Dorsal Protrusion Research Articles

The value of oblique versus ventrodorsal myelographic views for lesion lateralisation in canine thoracolumbar disc disease

To determine the value of oblique versus ventrodorsal myelographic views for lesion lateralisation in canine thoracolumbar disc disease. The ventrodorsal and oblique views from 196 lumbar myelograms of dogs with single thoracolumbar disc extrusions or protrusions were blindly and independently reviewed by two of the authors for evidence of lesion lateralisation. Medical records were reviewed for details regarding hemilaminectomy surgery. The side (left versus right) of the surgery and whether or not the disc material was retrieved were noted. Both reviewers lateralised significantly more disc lesions from the oblique views (93 and 95 per cent) than from the ventrodorsal views (59 and 70 per cent) (P<0.001). Using a combination of oblique and ventrodorsal views, 194 (99 per cent) and 195 (99.5 per cent) lesions were lateralised. Unilateral hemilaminectomy was performed in 193 dogs with myelographic lateralisation and in one dog without myelographic lateralisation. The side of spinal cord decompression corresponded with the myelographic findings in all dogs showing lateralisation on myelography. In the dog without myelographic lateralisation, a left (randomly chosen) hemilaminectomy revealed dorsal protrusion of the annulus fibrosus. Myelography, including oblique, ventrodorsal and lateral views, is an accurate method for determining lateralisation of extruded or protruded disc material in the vertebral canal before decompressive surgery. Combined oblique and ventrodorsal views are more useful than either view alone and should be routinely obtained in all lumbar myelographic studies when investigating thoracolumbar disc disease.

Atrial development in the human heart: an immunohistochemical study with emphasis on the role of mesenchymal tissues.

The development of the atrial chambers in the human heart was investigated immunohistochemically using a set of previously described antibodies. This set included the monoclonal antibody 249-9G9, which enabled us to discriminate the endocardial cushion-derived mesenchymal tissues from those derived from extracardiac splanchnic mesoderm, and a monoclonal antibody recognizing the B isoform of creatine kinase, which allowed us to distinguish the right atrial myocardium from the left. The expression patterns obtained with these antibodies, combined with additional histological information derived from the serial sections, permitted us to describe in detail the morphogenetic events involved in the development of the primary atrial septum (septum primum) and the pulmonary vein in human embryos from Carnegie stage 14 onward. The level of expression of creatine kinase B (CK-B) was found to be consistently higher in the left atrial myocardium than in the right, with a sharp boundary between high and low expression located between the primary septum and the left venous valve indicating that the primary septum is part of the left atrial gene-expression domain. This expression pattern of CK-B is reminiscent of that of the homeobox gene Pitx2, which has recently been shown to be important for atrial septation in the mouse. This study also demonstrates a poorly appreciated role of the dorsal mesocardium in cardiac development. From the earliest stage investigated onward, the mesenchyme of the dorsal mesocardium protrudes into the dorsal wall of the primary atrial segment. This dorsal mesenchymal protrusion is continuous with a mesenchymal cap on the leading edge of the primary atrial septum. Neither the mesenchymal tissues of the dorsal protrusion nor the mesenchymal cap on the edge of the primary septum expressed the endocardial tissue antigen recognized by 249-9G9 at any of the stages investigated. The developing pulmonary vein uses the dorsal mesocardium as a conduit to reach the primary atrial segment. Initially, the pulmonary pit, which will becomes the portal of entry for the pulmonary vein, is located along the midline, flanked by two myocardial ridges. As development progresses, tissue remodeling results in the incorporation of the portal of entry of the pulmonary vein in left atrial myocardium, which is recognized because of its high level of creatine. Closure of the primary atrial foramen by the primary atrial septum occurs as a consequence of the fusion of these mesenchymal structures.

The Formation of Catenate Foliar Gemmae and the Origin of Oil Bodies in the Liverwort Odontoschisma denudatum (Mart.) Dum. (Jungermanniales): a Light and Electron Microscope Study

This article describes the ultrastructural events associated with the differentiation and liberation of the exogenous gemmae produced in branched acropetal chains along the margins of the leaves in the liverwort Odontoschisma denudatum. Formation of a dorsal protrusion from young leaf cells containing a large central nucleus, small vacuoles, starch-free chloroplasts, scattered cytoplasmic lipid droplets but no oil bodies, signals the onset of the formation of the initial cell of a gemmiferous filament. The protrusion enlarges and the nucleus migrates into its base, therein dividing with the equator of the spindle virtually filling the central isthmus between the leaf surface and the now swollen tip of the initial cell. Subsequent divisions of the initial cell produce a chain of cells in atropetal succession. Transversely orientated microtubules line the cortical cytoplasm along the lateral walls of the terminal cells of the gemmiferous filaments, but are absent from the tips, thus suggesting that these cells elongate by intercalary, rather than by tip, growth. During mitosis microtubules are closely associated with the envelopes of spindle-shaped prophase nuclei, radiate from ill-defined spindle poles surrounded by plastids at metaphase and anaphase and form a dense phragmoplast array during telophase. Pre-prophase bands are absent and it may be that the nuclear equator determines the plane of division in gemmiferous filaments. Chloroplast division, associated with extremely transient plastid-dividing rings, takes place during interphase. Lateral branches of the growing filaments arise from subapical cells by reiteration of the first division mechanism. Immediately following the proliferative divisions, which take place in cells measuring only 5-6 μm in diameter, oil bodies suddenly appear as flat pleomorphic cisternae associated with endoplasmic reticulum and occasional microtubules. Their contents are electron-transparent apart from scattered osmiophilic droplets. Throughout their ontogeny the oil bodies are closely associated with cytoplasmic lipid bodies but there is no evidence of fusion. The nascent oil bodies swell rapidly to their final diameter, become ovoid to spherical in outline and are eventually suspended by fine cytoplasmic bridges within the vacuoles. The latter rapidly increase in size together with an expansion of the cells themselves until these reach their final diameter and length. The final event in gemma maturation is an endogenous division with the formation of a new internal wall along a phragmosome. Separation of the bicellular gemmae proceeds basipetally and involves the appearance of an electron-transparent line along the middle lamella in the cross walls, which often develop convex thickenings, and severing of the plasmodesmata. After their liberation shallow scars are visible on the leaf surface under the SEM. Gemma maturation sees a marked increase in the electron-opacity of the walls and dense staining of these together with Golgi vesicles with the periodic acid/thiocarbohydrazide/silver proteinate test for non-cellulosic carbohydrates. This change in wall chemistry and ultrastructure may be related to the fact that the maturing gemmae become extremely water repellant and are probably dispersed either on the surface of water films or in the air.

Hereditary myopathy of Devon rex cats

ABSTRACTSix closely related Devon rex cats afflicted with a congenital muscle disease were investigated over a three‐year period. Physical findings included passive ventroflexion of the head and neck, dorsal protrusion of the scapulae, megaoesophagus, generalised appendicular weakness and fatigability. Signs became evident at three to 23 weeks of age and then usually progressed slowly or remained static. Plasma levels of creatine kinase and aspartate aminotransferase were not elevated. Histological examination of tissues from affected cats showed changes indicative of a primary myopathy, with neither nerve nor spinal cord involvement. Four of the six cats died suddenly of laryngospasm after obstruction of the pharynx or larynx with food.

Central nervous system malformations induced by triamcinolone acetonide in nonhuman primates: pathogenesis.

The pathogenetic sequence for TAC-induced encephalocele is in agreement with hypotheses proposing that neural tube closure is followed by protrusion of the mesencephalon, with subsequent growth and development resulting in herniation of the cerebrum and cerebellum. This model could serve to clarify the pathogenesis of encephalocele and to stimulate further study in comparing this defect to other dysraphic states. Triamcinolone acetonide (TAC) was administered intramuscularly (10 mg/kg) to 16 pregnant rhesus monkeys (Macaca mulatta) for 5 alternate days of pregnancy, beginning on gestational day (GD) 23. Conceptuses were removed by hysterotomy at GD 35, 42, 50, or 70 and examined grossly and histologically. Length, area, and perimeter of the tectum and aqueduct area and perimeter were measured with an image analyzer. Changes in treated specimens were suggestive of forces within or ventral to the tectum resulting in dorsal protrusion, rostral-posterior stretching, and attenuation. The angle of the cephalic, pontine, and cervical flexures was also measured. The more acute angle of the cephalic flexure and less acute cervical flexure of treated specimens could represent altered orientation secondary to a mesenchymal deficiency. However, the less acute angle of the pontine flexure in treated specimens suggests an intrinsic alteration in the neural tube. This suggests that encephalocele may result from a combination of mesenchymal and neural tube abnormalities.

Disc Protrusion in the Cat: Ventral Protrusions and Radial Splits

SUMMARY Ventral protrusions and radial splits of the intervertebral discs have been investigated in 100 adult cats, 50 being of known age. Forty-eight of the latter were also examined for osteophytes. The ventral protrusions were either diffuse mounds or discrete knobs; clear splits of the annulus usually led towards the protrusion, but the annulus was seldom completely perforated. They were found in 23 cats. Forty-nine discs were affected, most of them (69 per cent) being between T10 and S1. There were no true lateral protrusions. In 15 cats with ventral protrusions there were 189 discs with osteophytes, and 21 of these had a ventral protrusion as well: 12 other discs had ventral protrusions, but no osteophytes. It cannot be said that osteophytes cause ventral protrusions, nor vice versa, but there was some statistical evidence that they may share causal factors in the cervical and lumbar regions. Radial splits consisted of outward distortion or radial rupture of lamellae unaccompanied by protrusion. These were found in 27 cats, affecting 43 discs, most of which (58 per cent) lay between T10 and S1, Ventral splits accounted for 60 per cent, and these occurred mostly between T10 and S1. Dorsal splits (19 per cent) were mainly cervical. Lateral splits (21 per cent) were irregularly scattered. Radial splits may be precursors of protrusions. Radial splits first occurred at 6 years old, ventral protrusions at 10. Over 80 per cent of both were found in cats 14 years old or more; therefore, both are essentially phenomena of senility. The nucleus pulposus was still gelatinous in 20 per cent of discs with ventral protrusions and 9 per cent with radial splits. This casts doubt on the orthodox concept that protrusions originate from degeneration of the nucleus pulposus. The findings suggest that one set of anatomical or biomechanical factors is needed to explain the distribution of dorsal protrusions and another for ventral protrusions. The low incidence of radial splits and ventral protrusions in the first 9 thoracic discs indicates that the conjugal ligament is not the only factor restricting dorsal protrusion in this region.