Biomedical subjects

P Santiago

Publications and source records attributed to P Santiago.

At least 19 recordsLinked to original sources

PubMed2006

[Diffuse uveal melanoma. A clinical case].

CASE REPORT: We report the case of a 58-year-old man who presented at our emergency department with ocular pain and progressive loss of vision in his left eye. Ophthalmic examination detected a pigmented mass in the iridocorneal angle, involving the ciliary body. Glaucoma had also developed secondary to the melanotic lesion. Ophthalmoscopy showed a large pigmented choroidal tumor. After enucleation, pathologic examination confirmed the diagnosis of a diffuse ocular melanoma. DISCUSSION: Diffuse uveal melanoma is a malignant tumor that metastasises early. Enucleation is the treatment of choice.

Eye Enucleation↗

PubMed2005

Graphite-incorporated MoS2 nanotubes: a new coaxial binary system.

Graphite-filled MoS2 nanotubes were synthesized by pyrolizing propylene inside MoS2 nanotubes prepared by a template-assisted technique. The large coaxial nanotubes were constituted of graphite sheets inserted between the MoS2 layers, forming the outer part, and coaxial multiwall carbon nanotubes intercalated with MoS2 inside. High-resolution electron microscopy (HREM) and electron energy loss spectroscopy techniques along with molecular dynamics simulation and quantum mechanical calculations were used to characterize the samples. The one-dimensional structures exhibit diverse morphologies such as long straight and twisted nanotubes with several structural irregularities. The interplanar spacing between the MoS2 layers was found to increase from 6.3 to 7.4 A due to intercalation with carbon. Simulated HREM images revealed the presence of mechanical strains in the carbon-intercalated MoS2 layers as the reason for obtaining these twisted nanostructures. The mechanism of formation of carbon-intercalated MoS2 tubular structures and their stability and electronic properties are discussed. Our results open up the possibility of using MoS2 nanotubes as templates for the synthesis of new one-dimensional binary-phase systems.

Journal Article↗

PubMed2005

Controlling the morphology of ZnO nanostructures in a low-temperature hydrothermal process.

ZnO nanostructures of different morphologies were grown in a controlled manner using a simple low-temperature hydrothermal technique. Controlling the content of ethylenediamine (soft surfactant) and the pH of the reaction mixture, nanoparticles, nanorods, and flowerlike ZnO structures could be synthesized at temperatures 80-100 degrees C with excellent reproducibility. High-resolution electron microscopy revealed the well crystalline nature of all the nanostructures with preferential growth along the [002] direction for linear structures. Photoluminescence spectra of the as-grown nanostructures revealed oxygen-vacancy-related defects in them, which could be reduced by air annealing at 250 degrees C. Possible mechanisms for the variation of morphology with synthesis parameters are discussed.

Journal Article↗

PubMed2005

Structure and growth mechanism study of Wurtzite CdSe nanorods grown by solvothermal techniques.

Hexagonal cadmium selenide nanorods 32-170 nm in length and 12-28 nm in diameter were grown by a solvothermal technique by reacting cadmium chloride and selenium powders in ethylenediamine at 140 degrees C. Using electron microscopy, the shape, size, and crystal structure of the nanorods were determined. A detailed microscopy analysis revealed that the nanorods grow through the coalescence of very small particles or fiberlike structures of the compound. The size, shape and strain structures in the nanorods are defined by their growth mechanism.

Cadmium↗

PubMed2005

HAADF imaging: an effective technique for the study of nonhomogeneous nanostructures.

Atomic number contrast (Z-contrast) imaging using high-angle annular dark field (HAADF) detector, along with high resolution electron microscopy (HREM), is used to study the nanostructured metal, semiconductor, mixed oxide, and soft matter composites of inhomogeneous nature. A comparison between the HREM and HAADF images for the analysis of crystal structure, defects, and compositional inhomogenity in those nanostructures has been made. While the HREM technique is efficient in determining bulk crystallinity and defect structures, the HAADF imaging technique is superior in determining the surface inhomogenity, defect structures in the interior of the nanostructures, even at atomic resolution. The efficiency of the HAADF imaging technique in determining the surface inhomogenity and defect structures is demonstrated for the Au-Pt bimetallic clusters, CdSe nanofibers and nanowires, Nb16W18O94 mixed oxide, and polystyrene-mormorillonite clay nanocomposites.

Cadmium Compounds↗

PubMed2004

Intramedullary tuberculoma mimicking primary CNS lymphoma.

The incidence of primary central nervous system lymphoma (PCNSL) has been on the rise in the setting of immunodeficiency syndromes such as acquired immune deficiency syndrome (AIDS). Its diagnosis has been facilitated by the advent of a cerebrospinal fluid (CSF) Epstein-Barr virus (EBV) PCR assay. The reported high sensitivity and specificity of this assay has made it the cornerstone of diagnosis of PCNSL, replacing more traditional methods such as an open CNS biopsy. Here, we have described a patient with a known history of C3 AIDS presenting with lower extremity weakness and eventual myelopathy who was later diagnosed as having intramedullary PCNSL after detection of EBV DNA in his CSF. After failing to respond to radiotherapy, he underwent a spinal cord biopsy revealing intramedullary tuberculoma. This case illustrates the risk of misdiagnosis with this assay and the importance of histological confirmation of a pathological lesion prior to implementation of therapy.

AIDS-Related Opportunistic Infections↗

PubMed2002

Synthesis and characterization of quantum dot superlattices.

Gold nanoparticles have been synthesized using n-alkylthiol molecules as a passivating agent. By fixing the length of the thiol chain, it is possible to produce nanocrystal arrays, such as 1D chains, 2D arrays of chains and 3D crystals.

Crystallization↗

PubMed2001

Physical characteristics of poly(vinyl alcohol) and calcium alginate hydrogels for the immobilization of activated sludge.

Hydrogels based on poly(vinyl alcohol), PVA, and calcium alginate were prepared by a freezing and thawing cycle process and characterized, in terms of the role of the polymer mixture percentage and the number of treatment cycles, on their weight swelling ratio, WSR, gel fraction, and activated sludge entrapment and immobilization. The results show that the morphology of these hydrogels is highly dependent on the PVA-Ca alginate ratio of 5 wt % total polymer content in the initial aqueous solution and that the number of entrapped microorganisms which survive the freezing-thawing procedure is independent of this ratio. For 80/20 PVA-Ca alginate hydrogels, results also show that for up to three freezing and thawing cycles, the WSR, which is in average 24, is not severely affected by the number of the cycles. For the hydrogels with three cycles, the calculated gel fraction for the composite hydrogel is 0.99. Immobilized microorganisms from sedimented activated sludge, constituted by bacteria and fungi, die in high numbers during the freezing and thawing treatment. However, with a proper time of incubation with glucose as carbon source, the population of bacteria is recovered and mainly proliferate inside the hydrogel, attached on top of the fibril network formed by the polymers, while fungi are recovered predominantly on the surface of the spheres.

Alginates↗

PubMed2001

Indocyanine green angiography of the anterior segment in patients undergoing strabismus surgery.

BACKGROUND: Anterior segment imaging using fluorescein angiography is only suitable in lightly pigmented irides as the brown pigmentation of the iris masks fluorescein transmission. Indocyanine green (ICG) angiography has excellent penetration of pigment epithelium and, therefore, has potential application in detecting perfusion changes of dark irides after strabismus surgery. METHODS: A prospective study was conducted on patients older than 15 years undergoing strabismus surgery. A fundus camera was focused on the arteriolar tufts of the pupillary margin and 50 mg of ICG (concentration of 12.5 mg/ml) was given intravenously. Images were then obtained at 1 minute intervals of 5 minutes' duration. RESULTS: 45 patients with a mean age of 54.6 years and a mean follow up period of 8.6 weeks were studied. There were 23 patients in the primary surgery group, 11 in the secondary surgery group, and 11 in the staged group. Iris ICG angiograms were successfully performed in all patients. No persistent filling defect was detected in the primary and secondary horizontal recti surgery groups or in the secondary or staged vertical and combined vertical rectus groups 6-8 weeks postoperatively. 57% of both primary vertical and combined vertical and horizontal groups showed defects in the early postoperative phase. Only three cases demonstrated late perfusion defects in this series. CONCLUSION: ICG can detect iris perfusion changes in dark irides after strabismus surgery. Iris reperfusion was achieved in the majority of the cases.

Adolescent↗

PubMed2000

Serum amyloid A protein in an echinoderm: its primary structure and expression during intestinal regeneration in the sea cucumber Holothuria glaberrima.

Serum amyloid A (SAA) proteins comprise a family of highly conserved apolipoproteins found in all mammals thus far investigated, and also in ducks and salmonid fishes. However, no invertebrate SAA homologues have been detected to date. Here we report the characterization of the first SAA homologue in a nonvertebrate deuterostome, the echinoderm Holothuria glaberrima. A 971-base-pair cDNA was obtained from a regenerating intestine cDNA library. The clone contains a 369-nucleotide open reading frame corresponding to a 122-amino-acid protein exhibiting a high degree of homology to members of the SAA superfamily. Sequence alignments of the holothuroid and vertebrate SAA proteins make evident a remarkable degree of conservation, even between phylogenetically disparate groups. Northern blots and immunohistochemistry show that SAA expression increases during regeneration of the holothuroid digestive tract as compared with normal nonregenerating tissue, and that the SAA protein is expressed by cells of the coelomic epithelium of the regenerating intestine. While SAA expression during the initial wound healing stage of regeneration is minimal, it increases during subsequent stages, peaking at day 15 of regeneration, concomitantly with lumen formation and the organization of the muscular layers of the regenerating digestive tract. Although in vertebrates SAA proteins may be part of a well-conserved anti-inflammatory mechanism, their exact biological function remains obscure. Our results suggest the possibility that SAA proteins, although structurally conserved, may possess enough functional diversity to participate in processes other than anti-inflammatory responses.

Amino Acid Sequence↗

PubMed2000

Identification of Hox Gene Sequences in the Sea Cucumber Holothuria glaberrima Selenka (Holothuroidea: Echinodermata).

The Echinodermata is a unique animal group forming an early branch in the deuterostomes phylogenetic tree. In echinoids and asteroids a single Hox cluster with nine cognates of the vertebrate Hox paralogous groups has been reported, but no data are available from other echinoderm classes. We report here nine Hox-type sequences from the sea cucumber Holothuria glaberrima, a member of the class Holothuroidea. Partial homeodomain sequences were amplified by polymerase chain reaction from genomic DNA and from a regenerating gastrointestinal tract complementary DNA library. Sequence analyses suggest that the holothuroid cluster has at least three genes of the anterior, one of the medial, and five of the posterior groups. This is the first evidence of five posterior sequences in echinoderms.

Journal Article↗

PubMed2000

Acute transient myopia induced by indapamide.

PURPOSE: To report on a case of acute transient myopia associated with ciliochoroidal detachment induced by indapamide. METHOD: Case report. Clinical examination, ultrasonography, and fluorescein angiography were performed during the acute phase of disease and convalescence. RESULTS: After indapamide was discontinued, acute bilateral myopia, which was associated with anterior chamber shallowing and diffuse choroidal thickening, resolved spontaneously 8 days after onset. The initial angiography showed scattered islands of delayed fluorescein filling that disappeared without any permanent change by day 30. CONCLUSION: Indapamide can induce spontaneously resolving transient myopia associated with diffuse choroidal thickening.

Acute Disease↗

PubMed2000

Granulomatous amebic encephalitis in a patient with AIDS: isolation of acanthamoeba sp. Group II from brain tissue and successful treatment with sulfadiazine and fluconazole.

A patient with AIDS, treated with highly active antiretroviral therapy and trimethoprim-sulfamethoxazole, presented with confusion, a hemifield defect, and a mass lesion in the right occipital lobe. A brain biopsy confirmed granulomatous amebic encephalitis (GAE) due to Acanthamoeba castellanii. The patient was treated with fluconazole and sulfadiazine, and the lesion was surgically excised. This is the first case of AIDS-associated GAE responding favorably to therapy. The existence of a solitary brain lesion, absence of other sites of infection, and intense cellular response in spite of a very low CD4 count conditioned the favorable outcome. We review and discuss the diagnostic microbiologic options for the laboratory diagnosis of infections due to free-living amebae.

Acanthamoeba↗

PubMed1999

Acute traumatic posteroinferior cerebellar artery aneurysms: report of three cases.

OBJECTIVE AND IMPORTANCE: Posterior fossa subarachnoid hemorrhage secondary to blunt head trauma is rarely associated with traumatic aneurysms of the posterior circulation. CLINICAL PRESENTATION: We present three cases of posterior fossa subarachnoid hemorrhage from ruptured posteroinferior cerebellar artery (PICA) aneurysms after blunt head trauma. In each case, there was no associated penetrating injury or cranial fracture. All three patients presented with acute hydrocephalus requiring ventriculostomy. Two of the three patients had a proximal PICA aneurysm visible on emergent angiography. The remaining patient's aneurysm, although not visible on his initial angiogram, was detected on a subsequent angiogram 72 hours later. INTERVENTION: All patients underwent successful surgical clipping of their aneurysms. Two cases required sacrificing of the parent vessels because of the friable nature of the false aneurysms. In each case, severe symptomatic vasospasm occurred, requiring angioplasty. All three patients also required a ventriculoperitoneal shunt for persistent hydrocephalus. CONCLUSION: Features of these three cases and similar cases reported in the literature support the theory that vascular ruptures and traumatic aneurysms of the proximal PICA may be related to anatomic variability of the PICA as it transverses the brainstem. This variability predisposes individuals to vascular lesions, which occur in a continuum based on the severity of the injury. Posterior fossa subarachnoid hemorrhage after head injury requires a high index of suspicion and warrants aggressive diagnostic and therapeutic interventions.

Adolescent↗

PubMed1999

Resolution of central pain after embolization of an arteriovenous malformation. Case report.

The authors describe a patient with right-sided central pain resulting from a left parietal arteriovenous malformation (AVM). The AVM was treated with staged embolization and stereotactic radiosurgery, and its obliteration was documented on follow-up angiographic studies. Surprisingly, the patient noted complete resolution of her pain syndrome after embolization, which is an extremely rare result. Central pain and its proposed mechanisms are discussed.

Angiography, Digital Subtraction↗

PubMed1999

Reduction in the cesarean section rate in nulliparous patients after administration of intravenous propranolol.

OBJECTIVE: A preliminary investigation to test the efficacy of intravenous propranolol in reducing the cesarean section rate in nulliparas in active labor and evaluate its effect on neonatal and maternal outcomes. METHODS: Fifty seven nulliparous patients admitted in active labor were randomly divided into two groups: a control group consisting of 23 patients, and a treatment group consisting of 34 patients given 2 mg of propranolol intravenously every 4 hours until delivery. Total length of labor, time from first administration of medication to delivery, incidence of cesarean section, APGAR scores, maternal and fetal morbidity were assessed. RESULTS: A total of 4 cesarean sections were performed in each group (11.7% in the treatment group and 17.3% in the control group). The rate of cesarean section due to dystocia was 6.25 and 13.6% respectively (P = .367). Statistical significance was not reached due to the small number of subjects (students t test analysis). There was no increase in the incidence of low APGAR scores, intensive care unit admissions, abnormal heart rate patterns during labor, cesarean sections for fetal distress or maternal morbidity in the treated group. CONCLUSIONS: Intravenous administration of 2 mg of propranolol every four hours is safe and not associated to increased neonatal or maternal morbidity. A 50% decrease in the incidence of cesarean sections can be documented among nulliparous patients treated with propranolol although the small numbers and overall low incidence of cesarean section in our population (14%) did not permit these differences to reach statistical significance.

Adrenergic beta-Antagonists↗

PubMed1998

Presurgical columellar elongation and primary retrograde nasal reconstruction in one-stage bilateral cleft lip and nose repair.

We present a new combined approach to primary bilateral cleft lip, nose, and alveolus repair using presurgical nasoalveolar molding combined with a one-stage lip, nose, and alveolus repair. Presurgical alveolar molding is used to bring the protruding premaxilla back into proper alignment with the lateral segments in the maxillary arch. Presurgical nasal molding produces tissue expansion of the short columella and nasal lining. A coordinated surgical approach involves a one-stage repair of the lip, nose, and alveolus. The nasal repair uses a retrograde approach in which the prolabial flap and columella are reflected over the nasal dorsum by continuing the dissection behind the prolabium up the membranous septum and over the septal angle. Tissues are dissected out from between the tip cartilages, and the domes are sutured together in the midline. This method joins a new class of bilateral cleft repairs that place the primary emphasis on correction of the deformity of the nasal tip cartilages.

Alveolar Process↗

PubMed1997

Identification of an osteoclast transcription factor that binds to the human T cell leukemia virus type I-long terminal repeat enhancer element.

Transgenic mice expressing human T cell leukemia virus type I (HTLV-I)-tax under the control of HTLV-I-long terminal repeat (LTR) promoter develop skeletal abnormalities with high bone turnover and myelofibrosis. In these animals, Tax is highly expressed in bone with a pattern of expression restricted to osteoclasts and spindle-shaped cells within the endosteal myelofibrosis. To test the hypothesis that lineage-specific transcription factors promote transgene expression from the HTLV-I-LTR in osteoclasts, we first examined tax expression in transgenic bone marrow cultures. Expression was dependent on 1alpha,25-dihydroxycholecalciferol and coincided with tartrate-resistant acid phosphatase (TRAP) expression, a marker of osteoclast differentiation. Furthermore, Tax was expressed in vitronectin receptor-positive mononuclear precursors as well as in mature osteoclast-like cells (OCLs). Consistent with our hypothesis, electrophoretic mobility shift assays revealed the presence of an OCL nuclear factor (NFOC-1) that binds to the LTR 21-base pair direct repeat, a region critical for the promoter activity. This binding is further enhanced by Tax. Since NFOC-1 is absent in macrophages and conserved in osteoclasts among species including human, such a factor may play a role in lineage determination and/or in expression of the differentiated osteoclast phenotype.

Acid Phosphatase↗