Neuronal ceroid lipofuscinosis in Merino sheep

OBJECTIVE: To characterise neuronal ceroid lipofuscinosis (NCL) in Merino sheep. DESIGN: A prospective clinical, pathological, biochemical and genetic study. PROCEDURE: NCL cases were studied from a medium-wool Merino flock, the stud of origin of its replacement rams, and an experimental flock established at the University of Sydney. RESULTS: Behavioural changes and visual impairment were first detected at 7 to 12 months of age and progressed, with associated motor disturbances and at later stages seizures, to premature death by 27 months of age. At necropsy there was severe cerebrocortical atrophy associated with neuronal loss, astrocytosis and the presence in neurons of eosinophilic intracytoplasmic storage bodies with the characteristics of a lipopigment. In the retina there was progressive loss of photoreceptor cells. Storage bodies isolated from fresh brain, liver and pancreas formed electron-dense aggregates and coarse multilamellar and fine fingerprint profiles ultrastructurally, and consisted mainly of the hydrophobic protein, subunit c of mitochondrial ATP synthase. A homozygosity mapping approach localised the gene causing the disease in Merino sheep to the chromosomal region (OAR7q13-15) associated with NCL in South Hampshire sheep. CONCLUSION: NCL in Merino sheep is a subunit c-storing disease, clinically and pathologically similar to NCL in South Hampshire sheep. We propose that the disease in both breeds represents mutation at the same gene locus in chromosomal region OAR7q13-15.     

The relationships between social behaviour of dairy cows and the occurrence of lameness in three herds

It is well known that lameness in cattle has a multifactorial causation, however it is still not clear why some individuals are more susceptible to foot lesions in the same environment. Behaviour is thought to play an important role. The aim of this study was to assess the relationships between social and individual behaviour and the incidence of lameness in three dairy herds. Low-ranking cows spent less time lying and more time standing still and standing half in the cubicles than middle- and high-ranking cows. As time spent standing half in the cubicle increased, the number of soft tissue lesions increased and as total time standing increased the number of cases of lameness increased. The survival rate to lameness for low-ranking cows was significantly lower than for middle- or high-ranking individuals.     

Timing and causes of piglet mortality in alternative and conventional farrowing systems

The causes and timing of piglet mortality were studied in different farrowing systems. In the first experiment 198 litters were recorded in three systems, two of which allowed the sows to move freely, and the third restricted them in conventional crates. More piglets were weaned from the conventional crates than from the open systems and they grew more quickly. More than half the liveborn mortality occurred during the first four days after parturition. In the open systems, 17 per cent and 14 per cent of the piglets born alive were crushed, compared with only 8 per cent in the crates. In the second experiment, 29 sows and litters were studied in detail in a communal pen system during the first seven days of lactation. Three-quarters of the liveborn mortality was due to crushing. The total number of piglets dying per litter, including stillbirths, was significantly associated with the total litter size and the sow's parity. The percentage liveborn mortality was significantly associated with the parity and body length of the sows and with the within-litter variation in the birth weight of the piglets. Individual birth weight was closely associated with percentage survival. Only 28 per cent of piglets weighing less than 1.1 kg at birth survived to seven days.     

Acanthocephalan infection and sparganosis in a green tree snake (Dendrelaphis punctulata)

Acanthocephalan and spargana parasites were identified within a body wall mass during exploratory surgery in a wild green tree snake. Acanthocephalan parasites have not previously been reported in this species. Surgical excision, the treatment of choice, could not be achieved because of the extensive infiltration of the coelomic cavity.     

Probing the Local Effects of Magnetic Impurities on Superconductivity

The local effects of isolated magnetic adatoms on the electronic properties of the surface of a superconductor were studied with a low-temperature scanning tunneling microscope. Tunneling spectra obtained near magnetic adsorbates reveal the presence of excitations within the superconductor's energy gap that can be detected over a few atomic diameters around the impurity at the surface. These excitations are locally asymmetric with respect to tunneling of electrons and holes. A model calculation based on the Bogoliubov-de Gennes equations can be used to understand the details of the local tunneling spectra.     

Spontaneous formation of macroscopic chiral domains in a fluid smectic phase of achiral molecules

A smectic liquid-crystal phase made from achiral molecules with bent cores was found to have fluid layers that exhibit two spontaneous symmetry-breaking instabilities: polar molecular orientational ordering about the layer normal and molecular tilt. These instabilities combine to form a chiral layer structure with a handedness that depends on the sign of the tilt. The bulk states are either antiferroelectric-racemic, with the layer polar direction and handedness alternating in sign from layer to layer, or antiferroelectric-chiral, which is of uniform layer handedness. Both states exhibit an electric field-induced transition from antiferroelectric to ferroelectric.     

Organic Glasses: A New Class of Photorefractive Materials

The performance of amorphous organic photorefractive (PR) materials in applications such as optical data storage is generally limited by the concentration of active molecules (chromophores) that can be incorporated into the host without forming a crystalline material with poor optical quality. In polymeric PR systems described previously, performance has been limited by the necessity of devoting a large fraction of the material to inert polymer and plasticizing components in order to ensure compositional stability. A new class of organic PR materials composed of multifunctional glass-forming organic chromophores is described that have long-term stability and greatly improved PR properties.     

Three-dimensional structure of human serum albumin

The three-dimensional structure of human serum albumin has been solved at 6.0 angstrom (A) resolution by the method of multiple isomorphous replacement. Crystals were grown from solutions of polyethylene glycol in the infrequently observed space group P42(1)2 (unit cell constants a = b = 186.5 +/- 0.5 A and c = 81.0 +/- 0.5 A) and diffracted x-rays to lattice d-spacings of less than 2.9 A. The electron density maps are of high quality and revealed the structure as a predominantly alpha-helical globin protein in which the course of the polypeptide can be traced. The binding loci of several organic compounds have been determined.     

Nanofabrication of Small Copper Clusters on Gold(111) Electrodes by a Scanning Tunneling Microscope

The use of scanning tunneling microscopy in an electrochemical environment as a tool for the nanoscale modification of gold electrodes was demonstrated. Small copper clusters, typically two to four atomic layers in height, were precisely positioned on a gold(111) electrode by a process in which copper was first deposited onto the tip of the scanning tunneling microscope, which then acted as a reservoir from which copper could be transferred to the surface during an appropriate approach of the tip to the surface. Tip approach and position were controlled externally by a microprocessor unit, allowing the fabrication of various patterns, cluster arrays, and "conducting wires" in a very flexible and convenient manner.     

Gonad development and spawning in Anadara granosa (L.) (Bivalvia: Arcidae)

A study of gonad development and spawning in Anadara granosa (L.) from the west coast of West Malaysia was carried out between September 1977 and November 1978 based on (a) changes in the condition of the whole animal and (b) histological changes in the gonad. Gonads did not develop until a length of 17.5 mm had been attained and the first spawning probably occurred at a length of 24–25 mm. There was evidence of a low level of spawning activity throughout the year but the largest size group spawned in October in 2 consecutive years. There was inconclusive evidence for a second spawning in May/June. A condition index of dry/wet weight of tissue adequately reflected spawning in specimens longer than 30 mm. There was no deviation from a 1 : 1 ratio of males to females in any of the size classes studied.