Biomedical subjects

M C Zrull

Publications and source records attributed to M C Zrull.

9 recordsLinked to original sources

PubMed2001

Chronic restraint stress enhances radial arm maze performance in female rats.

Effects of chronic restraint stress (21 and 28 days) on physiological and behavioral parameters in female rats were examined. Total (bound and free) and free corticosterone (CORT) levels were measured at different time points during the stress period. Higher total CORT levels were observed in stressed rats during the stress period but returned to baseline at 15 days post-stress. Additionally, free CORT levels decreased across the stress period. Estrous cyclicity was monitored daily in all animals. Stress had no apparent effects on estrous cyclicity, in rats with either normal length or elongated estrous cycles, but stressed females gained less weight than controls. Following the stress period, subjects were tested for open field activity and radial arm maze (RAM) performance. Females stressed for 21 days showed enhanced spatial memory performance on the RAM. A longer period of restraint, 28 days, also led to less weight gain by stressed subjects and unaltered estrous cycle lengths, but was not associated with enhanced RAM performance. Further analysis indicated that RAM performance was influenced by specific estrous cycle day, particularly during proestrus. Following 21 days of restraint stress all animals in proestrus, regardless of treatment, showed impaired acquisition. After 28 days, stressed females in proestrus performed better than proestrus controls. These results are discussed in relation to previously reported effects of stress in male rats.

Animals↗

PubMed1999

Spatial sound detection and the role of the inferior colliculus in the Long-Evans rat.

The ability of Long-Evans hooded rats (n = 10) to detect sounds presented from sources in the horizontal plane at 0 degrees elevation and the effects of bilateral lesions of the inferior colliculus on these abilities were examined. Rats were trained on a directional detection task which required animals to suppress licking responses in a conditioned avoidance paradigm when 100-ms noise bursts were presented at random from speakers at 45 degrees intervals beginning at azimuth (0 degrees). A task performance rate was determined by reducing the correct lick suppression rate for signal trials by the proportion of incorrect suppression responses on non-signal trials. Higher performance rates were observed for stimuli presented from 0-90 degrees than for stimuli presented in the caudal hemifield prior to surgical procedures. Bilateral lesions restricted to the inferior colliculus reduced detection performance (p < 0.05) and shifted the best performance rates from sounds presented at 0-45 degrees to stimuli emitted from a 90 degrees source (p < 0.05). These results demonstrate that pigmented rats show differential detection levels for noise bursts presented from different locations throughout the horizontal interaural plane, and suggest that the inferior colliculus is involved in this aspect of directional hearing.

Animals↗

PubMed1998

Differences between self- and peer ratings of interpersonal problems.

Interpersonal problems are frequently a source of distress for individuals and the focus of psychotherapeutic interventions. A self-report circumplex measure, the Inventory of Interpersonal Problems Circumplex (IIP-C), was modified for this investigation to acquire peer report data on interpersonal problems to help assess the validity of self-reported problems. The peer report data replicated the circumplex model of the IIP-C and when general interpersonal distress was removed (by ipsatizing), the data suggested that peers observed more domineering, vindictive, and emotionally cold types of problems than self-report (ipsatized) data. Individuals reported more other-pleasing, overly nurturant types of problems than peers observed. The findings both support the validity of the IIP-C and describe discrepancies in self- versus peer reported interpersonal problems. The results also describe differences in the general interpersonal distress factor accounted for by ipsatizing versus removing the general factor from unipsatized data. The results describe implications for clinicians and others assessing interpersonal problems.

Adult↗

PubMed1997

Effects of tectal grafts on sound localization deficits induced by inferior colliculus lesions in hooded rats.

The goals of this research were to examine the role of the inferior colliculus (IC) in mediating sound localization behavior and the ability of tectal grafts to restore function after IC ablation in the Long-Evans rat. Previous work has suggested that the IC is a major center for processing of information used in localizing sound sources in space. Adult rats were trained on a lick suppression paradigm to discriminate the location of the second pulse in a noise burst pair presented in the horizontal interaural plane. Following baseline testing, rats received bilateral IC lesions, bilateral lesions followed in 1 week by bilateral tectal grafts, or were sham operated. Sound localization ability was then tested 15 to 30 days and 40 to 50 days following surgical procedures. Performance across experimental groups was statistically the same during baseline testing. During the first operative test period lesion-only and grafted animals showed deficits in sound localization ability relative to controls. By the second postoperative test period control and grafted animals did not differ statistically in sound localization ability and performance of both groups was superior to that of lesion-only animals. Histology revealed a similar extent of IC damage in lesion-only and lesion-graft animals and revealed the presence of implanted tectal tissue in all grafted animals. There was significant neuron loss in the dorsal nucleus of lateral lemniscus (DNLL) in lesion-only animals relative to grafted rats and sham controls. Behavioral results suggest that the IC of pigmented rat is important for sound localization ability. The sparing of DNLL neurons in grafted animals suggests that the tectal grafts may directly integrate into or aid intrinsic recovery of the host auditory pathway.

Animals↗

PubMed1992

The inferior colliculus: calbindin and parvalbumin immunoreactivity in neural grafts.

The inferior colliculus was selected as a brain stem site for study of neural grafting and identification of calcium binding proteins. Unilateral ablation sites of eight midbrain inferior colliculus in adult Long-Evans rats were implanted with E17-18 caudal tectum. After 2 to 9 months animals were sacrificed and sections reacted using antibodies for calbindin and parvalbumin. The central nucleus of normal inferior colliculus shows high density of neuronal and fiber staining for parvalbumin. Typical graft cores had similar staining distributions including discoid and stellate neuron populations. Graft cores showed low densities of reactivity for calbindin comparable to central nucleus. In surrounding graft regions there was substantive-neuronal and fiber labeling for calbindin and parvalbumin including stellate neuron populations normally found in the dorsal and lateral nuclei of inferior colliculus. These results demonstrate that the expression of calcium binding proteins in tectal grafts resembles that of inferior colliculus.

Animals↗

PubMed1991

Structural features of neurons in whole grafts of the rat inferior colliculus.

The inferior colliculus (IC) is a midbrain structure that receives ascending auditory input from brainstem nuclei via the lateral lemniscus, sends efferent fibers to the medial geniculate body of thalamus and receives descending projections from auditory cortex. In the rat, the IC consists of dorsal and external cortices surrounding the central nucleus of IC (CNIC) which is populated by discoid and stellate neurons; the CNIC has a laminar appearance arising from organization of lemniscal fibers and processes of discoid cells. The IC of adult rats was chosen for implantation of whole grafts of E16-17 caudal tectum into unilateral lesion sites. Dendritic and somal architecture of graft neurons was examined 1 to 4.5 months following implantation using rapid Golgi, HRP and Nissl methods. The CNIC of rat is dominated by principal neurons with relatively flattened dendritic fields. In grafts of caudal tectum the most common neuron class observed possesses flattened dendritic arbors which often parallel one another. These neurons also resemble CNIC neurons of host tissue adjacent to the graft border. Spine formations appear on both proximal and distal dendrites of this neural type in both normal and implanted tissues. In addition, comparable somal features of graft neurons include ovoid or fusiform shapes with regular nuclear membranes as found in the normal colliculus. In Golgi stained material fewer stellate class neurons appear as in the normal CNIC, although stellate cell classes are more abundant in the pericentral areas of normal tissue. Both neuron populations are retrogradely labelled in graft and normal IC after HRP injection into the medial geniculate body. These features suggest that the graft core typically consists of prototypic CNIC cells. Other features of neuron and glial cell density vary in graft material which also shows a complex network of vasculature. These results demonstrate that whole grafts of caudal tectum placed into the inferior colliculus can form organized neural architecture similar to the normal CNIC. The somal, dendritic and spine features of these neurons form a potential substrate for connectional and functional properties which establish this preparation as suitable for further investigation as a model for development and recovery of function in the central auditory system.

Animals↗

PubMed1990

Fetal tectum grafted as a cell suspension into the adult rat inferior colliculus.

The known structural and functional features of the inferior colliculus provided an advantageous substrate for examining the outcome of neural transplantation. In the present study, tissue from the midbrain tectum of Sprague-Dawley rat fetuses was removed at 15, 16 and 19 days of gestation (E15, E16 and E19), incubated as a dissociated cell suspension for 12 to 15 h in a medium containing True Blue for prelabeling, and injected into the central nucleus of the inferior colliculus (CNIC) of 28 normal male adult conspecifics. Viable tectal grafts were found in 57.5% of host animals with 65.2% located in CNIC. Grafts of E16 tissue had a survival rate of 84.2%, which was twice that of E15 or E19 donors, and there was no difference in graft survival rate in hosts sacrificed up to 6 months after the implantation procedure. Neurons prelabeled with True Blue and counterstained with thionin were identified as uniquely green stained cells in brightfield illumination and brilliant opaque cells in darkfield microscopy. Grafts were organized in tightly packed clusters of cells including large rounded polygonal and smaller cells similar in size to normal CNIC large and small multipolar neurons. Cell morphology of the larger ovoid and fusiform grafted neurons most closely resembled that of typical adult CNIC cell populations; other implanted cell types appeared immature even when host post-implant survival was extended. At longer post-implant intervals graft and host cells further intermingled, and both cellular and fibrous bridges were observed at the interface between host and graft tissue. The present work demonstrates the viability and development of homotypic cells grafted into a central auditory structure utilizing a simple method of prelabeling donor tissue with a fluorescent dye.

Animals↗

PubMed1988

Recovery of sensorimotor function after frontal cortex damage in rats: evidence that the serial lesion effect is due to serial recovery.

Multiple-staged brain lesions produce fewer and smaller behavioral effects than does damage produced in a single surgery. This is called the serial lesion effect. Two hypotheses were tested, the reduced deficit hypothesis and the serial recovery hypothesis, which attempt to explain the serial lesion effect. The effects of lesions of the medial frontal cortex on sensorimotor behavior were investigated in rats that received bilateral damage in a single surgery (n = 7), in two unilateral stages separated by 3 weeks (n = 16), or unilateral damage followed 3 weeks later by a sham surgery (n = 5). Unilateral damage produced deficits on the contralateral side in responsivity to visual, tactile, and olfactory stimuli and impairments in roll-over and paw withdrawal motor responses. All behavioral impairments except visual placement recovered over the next 3 weeks. A second unilateral lesion on the contralateral side produced the same symptoms but on the opposite side of the body. There was no reinstatement of the previously recovered deficits. Bilateral damage incurred in a single stage produced these same deficits on both sides. Because the effects of the second unilateral lesion in the two-stage group produced comparable contralateral effects to those produced in the single-stage group, but no reinstatement of ipsilateral deficits occurred, the reduced deficit hypothesis was rejected. It was concluded that at least for medial frontal cortex damage, the serial lesion effect occurred as a result of serial recovery of the deficits.

Animals↗

PubMedDate not supplied

Effects of tectal grafts on sound detection deficits induced by inferior colliculus lesions in hooded rats.

The midbrain inferior colliculus (IC), a major integrating center for auditory processing, provides a model for structural, functional, and behavioral recovery. The present study examined the role of IC in spatial sound detection, and the effects of neural transplantation in sparing of behavioral performance. Hooded rats were presented noise bursts at ambient noise levels and 15 dB above this level randomly at one of eight locations in the horizontal plane, and rats were required to suppress licking upon detecting signal presentations. Following training, rats received bilateral IC lesions, bilateral lesions followed in 1 wk by bilateral tectal grafts (embryonic Day 18), or were sham operated. During repeated testing 15 to 30 days and 40 to 45 days following surgical procedures, rats with lesions showed impaired detection task performance when compared to grafted or sham animals. Detection ratios were statistically higher for grafted rats than for rats with lesions at repeated testing times. Performance of grafted animals was not statistically separable from the sham control group; however, grafted rats never achieved preoperative detection rates nor rates as high as sham rats. Postmortem implantation of diI crystals unilaterally into grafts demonstrated fiber labeling in the ipsilateral IC and lateral lemniscus, and retrograde labeling of neurons in the remaining host IC and dorsal nucleus of lateral lemniscus. Combined with results of previous studies, the results of this study suggest that sparing of detection performance for sounds occurring at random spatial locations may be attributable to partial integration of host-graft pathways.

Acoustic Stimulation↗