Configuration of sample points for the reduction of multicollinearity in regression models with distance variables

Regression models often suffer from multicollinearity that greatly reduces the reliability of estimated coefficients and hinders an appropriate understanding of the role of independent variables. It occurs in regional science especially when independent variables include the distances from urban facilities. This paper proposes a new method for deriving the configuration of sample points that reduces multicollinearity in regression models with distance variables. Multicollinearity is evaluated by the maximum absolute correlation coefficient between distance variables. A spatial optimization technique is utilized to calculate the optimal configuration of sample points. The method permits us not only to locate sample points appropriately but also to evaluate the location of facilities from which the distance is measured in terms of the correlation between distance variables in a systematic way. Numerical experiments and empirical applications are performed to test the validity of the method. The results support the technical soundness of the proposed method and provided some useful implications for the design of sample location.     

Programmed High‐Hole‐Mobility Supramolecular Polymers from Disk‐Shaped Molecules

In this paper a simple, casting solution technique for the preparation of two‐dimensional (2D) arrays of very‐high molecular weight (MW) 1D‐Pc supramolecular inorganic polymers is described. The soluble fluoroaluminium tetra‐tert‐butylphthalocyanine (ttbPcAlF) is synthesized and characterized, which can be self‐assembled to form 2D arrays of very‐high‐MW 1D‐Pc supramolecular inorganic polymers. High‐resolution transmission electron microscopy (HRTEM) demonstrates that the 1D‐ttbPcAlF, having a cofacial ring spacing of ～0.36 nm and an interchain distance of ～1.7 nm, self‐assembles into 2D‐nanosheets (～140 nm in length, ～20 nm in width, and equivalent to MW of 3.2 × 10⁵ g mol^?1). The film cast from a 1,2‐dichloroethane (DCE) solution shows a minimum hole‐mobility of ～0.3 cm² V^?1 s^?1 at room temperature by flash‐photolysis time‐resolved microwave conductivity (TRMC) measurements and a fairly high dark dc‐conductivity of ～1 × 10^?3 S cm^?1.     

Herpes viruses--herpes simplex virus, varicella-zoster virus, EB virus, cytomegalovirus

Herpes simplex encephalitis is the commonest viral encephalitis among individuals, and the mortality has been markedly decreased by the use of vidarabine and acyclovir. Early diagnoses and immediate treatment are essential for favorable prognoses. Neuro-imagings, such as MRI and SPECT, and PCR technique for detection of HSV-DNA in CSF, are useful for early diagnoses, without requiring brain biopsy. Varicella and herpes zoster viruses are complicated, only rarely, with neurological manifestations, such as meningoencephalitis, myelitis, or peripheral neuropathy. Acyclovir is mostly effective in these cases. Neurological complications of Epstein-Barr virus infections are variable, including meningitis, cerebellar ataxia, cranial neuropathy, and Guillain-Barré syndrome. Their prognoses are generally good. Cytomegalovirus encephalitis is one of the common complications in AIDS patients. Its clinical diagnosis is difficult and the prognosis is considered to be poor.     

Brain damage after aortic arch repair using selective cerebral perfusion

BACKGROUND: Selective cerebral perfusion is one of the most popular methods for cerebral protection during aortic arch repair. However, causes of postoperative brain damage are not fully understood. We analyzed brain damage after aortic arch repair using selective cerebral perfusion for true aortic arch aneurysm in regard to preoperative cerebral infarction and intracranial and extracranial occlusive arterial disease. METHODS: Over a 9-year period, 60 patients with true aortic arch aneurysm underwent aortic arch repair using selective cerebral perfusion. Postoperative brain damage was evaluated in regard to preoperative cerebral infarction detected by computed tomography, magnetic resonance imaging, or both in 50 patients and intracranial and extracranial occlusive arterial disease detected by digital subtraction angiography, magnetic resonance angiography, or both in 35 patients. RESULTS: Seven (12%) of the 60 patients died within 30 days of operation. Postoperative brain damage occurred in 6 (10.5%) (3, coma, and 3, hemiplegia) of 57 patients; 3 patients who died without awakening were excluded. Preoperatively, old cerebral infarction was detected in 9 patients (18%), and silent cerebral infarction (lacunar infarction and leukoaraiosis) was diagnosed in 26 patients (52%). Postoperative brain damage occurred in 3 (33%) of the 9 patients with preoperative cerebral infarction and in 3 (23%) of 13 patients with negative preoperative brain findings; this excludes 2 patients who died without awakening. No patient with silent cerebral infarction had postoperative brain damage. Occlusive arterial disease was detected in 7 patients (20%). The incidence of brain damage in these patients was 71% (5/7), which was significantly greater than that of 4% (1/28) in patients without occlusive arterial disease (p < 0.001). CONCLUSIONS: Silent cerebral infarction may not be a risk factor for postoperative brain damage. Preoperative evaluation of intracranial and extracranial occlusive arterial disease provides important information as to whether a patient might sustain brain damage after aortic arch repair using selective cerebral perfusion.     

Temperature-sensitive mutation in PEX1 moderates the phenotypes of peroxisome deficiency disorders

The peroxisome biogenesis disorders (PBDs), including Zellweger syndrome (ZS), neonatal adrenoleukodystrophy (NALD) and infantile Refsum disease (IRD), are autosomal recessive diseases caused by deficiency of peroxisome assembly as well as malfunction of peroxisomes, where >10 genotypes have been reported. ZS patients manifest the most severe clinical and biochemical abnormalities, while those with NALD and IRD show the least severity and the mildest features, respectively. PEX1 is the causative gene for PBDs of complementation group I (CG1), the highest incidence PBD, and encodes the peroxin, Pex1p, a member of the AAA ATPase family. In the present work, we found that peroxisomes were morphologically and biochemically formed at 30 but not 37 degrees C, in the fibroblasts from all CG1 IRD patients examined, whereas almost no peroxisomes were seen in ZS and NALD cells, even at 30 degrees C. A point missense mutation, G843D, was identified in the PEX1 allele of most CG1 IRD patients. The mutant PEX1, termed HsPEX1G843D, gave rise to the same temperature-sensitive phenotype on CG1 CHO cell mutants upon transfection. Collectively, these results demonstrate temperature-sensitive peroxisome assembly to be responsible for the mildness of the clinical features of PEX1 -defective IRD of CG1.     

Clofibrate-inducible, 28-kDa peroxisomal integral membrane protein is encoded by PEX11

We cloned a human PEX11 cDNA by expressed sequence tag homology search using yeast Candida boidinii PEX11, followed by screening of human liver cDNA library. PEX11 encoded a peroxisomal protein Pex11p comprising 247 amino acids, with two transmembrane segments and a dilysine motif at the C-terminus. Pex11p comigrated in SDS-PAGE with a 28-kDa peroxisomal integral membrane protein (PMP28) isolated from the liver of clofibrate-treated rats and was crossreactive to anti-PMP28 antibody, thereby indicating PEX11 to encode PMP28. Pex11p exposes both N- and C-terminal parts to the cytosol. PEX11 was not responsible for ten complementation groups of human peroxisome deficiency disorders.     

Correction by gene expression of biochemical abnormalities in fibroblasts from Zellweger patients

Zellweger syndrome is a prototype of peroxisomal biogenesis disorders and a fatal autosomal recessive disease with no effective therapy. We identified nine genetic complementation groups of these disorders, and mutations in peroxisome assembly factor-1 (PAF-1) and the 70-kD peroxisomal membrane protein (PMP70) genes have been detected by our group F and Roscher's group 1, respectively. We now describe permanent recovery from generalized peroxisomal abnormalities in fibroblasts of a Zellweger patient from group F, such as biochemical defects of peroxisomal beta-oxidation, plasmalogen biosynthesis, and morphologic absence of peroxisomes, by stable transfection of human cDNA encoding PAF-1. In the light of these observations, we designed a gene expression system using fibroblasts from patients with peroxisomal biogenesis disorders. In Zellweger fibroblasts obtained from Roscher's group 1 and transfected with human cDNA encoding PMP70, peroxisomes were not morphologically identifiable, and peroxisomal function did not normalize.     

Observation of switching related to bistability between twocross-coupled lateral modes in twin-stripe lasers

Switching between two cross-coupled lateral modes in gain-guided twin-stripe lasers has been experimentally observed with current injection of nominally identical pulses, which strongly indicates bistability. Near- and far-field patterns at both facets are presented, which clearly shows a skewed light field which couples from under one stripe to under the other. Cross-coupled mode operation was obtained only for relatively long cavity lasers, which is consistent with the theory for twin-stripe lasers with high interstripe gain     

Delayed and selective motor neuron death after transient spinal cord ischemia: a role of apoptosis?

OBJECTIVE: The mechanism of spinal cord injury has been thought to be related to tissue ischemia, and spinal motor neuron cells are suggested to be vulnerable to ischemia. We hypothesized that delayed and selective motor neuron death is apoptosis. METHODS: Thirty-seven Japanese domesticated white rabbits weighing 2 to 3 kg were used in this study and were divided into two subgroups: a 15-minute ischemia group and a sham control group. Animals were allowed to recover at ambient temperature and were killed at 8 hours, and 1, 2, 4, and 7 days after reperfusion (n = 3 at each time point). By means of this model, cell damage was histologically analyzed. Detection of ladders of oligonucleosomal DNA fragment was investigated with gel electrophoresis up to 7 days of the reperfusion. Immunocytochemistry, in situ terminal deoxynucleotidyl transferase-mediated deoxyuridine triphosphate-biotin nick-end labeling staining was also performed. RESULTS: After 15 minutes of ischemia, most of the motor neurons showed selective cell death at 7 days of reperfusion. Typical ladders of oligonucleosomal DNA fragments were detected at 2 days of reperfusion. Immunocytochemistry showed in situ terminal deoxynucleotidyl transferase-mediated deoxyuridine triphosphate-biotin nick-end staining was detected at 2 days of reperfusion selectively in the nuclei of motor neurons. CONCLUSION: These results suggest that delayed and selective death of the motor neuron cells after transient ischemia may not be necrotic but rather predominantly apoptotic.     

Surgical experience in patients with Marfan's syndrome and cardiovascular disease

10 patients with Marfan's syndrome and cardiovascular disease were operated at Tohoku University Hospital from 1971 to 1988. Surgery included composite valve graft replacement of ascending aortic aneurysm with aortic regurgitation in 5 patients and prosthetic mitral valve replacement in three patients; two had resection of aneurysm with Dacron tube replacement. Operative mortality was 10%. Two late death occurred (22%). It was suggested that regular follow-up examination is important in these patients to detect new lesions and to evaluate known lesion.