Modular architecture of the T4 phage superfamily: a conserved core genome and a plastic periphery

Among the most numerous objects in the biosphere, phages show enormous diversity in morphology and genetic content. We have sequenced 7 T4-like phages and compared their genome architecture. All seven phages share a core genome with T4 that is interrupted by several hyperplastic regions (HPRs) where most of their divergence occurs. The core primarily includes homologues of essential T4 genes, such as the virion structure and DNA replication genes. In contrast, the HPRs contain mostly novel genes of unknown function and origin. A few of the HPR genes that can be assigned putative functions, such as a series of novel Internal Proteins, are implicated in phage adaptation to the host. Thus, the T4-like genome appears to be partitioned into discrete segments that fulfil different functions and behave differently in evolution. Such partitioning may be critical for these large and complex phages to maintain their flexibility, while simultaneously allowing them to conserve their highly successful virion design and mode of replication.     

Arterial hypotension triggers perifocal depolarizations and aggravates secondary damage in focal brain injury

Perifocal depolarizations (PFD) have been observed after traumatic brain injury, are known to disturb cerebrovascular reactivity and thus may contribute to the morphological consequences of brain injury. In this investigation, the role of PFD was studied in focal brain lesions with/without induction of delayed hypotension. Cerebral freeze lesions were induced in anesthetized normotensive rats that underwent perfusion fixation of brains 5 min, 4 h or 24 h after lesioning, respectively, to obtain quantitative histopathology. In additional groups, a 45-min period of moderate hypobaric hypotension was applied 15 min post-trauma and brains were perfusion fixed after 4 h or 24 h. In a second series, the direct current (DC) potential and cortical laser-Doppler flow (LDF) were measured adjacent to lesions under normotensive or hypotensive conditions. Sham procedures were carried out in rats that underwent hypotension alone. Lesioning resulted in a significant LDF decrease to 50% of baseline, further decreased during hypotension to less than 40% of control (P < 0.05). Sham animals had LDF values between 60 and 70% of control when subjected to hypotension. Focal brain injury always induced a negative DC shift shortly after lesioning. In 6 of 8 rats that underwent cold lesion plus hypotension, a second PFD was observed approximately 2.5 min after onset of hypotension accompanied by a relative LDF increase by 25 +/- 12%. Lesion expansion was significantly worsened by hypotension (8.19 +/- 0.56 mm(3) at 24 h) compared with normotensive rats (7.01 +/- 0.3 mm(3) at 24 h, P < 0.01). We conclude that hypotension triggers depolarizations by an ischemic mechanism that contributes to final tissue damage.     

Biophysical parameters of skin: map of human face, regional, and age-related differences

The face showed anatomical variation on reaction to chemicals, which could be related to differences in biophysical specificities of the skin. The aim of this study was to establish a map of the face for 6 biophysical parameters.10 young human volunteers (24-34 years) and 10 old volunteers (66-83 years) were studied to prepare a map of the human face based on regional variations and age-related differences by measuring various biophysical parameters. 7 locations on the face, neck, and forearm were investigated. Skin blood flow, transepidermal water loss (TEWL), stratum corneum hydration (capacitance), temperature, pH, and sebum content of the skin surface were measured. In both groups, skin blood flow in the nose showed the highest value. Perioral and nasolabial areas showed the highest TEWL values. The neck showed the highest capacitance value. The highest skin temperature was detected in the neck in the young group and in the nasolabial area in the old group. The chin showed the most alkaline pH in both groups. Nasolabial area showed the highest sebum content in the young group, as did the chin in the old group. These baseline values provide a framework to build on for ascertaining disease and intervention-related effects.     

LDF研究动脉化静脉皮瓣血运的特点及注意事项

动脉化静脉皮瓣具有很多优点，但因坏死率较高使之在临床上不能广泛应用。有关动脉化静脉皮瓣血流分布研究及ＬＤＦ的应用报道均很多，但其血流分布特点仍无规律可循，ＬＤＦ的应用也存在很多问题。我们根据ＬＤＦ的特点对动脉化静脉皮瓣浅层组织的血流分布进行了监测，发现将静脉Ⅰ期原位动脉化同时扩张预制Ⅱ期行皮瓣转移可明显改善其术后血流分布及灌流量，提高其成活率。同时就有关ＬＤＦ的原理、参数调节、动物模型、与其它方法比较及注意事项等有关问题进行了探讨。     

Blood perfusion measurements in human tumours: Evaluation of laser Doppler methods

Laser Doppler flowmetry is a simple method of determining, directly and continuously, tissue blood flow. However, its applicability to monitoring tumour blood flow interstitially during hyperthermia treatments is still being evaluated. The purposes of this study were to physically characterize the measurement probes, to evaluate potential sources of artifact with the interstitital use of the probes during hyperthermia treatment, and to obtain measurements in human tumours during hyperthermia sessions.

The accuracy of the method in quantifying blood flow, velocity and volume during hyperthermia was found to be unaffected by heating the measurement probe to 42–46°C or by exposing it to various intensities of 915 MHz microwave fields (10–40 W), or 1 MHz ultrasound fields. Catheter insertion methods were developed to place the flow probes interstitially in tumours. Tissue damage was confined to a distance of no greater than 0.12 mm away from the catheter tract, and physical evidence of vascular disruption was within a distance of 0.05 mm as measured in a rat tumour model. This degree of damage/disruption is unlikely to affect LDF measurements which represent blood flow averaged over a 1.0–1.5 mm radius from the probe tip.

Concurrently, the device was used to monitor tumour blood flow parameters interstitially in human subjects during hyperthermia treatments given in combination with conventional radiotherapy. Blood-flow data from multiple sites of measurement showed marked heterogeneity within individual tumours (up to 55-fold differences) and between different tumours (> 100-fold differences). Measurements made by translating the probe along a tumour radius, beginning at the tumour core and advancing to me tumour edge, were consistent with a two-component tumour perfusion model (shell and core). Data are presented from one patient illustrating a persistent change in perfusion distribution during the hyperthermia treatment course, which occurred concomitantly with increases in thermal data. These results suggest mat the technique might be of value in monitoring change in flow between treatments. Responses during hyperthermia treatment sessions were also investigated. Four temporal patterns of flow were observed, ranging from a steady increase in flow to a plateau level to a steady drop in flow during heating. These patterns were not well correlated with average temperature recorded at the site of flow measurement. Further study is needed to determine if this LDF technique is to be useful for evaluation of heat transfer by blood perfusion.     

Failure of laser Doppler signal to correlate with total flow in muscle: is this a question of vessel architecture?

The signal strength from LDF probes positioned in perfused muscle can be altered by vasoconstrictors despite total flow being maintained constant. Apart from redistribution of flow via collateral channels outside the region of measurement, the change in LDF signal may arise because the vasoconstrictors have switched flow to vessels of different architecture or altered the architecture of the blood vessels being perfused. Thus we have examined the effect of tube architecture on LDF signal using polymer tubes of 250, 100, and 50 microm internal diameter. At 3% hematocrit the LDF signal was linear for each of the three tube sizes from 10 to 80 microl/h. The signal strength was greatest from the smallest tube and least from the largest tube. For a single tube (100 microm) that doubled back on itself twice to cross the field of measurement three times, the LDF signal at any flow (10-80 microl/h, hematocrit 3%) was approx threefold greater than that for the same tube crossing the field of measurement once. The effect of progressively switching flow (constant at 120 microl/h, hematocrit 9%) from five to one tube in a manifold of five tubes (100 microm) gave rise to a progressive increase in signal. It is concluded that LDF signal derives predominantly from nonvectorial cell speed and less from cell number. Thus any agent that alters the architecture has the potential to alter the LDF signal.     

通过测定外周组织氧分压及血液灌注诊断恶性肿瘤血瘀证的临床观察

目的:通过激光多普勒血流仪测定外周组织氧分压及血液灌注,判断其是否能诊断恶性肿瘤血瘀证。方法:选择健康人、恶性肿瘤非血瘀证患者、恶性肿瘤血瘀证患者各60例,用激光多普勒血流仪来测定3组的外周组织氧分压及血液灌注,选取受试对象的双上肢内关穴为检测部位,并设置32℃、36℃、38℃、40℃、42℃五个温度,记录不同温度下各组外周组织氧分压及血液灌注值。结果:3组的外周组织氧分压及在相同温度下的血流灌注值均有显著性差异,随着温度的升高,健康人组的外周组织血流灌注值显著升高,恶性肿瘤非血瘀证组次之,血瘀证组最差。结论:通过测定外周组织氧分压及血液灌注可以诊断中晚期恶性肿瘤血瘀证,且安全、方便、无创、无副作用,值得临床推广应用。     

Changes in maxillary incisor dental pulp blood flow during intrusion by mini-implants

Aim. The aim of this clinical study was to identify changes in pulpal blood flow (PBF) in human central incisors resulting from short- and long-term intrusive orthodontic forces from mini-implants. Materials and methods. A total of 40 sound upper central and lateral incisors in 20 patients scheduled for intrusion for orthodontic reasons were divided into two groups. From each group, 20 teeth were subjected to intrusive force from mini-implants (Group 1 = Light Force: 40 g; Group 2 = Heavy Force: 120 g), whereas the remaining 20 contralateral teeth were not subjected to forces from mini-implants and served as controls. Laser-Doppler flowmetry (LDF) measurements were recorded at baseline and at 3 days and 3 weeks following intrusion. Results. PBF decreased significantly at 3 days (Light Force Group: 7.72 ± 0.50; Heavy Force Group: 7.72 ± 0.52) and then increased towards baseline at 3 weeks (Light Force Group: 10.37 ± 0.58; Heavy Force Group: 10.31 ± 0.45) following intrusion. Conclusions. In other words, despite slight regressive changes in pulpal tissue in the short-term, PBF improved after 3 weeks following intrusion by mini-implants, indicating that the changes observed in PBF is reversible, even following radical incisor intrusion.