Multiple mechanisms contribute to the avoidance of avian epidermis by sensory axons.

In birds, sensory innervation of skin is restricted to dermis, with few axons penetrating into the epidermis. This pattern of innervation is maintained in vitro, where sensory neurites avoid explants of epidermis but grow readily on dermis. We have used this coculture paradigm to investigate the mechanisms that impede innervation of avian epidermis. The lack of epidermal innervation in birds has been attributed to diffusible chondroitin sulfate proteoglycans (CSPGs) secreted by the epidermis, although direct experimental evidence is weak. We found that elimination of CSPG function with either chondroitinase or neutralizing antibodies did not promote growth of DRG neurites onto epidermis in vitro, indicating that CSPGs alone are not responsible for preventing epidermal innervation. Moreover, the failure of sensory neurites to invade epidermis is not due exclusively to soluble chemorepulsive factors, since sensory neurites also avoid dead epidermis. This inhibition can be overridden, however, by coating epidermis with the growth-promoting molecule laminin, but only if the tissue is killed first. Epidermal innervation of laminin-coated epidermis is even more robust when CSPGs are also eliminated. Thus, the absence of growth-promoting or permissive molecules, such as laminin, may contribute to the failure of sensory neurites to invade avian epidermis. Together these results show that the inhibitory character of avian epidermis is complex. Cell- or matrix-associated CSPGs clearly contribute to the inhibition, but are not solely responsible.

Chronic leg pain: putting the diagnostic pieces together.

Chronic pain in the calf, tibia, fibula, or muscle compartments of the leg must be carefully evaluated to make the proper diagnosis and define the most appropriate course of treatment. The most common overuse leg injuries are stress fractures, chronic exertional compartment syndrome, medial tibial stress syndrome, and strains and sprains. The history is the key component of the evaluation. Targeted questions can suggest which ancillary tests can confirm the working diagnosis. Infection, tumors, radiculopathy, and vascular compromise other than compartment syndrome are rare but must be considered in the differential.

Noninvasive markers of bone metabolism in the rhesus monkey: normal effects of age and gender.

Measurement of bone turnover in conditions such as osteoporosis has been limited by the need for invasive iliac bone biopsy to reliably determine parameters of bone metabolism. Recent advances in the area of serum and urinary markers of bone metabolism have raised the possibility for noninvasive measurements; however, little nonhuman primate data exist for these parameters. The purpose of this experiment was to define the normal range and variability of several of the newer noninvasive bone markers which are currently under investigation in humans. The primary intent was to determine age and gender variability, as well as provide some normative data for future experiments in nonhuman primates. Twenty-four rhesus macaques were divided into equal groups of male and female according to the following age groupings: 3 years, 5-10 years, 15-20 years, and > 25 years. Urine was collected three times daily for a four-day period and measured for several markers of bone turnoverm including pyridinoline (PYD), deoxypyrodinoline (DPD), hydroxyproline, and creatinine. Bone mineral density measurements of the lumbar spine were performed at the beginning and end of the study period. Serum was also obtained at the time of bone densitometry for measurement of osteocalcin levels by radioimmunoassay. There were no significant differences in bone mineral density, urine PYD, or urine DPD based on gender. Bone density was lowest in the youngest animals, peaked in the 15-20-year group, but again decreased in the oldest animals. The osteocalcin, PYD, and DPD levels followed an inversely related pattern to bone density. The most important result was the relative age insensitivity of the ratio of PYD:DPD in monkeys up to age 20 years. Since bone density changes take months or years to become measurable and iliac biopsies are invasive, the PYD/DPD marker ratio may have important implications for rapid noninvasive measurement of the effects of potential treatments for osteoporosis in the non-human primate model.

Differential expression of cell adhesion molecules on trigeminal cutaneous and muscle afferents.

Previous work from our laboratory (Woodbury and Scott, 1995) suggested that embryonic cutaneous and muscle afferents might express different surface cell adhesion molecules (CAMs) on their growth cones. To examine this possibility directly we measured the relative levels of expression of various adhesion molecules on growth cones of neurons from the dorsomedial portion of the trigeminal ganglion (DM-TG), which are largely cutaneous, and from the trigeminal mesencephalic nucleus (TMN), which are exclusively muscle afferents. Axonin-1,L1, BEN, and N-cadherin were expressed more abundantly on DM-TG growth cones, whereas N-CAM was more abundant on TMN neurons. Expression of polysialated N-CAM was similar on the two populations, addition of NGF and NT-3 appeared to increase expression of polysialated N-CAM on TMN neurons. Although the levels of L1 and axonin-1, both of which bind L1, were markedly different on TMN and DM-TG neurons, these differences were not sufficient to cause dramatic differences in the growth rates of TMN and DM-TG neurons on L1.

College mental health programs: A paradigm for Comprehensive Community Mental Health centers.

Some of the dilemmas confronting the Comprehensive Community Mental Health movement are reviewed. Existent paradigms to this movement or aspects of it are documented on various college campuses with special reference to the College Community Mental Health Program present at the University of Florida. The major content of the paper clarifies areas of applicable usefulness such community oriented College Mental Health Programs can serve in overcoming some of the dilemmas of the Comprehensive Community Mental Health movement. University of Florida utilization of the College Community Model for training of the psychiatric resident is outlined.