Showing papers by "Tufts University published in 1976"

Concepts and Theories of Human Development

Abstract: Contents: Preface to the Third Edition. Preface to the Second Edition. Preface to the First Edition. Human Development: Facts or Theory? Historical Roots of Human Development Concepts and Theories. Philosophical Models of Development. The Nature-Nurture Controversy: Implications of the Question How? The Continuity-Discontinuity Issue. Resolving the Nature-Nurture Controversy: T.C. Schneirla and the Concept of Levels of Integration. Developmental Systems Theories. Developmental Systems Theories: The Sample Case of Developmental Contextualism. Life-Span, Action Theory, Life-Course, and Bioecological Perspectives. Nature Approaches to Human Development: Behavioral Genetics. Nature Approaches to Development: The Sample Case of Intelligence and the Work of Sir Cyril Burt and Arthur Jensen. Nature Approaches to Development: Konrad Lorenz and the Concept of "Instinct." Nature Approaches to Development: Sociobiology. Cognition and Development: From Neo-Nativism to Developmental Systems. Stage Theories of Development. The Differential Approach. The Ipsative Approach to Development. Methodological Issues in the Study of Human Development. Applied Developmental Science.

Protein-folding dynamics.

Abstract: In a discussion of the dynamics of protein folding two limiting models (random-search nucleation and chain propagation., diffusion–collision) are considered. It is suggested that the latter may have the dominant role in many proteins.

Left ventricular compliance: mechanisms and clinical implications.

Abstract: Left ventricular diastolic compliance is determined by the level of operating pressure and the diastolic pressure-volume relation. This relation is curvilinear and the slope of a tangent (operative chamber stiffness) to the pressure-volume curve increases as the chamber progressively fills. Such preload-dependent changes in compliance occur during any acute alteration in ventricular volume. At a given diastolic pressure, operative chamber stiffness (or its reciprocal, operative chamber compliance) is determined by the relative values for ventricular volume and muscle mass and by the stiffness of a unit of myocardium. Thus, there may be a leftward shift of the diastolic pressure-volume curve (increase in the modulus of chamber stiffness) as a consequence of ventricular hypertrophy or an increase in the stiffness of heart muscle itself (increase in modulus of muscle stiffness). To distinguish between hypertrophy and stiff muscle, it is useful to examine the modulus of chamber stiffness, derived from pressure-volume data, together with the volume/mass ratio of the ventricle. In this fashion, changes in the modulus of chamber stiffness that are inappropriate for a given volume/mass ratio may be attributed to changes in the material properties of the heart muscle. Examples of clinical and experimental pressure-volume studies are presented to illustrate the variety of mechanisms by which acute and chronic changes in ventricular chamber compliance evolve during the course of clinical heart disease. The pathophysiology of pulmonary congestion is best understood by considering the factors responsible for producing changes in chamber stiffness of the ventricle, whereas an examination of muscle stiffness is likely to provide more insight into the extent of irreversible functional and structural defects of the myocardium.

Microbial synergy in experimental intra-abdominal abscess.

Abstract: Intra-abdominal sepsis was studied in Wistar rats by using four microbial species: Escherichia coli, enterococci, Bacteroides fragilis, and Fusobacterium varium. These organisms were implanted into the peritoneal cavity singly and in all possible dual combinations. Results were evaluated by mortality rates and the incidence of intra-abdominal abscesses on autopsy following sacrifice after 7 days. Mortality was restricted to recipients of E. coli, thus implicating coliforms in the acute lethality associated with this experimental model. Intra-abdominal abscesses were produced in 61 of 95 (94%) animals that received the combination of an anaerobe and a facultative organism. Abscesses failed to form with any single strain or with E. coli plus enterococci, and they were detected in one 1 of 19 animals receiving B. fragilis plus F. varium. These results suggest that intra-abdominal abscess formation is related to synergy between anaerobes and facultative bacteria.

Spread of antibiotic-resistant plasmids from chicken to chicken and from chicken to man

Abstract: THE natural ecology of Escherichia coli and its infectious plasmids is not understood, although there is suggestive evidence that animals may serve as reservoirs for E. coli found in humans1,2. Investigation in this area becomes additionally important in view of the practice of introducing plasmids with pieces of foreign DNA into E. coli3,4. During an examination of the effects of antibiotic-supplemented animal feed on flora of farm animals and human personnel (ref. 5 and S.B.L., G.B.F. and A.B.M., unpublished), a study was initiated to determine if R plasmids and their E. coli hosts were naturally transferred among chickens and from chickens to human handlers. Our results illustrate the spread of antibiotic-resistant organisms from chicken to chicken and from chicken to man.

The structure and function of intercellular junctions in cancer.

Abstract: Publisher Summary Intercellular junctions are a set of structurally complex membrane components that are incorporated into the general plasma membrane at the sites of close cell-to-cell apposition. The primary function of some types of junctions, such as gap junctions, remains obscure; this is unfortunate because a considerable body of information on the occurrence, biochemical ultrastructure, and physical properties of junctions suggests that they probably do play a central role in important biological phenomena. The quantitative evaluations of the occurrence of junctions are subjective in most of the reports, although there are a few reports in which the data were obtained by quantitative electron microscopy techniques. There are a number of ways in which genes of neoplastic transformation may influence intercellular junction structure and function. Additional research is required to define the contribution of tumor gene products to the pathogenesis of junctional abnormalities in tumors and to elucidate the roles, if any, of these cell membrane defects in malignant growth.

Aerobic and Anaerobic Bacteria in Diabetic Foot Ulcers

Abstract: Twenty diabetic foot ulcers were cultured using optimal microbiologic techniques. Anaerobic bacteria coexisted with the more commonly recognized aerobic bacteria in 18 specimens. There were a total of 116 isolates with an average of 5.8 species per specimen (3.2 aerobes and 2.6 anaerobes). The principal isolates were Bacteroides species (sp.) (17 strains), peptococci (16), Proteus sp. (11), enterococci (9), Staphylococcus aureus (7), clostridia (7), and Escherichia coli (6). When antimicrobial therapy is indicated the selection of agents should consider the likelihood of a complex aerobic-anaerobic flora.

Areal and laminar distribution of some pulvinar cortical efferents in rhesus monkey.

Abstract: The areal and laminar distribution of the cortical efferents of the medial, lateral and inferior pulvinar nuclei (PM, PL and PI respectively) were determined in rhesus monkey using autoradiography and Horseradish Peroxidase (HRP). The autoradiographic data indicated that: areas 8a, 45 and 46 on the convexity and 11 and 12 on the orbital surface of the frontal lobe received projections from PM; areas 20, 21 and 22 in temporal lobe received projections from PM primarily with caudal-medial parts of PM projecting to more rostral-dorsal parts of temporal lobe and rostral-lateral parts of PM projecting to more caudal-ventral parts of temporal lobe but PL also sends some efferents to caudal temporal lobe; areas 5 and 7 in parietal lobe and 18 and 19 in occipital lobe received projections primarily from the region in pulvinar comprising PL and PI with the more ventral parts of this region porsal parts of this region projecting to the more dorsal-lateral and medial parts of parieto-occipital cortex and with PM comtributing slightly to these projections rostrally. The autoradiographic information on the pulvinar projections to frontal lobe and temporal pole was supplemented by data derived from cortical HRP injections. These indicated that although only PM of the pulvinar subnuclei projected to these regions, three other caudal thalamic structures, i.e., medial dorsal nucleus, nucleus limitans and suprageniculate nucleus also projected to these regions raising some questions about the identity of the densocellular part of the medial dorsal nucleus which has also been considered to be part of pulvinar. The laminar distribution of pulvinar cortical efferents was uniformly similar regardless of the pulvinar recipient area examined. Elevated numbers of silver grains were observed over all cortical layers, but the silver grains were densest over the deep parts of layer III. The thalamic reticular nucleus was the only diencephalic structure observed to receive projections from pulvinar and it did so from PM, PL and PI. The pulvinar's efferents are to homotypical rather than heterotypical cortex and its connections are most extensive with cortex rather than with subcortical structures.

Somatostatinergic neurons in anterior hypothalamus: immunohistochemical localization.

Abstract: The distribution of somatostatin was studied in the rat with an immunoperoxidase technique and rabbit anti-somatostatin. Somatostatinergic neurons were identified in the preoptic and anterior periventricular hypothalamus between the anterior commissure, optic chiasm, and the anterior portion of the ventromedial nucleus.

Characteristics and significance of the polyadenylate sequence in mammalian messenger RNA.

Abstract: Publisher Summary This chapter describes that the poly (A) segment in mRNA provides a dramatic example of an accessory polynucleotide sequence that is clearly not involved in the primary function of the RNA chain All RNA types seem to possess extra sequences of this kind The precursor molecules to ribosomal RNA, messenger RNA and transfer RNA also contain large polynucleotide segments that are eliminated during the maturation process The unique thing about poly (A) segment is that it represents a homopolymeric sequence and that its size is subject to variation This segment provides a highly specialized structure that identifies a class of RNA in the cell It does not allow for any diversity to permit discrimination between different species of mRNA This type of sequence is useful to the biochemist, as it permits the detection and isolation of a unique RNA class It is presumably also useful to the cell, although its precise function remains elusive Further studies will reveal a variety of regulatory functions for the accessory polynucleotide sequences in the cell

Adrenal medullary hyperplasia. A morphometric analysis in patients with familial medullary thyroid carcinoma.

Abstract: The syndrome of familial medullary thyroid carcinoma (MTC), pheochromocytoma, and parathyroid hyperplasia is inherited as an autosomal dominant trait, and is characterized by development of bilateral and multicentric thyroidal and adrenal medullary tumors. One of the earliest manifestations of adrenal medullary hyperfunction in patients with this syndrome is an increased ratio of epinephrine to norepinephrine in urine. In order to define the morphologic correlates of these early catecholamine abnormalities in a large kindred with familial MTC, a morphometric analysis based on a point-counting system to asses adrenal medullary volume was undertaken. These studies clearly revealed adrenal medullary hyperplasia as reflected by a two- to three-fold increase in medullary volume and weight as compared to age- and sex-matched controls. The increase in total medullary mass resulted from diffuse and multifocal modular proliferations of adrenal medullary cells primarily within the head and body regions of the glands. These results support the hypothesis that the pheochromocytomas in patients with familial MTC may, in fact, represent extreme degrees of nodular hyperplasia of the medulla.

Neural properties of cultured human endocrine tumor cells of proposed neural crest origin.

Abstract: Cells from human endocrine tumors of proposed neural crest origin--five pheochromocytomas, two medullary carcinomas of the thyroid, and two bronchial carcinoids--were grown in monolayer culture. Cells from all nine tumors, including epithelial forms of medullary carcinoma of the thyroid and bronchial carcinoid cells, and epithelial and neuron-like pheochromocytoma cells demonstrated all-or-nothing, short-duration action potentials.

Alpha1-Antitrypsin and Alpha-Fetoprotein: Protein Markers in Endodermal Sinus (Yolk Sac) Tumors

Abstract: A combined immunocytochemical and quantitative serum and tissue study was performed on a group of endodermal sinus (yolk sac) tumors, localizing and measuring both alpha1-antitrypsin (AAT) and alpha-fetoprotein (AFP) in tumor tissue and patient sera. Utilizing indirect immunofluorescent and triple-sandwich immunoperoxidase methods, both proteins were demonstrated within intra- and extracellular periodic acid-Schiff-positive hyaline globules characteristic of the tumor, as well as within the cytoplasm of tumor epithelial cells lining endodermal sinuses, where AAT deposition predominated. Tumor tissue extracts confirmed the presence of significant quantities of both proteins, and pretreatment serum elevations of both showed a parallel decline during therapy. In this study, AAT is characterized as a tumor protein marker for the first time, and a parallelism between AAT and AFP is demonstrated in both serum and tumor tissue. These findings represent additional supportive evidence for the yolk sac origin of endodermal sinus tumors in man.

A preliminary report on a chemomechanical means of removing caries

Abstract: In a two-part study evaluating both a chemical solution and the technique of use, an experimental method of caries removal is investigated for safety and effectiveness. A new experimental method of caries removal using a 0.05% solution of N-monochloroglycine (GK-101) buffered to a pH of 11.4 has been investigated for safety and effectiveness. The solution has been reported to be relatively nontoxic. Results of a double-blind clinical study comparing the compound with saline solution (where the solutions were applied to the lesions using a specially designed pump with a handpiece and removable tip) indicate that GK-101, when used in this total system, is more effective in removing carious material than the placebo. Additional long-term laboratory studies and clinical trials are being conducted to determine the safety and efficacy of GK-101, in compliance with regulations of the Food and Drug Administration.

Localization of LHRH in Neurons in Frog Brain (Rana pipiens and Rana catesbeiana)

Abstract: Hypothalamic extracts from frogs (Rana pipiens) were found to contain a significant quantity of immunoreactive LHRH (3.27 ± 0.63 ng/hypothalamus) (mean ± SE) measured by radioimmunoassay. In additional radioimmunoassay studies of gross brain LHRH distribution in R. pipiens and R. catesbeiana, 16% of the total frog brain LHRH was located within the telencephalon-septum-optic chiasm regions while the remainder was distributed within the infundibular hypothalamicpituitary complex. Immunohistochemical studies using the peroxidase-anti-peroxidase (PAP) unlabeled antibody enzyme technique demonstrated the presence of LHRH selectively within some neuronal perikarya located primarily in the median septal nucleus. Fibers containing immunoreactive LHRH were seen in the vicinity of these neuronal cell bodies and in the medial and lateral septal nuclei. In addition, LHRH-containing fibers extended to the median eminence and posterior pituitary, traversing a course beneath the preoptic recess or through the medial for...

The synthesis of glycosaminoglycans by cultures of rabbit corneal endothelial and stromal cells

Abstract: Confluent monolayer cultures of rabbit corneal endothelial and stromal cells were incubated independently with [35S]sulphate and [3H]glucosamine for 3 days. AFter incubation, labelled glycosaminoglycans were isolated from the growth medium and from a cellular fraction. These glycosaminoglycans were further characterized by DEAE-cellulose column chromatography and by sequential treatment with various glycosamino-glycan-degrading enzymes. Both endothelial and stromal cultures synthesized hyaluronic acid as the principal product. The cell fraction from the stromal cultures, however, had significantly less hyaluronic acid than that from the endothelial cultures. In addition, both types of cells synthesized a variety of sulphated glycosaminoglycans. The relative amounts of each sulphated glycosaminoglycan in the two cell lines were similar, with chondroitin 4-sulphate, chondroitin 6-sulphate and dermatan sulphate as the major components. Heparan sulphate was present in smaller amounts. Keratan sulphate was also identified, but only in very small amounts (1-3%). The presence of dermatan sulphate and the high content of hyaluronic acid are similar to the pattern of glycosaminoglycans seen in regenerating or developing tissues, including cornea.

Secondary Nucleation — A Review

Abstract: Crystallizing systems, that is supersaturated systems in which crystals are already present, can form new nuclei at conditions under which primary (spontaneous) nucleation would not occur. This phenomenon leads to the definitions which will be followed in this paper: a) Secondary is the nucleation which occurs, irrespectively of its mechanism, only because of the presence of crystals of the material being crystallized. When no crystals are present no nucleation occurs. b) The terms primary or spontaneous nucleation will be used to characterize any nucleation that is not secondary in nature. This includes both the classical homogeneous and the heterogeneous nucleation.

Genetics of expression of xenotropic virus and autoimmunity in nzb mice.

Abstract: CERTAIN retroviruses (RNA tumour viruses) have been implicated in the autoimmune disease of New Zealand mice1. These mice produce large numbers of xenotropic retroviruses2,3 and contain high concentrations of the retroviral envelope antigen gp 69/71 in their serum and tissues4. Moreover, gp 69/71 and the corresponding antibodies contribute to the immune deposits in the nephritic kidneys of NZB and (NZB × NZW)F1 mice4. Nevertheless, it is not established that xenotropic viruses are the primary cause of the autoimmune disease of NZB mice. Conceivably, these agents may be involved only secondarily. The presence of RNA viruses in NZB mice may explain neither the production of antibodies against DNA, nucleoproteins, and erythrocyte antigens nor the anomalies of T- and B-lymphocyte function5. Transmission of autoimmunity has not been achieved with cell-free filtrates from NZB mice6, nor by transplanting NZB lymphomas7 which are known to produce large numbers of virus particles8. Only spleen cells from old NZB mice can transmit the autoimmune disorder6. Transmission of the disease with cell-free extracts is unlikely to succeed because the NZB xenotropic virus cannot productively infect mouse cells; it can infect only cells of heterologous species2,3. Here we deal with the vertical transmission of NZB viral genes as Mendelian traits—a phenomenon that has been demonstrated with other retroviruses9—to test the hypothesis that the development of autoimmunity in NZB mice and their crosses is independent of the expression of high titres of xenotropic viruses. We have found that the high grade expression of infectious xenotropic virus characteristic of NZB mice is a genetically determined trait. Two independently segregating loci seem to specify the NZB phenotype. So far, animals that are virologically like NZB have failed to develop signs of autoimmune disease.

Activity of Cefamandole and Other Cephalosporins Against Aerobic and Anaerobic Bacteria

Abstract: The activity of cefamandole was comparable to that of cephalothin, cefazolin, and cephaloridine against Staphylococcus aureus, Streptococcus pyogenes, and Diplococcus pneumoniae. In contrast, cefamandole was considerably more active than cephalothin, cefazolin, or cephaloridine against gram-negative facultative bacilli, including Haemophilus influenzae, the most striking disparities being noted with indole-positive Proteus and Enterobacter. Bacteroides fragilis was more susceptible to cefoxitin than to cefamandole or cefazolin (median minimal inhibitory concentration, approximately 8, 32, and 32 mug/ml, respectively); cephalothin exhibited still less activity against this species. The majority of other anaerobes were inhibited by relatively low concentrations of all four cephalosporins. The results indicate a potentially valuable role for cefamandole against facultative gram-negative bacilli, including H. influenzae, but no exceptional activity against anaerobes.