Coding proprioceptive information to control movement to a target: Simulation with a simple neural network

When the stick insect walks, the middle and rear legs step to positions immediately behind the tarsus of the adjacent rostral leg. Previous reports have described this movement to a target as a relationship between the tarsus positions of the two legs in a Cartesian coordinate system. However, leg proprioceptors measure the position of the target leg in terms of joint angles and leg muscles bring the tarsus of the moving leg to the proper end-point by establishing appropriate angles at the joints. Representation of this task in Cartesian coordinates requires non-linear coordinate transformations; realizing such a transformation in the nervous system appears to require many neurons. The present simulation using the back-propagation algorithm shows that a simple network of only nine units — 3 sensory input units, 3 motor output units, and 3 hidden units — suffices. The simulation also shows that an analytic coordinate transformation can be replaced by a direct association of joint configurations in the moving leg with those in the target leg.     

Home treatment for acute psychiatric illness.

OBJECTIVE--To determine the factors influencing the successful outcome of community treatment for severe acute psychiatric illnesses that are traditionally treated in hospital. DESIGN--All patients from a single electoral ward who were either admitted to hospital or treated at home over a two year period (1 October 1987 to 30 September 1989) were included in the study and their case notes audited. The second year of the study is reported. SETTING--Electoral ward of Sparkbrook, Birmingham. SUBJECTS--99 Patients aged 16-65 with severe acute psychiatric illness. RESULTS--65 Patients were managed by home treatment alone; 34 required admission to hospital. The location of treatment was significantly (all p less than 0.05) influenced by social characteristics of the patients (marital state, age (in men), ethnicity, and living alone) and by characteristics of the referral (occurring out of hours; assessment taking place at hospital or police station). DSM-III-R diagnosis was more weakly associated with outcome. Violence during the episode was significantly related to admission, although deliberate self harm was not. CONCLUSIONS--Home treatment is feasible for most patients with acute psychiatric illness. A 24 hour on call assessment service increases the likelihood of success because admission is determined more strongly by social characteristics of the patient and the referral than by illness factors. Admission will still be required for some patients. A locally based mental health resource centre, a 24 hour on call service, an open referral system, and an active follow up policy increase the effectiveness of a home treatment service.     

Adoptive cell transfer studies to examine the role of T lymphocytes in immunity to Trypanosoma musculi

Previous studies in this laboratory utilizing monoclonal antibody-induced immunosuppression have demonstrated that the T-helper lymphocyte is primarily responsible for the T lymphocyte dependency of Trypanosoma musculi elimination from the bloodstream of mice, and that T-cytotoxic lymphocytes play a minimal role in this response. In the current study, these findings were extended by examining the effects of adoptive cell transfers on the course of infection with T. musculi using immune splenocytes enriched for T lymphocyte subpopulations. These studies demonstrated that adoptive transfer of immune splenic T lymphocytes resulted in a specific, dose-related enhancement of kinetics of trypanosome elimination. This effect was found to be due to the presence of L3T4+ T-helper cells in the immune splenocyte population. Adoptive transfer of Lyt-2+ T-cytotoxic cells or lymphokine-activated killer (LAK) cells was ineffective in altering the course of infection. In addition, it was found that immune B lymphocytes were equally capable of adoptively transferring immunity to T. musculi, suggesting that the primary role of the T-helper lymphocyte is to provide help in the induction of parasite-specific antibodies.     

Bias in leaf area — sapwood area ratios and its impact on growth analysis in Pinus contorta

Summary Two alternative estimators of individual tree leaf area (A₁) area are used to derive estimates of leaf-area index (L) for 40 plots in Pinus contorta Dougl. stands. One estimator of A₁ is based on the common assumption of a constant ratio between A₁ and sapwood cross-sectional area at breast height (A_s). The second estimator of A₁ accounts for tree-to-tree variation in the relation between A₁ and A_s. The apparent relationship between stand growth and leaf-area index is strongly dependent on the way leaf area is estimated. When L is derived from a constant A₁A_s ratio, stand growth appears to be strongly correlated with L. However, when L is based on estmates of A₁ that account for tree-to-tree variation in the A₁ — A_s relation, stand growth is seen to be only weakly related to L. Stand structure, quantified as percent live-crown, accounts for a great deal of the observed variation in leaf-area efficiency. These contrasting relationships illustrate the importance of unbiased estimates of L in interpreting the link between stand-level processes and leaf area.Utah Aggriculural Experiment Station Journal Paper No. 3333     

Age and growth of tarpon,Megalops atlanticus,larvae in the eastern Gulf of Mexico,with notes on relative abundance and probable spawning areas

Synopsis Leptocephali were collected in June 1981 and July 1989 over the continental shelf and slope of the Florida west coast. Tarpon larvae ranged 5.5–24.4 mm standard length (SL) and were the second most abundant leptocephalus species. Sagittae examined with compound microscopes and scanning electron microscopy had increments that were presumed to be formed daily. Increment counts made using the two microscopic techniques were not significantly different. Estimated ages ranged 2–25 days with a growth rate (± standard error) of 0.92 ± 0.04 mm d^–1 The least squares linear regression equation SL = 2.78 + 0.92 (age in days) best described the relationship between estimated age and length. Adult tarpon appear to undergo a substantial spawning migration from inshore areas frequented during spring and summer to offshore spawning grounds. Spawning occurs during May, June, and July, although the spawning season may be of greater duration.     

Glucocorticoid, interleukin-2, and prostaglandin interactions in a clonal human leukemic T-cell line.

We have studied the growth effects of conditioned media, interleukin-2 and PGE prostaglandin analogs on the glucocorticoid-sensitive human leukemic T-cell clone, CEM-C7. After 4 days, the glucocorticoid dexamethasone at approximately 10 nM kills 50% of CEM-C7 cells. To test the hypothesis that glucocorticoid-mediated lymphocytolysis was due to suppression of lymphokine expression only, we attempted to protect CEM-C7 cells from lysis by provision of lymphokine(s). Conditioned media from interleukin-2 secreting Jurkat T-cells as well as the glucocorticoid-insensitive, but receptor positive clone, CEM-C1, failed to prevent lymphocytolysis; exogenous interleukin-2 also did not provide protection. There were complex, biphasic interactions between dexamethasone and the synthetic PGEs, enisoprost and enisoprost free acid. Low doses of enisoprost alone (0.01 to 1 microgram/ml) stimulated growth, and in combinations completely reversed the growth inhibitory effects of 10 nM dexamethasone. Higher concentrations of enisoprost were inherently lethal and were additive to the steroid effect. Thus the glucocorticoid-induced lymphocytolysis in this human leukemic T-cell line may be modified biphasically by PGE prostaglandins, depending on their concentration. However, interleukin-2 or components in the conditioned media assayed had no effect in ameliorating the lethal response to glucocorticoid.