Identification and analysis of the Georgia 98 serotype, a new serotype of infectious bronchitis virus

Twenty-five field infectious bronchitis viruses (IBVs) similar to, but genetically distinct from, the DE072 serotype were isolated from several states in the United States from 1990 through 1999 and were examined molecularly and antigenically. A 421-bp sequence in the hypervariable region of the S1 gene was examined, and phylogenetic analysis on that region indicated that these viruses are closely related but fall into unique groups. Cross-virus neutralization testing and entire S1 sequence analysis on selected isolates further confirmed that fact, and we divided the viruses into the DE072 serotype and two other unique groups. In a vaccine protection trial, the commercially available DE072 vaccine showed less than 50% protection against viruses in one of the groups. The majority of the recent isolates belong to that group and share very low antigenic relatedness to the DE072 strain as well as other serotypes of IBV. Consequently, we designated this group as a new serotype, Georgia 98. We developed a restriction fragment length polymorphism analysis that can differentiate this new serotype from all other serotypes of IBV.     

Effect of dopamine on excretory urographic image quality and the prevention of contrast-induced nephropathy in dogs

The effect of low dose dopamine on the excretory urographic image quality and contrast media-induced nephropathy in normal dogs (experiment 1) and the dogs with decreased renal function (experiment 2) were assessed. In experiment 2, decreased renal function was induced by gentamicin overdose. In each experiment, animals were divided into 3 groups. In group 1, only contrast medium (iohexol) was administered. In group 2, contrast medium plus intravenous fluid (0.9% saline) were administered. And in group 3, contrast medium plus intravenous fluid and low dose dopamine were administered. Investigated parameters included intrarenal resistive index (RI), serum BUN and creatinine concentrations, contrast medium elimination time and radiographic image quality. In experiment 1, RI of group I increased at 80 min after contrast medium administration (p<0.05), but RI of group 3 decreased at 48 and 72 hr (p<0.05). Serum BUN concentration of group 1 was higher than that of group 2 and 3 (p<0.05); in radiographic examination, contrast medium elimination time decreased in group 2 and 3, but image quality of group 2 was inferior to that of group 3. In experiment 2, image quality of group 3 only provided adequate visualization of renal structures. The formula of contrast medium plus low dose dopamine was found to provide good nephrogram and pyelogram image quality without supplemental contrast medium, and to protect renal tubules from prolonged exposure to concentrated contrast medium.     

Heparin inhibits plaque formation by cell-free Marek's disease viruses in vitro

The mechanisms of Marek's disease virus (MDV) entry to host cells have not yet been analyzed. Heparan sulfate (HS) on the cell surface serves as a receptor for several herpesviruses in mammalian species. In this study, we demonstrated that plaque formation by cell-free MDV is inhibited by the addition of soluble heparin to the cell culture. Moreover, pretreatment of susceptible cells, chicken embryo fibroblasts, with heparinase, partially reduced infectivity of the cell-free MDV. From these results, it was suggested that the MDV entry, at least in the case of cell-free MDV, is dependent on the presence of cell surface glycosaminoglycans, principally HS.     

ULTRASONOGRAPHIC DIAGNOSIS—PYLOROGASTRIC INTUSSUSCEPTION IN A DOG

A 7-year-old female Maltese presented for evaluation of severe vomiting. A diagnosis of pylorogastric intussusception was made during ultrasonographic examination. The intussusception spontaneously underwent reduction by the following morning.     

Porphyric insecticides. IV: Structure-activity study of substituted phenanthrolines

The porphyric-insecticide-modulating activities of 1,10-phenanthroline and eight of its analogs were investigated. The insecticidal efficacy of these compounds was closely associated with their ability to enhance the conversion of exogenous δ-aminolevulinic acid (ALA) to protoporphyrin IX (Proto). As observed for photodynamic herbicidal effects in plants, the presence of nitrogen atoms at positions 1 and 10 of the macrocycle was essential for porphyric insecticidal activity. This was evidenced by the very limited activity of phenanthrene, in which positions 1 and 10 are occupied by carbon instead of nitrogen atoms. On the other hand, enhancement of Proto formation and porphyric insecticidal activity were maintained following methyl, chloro and nitro group substitution at the periphery of 1,10-phenanthroline. In contrast, Proto levels and photodynamic toxicity were reduced by hydroxy and phenyl substitution at the same positions. Benzyl substitution at the 2–3 and 8–9 positions was also inhibitory. Quantitative structure-activity calculations suggested a relationship between peripheral group substitution and physicochemical properties of the substituted compounds. Electron density changes in 1,10-phenanthroline and its analogs that appeared to be related to reduced efficacy included (a) appearance of positive charge-binding volumes at positions 4 and 7 of the 1,10-phenanthroline macrocycle, which flanks positive charge-repelling volumes, (b) a dramatic increase in superdelocalisability (i.e. electron density) over some unoccupied molecular orbitals, and (c) electronic charge at positions 1 and 10 of the macrocycle. Large increases in van der Waals volumes also exerted negative effects on insecticidal efficacy.     

Enzyme studies with the livers of chicks fed semi‐synthetic diets containing crystalline amino acids and diammonium citrate

The levels of glutamate dehydrogenase [NAD(P)], (GDH), aspartate trans‐aminase (AspT) and alanine transaminase (AlT) were measured in livers from chicks fed on a semi‐synthetic diet containing crystalline essential amino acids as the sole nitrogen source (diet A). The effects of a supplement of 12.0% glutamic acid (diet H) or 11.07% diammonium citrate (DAC) (diet B) or 12.0% glutamic acid plus 1.0% proline with an additional 0.6% glycine (diet C) on these enzymes were studied and the results compared with the levels found for control chicks given a typical diet based on cereal protein (diet J). The abilities of livers from chicks given diets A, B and C to synthesise [14C] glutamic acid from [14C]2‐oxoglutaric acid and diammonium citrate (DAC) were assessed.

The levels of GDH, AspT and AlT found in the livers of chicks given the control diet were 54.1, 966 and 123.7 units/mg protein respectively. Non‐essential nitrogen added as glutamic acid or as DAC did not cause induction of the enzymes studied above control levels. Glutamic acid (diets H and B) caused a depression of GDH levels (37.4 and 38.9 units/mg protein respectively) but had no effect on AspT and AlT compared with the controls, whereas DAC caused a decrease in AlT (43.9 units/mg protein) but had no effect on AspT and GDH; diet A depressed AlT and AspT levels (64.4 and 735 units/mg protein respectively).

The livers of chicks given diets A, C and B varied in their ability to synthesise glutamic acid, 39.3%, 31.9% and 24.0% respectively of the radioactivity being recovered as glutamic acid.     

A quantitative analysis of the literature concerning the restricted feeding of growing pullets

The sexual maturity of growing pullets can be retarded either by restricting calorie intake or by feeding a diet deficient in one or more essential amino acids, Several methods have been proposed for achieving either of these objectives. In this review the methods have been classified as (a) limiting the birds’ time of access to food, (b) quantitative food restriction, (c) the use of low energy diets and (d) dietary protein restriction.

Food restriction by limiting the time of access to food has given inconsistent results and is an unsatisfactory technique. Birds quickly learn to eat normal quantities of food in a very short space of time.

Quantitative food restriction has been widely used in experiments and is usually applied from about 6 to about 20 weeks of age. The available evidence enables relationships to be established between the degree of food restriction and subsequent body weight and sexual maturity. The effect of rearing treatment on mortality and rate of lay is also examined.

The ad libitum feeding of a low‐energy growing diet has always resulted in greater rearing food costs. This is because moderate reductions in energy content of the diet are offset by higher food intake. Diets sufficiently low in energy to cause a reduction in calorie intake will involve the purchase and handling of very large proportions of non‐nutritive material.

The use of protein‐deficient diets during the growing period, or from one day of age, offers a suitable means of delaying sexual maturity. The effects of such a treatment are apparently very similar to those of restricted feeding, but there is a lack of suitable comparisons of the alternative methods.     

Use of hyperimmune serum, vaccination, and certain management procedures for control of pseudorabies in swine

A program involving use of hyperimmune serum, vaccination, and certain management procedures for the control of pseudorabies was evaluated on several farms on which the disease was enzootic. Neonatal mortality and reproductive failures on farms utilizing the program were compared with death losses and reproductive failures on farms not utilizing the program. The reduction in preweaning mortality and reproductive failures between the treated and nontreated groups were 42.1% and 39.6%, respectively.