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Biomedical subjects

H A Robertson

Publications and source records attributed to H A Robertson.

At least 19 recordsLinked to original sources
PubMed1998

Production, faecal egg counts and worm burdens of ewe lambs which grazed six contrasting forages.

Lambs were grazed on monospecific swards of one of six forages, some containing condensed tannins (CT); sulla (Hedysarum coronarium), Lotus corniculatus and L. pedunculatus and some without CT (lucerne (Medicago sativa), plantain (Plantago lanceolata) and a ryegrass/white clover pasture (Lolium perenne/Trifolium repens)) to evaluate effects of forage type on gastrointestinal nematode burdens, faecal egg count as well as liveweight gain (LWG), wool growth and dag formation over a 42-day period. A new allotment of feed was provided at seven-day intervals, and feed was available ad libitum. Total worm burdens in a pre-treatment slaughter group were ca. 22000 of which ca. 5000 were in the abomasum. Within each forage type, 10 of the 25 lambs (NP) were given an anthelmintic drench at 14-day intervals and the remaining 15 lambs (P) were not drenched. Daily gains of the NP lambs were double that of P lambs which grazed either L. corniculatus, lucerne or pasture, but parasitism had a lesser effect on performance of lambs which grazed sulla and L. pedunculatus. Plantain was not palatable and all lambs performed poorly. Highest daily gains in P lambs were for those which grazed sulla (175 g/day) and L. pedunculatus (160 g/day) with total worm burdens of 13100 and 23000 for the respective treatment groups. The other forages resulted in lower daily LWG in P lambs, and performance was not related to either worm burdens or worm species. This experiment has shown that, when sulla is fed, there is a reduction in worm burdens and faecal egg count (FEC), but with Maku lotus which also contains CT, the good level of performance was achieved despite in high worm burdens and FEC. The mechanisms by which these forages enable high levels of productivity in the face of a parasitism appear to differ, but both could be incorporated into forage feeding systems to reduce dependence on anthelmintic drenches.

Abomasum↗
PubMed1998

Effect of topographical aspect and farm system on the population dynamics of Trichostrongylus larvae on a hill pasture.

The population dynamics of Trichostrongylus colubriformis larvae were compared over two years on contrasting topographical aspects north (warm and dry) and south-facing (cool and moist) hill slopes) on paddocks which form part of the 'non-chemical' and conventional' farm systems at the AgResearch Ballantrae Hill Country Station located in a summer-moist region of New Zealand. Sheep faeces containing 50,000 Trichostrongylus eggs were incubated for 4 days at 25 degrees C and then deposited on each of 36 sub-plots in each of 8 plots in a 2 x 2 factorial design in the summer (summer trial) and again in autumn (autumn trial). Pasture was removed to ground level and larvae extracted from six sub-plots from each plot 2, 4, 6, 8, 11 and 14 weeks after contamination in all trials. Larvae were recovered from two strata, 0-5 cm above the soil surface and > 5 cm above the soil surface. Fewer (p < 0.001) larvae were recovered from herbage (47 vs. 118) and residual faeces (28 vs. 246) from the autumn than from the summer trials. This coincided with more rapid (p < 0.001) faecal disappearance in the autumn trials. In the summer trials, fewer (p < 0.003) larvae were recovered from the herbage (101 vs. 182) and residual faeces (140 vs. 352) from plots on the south than the north facing aspect. In the autumn trials there was a rapid (p < 0.0001) faecal disappearance from the south-facing aspect. In the autumn trials there was a non-significant (p < 0.10) trend for fewer larvae to be recovered from the south-facing aspect (2 vs. 54). This also coincided with more rapid faecal disappearance from the south-facing aspect. There was no effect of farm system on the number of larvae recovered. Despite greater (p < 0.0001) numbers of larvae recovered from the bottom stratum of herbage, the density of larvae (L3/kg DM) tended (p < 0.12) to be higher in the top stratum of herbage. It was concluded that season and aspect have a marked effect on the number of larvae recovered from herbage and that this was inversely related to the rate of faecal disappearance.

Agrochemicals↗
PubMed1998

Intra-amygdala infusion of an end-capped antisense oligodeoxynucleotide to c-fos accelerates amygdala kindling.

The changes produced by repeated stimulation of the brain that result in the kindling effect remain unknown. It is known, however, that activation of immediate early genes including c-fos is a very early event in the development of kindling. Here we show that c-fos expression in the amygdala can be knocked-down by an end-capped antisense oligodeoxynucleotide (but not by vehicle, or control antisense oligodeoxynucleotides) and that this results in an acceleration of kindling. These results suggest that, at least in the amygdala, the expression of c-fos is associated with an attempt by the brain to retard the development of kindling.

Amphetamine↗
PubMed1998

Effect of plant species on the larvae of gastrointestinal nematodes which parasitise sheep.

Faeces containing Trichostrongylus colubriformis and/or Ostertagia circumcincta eggs were used to provide four contaminations in each of 2 years on plots of browntop, Yorkshire fog, ryegrass, tall fescue, lucerne, chicory, cocksfoot, white clover, and prairie grass and in the second year a mixed sward of ryegrass/white clover. Third stage larvae were recovered from faeces and from four strata of herbage, 0-2.5, 2.5-5, 5-7.5 and > 7.5 cm above the soil surface at 2, 4, 6, 8, 11, and 14 weeks after faeces were deposited on the swards. Herbage species had a significant (P < 0.0001) effect on the number of larvae recovered. Greatest numbers of larvae, as indicated by ranking analysis, were recovered from Yorkshire fog, ryegrass, and cocksfoot and lowest numbers from white clover and lucerne. The difference between herbages in numbers of larvae recovered was due to the "development success", the ability of larvae to develop to the infective stage and migrate on to herbage, rather than "survival", the rate of population decline once on the herbage. Faecal degradation was most rapid from white clover and browntop, intermediate from tall fescue, lucerne, prairie grass, cocksfoot, and ryegrass, and slowest from Yorkshire fog swards. The numbers of larvae recovered from herbages were related (r2 = 0.59, P < 0.05) with the faecal mass remaining. A greater proportion of the total larvae recovered from the herbage was recovered from the bottom stratum of Yorkshire fog and prairie grass than from white clover, with the other herbages intermediate, indicating that larvae had greater difficulty migrating up Yorkshire fog and prairie grass than the other herbage species. In most herbage species, despite more larvae being recovered from the lowest stratum, larval density (L3/kg herbage DM) was highest in the top stratum. This study has demonstrated that herbage species can have a significant impact on the population dynamics and vertical migration of T. colubriformis and O. circumcincta larvae.

Animals↗
PubMed1998

Acute administration of cocaine, but not amphetamine, increases the level of synaptotagmin IV mRNA in the dorsal striatum of rat.

Synaptotagmin IV (Syt IV) is an inducible member of a multi-gene family of synaptic vesicle proteins that participate in Ca2+-dependent and Ca2+-independent interactions during membrane trafficking. We have examined the pattern of expression of Syt IV mRNA following the administration of cocaine and amphetamine. A single acute dose of cocaine, but not amphetamine, resulted in a transient increase, as determined by in situ hybridization, in the steady-state level of Syt IV mRNA in the dorsal striatum of rats 1 h after the administration of the drug. No change in the hybridization pattern of the Syt IV-specific probe to other regions of the rat brain were observed following cocaine or amphetamine administration at the time points examined (1, 3, 6, 12 and 24 h). The pattern of synaptotagmin I-(Syt I) specific hybridization remained constant, relative to controls, for both the cocaine- and amphetamine-treated animals. Northern hybridization analysis of mRNA isolated from striatal tissue using oligonucleotide probes specific to Syt I and Syt IV demonstrated that the probes hybridized exclusively to transcripts of the sizes previously reported for these two synaptotagmins and confirmed that the relative level of Syt IV to Syt I mRNA increased following the administration of cocaine but not amphetamine. These results indicate that these drugs have different effects on altering the levels of Syt IV mRNA. This work, in conjunction with earlier work that demonstrated that cocaine and amphetamine have different effects on the expression of immediate early genes such as c-Fos, supports the hypothesis that these psychotropic agents evoke different patterns of gene expression which may lead to alteration in synaptic efficacy.

Amphetamine↗
PubMed1997

Constitutive expression of the 27-kDa heat shock protein (Hsp27) in sensory and motor neurons of the rat nervous system.

In this study, the constitutive expression of the 27-kDa heat shock protein (Hsp27) in the adult rat central nervous system has been examined by immunohistochemistry and by two-dimensional gel Western blot analysis. Hsp27 immunoreactivity was observed primarily in motoneurons of cranial nerve nuclei and spinal cord, and in primary sensory neurons and their central processes. Also, Hsp27 immunoreactivity was present in neurons of the arcuate nucleus and of the reticular formation. However, only a subset of these neurons was Hsp27-immunoreactive. Most general somatic efferent motoneurons of the hypoglossal nucleus and spinal motor columns and most special visceral efferent motoneurons of the cranial nerve nuclei were Hsp27-positive. In contrast, fewer general somatic efferent motoneurons for eye muscles were Hsp27-positive, and only a small proportion of general visceral efferent neurons, i.e., parasympathetic and sympathetic preganglionic neurons, were stained for Hsp27. Many pseudounipolar sensory neurons were Hsp27-immunoreactive, and the patterns of staining in central sensory nuclei suggested that specific subpopulations of sensory neurons contained Hsp27. The cellular distribution of Hsp27 was uniform throughout the cytoplasm, including the perikaryon, axon and dendrites, the latter often exhibiting varicosities or beading in distal processes. Western blot analyses revealed that at least three phosphorylated isoforms of Hsp27 were present in the spinal cord. These results suggest that constitutively expressed Hsp27 may be related to functional subpopulations of motoneurons and primary sensory neurons.

Animals↗
PubMed1997

A novel seizure-induced synaptotagmin gene identified by differential display.

Systemic administration of kainic acid, a cyclic analogue of glutamate, produces many of the clinical features of human temporal lobe epilepsy and status epilepticus in rats, including the induction of motor convulsions and the degeneration of neurons in the hippocampus and piriform cortex. Differential display PCR was used to identify mRNAs that are differentially expressed between degenerating and nondegenerating tissues in the brain after kainic acid-induced seizure activity. A novel cDNA fragment expressed in the degenerating hippocampus and piriform cortex, but not in the nondegenerating parietal cortex, was identified, cloned, and sequenced. This novel cDNA fragment identified a new member of the synaptotagmin gene family that is rapidly and transiently induced in response to seizure activity. Differential expression of this synaptotagmin gene, syt X, was confirmed by Northern blot analysis and in situ hybridization. This novel, inducible synaptotagmin gene may provide a direct link between seizure-induced neuronal gene expression and subsequent modulation of synaptic structure and function.

Amino Acid Sequence↗
PubMed1997

Atypical depressive symptoms in seasonal and non-seasonal mood disorders.

The authors examined the rates of atypical depression and prevalence of specific atypical symptoms in patients with seasonal versus non-seasonal depression. Fifty-three patients with seasonal affective disorder (SAD) were compared to 54 patients with non-seasonal major depressive disorder (MDD) using the atypical depression diagnostic scale (ADDS). SAD patients scored significantly higher than non-seasonal MDD patients in hyperphagia and hypersomnia, and significantly lower in interpersonal sensitivity and other rejection avoidance. There was no difference in the rate of ADDS diagnosis of atypical depression. Differences between atypical depression and SAD suggest that they are separate subtypes of depression with an overlapping symptom picture.

Adolescent↗
PubMed1997

Differential expression of c-fos, Hsp70 and Hsp27 after photothrombotic injury in the rat brain.

In situ hybridization and immunohistochemistry were used to examine the expression of c-fos, Hsp70 and Hsp27 following photothrombotic injury in the right fronto-parietal cortex of the rat. C-fos mRNA and protein were detected in the entire cerebral cortex on the lesioned side. Hsp70 mRNA accumulation was observed only adjacent and peripheral to the site of the lesion. At 1 h after photothrombotic injury, Hsp70 expression delineates the area of necrosis at 24 h after photothrombotic injury. Hsp27 protein was observed in the ipsilateral cerebral cortex with the exception of the deep layers of the cingulate cortex. In addition, while c-Fos immunoreactivity was localized in cell nuclei, Hsp27 immunoreactivity was detected in the cytoplasm of astrocytes. These results demonstrate that unilateral cortical injury induces changes in gene expression that vary according to cell type and brain region.

Animals↗
PubMed1997

End-capped antisense oligodeoxynucleotides effectively inhibit gene expression in vivo and offer a low-toxicity alternative to fully modified phosphorothioate oligodeoxynucleotides.

Sulfur modification of oligodeoxynucleotides produces nuclease resistance but also leads to toxic effects when these compounds are administered in vivo. To assess their potential as viable alternatives to full phosphorothioate derivatives, we have used rotational behavior and immunohistochemistry to investigate the efficacy and longevity of phosphorothioate, end-capped antisense oligodeoxynucleotides in suppression of c-fos and ngfi-a in the striatum of adult rats. Our results suggest that, despite having a limited duration of action, these end-capped, chimeric oligodeoxynucleotides are capable of specifically inhibiting gene expression in vivo and may, therefore, possess broader application potential in chronic suppression models as the reduction of sulfur content is likely to greatly minimize their toxic effects.

Animals↗
PubMed1997

The effects of hypoxia-ischemia on expression of c-Fos, c-Jun and Hsp70 in the young rat hippocampus.

The expression of c-Fos, c-Jun and Hsp70 was examined in the hippocampus at 6, 12, 24, 48, 72 h, 4, 7 and 42 days following a combination of unilateral common carotid artery ligation and 60 min of systemic hypoxia (8% oxygen, 92% nitrogen) in 25-day-old male rats. While pyknotic cells were not visible in the hippocampus of control animals, pyknosis was evident in the ipsilateral, but not the contralateral hippocampus, of hypoxic-ischemic animals beginning at 24 h post-hypoxia. Immunohistochemical analysis revealed no c-Fos-, c-Jun- or Hsp70-immunoreactivity (IR) in any control animals. However, at 6 h post-hypoxia, Fos- and Jun-IR was evident throughout the injured ipsilateral hippocampus and later appeared throughout the contralateral hippocampus, which never showed signs of pyknosis. In contrast, Hsp70-IR was first observed at 24 h post-hypoxia and was restricted to the injured ipsilateral hippocampus. Hsp70-IR was not, however, limited to dying neurons. H-I/seizure animals did not express these proteins at any time point. These results suggest that, even in irreversibly injured neurons, Fos, Jun and Hsp70 appear to be involved in the aftermath of ischemia but probably do not play a pivotal role in the outcome of H-I compromised cells. Furthermore, compounded injury (H-I/seizure) appears to block the synthesis these proteins.

Aging↗
PubMed1997

Coordinate suppression of striatal ngfi-a and c-fos produces locomotor asymmetry and up-regulation of IEGs in the globus pallidus.

We have studied the effects of inhibition of c-Fos and NGFI-A expression by intrastriatal infusion of end-capped antisense oligodeoxynucleotides to determine if their coordinate expression is conferred independently or through regulatory influences exerted between these two proteins. The previously reported locomotor bias that has been associated with unilateral c-Fos suppression was also investigated in animals receiving antisense oligodeoxynucleotides targeted to ngfi-a to determine if the behavior is specific to alterations in c-Fos expression, or if its cause may be a generalized imbalance of striatal IEGs. We show here that while unilateral suppression of c-Fos has negligible effects on NGFI-A, oligodeoxynucleotides targeted to ngfi-a markedly inhibit both NGFI-A and c-Fos expression. Animals with extensive unilateral reduction of either or both proteins demonstrated robust ipsiversive rotation when challenged with D-amphetamine. Infusions of random oligodeoxynucleotides produced neither a reduction in c-Fos or NGFI-A expression, nor a significant rotational bias following D-amphetamine challenge. Surprisingly, animals with extensive striatal IEG suppression were found to have marked up-regulation of c-Fos and NGFI-A in the ipsilateral globus pallidus, a finding which may ultimately shed light on the mechanism of antisense-induced rotational behavior.

Animals↗
PubMed1997

Putative roles for the inducible transcription factor c-fos in the central nervous system: studies with antisense oligonucleotides.

Although immediate-early genes such as c-fos are widely believed to play an important role in neuroplasticity, there is limited evidence to support involvement in the initiation of molecular events leading to medium- and long-term changes in brain function following a stimulus. Results using techniques such as transgenic knockout of the gene are often difficult to interpret. Antisense oligonucleotide technology offers an alternative. Infusion of antisense oligonucleotide to modify the expression of c-fos in the brain results in dramatic changes in rotation behaviour in animals challenged with psychostimulant drugs such as amphetamine. Similarly, the knockdown of c-fos expression using antisense oligonucleotides can also alter the rate of amygdala kindling in response to electrical stimulation of the brain. While studies using antisense oligonucleotides to knockdown c-fos expression provide evidence that the expression of c-fos plays an important role in regulating neuronal function, the use of antisense nucleotides has limitations and experiments must be very carefully controlled. Many details of antisense oligonucleotide actions remain unknown.

Animals↗
PubMed1997

Cortical application of potassium chloride induces the low-molecular weight heat shock protein (Hsp27) in astrocytes.

Spreading depression induces tolerance to ischemic injury, and ischemic tolerance has been associated with expression of heat shock proteins (Hsp). Here we examine Hsp27 expression after KCl-induced spreading depression. Twenty-minute cortical KCl application induced Hsp27 immunoreactivity in glial fibrillary acidic protein-positive astrocytes of the ipsilateral neocortex. Systemic administration of MK-801 (3 mg/kg) suppressed KCl-induced Hsp27 expression in the parietal cortex. Astrocytes in the posterior cingulate and retrosplenial cortex did not express Hsp27 after KCl application but did express Hsp27 after systemic administration of high dose MK-801 (9 mg/kg). Whereas Hsp27 was usually observed in all layers of the parietal cortex after 5-minute application of KCl, in 2 of 6 rats, Hsp27 was seen in clusters of astrocytes or in astrocytes in the superficial layers I to III of the parietal cortex. We conclude that (1) cortical application of KCl triggered Hsp27 astrocytic expression; (2) astrocytes in the cingulate and retrosplenial cortex responded differently compared with astrocytes of the parietal cortex; (3) Hsp27 expression progressed from small clusters of astrocytes throughout superficial layers of the cortex that joined and recruited astrocytes in deeper layers; (4) several mechanisms induced Hsp27 astrocytic expression. We propose that Hsp27 is involved in spreading depression-induced ischemic tolerance through protection of astrocyte function.

Animals↗
PubMed1996

Expression of fosB mRNA in the hamster suprachiasmatic nucleus is induced at only selected circadian phases.

We have studied the expression of fosB mRNA in the suprachiasmatic nucleus (SCN) of hamsters by in situ hybridization using oligonucleotides with sequences complementary to the C-terminal of the fosB mRNA sequence. In animals exposed for 48 h to darkness, there was little or no background expression in SCN cells of fosB mRNA at any circadian phase. Light pulses (30 min) were able to induce fosB expression only during the subjective night. Transcripts of fosB increased rapidly to peak by the end of a 30-min light pulse. Light-induced increases gradually declined in darkness, but levels were still elevated for up to 150 min after the light pulse. Induction in response to a light pulse was largely restricted to the ventrolateral portion of the nucleus which receives the heaviest retinal projection. The temporal and anatomical pattern of fosB mRNA expression in the hamster SCN therefore resembles that reported previously for other immediate-early genes, such as c-fos.

Analysis of Variance↗
PubMed1996

Spontaneous and light-evoked expression of JunB-like protein in the hamster suprachiasmatic nucleus near subjective dawn.

Some cells in the hamster suprachiasmatic nucleus (SCN) show a circadian rhythm of expression of junB mRNA in constant darkness, while others show junB mRNA only in response to light at night. We found that both the light-induced and spontaneous expressions of junB mRNA are translated into protein in SCN cells. In constant darkness, JunB-like immunoreactivity (lir) appears spontaneously in cells in the dorsal SCN around subjective dawn and persists for at least 4 h into the subjective day. During the subjective night, there is no spontaneous expression, but a light pulse can induce JunB-lir in cells throughout the SCN, and especially in the ventrolateral portion. As a component of AP-1 proteins, JunB may play a role both in mediating circadian responses to photic stimuli and in spontaneous oscillation of elements of the SCN circadian pacemaker.

Analysis of Variance↗
PubMed1996

Spontaneous circadian and light-induced expression of junB mRNA in the hamster suprachiasmatic nucleus.

We examined both spontaneous and light-evoked expression of junB mRNA in the hamster suprachiasmatic nucleus (SCN), an endogenous circadian pacemaker. junB was expressed in the SCN in response to a light pulse during the subjective night and early subjective day as well as spontaneously during the transition from subjective night to subjective day. Light-evoked expression was strongest in the ventral SCN, while spontaneous expression was stronger in the dorsal SCN. Spontaneous expression began around subjective dawn and persisted for at least 4 h into the subjective day. The expression of junB mRNA may play a role in both phase-shifting responses to light and in spontaneous oscillation of the SCN pacemaker.

Analysis of Variance↗