Biomedical subjects
Publications and source records attributed to R W Hoffmann.
Present knowledge on the capability of fish to feel pain and of suffering is presented. According to these data it has to be supposed, that fish are able to feel fish. Suffering and damage can be proven by biochemistry and morphology. Under these aspects, angling ponds and cesarean section in sturgeon have to be regarded as a violation of the German animal welfare act.
A systematic inventory of actinosporeans and oligochaetes conducted over 3 years at a trout fish farm in Bavaria, Germany, allowed the identification of 12 actinosporeans from five collective groups: four Triactinomyxon (Triactinomyxon nov. types 1-4), two Raabeia (Raabeia nov. types 1, 2), two Echinactinomyxon ( E. radiatum, Echinactinomyxon nov. type 1), two Aurantiactinomyxon ( A. pavinsis, Aurantiactinomyxon nov. type 1) and two Neoactinomyxum (Neoactinomyxum nov. types 1, 2). Nine forms are novel but can be placed within existing collective groups. All 12 forms were detected in the laboratory in aquarium water associated with farm sediment. However, only four of these could be linked with an oligochaete host. Three families of oligochaetes were identified from the sediment: Tubificidae, represented by eight species, Lumbriculidae with one species and Naididae with two species. Only tubificid oligochaetes were found to host actinosporeans.
The development of actinosporeans in their oligochaete host proceeding pansporocyst formation is relatively well documented, however, phases preceding it are not as well known. The initial stages in the development of two actinosporeans, Raabeia type 1 of Oumouna et al. [Parasitol. Res. 2002] and Aurantiactinomyxon pavinsis (Ormières, 1968) Marquès [Languedoc, Universite des Sciences et Techniques, Dissertation, 1984] from schizogony to gametogony and sporogony are described. Both actinosporeans begin their development as multinucleate stages near the basal lamina of the oligochaete intestine. Proximal to these stages and between the host epithelium cells are uninucleate cells whose nuclei divide to produce binucleate cells. These divide mitotically to produce cells with four nuclei which then undergo plasmotomy to yield a tetracellular stage and the first phase in pansporocyst formation. From the uninucleate stage to the tetranucleate stage, the cell membrane of the parasite is associated closely via finger-like projections with the intestinal epithelial and glandular cells of the host.
[see reaction]. The stereochemistry of electrophilic amination has been probed using the chiral Grignard reagent 5, in which the magnesium-bearing carbon atom is the sole stereogenic center. Amination with azidomethyl phenyl sulfide 1 and with O-sulfonyloxime 2 were found to proceed with full retention of configuration.
The cytology of a new microsporean parasite Microsporidium epithelialis sp. n. from the intestinal epithelial cells of the freshwater oligochaete Tubifex sp. (Tubificidae) is described. The microsporean occurred together with an actinosporean of the genus Triactinomyxon, which was found between the epithelial cells. The merogonic and sporogonic stages (mature spores included) of the microsporean parasite are monokaryotic. An individual sporophorous vesicle surrounds each spore. The fixed and stained spore has an average dimension of 1.9-2.5 x 0.9-1.2 microm. The spores are oval with a characteristic surface layer, showing ornamentation-like projections, which are in close contact to the exospore. A short polar filament forming three to four coils traverses the polaroplast with two lamellar layers. The ultrastructure and other characteristic features of this microsporean parasite are distinct from those of the microsporean species described so far from oligochaetes.
Scanning electron microscopic studies were conducted on rainbow trout Oncorhynchus mykiss in the first 60 min after their exposure to the triactinomyxon spores of Myxobolus cerebralis. The results demonstrated that as early as 1 min post exposure the whole process, from the attachment of the triactinomyxon spores to the complete penetration of their sporoplasm germs, had occurred. The triactinomyxon spores sought out the secretory openings of mucous cells of the epidermis, the respiratory epithelium and the buccal cavity of trout and used them as portals of entry. Exposure experiments of the triactinomyxon spores of M. cerebralis to non-salmonid fish, such as goldfish Carassius auratus, carp Cyprinus carpio, nose Chondrostoma nasus, medaka Oryzias latipes, guppy Poecilia reticulata and also the amphibian tadpole Rana pipiens as well as to rainbow trout fry indicated a specificity for salmonids. Attempts to activate the triactinomyxon spores by exposure to mucus prepared from cyprinid and salmonid fish showed no significant differences from those conducted in tap water. The results suggest that the simultaneous presence of both mechano- and chemotactic stimuli was required for finding the salmonid fish host.
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A reverse transcriptase-polymerase chain reaction (RT-PCR) assay was developed and applied to the detection and differentiation of viral haemorrhagic septicaemia virus (VHSV) and infectious hematopoietic necrosis virus (IHNV) in organ samples and cultured cells, regardless of the serotype. This method was developed by selecting primer sets corresponding to highly conserved regions of the glycoprotein G-gene sequences of the 2 viruses. The very fast RNA extraction, reverse transcription and PCR permitted us to read the agarose gels within 7 to 9 h after samples, cultured cells and whole fish arrived, which is of great importance when there is reason to believe that VHSV or IHNV may be present. This is also the first report of a large-scale field trial comparing the RT-PCR assay in trout from 30 German fish farms (a total of 330 rainbow trout) with the usual virus isolation and identification method in order to evaluate the efficiency of the RT-PCR assay for general use in fish health management programs. RT-PCR followed by semi-nested PCR using RNA directly extracted from fish tissue turned out to be the most sensitive method. It recognized 9 fish farms as VHS-positive and 7 as IHN-positive. This is 3 VHS- and 4 IHN-farms more than detected by the traditional virus isolation method. By directly examining the tissue by means of a PCR test it was possible to detect viral RNA in acutely and subacutely to chronically diseased fish as well as in asymptomatic VHS/IHN-carrier fish. Therefore, this effective and powerful assay for detecting VHSV and IHNV by means of PCR has great advantages compared with the presently used procedures.
Myxobolus cerebralis (Myxozoa: Myxosporea) has a complex two-host life cycle, which begins when waterborne triactinomyxon spores released from the infected oligochaete Tubifex tubifex contact a susceptible trout. Upon contact the triactinomyxon spores attach to the fish and release their sporoplasm cells into the epidermis. At approximately 50 days postinfection, sporogenesis begins, resulting in a large number of M. cerebralis spores in the cartilage of infected fish 6 weeks later. The spores of M. cerebralis can be released from infected fish only after the fish die or are eaten by predators. In both cases, spores released into the aquatic environment can be ingested by oligochaete worms of the species T. tubifex and then develop into the actinosporean triactinomyxon stage in the intestine within about 3 months. The triactinomyxon is the only stage infectious for salmonid fish. We determined the DNA concentration in sporoplasm cells, capsulogenic cells, and valvogenic cells of M. cerebralis spore stages from the trout and of triactinomyxon spore stages from T. tubifex. DNA was visualized using the DNA-specific fluorescent stain DAPI. Our results demonstrate that meiosis occurs only once in the developmental cycle of M. cerebralis in contrast to the previously published hypothesis. This takes place within the pansporocyst found in T. tubifex. Thereafter, the sporoplasm cells of the triactinomyxon spores in T. tubifex and M. cerebralis in trout are diploid.
Whirling disease caused by Myxobolus cerebralis has become the most widely known disease of salmonids in the 1990s. In the last 5 years we have studied many aspects regarding the host-pathogen relationship of this parasite. The parasite's histozoic development causes significant damage to cartilage and induces CNS symptoms by pressure on the brain and spinal cord. Myxobolus cerebralis has a two-host life-cycle involving a salmonid fish and a tubificid oligochaete. Two different stages of sporogony occur, one in each host. Early developmental stages in the fish can be found multiplying in the epidermis and peripheral and central nervous systems. The presporogenic stages then migrate to vertebral and cranial cartilages, where the first sporogonic phase occurs. Mature M. cerebralis spores found in fish cartilage are infectious for T. tubifex when ingested by the oligochaete after destruction of the infected fish. In the gut lumen of the tubificid, the spores extrude their polar capsules and attach to the gut epithelium by polar filaments. The shell valves then open along the suture line and the sporoplasm penetrates between the gut epithelial cells. The binucleate sporoplasm multiplies by schizogony, producing many one-cell stages which begin gamogonic development. As a result of the multiplication process, the intercellular space of the epithelial cells in more than 10 neighbouring worm segments may become infected. At this time (60-90 days p.i.), pansporocysts with eight zygotes start the sporogonic phase. The final stage of this development is a pansporocyst containing eight folded triactinomyxon spores. Shortly afterwards, the spores are liberated into the gut lumen. The spores reach the water either by egestion or following the death of the infected tubificids. Infected tubificids can release triactinomyxons for at least 1 year. The ultrastructure of all four phases, schizogony, gametogony, gametogamy and sporogony, is demonstrated and discussed.
Characteristics of poisonous snakes and their toxines are described. The appearance and biology of all European poisonous snakes, eight vipers (family Viperidae) and one opisthoglyph colubride snake (family Colubridae) are given in detail.
The outbreak of an infection with Clostridium bifermentans in grass carp (Ctenopharyngodon idella) from a polyculture fish pond is documented.
Seasonality and size-related infection of Raphidascaris acus larvae from the inner organs and intestine of roach (Rutilus rutilus) were studied in 4 lakes of differing water quality and pollution level in Central Finland between August 1985 and November 1986. The influence of R. acus larvae on the liver and pancreatic tissues of roach was examined histologically in additional material from 1989 and 1990. The inner organs of roach were most heavily infected with R. acus in the eutrophic, polluted Lake Vatia (63% of fish infected with 4.0 nematodes/fish) and in the two eutrophic lakes, compared to the oligotrophic Lake Peurunka (23%, 0.8). The prevalence of free R. acus larvae in the intestine of roach was almost as high but the intensity only about half of that found in the inner organs. The prevalence of infection had significantly higher values in autumn in most cases, and larvae accumulated in the inner organs and intestine of older roach. In histological studies it was found that larvae occurred more often in the pancreatic tissue than in the liver, but in both organs the majority of the larvae were dead and partly destroyed. The most typical host response against R. acus was a chronic granulomatous inflammatory reaction. Granulomas and developing granulomas containing worms at different stages of degeneration are described; they were found in all of the lakes studied throughout the year and also in one and the same fish. On average only 37 and 21% of the worms in the liver and pancreas, respectively, were alive. No obvious difference in the histological response against R. acus was noted between the lakes.
Trichloroethylene, an organochlorine compound used as solvent in numerous industrial processes, was studied with regard to its effects on rainbow trout Oncorhynchus mykiss. Fish were exposed to trichloroethylene via the surrounding water in sublethal concentrations (0.5; 2.5 mg/l) for a period of 21 or 28 days. Three different commercial products of trichloroethylene, all highly purified but varying in quality and amount of stabilizing agents were used. Subchronic exposure resulted in forced apoptosis as well as adaptive and degenerative changes at the subcellular and cellular level in gills, liver, spleen, head- and trunk kidney at the lower concentration. At the higher concentration, necrotic lesions mainly in liver, spleen and head-kidney were found. Trichloroethylene showed particular affinity to the haematopoietic tissue with proliferation and elevated phagocytic activity of reticulo-endothelial cells. Moreover, an increase in phagocytosis of red blood cells which showed abnormalities in ultrastructure was striking. The histopathologic changes after exposure to three different commercial products of trichloroethylene varying in content of stabilizing agents did not show distinct variations.
Rainbow trout (Oncorhynchus mykiss) developed a post-infectious chronic membranous glomerulonephritis 15 months after they had been experimentally infected with Renibacterium salmoninarum. Histologically, peritubular and periglomerular fibrosis, hypercellular glomeruli with occluded Bowman's space, and partial or complete adhesion to Bowman's capsule were constant features. Electron microscopy revealed thickened glomerular basement membranes with spikes accompanied by finely granular electron-dense deposits at the epithelial side and dense material in the mesangial matrix. Indirect immunofluorescence indicated linear immunoglobulin deposits along the glomerular basement membrane. The presence of R. salmoninarum was demonstrated by culture and by indirect immunofluorescence. Low serum hemagglutination-inhibiting antibody titers were demonstrated.
Important diseases of reptiles are described with references to the diagnostic material and patients of the Institute of Zoology and Hydrobiology between 1984 and 1990. The commonest causes of mortality were pneumonia, parasites and poor husbandry. Problems associated with the increasing popularity of reptiles as pets, and appropriate treatments are discussed.
Myxobolus pavlovskii from the gills of silver carp (Hypophthalmichthys molitrix) were used in attempts to transmit the infection under laboratory conditions. Spores of M. pavlovskii were placed in aquaria that contained sterilized sand and had been filled with tap water at 15-16 degrees C. Furthermore, oligochaetes (90% Tubifex tubifex) were added and examined by wet mounts and histology. Hexactinomyxon spores developed after about 3 months only in T. tubifex that had been exposed to M. pavlovskii. Myxosporea-free silver carp developed cysts in their gills that contained M. pavlovskii at 120 days after contact with Hexactinomyxon spores, proving that M. pavlovskii also needs an oligochaete intermediate host for its development.
The effects of the herbicide atrazine (2-Chlor-4-ethyl-amino-6-isopropyl-amino-s-triazine) on the kidney of rainbow trout (Oncorhynchus mykiss) were studied by exposing them to sublethal concentrations of 1.4 and 2.8 mg atrazine per liter of water for 96 h (acute exposure) respectively to 5, 10, 20, 40, and 80 micrograms/L for a period of 28 days (chronic exposure). Alterations of the different components of renal corpuscles and of renal tubules, as well as an increase in cells with mitotic figures in renal hemopoietic interstitium were constant features at lower chronic (5, 10, 20, 40 micrograms/L) exposure; necrosis of endothelial cells and renal hemopoietic tissue were prominent at concentrations of 80 micrograms/L, and 1.4 and 2.8 mg/L atrazine.