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H Mehlhorn

Publications and source records attributed to H Mehlhorn.

At least 19 recordsLinked to original sources
PubMed1979

Electron microscopical study on gamogony of Sarcocystis suihominis in human tissue cultures.

Sexual stages and oocysts of Sarcocystis suihominis were developed in human tissue cultures and studied with the electron microscope. This development was extremely rapid, being completed about 18--22 h post infection and there were no preceding schizogonic processes, thus confirming the earlier observations that schizogony is obligatorily restricted to the intermediate host in the sarcosporidian life cycle. Micro- and macrogamonts could be distinguished about 12 h post infection and were situated in a parasitophorous vacuole bounded by two membranes. These gamonts reached diameters of up to 10 micrometer. The large nucleus of every microgamont gave rise simultaneously to about 20--30 microgametes. Only dense projections of the nucleus were used as nuclei of microgametes. The microgametes were slender, about 4--5 micrometer long, and several were found to have three flagella, one of which was attached to the body for some distance. Besides these flagella additional microtubules were found and in several cases the attached flagellum was not complete and contained various numbers of single or paired microtubules. The macrogametes were bounded by two membranes and contained two types of inclusions similar to the wall-forming bodies known from the genus Eimeria. The oocysts were bounded by a wall consisting of a dense outer layer and four membranes, under which two other membranes covered the cytoplasm. Beginning from the 22nd h post infection a development similar to sporulation was noted inside these oocysts. This sporulation, i.e., the formation of two sporocysts inside an oocyst, was, however, not completed, probably due to the rapid degeneration of the parasitized host cell. The oocyst itself even appeared intact five days later.

Cell Nucleus↗
PubMed1979

Sarcocystinae: nomina dubia and available names.

Examination of the original descriptions of the species of Sarcocystis in cattle, sheep, and swine, and of isosporid oocysts shed sporulated by dogs, cats, man, and other carnivores, has shown that it is not possible in most instances to identify unambiguously recently recognized taxa. The original descriptions are insufficient, and because no type specimens exist, could apply to two or more of the presently recognized taxa. We consider the following nomina dubia: Sarcocystis hirsuta S. miescheriana S. tenella S. cruzi S. bertrami Isospora bigemina (S. bigemina) I. hominis (S. hominis) I. buteonis (Frenkelia buteonis) Because the former type species, Sarcocystis miescheriana, is an indeterminate nomen dubium, we are proposing S. muris as the new type species. Historically, it was the first species described clearly and unambiguously even in the light of present knowledge, and the stages of its life cycle are probably completely known; it was the second species to be named. Old and recent descriptions are reviewed, and definitions are proposed for the following taxa: S. bovifelis S. bovicanis S. bovihominis S. ovifelis S. ovicanis S. muris (type species) S. suihominis S. suicanis S. equicanis Frenkelia microti F. glareoli for which neotypes will be prepared and deposited with designated institutions and curators. A new subfamily, Cystoisosporinae, is created.

Animals↗
PubMed1979

Electron-microscopic studies on Theileria ovis Rodhain, 1916: development of kinetics in the gut of the vector tick, Rhipicephalus evertsi evertsi Neumann, 1897, and their transformation within cells of the salivary glands.

Gamogony of Theileria ovis Rodhain occurs within the gut of nymphs of the tick Rhipicephalus evertsi evertsi Neumann. After molting, spherical and ovoid parasites are found within the intestinal cells of the ticks. These stages are thought to be zygotes, because they undergo a transformation process leading ultimately (in 3 days) to the formation of a motile stage, the kinete, the fine structure of which is very similar to that of the ookinetes of the hemosporidia. The kinete leaves the gut cells of the tick and penetrates the salivary gland cells where it produces infective stages (the sporozoites). These stages may be transmitted to sheep during the next blood meal of the tick. The developmental processes of T. ovis are compared to those of Hemosporina.

Animals↗
PubMed1979

Electron microscopic studies on Blastocrithidia triatomae Cerisola et al. 1971 (Trypanosomatidae).

In the bug Triatoma infestans developmental stages of Blastocrithidia tritomae, which can be mistaken for T. cruzi during xenodiagnosis, were studied by means of electron microscopy. It turned out that three different forms appeared during the progressive divisions: "micro-", "pro-" and epimastigotes. The morphological study revealed significant criteria for a distinction from T. cruzi stages. Furthermore cyst-like bodies were observed often attached to the flagella of the different stages. As revealed by the presence of labyrinthine structures found in flagellated stages and in the cyst stages the latter were suggested as being specific cysts to be excreted with the feces and thus to establish new infections in other bugs. Apart from the cyst-like structures a comparison with the organelles known from other Trypanosomatidae showed only slight variations. A tubular cytopharynx-like structure, which was lined by microtubules, and the way of attachment of the flagellum to the surface of the host cell has not been described in Blastocrithidia before.

Animals↗
PubMed1979

Electron microscopical studies on the development of Babesia canis (Sporozoa) in the salivary glands of the vector tick Dermacentor reticulatus.

The formation of sporozoites of Babesia canis was studied by light- and electron microscopy in the salivary gland cells of adult female ticks from the 2nd day after attachment until 1 day after detachment. It was found that this process was initiated by the binary division of kinetes that had already entered or entered during the period examined. During division the kinetes (15 X 2.5 microns) lost their typical organelles, reduced their three-layered pellicle to a single membrane and became spherical. After nuclear division and a further time-lag cell division occurred, giving rise to two cells in which this process was repeated. After numerous binary divisions the parasites acquired more and more closely the shape of the later infectious, pyriform sporozoite. These sporozoites measured about 2.5 X 1.5 microns and also had a three-layered pellicle, with rhoptries and a few micronemes, but never contained "spherical bodies". The formation process needed about 2--3 days so that the transmission to the dog could be carried out while the tick engorges and this is probably the stimulation for the development. Finally the cytological features of this sporozoite formation were compared to those in the Theileria species studied by our group.

Animals↗
PubMed1978

Electron microscopic studies on the development of kinetes of Theileria parva Theiler, 1904 in the gut of the vector ticks Rhipicephalus appendiculatus Neumann, 1901.

The development of motile stages, called kinetes, from a stationary stage (regarded as zygote) has been followed in Theileria parva by means of electron miscroscopy. This process started after moult of the tick nymphs which had sucked on highly infected calves, i.e. about 20 days after repletion (a.r.) of the ticks. The transformation took place by formation of a growing protrusion (= anlage) into an inner, enlarging vacuole. During this process the limiting membrane of the enlarging vacuole serves as the outer membrane of the developing motile stage, whereas the two inner ones as well as the subpellicular microtubules are newly formed. This transformation proceeds rapidly, so that on the 25th day a.r. most of the kinetes have already left the gut cells and started penetration into the salivary gland cells. On the way to the salivary glands nuclear divisions occurred within the kinetes. The steps of the transformation described were compared to those in T. annulata and to ookinete formation in haemosporidia.

Animals↗
PubMed1978

Extraintestinal stages fo Isospora ohioensis from dogs in mice.

The development of Isospora ohioensis was studied in mice by feeding tissues of mice inoculated with oocysts to coccidia-free dogs and by the examination of mesenteric lymph nodes using light and electron microscopes. Extraintestinal organs of mice became infectious to dogs within 1 day after ingesting oocysts and remained infectious for at least 211 days after inoculation (DAI). Isospora ohioensis sporozoites were found in lymphoreticular cells of mesenteric lymph nodes of mice from 1-374 DAI. Intracellular sporozoites were located in parasitophorous vacuoles. Sporozoites grew from 5--6 to 11--16 micron in length on the 39th DAI but never lost the 2 crytalloid bodies typical for coccidian sporozoites. PAS-positive granules accumulated gradually in intracellular sporozoites with duration of infection in mice. The appearance of parasitophorous vacuoles varied with duration of infection. Beginning with 7 DAI, the vacuole contained a marginal zone of electron-dense material (up to 0.8 micron wide), giving the appearance of a cyst wall or sheath under the light microscope; a true cyst wall was was not found.

Animals↗
PubMed1977

Light and electron microscopical study on sarcocysts from muscles of the rhesus monkey (Macaca mulatta), Baboon (Papio cynocephalus) and Tamarin (Saguinus(=Oedipomidas) oedipus).

Sarcocystis cysts from muscles of monkeys (baboon, tamarin and rhesus monkey) were studied by means of light and electron microscopy. The differences in the morphology of the cyst wall and parasites clearly indicate that the three monkey species examined were each parasitized by at least a specific Sarcocystis species being not identical with S. nesbitti or S. kortei. The large numbers of cysts found within the muscle fibres point out the important role that have these monkeys as intermediate hosts in the life cycle of Sarcocystis species, where the final hosts are still unknown.

Animals↗
PubMed1977

Electron microscopic studies of the development of kinetes in Theileria annulata Dschunkowsky & Luhs, 1904 (Sporozoa, Piroplasmea).

Gamogony of Theileria annulata Dschunkowsky & Luhs occurs within the intestine of nymphs of the tick Hyalomma anatolicum excavatum Koch. After the 5th day post repletionem (p.r.) of the ticks spherical and ovoid parasites were found within the intestinal cells. These stages were thought to represent fertilized macrogametes. These underwent a transformation process leading ultimately to the differentiation of a motile stage, the kinete, which leaves the intestinal cells on the 14th-17th day p.r. and penetrates the alveoles of the salivary glands. The transformation of the stationary into a motile stage takes place by formation of a growing protrusion (= anlage) into an inner, enlarging vacuole. During this process the limiting membrane of the vacuole serves as the outer membrane of the developing motile stage, whereas the 2 inner membranes of its pellicle are newly formed. The steps of this differentiation in T. annulata are compared to the process of ookinete formation in haemosporina.

Animals↗
PubMed1977

[Light and electron microscope studies on two types of giant schizonts (globidial schizonts) in the small intestine of sheep (author's transl)].

The jujunum of sheep was investigated for globidial schizont infection. Two types of giant schizonts, which had a maximum diameter of about 500 mum, were observed. Each type was found to contain morphologically different parasites. In type 1 the parasites were hook-shaped with a length of about 15-18 mum. Often they had an additional tight lacing at the apcial pole. The merozoites of the second type were spindle-shaped, measuring only 9-12 mum in length. Both types of parasites had 22 subpellicular microtubles beneath their pellicle. The parasites observed here differed clearly from those of globidial schizonts from the abomasum as well as from those of sarcosporidian cysts of the same host. In light microscopy the globidial schizonts from the jejunum of sheep seemed to be covered by a thin, mono-layered wall. By means of electron microscopy, it was shown, that this layer is identical with the host-cell cytoplasm enclosing utricle-like a giant, membrane-bound parasitophorus vacuole, which in both types of schizonts was closely filled with parasites and an enclosing ground substance. The host cell of the second type of schizonts had always numerous microvilli at the outer surface. The inner surface of the host cell formed numerous intravacuolar tubules of about 50 nm in diameter and with a considerable length. The cytoplasm of the host cells appeared always very condensed. Summarizing it was shown that the globidial schizonts from the jejunum differed clearly from those in the abomasum as well as from the sarcosporidian cysts. Thus it can be stated that more species than supposed up to now form giant schizonts within the digestive system of sheep causing the lesions of high economical importance.

Abomasum↗
PubMed1976

[Electron microscope studies on developmental stages of Theileria parva (Theiler, 1904) in the intestine of the tick Hyalomma anatolicum excavatum (Koch, 1844) (author's transl)].

The developmental stages of Theileria parva within the intestine of ticks were studied by electron microscopy. On the 2nd-4th day post repletionem (p.r.) the intestine of the ticks contained numerous stages, which were very similar to microgamonts and microgametes of haemosporidia. From these results it seemed likely that gamogony of Theileria parva takes place in the intestine of ticks, too. The microgamont-like stages were spear-head-like; they measured about 10.5 mum in length with a maximum diameter of about 2.1 mum in their middle region. These parasites, which were limited by a unit membrane, had a stiletto-like apex, several flagellar-like protrusions of about 3 mum in length and mostly two slender posterior protrusions. The stiletto-like structure was electron-dense and measured about 2.0 mum in length; at its base it appeared spongy consisting of coiled, fibrillar elements of about 20 nm in diameter. Up to 4 flagellar-like protrusions were found in cross sections originating near the base of the stiletto-like structure. At most, up to six microtubules were seen within these protrusions, which, however, at their free ends usually contained only two microtubules. Near the base of the stiletto-like structure two groups of additional microtubules began. One group ran beneath a third of the peripheral margin to the posterior cell pole. The other group was bundle-like arranged. In cross sections through the posterior slender protrusions of the parasite about 10 microtubules appeared in an irregular pattern. The slender posterior protrusions had nearly double dimensions of the flagellar-like protrusions.

Animals↗
PubMed1976

[Light and electron microscope studies on two types of giant schizonts (globidial schizonts) in the abomasum of sheep (author's transl)].

25 sheep were investigated for globidial schizont infection in the abomasum. Two types of giant schizonts, which had a diameter of about 250 mum up to 500 mum, were observed. Each type was found to contain morphologically different parasites. In type 1 the parasites were ovoid with a length of about 4 mum and had 24 subpellicular microtubules, whereas in type 2 the parasites were spindle-shaped, measured about 6 mum in length and had only 22 subpellicular microtubules. Both types of parasites, however, were characterized by a 1.5-2 mum large vacuole, which was always situated anterior to the nucleus. Thus the parasites observed here differed from the fine structure of the merozoites of the Eimeria and Sarcocystis species. At the earliest stage observed in the development of the parasites the schizont cytoplasm was subdivided into many spheroidal blastophores, which were still present in old stages. The interior of the blastophores is filled with many nuclei resulting from repeated divisions, whereby they pass through three different shapes. Independently from the nuclear divisions the anlagen of the daughter cells appeared within the blastophores. First these anlagen consist of a conoid and a concentric ring of short microtubules (22 or 24). Up to 8 anlagen were seen close to each other. As development proceeds, the blastophore membrane is elevated into a cone-shaped projection which later elongated into a finger-like bud. This bud, the developing parasite, contained the primordia of the rhoptries, the newly formed inner membranes of the pellicle and a nucleus. In a late stage of development the parasites were completely formed except for an attachment of their posterior ends to the remains of the blastophore. Thus nuclear divisions and daughter cell formation are two different phases in the species studied here, whereas in the endodyogeny of sarcosphoridia these both processes are closely connected. In light microscopy the globidial schizonts from the abomasum of sheep seemed to be covered by a thick, two-layered cyst wall. By means of electron microscopy it was shown, that the inner layer is identical with the host-cell cytoplasm enclosing utricle-like a giant parasitophorous vacuole. The outer surface of the host cell had numerous, up to 14 mum long microvilli. These microvilli and numerous macrophages scattered between formed evidently the outer layer seen in light microscopy. The host cell itself was filled with numerous bundles of fibrillar origin, long rows of vacuoles and mitochondria and made a very dense impression. The inner surface of the host cell formed numerous intravacuolar tubules of about 50 nm in diameter and about 4 mum in length. Summarizing it was found that the globidial schizonts differed clearly from the cysts of sarcosporidia. The thickness of the limiting system, however, may probably retain the parasites longer than usual in the genus Eimeria. Finally these globidial schizonts from the abomasum of sheep were compared to those from the small intestine.

Abomasum↗