Search PubMed⌕ Search

Biomedical subjects

S Martinez

Publications and source records attributed to S Martinez.

At least 109 records · Page 6Linked to original sources
PubMed1992

Reduced junctional permeability at interrhombomeric boundaries.

Intercellular communication is considered to have a role during pattern specification processes in early embryonic development. This report analyzes the changing gap junctional communication properties of chick neuroepithelial cells depending on their position relative to the segmental partitions of the rhombencephalon. Intercellular electrical coupling and dye transfer were studied with microelectrode techniques. Neuroepithelial cells were electrically coupled irrespective of their location relative to interneuromeric boundaries. Iontophoretic injection of biocytin or Lucifer Yellow into single cells inside the rhombomeres was followed by transjunctional diffusion to the surrounding cells. In contrast, dye transfer was strictly limited when the diffusion zone contacted the cells forming the interneuromeric limits. Label injected into the boundary cells did not spread to other cells at all. Avian interrhombomeric boundaries are thus sites of reduced junctional permeability during early morphogenesis.

Animals↗
PubMed1992

Detection of acute avascular necrosis of the femoral head in dogs: dynamic contrast-enhanced MR imaging vs spin-echo and STIR sequences.

OBJECTIVE: Spin-echo MR imaging has been shown to be highly sensitive in the detection of avascular necrosis. Very early avascular necrosis can, however, appear normal on MR images. We compared dynamic contrast-enhanced MR imaging with conventional spin-echo and short Tl inversion-recovery (STIR) sequences for detecting acute osteonecrosis in an animal model. MATERIALS AND METHODS: Avascular necrosis was induced unilaterally in the femoral heads of five dogs that were imaged with a 1.5-T system within 3 hr of devascularization. After standard T1-weighted, T2-weighted, and STIR images, gradient-recalled echo images, 28/5 (TR/TE) with a 45 degrees flip angle, were obtained at 6-sec intervals for 90 sec synchronous with the IV administration of 0.2 mmol of gadoteridol per kilogram of body weight at a rate of 2 ml/sec via an automated injector. Two animals were reimaged after 7 days. RESULTS: Spin-echo and STIR images did not show any acute changes in the ischemic femoral heads. In contrast, significant differences were present in the enhancement profiles of the marrow spaces in the normal and ischemic femoral heads (p = .005). Normal marrow was characterized by rapid enhancement, with an average signal intensity increase of 83% peaking at 36 sec; no measurable enhancement was seen in the marrow of the ischemic femoral head. Spin-echo images, obtained 7 days after devascularization (n = 2), showed changes characteristic of avascular necrosis. Dynamic contrast-enhanced MR images showed persistent lack of enhancement in the avascular marrow of the ischemic femoral head. A junctional zone, characterized by rapid contrast enhancement in excess of 120% without early washout, was identified at the interface between normal and avascular marrow. CONCLUSION: In this experimental model, dynamic contrast-enhanced MR imaging proved significantly more sensitive than conventional spin-echo and STIR imaging in the detection of acute avascular necrosis.

Acute Disease↗
PubMed1992

Radiographic and geometric anatomy of the scapula.

In an effort to study anatomic parameters of the scapula that may be of clinical importance, scapulae were harvested from cadavers and stripped of their soft tissues. For each scapula, three roentgenograms then were obtained: a Y-scapular view, an axillary lateral view, and a glenoid fossa (or true anteroposterior) view. Computed tomographic pneumoarthrograms and randomly selected antero-posterior chest roentgenograms of skeletally mature adults were studied also to measure further roentgenographic parameters of the normal scapula. The geometric anatomy of the scapula is of fundamental importance in the pathomechanics of rotator cuff disease, total shoulder arthroplasty, and recurrent shoulder dislocation. This study presents in detail the exact geometry of scapula anatomy, giving precise figures for distances, angles, and radii of curvature of the scapula. All results then are discussed in terms of their clinical relevance to the above problems.

Arthrography↗
PubMed1991

Gonococcal osteomyelitis. Case report and review of the literature.

We report the 11th case of gonococcal osteomyelitis in the postantibiotic era. This case demonstrates the classic presentation of osteomyelitis associated with gonorrhea, a subacute illness with minimal systemic symptoms. In addition, we present radiologic evidence of the pathogenesis of this unusual osteomyelitis from a contiguous joint infection.

Adult↗
PubMed1991

X-linked hypophosphatemic rickets without "rickets".

Wrist and knee radiographs from children with X-linked hypophosphatemic rickets were analyzed and compared with those from normal children and children with established rickets to assess whether radiographically apparent rickets is a consistent abnormality in X-linked hypophosphatemia. The absence or presence of rickets was correctly identified in 94.8% of wrist and knee films from normal and positive controls. In contrast, patients with X-linked hypophosphatemia exhibited rachitic abnormalities in only 5 of 11 wrist and 13 of 15 knee radiographs. As a result, 4 patients within this study group had rickets at the knee and not at the wrist, whereas 5 displayed classic defects at both sites. Perhaps more important, 2 patients, aged 3.8 and 5.2 years, displayed no evidence of rickets in either wrist or knee films, although relatives exhibited demonstrable rachitic abnormalities. Our data indicate that radiographically detectable rickets is a variable abnormality of X-linked hypophosphatemia and does not provide an unambiguous index for the diagnosis of this disease.

Adolescent↗
PubMed1991

Induction of a mesencephalic phenotype in the 2-day-old chick prosencephalon is preceded by the early expression of the homeobox gene en.

The homeobox gene en, homologous to the gene en-grailed of Drosophila, is expressed in the metencephalic-mesencephalic segment of the vertebrate neural tube. Using quail-chick chimeras, an antibody against en proteins, and cytoarchitectonic techniques, we demonstrate that metencephalon transplanted to prosencephalon, at E2, maintains a high level of en proteins and its presumptive cerebellar fate. The ectopic metencephalon induces in the contiguous host prosencephalon the expression of en and, subsequently, a mesencephalic phenotype. These related genetic and phenotypic expressions indicate that the transcriptional regulatory en gene is involved in cerebellar and mesencephalic cyto-differentiation. The expression of en can also be induced in chick prosencephalon by a mammalian metencephalic graft, indicating that the factors regulating the transcription of en are phylogenetically well conserved.

Animals↗
PubMed1991

Uremic tumoral calcinosis: preliminary observations suggesting an association with aberrant vitamin D homeostasis.

Periarticular tumoral calcification is a unique form of soft tissue calcification that occurs infrequently in patients with end-stage renal disease. The mechanism underlying such massive periarticular calcifications is unknown. The radiographic similarity between uremic tumoral calcifications and those found in hereditary tumoral calcinosis, a disorder of calcitriol and phosphorus homeostasis, caused us to examine whether abnormalities in vitamin D metabolism were associated with uremic calcinosis as well. We examined two uremic subjects with massive periarticular tumoral calcifications and found that they had inappropriately high serum calcitriol levels for the degree of renal function, hyperparathyroidism, and hyperphosphatemia. The source of calcitriol could not be identified in one subject, but likely was derived from granulomatous tissue in the other. In the subject with marrow granulomas, we found that calcitonin administration further stimulated calcitriol production. Although epidemiological studies are needed to confirm this preliminary association between calcitriol and uremic tumoral calcinosis, our observations suggest that normal serum calcitriol levels in association with hyperphosphatemia may be a contributing factor in the development of this rare disorder.

Adult↗
PubMed1990

Molecular cloning and sequence determination of four different cDNA species coding for alpha-subunits of G proteins from Xenopus laevis oocytes.

A cDNA library prepared from Xenopus laevis oocytes in lambda gt10 was screened with a mixture of three oligonucleotide probes designed to detect sequences found in different mammalian genes coding for alpha-subunits of G-proteins. In addition to a clone coding for a G alpha o-type subunit previously reported [(1989) FEBS Lett. 244, 188-192] four additional clones have been found coding for different G alpha protein subunits. By comparison with mammalian alpha-subunits, these oocyte cDNAs correspond to two closely related G alpha s-1a, to a G alpha i-1 and to a G alpha i-3 species. The derived amino acid sequences showed that both G alpha s species contain 379 residues, corresponding to the short species without the serine residue and with a calculated Mr of 42720. The G alpha i-1 gene encodes a 354 amino acid protein with an Mr of 39,000 and the G alpha i-3 encodes an incomplete open reading frame of 345 residues, lacking the first 9 amino acid residues at the NH2 terminus. All these G alpha-subunits showed high identity with their respective mammalian counterparts (75-80%), indicating a great degree of conservation through the evolution and the important cellular regulatory function that they play.

Amino Acid Sequence↗
PubMed1990

Pluripotentiality of the 2-day-old avian germinative neuroepithelium.

In a previous study using chick/quail chimeric embryos with homotopic transplants (Martinez & Alvarado-Mallart, 1989b), we have delimited in the 2-day-old avian embryo the areas of the neural tube giving rise to optic tectum and mesencephalic grissea as well as to isthmic grissea and cerebellum: respectively, "mesencephalic" and "metencephalic" alar plates. To investigate the determination or the competence of these areas, portions of these germinative neuroepithelia from a quail embryo were transplanted in substitution for other areas of the chick neural tube. The analysis of the chimeric brains was done by comparing alternating transverse sections stained for cytoarchitecture and with two different techniques to recognize transplanted versus host cells: either the Feulgen and Rossenbeck DNA histochemical reaction and/or immunohistochemical methods with a monoclonal antibody recognizing quail but not chick cells. The eventual visual innervation of the quail graft was analyzed in many cases by injecting anterograde axonal tracers in the eye contralateral to the graft. The results are as follows: (1) caudal metencephalon transferred to mesencephalon maintained in all cases its presumptive cerebellar phenotype, whereas (2) rostral metencephalon transferred to mesencephalon changed its fate to a tectal phenotype but maintained its cerebellar fate when transferred to diencephalon; (3) caudal mesencephalon maintained its tectal fate in 65% of the cases when transferred to diencephalon, whereas (4) rostral mesencephalon transferred to a cerebellar domain changed its fate and became influenced by the surrounding structures in all cases, but only in 85% of the cases when it was transplanted to diencephalon; (5) the in situ host diencephalon, isolated from its normal environment by a mesencephalic graft, is competent to change its fate and express a mesencephalic phenotype. These results demonstrate that at least some regions of the germinative neuroepithelium from either metencephalon, mesencephalon, and diencephalon are still pluripotent in the 2-day-old avian embryo and that their fate seems to be under the influence of the surrounding structures. Rostral mesencephalon and rostral metencephalon have been more easily influenced by environmental factors than their caudal counterparts, suggesting that regions providing instructive positional factors exist within the 2-day-old germinative neuroepithelium. These regions might play an important role in the determination of the various segments of the neural tube.

Animals↗
PubMed1990

Expression of the homeobox Chick-en gene in chick/quail chimeras with inverted mes-metencephalic grafts.

The homeobox gene Chick-en, sharing homologies to the engrailed gene of Drosophila, is expressed, during early steps of development, in a restricted area of the chick embryo including mes-metencephalic neuroepithelia. The expression of the Chick-en gene has been analyzed in chick/quail chimeric embryos in which a portion of the 2-day-old mes-metencephalic neuroepithelium has been transplanted in an inverted position. By means of a monoclonal antibody, "Mab 4D9," recognizing engrailed proteins, it is shown that the expression of the Chick-en gene is regulated in the inverted neuroepithelium according to its new position in the host neural tube. The regulation takes place within 20 hr after transplantation. These results, together with previous data demonstrating that the phenotypic expression of the inverted neuroepithelium depends, also, on its new position in the host neural tube, strongly suggest that the engrailed protein could play an important role in the positional specification of the mes-metencephalic neuroepithelium.

Animals↗
PubMed1990

Iliopsoas bursitis: clinical features, radiographic findings, and disease associations.

Inflammation of the iliopsoas bursa is a common manifestation of a wide array of inflammatory, degenerative, and traumatic musculoskeletal conditions. The clinical presentation of iliopsoas bursitis is variable, and includes pain, mass lesion, or compression syndromes of the inguinal compartment. Affected individuals frequently have underlying synovitis of the hip or a history of occupational or recreational injury. Early and accurate diagnosis is facilitated by appropriate radiographic studies.

Aged↗
PubMed1990

Differential expression of the neuronal acetylcholine receptor alpha 2 subunit gene during chick brain development.

In situ hybridization histochemistry reveals localized expression of the nicotinic acetylcholine receptor (nAChR) alpha 2 subunit mRNA restricted to the lateral spiriform nucleus (SpL) of the chick diencephalon. The alpha 2 nAChR transcripts are not detected in immature SpL neurons at 4.5-5 days of embryonic development. They begin to accumulate in the SpL at embryonic day 11 and increase until the newborn stage. Specific alpha 2 cDNA amplification by the polymerase chain reaction shows that during this period, the absolute content of alpha 2 mRNA increases about 20-fold. The expression of the alpha 2 nAChR gene is thus developmentally regulated and appears concomitant with the entry of cholinergic fibers into the SpL, as demonstrated by choline acetyltransferase immunohistochemistry.

Afferent Pathways↗
PubMed1990

Imaging of tumoral calcinosis: new observations.

Five patients with tumoral calcinosis were evaluated with radiography, bone scintigraphy, computed tomography (CT), and magnetic resonance (MR) imaging. The arthropathy of calcium pyrophosphate dihydrate deposition disease was seen in two of the patients and pseudoxanthoma elasticum-like syndrome in three. Identification of calcific particular masses on radiographs is characteristic of tumoral calcinosis. Marrow lesions could be identified as patchy areas of calcification (calcific myelitis) in long bones and the calvarium. Bone scintigraphy appears to be the best modality for detection of the masses and marrow lesions and for monitoring therapy. At CT the masses demonstrated a varied appearance, from small and solid to large and cystic. The marrow abnormality appears as an area of increased attenuation and spotty calcification that in the skull may be associated with dural and vascular calcifications. MR imaging of the particular masses was remarkable in that the masses displayed high signal intensity on T2-weighted images despite a large calcific component. Marrow lesions also showed increased signal intensity on T2-weighted images. When calcified particular masses are present the diagnosis is rarely in question. The diagnosis may be overlooked, however, when calcific myelitis is the only manifestation.

Adult↗
PubMed1990

Cervical spondylolysis: imaging findings in 12 patients.

Cervical spondylolysis is defined as a corticated cleft between the superior and inferior articular facets of the articular pilar, the cervical equivalent of the pars interarticularis in the lumbar spine. Associated dysplastic changes and spina bifida suggest that the lesion is congenital. It is a rare condition; only 70 cases have been previously reported in the world literature. Recognition of this disorder and differentiation from traumatic articular pilar fracture or dislocation is of paramount importance in patients who have had cervical spine trauma. The present study details radiologic features in 12 patients 20-80 years old with cervical spondylolysis. Plain film radiologic findings were correlated with hypocycloidal high-resolution tomography (nine patients), CT (six patients), and MR imaging (one patient). Seven patients had spondylolysis at C6 (three bilateral) and five had the abnormality at C4 (all unilateral). Nine of 12 patients were initially misdiagnosed. Characteristic radiologic features include (1) a well-marginated cleft between the facets, (2) a triangular configuration of the pilar fragments on either side of the spondylolytic defect, (3) posterior displacement of the dorsal triangular pillar fragment, (4) hypoplasia of the ipsilateral pedicle, (5) spina bifida at the involved level, and (6) compensatory hyper- or hypoplasia of the ipsilateral articular pillars at the level above and/or below the defect. A multistudy approach was often necessary to demonstrate these findings. Heightened awareness of the radiologic features of cervical spondylolysis should allow one to differentiate it from articular pillar fracture or dislocation.

Adult↗
PubMed1990

Congenital absence of a cervical spine pedicle: clinical and radiologic findings.

Congenital absence of a cervical pedicle is an unusual disorder with potentially confusing clinical and radiologic manifestations. A review of the previously reported 42 cases as well as 13 new cases is presented. Congenital absence of a cervical pedicle was an incidental finding in 10 of the 55 total patients (age range, 3-65 years; mean 31 years). The remainder presented with an array of symptoms; the most common was cervical pain (31 patients), often after trauma (19/31). Neurologic examination was normal in the majority (65%) of patients. The most common neurologic finding, in an additional 19% of patients, was isolated diminished sensation in an upper extremity. Imaging included conventional radiographs, tomograms, myelograms, and CT. The typical radiologic triad of findings included (1) the false appearance of an enlarged neural foramen owing to the absent pedicle; (2) a dysplastic, dorsally displaced ipsilateral articular pillar and lamina; and (3) a dysplastic ipsilateral transverse process. The spectrum of this disorder also included absence of the ipsilateral pillar in four of 55 patients and absence of the entire ipsilateral neural arch in five of 55 patients. Other osseous anomalies were present in 28 (51%) of 55 cases. In 10 of 55 cases, initial misdiagnosis resulted in inappropriate therapy, with a poor clinical outcome after therapy in three cases. Conservative therapy was the only successful management in all cases in which follow-up information was available, with the exception of one patient who had partial improvement after surgery. Careful analysis of radiologic images and knowledge of the specific findings of absent cervical pedicle should decrease the potential for misdiagnosis and inappropriate, potentially harmful therapy.

Adolescent↗
PubMed1990

Pyomyositis in a temperate climate. Presentation, diagnosis, and treatment.

The cases of eighteen patients who were treated for pyomyositis between 1970 and 1988 were evaluated. The diagnosis was often delayed because other primary diagnoses were considered, including muscle strain, synovitis, thrombophlebitis, and neoplasm, and because the symptoms were vague and prolonged (maximum duration, one year). The muscles around the hip and thigh were most commonly involved (twelve patients), and Staphylococcus aureus most commonly grew on culture (twelve patients). Computed tomography aided in the accurate diagnosis of the infection and of the extent of involvement. Incision, drainage, and antibiotic therapy eradicated the infection in all patients, and they had no residual functional limitations and minimum residual symptoms.

Adolescent↗
PubMed1989

Transplanted mesencephalic quail cells colonize selectively all primary visual nuclei of chick diencephalon: a study using heterotopic transplants.

A portion of the quail mesencephalic alar plate (10-12 somites embryos, second day of incubation) was heterotopically transplanted to replace a portion of the diencephalic alar plate of a similar stage chick embryo. Analysis of the chimeric embryos on day 18 of incubation was performed both by Feulgen and Rossenbeck histochemical staining to recognize the transplanted cells, and by cytoarchitectonic methods. The heterotopically transplanted neuroepithelia were integrated in the host pretectal area, although their precise location, substituting some missing host pretectal nuclei, varied slightly from case to case. The cytoarchitecture of the graft and its extension allowed to distinguish two types of transplants: in 50% of the cases the graft developed a laminated, tectal-like structure appearing as a supernumerary optic tectum, whereas in the other 50% of the cases it gave rise to a smaller, not well-defined, non-laminated structure, which could not be recognized as tectal. Independent of the extension and cytoarchitecture of the grafts, in all cases numerous transplanted quail cells were observed beyond the limits of the graft spreading along the optic tract, into all the retino-recipient diencephalic nuclei and into the mesencephalic tectal gray. Conversely, the host optic tectum and the non-primary visual nuclei, even those in close apposition to the transplant, were always devoid of transplanted cells. Analysis of 5- to 10-day-old chimeric embryos has shown that the ectopically located mesencephalic quail cells start migrating from the transplant on day 7 of incubation and follow a tangential pathway at the surface of the diencephalon, throughout the optic tract and between the optic tract and the incipient primary visual nuclei. On day 10, many of these cells have already invaded most of the host retino-recipient nuclei. These observations are discussed with respect to both the phenotypic expression of the transplanted primordium and the tangential migration of tectal cells previously observed in homotopically transplanted chimeric embryos. The possible significance of these results is also discussed.

Animals↗