Biomedical subjects

J Cuevas

Publications and source records attributed to J Cuevas.

At least 19 recordsLinked to original sources

PubMed2006

Discrete breathers for understanding reconstructive mineral processes at low temperatures.

Reconstructive transformations in layered silicates need a high temperature in order to be observed. However, very recently, some systems have been found where transformation can be studied at temperatures 600 degrees C below the lowest experimental results previously reported, including sol-gel methods. We explore the possible relation with the existence of intrinsic localized modes, known as discrete breathers. We construct a model for nonlinear vibrations within the cation layer, obtain their parameters, and calculate them numerically, obtaining their energies. Their statistics show that, although there are far less breathers than phonons, there are much more above the activation energy, making them good candidates to explain the reconstructive transformations at low temperatures.

Journal Article↗

PubMed2006

Radiationless traveling waves in saturable nonlinear Schrödinger lattices.

The long-standing problem of moving discrete solitary waves in nonlinear Schrödinger lattices is revisited. The context is photorefractive crystal lattices with saturable nonlinearity whose grand-canonical energy barrier vanishes for isolated coupling strength values. Genuinely localized traveling waves are computed as a function of the system parameters for the first time. The relevant solutions exist only for finite velocities.

Journal Article↗

PubMed2005

Markers of fibrosis in early biopsies of renal transplants.

Many factors are involved in the development of chronic allograft nephropathy (CAN). Extracellular matrix turnover depends on the balance between fibrogenic and antifibrogenic cytokines. The aim of our study was to analyze the presence of transforming growth factor beta-1 (TGF-beta1), matrix metalloproteinase-2 (MMP-2), and mast cells in 53 early transplant biopsies using immunochemistry with specific monoclonal antibodies. We divided the patients into two groups depending on graft evolution (lost due to CAN versus functioning), renal function, presence of proteinuria, and graft survival. There were no differences in the demographic or immunological data. Renal function was worse and proteinuria greater among the group with CAN. The presence of mast cells was similar in both groups, but TGF-beta1 was expressed more and MMP-2 less in the CAN group. We observed a negative correlation between donor age and mast cells, and a positive correlation between TGF-beta1 and MMP-2. Grafts from younger donors showed better renal function, less proteinuria, greater graft survival, and less frequent development of CAN. According to our experience, cytokines involved in matrix turnover are expressed in early stages, correlating with donor age. The expressions of TGF-beta1 and MMP-2 seem to be important for the development of fibrosis in CAN.

Adult↗

PubMed2005

[Microscopic polyangiitis in a patient with rheumatoid arthritis].

Rheumatoid arthritis (RA) is a systemic disorder that primary involves joints, although renal disease has also been associated it is not common that rapidly progressive glomerulonephritis (RPGN) appears. We report the case of a patient with nodular and aggressive RA who had an acut renal failure secondary to ANCA positive RPGN due to a Microscopic polyangiitis who was not responsive to steroids and cyclophosphamide therapy.

Acute Kidney Injury↗

PubMed2004

Breather statics and dynamics in Klein-Gordon chains with a bend.

In this paper, we examine a nonlinear model with an impurity emulating a bend. We justify the geometric interpretation of the model and connect it with earlier work on models including geometric effects. We focus on both the bifurcation and stability analysis of the modes that emerge as a function of the strength of the bend angle, but we also examine dynamical effects including the scattering of mobile localized modes (discrete breathers) off of such a geometric structure. The potential outcomes of such numerical experiments (including transmission, trapping within the bend as well as reflection) are highlighted and qualitatively explained. Such models are of interest both theoretically in understanding the interplay of breathers with curvature, but also practically in simple models of photonic crystals or of bent chains of DNA.

Journal Article↗

PubMed2002

Co-existent ovarian mucinous cystadenocarcinoma and ovarian choriocarcinoma.

We present the case of a 63-year-old woman with an ovarian neoplasm in which mucinous cystadenocarcinoma and choriocarcinoma coexisted. Blood levels of beta-hCG were elevated and bilateral ovarian stromal luteinization was seen. The rarity of this association and its clinical and pathologic implications are discussed.

Choriocarcinoma↗

PubMed2001

Fine-needle aspiration cytology of "proximal-type" epithelioid sarcoma.

The cytologic and immunocytologic findings in a case of recurrent "proximal-type" epithelioid sarcoma (ES) of the vulva are presented. This is a recently described neoplasm that differs clinically and morphologically from conventional ES. Cytologic smears showed a dissociated population of large, atypical neoplastic cells with bi- and multinucleated cells, abundant cytoplasm, and rhabdoid-like morphology. Due to its different clinical management it must be differentiated from metastatic carcinoma and melanoma. From a practical perspective, its differentiation from other epithelial-like sarcomas is less important. In conclusion the cytopathologic findings of "proximal-type" ES show a good correlation with histopathology, permitting the diagnosis of recurrences and metastases. When accompanied by adequate clinical information and ancillary studies, a specific preoperative recognition seems possible.

Aged↗

PubMed2001

Olmsted syndrome.

Olmsted syndrome is an uncommon inherited disorder of keratinization that presents mutilating palmoplantar keratoderma, perioral hyperkeratosis, leukokeratosis and alopecia. We report a case of this rare syndrome diagnosed in a 48-year-old woman and confirms the existence of a generalized abnormality in keratin expression. Immunoreactivity in our case suggests an abnormal expression of keratins 5 and 14 similar to the observed in other hyperproliferative disorders.

Abnormalities, Multiple↗

PubMed2001

[Glaucoma related with photoreceptor outer segments in aqueous humor. Schwartz-Matsuo syndrome].

CASE REPORT: We present the case of a patient who was initially diagnosed of hypertensive uveitis with marked fluctuation that was resistant to the common treatment. After a systematic examination, retinal detachment of the ora serrata in the inferotemporal quadrant was diagnosed. The sample of aqueous humor showed melanic pigment and degenerated photoreceptor outer segments. After retinal detachment surgery, the intraocular pressure returned to normal levels without antiglaucoma medication. DISCUSSION: The presence of photoreceptor outer segments in aqueous humor confirms the diagnosis of Schwartz-Matsuo syndrome, which should be considered as a differential diagnosis of iritis and glaucoma.

Adult↗

PubMed2000

Two distinct classes of functional 7-containing nicotinic receptor on rat superior cervical ganglion neurons.

Nicotinic acetylcholine receptors (nAChRs) that bind alpha-bungarotoxin (alpha Bgt) were studied on isolated rat superior cervical ganglion (SCG) neurons using whole-cell patch clamp recording techniques. Rapid application of ACh onto the soma of voltage clamped neurons evoked a slowly desensitizing current that was reversibly blocked by alpha Bgt (50 nM). The toxin-sensitive current constituted on average about half of the peak whole-cell response evoked by ACh. Nanomolar concentrations of methyllycaconitine blocked the alpha Bgt-sensitive component of the ACh-evoked current as did intracellular dialysis with an anti-alpha 7 monoclonal antibody. The results indicate that the slowly reversible toxin-sensitive response elicited by ACh arises from activation of an unusual class of alpha 7-containing receptor (alpha 7-nAChR) similar to that reported previously for rat intracardiac ganglion neurons. A second class of functional alpha 7-nAChR was identified on some SCG neurons by using rapid application of choline to elicit responses. In these cases a biphasic response was obtained, which included a rapidly desensitizing component that was blocked by alpha Bgt in a pseudo-irreversible manner. The pharmacology and kinetics of the responses resembled those previously attributed to alpha 7-nAChRs in a number of other neuronal cell types. Experiments measuring the dissociation rate of 125I-labelled alpha Bgt from SCG neurons revealed two classes of toxin-binding site. The times for toxin dissociation were consistent with those required to reverse blockade of the two kinds of alpha Bgt-sensitive response. These results indicate that rat SCG neurons express two types of functional alpha 7-nAChR, differing in pharmacology, desensitization and reversibility of alpha Bgt blockade.

Acetylcholine↗

PubMed2000

Absence of point mutations at codon 17 of the mdm2 gene (serine 17) in human primary tumors.

Mdm2 is a phosphoprotein that interacts with protein p53, inhibiting its activity. A serine located in position 17 of Mdm2, has been implicated in its phosphorylation process. We hypothesize that point mutations at serine 17 could block its phosphorylation and thereby increase the p53-Mdm2 interaction. This mechanism could increase the p53 degradation and cause a loss of the protective effect of p53 against tumorigenesis. This hypothesis was based on recent studies in vitro, demonstrating that when serine 17 is mutated, the DNA-dependent protein kinase, activated by genomic damage, is unable to phosphorylate it. Thus, we investigated whether structural point mutations at exon 3 of the Mdm2 gene, affecting codon 17, were present in 162 human primary tumors, 70 breast carcinomas, 14 bladder tumors, 18 colon adenocarcinomas and 60 testicular tumors. Direct sequencing of a fragment (204 bp) of exon 3 of the Mdm2 gene that contains the codon 17 showed no mutations at this position, independently of the presence or absence of p53 gene mutations in the same tumors. These results do not support the hypothesis that mutations in the Mdm2 gene at this level are involved in the tumorigenic process of human cancers.

Codon↗

PubMed2000

Extramedullary plasmacytoma of the orbit.

PURPOSE: To report a case of extramedullary plasmacytoma of the orbit. METHODS: A 71-year-old patient presented with diplopia eyelid fullness and limitation of ocular motility in the left eye. Visual acuity was counting fingers, intraocular pressure 34 mmHg and fundus eye examination showed choroidal folds in the involved eye. RESULTS: CT scan showed a mass filling the superior and external left orbit without bone destruction. A biopsy was performed revealing that the tumour was composed of plasmacytoid cells positive with immunohistochemical stains for Kappa light chains and epithelial membrane antigen. Systemic work up was negative. The diagnosis of extramedullary orbital plasmacytoma was made. The patient was treated with external beam radiotherapy (40 Gy) and has remained disease free for four years (49 months). CONCLUSION: Extramedullary plasmacytomas of the orbit are extremely rare tumours. Accurate and early diagnosis is essential for the therapeutic approach. Extensive medical work up to rule out multiple myeloma or other malignant lymphoproliferative conditions involving the orbit is needed when the diagnosis of orbital extramedullary plasmacytoma is suspected because treatment and prognosis are very different.

Aged↗

PubMed2000

VIP and PACAP potentiation of nicotinic ACh-evoked currents in rat parasympathetic neurons is mediated by G-protein activation.

The effects of vasoactive intestinal polypeptide (VIP) and pituitary adenylate cyclase-activating polypeptide (PACAP27 and PACAP38) on isolated parasympathetic neurons of rat intracardiac and submandibular ganglia were examined under voltage clamp using whole-cell patch-clamp recording techniques. VIP and PACAP (</= 10 nM) selectively and reversibly increased the affinity of nicotinic acetylcholine receptor channels (nAChRs) for their agonists resulting in a potentiation of acetylcholine (ACh)-evoked whole-cell currents at low agonist concentrations. VIP-induced potentiation was observed with either ACh or nicotine as the cholinergic agonist. The VIP- but not the PACAP-induced potentiation of ACh-evoked currents was inhibited by [Ac-Tyr1, D-Phe2]-GRF 1-29, amide (100 nM), a selective antagonist of VPAC1 and VPAC2 receptors; whereas the PACAP38- but not the VIP-induced potentiation was inhibited by 100 nM PACAP6-38, a PAC1 and VPAC2 receptor antagonist. The signal transduction pathway mediating VIP- and PACAP-induced potentiation of nicotinic ACh-evoked currents involves a pertussis toxin (PTX)-sensitive G-protein. Intracellular application of 200 microM GTPgammaS or GDPbetaS inhibited VIP-induced potentiation of ACh-evoked whole-cell currents. GTPgammaS alone potentiated ACh- and nicotine-evoked currents and the magnitude of these currents was not further increased by VIP or PACAP. The G-protein subtype modulating the neuronal nAChRs was examined by intracellular dialysis with antibodies directed against alphao, alphai-1,2, alphai-3 or beta G-protein subunits. Only the anti-Galphao and anti-Gbeta antibodies significantly inhibited the effect of VIP and PACAP on ACh-evoked currents. The potentiation of ACh-evoked currents by VIP and PACAP may be mediated by a membrane-delimited signal transduction cascade involving the PTX-sensitive Go protein.

Acetylcholine↗

PubMed2000

Gastrointestinal motility during pregnancy: role of nitrergic component of NANC nerves.

This study evaluated whether increased release of nitric oxide (NO) from the nitrergic component of the nonadrenergic, noncholinergic (NANC) nerves may be partly responsible for the decrease in gastrointestinal motility observed during pregnancy. Segments of fundal strip, ileum, and colon were obtained from nonpregnant rats, rats in midpregnancy (days 9-11), and rats in late pregnancy (days 18-20). NANC activity was studied by assessing changes in tone after application of electric field stimulation (EFS). The role of NO was determined by observing the effects of EFS in the presence and absence of the NO synthase (NOS) inhibitor N(G)-nitro-L-arginine methyl ester (L-NAME) and the reversibility of the effects of L-NAME by L-arginine. The magnitude of change in cGMP levels in the tissues after application of EFS was also assessed. Our studies indicate that there was increased magnitude of relaxation of isolated strips of rat gastric fundus and rat colon, after application of EFS to tissues obtained only from animals in late pregnancy. These results paralleled the changes in cGMP levels in tissues. NOS activity in the gastric fundus was significantly increased in animals in late pregnancy compared with nonpregnant controls. Our studies suggest that the delay in gastric emptying and increase in colonic transit time observed in rats during pregnancy may be caused in part by increased activity of the nitrergic component of the NANC nerves innervating these organs.

Acetylcholine↗

PubMed2000

Substance P preferentially inhibits large conductance nicotinic ACh receptor channels in rat intracardiac ganglion neurons.

The effects of substance P (SP) on nicotinic acetylcholine (ACh)-evoked currents were investigated in parasympathetic neurons dissociated from neonatal rat intracardiac ganglia using standard whole cell, perforated patch, and outside-out recording configurations of the patch-clamp technique. Focal application of SP onto the soma reversibly decreased the peak amplitude of the ACh-evoked current with half-maximal inhibition occurring at 45 microM and complete block at 300 microM SP. Whole cell current-voltage (I-V) relationships obtained in the absence and presence of SP indicate that the block of ACh-evoked currents by SP is voltage independent. The rate of decay of ACh-evoked currents was increased sixfold in the presence of SP (100 microM), suggesting that SP may increase the rate of receptor desensitization. SP-induced inhibition of ACh-evoked currents was observed following cell dialysis and in the presence of either 1 mM 8-Br-cAMP, a membrane-permeant cAMP analogue, 5 microM H-7, a protein kinase C inhibitor, or 2 mM intracellular AMP-PNP, a nonhydrolyzable ATP analogue. These data suggest that a diffusible cytosolic second messenger is unlikely to mediate SP inhibition of neuronal nicotinic ACh receptor (nAChR) channels. Activation of nAChR channels in outside-out membrane patches by either ACh (3 microM) or cytisine (3 microM) indicates the presence of at least three distinct conductances (20, 35, and 47 pS) in rat intracardiac neurons. In the presence of 3 microM SP, the large conductance nAChR channels are preferentially inhibited. The open probabilities of the large conductance classes activated by either ACh or cytisine were reversibly decreased by 10- to 30-fold in the presence of SP. The single-channel conductances were unchanged, and mean apparent channel open times for the large conductance nAChR channels only were slightly decreased by SP. Given that individual parasympathetic neurons of rat intracardiac ganglia express a heterogeneous population of nAChR subunits represented by the different conductance levels, SP appears to preferentially inhibit those combinations of nAChR subunits that form the large conductance nAChR channels. Since ACh is the principal neurotransmitter of extrinsic (vagal) innervation of the mammalian heart, SP may play an important role in modulating autonomic control of the heart.

Acetylcholine↗

PubMed2000

Two cases of segmental multiple glomangiomas in a family: type 1 or type 2 segmental manifestation?

Several autosomal dominant skin diseases may manifest cutaneous mosaicism. Two types of segmental arrangement can be distinguished: type 1 is characterized by segmental lesions with similar severity to that observed in the diffuse phenotype, the remaining skin being normal; type 2 is characterized by segmental lesions showing a major degree of severity and milder lesions diffusely arranged. Multiple glomus tumours have recently been included in the group of genodermatoses showing type 2 segmental involvement. A family with 2 cases of multiple glomangiomas arranged in a segmental fashion is reported. A 12-year-old girl presented multiple nodular glomangiomas on her right buttock and thigh, in a band-like distribution. A sister of her paternal grandfather showed plaque-like multiple glomangiomas on her left thigh and various glomangiomas on her right buttock and arm. No other family members were known to be affected. Two new cases of familial segmental multiple glomangiomas are reported, with the particularity that one of these exhibited type 2 segmental manifestation and the other type 1 from a clinical point of view.

Child↗

PubMed2000

Effects of listening to Mozart and Bach on the performance of a mathematical test.

The purpose of the current study was to assess the effect of listening to Mozart and Bach on the immediate performance of a 10-min. mathematical test. The study consisted of 61 undergraduate participants. Participants were randomly assigned to a control group, a Mozart group, or a Bach group. Participants were then administered a mathematics pretest, listened to a selection of music for 10 min., and were then administered a mathematics posttest. The test was constructed to be similar to items taken from the University Mathematics Placement Examination. Analysis indicated no significant effect on the immediate mathematics test when participants listened to 10 min. of either Mozart or Bach. These findings suggest caution in measuring differences in various cognitive tasks as indicating increases in intelligence scores.

Achievement↗

PubMed1999

Syphilis in an HIV infected patient misdiagnosed as leprosy.

A 42-year-old man with uveitis and a widespread cutaneous eruption, histopathologically characterized by dermal granulomatous infiltrates with perineurial invasion, was incorrectly diagnosed and treated as having borderline leprosy. Further studies demonstrated secondary syphilis and human immunodeficiency virus (HIV) infection. Standard penicillin therapy resolved his cutaneous and ocular lesions. Reports on clinical and pathological findings of active syphilis in HIV infected patients are scarce but this case and isolated previous case reports suggest that granulomatous infiltrates might be a common feature in secondary syphilis with short evolution in HIV infected patients.

Adult↗