Blood flow to skeletal muscle during exercise is greater in the trained state. We hypothesized that intrinsic vasomotor reactivity of arteries to active muscle during training bouts would be altered to favor a relative vasodilation after training. To test this hypothesis, miniature swine were pen confined (Sed; n = 30) or treadmill trained for 5 days/wk over 16-20 wk (Trn; n = 32). Efficacy of training was indicated by myocardial hypertrophy (4.84 +/- 0.11 and 5.81 +/- 0.12 g/kg body wt for Sed and Trn, respectively, P < 0.0005), training bradycardia at several submaximal running speeds of a maximal exercise test, increased running time to exhaustion (26 +/- 1 and 35 +/- 1 min for Sed and Trn, respectively, P < 0.0005), and increased oxidative capacities of several locomotory skeletal muscles. Segments of femoral, brachial, mesenteric, renal, and hepatic arteries were isolated from Sed and Trn swine. Isometric contractile and relaxation properties of vascular rings cut from these segments were determined in vitro. Contractile responses to KCl and norepinephrine (NE) were determined, as were relaxation responses to sodium nitroprusside and adenosine, agents acting directly on vascular smooth muscle, and the endothelium-dependent agents bradykinin and the calcium ionophore A-23187. Responses to vasocontractile and vasorelaxation agents were not different between Sed and Trn swine for vessels serving active muscles (i.e., femoral, brachial). On the other hand, renal arterial rings from Trn swine exhibited lesser contractile responses than those from Sed swine across a range of NE concentrations (P < 0.05) and approximately 25% less maximal contractile response to NE (32.7 +/- 2.6 and 24.2 +/- 2.1 g for Sed and Trn, respectively, P < 0.01). Responses of other vessels serving viscera (i.e., mesenteric, hepatic) were unchanged with training. These data indicate that vasomotor reactivity of porcine conduit-type arteries generally does not change with exercise training. An exception is the lesser contractile response to NE in renal artery, which could permit better preservation of renal blood flow during acute exercise in trained animals.

The tunica media of the giraffe carotid artery is characterised by a predominantly muscular structure, except for a small area at the origins of the occipital and the vestigal internal carotid arteries. The latter has a preponderantly elastic structure and corresponds in extent to the parts of the carotid arterial wall innervated by a branch of the glossopharyngeal nerve. Sensory nerve terminals, characterised by an abundance of mitochondria, are found in the deeper parts of the adventitia bordering the elastic zone. It is concluded that the elastic zone at the cranial portion of the carotid arterial system in the giraffe constitutes the equivalent of a carotid sinus. It is further suggested that the preponderance of elastic tissue in this area is a morphological adaptation of the arterial wall to a baroreceptor function. Pertinent to this suggestion is the demonstration of a close structural relationship between the sensory nerve endings and the elastic fibres.

There is little knowledge of the existence of Alzheimer disease (AD) or Alzheimer type of dementia in indigenous populations of developing countries. In an effort to evaluate this, we assessed the deposition of amyloid beta (A beta) protein and other lesions associated with AD in brains of elderly East Africans. Brain tissues were examined from 32 subjects, aged 45 to 83 years with no apparent neurological disease, who came to autopsy at two medical Institutions in Nairobi and Dar es Salaam. An age-matched sample from subjects who had died from similar causes in Cleveland was assessed in parallel. Of the 20 samples from Nairobi, 3 (15%) brains exhibited neocortical A beta deposits that varied from numerous diffuse to highly localized compact or neuritic plaques, many of which were also thioflavin S positive. Two of the cases had profound A beta deposition in the prefrontal and temporal cortices and one of these also exhibited moderate to severe cerebral amyloid angiopathy. Similarly, 2 of the 12 samples from Dar es Salaam exhibited diffuse and compact A beta deposits that were also predominantly reactive for the longer A beta 42 species compared to A beta 40. We also noted that A beta plaques were variably immunoreactive for amyloid associated proteins, apolipoprotein E, serum amyloid P and complement C3. Tau protein reactive neurofibrillary tangles (NFT) were also evident in the hippocampus of 4 subjects. By comparison, 4 (20%) of the 20 samples from randomly selected autopsies performed in Cleveland showed A beta deposits within diffuse and compact parenchymal plaques and the vasculature. These observations suggest A beta deposition and some NFT in brains of non-demented East Africans are qualitatively and quantitatively similar to that in age-matched elderly controls from Cleveland. While our small scale study does not document similar prevalence rates of preclinical AD, it suggests that elderly East Africans are unlikely to escape AD as it is known in developed countries.

No abstract

We report the distribution of sympathetic nerves in the hindlimb arterial system of the giraffe based on the histochemical demonstration of monoamines by the sucrose-potassium phosphate-glyoxylic acid method. It is noted that the hindlimb arterial system shows regional variations in its sympathetic innervation with regard to the density and the penetration of the nerves into the tunica media not hitherto described. The femoral and popliteal arteries showed a paucity of sympathetic innervation. Distally the dorsal pedal and great metatarsal arteries showed sparse sympathetic innervation characterized by a tendency toward exclusion of the nerves toward the outer layers of the tunica media. In contrast, the anterior (cranial) tibial artery in the leg revealed a relatively rich pattern of sympathetic innervation and a greater penetration of the nerves into the tunica media. The latter part of the arterial system showed a marked thickening of the tunica media and luminal narrowing, thus suggesting a "sphincteric" function. It is conceivable that this sphincter subserves a dual function, namely, to modulate blood flow to the distal parts of the limbs, and secondly to channel blood to the thigh and crural musculature. Pertinent to this is the fact that the presumptive sphincter occurs immediately after the crural muscular branches are given off.