The role of CD27-CD70-mediated T cell co-stimulation in vasculogenesis, arteriogenesis and angiogenesis

BACKGROUND

T cells have a distinctive role in neovascularization, which consists of arteriogenesis and angiogenesis under pathological conditions and vasculogenesis under physiological conditions. However, the role of co-stimulation in T cell activation in neovascularization has yet to be established. The aim of this study was to investigate the role T cell co-stimulation and inhibition in angiogenesis, arteriogenesis and vasculogenesis.

METHODS AND RESULTS

Hind limb ischemia was induced by double ligation of the left femoral artery in mice and blood flow recovery was measured with Laser Doppler Perfusion Imaging in control, CD70^-/-, CD80/86^-/-, CD70/80/86^-/- and CTLA4^+/- mice. Blood flow recovery was significantly impaired in mice lacking CD70 compared to control mice, but was similar in CD80/86^-/-, CTLA4^+/- and control mice. Mice lacking CD70 showed impaired vasculogenesis, since the number of pre-existing collaterals was reduced as observed in the pia mater compared to control mice. In vitro an impaired capability of vascular smooth muscle cells (VSMC) to activate T cells was observed in VSMC lacking CD70. Furthermore, CD70^-/-, CD80/86^-/- and CD70/80/86^-/- mice showed reduced angiogenesis in the soleus muscle 10 days after ligation. Arteriogenesis was also decreased in CD70^-/- compared to control mice 10 and 28 days after surgery.

CONCLUSIONS

The present study is the first to describe an important role for T cell activation via co-stimulation in angiogenesis, arteriogenesis and vasculogenesis, where the CD27-CD70 T cell co-stimulation pathway appears to be the most important co-stimulation pathway in pre-existing collateral formation and post-ischemic blood flow recovery, by arteriogenesis and angiogenesis.

An unexpected intriguing effect of Toll-like receptor regulator RP105 (CD180) on atherosclerosis formation with alterations on B-cell activation

OBJECTIVE

In atherosclerosis, Toll-like receptors (TLRs) are traditionally linked to effects on tissue macrophages or foam cells. RP105, a structural TLR4 homolog, is an important regulator of TLR signaling. The effects of RP105 on TLR signaling vary for different leukocyte subsets known to be involved in atherosclerosis, making it unique in its role of either suppressing (in myeloid cells) or enhancing (in B cells) TLR-regulated inflammation in different cell types. We aimed to identify a role of TLR accessory molecule RP105 on circulating cells in atherosclerotic plaque formation.

APPROACH AND RESULTS

Irradiated low density lipoprotein receptor deficient mice received RP105(-/-) or wild-type bone marrow. RP105(-/-) chimeras displayed a 57% reduced plaque burden. Interestingly, total and activated B-cell numbers were significantly reduced in RP105(-/-) chimeras. Activation of B1 B cells was unaltered, suggesting that RP105 deficiency only affected inflammatory B2 B cells. IgM levels were unaltered, but anti-oxidized low-density lipoprotein and anti-malondialdehyde-modified low-density lipoprotein IgG2c antibody levels were significantly lower in RP105(-/-) chimeras, confirming effects on B2 B cells rather than B1 B cells. Moreover, B-cell activating factor expression was reduced in spleens of RP105(-/-) chimeras.

CONCLUSIONS

RP105 deficiency on circulating cells results in an intriguing unexpected TLR-associated mechanisms that decrease atherosclerotic lesion formation with alterations on proinflammatory B2 B cells.

Dissection of cytotoxic and helper T cell responses

Cytotoxic (CD8+) and helper (CD4+) T cells play a crucial role in resolving infections by intracellular pathogens. The development of technologies to visualize antigen-specific T cell responses in mice and men over the past decade has allowed a dissection of the formation of adaptive T cell immunity. This review gives a brief overview of the currently used detection techniques and possible future additions. Furthermore, we discuss our current understanding of the formation of antigen-specific T cell responses, with particular attention to the similarities and differences in CD4+ and CD8+ T cell responses, the functional heterogeneity within responder T cell pools and the regulation of CD8+ T cell responses by dendritic cells and CD4+ helper T cells.

Constitutive CD27/CD70 interaction induces expansion of effector-type T cells and results in IFNgamma-mediated B cell depletion

The interaction between the TNF receptor family member CD27 and its ligand CD70 provides a costimulatory signal for T cell expansion. Normally, tightly regulated expression of CD70 ensures the transient availability of this costimulatory signal. Mice expressing constitutive CD70 on B cells had higher peripheral T cell numbers that showed increased differentiation toward effector-type T cells. B cell numbers in CD70 transgenic (TG) mice progressively decreased in primary and secondary lymphoid organs. This B cell depletion was caused by CD27-induced production of IFNgamma in T cells. We conclude that apart from its role in controlling the size of the activated T cell pool, CD27 ligation contributes to immunity by facilitating effector T cell differentiation.

Magnetic resonance imaging of the upper airway structure of children with obstructive sleep apnea syndrome

The anatomical relationships between lymphoid, bony, and other tissues affecting the shape of the upper airway in children with obstructive sleep apnea syndrome (OSAS) have not been established. We therefore compared the upper airway structure in 18 young children with OSAS (age 4.8 +/- 2.1 yr; 12 males and 6 females) and an apnea index of 4.3 +/- 3.9, with 18 matched control subjects (age, 4.9 +/- 2.0 yr; 12 males and 6 females). All subjects underwent magnetic resonance imaging under sedation. Axial and sagittal T1- and T2-weighted sequences were obtained. Images were analyzed with image-processing software to obtain linear, area, and volumetric measurements of the upper airway and the tissues comprising the airway. The volume of the upper airway was smaller in subjects with OSAS in comparison with control subjects (1.5 +/- 0.8 versus 2.5 +/- 1.2 cm(3); p < 0.005) and the adenoid and tonsils were larger (9.9 +/- 3.9 and 9.1 +/- 2.9 cm(3) versus 6.4 +/- 2.3 and 5.8 +/- 2.2 cm(3); p < 0.005 and p < 0.0005, respectively). Volumes of the mandible and tongue were similar in both groups; however, the soft palate was larger in subjects with OSAS (3.5 +/- 1.1 versus 2.7 +/- 1.2 cm(3); p < 0.05). We conclude that in children with moderate OSAS, the upper airway is restricted both by the adenoid and tonsils; however, the soft palate is also larger in this group, adding further restriction.

Magnetic resonance imaging of the upper airway in children with Down syndrome

As compared with control subjects, children with Down syndrome have different size and shape relationships among tissues composing the upper airway, which may predispose them to obstructive sleep apnea (OSA). We hypothesized that Down syndrome children without OSA have similar subclinical differences. We used magnetic resonance imaging to study the upper airway in 11 Down syndrome children without OSA (age, 3.2 +/- 1.4 yr) and in 14 control subjects (age, 3.3 +/- 1.1 yr). Sequential T1- and T2-weighted spin-echo axial and sagittal images were obtained. We found a smaller airway volume in subjects with Down syndrome (1.4 +/- 0.4 versus 2.3 +/- 0.8 cm(3) in controls, p < 0.005). Subjects with Down syndrome had a smaller mid- and lower face skeleton. They had a shorter mental spine-clivus distance (5.7 +/- 0.6 versus 6.2 +/- 0.4 cm, p < 0.05), hard palate length (3.2 +/- 0.4 versus 3.7 +/- 0.2 cm, p < 0.005), and mandible volume (11.5 +/- 3.7 versus 16.9 +/- 2.9 cm3, p < 0.0005). Adenoid and tonsil volume was significantly smaller in the subjects with Down syndrome. However, the tongue, soft-palate, pterygoid, and parapharyngeal fat pads were similar to those of control subjects. This study shows that Down syndrome children without OSA do not have increased adenoid or tonsillar volume; reduced upper airway size is caused by soft tissue crowding within a smaller mid- and lower face skeleton.

Sleep and periodic limb movement in sleep in juvenile fibromyalgia

OBJECTIVES

Fibromyalgia has been recently recognized in children and adolescents as juvenile fibromyalgia (JF). In adult fibromyalgia, subjective complaints of nonrestorative sleep and fatigue are supported by altered polysomnographic findings including a primary sleep disorder known as periodic limb movements in sleep (PLMS) in some subjects. Although poor sleep is a diagnostic criterion for JF, few reports in the literature have evaluated specific sleep disturbances. Our objectives were to evaluate in a controlled study the polysomnographic findings of children and adolescents with JF for alterations in sleep architecture as well as possible PLMS not previously noted in this age group.

METHODS

Sixteen consecutive children and adolescents (15.0 +/- 2.6 years of age) diagnosed with JF underwent overnight polysomnography. Polysomnography was also performed on 14 controls (14.0 +/- 2.2 years of age) with no history of an underlying medical condition that could impact on sleep architecture. Respiratory variables, sleep stages, and limb movements were measured during sleep in all subjects.

RESULTS

JF subjects differed significantly from controls in sleep architecture. JF subjects presented with prolonged sleep latency, shortened total sleep time, decreased sleep efficiency, and increased wakefulness during sleep. In addition, JF subjects exhibited excessive movement activity during sleep. Six of the JF subjects (38%) were noted to have an abnormally elevated PLMS index (>5/hour), indicating PLMS in these subjects.

CONCLUSION

Our study demonstrated abnormalities in sleep architecture in children with JF. We also noted PLMS in a significant number of subjects. This has not been reported previously in children with this disorder. We recommend that children who are evaluated for JF undergo polysomnography including PLMS assessment. juvenile fibromyalgia; periodic limb movement in sleep; restless legs syndrome.

Periodic limb movement in sleep in children with Williams syndrome

OBJECTIVE

Williams syndrome (WS) is associated with neurobehavioral abnormalities that include irritability and attention-deficit/hyperactivity disorder. Parents often report children having difficulties initiating and maintaining sleep because of restlessness and arousals. Therefore we evaluated a group of children with WS for the presence of a movement arousal sleep disorder.

METHODS

Twenty-eight families of children with WS participated in a telephone survey aimed to screen for a movement arousal disorder. Of the 16 children identified as having such a disorder, 7 (mean age, 3.9 +/- 2.2 years) underwent polysomnography. Their studies were compared with those of 10 matched control subjects (mean age, 5.3 +/- 2.0 years).

RESULTS

The 7 subjects with WS who were screened by the survey had sleep latency, total sleep time, arousals, and awakenings that were similar to those of control subjects. However, they presented with a disorder of periodic limb movement in sleep (PLMS). The PLMS index in the subjects with WS was 14.9 +/- 6.2 versus 2.8 +/- 1.9 in control subjects (P < .0001). In addition, arousal and awakening in subjects with WS were strongly associated with PLMS. Moreover, children with WS spend more time awake during sleep periods than control subjects (10.0% +/- 7.0% vs 4.4% +/- 4.7%; P < .05). Five children were treated with clonazepam, and in 4 a significant clinical response was noted.

CONCLUSION

We report an association between WS and PLMS. Clonazepam may reduce the clinical symptoms of PLMS in some of these children.

Altered lung mechanics after double-lung transplantation

We studied lung mechanics and small airways function in 15 patients after double-lung (DL) transplantation. Patients were classified as stable (DL-S, n = 11), or having obliterative bronchiolitis syndrome (DL-OBS, n = 4). We performed pulmonary function tests (PFT), measured slope of phase 3 of the single-breath nitrogen test (N2SP3), and obtained pressure-volume curves and values: chord compliance (Cst,L), specific chord compliance (SCst,L), and elastic recoil pressure at 90% TLC. PFT showed mild restrictive pattern in DL-S and severe obstructive lung disease in DL-OBS. The N2SP3 measurement indicated small airways dysfunction in 82% of DL-S and in all DL-OBS patients. The Cst,L was 0.24 +/- 0.08 L/cm H2O in DL-S and 0.16 +/- 0.05 L/cm H2O in DL-OBS, both lower than control subjects 0.34 +/- 0. 09 L/cm H2O (p < 0.01; p < 0.001). Moreover, SCst,L was 0.09 +/- 0. 03 cm H2O-1 in DL-S, and 0.05 +/- 0.02 cm H2O-1 in DL-OBS, significantly lower than control subjects 0.12 +/- 0.02 cm H2O-1 (p < 0.05; p < 0.001). Elastic recoil at 90% TLC was normal in 14 of 15 patients. We found a linear correlation between N2SP3 and FEV1, and between FEV1 and Cst,L and SCst,L for combined DL-S and DL-OBS. Reduced compliance near FRC with normal elastic recoil at high lung volumes does not suggest changes in lung parenchyma. We speculate that structural or functional alterations in small airways may have contributed to low compliance measurements. Of special concern are our findings that DL-S had significant small airways dysfunction and reduced compliance in a pattern similar to the DL-OBS, only smaller in magnitude.

[Percutaneous transluminal coronary angioplasty (PTCA) as primary therapy in acute myocardial infarct]

BASIC PROBLEM AND OBJECTIVE

Percutaneous transluminal coronary angioplasty (PTCA) is being increasingly considered as an alternative to thrombolytic treatment of acute myocardial infarction. Studies performed so far, some on selected groups of patients, have produced high initial results of success. This prospective study was undertaken to determined primary success, complications and recurrence after primary PTCA in acute myocardial infarction (AMI).

PATIENTS AND METHODS

Primary treatment in the form of immediate PTCA of the infarct vessel was undertaken in 111 patients (84 men, 27 women; mean age 58.6 +/- 10.3 years) with AMI. PTCA was judged successful if the infarct vessel had been reopened to perfusion grade 3 and restenosis was < 50%. No thrombolytic treatment was given, but heparin infusions were given during and for 24-48 hours after the procedure. 13 patients (11.7%) were in cardiogenic shock or required cardiopulmonary resuscitation for infarct-related arrhythmias.

RESULTS

The primary success rate of PTCA for the whole group was 91% (101 of 111 patients), but only 77% (ten of 13) among patients in cardiogenic shock and (or) after resuscitation. Acute re-occlusion (0-6 days after PTCA) occurred in seven patients. Eight patients (7.2%) died during the hospital phase (0-4 weeks), seven of whom had been in shock or required resuscitation (death rate 54%). The overall complication rate of the intervention was 6.3%. No emergency aortocoronary bypass was necessary. Repeat coronary angiography was performed in 71 of the 101 successfully treated patients 6 or 12 weeks after the PTCA. Re-occlusion was demonstrated in four (5.6%), a restenosis of more than 50% in 25% of patients. Mean left ventricular ejection fraction, obtained by planimetry from the levocardiogram was 58.6 +/- 9.3%.

CONCLUSION

PTCA, performed immediately after acute myocardial infarction is an effective therapeutic measure with a high primary success rate.

Arousal and cardiorespiratory responses to hypoxia in Prader-Willi syndrome

Ventilatory responses to peripheral chemoreceptor stimuli are absent in patients with Prader-Willi syndrome (PWS) during wakefulness. Because arousal from sleep after rapidly developing hypoxia may require intact peripheral chemoreceptor function, we hypothesized that blunted hypoxic arousal responses during sleep Stage 3/4 would be present in PWS. Thirteen patients with PWS (mean age, 23.4 +/- 3.7 +/- SEM yr; 46% male; body mass index [BMI], 28.9 +/- 1.6 kg/m2) and 11 matched control subjects (mean age 28.0 +/- 5.4 yr; 54% male; BMI, 28.8 +/- 3.1 kg/m2) were studied. An abrupt decrease in inspired O2 tension to 80 mm Hg was introduced until arousal occurred or for a maximum of 3 min. One of the 13 patients with PWS and seven of the 11 control subjects were aroused by the hypoxic challenge (p < 0.02). During hypoxia, heart rate increased by 9 +/- 2% in the PWS group versus 22 +/- 4% in the control group (p < 0.005). Respiratory rate did not change in the PWS group (4 +/- 2%; p = NS), but it increased by 13 +/- 2% in the control group (p < 0.02). We conclude that abnormal arousal and cardiorespiratory responses to hypoxia are frequent in PWS. We postulate that intact peripheral chemoreceptor function is an important component underlying arousal mechanisms to rapidly developing hypoxia during sleep.

Hypercapnic arousal responses in Prader-Willi syndrome

STUDY OBJECTIVE

Prader-Willi syndrome (PWS) is characterized by a number of abnormalities of hypothalamic function, such as hyperphagia, short stature, temperature instability, hypogonadotropic hypogonadism, and neurosecretory growth hormone deficiency. Patients with PWS are reported to have sleep-disordered breathing and have blunted hypercapnic ventilatory responses secondary to abnormal peripheral chemoreceptor function. Thus, we hypothesized that hypercapnic arousal responses would be abnormal in PWS.

DESIGN

Hypercapnic arousal responses were tested in ten nonobese children and adults with PWS, aged 17.7 +/- 2.5 (SEM) years, 70% female, and nine control subjects, aged 14.2 +/- 2.6 years, 67% female. Hypercapnic challenges were performed during stage 3/4 non-rapid eye movement sleep.

RESULTS

The PWS subjects had a significantly higher arousal threshold to hypercapnia compared with the controls (53 +/- 1.0 vs 46 +/- 1.7 mm Hg; p < 0.01). The PWS subjects had significantly higher baseline end-tidal CO2 levels (42 +/- 0.8 vs 38 +/- 1.1 mm Hg; p < 0.01) and more central apneas greater than 15 s/h of sleep (1.5 +/- 0.3 vs 0.1 +/- 0.1; p < 0.01).

CONCLUSIONS

Elevated hypercapnic arousal thresholds during sleep are found in PWS subjects; these may be a manifestation of abnormal peripheral chemoreceptor function and may further contribute to sleep-disordered breathing in PWS patients.

Ventilatory response to consecutive short hypercapnic challenges in children with obstructive sleep apnea

In healthy adults, a ventilatory pattern characterized by progressively increased tidal volume (VT), and decreased respiratory rate (RR) accompany repeated short hypercapnic ventilatory challenges, while minute ventilation (VE) remains constant. We hypothesized that the peculiar ventilatory pattern seen in adults would be blunted in children with obstructive sleep apnea syndrome (OSAS) who undergo comparable intermittent or chronic alveolar PCO2 elevation. We measured ventilatory responses to five challenges of 2-min duration (C1-C5) with 5% CO2 in O2, separated by 5-min room-air breathing intervals (R1-R4), in nine children with OSAS and in eight age-, sex-, and body mass index-matched controls. In all children, CO2 significantly increased VE when compared with baseline conditions (22.3 +/- 2.2 vs. 9.5 +/- 0.9 (SE) l/min; P < 0.001). In control subjects, progressive VT increases from 0.67 +/- 0.10 liter in C1 to 0.92 +/- 0.13 liter in C5 occurred (P < 0.01), whereas RR decreased from 33.9 +/- 5.1 breaths/min in C1 to 27.8 +/- 3.7 breaths/min in C5 (P < 0.02), resulting in VE increases across CO2 challenges (22.3 +/- 4.9 l/min in C1 vs. 25.1 +/- 5.0 l/min in C5; P < 0.005). The RR decrease was primarily related to progressive prolongation of expiratory time (TE) (1.1 +/- 0.1 s in C1 to 1.5 +/- 0.2 s in C5; P < 0.002). In contrast, VT, RR, and TE did not change in a consistent fashion in OSAS patients with repeated CO2 challenges (OSAS vs. control: P < 0.0001). Furthermore, in OSAS, VE was similar with repeated challenges (22.4 +/- 2.2 1/min in C1 vs. 23.9 +/- 1.9 l/min; P = not significant), such that changes in VE over time significantly differed in OSAS and controls (P < 0.001). We conclude that healthy children modify their ventilatory strategy to repeated hypercapnia. We speculate that in OSAS these mechanisms are already fully implemented because of recurrent alveolar hypoventilation accompanying increased upper airway resistance, leading to blunted temporal trends of ventilatory response.

Peripheral chemoreceptor function in children with myelomeningocele and Arnold-Chiari malformation type 2

Blunted rebreathing hyperoxic hypercapnic ventilatory and arousal responses are frequent in older children with myelomeningocele (MMC) and Arnold-Chiari malformation type 2 (ACM). In contrast, isocapnic hypoxic rebreathing ventilatory responses are only occasionally affected. Thus, regions mediating the hypoxic ventilatory response appear usually preserved in children with MMC and ACM. Peripheral chemoreceptor function (PCR), however, has not been critically assessed in these children. To study this, PCR was measured in ten children and adolescents with MMC and ACM with normal alveolar ventilation during wakefulness, and in ten sex- and age-matched controls by measuring the ventilatory responses induced by 100% O2 breathing, five tidal breaths of 100% N2, and vital capacity breaths of 15% CO2 in O2. In general, tidal breathing of 100% O2 resulted in smaller decreases in minute ventilation (VE) responses in patients with MMC, although absent VE responses to hyperoxia were found in four patients. Vital capacity breaths of 15% CO2 elicited similar increases in VE in five patients and in ten controls, but no changes in VE were found in the remaining five patients (p < 0.02). Acute hypoxia induced by N2 tidal breathing resulted in significant linear regression correlations between VE and SpO2 in five patients with MMC, while absent responses were measured in those same five patients with absent hypercapnic responses. We conclude that PCR, when assessed by acute hypoxia, hyperoxia, or hypercapnia is abnormal in some children with MMC and ACM, particularly in those demonstrating abnormal ventilation during sleep. We postulate that the large interindividual variability of PCR is dependent on the severity of brainstem involvement of PCR afferents or central respiratory integration sites.

Absent peripheral chemosensitivity in Prader-Willi syndrome

Abnormalities in ventilatory control during wakefulness and sleep have been observed in patients with Prader-Willi syndrome (PWS). The role of peripheral chemoreceptors in the pathophysiology of abnormal ventilatory responses in PWS is unknown. We studied peripheral chemoreceptor function during wakefulness in 17 genetically confirmed PWS patients [age 27.0 +/- 2.5 (SE) yr; 7 males, 10 females; body mass index 31.1 +/- 1.4 kg/m2] and compared their responses with 17 control subjects matched for age, sex, and body mass index. All PWS and control subjects had normal resting end-tidal PCO2 and arterial O2 saturation while awake. Peripheral chemoreceptor function was assessed by the ventilatory responses to 100% O2 breathing, five tidal breaths of 100% N2, and vital capacity breaths of 15% CO2 in O2. Control subjects decreased minute ventilation (VE) by 15.5 +/- 3.6% during hyperoxia. However, PWS patients increased VE by 17.6 +/- 3.3%, indicating a paradoxical response to hyperoxia (P < 0.00001). After CO2 vital capacity breaths, PWS patients showed no significant change and control subjects showed a marked increase (P < 0.0001) in VE. During N2 breathing, again PWS patients showed no change and control subjects exhibited a marked increase (P < 0.00005) in VE. We conclude that PWS patients have absent peripheral chemoreceptor ventilatory responses. We speculate that the lack of ventilatory responses is due to primary peripheral chemoreceptor dysfunction and/or defective afferent pathways to central controllers.

Hypoxic and hypercapnic ventilatory responses in Prader-Willi syndrome

Abnormalities of ventilatory control may play a significant role in the pathophysiology of sleep-disordered breathing in patients with the Prader-Willi syndrome (PWS). We measured rebreathing hypercapnic and hypoxic ventilatory responses (HCVR and HPVR, respectively) during wakefulness in 8 nonobese PWS (NOB-PWS) and 9 obese PWS (OB-PWS) patients and compared their results with those from 24 healthy nonobese control (NOB-CON) and 10 obese control (OB-CON) subjects. The slope of HCVR was similar in NOB-PWS patients and NOB-CON subjects (NS). However, HCVR was significantly lower in OB-PWS patients than in OB-CON subjects (P < 0.02). In PWS patients, the mean point of origin of the positive slope of HCVR occurred at a significantly higher end-tidal PCO2 than in either control group. During isocapnic hypoxic challenges, six PWS patients had no significant HPVR. In the remainder, mean slopes of HPVR were -0.80 +/- 0.06 l.min-1.%arterial O2 saturation-1 in five NOB-PWS patients and -0.68 +/- 0.15 l.min-1.%arterial O2 saturation-1 in six OB-PWS patients. These responses were significantly decreased compared with those in the control groups (P < 0.006). We conclude that NOB-PWS patients have normal HCVR, which is blunted in OB-PWS patients. Furthermore, isocapnic HPVR is either absent or markedly reduced in PWS patients. The severity of abnormality of the HPVR is independent of the degree of obesity. We postulate that the primary abnormality of ventilatory control in PWS affects peripheral chemoreceptor pathways.

Comparison of high frequency chest compression and conventional chest physiotherapy in hospitalized patients with cystic fibrosis

Clearance of bronchial secretions is essential in the management of cystic fibrosis (CF) patients admitted for acute pulmonary exacerbation. Conventional physiotherapy (CPT) is labor-intensive, time-consuming, expensive, and may not be available as frequently as desired during hospitalization. High frequency chest compression (HFCC), which uses an inflatable vest linked to an air-pulse delivery system, may offer an attractive alternative. To study this, we prospectively studied 50 CF patients admitted for acute pulmonary exacerbation who were randomly allocated to receive either HFCC or CPT three times a day. On admission, clinical status and pulmonary function tests (PFT) in the HFCC group were not significantly different from those measured in the CPT group. Significant improvements in clinical status and PFT were observed after 7 and 14 d of treatment, and were similar in the two study groups, leading to patient discharge after similar periods of hospitalization. We conclude that HFCC and CPT are equally safe and effective when used during acute pulmonary exacerbations in CF patients. We speculate that HFCC may provide an adequate alternative in management of CF patients in a hospital setting.

Maturational differences in step vs. ramp hypoxic and hypercapnic ventilatory responses

The influence of the speed of stimulus presentation on hypoxic and hypercapnic ventilatory responses (step vs. ramp) is not known. Furthermore, it is unclear whether children and adults respond similarly. We tested ramp ventilatory responses to hypercapnia and hypoxia with use of rebreathing in 8 prepubertal children and 11 adults. We tested step ventilatory responses to hypercapnia with single vital capacity breaths of 15% CO2 in O2 and to hypoxia with five tidal breaths of 100% N2. For children, slopes of step hypercapnic ventilatory responses were always greater than those of ramp responses (0.85 +/- 0.07 vs. 0.71 +/- 0.07 l.min-1.Torr end-tidal PCO2-1; P < 0.0005). Conversely, for adults, step responses were always less than ramp responses (0.88 +/- 0.19 vs. 2.10 +/- 0.29 l.min-1.Torr end-tidal PCO2-1; P < 0.0007). Similarly, for children, the slopes of step hypoxic ventilatory responses were always greater than those of ramp responses (-0.71 +/- 0.09 vs. -0.45 +/- 0.04 l.min-1.Torr O2 saturation-1; P < 0.02), and for adults, step responses were always less than ramp responses (-0.68 +/- 0.14 vs. -1.85 +/- 0.46 l.min-1.Torr O2 saturation-1; P < 0.04). We conclude that ventilatory responses vary depending on step vs. ramp presentation of hypercapnia or hypoxia and that the ratio of these responses is reversed in children compared with adults. We speculate that the responsiveness of peripheral chemoreceptors is increased in children compared with adults and that it may play a role in the mechanisms leading to increased ventilatory responses observed during childhood.

[Emergency intracoronary stent implantation: complications and experiences with 124 patients]

From January 1990 to February 1993, 88 patients (group 1) received an emergency stent implantation with threatening vascular occlusion within the framework of an elective PTCA or a second emergency PTCA after up to 5 days following a primary successful PTCA. In addition, 36 patients (group 2) received an intracoronary stent during emergency PTCA of instable angina pectoris or acute myocardial infarction. The attempted stent implantation was not successful in 6 other patients. All patients were anticoagulated with heparin, aspirin (100 to 500 mg), and phenprocoumon. Since October 1991, 3 x 75 mg dipyridamole was given and heparinization was stopped after measuring the anticoagulation factor II (prothrombin time < 40%). Main complications within the first 2 to 3 weeks were acute and subacute stent thrombosis (21.8%) and complications of the puncture site (bleeding 19.3%, a. spurium/av-fistula 1.6%). The risk of acute stent thrombosis was significantly higher in patients of group 2 (instable angina pectoris despite of drug therapy or acute myocardial infarction) compared with group 1 (42.4 versus 14.8%). Implantation of multiple stents to stabilize extended dissections had a lower occlusion rate (6.3%). Acute myocardial infarctions were registered in group 1 in 25% (11.4% following implantation, 13.6% following stent occlusion, CK 153 to 3380 U/I, average 826 U/I) and in 58.3% of the high risk patients in group 2 (50% just before or following implantation, 36.1% infarctions or re-infarctions caused by stent occlusion, CK 152 to 1950 U/I, average 657 U/I). The risk of infarction could be limited to approximately 58% of the patients of group 2.(ABSTRACT TRUNCATED AT 250 WORDS)

Ventilatory responses during wakefulness in children with obstructive sleep apnea

The pathophysiology of the obstructive sleep apnea syndrome (OSAS) is not fully understood. In children, airway obstruction secondary to tonsilloadenoidal hypertrophy is the leading cause of OSAS. However, not all children with tonsilloadenoidal hypertrophy develop OSAS. Thus, other factors, including abnormalities in ventilatory control, may contribute to the etiology of OSAS. To test this, we performed polysomnography and hypercapnic and hypoxic ventilatory response testing in 20 children and adolescents with OSAS (mean age, 8 +/- 3 [SD] yr) and 19 control subjects. Only two children with OSAS were obese. Children with OSAS had an apnea index of 16 +/- 20, peak PETCO2 of 54 +/- 5 mm Hg, and SaO2 nadir of 84 +/- 13% during polysomnography. Ventilatory responses were performed by rebreathing techniques. The slope of the hypercapnic ventilatory responses, corrected for body surface area, was 1.74 +/- 0.79 L/min/m2/mm Hg PETCO2 in children with OSAS and 1.45 +/- 0.58 L/min/m2/mmHg PETCO2 in control subjects (NS). Hypoxic ventilatory responses, corrected for body surface area, were -0.94 +/- 0.49 L/min/m2/% SaO2 in children with OSAS and -0.95 +/- 0.45 L/min/m2/% SaO2 in control subjects (NS); however, the sample size was small. There was a weak inverse correlation between the slope of the hypercapnic ventilatory response and the duration of hypoventilation during polysomnography (r = -0.44, p < 0.05). We conclude that children with OSAS have normal ventilatory responses to hypercapnia, and they may have normal ventilatory responses to hypoxia. We speculate that abnormal central ventilatory drive plays little if any role in the pathogenesis of pediatric OSAS.(ABSTRACT TRUNCATED AT 250 WORDS)

Recurrent apparent life-threatening events during infancy: a manifestation of inborn errors of metabolism

To determine how often inborn errors of metabolism may cause unexplained apnea or recurrent apparent life-threatening events in infants, we retrospectively reviewed the records of 166 infants who were referred for apnea evaluation. A metabolic disorder was identified in 7 infants (4.2%), all of whom had recurrent apparent life-threatening events.

Prevalence of medium-chain acyl-coenzyme A dehydrogenase deficiency in the sudden infant death syndrome

Disorders of fatty acid beta-oxidation have been suggested as playing a significant role in the sudden infant death syndrome (SIDS). To elucidate the role of medium-chain acyl-coenzyme A dehydrogenase (MCAD) deficiency in SIDS, we identified all cases of SIDS occurring in Los Angeles County between January 1986 through December 1991. A total of 1304 SIDS deaths were identified; tissue samples were collected in 1236 cases (94.8%). Extraction of DNA was successful in 1224 tissue samples (93.9%), which were examined for the presence of the G985 mutation, identified as occurring in more than 88% of affected cases of MCAD deficiency. Three heterozygotes and no homozygotes were identified; this incidence does not differ from that reported in the general population. Review of the pathologic specimens from the identified heterozygotes and from 18 ethnic-, age-, and sex-matched control subjects revealed significant fatty infiltration of all organs examined in one of the three heterozygotes and in none of the control subjects. We conclude that MCAD deficiency does not play a significant role in the causation of SIDS.

New form of postaxial acrofacial dysostosis?

We report on a 2-month-old Sephardic Jewish girl with bilateral and symmetrical deficiency of the fifth digital rays of all 4 limbs, combined with severe deformations and other malformations of the limbs. These findings were associated with orofacial malformations, as well as with visceral anomalies differing from those found in other postaxial deficiency syndromes. Parents were closely consanguineous. We assume this patient represents a new form of postaxial acrofacial dysostosis.

Cerebral germinomas and Klinefelter syndrome. A review

Patients with Klinefelter syndrome appear to be predisposed to the development of extragonadal cerebral germinomas. A case of a pineal region germinoma in a boy 15 years of age with Klinefelter syndrome is documented in this article. In view of three other cases of cerebral germinomas associated with Klinefelter syndrome in the literature, a hypothesis for this predisposition is suggested.