Putrescine uptake regulation in response to alpha-difluoromethylornithine treatment in Leishmania infantum promastigotes

Summary The putrescine uptake/efflux regulation and their regulatory role on intracellular polyamine pools have been studied in the parasitic protozoa Leishmania infantum. Putrescine uptake was age-dependent with maximal values in logarithmic phase promastigotes and minimal in stationary phase. Moreover, putrescine uptake was activated in response to depletion of intracellular polyamines by alpha-difluoromethylornithine (DFMO) — a well known irreversible enzyme-activated inhibitor of ornithine decarboxylase. Kinetic studies of putrescine uptake induction showed a notable rise in Vmax without Km changes, suggesting a de novo synthesis of putrescine carriers. Putrescine uptake was able to replenish polyamine content and also to recover the proliferative rate in cells treated during 24 hours with DFMO.     

Lead and cadmium content of Indian flue-cured tobacco

Summary Studies on levels of lead and cadmium of Indian flue-cured tobacco indicated that the leaf contained very low amounts of these heavy metals as compared to tobacco from other countries. Indian tobacco can therefore be adjudged as ‘safe and clean’ and least hazardous to the smoker. Of the two heavy metals, lead content of soils is higher than cadmium. But in the leaf, cadmium content is more than lead indicating that soil cadmium may be more available to tobacco and hence more readily absorbed by the plant than lead.     

The role of environmental sodium chloride relative to calcium in gill morphology of freshwater salmonid fish

Summary Ultrastructure, distribution and abundance of cell types were examined in the gills of two freshwater salmonid species, Salmo fario and Salmo gairdneri, in media of selected ion content. In plain hard water (PW) with high concentrations of Ca²⁺, Na⁺, and Cl^-, gill chloride cells (CC) were confined to trailing edges and interlamellar regions of filaments whereas in mountain soft water (MW) with low concentrations of Ca²⁺, Na⁺, and Cl^-, CC were more numerous on filaments and covered lamellae, particularly along trailing edges. CC also appeared on lamellae of PW trout acclimated to soft water in a pond. This proliferation was not alleviated when ambient Ca²⁺ levels were raised (MW + Ca²⁺) but regressed in elevated NaCl media (MW + NaCl). The regression process involved an initial covering of CC by pavement cells followed by cytolysis and then eventual disappearance of CC. In MW, mucous cells were distributed mainly on trailing edges and, to a lesser extent, leading edges of filaments; they were absent from lamellae regardless of external ion levels.The results of this study shed some light on the functional significance of CC in freshwater fish. It is suggested that proliferation of CC is an adaptive response to dilute freshwater (i.e. [NaCl]<0.1 mequiv·1^-1).     

Ecdysteroid levels during adult reproductive and embryonic developmental stages of Sarcophaga bullata (Sarcophagidae: Diptera)

Ecdysteroid levels were determined during the period of the adult reproductive cycle in the ovovivparous fleshfly Sarcophaga bullata. Low levels were found in males during the 10 days following eclosion while the entire adult female showed a significant peak of ecdysteroid activity at 190 h post eclosion (i.e. during embryogenesis). When the female reproductive tract was analyzed it was observed that the ovaries became vitellogenic a short time after a protein meal was offered at 96 h post eclosion: at 140 h, ecdysteroid activity was recorded in the developing oöcytes. The major peak of ecdysteroids during the reproductive cycle was found in developing embryos at 190 h. The significance of these releases of ecdysteroids is discussed in relation to major embryonic developmental events.     

Assessment of temporal changes in haem and protein levels in Ixodid ticks following blood engorgement, and their use as age-grading parameters

Nymphs of Rhipicephalus appendiculatus and Hyalomma anatolicum anatolicum were fed on rabbits and maintained in the laboratory to allow moulting and further development. At specified time intervals from 0 to 500 days after engorgement, samples of ticks were ground individually in distilled water within the wells of an agglutination plate. A 0.1 ml aliquot was removed from each and levels of haemin and protein assessed from optical density values at specific wavelengths in a spectrophotometer.

Both protein and haemin levels showed an initial rapid decrease after engorgement; values did not fall to zero in either case but showed marked fluctuation throughout the study period. These fluctuations combined with the high standard errors of the results, made assessments of the physiological age of individual ticks impossible.

Such fluctuating values, however, suggested the possibility that haem biosynthesis might be taking place, and this was tested by injecting the radioactively-labelled haem precursor [4-¹⁴C]δ-amino laevulinic acid into engorged nymphs, immediately following their detachment. Both tick species revealed an incorporation of this compound into their haematin content, although neither incorporated the non-haem precursor [1-¹⁴C]2-amino isobutyric acid. These results indicate an ability of ticks to synthesize haem in vivo, although the underlying reasons for such a mechanism remain unknown.     

Ecdysteroid levels and integument changes in post-embryonic stages of Anastrepha suspensa

Ecdysteroid levels in larvae and pupae of Anastrepha suspensa (Diptera: Tephritidae) were measured by radioimmunoassay. These levels were correlated with histological changes throughout the development of the post-embryonic stages. Ecdysteroid levels increase rapidly throughout the last-larval instar and on the last day of this stage are 283 pg equivalents of 20-hydroxyecdysone per insect (14.5 ng/g) when wandering behaviour is initiated. At the end of this period the puparium is formed and within 24 h, the ecdysteroid rises to its highest peak (625 pg equivalents of 20-hydroxyecdysone/insect). Larval-pupal apolysis is initiated within 24 h later and the pupal cuticle is then secreted. Two days later, the ecdysteroids reach their lowest levels (75 pg equivalents of 20-hydroxyecdysone/insect or 0.6 ng/g) and most of the larval fat body and other tissues have been histolysed. In 5- to 10-day old pupae ecdysteroid levels again increase and remain relatively high throughout. During this period the larval epidermis is replaced by imaginal epidermis, imaginal discs begin to proliferate and the adult cuticle is secreted. Ecdysteroid levels finally fall 2 days prior to adult emergence. HPLC determinations indicate that 20-hydroxyecdysone is the predominant free ecdysteroid, and along with ecdysone, is readily detectable in all postembryonic stages of this species. An unusually high and unexplained peak of 20-hydroxyecdysone occurs in the pharate adult. This peak probably consists of ecdysone metabolites with retentions similar to that of 20-hydroxyecdysone and to which the antiserum is sensitive.     

Population dynamics of microfilarial production and eosinophilic levels in slow lorises infected with Breinlia sergenti. Petter (Filarioidea: Dipetalonematidae)

Population dynamics of microfilarial production and eosinophilic levels in slow lorises infected with Breinlia sergenti, Petter (Filarioidea: Dipetalonematidae). International Journal for Parsitology 4: 383388. Observations have been made on microfilarial and eosinophilic levels in slow lorises infected with Breinlia sergenti. Animals given a single inoculation of 100-150 infective larvae exhibited three different patterns of microfilaraemia while superinfected animals showed enhanced microfilarial levels. It appeared that the number of inoculations as well as the interval between inocula are important factors in enhancing microfilarial levels. Two different types of incubation periods were seen, one at 100-120 days and the other at 200 days. The eosinophilic levels were investigated in some of the animals and an attempt was made to correlate these levels with the microfilaraemia. Cortisone injection appeared to promote a vigorous eosinophilia in some of the infected animals tested.     

Vanadium levels in urine and cystine levels in fingernails and hair of exposed and normal persons

Vanadium was determined by radiochemical neutron activation analysis (RNAA) with proven accuracy in urine of workers occupationally exposed to vanadium-rich dust in a vanadium pentoxide production plant, and values in the range of 3.02–762 ng/mL (median 33.0 ng/mL) were found. In a control group consisting of administrative workers of the plant, urinary vanadium levels were found in the range of 1.05–53.4 ng/mL (median 2.53 ng/mL), whereas in an another control group of occupationally nonexposed persons, these values amounted to 0.066–0.489 ng/mL (median 0.212 ng/mL). Accuracy of the results was tested by analysis of reference material IAEA A-13 Animal Blood and NIST SRM-1515 Apple Leaves, and very good agreement was found with literature and the NIST certified values, respectively. Unlike urine, no significant differences were found for cystine levels in fingernails and hair of exposed and control persons.     

Effects of vanadate on the ATP content,ATPase activity and phosphate absorption capacity of maize roots

Although the sensitivity of the plasma membrane H⁺-ATPase to vanadate is well known, the metabolic response of plant cells to vanadate is less well characterised in vivo and its use as an inhibitor in whole plant experiments has had mixed success. Experiments with maize (Zea mays, L.) roots and with purified plasma membrane fractions from the same tissues showed that exposure to vanadate caused: (i) a reduction in the capacity for phosphate uptake; (ii) a reduction in the extractable ATPase activity from the tissue; and (iii) a significant increase in the ATP level. The measurements on the extractable ATPase activity and the ATP level showed that the effect of vanadate developed slowly, apparently reflecting the slow accumulation of intracellular vanadate. The marked effect of vanadate on the ATP level-exposure to 500 M vanadate for 5 h doubled the ATP content of the roots tips-indicates that there is no stringent control over the ATP level in the roots and that the plasma membrane H⁺-ATPase activity is likely to have a significant role in determining the ATP level under normal conditions.