Prevalence and correlates of 30-day suicidal ideation and intent: Results of the South African National Student Mental Health Survey.

BACKGROUND: Although suicide prevention is recognised as a priority among university students in South Africa (SA), it is unclear what proportion of students require urgent indicated interventions and what the characteristics are of these students. OBJECTIVE: To assess the prevalence and sociodemographic correlates of 30-day suicidal ideation, frequency of ideation and self-reported intention to act on ideation in the next year among a national sample of SA university students. METHODS: Self-report cross-sectional data were collected online from students (N=28 268) at 17 universities across SA as part of the national student mental health survey. Students reported suicidal ideation in the past 30 days, frequency of ideation and intention to act on ideation in the next year. Data were weighted within institutions by gender and population group, and across the four main types of universities (historically white, historically disadvantaged, technical and distance learning) to correct for response rate discrepancies. Prevalence was estimated with these weighted in the total sample and across types of universities. Poisson regression with robust error variances was used to investigate associations of sociodemographic characteristics with ideation and intention to act on suicidal ideation. Results are reported as relative risks (RRs) with design-based 95% confidence intervals (CIs). RESULTS: Thirty-day prevalence of suicidal ideation was 24.4% (standard error (SE) 0.3), with 2.1% (SE 0.1) and 4.1% (SE 0.1), respectively, reporting suicidal ideation all/almost all the time, or most of the time. A total of 1.5% (SE 0.1) of respondents reported being very likely to act on their suicidal ideation, while 3.9% (SE 0.2) were somewhat likely, 8.7% (SE 0.2) were not very likely and 85.8 (SE 0.5) either reported no suicidal ideation or that they were not at all likely to act on this ideation. Risk of suicidal ideation with high intent in the total sample was elevated among females (RR 1.9, 95% CI 1.3 - 2.7) and gender non-conforming students (RR 4.3, 95% CI 1.4 - 13.0) relative to males, black African students compared with white students (RR 3.6, 95% CI 1.9 - 7.1), students whose parents did not progress to secondary school compared with students whose parents had a university education (RR 1.6, 95% CI 1.0 - 2.5) and sexual minority students compared with heterosexual students (RR 1.9, 95% CI 1.3 - 2.6). Among students with 30-day ideation (controlling for frequency of ideation), only two of these predictors of high intent remained significant: identifying as black African (RR 2.7, 95% CI 1.4 - 5.1), and having parents with less than secondary education (RR 1.5, 95% CI 1.0 - 2.1). CONCLUSION: Scalable suicide prevention interventions are needed to reach the large number of SA students who report suicidal ideation with intent.

Consequences of group fission for the patterns of relatedness among rhesus macaques.

When mammalian social groups exceed their optimal size, they often tend to split. In view of the potential evolutionary benefits, it should be more advantageous for animals to stay with kin, rather than nonkin, during such fission events. In the present study, the spontaneous fission of two social groups, R and S, of rhesus macaques living on Cayo Santiago, Puerto Rico, provided the opportunity to compare the kinship structure of the corresponding parent and daughter groups, using information on both maternal and paternal relatedness. In both instances, maternal half-siblings and pairs of animals from the same family were significantly more prevalent in the fission products than in the parent group. During the split of group R, significantly more paternal half-siblings stayed in the remnants of the parent group than joined the seceding group. Our findings are compatible with previous behavioural studies demonstrating that female primates bias their social behaviour more to maternal than to paternal kin, but that both types of half-siblings prefer each other more than unrelated animals. It remains to be clarified by future research, however, whether the observed co-segregation of paternal half-sibs in our study reflects active choice or is a by-product of the group-specific kin structures, prior to fission.

Signs of glaucoma in rhesus monkeys from a restricted gene pool.

PURPOSE: To investigate the distribution of intraocular pressure (IOP) and cup properties in a colony of rhesus monkeys that has had no outside genetic input since 1938 (approximately 12 generations). This sample of sequestered monkeys is significantly larger than any previously reported. Comparisons are made with a sample of random-source monkeys to develop population estimates defining the limits of normalcy. METHODS: The IOP and cup/disc ratio estimates were collected from 701 eyes of 354 adult rhesus monkeys from the closed colony on Cayo Santiago, Puerto Rico. Results for IOP were compared with the normal rhesus IOP population distribution function calculated from an earlier sample of genetically heterogeneous rhesus. RESULTS: The mean +/- standard deviation IOP in the Cayo Santiago monkeys (15.8+/-3 mmHg) related well to the calculated "normal" rhesus distribution (14.5+/-2 mmHg) below and around the mean IOP only. Above the mean rhesus IOP, the samples from the Cayo monkeys were strongly skewed: 129 eyes had IOP more than two standard deviations above the normal mean IOP, and 54 eyes had IOP more than three standard deviations above the normal mean IOP. Cup/disc ratio estimations tended to cluster as higher values in the higher IOP quartiles. Some eyes with IOP below the mean had cup/disc ratios > 0.5. Values for IOP that were more than two standard deviations above the mean and cup/disc ratios > 0.4 were not uniformly distributed across social groupings, although incidence of high IOP was more than 25% in one group. CONCLUSION: After 12 generations with the same genetic pool, expression of ocular hypertension and large optic disc cups is high but not uniform.

Primigravidity, body weight, and costs of rearing first offspring in rhesus macaques.

Body size is associated with menarche and ovarian function, but the relationship to first conception is rarely examined. We conducted a longitudinal investigation of rhesus macaques, Macaca mulatta, to determine the effect of differences in body weight on both the age at first conception and survivorship of first progeny. Young females who became pregnant weighed significantly more than peers who remained barren, with weight changes for females who successfully raised offspring no different than those for females who did not produce offspring. Infant mortality among primiparae was not significantly greater than that among multiparae, although nearly twice as high. First-born males tended to have lower survivorship than first-born female offspring. We suggest that reproductive costs encountered by primiparous females are more likely to be modulated by immature neuroendocrine function than by inexperience, small body size, or infant suckling patterns. We conclude that body size influences probability of first conception, socioendocrine factors mediate the likelihood of infant survival, and primiparous production of male progeny seems to exert a greater reproductive cost than does production of female progeny.

Osteoarthritis of the hand in nonhuman primates: a clinical, radiographic, and skeletal survey of Cayo Santiago rhesus macaques.

We describe the relative prevalence and pattern of distribution of osteoarthritis (OA) in the hands of elderly (> 15 years) rhesus macaques using clinical, radiographic, and skeletal examinations. In the clinical study the prevalence of nodes was 72% and 16% in the distal inter-phalangeal joints (DIPJ) and proximal inter-phalangeal joints (PIPJ), respectively, 31% of all monkeys had polyarticular nodes. Radiographic OA was present in 55%, 9.1%, and 0% of the DIPJs, PIPJs, and thumb base, respectively. Skeletal OA as defined by joint surface eburnation for the DIPJ, PIPJ, and thumb base were 16%, 8%, and 2%, respectively. A similar pattern of hand OA with humans is described except for the thumb base OA. This may be due to the relatively rudimentary manipulative role of the macaque thumb. The finding of polyarticular nodal OA raises the possibility of a common pathogenensis for IPJ OA amongst primates.

Subcutaneous rabies vaccination of pigtail macaques.

Nonhuman primates housed in outside cages in rabies enzootic areas should be vaccinated against rabies because of the risk of exposure to rabid wildlife. This article reports that vaccination with an inactivated rabies vaccine for domestic animals induced levels of neutralizing antibodies against rabies in pigtail macaques (Macaca nemestrina) without causing adverse reactions.

Osteoarthritis in rhesus macaque knee joint: quantitative magnetic resonance imaging tissue characterization of articular cartilage.

OBJECTIVE: To assess cartilage matrix quality variation by anatomical location and extent of osteoarthritis (OA) using quantitative magnetic resonance imaging (MRI) and to compare the anatomic MR morphologic features with corresponding histological findings. METHODS: We studied 18 fully encapsulated right knee joints from a population of rhesus monkeys with a high incidence of degenerative arthritis resembling human OA. Relaxation times (T1 and T2) spin density, and cartilage thickness were determined along 8 contiguous anteroposterior segments of articular cartilage. Histological slides, prepared in the same plane as the MR image, were assessed for OA severity. Using a modification of Mankin's OA classification, each quadrant was grouped into normal (0), mild (1), moderate (2), or severe OA (3). Histopathological scores served as the standard and corresponding MR quadrants were classified accordingly. RESULTS: Cumulative results revealed a significant decrease in T1 relaxation time (p = 0.04) and an increase in T2 relaxation time (p = 0.03) in the mild and severe OA groups, respectively. Statistically significant changes in spin density and cartilage thickness measurements were not observed. MR signal intensity abnormalities in selected regions of interest were demarcated and studied histologically. Regions with histological proliferating chondrocytes or fibrillated cartilage showed bright signal intensity on MR images (TR = 3000 ms; TE = 10 ms) and corresponded with elevated T1 and T2 values. Histological regions of collagen condensation showed low signal intensity on MR images (TR = 3000 ms; TE = 10 ms) and corresponded with decreased T1 and T2 relaxation times. CONCLUSION: Topological quantitative MRI relaxation time assessment demonstrates increasing cartilage matrix quality variation with OA progression.

Osteoarthritis staging: comparison between magnetic resonance imaging, gross pathology and histopathology in the rhesus macaque.

Although osteoarthritis (OA) is the most common cause of articular skeletal disability in humans, assessing progression (staging) with noninvasive methods remains a major clinical problem. Using the rhesus macaque animal model, the objective of this study was to compare OA staging by noninvasive magnetic resonance imaging (MRI) against gross pathology and histopathology. Right knee joints from 18 rhesus macaques were used in this study. Using a four-point ordinal scale for each of the above-mentioned modalities, the lateral and medial femoral condyle and tibial plateau of each knee joint was independently scored for OA severity, i.e. normal, mild OA, moderate OA and severe OA. Correlation between each staging system was performed using Stuart's Tau-c correlation coefficient. By our criteria, MRI staging correlated as well with gross pathology (tau = 0.75) and histopathology (tau = 0.80) as did gross pathology with histopathology (tau = 0.78). Our study shows that MRI is a promising noninvasive modality to evaluate the severity of OA. MRI appears to be sensitive for demarcating the presence and extent of focal OA cartilage lesions. However, at this time, while MRI is sensitive for detecting OA change it cannot distinguish between certain lesions such as superficial cartilage matrix fibrillation and hypertrophy both of which show elevated signal intensity.

Effect of age and osteoarthritis on bone mineral in rhesus monkey vertebrae.

We have used vertebrae of free-ranging rhesus macaques to study the effect of age and osteoarthritis on bone mineralization and bone density and to relate these findings to weight, sex, parity, and mineral chemistry. Bone mineralization was determined using the density fractionation technique and bone density using dual-photon absorptiometry. Arthritis was determined osteologically. We found a relationship between mineralization, age, and osteophytes, such that mineralization rose with age in nonarthritics and decreased with age in arthritics. This could also be seen when the females were examined separately. In males, only an increase in mineralization with age could be seen. In females mineralization decreases with parity. Also in females, DPA density decreases with age and increases with parity. No relationships with DPA density could be seen using males and females together or males alone. In conclusion, we have shown that normal skeletal aging in rhesus monkeys is accompanied by an increase in mineralization similar to that in other species, but this is not true in the presence of osteoarthritis. In the females parity has an important effect because it seems to build up bone mass even though the bone present may be undermineralized.

The effects of diet, age, and sex on the mineral content of primate bones.

The effect of diet, age, and sex on the mineral content of primate bones was determined for free-ranging rhesus monkeys (Macaca mulatta) from the Caribbean Primate Research Center. Monkeys in this study were of known age and sex and had been provided with either a low protein (15%) or a high protein (25%) diet for most of their lives. Instrumental neutron activation analysis was used to assess bone mineral content. Results showed that diet had no significant effect on the bulk mineral composition of Ca, Mg, Br, and Cl in the bones. Of the minerals analyzed, only Na and Mn showed significant diet-related effects. The bone Ca content was found to be lower in females than in males when controlled for age. Finally, Ca content was found to be higher in young adults, lower at middle age, and higher in old age in both male and female monkeys. In conclusion, this study has shown that increasing protein content in the diet does not change the bulk mineral content of primate bones. The nondietary effect that Ca content of monkey bones is lower during middle age has not been previously reported.

Primary open angle glaucomas in the rhesus monkey.

Rhesus monkeys from the closed Cayo Santiago colony of the University of Puerto Rico demonstrate elevated (> or = 22 mm Hg) intraocular pressure in a pattern which significantly favours certain maternal lineage groupings. The colony had remained genetically pure since 1938. Of nine matriarchal lineages (matrilines) examined, two had an incidence of ocular hypertension of more than 40% and six of more than 10%. Information on 18 matrilines is currently located in the colony data base which identifies each individual and its vital statistics. In 1990, six animals were moved to the laboratory in Florida. Among those from a low incidence matriline, we found abnormal optic nerve cups, pallor, reduced function of (mainly peripheral) fields, progression and loss of optic nerve axons in the presence of ocular hypertension. In another individual where the cup/disc ratio for the right eye was 0.7 and left eye 0.4 and outflow facility was normal, we excluded all other causes of optic nerve atrophy, and low tension glaucoma was diagnosed. This female was from a matriline with a low incidence of ocular hypertension. Relatively rapid aging (3-4 years/human year) monkeys with ocular hypertension and familial clustering produce a near ideal glaucoma research model.

The combined assessment of cellular apoptosis, mitochondrial function and proliferative response to pokeweed mitogen has prognostic value in SIV infection.

Using the assessment of the mitochondrial metabolic activity of freshly isolated blood mononuclear cells, the flow cytometric detection of apoptosis and of the proliferative responses to PWM, SIV-infected macaques were classified in: stage 0, which included all animals with unaffected parameters, and stages 1, 2, and 3, which included animals having one, two, or all three parameters affected, respectively. This novel three-parametric staging system (ISS) provides a new prognostic tool in the longitudinal study of SIV infection.

Osteoarthritis in rhesus macaques: assessment of cartilage matrix quality by quantitative magnetic resonance imaging.

To assess cartilage quality with anatomical location and extent of osteoarthritis (OA), magnetic resonance imaging (MRI) of the knee joint from rhesus monkeys was performed. MRI measurements--T1 and T2 relaxation times, proton density and cartilage thickness were taken from 8 equal segments of articular cartilage volumes extending from anterior to posterior edge of 1 mm sagittal slices. To grade the severity of OA in each quadrant of the knee joint a modified Mankin score was applied on the histological sections. Our results suggest that MR relaxation times and proton density values vary with the severity of osteoarthritis.

A non-invasive technique for the control of intestinal parasites in rhesus macaques (Macaca mulatta).

Control of intestinal parasites is a major concern in maintaining the health and well-being of captive primates. This study established that percutaneous application of ivermectin was as effective as subcutaneous administration for the control of nematodes in captive rhesus macaques. The method is less intrusive than the standard subcutaneous or oral delivery routes and did not adversely affect the health of any of the study subjects.

A primate model for age related macular drusen.

A closed colony of semi-free-ranging rhesus monkeys maintained in isolation since 1938 by the Caribbean Primate Research Center (CPRC) is being studied as a model for age related macular drusen. Of examined colony animals 57.7% of the monkeys and 47.3% of their eyes have drusen. The prevalence and severity of drusen are linearly related to increasing age and are significantly higher in specific maternal lineages (matrilines). An electrophysiological estimate indicates loss of function associated with drusen. Prevalence of drusen in CPRC females is almost twice that of males, while the prevalence among CPRC animals in general appears to be several times that of monkeys from continental US facilities. Evidence suggests that the frequency of endstage lesions is also similar to that in human populations. The CPRC matriline monkeys appear to provide the best model yet reported for human age related macular drusen.

Species differences in the binding kinetics of 25-hydroxyvitamin D3 to vitamin D binding protein.

The specific binding of 25-hydroxyvitamin D3 to its binding protein was studied in serum of the human, rhesus monkey, cow, horse, and rat. The free fraction of 25-hydroxyvitamin D3 in the rat was 0.34 +/- 0.15 pmol free/nmol total (+/- SD) and this was lower than in any of the other species (p less than 0.01). In the human, the free fraction was 1.5 +/- 0.32 pmol free/nmol total, which was higher than in any of the other species (p less than 0.001). The differences in the free fraction were mainly due to differences in dissociation constant. The relative levels of free 25-hydroxyvitamin D should be taken into account when extrapolating findings about vitamin D metabolism in animals to the human. A technical outcome of this study is that of the species tested, vitamin D binding protein from rat serum is the most suitable as a reagent component for methods used to measure total 25-hydroxyvitamin D by competitive protein binding assay.

In vitro HIV infection of primate lymphocytes.

Peripheral blood mononuclear cells (PBMC) obtained from four different primate species were tested for their respective ability to support the "in vitro" replication of the human immunodeficiency viruses, HIV-1, and HIV-2. PBMC of Cebus apella, patas (Erythrocebus patas), green (cercopithecus aethiops sabaeus) and rhesus monkeys (Macaca mulatta) were infected "in vitro" with either HIV-1 or HIV-2. Cultures were assayed weekly for particle-associated reverse transcriptase activity. Both viruses were found to be cytolytic for all these monkey's PBMC. Low levels of HIV-1 and HIV-2 infection were observed in Cebus cells. However, productive infection was only detected in HIV-2 infected rhesus PBMC. The capacity of HIV-2 to replicate in rhesus cells may provide a useful model for evaluating antiviral drugs and vaccines.

Spontaneous osteoarthritis in rhesus macaques. II. Characterization of disease and morphometric studies.

From examination of the articular tissue of 35 animals from the Caribbean Primate Research Centre, we identified the epidemiological and histomorphometric features of the spontaneous osteoarthritis (OA) that affects the free-ranging rhesus macaques. The frequency of this disease increases with aging, and in females, with increased parity. Histological and morphological studies demonstrate that as in humans, the disease is characterized by persistence of the chondrocyte density typified by the cartilage of young animals. Owing to its epidemiologic and histologic resemblance to the disease in man, we conclude that degenerative arthritis affecting rhesus macaques provides a useful model for the study of factors contributing to the pathogenesis of OA.

Seroprevalence of B virus (Herpesvirus simiae) antibodies in a naturally formed group of rhesus macaques.

Eighty-two percent of a group of rhesus monkeys removed from Cayo Santiago were seropositive for B virus (Herpesvirus simiae) antibodies. Similar results were obtained from the Cayo Santiago macaque population two decades ago and from feral Indian rhesus monkeys. Thus it is likely that B virus has been enzootic in the Cayo Santiago population since 1938, when the colony was established with stock imported from India.