Senescence-like changes induced by hydroxyurea in human diploid fibroblasts

Hydroxyurea was found to inhibit the growth of human diploid fibroblasts, which resulted in senescence-like changes both in morphology and replicative potential similar to the replicative senescence. SA-beta-gal activity, a typical characteristic of the replicative senescence was also induced through a long-term treatment of the presenescent cells with 400-800 microgM of hydroxyurea for about 3 weeks. In addition, we determined the levels of cyclin-dependent kinase inhibitors, p21(Waf1) and p16(INK4a), and the p53 tumor suppressor in order to monitor its effect on cell cycle and stress responses. We observed a great induction of both p53 and p21(Waf1), but not of p16(INK4a) in the premature senescent cells. UV-irradiation of the premature senescent cells showed a decreased level of DNA fragmentation presumably ascribed to the reduced activation of stress-activated protein kinases. These results suggest that a chronic hydroxyurea treatment induces the cellular senescence in association with the induction of p53 and p21(Waf1).

Up-regulation of caveolin attenuates epidermal growth factor signaling in senescent cells

Senescent human diploid fibroblasts do not respond to growth factors like epidermal growth factor (EGF), although they have a normal level of receptors and downstream signaling molecules. To examine the mechanism of signaling attenuation, we investigated Erk activation after EGF stimulation in senescent cells. Senescent cells did not phosphorylate Erk-1/2 after EGF stimulation, whereas young cells did. In those senescent cells, we found an increased level of caveolin proteins and strong interactions between caveolin-1 and EGF receptor. Electron microscopic analysis demonstrated an increased number of caveolae structures in senescent cells. More interestingly, brain, spleen, and lung from 26-month-old rats showed substantial increases of caveolin proteins. However, in the case of p53-induced senescence, caveolin-1 was not induced, and EGF stimulation phosphorylated Erk-1/2 as much as young control cells. Finally, we overexpressed caveolin-1 in young human diploid fibroblasts in which the activation of Erk-1/2 upon EGF stimulation was significantly suppressed. These results suggest that the unresponsiveness of senescent fibroblasts to EGF stimulation may be due to the overexpression of caveolins, which seems to be independent of growth arrest and other aging phenotypes.

The cytoplasmic Purkinje onconeural antigen cdr2 down-regulates c-Myc function: implications for neuronal and tumor cell survival

Paraneoplastic cerebellar degeneration (PCD) is a disorder in which breast or ovarian tumors express an onconeural antigen termed cdr2, which normally is expressed in cerebellar Purkinje neurons. This leads to an immune response to cdr2 that is associated with tumor immunity and autoimmune cerebellar degeneration. We have found that cdr2, a cytoplasmic protein harboring a helix-leucine zipper (HLZ) motif, interacts specifically with the HLZ motif of c-Myc. Both proteins colocalize in the cytoplasm of adult cerebellar Purkinje neurons, and coimmunoprecipitate from tumor cell lines and cerebellar extracts. cdr2 down-regulates c-Myc-dependent transcription in cotransfection assays, and redistributes Myc protein in the cytoplasm. Disease antisera from six of six PCD patients specifically blocked the interaction between cdr2 and c-Myc in vitro. These data indicate that cdr2 normally sequesters c-Myc in the neuronal cytoplasm, thereby down-regulating c-Myc activity, and suggest a mechanism whereby inhibition of cdr2 function by autoantibodies in PCD may contribute to Purkinje neuronal death.

Formaldehyde treatment suppresses ruminal degradation of phytate in soyabean meal and rapeseed meal

Most of the P in oilseed meal is in the form of phytate P, and phytate forms complexes with protein. Phytate P has been considered to be absorbed easily in ruminants because of phytate degradation in the rumen. Treatment of oilseed meals with formaldehyde improves the nutritional value of protein through suppressing its ruminal degradation. The present experiment was conducted to study the effects of formaldehyde treatment on phytate degradation in the rumen. The ruminal degradation of phytate in formaldehyde-treated soyabean meal or rapeseed meal was determined by a nylon-bag technique in sheep. Soyabean meal and rapeseed meal were treated with formaldehyde at levels of 3, 5 or 10 g/kg. Treatment with formaldehyde suppressed phytate and protein degradation in both the oilseed meals. Compared with the regular soyabean meal, the regular rapeseed meal showed lower degradability of phytate in the rumen. These results suggest that treatment with formaldehyde suppresses ruminal degradation of phytate in oilseed meal. Thus, the absorption of P from oilseed meal is probably decreased by this treatment in ruminants.

Suppression of ceramide-mediated apoptosis by HSP70

Ceramide has been known as an important second messenger in programmed cell death (apoptosis) which is induced by various stimuli such as the tumor necrosis factor-alpha (TNF-alpha), Fas ligand, and environmental stresses such as UV-irradiation and heat shock. Although the precise molecular mechanism of apoptosis is not fully understood, ceramide generated by sphingomyelinase (SMase) mediates the activation of several downstream molecules that are implicated in the regulation of apoptosis. Here, we show that stress-inducible heat shock protein 70 (Hsp70) prevents apoptosis induced by increased level of intracellular ceramide. In T-cell hybridoma DO11.10, we examined the effect of Hsp70 on apoptosis mediated by TNF-alpha, Fas ligation, SMase, and C2-ceramide, all of which elevate intracellular ceramide levels. Hsp70 not only markedly reduced internucleosomal DNA fragmentation, but also enhanced cell viability measured by the Trypan blue dye exclusion test. Similarly, the ceramide-induced c-jun amino-terminal kinase (JNK/SAPK) activation is impaired in cells overexpressing Hsp70. These data strongly suggest that hsp70 functions as a regulator of apoptosis downstream of ceramide.

Expression of heat shock protein 70 blocks thymic differentiation of T cells in transgenic mice

Heat shock protein 70 (HSP70) is involved not only in protein folding, but also in processes of differentiation and cell-cycle progression. Recently, HSP70 has been implicated in mediation of functions of some immunosuppressive agents. To study the role of HSP70 in differentiation of haematopoietic cells, we generated transgenic mice using the human inducible hsp70 gene fused to the mouse H-2K promoter. These mice develop a T-cell deficiency that is characterized by thymic hypoplasia and a significant reduction in peripheral T cells. The total number of thymocytes is about 100-fold less than that in normal mice. The majority of the thymocytes are immature T cells that express neither CD4 nor CD8 molecules, indicating that T cells are affected at an early stage of thymic differentiation. Expression of the transgenic HSP70 was detected both in bone marrow cells and in thymocytes. Furthermore, injection of normal bone marrow cells into the T-cell deficient mice led to the generation of mature T cells indicating that the T-cell deficiency was caused by the action of HSP70 in T cells. The blockage of differentiation occurred only in T cells, both alphabeta- and gammadelta-T-cell receptor (TCR)-bearing cells, but not in B cells, granulocytes, and monocytes. The observations suggest that HSP70 may inhibit a cellular process that is essential for the differentiation of early stage T cells. Further experiments using this model system will widen our understanding of HSP70 and its function on a molecular level.

FGF-10 is a chemotactic factor for distal epithelial buds during lung development

Fibroblast growth factor (FGF) signaling is required for normal epithelial branching in the respiratory system of several species. Recent studies have shown that FGF-10 may be a key regulator of lung branching morphogenesis, based on its pattern of expression in the early lung and its ability to induce epithelial budding in vitro. In this study we investigate whether FGF-10 is able to direct lung epithelial buds to proper positions during development . We maintained localized high levels of FGF-10 in cultured lungs using FGF-10-soaked heparin beads. FGF-10 exerts a powerful chemoattractant effect on the distal but not on proximal lung epithelium. Epithelial buds grow toward an FGF-10 source within 24 h, and subsequently form concentric layers of epithelium around the bead. BrdU incorporation analysis suggests that FGF-10, in contrast to FGF-7, is a modest proliferation factor for the lung epithelium. In the absence of mesenchyme FGF-10 requires an associated proliferative signal to induce bud migration. This can be provided by extract from lung mesenchyme, or by FGF-7, a growth factor also present in the early embryonic lung. FGF-10 does not seem to interfere with early epithelial cell differentiation. The chemoattractant effect of FGF-10 in the lung epithelium is reminiscent of the patterning effect of the Drosophila FGF ortholog branchless in the developing tracheal epithelium, suggesting that the function of these genes has been conserved during evolution.

The role of inducible 70-kDa heat shock protein in cell cycle control, differentiation, and apoptotic cell death of the human myeloid leukemic HL-60 cells

Several studies have suggested a role for heat shock proteins (hsps) during development and differentiation. However, relatively little is known about the role of hsp70 in controlling human hematopoietic cell differentiation and death. Here, we show that constitutive expression of human inducible 70-kDa heat shock protein (hsp70) promotes differentiation of HL-60 cells and prevents apoptosis that occurred after terminal differentiation or directly by apoptotic agents. After treatment with phorbol 12-myristate 13-acetate (PMA), hsp70-overexpressing cells (HL-60/hsp70) underwent rapid growth arrest and plastic adherence and expressed more CD14 than parental HL-60 or empty vector-transformed cells (HL-60/puro). HL-60/hsp70 cells also rapidly differentiated into granulocytes by addition of all-trans-retinoic acid, as assessed by phenotypic changes after staining with Wright-Giemsa. After differentiation into monocyte/macrophage-like cells or granulocytes, hsp70-overexpressing cells showed little evidence for apoptosis and had a prolonged survival, indicating that the survival-enhancing properties of hsp70 counteract programmed cell death that accompanies terminal differentiation. HL-60/hsp70 cells also showed more resistance than parental cells against apoptotic agents such as sodium nitroprusside, a NO-generating agent, or Taxol, a microtubule stabilizing agent. Further, heat shock of parental HL-60 cells at 42 degrees C for 3 h increased hsp70 levels, promoted plastic adherence (< 6 h) of the cells in respond to PMA, and protected cells from SNP or Taxol. Taken together, these studies demonstrate that hsp70 plays a crucial role in the differentiation of myeloid cells, participating in cell cycle controls and phenotypic changes, with protecting effects on apoptosis induced by different pathways.

c-Fes tyrosine kinase binds to and activates STAT3 after granulocyte-macrophage colony-stimulating factor stimulation

Granulocyte-macrophage colony stimulating factor (GM-CSF) induces proliferation and maturation of myeloid progenitor cells and also activates neutrophils. In order to investigate the pleiotropic effects of GM-CSF stimulation, we examined the signaling pathways of protein tyrosine kinases (PTKs) and signal transducers and activators of transcription (STATs) in GM-CSF-dependent proliferation of leukemia cells. Using TF-1, a GM-CSF-dependent human erythroleukemia cell line, we found that GM-CSF enhanced DNA-binding and tyrosine phosphorylation of STAT3. GM-CSF receptor (GM-CSFR) and c-Fes tyrosine kinase were also activated upon GM-CSF stimulation. Furthermore, c-Fes formed a complex with STAT3. Experiments using a c-Fes mutant that lacked tyrosine kinase activity revealed that the activation of STAT3 is kinase-dependent, but that the c-Fes-STAT3 interaction is not affected by c-Fes tyrosine kinase activity. The results suggest that STAT3 is activated by c-Fes tyrosine kinase through direct interaction during hematopoietic cell proliferation induced by GM-CSF.

Thymic epithelial tumor progression in an SV40T transgenic mouse model. Cortical thymoma-thymic carcinoma sequence

There have been several reports that thymoma in human is a progressive disease, and that thymoma and thymic carcinoma form a continuum. We established a stable line of SV40T transgenic mice, which consistently produced thymic epithelial tumours progressing to thymic carcinoma within a predictable time span. Using this animal model and a morphological approach, thymic epithelial tumour progression was studied with reference to sequential changes at different time points in animals aged from 3 to 32 weeks. At all ages, SV40T was expressed in the nuclei of thymic epithelial cells; in these transgenic mice we observed the entire spectrum from cortical type thymoma to thymic carcinoma. Thymic size tended to increase with ageing in SV40T TG mice. While younger mice had predominantly cortical (organoid) or cortical thymoma, older mice had well-differentiated thymic carcinoma (WDTC) or poorly differentiated thymic carcinoma. When SV40T TG mice (248 line) reached a certain age, carcinoma of the thymus was present in all of them. Cortical-type thymoma became malignant within a predictable time span, suggesting a cortical thymoma-carcinoma sequence. When the mice were 9 weeks of age, the thymuses formed gross masses compatible with cortical thymoma. At 14 weeks of age, WDTC appeared against the background of cortical thymoma. Poorly differentiated thymic carcinoma was found after 15 weeks and affected all animals over 23 weeks of age. Most thymic carcinomas coexisted in varying proportions with cortical-type thymoma. Medullary thymomas did not develop in the mice, and no transition from medullary-type thymomas to thymic carcinomas was observed. In this SV40T transgenic mouse model, thymic carcinoma is clearly preceded by cortical-type thymoma. These transgenic mice may provide an interesting model for the progression from cortical thymoma to WDTC and/or high-grade carcinoma.

Development of thymic carcinoma in transgenic mice expressing SV40 T antigen

We produced transgenic mice using SV40 Tag gene under the control of its own enhancer and promoter. Three transgenic lines (SNU-SVT125, 127, 248) consistently developed thymic carcinoma as well as choroid plexus carcinoma and dysplastic renal tubule. In SNU-SVT248 line, SV40 Tag transgene was expressed at thymus, spleen and kidney. Thymic epithelium showed high level expression of SV40 Tag in immunohistochemistry. Histopathological and electron microscopic analysis revealed that poorly differentiated carcinoma was derived from type 2 to 4 thymic epithelial cell. Our transgenic mice would provide a model for studies on the pathogenesis of thymic carcinoma and on the regulation of thymopoiesis by epithelial cells.

Leucine zipper-like domain regulates the autophosphorylation and the transforming activity of P130gag-fps

P130gag-fps, the product of Fujinami sarcoma virus, has a leucine zipper (LZ) motif located in 729-756 amino acid residues. To explore the role of LZ-like domain in the transformation by P130gag-fps, we made a deletion (delta FpsLZ/SH2) and a site-directed substitution mutation (L746P). Deletion mutant did not transform the 3Y1 cells and the resulting protein did not show kinase activity. Substitution of Leu746 with Pro (L746P) reduced the transforming activity by 6-fold. Although the L746P mutant retained intact catalytic activity in vitro, it did not phosphorylate cellular proteins in vivo. We concluded that LZ-like domain might mediate the trans-activation of P130gag-fps tyrosine kinase by autophosphorylation, which is prerequisite for the transforming activity.

Patient-controlled sedation during epidural anesthesia

The purpose of this study was to evaluate the feasibility and advantages or disadvantages, if any, of patient-controlled sedation compared with sedation administered by the anesthesiologist during surgical epidural anesthesia. Forty patients were divided at random into two groups with 20 patients in each group. Patients in group 1 received 0.5-1.0 mg intravenous midazolam and 25-50 micrograms intravenous fentanyl in increments administered by the anesthesiologist to achieve intraoperative sedation; patients in group 2 self-administered a mixture of midazolam (0.5 mg) and fentanyl (25 micrograms) in increments using an Abbott Lifecare PCA infuser to achieve sedation. Demographics of the patients, the types of surgery performed, doses of midazolam and fentanyl administered in a given period of time, and the level of sedation maintained during epidural anesthesia and surgery were similar in both groups. Patients in the self-administered group, however, rated their level of comfort during anesthesia and surgery higher than did those in the anesthesiologist-controlled sedation group. This could have been due to a positive psychological effect produced by allowing patient to feel that they have some control over their situation. The findings of this study indicate that patient-controlled sedation using a combination of midazolam and fentanyl is a safe and effective technique that provides intraoperative sedation ranked better by patients than that provided by anesthesiologists using the same drugs. More studies are, however, needed to determine the best choice of drug(s), the doses, the lock-out intervals, and the possible use of continuous infusion with patient-controlled sedation.

Epidural anesthesia in patients undergoing thoracic surgery

Epidural anesthesia has been reported to exert beneficial effects in surgical procedures. Over the past 3 years at the Veterans Administration Medical Center in Washington, DC, thoracic surgical procedures have been done using a combined technique of epidural anesthesia with light general anesthesia. A retrospective review of this experience from January 1984 to November 1987 was done in 90 consecutive patients. Postoperative extubation of patients was accomplished immediately in 32%, within 1 hour in 34%, within 3 hours in 28%, within 18 hours in 4%, and was prolonged in only 1% of patients. Mortality was 2% and morbidity was 3%. This analysis indicates that the technique of epidural anesthesia with light general anesthesia provided satisfactory anesthesia with low mortality and morbidity in a high-risk group of patients undergoing surgery.

Incidence and cardiac effects of systemic venous air embolism. Echocardiographic evidence of arterial embolization via noncardiac shunt

Central nervous system dysfunction in venous air embolism may result from air entering the arterial circulation. Using two-dimensional and pulsed-wave Doppler echocardiography, this study not only documented the frequent presence of air in the right heart chambers of patients undergoing upright neurosurgery or pacemaker insertion, but also documented the presence of air in the left atrium and left ventricle of one patient via noncardiac shunt. Studies in dogs confirmed paradoxical air embolism in the absence of anatomic communications between right and left heart chambers. Systemic venous air also produced a dose-dependent increase in pulmonary artery pressure and diastolic flattening of the ventricular septum with increase in left ventricular filling pressure despite preserved systolic function.

Age and the spread of local anesthetic solutions in the epidural space

Sensory level of anesthesia following the injection of 20 ml of 1.5% lidocaine with epinephrine (1:200,000) in 238 adult males averaged T7.7, T5.6, and T5.1 at 10, 20, and 30 minutes, respectively. Patient age had no significant effect on local anesthetic requirements per spinal segment per unit height until age 40 years, which age the calculated amount of local anesthetic decreased significantly to 0.62 ml from 0.69 ml/segment/meter of height. Above age 40 there was no further decrease in epidural anesthetic requirement with advancing age. Patient height was inversely related to sensory level (p < 0.001). Time required for anesthesia ro recede to T12 averaged 164 minutes and was slightly but significantly (p < 0.05) prolonged with advancing age.

Effects of patient age, pH of cerebrospinal fluid, and vasopressors on onset and duration of spinal anesthesia

Two hundred twenty-two spinal anesthesias were administered with 10 mg. of tetracaine and 1 ml. of 10 percent dextrose to investigate the effects of vasopressors, patients age, and pH of cerebrospinal fluid on the onset and duration of spinal anesthesia. Neither the differences in overall age, cerebrospinal fluid pH, nor the addition of vasopressors had any significant effect on onset. Duration, however, was significantly prolonged by the addition of vasopressors, 53 percent prolongation by 0.2 mg. of epinephrine and 72 percent prolongation by 2 mg. of phenylephrine.