Sulfatide Preserves Insulin Crystals Not by Being Integrated in the Lattice but by Stabilizing Their Surface

BACKGROUND

Sulfatide is known to chaperone insulin crystallization within the pancreatic beta cell, but it is not known if this results from sulfatide being integrated inside the crystal structure or by binding the surface of the crystal. With this study, we aimed to characterize the molecular mechanisms underlying the integral role for sulfatide in stabilizing insulin crystals prior to exocytosis.

METHODS

We cocrystallized human insulin in the presence of sulfatide and solved the structure by molecular replacement.

RESULTS

The crystal structure of insulin crystallized in the presence of sulfatide does not reveal ordered occupancy representing sulfatide in the crystal lattice, suggesting that sulfatide does not permeate the crystal lattice but exerts its stabilizing effect by alternative interactions such as on the external surface of insulin crystals.

CONCLUSIONS

Sulfatide is known to stabilize insulin crystals, and we demonstrate here that in beta cells sulfatide is likely coating insulin crystals. However, there is no evidence for sulfatide to be built into the crystal lattice.

Lowering the hemoglobin threshold for transfusion in coronary artery bypass procedures: effect on patient outcome

BACKGROUND

There is controversy regarding the application of transfusion triggers in cardiac surgery. The goal of this study was to determine if lowering the hemoglobin threshold for red cell (RBC) transfusion to 8 g per dL after coronary artery bypass graft surgery would reduce blood use without adversely affecting patient outcome.

STUDY DESIGN AND METHODS

Consecutive patients (n = 428) undergoing elective primary coronary artery bypass graft surgery were randomly assigned to two groups: study patients (n = 212) received RBC transfusions in the postoperative period if the Hb level was < 8 g per dL or if predetermined clinical conditions required RBC support, and control patients (n = 216) were treated according to individual physician's orders (hemoglobin levels < 9 g/dL as the institutional guideline). Multiple demographic, procedure-related, transfusion, laboratory, and outcome data were analyzed. Questionnaires were administered for patient self-assessment of fatigue and anemia.

RESULTS

Preoperative and operative clinical characteristics, as well as the intraoperative transfusion rate, were similar for both groups. There was a significant difference between the postoperative RBC transfusion rates in study (0.9 +/- 1.5 RBC units) and control (1.4 +/- 1.8 RBC units) groups (p = 0.005). There was no difference in clinical outcome, including morbidity and mortality rates, in the two groups; group scores for self-assessment of fatigue and anemia were also similar.

CONCLUSIONS

A lower Hb threshold of 8 g per dL does not adversely affect patient outcome. Moreover, RBC resources can be saved without increased risk to the patient.

Blood use in patients undergoing repeat coronary artery bypass graft procedures: multivariate analysis

BACKGROUND

The prevailing clinical opinion is that patients undergoing repeat coronary artery bypass graft (CABG) operation require more blood transfusions than do patients undergoing primary CABG operation. To determine the extent of this increased demand and the variables responsible for it, the cases of 196 patients who had undergone primary procedures and 65 patients who had had repeat procedures at the same institution were reviewed.

STUDY DESIGN AND METHODS

To analyze the differences in transfusion requirements for these two groups, the following data were obtained: number of transfusions given between the time of surgery and the time of hospital discharge; preoperative hemoglobin (Hb), hematocrit (Hct), prothrombin time, and platelet count; Hb and Hct at hospital discharge; time the patient was on cardiopulmonary bypass; number and type of grafts; estimates of intraoperative blood loss; and chest-tube blood shed during the first 48 hours after surgery.

RESULTS

The groups were comparable with respect to age, body weight, preoperative Hb and Hct, number of grafts, and aspirin exposure. Patients in the repeat group had 35-percent greater blood loss and required 75-percent more blood components than did the patients undergoing primary procedures. The mean number of blood components transfused per patient was as follows: red cells, 3.8 +/- 0.5 units in repeat patients and 2.2 +/- 0.2 units in primary patients (p = 0.002); platelets, 2.9 +/- 0.9 vs. 1.1 +/- 0.2 (p = 0.043); fresh-frozen plasma, 1.6 +/- 0.4 vs. 0.8 +/- 0.1 (p = 0.044). Analysis of variables by regression method for repeat patients showed a predictive effect of blood loss (p < 0.0001), prolonged time on cardiopulmonary bypass (p < 0.0001), preoperative Hb (p = 0.0003), and aspirin exposure (p = 0.0094) on red cell transfusion rate in repeat patients (R-square = 0.7778, Prob > f = 0.0001).

CONCLUSION

Repeat CABG patients have higher transfusion rates. These findings may be attributed to the increased microvascular bleeding, prolonged time on cardiopulmonary bypass, lower preoperative Hb, and the use of preoperative antiplatelet medications.

The hematologic effects of cardiopulmonary bypass and the use of hemotherapy in coronary artery bypass grafting

Blood component therapy has always been important in coronary artery bypass grafting, and, initially, all patients undergoing bypass operations were given transfusions. The advent of hemodilution marked the beginning of blood conservation efforts that have reduced the transfusion requirements for these patients. We review the current state of cardiopulmonary bypass, blood loss, and blood use in coronary artery bypass grafting, including coagulation disturbances, preoperative autologous blood collection, blood conservation techniques, transfusion thresholds, blood component therapy, and blood use data.

Hypothermia and blood coagulation: dissociation between enzyme activity and clotting factor levels

Previous studies of hypothermia and blood coagulation have focused on alterations in the levels of blood clotting elements using coagulation tests performed under normothermic conditions. However, because of the enzymatic nature of activated clotting factors, hypothermia should also be expected to affect clotting factor activities. Multiple determinations of activated partial thromboplastin times (APTT), prothrombin times (PT), and thrombin times (TT) were performed on commercially available normal human plasma at assay temperatures similar to those encountered clinically (25-37 degrees C). Both the APTT and the PT were significantly prolonged at temperatures below 35 degrees C (P less than 0.05). Clotting time correlated significantly with assay temperature in a negative exponential fashion for all three tests (r = -0.97 for APTT, -0.93 for PT, -0.71 for TT, P less than 0.001 for all regressions). Clotting time prolongation appears proportional to the number of enzymatic steps involved. These data indicate that the coagulopathy observed during hypothermia is, in part, independent of clotting factor levels.

Coexistence of myelodysplastic syndrome and untreated chronic lymphocytic leukemia with development of acute myeloid leukemia immediately after treatment of chronic lymphocytic leukemia

A 72-year-old man originally seen for anemia and thrombocytopenia was determined to have chronic lymphocytic leukemia (CLL). Bone marrow examination at the time of CLL diagnosis revealed a small but significant population of atypical blasts. Cytogenetic analysis of the bone marrow aspirate disclosed chromosomal abnormalities (-7, +8) suggestive of a myelodysplastic syndrome. Shortly after treatment of the CLL, there was proliferation of the previously noted blast population, which cytochemical studies demonstrated to be of the myeloid series thus indicating acute myeloid leukemia superimposed on CLL. This report presents microscopic, cytogenetic, immunophenotypic, and cytochemical evidence to document the evolution of acute myeloid leukemia in the bone marrow of a patient with CLL after one course of chemotherapy.

Anti-A of donor lymphocyte origin in three recipients of organs from the same donor

The development of iso- and alloantibodies reactive with recipient red blood cells subsequent to organ transplantation is an established phenomenon. However, development of self-reactive antibodies in multiple recipients of organs from a single donor source has only been reported in one instance involving the formation of anti-D after transplantation. We observed the development of a delayed hemolytic transfusion reaction 10 days after transplantation of a group O liver into a group A recipient. Serologic studies revealed a positive direct antiglobulin test due to coating of autologous A cells with anti-A. Close follow-up of the group A recipients of the kidneys transplanted from the same group O donor revealed development of hemolysis secondary to anti-A on day 11 in one recipient and hemolysis due to anti-A on day 13 in a second recipient. Significant anemia, a 2-3 g/dl drop in hemoglobin, occurred in both kidney recipients. These findings suggest that recipient of organs from donors whose transferred lymphocytes have produced antirecipient RBC antibodies in another recipient may be at risk for developing a similar self-limited hemolytic episode and should be followed accordingly.

Platelet dysfunction associated with Wilms tumor and hyaluronic acid

Acquired von Willebrand disease (AVWD) has been described in two cases of nephroblastoma. We studied a patient with nephroblastoma who presented with a coagulopathy suggestive of AVWD. The subject had undetectable levels of F.VIIIR:Ag, diminished F.VIIIR:WF (16.3%), F.VIII:C activity (37%), and lack of platelet aggregation to ADP, epinephrine, collagen, and arachidonic acid. These results were associated with abnormally high serum levels (850 mg/dl) of hyaluronic acid (HA), which made the patient's serum hyperviscous. Examination of the neoplasm revealed HA in the tumor matrix. All abnormalities of coagulation resolved after chemotherapy and extirpation of the neoplasm, which produced normal serum HA levels. To study the effects of HA on platelet function, we added HA to normal platelet-poor plasma (NPP), which rendered F.VIIIR:Ag undetectable; treatment of HA with hyaluronidase eliminated F.VIIIR:Ag assay interference caused by HA. F.VIII:C activity decreased in vitro when HA was mixed with normal platelet-poor plasma (NPP). HA reduced the initial slope of normal platelet aggregation. Partial correction of platelet aggregation occurred after hyaluronidase treatment of HA-spiked PRP. Experiments in rabbits exposed to HA (serum level 400 mg/dl) demonstrated abnormalities similar to those noted in the patient. Shear rate studies of whole blood containing HA (500 mg/dl) yielded high shear stress, 27-136 dynes/cm2 over shear rates of 10-216 sec-1. We conclude that the coagulopathy demonstrated in this case is secondary to hyperviscosity produced by elevated levels of HA, which interferes with the assay for F.VIIIR:Ag. Thus the acquired coagulopathy associated with other cases of nephroblastoma may present as spurious von Willebrand disease.

Immune anti-A1 in A2 recipients of kidneys from group O donors

Antibodies specific for recipient red cell antigens have been demonstrated in patients who receive organs from ABO unmatched donors. In some cases, severe but self-limited hemolysis has been associated with the development of posttransplantation antibodies. We report a case in which an A2 recipient of a kidney from a group O donor formed anti-A1 antibody which reacted with homologous red cells. The patient developed a delayed hemolytic transfusion reaction. A radiochromium survival study revealed decreased survival of A1 red cells. A broader specificity of the antibody was not shown during follow-up. The anti-A1 was not detected in a sample tested 6 months after the initial study. It is probable that the anti-A1 noted in this case was formed by passenger lymphocytes. A2 patients who develop anti-A1 after renal transplantation should be transfused with red cells negative for A1.

Harvest of young red cells on an automated cell separator

Red cells can be fractionated by age on a blood processor (Model 2991, IBM). However, little data exist on processing a product for transfusion. This report details a method for collecting young erythrocyte (YE) units containing a mean hemoglobin content of 56.43 +/- 1.39 (SEM) grams. Enrichment with YEs was indicated by greater activity of the enzyme pyruvate kinase (PK) in aliquots of YE units. The mean ratio of PK activity in the young red cell product compared to unfractionated blood was 1.14 +/- 0.03 (SEM). An increased PK ratio was noted in 23 of 26 units studied. Based on the PK ratio, the mean age of the erythrocytes was 46 days, compared to 60 days for standard units of blood. In the 6 units assayed, the reticulocyte count was increased. Collection of YE units was relatively easy, no untoward donor reactions were observed, and no deleterious effects developed in the recipient. Although these data suggest enrichment with a young population of red cells, YE units produced by this method are experimental. Routine use of this procedure awaits demonstration of a significant decrease in transfusion frequency in patients receiving YE units for chronic red cell therapy.

Ex vivo selective isolation of young red blood cells using the IBM-2991 cell washer

Transfusion-induced hemochromatosis is a major complication in the therapy of severe chronic anemia. Improvement of transfused cell survival with a reduction in transfusion frequency is one possible approach to this problem. Using continuous-flow centrifugation (CFC), young red blood cells (YRBC) with enhanced in vivo survival have been isolated, but the expense and donor time required with this technique prohibit its widespread use for patient support. We studied the use of the IBM 2991 cell washer (CW) to isolate YRBC ex vivo from previously collected donor blood. Age-dependent red cell separation could be achieved using this instrumentation. Autologous mean red cell half-life (RBC-T50) (n = 9) for the younger cell fractions was 43.9 +/- 7.8 days compared to 34.7 +/- 5.8 days for the older cell fractions (n = 6, p less than 0.05). Paired measurement of RBC-T50 for young and old fractions in three donors showed an average survival increase of 41% for the YRBC. Adequate quantities of YRBC with enhanced survival can be obtained with less cost and less donor stress using the CW system compared to CFC. This approach could improve the management of patients with chronic transfusion requirements and merits further examination.

Rh mosaicism and aberrant MNSs antigen expression in a patient with chronic myelogenous leukemia

This is, to our knowledge, the first report of combined Rh and MNSs antigen alteration in a leukemic patient. Red blood cells of a chronic myelogenous leukemia patient demonstrated mixed field reactions with anti-Rho (D) reagents in August 1980. Earlier tests indicated he was Rho (D) positive in 1967, but Rho (D) and Du negative from 1973 to 1980. Titration studies with anti-hr' (c) and anti-hr" (e) indicated depressed expression, and there was also very weak s expression. One hundred per cent of cells studied from 1967 to 1980 were Philadelphia chromosome (Ph1) positive. No abnormalities in chromosomes associated with the Rh or MNSs blood groups 1 and 4, respectively, were noted. Phenotypes from August 1980 through September 1981 revealed normalization of red blood cell antigen status with an increase of Rho (D) positive cells from 35% to 100%. Chromosomal studies in October, 1980 and June, 1981 revealed Ph1 mosaicism with 25 and 75% Ph1 negative cells, respectively. These findings suggest that normalization of previously altered red blood cell antigen expression may reflect resurgence of normal stem cell lines.

Disseminated Petriellidium boydii and pacemaker endocarditis

Clinical and morphologic findings are described in a 62 year old woman with "mixed connective tissue disease" who received corticosteroid therapy, and in whom disseminated and fatal Petriellidium boydii infection with right-sided endocarditis developed. The patient was a gardener. The organism is ubiquitous in soil in many part of the United States; therefore, it is likely that the infection was introduced by this means. Endocarditis due to P. boydii has not been reported previously. In the patient described, massive vegetations nearly obliterated the tricuspid valve orifice, encasing a pacemaker catheter which had been inserted eight years earlier. Although never previously isolated from blood cultures, P. boydii was isolated from 11 consecutive blood cultures. P. boydii is a true fungus and has only recently been appreciated as an opportunistic pathogen in a compromised host.

Hemochromatosis heart disease: an unemphasized cause of potentially reversible restrictive cardiomyopathy

Cardiac involvement in hemochromatosis typically results in congestive cardiomyopathy; a restrictive cardiomyopathy due to hemochromatosis is distinctly rare. A restrictive cardiomyopathy, which developed in the patient described in this report, was due to hemochromatosis which mimicked constrictive pericarditis clinically, echocardiographically and hemodynamically, and resulted in a thoracotomy for attempted surgical therapy. The fact that hemochromatosis represents the only cause of a restrictive cardiomyopathy that is potentially reversible by medical therapy makes early recognition of hemochromatosis heart disease important.