Mechanical comparison of two suture constructs for extra-capsular stifle stabilization

Objective: Mechanical evaluation of 2 suture constructs for extracapsular stifle stabilization. Study Design: In vitro study. Sample Population: Crimped interlocking loop constructs (ILC) of 45 kg nylon leader line (NLL) and Orthofiber^® (OF). Methods: ILC were tightened to 100 N, then crimp secured. Ramp to failure (n=10/group)—Data were derived from force/displacement plots. Stress–relaxation testing (n=10/group)—ILC's were nondestructively loaded and held at resultant displacement as force data were recorded. Incremental, cyclic loading (n=10/group)—ILC's were loaded (5 cycles/set) starting at 100 N and incrementally increased by 50 N (1 and 3 Hz protocols). Loop tension and elongation were recorded after each set. Results: Ramp to failure—initial loop tension was similar (NLL 75.5 ± 9.5 N; OF 68.7 ± 10.4 N, P=.140). Tested OF constructs were stiffer (NLL 125.7 ± 4.0; OF 234.6 ± 25.0 N/mm, P≤.001), had lower yield load (NLL 193.6 ± 13.8; OF 137.3 ± 94.3 N, P≤.001), lower peak load (NLL 873.7 ± 68.6; OF 653.6 ± 80.2 N, P≤.001), and lower elongation at failure (NLL 19.1 ± 1.4; OF 5.2 ± 1.0 mm, P≤.001) and at yield (NLL 1.52 ± 0.2; OF 0.3 ± 0.6 mm, P=.003) than NLL constructs. Yield in NLL ILC's was variable knot tightening/crimp slippage, but only crimp‐suture slippage in OF. Stress–relaxation testing—OF demonstrated greater relaxation. Incremental, cyclic loading—induced ILC elongation and tension loss in both groups, independent of loading frequency. NLL lost tension at lower rate, but elongated more than OF. Conclusions: NLL construct is mechanically superior to OF construct.     

Norsesquiterpene glycosides in bracken ferns (Pteridium esculentum and Pteridium aquilinum subsp. wightianum) from Eastern Australia: reassessed poisoning risk to animals

Austral bracken Pteridium esculentum contains three unstable norsesquiterpene glycosides: ptaquiloside, ptesculentoside, and caudatoside, in variable proportions. The concentration of each of the glycosides was determined in this study as their respective degradation products, pterosin B, pterosin G and pterosin A, by HPLC-UV analysis. Samples of P. esculentum collected from six sites in eastern Australia contained up to 17 mg of total glycoside/g DW, with both ptaquiloside and ptesculentoside present as major components accompanied by smaller amounts of caudatoside. Ratios of ptaquiloside to ptesculentoside varied from 1:3 to 4:3, but in all Australian samples ptesculentoside was a significant component. This profile differed substantially from that of P. esculentum from New Zealand, which contained only small amounts of both ptesculentoside and caudatoside, with ptaquiloside as the dominant component. A similar profile with ptaquiloside as the dominant glycoside was obtained for Pteridium aquilinum subsp. wightianum (previously P. revolutum ) from northern Queensland and also P. aquilinum from European sources. Ptesculentoside has chemical reactivity similar to that of ptaquiloside and presumably biological activity similar to that of this potent carcinogen. The presence of this additional reactive glycoside in Australian P. esculentum implies greater toxicity for consuming animals than previously estimated from ptaquiloside content alone.     

Uptake and distribution of nitrogen and phosphorus in grain sorghum hybrids and their parents

Grain sorghum Sorghum bicolor (L.) Moench genotypes responded differently to nitrogen and phosphorus additions to soil, but very little information is available correlating responses of hybrids and their parents. A two‐year study of a set of four male and three female parents and their resulting hybrids was conducted under control and added N, P, or N + P conditions. The treatments caused differences in grain yield and total grain phosphorus among the genotypes. Days to bloom, stover yield, or percent grain and stover nitrogen were not influenced by additions of nitrogen or phosphorus in this soil. The only significant difference detected among groups (females, males or hybrids) was for total grain nitrogen; i.e., male parents had lower grain yields than female parents or hybrids. Differences were found among the four males only for total grain phosphorus and among the females only for days to bloom. Hybrids differed for days to bloom and stover yield. A significant genotype by year interaction occurred for all traits measured, which was due primarily to environmental stress in the first year that significantly lowered the magritude of genotypic differences in the first year compared with those in the second year. Nitrogen and phosphorus applied together generally exerted more influence on most of the measured traits than either element applied singly. The responses of hybrids were correlated more closely with the response of the female than of the male parent for the traits. The only exception was for percent stover nitrogen where the influence of the male and female parents was equal.     

Distribution of boron within barley genotypes with differing susceptibilities to boron toxicity 1

The B toxicity resistance mechanism was investigated by examining the distribution of B amongst and within plant parts of four barley genotypes transferred from normal to excessive B. After transfer, the B concentrations increased in all plant parts. In corresponding parts (roots and leaves) however, the B concentrations always reflected the relative susceptibility of each genotype to B toxicity, with susceptible genotypes having higher B concentrations than less susceptible genotypes. Despite large differences amongst genotypes in the B concentrations of corresponding leaf segments, the relative B concentrations along the leaves were similar for all genotypes.

Similarly, the amount of B in all parts increased after transfer, with B accumulation by leaves closely reflecting leaf size. Roots contained up to 10 percent of the total B accumulated at each harvest. This pattern was essentially the same for each genotype at each harvest, despite the large differences in total B accumulated. These results show that the pattern of B distribution was remarkably similar in the four genotypes examined despite great differences in the total amounts of B absorbed and the actual B concentrations of individual parts. Differences amongst barley genotypes in susceptibility to B toxicity do not result from an ability to control the internal distribution of the element, but rather are governed by the amount of B each accumulates.     

Root phosphatase activity of sorghum genotypes grown with organic and inorganic sources of phosphorus 1

Abstract

Relatively insoluble sources of phosphorus (P) may require solubilization, and organic P (P_o) may require hydrolysis to inorganic P (P_i) before P can be readily absorbed by plants roots. The mechanisms for these processes, however, are unknown. Root phosphatase (Pase) activity was measured to assess its relationships to P uptake by seven sorghum [Sorghum bicolor (L.) Moench] genotypes grown with P_o (ethylammonium phosphate, glycerophosphate, and phenylphosphate) and P_i (KH₂PO₄, calcium tribasic phosphate, calcium pyrophosphate, aluminum phosphate, and ferric phosphate) in nutrient solutions in a greenhouse.

Plants grown with P_o had lower root Pase activities than plants grown with P_i NB9040 and SC369–3–1JB (tolerant to low levels of P) had lower root Pase activities than CK60‐Korgi and SC33–9–8‐E4 (sensitive to low levels of P), with the other genotypes having intermediate root Pase activities. Higher root Pase activity was associated with lower root P concentrations, but Pase activity was not related to dry matter yield of roots. In experiments where genotypes were grown three weeks with KH₂PO₄ before being transferred to other sources of P, within four days root Pase activity patterns were similar to those for plants grown initially in the particular P_o or P_i compound. Root Pase activity of sorghum plants appeared to be an indicator of P status or P deficiency stress in the plants, and not associated with making P_o or P_i compounds more available for plant use.