Regional difference in sulcal infolding progression correlated with cerebral cortical expansion in cynomolgus monkey fetuses.

The present study aimed to specify the cerebral sulci developed by cortical expansion in cynomolgus monkey fetuses. The degree of sulcal infolding was evaluated by the gyrification index (GI), which was quantified using ex vivo magnetic resonance imaging. The correlation of cortical volume with the sulcal GI was most frequent during embryonic days (EDs) 100 to 120. Interestingly, the high correlation was marked during EDs 140 to 150 in restricted primary sulci in prefrontal, parietotemporal and medial temporal regions. The present results suggest that cortical expansion is involved in gyral demarcation by sulcal infolding, followed by the sulcal infolding progression in phylogenetically-newer cortices.

Fetal gyrification in cynomolgus monkeys: a concept of developmental stages of gyrification.

Our article summarizes a series of studies about fetal gyrification and its relation to cerebral growth in cynomolgus monkeys. Based on the cerebral growth (i.e., brain weight, cerebral volume, and frontooccipital length of the cerebral hemisphere) and the developmental pattern of gyrification in each sulcus of cynomolgus monkeys, we divided the gyrification process into four stages: Stage 1. Demarcation of cerebral lobes and limbic gyri; Stage 2. Demarcation of neocortical gyri; Stage 3. Emergence of secondary and tertiary sulci; and Stage 4. Growth of sulcal length and depth. Each stage of those gyrification processes was influenced by different developmental events, such as the emergence of corticocortical long-associative fiber tracts, cortical maturations, and subcortical white-matter development. This is the first report to systematically propose gyrification processes closely related to the order of phyologenetical development of the cerebral cortex in primates.

Neuroanatomic and magnetic resonance imaging references for normal development of cerebral sulci of laboratory primate, cynomolgus monkeys (Macaca fascicularis).

Cynomolgus monkey (Macaca fascicularis) is a popular laboratory primate belonging to Old World monkeys, which are the group most closely related to humans except for the apes. This paper summarizes a series of our studies regarding the development of cerebral sulci and gyri in this primate, and the stated possibility of evaluation of the sulcal development for assessing the developmental toxicity testing. The cerebrum of cynomolgus monkeys experienced a regular sequence of emergence of sulci and gyri on gross observation while such timetables corresponded to those obtained by magnetic resonance imaging (MRI) with a lag time of 10-30 days. When the timetables for the emergence of anatomically identical primary sulci and gyri were compared between cynomolgus monkeys and humans, their chronological sequences were comparable, while some sulci and gyri located on the phylogenetically newer cortical region in humans emerged earlier in monkeys. The present paper further indicates brief procedures for evaluating cerebral abnormalities and/or maturity using brain specimens without MRI measurements. The primary sulcal lengths measured by the 'cotton thread' method were a brief index of the degree of regional gyrification. As the development of a calcarine sulcus was closely correlated with morphological maturation of the lateral ventricle, which changed drastically during embryonic days (EDs) 90-100, the cerebral maturity on ED 100 could be evaluated by the infolding of that sulcus. Thus, the present paper provides gross anatomical and MRI references and brief procedures for investigating the normality of the development of cerebral sulci and gyri of laboratory primates, cynomolgus monkeys.

Correlation between formation of the calcarine sulcus and morphological maturation of the lateral ventricle in cynomolgus monkey fetuses.

In the present study developmental changes in the cerebral sulci and volumes of subcortical and archicortical structures of the cerebrum in cynomolgus monkey fetuses were examined with T(1)-weighted magnetic resonance (MR) images in 3D. On the embryonic day (ED) 90, the lateral ventricle had still an immature vesicular shape in the occipital region of the cerebrum, and it dramatically closed its lumen by ED 100. In that period the calcarine sulcus progressively infolded from the medial surface of the cerebral hemisphere narrowing the lumen of the lateral ventricle in the occipital region. Volume of the lateral ventricle decreased in the period ED 90-100, increasing afterwards in spite of increasing volumes of subcortical and archicortical structures such as the caudate nucleus, putamen, globus pallidus, amygdala and hippocampal formation. During the same time, the volume of the germinal matrix around lateral ventricles decreased to disappear completely by ED 120. These results suggest that the morphological maturation of lateral ventricle is linked to the development of calcarine sulcus in cynomolgus monkey fetuses. The degree of infolding of calcarine sulcus on ED 100 would be useful as a gross anatomical landmark for evaluating the cerebral maturation in cynomolgus monkey fetuses.

Developments of sulcal pattern and subcortical structures of the forebrain in cynomolgus monkey fetuses: 7-tesla magnetic resonance imaging provides high reproducibility of gross structural changes.

The aim of this study was to spatio-temporally clarify gross structural changes in the forebrain of cynomolgus monkey fetuses using 7-tesla magnetic resonance imaging (MRI). T(1)-weighted coronal, horizontal, and sagittal MR slices of fixed left cerebral hemispheres were obtained from one male fetus at embryonic days (EDs) 70-150. The timetable for fetal sulcation by MRI was in good agreement with that by gross observations, with a lag time of 10-30 days. A difference in detectability of some sulci seemed to be associated with the length, depth, width, and location of the sulci. Furthermore, MRI clarified the embryonic days of the emergence of the callosal (ED 70) and circular (ED 90) sulci, which remained unpredictable under gross observations. Also made visible by the present MRI were subcortical structures of the forebrain such as the caudate nucleus, globus pallidus, putamen, major subdivisions of the thalamus, and hippocampal formation. Their adult-like features were formed by ED 100, corresponding to the onset of a signal enhancement in the gray matter, which reflects neuronal maturation. The results reveal a highly reproducible level of gross structural changes in the forebrain using a high spatial 7-tesla MRI. The present MRI study clarified some changes that are difficult to demonstrate nondestructively using only gross observations, for example, the development of cerebral sulci located on the deep portions of the cortex, as well as cortical and subcortical neuronal maturation.

Clinical pathology data from cynomolgus monkeys from China in which diarrhea was observed during quarantine.

Shin Nippon Biomedical Laboratories, Ltd. (SNBL) imported and quarantined 3,148 cynomolgus monkeys (aged 2.5 to 6.5 years) from China in 2002. The hematology and blood biochemistry data obtained from these monkeys on Day 32 of quarantine were analyzed separately by sex [2,890 animals in which no abnormalities were observed during the 35-day quarantine period (normal group), and 258 animals which exhibited diarrhea 1 to 12 times (diarrhea group)]. The values obtained for all parameters were within the normal range (mean +/- SD), and no significant abnormalities were noted in either sex. The clinical pathology data from 11 animals (6 males and 5 females) exhibiting diarrhea repeatedly (10 to 12 times) were statistically analyzed, and significant differences were noted in PLT and ALP in both sexes. The PLT values of these animals were within the normal group mean +/- 2 SD, and were considered within the normal range. A significant difference was noted in some individual ALP values (males: Nos. 2 and 3, females: Nos. 1, 3, and 4). The clinical pathology data obtained from the normal group in this study basically correspond to the widely reported results already obtained from healthy cynomolgus monkeys, from which it can be concluded that the cynomolgus monkeys from China were generally healthy and presenting no particular abnormality. The clinical pathology data from the normal group will serve as valuable baseline data for experimenters using cynomolgus monkeys.

Development of cerebral sulci and gyri in fetuses of cynomolgus monkeys (Macaca fascicularis). II. Gross observation of the medial surface.

This study aimed to clarify chronological sequences of the appearances of sulci and gyri on the medial cerebral surface and its relation to the regional development of the cerebrum in cynomolgus monkeys. The lengths of cingulate and calcarine sulci were measured, and the ratios of these lengths to fronto-occipital length were estimated as indices of the size of the "frontoparietal" and "occipital" regions, respectively. The relative length of cingulate sulcus showed a biphasic increase: a slow phase from EDs 100 to 110, and a rapid phase from EDs 110 to 130. The gyri in the "frontoparietal region" were convoluted in the limbic cortex during the initial slow phase and in the neocortical region during the rapid phase. The relative length of calcarine sulcus lineally increased between EDs 90 and 130, and the gyri in the "occipital region" generated in a dorso-ventral manner: the gyrus convolutions occurred first in the "phylogenetically older" striate and dorsal extrastriate cortices, and then in the "phylogenetically newer" ventral extrastriate cortex. The results suggest that the chronological order of appearance of sulci and gyri is closely associated with the order of phylogenetical development of the cerebral cortex. The present study provides a standard reference for the development of cerebral sulci and gyri of cynomolgus monkeys together with our previous study (Fukunishi et al. Anat Embryol 211:757-764, 2006).

Twenty-six-week repeat-dose toxicity study of a recombinant human granulocyte colony-stimulating factor derivative (nartograstim) in cynomolgus monkeys.

An rhG-CSF derivative, nartograstim (NTG), at dose levels of 0 (saline), 0.1, 1, 10, and 100 microg/kg, was administered subcutaneously to groups of 3 male and 3 female cynomolgus monkeys once daily for 26 weeks to investigate its toxicity. In Week 4 or later, an increase in leukocyte counts consisting mainly of neutrophils was noted in all NTG dose groups, and was considered to be attributable to the pharmacological action of NTG. The degree of this increase was reduced with repetition of dosing. Increases in granulocytic cells and granulocytic cells/erythrocytic cells (G/E) ratio in the bone marrow, increase in serum ALP activity, and enlarged spleens with increase of neutrophils in the red pulp were observed at 10 microg/kg and higher. Anemia was noted at 10 microg/kg and higher in Week 4 and was accompanied by an increase in reticulocytes and a decrease in total cholesterol level at 100 microg/kg. Anti-NTG antibody was detected in 1 female at 100 microg/kg, but neutralizing antibodies were not detected at any dose levels in Week 4. In Weeks 13 and 26, these antibodies were detected sporadically at all dose levels. However, there were considerable individual variations in antibody titer, and no definite correlation could be found between the dose levels and the antibody titer. Seven NTG-dosed animals including 3 high dose-group animals showed obvious increases in leukocyte counts until Week 26 but no obvious elevation of anti-NTG or neutralizing antibody. In these animals, changes including anemia became slighter but were still observed in Week 26. Under the conditions in this study, 1 microg/kg was concluded to be the no-observed-adverse-effect level (NOAEL) in cynomolgus monkeys.