AEGIS autonomous targeting for ChemCam on Mars Science Laboratory: Deployment and results of initial science team use

Limitations on interplanetary communications create operations latencies and slow progress in planetary surface missions, with particular challenges to narrow-field-of-view science instruments requiring precise targeting. The AEGIS (Autonomous Exploration for Gathering Increased Science) autonomous targeting system has been in routine use on NASA's Curiosity Mars rover since May 2016, selecting targets for the ChemCam remote geochemical spectrometer instrument. AEGIS operates in two modes; in autonomous target selection, it identifies geological targets in images from the rover's navigation cameras, choosing for itself targets that match the parameters specified by mission scientists the most, and immediately measures them with ChemCam, without Earth in the loop. In autonomous pointing refinement, the system corrects small pointing errors on the order of a few milliradians in observations targeted by operators on Earth, allowing very small features to be observed reliably on the first attempt. AEGIS consistently recognizes and selects the geological materials requested of it, parsing and interpreting geological scenes in tens to hundreds of seconds with very limited computing resources. Performance in autonomously selecting the most desired target material over the last 2.5 kilometers of driving into previously unexplored terrain exceeds 93% (where ~24% is expected without intelligent targeting), and all observations resulted in a successful geochemical observation. The system has substantially reduced lost time on the mission and markedly increased the pace of data collection with ChemCam. AEGIS autonomy has rapidly been adopted as an exploration tool by the mission scientists and has influenced their strategy for exploring the rover's environment.

Expression of vascular endothelial growth factor (VEGF) in normal oral mucosa, oral dysplasia and oral squamous cell carcinoma

Vascular endothelial growth factor (VEGF) is a potent angiogenic cytokine implicated in tumour vasculogenesis. A significant increase in vascularity occurs during the transition from normal oral mucosa (NOM), through dysplasia, to squamous cell carcinoma (SCC). This study investigated the presence of VEGF in NOM, oral dysplasia and SCC. The correlation between VEGF expression and the grade of dysplasia or differentiation of SCC was also examined. Specimens consisting of NOM, oral dysplastic lesions and oral SCC were stained using standard immunohistochemistry methods to determine VEGF expression. Statistical analysis indicated an up-regulation of VEGF during the transition from NOM, through dysplasia to SCC. There was also a significant difference in expression according to differentiation of SCC, but not grade of dysplasia. As VEGF is a potent mediator of vascular development, these results suggest that VEGF may play an important role in the maintenance of a blood supply for developing pre-cancerous and invasive oral lesions.

TNFalpha and IL10 SNPs act together to predict disease behaviour in Crohn's disease

BACKGROUND

The cytokines tumour necrosis factor (TNF)alpha and interleukin (IL)10 have been implicated in the pathogenesis of Crohn's disease (CD), with increased concentrations reported in patients with active disease. However, limited data exist on their effects on disease phenotype in the same population. Certain single nucleotide polymorphisms (SNPs) within the promoter region of the IL10 (-1082G/A, -592C/A) and TNFalpha (-308G/A, -857C/T) genes have been associated with altered levels of circulating IL10 and TNFalpha.

METHODS

We conducted an Australian based case-control study (304 CD patients; 231 healthy controls) of these four SNPs. Further investigation of two SNPs was conducted using a logistic regression analysis.

RESULTS

We identified a possible association of both IL10 SNPs and TNFalpha-857 with CD. Further investigation of a relationship with disease severity showed a significant association of higher producing IL10-1082G and TNFalpha-857C alleles with stricturing behaviour, which was strongest when these alleles were combined and persisted after multivariate analysis (p = 0.007; odds ratio (OR) 2.37, 95% CI 1.26 to 4.43). In addition, the TNFalpha-857CC genotype was independently associated with familial CD (p = 0.03; OR 3.12; 95% CI 1.15 to 8.46).

CONCLUSION

These two SNPs may help to predict disease behaviour in CD patients, which may be clinically useful in shaping treatment of the disease at an earlier stage.

General and oral health implications of cannabis use

Cannabis, commonly known as marijuana, is the most frequently used illicit drug in Australia. Therefore, oral health care providers are likely to encounter patients who are regular users. An upward trend in cannabis use is occurring in Australia, with 40 per cent of the population aged 14 and above having used the drug. There are three main forms of cannabis: marijuana, hash and hash oil, all of which contain the main psychoactive constituent delta-9-tetrahydrocannabinol (THC). Cannabis is most commonly smoked, however it can be added to foods. THC from cannabis enters the bloodstream and exerts its effects on the body via interaction with endogenous receptors. Cannabis affects almost every system of the body, particularly the cardiovascular, respiratory and immune systems. It also has acute and chronic effects on the mental health of some users. Therefore, chronic abuse is a concern because of its negative effects on general physical and mental health. Cannabis abusers generally have poorer oral health than non-users, with an increased risk of dental caries and periodontal diseases. Cannabis smoke acts as a carcinogen and is associated with dysplastic changes and pre-malignant lesions within the oral mucosa. Users are also prone to oral infections, possibly due to the immunosuppressive effects. Dental treatment on patients intoxicated on cannabis can result in the patient experiencing acute anxiety, dysphoria and psychotic-like paranoiac thoughts. The use of local anaesthetic containing epinephrine may seriously prolong tachycardia already induced by an acute dose of cannabis. Oral health care providers should be aware of the diverse adverse effects of cannabis on general and oral health and incorporate questions about patients' patterns of use in the medical history.

Kupffer cells do not play a role in governing the efficacy of liposomal mitoxantrone used to treat a tumor model designed to assess drug delivery to liver

A tumor model designed to assess liposome-mediated drug delivery to liver has been used in an attempt to better understand the mechanism of activity of liposomal mitoxantrone, a liposomal anticancer drug formulation that appears to be uniquely effective in treating this tumor model. Reductions in liposomal mitoxantrone accumulation in the liver were achieved either by use of poly(ethylene)glycol (PEG)-modified lipids or by methods designed to deplete liver phagocytes, a method referred to as hepatic mononuclear phagocytic system (MPS) blockade. A 2-fold reduction in mitoxantrone delivery to the liver was obtained using a mitoxantrone formulation with PEG-modified lipids, and a 3-fold reduction was obtained when liposomal mitoxantrone was given to animals pretreated to induce hepatic MPS blockade. Results demonstrate that the liposomal mitoxantrone formulation prepared with PEG-modified lipids was significantly less active than the formulations that did not contain PEG lipids, with median survival times of 17 days and 100% 60-day survival, respectively. In contrast, hepatic MPS blockade had no effect on the therapeutic activity of 1,2-dimyristoyl phosphatidylcholine/cholesterol (DMPC/Chol) mitoxantrone (100% 60-day survival). These data suggest that the hepatic MPS does not play a role in mediating the therapeutic activity of DMPC/Chol mitoxantrone in the treatment of liver localized disease. Results with formulations prepared with a PEG-stabilized surface, however, suggest that nonspecific methods to decrease liposome cell interactions inhibit the therapeutic activity of DMPC/Chol mitoxantrone.

An investigation of language used by children to describe discomfort during dental pulp-testing

AIM

Studies of the descriptions of pain by children have neglected their linguistic development, therefore estimates of dental pain in children may not be accurate. This study sought (1) to identify words chosen by children to describe dental pain and (2) to establish the effect of linguistic development on that description.

SAMPLE

Seventy-eight consecutive children between the ages of 5 and 13 years attending a paediatric dental clinic.

METHOD

Each child completed the WORD reading comprehension test. They then underwent a pulp test and a simulated pulp test, administered by a dentist in a counterbalanced order, of a healthy primary canine or permanent incisor, according to the child's age. To describe each test, the children had to (1) select words from a list of 58 read by the experimenter and (2) give ratings on scales representing 'sore' and 'tingly'.

RESULTS

Analysis of variance confirmed that the children chose more words for the pulp test than for the simulated test (P < 0.001); the former also elicited higher ratings for 'sore' and 'tingly'. The numbers of words chosen were transformed by a square root constant to ensure a normal distribution. Multiple regression analysis then showed that (1) the better the children's reading comprehension, the fewer words they chose, possibly because they were less inclined to choose unfamiliar words, and (2) the older they were, the more words they chose, possibly because of having more experience of pain. There were similar findings for ratings of 'sore' and 'tingly'.

CONCLUSIONS

To assess children's experience of pain (1) they need to be presented with a list of words like the ones in this study, (2) the numbers of words chosen by them would represent the severity of pain, and (3) those numbers need to be adjusted for the children's reading comprehension and age.

Guided imagery: a strategy for improving relationships and human interaction

Guided imagery, rather than being a revolutionary complementary or alternative therapy, has been utilised for centuries to alleviate suffering and promote wellness. Its efficacy has been studied and documented in physical, psychological and spiritual dis-ease. This article reviews relevant literature supporting the premise that guided imagery is a strategy that can be used for improving therapeutic relationships and is an example of holistic health care.

A model for patient participation in quality of life measurement to improve rehabilitation outcomes

Health-related quality of life (HRQOL) measurement is being used to assess end-stage renal disease (ESRD) patients' functional status and well-being from the patient's perspective. Research shows that HRQOL can screen for patients at high risk for death, hospitalization, treatment adherence, and depression. This study investigated whether patient goal setting and interdisciplinary collaboration and support could increase HRQOL scores in ESRD patients on chronic maintenance hemodialysis. Differences were found to be statistically significant in two of the MOS Short Form 36 (SF-36) categories (role physical and role emotional) following the intervention at the 95% confidence interval using a t-test statistic. This indicates that the intervention had a positive impact on patient perceptions of their health status. Eighty-seven percent indicated that there had been at least some progress made in reaching the goal. The results of this study support the utilization of HRQOL data at the facility level to improve patient's perceptions of their health status. A further study is needed to examine the long-term impact on HRQOL and other patient outcome measures through consistent use of this intervention.

Recognizing and caring for the medically compromised child: 3. Disorders affecting the gastro-intestinal tract and human immunodeficiency virus infection

Oral manifestations of gastro-intestinal disease are commonly under-diagnosed. This paper is the third in the series entitled 'Recognizing and Caring for the Medically Compromised Child' and seeks to facilitate the process of diagnosis and management of disorders affecting the gastro-intestinal tract in terms of both oral and gut signs and symptoms. This paper concludes with a section devoted to the recognition of HIV disease in paediatric patients, both orally and generally, and its implications for management within the dental surgery.

Paracrine induction of stem cell renewal by LIF-deficient cells: a new ES cell regulatory pathway

The propagation of pluripotential mouse embryonic stem (ES) cells is sustained by leukemia inhibitory factor (LIF) or related cytokines that act through a common receptor complex comprising the LIF receptor subunit (LIF-R) and the signal transducer gp130. However, the findings that embryos lacking LIF-R or gp130 can develop beyond gastrulation argue for the existence of an alternative pathway(s) governing the maintenance of pluripotency in vivo. In order to define those factors that contribute to self-renewal in ES cell cultures, we have generated ES cells in which both copies of the lif gene are deleted. These cells showed a significantly reduced capacity for regeneration of stem cell colonies when induced to differentiate, confirming that LIF is the major endogenous regulatory cytokine in ES cell cultures. However, self-renewal was not abolished and undifferentiated ES cell colonies were still obtained in the complete absence of LIF. A differentiated, LIF-deficient, parietal endoderm-like cell line was derived and shown to support ES cell propagation via production of a soluble, macromolecular, trypsin-sensitive activity. This activity, which we name ES cell renewal factor (ESRF), is distinct from members of the IL-6/LIF family because (i) it is effective on ES cells lacking LIF-R; (ii) it is not blocked by anti-gp130 neutralizing antibodies; and (iii) it acts without activation of STAT3. ES cells propagated clonally using ESRF alone can contribute fully to chimaeras and engender germline transmission. These findings establish that ES cell pluripotency can be sustained via a LIF-R/gp130-independent, STAT-3 independent, signaling pathway. Operation of this pathway in vivo could play an important role in the regulation of pluripotency in the epiblast and account for the viability of lifr -/- and gp130 -/- embryos.

The relationship between census-derived socio-economic variables and general practice consultation rates in three town centre practices

BACKGROUND

The relationship between socio-economic factors and consultation rates is important in determining resource allocation to general practices.

AIM

To determine the relationship between general practice surgery consultation rates and census-derived socio-economic variables for patients receiving the same primary and secondary care.

METHOD

A retrospective analysis was taken of computerized records in three general practices in Mansfield, North Nottinghamshire, with 29,142 patients spread over 15 electoral wards (Jarman score range from -23 to +25.5). Linear regression analysis of surgery consultation rates at ward and enumeration district levels was performed against Jarman and Townsend deprivation scores and census socio-economic variables.

RESULTS

Both the Townsend score (r2 = 59%) and the Jarman score (r2 = 39%) were associated with surgery consultation rates at ward level. The Townsend score had a stronger association than the Jarman score because all four of its component variables were individually associated with increased consultations compared with four out of eight Jarman components.

CONCLUSIONS

Even in practices not eligible for deprivation payments there were appreciable differences in consultation rates between areas with different socio-economic characteristics. The results suggest that the variables used to determine deprivation payments should be reconsidered, and they support suggestions that payments should be introduced at a lower level of deprivation and administered on an enumeration district basis.

The use of mediation to manage patient-staff conflict in the dialysis clinic

The use of mediation to manage a disruptive incident between a staff nurse and a hemodialysis patient is the focus of this multidisciplinary case review. The growing interest in techniques to manage disruptive patient behavior in the dialysis clinic is analyzed. A mediation model designed for the dialysis clinic is presented for the reader. This case presentation also examines the experience of conflict from several perspectives including the patient, the nurse, the nurse manager, and the social worker. This discussion is intended to provide the reader with support for viewing conflict as unavoidable in the chronic dialysis treatment environment and for enlisting the support of the patient when responding to disruption in the treatment relationship.

Factors influencing the response to advertisements for general practice vacancies

OBJECTIVES

To investigate the extent of problems in recruiting general practitioners and to determine which practice characteristics affect recruitment--in particular, to see if practices with deprived patients have more recruitment problems.

DESIGN

Postal questionnaire survey in August 1995.

SUBJECTS

489 consecutive practices that had advertised for a partner in the BMJ from January to April 1995.

MAIN OUTCOME MEASURES

The number of applicants, the practices, satisfaction with their quantity and quality, and whether a successful appointment was made.

RESULTS

442 (90%) practices replied. 262 practices (60%) were not very satisfied or very dissatisfied with the number of applications they received; 15 (3%) received no applications. There was a significant difference in the number of applications received by practices in different NHS regions. The 32 practices with the highest proportions of patients eligible for deprivation payments received a median of five applicants compared with 10 for practices without deprivation.

CONCLUSION

There is a widespread problem in recruiting general practitioners. Recruitment is hardest in areas with the greatest health needs.

A multivariate analysis of factors related to the mortality of blunt trauma admissions to the North Staffordshire Hospital Centre

OBJECTIVE

To identify characteristics of blunt trauma admissions associated with mortality and to derive a linear logistic model for predicting the probability of mortality.

DESIGN

A prospective observational study.

MATERIALS AND METHODS

Data were collected on blunt trauma patients admitted via the Accident and Emergency Department, North Staffordshire Hospital Centre. Univariate and multivariate analyses were performed of potential risk factors associated with mortality.

MEASUREMENTS AND MAIN RESULTS

The main outcome variable was survival or death occurring in hospital within 30 days of admission. Injury Severity Score, age, Revised Trauma Score, and place of injury (road traffic, home, or elsewhere) were independently related to mortality. The effect of age on mortality was best described using three categories: 0-64 excluding 15-24, 15-24, 65+. The survival probability model suggests that a person whose injury occurs in the home has a lower probability of survival than a patient with similar age and trauma scores who is involved in a road traffic accident. A model validation check indicated good agreement between model predictions and patient outcomes.

CONCLUSIONS

The authors propose that use of this model may provide a more accurate evaluation of the mortality of British trauma admissions than would be obtained using models based on data from American trauma cases.

Delay, discriminatory, and modality specific neurons in striatum and pallidum during short-term memory tasks

The function of the striatum and its integrative capacities is addressed. The activity of single neurons in behaving Macaca mulatta is studied. Two new classes of neurons were found. In the striatum, but not in the pallidum, these neurons were visual modality specific. These neurons may represent a conjunction of sensory, mnemonic and motor information, and may be concerned with decisions about the emission or withholding of movements. The frontal dysfunction hypothesis of cognitive deficits in Parkinson's disease is considered.

Orientation illusions induced by briefly flashed plaids

Orientation illusions which occur when a vertical grating is surrounded by a plaid can be induced either by one of the plaid's orthogonal component gratings or by a virtual axis of symmetry of the plaid, whichever is nearest vertical. In six experiments in which such illusion displays were flashed for durations between 15 and 405 ms, it was found that when these two-dimensional illusions are induced by a component grating (direct effects) the illusions increase monotonically as duration decreases, from 1 degree-2 degrees to about 6 degrees-7 degrees, over this range. Effects induced by axes of symmetry (indirect effects), in contrast, begin to occur only at longer durations: for short exposures, illusions are directionally opposite and large, similar to direct effects. These results suggest that only plaid-component-selective mechanisms operate at the shortest exposure durations and that additional time is required to extract more global higher-order pattern structure. The data are discussed in relation to sustained and transient mechanisms and also with respect to recent reports of more global processing mechanisms in extrastriate cortex and related data on one-dimensional tilt illusions.

Pattern orientation, not motion, determines the two-dimensional tilt illusion

In the usual tilt illusion (TI) configuration, an inducing stimulus which has a single orientation is used psychophysically to explore orientation analysis in the human visual system. Recently, this approach has been extended to the use of inducing stimuli which have two orientations. Such a two-dimensional (2-D) stimulus permits investigation of the low-level analysis of visual patterns. Prior experimentation has left it unclear whether it is the spatial or the motion properties of a moving crossed-grating plaid which determine two-dimensional tilt illusions (2-D TIs) because these two parameters previously were perfectly correlated. In the present experiments pattern orientation and motion were decoupled. It is shown that 2-D TIs are determined by the spatial properties of an inducing annulus and not by its motion properties. The results also support the existence of a mechanism which extracts axes of symmetry, and which is difficult to account for in terms of local cross-orientation domain inhibition.

Two-dimensional tilt illusions induced by orthogonal plaid patterns: effects of plaid motion, orientation, spatial separation, and spatial frequency

Tilt illusions occur when a drifting vertical test grating is surrounded by a drifting plaid pattern composed of orthogonal moving gratings. The angular function of this illusion was measured as the plaid orientation (and therefore its drift direction) varied over a 180 degrees range. This was done when the test and inducing stimuli abutted and had the same spatial frequency, and when the test and inducing stimuli either differed in frequency by an octave, or were spatially separated by a 2 deg blank annulus, or both differed in frequency and were also separated by the annulus (experiments 1-4). The obtained angular function was virtually identical to that obtained previously with the rod and frame effect and other cases involving orthogonal inducing components, with evidence for illusions induced both by real-line components and by virtual axes of symmetry. Although the magnitude of the illusion was very similar in all four experiments, there was evidence to suggest that largest real-line effects occurred in the abutting same-frequency condition, with a pattern of results similar to that obtained previously with the simple one-dimensional tilt illusion. On the other hand, virtual-axis effects were more prominent with gaps between test and inducing stimuli. A fifth, repeated-measures, experiment confirmed this pattern of results. It is suggested that this pattern-induced tilt effect reflects both striate and extrastriate mechanisms and that the apparent influence of spatially distal virtual axes of symmetry upon perceived orientation implies the existence of AND-gate mechanisms, or conjunction detectors, in the orientation domain.

Spatial and orientation specific integration in the tilt illusion

Lateral inhibition across a population of cells in visual cortex which are tuned to local orientation has been proposed and widely accepted as a basic process in the analysis of contour in the visual field. The tilt illusion is usually explained in terms of this inhibition. Experiments are reported which cast new light on the analysis of visual orientation. It is shown that tilt illusions may be obtained with very thin inducing annuli which are spatially remote from the test figure. In experiments in which remote crossed-grating plaids were used, an illusion which was pattern (global) rather than component (local) selective was seen. It is difficult to account for these observations in terms of local inhibitory mechanisms. Rather, the results support the existence of a secondary mechanism which is involved in basic orientation analytic processes. The relevance of these observations to models of visual contour analysis is discussed.

The differential effects of brief exposures and surrounding contours on direct and indirect tilt illusions

Four experiments in which logarithmic intervals between 25 and 1600 ms were used for stimulus duration in tests for the tilt illusion are reported. It is demonstrated that the direct and the indirect tilt illusions both increase in magnitude inversely with length of stimulus presentation. The data suggest that whereas the direct effect peaks with a value of about +7 degrees at the shortest flash duration used (25 ms), peak indirect effects (of about +2 degrees) do not occur at this duration. In addition, whereas direct effects level out after 100 ms stimulus exposure times, to the usual magnitude obtained with long presentations (about +2 degrees), indirect effects reach their standard magnitude (-0.5 degrees to -1.0 degrees) later, at exposures of about 400 ms. Even at very short flash durations, a luminance square frame surrounding the illusion display reduces the indirect effect by two thirds of its magnitude but has no effect at all on the direct effect. It is suggested that direct effects arise early in visual processing, in area V1, where there are transient mechanisms and where corruption of orientation analysis by the inducing grating would occur prior to later, extrastriate, global analysis of the surrounding peripheral frame. Indirect effects, on the other hand, may arise later, along the sustained parvocellular colour-form pathway, where more global processing occurs and susceptibility to surrounding fields might be expected.

Psychophysical evidence for an extrastriate contribution to a pattern-selective motion aftereffect

A stationary vertical test grating appears to drift to the left after adaptation to an inducing grating drifting to the right, this being known as the motion aftereffect (MAE). Pattern-specific motion aftereffects (PSMAEs) induced by superimposed pairs of gratings in which the component gratings drift up and down but the observer sees a single coherent plaid drifting to the right have been investigated. Two experiments are reported in which it is demonstrated that the PSMAE is tuned more to the motion of the pattern than to the orientation and direction of motion of the component gratings. However, when subjects adapt to the component gratings in alternation, aftereffect magnitude is dependent upon the individual grating orientations and motion directions. These results can be interpreted in terms of extrastriate contributions to the PSMAE, possibly arising from the middle temporal area, where some cells, unlike those in striate cortex (V1), are tuned to pattern motion rather than to component motion.

The different mechanisms of the direct and indirect tilt illusions

Both the tilt illusion and aftereffect exhibit indirect effects under certain conditions: these are negative (assimilation) effects which occur with large (70-90 deg) angular separations between test and inducing gratings. They are opposite in direction to the positive, and much larger, contrast effects which occur at smaller (10-15 deg) separations. Evidence from six experiments shows that stimulus manipulations which reduce direct effects have little or no effect on indirect effects and vice versa, suggesting that the two effects have different determinants. It is proposed that direct effects arise from lateral inhibitory interactions between populations of neurones in striate cortex and that indirect effects occur at a higher level, possibly in areas concerned with stimulus-specific interactions beyond the classic receptive field. The implications of the data for theories of the tilt illusion are considered.

Possible neural substrates for orientation analysis and perception

Recent research into the response properties of extrastriate visual cortical mechanisms has revealed single-cell functional organisation which closely parallels certain global and apparently emergent properties of psychophysical observation. An attempt is made to relate previous data on orientation illusions and aftereffects to these extrastriate mechanisms and new data which cannot be explained adequately by V1 (striate) orientation channels are discussed. Conversely, properties of cells in areas such as V3, V4, MT, and others seem to provide an obvious neural substrate for global interactions. It is suggested that psychological 'explanations' couched in terms of 'hypotheses' or 'cognitive problem solving' lack heuristic value, and that, in contrast, the properties of extrastriate cells can suggest novel experimental psychophysical paradigms which are designed to probe these higher-order global mechanisms more or less selectively.

The influence of auditory stimulation on a visual oblique effect

It has previously been reported by Smets that there is an increase in the magnitude of the monocular oblique effect when a 70 dB(A), 1 kHz acoustic stimulus is presented contralaterally, but not ipsilaterally, to the viewing eye. This finding was interpreted as one which provided difficulties both for data-driven models of information processing and for the cortical simple cell explanation of the oblique effect. There are several logical and methodological difficulties in Smets's paper, and in the two experiments reported here the effect found by Smets was not replicated. The failure to observe the effect was robust under conditions that maximised the possibility of neural interaction. It is concluded that acoustic stimulation does not affect the magnitude of the oblique effect.

The role of a functionally distinct IgM anti-type III pneumococcal polysaccharide (SIII) in low-dose paralysis to SIII in mice

Prior treatment (priming) with a weakly immunogenic dose of Type III pneumococcal polysaccharide (SIII) results in the development of an antigen-specific state of unresponsiveness termed low-dose paralysis which is believed to be mediated by suppressor T cells. The present findings show that the passive administration of functionally distinct non-complement-fixing (NCF) IgM anti-SIII antibodies either in monoclonal form or from protein-A absorbed immune serum could significantly suppress the direct plaque-forming cell (PFC) response to an immunogenic dose of SIII administered concurrently. The degree of suppression was comparable with that induced by low-dose paralysis. Low-dose paralysis was consistently induced in athymic (nude) mice 4 days, but not 3 days, after priming with a low dose of SIII, and was associated with the delayed appearance of NCF-IgM anti-SIII in the serum of athymic mice. In contrast, low-dose paralysis was readily induced in normal BALB/c mice 3 days after priming when NCF-IgM anti-SIII antibodies were present. Comparable inhibiton of the direct anti-SIII PFC response was observed when Concanavalin A (Con A) or NCF-IgM anti-SIII serum was administered with SIII antigen. That Con A and NCF-IgM anti-SIII together did not produce additive suppression was attributed to the adsorption of NCF-IgM anti-SIII antibodies to Con A. Complement-dependent single radial haemolysis mediated by CF hybrid IgM/A or CF-IgM anti-SIII serum was blocked by monoclonal NCF-IgM or IgA anti-SIII antibodies and indicated that each of the antibodies was specific for the same SIII-determinant. Evidence is presented to show that low-dose paralysis in the CF-IgM response to SIII is not mediated by suppressor T cells but can be attributed to highly avid NCF-IgM anti-SIII antibodies, formed preferentially to low doses of SIII, being able to reduce the immunogenicity of SIII administered subsequently. We propose that low-dose paralysis to SIII is the result of an immunobiological function of highly avid NCF-IgM anti-SIII antibodies which not only confer resistance against capsulated pneumococci but preferentially bind soluble SIII-antigen to reduce its immunogenicity and thereby protect specific CF-IgM positive B cells from being rendered tolerant by direct contact with higher doses of SIII antigen.

Regulation of immunity and tolerance to type III pneumococcal polysaccharide (SIII) by functionally distinct IgM anti-SIII antibodies

When BALB/c mice and athymic (nude) mice are injected intraperitoneally (i.p.) with pneumococcal type III polysaccharide (SIII), their antibodies as measured by passive haemagglutination (HA) are inhibited more easily by high doses of SIII than antibody measured by passive haemolysis (HL). The HA activity, due mainly to a highly avid non-complement-fixing (NCF) type of IgM, was further distinguished from the HL activity (CF-IgM, or CF-IgM plus CF hybrid IgM/A anti-SIII antibodies) by the failure of the NCF-IgM anti-SIII to bind to protein-A of Staphylococcus aureus (Sa). High-dose tolerance in the HL anti-SIII antibody response of BALB/c and athymic mice was induced only in the absence of circulating NCF-IgM anti-SIII antibodies. The presence of NCF-IgM anti-SIII antibodies formed to multiple daily increasing amounts of SIII, commencing with 0.01 micrograms SIII, decreased the magnitude of the HL anti-SIII response to subsequent daily increments of SIII antigen injected into BALB/c and athymic (nude) mice. Thus, the effect on the HL anti-SIII response was independent of T-cells. The concomitant administration of NCF-IgM anti-SIII rendered SIII less tolerogenic in primed mice. In contrast to the HL activity, the NCF-IgM anti-SIII antibodies were induced to low doses of SIII, conferred protection against viable pneumococci, but did not precipitate the soluble antigen in agar. It is proposed that immune paralysis (as defined by the failure of SIII-injected mice to resist pneumococcal challenge) is not necessarily a condition of total unresponsiveness but is due to an absence of protective NCF-IgM anti-SIII antibodies. Thus, immune paralysis can co-exist with either the presence or absence of non-protective CF-IgM or CF-IgM/A anti-SIII antibodies.

Serum IgM/A, IgA and functionally distinct IgM anti-type III pneumococcal polysaccharide (SIII) antibodies in BALB/c and athymic (nude) mice

The influence of hereditary absence of thymus upon the synthesis of IgA, complement-fixing (CF) hybrid IgM/A, CF-IgM and non-CF-IgM antibodies to pneumococcal type III polysaccharide (SIII) injected into BALB/c and athymic nude mice was studied. Techniques involved the differential absorption of the serum antibodies by protein-A of Staphylococcus aureus (Sa), coprecipitation in gels with 125I-SIII and autoradiography. IgM/A anti-SIII activity was not demonstrable in nude mice but was produced in significant amounts, by day 5, in BALB/c mice injected with SIII. By day 8, nude mice produced more IgA anti-SIII antibodies than BALB/c mice injected with the same antigen. IgA anti-SIII antibodies were not detected in either strain 5 days after SIII administration. The absence of hybrid IgM/A anti-SIII antibodies in athymic mice, prior to the appearance of monotypic IgA anti-SIII antibodies at day 8, suggests that IgM/A and not IgA synthesis is largely T cell-dependent. The evidence also implies that hybrid IgM/A antibody production, maximal on day 5 in BALB/c mice, and absent from nude mice, is not an essential product in the switching from IgM to IgA synthesis. Both strains of mice produced comparable amounts of complement-fixing (CF)-IgM and NCF-IgM anti-SIII antibodies, with the production of non-complement-fixing (NCF)-IgM anti-SIII in athymic mice being delayed. Results indicate that attempts to quantitate the levels of IgA by assays incorporating anti-IgA anti-sera may be complicated by the presence of IgM/A hybrid antibody.(ABSTRACT TRUNCATED AT 250 WORDS)

Enrichment of differentiated, stellate astrocytes in cerebellar interneuron cultures as studied by GFAP immunofluorescence and autoradiographic uptake patterns with [3H]D-aspartate and [3H]GABA

A study was undertaken to correlate the morphology expressed by astroglial cells in post-natal cerebellar, interneuron-enriched primary cultures, and the ability of these cells to accumulate putative neurotransmitter amino acids. Astroglial cell morphology, as studied by GFAP immunofluorescence staining showed considerable changes during the culture period considered (up to 12 days in vitro). While the total number of GFAP-positive cells decreased with time (cell multiplication was prevented by cytosine arabinoside), a progressive enrichment of stellate astrocytes (cells bearing multiple radially arranged processes) and a striking increase in size of these cells was noted. In 12 DIV cultures stellate astrocytes accounted for 70-80% of the astrocytes present, and could reach a diameter of over 300 micron. The L-glutamate analogue, [3H]D-aspartate, was avidly taken up by all the astrocytes, independently of their shape and stage of differentiation. Astroglial cell morphology as delineated by [3H]D-aspartate autoradiography was identical to that evidenced by GFAP staining. On the other hand, [3H]GABA was accumulated in substantial amounts only by the stellate astrocytes, that is by the cells showing greater morphological differentiation. Astrocytes of other shapes were only lightly labelled by [3H]GABA in 2 DIV and 5 DIV cultures, and even less at later stages. Even within the stellate astrocyte population, the extent of [3H]GABA labelling was very variable, from one cell to another. Autoradiographic examinations and the determination of the IC50s for GABA uptake inhibitors consistently indicated that the GABA transport system present in stellate astrocytes did not have the features generally attributed to a glial transport system. In fact, beta-alanine was a very weak inhibitor, while nipecotic acid and ACHC were strongly inhibitory; DABA inhibitory potency fell somewhere in between. [3H]GABA uptake into the inhibitory interneurons present in the cultures showed similar sensitivity to GABA transport inhibitors.

The recovery of anaerobic bacteria from swabs

When a standard sample of simulated exudate containing known numbers of anaerobic bacteria was taken up on a swab and plated on solid medium, the number of colonies subsequently cultured represented a very small proportion of the original sample. Evidence is produced that the apparent loss is not primarily attributable to inactivation on the swab but rather to retention of organisms on the swab. This was demonstrable with Clostridium welchii and with Bacteroides species that have hitherto been regarded as relatively oxygen-sensitive.When stock strains of Bacteroides species were held for some hours on swabs, some progressive loss of viability was demonstrable. A measure of protection was afforded when these organisms were held aerobically on blood agar medium, but a very exacting anaerobe and some wild strains of faecal anaerobes showed gradual inactivation under these conditions.These findings may have important implications in relation to currently employed bacteriological sampling procedures with swabs in clinical practice.