Replicative enzymes, DNA polymerase alpha (pol alpha), and in vitro ageing

Normal cells in culture are used to investigate the underlying mechanisms of DNA synthesis because they retain regulatory characteristics of the in vivo replication machinery. During the last few years new studies have identified a number of genetic changes that occur during in vitro ageing, providing insight into the progressive decline in biological function that occurs during ageing. Maintaining genomic integrity in eukaryotic organisms requires precisely coordinated replication of the genome during mitosis, which is the most fundamental aspect of living cells. To achieve this coordinated replication, eukaryotic cells employ an ordered series of steps to form several key protein assemblies at origins of replication. Major progress has recently been made in identifying the enzymes, and other proteins, of DNA replication that are recruited to origin sites and the order in which they are recruited during the process of replication. More than 20 proteins, including DNA polymerases, have been identified as essential components that must be preassembled at replication origins for the initiation of DNA synthesis. Of the polymerases, DNA polymerase alpha-primase (pol alpha) is of particular importance since its function is fundamental to understanding the initiation mechanism of eukaryotic DNA replication. DNA must be replicated with high fidelity to ensure the accurate transfer of genetic information to progeny cells, and decreases in DNA pol alpha activity and fidelity, which are coordinated with cell cycle progression, have been shown to be important facets of a probable intrinsic cause of genetic alterations during in vitro ageing. This has led to the proposal that pol alpha activity and function is one of the crucial determinants in ageing. In this review we summarize the current state of knowledge of DNA pol alpha function in the regulation of DNA replication and focus in particular on its interactive tasks with other proteins during in vitro ageing.     

Prognostic value of exercise tests in male veterans with chronic coronary artery disease

PURPOSE: The authors evaluate the prognostic value of treadmill testing in a large consecutive series of patients with chronic coronary artery disease. Exercise testing is widely performed, but analyses of the prognostic value of test results have largely concentrated on patients referred for the diagnosis of coronary artery disease, patients after an acute coronary event or procedure, or patients with congestive heart failure. METHODS: All patients referred for evaluation at two university-affiliated Veterans Affairs Medical Centers who underwent exercise treadmill tests for clinical indications between 1987 and 2000 were determined to be dead or alive using the Social Security Death Index after a mean 5.8-year follow-up. Patients without established heart disease and those with congestive heart failure were excluded, leaving the target population of those with a history myocardial infarction or coronary intervention. Clinical and exercise test variables were collected prospectively according to standard definitions; testing and data management were performed in a standardized fashion using a computer-assisted protocol. All-cause mortality was used as the endpoint for follow-up. Standard survival analysis was performed including Kaplan Meier curves and the Cox Hazard Model. RESULTS: Of the 1,473 patients with coronary artery disease who had exercise testing, 273 (19%) patients had a revascularization procedure (Revascularization group); 813 (55%) had a history of myocardial infarction, diagnostic Q waves (MI group), or both; and 387 (26%) had a history of myocardial infarction or Q wave and revascularization (Combined group). Mean age of the patients was 61.8 +/- 9 years. A total of 401 deaths occurred during a mean follow-up of 5.8 years with an annual mortality rate of 4.5%. Only two variables, age and maximal exercise capacity, were independently and statistically associated with time to death in all three groups and were the strongest predictors of all cause mortality. CONCLUSION: A simple score based on METs, age, and history of myocardial infarction or diagnostic Q waves can stratify prognosis in patients with chronic coronary artery disease. The score enabled the identification of a group at low risk (32% of the cohort) with an annual mortality rate of 2%, a group at intermediate risk (42% of the cohort) with an annual mortality rate of about 4%, and a group at high risk (26% of the cohort) with an average annual mortality rate of approximately 7%.     

Reduced Motivation in Perinatal Fluoxetine-Treated Mice: A Hypodopaminergic Phenotype

Early life is a sensitive period, in which enhanced neural plasticity allows the developing brain to adapt to its environment. This plasticity can also be a risk factor in which maladaptive development can lead to long-lasting behavioral deficits. Here, we test how early-life exposure to the selective-serotonin-reuptake-inhibitor (SSRI), fluoxetine, affects motivation, and dopaminergic signaling in adulthood. We show for the first time that mice exposed to fluoxetine in the early postnatal period exhibit a reduction in effort-related motivation. These mice also show blunted responses to amphetamine and reduced dopaminergic activation in a sucrose reward task. Interestingly, we find that the reduction in motivation can be rescued in the adult by administering bupropion, a dopamine-norepinephrine reuptake inhibitor used as an antidepressant and a smoke cessation aid but not by fluoxetine. Taken together, our studies highlight the effects of early postnatal exposure of fluoxetine on motivation and demonstrate the involvement of the dopaminergic system in this process.SIGNIFICANCE STATEMENT The developmental period is characterized by enhanced plasticity. During this period, environmental factors have the potential to lead to enduring behavioral changes. Here, we show that exposure to the SSRI fluoxetine during a restricted period in early life leads to a reduction in adult motivation. We further show that this reduction is associated with decreased dopaminergic responsivity. Finally, we show that motivational deficits induced by early-life fluoxetine exposure can be rescued by adult administration of bupropion but not by fluoxetine.     

Partial tears of anterior cruciate ligament: Results of single bundle augmentation

Background:

Partial tears of the anterior cruciate ligament (ACL) are common and usually present with symptomatic instability. The remnant fibers are usually removed and a traditional ACL reconstruction is done. But with increased understanding of ACL double bundle anatomy, the remnant tissue preservation along with a single bundle augmentation of the torn bundle is also suggested. The purpose of this study was to evaluate the results of selective anatomic augmentation of symptomatic partial ACL tears. Our hypothesis is that this selective augmentation of partial ACL tears could restore knee stability and function.

Materials and Methods:

Consecutive cases of 314 ACL reconstructions, 40 patients had intact ACL fibers in the location corresponding to the anteromedial (AM) or posterolateral (PL) bundle and were diagnosed as partial ACL tears perioperatively. All patients underwent selective augmentation of the torn bundle, while keeping the remaining fibers intact using autogenous hamstring graft. A total of 38 patients (28 males, 10 females) were available with a minimum of 3 years followup. 26 cases had AM bundle tears and 12 cases had PL bundle tears respectively. Patients were assessed with International Knee Documentation Committee (IKDC) 2000 Knee Evaluation Form, Lysholm score; instrumented knee testing was performed with the arthrometer (KT 2000). Statistical analysis was performed to compare the preoperative and postoperative objective evaluation.

Results:

At 3 years followup, 31.6% patients were graded A, 65.8% were graded B and 2.6% was graded C at IKDC objective evaluation. Manual laxity tests, Lysholm''s score, mean side to side instrumental laxity and Tegner activity score improved significantly. 76% patients returned to preinjury level of sports activity after augmentation.

Conclusion:

The results of anatomic single bundle augmentation in partial ACL tears are encouraging with excellent improvement in functional scores, side to side laxity and return to sports activity.     

Durable engraftment and correction of hematological abnormalities in children with congenital amegakaryocytic thrombocytopenia following myeloablative umbilical cord blood transplantation

The use of HSCT is the only potentially curative treatment for CAMT, but access is limited by the availability of suitable donors. We report five consecutive patients with CAMT who received MAC and partially HLA‐mismatched, UCBT (unrelated, n = 4). Median times to neutrophil (>500/μL) and platelet (≥20 000 and ≥50 000/μL) engraftment were 19, 57, and 70 days, respectively. Acute GvHD, grade II, developed in one patient, who subsequently developed limited chronic GvHD. At median follow‐up of 14 yr, all patients are alive with sustained donor cell engraftment. To our knowledge, this is the largest single‐center series of UCBT for patients with this disease and suggests that UCBT is a successful curative option for patients with CAMT.     

Systemic mastocytosis with associated clonal hematological non-mast-cell lineage disease: analysis of clinicopathologic features and activating c-kit mutations

The majority of patients with systemic mastocytosis with associated clonal, hematological non-mast cell lineage disease (SM-AHNMD) have a myeloid stem cell malignancy including myelodysplastic syndromes (MDS), myelodysplastic/myeloproliferative disorders, acute myeloid leukemia (AML), or chronic myeloproliferative disease. The clinicopathologic features of SM-AHNMD have not been fully characterized. We describe seven cases of this entity: 3 with MDS, 3 with AML, and 1 with chronic myelomonocytic leukemia. In the majority of cases, SM was diagnosed concurrently with the myeloid malignancy and aberrant mast cell morphology was observed. The commonly described c-kit enzymatic site mutation Asp816Val was detected only in 2 cases, while 3 patients carried the Asp816His mutation. Among the 3 cases with AML, 2 patients carried the translocation t(8;21). On the basis of our results and other reported cases, there appears to be a specific association between SM and AML with t(8;21). Concurrent occurrence of SM may define a subset of patients with de novo AML and other myeloid malignancies who have an adverse prognosis. As clinically effective tyrosine kinase inhibitors that inhibit enzymatic-type c-kit mutations are being developed, detection of mast cell proliferation associated with myeloid malignancy may have important therapeutic implications.     

Functional connectivity in the resting brain: a network analysis of the default mode hypothesis

Functional imaging studies have shown that certain brain regions, including posterior cingulate cortex (PCC) and ventral anterior cingulate cortex (vACC), consistently show greater activity during resting states than during cognitive tasks. This finding led to the hypothesis that these regions constitute a network supporting a default mode of brain function. In this study, we investigate three questions pertaining to this hypothesis: Does such a resting-state network exist in the human brain? Is it modulated during simple sensory processing? How is it modulated during cognitive processing? To address these questions, we defined PCC and vACC regions that showed decreased activity during a cognitive (working memory) task, then examined their functional connectivity during rest. PCC was strongly coupled with vACC and several other brain regions implicated in the default mode network. Next, we examined the functional connectivity of PCC and vACC during a visual processing task and show that the resultant connectivity maps are virtually identical to those obtained during rest. Last, we defined three lateral prefrontal regions showing increased activity during the cognitive task and examined their resting-state connectivity. We report significant inverse correlations among all three lateral prefrontal regions and PCC, suggesting a mechanism for attenuation of default mode network activity during cognitive processing. This study constitutes, to our knowledge, the first resting-state connectivity analysis of the default mode and provides the most compelling evidence to date for the existence of a cohesive default mode network. Our findings also provide insight into how this network is modulated by task demands and what functions it might subserve.     

Cosmetic arm lengthening with monorail fixator

Upper limb length discrepancy is a rare occurrence. Humerus shortening may need specialized treatment to restore the functional and cosmetic status of upper limb. We report a case of humerus lengthening of 9 cm with a monorail external fixator and the result was observed during a 2-year follow-up. Humerus lengthening needs specialized focus as it is not only a cosmetic issue but also a functional demand. The monorail unilateral fixator is more functional and cosmetically acceptable, and thus becomes an effective treatment option.