The effect of sodium chlorate and nitrapyrin on the nitrification mediated nitrosation process in soils

Summary The influence of total nitrification to nitrate or partial nitrification to nitrite on the soil organic nitrogen status was examined. NH ₄ ⁺ –¹⁵N was added to the soil in the absence and the presence of NaClO₃, respectively nitrapyrin. The first chemical inhibits only nitrate formation, the second inhibits total nitrification. The accumulation of nitrite nitrogen in the soil at levels up to 5 mg kg^–1 increased the loss of nitrogen. Yet, it did not increase the binding of mineral nitrogen into soil organic matter, relative to the control soil. The data suggest that the biochemistry of the nitrite formation process, rather than the levels of nitrite ions formed, are of primary importance in the role of nitrification mediated nitrosation of soil organic matter.     

Linkages between seagrass,mangrove and saltmarsh as fish habitat in the Botany Bay estuary,New South Wales

Shallow-water vegetated estuarine habitats, notably seagrass, mangrove and saltmarsh, are known to be important habitats for many species of small or juvenile fish in temperate Australia. However, the movement of fish between these habitats is poorly understood, and yet critical to the management of the estuarine fisheries resource. We installed a series of buoyant pop nets in adjacent stands of seagrass, mangrove and saltmarsh in order to determine how relative abundance of fishes varied through lunar cycles. Nets were released in all habitats at the peak of the monthly spring tide for 12 months, and in the seagrass habitat at the peak of the neap tide also. The assemblage of fish in each habitat differed during the spring tides. The seagrass assemblage differed between spring and neap tide, with the neap tide assemblage showing greater abundances of fish, particularly those species which visited the adjacent habitats when inundated during spring tides. The result supports the hypothesis that fish move from the seagrass to the adjacent mangrove and saltmarsh during spring tides, taking advantage of high abundances of zooplankton, and use seagrass as a refuge during lower tides. The restoration and preservation of mangrove and saltmarsh utility as fish habitat may in some situations be linked to the proximity of available seagrass.     

Prevention of insulin resistance by environmental manipulation as young rats mature

This study was initiated in an attempt to see if the insulin resistance associated with maturation in young rats could be prevented by environmental manipulation. Consequently, seven week-old rats were either housed in standard laboratory cages and fed a calorie-restricted diet or placed individually in exercise wheel cages and allowed to eat chow ad lib. A control group of rats was housed in standard laboratory cages from seven weeks to five months of age, and also allowed to eat chow ad lib. When studied at five months of age, the chow-fed rats weighed more (624 +/- 8 g) than either the calorie restricted (479 +/- 9 g) or exercise trained (485 +/- 13 g) rats. Insulin action was compared in the three groups by assessing the steady-state serum glucose (SSSG) and insulin (SSSI) concentrations achieved during a continuous intravenous infusion of glucose and exogenous insulin. The results of these studies indicated that SSSG concentration was significantly higher (P less than 0.001) in chow-fed rats than in the two experimental groups. Since SSSI concentrations were the same in all three groups, lower SSSG concentrations in calorie-restricted and exercise trained rats indicates that insulin-stimulated glucose uptake was preserved in these two groups as compared to the chow-fed population. In an attempt to understand why exercise training and calorie restriction prevented the development of insulin resistance, muscle glycogen synthase activity and muscle capillary density were compared in the three groups of five month-old rats.(ABSTRACT TRUNCATED AT 250 WORDS)     

Cellulolytic activities ofChaetomium globosum on different cellulosic substrates

The effect of cellulosic substrates on the production of extra-cellular cellulases and their cellulolytic activity inChaetomium globosum has been studied in shake flask cultures. Production of endoglucanase, exoglucanase and filter paper cellulase was highest with pure cellulose whereas -glucosidase was maximally induced by wheat straw. A suitable pretreatment for wheat straw was peracetic acid followed by NaOH and that of bagasse with NaOH for saccharification.

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Résumé On a étudié l'effet de substrats cellulosiques sur la production de cellulases extracellulaires et leur activité cellulolytique chezChaetomium globosum en culture en flacons agités. La production d'endoglucanase, d'exoglucanase et de cellulase type papier-filtre est maximum avec la cellulose pure tandis que la -glucosidase est induite de manière maximum par la paille de froment. La paille de froment est traitée de manière adéquate pour la saccharification par l'acide peracétique suivi de NaOH, la bagasse, par NaOH.

     

Cytogenetic effects in a group of traffic policemen in Cairo

The aim of this study was to evaluate the cytogenetic effects in humans exposed to automobile exhaust. The induction of chromosome damage was studied in an exposed group of 28 traffic policemen with exposure of over 10 years and a control group of 15 policemen trainers from the Faculty of Police. The percentage of chromosomal aberrations as well as the mean sister-chromatid exchanges were significantly higher among the traffic policemen than in the control group. The cause for this elevated chromosome damage is most likely due to their exposure to pollutants from automobile exhaust, however, the increase is not correlated with the blood lead level or the duration of employment. On the other hand, the increase in chromosome damage among the traffic policemen is enhanced further by smoking.     

Somatic embryogenesis and shoot regeneration from intact seedlings of Phaseolus acutifolius A., P. aureus (L.) Wilczek,P. coccineus L., and P. wrightii L.

A rapid, one-step procedure has been developed for inducing direct organogenesis and somatic embryogenesis in cultures of Phaseolus coccineus L., P. acutifolius A., P. aureus L. [Vigna radiata L. Wilczek] and P. wrightii L. Development of somatic embryos and shoot buds occurred within 6–8 weeks of culture from intact seedlings raised on MS (Murashige and Skoog 1962) medium supplemented with N⁶-benzylaminopurine (BAP). Shoot buds or embryoids originated from subepidermal tissue of the regions adjacent to the shoot apex, hypocotyl and cotyledonary axils. While P. acutifolius and P. aureus were regenerated via shoot formation and P. wrightii by somatic embryogenesis, both embryogenesis and shoot regeneration were observed in P. coccineus. Relatively higher levels of BAP, 50–80 M, were found to be optimal for inducing regeneration while lower concentrations were ineffective. About 40–70 shoots and 70–250 somatic embryos were produced per responding seedling. Regenerated shoots and somatic embryos developed into whole plants on a basal medium or the one supplemented with 1 M naphthaleneacetic acid.     

Effect of dermal tumours on temperature distribution in skin with variable blood flow

Several investigations have been made for the heat flow problems in skin and subdermal tissues under normal physiological and atmospheric conditions. This paper considers the existence of a malignant tumour in the underlying tissues of epidermis of a human body. The surrounding tissues are assumed to have normal physiological functions, namely self-controlled metabolic activity, variable blood flow and perspiration. For the malignant portion the metabolic activity is taken to be continuous and uncontrolled. The effect of this factor is studied on the temperature profiles of the skin.     

Evidence for age-related changes in pyridine nucleotide content of isolated rat islets

The purpose of this study was to document the effect of age on alpha-glycerophosphate activity and pyridine nucleotide concentration in pancreatic islets isolated from rats. In order to do this, islets were isolated from pancreases of 2 and 12 month-old rats, and measurements made of alpha-glycerophosphate activity and of NAD+ and NADH, determinations were made following incubation at both basal (5.6 mM) and elevated glucose concentrations (28 mM). The results indicated that islet alpha-glycerophosphate dehydrogenase activity was decreased (P less than 0.001) by approximately 50% in the older rats. This was associated with an increase in mean (+/- SEM) basal NADH content (pmol/microgram DNA) in 12 month-old (4.48 +/- 0.31) as compared to 2 month-old rats (2.73 +/- 0.49). Although mean (+/- SEM) basal NAD+ levels (pmol/microgram DNA) were the same in 2 and 12 month-old rats (29.4 +/- 2.5 and 30.8 +/- 2.8, respectively), NAD+ content following incubation at elevated levels of glucose declined (absolutely and relatively) to a significantly greater degree in the younger rats. The incremental rise in islet NADH concentration following incubation at the elevated glucose concentration was similar in the two groups, but the relative increase was only approximately half as great in islets from 12 month-old rats. These data indicate that the age-related decline in the activity of alpha-glycerophosphate dehydrogenase, the enzyme regulating the glycerophosphate shuttle system in 12 month-old rats, is associated with alterations in islet pyridine nucleotide composition.(ABSTRACT TRUNCATED AT 250 WORDS)     

Identification of isoenzymic forms of hepatic Ca2+-activated-phospholipid-dependent protein kinase in various animal models

We have examined the protein kinase C that are present in mouse, rat, guinea pig and rabbit liver. Initial subcellular fractionation analysis indicated that the majority (75-85%) of the activity was associated with particulate fraction of the liver. The bound protein kinase C was dissociated by homogenization of livers in buffer containing EGTA, EDTA and various proteolytic inhibitors and the solubilized extract was used to resolve multiple forms of the enzyme. The fractionation procedure, sequentially utilized (NH4)2SO4 precipitation, ion exchange chromatography, gel permeation chromatography, and hydroxylapatite column chromatography. With hydroxylapatite, protein kinase C was resolved into three isoenzymic forms designated C-I, C-II and C-III. In each case, the predominant activity consisted of C-II and C-III and together they represented about 80-88% of the total activity. All three isoenzymes from each source demonstrated an absolute requirement for PS + Ca2+ (approximately 25-50 fold stimulation over basal activity); for maximal activity the isoenzymes also required the presence of divalent metal ion, Mg2+ (5-10 mM) and lysine rich histone (H1). Both diolein and TPA decreased the Ca2+ and PS requirement of the enzyme and directly stimulated enzyme activity in the presence of suboptimal concentrations of Ca2+ and PS. In conclusion, the present studies suggest that protein kinase C in mammalian liver exists in isoenzymic forms.     

Nitrification and organic nitrogen formation in soils

Summary The formation of mineral nitrogen species and of organic nitrogen was studied in three different types of soils in relation to the application of the nitrification inhibitor nitrapyrin. The results indicate that nitrification brings about a deficit in total mineral nitrogen and a concomitant surplus in non biomass organic nitrogen. This phenomenon increases with increasing levels of applied ammonium nitrogen and soil organic matter. The phenomenon is considered to be due to the reaction of the transient nitrite formed with soil phenolic compounds and appears to be of significance in all soils in which nitrification occurs, even neutral to alkaline and low carbon soils.