Completion of the cycle for transmission of sarcosporidiosis between cats and sheep reared specific pathogen free

The confirmation of a cat-sheep transmission for visible sarcocysts was achieved in specific pathogen free (SPF) animals by completing sheep-cat-sheep-cat passages during 1977-79. The study used 22 laboratory cats and 15 specially bred sheep. Experimental sheep were dosed with sporocysts recovered from cats fed visible sarcocysts. "Giant" or "fat" form of macroscopic sarcocysts commonly found on the oesophagus were first demonstrated in the SPF sheep at 17 months after dosing. The sarcocysts from these sheep were infective to cats. Thus, the cycle of transmission for cat-borne ovine sacosporidiosis was completed. Grazing sheep in some situations develop visible cysts earlier, around one year of age, hence it is considered that the infections of experimental sheep in SPF conditions may not reflect all the circumstances leading to natural infection.     

Surgical Repair of an Intrathoracic Esophageal Pulsion Diverticulum in a Horse

An intrathoracic esophageal pulsion diverticulum causing repeated episodes of esophageal obstruction in a Morgan weanling colt was diagnosed by endoscopy, positive contrast radiography, and pleuroscopy. Surgical excision of the diverticulum alleviated clinical signs, and the horse was able to resume a normal diet by day 6. After 9 months the colt remains asymptomatic.     

Morphology of the Structural Root System of Sitka Spruce 1. Analysis and Quantitative Description

Root systems of 16-year-old, plantation grown, Sitka spruceof a range of sizes were excavated by hand from a peaty gleysoil. The length of each root segment and position of each branchingpoint, bend, fork and proliferation was measured for four rootsystems using a plumb-bob after placing them in a rigid, metalframework. On three root systems measurements were made by tapeand protractor of numbers of roots, branching points, bends,root lengths, branching angles and distribution of root originsaround the bole. Statistical analysis of these measurements revealed the rootbranching process as inherently regular. First-order roots tendedto be regularly distributed around the main stem. The orientationof roots was determined by their initial direction either fromthe mainstem or where they were formed as laterals, and by changesin direction either from the mainstem or where they were formedas laterals, and by changes in direction at bends or branchingpoints which tended to be alternately clockwise and anticlockwise.Lateral branches subtended larger angles from their parent rootsthan the angles between the two arms of a root fork and, irrespectiveof the length of a root segment, the laterals arising from itwere evenly distributed along its length. The angles of lateralroots were generally more steeply downward than those of theirparents. Root angles and directions changed where changes insoil structure or ditches were encountered. We suggest that the root growth of Sitka spruce is inherentlyregular in that the species may possess mechanisms which ensurethat its structural root system is more extended and more evenlyspread than would result if growth was at random. However, rootgrowth takes place in a heterogenous environment and it is thiswhich causes the variability in final root pattern.     

Colopexy of the Left Large Colon to the Right Large Colon in the Horse

Three colopexy techniques were examined in 11 normal horses to determine which would prevent recurrence of targe colon displacement and volvulus. The medial free band of the left ventral colon was sutured to the medial free band of the right ventral colon (technique A). The free band of the left dorsal colon was sutured to the free band of the right dorsal colon (technique B). In technique C, both the ventral and dorsal colon were sutured as in techniques A and B, and the pelvic flexure was sutured to the mesocolon between the right dorsal and right ventral colon. Absorbable (surgical gut) and nonabsorbable (polypropylene) suture material were compared.
One horse from each group was euthanized 2 weeks and 6 months after surgery. The position of the colon and the integrity of the colopexy were examined. At necropsy, attempts were made to produce displacement and volvulus of the colon. In the remaining horses, exploratory celiotomy 1 year after surgery was used to examine the integrity of the colopexy.
Although all horses initially lost weight after surgery, all but one began gaining weight 2 to 4 weeks later and had attained their preoperative weight by 6 months. The horse that continued to lose weight was euthanized 2 months after surgery. Numerous small colon, omental, and large colon adhesions were found at necropsy.
For all colopexy techniques, the colopexy adhesion remained short and intact at polypropylene suture sites. At surgical gut sites, the adhesion had lengthened by 6 months and was absent at 1 year. At necropsy, all colopexies prevented manual displacement of the large colon and volvulus of the colon at the sternal and diaphragmatic flexures. The colopexies did not prevent manual creation of volvulus at the base of the colon. Technique A was the easiest to perform.     

Varying the timing of oyster transplant: implications for management from simulation studies

The transplanting of oysters from one ground to another is a common practice in the oyster industry. In Delaware Bay, for instance, oysters are typically transplanted from upper-bay low-salinity seed beds onto lower-bay leased grounds for growth and conditioning before market. The higher salinity on the leased grounds, however, also favours higher losses to predation and disease. A coupled oyster–Perkinsus marinus–predator model was used to investigate how varying the timing of transplant affects the ultimate yield of Eastern oysters, Crassostrea virginica, in Delaware Bay. Simulations were run in which oysters were moved from seed beds to leased grounds in November, January, March, April and May. The number of market-size (≥ 76 mm) adults available for harvest in the following July to November was compared for populations undergoing mortality from predation (crabs, oyster drills) and/or disease (Perkinsus marinus). In all simulations, the abundance of market-size oysters declined between July and November. However, transplanting oysters in November resulted in the largest yield of market-size oysters for all harvest times; transplanting in May resulted in the smallest yield. The autumn transplant allows oysters to benefit from the larger spring phytoplankton bloom over the leased grounds in the lower estuary. The effect of varying the season of transplant was most noticeable if oysters were harvested early (July or August). In all simulations, transplanting resulted in a higher abundance of market-size oysters than direct harvest from the seed beds. Direct harvest would rarely be advantageous if the cost of transplant were insignificant and the relative rates of mortality were as stipulated. However, a May transplant is only moderately better than a direct harvest and the economic benefits of either option are likely to be determined by the cost of transplanting and the mortality associated with the process. In the same vein, the decision as to when to harvest relies on balancing the increased price obtained for oysters in the autumn with the increased loss owing to predation and disease. Awaiting an autumn harvest is clearly much riskier if the principal source of mortality is disease rather than predation, because disease mortality is concentrated on the market-size oysters and is greatest in the autumn.     

A hereditary disorder of cornification and multiple congenital defects in five Rottweiler dogs

The clinical, biochemical, histological, or ultrastructural abnormalities of five related female Rottweiler dogs with a hereditary disorder of cornification are reported. Three of the five dogs also had multiple noncutaneous congenital defects. Cutaneous abnormalities included generalized, hyperkeratotic, variably pigmented plaques, which in one dog were distributed along Blaschko's lines. Moderate to severe parakeratosis involving the follicular infundibula and ostia and focal orthokeratosis with variable vacuolation of spinous cells was observed on histopathologic examination of all skin specimens. Supplementation with oral zinc in two dogs and vitamin A alcohol and calcitriol in one dog did not result in clinical or histological improvement of the hyperkeratotic lesions. This disorder of cornification in dogs is similar to human disorders of cornification that follow the lines of Blaschko. Blaschko's lines follow a V-shape over the spine, an S-shape on the abdomen, and an axial distribution on the limbs. No related male dogs were affected, suggesting an X-linked dominant mode of inheritance. Many features of this hereditary DOC correspond to the human condition CHILD syndrome.     

Morphology of the Structural Root System of Sitka Spruce 2. Computer Simulation of Rooting Patterns

In a previous paper (Henderson et al. 1983), it was suggestedthat the processes of root growth and development proceed witha geometric regularity and that, as a consequence, root distributionis further extended and spatially more even than if growth wereat random. We examine this hypothesis and the relative importanceof the component growth processes through computer simulationof a model for root distribution at a fixed time. Root segments were measured on 16 year trees and statisticaldistributions fitted to the occurrence of lengths, branchingfrequencies and growth directions. These distributions comprisethe model which assumes that a root system consists of a numberof first-order roots originating at the stem, a number of second-orderroots originating on first-order ones and so on. Each root includesa number of bends and lateral branching points and terminatesin either a fork or when diameter reaches 5 mm, smaller rootsnot being included. Parameter manipulation of the fitted distributions and furthersimulation showed that some regular growth mechanisms were necessaryfor the simulation of realistic rooting patterns. In particularit was important that direction changes at bends and of newroots at forks were typically small to ensure that the systemspread outwards, away from the stem. Lateral branches neededto subtend large angles to their parents in order to exploitseparate soil regions. Other necessary rules were that first-orderroots were almost regularly distributed around the stem andfor a tendency for azimuth changes at bends to be alternatelyclockwise then anticlockwise. Simulations were also used to examine the possibility of estimatingtotal root length from a study of only part of a root system.An example of excavating one quarter of the system is consideredand the results indicate that root systems may be so variablethat no reliable estimate can be obtained.     

Mechanics of mole drainage channel deterioration

The nature of the soil disturbance caused by standard mole ploughs is described and the major types of failure mechanism causing channel deterioration are identified. Direct links have been established between the kinds of mole plough disturbance and many of the channel failure mechanisms, opening up possibilities for the future for modifying the implement to improve channel stability.
Following mole channel observations on six different clay soil sites, the influence of soil conditions at channel installation and subsequent weather patterns on long-term channel stability were determined. The extent of the ageing period between channel formation and its first significant wetting and weather extremes later, were identified as being particularly important influences on the subsequent life of the channel.     

SEPARATION OF THE LIGHT FRACTION FROM SOILS BY ULTRASONIC DISPERSION IN HALOGENATED HYDROCARBONS CONTAINING A SURFACTANT

Partially humified material can be separated from other soil material by flotation on a bromoform-petroleum spirit mixture of density 2·0 g cm^-3. Maximum recovery of partially humified material requires ultrasonic dispersion and the addition of a surfactant to the suspension. For large-scale work‘Nemagon’ may be used in place of the bromoform-petroleum spirit mixture.