Longevity, stress response, and cancer in aging telomerase-deficient mice

Telomere maintenance is thought to play a role in signaling cellular senescence; however, a link with organismal aging processes has not been established. The telomerase null mouse provides an opportunity to understand the effects associated with critical telomere shortening at the organismal level. We studied a variety of physiological processes in an aging cohort of mTR-/- mice. Loss of telomere function did not elicit a full spectrum of classical pathophysiological symptoms of aging. However, age-dependent telomere shortening and accompanying genetic instability were associated with shortened life span as well as a reduced capacity to respond to stresses such as wound healing and hematopoietic ablation. In addition, we found an increased incidence of spontaneous malignancies. These findings demonstrate a critical role for telomere length in the overall fitness, reserve, and well being of the aging organism.

Telomere dysfunction promotes non-reciprocal translocations and epithelial cancers in mice

Aged humans sustain a high rate of epithelial cancers such as carcinomas of the breast and colon, whereas mice carrying common tumour suppressor gene mutations typically develop soft tissue sarcomas and lymphomas. Among the many factors that may contribute to this species variance are differences in telomere length and regulation. Telomeres comprise the nucleoprotein complexes that cap the ends of eukaryotic chromosomes and are maintained by the reverse transcriptase, telomerase. In human cells, insufficient levels of telomerase lead to telomere attrition with cell division in culture and possibly with ageing and tumorigenesis in vivo. In contrast, critical reduction in telomere length is not observed in the mouse owing to promiscuous telomerase expression and long telomeres. Here we provide evidence that telomere attrition in ageing telomerase-deficient p53 mutant mice promotes the development of epithelial cancers by a process of fusion-bridge breakage that leads to the formation of complex non-reciprocal translocations--a classical cytogenetic feature of human carcinomas. Our data suggest a model in which telomere dysfunction brought about by continual epithelial renewal during life generates the massive ploidy changes associated with the development of epithelial cancers.

High frequency transformation of Bacillus subtilis protoplasts by plasmid DNA

A highly efficient method for transformation of Bacillus subtilis by plasmid DNA is reported. The procedure, which involves polyethylene glycol-induced DNA uptake by protoplasts and subsequent regeneration of the bacterial cell wall, yields up to 80% transformants with an efficiency of 4 x 10(7) transformants per microgram of supercoiled DNA. Plasmids constructed by in vitro ligation or endonuclease-generated fragments of linear plasmid DNA can also transform PEG-treated protoplasts, but at a lower frequency.

Analysis of yeast protein kinases using protein chips

We have developed a novel protein chip technology that allows the high-throughput analysis of biochemical activities, and used this approach to analyse nearly all of the protein kinases from Saccharomyces cerevisiae. Protein chips are disposable arrays of microwells in silicone elastomer sheets placed on top of microscope slides. The high density and small size of the wells allows for high-throughput batch processing and simultaneous analysis of many individual samples. Only small amounts of protein are required. Of 122 known and predicted yeast protein kinases, 119 were overexpressed and analysed using 17 different substrates and protein chips. We found many novel activities and that a large number of protein kinases are capable of phosphorylating tyrosine. The tyrosine phosphorylating enzymes often share common amino acid residues that lie near the catalytic region. Thus, our study identified a number of novel features of protein kinases and demonstrates that protein chip technology is useful for high-throughput screening of protein biochemical activity.

Processing of the initiation methionine from proteins: properties of the Escherichia coli methionine aminopeptidase and its gene structure

Methionine aminopeptidase (MAP) catalyzes the removal of amino-terminal methionine from proteins. The Escherichia coli map gene encoding this enzyme was cloned; it consists of 264 codons and encodes a monomeric enzyme of 29,333 daltons. In vitro analyses with purified enzyme indicated that MAP is a metallo-oligopeptidase with absolute specificity for the amino-terminal methionine. The methionine residues from the amino-terminal end of the recombinant proteins interleukin-2 (Met-Ala-Pro-IL-2) and ricin A (Met-Ile-Phe-ricin A) could be removed either in vitro with purified MAP enzyme or in vivo in MAP-hyperproducing strains of E. coli. In vitro analyses of the substrate preference of the E. coli MAP indicated that the residues adjacent to the initiation methionine could significantly influence the methionine cleavage process. This conclusion is consistent, in general, with the deduced specificity of the enzyme based on the analysis of known amino-terminal sequences of intracellular proteins (S. Tsunasawa, J. W. Stewart, and F. Sherman, J. Biol. Chem. 260:5382-5391, 1985).

Involvement of integrins alpha v beta 3 and alpha v beta 5 in ocular neovascular diseases

Angiogenesis underlies the majority of eye diseases that result in catastrophic loss of vision. Recent evidence has implicated the integrins alpha v beta 3 and alpha v beta 5 in the angiogenic process. We examined the expression of alpha v beta 3 and alpha v beta 5 in neovascular ocular tissue from patients with subretinal neovascularization from age-related macular degeneration or the presumed ocular histoplasmosis syndrome or retinal neovascularization from proliferative diabetic retinopathy (PDR). Only alpha v beta 3 was observed on blood vessels in ocular tissues with active neovascularization from patients with age-related macular degeneration or presumed ocular histoplasmosis, whereas both alpha v beta 3 and alpha v beta 5 were present on vascular cells in tissues from patients with PDR. Since we observed both integrins on vascular cells from tissues of patients with retinal neovascularization from PDR, we examined the effects of a systemically administered cyclic peptide antagonist of alpha v beta 3 and alpha v beta 5 on retinal angiogenesis in a murine model. This antagonist specifically blocked new blood vessel formation with no effect on established vessels. These results not only reinforce the concept that retinal and subretinal neovascular diseases are distinct pathological processes, but that antagonists of alpha v beta 3 and/or alpha v beta 5 may be effective in treating individuals with blinding eye disease associated with angiogenesis.

Radiosurgery for brain metastases: is whole brain radiotherapy necessary?

PURPOSE

Because whole brain radiotherapy (WBRT) may cause dementia in long-term survivors, selected patients with brain metastases may benefit from initial treatment with radiosurgery (RS) alone reserving WBRT for salvage as needed. We reviewed results of RS +/- WBRT in patients with newly diagnosed brain metastasis to provide background for a prospective trial.

METHODS AND MATERIALS

Patients with single or multiple brain metastases managed initially with RS alone vs. RS + WBRT (62 vs. 43 patients) from 1991 through February 1997 were retrospectively reviewed. The use of upfront WBRT depended on physician preference and referral patterns. Survival, freedom from progression (FFP) endpoints, and brain control allowing for successful salvage therapy were measured from the date of diagnosis of brain metastases. Actuarial curves were estimated using the Kaplan-Meier method. Analyses to adjust for known prognostic factors were performed using the Cox proportional hazards model (CPHM) stratified by primary site.

RESULTS

Survival and local FFP were the same for RS alone vs. RS + WBRT (median survival 11.3 vs. 11.1 months and 1-year local FFP by patient 71% vs. 79%, respectively). Brain FFP (scoring new metastases and/or local failure) was significantly worse for RS alone vs. RS + WBRT (28% vs. 69% at 1 year; CPHM adjustedp = 0.03 and hazard ratio = 0.476). However, brain control allowing for successful salvage of a first failure was not significantly different for RS alone vs. RS + WBRT (62% vs. 73% at 1 year; CPHM adjusted p = 0.56).

CONCLUSIONS

The omission of WBRT in the initial management of patients treated with RS for up to 4 brain metastases does not appear to compromise survival or intracranial control allowing for salvage therapy as indicated. A randomized trial of RS vs. RS + WBRT is needed to assess survival, quality of life, and cost in good-prognosis patients with newly diagnosed brain metastases.

Inhibition of experimental liver cirrhosis in mice by telomerase gene delivery

Accelerated telomere loss has been proposed to be a factor leading to end-stage organ failure in chronic diseases of high cellular turnover such as liver cirrhosis. To test this hypothesis directly, telomerase-deficient mice, null for the essential telomerase RNA (mTR) gene, were subjected to genetic, surgical, and chemical ablation of the liver. Telomere dysfunction was associated with defects in liver regeneration and accelerated the development of liver cirrhosis in response to chronic liver injury. Adenoviral delivery of mTR into the livers of mTR(-/-) mice with short dysfunctional telomeres restored telomerase activity and telomere function, alleviated cirrhotic pathology, and improved liver function. These studies indicate that telomere dysfunction contributes to chronic diseases of continual cellular loss-replacement and encourage the evaluation of "telomerase therapy" for such diseases.

The nonhomologous end-joining pathway of DNA repair is required for genomic stability and the suppression of translocations

We have used spectral karyotyping to assess potential roles of three different components of the nonhomologous DNA end-joining pathway in the maintenance of genomic stability in mouse embryonic fibroblasts (MEFs). MEFs homozygous for mutations that inactivate either DNA ligase IV (Lig4) or Ku70 display dramatic genomic instability, even in the absence of exogenous DNA damaging agents. These aberrant events range from chromosomal fragmentation to nonreciprocal translocations that can involve several chromosomes. DNA-dependent protein kinase catalytic subunit deficiency also promotes genome instability. Deficiency for the p53 cell cycle checkpoint protein has little effect on spontaneous levels of chromosomal instability in Lig4-deficient fibroblasts. However, in the context of ionizing radiation treatment, p53 deficiency allowed visualization of massive acute chromosomal destruction in Lig4-deficient MEFs, which in surviving cells manifested as frequent nonreciprocal translocations. We conclude that nonhomologous DNA end-joining plays a crucial role as a caretaker of the mammalian genome, and that an alternative repair pathway exists that often leads to nonreciprocal translocations.

Hepatitis B virus X protein and p53 tumor suppressor interactions in the modulation of apoptosis

We have reported previously that the hepatitis B virus oncoprotein, HBx, can bind to the C terminus of p53 and inhibit several critical p53-mediated cellular processes, including DNA sequence-specific binding, transcriptional transactivation, and apoptosis. Recognizing the importance of p53-mediated apoptosis for maintaining homeostasis and preventing neoplastic transformation, here we further examine the physical interaction between HBx and p53 as well as the functional consequences of this association. In vitro binding studies indicate that the ayw and adr viral subtypes of HBx bind similar amounts of glutathione S-transferase-p53 with the distal C terminus of HBx (from residues 111 to 154) being critical for this interaction. Using a microinjection technique, we show that this same C-terminal region of HBx is necessary for sequestering p53 in the cytoplasm and abrogating p53-mediated apoptosis. The transcriptional transactivation domain of HBx also maps to its C terminus; however, a comparison of the ability of full-length and truncated HBx protein to abrogate p53-induced apoptosis versus transactivate simian virus 40- or human nitric oxide synthase-2 promoter-driven reporter constructs indicates that these two functional properties are distinct and thus may contribute to hepatocarcinogenesis differently. Collectively, our data indicate that the distal C-terminal domain of HBx, independent of its transactivation activity, complexes with p53 in the cytoplasm, partially preventing its nuclear entry and ability to induce apoptosis. These pathobiological effects of HBx may contribute to the early stages of hepatocellular carcinogenesis.

Extension of neurites on axons is impaired by antibodies against specific neural cell surface glycoproteins

We have developed an in vitro assay which measures the ability of growth cones to extend on an axonal substrate. Neurite lengths were compared in the presence or absence of monovalent antibodies against specific neural cell surface glycoproteins. Fab fragments of antibodies against the neural cell adhesion molecule, NCAM, have an insignificant effect on the lengths of neurites elongating on either an axonal substrate or a laminin substrate. Fab fragments of polyclonal antibodies against two new neural cell surface antigens, defined by mAb G4 and mAb F11, decrease the lengths of neurites elongating on an axonal substrate, but have no effect on the lengths of neurites elongating on a laminin substrate. G4 antigen is related to mouse L1, while F11 antigen appears to be distinct from all known neural cell surface glycoproteins. Our results suggest that the G4 and F11 antigens help to promote the extension of growth cones on axons.

A new criterion for automatic multilevel thresholding

A new criterion for multilevel thresholding is proposed. The criterion is based on the consideration of two factors. The first one is the discrepancy between the thresholded and original images and the second one is the number of bits required to represent the thresholded image. Based on a new maximum correlation criterion for bilevel thresholding, the discrepancy is defined and then a cost function that takes both factors into account is proposed for multilevel thresholding. By minimizing the cost function, the classification number that the gray-levels should be classified and the threshold values can be determined automatically. In addition, the cost function is proven to possess a unique minimum under very mild conditions. Computational analyses indicate that the number of required mathematical operations in the implementation of our algorithm is much less than that of maximum entropy criterion. Finally, simulation results are included to demonstrate their effectiveness.

Telomere dysfunction impairs DNA repair and enhances sensitivity to ionizing radiation

Telomeres are specialized nucleoprotein complexes that serve as protective caps of linear eukaryotic chromosomes. Loss of telomere function is associated with rampant genetic instability and loss of cellular viability and renewal potential. The telomere also participates in processes of chromosomal repair, as evidenced by the 'capture' or de novo synthesis of telomere repeats at double-stranded breaks and by the capacity of yeast telomeres to serve as repositories of essential components of the DNA repair machinery, particularly those involved in non-homologous end-joining (NHEJ). Here we used the telomerase-deficient mouse, null for the essential telomerase RNA gene (Terc), to assess the role of telomerase and telomere function on the cellular and organismal response to ionizing radiation. Although the loss of telomerase activity per se had no discernable impact on the response to ionizing radiation, the emergence of telomere dysfunction in late-generation Terc-/- mice imparted a radiosensitivity syndrome associated with accelerated mortality. On the cellular level, the gastrointestinal crypt stem cells and primary thymocytes showed increased rates of apoptosis, and mouse embryonic fibroblasts (MEFs) showed diminished dose-dependent clonogenic survival. The radiosensitivity of telomere dysfunctional cells correlated with delayed DNA break repair kinetics, persistent chromosomal breaks and cytogenetic profiles characterized by complex chromosomal aberrations and massive fragmentation. Our findings establish a intimate relationship between functionally intact telomeres and the genomic, cellular and organismal response to ionizing radiation.

Survival benefit of hyperthermia in a prospective randomized trial of brachytherapy boost +/- hyperthermia for glioblastoma multiforme

PURPOSE

To determine if adjuvant interstitial hyperthermia (HT) significantly improves survival of patients with glioblastoma undergoing brachytherapy boost after conventional radiotherapy.

METHODS AND MATERIALS

Adults with newly-diagnosed, focal, supratentorial glioblastoma < or = 5 cm in diameter were registered postoperatively on a Phase II/III randomized trial and treated with partial brain radiotherapy to 59.4 Gy with oral hydroxyurea. Those patients whose tumor was still implantable after teletherapy were randomized to brachytherapy boost (60 Gy at 0.40-0.60 Gy/h) +/- HT for 30 min immediately before and after brachytherapy. Time to progression (TTP) and survival from date of diagnosis were estimated using the Kaplan-Meier method.

RESULTS

From 1990 to 1995, 112 eligible patients were entered in the trial. Patient ages ranged from 21-78 years (median, 54 years) and KPS ranged from 70-100 (median, 90). Most commonly due to tumor progression or patient refusal, 33 patients were never randomized. Of the patients, 39 were randomized to brachytherapy ("no heat") and 40 to brachytherapy + HT ("heat"). By intent to treat, TTP and survival were significantly longer for "heat" than "no heat" (p = 0.04 and p = 0.04). For the 33 "no heat" patients and 35 "heat" patients who underwent brachytherapy boost, TTP and survival were significantly longer for "heat" than "no heat" (p = 0.045 and p = 0.02, respectively; median survival 85 weeks vs. 76 weeks; 2-year survival 31% vs. 15%). A multivariate analysis for these 68 patients adjusting for age and KPS showed that improved survival was significantly associated with randomization to "heat" (p = 0.008; hazard ratio 0.51). There were no Grade 5 toxicities, 2 Grade 4 toxicities (1 on each arm), and 7 Grade 3 toxicities (1 on "no heat" and 6 on the "heat" arm).

CONCLUSION

Adjuvant interstitial brain HT, given before and after brachytherapy boost, after conventional radiotherapy significantly improves survival of patients with focal glioblastoma, with acceptable toxicity.

Peptide formation in the prebiotic era: thermal condensation of glycine in fluctuating clay environments

As geologically relevant models of prebiotic environments, systems consisting of clay, water, and amino acids were subjected to cyclic variations in temperature and water content. Fluctuations of both variables produced longer oligopeptides in higher yields than were produced by temperature fluctuations alone. The results suggest that fluctuating environments provided a favorable geological setting in which the rate and extent of chemical evolution would have been determined by the number and frequency of cycles.

Generation of monoclonal antibodies to integrin-associated proteins. Evidence that alpha3beta1 complexes with EMMPRIN/basigin/OX47/M6

The alpha3beta1 integrin forms complexes with other cell-surface proteins, including transmembrane-4 superfamily (TM4SF) proteins (e. g. CD9, CD53, CD63, CD81, and CD82). To identify additional cell-surface proteins associated with alpha3beta1 integrin, a monoclonal antibody selection protocol was developed. Mice were immunized with integrin alpha3beta1-containing complexes isolated from HT1080 fibrosarcoma cells, and then 712 hybridoma clones were produced, and 95 secreted antibodies that recognized the HT1080 cell surface. Among these, 12 antibodies directly recognizing integrin alpha3 or beta1 subunits were eliminated. Of the remaining 83, 16 co-immunoprecipitated proteins that resembled integrins under non-stringent detergent conditions. These 16 included 15 monoclonal antibodies recognizing EMMPRIN/basigin/OX-47/M6, a 45-55-kDa transmembrane protein with two immunoglobulin domains. The EMMPRIN protein associated with alpha3beta1 and alpha6beta1, but not alpha2beta1 or alpha5beta1, as shown by reciprocal immunoprecipitation experiments. Also, association with alpha3beta1 was confirmed by cell-surface cross-linking and immunofluorescence co-localization experiments. Importantly, EMMPRIN-alpha3beta1 complexes appear not to contain TM4SF proteins, suggesting that they are distinct from TM4SF protein-alpha3beta1 complexes.

Methionine aminopeptidase gene of Escherichia coli is essential for cell growth

We localized the methionine aminopeptidase (map) gene on the Escherichia coli chromosome next to the rpsB gene at min 4. Genetically modified strains with the chromosomal map gene under lac promoter control grew only in the presence of the lac operon inducer isopropyl-beta-thiogalactoside. Thus, methionine aminopeptidase is essential for cell growth.

PIP kinase Igamma is the major PI(4,5)P(2) synthesizing enzyme at the synapse

Disruption of the presynaptically enriched polyphosphoinositide phosphatase synaptojanin 1 leads to an increase of clathrin-coated intermediates and of polymerized actin at endocytic zones of nerve terminals. These changes correlate with elevated levels of PI(4,5)P(2) in neurons. We report that phosphatidylinositol phosphate kinase type Igamma (PIPKIgamma), a major brain PI(4)P 5-kinase, is concentrated at synapses. Synaptojanin 1 and PIPKIgamma antagonize each other in the recruitment of clathrin coats to lipid membranes. Like synaptojanin 1 and other proteins involved in endocytosis, PIPKIgamma undergoes stimulation-dependent dephosphorylation. These results implicate PIPKIgamma in the synthesis of a PI(4,5)P(2) pool that acts as a positive regulator of clathrin coat recruitment and actin function at the synapse.

A family of molecules related to collapsin in the embryonic chick nervous system

Signaling molecules with either attractive or repulsive effects on specific growth cones are likely to play a role in guiding axons to their appropriate targets. A chick brain glycoprotein, collapsin, has been shown to be a good candidate for a repulsive guidance cue. We report here the discovery of four new molecules related to collapsin in chick brains. All contain a semaphorin domain. One is structurally very similar to collapsin but is only 50% identical in its amino acid sequence. We have named it collapsin-2. The collapsin-related genes exhibit distinct but overlapping patterns of mRNA expression in the developing spinal cord and the developing visual system. This family of collapsin-related molecules could potentially act as repulsive cues toward specific neuronal populations.

Laparoscopy as a routine approach for left lateral sectionectomy

BACKGROUND

Since 1997, the authors have performed laparoscopic left lateral sectionectomy of lesions of the liver in preference to open surgery. The aim of this study was to assess the outcome.

METHODS

Between October 1997 and March 2005, 36 laparoscopic left lateral sectionectomies were performed using five trocars and a small incision for specimen retrieval. Liver resection was performed mainly using a harmonic scalpel and staplers. The Pringle manoeuvre was used in 24 patients.

RESULTS

The mean patient age was 55.2 (range 31-80) years. Twelve patients had underlying cirrhosis. Surgery was performed for 20 malignant lesions and 16 benign lesions with a mean size of 42.7 (range 5-110) mm. Conversion to laparotomy occurred in one patient. The mean operating time was 171.5 (range 90-240) min. Operatiing time and use of the Pringle manoeuvre were significantly decreased in the second half of the series. Mean blood loss was 208 (range 50-600) ml. No transfusion was required. There were no deaths. Two patients had postoperative complications (one incisional hernia and one pneumonia). The median postoperative stay was 5.2 days.

CONCLUSION

The laparoscopic approach to left lateral sectionectomy was safe and feasible in this series and could be considered as a routine approach in selected patients.

Analysis of left ventricular wall motion by reflected ultrasound. Application to assessment of myocardial function

Ultrasound echocardiograms from the septal and posterior left ventricular walls were displayed with a simultaneously recorded electrocardiogram, phonocardiogram, and indirect carotid pulse. These echoes differed in both amplitude and waveform. The contour of the posterior wall echo resembled an inverted ventricular volume curve, while the septal echo was of smaller amplitude and had a characteristic notched appearance. Most of the movement of the left ventricular walls relative to the ultrasound transducer was attributable to systolic contraction and diastolic expansion of the cavity. However, superimposed on this motion due to change in cavity size was movement of the left ventricle as a whole, first anteriorly toward the ultrasound transducer during late systole then posteriorly away from it at the beginning of left ventricular relaxation. These movements added to the amplitude of posterior wall motion but subtracted from the motion of the septum and were responsible for the notch in the waveform of this echo. Attachment superiorly to the aortic root might also have limited septal motion which was less near the base than nearer the apex of the left ventricle.

The internal left ventricular dimension measured by ultrasound was standardized by using the mitral valve as a landmark and by recording the motion of the left side of the interventricular septum and endocardial surface of the posterior left ventricular wall simultaneously. This measurement was reproducible. In normal subjects, the ultrasonic dimension measured 4.40 ± 0.28 cm at the beginning of systole and shortened by 35.5 ± 3.9% at a rate of 1.22 ± 0.31 lengths/sec. By contrast, the average figures for six patients with primary myocardial disease were 6.96 ± 0.43 cm, 14.9 ± 4.2%, and 0.64 ± 0.11 lengths/sec. Calculation of such indices of left ventricular size and of rate and extent of myocardial shortening should be useful in the detection of impaired myocardial function and in following its progress.

Echocardiographic features of atrial septal defect

Echocardiographic studies were performed on 39 adult patients with atrial septal defects. Findings were compared with those from normal subjects, patients with other congenital left-to-right shunts (ventricular septal defect and patent ductus arteriosus), patients with uncomplicated right ventricular pressure overload (pulmonic stenosis and pulmonary hypertension), and patients with pulmonary hypertension complicated by tricuspid regurgitation. Two echocardiographic features were assessed: 1) a right ventricular dimension, or RVD Index, representing the distance between the right ventricular epicardial echoes and echoes from the right side of the interventricular septum divided by the patient's body surface area, and 2) motion of the interventricular septum.

The increased RVD Index and abnormal septal motion observed in the patients with atrial septal defects provided an ultrasound complex that could clearly separate these patients from normal individuals, those with ventricular septal defect and patent ductus arteriosus, and those with uncomplicated right ventricular pressure overload. However, patients with tricuspid regurgitation could not be differentiated from the group with atrial septal defects, indicating that this echocardiographic complex reflected a volume overload of the right ventricle.