Impaired hospitalized patient mobility is associated with nurse injuries.

BACKGROUND: Staff injuries adversely affect the health of staff members as well the ability of health care teams to effectively care for patients. Identifying patients who pose an increased risk of injury may allow for the planning of risk mitigation strategies, but few studies have examined patient factors associated with staff injury risk. AIMS: Examine the relationship between staff injury and patient mobility, which has been linked to other key hospital outcomes. METHODS: Linking occupational health and electronic medical record data, we examined documented patient mobility levels, based on the Activity Measure for Post-Acute Care (AM-PAC) and the Johns Hopkins Highest Level of Mobility (JH-HLM) Scale, on the day prior to injury. In addition, we created a matched cohort of control patients not associated with staff injury to examine the influence of patient mobility on the odds of staff injury. RESULTS: We identified 199 staff injuries associated with 181 patients with 1063 matched controls. Patients had median scores of 11 and 3 on the AM-PAC and JH-HLM, respectively, indicating moderate-severe mobility impairments. In addition, scores in the lowest AM-PAC tertile (6-15) and lowest JH-HLM tertile (1-4) were associated with a 4.46-fold and 2.90-fold increase in the odds of nurse injury, respectively. CONCLUSIONS: These results indicate that moderate-severe mobility impairments are associated with increased risk of nurse injury. Hospitals and clinical care teams should consider documenting mobility routinely and utilizing these values to identify patients who pose an increased risk of nurse injury.

Blood oxygen equilibration time after cessation of supplemental oxygen in chronic respiratory disease.

BACKGROUND: Measurement of the arterial partial pressure of oxygen (PaO2 ) while breathing air is an informative investigation in patients with hypoxaemia due to chronic respiratory disease, but there are a lack of published data on the time needed for blood oxygen levels to equilibrate after cessation of supplemental oxygen (O2 ) in such patients. AIM: To determine the blood oxygen equilibration time after cessation of O2 and thereby provide guidance on best timing of baseline arterial blood gas analysis in this population. METHODS: Medically stable subjects with chronic respiratory disease were administered O2 at a constant concentration. Continuous pulse oximetry was recorded from before cessation of O2 to beyond the point of oxygen saturation (SpO2 ) equilibration. Data were fitted to an exponential decay model. Blood oxygen equilibration time was defined as the t90, the time taken for SpO2 to fall 90% of the difference between initial (on O2 ) and final (on air) values. RESULTS: Eighty-two (82) subjects with a mean age of 66 years were included. The largest diagnostic category was chronic obstructive pulmonary disease (37), followed by interstitial lung disease (15) and bronchiectasis (12). The median t90 was 6 min 18 s (interquartile range: 4 min 32 s-10 min 30 s). The 95th centile t90 value was 20 min. CONCLUSION: In the majority of patients with chronic respiratory disease, a time delay of 20 min between cessation of supplemental O2 and PaO2 measurement allows confidence that the result is a true baseline value.

Missing data and censoring in the analysis of progression-free survival in oncology clinical trials.

Progression-free survival (PFS) is increasingly used as a primary endpoint in oncology clinical trials. However, trial conduct is often such that PFS data on some patients may be partially missing either due to incomplete follow-up for progression, or due to data that may be collected but confounded by patients stopping randomized therapy or starting alternative therapy prior to progression. Regulatory guidance on how to handle these patients in the analysis and whether to censor these patients differs between agencies. We present results of a reanalysis of 28 Phase III trials from 12 companies or institutions performed by the Pharmaceutical Research and Manufacturers Association-sponsored PFS Expert Team. We show that analyses not adhering to the intention-to-treat principle tend to give hazard ratio estimates further from unity and describe several factors associated with this shift. We present illustrative simulations to support these findings and provide recommendations for the analysis of PFS.

Cediranib with mFOLFOX6 vs bevacizumab with mFOLFOX6 in previously treated metastatic colorectal cancer.

BACKGROUND: Cediranib is a highly potent inhibitor of vascular endothelial growth factor (VEGF) signalling with activity against all three VEGF receptors. Bevacizumab is an anti-VEGF-A monoclonal antibody with clinical benefit in previously treated metastatic colorectal cancer (mCRC). METHODS: Patients with mCRC who had progressed following first-line therapy were randomised 1:1:1 to modified (m)FOLFOX6 plus cediranib (20 or 30 mg day(-1)) or bevacizumab (10 mg kg(-1) every 2 weeks). The primary objective was to compare progression-free survival (PFS) between treatment arms. RESULTS: A total of 210 patients were included in the intent-to-treat (ITT) analysis (cediranib 20 mg, n=71; cediranib 30 mg, n=73; bevacizumab, n=66). Median PFS in the cediranib 20 mg, cediranib 30 mg and bevacizumab groups was 5.8, 7.2 and 7.8 months, respectively. There were no statistically significant differences between treatment arms for PFS (cediranib 20 mg vs bevacizumab: HR=1.28 (95% CI, 0.85-1.95; P=0.29); cediranib 30 mg vs bevacizumab: HR=1.17 (95% CI, 0.77-1.76; P=0.79)) or overall survival (OS). Grade ≥ 3 adverse events were more common with cediranib 30 mg (91.8%) vs cediranib 20 mg (81.4%) or bevacizumab (84.8%). CONCLUSION: There were no statistically significant differences between treatment arms for PFS or OS. When combined with mFOLFOX6, the 20 mg day(-1) dose of cediranib was better tolerated than the 30 mg day(-1) dose.

Blinded independent central review of progression in cancer clinical trials: results from a meta-analysis.

PURPOSE: Progression free survival (PFS) is increasingly used as a primary end-point in oncology clinical trials. This paper provides observations and recommendations on the use of a blinded independent central review (BICR) for progression. PATIENTS AND METHODS: The findings and recommendations are based on extensive simulations and a meta-analysis based on 27 previously conducted randomised phase III trials with BICR performed by the Pharmaceutical Research and Manufacturers Association (PhRMA) sponsored PFS Independent Review Working Group. RESULTS: Results of the meta-analysis demonstrate a strong correlation between LE and BICR estimates of treatment effect (R=0.947). Further, differences between treatment groups in discordance rates predict the differences between LE and BICR estimates of treatment effect supporting the use of a sample-based BICR on a subgroup of patients. CONCLUSION: The meta-analysis demonstrates that local evaluation (LE) provides a reliable estimate of the treatment effect with little evidence for systematic evaluation bias. Therefore, when a trial is blinded or a large effect on PFS is observed a BICR may not be warranted. When a BICR is warranted, a sample-based BICR may provide a reduction in operational complexity without compromising the credibility of trial results. While for large trials that are not adequately blinded a sample-based BICR may be recommended. A full BICR should be considered in the case of smaller trials or in situations in which there is a particular need to increase the confidence in the LE results.

Research outcomes and recommendations for the assessment of progression in cancer clinical trials from a PhRMA working group.

PURPOSE: Progression free survival (PFS) is increasingly used as a primary end-point in oncology clinical trials. This paper provides recommendations for optimal trial design, conduct and analysis in situations where PFS has the potential to be an acceptable end-point for regulatory approval. PATIENTS AND METHODS: These recommendations are based on research performed by the Pharmaceutical Research and Manufacturers Association (PhRMA) sponsored PFS Working Group, including the re-analysis of 28 randomised Phase III trials from 12 companies/institutions. RESULTS: (1) In the assessment of PFS, there is a critical distinction between measurement error that results from random variation, which by itself tends to attenuate treatment effect, versus bias which increases the probability of a false negative or false positive finding. Investigator bias can be detected by auditing a random sample of patients by blinded, independent, central review (BICR). (2) ITT analyses generally resulted in smaller treatment effects (HRs closer to 1) than analyses that censor patients for potentially informative events (such as starting other anti-cancer therapy). (3) Interval censored analyses (ICA) are more robust to time-evaluation bias than the log-rank test. CONCLUSION: A sample based BICR audit may be employed in open or partially blinded trials and should not be required in true double-blind trials. Patients should be followed until progression even if they have discontinued treatment to be consistent with the ITT principle. ICAs should be a standard sensitivity analysis to assess time-evaluation bias. Implementation of these recommendations would standardize and in many cases simplify phase III oncology clinical trials that use a PFS primary end-point.

Metastatic dissemination of human malignant oral keratinocyte cell lines following orthotopic transplantation reflects response to TGF-beta 1.

This study examined the behaviour of nine human malignant oral keratinocyte cell lines following orthotopic transplantation to the floor of the mouth of athymic mice. Tumourigenesis, local spread, and metastatic dissemination were correlated with known cellular responses to transforming growth factor-beta 1 (TGF-beta 1). Six of nine cell lines were tumourigenic; four of these cell lines showed local spread which was characterized by vascular and bone invasion. Metastatic spread was uncommon, with only 9% of animals with primary tumours developing metastases and these were almost exclusively found in the regional lymph nodes; there was one pulmonary metastasis and no liver deposits. Tumour cell behaviour did not reflect the clinical stage of the original tumours. Cell lines that were resistant to TGF-beta 1-induced growth inhibition were more likely to form primary tumours, exhibit local spread, and metastasize than cells that were growth-inhibited by the ligand. The data demonstrate that tumourigenicity and tumour behaviour in this orthotopic mouse model varied between cell lines and that the pattern of local invasion and metastasis was similar to that seen in human oral cancer. Furthermore, cell lines that were refractory to the growth inhibitory effects of TGF-beta 1 behaved more aggressively than cells that underwent ligand-induced cell-cycle arrest.

Functional significance of MMP-2 and MMP-9 expression by human malignant oral keratinocyte cell lines.

This study examined the expression of MMP-2 and MMP-9 in normal and human malignant oral keratinocytes. The expression of pro-MMP-2 and pro-MMP-9 was heterogeneous in the malignant cell lines. Normal oral keratinocytes expressed less pro-MMP-2 and more pro-MMP-9 than their malignant counterparts. Cells that expressed high levels of both MMP-2 and MMP-9 showed the greatest degree of invasion through Matrigel in vitro compared to cells with either low or variable levels of these enzymes; normal keratinocytes were non-invasive in these conditions. The degree to which the cells invaded through Matrigel was similar to their motility in the absence of Matrigel and was not influenced by the activation of the pro-enzymes or the inhibition of enzyme activity using a chemical inhibitor of gelatinases. Cells were transplanted orthotopically to athymic mice and demonstrated a variable capacity not only to form tumours at the site of inoculation but, also, to metastasise; normal oral keratinocytes were non-tumorigenic. There was no correlation between the expression of either MMP-2 or MMP-9 and the tumorigenic/metastatic phenotype. The results emphasise the limitations of correlating in vitro and in vivo assays of tumour cell behaviour and suggest that invasion/motility in vitro may be a distinct phenotype from tumorigenicity/metastasis in vivo.

Overexpression of JunB in undifferentiated malignant rat oral keratinocytes enhances the malignant phenotype in vitro without altering cellular differentiation.

Our study examined the expression of AP-1 family members in keratinocytes derived from the rat-4NQO model of oral carcinogenesis in which extremes of epithelial differentiation and tumour cell aggressiveness are evident. The constitutive expression of JunB was diminished in the undifferentiated, more aggressive tumour phenotype compared with the well-differentiated, less aggressive keratinocytes, whereas the expression of other AP-1 family members (c-jun, junD, c-fos, fra1, fra2 and fosB) was either very weak or variable. After transfection of the undifferentiated keratinocytes with junB cDNA, clonal populations were isolated that expressed similar levels of JunB protein as the well-differentiated cells. Both untransfected and transfected cell lines were keratin negative and vimentin positive. Increased expression of JunB in the transfected cells resulted in up-regulation of c-Jun and Fra1 and an enhanced AP-1 activity as demonstrated by transcriptional activation of the prototypic AP-1 dependent promoter, MMP-1. JunB transfected cells grew more quickly than vector-only controls and were refractory to the growth inhibitory effects of TGF-beta1. Over-expression of JunB resulted in the elevated expression of the AP-1 dependent proteinase, MMP-9, whereas the expression of the AP-1 independent enzyme, MMP-2, was unaffected. JunB transfected keratinocytes were highly invasive in an in vitro assay of tumour cell invasion compared with vector controls. The results indicate that increased expression of JunB above baseline levels in undifferentiated rat keratinocytes does not alter epithelial differentiation but enhances the malignant phenotype in vitro, possibly by altering the dynamics of the AP-1 complex.

Stratified care vs step care strategies for migraine: the Disability in Strategies of Care (DISC) Study: A randomized trial.

CONTEXT: Various guidelines recommend different strategies for selecting and sequencing acute treatments for migraine. In step care, treatment is escalated after first-line medications fail. In stratified care, initial treatment is based on measurement of the severity of illness or other factors. These strategies for migraine have not been rigorously evaluated. OBJECTIVE: To compare the clinical benefits of 3 strategies: stratified care, step care within attacks, and step care across attacks, among patients with migraine. DESIGN AND SETTING: Randomized, controlled, parallel-group clinical trial conducted by the Disability in Strategies Study group from December 1997 to March 1999 in 88 clinical centers in 13 countries. PATIENTS: A total of 835 adult migraine patients with a Migraine Disability Assessment Scale (MIDAS) grade of II, III, or IV were analyzed as the efficacy population; the safety analysis included 930 patients. INTERVENTIONS: Patients were randomly assigned to receive (1) stratified care (n = 279), in which patients with MIDAS grade II treated up to 6 attacks with aspirin, 800 to 1000 mg, plus metoclopramide, 10 mg, and patients with MIDAS grade III and IV treated up to 6 attacks with zolmitriptan, 2.5 mg; (2) step care across attacks (n = 271), in which initial treatment was with aspirin, 800 to 1000 mg, plus metoclopramide, 10 mg. Patients not responding in at least 2 of the first 3 attacks switched to zolmitriptan, 2.5 mg, to treat the remaining 3 attacks; and (3) step care within attacks (n = 285), in which initial treatment for all attacks was with aspirin, 800 to 1000 mg, plus metoclopramide, 20 mg. Patients not responding to treatment after 2 hours in each attack escalated treatment to zolmitriptan, 2.5 mg. MAIN OUTCOME MEASURES: Headache response, achieved if pain intensity was reduced from severe or moderate at baseline to mild or no pain at 2 hours; and disability time per treated attack at 4 hours for all 6 attacks, compared among the 3 groups. RESULTS: Headache response at 2 hours was significantly greater across 6 attacks in the stratified care treatment group (52.7%) than in either the step care across attacks group (40.6%; P<.001) or the step care within attacks group (36.4%; P<.001). Disability time (6 attacks) was significantly lower in the stratified care group (mean area under the curve [AUC], 185.0 mm. h) than in the step care across attacks group (mean AUC, 209.4 mm. h; P<.001) or the step care within attacks group (mean AUC, 199.7 mm. h; P<.001). The incidence of adverse events was higher in the stratified care group (321 events) vs both step care groups (159 events in across-attack group; 217 in within-attack group), although most events were of mild-to-moderate intensity. CONCLUSION: Our results indicate that as a treatment strategy, stratified care provides significantly better clinical outcomes than step care strategies within or across attacks as measured by headache response and disability time. JAMA. 2000;284:2599-2605.

Endogenous TGF-beta1 inhibits the growth and metastatic dissemination of rat oral carcinoma cell lines but enhances local bone resorption.

This study examined the effect of stable transfection of latent transforming growth factor-beta1 (TGF-beta1) cDNA into a predominantly polygonal, 4 nitroquinoline N-oxide (4NQO)-induced rat oral keratinocyte cell line. Seven polygonal and five spindle clonal populations were isolated that overexpressed TGF-beta1 protein by approximately two- to four-fold compared to vector-only transfected controls. Neutralisation experiments indicated that the majority of protein was in the latent form. There was no change in the proportion of polygonal and spindle cells in vitro after transfection with TGF-beta1 cDNA. Polygonal and spindle cells that overexpressed TGF-beta1 produced similar amounts of protein and grew more slowly in vitro than controls. The parent cell line and all transfected cells were growth inhibited (60-75%) by exogenous TGF-beta1. Orthotopic transplantation of the parent and the vector-only control cell lines resulted in primary tumours in the floor of the mouth in almost 100% (20/21) of athymic mice, with no evidence of bone resorption at the site of the primary tumour and pulmonary metastatic tumour deposits in some 40% (7/20) of these animals. The polygonal and spindle cells that overexpressed TGF-beta1 behaved similarly following orthotopic transplantation. A 96% (23/24) primary tumour take was evident following transplantation of cells that overexpressed TGF-beta1, with a significantly (P<0.02) higher number of animals showing bone resorption at the site of the primary tumour (35%; 8/23) compared to controls. By contrast, there was a significant (P<0.03) decrease in the number of animals with pulmonary metastases (4%; 1/23) following transplantation of TGF-beta1 overexpressing cells compared to controls. Overexpression of TGF-beta1 did not alter tumour cell differentiation in vivo. The results demonstrate that endogenous TGF-beta1 functions as a tumour suppressor in the rat-4NQO model of oral carcinogenesis without altering tumour cell morphology or differentiation but can also act to promote local bone resorption.

Overexpression of autocrine TGF-beta 1 suppresses the growth of spindle epithelial cells in vitro and in vivo in the rat 4NQO model of oral carcinogenesis.

We examined the effect of the stable transfection of latent TGF-beta 1 cDNA, under the control of a cytomegalovirus promoter in the expression vector pcDNA3, into a 4NQO-induced clonal rat oral keratinocyte cell line that formed undifferentiated spindle cell tumours following subcutaneous transplantation to athymic mice. Test cells containing latent TGF-beta 1 cDNA produced a 2.3-fold increase in TGF-beta 1 protein compared to pcDNA3 controls as demonstrated by ELISA. Neutralisation experiments indicated that the majority of the protein was in the latent form. Untransfected and transfected (containing either TGF-beta 1 cDNA or pcDNA3) cell lines were keratin negative and vimentin positive. Cells transfected with TGF-beta 1 were inhibited more than pcDNA3 controls when cultured in an anchorage dependent or independent environment. Subcutaneous transplantation of cells overproducing TGF-beta 1 resulted in tumours of significantly smaller volume than vector-only controls. Further, orthotopic transplantation of cells containing TGF-beta 1 cDNA to the floor of the mouth in athymic mice markedly inhibited the development of pulmonary metastases compared to vector-only controls. Both test and control cell lines in athymic mice formed undifferentiated tumours with a complete absence of keratin elaboration. Subcutaneous xenografts were recultured and cells containing the TGF-beta 1 cDNA produced a similar amount of TGF-beta 1 peptide as the cells containing pcDNA3 only. The production of TGF-beta 1 by both of the xenograft-derived cell lines was significantly less than the parent, pre-transplanted cell lines and the untransfected cell line. All of the cell lines were inhibited by exogenous TGF-beta 1. Our results demonstrate that autocrine TGF-beta 1 functions as a tumour suppressor in vitro and in vivo in 4NQO-induced spindle tumour cells that are growth inhibited by the ligand. Furthermore, tumour formation in athymic mice is associated with selection for a cell phenotype with diminished autocrine TGF-beta 1 production.

Evaluation of the chimpanzee breeding program at the Southwest Foundation for Biomedical Research.

The history of the chimpanzee (Pan troglodytes) breeding colony of the Southwest Foundation for Biomedical Research was evaluated over a 24-year period to determine age at conception, breeder rearing history, maternal competence, and infant rearing history. The records of 107 breeders and 268 live births were reviewed. Of the breeders with known rearing histories, 40 were wild-born (12 male and 28 female), 16 were reared by their mothers for at least 1 month (8 male and 8 female), and 13 were removed from their mothers immediately after birth (2 males and 11 females). The age of successful mating for males ranged from 7 to 32 years and for females from 7 to 41 years, although the upper limit indicates the age of the population and not reproductive senescence. The mother's rearing history was related to her maternal competence, defined as caring for an infant for at least 1 month. Of the wild-born females, 82% (18/22) were competent mothers. For females that had been reared in captivity with their mothers for 1 to 12 months, 71% (5/7) were competent. For females that had been removed from their mothers immediately and reared in a nursery by humans, only 14% (1/7) were competent. The rearing strategies have changed during the period under consideration. The number of infants reared by their mothers increased in the 1980s, while the number of infants removed from their mothers immediately for experimental reasons decreased and dropped to zero in the 1990s. Information on the history of the breeding colony has been used to make management decisions and to determine the expectations of the Southwest Foundation chimpanzee breeding program.

Tumor necrosis factor alpha (rhTNF) fails to stimulate angiogenesis in the rabbit cornea.

BACKGROUND: The objective of this study was to thoroughly examine the in vivo angiogenesis activity of human recombinant tumor necrosis factor alpha (rhTNF). METHODS: rhTNF (0.5 ng to 1.0 microgram) was incorporated into the slow release polymers Hydron or HYPAN and implanted into the rabbit cornea. Release of biologically active rhTNF from the polymers was determined with the L929 cytotoxicity assay. RESULTS: All concentrations tested failed to elicit capillary formation beyond that observed for controls. Less than 2% of the rhTNF was released from the Hydron over 7 days. HYPAN released five times the amount of rhTNF in vitro, but even at doses of 500 ng (104.3 ng suggested release) no angiogenesis was stimulated. CONCLUSIONS: Under the circumstances tested, rhTNF is not angiogenic in vivo.

Long-term use of televisions, balls, and mirrors as enrichment for paired and singly caged chimpanzees.

The evaluation of environmental enrichment techniques for nonhuman primates over long periods of time has had mixed results. Some studies report rapid habituation to new enrichment items, while others note continued use. We have investigated the use of three different enrichments that had been available to paired and singly caged chimpanzees for several years. Twenty subjects were observed during 200 hr of scan sampling while singly caged and while pair housed. Each subject had a variety of enrichments available and their use of a television, ball, and mirror were recorded. The chimpanzees had previous exposure to all of the items: televisions had been available for a mean of 22.75 months, balls had been available for 55.9 months, and mirrors had been available for 25.9 months. The results indicated that the chimpanzees continued to use the enrichments for small amounts of time (0.27%-1.53% of the observations) even after such prolonged exposure. Television and ball use were significantly higher than mirror use. Housing condition was not a significant factor in the analyses, contrary to expectations. We concluded that several simple enrichment items may be effective in offering variety and choices to the nonhuman primate and can be one element in a comprehensive environmental enhancement plan. © 1996 Wiley-Liss, Inc.

Age-related alterations in the morphology of femoral artery vasa vasorum in the rat.

The objective of this study was to explore any age-related morphological changes in the vasa vasorum of the rat femoral artery. Vascular corrosion casts were prepared from 2, 12 and 24-month-old rats. Examination of the casts with the scanning electron microscope revealed dramatic differences in the appearance of the vessels of young and aged rats. The vasa vasorum of 2-month-old rats consisted of a dense network of capillaries. These vessels were dramatically reduced in number by 12 months, and even fewer capillaries were present at 24 months. This reduction in capillary density is consistent with the observed age-related decreases in oxygen tension and may explain why the aged are more prone to atherosclerosis.

Laparoscopic repair of vesicoureteral reflux utilizing the Lich-Gregoir technique in the pig model.

To date, laparoscopic urological surgery has largely been limited to diagnostic or ablative procedures. Herein we report our experience with laparoscopic reconstructive surgery to perform an extravesical ureteral reimplantation. Seven anesthetized pigs with iatrogenic ureteral reflux underwent a laparoscopic extravesical ureteral reimplantation. The newly created ureteral tunnel varied from 2 to 4 cm. In 3 pigs, the tunnel was created with tacking staples, while in the other 4 pigs, the tunnel was created with intracorporeal suturing techniques using a 3-zero polyglyconate running suture. The procedure required an average of 132 minutes. There was one anesthetic death. There were no urinary tract infections. At 3 to 8 weeks after reimplantation, the cystograms were repeated on 5 pigs. One of 2 stapled reimplant pigs still had reflux; 1 of 3 sewn reimplant pigs had reflux. At 6 months following the reimplantation, only 1 pig had residual grade I reflux and this was a sutured reimplantation. None of the stapled reimplantations exhibited any residual reflux on the surgical side; however, in 1 animal a submucosal staple was noted at the time of harvest.

Proliferation of wound derived capillary endothelial cells: young versus aged.

The objective of this study was to compare the proliferative potential of wound derived capillary endothelial cells (WCEC) from aged and young rats. Endothelial cells were isolated from subcutaneously implanted sponges in 2- and 24-month-old rats. The identity of the cells as endothelial was confirmed by staining for Ac-LDL uptake. Aged and young WCEC (20,000/well) were stimulated with increasing concentrations of fetal calf serum (0, 2.5, 5, 10 and 15%). The increase in cell number was determined with a Coulter counter. At all serum concentrations, the proliferative capacity of WCEC from aged rats was significantly higher than that of WCEC from young rats.

Vascular endothelial growth factor (rhVEGF165) stimulates direct angiogenesis in the rabbit cornea.

The object of this study was to test vascular endothelial growth factor (VEGF) for angiogenic activity in the rabbit corneal assay. VEGF doses ranging from 20 ng to 1000 ng were incorporated into a slow release polymer and implanted into the avascular rabbit cornea. Capillary formation in the cornea was visually analyzed on a daily basis and examined with histology, transmission electron microscopy and scanning electron microscopy of vascular corrosion casts on days 2 and 7 post-implantation. VEGF implants (200ng to 1000ng) consistently stimulated angiogenesis. This neovascularization occurred in the absence of inflammation. We conclude that VEGF acts directly on endothelial cells, initiating and mediating the formation of capillaries.

PDGF-BB induced chemotaxis is impaired in aged capillary endothelial cells.

The object of this study was to determine if the decreased angiogenesis in the healing wounds of the aged is due to the failure of endothelial cells to respond to locally produced growth factors. Endothelial cells isolated from wound sponges implanted in aged (24-month-old) and young (2-month-old) rats were tested for their chemotactic response to the BB isoform of platelet-derived growth factor (PDGF-BB). A similar number of cells isolated from both old and young rats stained positive (75-90%) for acetylated-LDL uptake, and the same number of viable cells was used in the chemotaxis assay. Endothelial cells from both old and young rats migrated in a dose-dependent (0.1-3.0 ng/ml) manner in response to PDGF-BB. At all concentrations tested, PDGF-BB elicited the migration of more endothelial cells from the young rats. The difference between the number of young and old cells that responded to PDGF-BB was statistically significant at the 1.0 ng/ml and 3.0 ng/ml concentrations. These results suggest that the impaired angiogenic response in the healing of wounds of the aged is due to altered endothelial cell reaction to the growth factors in the wound microenvironment.