Academic emergency medicine's future. The SAEM Task Force on Emergency Medicine's Future. Society for Academic Emergency Medicine

Emergency medicine (EM) will change over the next 20 years more than any other specialty. Its proximity to and interrelationships with the community, nearly all other clinicians (physicians and nonphysicians), and scientific/technologic developments guarantee this. While emergency physicians (EPs) will continue to treat both emergent and nonemergent patients, over the next decades our interventions, methods, and place in the medical care system will probably become unrecognizable from the EM we now practice and deliver. This paper, developed by the Society for Academic Emergency Medicine (SAEM) Task Force on Academic Emergency Medicine's Future, was designed to promote discussions about and actions to optimize our specialty's future. After briefly discussing the importance of futures planning, it suggests "best-case," "worst-case," and most probable future courses for academic EM over the next decades. The authors predict that EPs will practice a much more technologic and accurate form of medicine, with diagnostic, patient, reference, and consultant information rapidly available to them. They will be at the center of an extensive consultation network stemming from major medical centers and the purveyors of a sophisticated home health system, very similar to or even more advanced than what is now delivered on hospital wards. The key to planning for our specialty is for EM organizations, academic centers, and individuals to act now to optimize our possible future.

Slow recovery of impaired phrenic responses to hypoxia following perinatal hyperoxia in rats

1. Previous studies demonstrated that both ventilatory and phrenic nerve responses to acute hypoxia are greatly attenuated in adult rats (3-5 months old) previously exposed to 1 month of perinatal hyperoxia (60 % O2; perinatal treated rats). The present study tested the hypothesis that this functional impairment recovers spontaneously with advancing age in perinatal treated rats. 2. Hypoxia-induced chemoreflexes were examined by measuring integrated phrenic responses to strictly controlled isocapnic hypoxia in urethane-anaesthetized, vagotomized, paralysed and ventilated rats at different ages. 3. At 50 mmHg Pa,O2 (arterial O2 partial pressure), the hypoxia-induced increase in minute phrenic activity was significantly attenuated in both 3- to 5-month-old (166 +/- 15% of baseline) and 6-month-old (130 +/- 17%) perinatal treated rats, relative to 3- to 6-month-old, untreated control rats (279 +/- 28%; both P < 0.05). However, at 40 mmHg Pa,O2, the hypoxic minute phrenic activity response was attenuated only in 3- to 5-month-old (154 +/- 33%), but not 6-month-old (232 +/- 33%) perinatal treated rats versus control rats (293 +/- 30%). 4. The minute phrenic activity response to hypoxia was not significantly different between geriatric perinatal treated rats (14-15 months) and untreated geriatric control rats at either 50 mmHg (treated: 250 +/- 20% versus control: 274 +/- 23%) or 40 mmHg Pa,O2 (treated: 292 +/- 19% versus control: 315 +/- 36%). 5. These data suggest that partial spontaneous recovery may occur in 6-month-old perinatal treated rats and that full recovery occurs by 15 months of age.

Chemoafferent degeneration and carotid body hypoplasia following chronic hyperoxia in newborn rats

1. To define the role of environmental oxygen in regulating postnatal maturation of the carotid body afferent pathway, light and electron microscopic methods were used to compare chemoafferent neurone survival and carotid body development in newborn rats reared from birth in normoxia (21 % O2) or chronic hyperoxia (60 % O2). 2. Four weeks of chronic hyperoxia resulted in a significant 41 % decrease in the number of unmyelinated axons in the carotid sinus nerve, compared with age-matched normoxic controls. In contrast, the number of myelinated axons was unaffected by hyperoxic exposure. 3. Chemoafferent neurones, located in the glossopharyngeal petrosal ganglion, already exhibited degenerative changes following 1 week of hyperoxia from birth, indicating that even a relatively short hyperoxic exposure was sufficient to derange normal chemoafferent development. In contrast, no such changes were observed in the vagal nodose ganglion, demonstrating that the effect of high oxygen levels was specific to sensory neurones in the carotid body afferent pathway. Moreover, petrosal ganglion neurones were sensitive to hyperoxic exposure only during the early postnatal period. 4. Chemoafferent degeneration in chronically hyperoxic animals was accompanied by marked hypoplasia of the carotid body. In view of previous findings from our laboratory that chemoafferent neurones require trophic support from the carotid body for survival after birth, we propose that chemoafferent degeneration following chronic hyperoxia is due specifically to the loss of target tissue in the carotid body.

Xylem feeding by spittlebug nymphs: some observations by optical and cryo-scanning electron microscopy

The feeding of spittlebug nymphs (Philaenus spumarius) from mature xylem vessels was studied by optical and cryo-analytical scanning electron microscopy. Feeding did not produce xylem embolisms and vessels remained liquid-filled during the day. Saliva secreted by the insect forms a hardened lining (salivary sheath) between the stylet bundle and the plant tissues. This sheath is continuous through the hole made by the stylets as they enter a vessel, and it extends into the vessel and along its periphery beyond the breach. The sheath is heterogeneous, with a thin outer layer adjoining the plant tissues and a thicker layer that contacts the stylet bundle. Both layers give positive histochemical reactions for proteins and, in fresh tissues, contain a red, strongly autofluorescent pigment, possibly condensed tannin derived from the plant (which is lost during tissue preparation), and other phenyl propanoid compounds, which are retained and which may produce the intense reaction of the periodic-acid-Schiff's-positive inner layer. It is concluded that the salivary sheath allows the insects to feed from functioning vessels without embolizing them or losing xylem fluid to the surrounding tissues. These findings and others in the entomological literature indicate low daytime tensions in the xylem conduits of the host plants.

NF-kappaB-inducing kinase activates IKK-alpha by phosphorylation of Ser-176

Activation of the transcription factor NF-kappaB by inflammatory cytokines involves the successive action of NF-kappaB-inducing kinase (NIK) and two IkappaB kinases, IKK-alpha and IKK-beta. Here we show that NIK preferentially phosphorylates IKK-alpha over IKK-beta, leading to the activation of IKK-alpha kinase activity. This phosphorylation of IKK-alpha occurs specifically on Ser-176 in the activation loop between kinase subdomains VII and VIII. A mutant form of IKK-alpha containing alanine at residue 176 cannot be phosphorylated or activated by NIK and acts as a dominant negative inhibitor of interleukin 1- and tumor necrosis factor-induced NF-kappaB activation. Conversely, a mutant form of IKK-alpha containing glutamic acid at residue 176 is constitutively active. Thus, the phosphorylation of IKK-alpha on Ser-176 by NIK may be required for cytokine-mediated NF-kappaB activation.

Fibronectin type III repeats mediate RGD-independent adhesion and signaling through activated beta1 integrins

Many cell-surface and extracellular matrix proteins contain multiple modular domains known as fibronectin type III (FNIII) repeats. Cells adhere to the extracellular matrix proteins fibronectin and tenascin in part by the interaction of certain integrins with the Arg-Gly-Asp (RGD) sequence, displayed on specific FNIII repeats. We have found that, after experimental activation of beta1 integrins, a number of cell types adhere and spread on FNIII repeats lacking RGD, derived from extracellular matrix proteins and cytokine receptors. Interaction between individual FNIII domains and beta1 integrins mediates focal adhesion kinase phosphorylation and subsequent stress fiber and focal contact formation. These data suggest that many FNIII-containing proteins may bind and signal through activated beta1 integrins, dramatically expanding the potential for integrin-dependent intercellular and cell-matrix communication.

Developmental plasticity of the hypoxic ventilatory response

This paper will describe recent studies concerning the existence of developmental plasticity in the hypoxic ventilatory control system and the locus of the functional impairment following perinatal sensory suppression. Suppression of peripheral arterial chemoreceptor activity was achieved by exposing rats to hyperoxia (60% O2) for the first month of life; all measurements were conducted 2-5 months after the exposure (perinatal treated rats). Hypoxic (but not hypercapnic) ventilatory responses were severely attenuated in awake perinatal treated rats, but not in rats exposed to hyperoxia as adults, indicating that the persistent effect is unique to development and is not the nonspecific result of O2 toxicity. Impairments of the hypoxic ventilatory response due to changes in pulmonary mechanics, gas exchange or central integration of carotid chemoafferent inputs were all ruled out as primary causal factors. However, a persistent impairment of carotid chemotransduction in perinatal treated rats was apparent. These studies suggest that the hypoxic ventilatory response is susceptible to developmental plasticity, and that a carotid chemoreceptor deficit is the primary cause. These findings may have important clinical implications for patients subjected to excessive O2 therapy during neonatal intensive care.

Gain adaptation of eye and head movement components of simian gaze shifts

Gain adaptation of eye and head movement components of simian gaze shifts. J. Neurophysiol. 78: 2817-2821, 1997. To investigate the site of gaze adaptation in primates, we reduced the gain of large head-restrained gaze shifts made to 50 degrees target steps by jumping the target 40% backwards during a targeting saccade and then tested gain transfer to the eye- and head-movement components of head-unrestrained gaze shifts. After several hundred backstep trials, saccadic gain decreased by at least 10% in 8 of 13 experiments, which were then selected for further study. The minimum saccadic gain decrease in these eight experiments was 12.8% (mean = 18.4%). Head-unrestrained gaze shifts to ordinary 50 degrees target steps experienced a gain reduction of at least 9.3% (mean = 14.9%), a mean gain transfer of 81%. Both the eye and head components of the gaze shift also decreased. However, average head movement gain decreased much more (22.1%) than eye movement gain (9.2%). Also, peak head velocity generally decreased significantly (20%), but peak eye velocity either increased or remained constant (average increase of 5.6%). However, the adapted peak eye and head velocities were appropriate for the adapted, smaller gaze amplitudes. Similar dissociations in eye and head metrics occurred when head-unrestrained gaze shifts were adapted directly (n = 2). These results indicated that head-restrained saccadic gain adaptation did not produce adaptation of eye movement alone. Nor did it produce a proportional gain change in both eye and head movement. Rather, normal eye and head amplitude and velocity relations for a given gaze amplitude were preserved. Such a result could be explained most easily if head-restrained adaptation were realized before the eye and head commands had been individualized. Therefore, gaze adaptation is most likely to occur upstream of the creation of separate eye and head movement commands.

The amino-terminal region of Tyk2 sustains the level of interferon alpha receptor 1, a component of the interferon alpha/beta receptor

Tyk2 belongs to the Janus kinase (JAK) family of receptor associated tyrosine kinases, characterized by a large N-terminal region, a kinase-like domain and a tyrosine kinase domain. It was previously shown that Tyk2 contributes to interferon-alpha (IFN-alpha) signaling not only catalytically, but also as an essential intracellular component of the receptor complex, being required for high affinity binding of IFN-alpha. For this function the tyrosine kinase domain was found to be dispensable. Here, it is shown that mutant cells lacking Tyk2 have significantly reduced IFN-alpha receptor 1 (IFNAR1) protein level, whereas the mRNA level is unaltered. Expression of the N-terminal region of Tyk2 in these cells reconstituted wild-type IFNAR1 level, but did not restore the binding activity of the receptor. Studies of mutant Tyk2 forms deleted at the N terminus indicated that the integrity of the N-terminal region is required to sustain IFNAR1. These studies also showed that the N-terminal region does not directly modulate the basal autophosphorylation activity of Tyk2, but it is required for efficient in vitro IFNAR1 phosphorylation and for rendering the enzyme activatable by IFN-alpha. Overall, these results indicate that distinct Tyk2 domains provide different functions to the receptor complex: the N-terminal region sustains IFNAR1 level, whereas the kinase-like domain provides a function toward high affinity ligand binding.

Phrenic responses to isocapnic hypoxia in adult rats following perinatal hyperoxia

The purpose of this study was to test the hypothesis that carotid body-mediated, phrenic nerve responses to hypoxia are attenuated in adult rats that had been previously exposed to perinatal hyperoxia (one month of 60% O2; perinatal treated rats.) Integrated phrenic nerve responses to strictly controlled isocapnic hypoxia were measured in urethane-anesthetized, vagotomized, paralyzed and ventilated adult rats 2-5 months after perinatal hyperoxia, before and after bilateral carotid denervation. In untreated control rats, phrenic burst frequency, peak amplitude of integrated phrenic activity and minute phrenic activity increased 21 +/- 3 bursts/min (mean +/- SE), 158 +/- 20% and 279 +/- 34%, respectively, during hypoxia (50 Torr PaO2). In contrast, phrenic nerve activity increased to a significantly lesser degree in perinatal treated rats (frequency, 12 +/- 2 bursts/min; amplitude, 87 +/- 13%; minute activity, 150 +/- 19%; all P < 0.05). Hypoxic phrenic responses were abolished by carotid degeneration in both rat groups. In rats exposed to hyperoxia as adults, hypoxic phrenic responses were not attenuated versus untreated control rats. The data indicate that carotid body-mediated, isocapnic hypoxic chemoreflexes are impaired in perinatal treated rats, an effect unique to development. These effects cannot be accounted for by differences in blood gases (O2 or CO2) or pulmonary mechanics.

Integrated phrenic responses to carotid afferent stimulation in adult rats following perinatal hyperoxia

1. Hypoxic ventilatory responses are greatly attenuated in adult rats exposed to moderate hyperoxia (60% O2) during the first month of life (perinatal treated rats). The present study was designed to test the hypothesis that perinatal hyperoxia impairs central integration of carotid chemoreceptor afferent inputs, thereby diminishing the hypoxic ventilatory response. 2. Time-dependent phrenic nerve responses to electrical stimulation of the carotid sinus nerve (CSN) and steady-state relationships between CSN stimulation frequency and phrenic nerve output were compared in control and perinatal treated rats. The rats were urethane anaesthetized, vagotomized, paralysed and artificially ventilated. End-tidal CO2 was monitored and maintained at isocapnic levels; arterial blood gases were determined. 3. Two stimulation protocols were used: (1) three 2 min episodes of CSN stimulation (20 Hz, 0.2 ms duration, 3 x threshold), separated by 5 min intervals; and (2) nine 45 s episodes of CSN stimulation with stimulus frequencies ranging from 0.5 to 20 Hz (0.2 ms duration, 3 x threshold), separated by 4 min intervals. 4. The mean threshold currents to elicit phrenic responses were similar between groups. Burst frequency (f, burst min-1), peak amplitude of integrated phrenic activity (integral of Phr), and minute phrenic activity (integral of Phr x f) during and after CSN stimulation were not distinguishable between groups in either protocol at any time or at any stimulus intensity (P > 0.05). 5. Perinatal hyperoxia does not alter temporal or steady-state phrenic responses to CSN stimulation, suggesting that the central integration of carotid chemoreceptor afferent inputs is not impaired in perinatal treated rats. It is speculated that carotid chemoreceptors per se are impaired in perinatal treated rats.

Attenuation of the hypoxic ventilatory response in adult rats following one month of perinatal hyperoxia

1. This study was designed to test the hypothesis that perinatal suppression of peripheral arterial chemoreceptor inputs attenuates the hypoxic ventilatory response in adult rats. Perinatal suppression of peripheral chemoreceptor activity was achieved by exposing rats to hyperoxia throughout the first month of life. 2. Late-gestation pregnant rats were housed in a 60% O2 environment, exposing the pups to hyperoxia from several days prior to birth until they were returned to normoxia on postnatal day 28. These perinatally treated rats were then reared to adulthood (3-5 months old) in normoxia. In addition to the mother rats, adult male rats were also exposed to hyperoxia, creating an adult-treated control group. Two to four months after the hyperoxic exposure, treated rats were compared with untreated male rats of similar age. 3. A whole-body, flow-through plethysmograph was used to measure hypoxic and hypercapnic ventilatory responses of the unanaesthetized adult rats. In moderate hypoxia (arterial oxygen partial pressure, Pa,O2 approximately 48 mmHg). VE (minute ventilation) and the ratio VE/VCO2 (ventilation relative to CO2 production) increased by 16.7 +/- 4.0 and 35.4 +/- 3.4%, respectively, in perinatal-treated rats (means +/- S.E.M.), but increased more in untreated control rats (51.4 +/- 2.8 and 83.1 +/- 4.3%; both P < 10(-6)). 4. In contrast to the impaired hypoxic ventilatory response, ventilatory responses to hypercapnia (5% CO2) were similar between untreated control and perinatal-treated rats. 5. Impaired hypoxic responsiveness was unique to the perinatal-treated rats since hypoxic ventilatory responses were not attenuated in adult-treated rats. 6. The results indicate that ventilatory responses to hypoxaemia are greatly attenuated in adult rats that had experienced hyperoxia during their first month of life, and suggest that normal hypoxic ventilatory control mechanisms are susceptible to developmental plasticity.

Identification of the major autophosphorylation sites of Nyk/Mer, an NCAM-related receptor tyrosine kinase

Nyk/Mer receptor tyrosine kinase is a new member of the Ufo/Axl tyrosine kinase family and is characterized by its neural cell adhesion molecule-like extracellular domain. By using a vaccinia virus expression system to express a constitutively activated form of Nyk, we identified the major sites of Nyk autophosphorylation in tryptic peptide IY749SGDY753Y754R. Tyr-749, Tyr-753, and Tyr-754 in this peptide lie in the activation loop of the kinase domain. We also studied a series of Nyk mutants in which the three tyrosine residues were replaced individually, in pairs, or all together by phenylalanine. Single mutations of Tyr-749 or Tyr-753 to phenylalanine reduced Nyk kinase activity toward exogenous substrate to 39 or 10% of that of the wild type Nyk, respectively, whereas the Tyr-754 mutant is completely inactive. All of the double and triple Tyr-Phe mutants reduced Nyk kinase activity to a level below the background. Similar results were obtained when Nyk autophosphorylation levels were examined. Our studies suggest that full activity of Nyk/Mer kinase requires phosphorylation of all three tyrosine residues in the kinase domain (Tyr-749, Tyr-753, and Tyr-754) and that Nyk kinase activity is modulated by the level of autophosphorylation in the kinase domain. Given the highly conserved nature of this region among the Ufo/Axl receptor family members, the information presented in this report may provide insight to the biochemical properties of other members of this family.

The alpha1beta1 integrin is expressed during neointima formation in rat arteries and mediates collagen matrix reorganization

Remodeling of the extracellular matrix by activated mesenchymal cells (myofibroblasts) is a critical aspect of wound repair in all adult organs. Collagen-dependent gel contraction, a process requiring integrin function, is an established in vitro assay thought to mimic in vivo matrix remodeling. Numerous data have implicated the alpha2beta1 integrin in various cell types as the primary collagen receptor responsible for collagen gel contraction. However, evidence from the literature suggests that the major collagen binding integrin expressed on mesenchymally derived cells in situ is the alpha1beta1 integrin, not the alpha2beta1 integrin. In this report, we use a rat vascular injury model to illustrate that the alpha1beta1 integrin is the major collagen receptor expressed on vascular smooth muscle cells after injury. Using two smooth muscle cell lines, expressing either the alpha1beta1 integrin alone or both the alpha1beta1 and alpha2beta1 integrins, along with Chinese hamster ovary cells transfected with the alpha1 integrin, we demonstrate that alpha1beta1 supports not only collagen-dependent adhesion and migration, but also gel contraction. These data suggest that in vivo the alpha1beta1 integrin is a critical collagen receptor on mesenchymally derived cells potentially involved in matrix remodeling after injury.

Studies on fenestral contraction in rat liver endothelial cells in culture

Liver endothelial cells possess fenestrae, which are pores supported by a cytoskeleton ring composed of actin and myosin. Fenestrae are dynamic structures that can contract or dilate, although the mechanism for this phenomenon remains to be elucidated. Staining of actin and/or of myosin permitted measurement of fenestral diameter and area in cultured rat liver endothelial cells using digitized video-intensified fluorescence microscopy with image analysis. Within 1 minute of incubation with 0.1 micromol/L serotonin, fenestral diameter and area decreased by 24 +/- 5% and 56 +/- 7%, respectively. Contraction of fenestrae by serotonin was inhibited by chelation of extracellular Ca2+ with EGTA and by addition of Ca2+ channel blockers, such as dilthiazem and verapamil. The response of fenestrae to serotonin was mimicked by addition of a Ca2+ ionophore, A23187. Serotonin inhibited cAMP production, had no effect on inositol phosphate production, and activated phospholipase A2, causing release of arachidonic acid. These results suggest that contraction of fenestrae is associated with Ca2+ influx. In response to 0.1 micromol/serotonin, intracellular Ca2+ levels increased within 3 to 5 seconds from 150 nmol/L to >400 nmol/l followed by rapid phosphorylation of the 20-kd subunit of myosin light chain; both events dependent on extracellular Ca2+.

Inhibition of alpha interferon but not gamma interferon signal transduction by phorbol esters is mediated by a tyrosine phosphatase

Previous studies have indicated that the expression of viral oncoproteins, cell transformation, or phorbol ester treatment of cells can inhibit alpha/beta interferon (IFN-alpha/beta)-induced gene expression. The mechanisms by which these promoters of cell growth exert their inhibitory effects vary, but in most instances they involve a disruption of the IFN-alpha/beta-induced transcription complex ISGF3 such that the DNA-binding component of this complex (the 48-kDa ISGF3gamma protein) does not bind to the interferon-stimulated response element (ISRE). In this report, we demonstrated that phorbol ester treatment of human peripheral blood monocytes dramatically inhibits activation of IFN-alpha/B-stimulated early response genes but by a mechanism which does not involve abrogation of the ISRE binding of ISGF3gamma. Phorbol ester treatment of monocytes inhibited IFN alpha-stimulated tyrosine phosphorylation of the transcription factors Stat1alpha, Stat2, and Stat3 and of the tyrosine kinase Tyk2 but had no effect on IFN-gamma activation of Stat1alpha. IFNalpha-stimulated tyrosine phosphorylation of Jak1 and the alpha subunit of the IFN-alpha receptor were unaffected by phorbol 12-myristate 13-acetate (PMA). Moreover, PMA caused the dephosphorylation of Tyk2 but not of Jak1, which was activated by IFN. Pretreatment of cells with vanadate prevented the effects of PMA with regard to PMA-induced Tyk2 dephosphorylation. These observations suggest that PMA exerts its inhibitory effects by activation of a tyrosine phosphatase which selectively regulates Tyk2 but not Jak1 activity.

Stepwise transformation of astrocytes by simian virus 40 large T antigen and epidermal growth factor receptor overexpression

We have investigated the transformed phenotype of neonatal mouse cortical astrocytes immortalized by retrovirus-mediated transfer of the SV40 large T antigen gene. Expression of T antigen was driven by the Moloney murine leukemia virus long terminal repeat. Cell lines were selected based on coexpression of neomycin resistance, which provides a selection method believed to be unbiased for transformation state. Astrocyte cell lines derived in this manner express T antigen over a relatively narrow range (approximately 4-fold), are contact inhibited, are able to enter a quiescent state in the presence of growth factors, and do not readily form colonies in soft agar. Compared to mortal astrocytes, the population growth rate is increased 3-fold, saturation densities are 4-fold higher, and the genome is relatively unstable as measured by the presence of DNA-aneuploid stem lines and by changes in DNA ploidy over time. However, changes in transformation phenotype occur at a low rate, making the cell lines amenable to experimentation. Most often, the growth phenotype remained unchanged during months of culture. Transfection of an epidermal growth factor receptor (EGFR) gene was used to generate a subline that was conditionally transformed (colony formation in soft agar was dependent on transforming growth factor alpha). v-raf transfection was used to generate constitutive transformation. Thus, these cell lines appear to be excellent experimental models for progressive transformation. With them, untested hypotheses of brain tumor progression derived from human genetic studies may be tested experimentally.

Mitogenic signals and transforming potential of Nyk, a newly identified neural cell adhesion molecule-related receptor tyrosine kinase

Nyk/Mer is a recently identified receptor tyrosine kinase with neural cell adhesion molecule-like structure (two immunoglobulin G-like domains and two fibronectin III-like domains) in its extracellular region and belongs to the Ufo/Axl family of receptors. The ligand for Nyk/Mer is presently unknown, as are the signal transduction pathways mediated by this receptor. We constructed and expressed a chimeric receptor (Fms-Nyk) composed of the extracellular domain of the human colony-stimulating factor 1 receptor (Fms) and the transmembrane and cytoplasmic domains of human Nyk/Mer in NIH 3T3 fibroblasts in order to investigate the mitogenic signaling and biochemical properties of Nyk/Mer. Colony-stimulating factor 1 stimulation of the Fms-Nyk chimeric receptor in transfected NIH 3T3 fibroblasts leads to a transformed phenotype and generates a proliferative response in the absence of other growth factors. We show that phospholipase C gamma, phosphatidylinositol 3-kinase/p70 S6 kinase, Shc, Grb2, Raf-1, and mitogen-activated protein kinase are downstream components of the Nyk/Mer signal transduction pathways. In addition, Nyk/Mer weakly activates p90rsk, while stress-activated protein kinase, Ras GTPase-activating protein (GAP), and GAP-associated p62 and p190 proteins are not activated or tyrosine phosphorylated by Nyk/Mer. An analysis comparing the Nyk/Mer signal cascade with that of the epidermal growth factor receptor indicates substrate preferences by these two receptors. Our results provide a detailed description of the Nyk/Mer signaling pathways. Given the structural similarity between the Ufo/Axl family receptors, some of the information may also be applied to other members of this receptor tyrosine kinase family.

Polymorphism of human minor histocompatibility antigens: T cell recognition of human minor histocompatibility peptides presented by HLA-B35 subtype molecules

To investigate the polymorphism of human minor histocompatibility (mH) antigens, PBLs from 23 Japanese individuals and 25 German individuals with HLA-B35 were studied by using four human mH antigen-specific, HLA-B35-restricted CTL clones. The CTL clones killed PHA-stimulated PBLs from all 23 Japanese individuals. On the other hand, they killed the PHA-stimulated PBLs from 19 of 25 German individuals and partially killed the PHA-stimulated PBLs from three German individuals (CTL weakly sensitive cell line); those from another three individuals (CTL-resistant cell line) were not killed by the CTL clones. All of three CTL weakly sensitive cell lines carry HLA-B*3503 molecules, whereas the three CTL-resistant cell lines carry HLA-B*3502, B*3507, and B*3508 molecules. The cytotoxicity of the CTL clones for three CTL weakly sensitive cell lines was enhanced by stimulation of human mH peptides isolated from HLA-B*3501 molecules purified from C1R-B*3501 cells. Small amounts of human mH peptides were isolated from B*3503 molecules purified from these three CTL weakly sensitive cell lines. Taken together, these results indicate that weak recognition by the CTL clones of three CTL weakly sensitive cell line results from a small amount of the human mH peptides presented by B*3503 molecules. The CTL-resistant cell line carrying B*3507 loaded with the human mH peptides was killed by four CTL clones, whereas the cell lines carrying B*3502 or B*3508 loaded with the peptides were not. The human mH peptides were not isolated from B*3507 molecules purified from the cell lines expressing this subtype, whereas small amounts of the human mH peptides were isolated from B*3502 and B*3508 molecules purified from the cell lines expressing the subtypes. These results indicate that failure of the CTL recognition of the cell line carrying B*3507 is due to a lack of human mH antigens in this cell line. The failure of the CTL recognition of the cell lines carrying B*3502 and B*3508 is not explained by only the amount of the human mH peptides binding to these B35 subtype molecules because the amount of the human mH peptides eluted from B*3502 and B*3508 molecules purified from the cell lines carrying these B35 subtypes is almost the same as that eluted from B*3503 molecules purified from the cell lines carrying B*3503.(ABSTRACT TRUNCATED AT 400 WORDS)

[Simplified enzyme-linked immunoadsorbent assays for myelin basic protein and antibodies to myelin basic protein]

Synchronous quantitative determination using simplified enzyme-linked immuno adsorbent assay has been developed for myelin basic protein (MBP) and antibodies to myelin basic protein (Anti-MBP). Antisera were prepared by immunizing rabbits with purified MBP from human white matter. Antibodies to MBP was conjugated with horseradish peroxidase (HRP) by using modified periodate oxidation method. Minimum detection amounts of MBP and Anti-MBP are 0.25 ng/ml and 0.20 ng/ml respectively. The activities of Anti-MBP-HRP conjugates are stable (stored at -30 degrees C) for at least 2 years. The detection procedure can be accomplished within 24 hours.

Rapid horizontal gaze movement in the monkey

1. We studied horizontal eye and head movements in three monkeys that were trained to direct their gaze (eye position in space) toward jumping targets while their heads were both fixed and free to rotate about a vertical axis. We considered all gaze movements that traveled > or = 80% of the distance to the new visual target. 2. The relative contributions and metrics of eye and head movements to the gaze shift varied considerably from animal to animal and even within animals. Head movements could be initiated early or late and could be large or small. The eye movements of some monkeys showed a consistent decrease in velocity as the head accelerated, whereas others did not. Although all gaze shifts were hypometric, they were more hypometric in some monkeys than in others. Nevertheless, certain features of the gaze shift were identifiable in all monkeys. To identify those we analyzed gaze, eye in head position, and head position, and their velocities at three points in time during the gaze shift: 1) when the eye had completed its initial rotation toward the target, 2) when the initial gaze shift had landed, and 3) when the head movement was finished. 3. For small gaze shifts (< 20 degrees) the initial gaze movement consisted entirely of an eye movement because the head did not move. As gaze shifts became larger, the eye movement contribution saturated at approximately 30 degrees and the head movement contributed increasingly to the initial gaze movement. For the largest gaze shifts, the eye usually began counterrolling or remained stable in the orbit before gaze landed. During the interval between eye and gaze end, the head alone carried gaze to completion. Finally, when the head movement landed, it was almost aimed at the target and the eye had returned to within 10 +/- 7 degrees, mean +/- SD, of straight ahead. Between the end of the gaze shift and the end of the head movement, gaze remained stable in space or a small correction saccade occurred. 4. Gaze movements < 20 degrees landed accurately on target whether the head was fixed or free. For larger target movements, both head-free and head-fixed gaze shifts became increasingly hypometric. Head-free gaze shifts were more accurate, on average, but also more variable. This suggests that gaze is controlled in a different way with the head free. For target amplitudes < 60 degrees, head position was hypometric but the error was rather constant at approximately 10 degrees.(ABSTRACT TRUNCATED AT 400 WORDS)

Phrenic responses to contralateral spinal stimulation in rats: effects of old age or chronic spinal hemisection

Serotonin reveals ineffective spinal pathways from the C2-lateral funiculus to contralateral phrenic motoneurons in young adult rats with acute spinal hemisection. We tested the hypothesis that old age (1.5-2 years) or chronic hemisection (3-5 days) strengthens these pre-existing crossed spinal pathways. There were no consistent differences between young adult rats with acute hemisection versus young adult rats with chronic hemisection or old rat with acute hemisection except that one long-latency phrenic excitation could not be elicited in old rats. The results indicate that neither old age nor chronic hemisection strengthens crossed-spinal pathways, but that old age may selectively diminish spinal pathways involved in the neural control of breathing.

Three distinct loci on human chromosome 21 contribute to interferon-alpha/beta responsiveness

The species specificity of interferons (IFNs) depends on restricted recognition of these ligands by multisubunit cell surface receptors. Expression of the human receptor subunit IFNAR in mouse cells conferred sensitivity only to one subtype of human IFN, IFN-alpha B. Other genes on human chromosome 21 were required for responses to other subtypes of type I IFN. In contrast, IFNAR expression in hamster cells did not confer sensitivity to any human IFN tested, including IFN-alpha B. Using human-hamster somatic cell hybrids, we mapped the Ifnabr gene, encoding a ligand-binding subunit of the IFN-alpha/beta (type I) receptor, to human chromosome 21. Ifnabr colocalized with Ifnar to the distal region of q22.1. The presence of a chromosomal fragment encoding IFNABR and IFNAR was also not sufficient to confer sensitivity to human IFN. In contrast, hybrids carrying in addition the region 21q22.2 showed a full response to human IFN-alpha B, suggesting that a gene located in this region encodes a third factor required for type I IFN receptor activity.

Modulation of erbB kinase activity and oncogenic potential by single point mutations in the glycine loop of the catalytic domain

Avian c-erbB is activated to a leukemia oncogene following truncation of its amino-terminal ligand-binding domain by retroviral insertion. The insertionally activated transcripts encode protein products which have constitutive tyrosine kinase activity and can induce erythroleukemia but not sarcomas. We have previously found that a valine-to-isoleucine point mutation at position 157 (V157I mutant) within the tyrosine kinase domain of this truncated erbB can dramatically activate the sarcomagenic potential of the oncogene and increase the kinase activity of this oncoprotein. This mutation lies at position 157 of the insertionally activated c-erbB product, affecting a highly conserved valine residue of the glycine loop involved in ATP binding and phosphate transfer. To investigate the functional importance of this residue in the catalytic activity of kinases, we have introduced at this position, by site-directed mutagenesis, codons representing the remaining 18 amino acid residues. Most of the mutants have diminished activity, with six of them completely devoid of kinase activity, indicating the sensitivity of this region to conformational changes. Some of these mutants displayed increased kinase activity and greater transforming potential in comparison with IA c-erbB, but none had levels as high as those of the V157I mutant. In general, the sarcomagenic potential of the various erbB mutants correlated with their autophosphorylation state and their ability to cause phosphorylation of MAP kinase. However, there are important exceptions such as the V157G mutant, which lacks enhanced autophosphorylation but is highly sarcomagenic. Studies of this and other autophosphorylation site mutants point to the existence of an autophosphorylation-independent pathway in sarcomagenesis. The requirement for leukemogenic potential is much less stringent and correlates with positivity of kinase activity. When the valine-to-isoleucine substitution was put in context of the full-length erbB protein, the mutation relaxed the ligand dependence and had a positive effect on the transforming potential of the full-length c-erbB.

Pentoxifylline acts synergistically with A23187 to increase the penetration of zona-free hamster oocytes by cryopreserved human spermatozoa

The number of cryopreserved human spermatozoa which penetrated zona-free hamster oocytes after stimulation with 2 mumol A23187 per litre was increased by the further addition of 0.6 or 3.6 mmol pentoxifylline per litre. With spermatozoa prepared by washing by repeated centrifugation, the median numbers of sperm heads/egg were 1.9, 7.9 and 10.8 in the presence of 0, 0.6 or 3.6 mmol pentoxifylline per litre, respectively. A similar effect was observed with spermatozoa prepared on a Percoll gradient. As A23187 inhibited sperm motility, and this was exacerbated by pentoxifylline, the increased penetration rate of hamster oocytes cannot be explained by improved sperm motility. The number of spermatozoa stimulated to acrosome react by 2 mumol A23187 per litre was increased 3-fold by 3.6 mmol pentoxifylline per litre and 4-fold by 5 mmol caffeine per litre. These data suggest that cAMP may act synergistically with Ca2+ to stimulate the acrosome reaction. Pentoxifylline may improve the fertility of poor-quality human spermatozoa by enhancing their ability to respond to the Ca2+ signal produced by binding to the zona pellucida.

A chemoenzymatic synthesis of D-myo-inositol 1,4,5-trisphosphate

Enzyme-catalyzed esterification of racemic 2,3-O-cyclohexylidene-myo-inositol (DL-1) proceeded exclusively in 1,4-dioxane to give optically pure L-1-O-acetyl-2,3-O-cyclohexylidene-myo-inositol (L-2) and D-2,3-O-cyclohexylidene-myo-inositol (D-1). A new practical route has been developed for the synthesis of D-myo-inositol 1,4,5-trisphosphate starting from D-1 via selective acylation of the 6-hydroxyl group.

Nucleus tractus solitarius and excitatory amino acids in afferent-evoked inspiratory termination

This study tested the hypothesis that excitatory amino acid (EAA) neurotransmission at non-N-methyl-D-aspartate (non-NMDA), but not NMDA, receptors within medial regions of the nucleus tractus solitarius (NTS) is required in the inspiratory termination elicited by vagal or intercostal nerve (ICN) stimulation. Adult cats were anesthetized, decerebrated, vagotomized, and ventilated. After control responses to stimulation of the superior laryngeal nerve (SLN), vagus, and ICN were obtained, EAA receptor antagonists were injected into the medial aspects of the NTS. Injections of 6-cyano-7-nitroquinoxaline-2,3-dione (CNQX) or 6,7-dinitro-quinoxaline-2,3-dione (DNQX), EAA receptor antagonists; (+/-)-2-amino-5-phosphonopentanoic acid (AP5), an NMDA antagonist; or 2,3-dihydroxy-6-nitro-7-sulfamoyl-benzo(F)quinoxaline (NBQX), a non-NMDA antagonist, ipsilateral to the vagus abolished the termination response. The SLN-elicited response persisted after AP5 injection but was abolished by NBQX injections. The ICN-elicited response persisted after bilateral injections of CNQX/DNQX or procaine. We conclude that the inspiratory termination elicited by ICN stimulation is independent of the regions medial to the NTS. Inspiratory termination elicited by vagal or SLN stimulation requires non-NMDA-mediated EAA neurotransmission within medial aspects of the NTS, but the vagally elicited response also requires NMDA receptors.

Role of N-methyl-D-aspartate receptors in the pontine pneumotaxic mechanism in the cat

Systemic injection of MK-801, an N-methyl-D-aspartate (NMDA) receptor-associated channel blocker, induces an apneusis in vagotomized cats similar to that produced by pontine respiratory group (PRG) lesions, suggesting the possible involvement of NMDA receptors in the pontine pneumotaxic mechanism. Previous results from our laboratory indicate that the efferent limb of the pontine pneumotaxic mechanism is unlikely to require NMDA receptor-mediated neurotransmission. Therefore, the present study examined the potential involvement of PRG NMDA receptors in the pontine pneumotaxic mechanism. Experiments were conducted in decerebrate, paralyzed, and ventilated adult cats. The effects on inspiratory time (TI) of MK-801 microinjection into PRG were tested in 12 cats. Pressure microinjection of MK-801 (15 mM, 80-3,000 nl) significantly prolonged TI in all animals when lung inflation was withheld. TI progressively increased in most animals for > or = 30 min. After this period, partial recovery of the effect occurred in eight cats as TI shortened toward predrug levels. In three animals, microinjection of MK-801 induced a complete apneusis in the absence of lung inflation from which there was no detectable recovery. Microinjections into regions approximately 2 mm distant from PRG produced little or no effect. These results provide evidence that NMDA receptors located in the region of PRG play an important functional role in the control of the breathing cycle.

Serotonin reveals ineffective spinal pathways to contralateral phrenic motoneurons in spinally hemisected rats

Serotonin reveals ineffective (subthreshold) pathways from the C2 lateral funiculus to ipsilateral phrenic motoneurons in spinalized rats. The objective of the present study was to investigate serotonergic modulation of crossed-spinal pathways to contralateral phrenic motoneurons. Rats (n = 10) were anesthetized (urethane), paralyzed, vagotomized, and artificially ventilated. The spinal cord was hemisected at C1-C2 and, on the intact side, a tungsten stimulating electrode was placed ventral to the C2 dorsal root entry zone in the dorsolateral (approximately 1.1 mm) or the ventrolateral funiculus (approximately 2.2 mm depth). Single shocks (100-750 microA, 0.1-0.5 ms, 2 Hz) elicited a short-latency (approximately 1.0 ms to peak) excitation in the ipsilateral phrenic nerve, but usually evoked little or no response in the contralateral phrenic nerve at either stimulus site. Following systemic injection of the monoamine oxidase inhibitor pargyline (25 mg/kg) and the serotonin precursor 5-hydroxytryptophan (5-10 mg/kg), complex responses were revealed in the contralateral phrenic nerve, including: (1) spontaneous tonic activity; (2) a short-latency (approximately 1.0 ms to peak) evoked excitation; and (3) two long-latency (approximately 2.2 and 7.8 ms to peak) evoked excitations. The longest latency excitation was expressed only when the stimulating electrode was positioned in the dorsolateral funiculus. Contralateral evoked responses were blocked by systemic methysergide (2-6 mg/kg), a broad-spectrum serotonin receptor antagonist. These results indicate that serotonin converts ineffective crossed phrenic pathways in the spinal cord to effective pathways. It remains to be determined whether serotonin is both necessary and sufficient in this modulatory process, or if it is a nonspecific result of increased phrenic motoneuron excitability.

Substance use and alcohol abuse in emergency medicine training programs, by resident report. SAEM Residency Survey Task Force

OBJECTIVE

To determine the prevalence of substance use and alcohol abuse among emergency medicine residents.

METHOD

The study instrument was an anonymous, self-report survey that assessed the use of 13 substances and included the CAGE questions for measuring alcohol abuse. The survey was administered to emergency medicine residents at the time of the American Board of Emergency Medicine's annual In-Service Examination.

RESULTS

Alcohol was the substance most commonly used by emergency medicine residents for nonmedical reasons. Using the CAGE score, 4.9% of residents were classified as alcoholic and another 7.6% as suspect for alcoholism, rates similar to those for housestaff of all specialties as reported in earlier studies. Instruction related to physician impairment during training in their emergency medicine residency was reported by only 36% of the respondents.

CONCLUSIONS

Emergency medicine residents report a low rate of illicit substance use and do not appear to misuse alcohol differently than other housestaff. Interpretation of these results must be tempered with the potential for underreporting that may occur with a voluntary self-report survey of a sensitive nature.

Loss of ICG uptake in the process of rat hepatocarcinogenesis correlates to the disappearance of glutathione-S-transferase alpha subunit

Reduced indocyanine green (ICG) uptake is one of the functional changes of human hepatocellular carcinoma (HCC). To clarify the mechanisms of loss of ICG uptake, and determine which subunit of glutathione-S-transferase (GST), alpha or pi, plays a role in ICG transport in hepatocytes, an experimental HCC model was developed that used nodules induced by 2-acetylamino-fluorene (2-AAF) administration. Many of the ICG stained nodules, which consisted of benign and borderline lesions, were GST-alpha positive. However, the percentage of GST-alpha positive cells tended to decrease according to the disappearance of ICG staining in the process of hepatocarcinogenesis. HCCs unstained by ICG were also GST-alpha negative. GST-pi, not detected in normal rat hepatocytes, appeared in an earlier stage of hepatocarcinogenesis before the disappearance of GST-alpha, and was not observed in HCCs. No significant relationship between ICG staining and GST-pi was recognized. These results suggest that GST-alpha synthesis is disturbed in the process of hepatocarcinogenesis and results in loss of ICG uptake in HCCs, and also indicate that GST-pi may be useful for early diagnosis of preneoplastic hepatocytes showing no roles in ICG transport.

Enzymatic resolution of racemic 1,2:5,6-di-O-cyclohexylidene and 1,2:3,4-di-O-cyclohexylidene-myo-inositol

Enzyme-catalyzed regio- and enantioselective esterification of racemic 1,2:5,6-di-O-cyclohexylidene- and 1,2:3,4-di-O-cyclohexylidene-myo-inositol, which are key intermediates for syntheses of various naturally occurring myo-inositol phosphate derivatives, proceeded exclusively in organic solvent to give optically pure materials and selectively protected products in gram scale. Hydrolysis of mono-O-acetates of the corresponding racemic materials catalyzed by the same enzymes yielded complementary products. The present study provides a new and efficient method for obtaining optically pure myo-inositol derivatives.

Coincident indices of exons and introns

In this paper, the coincident index, proposed by W. F. Friedman in cryptology, is made use of in DNA sequence analysis and exon prediction. The coincident index of exons exceeds that of introns by many times, and is mainly affected by window length, which is correlated negatively with the coincident index. An optimal exon prediction scheme was obtained by experimental analysis with an orthogonal table. Besides exons, many other special sites such as tandem repeats can be identified by using the coincident index approach. The application of this approach to the ARV-2 (AIDS associated retrovirus 2) genome found three new possible coding regions and some unusual base composition regions which are probably related to definite biological functions.

Predominant mutations induced by the Thermococcus litoralis, vent DNA polymerase during DNA amplification in vitro

We have analyzed the predominant mutations created during DNA amplification by PCR utilizing a DNA polymerase isolated from the Thermococcus litoralis (Vent DNA polymerase). Exon 3 of the human hypoxanthine guanine phosphoribosyl transferase (HPRT) gene was amplified using conditions optimized for efficiency of DNA amplification. The resulting PCR product was subjected to denaturing gradient gel electrophoresis (DGGE) to separate polymerase-induced mutant sequences from correctly amplified sequences. The nature of induced mutations was determined by isolating and sequencing the mutant sequences from the gel. Eighteen predominant mutations were found in the 104-bp low temperature melting domain of exon 3 and consisted of 16 A/T to G/C transitions, a G/C to T/A transversion and a complex 4-bp deletion. Thus, the Vent exonuclease proofreading activity seems to affect all misincorporation events with apparently equal probability (i.e., by a factor of five). The comparison of the error rates between analogues of Vent DNA polymerase proficient and deficient in the proofreading 3'-->5' exonuclease activity indicates that the lack of proofreading resulting in an approximate five-fold increase in induced error rate. However, the similarity of the patterns of the mutant sequences observed in DGGE suggested that both enzymes created predominantly the same kinds of mutations and at the same positions in this DNA template under the in vitro reaction conditions studied. This predominance of A/T to G/C transition is also a characteristic of the Taq DNA polymerase, although the positions of most errors induced by both enzymes are not identical.

Excitatory amino acid neurotransmission in superior laryngeal nerve-evoked inspiratory termination

Superior laryngeal nerve (SLN) stimulation elicits a transient inhibition of inspiration (single shocks) or inspiratory termination (stimulus trains). The neural pathways mediating these responses are unknown, but the medial nucleus tractus solitarius (mNTS) has been implicated in the termination reflex. This study tested the hypothesis that SLN-evoked inspiratory termination requires excitatory amino acid (EAA) neurotransmission in medial aspects of the NTS. Experiments were conducted in decerebrate, vagotomized, and paralyzed adult cats. Inspiratory motor output was recorded from the phrenic nerve. After control responses to SLN stimulation were recorded, a unilateral injection of the EAA antagonist 6,7-dinitroquinoxaline-2,3-dione (DNQX, 10 mM) was made into the mNTS. The transient inhibitions were not altered by DNQX. Inspiratory termination elicited by stimulation of the SLN contralateral to the injection persisted after DNQX (n = 4). Stimulation of the ipsilateral SLN no longer elicited termination (5 of 9 animals) or did so only at greatly elevated thresholds (4 of 9). We conclude that EAA neurotransmission in the mNTS is not required in the transient reflex but is necessary for the production of the SLN-evoked inspiratory termination.

Pontine-evoked inspiratory inhibitions after antagonism of NMDA, GABAA, or glycine receptor

Single-shock stimulation of the pontine respiratory group (PRG) produces a transient short-latency inhibition of inspiratory motor activity. Stimulus trains delivered to the PRG can elicit a premature termination of inspiration. This study examined the involvement of N-methyl-D-aspartate (NMDA), gamma-aminobutyrateA (GABAA), or glycine receptors in these inhibitory responses. Experiments were conducted in decerebrate, paralyzed, and ventilated cats. Control responses to PRG stimulation were obtained from recordings of the left phrenic nerve activity. After systemic injection of MK-801, bicuculline, or strychnine (antagonists to NMDA, GABAA, or glycine receptors, respectively), responses to stimulation were again recorded. Inspiratory termination elicited by the PRG stimulation persisted after antagonism of NMDA, GABAA, or glycine receptors. The onset latency and duration of the transient inhibition were not changed after administration of bicuculline, but MK-801 administration did significantly prolong the duration of the transient inhibition. Strychnine significantly prolonged both the onset latency and the duration. These data suggest that none of the three receptor types is required in the inspiratory termination response elicited by electrical stimulation of the PRG region and that NMDA, GABAA, or glycine receptor-mediated neurotransmission is not solely responsible for the transient inhibitory response. However, the prolonged onset and duration of the transient inhibition after strychnine administration suggest that glycine does normally participate in this response.

Endogenous nitric oxide required for an integrative respiratory function in the cat brain

1. The involvement of nitric oxide (NO) in the respiratory function of the pons was examined by microinjecting NO synthase-related drugs into discrete regions of the pontine respiratory group (PRG) in decerebrate and decerebellate cats. 2. Microinjection of N omega-nitro-L-arginine (L-NNA, inhibitor of NO synthase), but not D-NNA (the inactive enantiomer), significantly prolonged the duration of inspiration in all 10 cats when lung inflation was withheld. 3. The prolongation of inspiration produced by L-NNA was partially reversed in three cats by microinjections of L-arginine (NO synthase substrate) at the same sites. 4. We conclude that endogenous production of NO from L-arginine in the PRG region is involved in the normal function of the pontine pneumotaxic mechanism. These findings provide the first conclusive evidence that endogenous NO formation is involved in the mechanisms associated with respiratory rhythm generation.

Maximum anal sphincter strength measured by the solid sphere test and anal pressure profiles

OBJECTIVE

To evaluate two methods of quantifying external anal sphincter function.

DESIGN

Open study.

SETTING

Helsingborg Hospital, Sweden.

SUBJECTS

73 patients (63 women and 10 men), of whom 25 were incontinent of gas and liquid or solid stool.

INTERVENTIONS

Anal pressure profiles and the "solid sphere" test.

OUTCOME MEASURE

Correlation between results of tests and presence of incontinence.

RESULTS

Continent patients were younger than incontinent ones. The correlation between the maximum force the patient could retain and the maximum anal squeeze pressure was good (r = 0.67, p < 0.001). Younger continent patients (n = 48) and significantly higher pressures than incontinent patients (n = 25), but the range and overlap were wide. The reproducibility of both methods was good.

CONCLUSIONS

Although the solid sphere test is easier and quicker to do, anal pressure profiles yield more information that is important in the evaluation of incontinence.

Discharge patterns of levator palpebrae superioris motoneurons during vertical lid and eye movements in the monkey

1. We recorded single-unit activity in the caudal central nucleus (CCN) of the oculomotor complex in monkeys trained to make vertical saccadic, smooth-pursuit, and fixation eye movements. We confirmed that our recordings were from motoneurons innervating the upper lid, because small lesions placed at the sites of responsive units were recovered among neurons labeled by horseradish peroxidase (HRP) injections into the levator palpebrae superioris muscle. 2. For fixations above a threshold lid position, levator motoneurons discharged at a steady rate, which increased linearly with upward lid position. The average position sensitivity during fixation was 2.9 spikes/s per deg, and the average lid motoneuron was recruited into steady firing when the eye was looking 10 degrees down. 3. During upward saccades, levator motoneurons discharged a burst of spikes that began, on average, 7.3 ms before the lid movement if the saccade started from a straight-ahead position; the lead time decreased considerably as the initial eye and lid positions shifted downward. The firing rate usually reached its peak (130-280 spikes/s) at the very onset of the burst and declined gradually during the course of the saccade. The steady rate associated with the new fixation position was reached about halfway during the saccade. All units exhibited a pause in firing during the initial half of large downward saccades; during small saccades, the pause was inconspicuous or absent. 4. During vertical sinusoidal smooth pursuit, levator motoneurons exhibited a sinusoidal modulation in firing rate, which led eye position by an average of 23 degrees at 0.3 Hz. The average velocity sensitivity calculated from such data was 0.63 spikes/s per deg/s. 5. Although they exhibit a number of qualitative similarities, the discharge patterns of levator motoneurons and superior rectus motoneurons differ in several respects. First, during a blink, when the lid undergoes a large depression but the eye exhibits only a brief transient displacement, levator motoneurons cease firing completely, whereas superior rectus motoneurons continue to discharge. Second, for all types of coordinated lid and eye movements, levator motoneurons discharge at lower firing rates than do superior rectus motoneurons. Third, during saccades, levator motoneurons have less conspicuous and shorter-lasting bursts and pauses than do motoneurons involved in rotating the eye. 6. During upward gaze, the qualitative similarity of their burst-tonic discharge patterns suggests that levator and superior rectus motoneurons receive input signals that originate from a common source, but that the signals are processed differently to deal with the different loads facing these muscles.(ABSTRACT TRUNCATED AT 400 WORDS)

Effects of intravenous bicuculline and strychnine on inspiratory inhibitory responses in the cat

Single shock stimulation of the superior laryngeal nerve (SLN), intercostal nerve (ICN), phrenic nerve (PN) or within the medullary respiratory groups (DRG-VRG) produces a transient, short-latency attenuation of inspiratory motor activity. Trains of stimuli delivered to SLN and ICN cause premature termination of inspiration. This study examined involvement of glycine and GABAA receptors in these reflex inhibitions. Experiments were conducted in decerebrate, vagotomized, and paralyzed cats. Control responses of left PN activity to threshold single shock stimulation of SLN, PN, ICN and the DRG-VRG were recorded and the thresholds for SLN- and ICN-evoked inspiratory termination were determined. Five min after intravenous injection of bicuculline (1 mg/kg) or strychnine (50 micrograms/kg), the responses to stimulation were again recorded. This procedure was reiterated until the cumulative dose elicited marked convulsions. Neither drug affected the inspiratory terminating reflexes. Systemic bicuculline had no effect on transient inspiratory inhibition. However strychnine prolonged the onset latency and the duration of all four inhibitory responses. Since the degree of transient inhibition was not lessened (only delayed), it appears that these inspiratory inhibitory reflexes do not rely exclusively on actions of glycine or GABAA receptors.

Rat liver nodules induced by 2-acetylaminofluorene lose an ability to take up indocyanine green in the process of hepatocarcinogenesis

Indocyanine green (ICG) was injected into rat liver nodules induced by 2-acetylaminofluorene (2-AAF) via portal vein. The relationship between ICG staining and cell atypism of liver nodules was examined by means of histology and DNA flow cytometry. After 2-AAF administration, many small nodules appeared on the liver surface. All hyperplastic nodules were ICG stained until 10 weeks after the administration, but some nodules were not stained after 14 weeks. ICG-stained nodules histologically consisted of benign tissues and borderline lesions, and many of them showed "diploidy" in DNA cytometry. ICG-unstained nodules consisted of hepatocellular carcinoma (HCCs) and borderline lesions, and many of them showed "aneuploidy". In this way, it has been suggested that HCC could derive from hyperplastic nodules and that they might lose an ability to take up ICG in the process of hepatocarcinogenesis. Immunohistochemical staining for glutathione-S-transferase alpha (GST-alpha), a carrier protein of ICG in hepatocytes, was well correlated with ICG staining in the nodules, suggesting that the loss of ICG uptake in HCC was partly due to the decrease of GST-alpha. Moreover, the appearance of ICG unstained and aneuploid nodules was significantly inhibited in rats which were fed on diet containing Syosaiko-to after the administration of 2-AAF. Chemopreventive effect of Syo-saiko-to on hepatocarcinogenesis was identified.

Beta 2-adrenergic receptor mRNA is overexpressed in neoplastic human thyroid tissues

The expression of beta 2-adrenergic receptor (AR) mRNA was investigated in normal and neoplastic human thyroid tissues. A combination of techniques for reverse transcribing mRNA into cDNA and the incorporation of 32P-gamma ATP into the polymerase chain reaction (PCR)-generated fragments allowed us to detect beta 2-AR mRNA in surgically excised thyroid specimens. The levels of beta 2-AR cDNA generated by PCR in thyroid adenomas and cancers were 3.3 and 6.9 times, respectively, as high as that of normal thyroid tissues. These findings suggest that the level of beta 2-AR mRNA is correlated with the extent of differentiation in neoplastic tissues. The present study provides new insights into the relationships between the AR-adenylate cyclase system and the regulation of the growth and differentiation in neoplastic human thyroid tissues.

Anal sphincter competence in healthy women: clinical implications of age and other factors

Normal variation in anal sphincter competence was examined with anal pressure profilometry, using a low compliant recording system and a perfused catheter, in 49 healthy women with a mean age of 51 years (range 20-79). Maximum resting anal pressure and maximum squeeze pressure declined with age (r = -0.61; P less than .001 for both), more rapidly so after menopause. Rectal pressure increased with body mass index (r = 0.60, P less than .001). Closing pressure (ie, the difference between maximum resting anal pressure and rectal pressure), an important determinant of anal continence, was more markedly reduced with age (r = -0.69, P less than .001) than was maximum resting anal pressure. Age-related changes were found for the length of the anal canal (r = -0.36, P less than .05). Parity and anal pressures were unrelated. Women are more frequently affected by anal incontinence than are men. Anal pressure profilometry is a useful diagnostic aid, though age-related changes must be taken into consideration when evaluating the results. The more rapid decline of anal pressures after menopause might imply that anal sphincter tissue is a target for estrogen.