The degradation profile of novel, bioresorbable PCL-TCP scaffolds: an in vitro and in vivo study.

Degradation studies of scaffolds are important in bone tissue engineering. Previously, novel poly(epsilon-caprolactone)-20% tricalcium phosphate (PCL-TCP) based scaffolds were developed and proven useful for bone regeneration. In this study in vitro degradation analyses were carried out with the PCL-TCP scaffolds immersed in standard culture medium for 24 weeks. In vivo degradation was performed with the scaffolds implanted in the abdomen of rats for the same period of time. Results demonstrated greater degradation of PCL-TCP scaffolds in vivo than in vitro. At 24 weeks, the increase of average porosity of the scaffolds in vivo was 29.2% compared to 2.65% in vitro. Gel permeation chromatography (GPC) analysis revealed a decrease of 29% and 20% respectively in the Mn and Mw values after 24 weeks in vitro. However, a significant decrease in Mn and Mw values (79.6% and 88.7% respectively) were recorded in vivo. The mechanical properties however, were relatively similar and closely match those of cancellous bone even at 24 weeks. The results showed that the scaffold can be used for dentoalveolar reconstruction and PCL-TCP scaffolds have shown to possess the potential to degrade within the desired time period of 5-6 months and favorable mechanical properties.

Jasmonic acid carboxyl methyltransferase: a key enzyme for jasmonate-regulated plant responses.

Methyl jasmonate is a plant volatile that acts as an important cellular regulator mediating diverse developmental processes and defense responses. We have cloned the novel gene JMT encoding an S-adenosyl-l-methionine:jasmonic acid carboxyl methyltransferase (JMT) from Arabidopsis thaliana. Recombinant JMT protein expressed in Escherichia coli catalyzed the formation of methyl jasmonate from jasmonic acid with K(m) value of 38.5 microM. JMT RNA was not detected in young seedlings but was detected in rosettes, cauline leaves, and developing flowers. In addition, expression of the gene was induced both locally and systemically by wounding or methyl jasmonate treatment. This result suggests that JMT can perceive and respond to local and systemic signals generated by external stimuli, and that the signals may include methyl jasmonate itself. Transgenic Arabidopsis overexpressing JMT had a 3-fold elevated level of endogenous methyl jasmonate without altering jasmonic acid content. The transgenic plants exhibited constitutive expression of jasmonate-responsive genes, including VSP and PDF1.2. Furthermore, the transgenic plants showed enhanced level of resistance against the virulent fungus Botrytis cinerea. Thus, our data suggest that the jasmonic acid carboxyl methyltransferase is a key enzyme for jasmonate-regulated plant responses. Activation of JMT expression leads to production of methyl jasmonate that could act as an intracellular regulator, a diffusible intercellular signal transducer, and an airborne signal mediating intra- and interplant communications.

Trehalose synthesis by sequential reactions of recombinant maltooligosyltrehalose synthase and maltooligosyltrehalose trehalohydrolase from Brevibacterium helvolum.

A DNA fragment encoding two enzymes leading to trehalose biosynthesis, maltooligosyltrehalose synthase (BvMTS) and maltooligosyltrehalose trehalohydrolase (BvMTH), was cloned from the nonpathogenic bacterium Brevibacterium helvolum. The open reading frames for the two proteins are 2,331 and 1,770 bp long, respectively, and overlap by four nucleotides. Recombinant BvMTS, BvMTH, and fusion gene BvMTSH, constructed by insertion of an adenylate in the overlapping region, were expressed in Escherichia coli. Purified BvMTS protein catalyzed conversion of maltopentaose to maltotriosyltrehalose, which was further hydrolyzed by BvMTH protein to produce trehalose and maltotriose. The enzymes shortened maltooligosaccharides by two glucose units per cycle of sequential reactions and released trehalose. Maltotriose and maltose were not catalyzed further and thus remained in the reaction mixtures depending on whether the substrates had an odd or even number of glucose units. The bifunctional in-frame fusion enzyme, BvMTSH, catalyzed the sequential reactions more efficiently than an equimolar mixture of the two individual enzymes did, presumably due to a proximity effect on the catalytic sites of the enzymes. The recombinant enzymes produced trehalose from soluble starch, an abundant natural source for trehalose production. Addition of alpha-amylase to the enzyme reaction mixture dramatically increased trehalose production by partial hydrolysis of the starch to provide more reducing ends accessible to the BvMTS catalytic sites.

A novel proteinase inhibitor gene transiently induced by tobacco mosaic virus infection.

A gene (NgPI) encoding a novel proteinase inhibitor (PI) has been isolated from tobacco leaves. Protein encoded by the gene consists of 241 amino acid residues having a predicted molecular mass of 26.7 kDa and a calculated pI of 8.7. A predicted N-terminal signal sequence followed by a vacuolar targeting signal and a peptide conserved in the Kunitz type PIs were identified. The deduced NgPI protein has sequence homology with aspartic and cysteine protease inhibitors. The gene is present as double copies in the Nicotiana glutinosa genome. Expression of the NgPI gene is rapidly and transiently induced by tobacco mosaic virus infection at a time earlier than apparent lesions of hypersensitive responses appear on the leaves.

Analysis of expressed sequence tags from Brassica rapa L. ssp. pekinensis.

Non-redundant expressed sequence tags (ESTs) were generated from six different organs at various developmental stages of Chinese cabbage, Brassica rapa L. ssp. pekinensis. Of the 1,295 ESTs, 915 (71%) showed significantly high homology in nucleotide or deduced amino acid sequences with other sequences deposited in databases, while 380 did not show similarity to any sequences. Briefly, 598 ESTs matched with proteins of identified biological function, 177 with hypothetical proteins or non-annotated Arabidopsis genome sequences, and 140 with other ESTs. About 82% of the top-scored matching sequences were from Arabidopsis or Brassica, but overall 558 (43%) ESTs matched with Arabidopsis ESTs at the nucleotide sequence level. This observation strongly supports the idea that gene-expression profiles of Chinese cabbage differ from that of Arabidopsis, despite their genome structures being similar to each other. Moreover, sequence analyses of 21 Brassica ESTs revealed that their primary structure is different from those of corresponding annotated sequences of Arabidopsis genes. Our data suggest that direct prediction of Brassica gene expression pattern based on the information from Arabidopsis genome research has some limitations. Thus, information obtained from the Brassica EST study is useful not only for understanding of unique developmental processes of the plant, but also for the study of Arabidopsis genome structure.

Imaging features of posttransplantation lymphoproliferative disorder in pancreas transplant recipients.

OBJECTIVE: The purpose of this study was to describe the imaging features of posttransplant lymphoproliferative disorder (PTLD) in pancreas transplant recipients. CONCLUSION: The prominent image finding of PTLD in pancreas transplant recipients is diffuse allograft enlargement, an appearance that may be indistinguishable from the image findings of acute pancreatitis or transplant rejection. However, failure of response to immunosuppressive therapy, presence of intraallograft or extraallograft focal masses, or organomegaly may suggest the diagnosis of PTLD.

MR imaging of prostate cancer.

MR imaging technology is continually evolving and improving. Endorectal MR imaging provides excellent anatomic detail and is the most accurate imaging modality for staging prostate cancer with the ability to affect therapy and cure in many men. Failure to detect microscopic disease and microscopic capsular invasion remain significant weaknesses. MR spectroscopy has great potential for improving the sensitivity and specificity of MR imaging and expanding its diagnostic and staging usefulness.

Percutaneous abdominal and pelvic interventional procedures using CT fluoroscopy guidance.

OBJECTIVE: The purpose of our study was to assess the use of low-milliamperage CT fluoroscopy guidance for percutaneous abdominopelvic biopsy and therapeutic procedures. MATERIALS AND METHODS: We reviewed the clinical records and relevant imaging studies of 97 patients who underwent 119 percutaneous CT fluoroscopy-guided abdominal or pelvic procedures: fluid collection aspiration or drainage catheter insertion (n = 59), biopsy (n = 49), hepatocellular carcinoma ethanol ablation (n = 6), chemoneurolysis (n = 4), and brachytherapy catheter insertion (n = 1). These procedures were guided using a helical CT scanner providing real-time fluoroscopy reconstruction at six frames per second. A control panel and video monitor beside the gantry allowed direct operator control during all interventional procedures. RESULTS: One hundred twelve (94.1%) procedures were successfully performed using either a stand-off needle holder and continuous real-time CT fluoroscopy guidance or incremental manual insertion and intermittent CT fluoroscopy to confirm position. Image quality using low milliamperage was adequate for needle or drainage tube placement in all but two low-contrast liver lesions. Two hematomas were accessed but yielded no fluid on aspiration; one drainage procedure was abandoned after the patient developed endotoxic shock. Imaging of ethanol distribution during injection facilitated tumor ablation and neurolytic procedures. CT fluoroscopy allowed rapid assessment of needle, guidewire, dilator, and catheter placement, especially in nonaxial planes. Average CT fluoroscopy time for biopsy and therapeutic procedures was 133 sec (range, 35-336 sec) and 186 sec (range, 20-660 sec), respectively. CONCLUSION: CT fluoroscopy is a practical clinical tool that facilitates effective performance of percutaneous abdominal and pelvic interventional procedures.

Acute pancreatic transplant rejection: evaluation with dynamic contrast-enhanced MR imaging compared with histopathologic analysis.

PURPOSE: To evaluate the use of dynamic contrast material-enhanced gradient-recalled-echo MR imaging for the diagnosis of acute pancreatic transplant rejection, as confirmed at histopathologic analysis. MATERIALS AND METHODS: Thirty MR imaging studies were performed in 25 patients within 3 days of percutaneous biopsy or pancreatectomy. The mean percentage of parenchymal enhancement (MPPE) at dynamic contrast-enhanced MR imaging was calculated. RESULTS: Biopsy findings were no evidence of rejection (n = 7 [23%]), mild rejection (n = 10 [33%]), moderate (n = 6 [20%]) and severe (n = 2 [7%]) acute rejection, and infarction (n = 5 [17%]). The corresponding MPPEs at 1 minute were 106%, 66%, 62%, 57%, and 3%, respectively. Overlap of cases in the normal and rejection groups occurred; however, using an MPPE cutoff of 100% resulted in a sensitivity of 96%. An MPPE over 120% was seen in the normal group only. The MPPE was significantly greater in the normal group than in the rejection or infarction group (P < .05). CONCLUSION: Dynamic contrast-enhanced MR imaging is highly sensitive for the detection of acute pancreatic transplant rejection. Because of overlap of cases in the normal and rejection groups, percutaneous biopsy may be needed in some cases. Pancreatic allografts with infarction can be clearly identified.

Evaluation of biopsy needles and prototypic needle guide devices for percutaneous biopsy with CT fluoroscopic guidance in simulated organ tissue.

The authors evaluated accuracy and success rates for placement of fine-aspiration, core, and coaxial biopsy needles in pork meat with three needle guide devices and computed tomographic fluoroscopic guidance. Accuracy and reliability with a metallic sponge-forceps needle holder was equal to or greater than those with other devices, and it was preferred by operators due to its lighter weight and single-handed manipulation. All needle holders functioned poorly with thin-walled needles.

Frequency of abdominal CT findings in AIDS patients with M. avium complex bacteraemia.

BACKGROUND: Use of blood culture studies for early diagnosis of Mycobacterium avium complex (MAC) infection has become important due to the recent development of effective antibiotic therapy for this condition. This study assessed the abdominal computed tomography (CT) findings in patients with AIDS who presented with bacteraemic MAC infection. METHODS: A retrospective analysis of abdominal CT scans was performed in 24 patients who presented with MAC-positive blood culture. CT images were reviewed specifically to evaluate for lymph node enlargement and attenuation, hepatomegaly, splenomegaly, bowel wall abnormality and for any other pathological changes. Comparison was made to prior reports of the CT findings in this disease process. RESULT: Enlarged intra-abdominal mesenteric and/or retroperitoneal lymph nodes were found in 10 patients (42%). These nodes were characterized by homogeneous, soft-tissue attenuation in eight of the 10 patients. Hepatomegaly, splenomegaly and small bowel wall thickening were noted in 12 (50%), 11 (46%) and four (14%) patients, respectively. CT findings were evaluated as normal in six (25%) patients. CONCLUSIONS: Enlarged mesenteric and/or retroperitoneal lymph nodes in AIDS patients with bacteraemic MAC were observed much less frequently on CT than previously reported in AIDS patient populations. Normal abdominal CT findings do not exclude this diagnosis and may reflect a trend towards earlier detection of MAC disease.

Torsion of intraperitoneal renal transplants: imaging appearances.

OBJECTIVE: Torsion of a renal transplant is a rare complication with nonspecific clinical manifestations. Prompt detection is necessary to allow surgical treatment and to preserve renal function. We describe the radiologic appearances of torsion of intraperitoneal renal transplants in patients who have undergone simultaneous renal and pancreatic transplantation or dual renal transplantation. CONCLUSION: Renal transplant torsion should be suspected when a change in renal axis associated with abnormal perfusion occurs in an intraperitoneal kidney.

Creating a digital video-based teaching file for interventional procedures using CT fluoroscopy.

A computerized radiology education teaching file application, MRW (Multimedia Radiology Workstation), was produced in our department as a collaboration of faculty, fellows and a doctoral student. This inexpensive and flexible system is novice-programmable and is capable of capturing images from multiple modalities (including still and cine image) and organizing them into individual electronic teaching cases. Help and tutorial functions support the main case display functions.

Transitional cell carcinoma of the urinary tract: radiologic-pathologic correlation.

The urothelium is a target tissue for carcinogens that lead to the development of transitional cell carcinomas (TCCs), both synchronous and metachronous. Although there are pathologic and imaging features common to transitional cell tumors occurring anywhere in the genitourinary tract, certain findings are more typical of tumors of the renal pelvis, ureter, or urinary bladder. A slightly irregular, fixed mass arising from any urothelial surface is characteristic of TCC. Although such masses are usually confined to the collecting system lumina, larger lesions that arise in the renal pelvis may extend into the renal parenchyma, typically in an infiltrative pattern that preserves the reniform shape. In contrast to the rapidly developing mural edema associated with obstructing calculi, the relatively slow growth of ureteral TCC allows for gradual expansion of the ureteral lumen around the tumor and is less likely to produce acute renal colic. Focal wall thickening, either eccentric or circumferential, may also be a manifestation of TCC of the ureter or, less commonly, other portions of the urinary tract. The urinary bladder is the most common site of TCC; lesions are generally confined to the lumen and typically do not extend beyond the bladder wall until quite large.

End stage renal transplant failure: allograft appearances on CT.

INTRODUCTION: Failed renal allografts often are left in situ in patients who revert to chronic dialysis therapy or who undergo retransplantation. These patients may be investigated with computed tomography (CT) imaging for allograft-related or other abdominopelvic disease. This study describes the appearances of failed renal transplants on CT. METHODS: A retrospective study was made of the clinical records and CT findings on 25 studies in 14 patients, 5-156 months (average, 44 months) following allograft failure. CT studies were reviewed for allograft position, size, shape, attenuation value, calcification, cyst formation, related abdominopelvic findings and the presence of other allografts. Correlation was made with clinical findings in all patients and with pathological findings in six. RESULTS: Global shrinkage was noted in eight failed allografts, all of which were asymptomatic. Enlargement of two failed allografts was due to symptomatic acute infarction of the allograft in one patient and subacute haemorrhagic infarction simulating a tumour mass in another. CT attenuation values in individual allografts varied markedly due to fatty replacement, hydronephrosis, haemorrhage or dense calcification. Both a failed longstanding and a functioning more recently placed renal allograft were present in seven patients, four of whom had acute complications related to the more recently transplanted kidney. Two of six calcified allografts were mistaken for opacified bowel on CT. CONCLUSION: A wide spectrum in size, shape and attenuation values may be detected in failed renal allografts by CT. These organs may be the site of acute disease despite their lack of physiological function or may be diagnostically confusing findings in patients with acute disease related to more recently transplanted organs.

Adult renal hamartomas.

Renal angiomyolipomas, the most familiar of the renal hamartomas, are well known to radiologists, despite being uncommon and of limited clinical importance, because angiomyolipomas represent one of the few lesions for which a specific diagnosis can be achieved on the basis of radiologic findings in the majority of cases. Because of the diversity in the relative amounts of various cellular components and because of the occasional association with acute hemorrhage, the radiologic features of angiomyolipomas can be somewhat varied. At sonography, angiomyolipomas appear echogenic with acoustic shadowing. At computed tomography (CT), these lesions typically appear as well-marginated, small (< 5 cm in size), cortical masses of predominantly fat attenuation with heterogeneous soft-tissue attenuation interspersed throughout. Some angiomyolipomas are larger and poorly marginated because of hemorrhage. Typical angiomyolipomas are largely composed of fat; those uncommon tumors without demonstrable fat cannot be radiologically distinguished from renal cell carcinoma. Renal leiomyoma, a lesion that pathologically overlaps with angiomyolipoma to some degree, has a quite different imaging appearance (ie, homogeneous, without detectable fat) that cannot be distinguished from malignant renal lesions.