Comparison of transferrin receptor-mediated endocytosis and drug- induced endocytosis in human neonatal and adult RBCs

Neonatal RBCs can undergo receptor-mediated endocytosis; normal adult RBCs cannot. Previously, we showed that drug-induced endocytosis, which can occur in adult RBCs exposed to amphipathic cations like primaquine, is greatly enhanced in all density-defined fractions of neonatal RBCs. To investigate the similarities and differences between receptor- mediated endocytosis and drug-induced endocytosis, we characterized transferrin receptor-mediated endocytosis in neonatal RBCs and compared it with drug-induced endocytosis. Primaquine drug-induced endocytosis is dependent on RBC ATP levels, is invariably preceded by stomatocytosis, and is inhibited by vanadate. In contrast, receptor- mediated endocytosis of transferrin is not preceded by stomatocytosis, is not nearly so dependent on ATP levels as is drug-induced endocytosis, and is not inhibited by vanadate. Furthermore, receptor- mediated endocytosis is quantitatively blocked by preincubation of neonatal RBCs with sodium cyanide, whereas cyanide does not inhibit drug-induced endocytosis in either adult or neonatal RBCs. Morphologic observation of the neonatal RBCs established the fact that only puckered RBCs that exhibited brilliant cresyl blue staining reticulum were capable of undergoing receptor-mediated endocytosis of transferrin. These characteristics identify them as motile R-1 reticulocytes. Reticulocytes in normal adult RBCs were incapable of exhibiting this phenomenon. Thus, receptor-mediated endocytosis, a property of motile reticulocytes in neonatal RBCs, differs from drug- induced endocytosis in its energy requirements, response to inhibitors, and morphologic concomitants.     

Profile of thoracic trauma–An analysis of 350 cases

The incidence of chest trauma is rising rapidly and opinion continues to differ on its management. Our experience with 350 consecutive patients of chest injuries between January, 1983 and June, 1986 was reviewed. There were 300 males and 50 females. The average age was 29 years. Two-hundred and seventy-five (80%) were under forty years of age. The commonest presenting features were pain (100%), and dyspnoea (58.57%). Features of peripheral circulatory failure were found in 20 per cent. Ninety (25.71%) had other associated injuries. Three hundred (85.71%) were treated conservatively with 20 (6.66%) deaths. Forty-eight (13.7%) patients underwent surgical exploration (thoracotomy in 34 and laparotomy in 14 patients) with 8 deaths. Remaining 2 patients died in the casualty soon after arrival. The overall mortality was 8.57 per cent. The average period of hospitalisation was 9.5 days.     

The thoracic aorta studied by MR imaging

Thirty-three patients with a variety of disorders of the thoracic aorta (aneurysm, dissection, Marfan syndrome, coarctation/pseudocoarctation, L-transposition, and Takayasu disease) were evaluated with magnetic resonance (MR) imaging. MR imaging delineated the presence and extent of thoracic aortic aneurysms and showed the relationship of the aneurysm to arch vessels; it also demonstrated intimal flaps and individual lumina in types A and B aortic dissection. Dilation of the ascending aorta in Marfan syndrome and focal narrowing of the aorta in coarctation were well visualized. The anteroposterior and side-to-side relationships of the aorta and pulmonary artery in L-transposition were demonstrated, as were aortic wall thickening and branch vessel narrowing in Takayasu arteritis. Initial experience suggests that MR imaging may provide a noninvasive method for evaluating thoracic aortic disease. Limitations include inferior spatial resolution, occasional difficulty in imaging the entire region of interest in one section, lack of signal from calcifications, and inability to monitor critically ill patients.     

Who wants to be a surgeon? A study of 300 first year medical students

Background  

While medicine in general is becoming more female-dominated, women are still under-represented in surgery. Opinion is divided as to whether this is due to lifestyle considerations, disinterest or perceived discrimination. It is not clear at what stage these careers decisions are made.     

Spontaneous resolution of cholelithiasis in infants

Follow-up sonographic studies of five infants whose initial sonograms had displayed evidence for the diagnosis of cholelithiasis demonstrated spontaneous resolution of the gallbladder defects. These defects may have been caused by tumefactive sludge with acoustic shadowing. Whether sludge or gallstones are being imaged, in the absence of other clinical or imaging evidence of biliary tract disease, conservative (i.e., nonsurgical) management and serial sonograms are recommended.     

Psoas muscle disorders: MR imaging

Nineteen patients with evidence of psoas and iliopsoas abnormalities on computed tomographic (CT) scans (12 with metastases, three with lymphoma, two with hematoma, and two with abscess) were examined with magnetic resonance (MR) imaging. The abnormal psoas could be identified on both T1- and T2-weighted spin-echo images, although T2-weighted sequences provided better contrast. The psoas muscle can be affected by one of three mechanisms: total replacement, lateral displacement, or medial displacement. In four patients in whom the CT study showed apparent enlargement of a psoas muscle, subsequent MR imaging examinations demonstrated that the psoas muscle was compressed and displaced laterally by a paraspinal mass. MR images provided better contrast between the normal and abnormal psoas than CT scans in nine cases; MR images were inferior to CT scans in two cases because calcifications (one case) and air bubbles within an abscess (one case) were not detectable.