RESUMO
Exceptionally preserved sauropod eggshells discovered in Upper Cretaceous (Campanian) deposits in Patagonia, Argentina, contain skeletal remains and soft tissues of embryonic Titanosaurid dinosaurs. To preserve these labile embryonic remains, the rate of mineral precipitation must have superseded post-mortem degradative processes, resulting in virtually instantaneous mineralization of soft tissues. If so, mineralization may also have been rapid enough to retain fragments of original biomolecules in these specimens. To investigate preservation of biomolecular compounds in these well-preserved sauropod dinosaur eggshells, we applied multiple analytical techniques. Results demonstrate organic compounds and antigenic structures similar to those found in extant eggshells.
Assuntos
Dinossauros/embriologia , Dinossauros/genética , Fósseis , Paleontologia/métodos , Animais , Antígenos/química , Argentina , Dinossauros/imunologia , Casca de Ovo/química , Casca de Ovo/diagnóstico por imagem , Casca de Ovo/ultraestrutura , Elementos Químicos , Embrião não Mamífero/química , Embrião não Mamífero/ultraestrutura , Imuno-Histoquímica , Microscopia Eletrônica , Radiografia , Pele/ultraestruturaRESUMO
Late Cretaceous avian bone tissues from Argentina demonstrate exceptional preservation. Skeletal elements are preserved in partial articulation and suspended in three dimensions in a medium-grained sandstone matrix, indicating unusual perimortem taphonomic conditions. Preservation extends to the microstructural and molecular levels. Bone tissues respond to collagenase digestion and histochemical stains. In situ immunohistochemistry localizes binding sites for avian collagen antibodies in fossil tissues. Immunohistochemical studies do not, however, guarantee the preservation of molecular integrity. A protein may retain sufficient antigenicity for antibody binding even though degradation may render it incapable of original function. Therefore, we have applied atomic force microscopy to address the integrity and functionality of retained organic structures. Collagen pull-off measurements not only support immunochemical evidence for collagen preservation for antibody recognition but also imply preservation of the whole molecular integrity. No appreciable differences in collagen pull-off properties were measured between fossil and extant bone samples under physiological conditions.
Assuntos
Osso e Ossos/química , Colágeno/química , Fósseis , Paleontologia , Animais , Argentina , Sítios de Ligação , Aves , Osso e Ossos/ultraestrutura , Colágeno/imunologia , Colagenases/metabolismo , Imuno-Histoquímica/métodos , Microscopia de Força Atômica/métodosRESUMO
En el Instituto de Neurocirugía Asenjo, se estudian 38 casos de Síndrome de Horner para establecer, a partir de la experiencia, pautas que contribuyan al estudio y manejo de estos pacientes. Considerando el examen clínico y las neuroimágenes (TAC cerebral y/o angiografía) se logra determinar con certeza cuál de las tres neuronas de la vía simpática está comprometida en el 90 por ciento de los casos
Assuntos
Humanos , Masculino , Feminino , Pré-Escolar , Adolescente , Adulto , Pessoa de Meia-Idade , Síndrome de Horner/diagnóstico , Sistema Nervoso Simpático/fisiopatologia , Anisocoria/diagnóstico , Síndrome de Horner/etiologia , Síndrome de Horner , Sistema Nervoso Simpático/citologiaRESUMO
Magnetic resonance imaging is frequently complicated by the presence of motion and susceptibility gradients. Also, some biologic tissues have short T2s. These problems are particularly troublesome in fast spin-echo (FSE) imaging, in which T2 decay and motion between echoes result in image blurring and ghost artifacts. The authors reduced TE in conventional spin-echo (SE) imaging to 5 msec and echo spacing (E-space) in FSE imaging to 6 msec. All magnetic gradients (except readout) were kept at a maximum, with data sampling as fast as 125 kHz and only ramp waveforms used. Truncated sinc radio-frequency pulses and asymmetric echo sampling were also used in SE imaging. Short TE (5.8 msec) SE images of the upper abdomen were compared with conventional SE images (TE = 11 msec). Also, FSE images with short E-space were compared with conventional FSE images in multiple body sites. Short TE significantly improved the liver-spleen contrast-to-total noise ratio (C/N) (7.9 vs 4.1, n = 9, P < .01) on T1-weighted SE images, reduced the intensity of ghost artifacts (by 34%, P < .02), and increased the number of available imaging planes by 30%. It also improved delineation of cranial nerves and reduced susceptibility artifacts. On short E-space FSE images, spine, lung, upper abdomen, and musculoskeletal tissues appeared crisper and measured spleen-liver C/N increased significantly (6.9 vs 4.0, n = 12, P < .01). The delineation of tissues with short T2 (eg, cartilage) and motion artifact suppression were also improved. Short TE methods can improve image quality in both SE and FSE imaging and merit further clinical evaluation.
Assuntos
Imageamento por Ressonância Magnética/métodos , Abdome/anatomia & histologia , Vértebras Cervicais/anatomia & histologia , Humanos , Perna (Membro)/anatomia & histologia , Pulmão/anatomia & histologiaRESUMO
A new sign of anterior cruciate ligament (ACL) tear based on secondary changes of the posterior cruciate ligament (PCL) is described. Thirty-one patients with magnetic resonance (MR) examinations of the knee suspicious for ACL injury and 50 normal controls were examined. In each patient a line was drawn adjacent and parallel to the posterior margin of the distal portion of the PCL and was extended proximally. A positive PCL line did not intersect the medullary cavity of the femur. A positive line correctly predicted ACL injury in 19 of 22 patients.
Assuntos
Lesões do Ligamento Cruzado Anterior , Ligamento Cruzado Anterior/patologia , Imageamento por Ressonância Magnética , Adolescente , Adulto , Idoso , Criança , Humanos , Traumatismos do Joelho/patologia , Pessoa de Meia-IdadeRESUMO
A 15 year old patient developed ataxia 2 weeks after an upper respiratory infection. Absent reflexes, external ophthalmoplegia, bilateral ptosis, isochoric mydriasis and week photomotor reflexes (Bell's phenomenon) were noted. A slight increase in protein but not cell content of the CSF was observed. Miller-Fisher syndrome was diagnosed on clinical grounds and visual and auditory evoked potentials were explored and found to be normal. This is in complete agreement to the literature and indicates indemnity of the central nervous system in Miller-Fisher's syndrome. Peripheral nervous system abnormalities that have been identified by pathologic and radiologic studies may explain all of the alterations observed in this syndrome.