Why Rudolph's nose is red: observational study.

OBJECTIVE: To characterise the functional morphology of the nasal microcirculation in humans in comparison with reindeer as a means of testing the hypothesis that the luminous red nose of Rudolph, one of the most well known reindeer pulling Santa Claus's sleigh, is due to the presence of a highly dense and rich nasal microcirculation. DESIGN: Observational study. SETTING: Tromsø, Norway (near the North Pole), and Amsterdam, the Netherlands. PARTICIPANTS: Five healthy human volunteers, two adult reindeer, and a patient with grade 3 nasal polyposis. MAIN OUTCOME MEASURES: Architecture of the microvasculature of the nasal septal mucosa and head of the inferior turbinates, kinetics of red blood cells, and real time reactivity of the microcirculation to topical medicines. RESULTS: Similarities between human and reindeer nasal microcirculation were uncovered. Hairpin-like capillaries in the reindeers' nasal septal mucosa were rich in red blood cells, with a perfused vessel density of 20 (SD 0.7) mm/mm(2). Scattered crypt or gland-like structures surrounded by capillaries containing flowing red blood cells were found in human and reindeer noses. In a healthy volunteer, nasal microvascular reactivity was demonstrated by the application of a local anaesthetic with vasoconstrictor activity, which resulted in direct cessation of capillary blood flow. Abnormal microvasculature was observed in the patient with nasal polyposis. CONCLUSIONS: The nasal microcirculation of reindeer is richly vascularised, with a vascular density 25% higher than that in humans. These results highlight the intrinsic physiological properties of Rudolph's legendary luminous red nose, which help to protect it from freezing during sleigh rides and to regulate the temperature of the reindeer's brain, factors essential for flying reindeer pulling Santa Claus's sleigh under extreme temperatures.

Monitoring microcirculatory alterations in oral squamous cell carcinoma following photodynamic therapy.

BACKGROUND: One of the mechanisms through which photodynamic therapy (PDT) is thought to elicit tumour destruction is by producing microvascular damage and obstruction of nutritive blood flow. The aim of this study was to directly monitor and quantify microcirculatory changes following tissue illumination by PDT for oral squamous cell carcinoma. METHODS: Ten consecutive patients receiving PDT for a carcinoma in situ, a T1 or T2 tumour in the oral cavity without evidence of lymph node metastasis were selected for this study. Tumour and marginal healthy mucosa total capillary density (TCD) and functional capillary density (FCD) inside the field of illumination were measured and compared using sidestream dark-field (SDF) imaging prior to tissue illumination, immediately after PDT, and again after 15min. RESULTS: Baseline mean tumour TCD was 21.2±5capillaries per square millimetres (cpll/mm²) and 24.9±19cpll/mm² in the surrounding marginal healthy tissue; there were no significant differences between tumour and healthy tissue or time points. Comparisons between baseline and post-illumination time points revealed significant differences in both tumour and healthy tissue FCD (P<0.05). No significant differences in FCD were observed between the two tissues. CONCLUSIONS: Our findings using SDF imaging demonstrate that PDT significantly attenuates tumour and marginal healthy tissue perfusion by directly disrupting the functionality of the microcirculation.