Comparison of bending modulus and yield strength between outer stratum medium and stratum medium zona alba in equine hooves

OBJECTIVE: To determine whether the bending modulus and yield strength of the outer stratum medium (SM) differed from those of the SM zona alba (SMZA) and to what degree they differed. In addition, a comparison was made among our values and values reported elsewhere. SAMPLE POPULATION: 10 normal equine feet. PROCEDURE: A 3-point bending technique was used to determine the bending modulus and yield strength of the outer SM and SMZA. Efforts were made to minimize biological and technical factors that could influence the bending modulus. RESULTS: Bending modulus of the outer SM was (mean +/- SD) 187.6 +/- 41.3 MPa, whereas mean value for the SMZA was 98.2 +/- 36.8 MPa. Mean yield strength was 19.4 +/- 2.6 MPa for the outer SM and 5.6 +/- 1.7 MPa for the SMZA. Values for bending modulus and yield strength differed significantly between the outer SM and SMZA. Significant differences were not detected when the outer SM was loaded in bending from the outer or inner surface. CONCLUSIONS AND CLINICAL RELEVANCE: Potentially, the SMZA could serve as a mechanical buffer zone between the rigid hoof wall and bone and laminar tissues. This buffer zone potentially assists the feet of horses in transmitting a load through the tissues and prevents the most susceptible tissues from becoming damaged. More consistency among tissue selection, preparation, and testing protocols must be attained before an accurate 3-dimensional finite-element model of an equine foot can be constructed.     

Comparative ocular anatomy of the western lowland gorilla

OBJECTIVE: To examine the lowland gorilla (Gorilla gorilla gorilla) eye and determine similarities to and differences between the mountain gorilla (Gorilla gorilla beringei) and the human eye. In addition, we compare our findings of G. g. gorilla to previous reports on the eye of this subspecies. PROCEDURES: A 13-year-old deceased male lowland gorilla and a 34-year-old deceased female lowland gorilla were included in the study. Gross and microscopic examinations of the formalin-fixed right eyeball of each gorilla were carried out. RESULTS: Globe dimensions of G. g. gorilla were similar to G. g. beringei and to humans. The limbal conjunctival epithelium and the choroid were densely pigmented. However, the distribution of the conjunctival pigment ring was different to that of G. g. beringei and the melanocytes of the choroid were unusually round. There were deep crypts in the anterior border layer of the iris, and the epithelium of the pars plana was uniquely irregular. Vertical corneal diameter was observed to be equal or greater than horizontal diameter in G. g. gorilla, which is in contrast to humans and to previous findings for G. g. beringei. Corneal thickness was closer to that of humans than to G. g. beringei. Posterior lens capsule thickness was noticeably greater than that of humans. CONCLUSIONS: Although some variation between the ocular anatomy of G. g. gorilla and G. g. beringei does exist, the gross and microscopic findings closely resemble each other in these two subspecies. In addition, the eye of Gorilla appears remarkably similar to the human eye. However, comparison of measurements with those in humans is somewhat limited because formalin-fixation can introduce tissue shrinkage and artifact.     

Immune responses of cattle to experimental anti-Fasciola hepatica vaccines.

Fasciola hepatica infection of cattle and sheep is an important cause of clinical disease and production losses, and is controlled at present by a combination of chemotherapy and management measures. However, the prospects for the control of F. hepatica infection by vaccination are good, and we have previously shown substantial protection of cattle against experimental challenge infection following immunisation with a combination of the purified fluke-derived enzymes cathepsin L1 (CATL 1), cathepsin L2 (CATL 2) and fluke-derived Hb fraction (FHB). This and other recent studies have also demonstrated fundamental differences between protective and non-protective immune responses to liver fluke infection. In this present study we have further analysed the response of animals to liver fluke challenge following experimental vaccination. Calves were vaccinated with either CATL 2 plus FHB, or CATL 1 plus CATL 2. Partial protection against challenge infection was achieved in both vaccinated groups, with the greatest level of protection (55 per cent reduction in fluke burdens) recorded in the group vaccinated with CATL 1 plus CATL 2. This latter group also showed the greater level of lymphocyte proliferation and the greater production of gamma-INF in response to stimulation with fluke antigen in vitro following challenge. These results are significant in our attempts to characterise the elements within the immune response to vaccination which are protective.     

Effects of calcium channel blockers on pharmacologically induced contractions of rainbow trout (Oncorhynchus mykiss) intestine

Calcium depletion/replacement studies were carried out to examine the role of calcium in contraction of trout intestinal smoot muscle in vitro. Three chemically distinct calcium channel blockers were used to determine whether voltage operated calcium channels (VOCs) were involved in calcium entry with either agonist or depolarization-induced contractions. Contractions induced by depolarizing intestinal smooth muscle with potassium were totally dependent on extracellular calcium, whereas receptor-mediated responses to 5-hydroxytryptamine (5-HT) and carbachol also relied on calcium derived from intracellular stores. The calcium channel blockers, verapamil, nitrendipine, and diltiazem, all shifted the calcium-response curve for potassium to the right, supporting the existence of VOCs in trout intestinal smooth muscle. The calcium-response curve for 5-HT was also shifted to the right, suggesting that 5-HT can induce calcium uptake into the smooth muscle via VOCs, in addition to mobilizing intracellular calcium. Verapamil also appeared to block 5-HT receptors directly. Carbachol-induced contractions were only reduced by diltiazem at low concentrations of calcium (0.1–1 mM), suggesting that diltiazem has some other mechanisms of action than the other calcium channel blockers. Activation of muscarinic receptors may induce calcium entry through channels other than the VOCs, in addition to mobilizing intracellular calcium.     

On the global distribution of aerosols

Aerosol concentrations were measured during a 54-hour circum-navigation of the earth at altitudes between 238 and 162 millibars and concurrently by a separate flight at lower altitudes over the Pacific Ocean. The aerosol concentrations were found to be symmetrically distributed about the earth. Concurrent meteorological measurements indicate that tropospheric aerosols enter the stratosphere in the vicinity of jet streams and that surface aerosols are carried aloft over the intertropical convergence and Antarctic polar front.