Early development of spiny neurons in fish and mouse: morphometric measures of dendritic spine formation pattern

Positions of spines on apical dendrites were evaluated using 4 pattern analysis techniques: spine counts, variance/mean ratio, Lloyd's patchiness index, and nearest neighbor distance matrix. Spiny tectal interneurons from jewel fish (100, 130, 160 and 1550 days old), and layer V pyramidal cells in layer IV auditory cortex of CBA/J mice (100 and 450 days old) were studied. Fish's spines became more numerous and more clumped on distal dendritic strata during development, while mice lost dendritic spines with age. Both species developed a significantly regular spacing pattern between neighboring spines during development. These changes are explained in the context of spine function and a biophysical model of dendritic spine patterns.     

Colchicine-induced Mallory body formation in the mouse

Long term griseofulvin treatment of mice results in the development of Mallory bodies (MB), Griseofulvin application apparently "primed" the liver cell for MB formation, and the hepatocytes were then able to respond almost immediately with MB to a griseofulvin challenge even after a 1-month griseofulvin-free period. Colchicine, in contrast to cytochalasin B, also induced MB under these latter experimental conditions. Since intermediate filaments increase in various types of cells in response to antitubulin agents, this observation further supports the hypothesis that MB are related to intermediate filaments.     

Brain development: genetic and exogenous factors

Growth disorders and differentiation of cerebral structures may be caused by mutations of exogenous noxae. The period of most active brain development is between the tenth week of pregnancy and the tenth year of life. In this period the brain is particularly sensitive to exogenous noxae. Basic research has revealed mechanisms that are responsible for normal development, and at the same time has led to the discovery of factors which may be associated with disturbance of these regulatory processess. Disorders of cerebral development may underlie minimal organic brain damage, though there is no proof of this as yet. Closer cooperation between basic and clinical research will be necessary to provide greater insight into the mechanisms of cerebral development. The knowledge thus obtained is one of the preconditions for the prevention, diagnosis and treatment of infantile minimal organic brain damage.     

Intergroup processes in childhood: Social categorization and sex role development.

When groups are created experimentally, in-group favoritism, stereotyping, exaggeration of between-groups differences and within-group similarities, and out-group homogenization occur among adults. This study explored whether the same phenomena influence children's perceptions of boys and girls. Ninety-six 8- to 10-yr-olds viewed videotapes of unfamiliar children and rated them on possession of masculine, feminine, and gender-neutral evaluative traits, on similarity to self, and on liking. Children also were observed while interacting with classmates. Interactions occurred primarily among children of the same sex. Targets were viewed stereotypically. They also were rated higher on liking, similarity, trait favorability (female targets only), and variability (male targets only) by children of the same sex. Furthermore, there were significant correlations among the rating measures, supporting an intergroup perspective on sex role development. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Strain and sex differences in mouse killing by rats.

Tendency to exhibit muricide was examined in 481 adult rats of 15 inbred strains. Marked strain differences were observed; frequency of mouse killing ranged from 0 to 91% among the males and from 0 to 68% among the females. Whether males and females differed in their propensity to kill mice also appeared to be strain-dependent. Overall, there was a significant correlation between the frequency of mouse killing by males of each strain and that of females. (26 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Class III P-glycoproteins mediate the formation of lipoprotein X in the mouse

Cholestasis is associated with hypercholesterolemia and appearance of the abnormal lipoprotein X (LpX) in plasma. Using mice with a disrupted Mdr2 gene, we tested the hypothesis that LpX originates as a biliary lipid vesicle. Mdr2-deficient mice lack Mdr2 P-glycoprotein, the canalicular translocator for phosphatidylcholine, and secrete virtually no phospholipid and cholesterol in bile. Bile duct ligation of Mdr2(+)/+ mice induced a dramatic increase in the plasma cholesterol and phospholipid concentration. Agarose electrophoresis, density gradient ultracentrifugation, gel permeation, and electron microscopy revealed that the majority of phospholipid and cholesterol was present as LpX, a 40-100 nm vesicle with an aqueous lumen. In contrast, the plasma cholesterol and phospholipid concentration in Mdr2(-)/- mice decreased upon bile duct ligation, and plasma fractionation revealed a complete absence of LpX. In mice with various expression levels of Mdr2 or MDR3, the human homolog of Mdr2, we observed that the plasma level of cholesterol and phospholipid during cholestasis correlated very closely with the expression level of these canalicular P-glycoproteins. These data demonstrate that during cholestasis there is a quantitative shift of lipid secretion from bile to the plasma compartment in the form of LpX. The concentration of this lipoprotein is determined by the activity of the canalicular phospholipid translocator.     

Beyond the reinforcement principle: Another step toward understanding sex role development.

40 21–25 mo olds participated in ongoing play groups (with almost equal numbers of boys and girls in each group of 12–25 children) while observers studied them and noted the reactions of both peers and teachers to behaviors that could be identified and coded as male, female, or neutral. Teachers, both female and male, responded primarily to the category of behavior. Regardless of the sex of the child, they gave positive reactions to behaviors that were female-preferred or neutral but seldom to those that were male-preferred. Responses among the peer group were more complicated. Girls responded more positively to other girls than to boys, regardless of the category (male, female, or neutral) of the behavior. Boys responded to the category of the behavior and to the sex of their peer and gave more positive responses to other boys when the boys were engaged in male-preferred activities. Both girls and teachers were effective in changing the behavior of other girls, but neither could influence boys to change; boys were effective in influencing other boys but not in influencing girls. It is suggested that although reinforcements do appear to affect the likelihood of a behavior continuing, other factors must be at work, for behaviors are maintained even under conditions of no responses, and, most important, the reinforcements themselves are most effective when they have been processed in terms of gender. (20 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Identification of aromatase in the reptilian brain

The present study tests the hypothesis that brain aromatase is an "ancient" property of nervous tissue and may be identified in homologues of the limbic system in a non-mammalian vertebrate, the turtle Chrysemys picta. Tissue homogenates (180 mg wet weight/2 ml) were incubated with [7 alpha-3H]androstenedione and cofactors for 60 min at 37 C. Estrone (E1) was isolated and characterized by thin layer chromatography, methylation and recrystallization to constant specific activity. No estradiol-17 beta was detected. Aromatase was found only in the forebrain but was diffusely distributed throughout this major brain division. No other neural or non-neural tissues, including mid- and hindbrain structures, testis, and ovary, synthesized detectable quantities of E1 in our system. The strio-amygdaloid complex of both sexes synthesized more E1 per unit weight than the preoptic-hypothalamic area (POA-HTH) or other forebrain structures. It is possible that the conversion of androgen to estrogen has biological significance in this species since the reaction occurred throughout the physiological temperature range experienced during activity in nature and sex differences in brain aromatase activity during the breeding season were apparent. These experiments in Chrysemys demonstrate that the synthesis of estrogen from androgen by the brain is not limited to mammals, but also occurs at a more primitive level of phylogenetic development. Restriction of aromatase to forebrain structures of the turtle is consistent with the neuroanatomic distribution of enzyme activity in the limbic system of mammals. Estrogen yield from adult turtle brain incubates (3.2-22.6 pmol/g) is more like that reported for fetal (2.7-33 pmol/g) than for adult (0.1-1.9 pmol/g) mammals. We suggest that the in situ synthesis of estrogen by the central nervous system has its orgins early in vertebrate evolution and may be a primitive characteristic of brain-steroid interactions that regulate physiological and behavioral sex in vertebrates.     

Polyembryonic development: insect pattern formation in a cellularized environment

THe polyembryonic wasp Copidosoma floridanum produces up to 2000 individuals from a single egg. During the production of individual embryos the original anteroposterior axis of the egg is lost and axial patterning must subsequently be reestablished within each embryo. The mechanism by which this occurs is unknown. In most insects, egg polarity is established during oogenesis and early development takes place in a syncytium. In Drosophila melanogaster, the syncytium is considered essential for establishing the morphogenetic gradients that initiate segmental patterning. However, we found that development of C. floridanum occurs almost exclusively in a cellularized environment. To determine whether the D. melanogaster patterning cascade is conserved in the absence of a syncytium, we analyzed the expression of Even-skipped, Engrailed and Ultrabithorax/Abdominal-A during polyembryonic development. Here we show that in spite of the absence of a syncytium, the elements of the D. melanogaster segmentation hierarchy are conserved. The segment-polarity gene Engrailed and the homeotic genes Ultrabithorax/Abdominal-A are expressed in a conserved pattern relative to D. melanogaster. However, we detect an alteration in the expression of the Even-skipped antigen. Even-skipped is initially expressed in segmentally reiterated stripes and not in the pair-rule pattern as it is in D. melanogaster. We also observe that the expression of these regulatory proteins does not occur during the early proliferative phases of polyembryony. Our results indicate that a syncytium is not required for segmental patterning in this insect.     

Pattern formation in epithelial development: the vertebrate limb and feather bud spacing

The ectoderm of the vertebrate limb and feather bud are epithelia that provide good models for epithelial patterning in vertebrate development. At the tip of chick and mouse limb buds is a thickening, the apical ectodermal ridge, which is essential for limb bud outgrowth. The signal from the ridge to the underlying mesoderm involves fibroblast growth factors. The non-ridge ectoderm specifies the dorsoventral pattern of the bud and Wnt7a is a dorsalizing signal. The development of the ridge involves an interaction between dorsal cells that express radical fringe and those that do not. There are striking similarities between the signals and genes involved in patterning the limb ectoderm and the epithelia of the Drosophila imaginal disc that gives rise to the wing. The spacing of feather buds involves signals from the epidermis to the underlying mesenchyme, which again include Wnt7a and fibroblast growth factors.     

Proceedings: An investigation into the immunosuppressive properties of oestrogen

An investigation into the immunosuppressive properties of estrogen is reported. Normal and thymectomized mature male rats were given daily intradermal injections of .2 ml arachis oil containing 200 mcg estradiol-17beta/ml for 14 days. Lymphocytes from healthy men were incubated with the rat sera and lymphocyte subpopulations were identified by 3 surface markers: 1) cells forming rosettes with sheep erythrocytes (E-rosettes) as a measure of T lymphocytes, 2) lymphocytes with surface immunoglobulin identified by direct immunofluorescence (IgF), and 3) lymphocytes with receptors for C3 observed by a rosette technique employing sheep eryhrocytes treated with rabbit hemolytic serum and human complement (EAC-rosettes). Comparison of the effects of incubating cells with normal or treated rat serum revealed that E-rosettes dropped from 67.4 to 49% and that lymphocytes lacking all markers rose from 2.4 to 17.7%, respectively. The number of cells forming EAC-rosettes, bearing IgF or having both these markers did not change, however, it was apparent that a greater proportion of lymphocytes expressed both markers after incubation with estrogen-treated rat serum (25.7% compared with 12.1%). It appears that estrogen caused both decreased T lymphocyte response and enhanced B lymphocyte activity resulting in increased expression of related markers. None of these phenomena was apparent when lymphocytes were cultured with sera from estrogen-treated thymectomized rats, suggesting that estrogen affects the thymus such that a factor appears in the blood capable of causing changes in the immune response.     

Immunohistochemical distribution of oestrogen receptor and luteinizing hormone B subunit in the ovine pituitary gland during foetal development

The presence of oestrogen receptor in the developing hypothalamo-hypophyseal system is an essential prerequisite for the development of sex-steroid feedback on gonadotrophin secretion. We have used dual immunocytochemistry to examine the ontogeny and regional distribution of oestrogen receptor and LHbeta subunit in the ovine pituitary gland during foetal development. At day 65 gestation (term= 145 days) oestrogen receptor and LH/ immunopositive cells are found in a small region at the base of the anterior pituitary gland, and also in a band immediately adjacent to the neurointermediate lobe. By day 100 gestation there was a significant increase in the number of immunopositive LHbeta cells accounting for around 12% of the total cell population, and these were widely distributed throughout the anterior pituitary gland. There was also a significant increase in the proportion of gonadotrophs which contain oestrogen receptor compared with day 65. By day 130 gestation the percentage of LH containing cells had declined to around 7% of the total population, but the proportion which also contained oestrogen receptor remained the same. There were no differences in the numbers or distribution of cells containing LH or oestrogen receptors between male and female foetuses, at any age. These data describing a parallel change in the number of oestrogen receptors and LHbeta containing cells in the pituitary gland throughout gestation suggest that the development of pituitary sex-steroid feedback is not solely dependent on changes in the numbers of oestrogen receptor containing cells alone.