High-resolution NMR structure of the chemically-synthesized melanocortin receptor binding domain AGRP(87-132) of the agouti-related protein.

The agouti-related protein (AGRP) is an endogenous antagonist of the melanocortin receptors MC3R and MC4R found in the hypothalamus and exhibits potent orexigenic (appetite-stimulating) activity. The cysteine-rich C-terminal domain of this protein, corresponding to AGRP(87-132), contains five disulfide bonds and exhibits receptor binding affinity and antagonism equivalent to that of the full-length protein. The three-dimensional structure of this domain has been determined by 1H NMR at 800 MHz. The first 34 residues of AGRP(87-132) are well-ordered and contain a three-stranded antiparallel beta sheet, where the last two strands form a beta hairpin. The relative spatial positioning of the disulfide cross-links demonstrates that the ordered region of AGRP(87-132) adopts the inhibitor cystine knot (ICK) fold previously identified for numerous invertebrate toxins. Interestingly, this may be the first example of a mammalian protein assigned to the ICK superfamily. The hairpin's turn region presents a triplet of residues (Arg-Phe-Phe) known to be essential for melanocortin receptor binding. The structure also suggests that AGRP possesses an additional melanocortin-receptor contact region within a loop formed by the first 16 residues of its C-terminal domain. This specific region shows little sequence homology to the corresponding region of the agouti protein, which is an MC1R antagonist involved in pigmentation. Consideration of these sequence differences, along with recent experiments on mutant and chimeric melanocortin receptors, allows us to postulate that this loop in the first 16 residues of its C-terminal domain confers AGRP's distinct selectivity for MC3R and MC4R.

Electron spin resonance of TOAC labeled peptides: folding transitions and high frequency spectroscopy.

The unnatural, conformationally constrained nitroxide amino acid TOAC (2,2,6,6-tetramethylpiperidine-1-oxyl-4-amino-4-carboxylic acid) stabilizes helical structure and provides a means for studying rigidly spin labeled peptides by electron spin resonance (ESR). Two new directions in TOAC research are described. The first investigates intermediates formed during alpha-helix unfolding. Double TOAC labeled alpha-helical peptides were unfolded at low temperature in aqueous solution with increasing concentrations of guanidine hydrochloride. Comparison of ESR spectra from two doubly labeled peptides suggests that 3(10)-helix emerges as an intermediate. The second research direction involves the use of high frequency ESR (140 GHz) at low temperature to assess dipolar couplings and, hence, distances between TOAC pairs in a series of 3(10)-helical peptides. Preliminary simulations suggest that high frequency ESR is able to extract correct distances between 6 and 11 A. In addition, the spectra appear to be very sensitive to the relative orientation of the TOAC labels.

Respiratory disease in non-smoking Western Australian goldminers.

Respiratory symptoms, spirometry, and transfer factor were measured in 208 non-smoking Western Australian underground goldminers (mean age 32) to identify the presence of respiratory abnormalities resulting from underground work. These subjects were part of a larger group of 771 subjects attending for statutory periodic chest x ray examinations in the industry. They had worked underground for a median of three years. The prevalence odds ratios of bronchitis, dyspnoea, wheeze, and asthma all tended to be related to duration of underground employment, even after adjusting for age, those for wheeze and asthma reaching statistical significance. After adjusting for age and height the duration of employment also had a significant effect on TL/VA but not on FEV1, FVC, or TL. These changes are consistent with the presence of airway narrowing and non-specific lung fibrosis or emphysema in non-smoking underground goldminers.

Population-based epidemiology of human immunodeficiency virus infection in Western Australia. Western Australian AIDS Advisory Committee.

A total of 328 cases of infection with human immunodeficiency virus (HIV) in Western Australia in 1983-1987 was studied with respect to demographic factors, the risk profile, the clinical progression of disease, the utilization of inpatient services and trends in incidence over time. The crude incidence rates were 8.8 cases/100,000 person-years in men and 0.4 cases/100,000 person-years in women. Age-specific rates peaked at 25 to 29 years of age in men. The risk of HIV infection was associated with metropolitan residence, low socioeconomic level, and two specific occupational groups. Homosexual and bisexual men constituted 86% of all cases; the incidence rate of HIV infection in such men was approximately 1000-times higher than was the incidence rate by apparent sexual transmission in heterosexual persons. However, the proportion of cases that occurred in women or that apparently was caused by heterosexual sexual transmission increased from zero in 1983-1984 to 7.5% and 5.4%, respectively, in 1987. After two years of follow-up, 71% of preclinical (category-C) patients had developed signs, symptoms or evidence of immune dysfunction, and 12% of those patients with lymphadenopathy or with other early clinical features of disease (category-B) had progressed to the acquired immunodeficiency syndrome (AIDS). At 21 months of follow-up, the survival rate with AIDS was 9%. Patients with AIDS utilized an average of 68.9 short-stay hospital bed-days per person-year, while category-B patients used 11.5 hospital bed-days per person-year. Notifications of HIV infection increased each year from 1983 to 1986, but fell by 22% in 1987. The latter may have been as a result of chance, a screening artefact or a real reduction in the incidence rate.

Variation in hospital morbidity in the male workforce of Western Australia.

The associations of hospital morbidity with occupation were studied in Western Australian men of working age in 1981-2. Data on hospital morbidity were derived from a population based system that covered all short stays in hospitals in the state. Occupations were grouped into 12 major categories and conditions were coded using the International Classification of Diseases. Armed services personnel had the highest overall rate of hospital admissions, followed by transport and communications workers and by administrative and managerial workers. Injuries were the most common cause of referral to hospital. Four occupational groups, farmers and allied workers, miners and quarrymen, transport and communications workers, and craftsmen, production workers, and labourers were often associated with injury. Diseases of the musculoskeletal system and connective tissue were the second most common cause for referral and were increased in transport and communications workers, and in craftsmen, production workers, and labourers. Several other associations between causes of hospital admission and major occupational groups were observed, including associations of circulatory system diseases with professional and technical work and with administrative and managerial work. The excess of hospital admissions due to factors associated with occupation was estimated to be 12,665 admissions a year or 24.9% of the total in working men.

Determinants of chronic bronchitis and lung dysfunction in Western Australian gold miners.

The relation of chronic bronchitis and respiratory dysfunction to age, tobacco smoking, and occupational exposure to surface and underground mining operations were examined in a cross sectional survey of 1363 men employed in the Kalgoorlie mining industry in 1985. Overall, the prevalence of chronic bronchitis was 14%. Eleven per cent of the workers had obstructive lung disorder (FEV1/FVC less than 0.70) and 9% had restrictive lung disorder (FVC less than 0.80 of predicted for height and age). There was little change in the prevalence of chronic bronchitis from that observed in a survey of the same industry in 1961-2. Only 1% of the workers in 1985 had radiographic signs of silicosis compared with 22% in 1961-2. Age, smoking, and underground mining experience all exerted strong effects on the development of chronic bronchitis with or without associated respiratory function abnormalities. After control of confounding by age and smoking, it was estimated that compared with a lifetime non-miner, the odds ratio (OR) of chronic bronchitis was 1.8 (95% confidence interval, 1.0-3.3) for one to nine years underground mining gold, 2.5 (1.2-5.2) for 10-19 years, and 5.1 (2.4-10.9) for 20 or more years. Underground mining of minerals other than gold was also associated with chronic bronchitis (OR = 5.1; 95% CI, 1.1-25.0) whereas exclusive surface mining had only a small empirical effect (OR = 1.3; 95% CI, 0.6-2.5). It is estimated that the proportion of cases of chronic bronchitis in working underground miners due to occupational factors is 50%. The results support the existence of an industrial cause of chronic bronchitis, although caution must be exercised in generalising the results to miners with progressive and sever respiratory impairment.

Mortality in gold and coal miners in Western Australia with special reference to lung cancer.

Cohorts of 1974 gold miners and 213 coal miners in Western Australia surveyed for respiratory symptoms, smoking habits, occupational history and radiographic evidence of pneumoconiosis have been followed up for 13-14 years. Overall, neither group had a significantly higher mortality than expected from the experience of Western Australian men in general. Lung cancer mortality was relatively high in the gold miners (59 deaths observed, 40.8 expected) but weakly and inconclusively related to the extent of their underground mining experience. Cigarette smoking may explain the excess of lung cancer in the gold miners because the prevalence of the habit in the latter (66.3%) was higher than in the coal miners (58.7%) or in other men in Western Australia (53.2%). Radiographic evidence of silicosis was present in 21.7% of the gold miners but did not appear to have contributed substantially to their mortality. The coal miners showed a lower than expected rate of lung cancer but an excess of deaths from all other forms of cancer (11 observed, 5.6 expected). This excess was not attributable to any one cancer site and cannot be explained readily.