Design and synthesis of m1-selective muscarinic agonists: (R)-(-)-(Z)-1-Azabicyclo[2.2.1]heptan-3-one, O-(3-(3'-methoxyphenyl)-2-propynyl)oxime maleate (CI-1017), a functionally m1-selective muscarinic agonist.

The synthesis and SAR of a series of (Z)-(+/-)-1-azabicyclo[2.2. 1]heptan-3-one, O-(3-aryl-2-propynyl)oximes are described. The biochemistry and pharmacology of 24Z (PD 142505) and its enantiomers are highlighted. 24Z is functionally an m1-selective muscarinic agonist. Efficacy and m1 selectivity reside in the R enantiomer, (R)-24Z (CI-1017).

Analysis of indications for intensive care unit admission. Clinical efficacy assessment project: American College of Physicians.

OBJECTIVE: To formulate recommendations for the development of intensive care unit (ICU) admission policies. DESIGN: Literature review of published reports over the period 1966 to 1991 pertaining to admission criteria for intensive care or coronary care units (CCUs). PATIENTS: Studies identifying patients least likely to benefit from ICU or CCU admission were analyzed. Patient populations of interest included adults (> or = 18 years of age) with medical conditions possibly requiring intensive care; trauma patients were excluded. MEASUREMENTS AND MAIN RESULTS: Of 970 articles identified as being pertinent to intensive care, only two case-control studies used the direct method of measuring the effect of ICU intervention on mortality. No studies were found that compared outcomes of low-risk patients treated in a CCU vs those treated in alternative hospital locations, and none identified patients with a very high probability of a bad outcome. CONCLUSIONS: The use of decision-making models for ICU and CCU admissions must be tested in prospective, randomized clinical trials. Critical care units and ICUs should be studied separately. Existing studies of early discharge from CCUs need to be summarized and evaluated. The triaging of ICU patients to alternative hospital locations needs to be evaluated, as do existing predictive models for early triage decision-making.

Analysis of indications for early discharge from the intensive care unit. Clinical efficacy assessment project: American College of Physicians.

OBJECTIVE: To formulate recommendations for the development of early intensive care unit (ICU) discharge criteria for low-risk monitor patients. DESIGN: Literature review of published reports over the period 1966 to 1991 pertaining to ICU discharge criteria. PATIENTS: Studies identifying patients admitted to ICUs who could be characterized as low risk. Patient populations of interest included adults (> or = 18 years of age) with low-risk medical or mixed medical/surgical conditions; cardiac care unit and burn patients were excluded. MEASUREMENTS AND MAIN RESULTS: Of 1,492 articles identified as being pertinent to ICU discharge, only 2 studies (by the same group of investigators) were found that distinguished low-risk populations among medical and mixed medical/surgical ICU patients. The physiologic component of the Acute Physiology and Chronic Health Evaluation (APACHE) was used in both of these studies to ascertain the degree of risk. No studies were found that compared outcomes of low-risk patients remaining in the ICU after 24 h with those transferred to other hospital locations. CONCLUSIONS: Objective methods (such as APACHE III) should be used to identify low-risk patients at 24 h post-ICU admission. A multicenter study should be conducted to compare outcomes on patients identified as low risk who are randomly assigned to alternative hospital locations for treatment versus those assigned to continued ICU treatment until routine ICU discharge. Mortality and quality of life data should be used as outcome measures (prior to ICU admission and 6 months post-ICU discharge).

Muscarinic acetylcholine receptor subtypes: localization and structure/function.

Based on the sequence of the five cloned muscarinic receptor subtypes (m1-m5), subtype selective antibody and cDNA probes have been prepared. Use of these probes has demonstrated that each of the five subtypes has a markedly distinct distribution within the brain and among peripheral tissues. The distributions of these subtypes and their potential physiological roles are discussed. By use of molecular genetic manipulation of cloned muscarinic receptor cDNAs, the regions of muscarinic receptors that specify G-protein coupling and ligand binding have been defined in several recent studies. Overall, these studies have shown that amino acids within the third cytoplasmic loop of the receptors define their selectivities for different G-proteins and that multiple discontinuous epitopes contribute to their selectivities for different ligands. The residues that contribute to ligand binding and G-protein coupling are described, as well as the implied structures of these functional domains.

In vitro and in vivo evaluation of the subtype-selective muscarinic agonist PD 151832.

PD 151832 is a potent partial muscarinic agonist that displays a high level of functional selectivity for the muscarinic m1 receptor subtype, as evidenced by its selective stimulation of PI turnover and cellular metabolic activity in transfected Hm1-CHO cells at concentrations that produce minimal stimulation of other cloned human muscarinic receptors. PD 151832 enhanced the amplification of Hm1-transfected NIH-3T3 cells at concentrations lower than those required to produce similar effects in Hm2 or Hm3-transfected cells. The functional m1 selectivity of PD 151832 is consistent with its improvement of mouse water maze performance at doses far lower than those required to produce peripheral parasympathetic side effects.

Follow-up of patients with saphenous vein bypass grafts for angina pectoris.

These studies are in agreement with others that aortocoronary vein grafts done for severe angina pectoris are associated with a low operative and late mortality rate. Most patients were significantly improved in regard to pain and exercise tolerance. "Optimal" graft site is associated with a graft patency rate of about 90 per cent. There is clear evidence that left ventricular function, particularly with exercise, is improved in some patients. When a graft is placed in an obstructed coronary artery supplying a segment of abnormally contracting myocardium, there frequently is significant improvement of contraction when the graft remains patent.

The basis and basics of mechanical ventilation.

The development of mechanical ventilators and the procedures for their application began with the simple foot pump developed by Fell O'Dwyer in 1888. Ventilators have progressed through three generations, beginning with intermittent positive pressure breathing units such as the Bird and Bennett device in the 1960s. These were followed by second-generation units--represented by the Bennett MA-2 ventilator--in the 1970s, and the third-generation microprocessor-controlled units of today. During this evolutionary process clinicians recognized Types I and II respiratory failure as being indicators for mechanical ventilatory support. More recently investigators have expanded, clarified, and clinically applied the physiology of the work of breathing (described by Julius Comroe and other pioneers) to muscle fatigue, requiring ventilatory support. A ventilator classification system can help the clinician understand how ventilators function and under what conditions they may fail to operate as desired. Pressure-support ventilation is an example of how industry has responded to a clinical need--that is, to unload the work of breathing. All positive pressure ventilators generate tidal volumes by using power sources such as medical gas cylinders, air compressors, electrically driven turbines, or piston driven motors. Positive end-expiratory pressures, synchronized intermittent mandatory ventilation, pressure support ventilation, pressure release ventilation, and mandatory minute ventilation, are examples of the special functions available on modern ventilators. Modern third-generation ventilators use microprocessors to control operational functions and monitors. Because these units have incorporated the experience learned from earlier ventilators, it is imperative that clinicians understand basic ventilator operation and application in order to most effectively prescribe and assess their use.

NFATc3 regulates BK channel function in murine urinary bladder smooth muscle.

The nuclear factor of activated T-cells (NFAT) is a Ca(2+)-dependent transcription factor that has been reported to regulate the expression of smooth muscle contractile proteins and ion channels. Here we report that large conductance Ca(2+)-sensitive potassium (BK) channels and voltage-gated K(+) (K(V)) channels may be regulatory targets of NFATc3 in urinary bladder smooth muscle (UBSM). UBSM myocytes from NFATc3-null mice displayed a reduction in iberiotoxin (IBTX)-sensitive BK currents, a decrease in mRNA for the pore-forming alpha-subunit of the BK channel, and a reduction in BK channel density compared with myocytes from wild-type mice. Tetraethylammonium chloride-sensitive K(V) currents were elevated in UBSM myocytes from NFATc3-null mice, as was mRNA for the Shab family member K(V)2.1. Despite K(V) current upregulation, bladder strips from NFATc3-null mice displayed an elevated contractile response to electrical field stimulation relative to strips from wild-type mice, but this difference was abrogated in the presence of the BK channel blocker IBTX. These results support a role for the transcription factor NFATc3 in regulating UBSM contractility, primarily through an NFATc3-dependent increase in BK channel activity.

Understanding and operating the Bennett MA-1 ventilator. Tips on adjusting the controls to avoid problems.

The Bennett MA-1 ventilator is a volume-cycled, constant flow generator that can act as an assistor, controller, or assist-controller. It is one of the most commonly used ventilators in clinical practice. With this unit, inspiration continues until a preset tidal volume is delivered to the patient--unless impedances to gas flow increase system pressures to a preselected limit. Thus, setting the maximum inspiratory pressure too low limits the ability of the ventilator to deliver the tidal volume, causing it to function as a pressure-cycled device. Other basic controls allow you to establish the sensitivity of the ventilator to spontaneous breathing attempts, the maximum flow rate, the frequency of respirations, and the oxygen percentage. Special controls permit delivery of a sigh breath and slowing of exhalation.

A clinician's guide to ventilators: how they work and why they can fail. A classification system to make sense of available options.

To select a ventilator (or a ventilatory mode), consider the most basic characteristics: How is tidal volume generated (with a constant or nonconstant flow or pressure generator)? How does the ventilator trigger a changeover from exhalation to inhalation and cycle back to exhalation? How is tidal volume delivered to the patient (either directly from a power source or indirectly from an intermediate chamber)? What special functions are available? The answers to these questions will not only let you make the best selection but will also help you troubleshoot when a ventilator fails to function properly.

Second- and third-generation ventilators: sorting through available options. When, and for which patients, are special functions needed?

Currently available ventilators offer a number of special options to meet the needs of critically ill patients. Intermittent mandatory ventilation allows a patient to breathe spontaneously without assistance. CPAP and PEEP ensure that the patient breathes at an elevated pressure either constantly or during expiration. Pressure support ventilation allows patients to participate in breathing but provides inspiratory assistance and is most useful during weaning. Airway pressure release ventilation facilitates venous return and decreases airway pressure. Sophisticated monitors provide detailed information on the patient's status, but alarm features are somewhat unreliable. Thorough knowledge of the controls on modern ventilators can help you provide the optimum form of respiratory support.

The technique of instituting mechanical ventilation. Patient preparation; endotracheal intubation; monitoring.

Potential indications for mechanical ventilation include hypoxemia unresponsive to oxygen administration, hypercapnia resulting in acidemia, and an unstable chest wall. For best results, carefully prepare the patient (both physically and emotionally) before instituting ventilation. Sedatives and local anesthesia can facilitate intubation; avoid paralytic agents unless you are experienced at intubation. The oral route is most commonly used. Once the patient circuit is attached to the endotracheal tube, reexamine the patient and double-check the inspiratory flow and I:E ratio; adjust the ventilator's settings as necessary. Monitor the patient frequently to ascertain the adequacy of alveolar ventilation and arterial oxygen.

Beyond the basics: operating the new generation of ventilator. A look at the features and functions of these units.

Most modern ventilators have several key features in common: microprocessor control of operational and monitoring functions; electromechanical valves to control and adjust gas flow patterns; and extensive monitoring systems. In addition, these machines can provide a number of different modes of ventilation (including pressure support). Though not microprocessor-controlled, the Siemens Servo 900 series ventilators use feedback electronics to adjust inspiratory flow based on expiratory flow to meet preset volumes. In contrast, the Bennett 7200 units use microprocessor-regulated solenoid valves to deliver preset tidal volume. High-frequency ventilators deliver smaller tidal volumes at rates greater than 60 bpm.

Techniques for weaning a patient from mechanical ventilation; when to begin, what method to use, and how to predict outcome.

A variety of methods have been employed to help wean patients from prolonged ventilatory support. Although synchronized intermittent mandatory ventilation is probably the most widely used, it has not been shown to be clearly superior to T piece or pressure support weaning. Regardless of the method you choose, begin weaning before the patient's lung function has returned to normal or baseline levels and end when the patient shows the minimum capacity necessary to sustain himself off the ventilator. The patient's response to the change in the level of ventilatory support governs the rapidity of weaning. The rapid shallow breathing index can be useful in predicting weaning outcome, as is the patient's ability to tolerate a weaning trial.

von Willebrand factor is a cofactor for thrombin-catalyzed cleavage of the factor VIII light chain.

The proteolytic activation of highly purified, heterodimeric porcine factor VIII and factor VIII-von Willebrand factor complex by thrombin was compared at I 0.17, pH 7.0, 22 degrees C. During the activation of factor VIII, heavy-chain cleavage is necessary to activate the procoagulant function, whereas light-chain cleavage is required to dissociate factor VIII from von Willebrand factor. The kinetics of activation of free factor VIII and factor VIII-von Willebrand factor complex were identical. The steady-state kinetics of thrombin-catalyzed heavy-chain cleavages and light-chain cleavage of factor VIII either free or in complex with von Willebrand factor were studied using sodium dodecyl sulfate-polyacrylamide gel radioelectrophoresis and scanning densitometry of fragments derived from 125I-labeled factor VIII. Association of factor VIII with von Willebrand factor resulted in an 8-fold increase in the catalytic efficiency (kcat/Km) of light-chain cleavage (from 7 x 10(6) to 54 x 10(6) M-1 s-1). The catalytic efficiencies of heavy-chain cleavage at position 372 (approximately 6 x 10(6) M-1 s-1) and position 740 (approximately 100 x 10(6) M-1 s-1) were not affected by von Willebrand factor. We conclude that von Willebrand factor promotes cleavage of the factor VIII light chain by thrombin which is followed by rapid dissociation of the complex, so that the rate-limiting step becomes heavy-chain cleavage at position 372. This accounts for the observation that von Willebrand factor has no effect on the kinetics of activation of factor VIII by thrombin.

High throughput assays of cloned adrenergic, muscarinic, neurokinin, and neurotrophin receptors in living mammalian cells.

Many receptors stimulate proliferation of NIH 3T3 cells in a ligand dependent fashion. Based on this observation, we developed a high throughput assay of cloned receptor pharmacology. In this assay, receptors are transiently co-expressed with the marker enzyme beta-galactosidase. Receptors that induce cellular proliferation select and amplify the cells that also express the marker, thus the ability of ligands to alter receptor activity are reported as changes in enzyme activity. In the present study, we used this assay to evaluate the ability of agonist ligands to stimulate four cloned receptors. The agonists phenylephrine, carbachol, substance P and nerve growth factor selectively stimulated cells transfected with the alpha-1b adrenergic, m4 muscarinic, NK1 neurokinin and trkA neurotrophin receptors, respectively. These data demonstrate that a high throughput colorimetric assay performed in 96 well plates can be used to evaluate the pharmacology of ligands for cloned receptors belonging to a wide range of functional and pharmacological classes.

Characterization of in vitro deoxyribonucleic acid breakage and cross-linking induced by bis-isopropylamine)-trans-dihydroxy-cis-dichloroplatinum(IV).

Bis(isopropylamine)-trans-dihydroxy-cis-dichloroplatinum(IV) (CHIP or JM-9), a derivative of Cisplatin, was found to have DNA breakage and interstrand cross-linking activities in vitro. DNA breakage was detected by alkaline and neutral sucrose gradient analysis, agarose gel electrophoresis, and alkaline ethidium bromide fluorescence assay employing covalently closed circular PM2 DNA. DNA cross-linking activity was detected by alkaline sucrose gradient analysis and by the "snap-back" assay employing PM2 DNAs. Non-sulfhydryl-containing reducing agents, e.g., NaBH4 and NADPH, stimulated both cross-linking and breakage activities. Alkaline buffers, cyanide, or sulfhydryl group containing agents inhibited both types of activities. The hydroxyl free radical scavenger sodium benzoate (100 mM) was found to inhibit 99% and 25% of DNA breakage and cross-linking activities, respectively, suggesting DNA breakage and cross-linking may be independently mediated.