Evaluation of an Unloading Concept for Knee Osteoarthritis: A Pilot Study in a Small Patient Group.

Joint compressive forces have been identified as a risk factor for osteoarthritis disease progression. Therefore, unloader braces are a common treatment with the aim of relieving pain, but their effects are not clearly documented in the literature. A knee brace concept was tested with the aim of reducing joint loads and pain in knee osteoarthritis patients by applying an extension moment exclusively during the stance phase. The ideal effects were evaluated during gait based on musculoskeletal modeling of six patients, and experimental tests with a prototype brace were conducted on one patient. The effects were evaluated using electromyography measurements and musculoskeletal models to evaluate the muscle activation and knee compressive forces, respectively. The ideal brace simulations revealed a varying reduction of the first peak knee force between 3.5% and 33.8% across six patients whereas the second peak was unaffected. The prototype reduced the peak vasti muscle activation with 7.9% and musculoskeletal models showed a reduction of the first peak knee compressive force of up to 26.3%. However, the prototype brace increased the knee joint force impulse of up to 17.1% and no immediate pain reduction was observed. The reduction of the first peak knee compressive force, using a prototype on a single patient, indicates a promising effect from an applied knee extension moment for reducing knee joint loads during normal gait. However, further clinical experiments with this brace method are required to evaluate the long-term effects on both pain and disease progression in knee osteoarthritis patients.

Development and Functional Testing of an Unloading Concept for Knee Osteoarthritis Patients: A Pilot Study.

This paper presents a knee brace design that applies an extension moment to unload the muscles in stance phase during gait, and thereby the knee, as alternative to conventional valgus braces for knee osteoarthritis patients. The concept was tested on one healthy subject during normal gait with a prototype, which was designed to activate and deactivate in order to apply the extension moment in the stance phase only and hereby avoid any interference during the swing phase. Electromyography measurements and musculoskeletal models were used to evaluate the brace effects on muscle activation and knee compressive forces, respectively. Simulations predicted an ideal reduction of up to 36%, whereas experimental tests revealed a reduction of up to 24% with the current prototype. The prototype brace also reduced the knee joint force impulse up to 9% and electromyography (EMG) peak signal of the vasti muscles with up to 19%. Due to these reductions on a healthy subject, this bracing approach seems promising for reducing knee loads during normal gait. However, further clinical experiments on knee osteoarthritis patients are required to evaluate the effect on both pain and disease progression.

Resistance training for explosive and maximal strength: effects on early and late rate of force development.

The aim of the present study was to verify whether strength training designed to improve explosive and maximal strength would influence rate of force development (RFD). Nine men participated in a 6-week knee extensors resistance training program and 9 matched subjects participated as controls. Throughout the training sessions, subjects were instructed to perform isometric knee extension as fast and forcefully as possible, achieving at least 90% maximal voluntary contraction as quickly as possible, hold it for 5 s, and relax. Fifteen seconds separated each repetition (6-10), and 2 min separated each set (3). Pre- and post-training measurements were maximal isometric knee extensor (MVC), RFD, and RFD relative to MVC (i.e., %MVC·s(-1)) in different time-epochs varying from 10 to 250 ms from the contraction onset. The MVC (Nm) increased by 19% (275.8 ± 64.9 vs. 329.8 ± 60.4, p < 0.001) after training. In addition, RFD (Nm·s(-1)) increased by 22-28% at time epochs up to 20 ms from the contraction onset (0-10 ms = 1679. 1 ± 597.1 vs. 2159.2 ± 475.2, p < 0.001; 0-20 ms = 1958.79 ± 640.3 vs. 2398.4 ± 479.6, p < 0. 01), with no changes verified in later time epochs. However, no training effects on RFD were found for the training group when RFD was normalized to MVC. No changes were found in the control group. In conclusion, very early and late RFD responded differently to a short period of resistance training for explosive and maximal strength. This time-specific RFD adaptation highlight that resistance training programs should consider the specific neuromuscular demands of each sport. Key PointsThe time-specific RFD adaptation evoked by resistance training highlight that the method of analyzing RFD is essential for the interpretation of results.Confirming previous data, maximal contractile RFD and maximal force can be differently influenced by resistance training. Thus, the resistance training programs should consider the specific neuromuscular demands of each sport.In active non-strength trained individuals, a short-term resistance training program designed to increase both explosive and maximal strength seems to reduce the adaptive response (i.e. increased RFDMAX) evoked by training with an intended ballistic effort (i.e. high-RFD contraction).

Regulation of a Rho-associated kinase expression during the corneal epithelial cell cycle.

PURPOSE: It has been recognized that an increased expression of the Rho-associated kinase (ROCK-I), a downstream target of Rho (a Ras-related small guanosine triphosphatase [GTPase]), is associated with limbal-to-corneal epithelial transition. The purpose of the present study was to determine whether the expression of ROCK-I is regulated during the cell cycle of corneal epithelial cells. METHODS: Rabbit corneal epithelial cells in culture were subjected to different culture conditions to enrich them in the G0, G1, and S phases of the cell cycle. Indirect immunofluorescence staining and western blot techniques were used for analyzing the changes in the relative intracellular concentrations of ROCK-I. Northern blot analysis of the isolated cellular RNA was performed to estimate the relative concentrations of ROCK-I mRNA. RESULTS: Serum deprivation did not cause all the corneal epithelial cells in culture to be arrested in the G0 phase of the cell cycle. However, the cells could be arrested in G0 by treating them with culture medium supplemented with transforming growth factor (TGF)-beta1. The relative concentration of ROCK-I in the G0-arrested cells was higher than in the corresponding control untreated cultures. G0-arrested cells were induced to enter G1, followed by the S phase of the cell cycle, by refeeding them with the medium devoid of TGF-beta1. The total intracellular concentration of ROCK-I significantly decreased during the G1 phase of the cell cycle and increased again during the S phase. The decrease in intracellular ROCK-I during the G1 phase was confirmed by arresting the cells in G1 with isoleucine deprivation and thymidine-mimosine treatments. ROCK-I mRNA levels were also found to be decreased during the G1 phase of the cell cycle. CONCLUSIONS: The levels of ROCK-I in the corneal epithelial cells were significantly lower in the G1 phase than those in the S and G0 phases of the cell cycle. Therefore, a Rho signaling pathway(s) involving ROCK-I may be regulated during the corneal epithelial cell cycle. The downregulation of ROCK-I during the G1 phase, at least in part, is due to the decreased levels of its mRNA. Based on these findings, ROCK-I may have a role in the progression of the cell cycle in the corneal epithelial cells as they migrate centripetally from the limbal to the corneal surface.

Ethanol improves adenovirus-mediated gene transfer and expression to the bladder epithelium of rodents.

OBJECTIVES: Replication deficient adenoviral vectors (rAds) are used as gene delivery systems that can efficiently transduce a variety of tissues and may be appropriate vectors to develop gene therapeutics for many urologic applications. However, the bladder epithelium has been shown to be highly resistant to transgene expression after intracystic administration. A potential explanation for this low gene transfer efficiency may be the protective structure of the urothelium. Since this protective barrier can be disrupted by organic solvents, we assessed whether ethanol co-administration can enhance adenovirus-mediated transgene expression. METHODS: Normal and bladder tumor-bearing rats received a single intracystic administration of rAd encoding beta-galactosidase (rAd-beta gal) or p53 (rAd-p53). rAd was administered in a saline solution or in solutions with increasing concentrations of ethanol. Transgene expression was evaluated in the bladder tissues. RESULTS: A dramatic increase in urothelial beta-galactosidase transgene expression was achieved by rAd-beta gal administered in a 22% ethanol solution. Transgene expression was enhanced in normal urothelium and in superficial bladder tumors. p53 transgene expression was similarly enhanced. CONCLUSIONS: Co-administration of 22% ethanol enhanced local rAd-mediated transgene expression in the normal and neoplastic bladder epithelium in rodents. Improvement of rAd-mediated transgene expression is progress toward local gene delivery to the urothelium and may enable local gene therapy for superficial bladder cancer or other bladder diseases.

Role of physician assistants in dialysis units and nephrology.

We surveyed physician assistants who work in nephrology to report their experience level, primary employer, salary, job responsibilities, and job satisfaction. Additional data were obtained from the Nephrology Manpower Study. The 67 responding physician assistants of 97 surveyed have 10.8 +/- 6.5 years (mean +/- standard deviation) total experience (6.2 +/- 5.0 years in nephrology). Typically, nephrologists (56.1%) or hospitals (30.3%) employ them. The majority (74%) earn $49,999 to $75,000; 79.1% work in outpatient units, 52.4% in inpatient units, 52.4% in hospitals, 43.3% in outpatient offices, and 23.9% in transplant units. In outpatient units, they manage 111 +/- 111 patients, mostly in free-standing (71.1%), for-profit (69.7%), corporately owned (87.3%) units in urban (80%) or suburban (18%) areas. Most (>85%) manage all dialysis- and nondialysis-related problems, including health maintenance; 84.3% are contacted first by staff, and 78% see patients more often than physicians. Of nephrologists who responded to the Manpower Study, 8.9% work with physician assistants and 20.7% work with nurse practitioners. Nephrologists in academic practice or private nephrology groups are more likely to use physician assistants (P < 0.05) and nurse practitioners (P < 0.005) than those in solo practice or multispecialty groups. Nephrologists with physician assistants (33.8 +/- 19.5 v 41.7 +/- 16.8 h/wk) or nurse practitioners (35.8 +/- 18.1 v 42.7 +/- 16.9 h/wk) tended to spend less time in direct patient care than those without physician extenders (P < 0.001). Nephrologists with renal fellows, however, spent the least time of all in direct patient care (30.0 +/- 15.9 v 47.3 +/- 14.9 h/wk; P < 0.001). Physician assistants can perform nearly all the medical tasks in dialysis units. They may offer one approach to providing effective and complete care for patients if nephrology manpower becomes limited.

p53 gene therapy in a rat model of hepatocellular carcinoma: intra-arterial delivery of a recombinant adenovirus.

p53 tumor suppressor gene therapy has been proposed for cancers characterized by inactivation of p53 function, and successful therapy will require efficient strategies for gene delivery. To maximize transgene expression in tumors, a clinical strategy has been proposed to treat neoplasms in the liver via hepatic artery administration of a recombinant adenovirus encoding wild-type p53 (rAd-p53). We have developed a syngeneic rat model using a p53mut hepatocellular carcinoma cell line (McA-RH7777) that results in multifocal liver tumor nodules to provide experimental support for this strategy. Treatment of McA-RH7777 cells with rAd-p53 in vitro resulted in efficient transgene expression, growth suppression, and apoptosis. Intrahepatic artery dosing with rAd-p53 or an adenovirus encoding beta-galactosidase (rAd-betagal) increased transgene expression in tumor tissue and decreased systemic exposure when compared with i.v. dosing. Daily hepatic artery dosing of rAd-p53 suppressed tumor growth when compared with untreated rats or animals treated with rAd-betagal. These data demonstrate the potential for arterial gene delivery to tumors using recombinant adenoviruses, and support continued investigation of rAd-p53 gene therapy for liver malignancies.

A Rho-associated protein kinase: differentially distributed in limbal and corneal epithelia.

PURPOSE: The authors have developed monoclonal antibodies (mAbs) to characterize the sequential biochemical changes in corneal epithelial cells after they differentiate from stem cells, located in the limbus, and migrate centripetally to follow the pathway of terminal differentiation. The purpose of this study was to identify a protein (recognized by mAb HE1/11F) with increased expression associated with the transition of the limbal epithelium to corneal epithelium. METHODS: The distribution and identification of the protein(s) were performed using an indirect immunohistochemical staining technique and a western blot analysis, respectively. A rabbit corneal epithelial cDNA library, constructed in the Uni-Zap XR vector, was screened with mAb HE1/11F to select cDNA clones expressing polypeptide(s) recognized by this mAb. Additional overlapping cDNA clones were obtained from a primer extension cDNA library to determine the sequence of the complete open reading frame encoding the protein recognized by mAb HE1/11F. RESULTS: Rabbit corneal epithelium exhibited strong immunostaining with mAb HE1/11F, however, the limbal epithelial cells stained weakly. HE1/11F recognized 160-kDa (HEBM1) and 100-kDa (HEBM2) polypeptides in the corneal epithelial extracts. The amino acid sequence of the protein deduced from the nucleotide sequence of the cDNA exhibited a close homology to that of a RhoA (Ras-related small GTPase)-associated serine-threonine kinase (ROCK-I or Rho-associated coiled-coil kinase). A 160-kDa RhoA-binding polypeptide with a molecular mass similar to that of HEBM1 and ROCK-I was detected in the corneal epithelial extracts. These findings strongly suggested that HEBM1 was rabbit ROCK-I. The identity of HEBM1 was further confirmed from the reactivity of mAb HE1/11F with ROCK-I immunoprecipitated from rabbit corneal epithelial extracts using anti-ROCK-I antibodies. CONCLUSIONS: The increased expression of a protein identified as ROCK-I from cDNA analyses is associated with rabbit corneal epithelial differentiation and transition from the limbal to corneal surface. Therefore, a RhoA signaling pathway is likely to be associated with corneal epithelial differentiation (maturation). A close homology among the cDNA sequences of rabbit, mouse, rat, and human ROCK-I indicates that this RhoA-associated kinase is a well-conserved protein.

Adenovirus-mediated p53 gene transfer suppresses growth of human glioblastoma cells in vitro and in vivo.

Alterations in the p53 tumor-suppressor gene occur in 35-60% of human glioblastomas, and re-introduction of p53 can suppress neoplastic growth. To evaluate the potential for p53 gene therapy of glioblastoma, we have analyzed the response of human glioblastoma cell lines in vitro and in vivo to experimental therapy with replication-deficient recombinant adenoviruses encoding wild-type p53 (rAd-p53). Western blot analyses showed high-level expression of p53 protein after treatment with rAd-p53, and transgene expression was dependent on promoter strength. A p53-specific dose-dependent inhibition of in vitro cellular proliferation was observed in 5 of 6 cell lines, and growth inhibition corresponded to adenovirus-mediated gene transfer and expression. p53-specific cell death was quantitated by release of the lactate dehydrogenase enzyme. Fragmentation of DNA into nucleosomal oligomers and the occurrence of a hypodiploid cell population detected by flow cytometry provided evidence for apoptosis. Studies in nude mice demonstrated that ex vivo infection with rAd-p53 suppressed the tumorigenic potential of human glioblastoma cells. Furthermore, direct injection of rAd-p53 into established s.c. xenografts inhibited tumor growth. Our observations suggest that re-introduction of wild-type p53 may have potential clinical utility for gene therapy of glioblastoma.

Photodynamic therapy of rat endometrium sensitized with tin ethyl etiopurpurin.

STUDY OBJECTIVE: To evaluate endometrial ablation in the rat using photodynamic therapy and the photosensitizer tin ethyl etiopurpurin (SnET2). DESIGN: Laboratory research. SETTING: A pharmaceutical and device manufacturing company. MATERIALS: Forty-five healthy female rats (age 8-10 wks). INTERVENTIONS: Groups of three to five rats were given SnET2 by either intrauterine or intravenous administration. Light treatment was given at either 3 or 24 hours after SnET2 administration at a light dose of 75, 150, or 200 J/cm. MEASUREMENTS AND MAIN RESULTS: A fluorescence detection system was employed to determine relative drug uptake of SnET2 into uterine tissue. The highest levels of SnET2 were detected at 3 hours. After light treatment, responses of uterine tissues were evaluated histologically. The best endometrial ablation was seen when SnET2 was given by intrauterine administration with light treatment at 150 J/cm 24 hours later. A consistent transmural response was seen with this route of administration at 200 J/cm. Intravenous SnET2 gave inconsistent responses. In light-only controls, all light doses caused no tissue response. The depth of necrosis in tissues treated with photodynamic therapy were light-dose dependent. CONCLUSION: With either route of SnET2 administration, drug uptake was confirmed and a light-dose-dependent response in the walls of rat uterine horns was demonstrated.

Adenoviral-mediated p53 tumor suppressor gene therapy of human ovarian carcinoma.

Mutations of p53 gene are reported in 50-60% of human cancers and reintroduction of wild-type p53 can suppress cell proliferation. In this study, replication deficient recombinant adenovirus encoding wild-type p53 (ACN53) under the control of the human cytomegalovirus (CMV) promoter was constructed. A specific incorporation of the p53 gene with ACN53 reduced 3 (deleted p53 gene) cells was observed. ACN53 reduced the colony-forming ability of SK-OV-3 cells 72-216 h after single infection. A highly aggressive ovarian xenograft model was established in which animals die between 25-45 days. A localization study with the adenovirus-containing beta galactosidase reporter gene showed effective gene transfer in the tumor tissues. Ex vivo treatment of SK-OV-3 cells with ACN53 followed by injection into nude mice, increased the survival of the p53 treated mice by more than 50% compared with control animals. Gene therapy with ACN53 in intraperitoneal model of SK-OV-3 cells in two independent experiments revealed that there were some long-term survivors in the group of mice [2/5 (66 and 120 days) and [2/8 (166 and 423 days)] treated with ACN53. These findings demonstrate the potential of the p53 tumor suppressor gene therapy in human ovarian carcinoma.

Purification and characterization of citrate synthase isoenzymes from Pseudomonas aeruginosa.

Two types of citrate synthase (CS) have been purified from Pseudomonas aeruginosa, a 'large' form (CSI) and a 'small' form (CSII). The M(r)s of the CSI and CSII isoenzymes were determined to be 240,000 +/- 16,000 (mean +/- S.E.M.) and 80,300 +/- 3800 respectively. Chemical cross-linking of the native enzymes with either dimethyl suberimidate or glutaraldehyde followed by electrophoretic analysis by SDS/PAGE showed that CSI is a hexamer and CSII is a dimer. SDS/PAGE showed that CSI and CSII each consist of a single subunit type, of M(r) 42,000 +/- 2000 and M(r) 36,500 +/- 2000 respectively. CSI and CSII were also shown to be distinct kinetically, immunologically and in terms of their regulatory properties. It is suggested that the CS isoenzymes are products of different structural genes.

Recombinant adenovirus-mediated gene transfer to genitourinary epithelium in vitro and in vivo.

Transitional cell carcinoma (TCC) of the bladder is associated with characterized lesions in dominant and recessive oncogenes. The understanding of the molecular basis of tumorigenesis in these instances makes possible the application of gene therapy strategies for TCC. In this regard, the ability to directly access the epithelium of the genitourinary (GU) tract via the urethra provides a practical means to implement these various gene therapy approaches. We thus explored vector strategies to accomplish direct in vivo transduction of GU epithelium. Initially, three human (HT 1197, HT 1376, T24) and one mouse (MBT-2) TCC cell lines were transduced using a recombinant adenoviral vector expressing the firefly luciferase reporter gene, rAd-CMV-Luc. In these studies, reporter gene expression was found to be significantly elevated above background for all four cell lines. Of note, the TCC cell lines HT 1197 and HT 1376 showed expression levels comparable with the cervical carcinoma cell line HeLa, a cell line previously shown to be highly susceptible to recombinant adenovirus-mediated gene transduction. An in vitro time course for T24 and MBT-2 using rAd-CMV-Luc showed peak expression 1 day after transduction for the T24 line and 3 days after transduction for the MBT-2 line, with detectable levels of expression persisting for at least 7 days. As a next step, human and mouse primary tissue deriving from the GU epithelium were transduced using rAd-CMV-Luc. In this assay, luciferase expression levels significantly above background were observed in both instances.(ABSTRACT TRUNCATED AT 250 WORDS)

Emerging multiply resistant enterococci among clinical isolates. II. Validation of the etest to recognize glycopeptide-resistant strains.

Accurate, quantitative susceptibility testing of the enterococci for glycopeptide (vancomycin and teicoplanin) activity has become very important to guide chemotherapy as a result of emerging resistance. Reference dilution tests using broth and agar are generally difficult to perform, or in some commercial forms have demonstrated interpretive error. An alternative method, the Etest has promise as a system with qualitative and quantitative accuracy. Nearly 2000 enterococci from 97 laboratories in the United States were tested using broth microdilution, disk diffusion, and Etest methods. The Etest quantitative accuracy (+/- 1 log2 dilution) compared to the broth microdilution minimum inhibitory concentration was 90.1% (teicoplanin) to 94.1% (vancomycin). The qualitative interpretive accuracy of the Etest ranged from 98.7% for vancomycin to 99.9% for teicoplanin (no false-susceptible errors). All three tests were in remarkable agreement, with < or = 0.8% maximal discord by interpretive category. The Etest appears to be an excellent alternative to reference and standardized methods for producing quantitative activity measurements of glycopeptide susceptibility or resistance.

Emerging multiply resistant enterococci among clinical isolates. I. Prevalence data from 97 medical center surveillance study in the United States. Enterococcus Study Group.

To assess the evolving problem of therapeutic drug resistances among enterococci, we organized a comprehensive national (United States) surveillance trial using 99 recruited microbiology laboratories in 48 of the 49 contiguous states or districts. All but two sites completed the protocol that generated information from nearly 2000 enterococci, usually isolated from blood cultures. All strains were speciated by the same method (API 20S) and were susceptibility tested by three methods (broth microdilution, disk diffusion, and Etest) against ampicillin, penicillin, vancomycin, teicoplanin, gentamicin, and streptomycin. Strains resistant to a glycopeptide or penicillin, or possessing high-level aminoglycoside resistance were referred to the monitor's laboratory for validation and additional susceptibility testing against other alternative antimicrobial agents. The most common species were Enterococcus faecalis and Enterococcus faecium. However, antimicrobial resistance occurred most often among the E. faecium isolates. Twenty-three percent of participant centers (22 sites) reported 87 vancomycin-resistant isolates, which accounts for 4.4% of the isolates evaluated. A recent audit (March 1994) of the laboratories not reporting vancomycin resistance during the study interval (October-December 1992) revealed that 61% of sites have now recognized these strains, a threefold increase in 12-15 months. Teicoplanin remained active against 28% (Van B phenotype) of vancomycin-resistant enterococci (10 E. faecalis, 13 E. faecium, and one Enterococcus spp.). Ampicillin-resistant beta-lactamase-positive strains were found only at one medical center (two strains, 0.2% of referred or validated strains); however, ampicillin-resistant strains represented 12% of all enterococcal, but nearly 60% of E. faecium strains.(ABSTRACT TRUNCATED AT 250 WORDS)

Comparison of two second-generation anti-hepatitis C virus ELISA on 21431 US blood donor samples.

We have compared two different second-generation (2.0) enzyme-linked immunosorbent assays (ELISA) for the presence of antibodies to hepatitis C virus (anti-HCV) in blood from volunteer, unpaid donors. At two separate blood centres, a total of 21,431 donor samples were tested with Abbott Anti-HCV 2.0 ELISA and Ortho Anti-HCV 2.0 ELISA. Samples found to be repeatedly reactive were tested by supplemental/investigational assays. MATRIX HCV (Abbott) and anti-HCV RIBA II (Ortho/Chiron), to 'confirm' the presence of anti-HCV. Discordant ELISA samples were additionally tested by the polymerase chain reaction (PCR) for the presence of HCV RNA. The Abbott anti-HCV assay had a repeatedly reactive rate of 0.59% (127/21,431) and the Ortho anti-HCV assay 0.51% (110/21,431). Overall agreement between assays was 99.76%, 72/127 (56.7%) of Abbott repeatedly reactive samples confirmed on MATRIX and 61/127 (48.0%) on RIBAII; 70/110 (63.6%) of Ortho repeatedly reactivate samples confirmed on MATRIX and 61/110 (55.5%) on RIBA II. Discordant ELISA samples tested by PCR yielded negative results. Hence the two ELISA had equal sensitivity, as defined by detection of true positive samples; the slightly lower specificity of the Abbott Anti-HCV 2.0 ELISA may be owing to culling of donors with a false positive test by Ortho's Anti-HCV 1.0 and 2.0 ELISA tests (the routine tests in place at each blood centre). A sample found to be repeatedly reactive by two different ELISA tests for anti-HCV is likely to be a true positive and may not require further 'confirmatory' testing.

A critical analysis of the concept of codependency.

This article addresses problems associated with conceptualizing interpersonal behaviors as addictions or diseases and pathologizing characteristics associated with women. The failure of the codependency model to focus on the unequal distribution of power and resources and the blurring of responsibility between the actor and audience are also discussed. Individual identity can be lost in the label, and the codependency model encourages separation from rather than connection with the family of origin.

Development and characterization of recombinant adenoviruses encoding human p53 for gene therapy of cancer.

We have constructed recombinant human adenoviruses that express wild-type human p53 under the control of either the Ad 2 major late promoter (MLP) or the human cytomegalovirus (CMV) immediate early gene promoter. Each construct replaces the Ad 5 E1a and E1b coding sequences necessary for viral replication with the p53 cDNA and MLP or CMV promoter. These p53/Ad recombinants are able to express p53 protein in a dose-dependent manner in infected human cancer cells. Tumor suppressor activity of the expressed p53 protein was assayed by several methods. [3H]Thymidine incorporation assays showed that the recombinant adenoviruses were capable of inhibiting DNA synthesis in a p53-specific, dose-dependent fashion. Ex vivo treatment of Saos-2 tumor cells, followed by injection of the treated cells into nude mice, led to complete tumor suppression using the MLP/p53 recombinant. Following a single injection of CMV/p53 recombinant adenovirus into the peritumoral space surrounding an in vivo established tumor derived from a human small cell lung carcinoma cell line (NIH-H69), we were able to detect p53 mRNA in the tumors at 2 and 7 days post-injection. Continued treatment of established H69 tumors with MLP/p53 recombinant led to reduced tumor growth and increased survival time compared to control treated animals. These results indicate that recombinant adenoviruses expressing wild-type p53 may be useful vectors for gene therapy of human cancer.