In-frame deletions of BRCA1 may define critical functional domains

The identification of genomic rearrangements involving more than 0.5 kb of the BRCA1 gene has confirmed a more complex mutation spectrum than was initially appreciated. Genomic rearrangements in BRCA1 represent 15% of all mutations in a group of French and American breast and ovarian cancer families and 36% of all mutations in a group of Dutch families. The rearrangements described to date range in size from 510 bp to 23.8 kb, are found throughout the gene, and are most frequently attributable to homologous recombination. We describe the identification of rearrangements in two breast and ovarian cancer families that involve 3.4 and 11.5 kb of the BRCA1 gene and span multiple exons but maintain the reading frame. Both gene rearrangements appear to result from Alu-mediated homologous recombination and have been detected by using a combination of protein truncation analysis and Southern blot analysis. These rearrangements result in the loss of amino acids that lie at the carboxy-terminus of the protein and that have previously been shown to have functional significance. Because these rearrangements result in the deletion of exons but maintain the reading frame, they may provide insights into specific regions and amino acids that have functional significance for the BRCA1 protein.

Effects of two adhesion boosters on the shear bond strength of new and rebonded orthodontic brackets

The purpose of this study was to evaluate the effects of 2 adhesion boosters, Enhance LC (Reliance, Itasca, Ill) and All-Bond 2 (Bisco, Schaumburg, Ill), on the shear bond strength of new and rebonded (previously debonded) brackets. Sixty new and 60 sandblasted rebonded brackets were bonded to 120 extracted human premolars with composite resin and divided equally into 6 groups based on the 2 adhesion boosters used: (1) new brackets/no booster (2) rebonded brackets/no booster (3) new brackets/Enhance (4) rebonded brackets/Enhance (5) new brackets/All-Bond (6) rebonded brackets/All-Bond. Shear bond strength of each sample was tested with an Instron machine (Instron Corp, Canton, Mass). Results show that the new brackets/All-Bond group yielded the highest strength (20.8 +/- 7.5 MPa), followed by the new brackets/Enhance group (18.6 +/- 6.5 MPa), rebond brackets/All-Bond group (17.3 +/- 7.2 MPa), new brackets/no booster group (16.8 +/- 6.3 MPa), rebonded brackets/no booster group (14.2 +/- 7.2 MPa), and rebonded brackets/Enhance group (13.6 +/- 6.7 MPa). No statistically significant difference was found among the 3 groups utilizing new brackets. For groups of rebonded brackets/no booster and rebonded brackets/Enhance, bond strength was significantly lower than groups of 3 new brackets and rebonded brackets/All-Bond. Rebonded brackets/All-Bond group had comparable bond strength to all 3 new brackets groups. It was concluded that in the process of replacing a failed bracket, (1) when new brackets are used, neither All-Bond 2 or Enhance LC improves bond strength significantly, (2) without the use of any adhesion booster, sandblasted rebonded brackets yield significantly less bond strength than new brackets, (3) Enhance LC fails to increase bond strength of sandblasted rebonded brackets, (4) All-Bond 2 significantly increases bond strength of sandblasted rebonded brackets, (5) sandblasted rebonded brackets with All-Bond 2 yield comparable bond strength to new brackets.

Acute epiglottitis presenting as the sensation of a foreign body in the throat

A 49-year-old man presented with dysphagia and the sensation of a foreign body in the throat, after he had swallowed chicken meat that contained bones during the previous evening. There were no respiratory symptoms. A plain lateral soft-tissue X-ray of the neck and oesophagogastroduodenoscopy showed a grossly swollen epiglottis. His condition improved rapidly with intravenous antibiotic therapy. As acute epiglottitis may be a sudden life-threatening condition, a high index of suspicion should be maintained for patients who present with an obstructive sensation in the throat.

Delays by patients, emergency physicians, and surgeons in the management of acute appendicitis: retrospective study

OBJECTIVES

To compare the contributions of patients, emergency physicians, and surgeons in the delay of diagnosis and treatment of appendicitis, and the effects of delay on disease stage and complication rate.

DESIGN

Retrospective study.

SETTING

Accident and emergency department of a district public hospital, Hong Kong.

PATIENTS

All patients undergoing emergency appendectomy between August 1998 to September 1999.

MAIN OUTCOME MEASURES

Patient delay in presentation, emergency physician delay in hospital admission, and surgeon delay in performing the operation; operative findings; and postoperative complications.

RESULTS

Of 158 patients undergoing emergency operation, 14 had no pathological diagnosis and four had a diagnosis other than that of acute appendicitis. Of the 140 pathologically confirmed cases of appendicitis, the mean emergency patient delay was greater in advanced appendicitis than it was in simple appendicitis (42.0 hours versus 24.9 hours; P<0.005). The mean emergency physician delay in advanced appendicitis was also greater than it was in simple appendicitis (17.9 hours versus 5.8 hours; P<0.05). The difference in the mean surgeon delay in simple (10.9 hours) and advanced (16.3 hours) appendicitis, however, was not significant. The mean emergency physician delay showed a significant association with the postoperative complication rate (P=0.05). The delay was mainly because of a failure to diagnose the condition and admit the patient at the first visit to the accident and emergency department (22.1%). The diagnostic accuracy showed a significant association with the level of experience of the emergency physician involved (P<0.05).

CONCLUSION

There should be a higher index of suspicion, better surgical training, and better senior supervision at accident and emergency departments, to avoid preventable morbidity and mortality in acute appendicitis.

The HslU ATPase acts as a molecular chaperone in prevention of aggregation of SulA, an inhibitor of cell division in Escherichia coli

HslVU is an ATP-dependent protease consisting of two multimeric components: the HslU ATPase and the HslV peptidase. SulA, which is an inhibitor of cell division and has high tendency of aggregation, is degraded by HslVU protease. Here we show that HslU plays a role not only as a regulatory component for the HslV-mediated proteolysis but also as a molecular chaperone. Purified HslU prevented aggregation of SulA in a concentration-dependent fashion. This chaperone activity required oligomerization of HslU subunits, which could be achieved by ATP-binding or in the presence of high HslU protein concentrations. hsl mutation reduced the SulA-mediated inhibition of cell growth and this effect could be reversed upon overproduction of HslU, suggesting that HslU promotes the ability of SulA to block cell growth through its chaperone function. Thus, HslU appears to have two antagonistic functions: one as a chaperone for promotion of the ability of SulA in cell growth inhibition by preventing SulA aggregation and the other as the regulatory component for elimination of SulA by supporting the HslV-mediated degradation.

Tissue-specificity, functional characterization and subcellular localization of a rat ubiquitin-specific processing protease, UBP109, whose mRNA expression is developmentally regulated

A cDNA encoding an ubiquitin-specific processing protease, UBP109, in rat skeletal muscle was cloned and its product was characterized. Northern analysis revealed that UBP109 mRNA is highly expressed in testis and spleen, compared with other tissues. Furthermore, in situ hybridization showed that the level of UBP109 mRNA in liver, spinal cord and brain dramatically changed during embryonic development, indicating that the expression of UBP109 mRNA is developmentally regulated. UBP109 was expressed in Escherichia coli and purified to apparent homogeneity using a (125)I-labelled ubiquitin-peptide fusion as a substrate. The purified enzyme cleaved at the C-terminus of the ubiquitin moiety in natural and engineered fusions irrespective of their sizes. UBP109 also released free ubiquitin from poly-His-tagged penta-ubiquitin. Moreover, it released free ubiquitin from poly-ubiquitinated protein conjugates of rabbit reticulocytes. In addition, UBP109 localized to both the cytoplasm and the nucleus and, among three putative nuclear localization sequences, only the one located near the C-terminus is responsible for nuclear localization. These results suggest that UBP109 may play an important role in generation of free ubiquitin from its precursors and its recycling from poly-ubiquitinated protein conjugates, and hence in regulation of ubiquitin-mediated cellular processes, particularly related to embryonic development.

Rice cooker steam hand burn in the pediatric patient

Burn injuries often lead to significant cosmetic and functional deformity. In the Orient, household electric rice cookers have caused a significant number of steam burns to infant hands. The clinical course and treatment outcome of these burns have been studied retrospectively in a review of the medical records of 79 pediatric patients treated for acute hand steam burns and of 38 other patients who underwent correction for postburn contracture. Electric rice cookers caused all of the acute pediatric steam burns treated at our institute. Of the 81 hands treated between 1995 and 1998, 38.3 percent healed with conservative treatment and 61.7 percent required skin grafting. The volar aspects of the index and middle fingers were those most frequently involved. Eighteen of 36 hands (50 percent) grafted with split-thickness skin developed late contractures requiring additional procedures. Among the 38 patients who underwent correction for postburn deformity, initial treatment was split-thickness grafting for 60.5 percent, full-thickness skin grafting for 7.9 percent, and spontaneous healing for 31.6 percent. Awareness among medical personnel and continued public education should be promoted to help prevent this unique type of pediatric steam burn from occurring.

A new SUMO-1-specific protease, SUSP1, that is highly expressed in reproductive organs

A full-length cDNA encoding a SUMO-1-specific protease, named SUSP1, was identified and cloned for the first time from the human brain. Nucleotide sequence analysis of the cDNA containing an open reading frame of 3336 base pairs revealed that the protease consists of 1112 amino acids with a calculated molecular mass of 126,116 Da. Like yeast Ulp1, SUSP1 is a cysteine protease containing the well conserved His/Asp/Cys catalytic triad. SUSP1 expressed in Escherichia coli cells efficiently released SUMO-1 from SUMO-1. beta-galactosidase fusion but not from other ubiquitin-like protein fusions, including Smt3.beta-galactosidase, suggesting its role in the generation of matured SUMO-1 specifically from its precursors. Interestingly, reproductive organs, such as testis, ovary, and prostate, contained much higher amounts of SUSP1 mRNA than colon and peripheral blood leukocyte, whereas other tissues, such as heart and spleen, had little or none. In addition, confocal microscopy using green fluorescent protein.SUSP1 fusion showed that SUSP1 is exclusively localized to the cytoplasm of NIH3T3 and HeLa cells. These results suggest that SUSP1 may play a role in the regulation of SUMO-1-mediated cellular processes particularly related to reproduction.

Retinoic acid and its geometrical isomers block both growth and fusion of L6 myoblasts by modulating the expression of protein kinase A

All-trans retinoic acid (RA) and its geometrical isomers, such as 9-cis RA, 13-cis RA, and 9,13-di-cis RA, strongly inhibited both growth and fusion of L6 myoblasts. However, illumination of white light diminished their inhibitory activity on membrane fusion with little effect on cell growth. During myogenic differentiation, the intracellular level of cAMP decreased whereas the total activity of protein kinase A as well as the protein level of its regulatory subunit Ialpha (RIalpha) and catalytic subunit (Calpha) increased. RAs raised the intracellular level of cAMP by over 3-fold, but decreased the total activity of protein kinase A. Like RAs, dibutyryl-cAMP inhibited myoblast fusion and reduced the expression of both RIalpha and Calpha subunits. These results suggest that RAs negatively modulate the differentiation of L6 myoblasts by increasing the intracellular level of cAMP, which may in turn down-regulate the expression of protein kinase A and hence its activity.

Involvement of the theta-type protein kinase C in translocation of myristoylated alanine-rich C kinase substrate (MARCKS) during myogenesis of chick embryonic myoblasts

The phosphorylation pattern of numerous proteins in the soluble extracts of chick embryonic muscle cells changes dramatically during myogenesis. One of these proteins, the 63 kDa protein, whose phosphorylation state declines during the differentiation process, was identified as the myristoylated alanine-rich C kinase substrate (MARCKS), a major, specific substrate of protein kinase C (PKC). This decrease in the phosphorylation state of MARCKS was due to a decrease in the level of protein in the cytosol with a simultaneous increase in its level in the membrane fraction. Immunostaining of the cultured myoblasts also revealed that MARCKS translocated from the cytosol to the plasma membrane and to the peripheral region of nuclei as the mononucleated myoblasts fused to form multinucleated myotubes. Immunoprecipitation with an anti-PKC-theta antibody, but not with the antibodies against the other PKC isoforms, such as conventional PKC-alpha, novel PKC-delta, and novel PKC-epsilon, inhibited phosphorylation of MARCKS. Moreover, expression of PKC-theta was found to be down-regulated during the course of myogenic differentiation. In addition, treatment of the cells with PMA, which activates PKC-theta and hence increases the phosphorylation state of MARCKS, reversibly inhibited both MARCKS translocation and myoblast fusion. These results suggest that MARCKS is preferentially phosphorylated by PKC-theta in cultured myoblasts and that the down-regulation of PKC-theta; is partly responsible for MARCKS translocation during myogenesis. These results also suggest that PKC-theta-controlled MARCKS translocation is associated with, or a requisite event for, myoblast fusion.

Development of a centrifugal pump with thick blades

We have developed a centrifugal blood pump with thick impeller blades (60% of pitch) to obtain a small tip clearance. An unshrouded impeller with 6 backward curved thick blades was used to reduce the dead zone between the shroud and upper casing. A streamline angle in volute was uniform in circumferential direction by continuity and angular momentum conservation. To prove the effectiveness of small tip clearance, performance and hemolysis tests were conducted on pumps with a tip clearance of 0.5, 1.5, and 2.0 mm at exit with the blade thickness of 60% of pitch, and with that of 1.0, 2.0, and 2.5 mm at exit with the thickness of 40% of pitch. The results showed that the smaller the tip clearance, the better the hydrodynamic and hemolytic performance. The best result was seen in the pump with tip clearance of 0.5 mm with a blade thickness of 60% of pitch. These results suggest that a centrifugal pump with thick blades and a small tip clearance can be a promising alternative as a cardiopulmonary bypass pump.

Deubiquitinating enzymes: their diversity and emerging roles

A growing number of important regulatory proteins within cells are modified by conjugation of ubiquitin, a well-conserved 76-amino-acid polypeptide. The ubiquitinated proteins are targeted to proteasome for degradation or alternative metabolic fates, such as triggering of plasma membrane endocytosis and trafficking to vacuoles or lysosomes. Deubiquitination, reversal of this modification, is being recognized as an important regulatory step. Deubiquitinating enzymes are cysteine proteases that specifically cleave off ubiquitin from ubiquitin-conjugated protein substrates as well as from its precursor proteins. Genome sequencing projects have identified more than 90 deubiquitinating enzymes, making them the largest family of enzymes in the ubiquitin system. This review will concentrate on recent important findings as well as new insights into the diversity and emerging roles of deubiquitinating enzymes in the ubiquitin-dependent pathway.

Selective degradation of unfolded proteins by the self-compartmentalizing HtrA protease, a periplasmic heat shock protein in Escherichia coli

HtrA, which has a high molecular mass of about 500 kDa, is a periplasmic heat shock protein whose proteolytic activity is essential for the survival of Escherichia coli at high temperatures. To determine the structural organization of HtrA, we have used electron microscopy and chemical cross-linking analysis. The averaged image of HtrA with end-on orientation revealed a six-membered, ring-shaped structure with a central cavity, and its side-on view showed a two-layered structure. Thus, HtrA behaves as a dodecamer consisting of two stacks of hexameric ring. HtrA can degrade thermally unfolded citrate synthase and malate dehydrogenase but cannot when in their native form. HtrA degraded partially unfolded casein more rapidly upon increasing the incubation temperature. However, it hydrolyzed oxidized insulin B-chain, which is fully unfolded, at nearly the same rate at all of the temperatures tested. HtrA also rapidly degraded reduced insulin B-chain generated by treatment of insulin with dithiothreitol but not A-chain or intact insulin. Moreover, HtrA degraded fully unfolded alpha-lactalbumin, of which all four disulfide bonds were reduced, but not the native alpha-lactalbumin and its unfolded intermediates containing two or three disulfide bonds. These results indicate that unfolding of the protein substrates, such as by exposure to high temperatures or reduction of disulfide bonds, is essential for their access into the inner chamber of the double ring-shaped HtrA, where cleavage of peptide bonds may occur. Thus, HtrA with a self-compartmentalizing structure may play an important role in elimination of unfolded proteins in the periplasm of Escherichia coli.

Comparison of nasal trauma associated with nasopharyngeal airway applied by nurses and experienced anesthesiologists

BACKGROUND

Insertion of a nasopharyngeal airway by nurses is considered to be invasive. We compared the incidence and severity of nasal injury associated with nasopharyngeal airway insertion by trained nurses to those by anesthesiologists to determine the safety of inserting a nasopharyngeal airway by nurses in cardiopulmonary resuscitation (CPR).

METHODS

One hundred and sixteen male and 96 female patients scheduled for general anesthesia were included in the study. The male and female patients were randomly assigned to two groups respectively. Anesthesia was induced with sodium thiopental and fentanyl intravenously. The patients were then ventilated with a bag-valve-mask by trained nurses or anesthesiologists. In the unsuccessfully ventilated patients, nasopharyngeal airways were inserted to facilitate subsequent ventilation. The nasopharyngeal airway, oropharynx, and nostrils were then examined. The incidence and severity of nasal trauma induced by trained nurses or by anesthesiologists were compared.

RESULTS

The study revealed that nasopharyngeal airways applied by trained nurses did not induce more severe nasal trauma than those by anesthesiologists.

CONCLUSION

We suggest that nasopharyngeal airways may be applied safely by trained nurses in CPR.

Promotion of skeletal muscle differentiation by K252a with tyrosine phosphorylation of focal adhesion: a possible involvement of small GTPase Rho

K252a, a protein kinase inhibitor, acts as a neurotrophic factor in several neuronal cells. In this study we show that K252a enhanced the differentiation of C2C12 myoblasts as well as tyrosine phosphorylation of several focal adhesion-associated proteins including p130(Cas), focal adhesion kinase, and paxillin. The tyrosine phosphorylation of these proteins, reaching a maximum at 30 min after K252a treatment, closely correlated with the colocalization of these proteins in focal adhesion complexes and the coimmunoprecipitation of these proteins with p130(Cas). In addition, K252a stimulated longitudinal development of stress fiber-like structures and cell-matrix interaction in postmitotic myoblasts and eventually formation of well-developed myofibrils in multinucleated myotubes. Herbimycin A, a potent inhibitor of Src family kinases, and cytochalasin D, a selective disrupting-agent of actin filament, completely inhibited K252a-induced tyrosine phosphorylation as well as myoblast differentiation. Similar inhibitory effect was observed in the cells scrape loaded with a Rho inhibitor, C3 transferase, and the treatment of K252a induced a rapid translocation of Rho. These results are consistent with the model that Rho-dependent tyrosine phosphorylation of focal adhesion-associated proteins plays an important role in skeletal muscle differentiation.

A new 30-kDa ubiquitin-related SUMO-1 hydrolase from bovine brain

SUMO-1 is a ubiquitin-like protein functioning as an important reversible protein modifier. To date there is no report on a SUMO-1 hydrolase/isopeptidase catalyzing the release of SUMO-1 from its precursor or SUMO-1-ligated proteins in mammalian tissues. Here we found multiple activities that cleave the SUMO-1 moiety from two model substrates, (125)I-SUMO-1-alphaNH-HSTVGSMHISPPEPESEEEEEHYC and/or GST-SUMO-1-(35)S-RanGAP1 conjugate, in bovine brain extracts. Of them, a major SUMO-1 C-terminal hydrolase had been partially purified by successive chromatographic operations. The enzyme had the ability to cleave SUMO-1 not only from its precursor but also from a SUMO-1-ligated RanGAP1 but did not exhibit any significant cleavage of the ubiquitin- and NEDD8-precursor. The activity of SUMO-1 hydrolase was almost completely inhibited by N-ethylmaleimide, but not by phenylmethanesulfonyl fluoride, EDTA, and ubiquitin-aldehyde known as a potent inhibitor of deubiquitinylating enzymes. Intriguingly, the apparent molecular mass of the isolated SUMO-1 hydrolase was approximately 30 kDa, which is significantly smaller than the recently identified yeast Smt3/SUMO-1 specific protease Ulp1. These results indicate that there are multiple SUMO-1 hydrolase/isopeptidases in mammalian cells and that the 30-kDa small SUMO-1 hydrolase plays a central role in processing of the SUMO-1-precursor.

Molecular cloning of chick UCH-6 which shares high similarity with human UCH-L3: its unusual substrate specificity and tissue distribution

A full-length cDNA encoding ubiquitin C-terminal hydrolase-6 (UCH-6) was isolated from the chick skeletal muscle cDNA library. The sequence of two peptides generated from purified UCH-6 matched perfectly with the predicted amino acid sequence. Nucleotide sequence analysis of the cDNA containing an open reading frame of 690 base pairs revealed that the protease consists of 230 residues with a calculated molecular mass of 26,315 Da. UCH-6 belonged to members of the UCH family containing highly conserved Cys, His, and Asp domains and showed 86% amino acid identity to human UCH-L3. Interestingly, most tissues examined contained significant amounts of UCH-6 mRNA, while human UCH-L3 is expressed only in the brain, lungs, and red cells. Moreover, UCH-6, unlike other UCH family enzymes including UCH-L3, could release free ubiquitin from ubiquitin-beta-galactosidase fusion proteins both in vivo and in vitro. The ubiquitous expression pattern and unusual substrate specificity of UCH-6 suggest that the enzyme may represent a distinct subfamily of UCH-L3.

Molecular cloning and sequence analysis of aggretin, a collagen-like platelet aggregation inducer

A cDNA library derived from the Malayan-pit-viper (Calloselasma rhodostoma) venom gland was constructed in the phagemid vector. Using the information of the N-terminal amino acid sequences of two subunits of aggretin, synthetic mixed-base oligonucleotides were employed as a screening probe for colony hybridization. Separate cDNA clones encoding for the alpha and beta chains of aggretin were isolated and sequenced. The results revealed that mature alpha and beta chains contain 136 and 123 amino acid residues, respectively. Aggretin subunits show high degrees of identity with respective subunits (50-60% for alpha, 49-58% for beta) of C-type lectin-like snake venoms. The identity to rattlesnake lectin is relatively lower (i.e., 39 and 30%). All cysteine residues in each chain of aggretin are well conserved and located at the positions corresponding to those of C-type lectins. Thus, three intracatenary disulfide bridges and an interchain disulfide bond between Cys83(alpha) and Cys75(beta) may be allocated. This is the first report regarding the entire sequence of venom GPIa/IIa agonist. According to the alignment of amino acid sequences, hypervariable regions among these C-type lectin-like proteins were revealed. These hypervariable regions are proposed to be the counterparts directly interacting with different receptors or different domains of a receptor on the surface of platelet.

Fist position for skin grafting on the dorsal hand: I. Analysis of length of the dorsal hand surgery in hand positions

In skin grafting for reconstruction of burns and contracture deformities of the dorsal hand, the hand is kept in a proper position to provide the greatest amount of skin and to avoid the secondary functional deformity. The safe position has been commonly used for immobilizing the hand, but this is to protect the hand function rather than to provide maximal surface for skin grafting. Split-thickness skin graft contracts up to 30 to 50 percent of the original size owing to secondary contraction. If insufficient skin is grafted, contracture deformity of the dorsal hand may occur. To graft the greatest amount of skin on the dorsal hand, the hand should be kept preoperatively in a position flexing all joints of the wrist, metacarpophalangeal joints, and interphalangeal joints and maximally stretching the dorsal hand (a fist position). We studied the surface length of the dorsal hand between the wrist, the metacarpophalangeal joint, and the eponychium in the anatomic, safe, and fist positions of the right hand in 60 adults. Difference of total length between the anatomic and safe positions was not statistically significant (p > 0.05). The total length in a fist position was significantly increased in comparison with the other two positions (p < 0.05). In a fist position compared with the safe position, the increase in length of the dorsal surface of the proximal hand was 11 to 20 percent except in the thumb, and the increase in length of the dorsal surface of the finger was 12 to 17 percent. The increase in total length of a fist position was about 9 mm (7 to 8 percent) in the thumb and 20 to 32 mm (14 to 18 percent) in the index to little fingers. It suggests that the safe position fails to provide an increased dorsal hand surface area for skin grafting compared with the anatomic position. The greatest amount of skin can be grafted in a fist position. Hand immobilization in a fist position for 7 to 9 days after skin grafting has not resulted in irrevocable joint stiffness in our experience. If injury of the deep structures is not present, the hand should be immobilized in a fist position before skin grafting on the dorsal hand.

Immunoglobulin A nephropathy in patients with non-insulin dependent diabetes mellitus

The occurrence of immunoglobulin A nephropathy (IgAN) in patients with noninsulin dependent diabetes mellitus (NIDDM) is a rare event and of pathogenetic interest. It is not clear whether this is merely coincidence. We report here five patients with IgAN in NIDDM associated with or without diabetic glomerulosclerosis. All of the patients were Korean males. In three patients, diabetes mellitus was diagnosed at the same time with diagnosis of IgAN, and the known duration of the diabetes in the other two patients were three and seven years, respectively. There was no evidence of diabetic retinopathy in four patients, but it was found in one patient. In all cases, the diagnosis of IgAN was made by immunohistology.

Role of hyperpolarization attained by linoleic acid in chick myoblast fusion

Our previous report has suggested that hyperpolarization generated by reciprocal activation of calcium-activated potassium (K(Ca)) channels and stretch-activated channels induces calcium influx that triggers myoblast fusion. Here we show that linoleic acid is involved in the process of generating hyperpolarization in cultured chick myoblasts and hence in promotion of the cell fusion. Linoleic acid dramatically hyperpolarized the membrane potential from -14 +/- 3 to -58 +/- 5 mV within 10 min. This effect was partially blocked by 1 mM tetraethylammonium (TEA) or 30 nM charybdotoxin, a selective K(Ca) channel inhibitor, and completely abolished by 10 mM TEA. Single-channel recordings revealed that linoleic acid activates TEA-resistant potassium channels as well as K(Ca) channels. Furthermore, linoleic acid induced calcium influx from extracellular solution, and this effect was partially blocked by 1 mM TEA and completely prevented at 10 mM, similar to the effect of TEA on linoleic acid-mediated hyperpolarization. Since the valinomycin-mediated hyperpolarization promoted calcium influx, hyperpolarization itself appears capable of inducing calcium influx. In addition, gadolinium prevented the valinomycin-mediated increase in intracellular calcium level under hypotonic conditions, revealing the involvement of stretch-activated channels in calcium influx. Furthermore, linoleic acid stimulated myoblast fusion, and this stimulatory effect could completely be prevented by 10 mM TEA. These results suggest that linoleic acid induces hyperpolarization of membrane potential by activation of potassium channels, which induces calcium influx through stretch-activated channels, and thereby triggers myoblast fusion.

Isolation and characterization of cytosolic and membrane-bound deubiquitinylating enzymes from bovine brain

The deubiquitinylating enzymes (DUBs), that release free ubiquitin (Ub) from its precursors or ubiquitinylated proteins, are known to comprise of a large protein family in eukaryotes, but those in mammalian tissues remain largely unknown. Here we report the existence of unexpectedly large species of DUBs in both soluble and membrane-bound fractions of bovine brain, based on their ability to cleave (125)I-labeled Ub-fused alphaNH-MHISPPEPESEEEEEHYC (designated as Ub-PESTc). Two cytosolic enzymes, tentatively called sDUB-1 and sDUB-2, with molecular masses of about 30 kDa were purified to near homogeneity by Ub-Sepharose affinity chromatography. sDUB-1 and sDUB-2 corresponded to UCH-L3 and UCH-L1/PGP 9.5, respectively. Intriguingly, the particulate fraction of the brain homogenate was found to also contain strong activities against (125)I-Ub-PESTc, which can be solubilized by treatment with 5% n-heptyl-beta-D-thioglucoside and 1% Nonidet P-40, but not by washing with 1 M NaCl. From the solubilized material, two new 30-kDa, membranous DUBs (called mDUB-1 and mDUB-2) were purified to apparent homogeneity by Ub-Sepharose chromatography. Two other Ub-aldehyde sensitive DUBs, designated as mDUB-3 and mDUB-4, were also partially purified by conventional chromatographic operations. These mDUBs differed from each other in substrate specificity and exhibited different characteristics from the sDUBs, revealing that they are a new type of membrane-bound DUB. These results indicate the presence of divergent DUBs in mammalian brain, which may contribute to regulation of numerous pivotal cellular functions mediated by the covalent modification of Ub.

Comparison of the accuracy of bracket placement between direct and indirect bonding techniques

An in vitro study was conducted to evaluate the accuracy of bracket placement for direct and indirect bonding techniques. Nineteen sets of duplicated Class II malocclusion models were divided into three groups: (1) one set for ideal bracket placement, (2) nine sets for direct bonding on mannequins, and (3) nine sets for indirect bonding. Both direct and indirect bonding were performed on all teeth except molars by nine faculty members from the Department of Orthodontics, University of Pennsylvania. The position of each bonded bracket from these two bonding groups was compared with that of the same tooth from the ideal group and to each other in terms of bracket height, mesiodistal position, and angulation. Our results indicated that both direct and indirect bonding techniques failed to execute ideal bracket placement. On individual teeth, there was no statistically significant difference in the accuracy of bracket placement between these two bonding techniques except for upper right second premolar and lower left central incisor, where indirect bonding yielded better results in bracket height (P < .05), and for lower left central incisor where indirect bonding was better in mesiodistal position (P < .05), and for upper right lateral incisor where direct bonding was closer to the ideal in angulation (P < .05). Overall, indirect bonding showed better bracket placement in bracket height (P < .05), whereas, no statistically significant difference was found between them regarding the angulation and mesiodistal position.