Publications

The 7S NGF complex from the male mouse submaxillary gland consists of the alpha, gamma, and beta subunits in the ratio alpha 2 gamma 2 beta. The beta (NGF) subunit contains all the known biolocial activity of 7S NGF. The alpha and gamma subunits are both members of glandular kallikrein gene family, yet only gamma subunit has protease activity. The gamma subunit plays a role in the processing of preproNGF to its mature form, while the role of the alpha subunit is not yet understood. Despite the fact that 7S NGF has been extensively characterized, no other NGF complex has been characterized, nor have the alpha or gamma subunits been observed in tissues which express NGF. We have therefore purified and characterized the NGF complex from the submaxillary glands of the rat Mastomys natalensis in order to more fully understand the roles of the alpha and gamma subunits. The NGF complex from M. natalensis contains subunits similar to those found in mouse 7S NGF. Although similar, there are significant differences between mouse and M. natalensis NGF complexes, especially in the degree of post-translational modification of the gamma and NGF subunits, the expression of esterase activity and the ease with which the complexes dissociate. Evidence is presented that suggests that the NGF complex from M. natalensis may consist of subunits in the ratio alpha 2 gamma beta. The amino acid sequence of the M. natalensis NGF suggests some, but not all, ways in which these differences arise.

The rate-limiting step in steroidogenesis is the conversion of cholesterol to pregnenolone. This reaction occurs in steroidogenic tissue in the inner mitochondrial membrane, and is mediated by the cholesterol side-chain cleavage enzyme. This enzyme system transfers electrons from NADPH to cholesterol through its three protein components: adrenodoxin reductase, adrenodoxin, and the terminal oxidase, P450scc. We have previously shown that P450scc mRNA is regulated by tropic hormones and cAMP by a cycloheximide-independent mechanism in mouse Leydig tumor MA-10 cells. We now show that the mRNA for adrenodoxin, another component of the cholesterol side-chain cleavage enzyme system, is regulated by tropic hormones and cAMP in MA-10 cells. We cloned rat adrenodoxin cDNA to analyze adrenodoxin mRNA in various rat tissues and in MA-10 cells by RNase protection assays. Adrenodoxin mRNA is found in virtually all rat tissues examined, although it is most abundant in adrenals, ovaries, and testes. MA-10 cells synthesize two species of adrenodoxin mRNA, one of 1.2 kb and the other of 0.8 kb. Both of these adrenodoxin mRNAs are increased approximately six-fold by 1 mM 8-Br-cAMP, five-fold by 10 microM forskolin, and three-fold by both 25 ng/ml hCG and by 100 ng/ml LH. Maximal adrenodoxin mRNA accumulation occurs by 4 h of hormonal stimulation. The cAMP-mediated increase in adrenodoxin mRNA accumulation is independent of protein synthesis, since treatment with cycloheximide or puromycin in the absence or presence of cAMP does not inhibit, and even increases, adrenodoxin mRNA accumulation.

OBJECTIVE

To examine the pathogenesis of metal fume fever in humans by studying functional, cellular, and biochemical responses after exposure to zinc welding fume.

DESIGN

Clinical experimental study.

PARTICIPANTS

We studied 14 welders recruited through public advertisements.

INTERVENTIONS

Participants welded galvanized steel.

MEASUREMENTS

We measured lung volumes, airflow, diffusing capacity for carbon monoxide, and airway reactivity at baseline as well as either 6 or 20 hours after welding. We carried out bronchoalveolar lavage either 8 hours (early follow-up, 5 participants) or 22 hours (late follow-up, 9 participants) after welding, assaying the fluid for total and differential cell counts and bronchoalveolar lavage supernatant concentrations of interleukin-1 and tumor necrosis factor (TNF).

MAIN RESULTS

Changes in pulmonary function and airway reactivity were minimal. Cumulative zinc exposure and polymorphonuclear leukocyte count in bronchoalveolar lavage fluid at late (r = 0.87; P less than 0.01) and early (r = 0.93; P less than 0.05) follow-up were positively correlated. Among the late follow-up group, the mean proportion of polymorphonuclear leukocytes was 37% (range, 19% to 63%), a statistically greater proportion than the 9% (range, 2% to 21%) seen among the early follow-up group (P less than 0.05). We did not detect TNF or more than a trace amount of interleukin-1 in the bronchoalveolar lavage supernatant.

CONCLUSIONS

Zinc oxide welding fume was associated with a marked dose-dependent increase in the number of polymorphonuclear leukocytes recovered in bronchoalveolar lavage fluid 22 hours after exposure but was not associated with a clinically significant change in pulmonary function or airway reactivity. Although we did not identify increases in either interleukin-1 or TNF levels in bronchoalveolar lavage fluid, cytokines or a cytokine-like mechanism may mediate the syndrome of metal fume fever.