Ultrastructure of capillaries in South African diabetics. II. Muscle capillaries

Demonstration of uniform capillary basal lamina thickness by computer technology

Blood capillaries are assumed to be circular cylinders composed of an inner layer of endothelial cells surrounded by an acellular uniformly thick basal lamina. The capillary basal lamina is the structural and functional interface between the capillary endothelial cells and the adjacent extracellular matrix, important in growth and control mechanisms of the endothelial cell. Capillaries examined in electron micrographs are cut randomly and a projected image of a capillary other than perpendicular to its long axis will produce artifactual thickening of the assumed uniformly thick basal lamina. We have developed an interactive computer program to determine the thickness of the capillary basal lamina that corrects the thickness resulting from the sectioning artifact. We have applied this methodology to demonstrate that the basal lamina of the pancreatic capillaries of the rat are uniformly thick.

Diabetic choroidal and iris vasculature scanning electron microscopy findings

Scanning Electron Microscopy (SEM) was used to study vascular casts of twenty-four autopsy eyes taken from patients with long-standing insulin-dependent Diabetes Mellitus. These casts were compared to casts of ten 'normal' autopsy eyes from patients without a history of diabetes or other vascular disease. The SEM findings in the choroidal vessels of the diabetic eyes included: increased tortuosity, focal vascular dilations and narrowings, hypercellularity, vascular loops and microaneurysm formation, 'drop-out' of choriocapillaries, and sinus-like structure formation between choroidal lobules in the equatorial area. In the iris, neovascularization was evident in the vascular casts in cases with clinically recognized rubeosis iridis. These findings indicate that there is significant involvement of the uveal tract in diabetic eyes. The present study strongly supports the Hidayat and Fine light microscopic observation that the diabetic choroid demonstrates significant vascular changes (e.g. narrowed vessels with possible 'drop-out' of capillaries and neovascularization). Changes in the diabetic choroid, especially in the choriocapillaris, may be a contributing factor in diabetic retinopathy, resulting in decreased oxygenation of the outer layer of the retina. Short reviews and updated information of diabetic eye disease provide some additional insights into the vascular problems in the eye.

Pathomorphologic aspects of muscular tissue in diabetes mellitus

Biopsy specimens from the myocardium were examined in a series of 145 patients who had elected coronary arterial bypass grafting. The patients were divided into three groups; 1) overtly diabetic (OD) patients; 2) chemically diabetic (CD) patients, who demonstrated impaired glucose tolerance only when stressed with a sugar load; and 3) normoglycemic, nondiabetic (ND) patients, who served as a control group. Tissue plugs from the left anterior apical segment of the heart and from the quadriceps femoris in 71 patients, for comparative evaluation, were prepared for ultrastructural examination. Findings were as follows: 1) Myocardial hypertrophy and interstitial fibrosis were twin characteristic abnormalities, seen in all but two of the biopsy specimens; capillary endothelial changes, the third most common abnormality, were present in approximately half of these specimens, regardless of the patients' metabolic status. 2) In patients matched by sex, age, weight, blood pressure, preoperative myocardial ventricular function, and coronary arterial integrity, capillary basal laminar thickening represented a pathomorphologic hallmark, distinguishing structural alterations in the diabetic from those in the normoglycemic patient. 3) Although clear-cut and statistically significant thickening of basal laminae was noticeable in OD patients, a) in the quadriceps markedly increased laminar thickening was present in a number of ND patients, rendering interpretation of this change in skeletal muscle as pathognomonic for diabetes doubtful; and b) within cardiac muscle this increase in laminar width was less than that seen in skeletal muscle, leaving the functional implications of this alteration in doubt. 4) Early but statistically significant increases in capillary basal laminar thickening were observed in the myocardium of CD patients; these patients demonstrated impaired glucose tolerance only when stressed with a sugar load, without exhibiting overt diabetic manifestations. 5) In this group of highly selected patients with epicardial coronary arterial disease, the histopathologic profile of the diabetic myocardium did not include distinctive abnormalities sufficient to warrant the designation of "diabetic cardiomyopathy," indicating that coronary arterial bypass grafting can be recommended for the diabetic patient who requires this procedure.

Electron microscopic observation of gastric mucosal capillaries in diabetics--relationship between diabetic microangiopathy and complications following gastrectomy

An electron microscopic study was made of the gastric mucosal capillaries (GMC) of diabetic patients. Ultrastructural findings, including diabetic microangiopathy (DMA), and clinical features of these diabetic patients were investigated in relation to anastomotic leakage after gastrectomy. The gastric mucosa of resected stomachs from 12 diabetics and 10 nondiabetics were examined. Ultrastructurally, DMA was demonstrated in the stomachs of diabetics, in which the basement membrane of GMC was thicker. The degree of this DMA in the stomach significantly correlated with the duration of diabetes and the degree of DMA found in the skin, but not with age and fasting plasma glucose (FPG) level. Marked DMA was observed with significant frequency in diabetics with anastomotic leakage after gastrectomy. In our hospital, anastomotic leakage after gastrectomy occurred in 9 out of 53 diabetics. Diabetics with anastomotic leakage had severe FPG, a long duration of diabetes and diabetic retinopathy. It seems reasonable to presume that anastomotic leakage after gastrectomy occurs more frequently in diabetics with ultrastructurally severe DMA, clinically severe FPG and relatively long duration of diabetes.

Overview article: basal lamina of epidermis, muscle fibers, muscle capillaries, and renal tubules: changes with aging and in diabetes mellitus

Using autopsy material from 14 diabetics and 10 controls (8-84 years old), the authors measured the thickness of basal lamina (BL) in skeletal muscle capillaries, renal tubules, skeletal muscle fibers, and epidermis to determine whether BL accumulation is a generalized phenomenon or limited only to certain anatomic structures. The four structures were selected because earlier experiments in animals have shown that in two (muscle capillaries and renal tubules) BL accumulates as a by-product of cell renewal while in the other two (muscle fibers and epidermis) it does not. In human tissues we found that BL accumulates in muscle capillaries and renal tubules but not in muscle fibers and epidermis, in muscle capillaries and in renal tubules it accumulates in controls and in diabetics as a function of aging, more BL in both anatomic structures accumulates in diabetics than in controls, and the extent of BL accumulation in muscle capillaries and renal tubules does not correlate with duration of diabetes mellitus. In addition to the fact that BL does not accumulate in all anatomic structures in which BL is normally present, the observations indicate that diabetes alone is not responsible for BL accumulation, diabetes exaggerates age-dependent accumulation of BL, and accumulation of BL in man is probably a by-product of cell renewal.

Proposed metabolic dysfunctions in diabetic microthromboses and microangiopathy

This report describes, at least in part, the role of prostaglandin and cyclic nucleotide metabolism in the etiology of the vascular disease associated with diabetes mellitus. Alterations in this metabolism seem associated with induction of platelet aggregation leads to microthromboses leads to microangiopathy sequences that are subtle but inexorable over a long period of time. Prostaglandins are generally elevated in blood from patients having frank signs of diabetic retinopathy when compared with nondiabetic subjects. Prostaglandin concentration remained elevated in diabetic retinopathy patients receiving indomethacin. We formed, therefore, the working hypothesis--yet to be fully tested either in patients or animal models with and without indomethacin treatment--that the increased prostacyclin (synthesized by endothelial microsomes) and cyclic-AMP production, both of which favor prevention of platelet aggregation, accompany the increased concentration of one or more of the prostaglandin E and F compounds. Concurrently, there may be an accompanying reduction of thromboxane A2 (synthesized by platelet microsomes) and cyclic-GMP (both of which favor platelet aggregation) production in the diabetic patients. The elevated prostaglandin in the diabetic patients not receiving indomethacin could possibly be directed toward slowing but not preventing the progression of the complex disease process in diabetes.

Basement membranes of small cardiac vessels in patients with diabetes and myxoedema: preliminary observations

Ultrastructural observations on the basement membranes of small vessels from hearts of patients with diabetes, myxoedema and neither disease collected post mortem, reveal that the membranes of those with diabetes are nearly three times as thick as those in normal hearts (P less than 0.001), while in patients with myxoedema they are twice normal thickness (P less than 0.001). A significant difference was demonstrated between the thickness of the basement membrane in patients with diabetes and those with myxoedema (P less than 0.001).

Quantitative electron microscopic study of capillaries in diabetes mellitus

A systematic microscopic examination of all elements of the capillary wall was performed on quadriceps muscle biopsies from 9 diabetic patients and 8 controls. The capillary basement membrane (CBM) was markedly thicker in diabetics; it consisted of several lamellae and contained large vacuoles which were never observed in non-diabetic subjects. Large magnifications revealed fibrils in greater number and markedly larger in diameter in diabetics, these accounting for a considerable volume of the CBM and the adventitia and increased diameter and thickness of the capillary wall, without encroaching on the lumen. The intracellular fibrils in pericytes and endothelial cells were also larger and thicker in diabetic subjects. The prevalence of fibrillar material in the vascular disease of diabetes mellitus suggests the importance of research into possible measures to arrest fibril formation.

Coronary graft flow and glucose tolerance: evidence against the existence of myocardial microvascular disease

Patients having coronary bypass for stable angina pectoris were grouped on the basis of the two hour plasma sugar of the glucose tolerance test: Group I, 120 mgs% (159 grafts); Group II, 120-150 (93 grafts); Group III, 150-200 (131 grafts) and Group IV, 200 (57 grafts) or patients receiving therapy for diabetes mellitus (10 patients, 21 grafts). Five of 10 diabetic patients had genetic evidence of diabetes and an average duration of therapy of 6.5 years. Blood flow was measured in 461 grafts with an electromagnetic flow probe after discontinuation of cardiopulmonary bypass in a stable state, after a 30 second graft occlusion and after injection of 15 mg of papaverine into the graft. Mean arterial pressure, graft flow and coronary resistance for each succeeding group did not vary significantly when compared with Group I. Analysis of phasic flow in 10 grafts to the left anterior descending indicates that the same proportion of flow occurs during systole and diastole in the basal state and after pappaverine. Coronary flow and resistance in patients with abnormal glucose metabolism and maturity onset diabetes do not provide evidence for the existence of myocardial microangiopathy.

Diabetic capillaropathy

Diabetic capillaropathy is defined and reviewed. A number of physiological and pathological variables, such as aging, venous stasis, and environment, may affect the thickness of the capillary basal lamina. Since these effects have not been adequately measured, it is impossible to know precisely what increment diabetes mellitus adds to the basal lamina. Because of these variables and technical difficulties, the detection of early diabetes is impossible at this time. However, the ultrastructure of the peripheral capillaries in the late stages of diabetes provides a means of detecting the presence of widespread capillaropathy when clinical evidence is difficult to obtain or uncertain.

Capillary basement membrane width in diabetic children

The effect of juvenile onset diabetes mellitus on quadriceps muscle capillary basement membrane (QCBM) width has been examined by the electron microscopic morphometric method previously developed in this laboratory. The results demonstrate that in this age group QCBM thickening is strongly related to the age of the diabetic subject. As a result, in contrast to the almost constant thickening of QCBM that has consistently been documented in diabetic adults, QCBM hypertrophy is present in only 40 per cent of children with diabetes mellitus. As was previously shown to be the case in adults, in children, too, QCBM thickening is unrelated to the duration of the diabetes. Finally, the finding that QCBM hypertrophy is present at the time of acute onset of juvenile diabetes mellitus in 30 per cent of children, coupled with the fact that this lesion is not affected by duration of hyperglycemia, strongly supports our previous conclusion that diabetic microangiopathy is independent of the hyperglycemia of this disease. On the other hand, barring the possibility that microangiopathy in the pancreas precedes that in muscle, these results represent evidence against the suggestion that basement membrane hypertrophy represents the primary lesion of the diabetic syndrome.

Microcirculation in diabetes mellitus: a study of gingival biopsies

Gingival biopsy specimens from 24 diabetic patients, six obese persons, and six controls were studied statistically and morphologically to detect vascular basement membrane changes using a proposed classification of microvessels. Statistically significant basement membrane thickening is seen in all diabetic groups in most true capillaries and vessels proximal to them, especially in terminal arterioles and metarterioles, although the degree and extent of the changes vary among different clinical groups and vessel types. The basement membrane thickening is characterized by increased amorphous, granular, and fibrillary material with occasional scattered collagenous fibrils. Although nonspecific, basement membrane thickening in microvessels at, and especially proximal to, the level of true capillaries is intimately related to diabetes. Gingival biopsy may possibly be used as an adjunct in the diagnosis of diabetes.

Diabetic retinopathy, duration of diabetes and risk factors of atherosclerotic cardiovascular disease

The present study, concerning 145 insulin-dependent diabetics showed positive relationships between the severity of retinal disease on the one hand, and body weight, blood pressure, and serum cholesterol level on the other. These relationships remain significant when the duration of the clinical diabetes and the age of the patient are taken into account. Two interpretations are suggested. They are not incompatible. In diabetic subjects, either the increase in blood pressure and serum cholesterol level causes an aggravation of diabetic retinopathy or there exists a common factor at the origin of retinal lesions and of an increase in risk of cardiovascular disease through atherosclerosis.

Diabetic angiopathy

The vascular complications occurring in diabetes mellitus are reviewed. In addition to the long recognised involvement of large vessels by atheroma and Monckeberg's sclerosis, the more recently described microangiopathy affecting arterioles, venules and, in particular, capillaries is also described. The significance of this microangiopathy in the diabetic syndrome is outlined, and possible pathogenetic mechanisms involved in its development are discussed.