Reverse electron flow in chloroplasts

Energy dependent reverse electron flow reactions in isolated thylakoids provide a unique tool to study, in the dark, the coupling between the ATP synthase, proton transport and the electron transfer system. Appropriate experimental conditions have been established to follow experimentally the following reactions:

1. ATP driven proton uptake into the inner-thylakoid space, which requires preactivation of the ATP synthase.
2. ATP driven reverse electron transport, which involves proton transport as an intermediate, and results in the reduction of Q_A by an externally added electron donor.
3. ATP driven luminescence, which requires the presence of an oxidized partner on the water side of photosystem II, and involves electron transport from Q_B to Q_A.
4. ΔpH driven reverse electron flow, which does not require the participation of the ATP synthase, and uses reduced intermediates between the two photosystems as electron donors for the reduction of Q_A.
5. ΔpH driven luminescence which again uses reduced intermdiates between the two photosystems as electron donors for Q_A reduction, and requires the presence of an oxidized partner on the water side of photosystem II.

Several of these reactions have been shown to occur in intact chloroplasts and may provide an important regulatory mechanism in vivo.     

A study on the rate of water transport of the clam katelysia opima in relation to environmental conditions

1. The neutral red technique was employed to study the rate of filtration in Katelysia opima.
2. The weight specific water filtration was found to be greater for younger clams compared to the older ones.
3. The rate of water filtration increased with decreasing salinity.
4. Water filtration was found to increase as temperature increased, reaching a maximum at 35°C. but then sharply decreasing at 39°C.
5. Light had no significant effect on the rate of filtration.
6. Suspended matter was found to affect the rate of water filtration.
7. The rate of filtration was low at high pH and high in low pH.
8. The rate of water filtration was found to be faster during high tide than during low tide.
9. The presence of the parasitic crab, Pennotheris sp., in the mantle cavity of clams had a marked effect on the particle filtration.
10. Accidental cut of the siphon tips had no effect on the rate of filtration.

     

Correlation of the effects of citric acid cycle metabolites on succinate oxidation by rat liver mitochondria and submitochondrial particles

1. Succinate dehydrogenase is inhibited by citrate and β-hydroxybutyrate in a complex manner, both in mitochondria and submitochondrial particles. Kinetics of inhibition in the particles points to a competitive component in the mechanism involved.
2. Pyruvate, α-ketoglutarate, malate, and glutamate stimulate oxidation of succinate by mitochondria.
3. Stimulation by α-ketoglutarate and glutamate is not influenced by the presence of rotenone.
4. Stimulation by pyruvate is higher in the absence of rotenone and increases significantly in the presence of K⁺ and valinomycin. Pyruvate supplies in mitochondria reducing equivalents for malate dehydrogenase operating in the reverse direction-reduction of oxaloacetate to malate.
5. Stimulation by malate is higher in the presence of rotenone.

     

EPR characterization of oxide supported transition metal ions: Relevance to catalysis

EPR spectroscopy is a powerful tool to identify at a molecular level, the different steps of catalyst preparation, and of catalytic reactions:

1. Deposition of paramagnetic transition metal ions onto a support is monitored, and the coordination sphere of the metallic center is characterized by EPR.
2. The catalyst is also characterized after activation (thermal oxidation or reduction):

- the distribution among the different sites in zeolites can be determined;

- the dispersion of the active phase may be appreciated;

- the unsaturation degree of the active site may be evaluated using probe molecules such as water or¹³C enriched carbon monoxide.

1. The catalytic mechanisms can be investigated by studying the elementary steps of the catalytic reaction, as illustrated for methanol oxidation over Mo/SiO₂ catalysts whose EPR results have extended the reaction mechanism proposed on the basis of kinetic data. In addition, reaction intermediates may be isolated inquasi-in situ conditions as in the case of olefin oligomerization catalyzed by Ni/SiO₂ systems.

     

Effet des androgènes sur l’activité sportive

Androgenic hormones seem to be of beneficial effects on sports performance:

- they increase motivation, will, aggressiveness, resistance to the stress and to the fatigue, leading to an increase of the training quantity,

- they increase bone mineralization and probably mechanical resistance,

- they stimulate the bone marrow and so, with the erythropoietin, the erythropoiesis,

- they increase the tendancy to hyperglycemia, but with a decrease of the tolerance to the glucose,

- they stimulate the fatty acids mobilization from the adipose tissue, for their utilization in the muscle during the exercise,

- they participate, for the trained sportmen, to a better gestion of the muscle glycogen storage: their utilization during exercise is decreased,

- they increase the lean body mass, with an increase of the protein synthesis and a decrease of the protein catabolism, leading also to an increase of the muscle force under training. There is no beneficial effect upon the tendons,

- they have an immunomodulation action.

     

Neurotransmitters of cephalopods

1. ACh, dopamine, noradrenaline, 5-HT,l-glutamate, and GABA are widely distributed in cephalopods and probably all function as neurotransmitters; octopamine also occurs and at one site is known to act as a neuromodulator.
2. Several peptides are also present, as well as nitric oxide synthase.
3. In the brain and sense organs cholinergic, aminergic, serotonergic and glutamatergic systems seem to be the most important.
4. ACh is also active in the gut, vascular system and some body muscles: it is generally inhibitory. The ACh receptors are similar to the vertebrate nicotinic type.
5. The catecholamines are important in the gut and vascular system: they are generally excitatory. The NA receptors are like the α-adrenergic subtype of vertebrates, but the nature of the DA and OA receptors is less certain.
6. 5-HT is important in the gut but is endogenous in some chromatophore nerves and acts on receptors that seem like the vertebrate 5-HT₁ type.
7. l-glutamate is an excitatory transmitter at the chromatophore (and probably at other) nerve-muscle junctions and is an extremely strong candidate for being the excitatory transmitter at the squid giant synapse. There are NMDA receptors on Schwann-cells but the receptors on neurons and muscles are like the vertebrate kainate type.
8. Little is known about the mode of action of cephalopod peptides; nor has it ever been shown that they co-exist with conventional transmitters in these animals.
9. The structure of one (FMRFamide) receptor has been elucidated, but apart from this nothing is known of the molecular biology of receptors in cephalopods.

     

Integration of function in the nervous system — A new theory

A new theory of synaptic function in the nervous system (Dempsher, 1978) is applied to the simplest system for integration of function in the nervous system. This system includes a sensory and motor neuron and three ‘synaptic’ regions associated with those two neurons; a receptor region, an interneuronal spinal synaptic region linking the two neurons, and an effector region. Information is first received and processed at the receptor region. The processing consists of five components:

1. A highly selective mechanism which allows only that information to enter the receptor system which is appropriate.
2. The ‘appropriateness’ of the information is determined by the alphabet (miniature potentials) already in that area.
3. The information entering the system is assembled in a pattern meaningful for the next processing operation.
4. The assembled information is then ‘disassembled’ into its subunits and mapped into the alphabet (miniature potentials).
5. These miniature potentials are assembled into another pattern meaningful to fit the role of the receptor region.
6. This new pattern is repacked for transit to the central synaptic region.

At the central synaptic region, essentially the same process takes place except here an additional operation takes place which determines its role in the processing system. The incoming information is disassembled into its subunits, mapped into the miniature potentials already there; these are collected together in a meaningful pattern, ‘operated’ on, then repacked for transit to the effector site, where again the same kind of processing sequence takes place. In all three regions, despite the difference in their roles, there are similar processing features:

1. In each region, three forms of the nerve impulse are involved: miniature graded potentials, graded potentials, action potentials.
2. In each region, each component of the process is carried out by a precise mathematical operation: four each in the receptor and effector regions; five in the central synaptic region.

It is suggested that integration of function in the nervous system consists of converting information into energy which is in turn converted into a number. Processing of information at each region then involves mathematical operations applied to these numbers. Function appears to be stereotyped in all three regions. The receptor region receives highly selective and restrictive information so that the universe we ‘perceive’ would appear to be a subset of a much larger universe.     

The use of toxicokinetics for the safety assessment of drugs acting in the brain

Pharmacological and toxicological studies undertaken on drugs that affect the brain are frequently performed in disparate species under various experimental conditions, at doses often greatly in excess of those expected to be administered to humans, and the findings are extrapolated implicitly or explicitly with scant regard to differences in the biodisposition of the drugs. Such considerations are necessary since:

1. Species;
2. Strain;
3. Gender;
4. Route;
5. Dose;
6. Frequency and time of administration;
7. Temperature;
8. Coadministration of drugs; and
9. Surgical manipulation

are but some of the factors that have been shown to influence the kinetics and metabolism of drugs. This article, using MDMA and other phenylethylamines as examples, provides evidence for the need to measure the exoosure of the drugs and their active metabolites in blood and brain (toxicokinetics) in order that conclusions based only on dynamic, biochemical, or histological evidence are more pertinent. Further, the combined use of toxicokinetic-dynamic modeling can lead to a better appreciation of the mechanisms involved and a more useful approach to the calculation of safety margins.     

Experimental problems using electronic particle counters

The following scheme lists the problems which have been and will continue to be encountered in grazing experiments on natural particle assemblages. In some cases there are solutions, but many of the problems listed below remain intractable. To solve them will require innovative approaches, most probably combining the use of particle counters with other techniques to approach the problem to be solved from several angles at once. Variance between samples due to

- statistical causes (especially caused by large particles) and

- differences between experimental bottles and between experimentals and controls at start of experiment. Shifts in particle distribution during experiment due to

- increase in small particles

- growth of bacteria and other organisms due to excretion of grazers and

- breakage during handling by grazers into fragments. Processes, independent of grazing, leading to changes in particle size distribution due to

- primary production

- grazing by additional components and

- bacterial growth on detrital particles and the formation of detrital flocs.

     

LCA in decision-making processes

Synthetic sulfuric acid is used in a wide range of applications in fine chemical industry. Despite an already performed optimization of input amounts, used sulfuric acid is still a quantitatively important waste by-product. As a result, different utilization technologies for used sulfuric acid exist:

1. production of gypsum
2. thermal reductive cracking
3. thermal cracking and oxidation

This makes an LCA study of this waste by-product quite interesting. In this paper:

? the starting point for a comparative LCA of the above mentioned utilization technologies at a concrete situation is explained, in a work of Ciba-Geigy Corp.

? a short summary of the comparative LCA is presented

? lessons learned from performing the LCA and using it in a decision process are described.

     

The use of a continuous assay system to show the stimulation of phosphoenolpyruvate production in intact mitochondria by valinomycin and by Mn2+

1. A method for the direct recording of the PEP efflux from isolated mitochondria is described.
2. This method has been used to show the stimulation of PEP efflux by externally added Mn⁺⁺ ions.
3. Valinomycin, uncoupler and oleate were also shown to stimulate PEP efflux.
4. Valinomycin caused an increase in the internal concentration of both PEP and citrate.
5. The results indicate that the major pathway of PEP synthesis in isolated mitochondria is via PEP carboxykinase and the results do not call for an unknown pathway of metabolism.
6. Two interactions between PEP and citrate are described; competition for the mitochondrial interior and the stimulation of PEP production by citrate.

     

The occurrence of the Entner-Doudoroff pathway in bacteria

The occurrence of the two key enzymes of the Entner-Doudoroff pathway, gluconate-6-phosphate dehydrase and 2-keto-3-deoxygluconate-6-phosphate aldolase, was determined in approximately 150 strains belonging to 37 different bacterial genera. The following results were obtained:

1. 24 out of 37 genera have at least one representative with the Entner-Doudoroff mechanism. It is thus more widespread than previously thought.
2. The Entner-Doudoroff mechanism occurs mainly in gram-negative bacteria with a DNA base composition in the range 52–70% GC. Eighty-five per cent of these organisms contain the system, while only 20% (6 strains) of the gram-negative organisms with less than 52% GC possess both enzymes.
3. This pathway is absent in all gram-positive organisms investigated except in 5 out of 12Nocardia strains.
4. Erwinia and some strains of theAchromobacter-Alcaligenes group are exceptional, since they possess only 2-keto-3-deoxygluconate-6-phosphate aldolase.

     

Seasonal variation in the biochemical composition of Mytilus viridis at Ratnagiri on the West Coast of India

1. The seasonal variation in the water, protein, fat and glycogen contents of the mussel, Mytilus viridis has been studied for the year March, 1974 to March, 1975.
2. The water level increased during the monsoon season and decreased in summer.
3. The level of protein, fat and glycogen showed correlation with the reproductive cycle of the mussel.
4. The protein level was high when the mussels were mature and dropped during the breeding period.
5. During sex change from male to female in May the protein level remained high whereas during sex change from female to male in October and November it was low.
6. The fat level was high in mature mussels and declined on spawning.
7. The glycogen level was at its peak in immature mussels and low in mature.

     

Protease and Amylase in the digestive tract ofBarbus paludinosus

1. Protease and amylase activity in the digestive system ofBarbus paludinosus Peters (Pisces, Cyprinidae) has been investigated.
2. Chromatographic analysis showed seven amino acids to be present in both the anterior and posterior intestine. Only leucine, phenylalanine, valine, glycine and aspartic acid were positively identified.
3. In the anterior intestine chromatography revealed two sugars, but only one in the posterior intestine which was identified as glucose.
4. The pH of the intestinal fluid was found to be 5.8 and 7.8 for the fore and hind gut respectively, This correlates well with the enzyme pH optima found in in vitro experiments.
5. Protease and amylase activity was found throughout the digestive tract. Maximum proteolytic activity being present in the anterior intestine. Amylase activity is similar in both regions of the gut.
6. Correlation between the digestive enzymes and the fishes diet is briefly discussed.

     

An ecological study of the Ponggol Estuary in Singapore

1. An ecological study of the Ponggol Estuary was conducted from July 1965 to June 1966 and the seasonal data on physical, chemical and biological characteristics were presented.
2. The Ponggol River represents a short, narrow and shallow estuary in Singapore. The river mouth is open throughout the year and water from eastern Johore Straits drains in twice a day at high tide. The upper reach, however, is left exposed at low tide.
3. The Ponggol River was classified as a vertically and laterally homogeneous estuary and was found to exhibit a mesohaline to polyhaline environment.
4. Significant hydrological gradients from the river mouth 10 the upper reach were noted in the river system. Salinity, dissolved oxygen and pH increased towards the mouth of the river and other parameters such as nutrients, dissolved organic matter and turbidity increased towards the source.
5. Although the river received organic pollutants at the upper reach the estuary was able to discharge them fairly rapidly through regular flushing by the tides. The transient rise of organic matter did not appear to impart any serious affect on the biota in the estuary.
6. Over 98% of the phytoplankton consisted of diatoms, most of which were brought into the estuary from eastern Johore Straits. Freshwater forms were relatively few.
7. Phytoplankton biomass was considerably higher than the adjoining waters. and was reduced at the upper reach due to high turbidity of the water.
8. 80% of the zooplankton was composed of dinoflagellates,Difflugia, copepods and bivalve larvae dominating at all sections of the estuary.
9. Percentage composition of the zooplankton showed that dinoflagellates and copepod nauplii predominated at high tide whileDifflugia and bivalve larvae were abundant at low tide.
10. Zooplankton standing crop, in general, was higher towards the source at high tide but the reverse was found at low tide, i.e. standing crop increased towards the river mouth. This was attributed to the process of concentration.
11. Species composition of zooplankton was found to be more or less similar to that of the eastern Johore Straits.
12. The nekton consisted predominantly of small and juvenile fish. Close correlation of fish and copepods was found to be statistically valid and it was concluded that the fish entered the estuary to feed rather than to spawn.
13. The squids formed an important catch of the beach seine unit and were caught throughout the year.
14. The fish population could be grouped into four categories: estuarine components, euryhaline components, marine components and migratory components.
15. Benthic invertebrates were abundant. Commercially important species consisted of prawns,Metapenaeus andPenaeus, and crabs,Neptunus pelagicus andScylla serrata.
16. The river bed was inhabited predominantly by molluscs and the distribution resembled that of the sheltered shore of muddy-sand type.

     

The chemical identification of root promoters extracted from avocado tissues

From the Avocado Rooting Promoter (ARP) 4 compounds were isolated and identified as:

1. 1 acetoxy - 2,4 dihydroxy-n-heptadeca-16-en;
2. 1 acetoxy - 2,4 dihydroxy-n-heptadeca-16-yn;
3. 1,2,4 trihydroxy-n-heptadeca-16-en;
4. 1,2,4 trihydroxy-n-heptadeca-16-yn.

The rooting activity of the pure compounds was verified using the mung bean rooting bioassay. Compound 2II is the most active.     

An analysis of amino acid composition of a few oxidoreductases by different methods

1. All methods used to analyze amino acid composition of different enzymes agree well with each other.
2. They lead to a relationship between amino acid composition and function of proteins.
3. Cytochrome oxidase is in a class by itself; copper-containing oxidases are closely related as expected.

     

Effects of Environmental Perturbations on Short-Term Phytoplankton Production off Lawson's Bay,A Tropical Coastal Embayment

1. The phytoplankton cycle off Lawson's Bay, Waltair follows a bimodal pattern with a major peak during March–May; a minor peak during October–November months and with a low production during the summer months i.e., June–August.
2. During the summer months of 1957, 1958, 1960 and 1962 dumping of dredged spoil from the entrance channel of the harbour into the sea resulted in a natural enrichment of waters.
3. Following this enrichment, there was a qualitative and quantitative increase in the phytoplankters thus leading to the development of a bloom.
4. Only Thalassiosira subtilis and Chaetoceros curvisetus commonly bloomed during the four years.
5. The increase in gross production which varied from 3–13 fold and the high photosynthesis-respiration ratios 5.1 to 10.5 indicated that the bloom populations were in a healthy state.
6. The decrease of the populations to the initial levels suggests that some unknown factor, other than those investigated must have been operating.
7. Consequences of eutrophication of different origins on stimulation of phytoplankton production are briefly discussed.

     

Erecteur a dépression (Vacuum erection device): Mise au point

The vacuum erection device (VED) is a nonsurgical alternative for the treatment of erectile dysfunction. This method is based on 2 phenomena:

1. an erection-like state occurs when the penis is placed in a vacuum
2. this state can be maintained by a constricting band placed around the base of the penis

The erection-like state thus obtained differs from a normal erection in the following ways:

1. blood flow into the penis decreases
2. penile skin temperature falls
3. congestion of extra-corporeal penile tissues occurs
4. the penis pivots at its base
5. the ejaculate is trapped in the proximal urethra

About 30 to 60% of men who trie the device at home purchase it for continued use. The others are unable to achieve sufficient rigidity, experience side-effects or dislike the use of the device despite good result. About 60 to 80% of the men who purchased the device continue to use it regulary at short or middle term. The VED seems to have lesser drop-out rate than the self injection therapy. The most frequently encountered side-effects of the device are pain, petechiaes, bruising and ecchymosis.     

Descending input from the vestibulolateral cerebellum suppresses electrosensory responses in the dorsal octavolateralis nucleus of the elasmobranch,Raja erinacea

1. The dorsal octavolateralis nucleus is the primary electrosensory nucleus in elasmobranchs and receives a major descending input from the dorsal granular ridge (DGR), a part of the vestibulolateral cerebellum. Removal of DGR altered the response properties of ascending efferent neurons (AENs), the projection neurons of the dorsal octavolateralis nucleus.
2. Elimination of DGR by lesion or lidocaine microinjection increased the excitability in AENs. Spontaneous activity increased by 680% and receptive fields became 1300% larger. The sensitivity of AENs to electric field stimuli increased by 560% and the time constant of adaptation increased by 300%, while threshold sensitivity remained unchanged.
3. Some electrosensory units responded to proprioceptive stimuli. In intact animals, the spontaneous activity of AENs was much less modulated by changes in fin position than primary electroreceptor afferents. Lesions to DGR appeared to increase the responsiveness of AENs to changes in fin position.
4. These results indicate that the action of DGR on the dorsal octavolateralis nucleus is primarily inhibitory and may function in a gain control mechanism. The possibility also exists for a mechanical-reafferent reduction mechanism in the electrosensory system of the elasmobranch that may be mediated by DGR.