Hydrologic regulation of gross methyl chloride and methyl bromide uptake from Alaskan Arctic tundra

The Arctic tundra has been shown to be a potentially significant regional sink for methyl chloride (CH₃Cl) and methyl bromide (CH₃Br), although prior field studies were spatially and temporally limited, and did not include gross flux measurements. Here we compare net and gross CH₃Cl and CH₃Br fluxes in the northern coastal plain and continental interior. As expected, both regions were net sinks for CH₃Cl and CH₃Br. Gross uptake rates (−793 nmol CH₃Cl m⁻² day⁻¹ and −20.3 nmol CH₃Br m⁻² day⁻¹) were 20–240% greater than net fluxes, suggesting that the Arctic is an even greater sink than previously believed. Hydrology was the principal regulator of methyl halide flux, with an overall trend towards increasing methyl halide uptake with decreasing soil moisture. Water table depth was one of the best predictors of net and gross uptake, with uptake increasing proportionately with water table depth. In drier areas, gross uptake was very high, averaging −1201 nmol CH₃Cl m⁻² day⁻¹ and −34.9 nmol CH₃Br m⁻² day⁻¹; in flooded areas, gross uptake was significantly lower, averaging −61 nmol CH₃Cl m⁻² day⁻¹ and −2.3 nmol CH₃Br m⁻² day⁻¹. Net and gross uptake was greater in the continental interior than in the northern coastal plain, presumably due to drier inland conditions. Within certain microtopographic features (low‐ and high‐centered polygons), uptake rates were positively correlated with soil temperature, indicating that temperature played a secondary role in methyl halide uptake. Incubations suggested that the inverse relationship between water content and methyl halide uptake was the result of mass transfer limitation in saturated soils, rather than because of reduced microbial activity under anaerobic conditions. These findings have potential regional significance, as the Arctic is expected to become warmer and drier due to anthropogenic climate forcing, potentially enhancing the Arctic sink for CH₃Cl and CH₃Br.     

DOG-SPOT database for comprehensive management of dog genetic research data

Research laboratories studying the genetics of companion animals have no database tools specifically designed to aid in the management of the many kinds of data that are generated, stored and analyzed. We have developed a relational database, "DOG-SPOT," to provide such a tool. Implemented in MS-Access, the database is easy to extend or customize to suit a lab's particular needs. With DOG-SPOT a lab can manage data relating to dogs, breeds, samples, biomaterials, phenotypes, owners, communications, amplicons, sequences, markers, genotypes and personnel. Such an integrated data structure helps ensure high quality data entry and makes it easy to track physical stocks of biomaterials and oligonucleotides.     

pH-dependent modulation of alkaline phosphatase activity in Serratia marcescens

Serratia marcescens is an opportunistic pathogen responsible for causing nosocomial infections, corneal ulcer, necrotizing fasciitis, cellulites, and brain abscess. Alkaline phosphatase (APase) is believed to play an important role in the survival of several intracellular pathogens and their adaptation. We have studied the effect of low phosphate concentration and acid pH on the APase activities of S. marcescens. In a low phosphate medium, some strains of S. marcescens synthesize two different types of APases, a constitutive (CAPase) and an inducible (IAPase). Both the CAPase and IAPase isoenzymes completely lost their enzyme activities at pH 2.3, within 10 min of incubation at 0°C. Acid-treated IAPase isoenzymes I, II, III, and IV solutions when adjusted to pH 7.8 showed recovery of 70%, 52%, 72%, and 60% of the lost activities, respectively. When the pH of the CAPase reaction mixture was raised to pH 7.8, the enzyme activity regained only 5% of its initial activity. Variations in protein concentration also affected the pH-dependent reversible changes of the IAPase activity. The higher the protein concentration, the faster the inactivation of enzyme activity observed at acidic pH at 0°C. Conversely, the lower the protein concentration, the higher the rate of reactivation of enzyme activity observed for IAPase at alkaline pH. Protein interaction studies revealed a lack of similarity between CAPase and IAPase, suggesting separate genetic origin of these potentially virulent genes of S. marcescens. Received: 4 December 2001 / Accepted: 7 January 2002     

Understanding down-regulation of photosynthesis under water stress: future prospects and searching for physiological tools for irrigation management

Photosynthetic down-regulation and/or inhibition under water stress conditions are determinants for plant growth, survival and yield in drought-prone areas. Current knowledge about the sequence of metabolic events that leads to complete inhibition of photosynthesis under severe water stress is reviewed. An analysis of published data reveals that a key regulatory role for Rubisco in photosynthesis is improbable under water stress conditions. By contrast, the little data available for other Calvin cycle enzymes suggest the possibility of a key regulatory role for some enzymes involved in the regeneration of RuBP. There are insufficient data to determine the role of photophosphorylation. Several important gaps in our knowledge of this field are highlighted. The most important is the remarkable scarcity of data about the regulation/inhibition of photosynthetic enzymes other than Rubisco under water stress. Consequently, new experiments are urgently needed to improve our current understanding of photosynthetic down-regulation under water stress. A second gap is the lack of knowledge of photosynthetic recovery after irrigation of plants which have been subjected to different stages of water stress. This knowledge is necessary in order to match physiological down-regulation by water stress with controlled irrigation programmes.     

Studies on the salivary gland chromosomes of an isolated population of Anopheles stephensi (Diptera, Culicidae)

The salivary gland chromosomes of Anopheles stephensi from a local wild population in Nadasahib (Haryana) have been studied. The banding pattern is compared with the standard pattern of Anopheles stephensi (NICD strain). Differences in the free ends of the X-chromosome and the autosomal arms have been seen. These differences are both in the shape and the banding pattern of the free ends. The impact of ecogeographic isolation on genetic variability between the two species is also discussed. The Nadasahib population is free from natural chromosomal polymorphism, whereas 32 different types of aberrations have been seen in the NICD strain.     

Distribution of beta-N-acetylglucosaminidase, hyaluronoglucosaminidase and acrosin in buffalo and goat spermatozoa.

The distribution of beta-N-acetylglucosaminidase, hyaluronoglucosaminidase and acrosin in buffalo and goat sperm acrosomes was studied. The three hydrolases were found to occur in soluble and bound forms. In the bound form, they were associated with the denuded sperm and were maximally solubilized at pH 3.0. The possible role of beta-N-acetylglucosaminidase in fertilization is discussed.     

Control experiments usingAgrotis segetum granulosis virus againstAgrotis ipsilon [Lep.: Noctuidae] on tobacco seedlings in Northern Pakistan

Agrotis segetum Schiff. granulosis virus propagated in Denmark was applied against released 2nd instar larvae ofAgrotis ipsilon (Hfn.) in tobacco plots in nurseries at Peshawar and Bhurbun (Murree), Northern Pakistan. Nursery bed plots were isolated from the surroundings by net roof and plastic sheets. Granulosis virus concentrations used were 5×10⁷ and 10⁹ capsules per ml water, and 250 ml water per plot (1–4 m²). Reductions of cutworms as well as cutworm damages varied between 72 and 100% as compared to plots only treated with water. Addition of active coal to the GV did not increase reduction percentages. A possible effect of the GV could be traced one year after treatment.

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Résumé Le virus de la granulose d'Agrotis segetum Schiff. multiplié au Danemark a été appliqué contre le 2^e stade des chenilles deAgrotis ipsilon (Hfn.) dans des parcelles expérimentales à Peshawar et Bhurbun (Murree), Pakistan du nord. Les parcelles isolées avec des filets et des feuilles plastiques furent infestées artificiellement en chenilles. Les concentrations de GV utilisées furent de 5×10⁷ et 10⁹ granules par ml d'eau, 250 ml de la suspension préparée étant distribués par parcelle de 1 à 4 m². La réduction du nombre de chenilles et celui des plantes endommagées varie de 72 à 100% par rapport aux notations effectuées dans les parcelles traitées avec de l'eau pure. L'addition du charbon actif au GV n'augmente pas son effet. Une action du traitement a été retrouvée un an après l'application.

     

STUDY ON THE PROLIFERATIVE STATE OF HAEMOPOIETIC STEM CELLS (CFU)

Hydroxyurea was used to study the proliferation rate of haemopoietic stem cells (CFUJ in normal mice, after irradiation or transplantation into irradiated recipients. It was demonstrated that the proliferation rate of endogenous CFU_S (endo-CFU,) and exogenous CFU_S (exo-CFU_s) are identical. After irradiation (650 R) the surviving endo-CFU_s begin to proliferate immediately. By contrast exo-CFU, transplanted into the irradiated recipient mouse (850 R), begin to proliferate only after about 30 hr. However, injection of isoproterenol (which stimulates adenyl cyclase) or dibutyryl cyclic adenosine 3′,5′-monophosphate shortly after marrow cell graft, triggers the transplanted CFU_S into cell cycle as shown by an almost immediately increased sensitivity to hydroxyurea. Isoproterenol is capable of inducing DNA synthesis also in stem cells of normal mice but it takes about 20 hr before CFU, become to be increasingly sensitive to hydroxyurea.