Effects of pregnancy on muscarinic receptor density and function in the rabbit urinary bladder.

The contractile response of the rabbit urinary bladder to field stimulation consists of both cholinergic and purinergic components. In general, approximately 60% of the contractile response to field stimulation is cholinergic and 40% is purinergic. Although the purinergic response represents a significant proportion of the initial (phasic) pressure response to field stimulation of the isolated whole bladder, it contributes only 10-15% of the ability of field stimulation to empty the bladder. The current study investigates the effects of pregnancy on the contractile responses of the isolated urinary bladder to cholinergic and purinergic stimulation. The results of these studies indicate that pregnancy induces substantial changes in the physiology and pharmacology of the urinary bladder. The following data are consistent with the theory that pregnancy substantially increases the relative purinergic component of the response to field stimulation (and presumably neuronal stimulation): (1) there was a significantly greater response of the bladders isolated from pregnant rabbits to low-frequency field stimulation; (2) atropine was more effective at inhibiting the pressure generation of bladders isolated from virgin female rabbits; (3) field stimulation was more effective at emptying bladders isolated from virgin female rabbits; (4) the response of the bladders from pregnant rabbits to bethanechol was significantly reduced, whereas the response to ATP was significantly increased. In addition to these effects of pregnancy on bladder physiology, pregnancy induced a 50% decrease in the muscarinic receptor density of the urinary bladder body, which correlated very well with the 50% decrease in the contractile response to bethanechol.     

Surface of the brain: three-dimensional MR images created with volume rendering

Image processing and volume rendering have been applied to magnetic resonance (MR) images to produce three-dimensional views of the surface of the brain. Four healthy volunteers and 17 patients with a variety of disorders underwent MR imaging of the head, and these images were processed and subjected to volume rendering. The resulting three-dimensional views depict abnormalities of the brain surface, as well as important landmarks of normal brain surface anatomy such as precentral, postcentral, superior temporal, and inferior frontal gyri, which are difficult to identify on cross-sectional images.     

Procedural memory during posttraumatic amnesia in survivors of severe closed head injury. Implications for rehabilitation

To investigate the possibility that learning of skills (ie, procedural memory) is preserved during posttraumatic amnesia, 16 amnesic survivors of severe closed head injury and 16 control subjects were studied. Procedural learning tasks included mirror reading, mazes, and a pursuit rotor task that involved tracking a rotating target. Declarative memory was assessed by testing recognition of the words used in mirror reading and a questionnaire concerning details of the previous testing session. Learning was evaluated on 3 consecutive days and a fourth session was scheduled after resolution of posttraumatic amnesia. Despite stable impairment of declarative memory during posttraumatic amnesia, the performance of head-injured patients improved across sessions on all procedural tasks and showed transfer to testing after resolution of posttraumatic amnesia.     

Pharmacological comparison of the isolated whole urethra model to urethral strip methodology

Urethral strips provide a sensitive method for quantitative pharmacology; however, it is not clear if the physiological response of the whole urethra to pharmacological agents can be extrapolated from these data. The intent of this study was to investigate whether the linear contraction of strips is consistent with the ability of the intact urethra to alter resistance to flow. To measure the effect of drugs on the ability of the intact urethra to alter resistance to flow in the absence of endogenous influences, we developed an in vitro whole rabbit urethra model. We characterized the effect of norepinephrine in the absence and presence of alpha-adrenergic antagonists (prazosin, yohimbine, and LY253352) on intraurethral pressure which was measured during constant saline infusion using a Statham pressure transducer. We compared this to the contractile function of urethral strips. The pA2 values for alpha-adrenergic antagonists, LY253352, prazosin, and yohimbine were 8.17 +/- 1.5, 6.49 +/- 1.2, and 5.58 +/- 0.9, respectively, as determined in the whole urethra. The pA2 values for these antagonists determined in urethral strips were as follows: LY253352 8.72 +/- 1.2; prazosin 7.52 +/- 1.5, and yohimbine 5.6 +/- 0.84. Pharmacologically, the whole urethra model and isolated strips appeared to respond similarly to alpha-adrenergic agonists and antagonists, and thus both models would be suitable for pharmacological studies on the normal urethra.     

Language functions following closed-head injury in children and adolescents

Fifty-six children and adolescents who sustained a closed-head injury were divided into two groups based on neurological criteria. Language performance was assessed using the Neurosensory Center Comprehensive Examination for Aphasia during the subacute stage of recovery. Naming, expressive, and written language were more impaired than receptive-language functions. At least 20% of the sample exhibited deficits on measures of describing the function of objects, sentence repetition, verbal associative fluency, writing to dictation, and copying sentences. No sparing of function was observed in children relative to adolescents. Moreover, written-language performance was more depressed in children than adolescents. Results were discussed in terms of acquired aphasia in children and posttraumatic linguistic deficits in adults.     

A recurrent neural network: Limitations and training

A recurrent, synchronous neural network is treated as a collection of independent perceptrons. The dynamics of the network can be described by a mapping: a finite set of transitions in the state space of the network. We define legal mapping as a mapping that a synchronous neural network is able to perform, and state the necessary and sufficient conditions for a mapping to be legal. A learning algorithm for the network, based on the perceptron's learning algorithm, is guaranteed to converge to a solution when the network is trained to realize a legal mapping. It is shown that the algorithm performs a gradient descent search for a minimum of a cost function that is a certain error measure in the weight space. Performance of the algorithm for the associative memory application and for temporal sequences production is illustrated by numerical simulations. A method is proposed for legalizing any given mapping at the expense of adding a finite number of neurons to the network. It is also shown that when the number of transitions in a random mapping is less than the number of neurons in the network, the probability that such a mapping is legal approaches unity.     

The distribution and utilization of CNSs on Long Island

The present study provides a data base concerning the professional characteristics and various roles and functions of the CNS. Data for this survey research were collected by questionnaire and compared to the literature and ANA's National Survey of Clinical Nurse Specialists which was done in 1984. Results obtained from this research should serve as a springboard for further study of this essential role.