Evolution of Spinal Cord Transection of Rhesus Monkey Implanted with Polymer Synthesized by Plasma Evaluated by Diffusion Tensor Imaging

In spinal cord injury (SCI) there is damage to the nervous tissue, due to the initial damage and pathophysiological processes that are triggered subsequently. There is no effective therapeutic strategy for motor functional recovery derived from the injury. Several studies have demonstrated neurons growth in cell cultures on polymers synthesized by plasma derived from pyrrole, and the increased recovery of motor function in rats by implanting the polymer in acute states of the SCI in contusion and transection models. In the process of transferring these advances towards humans it is recommended to test in mayor species, such as nonhuman primates, prioritizing the use of non-invasive techniques to evaluate the injury progression with the applied treatments. This work shows the ability of diffusion tensor imaging (DTI) to evaluate the evolution of the SCI in nonhuman primates through the fraction of anisotropy (FA) analysis and the diffusion tensor tractography (DTT) calculus. The injury progression was analysed up to 3 months after the injury day by FA and DTT. The FA recovery and the DTT re-stabilization were observed in the experimental implanted subject with the polymer, in contrast with the non-implanted subject. The parameters derived from DTI are concordant with the histology and the motor functional behaviour.

Sensory and memory processing in old female and male Wistar rat brain, and its relationship with the cortical and hippocampal redox state

The brain is one of the most sensitive organs damaged during aging due to its susceptibility to the aging-related oxidative stress. Hence, in this study, the sensory nerve pathway integrity and the memory were evaluated and related to the redox state, the antioxidant enzymes function, and the protein oxidative damage in the brain cortex (Cx) and the hippocampus (Hc) of young (4-month-old) and old (24-month-old) male and female Wistar rats. Evoked potentials (EP) were performed for the auditory, visual, and somatosensory pathways. In both males and females, the old rat groups' latencies were larger in almost all waves when compared to the young same-sex animals. The novel object test was performed to evaluate memory. The superoxide dismutase and catalase antioxidant activity, as well as the protein oxidative damage, and the redox state were evaluated. Magnetic resonance (MR) imaging was used to obtain the diffusion tensor imaging, and the brain volume, while MR spectroscopy was used to obtain the brain metabolite concentrations (glutamine, glutamate, Myo-inositol, N-acetyl-aspartate, creatine) in the Cx and the Hc of young and old females. Our data suggest that, although there are limited variations regarding memory and nerve conduction velocity by sex, the differences concerning the redox status might be important to explain the dissimilar reactions during brain aging between males and females. Moreover, the increment in Myo-inositol levels in the Hc of old rats and the brain volume decrease suggest that redox state alterations might be correlated to neuroinflammation during brain aging.

Computed tomography is a feasible method for quantifying bone density in Macaca mulatta

Osteopathologies are a result of advanced age and decreased bone density and represent a global health problem. It is therefore important to generate models for longitudinal studies of the pathophysiology in order to improve early diagnosis and develop preventive therapies. For this kind of research, the use of computed tomography (CT) to evaluate bone health offers advantages over other techniques since it provides more complete information. The aim of this prospective, pilot study was to obtain measurements of the left femur from a population in captivity of 32 rhesus monkeys (Macaca mulatta) in order to standardize the model for future research. Healthy subjects from 5 to 28 years old were chosen. Three groups with different ages were formed as follows: (1) 5-9 years, (2) 10-19 years, and (3) 20-28 years. Semi-automatic segmentation by threshold defined the regions of interest, which were subdivided in the range of 300-700 Hounsfield units (HU) for trabecular bone and >700 HU for cortical bone. Then, the proportional ratios of the volumes of trabecular bone and cortical bone were obtained. Significant differences (analysis of variance test) in the averages of Hounsfield units, cortical, and trabecular bone proportions from each age group proved that a decrease in bone density begins at approximately 20 years of age. The values presented here, as well as the method to obtain them from CT scans, can be used as a baseline in a primate model for long-term research in bone pathology diagnosis and treatment.

Electrical activity of sensory pathways in female and male geriatric Rhesus monkeys (Macaca mulatta), and its relation to oxidative stress

Synapses loss during aging has been related to decreased neuronal excitability and reduced electrophysiological activity in the nervous system, as well as to increased brain damage. Those physiological and biochemical alterations have been related to the oxidative stress increase associated with old age. The main substrate of lipid peroxidation (LPX) in the central and peripheral nervous systems are the myelin sheaths, and their damage generates a delayed nerve conduction velocity. However, studies in which the neural conduction velocity is related to changes in the redox state are still lacking. Therefore, our aim was to correlate the sensory neural pathways delay in healthy geriatric Rhesus monkeys (Macaca mulatta) with the oxidative stress associated with physiological aging. Twenty-four monkeys were divided into four groups according to age and gender. Auditory, visual, and somatosensory evoked potentials were obtained. Superoxide dismutase, catalase, and glutathione peroxidase enzymatic activity, as well as LPX, were determined from blood samples. Our results showed significant differences between the older and younger age groups in all neural generators of the different sensory pathways evaluated, along with an increase in LPX and the antioxidant enzymatic activities. It suggests that, even though the enzymatic activity was found to be higher in older monkeys, probably as a compensatory effect, it was not enough to avoid LPX damage and the declined electric activity associated with age.

Visual, auditive and somatosensory pathways alterations in geriatric rhesus monkeys (Macaca mulatta)

BACKGROUND

Synapses loss during aging is associated to neurophysiologic alterations that impair organism's health span, thus making the study and prevention of sensory decline relevant for healthy aging and welfare. Therefore the aim of this study was to obtain normative data related to the electrophysiological responses of the different neurosensory components in the visual, auditory and somatosensory pathways in healthy geriatric rhesus monkeys in captivity.

METHODS

Twenty-four rhesus monkeys were divided in two groups: (i) Geriatric monkeys, 20-30 years of age, and (ii) Young monkeys, 7 years of age. Evoked potentials were obtained from the visual, auditory and somatosensory pathways.

RESULTS

Regardless the sensory pathways evaluated, a significant delay in nerve conduction was observed in the geriatric group in comparison to the young group.

CONCLUSIONS

Evoked potentials allowed identifying changes generated during aging in rhesus monkeys and normative data for this species were obtained.

Multiple extrauterine pregnancy with early and near full-term mummified fetuses in a New Zealand white rabbit (Oryctolagus cuniculus)

Extrauterine pregnancy (EP) is infrequent in mammalian species and occurs when fertilized ova implant and develop outside the uterus. A common outcome is abdominal pregnancy resulting in mummified fetuses (lithopedia). Here we describe an unusual case of abdominal pregnancy with early and near full-term lithopedia. Macroscopic findings supported the diagnosis of lithopedia with distinct age differences and facilitated further characterization of primary ectopia and risk factors leading to this occurrence.

Changes in blood parameters in rhesus monkeys (Macaca mulatta) during the first trimester of gestation

BACKGROUND

Regarding the good practice in the laboratory work, it is essential to have a broad spectrum of biochemical and hematological references in pregnant females to determine the health status of the colony.

OBJECTIVE

To establish reference values to reveal changes in hematology and blood chemistry in pregnant rhesus monkeys (Macaca mulatta) in their first trimester of pregnancy.

METHODS

Twenty-eight females in reproductive stage were used, divided into two groups: 14 pregnant macaques in their first trimester and 14 non-pregnant used as the control group. Blood samples were collected for the hematological test and blood chemistry.

RESULTS

The results showed significant difference in the blood chemistry for the following parameters: glucose, total bilirubin, and total protein. The hematological evaluation revealed significant difference in leukocytes and neutrophils.

CONCLUSIONS

These findings offer a reference range and provide a basis for improvement in techniques and refinement of clinical processes in these specimens.

New approach for graded compression spinal cord injuries in Rhesus macaque: method feasibility and preliminary observations

BACKGROUND

Current models of spinal cord injury (SCI) have been ineffective for translational research. Primate blunt SCI, which more closely resembles human injury, could be a promising model to fill this gap.

METHODS

Graded compression SCI was produced by inflating at T9 an epidural balloon as a function of spinal canal dimensions in a non-uniform group of monkeys.

RESULTS

Sham injury and cord compression by canal invasion of 50-75% produced minimal morpho-functional alterations, if at all. Canal invasion of 90-100% resulted in proportional functional deficits. Unexpectedly, these animals showed spontaneous gradual recovery over a 12-week period achieving quadruped walking, although with persistent absence of foot grasping reflex. Histopathology revealed predominance of central cord damage that correlated with functional status.

CONCLUSIONS

Our preliminary results suggest that this model could potentially be a useful addition to translational work, but requires further validation by including animals with permanent injuries and expansion of replicates.

Characterization of spontaneous subclavian steal phenomenon in a female rhesus macaque (Macaca mulatta)

In subclavian steal phenomenon (SSP), the subclavian artery develops a stenoocclusive disease proximal to the origin of the vertebral artery, leading to pronounced hemodynamic changes such as arterial flow reversal. Although SSP is a common echographic finding in humans, the phenomenon occurs only rarely in animals; consequently its physiologic features have not been reported previously. Here we describe the clinical and morphologic features of a spontaneous left SSP that was an incidental finding in an 18-y-old female rhesus macaque (Macaca mulatta). Our findings were documented through high-quality imaging studies obtained by using a computerized 3D tomography apparatus and clinical assessment of systolic and diastolic blood pressures.

Latencies obtained of the somatosensory evoked potentials of the median and tibial nerve in rhesus monkey undergoing intrauterine laminectomy to simulate myelomeningocele

BACKGROUND

Somatosensory evoked potentials (SSEP) have been described as excellent indicators of the degree of medullar injury in degenerative and metabolic diseases of the central nervous system (CNS). The prevalence of neural tube defects (NTD) is 6 cases/10,000 live newborns worldwide. It is thought that genetic as well as environmental factors contribute to the etiology of NTD. The objective of this study was to analyze and compare the latencies obtained by means of SSEP in a clinically healthy monkey vs. rhesus monkeys with intrauterine surgery in order to simulate surgically the neural tube defect (myelomengocele) by performing an intrauterine laminectomy and in which later the defect was corrected.

METHODS

This study was performed using three non-human primates of the Macaca mulatta species. There were practice intrauterine surgeries in two monkeys to simulate the neurological defect produced by myelomeningocele, using the third monkey as control. For statistical methodology four monkeys were used. They were born by natural birth without any surgical manipulation. With the cesarean-obtained products, stimulation was performed of the tibial and median nerve.

RESULTS

We observed that the hind limbs were the most affected, in particular, the left afferent of the monkey. The spinal cord was exposed to amniotic fluid, and there were no significant differences in the forelimbs.

CONCLUSIONS

The use of SSEP provides valuable information regarding preservation of sensorial functions in a variety of experimental neurological abnormalities.

Radiographic incidence of spinal osteopathologies in captive rhesus monkeys (Macaca mulatta)

Degenerative spinal disease is a leading cause of chronic disability both in humans and animals. Although widely seen as a normal occurrence of aging, degenerative spinal disease can be caused by various genetic, iatrogenic, inflammatory, and congenital factors. The objective of this study was to characterize the degenerative spine-related diseases and the age at onset in a random subpopulation of 20 captive rhesus monkeys (Macaca mulatta; male, 13; female, 7; age: range, 4 to 27 y; median, 18.5 y). Spinal radiographic evaluation (left lateral, right lateral, and ventrodorsal views) of the spinal column (C1 to S1) was performed, and spinal degenerative disease was scored. The incidence of osteopathology was higher in the 14- to 18-y-old group, but incidence did not differ according to sex. In the studied population, degenerative changes were present in monkeys as young as 9 y of age.

[Development of an animal model of myelomeningocele and options for prenatal treatment in Macaca mulatta]

BACKGROUND

Myelomeningocele is the most common congenital malformation of the central nervous system, with a reported incidence of 4.4-4.6 cases/10,000 live births in the U.S. Experimental studies demonstrated that the neurological deficit is not a cause for a primary defect in neurulation but is probably due to the progressive mechanical and chemical damage of amniotic liquid into the nerve tissue, which remained without protection during gestation. We undertook this study to develop an animal model in myelomeningocele in Macaca mulatta and compare the results of prenatal management between the colocations of an impermeable silicone mesh and closed with skin.

METHODS

A total of nine macaques were surgically intervened, randomly assigned between 12 and 14 weeks of gestation. A laminectomy was carried out in a fetus with bone marrow exposure. The defect was closed with skin or mesh. Three fetuses were left completely exposed. Descriptive statistics were done by ANOVA.

RESULTS

Of the four surviving fetuses (44%), none presented complications in mobility in the somatosensory evoked potential, hydrocephalus, or in sphincter control. Only one fetus developed bony deformities. The majority of time of the surgical procedure was due to the use of mesh and the least amount of time was involved in skin closing (p<0.005).

CONCLUSIONS

Macaca mulatta is an appropriate model for reproducing myelomeningocele and to evaluate the different options for prenatal management. Colocation of an impermeable silicone mesh is feasible, protecting the spine from amniotic liquid, with results similar to skin closure.

Serum testosterone and electroencephalography spectra in developmental male rhesus Macaca mulatta monkeys

BACKGROUND

The main objectives in this work were to determine whether the relationship between serum testosterone concentration and electroencephalography (EEG) develop mental change observed in human males is also present in Macaca mulatta and, if so, to determine which frequency bands are involved and which regions change in pre-pubertal monkeys as a function of serum testosterone concentration.

METHODS

Nine healthy monkeys were divided into three groups according to age. Serum testosterone was measured using immunoenzymatic chemiluminescent assay. EEG results were processed using Fast Fourier transform; average relative spectral power analysis was calculated and separated into delta and theta bands.

RESULTS

The main findings were higher delta relative power in temporal area of the youngest group. Significant positive correlations were observed between serum testosterone levels and theta relative power across the entire scalp, and between theta relative power at frontal and temporal locations and in negative direction between delta relative power in temporal areas. Partial correlations controlling for cephalic perimeter remained significant between testosterone and total theta relative power and theta relative power in temporal areas. Partial correlations remained significant for theta relative power controlling for age at temporal locations.

CONCLUSIONS

Our data show that testosterone may be a significant covariate in EEG development in Macaca mulatta males.