A new method for determining levels of sedation in dogs: A pilot study with propofol and a novel neuroactive steroid anesthetic.

BACKGROUND: Different levels of consciousness are required in order to perform different medical procedures. Sedation scales established to objectively define various levels of sedation in humans have not been thoroughly characterized in non-human species. Postural changes in rats or dogs are useful as gross measures of sedation but are inadequate for quantitative assessment since graded levels of sedation are difficult to delineate and obscured by movement abnormalities. NEW METHOD: A new canine sedation scoring (CSS) method was developed based on the modified observer's assessment of alertness and sedation score (MOAA/S) used in humans. The method employed a combination of physical, auditory and somatosensory stimuli of increasing intensity. Cardiovascular, respiratory, and a neurophysiological measure of sedation (bispectral index: BIS) data were recorded. Validation studies were performed following intravenous loading and constant rate infusion of propofol or a novel synthetic neuroactive steroid (SGE-746). RESULTS: Four levels of consciousness were identified: 1) Awake, 2) Moderate Sedation (MS), 3) Deep Sedation (DS) and 4) General Anesthesia (GA). Cardiorespiratory measurements obtained after bolus administration of propofol and SGE-746 and at the end of each CRI remained within normal limits. Canine sedation scores correlated with BIS for SGE-746. SGE-746 exhibited a more gradual exposure-response relationship than propofol. Larger increases in the plasma concentration from awake values were required to achieve different levels of sedation with SGE-746 compared to propofol. COMPARISON WITH EXISTING METHODS: No other canine sedation scoring methods are widely accepted. CONCLUSION: A CSS method, based on the human MOAA/S scale defined four levels of consciousness in dogs and provided better resolution of sedation depth than BIS alone.

Long-term depression in hippocampal interneurons: joint requirement for pre- and postsynaptic events.

Long-term depression (LTD) is a well-known form of synaptic plasticity of principal neurons in the mammalian brain. Whether such changes occur in interneurons is still controversial. CA3 hippocampal interneurons expressing Ca2+-permeable AMPA receptors exhibited LTD after tetanic stimulation of CA3 excitatory inputs. LTD was independent of NMDA receptors and required both Ca2+ influx through postsynaptic AMPA receptors and activation of presynaptic mGluR7-like receptors. These results point to the capability of interneurons to undergo plastic changes of synaptic strength through joint activation of pre- and postsynaptic glutamate receptors.

Phenylethanolamines inhibit NMDA receptors by enhancing proton inhibition.

The phenylethanolamines, ifenprodil and CP-101,606, are NMDA receptor antagonists with promising neuroprotective properties. In recombinant NMDA receptors expressed in Xenopus oocytes, we found that these drugs inhibit NMDA receptors through a unique mechanism, making the receptor more sensitive to inhibition by protons, an endogenous negative modulator. These findings support a critical role for the proton sensor in gating the NMDA receptor and point the way to identifying a context-dependent NMDA receptor antagonist that is inactive at physiological pH, but is a potent inhibitor during the acidic conditions that arise during epilepsy, ischemia and brain trauma.

Comparative analysis of Native admissions and registrations to northwestern Ontario treatment facilities: hospital and community sectors.

OBJECTIVE: To study Native and non-Native admissions to acute psychiatric care in the northwestern region of Ontario in 1992. METHOD: To replicate a 1986 to 1987 study comparing Native to non-Native admissions to acute psychiatric care in the northwestern region of Ontario in 1992 and examine Native registrations to community mental health agencies in the first 6 months of 1993. RESULTS: The comparative analysis of hospital admissions revealed that: Natives are still being admitted at 33% more than the rate expected on the basis of population; depression appears to be underdiagnosed for Natives; they continue to be admitted mainly for reasons other than major psychiatric conditions; substance abuse and forensic history are commonly involved; they stay in hospital for twice as long as their non-Native control; they more often come from rural settings; and they are less likely to be followed by the outpatient service and more likely to be followed by the criminal justice system. The examination of registrations to community mental health agencies revealed that: the same overrepresentation of Natives; mood- and thought-presenting problems of Natives in this sector were identical to non-Natives; and their length of stay was similar. The psychiatric hospital appears to be providing acute care treatment, not for the serious psychiatric illnesses for which it is mandated, but for atypical admissions that result from economic, social and cultural dislocation. There may be underdiagnosis of atypical depression in the Native hospitalized population. When asked what they are being treated for the diagnostic profile of Natives and non-Natives is identical on mood and thought dimensions. CONCLUSION: No appreciable change has occurred over the 5 years in the way hospital psychiatric services are used by Natives. Cultural stereotypes may be influencing the diagnosis of Natives in inappropriate ways. Enhancing Native control of treatment programs and community development may provide a partial solution. Properly mandated and accountable community agencies (both generic- and culture-specific) will help reduce unnecessary hospitalization.

Recovery of Pseudomonas aeruginosa in respiratory specimens from HIV positive patients being evaluated for Pneumocystis carinii pneumonia.

BACKGROUND: Despite the immune suppression, frequent hospital admissions, and many intercurrent illnesses associated with HIV infection, Pseudomonas aeruginosa has been cited relatively infrequently as a respiratory pathogen in HIV positive patients. METHODS: The microbiological isolates, medical records, radiographic reports, and laboratory data from 224 patients undergoing sputum induction and/or bronchoalveolar lavage for evaluation of respiratory symptoms suspicious for Pneumocystis carinii pneumonia (PCP) from 1989 to 1992 were reviewed retrospectively. RESULTS: An increasing number of respiratory isolates with Pseudomonas aeruginosa was found over this time period. Eighteen of the 224 patients were identified in whom P aeruginosa was recovered on at least one occasion. These patients were more likely to have a history of smoking and prior PCP than those in whom Pseudomonas was not recovered. Mean CD4 counts were also significantly lower in these patients. CONCLUSIONS: Pseudomonas aeruginosa may be recovered from a substantial number of respiratory isolates from HIV positive patients suspected of having PCP. The prevalence of this phenomenon may be increasing.

Record linkage in a regional mental health planning study: accuracy of unique identifiers, reliability of sociodemographics, and estimating identification error.

Assembling information about individuals over time allows health managers and researchers to describe the progression of diseases, the care history of individuals and the sequences of care episodes that potentially result in improving individuals' health status. However, current mental health statistics generally focus on sets of events rather than groups of individuals making it impossible to distinguish between two different persons being admitted and the same person being admitted twice. Accurate figures on treatment prevalence cannot be generated and multiservice users across time or across agencies will inflate the statistics used to plan needed services. The capacity to link consistently defined bits of information together is critical to developing a reliable information system. This article examines the adequacy of using unique identifier codes to accomplish linkage by focusing on one example of record linkage that incorporates mental health information from both community and institutional sectors in one region of Ontario, Canada. Findings indicate that unique "cradle to grave" identifiers do not guarantee accuracy if manual transcription is involved.

Oxygen may improve dyspnea and endurance in patients with chronic obstructive pulmonary disease and only mild hypoxemia.

Oxygen (O2) has been reported to improve exercise tolerance in some patients with chronic obstructive pulmonary disease (COPD) despite only mild resting hypoxemia (PaO2 greater than 60 mm Hg). To confirm these prior studies and evaluate potential mechanisms of benefit, we measured dyspnea scores by numeric rating scale during cycle ergometry endurance testing and correlated the severity of dyspnea with right ventricular systolic pressure (RVSP) measured by Doppler echocardiography during a separate supine incremental exercise test. Both sets of exercise were performed according to a randomized double-blind crossover protocol in which patients breathed compressed air or 40% O2. We studied 12 patients with severe COPD (FEV1 0.89 +/- 0.09 L [mean +/- SEM], FEV1/FVC 37 +/- 2%, DLCO 9.8 +/- 1.5 ml/min/mm Hg[47% of predicted], PaO2 71 +/- 2.6 mm Hg). With endurance testing on compressed air, PaO2 did not change significantly in the group as whole (postexercise PaO2 63 +/- 5.1 mm Hg, p = NS), but did fall to less than 55 mm Hg in four patients from this group. Duration of exercise increased on 40% O2 from 10.3 +/- 1.6 to 14.2 +/- 1.5 min (p = 0.005), and the rise in dyspnea scores was delayed. Oxygen delayed the rise in RVSP with incremental exercise in all patients and lowered the mean RVSP at maximum exercise from 71 +/- 8 to 64 +/- 7 mm Hg (p less than 0.03). Improvement in duration of exercise correlated with decrease in dyspnea (r2 = 0.66, p = 0.001) but not with decreases in heart rate, minute ventilation, or RVSP.(ABSTRACT TRUNCATED AT 250 WORDS)

SSR alpha and associated calnexin are major calcium binding proteins of the endoplasmic reticulum membrane.

GTP phosphorylation of rough microsomes in vitro is limited to four integral membrane proteins. Two of these, a phosphoprotein (pp90) and a phosphoglycoprotein (pgp35) were purified as a complex with two nonphosphorylated membrane glycoproteins, gp25H and gp25L. The authenticity of this complex was confirmed using two different purification procedures and by coimmunoprecipitation. By immunofluorescence a reticulated cytoplasmic network was revealed for the proteins which was similar to that for Louvard et al. (Louvard, D., Reggio, H., and Warren, G. (1982) J. Cell Biol. 92, 92-107) marker antisera which also recognized purified pp90 on immunoblots. Amino acid sequencing of peptides derived from pgp35 identified this protein as SSR alpha, an endoplasmic reticulum constituent as identified by cross-linking of translocating nascent chains (Görlich, D, Prehn, S., Hartmann, E., Herz, J., Otto, A., Kraft, R., Wiedmann, M., Knespel, S., Dobberstein, B., and Rapoport, T. A. (1990) J. Cell Biol. 111, 2283-2294). The sequence of gp25H was determined from cDNA clones and was identical with SSR beta identified by Görlich et al. (1990) as being tightly bound to SSR alpha. Sequencing of gp25L revealed no similarity of the deduced sequence with other proteins. However, pp90 revealed a high degree of sequence identity with the Ca(2+)-binding protein, calreticulin. 45Ca2+ overlay studies indicated that pp90 bound Ca2+ and the name calnexin is proposed. Surprisingly, pgp25 (SSR alpha) also bound Ca2+ although gp25H (SSR beta) and gp25L did not. Triton X-114 partitioning of the integral membrane proteins of rough microsomes suggested that pgp35 (SSR alpha) and calnexin were major Ca(2+)-binding proteins of the endoplasmic reticulum membrane. We propose that the function of the complex is to regulate Ca(2+)-dependent retention mechanisms for luminal proteins of the endoplasmic reticulum.

Selective degradation of insulin within rat liver endosomes.

To characterize the role of the endosome in the degradation of insulin in liver, we employed a cell-free system in which the degradation of internalized 125I-insulin within isolated intact endosomes was evaluated. Incubation of endosomes containing internalized 125I-insulin in the cell-free system resulted in a rapid generation of TCA soluble radiolabeled products (t1/2, 6 min). Sephadex G-50 chromatography of radioactivity extracted from endosomes during the incubation showed a time dependent increase in material eluting as radioiodotyrosine. The apparent Vmax of the insulin degrading activity was 4 ng insulin degraded.min-1.mg cell fraction protein-1 and the apparent Km was 60 ng insulin.mg cell fraction protein-1. The endosomal protease(s) was insulin-specific since neither internalized 125I-epidermal growth factor (EGF) nor 125I-prolactin was degraded within isolated endosomes as assessed by TCA precipitation and Sephadex G-50 chromatography. Significant inhibition of degradation was observed after inclusion of p-chloromercuribenzoic acid (PCMB), 1,10-phenanthroline, bacitracin, or 0.1% Triton X-100 into the system. Maximal insulin degradation required the addition of ATP to the cell-free system that resulted in acidification as measured by acridine orange accumulation. Endosomal insulin degradation was inhibited markedly in the presence of pH dissipating agents such as nigericin, monensin, and chloroquine or the proton translocase inhibitors N-ethylmaleimide (NEM) and dicyclohexylcarbodiimide (DCCD). Polyethylene glycol (PEG) precipitation of insulin-receptor complexes revealed that endosomal degradation augmented the dissociation of insulin from its receptor and that dissociated insulin was serving as substrate to the endosomal protease(s). The results suggest that as insulin is internalized it rapidly but incompletely dissociates from its receptor. Dissociated insulin is then degraded by an insulin specific protease(s) leading to further dissociation and degradation.

Ligand-mediated internalization, recycling, and downregulation of the epidermal growth factor receptor in vivo.

EGF receptor internalization, recycling,a nd downregulation were evaluated in liver parenchyma as a function of increasing doses of injected EGF. The effect of ligand occupancy in vivo on the kinetics and extent of internalization was studied with changes in the receptor content of isolated plasmalemma and endosome fractions evaluated by direct binding, Scatchard analysis, and Western blotting. For all doses of injected EGF, receptor was lost from the plasmalemma and accumulated in endosomes in a time- and dose-dependent fashion. However, at doses of injected EGF equivalent to less than or equal to 50% surface receptor occupancy (i.e., less than or equal to 1 microgram/100 g body weight), receptor levels returned by 120 min to initial values. This return was resistant to cycloheximide and therefore did not represent newly synthesized receptor. Neither was the return due to replenishment by an intracellular pool of low-affinity receptors as such a pool could not be detected by Scatchard analysis or Western blotting. Therefore, receptor return was due to the recycling of previously internalized receptor. At doses of injected EGF greater than 50% receptor occupancy, net receptor loss-i.e., downregulation-was observed by evaluating the receptor content of total particulate fractions of liver homogenates. At the higher saturating doses of injected EGF (5 and 10 micrograms/100 g body weight), the majority of surface receptor content was lost by 15 min and remained low for at least an additional 105 min. As the kinetics of ligand clearance from the circulation and liver parenchyma were similar for all doses of EGF injected, then the ligand-mediated regulation of surface receptor content and downregulation were not a result of a prolonged temporal interaction of ligand with receptor. Rather, the phenomena must be a consequence of the absolute concentrations of EGF interacting with receptor at the cell surface and/or in endosomes.

Ligand-mediated autophosphorylation activity of the epidermal growth factor receptor during internalization.

The association of EGF with its receptor in endosomes isolated from rat liver homogenates was assessed biochemically by polyethylene glycol precipitation and morphologically by electron microscope radioautography. The proportion of receptor-bound ligand in endosomes at 15 min after the injection of doses of 0.1 and 1 microgram EGF/100 g body weight was 57%. This value increased to 77% for the dose of 10 micrograms EGF injected. Quantitative electron microscope radioautography carried out on endosomes isolated at 15 min after the injection of 10 micrograms 125I-EGF demonstrated that most radiolabel was over the endosomal periphery thereby indicating that ligand-receptor complexes were in the bounding membrane but not in intraluminal vesicles of the content. EGF receptor autophosphorylation activity during internalization was evaluated in plasmalemma and endosome fractions. This activity was markedly but transiently reduced on the cell surface shortly after the administration of saturating doses of EGF. The same activity, however, was augmented and prolonged in endosomes for up to 30 min after EGF injection. The transient desensitization of cell surface activity was not due to prior in vivo phosphorylation since receptor dephosphorylation in vitro failed to restore autophosphorylation activity. Transient desensitization of cell surface autophosphorylation activity coincided with a diminished capacity for endocytosis of 125I-EGF with endocytosis returning to normal after the restoration of cell surface autophosphorylation activity. The inhibition of cell surface autophosphorylation activity and the activation of endosomal autophosphorylation activity coincident with downregulation suggest that EGF receptor traffic is governed by ligand-regulated phosphorylation activity.