In vivo growth hormone treatment rapidly stimulates the tyrosine phosphorylation and activation of Stat3

The mechanisms by which GH regulates gene expression to alter growth and metabolism are unknown. We have demonstrated previously that in vivo GH treatment rapidly stimulates the tyrosine phosphorylation of multiple nuclear proteins and have identified the inducible transcription factor Stat1 (formerly Stat91) as one of the major GH-activated nuclear phosphoproteins. We now show that Stat3, a new member of the STAT (signal transducer and activator of transcription) family of transcription factors, is also phosphorylated on tyrosine residues and rapidly appears in the nucleus in response to GH. Activated Stat3 interacts with the naturally occurring c-sis-inducible element of the c-fos gene after GH treatment, as demonstrated by gel mobility shift assay, and is a component of gel-shifted bands A and B when the high affinity sis-inducible element is used as a probe. Our results suggest that multiple STAT proteins may mediate some of the pleiotropic effects of GH on gene expression.

Characterization of deoxyribonucleic acid-protein interactions at a growth hormone-inducible nuclease hypersensitive site in the rat insulin-like growth factor-I gene

Many of the growth-promoting effects of GH are mediated by insulin-like growth factor-I (IGF-I), a highly conserved, 70-residue basic peptide. Previous studies have demonstrated that GH rapidly stimulates IGF-I expression in vivo, and our laboratory has identified a GH-regulated alteration in chromatin configuration, manifested as a hormonally induced deoxyribonuclease-I (DNase-I)-hypersensitive site in the second IGF-I intron. In the current study, we have used in vivo DNase-I footprinting to map this hormonally responsive chromatin domain to an approximately 350-nucleotide region and have identified DNA-protein interactions within the hypersensitive site by in vitro gel mobility shift experiments and DNase-I footprinting studies. DNA-protein binding was localized to two adjacent segments of 32 and 48 nucleotides. In 1 of these regions, protein-DNA contacts were also detected in vivo on guanine residues by dimethylsulfate footprinting. DNA-binding activity was present in GH-deficient rats, but was not modified by hormone treatment. Our results define a rapid and reversible genomic alteration in response to GH in a GH-regulated gene and delineate a target within chromatin for GH action.

The role of free radicals and antioxidants: how do we know that they are working?

This review briefly discusses how free radicals are formed and the possible participation of free radicals in disease. The review describes the basic radical reactions and the types of products that are formed from the free-radical reactions of cellular constituents. In many cases, in vivo free-radical oxidation can be detected by measuring products that were derived from radical reactions. Since aerobic organisms generate oxygen-containing free radicals during oxygen metabolism, they carry chemicals and enzymes that reduce the threat posed by these radicals. The more common sources of in vivo free radicals are described in the article as well as the methods used by cells to protect themselves from free-radical damage. Generation of free radicals in vivo also may be the result of exposure to certain chemical agents present in the environment. Many of these agents cause pathologic changes to the exposed tissues and organs by initiating free-radical reactions.

Growth hormone rapidly activates rat serine protease inhibitor 2.1 gene transcription and induces a DNA-binding activity distinct from those of Stat1, -3, and -4

Transcriptional regulation by growth hormone (GH) represents the culmination of signal transduction pathways that are initiated by the cell surface GH receptor and are targeted to the nucleus. Recent studies have demonstrated that the activated GH receptor can stimulate Stat1, a cytoplasmic transcription factor that becomes tyrosine phosphorylated and translocates to the nucleus, where it can interact with specific DNA sequences to modulate gene expression. GH also has been found to induce protein binding to a portion of the rat serine protease inhibitor (Spi) 2.1 gene promoter that is required for GH-induced transcription of Spi 2.1. Using GH-deficient hypophysectomized rats as a model, we show that GH treatment rapidly and potently induces both nuclear Spi 2.1 mRNA expression in the liver and specific nuclear protein binding to a 45-bp segment of the Spi 2.1 gene promoter. A GH-inducible gel-shifted complex appears within 15 min of systemic hormone administration and can be inhibited by an antiphosphotyrosine monoclonal antibody but is not blocked by a polyclonal antiserum to Stat1, Stat3, or Stat4, even though the nucleotide sequence contains two gamma interferon-activated sequence-like elements that could interact with STAT proteins. By Southwestern (DNA-protein) blot analysis, approximately 41- and 35-kDa GH-inducible proteins were detected in hepatic nuclear extracts with the Spi 2.1 DNA probe. Thus, a GH-activated signaling pathway stimulates Spi 2.1 gene expression through a unique mechanism that does not appear to involve known members of the STAT family of transcription factors.

Chemical and biological characterization of oxo-eicosatetraenoic acids

Eicosatetraenoates (ETEs) with 5-oxo residues are known to induce human neutrophil (PMN) Ca2+ transients and chemotaxis. We find that 5-oxoETE, 5-oxo-8-trans-ETE, 5-oxo-15-hydroxy-ETE, 5-hydroxy-ETE, 5-hydroxy-15-oxoETE, 5,15-dioxoETE, and 5,15-dihydroxy-ETE have respective relative potencies of 10, 5, 3, 1, 0.2, 0.1, and 0.02 in: a) causing PMN to mobilize Ca2+, aggregate, and release small amounts of granule enzymes and b) promoting large degranulation and oxidative burst responses in PMN co-challenged with platelet-activating factor, tumor necrosis factor-alpha, or ATP. Contrastingly, 12(R)-hydroxy-ETE, 12(S)-hydroxy-ETE, and 12-oxoETE induced PMN Ca2+ transients and aggregation [respective potencies (5-hydroxy-ETE = 1) of 0.1, 0.01, and 0.003] but did not effect degranulation, and 15-hydroxy-ETE, 15-oxoETE, and 15-oxo-11-trans-ETE were inactive in all assays. Finally, 5-oxo/hydroxy-ETEs desensitized PMN to themselves but not to 12-oxo/hydroxy-ETEs or leukotriene (LT)B4; 12-oxo/hydroxy-ETEs and LTB4 desensitized PMN to themselves and each other but not to 5-oxo/hydroxy-ETEs; 15-oxo/hydroxy-ETEs did not desensitize PMN; and a LTB4 receptor antagonist blocked responses to LTB4 and 12-oxo/hydroxy-ETEs but not to 5-oxo/hydroxy-ETEs. Thus, 5-oxo/hydroxy-ETEs act by a common, LTB4 receptor-independent mechanism that recognizes 5- but not 12- or 15-oxo/hydroxy-ETEs and prefers oxo over hydroxy residues at C5 whereas 12-oxo/hydroxy-ETEs act via a LTB4 receptor mechanism that recognizes 12- but not 5- or 15-oxo/hydroxy-ETEs and prefers hydroxy over oxo residues at C12.

Rapid activation of rat insulin-like growth factor-I gene transcription by growth hormone reveals no alterations in deoxyribonucleic acid-protein interactions within the major promoter

Insulin-like growth factor-I (IGF-I) is an important mediator of prenatal and postnatal growth, but little is known about the control of IGF-I gene expression. Previously, we demonstrated that GH rapidly stimulates hepatic IGF-I transcription in vivo in hypophysectomized (hypox) rats. In this study, we show that GH induces IGF-I gene transcription through the major promoter, promoter 1, and identify and characterize DNA-protein interactions throughout the promoter. In vitro deoxyribonuclease-I footprinting was used to analyze 1711 nucleotides of promoter 1 and the entire 328-nucleotide 5'-untranslated region of exon 1, using hepatic nuclear protein extracts from male juvenile hypox rats given a single ip injection of GH or saline 60 min before death. Fourteen DNA-protein binding sites were identified, with 6 located in the highly conserved 5'-untranslated region of exon 1. These latter sites were further characterized for specificity and regulation by GH, using gel mobility shift assays. Two of these DNA-protein interactions were also detected by in vivo dimethylsulfate footprinting. All DNA-protein binding was seen using hepatic nuclear protein extracts from hypox rats and did not change within 15, 30, 60, or 120 min after treatment with GH. Our results thus define a series of constitutive DNA-protein interactions within the major rat IGF-I gene promoter that may be involved in mediating GH-activated nuclear signals to initiate IGF-I transcription.

Acinic cell carcinoma of salivary glands. Prognostic relevance of DNA flow cytometry and nucleolar organizer regions

OBJECTIVE

To test the prognostic ability of flow cytometry and counts of silver-enhanced intranuclear nucleolar organizing regions (AgNORs) in acinic cell carcinoma.

DESIGN

Using statistical methods to establish if analysis of DNA content, percentage DNA synthetic (S)-phase, and the AgNOR counts on 45 cases of acinic cell carcinoma with clinical follow-up ranging from 10 to 379 months are predictors of time to recurrence or time to death due to acinic cell carcinomas.

MAIN OUTCOME MEASURES

Whether tumors with low AgNOR counts and diploid DNA are favorable acinic cell carcinomas and the converse, aneuploid DNA and elevated AgNOR count, predict unfavorable neoplasms.

RESULTS

Tumors with a diploid DNA content had as unfavorable a clinical course as aneuploid acinic cell carcinomas. Similarly, S-phase and AgNOR count results showed considerable overlap when separated into carcinomas with or without local recurrence, metastasis, or death due to tumor. Statistical evaluation also failed to provide predictors of clinical course based on ploidy, percentage S-phase, or AgNOR counts.

CONCLUSION

The results, although negative, are important in showing that data on DNA content, cell cycle, and nuclear limits useful in other neoplasms are of limited practical application in establishing predictors of time to recurrence or time to death in acinic cell carcinomas. Solving the enigmas, for clinicians and pathologists, associated with acinic cell carcinomas will require further information about the biology of this neoplasm.

Relationship of clear cell oncocytoma to mitochondrial-rich (typical) oncocytomas of parotid salivary gland. An ultrastructural study

Nosologically, the designation clear cell oncocytoma seems illogical and contradictory when the definition of an oncocytoma relies on mitochondrial-rich cells; its relationship to the granular (mitochondrial-rich) oncocytoma needs further clarification. Electron microscopy of six examples of oncocytoma from five patients allowed assessment of cellular features in three clear cell variants, two typical oncocytomas and one with a roughly equal proportion of clear and granular tumor cells. Ultrastructurally, in the clear cell types of oncocytoma, a considerable to extensive portion of the central cytoplasm was occupied by monoparticulate glycogen with margination of mitochondria and other organelles. The degree of extraction of the glycogen during fixation and processing accounts for variation in the extent of the clear cell component as phosphotungstic acid-hematoxylin staining reveals considerable mitochondria in many of the tumor cells in the clear cell variant of oncocytoma. Ultrastructural findings further support an interrelationship between clear and granular cells, as some typical oncocytes are evident in the clear cell variant of oncocytoma, and one oncocytoma in this series had a roughly equal number of glycogen-rich and mitochondrial-rich tumor cells both of which took part in the formation of microlumens. The designation clear cell oncocytoma is appropriate within the oncocytoma subgroup of salivary gland tumors.

Lipoperoxidation in plasma and red blood cells of patients undergoing haemodialysis: vitamins A, E, and iron status

In 14 patients undergoing haemodialysis, lipoperoxidation (LPO) processes were determined in plasma and red blood cells (RBC) before and after a dialysis session by determining (a) the direct substrate, polyunsaturated fatty acids (PUFA); (b) the end product of LPO, malondialdehyde (MDA); and (c) the hydrophobic antioxidant systems, vitamins A and E. In plasma before dialysis, linoleic and arachidonic acid, and the antioxidant vitamin E, were significantly lowered as compared to the healthy controls (p < 0.05). On the contrary, the free MDA level was enhanced (p < 0.05). These results were emphasized by a dialysis session. In RBC of these patients, no difference in linoleic acid, free MDA, or vitamin E level were observed before or after dialysis when compared to controls. However, only vitamin A was significantly higher in haemodialysis patients (before and after dialysis) and in renal failure patients (p < 0.05) than in the healthy control group. The present results suggest that increased RBC vitamin A may offer some degree of protection against oxidative stress in erythrocytes, but not in plasma where LPO is demonstrated.

Human growth hormone

The study of human growth hormone is a little more than 100 years old. Growth hormone, first identified for its dramatic effect on longitudinal growth, is now known to exert generalized effects on protein, lipid, and carbohydrate metabolism. Additional roles for growth hormone in human physiology are likely to be discovered in the areas of sleep research and reproduction. Furthermore, there is some indication that growth hormone also may be involved in the regulation of immune function, mental well-being, and the aging process. Recombinant DNA technology has provided an abundant and safe, albeit expensive, supply of human growth hormone for human use, but the pharmacological properties of growth hormone are poor. Most growth hormone-deficient individuals exhibit a secretory defect rather than a primary defect in growth hormone production, however, and advances in our understanding of the neuroendocrine regulation of growth hormone secretion have established the basis for the use of drugs to stimulate release of endogenously synthesized growth hormone. This promises to be an important area for future drug development.

Fatty acid composition of low-density lipoprotein influences its susceptibility to autoxidation

Low-density lipoprotein (LDL) oxidation was studied using copper or the water-soluble initiator azobis(2-amidinopropane) dihydrochloride (ABAP) to catalyze the reaction. These studies were carried out with purified, native LDLs that had a well-defined composition and which contained different concentrations of polyunsaturated fatty acids (PUFA) and alpha-tocopherol. The LDL was obtained from nonhuman primates fed diets enriched in cholesterol and one of four types of fatty acids: saturated (Sat), monounsaturated (Mono), omega-6 (omega-6FA), or omega-3 (omega-3FA) fatty acids. The PUFA concentration of the LDLs depended upon the diet and had the following order: omega-6FA > Sat approximately Mono approximately omega-3FA. Linoleic acid was the predominant PUFA in all of the LDLs. The rates of oxidation were linearly dependent upon the concentration of PUFA. When ABAP was used to initiate oxidation the lag time was linearly related to the amount of alpha-tocopherol. However, with copper catalysis no linear correlation was evident. If the different enrichments were analyzed independently, it was found that copper-catalyzed oxidation of LDLs enriched with omega-6 and omega-3 fatty acids showed a linear correlation between the lag time and the amount of alpha-tocopherol but that LDLs enriched with Sat or Mono fatty acids did not show a correlation. These results demonstrate that the rate of oxidation is dependent upon PUFA concentration and that the ability of alpha-tocopherol to inhibit oxidation depends upon the lipid environment and the mode of initiation.

Rapid nuclear actions of growth hormone

The mechanisms by which growth hormone (GH) initiates its effect on growth are largely unknown. In this report we examine the acute actions of GH with a focus on the intracellular signaling pathways leading from the cell-surface GH receptor into the nucleus, and culminating in the activation of specific target genes. We show that in vivo GH treatment leads to the rapid appearance of tyrosine-phosphorylated nuclear proteins and the equally rapid induction of c-fos and insulin-like growth factor I gene transcription. A model is proposed for a GH-activated intracellular signal transduction pathway.

Effects of the excitatory amino acid receptor antagonists kynurenate and indole-2-carboxylic acid on behavioral and neurochemical outcome following experimental brain injury

The overactivation of the NMDA receptor is thought to be a major contributor to the pathophysiologic sequelae of traumatic brain injury (TBI), which commonly includes memory dysfunction. Uniquely, potentiation of the NMDA receptor is dependent on the binding of glycine to a distinct site on the receptor. Despite the potential role of the NMDA receptor in the development of post-TBI cognitive deficits, no studies to date have evaluated the efficacy of NMDA receptor antagonists on memory dysfunction after brain injury. Moreover, glycine site antagonists have not been employed as potential therapeutic agents in models of TBI. In the present study, we evaluated the effects of two glycine site antagonists, kynurenate (KYNA) and indole-2-carboxylic acid (I2CA), on memory and motor dysfunction, cerebral edema formation, and changes in regional total tissue brain [Na], [K], [Ca], [Mg], and [Zn], following lateral fluid-percussion brain injury in the rat. We found that both KYNA (300 mg/kg) and I2CA (50 mg/kg and 20 mg/kg) administered 15 min postinjury dramatically attenuated trauma-induced cognitive dysfunction (p < 0.01). In addition, both compounds improved neurologic motor deficits measured at 2 weeks following injury (p < 0.05). KYNA (300 mg/kg) reduced edema in the cortex, hippocampus, and thalamus, while I2CA (20 mg/kg) reduced edema formation only in the thalamus. Differential effects of KYNA and I2CA on cation concentrations were also noted. KYNA attenuated the postinjury increase in regional tissue [Ca]; however, it had little effect on other cation concentrations. I2CA reversed the postinjury regional increases in [Na] and decreases in [K], [Mg], and [Zn], but had little effect on [Ca] changes. These results indicate that KYNA and I2CA may have differential, but beneficial effects on both behavioral and neurochemical sequelae of TBI.

Synthesis and characterization of a new photocrosslinking CTP analog and its use in photoaffinity labeling E. coli and T7 RNA polymerases

A new photocrosslinking CTP analog that functioned as a substrate during transcription was synthesized and used to photoaffinity label E. coli and bacteriophage T7 RNA polymerases. This analog, 5-((4-azidophenacyl)thio) cytidine-5'-triphosphate (5-APAS-CTP) contains an aryl azide group approximately 10 A from the nucleotide base and specifically replaced CTP during synthesis of RNA by both polymerases. Analog was placed at the 3' end or internally within RNA. Both polymerases inefficiently incorporated two 5-APAS-CMP molecules sequentially, as was found for the related 5-APAS-UMP. Analog was placed at the 3' end of RNA in transcription complexes paused at the site of Q-modification of E. coli RNA polymerase, downstream of the lambda PR' promoter (+16), a pause that requires specific DNA sequences but no apparent RNA hairpin. Crosslinking was examined in the presence and absence of the NusA protein, which enhances the transcriptional pause at this site and is required for Q modification of the polymerase. Crosslinking of the 3' end of the RNA to NusA was not observed, consistent with our earlier results involving a NusA-enhanced pause site downstream from an RNA hairpin.

5-Oxo-eicosatetraenoate, a potent human neutrophil stimulus

5-Oxo-eicosatetraenoate (5-oxoETE), a newly defined arachidonate metabolite, resembled 5-hydroxyeicosatetraenoate (5-HETE) in stimulating neutrophils to mobilize Ca2+ an in promoting PMN degranulation responses to other agents. It was, however, 10-fold stronger than 5-HETE and, like leukotriene (LT) B4, had intrinsic PMN degranulating effects. Nonetheless, 5-oxoETE and 5-HETE desensitized PMN to themselves or each other but not to LTB4; LTB4 desensitized to itself but not to 5-oxoETE or 5-HETE; and an antagonist blocked LTB4 but not 5-oxoETE or 5-HETE. 5-OxoETE and 5-HETE thus induce diverse PMN responses using a shared, down-regulatable, and receptor-like mechanism that does not involve LTB4 receptors; 5-oxoETE is the preferred natural agonist for this mechanism.

Intracisternal collagen fibrils in proliferative fasciitis and myositis of childhood

During ultrastructural examination of a difficult to diagnose tumor, short spacing collagen fibrils (periodicity of banding, approximately 43.2 nm) and native collagen fibrils (periodicity of banding, approximately 53 nm) were found in dilated and vacuolated cisternae of rough endoplasmic reticulum and the perinuclear cistern. Original diagnoses from several histopathologists included alveolar soft part sarcoma, malignant fibrous histiocytoma, atypical fibroxanthoma, and myogenic tumor. The finding of intracisternal collagen (which is but a variety of intracellular collagen) led to the conclusion that this was a fibroblastic neoplasm. This, plus a review of the histologic findings, led to the diagnosis of proliferative fasciitis and myositis of childhood.

Endopeptidase inhibition and intestinal antigen processing in mice

The role of gastrointestinal digestive processes in the systemic availability of ingested protein antigens was examined by feeding the trypsin inhibitor aprotinin intragastrically to mice and measuring uptake of ovalbumin and 14C-polyethylene glycol (MW 4000) from the gastrointestinal tract. Trypsin and chymotrypsin activities in the intestinal lumen were significantly reduced by aprotinin feeding. Aprotinin slowed stomach emptying, but radioimmunoassays for immunoreactive ovalbumin in the serum of mice prefed aprotinin showed 12-fold elevations within 1 hr after ovalbumin feeding. Uptake of a nonmetabolized macromolecular probe, 14C-polyethylene glycol-4000, increased less than two-fold when fed with aprotinin under the same conditions, indicating that the increased uptake of immunoreactive ovalbumin was not due to changes in intestinal permeability. The results show that inhibition of luminal proteolysis caused significant increases in the serum concentration of immunoreactive ovalbumin, indicating that acute inhibition of luminal proteases permits larger quantities of relatively intact protein to interact with mucosal absorptive surfaces. These results support the hypothesis that pancreatic proteases modulate antigen absorption from the lumen in adult animals.

Renal oncocytoma and granular renal cell carcinoma. A comparative clinicopathologic and DNA flow cytometric study

Twenty-three renal oncocytomas and 18 granular renal cell carcinomas (GRCC) were comparatively studied clinicopathologically and by DNA flow cytometry to delineate their differences. Of the patients with renal oncocytomas, 15 were men and 8 were women, and their ages ranged from 42 to 81 years (mean, 64 years). The gross appearance of renal oncocytomas was characteristically homogeneous tan-brown, with variable scarring, without areas of large hemorrhage, and with no apparent necrosis. Twenty-two renal oncocytomas were confined within the kidney (Robson stage I) and one tumor extended into the renal vein (stage IIIa). Twenty-two renal oncocytomas, including the stage IIIa tumor, manifested diploid DNA content and only one neoplasm showed a feature suggestive of near-diploid DNA aneuploidy. Of the 17 patients with renal oncocytomas who had adequate follow-up, none developed metastasis or died of disease. Of the patients with GRCC, 13 were men and 5 were women, and their ages ranged from 30 to 73 years (mean, 53 years). The gross appearance of GRCC was variegated, yellow to tan, and punctuated with geographic areas of necrosis. Eleven patients with GRCC were stage I, 4 were stage II, 2 were stage IIIa, and 1 patient had metastases at initial examination (stage IV). Seven GRCCs were DNA diploid, one was DNA tetraploid, and 10 tumors were DNA aneuploid. Twelve patients were alive with no evidence of disease (12 to 36 months; median, 26 months). All patients with DNA diploid neoplasm pursued benign clinical courses. One patient was alive with metastatic disease and two patients developed metastases and died of their disease; all three patients had DNA aneuploid tumors. Two patients died of other causes and one patient was lost to follow-up. Our data indicate that renal oncocytoma is a distinct clinicopathologic disease with characteristic gross, histologic, DNA flow cytometric, and biologic features that are different from GRCC.

Selective vulnerability of dentate hilar neurons following traumatic brain injury: a potential mechanistic link between head trauma and disorders of the hippocampus

Despite intensive study, the neurobiological basis of epilepsy and persistent memory impairment following traumatic head injury remains unknown. Since abnormalities of the hippocampus are known to be associated with temporal lobe seizures and memory dysfunction, we investigated the effects of experimental traumatic brain injury on hippocampal structure and function in the rat. Using a model of fluid-percussion injury, we have discovered that neurons of the dentate hilus are vulnerable to a brief, unilateral impact to the extradural surface of the brain. One week after trauma, there was a dramatic reduction in hilar neurons ipsilateral to the impact, and a milder but significant decrease in neurons on the contralateral side as well. This neuronal loss was highly selective since adjacent dentate granule and pyramidal neurons appeared relatively unaffected. Immunocytochemistry showed that the hilar cell loss included a loss of somatostatin-immunoreactive neurons, and degeneration stains provided evidence that irreversible hilar injury occurred within 4 hr of impact. To assess the functional effects of the hilar damage, dentate granule cell field potentials were measured in response to perforant path stimulation. This revealed abnormal dentate granule cell hyperexcitability at 2.0 Hz stimulation in many of the injured animals. The presence of abnormal hyperexcitability correlated with the loss of hilar neurons. Thus, a momentary impact to the surface of the brain can cause selective, bilateral hippocampal injury with associated abnormalities in dentate gyrus physiology. Furthermore, the pattern of cell loss is similar to that observed in some patients with temporal lobe epilepsy.(ABSTRACT TRUNCATED AT 250 WORDS)

Cost-effectiveness of a back school intervention for municipal employees

This study investigated the effect of a back school rehabilitation program on lost work time, lost time cost, medical cost, and number of injuries in municipal employees. Seventy back-injured workers who participated in a 6-week back school were compared on the dependent variables with 70 randomly selected back-injured city employees who had not participated in a back school. Back school participants demonstrated a significant decrease on all dependent variables. Back school participants had significantly fewer injuries in the 6-month postintervention period. No statistically significant differences were found between groups on the time and cost variables. Actual dollars saved in lost time and medical costs between groups was of practical value to the city. Study findings offer support for the back school as a cost-effective measure.

Tissue clay: an experimental model to evaluate its performance in soft tissue augmentation and its biologic fate

Tissue clay (a mixture of autologous whole blood and microfibrillar collagen--Avitene) has been proposed as a medium for reconstruction in cosmetic and reconstructive deformities of the face. Its performance and biologic fate has not been evaluated experimentally. The current study employs a model using the rabbit pinna to determine, histologically, the fate of a tissue clay implant.