Tadashige Moriyama

Biochemical and histological sequences of membranous ossification in ectopic site

SummaryPorous hydroxyapatite ceramics alone (control) and ceramics combined with rat marrow cells were implanted subcutaneously in the back of syngeneic rats and harvested 1–8 weeks after implantation. The ceramics were examined biochemically and histologically. Alkaline phosphatase activity in the marrow cell/ceramic composites began to increase at 2 weeks and achieved a peak at 4 weeks, followed by a gradual decrease. Bone gla protein contents in the composites began to increase at 3 weeks and steadily increased as time passed. Histologically, osteoblastic cells were detected at 2 weeks and obvious de novo bone together with active osteoblasts began to appear at 3 weeks in the composites. The process was membranous ossification without cartilage formation and was observed in the pores of the composites. The pore areas occupied by bone increased as time passed. In contrast, ceramics alone did not show any bone formation and contained traces of these biochemical parameters. These results indicated that the biochemical sequences correlate with the histological sequences in the heterotopic membranous ossification.

The effects of frequently rotating shiftwork on sleep and the family life of hospital nurses.

The effects of three frequently rotating shifts in an irregular sequence on the daily activities of 239 Japanese female hospital nurses were studied by the time-budget method. The nurses recorded their daily activities for several consecutive days. The questionnaire was returned by 80.8% of the participants, and recordings of 1016 days were analysed. A two-way analysis of variance clarified that the shift combination influenced the daily activities. The most distinct result was that nurses spent significantly more time on free-time activities on the day when they worked the night shift followed by the evening shift than they did on the day when they worked any other shift combination. Nurses offset sleep deprivation either by sleeping during the day before and after working the night shift (82-100%) or by sleeping 2 to 4 h later in the morning after working the evening shift and on days off. There was a strong positive correlation between total sleep time (including day sleep) and the length of the interval between two consecutive shifts (r = 0.95, p < 0.001). This result suggests that more than 16 h between work shifts is required to allow more than 7 h of total sleep time. In an analysis by household status, nurses who had young children (average age, 2.8 years) slept less and spent less time on free-time activities than did other nurses.

Comparative effect of cadmium on osteoblastic cells and osteoclastic cells

Cadmium(Cd) has been thought to disturb the bone metabolism directly. The mechanism for the bone lesion is unknown, however. To examine the effects of cadmium on bone metabolism, we compared its effects on osteoblasts and osteoclasts in vitro. We used an established cell line, MC3T3-E1, as osteoblasts and tartrate resistant acid phosphatase (TRACP)-positive multi-nucleated cells (MNC) formed by a bone marrow culture system as osteoclasts. Alkaline phosphatase (ALP) activity was decreased by 10−7 M Cd and DNA content and hydroxyproline content of osteoblastic cells were decreased by 10−5 M Cd. Cadmium at 10−7 M inhibited the osteoclastic cell formation from mouse bone marrow in the presence of 10−8 M 1α,25(OH)2 vitamin D3. A 100-fold higher concentration of zinc(Zn) simultaneously added to the cadmium-containing medium prevented the toxicity of cadmium to osteoclastic cells as observed in the culture of osteoblastic cells. These results indicate that both bone formation and bone resorption are inhibited by cadmium. The responses of osteoclasts and osteoblasts to cadmium in this culture system were the same and the responses of cadmium-damaged osteoblasts and osteoclasts to zinc were also similar. These results suggest that another mechanism by which cadmium could cause bone damage should be considered in addition to the specific induction of osteoclastic cells by Cd.

Decrease in bone strength of cadmium-treated young and old rats

A decrease in mechanical strength of bones was observed both in young and old rats for long periods of administration of cadmium. Young (3-week-old) female rats were given 0 (control), 5 and 10 ppm cadmium in drinking water, respectively, for 20 weeks. Old (18-month old) female rats were given 0 (control) and 40 ppm cadmium in drinking water, respectively, for 7 months. The compression strengths of bones of young rats which were given 10 ppm cadmium, and those of old rats which were given 40 ppm cadmium, significantly decreased at the distal end portion of femur. Cadmium contents in bones in the 10 ppm and 40 ppm groups were about 110 and 210 ng/g dry weight, respectively. The present result confirmed that cadmium has a lesional effect on the mechanical strength of bone at the concentration of 100–200 ng/g in dry weight of bone, for both young and old rats.

Decrease in the mechanical strength of bones of rats administered cadmium

The mechanical properties of the bones of young, adult and old rats administered various concentrations of cadmium were measured to prove the direct effect of cadmium on the bones of young rats. The young rats were divided into three subgroups, which were administered 0 (control), 5 and 10 ppm cadmium, respectively. The adult rats were subdivided into six groups, administered 0, 10, 20, 40, 80 and 160 ppm cadmium, respectively. The old rats were divided into three subgroups, which were administered 0, 80, and 160 ppm cadmium, respectively. The length of the administration was 4 weeks in every group. The decrease in the mechanical strengths of bones of young rats administered with cadmium was observed. On the other hand, no change in mechanical strength of bones was observed in the case of adult and old rats, administered up to 160 ppm cadmium. The correlation between the cadmium in bones and the decrease in the strength of the bone shows that cadmium directly affects the mechanical properties of bones of young rats.

Effects of short chain fatty acid, sodium butyrate, on osteoblastic cells and osteoclastic cells.

1. Sodium butyrate increased alkaline phosphatase (ALP) activity of cloned osteoblastic cell line MC3T3-E1 by the stimulation of de novo enzyme synthesis. 2. Sodium butyrate did not affect mature osteoblastic cells but affected preosteoblastic cells. 3. Sodium butyrate decreased tartrate resistant acid phosphatase (TRACP)-positive multinucleated cells (MNC) formation from bone marrow cells. This related to the cytotoxicity of sodium butyrate on bone marrow cells.

An Association Between Raynaud's Phenomenon and Hearing Loss in Forestry Workers

Forestry workers using chain saws run the risk of both vibration disease and noise-induced hearing loss. It was reported that people with Raynauds phenomenon of occupational origin had more severe hearing loss than those without it. A possibility of confounding due to age and duration of noise exposure from the tools remained unsolved, however. A matched pair case-control study was conducted to eliminate such confounding. Forestry workers operating chain saws, bush cleaners and/or winches were investigated. For 37 men with Raynauds phenomenon a control was chosen from those unaffected whose age and operating hours for the tools were almost equal to those of the cases. Good matching was achieved for age and for total hours of work with the tools. The cases had higher median hearing threshold than the controls at every frequency. The difference was significant (p less than 0.05) at 4 and 8 kHz and almost significant at 2 kHz (p not equal to 0.06). According to our classification of the audiogram, the cases had more advanced types of noise-induced hearing loss than did the controls. Thus, an association between Raynauds phenomenon and hearing impairment in forestry workers handling chain saws and/or other tools was found to persist even after the effect of age and exposure time was eliminated.

Hearing of forest workers with vibration-induced white finger: a fiveyear follow-up

SummaryTo examine the association between vibration-induced white finger (VWF) and hearing loss, 108 male forest workers who regularly used vibrating tools were followed up for five years. Case-control pairs matched for initial age and hearing level and exposure time to noise during the study period were selected from men with and without VWF. The hearing levels significantly worsened during the follow-up period at 2, 4 and 8 kHz in the affected cases but only at 8 kHz in the controls. Since threshold shift at 4 kHz, which is a typical effect of noise exposure, was significant only in the affected cases, it is suggested that the hearing of people with VWF was more vulnerable to noise. A pathological change causing VWF might also increase the susceptibility of hearing to noise damage.

Zinc prevention of cadmium‐induced toxicity in osteoblastic functions

Abstract To obtain further information on the interaction between Cadmium (Cd) and Zinc (Zn) in bone, the effects of Cd or Zn alone, or Cd and Zn together on the osteoblastic cell line, MC3T3‐E1, were examined by quantifying protein content, alkaline phosphatase (ALP) activity and by‐droxyproline content. The cells were cultured for three days in a medium containing 10% fetal bovine serum. Then the metal ion(s) were added and the cells were cultured for another seven days at 37 °C in air which was 5% CO2. Morphological changes and decreases in ALP activity, protein content, and hydroxyproline content resulting from exposure to 10−5 M Cd were all reduced or eliminated by adding 10−4 M Zn to the culture medium with the Cd. Thus, Zn effectively protected the osteoblastic cells from certain toxic effects induced by Cd. The results suggest that the protective effects of Zn against Cd‐induced toxicity relate to the function of osteoblastic cells in bone, and that the mechanisms of prevention by Zn are not expla...

Aerobic capacity of forestry workers and physical demands of forestry operations

SummaryThe present study aimed at evaluating the aerobic capacities of forestry workers and the physical demands of their occupation. A submaximal cycle ergometer test was conducted on 22 male forestry workers and 15 male sedentary office workers aged 40–59 years. The slope of the regression line of heart rates on given exercise intensities was significantly smaller in the forestry workers than in the office workers. The mean heart rate of the forestry workers was 9 beats · min−1 less than that of the office workers at the initial exercise intensity of 50 W. This difference increased to 25 beats · mint−1 at 175 W. For 6 of the 22 forestry workers, heart rates were recorded continuously during a usual workday. The metabolic rates, as multiples of basal metabolic rate (in met) of various forestry activities were estimated from the average heart rate during the activity of interest and a predicted maximal oxygen consumption of the subject obtained from a submaximal cycle ergometer test. The mean energy expenditure was 4.5 met with a range of 3.3–6.3 met for an average of 509 min at a worksite. These results indicated that the forestry workers had high aerobic capacities and this was ascribed to the high physical demands of their occupation.