by 19%, compared to the maximum enzyme activity achieved with the standard inoculum.

Bacteriological Techniques↗
PubMed1997

Electron-nuclear double resonance spectroscopy investigation of 4-hydroxybutyryl-CoA dehydratase from Clostridium aminobutyricum: comparison with other flavin radical enzymes.

A FAD and [4Fe-4S]cluster-containing enzyme from Clostridium aminobutyricum catalyses the reversible dehydration of 4-hydroxybutyryl-CoA to crotonyl-CoA which involves the cleavage of an unactivated C-H bond at the beta-carbon. Transient oxidation of the substrate to an enoxy radical by FAD might facilitate the removal of this beta-proton, whereas no function could be attributed to the [4Fe-4S]cluster. In this paper the organic radical, which is formed by partial reduction of the enzyme with dithionite, was characterised as the neutral flavin semiquinone by EPR spectroscopy in H2O and D2O. The rapid electron-spin relaxation of the flavin semiquinone suggested a magnetic interaction with the [4Fe-4S]cluster. In order to obtain highly resolved information about nuclear spins in the vicinity of this paramagnetic centre, ENDOR spectroscopy was applied. The spectra were compared with those of the neutral semiquinone radicals of ferredoxin-NADP reductase and flavodoxin as well as with that of the anionic semiquinone radical of cholesterol oxidase. All ENDOR spectra showed strong couplings to the 8-methyl protons and to H-6 of the flavin. On addition of the substrates to the corresponding enzymes, the electron density changed significantly only at the 8-position. It decreased in the case of cholesterol oxidase and ferredoxin-NADP reductase, whereas an increase was observed with 4-hydroxybutyryl-CoA dehydratase. The results indicate an interaction of 4-hydroxybutyryl-CoA with the flavin as required by the proposed mechanism. Furthermore, the shift of electron density towards the benzoid ring of FAD in the dehydratase might be due to the location of the [4Fe-4S]cluster next to the 8-position as known from structurally characterised iron-sulfur flavoproteins.

Clostridium↗
PubMed1997

Bactericidal effect of enterocin 4 on Listeria monocytogenes in a model dairy system.

Enterococcus faecalis INIA 4 produced the bacteriocin enterocin 4 during growth in raw ewe's milk at 30 degrees C. Enterocin activity reached 2,200 to 3,600 AU/ml after 8 h, with a 1 to 8% (vol/vol) level of inoculum from an 18-h culture. An enterocin activity of 500 AU/ml significantly decreased counts of Listeria monocytogenes Ohio when incubated for 6 h in a model system consisting of filtrates from cultures of E. faecalis INIA 4 in raw ewe's milk, at pH 6.0 and 30 degrees C. However, an enterocin activity of 2,400 AU/ml was needed in the same conditions to significantly decrease counts of L. monocytogenes Scott A. All 22 wild L. monocytogenes strains isolated from ewe's milk and tested were inhibited by a filtrate containing 400 AU/ml of enterocin 4. Incubation in the filtrate for 6 h significantly lowered counts of 16 L. monocytogenes strains, and incubation for 24 h, counts of 21 strains.

Animals↗
PubMed1997

Risk factors of surgical wound infection in patients undergoing herniorrhaphy.

OBJECTIVE: To study the causes of surgical wound infection in patients being operated on for abdominal hernias. DESIGN: Prospective cohort study. SETTING: A tertiary hospital, Spain. SUBJECTS: 497 subjects undergoing herniorrhaphy. MAIN OUTCOME MEASURES: Incidence of surgical wound infection during hospital stay and with an extended follow-up to one month after hospital discharge. RESULTS: During follow-up, 40 patients (8%) developed wound infections. The risk was unrelated to ASA grade, sex, age, severity of underlying disease, or number of diagnoses. Logistic regression analysis included six variables in the model. The most important two were duration of intervention (OR for each hour = 2.1, 95% confidence interval (CI) = 1.1 to 4.0) and the infection risk of the surgeon (taking the medium-risk level as reference, OR for low risk = 0.16, 95% CI = 0.03 to 0.81; OR for high risk = 1.83, 95% CI = 0.84 to 3.96). Logistic regression also included cancer, morbid obesity, and serum creatinine and HDL-cholesterol concentrations in the final model. The deviance (as regarding a saturated model including the six variables) of a model including only duration of intervention and surgeon was lower than that of a model with the remaining four factors. CONCLUSIONS: The risk of infection is governed mainly by factors associated with the operation.

Female↗
PubMed1996

Spin-spin interactions between the Ni site and the [4Fe-4S] centers as a probe of light-induced structural changes in active Desulfovibrio gigas hydrogenase.

In typical NiFe hydrogenases like that from Desulfovibrio gigas, the active state of the enzyme which is obtained by incubation under hydrogen gas gives a characteristic Ni-C electron paramagnetic resonance (EPR) signal at g = 2.19, 2.14, and 2.01. The Ni-C species is light-sensitive, being converted upon illumination at temperatures below 100 K in a mixture of different Ni-L species, the most important giving an EPR signal at g = 2.30, 2.12, and 2.05. This photoprocess is considered to correspond to the dissociation of a hydrogen species initially coordinated to the Ni ion in the Ni-C state. When the [4Fe-4S] centers of the enzyme are reduced, the proximal [4Fe-4S]1+ cluster interacts magnetically with the Ni center, which leads to complex split Ni-C or split Ni-L EPR spectra only detectable below 10 K. In order to probe the structural changes induced in the Ni center environment by the photoprocess, these spin-spin interactions were analyzed in D. gigas hydrogenase by simulating the split Ni-L spectra recorded at different microwave frequencies. We shown that, upon illumination, the relative arrangement of the Ni and [4Fe-4S] centers is not modified but that the exchange interaction between them is completely canceled. Moreover, the rotations undergone by the Ni center magnetic axes in the photoconversion were determined. Taken together, our results support a Ni-C structure in which the hydrogen species is not in the first coordination sphere of the Ni ion but is more likely bound to a sulfur atom of a terminal cysteine ligand of the Ni center.

Binding Sites↗
PubMed1996

X-ray structure of the ferredoxin:NADP+ reductase from the cyanobacterium Anabaena PCC 7119 at 1.8 A resolution, and crystallographic studies of NADP+ binding at 2.25 A resolution.

The crystal structure of the ferredoxin:NADP+ reductase (FNR) from the cyanobacterium Anabaena PCC 7119 has been determined at 2.6 A resolution by multiple isomorphous replacement and refined using 15.0 A to 1.8 A data, collected at 4 degrees C, to an R-factor of 0.172. The model includes 303 residues, the flavin adenine dinucleotide cofactor (FAD), one sulfate ion located at the putative NADP+ binding site and 328 water molecule sites. The structure of Anabaena FNR, including FAD, a network of intrinsic water molecules and a large hydrophobic cavity in the C-terminal domain, resembles that of the spinach enzyme. The major differences concern the additional short alpha-helix (residues 172 to 177 in Anabaena FNR) and residues Arg 100 and Arg 233 which binds NADP+ instead of Lys 116 and Lys 244 in the spinach enzyme. Crystals of a complex of Anabaena FNR with NADP+ were obtained. The model of the complex has been refined using 15 A to 2.25 A X-ray data, collected at -170 degrees C, to an R-factor of 0.186. This model includes 295 residues, FAD, the full NADP+ (with an occupancy of 0.8) and 444 water molecules. The 2'-5' adenine moiety of NADP+ binds to the protein as 2'-phospho-5'-AMP to the spinach FNR. The nicotinamide moiety is turned towards the surface of the protein instead of stacking onto the FAD isoalloxazine ring as would be required for hydride transfer. The model of the complex agrees with previous biochemical studies as residues Arg 100 and Arg 233 are involved in NADP+ binding and residues Arg77, Lys 53 and Lys 294, located on the FAD side of the enzyme, remain free to interact with ferredoxin and flavodoxin, the physiological partners of ferredoxin: NADP reductase.

Amino Acid Sequence↗
PubMed1996

Protein kinases involved in the phosphorylation of human tau protein in transfected COS-1 cells.

Human tau phosphorylation has been studied in transfected COS-1 cells. Treatment with okadaic acid alters the electrophoretic mobility of human tau protein transiently expressed in transfected cells, due to an increase in the level of phosphorylation. Treatment with okadaic acid also results in an increased phosphorylation of Alzheimer's disease-type phosphoepitopes. Tau phosphorylation within COS-1 cells is partially inhibited by in vivo treatment with DRB, a protein kinase inhibitor. Double treatment of transfected cells with okadaic acid and DRB reveals that phosphorylation of tau protein at the AT8 epitope is achieved by a DRB-resistant protein kinase which is different from that responsible for tau phosphorylation at the SMI-31 epitope, which appears to be sensitive to DRB.

Alzheimer Disease↗
PubMed1996

Reversible hydrogenase of Anabaena variabilis ATCC 29413: catalytic properties and characterization of redox centres.

The catalytic and spectroscopic properties of the reversible hydrogenase from the cyanobacterium Anabaena variabilis have been examined. The hydrogenase required reductive activation in order to elicit hydrogen-oxidation activity. Carbon monoxide was a weak (Ki=35 microM), reversible and competitive inhibitor. A flavin with the chromatographic properties of FMN, and nickel were detected in the purified enzyme. A. variabilis hydrogenase exhibited electron paramagnetic resonance (EPR) spectra in its hydrogen-reduced state, indicative of [2Fe-2S] and [4Fe-4S] clusters. Although no EPR signals due to nickel were detected, the results are consistent with the enzyme being a flavin-containing hydrogenase of the nickel-iron type.

Anabaena↗
PubMed1996

The in vitro formation of recombinant tau polymers: effect of phosphorylation and glycation.

Tau Isolated from paired helical filaments, aberrant structures that appear in Alzheimer disease (AD) patients' brains, show at least two posttranslational modifications: phosphorylation (Grundke-Iqbal et al., 1986; Ihara et al., 1986) and glycation (Ledesma et al., 1994; Yan et al., 1994). To test whether these modifications could affect the capacity of tau to self-aggregate, recombinant tau was phosphorylated and glycated, and its capacity to form polymers analyzed. Our results indicate that on phosphorylation and glycation, the capacity of tau to form aggregates increases, and that glycation of tau could stabilize the assembled polymers and could facilitate formation of bundles from these polymers.

Alzheimer Disease↗