Size tunable Ge quantum dots for near-ultraviolet to near-infrared photosensing with high figures of merit

We report a unique approach for the inclusion of size-tunable (7-50 nm), spherical Ge quantum dots (QDs) into gate stacks of metal-oxide-semiconductor (MOS) diodes, through selective oxidation of SiGe layers over the buffer layer of Si3N4 deposited over the Si substrate. In this complementary MOS (CMOS)-compatible approach, we successfully realized high performance nm scale Ge-QD MOS photodetectors with high figures of merit of low dark current density (1.5 × 10(-3) mA cm(-2)), superior photo-current-to-dark current ratio (13 500), high photoresponsivity (2.2 A W(-1)), and fast response time (5 ns), which are ready for direct integration with Si CMOS electronic circuits. Most importantly, the detection wavelength of the Ge QDs is tunable from near infrared to near ultraviolet by reducing the QD size from 50 to 7 nm as well as the optimal photoresponsivity is tailored by the Ge QD size and the effective thickness of gate dielectrics.

Formation of Ge quantum dots array in layer-cake technique for advanced photovoltaics

We report a simple and manageable growth method for placing dense three-dimensional Ge quantum dot (QD) arrays in a uniform or a graded size distribution, based on thermally oxidizing stacked poly-SiGe in a layer-cake technique. The QD size and spatial density in each stack can be modulated by conditions of the Ge content in poly-Si(1-x)Ge(x), oxidation, and the underlay buffer layer. Size-dependent internal structure, strain, and photoluminescence properties of Ge QDs are systematically investigated. Optimization of the processing conditions could be carried out for producing dense Ge QD arrays to maximize photovoltaic efficiency.

Ischaemic infarction masking aortic dissection: a pitfall to be avoided before thrombolysis

Acute aortic dissection complicated by stroke is not uncommon but may be difficult to evaluate, especially in patients with impaired mental status. This report describes a patient who had evidence of an ischaemic stroke but was fortuitously not given thrombolytic treatment. She was subsequently found to have an extensive aortic dissection involving both carotid arteries. The decision of whether to give thrombolytic treatment is understandably an urgent one, but careful attention should be paid to subtle signs and symptoms such as atypical chest pain and carotid bruits that might suggest aortic dissection, especially involving the carotid arteries. There should be a high index of suspicion for acute aortic dissection in such cases and a low threshold for performing carotid ultrasound.

Expressed transcripts associated with high rates of egg production in chicken ovarian follicles

The purpose of this study was to characterize differentially expressed transcripts associated with varying rates of egg production in Taiwan country chickens. Ovarian follicles were isolated from two strains of chicken which showed low (B) or high (L2) rates of egg production, then processed for RNA extraction and cDNA library construction. Three thousand and eight forty clones were randomly selected from the cDNA library and amplified by PCR, then used in microarray analysis. Differentially expressed transcripts (P<0.05, log(2)> or = 1.75) were sequenced, and aligned using GenBank. This analysis revealed 20 non-redundant sequences which corresponded to known transcripts. Eight transcripts were expressed at a higher level in ovarian tissue prepared from chicken strain B, and 12 transcripts were expressed at a higher level in L2 birds. These differential patterns of expression were confirmed by semi-quantitative RT-PCR. We show that transcripts of cyclin B2 (cycB2), ferritin heavy polypeptide 1 (FTH1), Gag-Pol polyprotein, thymosin beta4 (TB4) and elongation factor 1 alpha1 (EEF1A1) were enriched in B strain ovarian follicles. In contrast, thioredoxin (TXN), acetyl-CoA dehydrogenase long chain (ACADL), inhibitor of growth family member 4 (ING4) and annexin II (ANXA2) were expressed in at higher levels in the L2 strain. We suggest that our approach may lead to the isolation of effective molecular markers that can be used in selection programs in Taiwan country chickens.

Ablation of advanced tongue or base of tongue cancer and reconstruction with free flap: Functional outcomes

AIM

To evaluate the functional outcomes of patients who underwent total or nearly total glossectomy for advanced tongue or base of tongue cancer.

MATERIAL AND METHODS

We used the radial forearm free flap (RFFF), anterior lateral thigh flap (ALTF) or fibular osteocutaneous flap (FOCF) to reconstruct the oral defect after radical resection in 39 patients undergoing total or nearly total glossectomy with laryngeal preservation.

RESULTS

Good functional outcomes, measured by independent feeding, speech and swallowing were achieved in 35, 36 and 35 patients, respectively. The cumulative 4-year survival rates were 63.8% for tongue cancer and 42.9% for base of tongue cancer.

CONCLUSION

Reconstruction with free flaps is a feasible method to restore the functional outcomes in speech and deglutition among patients who undergo total or nearly total glossectomy with laryngeal preservation.

Manufacturing artificial aggregates from industrial sludge and marine clay with addition of sodium salt

The potential of converting industrial sludge and dredged marine clay into building and construction materials as an alternative to disposal was investigated in this study. The industrial sludge was mixed with marine clay at various compositions and was shaped into round pellets to be used as concrete aggregates. The pellets were then dried and transferred into a high temperature kiln where they were heated at 1,135 degrees C. The artificial aggregates were more porous then the normal granite aggregate. The occurrence of this condition was suspected to be attributed to two factors, viz. the firing temperature and the amount of sodium in the aggregates. To validate this hypothesis, the aggregates with and without added sodium chloride were fired at temperatures of 1,100 and 1, 200 degrees C. Results showed a reduction in the densities of the aggregates with the addition of sodium chloride and the increase in firing temperature.

Network strength and dewaterability of flocculated activated sludge

Works in literature proposed the use of the rheological properties of wastewater sludges as an index for conditioner assessment and control. We demonstrated in this work, on the contrary, that one could not justify the consistency of the commonly used rheological characteristics of the sewage sludge samples taken from the same site but at different dates. A physically relevant index was proposed instead for describing the total network strength, which was hypothesized to correlate the dewatering efficiency of flocculated sludge. Based on this index, the network of a sludge was demonstrated to be largely destroyed after shearing, while the relaxation in an unbound environment or mild pouring over action could partially reinstall the structure. Moreover, a uniform shear rate field could produce network of greater strength when compared with that conditioned in a stirred tank.

Survival after early surgical revascularization in patients with both acute myocardial infarction and cardiogenic shock

BACKGROUND AND PURPOSE

Previous studies have reported encouraging results with percutaneous transluminal coronary angioplasty (PTCA) in patients with acute myocardial infarction (AMI) complicated by cardiogenic shock. However, PTCA is often unsuccessful and the mortality rate is more than 80%. The success rate of early surgical revascularization in patients with cardiogenic shock and failed PTCA is not clear. This study assessed the effect of early surgical revascularization on survival chances in patients with cardiogenic shock and failed PTCA.

PATIENTS AND METHODS

Nineteen patients referred to our hospital by cardiologists due to cardiogenic shock and failed PTCA were included in this study. During the period from February 1995 through August 1997, seven patients were treated using mechanical circulatory support with extracorporeal membrane oxygenation (ECMO) and no surgical revascularization, and from August 1997 through June 1999, 12 patients underwent emergency surgical revascularization. The patient characteristics and in-hospital mortality were compared between groups.

RESULTS

Ten patients were treated after acute infarction and nine were treated after cardiac intervention. No significant differences were found between the two groups in age, sex, hypertension, diabetes, smoking, and previous infarction. The in-hospital mortality rates were 100% in patients receiving mechanical circulatory support with ECMO and 25% in patients who underwent emergency surgical revascularization (p = 0.003). In the emergency revascularization group, four of 12 patients had surgical revascularization more than 18 hours after AMI and the in-hospital mortality rate was 25%.

CONCLUSION

Surgical revascularization improved survival in patients with cardiogenic shock and failed PTCA.

Thamnocephalis quadrupedata (Mucorales) as a mycoparasite of the entomophthoraceous fungus Basidiobolus ranarum

A mycoparasite identified as Thamnocephalis quadrupedata (Mucorales) was observed on cultures of the frog dung fungus, Basidiobolus ranarum. The parasitic fungus, T. quadrupedata possessed infection hyphae with appressoria and penetrating hyphae to attack their host prey and adhere firmly to the surface. The invasion was often by slender infection hyphae or infecting pegs which grew from the appressoria and penetrated the chitin-protein cuticle by both mechanical pressure and exocellular enzymes. The host fungus, B. ranarum, possessing primary conidia, capilliconidia, hyphal bodies, vegetative mycelia and zygospores, were infected by means of direct penetration and intrahyphal growth, resulting in host cell death. T. quadrupedata may also grow as a saprophyte on damp filter paper in a Petri dish, manifesting facultative necrosis.

Ventricular remodeling of the native heart after heterotopic heart transplantation

Although ventricular remodeling after long-term unloading of the heart has been reported in patients after the use of medical therapy or left ventricular assist devices, it has rarely been reported in patients after heterotopic heart transplantation. Here, we describe a case of ventricular remodeling of the native heart after heterotopic heart transplantation. A 61-year-old man with end-stage dilated cardiomyopathy underwent heterotopic heart transplantation because of high pulmonary vascular resistance and a small donor heart. After the operation, echocardiography showed ventricular remodeling of the native heart, with decreased size and improved contractility of the left ventricle. Six months after the transplantation, acute graft failure of the donor heart occurred. However, the patient remained in good condition with the support of the improved native heart.

Single-shot chirped-pulse spectral interferometry used to measure the femtosecond ionization dynamics of air

A novel interferometry technique is presented by which, in one shot, one can measure phase changes with a resolution of tens of femtoseconds while extending the measurement over picoseconds or even longer. The method is based on spectral (frequency-domain) interferometry with a pair of linearly chirped pules as probes. With this technique we obtained single-shot measurements of the rapid phase changes induced by optical field ionization of air. This allowed us to calculate the time profile of the electron density created by an intense short laser pulse.

HeartMate left ventricular assist device for long-term circulatory support

We describe three successful cases of HeartMate left ventricular assist device (LVAD; Thermo Cardiosystems, Woburn, MA, USA) implantation in patients with end-stage heart failure for long-term circulatory support. Patient 1 was a 34-year-old woman with postpartum cardiomyopathy. Patients 2 and 3 were both males with dilated cardiomyopathy, 50 years and 21 years of age, respectively. They all presented in cardiogenic shock with decreased sensorium and anuria. Temporary mechanical support with an intra-aortic balloon pump or extracorporeal membrane oxygenation (ECMO) was needed for life support. Because bleeding and right ventricular failure often occur after HeartMate LVAD implantation, we used a Vascutek tube (Vascutek Ltd, Inchinnan, Scotland) graft to wrap inflow and outflow valve conduits and ECMO as a bridge to HeartMate LVAD implantation. Following surgery, cardiac output increased from 2.70, 2.06 and 2.53 L/min to 4.50, 5.80 and 5.00 L/min in the three patients. HeartMate LVAD can provide safe and stable long-term circulatory support without the need for anticoagulation. One of the patients remained on HeartMate for 287 days before undergoing successful heart transplantation. Patients with HeartMate LVAD are ambulatory and may be discharged while awaiting heart transplantation. Heart function may recover after long-term ventricular unloading with HeartMate LVAD.

Partial left ventriculectomy as a biologic bridge to heart transplantation

Heart failure refractory to medical treatment is consuming an increasingly large proportion of health care resources. Partial left ventriculectomy has recently been used to treat patients with end-stage dilated cardiomyopathy. A 45-year-old man in end-stage heart failure had progressive exertional dyspnea for 3 years. Cardiac catheterization showed dilated cardiomyopathy with severe pulmonary hypertension and severely impaired left ventricular function. After partial left ventriculectomy, cardiac output increased from 2.11 L/min to 5.0 L/min. The left ventricular ejection fraction measured by radionuclide angiography increased from 13% preoperatively to 28% 1 month after the operation. The patient was discharged and monitored at the outpatient clinic. He had an exercise capacity of NYHA functional class II. However, he received heart transplantation 10 months after the partial left ventriculectomy because of recurrent heart failure. Partial left ventriculectomy improves heart function and may be used as a bridge to heart transplantation as an alternative to ventricular assist devices.

Combined heart transplantation and resection of dissecting aneurysm of ascending aorta and aortic arch: a case report

A 21-year-old male patient had suffered from palpitation and exertional dyspnea since October, 1997. He was admitted to our hospital, and a series of examinations were performed. Chest computed tomography (CT) revealed marked dilatation of the ascending aorta (about 7.5 cm at the proximal portion) and aortic annulus, an intimal flap in the ascending aorta and aortic arch was also noted. Cardiac catheterization revealed the pulmonary capillary wedge pressure was 33 mmHg, pulmonary artery pressure was 47/38 mmHg with a mean of 35.4. The cardiac index was 1.01 l/min/m2. Poor left ventricular contractility was shown by a left ventricular ejection fraction (LVEF) of 13.8% and a right ventricular ejection fraction (RVEF) of 5.13% by a radionuclide angiogram (RNA) study. Under the diagnosis of dilated cardiomyopathy and dissecting aortic aneurysm of the ascending aorta and aortic arch, he was put on a waiting list for heart transplantation. On November 11, 1997 he received heart transplantation. Resection of the dissecting aneurysm of the ascending aorta and the aortic arch and replacement with a 26 mm Vascutek graft were performed first under deep hypothermia and retrograde cerebral perfusion. Then while he was rewarming up, heart implantation was performed. He was discharged 30 days after surgery and has been doing well since then. As far as we know, no literature regarding combined heart transplantation and resection of a dissecting aneurysm of the ascending aorta and aortic arch has been reported.

Aorto-right artrial fistula: a rare complication of aortic dissection

We describe the successful surgical repair of an acute aortic dissection that had caused an aorto-right atrial fistula in a 67-year-old man. The patient was admitted to the hospital on an emergency basis because of severe heart failure. The diagnosis of acute aortic dissection with rupture into the right atrium was confirmed by use of intraoperative transesophageal echocardiography, although rupture of a sinus of Valsalva aneurysm into the right atrium had been suggested initially by 2-dimensional and Doppler transthoracic echocardiography. At surgery, we found the patient to have aortic arch dissection with complete separation of the right coronary artery from the sinus of Valsalva and a false lumen that had ruptured into the right atrium. The aortic arch was repaired directly. The ascending aorta was successfully replaced with a composite graft. Aortic dissection with rupture into the right atrium is extremely rare and leads to death rapidly. As shown in this case, such a condition might be mistaken for an aneurysmal rupture of the sinus of Valsalva, with use of transthoracic echocardiography alone. Transesophageal echocardiography is a useful noninvasive method to further define or confirm the diagnosis. Early surgical intervention is necessary in patients with this condition to prevent profound shock and end-organ failure.

Surgical revascularization for acute total occlusion of left main coronary artery

We report our experience with emergency surgical revascularization in 3 patients who were in cardiogenic shock as a result of acute total occlusion of the left main coronary artery. Because they were in profound shock, 2 patients required mechanical support with extracorporeal membrane oxygenation before the operation. Another patient was given moderate inotropic support and treated with an intraaortic balloon pump before surgery, because he had a dominant right coronary artery with extensive collateral circulation to the left coronary artery. All 3 patients underwent surgical revascularization within 20 hours of acute occlusion. Two patients survived, although 1 of them required extracorporeal membrane oxygenation support for 5 days postoperatively. The 3rd patient, despite successful weaning from extracorporeal membrane oxygenation immediately after coronary revascularization, died of hypoxic encephalopathy due to prolonged preoperative resuscitation. Immediate surgical revascularization was an effective treatment in our 3 patients who were in cardiogenic shock due to acute total occlusion of the left main coronary artery. Such factors as abundant collateral vessels from the right coronary artery to the left coronary artery, complete surgical revascularization within 20 hours of acute occlusion, and mechanical circulatory support were deemed important to recovery of left ventricular function. Two of our 3 patients survived.

Heart transplantation with marginal recipients and donors

With improvements in surgical techniques and management of postoperative complications, heart transplantation can now be performed with donors and recipients who were previously considered unsuitable. In this study, we report the results of heart transplantation with marginal donors and recipients in our hospital. From June 1993 through June 1998, we performed 79 heart transplantations. Marginal recipients were defined as those with high pulmonary vascular resistance (> 6 Wood units), severe renal impairment (serum creatinine > 2 mg/dL and creatinine clearance < 50 mL/min), or severe hepatic dysfunction (ALT and AST > 100 IU/L or serum bilirubin > 2.5 mg/dL). Marginal donors were those with any of the following conditions: old age (> 40 years), size mismatch (donor/recipient body weight ratio < 0.8), history of chronic alcohol use, previous cardiopulmonary resuscitation and hypotension, hepatitis B or C virus positivity, coronary artery disease, high-dose dopamine (> 10 micrograms.kg-1.min-1), or prolonged allograft ischemic time (> 4 hours). Of the 79 transplantations performed, 45 (58%) involved marginal recipients or donors. The 30-day mortality rate was 5%, and the 1-year and 5-year survival rates were 87% and 83%, respectively. The survival rates did not differ significantly between cases involving marginal donors or recipients and those involving nonmarginal donors and recipients. There were 27 marginal recipients (34%), only one of whom died during surgery. Five of six recipients with severe renal impairment needed short-term hemodialysis after transplantation. Recipients with high pulmonary vascular resistance had a higher incidence of early acute rejection (5/10 vs 22/69). Thirty-three (42%) of the patients received transplants from marginal donors, four of whom died during surgery; two died of acute vascular rejection, one of allograft failure caused by prolonged ischemic time, and one of bleeding secondary to preoperative sepsis and coagulopathy. These results show that heart transplantation may be performed in marginal recipients and donors, with acceptable operative mortality.

A new transnasal approach to endoscopic marsupialization of the nasolabial cyst

OBJECTIVE

Nasolabial cyst is a mucus-secreting, nonodontogenic cyst in the nasofacial area. It is usually situated behind the ala nasi, extending backward beneath the nasal floor into the inferior meatus and forward into the labio-gingival sulcus behind the upper lip. Patients with nasolabial cysts generally undergo surgical removal of the cyst via a transoral sublabial approach. This article reports a simple, less invasive surgical procedure for the treatment of nasolabial cysts.

STUDY DESIGN

A transnasal endoscopic marsupialization method was designed to treat patients with nasolabial cysts. From 1996 through 1998, 16 consecutive patients underwent this new surgical procedure.

METHODS

With patients under local anesthesia, the roof of the cyst, which was firmly attached to the mucous membrane of the anterior nasal floor, was removed transnasally with a sickle knife and scissors. Under the guidance of a nasoendoscope, the opening of the cyst was widened with bite forceps. Meanwhile, the cut edges of the nasal mucosa and the epithelium lining of the cyst were adequately matched. The nose was then loosely packed.

RESULTS

All but 1 of the 15 patients were successfully treated with this technique, and the whole surgical procedure was usually completed within 15 to 20 minutes. Postoperative endoscopic and radiological findings revealed that the cyst was replaced by an air-containing sinus with a persistent opening at the anterior or anterolateral nasal floor. There has been no evidence of mucus accumulation in the newly created sinus or recurrence of the cyst during a mean follow-up of 16 months.

CONCLUSIONS

Transnasal endoscopic marsupialization is a simple and effective surgical procedure for treatment of nasolabial cysts.

RNA binding by the novel helical domain of the influenza virus NS1 protein requires its dimer structure and a small number of specific basic amino acids

The RNA-binding/dimerization domain of the NS1 protein of influenza A virus (73 amino acids in length) exhibits a novel dimeric six-helical fold. It is not known how this domain binds to its specific RNA targets, one of which is double-stranded RNA. To elucidate the mode of RNA binding, we introduced single alanine replacements into the NS1 RNA-binding domain at specific positions in the three-dimensional structure. Our results indicate that the dimer structure is essential for RNA binding, because any alanine replacement that causes disruption of the dimer also leads to the loss of RNA-binding activity. Surprisingly, the arginine side chain at position 38, which is in the second helix of each monomer, is the only amino-acid side chain that is absolutely required only for RNA binding and not for dimerization, indicating that this side chain probably interacts directly with the RNA target. This interaction is primarily electrostatic, because replacement of this arginine with lysine had no effect on RNA binding. A second basic amino acid, the lysine at position 41, which is also in helix 2, makes a strong contribution to the affinity of binding. We conclude that helix 2 and helix 2', which are antiparallel and next to each other in the dimer conformation, constitute the interaction face between the NS1 RNA-binding domain and its RNA targets, and that the arginine side chain at position 38 and possibly the lysine side chain at position 41 in each of these antiparallel helices contact the phosphate backbone of the RNA target.

Crystal structure of the unique RNA-binding domain of the influenza virus NS1 protein

The nonstructural protein (NS1 protein) of the influenza A virus binds to several types of RNAs. X-ray crystallographic analysis of the RNA-binding domain reveals a unique topology for the monomer as well as a novel six-helix structure for the dimer.

A novel RNA-binding motif in influenza A virus non-structural protein 1

The solution NMR structure of the RNA-binding domain from influenza virus non-structural protein 1 exhibits a novel dimeric six-helical protein fold. Distributions of basic residues and conserved salt bridges of dimeric NS1(1-73) suggest that the face containing antiparallel helices 2 and 2' forms a novel arginine-rich nucleic acid binding motif.

Conical emission from laser plasma interactions in the filamentation of powerful ultrashort laser pulses in air

We performed detailed experimental and numerical investigations of the conical emission (CE) accompanying the filamentation of powerful ultrashort laser pulses in air. It was found that the CE originates from self-phase modulation in the plasma produced by the pulse during propagation. The experiment and the simulation agree on the essential features of the CE: The CE angle decreases with increasing wavelength and is independent of the position along the filament, and there is no CE at Stokes-shifted wavelengths.

Moving focus in the propagation of ultrashort laser pulses in air

The long light filaments generated in air by powerful ultrashort laser pulses, previously attributed to self-channeling, were investigated by use of gigawatt pulses from a Ti:sapphire chirped-pulse-amplification laser system. A filament contained only a small fraction of the pulse energy and always ended at the diffraction length of the beam (~100 m), independently of the pulse energy. These features are explained by the moving-focus model, which is presented as an alternative to the self-channeling model. Computer simulations involving ionization of the air also support the moving-focus model.

Phrenic nerve transfer in the repair of brachial plexus injuries: an animal model

Ten young mongrel dogs underwent unilateral denervation of the brachial plexus. In six dogs, a 2-cm segment of phrenic nerve autograft was sutured to either the resected musculocutaneous nerve or the radial nerve. A hemoclip was applied to either musculocutaneous or radial nerve in the control groups. Five months postoperatively, the grafted musculocutaneous nerve demonstrated less fibrous tissue and less muscle atrophy of the biceps when compared to the control group with clipped nerve. In the group with the grafted radial nerve, the electromyographic findings of multiphasic action potential and muscle contraction from electric stimulation suggested reinnervation of the radial nerve.

IN CONCLUSION

phrenic nerve transfer may be used to repair specific damages to nerve trunk with histological, electromyographic and clinical recovery.

Serum transferrin saturation, stroke incidence, and mortality in women and men. The NHANES I Epidemiologic Followup Study. National Health and Nutrition Examination Survey

Several studies have examined relatively large body iron stores and the risk of coronary heart disease with conflicting results. No reports of studies that associated body iron stores with stroke were found. To test the hypothesis that relatively high transferrin saturation is associated with increased stroke incidence and mortality in women and men, data from a follow-up study of a national cohort were examined. A total of 5,033 women and men aged 45-74 years from the First National Health and Nutrition Examination Survey Epidemiologic Followup Study who were free of stroke at baseline were followed an average of 12 years. Transferrin saturation (serum iron concentration divided by total iron binding capacity) was used as a measure of the amount of circulating iron available to tissues. In white women aged 45-74, after adjusting for age or for age and other risk variables, the authors observed a significant U-shaped association of transferrin saturation with risk of incident stroke (> 44% vs. 30-36%, relative risk = 1.96, 95% confidence interval 1.15-3.36; < 20% vs. 30-36%, relative risk = 1.80, 95% confidence interval 1.20-2.71). However, no significant associations were found in white men aged 45-74 after adjusting for other risk variables. Similar findings were observed for stroke mortality in whites, but no significant associations were seen in blacks. The significantly increased risk of stroke that was seen at both high and low levels of transferrin saturation in white women should be confirmed in other cohorts of women and men.

Regulation and molecular structure of a circadian oscillating protein located in the cell membrane of the prokaryote Synechococcus RF-1

When a light/light-adapted culture of Synechococcus RF-1 is exposed to a diurnal light/dark regimen, the synthesis of more than ten of its polypeptides is known to become entrained to a circadian oscillating pattern which persists for some time under free-running conditions. One of the circadian oscillating polypeptides, COP23, was found to be located in the cell membrane. The rate of COP23 synthesis is controlled at the transcription level. In addition to the protein synthesis rate, the content of COP23 also exhibited a circadian rhythm. Pulse labeling with [35S]methionine revealed that COP23 was relatively stable in an arrhythmic culture. However, the exposure of Synechococcus RF-1 to a light/dark regimen induced not only a circadian synthesis rhythm, but also a rapid degradation of COP23 protein at a defined period of time. The induction of rapid protein degradation was prevented by the presence of chloramphenicol. The gene encoding the COP23 polypeptide has been cloned and sequenced. The amino acid sequence derived from the open-reading frame revealed that a signal peptide (28 amino acids) does not appear to be part of the mature COP23. The mature COP23 does not have a membrane-associated segment, and it is suggested to be a peripheral molecule. With respect to their DNA base sequence and protein amino acid sequence, none of the proteins documented in the EMBL and PC/Gene data bases are significantly homologous with the COP23 molecule.

An amino-terminal polypeptide fragment of the influenza virus NS1 protein possesses specific RNA-binding activity and largely helical backbone structure

The NS1 protein of influenza A virus has the unique property of binding to three apparently different RNAs: poly A; a stem-bulge in U6 small nuclear RNA; and double-stranded RNA. One of our major goals is to determine how the NS1 protein recognizes and binds to its several RNA targets. As the first step for conducting structural studies, we have succeeded in identifying a fragment of the NS1 protein that possesses all the RNA-binding activities of the full-length protein. The RNA-binding fragment consists of the 73 amino-terminal amino acids of the protein. We have developed procedures for obtaining large amounts of the polypeptide in pure form. This has enabled us to establish the RNA-binding properties of this polypeptide and to demonstrate that it retains the ability to dimerize exhibited by the full-length protein. In addition, far-UV CD spectroscopy indicates that this RNA-binding polypeptide is largely (approximately 80%) helical, suggesting that the mode of dimerization of the NS1 protein and of its interaction with RNA is mediated, at least in part, by helices.

Time-resolved kiloelectron-volt spectroscopy of ultrashort plasmas

We describe a technique for spectrally and temporally resolving the kilo-electron-volt emission fromultrashort plasmas produced from solid targets with a tabletop terawatt 400-fs laser. The firsttime-resolved Al spectra (near 8 Å) obtained with a 2-ps time resolution are presented. The results clearly demonstrate that the resonance emission width decreases as the plasma density increases. The ultrafast K(α) emission component is also measured in our experimental conditions.

Nicotine-induced skeletal muscle vasodilation is mediated by release of epinephrine from nerve terminals

To determine the role of sympathetic innervation on nicotine-induced alterations in peripheral (hindlimb) blood flow in the pentobarbital-anesthetized dog, one hindlimb was acutely denervated and remained attached to the body by only the femoral artery and vein, whereas the contralateral limb remained innervated and intact. Measurements were made of aortic pressure, femoral artery and venous pressures, femoral artery flow, and plasma catecholamine levels during intravenous systemic infusion of nicotine. The response to nicotine (9-36 micrograms.kg-1.min-1) on the denervated side was a transient increase followed by a persistent decrease in flow and increase in vascular resistance. The response in the innervated limb was a large increase in blood flow and decrease in vascular resistance. The vasoconstrictor and vasodilator responses could be abolished by pretreatment with both propranolol and phentolamine. The vasodilator response could not be abolished by cholinergic or histaminergic receptor antagonism. Hexamethonium abolished all systemic and peripheral responses to nicotine. Desipramine selectively abolished the vasodilator response in the innervated hindlimb. The vasodilator and vasoconstrictor responses could be mimicked with systemic or local administration of epinephrine. We conclude that, in the hindlimbs of dogs, nicotine stimulates the release of epinephrine from nerve terminals and/or tissue stores to activate beta 2-adrenoceptors and promote vasodilation in skeletal muscle of innervated preparations.

High-performance liquid chromatography with electrochemical detection for the determination of nicotine in plasma

Nicotine in plasma can be determined by high-performance liquid chromatography with electrochemical detection to upper picogram levels. A simple one-step extraction, which requires only 0.1 mL of plasma and is able to recover greater than 85% of nicotine in plasma, is described. The precision and nicotine recovery of the method, and the application of this assay in nicotine-infused animal studies, are presented.

Effects of chronic smoke exposure on the cardiovascular responses to acute nicotine infusion in the rat

Rats were exposed daily to cigarette smoke for 17-22 weeks in order to characterize mean arterial pressure and regional hemodynamic effects of chronic smoke exposure and to determine if cardiovascular reactivity to acute nicotine infusions is altered by chronic smoke exposure. Urethane-anesthetized animals were instrumented with miniaturized pulsed-Doppler flow probes on the iliac and mesenteric vascular beds. Under resting conditions sham-smoked and smoke-exposed animals had similar levels of mean arterial pressure and mesenteric blood flow; however, resting heart rate was lower in the smoke-exposed group, while iliac blood flow was elevated in the smoke-exposed group. Acute nicotine infusion (6.25, 12.5 and 25 micrograms/kg per min) produced equivalent, dose-dependent pressor effects as well as increases in iliac and mesenteric resistance in sham and smoke-exposed groups. Thus, chronic cigarette smoke-exposure in rats may exert significant cardiovascular effects other than on arterial pressure such as lowered heart rate and elevated blood flow to skeletal muscle beds, while cardiovascular responses to nicotine are not altered by chronic smoke-exposure.