{'fraction_non_alphanumeric': 0.02533783783783784, 'fraction_numerical': 0.01632882882882883, 'mean_word_length': 4.9630872483221475, 'pattern_counts': {'":': 0, '<': 0, '<?xml version=': 0, '>': 0, 'https://': 0, 'lorem ipsum': 0, 'www.': 0, 'xml': 0}, 'pii_count': 0, 'substrings_counts': 0, 'word_list_counts': {'cursed_substrings.json': 0, 'profanity_word_list.json': 0, 'sexual_word_list.json': 0, 'zh_pornsignals.json': 0}}
Effect of Purified Heat‐Labile Toxin of Bordetella bronchiseptica on the Peripheral Blood Vessels in Guinea Pigs or Suckling Mice

The heat-labile toxin (HLT) produced by Bordetella species induces a hemorrhagic dermonecrosis with its surrounding ischemic lesions and a splenic atrophy when injected into animals (2, 10). Since its discovery, this toxin has been generally regarded as an important virulence factor (4) in the pathogenesis of the disease. However the mechanism by which HLT induces these lesions is poorly understood. Previously we described the purification and characterization of HLT from B. bronchiseptica (1). In the present work, we examined the in vivo effect of the purified HLT on the peripheral blood vessels to clarify its mode of action in guinea pigs and mice, and found that HLT affects the peripheral blood vessels to induce vasoconstriction. The purified HLT was obtained from B. bronchiseptica strain H-16 by the method described previously (1). Its minimum dermonecrotizing dose (MND) was approximately 0.75 ng in the shaved back of female Hartley guinea pigs, weighing 300 to 350 g. The ddY strain female or male mice, 2-day-old, were also used throughout the studies. Under pentobarbiturate anesthesis administrated intraperitoneally, a part of the dorsal skin was surgically reflected and fixed under a microscope so as to be able to observe the exposed peripheral blood vessels on the inner surface of skin. Before and after giving a 10 ,ƒÊl dose (10 MNDs) of HLT by instillation or intracutaneous injection, the vessels were microscopically observed continuously for 3 hr, and afterward at 30-min-intervals up to 12 hr. In the guinea pigs the peripheral arterioles exposed to HLT constricted remarkably after a lag period of about 15 min