Pneumococcal vaccine trials in Papua New Guinea: relationships between epidemiology of pneumococcal infection and efficacy of vaccine

Field trials in Papua New Guinea have shown that pneumococcal capsular polysaccharide vaccine protects children less than 2 years of age from death due to acute lower respiratory infections (ALRI). The vaccine appears to reduce mortality by preventing bacteremia. Evidence suggests that highly invasive "adult" pneumococcal serotypes are comparatively more important as a cause of ALRI in developing countries where ALRI-related mortality is higher than in North America. Capsular polysaccharide vaccines are more likely to be immunogenic for these serotypes than for the "pediatric" serotypes. The evaluation of pneumococcal vaccines in areas where mortality is high should have the highest priority. For such trials investigators should, at minimum, define epidemiologic circumstances in terms of (1) the invasive serotypes of pneumococci, (2) the protective levels of antibody, (3) the antibody response to vaccination, and (4) the general immune status of the population.

Relationships between growth and acute lower-respiratory infections in children aged less than 5 y in a highland population of Papua New Guinea

One hundred fifty-six children in the highlands of Papua New Guinea aged less than 5 y, studied for a total of 7019 child-weeks, had an incidence of 1.3 episodes per child-year of acute lower-respiratory-tract infections (ALRIs). There was a marked age trend with an incidence of almost three times this average for children aged less than 6 mo. Those with low weight-for-age or low height-for-age had a higher ALRI incidence rate, with no evidence of cutoffs above which nutritional status had no effect; there was no association between low weight-for-height and increased risk of ALRI. A slow weight gain was not a significant risk factor in the short term but weight gain was reduced during episodes of ALRI.

Restricted T-cell receptor V beta gene usage by myelin basic protein-specific T-cell clones in multiple sclerosis: predominant genes vary in individuals

Recent studies in experimental autoimmune encephalomyelitis as a model for multiple sclerosis (MS) have demonstrated limited heterogeneity in T-cell antigen receptors (TCR) specific for myelin basic protein (MBP). To investigate restricted beta-chain variable-region (V beta) gene usage in humans, we analyzed TCR gene rearrangements in two lines and 34 MBP-specific T-cell clones that were isolated from five MS patients and two healthy subjects. The T cells were characterized for their specificity to MBP epitopes and HLA-restricting molecules. We demonstrate here that MBP-specific T-cell clones from these different MS patients and healthy individuals, in contrast to T cells from rodents, display a more diverse V beta gene usage as evidenced by their TCR V beta gene rearrangements. However, the different MBP-specific T-cell clones isolated from each individual MS patient showed a common V beta gene usage, suggesting individual-specific TCR restriction. Out of 16 MBP-specific clones derived from a single MS patient, 12 clones (75%) utilized the V beta 15 gene for their TCR gene rearrangement. MBP-specific clones isolated from four other MS patients also showed a consistent tendency for a predominant, but different, TCR V beta gene rearrangement. These results suggest a TCR heterogeneity among MBP-specific T-cell clones from different individuals but a limited TCR V beta gene usage among MBP-specific T-cell clones of the same individual. The predominant V beta gene used by the MBP-specific T-cell clones studied here was not found to correlate with the epitope specificity of T cells or with their restricting HLA molecule. These findings may support the possibility of intervention with monoclonal antibodies to specific V beta gene products as an approach to immune therapy of MS but also imply the necessity for an individual-specific immunotherapeutic approach.

Antibodies to pneumococcal polysaccharides in pneumonia and response to pneumococcal vaccination in young children in Papua New Guinea

Antibodies against pneumococcal polysaccharides were measured by ELISA in Papua New Guinean children with pneumonia aged 0-14 months, in age-matched healthy Papua New Guinean controls and in healthy expatriate children living in Papua New Guinea. At 0-5 months of age, the IgG antibody titres against six of the eight polysaccharides measured were significantly lower in pneumonia patients than in both control groups. Antibody titres in 6-14-month-old Papua New Guinean controls were significantly lower than in control Papua New Guineans aged 0-5 months for five of the eight polysaccharides tested. In the 6-14-months age group the antibody titre was significantly lower in pneumonia patients than in controls for only one polysaccharide. For seven of the eight serotypes tested, antibody levels in expatriate controls did not decline with age. Antibody responses of Papua New Guinean children aged 6-18 months to a 23-valent pneumococcal vaccine were serotype dependent. Fold increases in response to the vaccine were greatest for the IgA isotype. IgG antibody responses were greater than three fold to four of the eight serotypes tested.

Effect of pneumococcal vaccine on morbidity from acute lower respiratory tract infections in Papua New Guinean children

The effect of a 14-valent pneumococcal polysaccharide vaccine on morbidity from acute lower respiratory tract infection (ALRI) was determined in a randomized double-blind controlled trial in children under the age of 5 years living in the Paupa New Guinea highlands. The vaccine did not protect against mild ALRI. Vaccine efficacy in the study as a whole was 28% for moderate/severe ALRI, which was not statistically significant though consistent with the significant effect on mortality. Children entered the trial in five separate cohorts 4 months apart. The incidence of disease and vaccine efficacy varied between cohorts and with age. There was no vaccine effect in the first cohort, which had a much higher proportion of older children. The effect was greatest and statistically significant among those groups encountering an epidemic of moderate and severe ALRI at a young age. It was therefore in children at the most vulnerable age in times of greatest incidence of disease that the vaccine had its most potent effect. It is postulated that the efficacy of pneumococcal vaccine is dependent on the predominant invading serotypes in the period after vaccination, the age at which children develop immunocompetence to specific vaccine serotypes, and the levels of naturally acquired specific immunity already present in children at the time of vaccination, and that for all of these conditions there will be a cohort effect.

Event-related potential components N1, P2 and P3 to rare and frequent stimuli in intellectually impaired neurological patients

Event-related potentials (ERPs) and attention performance data were collected in an auditory odd-ball paradigm from 24 intellectually impaired neurological patients, and compared with normal controls (n = 19). For the ERP components N1, P2 and P3, reference-independent measures (latency, global field power, current density at Cz, location of extreme potential, centroid location) were determined for the target stimulus and for the preceding and the following two "frequent" stimuli. In 8 of the 45 measures obtained, patients and controls differed significantly. To target stimuli, patients had shorter N1 latency and smaller current density, more posterior P2 location and longer P3 latency; to immediately following "frequent" stimuli, longer P2 latency; and to preceding and both following "frequent" stimuli, smaller P2 current density. Attention performance was significantly worse for the 15 patients who scored on at least one of the eight ERP measures above normal range than for the other 9 patients. Decreased N1 latency to targets is viewed as failure to activate normal attentional capacity; changed P2 location suggests activation of deviant neuronal populations in response to targets; and increased post-target P2 latency suggests abnormal persistence of induced state change.

Impact of active immunisation against enteritis necroticans in Papua New Guinea

Enteritis necroticans, known locally as pigbel, has been a major cause of illness and death among children in the highlands of Papua New Guinea. After a successful trial of active immunisation against the beta toxin of the causative organism, Clostridium perfringens type C, immunisation of children was begun in 1980. The effects of the immunisation programme on pigbel admissions in 3 of the 5 major highland hospitals were assessed. In each of the centres studied the proportion of admissions due to enteritis necroticans dropped significantly after immunisation was introduced (p less than 0.001) and hospital admissions for pigbel in 1984-86, when immunisation was well established, were less than one fifth of previous figures.

Bacterial colonization of the upper respiratory tract and its association with acute lower respiratory tract infections in Highland children of Papua New Guinea

Acute lower respiratory tract infection (ALRI) is the major cause of death among children in Papua New Guinea. This longitudinal study reports the bacteriologic findings for children observed in their hamlets. A total of 1,449 nasal swab specimens from 158 children less than 5 years of age who were studied intensively for 18 months were examined. Non-serotypable strains of Haemophilus influenzae were isolated from 91% of specimens, and serotypable strains were isolated from 35% (8% H. influenzae type b) of specimens. All children had acquired Streptococcus pneumoniae by the age of 3 months. The most frequently occurring serotypes of S. pneumoniae were 6, 19, and 23. Children more frequently carried invasive pneumococci during an episode of ALRI than when they were healthy. Also, children more frequently carried serotypable strains of H. influenzae during the 2 weeks preceding an episode of ALRI than when they were healthy. Between-children analyses showed that children who were susceptible to attacks of ALRI and those who were not susceptible had similar rates of carriage of bacteria.

Detection of Streptococcus pneumoniae and Haemophilus influenzae type b antigens in the serum and urine of patients with pneumonia in Papua New Guinea: comparison of latex agglutination and counterimmunoelectrophoresis

Latex agglutination (LA) was compared with counterimmunoelectrophoresis (CIE) for the diagnosis of pneumonia due to Streptococcus pneumoniae or Haemophilus influenzae type b in children less than 6 years old in Papua New Guinea. Neither LA nor CIE was sufficiently sensitive for the detection of pneumococcal antigens. CIE was superior to LA but had a sensitivity of only 60% (six of 10) in concentrated urine and a specificity of 90% (54 of 60). LA for the detection of H. influenzae type b had a sensitivity of 100% (eight of eight) relative to that of blood culture and a specificity of 99% (112 of 113) when urine diluted fivefold was tested, as compared with a sensitivity of 100% (nine of nine) and a specificity of 92% (56 of 61) in undiluted urine. Undiluted and concentrated urine specimens were unsuitable for LA because of the many false-positive reactions that resulted from nasal carriage of H. influenzae type b and nasal carriage of the cross-reactive S. pneumoniae type 6. CIE for the detection of H. influenzae type b had a sensitivity of only 44% (four of nine) in concentrated urine.

Diversity of outer membrane protein profiles of nontypable Haemophilus influenzae from children from Papua New Guinea and the Philippines

We determined capsular serotypes and, with use of SDS-PAGE, patterns of outer membrane proteins (OMP) of Haemophilus influenzae isolates from specimens of blood, lung, or CSF from children with acute respiratory tract infections or meningitis who were hospitalized in Papua New Guinea or the Philippines. Among 72 isolates from Papua New Guinea, 72% were type b, 14% were other encapsulated serotypes, and 14% were nontypable. The respective frequencies among 43 isolates from the Philippines were 56%, 7%, and 37%. The type b isolates could be subdivided into at least eight outer membrane subtypes, most of which have been described previously. In contrast, OMP profiles of the nontypable H. influenzae isolates from children in both countries were highly heterogeneous. These results differ markedly from those previously found for isolates from children with acute respiratory tract infections in Pakistan, for which encapsulated H. influenzae strains other than serotype b were not observed; 95% of type b isolates were of a single OMP subtype; and nontypable isolates showed evidence of clonal restriction. Candidate vaccines for use in developing countries as protection against disease caused by H. influenzae will need to include both capsular and noncapsular antigens and investigators must take into consideration regional differences among strains.

N1 and P2 of frequent and rare event-related potentials show effects and after-effects of the attended target in the oddball-paradigm

The effects of serial order of the stimuli on event-related potentials (ERPs) in an auditory oddball paradigm with 700 ms ISI were studied in 19 normals, recording from Fz, Cz, Pz and combined ears. N1 and P2 to the last preceding frequent stimulus, the rare (attended target) stimulus, and the following two frequent stimuli were evaluated using 6 reference-independent measures: latency (time of maximal potential range between any two locations), amplitude of maximal potential range, global field power, vertex (Cz) current source density, location of extreme potential, and location of potential centroid. Exploratory statistics were used to determine differences of interest. Eighteen of the 36 comparisons for N1, and 4 of the 36 comparisons for P2 showed double-ended P-values of less than 5%, 6 times the overall incidence expected by chance. For the ERP evoked 1400-ms post-target, global field power and location of N1, and latency and location of P2 still differed from pre-target ERP values. This suggests a new and temporarily persisting change of brain state following the target stimulus. The first 3 measures showed 'undershoot' below pre-target levels, contradicting a simple 're-habituation' model. All 6 measures of N1, as well as latency and location of P2 increased or anteriorized for the attended target; the location changes indicate that processing the attended target activates additional neural processes, and does not only increase the activation of the same neural processes which operate on frequent stimuli.

Intracerebral dipole source localization for FFT power maps

The method treats Fast Fourier Transforms (FFTs) of multichannel EEGs so that they can be used for intracerebral source localizations. For each frequency point, the FFT results are entered into a sine-cosine diagram. Into the diagram's entry constellation (FFT constellation), a straight line (single dipole model) is fitted which produces the least square deviation sum between the entry positions and their orthogonal projections onto the straight line. The map described by the voltages between the projected positions on the straight line is the single source 'FFT approximation' of the FFT constellation. The FFT approximation map is used for dipole source localization. The squared FFT approximation map and the squared map of the forward solution of the computed dipole (power maps) closely resemble the original power map.

Viruses associated with acute lower respiratory tract infections in children from the eastern highlands of Papua New Guinea (1983-1985)

This study, conducted at Goroka Hospital from January 1983 to June 1985, examined the viruses identified in nasopharyngeal aspirates (NPA) and urines collected from 716 hospitalised children with moderate or severe pneumonia, in NPA from 170 children with mild pneumonia treated as outpatients and in NPA from a control group of 428 children attending the outpatient department of Goroka Hospital suffering from minor ailments other than upper or lower respiratory tract infections. One or more viruses were identified from 68%, 51% and 43% of children with moderate or severe pneumonia, mild pneumonia and the control group, respectively. One-third of viruses were identified in conjunction with another virus in both control and sick children. Viral identification rates were highest in children under 1 year of age. Cytomegalovirus, adenoviruses, respiratory syncytial virus (RSV), measles and rhinoviruses were the most frequently identified viruses. RSV was associated with mild as well as moderate and severe disease. No virus was associated with an increased risk of death. Annual epidemics of RSV occurred during the wet season. An epidemic of influenza A virus and also influenza B virus and 3 epidemics of parainfluenza 3 virus occurred during the study period. The high viral identification rates in this study suggest a high frequency of transmission associated with the social structure and environment of Papua New Guinean highland villages and high population mobility.

[Synthesis and anticonvulsant action of propranolol derivatives with a tertiary nitrogen atom]

Tertiary derivatives of the beta-receptorblocker propranolol were synthesized and pharmacologically tested for anticonvulsive activities. The results show that it is possible, to separate the beta-receptor blocking from the anticonvulsive activities by modifying the chemical structure.

Past, present and future of topographic mapping

Traditional EEG and EP analysis is trace-oriented. When mapping became popular, results of waveform analysis were mapped. Increased exposure to brain field maps has begun to orient analysis to the spatial aspects. Different maps must be generated by different neuronal populations; this offers direct key to the analysis of higher brain function. Space-oriented data reduction selects maps with optimal signal/noise ratio using Global Dissimilarity index. Classification and statistics of map landscapes uses extracted descriptors (locations of extrema or centroids) or three-dimensional dipole models. Map classification leads to adaptive segmentation of evoked or spontaneous map series into functional micro-states, the putative building blocks of perception and cognition.

Clinical signs and risk factors associated with pneumonia in children admitted to Goroka Hospital, Papua New Guinea

This study examined the clinical signs and symptoms in 897 children aged under 5 years presenting with pneumonia to Goroka Hospital in the highlands of Papua New Guinea between June 1982 and July 1985. The usefulness of the signs in predicting severity of disease was determined and risk factors for severe disease were identified. While cyanosis and poor feeding were the strongest predictors of death, bronchial breathing, grunting, and nasal flaring also significantly increased the risk of dying. First-born children, children under 1 year of age, females, malnourished children, and children with symptoms for more than 7 days were at increased risk of severe disease and of dying. Fever alone did not increase the risk of dying unless it was present for more than 7 days. These clinical signs of severity and risk factors may be used to improve the efficiency of health education programmes, for both health workers and mothers, aimed at reducing childhood mortality from pneumonia.

Segments of event-related potential map series reveal landscape changes with visual attention and subjective contours

Changes of the event-related potential (ERP) map landscape with time and condition were used to identify qualitative changes in the ERP generating process which are indicative of a change in the functional microstate. Twelve subjects attended or ignored unilaterally presented visual stimuli with and without subjective contours. ERP map series from 16 electrodes were adaptively segmented to identify periods of stable map landscape, using topographic descriptions (map maxima and minima). Attention as well as the subjective contours changed the map topography and increased the map amplitude. From 170 to 380 msec, they had similar effects on the antero-posterior map topography. Topographic differences between the effects of attention and subjective contours were also present, but affected mainly the left-right topography. The results are in line with the notion of attentional involvement in subjective contour perception and show that global modulation of exogenous brain activity cannot account for topographic changes with attention or with subjective contours. They further establish space-oriented data reduction as a powerful tool to identify components and to distinguish among hypotheses about the underlying generator processes.

[Testing of a modified Toxoplasma immunosorbent-adsorption assay (IgM-ISAGA) for the detection of Toxoplasma-specific IgM antibodies in the routine laboratory]

Testing of a modified Toxoplasma immunosorbent adsorption assay (IgM-ISAGA) for proving of Toxoplasma specific IgM antibodies. The IgM-ISAGA was assessed for the possibility of its application as a routine method in the serodiagnosis of toxoplasmosis and was compared with the IgM-IFT. On examination for specific on 136 sera, no false-positive results were obtained in the IgM-ISAGA in contrast to 5 false-positives in the IgM-IFT, due to the presence of rheumatoid factor. Its sensitivity was tested on 162 sera. The IgM-ISAGA reacted positive in 89 cases, the IgM-IFT in only 51. It was concluded that the IgM-ISAGA is a simple, sensitive and highly specific test applicable in smaller laboratories as a confirmatory reaction in the control of toxoplasmosis during pregnancy and in confirmation of connatal toxoplasmosis.

Intracerebral dipole sources of EEG FFT power maps

The described method opens a way to compute intracerebral source localizations of ongoing EEG activity. A sine-cosine diagram of the Fourier-transformed data is constructed for each frequency point, forming a "FFT constellation" of entries. Into the FFT constellation of each diagram, a straight line is fitted which produces the least squared deviation sum between the original entry positions and their orthogonal projections onto that line. The map landscape described by the voltages between the projected positions ("FFT approximation") is the least error compromise landscape of all possible landscapes during the paradigmatic cycle of the given FFT frequency. The map thus constructed can be used in the usual dipole source localization procedures. There is one for each FFT frequency point. The squared forward solution of the fitted dipole source and the squared FFT approximation map are "power maps" which are very similar to the original power map. For an average-reference power map with two peaks, the source tends to lie between the peaks; a power map with one peak might show closely neighboring maximal and minimal potential values in the FFT approximation, indicative of a tangential source close to the surface.

Androgens inhibit proliferation of human peripheral blood lymphocytes in vitro

The effect of sex hormones on human lymphocytes was examined in vitro on cell cultures of human peripheral blood mononuclear cells (HPBM). Cells were stimulated using T- and B-cell mitogens, and hormones in physiological (nM) or pharmacological (microM) concentrations were added. Proliferation was determined by measuring the incorporation of tritiated thymidine. It was found that both testosterone and dihydrotestosterone, in physiological concentrations, can attenuate DNA synthesis. The effect was dose dependent in that pharmacological concentrations of both testosterone and dihydrotestosterone caused a strong inhibitory effect on proliferation of in vitro cultured HPBM. However, cell cultures of a few individuals were insensitive to the androgens even at pharmacological concentrations. Also, no difference could be detected in the response between cultured cells of females and males. Although a slight reduction in antibody production was evident in pokeweed mitogen-stimulated cultures, in the presence of both testosterone and dihydrotestosterone, it was, however, not statistically significant.

EEG alpha map series: brain micro-states by space-oriented adaptive segmentation

The spontaneous EEG, viewed as a series of momentary scalp field maps, shows stable map configurations (of periodically reversed polarity) for varying durations, and discontinuous changes of the configurations. For adaptive segmentation of map series into spatially stationary epochs, the maps at the times of maximal map relief are selected and spatially described by the two locations of maximal and minimal (extreme) potentials; a segment ends if over time an extreme leaves its pre-set spatial window. Over 6 subjects, the resting alpha EEG showed 210 msec mean segment duration; segments longer than 323 msec covered 50% of the total time; the most prominent segment class (1.5% of all classes) covered 20% of total time (prominence varied strongly over classes; not all possible classes occurred). Spectral power and phase of averages of adaptive and pre-determined segments demonstrated the adequacy of the strategy, and the homogeneity of adaptive segment classes by their reduced within-class variance. It is suggested that different segment classes manifest different brain functional states exerting different effects on information processing. The spatially stationary segments might be basic building blocks of brain information processing, possibly operationalizing consciousness time and offering a common phenomenology for spontaneous activity and event-related potentials. The functional significance of segments might be modes or steps of information processing or performance, tested, e.g., as reaction time.

Commercial latex agglutination tests for detection of Haemophilus influenzae type b and Streptococcus pneumoniae antigens in patients with bacteremic pneumonia

The validity of commercial latex agglutination kits for detection of Haemophilus influenzae type b and Streptococcus pneumoniae antigens in serum and urine specimens was studied. We tested serum and urine specimens from 44 patients with bacteremic pneumonia (23 S. pneumoniae, 13 H. influenzae type b, 11 other) with commercial latex agglutination kits (Directigen, Bactigen) for S. pneumoniae and H. influenzae type b antigens. All specimen samples were randomized and read blindly by two readers. Interreader reproducibility was 100%. The sensitivity and specificity of both kits for H. influenzae type b antigens in serum and urine were greater than 90%. None of the 24 urine samples from S. pneumoniae bacteremic patients were positive by either kit, although 6 ng of type 3 polysaccharide could be detected in spiked urine. Sensitivity for S. pneumoniae antigens in serum was 27% for Directigen and 38% for Bactigen. Specificity for S. pneumoniae antigens in serum was 95% for Directigen and 74% for Bactigen. The results suggest that the kits are useful in diagnosing H. influenzae type b pneumonia. However, the commercially available S. pneumoniae reagents tested appear to have limited utility for diagnosing S. pneumoniae pneumonia because both kits lack sensitivity and Bactigen lacks specificity, as well.

Role of immunological factors in male infertility. Immunohistochemical and serological evidence

Immunological deposits in the testis and circulating antibodies to spermatozoa are presented as a possible explanation for infertility in man. Testicular biopsy specimens from infertile patients (N = 52) as well as from fertile controls (N = 6) were analyzed immunohistochemically by using semithin sections. Immunoglobulin deposits were found in the testes of 21 patients. Antibody deposits were observed on the seminiferous tubule wall, on germ cells or in the interstitium. In two cases, the C3 complement component was detected on the tubular wall and in one case on atypical spermatogonia. Deposits of immunoglobulin class G were found most frequently, and were often attached to the seminiferous tubule wall. In addition, the occurrence of circulating antisperm antibodies in the sera of these patients was examined by a recently developed method, the immunobeads binding test. A significant number of patients with normal spermatogenesis had antibodies that exhibited a strong binding reaction to spermatozoa as observed by the immunobeads binding test. It is suggested that at least two different immunological mechanisms may be involved in pathological infertility: an immunoglobulin deposit, induced locally in the testis, in a manner specifically against the germ cells and the seminiferous tubular basement membrane, or in a manner nonspecifically against seminiferous tubular wall, and asystemically induced immunoglobulin production which is directed against spermatozoal antigens.

Analysis of the autoimmune response in an 'in situ' carcinoma of the testis

Immune response in a patient with an in-situ seminoma of the testis was studied. Immunohistochemical examination of the testicular biopsy demonstrated remarkable intracellular and membraneous accumulation of IgG antibodies in the atypical spermatogonia. Using FITC-conjugated Concanavalin A, an abnormally high binding of Concanavalin A was detected in the transformed cells. Circulating antibodies directed against an antigenic determinant (60 kD) which is expressed on normal human spermatozoa and lymphocytes were found only in the patient's serum and not in 500 control sera. The role and possible diagnostic value of this autoimmune reactivity in testicular malignancies are discussed.

Autoimmune phenomena and cytogenetic findings in a patient with carcinoma (seminoma) in situ

Routine examination of a testis biopsy from a patient with oligospermia and a large varicocele in his left testicle and who was childless for over 2 years showed carcinoma in situ (CIS) with atypic spermatogonia in his right testicle. Immunohistochemical investigations of this tissue revealed large intracellular deposits of immunoglobulin G (IgG) restricted to the atypical cells. By blot-immunobinding test of the patient's serum, circulating antibodies against a molecule with an approximate molecular weight of 60 kD were found. Such antibodies were not found in a total of over 500 infertile patients and fertile controls examined. This molecule was extracted from pooled normal human sperms by trypsin digestion and eluted out of a sodium dodecyl-sulphate polyacrylamide gel (SDS-PAGE). This elute is currently used for raising monoclonal antibodies. An analysis of the direct chromosome preparations from the testis biopsy showed both numerical and structural chromosomal aberrations. This might indicate that the atypical cells have already been transformed and hence could be considered as malignant.

Pneumococcal vaccine prevents death from acute lower-respiratory-tract infections in Papua New Guinean children

In three double-blind placebo-controlled trials of pneumococcal capsular polysaccharide vaccines against death from acute lower-respiratory-tract infections (ALRI), children were vaccinated at 6 months to 5 years of age. The efficacy of the vaccines against ALRI as the sole cause of death was estimated at 59% in children vaccinated when younger than 5 years (p = 0.008) and 50% in children vaccinated when younger than 2 years (p = 0.043). Mortality from all causes was 19% less in the vaccinated group.

Averaging of spectral power and phase via vector diagram best fits without reference electrode or reference channel

A method is proposed to average results of Fourier analysis over epochs without assigning zero amplitude values to any electrode or zero phase values to any channel. The Fourier sine and cosine values of each electrode define its entry location into a vector diagram for the frequency component. The entry constellations thus formed are translated so that the mean of all entries (the virtual average reference which is the location of best fit) is at the centre of each constellation, and then they are rotated around the means into angles of best fit so that the sum of the squared distances between corresponding entries is minimal. The method leads to non-ambiguous mean results, with variance information for all recording points. Approaches for the assessment of the constellations, their transformation into field maps, and the problems with conventional phase measurements vs. real electrodes are discussed. The virtual average reference (spatial high pass filter) is proposed for assessing the time sequence (phase differences) between entry points, thus describing the internal structure of the constellations without bias and without reference to a zero phase point. Comparison of voltage and current density result constellations and consideration of reference-independent descriptors of the scalp field potential maps support the validity of the average reference for the approach.

Event-related potentials of the brain and cognitive processes: approaches and applications

Event-related potentials (ERPs) are recordings of the electric field which the brain produces in fixed time-relation to an event. ERPs open a time and space window onto covert steps of brain information processing which need not be accompanied by overt behavior or private experiences. ERPs are the only noninvasive method which resolves the dynamic pattern of events in the human brain down to the millisecond range. Early ERP components are valuable tools in clinical testing of the afferent sensory systems in the absence of anamnestic or clinical pathology. Later components (e.g. the 'P300') index intermediate, covert steps of information processing and have clarified the time course and the contingencies of processes in attention, decisions and language. ERP waveshapes show electric potential differences between two recording points. Conventional analysis often ignores the fact that there is no unique voltage amplitude or signal latency for a single point, and interprets ambiguous results. Although important insights have emerged with such strategies, full utilization of ERP data requires unambiguous ERP assessment and converging evidence from neuropsychological and cognitive experimentation. Sequences of field distribution maps offer an unbiased display of ERP data. Spatial analysis yields unambiguous values for further comprehensive assessment, and should precede analysis over time. Examples of spatial analysis have shown that different ERP field configurations follow the presentation of noun and verb meaning of homophone words; that the ERP effects to subjective contours resemble those to attention in time course and topography; that the 'cognitive' P300 component reflects the specific stimulus location; and that subliminal information influences the configuration of late ERP fields.

Blot-immunobinding test for the detection of anti-sperm antibodies

A blot-immunobinding test was used to detect anti-sperm antibodies in human sera and to identify the corresponding auto- or iso-antigens on human sperm. A high proportion of sera at a 1:100 dilution from fertile persons, as well as infertile patients, contains antibodies reactive with sperm. This phenomenon might be physiological. At 1:2,000 dilution, a higher binding capacity was detected in the sera from infertile groups, but a few fertile persons were also positive. Antibodies to a single antigenic determinant with Mr of approximately 14,000 were found in a significantly higher proportion among males with unexplained infertility.

Oral rehydration therapy: combining anthropological and epidemiological approaches in the evaluation of a Papua New Guinea programme

The impact of an oral rehydration therapy (ORT) programme for diarrhoeal disease was evaluated by means of continuing surveillance of this Papua New Guinea population. Mortality from diarrhoeal disease in the under-fives fell from 3.3/1000/annum before the ORT programme to 1.3/1000/annum after the programme had become established. However there is evidence that the attendance rate for diarrhoea treatment has begun to fall from its previously high level. These trends are explicable in terms of the target population's expectations of Western treatments. The implications of these findings for the design and evaluation of similar health programmes are discussed.

Evoked potential correlates of figure and ground

Brain potentials averaged during the viewing of an alternating, positive and negative "hidden man" puzzle picture were averaged from 8 subjects before and after they learned to recognize the figure. After figure recognition in comparison to before recognition, there was significantly more evoked positivity at 64/96 ms latency, and more negativity at 224/256 ms and at 352-480 ms latency over parietal areas during the viewing of the positive picture (recognizable as face) referred to the values obtained during viewing of the negative picture (not recognizable as face). It is hypothesized that separate physiological changes might reflect learned meaningfulness of the figure (which entails increased attention) and figure extraction from ground.

[Temporal dynamics of spectral EEG parameters during nocturnal sleep in healthy adults]

We recorded all-night sleep EEG's of six healthy male volunteers (age 23 to 29 years) from F3, F4, P3, P4, 01, 02, T3, T4 to Cz as reference electrode. Power and coherence spectra were calculated for ten frequency bands from 0-30 cps. We examined their changes through the different cycles of all sleep stages. In general there was a decrease in power as well as in coherence from the 1st to the 4th cycle of the different sleep stages with some variations depending on frequency and derivation. The highest power was most often in the 1st cycle in stages REM, 2, 3 and 4, whereas in stage 1 it was most often in the 2nd cycle. The trends in power from the 1st to the 4th cycle were similar for stages REM and 2 with a power decrease from the 1st to the 2nd cycle. In stage 1 there was most often a power increase between these two cycles. Coherence maxima were for stages REM, 1, 2 and 3 most often in the 1st cycle, for stage 4 most often in the 2nd cycle. The coherence trends were similar for stages 1 and 2 with a decrease most often from the 1st to the 2nd cycle. In stage REM the decline was more constantly found from the 2nd to the 3rd cycle. The power trends were more consistent than the coherence trends. We found more often similar power changes from the 1st to the 4th cycle of a specific sleep stage than similar coherence changes.

EEG assessment of brain activity: Spatial aspects, segmentation and imaging

High temporal resolution and sensitivity to index different functional brain states makes the EEG a powerful tool in psychophysiology. Its full potential can now be utilized since recording technology and computational power for the large data masses has become affordable. However, basic traditional strategies in EEG need reviewing. Conventional, spontaneous or evoked EEG traces which are used for various complex analyses give ambiguous information on EEG power (amplitude) and phase for a given point on the scalp. Principally, analysis should first be done over space, then over time, to avoid ambiguities or pre-selections. First or second spatial derivative computations can provide "reference-free" data for analyses over time. We propose to use direct, spatial approaches for the analysis of the scalp EEG field distributions when simultaneous recordings in several EEG channels can be examined. The ambiguity of the conventional EEG waveshapes results in different, equally "correct" scalp maps of EEG power of the same multichannel data for different reference electrodes. An exception are scalp maps of EEG power computed against the common, average reference, as they are related to the reference-free spatial distribution (maps) of the maximal and minimal (extreme) field values over time, and thus are directly interpretable in terms of net orientation of the generator process. A proposed, reference-free EEG segmentation into epochs of periodically stationary spatial distributions of the mapped scalp EEG fields uses the locations of maximal and minimal (extreme) field values at each moment in time as classifiers, and thus avoids the priviledging of two arbitrarily chosen recording points in the field.

Spatial analysis of evoked potentials in man--a review

Steps in brain information processing are reflected on the scalp as changes of the electric potential which is evoked by the stimulus. However, for a given recording point on the scalp, there is no absolute amplitude or phase information of the electric brain potential. This means that the shape of an evoked potential waveform which is recorded from a given scalp location crucially depends on the location of the chosen reference. Only unbiased results of evoked potential data evaluation can be hoped to elucidate or map successfully into information processing models established by other methods, e.g. behavior measurements. Conventional recordings vs a common reference contain only one of many possible sets of waveshapes. In order to avoid ambiguities or bias of results, the entire evoked potential data set firstly must be analysed over space, and reference-independent parameters must be extracted. For each time point, the spatial distribution of the potentials is viewed as field map. The parameter extraction in a direct approach at each time point includes, e.g. locations of field peaks and troughs, voltage and gradient between them, and global electrical field power; or, parameters via the first or second spatial derivative of the electric field. In the second step, changes of these reference-independent field measurements are analysed over time. At component latency which is defined by maximal, global field power or by voltage range, mapped field distributions can be compared using maximal/minimal field value locations or complete maps. Significantly different field configurations establish the activity of non-identical neural generators. Classification of the field configurations (examination of orbits of field extrema over time) leads to the segmentation of series of field maps (multichannel EP data) into short epochs of stationary spatial configurations (i.e. spatially characterized components) with equal consideration of all recording points, and without the amplitude criterion. The application of these principles to the following problems is discussed: comparison of evoked potentials between different analysis times, in particular pre-stimulus and post-stimulus electric brain states; zero baseline for measurement; reference electrode; identification of evoked components in time and space. Illustrations of these problems include functional differences of input-analysing sub-systems, and the topography of cognition- and speech-related electric brain activity.

Fuzzy clustering of EEG signal and vigilance performance

An automatic method for classification of EEG data, based upon segmentation of the signal using the autoregressive model and decision making in fuzzy environment, is described. The classification is applied to explore the relations between EEG states during waking, and vigilance performance studied through auditory choice reaction time. The average auditory choice reaction time measured during occurrences of "alpha" segments was significantly shorter than that measured during occurrences of "nonalpha" signal segments. A significant negative correlation was also found between the segments auditory choice reaction time and the segments spectral power in the alpha or beta frequency band.

Monocular and binocular evoked average potential field topography: upper and lower hemiretinal stimuli

Scalp potentials evoked by monocular and binocular 2/s checkerboard reversals with checks of 56 or 14 min were recorded from four midline electrodes between inion and 7.5 cm above inion vs a common anterior reference in 31 normals. The electrode location and latency of the evoked maximal occipitally positive potential difference between any 2 of the 5 electrodes, between 80 and 140 ms latency was determined in each run. Mean maximum locations over subjects for upper hemiretinal, binocular stimuli were more anterior than for monocular stimuli; for lower hemiretinal stimuli, inverted location differences were found. Binocular responses also had shorter latencies than monocular responses. Since area 18 is more anterior to 17 for upper, more posterior to 17 for lower hemiretinal projection to cortex, the results suggest that neurons which respond only if both eyes are simultaneously stimulated are more frequent in higher than lower order visual areas.

A single dose of benzodiazepine hypnotics alters the sleep EEG in the subsequent drug-free night

All-night spectral analysis of the sleep EEG was used to study the effect and after-effect of a single bedtime dose of flunitrazepam (2 mg), flurazepam (30 mg) or triazolam (0.5 mg) in healthy young males. In the night of drug treatment all 3 hypnotics reduced the EEG slow waves and enhanced the activity in the frequency range of sleep spindles. In the subsequent drug-free night, the latter changes were no longer present after triazolam, whereas the reduction of slow wave activity persisted after all compounds.