Compressive/tensile stresses and lignified cells as resistance components in joints between cladodes of Opuntia laevis (Cactaceae): responses to applied stresses.

Cactaceae are a diverse group of plants with a wide variety of morphologies and reproductive strategies. Many species have segmented stems in which terminal cladodes may be separated from main stem cladodes with varying amounts of resistance. Previous results demonstrated that lignified xylem cells in tensile portions of stem joints provide the main resistance to separation of cladodes within cactus plants. The purpose of the present study was to determine if stem joints of Opuntia laevis would produce additional lignified xylem cells in response to additional externally applied stresses. Normal average stress levels, which accompany the addition of a new cladode, were applied to 12 plants. In contrast, double the average stress levels were applied to 13 other plants. After exposure to the two stress regimens for 6 months, the amount and location of lignified xylem cells in joint segments were similar for both stress treatments. So, although the results support the hypothesis that lignified xylem cells act as the main resistance to stress at joints of cladodes, doubling the normal amount of applied stress was insufficient to alter the amount or location of lignified xylem cells in stem joints. These results indicate that normal amounts of lignified xylem cells can resist up to two times the normal amount of stress for 6 months without producing additional lignified xylem cells.

Compressive/Tensile Stresses and Lignified Cells as Resistance Components in Joints between Cladodes of Opuntia laevis (Cactaceae).

The Cactaceae are a diverse group of plants with a wide variety of morphologies. Many species of Opuntia have segmented stems in which terminal cladodes may be separated from main-stem cladodes with varying amounts of resistance. From a geometric approach, derivations were used to calculate normal (axial and bending) and shear (transverse force and torque) stresses at joints due to the weight of the cladodes. Normal and shear stresses act perpendicular and parallel to (along) the cross sections of joints, respectively. Normal stress caused by bending was >10 times that of the mean value of any other stress. Analyses were performed to determine the relationship between maximum normal stress and the amount of lignified xylem cells. Such cells had thicker cell walls compared with the various other cells of stem joints that had thin cell walls and that thus would provide the most resistance to normal stresses. An analogy was made between cactus joints and a composite beam with reinforcing rods. In such joints, thin-walled parenchyma cells might be analogous to concrete that has little resistance to tensile stress, while the thick-walled, lignified xylem cells would be analogous to reinforcing rods. There were statistically significant relationships between normal stresses (from bending and axial loads) and mean percentage of lignified xylem cells (r=0.73) and between normal stresses and total areas of lignified xylem cells (r=0.65) (more stress, more reinforcing xylem cells). Tensile portions of cactus joints had 23% lignified xylem cells, while compressive portions had only 10% lignified xylem cells in joint areas (more tension, more reinforcing xylem cells). In addition, tensile joint tissues had two to three times more thick-walled, lignified xylem cells in the outer 30% of the radius compared with other joint tissues types (more reinforcing near the surface). To our knowledge, this is the first publication to present mechanical stresses at stem joints of cacti and the first to relate these stresses to characteristics of resisting tissues in the joints of a cactus.

Immunolocalization of connexin 26 in the developing mouse cochlea.

Gap junctions play a pivotal role in embryonic development by forming specialized regions of cell-cell communication. In this study, we demonstrate the temporal-spatial distribution of connexin 26 in the embryonic and early postnatal mouse cochlea. Our results show localization of this gap junction protein to specific cochlear structures, including the inner and outer sulcus cells, the supporting cells of the inner hair cells, the mesenchyme derived portion of the stria vascularis, and the cells of the spiral ligament that interface with the basal cells of the stria vascularis. This suggests that this gap junction protein of served patterns of connexin 26 distribution is important for the differentiation and development of these structures (e.g., the role of the inner sulcus cells in producing the tectorial membrane).

[Plastination histologic investigations on the inserting pars terminalis aponeurosis dorsalis of three-sectioned fingers]. / Plastinationshistologische Untersuchungen zur Insertion der Pars terminalis der Aponeurosis dorsalis an den dreigliedrigen Fingern.

With the help of thick transparent cross-sections of fingers, manufactured by plastination histology, it has been shown that fibres of the extensor aponeurosis insert not only the way described in current textbook on the basis phalangis distalis and on the capsule of the distal interphalangeal joint. Our studies prove that parts of the dorsal extension plate insert dorsally to the nail matrix and others run over the edge of the basis phalangis to the proximal part of the diaphysis where they intermingle with the periost of the phalanx.

[Does osseous extensor tendon avulsion or rupture really exist? Histologic plastination studies of insertion of the extensor aponeurosis and significance for operative therapy]. / Gibt es einen knöchernen Strecksehnenab- oder -ausriss? Plastinationshistologische Untersuchungen zur Insertion der Streckaponeurose und deren Bedeutung für die operative Therapie.

With the help of thick, transparent finger cross sections, it was shown that fibers of the extensor aponeurosis insert distal to the avulsed fragment of the distal phalanx. The consequence for hand surgery is not to expose the fragment through a dorsal incision, but through a mid-lateral one. In this way, the distant parts of the aponeurosis distal to the fracture remain intact, and there is no break in the continuation of the dorsal extension plate.

[Are "Busch fracture", "avulsion fracture of the extensor tendon" or "fracture of the dorsal terminal finger joint" synonyms? Anatomic studies of the insertion of the extensor aponeurosis and significance in hand surgery]. / "Busch-Fraktur", "Knöcherner Strecksehnenausriss" order "Fraktur der dorsalen Endphalanxbasis"--Synonyme? Anatomische Unterschungen zur Insertion der Streckaponeurose und deren handchirurgischen Bedeutung.

With the help of thick transparent cross-sections of fingers, it has been shown that fibers of the extensor aponeurosis insert distal to the avulsed fragment of the distal phalanx. The consequence for hand surgery is not to expose the fragment through a dorsal incision but through a mid-lateral one. In this way, the distant parts of the aponeurosis distal to the fracture remain intact and there is no break in the continuation of the dorsal extensior plate.

Bluetongue epidemiology in the Caribbean region: serological and entomological evidence from a pilot study in Barbados

Variations in the percentages of lambs seroconverting to bluetongue viruses was seen between sites and years in Barbados. Transmission at some sites was nearly absent whereas all lambs at one site became seropositive. The agar gel immunodiffusion test for bluetongue gave consistent results in series of serum samples from 112 of 121 sentinel lambs. Collections of biting midges in association with sheep yielded six species. Culicoides insignis Lutz, C. pusillus Lutz, C. phlebotomus (Williston), C. furens (Poey), C. jamaicensis Edwards and C. trilineatus Fox. The first two species comprised 92 percent of those caught during a sentinel lamb study and were the predominant species trapped for virus isolation. No viruses were recovered from 5517 C. insignis, 614 C. pusillus, three C. trilineatus and two C. furens placed into pools during two brief intensive trapping operations. (AU)

Bluetongue epidemiology in the Caribbean region: serological and entomological findings from a pilot sentinel system in Trinidad and Tobago

When monitored by the agar gel immunodiffusion test for antibody to bluetongue viruses, a sentinel flock of twenty-five lambs remained seropositive through the year, whereas in a sentinel herd of twenty calves only two individuals seroconverted and these became negative again within 2 months. A light trap operated with the calf herd yielded high numbers of culicoides insignis Lutz (over 18,000 per trap night) along with C. filariferus Hoffman, C. pusillus Lutz, C. leopoldi Ortiz, C. foxi Ortiz, C. limai Barretto, C. diabolicus Hoffman and C. guyanensis Floch and Abonnenc. Culicoides were trapped at the sheep station which had housed the lambs 3 years following the sentinel study. No virus was isolated from pools of C. insignis, C. filariferus and C. pusillus. Six outer species were collected in insufficient numbers to warrant attempted virus isolations. (AU)

Screwworm (Diptera: calliphoridae) myiasis in the Southern Caribbean, and proposals for its management

In a random sample of animal producers and animal health personnel, 33 percent of the respondents in Trinidad, 15 percent in Guyana, and 11 percent in Suriname recalled at least one case of human myiasis due to Cochliomyia hominivorax (Coquerel). During 1981, respondents in Suriname (88 percent), Guyana (85 percent), and Trinidad and Tobago (82 percent) found at least one case of myiasis in their livestock, mainly cattle, pigs, and dogs. Feral animals- e.g., jaguars- were also found to be infested. The initial wounds were mainly the umbilicus neonates, whereas arbitrary cuts, castration wounds, and vampire bite were also affected. Fifty-three to 78 percent of all respondents examined their livestock daily for wounds and infestation by the screwworm. Daily examinations of livestock are now done as a result of the screwworm threat. Annual estimates of losses (in U.S. dollars) due to surveillance and medication ranged from $4.82 to $10.71 per animal. These national losses amounted to $0.30 million (Suriname) $1.02 million (Trinidad and Tobago), and $4.33 million (Guyana). Other losses, such as failure to thrive, reduction in milk production, and hide injury due to screwworm activity, were not available. Most producers found that the greatest infestation occurred in the wet season. Also, most (68 to 83 percent) found the screwworm to be second in importance to the Boophilus spp. ticks as a pest of livestock, but of greater significance than biting flies such as tabanids and stable flies. Eradication of the screwworm can be recommended for the islands of Trinidad and Tobago. Eradication for Suriname and Guyana seems feasible only on the 100-km wide coastal strips, where most human and livestock populations exist. (AU)

Campylobacteriosis in Jamaican cattle

Infertility is a widespread problem among cattle herds in Jamaica and an intergovernmental project was initiated to investigate the problem. One aspect of the project included diagnosis of campylobacteriosis (vibriosis), which was suspected in some herds but had not been confirmed in the laboratory. Tests were undertaken in late 1978 using improved techniques for handling and transporting specimens to the laboratory. Campylobacter fetus subspecies fetus was isolated from five of six herds tested. The diagnosis of C fetus infection has led to improvements in farm management and a better appreciation of more efficient artificial insemination and veterinary services. (Summary)