Research review: DNA polymerases as molecular markers of the regenerating capacity of hepatocytes

Hepatocyte regeneration has been widely investigated, with the mitotic index and the incorporation of [³H]thymidine being used as regeneration markers. We focused on the induction of DNA replication enzymes, particularly DNA polymerases (pol) α, δ, and ε. Using rat models, we have shown that the activity of pol α in crude liver extract well represents the regenerating capacity of hepatocytes. Using pol α as an indicator, we analyzed liver regeneration in rat models under various conditions: obstructive jaundice, external or internal biliary drainage, and the obstruction of portal vein branches. It has been revealed that the ligation of the common bile duct alone induces a certain amount of hepatocyte proliferation. It was striking that external biliary drainage suppressed regeneration capacity in cholestatic rat liver after partial hepatectomy. The strong regeneration in nonligated lobes induced by portal branch ligation was similar to the liver regeneration seen after partial hepatectomy with respect to the induction of DNA polymerases. Taken together, the aspects of DNA replication, particularly the induction of DNA polymerases, may contribute to shedding new light on the regeneration of human liver. This work was supported in part by a Grant-in-Aid for General Scientific Research and for Cancer Research from the Ministry of Education, Science and Culture, Japan, and by grants from the Uehara Memorial Foundation     

Successful Treatment of Adult T-cell Leukemia/Lymphoma with MACOP-B,M-FEPA and VEPP-B Combination Chemotherapy

A 45-year-old man was referred to our department in March of 1989. Physical examination showed erythroderma, palmo-plantar hyperkeratosis, generalized lymphadenopathy, hepatosplenomegaly, and leukemic manifestation. The lymphocyte count in the peripheral blood before treatment was 1.7 × 10⁴ cells/mm³. Atypical lymphocytes such as flower cells and lobulated cells were seen in the peripheral blood. A sample excised from a lymph node showed immunoblastic, pleomorphic T cells by a modified classification scheme of the Working Formulation. A high level of serum LDH was detected (2.1 times the upper normal limit). Anti HTLV-1 antibody was also detected in the serum. The atypical lymphocytes were positive for CD3, CD4, CD5, CD7 and HLA-DR, and negative for CD8. Thus, the clinical, pathologic and immunologic features were those of typical acute-type ATL. The patient was treated with VEPA-M for three months starting in March of 1989. Because of poor response, the patient was then treated with MACOP-B, M-FEPA, and VEPP-B for about one year from June of 1989 and has been free of disease up to the time of writing, March of 1993.     

Effect of KB-2796, a new diphenylpiperazine Ca antagonist, on voltage-dependent Ca currents and oxidative metabolism in dissociated mammalian CNS neurons

The effects of KB-2796, 1-[bis(4-fluorophenyl)methyl]-4-(2,3,4-trimethoxybenzyl)piperazine-2HCl, on the low- and high-voltage activated Ca²⁺ currents (LVA and HVA I_Ca, respectively) and on oxidative metabolism were studied in neurons freshly dissociated from rat brain. KB-2796 reduced the peak amplitude of LVA I_Ca in a concentration-dependent manner with a threshold concentration of 10⁻⁷ M when the LVA I_Ca was elicited every 30 s in the external solution with 10 mM Ca²⁺. The concentration for half-maximum inhibition (IC₅₀) was 1.9 × 10⁻⁶M. At 10⁻⁵ M or more of KB-2796, a complete suppression of the LVA I_Ca was observed in the majority of neurons tested. There was no apparent effect on the current-voltage (I-V) relationship and the current kinetics. KB-2796 delayed the reactivation and enhanced the inactivation of the Ca²⁺ channel for LVA I_Ca voltage- and time-dependently, suggesting that KB-2796 preferentially binds to the inactivated Ca²⁺ channel. KB-2796 at a concentration of3.0 × 10⁻⁶M also decreased the peak amplitude of the HVA I_Ca without shifting the I-V relationship. In addition, KB-2796 reduced the oxidative metabolism (the formation of reactive oxygen species) of the neuron in a concentration-dependent manner with a threshold concentration of3 × 10⁻⁶M. It is suggested that the inhibitory action of KB-2796 on the neuronal Ca²⁺ influx and the oxidative metabolism, in combination with a cerebral vasodilatory action, may reduce ischemic brain damage.     

Induction chemoradiotherapy prior to surgery for non-small cell lung cancer invading the left atrium.

We present a case of a 58-year-old man with diagnosis of lung adenocarcinoma invading the left atrium. He was treated with induction chemoradiotherapy for T4N1M0 disease, showing objective response. Then, a left upper lobectomy with a partial resection of the left atrium was performed without cardiopulmonary bypass. No residual tumor cells existed in the resected specimens, showing pathological complete response. Our case suggests that induction chemoradiotherapy prior to surgery can be an appropriate strategy among carefully selected patients with non-small cell lung cancer invading the left atrium.     

Detection of proteinous toxins using the Bio-Threat Alert system, part 3: effects of heat pretreatment and interfering substances

We previously reported that the Guardian Bio-Threat Alert (BTA) system could detect (detection limit: about 0.1 μg/ml) staphylococcal enterotoxin B (SEB), botulinum toxins (BTX) A and B, and ricin, with no interference by white-powdered materials or colored matrices. In this study, the capability of the BTA system was further assessed. With 10 min of preheating at 60°C, all toxins could be detected, but with preheating at 80°C, BTX A and B and ricin became undetectable. About 20% SEB could be detected after heating at 80°C, but this detection ability was completely removed after heating at 100°C. The effects of chemicals usually used for decontamination, such as sodium hypochlorite, hydrogen peroxide, formaldehyde, and sodium nitrite, on the detectability of SEB, BTX A, or ricin in the BTA system were also tested. The concentrations giving 50% line intensity for SEB, BTX A, and ricin were 3.1, 11, and 15 μM for sodium hypochlorite and 88, 210, and 60 mM for formaldehyde, respectively. The addition of hydrogen peroxide or sodium nitrite did not decrease the detectability even when used at high concentrations.     

Prefrontal cerebral activity during a simple “rock, paper, scissors” task measured by the noninvasive near-infrared spectroscopy method

We conducted a noninvasive near-infrared spectroscopy (NIRS) study using the game of rock, paper, scissors (RPS) as a simple neurocognitive task for the prefrontal cortex (PFC) in 15 healthy volunteers. We employed an opposite “to lose” RPS task coupled with a normal “to win” RPS task, since the former requires inhibition of behavior, one of the most important functions of the prefrontal cortex. During the NIRS examination, subjects had to present one of the three RPS hands in response to hands displayed randomly on a computer screen every 1.5 s, and were required to show hands that lose to the computer, or that beat the computer. We measured the relative concentrations of oxyhemoglobin (oxy-Hb) using the prefrontal probes of the NIRS system during the tasks. The increases in oxy-Hb during the “to win” RPS task were small, but were quite large and laterally dominant during the “to lose” RPS task. The difference between the two tasks might have been due to the participants’ cognitive conflict with losing on the RPS. We conclude that losing is better than winning on the RPS as a sensitive indicator in the NIRS examination of PFC.     

Diagnostic Validity of Fecal Occult Blood Tests for Detecting Gastroenterological Cancers

In order to estimate the diagnostic validity of chemical fecal occult blood tests, i.e. orthotolidine (Shionogi A) and guajac (Shionogi B) slides for detecting cancers of the esophagus, stomach and colorectum, the authors followed up all the examinees (n=3,449) of comprehensive medical check-ups at the Center for Adult Diseases, Osaka, by means of record linkage to the Osaka Cancer Registry's files. Then, diagnostic validity was calculated based on the results of two years' follow-up. Sensitivity for the respective cancers was 20.0%, 11.8% and 62.5% for Shionogi A, and 20.0%, 5.9% and 43.8% for Shionogi B slides. Likelihood ratio for the respective cancers was 1.4, 0.8 and 4.5 for Shionogi A, and 3.3, 1.0 and 7.5 for Shionogi B. Specificity was analogous among the three cancer sites, being 86% for Shionogi A and 94% for Shionogi B. These results suggest that the diagnostic validity of chemical occult blood tests for detecting cancers of the esophagus and the stomach is very poor, and therefore imply that close examinations of these sites for screening positives is unnecessary in mass screenings for colorectal cancer.     

Mechanisms of pinacidil-induced vasodilatation

The mechanism of the vasodilator effect of pinacidil was examined. Pinacidil (0.1–100 μM) inhibited the increases in cytosolic Ca²⁺ ([Ca²⁺]_i) and muscle tension due to norepinephrine in rat aorta. In contrast, a Ca²⁺ channel blocker, verapamil, inhibited the norepinephrine-stimulated [Ca²⁺]_i more strongly than the contraction. Higher concentrations of pinacidil (3–100 μM) inhibited the verapamil-insensitive portion of the contraction and [Ca²⁺]_i. An inhibitor of ATP-sensitive K⁺ channels, glibenclamide, antagonized the inhibitory effect of low concentrations ( 10 pM) of pinacidol. Pinacidil did not change the contraction induced by Ca²⁺ in vascular smooth muscle permeabilized with Staphylococcus aureus -toxin. Norepinephrine (in the presence of GTP), 12-deoxyphorbol 13-isobutyrate (in the absence of GTP), and treatment with GTP_γS potentiated the contraction of permeabilized smooth muscle induced by the addition of Ca²⁺. Pinacidil (100 μM) inhibited the potentiation due to GTP_γS or noepinephrine but not to phorbol ester. These results suggest that pinacidil has dual effects on vascular smooth muscle contraction. At lower concentrations (>0.1 μM), it decreases [Ca²⁺]_i, possibly by activating ATP-sensitive K+ channels. At higher concentrations (> 3 μM), it may additionally inhibit the receptor-mediated, GTP-binding protein-coupled phosphatidyl inositol turnover.