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Biomedical subjects

M Angel

Publications and source records attributed to M Angel.

At least 19 recordsLinked to original sources
PubMed2001

Kinetic study of the phenolysis of bis(4-nitrophenyl) carbonate, bis(4-nitrophenyl) thionocarbonate, and methyl 4-nitrophenyl thionocarbonate.

The reactions of a homogeneous series of phenols with bis(4-nitrophenyl) carbonate (BNPC), bis(4-nitrophenyl) thionocarbonate (BNPTOC), and methyl 4-nitrophenyl thionocarbonate (MNPTOC) are subjected to a kinetic investigation in water, at 25.0 degrees C and ionic strength of 0.2 M (KCl). Under excess of phenol over the substrate, all the reactions obey pseudo-first-order kinetics and are first order in phenoxide anion. The reactions of BNPC show a linear Brönsted-type plot with slope beta = 0.66, consistent with a concerted mechanism (one step). In contrast, those of BNPTOC and MNPTOC show biphasic Brönsted-type plots with slopes beta = 0.30 and 0.44, respectively, at high pK(a), and beta = 1.25 and 1.60, respectively, at low pK(a), consistent with stepwise mechanisms. For the reactions of both thionocarbonates, the pK(a) value at the center of the Brönsted plot (pK(a)(0)) is 7.1, which corresponds to the pK(a) of 4-nitrophenol. This confirms that the phenolyses of the thionocarbonates are stepwise processes, with the formation of an anionic tetrahedral intermediate. By the comparison of the kinetics and mechanisms of the title reactions with similar reactions, the following conclusions can be drawn: (i) Substitution of S(-) by O(-) in an anionic tetrahedral intermediate (T(-)) destabilizes it. (ii) The change of MeO by 4-nitrophenoxy in T(-) results in an increase of both the rate constant and equilibrium constant, for the formation of T(-), and also in an enlargement of the rate coefficient for the expulsion of 4-nitrophenoxide from T(-). (iii) Substitution of an amino group in a tetrahedral intermediate by ArO destabilizes it. (iv) Secondary alicyclic amines and other amines show greater reactivity toward MNPTOC than isobasic phenoxide anions.

Journal Article↗
PubMed2001

Screening of selected genomic areas potentially involved in thyroid neoplasms.

Loss of heterozygosity (LOH) studies have been used to identify sites harbouring tumour suppressor genes (TSGs) involved in tumour initiation or progression. To further elucidate the genetic mechanisms for follicular and papillary thyroid tumours development, we studied the frequency of LOH in 36 thyroid tumours (21 follicular thyroid adenomas (FAs) and 15 papillary thyroid carcinomas (PTCs)) on 10 specific genomic areas: 3p22, 3p25, 7q21, 7q31, 10q23, 10q25-26, 11q13, 11q23, 13q13 and 17p13.3-13.2 using 20 polymorphic markers. We have selected these areas for two reasons: (a) Even though LOH in thyroid neoplasms has been described in some of these areas, results are controversial, and (b) we have also studied areas described as involved in other epithelial or endocrine tumour types, but not studied up to now in thyroid neoplasms. Two areas showed a high percentage of LOH: 7q31 and 11q23. A 62% LOH was found at 7q31 in the FAs, suggesting, as other authors have proposed, that at least one TSG must be present in the vicinity of the c-met locus. The second area in frequency was at the 11q23 locus, with a 45% LOH in the FAs. This area was studied because it has been described as being involved in the development of epithelial and endocrine cancers. This locus had not been studied before in thyroid neoplasms. This result is interesting because the LOH11CR2A gene is localised at this locus. We suggest that this gene and/or an other TSG nearby may be involved in the progression to FA. In our study, a low percentage of LOH was found in the PTC samples, indicating that TSGs present in the areas we have studied are not significantly involved in their progression. Our data also suggest that TSGs located in areas where no LOH was detected (PTEN, MEN1, Cyclin D1, BRCA2 and RFC3) are not involved or do not have an important role in tumour progression.

Adenoma↗
PubMed2001

Role of medical students in microsurgery research.

Microsurgery is an integral element in many surgical specialties, as well as an important technique for surgical research. Student participation in microsurgery research programs can be a source for both high quality training in skills and for research contributions. In this article, the authors review their experience in developing general principles for setting up medical student microsurgery research programs, and analyze the research output and career choices made by the students who have participated.

Adult↗
PubMed2001

Cell culture conditions affect LPS inducibility of the inflammatory mediators in J774A.1 murine macrophages.

Peripheral blood monocytes and tissue macrophages contribute significantly to the inflammatory response. Bacterial lipopolysaccharide (LPS) has profound effects on these cells including, but not limited, to differentiation into macrophages, production of reactive nitrogen and oxygen species and secretion of pro-inflammatory cytokines. Herein, we describe a variant of the J774A.1 murine macrophage line that is reversibly resistant to multiple effects of LPS when cultured in different types of media. J774A.1 cells are adherent and spread out when cultured in DMEM/F12; however, when cultured in RPMI 1640, the cells are rounded and relatively non-adherent. Different types of tissue culture plates, sera, and media supplements were not responsible for these changes. We examined LPS-induced reactive nitrogen species using the Greiss reagent. J774A.1 cells cultured in RPMI exhibit a 5-fold increase in nitrites in culture supernatants after LPS stimulation whereas those in DMEM/F12 do not. Zinc staining of total cellular protein of cells in COHLY ET AL. RPMI and DMEM/F12 electrophoresed on a SDS-PAGE showed noticeable banding differences. LPS-induced cytokine gene expression was studied by RT-PCR. LPS induced TNF-alpha, IL-1alpha, IL-1beta, and sIL-1Ra in cells cultured in RPMI but not those cultured in DMEM/F12 with the exception of TNFalpha. This report shows that environmental factors contained in the culture medium alone can reversibly alter the biochemical nature of monocytes and macrophages.

Animals↗
PubMed2000

An open standard platform for interoperability of medical devices.

Patient care in Intensive Care Units and Operating Rooms requires sophisticated instrumentation for monitoring, treatment and control. A major technical problem is the communication between devices, since the connection of medical devices from different manufacturers has similar problems to the communication between people from different countries who do not share a common language. Several proprietary solutions have been developed by initiatives from well-known international companies. These proprietary, non-open solutions have not gained general acceptability and have failed to draw upon the immense resources for instrumentation development which are available in the industry. Consequently, a set of open European standards for Medical Device Intercommunication has recently been created (ratified 1999) to provide the ability to connect devices to each other freely and to exchange data between them. The development of such standards has lead to the design and implementation of a network platform over which those standards could be tested and validated. At the same time guidelines have been defined for the development and deployment of open solutions for any kind of medical device, including existing legacy devices. The design and testing of this open standards implementation is described in this paper.

Computer Communication Networks↗
PubMed1999

Intravascular source of adenosine during forearm ischemia in humans: implications for reactive hyperemia.

It is believed that adenosine is released in ischemic tissues and contributes to reactive hyperemia. We tested this hypothesis in the human forearm using microdialysis to estimate interstitial and intravascular levels of adenosine and caffeine withdrawal to potentiate endogenous adenosine and determine its effect on reactive hyperemia. Forearm blood flow response to ischemia was measured by air plethysmography before and 60 hours after the last dose of caffeine (250 mg TID for 7 days, n=6). Forearm blood flow increased by 274+/-66% and 467+/-97% after 3 minutes of forearm ischemia, before and during caffeine withdrawal, respectively (P<0.05). Thus, caffeine withdrawal enhances reactive hyperemia. To determine the source of adenosine, we measured interstitial adenosine with the use of a microdialysis probe inserted into the flexor digitorum superficialis muscle of the forearm, and we measured intravascular adenosine with the use of a microdialysis probe inserted retrogradely into the medial cubital vein. Dialysate samples were collected at 15-minute intervals during resting, forearm ischemia, and recovery periods. Forearm ischemia failed to increase muscle dialysate concentrations of adenosine but did increase intravascular dialysate adenosine 2.1-fold, from 0.61+/-0.12 to 1.28+/-0.39 micromol/L (P<0.01, n=8). Intravascular dialysate concentrations of thromboxane B2 did not increase during ischemia, ruling out platelet aggregation as a source of adenosine. These results support the hypothesis that endogenous adenosine contributes to reactive hyperemia and indicate that the major source of adenosine in the human forearm is intravascular. We speculate that endothelial cells are the source of intravascular adenosine during ischemia.

Adenosine↗
PubMed1996

Intrathecal synthesis of anti-sulfatide IgG is associated with peripheral nerve disease in acquired immunodeficiency syndrome.

Peripheral nervous system involvement in the acquired immunodeficiency syndrome (AIDS) can take the form of an acute or chronic inflammatory demyelinating polyneuropathy, polyradiculopathy, mononeuropathy multiplex, or autonomic neuropathy. There is no widely held consensus on the etiology of PNS or other neurological complications associated with HIV infection. We report here that PNS disease in HIV-infected individuals is associated with intrathecal synthesis of an antibody directed against sulfatide, a major component of myelin. The anti-sulfatide antibody is also present nonspecifically in serum. The antibody requires the presence of the 3-O-sulfogalactosyl residue for binding and recognizes preferentially the hydroxy fatty acid-containing form of sulfatide. Anti-sulfatide antibodies are therefore one of the humoral factors responsible for demyelinating diseases in AIDS patients.

Acquired Immunodeficiency Syndrome↗
PubMed1991

Topography and morphology of retinal ganglion cells in Falconiforms: a study on predatory and carrion-eating birds.

The topographic distribution of retinal ganglion cells and their cell body size have been studied in five Falconiform species, including predatory (chilean eagle Buteo fuscenses australis, and sparrow hawk Falco sparverius) and carrion-eating (chimango caracara Milvago chimango; condor Vultur gryphus, and black vulture Coragyps atratus) birds. All these species had a well defined nasal fovea and a horizontal streak. Instead of a temporal fovea as in eagles and hawks, an afoveate temporal area is present in chimango, condor, and vulture. The highest ganglion cell density was found in the nasal fovea of Falco and Buteo with 65,000 and 62,000 cells/mm2, respectively. A negative correlation between ganglion cell density and cell body size was found in all the species studied. The specializations of the temporal retina showed a rather homogenous population of medium sized neurons, while the nasal foveas showed a homogeneous population of smaller ganglion cells. Finally, the peripheral retina showed a heterogeneous population of large, medium, and small ganglion cells. Predatory behavior appears to be closely related to foveal specializations, and is best exemplified in the eagle and hawk and to a lesser extent in the chimango.

Animals↗
PubMed1991

Velocardiofacial (Shprintzen) syndrome: an important syndrome for the dysmorphologist to recognise.

We report the dysmorphological, genetic, and speech therapy aspects of 38 cases of velocardiofacial syndrome presenting to a craniofacial clinic and a specialised children's hospital, to indicate a relatively low incidence of clefting, good response to pharyngoplasty, considerable variability of the syndrome, and two further familial cases. We emphasise the low index of suspicion by paediatricians and paediatric subspecialists which resulted in delayed diagnosis and delayed treatment for the hypernasal speech and velopharyngeal insufficiency for periods of four months to seven years.

Abnormalities, Multiple↗
PubMed1991

[A new demographic classification of the family for the use in primary health care].

The approach to the health-disease problem in the family requires a knowledge of demographic features. We propose a demographic classification based on the nuclear family. In addition to the extensive and single-parent families, the lack of family and the familial equivalents we subdivide the nuclear family depending on whether it has close relatives or not, the number of children, the existence of extended family or not, with relatives or aggregates, and the binuclear families or those of divorced people. On this basis, we have evaluated the demographic distribution of 917 families from the basic health areas of Albaicín and Cartuja in Granada, the Valle de Jaén, and Telde in Las Palmas. We have found the predominance of the nuclear family (76.8%) over the extensive (5.2%), as well as the relevance of the single-parent (8.9%) and the lack of family (7.7%) types. Among nuclear families, those with relatives in near areas come first (62.2%), followed by the extended type (19.6%). There is a remarkably low rate of numerous families (9.3%), while binuclear families are exceptional. As familial demography is a factor to be considered in clinical practice owing to its influence in the familial function and resources, we propose the routine use of this classification in the family history.

Demography↗
PubMed1987

Diagnosis of lung carcinoid with cutaneous hyperpigmentation eight years after bilateral adrenalectomy.

A 26-yr-old male was submitted to bilateral adrenalectomy in 1977 for Cushing's syndrome. Some months later he developed intense skin hyperpigmentation together with increased ACTH levels (149 to 4000 ng/l). The sellar region was always normal in X-ray studies. In April 1985, when the patient complained of chest pain, a chest x-ray showed a polycyclic mass in the upper left lobe of the lung. ACTH ranged from 20,000 to 100,000 ng/l, with no response to CRF or cyproheptadine administration. Urinary 5-OH-indolacetic acid was negative. Thoracotomy was performed in July 1985 with resection of two intrapulmonary masses. Histologic study demonstrated a carcinoid tumor, with positive neuron-specific enolase and ACTH immunochemical stain. ACTH concentration in tumoral tissue was 91 pg/g tissue. After surgery ACTH fell dramatically to 37 ng/l, and has remained at this level since then, associated with resolution of the skin hyperpigmentation.

Adrenalectomy↗