Intracellular behaviour ofLeishmania enriettii within murine macrophages

Summary Both promastigotes and amastigotes ofLeishmania enriettii were readily ingested by mouse peritoneal macrophages (MPM). Promastigotes after their entry within MPM were rapidly immobilized and their multiplication was never observed. Microscopic examination revealed that ingested promastigotes were degraded within MPM. Nonmotile amastigotes ofL. enriettii taken up by MPM, on the other hand, multiplied intracellularly and eventually destroyed the infected cells.     

Leishmania donovani in hamsters: Stimulation of non-specific resistance by novel lipopeptides and their effect in antileishmanial therapy

Several novel type of lipopeptides were synthesized and evaluated for their ability to stimulate non-specific resistance againstLeishmania donovani infection. Peritoneal macrophages isolated from young male hamsters treated with muramyl dipeptide (MDP) and various synthetic lipopeptides (6 mg/kg i.p.) 7 days earlier, were cultured in vitro and challenged 24 h later withL. donovani promastigotes. One lipopeptide, Central Drug Research Institute (CDRI) compound 86/450, exhibited significantly higher immunostimulatory activity than MDP. Its prophylactic activity was further confirmed in hamsters by giving 2 split doses of 3 mg/kg of the compound spaced at 2 weeks, i.e. on day –7 and +7 of challenge withL. donovani amastigotes. The prophylactic effect lasted for 7 days following the last treatment with compound 86/450. The antileishmanial action of sodium stibogluconate (SAG) was also found to be enhanced by 16% in hamsters primed with compound 86/450.CDRI Communication No. 5034.     

Apoptosis and apoptotic mimicry: the Leishmania connection

Different death-styles have been described in unicellular organisms. In most cases they evolve with phenotypic features similar to apoptotic death of animal cells, such as phosphatidylserine (PS) exposure, oligonucleosomal DNA fragmentation, and loss of mitochondrial transmembrane potential, hinting that similar mechanisms operate in both situations. However, the biochemical pathways underlying death in unicellular organisms are still unclear. Host recognition of PS exposed on the surface of unicellular parasites is an important feature of the process of infection and progression of the disease. Here, we discuss data showing that entirely different mechanisms of PS exposure co-exist during the life-cycle of Leishmania amazonensis: in the case of promastigotes, a sub-population dies by apoptosis; in the case of amastigotes, the entire population exposes PS, not necessarily followed by apoptotic death. This phenomenon has been called apoptotic mimicry. The elusive caspase-like activities described in protozoa are also discussed.     

Hemagglutination of neuraminidase-treated human erythrocytes by Leishmania enriettii infected guinea-pig sera.

Sera from guinea-pigs infected with the protozoan parasite Leishmania enriettii showed higher hemagglutination (HA) titres for neuraminidase treated human erythrocytes than those of normal guinea-pig sera. This HA activity was associated mostly with the 19S fraction of the immune serum and could be absorbed out with an antigenic fraction of the parasite membrane. Antigenic determinants involved in this HA reaction consisted of, at least, beta-D-galactosyl or lactosyl residues.     

Spontaneous infestation of Phlebotomus dubosqui by promastigotes of Leishmania in Senegal]

An epidemiological survey of cutaneous leishmaniasis in Senegal revealed the presence of numerous Phlebotomus duboscqi in the entrances of rodent burrows. Two P. duboscqi out of 45 females dissected showed infection of the gut by promastigotes which could be cultured on NNN medium.     

Role of serum components in the binding and phagocytosis of oxidatively damaged erythrocytes by autologous mouse macrophages

To investigate the role of autologous serum components in the recognition of damaged cells by macrophages, we examined the binding and phagocytosis of damage oxidatively damaged red blood cells with Cu2+ and ascorbate (oxRBCs) by autologous resident mouse peritoneal macrophages. The binding of oxRBCs by macrophages was independent of the presence of serum. However, phagocytosis by macrophages increased with serum concentration, and macrophages showed little ingestion of oxRBCs in a serum-free medium. Macrophages neither bound nor appreciably ingested native RBCs (before oxidation) in either the absence or presence of autologous serum. Mouse macrophages ingested significantly more native as well as oxRBCs in the presence of heat-inactivated fetal calf serum than in the presence of heat-inactivated mouse serum. Pretreated oxRBCs with normal serum were rarely ingested by macrophages in a serum-free medium. Phagocytosis of oxRBCs was significantly inhibited by depletion of IgG or calcium from serum, by heat inactivation of complement, or by antiserum against mouse C3. These results demonstrate that serum components such as IgG, C3, and calcium are involved in phagocytosis of oxRBCs by autologous macrophages.     

Diptera of Calliphora genus, potential carriers and spreaders of swine vesicular disease virus]

Swine Vesicular Disease virus ingested by the adult fly Calliphora persists several days in the digestive tract of the insect and is eliminated in feces. The virus ingested by the insect at larval stage has been recovered from the digestive tract and feces of adult flies. Thus, the dissemination of the virus, even in a limited fashion, seems to be possible and attention is chiefly centered on the second process.     

In vitro assessment of anti-Leishmania immunity of man acquired with a vaccine

Monocytes, obtained from a human volunteer immunized with a Leishmania infantum-derived vaccine, when cultured in vitro displayed a strong parasiticidal activity against L. major promastigotes. In addition, immune serum conferred leishmanicidal activities to monocytes of normal, unexposed donors, and to murine macrophages.     

Leishmania donovani in hamsters: stimulation of non-specific resistance by some novel glycopeptides and impact on therapeutic efficacy

Several glycopeptides structurally related to muramyl dipeptide (MDP) have been synthesized and evaluated for their ability to stimulate the non-specific resistance of hamsters against L. donovani infection. These compounds have been named CDRI compounds. The synthetic procedure used for compounds 86/448 and 84/212 is described. MDP and its synthetic congeners were administered as immunostimulants at a prophylactic dose of 3 mg/kg at two weeks interval. The challenge infection (1 x 10(7) amastigotes i.c./hamster) was given in between two doses of the compounds. One of the glycopeptides, CDRI comp. 86/448, has been found to be significantly more potent than MDP, effecting 92% inhibition of the challenge dose, whereas MDP produced only 26.5% inhibition. The effect of comp. 86/448 lasted until day 7 of challenge. The efficacy of sodium stibogluconate was appreciably improved in hamsters treated with comp. 86/448.     

Scanning electron microscopic observation of spermiophage cell within the lumen of the epididymal duct of the vasectomized Japanese monkey (Macacus fuscatus).

The spermiophagic process by intraluminal macrophages in the epididymal ducts of the vasectomized Japanese monkey was well visualized with scanning electron microscope. The fragments of disintegrated spermatozoa were seen in the phase enveloped in bulk by flap-like cytoplasmic extensions or in the phase ingested within the cytoplasm.     

In vitro assessment of anti-Leishmania immunity of man acquired with a vaccine

Summary Monocytes, obtained from a human volunteer immunized with aLeishmania infantum-derived vaccine, when cultured in vitro displayed a strong parasiticidal activity againstL. major promastigotes. In addition, immune serum conferred leishmanicidal activities to monocytes of normal unexposed donors, and to murine macrophages.     

Leishmania donovani in hamsters: Stimulation of non-specific resistance by some novel glycopeptides and impact on therapeutic efficacy

Summary Several glycopeptides structurally related to muramyl dipeptide (MDP) have been synthesized and evaluated for their ability to stimulate the non-specific resistance of hamsters againstL. donovani infection. These compounds have been named CDRI compounds. The synthetic procedure used for compounds 86/448 and 84/212 is described.MDP and its synthetic congeners were administered as immunostimulants at a prophylactic dose of 3 mg/kg at two weeks interval. The challenge infection (1×10⁷ amastigotes i.c./hamster) was given in between two doses of the compounds. One of the glycopeptides, CDRI comp. 86/448, has been found to be significantly more potent than MDP, effecting 92% inhibition of the challenge dose, whereas MDP produced only 26.5% inhibition. The effect of comp. 86/448 lasted until day 7 of challenge. The efficacy of sodium stibogluconate was appreciably improved in hamsters treated with comp. 86/448.     

Scanning electron microscopic observation of sperimophage cell within the lumen of the epididymal duct of the vasectomized Japanese monkey (Macacus fuscatus)

Summary The spermiophagic process by intraluminal macrophages in the epididymal ducts of the vasectomized Japanese monkey was well visualized with scanning electron microscope. The fragments of disintegrated spermatozoa were seen in the phase enveloped in bulk by flap-like cytoplasmic extensions or in the phase ingested within the cytoplasm.     

New data on the biology of gametocytes of Plasmodium yoelii yoelli gathered from morphological characteristics indicating their age]

A morphological study has been made of the gametocytes of P. yoelii (a parasite of Rodents belonging to the "vivax" group). The authors distinguish 4 types chronologically ordered. Moreover, morphology enables one to predict their infectivity. The morphological analysis represents a tool leading to new data on the biology of gametocytes: loss of infectivity as soon as the parasitaemia becomes high; infectivity restricted to the young stages; concentration of young stages in the blood ingested by the Mosquitoes; short periodicity and short lived infectivity.     

Methylmercury toxicity in insect: detection of mercury in lysosomes using electron microprobe]

Intoxication of Blattella by methylmercury leads to a storage of the ingested metal within the lysosomes of ileum. Mercury is always found associated with zinc, sulphur and copper. Lysosome, therefore, intervenes in a detoxication process in Insects which have been exposed to organic mercury. It is suggested that mercury might be trapped by metallothionein.     

Mechanism of urea nitrogen binding by proposed oxidized starch gastrointestinal absorbents.

By use of 14-C label it was demonstrated that apparent binding of urea N to polyaldehyde starch was probably preceeded by hydrolysis to ammonium ion. Thus direct urea binding was not the mechanism through which ingested polyaldehyde starch might increase fecal N excretion in uremic patients.     

Accumulation of 2-micron latex particles in mouse Peyer's patches during chronic latex feeding

2-micron latex particles accumulated in macrophages in intestinal Peyer's patches of mice given latex suspensions as drinking fluid for 2 months. The number of particles accumulating was a direct (but nonlinear) function of the number ingested. Some of the latex particles were still present in Peyer's patches 6 weeks after the cessation of latex feeding.     

A possible preferential inhibition of chemotaxis of polymorphonuclear neutrophils by a chemical modification.

The modification of neutrophils with amino group blocking reagents of different chemical specificities showed that dansyl chloride caused inhibition of chemotaxis without suppression of random movement. Dansylated neutrophils, like control cells, ingested bacteria. Neither the stimulated cyanide-insensitive respiration, nor lactate production during phagocytosis, was affected significantly by dansylation as compared with the inhibition of directed movement.     

Shedding by rod photoreceptors after sunrise in fish

Diurnal shedding by retinal rods was studied in wild cutthroat trout,Oncorhyncus clarki, hatchery rainbow trout,Oncorhyncus mykiss, and the plains killifish,Fundulus zebrinus, by counting the shed tips of rod outer segments ingested as phagosomes by pigment epithelial cells. After sunrise, phagosomes increased in all species, but fewer occurred in trout, and these were elevated from 3 to 9 hours after sunrise. Shedding occurred earlier in the light period and was more robust in killifish, with phagosomes elevated from 1.5 to 6 hours after sunset. The data suggest that both production of phagosomes by shedding and their subsequent disposal are slower at the lower temperatures experienced by trout. Otherwise, rod shedding produced under natural lighting is not appreciably different than that provoked by sudden onset of artificial light.     

A possible preferential inhibition of chemotaxis of polymorphonuclear neutrophils by a chemical modification

Summary The modification of neutrophils with amino group blocking reagents of different chemical specificities showed that dansyl chloride caused inhibition of chemotaxis without suppression of random movement. Dansylated neutrophils, like control cells, ingested bacteria. Neither the stimulated cyanide-insensitive respiration, nor lactate production during phagocytosis, was affected significantly by dansylation as compared with the inhibition of directed movement.