Document npwz565EggN7j9ODJJ8Z9D108

642 EXPERIMENTAL ASBESTOS1S--GROSS & DE TREVJLLE Tig 5.--Ash pattern of aeld-lntotuble material of tame field at In Fig 3 after microincineration and treatment with concentrated hydrochloric add. allowing the pretence of tangled mattes of atbettot fibert In the regiont of the tear tittue (X ISO). represented a healed or healing inflamma tion. Within this scar tissue, apparently sequestered compact masses of asbestos fibers were often strikingly prominent after microincineration (Fig 5.) On the other hand, many scars were seen that contained little or no demonstrable dust The sharp delimita tion of the scars was accentuated by the ad jacent normal delicate alveolar walls. These were characterized by single, nonbranching argyrophilic fibers. Nevertheless, in some of the rats, there were also fod of a more active inflammation. Such foci were marked by cellular thickening of alveolar walls and by considerable desquamation. Here, the stroma was arborescent, the side brandies tending to give structural support to the increased num ber of alveolar cells. Since similar inflamma tory foci of cellular alveolar mural thicken ing 6.--Hyperplasia of smooth musela In rat Infected twice with 3.3 mg chiysotile dust end killed 21 months later. Well-defined bundles of smooth muscle era found In relation to alveolar ducts where the only normelly present muscle Is sltueted around mouths of evagineting alveoli (hematoxylin and eosin, X ISO). ing were also found in the lungs of control rats not exposed to, or injected with, dust, it is believed that they were caused by un related spontaneous disease. No asbestos bodies were found in rats ex posed to or injected with chrysotile asbestos dust. Rats (Inhalation).--The characteristic minimal lesion, as found a year or more aft er the pulmonary deposition of chrysotile dust, consisted of focal collagenous thicken ing affecting patches of alveolar duct wall between some of the evagimting alveoli (Fig 3 and 4). With more extensive deposi tion of the chrysotile fibers, the mural fibro sis tended first to narrow the mouths of the evaginating alveoli and then to dose them Arch Environ Health--Vof IB, Nov 1967 8005 1462 PRODUCED BY FORD HFM -013205