Modulation of synaptic gain by light

Although synaptic transmission in the retina has been assumed to be static, it appears that the voltage gains of the synapses between photoreceptors and second-order cells can be enhanced by light. Voltage gains of the synapses between rods and bipolar (or horizontal) cells are about 10 times higher in the presence of dim background light than in darkness. This increase in synaptic gain may compensate for the loss of rod light responsiveness caused by weak background light so that the animal can maintain good rod sensitivity under moonlight or starlight, the natural lighting condition for mating and food catching.

Plasma amino acid responses of trained athletes to two successive exhaustion trials with and without interim carbohydrate feeding

The purpose of this research was to measure changes in selected plasma amino acids (AA) during two successive exercise trials to exhaustion. Eleven trained male athletes completed these trials at weeks 4, 6, 8 and 12. Blood samples for each test were collected after a 12-hour fast at times (in minutes) 0 (Resting), 45, 90, 135, 180, at exhaustion (EI), after a 20-minute recovery period, and at the second exhaustion (EII). At the end of EI, subjects consumed an artificially sweetened water replacement (placebo) treatment or a carbohydrate (CHO) replacement (1.1 g CHO/kg BW) in order to determine any effect of CHO replacement on changes in energy substrates or AA, adjusted for plasma volume changes. From baseline to EI, alpha-aminobutyric acid, alanine, glycine, isoleucine, serine, valine threonine, and tyrosine decreased significantly (p less than or equal to 0.05), while taurine increased significantly. During the recovery period following EI, isoleucine, leucine, ornithine, phenylalanine, tyrosine, urea and valine increased significantly. From the end of recovery until EII, alanine, aspartic acid, glycine, isoleucine, leucine, ornithine, phenylalanine, serine, threonine, tyrosine and valine decreased significantly. CHO replacement had no effect on the mean change scores for any AA from EI to the end of the recovery period and affected only serine, citrulline, glycine and threonine from the end of the recovery period to EII.

A Multi-Degree-of-Freedom Measuring System for CMM Geometric Errors

A precision multi-degree-of-freedom measuring (MDFM) system has been developed and implemented for the simultaneous measurement of straightness, pitch, yaw, and roll errors of the moving axes of a CMM. The system is based on the principles of laser alignment and autocollimator. Its measurement principles and the influence of laser beam drifts on its measurement quality have been investigated and some improvement schemes have been implemented. Through the measurements of actual as well as artificially created geometric errors of the CMM, it has been found that the system’s accuracy of measuring straightness error components is better than 1 μm and its accuracy for angular error measurements is better than 0.5 arcsec.

Feedback connections and operation of the outer plexiform layer of the retina

The primary feedback control apparatus in the outer retina is the sign-inverting feedback synapse between horizontal cells and cones. In many lower vertebrates horizontal cells release GABA in darkness, which opens Cl- channels in cones. Input-output relations of the feedback synapse reveal that the synaptic gain is light-dependent with the highest negative gain near the dark horizontal cell potential. The horizontal cell-cone feedback synapse improves the reliability of the photoreceptor output synapses. It also modulates the dynamic range and mediates color opponency and surround responses in second-order retinal neurons.

Cortisol content of eggs and larvae of teleosts

The whole-animal content of the cortisol was measured in embryos and larvae of tilapia (Oreochromis mossambicus), rainbow trout (Oncorhynchus mykiss), ayu (Plecoglossus altivelis), milkfish (Chanos chanos), and yellowfin bream (Acanthropagrus latus) by radioimmunoassay following the validation of an extraction method. The total cortisol content in tilapia was 50.3 +/- 19.1 pg immediately following fertilization, then decreased abruptly and maintained a lower level of 10-17 pg until larval hatching; after hatching the cortisol content increased to 47.2 +/- 11.9 pg by the seventh day. Newly hatched rainbow trout had 60.3 +/- 6.4 pg cortisol and then increased their cortisol level slowly to 83.0 +/- 7.2 pg by the fifth day after hatching. Ayu larvae contained 5.2 pg cortisol immediately following hatching. On the other hand, pelagic milkfish revealed a much lower cortisol level, being undetectable from hatching until the second day and ranging from 0.4 to 3.7 pg from the third to seventh day after hatching. Yellowfin bream, demonstrating a similarity to milkfish, were not found to have any detectable cortisol from hatching until the third day, but presented 1.6-7.7 pg from the fifth to seventh day after hatching. The presence and clearance of cortisol during early development of fertilized eggs of tilapia suggest a maternal origin of the hormone. The amount of cortisol deposited in the larval body of tilapia increased after hatching from 25% to nearly 100% of the total cortisol in whole larvae, while that in the larval yolk sac decreased to an undetectable level, implying that the increased cortisol may be produced or secreted by the larva. The possible role of cortisol in larval development is discussed.

Stereochemical analysis of betamethasone and dexamethasone by derivatization and high-performance liquid chromatography

A simple and economical high-performance liquid chromatographic method has been developed for the simultaneous determination of betamethasone and dexamethasone. The method is based on the derivatization of the structural epimers of betamethasone and dexamethasone with a homochiral reagent, N-carbobenzoxy-L-phenylalanine. The derivatives obtained were easily recognized by a non-chiral silica column with n-hexane-dichloromethane-isopropanol (100:100:4, v/v/v) as a mobile phase and a good separation was obtained for quantitation. The method was satisfactorily applied to the determination of betamethasone and dexamethasone in tablets.

Associations of cardiovascular disease risk factors with measures of energy expenditure and caloric intake in a farm population

The purpose of this study was to examine the relationships of several cardiovascular disease risk factors [blood pressure (BP), total cholesterol (TC), high-density-lipoprotein cholesterol (HDL-C), and the HDL-C:TC ratio], as well as the body mass index (BMI) and percent body fat with daily energy intake (EI) and daily energy expenditure (EE) of North Carolina farmers and their wives. Data were collected from 195 subjects. Daily EI and EE were estimated from 4-day food and 4-day activity records, respectively, collected on the same days. Pearson correlation coefficients for chronic disease risk factors with both EI and EE were generally low. When compared to EI, EE was more highly correlated with both lean body mass (r = 0.88) and BMI (r = 0.73), and was less time consuming and easier for the subjects to use. EE obtained from a reliable activity record may be a more practical tool for assessing the possible relationship(s) of energy metabolism to chronic disease risk factors.

Cloning and expression of the cDNA for human gamma-glutamyl carboxylase

The cDNA for human gamma-glutamyl carboxylase, which accomplishes the post-translational modification required for the activity of all of the vitamin K-dependent proteins, was cloned. The enzyme is a 758-residue integral membrane protein and appears to have three transmembrane domains near its amino terminus. The hydrophilic COOH-terminal half of the carboxylase has 19.3 percent identity with soybean seed lipoxygenase. Expression of the cloned cDNA resulted in an increase in carboxylase activity in microsomes of transfected cells compared to mock-transfected cells.

Identification of Joint Structural Parameters Between Substructures

A new methodology of combining the finite element model of a complex structure with its model obtained by experimental modal analysis techniques is presented to identify the joint stiffness and the damping characteristics between its substructures. First, the modal parameters of the structure with joints are extracted based on experimental data using Autoregressive Moving Average Vector models. Then, a condensation technique based on the Riccati iteration algorithm and the orthogonality conditions is applied to reduce the matrix order of the finite element model to match the order of the experimental model. Comparing the two models, the unknown joint parameters are estimated based on the least squares method. The accuracy and the effectiveness of the proposed method were verified through simulation studies.

Thin-layer chromatographic detection of glucocorticoids

An adsorption thin-layer chromatography (TLC) is described for the detection of glucocorticoids including triamcinolone, prednisolone, 6 alpha-methylprednisolone, betamethasone, dexamethasone, hydrocortisone, prednisone and cortisone. Separation of the glucocorticoids was performed on a silica stationary phase with chloroform-dioxane-methanol (15:4:1, v/v) as a mobile phase. The complete resolution of the epimers of betamethasone and dexamethasone was attained by derivatization of them with (1S)-(-)-camphanic chloride using triethylamine as a catalyst. The application of the method to the analysis of glucocorticoids in various samples is being smoothly developed.

Coexistence and function of glutamate receptor subtypes in the horizontal cells of the tiger salamander retina

Effects of the major glutamate receptor agonists, kainate (KA), alpha-amino-3-hydroxy-5-methylisoxazole-4-propionic acid (AMPA), quisqualate (QA), N-methyl-D-aspartate (NMDA), L-alpha-amino-4-phosphonobutyrate (L-AP4), and trans-1-aminocyclopentane-1,3-dicarboxylic acid (ACPD) on horizontal cells (HCs) were studied in superfused larval tiger salamander retina. 20 microM of KA, AMPA, and QA mimicked the action of 3 mM glutamate in the absence and presence of 1 mM Co2+. 20 microM 6-cyano-7-nitroquinoxaline-2,3-dione (CNQX) blocked the actions of KA and AMPA, but not those of QA and glutamate, indicative of the existence of CNQX-resistant QA receptors in the tiger salamander HCs. Prolonged application of ACPD hyperpolarized the HCs and enhanced the light responses, probably by shifting the resting HC voltage (Er) to a more hyperpolarized position. It is possible that the KA, AMPA, and CNQX-resistant QA receptors are involved in mediating the postsynaptic light responses in HCs, and ACPD receptors are involved in sensitivity adjustment of the HC responses.

Chronic disease risk factors in vitamin/mineral supplement users and nonusers in a farm population

Dietary, anthropometric, and chronic disease risk factors (CDRF) in vitamin/mineral supplement users (U) and non-users (NU) were measured in a farm population consisting of 162 subjects (46% females and 54% males; 20-79 years of age, mean age: 52 years). Subjects were white, except for two black males. Supplements were used by 62 subjects (38%); 47% of females and 31% of males used supplements; 43% of subjects over 50 years of age and 32% of subjects age 50 or under used supplements. Both dietary intake and energy expenditure were measured using 4-day records. Indices of adiposity included body weight, BMI, and estimated body fat. Total cholesterol (TC), high-density-lipoprotein cholesterol (HDL-C), serum ferritin, hemoglobin, hematocrit, zinc, copper, and vitamin C were based on 12-hr fasting blood samples. Dietary intake (excluding supplements) for vitamin/mineral U was greater than NU for vitamin C (p = 0.006), thiamin (p = 0.01), riboflavin (p = 0.03), niacin (p = 0.02), folic acid (p = 0.001), vitamin B6 (p = 0.01), and magnesium (p = 0.019). Vitamin C levels were significantly higher and the sum of four skinfolds was significantly lower among U than NU. In this population, 24% of males and 18% of females had TC levels over 240 mg%; 8% of both males and females had blood pressures (BP) greater than 140/90 mm Hg, while 49% of males and 46% of females had BP between 120/80 and 140/90; and 71% of males were more than 25% fat, and 56% of females were more than 35% fat. Despite the high prevalence of CDRF, there were no significant differences between supplement U and NU.

Input-output relations of the feedback synapse between horizontal cells and cones in the tiger salamander retina

1. The input-output relation of the feedback synapse between horizontal cells (HCs) and cones was studied by simultaneously recording the light responses of the HCs and of cones the outer segments of which were truncated off. 2. The postsynaptic light response of the truncated cone was depolarizing and free of direct influence of photocurrents. These postsynaptic light responses were graded and sustained; their waveform resembled that of the HC light responses. 3. Input-output relation of the HC-cone feedback synapse was obtained by plotting the simultaneous voltage points of the HC and truncated cone light responses. At the resting potential of the cone (-40 mV), the voltage gain of the feedback synapse was about -0.33 when VHC = -20 mV and it was about -0.03 when VHC = -60 mV. 4. At more hyperpolarized cone voltages, the feedback signals in cones became smaller, and they reversed at about -67 mV. The voltage gain of the feedback synapse at VHC = -20 mV was about -0.23, -0.18, -0.07, and +0.2 when Vcone = -44.5, -52.5, -65, and -77.5 mV, respectively. 5. Light hyperpolarized the HC, which resulted in a conductance change (delta Gs) in cones. The cone conductance decreased progressively as the HCs were increasingly hyperpolarized, and delta Gs reached a maximum value of 0.93 nS when the HCs were hyperpolarized from -20 to -52 mV. 6. The peak light responses of intact cones were plotted against the peak HC light responses. This gives the relationship between the pre- and postsynaptic voltages of the cone-HC (forward) and HC-cone (feedback) synapses at any given light intensity. Combining this relationship with the input-output relations obtained at various voltages of the truncated cones allows the input-output relation of the feedback synapse for light-evoked signals to be obtained. 7. The input-output relation of the feedback synapse for light-evoked signals was bell-shaped, because the feedback light responses were controlled by two opposing factors: as the light became brighter, the postsynaptic conductance change increased, but the driving force decreased. 8. For light-evoked signals, the slope gain (slope of the input-output relation) of the HC-cone feedback synapse was negative (varied from -0.33 to 0) when VHC lay between -20 and -52 mV; and it was positive (0 to +0.8) when VHC lay between -52 and -72 mV. 9.(ABSTRACT TRUNCATED AT 400 WORDS)

Feedforward lateral inhibition in retinal bipolar cells: input-output relation of the horizontal cell-depolarizing bipolar cell synapse

Lateral inhibition is the ubiquitous strategy used by visual neurons for spatial resolution throughout the animal kingdom. It has been a puzzle whether lateral inputs in retinal bipolar cells are mediated by the horizontal cell (HC)-cone feedback synapse, by the HC-bipolar cell feedforward synapse, or by both. By blocking the central inputs of the depolarizing bipolar cells (DBCs) with L-2-amino-4-phosphonobutyrate, we were able to eliminate the contribution of the feedback synapse and to demonstrate the postsynaptic light response in DBCs mediated by the HC-DBC feedforward synapse. The HC-DBC feedforward synapse contributes roughly one-third of the surround response whereas the HC-cone-DBC feedback synapse probably contributes the rest.

Impact of menstrual periodicity on serum lipid levels and estimates of dietary intakes

Nine eumenorrheic women were studied at five separate times each month for a minimum of 2 months. Fasting bloods and 1-day food records were obtained from all women at these times to describe the pattern and magnitude of within-person variation in selected nutrient and lipid indicators attributable to menstrual cyclicity. Serum cholesterol, beta-carotene, 17 beta-estradiol (E2), and dietary selenium intakes exhibited significant periodic regressions against time. For the group as a whole, however, only serum cholesterol and E2 measures exhibited significantly strong consistent periodicities. Future studies with a larger sample of women are warranted to confirm these findings. Unless strict blood sampling protocols are followed, variation attributable to menstrual cyclicity may mitigate the reliability of the serum cholesterol screenings advocated in the past few years.

Identification and purification to near homogeneity of the vitamin K-dependent carboxylase

Vitamin K-dependent carboxylase catalyzes the modification of specific glutamic acids to gamma-carboxyglutamic acid in several blood-coagulation proteins. This modification is required for the blood-clotting activity of these proteins and has thus been the subject of intense investigation. We have now identified the bovine vitamin K-dependent carboxylase and purified it to near homogeneity by an affinity procedure that uses the 59-amino acid peptide FIXQ/S (residues -18 to 41 of factor IX with mutations Arg----Gln at residue -4 and Arg----Ser at residue -1). The carboxylase as purified has a molecular weight of 94,000. It is also the major protein that can be cross-linked to iodinated FIXQ/S and is the only protein whose cross-linking is prevented by a synthetic factor IX propeptide. The degree of purification is about 7000-fold with reference to ammonium sulfate-fractionated microsomal protein from liver.

Diagnosis of the Tapping Process by Information Measure and Probability Voting Approach

A new method for the diagnosis of the tapping process using the information measure and multiple probability voting scheme is proposed. Considering the features of short cutting-duration and the large uncertainties existing in a tapping process, a set of indices based on the time-domain statistical analysis has been formed. These indices have then been evaluated and ranked using an algorithm that calculates the information gain of each index about the tapping process. The final classification decision can be made by a voting scheme based on the conditional probability functions for multiple indices. Furthermore, the information gains estimated in the index evolution process can be used as a weighting function during voting to improve efficiency and reliability. From a tapping test, which includes five different tapping conditions, a success rate of 95 percent has been achieved.

Independent influences of rod adaptation on cone-mediated responses to light onset and offset in distal retinal neurons

1. The influence of rod adaptation on cone-mediated intracellular responses of distal retinal neurons was examined in the larval tiger salamander. Rods were selectively stimulated by the use of 450-520 nm adapting stimuli too dim to appreciably influence cones. Cones were primarily stimulated with the use of deep-red stimuli (maximally sensitive to wavelengths greater than 650 nm). The qualitative properties of rod-cone interaction were assessed with the use of several different photic-stimulus paradigms. 2. Confirming results of prior studies, we showed that rod adaptation changed the time course of cone-mediated responses to the onset of square-wave light flashes in horizontal cells (HCs); rod adaptation had no similar influence in other distal retinal neurons. Rod adaptation also enhanced cone-mediated responses to rapid flicker in cones, hyperpolarizing (HPBCs) and depolarizing (DPBCs) bipolar cells, as well as HCs. 3. We also examined the influence of rod-stimulating background fields on cone-mediated responses to slow (approximately 1-Hz) flicker composed of sawteeth with a rapid onset (ramp offset) or with a rapid offset (ramp onset). Such stimulation maintained a constant state of long-term adaptation while providing cones with transient-ON or transient-OFF stimulation. 4. Rod adaptation speeds up the response of HCs to rapid onset and increases response amplitude. Rod adaptation had no reliable influence on response to rapid onset in cones or bipolar cells. 5. Rod adaptation enhanced the amplitude of responses of HCs to rapid offset without altering response time course. 6. Rod adaptation greatly enhanced the amplitude of DPBC responses to rapid offset having no reliable influence on the time course of the response. 7. Rod adaptation caused responses of HPBCs to rapid offset to become much more transient. Rod backgrounds had a similar but smaller and less reliable influence on the response of cones to rapid offset. 8. The foregoing results indicate that rod adaptation exerts a minimum of two separate influences on cone-mediated responses in distal amphibian retina. Changes at light onset must reflect the operation of a mechanism that alters response kinetics of the HC membrane. Changes at light offset reflect the operation of a separate mechanism or set of mechanisms that must act in part presynaptically to the HCs.

In vitro gamma-carboxylation of a 59-residue recombinant peptide including the propeptide and the gamma-carboxyglutamic acid domain of coagulation factor IX. Effect of mutations near the propeptide cleavage site

We report the expression in Escherichia coli of a fusion protein that contains the propeptide sequence and gamma-carboxyglutamic acid domain (residues -18 to 41) of human factor IX (FIXGla). CNBr was used to release FIXGla from the fusion protein. The 59-amino acid peptide is an efficient substrate for in vitro gamma-carboxylation. Its Km,app (0.55 microM) is several thousand-fold lower than that of the commonly used substrate FLEEL and about 5 times lower than proPT28 or proFIX28, (Hubbard, B. R., Jacobs, M., Ulrich, M. M. W., Walsh, C., Furie, B., and Furie, B. C. (1989) J. Biol. Chem. 264, 14145-14150). In addition, FIXGla is the first peptide substrate that is carboxylated in vitro to more than one gamma-carboxyglutamic acid/molecule (6-11 gamma-carboxyglutamic acids/molecule). We created peptides with mutations identical to FIXSan Dimas or FIXCambridge as well as a peptide with both mutations in the propeptide sequence and examined the effect of the mutations on in vitro carboxylation. Enzyme kinetic studies revealed no significant difference in Vmax/Km values between normal and mutant substrates. Maximum carbon dioxide incorporation was achieved with the double mutant. From these data we conclude the following. 1) FIXGla and its mutants are excellent substrates for studying the mechanism of gamma-carboxylase. 2) Although arginines at positions -4 and -1 are highly conserved in the propeptide sequence of all the vitamin K-dependent proteins, neither is critical for gamma-carboxylation.

Synaptic inputs from rods and cones to horizontal cells in the tiger salamander retina

Synaptic inputs from rods and cones to horizontal cells (HCs) were studied in the flatmounted isolated retinas of the tiger salamander. Voltage-intensity relations, spectral sensitivities and response waveforms of the rod, the cone, and the HC under dark- and light-adapted conditions were examined. HCs receive mixed inputs from rods and cones in both dark- and light-adapted retinas. The relative rod/cone input in HCs depends on the intensity of stimulus and background illumination, and it varies from HC to HC.

On-Line Detection of Drill Wear

An on-line system for drill wear detection has been developed by using a sensor fusion strategy. Both acceleration and thrust signals were analyzed. Flank wear area was used to evaluate drill wear states. The drill wear area was measured by a vision system and classified into two groups: usable and worn-out. The wear prediction model was obtained by a two-category linear classifier. On-line detection tests indicate that the prediction model has over a 90 percent success rate.

Deduced amino acid sequence of mouse blood-coagulation factor IX

A mouse fetal liver cDNA library was screened with a cDNA clone encoding human blood coagulation factor IX protein (hBCFIX). A bacteriophage lambda clone was isolated and the nucleotide sequence of a 2710-bp insert was determined. An open reading frame of 459 amino acids (aa) was identified within the sequence that has an 80% sequence similarity with hBCFIX. The cDNA contains a long 3'-untranslated sequence similar to that of BcfIX gene from human and canine sources. However, instead of a sequence that might form two hair-pins such as those found in hBcfIX, a (GA)16 repeat that has been reported to form H-DNA [Htun and Dahlberg, Science 241 (1988) 1791-1796; Johnston, Science 241 (1988) 1800-1804] was found in the 3'-untranslated region. The predicted aa sequence of mouse BCFIX serves as a comparative sequence for identifying key residues within hBCFIX where epitopes recognized by monoclonal antibodies produced from an immunized mouse are compared with respect to the human and mouse primary BCFIX sequence.

Localization of classical neurotransmitters in interneurons of the larval tiger salamander retina

Autoradiography was used to visualize the neurons in the tiger salamander retina that exhibit high-affinity uptake of 3H-dopamine, [3H]-serotonin, [3H]-glycine, and [3H]-GABA. Both [3H]-dopamine and [3H]-serotonin were accumulated by amacrine cells and by displaced amacrine cells. [3H]-glycine was taken up by amacrine cells, displaced amacrine cells, bipolar cells, and displaced bipolar cells. [3H]-GABA was accumulated by amacrine cells and by cells in the ganglion cell layer that may be displaced amacrine or ganglion cells. [3H]-GABA was also taken up by horizontal cells, bipolar cells, and displaced bipolar cells.

On-Line Detection of Localized Defects in Bearings by Pattern Recognition Analysis

For automatic detection/diagnosis of localized defects in bearings, a pattern recognition analysis scheme was developed for investigating vibration signals of bearings. Two normalized and dimensionless features are extracted by short-time signal processing techniques. Employing these two features, two linear discriminant functions have been established to detect defects on the outer race and rollers of bearings, respectively. Results of fault detection/diagnosis, based on the experimental data of imposed bearing defects, indicated the technique to be 14 percent better in the rate of success for the detection of defects than the best among the state-of-the-art. It takes 20 seconds for data processing and fault diagnosis on a PC-AT on-line implementation.

A preliminary report on the derivatization-gas chromatographic determination of nalidixic acid and 3,7-dicarboxynalidixic acid in urine

A preliminary study on the gas chromatographic analysis of urine spiked with nalidixic acid and 3,7-dicarboxynalidixic acid is described. The method is based on the transfer of an ion-pair of NA or CNA with tetradecyldimethylbenzylammonium chloride (benzalkonium chloride) from alkaline aqueous solution into methyl isobutyl ketone (MIBK), the organic phase, where these salts are derivatized with pentafluorobenzyl bromide. The derivatives formed by this process are chromatographed on an analytical column packed with 1.5% OV-101 and detected with a flame-ionization detector. Several parameters affecting the transfer and/or derivatization of NA or CNA were investigated. These parameters include the phase transfer catalyst employed, the organic solvent used, the concentration of the acid and base added, the amount of derivatizing agent required, and reaction time and temperature.

Selected indices of micronutrient status in adult patients with sickle cell anemia (SCA)

In 24 adults with hemoglobin SS followed at the Duke University Comprehensive Sickle Cell Center, we have studied the following nutritional parameters: reduced ascorbic acid; dehydroascorbic acid; alpha and beta carotenes; cryptoxanthin; and alpha and gamma tocopherols in whole blood, washed red blood cells, plasma, or serum. In the same population we also examined reduced glutathione (GSH) and oxidized glutathione (GSSG). Fifteen of these 24 patients also were interviewed for usual dietary intakes using a 28-day dietary history. Data obtained from patients with hemoglobin SS, sickle cell anemia (SCA) were compared to those found for seven healthy normal black adults of similar age. Plasma alpha tocopherol levels were significantly lower in SCA individuals than those of the controls (P less than 0.004). Alpha and gamma tocopherol levels in sickle RBCs were significantly higher than those from RBC suspensions of control subjects (P less than 0.007, and P less than 0.001, respectively). All serum values for carotenoids examined, specifically, beta carotene, alpha carotene, and cryptoxanthin were also markedly depressed when compared to those of healthy controls (P less than 0.001, P less than 0.002, and P less than 0.001, respectively). No other statistically significant differences were found between the two groups for any of the remaining variables, including dietary estimates. Dietary analyses suggest that dietary intakes of SCA individuals exceeded the recommended daily allowances (RDA) of all macro- and micronutrients measured, and intakes of most nutrients exceeded those of black controls interviewed. These results suggest that in individuals with SCA, several micronutrients vital to maintaining reducing capacity are present in diminished quantities in plasma/serum. These anomalies exist in SCA patients even though their intake of these micronutrients are similar to those of healthy black men and women.

Effects of CNQX, APB, PDA, and kynurenate on horizontal cells of the tiger salamander retina

Effects of 6-cyano-7-nitroquinoxaline-2,3-dione (CNQX), 2-amino-4-phosphonobutyrate (APB), cis-2,3-piperidine dicarboxylic acid (PDA), and kynurenate (KYN) on the depolarizing actions of glutamate and kainate on horizontal cells (HCs) were studied in the larval tiger salamander retina. APB, PDA, and KYN hyperpolarized the HCs, but they failed to block either the actions of glutamate and kainate, or the HC light responses. APB and PDA did not cause membrane polarizations in either rods or cones, suggesting that the HC hyperpolarizations were not mediated by presynaptic actions of these compounds. CNQX, the newly synthesized non-NMDA (N-Methyl-D-Aspartate) receptor antagonist, blocked the HC light responses and the action of kainate, but not that of glutamate. These results suggest that the synaptic receptors in the tiger salamander HCs are probably non-NMDA although extra-synaptic NMDA receptors may exist in these cells.

Chloroplast biogenesis: quantitative determination of monovinyl and divinyl chlorophyll(ide) a and b by spectrofluorometry

Simultaneous equations for the determination of monovinyl (MV) and divinyl (DV) Chl a and b by spectrofluorometry in unsegregated mixtures of these tetrapyrroles were derived. The same equations can also be used for the quantitative determination of MV and DV chlorophyllide (Chlide) a and b in unpurified mixtures, after extraction of the Chls in hexane. The equations used differences in the Soret excitation maxima of these tetrapyrroles in ether at 77 degrees K, in order to correct the Soret excitation overlap between MV and DV Chl(ide) a and between MV and DV Chl(ide) b.

Effects of prolonged light exposure, GABA, and glycine on horizontal cell responses in tiger salamander retina

1. The effects of prolonged light exposure, gamma-aminobutyric acid (GABA), and glycine on the horizontal cell (HC) light responses were studied in the superfused flat-mounted isolated retinas of the larval tiger salamander. 2. Under prolonged dark-adapted conditions, the time-to-peak of the HC light response was approximately 2-4 s, and after the termination of prolonged (6-8 min) light exposure, the time-to-peak became approximately 0.5-1 s. 3. This prolonged light-induced change in response rise time was not observed in either photoreceptors or bipolar cells, and thus the change in HC response rise time may occur postsynaptically in the HC membrane. 4. Application of 100 microM of GABA mimicked prolonged darkness and reversibly slowed down the HC response rise time, and application of 100 microM bicuculline mimicked prolonged light exposure and reversibly sped up the HC response rise time. 5. Glycine also slowed down the HC response rise course, but its effect was not observable until the concentration was raised to 1-3 mM. Strychnine did not exert any effect on HC responses when applied alone, but it could reverse the glycine actions. 6. The actions of glycine disappeared in the presence of bicuculline, indicating that the GABA and glycine pathways were probably not independent. Application of 5-10 mM glycine produced an increase of flow of preloaded 3H-GABA from the retina. 7. These results indicate that GABA may be the primary modulator that slows down the kinetics of the postsynaptic membrane proteins in the HCs. The extracellular concentration of GABA is probably high in prolonged darkness, and it is low after prolonged light exposure. Glycine, when applied at high dose, results in an increase of GABA release that slows down the HC response time course. 8. Prolonged darkness and light exposure appear to modulate the HC response in the time domain through GABA, and this change in HC response time course is probably responsible for shaping the bipolar cell responses and making the retinal signals more transient under light-adapted conditions.

A Fast Algorithm for On-Line Machining Process Modeling and Adaptive Control

A fast, on-line algorithm for machining process modeling and control is proposed. The modeling is accomplished via a new recursive estimator that offers good accuracy at a minimal computational load. Its Fast Kalman-type version, that further reduces its computational complexity, is also presented. The adaptive controller, which is based on on-line identification and closed-loop pole assignment, is characterized by a low computational load and no need for a priori process information. The analytical results are supplemented by numerical simulations, where the proposed scheme is used for the control of a turning operation and shown to offer very good performance under noisy conditions and suddenly changing machining dynamics.

Modulation of rod-cone coupling by light

Although electrical coupling between rods and cones in the retina has been assumed to be static, it has now been shown that rod-cone coupling can be strengthened by light. Increment threshold measurements reveal that cone input to rods increases progressively as background light becomes brighter. Current injection into cones produces larger responses in adjacent rods in the presence of background light than in darkness. Weak coupling under dark-adapted conditions facilitates synaptic transmission of small rod signals, and strong coupling under light-adapted conditions enhances transmission of large cone signals.

Effects of background illumination on the horizontal cell responses in the tiger salamander retina

Synaptic transmission between photoreceptors and horizontal cells (HCs) was studied in the flat-mounted isolated retinas of the tiger salamander. Background illumination expedited the rise time of the HC light response, and the HC response rise time (HCRRT) reached steady state about 2 sec after the onset of the background illumination. The change in HCRRT is probably responsible for the background-induced enhancement of the HC responses to short light stimuli. The amplitude of the HC responses to 100 msec light steps in the presence of background illumination was 2-5 times larger than that measured under dark-adapted conditions. Background illumination exerted little effect on the response rise time in cones and bipolar cells, and thus it caused no significant response enhancement in those cells. The background-induced change in HCRRT correlated closely with the rod voltage but not with the HC voltage. These results suggest that the background-induced change in HCRRT is probably mediated by postsynaptic events in HCs because no significant time course change is observed in photoreceptors and bipolar cells (which share the same synapses with the HCs). A suppressive rod action on the cone inputs in HCs may be responsible for modulating the HCRRT. By shortening the HCRRT, background illumination regulates the frequency response of the photoreceptor-HC synapse and alters the capacity of spatial resolution of retinal bipolar cells.

The coexistence of three neuroactive substances in amacrine cells of the chicken retina

For the first time in the vertebrate retina, we have demonstrated that 3 neuroactive substances coexist in a single neuron. Using immunofluorescence, immunoperoxidase, and autoradiographic techniques, we found a subpopulation of amacrine cells in the chicken retina exhibited enkephalin- and neurotensin-like immunoreactivity and high-affinity uptake of glycine. Biochemical evidence showed that glycine release in this retina is inhibited by enkephalin and enhanced by neurotensin1.14. It is therefore possible that the two peptides form a push-pull system in self-regulating the glycine release from retinal amacrine cells.

The off-overshoot responses of photoreceptors and horizontal cells in the light-adapted retinas of the tiger salamander

Depolarizing overshoot responses at the cessation of a test light step were observed in horizontal cells (HCs) and in a population of photoreceptors (rodCS) in light-adapted retinas of the tiger salamander. An anode break regenerative conductance may contribute to the overshoot responses in rodcS(o-wave). The overshoot responses in HCs consist of two components: a fast alpha-wave whose amplitude and time course follow those of the o-wave; and a slow beta-wave whose amplitude and time course vary with the HC membrane voltage. These results are consistent with the notion that the alpha-wave is a postsynaptic response to the voltage overshoots of the o-waves in rodCS and the beta-wave is mediated by voltage-dependent conductances in the HC membrane. A possible function of the HC overshoot responses is to reset the amplitude of the light-adapted HC responses during repetitive or rapidly changing light stimulation.

Monitoring Drilling Wear States by a Fuzzy Pattern Recognition Technique

This paper introduces a new approach for on-line monitoring of drill wear states by using a fuzzy C-means algorithm. Experimental and simulation results have shown that drill wear conditions can be represented by four fuzzy grades. They are: “initial,” “small,” “normal,” and “severe.” The grade “severe” is proposed to be used as the prediction of tool replacement. This fuzzy technique is more adequate than conventional pattern recognition technqiues.

An In-Process Flatness Error Measurement and Compensatory Control System

The principles of a new in-process measurement and control system for flatness errors in machining have been introduced. The laser-based system consists of a stylus, a geometrical table measurement system, and a forecasting compensatory controller. Through the application of the proposed system to simulated and actual cutting data it has been shown that improvements of flatness on the order of 80 percent are feasible.

Melatonin enhances horizontal cell sensitivity in salamander retina

Intracellular electrophysiological recording techniques were utilized to investigate the possible function of retinal melatonin in the larval tiger salamander. Endogenous retinal melatonin was present and appeared to bind a membrane-enriched fraction of the salamander retina, as determined by radioimmunoassay and receptor binding studies. Melatonin added through the perfusion bath to flat-mounted retinas resulted in a horizontal cell (HC) hyperpolarization of 10-20 mV. Additionally, the amplitude of HC responses to short test flashes increased in the presence of melatonin. Voltage-intensity plots revealed that application of 500 microM of melatonin caused an increase of the HC light sensitivity and this effect was reversible. These results suggest that melatonin synthesized and released during the dark period of the diurnal cycle may alter the sensitivity of second-order neurons at a time of day when photopic input is at its lowest level.

Localization of tyrosine-hydroxylase-like-immunoreactive amacrine cells in the larval tiger salamander retina

Immunocytochemistry was used to localize the populations of tyrosine-hydroxylase-like (TH)-immunoreactive cells in the tiger salamander retina. Ninety percent of these cells possessed somas that were situated in the innermost cell row of the inner nuclear layer and were classified as amacrine cells. Ten percent of TH-immunoreactive somas were located in the ganglion cell layer and were tentatively designated as those of displaced amacrine cells. The processes of TH-immunoreactive cells ramified most heavily in sublayer 1 of the inner plexiform layer, while a relatively small number of TH-labelled processes distributed in sublayers 3 and 5. Less than 1% of TH-immunoreactive cells in the amacrine cell layer exhibited a short process of somal origin that extended distally toward the outer plexiform layer. However, these processes did not cross the whole of the inner nuclear layer, and no immunolabelling was observed in the outer plexiform layer. An examination of retinal whole-mounts revealed that TH-immunoreactive amacrine and displaced amacrine cells were distributed throughout the center and periphery of the retina. The density of TH-immunolabelled amacrine cells was calculated to be 49 +/- 13 (mean +/- standard error) cells per mm2. The vast majority of TH-immunoreactive amacrine and displaced amacrine cells exhibited a stellate appearance and gave rise to three or more primary dendrites. A few TH-amacrine and displaced amacrine cells possessed two primary dendrites that emerged from opposite sides of their somas. The processes of TH-immunoreactive cells were generally poorly branched and varicose with terminal branches sometimes appearing thin and beaded. Because some TH-immunolabelled processes were very long, there was considerable overlap between the dendritic fields of neighboring TH-cells. Lastly, individual TH-immunoreactive amacrine and displaced amacrine cells were often observed in whole-mounts to provide processes that ramified at more than one level of the inner plexiform layer.

Sequence duplication and internal deletion in the integrated human papillomavirus type 16 genome cloned from a cervical carcinoma

Integrated human papillomavirus type 16 (HPV16) sequences were cloned from a cervical carcinoma and analyzed by restriction mapping and nucleotide sequencing. The viral integration sites were mapped within the E1 and E2 open reading frames (ORFs). The E4 and E5 ORFs were entirely deleted. An internal deletion of 376 base pairs (bp) was found disrupting the L1 and L2 ORFs. Sequencing analysis showed that an AGATGT/ACATCT inverted repeat marked the deletion junction with two flanking direct repeats 14 and 8 bp in length. A 1,330-bp sequence duplication containing the long control region (LCR) and the E6 and E7 ORFs was also found. The duplication junction was formed by two 24-bp direct repeats with 79% (19 of 24) homology located within the LCR and the E2 ORF of the prototype viral genome, respectively. This observation leads us to propose that the initial viral integration involved an HPV16 dimer in which the direct repeats in tandem units recombined, resulting in reiteration of only a portion of the original duplication. A guanosine insertion between nucleotides 1137 and 1138 created a continuous E1 ORF which was previously shown to be disrupted. Results from this study indicate that sequence reiteration and internal deletion in the integrated, and possibly in the episomal, HPV16 genome are influenced by specific nucleotide sequences in the viral genome. Moreover, reiteration of the LCR/E6/E7 sequences further supports the hypothesis that the E6/E7 ORFs may code for oncogenic proteins and that regulatory signals in the LCR may play a role in cellular transformation.

Neural interactions mediating the detection of motion in the retina of the tiger salamander

The neural circuitry underlying movement detection was inferred from studies of amacrine cells under whole-cell patch clamp in retinal slices. Cells were identified by Lucifer yellow staining. Synaptic inputs were driven by "puffing" transmitter substances at the dendrites of presynaptic cells. Spatial sensitivity profiles for amacrine cells were measured by puffing transmitter substances along the lateral spread of their processes. Synaptic pathways were separated and identified with appropriate pre- and postsynaptic pharmacological blocking agents. Two distinct amacrine cell types were found: one with narrow spread of processes that received sustained excitatory synaptic current, the other with very wide spread of processes that received transient excitatory synaptic currents. The transient currents found only in the wide-field amacrine cell were formed presynaptically at GABAB receptors. They could be blocked with baclofen, a GABAB agonist, and their time course was extended by AVA, a GABAB antagonist. Baclofen and AVA had no direct affect upon the wide-field amacrine cell, but picrotoxin blocked a separate, direct GABA input to this cell. The narrow-field amacrine cell was shown to be GABAergic by counterstaining with anti-GABA antiserum after it was filled with Lucifer yellow. Its narrow, spatial profile and sustained synaptic input are properties that closely match those of the GABAergic antagonistic signal that forms transient activity (described above), suggesting that the narrow-field amacrine cell itself is the source of the GABAergic interaction mediating transient activity in the inner plexiform layer (IPL). Other work has shown a GABAB sensitivity at some bipolar terminals, suggesting a population of bipolars as the probable site of interaction mediating transient action. The results suggest that two local populations of amacrine cell types (sustained and transient) interact with the two populations of bipolar cell types (transient forming and nontransient forming). These interactions underlie the formation of the change-detecting subunits. We suggest that local populations of these subunits converge to form the receptive fields of movement-detecting ganglion cells.

Quantitative studies of enkephalin's coexistence with gamma-aminobutyric acid, glycine and neurotensin in amacrine cells of the chicken retina

Previous double-label studies demonstrate that enkephalin coexists with gamma-aminobutyric acid, glycine or neurotensin in amacrine cells of the chicken retina. The present study utilizes double- and triple-label paradigms to quantitatively analyze these coexisting relationships. Twenty-eight percent of enkephalin-like immunoreactive amacrine cells were found to exhibit high-affinity uptake of [3H]GABA, while 53% of enkephalin-amacrine cells specifically accumulate [3H]glycine. Moreover, the present study predicts that at least 26% of enkephalin-amacrine cells which accumulate [3H]glycine should also be immunoreactive for neurotensin.

Localization of neurotensin-like immunoreactive amacrine cells in the larval tiger salamander retina

Light microscopic immunocytochemistry was used to localize the populations of NT-like immunoreactive amacrine cells in the larval tiger salamander retina. Seventy-nine percent of NT-immunostained cells observed in transverse cryo-prepared sections were classified as Type 1 amacrine cells. Another 6% were classified as Type 2 amacrine cells, while 15% of the NT-cells had their cell bodies situated in the ganglion cell layer and were tentatively designated as displaced amacrine cells. Each type of NT-like immunoreactive cell was observed in the central and peripheral retina. NT-immunostained processes were observed to ramify in sublayers 3 and 5 of the inner plexiform layer. An examination of retinal whole mounts revealed that NT-amacrine cells were distributed throughout the center and periphery of the retina at a density of 82 +/- 24 cells/mm2. The dendritic fields of NT-immunostained amacrine and displayed amacrine cells were observed to be either symmetrically or asymmetrically distributed about their somas. Symmetrical dendritic fields were generally oval-shaped and ranged in diameter from 250 to 500 micron (major axis) by 150 to 250 micron (minor axis). Asymmetrical dendritic fields were observed to encompass one-half or less of an imaginary circle surrounding their soma of origin and were orientated in all directions. The processes forming asymmetrical dendritic fields ranged from 75 to 260 micron in length. Furthermore, partial overlap was often observed between the dendritic fields of adjacent NT-amacrine cells.

Computer Models for the Mechanics of Three-Dimensional Cutting Processes—Part II: Results for Oblique End Turning and Drilling

Using the method described in Part I, numerical models for predicting chip form and the principal components of power consumption are developed for oblique end turning and drilling. Applying the method involves mainly specifying appropriate sets of independent variables for minimization calculations. Results predicted using the rigid-viscoplastic material model are compared with measurements from unlubricated tests on steel and aluminum alloy samples. The agreement between predicted and measured results for turning is generally good, particularly for chip thickness values, chip-tool contact lengths, and the qualitative effect of varying the depth of cut. The agreement is not as good for drilling; in drilling the main cutting edge torque contribution and qualitative effects of varying the spindle speed and feed rate are accurately predicted, but the average chip thickness is consistently underestimated while chip radii of curl are overestimated. The lack of agreement for the last two outputs appears to be due to constraint from the hole drill flute surf aces which would limit maximum radii of curl.

Computer Models for the Mechanics of Three-Dimensional Cutting Processes—Part I: Theory and Numerical Method

A numerical modeling method for predicting chip form and power requirements in three-dimensional cutting processes is described. The method is based on variational (energy) results from the theory of rigid-plastic materials and is applicable to the steady-state cutting of ductile metals. The analysis involves mainly material behavior assumptions and for simple material models yield results similar to the widely-used minimum work approach. In Part I the theoretical basis of the method and the appropriate numerical algorithm (gradient search or steepest descent) for implementation in specific processes are described. Results for the oblique end turning and drilling processes are compared with experimental data in Part II.

Electrical coupling between rods and cones in the tiger salamander retina

Electrical coupling between rods and cones was studied in the salamander (Ambystoma tigrinum) retina by measuring the light responses and spectral sensitivities of rods and cones and by measuring the voltage responses from a rod to current pulses injected into a cone. A population of 10-20% of the photoreceptors exhibited a mixed-response waveform of the rod and the cone under dark-adapted conditions, and a response waveform closely resembled that of a cone in the presence of background illumination. Lucifer yellow injection revealed that these cells are morphologically identical to rods, and thus they are named rodcs. Dark-adapted rodcs exhibited a rod-like spectral sensitivity with a peak at approximately 520 nm that shifted to a cone-like spectral sensitivity with a peak at approximately 620 nm in response to background light (Purkinje shift). The voltage response of a rodc to a -1-nA current step injected into an adjacent cone is approximately 3.6 times larger than that of a rod to the same current step. These results indicate that there is a population of rods (rodcs) in the tiger salamander retina that is strongly coupled to the cones and that these cells allow significant mixture of rod and cone signals at the photoreceptor level.

Development of a Forecasting Compensatory Control System for Cylindrical Grinding

A forecasting compensatory control (FCC) system was developed to improve workpiece roundness in cylindrical grinding operations. The spindle radial error motion (SREM) at the grinding position, identified as the dominant error source was modeled by an autoregressive model and compensated for by a forecasting algorithm. A digital method for measuring SREM at the grinding position which incorporates master roundness compensation was proposed and a piezo-electric drive system for the generation of the compensatory mechanical motion was developed. The implementation of the proposed method resulted in a substantial improvement of workpiece roundness.

An Analysis of the Drill Wandering Motion

An analytical model has been developed to investigate the drill wandering motion quantitatively. It has been shown mathematically why the resulting distorted polygon-shaped hole always has an odd number of sides during drill entry, and how the profile of the hole gradually becomes round with increasing hole depth. Drilling processes were simulated using this mathematical model and the results compared with experimental evidence. Subsequently, an experimental analysis on the influence of point geometry on drill wandering has been presented.

In-Process Control of Cylindricity in Boring Operations

This paper presents a new on-line control scheme utilizing the Forecasting Compensatory Control (FCC) method for improving cylindricity in boring operations. The proposed control method was implemented through the development of a laser-based in-process cylindricity measurement, a digital microcomputer, and a piezoelectric actuator system. Through on-line cutting experiments, the improvement in cylindricity accuracy was found to be in excess of 60 percent.

Signal clipping by the rod output synapse

The properties of synapses between retinal neurons make an essential contribution to early visual processing. Light produces a graded hyperpolarization in photoreceptors, up to 25 mV in amplitude, and it is conventionally assumed that all of this response range is available for coding visual information. We report here, however, that the rod output synapse rectifies strongly, so that only potential changes within 5 mV of the rod dark potential are transmitted effectively to postsynaptic horizontal cells. This finding is consistent with the voltage-dependence of the calcium current presumed to control neurotransmitter release from rods. It suggests functional roles for the strong electrical coupling of adjacent rods and the weak electrical coupling of adjacent rods and cones. The existence of photoreceptor coupling resolves the apparent paradox that rods have a 25 mV response range, while signals greater than 5 mV in amplitude are clipped during synaptic transmission. We predict that the strengths of rod-rod and rod-cone coupling are quantitatively linked to the relationship between the rod response range and the synapse operating range.