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Biomedical subjects

M Domínguez

Publications and source records attributed to M Domínguez.

At least 37 records · Page 2Linked to original sources
PubMed1998

A dorsal/ventral boundary established by Notch controls growth and polarity in the Drosophila eye.

In the Drosophila compound eye the dorsal and ventral fields of eye units (ommatidia) meet along the dorsoventral midline, forming a line of mirror image symmetry called the equator. The molecular mechanism establishing the equator is not fully understood, but it involves the transcription factors encoded by the Iroquois gene complex. The Iroquois genes are expressed in the dorsal half of the eye and here we show that they regulate the expression of the secreted molecule Fringe. A boundary between fringe-expressing and fringe-non-expressing cells is essential, from the time of the second larval instar, for eye growth and formation of the equator. Boundaries of fringe expression determine where the transmembrane receptor Notch is activated. We find that Notch is activated at the dorsoventral midline, where it is required to promote growth and set up the axis of mirror symmetry. As boundaries of fringe expression and Notch activation are also important during Drosophila wing formation and vertebrate somitogenesis, we suggest that these boundaries constitute a general mechanism that directs growth and patterning of large fields of cells.

Animals↗
PubMed1998

Multiple functions of the EGF receptor in Drosophila eye development.

BACKGROUND: During animal development, cells need to make spatially and temporally regulated fate decisions. These decisions are largely controlled by intercellular signalling, often through receptor tyrosine kinases. One of these, the epidermal growth factor receptor (EGFR), regulates multiple cell fate decisions. Its importance in the recruitment of photoreceptors in the developing fly eye, a useful model for neural development, has already been reported. Other EGFR functions in the eye have not been characterised. RESULTS: We have examined the consequences of removing or activating the EGFR at different stages of eye development. The earliest stages of assembly occurred normally within EGFR- clones--the morphogenetic furrow was unimpeded and the R8 photoreceptor was specified. All subsequent photoreceptor recruitment was blocked. EGFR- clones had a characteristic shape indicating that they had undergone substantial cell death posterior to the furrow, where the differentiation program is normally activated; consistent with this, excess apoptosis was detected. We found that the receptor also regulates cell proliferation in the disc, has an early function at the disc margin (where the morphogenetic furrow initiates) and contributes to the regulation of spacing of the R8 precursors. Finally, we found that activation of the receptor is sufficient to trigger non-R8 photoreceptor development, even in cells in front of the furrow or in the absence of the proneural gene atonal. CONCLUSION: At least five distinct functions of EGFR signalling need to be integrated during fly eye development. These include roles in cell proliferation, survival and differentiation.

Animals↗
PubMed1998

[Adherence of Acinetobacter baumannii to rat tracheal tissue].

BACKGROUND: Acinetobacter baumannii is an important nosocomial pathogen whose virulence factors have not been fully elucidated. AIM: To study the adherence and hemagglutinating capacity of several biotypes of Acinetobacter baumannii. MATERIAL AND METHODS: Thirty nine strains of Acinetobacter baumannii isolated from hospitalized patients were studied. The adherence of these strains to small pieces of rat tracheal tissue was studied. Additionally, their ability to hemagglutinate human erythrocytes and the effect of D-mannose and D-galactose on the adherence and hemagglutinating capacity was assessed. Transmission electron microscopy of strains was performed looking for the presence of fimbriae. RESULTS: All strains exhibited adherence to tissues. All strains had also D-mannose and D-galactose resistant hemagglutinating ability. Fimbriae were found in Acinetobacter baumannii and E coil cells. CONCLUSIONS: Adherence of Acinetobacter baumannii to rat tracheal tissue, apparently not related to the presence of fimbriae, may be a virulence mechanism of this bacterium.

Acinetobacter↗
PubMed1998

[Cardiorespiratory failure and diabetic autonomic neuropathy: a case report].

Advanced autonomic neuropathy in diabetic patients is associated with homeostatic cardiovascular response. Sympathetic compensation diminishes and the organism becomes more susceptible to the depressant effect of certain drugs. The incidence of undesirable cardiovascular effects (bradycardia, hypotension and sudden heart failure) during anesthesia is higher in such patients. We report the case of a woman with diabetes who suffered two episodes of sudden heart failure after brachial plexus block through the axilla, followed one year later by sudden heart failure during general anesthesia for kidney transplantation. The possible contributing mechanisms are described.

Adult↗
PubMed1997

Hedgehog directly controls initiation and propagation of retinal differentiation in the Drosophila eye.

Patterning of the compound eye begins at the posterior edge of the eye imaginal disc and progresses anteriorly toward the disc margin. The advancing front of ommatidial differentiation is marked by the morphogenetic furrow (MF). Here we show by clonal analysis that Hedgehog (Hh), secreted from two distinct populations of cells has two distinct functions: It was well documented that Hh expression in the differentiating photoreceptor cells drives the morphogenetic furrow. Now we show that, in addition, Hh, secreted from cells at the posterior disc margin, is absolutely required for the initiation of patterning and predisposes ommatidial precursor cells to enter ommatidial assembly later. These two functions of Hh in eye patterning are similar to the biphasic requirement for Sonic Hh in patterning of the ventral neural tube in vertebrates. We show further that Hh induces ommatidial development in the absence of its secondary signals Wingless (Wg) and Dpp and that the primary function of Dpp in MF initiation is the repression of wg, which prevents ommatidial differentiation. Our results show that the regulatory relationships between Hh, Dpp, and Wg in the eye are similar to those found in other imaginal discs such as the leg disc despite obvious differences in their modes of development.

Animals↗
PubMed1997

[Isolated vasculitis of the peripheral nervous system].

We present a patient with a subacute asymmetrical sensorimotor polyneuropathy. The pathological features were predominantly loss of nerve fibers, axonal degeneration and healed vasculitis. The epineural vessels were involved, while endoneurial capillaires were preserved. Muscle biopsy revealed neurogenic features with normal blood vessels. After three years, motor and sensory function was almost normal, without any specific treatment. No abnormal findings suggesting collagen diseases or other underlying immunological disorders were obtained by various laboratory tests. In conclusion, the present case strongly suggests that the vasculitis was confined to the peripheral nerves.

Humans↗
PubMed1996

Sending and receiving the hedgehog signal: control by the Drosophila Gli protein Cubitus interruptus.

Drosophila limb development is organized by interactions between anterior and posterior compartment cells. Posterior cells continuously express and require engrailed (en) and secrete Hedgehog (Hh) protein. Anterior cells express the zinc-finger protein Cubitus interruptus (Ci). It is now shown that anterior cells lacking ci express hh and adopt posterior properties without expressing en. Increased levels of Ci can induce the expression of the Hh target gene decapentaplegic (dpp) in a Hh-independent manner. Thus, expression of Ci in anterior cells controls limb development (i) by restricting hh secretion to posterior cells and (ii) by conferring competence to respond to Hh by mediating the transduction of this signal.

Animals↗
PubMed1995

Control of Drosophila photoreceptor cell fates by phyllopod, a novel nuclear protein acting downstream of the Raf kinase.

The phyllopod (phyl) gene regulates the fates of a subset of cells in the developing Drosophila eye; in the absence of phyl function, the R1, R6, and R7 photoreceptors are transformed into additional cone cells, whereas ectopic phyl expression in the cone cell precursors transforms these cells into additional R7 cells. Within this group of cells, phyl expression thus mimics activation of the Raf pathway in its ability to induce photoreceptor rather than cone cell development. Furthermore, the transformation of cone cells into R7 cells in response to Raf activation is both accompanied by and dependent upon ectopic phyl expression. phyl thus represents a possible target gene of the Raf pathway during eye development, controlling the fates of a novel subset of photoreceptors.

Amino Acid Sequence↗
PubMed1995

[Enzymatic mechanisms of resistance to aminoglycoside antibiotics in gram negative bacilli from Chilean hospitals].

The presence of aminoglycoside modifying enzymes (AMEs) has been investigated, by an agar diffusion method, in 344 strains of aminoglycoside-resistant Gram negative bacilli isolated in different Chilean hospitals. Most of the strains exhibited a combination of enzymatic mechanism of resistance, but two acetylating (AAC(3)II and AAC(6')I) and one phosphorylating (APH(3')I) enzymes were the main mechanism detected in the strains. A significant increase in the frequency of strains producing AAC(6')I, possible due to wide use of amikacin, has been found when results were compared with those of a report published in 1985.

Aminoglycosides↗
PubMed1995

[Fine needle aspiration biopsy of thyroid nodules. Analysis of results obtained using a new method with histological examination of the sample].

Fine needle aspiration biopsy (FNAB) is the most useful preoperative work up method for patients with nodular goiter. We analyze 173 patients that underwent FNAB and were subsequently operated. The sample with FNAB was processed both for cytological and histological study, using methods developed at the hospital. The preoperative diagnosis reached was compared with that obtained with the surgical piece. Results showed that the histological analysis of the FNAB sample improved the sensitivity of the method, when compared with the cytological study, from 68.5% to 87.8% (p < 0.035) without modifying specificity (100% for both methods). It is concluded that FNAB with histological study of the sample has a high diagnostic yield and is exempt of complications.

Adolescent↗
PubMed1994

[Peripheral neuropathy and mixed cryoglobulinemia: clinical, neuro- physiological and pathological signs in a group of 12 patients].

This retrospective study involved a series of 12 patients with peripheral neuropathy and mixed type III cryoglobulinemia. The predominating symptoms were sensory. In patients with essential cryoglobulinemia, neuropathy most often presented as multiple mononeuropathy, while polyneuropathic forms were most common among those with secondary cryoglobulinemia. The absence of cryosensitivity was evident in secondary forms. Both neurophysiological and morphological examination revealed a predominance of axonal neuropathy. Two cases of demyelinating neuropathy were found among those with secondary cryoglobulinemia associated with monoclonal gammopathy. Although the vascular lesion was clearly demonstrable in muscle and skin tissue, this was not so in the nervous system.

Adult↗
PubMed1993

asense, a member of the Drosophila achaete-scute complex, is a proneural and neural differentiation gene.

The asense (ase) gene of the achaete-scute complex (AS-C) is expressed in the precursors of all adult sensory organs (SOs), the sensory mother cells (SMCs) and in their immediate progeny. Its deletion causes the loss of some SOs and the abnormal differentiation of part of the remaining ones. These defects, which include malformations of the external part of the SOs, duplication of the innervating neuron etc, are enhanced by the haploid condition for the other AS-C genes and are corrected by an ase transgene. We conclude that ase participates, in combination with other members of the AS-C, in implementing the neural program of differentiation of the SMCs. ase also has a proneural function that participates in the singling out of the SMCs that give rise to the recurved bristles of the anterior wing margin. The proneural potential of ase is shown, in addition, by the generation of SOs induced by the generalized expression of an ase gene driven by a hsp70 promoter.

Animals↗
PubMed1993

Molecular characterization of the lethal of scute genetic function.

The lethal of scute (l'sc) genetic function, which plays an essential role in the early development of the central nervous system of the Drosophila embryo, is localized within the achaete-scute complex (AS-C). Several lines of evidence have suggested that the AS-C T3 transcription unit corresponds to the l'sc function. We demonstrate that short fragments of DNA, containing the T3 transcribed region and a few kilobases of flanking sequences, rescue, albeit partially, the lethality and neural phenotype of l'sc deletions. Still, the complex wild-type pattern of expression of T3 is not reproduced by the transduced genes. This depends on cis-control elements scattered within the entire AS-C DNA and intermingled with regulatory elements specific for other AS-C transcription units. These elements are necessary for the initial activation of T3 in the neuroectoderm, probably mediated by axis-patterning genes. The presence of a cluster of E-boxes, upstream of the T3 transcribed region, suggests another level of control of T3 expression by basic-helix-loop-helix proteins, among them its own gene product.

Amino Acid Sequence↗
PubMed1992

[Peripheral neuropathy and correlation with risk factors in material from autopsies and amputations].

A morphological study of a series of 100 human peroneal nerves proceeding from autopsies and amputations of patients hospitalized for different diseases was performed. A relation between the morphologic findings and the risk factors of neuropathy to which the patients may have been exposed is established. Following the analysis of their results the authors found that peripheral neuropathy is more frequent than suspected in clinical practice. The peripheral nerve is relatively resistant to regional ischemia. The risk factors considered in the casuist included diabetes as that which most influences in determining morphological alterations compatible with neuropathy.

Adolescent↗