Why Are Human Cells Resistant to Malignant Cell Transformation in vitro?1

Transformation of human cells, both induced and spontaneous, is an extremely rare event, whereas rodent cells are relatively easily transformed when treated with a single carcinogenic agent. The present review addresses the question of why human cells are resistant to malignant transformation in vitro. To facilitate understanding of the problem, the process of transformation is divided operationally into two phases, i.e. phase I, immortalization; and phase II, malignant transformation. In human cells, one-phase transformation, i.e., the consecutive occurrence of phases I and II due to the action of a single carcinogenic agent, is observed only rarely. Once human cells are immortalized, however, malignant transformation by chemical carcinogens or oncogenes proceeds, suggesting that for human cells, phase I immortalization is a prerequisite for such transformation to take place. To date, about 20 papers have been published describing protocols for the two-phase transformation of a variety of human epithelial cells and fibroblasts. In most experiments, SV40, human papilloma viruses and their transforming genes are utilized for induction of phase I (immortalization) followed by the use of chemical carcinogens or activated oncogenes for induction of phase II (malignant transformation). Possible mechanisms that would render human cells refractory to transformation are discussed below.     

Management of unruptured intracranial aneurysm in Japan: a Markovian decision analysis with utility measurements based on the Glasgow Outcome Scale.

The purpose of this study was to analyze the management of individual patients with unruptured intracranial aneurysms (UN-ANs) using a decision-analytic approach. Transition probabilities among Glasgow Outcome Scale (GOS) categories were estimated from the published literature and data from patients who had been treated at Kitasato University Hospital. Utilities were obtained from 140 health providers based principally on the GOS. Baseline analysis for a healthy 40-year-old man with an anterior UN-AN less than 10 mm in diameter showed that the quality-adjusted life expectancies for preventive operation and follow-up were 15.34 and 14.66 years, respectively. For a follow-up strategy to be preferred, the annual rupture rate had to be as low as 0.9%. These results were sustained through extensive sensitivity analysis. The results support preventive operation for UN-ANs, and identify problems that can be clarified with a well-designed stratified clinical trial.     

Conditions of Alzheimer-type dementia in the old-old and oldest-old patients with special reference to extreme conditions of brain aging

A neuropathological study on 1540 consecutive autopsy brains ranging from 60 to 107 years of age revealed the following points. (1) Of the of the demented cases of the plaque-predominant type, 93% were complicated with multiple tiny cortical infarcts. They showed a tendency for dementia to develop before or after the appearance or worsening of a systemic disorder such as cardiovascular disease, respiratory infection and cancer. However, there was no case showing Alzheimer-type dementia (ATD). (2) The plaque-predominant type might be an extreme condition of brain aging in terms of senile plaques (SP). It is likely that although the pathological appearance of SP alone is not responsible for dementia, its coexistence with multiple cortical infarcts could be the cause of dementia. Therefore, this type should be distinguished from ATD. (3) Primary hippocampal degeneration could also be an extreme condition of brain aging in terms of neurofibrillary tangles. This condition was different pathologically from the hippocampal lesion in ATD. (4) Several characteristics of old-old and oldest-old patients were clarified.     

Analysis of Responsive Cells in Tolerance by the Oral Administration of Ovalbumin

The induction of immune tolerance is the most common consequence of protein feeding, i.e., “oral tolerance”. In this study we investigated the genetic basis of oral tolerance using various kinds of recombinant and congenic mice, and the cells involved in the development of this phenomenon in mice. The footpad swelling response to ovalbumin (OVA) was inhibited in mice that were orally fed OVA 7 days before sensitization. No effect of strain of mouse was seen in this inhibition. This inhibition could be transferred by Peyer's patch cells. The CD4^-8⁺ T cells were responsible for the inhibition of footpad swelling. The number of CD4⁺ cells from OVA-fed tolerant mice decreased significantly, but CD8⁺ cells did not.

The number of CD4^-8⁺ T cells was increased in Peyer's patches of OVA-fed tolerant mice, and were involved in the development of oral tolerance.     

Ultrastructure of primary squamous cell carcinoma of the submandibular gland

Primary squamous cell carcinoma of the submandibular gland is a rare tumor. In this report, the histological and ultrastructural features of a case of primary squamous cell carcinoma arising in the left submandibular gland is presented. Light microscopically, the tumor consisted of well differentiated keratinizing squamous cell nests. Ultrastructurally, the tumor cells were oval or spindle-shaped, and several tumor cells had intracytoplasmic desmosome-like structures, resembling intercellular desmosomes. The majority of the tumor cells contained a large number of intermediate filaments (tonofilaments). Intercellular desmosomes were well developed. No secretory granules were found. These ultrastructural features may enable us to distinguish primary squamous cell carcinoma from mucoepidermoid carcinoma which is often misdiagnosed as squamous cell carcinoma.     

Tracheal dilatation by halothane and enflurane in man

The effect of halothane and enflurane on tracheal tone were studied in 21 patients during the induction of anesthesia. Endotracheal tube cuff pressure was used to measure tracheal tone. Anesthesia, maintained by nitrous oxide 70% in oxygen, was supplimented with succinylcholine drip infusion to immobilize the patient. Ventilation was controlled by a Volume-preset ventilator. In the halothane group, the initial cuff pressure was 14.8 ± 1.3 (mean ± SE) cmH₂O but 10min after 0.15mg/kg of pancuronium injection, it increased to 21.7 ± 2.3cmH₂O (control). Ten min after inhalation of 0.75% of halothane, cuff pressure decreased to 14.7 ± 2.3cmH₂O (34 ± 11% decrease from the control value). In the enflurane group, the initial cuff pressure was 17.6 ± 1.8cmH₂O and it increased to 21.0 ± 1.7cmH₂O (control) 10min after pancuronium injection. Ten min after 1.7% of enflurane inhalation, cuff pressure decreased to 17.1 ± 2.3cmH₂O (23.9 ± 6% decrease from the control value). Halothane and enflurane produced similar tracheal dilatation in healthy individuals.(Yasuda I, Irimada M, Hirano T et al.: Tracheal dilatation by halothane and enflurane in man. J Anesth 2: 46–49, 1988)     

Clinical significance of reverse redistribution in exercise thallium-201 SPECT after percutaneous transluminal coronary angioplasty

Clinical significance of reverse redistribution on thallium image was evaluated in 54 patients who had undergone PTCA. Thallium SPECT imaging was performed one week and three to six months after PTCA. Reverse redistribution was detected eight of 54 patients one week after PTCA and five of 38 patients three to six months after PTCA. In the segments with reverse redistribution, reduced regional wall motion and lesser degree of coronary stenosis was common features (p less than 0.05) angiography. In conclusion, reverse redistribution had a tendency to appear in the region with mild myocardial injury and relatively high coronary blood flow after PTCA. But in cases with new occurrence and disappearance of reverse redistribution during follow up period, we can not assess the factors to explain these phenomena. In these segments, "coronary flow reserve", "stunned myocardium", "hibernating myocardium" or other factors may be related.     

Transient induction of single GST-P positive hepatocytes by DEN

The single cells positive for placental glutathione S-transferase(GST-P), detectable in livers of rats soon after treatment withhepatocarcinogens, are possible ‘initiated cells’,the hypothesis tested in the present series of experiments.No low dose threshold was observed in male Sprague-Dawley ratsat different single doses of diethylnitrosamine (DEM) althougha plateau was reached between 160 and 200 mg/kg body weight.At the latter single dose 12 400 positive cells/cm³ were observedimmunohistochemically in rat livers after one week, the numbersthen decreasing to week 8 and thereafter rising again. In thenumbers then decreasing to week 8 and thereafter rising again.In the early stages single cells predominated but with timea gradual increase in mini-foci and larger lesions became evident.Application of selection pressure (feeding of diet containing0.02% 2-AAF plus partial hepatectomy) to rats 2–24 weeksafter single DEN-treatment resulted in the formation of largefoci positive for GST-P, especially in the early stages, thegrowth response being less pronounced with time. The numberof foci, on the other hand. was correlated with the number offoci, on the other hand, was correlated with the number ofsingle cells/mini-foci detected inhepatectomy tissue of thesame individuals. These results suggest that the early GST-Ppositive populations could be the precursor for preneoplasticfoci and nodules.     

Semaphorin3A signalling is mediated via sequential Cdk5 and GSK3beta phosphorylation of CRMP2: implication of common phosphorylating mechanism underlying axon guidance and Alzheimer's disease

Collapsin response mediating protein-2 (CRMP2) has been identified as an intracellular protein mediating Semaphorin3A (Sema3A), a repulsive guidance molecule. In this study, we demonstrate that cyclin-dependent kinase 5 (Cdk5) and glycogen synthase kinase 3beta (GSK3beta) plays a critical role in Sema3A signalling. In In vitro kinase assay, Cdk5 phosphorylated CRMP2 at Ser522, while GSK3beta did not induce any phosphorylation of CRMP2. Phosphorylation by GSK3beta was exclusively observed in Cdk5-phosphorylated CRMP2, but barely in CRMP2T509A. These results indicate that Cdk5 primarily phosphorylates CRMP2 at Ser522 and GSK3beta secondarily phosphorylates at Thr509. The dual-phosphorylated CRMP2, but not non-phosphorylated or single-phosphorylated CRMP2, is recognized with the antibody 3F4, which is highly reactive with the neurofibrillary tangles of Alzheimer's disease. 3F4 recognized the CRMP2 in the wild-type but not cdk5-/- mouse embryonic brain lysates. The phosphorylation of CRMP2 at Ser522 caused reduction of its affinity to tubulin. In dorsal root ganglion neurones, Sema3A stimulation enhanced the levels of the phosphorylated form of CRMP2 detected by 3F4. Over-expression of CRMP2 mutant substituting either Ser522 or Thr509 to Ala attenuates Sema3A-induced growth cone collapse response. These results suggest that the sequential phosphorylation of CRMP is an important process of Sema3A signalling and the same mechanism may have some relevance to the pathological aggregation of the microtubule-associated proteins.