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Search Results: 1 - 10 of 381768 matches for " L.C. Foxcroft "
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Dispersal of Dactylopius opuntiae Cockerell (Homoptera: Dactylopiidae), a biological control agent of Opuntia stricta (Haworth.) Haworth. (Cactaceae) in the Kruger National Park
L.C. Foxcroft,J.H. Hoffmann
Koedoe : African Protected Area Conservation and Science , 2000, DOI: 10.4102/koedoe.v43i2.194
Abstract: Chemical control efforts, the introduction of Cactoblastis cactorum and attempted releases of Dactylopius opuntiae Cockerell into the expanding infestation of Opuntia stricta in the Skukuza region of the Kruger National Park (KNP) have had limited suc- cess in preventing the spread and densification of 0. stricta. To boost the biological control component, a new strain of D. opuntiae was introduced into KNP during 1997. The new strain established readily and has destroyed large clumps of plants in the vicin- ity of the release site. A large-scale redistribution programme with D. opuntiae is now needed to exploit this biological control agent to the full. In order to match the frequency of manual releases with the natural rates of spread of the insects, surveys were conducted under field conditions to determine the dispersal abilities ofD. opuntiae, with regard to rate and direction of movement. Dispersal of D. opuntiae was found to be slow and restricted and that the insects need to be redistributed by placing them onto plants at approximately 10 m intervals to ensure that they become quickly and evenly distributed on the weed. This information will be crucial in the revision of the integrated management plan for 0. stricta in the KNP, in integrating the cochineal and other control mechanisms.
A revised list of alien plants for the Kruger National Park
L.C. Foxcroft,L. Henderson,G.R. Nichols,B.W. Martin
Koedoe : African Protected Area Conservation and Science , 2003, DOI: 10.4102/koedoe.v46i2.54
Abstract: Alien plants recorded in the Kruger National Park are listed, providing an update of species that have been recorded since the last published list in 1988. The serious consequences that invasive alien plants pose are widely recognised internationally and are regarded as the greatest threat to the Kruger National Park. It is extremely important to maintain an updated list of species to use as a reference and from which to monitor changes in the influx of invasive species. The list contains the invasive status of the plants, current impact, habitat types, biological control status and status according to the Conservation of Agricultural Resources Act (CARA), Act 43 of 1983, as amended in March 2001. The list comprises 370 species, of which 121 are invaders and two are transformer weeds, which may cause considerable damage and alterations to the indigenous biodiversity. A total of 91 species listed herein are also listed in the CARA regulations or are proposed additions to the CARA regulations.
Endogenous vasopressin and the central control of heart rate during dynamic exercise
Michelini, L.C.;
Brazilian Journal of Medical and Biological Research , 1998, DOI: 10.1590/S0100-879X1998000900012
Abstract: the present article contains a brief review on the role of vasopressinergic projections to the nucleus tractus solitarii in the genesis of reflex bradycardia and in the modulation of heart rate control during exercise. the effects of vasopressin on exercise tachycardia are discussed on the basis of both the endogenous peptide content changes and the heart rate response changes observed during running in sedentary and trained rats. dynamic exercise caused a specific vasopressin content increase in dorsal and ventral brainstem areas. in accordance, rats pretreated with the peptide or the v1 blocker into the nucleus tractus solitarii showed a significant potentiation or a marked blunting of the exercise tachycardia, respectively, without any change in the pressure response to exercise. it is proposed that the long-descending vasopressinergic pathway to the nucleus tractus solitarii serves as one link between the two main neural controllers of circulation, i.e., the central command and feedback control mechanisms driven by the peripheral receptors. therefore, vasopressinergic input could contribute to the adjustment of heart rate response (and cardiac output) to the circulatory demand during exercise.
Inter-Instrument Comparison of Bioimpedance Spectroscopic Analysers
L.C. Ward
The Open Medical Devices Journal , 2009, DOI: 10.2174/1875181400901010003]
Abstract: Three commercially available bioimpedance spectroscopy analysers were compared for technical performance and for their design purpose of prediction of body composition. All three analysers were electronically stable, remaining in calibration over a year, and provided highly reproducible (coefficients of variation < 0.5%) and accurate (within 0.5% of component values) measurements of impedances of a test circuit. Whole body impedances in humans were highly correlated between all three instruments although significant biases between instruments were observed, particularly for the measurement of intracellular resistance. However, when the measured impedances, and using instrument-specific resistivity coefficients, were used to predict fat-free mass of the subjects, the difference between instruments was approximately 1.7 kg fat-free mass, a value comparable with that observed for the error associated with reference methods such as multi-compartment models of body composition. It is concluded that, with appropriate regard to standardisation of measurement protocol, all three analysers are suitable for their design purpose of estimating body composition in humans.
Meat quality attributes of night-cropped Impala (Aepyceros melampus)
L.C. Hoffman
South African Journal of Animal Science , 2000,
Abstract: The aim of this experiment was to determine the effect of using a heavy or a light calibre rifle for night cropping of impala (Aepyceros melampus) on meat quality (pH, colour, cooking and drip loss, tenderness). The effect of gender on these parameters was also tested. Eight male and eight female impala were shot at night using either a heavy or a light calibre rifle. Sex and rifle calibre had an effect on some of the parameters tested. An exponential function (y = a + b e (ct) ) was fitted to the rate of pH decline with time. Constants for females were: a = 5.667 ± 0.0142, b = 2.097 ± 0.1777 and c = -0.451 ± 0.0541, and constants for males were: a = 5.792 ± 0.0142, b = 3.055 ± 0.1777 and c = -0.711 ± 0.0541. These constants differed (P < 0.05) between sexes. The impala showed a mean pH45 of 7.17 ± 0.0674 and a mean pHf of 5.70 ± 0.068. Mean drip and cooking loses were 2.55 ± 0.300%, 23.98 ± 0.367%, respectively, whilst a mean shear value of 3.65 ± 0.293 kg / 1.27 cm diameter was also noted. The darker colour of venison was reflected in the CIELAB values of the M. longissimus thoracis (L* = 29.22 ± 0.590, a* = 11.26 ± 0.319, b* = 7.36 ± 0.266). One of the animals was stressed prior to and during killing, and showed attributes associated with ante-mortem stress: higher pHf, lower drip loss and darker meat. The results indicate that the present method of cropping ungulates does not have a negative effect on the meat quality parameters tested. (South African Journal of Animal Science, 2000, 30(2): 133-138)
Effect of Dietary Phytase on Growth, Enzyme Activities and Phosphorus Load of Nile Tilapia (Oreochromis niloticus)
L.C. Nwanna
Journal of Engineering and Applied Sciences , 2012,
Abstract: This study assessed the effect of phytase on the growth and enzyme activities of Nile tilapia (Oroechromis niloticus) and on environmental Phosphorus (P) loadings. A basal diet of 30% crude protein, 2.0 g kg 1 phytate P and total P of 5.6 g kg 1 was supplemented with phytase (Ronozyme P (5000) CT) at 0, 2000, 4000, 6000 and 8000 units per kg diet. The diets were tested on Nile tilapia (14.0±0.60 g) for 70 days. Results indicated that all fish fed diets with phytase had higher Mean Weight Gain (MWG), Specific Growth Rate (SGR), mineral contents and better feed conversion ratio than the fish fed diet without phytase. The MWG (11.6 g) and SGR (0.86%) of the fish fed diet with 8000 units phytase kg 1 diet were higher (p< 0.05) than those of the fish fed diets 1 (8.30 g; 0.67%), 2 (8.70 g; 0.69%), 3 (8.90 g; 0.70% and 4 (9.60 g; 0.74%). Analyses of the gut of the fish after the feeding indicated increased amylase, lipase and protease activities in the fish fed diets with phytase in comparison with the fish fed diet without phytase. These activities increased with increase in the level of the phytase. Magnesium (Mg) contents of the fish fed diets with 6000 (72.4 mg g 1 DM) and 8000 (71.6 mg g 1 DM) units phytase kg 1 diet were statistically the same. These contents were however higher (p< 0.05) than those of the fish fed diets 1 (45.2 mg g 1 DM), 2 (59.6 mg g 1 DM) and 3 (68.5 mg g 1 DM). Ca and Zn deposition were the same in all the fish, while Mn contents of the fish fed diets with phytase, diet 2 (8.49 ug g 1 DM), diet 3 (8.29 ug g 1 DM), diet 4 (8.80 ug g 1 DM) and diet 5 (9.35 ug g 1 DM) were higher (p< 0.05) than that of the fish fed diet 1 (5.50 ug g 1 DM) without phytase. The Phosphorus (P) load decreased linearly with increase in the level of phytase, such that the P released by fish fed diets 2 (19.5 mg g 1 DM), 3 (19.1 mg g 1 DM), 4 (18.9 mg g 1 DM) and 5 (16.8 mg g 1 DM) was significantly lower than 24.0 mg g 1 (DM) P released by fish fed diet 1 without phytase.
Vergelyking van die voedingsgewoontes van die Rooikat Felis caracal binne en buite die Bergkwagga Nasionale Park
L.C Moolman
Koedoe : African Protected Area Conservation and Science , 1984, DOI: 10.4102/koedoe.v27i1.554
Abstract: Eenhonderd rooikatmismonsters uit die Berg-kwagga Nasionale Park is ontleed. In 94,9 het reste van soog- diere, in 4,3 reste van voels en in 0,8 reste van reptiele voorgekom. Van die soogdierreste was 52,5 reste van die klipdassie Procavia capensis. Vyf-en- tagtig mismonsters is van buite die Bergkwagga Nasionale Park ontleed. Hierin het 96,9 soogdier- reste, 2,1 voelreste en 1,0 reptielreste voorgekom, met die klipdassie Procavia capensis weer die volopste soogdierprooi (30,3). Knaagdiere en kleinvee het onderskeidelik 24 en 22,9 verteenwoordig. One hundred caracal scats collected in the Mountain Zebra National Park were analysed. Undigested remains of mammals were found in 94,9, 4,3 birds and 0,8 reptiles. Dassie Procavia capensis remains occurred most frequently, i.e. in 52,5 of the scats. From outside the Mountain Zebra National Park, 85 caracal scats were analysed. Here 96,9 contained the remains of mammals, 2,1 that of birds and 1,0 of reptiles. Again the remains of the dassie Procavia capensis were the most common, occurring in 30,3 of the scats, followed by rodents 24 and domestic stock 22,9.
The Incriminating Role of Reactive Oxygen Species in Idiopathic Male Infertility: An Evidence Based Evaluation
L.C. Saalu
Pakistan Journal of Biological Sciences , 2010,
Abstract: The male factor is considered a major contributory factor to infertility. Apart from the conventional causes for male infertility such as varicocoele, cryptorchidism, infections, obstructive lesions, cystic fibrosis, trauma and tumours, a new and important cause has been identified as being responsible for the so-called idiopathic male infertility: oxidative stress. Oxidative Stress (OS) is a condition that occurs when the production of Reactive Oxygen Species (ROS) overwhelms the antioxidant defense produced against them. In male reproductive pathological conditions, the OS significantly impairs spermatogenesis and sperm function, which may lead to male infertility. Reactive Oxygen Species (ROS) known as free radicals are oxidizing agents generated as a result of metabolism of oxygen and have at least one unpaired electron that make them very reactive species. Spermatozoa generate Reactive Oxygen Species (ROS) in physiological amounts, which play a role in sperm functions during sperm capacitation, Acrosome Reaction (AR) and oocyte fusion, but they need to be controlled and their concentrations maintained at a level that is not deleterious to the cells. Administration of antioxidants in patients with ‘male factor’ infertility has begun to attract considerable interest. The main difficulty of such an approach is our incomplete understanding of the role of free radicals in normal and abnormal sperm function leading to male infertility. The purpose of the present review is to address the relationship between ROS and idiopathic male factor infertility.
Rama’s sandalen op Bali
L.C. Heyting
Bijdragen tot de Taal-, Land- en Volkenkunde , 1967,
Abstract:
Risk Management in Aquaculture by Controlled Feeding Regimen
L.C. Nwanna
Pakistan Journal of Nutrition , 2003,
Abstract: Fish nutrition researchers often feed fishes at between 3-5% of their body weight daily. Environmental risks associated with excess feed leachate are so enormous in tropical waters leading to algal bloom which can toxify the aquaculture products and threaten their safety. Considering that feed requirements by fishes depend on a number of factors such as size, health status and the general condition of the culture environment; there is every need for the determination of the actual feed desired to meet their physiological needs, promote growth and reproduction based on peculiar conditions. This study was conducted to determine the appropriate feeding rate for tilapia, Oreochromis niloticus and consequential changes in the water quality. A 30% crude protein diet was fed to triplicate groups of O. niloticus fingerlings (10.13 0.58g) in glass tanks (75x45x40 cm) (20 fish/tank) at 2, 3, 4 and 5% body weight daily. The holding tanks were cleaned every two days after measuring the water quality parameters, pH, temperature and the dissolved oxygen. Results of the experiment indicated that the weight gain (WG, %) and specific growth rate (SGR) of the fishes fed at 3, 4 and 5% body weights were similar (p>0.05) but differed significantly (p<0.05) from the WG and SGR of the group of fishes fed at 2% body weight. However, there were no significant differences in FCR and PER of fishes fed at the various body weights. While the pH and the temperature of the culture media were not affected by the treatments, the dissolved oxygen was marginally lower in tanks fed at 4 and 5% body weights than in those fed at 2 and 3% body weights. The study established the optimum feeding rate for O. niloticus at 3% body weight daily, and the tendency for water quality deterioration with higher feeding rates.
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