Cochlear distortion: effect of direct-current polarization

Intermodulation components (combination tones) appearing in microphonic potentials were measured from guinea pig cochleas with and without polarizing direct currents passing through the cochlear partition. At moderate intensities of stimulus the polarization had a qualitatively different effect on the distortion components than on their eliciting primaries or on pure tones simulating the distortion products. At high intensities, the primaries and the combination tones were similarly influenced by the polarizing current. It is concluded that cochlear distortion is a two-stage process, mechano-electrical at low levels and mechano-hydraulic at high levels.     

A review of the infectious diseases of African wild ruminants

The important viral, protozoal and bacterial diseases of wild African ruminants are reviewed. Special attention is paid to the epidemiological factors that determine the role played by these animals in the transmission of diseases to domestic stock. Examples of the converse situation where livestock serve as a source of infection for wild ruminants are also given.     

Surface Deformation and Lower Crustal Flow in Eastern Tibet

Field observations and satellite geodesy indicate that little crustal shortening has occurred along the central to southern margin of the eastern Tibetan plateau since about 4 million years ago. Instead, central eastern Tibet has been nearly stationary relative to southeastern China, southeastern Tibet has rotated clockwise without major crustal shortening, and the crust along portions of the eastern plateau margin has been extended. Modeling suggests that these phenomena are the result of continental convergence where the lower crust is so weak that upper crustal deformation is decoupled from the motion of the underlying mantle. This model also predicts east-west extension on the high plateau without convective removal of Tibetan lithosphere and without eastward movement of the crust east of the plateau.     

Estimating the mass of asteroid 253 mathilde from tracking data during the NEAR flyby

The terminal navigation of the Near Earth Asteroid Rendezvous (NEAR) spacecraft during its close flyby of asteroid 253 Mathilde involved coordinated efforts to determine the heliocentric orbits of the spacecraft and Mathilde and then to determine the relative trajectory of the spacecraft with respect to Mathilde. The gravitational perturbation of Mathilde on the passing spacecraft was apparent in the spacecraft tracking data. As a result of the accurate targeting achieved, these data could be used to determine Mathilde's mass as 1.033 (+/- 0.044) x 10(20) grams. Coupled with a volume estimate provided by the NEAR imaging team, this mass suggests a low bulk density for Mathilde of 1.3 grams per cubic centimeter.     

Protection of piglets against a virulent New Zealand isolate of Aujeszky's disease virus by vaccination with a novel genetically-engineered vaccine

Abstract

AIMS: To modify and validate an existing swine erysipelas ELISA for use with poultry serum and to assess the safety of a swine erysipelas vaccine for use in New Zealand layer birds.

METHODS: An existing swine erysipelas ELISA was modified for use in domestic poultry and was validated using sera from birds injected with either 2 mL of a commercially available killed swine erysipelas vaccine (low-dose; n=12 birds), 4 mL of vaccine (high-dose; n=11 birds), or 2 mL saline (control; n=11 birds) on Day 0 and again on Day 21. Blood samples were collected on Days 0, 21, 42, and 63, and safety of the vaccine for use in layer birds was determined by assessing cloacal temperature and injection site reactions in birds at 0, 4, 24, 48, 72 and 96 h post-vaccination.

RESULTS: The ELISA that was developed had a diagnostic sensitivity and specificity of 93% and 98%, respectively, after being optimised for a positive cut-off at an optical density (OD) ≥1.50 read at 450-nm wavelength. OD readings were higher on Days 21, 42, and 63 than Day 0 in both the low-dose and high-dose groups (p<0.05), and differed amongst the three groups on Days 21, 42, and 63 (p<0.05), suggesting that vaccination using either dose induced detectable levels of antibody, even after a single dose. In addition, the high-dose protocol induced higher levels of antibody production than the low-dose protocol. No local or systemic reactions to the vaccine were observed and cloacal temperatures remained in the normal biological range after vaccination.

CONCLUSIONS: The ELISA that was developed had satisfactory diagnostic performance characteristics and the vaccine appeared to be safe for use in layer birds. However, the study design did not permit an assessment of the vaccine's efficacy to protect birds from clinical erysipelas.

CLINICAL RELEVANCE: A diagnostic ELISA has been developed for determining the exposure of layer birds to E. rhusiopathiae. The test will be useful for monitoring flock-level erysipelas, response to vaccination, and in epidemiological studies designed to identify risk factors for exposure to the disease.     

The Complement Fixation Test for Brucella Ovis

Abstract

Sir:- A project to investigate the efficacy of the complement fixation test (CFT) for the diagnosis of Brucella ovis infection in rams has recently been completed. The investigation was undertaken by field and laboratory staff of the Division of Animal Health and several practitioners. The results of CFT's done with 3 antigens by waim and cold fixation methods (WCFT and CCFT) were correlated with results of cultures done of semen from the same rams. It is our aim to publish a full report in this Journal at a later date. In view of the widespread interest in the subject some of the important findings are summarised below:

• ? Semen and blood samples were collected from 541 rams in 40 flocks.

• ? The type of antigen which has been used for a number of years in New Zealand was unsatisfactory. The CCFT using this antigen had a sensitivity of only 85% in 124 rams which gave positive semen cultures. These rams came from 16 infected flocks.

• ? The CCFT using the best of the 3 antigens proved to be a remarkably reliable test. In the same group of infected animals mentioned above, 120 of the 124 infected rams had positive or suspicious CFT's. The sensitivity of the test was therefore 97%. The specificity was > 99% in 144 rams in 16 uninfected flocks. Only 1 suspicious titre was found in the uninfected group.

• ? In 4 flocks in which B. ovis was never isolated, 18 of 58 sera gave positive or suspicious reactions. Recognition of this type of 'problem flock' is therefore important. A history and clinical picture which does not agree with serological results should always be thoroughly investigated. Semen should be collected from an appropriate number of cases for bacteriological examination. It is suspected that at least some ‘problem flocks’ may contain unreported vaccinated animals. Further investigation of ‘problem flocks’ will be an aim of the Animal Health Division in the future.

     

Frequency of a FAS ligand gene variant associated with inherited feline autoimmune lymphoproliferative syndrome in British shorthair cats in New Zealand

Abstract

AIMS

To determine the frequency of the FAS-ligand gene (FASLG) variant associated with feline autoimmune lymphoproliferative syndrome (FALPS) and the proportion of carriers of the variant in three British shorthair (BSH) breeding catteries in New Zealand.     

Serology and semen culture for the diagnosis of Brucella ovis infection in chronically infected rams

The serological response to Brucella ovis and the shedding of the organism in semen was followed for a period of 13–14 months in 42 naturally infected rams. Most rams remained chronically infected and excreted the organism in their semen throughout the investigation B. ovis was isolated from 87.9% of the semen samples from the infected rams. The most common sites from which B. ovis could be isolated at necropsy were the epididymides and accessory sexual glands. In one ram the organism was isolated from lung, spleen, kidney and iliac lymphnodes. Three rams ceased to shed B. ovis in their semen during the course of the investigation. Seventy-five (11%) of 686 sera from infected rams were negative in the complement fixation test (CFT) although 76% and 77% of CFT-negative sera were positive in the gel diffusion precipitin test (GDT) and enzyme labelled immunosorbent assay (ELISA) respectively. The high incidence of CFT-negative infected rams was due to the selection for the investigation of many rams with histories of negative or vacillating CFT titres. Sera from five rams which never shed B. ovisin their semen reacted erratically in the three serological tests. The five rams were from heavily infected flocks and were kept in contact with infected rams throughout the investigation.