Effects of lateral load and external twist on polarization-mode dispersion of spun and unspun fibers

Using the coupled-mode theory, we have developed a theoretical model to analyze the effects of lateral load and external twist on polarization-mode dispersion (PMD) of spun and unspun fibers. Modeling results show that spun and unspun fibers have very different PMD responses to lateral load and external twist. Experimental results show good agreement with the theory.

Generation of enhancer trap lines in Arabidopsis and characterization of expression patterns in the inflorescence

Eleven thousand, three hundred and seventy enhancer/promoter trap lines in Arabidopsis were generated via T-DNA transformation utilizing the binary vector pD991 that contains a minimal promoter fused to the uidA reporter gene. Overall 31% of the lines generated exhibit a staining pattern in the inflorescence. Flanking DNA has been cloned from 15 lines exhibiting inflorescence staining patterns by either thermal asymmetric interlaced PCR (TAIL-PCR), inverse PCR (IPCR), or partial library construction. Seeds from these lines are available from the ABRC and NASC Arabidopsis stock centers and DNA pools are available from the ABRC.

How nurses become leaders. Perceptions and beliefs about leadership development

Creating a professional work environment where nurses can develop the skills and expertise needed to be successful leaders is one strategy that can help ensure successful nursing leaders for the future. Understanding which factors influence leadership development is essential to create such an environment. The author considers what those factors may be and how they interact to facilitate the development of leadership skills and expertise among nurses.

The CArG boxes in the promoter of the Arabidopsis floral organ identity gene APETALA3 mediate diverse regulatory effects

APETALA3 is a MADS box gene required for normal development of the petals and stamens in the Arabidopsis flower. Studies in yeast, mammals and plants demonstrate that MADS domain transcription factors bind with high affinity to a consensus sequence called the CArG box. The APETALA3 promoter contains three close matches to the consensus CArG box sequence. To gain insights into the APETALA3 regulatory circuitry, we have analyzed the APETALA3 promoter using AP3::uidA(GUS) fusions. 496 base pairs of APETALA3 promoter sequence 5′ to the transcriptional start directs GUS activity in the same temporal and spatial expression pattern as the APETALA3 RNA and protein in wild-type flowers. A synthetic promoter consisting of three tandem repeats of a 143 base pair sequence directs reporter gene activity exclusively to petals and stamens in the flower. We have analyzed the role of the CArG boxes by site-specific mutagenesis and find that the three CArG boxes mediate discrete regulatory effects. Mutations in CArG1 result in a decrease in reporter expression suggesting that CArG1 is the binding site for a positively acting factor or factors. Mutations in CArG2 result in a decrease in reporter expression in petals, but the expression pattern in stamens is unchanged. By contrast, mutations in CArG3 result in an increase in the level of reporter gene activity during early floral stages suggesting that CArG3 is the binding site for a negatively acting factor.

Prevalence of lead intoxication in urban, adult medical inpatients

Medical inpatients in inner-city hospitals have both potentially lead-related disorders and potential lead exposure. To see whether there is substantial unexpected lead intoxication in this population, we did a cross-sectional study of 117 consecutively admitted patients to a general medical ward of an inner-city university hospital. The mean (SD) blood lead level was 6.7 (2.8) micrograms/dL, with a range of 0 to 37 micrograms/dL. Twenty-one patients (18%) had mildly elevated lead levels (10 to 19 micrograms/dL) and 2 patients (2%) had moderately elevated lead levels (20 to 44 micrograms/dL). Only 1 of 117 patients (0.9%, 95% CI: 0.0% to 2.6%) had lead intoxication (a lead level > or = 20 micrograms/dL or a lead level > or = 15 micrograms/dL and a free erythrocyte protoporphyrin level > 90 micrograms/dL of erythrocytes, with no alternative explanation for the laboratory abnormalities). We conclude that lead intoxication is uncommon in this population and that routine screening is not warranted. Although mild elevation of blood lead level is common, the clinical significance remains to be determined.

Cholesterol-loading of membranes of normal erythrocytes inhibits phospholipid repair and arachidonoyl-CoA:1-palmitoyl-sn-glycero-3-phosphocholine acyl transferase. A model of spur cell anemia

Spur cell anemia may occur in severe liver disease including alcoholic cirrhosis. Spur cell anemia red blood cells (RBCs) have a characteristic morphology, with irregular projections, an increased ratio of membrane cholesterol (Ch) to phospholipid, evidence of oxidative damage, and shortened survival resulting in hemolytic anemia. Normal RBCs may acquire many of the features of spur cells either by transfusion into a spur cell patient or in an in vitro model system that loads the RBC membrane with Ch relative to phospholipid by means of Ch-rich, phospholipid-Ch sonicates. We found evidence of abnormal phospholipid repair metabolism in spur cell anemia RBCs characterized by decreased arachidonate (Ar) uptake into phospholipids and by increased uptake into a fatty acid membrane repair intermediate, acylcarnitine (AcylCn). To study the possible modulation of phospholipid repair metabolism in spur cells by Ch-loading, we compared the Ar metabolism of RBCs loaded with Ch in vitro with that of control cells incubated in autologous serum. Ar, a polyunsaturated fatty acid, is especially sensitive to peroxidation and, thus, is likely to be involved in phospholipid repair. Ch-loading decreased the incorporation of [14C]Ar into total lipids (Ch-loaded, 1,113 +/- 48 pmol/10(10) RBCs; control, 1,525 +/- 48 pmol/10(10) RBCs) including phosphatidylethanolamine, phosphatidylserine, and phosphatidylcholine. Uptake of [14C]Ar into AcylCn increased (control AcylCn, 169 +/- 31 pmol/10(10) RBCs; Ch-loaded AcylCn, 196 +/- 35 pmol/10(10) RBCs; P = .0012). Thimerosal, an inhibitor of arachidonoyl- CoA:l-palmitoyl-sn-glycero-3-phosphocholine acyl transferase or lysophosphocholine acyl transferase (LAT), produced a similar pattern of metabolic abnormality, with decreased incorporation into phospholipid but relative increase into AcylCn. We assayed LAT in RBC membranes from Ch-loaded RBCs, using [14C]arachidonoyl CoA as precursor, and found similar decreased LAT activity at concentrations of 1-palmitoyllysophosphatidylcholine (LPC) from 1 to 30 micromol/L. Similar LAT assay results were obtained using [14C]palmitoyl LPC as the precursor. We conclude that Ch-loading of RBC membranes results in inhibition of LAT in the cell-free system in vitro and may account for the inhibited phospholipid repair in Ch-loaded intact RBCs in vitro and in spur cell anemia RBCs in vivo. Decreased ability to replace peroxidized membrane fatty acid by this metabolic pathway may contribute to the hemolytic process in spur cell anemia.

Tuberculin skin test reactivity, anergy, and HIV infection in hospitalized patients. Longcope Firm of the Osler Medical Housestaff

PURPOSE

Detection of latent tuberculosis infection is an important step in the control of tuberculosis because high-risk persons may be given preventive therapy. The value of tuberculin skin testing in individuals with human immunodeficiency virus (HIV) infection, however, is limited by anergy. We evaluated the prevalence of tuberculin skin test reactivity, anergy, and HIV infection in a group of hospitalized patients in an area where both tuberculosis and HIV infection are prevalent.

PATIENTS AND METHODS

Three hundred fifty-one patients consecutively admitted to a medical service of a large urban teaching hospital were enrolled in the study. All those with no documented history of a positive tuberculin skin test were evaluated on admission with purified protein derivative (PPD) by the Mantoux test, and with anergy testing using a multiple-puncture device. HIV testing was offered to all patients who did not have a known history of HIV infection, and was performed when informed consent was obtained.

RESULTS

Forty-one patients (12%) had a documented history of a positive PPD. Of the remaining 310 patients, 62 (20%) had a PPD response of > or = 10 mm induration. Fifty-two (15%) of the 351 patients were HIV positive. None of the HIV-infected patients was PPD positive. Anergy was found in 63% of the HIV-infected patients and 28% of the HIV-seronegative patients. Independent risk factors for a positive PPD included age > 55, male sex, and hypertension. HIV infection, current steroid use, and a history of cancer were associated with a negative PPD. Independent risk factors for anergy included HIV infection, current corticosteroid use, renal failure pneumonia, and a history of cancer. Of the 62 new PPD-positive patients, 30 (48%) were candidates for chemoprophylaxis. Additionally, 30 (63%) of 48 HIV-seropositive patients who were completed testing were anergic and might be candidates for chemoprophylaxis. Almost all of the patients eligible for chemoprophylactic therapy would have been detected if only patients at increased risk for developing tuberculosis were screened.

CONCLUSIONS

Tuberculosis infection, HIV infection, and anergy were common in patients admitted to this medical service. Interpretation of PPD reactivity was confounded by a high prevalence of anergy, particularly in HIV-infected patients. A large proportion of patients tested were candidates for chemoprophylaxis. Routine tuberculin skin testing with anergy testing for high-risk patients on admission to the hospital is useful for identifying patients who might benefit from prophylaxis to help control the spread of tuberculosis.

Effects of central apnea on cerebral blood flow velocity in healthy term infants

We evaluated a new method of monitoring cerebral blood flow velocity (CBFV) and described changes in CBFV in relation to central apnea in 17 healthy term infants. The area under the velocity curve during apnea did not change, whereas area under the velocity curve per the waveform showed a significant difference, suggesting that stability is maintained through an increase in CBFV with each heartbeat. The maintenance of cerebral hemodynamics during isolated central apnea supports the assumption that these episodes are benign.

Abnormal phospholipid metabolism in spur cell anemia: decreased fatty acid incorporation into phosphatidylethanolamine and increased incorporation into acylcarnitine in spur cell anemia erythrocytes

Spur cell anemia is a hemolytic anemia seen in severe alcoholic cirrhosis that is characterized by unusual morphology and a decreased ratio of phospholipids to cholesterol in the erythrocyte membrane. We hypothesized that defective phospholipid repair may contribute to the red blood cell (RBC) phospholipid abnormalities of spur cell anemia. Therefore, we compared RBCs from normal control subjects with RBCs from spur cell anemia patients. The incorporation of [14C] arachidonic acid into the phospholipids and acylcarnitine (acyl-Cn) of spur cells and normal RBCs was analyzed by a direct-phase high performance liquid chromatography column to separate both the phospholipids and acyl-Cn. There was less uptake of the [14C] arachidonate into phosphatidylethanolamine of spur cell RBCs (12.9% +/- 1.0%) compared with normal RBCs (20.5% +/- 2.8%; P = .0245). However, more arachidonate was incorporated into the acyl-Cn of spur cells (spur cell acyl-Cn [24.5% +/- 2.9%] v normal control acyl-Cn [10.1% +/- 1.9%]; P = .0018). We conclude that phospholipid biosynthesis is inhibited and that acyl-Cn formation is spared in spur cell anemia RBCs. These metabolic changes may help account for the lipid abnormalities seen in spur cell anemia RBCs and contribute to the hemolytic process.

Planning for the future of behavioral health services

Psychiatric and chemical dependency services are increasingly being delivered through managed care with greater emphasis on ambulatory and outpatient treatments. Inpatient facilities can preserve their involvement in behavioral health services by actively developing a managed care product line. This article describes the nature of change in behavioral services, what competitive behavioral health providers will look like in the future, and the actions hospital administrators should be taking now.

Field trial of two Bacillus thuringiensis var. israelensis formulations for control of Aedes species mosquitoes in Michigan woodlands

Vectobac and Bactimos corn cob granules were evaluated for control of Aedes species mosquito larvae in woodland pools. No significant differences were seen between the 2 formulations. Both provided greater than 90% control at application rates as low as 100 mg/m2 (0.89 lb/acre) and greater than 98% control at label-specified field application rates (2.5 or 5 lb/acre).

Organic peroxides inhibit neutrophil leukotriene B4 biosynthesis

Leukotriene B4, an autacoid metabolite of arachidonic acid produced by polymorphonuclear neutrophils, induces chemokinesis, chemotaxis, and adhesion of these cells at sites of inflammation. Because neutrophil infiltration is a self-limited process, we hypothesized that oxidized lipid products of neutrophil-damaged tissue might inhibit leukotriene B4 biosynthesis, thereby preventing additional neutrophil infiltration and limiting peroxidative tissue damage. Erythrocyte ghosts exposed to a hydrogen peroxide-generating system served as a model of peroxidized tissue in inflammation and inhibited neutrophil leukotriene B4 production by 50% compared with unoxidized ghosts. Organic peroxides, including tert-butylhydroperoxide, peracetic acid, and linoleic hydroperoxide, resembling the product(s) of tissue membrane peroxidation in lipid solubility and catalase resistance, inhibited leukotriene B4 biosynthesis in a dose-dependent manner (50% inhibitory concentration of 3.9 microM compared to 530 microM for H2O2). Biosynthetic steps prior to the 5-lipoxygenase did not appear to be the site of inhibition. Likewise, the step after the 5-lipoxygenase, the leukotriene A4 hydrolase, was not primarily involved. Thus a possible mechanism for controlling the influx of neutrophils and their oxidative damage during inflammation may be inhibition of the 5-lipoxygenase by catalase-resistant lipid peroxides released by tissue membranes.

Massive strychnine intoxication: serial blood levels in a fatal case

A fatal case of strychnine intoxication is reported. The patient expired despite early aggressive management and prevention of metabolic complications. Serial blood levels are reported. In contrast to a previous report describing first order elimination kinetics, our data suggest that strychnine follows Michaelis-Menton elimination kinetics. The case illustrates the rapid, dramatic course of severe strychnine ingestions. A review of the toxicokinetics, mechanism of action and treatment of strychnine intoxication follows.

Inhibition of arachidonic acid incorporation into erythrocyte phospholipids by peracetic acid and other peroxides. Role of arachidonoyl-CoA: 1-palmitoyl-sn-glycero-3-phosphocholine acyl transferase

To explore possible mechanisms of the arachidonic acid deficiency of the red blood cell membrane in alcoholics, we compared the effect of ethanol and its oxidized products, acetaldehyde and peracetic acid, with other peroxides on the accumulation of [14C]arachidonate into RBC membrane lipids in vitro. Incubation of erythrocytes with 50 mM ethanol or 3 mM acetaldehyde had no effect on arachidonate incorporation. Pretreatment of erythrocytes with 10 mM hydrogen peroxide, 0.1 mM cumene hydroperoxide or 0.1 mM t-butyl hydroperoxide had little effect on [14C]arachidonate incorporation in the absence of azide. However, pretreatment of cells with N-ethylmaleimide, 0.1 mM peracetic acid or performic acid, with or without azide, inhibited arachidonate incorporation into phospholipids but not neutral lipids. In chase experiments, peracetate also inhibited transfer of arachidonate from neutral lipids to phospholipids. To investigate a possible site of this inhibition of arachidonate transfer into phospholipids by percarboxylic acids, we assayed a repair enzyme, arachidonoyl CoA: 1-palmitoyl-sn-glycero-3-phosphocholine acyl transferase (EC 2.3.1.23). As in intact cells, phospholipid biosynthesis was inhibited more by N-ethylmalemide and peracetic acid than by hydrogen peroxide, cumene hydroperoxide, and t-butyl hydroperoxide. Peracetic acid was the only active inhibitor among ethanol and its oxidized products studied and may deserve further examination in ethanol toxicity.

Relative susceptibility of lipids to peroxidation in intact erythrocytes

Factors relating the site and metabolic state of erythrocyte lipids to their susceptibility to oxidative stress are poorly understood. Therefore red cell lipids were labeled with serum albumin-bound (carbon 14 [ul]) fatty acids in timed experiments. Susceptibility of sequentially labeled lipids to peroxidation in intact cells was determined by the percent conversion of the [14C]lipid to [14C]malondialdehyde (MDA). Other effects of alteration of incubation times could be ruled out by the equality of the conversion of total cell lipid to MDA. Polyunsaturated fatty acids but not other fatty acids served as MDA precursors. In 12 normal subjects the percentage of [14C]arachidonate converted to MDA after 15 minutes of labeling (3.08% +/- 0.69%) exceeded the percentage after 3 hours of labeling (2.01% +/- 0.83%) (paired, two-sided t test, p less than 0.0001). This susceptibility was caused by presence of rapidly labeled polyunsaturated fatty acids not extractable with defatted albumin (F2). Depletion of erythrocyte adenosine triphosphate before incubation favored accumulation of F2 and increased percentage conversion to MDA. Peroxidative susceptibility is determined by the metabolic state of the cell and the site of the peroxidized lipid within the intracellular pools.

Comparison of hemoglobin Köln erythrocyte membranes with malondialdehyde-reacted normal erythrocyte membranes

Splenectomized patients with hemoglobin (Hb) Köln have rigid RBCs with membrane polypeptide aggregates that are not dissociable with disulfide-reducing agents. Malondialdehyde (MDA) action on normal RBCs produced rigid RBCs with similar nondissociable aggregates. To test the hypothesis that Hb Köln RBC aggregates contained unsaturated MDA-type bonds, we reduced normal control RBC membranes, Hb Köln RBC membranes, and MDA-reacted membranes with [3H]NaBH4. Hb Köln RBC membranes and MDA-reacted membranes both had significantly more 3H incorporation than control membranes. Furthermore, 3H incorporation in both Hb Köln and MDA-treated membranes was located in the membrane polypeptide aggregates, presumably saturating the crosslinking bonds. After reaction of RBCs with [14C]MDA, the MDA label was similarly concentrated in the membrane polypeptide aggregates. Normal RBC membranes incubated with MDA were analyzed with and without reduction by NaBH4 prior to amino acid determination by high-performance liquid chromatography (HPLC). Reduction with NaBH4 after MDA treatment decreased the lysyl residues by 33% and the serine by 7% and increased by 10% the methionyl residues, but did not affect 12 other amino acids. Similar changes could be detected in NaBH4-reduced Hb Köln aggregates in methionine and serine content. MDA may also alter protein configuration, as evidenced by an increase in the protease susceptibility of membrane proteins from MDA-treated and Hb Köln RBCs. We conclude that Hb Köln RBC membranes, like MDA-treated membranes, have similar high molecular weight aggregates conferring decreased membrane deformability, [3H]NaBH4-reducible unsaturated bonds, changes in amino acid composition upon reduction, and protease-sensitive configurational changes.

Oxidant damage of the lipids and proteins of the erythrocyte membranes in unstable hemoglobin disease. Evidence for the role of lipid peroxidation

Since unstable hemoglobins have been considered a source of reactive oxygen radicals, and oxidative membrane damage a prehemolytic event, we examined the erythrocyte membranes of six patients (three splenectomized) with hemoglobin Köln disease. In the hydrogen peroxide stress test, the patients' erythrocytes generated more than twice the malonyldialdehyde (a lipid peroxidative product) than control erythrocytes. Fluorescence spectra of lipid extracts of the patients' erythrocytes showed an excitation maximum at 400 nm and an emission maximum of 460 nm, characteristic of malonyldialdehyde lipid adducts. Two types of membrane polypeptide aggregates were found in the erythrocytes of the splenectomized patients. The first, which were dissociable by treatment with mercaptoethanol, contained disulfide-linked spectrin, band 3 and globin. The second, not dissociable by mercaptoethanol, had an amino acid composition similar to that of erythrocyte membranes and spectrin (unlike globin) and like that of aggregates produced by the action of malonyldialdehyde on normal erythrocyte membranes. Atomic absorption spectroscopy of hemoglobin Köln erythrocytes showed no increase in calcium content implying that these cross-links were not due to calcium-stimulated transglutaminase. Using a micropipette technique, we demonstrated that erythrocytes containing membrane aggregates from splenectomized patients were less deformable while aggregate-free erythrocytes from non-splenectomized patients had normal deformability. We conclude that the erythrocyte membranes in hemoglobin Köln disease show evidence of lipid peroxidation with production of malonyldialdehyde, and that the nondissociable membrane aggregates formed in this disease are likely cross-linked by malonyldialdehyde. Because the erythrocytes containing membrane aggregates from splenectomized patients with unstable hemoglobin disease show decreased membrane deformability, we hypothesize that this abnormality results in premature erythrocyte destruction in vivo.

Increased adsorption of cytoplasmic proteins to the erythrocyte membrane in ATP-depleted normal and pyruvate kinase-deficient mature cells and reticulocytes

How the metabolic defect of pyruvate kinase deficiency (PK(-)) accelerates red blood cell (RBC) destruction is not established, but may be related to RBC membrane abnormalities associated with altered cellular metabolism. Furthermore, it has been shown that PK(-) reticulocytes are especially sensitive to metabolic depletion. Therefore, we compared the membranes of reticulocyte-rich PK(-) RBC, both fresh and ATP depleted, with membranes of fresh and ATP depleted normal mature RBC and reticulocytes. There was no difference between the specific gravity (SG) of the membranes of normal mature RBC (SG 1.152 +/- 0.004) and membranes of reticulocyte-rich RBC from several anemias (SG 1.150 +/- 0.002). However, membranes from fresh, reticulocyte-rich PK(-) RBC were dense with SG of 1.165 +/- 0.004 which correlated with a corresponding increase of protein to lipid phosphorus ratio of 66 +/- 8 micrograms protein/micrograms lipid phosphorus (normal 52 +/- 6 micrograms/micrograms). The membrane density of PK(-) RBC was further increased when the PK(-) RBC ATP was depleted by anaerobic incubation (SG 1.188 +/- 0.004) or cyanide inhibition (SG 1.182 +/- 0.001). When ATP was depleted in normal RBC and in non-PK(-) reticulocytes, corresponding increases in membrane SG occurred. A distinctive 50,000 MW peptide is adsorbed from the cytoplasm to the membranes of reticulocytes (both normal and PK(-) when these cells were depleted of ATP. The increased membrane adsorption of cytoplasmic proteins by PK(-) RBC was not associated with increased RBC calcium uptake, sulfhydryl oxidation, or altered membrane protein phosphorylation. All the observed abnormalities of PK(-) RBC membranes could by reproduced by ATP depletion of reticulocyte-enriched non-PK(-) RBC.

Polychlorinated biphenyls in clams and oysters from New Bedford Harbor, Massachusetts, March 1978

Polychlorinated biphenyl (PCB) concentrations in clams (Mercenaria mercenaria) and oysters (Crassostrea virginica) from 17 stations of the western and New Bedford Harbor areas of Buzzards Bay, Massachusetts, clearly show that the New Bedford Harbor area is severely polluted. Up to 5 ppm PCBs (dry weight) were found in shellfish tissue. The most likely sources of the PCBs are chronic releases from two electrical component manufacturers in New Bedford. Close proximity of the shellfish to the source of input is indicated by a high relative abundance of the di-, tri-, and tetrachlorobiphenyls. The data suggest that the New Bedford Harbor area should be considered, along with the Hudson River and Chesapeake Bay, one of the major sources of PCB inputs to the northeastern United States coastal area.

Amino acid sequence of p15 from avian myeloblastosis virus complex

The complete amino acid sequence of the p15 gag protein from avian myeloblastosis virus (AMV) complex has been determined by sequential Edman degradation of the intact molecule and of peptide fragments generated by limited tryptic cleavage, cleavage with staphylococcal protease, and cyanogen bromide cleavage. AMV p15 is a single-chain protein containing 124 amino acids. The charged amino acids tend to be clustered in the primary structure. p15 contains a single cysteine at position 113 which may be essential for the p15 associated proteolytic activity. However, p15 shows no appreciable sequence homology with papain or other classical thiol proteases.

Sucrose density gradient analysis of erythrocyte membranes in hemolytic anemias

To investigate the membrane abnormalities that may play a pathophysiologic role in several hemolytic anemias we determined the density distribution on sucrose density gradients of human red blood cell (RBC) membranes from patients with these disorders, from normal controls, and from incubated normal RBC. We analyzed the fractions for membrane-adsorbed hemoglobin (Hb), globin, and nonglobin cytoplasmic proteins. The relationship between the cytoplasmic proteins adsorbed on the membranes and the specific gravity (SG) of the membranes was linear. An increase in SG of the entire membrane population was seen in Hb C disease due to adsorbed Hb. Subpopulations of membranes with increased SG due to adsorption of nonglobin protein were evident in the membranes from two splenectomized patients with hemolytic glucose-6-phosphate dehydrogenase (G6PD) variants. Dense membrane subpopulations found in RBC membranes from three splenectomized patients with Hb Köln were associated with adsorbed globin, while similar subpopulations in RBC membranes from three splenectomized patients with hereditary spherocytosis demonstrated increased SG due to adsorbed Hb. Splenectomized normals had no such abnormality in membrane density. Sucrose density gradients demonstrate that membrane bound cytoplasmic protein is characteristic of the RBC membranes in several hemolytic disorders. Additionally, gradients are useful for the isolation and further analysis of those subpopulations of RBC membranes with abnormal SG and exaggerated membrane protein abnormalities.

Decreased survival in vivo of diamide-incubated dog erythrocytes. A model of oxidant-induced hemolysis

Erythrocytes from patients with chronic hemolytic variants of glucose-6-phosphate dehydrogenase (G-6-PD) deficiency have structural membrane protein abnormalities accompanied by decreased cell membrane deformability which we postulate represent the consequences of oxidant-induced membrane injury. To evaluate the pathophysiologic significance of oxidant-induced membrane injury, we studied the in vitro and in vivo effects of the thiol-oxidizing agent, diamide, on dog erythrocytes. In vitro incubation of dog erythrocytes with 0.4 mM diamide in Tris-buffered saline for 90 min at 37 degrees C resulted in depletion of GSH, formation of membrane polypeptide aggregates (440,000 and > 50,000,000 daltons) and decreased cell micropipette deformability, abnormalities similar to those observed in the erythrocytes of patients with chronic hemolytic variants of G-6-PD deficiency. In addition, diamide-incubated cells had increased viscosity and increased membrane specific gravity, but no change in ATP. Reinjection of 51Cr-labeled, diamide-incubated cells was followed by markedly shortened in vivo survival and splenic sequestration. Further incubation of diamide-incubated cells in 4 mM dithiothreitol reversed the membrane polypeptide aggregates, normalized micropipette deformability, decreased cell viscosity, prolonged in vivi survival, and decreased splenic sequestration. These studied demonstrate that diamide induces a partially reversible erythrocyte lesion which is a useful model of oxidant-induced membrane injury. They suggest that oxidant-induced erythrocyte membrane injury plays an important role in the pathophysiology of chronic hemolysis which accompanies some G-6-PD variants.

Red-cell-membrane polypeptide aggregates in glucose-6-phosphate dehydrogenase mutants with chronic hemolytic disease. A clue to the mechanism of hemolysis

Red-cell membranes from patients with glucose-6-phosphate dehydrogenase deficiency were studied with polyacrylamide gel electrophoresis and gel filtration chromatography in sodium dodecyl sulfate. Membranes from each of five such patients who also had chronic hemolytic disease contained polypeptide aggregates within two molecular-weight ranges (4.4 X 10(5) and greater than 50 X 10(6) daltons). The 4.4 X 10(5) dalton aggregates were not detectable in red-cell membranes of patients with the enzyme deficiency without chronic hemolysis or in membranes from normal subjects, and the greater than 50 X 10(6) dalton aggregates were not found in appreciable amounts in these cells. The aggregates were dissociated by mercaptoethanol or dithiothreitol -- indicating that they were formed by intermolecular disulfide bonds. The polypeptide aggregates contained spectrin but not globin. Red-cell deformability was decreased in aggregate-containing cells. We postulate that the polypeptide aggregates are indicators of oxidant damage to the red-cell membrane, which results in decreased deformability and chronic hemolysis.

Hidden stresses in success

There are many measures of success. For example, Logan Pearsall Smith, the English essayist, wrote: "How can they say my life is not a success? Have I not for more than sixty years got enough to eat and escaped being eaten?" (quoted in Flesch). Conventional measures of success include the attainment of wealth, position, esteem, favor, or eminence, but these things without an accompanying enforcement of self-esteem cause stress--emotional discomfort or strain. Self-esteem, then, is perhaps the essence of the conscious, pleasurable experiencing of success.

Calcium-induced erythrocyte membrane changes. The role of adsorption of cytosol proteins and proteases

Changes in the membranes of human red cells similar to those of certain hemolytic anemias were produced by calcium in three model systems and found to result from membrane adsorption of cytosol proteins and from proteolysis. Proteins of the cytosol adsorbed to human erythrocyte membranes in the presence of calcium and extractable by EDTA were compared to those of the total cytosol by polyacrylamide gel electrophoresis and by isoelectric focusing. Catalase (EC 1.11.1.6) and band 8 were adsorbed to the membranes from the supernatant cytosol with calcium. Band 8 was a normal constitutent of the cytosol, apparently a single chain of molecular weight 24,000 with a pI of 5.35. Other calcium-induced membrane changes could be demonstrated to be due to cytosol protease(s) adsorbed to the membrane in the presence of calcium and extractable with EDTA. When membranes were incubated with the proteases and calcium the decrease in bands 1,2,3 and 4.1 and the appearance of multiple low molecular weight peptides typical of calcium-induced membrane effects resulted.

A cervimeter for continuous measurement of cervical dilatation in labour-preliminary results

We briefly review instruments that have been used to measure cervical dilatation and describe the development of a new cervimeter. Curves derived from cervical dilatation and intrauterine pressure traces are presented in a form that clearly records the activity of the uterus and the response of the cervix to individual contractions. Our results suggest a new concept for behaviour of the cervix in labour.

Membrane polypeptide aggregates in glucose 6-phosphate dehydrogenase-deficient and in vitro aged red blood cells

RBC membrane polypeptide aggregates have been quantitated by PAGE SDS and by gel filtration. Aggregates were absent in fresh RBC's from normal controls, but aggregates with MW 4.4 X 10(5) and greater than 50 X 10(6) increased progressively as GSH levels fell in RBC's incubated in PBS without added glucose or calcium. Aggregates of both MW ranges were also present in fresh RBC's from a patient with compensated congenital nonspherocytic hemolysis associated with a mutant RBC G-6-PD, Long Prairie. Since the aggregates were dissociable by treatment with mercaptoethanol or dithiothreitol, they are probably cross-linked by intermolecular disulfide bonds. Membranes containing these aggregates may represent an early and sensitive indicator of oxidative damage to red cells.

The role of physical activity in the control of obesity

An exercise programme is an important part of the management of the obese patient. Exercise may increase both the specific dynamic action of food and the post-exercise metabolic rate, in addition to its direct caloric cost. Moderate daily exercise aids regulation of the appetite and may reduce the voluntary caloric intake of otherwise sedentary persons. Post-prandial activity may utilize more calories; therefore an adequate breakfast and avoidance of late night eating may be effective in weight control. A better tolerated and more nutritious diet may be allowed, and lean body weight better preserved, by combining exercise with a dietary programme. Regular exercise may also reduce some of the more serious life-threatening complications of obesity and poor dietary habits, allowing greater freedom in the pursuit of other pleasures.

Increased membrane binding of erythrocyte catalase in hereditary spherocytosis and in metabolically stressed normal cells

Normal red blood cell (RBC) membranes were compared with (1) RBC membranes from six patients with hereditary spherocytosis (HS), (2) normal membranes after hemolysis of the RBC in the presence of calcium, or (3) normal membranes after incubation of RBC for 24 hr in phosphate-buffered saline containing calcium without added glucose. When compared with normal controls, polyacrylamide gel electrophoresis with sodium dodecyl sulfate (PAGE SDS) of all three preparations showed an increase in membrane binding of globin and protein band 4.5 (60,000 molecular weight). In an attempt to identify band 4.5, 14 enzymes were assayed in the RBC membranes. Of these, catalase and lactate dehydrogenase were increased in membranes from HS RBC and from normal cells exposed to calcium. Only catalase, however, was present in sufficient quantity and had the correct subunit molecular weight on PAGE SDS and calcium-dependent membrane binding to account for an appreciable portion of 4.5. Caralase was further identified with a component of band 4.5 by double immunodiffusion using a specific anti-catalase antibody.