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J R Wrathall

Publications and source records attributed to J R Wrathall.

15 recordsLinked to original sources
PubMed1992

Effect of kynurenate on functional deficits resulting from traumatic spinal cord injury.

The potential role of excitatory amino acid (EAA) receptors in spinal cord trauma was examined in a standardized rat model of contusive injury. EAA antagonists were administered in a split-dose protocol with half given 5 min prior to and the remainder 15 min after contusion produced at the T8 vertebral level. Hindlimb function was assessed using a battery of tests of reflex and more complex behaviors at 1 day after injury and weekly thereafter through 4-8 weeks. Functional deficits were compared for groups administered intravenous MK 801 (1 mg/kg), dextromethorphan (10 mg/kg) and kynurenate (300 mg/kg) or the vehicle, saline, alone. In addition, possible effect of the drugs themselves on hindlimb function were assessed in uninjured controls. None of the drugs produced more than transient effect on uninjured rats. In contused rats, only kynurenate produced significant reductions in functional deficits as compared to saline controls. Significant improvement of hindlimb function was also observed when the thoracic cord was locally perfused with kynurenate via intrathecal cannulas and when kynurenate was directly infused into the contusive injury site by stereotaxic microinjection. Using the latter route of administration, a dose-dependent effect of kynurenate (100, 200 and 400 nmol) on the ability of contused rats to use their hindlimbs in locomotion was demonstrated. The highest dose also resulted in a significant reduction in overall functional deficits from 1 week through 1 month and at 2 months after injury. Our results support the hypothesis that EAA receptors at or near the injury site are involved in producing a proportion of the overall functional deficits stemming from traumatic injury.(ABSTRACT TRUNCATED AT 250 WORDS)

Amino Acids↗
PubMed1992

Evidence that local non-NMDA receptors contribute to functional deficits in contusive spinal cord injury.

To investigate the role of non-N-methyl-D-aspartate (non-NMDA) types of excitatory amino acid (EAA) receptors in traumatic spinal cord injury, we administered 2,3-dihydroxy-6-nitro-7-sulfamoyl-benzo(F)-quinoxaline (NBQX), a potent and specific antagonist of non-NMDA receptors, to rats with a standardized contusive spinal cord injury. Focal infusion of NBQX into the injury site significantly reduced long-term hindlimb functional deficits as well as decreasing the time required for the rats to establish a reflex bladder. The results suggest that non-NMDA receptors at or near the injury site are involved in producing a portion of the functional deficits that result from contusive spinal cord injury.

Animals↗
PubMed1992

Spinal cord injury models.

Spinal cord injury models continue to be used to learn more about the pathophysiology of injury as well as potential therapeutic interventions. Most researchers now rely on rat models of injury with injury produced by impact, compression, or even photochemical techniques. A number of laboratories have confirmed that reproducible and graded injury can be produced in the rat with outcome monitored by behavioral, neurophysiologic, and morphologic analyses. Biochemical, physiologic, and pharmacologic studies with these models are being used to further define factors that contribute to chronic injury and thus may be the subject of therapeutic intervention. In addition, a new approach to therapy is being explored via implantation of cells into the injured spinal cord. Cell suspensions can be implanted in clinically relevant injury models without exacerbating the effects of injury and with some indications of beneficial effect. The potential usefulness of such an approach is just beginning to be evaluated.

Animals↗
PubMed1991

Localization of nerve growth factor receptor mRNA in contused rat spinal cord by in situ hybridization.

Northern blot analysis using a probe for the low-affinity nerve growth factor receptor (NGFR) revealed that a mild contusive injury induces the expression of NGFR mRNA in rat spinal cord with a maximal expression at 7 days post-injury. We have now localized this induction using in situ hybridization and found the highest concentration of NGFR mRNA at the lesion epicenter. The location and pattern of autoradiographic grains were compared with that of various cell types at the injury site as determined by immunocytochemical studies. The results suggest that cells associated with blood vessels at the epicenter are induced to express NGFR mRNA at 7 days post-injury.

Animals↗
PubMed1991

Increase in nerve growth factor-like immunoreactivity and decrease in choline acetyltransferase following contusive spinal cord injury.

We have previously described a graded spinal cord injury model in the rat. Mild contusive injury results in an initially severe functional deficit that is attenuated over time to reveal the mild chronic deficits that characterize this injury. In this study, we have shown that mild contusive injury also results in a significant decrease in choline acetyltransferase (ChAT) activity during the first week after injury. At 1 week ChAT activity is maximally reduced at the site of the contusion and is also significantly lowered throughout the spinal cord. ChAT activity then rebounds during the following 3 weeks, partially at the injury site where there is considerable loss of gray and white matter, and completely in rostral and caudal cord segments. The rebound in ChAT activity is temporally associated with the partial recovery of function. Further, the changes in ChAT activity after injury are mirrored by changes in nerve growth factor-like immunoreactivity (NGF-LI) as determined by a specific two-site ELISA. NGF-LI increases significantly after injury, reaching a maximum at 7 days after contusion and at the injury site. However, levels of NGF-LI are also significantly increased throughout the spinal cord. NGF-LI then decreases at 2 and 4 weeks as ChAT activity rebounds. Further experiments will be needed to examine the possibility of a role for NGF in promoting the recovery of function after spinal cord injury.

Animals↗
PubMed1991

Implantation of neuronal suspensions into contusive injury sites in the adult rat spinal cord.

Implants of various types of neuronal and nonneuronal tissue have shown promise for the amelioration of certain disorders of the adult mammalian brain. Implants may also have therapeutic potential for some lesions of the spinal cord. To examine the feasibility of implantation for clinically relevant spinal cord injuries, we have implanted cells into injury sites produced by a well-characterized and standardized rat model of contusive injury. To reduce the possibility of the implantation procedure itself causing damage to the spinal cord, the tissue was dissociated and a suspension of cells introduced into the cord via a small bore needle. To test the implantation procedure, dissociated adult rat dorsal root ganglia were used because of the ease with which these neurons could be distinguished after implantation. The extent to which functional deficits were produced or exacerbated by the implantation procedure was assessed by behavioral tests of groups of rats that had been implanted (implant controls), contused (injury only) or contused and implanted (injury-implant). Survival of the implanted neurons was assessed by quantitative morphological analysis of histological sections taken through the injury/implant sites at different times following injury. In addition, the histopathology of the contusive injury sites was compared for rats that had or had not received immediate or delayed implants. Results indicated that cell suspensions could be implanted into the spinal cord without causing a functional deficit in an otherwise uninjured animal or exacerbating a standardized incomplete contusive injury. Implanted neurons survived for at least 4 weeks in all contusion sites whether implantation was performed immediately following injury or after a delay of 1 week.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1990

Increased nerve growth factor receptor mRNA in contused rat spinal cord.

Peripheral nerve injury induces the expression of nerve growth factor receptor (NGFR). To determine whether a similar induction results from injury of the spinal cord, NGFR mRNA content was determined using Northern blot hybridization analysis of total RNA from spinal cords of rats contused in the mid-thoracic region. By four days after contusion NGFR mRNA was significantly increased in the thoracic segments that included the injury site. The induction was maximal at 7 days, about 5- to 7-fold the level of uninjured controls, and remained 4 times higher than controls at 14 and 28 days after injury. These results suggest that axotomy in the CNS may also trigger the molecular mechanism(s) leading to up-regulation of NGFR expression.

Animals↗
PubMed1989

Distribution and time course of protein extravasation in the rat spinal cord after contusive injury.

We have previously characterized a graded, spinal cord contusive injury in the rat. We have now used this reproducible model to examine vascular permeability to horseradish peroxidase (HRP) after injury. The relationship between severity of injury and distribution of protein extravasation was evaluated at 3 h after injury. After mild injury, tracer was primarily confined to central gray matter and the ventral part of the dorsal columns. After moderate injury, protein extravasation was similar to that observed after mild injury, with the exception that the central hemorrhage included pericentral while matter and occasionally extended to the pial surface. After severe injury, reaction product (RP) was more densely distributed within the central cord and peripheral white matter. The axial extent of tracer at sites proximal and distal to the impact site increased with severity of injury. At 2.0 cm from the injury, no leakage of tracer was noted after mild injury. In contrast, after moderate and severe injury limited microvascular leakage of HRP was noted. Furthermore, after severe injury, in addition to local sites of microvascular leakage, intense RP was present in the dorsal columns up to at least 2.0 cm from the injury. The time course for re-establishment of the blood-spinal cord barrier to protein was evaluated from 3 h to 14 days after moderate injury. At 3 h to 1 day, protein leakage was maximal and coincided with sites of extravasated blood components, although was consistently more extensive. By 7 days, despite resolution of the initial hemorrhage, there remained scattered evidence for protein extravasation at the injured site and at sites along the axis of the cord. The blood-spinal cord barrier to HRP was reestablished by 14 days after injury.

Animals↗
PubMed1989

Correlative analyses of lesion development and functional status after graded spinal cord contusive injuries in the rat.

The development of both histopathological changes and functional deficits was quantitatively assessed after mild, moderate, and severe spinal cord contusive injuries. The cross-sectional area of the spinal cord at the epicenter (region of maximal damage) and the areas of hemorrhage, lesion, and remaining gray and white matter were determined from 15 min to 8 weeks after injury. From 24 h to 8 weeks after injury, functional deficits were quantified using a combined behavioral score (CBS) based on the results from a number of behavioral tests of function. Regression analysis was used to examine the correlations between the amount of residual white matter and both the severity of contusive impact and the functional deficit over time after injury. The area of hemorrhage at 15 min and 24 h was greater in the mild and moderate injury groups than after the severe contusive injury. Significant loss of gray and white matter occurred primarily between 24 h and 1 week after injury along with concomitant increases in the area of lesion. In the mild injury group the rate of lesion development appeared slower than that in the moderate and severe injury groups and significant white matter loss continued to occur between 1 and 4 weeks after injury. Behavioral tests of functional deficit were performed at 24 h and weekly thereafter. The development of stable functional deficits was observed beginning at 3 weeks after injury. There was a significant correlation between residual white matter and the degree of initial injury at 24 h after injury and all subsequent time points. However, a significant correlation between residual white matter and functional deficit, as measured by the CBS, was not observed at 24 h or 1 week but did develop by 4 weeks after injury.

Animals↗
PubMed1988

Blood-spinal cord barrier disruption proximal to a spinal cord transection in the rat: time course and pathways associated with protein leakage.

The effects of spinal cord transection on the blood-spinal cord barrier of the rat were examined at the ultrastructural level at sites 0.5 and 1.0 cm proximal to the injury. Using the vascular tracer horseradish peroxidase (HRP), the time course and pathways of barrier disruption were evaluated. At 0.5 cm, barrier disruption was noted from as early as 15 min and continued to 12 h after injury, whereas at 1.0 cm, evidence for vascular permeability was confined to between 15 min and 3 h. The presence of barrier breakdown to exogenous protein at a distance from the transection emphasizes that injury promotes a more generalized vascular response which likely contributes to subsequent edematous changes. The mechanism(s) involved in increased permeability appears to be primarily related to transendothelial vesicular transport of the tracer. There was no evidence for interendothelial leakage of the tracer across compromised tight junctions. In comparing these findings with those reported on sites distal to a transection, it is clear that there is an asymmetry in the vascular response to HRP. The pinocytotic index, an indicator of endothelial uptake of HRP, was significantly elevated (compared with control) distal to a transection from 3 h through 3 days after injury, attaining a maximum at 12 h. In contrast, the pinocytotic index proximal to a transection was significantly elevated compared to control values at only 1 h after injury. Furthermore, at 3 h after injury, when barrier disruption was most prominent, there was a smaller percentage of vessels exhibiting leakage to HRP proximal as opposed to distal to a transection.

Animals↗
PubMed1988

Spinal cord contusion in the rat: somatosensory evoked potentials as a function of graded injury.

A weight-drop technique was used to produce mild, moderate, or severe spinal cord contusive injury in rats. At 4 weeks after injury, somatosensory evoked potentials (SEPs) were recorded with silver ball electrodes placed over the somatosensory cortex of anesthetized rats to measure the response to sciatic nerve stimulation. Both SEP area and amplitude were measured and were highly correlated with each other. Both indices of the SEP correlated inversely with the height of the weight drop and directly with the degree of residual function assessed at 4 weeks after injury. Measures of residual function consisted of a motor score, inclined plane test, and a combined behavioral score based on several neurologic functions. No correlation between latency of the SEP with degrees of contusive injury was observed. The data indicate that the SEP can be used as one criterion in the assessment of the severity of a lesion in a rat model of a graded spinal cord injury.

Animals↗
PubMed1988

Biomechanical analysis of experimental spinal cord injury and functional loss.

Spinal cord injury was studied using a drop-weight technique in a rat model. A constant weight of 10 g was dropped from 2.5, 5.0 and 17.5 cm heights. The trauma delivered was quantified by biomechanical parameters of weight drop height, maximum force, and impulse, while the functional deficit produced by injury was quantified in terms of the maximum inclined plane score, hindlimb motor score, and combined behavioral score. Highly significant (P = 0.0001) relationships were found within the biomechanical parameters of trauma as well as between the trauma and the functional parameters at 4 weeks after injury. The impulse was found to be the best predictor of the functional loss (r = 0.79, P = 0.0001).

Animals↗
PubMed1986

Localization of dynorphin gene product-immunoreactivity in neurons from spinal cord and dorsal root ganglia.

Using spinal cord and dorsal root ganglion cell cultures, we have studied the immuno-histochemical distribution of several peptide products of the dynorphin gene. With antibody directed toward the midregion of dynorphin A, peptide-immunoreactivity was found exclusively in the cell bodies of spinal cord neurons. Antibody directed toward the amino- or carboxy-terminus of dynorphin A revealed peptide-immunoreactivity in the neurites, as well as perikarya. Spinal cord neurons also expressed dynorphin B- and alpha-neo-endorphin-immunoreactivities in both cell bodies and neurites. Dorsal root ganglion neurons cultured from embryonic tissue expressed dynorphin A-(1-13)-, dynorphin A-(9-17)- and dynorphin B-immunoreactivities in their perikarya. Sensory neurons obtained from dissociated adult ganglia similarly expressed dynorphin-immunoreactivity immediately upon inoculation into culture. Embryonic and adult murine sensory ganglia from the sacral region more frequently expressed dynorphin than did cells obtained from other spinal levels. Expression of dynorphin-immunoreactivity by sensory neurons was not influenced by elevated levels of Nerve Growth Factor or spinal cord conditioned medium. These data indicate that intrinsic spinal cord neurons may modulate sensory and spinal function in rather subtle ways via the expression of several different opioid peptide products of the dynorphin gene, in addition to the opioid peptides produced by the proenkephalin A gene. Beyond this, the observation of dynorphin-related peptides in dorsal root ganglion neurons suggests that these opioid peptides may have a specialized role in primary afferent neurotransmission.

Animals↗
PubMed1975

Suppression of melanoma cell tyrosinase activity and tumorigenicity after incorporation of bromouracil for one or two cell divisions.

We have studied the kinetics of suppression of tyrosinase activity and tumorigenicity in unsynchronized B16 mouse melanoma cells (clone B559) exposed to 5-bromodeoxyuridine (BrdU, 3 mug/ml) for one or two cell divisions, then cultured in BrdU-free medium (RM) for five or six days. Bromouracil replaced about 23% of thymine residues after 24 hours (1 cell division) and almost 40% after 48 hours (2 cell divisions) in the presence of BrdU. Upon subsequent growth in RM the extent of replacement declined in a manner consistent with dilution by new DNA synthesis, reaching 5-10% substitution by day 7 of these experiments. Tyrosinase activity was significantly reduced after treatment with BrdU for 24 or 48 hours but continued to decline after the cultures were changed to RM, approaching undetectable levels on day 7. The time course of reduction was similar to that previously determined in cells grown continuously for seven days in the presence of BrdU. Therefore, suppression of tyrosinase activity can result from incorporation of BrdU during a single cell cycle, but requires about seven days for full manifestation of the effect. Tumorigenicity decreased to 55% after 24 hours and to 15% after 48 hours with BrdU but rapidly reversed to approach that of untreated melanoma cells when subsequently grown in RM for 5-6 days. The effects of BrdU on total RNA or protein synthesis, or on plating efficiency appeared insufficient to account for the degree of suppression observed. Our results indicate that substitution by bromouracil into either strand of DNA loci controlling tyrosinase activity or tumorigenic potential may be sufficient for suppression. In addition, they demonstrate that such brief treatment with BrdU may be used to probe the regulation of differentiated function and tumorigenicity in these melanoma cells.

Animals↗