A quantitative study of blood capillary formation (angiogenesis) concomitant with parenchymal tissue differentiation.

Examination of the rat corpus luteum (CL) provided quantitative data supporting adaptation of the developing vasculature to maximise efficient acceptance of steroids secreted from the luteal cells. Numbers of endothelial cells (ECs) significantly increased during the initial formation of the CL, followed by a further significant proliferation from day 10 to day 16 when there was maximal growth of the CL. As a consequence, there was significant growth of the vascular compartment during this time interval. The final phase of expanding endothelium (days 10 to 16) was a result of increased ECs volume with elongation of the EC in the direction of growth. Continued increase in capillary surface area and a corresponding marked reduction in diffusion distance between LC and ECs evidenced adaptation of the developing microvasculature to enable efficient endocrine function by day 16, when steroid secretion is maximal. Furthermore, from day 1 to day 3 there was close apposition of pericytes to the endothelium, suggesting the important role of pericytes in the initiation of angiogenesis. However, this degree of association was reduced from day 10 to day 16 and was a consequence of expansion of the EC cytoplasm to provide a greater surface area for transport of steroids.

Posterior ponticles and rotational stenosis of vertebral arteries. A pilot study using Doppler ultrasound velocimetry and magnetic resonance angiography.

OBJECTIVE: To determine whether the presence of posterior ponticles markedly increases by 30% or more, the incidence of major rotational stenosis of vertebral arteries. METHODS: Doppler ultrasound studies were performed in 3 private chiropractic clinics and in the radiology department of a public hospital, and magnetic resonance angiography (MRA) studies were made in the latter location. Thirty-two chiropractic patients had Doppler velocimetery, and 16 of these patients had MRA scanning. The outcome measures included changes in Doppler velocimetry signals and MRA images indicative of marked rotational stenosis of vertebral arteries. RESULTS: All vertebral arteries from the 32 patients displayed no signs indicative of marked rotational stenosis. CONCLUSION: The findings of this study show that the incidence of major rotational stenosis of vertebral arteries is not markedly increased by the presence of posterior ponticles.

Vertebral arteries and cervical rotation: modeling and magnetic resonance angiography studies.

OBJECTIVE: To determine whether lumen narrowing in vertebral arteries during atlanto-axial rotation is due to stretch or localized compression. DESIGN AND SETTING: Experiments with models were made in a private chiropractic clinic, whereas studies of cadaveric specimens were performed in an anatomy laboratory. Doppler ultrasound and magnetic resonance angiography (MRA) studies were carried out in the radiology department of a public hospital. PATIENTS: Eight patients had their vertebral arteries examined by use of a Doppler velocimeter and MRA. MAIN OUTCOME MEASURE: Stenosis of the vertebral arteries caused by stretch, localized compression, or kinking. RESULTS: All 16 vertebral arteries from the 8 patients displayed no changes in their lumen dimensions with full cervical rotation, although curves in each of the arteries did change. The model and cadaveric vertebral arteries demonstrated localized compression or kinking of the vessel wall with atlanto-axial rotation contralaterally but revealed no evidence of major contribution of stretching to stenosis. CONCLUSION: The lumen of vertebral arteries is usually unaffected by atlanto-axial rotation. In cases where there is stenosis, this is mainly due to localized compression or kinking. These findings are relevant to premanipulative screening of vertebral arteries with Doppler ultrasound scanning.

Anatomy of the lingual nerve in relation to possible damage during clinical procedures.

Damage to the lingual nerve, resulting in transient or permanent paraesthesia or anaesthesia, is a common undesirable complication of surgical interventions to the lower third molar region. The anatomy of the nerve, as it travels from its origin high in the infra-temporal fossa, to the floor of the mouth is quite variable. The most critical part of its course is where it enters the sublingual region just alongside the lingual alveolar plate of the lower third molar. A significant number of lingual nerves are located above the alveolar bone in the gingival tissues, or very close to the bone. Retraction of the lingual mucosa can lead to lingual nerve trauma. There is no doubt that the lingual nerve is extremely vulnerable in this region and clinicians must assume that it is closely adjacent to the lingual region of the lower third molar, in all cases, in order to minimize possible damage.