R W Mann — Page 6 | Search PubMed

PubMedDate not supplied

The role of muscular co-contraction of the hip during movement.

The joint biomechanics of the hip was studied analyzing the kinematic, kinetic, electromyographic and in vivo pressure parameters during walking, going up stairs, and getting up from a chair. The most significant clinical and biomechanical data emerged when the temporal correlation between intra-articular pressure variations and electric activity of the bi-articular muscles was studied. The presence of co-contraction of the bi-articular muscles during the support and oscillation phases was evident. The maximum joint pressure values were measured while getting up from a chair when the hip was flexed more than 100 degrees. The posterior region of the acetabulum was that most submitted to loading. This data is useful in gaining an understanding of joint physiology, in correctly setting up physio-kinesitherapeutic protocols, and in setting up pre-clinical prosthetic mechanical tests.

Biomechanical Phenomena↗

PubMedDate not supplied

Salivary glands and human selection: a hypothesis.

Stafne static bone defect (SSBD) of the mandible is the only described destructive bone lesion that is highly localized, nonprogressive, but nonhealing. This common defect in male is found in the region of the major salivary glands that produce a cornucopia of biologically active factors. We describe rare phenocopies caused by mandibular immobility that hold the gland in a constant position thus implicating a localized chronic "leak" of an osteoclast induction factor from the major salivary glands as the pathologic agent. This finding suggests that increased salivary gland size could simulate immobility by apposing the gland to bone, thus allowing the "leaked" factor's gradient to have an effect. In one step, the putative genetic enlargement of a critical gland that produces many factors important for survival, a broad biological vista would be available to the massive potential for both positive and negative selection. Positive selection was identified by observing a correlation between the prevalence of enhanced androgen-induced enlarge salivary glands (SSBD) as a marker, with a great preponderance of males) and the conjectured resulting increased production of immunoreactive factors, with pole-to-equator isotherm and broad ranged infection clines. Negative selection was observed among the slave ancestors of African Americans for a potential embryonic homeotic mutation causing larger salivary glands in both sexes (decreased prevalence of SSBD, with an equal sex ratio). The decreased production of saliva and electrolytes diminished the salt and water depletive effects of severe diarrhea and vomiting induced by enteric diseases, which killed many slaves. Data presented suggests that SSBD is a polymorphism and a marker of selection processes that cause variation in size, or structure, of the major salivary glands.

Adult↗