Rates and Equilibria for a Photoisomerizable Antagonist at the Acetylcholine Receptor of Electrophorus Electroplaques

Voltage-jump and light-flash experiments have been performed on isolated Electrophorus electroplaques exposed simultaneously to nicotinic agonists and to the photoisomerizable compound 2,2'-bis-[α-(trimethylammonium)methyl]-azobenzene (2BQ). Dose-response curves are shifted to the right in a nearly parallel fashion by 2BQ, which suggests competitive antagonism; dose-ratio analyses show apparent dissociation constants of 0.3 and 1 µM for the cis and trans isomers, respectively. Flash-induced trans → cis concentration jumps produce the expected decrease in agonist-induced conductance; the time constant is several tens of milliseconds. From the concentration dependence of these rates, we conclude that the association and dissociation rate constants for the cis-2BQ-receptor binding are approximately ~ 10^8 M^(-1) s^(-1) and 60 s^(-1) at 20ºC; the Q_(10) is 3. Flash-induced cis → trans photoisomerizations produce molecular rearrangements of the ligand-receptor complex, but the resulting relaxations probably reflect the kinetics of buffered diffusion rather than of the interaction between trans-2BQ and the receptor. Antagonists seem to bind about an order of magnitude more slowly than agonists at nicotinic receptors

Acute complete heart block in dogs

A study has been conducted immediately and up to 18 days after the surgical production of complete heart block in dogs. Immediately after surgery cardiac output, coronary flow, and mean arterial pressure were reduced in rough proportion to the degree of bradycardia. In time, these measures began to return toward preoperative levels. Paralleling the diminished left ventricular work was a diminished left ventricular oxygen consumption with little consequent change in myocardial efficiency. Small rises were detected in central venous pressure. At autopsy, the only unequivocal abnormality was myocardial hypertrophy which became measurable between 2 and 18 days after operation

A covalently bound photoisomerizable agonist. Comparison with reversibly bound agonists at electrophorus electroplaques

After disulphide bonds are reduced with dithiothreitol, trans-3-(alpha-bromomethyl)-3’-[alpha-(trimethylammonium)methyl]azobenzene (trans-QBr) alkylates a sulfhydryl group on receptors. The membrane conductance induced by this “tethered agonist” shares many properties with that induced by reversible agonists. Equilibrium conductance increases as the membrane potential is made more negative; the voltage sensitivity resembles that seen with 50 [mu]M carbachol. Voltage- jump relaxations follow an exponential time-course; the rate constants are about twice as large as those seen with 50 mu M carbachol and have the same voltage and temperature sensitivity. With reversible agonists, the rate of channel opening increases with the frequency of agonist-receptor collisions: with tethered trans-Qbr, this rate depends only on intramolecular events. In comparison to the conductance induced by reversible agonists, the QBr-induced conductance is at least 10-fold less sensitive to competitive blockade by tubocurarine and roughly as sensitive to “open-channel blockade” bu QX-222. Light-flash experiments with tethered QBr resemble those with the reversible photoisomerizable agonist, 3,3’,bis-[alpha-(trimethylammonium)methyl]azobenzene (Bis-Q): the conductance is increased by cis {arrow} trans photoisomerizations and decreased by trans {arrow} cis photoisomerizations. As with Bis-Q, ligh-flash relaxations have the same rate constant as voltage-jump relaxations. Receptors with tethered trans isomer. By comparing the agonist-induced conductance with the cis/tans ratio, we conclude that each channel’s activation is determined by the configuration of a single tethered QBr molecule. The QBr-induced conductance shows slow decreases (time constant, several hundred milliseconds), which can be partially reversed by flashes. The similarities suggest that the same rate-limiting step governs the opening and closing of channels for both reversible and tethered agonists. Therefore, this step is probably not the initial encounter between agonist and receptor molecules

A photoisomerizable muscarinic antagonist. Studies of binding and of conductance relaxations in frog heart

These experiments employ the photoisomerizable compound, 3,3'-bis- [alpha-(trimethylammonium)methyl]azobenzene (Bis-Q), to study the response to muscarinic agents in frog myocardium. In homogenates from the heart, trans-Bis-Q blocks the binding of [3H]-N-methylscopolamine to muscarinic receptors. In voltage-clamped atrial trabeculae, trans- Bis-Q blocks the agonist-induced potassium conductance. The equilibrium dose-response curve for carbachol is shifted to the right, suggesting competitive blockade. Both the biochemical and electrophysiological data yield a dissociation constant of 4-5 microM for trans-Bis-Q; the cis configuration is severalfold less potent as a muscarinic blocker. Voltage-clamped preparations were exposed simultaneously to carbachol and Bis-Q and were subjected to appropriately filtered flashes (less than 1 ms duration) from a xenon flashlamp. Trans leads to cis and cis leads to trans photoisomerizations cause small (less than 20%) increases and decreases, respectively, in the agonist-induced current. The relaxation follows an S-shaped time course, including an initial delay or period of zero slope. The entire waveform is described by [1 - exp(-kt)]n. At 23 degrees C, k is approximately 3 s-1 and n is 2. Neither k nor n is affected when: (a) [Bis-Q] is varied between 5 and 100 microM; (b) [carbachol] is varied between 1 and 50 microM; (c) carbachol is replaced by other agonists (muscarine, acetylcholine, or acetyl-beta-methylcholine); or (d) the voltage is varied between the normal resting potential and a depolarization of 80 mV. However, in the range of 13-30 degrees C, k increases with temperature; the Q10 is between 2 and 2.5. In the same range, n does not change significantly. Like other investigators, we conclude that the activation kinetics of the muscarinic K+ conductance are not determined by ligand-receptor binding, but rather by a subsequent sequence of two (or more) steps with a high activation energy

Attitudes toward child mental health services: adaptation and development of an attitude scale

Research shows that a considerable number of children and adolescents suffer needlessly from psychological problems and only about 50% of those receive the necessary services. Considering the impact of untreated child psychological problems on problems in adulthood, it is important to examine the influence of attitudes on seeking mental health service for children. Currently, no known measure exists to measure attitudes toward mental health services for children. Building on previous research, the goal of the present study was to develop a measure of individuals' attitudes toward mental health services for children. Using confirmatory factor analysis, the factor structure was assessed using a sample of university students (N = 250). In addition, several hypotheses were tested examining the influence of previous experience with mental health services on attitudes towards psychological services and mental health stigma. Finally, differences in child characteristics on intended help-seeking were examined. The measure developed consists of 26-items scored from 0 (strongly disagree) to 5 (strongly agree). Overall, results indicated that the 3-factor structure of the measure developed was valid and reliable. Also, consistent with previous research on mental health services results supported the hypotheses of the current study. Future research will examine whether the 3-factor structure is replicated using a sample of parents

Parental Attitudes Toward Child Mental Health Services: The Influence of Ethnicity and Child Characteristics on Help-Seeking Intentions

Help-seeking has been studied for over 20 years, but much is yet to be known about what variables influence parental help-seeking. In the present studies, participants were recruited from Texas, Mississippi, and Louisiana. Study 1, included 260 caregivers recruited from local school districts and a church. Using confirmatory factor analysis, results supported the hypothesized 3-factor structure of the Parental Attitudes Toward Psychological Services Inventory (PATPSI) and internal consistency ranged from moderate to high. Study 2 conducted subsequent analyses on the data from Study 1. Correlation analyses supported the relationships among parental attitudes, stigma, and help-seeking. Secondly, parents with previous use of child mental health services reported more positive attitudes and less stigma than parents with no previous use. Thirdly, no significant gender differences were found, but there was a trend toward parents reporting higher intentions for boys than girls. Additionally, African Americans reported less positive attitudes and more stigma than the other ethnic groups. Finally, moderation analyses suggested that attitudes are more likely to influence help-seeking for European Americans but not for African Americans, and stigma appeared to influence helpseeking for Hispanic Americans but not for European Americans; no moderation effects were found for child gender. Finally, analyses indicated that only stigma and attitudes were significant independent predictors of help-seeking. Study 3 was a sub-sample from Study 1 (N = 118) who completed additional measures. The purpose was to replicate findings from Study 2 and examine test-retest reliability of the PATPSI. Test-retest reliability for the PATPSI was low in this sample. Overall, results were consistent with Study 2. Results indicated that parents with previous service use reported higher externalizing symptoms (not internalizing) than those with no previous use. Inconsistent with Study 2, Asian Americans reported less positive attitudes, and African Americans reported less stigma than European Americans and Asian Americans. Additionally, stigma tolerance was found to have a stronger influence on European Americans likelihood of future service use than for African Americans. Furthermore, the interaction between problem type and gender was not a significant predictor of likelihood of future use. Finally, only previous service use and attitudes (not stigma) were independent predictors of likelihood of future use. Implications for future research and practice are discussed

The Effect Of A Medical Decompression Protocol On The Use Of Antiemetics, Nasogastric Tube Usage And Diet Advance In Late Stage Cancer Patients With Functional Intestinal Obstruction

At the end of life, many patients suffer from a syndrome that simulates classic small bowel obstruction. The traditional approach to intestinal obstruction is relief of pressure in the gastrointestinal tract using mechanical methods such as naso-gastric tube insertion and suctioning. This relieves the distension of the hollow organs and thus the nausea.. Pharmacologic methods are also used in the care of these patients, however, there is debate as to which agents to use and when to use them. The Medical Decompression protocol is a non-invasive pharmacologic approach to this problem. It brings with it ease and economy of delivery, the ability to administer it in intravenous as well as oral form, and is a multi-agent protocol of tried and true drugs used at the end of life: 1/2 Metoclopramide, Dexamethasone, Diphenhydramine, and Pantoprazole Prior to initiating this intervention, patients and their families are educated and are aware that this intervention is most likely a temporary measure aimed at symptom relief, as well as an attempt to improve quality of life. Our sample contained 42 males and 62 females, with an average age of about 70 years. About 51% of participants received MD (n = 53). Results indicated that there was a statistically significant difference between the two groups related to days to progress diet. We propose that a pharmacologic method such as MD is strongly considered as first line treatments for the functional intestinal obstruction syndrome and indeed be considered as adjuncts to allow the removal of invasive mechanical interventions in the end of life patient

Chronic heart block in dogs; a method for producing experimental heart failure

A method is described for the production of chronic atrioventricular block in dogs, by incision of the region of the bundle of His through the open right atrium during temporary caval occlusion. Exercise tolerances, chest x-ray films, electrocardiograms, phonocardiograms, cardiac outputs, intracardiac pressures, femoral pressures, and left ventricular coronary flows were obtained preoperatively and from 1 to 10 months postoperatively. The majority of the animals developed clinical, laboratory, and pathological evidence of congestive heart failure. All animals had generalized myocardial hypertrophy

A primary breast cancer with distinct foci of estrogen receptor-alpha positive and negative cells derived from the same clonal origin as revealed by whole exome sequencing

© 2018, Springer Science+Business Media, LLC, part of Springer Nature. Background/purpose: Tumor heterogeneity is a now well-recognized phenomenon that can affect the classification, prognosis and treatment of human cancers. Heterogeneity is often described in primary breast cancers based upon histologic subtypes, hormone- and HER2-receptor status, and immunolabeling for various markers, which can be seen within a single tumor as mixed cellular populations, or as separate discrete foci. Experimental design/methods: Here, we present a case report of a patient’s primary breast cancer that had two separate but adjacent histologic components, one that was estrogen receptor (ER) positive, and the other ER negative. Each component was subjected to whole exome sequencing and compared for gene identity to determine clonal origin. Results: Using prior bioinformatic tools, we demonstrated that both the ER positive and negative components shared many variants, including passenger and driver alterations. Copy number variations also supported the two components were derived from a single common clone. Conclusions: These analyses strongly suggest that the two ER components of this patient’s breast cancer were derived from the same clonal origin. Our results have implications for the evolution of breast cancers with mixed histologies, and how they might be best managed for optimal therapy

IMMUNOLOGIC STUDIES OF AUTOIMMUNE DISEASE IN NZB/NZW F1 MICE : I. BINDING OF FLUORESCEIN-LABELED ANTINUCLEOSIDE ANTIBODIES IN LESIONS OF LUPUS-LIKE NEPHRITIS

For the past 3 years NZB and NZW mice have been maintained by sister-brother matings from English breeder stock. NZB/NZW F1 hybrids developed lupus-like nephritis during the 6th to 7th month and few survived beyond the 8th month. Renal tissues of these animals were examined with fluorescein-labeled antinucleoside sera, specific for thymine and cytosine, for the presence of denatured DNA in GCW, and with labeled antibody to mouse IgG for the presence of excess host globulin in the same areas. The following results have been obtained: (a) All 51 hybrids, over 5 months of age, had an excess of mouse globulin in GCW. 40 animals between the ages of 5 and 12 months showed, in the same areas, antigens which bound one or both of the antinucleoside antibodies. (b) Renal tissues of 19 NZB mice, 5–19 months old, and 27 NZW mice, 2–18 months old, were examined. Excess host globulin was seen in GCW of 13 NZB and 20 NZW animals. The tissues of only two old NZB mice, 14 months of age, bound antinucleoside antibody but none of the other animals did. The association of rapidly fatal lupus-like nephritis in NZB/NZW F1 mice with denatured DNA and mouse globulin in GCW supports the hypothesis involving this antigen-antibody complex in the pathogenesis of the disease