A component of an antigenic rhoptry complex of Plasmodium falciparum is modified after merozoite invasion

Human antibodies affinity purified on an adsorbent prepared from a cDNA clone (Ag44) expressing a portion of a rhoptry antigen were used to characterize the synthesis and fate of the antigen in the asexual blood stages of Plasmodium falcipartum. The rhoptry antigen is synthesized in the mature trophozoite-stage parasites as a 103 kDa polypeptide, is present in the schizonts and merozoites as a 105 kDa polypeptide, is discharged from the rhoptries and found in the newly invaded red cells as a 110 kDa polypeptide. Anti-Ag44 antibodies immunoprecipitate the antigen and two additional polypeptides of 135 and 150 kDa from lysates of infected cells and from culture supernatants. The three polypeptides are associated in a non-covalent complex that persists in the newly invaded red cells. All the components of the high molecular weight rhoptry complex are antigenic and can be precipitated with immune human serum. The 135 kDa polypeptide is identical to a 140 kDa rhoptry antigen previously identified by a monoclonal antibody.     

The distribution of somatomedins in the nervous system of the cat and their release following neural stimulation

Recent evidence suggests a regulatory role in the nervous system for somatomedins. The present study, using a somatomedin radioreceptorassay which primarily detects insulin-like growth factors 1 and 2, shows that somatomedins are widely distributed throughout the nervous system of the cat. Whilst somatomedins were present in all CNS regions, the highest concentration occurred in the hypothalamus followed by cerebral cortex. In the spinal cord, the dorsal roots contained twice the concentration found in the ventral roots. Activity was also present in the sympathetic ganglia, vagus nerve and sciatic nerves. Following electrical stimulation of the brachial and sciatic nerves somatomedins were released into perfusates from extirpated cut limbs. These findings suggest that somatomedins may be neuroregulatory hormones.     

Pre-exposure of murine macrophages to lipopolysaccharide inhibits the induction of nitric oxide synthase and reduces leishmanicidal activity

Murine macrophages produce nitric oxide (NO) from L-arginine on stimulation with lipopolysaccharide (LPS), alone or with interferon-γ (IFN-γ). The effect of incubation of macrophages with low concentrations of LPS on NO synthesis on subsequent stimulation was investigated, using a murine macrophage cell line, J774, and peritoneal macrophages from CBA mice. Cells which had been incubated with LPS produced significantly lower amounts of NO, and expressed lower levels of NO synthase activity, following stimulation with IFN-γ and LPS, or with a high concentration of LPS. This effect was not reversed by tumor necrosis factor-α. The ability of CBA macrophages to kill the intracellular parasite Leishmania major was markedly reduced by pre-incubation with LPS. Reduced NO production by macrophages previously exposed to LPS is a manifestation of endotoxin tolerance, and may represent an important means of regulation of NO synthesis and thus a survival mechanism for intracellular parasites.     

Cell proliferation depends on mitochondrial Ca2+ uptake: inhibition by salicylate

Store-operated Ca²⁺ entry (SOCE) is a ubiquitous Ca²⁺ influx pathway involved in control of multiple cellular and physiological processes including cell proliferation. Recent evidence has shown that SOCE depends critically on mitochondrial sinking of entering Ca²⁺ to avoid Ca²⁺-dependent inactivation. Thus, a role of mitochondria in control of cell proliferation could be anticipated. We show here that activation of SOCE induces cytosolic high [Ca²⁺] domains that are large enough to be sensed and avidly taken up by a pool of nearby mitochondria. Prevention of mitochondrial clearance of the entering Ca²⁺ inhibited both SOCE and cell proliferation in several cell types including Jurkat and human colon cancer cells. In addition, we find that therapeutic concentrations of salicylate, the major metabolite of aspirin, depolarize partially mitochondria and inhibit mitochondrial Ca²⁺ uptake, as revealed by mitochondrial Ca²⁺ measurements with targeted aequorins. This salicylate-induced inhibition of mitochondrial Ca²⁺ sinking prevented SOCE and impaired cell growth of Jurkat and human colon cancer cells. Finally, direct blockade of SOCE by the pyrazole derivative BTP-2 was sufficient to arrest cell growth. Taken together, our results reveal that cell proliferation depends critically on mitochondrial Ca²⁺ uptake and suggest that inhibition of tumour cell proliferation by salicylate may be due to interference with mitochondrial Ca²⁺ uptake, which is essential for sustaining SOCE. This novel mechanism may contribute to explaining the reported anti-proliferative and anti-tumoral actions of aspirin and dietary salicylates.     

Effect of ageing of serum on consumption of antibody by B1C-globulin determinants; evidence for circulating breakdown products in glomerulonephritis

Changes in antibody consumption by the A and D determinants of β_1C-globulin were found to increase as serum aged in vitro. Consumption by the A determinant was 1·6 times and by the D determinant, 2·5–3 times greater in aged serum than in fresh EDTA plasma. The most likely explanation for the increased consumption with ageing is steric changes occurring as the β_1C molecule fragments into β_1A and α_2D, resulting in exposure of additional antibody combining sites. In specimens from patients with hypocomplementemic nephritis, the increase in consumption with ageing was less than in normal subjects. The data add to the evidence presented in earlier studies of the presence in vivo, in certain nephritics, of breakdown products of β_1C-globulin. The most abundant breakdown product would be α_2D-globulin.     

The neural basis of the psychomotor vigilance task

STUDY OBJECTIVE: To identify brain regions underlying the fastest and slowest reaction times on the Psychomotor Vigilance task (PVT) under well-rested conditions, as well as brain regions related to particularly poor performance after sleep deprivation. DESIGN: Subjects took the PVT twice while undergoing functional magnetic resonance imaging: once 12 hours after waking from a normal night of sleep and once after 36 hours of total sleep deprivation (TSD). Session order was counterbalanced. SETTING: UCSD J. Christian Gillin Laboratory for Sleep and Chronobiology (the sleep core of the General Clinical Research Center) and UCSD Magnetic Resonance Institute. PATIENTS OR PARTICIPANTS: Twenty right-handed healthy adults (8 women; age = 27.4 +/- 6.7 years; education = 15.6 +/- 1.5 years). MEASUREMENTS AND RESULTS: After a normal night of sleep, optimal performance was related to greater cerebral responses within a cortical sustained attention network and the cortical and subcortical motor systems. Slow reaction times, particularly after TSD, were associated with greater activity in the "default mode network" consisting of frontal and posterior midline regions. CONCLUSIONS: Optimal performance on the PVT appears to rely on activation both within the sustained attention system and within the motor system. Poor performance following TSD may result from a disengagement from the task and related inattention, and brain regions responsible for this localize within midline structures shown to be involved in the brain's "default mode." Finally, particularly poor performance after TSD may elicit a subsequent attentional recovery that manifests as greater activation within the same regions normally responsible for fast reaction times.     

Murine model of pulmonary anthrax: kinetics of dissemination, histopathology, and mouse strain susceptibility

Bioweapons are most often designed for delivery to the lung, although this route is not the usual portal of entry for many of the pathogens in the natural environment. Vaccines and therapeutics that are efficacious for natural routes of infection may not be effective against the pulmonary route. Pulmonary models are needed to investigate the importance of specific bacterial genes in virulence, to identify components of the host immune system that are important in providing innate and acquired protection, and for testing diagnostic and therapeutic strategies. This report describes the characteristics of host and Bacillus anthracis interactions in a murine pulmonary-infection model. The infective dose varied depending on the route and method of inoculation. The germination process in the lung began within 1 h of inoculation into the lung, although growth within the lung was limited. B. anthracis was found in the lung-associated lymph nodes approximately 5 h after infection. Minimal pneumonitis was associated with the lung infection, but significant systemic pathology was noted after dissemination. Infected mice typically succumbed to infection approximately 3 to 4 days after inoculation. The 50% lethal doses differed among inbred strains of mice, but within a given mouse strain, neither the age nor the sex of the mice influenced susceptibility to B. anthracis.     

Genetic requirements for salmonella-induced cytopathology in human monocyte-derived macrophages

Infection of human macrophages with Salmonella enterica serovar Typhimurium or Salmonella enterica serovar Dublin produces delayed cytotoxicity characterized by cell detachment and associated apoptosis. Using a site-specific mutant in the SpvB active site, we verify that the ADP-ribosylation activity of SpvB is required for delayed cytotoxicity in human macrophages infected with Salmonella: SipB and the type III protein secretion system (TTSS) encoded by Salmonella pathogenicity island 1 (SPI1) are not involved, whereas the SPI2 TTSS is absolutely required for SpvB-dependent cytotoxicity. Furthermore, we show that infection of macrophage cultures with wild-type or sipB mutant bacteria led to a complete loss of polymerized actin in over half of the cells after 24 h. In contrast, macrophages infected with the spvB or SPI2 (ssaV or ssaJ) mutant strain retained normal F-actin filaments, despite similar numbers of intracellular bacteria. We conclude that SpvB and a functional SPI2 TTSS are essential for Salmonella-induced delayed cytotoxicity of human macrophages.