Biomedical subjects

J S McClintock

Publications and source records attributed to J S McClintock.

5 recordsLinked to original sources

PubMed1997

Regional differences of dura osteoinduction: squamous dura induces osteogenesis, sutural dura induces chondrogenesis and osteogenesis.

Dura plays an important role in calvarial morphogenesis. However, precisely what that role is remains unclear. We present here in vivo evidence that dura without other central nervous system components induces both chondrogenesis and osteogenesis. The mechanism is, at least in part, by proximate tissue interaction. The objectives of this experiment were to answer the following: (1) Can dura actually induce osteogenesis without the influence of the underlying brain? (2) What are the requirements of this dura-induced heterotopic osteogenesis? (3) What are the differences between dura underlying sutures and dura underlying the squamous portions of the cranial bones? Dura underlying the metopic, sagittal, and lambdoidal sutures and dura underlying the flat portions of frontal and parietal bones were obtained from neonatal Lewis rats and transplanted into the posterior thoraces of adult Lewis recipients. In group I, dura underlying the metopic, sagittal, and lambdoidal sutures (n = 20) and dura underlying the flat portions of frontal and parietal bones (n = 20) were transplanted individually into separate epitheliomesenchymal pockets. Group II animals had dura underlying the metopic, sagittal, and lambdoidal sutures (n = 10) and dura underlying the flat portions of frontal and parietal bones (n = 10) transplanted individually into surgically created mesenchymal pockets by placing the dura grafts between panniculus carnosus and latissimus dorsi muscles. The animals were sacrificed at 2-week intervals. Light microscopy, special histochemical analysis, immunohistochemistry, and electron microscopy were performed. Bone formation was seen in 15 of the 18 animals (83 percent) in group I. No bone or cartilage formation was seen in group II. Chondrogenesis was seen in 4 animals receiving dura underlying the metopic, sagittal, and lambdoidal sutures in group I. Cellular hyperproliferation was seen at 2 weeks when dura was transplanted close to the hair follicles. These cells had a high nucleus-to-cytoplasm ratio and were positive for transforming growth factor beta. This hyperproliferation was followed by production and accumulation of Alcian blue-positive extracellular matrix that resisted digestion by hyaluronidase. Cellularly active cartilage was seen at 6 weeks. There was no chondrogenesis in animals receiving dura underlying the flat portions of frontal and parietal bones in group I. Electron microscopy demonstrated the presence of proteoglycan-like ground substance and type II collagen in the inner layer of sutural dura and the predominance of dense type I collagen in the squamous dura and the external layer of the sutural dura. The important findings of this experiment are that (1) heterotopically transplanted neonatal dura can induce osteogenesis, (2) this heterotopic osteoinduction by dura requires epitheliomesenchymal interaction, and (3) separating dura into sutural dura and squamous dura, chondrogenesis occasionally occurred in addition to osteogenesis with the former, while only membranous ossification occurred with the latter, indicating intrinsic differences within the dura mater. This dural heterogeneity is supported by direct ultrastructural data.

Animals↗

PubMed1995

Pyogenic versus pseudopyogenic granulomas.

Surgeons are confronted daily with a myriad of skin pathology. Pyogenic and pseudopyogenic granulomas are certainly among the differential diagnoses to many nonhealing dermal lesions. This article revisits two types of vascularized lesions that are perhaps part neoplastic and part inflammatory/reparative. The differences clinically between these two types of lesions are few. The classical form generally is found along mucosal surfaces and upper extremities. The pseudopyogenic granuloma is more often found on the scalp and ears. Confirmation in their diagnoses is based strictly on their histological criteria. The management of these two types of lesions is identical. Excisional biopsies for all nonhealing lesions are warranted to rule out lesions with an ominous progression.

Basal Cell Carcinoma↗

PubMed1982

Progesterone secretion by granulosa cells from different sized follicles of human ovaries after short term incubation.

Studies on the ability of granulosa to secrete progesterone after hormonal treatment have not addressed the possibility of variations in response associated with the stage of follicular development. Accordingly, granulosa were isolated from follicular fluid obtained from apparently healthy ovaries of patients undergoing tubal bypass. Follicle size was estimated by laparoscopic and ultrasonic measurements, and granulosa cells were prepared by centrifugation and treatment with EGTA and hypertonic sucrose solution to minimize aggregation. Cell viability was determined and 10(6) cells/ml medium 199D were incubated for 24 h without or with ovine LH (1 microgram/ml) or 17 beta-estradiol (5 micrograms/ml). Progesterone secretion by granulosa increased from 6 to 30 ng/24 h/10(6) cells and correlated with follicle sizes of 5--25 mm. Compared to untreated cells obtained from the same follicle, granulosa from follicles ranging from 5--15 mm secreted 2.5 times more progesterone when treated with LH. This effect of LH diminished with further increases in follicle size, with LH having no effect on cells from follicles larger than 20 mm. Compared to untreated cells from the same follicles, 17 beta-estradiol caused a progressive inhibition of progesterone secretion by granulosa that correlated with follicle sizes between 5--18 mm, with almost 60% inhibition occurring in cells from 18-mm follicles. Thereafter, the inhibitory effect of 17 beta-estradiol diminished, and no effect was found in granulosa from follicles larger than 22 mm. These results indicate that LH and 17 beta-estradiol have maximal in vitro effects on progesterone secretion by granulosa from follicles with diameters of 15--18 mm. The change in response to LH and 17 beta-estradiol observed in samples from larger follicles may be due to the fact that these cells already have maximal binding of LH and 17 beta-estradiol to their receptors. Alternatively, it is possible that cells from larger follicles are desensitized to LH and 17 beta-estradiol.

Androstenedione↗

PubMedDate not supplied

Nasal correction in Binder's syndrome: the evolution of a treatment plan.

Maxillofacial dysplasia, or Binder's Syndrome is a challenge for the surgeon. The evolution of a surgical treatment plan has led to improved facial contour and patient self-image. We studied 27 patients with maxillonasal dysplasia of variable degrees, both on a short- and long-term basis. In some patients, surgical treatment began as early as 3 years of age, while others were treated as teenagers or young adults. Surgical options included cartilaginous onlay grafts to the pyriform area, nasal dorsal grafts (linear or L-strut in design), and columellar strut grafts. Le Fort osteotomies were reserved for those patients with Class III malocclusion (15% in this series). The overall goals were to augment skeletal deficiencies of the midface and begin the soft tissue expansion process as early as possible. From our long-term follow-ups (up to 15 years) it has become apparent that surgical treatment should begin early. This leads to improved self-image by the child's preschool years, taking advantage from their youthful skin elasticity. In the young patient, sequential lengthening procedures of the dorsum and columella are beneficial. Paranasal and midfacial augmentation is reserved until midfacial growth is near complete when the patient is in their midteenage years.

Abnormalities, Multiple↗

PubMedDate not supplied

Efficacy of growth factors in the accelerated closure of interstices in explanted meshed human skin grafts.

Meshed split-thickness skin grafts, especially when required to be widely spread, do not obtain immediate biologic wound closure. In cases of patients with burns that cover a large percentage of the body surface area, this leaves the patient at risk for metabolic problems and life-threatening infection. Several cytokines and growth factors could theoretically affect the rate of epithelialization and, therefore, the rate of meshed graft interstitial closure. With the use of human meshed skin grafts explanted onto athymic "nude" rats, the epithelialization kinetics of interleukin-4 (IL-4), macrophage colony-stimulating factor (MCSF), keratinocyte growth factor-1 (KGF-1), keratinocyte growth factor-2 (KGF-2), basic fibroblast growth factor (bFGF), and transforming growth factor beta-2 (TGF(B2)) were investigated; the results were compared with the rates of epithelialization of grafts treated with a vehicle control. On postoperative day 3, wounds treated with IL-4, KGF-2, bFGF, and TGF(B2) showed a significantly increased rate of interstitial closure (P < .05). On postoperative days 5 and 7, wounds treated with KGF-2, bFGF, and TGF(B2) all exhibited a significantly higher rate of interstitial closure than the grafts in the control group (P < .05). These data suggest that epithelialization kinetics can be accelerated with the use of several topical growth factors, and they provide support for a future clinical trial.

Animals↗