Is thickening of the basal lamina in the saphenous vein a hallmark of smoking?

Vasa Vasorum in Saphenous Vein for CABG: A Review of Morphological Characteristics

This short article discusses selected scanning electron microscope and transmission electron microscope features of vasa vasorum including pericytes and basement membrane of the human saphenous vein (SV) harvested with either conventional (CON) or no-touch (NT) technique for coronary artery bypass grafting. Scanning electron microscope data shows the general damage to vasa vasorum of CON-SV, while the transmission electron microscope data presents ultrastructural features of the vasa in more detail. Hence there are some features suggesting pericyte involvement in the contraction of vasa blood vessels, particularly in CON-SV. Other features associated with the vasa vasorum of both CON-SV and NT-SV preparations include thickened and/or multiplied layers of the basement membrane. In some cases, multiple layers of basement membrane embrace both pericyte and vasa microvessel making an impression of a "unit" made by basement membrane-pericyte-endothelium/microvessel. It can be speculated that this structural arrangement has an effect on the contractile and/or relaxing properties of the vessels involved. Endothelial colocalization of immunoreactive inducible nitric oxide synthase and endothelin-1 can be observed (with laser confocal microscope) in some of the vasa microvessels. It can be speculated that this phenomenon, particularly of the expression of inducible nitric oxide synthase, might be related to structurally changed vasa vessels, e.g., with expanded basement membrane. Fine physiological relationships between vasa vasorum endothelium, basement membrane, pericyte, and perivascular nerves have yet to be uncovered in the detail needed for better understanding of the cells'specific effects in SV preparations for coronary artery bypass grafting.

The effect of smoking on the symptoms and progression of multiple sclerosis: a review

Multiple sclerosis (MS) is a chronic inflammatory neurodegenerative disorder of the central nervous system with characteristic demyelinating lesions and axonal loss. MS accounts for the most common cause of neurological disability in young adults in the Western world. The clinical manifestations and the course of MS are highly variable. The early stage of the disease is usually characterized by attacks of neurological dysfunction with complete or incomplete recovery, however, with time disability accumulates in many patients. MS is believed to result from an interplay between susceptibility genes and environmental factors, one of which is smoking. Smoking, a worldwide epidemic, can be regarded as an important risk factor for MS particularly because of its modifiable nature in the quest to prevent or temper the disease course in MS as well as providing possible insights into MS pathogenesis. There are also reports that smoking may influence the symptoms and disease progression in patients with MS. The purpose of this article is to review the effects of smoking on MS symptoms and progression. We conclude that (1) although there are some early reports on worsening of MS symptoms by smoking, the existing evidence is insufficient to thoroughly assess the effects of smoking on the myriad of MS symptoms and (2) smoking seems to adversely influence disease progression in MS patients. We also discuss the potential biological mechanisms linking smoking and MS.

Prebypass histological and ultrastructural evaluation of the long saphenous vein as a predictor of early graft failure

BACKGROUND

Twenty percent of the long saphenous vein (LSV) grafts that are employed as coronary bypass conduits occlude during the first year after the operation. The aim of this study was to evaluate the morphological parameters of the LSV grafts before implantation as predictors for the early occlusion of the grafts.

METHODS

Forty-two samples of LSV grafts were examined via light, transmission electron, and scanning electron microscopy and evaluated clinically and by angiography at 6 months and 2 years after the operation. Morphological parameters were statistically analyzed and examined for their significance on the viability of the vein grafts.

RESULTS

Six (14.28%) of the examined grafts occluded within the first 6 months after the operation, and 11 grafts (26.19%) occluded within the first 2 years. The grafts that occluded at 6 months were characterized by thick intima (mean value, 206+/-32.29 vs. 67.44+/-10.17 in the group functioning normally and 98.42+/-34 in the group occluded within 2 years), low endothelial coverage (22.7+/-4.04 vs. 64.61+/-2.89 and 26.06+/-1.78 in the corresponding groups), and narrow lumen (46.73+/-9.69 vs. 527.18+/-45.78 and 204.26+/-16.5 in the corresponding groups). The presence of foam cells, edema, calcification, neovascularization, and thrombus in the lumen of the veins is frequently observed in the wall of the occluded vein grafts, whereas fibrosis does not seem to be related.

CONCLUSIONS

LSV grafts with low endothelial cell coverage, stenosis of the lumen, and thick walls are at an increased risk of developing intrawall lesions that lead to early graft failure.

Predictors of death during 10 years after coronary artery bypass grafting with particular emphasis on age

OBJECTIVES

To describe predictors of death during 10 years of follow-up after coronary artery bypass grafting (CABG); to evaluate whether age interacts with the influence of various predictors on outcome; and to compare the mortality during 10 years after CABG with the mortality in an age- and sex-matched control population.

DESIGN

Prospective, observational study.

SETTING

Department of Thoracic and Cardiovascular Surgery at Sahlgrenska University Hospital and Scandinavian Heart Centre in Göteborg, Sweden.

PARTICIPANTS

All patients from western Sweden who underwent CABG between 1 June 1988 and 1 June 1991 without simultaneous valve surgery and with no previous CABG.

MAIN OUTCOME MEASUREMENTS

All-cause mortality during 10 years but more than 30 days after CABG.

RESULTS

In all, 2000 patients participated in the survey. The following factors appeared as independent predictors of death: preoperative factors-age, history of congestive heart failure, cerebrovascular disease, history of intermittent claudication, current smoking, degree of left ventricular impairment, valvular disease and duration of angina pectoris; peroperative factors-ventilator time and neurological complications; postoperative factors-arrhythmia, requirement of digitalis and requirement of antidiabetics. There was an interaction between age and history of cerebrovascular disease with a stronger impact on outcome in younger patients. The late (>30 days after CABG) 10-year mortality in the study cohort was 29.6% compared with 25.9% in the control population (P=0.02).

CONCLUSION

Among patients who underwent CABG, 13 independent predictors for mortality were found, mainly among preoperative factors but also among peroperative factors, postoperative complications and medication requirement after CABG.

Immunolabeling of type IV collagen, laminin, and alpha-smooth muscle actin cells in the intima of normal and varicose saphenous veins

Smooth muscle cells (SMC) of normal and varicose human saphenous intima were studied on cryostat sections by immunohistochemistry with alpha-smooth muscle actin (ASMA), type IV collagen, and laminin antibodies and also by transmission electron microscopy. The findings suggest two structurally distinct subtypes of smooth muscle cells with thin and thicker external lamina. Thin external lamina SMC were characterized by laminin, type IV collagen, weaker external lamina reactivity, and intense cytoplasmic alpha-smooth muscle actin immunoreactivity. Ultrastructurally, they exhibited abundant cytoplasmic microfilaments and thin external lamina. These cells were found isolated or, more frequently, clustered in fascicles close to the subendothelium in focal or zonal cushions, or in diffuse enlargement of the intima. In contrast, thicker external lamina smooth muscle cells were intensely immunolabeled for laminin and collagen IV, showing irregular cytoplasmic ASMA reaction. Single or clustered thicker external lamina SMC were seen predominantly in zonal cushions and in intima diffuse enlargement. It is very likely that these cells secrete these matrices in a nonpolarized fashion. The thicker external lamina of these SMCs showed a fine granular amorphous aspect sometimes intermingled with microfibrils. These external lamina were interposed between neighboring cells and exposed to collagen fibrils and elastic fibers. The cells also exhibited rarefaction of the cytoplasmic filaments. Intermediary cells exhibiting both features were rarely seen. Thicker external lamina SMC should be discussed in the context of an adaptive/proliferative response leading to dysfunction of the fibroelastic properties of the vein wall.

Predictors of death during 5 years after coronary artery bypass grafting

AIM

To describe predictors of death during five years of follow-up after coronary artery bypass grafting (CABG).

METHODS

All patients who underwent CABG during a period of three years in Western Sweden were included in the analysis and were prospectively followed for five years. Mortality was related to preoperative and peroperative factors as well as findings at physical examination and medication 4-7 days after the operation.

RESULTS

In all 2121 patients underwent CABG without simultaneous valve surgery during the study period. The overall five-year mortality was 14.6%. The following appeared as independent predictors of death during five years but >30 days after CABG: Current smoking (relative risk ratio 2.43 [95% Ci 1.64-3.61]) degree of impairment of left ventricular function (1.51 [1.23-1.86]), a history of congestive heart failure (1.91 [1.35-2.701), age (1.04 [1.02-1.06]) arrhythmia 4-7 days after CABG (1.89 [1.26-2.83]), intermittent claudication (1.73 [1.19-2.52]), a history of diabetes (1.71 [1.16-2.51]), time in respirator (1.43 [1.13-1.81]), a history of cerebrovascular disease (1.72 [1.13-2.64]), treatment with digitalis at day 4-7 (1.48 [1.07-2.05]), enzyme release (1.49 [1.03-2.16]).

CONCLUSION

Among patients who underwent CABG 11 independent predictors for mortality were found including smoking habits at CABG, history of cardiovascular diseases, left ventricular dysfunction, age, post operative complications and medication after CABG.

Nicotine and its metabolite cotinine are mitogenic for human vascular smooth muscle cells

PURPOSE

Intimal hyperplasia caused by smooth muscle cell (SMC) proliferation is the major cause of infrainguinal graft failure within the first 12 months. Tobacco smoking is associated with a twofold increase in graft failure within the first year of extremity bypass surgery, but the mechanism is not clearly understood. This study evaluated the effect of nicotine and its major stable metabolite cotinine on vascular SMC proliferation in vitro.

METHODS

SMC were harvested from human arteries and grown in culture with standard methods. Cells were seeded at a density of 1.8 x 10(4) cells/well in 24 multiwell dishes and cell cycle-synchronized. Subsequently the SMC were incubated with media containing 0.1% or 15% fetal bovine serum and nicotine or cotinine at concentrations ranging from 10(-9) mol/L to 10(-6) mol/L. Control samples were incubated with corresponding media but without the drugs. SMC proliferation was determined at 4 days with a cell counter. DNA synthesis was assessed at 24 hours with 3H-thymidine uptake. The results were expressed as a percentage change compared with the control samples (mean +/- SEM). Results were analyzed by analysis of variance and t tests.

RESULTS

In the presence of serum both nicotine and cotinine at concentrations of 10(-7) and 10(-8) mol/L were mitogenic for SMC in vitro (p < 0.05). A weak mitogenic effect was observed at a low serum concentration for cotinine but not nicotine. Cotinine at a concentration of 10(-9) mol/L, a level seen among passive smokers, was a statistically significant stimulus for DNA synthesis in both minimum serum and serum-supplemented media. At high concentrations both substances were toxic for the cells.

CONCLUSION

We have demonstrated a potential role for nicotine and cotinine in the development of intimal hyperplasia and ultimately failure of the vascular reconstruction.

Smoking impairs the activity of endothelial nitric oxide synthase in saphenous vein

Smoking impairs the endothelium-dependent relaxation of arteries and veins, with the maximum relaxation in response to the calcium ionophore A23187 of saphenous vein rings being reduced from 53 +/- 4% in nonsmokers to 27 +/- 5% in smokers. We have investigated whether this endothelial dysfunction was attributable to altered activity or concentration of nitric oxide synthase (NOS). The concentration of NOS in saphenous vein endothelium, determined by Western blotting and immunohistochemistry, was not different in nonsmokers and smokers. Nitrite production from vein strips stimulated with A23187 was higher in nonsmokers (median 23.6 nmol.cm-2.h-1) than smokers (median 3.3 nmol.cm-2.h-1), P=.001, this difference being abolished when vein strips were preincubated in the presence of NG-monomethyl-L-arginine. Organ chamber studies to monitor the endothelium-dependent relaxation of vein rings in response to A23187 showed that preincubation of rings from smokers with either L-arginine (3mmol/L) or superoxide dismutase (250 U/mL) did not improve the maximum relaxation. In contrast, preincubation of vein rings from smokers with 20 micromol/L tetrahydrobiopterin increased the maximum relaxation from 27 +/- 5% to 51 +/- 6%, P=.01. Preincubation of vein from smokers with tetrahydrobiopterin also significantly increased nitrite and cGMP production in response to stimulation with A23187. The impaired endothelium-dependent relaxation of saphenous vein rings from smokers appears to be caused by a reduction in the activity of endothelial NOS that is attributable to an inadequate supply of the coenzyme tetrahydrobiopterin.