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C Frenz

Publications and source records attributed to C Frenz.

6 recordsLinked to original sources
PubMed2001

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.

Journal Article↗
PubMed2000

[Plastination histologic investigations on the inserting pars terminalis aponeurosis dorsalis of three-sectioned fingers].

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.

Dissection↗
PubMed2000

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.

Journal Article↗
PubMed1999

[Does osseous extensor tendon avulsion or rupture really exist? Histologic plastination studies of insertion of the extensor aponeurosis and significance for operative therapy].

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.

Finger Injuries↗
PubMed1994

[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].

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.

Adult↗