The relationship of the central motor pattern to the feeding cycle of Lymnaea stagnalis

Electromyographic recordings from the buccal muscles of Lymnaea during feeding has shown that there are 4 component phases in the feeding cycle. Cinephotography of feeding cycles has confirmed that these correspond to protraction, 2 phases of retraction, and an inactive phase. The 4 phases of muscle activity can also be related to the cycle of neural activity described previously (Benjamin & Rose, 1979). Thus types 6, 4 group, and type 8 cells are motoneurones involved in protraction and the two retraction phases, while the type 5 cell fires in the inactive period. The combination of physiological and anatomical approaches has led to the suggestion that the single and double input cells described by Benjamin & Rose (1979) are involved with the control of buccal and oesophageal activity respectively.

Central generation of bursting in the feeding system of the snail, Lymnaea stagnalis

The central generation of burst activity was investigated in the buccal ganglia of Lymnaea. Eight different patterns of burst activity were generated by one or two consecutive phases of compound synaptic potentials resulting from activity of neurones. These inputs acted upon the different endogenous properties of buccal neurones such as post-inhibitory rebound and spike adaptation. Effects of synaptic inputs were reinforced by by electrotonic coupling of some buccal neurones of the same type.

Life changes. Do people really remember?

The question, "How well do people remember life changes?" was approached in a longitudinal study of nearly 400 healthy men in a responsible profession. Three scales for assessing life changes were administered by questionnaire at two examinations nine months apart. The subjects were asked to report life change events occurring during a specific six-month period--that which immediately preceded the first examination. For all three life change scales there was substantial forgetting over the interval between reports, with a second report yielding total scores 34% to 46% less than those from the first report for the same period. The amount of change over time varied greatly across persons. These findings raise serious questions about the validity of retrospective studies of life change and illness when the period being reported is greater than six months in the past. They do not, however, jeopardize the potential of the method for prospective studies.

Prevalence of depression over a 12-month period in a nonpatient population

A nonpatient population of air traffic controllers, all of whom remained employed during the observation period, was examined monthly for one year for level of depression using the Zung Self-Rating Depression Scale. The average monthly prevalence of depression was 9.1%, with 7.0% at the symptom level, 1.9% at a level comparable to outpatients, and 0.2% with moderately severe levels. These figures were generally similar to those for other reported population groups, although exact comparisons were difficult because of the preselection for health in this population. Two patterns of depression were observed. One was characterized by an acute, episodic symptomatology returning to nonsymptomatic levels for most of the year, similar to Research Diagnostic Criteria (RDC) category "episodic minor depressive disorder." The other showed a chronic, fluctuating course with significant depressive symptomatology over half the year, similar to RDC category "chronic and intermittent minor depressive disorder."

Is chondromalacia patellae a separate clinical entity?

The articular cartilage of the patella was studied in 100 knees at necropsy. In twenty-one of these knees the cartilage changes were related to the trabecular architecture of the underlying bone. It would appear that the initiation and location of cartilage damage and its rate and degree of progression are related to the relative stiffness of the underlying cancellous bone. On the basis of our observations we suggest that the diagnosis "chondromalacia of the patella" should be reserved for patients with asymptomatic or transiently symptomatic fibrillation of the articular cartilage of the central medial patellar facet. Those patients with persistent patellofemoral pain should be considered to have some other syndrome.

The assessment of life change stress: a comparative and methodological inquiry

A comprehensive life events questionnaire was administered to 416 men. Total life change scores were computed from published normative weights and from individuals' own ratings of events that occurred. The results showed that the rank order of life events was highly correlated between our sample and the original normative groups. However, in the population of men we studied, there were significant differences between the total life event scores derived by summing the published normative weights and the total adjustment or distress reported by those men who experienced the events. Other results indicated that life event scores based on normative weights reflect more on the number of life events that are experienced, whereas life change scores based on individuals' ratings may better reflect on the potential impact of life change. Finally, the psychometric properties of several life change inventories are poor.

Health change in air traffic controllers: a prospective study. I. Background and description

The background, rationale, and design of a 3-year prospective study of health change in 416 air traffic controllers is described. This study was designed to assess the relevant variables that might predict future physical and psychological health change. This report describes the major variables that were assessed in all participants, which included endocrine, cardiovascular, and behavioral differences in response to work, the occurrence of significant life events, work attitude and morale, availability and usefulness of psychosocial supports, and job commitment and performance. Future reports will describe the contribution, both individually and interactively, of these various factors to the risk for future illness. A major hypothesis to be tested by this study is that health change among air traffic controllers can be predicted by differential responsivity to work.

Effect of repetitive impulsive loading on the knee joints of rabbits

To simulate the forces from hopping, the right foot of adult rabbits was subjected to 1 1/2 the animal's body weight 40 times a minute for 20-40 minutes per day. During these brief periods of repetitive impulsive loading the legs were held in short-leg splints to eliminate the natural shock-absorbing mechanism associated with ankle dorsiflexion and calve muscle stretching. Under these conditions subchondral bone stiffening occurred and was associated with the earliest metabolic changes of cartilage damage. When bone stiffening returned to normal the effect on the cartilage did not completely disappear, although these effects diminished. The results suggested that subchondral bone stiffening accompanies the earliest metabolic changes in osteoarthrosic chondrocytes and suggests that trabecular microfracture may occur very early in this sequence of events.

Changes in testosterone and behavior during adolescence in the male rhesus monkey

Five adolescent male rhesus were followed for 3 years, from age 2 through age 4, with the collection of monthly testosterone levels, along with observation of behavior. Testosterone levels showed initial rises by age 3, but did not show the adult male seasonal pattern until 4. Play behavior fell significantly from age 2 to age 3, while sex behavior showed seasonal increases in both Year 2 and Year prior to the rise in plasma testosterone. The number of adult males in the social group may influence the timing of the rise in testosterone during adolescence. Injury may also serve to delay the increase in testosterone in males during their third year of development.

Diurnal variation in plasma testosterone and cortisol in rhesus monkeys living in social groups

Concentrations of cortisol and testosterone in the plasma of adult male rhesus monkeys living in social groups were determined during a 27-h period. Capture and venipuncture of experienced, conditioned animals did not lead to a fall in the concentration of testosterone in the plasma during the 90 min immediately after removal from the group. Both plasm cortisol and plasma testosterone concentrations showed a significant fall and rise in samples collected every 3 h during a 27-h period, even though there was considerable individual variation. During the autumn breeding season, animals showed higher concentrations of testosterone at both 10.00 and 22.00 h compared with those observed at the same times during the summer. Even though animals demonstrated significant diurnal changes, testosterone samples withdrawn at the same time of day (10.00 h) on consecutive days were significantly correlated with one another (r = 0.65, n = 27, P less than 0.01), suggesting the usefulness of sampling once a day to study potential environmental influences on plasma testosterone concentrations.

Behavioural and hormonal responses of male rhesus monkeys introduced to females in the breeding and non-breeding seasons

Six adult male rhesus monkeys were introduced individually to an all-female group for 10 days during the mating season. The initial aggressive responses of the females were rapidly replaced by positive social behaviour, and each male achieved alpha status and had access to social and sexual partners. A repetition of this paradigm in the non-breeding season produced significantly more female aggression, and no male attained high rank or engaged in sexual or other social behaviour. Male testosterone levels rose following introduction to the females in both seasons, but were significantly higher during the breeding season. Hormonal levels following removal from the females suggest a complex interplay between social, sexual and seasonal variables and recent social experiences. The differences in female social behaviour with newly introduced males, as a function of season, suggest an explanation for the seasonal limitation of male troop transfers.

Cortisol and growth hormone responses to psychological stress during the menstrual cycle

Twenty-one healthy women were studied during one menstrual cycle in order to determine whether cortisol and growth hormone responsivity to psychological stress was related to estrogen levels. Blood was drawn approximately three times per week for analysis of estradiol, progesterone, cortisol, and human growth hormone. During either the menstrual or intermenstrual phase, each subject participated in an interview that was designed to be mildly stressful. State and trait anxiety were assessed using the Spielberger State-Trait Anxiety Inventory. Anxiety state was measured prior to and immediately following exposure to the psychological stress; trait anxiety was assessed at the end of the study. Cortisol and growth hormone responses to the psychological stress were not related to menstrual cycle phase. Anxiety levels were also independent of menstrual cycle phase. Subjects who displayed significant cortisol and/or growth hormone responsivity to the interview had significantly higher anxiety levels post stress than did nonresponders, although anxiety level prior to the interview was not different for the two groups.

Structure and function of the human patella: the role of cancellous bone

Total joint and other prosthesis often require the removal and replacement of considerable quantities of cancellous bone, and often are anchored in place by grouting into cancellous bone. Thus, a possible source of failure or loosening of many types of prostheses may be rooted in the lack of understanding of the structure, properties, and function of this material. In addition, as we have pointed out before, cancellous bone may play an important biomechanical role in the etiology of joint degeneration. With these considerations in mind, the architecture of the cancellous bone in the human patella was studied by serial sectioning and microradiography, using an improved technique developed in our laboratory. Volumes of cancellous bone with apparently different functional roles were identified. Stereological techniques were used to quantify the structural characteristics and geometrical relationships throughout the patella. These results led to a structural model for the cancellous bone of the patella, and a comprehensive picture of the internal architecture. The distribution of mechanical compliance and yield stress was also measured, as a function of location and orientation, by a specially constructed microcompression testing machine. The measurements reflected the distribution of trabecular architecture, and both the properties and architecture reflected the gross biomechanical function of the patella. Furthermore, a true structure-function relationship was derived. Patellar contact area studies were performed on fresh cadavers and mapped for various angles of flexion. The variation in contact areas and the spatial variations in stiffness are discussed relative to the biomechanics and clinical aspects of the patella.

Analysis of burst activity of the buccal ganglion of Aplysia depilans

1. Certain nonlinear properties of molluscan neurones suggest that network activity could be described in relation to nonlinear relaxation oscillators. 2. A specific example is fitted by the Van der Pol equation with an exponentially decaying damping coefficient, and changes in the associated energy and sensitivity are considered. 3. More precise details of the interaction pattern determined by analysis of a single cycle of burst activity, and it is shown that there are two states of activity, depending on the balance of presumed inhibitory components. 4. Previous results are discussed in relation to an overall decaying oscillation. 5. Changes in subcomponents of a cycle are described for decaying sequences and the constancy of synaptic interaction is demonstrated. The results are briefly discussed in relation to catastrophe theory and learning.

Giant cell synovitis associated with failed polyethylene patellar replacements

Destroyed patellar articular surfaces were replaced with a high molecular weight polyethylene prosthesis in two patients. The patellofemoral articulation of the femur consisted of eburnated bone in one case and degenerative cartilage in the other. Both operations failed within one year because of a giant cell synovitis caused by a high volume (0.2 cc) of fine polyethylene (1-100 mu) wear particles. Ultra high molecular weight polyethylene should not be used as a prosthetic bearing surface to articulate against cortical, cancellous or eburnated bone or against degenerative articular cartilage in a major joint.

Sleep during transcendental meditation

Five experienced practitioners of transcendental meditation spent appreciable parts of meditation sesions in sleep stages 2, 3, and 4. Time spent in each sleep stage varied both between sessions for a given subject and between subjects. In addition, we compare electroencephalogram records made during meditation with those made during naps taken at the same time of day. The range of states observed during meditation does not support the view that meditation produces a single, unique state of consciousness.

"Stiction-friction" of total hip prostheses and its relationship to loosening

The static friction, or "stiction-friction", in McKee-Farrar and Charnley-Müller prostheses in a hip joint simulator was compared with dynamic friction determined while the prostheses were oscillated. Under physiological conditions stiction-friction differed little from dynamic friction in both metal-on-metal and metal-on-plastic prostheses, and was affected very little by the lubricant as long as some fluid was present. Stiction-friction increased significantly only after relatively long stationary periods and high loads. However, the frictional forces generated in total hip-replacement prostheses were at least forty times higher than those generated in normal joints and may well be enough to cause late loosening of acetabular components by fatigue failure.

Plasma cortisol and growth hormone responses to intravenous characterization

Plasma cortisol and growth hormone (HGH) responses to venous catheterization were studied in 29 volunteer subjects. Repeat characterizations were performed in 18 individuals. Mean plasma cortisol levels were significantly elevated during the first hour of the initial catheterization experience. Morning and afternoon levels of cortisol were not distinguishable during the first catheterization, but PM levels were significantly lower than AM levels during the second catheterization experience. Growth hormone responses were much more variable than cortisol and were distributed logarithmically. Growth hormone responses tended to parallel cortisol responses during the first catheterization experience. Individuals who listed more symptoms in response to venipuncture and catheterization after finishing their first catheterization had significantly higher cortisol and growth hormone levels during this experience. These data suggest a definite endocrine adaptation to catheterization by the second or third hour of the experience.

Consequences of social conflict on plasma testosterone levels in rhesus monkeys

Four adult male rhesus monkeys formed a new social group with 13 adult females. The male who became dominant [alpha] showed a progressive increase in plasma testosterone. The male who became subordinate to the other three males showed an 80% fall in testosterone from baseline levels. After 7 weeks, this group was introduced to a well-established breeding group, and all four males became subordinate to all members of the breeding group. All four males evidenced a fall in testosterone during the first week after introduction, and within 6 weeks their levels were approximately--80% of pre-introduction values. The alpha male of the breeding group showed a large increase in testosterone [238%] 24 hr after he successfully defended his group and became the dominant animal of the larger, newly-formed group. Thus, plasma testosterone levels appear to be significantly influenced by the outcome of conflict attendant to alterations in status of rhesus monkeys living in social groups.