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Biomedical subjects

J Fernandez

Publications and source records attributed to J Fernandez.

At least 55 records · Page 3Linked to original sources
PubMed1999

Glucose-dependent stimulatory effect of glucagon-like peptide 1(7-36) amide on the electrical activity of pancreatic beta-cells recorded in vivo.

The stimulatory effect of the glucagon-like peptide (GLP)-1(7-36) amide on electrical activity in pancreatic b-cells recorded in vivo was studied. The injection of GLP-1 produces a lengthening of the active phase with respect to the silent phase, leading to a stimulation of insulin release, which produces a secondary decrease in blood glucose concentration and eventually, to the hyperpolarization of the membrane at a blood glucose level of approximately 5 mmol/l. The injection of GLP-1 at a glycemic level <5 mmol/l does not stimulate electrical activity. This is in contrast to the effect of tolbutamide, which stimulates electrical activity at low glucose concentrations. These results demonstrate that in vivo, the stimulatory effect of GLP-1 on insulin secretion is at least partially mediated by its effect on beta-cell electrical activity. Furthermore, the glucose dependence of the effect confers to GLP-1, a security factor that supports its potential use in the treatment of type 2 diabetes.

Animals↗
PubMed1998

Trehalose-6P synthase is essential for trehalase activation triggered by glucose, nitrogen source or heat shock, but not by osmostress, in Schizosaccharomyces pombe.

Cells of Schizosaccharomyces pombe disrupted in the tps1+ gene, which encodes trehalose-6P synthase, were unable to increase trehalase activity in response to the addition of glucose or nitrogen source. Moreover, in contrast to normal cells, Deltatps1 cells did not increase trehalase activity by heat shock. Overexpression of tps1+ in cells devoid of trehalose-6P synthase restored the ability to increase trehalase after addition of nutrients or by heat shock. In glucose-repressed cells, which are normally refractory to the activation of trehalase by glucose, overexpression of tps1+ enabled the cells to increase trehalase activity upon addition of the sugar. Northern hybridisations were used to determine the level of mRNA for trehalase in normal and Deltatps1 cells. Transcription for trehalase was not significantly altered upon addition of glucose or nitrogen source, but increased markedly in heat-shocked cells even though trehalase activity remained unchanged in Deltatps1 cells. These findings provide evidence for a role of trehalose-6P synthase in the signalling pathway causing post-transcriptional activation of neutral trehalase induced by nutrients or heat shock. However, trehalase increased in Deltatps1 cells under hypertonic conditions suggesting the existence in Schiz. pombe of a distinct regulatory mechanism for enhancement of trehalase, specifically triggered by osmostress.

Enzyme Activation↗
PubMed1998

Antibacterial agents that inhibit two-component signal transduction systems.

A class of antibacterials has been discovered that inhibits the growth of Gram-positive pathogenic bacteria. RWJ-49815, a representative of a family of hydrophobic tyramines, in addition to being a potent bactericidal Gram-positive antibacterial, inhibits the autophosphorylation of kinase A of the KinA::Spo0F two-component signal transduction system in vitro. Analogs of RWJ-49815 vary greatly in their ability to inhibit growth of bacteria and this ability correlates directly with their activity as kinase A inhibitors. Compared with the potent quinolone, ciprofloxacin, RWJ-49815 exhibits reduced resistance emergence in a laboratory passage experiment. Inhibition of the histidine protein kinase::response regulator two-component signal transduction pathways may present an opportunity to depress chromosomal resistance emergence by targeting multiple proteins with a single inhibitor in a single bacterium. Such inhibitors may represent a class of antibacterials that potentially may represent a breakthrough in antibacterial therapy.

Anti-Bacterial Agents↗
PubMed1998

DNA gyrase inhibitory activity of ellagic acid derivatives.

Ellagic acid was found to inhibit E. coli DNA gyrase supercoiling with approximately the same potency as nalidixic acid. Tricyclic analogs of ellagic acid, which vary in the number and position of the hydroxy groups as well as their replacement with halogens, have been synthesized. The biological activity of these analogs is discussed.

Ellagic Acid↗
PubMed1998

Routine identification of proteins from sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) gels or polyvinyl difluoride membranes using matrix assisted laser desorption/ionization-time of flight-mass spectrometry (MALDI-TOF-MS).

As the resource laboratory for Rockefeller University our emphasis continues to be on methodology development for the routine analysis of low abundance proteins isolated from native sources. In the past ten years, gel electrophoresis of proteins has become the method of choice for the preparation of microgram and submicrogram quantities of protein for primary structural characterization, and over 95% of the samples submitted for protein identification are either in a gel or bound to polyvinyl difluoride membranes (PVDF). As such, we employ multiple microanalytical approaches encompassing Edman sequence degradation, amino acid and matrix assisted laser desorption/ionization-time of flight (MALDI-TOF) mass spectrometric analysis to provide an integrated protein characterization of such samples. Here we describe the two major services we employ when providing protein identification from in-gel or PVDF-bound proteins.

Amino Acid Sequence↗
PubMed1998

Differential growth patterns in SCID mice of patient-derived chronic myelogenous leukemias.

The development of an in vivo model for the study of CML would be of significant importance in studying its biological behavior and developing novel therapeutic strategies. We examined the ability of human leukemic cells derived from patients in either chronic (CP), accelerated (AP) or blast phase (BP) CML to grow and disseminate in CB17-SCID mice by subcutaneous (s.c.) inoculation without conditioning treatment or administration of cytokines. Additionally, samples derived from patients with CP-CML were injected s.c. into CB17-SCID mice treated with anti-Asialo GM1 (an anti-NK cell antibody) and NOD-SCID mice (absent NK cell activity) to study the potential role of NK cell-mediated anti-leukemic activity in preventing the propagation of CP-CML cells. We observed a significant differential growth pattern of CML cells in the mice such that BP-CML grew rapidly as s.c. tumors and disseminated, while AP-CML or CP-CML cells grew temporarily as small nodules that spontaneously regressed and did not disseminate. This differential growth pattern suggests possible important biological differences. Furthermore, no significant difference in s.c. growth or dissemination of CP-CML samples derived from newly diagnosed patients in untreated CB17-SCID mice and CB-17 SCID mice treated with Anti-Asialo GM1 and NOD-SCID mice occurred, suggesting that factors other than NK cell anti-leukemic activity may be important.

Adolescent↗
PubMed1998

Characterization of mutants devoid of neutral trehalase activity in the fission yeast Schizosaccharomyces pombe: partial protection from heat shock and high-salt stress.

Exposure of cells of Schizosaccharomyces pombe to heat shock or osmotic upshift results in an increased level of neutral trehalase activity, which is responsible for hydrolysis of intracellular trehalose. We constructed S. pombe mutants lacking neutral trehalase activity by gene replacement at the newly defined ntp1+ locus. Analysis of these mutants revealed that a twofold increase in trehalose accumulation, enhanced acquired thermoresistance, and marked salt tolerance characterized their ability to grow in liquid and solid media. Analysis of the expression of the trehalase gene under heat shock and osmotic upshift revealed the transcriptional activation of ntp1+ in response to both stresses.

Culture Media↗
PubMed1998

Defective human T-cell lymphotropic virus type I (HTLV-I) provirus in 10 Chilean seronegative patients with tropical spastic paraparesis or HTLV-I-associated myelopathy.

We studied the presence of tax and ltr genes from human T-cell lymphotropic virus type I (HTLV-I) provirus in the peripheral blood mononuclear cells from 15 seronegative patients with tropical spastic paraparesis or HTLV-I-associated myelopathy by PCR. Only a region of the tax gene from 10 patients was amplified. The nucleotide homologies of six Chilean isolates to the ATK-1 clone ranged between 98.7 and 99.4%.

Adult↗
PubMed1998

Dorsal-mediated repression requires the formation of a multiprotein repression complex at the ventral silencer.

Dorsal functions as both an activator and repressor of transcription to determine dorsoventral fate in the Drosophila melanogaster embryo. Repression by Dorsal requires the corepressor Groucho (Gro) and is mediated by silencers termed ventral repression regions (VRRs). A VRR in zerknüllt (zen) contains Dorsal binding sites as well as an essential element termed AT2. We have identified and purified an AT2 DNA binding activity in embryos and shown it to consist of cut (ct) and dead ringer (dri) gene products. Studies of loss-of-function mutations in ct and dri demonstrate that both genes are required for the activity of the AT2 site. Dorsal and Dri both bind Gro, acting cooperatively to recruit it to the DNA. Thus, ventral repression may require the formation of a multiprotein complex at the VRR. This complex includes Dorsal, Gro, and additional DNA binding proteins, which appear to convert Dorsal from an activator to a repressor by enabling it to recruit Gro to the template. By showing how binding site context can dramatically alter transcription factor function, these findings help clarify the mechanisms responsible for the regulatory specificity of transcription factors.

Animals↗
PubMed1998

Increased levels of free fatty acids in fasted mice stimulate in vivo beta-cell electrical activity.

The electrical activity of pancreatic beta-cells in 48-h fasted mice has been recorded in vivo. Their electrical activity is exceedingly high at low levels of blood glucose when compared with control animals. For example, at a blood glucose concentration of 4.5 mmol/l, at which beta-cells are permanently hyperpolarized in control animals, fasted animals show continuous spiking activity. In fasted animals, hyperpolarization only occurs at glycemias below 2.2 mmol/l. As in fed animals, the electrical activity in fasted mice can be decreased or suppressed by the injection of diazoxide, indicating the participation of K(ATP) channels. The treatment of fasted animals with nicotinic acid, an inhibitor of lipolysis, produces a decrease in the levels of free fatty acids (FFAs) and a decrease in electrical activity, thereby restoring the dose-response curve for glucose in fasted animals to values close to those found in fed animals. Conversely, the injection of palmitic acid produces an increase in electrical activity without a change in blood glucose. These results point to FFAs as important regulators of electrical activity during fasting in vivo. They also indicate a dissociation of electrical activity and insulin release in fasted animals, since an increase in electrical activity is not associated with increased insulin secretion.

Animals↗
PubMed1998

Formation of polar cytoplasmic domains (teloplasms) in the leech egg is a three-step segregation process.

Segregation and proliferation of mitochondria, leading to formation of the teloplasms (pole plasms), were studied in eggs of the leech T. rude by immunocytochemistry, fluorescent time lapse video imaging, confocal and electron microscopy. The translocation of mitochondria was analyzed after loading the egg with either Rhodamine 123 or a Mitotracker. Mitochondrial proliferation was assessed after pulse labeling with BrdU. The involvement of the cytoskeleton in the segregation process was determined by drug action. The teloplasms form during the first interphase as consequence of a 3-step sequential process of mitochondrial redistribution throughout the egg cytoplasm. The first step is a microtubule dependent process of ectoplasm thickening due to centrifugal mitochondrial transportation from the neighboring endoplasm. During the second step mitochondria move in the plane of the ectoplasm to become concentrated at the wall of rings (polar rings) and bands of contraction. This process appears to mostly depend on actin. The furrowing pattern of the egg during this step can be modified by cold treatment and seems to be determined during oogenesis. During the third step the ectoplasm flows to either of the poles in conjunction with bipolar displacement of the polar rings and shortening of the contraction bands. This step depends on both microtubules and microfilaments. Mitochondria of first interphase eggs have three special features: (1) they move in clusters, (2) their movement depends on both microtubules and microfilaments and (3) they proliferate continuously. During the first interphase the polarized meiotic egg becomes a bipolar cell.

Actins↗
PubMed1998

[Psoas abscess secondary to lumbar spondylodiscitis caused by gram negative bacilli].

The association between psoas abscess and lumbar spondylodiscitis by Gram negative bacilli represents a rare clinical entity. Sometimes the absence of demonstrative symptoms complicates the diagnostic schema. We report about a 72 year-old woman, without previous known diabetes mellitus, who was admitted because of fever of one week duration and a non-ketotic hyperosmolar coma. A left psoas abscess was identified by abdominal computed tomography (CT). The abscess was in communication with the L1-L2 intervertebral space. Although Escherichia coli was identified as the causing agent and appropriate antibiotic therapy was administered, the resolution of the abscess occurred only after the implantation of a percutaneous catheter guided by CT without additional surgery. Percutaneous drainage as a diagnostic-therapeutic technique has rendered the surgery as the last resort in the treatment of psoas abscess.

Aged↗
PubMed1997

Determination of IgE antibodies to the benzylpenicilloyl determinant: a comparison of the sensitivity and specificity of three radio allergo sorbent test methods.

The quantitation of in vitro IgE antibodies to the benzylpenicilloyl determinant (BPO) is a useful tool for evaluating suspected penicillin allergic subjects. Although many different methods have been employed, few studies have compared their diagnostic specificity and sensitivity. In this study, the sensitivity and specificity of three different radio allergo sorbent test (RAST) methods for quantitating specific IgE antibodies to the BPO determinant were compared. Thirty positive control sera (serum samples from penicillin allergic subjects with a positive clinical history and a positive penicillin skin test) and 30 negative control sera (sera from subjects with no history of penicillin allergy and negative skin tests) were tested for BPO-specific IgE antibodies by RAST using three different conjugates coupled to the solid phase: benzylpenicillin conjugated to polylysine (BPO-PLL), benzylpenicillin conjugated to human serum albumin (BPO-HSA), and benzylpenicillin conjugated to an aminospacer (BPO-SP). Receiver operator control curves (ROC analysis) were carried out by determining different cut-off points between positive and negative values. Contingence tables were constructed and sensitivity, specificity, negative predictive values (PV-), and positive predictive values (PV+) were calculated. Pearson correlation coefficients (r) and intraclass correlation coefficients (ICC) were determined and the differences between methods were compared by chi 2 analysis. Analysis of the areas defined by the ROC curves showed statistical differences among the three methods. When cut-off points for optimal sensitivity and specificity were chosen, the BPO-HSA assay was less sensitive and less specific and had a lower PV- and PV+ than the BPO-PLL and BPO-SP assays. Assessment of r and ICC indicated that the correlation was very high, but the concordance between the PLL and SP methods was higher than between the PLL and HSA or SP and HSA methods. We conclude that for quantitating IgE antibodies by RAST to the BPO determinant, BPO-SP or BPO-PLL conjugates offer advantages in sensitivity and specificity compared with BPO-HSA. These results support and extend previous in vitro studies by our group and highlight the importance of the carrier for RAST assays.

Adult↗
PubMed1997

Lobular carcinoma of the male breast associated with the use of cimetidine.

A case of carcinoma in the breast of a male patient with a chronic gastric ulcer is described. The patient had received cimetidine for 17 years. Histological examination of an excisional biopsy showed lobular in situ and infiltrating carcinoma. In our review of the English literature, this is the 18th case of lobular carcinoma of the male breast to be reported; it is also the first report of lobular carcinoma associated with the use of cimetidine, and the second in a man with documentation of genotype.

Anti-Ulcer Agents↗
PubMed1997

Toxicological and immunological evaluation of the MHC-non-restricted cytotoxic T cell line TALL-104.

The human MHC-non-restricted cytotoxic T cell line TALL-104 has been shown to display potent antitumor effects in several animal models with spontaneous and induced malignancies. In view of its potential future use in cancer therapy, we investigated the tolerability and target-organ toxicity of these cells in various animal species. The acute toxicity of TALL-104 cell administrations was evaluated in: (a) healthy immunocompetent mice and immunodeficient (SCID) mice bearing human tumors using multiple (up to 15) intraperitoneal (i.p.) injections, and (b) healthy dogs, tumor-bearing dogs, and healthy monkeys using multiple (up to 17) intravenous (i.v.) injections. TALL-104 cells were gamma-irradiated (40 Gy) prior to administration to mice and dogs, but administered without irradiation in monkeys. Cell doses ranged from 5 x 10(7)/kg to 10(10)/kg for each injection. All regimens were well tolerated, the main clinical signs observed being transient gastrointestinal effects. Moderate and transient increases in liver transaminase levels were observed in all animal species. Discrete and transient leukocytosis with neutrophilia was also noted in dogs and monkeys after i.v. injections of TALL-104 cells. Histological analysis revealed foci of hepatic necrosis with lympho-/mono-/granulocytic infiltration in immunocompetent mice injected i.p. with 5 x 10(9)-10(10) cells/kg. In the same mice, the colon showed an increased number of muciparous cells and alterations in the villi structure: these alterations were completely reversed by 72 h after the last injection, while liver alterations reversed more slowly (1 week). No delayed or chronic toxicity was observed in any of the animals even when non-irradiated TALL-104 cells were administered: both immunocompetent mice and healthy dogs were found to be grossly and histopathologically normal when sacrificed (1 year and 1 month after the last TALL-104 injection respectively). TALL-104 cells did not persist in these hosts. In addition, monkeys showed no molecular signs of TALL-104-cell-induced leukemia in their blood 1 year after the last cell injection. Despite immunosuppression, most of the tumor-bearing dogs as well as the healthy dogs and monkeys developed both humoral and cellular immune responses against TALL-104 cells. The data derived from these preclinical studies suggest that administration of high doses of irradiated TALL-104 cells is well tolerated and would be unlikely to induce severe toxicity if applied in clinical trials to the treatment of patients with refractory cancer.

Animals↗
PubMed1997

Reducing costs and length of stay and improving efficiency and quality of care in cardiac surgery.

BACKGROUND: The present era of health care places major emphasis on significantly reducing cost and resource utilization while maintaining quality of care and patient satisfaction. Clinicians are being challenged to achieve this within the framework of a patient subset that is increasing in severity of disease and risk-adjusted mortality. The Brigham and Women's Cardiac Surgical Services Management Group was formed in 1987 to help accomplish these goals. METHODS: The principles we have followed involve protocols and people. The multidisciplinary group includes the chiefs of cardiac surgery and anesthesia, chief residents, physician assistants, perfusionists, intensive care unit nursing personnel, and case managers. Weekly meetings address every aspect of problems arising in the cardiac surgical service; separate weekly morbidity and mortality conferences are held. The Care Coordination Team establishes and monitors clinical pathways and recommends ways of improving all aspects of the service through a process of daily review on an individual patient basis. RESULTS: The volume of cardiac surgery at Brigham and Women's Hospital has increased steadily. The length of stay overall has decreased about 15%, and similarly, cost and total charges have also decreased. In addition, patient satisfaction has increased to a level of about 95%. CONCLUSIONS: The goals of cost-containment with improved patient care and outcome are possible through the collaborative efforts of representatives of all the personnel involved in cardiac care, as well as leadership by the surgical faculty.

Administrative Personnel↗