No abstract

Changes in enzyme activity due to in vivo dusting with quartz were investigated in guinea-pig lungs before the formation of collagen. Of the three enzymes investigated, succindehydrogenase and succinoxidase are increased, and cytochrome c oxidase is not affected by inhalation of quartz dust. The increases tend to reach a maximum which is more rapidly approached by succindehydrogenase than by succinoxidase. The results are discussed in relation to results obtained by other workers on the in vitro effects of silicon compounds. The lung weight increased markedly with increased period of inhalation of dust. This increase is discussed in relation to fat and ash content.

FoR.) (STELLENBOSCH)t SUMMARY Part I describes the relative effect of 3·0 per cznr sulphuric acid on six timbers. These were tested by the following combina.tion of methods at atmospheric tempeuuuie:-sla. Determination of hardness and lb. cTILshing strength in comparison with unexposed control timbers and with control specimens immersed in water. La. Q:wntity of sulphuric acid a!Jsorbed and 2b the rate of absorption. 3. Temporary and permanent expansion or shrinkage. 4. Loss of weight of timbers after four weeks' exposure. 5. Colour imparted by the timber to acid, and the condition of the test pieces after immersion and drying. In these tests Balau gave the best iesuus from nearly all aspects j South African Pine was the least satisfactory. For four out of the seven tests Balau, Merbau and Pitch Pine are amongst the three best, and for six out of seven tests they are a'l1Jngst th~first four. N J WJJd t~std beh1.:;;d similar to C.Jlifomian RedwJJd in all respects. O?30MMING Deel I beskrywe die relatieuie uitwerhing van 3·0 pzrsen: swaelsaur op ses iunusootte wat deu: die volgende kombinasie van metodes by atmJSferiese temperatuur getoets is:-la. Bepaling van hardheid en lb. drukvastheid in vergelyking met nie-blootgestelde kontrole monsters en met kontroles in water gedompel. 2a. Hoeveelheid swaelsuur geabsorbeer en 2b. die snelheid daarvan. 3. Tydelike en permanente uitsetting of krimping. 4. Gewigsverlies van die hout na vier weke se blootstelling. 5. Verkleuring van die suur deur die hout en die toestand van die toetsmonsters na onderdompeling en droging. * Senior Chemist, Transvaal and Orange Free State Chamber of Mines Timber Research Laboratory, Johannesburg. t Timber Mechanics Officer, Forest Research In stitute, Pretoria. c Downloaded by [University of California, San Diego] at 12:25 29 June 2016 8 THE SOUTH AFRICAN FORESTRY ASSOCIATION In hierdie toetse het Balau in alle opsigte die beste resuuate gelewer; terwyl Suid-Afrikaanse Den die swakste vertoon het. Vir vier uit die sewe toetse is Balau, Merbau en Harsden tussen die drie beste, en vir ses uit die sewe is hul tussen die eerste vier. Qeen houtsoort wat getoets is, het in aue opsigte met Kaliforniese Rooihout vcrgelyk.

Previous studies have shown the relation between enzymatic activities in the succinate oxidase system including succinate dehydrogenase, and the early changes in the lungs of guinea-pigs exposed to the inhalation of quartz dust.We have now investigated whether the increase of enzyme activity depends on maintaining the dust inhalation or not.Animals exposed to the inhalation of quartz dust for a short period of 28 days, sufficient to produce only small changes in the specific activities of the enzymes, and then removed from the dusty atmosphere for a further period of 113 days showed increases of the same order as animals which remained in the dusty atmosphere for a period of 133 days and were then taken out of this atmosphere for eight days. These increases of enzymatic specific activities are paralleled by increases in lung weight. Hence, in this respect also, the increases in activity of the enzymes follow the same pattern as the fibrogenesis.