Comments on "A training rule which guarantees finite-region stability for a class of closed-loop neural-network control systems" [with reply]

In the above paper by Kuntanapreeda-Fullmer (ibid., vol.7, no.3 (1996)) a training method for a neural-network control system which guarantees local closed-loop stability is proposed based on a Lyapunov function and a modified standard backpropagation training rule. In this letter, we show that the proof of Proposition 1 and the proposed stability condition as training constraints are not correct and therefore that the stability of the neural-network control system is not quite right. We suggest a modified version of the proposition with its proof and comment on another problem of the paper. In reply, Kuntanapreeda-Fullmer maintain the proof in the original paper is correct. Rather than identifying an error, they believe Park et al. have made a significant extension of the proof for application to stable online training networks.

The multiple murine 3 beta-hydroxysteroid dehydrogenase isoforms: structure, function, and tissue- and developmentally specific expression

The enzyme 3 beta-hydroxysteroid dehydrogenase (3 beta-HSD) is essential for the biosynthesis of all active steroid hormones. To date five distinct isoforms have been identified in the mouse. The different isoforms are indicated by roman numerals (I-V) in the chronological order in which they have been isolated. The different isoforms are expressed in a tissue- and developmentally specific manner and fall into two functionally distinct groups. 3 beta-HSD I, II, and III function as NAD(+)-dependent dehydrogenaselisomerases, and IV and V function as NADPH-dependent 3-keto steroid reductases. These latter two isoforms, therefore, are not involved in the biosynthesis of steroid hormones, but most likely in the inactivation of steroid hormones. In the adult mouse 3 beta-HSD I is expressed in the classical steroidogenic tissues, the adrenal glands and the gonads. 3 beta-HSD II and III are expressed in the liver and kidney, with III being the major isoform expressed in the adult liver. 3 beta-HSD IV is expressed almost exclusively in the kidney of both sexes, and expression of 3 beta-HSD V is observed only in the male liver starting late in puberty. In the fetal liver of both sexes, 3 beta-HSD I is the major or only isoform expressed at 13.5 days postconception and remains the major isoform until the day of birth, after which 3 beta-HSD III becomes the major isoform. Expression of 3 beta-HSD I in the liver decreases after birth and ceases by day 20 postnatally. Thus the liver expresses four distinct isoforms of 3 beta-HSD, I, II, III, and V, at different times during development. The mouse 3 beta-HSD genes, Hsd3b, have been mapped to a small region on mouse chromosome 3. Analysis of two yeast artificial chromosome (YAC) libraries identified one clone that contains the entire Hsd3b locus within a 1400-kb insert. Hybridization by Southern blot analysis of restriction-enzyme-digested YAC DNA using an 18-base oligonucleotide that hybridizes without mismatch to all known Hsd3b sequences indicates that there are a total of seven Hsd3b genes or pseudogenes in the mouse genome. Further analysis of mouse genomic DNA by pulse field gel electrophoresis suggests that all of the Hsd3b gene family is found within a 400-kb fragment.

Back Pain among U.S. Workers: Comparison of Worker Attributes According to Self-reported Causes of Back Pain

Back pain is a significant health problem, especially in industry. To gain a better understanding of back pain in light of its diverse causality, data for 29,322 working adults interviewed in the Occupational Health Supplement to the 1988 National Health Interview Survey were analyzed by self-reported cause of back pain. The 12-month prevalences of back pain for "injury or repeated activities at work," "injury or repeated activities not at work," and "other reasons," were 9.1%, 4.4%, and 4.0%, respectively. The worker attributes and work impacts associated with these self-reported causes were compared for this nationally representative sample. Results from multivariate logistic regressions indicated different profiles of worker attributes among the three cause-specific subgroups of back-pain sufferers. Work impact was substantial in all cases, but was highest for workers with work-related back pain.

Application of genetic algorithms to parameter estimation of bioprocesses

The paper explains the application of a genetic algorithm (GA) to the problem of estimating parameters for a kinetic model of a biologically reacting system. It is demonstrated that the GA is a powerful tool for quantifying the kinetic parameters using kinetic data. As the operation of the GA does not depend on the form of the model equation, it can be applied to the wide spectrum of kinetic modelling problems without any complex formulation procedure.

Single-photon-emission computed tomography (SPECT) in neurotologic assessment: a preliminary report

The single-photon-emission computed tomography (SPECT) scan enables clinicians to probe dynamic and metabolic changes in brain tissue through measurement of regional cerebral blood flow (rCBF). Diagnostic benefits of the SPECT scan in clinical neurology have been demonstrated. SPECT scanning has been shown to be more sensitive than morphologic imaging techniques [magnetic resonance imaging (MRI) and computed tomography (CT)] in many conditions. However, the use of the scan in assessing neurotologic complaints remains inadequately investigated. Few studies have explored the value of SPECT in establishing the causes of dizziness, hearing loss, and tinnitus. We studied SPECT along with MRI, CT scan, electroencephalogram (EEG), and other evaluations in patients with these neurotologic complaints, SPECT abnormalities were more frequent and prominent than those visualized by other imaging modalities. Overall, 78% of SPECT scans revealed abnormalities. Abnormalities were found in 46% of MRIs, 40% of CTs, and 29% of EEGs. The disparity between SPECT scanning and other procedures was also seen once patients were divided by their chief complaints. This study illustrates the sensitivity of SPECT scanning in evaluating neurotologic complaints and highlights the need for additional research into the importance of SPECT scanning in comprehensive neurotologic evaluation.

Total artificial heart using neural and fuzzy controller

The aortic pressure (AoP) and pulmonary artery pressure (PAP) are important factors for the long-term survival of the patient receiving an implant of a total artificial heart (TAH). A new afterload regulation method using neural controllers has been developed for a moving actuator type TAH. Without any transducer, the proposed neural controller, based on the predetermined peak level of the motor current, regulates AoP by adjusting the actuator velocity. At the same time, a fuzzy controller based on expert knowledge prevents the PAP from being abnormally high. The proposed controller not only regulates the pump output on the maintenance of the normal AoP and PAP, but it also successfully controls the suction in the right heart. In vitro tests show that the proposed neural and fuzzy controllers effectively regulate AoP and PAP as well as prevent atrial suction.

Isolation of Shiga-like toxin producing Escherichia coli (O157 and non-O157) in a community hospital

During a 25-week period (June to November 1995), stool specimens with an abnormal appearance (semiliquid to liquid, containing gross mucus or blood) were selected for testing with a new EIA method for detection of Shiga-like toxin-producing Escherichia coli (O157:H7 and non-O157 serotypes). The 270 specimens tested originated from different patients. Eleven of the 270 were positive by EIA for Shiga-like toxin (SLT). Escherichia coli O157:H7 was recovered from six of the EIA-positive specimens, and the remaining five positive samples produced non-O157 isolates.

Novel anticholinesterase and antiamnesic activities of dehydroevodiamine, a constituent of Evodia rutaecarpa

To find a new compound with antiamnesic activity, we screened 29 natural products for their abilities to inhibit acetylcholinesterase and reverse scopolamine-induced amnesia. Among the plants tested Evodia rutaecarpa Bentham showed a strong inhibitory effect on acetylcholinesterase in vitro and an anti-amnesic effect in vivo. By sequential fractionation of E. rutaecarpa, the active component was finally identified as dehydroevodiamine hydrochloride (DHED). DHED inhibited acetylcholinesterase activity in a dose-dependent and non-competitive manner. The IC50 value of DHED is 37.8 microM. A single administration of DHED to rats (6.25 mg/kg) significantly reversed the scopolamine-induced memory impairment in a passive avoidance test. The antiamnesic effect of DHED was more potent than that of tacrine which is the only drug for Alzheimer's disease approved by FDA. This potent antiamnesic effect of DHED was thought to be due to the combined effects of acetylcholinesterase inhibition and the known cerebral blood flow enhancement. These results indicate that DHED has novel anti-cholinesterase and antiamnesic activities and might have therapeutic potential in various disorders including Alzheimer's disease.

Studies on bone markers and bone mineral density in patients with chronic renal failure

Renal osteodystrophy has become a frequent complication in patients with chronic renal failure (CRF), and various histologic forms such as high turnover, low turnover and mixed bone disease have been demonstrated. The only reliable method for distinguishing patients with high turnover from those with low turnover bone disease is bone histomorphometric study, but its clinical utility is restricted. Because of its invasive nature, efforts have been made to predict indirectly the type and severity of this metabolic bone disease by serum assays. In this cross-sectional study, we measured total and regional (head, arms, trunk, ribs, legs, spine and pelvis) bone mineral densities (BMD) by dual X-ray absorptiometry (DXA) in patients with variable degrees of CRF and correlated them with various bone markers. Decreased BMDs were detected in various skeletal sites (trunk and pelvis) in the patients' group. Total BMD Z score was lower in predialysis CRF patients than in the control subjects. Decreased BMD Z scores on weight-bearing bone were pronounced at L1 lumbar vertebra, femur trochanter, femur neck and Ward's triangle. Positive linear correlations were found between creatinine clearance and trunk, ribs, pelvis, and spine BMDs. There were inverse linear correlations between total BMD and total BMD Z score and alkaline phosphatase (AP), urine deoxypyridinoline (U-DPD) in the patients' group. There were no correlations between regional and total BMD, total BMD Z score and serum calcium, ionized calcium, and serum phosphate. There were inverse linear correlations between BUN, creatinine and bone-specific alkaline phosphatase in the predialysis CRF group. We evaluated the correlations between intact parathyroid hormone (i-PTH) and biochemical and other bone markers. There was statistically significant linear correlation between i-PTH and AP. Other bone markers have no significant correlations with i-PTH. Our results demonstrated that there is significant bone loss in patients with CRF before the start of dialysis and also regional variations of BMDs in predialysis CRF patients. DXA is a useful method for evaluating regional and total BMDs and provides information about diverse regional skeletal changes. AP, i-PTH and U-DPD can predict BMD of predialysis CRF patients.

Excitation Gap in the Normal State of Underdoped Bi2Sr2CaCu2O8+delta

Angle-resolved photoemission experiments reveal evidence of an energy gap in the normal state excitation spectrum of the cuprate superconductor Bi2Sr2CaCu2O8+delta. This gap exists only in underdoped samples and closes around the doping level at which the superconducting transition temperature Tc is a maximum. The momentum dependence and magnitude of the gap closely resemble those of the dx2-y2 gap observed in the superconducting state. This observation is consistent with results from several other experimental techniques, which also indicate the presence of a gap in the normal state. Some possible theoretical explanations for this effect are reviewed.

Replication protein A confers structure-specific endonuclease activities to the XPF-ERCC1 and XPG subunits of human DNA repair excision nuclease

XPF-ERCC1 and XPG proteins are nucleases that are involved in human nucleotide excision repair. In this study, we characterized the structure-specific junction-cutting activities of both nucleases using DNA substrates containing a bubble or loop structure. We found that the junction-cutting activities of XPF-ERCC1 and XPG were greatly stimulated by human replication protein A (RPA), while heterologous single-stranded DNA-binding proteins could not substitute for human RPA. To test for specific interaction between RPA and XPF-ERCC1 as is known to occur between RPA and XPG, we employed a pull-down assay with immobilized "bubble" substrate. We found that the binding of XPF-ERCC1 complex to the bubble substrate was enhanced by RPA, suggesting a possible mechanism for RPA in the excision nuclease system, that is the targeting of the nuclease subunits to their specific sites of action. Furthermore, the RPA-promoted junction cutting by XPF-ERCC1 and XPG nucleases was observed with "loop" substrates as well, raising the possibility that XPF-ERCC1, XPG, and RPA may function in removing loop structures from DNA, independent of the other subunits of the human excinuclease.

Analysis of right ventricular function during bypass of the left side of the heart by afterload alterations in both normal and failing hearts

This study investigated the mechanism of right ventricular failure during bypass of the left side of the heart by precisely assessing right ventricular function with use of a conductance catheter. Bypass of the left side of the heart was established with a centrifugal pump in 10 mongrel dogs weighing 11 to 19 kg. Right ventricular function during left heart bypass was evaluated by two parameters that were both derived from measurement of relative change in right ventricular volume by the conductance catheter technique. One parameter was the right ventricular end-systolic pressure-volume relationship as a load-independent index, and the other was the peak right ventricular pressure-right ventricular stroke volume relationship as a "force-velocity relationship." These parameters were measured in both normal and failing hearts while afterload was increased by bilateral intrapulmonary balloon inflation. Moreover, changes in these relationships were observed by varying assist ratios of left heart bypass from 0% to 100%. Failing heart models were induced by normothermic aortic clamping for 20 minutes. The right ventricular end-systolic pressure-volume relationship in normal hearts did not change, irrespective of the assist ratio of left heart bypass, whereas that in failing hearts decreased from 4.25 +/- 1.41 mm Hg/ml without bypass of the left side of the heart to 3.53 +/- 1.30 mm Hg/ml after 100% assist of left heart bypass (p < 0.05). In the peak right ventricular pressure-right ventricular stroke volume relationship, right ventricular stroke volume was almost constant in normal hearts when afterload was increased regardless of the assist ratio of left heart bypass. Moreover, right ventricular stroke volume was maintained at a higher level during bypass of the left side of the heart compared with that without left heart bypass. However, that slope of the relationship in failing hearts was inversely linear and became significantly steeper after 100% assist of bypass of the left side of the heart compared with that without left heart bypass (-0.131 +/- 0.042 versus -0.051 +/- 0.038, p < 0.005). Therefore ++these two slopes of the relationship intersected at a point that was considered the critical point of afterload during bypass of the left side of the heart. In other words, right ventricular stroke volume was decreased by 100% left heart bypass above the critical point of afterload. In conclusion, this study demonstrates not only that bypass of the left side of the heart results in an increase in right ventricular stroke volume in both normal and failing hearts at the physiologic range of afterload, but also that right ventricular function against higher afterload is impaired by 100% assist of bypass of the left side of the heart in failing hearts.

Tc-99m MIBI brain SPECT of cerebellopontine angle tumors

To prospectively evaluate the imaging feasibility of Tc-99m sestamibi brain SPECT of cerebellopontine angle (CPA) tumors, seven patients with CPA lesions seen on CT or MRI and five normal control subjects underwent brain SPECT using a triple-headed camera. Five of these patients had acoustic neuromas, one had a meningloma, and the other had a vascular loop. Subsequently, four patients underwent surgery. In normal control subjects and patients with CPA lesions, there was Tc-99m sestamibi activity in the pituitary gland, choroid plexi, and extraocular muscles. The uptake in these structures, especially the choroid plexi could not be blocked by the oral administration of potassium perchlorate in two normal subjects. Four of seven patients with CPA lesions larger than 1.0 cm in diameter showed tumor uptake (3 acoustic schwannomas, 1 meningloma). Two small ( > 1.0 cm in diameter) intracanalicular type acoustic neuromas failed to show uptake, despite additional attenuation correction for the petrous bone. There was no abnormal uptake in the patient with a vascular loop in the CPA. Preliminary data suggest that, with the exception of small intracanalicular neuromas, CPA tumors can be imaged using Tc-99m sestamibi brain SPECT.

Giant infantile hemangioendothelioma of the liver. Scintigraphic diagnosis

Infantile hemangioendothelioma of the liver is benign mesenchymal tumor composed of anastomosing vascular channels lined with plump endothelial cells. It is a congenital lesion noted at birth or during the first 6 months of life. The authors report a large infantile hemangioendothelioma that was imaged with anatomical modalities and Tc-99m RBC scintigraphy. An early "blush" on Tc-99m RBC hepatic scintigraphy is a diagnostic feature of infantile hemangioendothelioma.

To culture or not to culture: fecal lactoferrin screening for inflammatory bacterial diarrhea

Because of its low yield in unselected specimens, stool culture is often cost ineffective. We tested 55 fecal samples from Fairfax Hospital (46 patients with diarrhea and 9 from controls without diarrhea) for lactoferrin by latex agglutination (LFLA) with the Leukotest (Techlab, Blacksburg, Va.) as a marker for inflammatory diarrhea. Of the 28 samples with Salmonella, Shigella, or Campylobacter infection, 93% had detectable fecal lactoferrin at > or = 1:50 (61% had LFLA titers of > or = 1:400), while 83% of 18 samples with rotavirus or no detectable pathogen were LFLA negative at a titer of 1:50 (100% were negative at 1:400). All 9 controls without diarrhea were LFLA negative at 1:50. The use of fecal lactoferrin to screen for inflammatory diarrhea selects specimens for which stool culture is fivefold more likely to yield an invasive bacterial pathogen (reducing the cost per positive result by over $800) and thus may greatly enhance a cost-effective approach to evaluating diarrheal illness.