Long-term nutritional effects on the primary liver and kidney metabolism in rainbow trout (Oncorhynchus mykiss). II. Adaptive response of glucose 6-phosphate dehydrogenase activity to high-carbohydrate/low-protein and high-fat/non-carbohydrate diets

The influence of long-term administration of high-carbohydrate/low-protein and high-fat/non-carbohydrate diets were studied in relation to kinetic behaviour of glucose 6-phosphate dehydrogenase in liver and kidney of rainbow trout. In all cases studied, the saturation curves of these enzyme showed typical hyperbolic kinetics without evidence of sigmoidicity. After 30 days of feeding with a high-fat diet (170 g kg^?1), there was a significant decrease in V_max and specific activity (45%) as well as catalytic efficiency (39%) without changes in K_m or activity ratio of hepatic glucose 6-phosphate dehydrogenase. These changes agree more with a clearly decreased cell concentration than with an inhibition of the pre-existing enzyme. The administration of a high-carbohydrate diet (60 g kg^?1), contrary to what was previously thought, decreased V_max by 21% and specific activity and catalytic efficiency by 30%, without significant changes in the other kinetic parameters of the hepatic enzyme. The kinetic behaviour under these nutritional conditons was due to the rejection of this diet by the fish and thus could be considered a low-feeding situation. On the other hand, no variations in the kinetics of renal glucose 6-phosphate dehydrogenase were found, clearly demonstrating that in this organ, the pentosephosphate pathway showed no adaptive response related to fattyacid and other lipid synthesis. The activity of the renal enzyme was consistently half that of the hepatic enzyme.     

Effects of different five-day progesterone-based synchronization protocols on the estrous response and follicular/luteal dynamics in dairy cows

This study compared the responses shown by lactating dairy cows to four different P4-based protocols for AI at estrus. Cows with no estrous signs 96 h after progesterone intravaginal device (PRID) removal were subjected to fixed-time AI (FTAI), and their data were also included in the study. In Experiment I, follicular/luteal and endometrial dynamics were assessed every 12 h from the beginning of treatment until AI. The estrous response was examined in Experiment II, and fertility was assessed in both experiments. The protocols consisted of a PRID fitted for five days, along with the administration of different combinations of gonadotropin releasing hormone (GnRH), equine chorionic gonadotropin and a single or double dose (24 h apart) of prostaglandin F_2α. In Experiment I (40 cows), animals receiving GnRH at the start of treatment showed a significantly higher ovulation rate during the PRID insertion period while estrus was delayed. In Experiment II (351 cows), according to the odds ratios, cows showing luteal activity at the time of treatment were less likely to show estrus than cows with no signs of luteal activity. Treatment affected the estrous response and the interval from PRID removal to estrus but did not affect conception rates 28–34 days post AI. Primiparous cows displayed a better estrous response than multiparous cows. Our findings reveal acceptable results of 5-day P4-based protocols for AI at estrus in high-producing dairy cows. Time from treatment to estrus emerged as a good guide for FTAI after a 5-day P4-based synchronization protocol.     

DIE INVLOED VAN RADIALE HARSGEïNFILTREERDE KERNSKEURE OP DIE GESAAGDE OPBRENGS UIT PINUS ELLIOTTII ENGELM.-SAAGBLOKKE / THE EFFECT OF RADIAL RESIN-INFILTRATED SPLITS ON THE YIELD OF SAWN TIMBER FROM PINUS ELLIOTTII ENGELM. SAWLOGS

A number of complaints, regarding the presence of resin-infiltrated splits in seasoned boards produced from Pinus elliottii sawlogs supplied from certain stands in State Forests, led to an investigation to determine the incidence of the defect and to find possible causes.

This paper deals mainly with the study of the first aspect. In the investigation two samples of stems were selected by a semi-random method from one mature stand, being clearfelled, in Entabeni State Forest (Northern Transvaal) and from three stands receiving, or due to receive, their fifth thinning. The clearfelling and thinning had produced logs containing heart shakes and this had given rise to the complaints.

During log preparation it was attempted to prepare as much as possible of the stem length into the longest sawlogs, working as closely as possible to the maximum limits for sweep and knots allowed by the departmental log specifications. This attempt resulted in the preparation of some logs containing slightly more than the permissible defects. Observations were made on stump surfaces of the orientation of shakes, and on log ends of their occurrence higher up in the stem, in an attempt to find a link between shake orientation and the known direction of strong winds, and to determine the height in the stem to which shakes extended from the stump. The orientation study produced no definite proof that wind was responsible, although there were strong indications.

This was followed by sowings up the logs mainly into structural timber, kiln seasoning and grading in two ways, viz A ignoring the resin-infiltrated checks and splits but taking all other defects pertinent to the relevant grades into consideration, and B taking all defects, including the checks and splits into consideration (Table 4). During the grading further measurements were taken on boards containing splits, to determine to what heights in the stem the shakes extended.

From the grading results, total and graded yields of sawn timber were computed, the differences in yields between the two grading procedures being a measure of the incidence and seriousness of the shake defect. Within log classes, (see footnote to Table 2) the yields obtained separately for each 2 cm top U.B. diameter class into which the logs had been segregated prior to sawing, were weighted according to the percentage size distributions of the logs yielded by the clearfelling and thinning operations in the relevant compartments, to obtain a weighted average for the log class.

The heights to which shakes were present in the stems of the two samples are shown in Table 3(a) while their incidence in logs of the various size classes are shown in Table 3(b). It is seen that shakes were more frequent and serious in the larger logs.

The presence of shake in the log samples, taken as a whole, caused only minimal yield losses (Table 4) but had the effect of somewhat reducing average board length (Table 5). However, sawn and graded yields are still excellent and the species should not be discriminated against in afforestation, because of the sporadic occurrence of the defect.

The yield figures should be of some value to sawmillers processing both normal and shake-containing logs of this species.     

CHEMICAL AND BIOLOGICAL PROPERTIES OF TWO NEW HERBICIDES—IOXYNIL AND BROMOXYNIL

Summary. The preparation of ioxynil, bromoxynil, and their salts is described, and information on solubilities and stability to storage is summarized. Although the toxicology of the herbicides is to be reported in greater detail, a preliminary statement is made here. Evidence of herbicidat activity under glasshouse conditions is indicated briefly, and supports the conclusion that both compounds are effective when applied to the foliage of a wide range of dicotyledon weed species. Seedlings of some weed species resistant to the phenoxy alkanoic acids are controlled under glasshouse conditions at doses as low as 0.125 lb/ac, and ioxynil has a wider range of activity than bromoxynil at these low doses. Graminaceous species tolerate 4–8 lb/ac of both herbicides without injury, and certain leguminous crops tolerate one or other herbicide at doses of 0.5–0.75 lb/ac. The contact action of the herbicides is rapid, there are also slower systemic effects, and seed germination is inhibited. In susceptible species the level of post-emergence activity is shown to be influenced by the growth stage of the weed, the distribution of herbicide on the foliage, and environmental factors of which light intensity appears to be most important.
Propriétés chimiques et biologiques de deux nouveaux herbicides: ioxynil et bromoxynil     

Detection of potato virus Y in early-harvested potato tubers by cDNA hybridization and three modifications of ELISA1

The standard ELISA method for detection of PVY in dormant potato tubers was compared with recently developed methods: (1) a hybridization technique, using a complementary DNA-probe to PVY^N; (2) three modifications of ELISA (standard monoclonal, Flegg & Clark polyclonal or monoclonal). Sap of six Dutch cultivars secondarily infected with PVY was subjected to these methods directly after lifting and after six subsequent one-week intervals during storage at 20°C. During storage the detectability of PVY decreased, irrespective of the diagnostic method applied. However, decrease was less in susceptible than in resistant cultivars. Although the hybridization technique yielded slightly better results than the standard ELISA procedure, it was time-consuming and involved hazardous reagents. The modifications of ELISA investigated were not, in general, more sensitive than standard ELISA.     

Observations on the potential of microwaves for weed control

Field tests of a prototype microwave‐based weed killer machine were conducted on Abutilon theophrasti, Panicum miliaceum, lucerne and oilseed rape pure stands. The approach can be considered a thermal weed control method, the microwave radiation causing dielectric heating of plant tissue water that eventually kills the plant. The method could overcome the limitations of other thermal methods, such as fire risk with flaming or the heavy loads required for hot water treatments. Species were effectively controlled by microwave irradiation, but their sensitivity and the evolution of damage symptoms over time differed. Lucerne showed no sigmoidal response and was the least affected by the treatment, while a log‐logistic curve expressed the dose–response relationships of the other species quite well. The estimated microwave dose for a 90% dry weight reduction ranged from 1015 kJ m^?2 in A. theophrasti to 3433 kJ m^?2 in P. miliaceum. Energy cost evaluation indicated that increased efficiency is required for this technique to compete with other thermal methods. Microwave efficiency could be increased by a flux configuration that minimizes soil penetration and maximizes absorption by plants, which, in turn, depends on plant growth form.     

Windborne spread of ergot disease (Claviceps africana) in sorghum A-lines in Zimbabwe

Ergot disease spread rapidly in Zimbabwe amongst replicated plots of male-sterile sorghum A-lines, from a group of centrally situated and precociously inoculated plants. Prominent secondary conidiation by the pathogen, Claviceps africana , on the surface of exuded honeydew provided airborne spores which were trapped in a Burkard continuous spore trap and showed diurnal peaks of concentration in air close to the primary source of inoculum. The rate of disease spread ( r =0·2; range 0·14–0·58) closely matched that recorded for other plant pathogens such as Phytophthora infestans and Puccinia graminis tritici , and it is concluded that the characteristic secondary conidia of C. africana were the principal epidemiological agents within the experimental area. Ergot spread by windborne secondary conidia has significant epidemiological and economic implications for sorghum hybrid breeding in southern Africa.