Microbial communities in various waters used for fish larval rearing

A major concern in larvae production is a mass mortality caused by fish diseases. In larvae production, pumped‐up natural seawater filtered through a sand filter system is used for fish rearing, and microalgae and rotifer cultures. Here, we investigated the community structures of eukaryotic microbes, as well as total bacteria and vibrios, in various processed ‘waters’ used in a larvae production site. We observed that ultraviolet irradiation of seawater was effective to reduce not only total bacteria and vibrios but also eukaryotic microbes. Moreover, the community structures of total bacteria and vibrios in rearing waters for fish larvae were different from those in rotifer cultures fed with Chlorella, but rather similar to those in natural seawater and microalgae cultures. These results suggest that the bacterial community in rearing waters may originate mainly from natural seawater and then be selected by microalgae in rearing water. Overall, this study provides useful information for avoiding the risk of fish disease outbreaks in a larvae production site.     

Development of a PCR test for rapid diagnosis of contagious equine metritis

In order to establish a rapid diagnostic method for contagious equine metritis (CEM), we developed and evaluated a polymerase chain reaction (PCR) test. Species-specific PCR primer sets were derived from the DNA sequence of a cloned DNA fragment of Taylorella equigenitalis that did not hybridize with the genome of a taxomonically related species, Oligella urethralis. Single step PCR with primer set P1-N2 and two-step semi-nested PCR with primer sets P1-N2 and P2-N2 detected as low as 100 and 10 CFU of the bacteria, respectively. Single-step PCR detected T. equigenitalis from genital swabs of experimentally infected mares with sensitivity comparable to that of bacterial isolation. Furthermore, two-step PCR was more sensitive than the culture method. Upon examination of field samples, 12 out of 3,123 samples were positive by single-step PCR while only 2 were positive by bacterial culture. The 12 PCR-positive samples originated from 5 mares, of which 3 animals were considered to be carriers based on previous bacteriologic and serologic diagnoses for CEM. The PCR test described in this study would provide a specific and highly sensitive tool for the rapid diagnosis of CEM.     

Effects of epidermal growth factor (EGF) on fetal islet B cells in vitro

ABSTRACT. It has been reported that when the rat fetus is treated with streptozotocin (STZ) in vivo, islet B cells are destroyed but later recover. To investigate the process of the recovery of B cells after in vitro treatment of the fetal pancreas with STZ and the role of epidermal growth factor (EGF) in the recovery of B cells, we measured the level of insulin released from the cultured fetal pancreas and examined it histologically. As a result, we immunohistologically confirmed the regeneration of B cells in the pancreas that had been cultured for 48 hr after destruction of islet B cells by STZ treatment. An immunohistologic study using proliferating cell nuclear antigen (PCNA) showed that without the addition of EGF, the cell division index was significantly higher in the STZ-treated group (STZ group) than in the untreated group (intact group), whereas with the addition of EGF, the cell division index increased in both groups, but EGF did not have a significant cell division-promoting effect on the pancreas in the STZ group. The addition of EGF caused a significant decrease in the concentration of insulin in culture medium in both groups. These results indicate that EGF has a cell growth-promoting effect on intact fetal pancreas in vitro but has the effect of inhibiting the release of insulin, and thus suggest that EGF does not trigger the regeneration of islet B cells.     

Lignan production inDaphne odora cell cultures

Lignan production in callus and cell suspension cultures ofDaphne odora is reported for the first time. The cell suspension culture produced pinoresinol, lariciresinol, secoisolariciresinol, matairesinol, and wikstromol. The production of matairesinol in the cell suspension culture was much higher than that inDaphne odora stem tissues.Part of this report was presented at the 51th annual meeting of the Japan Wood Research Society, Tokyo, April 2001     

Stereochemistry of matairesinol formation by <Emphasis Type="Italic">Daphne</Emphasis> secoisolariciresinol dehydrogenase

Secoisolariciresinol dehydrogenase activity was detected for the first time from Daphne odora and Daphne genkwa (Thymelaeaceae), which are known to produce optically pure (+)-matairesinol. In sharp contrast, (–)-matairesinol was formed selectively over the (+)-antipode by the secoisolariciresinol dehydrogenase preparation from both D. odora callus and D. genkwa shoots.     

Humoral immune response to non-viable Mycoplasma pulmonis in mice enhanced by dextran sulfate

The enhancing effect of dextran sulfate on the humoral immune response to nonviable Mycoplasma pulmonis in mice was evaluated by means of the indirect haemagglutination test. The serum antibody titres in mice immunized subcutaneously with a mixture of non-viable M. pulmonis and dextran sulfate were greater and persisted longer than those in mice immunized with non-viable M. pulmonis alone. DEAE-dextran also enhanced the humoral immune response to non-viable M. pulmonis in mice.     

Relationship between the development of the gubernaculum and the testicular descent in the rat fetus: macroscopic and light and electron microscopic observation

The gubernaculum consists of the gubernacular cord connected with the vas deferens and the gubernacular bulb connected with the retroabdominal wall. The cord was first distinguished on day 15 of gestation. Its length reached the peak on day 16, followed by a reduction until day 18 to be almost constant thereafter. The bulb was first distinguished on day 16, and its length was steadily increased toward term. The testis began to descend with a reduced length of the cord. By day 19, the testis descended close to the caudal part of the bulb by the sharp bending of the cord. Microscopically, the bulb consisted at first of a centrally located mesenchymal mass and of a covering layer of myoblasts. Thereafter, the mesenchymal mass was gradually shifted toward the cranial part of the bulb, trailing loose mesenchymal tissue in the caudal part of the bulb. On day 19, the mass was decreased in cell population but increased in amount of collagen fibers. It is suggested that the testicular descent starts on day 16 together with the commencement of shortening of the gubernacular cord and enlargement of the gubernacular bulb.     

Macrolides and lincomycin susceptibility of Mycoplasma hyorhinis and variable mutation of domain II and V in 23S ribosomal RNA

A total of 151 strains of Mycoplasma hyorhinis isolated from porcine lung lesions (weaned pigs, n=71, and finishers, n=80) were investigated for their in vitro susceptibility to 10 antimicrobial agents. Thirty-one strains (28 from weaned pigs and 3 from finishers) showed resistance to 16-membered macrolide antibiotics and lincomycin. The prevalence of the 16-membered macrolide-resistant M. hyorhinis strain in weaned pigs from Japanese herds has approximately quadrupled in the past 10 years. Several of the 31 strains were examined for mutations in the 23S ribosomal RNA (rRNA). All field strains tested showed a transition of A to G at position 2059 of 23S rRNA-rendered Escherichia coli. On the other hand, individual tylosin- and lincomycin-resistant mutants of M. hyorhinis were selected in vitro from the susceptible type strain BTS7 by 3 to 9 serial passages in subinhibitory concentrations of each antibiotic. The 23S rRNA sequences of both tylosin and lincomycin-resistant mutants were compared with that of the radical BTS7 strain. The BTS7 mutant strain selected by tylosin showed the same transition as the field-isolated strains of A2059G. However, the transition selected in lincomycin showed mutations in domains II and V of 23S rRNA, G2597U, C2611U in domain V, and the addition of an adenine at the pentameric adenine loop in domain II. The strain selected by lincomycin showed an additional point mutation of A2062G selected by tylosin.