Breakdown and macroinvertebrate colonization of needle and leaf litter in conifer plantation streams in Shikoku,southwestern Japan

Breakdown and macroinvertebrate colonization of conifer needles (Cryptomeria japonica) and deciduous broadleaves (Euptelea polyandra) were investigated using litter bags in two study sites in streams flowing through a conifer plantation of C. japonica in Shikoku, southwestern Japan (one site with conifer canopy and another with mixed conifer and broadleaved canopy). Breakdown rates and macroinvertebrate densities were compared between litter species (conifer needle vs broadleaf) and between the two sites (conifer vs mixed canopy) to determine (1) whether breakdown rate of broadleaves is higher than conifer needles, (2) whether macroinvertebrates prefer broadleaves to conifer needles, and (3) whether the difference in riparian canopy is reflected in macroinvertebrate abundance. The results indicated that breakdown rates of broadleaves were higher than those of conifer needles, suggesting poorer quality of the latter as food for macroinvertebrates. Differences in macroinvertebrate density between needles and broadleaves were generally consistent with those in breakdown rates: broadleaves tended to have higher densities than needles, suggesting that conifer needles were not preferred by macroinvertebrates. However, total macroinvertebrate density in the conifer site was not significantly different from that in the mixed site, although the dominant shredder taxon differed (conifer site: gammarids; mixed site: lepidostomatids). Although conifer needles are low-quality food for macroinvertebrates, this may offer some advantages. Conifer needles remain on the streambed for longer periods owing to their lower breakdown rates, being a constantly available resource. In addition, accumulations of conifer litter may effectively trap and retain particulate organic matter.     

Suppression subtractive hybridization library construction and identification of epidermal bladder cell related genes in the common ice plant,Mesembryanthemum crystallinum L.

Mesembryanthemum crystallinum L., a halophytic species, displays modified trichomes, epidermal bladder cells (EBC), on the surfaces of its aerial organs. EBCs serve to sequester excessive salt from underlying metabolically active tissues. To elucidate the molecular determinants governing EBC development in the common ice plant, we constructed a cDNA-based suppression subtractive hybridization library and identified genes differentially expressed between the wild-type and the EBC-less mutant. After hybridization, 38 clones were obtained. Among them, 24 clones had homology with plant genes of known functions, whose roles might not be directly related to EBC-morphology, while 14 clones were homologous to genes of unknown functions. After confirmation by northern blot analysis, 12 out of 14 clones of unknown functions were chosen for semi-quantitative RT-PCR analysis, and the results revealed that three clones designated as MW3, MW21, and MW31 preferentially expressed in the EBC-less mutant, whereas the other two designated as WM10 and WM28 preferentially expressed in the wild type. Among these genes, the expression of a putative jasmonate-induced gene, designated as WM28 was completely suppressed in the EBC-mutant. In addition, the deletion of C-box cis-acting element was found in the promoter region of WM28 in the EBC-less mutant. Overexpression of WM28 in Arabidopsis resulted in increased trichome number due to the upregulation of key trichome-related genes GLABRA1 (GL1), and GLABRA3 (GL3). These results demonstrate that WM28 can be an important factor responsible for EBC formation, and also suggest the similarity of developmental mechanism between trichome in Arabidopsis and EBC in common ice plant.     

Changes in Activities of Enzymes Related to Energy Metabolism in Peripheral Leukocytes of Fattening Steers

Glucose, triglyceride, cholesterol and immunoreactive insulin (IRI) concentrations, some enzyme activities in plasma, and activities of enzymes related to energy metabolism in peripheral leukocytes were measured in fattening Japanese Black Wagyu x Holstein steers fed on different diets at 8, 12, 16, 20 and 24 months of age. The plasma IRI concentrations at 20 and 24 months of age were significantly higher than those at 8 months of age. Activities of hexokinase (HK), glucose-6-phosphate dehydrogenase (G6PD), aspartate aminotransferase (AST), and malate dehydrogenase (MDH) in cytosolic fractions, and glutamate dehydrogenase (GLDH), MDH and AST in mitochondrial fractions in peripheral leukocytes of steers at 24 months of age were significantly higher than those at 8 months. Increasing plasma insulin concentration was considered to induce acceleration of glucose utilization in leukocytes of fattening steers. The cytosolic ratio of MDH/lactate dehydrogenase (LDH) activity in leukocytes increased significantly in the fattening process and was considered to be a useful indicator for evaluating changes in energy metabolism in steers.     

Poxvirus infection in Nile crocodiles (Crocodylus niloticus)

An outbreak was encountered of numerous yellowish cutaneous nodules in one- to two-year-old farmed Nile crocodiles (Crocodylus niloticus) in Kasaba Bay Crocodile Farm at Lake Tanganyika in Zambia during 1988. Out of 4000 crocodiles of different age groups, 300 yearlings were affected and 82 of those affected died. The lesions were prominent on the head, especially around the eyelids, the nostrils, both sides of the mouth, ventral neck, ventral pale belly, limbs and the root of the tail. Histologically, the epidermal lesions revealed large focal areas of marked acanthosis accompanied by hyperkeratosis and parakeratosis. In the prickle cells, there were multiple small neutrophilic granular inclusions and large eosinophilic homogeneous cytoplasmic inclusions. Electron microscopically, there were numerous poxvirus particles and matrices in the cytoplasm of many prickle cells. Dark blue homogeneous cytoplasmic inclusions in toluidine blue sections consisted of an electron opaque matrix with mature viral particles (160 x 200 x 230 nm). Furthermore, there were clumps of granular matrix containing immature viral particles (200 x 399 nm) in the cytoplasm. Various features of viral developing processes were observed.     

Involvement of a vascular hypersensitive response in quantitative resistance to Ralstonia solanacearum on tomato rootstock cultivar LS‐89

Ralstonia solanacearum causes bacterial wilt disease in Solanaceae spp. Expression of the Phytophthora inhibitor protease 1 (PIP1) gene, which encodes a papain‐like extracellular cysteine protease, is induced in R. solanacearum‐inoculated stem tissues of quantitatively resistant tomato cultivar LS‐89, but not in susceptible cultivar Ponderosa. Phytophthora inhibitor protease 1 is closely related to Rcr3, which is required for the Cf‐2‐mediated hypersensitive response (HR) to the leaf mould fungus Cladosporium fulvum and manifestation of HR cell death. However, up‐regulation of PIP1 in R. solanacearum‐inoculated LS‐89 stems was not accompanied by visible HR cell death. Nevertheless, upon electron microscopic examination of inoculated stem tissues of resistant cultivar LS‐89, several aggregated materials associated with HR cell death were observed in xylem parenchyma and pith cells surrounding xylem vessels. In addition, the accumulation of electron‐dense substances was observed within the xylem vessel lumen of inoculated stems. Moreover, when the leaves of LS‐89 or Ponderosa were infiltrated with 10⁶ cells mL^?1 R. solanacearum, cell death appeared in LS‐89 at 18 and 24 h after infiltration. The proliferation of bacteria in the infiltrated leaf tissues of LS‐89 was suppressed to approximately 10–30% of that in Ponderosa, and expression of the defence‐related gene PR‐2 and HR marker gene hsr203J was induced in the infiltrated tissues. These results indicated that the response of LS‐89 is a true HR, and induction of vascular HR in xylem parenchyma and pith cells surrounding xylem vessels seems to be associated with quantitative resistance of LS‐89 to R. solanacearum.     

Androgen- and estrogen-dependent sex differences in host resistance to Strongyloides venezuelensis infection in Wistar rats

The effects of male and female sex hormones on the protective capacity of Wistar rats against infection with Strongyloides venezuelensis were investigated. Male rats were more susceptible than females in terms of worm recovery from the lungs. Orchidectomy of male animals significantly reduced the plasma testosterone concentration and increased host resistance to the migratory stages of S. venezuelensis larvae. In contrast, ovariectomy of female animals significantly decreased host resistance in association with a significant reduction of estrogen levels. To examine the direct effect of sex hormones, exogenous testosterone and estrogen were implanted into animals. Susceptibility significantly increased or decreased in ovariectomized females given testosterone or estrogen, respectively. These results suggest that male and female sex hormones are important in the down- and up-regulation of host resistance against S. venezuelensis in Wistar rats.     

A case report of traumatic neuroma of the cervical spinal cord in a dog

Traumatic neuroma of the cervical spinal cord was diagnosed in a 14-year-old male mixed-breed dog. A gross view showed two intradural extramedullary masses, measuring 1 and 0.6 cm in length and 0.7 and 0.4 cm in diameter, attached to the left side of the spinal cord at the level of the sixth and seventh cervical vertebrae. Microscopically, the cervical spinal masses comprised interlacing fascicles of axons and Schwann cells surrounded by collagenous stroma. Immunohistochemically, the fascicles were stained positively for neurofilament and S-100 proteins. Ultrastructurally, variably sized myelinated fibers and onion bulb-like structures were observed. To our knowledge, this is the first report of a traumatic neuroma in the cervical spinal cord of a dog.     

Novel species specific antigens of trypanosoma congolense and their different localization among life-cycle stages

Seven monoclonal antibodies (mAbs) were raised against Trypanosoma congolense procyclic form (PCF). Localization of the antigens recognized by the mAbs was determined in bloodstream form (BSF), PCF, epimastigote form (EMF) and metacyclic form (MCF) by confocal laser scanning microscopy (CLSM). Two mAbs (10F9 and 20H12) showed different fluorescent patterns among different life-cycle stages of the parasite. The 10F9 recognized a 76 kDa antigen of all life-cycle stages of the parasite and the antigen localization corresponded with that of a mitochondrion. While the 20H12 recognized 119 and 122 kDa antigens of all the life-cycle stages and the antigen localization corresponded with a flagellum in BSF and MCF, tip of a flagellum in PCF, and part of cytoplasm in EMF. Moreover, the 20H12 did not react to T. brucei gambiense, T. b. rhodesiense and T. evansi antigens in both CLSM and immunoblotting. Therefore, the antigens recognized by the 20H12 seem to be T. congolense specific. Although, further studies will be required for a full characterization of the T. congolense specific 119 and 122 kDa antigens, the mAb 20H12 and the specific antigens may be useful in not only establishment of T. congolense specific diagnosis methods but also studies on molecular mechanisms regulating differentiation of the parasite during life-cycle.     

Preliminary immunohistochemical study of natriuretic peptide receptor localization in canine and feline heart

We examined the immunohistochemical distributions of natriuretic peptide receptor (NPR)-A, -B and -C that bind with natriuretic peptide hormones A, B and C in four healthy crossbreed young canine and feline cardiac tissues using specific antibodies against human antigens. Cross-immunoreactivities between antigens and antibodies were confirmed using western blot analysis. NPR-A and -C were expressed more strongly in dogs than cats. In both species, these expressions were stronger in the atria than the ventricles, with stronger expression in the left ventricles than the right. NPR-B was largely very weekly or undetected. In canine and feline cardiac tissues, the expressional distribution of NPR-A, -B, and -C closely matched with that of atrial natriuretic peptide, brain natriuretic peptide, and C-type natriuretic peptide as the ligands for corresponding receptors.