Drivers of aboveground wood production in a lowland tropical forest of West Africa: teasing apart the roles of tree density,tree diversity,soil phosphorus,and historical logging

Tropical forests currently play a key role in regulating the terrestrial carbon cycle and abating climate change by storing carbon in wood. However, there remains considerable uncertainty as to whether tropical forests will continue to act as carbon sinks in the face of increased pressure from expanding human activities. Consequently, understanding what drives productivity in tropical forests is critical. We used permanent forest plot data from the Gola Rainforest National Park (Sierra Leone) – one of the largest tracts of intact tropical moist forest in West Africa – to explore how (1) stand basal area and tree diversity, (2) past disturbance associated with past logging, and (3) underlying soil nutrient gradients interact to determine rates of aboveground wood production (AWP). We started by statistically modeling the diameter growth of individual trees and used these models to estimate AWP for 142 permanent forest plots. We then used structural equation modeling to explore the direct and indirect pathways which shape rates of AWP. Across the plot network, stand basal area emerged as the strongest determinant of AWP, with densely packed stands exhibiting the fastest rates of AWP. In addition to stand packing density, both tree diversity and soil phosphorus content were also positively related to productivity. By contrast, historical logging activities negatively impacted AWP through the removal of large trees, which contributed disproportionately to productivity. Understanding what determines variation in wood production across tropical forest landscapes requires accounting for multiple interacting drivers – with stand structure, tree diversity, and soil nutrients all playing a key role. Importantly, our results also indicate that logging activities can have a long‐lasting impact on a forest's ability to sequester and store carbon, emphasizing the importance of safeguarding old‐growth tropical forests.     

The efficiency of 1M NH4Cl and 2 M NaCl for the isolation of pathogenic Nocardia from soil

The present paper reports an improvement to the classical method of the paraffin bait, by the usage of 1 M NH₄Cl or 2 M NaCl to eliminate contaminant microflora of soil.The purpose is to introduce a change in the paraffin bait method in order to reduce time required to isolate pathogenic strains of Nocardia from their natural sources.For this study three main criteria were used: a) Determination of the inhibitory effect of different concentrations of salts on soil microflora; b) The tolerance of Nocardia brasiliensis, Nocardia asteroides and Nocardia caviae (Nocardia otitidis caviarum) strains to these chemical inhibitors; c) Determination of the efficiency of salts in the isolation of Nocardia from soil when strains are grown on paraffin baits.     

An explanation of the induction of mutations by 2-aminopurine from an ab initio molecular orbital study

The molecular mechanism of induction of mutations by 2-aminopurine (AP) was studied by an ab initio molecular orbital method. Cytosine (C) is converted to its disfavored imino tautomer more easily than AP, judging from the calculated total energies of the bases and the base analogue. This suggests that a stable AP:C base mispair via two hydrogen bonds can be formed with the imino tautomer of C. These results stress the importance of the imino form of C in AP-induced mutagenesis and support the 'trigger mechanism', in which formation of one hydrogen bond between AP and C is considered to stimulate the tautomeric shift of AP or C. The calculated relative stabilities of various base pairs and mispairs were in good agreement with experimental findings.     

A quantitative study of synaptic ribbons in pinealocytes of adult Chinese hamsters (Cricetulus griseus) under different photoperiodic conditions

Summary Synaptic ribbons (SR) in pinealocytes of adult (120–130 day-old) male Chinese hamsters (Cricetulus griseus) were classified into types 1, 2 and 3; these have a central dense structure showing rod-like, various and ringlike profiles, respectively. The central structure of the type-2 SR usually appeared as round, oval or comma-like bodies, and occasionally as plates showing various profiles or clubshaped bodies. The quantity of each type of SR, expressed as the SR index, was determined over a 24-h period under a light/dark regime (LD) 1212 or LD 1410. On comparing the results obtained from adults with previously published data from young (60–70-days-old) animals under LD 1212, it was found that, in both young and adult animals, the type-1 and type-3 SR indices exhibited different 24-h variations, whereas the type-2 SR index remained constant over a 24-h period. In addition, the indices of the type-2 SR, but not those of the other SR types, were found to be significantly larger in adult than in young animals. In adult animals, the effects of the photoperiod were different between the three types of SR. A nocturnal increase in the type-1 SR index was observed under both LD 1212 and LD 1410, its time course being different for each of these photoperiods. Under LD 1410, the type-2 SR index showed a significant 24-h rhythm with larger values during the dark period; this was not observed under LD 1212. The type-3 SR index was almost the same under LD 1212 and LD 1410. The results suggest that pinealocyte SR of the Chinese hamster may be composed of three types of SR, each with a different functional role.     

Arginine metabolism inLactobacillus leichmannii

Lactobacillus leichmannii ATCC 4797 metabolizes arginine via the arginine dihydrolase pathway producing ornithine, ammonia, carbon dioxide, and ATP. The specific activities of arginine deiminase and ornithine transcarbamylase were two-or threefold lower (stationary growth phase) in galactose-grown cells. The addition of arginine increased the specific activities of these two enzymes with all growth sugars. When glucose was virtually exhausted from the medium, maximum activities of both enzymes were achieved. The formation of two first enzymes of the arginine dihydrolase pathway inL. leichmannii ATCC 4797 seems to be under the control of two processes: induction by arginine and repression of the induced synthesis by glucose.Dedicated to Dr. Luis F. Leloir on the occasion of his 80th birthday, 6 September 1986.     

Steroid nitrogen compounds. 3. A general method for introduction of O, N, S and other functionality into position-5 of cholestanes. Conjugate addition of nucleophiles to 6-nitrosocholesteryl acetate generated in situ from the 5 -chloro-6-oxime

The conjugate addition of organic and inorganic nucleophiles to 6-nitrosocholesteryl acetate (II) generated in situ from 3β-acetoxy-5-chloro-6-hydroxyimino-5α-cholestane (I) has been shown to give high yields of 5α-substituted 6-oximes (IIIa-h) under mild reaction conditions. Nucleophiles include ethanethiol, ethanol, methylamine, ammonia, nitrite, cyanide, thiocyanate and azide. Validity of the proposal that the replacement of chlorine atom of α-chlorooximes by nucleophiles proceeds via an elimination-addition mechanism through nitrosoolefins has been confirmed by the isolation and conversion of II into methoxy oxime (III, X = OMe) by the treatment with methanol. Due to the steric hindrance exerted by α-hydrogen atoms at λ-positions, bulky nucleophiles, which have been reported to react with α-chlorooximes, failed to react with the chlorooxime (I). Effects of 5α-substituents upon the signal position of the 3α-proton are described.     

Production of L-glutamic acid from hydrocarbons: Incorporation of molecular oxygen

The production of L -glutamic acid from hydrocarbons by a newly isolated bacterium, which was identified as Corynebacterium, was investigated. The outstanding characteristic of this bacterium was found to be an accessory requirement of thiamine for growth. The optimum concentration of thiamine for growth was 50 μg./liter, while that for L -glutamic acid production was 3–5 μg./liter. n-Paraffins ranging from dodecane to heptadecane were best for L -glutamic acid production, and about 5 g. of L -glutamic acid were obtained from 30 g. of these individual n-paraffins. On the other hand, a tracer experiment using oxygen-18 revealed that molecular oxygen was incorporated into L -glutamic acid produced from dodecane. Based on the incorporation value of molecular oxygen in L -glutamic acid, a hypothetical pathway for the biosynthesis of L -glutamic acid from dodecane was discussed.     

Toxicity and toxins of natural blooms and isolated strains of Microcystis spp. (Cyanobacteria) and improved procedure for purification of cultures

All samples of cyanobacterial blooms collected from 1986 to 1989 from Lake Kasumigaura, Ibaraki Prefecture, Japan, were hepatotoxic. The 50% lethal doses (LD50s) of the blooms to mice ranged from 76 to 556 mg/kg of body weight. Sixty-eight Microcystis cell clones (67 Microcystis aeruginosa and 1 M. viridis) were isolated from the blooms. Twenty-three strains (including the M. viridis strain) were toxic. However, the ratio of toxic to nontoxic strains among the blooms varied (6 to 86%). Microcystins were examined in six toxic strains. Five toxic strains produced microcystin-RR, -YR, and -LR, with RR being the dominant toxin in these strains. Another strain produced 7-desmethylmicrocystin-LR and an unknown microcystin. This strain showed the highest toxicity. Establishment of axenic strains from the Microcystis cells exhibiting extracellularly mucilaginous materials was successful by using a combination of the agar plate technique and two-step centrifugation.     

Clinical efficacy of a stable prostacyclin analog, iloprost, in diabetic neuropathy

Iloprost, a stable prostacyclin analog, was evaluated clinically for its ability to ameliorate the symptoms of peripheral neuropathy associated with diabetes. In an open, nonrandomized trial, 13 diabetic patients with neuropathy but without proliferative retinopathy received an intravenous infusion of iloprost at a dose of 10 μg, at a rate of 0.1 μg/kg/h, twice daily for two weeks.The administration of Iloprost relieved the majority of such subjective symptoms as pain, numbness or sensation of cold and to a lesser extent, such autonomic symptoms as dizziness. In contrast, there was little evidence of objective improvement, e.g., in motor nerve conduction velocity. Iloprost treatment significantly inhibited the platelet aggregation rate stimulated by collagen . In the one patient tested, thermography revealed an increase in skin temperature by more than 2°C.Side effects associated with Iloprost included headache (3 patients) or aggravation of pain in the extremities (2 patients) and could be ameliorated by slowing the infusion rate or by discontinuing the drug (one patient). Iloprost appears to be safe and effective for relieving the symptoms of diabetic neuropathy. Our results provide the rationale for a double-blind, clinical trial in larger populations of diabetics with peripheral neuropathy.