β-2-adrenergic stimulation of ornithine decarboxylase activity in porcine granulosa cells in vitro

Epinephrine, norepinephrine, and isoproterenol produced dose-dependent stimulation of ornithine decarboxylase (EC 4.1.1.7) activity in isolated porcine granulosa cells maintained under defined conditions in vitro. β- but not α-receptor-blocking agents prevented enzyme stimulation by catecholamines. Application of preferential β-1 and β-2-receptor antagonists and agonists localized the epinephrine effect to β-2-adrenergic mediation. Epinephrine action was enhanced by the phosphodiesterase inhibitor, 1-methyl-3-isobutyl-xanthine, but not by saturating concentrations of the cyclic AMP analogue, 8-bromocyclic AMP, of follicle-stimulating hormone, or of prostaglandin E₂. However, stimulation by epinephrine was additive to that of luteinizing hormone. Follicular fluid obtained from immature Graafian follicles contined concentrations of norepinephrine and epinephrine active in vitro.Thus, catecholamines may participate in the regulation of ornithine decarboxylase activity in the ovary. Catecholamine effects may be mediated by β-2-receptors linked to the adenylate cyclase system.     

Capillary-venous differences of free plasma catecholamines at rest and during graded exercise

Levels of free plasma catecholamines were simultaneously determined in 10 cyclists using capillary blood from one ear lobe and venous blood from one cubital vein. Catecholamine concentrations were higher in the ear lobe blood than in the venous blood at rest and during graded exercise. Average differences amounted to 1.7 nmol X 1(-1) (dopamine), 2.1 nmol X 1(-1) (noradrenaline) and 1.9 nmol X 1(-1) (adrenaline) at rest and increased only to 8.8 nmol X 1(-1) for noradrenaline during exercise. We assume that higher concentrations of dopamine and adrenaline in the capillary blood point to a significant neuronal release of these catecholamines, similar to noradrenaline. Catecholamine concentrations in capillary blood may better reflect sympathetic drive and delivery of catecholamines to the circulation than the concentrations in venous blood.     

Effect of guanethidine sympathectomy on cardiac functions in rat pups

Catecholamine level in the blood, heart and adrenal tissues, and heart sensitivity to catecholamines were determined in 3-week-old rats after chemical sympathectomy. It was shown that tachycardia in sympathectomy rats was caused by increased heart sensitivity to catecholamines due to the reduction in their concentration.     

Rat carotid body catecholamines determined by high performance liquid chromatography with electrochemical detection

Catecholamine contents in the rat carotid body were determined using high performance liquid chromatography with electrochemical detection (LCEC). Dopamine was found to be the predominant catecholamine present, representing about 53% of all catecholamines in the carotid body. Norepinephrine accounted for about 36% and epinephrine for about 10% of total carotid body catecholamines.     

Identification and quantification of catecholamines in potato plants (Solanum tuberosum) by GC-MS

Dopamine, norepinephrine, and normetanephrine were identified by GC-MS in potato (Solanum tuberosum L.) plants, the latter was new for plants. The highest amount of catecholamines was found in leaves. A developmental stage dependent variation in potato leaf catecholamines accumulation was also observed with highest level in third leaves. Catecholamine contents decrease during cold storage of tubers to undetectable levels. Mechanical wounding of leaves led to a small increase in the level of catecholamines investigated.     

Biogene Amine in Rezeptororganen von Gastropoden (Prosobranchia,Opisthobranchia)

Zusammenfassung Im Osphradium, in den Kopfanhängen und im Sipho verschiedener Prosobranchia sowie in Rhinophoren und Rückenanhängen von Opisthobranchiern wurden fluoreszenzmikroskopisch Nervenfasern und -endigungen festgestellt. Diese aminergen Strukturen liegen stets an der Basis von Sinnesepithelien. Mit Hilfe unterschiedlicher Bedampfungsmethoden konnten sowohl 5-Hydroxytryptamin als auch Catecholamine nachgewiesen werden. HCl-Behandlung der Paraffinschnitte ergab, daß die Catecholamine aus Dopamin und sehr wahrscheinlich auch aus Noradrenalin bestehen. Diese lichtmikroskopischen Befunde wurden durch mikrospektrofluorimetrische Messungen von Excitationsspektren bestätigt.

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Biogenic amines in receptor organs of gastropods (Prosobranchia, Opisthobranchia)

Summary In the osphradium, the cephalic tentacles and in the sipho of various prosobranch snails as well as in the rhinophores and dorsal appendages of opisthobranch snails, nerve-fibres and -endings have been demonstrated with the fluorescence microscope. These aminergic structures have been found constantly at the basis of sensory epithelia. By means of different types of vapour exposure 5-hydroxytryptamine and catecholamines were shown to be present. HCl treatment of the paraffin sections demonstrated that the catecholamines consist of dopamine and with a high degree of probability also of noradrenaline. These lightmicroscopical observations were confirmed by microspectrofluorimetric measurements of excitation spectra.

Herrn Prof. A. G. E. Pearse, Dept. of Histochemistry, und besonders Herrn Dr. F. W. D. Rost, Unit of Microspectrofluorimetry, Royal Postgraduate Medical School, London, danke ich für ihre Hilfe bei der Benutzung ihrer mikrospektrofluorimetrischen Anlage und des Computers beim Auswerten der Daten.     

Ultrastructural characterization of the tegument in protoscoleces of Echinococcus ortleppi

Cystic echinococcosis is a globally distributed zoonosis caused by cestodes of the Echinococcus granulosus sensu lato (s.l.) complex, with Echinococcus ortleppi mainly involved in cattle infection. Protoscoleces show high developmental plasticity, being able to differentiate into either adult worms or metacestodes within definitive or intermediate hosts, respectively. Their outermost cellular layer is called the tegument, which is important in determining the infection outcome through its immunomodulating activities. Herein, we report an in-depth characterization of the tegument of E. ortleppi protoscoleces performed through a combination of scanning and transmission electron microscopy techniques. Using electron tomography, a three-dimensional reconstruction of the tegumental cellular territories was obtained, revealing a novel structure termed the ‘tegumental vesicular body’ (TVB). Vesicle-like structures, possibly involved in endocytic/exocytic routes, were found within the TVB as well as in the parasite glycocalyx, distal cytoplasm and close inner structures. Furthermore, parasite antigens (GST-1 and AgB) were unevenly localised within tegumental structures, with both being detected in vesicles found within the TBV. Finally, the presence of host (bovine) IgG was also assessed, suggesting a possible endocytic route in protoscoleces. Our data forms the basis for a better understanding of E. ortleppi and E. granulosus s.l. structural biology.     

SEPARATION OF CATECHOLAMINE STORING SYNAPTOSOMES IN COLLOIDAL SILICA DENSITY GRADIENTS

Abstract— Catecholamine storing particles mainly from rat brain hypothalamus and corpus striatum have been isolated by isopycnic centrifugation in density gradients made of colloidal silica. As markers, tritium-labelled noradrenaline, endogenous noradrenaline and dopamine were measured. Cytochrome oxidase was determined as an indicator of mitochondria.
Two distinct populations of amine containing particles were recognized with densities of 1 , 03–1.04 g/ml and 1 , 045–1.065 g/ml in continuous isotonic gradients made of silica sol and a polymer. The light fraction was assumed to contain myelin fragments, light synaptosomes and possibly also catecholamine storage vesicles, while the other one was probably a heavy population of synaptosomes containing more mitochondria. Free mitochondria were found in a band at a density of 1 , 09–1.11.
The distribution pattern in isotonic gradients was compared with that in density gradients made of silica sol and sucrose or sucrose alone. The heavy population of the catecholamine particles was found to have a higher density in hypertonic gradients. Furthermore these synaptosomes seemed to lose more mitochondria and catecholamines than those in isotonic gradients probably due to the hypertonicity.
The present results confirm similar findings by other workers separating brain sub- cellular particles in isotonic gradients of Ficoll and sucrose.
Colloidal silica solutions might be of value for analytical centrifugation of brain sub-cellular particles, since it has a lower tonicity than sucrose, lower viscosity than Ficoll and furthermore it is very easy to handle. The silica sol is inexpensive and allows large scale work.     

Schistosoma haematobium: histochemistry of glycogen, glycogen phosphorylase a and glycogen branching enzyme in niridazole-treated females.

The body posterior to the ovary of Schistosoma haematobium females was investigated. Glycogen, glycogen phosphorylase a (EC 2.4.1.1) and glycogen branching enzyme (EC 2.4.1.18) activities were detected in the subtegumental muscle system, parenchyma and mature vitelline cells, whereas no activities were detected in the tegument and immature vitelline cells of the parasite. Administration of a single niridazole dose of 250 mg kg-1 to the pouched mouse (Saccostomus camestris) produced the following changes in S. haematobium females: a relatively rapid depletion of glycogen stores due to disruption of the absorptive surface of the parasite, and to an increase in the activity of glycogen phosphorylase a; a reduction in the phosphorylase a to phosphorylase b-conversion capacity of glycogen phosphorylase phosphatase (EC 3.1.3.17); a decrease in glycogen branching enzyme activity; and a relatively rapid degeneration of parasite cells possibly due to their loss of endogenous energy reserves.     

CmPEX6, a Gene Involved in Peroxisome Biogenesis,Is Essential for Parasitism and Conidiation by the Sclerotial Parasite Coniothyrium minitans

Coniothyrium minitans is a sclerotial parasite of the plant-pathogenic fungus Sclerotinia sclerotiorum, and conidial production and parasitism are two important aspects for commercialization of this biological control agent. To understand the mechanism of conidiation and parasitism at the molecular level, we constructed a transfer DNA (tDNA) insertional library with the wild-type strain ZS-1. A conidiation-deficient mutant, ZS-1TN22803, was uncovered through screening of this library. This mutant could produce pycnidia on potato dextrose agar (PDA), but most were immature and did not bear conidia. Moreover, this mutant lost the ability to parasitize or rot the sclerotia of S. sclerotiorum. Analysis of the tDNA flanking sequences revealed that a peroxisome biogenesis factor 6 (PEX6) homolog of Saccharomyces cerevisiae, named CmPEX6, was disrupted by the tDNA insertion in this mutant. Targeted gene replacement and gene complementation tests confirmed that a null mutation of CmPEX6 was responsible for the phenotype of ZS-1TN22803. Further analysis showed that both ZS-1TN22803 and the targeted replacement mutants could not grow on PDA medium containing oleic acid, and they produced much less nitric oxide (NO) and hydrogen peroxide (H₂O₂) than wild-type strain ZS-1. The conidiation of ZS-1TN22803 was partially restored by adding acetyl-CoA or glyoxylic acid to the growth media. Our results suggest that fatty acid β-oxidation, reactive oxygen and nitrogen species, and possibly other unknown pathways in peroxisomes are involved in conidiation and parasitism by C. minitans.     

Identification and localization of catecholamines in the nervous system of Limulus polyphemus

The concentrations of various catecholamines in the nervous system of the horseshoe crab Limulus polyphemus have been determined by high-performance liquid chromatography with electrochemical detection. Dopamine, norepinephrine, epinephrine, and their precursor L -Dopa were present in appreciable quantities in discrete regions of the central nervous system and cardiac ganglion. The catecholamines were localized more precisely by use of the glyoxylic-acid-histofluorescence technique of de la Torre and Surgeon (1976). Catecholamine fluorescence appeared in protocerebral and tritocerebral neuropile, including regions of the central body and optic medulla. Posterior to these brain areas, tracts extended through the circumesophageal ganglionic ring and laterally out each of the pedal ganglia. Small clusters of large fluorescent somata were present in the protocerebrum. No fluorescence was observed in the corpora pedunculata.     

Further study on Ascogregarina culicis in temperate Argentina: Prevalence and intensity in Aedes aegypti larvae and pupae

The bionomics of South American strains of Ascogregarina spp. are poorly known and the first studies were performed a few years ago. Our main objective was to characterize Ascogregarina culicis population in Aedes aegypti immatures in temperate Argentina. A total of 1800 water-filled containers were inspected within a cemetery of Buenos Aires City through a reproductive period of the host (October 2006-June 2007). The parasite was detected in 16.7% (329/1974) of the immatures and 8.5% (15/177) of the breeding sites. The prevalence decreased from 19.9% in larvae to 6.5% in pupae. In those infected breeding sites, about 85% of the immature mosquitoes harbor the parasite with a median intensity of nine trophozoites per larva and six gametocysts per pupa. The prevalence in shaded containers was higher than in sun exposed ones but the intensity of the infection was quite similar between both lighting conditions. Sun-exposed containers recorded water temperatures significantly higher than those under shade throughout the study period. Parasite trophozoites were only found from January to May with a clear seasonal pattern of prevalence. Monthly values of parasite prevalence and mosquito host (percentage of breeding sites and number of immatures) were significantly correlated at p < 0.05 when a temporal delay of two months was considered. Our results suggest that parasite prevalence is spatially and temporally heterogeneous in temperate urban Argentina, and these variations are associated with the host abundance.     

The frequency of Sarcocystis spp. and its effect on winter carcass composition of mottled ducks

Macrocysts of the protozoan parasite Sarcocystis spp. occurred in 34 of 241 (14%) adult and 6 of 70 (8.6%) immature mottled ducks (Anas fulvigula) that were collected in southwestern Louisiana from 1987 to 1989. The prevalence of Sarcocystis spp. among immature ducks was higher than previously reported, possibly because of a longer exposure period. No differences in carcass composition variables were found between heavily infected and uninfected adult mottled ducks during the winter period of the annual cycle. We concluded that macrocysts of Sarcocystis spp. did not influence carcass composition and probably exert negligible effects on survival of parasitized mottled ducks during winter.     

Effects of the allelopathically active macrophyte Myriophyllum spicatum on a natural phytoplankton community: a mesocosm study

The objective of this study was to identify potential effects of habitat conditions on parasite infection risk in reservoirs. For this, we compared parasite infection in 0+ perch (Perca fluviatilis L.) between reservoir sections: (1) along the longitudinal profile of Brno reservoir (inflow—main body—outflow), and (2) the transversal profile of Hamry reservoir (littoral and pelagic zones). Perch were predominantly infected with trophically transmitted endoparasites. Longitudinal parasite infection differed between sampling sections, showing different trends in particular parasite species between sections. The abundance of dominant Bunodera luciopercae was highest in the main body and lowest in the outflow, abundance of Proteocephalus sp. and Camallanus spp. decreased between the inflow and outflow, and abundance of Acanthocephalus lucii and ectoparasites (Gyrodactylus sp. and Argulus foliaceus) increased from the inflow to the outflow. Parasite diversity was higher in the outflow compared to other sections. No difference was observed in parasite abundance between littoral and pelagic perch subpopulations, though higher endoparasite diversity was found in the littoral zone. The results indicate that habitat type can influence parasite infection in perch through local food (intermediate host) availability. Fish–host behaviour is also discussed as a factor possibly influencing infection in perch.     

Properties of detergent-dispersed myocardial adenylate cyclase

Adenylate cyclase from rabbit ventricle was solubilized in 30 to 50% yield by the nonionic detergent Lubrol PX. The detergent, when present in the assay at concentrations above 0.05%, rapidly inactivated the enzyme in assays conducted above 26 °C; assays were valid only when conducted below this temperature. The solubilized enzyme was eluted from diethylaminoethyl (DEAE)-Bio-Gel A (DEAE-agarose) with 100 mm NaCl in a yield of 25% and was free of detergent. Several properties of the solubilized detergent-free enzyme were similar to properties of the native membrane-bound species. The K_m for substrate was 0.1 mm, the K_a for Mg²⁺ was 2.5 mm, and ATP in excess of Mg²⁺ was inhibitory. The enzyme was activated by F^? and guanyl-5′-yl imidodiphosphate [Gpp(NH)p] in a time- and temperature-dependent manner, and activation by the latter was persistent. Activation by F^? and Gpp(NH)p reduced the K_a for Mg²⁺. Activation by Gpp(NH)p was increased by Mg²⁺; the apparent K_a for activation was 0.1 μm. Multiple binding sites for Gpp(NH)p were present: one class with a K_d value of 0.11 μm was probably associated with activation of the enzyme. The soluble enzyme was insensitive to catecholamines, in both the presence and the absence of Gpp(NH)p. Sensitivity to catecholamines was not restored by the addition of phospholipids, particularly phosphatidyl inositol, in either the presence or the absence of Gpp(NH)p, and this phospholipid did not increase the sensitivity of the membrane-bound enzyme to epinephrine. Catecholamine binding sites were present, and their association with adenylate cyclase was seemingly not affected by phospholipids.     

Histofluorescent labelling of catecholaminergic structures in rotifers (Aschelminthes) in whole animals

1. Catecholaminergic neuronal structures were investigated in the rotifers Brachionus plicatilis, Asplanchna priodonta and Asplanchna herricki, using three different aqueous histofluorescent methods. 2. The adrenergic receptors were labelled using the dansyl analog of propranolol, a beta-adrenergic blocker. Catecholamine neurotransmitters were visualized by derivatizing with glyoxylic acid and formaldehyde respectively. 3. Although all three methods lead to similar results, dansyl-propranolol gave the most rapid and strong fluorescence. 4. The results reveal a complex and highly developed catecholaminergic neuronal system in all adult organs and sensory structures. While developed embryos in the egg show strong fluorescence, immature eggs do not.     

The EG95 Antigen of Echinococcus spp. Contains Positively Selected Amino Acids,which May Influence Host Specificity and Vaccine Efficacy

Echinococcosis is a worldwide zoonotic parasitic disease of humans and various herbivorous domestic animals (intermediate hosts) transmitted by the contact with wild and domestic carnivores (definitive hosts), mainly foxes and dogs. Recently, a vaccine was developed showing high levels of protection against one parasite haplotype (G1) of Echinococcus granulosus, and its potential efficacy against distinct parasite variants or species is still unclear. Interestingly, the EG95 vaccine antigen is a secreted glycosylphosphatydilinositol (GPI)-anchored protein containing a fibronectin type III domain, which is ubiquitous in modular proteins involved in cell adhesion. EG95 is highly expressed in oncospheres, the parasite life cycle stage which actively invades the intermediate hosts. After amplifying and sequencing the complete CDS of 57 Echinococcus isolates belonging to 7 distinct species, we uncovered a large amount of genetic variability, which may influence protein folding. Two positively selected sites are outside the vaccine epitopes, but are predicted to alter protein conformation. Moreover, phylogenetic analyses indicate that EG95 isoform evolution is convergent with regard to the number of beta-sheets and alpha-helices. We conclude that having a variety of EG95 isoforms is adaptive for Echinococcus parasites, in terms of their ability to invade different hosts, and we propose that a mixture of isoforms could possibly maximize vaccine efficacy.     

Toxoplasma gondii-Induced Activation of EGFR Prevents Autophagy Protein-Mediated Killing of the Parasite

Toxoplasma gondii resides in an intracellular compartment (parasitophorous vacuole) that excludes transmembrane molecules required for endosome - lysosome recruitment. Thus, the parasite survives by avoiding lysosomal degradation. However, autophagy can re-route the parasitophorous vacuole to the lysosomes and cause parasite killing. This raises the possibility that T. gondii may deploy a strategy to prevent autophagic targeting to maintain the non-fusogenic nature of the vacuole. We report that T. gondii activated EGFR in endothelial cells, retinal pigment epithelial cells and microglia. Blockade of EGFR or its downstream molecule, Akt, caused targeting of the parasite by LC3⁺ structures, vacuole-lysosomal fusion, lysosomal degradation and killing of the parasite that were dependent on the autophagy proteins Atg7 and Beclin 1. Disassembly of GPCR or inhibition of metalloproteinases did not prevent EGFR-Akt activation. T. gondii micronemal proteins (MICs) containing EGF domains (EGF-MICs; MIC3 and MIC6) appeared to promote EGFR activation. Parasites defective in EGF-MICs (MIC1 ko, deficient in MIC1 and secretion of MIC6; MIC3 ko, deficient in MIC3; and MIC1-3 ko, deficient in MIC1, MIC3 and secretion of MIC6) caused impaired EGFR-Akt activation and recombinant EGF-MICs (MIC3 and MIC6) caused EGFR-Akt activation. In cells treated with autophagy stimulators (CD154, rapamycin) EGFR signaling inhibited LC3 accumulation around the parasite. Moreover, increased LC3 accumulation and parasite killing were noted in CD154-activated cells infected with MIC1-3 ko parasites. Finally, recombinant MIC3 and MIC6 inhibited parasite killing triggered by CD154 particularly against MIC1-3 ko parasites. Thus, our findings identified EGFR activation as a strategy used by T. gondii to maintain the non-fusogenic nature of the parasitophorous vacuole and suggest that EGF-MICs have a novel role in affecting signaling in host cells to promote parasite survival.     

Isolation and characterization of a novel serine protease inhibitor,SjSPI, from Schistosoma japonicum

Serine proteinase inhibitor (Serpin, SPI) is a vital superfamily of endogenous inhibitors that monitor proteolytic events active in a number of biological functions. In this study, we isolated a full length gene encoding a novel serine protease inhibitor of Schistosoma japonicum (SjSPI) and characterized its molecular properties. Our result showed that SjSPI contained an open reading frame of 1,218?bp, which encoded 405 amino acid residues. Chromosomal structure analysis showed that SjSPI gene was comprised of six exons separated by five introns. It had essential structural motifs which were well conserved among the Serpin superfamily and showed 17-33% sequence identities with Serpins from other helminthic parasites. Trematode Serpin diverged separately into two different subclades and that the SjSPI clustered Subclade I. Exon-intron structures of trematode Serpins were highly conserved, closely with cestode Serpins. No signal peptide but a strongly transmembrane domain was predicted to exist in SjSPI, suggesting that the protein might be a soluble membrane-associated protein. Homology modeling predicted in silico confirmed that the SjSPI structure also belonged to the Serpin superfamily, containing nine α-helices and a reactive central loop. The bacterially expressed recombinant GST-SjSPI protein effectively inhibited the activities of chymotrypsin, trypsin and thrombin. Expression of SjSPI was detected throughout various developmental stages of the parasite in host and reached its maximal levels at the adult and egg stages, which suggests that SjSPI may be possibly involved in maintaining the physiology of eggs by regulating endogenous serine proteases.     

Evaluation of splenic accumulation and colocalization of immature reticulocytes and Plasmodium vivax in asymptomatic malaria: A prospective human splenectomy study

BackgroundA very large biomass of intact asexual-stage malaria parasites accumulates in the spleen of asymptomatic human individuals infected with Plasmodium vivax. The mechanisms underlying this intense tropism are not clear. We hypothesised that immature reticulocytes, in which P. vivax develops, may display high densities in the spleen, thereby providing a niche for parasite survival.Methods and findingsWe examined spleen tissue in 22 mostly untreated individuals naturally exposed to P. vivax and Plasmodium falciparum undergoing splenectomy for any clinical indication in malaria-endemic Papua, Indonesia (2015 to 2017). Infection, parasite and immature reticulocyte density, and splenic distribution were analysed by optical microscopy, flow cytometry, and molecular assays. Nine non-endemic control spleens from individuals undergoing spleno-pancreatectomy in France (2017 to 2020) were also examined for reticulocyte densities. There were no exclusion criteria or sample size considerations in both patient cohorts for this demanding approach.In Indonesia, 95.5% (21/22) of splenectomy patients had asymptomatic splenic Plasmodium infection (7 P. vivax, 13 P. falciparum, and 1 mixed infection). Significant splenic accumulation of immature CD71 intermediate- and high-expressing reticulocytes was seen, with concentrations 11 times greater than in peripheral blood. Accordingly, in France, reticulocyte concentrations in the splenic effluent were higher than in peripheral blood. Greater rigidity of reticulocytes in splenic than in peripheral blood, and their higher densities in splenic cords both suggest a mechanical retention process. Asexual-stage P. vivax-infected erythrocytes of all developmental stages accumulated in the spleen, with non-phagocytosed parasite densities 3,590 times (IQR: 2,600 to 4,130) higher than in circulating blood, and median total splenic parasite loads 81 (IQR: 14 to 205) times greater, accounting for 98.7% (IQR: 95.1% to 98.9%) of the estimated total-body P. vivax biomass. More reticulocytes were in contact with sinus lumen endothelial cells in P. vivax- than in P. falciparum-infected spleens. Histological analyses revealed 96% of P. vivax rings/trophozoites and 46% of schizonts colocalised with 92% of immature reticulocytes in the cords and sinus lumens of the red pulp. Larger splenic cohort studies and similar investigations in untreated symptomatic malaria are warranted.ConclusionsImmature CD71⁺ reticulocytes and splenic P. vivax-infected erythrocytes of all asexual stages accumulate in the same splenic compartments, suggesting the existence of a cryptic endosplenic lifecycle in chronic P. vivax infection. Findings provide insight into P. vivax-specific adaptions that have evolved to maximise survival and replication in the spleen.

Dr. Anstey and co-authors found that P. vivax-infected immature reticulocytes and erythrocytes accumulate in the same splenic compartments, suggesting existence of a cryptic endosplenic lifecycle in chronic P. vivax infection that maximizes survival and replication in the spleen.