Biomechanical Comparison of Four Soft Tissue Replacement Materials: An In Vitro Evaluation of Single and Multilaminate Porcine Small Intestinal Submucosa, Canine Fascia Lata, and Polypropylene Mesh

Objective— To compare mechanical performance of 4 soft tissue replacement materials.
Study Design— Experimental.
Sample Population— Polypropylene mesh (PM), single-layer porcine small intestinal submucosa (SIS), multilaminate (4-layer) porcine small intestinal submucosa (MLSIS), and canine fascia lata (FL).
Methods— The mechanical properties of each material were determined by testing to failure on a materials testing machine. Samples of each material (n=10) were tested in 3 different modes: resistance to suture pullout, tensile testing, and push-through testing. PM was tested both parallel (PMa) to and perpendicular (PMb) to its longitudinal cord orientation. SIS and FL were similarly tested in 2 orthogonal directions.
Results— With some exceptions, the following generalizations can be made regarding the mechanical performance of the materials tested:
Suture pullout— FL>PMa=PMb>MLSIS>SIS ( P ≤.04).
Tensile testing —FL>PMa>PMb>MLSIS>SIS ( P ≤.02).
Push-through testing— FL>PM>MLSIS>SIS ( P ≤.003).
Conclusions— PM accommodated a significantly higher load and energy to yield when its longitudinal cords were oriented parallel with the tension axis (PMa). FL performed similarly to the PM, with the exception of limited elongation in tension. MLSIS had biomechanical characteristics that were inferior to FL and PM but superior to SIS.
Clinical Relevance— PM's orientation may need to be considered when used clinically. FL is a biomechanically suitable soft tissue replacement material but its use may be limited by currently available sizes. SIS cannot be recommended in high-strain environments.     

DYNAMIC CONTRAST‐ENHANCED MAGNETIC RESONANCE IMAGING OF CANINE BRAIN TUMORS

We evaluated dynamic contrast‐enhanced magnetic resonance imaging (DCE‐MRI) in canine brain tumors. Magnetic resonance data sets were collected on seven canine intracranial tumors with a 3 T magnet using a T1‐weighted fast spin echo fluid attenuated inversion recovery sequence after an IV bolus injection (0.2 mmol/kg) of Gd‐DTPA. The tumors were confirmed histopathologically as adenocarcinoma (n=1), ependymoma (n=1), meningioma (n=3), oligodendroglioma (n=1), and pituitary macroadenoma (n=1) The data were analyzed using a two‐compartment pharmacokinetic model for estimation of three enhancement parameters, E_R (rate of enhancement), K_el (rate of elimination), and K_ep (rate constant), and a model‐free phenomenologic parameter initial area under the Gd concentration curve (IAUGC) defined over the first 90 s postenhancement. Pearson's correlations were calculated between parameters of the two methods. The IAUGC has a relatively strong association with the rate of enhancement E_R, with r ranges from 0.4 to 0.9, but it was weakly associated with K_ep and K_el. To determine whether any two tumors differed significantly, the Kolmogorov–Smirnov test was used. The results showed that there were statistical differences (P<0.05) between distributions of the enhancement pattern of each tumor. These kinetic parameters may characterize the perfusion and vascular permeability of the tumors and the IAUGC may reflect blood flow, vascular permeability, and the fraction of interstitial space. The kinetic parameters and the IAUGC derived from DCE‐MRI present complementary information and they may be appropriate to noninvasively differentiate canine brain tumors although a larger prospective study is necessary.     

Tillering and leaf area index in grasses in the vegetative phase

The relationship between tillering of a vegetative grass stand and Leaf Area Index (LAI) has been studied during sward establishment of perennial ryegrass and Italian ryegrass with different seedling densities and nitrogen fertilizer rates and on established swards of tall fescue during winter and early spring after different dates of last cut in autumn.
The different experiments on different species led to the conclusion that in every instance the tillering rate slows down as soon as the LAI reaches a value of 3 and terminates rapidly at higher LAI, which corresponds with the almost complete extinction of light at the level of the tiller buds. The results confirm the direct role of light on morphogenesis previously demonstrated by several authors. The existence of such a limit of LAI helps to explain some contradictory effects of temperature or nitrogen on tillering.     

Microbial control of soil-borne pathogens in Hungary1

Biological control of soil-borne pathogens has been the aim of the Biological Control Laboratory in Hódmezövásárhely since 1982. In Hungarian glasshouses (this means areas both under glass and plastic foil cover), the growing medium is still the natural soil or mixtures based on soil. This is the reason why soil-borne pathogens, such as species of Fusarium, Sclerotinia, Pythium, Botrytis, Rhizoctonia and Alternaria, cause increasing problems, especially at sites where there has been intensive continuous cropping for many years. Soil steaming is very expensive, while methyl bromide and other soil disinfectants are harmful for the environment and especially for the soil microflora. All this favours the introduction of biological control against soil-borne plant diseases. After laboratory tests, experiments have been carried out over a 9-year period, with good results, on several Trichoderma species and strains in relation to practically all glasshouse crops (capsicum, lettuce, tomato, ornamentals, etc.) and in some field crops also. Since 1986, experiments have been done with Finnish-originated strains of Streptomyces griseoviridis, then with the preparation Mycostop which was developed from this actinomycete. These were carried out on ornamentals, on vegetables and on some cereals. The preparation was especially effective against Fusarium spp. but also against other pathogens.