Patterns of oxygenation during periodic breathing in preterm infants

The characteristics of the arterial oxygen saturation (SaO2) signal during episodes of hypoxaemia (SaO2 less than or equal to 80% for greater than or equal to 4 s) associated with periodic and non-periodic apnoeic pauses were studied in 16 preterm infants with cyanotic episodes (patients). and 15 asymptomatic preterm infants (controls), matched on birthweight and gestational age. The patients showed a significantly higher percentage of apnoeic pauses followed by a hypoxaemic episode (25 vs. 6%, P less than 0.01), and a two-fold increase in the slope of the desaturation curve (8.4 vs. 4.3% per s, P less than 0.005) in periodic compared with non-periodic breathing. All other characteristic of oxygenation (baseline SaO2 before episodes of hypoxaemia, delay between onset of apnoeic pause and onset of desaturation, lowest SaO2 during episodes of hypoxaemia) were similar for periodic and non-periodic breathing patterns. Similar, but not significant, differences between isolated and periodic apnoeic pauses were also present in the controls. An analysis of episodes of bradycardia (less than or equal to 100 beats per minute (bpm] showed that out of 121 episodes in the patients 118 were accompanied by a fall in SaO2 to less than or equal to 80%, and in the remaining three SaO2 fell to 82%, 85% and 86%, respectively. Thus all episodes of bradycardia (less than or equal to 100 bpm) were associated with a fall in SaO2 detected by beat-to-beat pulse oximetry. Examination of hypoxaemic episodes and their relationship with bradycardia and with apnoeic pauses, periodic and non-periodic, may help the further understanding of the control of arterial oxygenation in preterm infants with cyanotic episodes.     

Upper Airway Obstruction With Hypoxaemia And Sleep Disruption In Down Syndrome

Six of 12 children with Down syndrome (DS) tested by means of long-term tape-recordings of oxygen saturation, breathing movements and expired CO2 were found to have previously undetected and severe upper airway obstruction during sleep. In five cases the obstruction occurred in the pharynx and in the sixth it was due to bilateral choanal stenosis. When compared with age-matched controls, overnight tape-recordings showed episodes of abnormal arterial hypoxaemia and an abnormally elevated end-tidal CO2. Episodes of obstruction were most marked during sleep associated with a non-regular breathing pattern. Abnormal episodes of hypoxaemia were associated with continued breathing movements. Sometimes there was no airflow (complete obstruction); at other times airflow continued normally or was reduced in amplitude (partial obstruction). During episodes of partial or complete airway obstruction the inspiratory waveform showed a characteristic shape. These results show sleep-related upper airway obstruction to be an often undetected complication of DS and all necessary measures should be taken to overcome the obstruction when it reaches the stage of producing abnormal hypoxaemia. Choanal dilatation and tracheostomy were successful in treating two of the children. Tonsillectomy and adenoidectomy were successful for one child, but only of marginal benefit for two others.     

Graded stress radiography of injured anterior cruciate ligaments.

Fifty-five patients with clinical suspicion of injury to their anterior cruciate ligament (ACL) were examined by graded stress radiography before arthroscopic verification in an effort to determine the loss of ACL function as a result of ligament tearing. Using a commercially available stress device capable of applying varying pressures to the mid-calf, anterior drawers were measured from lateral radiographs at 0-, 7-, 14-, and 21-kiloPascal pressures and used to calculate the equivalent elastic modulus of the remaining ACL fibers. According to viscoelastic theory, this modulus is proportional to the number of elastically active fibers in the ligament. To verify the validity of this concept, the stress-strain relationship of a freshly excised ACL ligament was examined in a tensile testing machine, and the procedure was repeated after the ligament had been partially transsected with a scalpel. Comparison with the elastic modulus of the (intact) ACL of the opposite knee permits an estimate of the percentage of rupture in cases of partial tears. Overstretched ligaments show essentially normal viscoelastic properties once the slack in the ligament has been taken up. Complete tears, on the other hand, show a complete breakdown in the viscoelastic properties of the ACL. The results show that partial tears can be diagnosed by graded stress radiography with a sensitivity of 20% and specificity of 90%. Diagnosis of overstretched ligaments had sensitivity of 50% and specificity of 94%. Complete tears were detected with sensitivity of 88% and specificity of 75% as diagnosed against all other ACL lesions and including normals.(ABSTRACT TRUNCATED AT 250 WORDS)     

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.     

Inhibition of growth and induction of apoptosis in human cancer cell lines by tea polyphenols

In order to study the biological activities of tea preparations and purified tea polyphenols, their growth inhibitory effects were investigated using four human cancer cell lines. Growth inhibition was measured by [3H]thymidine incorporation after 48 h of treatment. The green tea catechins (-)-epigallocatechin-3-gallate (EGCG) and (-)- epigallocatechin (EGC) displayed strong growth inhibitory effects against lung tumor cell lines H661 and H1299, with estimated IC50 values of 22 microM, but were less effective against lung cancer cell line H441 and colon cancer cell line HT-29 with IC50 values 2- to 3- fold higher. (-)-Epicatechin-3-gallate, had lower activities, and (-)- epicatechin was even less effective. Preparations of green tea polyphenols and theaflavins had higher activities than extracts of green tea and decaffeinated green tea. The results suggest that the growth inhibitory activity of tea extracts is caused by the activities of different tea polyphenols. Exposure of H661 cells to 30 microM EGCG, EGC or theaflavins for 24 h led to the induction of apoptosis as determined by an annexin V apoptosis assay, showing apoptosis indices of 23, 26 and 8%, respectively; with 100 microM of these compounds, the apoptosis indices were 82, 76 and 78%, respectively. Incubation of H661 cells with EGCG also induced a dose-dependent formation of H2O2. Addition of H2O2 to H661 cells caused apoptosis in a manner similar to that caused by EGCG. The EGCG-induced apoptosis in H661 cells was completely inhibited by exogenously added catalase (50 units/ml). These results suggest that tea polyphenol-induced production of H2O2 may mediate apoptosis and that this may contribute to the growth inhibitory activities of tea polyphenols in vitro.      

受体介导的凝血酶对成骨细胞增殖及分化的作用

目的 通过凝血酶对成骨细胞的增殖及分化作用的研究来探讨受体介导的凝血酶的功能.方法 原代成骨细胞分别取自于蛋白酶激活受体(protease-activated receptor,PAR)-1敲除鼠和野生对照鼠的头颅骨.并利用凝血酶,人工合成的PAR-1或PAR-4特异性激活短肽对细胞进行处理,通过对5.溴-2-脱氧尿嘧啶的嵌入及细胞碱性磷酸酶活性的测定探讨PAR-1或PAR-4激活对细胞增殖和分化的影响.结果 在野生鼠成骨细胞,凝血酶及PAR-1激活肽均能促进的细胞增殖和降低碱性磷酸酶的活性,但PAR-4激活肽却无这些作用.然而在PAR-1 敲除鼠的成骨细胞无论是凝血酶还是PAR-4激活肽均不能改变细胞的增殖及碱性磷酸酶的活性.结论 本研究结果 表明凝血酶促进成骨细胞增殖及抑制其分化是通过PAR-1介导的.其他凝血酶受体并不具有此作用.     

Selective uptake of toxic nucleoside (125IUdR) by resistant cancer

We report uptake of a thymidine analogue 125-Iodine-5-iodo-2'-deoxyuridine (125IUdR) by nude mice bearing human xenografts of choriocarcinoma or colonic cancer. When 125IUdR was given alone, uptake by intestinal tissues was 5-10 times greater than by the tumours as measured by tissue gamma counting. This ratio was reversed when hydroxyurea or cytosine arabinoside were used as inhibitors of ribonucleotide reductase and were given in combination with 5-fluorouracil or methotrexate to inhibit thymidine synthesis shortly before injecting 125IUdR. Counting the radioactivity in tissues removed 24 hours after 125IUdR gave tumour to highest normal tissue ratios of up to 15:1, but the corresponding nuclear grain counts, which is probably a more reliable indicator of selective uptake into DNA, were in excess of 100:1. The addition of unlabelled IUdR to the regimen only reduced the uptake of 125IUdR when given in relatively large amounts. For this approach to be exploited it is concluded that the tumour must be resistant at the cell level to the inhibitor of DNA synthesis either de novo or as a result of prior exposure to it. This inhibitor can then be used to block uptake of the potentially toxic nucleoside analogue by normal renewal tissues while it is taken up by the resistant cancer cells. By inhibiting synthesis of the corresponding normal nucleosides with inhibitors to which the cancer cells are not resistant, incorporation of the toxic analogues into tumour DNA was enhanced. Although 125IUdR is a convenient agent for exploring this approach and is highly cytotoxic when incorporated in DNA, the clinical potential of reverse role chemotherapy probably lies with the development of toxic non-radioactive nucleoside analogues.