The effect of an osmotic stimulus on the release of neurohypophysial hormones in the cat: preferential release of vasopressin with a possible involvement of the area postrema.

Abstract In cats anaesthetized with intravenous chloralose, the injection of 0.05 to 0.4 ml 1.54 M NaCl solution (hypertonic saline, HS) into a lateral cerebral ventricle caused a large release of vasopressin. The concentration of vasopressin greatly exceeded that of oxytocin in the same samples of plasma. Vasopressin was also released when HS was injected into the fourth ventricle and into the cisterna magna from which there is no access in the cat to the ventricles, but it was less effective by these routes than when injected into a lateral ventricle in the same cat. This suggests a possible action of HS on circumventricular organs related to the third ventricle but also indicates an additional site of action reached from the subarachnoid space which would give access to the ventral and dorsal surfaces of the brainstem. Vasopressin was not released on topical application of HS to the 'nicotine sensitive area' on the ventral surface of the brainstem where nicotine acts to release vasopressin without oxytocin. Vasopressin, however, was released without detectable oxytocin on topical appliction of HS to the dorsal surface of the brainstem either outside the fourth ventricle or to the floor of the ventricle at its distal extremity, in the region of the obex. A possible site where HS acts to cause a preferential release of vasopressin on injection into a lateral ventricle is the area postrema, a circumventricular organ which impinges on the walls of the fourth ventricle at the obex. Preferential release of vasopressin might then be mediated by a selective neural input, possibly through the nucleus of the tractus solitarius, from osmoreceptors in the area postrema to the vasopressin-secreting cells in the supraoptic and paraventricular nuclei.

MR imaging of soft-tissue masses in children.

Soft-tissue tumors represent a relatively common problem in the pediatric age group. The MR imaging of these masses is an important part of the evaluation. The heterogeneous appearance of the various tumors makes biopsy necessary in all but the absolutely characteristic lesions. The nonspecific tumors and the "Aunt Minnies" are characterized in this article.

Percutaneous gastrostomy and percutaneous gastrojejunostomy in children: antegrade approach.

Twenty-five percutaneous gastrostomies and nine percutaneous gastrojejunostomies were performed in 24 children aged 4 months to 22 years. Indications for percutaneous gastrostomy included severe injury to the central nervous system (nine patients), malignancy (seven patients), failure to thrive (four patients), degenerative central nervous system disease (one patient), and miscellaneous conditions (three patients). All procedures were performed under local anesthesia and sedation. An antegrade approach is described for percutaneous gastrostomy and percutaneous gastrojejunostomy placement. No major complication occurred, and only three skin infections have been encountered. The children were evaluated and followed up by a nutritional support team. Early experience with percutaneous gastrostomy and percutaneous gastrojejunostomy in the pediatric population suggests that the technique is safe and applicable to children of all ages and sizes. In particular, the antegrade approach appears to be an acceptable solution for enteric alimentation.

Normal changes in the MR appearance of the spleen during early childhood.

OBJECTIVE: During the first year of life, the spleen undergoes histologic changes as the lymphoproliferative system matures. The purposes of this study were to describe the normal MR appearance of the spleen during infancy and early childhood and to correlate imaging findings with age-related histologic changes. MATERIALS AND METHODS: The spleen was evaluated on 28 abdominal MR studies obtained during the first 23 months of life. Splenic signal intensity was compared to that of the liver. Selected autopsy specimens were compared with the imaging results. RESULTS: The T2-weighted signal intensity of the spleen gradually increased from isointense to hypointense relative to the liver during the first week of life to moderately hyperintense to the liver by 8 months of age. T1-weighted splenic signal intensity gradually decreased. These findings corresponded to histological increases in white-pulp-red-pulp ratios. CONCLUSION: Before the lymphoid system completely matures, the T2-weighted signal intensity of the normal neonatal spleen appears decreased compared with the moderately hyperintense splenic signal seen in older children and adults. This finding should not be mistaken for disease.

MR features of soft-tissue abnormalities due to acute marrow infarction in five children with sickle cell disease.

OBJECTIVE: The purpose of this investigation was to illustrate a variety of soft-tissue abnormalities on MR imaging encountered in connection with acute marrow infarction in children with sickle cell disease. CONCLUSION: Extraosseous abnormalities on MR imaging preclude differentiation of acute marrow infarction from osteomyelitis in children with sickle cell disease.

Cementless femoral fixation in the rheumatoid patient undergoing total hip arthroplasty: minimum 5-year results.

Sixty-two total hip arthroplasties in 49 patients with a diagnosis of rheumatoid arthritis were performed between November 1986 and December 1992. All components were titanium alloy with a circumferential plasma-spray porous coating. Four patients (4 hips) died before 5-year follow-up, and 6 patients (8 hips) were lost to follow-up, leaving 39 patients (50 hips) for review at a minimum 5-year follow-up after surgery (mean, 8 years; range, 5-12 years). There were 12 men and 27 women, with a mean age at time of surgery of 55 years (range, 25-77 years) and a mean weight of 69 kg (range, 42-109 kg). Compared with the preoperative Charnley scores, there was significant improvement in the postoperative scores: pain, from 2.7 to 5.7, and function, from 3.2 to 5.3. Thigh pain was present in 1 patient (1 hip) (2.0%). No femoral fractures occurred intraoperatively with the insertion of the prosthesis. Spot welds consistent with bone ingrowth were identified in all of the femoral components. No femoral components showed evidence of radiographic loosening or required revision for aseptic loosening or incapacitating thigh pain, but 7 acetabular revisions were performed. Uncemented femoral fixation with this component design in rheumatoid patients appears to be a promising treatment.