SURFACE MORPHOLOGY OF THE FOREBRAIN OF THE BOWHEAD WHALE, BALAENA MYSTICETUS

Observations were made on 11 brains from bowhead whales subsistence-harvested by Alaskan Eskimos under International Whaling Commission guidelines. This study is part of a larger project to determine the basic morphology of this endangered species. The bowhead brain is similar to other cetacean brains, particularly that of the southern right whale. Long olfactory peduncles are reflected upon the rostrodorsal surface of the cerebral hemispheres. Olfactory bulbs have not been recovered but are presumed to exist since nerve fibers have been identified histologically in the olfactory peduncles. The induseum griseum is evident on the corpus callosum. The hippocampus proper is small but protrudes into the lateral ventricle. The cruciate sulcus runs diagonally across the rostral surface, limiting a small frontal lobe. The structure of the floor of the sylvian fissure varies from a few short gyri radiating toward the circular sulcus to a more extensive and complex two-tiered arrangement including numerous gyri perpendicular to the gyrus bordering the paleocortex. Pineal-body-like tissue was present in one specimen. There is no interthalamic adhesion. The lateral geniculate body is elevated but smaller than the large medial geniculate body. The neurohypophysis was adherent on most brain specimens received.     

The cortical EEG in the acallosal mouse

The congenital absence of the corpus callosum has recently been found to occur among some mice of the ddN strain in our laboratory. Morphologically, the absence of corpus callosum was classified into two types. One was complete agenesis of corpus callosum, and the other revealed partial agenesis (genu or splenium, or both). In this experiment, the differences of cortical EEG spectral characteristics were studied on the normal, hypogenesis and acallosal mice. A total of 75 male and female adult mice were used. Under light ether anesthesia, five stainless steel electrodes (0.29 mm) were implanted stereotaxically in the bilateral cerebral cortex and cerebellum at a depth of 1.0 mm. After one week recovery period, the correlations of EEG of five combinations, such as homotopic anterior vs. posterior, left vs. right hemispheres, crossed contralateral, and homotopic anterior and posterior to the reference electrode, were analysed with a signal processor. In the complete acallosal mice (n = 11), the correlation coefficients were significantly lower (p less than 0.05), in the crossed contralateral, left vs. right hemispheres, and homotopic posterior to reference. In the hypogenesis of corpus callosum (n = 7), however, they were no significant differences in the correlation compared with normal mice (n = 57). At the end of experiment, the brain was removed and fixed with 10% formalin, then it was cut in half along the midsagittal plane. The midsagittal section was used to examine an outline of the corpus callosum.     

Morphology of the human corpus callosum: the shape of its mediosagittal section

The shape of the corpus callosum was studied on mediosagittal sections of 50 human brains. The terms "facies corticalis" and "facies profunda" are proposed for the sides of corpus callosum. Each of 50 brains had a different shape of callosal mediosagittal section and any available classification was not possible. In 94% of cases, the contour of callosal cortical surface exhibited a posterior depression and in 46% also an anterior one. Other details of callosal morphology influencing its shape on mediosagittal section (transverse folds, circumscribed depressions) were described. The junction of fornix and corpus callosum in 78% was in 3rd and in 14% in 4th quarter of callosal length. The possible significance of these findings for further studies of human brain morphology is discussed.     

The effects of the interthalamic adhesion position on cerebrospinal fluid dynamics in the cerebral ventricles

The interthalamic adhesion is a unique feature of the third ventricle in the brain. It differs in shape and size and its location varies between individuals. In this study, computational fluid dynamics was performed on 4 three-dimensional models of the cerebral ventricular system with the interthalamic adhesion modeled in different locations in the third ventricle. Cerebrospinal fluid (CSF) was modeled as incompressible Newtonian fluid and flow was assumed laminar. The periodic motion of CSF flow as a function of the cardiac cycle starting from diastole was prescribed as the inlet boundary condition at the foramen of Monroe. Results from this study show how the location of the interthalamic adhesion influences the pattern of pressure distribution in the cerebral ventricles. In addition, the highest CSF pressure in the third ventricle can vary by ～50% depending on the location of the interthalamic adhesion. We suggest that the interthalamic adhesion may have functional implications on the development of hydrocephalus and it is important to model this anatomical feature in future studies.     

Vascularization of the corpus callosum in humans

The blood supply of the corpus callosum is studied in 20 brains by injecting the vascular system with gelatinous Indian ink. The arterial vascularization derives mainly from the anterior cerebral arteries, accessed from the median artery of the corpus callosum or from the terminal and choroidal branches of the posterior cerebral arteries. The various arteries give off perforating branches which are direct or indirect, short, of middle length or long. All these arteries concentrate on the peripheral wall of the corpus callosum. Inside of it these various arteries give off numerous terminal and collateral branches running between the nervous fibres and forming a characteristic vascular network which nourishes the capillary network. The venous vascularization of the corpus callosum is tributary to the deep venous system of the brain and concentrates on the central wall of the commissure.     

Sex differences in dog corpus callosum.

Human studies reported sex differences in size and shape of the corpus callosum. These observations have been contested. The purpose of the present study is to investigate possible sex differences in the corpus callosum of dogs. The entire brains including the medulla from 12 female and 9 male adult mongrel dogs were removed and weighed. Total and partial area measurements of the callosum were made from photographic tracings of its outline. The callosum was partitioned into 3 regions; anterior half, posterior half, posterior one-fifth. The total corpus callosum, anterior half, posterior half, and posterior fifth or splenium areas were measured. Sex differences were found. The anterior half, the posterior half, the posterior fifth, and the total callosum were significantly greater in absolute area in males than in females.     

On the neurons with dendrites intermingling with the fibers of the human corpus callosum: a Golgi picture

Golgi preparations of the anterior part of the truncus of the corpus callosum from 11 adult human brains were investigated. The vertical plane of section was situated symmetrically between the frontal and sagittal plane. The use of this oblique plane of section enabled easy identification of the neurons with dendrites intermingling with transcallosal fibers, what was not possible in standard frontal sections. 2 types of such neurons (with features of other interstitial neurons) were described: fusiform and multipolar. Both types of neurons were more frequently impregnated in areas adjacent to induseum griseum, cingular cortex, and in the depth of the callosal sulcus. Multipolar neurons were also present in the central core and in ventral parts of the corpus callosum, but fusiform ones were not present in ventral parts of the corpus callosum truncus. The dentrites of both types of neurons usually were perpendicular to, sometimes also parallel to transcallosal fibers. The impregnation of these neurons in groups and pairs suggest their integrative role, and their planar orientation in mentioned oblique plane corresponds to oblique direction of transcallosal cingulostriatal decussating fibers.     

Erythropoietin treatment alleviates ultrastructural myelin changes induced by murine cerebral malaria

ABSTRACT: BACKGROUND: Cerebral malaria (CM) is a severe complication of malaria with considerable mortality. In addition to acute encephalopathy, survivors frequently suffer from neurological sequelae. The pathogenesis is incompletely understood, hampering the development of an effective, adjunctive therapy, which is not available at present. Previously, erythropoietin (EPO) was reported to significantly improve the survival and outcome in a murine CM model. The study objectives were to assess myelin thickness and ultrastructural morphology in the corpus callosum in murine CM and to adress the effects of EPO treatment in this context. METHODS: The study consisted of two groups of Plasmodium berghei-infected mice and two groups of uninfected controls that were either treated with EPO or placebo (n = 4 mice/group). In the terminal phase of murine CM the brains were removed and processed for electron microscopy. Myelin sheaths in the corpus callosum were analysed with transmission electron microscopy and stereology. RESULTS: The infection caused clinical CM, which was counteracted by EPO. The total number of myelinated axons was identical in the four groups and mice with CM did not have reduced mean thickness of the myelin sheaths. Instead, CM mice had significantly increased numbers of abnormal myelin sheaths, whereas EPO-treated mice were indistinguishable from uninfected mice. Furthermore, mice with CM had frequent and severe axonal injury, pseudopodic endothelial cells, perivascular oedemas and intracerebral haemorrhages. CONCLUSIONS: EPO treatment reduced clinical signs of CM and reduced cerebral pathology. Murine CM does not reduce the general thickness of myelin sheaths in the corpus callosum.     

Angulate and leopard tortoises in the Thicket Biome, Eastern Cape, South Africa: populations and biomass estimates

The population parameters (morphometrics, population size and biomass) were determined for leopard and angulate tortoises in the Thicket Biome, Eastern Cape, South Africa. Leopard tortoises had a mean total length of 306.47mm (SD = 94.65mm, range 59–496mm, n = 89). Males were smaller (mean total length 277.31mm, SD = 71.85mm, range 73–377mm, n = 36) than females (mean total length = 332.33mm, SD = 97.64mm, range 59–496mm, n = 53). Angulate tortoises had a mean total length of 155.17mm (SD = 33.89mm, range 59–194mm, n = 18). Males were larger (mean total length = 186mm, SD = 8.40mm, range 174–194mm, n = 5) than females (mean total length = 143.31mm, SD = 32.48mm, range 59–178mm, n = 13). The estimated population density for leopard tortoises was 0.85 tortoises ha⁻¹ with an estimated biomass of 6.02kg ⁻¹. Angulate tortoise population density was estimated at 0.12 tortoises ha⁻¹ with a mean biomass of 0.06kg ha⁻¹. The possible consequences of this high density and biomass are discussed.     

The relationship of callosal anatomy to paw preference in dogs

Previous studies have described the paw preference and asymmetry in dog brains, based on experimental studies. The purpose of the present study is to investigate a possible association between callosal anatomy and paw preference in dogs. The midsagittal area of the dog corpus callosum was measured in its entirety and in six subdivisions in a sample of 21 brains obtained from 9 male and 12 female mongrel dogs which had paw preference testing. The present study showed significant paw differences in dog corpus callosum. A posterior segment of the callosum, the isthmus, was significantly larger in the right pawedness than the left.     

A comparative MRI-based morphometric study of the corpus callosum in term and preterm infants

A comparative morphometric study was performed with MRI brain scans of term- and preterm-born infants. The structural characteristics of the brain were analyzed using conventional morphometric indices, and a novel quantitative parameter, the corpus callosum coefficient (kCC), was introduced based on patterns of the prenatal cortex ontogeny. All these quantitative indices reflected anatomical features of the preterm brain. It was found that reduced kCC values in preterm infants were associated with an altered proportion between the rostral and caudal segments of the corpus callosum. The threshold kCC value was established that allowed significant discrimination between the brains of full-term and preterm infants.     

Tractography of the Spider Monkey (Ateles geoffroyi) Corpus Callosum Using Diffusion Tensor Magnetic Resonance Imaging

The objective of this research was to describe the organization, connectivity and microstructure of the corpus callosum of the spider monkey (Ateles geoffroyi). Non-invasive magnetic resonance imaging and diffusion-tensor imaging were obtained from three subjects using a 3T Philips scanner. We hypothesized that the arrangement of fibers in spider monkeys would be similar to that observed in other non-human primates. A repeated measure (n = 3) of fractional anisotropy values was obtained of each subject and for each callosal subdivision. Measurements of the diffusion properties of corpus callosum fibers exhibited a similar pattern to those reported in the literature for humans and chimpanzees. No statistical difference was reached when comparing this parameter between the different CC regions (p = 0.066). The highest fractional anisotropy values corresponded to regions projecting from the corpus callosum to the posterior cortical association areas, premotor and supplementary motor cortices. The lowest fractional anisotropy corresponded to projections to motor and sensory cortical areas. Analyses indicated that approximately 57% of the fibers projects to the frontal cortex and 43% to the post-central cortex. While this study had a small sample size, the results provided important information concerning the organization of the corpus callosum in spider monkeys.     

Effect of secular acceleration on the human brain weight and its changes during aging

The presented examinations on humans are based on 26 publications regarding the secular acceleration and 16 regarding the brain weight (each of the latter containing at least 500 values). The secular acceleration of the body length was only insignificant up to 1800 AD (about 1 mm per 100). From 1800 to 1900, the size of the length increased steadily and reached finally a size of 1 to 1.2 mm/a which is probably unchanged at present. This behaviour can be observed in every country in which such data were sampled. A positive correlation between brain size and body length can be found in a sample of about 11,000 values. An increase of 10 cm body-length corresponds to an increase of 59 g in brain weight, respectively 10 g brain weight are equal to 1.7 cm body-length. 21,300 values of 15 transversal examinations regarding brain weight and age compare the brains of the older and smaller generation having primarily smaller brains with those of the younger generation having primarily larger brains. Therefore the observed diminution of the brain weight during ageing is partly fictitious. With the help of correlation between brain weight and body length on the one hand and the secular acceleration of the body length on the other hand it is possible to correct the fictitious part of this diminishing. The result can state that the real diminution of the brain begins around the 60th year of age. However, it is probable that a high individual variability concerning time and speed exists. At present, the ideas regarding the sources of the secular acceleration are highly speculative.     

White Matter Changes in Patients with Amnestic Mild Cognitive Impairment Detected by Diffusion Tensor Imaging

Compared to normal aging adults, individuals with amnestic mild cognitive impairment (aMCI) have significantly increased risk for progressing into Alzheimer’s disease (AD). Autopsy studies found that most of the brains of aMCI cases showed anatomical features associated with AD pathology. The recent development of non-invasive neuroimaging technique, such as diffusion tensor imaging (DTI), makes it possible to investigate the microstructures of the cerebral white matter in vivo. We hypothesized that disrupted white matter (WM) integrity existed in aMCI. So we used DTI technique, by measuring fractional anisotropy (FA) and mean diffusivity (MD), to test the brain structures involved in patients with aMCI. DTI scans were collected from 40 patients with aMCI, and 28 normal controls (NC). Tract-based spatial statistics (TBSS) analyses of whole-brain FA and MD images in each individual and group comparisons were carried out. Compared to NC, aMCI patients showed significant FA reduction bilaterally, in the association and projection fibers of frontal, parietal, and temporal lobes, corpus callosum, bilateral corona radiation, right posterior thalamic radiation and right sagittal stratum. aMCI patients also showed significantly increased MD widespreadly in the association and projection fibers of frontal, parietal and temporal lobes, and corpus callosum. Assessment of the WM integrity of the frontal, parietal, temporal lobes, and corpus callosum by using DTI measures may aid early diagnosis of aMCI.     

Tests of genetic allelism between four inbred mouse strains with absent corpus callosum.

Inbred mouse strains that lack the corpus callosum connecting the cerebral hemispheres in the adult differ from the C57BL/6J strain at several relevant but unknown loci. To identify at least one major locus that influences axon guidance, different strains showing phenotypically similar defects were crossed to test for allelism. If the F1 hybrid between two strains with the same brain defect is phenotypically normal, it is much more likely that the two strains will differ at fewer loci than will an acallosal strain and C57BL/6J. This approach proved to be very informative. Five reasonable models of inheritance involving two or three loci were assessed, and the data justified rejection of all but one hypothesis. A total of 479 mice were obtained from four inbred strains prone to absence of the corpus callosum (BALB/cWah1, BALB/cWah2, I/LnJ, and 129/ReJ), one normal strain (C57BL/6J), and 11 F1 hybrids among them. Because the size of forebrain axon bundles is generally greater in mice with larger brains, and because whole brain size is certainly polygenic, the phenotypically normal groups were used to derive a standard index of the degree of corpus callosum deficiency relative to brain size. Results demonstrated clearly that the hybrid between BALB/cWah1 and 129/ReJ is normal, whereas the crosses among the BALB/c substrains and I/LnJ yielded many mice with deficient corpus callosum. I/LnJ crossed with 129/ReJ also produced some animals with callosal defects. The data were consistent with a model in which the difference between BALB/c and 129/ReJ involves two loci, whereas the defect in I/LnJ involves homozygosity at three loci, which impairs development more severely.(ABSTRACT TRUNCATED AT 250 WORDS)     

Behavioral asymmetry in BALB/cCF mice with corpus callosum abnormalities]

The possible homology between anomalies of the corpus callosum in mice and in humans remains questionable. The small number of existing behavioural studies in mice have not shown effects, at the behavioural level, of the absence or reduction in size of the corpus callosum. We therefore examined the development, during the first 3 weeks of postnatal life, of a number of simple reflex and integrative responses in the members of a sample of 101 BALB/cCF mice; at autopsy carried out at 50 days of age, 29 mice showed anomalies of the corpus callosum (total absence or an area less than 0.75 mm2). Asymmetry of the development of these responses was measured either as the proportion of animals showing asymmetrical appearance of responses on the left and right sides, and as the delay between appearances on the left and right sides in "asymmetrical" mice. Both measures decreased over the first 15 postnatal days, at the same rate in normal and abnormal mice; in each case the decrease is better described by a second-order, quadratic, function than by a simple linear function. We therefore conclude that the integrity of the corpus callosum is not necessary for the normal maturation of sensorimotor behaviour in mice, and suggest that this conclusion may possibly be explained by the relatively recent appearance of mice in the mammalian radiation.     

Sorting grid trials to improve size selectivity of red mullet (Mullus barbatus) and annular sea bream (Diplodus annularis) in Turkish bottom trawl fishery

Sorting grids with two different bar spacings (12 mm and 14 mm) were tested to improve size selectivity of the commercially important fish species, red mullet (Mullus barbatus) and annular sea bream (Diplodus annularis), in Turkish bottom trawl fishery. Fishing trials were carried out with R/V ‘Egesüf’ between April and May 2003 in Izmir Bay, Aegean Sea, using a traditional bottom trawl. Selectivity data were collected by the top cover method and analyzed by means of a logistic equation with the maximum likelihood method. Selectivity parameters for individual hauls were obtained with the software program cc 2000 . Mean selectivity was also estimated and compared using the EC Model software that takes between‐haul variations into account. The codend catch size as an additional explanatory variable was used in the comparison. The Kolmogorov–Smirnov (K–S) test was also applied to detect differences between length‐frequency distributions in the upper and lower bags of the 12 and 14 mm bar spacings for red mullet and annular sea bream. The mean L₅₀ values of red mullet were 8.7 and 10.0 cm with the 12 and 14 mm grids, respectively. The L₅₀ value of 14 mm was comparable with the L₅₀ value of the codend mesh size; however, the 12 mm value was rather low. The mean L₅₀ values of 12 and 14 mm bar spacings were 8.8 and 10.4 cm for annular sea bream, respectively; the value of 14 mm bar spacing was very close to 50% size at sexual maturity of the species (10.5 cm). The K–S test indicated length distributions of red mullet and annular sea bream in the 12 and 14 mm upper and lower bags as significantly different (P < 0.05). These results show that improving the size selectivity in a multi‐species fishery using a single selective device is rather difficult. However, higher size selectivity can be obtained when considering the minimum landing size or the 50% sexual maturity size for a given species.     

Reproductive cycle of gilt sardine,Sardinella aurita,Valenciennes 1847, in the eastern middle Adriatic Sea

The annual reproduction cycle of gilt sardine, Sardinella aurita, based on gonad maturity stages, gonad weight and gonadosomatic index was the subject of this study. A total of 2033 gilt sardines (983 males, 1021 females and 29 undetermined) were analysed. Fish were collected monthly from commercial purse seiners between November 2007 and January 2009 in the eastern middle Adriatic Sea (mesh size 8 mm/bar length/; sampling: five boats per month). Based on the monthly evolution of gonad maturation stages, gonad weights and gonadosomatic index, the peak spawning season was determined to be from June to August. Variations in sea surface temperature (SST) coincided with monthly variations of the gonadosomatic index. Highest monthly average values for both analysed parameters were recorded in July (GSI = 3.38; T = 26.5°C). Fifty per cent (L₅₀) of males and females reached sexual maturity at TL 15.8 cm and at 16.6 cm, respectively. Absolute fecundity ranged from 8458 to 48 032 (mean 34 565 ± 10 310), whereas relative fecundity was from 171 to 722 (mean 385 ± 104.35). Mean value of the oocyte size was 0.53 ± 0.10 mm.     

The effect of the cingulate cortex on the development of the frontal lobe in the human

In the study, measurements of cortical structures of the medial surfaces of cerebral hemispheres of adults were taken. Its aim was to test whether the examined values were correlated with one another, and if so, then to what degree. Studies were conducted on 100 brains of adult people. It was assumed that the span of the corpus callosum (the genual retrosplenial length) of the left and the right hemisphere of the given brain was constant. The results of measurements and their statistical analysis prove that in both hemispheres the parameters concerning the cingulate gyrus, mainly of its paragenual width, are situated within the limits of significance. The mean values of the length of this gyrus were bigger on the left hemisphere. Differences in size of the hemispheres appeared to be statistically insignificant. The mean arithmetic values of the fronto-occipital distance of the hemispheres were greater for the right hemisphere. The results suggest that certain changes in the values of the frontal lobes depend on changes in values concerning the cingulate gyrus. This fact may confirm suggestions of certain authors that limbic structures of man, encompassing also the cortex of the cingulate gyrus, are not retarded and that their effect on the development of the frontal lobes may be as considerable as the one of the gyri.