The Right Ventricular Outflow Tract as an Alternative Permanent Pacing Site: Long-Term Follow-Up

The long-term characteristics of the right ventricular outflow tract have been assessed as an alternative permanent pacing site to the right ventricular apex. Thirty-three consecutive patients requiring ventricular pacing were randomized to be paced from one of the two sites. Pacing was performed using a screw-in lead, and a programmable pacemaker was used to facilitate threshold testing. There was no significant difference in the lead positioning time or any acute implant measurement (e.g., threshold at 0.5 msec 0.4 +/- 0.2 V for both sites, P = 0.99). Chronic measurements were also comparable during follow-up (mean 73 months) with a mean threshold at most recent follow-up of 0.15 +/- 0.2 msec (apex) and 0.13 +/- 0.21 msec (outflow tract) at 5 V, P = 0.81. There was only one pacing related complication, a lead dislodgment (outflow tract) in a pacemaker twiddler. Overall, both sites were highly satisfactory.     

Evaluation of an In-Line Bipolar Polyurethane Ventricular Pacing Lead

A study was undertaken to evaluate the performance of the Medtronic 4012 polyurethane in-line bipolar pacing electrode. One hundred twenty six patients implanted with the 4012 lead were followed by our clinic with 116 of these leads implanted at our institution. Patients were followed a minimum of every 4 months. Testing included the performance of stimulation thresholds, sensing thresholds, and provocative maneuvers to evaluate for myopotential inhibition testing a minimum of every eight months. There were 12 documented lead failures of the total 126 patients. Further analysis was limited to the ten failures occurring in the 116 leads implanted at our center. All ten failed leads utilized the suture anchoring sleeve. Six of the leads were left cephalic implants, three were right cephalic, and one was right subclavian. Manifestations of failure included: seven oversensing abnormalities, three undersensing, four loss of ventricular capture, one premature end of service, four lead impedance decreases to < 250 Ω and some presentations in combination. No leads were explanted for evaluation. The Kaplan-Meier product limit method was used to estimate the time to lead failure. The probability of not experiencing a lead failure within the first 4 years of implant is estimated to be 0.9103 (SE = 0.0338). Pacemaker dependent patients implanted with the 4012 lead should be given special consideration for prophylactic replacement.     

THE EFFECTS OF EXTRACELLULAR MATRIX AND OSTEOGENIC PROTEIN-1 ON THE MORPHOLOGICAL DIFFERENTIATION OF RAT SYMPATHETIC NEURONS

The growth patterns of axons and dendrites differ with respect to their number, length, branching, and spatial orientation; therefore, it is likely that these processes differ in their growth requirements. To examine this hypothesis, we have been analyzing the responses of cultured rat sympathetic neurons to three types of stimuli: large structural proteins of the extracellular matrix, matrix-associated growth factors, and neurotrophins. Purified structural proteins such as laminin and collagen IV have been found to promote only axonal growth; whereas the matrix associated growth factor, osteogenic protein-1, selectively stimulates dendritic growth. In contrast, nerve growth factor modulates the growth of both types of processes. These data suggest that process-specific interactions with the extracellular environment may be critical determinants of cell shape in neurons. Perinatal rat sympathetic neurons grown in culture in the absence of serum or glial cells extend a single process which is axonal in nature. Exposure to osteogenic protein-1 causes the formation of additional processes which express the morphological, cytoskeletal, and ultrastructural characteristics of dendrites. Consistent with observations on the regulation of dendritic growth in sympathetic neurons in situ, the dendrite-promoting activity of osteogenic protein-1 is independent of synaptic or electrical activity, but is modulated by nerve growth factor. In the presence of optimal concentrations of osteogenic protein-1 and nerve growth factor, the size of the dendritic arbor extended by cultured sympathetic neurons approximates that seen in situ at comparable developmental stages. Osteogenic protein-1 does not promote dendritic growth in cultured neurons obtained from embryonic ciliary, dorsal root, trigeminal or nodose ganglia, suggesting that its morphogenetic effects are cell selective. Since mRNA for osteogenic protein-1 is expressed in mature as well as embryonic target tissues of the sympathetic nervous system, we also examined the effects of osteogenic protein-1 on cultures of sympathetic neurons derived from adult rats. Consistent with results obtained with perinatal neurons, osteogenic protein-1 selectively promoted dendritic growth in adult neurons. These data suggest that this matrix-associated growth factor could play a role not only in the morphogenesis of the developing nervous system, but also in the maintenance and remodeling of dendritic structures in the mature animal. Copyright © 1996 ISDN. Published by Elsevier Science Ltd.     

IN VIVO PHOTOINDUCTION OF METALLOTHIONEIN IN HUMAN SKIN BY ULTRAVIOLET IRRADIATION

The aims of this study were to confirm and substantiate the in vivo cutaneous induction of metallothionein (MT) in human skin by UVR, which we have reported in brief previously, and to make a preliminary attempt to characterize the time course of this phenomenon. Buttock skin in 32 volunteers was irradiated with 2 MED of UVB and biopsies were taken at 24 h from matched non-irradiated and irradiated sites. In the kinetic study, skin biopsies from six volunteers were taken at 0, 2, 8, 24, and 48 h after 2 MED UVB irradiation. MT was immunolocalized in formalin-fixed, paraffin-embedded tissue with the monoclonal antibody E9 by an indirect immunoperoxidase method. Statistically significant differences between immunocytochemical scores were identified between non-irradiated (NI) and irradiated (I) skin within suprabasal keratinocytes (mean: NI=1·2, I=5·1; P =0·01), superficial dermal fibroblasts (mean: NI=2, I=43; P <0·001), mid-dermal fibroblasts (mean: NI=0, I=27; P<0·001), and deep dermal fibroblasts (mean: NI=0,1=11; P<0·001. In the kinetic study, no consistent rise in MT score with time was observed for the epidermal component. In dermal fibroblasts, however, the first statistically significant rise in immunocytochemically detectable MT was detected at 2 h and this was found to plateau beyond 8 h. These results confirm that ambient levels of UV irradiation are capable of inducing MT in human skin in vivo . Taken together with the relative rapidity of the response, this suggests a physiological photoprotective role for MT in human skin cells. The lack of a kinetic increase in epidermal MT may be due to high basal levels. Induction of MT in dermal fibroblasts may reflect the effects of a diffusible factor released from keratinocytes after UVR.     

BAYESIAN IMPUTATION OF PREDICTIVE VALUES WHEN COVARIATE INFORMATION IS AVAILABLE AND GOLD STANDARD DIAGNOSIS IS UNAVAILABLE

We suggest a conceptually simple Bayesian approach to inferences about the conditional probability of a specimen being infection-free given the outcome of a diagnostic test and covariate information. The approach assumes that the infection state of a specimen is not observable but uses the outcomes of a second test in conjuction with those of the first, that is, dual testing data. Dual testing procedures are often employed in clinical laboratories to assure that positive samples are not contaminated or to increase the likelihood of correct diagnoses. Using the CD4 count and a proxy for risk behaviour as covariates, we apply the method to obtain inferences about the conditional probability of an individual being HIV-1 infection-free given the individual's covariates and a negative outcome with the standard enzyme-linked immunoadsorbent assay/Western blotting test for HIV-1 detection. Inferences combine data from two studies where specimens were tested with the standard and with the more sensitive polymerase chain reaction test.     

尺骨喙突前内侧面骨折

背景：最近，尺骨喙突前内侧面骨折已被划为尺骨喙突骨折的一个独立类型，多由后内侧内翻旋转暴力引起。目前，只有少量报道涉及尺骨喙突前内侧面骨折的治疗。方法：6年中共收治18例尺骨喙突前内侧面骨折患者，其中，12例急诊处理，6例在外院处理后在我院接受治疗。18例患者中，15例外侧副韧带复合体从其在外上髁的起点撕脱，2例合并尺骨鹰嘴骨折，1例合并尺骨喙突基底部骨折。15例患者初始接受手术治疗，3例接受非手术治疗。所有尺骨喙突骨折中，9例使用钢板固定尺骨喙突的内侧面，1例使用螺钉，1例使用缝线缝合，其余7例患者未进行修复。结果：最后一次对患者的评估距伤后平均为26个月，结果显示：6例尺骨喙突前内侧面对线不良，肘关节内翻半脱位。其中，4例源于没有处理尺骨喙突内侧面骨折，2例源于固定失效。所有这6例均发生了关节病，患者按照Broberg和Morrey评分系统，结果为可或差。其余12例肘关节功能评定为良或优。结论：尺骨喙突前内侧面骨折多伴有肘关节半脱位或全脱位，对其采用坚强内固定，通常可以恢复肘关节功能。可信水平：治疗性研究，Ⅲ级。进一步可信度参见作者介绍。