T cells translate individual, quantal activation into collective, analog cytokine responses via time-integrated feedbacks.

Variability within isogenic T cell populations yields heterogeneous 'local' signaling responses to shared antigenic stimuli, but responding clones may communicate 'global' antigen load through paracrine messengers, such as cytokines. Such coordination of individual cell responses within multicellular populations is critical for accurate collective reactions to shared environmental cues. However, cytokine production may saturate as a function of antigen input, or be dominated by the precursor frequency of antigen-specific T cells.

Distinct influences of peptide-MHC quality and quantity on in vivo T-cell responses.

The strength of T-cell receptor (TCR) stimulation and subsequent T-cell response depend on a combination of peptide-major histocompatibility complex (pMHC) density and potency. By comparing two different pMHC at doses yielding similar proliferation in vivo, we have highlighted unexpected differences in the qualitative and quantitative effects of TCR ligand. Measurements of cytokine sensitivity and two-photon imaging of T cell-dendritic cell (T-DC) interactions reveal discrimination between comparably weak stimuli resulting from either decreased pMHC potency or pMHC density.

Single-cell quantification of IL-2 response by effector and regulatory T cells reveals critical plasticity in immune response.

Understanding how the immune system decides between tolerance and activation by antigens requires addressing cytokine regulation as a highly dynamic process. We quantified the dynamics of interleukin-2 (IL-2) signaling in a population of T cells during an immune response by combining in silico modeling and single-cell measurements in vitro. We demonstrate that IL-2 receptor expression levels vary widely among T cells creating a large variability in the ability of the individual cells to consume, produce and participate in IL-2 signaling within the population.

Cardiac contraction affects respiratory airflow in the term newborn infant.

In studies in the newborn infant, it is often assumed that there are similarities in airflow in successive breaths, and, therefore, it is only necessary to measure parameters in a small number of breaths. However, other studies have shown considerable variability in breathing patterns in successive breaths. It was, therefore, decided to examine the variability in the patterns of airflow.

Optimization of inspiratory work in periodic breathing in infants.

In periodic breathing, there are repeated cycles of bursts of breaths separated by pauses several seconds long. We consider the mechanics of periodic breathing in human infants using calibrated traces of tidal volume and esophageal pressure recorded during the first few days after delivery. Each cycle of periodic breathing was analyzed in terms of the inspiratory time and beginning and end inspiratory volumes for each breath, the number of breaths in the cycle, and the total observed inspiratory work.

Thermal entrainment of heart rate in the preterm infant.

Using spectral analysis we have studied changes in the heart rate during periodic thermal stimulation of one foot of infants during quiet sleep. Twenty-two appropriately grown preterm infants were studied in the first 15 d after birth to quantify responses in comparison with previously reported term infants. Babies were stimulated at 0.

The deep breath vasoconstriction reflex--a new tool for autonomic assessment in infancy?

We describe the presence of the deep breath vasoconstriction reflex in the neonatal and postneonatal period in a group of 24 infants, of whom 11 were term and 13 were preterm. Our results suggest that the development of this reflex correlates to postnatal rather than postconceptional age. The reflex is suggested for future use in autonomic assessment of babies to define normal and abnormal development and in the assessment of infants thought to be at risk of Sudden Infant Death Syndrome (SIDS).

Effect of periodic thermal stimulus on heart rate in term newborn infant.

We studied heart rate changes in 25 term infants aged 1-7 days in quiet sleep during periodic thermal stimulation of one foot to widen the range of frequencies previously studied by others and to develop spectral analysis methods to quantify responses to thermal and other periodic sensory stimuli. The stimulation frequency was 0.10 Hz in all babies and ranged from 0.

Respiratory modulation of heart rate in newborn infants.

Spectral analysis was performed on ventilation and instantaneous heart rate data recorded in 15 term infants during quiet sleep in the first week after delivery, and in 11 of these infants during active sleep. There was a close relation between the main peaks of the ventilation spectra and the corresponding histograms of the reciprocals of Ttot. The spectra for instantaneous heart rate showed power at the rate of breathing (HF) and also at lower frequencies, 0.

Analysis of components of fetal breathing cycles.

The duration of the inspiratory phase (Ti) and the expiratory phase (Te) together with the relative amplitude (Amp) of successive breathing movements of the chest wall or abdominal wall were measured by real-time ultrasound in 12 fetuses of normal gestation. The observations were performed at 33-39 gestational weeks. The distributions of Ti, Te, the duration of the breathing cycle (Ttot), Amp and the ratios Amp/Ti and Ti/Te were all considerably skewed.

Oesophageal motor activity and sleep state in the newborn human infant.

Oesophageal pressure and ventilation were recorded during sleep in healthy full-term neonates with sleep state defined by one of two methods; in 35 infants by combined behavioural and electroencephalographic criteria, and in a further 13 infants by behavioural criteria alone. Spontaneous oesophageal contractions occurred in all infants during active sleep but rarely during quiet sleep. The transition from active to quiet sleep was accompanied by a gradual reduction in the frequency of these contractions.

Respiratory sinus arrhythmia in new-born infants.

1. Ventilation was measured in eleven healthy term infants during both quiet and active sleep, using the trunk plethysmograph, and instantaneous heart rate was derived from the electrocardiogram. Variations in individual respiratory and cardiac cycles were compared in each sleep state, and cross-correlations between ventilation and heart rate were used in the analysis of the data.

An estimation of intracranial blood flow in the new-born infant.

1. A non-invasive method for the estimation of the intracranial blood flow of the new-born infant is described, and results obtained with it are presented. 2.

Analysis of periodic changes in ventilation in new-born infants.

1. Ventilation was recorded in thirty term infants during the first week after delivery using the trunk plethysmograph, during periods of rapid eye movement sleep (r.e.

A new look at the protection of hemoglobin AS and AC genotypes against plasmodium falciparum infection: a census tract approach.

A total of 4,097 randomly selected children under 5 years in Accra, Ghana were investigated for Hb type, malarial parasite species, and parasite density. Even though malarial infection rates in this metropolitan population were lower as compared to holoendemic areas, the differential survival of Hb S carriers was confirmed. In addition, similar but less pronounced survival effects were seen in Hb C heterozygotes.

Prevalence of asbestos bodies in a necropsy series in East London: association with disease, occupation, and domiciliary address.

The prevalence of asbestos bodies was measured in lung sections in a necropsy series carried out at the London Hospital (1965-66) after exclusion of all known asbestos factory workers and cases of asbestosis and of mesothelioma. Associations were sought between the presence and number of asbestos bodies with the patients' sex, domiciliary address, occupation, industry, and diseases recorded at necropsy. Asbestos bodies were present in 42% of the 216 men in the series and in 30% of the 178 women.

The rate and depth of breathing in new-born infants in different sleep states.

1. Ventilation was recorded on ten male and ten female healthy full-term infants during the first week after delivery, using a trunk plethysmograph. Tidal volume (V(T)), respiration rate (f) and pulmonary ventilation (V) for each respiratory cycle were measured during periods of rapid eye movement sleep (REM) and during quiet sleep when eye movements were absent (NREM).