Plasmodium knowlesi: a superb in vivo nonhuman primate model of antigenic variation in malaria.

Antigenic variation in malaria was discovered in Plasmodium knowlesi studies involving longitudinal infections of rhesus macaques (M. mulatta). The variant proteins, known as the P. knowlesi Schizont Infected Cell Agglutination (SICA) antigens and the P. falciparum Erythrocyte Membrane Protein 1 (PfEMP1) antigens, expressed by the SICAvar and var multigene families, respectively, have been studied for over 30 years. Expression of the SICA antigens in P. knowlesi requires a splenic component, and specific antibodies are necessary for variant antigen switch events in vivo. Outstanding questions revolve around the role of the spleen and the mechanisms by which the expression of these variant antigen families are regulated. Importantly, the longitudinal dynamics and molecular mechanisms that govern variant antigen expression can be studied with P. knowlesi infection of its mammalian and vector hosts. Synchronous infections can be initiated with established clones and studied at multi-omic levels, with the benefit of computational tools from systems biology that permit the integration of datasets and the design of explanatory, predictive mathematical models. Here we provide an historical account of this topic, while highlighting the potential for maximizing the use of P. knowlesi - macaque model systems and summarizing exciting new progress in this area of research.

Mitogen activation induces the enhanced synthesis of two heat-shock proteins in human lymphocytes.

We have used mitogenic lectin (PHA) and a monoclonal antibody (OKT3) to stimulate human peripheral blood (G0) lymphocytes, in the presence of monocytes, and have found two major preferentially synthesized proteins, 73 and 95 kD, which are induced by the mitogens. The elevated synthesis of both proteins begins approximately 4-6 h after mitogen addition (early to mid G0/G1) before entry into first S phase. Maximum synthesis of both proteins is reached by 12 h after mitogen addition when P95 synthesis represents approximately 4%, and P73 approximately 2%, of the total protein synthesis, compared with less than 0.5% for each protein in cells cultured without mitogen. Thus, the proteins appear to be major components of activated cells. We find that both P73 and P95 are induced by heat stress as well as mitogenic stimulation. The induction of the proteins is not affected by either deleting glucose from the culture media or, alternatively, by supplementing it. Using polyclonal antibodies prepared to each of the proteins isolated from mitogen activated cells and monoclonal antibodies that were raised to heat shock proteins, we are able to show that P95 is electrophoretically and immunologically identical to the HSP 90 induced by heat stress. P73 is one of the 70 kD HSPs, (termed HSC 70; Pelham, H. R. B. 1986. Cell. 46: 959-961), but is different from the most strongly heat inducible form of HSP 70 (72 kD). The distribution of both proteins in subcellular fractions of mitogen activated lymphocytes is similar to the reported localization of the respective HSP's in other cell types. The results suggest that HSP 90 and HSC 70 may have functional roles in stress response and growth processes of human lymphocytes.

Acute lung injury. Pathogenesis of intraalveolar fibrosis.

In patients dying with acute lung injury, interstitial mesenchymal cells migrate into the airspace where they replicate and deposit connective tissue. We therefore hypothesized that peptides capable of promoting mesenchymal cell migration and replication would be present in the alveolar airspace. To examine this hypothesis, patients with severe acute diffuse lung injury (n = 26) underwent bronchoalveolar lavage. Acutely ill patients without lung injury served as controls (n = 12). Recovered effluent was examined for mesenchymal cell growth-promoting and migration-promoting activity. Lavage cell supernates from both patients and controls were devoid of bioactivity. However, substantial growth-promoting and migration-promoting activity was present in lavage fluid from nearly every patient, whereas little or none was present in fluid from controls. Characterization of the bioactivity indicated a significant proportion consisted of three peptides related to PDGF: (a) a 14-kD peptide that shared with PDGF several biophysical, biochemical, receptor-binding, and antigenic properties; (b) a 29-kD peptide that appeared identical to PDGF of platelet origin; and (c) a 38-kD peptide that was biophysically and antigenically similar to PDGF. These data indicate that peptide moieties are present in the airspace of patients after acute lung injury that can signal mesenchymal cell migration and replication.

Radiologic diagnosis of hepatocellular carcinoma.

Substantial recent technologic improvements in CT scanning, US scanning, and MR imaging, together with advances in the understanding of the optimal application of contrast administration techniques, have facilitated advances in radiologic imaging detection for HCC diagnosis. Despite a large number of earlier publications reporting a high sensitivity for imaging detection of HCC, more recent screening studies of large cirrhotic populations confirm that only 37% to 45% of HCC tumor nodules are detected by CT scanning, US scanning, or MR imaging. Future investigation will include efforts to improve the detection of small tumors and to characterize with greater specificity the spectrum of nodular changes that occur with cirrhosis. Although several small series have attempted to characterize cirrhotic nodules by evaluating the relative arterial or portal blood supply, these preliminary results require substantiation with larger series. Continued technologic advances such as multidetector helical CT scanning and new US and MR contrast agents under investigation may improve the imaging characterization of cirrhotic nodules.

Scale-up and optimization of the low-temperature inducible cspA promoter system.

The performance of the major Escherichia coli cold-shock promoter in directing the synthesis of recombinant proteins at low temperatures was investigated in batch fermentations using a plasmid-encoded transcriptional gene fusion between the cspA promoter region and the lacZ gene. Rapid synthesis of beta-galactosidase was observed when the fermentation broth was chilled to 15 degreesC using a variety of cooling profiles, including one modeling the heat-transfer characteristics of a 60-L pilot plant unit. A linear cooling rate of 0.5 degreesC/min led to optimum recovery yields. For all single-temperature downshift experiments, however, the promoter became repressed 60-120 min after initiation of cooling. Both temperature cycling between 15 and 25 degreesC and stepwise temperature downshifts between 37, 29, 21, and 13 degreesC led to multiple inductions of the cspA promoter. Nevertheless, high-efficiency reinduction was only observed during the first temperature pulse when the former strategy was used and when the cells were held at intermediate temperatures for less than 60 min or more than 120 min in the case of successive downshifts. Promoter repression was abolished in host cells bearing a null mutation in the gene encoding the ribosomal binding factor RbfA, leading to the constitutive and high-level expression of beta-galactosidase for 7 h postshift when shake flask cultures were transferred from 42 to 23 degreesC. The suitability of rbfA cells for cspA-driven recombinant protein production was confirmed in high-density fed-batch fermentations. Our results are consistent with the existence of a cold-shock-induced repressor molecule that must accumulate at a threshold concentration before interfering with the production of proteins placed under cspA transcriptional control.

A simultaneous multichannel monophasic action potential electrode array for in vivo epicardial repolarization mapping.

While the recording of extracellular monophasic action potentials (MAPs) from single epicardial or endocardial sites has been performed for over a century, we are unaware of any previous successful attempt to record MAPs simultaneously from a large number of sites in vivo. We report here the design and validation of an array of MAP electrodes which records both depolarization and repolarization simultaneously at up to 16 epicardial sites in a square array on the heart in vivo. The array consists of 16 sintered Ag-AgCl electrodes mounted in a common housing with individual suspensions allowing each electrode to exert a controlled pressure on the epicardial surface. The electrodes are arranged in a square array, with each quadrant of four having an additional recessed sintered Ag-AgCl reference electrode at its center. A saline-soaked sponge establishes ionic contact between the reference electrodes and the tissue. The array was tested on six anesthetized open-chested pigs. Simultaneous diagnostic-quality MAP recordings were obtained from up to 13 out of 16 ventricular sites. Ventricular MAPs had amplitudes of 10-40 mV with uniform morphologies and stable baselines for up to 30 min. MAP duration at 90% repolarization was measured and shown to vary as expected with cycle length during sustained pacing. The relationship between MAP duration and effective refractory period was also confirmed. The ability of the array to detect local differences in repolarization was tested in two ways. Placement of the array straddling the atrioventricular (AV) junction yielded simultaneous atrial or ventricular recordings at corresponding sites during 1:1 and 2:1 AV conduction. Localized ischemia via constriction of a coronary artery branch resulted in shortening of the repolarization phase at the ischemic, but not the nonischemic, sites. In conclusion, these results indicate that the simultaneous multichannel MAP electrode array is a viable method for in vivo epicardial repolarization mapping. The array has the potential to be expanded to increase the number of sites and spatial resolution.

Computed tomography-guided wire localization of pulmonary lesions before thoracoscopic resection: results in 101 cases.

The authors determine the success rate, safety, and potential complications of computed tomography-guided preoperative hookwire localization of small peripheral pulmonary nodules. One hundred one consecutive wire localizations with addition of methylene blue injection were performed in 94 patients immediately before thoracoscopic resection of small lung lesions. Sixty-two patients had a known primary malignancy, whereas 32 had an asymptomatic nodule. Eighty-eight patients underwent single lesion localization, five underwent double localization, and one underwent triple wire placement. Five patients had previously undergone percutaneous biopsy that was nondiagnostic. The nodule was within the first wedge biopsy of lung tissue in 95 of 97 specimens (98%). A second wedge and an open lobectomy were required in one patient each. Three additional biopsies were intraoperatively deferred after the histologic diagnosis was established after removal of another nodule. The procedure was terminated before wire placement in one patient who was unable to successfully hold his breath. The wire dislodged with the tip in the pleural space rather than in the lung parenchyma in 22 cases; however, methylene blue tattoo allowed localization in 13 of these (59%). In the other nine cases, extra portals, digital palpation, or expanded wedge resection was required. Complications included pneumothorax in 48 cases, moderate pleuritic pain in five cases, seven small intercostal hematomas, and a 7-mm wire fragment retained in one patient's lung along the suture line. No patient required a preoperative drain for treatment of pneumothorax. Wire dislodgement occurred in 6 of 52 (12%) cases without an initial pneumothorax and in 16 of 48 (33%) cases if a pneumothorax occurred. Wires dislodged less frequently if placed either directly into or through the nodule in 11 of 64 (17%) cases than if placed adjacent to the nodule in 11 of 36 (31%) cases. Average wire tip depth from the visceral pleura was significantly less when the wire dislodged (11 mm) than when the wire remained in place (25 mm). Wire localization of small peripheral pulmonary nodules is a safe and effective procedure to assist thoracoscopic sublobectomy resection.

Evidence for distinct attentional bottlenecks in attention switching and attentional blink tasks.

E. Weichselgartner and G. A. Sperling (1987), using rapid serial visual presentation (RSVP), estimated that attention could be moved to a new spatial location within 300-400 ms. H. J. Müller and P. M. Rabbit (1989) used a spatial cuing task and found a similar time course for voluntarily redeploying attention. A separate phenomenon known as the attentional blink (AB) also follows a similar time course, yet occurs when participants attend to a single spatial location. The present study found that attention can be shifted more quickly than previously estimated and that part of the deficit observed during searches of spatially distinct RSVP streams is due to an AB. The results support some early and late selection accounts for the temporal dynamics of visual attention and suggest different bottlenecks during visual selection. The implications for visual search and visual processing are discussed.

Screening and evaluating abused and neglected children entering protective custody.

Clinical research has documented a variety of problems that abused and neglected children present as a result of their having been maltreated. When these children enter protective custody, however, they rarely receive systematic screening and/or assessment of their current mental health functioning as a part of case management. The Screening and Evaluation Project (SEP) is a clinical research study examining the range of problems in 167 children entering protective custody. Both empirical and theoretical grounds support the importance of early screening and evaluation programs for children in these circumstances. Practical issues in implementing such programs are also discussed.

From the RSNA refresher courses: screening the cirrhotic liver for hepatocellular carcinoma with CT and MR imaging: opportunities and pitfalls.

The inherent distortion of the appearance of liver parenchyma by the underlying pathologic changes of cirrhosis can obscure and simulate malignancy at imaging. That hepatocellular carcinoma is the most common abdominal malignancy worldwide and occurs most often in patients with chronic liver disease and cirrhosis compounds this problem. Magnetic resonance (MR) imaging and, to a lesser extent, computed tomography (CT) can depict the underlying nodular and fibrotic changes in patients with cirrhosis, particularly when siderotic nodular regeneration is present. Application of state-of-the-art helical CT and MR imaging techniques has improved the ability to detect hepatocellular carcinoma in this population, but, even with these advances, fewer than 50% of small tumors are detected with either of these techniques in a screening population. Dynamic hepatic arterial-phase contrast material-enhanced imaging is essential with both CT and MR imaging to achieve even these levels of success. Benign lesions that simulate tumor tissue are encountered in many patients with cirrhosis and include focal fibrosis, infarcted regenerative nodules, arteriovenous shunts, hemangiomas, pseudoaneurysms, and focal transient hepatic enhancement. An awareness of the imaging characteristics of these lesions can help one avoid a mistaken diagnosis of hepatocellular carcinoma in many cases.

Attentional guidance of the eyes by contextual information and abrupt onsets.

Contextual cuing is a memory-based phenomenon in which previously encountered global pattern information in a display can automatically guide attention to the location of a target (Chun & Jiang, 1998), leading to rapid and accurate responses. What is not clear is how contextual cuing works. By monitoring eye movements, we investigated the roles that recognition and guidance play in contextual cuing. Recognition does not appear to occur on every trial and sometimes does not have its effects until later in the search process. When recognition does occur, attention is guided straight to the target rather than in the general direction. In Experiment 2, we investigated the interaction between memory-driven search (contextual cuing) and stimulus-driven attentional capture by abrupt onsets. Contextual cuing was able to override capture by abrupt onsets. In contrast, onsets had almost no effect on the degree of contextual cuing. These data are discussed in terms of the role of top-down and bottom-up factors in the guidance of attention in visual search.

Santorinicele in pancreas divisum: diagnosis with secretin-stimulated magnetic resonance pancreatography.

A Santorinicele, or cystic dilatation of the dorsal pancreatic duct at the minor papilla, is seen in a small number of patients with pancreas divisum and may indicate obstruction at the minor papilla, a risk factor for pancreatitis. We present a case of a Santorinicele that was diagnosed with secretin-stimulated magnetic resonance pancreatography and treated with minor papillotomy.

2'-deoxyribosyl analogues of UDP-N-acetylglucosamine in cells treated with methotrexate or 5-fluorodeoxyuridine.

dUDP-GlcNAc, the 2'-deoxyribosyl analogue of UDP-GlcNAc, has been identified in human lymphoid cells treated with the dihydrofolate reductase inhibitor, methotrexate. It was shown previously that elevation of dUTP accompanies the gross expansion in intracellular deoxyuridylate pools that results from the methotrexate-induced block in thymidylate synthetase activity (1). dUDP-GlcNAc presumably is formed from dUTP acting in place of UTP in the normal pathway for formation of UDP-GlcNAc. Neither dUTP nor dUDP-GlcNAc has been detected in untreated cells. Inhibition of thymidylate synthetase by treatment of cells with 5-fluorodeoxyuridine (5-FdUrd) also causes the appearance of dUDP-GlcNAc, and, in addition, 5-FdUDP-GlcNAc, synthesized from 5-FdUTP. The metabolic effects, if any, of these analogues are not known. Synthesis of the analogues may help to limit accumulation of dUTP and 5-FdUTP under circumstances in which the deoxyuridine triphosphatase mechanism is insufficient.

MR imaging patterns of gadolinium retention within liver neoplasms.

BACKGROUND: To determine the spectrum of appearances of gadolinium retention within cholangiocarcinoma (CCA) and other liver neoplasms. METHODS: Two hundred ten patients underwent hepatic magnetic resonance imaging (MRI) at 1.5 T with precontrast T1- and T2-weighted spin-echo (SE) images and delayed Gd-DTPA- or gadoteridol- (0.1 mmol/kg) enhanced T1-weighted SE images. Postcontrast images were evaluated for lesions suspicious for tumors, and lesion signal intensity was characterized as homogeneously or heterogeneously hypo-, iso-, mildly hyper-, or markedly hyperintense to liver. Data from 94 patients with benign or malignant neoplasms are presented. RESULTS: Imaging demonstrated 237 malignant neoplasms (121 hepatocellular carcinoma [HCC], 26 CCA, 17 colon carcinoma metastases, 73 other tumors) and 28 benign neoplasms (22 hemangioma, six focal nodular hyperplasia [FNH]). One hundred forty malignant lesions appeared as homogeneous postcontrast (29 hypointense, 75 isointense, 17 mildly hyperintense, 19 markedly hyperintense) and 97 as heterogeneous (15 isointense, 50 mildly hyperintense, 32 markedly hyperintense). Malignant lesions showing homogeneous, mildly or markedly hyperintense signal intensity postcontrast included 10 CCA, seven HCC, six epithelioid hemangioendothelioma, eight neuroendocrine tumor metastases, three adenocarcinoma metastases of unknown origin, and one breast carcinoma metastasis. Hemangiomas appeared as homogeneous postcontrast in 19 lesions (six isointense, one mildly hyperintense, 12 markedly hyperintense) and as heterogeneous in three lesions (markedly hyperintense). FNH appeared as homogeneous postcontrast in one lesion (isointense) and as heterogeneous in five lesions (one isointense, four mildly hyperintense). CONCLUSION: Homogeneous gadolinium retention on delayed postcontrast images of malignant hepatic neoplasms is seen in a high percentage of CCA lesions and less commonly with other neoplasms.

Priming effects in attentional gating.

Three experiments were conducted to determine the effects of amount of prior target information (Experiment 1) and semantic priming (Experiment 2) in an attentional gating task. The goal was to determine some causes of the processing deficits commonly observed in perceiving successive visual stimuli. Items in a rapid serial visual presentation (RSVP) stream are subject to processing deficits before they are processed to the level of recognition (early selection) and after they have been recognized (late selection). Deficits in the former case presumably are due to an early filter that prevents complete recognition and semantic analysis, whereas deficits in the latter case arise from interference or response competition, producing forgetting among a set of recognized items. The semantic-priming effects found between a cue and a target (Experiment 2) and between two successive targets (Experiment 3) indicate that top-down processes can increase the subjective availability of related items. The results are consistent with the idea that most processing deficits observed in search through an RSVP sequence are due to limited capacity in our ability to form episodic representations of all the items in the sequence.

Hepatic malignancies: usefulness of acquisition of multiple arterial and portal venous phase images at dynamic gadolinium-enhanced MR imaging.

PURPOSE: To determine whether liver tumor detection is increased by acquiring multiple dynamic arterial phase and portal venous phase magnetic resonance (MR) images. MATERIALS AND METHODS: Dynamic MR imaging was performed in 205 patients at 1.5 T with use of a fast spoiled gradient-echo technique (repetition time, 9-12 msec; echo time, 2.1-3.0 msec; flip angle, 30 degrees). During intravenous bolus injection of gadopentetate dimeglumine or gadoteridol (0.1 mmol/kg), nine images were acquired at each of 10-12 locations over approximately 120 seconds. The number of tumors detected on arterial phase and portal venous phase images and unenhanced T1- and T2-weighted spin-echo (SE) images was evaluated separately. Data obtained in 75 patients with proved malignancies were analyzed. RESULTS: At imaging, 220 malignant tumor nodules were depicted. At prospective review of all images, 110 hepatocellular carcinomas (HCCs) were detected: 82 (75%) on unenhanced T1-weighted SE images, 83 (75%) on unenhanced T2-weighted SE images, 92 (84%) on arterial phase images, and 76 (69%) on portal venous phase images. At prospective review, eight HCCs were detected on only arterial phase images, one on only portal venous phase images, nine on both arterial and portal venous phase images, and 11 on only unenhanced SE images. The 18 additional HCCS detected prospectively on only dynamic images increased HCC detection by 21% over prospective detection on only SE images. Detection of non-HCC tumors (including metastases) did not increase with dynamic images. CONCLUSION: Acquisition of multiple dynamic arterial phase and portal venous phase images increased detection of HCC but not metastases.

Hepatic angiosarcoma: findings on multiphasic contrast-enhanced helical CT do not mimic hepatic hemangioma.

OBJECTIVE: The objective of our study was to identify multiphasic contrast-enhanced helical CT findings of angiosarcoma of the liver to determine whether this tumor could be confused with hemangioma of the liver. CONCLUSION: Angiosarcoma of the liver is a multifocal tumor with a variety of findings on multiphasic contrast-enhanced helical CT. None of the findings would usually be confused with the typical findings of hepatic hemangioma.

Liver necrosis and regeneration after fulminant hepatitis: pathologic correlation with CT and MR findings.

PURPOSE: To characterize computed tomographic (CT) and magnetic resonance (MR) findings of liver necrosis and regeneration after fulminant hepatitis. MATERIALS AND METHODS: Three patients with fulminant hepatitis underwent CT before orthotopic liver transplantation; one also underwent MR imaging. These findings were retrospectively reviewed and compared with gross and histologic findings obtained after transplantation. RESULTS: Regions of liver necrosis demonstrated low attenuation on CT scans before contrast material was administered and enhanced to attenuation equal to or greater than that of liver regeneration on postcontrast CT images. Conversely, nodular liver regeneration demonstrated hyperattenuation on precontrast and hypoattenuation on postcontrast CT images, which simulated neoplastic lesions. The necrotic liver parenchyma was seen as high and low intensity on T2- and T1-weighted MR images, respectively, whereas areas of regeneration appeared as hypo- and hyperintense. CONCLUSION: Characteristic patterns of liver regeneration after fulminant hepatitis may be seen at CT and MR imaging. Recognition of this regeneration process may avoid an incorrect diagnosis of malignancy.