The effects of acute Methylene Blue administration on cerebral blood flow and metabolism in humans and rats

Methylene Blue (MB) is a brain-penetrating drug with putative neuroprotective, antioxidant and metabolic enhancing effects. In vitro studies suggest that MB enhances mitochondrial complexes activity. However, no study has directly assessed the metabolic effects of MB in the human brain. We used in vivo neuroimaging to measure the effect of MB on cerebral blood flow (CBF) and brain metabolism in humans and in rats. Two doses of MB (0.5 and 1 mg/kg in humans; 2 and 4 mg/kg in rats; iv) induced reductions in global cerebral blood flow (CBF) in humans (F(1.74, 12.17)5.82, p = 0.02) and rats (F(1,5)26.04, p = 0.0038). Human cerebral metabolic rate of oxygen (CMRO2) was also significantly reduced (F(1.26, 8.84)8.01, p = 0.016), as was the rat cerebral metabolic rate of glucose (CMRglu) (t = 2.6(16) p = 0.018). This was contrary to our hypothesis that MB will increase CBF and energy metrics. Nevertheless, our results were reproducible across species and dose dependent. One possible explanation is that the concentrations used, although clinically relevant, reflect MB's hormetic effects, i.e., higher concentrations produce inhibitory rather than augmentation effects on metabolism. Additionally, here we used healthy volunteers and healthy rats with normal cerebral metabolism where MB's ability to enhance cerebral metabolism might be limited.

Mapping acute neuroinflammation in vivo with diffusion-MRI in rats given a systemic lipopolysaccharide challenge

It is becoming increasingly apparent that neuroinflammation plays a critical role in an array of neurological and psychiatric disorders. Recent studies have demonstrated the potential of diffusion MRI (dMRI) to characterize changes in microglial density and morphology associated with neuroinflammation, but these were conducted mostly ex vivo and/or in extreme, non-physiological animal models. Here, we build upon these studies by investigating the utility of well-established dMRI methods to detect neuroinflammation in vivo in a more clinically relevant animal model of sickness behavior. We show that diffusion tensor imaging (DTI) and neurite orientation dispersion and density imaging (NODDI) indicate widespread increases in diffusivity in the brains of rats given a systemic lipopolysaccharide challenge (n = 20) vs. vehicle-treated controls (n = 12). These diffusivity changes correlated with histologically measured changes in microglial morphology, confirming the sensitivity of dMRI to neuroinflammatory processes. This study marks a further step towards establishing a noninvasive indicator of neuroinflammation, which would greatly facilitate early diagnosis and treatment monitoring in various neurological and psychiatric diseases.

Erbb4 Deletion From Inhibitory Interneurons Causes Psychosis-Relevant Neuroimaging Phenotypes

BACKGROUND AND HYPOTHESIS

Converging lines of evidence suggest that dysfunction of cortical GABAergic inhibitory interneurons is a core feature of psychosis. This dysfunction is thought to underlie neuroimaging abnormalities commonly found in patients with psychosis, particularly in the hippocampus. These include increases in resting cerebral blood flow (CBF) and glutamatergic metabolite levels, and decreases in ligand binding to GABAA α5 receptors and to the synaptic density marker synaptic vesicle glycoprotein 2A (SV2A). However, direct links between inhibitory interneuron dysfunction and these neuroimaging readouts are yet to be established. Conditional deletion of a schizophrenia susceptibility gene, the tyrosine kinase receptor Erbb4, from cortical and hippocampal inhibitory interneurons leads to synaptic defects, and behavioral and cognitive phenotypes relevant to psychosis in mice.

STUDY DESIGN

Here, we investigated how this inhibitory interneuron disruption affects hippocampal in vivo neuroimaging readouts. Adult Erbb4 conditional mutant mice (Lhx6-Cre;Erbb4F/F, n = 12) and their wild-type littermates (Erbb4F/F, n = 12) were scanned in a 9.4T magnetic resonance scanner to quantify CBF and glutamatergic metabolite levels (glutamine, glutamate, GABA). Subsequently, we assessed GABAA receptors and SV2A density using quantitative autoradiography.

RESULTS

Erbb4 mutant mice showed significantly elevated ventral hippccampus CBF and glutamine levels, and decreased SV2A density across hippocampus sub-regions compared to wild-type littermates. No significant GABAA receptor density differences were identified.

CONCLUSIONS

These findings demonstrate that specific disruption of cortical inhibitory interneurons in mice recapitulate some of the key neuroimaging findings in patients with psychosis, and link inhibitory interneuron deficits to non-invasive measures of brain function and neurochemistry that can be used across species.

Relevance of sleep and associated structural changes in GBA1 mouse to human rapid eye movement behavior disorder

Rapid eye movement (REM) sleep behaviour disorder (RBD) is a REM parasomnia that often predicts the later occurrence of alpha-synucleinopathies. Variants in the gene encoding for the lysosomal enzyme glucocerebrosidase, GBA, strongly increase the risk of RBD. In a GBA1-mouse model recently shown to mimic prodromal stages of α-synucleinopathy, we now demonstrate striking REM and NREM electroencephalographic sleep abnormalities accompanied by distinct structural changes in the more widespread sleep neurocircuitry.

How did we get here: what are droplets and aerosols and how far do they go? A historical perspective on the transmission of respiratory infectious diseases

The COVID-19 pandemic has exposed major gaps in our understanding of the transmission of viruses through the air. These gaps slowed recognition of airborne transmission of the disease, contributed to muddled public health policies and impeded clear messaging on how best to slow transmission of COVID-19. In particular, current recommendations have been based on four tenets: (i) respiratory disease transmission routes can be viewed mostly in a binary manner of ‘droplets’ versus ‘aerosols’; (ii) this dichotomy depends on droplet size alone; (iii) the cut-off size between these routes of transmission is 5 µm; and (iv) there is a dichotomy in the distance at which transmission by each route is relevant. Yet, a relationship between these assertions is not supported by current scientific knowledge. Here, we revisit the historical foundation of these notions, and how they became entangled from the 1800s to today, with a complex interplay among various fields of science and medicine. This journey into the past highlights potential solutions for better collaboration and integration of scientific results into practice for building a more resilient society with more sound, far-sighted and effective public health policies.

Implementation and evaluation of nationwide scale-up of the Surgical Safety Checklist

Background

The WHO Surgical Safety Checklist improves surgical outcomes, but evidence and theoretical frameworks for successful implementation in low‐income countries remain lacking. Based on previous research in Madagascar, a nationwide checklist implementation in Benin was designed and evaluated longitudinally.

Methods

This study had a longitudinal embedded mixed‐methods design. The well validated Consolidated Framework for Implementation Research (CFIR) was used to structure the approach and evaluate the implementation. Thirty‐six hospitals received 3‐day multidisciplinary training and 4‐month follow‐up. Seventeen hospitals were sampled purposively for evaluation at 12–18 months. The primary outcome was sustainability of checklist use at 12–18 months measured by questionnaire. Secondary outcomes were CFIR‐derived implementation outcomes, measured using the WHO Behaviourally Anchored Rating Scale (WHOBARS), safety questionnaires and focus groups.

Results

At 12–18 months, 86·0 per cent of participants (86 of 100) reported checklist use compared with 31·1 per cent (169 of 543) before training and 88·8 per cent (158 of 178) at 4 months. There was high‐fidelity use (median WHOBARS score 5·0 of 7; use of basic safety processes ranged from 85·0 to 99·0 per cent), and high penetration shown by a significant improvement in hospital safety culture (adapted Human Factors Attitude Questionnaire scores of 76·7, 81·1 and 82·2 per cent before, and at 4 and 12–18 months after training respectively; P < 0·001). Acceptability, adoption, appropriateness and feasibility scored 9·6–9·8 of 10. This approach incorporated 31 of 36 CFIR implementation constructs successfully.

Conclusion

This study shows successfully sustained nationwide checklist implementation using a validated implementation framework.

Implementation works

Emergent Medical Illnesses Related to Cannabis Use

As more states rush to legalize the use of cannabis products, both medically and recreationally, there are more medical harms being seen in emergency departments (ED). The tetrahydrocannabinol (THC) concentration today is much stronger than the concentration from the 90s. In the 1990s most typical "joints" contained 1-3 mg of THC. Today, plants are being raised and modified to produce a higher concentration of THC. In turn, the amount of cannabidiol (CBD) is decreasing. Previously, people would smoke 1-3 mg of THC. The typical joint in Colorado contains 18 mg of THC or more. Currently, in the ED, we see patients who self-report smoking 2,000 mg or more of THC in a day. In 2015, 2.6 million individuals started cannabis use, 45% were 12-17 years of age.3 This brief report includes some of the more common illnesses that have been seen over the last four years of legalization in Colorado, and is by no means inclusive of all the potential problems that can occur. Among the many untoward effects being seen, illnesses that will be discussed are: cannabinoid associated hyperemesis, acute psychosis, cannabinoid catatonia syndrome, acute myo-pericarditis and ingestions.

A comparison of sonography and radiography student scores in a cadaver anatomy class before and after the implementation of synchronous distance education

Distance education is a solution to expand medical imaging education to students who might not otherwise be able to obtain the education. It can be a mechanism to reduce the health care worker shortage in underserved areas. In some cases, distance education may be a disruptive technology, and might lower student performance. This study compares student scores in a cadaver anatomy course in the four cohorts preceding the implementation of distance education to the first three cohorts that took the course using a multiple campus design. The means and medians of the lecture exam average, the laboratory component score, and the final course score of the nondistance education cohorts were compared with those of the distance education cohorts using nonparametric statistical analysis. Scores in an anatomy course were compared by campus placement among the distance education cohorts, and the independent effect of distance education on the laboratory component, lecture examination average, and final course scores, while controlling for cumulative grade point average and site (originating/distant), was assessed. Students receiving the course in a nondistance education environment scored higher in the anatomy course than the students who took the course in a distance education environment. Students on the distant campus scored lower than students on the originating site. Distance education technology creates new opportunities for learning, but can be a disruptive technology. Programs seeking to implement distance education into their curriculum should do so with knowledge of the advantages and disadvantages.

The Effect of Whole-body γ-irradiation on Localized β-irradiation-induced Skin Reactions in Mice

The combined effects of whole-body radiation and localized radiation trauma have received scant experimental attention. However, in the recent accidents at Chernobyl and Goiania skin damage from beta-contamination was combined with total-body radiation and in many cases the skin lesions which covered large surfaces of the body were severe and recovery was prolonged. This paper models the immunosuppressive effects of whole-body gamma-radiation in the sublethal to lethal range (1-11 Gy) on the skin reactions produced by 50 Gy of superficial beta-radiation. For gamma ray doses < 4 Gy no synergistic effects were detectable. For gamma-ray doses of 4, 6 and 8 Gy there was a 4-5-day prolongation in time-course of the skin reaction but no significant exacerbation of its severity. The overall time for the resolution of the skin reaction (45 days) was also unaffected by the relatively high whole-body doses. These rather surprising findings of minimal synergy between whole-body exposure and a localized severe beta burn to the skin are perhaps explained by the mismatch between the maximal immunosuppression at 2-10 days postirradiation and the timing of the skin damage at 10-25 days.

Drug errors in obstetric anaesthesia: a national survey

We conducted a postal survey of lead obstetric anaesthetists in all consultant-led maternity units in the UK about drug errors and the measures taken to reduce or prevent them. Of the 179 out of 240 (75%) who responded, 70 (39%) knew of at least one drug error in their unit during the last year, with 28 of them (40%) experiencing more than one. Of the most recent errors, giving the wrong drug (most commonly thiopental instead of antibiotics or vice versa [14 cases], or suxamethonium instead of [Formula: see text] [8 cases] or other drugs [4 cases]) was the most common error, occurring in 27 units (15%). Errors involving epidural/spinal analgesia/anaesthesia (including drugs intended for these routes but given via other routes) occurred in 20 cases. Only 36 respondents (20%) described protocols for checking anaesthetic drugs. Methods described for reducing drug errors were use of coloured labels (20%) or pre-filled labelled syringes (6%), limiting the range of drugs available (6%) and keeping drugs in separate trays once drawn up (6%).

Effect of the Confidential Enquiries into Maternal Deaths on the use of Syntocinon at Caesarean section in the UK

The recommended dose of Syntocinon used for uterine contraction at Caesarean section is5 units intravenously, given slowly. We conducted a survey of the use of Syntocinon at Caesarean section among 240 lead obstetric anaesthetists in the UK in 2001 and found that 155 (87%) of the 179 (75%) respondents gave 10 units, 77 of them (50%) by rapid bolus. The risks of Syntocinon, especially given by rapid injection, were highlighted in the report of the Confidential Enquiries into Maternal Deaths in the UK (1997-99), which was published at the end of 2001, and so the survey was repeated in 2002. Of the 256 forms sent, 198 completed replies were returned (77%); these indicated a dramatic change of practice: only 30 (15%) now gave 10 units and only 7 of these (23%) by a rapid injection. One hundred and sixty-seven respondents to the second survey (84%) stated they had changed their practice and 159 of these (95%) gave the Confidential Enquiries report as the main reason for change. These results highlight the importance of the Confidential Enquiries as a means of improving practice.

Near infra-red spectra of urea with glycine betaine or trimethylamine N-oxide are additive

Glycine betaine and trimethylamine-N-oxide counteract urea denaturation in solutions containing urea and the methylamine in the mole ratio of 2:1. Near infra-red difference spectra (water spectrum subtracted) of solutions containing both urea with either glycine betaine or trimethylamine-N-oxide can be predicted from the spectra of the single solutes, with r(2)>0.999 both using the spectrum from 1200 to 2100 nm (where most absorbance is attributable to hydrogen bonding) and using an extended range 1000 to 2500 nm, which includes solute specific bands. Thus urea and the kosmotropes appear to interact with water independently and the counteraction cannot be attributed to specific interactions between them. The spectrum of aqueous glycine betaine can be predicted from tetramethylammonium and formate ions (r(2)=0.998), suggesting that independent interactions of the quaternary amine, and of the carboxyl function, with water are dominant. The exceptional properties of glycine betaine do not arise from specific intramolecular interactions between the charged groups.

Inhibitors of bacterial growth in urine: what is the role of betaines?

It has long been recognised that some individuals produce urine that is inhibitory to uropathogens. This may be partly explained by inhibitors. Several inhibitors have been identified in urine including urea and organic acids. Bacteria adapt to high osmolarity by activating osmoregulated betaine porters and accumulating organic osmolytes intracellularly. The preferred substrate is glycine betaine, which is present in urine, and promotes rapid growth by balancing osmotic forces and stabilising macromolecular structures against the toxicity of urea and low pH. Other dietary betaines such as trigonelline may also be taken but enhance urea toxicity. The importance of such compounds in vivo is unknown.

Osmoprotective activity, urea protection, and accumulation of hydrophilic betaines in Escherichia coli and Staphylococcus aureus

The hydrophilic betaines, deanol betaine, triethanol betaine, diethanolthetin and methylethanolthetin, and also thioxanium betaine and citrulline betaine, were accumulated by Escherichia coli. All betaines tested had significant osmoprotective activity for E. coli and, with the exception of citrulline betaine and diethanolthetin, also demonstrated urea protection. Staphylococcus aureus accumulated only methylethanolthetin, deanol betaine and thioxanium betaine: the first two had an osmoprotective effect but conferred no urea protection. Diethanolthetin and thioxanium betaine significantly decreased urea tolerance for S. aureus.

Osmoprotective properties and accumulation of betaine analogues by Staphylococcus aureus

Betaines were evaluated as potential antistaphylococcal agents for urinary tract infections. Staphylococcus aureus accumulated all tested betaines except trigonelline. S. aureus transport systems were less sensitive to carbon chain length than those of Escherichia coli. Betaines were accumulated in the absence of osmotic stress, and 10-fold more in hyperosmotic medium. Most betaines increased the osmotolerance of S. aureus in defined minimal medium. Unlike E. coli, S. aureus did not significantly accumulate a second betaine in the presence of glycine betaine. Betaines are less likely to be useful in treating staphylococcal than E. coli urinary infections.

Carpal bone titanium implant arthroplasty. 10 years' experience

In 1984, in an effort to address the silicone wear particle problem, titanium implants were developed for the scaphoid, lunate, and trapeziometacarpal joint. The design of these implants closely resembled their silicone counterparts, though some modifications were made to accommodate the properties of unalloyed titanium and enhance their stability. Carpal bone implants act as articulating spacers to help maintain the relationship of adjacent carpal bones after local resection procedures. Their use allows carpal stabilization procedures and provides functional mobility with good strength and pain relief. Their surgical application began in 1985. The 10-year clinical experience seems very promising to date.

Natural and synthetic betaines counter the effects of high NaCl and urea concentrations

Escherichia coli was used as a model system to evaluate a range of betaines for their ability to protect against salt and urea stresses. Betaine structure determined the salt and urea protective effects. Dimethylthetin conferred salt protection similar to glycine betaine, whereas dimethylsulfoniopropionate (DMSP) was less effective than either glycine betaine or dimethylthetin, but similar to propionobetaine (its nitrogen analogue). Hydrophobic alpha-substituents altered salt tolerance. Valine betaine with an aliphatic side group conferred salt tolerance similar to glycine betaine. Betaines containing phenyl groups (phenylglycine, phenylalanine and N-phenylglycine betaines) did not confer salt protection, growth being similar to, or less than the control (no betaine). Hydrophobic groups decreased the ability to protect against urea stresses; valine betaine conferred poor urea tolerance. The addition of an hydroxyl group increased the ability of a betaine to protect against urea denaturation. Proline betaine, an effective salt protector, conferred poor urea tolerance. Increasing the charge separation in the betaine molecule decreased the ability to confer urea tolerance. Thiolanium, pyridinium and triethylglycine betaines, with larger cationic functions, conferred no urea tolerance to E. coli.

Long-term expression of transforming growth factor TGF beta 1 in mouse skin after localized beta-irradiation

The long-term expression of TGF beta 1 in mouse skin after localized irradiation with a beta-emitting source is reported. The skin of CBA/ca mice was exposed to 50 Gy superficial beta radiation from an 11 mm strontium-90 source. Such a dose produced an acute moist desquamation reaction in 100% of the animals, which was macroscopically resolved within 30 days. The acute response was followed by progressive remodelling of dermal tissues as characterized by histological means. The expression of TGF beta 1 was followed for 12 months after irradiation and showed three distinct waves of expression at the RNA level. Levels of expression initially rose to 230% above controls at 6 h before returning to control levels around 24-48 h. Expression then rose again to 169 and 234% above controls at 14 and 28 days post-irradiation respectively. Levels then declined to those of the controls by 2 months. A progressive increase in expression was then noted after 3 months, which peaked around 9 months and was resolved by 12 months. In a parallel study the skin of 144 CBA/ca mice was exposed to 50 Gy superficial beta radiation from 2 x 4 cm Thulium-170 source and compared with a similar group of sham-irradiated controls. The irradiated group showed a cumulative tumour incidence of 54.3% compared with 0% incidence in the sham-irradiated group. Of the 45 radiation-induced tumours a representative sample of 16 (nine malignant fibrous histiocytomas; three fibrosarcomas; two fibromas; one squamous cell carcinoma; one rhabdomyosarcoma) were selected for further study. Semiquantitative PCR on all these tumours showed elevated levels of TGF beta 1 expression ranging from 1.8 to 87-fold above the levels found in normal skin. This study is part of ongoing investigations into the long-term effects of single accidental exposures. The 50 Gy dose used is comparable with the surface doses obtained by some of the victims of the Chernobyl accident.

Accumulation of natural and synthetic betaines by a mammalian renal cell line

Intracellular accumulation of different betaines was compared in osmotically stressed Madin Darby canine kidney (MDCK) cells to model the betaine accumulation specificity of the mammalian inner medulla and to show how this accumulation differed from that of bacteria. All betaines accumulated less than glycine betaine. Arsenobetaine (the arsenic analogue of glycine betaine) accumulated to 12% of the glycine betaine levels and the sulphur analogue dimethylthetin accumulated to >80%. Most substituted glycine betaine analogues accumulated to 2-5% of intracellular glycine betaine concentrations, however, serine betaine accumulated to <0.5% of glycine betaine levels. Inhibition studies to distinguish the betaine ports were performed by the addition of proline. Butyrobetaine and carnitine accumulation was not proline sensitive, whereas that of other betaines was. As with glycine betaine, the accumulation of propionobetaine and dimethylthetin was proline sensitive and osmoregulated. Pyridinium betaine was accumulated by both proline-sensitive and -insensitive systems, with a small increase under osmotic stress. High concentrations (10 times that of glycine betaine) of the dietary betaines proline betaine and trigonelline inhibited total betaine accumulation. Because alpha-substituted betaines are accumulated by bacteria and not by MDCK cells, these betaines may be the basis for design of antimicrobial agents.

Expression of transforming growth factor-beta 1 in mouse skin during the acute phase of radiation damage

Transforming growth factor-beta (TGF beta 1) plays a central role in wound healing, so its perturbation by radiation may contribute to the acute and late effects seen in irradiated skin. TGF beta 1 mRNA expression was measured by PCR, in the skin of the CD1 and CBA mouse, exposed to Sr-90 beta from an 11-mm diameter source. TGF beta 1 mRNA expression increased sharply after doses between 1 and 10 Gy and plateaued at approximately 200% above controls after doses between 20 and 50 Gy. Immunohistochemistry showed that the TGF beta 1 protein was confined to the dermis and suprabasal cells with none in basal cells. A dose of 50 Gy produces an acute desquamative reaction in 100% of mice that is resolved in 30 days. After the same dose, TGF beta 1 mRNA expression fell below the controls at 3 h (-9.4% in the CD1 and -44% in the CBA mouse); rose sharply at 6-12 h (+124% CD1, +230% CBA), returned to control levels by 24-48 h, then rose progressively to approximately 200% above the controls between days 7 and 14. TGF beta 1 mRNA expression remained elevated at 100-200% above controls until the end of the experiment at 55 days. The significance of these changes in TGF beta 1 is discussed in the context of the early stress response reaction to radiation, the acute inflammatory and the later chronic fibrosis of the skin.

Competitive accumulation of betaines by Escherichia coli K-12 and derivative strains lacking betaine porters

Escherichia coli was grown in hyperosmotic media containing both glycine betaine and one other betaine. E. coli K-12 derivative WG439 (putP- proP- proU-) did not accumulate any of 15 betaines. Strains WG445 (putP- proP- proU+), WG443 (putP- proP+ proU-) and the control strains all accumulated less betaine, (CH3)3N(+)-(CH2)n-COO-, when n was greater than 1. Accumulation was not detectable when n = 5. Both L- and D-isomers of alpha-substituted betaines were accumulated by both strains WG443 and WG445, the D-isomers more slowly. Hydroxylated alpha-substituted betaines were accumulated relatively more through the osmoregulated transport protein ProU than through ProP. In actively growing cultures glycine betaine appeared to be the preferred substrate for accumulation, but the proportion of the second accumulated betaine increased as cultures approached stationary phase.

Fracture of the anterior colliculus

The authors retrospectively reviewed 33 cases of fracture involving the anterior colliculus of the medial malleolus to examine clinical results of operative treatment for these fractures. Although this injury appears innocuous, it can be difficult to obtain stable fixation of the fragment intraoperatively, and painful nonunion can result. A simple reduction maneuver and method of tension band fixation are described.

The cortical neuritic pathology of Huntington's disease

We have studied the brains of 10 patients with clinically and pathologically defined Huntington's disease and graded the degree of striatal pathology according to the Vonsattel grading system. Sections from nine cerebral cortical areas (Brodmann areas 8, 10, 24, 33, 28, 38, 7, 39, 18), the cerebellum, hypothalamus, medulla and caudate nucleus were stained with antibodies to ubiquitin and ubiquitin C-terminal hydrolase (PGP 9.5). Dystrophic neurites, immunoreactive with ubiquitin and PGP 9.5 were detected in all cortical areas, in layers 3, 5 and 6, of all brains studied. No dystrophic neurites were found in subcortical areas or cerebellum. Sections from cortical areas 8 and 24 from the two brains with the most and least ubiquitin-immunoreactive neurites were stained with antibodies to beta-amyloid precursor protein, tau, glial fibrillary acidic protein, neurofilament protein, alpha B crystallin, GABA, cholecystokinin and somatostatin. The dystrophic neurites were found to also react with beta-amyloid precursor protein. Electron microscopy showed the abnormal neurites to contain granulofilamentous material. Granular deposits with a diameter of 40-100 nm were interspersed between randomly orientated 'fuzzy' or coated, straight or slightly curved filaments measuring 10-15 nm in diameter. These structures have not been seen in control brain and differ from age-related neuritic degeneration and neurites associated with amyloid. Immunohistochemically these structures most resemble CA 2/3 neurites seen in Lewy body disease, and, ultrastructurally, the intraneuronal filamentous inclusions in motor neuron disease.(ABSTRACT TRUNCATED AT 250 WORDS)

Relationship between osmoprotection and the structure and intracellular accumulation of betaines by Escherichia coli

Naturally occurring betaines, especially glycine betaine and proline betaine, were accumulated by Escherichia coli from urine. In synthetic hyperosmotic medium, with an homologous series of added betaines, (CH3)3N(+)-(CH2)n-COO-, osmoprotective activity and intracellular accumulation decreased monotonically as n increased from 1 to 5. In contrast, alpha-substituted glycine betaines were accumulated in a similar manner to glycine betaine, but with different osmoprotective activities. Arsenobetaine, with a quaternary arsonium group, was also accumulated but amino acids which can become negatively charged in a chemically basic environment were not.

Dopamine autoreceptors and the effects of drugs on locomotion and dopamine synthesis

Criteria for distinguishing dopamine autoreceptor agonism from other mechanisms of inhibiting locomotion were examined, together with the relationship between inhibition of locomotion and dopamine synthesis. ED50 potencies to inhibit locomotion of mice were established for drugs from a number of categories. Spiperone 0.02 mg kg-1 significantly (P less than 0.05) reversed inhibition of locomotion by known dopamine agonists but not that by the other types of drug. Idazoxan antagonized inhibition of locomotion due to alpha 2-agonists but not dopamine agonists. RU 24926 (N-propyl-N,N-di[2-(3-hydroxyphenyl)ethyl]amine) was antagonized by both spiperone and idazoxan. Only for dopamine agonists was there good correlation (r = 0.97) between potencies to inhibit locomotion in mice and L-dihydroxyphenylalanine (L-DOPA) accumulation in the nucleus accumbens of rats treated with gamma-butyrolactone and 3-hydroxybenzylhydrazine. The specific dopamine D1-agonist, SK&F 38393 (2,3,4,5-tetrahydro-7,8-dihydroxy-1-phenyl-1H-3-benzazepine), was inactive in both tests at doses up to 10 mg kg-1. The mixed dopamine agonist/antagonist, (-)-3-(3-hydroxyphenyl)-N-propylpiperidine, commonly known as (-)-3-PPP, acted as a dopamine agonist in both tests but inhibited locomotion more potently than L-DOPA accumulation. The inhibitory effects of dopamine agonists on locomotion were not prevented by alpha-methyl-p-tyrosine pretreatment. The data suggest that spiperone-reversible inhibition of locomotion in mice is a good criterion for dopamine autoreceptor agonists. The receptors involved are affected by low doses of both dopamine agonists and antagonists and seem similar to those involved in the autoreceptor mediated inhibition of dopamine synthesis. However, inhibition of locomotion is not due simply to suppression of dopamine release brought about as a secondary consequence of effects on synthesis; a separate mechanism for inhibiting dopamine release is probably involved.