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R R Kretschmer

Publications and source records attributed to R R Kretschmer.

At least 19 recordsLinked to original sources
PubMed1997

Does the eosinophil have a protective role in amebiasis?

While normal human eosinophils are destroyed in vitro by virulent Entamoeba histolytica, notwithstanding the presence of antibodies and complement, activated eosinophils promptly destroy the parasite although dying also at the end of the process. To study the possible in vivo participation of eosinophils in invasive amebiasis, we compared the induction of experimental amebic abscess of the liver (AAL) in gerbils (Meriones unguiculatus) previously made eosinophilic through Toxocara canis antigen injection and in normal control gerbils. After intraportal inoculation of 10(5) ameba trophozoites (6 and 24 hr), the ratio of gerbils with AAL, as well as the number and size of the microabscesses was comparable in eosinophilic and control gerbils. However, at 96 hr the number and size of the microabscesses were significantly smaller (p < 0.05) in eosinophilic gerbils. On the other hand the actuarial AAL survival curve up to 45 days post-amebic inoculation was significantly (p < 0.05) shifted to the right in controls. These results suggest that antigen-induced eosinophilia may exert a protective effect against AAL in gerbils.

Amebiasis↗
PubMed1996

The ultrastructure of Entamoeba histolytica locomotion.

This quantitative ultrastructural survey of E. histolytica locomotion in Boyden chambers supports the concept that this parasite is capable of random, chemokinetic and chemotactic motility. An E. histolytica committed to chemotaxis will flatten over the filter, accumulate smaller vacuoles at the front of the cell, and will also project pseudopods and its polarized body towards and alongside the chemoattractant axis, respectively. Other cell features such as cell polarization, membrane ruffling, hyaline, total number of pseudopods and caudal displacement of the nucleus appear to be associated with the locomotion efforts as such, perhaps reflecting speed (chemokinesis) but irrespective of orientation (chemotaxis). Finally, only one of the 11 features that were analyzed (i.e., number of vacuoles) failed to be distinctly associated with any of the movement forms studied. E. histolytica appears to possess the full repertoire of locomotion modalities observed in free moving eukaryots, and its motility translates into ultrastructural landmarks that could be useful indicators of subcellular events related to locomotion.

Animals↗
PubMed1995

Cyclic nucleotide changes induced in human leukocytes by a product of axenically grown Entamoeba histolytica that inhibits human monocyte locomotion.

Pulse exposure of human mononuclear phagocytes to the monocyte locomotion-inhibitory factor produced by Entamoeba histolytica (i.e., the 369- to 765-Da chromatographic fraction obtained from the supernatant fluid of axenically grown E. histolytica) led to a swift increase in the intracellular concentration of adenosine 3':5' cyclic monophosphate (cAMP). A weaker response was observed in human polymorphonuclear leukocytes, the locomotion of which, however, is not inhibited by this amebic factor. The same chromatographic fraction obtained from the axenic medium control lacked this effect, at least upon mononuclear phagocytes. On the other hand, both the monocyte locomotion-inhibitory factor and the axenic medium control, possibly through shared cultured medium components, induced comparable increases in guanosine 3':5' cyclic monophosphate (cGMP) in human mononuclear phagocytes and in polymorphonuclear leukocytes, thus suggesting that the latter-nucleotide is not critical for the leukotactic inhibitory phenomenon. Our results suggest that like other leukotactic inhibitors, the monocyte locomotion-inhibitory factor produced by E. histolytica operates through modulations of intracellular cAMP.

Animals↗
PubMed1995

Antigen induced eosinophilia protects gerbils (Meriones unguiculatus) against experimental amebic abscess of the liver.

While the normal human eosinophil is destroyed in vitro by virulent Entamoeba histolytica, notwithstanding the presence of antibodies and complement, activated eosinophils promptly destroy the parasite even though succumbing in the process as well. To study the possible in vivo participation of eosinophils in invasive amebiasis, we compared the induction of experimental amebic abscess of the liver (EAAL) in gerbils (Meriones unguiculatus) previously made eosinophilic (532 +/- 80 eosinophils/mm3) through Toxocara canis antigen injection and normal control gerbils (101 +/- 15 eosinophils/mm3). Shortly (6 and 24 h) after intraportal injection of 10(5) virulent E. histolytica, the ratio of gerbils with EAAL, as well as the number and size of the abscesses was comparable in eosinophilic and control gerbils. At 96 h post-inoculation, the ratio of animals with EAAL was still the same in both groups, yet number and size of abscesses were significantly (p < 0.05) smaller in eosinophilic gerbils. The actuarial EAAL survival curve up to 45 days post-amebic inoculation was significantly (p < 0.05) shifted to the right in eosinophilic gerbils. No significant changes in IL-5 levels were recorded throughout these experiments. The results suggest that antigen-induced eosinophilia may exert a protective effect against EAAL in gerbils. It is speculated that a less overwhelming EAAL strategy--more akin to human amebic abscesses--may reveal this protective effect more clearly.

Animals↗
PubMed1992

The destruction of virulent Entamoeba histolytica by activated human eosinophils.

Unlike normal (i.e., non-activated) human eosinophils that are unable to destroy virulent Entamoeba histolytica even in the presence of antibodies and complement, activated eosinophils effectively destroy the parasite in vitro without the help of opsonins, yet increase this capacity with their assistance. Many activated eosinophils succumb in the process as well, probably victims of toxic products released by dying amoebae. Human activated eosinophils thus behave more like activated macrophages than like neutrophil polymorphonuclear leucocytes that are notoriously incompetent in dealing with virulent amoebae. As a regular constituent of early inflammatory reactions, and notwithstanding the absence of blood and tissue eosinophilia in invasive amoebiasis, the activated eosinophil may play a role in the defence against E. histolytica.

Adult↗
PubMed1992

The killing of Entamoeba histolytica by activated human eosinophils.

Unlike normal, opsonin aided human eosinophils, fMLP-activated human eosinophils are capable of destroying virulent E. histolytica. Opsonins are not required for this action, although they enhance the effect. Some activated eosinophils succumb in the action as well, probably victims of toxic products released by dying amebas. Activated eosinophils thus appear to resemble activated macrophages in their dealing with this parasite.

Adult↗
PubMed1992

Further physicochemical characterization of the monocyte locomotion inhibition factor (MLIF) produced by Entamoeba histolytica.

Ultrafiltration, gel-sieve chromatography and HPLC were used to purify MLIF. This material was HCl-hydrolyzed and the amino acids analyzed by HPLC-ortho-ophthaldialdehyde. Two hydrophobic non-polar (ile,leu), two uncharged polar (thr,tyr) and two positively charged (basic) (his, arg) amino acids were found in clear excess to their concentration in AMC and thus may intervene in the composition of MLIF.

Amino Acids↗
PubMed1992

Effect of the monocyte locomotion inhibitory factor (MLIF) produced by Entamoeba histolytica upon the respiratory burst of human leukocytes.

In addition to inhibiting the locomotion of human MP, MLIF appears capable of inhibiting the respiratory burst (measured by chemiluminescence) of MP and of PMN as well. The effect on the latter cells may or may not be relevant in the host-E. histolytica interaction, as PMN have been found to be notoriously inefficient in dealing with amebas and, foremost, do not use oxidative mechanisms in dealing with the parasite. On the other hand, the inhibitory effect on MP may represent a true evasion mechanism inasmuch as activated MP are capable of destroying virulent amebas, and do so by both oxidative and non-oxidative mechanisms.

Adult↗
PubMed1992

Increased frequency of HLA-DR3 in Mexican mestizo pediatric patients with amebic liver abscess (ALA).

Mexican mestizo pediatric patients with ALA revealed a significantly increased frequency of HLA-DR3 alone, or in its haplotype form HLA-A2, DR3, which confirms our previous observation in adult patients with ALA in the same ethnic group. However, the relative increase in these HLA specificities in pediatric ALA patients when compared to adult patients was not statistically significant, and calls for an enlargement of the population studied.

Adolescent↗
PubMed1991

The role of mannose in the receptor of the monocyte locomotion inhibitory factor produced by Entamoeba histolytica.

The effect of the monocyte locomotion inhibitory factor (MLIF) produced by Entamoeba histolytica is diminished, if not cancelled, when human monocytes are pre-exposed to concanavalin A or sodium periodate, respectively, but not when MLIF is pretreated with sodium periodate. When the MLIF-inhibited monocyte locomotion assays were performed in the presence of 12 different carbohydrates, only the runs containing D-mannose, 4-O-beta-galactosyl-mannoside or mannan revealed a significant reduction in the inhibitory effect. Finally, the MLIF activity was virtually absorbed out with mannan-coupled Sepharose 4B beads. This suggests that D-mannose constitutes an essential part of the receptor for MLIF on the human monocyte membrane.

Animals↗
PubMed1991

Increased frequency of HLA-DR3 and complotype SC01 in Mexican mestizo patients with amoebic abscess of the liver.

Our preliminary study (31 patients) of HLA frequencies and amoebic abscess of the liver (AAL) in Mexican mestizos was extended to include 110 patients with this condition. The previously found increase in HLA-B16 was not confirmed, but the frequency of HLA-DR3 was again found significantly increased in patients with AAL when compared to the normal, ethnically matched control population, both in its isolated (35.5% vs 12.7%) and in the HLA-A2, DR3 haplotypic version (20.9% vs 4.5%). Moreover, seven of the 17 HLA specificities that were found to be individually different at P (yet not at PC) level in patients with AAL when compared to the control population, were actually HLA-DR3 containing haplotypes. HLA-DR3 may thus encode a risk factor(s) for AAL, at least in the Mexican mestizo population. Furthermore a significant increase in the complotype SC01 and its haplotypic version SC01, DR4 were identified in 45 non selected patients with AAL when compared to normal controls (31.1% vs 6.7% and 17.8% vs 0% respectively). Even though a relationship between allelic forms of complement components and their function has not been fully established, this complotype could represent a risk factor as well, since complement appears to play a role in host defence against amoebic invasion. Finally, no extended haplotype preference was found in these AAL patients.

Adult↗
PubMed1990

[Monocyte locomotion inhibiting factor (MLIF) produced by E. histolytica induces an increase of cAMP in human monocytes].

The supernatant fluid of axenically grown E. histolytica contains a factor (MLIF) which inhibits the locomotion of human monocytes (including chemotaxis) without affecting that of human polymorphonuclear leucocytes. Locomotion, like other cellular functions, is modulated by changes in intracellular cAMP and cGMP. The consensus--with some exceptions--is that while rises in cGMP accompany locomotion, an increase in cAMP (without a concomitant fall in -cGMP) occurs with inhibition of cellular movement. We measured by radioimmunoassay the cAMP concentration of human monocytes exposed to inhibitory concentrations of MLIF. A significant (p less than 0.005) rise in monocyte cAMP was found, comparable to that observed with the use of forskolin, a well known cAMP stimulator. The control studies using plain axenic medium, not only failed to reveal any rise in cAMP but disclosed a small, yet not significant drop in intracellular cAMP. These results suggest that MLIF (like other locomotion inhibitors, i.e. prostaglandins E1, A1 and isoproterenol) produces a significant increase in intracellular monocyte cAMP. This modification in intracellular signals may contribute to the inhibition in monocyte locomotion, an event during which an increase in pericentriolar microtubules has also been observed.

Animals↗
PubMed1990

[HLA antigens, complement types, and amebic liver abscess in Mexican mestizos].

The association between parasitic diseases, and antigens of the major histocompatibility complex in man (HLA) has been poorly studied. The only study of the association between the HLA system and amebic abscess of the liver was performed by our group, and revealed a significant increase in HLA-BI6 and HLA-DR3 in patients with amebic abscess of the liver. The present study covered a larger number of patients and controls (110 of each) and it confirmed the association with HLA-DR3, it failed to confirm the association with HLA-BI6.

Adult↗