World food supply: PSAC panel warns of impending famine.
Explore the source record for details and available documents.
Economics↗
SEARCH · Search PubMed
Results for “PSAC”
Search indexed PubMed citations on genomics, clinical trials, systematic reviews and public health. Explore titles, authors and supplied subject terms, then open the PubMed record.
Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.
PSAC hiccoughs over 2,4,5-T.
Explore the source record for details and available documents.
Abnormalities, Drug-Induced↗
Suppressor mutations in the study of photosystem I biogenesis: sll0088 is a previously unidentified gene involved in reaction center accumulation in Synechocystis sp. strain PCC 6803.
In previous work, some members of our group isolated mutant strains of Synechocystis sp. strain PCC 6803 in which point mutations had been inserted into the psaC gene to alter the cysteine residues to the F(A) and F(B) iron-sulfur clusters in the PsaC subunit of photosystem I (J. P. Yu, I. R. Vassiliev, Y. S. Jung, J. H. Golbeck, and L. McIntosh, J. Biol. Chem. 272:8032-8039, 1997). These mutant strains did not grow photoautotrophically due to suppressed levels of chlorophyll a and photosystem I. In the results described here, we show that suppressor mutations produced strains that are capable of photoautotrophic growth at moderate light intensity (20 micromol m(-2) s(-1)). Two separate suppressor strains of C14S(PsaC), termed C14S(PsaC)-R62 and C14S(PsaC)-R18, were studied and found to have mutations in a previously uncharacterized open reading frame of the Synechocystis sp. strain PCC 6803 genome named sll0088. C14S(PsaC)-R62 was found to substitute Pro for Arg at residue 161 as the result of a G482-->C change in sll0088, and C14S(PsaC)-R18 was found to have a three-amino-acid insertion of Gly-Tyr-Phe following Cys231 as the result of a TGGTTATTT duplication at T690 in sll0088. These suppressor strains showed near-wild-type levels of chlorophyll a and photosystem I, yet the serine oxygen ligand to F(B) was retained as shown by the retention of the S > or = 3/2 spin state of the [4Fe-4S] cluster. The inactivation of sll0088 by insertion of a kanamycin resistance cartridge in the primary C14S(PsaC) mutant produced an engineered suppressor strain capable of photoautotrophic growth. There was no difference in psaC gene expression or in the amount of PsaC protein assembled in thylakoids between the wild type and an sll0088 deletion mutant. The sll0088 gene encodes a protein predicted to be a transcriptional regulator with sequence similarities to transcription factors in other prokaryotic and eukaryotic organisms, including Arabidopsis thaliana. The protein contains a typical helix-turn-helix DNA-binding motif and can be classified as a negative regulator by phylogenetic analysis. This suggests that the product of sll0088 has a role in regulating the biogenesis of photosystem I.
Amino Acid Sequence↗
Assembly of protein subunits within the stromal ridge of photosystem I. Structural changes between unbound and sequentially PS I-bound polypeptides and correlated changes of the magnetic properties of the terminal iron sulfur clusters.
The X-ray structure of Photosystem I (PS I) from Synechococcus elongatus was recently solved at 2.5A resolution (PDB entry 1JB0). It provides a structural model for the stromal subunits PsaC, PsaD and PsaE, which comprise the "stromal ridge" of PS I. In a separate set of studies the three-dimensional solution structures of the unbound, recombinant PsaC (PDB entry 1K0T) and PsaE (PDB entries 1PSF, 1QP2 and 1GXI) subunits were solved by NMR. The PsaC subunit of PS I is a small (9.3 kDa) protein that harbors binding sites for two [4Fe-4S] clusters F(A) and F(B), which are the terminal electron acceptors in PS I. Comparison of the PsaC structure in solution with that in the X-ray structure of PS I reveals significant differences between them which are summarized and evaluated here. Changes in the magnetic properties of [4Fe-4S] centers F(A) and F(B) are related to changes in the protein structure of PsaC, and they are further influenced by the presence of PsaD. Based on experimental evidence, three assembly stages are analyzed: PsaC(free), PsaC(only), PsaC(PS I). Unbound, recombinant PsaD, studied by NMR, has only a few elements of secondary structure and no stable three-dimensional structure in solution. When PsaD is bound in PS I, it has a well-defined three-dimensional structure. For PsaE the three-dimensional structure is very similar in solution and in the PS I-bound form, with the exception of two loop regions. We suggest that the changes in the structures of PsaC and PsaD are caused by the sequential formation of multiple networks of contacts between the polypeptides of the stromal ridge and between those polypeptides and the PsaA/PsaB core polypeptides. The three-dimensional structure of the C(2)-symmetric F(X)-binding loops on PsaA and PsaB were also analyzed and found to be significantly different from the binding sites of other proteins that contain interpolypeptide [4Fe-4S] clusters. The aim of this work is to relate contact information to structural changes in the proteins and to propose a model for the assembly of the stromal ridge of PS I based on this analysis.
Amino Acid Motifs↗
Control of electron transport in photosystem I by the iron-sulfur cluster FX in response to intra- and intersubunit interactions.
Photosystem I (PS I) is a transmembranal multisubunit complex that mediates light-induced electron transfer from plactocyanine to ferredoxin. The electron transfer proceeds from an excited chlorophyll a dimer (P700) through a chlorophyll a (A0), a phylloquinone (A1), and a [4Fe-4S] iron-sulfur cluster FX, all located on the core subunits PsaA and PsaB, to iron-sulfur clusters FA and FB, located on subunit PsaC. Earlier, it was attempted to determine the function of FX in the absence of FA/B mainly by chemical dissociation of subunit PsaC. However, not all PsaC subunits could be removed from the PS I preparations by this procedure without partially damaging FX. We therefore removed subunit PsaC by interruption of the psaC2 gene of PS I in the cyanobacterium Synechocystis sp. PCC 6803. Cells could not grow under photosynthetic conditions when subunit PsaC was deleted, yet the PsaC-deficient mutant cells grew under heterotrophic conditions and assembled the core subunits of PS I in which light-induced electron transfer from P700 to A1 occurred. The photoreduction of FX was largely inhibited, as seen from direct measurement of the extent of electron transfer from A1 to FX. From the crystal structure it can be seen that the removal of subunits PsaC, PsaD, and PsaE in the PsaC-deficient mutant resulted in the braking of salt bridges between these subunits and PsaB and PsaA and the formation of a net of two negative surface charges on PsaA/B. The potential induced on FX by these surface charges is proposed to inhibit electron transport from the quinone. In the complete PS I complex, replacement of a cysteine ligand of FX by serine in site-directed mutation C565S/D566E in subunit PsaB caused an approximately 10-fold slow down of electron transfer from the quinone to FX without much affecting the extent of this electron transfer compared with wild type. Based on these and other results, we propose that FX might have a major role in controlling electron transfer through PS I.
Chlorophyll↗
Extracellular lysines on the plasmodial surface anion channel involved in Na+ exclusion.
The human malaria parasite, Plasmodium falciparum, induces an unusual ion channel, the plasmodial surface anion channel (PSAC), on its host red blood cell (RBC) membrane. PSAC has a broad selectivity with permeability to anions, sugars, amino acids, purines, and certain vitamins, suggesting a role in nutrient acquisition by the intracellular parasite. Permeating solutes cover a range of molecular sizes and may be either neutral or carry a net negative or positive charge. Despite this broad selectivity, PSAC must efficiently exclude Na+ to avoid osmotic lysis of infected RBCs in the bloodstream. Here, we used amine-reactive N-hydroxysulfosuccinimide esters to probe PSAC's unusual selectivity. PSAC permeation rates, measured with both a kinetic osmotic lysis assay and single-channel patch-clamp, irreversibly decrease after treatment with these reagents. Sequential labelings with different esters and the effects of their chain length suggest that PSAC has multiple lysine residues near its extracellular pore mouth and that inhibition occurs via steric hindrance of its pore by the amide-linked side chain. When combined with the effects of pH on permeation, these findings implicate a combination of cation repulsion by pore mouth charges and a weak binding site for permeant solutes in PSAC's broad selectivity yet effective exclusion of Na+.
Animals↗
Plasmodial surface anion channel-independent phloridzin resistance in Plasmodium falciparum.
The plasmodial surface anion channel (PSAC) is an unusual ion channel induced on the human red blood cell membrane after infection with the malaria parasite, Plasmodium falciparum. Because PSAC is permeant to small metabolic precursors essential for parasite growth and is present on red blood cells infected with geographically divergent parasite isolates, it may be an ideal target for future antimalarial development. Here, we used chemically induced mutagenesis and known PSAC antagonists that inhibit in vitro parasite growth to examine whether resistance mutations in PSAC can be readily induced. Stable mutants resistant to phloridzin were generated and selected within 3 weeks after treatment with 1-methyl-3-nitro-1-nitrosoguanidine. These mutants were evaluated with osmotic lysis and electrophysiological transport assays, which indicate that PSAC inhibition by phloridzin is complex with at least two different modes of inhibition. Mutants resistant to the growth inhibitory effects of phloridzin expressed PSAC activity indistinguishable from that on sensitive parasites, indicating selection of resistance via mutations in one or more other parasite targets. Failure to induce mutations in PSAC activity is consistent with a highly constrained channel protein less susceptible to resistance mutations; whether this protein is parasite- or host-encoded remains to be determined.
Algorithms↗
The association between primary source of ambulatory care and access to and outcomes of treatment among AIDS patients.
OBJECTIVES: To examine the relationship between having a primary source of ambulatory care (PSAC), access to AIDS treatment and prophylaxis for opportunistic infection, and hospital and mortality outcomes among heterosexual men and women with AIDS. METHODS: Using a linked AIDS Registry-Medicaid database, 366 adults were identified (1989-1991) with at least 1 year of continuous Medicaid enrollment before AIDS diagnosis, who survived 2 weeks after diagnosis, and with no antiretroviral use or Pneumocystis carinii pneumonia (PCP) prophylaxis during the pre-diagnosis year. Outcomes included times to zidovudine treatment, PCP prophylaxis, hospitalization and death following diagnosis. Multivariate proportional hazards models were used to estimate the effects of patients' PSAC status in the 12-month post-diagnosis period on outcomes, controlling for demographic and case-mix variables. RESULTS: Study criteria preferentially included females, non-whites and enrollees eligible on the basis of aid to families with dependent children. A total of 49% of the patients had no PSAC. Patients with a PSAC were more likely to have received zidovudine [relative risk (RR) = 1.75, 95% confidence interval (CI) = 1.2, 2.2] or PCP prophylaxis (RR = 2.22, 95% CI = 1.5, 3.3). Regression models simultaneously examining association of the propensity to use zidovudine and PCP prophylaxis agents with death indicated that zidovudine-treated and PCP-prophylaxed patients were 64% and 51% less likely to die, respectively (RRdeath,zidovudine = (.36, 95% CI = 0.2, 0.4; RRdeath, PCP prophylaxis = 0.49, 95% CI = 0.3, 0.8). CONCLUSIONS: Patients' underuse of zidovudine and PCP prophylaxis was systematically associated with not having a PSAC. Lack of PSAC, in turn, predicted shorter survival but not increased hospitalization. Female gender, injecting drug use, non-white race and earlier diagnosis year also predicted poorer outcomes.
AIDS-Related Opportunistic Infections↗
Malaria parasites are rapidly killed by dantrolene derivatives specific for the plasmodial surface anion channel.
Dantrolene was recently identified as a novel inhibitor of the plasmodial surface anion channel (PSAC), an unusual ion channel on Plasmodium falciparum-infected human red blood cells. Because dantrolene is used clinically, has a high therapeutic index, and has desirable chemical synthetic properties, it may be a lead compound for antimalarial development. However, dantrolene derivatives would need to preferentially interact with PSAC over the sarcoplasmic reticulum (SR) Ca2+ release channel to avoid unwanted side effects from antimalarial therapy. Furthermore, dantrolene's modest affinity for PSAC (K(m) of 1.2 microM) requires improvement. In this study, we tested 164 derivatives of dantrolene to examine whether these hurdles can be surmounted. A simple screen for PSAC block defined the minimal scaffold needed and identified compounds with > or =5-fold higher affinity. Single-channel patch-clamp recordings on infected human red blood cells with two derivatives also revealed increased blocking affinity that resulted from slower unbinding from a site on the extracellular face of PSAC. We tested these derivatives in a frog skeletal muscle contractility assay and found that, in contrast to dantrolene, they had little or no effect on SR Ca2+ release. Finally, these blockers kill in vitro parasite cultures at lower concentrations than dantrolene, consistent with an essential role for PSAC. Because, as a class, these derivatives fulfil the requirements for drug leads and can be studied with simple screening technology, more extensive medicinal chemistry is warranted to explore antimalarial development.
Animals↗
Specific inhibition of the plasmodial surface anion channel by dantrolene.
The plasmodial surface anion channel (PSAC), induced on human erythrocytes by the malaria parasite Plasmodium falciparum, is an important target for antimalarial drug development because it may contribute to parasite nutrient acquisition. However, known antagonists of this channel are quite nonspecific, inhibiting many other channels and carriers. This lack of specificity not only complicates drug development but also raises doubts about the exact role of PSAC in the well-known parasite-induced permeability changes. We recently identified a family of new PSAC antagonists structurally related to dantrolene, an antagonist of muscle Ca++ release channels. Here, we explored the mechanism of dantrolene's actions on parasite-induced permeability changes. We found that dantrolene inhibits the increased permeabilities of sorbitol, two amino acids, an organic cation, and hypoxanthine, suggesting a common pathway shared by these diverse solutes. It also produced parallel reductions in PSAC single-channel and whole-cell Cl- currents. In contrast to its effect on parasite-induced permeabilities, dantrolene had no measurable effect on five other classes of anion channels, allaying concerns of poor specificity inherent to other known antagonists. Our studies indicate that dantrolene binds PSAC at an extracellular site distinct from the pore, where it inhibits the conformational changes required for channel gating. Its affinity for this site depends on ionic strength, implicating electrostatic interactions in dantrolene binding. In addition to the potential therapeutic applications of its derivatives, dantrolene's specificity and its defined mechanism of action on PSAC make it a useful tool for transport studies of infected erythrocytes.
Animals↗
Polypeptide composition of the Photosystem I complex and the Photosystem I core protein from Synechococcus sp. PCC 6301.
The polypeptide composition of the Photosystem I complex from Synechococcus sp. PCC 6301 was determined by sodium-dodecyl sulfate polyacrylamide gel electrophoresis and N-terminal amino acid sequencing. The PsaA, PsaB, PsaC, PsaD, PsaE, PsaF, PsaK and PsaL proteins, as well as three polypeptides with apparent masses less than 8 kDa and small amounts of the 12.6 kDa GlnB (PII) protein, wee present in the Photosystem I complex. No proteins homologous to the PsaG and PsaH subunits of eukaryotic Photosystem I complexes were detected. When the Photosystem I complex was treated with 6.8 M urea and ultrafiltered using a 100 kDa cutoff membrane, the resulting Photosystem I core protein was found to be depleted of the PsaC, PsaD and PsaE proteins. The filtrate contained the missing proteins, along with five proteolytically-cleaved polypeptides with apparent masses of less than 16 kDa and with N-termini identical to that of the PsaD protein. The PsaF and PsaL proteins, along with the three less than 8 kDa polypeptides, were not released from the Photosystem I complex to any significant extent, but low-abundance polypeptides with N-termini identical to those of PsaF and PsaL were found in the filtrate with apparent masses slightly smaller than those found in the native Photosystem I complex. When the filtrate was incubated with FeCl3, Na2S and beta-mercaptoethanol in the presence of the isolated Photosystem I core protein, the PsaC, PsaD and PsaE proteins were rebound to reconstitute a Photosystem I complex functional in light-induced electron flow from P700 to FA/FB. In the absence of the iron-sulfur reconstitution agents, there was little rebinding of the PsaC, psaD or PsaE proteins to the Photosystem I core protein. No binding of the truncated PsaD polypeptides occurred, either in the presence or absence of the iron-sulfur reagents. The reconstitution of the FA/FB iron-sulfur clusters thus appears to be a necessary precondition for rebinding of the PsaC, psaD and psaE proteins to the Photosystem I core protein.
Amino Acid Sequence↗
Biogenesis of PSI involves a cascade of translational autoregulation in the chloroplast of Chlamydomonas.
Photosystem I comprises 13 subunits in Chlamydomonas reinhardtii, four of which-the major reaction center I subunits PsaA and PsaB, PsaC and PsaJ-are chloroplast genome-encoded. We demonstrate that PSI biogenesis involves an assembly-governed regulation of synthesis of the major chloroplast-encoded subunits where the presence of PsaB is required to observe significant rates of PsaA synthesis and the presence of PsaA is required to observe significant rates of PsaC synthesis. Using chimeric genes expressed in the chloroplast, we show that these regulatory processes correspond to autoregulation of translation for PsaA and PsaC. The downregulation of translation occurs at some early stage since it arises from the interaction between unassembled PsaA and PsaC polypeptides and 5' untranslated regions of psaA and psaC mRNAs, respectively. These assembly-dependent autoregulations of translation represent two new instances of a control by epistasy of synthesis process that turns out to be a general feature of protein expression in the chloroplast of C. reinhardtii.
5' Untranslated Regions↗
A blasticidin S-resistant Plasmodium falciparum mutant with a defective plasmodial surface anion channel.
Erythrocytes infected with malaria parasites exhibit marked increases in permeability to organic and inorganic solutes. The plasmodial surface anion channel (PSAC), an unusual voltage-dependent ion channel induced on the host membrane after infection, may play a central role in these permeability changes. Here, we identified a functional PSAC mutant through in vitro selection with blasticidin S. Resistance to blasticidin S was generated during culture and correlated with significant reductions in permeability to multiple solutes, consistent with uptake via a common pathway. Single channel recordings revealed marked changes in PSAC gating with the addition of a subconductance state not present in wild-type channels. The channel's selectivity profile and pharmacology also were significantly altered. Eventual loss of the mutant phenotype upon removal of selective pressure and slower growth of mutant parasites suggest that PSAC serves an important role in intracellular parasite survival. These findings provide solid evidence for the uptake of diverse solutes via PSAC and implicate one or more parasite genes in expression of this channel.
Animals↗
The plasmodial surface anion channel is functionally conserved in divergent malaria parasites.
The plasmodial surface anion channel (PSAC), a novel ion channel induced on human erythrocytes infected with Plasmodium falciparum, mediates increased permeability to nutrients and presumably supports intracellular parasite growth. Isotope flux studies indicate that other malaria parasites also increase the permeability of their host erythrocytes, but the precise mechanisms are unknown. Channels similar to PSAC or alternative mechanisms, such as the upregulation of endogenous host transporters, might fulfill parasite nutrient demands. Here we evaluated these possibilities with rhesus monkey erythrocytes infected with Plasmodium knowlesi, a parasite phylogenetically distant from P. falciparum. Tracer flux and osmotic fragility studies revealed dramatically increased permeabilities paralleling changes seen after P. falciparum infection. Patch-clamp of P. knowlesi-infected rhesus erythrocytes revealed an anion channel with striking similarities to PSAC: its conductance, voltage-dependent gating, pharmacology, selectivity, and copy number per infected cell were nearly identical. Our findings implicate a family of unusual anion channels highly conserved on erythrocytes infected with various malaria parasites. Together with PSAC's exposed location on the host cell surface and its central role in transport changes after infection, this conservation supports development of antimalarial drugs against the PSAC family.
Animals↗
Genes encoding eleven subunits of photosystem I from the thermophilic cyanobacterium Synechococcus sp.
We have isolated the genes encoding 11 photosystem I (PSI) subunits from Synechococcus sp., from which this reaction center has been crystallized. The recombinant DNAs, including psaA, psaB, psaC, psaD, psaE, psaF, psaI, psaJ, psaK and psaL, were obtained by heterologous hybridization with probes from appropriate cDNAs or genes from spinach and Synechocystis sp. PCC 6803, or with synthetic oligodeoxyribonucleotides. Genes psaA/psaB, psaF/psaJ and psaL/psaI are each closely linked. The open reading frames predict polypeptides of 83 kDa (subunits Ia and Ib, encoded by genes psaA and psaB, respectively), 15.4 kDa (II, psaD), 17.7 kDa (III, psaF), 8.4 kDa (IV, psaE), 8.8 kDa (VII, psaC), 4.6 kDa (VIII, psaI), 4.8 kDa (IX, psaJ), 8.5 kDa (X, psaK) and 15.5 kDa (XI, psaL). A novel subunit (XII, psaM) was also identified. Subunits II, III, IV and VII seem to be peripheral, while the others seem to be intrinsic components of the reaction center. These data imply a striking similarity of cyanobacterial and eukaryotic PSI. All subunits studied are encoded by single-copy genes which seem to be transcribed into monocistronic (psaC, psaD, psaC, psaK) or dicistronic (psaA/psaB, psaF/psaJ, psaL/psaI) RNA species. Subunit III is translated as a 17.7-kDa precursor, including a transit peptide of 23 amino acid residues. This is consistent with its location in the thylakoid lumen.
Amino Acid Sequence↗
In vitro simulation of therapeutic plasmatic fibrinolysis.
One type of therapy for thromboembolism is plasmatic thrombolysis. Several plasminogen activators (PA) are clinically available, including urokinase (u-PA), tissue plasminogen activator (t-PA), streptokinase (SK), plasminogen-streptokinase-activator-complex (PSAC), or mutants of t-PA such as reteplase (RP) or tenecteplase (TP). Therapeutic plasmatic fibrinolysis was simulated, using the PA at relevant plasma concentrations, and plasmin (Pli) and PA activities were determined. Normal citrated plasma was supplemented with 31 to 1,000 IU/mL u-PA, 0.31 to 20 microg/mL t-PA, 125 to 4,000 IU/mL SK, 12.5 to 400 U/mL PSAC, 125 to 4,000 U/mL RP, or 0.31 to 10 microg/mL TP. Ten IU/mL urokinase was also incubated with pooled plasma of stroke patients, that was previously oxidized with the singlet oxygen (1O2) donor chloramine T (CT), to destroy plasmatic PAI-1 and alpha2-antiplasmin. After 0 to 80 minutes (37 degrees C), 50-microL samples were withdrawn and added to 100 microL 1.5 M arginine, pH 8.7, and oxidized with 50 microL of 20 mM CT. For determination of plasmin activity, 10 microL thereof was incubated with 150 microL 1.5 M arginine, pH 8.7, and 100 microL 20 mM CT preoxidized (15 minutes 37 degrees C) pooled normal citrate buffered EDTA-plasma for 30 minutes (37 degrees C). For determination of [PA+Pli]-activity, arginine was added after this incubation. 25-microL 6 mM Val-Leu-Lys-pNA were added and deltaA/h at room temperature (RT) was monitored, using a microtiterplate reader. [PA+Pli]-Pli = PA. The PA concentration required to induce 25% [ED25] of the maximally inducible Pli-activity in plasma (= 1 U/mL = 45 mg/L = 0.53 micromol/L active Pli; deltaA = 363 +/- 8 mA/h RT) after 10 minutes (37 degrees C) were 320 IU/mL u-PA, 8 microg/mL t-PA, 140 U/mL PSAC, 6,000 IU/mL SK, 720 U/mL RP, and approximately 150 microg/mL TP. The approximate activity half-lives of the PA in plasma were 30 minutes for u-PA, 30 minutes for t-PA, greater than 80 minutes for SK, greater than 80 minutes for PSAC, 50 minutes for RP, and 80 minutes for TP. The present study shows--for the first time--a combined kinetic in vitro simulation of the plasmatic activity of six different PAs. At clinically used concentrations, RP induces the highest plasmatic Pli activity. Due to unselective generation of plasmin in plasma, all PA are of some danger in inducing severe hemorrhagias. Clinical thrombolysis might be improved by usage of more physiologic activators of thrombolysis, such as activators of polymorphonuclear neutrophils.
Fibrinolysin↗
Plasmodium falciparum likely encodes the principal anion channel on infected human erythrocytes.
Invasion by the human malaria parasite, Plasmodium falciparum, is associated with marked yet selective increases in red blood cell (RBC) membrane permeability. We previously identified an unusual voltage-dependent ion channel, the plasmodial surface anion channel (PSAC), which may account for these increases. Since then, controversy has arisen about whether there are additional parasite-induced anion channels on the RBC membrane and whether these channels are parasite-encoded proteins or the result of modifications of an endogenous host protein. Here, we used genetically divergent parasite isolates and quantitative transport measurements to examine these questions. Our studies indicate that PSAC alone can adequately account for the increased permeability of infected RBCs to key solutes. Two distinct parasite isolates, grown in RBCs from a single donor, exhibit channel activity with measurably different voltage-dependent gating, a finding difficult to reconcile with simple activation or modification of a host protein. Instead, this difference in channel gating can be conservatively explained by a small number of polymorphisms in a parasite gene that encodes PSAC. The absence of known eukaryotic ion channel homologues in the completed P falciparum genome suggests a novel channel gene, and substantiates PSAC as a target for antimalarial development.
Animals↗
[Environment, nutrition and intellectual development].
The differential effects of malnutrition and psychosocial cultural deprivation (PSAC) upon intellectual performance and psychomotor development were studied in 52 preschool children attending nursery schools in urban Santiago (Chile). Nutritional status was evaluated according to Gómez, intellectual performance according to Weschler's scale (WISP and WISC tests), psychomotor development according to the Denver Developmental Screening Test and PSAC according to a numerical scale constructed from maternal I.Q.; socioeconomic status (Graffar) and a psychological questionnaire the correlational analysis, undernutrition was assigned a single value calculated from the severity and duration of the disease. An inverse correlation of - 0.36 existed between malnutrition and intellectual performance, and of - 0.39 between malnutrition and psychomotor development. Also, there was an inverse and significant correlation of - 0.73 between PSAC and psychomotor development; there was no correlation between PSAC and intellectual performance. Verbal I.Q. was more affected (r = - 0.52) than manual I.Q. (r = - 0.18) and children malnourished during the first 6 months of life attained lower scores of I.Q. than normals. The duration of malnutrition (mild in all cases) had no influence upon subsequent I.Q. This study was the basis for a rehabilitation program (educational-nutritional) to be applied in preschool children from nonprivileged areas.
Affective Symptoms↗