Urinary fluoride levels after consumption of fluoride-poor drinking waters in Hungary.

Fluoride concentration in the urine of subjects drinking fluoride-poor water was investigated. In the first series of experiments, mean F concentration in the urine collected for 24 hours was 0.26 mg/litre, in the second series, 0.28 mg/litre, and in group fractions 0.20 mg/litre. Standard deviations ranged from 0.07 to 0.12 mg/litre. No conclusion could be drawn from the F level of a single urine fraction to the 24-hour F level of the same subject. In group tests, means reflected the expected 24-hour values. There were differences in the urinary F levels of the subjects. Values for the same subject also varied; they were different on different days and the fractions collected on the same day showed variations. Older people excreted more fluoride than young ones. These findings are in good agreement with published data.     

Effect of drinking waters of high fluorine content on the urinary fluoride level.

The urinary fluoride level has been studied in 307 subjects consuming drinking waters of different fluoride concentrations. The urinary fluoride level was found to increase with the fluoride content of the drinking water. The urinary F level of the population group drinking water of optimum fluoride concentration was 1.14 mg of fluoride per litre. Thus, in regions where the drinking water contains an insufficient amount of fluoride, the fluoride content of domestic salt must be adjusted so as to ensure an about 1.14 mg/litre urinary F level of the population.     

Factors influencing the short-term variation in phytoplankton composition and biomass in coral reef waters

The short-term temporal dynamics of phytoplankton composition was compared among coral reef waters, the adjacent ocean and polluted harbour water from July until October along the south-western coast of Curaçao, southern Caribbean. Temporal variations in phytoplankton pigment 'fingerprints' (zeaxanthin, chlorophyll b, 19'-hexanoyloxyfucoxanthin, fucoxanthin, 19'-butanoyloxyfucoxanthin, chlorophyll c₂ and c₃ relative to chlorophyll a) in the ocean were also observed in waters overlying the reef. However, with respect to specific pigments and algal-size distribution, the algal composition in reef waters was usually slightly different from that in the oceanic water. Phytoplankton biomass (chlorophyll a) was either higher or lower than in the oceanic water. The relative amount of fucoxanthin and peridinin was usually higher, and the relative and absolute amount of zeaxanthin was significantly lower than in oceanic water. Zeaxanthin-containing Synechococci were significantly reduced in reef water. Average algal cell size increased from the open water to the reef and the harbour entrance. Large centric diatoms (>20 m Ø) were better represented in reef than in oceanic water. In reef-overlying waters, the nitrate and nitrite concentrations were higher than in oceanic water. In front of the town, anthropogenic eutrophication (sewage discharge and ground water seepage) resulted in higher NH₄, NO₃ and PO₄ concentrations than at other reef stations. This concurred with significantly enhanced phytoplankton biomass (chlorophyll a), chlorophyll c₂ and peridinin amounts at Town Reef compared with the other reef stations. Polluted harbour water usually showed the highest phytoplankton biomass of all stations, dominated by diatoms and dinoflagellates. Conditions in reef waters and harbour water promoted the occurrence and the relative abundance of diatoms and dinoflagellates. Harbour water did not influence the phytoplankton composition and biomass at reef stations situated >5 km away from the harbour entrance. We conclude that phytoplankton undergoes a shift in algal composition during transit over the reef. The dominant processes appear to be selective removal of zeaxanthin-containing Synechococcus (by the reef benthos) and (relative) increase in diatoms and dinoflagellates. The difference in the phytoplankton composition between reef and oceanic waters tends to increase with decreasing dilution of reef water with ocean water.     

Algae in urban drinking waters in N.E. Spain

Tap waters from Barcelona and several other locations in N.E. Spain were analyzed to determine the algal occurrence and to assess their probable origin and fate. In general, a low number of taxa (2–9) occurred per sample, while cell density was highly variable (from 20 to more than 1000 cells ml^-1). Green algae were usually the most abundant, most of the taxa being common in natural phytoplankton assemblages from mesotrophic or eutrophic waters. The proportion of planktonic to benthic taxa differed between samples, there being only one sample (Lérida) with a predominant planktonic composition. Analysis of treated water revealed that algae were not completely removed at the end of the treatment, meaning that a low number could reach the distribution network. Moreover, other organisms (flagellates) had their origin in storage water tanks. No seasonal pattern of occurrence was apparent since there were many occasional taxa, implying a lack of direct connection between natural populations and tap water algae. It is therefore suggested that algae can reach the distribution network by several possible origins. Algae were sometimes viable; culture experiments showed occasional growth in June, but not in August samples.     

Factors influencing species diversity in saline waters of Death Valley,USA

Salinity is a major factor influencing the distributions and abundances of aquatic macroinvertebrates of saline waters in Death Valley, California, USA. A general pattern of declining numbers of species with increasing salinity is seen in Death Valley waters. Some species are restricted to low salinities, others are found only in highly saline pools, and still others are widely distributed over a broad range of salinities.Salinity alone cannot explain distributions seen in the field. Distributions and abundances of species such as the caddisfly Limnephilus assimilis Banks are broader than would be predicted on the basis of laboratory studies of salinity and temperature. I present evidence that for such species, biotic factors such as reduced predation at high salinities may compensate for increased physiological stress.     

A simplified method for the preparation of rat thyroxine-binding prealbumin. Factors influencing its circulating level

Rat thyroxine-binding prealbumin (TBPA) was isolated in three simple steps by means of a serum precipitation by a 5% phenol solution and two consecutive semi-preparative polyacrylamide gel electrophoreses. The overall yield was 15% and the TBPA preparation contained less than 1% impurities. In addition a monospecific antiserum was raised in the rabbit. In polyacrylamide gel, rat TBPA, as with its human counterpart, migrated anodally to albumin while in agarose gel, its electrophoretic mobility was similar to that of albumin. Serum TBPA measured in adult male Wistar rats did not exhibit a circadian rhythm. However, a significant 13% decrease was observed between 9 and 15 h, followed by the restoration of the initial value by 21 h. TBPA concentration was measured in 1-, 15- and 28-day-old male and female pups as well as in adult rats. The level of this protein increased from 1 to 28 days of age and did not display any sexual difference. Yet, while TBPA concentrations in adult males were similar to those recorded in the 28-day-old pups, for adult females, they returned to the levels measured in the 1-day-old pups.     

Review of Campylobacter spp. in drinking and environmental waters

Consumption of contaminated drinking water is a significant cause of Campylobacter infections. Drinking water contamination is known to result from septic seepage and wastewater intrusion into non-disinfected sources of groundwater and occasionally from cross-connection into drinking water distribution systems. Wastewater effluents, farm animals and wild birds are the primary sources contributing human-infectious Campylobacters in environmental waters, impacting on recreational activities and drinking water sources. Culturing of Campylobacter entails time-consuming steps that often provide qualitative or semi-quantitative results. Viable but non-culturable forms due to environmental stress are not detected, and thus may result in false-negative assessments of Campylobacter risks from drinking and environmental waters. Molecular methods, especially quantitative PCR applications, are therefore important to use in the detection of environmental Campylobacter spp. Processing large volumes of water may be required to reach the desired sensitivity for either culture or molecular detection methods. In the future, applications of novel molecular techniques such as isothermal amplification and high-throughput sequencing applications are awaited to develop and become more affordable and practical in environmental Campylobacter research. The new technologies may change the knowledge on the prevalence and pathogenicity of the different Campylobacter species in the water environment.     

Factors influencing Pneumocystis infection in the immunocompromised rat.

A compromised immune system is the primary predisposing condition for Pneumocystis infection. Factors that contribute to this underlying state of immunosuppression are poorly understood. The presence of common rodent viruses and the role of anti-Pneumocystis antibodies on the progression of natural infection in the corticosteroid-treated rat model of Pneumocystis pneumonia were evaluated. The development and intensity of infection were not affected by the presence or absence of antibodies to these viruses or to major Pneumocystis antigens. A significant increase in survival of Pneumocystis-infected viral antibody-positive rats was observed when these rats were housed under barrier conditions.     

Factors influencing nursing in Macaca fascicularis.

Nursing by two mother-infant pairs in a caged colony of Macaca fascicularis was monitored at 1-min intervals for 8 h beginning 8:30 a.m. BST, once a week for 3 months in the summer of 1973. Nursing occupied about 210 min in 8 daylight hours for the infants at 10 weeks of age, and the time spent nursing decreased at the average rate of 9.4 min per week until the infants were about 6 months old. The time spent nursing by the infants studied here resembles closely the times spent nursing by some other macaques and by baboons. In the course of a day the amount of time spent nursing varies significantly with a diurnal peak. If nursing by one mother-infant pair is independent of nursing by the other pair, then the time the two pairs spend nursing together would be a function of the product of the frequencies of nursing by each pair. The expected times for the pairs nursing together based on the hypothesis of independent events were significantly less than the observed times the pairs nursed together. Nursing, therefore, involves a positive influence or imitation of one nursing pair by the other. Nursing sessions involving both mother-infant pairs were longer on the average than sessions involving only one pair.     

Recovery and diversity of heterotrophic bacteria from chlorinated drinking waters.

Heterotrophic bacteria were enumerated from the Seattle drinking water catchment basins and distribution system. The highest bacterial recoveries were obtained by using a very dilute medium containing 0.01% peptone as the primary carbon source. Other factors favoring high recovery were the use of incubation temperatures close to that of the habitat and an extended incubation (28 days or longer provided the highest counts). Total bacterial counts were determined by using acridine orange staining. With one exception, all acridine orange counts in chlorinated samples were lower than those in prechlorinated reservoir water, indicating that chlorination often reduces the number of acridine orange-detectable bacteria. Source waters had higher diversity index values than did samples examined following chlorination and storage in reservoirs. Shannon index values based upon colony morphology were in excess of 4.0 for prechlorinated source waters, whereas the values for final chlorinated tap waters were lower than 2.9. It is not known whether the reduction in diversity was due solely to chlorination or in part to other factors in the water treatment and distribution system. Based upon the results of this investigation, we provide a list of recommendations for changes in the procedures used for the enumeration of heterotrophic bacteria from drinking waters.     

Factors influencing the efficiency of chelation therapy.

The purpose of the present study was to obtain new data on the effect of age, route, dose and time of metal and chelating agent administration on the efficiency of chelation therapy. The experiments were performed on 1-2 and 6-week-old rats which received radioisotopes of metals--203Pb, 115 mCd, 203Hg and 141Ce intraperitoneally or orally. Chelating agents calcium ethylenediaminetetraacetate (CaEDTA), calcium and zinc diethylenetriaminepentaacetate (CaDTPA, ZnDTPA), 2,3-dimercapto-propane-sulfonate-1 (DMPS), dimercaptosuccinic acid (DMSA) and sodium N-(4-methoxybenzyl)-D-glucamine dithiocarbamate monohydrate (MeOBDCG) were administered twice by intraperitoneal or oral administration as early (immediately and 24 hr after metals) or delayed treatment (24 and 48 or 48 and 72 hr after metals). The animals were killed six days after metal administration and the retention was determined in the whole body, carcass and gut. After intraperitoneal administration of metals and chelating agents chelation therapy had much lower efficacy in younger than older animals. After ingestion of metals oral chelation therapy was more effective in younger than older animals. In suckling rats the treatment effectively reduced metal retention and this was mostly due to decrease in gut retention. This treatment in sucklings was also very effective in condition of late administration. In older rats early oral DMPS treatment after 203Hg ingestion is contraindicated since it increases significantly mercury retention while DMSA and ZnDTPA treatments reduced mercury retention. Delayed oral treatment with ZnDTPA and DMSA caused increased cadmium retention in older rats and decreased retention in sucklings. Opposite to results with CaDTPA, MeOBDCG was effective in reducing cadmium retention also when given as delayed treatment.(ABSTRACT TRUNCATED AT 250 WORDS)