The instability of the membrane skeleton in thalassemic red blood cells

The thalassemias are a heterogeneous group of disorders characterized by accumulation either of unmatched alpha or beta globin chains. These in turn cause the intramedullary and peripheral hemolysis that leads to varying anemia. A partial explanation for the hemolysis came our of our studies on material properties that showed that beta-thalassemia (beta- thal) intermedia ghosts were very rigid but unstable. A clue to this instability came from the observation that the spectrin/band 3 ratio was low in red blood cells (RBCs) of splenectomized beta-thal intermedia patients. The possible explanations for the apparent decrease in spectrin content included deficient or defective spectrin synthesis in thalassemic erythroid precursors or globin chain-induced membrane changes that lead to spectrin dissociation from the membrane during ghost preparation. To explore the latter alternative, samples from different thalassemic variants were obtained, ie, beta-thal intermedia, HbE/beta-thal, HbH (alpha-thal-1/alpha-thal-2), HbH/Constant Spring (CS), and homozygous HbCS/CS. We searched for the presence of spectrin in the first lysate of the standard ghost preparation. Normal individuals and patients with autoimmune hemolytic anemia, sickle cell anemia, and anemia due to chemotherapy served as controls. Using gradient sodium dodecyl sulfate-polyacrylamide gel electrophoresis analysis, no spectrin was detected in identical aliquots of the supernatants of normals and these control samples. Varying amounts of spectrin were detected in the first lysate supernatants of almost all thalassemic patients. The identification of spectrin was confirmed by Western blotting using an affinity-purified, monospecific, rabbit polyclonal antispectrin antibody. Relative amounts of spectrin detected were as follows in decreasing order: splenectomized beta-thal intermedia including HbE/beta-thal; HbCS/CS; nonsplenectomized beta-thal intermedia, HbH/CS; and, lastly, HbH. These findings were generally confirmed when we used an enzyme-linked immunosorbent assay technique to measure spectrin in the first lysate. Subsequent analyses showed that small amounts of actin and band 4.1 also appeared in lysates of thalassemic RBCs. Therefore, the three major membrane skeletal proteins are, to a varying degree, unstably attached in severe thalassemia. From these studies we could postulate that membrane association of abnormal or partially oxidized alpha- globin chains has a more deleterious effect on the membrane skeleton than do beta-globin chains.     

Delayed hypersensitivity to herpes simplex virus: murine model.

Cell-mediated immunity has been shown to be clinically important in recovery from herpes simplex virus (HSV) infections. To investigate the role of delayed hypersensitivity (DH) in immunity and protection against HSV, we developed a murine model using the ear-swelling assay. Mice were infected subcutaneously with HSV-1 and ear-challenged, and the swelling was quantified. Significant ear swelling was detected by 3 to 4 days postinfection and peaked at 6 days. The kinetics of development of ear swelling were typical of DH: maximal swelling occurred 24 h post challenge and was diminished by 48 h, and the cellular infiltrate was predominantly mononuclear. Four-hour swelling, indicative of antibody-mediated, immediate-type hypersensitivity, was not detected until 15 days post immunization. The DH response was virus specific and could be transferred to normal recipients with lymph node T cells, but not with B cells or immune serum. This system will provide a useful model for evaluating the protective role of DH in HSV infection and for studying the specificity and interaction of T cells which mediate the response.     

The doctor/patient relationship in geriatric care

Information derived from the relationship of the primary care physician with an older patient provides the best possible way to eliminate or minimize many ethical conflicts that arise in the care of the very old. The conscientious physician can seek information regarding the patient's personal value scheme and his or her expectations and utilize the breadth of available technology to best serve the patient. Many of the issues raised in this article are discussed in much greater detail in subsequent articles. The discussions of the issues they encompass are intended to inform and to stimulate. There is legitimate reason for optimism that, with education and thoughtful review, physicians will be able to improve the manner in which we care for older individuals.     

A colo-colic invagination on the basis of MutYH-associated polyposis in a boy aged 14

A 14-year-old boy presented with acute abdominal pain, vomiting and diarrhoea. Colo-colic intussusception was diagnosed by means of a colonic contrast X-ray. The intussusception was successfully reduced during this procedure. Hundreds of polyps were seen throughout the entire colon. Genetic research showed a mutation of the MutYH gene. Proctocolectomy with ileoanal pouch anastomosis was carried out. The pathology specimen showed an intramucosal carcinoma and multiple adenomas. MutYH-associated polyposis coli is an autosomal recessive disease that occurs as a result of a mutation in the MutYH gene. This will lead to polyposis coli. An intussusception is a rarely seen symptom. Patients need preventive surgical treatment because of the high risk developing a colorectal carcinoma.     

Effect of beta adrenergic blockade on renin response to renal nerve stimulation.

The ability of d,l-propranolol to block renin secretion in response to various extrarenal stimuli, such as hemorrhage and hypoglycemia, has been interpreted to indicate the presence of an intrarenal beta receptor regulating renin release. However, two problems complicate this interpretation: (a) the stimuli have effects outside the kidney, and (b) d,l-propranolol has a local anesthetic, as well as a beta adrenergic blocking, action. In the present study, the effects of a purely intrarenal stimulus, in the form of renal nerve stimulation (RNS), on renin secretion was examined. The effects of d,l-propranolol (anesthetic and beta-blocking activity), l-propranolol (beta-blocking activity only), and d-propranolol (local anesthetic activity only) on the renin response to RNS were examined. In a control group of animals, two sequential RNS increased mean renin secretion from 401 to 1,255 U/min (P less than 0.25) and from 220 to 2,179 U/min (P less than 0.01). In a second group the first RNS increased renin secretion from 201 to 1,181 U/min (P less than 0.01), but after d,l-propranolol was given RNS did not significantly alter renin secretion (33 to 55 U/min). In a third group the initial RNS increased renin secretion from 378 to 1,802 U/min (P less than 0.025), but after l-propranolol was given RNS had no significant effect on renin secretion (84 to 51 U/min). A fourth group of dogs showed a rise in renin secretion from 205 to 880 U/min (P less than 0.001) in response to the first RNS, while the second RNS, given after an infusion of d-propranolol, caused a rise in renin secretion from 80 to 482 (P less than 0.005). The nature of the electrical stimulus was consistent in all groups and caused no detectable changes in renal or systemic hemodynamics or in urinary electrolyte excretion. The results, therefore, indicate that renin secretion can be stimulated through intrarenal beta receptors independent of changes in systemic or renal hemodynamics or in tubular sodium reabsorption. Hence the effect of beta stimulation on renin secretion would appear to result from a direct action on the renin-secreting cells of the juxtaglomerular apparatus.     

Smooth muscle calcium and endothelium-derived relaxing factor in the abnormal vascular responses of acute renal failure.

Abnormal renovascular reactivity, characterized by paradoxical vasoconstriction to a reduction in renal perfusion pressure (RPP) in the autoregulatory range, increased sensitivity to renal nerve stimulation (RNS), and loss of vasodilatation to acetylcholine have all been demonstrated in ischemic acute renal failure (ARF). To determine if ischemic injury alters vascular contractility by increasing smooth muscle cell calcium or calcium influx, the renal blood flow (RBF) response to reductions in RPP within the autoregulatory range and to RNS were tested before and after a 90-min intrarenal infusion of verapamil or diltiazem in 7-d ischemic ARF rats. Both calcium entry blockers, verapamil and diltiazem, blocked the aberrant vasoconstrictor response to a reduction in RPP and RNS (both P less than 0.001). In a second series of experiments the potential role of an ischemia-induced endothelial injury and of the absence of endothelium-derived relaxing factor (EDRF) production were examined to explain the lack of vasodilatation to acetylcholine. Acetylcholine, bradykinin (a second EDRF-dependent vasodilator), or prostacyclin, an EDRF-independent vasodilator, was infused intrarenally for 90 min, and RBF responses to a reduction in RPP and RNS were tested in 7-d ischemic ARF rats. Neither acetylcholine nor bradykinin caused vasodilatation or altered the slope of the relationship between RBF and RPP. By contrast, prostacyclin increased RBF (P less than 0.001), but did not change the vascular response to changes in RPP. It was concluded that the abnormal pressor sensitivity to a reduction in RPP and RNS was due to changes in renovascular smooth muscle cell calcium activity that could be blocked by calcium entry blockers. A lack of response to EDRF-dependent vasodilators, as a result of ischemic endothelial injury, may contribute to the increased pressor sensitivity of the renal vessels.