bluuebunny/crossref_metadata_2025 huggingface dataset:
Endotoxin triggers the expression of an inducible isoform of nitric oxide synthase and the formation of peroxynitrite in the rat aorta in vivo
Authors: Szabó Csaba , Salzman Andrew L. , Ischiropoulos Harry
Published: July 2002

The free radicals nitric oxide (·NO) and superoxide (O2
−) are known to react to form peroxynitrite (ONOO−), a highly reactive species. Peroxynitrite has been suggested to play an important role in the cellular damage associated with the overproduction of ·NO, but there are very limited data regarding its in vivo formation. Here we demonstrate that injection of endotoxin into rats leads to the expression of an inducible isoform of ·NO synthase (iNOS) in the thoracic aorta at 6 h and an increase in the circulating levels of nitrite/nitrate. Moreover, at the same time point, there is a marked increase in the immunoreactivity of nitrotyrosine, a marker of peroxynitrite in the aorta. The formation of nitrotyrosine was prevented by inhibiting the activity of NOS by in vivo. Our data suggest that during endotoxin shock, part of ·NO, produced following the induction of iNOS, is converted into peroxynitrite in the vicinity of large blood vessels. The demonstration of the in vivo formation of peroxynitrite at sites of ·NO overproduction may necessitate the development of novel and additional approaches for limiting or preventing ·NO‐related cytotoxic or vasodilatory actions during circulatory shock.
Lipid hydroperoxide‐induced apoptosis: lack of inhibition by Bcl‐2 over‐expression
Authors: Sandstrom Paul A. , Pardi Diane , Tebbey Paul W. , Dudek Ronald W. , Terrian David M. , Folks Thomas M. , Buttke Thomas M.
Published: July 2002

Increased membrane lipid peroxidation has recently been implicated as being associated with apoptosis. In the present study the addition of 15‐hydroperoxyeicosatetraenoic acid (15‐HPETE) or 13‐hydroperoxydodecadienoic acid (13‐HPODE) to A3.01 T cells is shown to induce marked chromatin condensation coincident with DNA fragmentation, indicative of apoptosis. 15‐HPETE also evoked an immediate and sustained rise in cytoplasmic calcium which was required for the induction of apoptosis. A3.01 cells transfected with the bcl‐2 proto‐oncogene were 6‐ to 8‐fold more resistant to apoptotic killing by tumor necrosis factor‐α, but only 0.4‐fold more resistant to 15‐HPETE. Thus, Bcl‐2 is not capable of protecting cells from undergoing apoptosis following the direct addition of lipid hydroperoxides.
DNA damage in human respiratory tract epithelial cells: damage by gas phase cigarette smoke apparently involves attack by reactive nitrogen species in addition to oxygen radicals
Authors: Spencer Jeremy P.E , Jenner Andrew , Chimel Ken , Aruoma Okezie I , Cross Carroll E , Wu Reen , Halliwell Barry
Published: July 2002

Treatment of human respiratory tract tracheobronchial epithelial cells with gas‐phase cigarette smoke led to dose‐dependent DNA strand breakage that was highly correlated with multiple chemical modifications of all four DNA bases. The pattern of base damage suggests attack by hydroxyl radicals (OH:). However, by far the most important base damage in quantitative terms was formation of xanthine and hypoxanthine, presumably resulting from deamination of guanine and adenine respectively. Hence, DNA damage by cigarette smoke may involve reactive nitrogen species as well as reactive oxygen species.
Stimulation of the yeast high osmolarity glycerol (HOG) pathway: evidence for a signal generated by a change in turgor rather than by water stress
Authors: Tamás Markus J. , Rep Martijn , Thevelein Johan M. , Hohmann Stefan
Published: July 2002

The Saccharomyces cerevisiae HOG pathway controls responses to osmotic shock such as production of the osmolyte glycerol. Here we show that the HOG pathway can be stimulated by addition of glycerol. This stimulation was strongly diminished in cells expressing an unregulated Fps1p glycerol channel, presumably because glycerol rapidly equilibrated across the plasma membrane. Ethanol, which passes the plasma membrane readily and causes water stress by disturbing the hydration of biomolecules, did not activate the HOG pathway. These observations suggest that stimulation of the HOG pathway is mediated by a turgor change and not by water stress per se.
α‐Actinin is a potent regulator of G protein‐coupled receptor kinase activity and substrate specificity in vitro
Authors: Freeman Jennifer L.R. , Pitcher Julie A. , Li Xiaolin , Bennett Vann , Lefkowitz Robert J.
Published: July 2002

G protein‐coupled receptor kinases (GRKs) phosphorylate G protein‐coupled receptors, thereby terminating receptor signaling. Herein we report that α‐actinin potently inhibits all GRK family members. In addition, calcium‐bound calmodulin and phosphatidylinositol 4,5‐bisphosphate (PIP2), two regulators of GRK activity, coordinate with α‐actinin to modulate substrate specificity of the GRKs. In the presence of calmodulin and α‐actinin, GRK5 phosphorylates soluble, but not membrane‐incorporated substrates. In contrast, in the presence of PIP2 and α‐actinin, GRK5 phosphorylates membrane‐incorporated, but not soluble substrates. Thus, modulation of α‐actinin‐mediated inhibition of GRKs by PIP2 and calmodulin has profound effects on both GRK activity and substrate specificity.
Identification of key amino acid residues in Neisseria polysaccharea amylosucrase
Authors: Sarçabal Patricia , Remaud-Simeon Magali , Willemot René-Marc , Potocki de Montalk Gabrielle , Svensson Birte , Monsan Pierre
Published: July 2002

Amylosucrase from Neisseria polysaccharea catalyzes the synthesis of an amylose‐like polymer from sucrose. Sequence alignment revealed that it belongs to the glycoside hydrolase family 13. Site‐directed mutagenesis enabled the identification of functionally important amino acid residues located at the active center. Asp‐294 is proposed to act as the catalytic nucleophile and Glu‐336 as general acid base catalyst in amylosucrase. The conserved Asp‐401, His‐195 and His‐400 residues are critical for the enzymatic activity. These results provide strong support for the predicted close structural and functional relationship between the sucrose‐glucosyltransferases and enzymes of the α‐amylase family.
Phosphorylation of Hic‐5 at tyrosine 60 by CAKβ and Fyn
Authors: Ishino Masaho , Aoto Hiroshi , Sasaski Hiroko , Suzuki Rumiko , Sasaki Terukatsu
Published: July 2002

Hic‐5 is a CAKβ‐binding protein localized at focal adhesions. Here we show that overexpression of CAKβ or Fyn, but not FAK, enhanced the tyrosine phosphorylation of coexpressed Hic‐5 in COS‐7 cells. These phosphorylations were further augmented by stimulating cells with osmotic stress. The Y60F mutant of Hic‐5 was not phosphorylated, and Hic‐5 phosphorylated on tyrosine 60 was bound specifically to the SH2 domain of Csk. Coexpression experiments revealed that the phosphorylation of Hic‐5 by CAKβ required the kinase activation of CAKβ and binding of Hic‐5 by CAKβ. Specific phosphorylation of Hic‐5 by CAKβ and Fyn may activate a signaling pathway mediated by Hic‐5.
Protein phosphorylation/dephosphorylation in the inner membrane of potato tuber mitochondria
Authors: Struglics André , Fredlund Kenneth M. , Konstantinov Yuri M. , Allen John F. , Møller Ian M.
Published: July 2002

Inside‐out inner mitochondrial membranes free of matrix proteins were isolated from purified potato tuber (Solanum tuberosum L.) mitochondria and incubated with [γ‐32P]ATP. Proteins were separated by SDS–PAGE and visualized by autoradiography. Phosphorylation of inner membrane proteins, including ATPase subunits, was strongly inhibited by the phosphoprotein phosphatase inhibitor NaF. We propose that an inner membrane phosphoprotein phosphatase is required for activation of the inner membrane protein kinase. When prelabelled inner membranes were incubated in the absence of [γ‐32P]ATP, there was no phosphoprotein dephosphorylation unless a soluble matrix fraction was added. This dephosphorylation was inhibited by NaF, but not by okadaic acid. We conclude that the mitochondrial matrix contains a phosphoprotein phosphatase that is responsible for dephosphorylation of inner membrane phosphoproteins.
The redox state of plastoquinone pool regulates state transitions via cytochrome b6f complex in Synechocystis sp. PCC 6803
Authors: Mao Hai-Bin , Li Guo-Fu , Ruan Xiang , Wu Qing-Yu , Gong Yan-Dao , Zhang Xiu-Fang , Zhao Nan-Ming
Published: July 2002

The effects of benzoquinone analogues, phenyl‐1,4‐benzoquinone (PBQ) and 2,5‐dibromo‐3‐methyl‐6‐isopropyl‐1,4‐benzoquinone (DBMIB), on state transitions in Synechocystis sp. PCC 6803 were investigated. PBQ induced a transition from state 2 to state 1 in the absence of actinic light whereas DBMIB caused a state 2 transition. 3‐(3,4‐Dichlorophenyl)‐1,1‐dimethyl urea could not eliminate the effects of PBQ and DBMIB. These results imply that the redox state of the plastoquinone pool controls the state transitions in vivo and cytochrome b
6
f complex is involved in this process. As a working hypothesis, we propose that the occupancy of the quinol oxidation site and the movement of the Rieske protein may be pivotal in this regulation.
Rhythmic transcription: The molecular basis of circadian melatonin synthesis
Authors: Foulkes Nicholas S. , Whitmore David , Sassone‐Corsi Paolo
Published: July 2002

Adaptation to a changing environment is an essential feature of physiological regulation. The day/night rhythm is translated into hormonal oscillations governing the physiology of all living organisms. In mammals the pineal gland is responsible for the synthesis of the hormone melatonin in response to signals originating from the endogenous clock located in the hypothalamic suprachiasmatic nucleus (SCN). The molecular mechanisms involved in rhythmic synthesis of melatonin involve the CREM gene, which encodes transcription factors responsive to activation of the cAMP signalling pathway. The CREM product, ICER, is rhythmically expressed and participates in a transcriptional autoregulatory loop which also controls the amplitude of oscillations of serotonin N‐acetyl transferase (AANAT), the rate‐limiting enzyme of melatonin synthesis. In contrast, chick pinealocytes possess an endogenous circadian pacemaker which directs AANAT rhythmic expression. cAMP‐responsive activator transcription factors CREB and ATF1 and the repressor ICER are highly conserved in the chick with the notable exception of ATF1 that possesses two glutamine‐rich domains in contrast to the single domain encountered to date in mammalian systems. ICER is cAMP inducible and undergoes a characteristic day‐night oscillation in expression reminiscent of AA‐NAT, but with a peak towards the end of the night. Interestingly CREB appears to be phosphorylated constitutively with a transient fall occurring at the beginning of the night. Thus, a transcription factor modulates the oscillatory levels of a hormone.
Protease‐Containing Silicates as Active Antifouling Materials
Authors: Kim Jungbae , Delio Ray , Dordick Jonathan S.
Published: July 2002

Biocatalytic silicates, composite materials composed of α‐chymotrypsin and a silicate prepolymer, were prepared via a two‐step polymerization process following solubilization of the enzyme in the polymerization media. This new approach resulted in active and stable composites, and a calculated half‐life of over 350 days in aqueous buffer at 30 °C. The high stability and activity of this biocatalytic silicate was likely due to the covalent attachment between α‐chymotrypsin and the silicate matrix. The protease‐containing silicate was resistant to fouling by nonselective protein binding, as demonstrated by the dramatically reduced binding of human serum albumin to the silicate material when compared to that of a silicate containing pre‐inactivated α‐chymotrypsin.
Disruption of iron-sulphur cluster N2 from NADH:ubiquinone oxidoreductase by site-directed mutagenesis
Authors: DUARTE Margarida , PÓPULO Helena , VIDEIRA Arnaldo , FRIEDRICH Thorsten , SCHULTE Ulrich
Published: July 2002

We have cloned and inactivated, by repeat-induced point mutations, the nuclear gene encoding the 19.3kDa subunit of complex I (EC 1.6.5.3) from Neurospora crassa, the homologue of the bovine PSST polypeptide. Mitochondria from mutant nuo19.3 lack the peripheral arm of complex I while its membrane arm accumulates. Transformation with wild-type cDNA rescues this phenotype and assembly of complex I is restored. To interfere with assembly of a proposed bound iron-sulphur cluster, site-directed mutants were constructed by introducing cDNA with altered codons for two adjacent cysteines, Cys-101 and Cys-102. The mutant complexes were purified and their enzymic activities and EPR and UV/visible spectra were analysed. Either of the mutations abolishes assembly of iron-sulphur cluster N2, showing that this redox group is bound to the 19.3kDa protein. We also observed an interference with the reduction of redox group X, suggesting that cluster N2 is the electron donor to this high-potential redox group.
RGS3 interacts with 14-3-3 via the N-terminal region distinct from the RGS (regulator of G-protein signalling) domain
Authors: NIU Jiaxin , SCHESCHONKA Astrid , DRUEY Kirk M. , DAVIS Amanda , REED Eleanor , KOLENKO Vladimir , BODNAR Richard , VOYNO-YASENETSKAYA Tatyana , DU Xiaoping , KEHRL John , DULIN Nickolai O.
Published: July 2002

RGS3 belongs to a family of the regulators of G-protein signalling (RGS), which bind and inhibit the Gα subunits of heterotrimeric G-proteins via a homologous RGS domain. Increasing evidence suggests that RGS proteins can also interact with targets other than G-proteins. Employing yeast two-hybrid screening of a cDNA library, we identified an interaction between RGS3 and the phosphoserine-binding protein 14-3-3. This interaction was confirmed by in vitro binding and co-immunoprecipitation experiments. RGS3-deletion analysis revealed the presence of a single 14-3-3-binding site located outside of the RGS domain. Ser264 was then identified as the 14-3-3-binding site of RGS3. The S264A mutation resulted in the loss of RGS3 binding to 14-3-3, without affecting its ability to bind Gαq. Signalling studies showed that the S264A mutant was more potent than the wild-type RGS3 in inhibition of G-protein-mediated signalling. Binding experiments revealed that RGS3 exists in two separate pools, either 14-3-3-bound or G-protein-bound, and that the 14-3-3-bound RGS3 is unable to interact with G-proteins. These data are consistent with the model wherein 14-3-3 serves as a scavenger of RGS3, regulating the amounts of RGS3 available for binding G-proteins. This study describes a new level in the regulation of G-protein signalling, in which the inhibitors of G-proteins, RGS proteins, can themselves be regulated by phosphorylation and binding 14-3-3.
Maturation of Pichia pastoris‐derived recombinant pro‐Der p 1 induced by deglycosylation and by the natural cysteine protease Der p 1 from house dust mite
Authors: van Oort Erica , de Heer Pleuni G. , van Leeuwen W. Astrid , Derksen Ninotska I. L. , Müller Marcel , Huveneers Stephan , Aalberse Rob C. , van Ree Ronald
Published: July 2002

The mature cysteine protease from Dermatophgoides pteronyssinus, Der p 1, is a major house dust mite allergen. Its enzymatic activity has been shown to have pro‐inflammatory effects that could also negatively influence efficacy of allergen‐specific immunotherapy. The aim of this study was to express recombinant pro‐Der p 1 (rpro‐Der p 1) in the yeast Pichia pastoris and to study its maturation. Expression was achieved at a concentration ranging from 45 mg·L−1 (methanol‐induced expression) to 168 mg·L−1 (constitutive expression). No significant spontaneous maturation of the secreted proenzyme was observed. rpro‐Der p 1 with a sequence‐based molecular mass of 34 kDa was hyperglycosylated by the yeast, migrating at 50–60 kDa on SDS/PAGE. Compared with its natural counterpart (nDer p 1), the recombinant proenzyme demonstrated decreased IgE reactivity, resulting in a 30‐fold lower capacity to induce histamine release from human basophils. Decreased immunoreactivity was also shown by competitive RIA and sandwich ELISA with Der p 1‐specific antibody reagents. CD spectra of rpro‐Der p 1 and nDer p 1 revealed significant structural differences. Deglycosylation of rpro‐Der p 1 with endoglycosidase H resulted in a decrease in apparent molecular mass from 50 kDa to 34 kDa, but did not affect nDer p 1. On removal of N‐glycans from rpro‐Der p 1, which harbours two putative N‐glycosylation sites in both propeptide and mature sequence, the mature rDer p 1 appeared. This suggests that hyperglycosylation hampers spontaneous maturation. Maturation of the recombinant pro‐enzyme was also achieved by addition of the active natural cysteine protease, nDer p 1. In conclusion, high‐level expression of rpro‐Der p 1 in P. pastoris results in a stable hypoallergenic proenzyme with potential for use in allergen‐specific immunotherapy.
Unusual T‐cell receptor‐δ gene rearrangement patterns revealed by screening of a large series of childhood acute lymphoblastic leukaemia by multiplex polymerase chain reaction
Authors: Seeger Karlheinz , Taube Tillmann , Eckert Cornelia , Hanel Claudia , Pogodda Michael , Henze Günter
Published: July 2002

Rearrangements of the T‐cell receptor (TCR) and immunoglobulin genes are considered as useful clonal markers in lymphoproliferative disorders of B‐ and T‐cell lineage, and are frequently used for the detection of minimal residual disease (MRD). In this paper, we report on the unexpected results of an extensive analysis of TCR‐δ chain gene rearrangement frequencies and patterns in leukaemic bone marrow DNA samples collected from 438 children with initial (n = 112) or relapsed (n = 326) acute lymphoblastic leukaemia (ALL). By applying a previously described multiplex polymerase chain reaction, the overall incidence of non‐deleted TCR‐δ gene rearrangements in ALL was 47% (206/438), 52% in initial ALL (58/112) and 45% in relapsed ALL (148/326). As expected, the majority of B‐cell precursor (BCP) ALL had incomplete Vδ2‐Dδ3 or Dδ2‐Dδ3 TCR‐δ gene rearrangements, whereas most T‐ALL showed complete rearrangements of the TCR‐δ gene locus (Vδ1‐Jδ1, Vδ2‐Jδ1, Vδ3‐Jδ1). However, unexpectedly, 5/206 rearranged TCR‐δ alleles in BCP‐ALL showed a complete Vδ‐(Dδ)‐Jδ gene rearrangement pattern, and 3/31 T‐ALL had an incomplete recombination. Theoretically, complete TCR‐δ gene rearrangements should not occur in cells other than T‐lymphocytes and have only been reported once previously in BCP‐ALL. The data contribute to the discussion about the reliable screening for clonal markers in ALL.
Susceptibility of oral Candida species to calcium hydroxide in vitro
Authors: Waltimo T. M. T. , Sirén E. K. , Òrstavik D. , Haapasalo M. P. P.
Published: July 2002

Aim The susceptibility of common oral Candida species to saturated aqueous calcium hydroxide solution was studied.

Methodology The yeast species tested were C. albicans (16 strains), C. glabrata (three strains), C. guilliermondii (three strains), C. krusei (two strains), and C. tropicalis (two strains). At least one reference strain of each species was used; the others were clinical isolates either from persistent apical periodontitis or from marginal periodontitis. The susceptibility of Enterococcus faecalis (ATCC 29212) was studied for comparative purposes. Standardized inocula of the strains were incubated in aqueous calcium hydroxide solution, pH 12.4, for time‐periods ranging from 5 min to 6 h. Volumes of 0.1 mL of the test suspension were cultured directly on Brucella blood agar and incubated in air at 37C. The plates were inspected for growth at 24 and 48 h and the colonies were counted. The time

required to reduce the number of colony‐forming units to less than 0.1% of the initial number was determined for each strain.

Results The sensitivity of the C. albicans strains was generally low, with 16 h of incubation required to kill 99.9% of the colony‐forming units. No differences in susceptibility between C. albicans strains isolated from root‐canal infections and from periodontitis were found. Both strains of C. tropicalis were killed between 3 and 6 h of incubation, whilst strains of C. guilliermondii were killed after only 1020 min of incubation. All strains of C. glabrata survived 20 min, but not 1 h, of incubation, whilst 13 h were required to kill C. krusei. Compared with E. faecalis, all Candida spp. showed either equally high or higher resistance to aqueous calcium hydroxide.

Conclusions This study indicates that Candida spp. are resistant to calcium hydroxide in vitro, which may explain the isolation of yeasts from cases of persistent apical periodontitis.
Induced resistance of host tree foliage during and after a natural insect outbreak
Authors: Kaitaniemi Pekka , Ruohoma­KI Kai , Tammaru Toomas , Haukioja Erkki
Published: July 2002

1. Plant resistance against insect herbivores often increases after experimental damage to foliage, but few studies have obtained field estimates of the effect of induced resistance on insect populations during and after a natural insect outbreak.

2. This study measured the effect of quality of the host tree, mountain birch (Betula pubescens ssp. czerepanovii), on the periodically fluctuating folivore Epirrita autumnata (Lepidoptera, Geometridae) during peak and postpeak years of an outbreak in Finnish Lapland. Comparisons were made both within and between study sites to assess host plant quality, and thereby the effect of delayed induced resistance (DIR).

3. In within‐site comparisons, a set of experimental trees was defoliated by wild larvae in the peak year of the outbreak, whereas control trees were protected from defoliation by spraying with an insecticide. The effect of host plant quality was quantified in the following year by measuring the pupal mass of E. autumnata larvae reared in enclosures on these trees.

4. In between‐site comparisons, the sizes of pheromone‐trapped males were measured at both outbreak and low density sites during the progress of the outbreak. The size of trapped males was subsequently used to estimate the corresponding fecundity of females at the same sites.

5. Pupal mass of E. autumnata reared on trees defoliated in the previous year was 0–10% lower than on those trees protected from defoliation by the insecticide. Field‐collected adults indicated a similar pattern: they were smaller at outbreak sites than at low‐density sites, and the size reached its minimum in the post‐peak year. However, the estimated loss of reproductive capacity of females resulting from DIR was too small to be the sole explanation for the termination of the outbreak.

6. Whether the weak DIR response in this system was a characteristic of the 1990s outbreak alone remains unclear, because different terminating agents may be important for different individual outbreak peaks. During this outbreak, larval parasitism and developmental asynchrony between larvae and birch were probably more important reasons for population collapse than DIR.
Quantitative assessment of hepatitis C virus RNA in peripheral blood mononuclear cells during therapy with interferon‐α2a
Authors: Moonka D. K. , Henzel B. S. , Gutekunst K. , O’Brien C. B.
Published: July 2002

A significant number of patients with hepatitis C (HCV) treated with interferon (IFN) will initially clear their serum of HCV RNA, but will then have recurrence of viraemia either during or after therapy. One proposed mechanism for relapse is that HCV may persist in peripheral blood mononuclear cells (PBMCs) and that the PBMCs serve as a ‘viral reservoir’ that is resistant to IFN. To address this hypothesis, we performed serial, quantitative polymerase chain reaction (PCR) of HCV RNA in serum and PBMCs from 26 consecutive patients treated with IFN‐α2a. Of the 26 patients, 11 (42%) did not clear virus from their serum during therapy and were termed non‐responders. Five patients (19%) had sustained clearance of virus from serum and were termed complete responders. The remaining 10 patients (39%) initially eliminated HCV RNA from their serum, but had relapse of viraemia. They were termed partial responders. In all 10 partial responders HCV RNA was undetectable in PBMCs at the same time that it was undetectable in serum. When virus recurred in serum, it was preceded by or occurred at the same time as the return of virus in PBMCs. The results of our study indicate that PBMCs did not serve as an IFN‐resistant ‘viral reservoir’ during therapy. Partial responders who transiently cleared virus from serum also cleared virus from PBMCs and the presence or titre of HCV RNA in PBMCs at the initiation of therapy did not predict response to therapy.
PANCREATIC TRAUMA: UNIVERSITIES OF MELBOURNE HPB GROUP
Authors: Fleming William R. , Collier Neil A. , Banting Simon W.
Published: July 2002

Background: Pancreatic trauma is uncommon, but carries high morbidity and mortality rates, especially when diagnosis is delayed or inappropriate surgery is attempted. Although the retroperitoneal position of the pancreas confers it some immunity to injury, the force required to do so often results in severe associated injuries to other organs, which may be life threatening. Diagnosis may be difficult and surgery can be a considerable technical challenge.

Methods: All patients with pancreatic trauma who attended one of three Melbourne teaching hospitals from 1977 to 1998 were identified. Injuries were graded and the method of diagnosis and treatment studied. The incidence and causation of postoperative morbidity and mortality was identified.

Results: Thirty‐eight patients (26 men and 12 women) were studied. Blunt trauma was responsible in 30 patients, stab wounds in five, gunshot wounds in two and iatrogenic injury in one. Injuries to other organs occurred in 30 patients. Surgical procedures were undertaken in 34 patients, resulting in the death of five and complications in 25.

Conclusion: Complications and death are related to the associated injuries, as much as to the pancreatic injury itself. In this study, we review the experience of the management of pancreatic trauma in three large teaching hospitals in Melbourne over a 21‐year period, and suggest a strategy for dealing with these difficult patients. Adherence to the basic concepts of control of bleeding from associated vascular injury, minimization of contamination, accurate pancreatic assessment, judicious resection and adequate drainage can diminish the risk. By approaching the problem in a systematic way and adopting a generally conservative management plan, complications and deaths can be minimized in these complex cases.
TESTICULAR TORSION: TIME IS THE ENEMY
Authors: Dunne Patrick J. , O’Loughlin Barry S.
Published: July 2002

Background: The acute scrotum is a diagnostic dilemma, and testicular torsion is of primary interest because of its fertility problems for the patient and medico‐legal issues for the surgeon. The present study aimed to correlate operative findings of patients with suspected testicular torsion with certain clinical variables and investigations to see if diagnosis and outcome could be improved.

Methods: A total of 99 patients underwent scrotal exploration for suspected testicular torsion at the Royal Brisbane Hospital between 1990 and 1995. Colour Doppler ultrasound, white blood count and urine microscopy results were documented, along with the patient’s age and duration of testicular pain.

Results: Fifty‐six patients were found to have torsion, and the testicular loss rate was 23%. Patients who experienced testicular pain for longer than 12 h had a testicular loss rate of 67%. A negative urine microscopy was suggestive of testicular torsion, but was not diagnostic. The white blood count did not aid in the diagnosis. Colour Doppler ultrasound of the scrotum was used on nine occasions with three false negative results and a sensitivity of only 57%.

Conclusions: Time is the enemy when managing the acute scrotum. No investigation substantially improves clinical diagnosis enough to warrant any delay in definitive surgical intervention.
ABSORPTION AND UTILIZATION OF IRRADIANCE BY CYANOBACTERIAL MATS IN TWO ICE‐COVERED ANTARCTIC LAKES WITH CONTRASTING LIGHT CLIMATES
Authors: Hawes I. , Schwarz A‐M. J.
Published: July 2002

We investigated the under‐ice light climate and the efficiency with which light was absorbed and utilized by benthic algal mats in Lakes Hoare and Vanda, two perennially ice‐covered lakes in the McMurdo Dry Valleys area of Southern Victoria Land, Antarctica. The ice cover and water column of Lake Vanda were much more transparent than those of Lake Hoare (18% vs. 2% transmission though ice and attenuation coefficients for downwelling irradiance of 0.05 vs. 0.12 m−1, respectively). In both lakes the under‐ice spectra were dominated by blue‐green wavelengths. The benthic flora under perennial ice covers of both lakes comprised thick mucilaginous mats, dominated by cyanobacteria. The mats were well suited to absorb the dominant blue‐green wavelengths of the under‐ice light, with phycoerythrin being present at high concentrations. The pigment systems of the benthic mats absorbed 30%–50% of the light that reached them, varying with depth and lake. There was a tendency for the percentage of absorption to increase as ambient irradiance decreased. The efficiency of utilization of absorbed irradiance was examined by constructing absorbed irradiance/oxygen evolution curves to estimate community quantum yield. Mats from 13 m in Lake Hoare showed the highest quantum yields, approaching 1 mol of carbon fixed for every 8 mol quanta absorbed under light‐limiting conditions. Lake Vanda mats had lower quantum yields, but these increased with depth. Calculated in situ irradiance occasionally exceeded the measured saturating irradiance for oxygen evolution in both lakes, thus efficiency in situ was below the maximum at times. As in other environments, optimization strategies allowed efficient capture and utilization of the lower and middle ranges of experienced irradiance but led to a compromised capacity to use the highest irradiances encountered at each depth.
Coordinated Diurnal Regulation of Low‐ and High‐Affinity Nitrate Transporters in Tomato
Authors: Ono F. , Frommer W. B. , von Wirén N.
Published: July 2002

Abstract: Two new members of the NRT2 gene family encoding high‐affinity NO3− transporters were isolated from tomato by heterologous screening. Both cDNAs, LeNRT2;1 and LeNRT2;2, are highly similar in the coding region, however, significant nucleotide differences were found in the 3′‐untranslated region. High‐stringent Southern analysis with gene‐specific probes indicated that the two genes are linked in the genome and are most probably derived from a recent gene duplication. Expression of both genes was restricted to roots. Although no difference in expression between both genes could be demonstrated by Northern analysis, LeNRT2;1 and LeNRT2;2 were isolated 56 and 3 times, respectively, from a cDNA library of root hairs, indicating a dominant expression of LeNRT2;1 in root hairs of tomato seedlings. Maximum transcript levels of LeNRT2 peaked 4 h after NO3− induction and coincided with those of the putative low‐affinity NO3− transporter gene, LeNRT1;2. In contrast, 4 h after NO3− supply LeNRT1;1 transcription was maximally repressed, reflecting an opposite regulation. As transcript levels of LeNRT2 also increased independently from NO3− induction, diurnal gene expression was monitored. All investigated genes, LeNRT2, LeNRT1;1, LeNRT1;2 and LeNR, showed the highest peak in transcript levels 4 h after the onset of the light period and a second peak at the end of the light period. Although expression of these genes was highly coordinated at these times of the day, LeNRT1;1, LeNRT1;2 and LeNR showed additional peaks. This indicates that diurnal oscillation of these genes is most likely based on multiple factors, such as carbohydrate supply to the roots, feedback regulation from N assimilates and phytochrome‐mediated regulation.
A Survivor Following Repair of Laryngotracheo-Esophageal Cleft: Lessons Learned
Authors: Ratan Simmi K. , Ratan John , Vinay Becshea , Seth Rajiv
Published: July 2002

A survivor, following successful repair of laryngotracheo-esophageal cleft extending up to cervical trachea, is being described. The cleft was repaired with anterior laryngofissure approach, using no interposition of tissue between trachea and esophagus. The patient had an uneventful recovery, short hospitalization, and satisfactory outcome on follow-up for over 11/2 years, as of now. Optimum ventilation was achieved intra-operatively via an endotracheal tube passed through operative field, following visualization of the cleft. Postoperatively, mechanical ventilation was given via nasotracheal tube left indwelling in trachea following completion of tracheal repair. Early nutrition through enteral route was started 72 hours postoperatively by drip feeds (using infusion pump) through a soft nasogastric tube that was left indwelling following esophageal repair. This maneuver, along with positional and medical therapy, helped us to gain control over gastro-esophageal reflux that is known to be incapacitating in these patients. The authors recommend a reexamination of existing management strategies for patients with laryngotracheo-esophageal clefts and suggest that conservative approach in dealing with associated problems can help decrease morbidity in these patients.
Time jitter in multimode Fabry–Perot laser diodes
Authors: D’Ottavi A. , Mecozzi A. , Spano P. , Piazzolla S.
Published: July 2002

Time jitter, which affects the switch-on instant of pulse modulated semiconductor lasers, has recently been shown to be lower in Fabry–Perot than in distributed feedback lasers. In this letter starting from the rate equations for the field and the number of excited carriers in multimode lasers, and considering the stochastic nature of spontaneous emissions, we are able to find an expression for time jitter which explains the above-mentioned experimental results.
Radiation-induced formation of cavities in amorphous germanium
Authors: Wang L. M. , Birtcher R. C.
Published: July 2002

Prethinned polycrystalline Ge TEM samples were irradiated with 1.5 MeV Kr+ ions at room temperature while structural and morphological changes were observed in situ in the Argonne High Voltage Electron Microscope-Tandem Facility. After a Kr+ dose of 1.2×1014 ions/cm2, the irradiated Ge was completely amorphized. A high density of small void-like cavities was observed after a Kr+ dose of 7×1014 ions/cm2. With increasing Kr+ ion dose, these cavities grew into large holes transforming the irradiated Ge into a sponge-like porous material after 8.5×1015 ions/cm2. The radiation-induced nucleation of void-like cavities in amorphous material is astonishing, and the final structure of the irradiated Ge with enormous surface area may have potential applications.
InAsyP1−y/InP multiple quantum well optical modulators for solid-state lasers
Authors: Woodward T. K. , Sizer Theodore , Chiu T. H.
Published: July 2002

We report the operation of strained-layer InAsyP1−y/InP multiple quantum well optical modulators at wavelengths compatible with solid-state lasers such as neodymium-doped yttrium aluminum garnet. A structure having 50 periods of 100 Å InAsyP1−y quantum wells with 100 Å InP barriers is described that has an exciton peak at 1.05 μm and a single pass transmission contrast ratio of 1.4. Favorable comparison is made to similar InxGa1−xAs/GaAs structures.
Properties of diamond composite films grown on iron surfaces
Authors: Ong T. P. , Chang R. P. H.
Published: July 2002

We report for the first time that diamond composite films consisting of diamond particles, hydrogenated amorphous carbon, and/or fluorocarbon films can be successfully deposited on carbon steel and 304 stainless-steel substrates by plasma-assisted chemical vapor deposition. The use of thin (∼200 Å) silicon buffer layer proves to be effective in inhibiting surface catalytic effect of iron and also prevents carbon species from diffusing into the bulk. The composite films adhere well to the substrates even upon imposing a scratch load of 68 newtons. They can also be bent up to 10° and still remain chemically inert and impermeable to salt solution. One of the potential applications of these films is for protective coating on sheet metal surfaces.
Strongly enhanced critical current density in Nb 47 wt. % Ti having a highly aligned microstructure
Authors: Cooley L. D. , Jablonski P. D. , Lee P. J. , Larbalestier D. C.
Published: July 2002

The transport critical current density increased from 2610 to 5200 A/mm2 at 5 T, 4.2 K, when a round monofilament Nb 47 wt. % Ti composite was rolled to an aspect ratio of 9.7 and was tested with the broad face of the tape parallel to the field. This value exceeds the previous maximum of 3700 A/mm2 by about 50%. Transmission electron micrographs show that more than 90% of the α-Ti precipitates in the optimum-rolled filament are aligned within 10° of the broad face of the tape, whereas the precipitates had a random azimuthal orientation prior to rolling. The strong alignment caused the elementary pinning force to be greatly enhanced in the parallel-field orientation; however, in the orthogonal orientation the Jc fell to low values characteristic of conventional wires having no α-Ti flux pinning centers.
Epi-less bond-and-etch-back silicon-on-insulator by MeV ion implantation
Authors: Maszara W. P. , Pronko P. P. , McCormick A. W.
Published: July 2002

A modified approach to silicon-on-insulator (SOI) by bond-and-etch-back technology was studied where a high-energy (MeV) boron implant was utilized as an etch stop to eliminate the need for an epitaxial layer growth in forming a device film. Also a second (retro) MeV implant, applied after the first stage of the etch-back process, was investigated as an improved method for achieving uniform thinning of a thick (3 μm) SOI film. Significantly improved thickness uniformities (σ<10 nm across a 3×3 in. area) were obtained by this method for a 490-nm-thick silicon device film.
Operation of five individual diode lasers as a coherent ensemble by fiber coupling into an external cavity
Authors: Corcoran C. J. , Rediker R. H.
Published: July 2002

Five diode lasers that each have one facet antireflection coated were fiber coupled into an external cavity and operated as a coherent ensemble by the use of a spatial filter placed at the Fourier plane of the cavity. The resulting output was shown to be in a single spectral line with a linewidth less than the instrumental resolution (7.5 MHz) of the Fabry–Perot spectrum analyzer used. The effect of rotating the polarization of the radiation inside one of the fibers is described.
Lithographic spiral antennas at short wavelengths
Authors: Grossman E. N. , Sauvageau J. E. , McDonald D. G.
Published: July 2002

We have extended the high efficiency of lithographic antennas to mid-infrared wavelengths. Pattern measurements made at 9.5 μm wavelength on a 65°, self-complementary, spiral antenna exhibit a ratio of response to orthogonal linear polarizations of 1.35 dB, a beamwidth of 85° (3 dB full width), a directivity of 8.2 dB, and surprisingly, a close resemblance to the theoretical pattern for a 65° spiral in free space. Direct detection measurements made with an ambient temperature blackbody source yield an antenna efficiency of 52±7%, when corrected for incomplete filling of the antenna beam by the source, at a mean effective wavelength of 19 μm.
Epitaxy of LiF on Ge(100)
Authors: Lapiano-Smith D. A. , Eklund E. A. , Himpsel F. J. , Terminello L. J.
Published: July 2002

It is shown that LiF(100) films with the electronic properties of cleaved bulk LiF crystals can be grown epitaxially on Ge(100). These include an exceptionally large, negative electron affinity of −2.7 eV, which leads to intense photoemission at zero kinetic energy. The valence band offset ranges from 7.3–7.6 eV.
Real-time Raman measurements of graphite under Ar+ irradiation
Authors: Nakamura Kazutaka , Kitajima Masahiro
Published: July 2002

The time dependence of the Raman spectra of graphite is measured under 3-keV Ar+-ion irradiation by developing a real-time Raman measurement apparatus. An ion flux of 3×1011 ions/cm2 s is used and the time resolution of the Raman measurement is about 6 s. The lattice damage of graphite is evaluated by the relative intensity of the disorder-induced peak (∼1360 cm−1) with respect to the Raman active E2g2 mode peak (∼1580 cm−1). An initial steep rise and a successive slow increase to saturation of the relative intensity ratio are observed.
Determination of the densities of gap states in hydrogenated polycrystalline Si and Si0.8Ge0.2 films
Authors: Cao Min , King Tsu-Jae , Saraswat Krishna C.
Published: July 2002

The densities of gap states are determined using the field-effect conductance method for hydrogenated polycrystalline Si0.8Ge0.2 for the first time, and also for polycrystalline Si. The polycrystalline films were hydrogenated by high dose H+ implantation and subsequent low-temperature anneal. The density of states is found to be higher in hydrogenated Si0.8Ge0.2 than in hydrogenated Si, for the low-pressure chemical vapor deposited films used in this work. The Si0.8Ge0.2 film is slightly n-type whereas the Si film is slightly p-type. The polycrystalline Si density of states shows the characteristic hump associated with silicon dangling bonds. These dangling bond states are located 0.63 eV below the conduction band. In the case of polycrystalline Si0.8Ge0.2, the dangling bond states are more complicated.
Stabilized cubic zirconia: A Raman study under uniaxial stress
Authors: Cai Jiguang , Raptis Y. S. , Anastassakis E.
Published: July 2002

Yttria-stabilized cubic zirconia has been studied at 300 K by use of Raman spectroscopy under uniaxial stress along the [001] and [111] directions. The main effects observed are the frequency shifts of the F2g-type Raman band at ∼610 cm−1 which vary linearly with the applied stress and tend to increase with Y2O3 concentration. Effective deformation potentials are determined for the F2g band. These potentials are necessary for strain characterization of stabilized cubic zirconia, in buffer or epitaxial film configurations. Polycrystalline yttria-stabilized tetragonal zirconia is likewise studied.
Low energy ion implantation and electrochemical separation of diamond films
Authors: Marchywka Mike , Pehrsson Pehr E. , Vestyck Daniel J. , Moses Daniel
Published: July 2002

We combine low energy and low dose ion implantation with an electrochemical etch to fabricate thin diamond layers suitable for seeding homoepitaxial or polycrystalline chemical vapor deposited (CVD) diamond growth. Implantation of a carbon ion dose of 1×1016 cm−2 at 175 keV creates subsurface damage in a bulk crystal which is selectively removed by the electrochemical etch. Implanted substrates were subjected to CVD diamond deposition prior to etching of the damage layer. We discuss the effect of implantation and subsequent annealing conditions on the morphology and Raman spectra of the CVD films. All results indicate that the seed layer nucleated high quality CVD diamond film growth.
Room-temperature electroluminescence from Er-doped crystalline Si
Authors: Franzò G. , Priolo F. , Coffa S. , Polman A. , Carnera A.
Published: July 2002

We have obtained room-temperature electroluminescence (EL) at ∼1.54 μm from Er and O co-doped crystalline p-n Si diodes fabricated by ion implantation, under both forward and reverse bias conditions. Under forward bias, the EL intensity decreases by a factor of ∼15 on going from 110 to 300 K, where a weak peak is still visible. In contrast, we report the first sharp luminescence peak obtained under reverse bias conditions in the breakdown regime. In this case the EL intensity decreases only by a factor of 4 on going from 110 to 300 K and the room-temperature yield is more than one order of magnitude higher than under forward bias. The data suggest that Er excitation occurs through electron-hole mediated processes under forward bias and through impact excitation under reverse bias.
Synthesis and processing of silicon nanocrystallites using a pulsed laser ablation supersonic expansion method
Authors: Werwa E. , Seraphin A. A. , Chiu L. A. , Zhou Chuxin , Kolenbrander K. D.
Published: July 2002

We report the preparation of nanometer sized crystallites of silicon by a pulsed laser ablation supersonic expansion technique. High resolution transmission electron microscopy is used to verify that particles with diameter in the range of ∼3 nm and greater are produced. Glancing angle x-ray diffraction results confirm that the particles formed have the silicon diamond cubic crystal structure. Visible photoluminescence emission from self-supporting thin films of agglomerated nanocrystallites is observed under excitation with ultraviolet light.
Growth of SiC using hexamethyldisilane in a hydrogen-poor ambient
Authors: Nordell N. , Nishino S. , Yang J.-W. , Jacob C. , Pirouz P.
Published: July 2002

Growth of cubic SiC has been carried out on Si(111), Si(100), and SiC(0001) substrates using chemical vapor deposition at atmospheric pressure. Hexamethyldisilane (HMDS) was used as the only precursor and pure Ar or a nonflammable mixture of Ar and H2 was used as the carrier gas. The crystallinity was characterized by x-ray diffraction, reflection high energy electron diffraction (RHEED), and transmission electron microscopy. It was found that polycrystalline layers were obtained at low growth temperatures and with pure Ar as the carrier gas, while the crystallinity improved at temperatures above 1300 °C and when H2 was added. Under optimum growth conditions most of the grains are oriented with parallel epitaxy or with twinned epitaxy with respect to an (111) substrate. A Si/SiC heterodiode was also grown and it shows a breakdown voltage of more than 100 V.
Van der Waals epitaxy of three-dimensional CdS on the two-dimensional layered substrate MoTe2(0001)
Authors: Löher T. , Tomm Y. , Pettenkofer C. , Jaegermann W.
Published: July 2002

Epitaxial films of Wurtzite CdS in (0001) orientation have been grown on MoTe2 (0001) substrates in spite of a lattice mismatch of 15%. The film growth was in situ monitored by soft x-ray photoelectron spectroscopy and low energy electron diffraction. The interface is found to be nonreactive and atomically abrupt. The CdS overlayer tends to grow in three-dimensional clusters (Volmer–Weber growth mode).
Growth and characterization of GaInP unicompositional disorder-order-disorder quantum wells
Authors: Schneider R. P. , Jones E. D. , Follstaedt D. M.
Published: July 2002

Metalorganic vapor phase epitaxy (MOVPE) is used to grow unicompositional quantum-well (QW) structures, in which the QW and barrier layers are composed of ordered and disordered GaInP, respectively. Transmission electron dark-field micrographs reveal abrupt interfaces between highly ordered QWs and disordered barriers, with no evidence of defect formation. Low-temperature photoluminescence from the structures exhibits relatively broad emission peaks, with emission energy increasing with decreasing QW thickness. The dependence of emission energy on well thickness can be described by a finite square well model only when a type-II band alignment is taken for the heterostructure, in which the conduction band edge of the ordered GaInP QW lies about 135–150 meV below that of the disordered barrier material. These results demonstrate a high degree of control over the ordering process in MOVPE, such that quantum size effects can be realized solely through disorder-order phenomena. Further, the data provide strong support for a type-II (spatially indirect) recombination transition between ordered and disordered GaInP.
Single-beam time-resolved Z-scan measurements of slow absorbers
Authors: Oliveira L. C. , Zilio S. C.
Published: July 2002

A single-beam time-resolved Z-scan method is introduced to characterize the nonlinear refraction of slow (millisecond) response absorbers with cw radiation. Owing to the elimination of parasitic linear effects, the technique is able to measure induced phase distortions as small as λ/104. We demonstrate this method on several materials using low power Ar+ and He-Ne lasers.