Bone anchor mesh fixation for complex laparoscopic ventral hernia repair.

BACKGROUND: Laparoscopic ventral hernia repair (LVHR) has gained wide acceptance by both surgeons and patients, but hernias that approach a bony prominence are more complex due to the difficulty of proper fixation. This study was conducted to evaluate the use of bone anchor mesh fixation for complex LVHR. METHODS: A prospective study of patients having complex LVHR with bone anchors was conducted using patients from 2 academic institutions between July 2003 and December 2007. Patient demographic data, characteristics of the hernia, operative details, and postoperative outcomes were recorded. RESULTS: A total of 30 patients who had LVHR using bone anchors were evaluated (20 women, 10 men; mean age 60.9 years, range 41-83 years). In all, 17 suprapubic and 13 lateral hernias were included, requiring a mean of 2.8 and 3.2 bone anchors, respectively. The average hernia defect was 263 cm(2) (range 35-690 cm(2)), and the average mesh size was 663 cm(2) (range 255-1360 cm(2)). Mean operative time was 218 minutes (range 98-420 minutes), with an estimated blood loss of 46 mL (range 10-100 mL). The average length of stay was 5.2 days (range 1-26 days). Seven patients (23.3%) developed postoperative complications, and 1 patient in this study died (mortality 3.3%). During follow-up of 13.2 months (range 1-26 months), 2 patients (6.7%) developed a recurrent hernia. CONCLUSIONS: Bone anchors can be used successfully in the laparoscopic repair of complex ventral hernias, particularly with suprapubic and lateral hernias that approach a bony prominence. The complication rate is acceptable, with a short hospital stay and low recurrence rate.

Thermostable (SULT1A1) and thermolabile (SULT1A3) phenol sulfotransferases in human osteosarcoma and osteoblast cells.

Sulfate conjugation is an important pathway in the metabolism of many drugs, xenobiotic compounds, and hormones. Sulfotransferases (SULTs) catalyze these reactions and have been detected and characterized in various human tissues including the liver and small intestine. Substrates for SULTs that include estrogen and thyroid hormones have well-established roles affecting skeletal integrity and disease processes. We performed the following studies to determine the presence of SULTs in human osteoblast-like cells, and to compare their characteristics to SULTs expressed in other human tissues. Four osteosarcoma cell lines (SaOS-2, U2-OS, PR, and HOS-TE85) were screened for the presence of four different SULT activities. Predominant activities were found for SULT1A1 in SaOS-2 cells, and SULT-1A3 in HOS-TE85 cells. Several biochemical properties of each enzyme that included apparent K(m) values, thermal stabilities, and responses to the inhibitors 2,6-dichloro-4-nitrophenol and NaCl were used to further characterize the SULT activities. High-performance liquid chromatography (HPLC) of the reaction products confirmed the known products of SULT1A1 and SULT1A3. When the mature human osteoblast HOB-03-CE6 cell line was tested for activity alone, the predominant activity was SULT1A3, with minimal SULT1A1. The results indicate that SULT1A1 and SULT1A3 are present in human osteosarcoma and mature osteoblast cell lines, and that the characteristics of the osteosarcoma cell SULTs are similar to those expressed in other human tissues. SULTs may have regulatory roles in the deactivation of thyroid hormones or estrogenic compounds in bone, and thus may affect hormone action and bone responses in the human skeleton.

Dietary supplementation with secoisolariciresinol diglycoside (SDG) reduces experimental metastasis of melanoma cells in mice.

We investigated the effect of dietary supplementation with secoisolariciresinol diglycoside (SDG), a lignan precursor isolated from flaxseed, on experimental metastasis of B16BL6 murine melanoma cells in C57BL/6 mice. Four diets were compared: a basal diet (control group) and the basal diet supplemented with SDG at 73, 147 or 293 micromol/kg (equivalent to SDG provided in the 2.5, 5 or 10% flaxseed diet). Mice were fed the diet for 2 weeks before and after an intravenous injection of 0.6 x 10(5) tumor cells. At necropsy, the number and size of tumors that formed in the lungs were determined. The median number of tumors in the control group was 62, and those in the SDG-supplemented groups were 38, 36 and 29, respectively. The last was significantly different from the control (P < 0.01). Dietary supplementation with SDG at 73, 147 and 293 micromol/kg also decreased tumor size (tumor cross-sectional area and volume) in a dose-dependent manner compared with the control values. These results show that SDG reduced pulmonary metastasis of melanoma cells and inhibited the growth of metastatic tumors that formed in the lungs. It is concluded that dietary supplementation with SDG reduces experimental metastasis of melanoma cells in mice.

Dietary supplementation of selenomethionine reduces metastasis of melanoma cells in mice.

The present study investigated the effect of dietary supplementation of selenomethionine on pulmonary metastasis of B16BL6 murine melanoma cells in C57BL/6 mice. Mice were assigned to four groups of 15 each. They were fed a basal AIN93G diet and the basal diet supplemented with 2.5 ppm or 5 ppm selenium as selenomethionine or with 2.5 ppm selenium as selenite for two weeks before and after the intravenous injection of 0.5 x 10(5) tumor cells. At necropsy, the number and size of tumors that developed in the lungs were determined. The number of mice that had > or = 11 tumors was 13, 8, 8, and 6 (p < 0.02 compared with the control), and the median number of lung tumors was 64, 14, 12 (p < 0.05 compared with the control), and 8 (p < 0.01 compared with the control) in the control group and the groups with 2.5 ppm and 5 ppm selenium as selenomethionine and 2.5 ppm selenium as selenite. Dietary supplementation of selenomethionine decreased tumor cross-sectional area and tumor volume compared with the controls. At the same dietary level, selenite had a greater inhibitory effect on tumor size than selenomethionine. These results demonstrate that dietary supplementation of selenomethionine reduced experimental metastasis of melanoma cells in mice and inhibited the growth of metastatic tumors that formed in the lungs. It is concluded that selenomethionine is an active form of selenium that reduces experimental metastasis.

Soybean isoflavones reduce experimental metastasis in mice.

We investigated the effect of dietary supplementation with isoflavones on pulmonary metastasis of B16BL6 murine melanoma cells in C57BL/6 mice. Mice were fed a basal AIN-93G diet or the basal diet supplemented with the isoflavones genistein and daidzein at 113 micromol/kg, 225 micromol/kg, 450 micromol/kg, or 900 micromol/kg for 2 wk before and after the intravenous injection of 0.5 x 10(5) melanoma cells. At necropsy, the number and size of tumors that formed in the lungs were determined. The number of mice that had >15 lung tumors was 17 in the control group, and 16, 15, 13, and 10 in the groups fed isoflavones at 113 micromol/kg, 225 micromol/kg, 450 micromol/kg and 900 micromol/kg, respectively. The latter two were significantly different from the control (P

Time course of osteoblast appearance after in vivo mechanical loading.

The time course of the bone cellular response to mechanical loading is important in the design of optimal exercise prescriptions. This study examined the time course of periosteal cellular changes in the rat tibia following a single exposure of mechanical loading in four-point bending. The right tibiae of adult female Sprague Dawley rats (n = 48, 346 +/- 29 g) were loaded at 40 N (2000 mu epsilon) for 36 cycles at 2 Hz. Right loaded (L) and left nonloaded (NL) tibiae were collected on days 1, 2, 3, 4, 6, and 9 after loading. Cross sections from the loaded region were examined for periosteal differences in bone lining cell surface length, osteoblast surface length, and both alkaline phosphatase-positive cell surface length and width in the cellular layer. A single loading session increased osteoblast surface length as early as day 2, with a peak in expression on day 3. Nine days after a single loading session osteoblast surface length was not different from nonloaded control levels. Alkaline phosphatase width in the cellular periosteum was elevated by day 2 and remained elevated through day 9. This study shows the transient increase in osteoblast surface following a single loading session. It provides fundamental information regarding the timing of osteoblast appearance and the longevity of the response following mechanical stimulation.

Dietary flaxseed supplementation and experimental metastasis of melanoma cells in mice.

The present study investigated the effect of dietary supplementation of flaxseed, the richest source of lignans, on experimental metastasis of B16BL6 murine melanoma cells in C57BL/6 mice. Mice were fed a basal diet or the basal diet supplemented with 2.5, 5 or 10% flaxseed for 2 weeks before and after the intravenous injection of 0.75 x 10(5) melanoma cells. At necropsy, the number of tumors that developed in the lungs was counted, the cross-sectional area of tumors was measured and the volumes of tumors were calculated. The median number of tumors in mice fed the 2.5, 5 and 10% flaxseed-supplemented diets was 32, 54 and 63% lower than that of the controls, respectively. The addition of flaxseed to the diet also caused a dose-dependent decrease in the tumor cross-sectional area and the tumor volume. These results provide the first experimental evidence that flaxseed reduces metastasis and inhibits the growth of the metastatic secondary tumors in animals. It is concluded that flaxseed may be a useful nutritional adjuvant to prevent metastasis in cancer patients.

Prostaglandin E2 increases the skeletal response to mechanical loading.

The study tested the influence of prostaglandin E2 (PGE2) on the skeletal response to increased in vivo mechanical loading through a four-point bending device. One hundred and twenty Sprague-Dawley female rats (6 months old, 354 +/- 34 g) were divided into 12 groups to accommodate all possible combinations of doses of loads (25, 30, or 35 N) and PGE2 (0, 0.1, 0.3, or 1 mg/kg). Rats received subcutaneous injections of PGE2 daily and in vivo loading of the right tibia every Monday, Wednesday, and Friday for four weeks. Histomorphometric analysis of the periosteal and endocortical surfaces following in vivo dual fluorochrome labeling was performed on both the loaded region of the right tibial diaphysis and a similar region of the left tibial diaphysis. Without PGE2, the threshold for loading to stimulate bone formation was 30 N (peak strain 1360 mu epsilon) at the periosteal surface and 25 N (peak strain 580 mu epsilon) at the endocortical surface. Without loading, the minimum dose of PGE2 to stimulate bone formation at all surfaces was 1 mg/kg/day. When 1 mg/kg/day PGE2 was combined with the minimum effective load, an additive effect of PGE2 and loading on bone formation was observed at the endocortical surface, but a synergistic effect was noted at the periosteal surface. No combined effect of ineffective doses of loading and PGE2 was found. A synergistic effect at peak strains of approximately 1625 mu epsilon on the periosteal surface could suggest either the involvement of locally produced growth factors or autoregulation of endogenous synthesis of PGE2 by exogenously administered PGE2.

Effect of dietary supplementation of selenite on pulmonary metastasis of melanoma cells in mice.

The purpose of the present study was to determine the effect of dietary supplementation of selenite on experimental pulmonary metastasis of B16BL6 murine melanoma cells in C57BL/6 mice by means of an intravenous injection model. Three groups of mice were fed a basal AIN-93G diet containing 0.1 ppm selenium (control group) or the basal diet supplemented with 2 or 4 ppm selenium as selenite (experimental groups). Mice were fed the diet for two weeks before and after the intravenous injection of 0.75 x 10(5) viable tumor cells. At necropsy the number of tumors that developed in the lungs and their cross-sectional area were determined, and tumor volume was calculated. In the control group, 12 of the 15 mice had > or = 1 lung tumors. In contrast, only 4 of the 15 mice in each of the selenite-supplemented groups had > or = 11 tumors. The incidence of metastasis in mice fed the control and the 2- and 4-ppm selenium diets was 93%, 73%, and 53%, respectively. The median number of lung tumors was 53, 1, and 1 in mice fed the basal and the 2- and 4-ppm selenium diets, respectively. Tumor cross-sectional area and tumor volume were significantly decreased in selenite-supplemented groups. These results demonstrate that dietary supplementation of selenite reduced pulmonary metastasis of B16BL6 melanoma cells in C57BL/6 mice and also inhibited the growth of the metastatic tumors that developed in the lungs. It is concluded that selenite may be a useful adjuvant to prevent metastatic diseases in cancer patients.

Effect of dietary supplementation of soybeans on experimental metastasis of melanoma cells in mice.

The purpose of the present study was to determine the effect of dietary supplementation of soybean protein isolate (SPI) on experimental metastasis of B16BL6 murine melanoma cells in C57BL/6 mice. Four groups of mice were fed a basal AIN-93G diet or the basal diet supplemented with 10%, 15%, or 20% SPI for two weeks before and after the intravenous injection of 0.75 x 10(5) cells. At necropsy the number of tumors that developed in the lungs and their cross-sectional area were determined, and tumor volume was calculated. In the control group, 12 of the 15 mice had > or = 11 lung tumors. In contrast, only 3 or 4 of the 15 mice fed the SPI diets had > or = 11 tumors. The incidence of metastasis was 93%, 60%, 53%, and 53%, and the median number of lung tumors was 53, 2, 2, and 1 in mice fed the basal, 10%, 15%, and 20% SPI diets, respectively. Tumor cross-sectional area and tumor volume of SPI groups were significantly decreased compared with the controls. These results demonstrate that dietary supplementation of SPI reduced pulmonary metastasis of B16BL6 cells in mice and inhibited the growth of tumors that developed in the lungs. It is concluded that soybeans may be a useful adjuvant for preventing metastatic diseases in cancer patients.

Immunoassay for detection of antibodies to simian immunodeficiency virus and human immunodeficiency virus in serum.

We developed a simple, inexpensive, rapid assay for the detection of antibodies to simian immunodeficiency virus (SIV) and human immunodeficiency virus type 1 (HIV-1) in serum. The immunoassay uses inactivated SIV and HIV-1 gp41 transmembrane recombinant protein as antigenic adsorbents on a nitrocellulose filter membrane. Diluted serum, with the addition of Protein-A-Gold, is gravity-filtered through the filter membrane, blocked, and buffer-washed. Antibodies to HIV or SIV or both in serum bind to the appropriate antigen, and the resulting antigen-antibody complex reacts with Protein-A-Gold to produce a readable pink color. Field evaluation of the test on 30 human and 70 nonhuman primate sera in Kenya and Zaire indicated that the test had at least 93 and 90% correlation with Western blot sensitivity and specificity respectively. Prior refrigeration of the test kit and incubation of sera during testing were not required. This result indicates that the test may be a rapid, economical, and simple test for detecting HIV, SIV, or both in serum. This immunoassay can be useful for carrying out HIV and SIV serosurveys in countries with limited or no laboratory facilities.

Functional characterization of prostaglandin E2 inducible osteogenic colony forming units in cultures of cells isolated from the neonatal rat calvarium.

Prostaglandin E2 (PGE2) increases the number of mineralized nodules that form in cultures of rat calvarial (RC) cells. The purpose of our study was to characterize PGE2-inducible osteogenic colony forming units (CFU-Os) by determining their number, the cell populations from which they were released, their specific responsive period to PGE2, and their proliferating and differentiating characteristics under the stimulation of PGE2. Limiting dilution analysis was used to determine the number of PGE2-inducible CFU-Os. Sequential digestion of intact rat parietal bones with collagenase isolated 5 subpopulations of RC cells that were used to estimate the cell populations where PGE2-inducible CFU-Os resided. The responsive period of PGE2-inducible CFU-Os to PGE2 was evaluated by treating cultures of mixed RC cells for all possible combinations of days 1-10, 11-20, and 21-30. PGE2 effects on proliferation and differentiation of CFU-Os were evaluated by comparing the DNA synthesis and AP activity in subpopulations I and IV on days 3, 6, and 9. Results showed: (1) PGE2-inducible CFU-Os represent 0.27% of cells in the mixed RC population, (2) the majority of determined and PGE2-inducible CFU-Os were found in the subpopulations released during the 60-100 min digestion periods, (3) the response of PGE2-inducible CFU-Os is limited to the first 10 days of culture, and (4) PGE2-stimulated nodule formation is associated with an early increase in DNA synthesis and a sustained increase in alkaline phosphatase activity. We conclude that, functionally, PGE2-inducible CFU-Os are slowly proliferating AP negative cells primarily found in the subpopulations III-V. PGE2 stimulates them to proliferate and become AP+, and function as determined CFU-Os to form mineralized nodules in vitro.

Sexual transmission of simian T-lymphotropic virus type I: a model of human T-lymphotropic virus type I infection.

Simian T-lymphotropic virus type-I (STLV-I) seronegative females placed together with seropositive males for breeding purposes were followed from 1984-1990 to determined seroconversion rates by enzyme immunoassay and western immunoblot analysis. Two of 26 females and 1 of 4 males previously negative for antibodies to STLV-I seroconverted during the study period. Statistical analysis of sexual encounters indicated that the probability of a seronegative female testing positive for STLV-I after a sexual encounter with a seropositive male is less than 4%. These data indicate that even though sexual contact is important in the transmission of STLV-I, it may not be an efficient mode of viral infection. These data also suggest that female-to-male transmission of STLV-I occurs, as recently reported for human T-lymphotropic virus type-I (HTLV-I) infection. These results are important because HTLV-I and STLV-I share many features in common including routes of viral transmission. In addition, the difficulty of clearly quantitating the risk of sexual transmission in humans makes the primate animal model a valuable alternative to study the human infection.

Passive immunization of macaques against SIV infection.

Passive immunization with plasma from an inactivated-whole SIVmac vaccine protected monkey conferred complete or partial protection to rhesus macaques challenged intravenously 4 or 18 hours later with 10 AID50 of homologous cell-free virus. In contrast, passive immunization with inactivated plasma or purified immunoglobulin (Ig) from SIVmac infected asymptomatic monkeys failed to protect any recipients similarly challenged and may have enhanced infection and accelerated disease. Administered 24 hours post challenge, anti-SIV Ig may also have enhanced the infection.

Plasminogen-dependent activation of latent transforming growth factor beta (TGF beta) by growing cultures of osteoblast-like cells.

Osteoblasts secrete transforming growth factor beta (TGF beta) as a biologically inert, latent complex that must be dissociated before the growth factor can exert its effects. We have examined the production and proteolytic activation of latent TGF beta (LTGF beta) by clonal UMR 106-01 rat osteosarcoma cells and neonatal mouse calvarial (MC) osteoblast-like cells in vitro. Synthetic bPTH-(1-34) increased the activity of tissue-type (tPA) and urokinase-type (uPA) plasminogen activators (PA) in cell lysates (CL) of UMR 106-01 cells. The concentration of active TGF beta in serum-free CM from cultures treated with bPTH-(1-34) and plasminogen was significantly greater than in CM from untreated controls and cultures treated with either bPTH-(1-34) or plasminogen alone. This effect occurred at concentrations of PTH-(1-34) that increased PA activity and was prevented by aprotinin, an inhibitor of plasmin activity. Treatment with bPTH-(1-34) had no effect on the concentration of TGF beta in acid-activated samples of CM. Functional consequences of proteolytically activated TGF beta was examined in primary cultures of neonatal MC osteoblast-like cells. Human platelet TGF beta 1 caused a dose-dependent increase in the migration of these cells in an in vitro wound healing assay. Cell migration was also stimulated in cultures treated with bPTH-(1-34) and plasminogen together. This effect was blocked by an anti-TGF beta 1 antibody. The results of these studies demonstrate that (1) LTGF beta secreted by osteoblasts in vitro is activated under conditions where the plasmin activity in the cultures is increased, and (2) the TGF beta generated by plasmin-mediated proteolysis is biologically active. We suggest that the local concentration of TGF beta in bone may be controlled by the osteoblast-associated plasminogen activator/plasmin system. Furthermore, since several calciotropic factors influence osteoblast PA activity, this system may have an important role in mediating their anabolic and/or catabolic effects.

NADPH-diaphorase-positive nerves and the role of nitric oxide in CGRP relaxation of uterine contraction.

We previously demonstrated calcitonin gene-related peptide (CGRP) immunoreactivity in sensory nerves in the rat uterus and that CGRP inhibits stimulated uterine contraction in vitro. The present study was undertaken to: 1) examine possible roles nitric oxide (NO) may have in the inhibitory action of CGRP on uterine contraction and 2) identify sites where NO may be synthesized. The relaxing effect of CGRP on SP-stimulated uterine contraction was established in vitro on uterine horns from diethylstilbestrol-treated rats. These experiments were repeated with or without an arginine analog [NG-monomethyl-L-arginine (L-NMMA)] that inhibits NO formation. The localization of the synthetic enzyme for NO production, NO synthase, was accomplished by histochemically staining for NADPH-diaphorase. Calcitonin gene-related peptide (10(-7) M) significantly reduced SP (10(-5) or 10(-6) M)-stimulated uterine contraction. The L-NMMA (10(-3) M) blocked the relaxing action of CGRP on SP-stimulated uterine contraction. The L-NMMA alone had no effect on SP-stimulated uterine contraction. NADPH-diaphorase-positive nerve fibers were located in the myometrium, endometrium, and adjacent to the vasculature. These data demonstrate that: 1) L-NMMA suppresses the relaxant effect of CGRP on myometrial activity and 2) NADPH-diaphorase (indicative of NO synthase) is localized in uterine nerve fibers. These data suggest that the inhibitory action of CGRP may be dependent on NO formation and that the enzyme necessary for NO production is present in nerves in areas optimal to affect myometrial activity.

Cranial neural crest cells synthesize and secrete a latent form of transforming growth factor beta that can be activated by neural crest cell proteolysis.

Transforming growth factor beta (TGF-beta) is an important regulator of cell growth and differentiation. TGF-beta is usually secreted in a latent form (i.e., not biologically active) that can be activated by limited exposure to low pH or specific proteolytic cleavage. In this study, we (1) assayed cranial neural crest (NC) cell-conditioned medium for the presence of active and latent TGF-beta, (2) determined whether TGF-beta was activated by NC-generated plasmin, and (3) examined whether active TGF-beta 1 regulates NC cell plasminogen activator activity. Results show that under serum-free conditions, essentially all of the TGF-beta secreted by NC cells is in a latent form. However, 24 hr after adding plasminogen to the cultures, active TGF-beta was detectable. Treatment of NC cells with active TGF-beta 1 significantly decreased NC cell plasminogen activator activity. These data suggest that NC cells secrete a latent form of TGF-beta that can be activated under conditions favoring the generation of local proteolytic activity and that levels of plasminogen activator activity may be autoregulated via an autocrine effect of this growth factor.

Plasminogen activator regulation in osteoblasts: parathyroid hormone inhibition of type-1 plasminogen activator inhibitor and its mRNA.

In order to determine the mechanism by which parathyroid hormone (PTH) stimulates plasminogen activator (PA) activity in rat osteoblasts, we investigated the effect of human PTH(1-34) [hPTH(1-34)] on the synthesis of mRNAs for tissue-type PA (tPA), urokinase-type PA (uPA), and PA inhibitor-1 (PAI-1), and on release of PA activity and PAI-1 protein in both normal rat calvarial osteoblasts and UMR 106-01 osteogenic sarcoma cells. hPTH(1-34) (0.25-25 nM) decreased PAI-1 mRNA and protein, and increased PA activity in both cell types in a dose-dependent manner with ED50 of about 1 nM for both responses. Forskolin and isobutylmethylxanthine also stimulated PA activity and decreased PAI-1 protein and mRNA in both cell types. hPTH(1-34) did not show any consistent effect on tPA and uPA mRNA in calvarial osteoblasts, but a modest (two-fold) increase of both mRNAs was observed in UMR 106-01 cells treated with 25 nM hPTH(1-34). However, when protein synthesis was inhibited with 100 microM cycloheximide, the increase of tPA and uPA mRNA by hPTH(1-34) was enhanced in UMR 106-01 cells and became evident in calvarial osteoblasts. Fibrin autography also revealed that hPTH(1-34) increases tPA and uPA activity, especially after cycloheximide treatment in UMR 106-01 cells. These results strongly suggest that PTH increases PA activity predominantly by decreasing PAI-1 protein production through a cyclic adenosine monophosphate (cAMP)-dependent mechanism in rat osteoblasts. The reduction of PAI-1 protein by PTH results in enhanced action of both tPA and uPA, and would contribute to the specific roles of these PAs in bone.

Transforming growth factor beta inhibits plasminogen activator (PA) activity and stimulates production of urokinase-type PA, PA inhibitor-1 mRNA, and protein in rat osteoblast-like cells.

Transforming growth factor beta (TGF beta) treatment of rat osteoblast-rich calvarial cells or of the clonal osteogenic sarcoma cells, UMR 106-01, resulted in dose-dependent inhibition of plasminogen activator (PA) activity, and increased production of 3.2 kb mRNA and protein for PA inhibitor -1 (PAI-1). Although tissue-type PA (tPA) protein was not measured, TGF beta did not influence production of mRNA for tPA. Production of 2.3 kb mRNA for urokinase-type PA (uPA) was also increased by TGF beta in a dose-dependent manner. The effects of TGF beta on synthesis of mRNA for PAI-1 and uPA were maintained when protein synthesis was inhibited, and were abolished by inhibition of RNA synthesis. Although uPA had not been detected previously as a product of rat osteoblasts, treatment of lysates of osteoblast-like cells with plasmin yielded a band of PA activity on reverse fibrin autography, corresponding to a low Mr form of uPA. Untreated conditioned media from normal osteoblasts or UMR 106-01 cells contained no significant TGF beta activity, but activity could be detected in acidified medium. Treatment of conditioned media with plasmin resulted in activation of approximately 50% of the TGF beta detectable in acidified media. The results identify several effects of TGF beta on the PA-PA inhibitor system in osteoblasts. Net regulation of tPA activity through the stimulatory actions of several calciotropic hormones and the promotion of PAI-1 formation by TGF beta could determine the amount of osteoblast-derived TGF beta activated locally in bone. Stimulation of osteoblast production of mRNA for uPA could reflect effects on the synthesis of sc-uPA, a precursor for the active form of the enzyme.