Towards understanding knee joint laxity: errors in non-invasive assessment of joint rotation can be corrected.

The in vivo quantification of rotational laxity of the knee joint is of importance for monitoring changes in joint stability or the outcome of therapies. While invasive assessments have been used to study rotational laxity, non-invasive methods are attractive particularly for assessing young cohorts. This study aimed to determine the conditions under which tibio-femoral rotational laxity can be assessed reliably and accurately in a non-invasive manner. The reliability and error of non-invasive examinations of rotational joint laxity were determined by comparing the artefact associated with surface mounted markers against simultaneous measurements using fluoroscopy in five knees including healthy and ACL deficient joints. The knees were examined at 0°, 30°, 60° and 90° flexion using a device that allows manual axial rotation of the joint. With a mean RMS error of 9.6°, the largest inaccuracy using non-invasive assessment was present at 0° knee flexion, whereas at 90° knee flexion, a smaller RMS error of 5.7° was found. A Bland and Altman assessment indicated that a proportional bias exists between the non-invasive and fluoroscopic approaches, with limits of agreement that exceeded 20°. Correction using average linear regression functions resulted in a reduction of the RMS error to below 1° and limits of agreement to less than ±1° across all knees and flexion angles. Given the excellent reliability and the fact that a correction of the surface mounted marker based rotation values can be achieved, non-invasive evaluation of tibio-femoral rotation could offer opportunities for simplified devices for use in clinical settings in cases where invasive assessments are not justified. Although surface mounted marker based measurements tend to overestimate joint rotation, and therefore joint laxity, our results indicate that it is possible to correct for this error.

Characteristics of gonads and oviducts in hatchlings and young of Chelydra serpentina resulting from three incubation temperatures.

Eggs of Chelydra serpentina were incubated at 30 degrees C and 26 degrees C. In addition, incubation was done at 20 degree C during the temperature-sensitive period for sex determination. Incubation at 20 degrees C and 30 degrees C resulted in females; incubation at 26 degrees C resulted in males in 99% of the cases. The average gonadal length was less in the males. The average length of the 20 degree C ovaries did not vary significantly from that of the 30 degrees C ovaries. The condition of the oviducts was correlated with histology of the gonads in hatchlings and in 3-month-old animals. When at least one of the oviducts was obvious and intact, ovaries were present. If the oviducts were absent or interrupted, testes were present. Histological characteristics of the gonads resulting from the three incubation temperatures are described. In the 26 degree C testes, cellular infiltrations occurred frequently. The ovaries of 20 degrees C hatchlings tended to have a less developed germinal epithelium than that of the 30 degrees C animals. Also, epithelial cysts occurred frequently in the 20 degrees C ovaries. The incidence of follicles at 3 months was not differential.

Temperature levels and periods of sex determination during incubation of eggs of Chelydra serpentina.

Eggs of Chelydra serpentina were shifted during incubation between the female producing temperatures of 20°C or 30°C and the male producing temperature of 26°C. In the 20°C and 26°C combination, the stages during which incubation temperature determined sex were stage 14 through stage 16 (stages of normal series, Yntema, '68). In the 30°C and 26°C combination, the temperature sensitive stages for sex determination were stage 14 through stage 19. Incubation at 26°C throughout this period was needed to produce all males. Incubation at 30°C during either the first or second half of the period produced nearly all females; shorter periods of incubation at 30°C were more effective in producing females during the second half of the sensitive period. In the 20°C and 26°C combination, incubation at 20°C or 26°C for parts of the sensitive period produced both males and females. In three of the 57 clutches of eggs used in the experiments, incidence of females was atypically high.

Fine structure of the chromophobe in the pars distalis of the common snapping turtle, Chelydra serpentina.

Chromophobes of the pars distalis in young Chelydra serpentina have sparse cytoplasm with no specific granules; however, many cytoplasmic filaments are present. The chromophobes are connected to the other cell types by desmosomes, while different types of junctional specializations occur between adjacent chromophobes. Cytoplasmic filaments traverse the cytoplasm in a random manner and terminate on both the junctional complexes and the nuclear envelope. It is proposed that, in addition to providing a structural framework, the chromophobes may be involved in integrating cellular responses of the parenchyma to changes in the endocrine milieu.

Effects of incubation temperatures on sexual differentiation in the turtle, Chelydra serpentina.

Eggs of the common snapping turtle, Chelydra serpentina, were incubated at constant temperatures ranging from 20°C to 30°C, At hatching, the oviducts were absent or incomplete in males; the testes were differentiated. In females at hatching, the oviduct was intact hut in some cases the gonad retained bisexual characteristics. Three months after hatching, the ovary was differentiated and contained follicles. Eggs incubated at 20°C and at 30°C developed into females in 100% of the cases. At 26°C, 99% of the individuals were males; at 24°C, 100% were males. More males than females developed at incubation temperatures of 22°C and 28°C.

Incidence and progress of rejection of embryonic limb bud transplants in the turtle, Chelydra serpentina.

Allografts of embryonic limb buds were grafted orthotopically on embryos of Chelydra serpentina. Donors were from a different geographic area, the same geographic area, or siblings. The initial indication of rejection was excessive sloughing of epidermis. This was followed by loss of muscle, claws and bone. Early histological changes involved an infiltration of mononuclear or rejection cells primarily associated with small blood vessels of the connective tissue. Subsequently, muscle and bone were lost and they were replaced by connective tissue. Epidermis and nerves persisted. The skeletal cartilages were isolated from immunological activity. Although the incidence of rejection was essentially the same in sibling and non-sibling combinations, the initial external signs of rejection occurred earliest when donor and host were from different geographic areas but not later than two years after hatching. The first signs of rejection in sibling allografts occurred not later than three years after hatching. Animals that survived these periods without rejection did not show subsequent rejection.

Survival of skin allografts following embryonic limb bud transplants in the turtle, Chelydra serpentina.

Allografts of skin were observed in Chelydra serpentina. The response to these grafts was modified by a previous transplantation of a limb bud at an early embryonic stage. When the same donor was used for all transplants, the first skin graft was accepted by the host. A second skin graft, however, was rejected at about the rate of a simple first set allograft of skin. The animals were conditioned by the embryonic limb graft; this embryonic graft can be undergoing rejection at the same time a first set skin graft from the same donor was being accepted. The tolerance induced by the embryonic graft was sepcific for its donor.