Nuclear abnormalities in erythrocytes of parrots (Aratinga canicularis) related to genotoxic damage.

Nuclear abnormalities in erythrocytes, as micronuclei and nuclear buds (BE), are considered potential biomarkers of genotoxic exposure. We described previously the frequency of spontaneous micronucleated erythrocytes (MNE) in the species Aratinga canicularis. Here, we have used this species to evaluate the induction of MNE and BE by mitomycin-C. Animals were given a single intracoelomic injection of 0, 2, 3 or 4 mg/kg mitomycin-C on two consecutive days. A drop of blood was obtained after 0, 24, 48 and 72 h, and stained smears were used to count micronucleated polychromatic erythrocytes (MNPCE) and polychromatic erythrocytes with buds (BPCE)/1000 polychromatic erythrocytes. The number of MNE and BE in 10 000 total erythrocytes was also counted. MNPCE and BPCE frequencies were elevated at 24, 48, and 72 h after the administration of the lower dose (P<0.03). At a 3 mg/kg dose, the frequency of MNPCE increased at 48 and 72 h (P<0.04) whereas the number of BPCE increased, but not significantly. Administration of 4 mg/kg mitomycin-C increased the number of MNE observed at 72 h (P<0.03), the number of MNPCE at 48 h (P<0.01) and 72 h (P<0.006), the BE frequency at 72 h (P<0.05), and the frequency of BPCE at 48 and 72 h (P<0.001). While mitomycin-C appears to produce a parallel increase in MNPCE and BPCE frequencies, the MNE seemed to be a more sensitive indicator of genotoxicity than the BE. This suggests that evaluating BE and MNE in routine haematological analysis should be considered to evaluate environmental genotoxic exposure.     

Micronucleated erythrocyte frequencies in old and new world primates: measurement of micronucleated erythrocyte frequencies in peripheral blood of Callithrix jacchus as a model for evaluating genotoxicity in primates

Nonhuman primates are of particular relevance in evaluating the potential toxicity of drugs and environmental agents. We have used previously published information and data from the present study to establish a relationship for New World (NW) and Old World (OW) primates on the basis of the frequency of spontaneous micronucleated erythrocytes (MNEs) observed in peripheral blood. Data on spontaneous MNEs in peripheral blood from 15 species of primates, including humans, indicate that NW primates have significantly (P < 0.01) higher MNE frequencies (group mean, 9.5 +/- 7.3 MNEs/10,000 erythrocytes; range, 0.7-20.5/10,000 erythrocytes) than OW primates (group mean, 1.0 +/- 0.9 MNEs/10,000 erythrocytes; range, 0.0-2.6 MNEs/10,000 erythrocytes). Humans are believed to have developed in the OW, and human MNE frequencies were similar to those described for OW primate species. We selected the common marmoset (Callithrix jacchus), a NW primate, to determine whether therapeutic pediatric doses of Metotrexate (MTX; 2.5 mg/kg), Cyclophosphamide (CP; 5 mg/kg), Cytosine-arabinoside (Ara-C; 3 mg/kg), or 5-Fluorouracil (5-FU; 10 mg/kg), administered daily for two consecutive days, increase the frequency of micronuclei. Micronucleated polychromatic erythrocyte frequencies were increased significantly in groups receiving MTX, CP and Ara-C, while MNE frequencies were increased by the Ara-C treatment. The results of this study indicate that NW primates have higher spontaneous MNE frequencies than OW primates, and because of this, NW primates like the common marmoset, may be suitable for evaluating the genotoxicity of chemical agents.     

Species-specific transformation of T cells by HV(MNE)

HV(MNE) is an Epstein-Barr virus (EBV)-like lymphocryptovirus (LCV) originally isolated from a Macaca nemestrina with CD8(+) T cell mycosis fungoides/cutaneous T cell lymphoma (Blood 98 (2001), 2193). HV(MNE) transforms rabbit T cells in vitro and causes T cell lymphoma in New Zealand white rabbits. Here we demonstrate that HV(MNE) also immortalizes T cells from mustached tamarins but not those from owl monkeys, common marmosets, squirrel monkeys, black-capped capuchins, and humans. Cytogenetic and FACS analysis revealed the true origin and T cell lineage of the transformed tamarin T cell lines. Tamarin T cells contained HV(MNE) DNA sequence and displayed a decreased requirement for the IL-2 cytokine for growth. Thus, this EBV-like virus from M. nemestrina differs from the other EBV-like viruses found in nonhuman primates inasmuch as it appears to preferentially transform T cells.     

Response to glucose loading of the lean squirrel monkey in unrestrained conditions.

The response of blood glucose (BG), free fatty acids (FFA), and insulin (IRI) to both intravenous (IVGTT) and oral (OGTT) glucose tolerance tests was evaluated in unrestrained, permanently catheterized squirrel monkeys. The mean glucose assimilation rate (K value) for 25 IVGTT was 7.75 +/- 2.84. FFA maximally decayed 54 percent from a mean basal of 1,008 +/- 221 mueq/l associated with a onefold increment inIRI from basal (7.5 +/- 3.5 muU/ml) at 2-5 min. No significant changes were found during intravenous saline loading alone. OGTT (4g/kg) produced peak BG levels at 15-30 min with an immediate FFA decrease of 63 percent and a onefold IRI increment. Carcass composition analyses from 17 animals showed a total extractable lipid content of 6.2 percent. The K value, significantly higher than previously reported, appears to fit well with that expected for the species. The rapid decrease in FFA and BG concentrations demonstrate an apparent high efficiency of a low IRI increment. The association of the low IRI after loading with a low triglyceride depot is discussed.     

Rearing condition may alter neonatal development of captive Bolivian squirrel monkeys (Saimiri boliviensis boliviensis)

Nursery rearing has well-known consequences for primate species. Relative to some other primate species, research has indicated a reduced impact of nursery rearing on squirrel monkeys, particularly in terms of rates, severity, and persistence of abnormal behavior. We administered the Primate Neonatal Neurobehavioral Assessment to 29 dam-reared and 13 nursery-reared squirrel monkeys (Saimiri boliviensis boliviensis) at 2 and 6 weeks of age. Mixed-model ANOVAs comparing composite scores and individual assessment items across age, rearing status, and sex revealed a number of developmental differences. Dam-reared infants scored higher on all four composite measures compared to nursery-reared infants (p < .05) indicating that nursery-reared animals had slower motor development, were less active and attentive, and were more passive than their dam-reared counterparts. Consistent with infant rhesus macaques, nursery-reared squirrel monkeys showed an increased sensitivity to tactile stimulation (p < .05). Altogether, these results suggest a disruption of species-typical development when squirrel monkey infants are reared in a nursery setting, with activity, orientation, and state control areas most affected, though experimental research is needed to determine if this is a causal relationship. Contrary to previous behavioral research, there are likely developmental differences between dam-reared infant squirrel monkeys and those reared in a nursery setting.     

Spinal section and opioid receptor blockade induce the appearance of Fos-like immunoreactivity in the spinal cord of the decerebrated rabbit

The expression of Fos-like immunoreactivity has been studied in spinal segments L5-S1 of decerebrated, unanaesthetized, but otherwise unstimulated rabbits. The aim of the study was to establish baseline levels of Fos in such preparations, and to examine how these might change after spinalization and opioid receptor blockade. In animals with an intact spinal cord, approximately 30 Fos-positive profiles per section were found in the superficial dorsal horns (i.e. laminae I and II) of each 40-microm section, while about 20 profiles per section were found immediately adjacent to the central canal (lamina X). Fos-like immunoreactive profiles were rare elsewhere in the gray matter. When the spinal cord was sectioned at L1 (after blockade with local anaesthetic), significantly more Fos-like immunoreactivity was found in superficial and central regions of the gray matter (approximately 90 profiles per section) in animals perfused 4 h after decerebration, but not when perfusion was performed 2 or 8 h after decerebration. The opioid antagonist naloxone (0.25 mg/kg/h) had little effect on expression of Fos-like immunoreactivity in spinalized preparations, but significantly increased the numbers of Fos-positive profiles in all but the ventral areas of the spinal gray matter in non-spinalized preparations. The present data show that spinal section induces a transient increase in expression of Fos in the superficial and central parts of the spinal gray matter. It appears that spinalization induces spontaneous activity in some neurons in these regions of the cord, presumably as a result of relief of descending inhibition. The effects of naloxone indicate that endogenous opioids exert tonic inhibition over Fos-expressing spinal neurons in non-spinalized rabbits.     

Flow cytometric scoring of micronucleated erythrocytes: an efficient platform for assessing in vivo cytogenetic damage

The relative simplicity of the micronucleated erythrocyte endpoint has made it amenable to automated scoring approaches. Flow cytometry is one such scoring platform that has been employed successfully. This review describes the evolution and properties of flow cytometry-based scoring of micronucleated erythrocytes. The methodology has become widely applied to rodent blood specimens and the high throughput nature of the technology provides a number of advantages over manual microscopic scoring. For instance, the ability to efficiently survey many dose levels and many more cells per specimen relative to microscopy benefits studies that are designed to identify no observable effect levels or lowest observable effect levels. Furthermore, flow cytometry makes it practical to study species with low spontaneous reticulocyte (RET) counts and micronucleus (MN) frequencies, thereby facilitating integration of blood-based micronucleated reticulocyte (MN-RET) frequency measurements into experiments conducted across species of toxicological interest. This capability enhances genotoxicity assessments that have historically been made in dedicated MN tests performed in one species. Importantly, the feasibility of using MN-RET frequencies in blood from humans as an index of genetic damage in bone marrow opens a critical area of application that had not been practical previously. We conclude with recommendations for additional work that is needed to more fully realise the potential of flow cytometric in vivo MN scoring.     

Projections of the ventrolateral pontine vocalization area in the squirrel monkey

In four squirrel monkeys (Saimiri sciureus), the tracer biotin dextranamine (BDA) was injected into the ventrolateral pons at a site at which injection of the glutamate antagonist kynurenic acid blocked vocalization electrically elicited from the periaqueductal gray (PAG). Anterograde projections could be traced into all cranial motor and sensory nuclei involved in phonation, that is, the nucleus ambiguus, facial, hypoglossal and trigeminal motor nuclei, the motorneuron column in the ventral gray substance innervating the extrinsic laryngeal muscles, the nucleus retroambiguus, solitary tract and spinal trigeminal nuclei. Projections were also found into a number of auditory nuclei, namely the nucleus cochlearis-complex, superior olive, ventral and dorsal nuclei of the lateral lemniscus and inferior colliculus. Furthermore, there were projections into the reticular formation of the lateral and dorsocaudal medulla and lateral pons, into nucleus gracilis, inferior and medial vestibular nuclei, lateral reticular nucleus, ventral raphe, pontine gray, superior colliculus, PAG and mediodorsal thalamic nucleus. Injection of the tracer wheat germ agglutinin-conjugated horseradish peroxidase into the ventrolateral pontine vocalization-blocking area in one animal yielded retrograde labeling throughout the PAG. Injection of BDA into a vocalization-eliciting site of the PAG in another animal yielded projections into the ventrolateral pontine vocalization-blocking area. It is concluded that the ventral paralemniscal area in the ventrolateral pons represents a relay station of the descending periaqueductal vocalization-controlling pathway.     

Response properties of neurons in the rostroventromedial medulla of neuropathic rats: attempted modulation of responses by [1DMe]NPYF, a neuropeptide FF analogue.

We determined whether chronic neuropathy changes response properties of neurons in the rostroventromedial medulla of rats, and whether (d-Tyr)L(Me-Phe)QPQRF-amide, a neuropeptide FF analogue, in the periaqueductal gray produces changes in responses of rostroventromedial medullary neurons that might underlie its antiallodynic effect described earlier. Single unit recordings of medullary neurons were performed in lightly anesthetized neuropathic and control animals. Spontaneous activity and the responses to noxious thermal and mechanical stimulation of the hind paw were determined with and without administration of (d-Tyr)L(Me-Phe)QPQRF-amide. The neurons were classified into three groups: ON-neurons increased, OFF-neurons decreased, and NEUTRAL-neurons did not change their discharge rate prior to a limb withdrawal induced by noxious stimulation of the skin. Spontaneous activity and heat-evoked responses of ON-neurons were not different between neuropathic and control animals, whereas their mechanically evoked responses were reduced in neuropathy. Response properties of OFF-neurons were not different between neuropathic and control animals. Spontaneous activity of NEUTRAL-neurons was not different between neuropathic and control animals. (d-Tyr)L(Me-Phe)QPQRF-amide in the periaqueductal gray had no significant effect on evoked responses or spontaneous activity of ON- or OFF-neurons, independent of the experimental group. However, (d-Tyr)L(Me-Phe)QPQRF-amide produced a significant attenuation of spontaneous activity of NEUTRAL-neurons in neuropathic animals. In a behavioral study performed in unanesthetized animals it was found that intrathecal administration of methysergide, a serotonin antagonist, selectively attenuated neuropathic symptoms. Also, light pentobarbitone anesthesia markedly attenuated, but did not abolish, behaviorally determined neuropathic symptoms. From these results we suggest that NEUTRAL-neurons of the rostroventromedial medulla may have a role in neuropathy and they may be involved in attenuation of mechanical hypersensitivity by (d-Tyr)L(Me-Phe)QPQRF-amide in the periaqueductal gray. It is proposed that in neuropathy the synaptic effects of descending impulses from medullary NEUTRAL-neurons on their axonal targets in the spinal cord are changed so that this contributes to mechanical hypersensitivity, due to mechanisms that are at least partly serotoninergic.     

Myocardial morphology in spontaneously hypertensive and aortic-constricted rats

The cellular and subcellular adaptations in the myocardium of spontaneously hypertensive rats (SHR) were compared with those in Kyoto-Wistar normotensive rats with cardiac hypertrophy induced by constriction of the abdominal aorta (ACR). Hypertensive blood pressure levels were attained at eight weeks of age in SHR and coincided with the surgically-induced pressure-overload in ACR at this age. Specimens from the subepicardial and subendocardial regions of the myocardium from glutaraldehyde-perfused-fixed hearts of 16-week-old animals were compared. Spontaneous hypertension and aortic constriction are associated with significant and comparable increases in heart rate, blood pressure, heart weight, and left ventricular muscle fiber diameter. While the cardiomegaly in both models was accompanied by a decrease in capillary density, the decrement was greater in the aortic-constricted rats. Stereological analysis of cardiocytes revealed an increase in myofibril/cell-volume, and a decrease in mitochondria/myofibril-volume ratios in both models of cardiomegaly. In addition, double intercalated discs and subsarcolemmal foci containing abundant sarcoplasm with numerous small mitochondria, free filaments and Golgi complexes were commonly observed in both experimental groups. Cell diameter increased by a larger increment in the subendocardium than in the subepicardium, but capillary density was similar in these two regions. While aortic constriction was associated with dilatation of T-tubules and the non-specialized junctions of the intercalated disc, the myocardial ultrastructure of SHR was characterized by a greater number of lipid droplets and an increased folding of the intercalated discs comprising the subendocardial region. These findings suggest that data based on surgically-induced pressure-overload should be extrapolated cautiously to cardiomegaly associated with spontaneous hypertension. The differences between the adaptations in the two models may be due to either (1) the rate at which hypertrophy occurs or (2) some other, possibly genetic, factors unique to SHR.     

Subgingival microbiota in squirrel monkeys with naturally occurring periodontal diseases.

The squirrel monkey (Saimiri sciureus) has been proposed as an in vivo model for the study of subgingival colonization by suspected periodontopathogens, such as black-pigmented porphyromonads and prevotellas (BP/P). However, the indigenous microbiota of the squirrel monkey has not been well described. Therefore, in order to more fully characterize the oral microbiota of these animals, we studied two groups of squirrel monkeys from widely different sources. Group I consisted of 50 breeding colony monkeys ranging in age from 9 months to over 6 years which had been raised in captivity; group II consisted of 16 young sexually mature monkeys recently captured in the wild in Guyana. Group I animals in captivity had developed moderate to severe gingivitis, with a mean gingival index (GI) of 2.6; 52% of the sites bled, 26% had detectable calculus, and 83% had detectable BP/P. A group I subset (six animals), for which predominant cultivable microbiota was described, had a mean GI of 2.4. Colony morphology enumeration revealed that five of the six subset animals were detectably colonized with BP/P (range, 0 to 16.9%) and Actinobacillus actinomycetemcomitans (range, 0 to 3.9%); all subset animals were colonized with Fusobacterium species (range, 0.8 to 3.6%), Actinomyces species (range, 2.3 to 11%), and gram-positive cocci (range, 1.4 to 21.4%). Predominant cultivable microbiota results revealed the presence of many bacterial species commonly found in the human gingival sulcus. At baseline, group II animals were clinically healthy and had a mean GI of 1.4; 67% of the sites bled and 2.1% had calculus, and none of the animals had detectable BP/P. Neisseriae were very common in noninflamed sites. Subsequently, when inflamed sites were compared with noninflamed sites in group II animals after they had been maintained in captivity for 6 months, inflamed sites exhibited a more complex microbiota and increased proportions of gram-negative rods and asaccharolytic bacteria.     

Recombinant interleukin 2 enhances spontaneous insulin-dependent diabetes in BB rats

Treatment of BB rats with recombinant interleukin 2 (IL2) enhanced the development of spontaneous diabetes in these animals. A dose of 20 micrograms IL 2/kg body weight was administered twice daily for 80 days starting at 42 days of age. The rate of diabetes was doubled after IL 2 administration (53% vs. 23%) and the onset of diabetes was found to be accelerated by a mean of 18 days. Histological analysis showed enhanced inflammation of islets and in addition interstitial pancreatis. It is concluded that IL 2 has a regulatory effect on spontaneous organ-specific autoimmunity.     

Mast cells and postnatal topographic anomalies in mammalian subfornical body and supraoptic crest

Summary In the central nervous system of 22 animal species, mast cells occur (1) in both the subfornical body and the supraoptic crest in chimpanzee, stumpatailed monkey, agouti and flying squirrel and in cynomolgus monkey from 1 day of age; (2) in the subfornical body in paca, ground squirrel, woodchuck and prairie dog; and (3) in the supraoptic crest in cats from 2 days of age through the fourth month, and capybara. The medial habenular nucleus and the area postrema contain mast cells in many of the animals, but differences in number with species and with age do not follow the same pattern as in the above regions. Not infrequently, the thalamus has a considerable number of mast cells, and occasionally other regions, such as the dentate nuclei and the medulla oblongata, have a few mast cells.The number of mast cells, amounting to several hundreds in the circumventricular regions, varies with region, species, individual animal and age. The marked qualitative and quantitative differences, which complicate interpretation of experimental results, are associated with differences in functional requirements; the migratory faculty of the mast cell would enable each of its many biogenic amines to act separately on specific elements at different sites as demand arises.Study of newborn animals disclosed mitotic cells in several of the circumventricular regions. The formation of dysmitotic elements, as an expression of anomalous mitosis, may be the cause of disproportionate growth of the tissue and the overlying ependyma, whereby aberrations in the development of the ventricular wall ensue.     

Cerebrum in offspring of mercury-treated rats

This study was conducted to evaluate the effects of different doses of mercury on fetal cerebrum. Twenty adult female rats were divided in four groups. All animals became pregnant by natural mating. Mercuric oxide was induced in three groups by different doses at ten terminal days of pregnancy. After parturition, the cerebrum was collected from the offspring of all rats and the weight of the neonates and mothers was measured. Various histological parameters were determined using histological techniques. Results revealed a decrease in neonatal and maternal body weight after parturition compared to control. The thicknesses of the gray and white matter showed a decrease in all test groups. The number of cells in gray matter and white matter reduced in all test groups. The maternal body weight of group T3, the number of cells in gray matter of group T3 and the number of cells in white matter of group T2 and T3 decreased significantly (p?<?0.05) compared to that of control. Mercury exposure exhibited deleterious effects on cerebrum during fetal life, which remained persistent during the post-neonatal period.     

Effect of treatment protocol and sample time on the frequencies of micronucleated polychromatic erythrocytes in mouse bone marrow and peripheral blood

Studies were conducted to evaluate the effect of experimental protocol on the ability of benzidine (BZD), dimethylbenzanthracene (DMBA) and mitomycin C (MMC), administered by intraperitoneal injection, to induce micronuclei in polychromatic erythrocytes (PCE) of B6C3F1 mice. Three different treatment/sampling protocols were used, involving from one to three consecutive daily treatments and from three to one, respectively, consecutive daily samplings beginning 24 h after the last injection. DMBA and MMC elicited a significant micronucleus response in all three experimental protocols, while BZD induced a significant response only in the multiple injection protocols. Of the three protocols, the 3-day injection/single sample time protocol offers the greatest efficiency in minimizing the number of animals required in a study, in decreasing the time needed for scoring and in simplifying the statistical analysis. In addition, a comparison of the frequency of micronucleated PCE in peripheral blood and bone marrow following the treatment of mice with either BZD or DMBA suggests that, following a three injection protocol, either tissue can be used with equal efficacy.     

Elevated frequencies of micronucleated erythrocytes in infants exposed to zidovudine in utero and postpartum to prevent mother-to-child transmission of HIV

Zidovudine-based antiretroviral therapies (ARTs) for treatment of HIV-infected pregnant women have markedly reduced mother-to-child transmission of the human immunodeficiency virus (HIV-1) from approximately 25% to <1%. However, zidovudine (ZDV; AZT), a nucleoside analogue, induces chromosomal damage, gene mutations, and cancer in animals following direct or transplacental exposure. To determine if chromosomal damage is induced by ZDV in infants exposed transplacentally, we evaluated micronucleated reticulocyte frequencies (%MN-RET) in 16 HIV-infected ART-treated mother-infant pairs. Thirteen women received prenatal ART containing ZDV; three received ART without ZDV. All infants received ZDV for 6 weeks postpartum. Venous blood was obtained from women at delivery and from infants at 1-3 days, 4-6 weeks, and 4-6 months of life; cord blood was collected immediately after delivery. Ten cord blood samples (controls) were obtained from infants of HIV-uninfected women who did not receive ART. %MN-RET was measured using a single laser 3-color flow cytometric system. Tenfold increases in %MN-RET were seen in women and infants who received ZDV-containing ART prenatally; no increases were detected in three women and infants who received prenatal ART without ZDV. Specifically, mean %MN-RET in cord blood of ZDV-exposed infants was 1.67 +/- 0.34 compared with 0.16 +/- 0.06 in non-ZDV ART-exposed infants (P = 0.006) and 0.12 +/- 0.02 in control cord bloods (P < 0.0001). %MN-RET in ZDV-exposed newborns decreased over the first 6 months of life to levels comparable to cord blood controls. These results demonstrate that transplacentalZDV exposure is genotoxic in humans. Long-term monitoring of HIV-uninfected ZDV-exposed infants is recommended to ensure their continued health.     

Age-dependent changes in the cellularity and ultrastructure of the spleen of Fischer F344 rats

The age-related changes in the cellularity (cells/gram of tissue) of the spleens and thymuses of Fischer F344 male rats were determined. A decline in the weight of the thymus with age was observed as previously reported by others. The decline was most drastic between 4 and 20 months of age. The spleen, however, increased in weight with age. The increase was almost linear between 4 and 30 months of age. Yet when the number of cells recovered from each organ as a function of age was determined, a decrease for both the thymus and the spleen was observed with increasing age. It was surprising to find that fewer cells were recovered from the spleens of old animals even though the weight of the spleen of the old animals was greater than the spleens from the younger animals. The ultrastructure of the splenic white pulp of rats ranging from 4 to 30 months of age was studied to determine the possible cause for the age-related decrease in cellularity of the spleen. The white pulp of the 4-month-old rats contained a large number of small lymphocytes, and the number of cells was found to decrease with increasing age. The 30-month-old animals had less than 20% the number of lymphocytes in the white pulp as the 4-month-old animals, and the white pulp exhibited an increased number of reticular cells and macrophages with enlarged cytoplasm. The decreased cellularity and increased structural disturbance might be significant in the age-related decline of spleen lymphocyte functions.     

Natural occurrence of black-pigmented Bacteroides species in the gingival crevice of the squirrel monkey.

The objective of this study was to determine whether the squirrel monkey (Saimiri scuireus) is indigenously colonized with black-pigmented bacteroides (BPB) resembling human Bacteroides gingivalis and Bacteroides intermedius (suspected periodontal pathogens) and to determine the usefulness of the squirrel monkey as an in vivo model for studying colonization by putative pathogens. We assayed the subgingival plaques of 138 monkeys of various ages and in four different colonies for the presence of anaerobic BPB microorganisms. We also tested half the animals for the presence of Actinobacillus actinomycetemcomitans. Clinical indices and levels of serum antibody to B. gingivalis were recorded. We detected BPB in 50% of the animals and A. actinomycetemcomitans in 69% of the animals. The presence of BPB was generally associated with increased age, increased gingival index, presence of calculus, and increased levels of serum antibody. These data indicate that the squirrel monkey may be a good model for studying the parameters of natural infection of the gingival crevice with suspected periodontopathogenic BPB microorganisms.     

Replication of simian immunodeficiency virus (SIV) in ex vivo lymph nodes as a means to assess susceptibility of macaques in vivo

Six macaques, apparently uninfected, following low-dose exposure to the pathogenic SIV(mac251) and SIV(SME660) by the mucosal route, were used in a pilot study to investigate whether infectability of ex vivo lymph nodes could predict resistance and/or susceptibility to SIV infection in vivo. Of six macaques exposed to the less-pathogenic virus SIV(MNE), four resisted viral infection. Analysis of the susceptibility of the PBMC of these four animals before SIV(MNE) challenge indicated that all of them were resistant to infection by the SIV(BK28) isolate and, in three of them, this resistance was dependent on CD8+ T cells. Blocks of lymph nodes of these four macaques were resistant to SIV(MNE) infection ex vivo following SIV(MNE) viral challenge exposure. However, the same blocks from the same animals were permissive to the more virulent SIV(251(32H)). Accordingly, three of these macaques were readily infected following challenge exposure with SIV(251(32H)). Lymphoproliferative responses in blood or lymph nodes, local C-C chemokine production in the lymph-node explants, and cytotoxic T-cell activity measured throughout the study did not correlate with ex vivo resistance or susceptibility to in vivo infection. In conclusion, PBMC and lymph-node resistance or susceptibility to infection ex vivo appeared to correlate with in vivo infectivity and, thus, these approaches should be further tested for their predictive value for in vivo infection.     

Comparison between micronucleated lymphocyte rates observed in healthy subjects and cancer patients

Micronucleated cell rates were assessed in cytokinesisblockedlymphocytes of 198 male and female healthy subjects (HS) notoccupationally exposed to genotoxic risks and of 70 male andfemale cancer patients (CP) prior to any anticancer treatment.In the HS group, spontaneous micronucleated cell rates (MN cellrates) were 9.7 ± 2.8 per 1000 binucleated lymphocytesand 9.8 ± 3.1 for males and females respectively. Inthe CP group, spontaneous MN cell rates were 21.1 ± 15.3per 1000 binucleated lymphocytes and 19.1 ± 11.2 formales and females respectively. Moreover, they were shown tohave a large inter–individual variability in the two groups.The study of inter-individual variation factors showed thatonly tobacco could affect MN cell rate in HS whereas age andsex apparently had no significant effect. In the CP group, onlyage significantly affected MN cell rate, whereas sex, tobacco,alcohol, imaging techniques and tumour stage had no significanteffect. There was no significant difference in the distributionof gender between HS and CP, whereas there was a significantdifference in the distribution of age and tobacco between thetwo groups. The comparison of MN cell rates in 54 HS and 54CP matched for age and sex showed a statistically significantdifference. Spontaneous MN cell rates of these two populationsreflect environmental exposure. Moreover, for CP it most probablyrefers to various cellular lesions and genetic damage. ⁵To whom correspondence should be addressed