Localization of human immunodeficiency virus core antigen in term human placentas.

Evidence of human immunodeficiency virus (HIV) replication was sought in human placentas obtained at term from pregnancies complicated by maternal HIV infection. Placentas were obtained from the pregnancies of 19 HIV-seropositive women, 4 women who were seronegative, and 4 untested women with no risk factors for HIV infection. These placentas were each examined by immunoperoxidase immunocytochemistry using monoclonal anti-p24/55 antibodies. In addition, minced placental tissue from 11 of the seropositive pregnancies and the 3 seronegative pregnancies were co-cultivated with stimulated human peripheral blood mononuclear cells. The clinical status of the infants born to the HIV-seropositive women was assessed when the infants were 8 to 28 months of age. P24/55 antigen was detected in 5 of the 19 placentas of the HIV-seropositive pregnancies and in none of the 8 placentas of seronegative or low-risk pregnancies. This HIV core viral antigen was located exclusively in the cytoplasm of villous cells with morphological characteristics of macrophages. The HIV antigen-containing cells were very sparsely distributed. Staining of the trophoblast was not observed in any placental specimen. Human immunodeficiency virus was isolated in culture from 3 of the 11 placentas from seropositive pregnancies. Clinical follow-up has not revealed a relationship between infection of the infant and either p24/55 antigen identification or isolation of virus from the placenta. Virological and histological evidence of HIV replication is found in approximately one fourth of placentas obtained at term from pregnancies complicated by maternal HIV infection. Replicating virus appears localized to sparse macrophages located within the chorionic villi, but specifically not within the trophoblastic layer.(ABSTRACT TRUNCATED AT 250 WORDS)

Lectin and toxin-like activities of Entamoeba histolytica: comparison of properties.

A comparison was made between properties of a recently discovered Entamoeba histolytica lectin which has a carbohydrate specificity for N-acetylglucosamine oligosaccharides and the previously found toxin-like principle of the ameba. A separation between these two activities was achieved upon subcellular fractionation by high speed centrifugation of freeze-thawed disrupted E. histolytica trophozoites (strain HM-1). Practically all of this lectin activity, as determined by hemagglutination of glutaraldehyde-fixed human erythrocytes, was found associated with the sedimented membrane fraction. This fraction did not affect monolayers of tissue-cultured mammalian cells. On the other hand, the soluble supernatant solution caused extensive damage to the tissue-cultured cells (change in morphology and detachment of cells). Both the lectin and toxin activities were heat-labile and their activities were preserved by the presence of reducing agents and proteolytic enzyme inhibitors. In contrast to the toxin, the isolated lectin was inactive at pH 7.2 and active only at pH 5.7-6.0. Both the lectin and toxin were inhibited by a number of macromolecular compounds such as chitin, peptidoglycan, bovine serum and an IgA fraction isolated from human colostrum. Only the lectin activity, however, was inhibited by low molecular weight chitin oligosaccharides (GlcNAc)n=2-6 or by lysozyme-digested peptidoglycan subunits. Moreover, fetuin and a ganglioside mixture extracted from ox brain were found to inhibit only the toxin-like activity. The IgG fraction of sera from patients with invasive amebiasis neutralized both lectin and toxin-like activities, while IgG from normal sera failed to neutralize either activity. Although our results indicate that in E. histolytica, lectin and toxin are two separate activities, both of them share a considerable number of properties which does not exclude the possibility that they may be related.

Tritrichomonas muris in the hamster: pseudocysts and the infection of newborn.

Female golden hamsters, either in the last week of pregnancy or in the first weeks of nursing, excreted in their feces variable numbers of pseudocysts of Tritrichomonas muris. Pseudocysts examined by electron microscopy had internalization of the 3 anterior flagella and the undulating membrane with its recurrent flagellum. The undulating membrane and the associated marginal lamellae were characteristic of T. muris. Pseudocysts gradually become motile after 2 or more hours of incubation in medium. The "excysted" trophozoites were identified ultrastructurally as T. muris. Newborn hamsters were not infected with T. muris at 3 days of age, but by the 7th day essentially all were found to have infected ceca, concomitant with cecal enlargement and the appearance of adult-type feces.

Entamoeba histolytica "toxin": fetuin neutralizable and lectin-like.

Extracts of Entamoeba histolytica produce rounding and agglutination of mammalian cells in tissue culture. This effect is inhibited or reversed by serum, by the serum glycoprotein, fetuin, or by N-acetyl-D-galactosamine. Concanavalin A produces a similar cytotoxic effect that is blocked or reversed by alpha-methyl mannoside. These properties suggest that the amebal "toxin" has a lectin-like activity.

Experimental amebiasis. IV. Amebal viruses and the virulence of Entamoeba histolytica.

We have attempted to determine whether amebal viruses are capable of viral conversion of the virulence of Entamoeba histolytical. Amebae of little or no virulence for the newborn hamster liver were infected with viruses obtained from four amebal strains of different virulence. Cultures of surviving amebae were increased in virulence by viruses from amebae of high, moderate, or low virulence, but decreased in virulence by the virus of the second most pathogenic amebal strain. Sequential infection with two viruses did not produce consistent cumulative effects on virulence. The changes in virulence noted are considered to be the unpredictable result of either selection pressures exerted by the lytic virus infection or possibly viral alterations of the amebae.

Experimental amebiasis. III. A rapid in vitro assay for virulence of Entamoeba histolytica.

A rapid and simple assay for cytopathogenicity of axenically cultivated Entamoeba histolytica has been developed employing baby hamster kidney (BHK) or mouse 3T3 cells conventionally tissue cultured. Three of the twelve amebal strains tested produced total destruction of the BHK cell monolayer in 2--3 hours, and these three strains are the three most virulent strains for the newborn hamster liver. Two additional strains were of moderate cytopathogenicity in vitro and of moderate virulence in vivo. Seven strains were of low cytopathogenicity and virulence. Within these three major groupings, however, the cytopathogenicity ranking was not entirely reproducible. The general correspondence of cytopathogenicity in vitro and virulence in vivo and the possibility of obtaining data within a few hours suggest such an assay may prove a useful tool in amebiasis research.

Viruses of Entamoeba histolytica. VII. Novel beaded virus.

A third amoebal virus type was isolated from four different strains of Entamoeba histolytica. The virus was most frequently seen as a linear structure about 235 nm long and consisting of 14 beadlike structures about 19 nm in diameter. A "dimer" of twice the length and consisting of 28 beads was occationally encountered. The virus replicated in the nucleus, forming ordered arrays. Acridine orange staining of viral aggregates in infected nuclei suggested the presence of double-stranded nucleic acid.

Experimental amebiasis. I. Pathogenicity of axenically cultured Entamoeba histolytica in the brain of the newborn mouse.

Axenically cultured Entamoeba histolytica inoculated intracerebrally into newborn Swiss mice invaded the cerebrum and produced multiple abscesses containing viable trophozoites. As few as 20 amebae of a virulent strain (HM-1:IMSS) occasionally produced fatal disease, 200 killed about 75% of animals and higher doses regularly killed all animals. In contrast, avirulent strains (HK-9 and HB-301:NIH) failed to produce acute brain disease in comparable time periods even when mice were inoculated with as many as 20,000 amebae. Two other strains (1295 and H-458:CDC) were of intermediate virulence. High doses of avirulent amebae often produced hydrocephalus as a late manifestation. In newborn, 3 week-old, and 6-week-old mice resistance to infection increased with age, and older animals often responded late to virulent strains by developing hydrocephalus.

Experimental amebiasis. II. Hepatic amebiasis in the newborn hamster.

Newborn hamsters inoculated intrahepatically were highly susceptible to infection by axenically cultured Entamoeba histolytica. Inoculations were performed through the abdominal wall, and lesions could be observed through the skin as early as 4 days after inoculation. The most virulent amebal strain, HM-1:IMSS, produced liver lesions in 19% of newborn animals inoculated with 20 amebae, and in about 90% receiving 2,000 amebae. Eleven other strains similarly tested either produced no lesions with 20,000 amebae or were of intermediate virulence. Two hamster strains did not show appreciable differences in susceptibility to the HM-1:IMSS amebal strain. Newborn hamsters were more susceptible to HM-1:IMSS amebae than animals which were 2, 4, or 7 days old at the time of inoculation. Three-week-old animals were resistant to doses below 20,000 virulent amebae.

Ultrastructure of the taste bud of the human fungiform papilla.

The taste bud of the human fungiform papilla was examined by electron microscopy. Typical type I, type II, and type III cells were found along with contact sites with nerve endings. Vesicles in nerve fibers contacting type I and type II cells suggest that these cells may receive efferent impulses, whereas vesicles and granules in type III cells adjacent to (afferent) nerve fibers support the view that type III cells are sensory receptors. All of these features are virtually indistinguishable from those previously reported in fungiform taste buds of other mammals.

The distribution of acetylcholinesterase in buds of the rat vallate papilla as determined by electron microscope histochemistry.

The distribution of acetylcholinesterase (AChE) in the rat vallate papillary bud was investigated by histochemical electron microscopy. Previous reports of specific AChE activity around subgemmal and intragemmal nerves and between some taste bud cells have been confirmed. In addition we have consistently observed dense precipitation between microvilli in the taste pore. The studies suggest that the neurotransmitter, acetylcholine, may be involved in early events in the taste process which are believed to occur in the pore.