Myocardial high-energy phosphate metabolism in patients with stable chronic dilated cardiomyopathy under a dobutamine-induced prolonged mild workload

BACKGROUND

The myocardial phosphocreatine (PCr) to beta-adenosine triphosphate ratio measured by phosphorus 31 nuclear magnetic resonance spectroscopy, which is analogous to energy reserve, is one of the important clinical predictors in patients with dilated cardiomyopathy (DCM). However, it may vary with the cardiac workload.

METHOD

The myocardial PCr to beta-adenosine triphosphate ratio was measured before and during a 5 and 10 microgram/kg/min infusion of dobutamine in 7 patients with DCM and in 8 normal patients. Dobutamine infusion was kept constant for 50 minutes in each stage. Myocardial contractility and ventricular size were determined by echocardiography with the same protocol.

RESULTS

This ratio was unchanged from 1.5 +/- 0.4 to 1.8 +/- 0.6 in the low-dose stage and stable (1.7 +/- 0.3) in the high-dose stage in patients with DCM. The heart rate and the mean rate of circumferential fiber shortening increased dose dependently both in patients with DCM and in patients without.

CONCLUSION

These results demonstrate that constant loading of dobutamine for hours is tolerated without deterioration of myocardial metabolic function by patients with nonischemic DCM. We concluded that the high-energy phosphate metabolism of stable patients with cardiomyopathy is stable if the workload is temporary and weak. This implies the possibility that mild exercise can be tolerated in patients with heart failure.

Effectiveness of an inferior vena caval filter as a preventive measure against pulmonary thromboembolism after abdominal surgery

In three patients with a previous history of pulmonary thromboembolism, inferior vena caval filters were inserted before elective laparotomies to prevent a recurrent pulmonary thromboembolism. Two patients had colon cancer and underwent colectomies, while the other had myoma uteri, which might have been the cause of deep vein thrombosis, and thus a hysterectomy was performed. In spite of their poor risks, their postoperative courses were fairly good owing to perioperative management including anticoagulant therapy, and no recurrence has been observed since the operation in every case. A pulmonary thromboembolism is a fatal complication which follows deep vein thromboses. In patients with such a previous history, the risk is much higher after a laparotomy because of long-term bed rest, hypercoagulability, and so on. The mortality rate after a recurrence of pulmonary thromboembolism is reported to reach 30% without adequate therapy, whereas it is reduced to 8% with anticoagulant therapy, and to 0.8% with additional inferior vena caval filter placement. Considering the feasibility of insertion and the low incidence of complications, preoperative inferior vena caval filter placement is thus recommended for patients having a previous history of either pulmonary thromboembolism or deep vein thrombosis.

Influence of motor activities on the release of transmitter quanta from motor nerve terminals in mice

We investigated the effects of motor activities on transmitter release in mouse nerve-muscle preparations of the diaphragm muscle (DPH), extensor digitorum longus muscle (EDL), and soleus muscle (SOL). Mice were divided into a control group, a motor-restricted (RST) group, and a motor-compelled (CMP) group. The quantal content (m) of endplate potentials was measured intracellularly. In DPH the motor activity was unaffected. In the CMP group the m value of the EDL group increased with increases in the cooperativity of Ca2+ in transmitter release. Compared with the CMP group, the SOL of the RST group had a smaller m value with increases in the cooperativity of Ca2+ in transmitter release. These results suggest that motor activities can influence neuromuscular activity specific to different systems, however, the motor compulsion specifically activated the function of EDL and the motor restriction activated the function of SOL, and these effects might lead to altered activity of the release of transmitter quanta in motor nerve terminals of mice.

Structural requirement of leucine for activation of p70 S6 kinase

The addition of leucine induced activation of p70S6k in amino acid-depleted H4IIE cells. Whereas the activation of p70S6k by leucine was transient, the complete amino acid stimulated p70S6k more persistently. The effect of leucine on p70S6k was sensitive to rapamycin, but less sensitive to wortmannin. Using various amino acids and derivatives of leucine, we found that the chirality, the structure of the four branched hydrocarbons, and the primary amine are required for the ability of leucine to stimulate p70S6k, indicating that the structural requirement of leucine to induce p70S6k activation is very strict and precise. In addition, some leucine derivatives exhibited the ability to stimulate p70S6k and the other derivatives acted as inhibitors against the leucine-induced activation of p70S6k.

Alpha4 protein as a common regulator of type 2A-related serine/threonine protein phosphatases

The catalytic activity of the C subunit of serine/threonine phosphatase 2A is regulated by the association with A (PR65) and B subunits. It has been reported that the alpha4 protein, a yeast homolog of the Tap42 protein, binds the C subunit of serine/threonine phosphatase 2A and protein phosphatase 2A-related protein phosphatases such as protein phosphatase 4 and protein phosphatase 6. In the present study, we showed that alpha4 binds these three phosphatases and the association of alpha4 reduces the activities of these phosphatases in vitro. In contrast, PR65 binds to the C subunit of serine/threonine phosphatase 2A but not to protein phosphatase 4 and protein phosphatase 6. These results suggest that the alpha4 protein is a common regulator of the C subunit of serine/threonine phosphatase 2A and protein phosphatase 2A-related protein phosphatases.

Regulation of translational effectors by amino acid and mammalian target of rapamycin signaling pathways. Possible involvement of autophagy in cultured hepatoma cells

Amino acid deprivation of Chinese hamster ovary cells overexpressing human insulin receptors results in deactivation of p70 S6 kinase (p70) and dephosphorylation of eukaryotic initiation factor 4E-binding protein 1 (4E-BP1), which become unresponsive to insulin; readdition of amino acids restores these responses in a rapamycin-sensitive manner, suggesting that amino acids and mammalian target of rapamycin signal through common effectors. Contrarily, withdrawal of medium amino acids from the hepatoma cell line H4IIE does not abolish the ability of insulin to stimulate p70 and 4E-BP1. The addition of 3-methyladenine (3MA) to H4IIE cells deprived of amino acids inhibited the increment in protein degradation caused by amino acid withdrawal nearly completely at 10 mM and also strongly inhibited the ability of insulin to stimulate p70 and 4E-BP1 at 10 mM. Treatment of H4IIE cells with 3MA did not alter the ability of insulin to activate tyrosine phosphorylation, phosphoinositide 3-kinase, or mitogen-activated protein kinase. In conclusion, the ability of H4IIE cells to maintain the insulin responsiveness of the mammalian target of rapamycin-dependent signaling pathways impinging on p70 and 4E-BP1 without exogenous amino acids reflects the generation of amino acids endogenously through a 3MA-sensitive process, presumably autophagy, a major mechanism of facultative protein degradation in liver.

Frequent expression of the c-kit proto-oncogene in canine malignant mammary tumor

The mammary tumor is one of the popular neoplastic diseases in female dogs. In the present study, the expression of canine c-kit proto-oncogene in mammary tumor specimens was investigated to evaluate its potential usefulness as a tumor marker. By comparing the homology among the nucleotide sequences reported for human mouse, rat and feline c-kit c-DNA, a pair of primers was synthesized for the reverse transcriptase-polymerase chain reaction (RT-PCR) method. The RT-PCR product of canine spleen total RNA was shown to have 756 bp in size and to be highly homologous to the corresponding sequences reported for the mammalian species. The expression of c-kit transcript was detected in 11 mammary tumors of different histopathology including adenocarcinomas, benign and malignant mixed tumors. The level of the transcription in adenocarcinomas was significantly higher than those in malignant mixed tumors. Fifteen canine tumor specimens originated from various tissues were also tested for their c-kit transcript. In all of the mastocytoma samples examined, high expression of the mRNA was detected. Of other 12 tumors, only low level of RT-PCR products were detected in 5 samples, whereas no apparent amplification was observed in 7 tumors. These results indicate that the high expression of c-kit transcript is helpful for the diagnosis of canine mammary tumors.

Characterization of the phosphoproteins and protein kinase activity in mTOR immunoprecipitates

The mammalian target of rapamycin, mTOR, has been shown to be an upstream regulator of translational effectors. In the present study, in order to detect potential molecules involved in the mTOR signaling, an in vitro phosphorylation assay using mTOR immunoprecipitates from HEK293 cells was carried out. In addition to the autophosphorylation of mTOR, 32P incorporation into 80-kDa (pp80) and 175-kDa (pp175) bands was observed in mTOR immunoprecipitates. The protein kinase activity toward the recombinant eIF-4E binding protein 1 (4E-BP1) was also detected as previously described. When mTOR immunoprecipitates from HEK293 cells were prepared in the presence of a detergent, Nonidet P-40, the 4E-BP1 kinase activity and 32P incorporation into pp175 dramatically diminished, while the phosphorylation of mTOR and 32P incorporation into pp80 did not change. These results raised a possibility that mTOR may associate with protein cofactors, some of which may be involved in the regulation of kinase activities associated with mTOR.

Molecular cloning and characterization of a novel p70 S6 kinase, p70 S6 kinase beta containing a proline-rich region

A novel ribosomal S6 kinase, termed p70 S6 kinase beta (p70beta), which has a highly conserved amino acid sequence compared with that of p70/p85 S6 kinase (p70alpha) within the catalytic, kinase extension, and autoinhibitory pseudosubstrate domains, was identified. However, the amino acid sequence of p70beta differs from that of p70alpha in the noncatalytic amino-terminal region and in the carboxyl-terminal tail, which contains a proline-rich region. The majority of the regulatory phosphorylation sites identified in p70alpha are conserved in p70beta. Two isoforms of p70beta, referred to as beta1 (495 amino acids) and beta2 (482 amino acids), could be expressed from the single gene either by alternative mRNA splicing or by the use of alternative start codons. Here we report the characterization of p70beta2. Similarly to p70alpha, the catalytic activity of p70beta toward ribosomal protein S6 could be rapidly activated by serum, insulin, and phorbol ester in transiently transfected cells. The p70beta kinase was found to be significantly less sensitive to wortmannin and rapamycin than p70alpha. These results indicate that p70beta has the potential to participate in the regulation of protein synthesis and the cell cycle.

Skeletal muscle metabolism limits exercise capacity in patients with chronic heart failure

BACKGROUND

Several studies have indicated that skeletal muscle is important in determining the exercise capacity of patients with chronic heart failure (CHF). However, this theory has been investigated only in experiments based on local exercise involving a small muscle mass. We investigated skeletal muscle metabolism during maximal systemic exercise to determine whether muscle metabolism limits exercise capacity in patients with CHF. We also studied the relationship between muscle metabolic abnormalities during local and systemic exercise.

METHODS AND RESULTS

Skeletal muscle metabolism was measured during maximal systemic exercise on a bicycle ergometer by a combination of the metabolic freeze method and 31P magnetic resonance spectroscopy in 12 patients with CHF and 7 age- and size-matched normal subjects. We also evaluated skeletal muscle metabolism during local exercise while subjects performed unilateral plantar flexion. Muscle phosphocreatine (PCr) was nearly depleted during maximal systemic exercise in patients with CHF and normal subjects (12.5+/-0.04% and 12.3+/-0.07%, respectively, of initial level). PCr depletion occurred at a significantly lower peak oxygen uptake (peak VO2) in patients with CHF than in normal subjects (CHF, 20.2+/-3.0 versus normal, 31.8+/-3.7 mL . min-1 . kg-1, P<0. 0001). Muscle metabolic capacity, evaluated as the slope of PCr decrease in relation to increasing workload, was correlated with peak VO2 during maximal systemic exercise in patients with CHF (r=0.83, P<0.001). Muscle metabolic capacity during local exercise was impaired in patients with CHF and was correlated with capacity during systemic exercise (r=0.76, P<0.01) and with peak VO2 (r=0. 83, P<0.001).

CONCLUSIONS

These results suggest that impaired muscle metabolism associated with early metabolic limitation determines exercise capacity during maximal systemic exercise in patients with CHF. There was a significant correlation between muscle metabolic capacity during systemic and local exercise in patients with CHF.

Regulation of protein phosphatase 2A catalytic activity by alpha4 protein and its yeast homolog Tap42

Recent studies have revealed that the alpha4 protein, a mammalian homolog of yeast Tap42, is associated with the protein phosphatase 2A catalytic subunit (PP2A-C), however, effects of the association of alpha4 with PP2A-C on its phosphatase activity have not been examined, especially using physiologically relevant substrates in the signaling pathway of mTOR (the mammalian target of rapamycin) protein. Here, we report how this association affects the enzymatic activity of PP2A-C using the recombinant eIF-4E binding protein (4E-BP1) phosphorylated by immunoprecipitated mTOR as a substrate. PP2A-C dephosphorylated 4E-BP1 in vitro. The association of alpha4 and Tap42 with PP2A-C inhibited the phosphatase activity toward 4E-BP1. Rapamycin treatment, however, neither induced restoration of the phosphatase activity of PP2A-C nor caused dissociation of alpha4 and Tap42 from PP2A-C. Our study is the first report to reveal a potential regulatory role of alpha4 and Tap42 to inibit the phosphatase activity of PP2A-C toward the physiologically relevant substrate in the mTOR signaling.

[Effects of mesalazine on liver carcinogenesis in medium-term bioassay using rats]

A two stage carcinogenesis promotion test using phenobarbital (PB) as a positive control was performed on mesalazine in rats (F344,male). Pathological and immunohistological examinations were performed to examine the cell damage and proliferation in the liver and kidneys. As the initiation treatment, groups 1,2,3 and 5 were administered 300 mg/kg diethylnitrosamine (DEN)dissolved in 0.9% physiological saline, and group 4 was administered 5 ml/kg 0.9% physiological saline once intraperitoneally. Then group 1 was orally administered a water solution (5 ml/kg) containing 0.5% CMC-Na, and groups 2,3 and 4 similar water solution but containing 150, 300 and 300 mg/kg mesalazine, respectively. Group 5 was administered 0.05% PB mixed in feed from weeks 2 to 8. Partial (2/3) hepatectomy was performed in all 5 groups at week 3 after DEN administration. NO clear differences between the groups were observed in general conditions, body weight or amount of food consumption. The number or area-size of hepatic GST-P positive altered cell foci revealed no significant differences between groups 1,2 and 3, but a significant increase in number and area-size was observed in group 5. No GST-P positive cell foci were detected in group 4. The number of altered cell foci (H.E. staining) in the DENgroups administered mesalazine was the same as that in group 1. Thus, mesalazine did not promote hepatocarcinogenesis in the present experimental system. Statistically insignificant appearances of basophilic and acidophilic changes were observed in the renal tubular epithelium and mineral deposits in the renal papillary region and cortical margin region. The PCNA labeling rate was significantly lower in group 4, corresponding with the histological finding showing no proliferation of the renal tubular epithelium. Judging from the above test results, mesalazine was likely to show neither a promotion effect on the initiation induced by DEN nor cell proliferative activity on the kidneys by administration for this experimental period.

Amino acid sufficiency and mTOR regulate p70 S6 kinase and eIF-4E BP1 through a common effector mechanism

The present study identifies the operation of a signal tranduction pathway in mammalian cells that provides a checkpoint control, linking amino acid sufficiency to the control of peptide chain initiation. Withdrawal of amino acids from the nutrient medium of CHO-IR cells results in a rapid deactivation of p70 S6 kinase and dephosphorylation of eIF-4E BP1, which become unresponsive to all agonists. Readdition of the amino acid mixture quickly restores the phosphorylation and responsiveness of p70 and eIF-4E BP1 to insulin. Increasing the ambient amino acids to twice that usually employed increases basal p70 activity to the maximal level otherwise attained in the presence of insulin and abrogates further stimulation by insulin. Withdrawal of most individual amino acids also inhibits p70, although with differing potency. Amino acid withdrawal from CHO-IR cells does not significantly alter insulin stimulation of tyrosine phosphorylation, phosphotyrosine-associated phosphatidylinositol 3-kinase activity, c-Akt/protein kinase B activity, or mitogen-activated protein kinase activity. The selective inhibition of p70 and eIF-4E BP1 phosphorylation by amino acid withdrawal resembles the response to rapamycin, which prevents p70 reactivation by amino acids, indicating that mTOR is required for the response to amino acids. A p70 deletion mutant, p70Delta2-46/DeltaCT104, that is resistant to inhibition by rapamycin (but sensitive to wortmannin) is also resistant to inhibition by amino acid withdrawal, indicating that amino acid sufficiency and mTOR signal to p70 through a common effector, which could be mTOR itself, or an mTOR-controlled downstream element, such as a protein phosphatase.

[A case of systemic lupus erythematosus developed with intestinal perforation]

A case of intestinal perforation associated with SLE is presented. A 54-year-old woman was diagnosed as having SLE twenty-five years ago when she had facial erythema, photosensitivity, oral aphtha, polyarthraliga, leukopenia, positive LE cell and positive antinuclear antibody. She had been treated with prednisolone and admitted to Kushiro City General Hospital because of one month history of fever and anorexia in February 1996. Laboratory findings did not reveal activity of SLE, and a diagnosis of urinary tract infection was made based on the findings of urinalysis. After severe diarrhea, disseminated intravascular coagulation (DIC) developed. A rectal perforation was revealed by endoscopic and radiological examination. An emergency laparotomy revealed necrosis of the rectum and sigmoidostomy was performed. The biopsied specimen of the rectum were diagnosed as gangrene of ischemic colitis histologically. Because of a penetration to the urinary bladder, an ureterocutaneostomy was performed. She died of sepsis and DIC on the 127th day of admission. Only 11 cases of intestinal perforation associated with SLE have been reported in Japan, and the association of vasculitis has been considered. In the present case, the prolonged use of prednisolone might cause the necrotizing ischemic colitis.

[A recovered case of SLE with central nervous system involvement who relapsed presenting new symptoms associated with development of serum anti-Sm antibody]

A rare SLE patient with central nervous system involvement (CNS-SLE) who relapsed presenting new symptoms associated with the development of serum anti-Sm antibody and was then successfully treated with cyclophosphamide (CY) pulse therapy is presented here. A 47-years old housewife was admitted to Kushiro City General Hospital because of fever, limb erythema and drowsy consciousness in September 1995. On the basis of convulsion, proteinuria, leukopenia, thrombopenia, serum positive tests for both anti-nuclear antibody and anti-SSA antibody and low complement levels, as well as elevations of IgG index and IL-6 in the cerebrospinal fluid (CSF), she was diagnosed as having CNS-SLE. Serum tests for anti CL-beta 2 GPI antibody and lupus anticoaglant was negative. Serum test for HBs antigen was positive. She was treated successfully with methylprednisolone (mPSL) pulse therapy and plasma exchange (PE). Prednisolone was gradually tapered to the dosage of 17.5 mg per day and she was discharged in April 1996. She was re-admitted because of fever, an exacerbation of skin eruption and arthralgia in October 1996. Serum anti-Sm antibody was found to be positive. mPSL pulse therapy was not effective. On the basis of hallucination and elevations of IgG index and IL-6 in the CSF, a diagnosis of relapsed CNS-SLE was made. However the level of IFN-alpha in the CSF was normal. Although PE was not effective, CY pulse therapy was markedly effective.

Skeletal muscle metabolism in maximal bicycle and treadmill exercise distinguished by using in vivo metabolic freeze method and phosphorus-31 magnetic resonance spectroscopy in normal men

This study indicates that skeletal muscle metabolism may affect the results of maximal bicycle and treadmill exercise differently, and that maximal bicycle exercise was limited by quadriceps muscle metabolism rather than by cardiopulmonary capacity. In contrast, maximal treadmill exercise was not limited, eliciting more cardiopulmonary reserve and attaining greater peak oxygen uptake than maximal bicycle exercise.

Effects of bromocriptine and terguride on cell proliferation and apoptosis in the estrogen-stimulated anterior pituitary gland of the rat

The effects of bromocriptine and terguride on the estrogen-stimulated anterior pituitary gland of the female Wistar rat were investigated. Pituitary weight and serum prolactin (PRL) levels were reduced by treatment with bromocriptine or terguride. Immunohistological staining for proliferating cell nuclear antigen (PCNA) revealed that the PCNA labeling index of PRL-producing cells was significantly decreased by treatment with bromocriptine or terguride compared with untreated cells. The number of apoptotic cells analyzed by the terminal deoxynucleotidyl transferase-mediated deoxyuridinetriphosphate-biotin nick end labeling method was significantly increased in rats treated with bromocriptine or terguride. Suppression of cell proliferation and induction of apoptosis are important effects of bromocriptine and terguride in the treatment of prolactinomas and other hyperprolactinemias.

A novel transmembrane semaphorin can bind c-src

The semaphorins/collapsins constitute a family of genes unified by the presence of a "semaphorin domain" which has been conserved through metazoan evolution. The semaphorin family comprises both secreted and transmembrane molecules and is thought to be made up of ligands for as yet unidentified receptors. The functions are not known, with the exception of those of sema III (also referred as sem D and collapsin 1), D-sema I, and D-sema II, which have been shown to be involved in axonal pathfinding. Here report the identification of a mouse semaphorin cDNA, termed Sema VIb. Although Sema VIb contains the extracellular semaphorin domain, it lacks the immunoglobulin domain or thrombospondin repeats which are present in other described vertebrate (but not invertebrate) transmembrane semaphorins. During development Sema VIb mRNA is expressed in subregions of the nervous system and is particularly prominent in muscle. In adulthood, Sema VIb mRNA is expressed ubiquitously. The cytoplasmic domain of Sema VIb contains several proline-rich potential SH3 domain binding sites. Using an in vitro binding assay, we show that Sema VIb binds specifically the SH3 domain of the protooncogene c-src. In transfected COS cells Sema VIb coimmunoprecipitates with c-src. These results, along with our evidence that Sema VIb can form dimers, suggests that the semaphorin family not only serves as ligands but may include members, especially those which are transmembrane, which serve as receptors, triggering intracellular signaling via an src-related cascade.

Metabolic abnormality of calf skeletal muscle is improved by localised muscle training without changes in blood flow in chronic heart failure

OBJECTIVE

To investigate whether localised skeletal muscle training, which does not have a great influence on the heart, improves abnormalities of calf muscle metabolism in patients with chronic heart failure.

METHODS

Seven cardiac patients in New York Heart Association class II and III undertook a random order crossover trial. Training consisted of unilateral calf plantar flexion exercise. Before and after training, the patients' metabolic responses were examined during the calf exercise test with phosphorus-31 nuclear magnetic resonance spectroscopy (31P-MRS) and calf blood flow with plethysmography. The new Borg scale was employed as a subjective fatigue scale.

RESULTS

In a constant load exercise test (70% of maximum load achieved during the incremental exercise), standardised phosphocreatine and intracellular pH decreased less after training (p < 0.05, repeated measures analysis of variance). The new Borg scale improved significantly after training (p < 0.05). Blood flow did not change significantly in either test.

CONCLUSIONS

In patients with chronic heart failure, localised calf skeletal muscle training improved oxidative capacity without changes in calf blood flow. This training also improved the subjective fatigue scale. This training method may therefore alleviate leg fatigue experienced in daily activities.

Clinical features and growth fractions of pituitary adenomas

BACKGROUND

The Ki-67 monoclonal antibody is expressed by proliferating and dividing cells, but not by resting cells. The specificity of the monoclonal antibody, MIB-1, against the Ki-67 antigen has been established by immunostaining of formalin-fixed paraffin-embedded tissue in a microwave oven.

METHODS

The growth fraction of 85 pituitary adenomas was studied retrospectively by immunohistochemical analysis using the monoclonal antibody MIB-1. The adenomas were classified into three types: microadenoma, expansive type, and invasive type, based on findings on Gd DTPA enhanced magnetic resonance imaging.

RESULTS

The mean MIB-1 index in nonfunctioning microadenomas was higher than in expansive and invasive adenomas, but this difference was not significant. The MIB-1 index in younger patients (under 30 years) with nonfunctioning adenomas was significantly higher than in patients over 40 years of age. One of 14 patients with recurrent disease had an elevated MIB-1 index, but generally patients with an MIB-1 index over 2.0% did not suffer recurrence. The mean MIB-1 index was higher in expansive and invasive functioning adenomas than microadenomas, but not significantly. No correlation between the MIB-1 index and the serum GH or PRL concentration was established. No MIB-1 positive nuclei were observed in two GH-producing adenomas treated with the somatostatin analog SMS 201-995.

CONCLUSIONS

No significant relationship was identified between growth fraction and the invasiveness or recurrence of pituitary adenomas. The growth fraction of nonfunctioning pituitary adenomas was higher in patients under 30 years than over 40 years of age.

Regulation of eIF-4E BP1 phosphorylation by mTOR

The proteins eIF-4E BP1 and p70 S6 kinase each undergo an insulin/mitogen-stimulated phosphorylation in situ that is partially inhibited by rapamycin. Previous work has established that the protein known as mTOR/RAFT-1/FRAP is the target through which the rapamycin.FKBP12 complex acts to dephosphorylate/deactivate the p70 S6 kinase; thus, some mTOR mutants that have lost the ability to bind to the rapamycin.FKBP12 complex in vitro can protect the p70 S6 kinase against rapamycin-induced dephosphorylation/deactivation in situ. We show herein that such mTOR mutants also protect eIF-4E BP1 against rapamycin-induced dephosphorylation, and for both p70 S6 kinase and eIF-4E BP1, such protection requires that the rapamycin-resistant mTOR variant retains an active catalytic domain. In contrast, mutants of p70 S6 kinase rendered intrinsically resistant to inhibition by rapamycin in situ are not able to protect coexpressed eIF-4E BP1 from rapamycin-induced dephosphorylation. We conclude that mTOR is an upstream regulator of eIF-4E BP1 as well as the p70 S6 kinase; moreover, these two mTOR targets are regulated in a parallel rather than sequential manner.

Analysis of thermal injury-induced insulin resistance in rodents. Implication of postreceptor mechanisms

Burn injury is associated with insulin resistance. The molecular basis of this resistance was investigated by examining insulin receptor signaling in rats after thermal injury. The impaired insulin-stimulated transport of [3H]2-deoxyglucose into soleus muscle strips confirmed the insulin resistance following burns. In vivo insulin-stimulated phosphoinositide 3-kinase activity, pivotal in translocation of GLUT4, was decreased in burns when assessed by its insulin receptor substrate-1 (IRS-1)-associated activity. Insulin-induced tyrosine kinase activity of insulin receptor (IR) and tyrosine phosphorylation of IRS-1 were also attenuated. Immunoprecipitated IR, however, appeared to have normal insulin-responsive kinase activity. Finally, immunoprecipitated IRS-1 was tested for its effect on partially purified recombinant IR and was found to inhibit its kinase activity. This inhibitory effect of IRS-1 was abolished by prior treatment of IRS-1 with alkaline phosphatase, indicating that burn injury-related hyperphosphorylation of IRS-1 is similar to that observed in TNFalpha-induced inhibition of IR signaling. All of these changes were observed in the absence of quantitative changes in IR, IRS-1, and phosphoinositide 3-kinase. Alterations in postreceptor insulin signaling, therefore, may be responsible for the insulin resistance after thermal injury.

Prophylactic perioperative treatment in a patient with colon carcinoma complicated by polycythemia vera

A patient with colon carcinoma complicated by polycythemia vera (PV) who underwent a partial colectomy concomitant with prophylactic perioperative treatment resulting in successful outcome is herein described. Seven weeks after the cessation of the latest exacerbation of PV, a partial colectomy was performed. In order to prevent the development of disseminated intravascular coagulation and thrombotic complications, the following perioperative treatment was performed: administration of gabexate mesilate (2,000 mg/day), fresh frozen plasma (300 ml/day), heparin (5,000 IU/day) for 7 days and anti-thrombin-III for 4 days, and a potent antibiotic therapy for 12 days and graded elastic bandages around the bilateral lower extremities for 14 days. As a result, an uneventful postoperative course was achieved. The present case suggests that these treatments are useful in the perioperative management of PV patients.