Notch Morphology Research Articles

Cytokinins Induce Photomorphogenic Development in Dark-grown Gametophytes of Ceratopteris richardii

The cytokinins benzylaminopurine, kinetin and isopentenyladenine induce photomorphogenesis in dark-grown gametophytes of the fern Ceratopteris richardii. At sub-nanomolar concentrations each altered the rate and pattern of cell division, elongation and differentiation, mimicking aspects of the light-mediated transition from filamentous to prothallial growth. Untreated dark-grown gametophytes grow as narrow, elongate, asexual filaments with an apical meristem. Cytokinin treatments as low as 10(-12) M reduced the length-to-width ratio through decreased cell elongation, increased periclinal cell division and induced the formation of rhizoid initials in the cells immediately below the apical meristem. Higher concentrations (10(-9)-10(-8) M) induced conversion of the meristem from apical to notch morphology. Cytokinins induced both red- and blue-light-mediated photomorphogenic events, suggesting stimulation of both phytochrome and cryptochrome signaling; however, cytokinin treatment only partially substituted for light in that it did not induce hermaphroditic sexual development or spore germination in the dark. Additionally, cytokinins did not increase chlorophyll synthesis in dark-grown gametophytes, which unlike angiosperms are able to produce mature chloroplasts in the dark. Cytokinin treatment had only slight effects on light-grown gametophytes. These results suggest evolutionary conservation between angiosperms and pteridophytes in the role of cytokinins in regulating photomorphogenesis.

Gough's Cave 1 (Somerset, England): an Assessment of the Sex and Age at Death

The overall impression of the sexually dimorphic characteristics of Gough's Cave 1 is that the remains are those of a male. However, the specimen does present some ‘female’ features in the facial skeleton, the ischiopubic rami and pelvic apertures, combined with relatively small overall size, and an ambiguous greater sciatic notch morphology. Nevertheless, the various features employed for sexual diagnosis of Gough's Cave are predominantly those which indicate or strongly suggest that it is male, but this must be accompanied with the caveat that either this individual falls at the feminine end of the male range of variation or that the patterns of skeletal sexual dimorphism of the population from which it derived were modestly different from those of the mostly European and European-derived reference samples used for this assessment. In contrast to the ambiguities of sex determination for Gough's Cave 1, the various indicators of his age-at-death are highly consistent. All of them agree in placing Gough's Cave 1 between his late second decade and middle third decade. He was unlikely to have been younger than about 18 years, and most likely was not older than about 23 years at death.

Simultaneous bilateral anterior cruciate ligament ruptures in a cheerleader

The anterior cruciate ligament (ACL) is frequently injured during both recreational and competitive activity. It is common to see patients who have ruptured both ACLs at different times. Intercondylar notch width, notch morphology, gender, and family history have all been implicated as factors that may predispose an individual to contralateral ACL rupture following unilateral injury. Simultaneous bilateral ACL rupture is a rare occurrence. Only 1 other case has previously been reported. We report the case of a 17-year-old high school cheerleader who sustained simultaneous bilateral ACL ruptures. Some of the commonly implicated risk factors for ACL rupture are examined and a review of the literature is also presented.Arthroscopy: The Journal of Arthroscopic and Related Surgery, Vol 17, No 4 (April), 2001: pp E17–E17

Cruciate Injury Patterns in Knee Hyperextension: A Cadaveric Model

Summary: We created an experimental model to evaluate the effects of strain rate on the mechanism of combined cruciate ligament injuries in knee hyperextension. Using straight knee hyperextension to rupture the anterior and posterior cruciates, two strain rates (approximately 100% per second and 5400% per second) were applied to reproduce two clinical injury patterns of the knee: low energy (sporting) and high energy (pedestrian–motor vehicle accident). Ten pairs of fresh-frozen cadaveric knees were injured to 45° of hyperextension. Strain rate sensitivity of the posterior cruciate ligament was shown in this model, with midsubstance tears occuring in specimens tested at a low rate and avulsion “stripping” injuries from the femoral side occuring at a high rate. A variable pattern of anterior cruciate ligament tears at both high and low rates suggests that the specific injury mechanism may also involve other factors including notch morphology. We present a simplified mathematic model used to estimate posterior cruciate ligament strain during knee hyperextension.Arthroscopy: The Journal of Arthroscopic and Related Surgery, Vol 15, No 5 (July-August), 1999: pp 489–495