Biomedical subjects

A G Hendrickx

Publications and source records attributed to A G Hendrickx.

At least 19 recordsLinked to original sources

PubMed2004

Effects of 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) on fatty acid availability and neural tube formation in cynomolgus macaque, Macaca fascicularis.

2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) is known to alter carbohydrate utilization and specific steps in lipid metabolism. TCDD interacts with estradiol in mobilizing specific fatty acids in chickens that may be a cause of cranial/beak malformations in this species. This study was designed to test the hypothesis that TCDD simultaneously alters critical fatty acid mobilization during early pregnancy and determine if those changes correlate to morphological defects of the developing neural tube in the nonhuman primate. Cynomolgus macaques were treated with a single dose of 4 microg/kg body weight (BW) TCDD on gestational day 15 or 20. Pregnancies were terminated by hysterectomy on gestational day 24-26 and embryos were examined to determine morphology of the developing neural tube. Maternal blood samples were used for fatty acid quantification. Embryos exhibited cellular changes, mainly increased cell death, and intercellular spaces in the neural tube, suggestive of an adverse effect on the developing nervous system. Significant decreases on fatty acid composition were found on some of the eight classes of lipids analyzed. Particularly, a decrease was observed in the n-3 (40-60%) and n-6 (47-75%) essential fatty acids in treated pregnancies compared to untreated controls. These data demonstrate the effect of TCDD in decreasing maternal levels of n-3 and n-6 fatty acids that are considered necessary for normal development in mammals. Since neural tube development is dependent, in part, on n-3 and n-6 fatty acids, it is possible that the limitation of these essential fatty acids in plasma resulted in the observed detrimental effects on early brain development.

Animals↗

PubMed2002

Exposure of cynomolgus monkey embryos to retinoic acid causes thymic defects: effects on peripheral lymphoid organ development.

We have previously reported that exposure of monkey embryos to 13-cis-retinoic acid (cRA) results in thymic defects. In this study, we analyzed lymphocyte and antigen-presenting cell populations at gestational days (GDs) 80-100 in the thymus, spleen, mesenteric lymph nodes, and gut-associated lymphoid tissue following a teratogenic dosing regimen of cRA (2.5 and 5 mg/kg) at GD14-27. Tissue sections were immunostained for T-cells (anti-CD3), B-cells (anti-CD20), dendritic cells (p55), and major histocompatibility class II (anti-HLA-DR). Digital images of spleen sections were analyzed to obtain the relative area occupied by the cell subsets within the white pulp (WP). Compared with controls, the T-cell dependent compartment of the spleen WP in specimens with perturbed thymic development (aplasia and severe hypoplasia) showed a reduction in size and proportion of CD3(+) T cells. Our findings indicate that cRA-induced thymic defects result in disrupted development of the splenic T-cell dependent compartment.

Abnormalities, Drug-Induced↗

PubMed2002

Two cases of digital defects in Macaca mulatta infants and a survey of the literature.

Although congenital digital defects, particularly polydactyly, have been reported frequently in humans, their occurrence in rhesus macaques is relatively rare. We observed two cases of spontaneous digital defects in male rhesus monkey infants recently born at the California Regional Primate Research Center. One infant exhibited bilateral postaxial polydactyly and the other infant had bilateral oligodactyly with unilateral phalangeal duplication. In this report, we present the clinical/pathological details of these cases as well as discuss the embryology of normal and abnormal limb development. We will also summarize a variety of spontaneous and experimentally induced digital defects that have been reported in several nonhuman primate species.

Animals↗

PubMed2001

Titration of an SIVmac251 stock by vaginal inoculation of Indian and Chinese origin rhesus macaques: transmission efficiency, viral loads, and antibody responses.

The purpose of this study was to determine whether rhesus monkeys of Chinese origin are suitable for studies of mucosal lentivirus transmission by comparing the relative ability of these animals and rhesus macaques of Indian origin to become infected by vaginal (IVAG) inoculation with SIVmac251. In addition, we sought to test the hypothesis that differences in viral load during the first few weeks after inoculation were due to the relative strength of the anti-SIV immune responses in the two populations of rhesus macaques. Significant difference was not observed between the number of Indian and Chinese origin monkeys that were infected after IVAG SIV inoculation in this study. For 8-9 weeks after infection there was considerable overlap in the range of viral loads among the Indian and Chinese animals and the variation among the Indian origin animals was greater than the variation among the Chinese origin monkeys. By 6 weeks postinfection, viral loads in SIV-infected Chinese origin monkeys tended to be at the lower end of the range of viral loads observed in SIV-infected Indian origin monkeys. The strength of the anti-SIV antibody response was also more variable in the Indian origin rhesus macaques, but at 6-8 weeks postinfection, Chinese and Indian origin rhesus macaques had similar titers of anti-SIV antibodies. Microsatellite allele frequencies differed between Chinese and Indian rhesus macaques; however, the majority of alleles present in Indian-origin animals were also found in Chinese macaques. Together these results show that host factors, other than geographic origin, determine the ability of a rhesus macaque to be infected after IVAG SIV exposure and that geographic origin does not predict the viral load of SIV-infected animals during the first 8-9 weeks after IVAG inoculation.

Animals↗

PubMed2001

13-cis-retinoic acid causes patterning defects in the early embryonic rostral hindbrain and abnormal development of the cerebellum in the macaque.

BACKGROUND: We have previously reported that exposure of embryos to 13-cis-retinoic acid (cRA) results in an abnormal phenotype of the fetal cerebellum. In this study, we analyzed early changes in the cerebellar anlagen (midbrain-hindbrain junction) as well as lesions of the fetal cerebellar vermis after a teratogenic dosing regimen of cRA in the macaque model. METHODS: We examined embryo coronal sections of the midbrain-hindbrain junction immunostained for Pax-2, Engrailed-2 (En-2) and Krox-20. To characterize the cerebellum foliation and fissure formation processes, we analyzed vermal cortical cell layer development and the number and depth of the major fissures on sagittal sections of fetal vermis. We also examined Purkinje cell development in vermal sections immunostained for CD3. RESULTS: Compared with controls, there was a consistent truncation of the midbrain-hindbrain region of early embryos exposed to cRA. The cRA-induced fetal vermis lesions included inhibition in its anteroposterior growth, altered folial patterning, a general loss of prominence of the fissures accompanied by a total loss of sublobular fissures, and changes in cortical cell layer development. CD3(+) Purkinje cells were abnormally dispersed deep into the molecular layer in the vermis. CONCLUSIONS: Our findings indicate that the effects of cRA on the developing cerebellum involve interference with the hierarchy of complex cellular and genetic interactions that lead to the growth and subdivision of the cerebellum into smaller units. The regional vermal defects may be related to early postnatal functional deficits.

Animals↗

PubMed2001

Effect of vaginally administered fumagillin on the morphology of implantation stage endometrium in the rhesus monkey.

Intravaginal administration of an anti-angiogenic agent, fumagillin, during blastocyst implantation, inhibits pregnancy establishment in a dose-related manner in the rhesus monkey. In the present study, mated female rhesus monkeys were vaginally inserted with tampons containing vehicle (group 1; n = 5) and test agent (fumagillin, 4 mg/animal; group 2; n = 6) on cycle day 20, and endometrial tissue samples were collected on cycle day 24 from all monkeys and processed for morphometric and ultrastructural analysis. Concentrations of estradiol-17beta, progesterone and chorionic gonadotrophin in peripheral circulation were determined. From serum profiles of hormones, two monkeys in group 1, and one animal in group 2 appeared pregnant. Endometrial morphology revealed histologic evidence of pregnancy in three of six fumagillin-treated animals, while other three fumagillin-treated animals showed degenerative changes in glands and venules along with marked extravasation. It is possible that the function of corpus luteum was affected by fumagillin treatment resulting in inadequate progesterone production (p <0.05), and consequent inadequate endometrial secretory preparation and receptivity, as revealed from decline in apical movement of vacuoles (p <0.05) and increase (p <0.05) in extravasation of red cells and leukocytes.

Administration, Intravaginal↗

PubMed2001

Effect of vaginally administered (Ala(8,13,18))-magainin II amide on the morphology of implantation stage endometrium in the rhesus monkey (Macaca mulatta).

Intravaginal administration of an anti-microbial agent, (Ala(8,13,18))-magainin II amide, during blastocyst implantation inhibits pregnancy establishment in a dose-related manner in the rhesus monkey (Macaca mulatta). In the present study, mated female rhesus monkeys were vaginally inserted with tampons containing vehicle (Group 1; n = 5) and test agent (magainin, 0.5 mg/animal; Group 2; n = 6) on cycle day 20. Endometrial tissue samples were collected on Cycle Day 24 from all monkeys and processed for morphometric and ultrastructural analysis. Concentrations of estradiol-17beta, progesterone, and chorionic gonadotrophin in peripheral circulation were determined, which revealed that two monkeys in Group 1 were pregnant while no animals were pregnant in Group 2. Endometrial morphology, however, revealed histologic evidence of pregnancy in three out of the six magainin-treated animals. It appears that intra-vaginal administration of magainin II amide had a marginal effect on the implantation stage endometrium and the initiation of the implantation process in the rhesus monkey.

Administration, Intravaginal↗

PubMed2001

Exposure to the dioxin 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) induces squamous metaplasia in the endocervix of cynomolgus macaques.

Female cynomolgus macaques (n = 11) were treated orally with graded doses of 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD). Cervical tissue was recovered at necropsy 1.2-2.7 years later and examined using routine histopathology. Results were compared histologically with cervical tissue from untreated, age- and parity-matched controls. Significant squamous epithelial metaplasia was observed in the endocervix of 9 of 11 TCDD-treated animals, and the degree of severity was dose dependent. In contrast, minimal or no pathological changes were observed in eight of nine control animals and one animal had only mild squamous metaplasia. These results suggest that TCDD exposure induces epithelial transdifferentiation in the primate cervix. Consequently, the TCDD-treated macaque may serve as a predictable animal model for the study of cervical epithelial transdifferentiation and for examining the relationship between squamous metaplasia and cervical oncogenesis both at the cellular and at the molecular level.

Administration, Oral↗

PubMed2000

Humans and old world monkeys have similar patterns of fetal globin expression.

The expression of epsilon- and gamma-globin mRNA and protein has been determined in three Old World monkey species (Macaca mulatta, Macaca nemestrina, and Cercopithecus aethiops). Using RT-PCR with primers for epsilon- and gamma-globin, both mRNAs were detected in early fetal stages, whereas at 128 days (85% of full term), only gamma was expressed. High-performance liquid chromatography was used for separation and quantitation, and matrix-assisted laser desorption/ionization mass spectrometry was used for identification of globin polypeptides. An alpha-globin polymorphism was observed in all of the species examined. During fetal life, gamma-globin was the predominant expressed beta-type globin. The red blood cells of infants still contained substantial amounts of gamma-globin, which declined to negligible levels in 14 weeks as beta-globin expression reached adult values. The ratio of gamma1- to gamma2-globins (equivalent to Ggamma/Agamma in humans) was approximately 2.5, similar to the Ggamma/Agamma ratio observed in humans. Thus, gamma-globin gene expression in these Old World monkeys species has three features in common with human expression: expression of both duplicated gamma genes, the relative preponderance of gamma1 over gamma2 expression, and the delay of the switch from gamma- to beta-globin until the perinatal period. Thus, the catarrhines seem to share a common pattern of developmental switching in the beta-globin gene cluster, which is distinct from the timing of expression in either prosimians or the New World monkeys. Our results indicate that an Old World monkey, such as Rhesus, could serve as a model organism (resembling humans) for experimentally investigating globin gene expression patterns during the embryonic, fetal, and postnatal stages.

Animals↗

PubMed2000

Preimplantation embryo morphology following early luteal phase anti-nidatory treatment with mifepristone (RU486) in the rhesus monkey.

The ultrastructural characteristics of peri-implantation stage embryos recovered on day 6 after ovulation from rhesus monkeys with or without mifepristone (RU486) treatment during the early luteal phase were examined in the present study. Monkeys were randomly allocated to two groups; group 1 animals were injected s.c. with 2 ml vehicle (1:4, benzyl benzoate: olive oil, v/v, n = 21) and group 2 animals received a single dose of mifepristone (2 mg/kg body weight, w/v, n = 30) in the same volume of vehicle on day 2 after ovulation in mated cycles. On day 6 after ovulation, female monkeys of both groups were laparotomized and their reproductive tracts were flushed to retrieve preimplantation stage embryos. Embryos that showed frank degeneration or desynchrony on gross microscopical examination were not included in the present study. Preimplantation embryo growth on day 6 after ovulation was significantly (P < 0.05) affected in the morula-blastocyst transition stage in mifepristone-treated monkeys compared with that in the control group of monkeys. Ultrastructurally, administration of mifepristone on day 2 after ovulation depressed preimplantation stage embryo development, characterized by loss of cell polarity, lack of mitochondrial maturity, and lack of differentiation in trophoblast cells. Furthermore, preimplantation embryos from mifepristone-treated animals displayed a higher occurrence of inter-blastomere space, intra-cytoplasmic vacuoles, myelinoid bodies, accumulation of lipid droplets, lysosomes, lipofuscins, autophagosomes and multivesicular bodies. Collectively, it appears that the developmental potential of preimplantation embryos was significantly compromised in mifepristone-treated cycles.

Animals↗

PubMed2000

Conjoined twins in a rhesus monkey (Macaca mulatta).

Conjoined twinning is an extremely rare occurrence among human and nonhuman primates. The current report describes a case of minimally conjoined omphalopagus rhesus monkey twins that were observed in the breeding colony at the California Regional Primate Research Center. The full-term nonviable male twins were morphologically normal and united in the umbilical region, involving the liver, xiphoid, umbilicus, body wall, and skin. The umbilical cords were separate, but closely aligned, within an ensheathing amnion; each cord contained two arteries and a vein. The closely associated cords were centrally inserted on a large bidiscoid placenta. There were no gross or histologic abnormalities in the viscera, with the exception of enlargement of the left central liver lobes, which constituted the area of attachment. The cause of death was attributed to asphyxia and trauma experienced during parturition.

Animals↗

PubMed2000

Nonhuman primates: their role in assessing developmental effects of immunomodulatory agents.

There are close physiologic similarities between humans and macaques that make them well suited for preclinical testing of biopharmaceutics. These include menstrual cycles of similar length and hormonal control, comparable cellular and endocrine processes of implantation, and similar timetables of prenatal development. Three teratogenic agents have induced abnormal development of the macaque thymus that is a key organ in the development of the fetal immune system. Embryonic exposure to triamcinolone acetonide, a potent corticosteroid, during critical periods of thymus development caused marked hypoplasia, depletion of thymic lymphocytes, and reduction of epithelial elements. Aplasia and hypoplasia of the thymus were a distinct feature of the "retinoid syndrome" in cynomolgus macaques following exposure to 13-cis-retinoic acid (Accutane) in early pregnancy, the time of neural crest migration. Experimentally induced zinc deficiency in rhesus macaques from conception to 1-year of age caused severe alterations in immunocompetence. More recent studies have shown that the levels of IgG and IgA in cervicovaginal lavages of the rhesus macaque exhibit specific temporal patterns during the normal menstrual cycle. Taken together, theses data suggest that several macaque species are appropriate animal models for preclinical safety assessment of immunomodulatory drugs. Current teratology protocols in these models may require slight modifications to adequately assess the safety of these biologics.

Adjuvants, Immunologic↗

PubMed2000

The origin and development of the upper lateral incisor and premaxilla in normal and cleft lip/palate monkeys induced with cyclophosphamide.

OBJECTIVE: Cleft lip/palate (CLP) is a common human congenital defect in which the maxillary lateral incisors are often absent, malformed, and malpositioned. The present study was designed to examine the origin of the upper primary lateral incisor relative to the medial nasal process (MNP) and maxillary process (MP) fusion area and to the premaxillary/maxillary (incisive) suture in monkeys. METHOD: Scanning electron microscopy, histology, skeletal staining, and drying techniques were used to study facial development in embryo and fetal monkey specimens. A teratogenic dose of cyclophosphamide was administered to pregnant monkeys prior to fusion of the MNP and MP and fetuses were examined for CLP. RESULTS: Formation of the anterior maxilla involved fusion of the MNP and MP at stages 14-18. At stages 18-20, the palatal portion of the MNP had formed the medial and lateral incisive mounds. By stage 22, the upper primary lateral incisor has formed within the MP, lateral to the MNP/MP fusion area and to the ossifying premaxilla. Ossification of the premaxilla begins in the MNP and subsequently spreads laterally across the MNP/MP fusion area into the MP. Accordingly, the lateral incisor undergoes a complex positional shift (mainly medial) relative to the incisive suture both prenatally and postnatally and is finally located medial to the suture. Examination of the cyclophosphamide-induced CLP fetuses showed that the lateral incisor is located lateral to the alveolar cleft and does not shift medial to the incisive suture. CONCLUSION: Understanding the origin of the lateral incisor (the tooth closest to the cleft) and the shift after its formation provides clues to high incidence of malformations and ectopia of this incisor in cleft patients.

Alveolar Process↗

PubMed1999

13-cis-Retinoic acid alters neural crest cells expressing Krox-20 and Pax-2 in macaque embryos.

This study investigates hindbrain and associated neural crest (NCC), otocyst, and pharyngeal arch development in monkey embryos following teratogenic exposure to 13-cis-retinoic acid (cRA). cRA was orally administered (5 mg/kg) to pregnant long-tailed macaques (Macaca fascicularis) between gestational days (GD) 12 and 27. Embryos were surgically collected at desired stages during treatment, analyzed for external morphological changes, and processed for immunohistochemistry. Two transiently expressed nuclear proteins, Krox-20 and Pax-2, were used as markers for the target cellular and anatomical structures. Rhombomere (r) expression patterns of Pax-2 (r4/r6) and Krox-20 (r3/r5) were maintained after cRA treatment, but r4 and r5 were substantially reduced in size. In untreated embryos, Krox-20 immunoreactive NCC derived from r5 migrated caudally around the developing otocyst to contribute to the third pharyngeal arch mesenchyme. In cRA-treated embryos, a subpopulation of NCC rostral to the otocyst also showed Krox-20 immunoreactivity, but there was a substantial reduction in Krox-20 post-otic NCC. Pax-2 immunoreactive NCC migrating from r4 to the second pharyngeal arch were substantially reduced in numbers in treated embryos. Alteration in the otic anlage included delayed invagination, abnormal relationship with the adjacent hindbrain epithelium, and altered expression boundaries for Pax-2. cRA-associated changes in the pharyngeal arch region due to cRA included truncation of the distal portion of the first arch and reduction in the size of the second arch. These alterations in hindbrain, neural crest, otic anlage, and pharyngeal arch morphogenesis could contribute to some of the craniofacial malformations in the macaque fetus associated with exposure to cRA.

Animals↗

PubMed1999

Pathogenesis of retinoic acid-induced ear malformations in primate model.

13-cis retinoic acid (RA) is a causative agent for human/monkey retinoic acid embryopathy (RAE), in which the most common type of malformation is microtia or anotia. In the present study, malformed ears of monkey fetuses exposed to RA during early embryogenesis were analyzed and revealed a subtype of defects., i.e., apparent duplication of the external/middle ear. A part of the posterior auricle appeared to be ectopically formed in the anterior auricular region or in the region posterior to the auricle. Additionally, there was duplication of the zygomatic arch, malleus, and incus. In order to characterize possible pathogenetic events underlying these malformations, embryos at selected stages were collected after dosing dams with RA at 5 mg/kg/day during gestational days 12-27. Cellular retinoic acid binding protein I whole-mount immunostaining showed that RA induced specific alterations in the migration of cranial neural crest cells (NCC). NCC en route to the second pharyngeal arch were bifurcated, and some of these NCC migrated abnormally into the first and/or third arches, which may underlie external ear duplication. Scanning electron microscopy and neurofilament immunostaining provided evidence that there was partial duplication of trigeminal nerve/ganglion following RA insult. The duplication of NCC neuronal derivatives in the first pharyngeal arch is consistent with duplication of NCC mesenchymal components (zygomatic arch, malleus, and incus). Therefore, RA-induced alterations in cranial NCC migration patterns are likely to be a pathogenetic event underlying ear malformations (including duplication) of RAE in monkeys.

Animals↗

PubMed1999

Endocrine biomarkers of early fetal loss in cynomolgus macaques (Macaca fascicularis) following exposure to dioxin.

This study examines the endocrine alterations associated with early fetal loss (EFL) induced by an environmental toxin, TCDD (2,3,7, 8-tetrachlorodibenzo-p-dioxin), in the cynomolgus macaque, a well-documented reproductive/developmental model for humans. Females were administered single doses of 1, 2, and 4 microgram/kg TCDD (n = 4 per dose group) on gestational day (GD) 12. Urinary estrogen metabolites (estrone conjugates) were monitored to establish the day of ovulation, and serum hormones (estradiol, progesterone, chorionic gonadotropin, relaxin) were measured to assess ovarian and placental endocrine status before and after treatment. EFL occurred between GDs 22 and 32 in 10 of the 12 animals treated with TCDD. The primary endocrine alterations associated with TCDD treatment were significant decreases in serum estradiol and bioactive chorionic gonadotropin concentrations (p < 0.02). Less pronounced decreases in serum progesterone (p = 0.10) and relaxin (p < 0.08) also followed TCDD treatment. In contrast, immunoreactive chorionic gonadotropin concentrations were not reduced by TCDD exposure at any level, indicating that TCDD targets specific components of the chorionic gonadotropin synthesis machinery within the trophoblast to alter the functional capacity of the hormone. These data demonstrate the value of endocrine biomarkers in identifying a toxic exposure to primate pregnancy many days before direct signs of reproductive toxicity were apparent. The increased EFL that occurred after exposure to TCDD might reflect a toxic response initially mediated via endocrine imbalance, leading to placental insufficiency, compromised embryonic circulation, and subsequent EFL.

Abortion, Spontaneous↗

PubMed1998

Neuropathogenesis induced by rhesus cytomegalovirus in fetal rhesus monkeys (Macaca mulatta).

Rhesus cytomegalovirus (RhCMV) infection of rhesus macaques offers opportunities to analyze mechanisms of CMV pathogenesis in a primate species. Four fetal rhesus monkeys were inoculated intraperitoneally with RhCMV early in the second trimester, and pregnancies were terminated by hysterotomy during the third trimester. Three fetuses had evidence of severe CMV disease, including intrauterine growth restriction, ventriculomegaly, microcephaly, lissencephaly, and extensive degenerative changes of the cerebral parenchyma. Histopathologic examination revealed polymicrogyria, gliosis, leptomeningitis, periventricular calcifications, and inclusion-bearing cells. These results demonstrate that the developing macaque brain is susceptible to infection with RhCMV early in the second trimester and that intrauterine infection results in neuropathologic outcomes similar to those observed in humans congenitally infected with CMV.

Animals↗

PubMed1998

Effects of 13-cis-retinoic acid on hindbrain and craniofacial morphogenesis in long-tailed macaques (Macaca fascicularis).

Hindbrain and craniofacial development during early organogenesis was studied in normal and retinoic acid-exposed Macaca fascicularis embryos. 13-cis-retinoic acid impaired hindbrain segmentation as evidenced by compression of rhombomeres 1 to 5. Immunolocalization with the Hoxb-1 gene product along with quantitative measurements demonstrated that rhombomere 4 was particularly vulnerable to size reduction. Accompanying malformations of cranial neural crest cell migration patterns involved reduction and/or delay in pre- and post-otic placode crest cell populations that contribute to the pharyngeal arches and provide the developmental framework for the craniofacial region. The first and second pharyngeal arches were partially fused and the second arch was markedly reduced in size. The otocyst was delayed in development and shifted rostrolaterally relative to the hindbrain. These combined changes in the hindbrain, neural crest, and pharyngeal arches contribute to the craniofacial malformations observed in the retinoic acid malformation syndrome manifested in the macaque fetus.

Animals↗