Juvenile Macaques Research Articles

Association of interleukin-6 in the pathogenesis of acutely fatal SIVsmm/PBj-14 in pigtailed macaques.

Infection with a variant of simian immunodeficiency virus (SIVsmm/PBj-14) causes death in juvenile pigtailed macaques within 8 days of infection. The primary pathology is localized to the lymphoid tissues of the gut and spleen. Although the virus is present, the lesions are most consistent with acute reactive inflammation. We studied the serum and tissues for evidence of acute cytokine production often associated with acute inflammation. One factor, IL-6, was found to be significantly increased (> 1000-fold) over all other measured cytokines in all the pigtailed macaques who died acutely. Increased levels of IL-6 were found both in the serum and in the inflamed tissues. mRNA for IL-6 was found in the tissues with the highest protein levels of IL-6. The marked increase in IL-6 and IL-6 mRNA correlated with the virus levels in the tissues and serum as determined by viral isolation, immunohistochemistry, and Northern blot analysis. These findings suggest that the underlying pathogenesis of primary tissue damage, necrosis, and death by PBj-14 is the induction of cytokine production. Although the presence of the virus may be critical for the initiation of these events, the intense inflammatory reaction is associated with the cause of death.

Arcobacter (Campylobacter) butzleri-associated diarrheal illness in a nonhuman primate population

After DNA hybridization identified an isolate from an ill rhesus macaque (Macaca mulatta) as Arcobacter (Campylobacter) butzleri, we initiated a study to determine whether A. butzleri was associated with diarrheal disease in nonhuman primates at the Yerkes Primate Research Center. By using Campy-CVA medium incubated at 35 degrees C, 15 A. butzleri isolates were obtained from 14 macaques; 7 macaques were coinfected with Campylobacter coli and Campylobacter jejuni. A. butzleri was not isolated from normal feces, despite the fact that feces from 76 macaques were cultured at necropsy. Histologic evaluation of colonic specimens from three macaques from which A. butzleri had been isolated showed mild to moderately severe chronic, active colitis. Ribotype analysis of the 15 A. butzleri isolates revealed nine different strains; these data suggest that A. butzleri may be endemic in this primate population and that a point source of infection is unlikely. This is the first report of the presence of A. butzleri in juvenile and adult macaques with diarrhea, and it may present an opportunity to study the pathogenesis of this organism, which appears to be associated with persistent diarrhea in humans.

Development of visual preference for closely related species by infant and juvenile macaques with restricted social experience

Japanese and rhesus monkeys aged between 9 months old and 5 yrs old pressed a lever to see a variety of pictures of seven macaque species. These monkeys had various restricted social experience: namely, either reared by humans with conspecific or heterospecific peers, or cross-fostered between these two species. Rhesus monkeys tended to prefer seeing rhesus monkeys best among the pictures of the seven species without regard to their age or social experience. Japanese monkeys having restricted experience also liked to see rhesus monkeys better than Japanese monkeys, but not the best among the seven species. In a previous study, mother-reared infants of Japanese monkeys preferred seeing pictures of their own species over those of rhesus monkeys. These results suggest a dissociation of the determinants of this basic social preference: rhesus monkeys prefer to see their own species by nature while Japanese monkeys may learn to prefer their own species.

Cortical astrocytosis in juvenile rhesus monkeys infected with simian immunodeficiency virus.

The pattern of expression of GFAP immunoreactivity in astrocytes of the juvenile rhesus monkey cortex was examined following infection with simian immunodeficiency virus (SIV). Blocks of cerebral cortex plus subjacent white matter from saline- and formalin-perfused brain were examined by peroxidase-linked immunochemical and immunofluorescence staining of deparaffinized sections. Strong GFAP immunoreactivity was found in astrocytic cells in both uninfected and SIV-infected juvenile macaque in the subpial cerebral cortex and in subcortical white matter, where GFAP-positive cells were abundant. GFAP staining of cortical layers 2-6 on the other hand was weak or absent in three uninfected controls and one infected animal without cognitive impairment, but moderate to strong in animals productively infected with SIV that demonstrated cognitive and/or motor impairment. These data demonstrate a cortical locus of astrocytic activation in rhesus monkeys infected with primate immunodeficiency virus isolate SIVB670 which, like HIV-1 in man, causes motor/cognitive impairment as well as immunodeficiency disease.

Immunogenicity and toxicity testing of an experimental HIV-1 vaccine in nonhuman primates.

A highly purified saponin from Q. saponaria (QS-21) was tested in juvenile rhesus macaques for adjuvant activity and toxicity. The QS-21 was tested alone or as part of an experimental subunit HIV-1 vaccine containing a truncated recombinant HIV-1 envelope protein (gp160D) adsorbed to alum. Antibody responses were measured using ELISA and cell-mediated immunity was measured using cellular proliferation assays. Potential toxicity was monitored by standard clinical pathology testing using peripheral blood and urine samples. No toxic effects were observed, even after the administration of the experimental vaccines three times at monthly intervals. The QS-21 saponin adjuvant enhanced total antibody production levels by greater than 100-fold and broadened the specificity of the response so that additional epitopes were recognized, when compared with alum-adsorbed HIV-1 gp160D formulation. Low-level, antigen-specific proliferative responses to HIV-1 recombinant gp160 were induced by either vaccine formulation. Proliferative responses were induced by a sham challenge with soluble recombinant HIV-1 gp160 for all of the animals that had been vaccinated. However, those that received the HIV-complete vaccine formulation containing QS-21 responded significantly better. These data demonstrated that the QS-21 adjuvant augmented both antibody responses and cell-mediated immunity and established immunological memory. The potent adjuvant activity and lack of toxicity suggest that this adjuvant should be safe and effective for use in HIV-1 vaccines.

Cognitive and motor impairments associated with SIV infection in rhesus monkeys.

Cognitive and motor deficits are now recognized as significant clinical features of infection with the human immunodeficiency virus (HIV). Juvenile rhesus macaques infected with simian immunodeficiency virus (SIV) were found to exhibit cognitive and motor deficits characteristic of HIV infection. Impairment on a motor skill task was the most reliable indicator of infection. Various cognitive impairments were also evident. These deficits were related to SIV infection of the brain but not to inflammatory lesions at a particular locus. The results suggest that the SIV-infected rhesus macaque is a valuable model for understanding the cause of HIV-associated central nervous system dysfunction and for developing a treatment.

Opiate receptor blockade in juvenile macaques: effect on affiliative interactions with their mothers and group companions

The aim of this study was to test the hypothesis that, in non-human primates, the offspring-mother attachment and other social bonds within the group have in common neural mediating mechanisms involving brain opioids. The subjects were 10 juvenile macaques living in a stable social group with their mothers and other group companions. A within-subjects design, balanced for the order of drug administration (naloxone 1 mg/kg i.m. and saline), was used. In the naloxone condition, the juveniles increased their relative role in maintaining proximity with their mothers, made more grooming solicitations, and received more grooming. We found no evidence for differential effects of naloxone on the affiliative bonds the subjects had with their mothers and other group companions. The subjects' increased demands for social comfort were evenly addressed to, and responded to by, both their mothers and other group companions. This finding supports the hypothesis that, at a neural level, the endogenous opioid peptides form a common substrate for different types of social attachments in primates.

Immunocytochemical localization of progestin receptors in monkey hypothalamus: effect of estrogen and progestin.

The increase in PRL secretion which follows progesterone (P) administration to estradiol (E)-primed women and monkeys cannot be due to an action of P at the pituitary level because lactotropes do not contain progestin receptors (PR). To further the hypothesis that P increases PRL secretion by an action in the hypothalamus, PR-expressing neurons were studied in free-ranging and steroid-manipulated monkeys using immunocytochemistry with a monoclonal antibody to human PR. Specific PR immunoreactivity is localized in the nucleus of individual hypothalamic neurons. Male and female adult and juvenile macaque hypothalami contain significant populations of PR-positive neurons throughout the anterior and medial basal hypothalamus. Ovariectomy decreases, but does not abolish, the number of neurons expressing PR. PR expression was not altered in the supraoptic nucleus (SON) by ovariectomy. Estrogen treatment for 28 days caused a significant increase in the number of PR-positive neurons in the medial preoptic area, the ventro-medial nucleus, the arcuate nucleus, and the median eminence, but not in the SON. P treatment added to the E treatment from day 14 to day 28 did not alter the number of PR-positive neurons in any area. These data suggest that PR may be constitutively expressed in the magnocellular neurons of the SON and in certain other cells throughout the hypothalamus. E induces PR in a large proportion of neurons in the medial basal hypothalamus and this action is not blocked by subsequent P treatment. The inability of P to down-regulate PR in the hypothalamus differs from the reproductive tract and pituitary. Indeed, this observation is consistent with the fact that PRL secretion remains elevated during chronic P administration.

Estrogen Action on Growth Hormone in Pituitary Cell Cultures from Adult and Juvenile Macaques*

Basal growth hormone (GH) levels are higher in female than male primates, and estradiol (E) treatment of gonadectomized primates increases serum GH. To determine if the effect of E is mediated at the level of the somatotroph, we verified the effect of E-treatment on serum GH in spayed macaques, and then examined the effect of E on GH secretion in serum-free monkey pituitary cultures. Daily blood samples were obtained from cynomolgus macaques which were spayed upon detection of menstruation and immediately implanted with either empty (n = 5) or E-filled (n = 5) 2-cm silastic capsules. The average level of GH was significantly higher (P less than 0.003) in the E-treated group than in the control group (6.4 +/- 0.7 vs. 3.7 +/- 0.6 ng/ml). Pituitaries from rhesus monkeys were dispersed and cultured in 48-well plates on extracellular matrix in DME/F12 with insulin, transferrin, selenium. Using pituitary cells from a long-term spayed female, two plates were established with and without phenol red. Each plate was treated with E in a dose-related manner (0.001-10 nM) from days 0-18 (4 wells per dose). There was a significant dose-related increase in medium prolactin (PRL) in both plates, but E had no effect on GH. Therefore, the effect of E on GH in spayed monkeys cannot be accounted for by a direct action on somatotrophs. Additional phenol red-free pituitary cultures were established from four juvenile males, one adult male, two juvenile females, and two adult females and treated with E in a dose-related fashion for 28 days. Neither the adult male, the adult female, nor the juvenile female cultures exhibited an increase in GH with E treatment. Only the four juvenile male pituitary cultures showed a variable increase in GH with maximal responses ranging from 5 to 40% over control. This data suggested that the juvenile male pituitary contained an E-sensitive GH-secreting cell population which is not present in the other pituitary cultures. PRL and GH double-immunocytochemical staining of pituitary cultures from an adult female and a juvenile male revealed a significant population of rounded and possibly double-labeled cells in the juvenile male culture which were infrequently seen in the adult female culture. Speculatively, this population could represent mammosomatotroph stem cells that corelease GH and PRL upon stimulation.

31P saturation transfer and phosphocreatine imaging in the monkey brain.

31P magnetic resonance imaging with chemical-shift discrimination by selective excitation has been employed to determine the phosphocreatine (PCr) distribution in the brains of three juvenile macaque monkeys. PCr images were also obtained while saturating the resonance of the gamma-phosphate of ATP, which allowed the investigation of the chemical exchange between PCr and the gamma-phosphate of ATP catalyzed by creatine kinase. Superposition of the PCr images over the proton image of the same monkey brain revealed topological variations in the distribution of PCr and creatine kinase activity. PCr images were also obtained with and without visual stimulation. In two out of four experiments, an apparently localized decrease in PCr concentration was noted in visual cortex upon visual stimulation. This result is interpreted in terms of a possible role for the local ADP concentration in stimulating the accompanying metabolic response.

Pubertal changes in pro-opiomelanocortin and gonadotropin-releasing hormone gene expression in the brain of the male monkey

Puberty in the primate is initiated by an amplification of the pulsatile secretion of gonadotropin-releasing hormone (GnRH); however, the factors responsible for this a pubertal activation of GnRH neurons are unknown. We examined whether the biosynthetic capacity of GnRH neurons could be limiting for GnRH secretion in the juvenile monkey by determining whether the prepubertal macaque ( Maraca fascicularis) expresses the GnRH gene. Using in situ hybridization for GnRH mRNA, we found no evidence for differences between prepubertal and adult animals in either the cellular level of GnRH mRNAs or the number of GnRH mRNA-containing cells in any area of the brain. These observations suggest that expression of the GnRH gene, at least to the point of messenger mRNA production, is not limiting for puberty onset. β-Endorphin, derived from its precursor proopiomelanocortin (POMC), has been implicated as an inhibitory neurotransmitter in the control of GnRH secretion. We examined whether expression of the POMC gene changes as a function of sexual maturation by comparing the cellular content of POMC mRNA in the arcuate nucleus between prepubertal and adult male macaques. We report that cellular POMC mRNA levels are significantly higher in the adult than in the juvenile macaque ( P < 0.02). We suggest that an increase in POMC biosynthesis may be part of the mechanism whereby a continuous mode of GnRH secretion is shaped into discrete pulses, which in turn initiate puberty in the primate.

Juvenile rheumatoid arthritis in a rhesus monkey (Macaca mulatto)

A juvenile rhesus macaque (Macaca mulatta) developed a symmetrical erosive polyarthritis involving both large and small diarthrodial joints. Neither an infectious nor a metabolic etiology could be determined. This case shares many clinical and pathological features with the polyarticular form of human juvenile rheumatoid arthritis.

Opioid synapses on vasopressin neurons in the paraventricular and supraoptic nuclei of juvenile monkeys

Opioid peptide- as well as vasopressin-containing neurons synapse on gonadotropin releasing hormone neurons in juvenile macaques. In this study we performed double-label immunostaining for opioid and vasopressin neurons in the paraventricular and supraoptic nuclei in order to assess their interrelationships. Neuroendocrine neurons in the hypothalamus were prelabeled by microinjection of electron-dense retrograde tracer into the median eminence, and were easily identified in frontal Vibratome sections. Sections through the paraventricular and supraoptic nuclei were immunostained for vasopressin with the peroxidase-antiperoxidase technique, and for opioids using the indirect immunogold method. By light microscopy, opioid-immunoreactive inputs appeared to innervate an average of 39% of the vasopressin neurons in the paraventricular nucleus and 33% in the supraoptic nucleus, and were more prevalent anteriorly. Clusters of opioid afferents formed cup-like calices around major processes of many vasopressin neurons, especially in the paraventricular nucleus. Electron microscopy revealed that these groups of opioid axon terminals made frequent symmetrical and fewer asymmetrical synapses on both neuroendocrine and non-neuroendocrine vasopressinergic cell bodies and dendrites. Our study did not reveal vasopressin opioid synapses in these hypothalamic nuclei, but this does not preclude the possibility of their existence elsewhere. These results indicate that opioid afferents modulate vasopressin neuronal activity in the monkey paraventricular and supraoptic nuclei. Previous results have suggested that corticotropin releasing hormone acts via vasopressinergic neurons to stimulate opioid neuronal activity and to inhibit gonadotropin releasing hormone release. Taken together, the data suggest that stressful stimuli could initiate a series of neuropeptidergic interactions which ultimately alter pulsatile gonadotropin releasing hormone secretion and thus gonadotropin secretion in primates.

Persistent infection of rhesus macaques with a molecular clone of human immunodeficiency virus type 2: evidence of minimal genetic drift and low pathogenetic effects

In an attempt to generate a suitable animal model to study the infectivity and possible pathogenicity of human immunodeficiency viruses, we intravenously inoculated juvenile rhesus macaques and African green monkeys with a molecularly cloned virus, human immunodeficiency virus type 2 HIV-2sbl/isy, as well as with the uncloned HIV-2nih-z virus. Infection was monitored by virus recovery from the peripheral blood cells and by seroconversion against HIV-2 antigens measured by Western immunoblot, radioimmunoprecipitation, and enzyme-linked immunosorbent assay. We successfully infected two out of two macaques with the molecularly cloned virus and one macaque out of two with the HIV-2nih-z. No evidence of infection was seen in the African green monkeys with either virus. We followed the infected animals for 2 years. The animals remained healthy, although we observed intermittent lymphadenopathy and a transient decrease in the absolute number of circulating CD4+ T lymphocytes in both animals infected with the molecularly cloned virus. Virus isolation from the peripheral blood cells of the infected animals was successful only within the first few months after inoculation. Evidence of persistent infection was provided by the detection of proviral DNA by polymerase chain reaction analysis of the blood cells of the inoculated animals and by the stability of antiviral antibody titers. To evaluate the genetic drift of the proviral DNA, we molecularly cloned viruses which were reisolated 1 and 5 months postinoculation from one of these animals. Comparison of the DNA sequences of the envelope genes of both these isolates indicated that a low degree of variation (0.2%) in the envelope protein had occurred in vivo during the 5-month period. These data suggest that the use of HIV-2sbl/isy in rhesus macaques may represent a good animal model system to study prevention of viral infection. In particular, molecularly cloned virus can be manipulated for functional studies of viral genes in the pathogenesis of acquired immune deficiency syndrome and provides a reproducible source of virus for vaccine studies.

Location of the Neuroendocrine Dopamine Neurons in the Monkey Hypothalamus by Retrograde Tracing and Immunostaining*,**

Abstract In order to localize neuroendocrine dopamine neurons in the monkey hypothalamus, one female and three male juvenile cynomolgus macaques were each given two or three microinjections (0.2 to 0.3 mul per site) of the retrograde tracer wheat germ agglutinin-apoHorseradish peroxidase-10 nm colloidal gold into the superficial, median eminence region of the infundibular stalk. Five to 15 days following surgery, the brains were fixed by perfusion, and vibratomed at 40 pm in the frontal plane. Every 12th section was immunostained with rabbit anti-tyrosine hydroxylase using the peroxidase anti-peroxidase technique with diaminobenzidine as the chromogen. Neuroendocrine, immunoreactive neurons were easily recognized as brown, immunopositive cell bodies containing more than three distinct dark blue granules, confirmed by electron microscopy to be tracer-filled lysosomes. Neuronal counts from each complete series of sections were compiled by anatomical region, and the percentages of tyrosine hydroxylase-immunoreactive and neuroendocrine, immunoreactive neurons determined. Although regional and interanimal variations were observed, we estimated that 5,400 of the total 19,000 tyrosine hydroxylaseimmunoreactive neurons in the juvenile macaque hypothalamus were neuroendocrine. When averaged by anatomical region, the suprachiasmatic nuclear groups contained 7% of all immunoreactive neurons (50% were neuroendocrine) and 15% of all neuroendocrine, immunoreactive neurons in these animals. The combined periventricular zones contained 20% of all immunoreactive neurons (more than 50% of ventral and 38% of dorsal were neuroendocrine) and 58% of all neuroendocrine, immunoreactive neurons. The paraventricular nucleus included 50% of all immunoreactive neurons, more than any other nucleus, (3% were neuroendocrine) and 11% of the total neuroendocrine, immunoreactive neurons. The ventral paraventricular nucleus contained only 2% of all immunoreactive neurons (13% were neuroendocrine) and 3% of the total neuroendocrine group. The zona incerta contained 15% of all immunoreactive neurons (0% were retrogradely labeled) but 0% of the neuroendocrine cells. The arcuate nucleus subdivisions contained about 5% of all immunoreactive neurons (more than 60% were neuroendocrine) and 8% of the neuroendocrine population. The ventral hypothalamic tract contained about 1% of all immunoreactive neurons (medially, 63%, and further laterally, 25% were neuroendocrine) and 5% of all neuroendocrine, immunoreactive neurons in these animals. The presence of the retrograde tracer from the median eminence in tyrosine hydroxylase-immunoreactive neurons, combined with knowledge of the location of dopaminergic cell groups, permitted assessment of the A11-A14 dopaminergic neurons which project to the primate infundibulum. Neuroendocrine dopamine neurons occurred predominantly in the All periventricular zones (65% of the total), being greatest around the ventral aspect of the entire third ventricle. They were less numerous in more dorsal regions of All extending up to the level of the paraventricular nucleus. The A12 arcuate (tuberoinfundibular) projection (15% of the total) was not nearly as prominent as All in primates, in contrast to rodents. None of the A13 incertohypothalamic dopamine neurons (0%) projected to the median eminence. The A14 anterior-ventral periventricular region, including the suprachiasmatic nuclear groups, provided the substantial remainder (20%) of all neuroendocrine dopamine neurons. In summary, our results suggest the involvement of a regionally specific dopaminergic system in the hypothalamic control of anterior pituitary hormone secretion in primates. The data also indicate that 75% of all tyrosine hydroxylase-immunopositive neurons do not project to the median eminence, and probably serve other functions. Although the retrograde tracer may not have labeled all neuroendocrine dopamine neurons, it may have identified some dopamine neurons which only interact with other median eminence nerve terminals, or other types of tyrosine hydroxylase-containing, neuropeptidergic neurons which project to the infundibulum. However, considering the known locations of dopaminergic neurons and the large numbers of labeled cells, the results here are a reliable indication of the diverse origins of median eminence-directed dopamine neurons in the juvenile primate.

Location of the Neuroendocrine Gonadotropin‐Releasing Hormone Neurons in the Monkey Hypothalamus by Retrograde Tracing and Immunostaining*,**

Abstract In order to localize neuroendocrine gonadotropin-releasing hormone (GnRH) neurons in the monkey hypothalamus, four juvenile cynomolgus macaques (one female, three males) were each given two or three microinjections (0.2 to 0.3 mul per site) of the retrograde tracer wheat germ agglutinin-apoHorseradish peroxidase-10 nm colloidal gold into the superficial, median eminence region of the infundibular stalk. Five to 15 days following surgery, the brains were fixed by perfusion and vibratomed at 40 mum in the frontal plane. Every 12th section was immunostained with rabbit anti-GnRH using the peroxidase anti-peroxidase technique with diaminobenzidine as the chromogen. Neuroendocrine GnRH neurons were easily identified in tissue sections as brown, immunostained cell bodies containing more than three distinct, dark blue, tracer-filled lysosomes. Neuronal counts from each complete series of sections were compiled by anatomical region, and the percentages of GnRH and neuroendocrine GnRH neurons determined. The highest proportion of neuroendocrine GnRH neurons (with projections to the median eminence) occurred in the ventral hypothalamic tract, especially in its medial third (71%), and in the supraoptic decussation just anterior to it. Proportions decreased moving laterally into the middle third (58%) and lateral third (25%) of the ventral hypothalamic tract. Further anterior and lateral, progressively smaller but significant neuroendocrine GnRH contributions were found in the supraoptic nucleus (57%) and lateral hypothalamus (33%), and in the medial preoptic area (26%). Although the medial preoptic area contained a greater percentage of the total GnRH-immunoreactive cell bodies (36%) than the ventral hypothalamic tract (27%), as a whole, the ventral hypothalamic tract contained 60% of the neuroendocrine GnRH neurons compared to only 25% from the medial preoptic area. Large numbers of GnRH cell bodies found in the diagonal band of Broca near the organum vasculosum of the lamina terminalis were not retrogradely labeled. GnRH neurons were not observed in the arcuate nucleus, the few in the paraventricular nucleus were not neuroendocrine, and the contribution from the periventricular zone was negligible. Our results here are the first to identify the neurons giving rise to the neuroendocrine GnRH system in juvenile monkeys. The data indicate that more GnRH neurons close to the infundibulum serve a neuroendocrine (perhaps hypophysiotropic) role than do those in more anterior areas. Furthermore, they suggest that the ventral hypothalamic tract is the most important, and perhaps most influential, neuroendocrine GnRH cell group in primates. The data substantiate the observed autonomy of the medial basal hypothalamus in controlling gonadotropin secretion and menstrual cyclicity in these animals. However, they also infer that perhaps 60% of the GnRH neurons do not project to the primate median eminence, and thus may serve other non-neuroendocrine functions.

Simian immunodeficiency virus-specific T-cell-mediated proliferative response of infected rhesus macaques

While cell-mediated immunity is known to play an important role in controlling viral infections, its role in human and experimental animal models of human AIDS has not been established. To address this issue, four juvenile rhesus macaques were infected with simian immunodeficiency virus SIVMAC. Freshly isolated peripheral blood mononuclear cells from these SIVMAC-infected macaques and four uninfected control macaques were assessed for T-cell proliferative activity to SIV, monthly, for 10 consecutive months. T cells from SIV-infected monkeys failed to proliferate in response to SIV added directly to the culture. However, when SIV was processed by autologous antigen-presenting cells prior to culture with purified T cells, proliferative responses were uniformly demonstrated in SIV-infected monkeys, but not in uninfected controls. Proliferation in response to heat-inactivated SIV was mediated by CD4+ T cells and was shown to be MHC class II-restricted. However, the proliferative response to infectious SIV was mediated by both CD4+ and CD8+ T cells and was MHC class-restricted. As disease progressed, a decline in the T-cell proliferative response was observed.

Altered responses to cutaneous stimuli in the second somatosensory cortex following lesions of the postcentral gyrus in infant and juvenile macaques

Infant macaques recover tactile abilities better than older animals after somatosensory cortical lesions. To investigate the neural basis of this phenomenon, we ablated the hand representation in primary somatosensory cortex (SI) of infant and juvenile Macaca mulatta and recorded in ipsilateral second somatosensory cortex (SII) a year later. We also made tracer injections to verify the lesion boundaries and to study the connections of SII after the lesion of SI. Similar to the report of Pons et al. (Science 237:417-420, '87), we found that substantial portions of the SII hand area were unresponsive to cutaneous stimulation of the hand in both age groups. Particularly, there were no cutaneous receptive fields restricted to the digits. Some responses were elicited in each animal by mechanical stimulation of the hand, including a proportion related to cutaneous receptive fields. This proportion was higher in the infants than in the juveniles, which may explain the greater capacity of the infants for recovery of tactile function after SI lesions. The residual somatic drive in the SII hand area of the juveniles was attributable to sparing of parts of areas 3a and 3b. However, in the infants, this explanation was not tenable since the responses noted in SII occurred even after total ablations of the postcentral gyrus. The pattern of corticocortical connections revealed by injections of HRP into the medial margin of the SI lesion and of Fast Blue into SII in one infant confirmed the absence of SI inputs to the region of SII where responses were recorded from the hand. Representations of body parts other than the hand were normally responsive, and their location was consistent with normal somatotopy in SII.

Characterization of simian immunodeficiency virus-specific T-cell-mediated cytotoxic response of infected rhesus macaques

Four juvenile rhesus macaques were infected with simian immunodeficiency virus (SIV)MAC-Freshly isolated peripheral blood mononuclear cells (PBMC) from these SIVMAC-infected and from uninfected control macaques were assessed for cytotoxic T-lymphocyte (CTL) activity monthly for 7 consecutive months, beginning 2 months after infection. Target cells consisted of major histocompatibility complex (MHC) haploidentical parental PBMC which were stimulated with mitogen and then pulsed with heat-killed SIVMAC. CTL activity was demonstrated on all four infected animals. The effector cells are T cells which mediate cytotoxicity against SIVMAC-pulsed target cells in an MHC-restricted manner. Furthermore, the cytotoxicity is virus specific and predominantly, if not exclusively, mediated by CD8+ T cells; it is also MHC class-I restricted. Incubation of target cells with leupeptin prior to the cytotoxic assay inhibited target cell generation, suggesting that viral antigens are processed via an endocytic pathway.

Corticotropin-Releasing Factor Neurons Innervate Dopamine Neurons in the Periventricular Hypothalamus of Juvenile Macaques

Corticotropin-releasing factor (CRF) and dopamine (DA) are important integrators of the endocrine and autonomic response to stress. CRF neurons in the anterior portions of the periventricular nucleus (PV) and parvocellular paraventricular nucleus (pvPVN) occur close to A14 DA neurons in these same locations. Since CRF has been shown to act as an excitatory neurotransmitter, possible CRF interactions with the DA system were investigated using double-label immunocytochemistry. Coronal vibratome sections through the PV and pvPVN were obtained from colchicine-treated and nontreated juvenile female cynomolgus macaques. They were sequentially immunostained for tyrosine hydroxylase (TH) (to identify DA neurons) with PAP and DAB, and for CRF using 15 nm colloidal gold. By light microscopy, areas of coincidence of TH- and CRF-immunoreactive cell bodies in the PV and pvPVN were obvious, but double-stained elements were not observed. By electron microscopy, asymmetrical synapses frequently occurred between CRF axons and TH dendrites or somata. Symmetrical axosomatic synapses sometimes appeared adjacent to these CRF/TH synapses, while symmetrical axoaxonic synapses were rare. We conclude that CRF neuronal efferents synaptically activate A14 DA neurons in the primate PV and pvPVN. Parallel CRF/DA symmetrical synapses also suggest coexistence of a companion transmitter within some of these same CRF neurons. Our own previous work and recent independent studies indicate that this transmitter is probably GABA. Thus the CRF neuronal system, which is known to alter secretion of several pituitary hormones, may also act through hypothalamic periventricular DA neurons to mediate other responses to stress.