Neuropeptide Y action in the rat hippocampal slice: site and mechanism of presynaptic inhibition

Neuropeptide Y (NPY), the most abundant peptide in mammalian CNS, has been shown to inhibit excitatory neurotransmission presynaptically at the stratum radiatum-CA1 synapse in the in vitro rat hippocampal slice. We examined the site and mechanism of this inhibition in a series of in vitro intra- and extracellular recordings in areas CA1 and CA3, the source of much of the excitatory synaptic input to the CA1 neurons. NPY's inhibitory action at the stratum radiatum-CA1 synapse was unaffected by high concentrations of the antagonists bicuculline, theophylline, or atropine, suggesting that it does not act by stimulating the release of the known presynaptic inhibitory transmitters GABA, adenosine, or ACh, respectively. Bath application of 10(-6) NPY, a concentration that strongly inhibited the stratum radiatum-CA1 synapse had no effect on CA3 neuron resting potential, input resistance or action potential amplitude, threshold, or duration. NPY also does not alter the amplitude or duration of the prolonged CA3 action potentials evoked in the presence of TTX, tetraethyl-ammonium, and elevated external Ca2+ or those evoked in the presence of TTX and Ba2+ ions. NPY therefore does not alter the passive or active properties of the somata of the presynaptic CA3 neurons. Neither the afferent fiber volley of the Schaffer collaterals in stratum radiatum of area CA1 nor the excitability of the CA3 terminals in CA1 was affected by NPY application. However, application of the transient K+ current blocker, 4-aminopyridine (4-AP) at concentrations of 10 and 50 microM, completely abolished the action of 10(-6) M NPY on the stratum radiatum-CA1 excitatory synaptic potentials. This action of 4-AP could be reversed by reducing extracellular Ca2+ concentrations from a control level of 1.5 to 0.7 mM (in 10 microM 4-AP) and to 0.5 mM (in 50 microM 4-AP). The evidence suggests that NPY inhibits excitatory synaptic transmission at the Schaffer collateral-CA1 synapse by acting directly at the terminal to reduce a Ca2+ influx.     

Percutaneous transluminal coronary angioplasty. A growing surgical problem

The incidence of prior percutaneous transluminal coronary angioplasty in surgical cases is nearly doubling yearly. In 1985, 11.4% of our bypass patients had one or more prior angioplasties. One hundred thirty-five patients with prior angioplasty are compared to 2,205 patients without angioplasty undergoing surgical revascularization. The mortality is 3.2 times higher in the angioplasty patients than in the control patients and the perioperative infarction rate is 2.5 times higher. Forty-four patients were taken directly to the operating room from the catheterization laboratory, 50 were operated on within 10 days, and 41 underwent operation more than 10 days after angioplasty. All of these late failures were of the lesion previously dilated. The infarction rate was less in patients taken immediately to the operating room on an emergency basis than in those whose operation was delayed up to 10 days (30% versus 70%). All patients who died had angioplasty of the anterior descending coronary artery. Angioplasty of this artery increases operative mortality should surgical treatment become necessary acutely. Patients should be informed before angioplasty of the increased surgical risks after a failed angioplasty procedure.     

Investigation of an artificial intelligence technology--Model trees. Novel applications for an immediate release tablet formulation database.

This study has investigated an artificial intelligence technology - model trees - as a modelling tool applied to an immediate release tablet formulation database. The modelling performance was compared with artificial neural networks that have been well established and widely applied in the pharmaceutical product formulation fields. The predictability of generated models was validated on unseen data and judged by correlation coefficient R(2). Output from the model tree analyses produced multivariate linear equations which predicted tablet tensile strength, disintegration time, and drug dissolution profiles of similar quality to neural network models. However, additional and valuable knowledge hidden in the formulation database was extracted from these equations. It is concluded that, as a transparent technology, model trees are useful tools to formulators.     

Toluene vapor exposure and urinary excretion of hippuric acid among workers in China.

A factory survey was conducted in three provinces in China from 1985 to 1989. The time-weighted average toluene concentrations in breathing zone air were monitored by diffusive sampling, whereas hippuric acid (HA) concentrations in shift-end urine samples were measured by high performance liquid chromatography (HPLC). Exposed workers (456 men and women) were those for whom toluene (up to 548 ppm toluene) accounted for greater than or equal to 90% of total exposure (by vapor concentration in ppm), whereas 517 nonexposed controls were recruited from the same factories or from factories of the same region. There was a linear correlation between the intensity of toluene exposure and HA concentration in the shift-end urine. Comparison of the results with findings in the literature shows that the toluene-induced increase in urinary HA concentration among workers in China is significantly smaller than the published values, whereas HA concentrations in urine samples from nonexposed controls are comparable to the levels previously reported.     

Resuscitation in northern Iraq.

The principles of Advanced Trauma Life Support (ATLS) were adopted by a Royal Navy surgical team deployed to northern Iraq. Over a 6-week period, 18 casualties of both military and civil trauma required active resuscitation, 10 being under the age of 16 years. Triage of multiple casualties was necessary on three occasions. Two patients died. It was difficult to exclude cervical spine injury. Venous cut-down was frequently unsuccessful, so that internal jugular vein cannulation was life-saving. Crystalloid was used as the primary infusion without apparent disadvantage. Cross-matched blood was unavailable and one patient died with haemolysis after massive transfusion. Hypothermia was a problem despite the high environmental temperature. Laboratory and radiological facilities were extremely limited. Non-medical staff were trained most effectively to assess vital signs, although sophisticated monitors became available. These problems are discussed and compared with previous experience. Recommendations are made to improve future outcome.     

Nitric oxide: a revolution of free radicals theory of aging

There are two kinds of free radicals in the aging process, 'bad' and 'good'. Nitric oxide is a good free radical.     

Further studies on interactions between periaqueductal gray, nucleus accumbens and habenula in antinociception.

Previous findings from this laboratory with the intracerebral microinjection technique suggested that the periaqueductal gray (PAG), nucleus accumbens, and habenula might constitute a unidirectional loop to play their roles in pain modulation. In the present study we demonstrate that intra-habenular injection of naloxone antagonizes the analgesia elicited by morphine injected into the periaqueductal gray (PAG) and that intra-accumbens injection of naloxone is capable of attenuating the analgesic effects of morphine injected into the habenula. These results indicate that the relationships between these nuclei may be more complex than the putative unidirectional loop.