Showing papers by "Boston University published in 1978"

Introduction to formal language theory

Abstract: From the Publisher: Formal language theory was fist developed in the mid 1950's in an attempt to develop theories of natural language acquisition. It was soon realized that this theory (particularly the context-free portion) was quite relevant to the artificial languages that had originated in computer science. Since those days, the theory of formal languages has been developed extensively, and has several discernible trends, which include applications to the syntactic analysis of programming languages, program schemes, models of biological systems, and relationships with natural languages.

Social class and arts consumption

Abstract: The last decade has witnessed a burgeoning of American high culture. The number of museums and theaters has increased, the number of orchestras, opera companies, and dance companies has skyrocketed, and attendance at all of them is up.1 Ironically, however, the upsurge in public enthusiasm has been accompanied by financial tension. Earnings from admission and ticket prices have risen far less quickly than expenses, traditional patrons have been unable or unwilling to bridge the gap, and inherently labor-intensive production systems, inflation, energy costs, urban fiscal crises, and constraints on ticket and admission fees promise to make the situation worse.2 The effect of this fiscal malaise has been to involve the government federal, state, and municipal in American high culture to a degree unprecedented in this country. In twelve years the National Endowment for the Arts' budget has grown from $3 million to $96 million, the number of state arts agencies has increased from 18 to 55, and the number of local arts councils has expanded from 175 to 900.3

Sensorimotor functioning and communication in mute autistic children.

Abstract: There were two purposes underlying this study: to describe the sensorimotor functioning of mute autistic children and to relate their sensorimotor performance to nonverbal communication. Twelve mute children, diagnosed autistic, ranging from 4 years 9 months to 12 years of age, were administered four scales of sensorimotor development from the Uzgiris and Hunt (1975) series: object permanence, gestural imitation, means for obtaining environmental events, and causality. Subjects performed most poorly on the imitation scale with 9 of 12 performing below Piaget's fifth sensorimotor stage. In contrast, performance was highest on the object permanence scale: No child scored below Stage V. Regarding the subjects' non-verbal communication, Stage V performance on the means and causality scales and Stage III on the imitation scale appeared to form minimal prerequisites for intentional communication in a variety of situations. Finally, none of the subjects, even those with relatively complete sensorimotor development, spontaneously used what Bates (1976) has called “protodeclarative” gestures to point out or show objects to adults. The absence of protodeclarative gestures may represent a qualitatively distinct pattern of prelinguistic development in certain autistic children.

The development of the cerebral cortex in the embryonic mouse: an electron microscopic serial section analysis.

Abstract: The techniques of reconstructions of cells from serial thin sections and autoradiography after tritiated thymidine injections have been employed to study the early histogenesis of the cerebral cortex in the embryonic day-15 (E15) mouse. The autoradiographic studies show that cells below the E15 cortical plate in the intermediate layer are destined to migrate through the preexisting cortical plate cells to take up a more superficial position. Having this information, it has been possible, through reconstructions of large numbers of cells (more than 150) throughout the thickness of the cerebral vesicle, to identify some of the important morphogenetic events of cortical histogenesis. The following scheme is proposed. The first step in neuronal differentiation involves the detachment of the ventricularly directed process of the ventricular cell from the junctional region next to the ventricle. In thin sections, these junctions have the appearance of zonulae adherentes, but freeze cleavage experiments performed in this study show that, in addition, some of them resemble small gap junctions while others appear to be remnants of tight junctions or possibly linear gap junctions. Detachment of the ventricular process accompanies the migration of the nucleus and perikaryon through the ventricular layer. Within the intermediate layer the migrating cells become rounded and sprout numerous processes. Some cells may undergo a mitotic division at this stage. Eventually the differentiating cells sprout a longer lateral process which is oriented tangentially to the pial surface. This process originates from the anterior surface of the soma and at its tip has the characteristics of an axonal growth cone. The cells migrate externally and radially with simultaneous elongation of the primitive axon. In the subcortical plate region of the intermediate layer all cells contain an anteriorly directed axon. Subsequently the cells sprout an apical process which extends into the cortical plate, and the nucleus and perikaryon apparently migrate radially within this process. The result is that the primitive axon first descends into the intermediate layer proper before turning to run tangentially. Dendritic growth and further differentiation begins once the cells reach their definitive position in the cortical plate. One interesting finding is the presence of eight cells in the cortical plate without long anteriorly directed axons. Yet, autoradiographic data show that subcortical plate cells are the immediate precursors of cortical plate cells, and all 28/s28 reconstructed subcortical plate cells have long anteriorly directed axons. Thus, it is possible that the long axon of some cells may be lost as the cells continue to differentiate in the cortical plate. In fact, one cell has been found which appears to be in the process of losing its anteriorly directed axon. A number of molecular layer cells have also been reconstructed. These cells have several processes oriented tangentially to the pial surface. The identity of these processes could not always be determined. Occasional asymmetric synapses have been found between unidentified axons and the horizontal cell soma or its processes. Autoradiographic studies show that horizontal cells have the earliest time of origin of any cortical cell type.

The forms of non-pyramidal neurons in the visual cortex of the rat

Abstract: Rapid Golgi preparations from area 17 of young adult rats have been studied to determine the morphology and distribution of non-pyramidal neurons. Such cells were observed in all of the cellular laminae of the cortex, but were particularly prevalent in layers IV and V. Non-pyramidal neurons were categorized according to two features: (1) dendritic projection pattern, and (2) abundance of dendritic spines. Dendritic patterns were classified as multipolar, bitufted, and bipolar, and spine patterns as spinous, sparsely spinous, and spine-free. Spinous dendrites were associated only with multipolar neurons, while sparsely spinous and spine-free dendrites were each associated with cells of all three non-pyramidal dendritic patterns. The most frequently observed non-pyramidal cell types were multipolar cells of the spine-free and sparsely spinous varieties. All of the general cell types encountered have been described in the literature on non-pyramidal neurons, indicating the lack of any unique forms in rat area 17. An analysis of the dendritic projections of individual non-pyramidal neurons through particular cortical laminae made possible an evaluation of common sources of dendrites present in the neuropil of each layer. Non-pyramidal cell axons were impregnated only in small numbers. Spinous multipolar axons invariably exhibited a descending main branch, while the axons of bipolar neurons were distributed in a narrow vertical field. Axonal patterns of remaining cell types, including Golgi type II arborizations, did not appear to correlate consistently with dendritic morphology. Axons of the basket cell type and "horsetail" axons associated with double bouquet cells of Cajal's original type were not impregnated.

Identified neurons in mouse smi cortex which are postsynaptic to thalamocortical axon terminals: A combined golgi‐electron microscopic and degeneration study

Abstract: A recently developed Golgi-electron microscopic technique (Fairen et al., '77) has been used to identify neurons in mouse SmI cortex which that thalamic axon terminals synapsed with dendrites of several distinct neuronal types whose cell bodies occurred either in layer III, IV or V. The procedures employed were as follows: electrolytic lesions were used to destroy the cortical projections of the nucleus ventralis posterior pars lateralis thalami (homologous to medial portion of ventrobasal complex) and the nucleus posterior thalami. These two thalamic nuclei project to the posteromedial barrel subfield (PMBSF) in mouse somatosensory cortex. Blocks of cortex containing the PMBSF were processed by the Golgi method, sectioned at 150 μm and examined with the light microscope. Neurons of interest were then selected for Golgi deimpregnation (Fairen et al., '77). Portions of these cells were serial thin sectioned and subsequently examined with the electron microscope to determine if they synapsed with degenerating axon terminals. Degenerating thalamocortical axon terminals synapsed at asymmetrical synaptic junctions with dendritic spines of pyramidal cells whose somata occurred in layers III and V, and with dendritic spines of spiny stellate cells with somata in layer IV. Only normal, symmetrical synapses occurred on the cell bodies of these neurons, and no degenerating axon terminals synapsed with the shafts of their dendrites. Two, unimpregnated, non-spiny stellate cells whose somata occurred in layers IV and IV/V were partially reconstructed from serial thin sections. Many degenerating thalamocortical axon terminals synapsed with the dendrites and somata of these non-spiny cells. In fact, for similar lengths of dendrite, the non-spiny stellate cells made the most synapses with thalamocortical axon terminals, followed in order of decreasing frequency by the layer IV spiny stellate cells, the layer III pyramids and finally the layer V pyramids which received only few synapses from thalamocortical axon terminals. Direct evidence has been provided that at least six different types of neurons whose somata occur in several layers of the neocortex receive synapses from thalamocortically projecting neurons. It has been proposed that the cortex is organized such that thalamic input is processed sequentially by neurons of increasingly complex response properties beginning with cells in layer IV and proceeding to cells in other layers (Hubel and Wiesel, '62, '68). The results of this study now suggest that any such hierarchical processing of thalamic input must occur in conjunction with the parallel, and perhaps simultaneous, processing of thalamic input by neurons at several hierarchical levels. The evidence for, and some implications of, a newly proposed model of cortical organization which combines hierarchical and parallel processing are discussed.

Smooth and sparsely-spined stellate cells in the visual cortex of the rat: A study using a combined golgi-electron microscope technique

Abstract: The visual cortex of the rat was impregnated by the rapid Golgi procedure. From these preparations, smooth (spine-free) and sparsely-spined multipolar stellate cells with well impregnated axons were selected and drawn in the light microscope using a camera lucida. Five suitably impregnated cells were then gold-toned and deimpregnated by removal of the silver chromate produced by the Golgi impregnation, so that they could be examined in the electron microscope to determine both their cytological features and their pre- and postsynaptic relationships. A sixth neuron was not deimpregnated, and was examined in the electron microscope only to evaluate the types of synapses formed by its axons terminals. Five of these cells had extensive local axonal plexus and the sixth had a plexus which was less profuse. In the electron microscope the various portions of the deimpregnated neurons were readily identified by their content of fine gold particles, and it was found that their perikarya possessed a rather dark cytoplasm containing many ribosomes. Both symmetric and asymmetric synapses were present on the perikarya, and some of the perikarya had spines. The dendrites of the cells had relatively smooth contours and contained rather closely packed microtubules. The dendrites also had both symmetric and asymmetric synapses along their shafts, with the symmetric synapses being more frequent on the proximal portions of the dendrites. The axons of the neurons were unmyelinated and all of them formed symmetric synapses with their postsynaptic partners. The synapses occurred at dilatations of the axons at both en passant and terminal boutons. Neuronal elements identified as being postsynaptic to the axon terminals of the stellate cells included the perikarya and apical dendritic shafts of pyramidal neurons, the perikarya and dendritic shafts of other stellate cells, and an axons initial segment. Reasons are given for concluding that these multipolar, smooth and sparsely-spined stellate cells are inhibitory in function, and their relationships with some other neuronal components of the rat visual cortex are considered.

A Review: Lessons From an Animal Model of Intra-abdominal Sepsis

Abstract: Intra-abdominal sepsis that involves multiple aerobic and anaerobic bacteria derived from the colonic flora was studied in Wistar rats to determine the relative roles of various microbial species. The rats challenged with pooled colonic contents showed a biphasic disease. Initially, there was acute peritonitis, Escherichia coli bacteremia, and high mortality. In rats that survived this acute peritonitis stage, intra-abdominal abscesses developed, and anaerobic bacteria were the preponderant organisms. Subsequent experiments showed that antibiotics directed against coliforms prevented mortality, whereas agents active against anaerobes reduced the incidence of abscesses. Challenges with Escherichia coli alone produced bacteremia and death, whereas pure cultures of Bacteroides fragilis caused intra-abdominal abscesses. These observations suggest that both coliforms and anaerobes are important pathogens in intra-abdominal sepsis, although the different types of microbes appear to play distinctive roles in the sequence of pathological events.

Early development of amacrine cells in the mouse retina: an electron microscopic, serial section analysis.

Abstract: The development of retinal amacrine cells in mice at the fifteenth day of gestation (E-15) has been analyzed by reconstructing large numbers of cells from serial thin sections. This information has been supplemented by reconstructing cells from E13 and E17 retinas as well as autoradiographic studies of time of origin of cells arising in the period before E15. The presence of bipolar amacrine cells in the outer ventricular layer, first suggested by Cajal, has been confirmed by reconstructing cells from the E17 retina when a clearly defined inner plexiform layer (IPL) is first found. The less mature bipolar amacrine cells present at E17 resemble similar cells found in the E15 retina; they are distinguished from the pre-axonic, migratory stage of ganglion cells by their flattened rather than cylindrical processes, the darker cytoplasm of these processes, and the position of their centrioles closer to the nucleus. Examination of large numbers of reconstructed cells throughout the thickness of the E15 retina has revealed no forms directly transitional from ventricualr cells to bipolar amacrine cells; insted, bipolar amacrine cells appear to be derived by retrograde (sclerally directed) migration of cells in the ganglion cell layer that resemble normal ganglion cells but lack axons. The origin of these anaxonic cells of the ganglion cell layer is not certain but several findings, including evidence of degenerating axons in the optic nerve, sugest that they are derived by loss of the primitive axons of ganglion cells. Thus amacrine cells may be formed by a relatively late differentiating event that occurs after migration of cells to the ganglion cell layer. Such a developmental origin would offer a plausible explanation for the displaced amacrine cells in the ganglion cell layer and IPL described in the adult, as well as perhaps the close similarity of the dendritic trees of certain subtypes of normal, nondisplaced, ganglion and amacrine cells.

Ultrastructure of developing alveoli. I. The role of the interstitial fibroblast.

Abstract: We examined the ultrastructural features of postnatal alveolar septal formation in rats from birth to 28 days of age. At birth, the rat lung consists of large saccules with thick walls and cellular interstitium. Interstitial cells have large oval nuclei with scant cytoplasm containing few organelles and scattered lipid droplets. These cells appear to be poorly differentiated mesenchymal cells not engaged in active protein synthesis or secretion. Between 5 and 15 days of age, saccule walls thin and many new alveolar septa form. Two types of interstitial fibroblasts are present: one which appears at the tips of newly formed septa has the characteristics of a myofibroblast and appears to be engaged in synthesis and secretion of elastin; the other fibroblast appears at the base of new septa, is filled with lipid and contains few other cytoplasmic organelles. After 15 days of age, alveolar walls become thinner, few new septa form and interstitial fibroblasts begin to resemble the dormant type of fibroblasts seen at birth. Thus, the process of postnatal alveolarization of lung parenchyma involves differentiation of the interstitial fibroblast and elastogenesis. The factors which control this process, the precise role of elastogenesis in alveolar septal formation, the origin and fate of the lipid filled fibroblast and the ultimate fate of the myofibroblast remain to be determined.

Structure-Activity Study of the Inhibition of Microtubule Assembly in Vitro by Podophyllotoxin and Its Congeners

Abstract: This study investigates the inhibition of microtubule assembly in vitro by podophyllotoxin and its derivatives, which include in part the antitumor compounds 4′-demethylepipodophyllotoxin ethylidene β-d-glucoside (VP-16-213) and 4′-demethylepipodophyllotoxin thenylidene β-d-glucoside (VM-26); the cyclic ethers, cyclic sulfides, and cyclic sulfones of podophyilotoxin and deoxypodophyliotoxin; epipodophyliotoxin; picropodophyliotoxin; and several 4′-demethyl compounds. The inhibitory activity of these derivatives is sensitive to the configuration and size of substituents at position 4 in ring C and to steric features of substituents at position 12 in ring D. Decreasing activity correlates with the increasing size of the substituent at position 12, as indexed by their van der Waals radii. These results suggest that rings C and D of these drugs are involved in their interaction with the podophyllotoxin-binding site in tubulin.

Protist classification and the kingdoms of organisms

Abstract: Traditional classification imposed a division into plant-like and animal-like forms on the unicellular eukaryotes, or protists; in a current view the protists are a diverse assemblage of plant-, animal- and fungus-like groups. Classification of these into phyla is difficult because of their relatively simple structure and limited geological record, but study of ultrastructure and other characteristics is providing new insight on protist classification. Possible classifications are discussed, and a summary classification of the living world into kingdoms (Monera, Protista, Fungi, Animalia, Plantae) and phyla is suggested. This classification also suggests groupings of phyla into superphyla and form-superphyla, and a broadened kingdom Protista (including green algae, oomycotes and slime molds but excluding red and brown algae). The classification thus seeks to offer a compromise between the protist and protoctist kingdoms of Whittaker and Margulis and to combine a full listing of phyla with grouping of these for synoptic treatment.

Methanogenesis, fires and the regulation of atmospheric oxygen

Abstract: The Gaia hypothesis states that the composition, oxidation-reduction potential and the temperature of the Earth's lower atmosphere are modulated by and for the biota living on the surface (Lovelock, 1972; Margulis and Lovelock, 1974). A corollary is that atmospheric oxygen is presently regulated at about 21% for the dominant life forms today: vascular plants and metazoa. We suggest that the enormous annual production of methane (of the order of 10 14 mol) is directly related to the short term modulation of oxygen concentration. Atmospheric oxygen results from the burial of reduced carbon; methanogenesis and subsequent atmospheric oxidation of methane prevents that burial. We also present experimental work on the probability of ignition of vegetation as a function of increasing oxygen concentration (Watson, 1978). Both the experiments and consideration of the fossil record lead us to conclude that oxygen has been regulated by methane (and perhaps by N 2 O and others) at about 10–25% for very long periods relative to the atmospheric residence times of these reactive gases.

The costs of rheumatoid arthritis. A patient-oriented study of chronic disease costs.

Abstract: To detail the cost for one year of a chronic disease, 50 patients with Stage III rheumatoid arthritis were surveyed. Direct medical costs for this group were three times the national average, and 58% of these costs were covered by insurance. Indirect costs due to lost income were at least three times the direct medical costs, and transfer payments covered only 42% of these costs. Fifty-eight percent of the study group also sustained a major psychosocial loss. Uncovered income losses were the greatest economic burden for individuals with chronic rheumatoid arthritis. This striking ratio of indirect to direct medical costs has important implications for medical practice and health policy.

How supine postural preferences of infants can contribute toward the development of handedness

Abstract: During their first three months postpartum, infants manifest an asymmetrically lateralized head position preference, typically turned to the right. This head position preference elicits an asymmerical tonic neck reflex, which places one hand in the infant's visual field. As a result, infants have differential visual experience of their two hands. The majority of infants have more visual experience with their right hands than their left. Knowledge of which hand an infant has had more visual experinece of, as a result of its postural preference, reliably predicts the hand that will be used most in a visually-elicited reaching task at 12 weeks postpartum. Therefore, the origin of human handedness status may reside in an asymmetrical postural preference during early infancy, which biases visual experience of the hands, giving one hand an advantage in eye-hand coordination tasks.

Carcinoembryonic antigen (CEA) levels in benign gastrointestinal disease states.

Abstract: Elevated circulating CEA levels occur in patients with benign gastrointestinal and hepatic disorders These are usually less than 10 ng/ml Of clinical importance is the influence of liver disease on the interpretation of CEA At least 50% of patients with severe benign hepatic disease have elevated CEA levels, most often active alcoholic cirrhosis, and also chronic active and viral hepatitis, and cryptogenic and biliary cirrhosis Patients with benign extrahepatic biliary obstruction may have increased plasma CEA, the highest in patients with co-existent cholangitis and especially liver abscess The liver appears to be essential for the metabolism and/or excretion of CEA Hence, liver work-up is needed to assess any patient with an elevated CEA A damaged liver may further augment elevated CEA levels due to cancer The increased circulating CEA observed in some patients with active ulcerative colitis tends to correlate with severity and extent of disease and usually returns to normal with remission CEA levels also may be mildly elevated in patients with pancreatitis and in adults with colonic polyps Smoking may contribute to the increased CEA levels seen in patients with alcoholic liver disease and pancreatitis Therefore, in interpreting mildy elevated circulating CEA levels in patients with GI tract diseases, one must consider benign as well as malignant etiologies