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Biomedical subjects

M T Perez

Publications and source records attributed to M T Perez.

At least 19 recordsLinked to original sources
PubMed2003

Hydrolysis of lactose by free and immobilized beta-galactosidase from Thermus sp. strain T2.

The hydrolysis of lactose by a beta-galactosidase from the thermophilic microorganism Thermus sp. strain T2, both in solution and immobilized on a commercial silica-alumina, has been studied. The enzyme has been previously produced by Escherichia coli JM101 harboring the plasmid pBGT1, which contains the codifying gene under the promoters lpp(P) and lac(PQ). The enzyme was immobilized on the support activated with tris-hydroxymethylphosphine (THP). Activity and stability of the free and the immobilized enzyme towards pH and temperature were tested. To study the activity at different pH and temperature values, lactose was used as substrate. To check the stability, the enzyme was incubated either in buffer BP or in a solution of lactose in buffer BM at different pH and temperatures, being the remaining activity tested by withdrawing samples and determining their activity toward ONPG at 70 degrees C in buffer BP. Afterward, runs were performed to obtain kinetic models adequate for the description of the hydrolysis of lactose by the free and the immobilized enzyme. These data were fitted to the kinetic models proposed (all based on the Michaelis-Menten mechanism) by non-linear regression, being the models and their parameters compared to determine the effect of the immobilization on the kinetic behavior of the enzyme. Both the free and the immobilized enzyme are competitively inhibited by galactose, while glucose inhibited only the action of the free enzyme, in an uncompetitive way. The immobilization step seems to eliminate the inhibition by glucose. Moreover, the immobilization reduced to a half the inhibitory action of galactose. In general, the immobilization reduced the activity of the enzyme, but increased its thermal stability. Finally, a comparison between the kinetic behavior of this thermophilic enzyme and enzymes of mesophile microorganisms previously studied by us (E. coli and K. fragilis) and by other authors (Aspergillus niger) is performed.

Enzyme Stability↗
PubMed2001

Extranodal lymphoplasmacytoid lymphoma (immunocytoma) presenting as small intestinal obstruction.

A 57-year-old woman presented with intermittent symptoms of intestinal obstruction. Workup provided nondiagnostic radiologic studies. An exploratory laparotomy revealed a segmental dilatation in the proximal ileum, which showed diffuse thickening of the intestinal wall. Microscopic examination of the affected area disclosed a diffuse transmural infiltrate composed of small lymphocytes, mature plasma cells, and lymphoplasmacytoid cells in different stages of maturation associated with extracellular periodic acid-Schiff-positive material. In addition, serum protein electrophoresis showed a monoclonal immunoglobulin M kappa paraprotein. Postoperative workup did not demonstrate evidence of systemic involvement. The morphologic features and immunohistochemical and molecular analyses were consistent with lymphoplasmacytoid lymphoma (immunocytoma). We report an unusual case of primary extranodal immunocytoma involving the small intestine and discuss its clinicopathologic features.

Female↗
PubMed1999

Mouse ten-m/Odz is a new family of dimeric type II transmembrane proteins expressed in many tissues.

The Drosophila gene ten-m/odz is the only pair rule gene identified to date which is not a transcription factor. In an attempt to analyze the structure and the function of ten-m/odz in mouse, we isolated four murine ten-m cDNAs which code for proteins of 2,700-2, 800 amino acids. All four proteins (Ten-m1-4) lack signal peptides at the NH2 terminus, but contain a short hydrophobic domain characteristic of transmembrane proteins, 300-400 amino acids after the NH2 terminus. About 200 amino acids COOH-terminal to this hydrophobic region are eight consecutive EGF-like domains. Cell transfection, biochemical, and electronmicroscopic studies suggest that Ten-m1 is a dimeric type II transmembrane protein. Expression of fusion proteins composed of the NH2-terminal and hydrophobic domain of ten-m1 attached to the alkaline phosphatase reporter gene resulted in membrane-associated staining of the alkaline phosphatase. Electronmicroscopic and electrophoretic analysis of a secreted form of the extracellular domain of Ten-m1 showed that Ten-m1 is a disulfide-linked dimer and that the dimerization is mediated by EGF-like modules 2 and 5 which contain an odd number of cysteines. Northern blot and immunohistochemical analyses revealed widespread expression of mouse ten-m genes, with most prominent expression in brain. All four ten-m genes can be expressed in variously spliced mRNA isoforms. The extracellular domain of Ten-m1 fused to an alkaline phosphatase reporter bound to specific regions in many tissues which were partially overlapping with the Ten-m1 immunostaining. Far Western assays and electronmicroscopy demonstrated that Ten-m1 can bind to itself.

Alkaline Phosphatase↗
PubMed1999

Intraductal carcinoma (carcinoma in situ) of the pancreas with microinvasion.

We report a case of predominantly intraductal carcinoma of the pancreas with microscopic foci of invasive carcinoma in a patient with chronic pancreatitis. In this article, we discuss the pathologic and prognostic features of pancreatic carcinoma in situ. This entity is probably overlooked due to a number of reasons, including the fact that, in most cases, pancreatic ductal carcinomas are extensively infiltrative at the time of surgical removal; the atypical epithelial changes in the intraductal carcinoma had been overlooked in the presence or absence of an invasive component; epithelial changes may be missed due to insufficient sampling; and last, the differentiation with atypical epithelial hyperplasia is a subjective matter. Intraductal carcinoma of the pancreas is a distinct pathological entity with characteristic morphologic changes restricted to the ductal epithelium, bearing important prognostic implications.

Aged↗
PubMed1999

Balloon cell change in cellular blue nevus.

Balloon cells are altered melanocytes with clear vacuolated cytoplasm caused by a defect in the process of melanogenesis. Although rare, balloon cell change has been observed in a variety of melanocytic proliferations, particularly intradermal melanocytic nevi and melanoma. When present, such features may lead to difficulties in diagnosis, particularly with other clear cell neoplasms. We report an unusual case of the development of balloon cell change in a cellular blue nevus, a phenomenon that has not been extensively addressed in the literature. The importance of recognizing this change in cellular blue nevus to avoid misinterpreting the lesion as malignant is discussed.

Cell Transformation, Neoplastic↗
PubMed1999

Pulmonary artery fibrous bands: report of a case with extensive lung infarction and superinfection with Coccidioides immitis, Pseudomonas, and acid-fast bacilli.

A 46-year-old woman presented with shortness of breath and frequent lower respiratory tract infections. A ventilation-perfusion scan showed markedly reduced perfusion of the right lung, and pulmonary arteriogram showed stenosis of the right pulmonary artery. A right pneumonectomy revealed dense white fibrous bands partially occluding the pulmonary artery branches and two large abscess cavities filled with pus in the upper and lower lobes. Microscopic examination revealed extensive necrosis of lung parenchyma, suppurative granulomatous inflammation with Coccidioides immitis organisms and rare acid-fast bacilli. Pulmonary artery fibrous bands were originally believed to be congenital; however, they are now known to be sequelae of thromboembolic phenomena.

Coccidioides↗
PubMed1999

Nitric oxide-producing cells project from retinal grafts to the inner plexiform layer of the host retina.

PURPOSE: Amacrine cells expressing nitric oxide synthase (NOS) are seen in normal retinas and retinal grafts to extend long processes, which can be followed for long distances. Taking advantage of the morphologic features of these cells, the present study examined whether graft-host connections involve cells capable of producing nitric oxide, a recognized retinal neuromodulatory compound. METHODS: Embryonic day 15 rabbit retinas were transplanted to the subretinal space of adult rabbits. The localization of the neuronal form of NOS was assessed by immunocytochemistry in grafts that had reached the equivalent ages of postnatal days 5, 12, 20, 45, 90, and 102. RESULTS: NOS-containing cells and processes were seen in all the transplants. Processes were found to project mainly toward areas within the graft. Yet, at all survival times examined, single immunolabeled fibers could be seen to cross the graft- host border. In fortuitous cases, it was possible to establish that the bridging fiber originated in the graft. Further, bridging fibers were seen to reach the NOS-immunolabeled host inner plexiform layer. CONCLUSIONS: Graft NOS-containing cells are not only capable of projecting into the host but also of reaching the appropriate target for NOS-containing fibers within the host retina. This indicates that at least some graft-host connections are established by graft cells that retain their ability to synthesize a modulatory compound and which potentially could contact their partner cells in the host retina.

Animals↗
PubMed1998

Pleural body cavity-based lymphoma.

We report a case of recurrent body cavity-based non-Hodgkin's lymphoma in a patient with advanced acquired immunodeficiency syndrome who presented with bilateral pleural effusions, without evidence of an associated tumor mass. The lymphoma cells were large and pleomorphic, lacking pan-T- and pan-B-cell markers, but expressing activation markers (CD30, CD38, and HLA-DR). The purpose of this article is to discuss the radiological-pathological correlation of body cavity-based lymphoma with a review of the entities that should be included in the differential diagnosis of patients with malignant pleural effusions.

Acquired Immunodeficiency Syndrome↗
PubMed1998

Apoptosis of renal cortical cells in the hemolytic-uremic syndrome: in vivo and in vitro studies.

This study examined apoptotic cell death associated with Shiga-like toxin (Stx)-producing Escherichia coli. Renal cortices from three children with postenteropathic hemolytic-uremic syndrome (HUS) and from mice infected with E. coli O157:H7 and pediatric renal tubular epithelial cells stimulated with Stx and E. coli O157:H7 extracts were examined for apoptotic changes. Apoptotic cells were detected by terminal dUTP nick end labeling of tubuli and glomeruli from HUS patients and from mice inoculated with Stx-2-positive and Stx-negative strains. Apoptosis was more extensive and severe ultramorphological nuclear and cytoplasmic changes were seen in the Stx-2-positive group. Stx caused DNA fragmentation and ultramorphological changes indicating apoptosis in cultured pediatric tubular cells. DNA fragmentation increased when cells were pre-stimulated with tumor necrosis factor alpha. Polymyxin extracts from Stx-2-positive and Stx-negative strains induced DNA fragmentation, but only extracts from Stx-2-positive strains caused ultramorphological changes and extensive DNA fragmentation. The results indicate that HUS is accompanied by increased apoptosis of kidney cells and that bacterial factors, possibly together with host cytokines in vivo, may activate apoptotic tissue injury.

Animals↗
PubMed1997

Immunocytochemical localisation of neuronal nitric oxide synthase in developing and transplanted rabbit retinas.

Nitric oxide (NO) acts as a modulator of neuronal transmission in mature neuronal systems, including the retina. Recently, NO has also been suggested to have a trophic function during development. We examined immunocytochemically the distribution of NO-producing cells in developing and transplanted rabbit retinas. An antibody detecting the neuronal isoform of its biosynthetic enzyme, nitric oxide synthase (NOS), was used on normal developing retinas [starting at embryonic day (E) 15] and on rabbit retinal transplants after various survival times (1-139 days after surgery). Weakly stained cell bodies were first observed in the proximal margin of the neuroblastic layer at E 29. Stained processes projecting towards a developing inner plexiform layer were also visible at this time point. Immunoreactive cells were located at later stages in the innermost part of the inner nuclear layer and in the ganglion cell layer, and are likely to correspond mainly to amacrine cells. NOS-labelled cells were also found in retinal transplants. The first NOS-labelled cells appeared, as in normal developing retinas, in ages corresponding to E 29 and were still detected in transplants corresponding to postnatal day 123. NOS-labelled cells were seen in areas between rosettes, where amacrine cells are located. NOS-labelled processes were at times seen to project for long distances, forming very distinct plexuses. NOS-containing amacrine cells thus appear both in the transplants and in developing retinas in the embryonic stages, long before synaptic function involving these cells can be expected, suggesting a role for NO not only in neuromodulation but also in retinal development.

Age Factors↗
PubMed1997

DNA fragmentation characteristic of apoptosis and cell loss induced by kainic acid in rabbit retinas.

We have examined whether in vivo exposure to the glutamate analogue, kainic acid, induces cell loss through apoptosis and/or through necrosis. The vulnerability of rabbit retinal cells was evaluated by routine histopathology. The DNA fragmentation was examined using an in situ method (TUNEL: TdT-mediated biotin-dUTP nick-end labelling) and agarose gel electrophoresis of extracted retinal DNA. Retinas were examined at 30 min, and 4, 16, 24 and 36 h, and 2-5 days following the intraocular administration of 140 nmol kainic acid. Although pyknotic cells could be seen already at 30 min post-injection, TUNEL-labelled nuclei were first observed 4 h after the injection. A relatively large number of pyknotic cells and of TUNEL-labelled nuclei were still seen at 5 days post-injection. Pyknotic cells were seen throughout the inner nuclear layer (mostly in the proximal half of the layer) and in the ganglion cell layer. The TUNEL-labelled nuclei were almost only seen in the proximal inner nuclear layer. Analysis of DNA by electrophoresis revealed the presence of large molecular weight fragments 4 h after the injection, and of oligonucleosome-size fragments between 16 h and 2 days after the injection. The present study thus presents evidence that, in our model, the retinal cell loss induced by kainic acid is preceded, probably in most cells, by a fragmentation of DNA characteristic of apoptotic cell death. The process of cell loss following kainic acid administration was found to be relatively slow, further suggesting that a programmed type of cell death, which eventually induces apoptosis, is involved. No indication that cells were lost also through necrosis was obtained.

Animals↗
PubMed1997

Pancreatic enzyme secretion in response to test meals differing in the quality of dietary fat (olive and sunflowerseed oils) in human subjects.

The aim of the present study was to investigate in human subjects whether or not the ingestion of two liquid meals that differed only in their fatty acid composition (due to the addition of olive oil (group O) or sunflowerseed oil (group S) as the source of dietary fat) would lead to differences in the pancreatic enzyme activities secreted into the duodenum. The experiments were performed in eighteen cholecystectomized subjects who, during the 30 d period immediately before surgery, modified their habitual diets in such a way that their fat composition would reflect, as far as possible, that of the experimental meals. Lipase (EC 3.1.1.3), colipase, amylase (EC 3.2.1.1), chymotrypsin (EC 3.4.21.1) and trypsin (EC 3.4.21.4) activities were measured in duodenal contents aspirated before and after the ingestion of the test meals. The plasma levels of secretin and cholecystokinin (CCK) were also examined. Duodenal enzyme activities were similar in resting conditions. No significant differences were revealed in postprandial enzyme activities, except for lipase activity, which was higher in group O, probably in relation to the greater plasma CCK concentrations observed in this group. In the absence of enzyme output data, we should not exclude the possibility that the type of dietary fat will affect human pancreatic enzyme secretion to a greater extent than is evident from the present study, for instance through a flow-mediated effect, as we previously observed in dogs.

Amylases↗
PubMed1995

Expression of brain-derived neurotrophic factor and of its functional receptor in neonatal and adult rat retina.

The expression of mRNA coding for brain-derived neurotrophic factor (BDNF) and for its functional receptor, the full-length tyrosine kinase receptor trkB (trkB mRNA), was examined in early postnatal and adult rat retina by in situ hybridization using digoxygenin and radioactively-labeled oligonucleotide probes. BDNF and trkB mRNAs are expressed in the ganglion cell layer at postnatal-days (PN) 1, 4, 7, 14, 60, in proximal neuroblastic layer (PN 1, 4, 7), and proximal inner nuclear layer (PN 14, 60). Subpopulations of developing and mature retinal cells are thus capable of synthesizing BDNF.

Animals↗
PubMed1995

Localisation of neuronal nitric oxide synthase-immunoreactivity in rat and rabbit retinas.

The distribution of neuronal nitric oxide synthase (NOS) immunoreactivity was examined in rat and rabbit retinas and was compared with the distribution of nicotinamide adenine dinucleotide phosphate (NADPH)-diaphorase reactivity and vasoactive intestinal peptide (VIP) immunoreactivity. An antibody raised against a C-terminal fragment of a cloned rat cerebellar NOS was used to localise NOS immunoreactivity. NOS immunoreactive cells were not detected in rat retinas at postnatal day 1 or 4, but were seen from postnatal day 7 onwards. NOS immunolabelling was seen in a small population of cells in the proximal inner nuclear layer. Most of the labelled cells had the position of amacrine cells and were seen to send processes into the inner plexiform layer. A few labelled cells were at times also seen in the ganglion cell layer, which are likely to correspond to displaced amacrine cells. The same NOS-labelling pattern was seen in rat and rabbit retinas. NADPH-diaphorase staining was observed in both species, in photoreceptor inner segments, in cells with the position of horizontal cells, in a subset of amacrine and displaced amacrine cells, in large cell bodies in the ganglion cell layer, in both plexiform layers, and in endothelium. Colocalisation of NOS immunoreactivity and NADPH-diaphorase staining was only observed among amacrine cells. However, not all NADPH-diaphorase-reactive amacrine cells were found to be NOS immunoreactive. VIP immunoreactivity was also localised in rat retinas in a subpopulation of amacrine cells, but no colocalisation of NOS and VIP immunoreactivity was observed. Our observations indicate that only amacrine cells contain the NOS form recognisable by the antibody used, and suggest that different isoforms of neuronal NOS may be present in retinal cells. Further, the onset of NOS expression in rat amacrine cells appears to occur independently of neuronal activity.

Amino Acid Oxidoreductases↗
PubMed1995

Localization of enkephalinergic neurons in the central nervous system of the salmon (Salmo salar L.) by in situ hybridization and immunocytochemistry.

The distribution of neurons expressing preproenkephalin (PPE) mRNA in the brain of the salmon was investigated by means of non-radioactive in situ hybridization, and directly compared with the distribution of enkephalin-immunoreactive (ENKir) neurons. This approach, utilized here for the first time in a non-mammalian vertebrate for the identification of neurons containing opioid peptides, permitted a detailed analysis of the distribution of putative enkephalinergic neurons in the salmon brain. Several cell groups containing neurons that express PPE mRNA also contain ENKir neurons. Such cell groups are located in the ventral telencephalic area, the nucleus of the rostral mesencephalic tegmentum and another nucleus immediately dorsal to it, the torus semicircularis, the valvula cerebelli and the corpus cerebelli. These cell groups consistently contain larger numbers of PPE mRNA expressing cells than ENKir ones. Some cell groups express PPE mRNA, but do not contain ENKir neurons. These cell groups are located in the dorsal telencephalic area, the inferior lobes of the hypothalamus, the pretectal area, the magnocellular superficial pretectal nucleus, the optic tectum, the oculomotor nucleus, the trochlear nucleus, the magnocellular vestibular nucleus, the secondary gustatory nucleus, the superior and medial reticular nuclei, the motor nucleus of the vagus and the ventral horn of the spinal cord. Moreover, some cell groups contain ENKir neurons, but no PPE mRNA expressing neurons. These cell groups are located in the ventromedial thalamic nucleus, the lateral tuberal nucleus, the nucleus of the lateral recess and the nucleus of the posterior recess. The majority of these periventricular ENKir neurons were of the cerebrospinal fluid-contacting type. ENKir neurons were also located in the dorsal lateral tegmental nucleus and in area B9. The results also permitted a tentative identification of enkephalinergic neurons afferent to the optic tectum, that have previously not been identified with immunocytochemistry, located in the dorsal telencephalic area, as well as enkephalinergic neurons intrinsic to the tectum that may contribute to the laminar arrangement of ENKir fibers in the optic tectum.

Animals↗
PubMed1994

In situ hybridization of neuropeptide Y (NPY) mRNA in the goldfish brain.

The distribution of neurones expressing neuropeptide Y (NPY) mRNA in the brain of the goldfish was investigated using a non-radioactive in situ hybridization technique. Neurones expressing NPY mRNA were located in cell groups previously shown to exhibit NPY immunoreactivity in the ventral telencephalon, thalamus, optic tectum and a region adjacent to the locus coeruleus. In addition, neurones expressing NPY mRNA were observed in the diffuse nucleus of the torus lateralis and in the mesencephalic tegmentum. Our results suggest that in the two latter groups of neurones the rate of transport of NPY from the perikarya is higher, or that NPY is not synthesized at levels detectable by immunocytochemistry.

Animals↗