Differences in gastric emptying between highly selective vagotomy and posterior truncal vagotomy combined with anterior seromyotomy

Gastric emptying has been reported to be both delayed and unchanged following posterior truncal vagotomy combined with anterior seromyotomy (PTV + AS). When compared to highly selective vagotomy (HSV), our clinical experience was that PTV + AS not uncommonly produced postprandial distress. We studied gastric emptying of both liquids and solids 3 and 12 months following HSV and PTV + AS to determine what if any differences there were in gastric emptying between the two procedures. We compared these results with those from studies done in both normal subjects and unoperated duodenal ulcer patients. In 26 duodenal ulcer patients with perforation (n = 18) or bleeding (n = 8), who were treated with HSV (n = 10) or PTV + AS (n = 16), gastric emptying of liquids and solids was evaluated at 3 months and 12 months postoperatively. At 3 months, gastric emptying of liquids was delayed in both the HSV and PTV + AS groups as compared to values in both normal subjects and unoperated duodenal ulcer patients. The emptying of solids was markedly delayed by PTV + AS in contrast to HSV at 3 months (167.1 +/- 28.4 minutes vs. 79.9 +/- 16.7 minutes; P <0.05). The lag duration was not affected. A limited number of patients studied at 12 months showed similar and near-normal emptying of solids in both the HSV and PTV + AS groups (67.5 +/- 7.0 minutes vs. 70 +/- 6.6 minutes). PTV + AS in contrast to HSV produces more marked delayed emptying of liquids and solids at 3 months; with time (1 year) these values return to near normal.

Line probe assay for rapid detection of mutations in the rpoB gene of Mycobacterium tuberculosis

Detection of mutations in the rpoB gene of Mycobacterium tuberculosis has been reported to be an accurate predictor of rifampin resistance. DNA sequence analysis and screening methods such as single-strand conformation polymorphism analysis and dideoxy fingerprinting are labor-intensive, expensive, or yield results that may prove difficult to interpret. We evaluated the accuracy of a commercial line probe assay for rapid identification and characterization of mutations in the rpoB gene in 72 isolates of M. tuberculosis, including 50 rifampin-resistant and 22 rifampin-susceptible strains. Ten distinct rpoB mutations were identified. Concordances with automated sequencing results and phenotypic rifampin susceptibility testing results were 99% and 93%, respectively. The results demonstrate the line probe assay to be a rapid (as short as 1 day) and informative tool for the early detection and characterization of rpoB mutations associated with rifampin resistance in a clinical laboratory setting.

Neuronal Fos activation in olfactory bulb and forebrain of male rats having erections in the presence of inaccessible estrous females

Volatile odors from estrous female rats are necessary and sufficient to induce non-contact penile erections in male rats. It is not known whether these pheromones are detected by the accessory as opposed to the main olfactory system or whether they are processed by forebrain regions that receive olfactory inputs. Using nuclear Fos immunoreactivity as a marker of neuronal activation, we asked how the detection and processing of distal cues from inaccessible estrous females, which elicited non-contact penile erections, compared with the processing of sensory cues from soiled estrous bedding which did not elicit non-contact penile erections. In Experiment 1, groups of sexually experienced males were given one of five treatments. A control group was placed on clean bedding. A second group displayed non-contact penile erections when exposed to the smell, sight and sound of an estrous female restrained behind a permeable barrier. A third group was exposed to the same stimuli as the second (an estrous female) but failed to exhibit non-contact penile erections during the first hour of testing. A fourth group was placed on soiled estrous bedding, and a fifth group was allowed two ejaculations with an estrous female. All males were perfused with 4% paraformaldehyde 2 h after the onset of these respective treatments, and their brains were later processed for Fos immunoreactivity. Non-contact penile erections were observed in males that were exposed to distal cues from an estrous female but not in males exposed to soiled estrous bedding. Males that displayed non-contact penile erections or that were exposed to estrous bedding showed significantly more neuronal Fos immunoreactivity than clean-bedding controls in the nucleus accumbens core and shell, anterior and posterior medial amygdala, bed nucleus of the stria terminalis and the medial preoptic nucleus. Even greater neuronal Fos responses occurred in these regions in mated males. In Experiment 2 these same treatments were given to another cohort of sexually experienced males. Increased neuronal Fos immunoreactivity was observed in the granule and mitral cell layers of the accessory olfactory bulb of males that were either mated or exposed to estrous bedding, but not in males that displayed non-contact penile erections in response to distal cues from an estrous female. The volatile odors which presumably caused non-contact penile erections failed to stimulate significant neuronal Fos immunoreactivity in five main olfactory bulb sites examined. Even so, it seems likely that these pheromones are detected via the main olfactory system and are subsequently processed by the same projection circuit that responds to other pheromones present in estrous bedding that are incapable of eliciting non-contact penile erections.

The prophylactic effect of dexamethasone on postoperative nausea and vomiting in women undergoing thyroidectomy: a comparison of droperidol with saline

The aim of this study was to evaluate the prophylactic effect of dexamethasone on postoperative nausea and vomiting (PONV) in women undergoing thyroidectomy. Droperidol and saline served as controls. One hundred twenty women (n = 40 in each of three groups) undergoing thyroidectomy under general anesthesia were enrolled in this randomized, double-blinded, placebo-controlled study. Immediately before the induction of anesthesia, Group 1 received IV dexamethasone 10 mg, whereas Groups 2 and 3 received IV droperidol 1.25 mg and saline, respectively. We found that both dexamethasone and droperidol significantly decreased the total incidence of PONV compared with saline, with an incidence of 32%, 35%, and 76%, respectively (P<0.01; Group 1 versus Group 3, Group 2 versus Group 3). Patients who received droperidol, however, reported a higher intensity of sore throat and a more frequent incidence of restlessness than those who received dexamethasone. We conclude that, although both dexamethasone and droperidol are effective as prophylactic antiemetics in women undergoing thyroidectomy, droperidol produces more side effects.

IMPLICATIONS

We compared the prophylactic administration of dexamethasone to prevent nausea and vomiting with droperidol and saline in women undergoing thyroidectomy. Both dexamethasone and droperidol significantly reduced postoperative nausea and vomiting, but droperidol produced more side effects, which suggests that dexamethasone is a useful treatment in these patients.

Development of a coronary artery aneurysm three months after stent implantation: a case report

Coronary artery stents have been used widely to prevent acute closure as a bailout procedure, or to decrease restenosis after balloon angioplasty. Stent use has increased substantially in recent years due to the ease and simplicity with which stents provide a predictable angiographic result. However, few data exist on the long-term safety of stents. This case report describes a 63-year-old male patient who developed intimal dissection after balloon angioplasty and who underwent coronary stent placement of a sheathed stent (half Palmaz-Schatz stent, 3.5 mm in diameter and 7 mm in length) as a bailout procedure. Postdilatation with a 3.5-mm balloon was performed at the maximum pressure of 14 atmospheres with a satisfactory angiographic result. However, an aneurysmal dilatation at the stent site was noted three months later. High-pressure stent use without immediately visible vascular dissection by angiography may not be effective for prevention of coronary aneurysm development in a case such as this. Aneurysmal dilatation may be a late complication in cases of coronary artery stent placement.

Protein kinase C activation inhibits tyrosine phosphorylation of Cbl and its recruitment of Src homology 2 domain-containing proteins

One of the major proteins that is rapidly tyrosine phosphorylated upon stimulation of the TCR/CD3 complex is the 120-kDa product of the c-cbl protooncogene (Cbl). Upon activation, tyrosine-phosphorylated Cbl interacts with the Src homology 2 (SH2) domains of several signaling proteins, e.g., phosphatidylinositol 3-kinase (PI3-K) and CrkL. In the present study, we report that pretreatment of Jurkat T cells with PMA reduced the anti-CD3-induced tyrosine phosphorylation of Cbl and, consequently, its activation-dependent association with PI3-K and CrkL. A specific protein kinase C (PKC) inhibitor (GF-109203X) reversed the effect of PMA on tyrosine phosphorylation of Cbl and restored the activation-dependent association of Cbl with PI3-K and CrkL. We also provide evidence that PKCalpha and PKCtheta can physically associate with Cbl and are able to phosphorylate it in vitro and in vivo. Furthermore, a serine-rich motif at the C terminus of Cbl, which is critical for PMA-induced 14-3-3 binding, is also phosphorylated by PKCalpha and PKCtheta in vitro. These results suggest that, by regulating tyrosine and serine phosphorylation of Cbl, PKC is able to control the association of Cbl with signaling intermediates, such as SH2 domain-containing proteins and 14-3-3 proteins, which may consequently result in the modulation of its function.

Nonalcoholic fatty liver disease: a spectrum of clinical and pathological severity

BACKGROUND & AIMS

The spectrum of nonalcoholic fatty liver disease ranges from fatty liver alone to nonalcoholic steatohepatitis. Most previous studies have short follow-up and have not carefully delineated different histological types when determining clinical outcomes. The aim of this study was to compare clinical characteristics and outcomes of patients with different types of nonalcoholic fatty liver.

METHODS

All liver biopsy specimens from 1979 to 1987 with fat accumulation were assessed for inflammation, ballooning degeneration, Mallory hyaline, and fibrosis. Biopsy specimens were also assessed for histological iron and hepatitis C RNA. Outcomes were cirrhosis, mortality, and liver-related mortality.

RESULTS

Of 772 liver biopsy specimens, complete data were available in 132 patients. Fatty liver (type 1) did not differ from the other three types combined with respect to gender, race, age, or obesity. Cirrhosis was more common in the other types combined (22%) than fatty liver alone (4%; P </= 0.001). Overall mortality, histological iron, and hepatitis C did not differ between groups. Most of the liver-related deaths were in type 4.

CONCLUSIONS

The outcome of cirrhosis and liver-related death is not uniform across the spectrum of nonalcoholic fatty liver. These poor outcomes are more frequent in patients in whom biopsies show ballooning degeneration and Mallory hyaline or fibrosis.

Detection of antimicrobial activity in urine for epidemiologic studies of antibiotic use

Antibiotic resistance is the inevitable consequence of the selective pressure of antimicrobial drug use and the adaptive plasticity of the microorganisms. Excessive and irrational use of antimicrobial drugs is a problem in all countries. It is particularly troublesome in developing countries where there is a heavy burden of infectious diseases. This study was designed to determine whether detection of antimicrobial activity in the urine might be a useful tool for epidemiologic studies of the interaction between antibiotic use and resistance in developing countries. A laboratory marker is necessary because the history of antimicrobial drug use may be unreliable. Serial specimens or spontaneously voided urine were obtained from healthy volunteers given a single oral dose of commonly used antimicrobial drugs. Urine was also obtained from hospitalized patients the morning after the last dose of an antimicrobial drug and from untreated controls. Assays were performed with standard American Type Culture Collection (Rockville, MD) stains of Bacillus stearothermophilus, Escherichia coli, and Streptococcus pyogenes. Antimicrobial activity could not be detected in pretreatment urine. After a single oral dose, the beta lactam antibiotics and erythromycin could be detected for about 12 to 24 hours, whereas clindamycin, tetracycline, trimethoprim/sulfamethoxazole, and ciprofloxacin could be detected for 48 or more hours. In hospitalized patients, receiving multiple drugs, the following were the sensitivity and specificity for detection of antimicrobial activity: for B. stearothermophilus, 100.0% and 85.9%, respectively; for S. pyogenes, 94.9% and 94.9%, respectively; and for E. coli, 71.8% and 98.7%, respectively. The combination of E. coli and Streptococcus pyogenes exhibited a sensitivity of 97.4% and specificity of 94.9%. Detection of antimicrobial activity in urine is a promising method to determine antimicrobial drug use in epidemiologic studies, particularly in populations in which drug use history is unreliable.

Once daily isepamicin treatment in complicated urinary tract infections

Isepamicin is a new aminoglycoside, derived from gentamicin B, which is more stable than other aminoglycosides against inactivating enzymes, and is less nephrotoxic. We evaluated the efficacy and safety of a once daily isepamicin in the treatment of complicated urinary tract infections (UTIs), as compared with amikacin. During the period May, 1997, to January, 1998, a total of 52 patients with similar demographic and baseline characteristics were enrolled into a prospective, randomized, open-label, single-center trial at the Veterans General Hospital-Kaohsiung. Eleven patients were excluded for protocol violation. The remaining 41 patients were included in the efficacy analysis. Study subjects included 16 men and 25 women, with a mean age of 57.9 (range 18-95) years. Clinical improvement was noted in 100% of patients in both the isepamicin and amikacin group. No statistically significant difference was observed between the 2 groups in regard to the rapidity of defervescence, relief of dysuria and urinary frequency, and clearance of bacteriuria and pyuria. Bacteriological cure rates were 89.4% for the isepamicin group and 100% for the amikacin group. Fifteen of 25 subjects who received isepamicin and 16 of 27 subjects who received amikacin had an adverse effect, all of which were considered to be mild except for one in the amikacin group, who had an adverse event of moderate severity (vomiting). Seven (3 isepamicin and 4 amikacin) adverse events were considered probably or possibly related to the study drug, which included eosinophilia (2 isepamicin), liver function impairment (1 isepamicin, 2 amikacin), renal function impairment (1 amikacin) and flushed face (1 amikacin). However, none of the patients had a life-threatening or severe adverse event that required discontinuation of the drug. These results show that once daily administration of isepamicin is as effective and safe as amikacin in treatment of complicated UTIs.

UV inducibility of rat proliferating cell nuclear antigen gene promoter

Proliferating cell nuclear antigen (PCNA), also known as a cofactor of DNA polymerase delta, is required for eukaryotic cell DNA synthesis and nucleotide excision repair. Expression of PCNA gene is growth-regulated and UV inducible. In our previous study, we have observed that the rat PCNA promoter has the serum responsiveness. In this study, we demonstrate its UV inducibility in CHO.K1 cells. The UV induction of the rat PCNA promoter activity was dose-dependent in the cells synchronized at different phases. In addition, the sequences of the promoter responsible for the UV inducibility were delimited to the region between nucleotides -70 and +125, which contains an AP-1 site and a downstream proximal ATF/CRE site. While mutation of the AP-1 site abrogated the UV inducibility, mutation of the ATF/CRE site enhanced the UV inducibility, suggesting that the two sites play different roles in the UV induction of the promoter. In addition, the role of p53 in the UV induction of rat PCNA promoter was investigated. We found that exogenous p53 was unable to mimic the UV irradiation to induce rat PCNA promoter and that the UV induction of the rat PCNA promoter was seen in p53 deficient cells. Therefore, it is unlikely that the UV induction of the rat PCNA promoter is p53 dependent.

Peripheral nerves mediating penile erection in the rat

We examined the effects in male rats of bilateral transection of two nerves previously implicated in erectile function, the viscerocutaneous branch of the pelvic nerve (Vc) and the hypogastric nerve (HgN). In Experiment 1 (conducted in Storrs), males underwent simultaneous or successive section of Vc and HgN and were tested for copulation, reflexive erection, and noncontact erection (NCE), i.e. in response to remote cues from estrous females. NCE is considered to be analogous to 'psychogenic' erection in humans, for which the HgN has been ascribed a significant role. In all three types of test, males had a moderate to severe deficit in erectile function after Vc transection. Section of HgN alone had no apparent pro- or anti-erectile effect in any context, nor did it affect the decrement resulting from Vc surgery. Regardless of treatment, all groups retained some erectile potential in each type of test. The loss of bladder function after Vc surgery and of seminal plug deposition after HgN section gave evidence that the targeted nerves were in fact severed. In Experiment 2 (conducted in Xalapa), males were tested only for NCE, but (a) they were tested every 3 days beginning 3 days after each surgery, (b) the interval between the two surgeries was more than 2 weeks, rather than 1 week as in Experiment 1, to allow more time for recovery from general effects of surgery and for hypothetical plasticity of neural function. In the first test after the first surgery, all groups had a modest reduction in the proportion of males displaying NCE, relative to sham-operated males. However, this deficit did not extend to measures of NCE latency or number, and was absent after the second test. After the second surgery, when all males except those with sham operations had both nerves cut, none of the groups exhibited a significant deficit in NCE, and all groups had at least one test in which at least half the males responded. Thus, (a) HgN section did not significantly impair NCE, reflexive erection, or copulation; (b) Vc section impaired, but did not eliminate, erection in all three contexts, but even those effects may be transient; and (c) transection of both nerves, simultaneously or successively, did not cause a greater impairment in erection than did cutting just the Vc. We infer that the HgN may have no pro-erectile role in erection in rats, even in a model analogous to psychogenic erection. The Vc is probably the most important nerve mediating pro-erectile function in NCE, as in reflexive erection and copulation, but this nerve may not be essential for erection in rats in any context, at least in some males.

A MHC-encoded ubiquitin-like protein (FAT10) binds noncovalently to the spindle assembly checkpoint protein MAD2

Recently a number of nonclass I genes were discovered in the human MHC class I region. One of these, FAT10, encodes a protein consisting of two domains with homology to ubiquitin. FAT10 mRNA is expressed constitutively in some lymphoblastoid lines and dendritic cells and in certain other cells after gamma-interferon induction. FAT10 protein expression is controlled at several levels including transcription, translation, and protein stability. Yeast two-hybrid screening of a human lymphocyte library and immunoprecipitation studies revealed that FAT10 noncovalently associated with MAD2, a protein implicated in a cell-cycle checkpoint for spindle assembly during anaphase. Thus, FAT10 may modulate cell growth during B cell or dendritic cell development and activation.

Protein kinase C mu is negatively regulated by 14-3-3 signal transduction proteins

Recent studies have documented direct interaction between 14-3-3 proteins and key molecules in signal transduction pathways like Ras, Cbl, and protein kinases. In T cells, the 14-3-3tau isoform has been shown to associate with protein kinase C theta and to negatively regulate interleukin-2 secretion. Here we present data that 14-3-3tau interacts with protein kinase C mu (PKCmu), a subtype that differs from other PKC members in structure and activation mechanisms. Specific interaction of PKCmu and 14-3-3tau can be shown in the T cell line Jurkat by immunocoprecipitiation and by pulldown assays of either endogenous or overexpressed proteins using PKCmu-specific antibodies and GST-14-3-3 fusion proteins, respectively. Using PKCmu deletion mutants, the 14-3-3tau binding region is mapped within the regulatory C1 domain. Binding of 14-3-3tau to PKCmu is significantly enhanced upon phorbol ester stimulation of PKCmu kinase activity in Jurkat cells and occurs via a Cbl-like serine containing consensus motif. However, 14-3-3tau is not a substrate of PKCmu. In contrast 14-3-3tau strongly down-regulates PKCmu kinase activity in vitro. Moreover, overexpression of 14-3-3tau significantly reduced phorbol ester induced activation of PKCmu kinase activity in intact cells. We therefore conclude that 14-3-3tau is a negative regulator of PKCmu in T cells.

Function and sequence analyses of tumor suppressor gene p53 of CHO.K1 cells

The tumor suppressor gene p53 plays an important role in guarding genomic integrity. When induced in response to environmental results, the gene product of p53 functions as a transcription factor to transactivate genes involved in arresting the cell cycle and as a facilitator of DNA repair. In contrast, the status of p53 in Chinese hamster ovary (CHO) cells, commonly used as a model system for various studies including those involving the cell cycle and transformation, remains an enigma. In this study, the function and sequence of p53 in CHO.K1 cells were investigated. The level of p53 proteins was elevated on ultraviolet (UV) irradiation of the cells, and the proteins formed specific complexes as probed with DNA containing p53-binding sequences. Its activities toward responsive promoters were inducible by UV in a dose-dependent manner. Although p53 in CHO.K1 contained a single missense mutation at codon 211, the mutation apparently had no effect on the functional properties of the protein. The CHO.K1 cells on X-ray irradiation failed to arrest at G1 phase even when the cells were transfected with a wildtype human p53 gene, indicating that the failure probably was not caused by dysfunction of its p53, but by some other mechanism. This result is consistent with the finding that p21(Waf1/Cip1) is undetectable in UV-treated CHO.K1 cells, whereas Gadd45 is induced by UV light in the cells.

Erectile function in male rats after lesions in the lateral paragigantocellular nucleus

In previous research on rats, lesions of the lateral paragigantocellular nucleus (LPGi) in the medulla have facilitated the display of reflexive erection and ejaculation. The present research sought to replicate and extend these findings by determining whether LPGi lesions would also promote erection during copulation and during exposure of the male to inaccessible females, i.e. non-contact erections (NCEs). As expected, males with LPGi lesions (n = 10) had a greater incidence of reflexive erection than males with sham lesions (n = 8), and during copulation LPGi-damaged males required fewer intromissions before ejaculation. However, the lesions did not change the copulatory intromission ratio, a partial measure of erectile function, nor did they change the incidence, latency, or number of NCEs displayed. More direct measures of erection will be necessary to determine whether the inhibitory role of LPGi on sexual reflexes is absent in some erectile contexts, or whether its role in some contexts is too small to be evident in behavioral measures.

A comparison among nalbuphine, meperidine, and placebo for treating postanesthetic shivering

Postanesthetic shivering (PS) is distressing for patients and may induce a variety of complications. In this prospective, double-blinded, randomized study, we evaluated the value of nalbuphine, compared with meperidine and saline, for treating PS. Ninety adult patients were included in the study. Group 1 (n = 30) received i.v. nalbuphine 0.08 mg/kg, Group 2 (n = 30) received i.v. meperidine 0.4 mg/kg, and Group 3 (n = 30) received i.v. saline. Treatment that stopped shivering was considered to have been successful. The results demonstrated that, 5 min after treatment, both nalbuphine and meperidine provided a rapid and potent anti-shivering effect on PS, with high response rates of 80% and 83%, compared with those of saline (0%) (P < 0.01). Thirty minutes after injection, the response rates of nalbuphine and meperidine were 90% and 93%, respectively, compared with 17% in the saline group (P < 0.01). The differences between nalbuphine and meperidine were not significant. We conclude that nalbuphine may be an alternative to meperidine for treating PS.

IMPLICATIONS

We evaluated nalbuphine versus meperidine and saline for treating postanesthetic shivering. Our results demonstrate that both nalbuphine and meperidine provide a similar rapid and potent anti-shivering effect. Nalbuphine may be an alternative to meperidine for treating postanesthetic shivering.

A direct interaction between the adaptor protein Cbl-b and the kinase zap-70 induces a positive signal in T cells

Engagement of the T-cell receptor (TCR)-CD3 complex induces a rapid increase in the activities of Src-family and Syk/Zap-70-family kinases [1] [2]. These activated kinases then induce the tyrosine phosphorylation of multiple intracellular proteins, eventually leading to T-cell activation. One of the prominent substrates for these kinases is the adaptor protein Cbl [3] and recent studies suggest that Cbl negatively regulates upstream kinases such as Syk and Zap-70 [4] [5]. Cbl-b, a homologue of Cbl, is widely expressed in many tissues and cells including hematopoietic cells [6] [7]. Cbl-b undergoes rapid tyrosine phosphorylation upon stimulation of the TCR and cytokine receptors [8] [9]. The role of Cbl-b is unclear, however. Here, we show that overexpression of Cbl-b in T cells induced the constitutive activation of the transcription factor nuclear factor of activated T cells (NFAT). A loss-of-function mutation in Cbl-b disrupted the interaction between Cbl-b and Zap-70 and nearly completely abrogated the Cbl-b-mediated activation of NFAT. Unlike the proposed role of Cbl as a negative regulator, our results suggest that the Cbl homologue Cbl-b has a positive role in T-cell signaling, most likely via a direct interaction with the upstream kinase Zap-70.

Dual regulation of T cell receptor-mediated signaling by oncogenic Cbl mutant 70Z

We previously showed that an oncogenic Cbl mutant (70Z) is constitutively active in transcriptional activation of nuclear factor at activated T cells (NFAT). However, the mechanism underlying this effect remains unclear. Here we analyzed the effects of 70Z mutations at an amino-terminal loss of function site (Gly-306) and at carboxyl-terminal potential tyrosine or serine phosphorylation sites on association with signaling proteins and on NFAT activation. Mutation at Gly-306 of 70Z disrupted its association with Zap-70 and almost completely abolished its ability to induce NFAT activation under basal and ionomycin-stimulated conditions. However, mutations at potential tyrosine or serine phosphorylation sites had little effect. In fact, expression of 70Z with Tyr-700, Tyr-731, or Tyr-774 mutated to Phe increased NFAT activity in comparison with unmutated 70Z. These findings suggest that an amino terminus-mediated interaction of 70Z with Zap-70 plays a positive role and that a carboxyl terminus-mediated, phosphotyrosine-dependent interaction with their binding proteins plays a negative role in 70Z-mediated NFAT activation. In support of this notion are the observations that 70Z reduced T cell receptor-induced NFAT activation and that wild-type Cbl further inhibited this event, suggesting that both 70Z and wild-type Cbl employ a similar mechanism by which Cbl proteins dually regulate T cell receptor-mediated signaling.

Tyrosine phosphorylation and complex formation of Cbl-b upon T cell receptor stimulation

Cbl-b, a mammalian homolog of Cbl, consists of an N-terminal region (Cbl-b-N) highly homologous to oncogenic v-Cbl, a Ring finger, and a C-terminal region containing multiple proline-rich stretches and potential tyrosine phosphorylation sites. In the present study, we demonstrate that upon engagement of the T cell receptor (TCR), endogenous Cbl-b becomes rapidly tyrosine-phosphorylated. In heterogeneous COS-1 cells, Cbl-b was phosphorylated on tyrosine residues by both Syk- (Syk/Zap-70) and Src- (Fyn/Lck) family kinases, with Syk kinase inducing the most prominent effect. Syk associates and phosphorylates Cbl-b in Jurkat T cells. A Tyr-316 Cbl-binding site in Syk was required for the association with and for the maximal tyrosine phosphorylation of Cbl-b. Mutation at a loss-of-function site (Gly-298) in Cbl-b-N disrupts its interaction with Syk. Cbl-b constitutively binds Grb2 and becomes associated with Crk-L upon TCR stimulation. The Grb2- and the Crk-L-binding regions were mapped to the C-terminus of Cbl-b. The Crk-L-binding sites were further determined to be Y655DVP and Y709KIP, with the latter being the primary binding site. Taken together, these results implicate that Cbl-b is involved in TCR-mediated intracellular signaling pathways.

Molecular cloning and characterization of porcine cDNA encoding a 90-kDa heat shock protein and its expression following hyperthermia

We have isolated and sequenced cDNA clones encoding a 90-kDa heat shock protein (HSP90) from a porcine brain cDNA library. The sequence of the 2202-nucleotide coding region showed 88.6% homology with that of the human homologue. Moreover, the deduced amino acid sequence of the porcine hsp90 cDNA was 99.7% identical to that of the human counterpart, with a difference of only three amino acids in a total of 733 residues. Expression of the gene was greatly increased in cultured cells during recovery from heat shock treatment at 45 degrees C for 60 min. Three major transcripts 2.2, 3.0, and 4.1kb in size were detected by Northern blot hybridization. These transcripts were further identified in a whole-pig hyperthermia experiment. These three hsp90 transcripts were constitutively expressed in porcine tissues including kidney, liver, brain, and heart, and their levels were markedly enhanced during recovery from 30-min hyperthermia treatment at 43 degrees C. Furthermore, we found that HSP90 was preferentially expressed in pituitary gland, brain, adrenal gland, and testis, in comparison to the other tissues.

Serum responsiveness of the rat PCNA promoter involves the proximal ATF and AP-1 sites

We have previously shown that the rat PCNA (proliferating cell nuclear antigen) gene promoter is responsive to serum stimulation. In this study, the sequence of the promoter responsive to serum stimulation has been localized in the region between nucleotides -70 and +125 relative to the transcription initiation site. This region contains an ATF site (nucleotides -51 to -44) and an AP-1 site (nucleotides -64 to -58). Mutation at either the ATF or the AP-1 site reduced the serum responsiveness of the promoter. In gel mobility shift assays, nuclear extracts from serum stimulated cells, compared to those from quiescent cells, exhibit an increasing binding activity toward a promoter related oligonucleotide (-70 to -42) which includes the ATF site and the AP-1 site. Formation of the DNA:protein complexes requires the simultaneous involvement of ATF and AP-1 sites as either element can abrogate the complexes in the competition experiment. Both the distance and sequence are essential to complex formation. Moreover, ATF-1 but not ATF-2 (or CREB) has been identified as a major component of the complexes in the antibody supershift or interference experiment. The results of this study suggest that ATF-1 in association with other factors is involved in regulating the serum stimulation of the rat PCNA promoter activity via the proximal ATF and AP-1 sites.