Yasuhiro Yoshikawa

Carboxyl end-specific monoclonal antibodies to amyloid β protein (Aβ) subtypes (Aβ40 and Aβ42(43)) differentiate Aβ in senile plaques and amyloid angiopathy in brains of aged cynomolgus monkeys

Abstract Senile plaques (SPs) and cerebral amyloid angiopathy (CAA) in the brains of five aged (20–26 years old) cynomolgus monkeys were investigated immunohistochemically using two monoclonal antibodies (anti-Aβ 40 (BA27) and anti-Aβ 42(43) (BC05)) that can differentiate the carboxyl termini of amyloid β protein (Aβ) subtypes. In four of five animals, all types of SPs (i.e. diffuse, primitive, and classical plaques; DPs, PPs, and CPs, respectively) were identified by BC05. However, BA27 did not label DPs and stained only about one third of PPs and CPs, mainly labeling granular structures and cored portions, respectively. In CAA, lesions of cortical capillaries reacted to BC05 in four of five cases, but rarely and weakly to BA27 in two of five cases. On the other hand, lesions of parenchymal and meningeal arterioles were stained by both BA27 and BC05. These staining profiles of SPs in cynomolgus monkeys correspond well to those in humans, although there are two remarkable features in cynomolgus monkeys. First, BA27 stained PPs associated with granular structures. Secondly, capillary Aβ reacted intensely to BC05 but only slightly to BA27. Despite these unique features, the results suggest that aged cynomolgus monkeys can be used to investigate the pathogenesis of Aβ deposition in SPs and CAA.

Deposition of amyloid β protein (Aβ) subtypes [Aβ40 and Aβ42(43)] in canine senile plaques and cerebral amyoloid angiopathy

Abstract To clarify the immunohistochemical features of canine senile plaques (SPs) and cerebral amyloid angiopathy (CAA), the distribution of the amyloid β protein (Aβ) subtypes Aβ40 and Aβ42(43), Aβ precursor protein (APP), and glial cell reaction were examined in the brains of seven aged dogs (12–18 years). Aβ42(43) was found to be deposited in all types of SPs, whereas Aβ40 was deposited only in mature (classical and primitive) plaques. CAA, which was located along parenchymal and meningeal arterioles and capillaries, consisted of both subtypes of Aβ. APP was exhibited in normal and degenerative neurons and swollen neurites of mature plaques. It was, therefore, considered that Aβ42(43) in diffuse plaques might be derived from APP in neurons, while Aβ40 and Aβ42(43) in mature plaques might be generated from APP in swollen neurites in the plaque. In contrast to the case in humans, in whom deposition of Aβ40 and Aβ42(43) in the mature plaques is predominantly associated with microglial reaction, in dogs we found that it was closely associated with astroglial reaction. The present findings showed characteristics of canine SPs which are different from those of humans.

AGE-DEPENDENT REMODELING OF PERIPHERAL BLOOD CD4+ CD8+ T LYMPHOCYTES IN CYNOMOLGUS MONKEYS

Recently, we have found in adult cynomolgus monkeys that substantial peripheral blood CD4+ CD8+ double-positive (DP) T lymphocytes exhibit a resting memory phenotype and increase in proportion with age. In this study, we investigated whether phenotypic changes occur in the course of the increase in proportion of the DP T cells. The results obtained from 195 clinically healthy monkeys aged from 1 month to 31 years showed that the CD29hi and CD28 subpopulation in the DP T subset increased in proportion with age and that the increase reached a plateau at six years old for the CD29hi subpopulation and at eleven years old for the CD28 one, respectively. The phenotypic alteration preceded the abrupt increase in proportion of the DP T cells and was able to be classified into four phases on the basis of the qualitative and quantitative alteration.

Accumulation of MAC387+ macrophages in paracortical areas of lymph nodes in rhesus monkeys acutely infected with simian immunodeficiency virus

We investigated the histological features of lymph nodes, focusing on monocytes/macrophages, in rhesus monkeys (Macaca mulatta) acutely infected with simian immunodeficiency virus (SIV). In monkeys infected with a pathogenic SIV, SIVmac239, MAC387(+) newly blood-derived macrophages markedly increased in number at paracortical areas at 11 to 14 days postinoculation, concomitant with the peak of the primary SIV antigenemia. The MAC387(+) macrophages densely gathered around high endothelial venules and formed cell clusters with CD3(+) T lymphocytes, tingible body macrophages, and plasmacytoid monocytes. In the cell clusters, CD3(+) T lymphocytes which closely adhered to the MAC387(+) macrophages enlarged in size, suggesting a histological manifestation of T-lymphocyte activation by macrophages. By 54 days postinoculation, when SIV antigenemia became undetectable, the MAC387(+) macrophages decreased in number and the cell cluster disappeared from paracortical areas. In contrast, the monkeys infected with a nef-deleted mutant of SIVmac239 showed lower levels of SIV antigenemia and lower numbers of MAC387(+) macrophages in paracortical areas than those infected with SIVmac239. These results indicate that MAC387(+) macrophages accumulate in paracortical areas for the period of the intense primary SIV antigenemia and may play an important role in activating naive T lymphocytes.

In vitro fertilization and preimplantation embryo development of African green monkeys (Cercopithecus aethiops).

Ovaries of five adult female African green monkeys were stimulated by repeated administrations of equine chorionic gonadotrophin (eCG), followed by a single administration of human chorionic gonadotrophin (hCG). Oocytes were collected from enlarged follicles 28 h after hCG administration and incubated in vitro for 288 h. Oocytes that had extruded the first polar body were inseminated with spermatozoa that had been incubated for 4 to 6 h in medium with caffeine and dibutyryl cyclic AMP. Of these oocytes, 66% were fertilized and the incidence of polyspermy was 37%. Eighty‐two percent of the fertilized eggs cleaved, with some developing into expanded blastocysts. Am. J. Primatol. 43:43–50, 1997.

A two‐step extraction method to measure fecal steroid hormones in female cynomolgus monkeys (Macaca fascicularis)

We developed a two‐step extraction method for measuring fecal steroid concentrations. In the first step, distilled water was used to extract steroids from fecal samples. In the second step, a mixture of organic solvents (hexane and ether) was used to re‐extract water extracts that had been transferred to a glass tube. A portion of the upper layer of the organic solvents was transferred to separate assay‐tubes for measurement of estradiol (E2) or progesterone (P), and the organic solvents were evaporated in vacuo.

Localization of testosterone and 3β-hydroxysteroid dehydrogenase/Δ5-Δ4-isomerase in cynomolgus monkey (Macaca fascicularis) testes

The enzyme 3β‐hydroxysteroid dehydrogenase /Δ5‐Δ4‐isomerase (3β‐HSD) is essential for the biosynthesis of all classes of steroid hormones, including androgens. We localized testosterone and 3β‐HSD by light microscopic immunocytochemistry in the testes of adult cynomolgus monkeys. Immunoreactive testosterone was located as intense deposits in the labeled cytoplasm of Leydig cells, and located weakly in the interstitial tissues, basement membranes, and the regions near tubular walls within tubules. Immunoreactive 3β‐HSD was located in the cytoplasm of all Sertoli cells and was especially intense in the parts near tubular walls and located weakly to intensely in the cytoplasm of some Leydig cells. This is the first immunocytochemical evidence that Sertoli cells of cynomolgus monkeys, as well as Leydig cells, are involved in biosynthesis of androgens.

Localization of immunoreactive testosterone and 3β-hydroxysteroid dehydrogenase/Δ5-Δ4 isomerase in cynomolgus monkey (Macaca fascicularis) testes during postnatal development

Abstract: The age‐related expression of testosterone and 3β‐HSD in the testes of cynomolgus monkeys was detected using light‐microscopic immunocytochemistry. Intense deposits of immunoreactive testosterone were labeled in parts of Leydig cells in neonatal, late infantile, pubertal, and adult testes, and only a few Leydig cells in early infantile testes. The immunoreactive 3β‐HSD was labeled in parts of Leydig cells and in all Sertoli cells in neonatal, late infantile, pubertal, and adult testes, whereas only a few Leydig cells, but no Sertoli cells, were labeled in early infantile testes. The fluctuations of testosterone and 3β‐HSD expression in testes correlated well with those already observed plasma testosterone levels during postnatal development in cynomolgus monkeys.

Sequence Analysis and Variation of EBNA-1 in Epstein-Barr Virus-Related Herpesvirus of Cynomolgus Monkey

Objectives: The Epstein-Barr virus (EBV) nuclear antigen 1 (EBNA-1) is an important protein for immortalization and tumorigenesis of infected cells. EBNA-1 gene variants may play a role in tumorigenesis. We determined the nucleotide and amino acid (aa) sequences of EBNA-1 in EBV-related herpesviruses from cynomolgus monkeys (cynomolgus-EBV) which induced malignant lymphomas in its natural host and in rabbits, and compared them with sequences of EBV and other lymphocryptoviruses (LCVs). Methods: Polymerase chain reaction and direct sequencing methods were performed using extracted DNA from cynomolgus-EBV-infected cell lines. Results: The amino acid sequences of cynomolgus-EBV EBNA-1 from two cell lines (Si-IIA: 588 aa; Ts-B6: 619 aa) which are antigenically cross-reactive to human EBV EBNA-1 showed homology with human EBV (Si-IIA: 53%; Ts-B6: 58%) and other LCVs from baboons (54 and 52%) and rhesus monkeys (60 and 58%), especially in the C-terminal unique domain. Homology of the EBNA-1 sequence between Si-IIA and Ts-B6 was 92%. The sequence difference between EBV and the related LCVs was manifested mainly in the length of the internal repeat 3-corresponding region, which contains serine in the glycine/alanine repeat region of nonhuman LCVs. Conclusion: Sequence variation of cynomolgus-EBV EBNA-1 from different cell lines was observed. However, their sequences show a relatively high homology with human EBV and share the common features of EBNA-1 of EBV and other LCVs.

Immunolocalization of proliferating cell nuclear antigen (PCNA) in cynomolgus monkey (Macaca fascicularis) testes during postnatal development.

The age‐related distribution of proliferating cell nuclear antigen (PCNA) in the testes of cynomolgus monkeys (Macaca fascicularis) during postnatal development was detected using light‐microscopic immunohistochemistry. In neonatal testes, some PCNA‐positive spermatogonia, Sertoli cells, peritubular cells, and Leydig cells were detected. In early infantile testes, only a few of these cell types were positive. In late infantile testes, the numbers of positive cells were greater than in the earlier developmental stages. In pubertal testes, the numbers of positive spermatogonia, spermatocytes, Sertoli cells, peritubular cells, and Leydig cells were considerably higher. In adult testes, a larger percentage of spermatogonia and spermatocytes was positive, and peritubular cells and Leydig cells were occasionally positive; secondary spermatocytes, spermatids, and Sertoli cells were not positive. We concluded that immunolocalization of PCNA can serve as a tool for studying proliferation status in developing testes of cynomolgus monkeys. A relatively low proliferative activity in early infantile testes and a remarkable increase of proliferative activity in pubertal testes correlate with the fluctuations of steroidogenic functions during postnatal development in cynomolgus monkeys.