Intensification of redclaw crayfish Cherax quadricarinatus culture: I. Hatchery and nursery system

Intensification of an indoor hatchery and nursery system for the Australian redclaw crayfish Cherax quadricarinatus (von Martens) (Decapoda: Parastacidae) was obtained by increasing the surface area available for the crayfish juveniles and by synchronizing the age of the hatchlings held in each tank. The former improvement was facilitated by distributing an artificial seaweed-like material throughout almost the entire volume of small (275 l) hatching tanks. As the number of egg-bearing females was increased from 3 to 8 per hatching tank, the number of juveniles per liter also increased to as many as 6.5 juveniles/l, without reaching an apparent upper limit. The hatchlings were kept in the tanks for 75 days from the day females were found to be gravid and then harvested and graded according to size. The average juvenile weight at harvest was 0.34±0.04 g. The weight distribution of the juvenile males was not significantly different from that of the juvenile females on the day of harvest, and in both the distribution was positively skewed.     

Spirocercosis-associated esophageal sarcomas in dogs. A retrospective study of 17 cases (1997-2003)

Seventeen client-owned dogs diagnosed with spirocercosis-associated esophageal sarcomas were retrospectively reviewed. The most common clinical signs noticed were vomiting and/or regurgitation (94%), lethargy and depression (59%), pyrexia and anorexia (41% each). Leukocytosis (82%) and microcytic hypochromic anemia (30%) were the most common hematological abnormalities. Caudal thoracic masses were demonstrated on survey radiographs of 13/15 of the dogs and thoracic spondylitis was detected in 12/15 dogs. Spirocerca lupi eggs were detected in 2/8 patients and worms were demonstrated on 1/11 at necropsy. Ten cases underwent surgical attempt to remove the tumors. In six of them partial esophagectomy (PE) was performed and all of them survived the immediate postoperative hospitalization. Five of the cases that underwent PE also received chemotherapy after surgery (doxorubicin (Adriamycin, Upjohn)) with an average survival time of 267 days. The histopathological results of the esophageal tumors were osteosarcoma (9), fibrosarcoma (5) and undifferentiated sarcoma (1). In areas endemic to spirocercosis, regurgitation or vomiting in dogs and microcytic hypochromic anemia and neutrophilia warrant ruling out esophageal sarcomas. Proper surgical treatment could prolong the dogs' lifespan for months, and improve their quality of life.     

Manganese nutrition of pepper (Capsicum annuum L.): Growth,Mn uptake and fruit disorder incidence

This research included two independent yet build up objectives: (i) to examine the effects of Mn concentration in the irrigation water on the yield and fruit quality of greenhouse-grown bell pepper exposed to heat stress; and (ii) to investigate in a laboratory experiment the role of Mn addition on oxidative and anti-oxidative components of fruit apoplast. The field experiment included four concentrations of Mn in the irrigation water (0, 0.2, 0.6 and 1.0 mg L⁻¹). The effect of Mn application rate on vegetative growth and total fruit yield was insignificant and despite low Mn concentrations in zero-Mn-fed plants, no visible foliar Mn symptoms were observed. A quadratic regression was obtained between high-quality fruit yield and Mn concentration in fruit. Based on the quadratic equation, maximum high-quality yield was obtained when fruit-Mn concentration approached 44 mg kg⁻¹ DW. The correlation also indicates that variations in high-quality yield could be explained by differences in fruit-Mn concentration. The combination of low-Mn nutrition and high air temperature which prevailed during the experiment (summer season) induced severe pale spots and blemished fruits; approximately 50% of fruits were infected in zero-Mn-fed plants. In a laboratory experiment with detached-fruit under high temperature the H₂O₂ concentration increased whereas ascorbic acid concentration decreased in the apoplast. In Mn-fed fruit the H₂O₂ concentration was attenuated and the activity of ascorbate oxidase was suppressed, with the result that apoplastic ascorbic acid concentration increased. In light of the known crucial role of Mn in enzyme activities and in detoxification of oxygen free-radicals, the pale spots might be related to Mn effect on oxidative stress-related apoplastic activities. The relationships between incidence of pale spots and plant-Mn concentration may support this hypothesis, but further research is needed to validate it.     

Superconducting bi-ca-sr-cu-o fibers grown by the laser-heated pedestal growth method

Superconducting fibers of several compositions including the nominal composition Bi(2)CaSrCu(2)O(8) have been grown by means of the laser-heated pedestal growth method. The influence of starting composition and growth conditions on structure and superconducting properties is discussed. The a-b planes of the material are parallel to the fiber axis (along the growth direction), providing the ideal condition for conduction along the copper-oxygen planes.     

Resistance of soybean vegetative storage proteins (S-VSPs) to proteolysis by rumen microorganisms

Soybean vegetative storage proteins (S-VSPs) are lysine-rich and, hence, are potentially of high nutritive value for high productive ruminants. Using S-VSPs from wild-type soybean and from transgenic tobacco plants expressing either one of the two S-VSPs subunits (S-VSP alpha or S-VSP beta) or both, we tested their stability in cow rumen fluid under in situ conditions, using SDS-polyacrylamide gel electrophoresis. Proteolysis and degradation pattern of S-VSPs from transgenic tobacco leaves occurred relatively fast compared with that of wild-type (WT) soybean plants. Comparing the two S-VSPs subunits expressed in transgenic plants, we found that S-VSP alpha was degraded much faster than S-VSP beta. The degradation pattern of S-VSPs in transgenic tobacco plants expressing both subunits resembled that of WT soybean. In contrast, the degradation pattern of transgenic tobacco plants expressing a single subunit was different. These finding suggest that the quaternary structure of S-VSPs may be an important factor determining their resistance to rumen degradation. Our results also suggest that the stability to rumen proteolysis of a given protein, when expressed in a transgenic plant, may not always be predictable and has to be verified.     

Urea retention and uptake by avocado and apple leaves

Solution retention by avocado (Persea americana cv. Fuerte) and apple (Mallus domestica Burkh. cv. Anna) leaves was measured by weight gain of detached leaves after dipping them in solutions of two surfactants and by analysis of various concentrations of urea retained at zero time on surfaces of attached leaves. Linear regression equations were calulated, relating leaf area and retention of solution. The slope of the equation represents the retention of solution on the leaf surface, and its intercept represents the value retained on the leaf margin. Solution retained on leaf surface was 2.5–2.6 and 5.4–6.4 mg/cm² for ‘old’ avocado and apple leaves, respectively. Retention on the serrated leaf margin of the apple was greater than on the smooth margin of the avocado. The abaxial leaf surfaces retained approximately 62% and 83% of the total solution retained by the avocado and the apple leaves, respectively.

The rate of urea uptake was proportional to the applied concentration and reached in avocado 65–85% within 2–5 days and over 90% in apple within 2 days. The rate of urea uptake by avocado was similar on ‘Young’ and ‘old’ leaves, similar from either Triton X‐100 or L‐77 surfactants, and similar through abaxial and adaxial surfaces. The nitrogen enrichment from foliar application of urea was related to retention and threshold of phytotoxicity rather than to rate of uptake. Older leaves of avocado showed some phytoxicity to 4% urea. Young leaves were damaged by repeated 2% application and flowers by 0.5–1.0%.

The actual nitrogen enrichment in avocado, which could be predicted accurately from measurement of urea retention, was 43% following three successive applications of 3% urea in 12 days.     

DNA probes for Mycoplasma gallisepticum and Mycoplasma synoviae: application in experimentally infected chickens

DNA probes specific for Mycoplasma gallisepticum and M. synoviae were selected from genomic libraries prepared in the pUC13 vector. The probes hybridized with the DNA of a wide spectrum of strains within each homologous species, but did not react with the heterologous species or with DNA from any other avian mycoplasma or bacteria tested. Experimental infection and contact exposure of chickens to M. gallisepticum served as models to test the effectiveness of the DNA probe in diagnosis as compared with serological and culture detection methods carried out in parallel. A correlation was generally found between the level of M. gallisepticum in tracheal swabs and the effectiveness of the probe, although a predictably reactive level of mycoplasmas was not always detected. Treatment of clinical specimens with acetylcysteine to disrupt mucus improved the detection rate. Dot-blot hybridization with probe pMG4 enabled positive identification of M. gallisepticum at an early stage of infection, prior to the development of a serological response in the infected chicken. Results are obtainable within 4 days of sampling, much more rapidly than culture, and also in clinical specimens from which mycoplasma isolation is impossible, such as carcasses. The results indicate that the use of DNA probes for the early and rapid detection of M. gallisepticum infection is feasible; a development which can replace laborious culture techniques and less effective serological methods, and thus reduce the time required for diagnosis.     

Sensitivity of Neurospora crassa to a Marine-Derived Aspergillus tubingensis Anhydride Exhibiting Antifungal Activity That Is Mediated by the MAS1 Protein

The fungus Aspergillus tubingensis (strain OY907) was isolated from the Mediterranean marine sponge Ircinia variabilis. Extracellular extracts produced by this strain were found to inhibit the growth of several fungi. Among the secreted extract components, a novel anhydride metabolite, tubingenoic anhydride A (1) as well as the known 2-carboxymethyl-3-hexylmaleic acid anhydride, asperic acid, and campyrone A and C were purified and their structure elucidated. Compound 1 and 2-carboxymethyl-3-hexylmaleic acid anhydride inhibited Neurospora crassa growth (MIC = 330 and 207 μM, respectively) and affected hyphal morphology. We produced a N. crassa mutant exhibiting tolerance to 1 and found that a yet-uncharacterized gene, designated mas-1, whose product is a cytosolic protein, confers sensitivity to this compound. The ∆mas-1 strain showed increased tolerance to sublethal concentrations of the chitin synthase inhibitor polyoxin D, when compared to the wild type. In addition, the expression of chitin synthase genes was highly elevated in the ∆mas-1 strain, suggesting the gene product is involved in cell wall biosynthesis and the novel anhydride interferes with its function.     

All-male broods of Tilapia nilotica × T. aurea hybrids

The proportion of males in single pair crosses between Tilapia nilotica females and T. aurea males was found to vary between 50 and 100%. There was no apparent influence of the T. aurea males on these proportions. In a similar test nine T. vulcani females were paired with T. aurea males, and the proportion of males in their hybrid offspring ranged between 93 and 98%. Two T. nilotica mothers of all-male hybrid broods mated with unselected T. nilotica males, and all their daughters also reproduced all-male hybrid broods when crossed with T. aurea males. The reciprocal cross of T. aurea females with T. nilotica males reproduced three males to each female offspring. Growth rate tests of the all-male T. nilotica × T. aurea hybrids, and the T. vulcani × T. aurea hybrids did not reveal heterosis.