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PubMed1982

A HRP study of the relation between cell size and motor unit type in cat ankle extensor motoneurons.

The dimensions of the somata and stem dendrites of 57 alpha- and three gamma-motoneurons, identified as to motor unit type and labeled by intracellular injection of horseradish peroxidase, were measured in the triceps surae and plantaris motor pools. The somata of type S motoneurons tended to be smaller (mean diameter 47.9 micrometers) than those of FF and FR units (52.5 and 53.1 micrometer, respectively) but these mean values were not significantly different and the data distributions showed considerable overlap between the unit types. The mean numbers and diameters of stem dendrites exhibited somewhat larger differences related to motor unit type and some of these were statistically significant. The total membrane area (AN) of each cell was estimated from measurements of the soma and stem dendrites, by using recent data and Ulfhake and Kellerth ('81) to calculate the membrane area of a dendritic tree from stem dendrite diameter. Mean AN varied with motor unit type in the sequence FF greater than FR greater than S (average values: 369 X 100(3) micrometers 2, 323 X 100(3) micrometers 2, and 250 X 100(3) micrometers 2, respectively). There was covariation between AN and the conduction velocity of the motor axon as well as with the force output from the muscle unit. Comparison of AN and motoneuron input resistance (RN) in 19 alpha-motoneurons suggested that the specific resistivity of the cell membrane in type S motoneurons was systematically higher than that characteristic of type FF or FR motoneurons.

Animals↗
PubMed1967

Isolation of phytochrome from the alga mesotaenium and liverwort sphaerocarpos.

Phytochrome has been isolated from the green alga Mesotaenium and the liverwort Sphaerocarpos. The Mesotaenium pigment had absorption peaks at 649 and 710 nm for the P(R) and P(FR) forms, respectively. Corresponding difference spectrum maxima for the Sphaerocarpos pigment were at 655 and 720 nm. While the absorption maxima differ, the reversibility and efficiency with which red and far-red light transform the Mesotaenium pigment are very similar to that reported for phytochrome isolated from etiolated seedlings of higher plants. Methods are described which allow efficient separation of phytochrome from highly pigmented light-grown material.

Journal Article↗
PubMed1968

Ultrastructural details in germinating sporangiospores of Rhizopus stolonifer and Rhizopus arrhizus.

Electron microscope examination of sporangiospore sections from Rhizopus stolonifer (Ehrenb. ex Fr.) Lind. and R. arrhizus Fischer revealed details on intracellular organization not previously reported. Aldehyde fixation followed by chromeosmium postfixation permitted clear depiction of ribosomes hitherto unrevealed in these cells. Mitochondria were diversiform. Spore wall structures in the two species were generally similar, but outer contours differed sufficiently to permit easy species identification in examination of sections. The spores of both species abounded in cytosomes, corresponding in size, shape, and heavy-metal "stain" affinities to spherosomes in cells of higher plants. The osmiophilic response of these spherosome-like inclusions was intensified by treatment of sections with thiocarbohydrazide solution and subsequent application of aqueous osmium tetroxide, which strengthens an assumption that they are lipid-rich. The margins of the spherosome-like inclusions in lead citrate-stained sections included dense particles, about 60 A across, whose crystalline-like arrangements suggested that protein as well as lipid was present. Frequent and close associations between the spherosome-like inclusions and various cell membranes suggested that such bodies participate in membrane elaboration during germination.

Cell Wall↗
PubMed2003

Utility of a 0.014" pressure-sensing guidewire to assess renal artery translesional systolic pressure gradients.

Renal ischemia due to renal artery stenosis (RAS) is an important cause of secondary hypertension and renal insufficiency. Several methods are available to diagnose RAS; however, the identification of clinically significant lesions remains problematic. We measured the translesional systolic pressure gradient (TSPG) with a 4 Fr catheter and a 0.014" pressure-sensing guidewire and compared these data to angiographic findings. The TSPG obtained by pressure-sensing guidewire correlated more strongly with angiographic minimal lumen diameter (r(2) = 0.801) than those obtained by 4 Fr catheter (r(2) = 0.360). The relationship of TSPG with percent stenosis was not strong, regardless of the method used (r(2) = 0.228 with pressure-sensing guidewire, 0.358 with 4 Fr catheter). Using a 0.014" pressure-sensing guidewire is effective for assessing TSPG and provides a more reliable indication of stenosis significance than use of a 4 Fr catheter.

Aged↗
PubMed2001

FHY1: a phytochrome A-specific signal transducer.

Phytochromes are plant photoreceptors that regulate plant growth and development with respect to the light environment. Following the initial light-perception event, the phytochromes initiate a signal-transduction process that eventually results in alterations in cellular behavior, including gene expression. Here we describe the molecular cloning and functional characterization of Arabidopsis FHY1. FHY1 encodes a product (FHY1) that specifically transduces signals downstream of the far-red (FR) light-responsive phytochrome A (PHYA) photoreceptor. We show that FHY1 is a novel light-regulated protein that accumulates in dark (D)-grown but not in FR-grown hypocotyl cells. In addition, FHY1 transcript levels are regulated by light, and by the product of FHY3, another gene implicated in FR signaling. These observations indicate that FHY1 function is both FR-signal transducing and FR-signal regulated, suggesting a negative feedback regulation of FHY1 function. Seedlings homozygous for loss-of-function fhy1 alleles are partially blind to FR, whereas seedlings overexpressing FHY1 exhibit increased responses to FR, but not to white (WL) or red (R) light. The increased FR-responses conferred by overexpression of FHY1 are abolished in a PHYA-deficient mutant background, showing that FHY1 requires a signal from PHYA for function, and cannot modulate growth independently of PHYA.

Alleles↗
PubMed2005

Reduction of peripheral flow reserve impairs endothelial function in conduit arteries of patients with essential hypertension.

BACKGROUND: A diminished flow reserve in resistance vessels is a hallmark of hypertensive microvascular disease. Hypertension is associated with structural alterations in the microcirculation and a reduced endothelium-dependent dilation in conduit arteries. Both have been demonstrated to predict future cardiovascular events. OBJECTIVE: We hypothesized that a reduced peripheral flow reserve impairs endothelial function in upstream conduit arteries in patients with arterial hypertension. DESIGN: In 43 hypertensive patients (HT) and 38 normotensive controls (NT) endothelial function of the brachial artery was assessed by measurement of flow-mediated dilatation (FMD), using high-resolution ultrasound. Peripheral flow reserve (FR) was determined via measurements of forearm blood flow at rest and during increments of reactive hyperaemia, using venous occlusion plethysmography. RESULTS: FMD was markedly impaired in HT (3.6 +/- 0.3%) as compared with NT (10.2 +/- 0.3%), whereas maximum brachial artery diameter following endothelium-independent dilatation was similar in both groups. In hypertensive patients FR was significantly reduced (HT, 3.2 versus NT, 6.0) during reactive hyperaemia after 5 min of ischaemia. FR was associated with FMD (r = 0.68, P < 0.01). Multiple stepwise regression analysis identified FR as a strong independent variable determining the extent of FMD (r2 = 0.46, P < 0.01). In HT the dose-response curve of FMD upon stepwise increases of FR was shifted significantly to the right. Normalization of FR improved FMD in HT by more than 60%. CONCLUSIONS: In essential hypertension a reduced FR contributes to the endothelial dysfunction of upstream conduit arteries. These findings may have therapeutic and prognostic implications in patients with arterial hypertension.

Adult↗
PubMed2003

Calf flow reserve with H(2)(15)O PET as a quantifiable index of lower extremity flow.

UNLABELLED: Objective measures of recruitable blood flow are of importance in angiogenesis trials. We validated a new PET-derived flow reserve (FR) measurement in healthy subjects and subjects with peripheral artery disease (PAD). METHODS: Five healthy volunteers and 5 subjects with PAD underwent cannulation of the femoral artery and vein. Basal and maximal flow (100 micro g/kg/min of adenosine infused intraarterially) in the lower extremity was determined using thermodilution (TD) techniques. Subjects then underwent plethysmography (PL) followed by PET measurements of blood flow at the calf level. For the PET studies, a transmission scan followed by injection of 1.85 GBq (50 mCi) H(2)(15)O and dynamic scanning for 5 min were acquired in five 1-min frames. Regions of interest were drawn on successive PET image slices, and radioactivity was quantified from the first-minute scan after injection. FR for each of the 3 modalities was expressed as the ratio of adenosine to basal flow. RESULTS: PET-derived FR correlated strongly with TD (r = 0.82; P = 0.004) but not with PL (r = 0.17; P = 0.85). The mean average difference in FR between healthy volunteers and PAD subjects was 13.0 with PET and 4.5 with TD. The intra- and intersubject variability for PET expressed as the coefficient of variation was 10.5% and 29.0% for healthy subjects and 7.0% and 52.9% in PAD, respectively. CONCLUSION: As expected, FR was significantly lower in PAD subjects compared with healthy subjects as assessed with TD and PET but not with PL. PET-derived FR appears to be reproducible and generates sharper and higher indices of recruitable flow in healthy subjects and PAD. These findings have implications for the use of PET-derived FR as a sensitive index of recruitable flow in angiogenesis trials.

Adenosine↗
PubMed1968

Some Properties of Phytochrome Isolated From Dark-grown Oat Seedlings (Avena sativa L.).

Phytochrome was partially purified from etiolated seedlings of Avena sativa L. Several properties of the red-absorbing (P(R)) and far-red absorbing (P(FR)) forms of the pigment were compared. The 2 forms could not be shown to differ with respect to their sedimentation velocity in sucrose density gradients, elution volume from Sephadex G-200 columns, binding properties on calcium phosphate, or electrophoretic mobility. P(FR), however, was more labile than P(R) during precipitation with 50% ammonium sulfate. Sephadex G-200 elution diagrams obtained with fresh phytochrome preparations revealed 2 components of different molecular weights, 1 roughly 180,000, and 1 roughly 80,000. Native phytochrome had an absorption spectrum in vivo showing an absorption maximum for P(R) of 667 nm. Both the large and small forms of phytochrome mentioned above can be maintained with an absorption maximum for P(R) of 667 nm. However, allowing them to remain for several hours as P(FR), even at 4 degrees , shifted this peak to 660 nm. The protein conformational change during phytochrome transformation may be quite small, though the various comparative techniques used do not strictly rule out a fairly large one. The need for maintaining the pigment as P(R) during all steps of purification, but particularly during ammonium sulfate precipitation is underscored.

Journal Article↗
PubMed1999

Targeting and subsequent selection of somatic hypermutations in the human V kappa repertoire.

The number and distribution of nucleotide substitutions in human VkappaJkappa genes were examined using a PCR technique that analyzed nonproductive and productive rearrangements amplified from genomic DNA of individual B cells. The results indicate that the mutational mechanism introduces replacement (R) mutations comparably throughout the length of the VkappaJkappa rearrangement, but tends to target specific triplets. Moreover, hotspots of mutational activity were identified in complementarity determining regions (CDR). A marked increase in the frequency of R mutations in CDR was noted when productive were compared to nonproductive rearrangements, indicating that these were selected into the expressed repertoire. Of note, amino acids encoded by codons adjacent to hotspots of mutation were also positively selected implying that similar regions were targeted for hypermutation and subsequent selection. In contrast to the distribution of CDR mutations, R mutations in the framework (FR) regions tended to be eliminated from productive VkappaJkappa rearrangements, implying that the somatic hypermutational machinery frequently introduced amino acid changes that were deleterious to the structural integrity of the kappa chain protein. The difference in the ratio of R to silent mutations in CDR and FR in the expressed repertoire, therefore, reflects the summation of positive selection of R mutations in the CDR and the elimination of R mutations in the FR. The data indicate that the balance between targeted mutation of VkappaJkappa rearrangements and subsequent selection and elimination governs the pattern of mutations manifest within the expressed kappa repertoire.

Alleles↗
PubMed2002

Role of endothelin ET(A)- and ET(B)-receptors in haemodynamic compensation following haemorrhage in anaesthetized rats.

1. This study examined the role of endothelin ET(A) and ET(B) receptors on haemodynamic compensation following haemorrhage (-17.5 ml kg(-1)) in thiobutabarbitone-anaesthetized rats. Rats were divided into four groups (n=6 each): time-control, haemorrhage-control, haemorrhage after treatment with FR 139317 (ET(A)-receptor antagonist), and haemorrhage after treatment with BQ-788 (ET(B)-receptor antagonist). 2. In the time-control rats, there were no significant changes in any haemodynamics for the duration of the experiments. Relative to the time-control rats, rats given haemorrhage had reduced mean arterial pressure (MAP), cardiac output (CO) and mean circulatory filling pressure (MCFP), but increased systemic vascular resistance (R(SV)). Venous resistance (R(V)) was slightly (but insignificantly) reduced by haemorrhage. MAP, however, gradually returned towards baseline (-17+/-4 and -3+/-2 mmHg at 10 and 60 min after haemorrhage, respectively) as a result of a further increase in R(SV). 3. Pre-treatment with FR 139317 (i.v. 1 mg kg(-1), followed by 1 mg kg(-1) h(-1)) accentuated haemorrhage-induced hypotension through abolition of the increase in R(SV). FR 139317 did not modify haemorrhage-induced changes in CO, MCFP and R(V). 4. Pre-treatment of BQ-788 (3 mg kg(-1)) did not affect MAP or MCFP following haemorrhage; however, CO was lower, and R(SV) as well as R(V) were higher relative to the readings in the haemorrhaged-control rats. 5. These results show that following compensated haemorrhage, ET maintains arterial resistance and blood pressure via the activation of ET(A) but not ET(B) receptors.

Anesthetics↗
PubMed2001

Folate receptor function is regulated in response to different cellular growth rates in cultured mammalian cells.

The folate receptor (FR) binds physiologic folates with nmol/L affinities and is expected to play an important role in transporting serum folates into cells that express this receptor. Although it has been shown that FR expression increases when extracellular levels of folate are low, whether this receptor is regulated in response to altered cellular requirements for folates or by intracellular levels of this vitamin has not been investigated. In this study, FR levels, FR function and cellular folate levels were measured in cells with different growth rates to investigate FR regulation of this receptor under conditions in which cellular requirements for folate are altered. These experiments used cells that endogenously express FR (JAR, Caco-2 and MA-104) and cells stably transfected with this receptor (FRGPI-16 and FRTM-8). FR function decreased as cellular growth slowed in four of the five cell lines examined. Although cellular folate levels also decreased as cells reached confluence, the total amount of cellular folate in the culture remained constant, suggesting the depleted cellular folate was because of the cell partitioning its pool throughout cell division, not because of decreased FR function. Conversely, there was an inverse association with FR levels and cell growth (r = -0.998 to -0.999, P < 0.05) in cells endogenously expressing FR, with a significant increase in the percentage of total FR located in an intracellular compartment as growth slowed. These results suggest FR function is regulated by cellular requirements for folates but not in response to changing FR levels or cellular levels of this vitamin.

Caco-2 Cells↗
PubMed1981

Simultaneous Phytochrome-controlled Promotion and Inhibition of Arginine Decarboxylase Activity in Buds and Epicotyls of Etiolated Peas.

The specific activity of arginine decarboxylase (ADC; l-arginine carboxylase; EC 4.1.1.19) rises steadily over an 8 hour experimental period in the growing buds and subapical epicotyl internodes of 6-day-old totally etiolated pea seedlings. Treatment with red light (R) completely annuls this rise in epicotyls but increases it in buds, thus paralleling the opposite effects of R on the growth of these two organs. Far red light (FR) reverses both effects of R on ADC and is, in turn, reversed by R, indicating phytochrome control. Effects in both organs are clearly seen within 2 hours. By 6 hours after R, the post-irradiation rise in ADC specific activity in buds is 3 times greater than that of the dark controls. Over the same period, ADC specific activity in epicotyls is inhibited by 56% relative to dark controls, reflecting zero net change after R and a continued rise in the dark. Cycloheximide inhibits the rise in ADC activity in both rapidly growing organs (epicotyls in dark and buds after R) but is without effect in both slower growing organs. Actinomycin D inhibits only in dark grown epicotyls, whereas chloramphenicol produces no inhibition in any system tested.ADC is the first enzyme to show a two-way, organ-specific response to phytochrome conversion from Pr to Pfr. This finding is discussed in relation to the growing evidence that polyamines formed from arginine may be important growth regulators in plants, as well as in microbial and animal cells.

Journal Article↗
PubMed2001

A plastidic ABC protein involved in intercompartmental communication of light signaling.

Plants perceive light via specialized photoreceptors of which the phytochromes (phyA-E), absorbing far-red (FR) and red light (R) are best understood. Several nuclear and cytoplasmic proteins have been characterized whose deficiencies lead to changes in light-dependent morphological responses and gene expression. However, no plastid protein has yet been identified to play a role in phytochrome signal transduction. We have isolated a new Arabidopsis mutant, laf (long after FR) 6, with reduced responsiveness preferentially toward continuous FR light. The disrupted gene in laf6 encodes a novel plant ATP-binding-cassette (atABC1) protein of 557 amino acids with high homology to ABC-like proteins from lower eukaryotes. In contrast to lower eukaryotic ABCs, however, atABC1 contains an N-terminal transit peptide, which targets it to chloroplasts. atABC1 deficiency in laf6 results in an accumulation of the chlorophyll precursor protoporphyrin IX and in attenuation of FR-regulated gene expression. The long hypocotyl phenotype of laf6 and the accumulation of protoporphyrin IX in the mutant can be recapitulated by treating wild-type (WT) seedlings with flumioxazin, a protoporphyrinogen IX oxidase (PPO) inhibitor. Moreover, protoporphyrin IX accumulation in flumioxazin-treated WT seedlings can be reduced by overexpression of atABC1. Consistent with the notion that ABC proteins are involved in transport, these observations suggest that functional atABC1 is required for the transport and correct distribution of protoporphyrin IX, which may act as a light-specific signaling factor involved in coordinating intercompartmental communication between plastids and the nucleus.

ATP-Binding Cassette Transporters↗
PubMed1991

An evaluation of ibuprofen bioinversion by simulation.

Using a pharmacokinetic model recently proposed to explain ibuprofen disposition in man, plasma concentrations of pure ibuprofen enantiomers were simulated following oral administration of (-)-(R)-ibuprofen, (+)-(S)-ibuprofen, or rac-ibuprofen. Simulated and literature values for AUC's were used to compare S/R ratios for different cases of the model and for different methods of calculating the fraction of R bioinverted to S. Numerical simulation using STELLA confirmed previous results for different cases of bioinversion. Simulated S/R AUC ratios, for administration of the racemate, ranged from 4.0 (presystemic bioinversion) to 1.66 (systemic bioinversion). Literature values for S/R AUC ratios averaged 1.53 +/- 0.2 for administration of the racemate; therefore, systemic bioinversion was concluded to be representative of ibuprofen disposition. Additional simulations of S/R AUC ratios, for administration of (-)-(R)-ibuprofen only, ranged from 1.5 (presystemic bioinversion) to 0.66 (systemic bioinversion). Literature values for S/R AUC ratios averaged 0.50 +/- 0.9 for administration of (-)-(R)-ibuprofen only, which again supported conclusions of systemic bioinversion. Using different equations for estimation of fraction of R inverted to S (FR----S), results based on simulated data were identical; however, FR----S values based on literature data were different. Therefore, assumptions made for different FR----S equations do not appear to be rigorous. Calculations of FR----S, based on literature data, averaged 0.52 overall, indicating bioavailability of (+)-(S)-ibuprofen may be similar for a 150 mg dose of (+)-(S)-ibuprofen compared to a 200 mg dose of racemate.

Humans↗
PubMed2001

Light reflected from red mulch to ripening strawberries affects aroma, sugar and organic acid concentrations.

Strawberry (Fragaria ananassa) fruit size and flavor are important to both growers and consumers. Plastic mulches are frequently used in raised-bed culture to conserve water, control weeds with less herbicides, keep fruit clean and produce ripe berries earlier in the season. The most commonly used plastic mulch color is black. We hypothesized that changing mulch color to reflect more far-red (FR) and red light (R) and a higher FR/R photon ratio would keep those benefits and improve berry size and flavor by altering phytochrome-mediated regulation of pathways in ripening berries. Size and chemical composition of berries developed in sunlight over a specially formulated red plastic were compared with those that developed over standard black plastic mulch. Berries that ripened over red were about 20% larger, had higher sugar to organic acid ratios and emitted higher concentrations of favorable aroma compounds. We conclude that FR and the FR/R ratio in light reflected from the red mulch on the soil surface acted through the natural phytochrome system within the growing plants to modify gene expression enough to result in increased fruit size and improved concentrations of phytonutrient, flavor and aroma compounds.

Acids↗
PubMed1997

Separation of Photolabile-Phytochrome and Photostable-Phytochrome Actions on Growth and Microtubule Orientation in Maize Coleoptiles (A Physiological Approach).

For separating the physiological actions of photolabile (phy-l) and photostable phytochromes, we compared the effects of red (R) and far-red (FR) light on elongation growth and microtubule reorientation in segments of maize (Zea mays L.) coleoptiles raised either in darkness (phy-l present) or preirradiated with R (phy-l eliminated). In 4.5-d-old dark-grown seedlings R first promoted growth and induced a transverse microtubule orientation. In continuous R the phytochrome action responsible for these responses was replaced by an opposite phytochrome action that produced a stable growth inhibition and longitudinal microtubule orientation. In R-preirradiated segments only the second type of phytochrome action could be observed. Reversion experiments with FR light pulses demonstrated that both types of phytochrome action were dependent on the FR-absorbing form of phytochrome and mirrored the actual phytochrome state after 1 h. We conclude from these and related results that growth promotion and transverse microtubule orientation are mediated by phy-l, whereas growth inhibition and longitudinal microtubule orientation are mediated by photostable phytochrome. The opposite actions of the two phytochromes can be separated by preirradiating the seedlings with R. Photoresponsiveness ascribed to phy-l disappeared after 5 d. phy-l appears to play a distinct but transitory role in coleoptile development.

Journal Article↗
PubMed2000

Resonance Raman spectroscopic study of the tryptic 39-kDa fragment of phytochrome.

The 39-kDa fragment of oat phytochrome phyA, obtained by tryptic digestion at the amino acids 65 and 425, was studied by resonance Raman spectroscopy. The parent state P(r) reveals far-reaching similarities with that of the native phytochrome implying that the structures of the tetrapyrrole chromophore and its immediate protein environment are not affected by the proteolysis. However, the resonance Raman spectrum of the final product of the P(r) phototransformation, denoted as P(bl), is more closely related to that of the P(fr) precursor of the native phytochrome, i.e. meta-R(C), rather than to that of P(fr) itself. The resonance Raman spectra indicate a high conformational flexibility of the chromophore in P(bl) so that, unlike in P(fr), the tetrapyrrole rings C and D adopt a largely coplanar conformation. The protein interactions with ring D of the chromophore, which in the native phytochrome stabilize the specific chromophore structure of P(fr), cannot be established in the 39-kDa fragment due to the lack of the major C-terminal part of the protein. These findings, furthermore, support the view that the meta-R(C)-->P(fr) transition is associated with a coupling of chromophore and protein structural changes that represent crucial events for the photoactivation of phytochrome.

Avena↗