Transplantation of transduced nonhuman primate CD34+ cells using a gibbon ape leukemia virus vector: restricted expression of the gibbon ape leukemia virus receptor to a subset of CD34+ cells.

The transduction efficiencies of immunoselected rhesus macaque (Macaca mulatta) CD34+ cells and colony-forming progenitor cells based on polymerase chain reaction (PCR) analysis were comparable for an amphotropic Moloney murine leukemia virus (MLV) retroviral vector and a retroviral vector derived from the gibbon ape leukemia virus (GaLV) packaging cell line, PG13. On performing autologous transplantation studies using immunoselected CD34+ cells transduced with the GaLV envelope (env) retroviral vector, less than 1% of peripheral blood (PB) contained provirus. This was true whether bone marrow (BM) or cytokine-mobilized PB immunoselected CD34+ cells were reinfused. This level of marking was evident in two animals whose platelet counts never fell below 50,000/microliter and whose leukocyte counts had recovered by days 8 and 10 after having received 1.7 x 10(7) or greater of cytokine-mobilized CD34+ PB cells/kg. Reverse transcriptase(RT)-PCR analysis of CD34+ subsets for both the GaLV and amphotropic receptor were performed. The expression of the GaLV receptor was determined to be restricted to CD34+ Thy-1+ cells, and both CD34+ CD38+ and CD34+ CD38dim cells, while the amphotropic receptor was present on all CD34+ cell subsets examined. Our findings suggest that, in rhesus macaques, PG13-derived retroviral vectors may only be able to transduce a subset of CD34+ cells as only CD34+ Thy-1+ cells express the GaLV receptor.

Inward rectifier K+ channel from human heart and brain: cloning and stable expression in a human cell line.

We have cloned the human homologue of the inward rectifier K+ channel from both heart and brain tissue (HHBIRK1). The human clones were identical to each other in their coding regions and were highly homologous to the mouse macrophage (IRK1) channel. The inward rectifier currents from human and mouse clones were characterized using a novel strategy for stable ion channel expression in a human cell line. The permeability of the expressed inwardly rectifying channels was greater for K+ than for Rb+, whereas no current was observed when K+ was replaced by Na+. A prominent time- and voltage-dependent block was observed in the presence of Ba2+, whereas a small decay in the steady-state current was observed with millimolar concentrations of Na+. Single-channel conductances of 49.1 +/- 3.3 pS (n = 6) and 40.2 +/- 2.5 pS (n = 3) (P = 0.005) were obtained for the HHBIRK1 and IRK1 clones, respectively. These results indicate that sequence dissimilarities between human and mouse inward rectifier K+ channels may have significant functional consequences.

Correlations between cardiorespiratory measures in normal infants and victims of sudden infant death syndrome.

Coordination between physiological measures (i.e., the tendency for measures to co-vary with each other) develops with maturation in the infant. We hypothesized that correlations between cardiorespiratory measures would increase with maturation in normal infants and that infants destined to die of sudden infant death syndrome (SIDS) would show lower correlations than those of age-matched controls. Twenty-two recordings of electrocardiogram and respiratory movements were obtained from infants who subsequently succumbed to SIDS and compared with 66 recordings from control infants. Each 1-min epoch of data was sleep-state classified. Median heart and respiratory rate, respiratory variability, and median extent of three types of heart rate variation were determined for each epoch, and the minute-by-minute correlations between seven pairs of parameters were determined for quiet sleep, rapid eye movement sleep, and waking in each recording. Most cardiorespiratory measures showed correlations that increased with age; the correlation coefficients for these measures tended to be lower in SIDS victims than in controls prior to 2 weeks of age. The correlations between heart rate and heart rate variability became lower with maturation; correlations between these measures tended to be higher in the SIDS victims. In all analyses showing significant maturational trends, the SIDS victims showed "less mature" correlations than those of the controls.

Development of heart rate variation over the first 6 months of life in normal infants.

Development of heart rate variation in three frequency ranges was examined during sleep-walking states in normal infants over the first 6 mo of life. Extent of all three types of heart rate variation decreased from 1 wk to 1 mo of age. Extent of respiratory sinus arrhythmia increased from 1 mo to 6 mo during all sleep-waking states, with the increase most pronounced during quiet sleep. Variation in two bands of lower frequencies showed increases in extent from 1 to 3 mo, then a slowing or reversal of the increase between 3 and 4 mo of age. During rapid eye movement sleep, the two types of lower frequency heart rate variation decreased in extent from 3 through 6 mo of age. These results suggest that alterations in autonomic control of heart rate occur at several time periods over the first 6 mo of life and that these alterations may have an effect only on particular types of heart rate variation and only during particular sleep-waking states. The diminution of all three types of heart rate variation at 1 mo may indicate a reduction in vagal tone at this age.

Heart rate variation in normal infants and victims of the sudden infant death syndrome.

Infants who later succumb to the sudden infant death syndrome (SIDS) exhibit lower overall heart rate variability during waking than do other infants. This study attempts to determine which type or types of heart rate variation are reduced in SIDS victims. Long-term recordings of heart rate and respiration were obtained from normal infants and infants who later died of SIDS, and heart rate variation in three frequency bands was examined: respiratory sinus arrhythmia (periods 0.9-3.0 s), 'mid-frequency' (periods 4.0-7.5 s) and 'low-frequency' (periods 12-30 s). All three types of heart rate variation were diminished in SIDS victims under 1 month of age during waking and rapid eye movement (REM) sleep compared with controls. Partitioning heart rate effects showed that in waking, and to a lesser extent in REM sleep, the reduction in all types of heart rate variation exceeded that which would have been predicted based on higher heart rates in SIDS victims. No heart rate-independent reduction in any type of heart rate variation was observed in quiet sleep. This state-dependent reduction in three types of heart rate variation could indicate an abnormality of autonomic control mechanisms during waking and REM sleep in infants who later succumb to SIDS.

Spectral analysis assessment of respiratory sinus arrhythmia in normal infants and infants who subsequently died of sudden infant death syndrome.

Reduced heart rate variability has been found in infants who later succumb to the sudden infant death syndrome (SIDS). To determine whether respiratory sinus arrhythmia, a major component of heart rate variability, is also reduced in SIDS victims, nighttime portions of eighteen 24-h recordings of ECG and respiration from infants who later died of SIDS and 52 recordings from control infants were assessed using spectral analysis. Two aspects of respiratory sinus arrhythmia were examined: "extent" (the absolute heart rate variation at the respiratory frequency) and "coherence" (the degree to which heart rate follows respiration regardless of the absolute amount of variation). Respiratory parameters were used to classify each 1-min epoch as quiet sleep, rapid eye movement sleep, waking, or indeterminate state. Median extent and coherence values across the night were then computed for each sleep-waking state. Two-way (group X state) repeated measures analysis of variance tests were then used to compare respiratory sinus arrhythmia values for 13 SIDS victims and 13 control infants matched by postnatal age, birth weight, sex, and gestational age. Extent of respiratory sinus arrhythmia was significantly lower in the SIDS victims across all sleep-waking states, a finding that persisted after adjusting for heart rate. Coherence values did not differ significantly. These results suggest that even before the time of maximal risk for the syndrome, SIDS victims, as a group, differ from controls in the extent to which cardiac and respiratory activity couple, and this difference is independent of basal heart rate.

Cardiac and respiratory patterns in normal infants and victims of the sudden infant death syndrome.

Victims of the sudden infant death syndrome (SIDS) have higher overall heart rates prior to death than do control infants (1). The objective of this study was to partition these heart rate differences by state and to identify any state-dependent differences in heart rate variability and respiratory rate and variability. Twenty-two recordings of electrocardiogram (ECG) and respiration from 16 infants who subsequently died of SIDS were compared with 66 recordings of age-matched control infants. Median cardiac and respiratory rate and variability were computed for each sleep state in each recording, and one-way analysis of variance tests were performed for each variable for infants less than 1 month and for infants greater than 1 month of age. Heart rate was higher in SIDS victims less than 1 month of age than in age-matched controls during all sleep-waking states. SIDS victims greater than 1 month showed higher heart rates during rapid eye movement sleep only. Heart rate variability was also diminished during waking in victims less than 1 month, but much of this difference could be attributed to increased heart rate. These results suggest that, as a group, SIDS victims differ physiologically from control infants and that these differences may be especially prominent during particular sleep-waking states.

Machine classification of infant sleep state using cardiorespiratory measures.

We examined the potential to classify sleep and waking state over the first 6 months of life in normal infants using only cardiac and respiratory measures. Twelve hour all-night polygraph recordings which included EEG, eye movement, whole body movement, facial muscle electromyographic, cardiac, and respiratory activity from 25 normal infants were collected at 1 week, and at 1, 2, 3, 4, and 6 months of age. Each minute of these recordings was classified into quiet sleep, waking, or rapid eye movement sleep by trained observers using EEG and somatic criteria. Respiratory rate and variability, heart rate and variability, and cardiac interbeat interval variation at respiratory and lower frequencies from 12 of the 25 infants were used as measures in discriminant analyses of sleep state for test on the 13 remaining infants. Using all 7 cardiac and respiratory measures, sleep states were classified with an accuracy approximating that attained by trained observers who had available all polygraph tracings (84.8% overall correct classification). Using only cardiac measures, the accuracy of classification decreased slightly, with an overall correct classification of 82.0%. Using only respiratory measures, the accuracy of classification diminished further, with an overall correct classification of 80.0%. Cardiac and respiratory measures provide quantifiable indications of sleep and waking states over the first 6 months of life in normal infants.