Decreased fluidity of red cell membrane lipids in abetalipoproteinemia

Acanthocytic red cells in patients with abetalipoproteinemia are morphologically similar to the red cells in spur cell anemia. Fluidity of membrane lipids is decreased in spur cells due to their excess cholesterol content. Acanthocyte membranes have an increased content of sphingomyelin and a decreased content of lecithin. To assess the effect of this abnormality of acanthocyte membrane lipid composition on membrane fluidity, we studied red cells from five patients with abetalipoproteinemia and four obligate heterozygote family members. Membrane fluidity was measured in terms of microviscosity ( eta) at 37 degrees C, assessed by means of the fluorescence polarization of 1,6-diphenyl-1,3,5-hexatriene. It was increased from 3.2+/-0.1 poise in normals to 4.01-4.14 poise in acanthocytes. This was associated with an increase in the sphingomyelin/lecithin ratio from 0.84+/-0.08 in normals in 1.45-1.61 in acanthocytes. The eta of acanthocyte membranes was not influenced by the degree of vitamin E deficiency. Similar changes in eta were observed in liposomes prepared from red cell lipids. Heterozygotes had normal sphingomyelin/lecithin ratios and normal values for eta. The flow activation energy for viscosity, a measure of the degree of order in the hydrophobic portion of the membrane, was decreased from 8.3 kcal/mole in normal red cells to 7.2 kcal/mole in acanthocytes, indicating that acanthocyte membrane lipids are more ordered. Variations in the sphingomyelin/lecithin mole ratio of liposomes prepared from brain sphingomyelin and egg lecithin with equimolar cholesterol caused similar changes in both eta and activation energy. The deformability of acanthocytes, assessed by means of filtration through 3-mum filters, was decreased. These studies indicate that the increased sphingomyelin/lecithin ratio of acanthocytes is responsible for their decreased membrane fluidity. As in spur cells and in red cells enriched with cholesterol in vitro, this decrease in membrane fluidity occurs coincidentally with an abnormality in cell contour and an impairment in cell deformability.

A randomized clinical trial of granulocyte transfusions for infection in acute leukemia

In a prospective, controlled, randomized study to evaluate the efficacy of filtration-leukapheresis granulocytes in granulocytopenic, febrile patients with leukemia, 19 patients received antibiotics alone, and 12 received antibiotics plus daily granulocyte transfusions from ABO-matched donors. In skin-chamber studies the granulocytes appeared at sites of inflammation for at least six hours after transfusion. Infected subjects survived longer if they received granulocytes. Differences between control and transfused patients were greatest in patients with persistent bone-marrow failure, the 21-day survival being 20 per cent in controls, and 75 per cent in transfused patients. Granulocytes appeared to have no effect on the outcome of febrile episodes in which infection was not documented, the 21-day survival being 79 per cent for controls and 88 per cent for transfused patients. The transfusion of granulocytes thus appears to offer a survival advantage to infected, persistently granulocytopenic patients.

High ectopic kidney presenting as an abnormal liver-lung scan: case report

An unusual cause for a positive liver-lung scan is presented. A cold area between the base of the right lung and the liver in a 78-year-old woman was reported as being due to a subphrenic abscess. This defect was subsequently found to be a right subphrenic kidney.

Pyruvate formation during the catabolism of simple hexose sugars by Escherichia coli: studies with pyruvate kinase-negative mutants

Escherichia coli K-12 mutants lacking the adenosine 5'-monophosphate-activated pyruvate kinase have been isolated accidentally and used to prepare further mutants additionally devoid of the fructose bisphosphate-activated pyruvate kinase. Such double mutants totally devoid of pyruvate kinase activity still grow well under aerobic conditions on sugars that are catabolized by the phosphoenolpyruvate (PEP):sugar phosphotransferase system, but they grow poorly on non-phosphotransferase system sugars. This suggests that although pyruvate kinase plays a major role in the formation of pyruvate from PEP during growth on non-phosphotransferase system sugars, the operation of the PEP:sugar phosphotransferase system can contribute significantly to pyruvate production from PEP. In the absence of pyruvate kinase and an active PEP:sugar phosphotransferase system the methylglyoxal glycolytic bypass may also function to some extent for the formation of pyruvate during the catabolism of simple hexose sugars. No unique physiological role can yet be ascribed to the adenosine 5'-monophosphate-activated pyruvate kinase as a result of these studies.

Effect of cytochalasin B on human monocyte binding and sphering of IgG-coated human erythrocytes

The ability of human mononuclear phagocytic cells to bind IgG-coated human erythrocytes (EA) and to cause bound EA to become osmotically fragile (sphered) was investigated in the presence of cytochalasin B, a known inhibitor of phagocytosis. Cytochalasin B inhibited the binding of EA to mononuclear cells in a dose-dependent fashion; 80% inhibition of binding was observed at a concentration of 5 mug/ml. This profound effect on EA binding together with presently available data suggested a role for IgG receptor mobility in the macrophage binding of IgG-coated erythrocytes. Cytochalasin B, however, had a minimal effect on the capacity of mononuclear cells to sphere adherent EA, suggesting that the processes involved in macrophage-induced spherocytosis may differ from those operable in phagocytosis.

Concanavalin A-mediated binding and sphering of human red blood cells by homologous monocytes

Human red blood cells sensitized with concanavalin A became bound to homologous peripheral blood monocytes. Binding occured at a concentration of 10(5) molecules of tetrameric Con A per red blood cell (RBC) and increased with additional Con A. RBC binding began within 5 min and was maximal at 90 min. Phagocytosis of sensitized RBCs was minimal. RBC attachment was prevented by 0.01 M alpha-methyl-D-mannopyranoside, and, once the RBC-monocyte rosette was established, bound RBCs were largely removed with this specific saccharide inhibitor of Con A. RBCs attached to monocytes became spherocytic and osmotically fragile. The recognition of concanavalin A (Con A)-coated RBCs was not mediated through the monocyte IgG-Fc receptor. These studies demonstrate that, like IgG and C3b, Con A is capable of mediating the binding of human RBCs to human monocytes. Red cells so bound are damaged at the monocyte surface.

Membrane microviscosity and human platelet function

An increased sensitivity to epinephrine-induced aggregation has been observed both in platelets obtained from patients with type IIa hyperlipoproteinemia and in normal platelets following incubation with cholesterol-rich lecithin dispersions. We have reported previously that the membrane fraction of platelets is enriched with cholesterol relative to phospholipid under each of these conditions. To further explore the effect of cholesterol on platelet membranes, we have examined the fluidity (microviscosity) of whole platelets and platelet subcellular fractions using a hydrophobic fluorescent probe, 1,6-diphenyl-1,3,5-hexatriene (DPH), under conditions in which the cholesterol-to-phospholipid mole ratio (C/PL) of platelets was varied by incubation with various cholesterol-lecithin sonicated dispersions. The C/PL of platelets directly influenced the rotational diffusion of DPH, as indicated by changes in fluorescence polarization. This was reflected in an increase in microviscosity at 37 degrees C (ETA37) from 2.84 P in normal platelets to 4.06 P in platelets with a 118% increase in C/PL. Conversely, platelets with a 43% decrease in C/PL had a 13% decrease in eta37. A strong correlation (r = 0.94) existed between C/PL and eta37 throughout this entire range. However, C/PL had no effect on the excited-state fluorescence lifetime of DPH. Both C/PL and eta37 were lower in isolated platelet membranes than in the platelet granule fraction. When platelets were incubated for 20 h with cholesterol-rich dispersions, there was an increase in C/PL and eta37 in both the membrane and granule fractions. However, this occurred more rapidly in membranes so that, at 5 h (a time when an increased sensitivity of whole platelets to epinephrine is evident), membrane C/PL had increased 55% and eta37 had increased 42%, whereas granule C/PL and eta37 had changed minimally. Cholesterol-rich platelets and subcellular fractions had a lower fusion (or flow) activation energy for viscosity (deltaE), reflecting a higher degree of order, and the converse was true in cholesterol-poor platelets. Moreover, a strong negative correlation existed between the percent change in deltaE and the percent change in eta37 induced either by cholesterol incorporation or depletion. These data demonstrate that cholesterol influences the fluidity and the degree of order within the hydrophobic core of platelet membranes. Changes induced in these physical properties by an excess of cholesterol relative to phospholipid may underlie the abnormal reception or transmission of the aggregation stimulus in cholesterol-rich platelets.

Carcinoma of the small bowel. A complication of regional enteritis

The 35th and 36th cases of adenocarcinoma arising in small bowel affected with regional enteritis are presented. The pathology of all reported cases is reviewed. An association between regional enteritis and carcinoma of the small bowel is suggested.

Cellular cholesterol ester accumulation induced by free cholesterol-rich lipid dispersions

The influence of lipoprotein composition on free cholesterol (RC) esterification and accumulation of esterified cholesterol (EC) was studied in cells of Fu5AH rat hepatoma exposed to culture media supplemented with (FC/P) ranging from 0.6 to 2.8. In the presence of normal human serum, FC-lecithin dispersions witb a FC/P greater than one stimulated both the esterification of FC and the accumulation of cellular EC. Conversely, dispersions with FC/P values of approximately one had no effect on either FC esterification or the accumulation of EC when compared to cells grown in the absence of lipid dispersions. No stimulation of cellular response was obtained when FC-rich dispersions were added to cells in the absence of serum; however, stimulation was observed when cells were exposed to isolated human serum lipoproteins (very low density, low density, and high density). With each lipoprotein, FC-lecithin dispersions with FC/P values less than one inhibited cholesteryl ester accumulation, FC-rich dispersions stimulated, and dispersions with FC/P values of approximately one had an effect equivalent to that of isolated lipproteins alone. These studies extablish that cellular FC esterification and EC content are not influenced solely by the FC concentration of medium, but rather respond to the ratio of FC to phospholipidl These studies also suggest that serum lipoproteins participate in the transfer of FC carried by FC-rich lecithin dispersions to cells.

Halofenate: a potent inhibitor of normal and hypersensitive platelets

Platelet hypersensitivity has been documented in diabetes and angina pectoris and can be partially reversed in hyperbetalipoproteinemia by clofibrate. We therefore examined the effects of incubating another lipid-lowering agent, halofenate, with both normal platelets and platelets made hypersensitive in vitro by incorporation of 55 per cent excess cholesterol into their membranes. At therapeutic concentrations, halofenate caused a time- and dose-dependent inhibition of the aggregation of normal platelets by epinephrine. After 30 minutes' incubation at 37 degrees C., halofenate significantly inhibited the extent of aggregation by 88 per cent (p less than 0.01), whereas clofibrate inhibited aggregation by 44 per cent (p less than 0.01). Halofenate was a more potent inhibitor of platelets than clofibrate (p less than 0.01). The mean threshold concentration of epinephrine necessary for aggregation of normal platelets (4.2 muM) was not significatnly increased with clofibrate (10 muM) but was markedly elevated with halofenate (245 muM; p less than 0.001). Significant but less dramatic increases in threshold concentration of ADP and collagen were found with halofenate but no clofibrate. Cholesterol-rich platelets were 114-fold more sensitive to epinephrine and twofold more sensitive to ADP than normal platelets but after incubation with halofenate became even less sensitive than normal. Clofibrate inhibited the extent of aggregation of hypersensitive platelets but did not alter the threshold concentration of epinephrine necessary for aggregation. Thus, halofenate is more potent than clofibrate in reducing the sensitivity of normal platelets to aggregating agents in vitro and can completely reverse experimentally produced platelet hypersensitivity. These data suggest that halofenate might be useful in reversing increased platelet sensitivity in cardiovascular diseases.

Overview of cancer pathology

A brief review of cancer pathology is presented for physical therapists interested in cancer treatment programs. The relationship of cancer pathology to diagnosis and treatment is illustrated. Cancer biology definitions, cancer classification, grading and staging, and the multidisciplinary approach to treatment are discussed.

Carcinoma of the small bowel. A complication of regional enteritis

The 35th and 36th cases of adenocarcinoma arising in small bowel affected with regional enteritis are presented. The pathology of all reported cases is reviewed. An association between regional enteritis and carcinoma of the small bowel is suggested.

Inhibition of cation cotransport by cholesterol enrichment of human red cell membranes

1. Human red cells were enriched with cholesterol by incubation with lipid dispersions having a high cholesterol: phospholipid mol ratio and the kinetics of the furosemide-sensitive cotransport for Na+ and K+ were measured. 2. Influxes of both K+ and Na+ through this system were inhibited by 70 and 76% in cholesterol-rich cells (cholesterol: phospholipid mol ratio 1.80) and the Km of the furosemide-sensitive flux components for both K+ and Na+ decreased. 3. Effluxes of both K+ and Na+ are inhibited by furosemide and the magnitudes of these furosemide-sensitive components are markedly decreased in cholesterol-rich cells. 4. The inhibitory effect of cholesterol enrichment on this carrier-mediated transport of cations suggests that cholesterol may either alter the position of the carrier or retard its movement within a more viscous membrane micro-environment.

Effect of corticosteroids on the human monocyte IgG and complement receptors

A quantitative in vitro assay was employed to directly assess the effect of corticosteroids on the IgG and complement receptor function of human mononuclear phagocytic cells. In this system corticosteroids were solubilized with cholesterol-phospholipid sonicated dispersions before exposure to mononuclear cells. Solubilized corticosteroids at concentrations between 10(-4) and 10(-3) M inhibited both IgG and complement receptor activity in a dose-response fashion. Inhibition was dependent upon the time of interaction of the mononuclear cells with corticosteroids and was half-maximal by 15 min. The inhibitory effect at all concentrations of hydrocortisone was partially overcome by increasing the number of IgG molecules per erythrocyte. Hydrocortisone also inhibited the binding of erythrocytes coated with both IgG and C3, despite the fact that when both were on the erythrocyte surface a synergistic effect on binding to mononuclear cells was observed. At the steroid concentrations employed, the capacity of mononuclear cells to exclude trypan blue and to take up latex particles and neutral red was unaffected. Mineralocorticoids also inhibited receptor activity, but the sex hormones were less effective. These studies demonstrate an effect of steroid hormones on cell membrane receptor function, and they suggest that an inhibition of the recognition system for IgG and C3 in vivo may explain, in part, the effect of corticosteroids in man.

Neoplasms in persons treated with x-rays in infancy: fourth survey in 20 years

The incidence of neoplastic disease was determined by a mail survey of 2,872 young adults given X-ray treatments in infancy and of their 5,005 nonirradiated siblings. Newly diagnosed benign and malignant neoplasms appeared more frequently in the irradiated subjects than in their siblings or the age- and sex-matched general population of upstate New York. Only thyroid neoplasms occurred in sufficient numbers to permit statistical analysis for the effects on incidence of sex, age, and dose, and of being in a high-risk group (sub-group C). Thyroid cancers developed earlier in life than did benign neoplasms, especially in boys; benign goiters occurred after smaller doses, predominantly in females. Females had a greater risk of developing thyroid cancer than males--2,3 times for females of all ages and 5 times for young adults. Except for young adult females, there was no definite age effect. The risk of cancer (but not of benign goiter) was proportional to the thyroid dose, with a linear risk coefficient of 2.5/year/million people exposed to 1 rad for the entire irradiated population and 4.0 for subgroup C. The high risk of thyroid cancer in subgroup C may be the result of the high percentage of Jews, who had a 3.4-fold greater risk than non-Jews. Young adult Jewish females had a 17-fold increased risk. An incidental observation was an apparent increased incidence of asthma and rare diseases with abnormal immunologic features in the irradiated population.

Characteristics of the membrane defect in the hereditary stomatocytosis syndrome

Cation permeability and lipid composition have been studied in the red cells of five patients with various features of the hereditary stomatocytosis syndrome. Hemolysis was compensated in four patients, and only one patient was anemic. Cell NA+ was increased an average of 3 mueq per ml cells and cell K+ decreased 14 mueq per ml cells. Both active and passive fluxes of Na+ and K+ were increased by two to six times normal. Tritiated ouabain binding was increased an average of 2.5-fold, suggesting a proportionally greater number of cation pumps per cell. The coupling ratio of active Na+:K+ fluxes was normal (3:2). Calcium permeability was increased compatible with the degree of reticulocytosis, and cell Ca2+ content was normal. The lowered sum of Na+ plus K+ was associated with a high MCHC and low cell water. When examined in wet preparations, red cells assumed either a bowl-shaped or an irregular contour, and they appeared as target cells on dry smears. Only when cell water was increased in hypotonic media were stomatocytes seen on smear. The total lipid content of red cells was increased in four patients, although it was normal in one. The mole ratio of cholesterol to phospholipid was always normal; however, phospholipid analysis showed an increased proportion of phosphatidyl choline. The abnormal cells were osmotically resistant due to both an increased membrane surface area and a low total cation content. These patients show two hallmarks of hereditary stomatocytosis: bowlshaped red cells observed on wet preparations and a marked increase in Na+ and K+ permeability. The heterogeneity of this syndrome in our patients and in others reported with hereditary stomatocytosis appears to result from (1) variability in the increase in surface area which results from an excess of membrane lipid content, particularly phosphatidylcholine, and (2) a variability in cell water content which may be either decreased or increased as a result of changes in the sum of Na+ plus K+ ions.

Effect of papain on the interaction between human monocytes, erythrocytes, and IgG

The mechanism by which papain detaches IgG-sensitized erythrocytes from the monocyte surface has been explored in an in vitro assay for the monocyte IgG receptor using red cells quantitatively sensitized with IgG anti-Rh D immunoglobulin. Papain treatment of IgG-sensitized erythrocytes diminished the ability of these cells to bind to the monocyte surface; however, treatment of erythrocytes with papain prior to sensitization with IgG did not inhibit binding, and at papain concentrations is greater than or equal to 38 mug/ml binding was enhanced. IgG receptor activity was not diminished by prior treatment of monolayer cells with papain and was enhanced with high concentrations of papain. These studies suggest that papain detaches erythrocytes from the monocyte surface by virtue of its proteolytic effect on IgG and not by an effect of papain on the D antigen of red cells or the IgG receptor on monocytes.

Two ribose-5-phosphate isomerases from Escherichia coli K12: partial characterisation of the enzymes and consideration of their possible physiological roles

Two physically and genetically distinct forms of ribosephosphate isomerase have been identified in Escherichia coli K12. The constitutive ribosephosphate isomerase A has a Km for ribose 5-phosphate (4.4 +/- 0.5 mM) six times greater than that of the inducible ribosephosphate isomerase B (0.83 +/- 0.13 mM). Treatment of the enzymes with 1.25 mM iodoacetate resulted in 100% loss of activity for ribosephosphate isomerase B, whereas ribosephosphate isomerase A was unaffected. Various cellular metabolites were tested and found to be without significant effect on either enzyme. The two enzymes could be separated by filtration on Sephadex G75 superfine and their apparent molecular weights were 45000 for ribosephosphate isomerase A and 32000-34000 for ribosephosphate isomerase B. Under certain conditions the two enzymes showed different patterns of heat inactivation but the results with ribosephosphate isomerase A varied in an unusual way with the protein concentration. Ribosephosphate isomerase B was formed inducibly in a mutant lacking ribosephosphate isomerase A but there was no evidence for the production of ribosephosphate isomerase B in wild-type cells. The formation of ribosephosphate isomerase B was not a consequence of the ribosephosphate isomerase B mutation, since strains could be constructed which formed both enzymes constitutively in the anticipated amounts. The ribosephosphate isomerase formed by a secondary mutant obtained from a ribosephosphate-isomerase-A-negative strain was identified as ribosephosphate isomerase B on the basis of its Km, elution profile from Sephadex G75, inhibition of iodoacetate, and heat inactivation. The ribosephosphate isomerases of another Escherichia coli K12 strain, X289, were investigated, since their properties were reported to be different from many of these described here for ribosephosphate isomerases A and B. In our hands strain X289 contained two ribosephosphate isomerases apparently identical to ribosephosphate isomerases A and B. The evidence to date suggests that ribosephosphate isomerase A catalyses the formation of ribose 5-phosphate from ribulose 5-phosphate and also participates in the reverse reaction during ribose and adenosine catabolism. The normal physiological role of the inducible ribosephosphate isomerase B is still uncertain.