An evaluation of the concept of innateness

The concept of innateness is often used in explanations and classifications of biological and cognitive traits. But does this concept have a legitimate role to play in contemporary scientific discourse? Empirical studies and theoretical developments have revealed that simple and intuitively appealing ways of classifying traits (e.g. genetically specified versus owing to the environment) are inadequate. They have also revealed a variety of scientifically interesting ways of classifying traits each of which captures some aspect of the innate/non-innate distinction. These include things such as whether a trait is canalized, whether it has a history of natural selection, whether it developed without learning or without a specific set of environmental triggers, whether it is causally correlated with the action of certain specific genes, etc. We offer an analogy: the term ‘jade’ was once thought to refer to a single natural kind; it was then discovered that it refers to two different chemical compounds, jadeite and nephrite. In the same way, we argue, researchers should recognize that ‘innateness’ refers not to a single natural kind but to a set of (possibly related) natural kinds. When this happens, it will be easier to progress in the field of biological and cognitive sciences.     

Human brain tubulin purification: Decrease in soluble tubulin with age

The soluble tubulin of human cerebral cortex, as assessed by [³H]colchicine binding of the 100,000g supernatant fraction, decreases drastically with age, 75 percent from age 0 to age 90. There is also a considerably lower concentration of high molecular weight proteins in the soluble fraction of postmortem human cerebral cortex than in that of nonhuman species. Human brain tubulin can be polymerized into microtubules with DEAE-dextran. The DEAE-dextran induced microtubules are stable to cold temperature (4°) and calcium. However, in the presence of 1 M glutamate, the microtubules become cold labile and depolymerize at 4°. Thus we have developed a novel method for purifying polymerization competent tubulin from fresh or frozen human cerebral cortex. Human brain tubulin purified by our novel method is very similar to tubulin from the brains of other mammals in molecular weight, amino acid composition, polymerization-depolymerization parameters, and structural dimensions of the microtubules formed.Some aspects of this work have been published as an abstract in 1981. Fed. Proc. 40:1548.     

Special features of age development of the brain in children living in the north

Special features of morphological functional age development of the brain in children living in difficult climatic-geographical and social-economical conditions of the North (Archangelsk region) were studied. It was found that among 62 examined pupils of middle country school only in 10 persons (16%) amplitude-frequency and temporal-spatial EEG parameters are in accordance with passport age (European standards). 38 pupils (61%) have insignificant deviations such as insufficient regularity of EEG spatial-temporal pattern in frontal and temporal parts of the brain, increased theta- and delta-rhythms, absence of distinct "functional nuclear" in alpha range. In remaining 14 pupils (23%) EEG parameters suggest a more expressed retardation of mental development coupled with problems in the learning and inadequate behavior. Retardation of terms of morphological functional development of the brain in children--northerners equals 1.5 - 2 years, which is in accordance with terms of hormonal and physical development' retardation, described by different authors.     

Effect of reactive oxygen species on the metabolism of tryptophan in rat brain: Influence of age

In an earlier study, oxidation of tryptophan hydroxylase was implicated as its affinity was decreased with aging in rat brain. To establish any potential link between its oxidative damage and aging, we have determined the activities of antioxidant enzymes in midbrain, pons and medulla of 2, 12 and 24 month old Fisher 344 BNF1 rats. The results obtained suggest that the activities of antioxidant enzymes varied considerably with age and brain regions studied. Activities of Cu/Zn superoxide dismutase and glutathione peroxidase were found to increase from 2 to 12 months and then decrease in 24 month old rats. However catalase activity decreased consistently with the age. A parallel increase in the carbonyl content was observed in these brain regions indicating the oxidation of proteins. Reactive oxygen species when included in the incubation mixture decreased the activity of tryptophan hydroxylase in a concentration dependent manner. The loss of tryptophan hydroxylase activity induced by hydrogen peroxide and superoxide anion was prevented by catalase. However superoxide dismutase did not provide such protection. Sulfhydryl agents, cysteine, glutathione and dithiothreitol partially prevented the loss of activity. These studies suggest an involvement of reactive oxygen species for sulfhydryl oxidation of tryptophan hydroxylase in aging.     

Activity of sterol-sulphate sulphohydrolase in rat brain: characterization, localization and change with age

Abstract— Homogenates of rat brain hydrolysed the sulphate esters of dehydroepiandrosterone, oestrone and pregnenolone to free steroids. The pH optimum was 6.6 for all three steroid sulphates. Under similar conditions, cholesterol sulphate was not hydrolysed to a significant extent. Unlike sterol sulphatases (EC 3.1.6.2) from extraneural tissues, most of the activity in brain was found in the crude nuclear fraction. The remainder of the activity was found in the crude mitochondrial fraction and almost none was detected in microsomal or cytosol fractions. Sterol sulphatase activity was present in the foetal brain and increased rapidly with increasing postnatal age to a plateau at approx. 25 days of postnatal age. The enzymic activity did not differ significantly with the sex of the animal. The sulphatase activity was found throughout the brain, with cerebellum and brain stem exhibiting a slightly higher activity per wet wt. of tissue than other regions. Inhibition of enzymic activity occurred in the presence of sodium deoxycholate, Triton X-100, sodium dodecyl sulphate and inorganic phosphate or sulphate.     

Influence of age on brain edema formation, secondary brain damage and inflammatory response after brain trauma in mice

After traumatic brain injury (TBI) elderly patients suffer from higher mortality rate and worse functional outcome compared to young patients. However, experimental TBI research is primarily performed in young animals. Aim of the present study was to clarify whether age affects functional outcome, neuroinflammation and secondary brain damage after brain trauma in mice. Young (2 months) and old (21 months) male C57Bl6N mice were anesthetized and subjected to a controlled cortical impact injury (CCI) on the right parietal cortex. Animals of both ages were randomly assigned to 15 min, 24 h, and 72 h survival. At the end of the observation periods, contusion volume, brain water content, neurologic function, cerebral and systemic inflammation (CD3+ T cell migration, inflammatory cytokine expression in brain and lung, blood differential cell count) were determined. Old animals showed worse neurological function 72 h after CCI and a high mortality rate (19.2%) compared to young (0%). This did not correlate with histopathological damage, as contusion volumes were equal in both age groups. Although a more pronounced brain edema formation was detected in old mice 24 hours after TBI, lack of correlation between brain water content and neurological deficit indicated that brain edema formation is not solely responsible for age-dependent differences in neurological outcome. Brains of old naïve mice were about 8% smaller compared to young naïve brains, suggesting age-related brain atrophy with possible decline in plasticity. Onset of cerebral inflammation started earlier and primarily ipsilateral to damage in old mice, whereas in young mice inflammation was delayed and present in both hemispheres with a characteristic T cell migration pattern. Pulmonary interleukin 1β expression was up-regulated after cerebral injury only in young, not aged mice. The results therefore indicate that old animals are prone to functional deficits and strong ipsilateral cerebral inflammation without major differences in morphological brain damage compared to young.     

Alterations in atropine sites of the brain of rats as a function of age

Binding of (³H)-atropine to synaptosomal fractions prepared from cerebral and cerebellar cortices of young, adult and old male and female rats were studied. Picomoles of labelled atropine bound/mg protein was highest in the cerebral cortex of young rats and decreased with increasing age in both sexes, whereas in cerebellar cortex the peak binding was in adult rats. Acetylcholinesterase activity of the same fractions showed corresponding changes with age.     

Neuroactive steroids in the brain and age and sex specificity of behavior and anxiety: An experimental study

Changes in the brain’s neuroactive steroid levels, behavior in the open field, and the anxious-phobic status of male and female rats in the course of development have been studied. An increase in the motor and exploratory activity and emotionality in rats of both sexes in the pubertal period and a decrease in their values in mature and old animals have been detected. Anxiety has no sexual dimorphism in adult animals; it is significantly higher in males than in females in the prepubertal and pubertal periods of development and is higher in old females than in males of the same age. An increase in the level of corticosterone in some brain structures in maturing and old rats has been found; the testosterone concentration increases in one-month-old and adult animals but decreases in old individuals, while the estradiol concentration in all studied brain structures of male and female rats was low in all periods of postnatal life. Correlation analysis has shown modulation by steroid hormones of the changes in behavioral responses during development.     

Relation between the age of specimen and the shrinkage of brain frozen sections

The aim of the study was to assess the effect of age of the animal upon the real thickness of the frozen sections. The study was performed on 19 rabbit brains. The thickness of the frozen sections regardless of their staining is age-dependent. The relation is proportional during the period from 7 to 180 postnatal day and characterizes both immunohistochemical as well as cresyl violet-stained sections; moreover, changes of the section thickness proceed parallelly. It is suggested that especially for some stereological parameters all required procedures should be standardized to achieve comparable and unbiasedly interpretable results.     

Keratan sulfate-like glycosaminoglycan in the cerebral cortex of the brain and its variation with age

A keratan sulfate-like substance was found in the cerebral cortex proteoglycans of rats. This substance tripled during the rapid growth phase from 1 to 3 monts of age and then decreased steadily to a negligible quantity in the senescent rat, aged 25 months. In contrast, the uronic acid-containing glycosaminoglycans remained constant during the life span studied.The marked decrease observed in the proportion of keratan sulfate-like moiety to the other glycosaminoglycans in the cerebral cortex of the senescent rat (aged 25 months) compared with the young adult rat (aged 3 months) may explain the reduced extracellular volume observed by others in the senescent brain.     

Influence of age on brain vascular and cardiovascular monoamine oxidase activity in the rat

Monoamine oxidase (MAO) activity in brain microvessels and cardiovascular tissues was examined in rats of different age. MAO activity continued to increase with age in the heart, but in contrast, reached maximum activity in three weeks in the aorta, mesenteric artery and mesenteric vein. Between 7 and 60 weeks, there was a small decline in the MAO activity in the testicular artery. The highest MAO activity was found in the cerebral microvessels and increased with age. The half-life of MAO was estimated in the heart and peripheral blood vessels in young and old animals. The half-life of cardiac MAO was increased with age whereas that of the mesenteric vein, mesenteric artery and aorta remained constant between 7 and 112 weeks. Thus an explanation for this increased cardiac MAO activity in old rats was a reduced rate of degredation of this enzyme. The high activity of the enzyme in the brain microvessels suggests that it may participate in regulating the influx and efflux of monoamines in the central nervous system.     

Human brain gangliosides: developmental changes from early fetal stage to advanced age

The developmental profiles of the four major brain gangliosides, GM1, GD1a, GD1b, and GT1b, were examined in human frontal lobe covering the period from 10 fetal weeks to 80 years of age. The ganglioside concentration increased approx. 3-fold from the 10th gestational week to the age of about 5 years. Gangliosides GM1 and GD1a increased 12-15-fold during the same period. The most rapid increase of GM1 and GD1a occurred around term, during the period for dendrite arborization, outgrowth of axons and synaptogenesis. GT1b showed a quite different developmental curve. It was the major ganglioside during the 3rd to 5th gestational month, whereafter its concentration dropped rapidly to term, from which time the concentration then increased up to 50 years of age. Similar curves were found for the other gangliosides of the b-series, GD3, GD2, GD1b and GQ1b. Ganglioside 3'-isoLM1 was a characteristic early fetal ganglioside which dropped rapidly to the 5th gestational month, reached a small peak around term and then disappeared during adulthood. The concentration of gangliosides of the neolacto series was larger than that of the lacto series during the whole developmental period. In the beginning of the second trimester, 3'-LM1 constituted 2% and LD1 10% of total ganglioside sialic acid. The new findings demonstrate more dynamic changes of the ganglioside patterns during development than noted in previous studies.     

Effect of age on adrenergic and dopaminergic receptor binding in rat brain

The effects of age on receptor binding of adrenergic and dopaminergic ligands were studied in rat cerebral cortex and striatum respectively. Compared to rats 5 months of age, 25-month old rats had a significant decrease in specific binding of the β-adrenergic antagonist ligand ³H-DHA, the α-adrenergic ligand ³H-WB-4101 in cortex, and the dopaminergic antagonist ³H-spiperone in striatum. Scatchard analysis of ligand binding indicated that the decrease in specific binding was due to a decrease in the number of receptors and not to a change in the affinity of the ligand for the receptor.