Showing papers by "Johns Hopkins University published in 1976"

The SCL-90 and the MMPI: a step in the validation of a new self-report scale.

Abstract: The present investigation was intended principally as a concurrent validation study for a new self-report symptom inventory: the SCL-90. A sample of 209 'symptomatic volunteers' served as subjects and were administered both the SCL-90 and the MMPI prior to participation in clinical therapeutic drug trials. The MMPI was scored for the Wiggins content scales and the Tryon cluster scales in addition to the standard clinical scales. Comparisons of the nine primary symptom dimensions of the SCL-90 with the set of MMPI scales reflected very high convergent validity for the SCL-90. Peak correlations were observed with like constructs on eight of the nine scales, with secondary patterns of correlations showing high interpretative consistency.

Remembrance of places passed: Spatial memory in rats.

Abstract: Rats were tested on an eight-arm maze in a paradigm of sampling with replacement from a known set of items until the entire set was sampled. The first three experiments demonstrated that the animals performed efficiently, choosing an average of more than seven different arms within the first eight choices, and did not utilize intramaze cues or consistent chains of responses in solving the task. The second three experiments examined some characteristics of the rats' memory storage. There was a small but reliable recency effect with the likelihood of a repetition error increasing with the number of choices since the initial instance. This performance decrement was due to interference from choices rather than just to the passage of time. No evidence was found for a primary effect. The data also suggest that there was no tendency to generalize among spatially adjacent arms. The results are discussed in terms of the memory processes involved in this task and human serial learning. When distinctive exteroceptive discriminative stimuli are consistently associated with a particular spatial location, rats preferentially use these stimuli for discrimination learning, a phenomenon that is usually referred to as "place learning." If place learning can be used to solve a discrimination problem, rats learn very rapidly. If place learning cannot be used to solve a discrimination problem, rats learn slowly and almost invariably adopt a "position habit" or "spatial hypothesis" before finding the correct solution. (Relevant literature reviews may be found in Gleitman, 1955; Kimble, 1961, p. 223; Olton & Samuelson,

Hemodynamic determinants of the time-course of fall in canine left ventricular pressure.

Abstract: The hemodynamic determinants of the time-course of fall in isovolumic left ventricular pressure were assessed in isolated canine left ventricular preparations. Pressure fall was studied in isovolumic beats or during prolonged isovolumic diastole after ejection. Pressure fall was studied in isovolumic relaxation for isovolumic and ejecting beats (r less than or equal to 0.98) and was therefore characterized by a time constant, T. Higher heart rates shortened T slightly from 52.6 +/- 4.5 ms at 110/min to 48.2 +/- 6.0 ms at 160/min (P less than 0.01, n = 8). Higher ventricular volumes under isovolumic conditions resulted in higher peak left ventricular pressure but no significant change in T. T did shorten from 67.1 +/- 5.0 ms in isovolumic beats to 45.8 +/- 2.9 ms in the ejecting beats (P less than 0.001, n = 14). In the ejecting beats, peak systolic pressure was lower, and end-systolic volume smaller. To differentiate the effects of systolic shortening during ejection from those of lower systolic pressure and smaller end-systolic volume, beats with large end-diastolic volumes were compared to beats with smaller end-diastolic volumes. The beats with smaller end-diastolic volumes exhibited less shortening but similar end-systolic volumes and peak systolic pressure. T again shortened to a greater extent in the beats with greater systolic shortening. Calcium chloride and acetylstrophanthidin resulted in no significant change in T, but norepinephrine, which accelerates active relaxation, resulted in a significant shortening of T (65.6 +/- 13.4 vs. 46.3 +/- 7.0 ms, P less than 0.02). During recovery from ischemia, T increased significantly from 59.3 +/- 9.6 to 76.8 +/- 13.1 ms when compared with the preischemic control beat (P less than 0.05). Thus, the present studies show that the time-course of isovolumic pressure fall subsequent to maximum negative dP/dt is exponential, independent of systolic stress and end-systolic fiber length, and minimally dependent on heart rate. T may be an index of the activity of the active cardiac relaxing system and appears dependent on systolic fiber shortening.

Regulatory actions of human stretch reflex

Abstract: 1. The stretch reflex in the elbow flexor musculature was studied in 23 human subjects. The subjects were required to establish an initial force equivalent to 10% maximum at a prescribed initial length; mechanical disturbances delivered at random times increased load force to 15% or reduced it to 5%. We measured arm force, displacement, and EMG (usually biceps); acceleration was calculated from displacement, and average responses from sets of 10 like trials. 2. Modification of the stretch reflex was studied by comparing average responses obtained with different instructions, but with the same disturbance. The usual introductions were "compensate for arm deflection" and "do not intervene voluntarily". The initial response did not depend on instruction; changes in response that depended on instruction began abruptly after a latent period which ranged from 70 to 320 ms (measured from force and acceleration), depending on conditions and subject. The latency became longer (10-50 ms) and more variable when the subject did not know the direction of disturbance in advance. This and other observations indicate that modifications of the stretch reflex are not produced by servo actions. They are produced by triggered reactions, which occur at both short and long latencies and which have properties resembling the movements produced in a reaction-time task. 3. We confirmed that most subjects can suppress triggered reactions when the instruction calls for no intervention, leaving an unmodified reflex response. This response consists of a compliant deflection of the arm in the direction of the disturbance. 4. The compensatory actions associated with unmodified stretch (and unloading) reflexes were assessed from EMG responses of biceps. During a 300-ms transient phase, EMG changes were notably asymmetric when responses to symmetric disturbances were compared. Increased force stretched biceps and produced a prominent increase in EMG, whereas decreased force allowed biceps to shorten and produced either an EMG decrease of smaller magnitude or an actual increase. These asymmetric reflex actions produced quite symmetric mechanical responses (arm displacements and forces), which implies the existence of and compensation for nonlinear muscle mechanical properties. This result is discussed in relation to the hypothesis that the function of the stretch reflex is to compensate for variations in muscle properties, thus maintaining stiffness. 5. Effective control of muscle length or joint position does not result from servo action by the stretch reflex. Errors in position are corrected only when triggered reactions are superimposed on the reflex response.

Opiate receptor: autoradiographic localization in rat brain.

Abstract: Opiate receptor sites in rat brain can be labeled in vivo by [3H]diprenorphine, a potent opiate antagoinst. Using techniques to minimize diffusion in fresh, frozen, unfixed brain, we have localized [3H]diprenorphine by autoradiography to visualize the distribution of opiate receptors. Silver grains indicative of the binding of labeled [3H]diprenorphine are discretely localized in numerous areas of the brain with very high densities in the locus coeruleus, the substantia gelatinosa of the spinal cord, and in clusters within the caudate-putamen, amygdala, and parts of the periventricular gray matter.

The dopamine hypothesis of schizophrenia: focus on the dopamine receptor

Abstract: Alleviation of schizophrenic symptoms by phenothiazines and butyrophenones is associated with blockade of dopamine receptors, while exacerbation of symptoms by amphetamines appears to result from enhanced synaptic activity of dopamine and/or norepinephrine. The author suggests that biochemical labeling of the dopamine receptor with 3H-dopamine and 3H-haloperidol may clarify mechanisms of drug effects on the dopamine receptor.

Human reovirus-like agent as the major pathogen associated with "winter" gastroenteritis in hospitalized infants and young children.

Abstract: We found a human reovirus-like agent in the stools of 42 per cent of 143 infants and young children hospitalized with acute gastroenteritis between January, 1974, and June, 1975. Half the patients studied by electron microscopy and serologic technics had evidence of infection with the agent. The infection had a seasonal pattern: 59 per cent of those admitted during the cooler months (November to April) shed the agent, with a peak of 78 per cent in December, 1974, and January, 1975, combined. None of the patients admitted during the warmer months (May to October) shed the agent. None of 275 Escherichia coli isolates from 32 patients with diarrhea produced heat-labile enterotoxin, whereas 17 of the 32 had evidence of infection with the reovirus-like agent. In addition, 14 of 40 parents of 37 patients with diarrhea associated with the reovirus-like agent were also infected, but most infectious were inapparent. This agent appears to be the major cause of diarrheal illness in the young during the cooler months.

The Energy Balance and Deformation Mechanisms of Thrust Sheets

Abstract: The total energy involved in emplacing a thrust sheet is expended in initiation and growth of the thrust surface, slip along this surface, and deformation within the main mass of the sheet. This total energy can be determined from potential energy considerations knowing the initial and final geometry from balanced cross sections after defining the thrust’s thermodynamic system boundaries. Emplacement of the McConnell thrust in the Canadian Rockies involved ca. 1019 J of gravitational work, an order of magnitude greater than any possible work by longitudinal compressive surface forces. A new theory for the initiation and growth of thrusts as ductile fractures is based on a demonstration that thrust displacement is linearly related to thrust map length and that fold complexes at the ends of thrusts are constant in size for a given metamorphic grade. Much of the total work is dissipated within the body of the sheet. Field observations show which mechanisms of dissipation are most important at various positions within the thrust sheet, and it is found that only the top 5 km of the McConnell was dominated by frictional sliding. A novel type of sliding along discrete surfaces is pressure solution slip, in which obstacles are by-passed by diffusive mass transfer. Fibres and pressure solution grooves are diagnostic features of this sliding law, in which slip velocity is linearly related to shear stress. Pressure solution slip is widespread at depths greater than about 5 km, but at this depth penetrative whole rock deformation by pressure solution becomes dominant - marked by cleavage and stretching directions - and accounts for much of the finite strain within the thrust sheet. The McConnell thrust has an outer layer which deformed by frictional sliding and this overlies a massive linearly viscous core responsible for much of the energy dissipation and gross mechanical behaviour.

Genetic dissection of the photoreceptor system in the compound eye of Drosophila melanogaster

Abstract: 1. Three mutations which eliminate specific types of photoreceptors in Drosophila were characterized. 2. Of the eight photoreceptors in each facet, two mutations delete the outer six (R 1-6). The third eliminates R 7, one of the two central photoreceptors. Double mutants can be constructed in which only photoreceptor R 8 is present. 3. The spectral sensitivities, photopigments, and behavioural properties of these mutants were investigated. 4. R 1-6 have two sensitivity peaks, near 350 and 470 nm. These receptors contain a rhodopsin with these absorption peaks. It interconverts with a metarhodopsin that absorbs around 570 nm. 5. R 7 is a U.V.-receptor, containing rhodopsin that absorbs around 370 nm and interconverts with a metarhodopsin which absorbs around 470 nm. 6. R 8 is a non-adapting blue-receptor with a third type of rhodopsin. 7. The properties of these photopigments explain the different sensitivities and spectral adaptation phenomena of the various photoreceptors. 8. All the photoreceptors have input into phototaxis. Spectral analysis of this behaviour provides evidence for integration of the input from the different photoreceptors.

The Concept and Measurement of the Quality of School Life

Abstract: The Quality of School Life (QSL) is defined by three dimensions of student reactions: (1) satisfaction with school in general, (2) commitment to school work, and (3) attitudes toward teachers. A 27-item QSL scale is presented that shows reliability and validity across educational levels (elementary, middle and high school) based on 4,266 student survey responses. Concurrent and discriminative validity is demonstrated using measures of academic achievement, participation, personality, family background, and sociometric data from peers and teachers. Scaling techniques, factor analysis, and an extension of Sechrest’s test for incremental validity document the multi-dimensional design of the scale.

Improved Outcomes in Hypertension After Physician Tutorials: A Controlled Trial

Abstract: Physicians working at the General Medical Clinic of the Johns Hopkins Hospital entered into tutorials to improve their effectiveness as managers and educators of patients with essential hypertension. After exposure to a single teaching session, tutored physicians allocated a greater percent of clinic-visit time to patient teaching than did control physicians, achieving increased patient knowledge and more appropriate patient beliefs regarding hypertension and its therapy. Patients of tutored physicians were more compliant with drug regimens and had better control of blood pressure than patients of untutored physicians. The personal physician, if he is provided with strategies for identifying the noncompliant patient and for intervening in that behavior, can apply a stimulus to his patients that results in improved compliance and better control of hypertension.

Travelers' diarrhea in Mexico. A prospective study of physicians and family members attending a congress.

Abstract: We conducted a prospective study of travelers' diarrhea on 73 physicians and 48 family members attending a medical congress in Mexico City, in October, 1974. Fecal and blood specimens were collected before, during and after their visit and examined for enteric bacterial pathogens, viruses and parasites. In 59 (49 per cent) participants travelers' diarrhea developed. Median duration of illness was five days. Onset occurred a median of six days after arrival. An etiologic agent was found in 63 per cent of ill participants. Enterotoxigenic Escherichia coli of different, non-"enteropathogenic" serotypes was the most common cause; other responsible pathogens included salmonellae, invasive Esch. coli., shigellae, Vibrio parahaemolyticus, Giardia lamblia and the human reovirus-like agent. Consumption of salads containing raw vegetables was associated with enterotoxigenic Esch. coli infection (P = 0.014). Travelers' diarrhea in Mexico is a syndrome caused by a variety of pathogens, the most common of which is enterotoxigenic Esch. col.

Electron microscopic autoradiographic studies of gliogenesis in rat optic nerve I. Cell proliferation

Abstract: Electron microscopy and 3H-thymidine autoradiographic techniques were used to study the fine structure of proliferating cells in developing rat optic nerve. Before the closure of the optic canal almost all of the cells incorporating radioactive thymidine are ventricular cells, but after closure (16 days of gestation) the vast majority are differentiating astroblasts or oligodendroblasts. Labeled astroblasts show a range in their degree of differentiation; some cells lack 90 A cytoplasmic filaments while others have glial filaments and abundant cytoplasmic organelles. In contrast to astroblasts, all of the labeled oligodendroblasts are in the early stages of differentiation. The proliferation of oligodendroblasts starts at five days postnatal, approximately a day or two before the onset of myelination.During myelinogenesis a few of the labeled oligodendroblasts show presumptive connections to myelin sheaths. Microglial cells do not appear to play a major role in gliogenesis since they form less than 2% of all the labeled cells. The results of this study indicate that astroblasts and oligodendroblasts, rather than undifferentiated glioblasts, are the major source of macroglia. The finding that proliferating glia are in the processof differentiation agrees with recent studies which show that differentiated cells can divide.

Electron microscopic autoradiographic studies of gliogenesis in rat optic nerve. II. Time of origin

Abstract: The time of origin for astrocytes and oligodendrocytes in rat optic nerve was studied by 3H-thymidine autoradiographic techniques similar to those used in dating the time of origin for neurons. This study shows that astrocytes are formed throughout late embryonic and all of postnatal development, while oligodendrocytes are generated only during the postnatal period. A few astroglia undergo their final cell division as early as 15.5 days of gestation, but most astrocytes are not generated until the first week of postnatal development. Although the final cell division for more than half of the astrocytes takes place before the end of the first postnatal week, fully mature, fibrous astrocytes are not observed in electron micrographs until after 14 days of age. This time lag implies that the differentiation of these early generated cells takes place gradually over a 2-to 3-week interval. Oligodendroglia begin their final division a day or two before the onset of myelination (6–7 days postnatal), but the vast majority are produced during the period of myelinogenesis. After almost all of the axons have been myelinated, oligodendrocytes are still being generated in small numbers. These late forming cells are generally less differentiated in appearance than those formed earlier; this suggests that the degree of differentiation of oligodendrocytes may be dependent upon the number of axons available for myelination. As with astrocytes, oligodendrocytes show a lag of about two weeks from the time of final cell division until they transform into morphologically differentiated cells. In transverse sections of the optic nerve heavily labeled neuroglia are randomly distributed, indicating there are no temporal-radial gradients for the individual cell types. This observation taken together with the other information obtained from the present and the previous study (Skoff et al., '76) strongly suggest that the factors controlling gliogenesis are different from those governing neuronogenesis.

Measurement of membrane protein lateral diffusion in single cells.

Abstract: Fluorescence rapidly returns to spots bleached by a laser beam in the continuous fluorescence of cultured cells labeled on the surface with fluorescein isothiocyanate. The rate of recovery of fluorescence after bleaching can be interpreted as a measure of the lateral diffusion of integral membrane proteins labeled with fluorescein.

Arsenate adsorption on amorphous aluminum hydroxide

Abstract: Arsenate adsorption on amorphous aluminum hydroxide was studied as a model system for aqueous anion adsorption on oxide surfaces. Adsorption and electrophoretic mobility of the suspended adsorbent particles were measured as functions of equilibrium pH. A transformation of variables allowed the adsorption to be explained in terms of the chemical and physical forces controlling the adsorption reaction. When used in conjunction with the Langmuir adsorption equation, the results allow calculation of levels of arsenate removal for any given amount of adsorbent and any pH.

Perinatal events associated with maternal smoking during pregnancy

Abstract: To identify components of smoking-related increased perinatal mortality detailed analyses of data from the Ontario Perinatal Mortality Study (50000 births 1300 deaths 1960-1961) measured the relationship of maternal smoking to birth weight gestation placental complications and perinatal mortality. Cross-tabulations with other factors and multiple adjustment showed increases with amount smoked of birth weights < 2500 gm gestations < 38 weeks placenta previa abruptio placentae and perinatal mortality. These significant smoking-related increases were independent of mothers height weight hospital status age-parity group birthplace previous pregnancy history weight gain time of registration and sex of child. Maternal smoking had the strongest effect on birthweight in the 8 factor regression and birth < 2500 gm increased directly with smoking level from 20 to 340% in 37 data subgroups. Births < 38 weeks increased 20 and 50% and perinatal mortality increased 20 and 35% for < 1 pack and 1 + pack smokers respectively adjusted for 7 other factors. Placental complications increased consistently with smoking level in all of 37 subgroups except for primiparous < 1 pack smokers. Adjusted rates increased 25 and 92% for placenta previa 23 and 86% for abruptions among smokers of < 1 pack and 1 + packs respectively. These complications carry high perinatal mortality risk and account for 1/3 to 1/2 of the perinatal deaths attributable to maternal smoking.(AUTHORS)

A fuzzy set approach to modifiers and vagueness in natural language.

Abstract: SUMMARY Recent developments in semantic theory, such as the work of Labov (1973) and Lakoff (1973), have brought into question the assumption that meanings are precise. It has been proposed that the meanings of all terms are to a lesser or greater degree vague, such that, the boundary of the application of a term is never a point but a region where the term gradually moves from being applicable to nonapplicable. Developments in fuzzy set theory have made it possible to offer a formal treatment of vagueness of natural language concepts. In this article, the proposition that natural language concepts are represented as fuzzy sets of meaning components and that language operators—adverbs, negative markers, and adjectives— can be considered as operators on fuzzy sets was assessed empirically. In a series of experiments, we explored the application of fuzzy set theory to the meaning of phrases such as very small, sort of large, and so on. In Experiment 1, subjects judged the applicability of the set of phrases to a set of squares of varying size. The results indicated that the group interpretation of the phrases can be characterized within the framework of fuzzy set theory. Similar results were obtained in Experiment 2, where each subject's responses were analyzed individually. Although the responses of the subjects, in general, could be interpreted in terms of fuzzy logical operations, one subject responded in a more idiomatic style. Experiments 3 and 4 were attempts to influence the logical-idiomatic distinction in interpretatio n by (a) varying the presentation mode of the phrases and by (b) giving subjects only a single phrase to judge. Overall, the results were consistent with the hypothesis that natural language concepts and operators can be described more completely and more precisely using the framework of fuzzy set theory.

Slow saccades in spinocerebellar degeneration.

Abstract: Two patients with spinocerebellar degeneration made abnormally slow horizontal refixations. One patient produced quick phases of nystagmus with identical maximum velocities, suggesting her refixations were abnormal saccades and not voluntary pursuit movements. In response to double target jumps, neither patient showed an obligatory refractory period after each saccade; they responded to every target movement after one reaction time. Their slow refixations were not preprogrammed since they could be modified in flight. To reconcile these observations with normal saccadic behavior, we hypothesized a neural network that made saccades by driving the eyes to an orbital position rather than preprogramming a distance for movement. Computer simulation of this model produced both realistically appearing normal saccades and, when appropriately "lesioned" to simulate a loss of saccadic "burst" neurons in the pontine reticular formation, slow saccades that could be modified in flight.

Radioimmunoassay of myelin basic protein in spinal fluid. An index of active demyelination.

Abstract: With a sensitive radioimmunoassay that can measure as little as 2 ng of basic protein in cerebrospinal fluid we studied 303 patients with a variety of neurologic diseases. Patients with active demyelinating diseases had high levels (17 to 100 ng per milliliter) of basic protein. Moreover, patients with multiple sclerosis in acute exacerbation had these high levels, those with slowly progressive multiple sclerosis had lower levels (6 to 16 ng per milliliter), and those in remission had less than 4 ng per milliliter, comparable to the control population. Thus, the assay appears to be a useful index of active demyelination. (N Engl J Med 295:1455–1457, 1976)

Botulinum Toxin: Mechanism of Presynaptic Blockade

Abstract: The mechanism of action of botulinum toxin was analyzed by the use of calcium ionophores and black widow spider venom. Addition of calcium ionophores to nerve-muscle preparations blocked by botulinum toxin did not increase the frequency of miniature end plate potentials. However, the spider venom elicited a barrage of miniature end plate potentials after blockade by botulinum. Electron micrographs of preparations treated with botulinum toxin and then the spider venom revealed clumping of synaptic vesicles at release sites in the otherwise depleted nerve terminals. These findings indicate that the action of botulinum toxin is not due to deficient storage of acetylcholine in vesicles or blockade of calcium entry into nerve terminals. They suggest that the toxin interferes with the acetylcholine release process itself, possibly by blocking exocytosis at the release sites.

Special Escherichia coli serotypes among enterotoxigenic strains from diarrhoea in adults and children.

Abstract: 106 enterotoxigenicEscherichia coli strains from children and adults from many parts of the world were serotyped for O and H antigens. Some O∶H types,i.e. O6∶H16, O8∶H9, O15∶H11, O25∶H42, O78∶H11 and O78∶H12, were found repeatedly from different geographical locations. Some of these O∶H serotypes were only found rarely among more than 20000E. coli strains collected over many years from different locations and sources. It is suggested that these special O∶H serotypes represent clones which have been selected to the special conditions in the small intestine and selected to carry the plasmids necessary to provoke diarrhoea.