Electron-beam CT-angiography in abdominal aortic aneurysms. Initial results

PURPOSE: To evaluate the suitability of ultrafast electron-beam tomography (EBT) for the investigation of abdominal aortic aneurysms using CTA. METHODS: Thirty-one patients with suspected abdominal aortic aneurysm were investigated with EBT using an Evolution XP scanner (Siemens, Erlangen) with the newest software version 12.34 with continuous volume scanning of 140 images in 17 s. Collimation was 3 mm, table increment 4 mm with overlapping image reconstruction every 2 mm, exposure time 200 ms (124 mAs), resulting in a scan-range of 28 cm. A quantity of 80 ml contrast material was administered (flow 4 ml/s). Visualization of the abdominal aorta and its branches was performed with MIPs and shaded surface display. Evaluation of image quality was based on a four-step classification scale (1 = good, 4 = insufficient) for the demonstration of the abdominal aorta and the visceral, renal and iliac arteries. RESULTS: All EBT examinations demonstrated high and homogeneous density values along the whole vessel course with a mean density value of 258.7 +/- 47.3 HU for the abdominal aorta and the iliac arteries. Quality evaluation for the vessel demonstration showed mean values between 1.22 and 1.57 for the abdominal aorta and the visceral, renal and iliac arteries. CONCLUSIONS: EBT with 140 slices and slice reconstruction every 2 mm offers a high z-axis resolution resulting in high-quality CT angiographies of the whole abdominal aorta and its branches.     

Hemostatic and fibrinolytic indices in neonatal foals with presumed septicemia

Gerbils learned to approach a spatial-olfactory stimulus that signaled access to their pairmate. Experiments 1 and 3 used a discrimination procedure in which 1 conditioned stimulus (the CS+) was presented immediately before access to the pairmate and another (the CS-) was presented alone. Both male and female gerbils came to approach the CS+ sooner than the CS- and spent more time near the CS+ than the CS-. Discrimination learning was facilitated by making the CS+ and CS- spatially distinct (Experiment 3). Learning also was demonstrated in male gerbils, using a between-subjects design with a single CS. Pairing the CS with the opportunity for social interaction resulted in greater approach to the CS within 10 trials than presenting the CS and social opportunity in an unpaired fashion (Experiment 2). These findings demonstrate social-affiliative learning in the Mongolian gerbil. Similarities and differences between these findings and sexual conditioning effects in other species are discussed.     

Membrane topology of Borrelia burgdorferi and Treponema pallidum lipoproteins

A critical issue regarding the molecular architectures of Treponema pallidum and Borrelia burgdorferi, the agents of venereal syphilis and Lyme disease, respectively, concerns the membrane topologies of their major lipoprotein immunogens. A related question is whether these lipid-modified membrane proteins form intramembranous particles during freeze fracture electron microscopy. To address these issues, native borrelial and treponemal lipoproteins were reconstituted into liposomes of diverse composition. The importance of the covalently associated lipids for membrane association of lipoproteins was revealed by the observation that nonlipidated recombinant forms of both B. burgdorferi OspA and the T. pallidum 47-kDa immunogen (Tpp47) showed very weak or no binding to model bilayer vesicles. In contrast to control liposomes reconstituted with bacteriorhodopsin or bovine rhodopsin, two well-characterized transmembrane proteins, none of the lipoprotein-liposomes contained particles when examined by freeze fracture electron microscopy. To extend these findings to prokaryotic lipoproteins with relatively amphiphilic polypeptides, similar experiments were conducted with a recombinant nonlipidated form of Escherichia coli TraT, a lipoprotein which has putative transmembrane domains. The nonlipidated TraT oligomers bound vesicles derived from E. coli lipids but, surprisingly, did not form particles in the freeze-fractured liposomes. These findings support (i) a proposed topology of spirochetal lipoproteins in which the polypeptide is extrinsic to the membrane surface and (ii) the contention that particles visualized in freeze-fractured spirochetal membranes represent poorly characterized transmembrane proteins.     

Treatment outcome with radiation therapy after breast augmentation or reconstruction in patients with primary breast carcinoma

BACKGROUND: Analyses were performed to determine local control and cosmetic outcome of breast carcinoma patients with prosthetically augmented or reconstructed breasts who had received radiation therapy (RT). METHODS: Twenty-one newly diagnosed breast carcinoma patients with prosthetically augmented or reconstructed breasts were treated with external beam RT. All patients received whole breast RT (median dose, 50.4 gray [Gy]) and 19 were boosted to a median dose of 60.4 Gy. A median dose of 50.4 Gy was delivered to the regional lymph nodes in 12 patients. Tissue equivalent bolus material was used in six patients. Seventeen patients received adjuvant systemic therapy. Cosmetic results were evaluated at 3-6-month intervals. RESULTS: With a median follow-up of 32 months, good/excellent cosmetic results were observed in 71% of patients (100% in those with augmented breasts and 54% in those with reconstructed breasts). Four patients (19%) with fair/poor cosmetic outcomes required implant removal and/or revision. Multiple clinical and treatment-related factors were analyzed for their impact on cosmetic outcome. A worsened cosmetic result was observed with increasing stage (P = 0.076), breast reconstruction (vs. augmentation) (P = 0.030), and bolus application (P = 0.016). All patients with fair/poor cosmetic outcomes had time intervals from implant insertion to RT ranging from 53-213 days. Two patients developed an isolated local recurrence within the augmented breast. CONCLUSIONS: Patients with prosthetically augmented breasts can undergo RT and expect good/excellent cosmetic results. Patients with reconstructed breasts are at a significantly greater risk for cosmetic failure. This risk may be related to the higher percentage of patients with advanced disease, those who received bolus application, and those who received earlier delivery of RT (after the cosmetic procedure) in reconstructed breasts.     

Using the latissimus dorsi flap for breast reconstruction

The preferred method for breast reconstruction is the simplest type that can meet the patient's needs and expectations (Bostwick, 1989). Several breast reconstruction procedures are presented in this issue. In this article, only breast reconstruction using the latissimus dorsi flap is discussed.     

Cloning of cDNAs encoding xenopus neuregulin: expression in myotomal muscle during embryo development

The ontogeny of the myotome was investigated using [3H]thymidine or Brdu treatment in conjunction with 1,1', di-octadecyl-3, 3, 3', 3',-tetramethylindo-carbocyanine perchlorate (DiI) labeling and expression of specific markers. We have identified a subset of early post-mitotic cells that is present in the dorsomedial aspect of epithelial somites and is homogeneously distributed along their entire rostrocaudal extent. The post-mitotic quality of this cell subset enabled us to trace their fate in time-course experiments. Following initial somite dissociation, this epithelial post-mitotic layer bends underneath the medial portion of the nascent dermomyotome. Then, these cells progressively lose epithelial arrangement and migrate in a rostral direction where they accumulate temporarily. Subsequently, these early post-mitotic precursors extend processes that reach both rostral and caudal edges of each segment. Medial somite-derived myofibers also fill the entire mediolateral extent of the segment and reach the dorsomedial lip of the dermomyotome, thus forming the primary myotome. During this process, their large nuclei localize to a narrow stripe in the middle of the nascent myotome. Consistent with the proliferation studies, DiI labeling of the medial epithelial somite cells gave rise to a primary myotomal structure, and continuous pulsing of the DiI-injected embryos with radioactive thymidine revealed that these fibers indeed developed from post-mitotic progenitors. As these early post-mitotic cells that arise prior to somite dissociation are the first wave of progenitors that constitutes the myotome, we have termed them avian muscle pioneers. We propose that the primary myotome formed by the muscle pioneers constitutes a longitudinal scaffold that serves as a substrate for the addition of subsequent waves of myotomal cells.     

The relationship between arm-ankle pressure difference and peak systolic velocity in patients with stenotic lower extremity vein grafts

The relationship between the measured arm-ankle pressure difference (AAPD), or the ankle/arm index (AAI), and the focal peak systolic velocity (PSV) at stenotic sites of infrainguinal vein grafts has not been determined. We attempted to relate these two parameters. We used Doppler systolic pressures and duplex ultrasonography to study 35 infrainguinal vein bypass grafts followed in a surveillance protocol. The following graft groups were identified: grafts in nondiabetic patients (n = 26), grafts in diabetic patients (n = 9), nonrevised stenotic grafts (n = 14), revised stenotic grafts (n = 14), and normal grafts (n = 7). AAPD and AAI were measured in both lower extremities. Pressure gradients across graft stenoses were indirectly estimated using the modified Bernoulli equation (delta P =4V2). Measured AAPDs and estimated pressure gradients showed moderate correlation in nondiabetic (r = 0.58) and diabetic (r = 0.63) patients. Correlation was fair (r = 0.3) prior to graft revision. There was no correlation (r = 0.1) in the nonrevised stenotic grafts. For individual patients with stenotic grafts who were followed in consecutive visits, the correlation varied from none to good (r range 0.01 to 0.71). We conclude that there is a lack of consistent correlation between the measured AAPD, or AAI, and the estimated stenotic graft pressure gradient. This finding illustrates the limitation of the AAI as a monitoring test to predict failure of stenotic infrainguinal vein grafts.     

Oberflächenschutzschichten für metallische Hochtemperatur-Werkstoffe. Teil 2: Schutzschichten auf Superlegierungen und hochschmelzenden Metallen

Protection of High Temperature Metallic Materials against Oxidation , part 2; Protective Layers on Superalloys and High Temperature Materials. The structures of typical protective coatings of superalloys and Nb-alloys are briefly described and possible reasons for their failure are given. The importance of self-healing properties and of the reliability of such protective layers in any technical application is stressed. An order of magnitude of the duration of protection for different alloys is indicated for several coating types.