Poly(ethylene glycol) (PEG)-mediated fusion between pure lipid bilayers: a mechanism in common with viral fusion and secretory vesicle release?

Membrane fusion is fundamental to the life of eukaryotic cells. Cellular trafficking and compartmentalization, import of food stuffs and export of waste, inter-cellular communication, sexual reproduction, and cell division are all dependent on this basic process. Yet, little is known about the molecular mechanism(s) by which fusion occurs. It is known that fusing membranes must somehow be docked and brought into close contact. Specific proteins, many of which have been identified within the past decade, accomplish this. An electrical connection or 'fusion pore' is established between compartments surrounded by the fusing membranes. Three primary views of the mechanism of pore formation during secretory and viral fusion have been proposed within the past decade. In one view, a protein ring forms an initial transient connection that expands slowly by recruiting lipid so as to form a lipidic junction. In another view, the initial fusion pore consists of a protein-lipid complex that transforms slowly until the fusion proteins dissociate from the complex to form an irreversible lipidic pore. In a third view, the initial pore is a transient lipid pore that fluctuates between open and closed states before either expanding irreversibly or closing. Recent work has helped define the mechanism by which poly(ethylene glycol) (PEG) mediates fusion of highly curved model membranes composed only of synthetic phospholipids. PEG is a highly hydrated polymer that can bring vesicle membranes to near molecular contact by making water between them thermodynamically unfavourable. Disrupted packing in the contacting monolayers of these vesicle membranes is necessary to induce fusion. The time course and sequence of molecular events of the ensuing fusion process have also been defined. This sequence of events involves the formation of an initial, transient intermediate in which outer leaflet lipids have mixed and small transient pores join fusing compartments ('stalk'). The transient intermediate transforms in 1-3 min to a fusion-committed, second intermediate ('septum') that then 'pops' to form the fusion pore. Inner leaflet mixing, which is shown to be distinct from outer leaflet mixing, accompanies contents mixing that marks formation of the fusion pore. Both the sequence of events and the activation energies of these events correspond well to those observed in viral membrane fusion and secretory granule fusion. These results strongly support the contention that both viral and secretory fusion events occur by lipid molecule rearrangements that can be studied and defined through the use of PEG-mediated vesicle fusion as a model system. A possible mechanism by which fusion proteins might mediate this lipidic process is described.

Cloning and characterization of a mammalian N-acetylglucosamine-6-sulfotransferase that is highly restricted to intestinal tissue

Using the sequences of a galactose 6-O-sulfotransferase and an N-acetylglucosamine 6-O-sulfotransferase as probes in an EST approach, we have identified a highly related cDNA in human and an apparent orthologue in mouse. The cDNAs predict type II transmembrane proteins that constitute new members of the Gal/GalNAc/GlcNAc 6-O-sulfotransferase (GST) family. Members of this family have previously been implicated in the sulfation of GAG chains within proteoglycans and the sulfation of O-linked chains within sialomucin ligands for l-selectin. Expression of the newly identified cDNA in COS cells led to the addition of sulfate to C-6 of GlcNAc in an acceptor glycoprotein. The tissue expression of transcripts corresponding to the cDNA was highly restricted to the small intestine and colon in humans. Based on these characteristics, the novel sulfotransferase is designated I-GlcNAc6ST for intestinal GlcNAc 6-O-sulfotransferase.

Conceptually new sulfone analogues of the hormone 1alpha, 25-dihydroxyvitamin D(3): synthesis and preliminary biological evaluation

A conceptually new series of vitamin D(3)-like nonfluorinated and fluorinated 16-ene side chain tert-butyl sulfones 3-7 has been synthesized. Even though these novel C,D-ring side chain analogues of the hormone 1alpha,25-dihydroxyvitamin D(3) (1,1,25D(3)) lack a terminal OH group, thought previously to be essential for high biological activity, they are highly antiproliferative and, in several cases, transcriptionally active in vitro but desirably noncalcemic in vivo. The side chain sulfone group may be binding to the nVDR as a hydrogen-bond acceptor, in contrast to the hydrogen-bond donor function of the 25-OH group of natural 1,25D(3).

Evaluation of regional cerebral blood flow with 99mTc-HMPAO in primary antiphospholipid antibody syndrome

In this study, 99mTc-hexamethyl propyleneamine oxime (HMPAO) SPECT was used to evaluate the regional cerebral blood flow (rCBF) of the brain in patients with primary antiphospholipid antibody syndrome (PAPS).

METHODS

Twenty-two women who were PAPS patients, aged 28-60 y, with mild neuropsychiatric manifestations and normal brain MRI findings were enrolled in this study. Brain HMPAO SPECT was performed to detect brain abnormalities. Meanwhile, serum anticardiolipin antibodies (ACA) and lupus anticoagulant (LA) were measured.

RESULTS

HMPAO SPECT revealed hypoperfusion lesions in 16 of 22 (73%) PAPS patients. Cerebral cortex and cerebellum were the most and the least commonly involved areas, respectively. Eighteen of 22 (82%) and 14 of 22 (64%) patients had positive ACA and positive LA, respectively. ACA and LA results were related to HMPAO SPECT findings.

CONCLUSION

HMPAO SPECT is a sensitive tool for detecting brain abnormalities in PAPS patients with only mild neuropsychiatric manifestations and normal brain MRI findings.

Cytokeratin fragment 19 (CYFRA 21-1) in healthy smokers

Two hundred and ninety-three normal female non-smokers, 268 normal male non-smokers, and 224 normal male smokers were included in our comparative study to determine possible effect of smoking on the serum levels of cytokeratin fragment 19 (CYFRA 21-1). Immunoradiometric assay (IRMA) was used, and the results revealed that the mean +/- SD CYFRA 21-1 levels in the 293 normal female non-smokers, 268 normal male non-smokers, and 224 normal male smokers were 1.28 +/- 0.82, 1.38 +/- 0.74, and 1.47 +/- 0.62 ng/ml, respectively. There is no significantly statistical difference in the CYFRA 21-1 level among the three groups. In conclusion, we suggest that smoking has no effect on the serum levels of CYFRA 21-1.

Adult intussusception detected at CT or MR imaging: clinical-imaging correlation

PURPOSE

To determine the clinical presentation in cases of adult intussusception demonstrated at computed tomography (CT) or magnetic resonance (MR) imaging and to correlate the imaging appearance with clinical diagnosis.

MATERIALS AND METHODS

Retrospective review of CT and MR images and clinical records of all patients with an intussusception demonstrated on CT or MR images from January 1, 1991, through April 30, 1998.

RESULTS

Thirty-three patients had one or more intussusceptions demonstrated on CT (n = 30) or MR (n = 3) images. Twenty-nine patients had enteroenteric intussusceptions, and four had intussusceptions involving the colon. Ten patients (30%) had a neoplastic lead point, including all four of the intussusceptions involving the colon (benign mass, n = 3; malignant mass, n = 7). In 23 cases (70%), no neoplastic lead point was identified. A variety of causes were implicated in these cases, with 16 cases (48%) classified as idiopathic. Enteric intussusceptions in the nonneoplastic group were shorter in length (median, 4 vs 10.8 cm; P = .002), smaller in diameter (median, 3 vs 4 cm; P = .002), and less likely to be associated with obstruction (4.3% vs 50%; P = .02).

CONCLUSION

Less than one-third of adult intussusceptions demonstrated at CT or MR imaging were caused by a neoplastic lead point. Almost half of adult cases in this series were idiopathic.

Respiratory diphtheria in three paediatric patients

From August till November 1998, the Paediatric and Anaesthetic Units of Hospital Kuala Terengganu managed three patients from Kuala Terengganu District who were ventilated for respiratory diphtheria. Their ages were 5, 4 and 7 years old and their immunisation for diphtheria were not complete. All three patients presented with respiratory distress and were ventilated for upper airway obstruction. Their treatment included intravenous penicillin and diphtheria antitoxin. One patient died of cardiogenic shock with secondary pneumonia. Pharyngeal and tonsillar swabs of all three patients grew toxigenic Corynebacterium diphtheriae biotype mitis. There were 765 throat cultures taken from contacts. The confirmed positive cultures grew 2 toxigenic and 3 non-toxigenic Corynebacterium diphtheriae biotype mitis and surprisingly, 10 non-toxigenic biotype gravis. A prevalence study is needed to document the endemicity of diphtheria in Kuala Terengganu and to determine the carrier rate of both biotypes. Steps have been taken to increase the immunisation coverage in children. The giving of regular booster doses of diphtheria toxoid to the adult population should be considered.

Expression of collagenase-3 (MMP-13) in human abdominal aortic aneurysms and vascular smooth muscle cells in culture

Collagen degradation is important in the pathogenesis of abdominal aortic aneurysms (AAA) but the enzymes responsible are undefined. Collagenase-3 is a recently described matrix metalloproteinase (MMP-13) with limited tissue distribution and a highly regulated pattern of expression. Using reverse transcription-polymerase chain reaction and Southern blots, amplification products corresponding to MMP-13 were uniformly detected in samples of AAA and atherosclerotic aorta (ATH), but not in normal aortic controls. By densitometric analysis of blots normalized to beta-actin, the expression of MMP-13 was 1.8-fold higher in AAA compared to ATH (P < 0.05). Immunoreactive MMP-13 was localized to medial smooth muscle cells (SMC) in AAA tissue and to human vascular SMC in culture, which also expressed MMP-13 mRNA. These findings indicate for the first time that SMC production of MMP-13 may contribute to the pathophysiologic progression of AAA.

Chemotherapy-treated liver metastases mimicking hemangiomas on MR images

BACKGROUND

To report the observation that chemotherapy-treated liver metastases may mimic the appearance of hemangiomas on T2-weighted and serial postgadolinium gradient-echo magnetic resonance (MR) images.

METHODS

T2-weighted and serial postgadolinium spoiled gradient-echo images were prospectively and retrospectively analyzed in six patients. All patients had been treated with chemotherapy for a duration of 2-12 months. Histopathologic evaluation of liver lesions was performed in three patients.

RESULTS

Twelve lesions that resembled hemangiomas were identified. Lesions were 0.8-5.5 cm in diameter. All were well defined, oval or lobulated, and demonstrated decreased signal intensity on T1-weighted images and increased signal intensity on T2-weighted images. On immediate postgadolinium images, all lesions demonstrated peripheral nodular enhancement, which coalesced on delayed imaging. Final histopathologic diagnoses were as follows: hepatic metastases from colon cancer (two patients), ovarian cancer (two patients), pancreatic islet cell tumor (one patient), and breast cancer (one patient).

CONCLUSIONS

Metastases treated by chemotherapy may mimic the appearance of hemangiomas on a variety of commonly employed MR techniques. In patients undergoing MR imaging for the evaluation of liver metastases, a history of prior chemotherapy administration and duration should be sought to prevent inaccurate staging and inappropriate therapeutic decision making.

Regional cerebral blood flow in patients with systemic lupus erythematosus

Patients with systemic lupus erythematosus (SLE) with or without definite neuropsychiatric symptoms/signs were studied. Technetium-99m (Tc-99m) hexamethylpropylenamine (HMPAO) brain images were used to detect basal ganglion and cerebral cortex regional cerebral blood flow (rCBF) in patients with SLE with brain involvement. One hundred nine female patients with SLE were investigated using Tc-99m HMPAO brain images with fan-beam single-photon emission computed tomography (SPECT) and surface three-dimensional (3D) display. These patients were separated into 2 subgroups: group 1, 74 cases with definite neuropsychiatric symptoms/signs; and group 2, 35 cases without any neuropsychiatric symptoms/signs. Fan-beam SPECT demonstrated unilateral or bilateral hypoperfusion of basal ganglia or thalamus in 22% and 9% of patients in groups 1 and 2, respectively. Local hypoactivity anomalies were found in the brain cortex of 89% and 20% of patients in groups 1 and 2, respectively, using surface 3D display of the brain. In either group 1 or group 2 patients, parietal and frontal lobes are the most common areas and cerebellum and thalamus are the least common areas of brain involvement, respectively. This study suggests that in comparison with traditional brain imaging techniques, Tc-99m HMPAO brain imaging with fan-beam SPECT in combination with surface 3D display may provide objective information for detection of anomalies of rCBF in patients with SLE.

MRI of normal and abnormal duodenum using Half-Fourier Single-Shot RARE and gadolinium-enhanced spoiled gradient echo sequences

The objective of this research was two-fold: First, to describe the normal and abnormal MR appearances of the duodenum using combined Half-Fourier Acquisition Single Shot RARE (HASTE) and gadolinium-enhanced standard and fat suppressed spoiled gradient echo (SGE) sequences. The second objective was to assess the ability of these combined sequences to detect and characterize duodenal diseases. MR examinations were performed on fifty consecutive patients with no clinical history of duodenal diseases, who were 1) imaged with HASTE and gadolinium-enhanced standard and fat suppressed SGE sequences and 2) referred to MR examination for reasons other than duodenal diseases, and were reviewed retrospectively to determine the normal MR appearances of the duodenum. A second population of patients with abnormal duodenum who were imaged with the same MR sequences were included in the second part of this study. This population was composed of 20 consecutive patients with subsequently proven duodenal abnormalities, including: malrotation (2), diverticula (4), intussusception (1), sprue (1), polyps (2), neurofibroma (1), lymphoma (1), Zollinger Ellison syndrome (1), metastatic disease (1), Crohn's disease (1), and wall thickening and duodenitis (5). Normal measurements of the duodenum are described. Abnormalities of wall thickness and duodenal masses required combined HASTE and gadolinium-enhanced SGE images to evaluate well. Abnormalities of the bowel lumen (e.g., diverticula and intussusception), and developmental variants (e.g., malrotation), were sufficiently visualized on HASTE images alone. Bowel inflammation was best shown on gadolinium-enhanced fat suppressed SGE images. HASTE and gadolinium-enhanced fat suppressed SGE sequences are complementary techniques for the demonstration of normal and abnormal duodenum. The combined use of both sequences allows evaluation of different aspects of bowel diseases; abnormalities of position, lumen, and contents are well shown on HASTE, while inflammation is best shown on gadolinium enhanced fat suppressed SGE, and wall thickening and masses are best evaluated with the combined use of both techniques.

Distinct localization of SAPK isoforms in neurons of adult mouse brain implies multiple signaling modes of SAPK pathway

Various cellular and environmental stresses lead to the activation of stress-activated protein kinase (SAPK), which is also referred to as c-Jun N-terminal kinase (JNK). In mammals, multiple SAPK isoforms, encoded by three independent genes, were identified. To gain insight into the roles of SAPK pathway in adult mouse brain, detailed expression patterns of three SAPK isoforms in brain were examined by using immunohistochemical and cell biological analyses. SAPKbeta was heavily expressed in almost all regions of brain as previously reported. Interestingly, SAPKgamma was also widely expressed at high levels. SAPKgamma expression was generally overlapped with SAPKbeta although there were some exceptions such as in hippocampus, where SAPKgamma was restricted to CA3 and CA4 regions while SAPKbeta was evenly expressed. SAPKalpha was widely expressed, but at low levels. It is particularly intriguing to note the differential subcellular localization of SAPK isoforms in neurons. In brain of normally reared mice, SAPKbeta was identified in nucleus as well as in cytoplasm of neurons, while SAPKgamma was detected mainly in cytoplasm and dendrites. Biochemical and immunological analyses revealed extraordinarily high basal activities of all SAPK isoforms in brain compared to peripheral organs, indicating that SAPK pathway may play a role in normal brain physiology. In addition, differential regional and subcellular localizations of SAPK isoforms allow us to speculate multiple signaling modes for SAPK activation in brain.

A study of deleterious gene structure in plants using Markov chain Monte Carlo

The characteristics of deleterious genes have been of great interest in both theory and practice in genetics. Because of the complex genetic mechanism of these deleterious genes, most current studies try to estimate the overall magnitude of mortality effects on a population, which is characterized classically by the number of lethal equivalents. This number is a combination of several parameters, each of which has a distinct biological effect on genetic mortality. In conservation and breeding programs, it is important to be able to distinguish among different combinations of these parameters that lead to the same number of lethal equivalents, such as a large number of mildly deleterious genes or a few lethal genes, The ability to distinguish such parameter combinations requires more than one generation of mating. We propose a model for survival data from a two-generation mating experiment on the plant species Brassica rapa, and we enable inference with Markov chain Monte Carlo. This computational strategy is effective because a vast amount of missing genotype information must be accounted for. In addition to the lethal equivalents, the two-generation data provide separate information on the average intensity of mortality and the average number of deleterious genes carried by an individual. In our Markov chain Monte Carlo algorithm, we use a vector proposal distribution to overcome inefficiency of a single-site Gibbs sampler. Information about environmental effects is obtained from an outcrossing experiment conducted in parallel with the two-generation mating experiments.

Sulfotransferases of two specificities function in the reconstitution of high endothelial cell ligands for L-selectin

L-selectin, a lectin-like receptor, mediates rolling of lymphocytes on high endothelial venules (HEVs) in secondary lymphoid organs by interacting with HEV ligands. These ligands consist of a complex of sialomucins, candidates for which are glycosylation- dependent cell adhesion molecule 1 (GlyCAM-1), CD34, and podocalyxin. The ligands must be sialylated, fucosylated, and sulfated for optimal recognition by L-selectin. Our previous structural characterization of GlyCAM-1 has demonstrated two sulfation modifications, Gal-6-sulfate and GlcNAc-6-sulfate in the context of sialyl Lewis x. We now report the cloning of a Gal-6-sulfotransferase and a GlcNAc-6-sulfotransferase, which can modify GlyCAM-1 and CD34. The Gal-6-sulfotransferase shows a wide tissue distribution. In contrast, the GlcNAc-6-sulfotransferase is highly restricted to HEVs, as revealed by Northern analysis and in situ hybridization. Expression of either enzyme in Chinese hamster ovary cells, along with CD34 and fucosyltransferase VII, results in ligand activity, as detected by binding of an L-selectin/IgM chimera. When coexpressed, the two sulfotransferases synergize to produce strongly enhanced chimera binding.

Technetium-99m methylene diphosphonate scintimammography for evaluation of palpable breast masses

Technetium-99m-methylene diphosphonate (Tc-99m MDP) scintimammography (SMB) was used to investigate palpable breast masses during routine presurgical bone scintigraphy, for women at high risk for cancer and who were candidates for surgery or excisional biopsy. Upright anterior and prone lateral views of the breasts were acquired from 65 women with palpable breast masses, 5-10 min after intravenous injection of 740 MBq of Tc-99m MDP. Breast cancer was histologically diagnosed in 50 women (77%) and benign disease was found in 15 women (23%). Of these 50 breast cancer patients, 44 (88%) showed abnormal MDP uptake in breasts. Among the 15 cases of benign lesions, only 1 (7%) showed abnormal MDP uptake in the breasts. The diagnostic sensitivity, specificity, and accuracy were 88%, 93%, and 89%, respectively, for the differentiation of malignant and benign breast masses. Scintimammography with Tc-99m MDP is a useful and cost-effective tool for differentiating malignant breast masses from benign breast masses.

Treatment of seizures in subcortical laminar heterotopia with corpus callosotomy and lamotrigine

Focal and generalized cortical dysgeneses are sometimes seen on the magnetic resonance images (MRI) of patients with epilepsy. Subcortical laminar heterotopia are bilateral collections of gray matter in the centrum semiovale that resemble a band or "double cortex" on MRI. We studied one male and two female patients with subcortical laminar heterotopia who had moderate to severe developmental delay, early-onset epilepsy, and medically refractory seizures. Atonic, atypical absence, tonic, myoclonic, complex partial, and generalized tonic-clonic seizures were recorded. Interictal and ictal electroencephalographic patterns were generalized and, less commonly, multifocal. Two years after corpus callosotomy, one patient was free of generalized tonic-clonic and atonic seizures, but the other patient who had undergone callosotomy had no significant reduction in seizure frequency. With lamotrigine treatment, the patient who had not had surgery had complete cessation of monthly episodes of status epilepticus and a dramatic reduction of generalized tonic-clonic seizures, and the other patient who received lamotrigine had a 50% reduction of her atonic seizures. In patients with subcortical laminar heterotopia, atonic and generalized tonic-clonic seizures can be substantially reduced or eliminated by corpus callosotomy or treatment with lamotrigine.

Evaluation of chemotherapy response in patients with small cell lung cancer using Technetium-99m-tetrofosmin

The aim of this study was to investigate the relationship between Technetium-99m (Tc-99m) tetrofosmin accumulation in tumors which may represent the expression of multidrug resistance (MDR)--mediated P-glycoprotein (Pgp) and multidrug resistance-associated protein (MRP) as well as response to chemotherapy in patients with untreated small cell lung cancers (SCLC). Twenty patients with SCLC were studied with Tc-99m tetrofosmin lung scintigraphy before chemotherapeutic induction. Tc-99m tetrofosmin lung scans were interpreted both visually and quantitatively. Response was evaluated upon completion of chemotherapy. Patients with good chemotherapy response had a significantly higher incidence (93%) of positive Tc-99m tetrofosmin lung single photon emission computed tomography (SPECT) findings than patients with poor response (33%) (p value < 0.05). The tumor/background ratios (T/B) were 1.8 +/- 0.4 and 1.2 +/- 0.3, for patients with good response and poor response, respectively (p < 0.05). However, other prognostic factors (tumor size and stage) were not significantly related to Tc-99m tetrofosmin lung scan findings and chemotherapy responses. Tc-99m tetrofosmin lung scintigraphy can predict chemotherapy response in patients with SCLC.

Modification of chitosan to improve its hypocholesterolemic capacity

Cholestyramine is the most widely used bile acid sequestrant in the treatment of hypercholesterolemia. However, cholestyramine has unpleasant side effects as a consequence of its hydrophobic backbone. Therefore, high-capacity bile acid sequestering biopolymers with cationic chitosan derivatives were developed, because electrostatic interactions are important for binding with bile acid anions. Dialkylaminoalkylation and reductive amination of chitosan were done to add dialkylaminoalkyl and an additional free amino group at a hydroxyl site in the chitosan backbone respectively and the amino-derivatized chitosan derivatives were quaternized with methyl iodide to produce a cationic polyelectrolyte. The in vitro bile acid binding capacity of the chitosan derivatives in aqueous NaCl was measured by reversed-phase HPLC. The binding capacities of sodium glycocholate (a major bile acid) to chitosan, DEAE-chitosan, quaternized DEAE-chitosan, and cholestyramine were 1.42, 3.12, 4.06, and 2.78 mmol/g resin, respectively. With quaternized DEAE-chitosan, the bile acid binding capacity increased approximately 50% over that of cholestyramine. The bile acid binding capacity of dialkylaminoalkyl chitosan derivatives increased with the number of carbons in the alkyl groups, indicating that hydrophobic interaction is a secondary factor for the sequestration of bile acids.

Novel gating mechanism of polyamine block in the strong inward rectifier K channel Kir2.1

Inward rectifying K channels are essential for maintaining resting membrane potential and regulating excitability in many cell types. Previous studies have attributed the rectification properties of strong inward rectifiers such as Kir2.1 to voltage-dependent binding of intracellular polyamines or Mg to the pore (direct open channel block), thereby preventing outward passage of K ions. We have studied interactions between polyamines and the polyamine toxins philanthotoxin and argiotoxin on inward rectification in Kir2.1. We present evidence that high affinity polyamine block is not consistent with direct open channel block, but instead involves polyamines binding to another region of the channel (intrinsic gate) to form a blocking complex that occludes the pore. This interaction defines a novel mechanism of ion channel closure.

Molecular cloning of multiple splicing variants of JIP-1 preferentially expressed in brain

Stress-activated protein kinase/c-Jun N-terminal kinase (SAPK/JNK) is activated by a variety of cellular or environmental stresses. Proper regulation of the SAPK/JNK pathway may be critical for cell survival or death under various conditions. In this study, we report the molecular cloning of novel isoforms of JIP-1, which harbor a putative phosphotyrosine interaction domain and a helix-loop-helix domain, as well as an SH3 homologous region in the C terminus. Northern analysis indicates that transcription variant jip-1 is expressed in brain and kidney and transcription variants jip-2 and jip-3 are specifically expressed in brain. In situ hybridization data showed that the hybridized jip messages were heavily concentrated in adult brain, and were particularly enriched in the cerebral cortex and hippocampus, the brain regions vulnerable to pathological states such as hypoxia-ischemia, epilepsy, and Alzheimer's disease. All the deduced protein products of the jip transcription variants appear to have a similar property in that they inhibit the SAPK/JNK stimulation when overexpressed. Inhibition of SAPK activation by overexpression of the novel isoform JIP-2a resulted in suppression of etoposide-induced cell death in a neuroglioma cell line, N18TG. These findings suggest that JIP may play an important role in regulation of the SAPK pathway that is involved in stress-induced cellular responses.

Acute testing of the rate-smoothed pacing algorithm for ventricular rate stabilization

We evaluated the capability of a new pacemaker-based rate-smoothing algorithm (RSA) to reduce the irregular ventricular response of AF. RSA prevents sudden decreases in rate using a modified physiological band and flywheel feature. Twelve patients (51 +/- 21 years) with hemodynamically tolerated AF of 4 months to 20 years duration were studied. Atrial and ventricular leads were connected to the external pacemaker device in the electrophysiology laboratory. Consecutive RR intervals during AF were measured at baseline and after ventricular pacing with RSA ON. Ventricular pacing with the rate smoothing algorithm reduced maximum RR intervals (1,207 +/- 299 vs 855 +/- 148 ms, P = 0.0005), with no significant change in the minimum RR interval (401 +/- 55 vs 393 +/- 74 ms, P = 0.292). A small shortening of the mean RR interval (634 +/- 153 vs 594 +/- 135 ms, P = 0.007) was seen with no change in the median RR interval (609 +/- 153 vs 595 +/- 143 ms, P = 0.388). There was a 43% reduction in RR standard deviation (145 +/- 52 vs 82 +/- 28, P = 0.0005), 49% reduction in mean absolute RR interval difference (MAD) (152 +/- 64 vs 77 +/- 34, P = 0.0005) and MAD/mean RR ratio (0.23 +/- 0.05 vs 0.13 +/- 0.04, P = 0.0005). We conclude that rate-smoothed pacing effectively reduces RR variability of AF in the acute setting.

Dynamic expression of SEK1 suggests multiple roles of the gene during embryogenesis and in adult brain of mice

Stress-activated protein kinase (SAPK)/c-Jun N-terminal kinase (JNK), a member of the MAP kinase (MAPK) superfamily, plays a key role in a variety of cellular processes. It is well established that SAPK/JNK activation is controlled by SEK1/MKK4, an up-stream MAP kinase kinase. To gain insight into the role of SEK1 during embryonic development and in adult life, we examined the temporal and spatial patterns of sek1 expression in mice by using in situ hybridization and immunohistochemical study. Dynamic changes of sek1 expression were observed during embryogenesis. Strong sek1 expression was detected in most of the central nervous system and in liver and thymus during early stages of development. While the sek1 expression in nervous system increases over time, expression in fetal liver and thymus gradually decreases as embryogenesis proceeds. High level of the sek1 expression in the central nervous system was persisted throughout postnatal development and remained at a stable level in adult brain. These observations provide an anatomical basis for the vital role(s) of SEK1 in development, for example, in hepatogenesis and/or neurogenesis. Although SEK1 was widely expressed in adult brain, more strong expression of the sek1 was observed at layers 2 and 6 in cerebral cortex, in Purkinje cells of cerebellum, and also in hypothalamic nuclei. The strongest expression of the sek1 was found in the CA3 region of hippocampus, the region being highly vulnerable to exitotoxicity-induced apoptosis in kainate-treated animal models. Interestingly, SEK1 was localized not only in cytoplasm but in dendrites and/or in nucleus of neurons depending on the regions of adult mouse brain. Taken together, these results suggest multiple roles of the SEK1 during embryogenesis and in adult brain.

Long-lasting effects of chronic ozone exposure on rat nasal epithelium

Ozone, the principal oxidant pollutant in photochemical smog, causes airway epithelial injury in the upper and lower respiratory tract of laboratory animals. We have recently reported that long-term inhalation exposure to ozone causes mucous-cell metaplasia (MCM) in the surface epithelium lining the nasal airways of F344 rats. The principal objective of the present study was to determine the persistence of ozone-induced MCM in the nasal epithelium after the end of a chronic exposure. Male F344/N rats were exposed to 0, 0.25, or 0.5 ppm ozone, for 8 h/d, 7 d/wk for 13 wk. Animals were killed 8 h, 4 wk, or 13 wk after the end of the chronic exposure. Ozone-related alterations in the nasal epithelium were qualitatively and quantitatively characterized through histochemistry, image analysis, and morphometric techniques. Some rats were exposed for an additional 8 h to 0.5 ppm ozone at 13 wk after the end of the chronic exposure to determine whether previous ozone exposure results in persistent changes in the sensitivity of nasal epithelium to acute injury. At the end of the chronic exposure, hyperplasia was present in the nasal epithelium of rats exposed to 0.25 and 0.5 ppm ozone. By 13 wk postexposure, this proliferative alteration was still evident only in the rats exposed to 0.5 ppm ozone. Ozone-induced MCM with associated intraepithelial mucosubstances was evident only in the nasal tissues of rats exposed to 0.5 ppm ozone. Though attenuated, these alterations in the nasal mucous apparatus were still detectable at 13 wk after the end of the exposure. At this same time after the chronic exposure, an acute (8 h) exposure to 0.5 ppm ozone induced an additional increase of mucosubstances in the nasal epithelium of rats previously exposed to 0.5 ppm ozone, but not in rats chronically exposed to 0 or 2.5 ppm ozone. The persistent nature of the ozone-induced MCM in rats documented in this report suggests that ozone exposure may have the potential to induce similar long-lasting alterations in the airways of humans.

Anterior cervical spinal epidural abscess in an infant

Spinal epidural abscess (SEA) is rare in children, especially in newborns and infants, groups in which only very few cases have been reported. Because of the nonspecificity of presenting symptoms in children the diagnosis may be delayed, resulting in major permanent neurological deficits. In this paper, we report a case of cervical SEA in a 6-week-old infant who initially presented with fever and developed quadriparesis 19 days prior to admission. After emergency anterior decompression of the abscess the neurological function was improved immediately. Five months after surgery the neurological status was normal, an MR study showing disappearance of the epidural abscess and spinal cord indentation, and progressive fusion of the C3, C4 and C5 vertebral bodies. Anterior decompression without bone graft can provide an excellent prognosis in case of an anterior cervical SEA in infants.