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Biomedical subjects

M B Herring

Publications and source records attributed to M B Herring.

15 recordsLinked to original sources
PubMed1992

Initial results of endothelial cell seeding following argon laser carotid endarterectomy.

This study evaluates the initial results of endothelial cell (EC) seeding following argon laser carotid endarterectomy. Venous endothelial cells were harvested from 12 dogs and cultured. A laser endarterectomy was performed on both carotids of each dog. One side was seeded with endothelial cells. Six dogs had both carotids harvested 1 hour after restoring blood flow. The others were harvested in 24 hours. The percentage of lumen covered with EC was evaluated by scanning electron microscopy. At 1 hour, the seeded arteries demonstrated 35 +/- 3 percent EC coverage, whereas the unseeded arteries had no EC coverage (P = 0.0002). At 24 hours, the seeded arteries had 58 +/- 15 percent EC coverage, whereas the unseeded arteries had no coverage (P = 0.01). Significant gross thrombus developed only in unseeded arteries (P = 0.047), two of which were occluded at 24 hours. EC seeding is beneficial following argon laser carotid endarterectomy resulting in improved patency and less surface thrombogenicity.

Animals↗
PubMed1992

Endovascular infrainguinal in situ saphenous vein bypass: a multicenter preliminary report.

The ideal operative approach for infrainguinal in situ bypass grafting would render the saphenous vein (SV) valves incompetent while occluding venous tributaries from within the SV: an endovascular in situ SV bypass. Forty-six femoropopliteal-tibial in situ bypasses were performed in part by the endovascular occlusion technique. Valvulotomy was accomplished with a retrograde "cutter" valvulotome, and endoluminal cannulation of 84 SV tributaries was performed with a shape memory metal alloy (nickle-titanium), electronically steerable catheter under angioscopic surveillance. Sixty-nine SV tributaries (82%) were totally occluded and 15 (18%) were partially occluded with platinum occlusion coils. Twelve coils that "recoiled" into the SV lumen were retrieved uneventfully. The valvulotomes caused six SV perforations that were repaired without consequence. Intraoperative fluoroscopy confirmed coil placement and verified venous tributary occlusion, as well as SV graft patency. During short-term follow-up (mean 9.2 months; range 1 to 15 months), all patients have undergone ultrasonography of the in situ bypasses. All 69 of the SV tributaries that occluded initially have remained occluded and 84% (39/46) of the in situ bypasses have remained patent. This study demonstrates that an electronically steerable nitinol catheter can be used safely to occlude venous tributaries from within the SV. Endovascular occlusion of SV tributaries may ultimately obviate the need for long incisions the length of the leg, thus reducing wound-related problems and shortening recuperation.

Aged↗
PubMed1991

Inhibition of neutrophil superoxide production by adenosine released from vascular endothelial cells.

To investigate the inhibitory effect of adenosine released by endothelium on neutrophil superoxide (O2-) production, we treated confluent monolayers of cultured human umbilical vein endothelial cells with the enzyme adenosine deaminase, and then added human neutrophils. Superoxide (O2-) production by human neutrophils stimulated with 10(-6) M formyl-methionyl-leucyl-phenylalanine was inhibited by 49% in the presence of a confluent monolayer of human umbilical vein endothelial cells (5.1 +/- 0.1 versus 2.6 +/- 0.3 nmols O2-/10(6) neutrophils). Addition of 0.25 U/ml adenosine deaminase to neutrophils plus endothelial cells restored formyl-methionyl-leucyl-phenylalanine-stimulated neutrophil superoxide production to the level seen with neutrophils alone. Deoxycoformycin (10(-4) M), an inhibitor of adenosine deaminase activity, prevented the increase in superoxide production associated with adenosine deaminase addition. The adenosine analogue 5'-(N-ethylcarboxamido)- adenosine (3 x 10(-4) M) caused increased inhibition of formyl-methionyl-leucylphenylalanine-stimulated superoxide release by neutrophils in the presence of endothelial cells and prevented neutrophil-mediated endothelial cell damage, as measured by release of 3H-2-deoxy-D-glucose. Pairing 2-chloroadenosine (10(-5) M) or 5'-(N-ethylcarboxamido)-adenosine (3 x 10(-4) M) with a cyclic adenosine monophosphate phosphodiesterase inhibitor, 3-isobutyl-l-methyl-xanthine (10-4 M), produced greater inhibition of neutrophil superoxide production than occurred with either compound alone. The results support the hypothesis that vascular endothelial cells protect themselves from neutrophil attack by releasing adenosine to inhibit superoxide production.

1-Methyl-3-isobutylxanthine↗
PubMed1991

111Indium is an unreliable in vivo label for vascular endothelial cells.

We studied the retention of 111Indium-labeled canine endothelial cells on 32 grafts (16 dogs). Canine endothelial cells were harvested from the external jugular veins, grown in culture, and labeled with 111Indium oxine; 10(6) factor VIII positive cells were inoculated on fibronectin-coated, 4 mmID Hytrel grafts and cultured 18 hours to reach confluence. An autologous seeded graft was interposed in each of the common carotid arteries and exposed to flow for six hours. 111Indium label was measured pre- and postperfusion and corrected for decay. Twenty-five grafts from 13 dogs were available for study. Scanning electron microscopic planimetry was used to determine percent surface coverage by six mutually exclusive surface characteristics: endothelial cells, bare graft, white blood cells on graft, white blood cells on endothelium, white blood cells under endothelium, and thrombus. 111Indium retention was compared with percent coverage by scanning electron microscopy using regression analysis. 111Indium labeling projected an erroneous retention of 41% at zero percent coverage (r = 0.67; p less than 0.01). Multiple regression analysis revealed an equivalent distribution of 111Indium label over nonendothelial portions of the flow surface and indicated a leak rate into the circulation of 25.6% of the initial 111Indium label over six hours. We conclude that: 1) 111Indium labeling data usually overestimates endothelial cell retention; 2) an average of 4.67%/hour is lost into the general circulation; 3) 111Indium label can be found equally on surfaces of thrombus, white blood cells, and hydrophilic Hytrel graft; and 4) 111Indium labeling is not a reliable method for in vivo studies of endothelial cell retention.

Animals↗
PubMed1991

Endothelial cell seeding.

Endothelial cell seeding is the transplantation of vascular endothelial cells to denuded vascular surfaces. Seeding theoretically reduces the probability of graft or vessel thrombosis and of neointimal fibrous hyperplasia. Thus far, clinical seeding trials disclosed modest improvements in patency and the development of hyperplastic anastomotic lesions in failed grafts. Seeding inefficiency theoretically contributes to anastomotic hyperplasia. The inefficiency is linked to two steps in the seeding process, namely harvesting and cell retention. Of these, cell retention on the seeded surface is the more critical. Priorities for future research should be set first on the retention of seeded endothelium in vitro and second on improved and standardized methods of cell harvesting.

Animals↗
PubMed1991

The use of endothelial seeding of prosthetic arterial bypass grafts.

Endothelial seeding is the transplantation of vascular lining cells. On the basis of animal studies and theoretical considerations, seeding is expected to reduce acute thrombosis and stenoses because of NFH when segments of the vascular system are denuded of endothelium. Endothelialization may reduce the susceptibility of synthetic grafts to blood-borne bacterial infection. Seeding demonstrably transfers endothelium in humans. The indications for its use are limited to clinical trials in aorta-femoral and femoral-popliteal bypass operations, and the results of those trials will begin to define its indications further. In the future, endothelium may be applied to tibial and coronary synthetic arterial grafts; sites of endarterectomy, PTA, atherectomy, and laser treatments; vascular access; and venous replacement grafts.

Arterial Occlusive Diseases↗
PubMed1989

The histology of seeded PTFE grafts in humans.

To define the histology of PTFE femoral-popliteal grafts seeded with enzymatically-derived endothelium, we examined light level and selected scanning electron micrographs of 20 graft biopsies. Thirteen grafts were chronically occluded and the midgraft samples had a thin lining of fibrin with scattered erythrocytes and leukocytes. One anastomotic sample showed a similar pattern, while three others had neointimal fibrous hyperplasia. Six of the seven remaining midgraft samples demonstrated confluent endothelial healing over parts of the flow surface. The cells were commonly distributed along one side of the graft as viewed in cross-section. Distribution patterns were not improved by changing from a single inoculum with two graft rotation-incubation periods to a sequential inoculation separated by a graft rotation. Circumferential distribution was achieved in one instance in which inoculation was characterized by a relatively high cell density. No luminal endothelium was seen when inoculation cell densities were very low. Smooth muscle cells and fibroblasts were not seen in the subendothelial "inner capsules" of the midgrafts. We conclude that endothelialization occurs in a high proportion of seeded PTFE grafts in humans, that the donor vein surface area should measure at least 5.25% of the inoculated graft surface, that further modifications in the seeding technique will be required to achieve consistent circumferential endothelial distribution, that subendothelial smooth muscle cell invasion is uncommon in the midgraft, but that anastomotic neointimal fibrous hyperplasia probably contributed to some graft failures.

Blood Vessel Prosthesis↗
PubMed1989

An experimental collagen-impregnated Dacron graft: potential for endothelial seeding.

This study evaluates the potential for endothelial seeding of a collagen-impregnated Dacron graft with or without surface modifiers (fibronectin, heparin) to attach and retain these cells during flow. Human umbilical endothelial cells were harvested, cultured, labeled with Indium111-oxine and seeded onto 30 mm X 4 mm diameter grafts. Six graft surfaces were studied: 1) a collagen-impregnated Dacron graft, HemashieldR (C); 2) C + fibronectin (C + F); 3) C + heparin (C + H); 4) C + F + H; 5) HytrelR + F (Hyt + F); and 6) Hyt + F + H. Radioactive loss determined the percentage attachment and then percentage retention of labeled inoculum after a one-hour in vitro perfusion. Scanning electron and light microscopy demonstrated the endothelium on the graft surface following perfusion. Fibronectin-coated grafts had a significantly higher percentage attachment than those without fibronectin (ANOVA, P less than 0.05). However, the percentage retention following perfusion was similar for all Dacron grafts and statistically inferior to the HytrelR grafts studied (ANOVA, P less than 0.05). SEM evaluation of the C + F + H graft surface was qualitatively the most impressive Dacron surface for seeding, yet was inferior to the HytrelR graft. We conclude that fibronectin benefits the initial attachment of endothelium to collagen-coated Dacron rivaling the HytrelR surface. Fibronectin does not improve percentage retention of the HemashieldR surface during perfusion, therefore, some of its initial benefit is lost.

Blood Vessel Prosthesis↗
PubMed1988

Vascular laboratory prediction of pedal pressure following femoropopliteal bypass.

This study examines the hypothesis that postoperative ankle-brachial pressure index (postop ABI) can be accurately predicted using noninvasive preoperative segmental leg pressure measurements. Seventy-three patients who underwent successful reverse autogenous vein femoropopliteal bypass and who had pre- and postoperative segmental leg pressure measurements were examined. Predicted postop ABI was estimated using the following formula: Postop ABI = 1 + (Preop ABI) - (Preop BKI). (BKI = below-knee brachial pressure index). Using this formula, 56 out of 73 (81%) patients had a measured postop ABI +/- 20% of predicted postop ABI. Five out of 73 (7%) patients had postop ABI less than 80% predicted, while 12 out of 73 (16%) patients had postop ABI greater than 120% of predicted. All patients with postop ABI greater than 120% of predicted had apparent tibial artery occlusive disease as indicated by preoperative gradients (BKI-ABI) greater than 0.15.

Anastomosis, Surgical↗
PubMed1987

Endothelial linings: the effect of serine protease inhibition.

The purpose of this investigation was to determine if the inhibition of the serine proteases, thrombin and plasmin, by heparin and epsilon-aminocaproic acid (EACA) would improve endothelial cell retention on synthetic grafts. Endothelium was harvested from the external jugular veins of mongrel dogs using an enzymatic technique. The cells were grown in tissue culture for 3-4 weeks, labeled with 111In oxine, inoculated (2000 cells/mm2) into fibronectin-coated 4 mm-diameter tubes of polyester elastomer (PE, Hytrel 4056, DuPont), and cultured for 18 hr. Each animal received iv heparin (100 U/kg) prior to implantation, and a 4 X 30-mm segment of the culture-lined PE was interposed in the dog's own carotid artery. After 6 hr of flow the grafts were perfusion fixed; the percentage of endothelial retention was determined by 111In counting, and the surfaces of the grafts were analyzed by scanning electron microscopy. Six experiments were performed in each of three treatment groups. Animals in Group I received no additional drugs. Group II animals received a continuous infusion of heparin at 30 U/kg/hr. Group III animals received a bolus of 200 mg/kg of EACA with the initial heparin dose and a continuous infusion of heparin at 30 U/kg/hr and EACA at 200 mg/kg/hr. Group I grafts retained an average of 36.1 +/- 23.3% of the cells; Group II retained 67.5 +/- 24.9%; and Group III retained 83.4 +/- 9.8%. Although continuous heparin infusion resulted in a trend (P = 0.067) toward better retention, a combined infusion of heparin and EACA resulted in significantly better retention (P = 0.002).(ABSTRACT TRUNCATED AT 250 WORDS)

Aminocaproic Acid↗
PubMed1986

Short-term in vivo stability of endothelial-lined polyester elastomer and polytetrafluoroethylene grafts.

A fibronectin substrate will significantly enhance the strength of endothelial cell attachment on grafts constructed of polyester elastomer (PE) and polytetrafluoroethylene (e-PTFE). This experiment was undertaken to determine the short-term in vivo stability of endothelium on these fibronectin coated surfaces. Eight mongrel dogs underwent bilateral carotid artery replacement with both graft materials. All grafts were inoculated with 2,000 cells/mm2 using cultured autogenous venous endothelium labelled with Indium-111-oxine. The Indium-111 label in the grafts was measured immediately prior to implantation, after 1 hour of in vivo perfusion, and at explantation after 24 hours. The percentage of inoculated cells attached to the grafts before perfusion was similar for both materials, 93.3 +/- 3.0% versus 92.2 +/- 7.2%, for PE and e-PTFE respectively. All grafts were patent at one hour after implantation. PE grafts were found to have 93.8 +/- 3.9% of the attached cells present at one hour while e-PTFE grafts had only 54.5 +/- 10.8% remaining, p less than .001. After 24 hours, 5/8 (62.5%) e-PTFE grafts and 2/8 (25.0%) PE grafts remained patent, p = .13. Of the patent grafts however, endothelial cell retention was still superior on the PE grafts with 78.0 +/- 0.6% of the attached cells remaining compared to only 24.5 +/- 6.1% on e-PTFE, p less than .001. Occluded PE grafts had fewer cells remaining at 24 hours than patent ones, 78.0 +/- 0.6% versus 31.1 +/- 32.8%, respectively, p = .13. Histologically, patent PE grafts demonstrated nearly confluent endothelial monolayers while e-PTFE had patches of endothelial cells surrounded by a platelet-fibrin carpet.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1986

Enhanced strength of endothelial attachment on polyester elastomer and polytetrafluoroethylene graft surfaces with fibronectin substrate.

Successful development of a vascular prosthesis lined with endothelium may depend on the ability of the attached cells to resist shear forces after implantation. The purpose of this article is to describe a model for measurement of endothelial detachment caused by shear stress and to identify biomaterials that resist loss of attached cells as a result of shear stress. With human umbilical venous endothelium labeled with indium 111-oxine, cellular attachment to uncoated and fibronectin-coated polyester elastomer and expanded polytetrafluoroethylene (e-PTFE) graft surfaces was quantified after an 18-hour incubation. PTFE grafts prepared by immediate seeding were also studied. The relative strength of endothelial attachment was determined by the percentage of the original inoculum remaining after the seeded graft surfaces were subjected to a physiologic shear stress of 15 dynes/cm2 during in vitro perfusion. In polyester elastomer grafts, fibronectin did not significantly increase initial attachment but did increase the percentage of inoculum remaining after perfusion (92.1% vs. 39.74%, p = 0.001). A similar relationship existed between fibronectin-coated e-PTFE and immediately seeded e-PTFE preparations with 61.6% and 25.8%, respectively, of the inoculum remaining after perfusion (p = 0.001). Furthermore, the percentage of inoculum retained on fibronectin-coated polyester elastomer was significantly greater than on fibronectin-coated e-PTFE (p = 0.001). In comparing uncoated grafts, polyester elastomer had 39.7% of the inoculum retained after perfusion whereas only 1.8% was remaining on the e-PTFE grafts (p = 0.0001). We conclude that polyester elastomer permits better endothelial cell attachment than e-PTFE and that fibronectin coating enhances the strength of attachment to both graft materials.

Biocompatible Materials↗
PubMed1979

Seeding arterial prostheses with vascular endothelium. The nature of the lining.

Arterial prostheses seeded with autogenous vascular endothelium demonstrate a well-organized, cellular, inner lining. To determine the nature of the lining cells, six animals underwent replacement of the infrarenal aorta with Dacron prostheses. During the preparation of three such grafts, endothelium was scraped from the saphenous vein with a steel wool pledget, suspended in chilled Sack's solution, and mixed with blood used to preclot the graft. This suspension was omitted from the three control grafts. After six weeks, the grafts were removed, rinsed and examined. Fluorescent Factor VIII related antigen (F VIII-RA) strongly stained the lining cells. Silver nitrate Haütchen and electron microscopy preparations revealed a lining pattern characteristic of vascular endothelium. Endothelial cell-specific Weibel-Palade bodies were identified in the lining cell cytoplasm. Masson's trichrome staining revealed a relatively collagen-poor connective tissue within the seeded fabric. Transmission electron microscopy disclosed vascular smooth muscle cells between the seeded graft fabric and the lining cells. Vasa vasorum, arising from the outer capsule, penetrated the fabric to supply the inner capsules of the seeded grafts. It is concluded that the cells lining seeded canine arterial prostheses are true vascular endothelium supported by vascular smooth muscle cells, that the lining contains minimal connective tissue, and that vasa vasorum develop. Unseeded control grafts lacked these features.

Animals↗