Skin blood flow during histamine flare using the clearance of epicutaneous applied Xenon-133 in diabetic and non-diabetic subjects

Nervous control of blood flow in the orofacial region

The blood vessels of orofacial tissues are innervated by cranial parasympathetic, superior cervical sympathetic, and trigeminal nerves, a situation somewhat different from that seen in body skin. This review summarizes our current knowledge of the nervous control of blood flow in the orofacial region, and focuses on what we know of the respective roles of sympathetic, parasympathetic, and trigeminal sensory nerves in the regulation of blood flow in this region, with particular attention being paid to the mutual interaction between them.

Blood flow in diabetics with foot lesions due to 'small vessel disease'

Blood flow was measured in the feet and toes of 23 diabetics, 7 controls and 6 non-diabetic neuropathic controls, using venous occlusion plethysmography. All of the diabetics showed a characteristic flow abnormality with mild hyperperfusion of the foot at rest but impaired peak flow following arterial occlusion. When the diabetics were subdivided into those with 'small vessel disease', those with neuropathic ulceration and those with neuropathy but no ulceration, the groups had remarkably comparable blood flows, except that peak great toe blood flow was rather lower in small vessel disease. In small vessel disease, the combination of high resting blood flow and elevated foot venous oxygen saturation suggests that the hyperperfusion is due to arteriovenous shunting. It seems likely that the toe lesions ascribed to small vessel disease were in fact manifestations of severe diabetic neuropathy. The term small vessel disease should be avoided in the context of diabetic foot lesions.

Non-invasive tests of neurovascular function: reduced axon reflex responses in diabetes mellitus of man and streptozotocin-induced diabetes of the rat

The prevalence of neuropathy and microangiopathy complicating diabetes mellitus led to our development of non-invasive tests of neurovascular function. On the foot dorsum of consenting normal subjects, diabetic patients, normal and streptozotocin-induced (STZ) diabetic rats, transcutaneous electrical nerve stimulation (TENS) with 1, 2, 4, 8, 16 pulses at 150 V, 0.75 ms, at 2 Hz, evokes transient cutaneous axon reflex vasodilatation measured by a laser Doppler (Periflux Pfld). This tests the integrity of both the polymodal nociceptor/primary afferent nerves and microvessels in the skin. TENS-evoked axon reflexes are reduced in diabetics (particularly with neuropathy) and progressively in rats 40-100 days after STZ administration. This could be reversed in rats by a single injection of 3 units of soluble insulin at 100 days post STZ. The microvascular endothelium and smooth muscle are tested in man by measuring vasodilatation induced by iontophoretic application of 2 mC acetylcholine (ACh) and 4 mC sodium nitroprusside (NaNP), respectively. Diabetics show reduced ACh-evoked endothelium-dependent vasodilator responses, but the direct smooth muscle (endothelium-independent) responses evoked by NaNP are not reduced. Such functional neurovascular disturbances probably underlie many complications of diabetes mellitus, and the potential for these to be reversible with appropriate therapy can now be examined with such neurovascular tests.

Blood flow and epithelial thickness in different regions of feline oral mucosa and skin

The relationship between epithelial thickness and blood flow was examined in 6 mucosal and 3 skin regions of the cat. Blood flow to these tissues was determined using the radiolabelled microsphere method. From histologic sections the proportion of the tissue biopsy occupied by epithelium and the average epithelial thickness were calculated. The oral tissues had a significantly higher blood flow than the skin regions (p less than 0.05). In terms of epithelial thickness, the tissues could be divided into 4 groups (p less than 0.05). These were: a) palate; b) gingival regions and dorsum of the tongue; c) lip and buccal mucosa; d) all skin regions. When epithelial thickness was related to blood flow there was a significant positive correlation (p less than 0.005) indicating that a thicker epithelium is associated with a higher blood flow. This finding may reflect the greater metabolic demands of the thicker epithelia.