Genetic interaction between Non-MHC T- and B-cell alloantigens in response to rous sarcomas in chickens

Chickens of Regional Poultry Research Laboratory (RPRL) inbred line 6₃ regress sarcomas induced by Bryan high-titer Rous sarcoma virus to a greater extent than chickens of line RPRL 100, although these lines are identical for the major histocompatibility B complex. They differ, however, at three independent autosomal loci: Ly-4 and Th-1 determine the surface alloantigens of partly overlapping subsets of T lymphocytes, and Bu-1 determines a surface alloantigen of B lymphocytes. The association of genotypes at these loci with quantitative variation in their ability to regress Rous sarcomas was tested in segregating F₄ generation progeny derived from crosses of lines 100 and 6₃. The Ly-4 and Bu-1 genotypes showed association with Rous sarcoma regression, but the Th-1 genotype did not. Chickens of the Ly-4 ^a/Ly-4 ^a, Bu-1 ^b/Bu-1 ^b and Ly-4 ^b/Ly-4 ^b, Bu-1 ^a/Bu-1 ^a genotypes had a significantly higher regressor ability than the other two double homozygous genotypes. These results indicate that higher regression is associated with (1) interaction between the Ly-4 and Bu-1 loci, and (2) complementation between either the line 6 Ly-4 ^a allele and the line 100 Bu-1 ^b allele, or the line 100 Ly-4 ^b allele and the line 6 Bu-1 ^a allele.     

Nephelometric and turbidometric assays of cellulase activity

Extensively ball-milled cellulose fibers were used as natural substrate for the determination of cellulase activity. This physical treatment breaks the large cellulose fibers to small but insoluble particles yielding a substrate accessible for complete enzymatic breakdown. The parameters studied to estimate the activity of cellulases were (a) the decrease in optical density of ball-milled suspension of fibers and (b) simultaneous measurement of liberated sugars during hydrolysis. A good correlation was found between the initial rate of reaction and the amount of sugar released at given times.     

Tropical Vine Growth and the Effects on Forest Succession: A Review of the Ecology and Management of Tropical Climbing Plants

The climbing habit has evolved independently in many plant taxa, offering vines the ability to compete with non-climbing vegetation for resources such as light, nutrients, and water. This review examines the structural and functional characteristics that allow climbing plants to (1) achieve widespread dispersal, (2) transport large amounts of water throughout vessels, (3) maintain high photosynthesis levels through a large leaf area to biomass ratio, (4) achieve rapid vertical and horizontal expansion by fast growth rates and various climbing mechanisms and (5) survive and recover from disturbances. Due to the competitive effects of vines on trees, management of vine growth is used to preserve tropical timber plantations, combat invasive weeds, and promote rainforest recovery. In order to sustainably manage the vines into the future, it is necessary to understand the mechanisms by which they can alter tropical forest succession and the impacts of various management techniques.     

The Effect of Dietary Energy Restriction on Body Weight Gain and the Development of Noninsulin-Dependent Diabetes Mellitus (NIDDM) in Psammomys obesus

Food intake was restricted to 75% of ad libitum levels in 37 male Psammomys obesus (Israeli Sand Rats) from the ages of 4 (weaning) to 10 weeks. Energy restriction reduced the mean body weight at 10 weeks by 29% compared with 44 ad libitum fed controls. Hyperglycemia was prevented completely in the food-restricted group, and mean blood glucose concentrations were significantly reduced (3.8 ± 0.2 vs. 5.5 ± 0.4 μmol/L; p<0.05) compared with control animals. Plasma insulin concentrations were also decreased significantly compared with ad libitum fed controls (105 ± 13 vs. 241 ± 29 mU/L;p<0.05). Although energy restriction prevented hyperglycemia from developing in 10-week-old P. obesus, 19% of the food restricted animals still developed hyperinsu-linemia. We concluded that hyperphagia between the ages of 4 to 10 weeks may be essential for the development of noninsulin-dependent diabetes mellitus in P. obesus, but that hyperinsulinemia may still occur in the absence of hyperphagia and hyperglycemia, suggesting a significant genetic influence on the development of hyperinsulinemia in this animal model.     

Effects of Δ8- and Δ9-Tetrahydrocannabinol on experimentally induced seizures

Effects of Δ⁸- and Δ⁹-tetrahydrocannabinol (Δ⁸- and Δ⁹-THC) on three experimentally induced seizure models, i.e., audiogenic seizure (AS) test, maximal electroshock seizure (MES) test and pentylenetetrazol (PTZ)-induced seizure test were determined in the audiogenic rat. Both tetrahydrocannabinols possess a dose-related anticonvulsant effect against AS, MES and PTZ-induced maximal seizure. Although anticonvulsant potencies do not significantly differ, Δ⁸THC is three times more neurotoxic than Δ⁹THC. In addition, both THC's are without effect on minimal seizure and lethality induced by PTZ. Furthermore, the low protective indexes (TD50/ED50) determined in this study suggest that Δ⁸ and Δ⁹ THC may have poor therapeutic potentials as antiepileptic drugs.