The manganese stabilizing protein (MSP) and the control of O2 evolution in the unicellular, diazotrophic cyanobacterium, Cyanothece sp. ATCC 51142.

The unicellular diazotrophic cyanobacterium, Cyanothece sp. ATCC 51142 temporally separates N2 fixation from photosynthesis. To better understand the processes by which photosynthesis is regulated, we have analyzed Photosystem (PS) II O2 evolution and the PSII lumenal proteins, especially the Mn stabilizing protein (MSP). We describe a procedure using glycine betaine to isolate photosynthetic membranes from Cyanothece sp. that have high rates of PSI and PSII activity. Analysis with these membranes demonstrated similar patterns of O2 evolution in vivo and in vitro, with a trough at the time of maximal N2 fixation and with a peak in the late light period. The pattern of PSI activity was also similar in vivo and in vitro. We cloned the genes for MSP (psbO) and the 12 kDa protein (psbU) and analyzed their transcriptional properties throughout the diurnal cycle. We suggest that the changes in PSII activity in Cyanothece sp. were due to conformational changes in a highly flexible MSP, a suggestion which can now be studied in a chimera. The Cyanothece sp. psbO gene has been transformed into Synechocystis sp. PCC 6803; MSP and O2 evolution in the resulting transformant had properties that were similar to those in Cyanothece sp., providing additional confirmation for the properties of Cyanothece sp. MSP.

Deep dysphasic performance in non-fluent progressive aphasia: a case study.

We present a patient (PW) with non-fluent progressive aphasia, characterized by severe word finding difficulties and frequent phonemic paraphasias in spontaneous speech. It has been suggested that such patients have insufficient access to phonological information for output and cannot construct the appropriate sequence of selected phonemes for articulation. Consistent with such a proposal, we found that PW was impaired on a variety of verbal tasks that demand access to phonological representations (reading, repetition, confrontational naming and rhyme judgement); she also demonstrated poor performance on syntactic and grammatical processing tasks. However, examination of PW's repetition performance also revealed that she made semantic paraphasias and that her performance was influenced by imageability and lexical status. Her auditory-verbal short-term memory was also severely compromised. These features are consistent with 'deep dysphasia', a disorder reported in patients suffering from stroke or cerebrovascular accident, and rarely reported in the context of non-fluent progressive aphasia. PW's pattern of performance is evaluated in terms of current models of both non-fluent progressive aphasia and deep dysphasia.

The management of endometriosis: a survey of patients' aspirations.

The aim of this study was to determine the aspirations of women with endometriosis in terms of the management of their disease. We interviewed 32 women with confirmed endometriosis and asked them to discuss the potential benefits of the establishment of a specialist endometriosis clinic. Eighty-eight per cent of the participants agreed that a separate specialist clinic would be beneficial. The reasons they cited can be grouped under four main themes: information provision, quality and type of care, peer support and endometriosis awareness. On the basis of these responses we propose that a strategy utilised in the management of other chronic diseases, drop-in group medical appointments, may provide a way forward. In addition, on the basis of the range of symptoms reported by our participants, we would argue that a multidisciplinary approach is necessary if endometriosis management is to be effective.

Competitor priming in spoken word recognition.

Most models predict that priming a word should retard recognition of another sharing its initial sounds. Available short lag priming data do not clearly support the prediction. The authors report 7 continuous lexical-decision experiments with 288 participants. With lags of 1-5 min between prime and probe, response time increased for a monosyllabic word preceded by a word sharing its onset and vowel (but not one sharing its rime) and for a polysyllabic word preceded by another sharing its first syllable. The effect was limited to words primed by words, suggesting that identifying the prime strengthens its lexical attractor, making identification of a lexical neighbor more difficult. With lags of only a few trials, facilitatory effects of phonological similarity or familiarity bias effects were also seen; this may explain why clear evidence for inhibitory priming has been lacking hitherto.

Picture preferences of thoracic surgeons.

A mail survey instrument assessed whether thoracic surgeons prefer schematic, semi-schematic or realistic surgical illustrations for educational purposes in print media. Respondents, active members of the American Association of Thoracic Surgeons (N = 292), ranked preferences for the illustration treatments and supplied demographic information. Data analysis revealed significant differences between preferences for illustration treatments. The schematic treatment was the least preferable treatment. Realistic and semi-schematic illustrations were preferred about equally.

Caffeine tolerance: behavioral, electrophysiological and neurochemical evidence.

The development of tolerance to the stimulatory action of caffeine upon mesencephalic reticular neurons and upon spontaneous locomotor activity was evaluated in rats after two weeks of chronic exposure to low doses of caffeine (5-10 mg/kg/day via their drinking water). These doses are achievable through dietary intake of caffeine-containing beverages in man. Concomitant measurement of [3H]-CHA binding in the mesencephalic reticular formation was also carried out in order to explore the neurochemical basis of the development of tolerance. Caffeine, 2.5 mg/kg i.v., markedly increased the firing rate of reticular neurons in caffeine naive rats but failed to modify the neuronal activity in a group exposed chronically to low doses of caffeine. In addition, in spontaneous locomotor activity studies, our data show a distinct shift to the right of the caffeine dose-response curve in caffeine pretreated rats. These results clearly indicate that tolerance develops to the stimulatory action of caffeine upon the reticular formation at the single neuronal activity level as well as upon spontaneous locomotor activity. Furthermore, in chronically caffeine exposed rats, an increase in the number of binding sites for [3H]-CHA was observed in reticular formation membranes without any change in receptor affinity. We propose, therefore, that up-regulation of adenosine receptors may underlie the development of tolerance to the CNS effects of caffeine.

Assessment of blood platelets as a model for CNS response: comparative effects of caffeine on 5-HT uptake and release mechanisms in rat platelets and rat brain serotonin neurons.

We have previously reported that caffeine significantly enhanced 5-HT uptake and reduced 5-HT release from crude synaptosomal fractions obtained from rat cerebral cortex and from midbrain raphe region. Blood platelets, as reported by many laboratories and also demonstrated in our own labs, have a very active mechanism for 5-HT uptake and storage. In this regard platelets bear a high degree of similarity to brain serotonin neurons. The present experiments were, therefore, carried out to investigate the effects of caffeine on 5-HT uptake and release from rat platelets in an attempt to assess the possibility of using platelets as a model for studying the CNS effects of caffeine. Platelet rich plasma was prepared from the trunk blood of decapitated rats. Effects of caffeine were investigated at 10(-7), 10(-6), 10(-5) and 10(-4)M, on both the high affinity 3H-5-HT uptake and the spontaneous 5-HT release from 3H-5-HT preloaded platelets. The results show that caffeine did not change 5-HT uptake into platelets. In brain synaptosomes the same concentration of caffeine, however, increased 5-HT uptake dose-dependently. The results also revealed that caffeine increased 5-HT release from rat platelets in a concentration-dependent manner. The concentrations 10(-6), 10(-5), and 10(-4)M increased release significantly compared to control. This finding is also in contrast to that observed in synaptosomes of brain serotonin neurons where caffeine decreased 5-HT release. It is concluded, therefore, that the rat blood platelet is not a suitable model for studying these CNS actions of caffeine. Furthermore, our observations imply that rat platelet serotonin uptake and release mechanisms are not identical to those mechanisms in brain serotonin neurons.

Unit activity in medial thalamus: comparative effects of caffeine an amphetamine.

The effects of caffeine and d-amphetamine sulfate were evaluated upon single unit activity of medial thalamus in chloral hydrate anesthetized rats. Single unit activity recorded extracellularly with platinum-iridium microelectrodes. It was found that caffeine, 0.1 to 0.5 mg/kg i.v., markedly suppressed and that amphetamine, 0.1 to 1 mg/kg i.v., markedly augmented the spontaneous firing rates of medial thalamic neurons. It was also demonstrated that amphetamine was capable of activating the medial thalamic neuronal activity while it was suppressed by caffeine. On the other hand, while the firing rate was increased by a previous amphetamine injection, administration of caffeine suppressed the amphetamine-induced augmentation of neuronal activity. The data imply that these two central nervous system (CNS) stimulants, caffeine and amphetamine, have different mechanisms of action at least at the medial thalamic site. Moreover, since medial thalamus participates in the recruitment phenomenon and exerts a stabilizing action on the cerebral cortex, our findings that caffeine suppressed this brain area suggest that the medial thalamus may be an important site of action for the arousal induced by caffeine. In addition, the demonstration of inhibitory effects of caffeine on the medial thalamus in this study and excitatory effects on brain stem reticular formation from our previous studies indicate that caffeine has differential actions on different brain areas. This observation broadens the generally held belief that caffeine excites at all levels of the CNS to specifically include inhibition of inhibitory influences in at least one functional system of the brain.

Respiratory stimulant effects of ethamivan and picrotoxin.

The respiratory stimulant effects of ethamivan and picrotoxin were studied in unanesthetized decerebrate cats. It was found that neither compound exhibited selective stimulant action on the respiratory neurons. Ethamivan evoked increases in respiratory rate but not in tidal volume, whereas picrotoxin profoundly altered both of these variables. The increases in respiratory rate evoked by ethamivan required intact vagus nerves since midcervical vagotomy abolished this effect. It is conceivable that ethamivan stimulated pulmonary chemoreflexes which then led to increased respiratory rate. Picrotoxin had no discernible effect on peripheral chemoreflexes. It altered, however, the central respiratory rhythmicity, or rate, depth and rhythm of respiration. There was a marked effect on central respiratory control which led to cycling between slow and deep, and rapid and shallow breathing. These were interspersed with periods of rapid and deep respiration.