Musculoskeletal symptoms and perceived work strain among reindeer herders in Sweden.

BACKGROUND: There is a shortage of knowledge on the extent of musculoskeletal symptoms in reindeer husbandry. AIMS: To investigate the prevalence and relative risk for musculoskeletal symptoms and perceived psychosocial work strain among reindeer herders. METHODS: The prevalence of self-reported musculoskeletal symptoms during the last week and last year, respectively, were obtained from male reindeer herders (n=74) of northern Sweden. Prevalence ratios (PRs) were calculated using two reference groups-women of reindeer-herding families (n=53) and men in blue-collar occupations (n=194). Comparisons were made of perceived job strain between the study and reference groups. Associations between job strain factors and the occurrence of musculoskeletal symptoms from different body regions were analysed with regression statistics. RESULTS: The PRs for musculoskeletal symptoms from the hand/wrist (PR 3.48, 95% CI 1.86-6.50) and lower back (PR 1.44, 95% CI 1.06-1.95) were significantly higher among the reindeer herders in comparison with men working with other blue-collar occupations. The reindeer herders reported significantly higher work demands and decision latitude compared with both reference groups (P<0.05). Significant associations were observed between demands and prevalence of symptoms from the lower back (OR 1.42, 95% CI 1.01-2.01) and from at least one body region (OR 1.58, 95% CI 1.07-2.32). CONCLUSIONS: The relative risk for musculoskeletal symptoms, particularly from the hands/wrists and lower back, was high among reindeer herders. It is suggested that musculoskeletal symptoms constitute a considerable health problem in modern reindeer husbandry, which calls for implementation of preventive measures addressing psychosocial, physical and socio-economic risk factors.

Risk factors for cardiovascular diseases among Swedish Sami--a controlled cohort study.

OBJECTIVE: To investigate the occurrence of clinical, psychosocial and behavioural risk factors for cardiovascular diseases (CVD) among reindeer herding (RS) and non-reindeer herding Sami (NRS). STUDY DESIGN: A retrospective cohort study, comparing risk factors behind CVD between Sami and non-Sami, RS and NRS, and Sami men and women. METHODS: A cohort of 611 Swedish Sami (276 men and 335 women) was constructed from national population registers. A twice as large control cohort of non-Sami was created, matched by age, gender and area of residence. Information on risk factors was obtained from a database containing clinical and psychosocial-behavioural data from a regional CVD preventive programme for the period 1990-2001. RESULTS: The Sami and the non-Sami showed similar risk factor patterns. The main differences were related to working conditions and lifestyle factors of the RS. The RS men had lower blood pressure, were more physically active and had higher job demand and decision latitude. The RS women showed more negative scores on the indices of the job strain model. CONCLUSIONS: Previously reported differences in CVD mortality between Sami and non-Sami, and Sami men and women, can only partly be explained by different exposure to the psychosocial and behaviour risk factors investigated in this study.

The importance of glucose for the Escherichia coli mediated citrate depletion in synthetic and human urine.

OBJECTIVE: Escherichia coli has previously been shown to reduce urine citrate and influence urine pH. In this study the influence of glucose on the E. coli mediated citrate decrease has been investigated. MATERIAL AND METHODS: In synthetic urine, a glucose concentration of > or = 1 mmol/l was a prerequisite for bacteria to grow and lower citrate. At glucose concentrations > or = 5 mmol/l an E. coli mediated pH decrease correlated to urine glucose was observed. RESULTS: In human urine, variations in urine glucose influenced the citrate decrease and addition of glucose accelerated the E. coli mediated citrate decrease, which in certain urines could be very pronounced. CONCLUSIONS: Citrate has a pronounced effect on the activity product of calcium oxalate and calcium phosphate and the E. coli mediated decrease in urine citrate may be involved in the formation of urinary tract stones and catheter encrustations.

E. coli and urease-induced crystallisation in urine.

The effects of urine preinoculation with E. coli for 20 h on urease activities in urine have been studied in synthetic as well as human urine. The E. coli preinoculation increased pH in both synthetic and human urine. Urease enzymatic activity was enhanced in E. coli-preinoculated synthetic urine. The intraluminal urease-induced precipitation was increased in E. coli-preinoculated synthetic urine. The precipitation on glass rods, which more closely reflects crystal growth and aggregation, was reduced. The process of urease-induced crystallisation thus appears to be influenced by E. coli. In human urine, the effects of E. coli preinoculation were less uniform but a significantly increased urease-induced precipitation after E. coli preinoculation could be reproduced in human urine also.

The influence of pH and urine composition on urease enzymatic activity in human urine.

It is reasonable to assume that the rate of pH increase in urine induced by urease-producing microorganisms is one of the factors which determine whether crystallisation with subsequent stone formation will occur or not. To evaluate how the time needed to increase urine pH varies between different urine samples and how it depends on urine composition, a standardised amount of urease was added to different human urine samples. The incubations were performed in a pH-stat. This allowed simultaneous study of how urease enzymatic activity depends on urine pH and how it varies between different urines. The enzymatic activity was found to be negatively correlated to urine pH and to vary between different urines. The rate of the pH increase varied markedly between different urines. Small pH increases depended on the native urine pH and urease enzymatic activity. Higher pH increases up to the levels of phosphate crystallisation depended more on urine phosphate, the major urine buffer. The results presented show that urine composition influences the urease-induced pH increase. This might have clinical implications.

Long-term studies of urease-induced crystallization in human urine.

Urine samples were inoculated with viable Proteus mirabilis or purified Jack bean urease. The subsequent pH increase and crystallization were followed for 2 weeks. Particle formation was detected much earlier and at a lower pH in urines inoculated with Proteus, in which a higher end pH was also reached. The crystal configuration in bacteria and urease inoculated samples was different. Crystal aggregation was also much more pronounced in the Proteus mirabilis inoculated samples. The total precipitation was markedly increased in the Proteus mirabilis inoculated samples. The presence of live Proteus mirabilis thus has a profound influence on urease-induced crystallization in human urine. Despite the formation of rather large crystal aggregates in the Proteus-inoculated urines, no firm aggregates of a "prestone" type were observed.

Impact of Escherichia coli on urine citrate and urease-induced crystallization.

Escherichia coli (E. coli) is usually not a urease producer. It is, however, often cultured in urinary phosphate containing calculi including ammonium magnesium phosphate stones. This suggests the possibility that E. coli might be involved in stone forming process. The effect of E. coli on urine citrate and urease-induced crystallization in human urine has been studied in vitro. E. coli was found to strongly reduce urine citrate (after 48 hours). In the E. coli inoculated samples, the urease-induced crystallization was increased. There was a strong correlation, r = 0.8, between the citrate decrease and the increase in calcium precipitation. The results indicate that E. coli and the reduced urine citrate influences urease-induced crystallization in vitro.

Unique ability of the Proteus mirabilis capsule to enhance mineral growth in infectious urinary calculi.

Struvite (MgNH4PO4.6H2O) calculi are a common complication of Proteus mirabilis urinary tract infections. Although urease is a major virulence factor in calculus formation, the polysaccharide capsule (CPS) of this organism also enhances struvite crystallization and growth in vitro (L. Clapham, R. J. C. McLean, J. C. Nickel, J. Downey, and J. W. Costerton, J. Crystal Growth 104:475-484, 1990). We obtained purified CPS, of known structure and varying anionic character, from P. mirabilis ATCC 49565 and several other organisms. Artificial urine was added to CPS, and the pH was elevated from 5.8 to 8.5 by the addition of urease or titration with 0.25 M NH4OH to induce struvite crystallization. Crystallization was measured by particle counting (Coulter counter), and the morphology (crystal habit) was examined by phase-contrast microscopy. In the presence of partially anionic P. mirabilis CPS, struvite formation occurred at a lower pH than in the absence of CPS or in the presence of other neutral, partially anionic, or anionic CPS. At pH 7.5 to 8.0, significantly more struvite crystals formed in the presence of P. mirabilis CPS than under other experimental conditions. With the exception of one polymer (curdlan) which did not bind Mg2+, enhancement of struvite formation by CPS polymers was inversely proportional to their Mg2+ binding ability. We speculate that the structure and partial anionic nature of P. mirabilis CPS enable it to enhance struvite formation by weakly concentrating Mg2+ ions during struvite crystal formation. This illustrates a new virulence aspect of bacterial CPS during infection.

Concrement formation and urease-induced crystallization in urine from patients with continent ileal reservoirs.

OBJECTIVES: To study the relationship between urinary tract infection, urine composition and concrement formation in patients with continent ileal reservoirs for urinary diversion. PATIENTS AND METHODS: The study comprised 27 patients (seven men and 20 women, mean age 47 years, range 23-76) with continent ileal reservoirs who were followed for a mean of 67 months (range 13-146) by annual reservoiroscopy, intravenous urography and urine culture; at the final follow-up, a sample of their morning urine was analysed for a range of compounds and the number and size of any particles present or produced in response to incubation with urease. RESULTS: The presence of urease-producing bacteria was associated with the formation of concrement. However, a few patients in whom an infection with urease-producing organisms was not detected also formed concrement. Urine from those patients forming stones tended to have a high calcium and a low citrate concentration. After incubation with urease, significantly more and larger particles were formed in the urine from stone formers. There was a strong correlation (r = 0.8) between urinary calcium content and urinary pH when the urease-induced precipitation commenced, and between urinary calcium and the size and volume of the crystals developed (r = 0.9) after 4 h of incubation. CONCLUSIONS: There are many factors which might influence the formation of concrement, e.g. outflow conditions, the presence of staples or infection in the reservoir, and the composition of the urine is also important. It thus appears appropriate to determine if measures to reduce urinary calcium and increase urinary citrate can decrease the episodes of stone formation in those patients with continent ileal reservoirs for urinary diversion who frequently form stones.

Influence of Escherichia coli on urease-induced crystallisation in human urine.

Urease was added to urines inoculated with Escherichia coli 24 hours earlier and to control urines not inoculated with E. coli. The inoculation did not change the concentration of the measured urine components. The urease-induced ammonium ion production and pH increase was reduced in E. coli-inoculated urines compared to control urines. This suggests that E. coli can inhibit urease. The precipitation of both phosphate and magnesium on glass rods inserted in the urine was reduced with 40-50% in the E. coli-inoculated urines. The results demonstrate that E. coli can influence urease-induced crystallisation.