Maximizing rhizosphere populations of fluorescent pseudomonads on potatoes and their effects onErwinia carotovora

Field-grown potato plants were treated withPseudomonas putida andP. fluorescens strains in order to maximize the rhizosphere populations of the pseudomonads and determine their effects on indigenous populations ofErwinia carotovora. Single applications of the pseudomonads to seed pieces at planting resulted in peak populations of approximately 10⁵ colony-forming units (CFU) per gram (fresh weight) of root in July, whereas a second application in June boosted rhizosphere populations 10- to 100-fold higher throughout the remainder of the growing season; they composed nearly 20% of the average total population of rhizosphere bacteria in early July. Although rhizosphere populations of the introduced pseudomonads were high,E. carotovora populations sharply increased from very low numbers to reach populations ranging between 10⁵ and 10⁷ CFU/g by early July. Furthermore, coapplications of pseudomonad strains failed to suppress native populations ofE. carotovora despite the growth and maintenance of high rhizosphere populations of both pseudomonad strains.     

Biocontrol potential of Pseudomonas azotoformans,Serratia marcescens and Trichoderma virens against Fusarium wilt of Dalbergia sissoo

Wilt disease caused by Fusarium solani is a serious constraint to Dalbergia sissoo (shisham) plantations in northern India. In this study, the antagonistic potential of 40 bacterial isolates recovered from rhizophere soil of healthy shisham trees, and a well‐characterized Trichoderma species (Trichoderma virens) were tested for their possibility as biocontrol agents for F. solani. Two promising isolates (S1 and S15) were identified which inhibited pathogen growth, caused chitin degradation, produced siderophores and solubilized phosphate in vitro. Isolate S15 scored highest for hydrogen cyanide (HCN) production while isolate S1 was a non‐HCN producer. These two isolates were identified as Serratia marcescens (S1) and Pseudomonas azotoformans (S15) following sequence analysis of 16S rDNA. In dual culture assays, T. virens caused 80% inhibition of mycelial growth of the test fungus. The three selected antagonists when tested in planta in the glasshouse completely suppressed production of wilt symptoms on 12‐month‐old shisham plants. Further work is needed to ascertain the potential of these isolates to be used as biocontrol agents to manage shisham wilt under field conditions.     

Automated method for the determination of niacin and niacinamide in cereal products: collaborative study.

In a collaborative study, an automated method for the determination of niacin and niacinamide in cereal products was compared with the official final action microbiological (43.121-43.125) and chemical (43.044-43.046) methods. Ten samples of cereal products, including enriched flour, yeast-leavened baked products, fortified breakfast cereals, and baked pet food products, were submitted to 14 laboratories. Nine laboratories reported values by the automated method, 6 reported values by the microbiological method, and 7 reported values by the chemical method. The results from the microbiological method were not subjected to analysis of variance because of the unusually large between-laboratory variation. The between-laboratory coefficients of variation for the automated and chemical methods were 10.90 and 10.18%, on the basis of results from 7 and 4 laboratories, respectively. There was no significant (p greater than 0.05) difference between methods when results from the 4 laboratories who used both methods were compared. The automated chemical method has been adopted as official first action.     

Factors affecting chicken thrombocyte morphology and the relationship with heterophil:lymphocyte ratios

1. Thrombocytes were observed in a haemocytometer chamber and cells were classified into 5 morphological groups which were related to the extent of environmental stress. Thrombocyte morphology scores (TMS) were calculated for each blood sample. 2. Following exposure to social stress, chilling, or the injection of killed Escherichia coli, both TMS and heterophil:lymphocyte (H:L) ratios were increased. From maximum values 1 d after chilling H:L and TMS values returned to normal within 2 and 11 d respectively. 3. The addition of corticosterone (200 mg/kg) to the food resulted in increased H:L ratios whereas TMS were not affected. 4. The injection of an adrenal blocker, 1,1-dichloro-2,2 bis p-choro-phenyl ethane, resulted in decreased H:L values whereas TMS were not affected. 5. Resistance to E. coli challenge infection was not affected by TMS.     

Pharmacodynamics and pharmacokinetics of orally administered bishydroxycoumarin in the goat

Eight goats, 2 nontreated controls and 6 treated, were used to study the pharmacodynamics and pharmacokinetics of bishydroxycoumarin. In 5 of the 6 treated goats, there was a significant relationship between prothrombin times and drug concentrations. Activated clotting times did not change with time in either the controls or the treated goats. Five of 6 treated goats reached a plateau of drug concentration after 24 to 36 hours. Lag times for onset of pharmacologic effect ranged from 12 to 24 hours. The one goat (No. 3) that did not respond in concert with the other 5 was extremely nervous and became anorectic during the period of indoor confinement.     

Lesions of experimental flea bite hypersensitivity in the dog

Hypersensitivity to fleas was induced in flea-naive dogs by controlled challenge exposure to virgin fleas. By week 10 of the investigation, immediate (15 minute) and delayed (24-48 hours) responses could be elicited in the skin by flea bites. Histologically, the immediate response consisted of edema and eosinophils which sometimes overlapped with a delayed inflammatory response comprised of perivascular lymphocytes and fewer histiocytes. These inflammatory patterns correlated with type I or immediate, and type IV or cellular, allergic reactions. The combined immediate and delayed responses to fleas in the dog are as observed by other investigators in man and guinea pigs.     

Environment-genetic influences on immunocompetence

The immunological responses of an animal are changing continually in response to perceived environmental changes. This is because the genetic background, the lifelong environment of animals and their interaction greatly influence immunological responsiveness. An animal's genetic background influences all factors related to immunocompetence. Among these are age of onset of immunocompetence, responsiveness to specific antigens, antibody titers, type of antibody and immune response, as well as the persistence of the responses. Defense by immunity must require considerable resources, because chickens with a high antibody response are smaller and have poorer feed efficiencies than those chickens whose antibody response is lower. An increase in the effectiveness of one defensive factor may result in reduced effectiveness of another factor. For example, chickens selected for a high antibody titer response to antigen have reduced effectiveness of macrophages. Environmental stresses influence the immune response. Stress at the time of the animal's contact with antigen results in a reduced antibody response. After the antibody response begins, stress has little effect. Stress promotes the sensitization of cell-mediated immunity but inhibits its effectiveness. A short-term stressor such as weaning is followed, in about 24 h, by a short period of reduced immunocompetence, even though lymphoid mass may be reduced. Reduced immunocompetence during stressful periods can be reduced by employing adrenal blocking chemicals, or by socializing animals to their handlers.     

Effects of dietary corticosterone in young Leghorn and meat-type cockerels

1. Cockerels from meat-type (MT) and Leghorn (LG) stocks were fed on diets containing 0, 20, or 30 mg corticosterone/kg from 1 to 22 d after hatching. 2. Within MT and within LG stocks, responses to dietary corticosterone inclusion rates were similar; however, patterns differed between these major classes resulting in stock X diet interactions. 3. Traits responding to different inclusion rates of corticosterone in a dissimilar manner for MT and LG chickens included: immunoresponsiveness, body weight, efficiency of food utilisation, feathering; relative weights of liver, spleen, bursa, testes, breast and abdominal fat pad, as well as the proportion of liver lipid. 4. No differential responses occurred for relative adrenal weight, plasma xanthophyll concentrations, proportion of breast lipid and abdominal fat, or surface and cloacal temperatures. 5. Results indicated genetic differences in thresholds for response to corticosterone and in degree of response once thresholds were reached. Within populations, sensitivities varied between target organs.     

Effect of ascorbic acid on the disease caused by Escherichia coli challenge infection

In a series of experiments, leghorn-type chickens were fed diets containing from 0 to 880 mg of ascorbic acid/kg of feed beginning 1 day before air-sac challenge with Escherichia coli. Infection occurred in 46/60 (76%) of the controls and in 12/63 (19%) of those given feed containing 330 mg of ascorbic acid/kg. Levels of ascorbic acid above and below 330 mg/kg feed were less effective.