hydra Mutants of Arabidopsis are defective in sterol profiles and auxin and ethylene signaling

The hydra mutants of Arabidopsis are characterized by a pleiotropic phenotype that shows defective embryonic and seedling cell patterning, morphogenesis, and root growth. We demonstrate that the HYDRA1 gene encodes a Delta8-Delta7 sterol isomerase, whereas HYDRA2 encodes a sterol C14 reductase, previously identified as the FACKEL gene product. Seedlings mutant for each gene are similarly defective in the concentrations of the three major Arabidopsis sterols. Promoter::reporter gene analysis showed misexpression of the auxin-regulated DR5 and ACS1 promoters and of the epidermal cell file-specific GL2 promoter in the mutants. The mutants exhibit enhanced responses to auxin. The phenotypes can be rescued partially by inhibition of auxin and ethylene signaling but not by exogenous sterols or brassinosteroids. We propose a model in which correct sterol profiles are required for regulated auxin and ethylene signaling through effects on membrane function.     

Arterial pulse modulated activity is expressed in respiratory neural output.

Although it is well-established that sympathetic activity is modulated with respiration, it is unknown whether neural control of respiration is reciprocally influenced by cardiovascular function. Even though previous studies have suggested the existence of pulse modulation in respiratory neurons, they could not exclude the possibility that such cells were involved in cardiovascular rather than respiratory motor control, owing to neuroanatomic and functional overlaps between brain stem neurons involved in respiratory and cardiovascular control. The aim of this study was to test the hypothesis that respiratory motoneurons and putative premotoneurons are modulated by arterial pulse. An existing data set composed of 72 well-characterized, respiratory-modulated brain stem motoneurons and putative premotoneurons was analyzed using delta(2), a recently described statistic that quantifies the magnitude of arterial pulse-modulated spike activity [Dick TE and Morris KF. J Physiol 556: 959-970, 2004]. Neuronal activity was recorded in the rostral and caudal ventral respiratory groups of 19 decerebrate, neuromuscular-blocked, ventilated cats. Axonal projections were identified by rectified and unrectified spike-triggered averages of recurrent laryngeal nerve activity or by antidromic activation from spinal stimulation electrodes. The firing rates of approximately 30% of these neurons were modulated in phase with both the respiratory and cardiac cycles. Furthermore, arterial pulse modulation occurred preferentially in the expiratory phase in that only expiratory neurons had high delta(2) values and only expiratory activity had significant delta(2) values after partitioning tonic activity into the inspiratory and expiratory phases. The results demonstrate that both respiratory motoneurons and putative premotoneuronal activity can be pulse modulated. We conclude that a cardiac cycle-related modulation is expressed in respiratory motor activity, complementing the long-recognized respiratory modulation of sympathetic nerve activity.     

Ventrolateral medullary respiratory network and a model of cough motor pattern generation

The primaryhypothesis of this study was that the cough motor pattern is produced,at least in part, by the medullary respiratory neuronal network inresponse to inputs from "cough" and pulmonary stretch receptorrelay neurons in the nucleus tractus solitarii. Computer simulations ofa distributed network model with proposed connections from the nucleustractus solitarii to ventrolateral medullary respiratory neuronsproduced coughlike inspiratory and expiratory motor patterns. Predictedresponses of various "types" of neurons (I-DRIVER, I-AUG, I-DEC,E-AUG, and E-DEC) derived from the simulations were tested in vivo.Parallel and sequential responses of functionally characterizedrespiratory-modulated neurons were monitored during fictive cough indecerebrate, paralyzed, ventilated cats. Coughlike patterns in phrenicand lumbar nerves were elicited by mechanical stimulation of theintrathoracic trachea. Altered discharge patterns were measured in mosttypes of respiratory neurons during fictive cough. The resultssupported many of the specific predictions of our cough generationmodel and suggested several revisions. The two main conclusions were asfollows: 1) TheBötzinger/rostral ventral respiratory group neurons implicated inthe generation of the eupneic pattern of breathing also participate inthe configuration of the cough motor pattern.2) This altered activity ofBötzinger/rostral ventral respiratory group neurons istransmitted to phrenic, intercostal, and abdominal motoneurons via thesame bulbospinal neurons that provide descending drive during eupnea.

     

Large-scale production of class I bound peptides: assigning a signature to HLA-B*1501

 A peptide-based vaccine must be bound and presented by major histocompatibility complex class I molecules to elicit a CD8⁺ T-cell response. Because class I HLA molecules are highly polymorphic, it has yet to be established how well a vaccine peptide that stimulates one individual’s CD8⁺ cytotoxic T lymphocytes will be presented by a second individual’s different class I molecules. Therefore, to facilitate precise comparisons of class I peptide binding overlaps, we uniquely combined hollow-fiber bioreactors and mass spectrometry to assign precise peptide binding signatures to individual class I HLA molecules. In applying this strategy to HLA-B^*1501, we isolated milligram quantities of B^*1501-bound peptides and mapped them using mass spectrometry. Repeated analyses consistently assign the same peptide binding signature to B^*1501; the degree of peptide binding overlap between any two class I molecules can thus be determined through comparison of their peptide signatures. Received: 3 October 1996 / Revised: 20 November 1996     

A servo-controlled respiration system for inhalation studies in anesthetized animals

Rosenthal, Frank S., and Changhong Li. Aservo-controlled respiration system for inhalation studies inanesthetized animals. J. Appl.Physiol. 83(5): 1768-1774, 1997.To facilitate aerosol deposition experiments and aerosol exposures in anesthetized animals, a servo-controlled respiration system was developed and tested. The system induces ventilation by varying extrathoracic pressure in a whole body respirator in which an intubated animal isplaced. The pressure inside the whole body respirator is varied with athree-way servo-controlled spool valve connected to sources of positiveand negative pressure. A computer-based system detects respiratory flowand computes the controlling signal for the valve by using aproportional-integral-derivative algorithm, to achieve desired patternsof flow and volume vs. time. The system was used with dogs and found toaccurately induce various single-breath breathing patterns involvingconstant-flow inspirations and expirations as well as breath-holdperiods. A similar system was used to induced repeated breaths withdesired parameters for continuous exposure to particles and forventilation of animals between experiments.

     

Age,growth and life history of Culaea inconstans (Pisces: Gasterostidae) in Delta Marsh Lake Manitoba

Culaea inconstans in delta Area, Lake Manitoba matures in the second summer of life, when between 29 and 65 mm in total length and one year of age. Spawning starts at the end of May after migration into the creeks and channels in the marsh. By June 11–12 the yearlings are under 20 mm in total length. The greatest part of growth is completed in the first summer of life. The asymptotic or average maximum length, L was 89.06 mm. Aging of fish was done by reading otoliths and plotting length frequency histograms. Fish set the first ring, a false check, in otoliths within the first month of life and the annual ring is set by the adults on June 1 of the second summer of life. Culaea inconstans was generally found to be an annual fish which died after spawning in the second summer of life. A high positive correlation coefficient was found for body-otolith relationship. The length-weight regression lines were significantly different from one another and from zero, the F-value being significant at 1% level. The condition factor was found to be variable.     

Promotion of Mycoplasma pulmonis growth in rat tracheal organ cultures by ammonium chloride

During exacerbation of respiratory mycoplasmosis in rats by environmental ammonia, numbers of Mycoplasma pulmonis organisms in the respiratory tract are increased. To test whether or not exposure of respiratory epithelium to ammonia in vitro promotes growth of the organism, rat tracheal organ cultures were treated with 50 mM ammonium chloride, inoculated with M. pulmonis, and quantitatively cultured. After 48 hours, treated tracheas harbored almost 10 times more M. pulmonis colony-forming units than control tracheas. Cellular lesions in the epithelium of treated tracheas resembled those in the nasal passages of rats exposed to gaseous ammonia. To determine whether or not growth-modifying factors were released from tracheal epithelium exposed to ammonium chloride, M. pulmonis growth was assessed in medium collected from ammonium chloride-treated and control tracheas. Growth in medium from treated tracheas was greater than that in medium from untreated tracheas.     

Taurine enhances low density lipoprotein binding. Internalization and degradation by cultured Hep G2 cells

To evaluate the impact of taurine on hepatic cholesterol catabolism low density lipoprotein (LDL) binding, internalization and degradation were measured in cultured Hep G2 cells. Preincubation of cells with 0.1-10 mM taurine for 24 h stimulated LDL receptor activity by as much as 100%. Only the high affinity LDL receptor activity (specific) was increased by taurine preincubation, whereas the low affinity receptor activity (nonspecific) remained unchanged. Scatchard analysis of the binding data revealed that taurine doubled the number of LDL receptors without affecting receptor affinity. Taurine-enhanced LDL receptor activity was most pronounced when LDL concentrations exceeded 100 micrograms/ml, but was noted at taurine concentrations as low as 0.1 mM (plasma level). Interestingly, taurine had no effect on LDL receptor activity when it was added simultaneously with 125I-LDL to Hep G2 cells, or when non-bile acid-producing human skin fibroblasts were tested. Stimulation of LDL receptor activity was also obtained with 10 mM cysteine, a taurine precursor, but not with glycine. Increased cellular concentrations of taurine and cysteine were associated with an elevated rate of bile acid synthesis and a reduced cellular free cholesterol concentration. The data suggest that taurine enhanced LDL receptor activity by sparing cysteine, a known sulfhydryl group donor and stimulator of 7 alpha-hydroxylase activity, and that the latter stimulated bile acid production leading to increased utilization of cellular free cholesterol and enhanced LDL uptake.