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At least 37 records · Page 2Linked to original sources
PubMed1978

Experimental studies of infection dynamics: infection of the definitive host by the cercariae of Transversotrema patialense.

The number of cercariae of Transversotrema patialense which attach to the fish host Brachydanio rerio, during a fixed exposure period, is shown to be directly proportional to cercarial density within an experimental infection arena. The distribution of successful infections/host is shown to change from a random pattern to an over-dispersed form as cercarial exposure density or duration of host exposure to infection increases. A stochastic simulation model is used to demonstrate that small differences in host susceptibility to infection, within a population of hosts, can generate patterns of dispersion in parasite numbers/host similar to those observed in the experimental studies. Differences in host behaviour, during the period of exposure to infection, are thought to generate variability in host susceptibility to cercarial infection.

Animals↗
PubMed1977

Propagation of Pneumocystis carinii in vitro.

Pneumocystis carinii was propagated in vitro with primary embryonic chick epithelial lung (CEL) cells. Viability and growth of the organism were demonstrated by direct observation of the reproductive cycle in the Sykes-Moore chamber, serial passage with an increase in the number of mature cysts forms, the cytopathic effect of the organism on cell culture, and inhibition of growth of the organism by specific antiserum and pentamidine isethionate. Attempts to culture P. carinii indefinitely were not successful. However, cyst forms derived from murine and human sources increased 100-fold and 10-fold, respectively, during CEL cell culture passages. Serial passage of trophozoites alone resulted in the development of typical CPE and a maximum number of 2.8 X 10(3) cyst forms. Autoradiographic methods demonstrated active DNA, RNA, and protein synthesis within the cyst and suggest that metabolic interaction between the host cells and the organisms occurred. The nature of the attachment of P. carinii to the host CEL cell was clearly discernible by scanning electron microscopy (SEM). In the reproductive cycle a vegetative cell (designated "trophozoite") attached by tubular expansions to the hhed without entering the cell. Sporozoites developed within the detached young cyst, reaching a maximum number of eight within the mature cyst. Excystment occurred through single or multiple sites in the cyst wall, after which the released trophozoite attached to a new host cell.

Animals↗
PubMed1977

Intracerebral transplantation of the genital tubercle in the rat: the fate of the penile bone and cartilages.

Genital tubercles of 70 newborn male and female rats were transplated into the brains of unrelated infant rats. Seven other tubercles were placed subcutaneously. All female, and some male, hosts were injected with testosterone propionate. After surviving from 2-24 days,, histological study of 49 successful grafts showed survival of the urethral and balano-preputial epithelia and growth of the preputial glands, which formed secretion-filled cysts and became the major component of the graft. The fate of the mesodermal tissues witin the glands varied between remaining in an undeveloped state, with only pale fibrouw tissue and an area of granular degeneration and giant cells, and achieving an incompletely differentiatel state in which erectile tissue and the anterior process of fibrocartilage had formed and the glans had grown but the penile bone and its secondary growth cartilage failed to appear. Grafts could reach this degree of differentiation of the glands irrespective of transplantation site, attachment to the host dura, the sex of donor or host, and whether or not male hosts were given exogenous hormone.

Animals↗
PubMed1976

Inactivation of the enveloped bacteriophage phi6 by butylated hydroxytoluene and butylated hydroxyanisole.

Butylated hydroxytoluene (BHT) is a potent inactivator of the enveloped bacterial virus ø6 at concentrations as low as 3 x 10(-5) M. The viral envelope is not removed by BHT treatment, in contrast to the effects of exposure to the detergent Triton X-100. BHT-treated viruses are morphologically indistinguishable from controls but are defective in their ability to attach to the host cell. Temperature at the time of exposure was found to be a crucial factor in the effectiveness of BHT against ø6. A precipitous drop in the degree of inactivation by 3 x 10(-5) M BHT occurred when the temperature was lowered from 20 to 15 C. Calcium ions were found to potentiate the effect of BHT, particularly at lower temperatures where BHT alone was relatively ineffective. Barium and strontium, but not magnesium, were also effective in enhancing the activity of BHT. A structurally related molecule, butylated hydroxyanisole (BHA), was also found to inactivate ø6 virus, but higher concentrations were required than with BHT. Both BHT and BHA are commonly used as food additives, have apparent low toxicity to humans and other animals, and are potentially useful as antiviral agents.

Anisoles↗
PubMed1977

Inactivation and inhibition of replication of the enveloped bacteriophage phi6 by fatty acids.

The enveloped bacteriophage phi6 has been shown to be an interesting model system for the study of chemical agents that might have specific antiviral effects against lipid-containing mammalian viruses. In this report, we describe two types of antiviral activity exhibited by several fatty acids against bacteriophage phi6. Oleic acid (18:1) and palmitoleic acid (16:1) were potent inactivators of the virus. Treatment with either fatty acid at 50 mug/ml at 25 or 0 degrees C for 30 min reduced the virus titer to about 0.1% of the initial titer. Oleic acid at a concentration as low as 3 mug/ml ( approximately 10(-2) mM) reduced the virus titer to <1% of the initial titer within 30 min. Ultracentrifugation analyses of (14)C-amino acid- and (32)P-labeled virus treated with oleic acid indicated that the virion is largely disassembled by the treatment. Myristic acid (14:0) and palmitic acid (16:0) did not inactivate phi6 at 50 mug/ml, but nevertheless did prevent phi6 plaque production. Single-step virus growth experiments in which fatty acid was added at various times before or after infection indicated that it was an early stage of the phi6 replication cycle that was inhibited by the presence of myristic acid and that the inhibition occurred only if the myristic acid concentration in the extracellular growth medium was greater, similar10 mug/ml. phi6 could attach to its host cell in the presence of myristic acid at 50 mug/ml. We conclude that the fatty acids that prevent phi6 replication probably do so by interfering with the entry of the viral genome into the host cell.

Coliphages↗
PubMed1977

The early ingrowth of an autogenous bone inlay into an artificial defect in the rabbit mandibula.

The "take" and incorporation of two different autogenous bone grafts to an artificial defect in the rabbit mandibula was studied by means of conventional light microscopy, fluorescence miscroscopy and X-ray photography. The ingrowth rate was compared between a longitudinally split autogenous full thickness humeral bone graft in 21 rabbits and an autogenous full bone graft from the iliac crest in 14 rabbits. The rabbits were sacrificed at weekly intervals right to the end of the first month postoperatively, and morphological analyses were made. It was found that both types of graft became progressively incorporated into the mandibular defect. The humeral graft was better attached to the host bone but the graft cortex was not bone labelled to the same extent as when an iliac graft was used.

Animals↗
PubMed1979

An ultrastructural study on the interaction of Mycoplasma gallisepticum with the chicken tracheal epithelium.

Seven-day-old chickens wee intratracheally inoculated with Mycoplasma gallisepticum. The tracheas collected 6 and 14 days after chickens were inoculated were subjected to titration of mycoplasma and examination by light and electron microscopy. The mycoplasma organisms grew well; 10(7) to 10(8) color-changing units in a milligram of tissue were determined. Tracheal lesions occurred in close association with the presence of mycoplasmas and were characterized by degeneration of the epithelial cells and inflammatory cellular infiltration of the mucosa. Mycoplasmas were predominantly found extracellularly and only rarely in phagocytic vacuoles of the epithelial cells. Although the mycoplasmas exhibited considerable pleomorphism in size and shape, most of them were oval or round, and the largest diameters were between 300 and 700 mn. Elongated and irregular forms were also observed, particularly in those mycoplasmas adhering to the epithelial cells. The organism had a limiting unit membrane, the fibrillar nuclear area, the peripheral cytoplasmic area containing numerous ribosomes, and a terminal bleb structure. Mycoplasmas attached to the epithelial cells by their blebs close to the host cell membrane. At the attachment site, neither fusion of the membranes of the mycoplasma and host cell nor injury to the host cell membrane could be demonstrated. Nevertheless, seemingly, the intimate association between the adhering mycoplasmas and the epithelial cells might be an important factor in pathogenesis of the disease.

Animals↗
PubMed1976

Ultrastructure and life cycle of the lipid-containing bacteriophage phi 6.

An electron microscopic study of the lipid-containing bacteriophage phi 6 revealed an electron dense compact inner core of 30 nm in diam., which apparently contains the nucleic acid of the virus. This inner particle is surrounded by a complex polyhedral capsid with an outer diam. of 50 nm. Outside this is the envelope, which gives the virus a total diam. of 65 to 75 nm. The envelope, which has a thickness of a unit membrane, could be removed by treating the phage with Triton X-100. A definite structure is seen inside the envelope of the phage tail. In infection, phages are attached by their tails to the host cell pili. Occasional pili with a few attached phages were seen in a phage resistant mutant. In the course of the infection phages were also seen attached to the outer membrane of the cell. In a phage-tolerant mutant many normal-looking pili with adsorbed phages were visible, but we could never see phage-cell membrane associations. The membrane of the phage appears to fuse with the bacterial outer membrane and 50 nm virus particles could be seen in the periplasmic space of the bacterium, probably attached to the cytoplasmic membrane. Newly formed 50 nm particles appeared 45 min post infection (p.i.) cnetrally in the host cell. Assembly of the envelope also began at this time and by 80 minutes p.i. all the 50 nm particles were covered by the virus membrane. At no stage were phages seen in the periphery of the bacterium. Mature phages were finally released by a rupture of the host cell without spheroplast formation.

Adsorption↗
PubMed1978

Acquired resistance to ticks. III. Cobra venom factor and the resistance response.

Guinea-pigs developed resistance to larvae of the ixodid tick, Dermacentor andersoni, after one infestation. Resistant hosts were characterized by allowing significantly fewer larvae to engorge than non-resistant hosts. Larvae engorging on non-resistant hosts had a mean weight six times that of larvae obtained from resistant hosts at the end of a 5-day infestation. This immunologically based resistance was previously shown to have a cell-mediated and a humoral component. In an attempt to ascertain the role of complement in the resistance response, cobra venom factor (CoF) was administered to guinea-pigs producing prolonged (85--95 per cent) depletion of complement titres. CoF was administered during an initial infestation with tick larvae to determine if complement depletion altered the acquisition of tick resistance. CoF was also administered to tick-resistant hosts in an attempt to determine if the expression of tick resistance and the development of the basophil-packed lesion, characteristic of the tick-attachment site in resistant hosts, could be altered by complement depletion. CoF did not alter the acquisition of resistance when complement levels were reduced during a primary infestation. However, complement depletion of an animal which had acquired tick resistance blocked the expression of that resistance during a challenge infestation. In addition to increased numbers and weights of larvae engorging on tick-resistant animals depleted of complement, the basophil packed lesion at the tick attachment site was greatly reduced. Complement plays an important role in the expression of tick resistance in guinea-pigs.

Animals↗
PubMed1977

Histology of bovine skin reactions to Ixodes holocyclus Neumann.

The histology of skin responses to infestations with female Ixodes holocyclus ticks was investigated in naive and previously infested cattle. In the latter hosts, infiltration of the skin site with basophil leucocytes was an early event. Concurrent spongiosis and vesiculation occurred in the epidermis adjacent to the tick mouthparts. This was followed by infiltration of the upper dermis by eosinophils and other leukocytes. Such reactions were evident one hour after attachment of ticks in hosts which had received two prior infestations. Pronounced epidermal vesiculation and bulla formation with eventual serous exudation followed in previously infested cattle, leading to entrapment of ticks.

Animals↗
PubMed1978

Kinetics of phagocytosis of Chlamydia psittaci by mouse fibroblasts (L cells): separation of the attachment and ingestion stages.

The kinetics of phagocytosis of Chlamydia psittaci (6BC) by monolayers of mouse fibroblasts (L cells) was studied with an assay that distinguished between the attachment and ingestion phases of phagocytosis. At multiplicities of 10 and 100 50% infectious doses (ID50) per L cell, virtually all of the inoculated C. psittaci had been attached and ingested after 60 min at 37 degrees C. At multiplicities of 500 to 5,000 ID50 per L cell, the initial rates of attachment and ingestion of C. psittaci to L cells increased with the multiplicity of infection, but phagocytosis stopped even though many chlamydial cells remained free in suspension and readily available for attachment to the host-cell monolayers. Phagocytosis probably ceased because the L cells were injured when they took up large numbers of chlamydial cells. This injury prevented direct determination of the number of potential binding sites for C. psittaci on each L cell. However, this number is large enough to make the rates of chlamydial attachment and ingestion predominantly dependent on the multiplicity of infection.

Binding Sites↗
PubMed1978

Host-parasite relationships of Zygocotyle lunata (Trematoda) in the domestic chick.

Domestic chicks were infected with Zygocotyle lunata to determine gross and histopathological effects on the caecal tissues, to observe the method of feeding by worms and to examine the effects of crowding on the growth and development of the worm. Caecal weights and dimensions were significantly reduced in infected chicks. Caecal debris, abundant in control chicks, stained positive for proteins, polysaccharides, acid mucopolysaccharides and neutral fats. Caecal debris was rarely seen in infected chicks. The lumen of the intestinal caeca of the worms contained acellular material which showed protease activity and stained positive for proteins, polysaccharides and acid mucopolysaccharides. Histopathological effects of the infection showed a disruption of the architecture of host caecal mucosa, worm to worm attachment, tissue plugs in the worm acetabulum, and an engorgement of host mucosal tissue with erythrocytes. Stunting due to worm crowding was very evident and by 2 weeks post-infection, worms from single-worm infections were sexually mature and more than twice the length of immature flukes obtained from chicks infected with 100-500 cysts.

Animals↗
PubMed1977

Comparative physical and immunological aspects of the chimpanzee and guinea-pig subcutaneous chamber models of Neisseria gonorrhoeae infection.

Physical and immunological characteristics of the chimpanzee and guinea-pig subcutaneous chamber models for Neisseria gonorrhoeae infection were compared to evaluate their usefulness for gonococcal research. Urethral infection in chimpanzees anatomically resembled the human infection; however, individual variation in response, limited availability, and the presence of interfering micro-organisms in the urethra were found to limit the usefulness of the chimpanzee in immunological research. Although the guinea-pig subcutaneous chamber model may not be suitable for studying the attachment of gonococci to host cells or for the local production of IgA, it does have the immunological advantages of being more sensitive to infection, less variable in response, free of interfering micro-organisms, and is readily available to investigators. Except for differences in sensitivity and variability, results with the guinea-pig model paralleled results obtained in experiments with chimpanzees. Unlike chimpanzees, guinea-pigs are a comparatively inexpensive, rapidly replenishable animal, which after subcutaneous implantation with small porous chambers provide a convenient model for studying most immunological aspects of gonococcal infections.

Animals↗
PubMed2003

Identification of a Treponema pallidum laminin-binding protein.

Host extracellular matrix (ECM) components represent ideal microbial adhesion targets that many pathogens use for colonization of tissues and initiation of infection. This study investigated the interaction of the spirochete Treponema pallidum with the ECM component laminin. To identify candidate laminin-binding adhesins, the T. pallidum genome was analyzed to predict open reading frames that encode putative outer membrane proteins, as these proteins interact directly with host ECM components. Subsequent recombinant expression of these proteins and analysis of their laminin-binding potential identified one protein, Tp0751, that demonstrated specific attachment to laminin. Tp0751 attached to laminin in a dose-dependent, saturable manner but did not attach to the ECM component collagen type I or IV or to the negative control proteins fetuin or bovine serum albumin. Sodium metaperiodate treatment of laminin reduced the Tp0751-laminin interaction in a concentration-dependent manner, suggesting that oligosaccharides play a role in this interaction. In addition, Tp0751-specific antibodies were detected in serum samples collected from both experimental and natural syphilis infections, indicating that Tp0751 is expressed in vivo during the course of infection. Collectively, these experiments identified Tp0751 as a laminin-binding protein that is expressed during infection and may be involved in attachment of T. pallidum to host tissues.

Adhesins, Bacterial↗
PubMed1978

The presence of liver auto-antibodies induced by Entamoeba histolytica in the sera from both naturally infected humans and immunized rabbits.

Auto-antibodies against normal human liver have been detected in the sera of humans with highly positive indirect hemagglutination (IHA) amebiasis titers and with clinically-proven amebic liver abscess. Sera of amebiasis patients and rabbits immunized with killed Entamoeba histolytica were tested for anti-amebic antibodies by the IHA test and for auto-antibodies by the complement fixation test, using the antigens prepared from extracts of human liver and rabbit liver. A direct correlation was found to exist between high anti-Entamoeba antibody titers and the presence of anti-liver antibody in the serum. It is proposed that, in addition to direct parasite damage to host tissue, immunological damage could result from the attachment of circulating antigen to the cell surfaces of host tissues such as the liver.

Adolescent↗
PubMed1978

External layers of Rickettsia prowazekii and Rickettsia rickettsii: occurrence of a slime layer.

Using a simple specific-antibody stabilization procedure on organisms gently liberated from their host cells, we have demonstrated by electron microscopy that Rickettsia prowazekii and Rickettsia rickettsii possess a coat of variable thickness, external to the outer leaflet of the cell wall and the structure designated by others as a "microcapsule," which corresponds most closely to the slime layer of certain other bacteria. Reactions in the methenamine silver and ruthenium red staining procedures and the failure to be visualized by standard procedures suggest that the slime layer is largely polysaccharide in nature. It is postulated that this slime layer accounts in large part for the large, electron-lucent, halo-like zone which is found by electron microscopy to surround organisms of the typhus and spotted fever groups in the cytoplasm of their host cells, that it may be the locus of some major group-specific antigens, and that it may function as an antiphagocytic mechanism, as an aid for attachment of rickettsiae to potential host cells, or both. Moreover, because the attenuated E strain of R. prowazekii has been shown to possess a substantial slime layer, the basis for attenuation is not likely to be a simple smooth-to-rough variation.

Antigens, Bacterial↗
PubMed1976

The influence of temperature on the infectivity of Fasciola hepatica miracidia to Lymnaea truncatula.

Experiments were performed to study the effect of water temperature on the host-finding capacity (snail localization, attachment, and penetration) of Fasciola hepatica miracidia. Specimens of Lymnaea truncatula were exposed to miracidia labeled in vivo with radioselenium, and the radioactivity which subsequently was confined to the snails was taken as a measure of the host-finding capacity of the parasite. The minimum temperature required for host-finding was 5 to 6 C and the optimum temperature was in the range between 15 and 26 C. The lack of host-finding capacity below 5 to 6 C could be reversed experimentally by raising the temperature. A clear inverse relationship was demonstrated between the environnd 24 C the host-finding capacity ceased after 24 to 30, 20 to 24, and 13 to 20 hr, respectively.

Animals↗