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.

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.

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.

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.

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.

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.

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.

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.

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.

Synaptic connections between neurons in living slices of the larval tiger salamander retina

Synaptic connections between retinal cells were studied by recording simultaneously from pre- and postsynaptic cells in the retinal slice preparation. The time course and waveform of the pre- and postsynaptic light responses were monitored, and the postsynaptic voltage responses to presynaptic current injection were measured. Results obtained provide direct evidence showing that the rod-HBC and rod-HC synapses are sign-preserving, and the rod-DBC, HC-HBC and amacrine-DBC synapses are sign-inverting. Moreover, the synaptic delays between rods and bipolar cells are shorter than that between rods and horizontal cells. The methodology of making retinal slices and the subsequent recording and stimulation procedures are described. The advantages of the retinal slice preparation and its potential in retinal research are discussed.

Interactions between enkephalin and gamma-aminobutyric acid in the larval tiger salamander retina

Both double-label and intracellular electrophysiological recording techniques were utilized to investigate the interactions between enkephalin and gamma-aminobutyric acid in the larval tiger salamander retina. Double-label studies revealed that the vast majority (greater than 96%) of enkephalin-immunostained amacrine cells also exhibit high affinity uptake of [3H]gamma-aminobutyric acid. Electrophysiological evidence demonstrated that morphine and gamma-aminobutyric acid exert opposite effects on a population of On-Off ganglion cells. gamma-Aminobutyric acid decreased the activity of these cells, while enkephalin increased their activity. These findings support the idea that opiate-mediated pathways inhibit GABAergic pathways in the vertebrate retina.

Light-dependent synaptic delay between photoreceptors and horizontal cells in the tiger salamander retina

A long delay between the time to peak of the photoreceptor and horizontal cell light responses was observed in dark-adapted tiger salamander retinas. The rise of the HC light responses follows a biphasic time-course which is probably mediated by the removal of the rod and cone transmitters, but not by voltage-dependent mechanisms in the HC membrane. A bleaching white light shortens the signal delay and results in a faster and monophasic rise of the HC light responses mediated predominantly by the cones.

Changes in response waveform of retinal horizontal cells during dark and light adaptation

Changes in response waveform of retinal horizontal cells during dark and light adaptation were examined in the tiger salamander retina. In addition to sensitivity changes, the response waveform of HC was altered during visual adaptation: following bleaching or in the presence of background illumination, a transient depolarizing overshoot was observed at the cessation of the test flash. In contrast to the hyperpolarizing light responses, the depolarizing off-overshoots do not follow the standard threshold recovery time course during dark adaptation, neither do they obey Weber's law for increment thresholds during light adaptation. Simultaneous intracellular recordings from photoreceptors and HC revealed that the off-overshoot responses in light-adapted HC are probably originated from a population of cells in the photoreceptor layer which are strongly coupled with the cones.

Analysis of six distinct integrated hepatitis B virus sequences cloned from the cellular DNA of a human hepatocellular carcinoma

Six distinct hepatitis B virus (HBV) integrations and the flanking cellular sequences were cloned from a hepatoma DNA preparation. None of the cloned fragments retains the entire HBV sequences but the surface antigen (HBsAg) gene and the HBV enhancer are retained in three of the six clones. The other three clones carry only short and possibly highly rearranged HBV genomic sequences and seem to contain some GC-rich clusters. Members of the repetitive Alu family are also found in the vicinity of five of the six integration regions which may have contributed to genome instability. In these six clones, the preferred integration sites are shown to lie within the single-strand region of the HBV genome. None of the clones carries in the flanking cellular sequences any of the 17 oncogenes tested, although the possibility still exists that an oncogene may be found on the side of the genome which has not been cloned. This work thus paves the way for detailed sequence analysis of virus-host junctions, for transfection studies of the HBV integration events, and for a search of genes in the flanking cellular sequences which may have been activated by the retained HBV enhancer using the clones described.

Effect of vector type, host strains and transcription terminator on heterologous gene expression in yeast

Using the surface antigen gene of the hepatitis B virus, and the promoter and terminator sequences of the yeast pho5 gene as a model system, a series of closely related expression plasmids were constructed to investigate the effect of vector type, genetic background of host strains and the presence of transcription terminator on the expression of heterologous gene in yeast. Plasmids carrying the replication origin of the 2 mu plasmids were found to be much more stable than those either independently or simultaneously carrying ars1 sequences. Gene expression was also higher with 2 micron-based plasmids. Yeast selection marker (trp1 or leu2) and therefore the host strains used did not have significant effects on gene expression. Addition of transcription terminator sequences downstream to the HBsAg gene also contributed only limited increases in gene expression levels.

Effects of gamma-aminobutyric acid on cones and bipolar cells of the tiger salamander retina

The gamma-aminobutyric acid (GABA) system in the tiger salamander retina was studied using autoradiographic and electrophysiological techniques. A high-affinity uptake mechanism for GABA has been localized in about 60% of the horizontal cells and about 30% of the amacrine cells. Effects of exogeneously applied GABA on the membrane conductance of cones and hyperpolarizing bipolar cells (HBC) were examined using the two electrode current-clamp technique in the living retinal slices. In both cell types, 1 mM of GABA caused a conductance increase. In perfused eyecups, 2 mM of GABA selectivity abolished the surround response of the HBC and left the center response unchanged. These results are consistent with the notion that a population of horizontal cells and a population of amacrine cells in the salamander retina may use GABA as their neurotransmitter.

Restriction fragment length polymorphism of the human beta-globin gene cluster: analysis of a beta-thalassemic family in Taiwan

We have analysed seven polymorphic restriction sites of the human beta-globin gene cluster of six members of a Chinese family with a beta +-thalassemic sibling. The seven polymorphic sites analysed are the HincII site at the 5'-end of the epsilon-globin gene, the HindIII sites in the two gamma-globin genes, two HincII sites within and at the 3'-end of the psi beta 1 pseudogene, the AvaII site in the beta-globin gene and the BamHI site located at the 3' side of the beta-globin gene. The beta thal chromosome has been identified to have a haplotype of +----++ with respect to these seven polymorphic sites. This is also the most predominant haplotype associated with beta +-thalassemia in Mediterranean and Chinese populations (Chen et al., 1984; Orkin et al., 1982). Of the seven sites analysed in this family, four will be useful in prenatal diagnosis of beta-thalassemia in subsequent pregnancies in the family.

The effect of light on the spread of signals through the rod network of the salamander retina

Adjacent rods in the amphibian retina are electrically coupled to each other by gap junctions. By injecting current pulses into one rod and recording the voltage change produced in nearby rods, we have studied the extent to which signals spread between rods in the presence and absence of illumination. Light has little effect on the steady potentials produced in nearby rods by the injection of a hyperpolarizing current, but does affect the propagation of transient signals through the rod network. The responses to injection of depolarizing current are increased by light. These effects of light were mimicked by hyperpolarizing the rod network (non-uniformly) by injecting continuous current (on top of which current pulses were superimposed to monitor signal spread). This suggests that the effects of light are due solely to the rod hyperpolarization produced by light. The effects of light are not completely predicted from computer simulations based on a previous characterization of the properties of isolated rods; these experiments thus reveal an inadequacy in the description of the rod membrane currents in that model. Light-induced hyperpolarization of cones has no effect on signal spread between rods. The functional significance of these results is discussed.

State of hepatitis B virus DNA in leucocytes of hepatitis B patients

Hepatitis B virus (HBV) DNA in leucocytes from 50 hepatitis patients with various patterns of HBV serological markers and serum HBV DNA and 13 normal controls were examined by Southern blot hybridization with 32P-labeled 3.2 Kb HBV DNA. A free form of HBV DNA was observed in leucocytes of 8 patients, 7 of whom were positive for serum HBeAg, and in 6 patients an integrated form of HBV DNA was identified. HBV DNA was not identified in leucocytes from 13 normal controls. The free form of HBV DNA in leucocytes existed as a heterogeneous smear from 2.0 to 3.2 Kb, similar to the pattern in liver and hepatocellular carcinoma cells but different from serum HBV DNA in which the 3.2 Kb band was absent. The banding pattern of the integrated form of HBV DNA in leucocytes varied among different patients. During preparation of white blood cells and purification of HBV DNA probes, it was important to remove plasma contamination and traces of pBR322, respectively. The presence of extrachromosomal DNA sequences partially homologous to pBR322 could cause false results. The presence of a free and integrated form of HBV DNA in leucocytes is important for explaining the biology of HBV, the harbouring and replication sites of extrahepatic origin, the mechanism of recurrent infection, and the rationale of the treatment of hepatitis B.

Characteristics of hepatitis B surface antigen produced in yeast

We have constructed an expression plasmid for regulated expression of the hepatitis B surface antigen gene in yeast using promoter of the yeast Pho5 gene. In the yeast transformants, the monomeric HBsAg (22K dalton) was estimated to constitute approximately 3% of the total proteins. On extraction, the HBsAg was found to have a buoyant density of 1.18 g/ml and an Sw.20 value of 54. Electron microscopy revealed particles of heterogeneous size ranging from 18-28 nm. When the yeast HBsAg was used to immunize guinea pigs, the anti-HBsAg antibodies produced could react with human serum HBsAg.

Microbiological examination of foods sold via vending machines

A total of 153 food specimens obtained from vending machines in Taipei city were subjects for the microbiological examination. Based on the standards for total microbial counts and total coliform counts established by the Department of Public Health, Republic of China, the unsatisfactory percentage of such counts for foods sold from vending machines were: 14% for carbonated beverages, 71% for non-carbonated beverages, 73% for ice cubes, and 100% for soft ice cream. Among the non-carbonic acid beverages examined, the unsatisfactory percentage for iced coffee, cocoa, chocolate milk, and fruit milk reached 90%. Escherichia coli and fecal streptococci each were found once. None of the pathogens causing food-poisoning were found during the study. As for the sanitation control of vending machines examined, 66 to 74% percent were unsatisfactory.

Chloroplast biogenesis. Molecular structure of chlorophyll b (E489 F666)

Nuclear magnetic resonance analysis established the presence of two vinyl groups/macrocycle of chlorophyll b (E489 F666). The latter is the only chlorophyll b that accumulates in a corn mutant (ON 8147). On the other hand the presence of only one vinyl group/macrocycle of authentic monovinyl chlorophyll b (E475 F660) was confirmed.

A quantitative analysis of interactions between photoreceptors in the salamander (Ambystoma) retina

A quantitative description of the electrical properties of the photoreceptor layer in the salamander retina was obtained from earlier data on the characteristics of isolated rods and cones and on rod-rod coupling, and from new data on rod-cone and cone-cone coupling and on the rod photocurrent. Injecting -1 nA current into a rod elicits hyperpolarizations of about 20 mV in an adjacent rod and 4 mV in an adjacent cone. Responses of more distant receptors are smaller. Injecting -1 nA into a cone elicits hyperpolarizations of about 4 mV in an adjacent rod and 0.4 mV in a nearby cone. Depolarizing current evokes smaller responses. Assuming, in agreement with anatomical evidence, that each rod is electrically coupled to four rods and to four cones around it, and that there is no direct electrical coupling between cones, we found these results could be predicted from the properties of isolated rods and cones if adjacent rods are coupled by a resistance of 300 M omega and adjacent rods and cones are coupled by a resistance of 5000 M omega. The small cone-cone coupling seen is due to coupling via intervening rods. The two halves of double cones are not electrically coupled. The spectral sensitivity of both halves is a maximum around 620 nm wave-length. The rod photocurrent has been characterized by voltage-clamping rods isolated from the retina. In agreement with Bader, MacLeish & Schwartz (1979) we found the time course of the photocurrent to be approximately independent of voltage between -35 and -85 mV. The voltage responses of rods, single cones and double cones isolated from the retina obey the principle of univariance. Responses of receptors in the retina do not obey univariance. The main deviations from univariance observed can be explained if adjacent rods and cones are coupled by a resistance of 5000 M omega. Our data demonstrate that rod-cone coupling is relatively weak. We simplified our description of the photoreceptor network, by omitting cones, to investigate the spatiotemporal processing that the rod network is capable of. Computer simulations predict, as is found experimentally, that the rod voltage response to a large spot of bright light should show a much more pronounced initial transient hyperpolarization than the response to a small spot of light of the same intensity. This difference is produced by the combination of electrical coupling of the rods with the existence of a voltage-gated current, IA, in the rod membrane.(ABSTRACT TRUNCATED AT 400 WORDS)