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Introduction: The increase in demand for post-bariatric plastic surgery has revealed a high prevalence of psychopathologies in patients undergoing the procedure, requiring the need to diagnose these diseases in the preoperative period. The use of specific psychological screening tools has been promoted; however, a gold-standard method has not yet been fully established. Objective: To carry out a review of the literature for alternatives available for the preliminary psychological evaluation of patients who are candidates for post-bariatric plastic surgery, presenting the method recommended in the Post-Bariatric Plastic Surgery outpatient clinic of the Federal University of Mato Grosso do Sul (UFMS). Methods: We reviewed the clinical trials which employed psychological screening tools preoperatively in patients who were candidates for post-bariatric plastic surgery; the MEDLINE/PubMed database was searched using keywords such as “bariatric surgery”, “body image”, “quality of life”, “obesity”, “plastic surgery” and “psychiatry”, for clinical trials published in the last 20 years. Herein, we discuss the findings and analyze the most common methodologies used. Results: Only four clinical trials used psychopathology screening tools in postbariatric plastic surgeries preoperatively, and one method could not be identified. Conclusion: The use of appropriate strategies to screen for psychopathologies helps prevent significant losses in the postoperative period, but the tools still lack validation in the post-bariatric population. Besides possessing extensive clinical-surgical technical knowledge, the plastic surgeon must remain attentive to the signs and psychopathological symptoms in these patients, referring them for psychological and psychiatric evaluation when indicated.

DELLA proteins restrain the cell proliferation and enlargement that characterizes the growth of plant organs. Gibberellin stimulates growth via 26S proteasome-dependent destruction of DELLAs, thus relieving DELLA-mediated growth restraint. Here, we show that the Arabidopsis thaliana sleepy1gar2-1 (sly1gar2-1) mutant allele encodes a mutant subunit (sly1gar2-1) of an SCF(SLY1) E3 ubiquitin ligase complex. SLY1 (the wild-type form) and sly1gar2-1 both confer substrate specificity on this complex via specific binding to the DELLA proteins. However, sly1gar2-1 interacts more strongly with the DELLA target than does SLY1. In addition, the strength of the SCFSLY1-DELLA interaction is increased by target phosphorylation. Growth-promoting DELLA destruction is dependent on SLY1 availability, on the strength of the interaction between SLY1 and the DELLA target, and on promotion of the SCFSLY1-DELLA interaction by DELLA phosphorylation., (Copyright 2004 American Society of Plant Biologists)

The phytohormone gibberellin (GA) regulates the development and fertility of Arabidopsis flowers. The mature flowers of GA-deficient mutant plants typically exhibit reduced elongation growth of petals and stamens. In addition, GA-deficiency blocks anther development, resulting in male sterility. Previous analyses have shown that GA promotes the elongation of plant organs by opposing the function of the DELLA proteins, a family of nuclear growth repressors. However, it was not clear that the DELLA proteins are involved in the GA-regulation of stamen and anther development. We show that GA regulates cell elongation rather than cell division during Arabidopsis stamen filament elongation. In addition, GA regulates the cellular developmental pathway of anthers leading from microspore to mature pollen grain. Genetic analysis shows that the Arabidopsis DELLA proteins RGA and RGL2 jointly repress petal, stamen and anther development in GA-deficient plants, and that this function is enhanced by RGL1 activity. GA thus promotes Arabidopsis petal, stamen and anther development by opposing the function of the DELLA proteins RGA, RGL1 and RGL2.

Bioactive gibberellin (GA) regulates the growth and development of a wide array of plant species. GA exerts its effects via members of the DELLA protein family of putative transcriptional regulators. The GAI gene encodes GAI, a DELLA protein from Arabidopsis thaliana (L.) Heyhn. A mutant allele, gai, encodes a mutant protein (gai) that has altered properties, and confers a dominant, reduced GA-response, dwarf phenotype. Here we describe experiments to investigate the effects of transgenic expression of GAI and gai in tobacco. Constructs permitting the expression of the GAI and gai open reading frames (ORFs) at higher (driven by the cauliflower mosaic virus 35S promoter) and lower (driven by the original Arabidopsis GAI promoter) levels in tobacco were made. We show that low-level expression of GAI has no detectable effect on tobacco GA-responses. In contrast, high-level expression of GAI clearly affects the growth of adult tobacco plants and the GA-responsiveness of tobacco hypocotyls. Both low- and high-level expression of gai have effects on tobacco GA responses. Thus, tobacco GA-responses are affected by transgenic expression of GAI/gai, and the degree to which these responses are affected is related to the level of transgene expression.

DELLA proteins are nuclear repressors of plant gibberellin (GA) responses. Here, we investigate the properties of SLN1, a DELLA protein from barley that is destabilized by GA treatment. Using specific inhibitors of proteasome function, we show that proteasome-mediated protein degradation is necessary for GA-mediated destabilization of SLN1. We also show that GA responses, such as the aleurone alpha-amylase response and seedling leaf extension growth, require proteasome-dependent GA-mediated SLN1 destabilization. In further experiments with protein kinase and protein phosphatase inhibitors, we identify two additional signaling steps that are necessary for GA response and for GA-mediated destabilization of SLN1. Thus, GA signaling involves protein phosphorylation and dephosphorylation steps and promotes the derepression of GA responses via proteasome-dependent destabilization of DELLA repressors.

Bioactive gibberellin (GA) is an essential regulator of vascular plant development. The GAI gene of Arabidopsis thaliana (L.) Heynh. encodes a product (GAI) that is involved in GA signalling. The dominant mutant gai allele encodes an altered product (gai) that confers reduced GA responses, dwarfism, and elevated endogenous GA levels. Recessive, presumed loss-of-function alleles of GAI confer normal height and resistance to the GA biosynthesis inhibitor paclobutrazol. One explanation for these observations is that GAI is a growth repressor whose activity is opposed by GA, whilst gai retains a constitutive repressor activity that is less affected by GA. Previously, we described gai-t6, a mutant allele which contains an insertion of a maize Ds transposable element into gai. Here we describe the molecular and physiological characterization of two further alleles (gai-t5, gai-t7) identified during the Ds mutagenesis experiment. These alleles confer paclobutrazol resistance and normal endogenous GA levels. Thus the phenotype conferred by gai-t5, gai-t6 and gai-t7 is not due to elevated GA levels, but is due to loss of gai, a constitutively active plant growth repressor.

Bioactive gibberellins (GAs) are essential endogenous regulators of plant growth. GA signaling is mediated via GAI, a nuclear member of the GRAS family of plant transcription factors. Previous experiments have suggested that GAI is a GA-derepressible repressor of plant growth. Here we test this hypothesis by examining the effects of the expression of Arabidopsis GAI in transgenic Basmati rice. High-level expression of GAI caused dwarfism and reduced GA responses, and the strength of this effect was correlated with the level of transgene expression. In particular, the expression of GAI abolished the GA-mediated induction of rice aleurone alpha-amylase activity, thus implicating GAI orthologs in the well-characterized cereal aleurone GA response. The GA derepressible repressor model predicts that high-level expression of GAI should confer dwarfism, and these observations are consistent with this prediction.

Gibberellins are hormones that control growth and a wide variety of other plant developmental processes. In recent years, significant progress has been made on the biochemistry of gibberellin biosynthesis and on the mechanisms by which gibberellin levels are regulated in plants. There have also been major advances in the understanding of gibberellin signaling, with several key genes being cloned. This review discusses our current understanding of gibberellin signaling, as seen from the perspective of molecular genetic analysis, and relates these observations to previous biochemical studies. In particular, we highlight an important conclusion of recent years: that GAI/RGA and orthologs play major roles in gibberellin signaling in diverse plant species, and that gibberellin probably stimulates growth by derepression of GAI/RGA.

GRAS is a recently discovered family of plant-specific proteins that play important regulatory roles in diverse aspects of plant development. Several of the motifs present in the GRAS proteins suggest that they function as transcription factors, although homology-searching programs have revealed no significant similarity to any non-plant proteins. Here we propose that the GRAS proteins are related to the Signal Transducers and Activators of Transcription (STAT) family of proteins. STATs are known in many non-plant species, and act as intracellular intermediaries between extracellular ligands and the transcription and activation of genes. Our hypothesis is that the GRAS proteins perform this function in plants, with mechanisms similar to those of the animal STATs. If true, this hypothesis has important implications for the evolution of phosphotyrosine based signal transduction systems in eukaryotic organisms. BioEssays 22:573-577, 2000., (Copyright 2000 John Wiley & Sons, Inc.)

World wheat grain yields increased substantially in the 1960s and 1970s because farmers rapidly adopted the new varieties and cultivation methods of the so-called 'green revolution'. The new varieties are shorter, increase grain yield at the expense of straw biomass, and are more resistant to damage by wind and rain. These wheats are short because they respond abnormally to the plant growth hormone gibberellin. This reduced response to gibberellin is conferred by mutant dwarfing alleles at one of two Reduced height-1 (Rht-B1 and Rht-D1) loci. Here we show that Rht-B1/Rht-D1 and maize dwarf-8 (d8) are orthologues of the Arabidopsis Gibberellin Insensitive (GAI) gene. These genes encode proteins that resemble nuclear transcription factors and contain an SH2-like domain, indicating that phosphotyrosine may participate in gibberellin signalling. Six different orthologous dwarfing mutant alleles encode proteins that are altered in a conserved amino-terminal gibberellin signalling domain. Transgenic rice plants containing a mutant GAI allele give reduced responses to gibberellin and are dwarfed, indicating that mutant GAI orthologues could be used to increase yield in a wide range of crop species.

Active gibberellins (GAs) are endogenous factors that regulate plant growth and development in a dose-dependent fashion. Mutant plants that are GA deficient, or exhibit reduced GA responses, display a characteristic dwarf phenotype. Extragenic suppressor analysis has resulted in the isolation of Arabidopsis mutations, which partially suppress the dwarf phenotype conferred by GA deficiency and reduced GA-response mutations. Here we describe detailed studies of the effects of two of these suppressors, spy-7 and gar2-1, on several different GA-responsive growth processes (seed germination, vegetative growth, stem elongation, chlorophyll accumulation, and flowering) and on the in planta amounts of active and inactive GA species. The results of these experiments show that spy-7 and gar2-1 affect the GA dose-response relationship for a wide range of GA responses and suggest that all GA-regulated processes are controlled through a negatively acting GA-signaling pathway.

Gibberellin is an endogenous plant growth regulator. Here, we describe our present understanding of how gibberellin regulates plant growth, using recent results gained from studies of gibberellin-signalling mutants of Arabidopsis. These results show that a signalling pathway represses plant growth and that gibberellin releases this repression. In consequence, the well-known growth-promoting properties of gibberellin are due to its activity as an "inhibitor of an inhibitor" [Brian Pw. Sym Soc. Exp Bio 1957; 11:166-182 (Ref. 1)] of plant growth.

The Arabidopsis gai mutant allele confers a reduction in gibberellin (GA) responsiveness. Here we report the molecular cloning of GAI and a closely related gene GRS. The predicted GAI (wild-type) and gai (mutant) proteins differ only by the deletion of a 17-amino-acid segment from within the amino-terminal region. GAI and GRS contain nuclear localization signals, a region of homology to a putative transcription factor, and motifs characteristic of transcriptional coactivators. Genetic analysis indicates that GAI is a repressor of GA responses, that GA can release this repression, and that gai is a mutant repressor that is relatively resistant to the effects of GA. Mutations at SPY and GAR2 suppress the gai phenotype, indicating the involvement of GAI, SPY, and GAR2 in a signaling pathway that regulates GA responses negatively. The existence of this pathway suggests that GA modulates plant growth through derepression rather than through simple stimulation.

Industrial exposure and pharmaceutical use of antimony compounds have been linked to altered cardiovascular function and pathology. Antimony compounds induce hypotension, bradycardia, and cardiac arrhythmias, all of which can arise from aberrations in myocyte regulation of intracellular free calcium concentration ([Ca2+]i). To determine if trivalent antimony affects [Ca2+]i during excitation-contraction, we developed an in vitro cardiac myocyte model that was exposed for 24 hr to potassium antimonyl tartrate (PAT) at 0-10 microM. Control myocytes received sodium potassium tartrate. Concentrations of up to 10 microM PAT were without effect on total DNA and protein content of cultures, indicating that PAT exposures were not overtly toxic. However, spontaneous beating rates of myocytes were significantly reduced by 5 and 10 microM PAT. Myocytes were paced by electric field stimulation at 0.5 Hz, and the effect of PAT on [Ca2+]i transients during excitation-contraction was monitored with fura-2. PAT (2-8 microM) significantly reduced systolic [Ca2+]i in a concentration-dependent fashion, but was without effect on diastolic [Ca2+]i or on the first derivative of the transient rise (d[Ca2+]i/dt). Myocytes from control cells responded to epinephrine (10(-8)-10(-5) m) in concentration-dependent fashion with elevated systolic [Ca2+]i and an increase in the rate of decay of transients. In PAT-exposed myocytes, the systolic response was blunted while the decay rate was enhanced. PAT-exposed cells also exhibited a reduced basal [Ca2+]i when depolarized by 90 mm KCl and a reduced caffeine-releasable Ca2+ pool of the sarcoplasmic reticulum. Both control and PAT-treated cells responded to ryanodine in a comparable fashion. Results indicate that a nonlethal exposure to PAT reduces Ca2+ availability during excitation-contraction. Decreased influx of Ca2+ across the sarcolemma and enhanced removal of Ca2+ appear to be responsible., (Copyright 1997 Academic Press.)

Ouabain-sensitive uncoupled Na+ efflux has been studied in human, pig, and rat red cells and in vesicles containing reconstituted kidney Na+/K+ pumps obtained from these same species. The red cells from the different species gave qualitatively similar results; the uncoupled Na+ efflux was 15-30% of the Na+/K+ exchange rate, and this flux was inhibited at 5 mM extracellular Na+ (Na+o). At higher levels of Na+o there was a monotonic increase in the Na+ efflux. As has previously been observed in human red cells, the uncoupled efflux from pig red cells consists of Na+ and anion cotransport, suggesting that anion cotransport may be a general characteristic of uncoupled Na+ efflux in red cells. The uncoupled Na+ efflux carried out by pig and rat kidney Na+/K+ pumps differs from the red cell activity in that it represents no more than 2-4% of the Na+/K+ exchange rate and that 5 mM Na+o does not inhibit this efflux. Furthermore, the efflux does not appear to be dependent on anion cotransport. Vesicles containing human kidney Na+/K+ pumps differ from vesicles derived from pig or rat kidneys in that the Na+ efflux is not inhibited or stimulated by Na+ present on the opposite side; it thus appears that the Na+,K(+)-ATPase in these vesicles may be incapable of Na+/Na+ exchange. These results indicate that the ligand and kinetic properties of the uncoupled Na+ efflux mode of red cells are markedly different from kidney-derived Na+/K+ pumps reconstituted into proteoliposomes. The basis for these differences may be inherent in the Na+/K+ pumps themselves or represent differences between the two types of preparations studied.

Calretinin is a member of the EF-hand calcium-binding protein family, with a high similarity with calbindin D28k. The chick calretinin cDNA sequence was reconstructed in a M13 vector and transferred into an expression plasmid derived from the pET series. The calretinin gene was expressed in Escherichia coli and produced immunoreactive calretinin of the expected size. Bacterially expressed calretinin was purified with successive ammonium-sulfate precipitation, DEAE chromatography, hydroxyapatite chromatography, Sephadex G-75 chromatography and Mono-Q chromatography. Normally, 1.0-1.5 mg calretinin was obtained from 1 l bacterial culture with a protein recovery of 0.5-1.5%. Calbindin D28k was purified similarly from bacteria using an expression plasmid provided by W. Hunziker. Calcium-binding activity of purified proteins was measured by equilibrium dialysis in calcium/EGTA mixtures with 45Ca as tracer. Both calretinin and calbindin D28k bound 3-4 Ca2+/molecule (calretinin, 4.0 +/- 0.5; calbindin D28k, 3.5 +/- 0.4), implying that at least one of the canonical EF-hand domains does not bind calcium. The Kd was 0.3-0.5 microM with little difference between the values for the two proteins.

The metabolism of the reproductive and developmental toxicant bis(2-methoxyethyl)ether (diglyme) was studied in isolated rat hepatocytes and in the intact rat. Male Sprague-Dawley rats (190-220 g) were used in both studies. Hepatocytes, isolated by a two-step in situ collagenase perfusion of the liver, were cultured as monolayers and incubated with [14C]diglyme at 1, 10, 30, and 50 microM for up to 48 h. For the in vivo study, rats were given single oral doses of [14C]diglyme at 5.1 mmol/kg body wt, and urine was collected for up to 96 h. Radioactive compounds in the culture medium or in the urine were separated by high performance liquid chromatography and quantified with an in-line radioactivity monitor. Metabolites were identified by comparison of their chromatographic retention times and their mass spectra with those of authentic compounds. The principal metabolite from hepatocytes and in the urine was (2-methoxyethoxy)acetic acid (MEAA). This metabolite accounted for approximately 36% of the radioactivity in the 48-h culture medium and about 67% of the administered dose in the 48-h urine. Other prominent metabolites common to both systems included 2-(2-methoxyethoxy)ethanol, methoxyacetic acid (MAA), 2-methoxyethanol, and diglycolic acid. The diglyme metabolite profiles from urine and from hepatocytes were qualitatively similar, demonstrating that, in the rat, hepatocytes serve as a good model system for predicting the urinary metabolites of diglyme. Moreover, MEAA was shown to be the metabolite best suited for use as a short-term biological marker of exposure to diglyme.(ABSTRACT TRUNCATED AT 250 WORDS)

Calretinin and calbindin-D28k are two calcium-binding proteins that are present in largely different sets of nerve cells in the central nervous system. Their appearance during development of the chick retina was studied by immunohistochemistry and Western blots. The patterns are mature one day before hatching. Each cell type acquires its characteristic calcium-binding protein several days after its differentiation has started, but in most cases before morphological maturation is complete. There is also an early phase of calbindin immunoreactivity in many immature amacrine cells, and of calretinin immunoreactivity in the presumptive photoreceptor layer, suggesting that these proteins may have distinct functions in differentiating cells.

An embryotoxic oral dose of bis(2-methoxyethyl) ether (DGDME), 3.73 mmol/kg body wt (500 mg/kg), administered on the 11th day of gestation to pregnant CD-1 mice was metabolized predominantly by O-demethylation to 2-(2-methoxyethoxy)ethanol with subsequent oxidation to (2-methoxyethoxy)acetic acid. Urinary excretion of this metabolite over 48 hr amounted to 63 +/- 2% of the dose. A smaller percentage of the administered dose was metabolized at the central ether linkage to produce 2-methoxyethanol, which was further metabolized by alcohol dehydrogenase to methoxyacetic acid. Urinary excretion of methoxyacetic acid, a potent developmental toxicant, amounted to 28 +/- 1% of the administered dose by 48 hr and was the second most prominent urinary metabolite. Unchanged DGDME and methoxyacetic acid were detected in the embryonic tissues from these animals, and embryos harvested after the initial 6-hr period showed detectable amounts of only methoxyacetic acid. The average amount of methoxyacetic acid per embryo was calculated to be 1.5 +/- 1.0 mumol (5.9 mmol/kg body wt) at the 6-hr termination time. This finding suggests that the reported teratogenic effects of DGDME are due to methoxyacetic acid formed, either in the fetus or by hepatic metabolism in the dam with subsequent distribution to the embryonic tissue. These results suggest that such developmental toxicity may occur with structurally similar aprotic ethylene glycol ethers in which metabolic O-dearylation would yield 2-methoxy-ethanol.

The macromolecular binding of 4,4'-methylenebis(2-chloroaniline) (MOCA), a suspect human carcinogen, was studied in the adult male Sprague-Dawley rat after both oral and dermal administration. Rats were euthanized 1, 3, 7, 10, 14, and 29 days after a single 281 mumol/kg body wt dose of [14C]MOCA (oral, 213 muCi/kg; dermal, 904 muCi/kg). DNA from various tissues and hemoglobin were isolated for determination of the time course of MOCA macromolecular binding. After oral administration adduct formation was rapid with maximum levels appearing at 24 hr. The 24-hr covalent binding associated with the globin was 7.84 pmol/mg globin (t1/2 = 14.3 days). More extensive 24-hr covalent binding was detected for liver DNA with 49.11 pmol/mg DNA (t1/2 = 11.1 days). After dermal administration of MOCA the major portion of the dose, 86.2%, remained at the application site throughout the study. For these rats the 24-hr covalent binding determined for liver DNA was 0.38 pmol/mg DNA (t1/2 = 15.6 days). Although lower levels were detected after dermal application, similar stability of MOCA-DNA adducts indicates that quantification of such MOCA adducts may be useful for the long-term industrial biomonitoring of MOCA exposure and for the evaluation of human DNA-MOCA adduct formation, a lesion thought to be associated with the production of cancer.

The mechanism of biologic response from exposure to a 12% subtilisin Carlsberg preparation is shown to be one of histamine release in the guinea pig. Three groups of guinea pigs were pretreated by intradermal injections withsaline solution of (1) the commercial proteolytic enzyme preparation containing 12% subtilisin Carlsberg, (2) an alkaline protease preparation obtain from Aspergillus oryzae that was isolated from cotton dust, or (3) a nonproteolytic mixture of proteins and lipases obtained from cotton seeds. The histamine content of the ling, liver, and ear tissues of guinea pigs that were pretreated with any one of the three preparations showed an in untreated animals. Following challenge by intratracheal injection of a saline solution containing the subtilisin preparation, the guinea pigs pretreated with the same preparation showed a markedly reduced liver histamine level. Challenge by inhalation exposure to the subtilisin preparation of guinea pigs that were pretreated with any one of the above preparations resulted in a lower histamine concentration in the lungs and livers.

Dietary disulfiram enhances the toxicity of inhaled 1,2-dibromoethane in rats. This study was undertaken to determine whether the differential toxicity noted was associated with alterations in the levels of the compound and/or its metabolites in the target organs. A comparison of the levels of 14C in selected tissues of male rats, with and without dietary disulfiram, following the oral administration of 14C-1,2-dibromoethane was made. The results indicated that levels of radioactivity in the target organs of animals in the disulfiram group were significantly elevated both at 24 and 48 hours following compound administration. The data indicate a direct correlation between tissue levels and the enhancement of toxicity noted in the disulfiram-treated rats in the inhalation study. A significant elevation in the levels of radioactivity in washed liver nuclei obtained from animals receiving dietary disulfiram was also noted, suggesting a relationship between nuclear uptake and the increased incidence of liver tumors appearing in the disulfiran group in the inhalation study.

1. When magnesium and orthophosphate are added to Na+,K+-ATPase containing occluded rubidium ions, and suspended in a medium containing free rubidium ions, only 50% of the occluded rubidium is released rapidly. This is because the release of occluded rubidium is ordered, and the replacement (by rubidium ions from the medium) of the first occluded rubidium ions to leave slows the departure of the remaining occluded ions. 2. Since the Na+,K+-ATPase probably exists in the membrane as a structural dimer, the ordered release might represent either the ordered emptying of the two halves of the dimer, or the ordered release of the two rubidium ions thought to be contained in each promoter. 3. The present experiments were designed to decide between these possibilities by examining the behaviour of Na+,K+-ATPase in which about half of the protomers had been randomly inactivated by pre-treatment either with fluorescein isothiocyanate or with alpha-chymotrypsin. 4. The results show that the release of rubidium ions from each protomer is ordered.

The routes of 14C excretion following the administration of a single oral 230 mg/kg body weight dose of 2-ethoxyethanol [ethanol-1,2-14C] or 2-ethoxyethanol [ethoxy-1-14C] to male Sprague-Dawley rats were investigated. Elimination of the 14C by the urinary route accounted for 76 to 80% of the dose within 96 hr. The main pathway of biotransformation is oxidation to the corresponding acid, with some subsequent conjugation of the acid metabolite with glycine. The major metabolites, ethoxyacetic acid and N-ethoxy-acetyl glycine, representing 73 to 76% of the administered dose, were eliminated in the urine. The major difference in the metabolic profiles of the two radiochemicals was in the rate and amount of 14CO2 expired via the lung. Of the administered 14C, 11.7% of the ethoxy-labeled and 4.6% of the ethanol-labeled compounds were eliminated as CO2. The biological half-time was 9.9 +/- 1.5 hr for the ethoxy-labeled compound and 12.5 +/- 1.9 hr for the ethanol label. After administration of the ethanol-labeled compound, the only radiolabeled component found in the rat testes was identified as ethoxyacetic acid. Results of this study suggest that the reported testicular effects in the rat may be a result of tissue levels of ethoxyacetic acid.

The effects of DPI 201-106 were examined on contractions of papillary muscles from the right ventricle of feline heart, on [3H]-ouabain binding and Na+, K+-ATPase activity in feline ventricular membrane particles and on ouabain-sensitive 86Rb uptake in human erythrocytes. DPI 201-106 partially inhibited the Na+ pump at concentrations that caused pronounced positive inotropic effects.

Treatment of human red cell membranes with pure phospholipase A2 results in a progressive inactivation of both Ca2+-dependent and (Ca2+ + K+)-dependent ATPase and phosphatase activities. When phospholipase C replaces phospholipase A2, Ca2+-dependent ATPase activity and Ca2+-dependent phosphorylation of red cell membranes are lost, while Ca2+-dependent phosphatase activity is enhanced and its apparent affinity for Ca2+ is increased about 20-fold. Activation of Ca2+-dependent phosphatase following phospholipase C treatment was not observed in sarcoplasmic reticulum preparation. Phospholipase C increases the sensitivity of the phosphatase to N-ethylmaleimide but has little effect on the kinetic parameters relating the phosphatase activity to substrate and cofactors, suggesting that no extensive structural disarrangement of the Ca2+-ATPase system has occurred after incubation with phospholipase C.