Substantial Organic and Particulate Nitrogen and Phosphorus Export from Geomorphologically Stable African Tropical Forest Landscapes

Ecosystems - Aquatic losses of nutrients are important loss vectors in the nutrient budgets of tropical forests. Traditionally, research has focused mainly on losses of inorganic nutrient forms,...     

Histochemically demonstrable catecholamines and cholinesterases in nerve fibres of rat dorsal skin

Summary Histochemically demonstrable cholinesterases of rat skin and cutaneous nerves hydrolyze acetylthiocholine iodide and butyrylthiocholine iodide. Cholinesterase activity of the skin was located in the epidermis, in the hair follicles at the level of the sebaceous glands, in adjacent parts of the sebaceous glands, in erector pili muscles and their nerves, in cutaneous and subcutaneous nerves and nerve trunks, including some nerves accompanying cutaneous blood vessels, and in the membranes of fat cells. No encapsulated nerve endings were found. In the nerves of erector pili muscles there was some neurilemmal non-specific cholinesterase activity, demonstrated in the presence of 10^–5 M BW 284C 51, and specific acetylcholinesterase activity resistant to 10^–5 M iso-OMPA. The cholinesterase activity in other cutaneous nerves was inhibited by 10^–5 M iso-OMPA but was resistant to 10^–5 M BW284 C 51, thus representing mainly non-specifc cholinesterase (nsChE) activity.The adrenergic nerves of the dorsal skin, as revealed by glyoxylic acid-induced fluorescence (GIF), were located in association with erector pili muscles and surrounded arteries and arterioles. Small fluorescent nerves were situated in subcutaneous nsChE-positive nerve trunks.Using GIF and cholinesterase techniques performed either simultaneously or consecutively, it was found that the nsChE-positive, probably sensory, nerves accompanying blood vessels were fewer in number than the fluorescent adrenergic nerves and ran a course independent of them. No cholinesterase reaction was seen in the fluorescent adrenergic nerves when short incubation times were used. When the incubation time was prolonged overnight, the nsChE reaction closely followed the course of fluorescent adrenergic nerves.     

Growth of the metal framework in linear ruthenium and osmium carbonyls

Formation of the linear chain ruthenium and osmium carbonyls by successive linkage of mononuclear [M(CO)₄Cl₂] units and by opening trinuclear clusters [M₃(CO)₁₂] and [FeM₂(CO)₁₂] (M = Ru, Os) with chlorine gas have been studied by computational DFT methods. Energetically the formation of dinuclear [M₂(CO)₈Cl₂] from [M(CO)₄Cl₂] units is the most demanding step. The following chain growth by adding new mononuclear units proceeds more easily with nearly constant energy per step. Cluster opening by chlorine gas to obtain trinuclear [M₃(CO)₁₂Cl₂] is a facile reaction for both ruthenium and osmium clusters as well as for mixed metal clusters. Mixed metal clusters [FeOs₂(CO)₁₂] and [FeRu₂(CO)₁₂] open preferably between iron-osmium or iron-ruthenium bonds producing linear trinuclear Fe-M-M-type of compound. In the case of mixed metal Os-Ru clusters, the cleavage of Os-Ru bond is not clearly preferred. Fragmentation of the cluster to shorter units cis(Cl)-[M(CO)₄Cl₂] or [M₂(CO)₈Cl₂] with equatorial chlorides is highly favorable and competes with the cluster opening. No preferences on the bond type (Os-Ru, Os-Os, or Ru-Ru) that are broken can be found in the case of mixed metal Os-Ru clusters.     

Noradrenaline content of the tissue and nerve in the rabbit ear after freezing injury.

The aim of this study was to investigate the development of the demarcation line in the rabbit ear upon injury by experimental freezing and thawing. For this purpose the sequential changes in noradrenaline (NA) content in the tissue and nerve of the ear were determined by liquid chromatography. Frostbite was inflicted with a glass bottle filled with liquid nitrogen and specimens were taken from the injured area, the probable demarcation line area and the healthy area 1, 3, and 7 days after frostbite. Control samples were taken from the normal contralateral ear. Tissue NA levels in the injured area and the probable demarcation line area were significantly lower than those in corresponding areas of the control ear after 1 day. Day 3 NA levels in the demarcation line area were 90% higher than those on Day 1 in this area and were not significantly different from Day 3 levels in the control ear. By Day 7, NA levels in the demarcation line area were down to 70% of the Day 3 levels. NA levels in the central nerve at the probable demarcation line were much higher than those in the control ear nerve and also showed a peak on Day 3. In conclusion, the results suggest that NA is released from the adrenergic nerves and the reaction at the probable demarcation line is strongest on the third day.     

Metabolic adaptation allows Amacr-deficient mice to remain symptom-free despite low levels of mature bile acids

Bile acids play multiple roles in the physiology of vertebrates; they facilitate lipid absorption, serve as signaling molecules to control carbohydrate and lipid metabolism, and provide a disposal route for cholesterol. Unexpectedly, the α-methylacyl-CoA racemase (Amacr) deficient mice, which are unable to complete the peroxisomal cleavage of C27-precursors to the mature C24-bile acids, are physiologically asymptomatic when maintained on a standard laboratory diet. The aim of this study was to uncover the underlying adaptive mechanism with special reference to cholesterol and bile acid metabolism that allows these mice to have a normal life span. Intestinal cholesterol absorption in Amacr −/− mice is decreased resulting in a 2-fold increase in daily cholesterol excretion. Also fecal excretion of bile acids (mainly C27-sterols) is enhanced 3-fold. However, the body cholesterol pool remains unchanged, although Amacr-deficiency accelerates hepatic sterol synthesis 5-fold. Changes in lipoprotein profiles are mainly due to decreased phospholipid transfer protein activity. Thus Amacr-deficient mice provide a unique example of metabolic regulation, which allows them to have a normal lifespan in spite of the disruption of a major metabolic pathway. This metabolic adjustment can be mainly explained by setting cholesterol and bile acid metabolism to a new balanced level in the Amacr-deficient mouse.     

30 years brings changes to the arthropod community of Kibale National Park,Uganda

World-wide declines in arthropod abundance and diversity are a major concern, particularly given their importance in ecosystem functioning. Yet, data documenting long-term trends are rare from the tropics, particularly the Afrotropics. Here we evaluate changes in the arthropod communities in Kibale National Park, Uganda across almost four decades. Systematic sweep-net sampling was conducted in two forested sections of the park that had been logged and in one old-growth forest area over 12 consecutive months in 1983/1984 and 2020/2021. This data was augmented with intermittent samples taken in 1986 and 1995. Arthropod abundance declined in all areas, but only significantly so in the moderately logged forestry compartment (41%). Permutational multivariate analysis of variance indicated that community compositions of arthropods differed between the censuses. Understanding the drivers of changes in the arthropod communities is difficult as the system is complex and dynamic. We document an increase in temperature, but no change in rainfall, increases in 11 mammal species, including a marked increase in elephant numbers, and changes in forest structure. We also report on changes in the landscape outside of the park, which includes the human population increasing by a factor of four and agricultural intensification that now includes the use of pesticides. We document that many components of the ecosystem we studied changed simultaneously, which signals that for effective conservation planning, more long-term multi-disciplinary efforts are needed.     

Structural Co-Evolution of Viruses and Cells in the Primordial World

Viruses and cells co-evolve due to the parasitic nature of viruses. Yet there are no models suggesting how the unicellular organisms and their viruses might co-evolve structurally. Here, in this study, we plunge into this unexplored field from a wide perspective and try to describe some of the intriguing ways in which viruses may have shaped the cellular life forms on the ancient Earth. At first we propose a scenario where viruses act as a driving force in the emergence of bacterial cell walls by providing favorable intermediates for the otherwise improbable steps in the cell wall generation. We also discuss the role of viruses in the evolution of cell surface components such as receptors and second membranes. Finally we focus on hypothetical proto-viruses, the selfish abusers of the RNA-world, in explaining some of the very early stages in the origin and evolution of life. Proto-viruses may be responsible for creating the first true cells in order to support their selfish needs. In this model we also suggest a logical pathway to explaining the emergence of modern viruses.