Mouse frontal cortex mediates additive multisensory decisions

The brain can combine auditory and visual information to localize objects. However, the cortical substrates underlying audiovisual integration remain uncertain. Here, we show that mouse frontal cortex combines auditory and visual evidence; that this combination is additive, mirroring behavior; and that it evolves with learning. We trained mice in an audiovisual localization task. Inactivating frontal cortex impaired responses to either sensory modality, while inactivating visual or parietal cortex affected only visual stimuli. Recordings from >14,000 neurons indicated that after task learning, activity in the anterior part of frontal area MOs (secondary motor cortex) additively encodes visual and auditory signals, consistent with the mice's behavioral strategy. An accumulator model applied to these sensory representations reproduced the observed choices and reaction times. These results suggest that frontal cortex adapts through learning to combine evidence across sensory cortices, providing a signal that is transformed into a binary decision by a downstream accumulator.

A modular architecture for organizing, processing and sharing neurophysiology data

We describe an architecture for organizing, integrating and sharing neurophysiology data within a single laboratory or across a group of collaborators. It comprises a database linking data files to metadata and electronic laboratory notes; a module collecting data from multiple laboratories into one location; a protocol for searching and sharing data and a module for automatic analyses that populates a website. These modules can be used together or individually, by single laboratories or worldwide collaborations.

Mouse Visual Cortex Is Modulated by Distance Traveled and by Theta Oscillations

The visual responses of neurons in the primary visual cortex (V1) are influenced by the animal's position in the environment [1-5]. V1 responses encode positions that co-fluctuate with those encoded by place cells in hippocampal area CA1 [2, 5]. This correlation might reflect a common influence of non-visual spatial signals on both areas. Place cells in CA1, indeed, do not rely only on vision; their place preference depends on the physical distance traveled [6-11] and on the phase of the 6-9 Hz theta oscillation [12, 13]. Are V1 responses similarly influenced by these non-visual factors? We recorded V1 and CA1 neurons simultaneously while mice performed a spatial task in a virtual corridor by running on a wheel and licking at a reward location. By changing the gain that couples the wheel movement to the virtual environment, we found that ∼20% of V1 neurons were influenced by the physical distance traveled, as were ∼40% of CA1 place cells. Moreover, the firing rate of ∼24% of V1 neurons was modulated by the phase of theta oscillations recorded in CA1 and the response profiles of ∼7% of V1 neurons shifted spatially across the theta cycle, analogous to the phase precession observed in ∼37% of CA1 place cells. The influence of theta oscillations on V1 responses was more prominent in putative layer 6. These results reveal that, in a familiar environment, sensory processing in V1 is modulated by the key non-visual signals that influence spatial coding in the hippocampus.

Dopaminergic and Prefrontal Basis of Learning from Sensory Confidence and Reward Value

Deciding between stimuli requires combining their learned value with one's sensory confidence. We trained mice in a visual task that probes this combination. Mouse choices reflected not only present confidence and past rewards but also past confidence. Their behavior conformed to a model that combines signal detection with reinforcement learning. In the model, the predicted value of the chosen option is the product of sensory confidence and learned value. We found precise correlates of this variable in the pre-outcome activity of midbrain dopamine neurons and of medial prefrontal cortical neurons. However, only the latter played a causal role: inactivating medial prefrontal cortex before outcome strengthened learning from the outcome. Dopamine neurons played a causal role only after outcome, when they encoded reward prediction errors graded by confidence, influencing subsequent choices. These results reveal neural signals that combine reward value with sensory confidence and guide subsequent learning.

High-Yield Methods for Accurate Two-Alternative Visual Psychophysics in Head-Fixed Mice

Research in neuroscience increasingly relies on the mouse, a mammalian species that affords unparalleled genetic tractability and brain atlases. Here, we introduce high-yield methods for probing mouse visual decisions. Mice are head-fixed, facilitating repeatable visual stimulation, eye tracking, and brain access. They turn a steering wheel to make two alternative choices, forced or unforced. Learning is rapid thanks to intuitive coupling of stimuli to wheel position. The mouse decisions deliver high-quality psychometric curves for detection and discrimination and conform to the predictions of a simple probabilistic observer model. The task is readily paired with two-photon imaging of cortical activity. Optogenetic inactivation reveals that the task requires mice to use their visual cortex. Mice are motivated to perform the task by fluid reward or optogenetic stimulation of dopamine neurons. This stimulation elicits a larger number of trials and faster learning. These methods provide a platform to accurately probe mouse vision and its neural basis.

Effect of water table management and elevated CO2 on radish productivity and on CH4 and CO2 fluxes from peatlands converted to agriculture

Anthropogenic activity is affecting the global climate through the release of greenhouse gases (GHGs) e.g. CO₂ and CH₄. About a third of anthropogenic GHGs are produced from agriculture, including livestock farming and horticulture. A large proportion of the UK's horticultural farming takes place on drained lowland peatlands, which are a source of significant amounts of CO₂ into the atmosphere. This study set out to establish whether raising the water table from the currently used -50cm to -30cm could reduce GHGs emissions from agricultural peatlands, while simultaneously maintaining the current levels of horticultural productivity. A factorial design experiment used agricultural peat soil collected from the Norfolk Fens (among the largest of the UK's lowland peatlands under intensive cultivation) to assess the effects of water table levels, elevated CO₂, and agricultural production on GHG fluxes and crop productivity of radish, one of the most economically important fenland crops. The results of this study show that a water table of -30cm can increase the productivity of the radish crop while also reducing soil CO₂ emissions but without a resultant loss of CH₄ to the atmosphere, under both ambient and elevated CO₂ concentrations. Elevated CO₂ increased dry shoot biomass, but not bulb biomass nor root biomass, suggesting no immediate advantage of future CO₂ levels to horticultural farming on peat soils. Overall, increasing the water table could make an important contribution to global warming mitigation while not having a detrimental impact on crop yield.

Utilising green and bluespace to mitigate urban heat island intensity

It has long been recognised that cities exhibit their own microclimate and are typically warmer than the surrounding rural areas. This 'mesoscale' influence is known as the urban heat island (UHI) effect and results largely from modification of surface properties leading to greater absorption of solar radiation, reduced convective cooling and lower water evaporation rates. Cities typically contain less vegetation and bodies of water than rural areas, and existing green and bluespace is often under threat from increasing population densities. This paper presents a meta-analysis of the key ways in which green and bluespace affect both urban canopy- and boundary-layer temperatures, examined from the perspectives of city-planning, urban climatology and climate science. The analysis suggests that the evapotranspiration-based cooling influence of both green and bluespace is primarily relevant for urban canopy-layer conditions, and that tree-dominated greenspace offers the greatest heat stress relief when it is most needed. However, the magnitude and transport of cooling experienced depends on size, spread, and geometry of greenspaces, with some solitary large parks found to offer minimal boundary-layer cooling. Contribution to cooling at the scale of the urban boundary-layer climate is attributed mainly to greenspace increasing surface roughness and thereby improving convection efficiency rather than evaporation. Although bluespace cooling and transport during the day can be substantial, nocturnal warming is highlighted as likely when conditions are most oppressive. However, when both features are employed together they can offer many synergistic ecosystem benefits including cooling. The ways in which green and bluespace infrastructure is applied in future urban growth strategies, particularly in countries expected to experience rapid urbanisation, warrants greater consideration in urban planning policy to mitigate the adverse effects of the UHI and enhance climate resilience.

Excellence in teaching end-of-life care: a new multimedia toolkit for nurse educators

Nursing strongly values comfort and patient-centered care at the end of life, but little end-of-life content is included in most basic nursing education programs. An innovative way to improve nursing education about the end-of-life transition is to provide nurse educators with an electronic toolkit. This article describes a newly created multimedia toolkit (TNEEL), which includes engaging strategies for teaching and learning about end-of-life care.

Comparison among soil Series and extraction methods for the analysis of trifluralin

Accurate analytical procedures are needed to improve understanding of the fate and transport of trifluralin, a chemical widely used as a herbicide. Analytical determination of trifluralin is challenging due to its hydrophobic, yet volatile, character and its tendency to degrade into numerous metabolites. In this research, efficient analytical methods for fortified and field-incurred soils were developed for simultaneous quantitation of trifluralin, I [2,6-dinitro-N,N-dipropyl-4-(trifluoromethyl)benzenamine, CAS Registry No. 1582-09-8; CAS Registry No. have been provided by the author], a trifluralin metabolite, II [2,6-dinitro-N-propyl-4-(trifluoromethyl)benzenamine, CAS Registry No. 2077-99-8], and a related trifluoromethyldinitroaniline isomer of trifluralin, III [2,4-dinitro-N,N-dipropyl-6-(trifluoromethyl)benzenamine, CAS Registry No. 23106-20-9]. Extractions of trifluralin (0.5 and 2.5 microg/g) from silt loam, sandy loam, and silty clay soils were compared. A method was developed for the supercritical fluid extraction of trifluralin from soil using modified supercritical carbon dioxide, and the effects of cosolvent, pressure, and flow rate on recovery were evaluated. Supercritical fluid extraction was compared to liquid vortex extraction and automated Soxhlet (soxtec) extraction. Solid-phase extraction was examined for purifying soil extracts. Protocols were developed for analysis of extracts by gas and/or liquid chromatography. Immunoassay was investigated but proven to be impractical for this analysis. Soil properties and extraction methods were observed to affect the level of coextracted background interferences. Trifluralin exhibited concentration-dependent recovery regardless of soil series or extraction method.

Solid-phase extraction of acidic herbicides

A discussion of solid-phase extraction method development for acidic herbicides is presented that reviews sample matrix modification, extraction sorbent selection, derivatization procedures for gas chromatographic analysis, and clean-up procedures for high-performance liquid chromatographic analysis. Acidic herbicides are families of compounds that include derivatives of phenol (dinoseb, dinoterb and pentachlorophenol), benzoic acid (acifluorfen, chloramben, dicamba, 3,5-dichlorobenzoic acid and dacthal--a dibenzoic acid derivative), acetic acid [2,4-dichlorophenoxyacetic acid (2,4-D), 4-chloro-2-methylphenoxyacetic acid (MCPA) and 2,4,5-trichlorophenoxyacetic acid (2,4,5-T)], propanoic acid [dichlorprop, fluazifop, haloxyfop, 2-(4-chloro-2-methylphenoxy)propanoic acid (MCPP) and silvex], butanoic acid [4-(2,4-dichlorophenoxy)butanoic acid (2,4-DB) and 4-(4-chloro-2-methylphenoxy)butanoic acid (MCPB)], and other miscellaneous acids such as pyridinecarboxylic acid (picloram) and thiadiazine dioxide (bentazon).

The protective effects of hypoxia-induced hypometabolism in the Nautilus

Specimens of Nautilus pompilius were trapped at depths of 225-300 m off the sunken barrier reef southeast of Port Moresby, Papua New Guinea. Animals transported to the Motupore Island laboratory were acclimated to normal habitat temperatures of 18 degrees C and then cannulated for arterial and venous blood sampling. When animals were forced to undergo a period of progressive hypoxia eventually to encounter ambient partial pressure of oxygen (PO2) levels of approximately 10 mmHg (and corresponding arterial PO2's of approximately 5 mmHg), they responded by lowering their aerobic metabolic rates to 5-10% of those seen in resting normoxic animals. Coincident with this profound metabolic suppression was an overall decrease in activity, with brief periods of jet propulsion punctuating long periods of rest. Below ambient PO2 levels of 30-40 mmHg, ventilatory movements became highly periodic and at the lowest PO2 levels encountered, ventilation occasionally ceased altogether. Cardiac output estimated by the Fick equation decreased during progressive hypoxia by as much as 75 80%, and in the deepest hypometabolic states heart rates slowed to one to two cycles of very low amplitude per minute. By the end of 500 min exposure to ambient PO2 levels of 10 mmHg or less, the anaerobic end products octopine and succinate had increased significantly in adductor muscle and heart, respectively. Increased concentrations of octopine in adductor muscle apparently contributed to a small intracellular acidosis and to the development of a combined respiratory and metabolic acidosis in the extracellular compartment. On the other hand, increases in succinate in heart muscle occurred in the absence of any change in cardiac pHi. Taken together, we estimate that these anaerobic end products would make up less than 2% of the energy deficit arising from the decrease in aerobic metabolism. Thus, metabolic suppression is combined with a massive downregulation of systemic O2 delivery to match metabolic supply to demand.

The use of an independent visual background to reduce simulator side-effects

BACKGROUND

Simulator sickness (SS) is a major problem which potentially limits interface applications that feature simulated motion. While display imperfections play a role, a large part of SS is motion sickness (MS). Sensory rearrangement theory holds that MS is related to conflicting motion cues; in the case of simulators, mainly a conflict between inertial cues (usually indicating no self-motion) and visual stimuli from the display (indicating self-motion). It is suggested that MS does not arise from conflicting motion cues per se, but rather from conflicting rest frames selected from those motion cues. There is strong evidence that the visual rest frame is heavily influenced by the visual background. Providing an independent visual background (IVB) consistent with the inertial rest frame may reduce SS, even when the simulator's content-of-interest (CI) is not consistent with the inertial rest frame.

METHODS

In two experiments, a circular vection stimulus was shown for 3-4.5 min in a head-mounted display, comparing see-through (i.e., IVB) to occluded (i.e., no IVB) modes. Measures included a standard SS questionnaire and a pre-exposure ataxia measure. Experiment 2 added a visual task which forced attention into the CI and a post-exposure ataxia measure. In both experiments, subjects rated the CI as significantly more visible than the IVB.

RESULTS

A large effect was found for the reduction of SS and ataxia in the first experiment, and for pre-exposure ataxia in the second.

CONCLUSIONS

Future research will further test the IVB idea and examine applications to high-end simulators.

In vivo clearance of ternary complexes of vitronectin-thrombin-antithrombin is mediated by hepatic heparan sulfate proteoglycans

Thrombin is inhibited by its cognate plasma inhibitor antithrombin, through the formation of covalent thrombin-antithrombin (TAT) complexes that are found as ternary complexes with vitronectin (VN-TAT). To determine whether the metabolism of VN-TAT ternary complexes is different from that previously reported for binary TAT complexes, plasma clearance studies were done in rabbits using human VN-TAT. 125I-VN-TAT was shown to be cleared rapidly from the circulation (t1/2alpha = 3.8 min) in a biphasic manner mainly by the liver. 125I-TAT had a similar initial clearance (t1/2alpha = 5.3 min) but had a significantly faster beta-phase clearance (t1/2beta = 42.8 min versus 85.4 min for VN-TAT; p = 0.005). Protamine sulfate and heparin abolished the rapid initial alpha-phase of 125I-VN-TAT clearance and reduced its liver-specific association and in vivo degradation. Heparin also reduced the alpha-phase clearance of 125I-TAT and was associated with the appearance of high molecular weight complexes, suggesting enhanced complex formation between VN and TAT. 125I-VN-TAT binding to HepG2 cells was reduced by competition with VN-TAT or heparin but to a much lesser extent in the presence of TAT. The binding of VN-TAT to HepG2 cells was not inhibited by competition with the low density lipoprotein receptor-related protein ligand, methylamine-alpha2-macroglobulin. 125I-VN-TAT binding was also inhibited by treating HepG2 cells with heparinase or by growing the cells in the presence of beta-D-xyloside. Finally, both heparin and chloroquine, but not methylamine-alpha2-macroglobulin, reduced the internalization and degradation of VN-TAT by HepG2 cells. Taken together, these data indicate the importance of VN in TAT metabolism and demonstrate that VN-TAT binds to liver-associated heparan sulfate proteoglycans, which mediate its internalization and subsequent intracellular degradation.

Cytokeratin 18 is expressed on the hepatocyte plasma membrane surface and interacts with thrombin-antithrombin complexes

During experiments to identify putative hepatic receptors for thrombin-antithrombin (TAT) complexes, a 45-kDa protein was identified by ligand blotting. Following gel purification, amino acid sequencing revealed the 45-kDa TAT-binding polypeptide to be cytokeratin 18 (CK18). The presence of CK18 on the surface of intact rat hepatoma cells was demonstrated by binding of 125I-anti-CK18 antibodies. Anti-CK18 antibodies reduced the binding and internalization of 125I-TAT by rat hepatoma cells. Immunocytochemical analysis, to determine the location of CK18 in vivo, revealed a periportal gradient of CK18 staining; with hepatocytes around the portal triads demonstrating striking pericellular staining. In addition, anti-CK18 IgG associated with perfused livers to a significantly greater extent than preimmune IgG. Taken together, these data provide evidence that CK18 is found on the extracellular surface of hepatocytes and could play a role in TAT removal. Finally, these data, in conjunction with recent reports of CK8 (Hembrough, T. A., Li, L., and Gonias, S. L. (1996) J. Biol. Chem. 271, 25684-25691) and CK1 cell membrane surface expression (Schmaier, A. H. (1997) Thromb. Hemostasis 78, 101-107), indicate a novel role for these proteins as putative cellular receptors or cofactors to cellular receptors.

Pharmacokinetics and pharmacodynamics of subcutaneous interleukin-2 in HIV-infected patients

STUDY OBJECTIVES

To assess the pharmacokinetics and pharmacodynamics of subcutaneously administered interleukin-2 (IL-2) in patients infected with the human immunodeficiency virus (HIV).

DESIGN

Open, dose-escalating phase I clinical trial.

SETTING

Government research hospital.

PATIENTS

Eighteen patients infected with HIV.

INTERVENTIONS

Recombinant IL-2 at dosages of 12, 15, or 18 MIU/day was administered subcutaneously once or twice/day for 5 consecutive days every 2 months. A total of 28 cycles of therapy were included in the analysis.

MEASUREMENTS AND MAIN RESULTS

Concentrations of IL-2 in serum were determined by a commercial enzyme-linked immunosorbent assay. Interleukin-2 was well absorbed, with peak concentrations from 21.9-112.9 IU/ml. Absorption was slow, with mean (+/- SD) time to maximum of 4.4 +/- 1.8 hours and a lag time of 26.9 +/- 13.7 minutes. Elimination half-life was 3.3 +/- 0.9 hours. The concentrations had wide variability both within and among patients. Levels of tumor necrosis factor-alpha were increased. Maximum body temperature and systemic side effects were associated with peak serum levels.

CONCLUSION

Interleukin-2 is well absorbed after subcutaneous injection in HIV-infected patients, and that route of administration is an alternative to intravenous infusions.

Concerns on little league elbow

Little League elbow is a common overuse injury that will become more prevalent as more youths participate in baseball programs and other sports that involve overhead arm activities. The condition is highly treatable if diagnosed early in its development. Symptoms such as swelling and limited range of motion usually indicate an advanced overuse condition. Prevention and treatment should emphasize education of athletes, parents, and coaches about coaches about its etiology. Factors involved are proper pitching mechanics, stretching and strengthening programs, improving early recognition, and, most importantly, limiting the number of pitches thrown daily.

Prevalence of antithrombin deficiency in healthy blood donors: a cross-sectional study

The prevalence of antithrombin (AT) deficiency in the general population has been variously estimated to be between 0.05 and 5 per 1,000 in the population; 2,491 blood donors were screened in an attempt to clarify this issue using plasma samples taken from the blood donor units. From this initial population, 122 individuals were identified as having plasma AT levels lower than 2 standard deviations below the normal mean. Twenty-two samples had evidence that thrombin had been generated during blood collection and the remaining cohort of 100 blood donors were asked to return but only 59 complied. The data obtained from these 59 were compared with that from 51 age- and sex-matched control blood donors. Both groups of subjects were assessed for previous evidence, or family history, of thrombotic events, as well as exposure to risk factors associated with the development of deep vein thrombosis (DVT). All had venous blood samples taken from which the supernatant plasma was immediately removed and quick frozen for later assaying. Only 6 of the 59 subjects with initial low AT levels had repeat AT-Xa levels below 0.80 units/ml (normal range 0.94 +/- 0.14). Upon repeating the AT-Xa determinations on new samples from these six individuals, only three were found again to be low. One was found to have a type 3 AT deficiency (an Arg47Cys substitution). The other two with a low AT level had mean functional AT-Xa levels of 0.61 and 0.71 units/ml, respectively, with correspondingly low AT:Ag levels consistent with a type 1 AT deficiency. Two of these three subjects has been in high risk situations without evidence of having developed DVT and none had evidence of venous reflux on Doppler venography. In addition, none had personal or family histories of previous thrombotic events. These present data indicate that the prevalence of AT deficiency in our blood donor population is 2 per 1,000 (95% confidence intervals: 0.7-6/1,000).

An antithrombin III assay based on factor Xa inhibition provides a more reliable test to identify congenital antithrombin III deficiency than an assay based on thrombin inhibition

OBJECTIVES

To determine whether functional antithrombin III (AT-III) levels measured by a factor Xa inhibition (AT-III-Xa) assay identifies AT-III deficient individuals more reliably than functional AT-III levels measured by a thrombin inhibition (AT-III-IIa) assay.

STUDY DESIGN

Cross-sectional study.

PATIENT POPULATION

Sixty-seven members of a large family with type 2 AT-III deficiency.

INTERVENTION

DNA analysis was used as the reference diagnostic standard for AT-III status and subjects were classified as AT-III deficient or non deficient according to these results. Functional AT-III levels were measured in all subjects using: 1) a chromogenic substrate for thrombin and added human thrombin (AT-III-IIa), and 2) a chromogenic substrate for factor Xa and added bovine factor Xa (AT-III-Xa). Functional heparin cofactor II (HC-II) levels were measured using a commercially available kit. The proportions of 125I-alpha-thrombin complexed to AT-III and HC-II were measured by polyacrylamide gel electrophoresis and autoradiography.

RESULTS

Thirty-one (46%) individuals were classified as AT-III deficient and 36 (54%) as AT-III non deficient. AT-III-Xa assay measured a significantly lower mean AT-III value and a narrower range for individuals classified as AT-III deficient than the AT-III-IIa assay. Using the AT-III-IIa assay, six subjects had borderline AT-III levels compared to none with the AT-III-Xa assay.(ABSTRACT TRUNCATED AT 250 WORDS)

Interdisciplinary Treatment of Musculoskeletal Pain: The EMPOWER Program

Many individuals who experience chronic pain are able to return to work in some capacity but continue to suffer from ongoing pain problems resulting in increased absenteeism and reduced productivity on the job. These individuals continue to require ongoing medical interventions. Monthly follow-up visits to a physician rarely provide effective treatment strategies that patients can use at home. The challenge is to develop an effective and inexpensive treatment program that will assist patients in regaining or maintaining employment and decrease reliance on health care facilities. A program of this type has been developed for chronic pain sufferers, primarily those with low back and cervical spine pain. The treatment is a six-week interdisciplinary program including relaxation training, gradually increasing exercise, and significant education on behavioral and exercise strategies and nutrition for long-term pain management. This program is inexpensive, cost efficient, and may be implemented easily in a variety of settings.

Molecular cloning and expression of rabbit antithrombin III

A cDNA containing the complete open-reading frame encoding rabbit antithrombin III (AT-III) was isolated from a rabbit liver cDNA expression library, using a specific antibody as a probe. Sequence analysis showed 84% identity between the deduced amino acid sequences of the rabbit and human proteins. A previously described cell-free expression system was used to verify the identity of the clone. The full-length cDNA was inserted into an expression vector, and messenger RNA (mRNA) transcripts generated. In vitro translation of these transcripts, in the presence of [35S]methionine, in an mRNA-dependent rabbit reticulocyte lysate system resulted in the synthesis of a 51-Kd polypeptide, as shown by sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE). This nonglycosylated protein was capable of forming SDS-stable complexes with human alpha-thrombin. Complex formation was significantly enhanced following the deletion of nucleotides encoding the signal peptide, and the resultant generation of a 47-Kd nonglycosylated mature protein product. When the template DNA giving rise to this product was internally truncated, two rabbit AT-III deletion mutants were generated that lacked the ability to interact with thrombin, but retained the ability to bind heparin. Cell-free expression plasmids encoding the human and rabbit AT-III mature molecules were manipulated to produce two interspecies fusion proteins. For the first, human codons were used to replace rabbit codons from residue 369-433, while in the second human codons replaced rabbit codons from residue 217-433. Both fusion proteins exhibited less efficient thrombin-complexing ability than the original cell-free-derived mature rabbit AT-III. Thus, portions of AT-III molecules from the two species, despite their high degree of homology, are not interchangeable. Knowledge of the structure of rabbit AT-III, combined with the availability of the rabbit cDNA, will permit defined experimentation aimed at understanding antithrombin III structure relative to its function in vivo.

Smodingium dermatitis

Smodingium argutum is the plant most commonly responsible for causing acute allergic contact dermatitis in South Africa. When an outbreak of Smodingium dermatitis occurred in a local school the allergenic principle present in this plant was chemically isolated and identified, and its allergenic property proved in the clinic by patch testing. The value of using an extract of fresh Smodingium leaves in lieu of fresh leaves themselves was confirmed, but freeze-dried material was found to be unsuitable for patch-test purposes.

Flight trial of a helmet-mounted display image stabilisation system

An image stabilisation system for improving reading performance with a helmet-mounted display (HMD) during whole-body vibration was tested at night in a helicopter. Six subjects read arrays of 50 numerals as quickly and as accurately as possible while flying in three different flight conditions. The mean reading time for each array while stationary on the ground was approximately 21 s, and the mean reading error was 0.4% without stabilisation. In-flight mean reading time increased to approximately 40 s, and reading error was 18% without the stabilisation system. Stabilising the image significantly reduced the mean in-flight reading time to approximately 25 s with a 4% reading error. Data from the flight trial support the results of previous experiments, which suggest that HMD reading performance with vibration and night viewing conditions may be inferior to performance with daylight conditions.

Anticonvulsant activity of some 4-aminobenzamides

A series of 4- aminobenzamides of some simple primary and secondary amines were prepared and evaluated for anticonvulsant effects. The compounds were tested in mice against seizures induced by electroshock and pentylenetetrazole ( metrazole ) and in the rotorod assay for neurologic deficit. For those N-alkyl amides tested, 4-amino-N- amylbenzamide (6) was the most potent against maximal electroshock seizures (MES): ED50 = 42.98 mg/kg; however, the N- cyclohexylbenzamide (8) showed the greatest protective index (PI = TD50/ED50), 2.8. The introduction of a second aromatic ring produced more potent compounds, with d,l-4-amino-N-(alpha-methylbenzyl)-benzamide (12) showing the highest level of activity. This compound has an anti-MES ED50 of 18.02 mg/kg in mice when administered intraperitoneally (ip) and a TD50 of 170.78 mg/kg (PI = 9.5) in the same species. These data compare quite favorably with those for phenobarbital and phenytoin in the same assays.

Effects of phenobarbital, 3-methylcholanthrene, and retinoid pretreatment on disposition of orally administered retinoids in mice

Following oral administration of doses of 10 mg/kg, the concentrations of all-trans-retinoic acid (RA), N-(2-hydroxyethyl)retinamide (N-HOERA), and 13-cis-retinoic acid (13-cis-RA) were measured in serum and tissues of mice with and without pretreatment with phenobarbital (PB), 3-methylcholanthrene (3MC), or the respective retinoid. For RA, the areas under the concentration-time curves (AUC values) for serum and tissues, relative to controls, were reduced, on the average, by 54 or 37% on pretreatment with RA or PB, respectively. Pretreatment with 3MC did not affect disposition of RA. The AUC values for N-HOERA were reduced, on the average, by 39 or 30% following pretreatment with PB or 3MC, respectively, but only 13% by the retinoid. For 13-cis-RA, the AUC values were reduced, on the average, by 56 or 37% following pretreatment with PB or 3MC, respectively; pretreatment with the retinoid had no appreciable effect. Thus, the disposition of orally administered retinoids appears to be affected by several inducible metabolic processes. Furthermore, comparison of data on the tissue distribution of retinoids with in vivo results demonstrates a general correlation between distribution and anticarcinogenic activity.

Benefits of helmet-mounted display image stabilisation under whole-body vibration

The effects of whole-body vertical vibration in the range 2.5-25 Hz on visual performance with two types of raster scan helmet-mounted display have been determined. The benefit of an image stabilisation system on numeral reading performance during vibration was also assessed with both display systems. Increases in mean reading time of over 130%/m . s-2 R.M.S. and increases in percentage reading error of more than 30%/m . s-2 R.M.S. were recorded with unstabilised displays. With vertical and horizontal image stabilisation, these decrements in performance were reduced to less than 40%/m . s-2 R.M.S. increase in reading time and less than 10%/m . s-2 R.M.S. increase in reading error. Data on the transmission of vibration from the seat to the head and from the head to the helmet were also obtained. These indicate a relation between biodynamic behaviour and visual performance during vibration.

Disposition of 13-cis-retinoic acid and N-(2-hydroxyethyl)retinamide in mice after oral doses

The concentrations of 13-cis-retinoic acid and N-(2-hydroxyethyl)retinamide in serum and tissues from mice were measured after oral dosing with 10 mg/kg. Serum levels of the drugs reached their maxima within 15-30 min and then declined in an exponential fashion with t1/2 values of 19 min and 2.9 hr, respectively. Tissue levels of 13-cis-retinoic acid reached their maxima within 15-30 min, then declined exponentially with t1/2 values of 11-19 min. Tissue levels of N-(2-hydroxyethyl)retinamide reached their maxima within 30 min to 2 hr, then declined exponentially with t1/2 values of 2.1-4.7 hr. Longer t1/2 values were observed for both 13-cis-retinoic acid and N-(2-hydroxyethyl)retinamide in the bladder (51 min and 7.3 hr, respectively). Only small amounts of the unchanged retinoids were observed in bile and feces, and none was found in urine. Polar materials, however, were present in bile, feces, and urine.

Distortion and adaptation in underwater sound localization

Sounds should be localized at more medial positions under water than in air, because the values of the interaural temporal and intensity differences are reduced in water. Thirteen blindfolded divers were required to move a pointer towards the apparent location of a sound source under water, and they showed significant errors towards the median plane. In a second experiment, five divers were tested in air before and after underwater training at swimming towards a sound source. The search patterns of these divers showed systematic errors towards the median plane. A comparison of the first and second air tests showed some evidence of an aftereffect away from the median plane, discounting the most lateral angles (80 degrees left and right) where little effect would be expected. It is concluded that both a distortion of localization and some adaptation to the distortion occur under water.

Nervous control of the heartbeat in octopus

The circulatory system of cephalopods is based on a trio of hearts, with two pairs of associated ganglia linked to the CNS by a pair of visceral nerves. The beat of the hearts was recorded from free-moving octopuses before and after surgical removal or disconnexion of elements of the nervous system. Severing the visceral nerves does not stop the hearts, which continue to beat in a powerful well co-ordinated manner in isolation from the CNS. The nerves seem to be concerned in raising the cardiac output in exercise, and with stopping the hearts when mantle movements cease, but they are not necessary for the initiation of maintenance of the normal rhythm. Removal of the fusiform ganglia severs all nervous connexions between the ywo gill hearts, and deprives the systemic heart of its nerve supply. The trio of hearts continues to beat as strongly as before. Removal or disconnexion of a cardiac ganglion disrupts the beat of the corresponding gill heart which now tends to contract in an ill-coordinated and rather feeble manner, though at much the same frequency as before; with both cardiacs gone the systemic heart, which contracts only when it is filled, tends to drop in frequency and the mean aortic pressure falls. The system remains rhythmic, however, and the beat may recover, to the point where aortic pressures and frequencies approach those found in intact animals at rest; even octopuses with both fusiform and both cardiac ganglia removed can survive for many hours. From the performance of the isolated branchial heart, the existence of a pulsating vesicle in each cardiac ganglion, the effects of cardiac ganglion removal and the remarkable steadiness of heartbeat frequency shown by intact animals under a variety of conditions, it is argued that the heartbeat rhythm is normally controlled by pacemakers in the branchial heart/ cardiac ganglion complexes, and perhaps, in intact animals, from within the cardiac ganglia themselves. The picture of the control of the heartbeat that emerges from the study of free moving essentially intact animals is quite different from that arising from in vitro and acute preparation studies. It suggests that the conventional wisdom about the control of the heartbeat in cephalopods (and perhaps by implication, in other molluscs) may need to be considerably revised.

The effects of extracts from neurosecretory cells in the anterior vena cava and pharyngo-ophthalmic vein upon the hearts of intact free-moving octopuses

Recordings of pressure and frequency were made from the hearts of free-moving Octopus vulgaris. The effects of extracts from neurosecretory endings in the anterior vena cava (AVC) and the pharyngo-ophthalmic vein (POV), injected through fine cannulae into a branchial heart, efferent branchial vessel or the dorsal aorta, were studied and compared with the effects of acetylcholine, 5-hydroxytryptamine, adrenaline, histamine and tyramine. AVC and POV extracts each produce a different spectrum of effects, unlike those of any of the drugs tested. AVC extract is effective at doses of less than 2% of the material extractable from a single vein per kg, increasing the force and amplitude of the heartbeats. With a natural release point just upstream of the branchial hearts the AVC material must be relevant to the normal performance of the hearts. POV extract is effective only at doses equivalent to several veins per kg, and is unlikely to have a role in cardiac regulation. Section of the visceral nerves did not affect the action of drugs or extracts, indicating that effects were not indirectly mediated via the CNA. Further experiments were made with hearts and the aorta in vitro with effects that did not always parallel those found in vivo. Reasons for these differences are discussed.

Reproduction Versus Somatic Growth: Hormonal Control in Octopus Vulgaris

Octopus vulgaris can be forced into precocious maturity by removal of the subpedunculate lobe from the brain, an operation that releases the optic glands from inhibition, and allows them to secrete a gonadotropin.

14C-leucine was injected into the bloodstream of immature animals and its subsequent incorporation into muscle protein followed by taking successive samples from the arms. The optic glands were then activated, and a further injection of 3H-leucine given and followed by means of further arm samples.

Optic gland secretion suppresses protein synthesis in the muscles. This is associated with an increase in the total amino acid pool in the muscles and with a considerable increase in the concentration of free amino acids circulating in the blood.

If an ovary is present these events are associated with a rapid growth of the ovary and its ducts, and a loss of weight elsewhere. In ovariectomized animals the ducts grow, but there is no yolk to absorb the large pool of free amino acids, and the animals gain weight by osmotic uptake of water into the muscles.

The developing ovary may produce a hormone that increases the release of amino acids from muscle, since the concentration circulating in the blood of intact animals remains at least as high as in ovariectomized octopuses, despite the demands of the developing ovary.

These matters are discussed in relation to other evidence for a gonadial hormone and in relation to the ‘self-destruct’ effect of the optic gland secretion in determining the post-reproductive death of octopuses.

The subfrontal lobe and touch learning in the octopus

Octopuses with the supraoesophageal lobes of the brain divided longitudinally can be taught to discriminate using the arms on either side. If there is no further lesion the two sides behave alike. Lesions limited to one side did not affect the performance of the contralateral, "control" side. Lesions made in the vertical (n=7) lobes led to a slight drop in the quality of performance in training to take a smooth sphere, in discrimination training (rough vs. smooth spheres) and in subsequent extinction and transfer tests. After removal of the median inferior frontal lobe (n = 10) there were somewhat greater effects in the same direction. Much larger effects followed interference with the subfrontal lobe (n = 20). Removal of parts from this always led to a marked loss of capacity for touch learning, broadly dependent on the amount of tissue removed. Removal of the whole of the subfrontal lobe (n = 6) produced animals that showed, at best, only very slight signs of learning. Such animals can adjust their overall level of response as a result of training but they seem incapable of adjusting response levels to two objects independently. These results are discussed in relation to the function of the subfrontal lobe as a memory store.

Optic gland implants and their effects on the gonads of Octopus

1. Optic glands transplanted from one Octopus vulgaris into another cause enlargement of the gonads and ducts of the recipient. 2. Enlargement occurs whether or not the gland was secreting when implanted and regardless of the sex of the donor or recipient. 3. Glands derived from Eledone moschata or Octopus macropus implanted into O. vulgaris are as effective as glands derived from O. vulgaris. 4. Implants derived from Sepia officinalis or Loligo vulgaris appear to be ineffective.

An in vitro bioassay for a mulluscan gonadotropin

1. Protein synthesis occurs at a high rate in the ovaries of maturing Octopus vulgaris and can be measured from the incorporation of [14C]leucine in vivo and in isolated groups of eggs in vitro. 2. Removal of the optic glands in vivo 1--3 days prior to testing markedly reduces amino acid incorporation in vivo or in vitro. After 5 days in vivo incorporation stops. 3. The rate of incorporation in vitro is increased by the addition of optic gland extract. 4. Analysis of the kinetics of leucine uptake and incorporation in vitro indicates that the hormone has an effect on the inward transport of leucine which is independent of its action on protein synthesis. 5. Electron-microscope studies of the follicle cells and ova show that the former are the site of protein synthesis. 6. Changes in either uptake or incorporation into protein by the follicle cells can be used as a qualitative biolobical assay for the optic gland hormone. Uptake is very easy to measure but incorporation is the more sensitive parameter. Either is potentially suitable as a quantitative assay for this and perhaps also for other molluscan gonadotropins.

Yolk Protein Synthesis in the Ovary of Octopus Vulgaris and its Control by the Optic Gland Gonadotropin

1. Over 98% of a dose of [14C]leucine injected into the circulation of Octopus vulgaris is removed from the blood during the first hour.

2. There is a rapid accumulation of labelled protein in the ovaries of maturing animals within 2 h of injection. Within 5-7 h the ovaries contain nearly 40% of the injected label in protein form.

3. Removal of the optic glands prevents this accumulation of protein.

4. There is little labelled protein in the livers of either control or maturing animals at any time; but a slow, steady accumulation occurs in their blood.

5. The level of labelled protein appearing in the blood of acutely ovariectomized, maturing females is no higher than in controls; and when blood protein from ovariectomized animals is injected into normal maturing females it is not taken up by the ovaries.

6. The labelled protein which accumulates in the blood is probably haemocyanin. Preliminary experiments indicate that the branchial glands, which are already believed to be a site of haemocyanin synthesis on morphological grounds, show a high rate of protein synthesis and release.

7. Isolated ovarian follicles in a liquid medium synthesize protein at a rate somewhat lower, but comparable with, the apparent in vivo rate.

8. The combined evidence from these experiments indicates that in Octopus yolk proteins are formed within the ovary-probably by the follicle cells-rather than being synthesized elsewhere and transported through the blood, as in arthropods and vertebrates.

9. The optic gland gonadotropin is essential for maintenance of protein synthesis during secondary vitellogenesis and the follicle cells are a likely site for its action during this stage of development.

The Median Inferior Frontal Lobe and Touch Learning in the Octopus

1. After removal of the median inferior frontal lobe, blinded octopuses already trained to discriminate by touch between rough and smooth spheres continued to do so, but at a lower level of accuracy.

2. Animals without pre-training showed a strong tendency to take rough objects after this operation and learned to discriminate well only when trained to take rough and reject smooth.

3. When animals with intact inferior frontal lobes were given food in the presence of a smooth sphere they learned to take the smooth; in subsequent extinction tests they continued to take the smooth but soon ceased to take rough objects.

4. Animals without median inferior frontal lobes also increased their tendency to take a smooth object associated with food. But they did not behave in the same way as controls in extinction tests; they continued to take the rough objects even if they had not been rewarded for doing so.

5. Operated animals thoroughly pre-trained to take smooth objects showed some capacity to discriminate these from rough objects in subsequent successive training with food and shock, though continuing to take the rough far more than control animals.

6. Animals without brain damage could be taught to take smooth rather than rough objects on one side, and continued to do so when trained in the reverse direction on the other. There was, however, some lateral interference; performance on the unreversed side was worse after the introduction of reversed training.

7. Animals with lesions to the median inferior frontal lobe failed to learn on the reversal (rough+/smooth-) side, responses to both objects declining progressively as training continued. At the same time as this discrimination by the non-reversal (smooth+/rough-) side continued to develop. There was thus no evidence of lateral transfer in these animals.

8. It was confirmed that tactile learning is still possible after removal of the vertical and basal lobes, but with some decrease in the normal preference for smooth objects.

9. The median inferior frontal is thus not essential for tactile learning, but greatly facilitates it, making some contribution to the acquisition of both positive and negative responses, perhaps by spreading information through both sides of the touch-learning system. The effect of its removal in touch learning can be compared with the effect of vertical lobe removal on visual learning. It is concluded that one function of these parts is to compensate for the intensity of stimulation so that animals do not pay undue attention to brightly reflective or texturally rough objects.

The Effect of Splitting part of the Brain or Removal of the Median Inferior Frontal Lobe on Touch Learning in Octopus

1. Octopuses with the whole supraoesophageal lobe divided in the mid-line show a lesser preference for smooth objects than normals.

2. Learning of a simple successive tactile discrimination can proceed as fast in such a half-brain as in a whole brain.

3. Animals in which the anterior part of the supraoesophageal lobe alone was split also learned approximately as fast as normals. When tested on the untrained side they showed at most slight signs of ‘transfer’. The unsplit vertical lobe system apparently mediates little transfer, either of learning to take or not to take an object.

4. Animals with the posterior part of the supraoesophageal lobe alone split learned less well than normals or those with anterior splits, the deficit being due to the large number of takes of the negative object. Tests on the untrained side showed that good transfer of the capacity for positive and negative learned response occurred through the intact inferior frontal commissures.

5. Animals without the median inferior frontal lobe showed a marked preference for rough objects. Of six trained with smooth positive only two showed increasingly correct discrimination. Four out of seven animals trained with rough positive showed an increasingly correct performance as a result of training. The performance of the others got worse as training proceeded. It is not clear whether this learning deficit is due to the excessive rough preference or to the absence of some part of the learning mechanism owing to removal of the median inferior frontal lobe.

6. Tests on the untrained side of animals without median inferior frontal show no capacity to discriminate. This shows that the median inferior frontal is vital to lateral transfer and confirms that learning cannot readily be transferred through the vertical lobe system.

Short-Term Learning and Interocular Transfer in Detour Experiments with Octopuses

1. Octopuses will make detours down a corridor with opaque walls and will make a correct left-right choice at the far end in order to attack a crab seen to one side of the passage through the transparent windows of a home compartment.

2. In all, 1071 trials were carried out. In 883 of these a detour was completed, rightly or wrongly; in the remaining trials the octopuses failed to complete detours within 5 min. of the start of the trial.

3. The percentage of errors rose with the time spent in the maze. Animals that completed their runs within 20 or 30 sec. of entering the corridor rarely made a mistake; animals that took 2 min. or more, whether due to imposed delays (animal shut in the corridor) or to slow exploration of the maze, made as many errors as correct responses.

4. After removal of the vertical lobe from the brain the octopuses made more errors, particularly in the slower runs. There was also a higher proportion of trials at which they failed to complete a detour at all. These failures are not due to a failure of interocular transfer or to locomotor defects.

6. The results are discussed in relation to the function of the vertical lobe, interocular transfer, the nature of representations of recent events within the optic lobes and the establishment of more permanent memory traces in discrimination experiments.