Search PubMed⌕ Search

Biomedical subjects

K Rohde

Publications and source records attributed to K Rohde.

At least 55 records · Page 3Linked to original sources
PubMed1996

Crystallization and preliminary X-ray analysis of a thiol-activated cytolysin.

We present the first reported crystallization of a member of the thiol-activated family of protein toxins. Perfringolysin O, a virulence factor of Clostridium perfringens, has been crystallized in two different forms by the hanging drop vapor diffusion method. In one form the toxin crystallizes with PEG 20000 in the orthorhombic space group C222(1) with cell dimensions of a = 47.8 A, b = 182.0 A and c = 175.5 A and the crystals diffract to beyond 2.5 A resolution. In the second form the toxin crystallizes in a large variety of organic solvents including malt whisky. This crystal form belongs to the orthorhombic space group P222(1) with unit cell dimensions a = 47.1 A, b = 166.1 A and c = 214.0 A and with diffraction observed to 2.4 A resolution.

Bacterial Toxins↗
PubMed1996

BRCA1 mutations in German breast-cancer families.

We analyzed germline mutations of the BRCA1 gene in 20 German breast/ovarian-cancer families. BRCA1 mutations co-segregating with breast-cancer susceptibility were identified in 3 of these families. All mutations were found to generate a premature stop codon leading to the synthesis of truncated BRCA1 proteins of different length. Nine polymorphisms were detected in BRCA1, 4 of which have not been described previously. Analysis of familial tumors for LOH revealed that only the disease-related allele of BRCA1 was present.

Adult↗
PubMed1996

DNA polymorphisms in adhesion molecule genes--a new risk factor for early atherosclerosis.

To contribute to the analysis of the genetic background of atherosclerosis, especially endothelial dysfunction, we searched for DNA polymorphisms in the genes encoding E-, P-, and L-selectin, and ICAM-I and VCAM-I. We detected 17 mutations by single-strand conformation polymorphisms analysis and direct sequencing. Five of them resulted in an amino acid substitution. In E-selectin, exchanges from serine to arginine (position 128), from leucine to phenylalanine (position 554), and a DNA mutation from guanine to thymine (position 98) present significantly different allele frequencies in young patients with angiographically established, severe atherosclerosis, compared with an unselected population. Results suggest that these polymorphisms are associated with a higher risk for early severe atherosclerosis.

Adult↗
PubMed1996

Secondary acute leukaemias with 11q23 rearrangement: clinical, cytogenetic, FISH and FICTION studies.

Three patients with secondary acute leukaemia after treatment with topoisomerase II inhibitor agents are described. Two patients had acute myeloid leukaemia (AML). FAB M5a, one had pro-B-acute lymphoblastic leukaemia (ALL). The interval between initiation of chemotherapy and the onset of secondary acute leukaemia was 19-20 months. 11q23 rearrangements were detected in all cases. They were due to translocations t(11;19) (q23;p13.3), t(11;16)(q23;p13) and t(4;11)(q21;q23), respectively. Fluorescence in situ hybridization (FISH) with Yeast Artificial Chromosome (YAC) probe 13HH4 spanning the ALL-1 gene on 11q23 confirmed that in each case the ALL-1 gene had been disrupted by the translocations. The study underlined the relationship between the development of secondary acute leukaemias with 11q23 rearrangement and previous chemotherapy with topisomerase II inhibitor agents. So far, however, only six adult patients with secondary ALL with t(4;11) after treatment with topoisomerase II inhibitor agents have been reported. All with t(4;11) mostly occurs in infants or young children. Our patient received epirubicin continuously for >19 months. This indicates that both myeloid and lymphoid leukaemias with involvement of the ALL-1 gene can be induced by exogenous agents, especially topoisomerase II inhibitors. Thus they may have a common biological background. This hypothesis was substantiated by means of combined immunophenotyping and FISH (FICTION). In the case of AML M5a with t(11;19), the tumour cells with ALL-1 rearrangement expressed CD34. Moreover, the pro-B-ALL with t(4;11) was CD34 positive. These findings suggest that the cell of origin of secondary AML and ALL with 11q23 rearrangement is an immature haemopoietic progenitor cell.

Acute Disease↗
PubMed1995

Ultrastructure of spermiogenesis and spermatozoa of Neopolystoma spratti (Platyhelminthes, Monogenea, Polystomatidae).

Spermiogenesis in Neopolystoma spratti conforms to the basic pattern found in polyopisthocotylean monogeneans and in Trematoda Digenea and Trematoda Aspidogastrea. The zone of differentiation exhibits a complete ring of cortical microtubules, two initially free flagella with prominent striated rootlets and an intercentriolar body between them. Mitochondria and nucleus migrate into a median cytoplasmic process and flagella rotate and fuse with this process. Mitochondria fuse to form a single elongated mitochondrion and the nucleus moves to a distal location. Mature sperm have two incorporated axonemes for most of their length, a single elongate mitochondrion and a nucleus. Peripheral microtubules form an incomplete ring in the most proximal region and a complete ring in the adjacent region containing two axonemes and the mitochondrion. In the principal region (where the nucleus is present) they form an incomplete ring and are interpreted as originating from the dorsal and ventral faces of the median cytoplasmic process. Thus, although there are more microtubules in the principal region than at either end, the situation is essentially the same as that found in polyopisthocotylean monogeneans, digeneans and aspidogastreans, with no addition of extra lateral microtubules.

Animals↗
PubMed1995

Ultrastructure of the buccal complex of Polylabroides australis (Monogenea, Polyopisthocotylea, Microcotylidae).

The two buccal suckers have a largely muscular septum each and, near the pharynx, dorsal swellings ("valve apparatus") extend into the lumen of the suckers. In the posterior parts of the suckers, the tegument forms a "rim" containing much electron-dense material. The walls of the suckers are mainly formed by muscle filaments, and there are several large vacuolated masses containing lipid (?) globules and vacuoles. The most anterior part of the pharynx contains a thick layer of electron-dense material which also lines the pharyngeal wall facing the lumen. Nine types of sensory receptors, all with electron-dense collars, were observed in the tegument near the suckers, in the mouth cavity and its extensions, and in the anterior part of the pharynx. Some are uniciliate, one is biciliate, one multiciliate, and two (including the pharyngeal receptors) are nonciliate. The greatest variety of receptors, including receptor complexes consisting of three receptor types, is found in a posterior ventral extension of the mouth cavity. It is suggested that this extension can be protruded into the suckers, facilitated by numerous muscle filaments in the tissue around it.--Septate suckers, mouth cavity and its extension, valve apparatus and pharynx are likely to form a functional whole, the "buccal complex", used for food intake.

Animals↗
PubMed1995

Re-examination of spermatogenesis of Multicotyle purvisi (Platyhelminthes, Aspidogastrea).

Examination of spermatogenesis in Multicotyle purvisi revealed that the process follows the classical pattern previously described for many parasitic platyhelminths, especially other Aspidogastrea and Digenea. Free flagella (with an intercentriolar body between the basal bodies and with striated flagellar rootlets) and a median cytoplasmic process grow from a zone of differentiation. The flagella then fuse with the process in a proximo-distal direction and nucleus and mitochondrion grow out into the elongating spermatid. Spermatids are pinched off at the base, and rootlets and intercentriolar body remain behind in the residual cytoplasm. It is suggested that the aberrant processes described in an earlier report constitute a pathological condition or a response to stress. Changes in the intercentriolar body during spermiogenesis are documented and for the first time in a platyhelminth it is demonstrated that rootlets and intercentriolar bodies are discarded and left behind in the residual cytoplasm.

Animals↗
PubMed1995

Aspects of the ecology of metazoan ectoparasites of marine fishes.

Numerous (3947) individuals of 102 marine fish species from Papua New Guinea, New Zealand, the North Sea, Antarctica, the deepsea and coast of southeastern Australia, Pacific Canada, Brazil, Argentina and the Great Barrier Reef were examined for metazoan ectoparasites. Of the 102 fish species, 86 harboured at least 1 parasite species, and only in Antarctica and the deepsea were large proportions of fish species found to be free of ectoparasites. The mean prevalence of infection was 30.1%, the average of abundances was 6.7 parasites per fish, due to very heavy intensities of some parasite species (mean median abundance 4.31). Most parasite species exhibited a clustered distribution in the host populations, as measured by variance to mean ratios, i.e. some fish were more, and others less, heavily infected than if infection were random. Core and satellite species cannot be distinguished unambiguously, because numbers of parasites on almost all hosts are too small for any bimodality to become apparent. On average, the most dominant species represented 90% of all parasite individuals of a particular fish; different parasite species were often dominant on different fish individuals of a particular host species. Both abundances and maximum intensities of infection were positively correlated with prevalence of infection. Community richness varies greatly at and between localities, with the lowest richness found in Antarctic and deepsea fish and the highest richness in tropical fish. Species richness, abundance and prevalence of infection in many fish groups (with different ecological characteristics) are strongly correlated with temperature. If fish from all localities were pooled, pelagic fish had fewer intensities and (jointly with benthopelagic fishes) fewer species than benthic fish, and planktivorous fish had lower abundances and prevalences of infection than predatory and omnivorous fish. Prevalences of infection, abundance and parasite species richness were significantly correlated with host length. Fifteen positive and 1 negative associations among species were found. This and the generally low prevalences and abundances of infection indicate that competitive interactions are probably scarce. Overall, the findings indicate that most (if not all) metazoan ectoparasite communities of marine fish live in non-saturated, little-ordered assemblages.

Animals↗
PubMed1995

Cytokine autoantibodies in rheumatoid arthritis.

Sera from 42 patients with rheumatoid arthritis (RA) and 40 healthy controls (HC) were examined for cytokine autoantibodies (CK-aAb) by accurate and sensitive radioimmunoassays. The prevalences of detectable CK-aAb in RA (HC) were: aAb-IL-1 alpha = 36% (38%); aAb-IL-6 = 29% (13%), p = 0.06; aAb-IL-8 = 0% (0%); aAb-IFN alpha = 12% (3%), p = 0.11. The levels of the individual CK-aAb did not correlate, and there were no correlations between CK-aAb levels and clinical or laboratory variables. CK-aAb levels remained constant in 8 RA patients tested over a period of 6 months. With regard to alterations in aAb-IL-1 alpha levels, 4/11 HC were consistently positive over 18-36 months; 2/11 converted and became highly positive. The levels of aAb-IFN alpha and aAb-IL-6, but not aAb-IL-1 alpha, tended to be increased in RA patients; aAb-IL-8 were undetectable in both RA and HC.

Adult↗
PubMed1994

Two new sensory receptors in Gyrodactylus sp. (Platyhelminthes, Monogenea, Monopisthocotylea).

Two pairs of sub-surface ciliary aggregations, not previously described in gyrodactylid monogeneans, have been found in the antero-dorsal region of adult Gyrodactylus sp. One pair lies more anteriorly and has several basal bodies without rootlets as well as modified cilia with single microtubules projecting into an extra-cellular cavity. A neuronal process extends posteriad. An anterior pocket connecting to this cavity is surrounded by cytoplasm that adjoins the ciliated cell by a septate junction. This type may have a pressure/contact or photoreceptoral function. Each of the second pair of receptors contains approximately 12 basal bodies without rootlets in the periphery of a cytoplasmic cavity. Flattened ciliary membranes extend from the basal bodies into the interior, forming a number of whirls. A neuronal projection extends posteriad. This structure closely resembles presumed photoreceptors found in several other parasitic and free-living platyhelminths. The first type does not appear to have been described for any other species.

Animals↗
PubMed1994

The phylogenetic relationships of Kronborgia (Platyhelminthes, Fecampiida) based on comparison of 18S ribosomal DNA sequences.

Approximately 580 bp at the 5' end of the small subunit RNA gene were amplified by PCR for 19 platyhelminth taxa, and Homo and Artemia were used as outgroups. These were analysed to test the hypothesis that fecampiids and Neodermata are sister groups. No evidence was found that the fecampiid Kronborgia isopodicola is closely related to the Neodermata or to the Rhabdocoela (in which the fecampiids are usually included). Morphological, including ultrastructural, characters and DNA data do not support a close relationship of fecampiids with any other platyhelminth taxon, although the DNA sequence analysis provides some evidence that the Acoela and Tricladida are closest. Fecampiids are sufficiently different from any other platyhelminth group to warrant establishment of a class, Fecampiida, for them. A diagnosis of the new class is given.

Animals↗
PubMed1994

Ultrastructure of sperm and spermiogenesis in the monocotylid monogeneans Monocotyle helicophallus and Calicotyle australiensis (Platyhelminthes).

Spermiogenesis in Monocotyle helicophallus involves formation of free flagella which rotate to lie parallel before fusing. There is no median cytoplasmic process. A small number of microtubules (usually 2-4) is associated with the axonemes in the zone of differentiation. Nucleus and a fused mitochondrion migrate alongside the axonemes and one basal body moves distally. A coil of nucleus, originally in the cytophore, also moves out along the shaft. The mature spermatozoan has only a single axoneme for a short distance at each end, with two associated microtubules at the proximal end, as well as one axoneme, nucleus and mitochondrion throughout most of its length (the nucleus being enlarged and roughly coiled in one region), and a short region of two overlapping axonemes. We interpret our findings as two axonemes arranged almost end to end, one extending from the proximal end to some point in the mid-region, where the second axoneme begins and continues to the distal end of the sperm. Spermatozoa of Calicotyle australiensis develop from a zone of differentiation which has two basal bodies and a complete ring of cortical microtubules. Two initially free axonemes fuse with each other and there is no median cytoplasmic process. Spermatids form within parallel canals in the cytophore, by backward movement of the zone of differentiation. Prior to detachment, an electron-dense spiral end-piece forms around and proximal to the basal body region. Sixty-four spermatids are present in each isogenic group. With the study of spermiogenesis in more species of Monogenea Monopisthocotylea, it is apparent that the previously designated sperm patterns 2 and 3 are not distinct and should be combined and re-defined. Species previously designated as having sperm patterns 2 and 3 can all be accommodated by the description "two normal axonemes or one normal and one shortened, altered or displaced axoneme, and none, one or a few cortical microtubules remaining in a region of the sperm derived from the zone of differentiation in which a few or a complete ring of microtubules was present".

Animals↗
PubMed1994

A tropical assemblage of ectoparasites: gill and head parasites of Lethrinus miniatus (Teleostei, Lethrinidae).

Aspects of the community ecology of metazoan ectoparasites of Lethrinus miniatus (Teleostei. Lethrinidae) from 3 localities on the Great Barrier Reef were examined. Twelve species of Monogenea, 6 of Copepoda, 2 species of adult and several larval Isopoda and 1 leech were found. Total parasite numbers reach 3500 per host, and prevalence of infection with a particular parasite species reached 100% in some species. Numbers of parasite species per fish varied from 5 to 11. Four parasite species were most dominant on different fish if intensities of infection were used to calculate dominance, one species representing about 80% of all parasite individuals on a particular fish at 2 localities and about 50% at the third locality. Ten parasite species were most dominant on different fish, if volume (biomass) was used for calculating dominance, one species representing about 55% at one and 80% of total parasite volume at 2 localities. Parasites included at least 12 congeneric species of 4 or more genera, and those (of 2 genera) occurring on the gills showed much overlap in their distribution. Congeneric Monogenea of the families Dactylogyridae and Diplectanidae occurring in the same sites differ markedly in the size and structure of their copulatory sclerites. Positive associations between species were much more common than negative ones. The bony parts of the gills (gill arches) were never found to be infected, indicating the availability of empty niches.

Animals↗
PubMed1994

The origins of parasitism in the platyhelminthes.

Symbiotic associations have arisen independently in several groups of the largely free-living turbellarians. Morphological adaptations of turbellarians to a symbiotic way of life include suckers and adhesive glands for attachment, elaborate systems of microvilli and other epidermal structures for absorption of food, glands for the formation of cysts, cocoons and cement material, and lack of a pharynx and intestine in some species. However, many species closely resemble their free-living relatives. Egg production is greatly increased at least in some species, and life cycles are always direct. Food of symbiotic turbellarians consists of host food and/or host tissue. Ectosymbiotes show fewer physiological adaptations than entosymbiotes. The major groups of parasitic Platyhelminthes (Trematoda Aspidogastrea, Trematoda Digenea, Monogenea, Udonellidea, Cestoda including Gyrocotylidea, Amphilinidea and Eucestoda), form one monophylum, the Neodermata, characterized by a neodermis (tegument) replacing the larval epidermis, epidermal cilia with a single horizontal rootlet, sensory receptors with electron-dense collars, spermatozoa with axonemes incorporated in the sperm body by proximodistal fusion, and protonephridial flame bulbs formed by two cells each contributing a row of longitudinal ribs to the filtration apparatus. The sister group of the Neodermata is unknown but is likely to be a large taxon including the Proseriata and some other turbellarian groups. Among the Neodermata, the Aspidogastrea is likely to be the most archaic group, as indicated by DNA studies, morphology, life cycles and physiology. Aspidogastreans can survive for many days or even weeks outside a host in simple media, they show little host specificity, and have an astonishingly complex nervous system and many types of sensory receptors, both in the larva and the adult. It is suggested that Aspidogastrea were originally parasites of molluscs (and possibly arthropods and other invertebrates) and that they are archaic forms which have remained at a stage where vertebrates represent facultative hosts or obligatory final hosts into which only the very last stages of the life cycle (maturation of the gonads) have been transferred. The complex life cycles of Digenea have evolved from the simple aspidogastrean ones by intercalation of multiplicative larval stages (sporocysts, rediae) in the mollusc host, and of cercarial stages ensuring dispersal to the now obligatory final host. Monogenea may have lost the molluscan host or evolved before the early neodermatans had acquired it. Cestoda either replaced the original molluscan with an arthropod host, retained an original arthropod host or evolved from an early neodermatan before molluscan hosts had been acquired, newly acquiring an arthropod host.(ABSTRACT TRUNCATED AT 400 WORDS)

Animals↗
PubMed1994

Niche restriction in parasites: proximate and ultimate causes.

Hutchinson's (1957) definition of an ecological niche as a multidimensional hypervolume determined by a number of physical and biotic variables is adopted. The number of niche dimensions is very great, but as a working hypothesis it is assumed that a few are sufficient to characterize the niche of a parasite species to a high degree of accuracy. They are host species, microhabitat(s), macrohabitat(s), geographical range, sex and age of host, season, food and hyperparasites. Methods to measure niche width, in particular specificity indices, are discussed, and some examples of niche restriction are described. Proximate and ultimate causes of niche restriction are discussed, mainly using marine parasites as examples. Among proximate causes of one niche dimension, host specificity, are ecological factors restricting exposure to infection to certain host species; host-specific chemical factors that induce hatching, direct infective stages to a host and bring about settlement of a parasite; factors that lead to mortality in or on the wrong host; morphological adaptations that guarantee survival in or on the 'correct' host; and availability of suitable hosts. Many factors are likely to be responsible for microhabitat specificity, but have been little studied, except for some physiological and morphological adaptations to particular microhabitats. Macrohabitats and geographical range may be determined by the distribution of intermediate hosts and certain food items, and by a variety of chemical and physical factors. Hosts of different sexes may differ in feeding habits and the composition of the skin, and thus acquire parasites differentially. Hosts of different age may be differentially infected due to accumulation of parasites with age, loss of parasites due to developing resistance (or immunity), and different size and feeding habits. Among ultimate causes of niche restriction and segregation are avoidance of competition, predation and hyperparasites; facilitation of mating; reinforcement of reproductive barriers; and adaptations to environmental complexity. Few studies permit a decision on which factor or factors are responsible in particular cases. Interspecific competition may play a greater role in helminth communities of some host groups than of others, but it seems that, overall, its role has been exaggerated at least for marine parasites. Some 'classical' examples of microhabitat segregation explained by interspecific competition can also be explained by reinforcement of reproductive barriers. There is evidence for the importance of facilitation of mating in microhabitat restriction, and the availability of many vacant niches indicates that competition, overall, is not of great importance.

Animals↗
PubMed1994

E-selectin polymorphism and atherosclerosis: an association study.

Adhesion molecules like the members of the selectin family participate in the interaction between leukocytes and the endothelium. They are also involved in the pathogenesis of atherosclerotic processes. To contribute to the analysis of the genetic background of atherosclerosis we searched for DNA polymorphisms in the genes encoding adhesion molecules especially E-selectin which seems to be expressed only in activated endothelium. An adenine to cytosine substitution for cDNA position 561 resulting in an amino acid exchange from serine to arginine (position 128) was detected in the epidermal growth factor like domain. A significantly higher mutation frequency (P = 0.02) was observed in 97 patients aged 50 years or less with angiographically proven severe atherosclerosis (allele frequency of arginine 0.155) compared with an unselected population (allele frequency of arginine 0.088) as well as in 40 patients aged 40 years or less (allele frequency of arginine 0.21, P = 0.0025). These data suggest that the 128-serine/arginine polymorphism is associated with a higher risk for early severe atherosclerosis.

Adult↗