Regional differences in phorbol 12-myristate 13-acetate stimulation of PDGF production in the normal canine aorta.

OBJECTIVE: Platelet-derived growth factor (PDGF) is a potent smooth muscle cell mitogen implicated in the development of intimal hyperplasia and atherosclerosis. A regional variation in canine aortic production of PDGF (greater in the distal than in the proximal aorta) was demonstrated previously in organ culture. The response of aortic segments in organ culture, as well as of aortic endothelial cells and smooth muscle cells, to stimulators of PDGF secretion-phorbol 12-myristate 13-acetate (PMA) and thrombin-was assessed to elucidate whether these regional variations were due to intrinsic differences in the abilities of cells to produce PDGF. METHODS: Proximal and distal aortic segments were removed from 10 dogs and placed in organ culture, then treated with PMA or thrombin for 72 hours. PDGF in the conditioned media was measured by radioreceptor assay. RESULTS: PDGF production in the distal, unstimulated aorta was 2.5-fold higher than that in the proximal aorta (P <.05). Treatment of the proximal aorta with 10 nmol/L and 100 nmol/L PMA increased PDGF production twofold and threefold, respectively, whereas no increase with PMA treatment was seen in the distal aorta. After thrombin treatment, no increase in PDGF production was noted in the proximal aorta and only a minimal increase was noted in the distal aorta. Endothelial cells and smooth muscle cells (n = 6) were cultured from four aortic segments (ascending thoracic, descending thoracic, abdominal, and infrarenal) and treated with PMA. PDGF production by unstimulated endothelial cells from the infrarenal aorta was 2.5-fold higher (P <.01) than that from the ascending thoracic aorta. With PMA treatment, PDGF secretion increased in endothelial cells from all segments, the greatest percentage increase being observed in the proximal segments. Thrombin also increased PDGF release from endothelial cells, but with no regional variation. Unstimulated smooth muscle cells did not exhibit regional variation in PDGF production and did not increase PDGF secretion after treatment with PMA or thrombin. CONCLUSIONS: These findings suggest that endothelial cells in the aorta may have a differential capacity to produce PDGF in response to stimulants, reflecting intrinsic differences in endothelial cells from the proximal aorta versus the distal aorta, and this may account in part for the propensity of the distal aorta to develop atherosclerosis.

Debilitating chronic pain syndromes after presumed intraneural injections.

This report presents seven patients with severe disability established at the time of a peripheral nerve block. In most of the cases, the injection was administered as a routine procedure by an experienced anesthesiologist. The patient histories suggest that the condition, which can be resistant to all treatment, in most cases could have been avoided if careful attention had been given to the occurrence of pain during the nerve block. It is likely that the risk of devastating iatrogenic disability can be minimized if a few basic principles are respected during the administration of peripheral nerve blocks.

Venous gangrene of the upper extremity.

Venous gangrene of the upper extremity is a rare entity and is the result of massive occlusion of all venous outflow of the extremity. The syndrome is strongly associated with hypercoagulable states including malignancy, low cardiac output states, and hereditary or acquired hematological abnormalities. Diagnosis can be straightforward but must be made early in the course of the process for treatment to be effective. Treatment has historically produced only modest results, and patients continue to suffer a high morbidity and mortality. We present a series of 6 patients with venous gangrene or impending venous gangrene of the upper extremities--a relatively large series. Two patients suffered from malignancy, 3 patients suffered from low-flow cardiac states, and 1 patient suffered from an overdose of calcium channel blockers. Hematological abnormalities included heparin-induced thrombocytopenia and thrombosis in 3 patients, activated protein C resistance in 1 patient, and lupus anticoagulant in 1 patient. Three patients experienced other major venous thrombotic complications, two of whom died (renal and cerebral venous infarction). Venous gangrene of the upper extremity remains a rare occurrence but one in which early identification and intervention may lead to improved outcomes.

Sports-related facial injuries.

Facial injuries suffered by the athlete will range from very minor to extremely complex. Regardless, all injuries can be accurately diagnosed if one is familiar with normal anatomy and conducts a thorough physical examination. Radiographs are then obtained as directed by the physical examination. Specific and timely treatment directed at correcting functional and cosmetic deformities will help to avoid lifelong disability and deformity. With adherence to these guidelines, many of the injuries suffered by athletes can be safely treated by a variety of physicians. More complex soft-tissue and bone injuries should be referred to a surgeon familiar and comfortable with facial plastic and reconstructive surgery.

Regional differences in platelet-derived growth factor production by the canine aorta.

Platelet-derived growth factor (PDGF) is a potent mitogen and chemotactic agent which may be involved in the formation of proliferative lesions of the arterial system, such as intimal hyperplasia and atherosclerosis. To examine the regional variation in vessel wall production of this mitogen, PDGF production and PDGF A chain mRNA expression by normal arterial wall was studied as a function of vessel location. PDGF production by canine aortic segments was measured after 72 h in organ culture, revealing significantly more PDGF produced by the distal compared to proximal aorta at 77 +/- 10 versus 14 +/- 6 pg/cm2/72 h (p<0.05). Endothelial cells (EC) and smooth muscle cells (SMC), isolated from analogous aortic sites, were grown in tissue culture and the conditioned medium was assayed for PDGF. EC in vitro demonstrated a similar geographic trend in PDGF production (distal=1,501 +/- 389 pg/microgram DNA/72 h, proximal=759 +/- 230 pg/microgram DNA/72 h; p=0.17). PDGF production by SMC in cell culture had a similar pattern with cells from the distal aorta producing 58 +/- 28 pg PDGF/microgram DNA/72 h, compared to cells from the proximal aorta producing 37 +/- 15 pg PDGF/microgram DNA/72 h (p=0.13). Freshly harvested EC and SMC, isolated from the same aortic sites, were subjected to quantitation of PDGF mRNA levels using a coupled reverse transcriptase and polymerase chain reaction amplification method, with glyceraldehyde-phosphate dehydrogenase (GAPDH) as a control. The ratio of PDGF A chain:GAPDH mRNA was significantly greater in distal aortic SMC, 2.30 +/- 0.99, compared to proximal aortic SMC, 1.27 +/- 0.46 (p=0.05), but was not significantly different between proximal and distal aortic EC (p=0.86). These findings demonstrate significant regional differences in PDGF production in the normal canine aorta. Additionally, SMC are implicated as a significant contributor to the regional variation in PDGF production.

Increased platelet-derived growth factor production and intimal thickening during healing of Dacron grafts in a canine model.

PURPOSE: Growth factor production by endothelial cells on grafts may play a role in the development of intimal hyperplasia and subsequent graft failure. METHODS: To study the relationship between platelet-derived growth factor production and graft healing, 26 beagles underwent placement of 20 cm long, 6 mm internal diameter, knitted Dacron thoracoabdominal grafts, either seeded with autologous endothelial cells (n = 14) or unseeded controls (n = 12). The grafts and adjacent arteries were removed 4 or 20 weeks after implantation for measurement of platelet-derived growth factor production in organ culture, endothelial cell coverage, and intimal thickness. RESULTS: Midgraft platelet-derived growth factor production by seeded graft segments increased from 41 +/- 6 to 148 +/- 27 pg/cm2/72 hr (p < 0.002) between 4 and 20 weeks. This was accompanied by a significant increase in inner-capsule thickness. Platelet-derived growth factor production by control graft segments also increased from 58 +/- 21 to 163 +/- 42 pg (p < 0.05) and was similar to that of seeded grafts despite more rapid endothelialization of seeded grafts. The increase in growth factor production by Dacron grafts was greater than that of the expanded polytetrafluoroethylene grafts studied previously despite similar endothelial cell coverage. CONCLUSION: This increase corresponded with the rapid appearance of smooth muscle cells in the pseudointima of Dacron grafts, suggesting that these cells may be responsible for the observed increase in platelet-derived growth factor production.

Elevated platelet-derived growth factor production by aortic grafts implanted on a long-term basis in a canine model.

An endothelial cell lining in a prosthetic vascular graft has been shown to decrease graft thrombogenicity. However, previous studies in our laboratory demonstrated that grafts seeded with endothelial cells produced platelet-derived growth factor, a potent smooth muscle cell mitogen that may promote intimal hyperplasia. This study was undertaken to assess temporal changes in platelet-derived growth factor production by grafts seeded with endothelial cells and unseeded grafts and adjacent arteries. Adult beagles underwent placement of 20 to 22 cm long, 8 mm inner diameter, expanded polytetrafluoroethylene thoracoabdominal aortic grafts that were either seeded with autologous jugular vein endothelial cells or were unseeded controls. Grafts and adjacent arteries were removed at times up to 2 years after implantation. The tissue was studied in organ culture and platelet-derived growth factor production was measured after 72 hours with use of a radioreceptor assay. Platelet-derived growth factor production by endothelialized grafts increased significantly over the period studied, especially at the anastomoses, whereas that by arterial segments did not change significantly. The increase in platelet-derived growth factor production was greater in the distal than the proximal anastomotic segment suggesting a possible explanation for the clinical finding of more severe intimal hyperplasia at the distal anastomosis.

Platelet-derived growth factor production by canine aortic grafts seeded with endothelial cells.

The advantages of an endothelial cell surface on a prosthetic graft may be compromised by endothelial cell production of mitogens for smooth muscle cells. To study platelet-derived growth factor (PDGF) production by cells lining prosthetic grafts, 15 beagles underwent placement of 20 to 22 cm long, 8 mm inner diameter, expanded polytetrafluoroethylene thoracoabdominal aortic grafts, of which seven were seeded with autologous jugular vein endothelial cells, and eight were unseeded control grafts. Grafts and adjacent arteries were explanted after 4 weeks, divided into segments, and studied in organ culture. Platelet-derived growth factor production during a 72-hour incubation period was measured by radioreceptor assay. Midgraft segments of seeded grafts produced significantly more PDGF than control grafts, 43 +/- 8 pg/cm2 and 22 +/- 5 pg/cm2, respectively (mean +/- SEM), p less than 0.05. Platelet-derived growth factor production correlated directly with endothelial cell coverage on graft segments as measured by scanning electron microscopy (r = 0.63, p = 0.01), and inversely with platelet deposition (r = -0.48, p = 0.07). For all dogs, PDGF production by the distal aorta was significantly greater than that by the proximal aorta, 89 +/- 6 and 17 +/- 4 pg/cm2, respectively (p less than 0.0001). These results suggest that endothelial cells on prosthetic vascular grafts are a significant source of PDGF. Furthermore, the higher PDGF production by the distal arteries may offer an explanation for the clinical finding of more severe intimal hyperplasia adjacent to the distal anastomosis.

Effect of complement and arachidonic acid pathway inhibition on white blood cell count and deposition on vascular grafts.

To determine the role of complement and arachidonic acid metabolites in the decrease in peripheral white blood cell count (pWBC) observed with graft implantation, Dacron aortic grafts were implanted in control rabbits (Group I, n = 13), or rabbits pretreated with cobra venom factor (80 U/kg) to deplete complement (Group II, n = 13), indomethacin (2.5 mg/kg) to inhibit cyclooxygenase (Group III, n = 7), or diethylcarbamazine (DEC, 90 mg/kg) to inhibit leukotriene synthesis (Group IV, n = 7). pWBC was measured 15 min and 1 hr after graft implantation. After graft removal, the WBC count on grafts (gWBC) was determined by light microscopy (LM) and scanning electron microscopy (SEM). One hr after graft implantation, pWBC decreased significantly in Groups I-IV to 46%, 52%, 40%, and 45% of preoperative pWBC, respectively. There was no significant difference among the groups. LM revealed gWBC per 63x field of 8.0, 12.3, 5.8, and 6.8 in Groups I-IV, respectively. Similarly, SEM showed gWBC per 2000x field of 2.5, 5.6, 0.7, and 1.5 in Groups I-IV, respectively. SEM gWBC was significantly greater in Group II than I (p less than 0.01), and significantly less in Group III than I (p less than 0.05). Results suggested that complement and arachidonic acid pathways alone do not affect the fall in pWBC, but may influence gWBC.