PubMed Health⌕ Search

Biomedical subjects

D C Gordon

Publications and source records attributed to D C Gordon.

At least 19 recordsLinked to original sources
PubMed2002

Phenotype/genotype associations for yield and salt tolerance in a barley mapping population segregating for two dwarfing genes.

Barley traits related to salt tolerance are mapped in a population segregating for a dwarfing gene associated with salt tolerance. Twelve quantitative trait loci (QTLs) were detected for seven seedling traits in doubled haploids from the spring barley cross Derkado x B83-12/21/5 when given saline treatment in hydroponics. The location of QTLs for seedling growth stage (leaf appearance rate), stem weight prior to elongation, and tiller number are reported for the first time. In addition, four QTLs were found for the mature plant traits grain nitrogen and plot yield. In total, seven QTLs are co-located with the dwarfing genes sdw1, on chromosome 3H, and ari-e.GP, on chromosome 5H, including seedling leaf response (SGa) to gibberellic acid (GA(3)). QTLs controlling the growth of leaves (GS2) on chromosomes 2H and 3H and emergence of tillers (TN2) and grain yield were independent of the dwarfing genes. Field trials were grown in eastern Scotland and England to estimate yield and grain composition. A genetic map was used to compare the positions of QTLs for seedling traits with the location of QTLs for the mature plant traits. The results are discussed in relation to the study of barley physiology and the location of genes for dwarf habit and responses to GA.

Adaptation, Physiological↗
PubMed2001

Reduced lighting does not improve medical outcomes in very low birth weight infants.

OBJECTIVE: To objectively assess the effect of light reduction as an isolated environmental intervention on neonatal morbidity. STUDY DESIGN: Randomized multicenter trial. Neonates < 1251 g birth weight and < 31 weeks gestational age were randomly assigned to receive goggles or to a control group. Goggles that reduced visible light by 97% were placed within 24 hours of birth and remained in use until 31 weeks postmenstrual age or for a minimum of 4 weeks. RESULTS: Four hundred nine infants were enrolled, and outcome data are reported for 359 surviving infants. There were no significant differences between the groups in weight gain, duration of oxygen therapy, mechanical ventilation, or hospital stay either in the unadjusted analyses or in the analyses adjusted for birth weight, gestational age, race, sex, and inborn (born in study hospital) status. There was no difference between the groups in the incidence of intracranial hemorrhage. CONCLUSIONS: This randomized trial of continuous light reduction in the first few weeks of life for very low birth weight infants showed no effect on medical outcomes.

Child Development↗
PubMed2000

A lipopolysaccharide-specific enhancer complex involving Ets, Elk-1, Sp1, and CREB binding protein and p300 is recruited to the tumor necrosis factor alpha promoter in vivo.

The tumor necrosis factor alpha (TNF-alpha) gene is rapidly activated by lipopolysaccharide (LPS). Here, we show that extracellular signal-regulated kinase (ERK) kinase activity but not calcineurin phosphatase activity is required for LPS-stimulated TNF-alpha gene expression. In LPS-stimulated macrophages, the ERK substrates Ets and Elk-1 bind to the TNF-alpha promoter in vivo. Strikingly, Ets and Elk-1 bind to two TNF-alpha nuclear factor of activated T cells (NFAT)-binding sites, which are required for calcineurin and NFAT-dependent TNF-alpha gene expression in lymphocytes. The transcription factors ATF-2, c-jun, Egr-1, and Sp1 are also inducibly recruited to the TNF-alpha promoter in vivo, and the binding sites for each of these activators are required for LPS-stimulated TNF-alpha gene expression. Furthermore, assembly of the LPS-stimulated TNF-alpha enhancer complex is dependent upon the coactivator proteins CREB binding protein and p300. The finding that a distinct set of transcription factors associates with a fixed set of binding sites on the TNF-alpha promoter in response to LPS stimulation lends new insights into the mechanisms by which complex patterns of gene regulation are achieved.

Animals↗
PubMed2000

Wild barley: a source of genes for crop improvement in the 21st century?

The development of new barleys tolerant of abiotic and biotic stresses is an essential part of the continued improvement of the crop. The domestication of barley, as in many crops, resulted in a marked truncation of the genetical variation present in wild populations. This process is significant to agronomists and scientists because a lack of allelic variation will prevent the development of adapted cultivars and hinder the investigation of the genetic mechanisms underlying performance. Wild barley would be a useful source of new genetic variation for abiotic stress tolerance if surveys identify appropriate genetic variation and the development of marker-assisted selection allows efficient manipulation in cultivar development. There are many wild barley collections from all areas of its natural distribution, but the largest are derived from the Mediterranean region. The results of a range of assays designed to explore abiotic stress tolerance in barley are reported in this paper. The assays included; sodium chloride uptake in wild barley and a mapping population, effects for delta 13C and plant dry weight in wheat aneuploids, effects of photoperiod and vernalization in wild barley, and measurements of root length in wild barley given drought and nitrogen starvation treatments in hydroponic culture. There are examples of the use of wild barley in breeding programmes, for example, as a source of new disease resistance genes, but the further exploration of the differences between wild barley and cultivars is hampered by the lack of good genetic maps. In parallel to the need for genetic studies there is also a need for the development of good physiological models of crop responses to the environment. Given these tools, wild barley offers the prospect of a 'goldmine' of untapped genetic reserves.

Chlorides↗
PubMed2000

Using stable isotope natural abundances (delta 15N and delta 13C) to integrate the stress responses of wild barley (Hordeum spontaneum C. Koch.) genotypes.

To integrate the complex physiological responses of plants to stress, natural abundances (delta) of the stable isotope pairs 15N/14N and 13C/12C were measured in 30 genotypes of wild barley (Hordeum spontaneum C. Koch.). These accessions, originating from ecologically diverse sites, were grown in a controlled environment and subjected to mild, short-term drought or N-starvation. Increases in total dry weight were paralleled by less negative delta 13C in shoots and, in unstressed and droughted plants, by less negative whole-plant delta 13C. Root delta 15N was correlated negatively with total dry weight, whereas shoot and whole-plant delta 15N were not correlated with dry weight. The difference in delta 15N between shoot and root varied with stress in all genotypes. Shoot-root delta 15N may be a more sensitive indicator of stress response than shoot, root or whole-plant delta 15N alone. Among the potentially most productive genotypes, the most stress-tolerant had the most negative whole-plant delta 15N, whether the stress was drought or N-starvation. In common, controlled experiments, genotypic differences in whole-plant delta 15N may reflect the extent to which N can be retained within plants when stressed.

Carbon Isotopes↗
PubMed1994

A multistate outbreak of Escherichia coli O157:H7-associated bloody diarrhea and hemolytic uremic syndrome from hamburgers. The Washington experience.

OBJECTIVE: To determine the source of and describe a large outbreak of Escherichia coli O157:H7 infections in Washington State. DESIGN: Case-control study; environmental investigation; provider-based surveillance for E coli O157:H7 infections. SETTING: Chain of fast-food restaurants, hospitals, physician offices, local laboratories, and local health departments. PARTICIPANTS: Patients with diarrhea and neighborhood controls. A case was defined as diarrhea with culture-confirmed E coli O157:H7 infection or postdiarrheal hemolytic uremic syndrome (HUS) occurring from December 1, 1992, through February 28, 1993, in a Washington State resident. Controls were age- and neighborhood-matched friends of the first 16 case patients. INTERVENTIONS: Announcement to the public; recall of implicated hamburger lots. MAIN OUTCOME MEASURE: Abatement of outbreak due to E coli O157:H7. RESULTS: Infection was associated with eating at a fast-food chain (chain A) in the 10 days before symptoms began. Twelve (75%) of 16 case patients but no controls had eaten at chain A (matched odds ratio undefined; lower 95% confidence interval, 3.5; P < .001). In total, 501 cases were reported, including 151 hospitalizations (31%), 45 cases of HUS (9%), and three deaths. Forty-eight patients (10%) had secondary infections. Of the remaining 453 patients (90%), 398 (86%) reported eating at a Washington chain A restaurant; 92% of them reported eating a regular hamburger. The pulsed-field gel electrophoresis pattern of the E coli O157:H7 strains isolated from all regular hamburger lots of a single production date shipped to Washington was identical to that of the strains isolated from patients. Ten (63%) of 16 regular hamburgers cooked according to chain A policy had internal temperatures below 60 degrees C. Public health action removed more than 250,000 potentially contaminated hamburgers, preventing an estimated 800 cases. CONCLUSIONS: This E coli O157:H7 outbreak, the largest reported, resulted from errors in meat processing and cooking. Public health surveillance through state-mandated reporting of E coli O157:H7 infection as is carried out in Washington State was critical for prompt outbreak recognition and control. Measures should be developed to reduce meat contamination. Consumers and food service workers should be educated about cooking hamburger meat thoroughly.

Adolescent↗
PubMed1993

Synaptic mechanisms of cortical representational plasticity: somatosensory and corticocortical EPSPs in reorganized raccoon SI cortex.

1. Reorganizations of representational maps have been described for a variety of sensory and motor regions of cerebral neocortex in several species. The purpose of this study was to investigate synaptic mechanisms of the reorganizations of primary somatosensory cortex that follow removal of a digit or the joining of two digits into a syndactyly. We examined neurons in the cortical representation of digit 4 (d4). Intracellular recording was used to compare somatosensory and corticocortical excitatory postsynaptic potentials (EPSPs) in normal raccoons, with EPSPs recorded in two experimental groups of animals surviving for a mean of 22 wk after removal of d4, or union of d4 with digit 3 (d3). 2. In normal animals with d4 intact, EPSPs were evoked from this on-focus digit in 100% of cortical neurons. EPSPs were evoked from d3 and digit 5 (off-focus digits) in only a minority of neurons in normal raccoons. The incidence of somatosensory EPSPs from off-focus digits increased dramatically after removal of d4 or its union with d3. Latencies of EPSPs evoked from off-focus digits decreased after d4 removal, so that they were as short as latencies from d4 in normal animals. In contrast, for the group of animals with d3-d4 syndactyly, latencies of EPSPs from off-focus digits were not shorter than responses from these digits in normal animals. 3. Corticocortical EPSPs were no more common in animals with d4 removed than in intact animals. Furthermore, corticocortical EPSPs after d4 removal did not differ in their latencies, amplitudes, half-widths, or integrated amplitudes. The only detected change was that corticocortical EPSPs had faster rising phases after removal of d4. In contrast, after d3-d4 syndactyly, corticocortical EPSPs were more common than in normal animals. 4. Digit removal and digital syndactyly had distinctive effects on somatosensory and corticocortical EPSPs. These results do not identify unique synaptic mechanisms for cortical representational plasticity, nor do they specify the involved CNS site(s). Several synaptic mechanisms consistent with the results are considered in the DISCUSSION, including synaptic proliferation to form new synaptic connections and enhanced effectiveness of existing corticocortical synapses.

Afferent Pathways↗
PubMed1993

Auditory evoked potentials in cats with neonatal high frequency hearing loss. Evidence of abnormal frequency representation in the midbrain.

We have recorded auditory evoked potentials, of both neurogenic and myogenic origin, in cats having neonatal high frequency cochlear hearing loss. Using frequency specific stimuli (tone pips) and by measuring responses near to threshold, we have probed tonotopic (or cochleotopic) representation within the brainstem-midbrain auditory pathway. At stimulus frequencies corresponding to the high frequency cut-off of the cats' audiograms we have observed enhanced amplitudes of both auditory brainstem evoked responses (ABR) and postauricular myogenic (PAM) potentials. We interpret our findings as evidence of a larger than normal population of neurons tuned to this frequency region. We suggest that such abnormal frequency representation results from a long-term sensory deficit caused by lesions to the basal, high frequency region of the cochleas.

Animals↗
PubMed1991

Distribution of motoneurons supplying dorsal suboccipital and intervertebral muscles in the cat neck.

Multiple labelling methods were used to examine the topographical organization of motoneurons supplying the suboccipital muscles, rectus capitis posterior (RCP) and obliquus capitis inferior (OCI); the intervertebral muscles, spinalis dorsi (SD) and semispinalis cervicis (SSC); and the dorsal extensor biventer cervicis (BC). Muscle nerves were isolated, cut, and exposed in the same animal to one of three different retrograde tracers, Fluorogold, Fast Blue, and horseradish peroxidase. Motoneurons supplying suboccipital muscles were found to be located in the rostral two cervical segments. The RCP motor nucleus was confined to C1 and the caudal brainstem, whereas the OCI nucleus usually originated in mid-C1 and extended caudally as far as mid-C2. Most motoneurons supplying OCI and SD were concentrated in the deepest part of the ventral horn, but some cells were found in the commissural region, the contralateral ventral horn, the dorso-medial aspect of the ipsilateral ventral horn, and the ventromedial white matter. Cells supplying the functional extensor RCP were intermingled with those supplying the turning muscle OCI, although a gradient in mediolateral distribution was detected. Motoneurons supplying the intervertebral muscles SD and SSC were found caudal to C3. Within the ventral horn, they occupied locations similar to those occupied by suboccipital motoneurons in C1 and C2. The cell column for intervertebral motoneurons was just medial to that of BC and some cells supplying SD and SSC were found in the territory occupied by BC motoneurons. Motoneurons supplying intervertebral and suboccipital muscles had unimodal diameter spectra, and most cells had mean equivalent diameters smaller than 35 microns.

Animals↗
PubMed1991

Distribution of motoneurons supplying cat sartorius and tensor fasciae latae, demonstrated by retrograde multiple-labelling methods.

Sartorius (SART) and tensor fasciae latae (TFL) in the cat hindlimb are functionally heterogeneous muscles with regions that differ in their skeletal actions and electromyographic recruitment during normal activity. The topographical organization of motoneurons supplying different regions of SART or TFL has been investigated by exposing cut nerve branches supplying different peripheral territories to a combination of retrograde tracers, including Fast Blue (FB), Fluorogold (FG), and horseradish peroxidase (HRP). Motoneurons supplying medial, central, and anterior regions of SART were intermixed extensively throughout a single columnar nucleus located in the ventrolateral part of segments L4 and L5. With this column, motoneurons supplying medial SART tended to lie more rostrally than those supplying anterior regions, but the gradient was modest and showed some cat-to-cat variation. Two major branches entered anterior SART at different proximodistal levels. When these two branches were exposed to different tracers, most motoneurons contained a single tracer; only a few double-labelled cells were apparent. The labelling suggests that anterior SART may contain two separate, in-series divisions of motor units. In TFL, motoneurons supplying nerve branches to posterior, central, and anterior parts of the muscle were intermingled indiscriminately in a single ventrolateral cell column in L6 and rostral L7. These results suggest that topographical organization in lumbar motor nuclei does not always reflect the highly ordered biomechanical and functional specialization evident in the peripheral organization of the muscles themselves.

Amidines↗
PubMed1991

Synaptic potentials evoked by convergent somatosensory and corticocortical inputs in raccoon somatosensory cortex: substrates for plasticity.

1. "Unmasking" of weak synaptic connections has been suggested as a mechanism for the early changes in cortical topographic maps that follow alterations of sensory activity. For such a mechanism to operate, convergent sensory inputs must already exist in the normal cortex. 2. We tested for topographic and cross-modality convergence in primary somatosensory cortex of raccoon. The representation of glabrous skin of forepaw digits was chosen because, even though it is dominated by inputs from the glabrous skin of a single digit, it nevertheless comes to respond to stimulation of other digits when, e.g., a digit is removed. 3. Intracellular recordings were made from 109 neurons in the representation of glabrous skin of digit 4. Neurons were tested for somatosensory inputs with electrical and natural stimulation of digits. 4. Excitatory postsynaptic potentials (EPSPs) were evoked in 100% of the neurons (109/109) by electrical stimulation of glabrous skin of digit 4, and in 79% (31 of 39) by vibrotactile stimulation. 5. Glabrous skin of digit 4 was not the sole source of somatosensory inputs. A minority of neurons generated EPSPs after electrical stimulation of hairy skin of digit 4 (10 of 98 neurons, 10%). Electrical stimulation of digits 3 or 5 evoked EPSPs in 22 of 103 neurons (21%). Natural stimulation (vibrotactile or hair bending) was also effective in most of these latter cases (digit 3, 6/7; digit 5, 9/10). 6. Intracortical microstimulation of the "heterogeneous zone" was used to test for corticocortical connections to neurons in the glabrous zone.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1990

Topography in the phrenic motoneuron nucleus demonstrated by retrograde multiple-labelling techniques.

A combination of retrograde tracing methods was employed to distinguish populations of motoneurons supplying different motor unit territories in the feline diaphragm. The compatibility of the tracers--horseradish peroxidase, fast or true blue, diamidino yellow, and fluorogold--was first assessed by applying the different tracers concurrently to separate cut branches of hindlimb and neck muscle nerves. On the basis of these initial observations fast blue, fluorogold, and horseradish peroxidase were chosen to compare the distribution of motoneurons whose axons ran in different primary branches of the phrenic nerve. Motoneurons with different target territories were extensively intermixed throughout most of the phrenic motor nucleus. However, motoneurons innervating the sternal and medial costal part of the diaphragm were distributed more densely in the rostral part of the phrenic motor pool, whereas motoneurons serving the lateral costal part were concentrated more caudally. Crural motoneurons were intermingled with costal motoneurons in the middle and caudal portions of the nucleus. Motoneurons within the phrenic nucleus are distributed in clusters. Such clusters commonly contained motoneurons labelled from two or more primary branches. Thus, the highly ordered topography of muscle units in the diaphragm is not mirrored by the intraspinal distribution of phrenic motoneurons.

Amidines↗
PubMed1989

Muscle-fiber architecture, innervation, and histochemistry in the diaphragm of the cat.

Previous anatomical descriptions of the diaphragm have contained several contradictory findings. To validate and extend the previous work, diaphragmatic architecture, histochemistry, and end-plate distribution were examined by use of a combination of anatomical methods, including fiber microdissections, cholinesterase staining, and enzyme histochemistry. Microdissections showed that muscle-fiber fascicles throughout the diaphragm contain both long fibers that run from origin to insertion and shorter fibers with intrafascicular terminations. Fibers with intrafascicular terminations were particularly common in the costal diaphragm, where they accounted for the majority of sampled fibers. The heterogeneity of fiber length was reflected in the pattern of end-plate banding. Cholinesterase studies showed that fiber fascicles in cat and kitten diaphragms were crossed by two to four end-plate bands distributed in discontinuous arrays across the width of the muscle. A similar pattern of multiple banding was also demonstrated in the adult and neonatal dog. However, rat and rabbit diaphragms had only a single, continuous end-plate band. Histochemical studies of fiber types in different parts of the feline diaphragm showed that costal, crural, and sternal subregions had similar overall proportions of fiber types. However, type SO (slow oxidative) fibers were distributed more densely on the thoracic than the abdominal surface of costal and crural, but not sternal subregions. Type SO fibers were also concentrated in fiber fascicles bordering the esophageal hiatus.

Animals↗
PubMed1989

Motor unit territories supplied by primary branches of the phrenic nerve.

Recent studies have demonstrated that, under certain circumstances, the diaphragm does not contract as a homogeneous unit. These observations suggest that motor units may not be randomly distributed throughout the muscle but confined to localized subvolumes. In the present study, electromyographic (EMG) and glycogen depletion methods were combined to investigate the organization of motor units supplied by the primary branches of the phrenic nerve in the cat. Four primary branches are generally present, one branch to the crus and three branches to the sternocostal region. The gross motor-unit territory of each of the four phrenic primary branches was determined by stimulating each nerve separately, while recording from nine EMG electrodes distributed over the hemidiaphragm. Stimulation of the crural branch evoked activity in the ipsilateral crus, whereas stimulation of each of the remaining branches evoked activity in discrete but overlapping areas of the sternocostal diaphragm. A more precise analysis of the distribution and borders of the motor territories was obtained by mapping regions depleted of muscle glycogen due to stimulation of each primary branch for 90 min. Glycogen depletion results closely matched the EMG findings of a localized distribution of motor units served by single primary branches. Stimulation of the crural branch typically caused depletion of the ipsilateral crus, whereas the sternocostal branches each served a striplike compartment. In the majority of cases, the borders of the sternocostal compartments were relatively abrupt and consisted of a 1- to 2-mm transition zone of depleted and nondepleted fibers. These studies demonstrate that motor unit territories of the primary branches of the phrenic nerve are highly delineated. This compartmentalization provides the central nervous system with the potential for a more precise regional motor control of costal and crural diaphragm than previously suspected.

Animals↗
PubMed1988

Developing capital investment guidelines for acquisitions.

Financial managers are now being asked to evaluate new investment opportunities, such as acquisitions. To do a thorough evaluation, however, it is important to have a plan of action to follow. Strategies such as establishing a framework for evaluating acquisitions based on strategic compatibility with the existing organization, establishing suitable risk-adjusted discount rates for assessing investments, and selecting the proper type of capital allocation method are all necessary steps to ensure a successful acquisition.

Capital Expenditures↗