ABSTRACT
Although born blind and deaf, newborn rats exhibit a remarkable capacity to recognize and gain access to the nipples of the lactating mother. However, it is well-known that full-term rat neonates will not attach to an artificial nipple. In the present study, an artificial nipple fashioned from soft vinyl was presented to rat fetuses from E17-E21 of gestation. Fetuses showed side-to-side head movements that resulted in oral capture of the nipple on E18 and exhibited a direct nipple-grasping response from E19 through term. Frame-by-frame analysis of videotape records of E21 rat fetuses revealed that tactile contact with the artificial nipple elicited mouthing, licking directed at the nipple, forelimb treadling, and grasping of the nipple. Fetuses also exhibited components of aversive behavior, including facial wiping and head turning, that appeared to terminate oral contact with the nipple. Morphine pretreatment reduced the expression of aversive responses and promoted licking and grasping of the artificial nipple. In addition to documenting the prenatal ontogeny of this important neonatal behavior, these findings imply a role for endogenous opioids in the newborn rat's first suckling episode.
Subject(s)
Embryo, Nonmammalian/physiology , Motor Activity/physiology , Sucking Behavior , Animals , Animals, Newborn , Behavior, Animal , Female , Male , Motor Activity/drug effects , Narcotics , Nipples , Pregnancy , Rats , Rats, Sprague-Dawley , Videotape RecordingABSTRACT
Degenerative arthritis of the knee is a complication of femoral or tibial fractures potentially avoidable by the correction of various degrees of malalignment. To better clarify the malalignment problem, the records of 14 patients (15 limbs), with degenerative arthritis of the knee and a history of tibial or femoral fracture were retrospectively reviewed. The average follow-up was 31.7 years. Static biomechanical frontal plane analyses were evaluated. The calculated increased force on either the medial or lateral tibial plateau, due to the malunion, was strongly associated with presence of a varus or valgus deformity at the knee (p less than 0.0005). A normal tibial plateau force for the malaligned condition multiplied by the time since fracture correlated directly with the amount of subsequent varus or valgus deformity at the knee (p less than 0.01). Lower limb fracture alignment should be restored to as near normal as possible to reduce the likelihood of gonarthrosis.
Subject(s)
Femoral Fractures/complications , Knee Joint/physiopathology , Osteoarthritis/etiology , Tibial Fractures/complications , Adult , Aged , Aged, 80 and over , Biomechanical Phenomena , Female , Femoral Fractures/physiopathology , Humans , Male , Middle Aged , Retrospective Studies , Tibial Fractures/physiopathologySubject(s)
Adaptation, Physiological , Blood Viscosity , Temperature , Animals , Antarctic Regions , Birds , Ducks , Humans , Seals, Earless , Species SpecificitySubject(s)
Air Sacs/physiology , Ducks/physiology , Vocalization, Animal , Animals , Catheterization , Female , Male , Pressure , Time Factors , Vocalization, Animal/physiologyABSTRACT
The withdrawal of water from the lizard cloaca can be a passive process resulting from the colloidal osmotic pressure of the plasma proteins. The forces necessary to withdraw water from lizard urine, the forces prevailing within the cloaca in vivo, and the counterbalancing of these forces by a protein solution placed in the cloaca all are in accord with this hypothesis.
