A request for sheep with testicular feminization

Extract

Sir,—I should like to make a request to interested veterinarians for live specimens of the rare condition in sheep — testicular feminization.     

Effects of humidity and Ca level on dry-matter and Ca accumulation by leaves of cucumber (Cucumis sativus L.)

Two cucumber cultivars (Corona and Rebella) were grown under a range of day and night humidity combinations and at two levels of Ca (180 and 270 mg I-1) in the nutrient solution applied to the rockwool substrate. High humidity increased the incidence of Ca defi-. cigacy symptoms and decreased the drvweTiTrToT the leaves. The concentration of Ca (%) in the leaf dry matter was reduced by high humidity at night in Experiment A and equally by high humidity during the day or night in Experiment^}. The response of the leaf tips (% Ca in the terminal 7 cm) was greater than that of the complete laminae, and similar to that of the total amount of Ca (mg) accumulated per complete lamina. Increasing the level of applied Ca increased the concentration of Ca (%) in the complete laminae and leaf tips, but the increase in total Ca per lamina (mg) was more marked. ‘Corona’ Had heavier leaves than ‘Rebella’ and a higher concentration of Ca (%), resulting in a greater accumulation of Ca (mg) per leaf lamina.     

The development and evaluation of techniques to predict when to harvest iceberg lettuce heads

Twenty-seven crops of iceberg lettuce, cv. Saladin, were grown in 1988 and 1989 at four sites and sampled twice weekly to study heart growth under a range of environmental conditions. The aim of the work was to develop a technique to predict when heads reached a specified weight or size. Changes in heart fresh weight were best described by a Gompertz curve using effective day-degrees from transplanting as the explanatory variable. Changes in heart diameter were best described by a logistic curve using effective day-degrees from transplanting as the explanatory variable. The accuracy of prediction of the day of maturity was tested on nine independent crops using four mechanistic models describing heart growth and four other empirical models based on the duration of crop growth from transplanting. The deviations of actual from predicted dates of maturity were smaller using the simple empirical models based on days, day-degrees and effective day-degrees from transplanting than using the more general mechanistic models based on heart fresh weight or diameter. This suggests that heart formation and growth is affected in a complex way by environmental conditions during growth.     

Proximity to Natural Amenities: A Seemingly Unrelated Hedonic Regression Model with Spatial Durbin and Spatial Error Processes

The existing literature suggests that the presence of natural amenities, such as open spaces, can be highly valued and affect economic decisions about where people live and work. This article contributes to previous research by testing this hypothesis using a unique micro‐level data set and by examining spatial variations in income levels and housing prices in the presence of natural amenities in a case study of Arizona. Proximity effects are estimated based on a geographic information system road network in which each variable represents the road mile distance from house i to its closest natural amenity within each category. Using a seemingly unrelated regression approach, spatial hedonic regressions of housing prices and income levels indicate that the total effect of various natural amenities calculated for the sample average income household and average home value, ranges from $2,382 (National Forests) to $1,560 (Wilderness areas). The presence of compensating differentials has policy relevance in considering the regional value of natural amenities. It also implies that valuation approaches such as the travel cost method may not reflect the full price of recreation site access, and may lead to underestimates of such values.     

Sensitivity of boreal forest carbon balance to soil thaw

We used eddy covariance; gas-exchange chambers; radiocarbon analysis; wood, moss, and soil inventories; and laboratory incubations to measure the carbon balance of a 120-year-old black spruce forest in Manitoba, Canada. The site lost 0.3 +/- 0.5 metric ton of carbon per hectare per year (ton C ha-1 year-1) from 1994 to 1997, with a gain of 0.6 +/- 0.2 ton C ha-1 year-1 in moss and wood offset by a loss of 0.8 +/- 0.5 ton C ha-1 year-1 from the soil. The soil remained frozen most of the year, and the decomposition of organic matter in the soil increased 10-fold upon thawing. The stability of the soil carbon pool ( approximately 150 tons C ha-1) appears sensitive to the depth and duration of thaw, and climatic changes that promote thaw are likely to cause a net efflux of carbon dioxide from the site.     

Shear-wave splitting and implications for mantle flow beneath the MELT region of the east pacific rise

Shear-wave splitting across the fast-spreading East Pacific Rise has been measured from records of SKS and SKKS phases on the ocean-bottom seismometers of the Mantle Electromagnetic and Tomography (MELT) Experiment. The direction of fast shear-wave polarization is aligned parallel to the spreading direction. Delay times between fast and slow shear waves are asymmetric across the rise, and off-axis values on the Pacific Plate are twice those on the Nazca Plate. Splitting on the Pacific Plate may reflect anisotropy associated with spreading-induced flow above a depth of about 100 km, as well as a deeper contribution from warm asthenospheric return flow from the Pacific Superswell region.     

Studies on triploid oysters in Australia: effect of initial size on growth of diploid and triploid Sydney rock oysters, Saccostrea commercialis (Iredale & Roughley)

In a 2-year grow-out trial, triploid Sydney rock oysters, Saccostrea commercialis (Iredale & Roughley), from two initial size grades grew faster (in terms of both mean whole weight and shell height) than the equivalent initial size grades of sibling diploids (P < 0.05). Small size grade triploids caught up with and had significantly heavier (P < 0.05) final whole weights than large size grade diploids after a 2-years grow-out period. The initial size grade had a significant effect on final mean whole weight and shell height for both ploidy types. After the 2-years grow-out trial, the final mean whole weights (but not shell heights) of small and large diploids (35.8 ± 0.6 g and 39.4 ± 0.5 g, respectively) were significantly different (P < 0.05). Small and large triploids grew at a similar rate for the first 18 months despite the significantly (P < 0.05) heavier final mean weight of large grade triploids (48.4 ± 0.8 g and 61.2 ± 0.7 g, respectively). The effect of the initial size grade on subsequent growth of both diploid and triploid oysters which was demonstrated in the present study is of significant commercial value to hatchery and nursery operators as well as growers of single seed oysters. In addition, small-grade triploids appeared to be more valuable in terms of potential growth rate than all diploid grades. There was no significant difference in the final percentage triploidy between small and large grade triploids. A large proportion of diploid/triploid mosaicism was detected in adult oysters.     

Monitoring of the winter populations of cereal aphids near Wageningen,the Netherlands,in 1982/1983

Cereal aphids on a wheat crop were sampled through the winter of 1982/1983 using both fixed and random quadrats.Sitobion avenae overwintered successfully anholocyclically although there was a substantial decline in the population of this species. No evidence for successful anholocyclic overwintering in other aphid species was found, althoughRhopalosiphum padi was seen to colonise the crop in early winter and was found until the end of December.Eggs ofR. padi onPrunus padus were observed through the winter. A steady decline in their numbers occurred. The overall survival rate of the 5385 eggs was c.30%.Eggs ofMetopolophium dirhodum onRosa spp. were also monitored. They also showed a steady decline in numbers through the winter. The overall survival rate of the 1360 eggs was c.34%.Egg hatch in bothR. padi andM. dirhodum was closely synchronised with bud burst of their host plant. For the latter species this resulted in egg hatch starting in January.Samenvatting In de winter van 1982/1983 werden de graanluizen in een tarwegewas regelmatig geteld in willekeurig en in van tevoren gekozen monstereenheden. Hoewel er een aanmerkelijke afname van de populatie vanSitobion avenae werd waargenomen, overwinterde deze soort toch anholocyclish. Er werden geen aanwijzingen gevonden dat de andere bladluissoorten anholocyclish overwinterden hoewel kolonies vanRhopalosiphum padi tot eind december werden waargenomen.De gehele winter werden eieren vanR. padi opPrunus padi aangetroffen, de aantallen ervan namen geleidelijk af; van de 5385 getelde eieren overleefde ongeveer 30%. Ook de aantallen eieren vanMetopolophium dirhodum opRosa spp. werden reglematig vastgesteld; ook hier werd een geleidelijke afname geconstateerd. Van de oorspronkelijk getelde 1360 eieren overleefde ongeveer 34%.Het uitkomen van de eieren vanR. padi enM. dirhodum viel nauw samen met het uitlopen van de knoppen van hun waardplant. VoorM. dirhodum betekende dit dat de eerste eieren al begin januari uitkwamen.     

CLINICAL AND PATHOLOGICAL STUDIES OF BORDER LEICESTER RAMS NATURALLY INFECTED WITH ACTINOBACILLVS SEMINIS

Clinical examination of 31 rams with evidence of Actinobacillus seminis infection revealed 15 cases with marked lesions of the scrotal contents, two cases with very mild lesions, one with testicular atrophy but no abnormality of the epididymides, and another 13 without any palpable abnormalities of the genitalia. The rams were from a Border Leicester flock and included 27 un-mated rams from 6 to 12 months old. Histological examinations of affected epididymides showed a mixed purulent and non-purulent inflammation, with cystic hyperplasia of the ductus epididymis. Interstitial fibrosis and spermatic granulomas were seen in chronic lesions. Bilateral testicular atrophy and seminal degeneration were found in the nine rams that were autopsied. The clinical and pathological features of the disease are similar to those of ovine brucellosis. A pyelonephritis of unknown significance was found in four of the nine rams examined.