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Biomedical subjects

S M Johnson

Publications and source records attributed to S M Johnson.

At least 91 records · Page 5Linked to original sources
PubMed1996

Notations for high efficiency data presentation in mammography.

As a result of improvements in Medical Language Processing, the availability of categorical information (such as diagnoses or radiology findings) is increasing rapidly. This increased availability has created a need for more efficient methods for computer presentation. One method for developing such presentations would be to adapt the hand-written notation systems already used in paper-based records. We have characterized one such notation system, the Mammography Notation Sublanguage(MNS). The MNS is a true medical sublanguage, with a definable lexicon and syntax. Compared with text reports, it represents a 37-fold size compression. A single "base", sublanguage pattern is identified for possible computer presentation of mammography findings. The issues involved in using such sublanguages for data presentation are discussed.

Language↗
PubMed1995

Low sexual desire in women: the effects of marital therapy.

A total of 49 couples, in which the women were experiencing inhibited sexual desire (ISD), received Emotionally Focused Therapy for Couples (EFT) or were assigned to a wait-list control group. An additional 15 couples were recruited as a non-ISD comparison sample. Only very modest treatment and control group differences were found after treatment. Females treated with marital therapy made significant gains on one measure of sexual desire and on level of depressive symptomatology. Overall, the marital treatment group seemed to make clinically significant gains from pre- to posttreatment which were largely maintained at follow-up. Lower levels of initial marital distress resulted in greater treatment gains, and better pretreatment marital adjustment predicted better posttreatment overall sexual adjustment. The main difference found between ISD and non-ISD couples was that ISD couples had significantly more sexual distress. Results are discussed in light of the unique features of this subject population, and suggestions are given for future research.

Adult↗
PubMed1994

Pacemaker behavior of respiratory neurons in medullary slices from neonatal rat.

1. We have hypothesized that pacemaker neurons in the pre-Bötzinger complex (pre-BötC) form the kernel for respiratory rhythm generation. A prediction of this hypothesis is that oscillatory behavior in some respiratory neurons could persist in the absence of synaptic transmission. In this study we used extracellular recording of neuronal activity in slice preparations from neonatal rat medulla that generate respiratory rhythm in vitro to determine 1) whether pacemaker properties are present in pre-BötC and unique to respiratory neurons, 2) whether pacemaker properties are common to all respiratory neurons, and 3) the spatiotemporal patterns of pacemaker neuron activity. 2. Whole cell recordings from respiratory neurons verified that bathing the slices in a low-Ca2+/high-Mg2+ solution (low-Ca2+ solution) eliminated endogenous respiratory synaptic inputs and electrically evoked synaptic inputs. 3. Sixty-three neurons spontaneously generated rhythmic bursts of action potentials in low-Ca2+ solution. After we switched to control solution to reactivate the respiratory network, these neurons were classified on the basis of their spike discharge patterns relative to the respiratory cycle as: 1) inspiratory (I) neurons (n = 41), 2) tonic expiratory (tonic E) neurons (n = 4), and 3) tonic neurons (n = 18). 4. In other experiments we tested I and tonic E neurons identified first in control solution for bursting behavior in low-Ca2+ solution. Several I neurons (n = 5 of 33), but none of the tonic E neurons (n = 0 of 13), continued to burst rhythmically. 5. Bursting and nonbursting respiratory neurons were distributed throughout the ventrolateral reticular formation within the pre-BötC as well as in the ventral respiratory group (VRG) immediately caudal to the pre-BötC. 6. We conclude that subpopulations of VRG neurons in vitro have rhythmic bursting properties when synaptic transmission is abolished. Respiratory neurons, especially I neurons, were the most prevalent class of bursting cells. Only a small percentage of respiratory neurons, however, had pacemaker properties. These findings are consistent with the hypothesis that the respiratory oscillator includes specialized neurons with intrinsic oscillatory properties.

Action Potentials↗
PubMed1993

In-session change in emotionally focused therapy.

This article presents 3 different studies of in-session changes in emotionally focused couples therapy (EFT). Studies of in-session conflict events demonstrate both that couples' conflict interaction at the end of treatment is more affiliative and interdependent than at the beginning of treatment and that peak session conflict interaction is deeper in level of experience and more affiliative than the interaction in poor session conflict episodes. In addition, events beginning with intimate, affective self-disclosure by one partner were found to involve greater affiliation in spouses' responses to the self-disclosure than in a control event not involving self-disclosure. The possible change processes in EFT are discussed in light of these results.

Adult↗
PubMed1993

Amino-terminal sequence analysis of the Coccidioides immitis chitinase/immunodiffusion-complement fixation protein.

A chitinase isolated from Coccidioides immitis was subjected to amino-terminal protein sequence analysis. The resulting 18-amino-acid sequence was compared with the previously reported amino acid sequence of coccidioidal immunodiffusion-complement fixation (IDCF) antigen. From the homology of the two sequences, the results support the identification of the IDCF antigen with a chitinase.

Amino Acid Sequence↗
PubMed1993

Effects of aging on the intrinsic membrane properties of medial NTS neurons of Fischer-344 rats.

1. Recent studies have demonstrated that the arterial baroreflex is imparied with aging and have implicated central components of the baroreflex arc in this autonomic dysfunction. Neurons in the medial portion of the nucleus tractus solitarius (mNTS) receive a major input from the arterial baroreceptors. The present study was undertaken to characterize the intrinsic membrane properties of mNTS neurons in young rats and to test the hypothesis that these properties are altered with aging. An in vitro brain stem slice preparation was used to record intracellularly from mNTS neurons; passive membrane properties, action potential characteristics, and repetitive firing properties were examined and compared. 2. Neurons in the mNTS of young (3-5 mo old) Fischer-344 rats (F-344; n = 35) had a resting membrane potential of -57 +/- 6.9 mV (mean +/- SD), a membrane time constant of 18 +/- 9.0 ms, and an input resistance of 110 +/- 60 m omega. Action potential amplitude was 81 +/- 7.5 mV with a duration at half-height of 0.83 +/- 0.15 ms. The spontaneous firing rate in 24 cells was 4.3 +/- 2.9 Hz. The amplitude and duration of the action potential afterhyperpolarization (AHP) were 6.6 +/- 3.0 mV and 64 +/- 34 ms, respectively. All neurons expressed spike frequency adaptation, action potential AHP, and posttetanic hyperpolarization. Delayed excitation and postinhibitory rebound were present in 34 and 14% of neurons tested, respectively. Neurons from adult (10-12 mo old) F-344 rats (n = 34) were similar to the young F-344 rats with respect to all of these variables. 3. Neurons from aged (21-24 mo old) F-344 (n = 32) were similar to those from young and adult rats, but there were two potentially important differences: the mean input resistance of the aged neurons was higher (170 +/- 150 M omega), with a larger proportion (46% of aged neurons vs. 20% of young neurons and 21% of adult neurons) having input resistances > 150 M omega; and there was a tendency for a smaller percentage of aged neurons (16% of aged neurons vs. 34% of young neurons and 29% of adult neurons) to express delayed excitation. 4. The potential significance of a high input resistance was tested by comparing the steady-state current-voltage (I-V) relationships and the frequency-current (f-I) relationships among low-resistance (1-100 M omega), medium-resistance (101-200 M omega).(ABSTRACT TRUNCATED AT 400 WORDS)

Aging↗
PubMed1992

Excitatory effects of thyrotropin-releasing hormone on neurons within the nucleus ambiguus of adult guinea pigs.

The electrophysiological effects of thyrotropin-releasing hormone (TRH) on neurons within the nucleus ambiguus (NA) of adult guinea pigs were studied using an in vitro brain stem slice preparation. In 0.01-1.0 micron TRH, NA neurons depolarized (25/39), expressed enhanced postinhibitory rebound (8/8 tested), or exhibited oscillations of the membrane potential (17/39). Because the amplitude of postinhibitory rebound in tetrodotoxin (TTX) at various membrane potentials was not altered by TRH, it suggests that TRH enhanced postinhibitory rebound indirectly by depolarizing the cell membrane. The membrane potential oscillations in NA neurons were persistent in TTX and their frequency was dependent on the membrane potential, suggesting that these oscillations were due to intrinsic membrane properties and not to synaptic inputs. The excitation of NA neurons in vitro by TRH suggests that endogenous TRH may modulate the activity of neurons involved in the regulation of respiratory and autonomic function.

Action Potentials↗
PubMed1992

Measuring marital distress in couples with chronically ill children: the Dyadic Adjustment Scale.

The idea that couples with chronically ill children are particularly at risk for marital distress has been supported by clinical observation and empirical research. Three recent controlled studies, however, did not find evidence for this increased risk. A possible explanation for the discrepant findings is that these three studies employed Spanier's Dyadic Adjustment Scale (DAS) as a unidimensional measure of marital adjustment. To develop a better understanding of the discrepant findings of risk for marital distress in couples with chronically ill children, the present study examined both the appropriateness of the DAS's published norms as well as the criterion validity of the DAS for use in this population of couples. Three hundred and sixteen parents (158 couples) from a large urban pediatric health care setting completed a survey investigating interest and need to participate in an intervention program for marital distress. Results indicated that this instrument can reliably predict marital distress in this population of couples, however, mean DAS scores are higher than those established by Spanier.

Adaptation, Psychological↗
PubMed1992

Teaching the process of obtaining informed consent to medical students.

This paper describes a unit on the informed consent process taught to 119 first-year students at the Michigan State University College of Osteopathic Medicine in 1988-89. The unit consisted of a pretest and a posttest, a lecture, readings, small-group discussions, a model videotaped interview, and the students' videotaped interviews with one of two simulated patients. In the interviews, the students were most successful in establishing rapport and engaging the patients in discussions of treatment alternatives, and were less successful in perceiving the patients as unique individuals and in dealing with situations that involved conflict or confrontation. The authors suggest that curricula can be enhanced by focusing on the importance of patients' participation in the informed consent process.

Curriculum↗
PubMed1992

The coccidioidal complement fixation and immunodiffusion-complement fixation antigen is a chitinase.

Culture filtrates and autolysates of Coccidioides immitis have provided suitable crude antigens for the serodiagnosis and prognosis of coccidioidomycosis. One of these, a heat-labile antigen which participates in the immunodiffusion reaction corresponding to the complement fixation reaction (IDCF), has been characterized as a 110-kDa native protein that, when subjected to reducing conditions and heat, yields a 48-kDa component. The present report provides serologic and biochemical evidence that this antigen is a chitinase. This chitinase, isolated from 48-h culture filtrate of the spherule-endospore-phase C. immitis by affinity adsorption to chitin, formed a line of identity with the IDCF reference antigen and participated in the complement fixation reaction with human serum. It lost its enzymatic as well as antigenic activity when heated, but when not heated it retained its enzymatic activity even when precipitated with coccidiodal antibody present in human serum. This chitinase represents a significant serodiagnostic substance and may be important in the morphogenesis of C. immitis.

Antigens, Fungal↗
PubMed1992

Passive smoking: directions for health education among Malaysian college students.

This study investigated knowledge, attitudes, and preventive efforts of Malaysian college students regarding health risks associated with passive smoking, as well as possible directions for intervention and health education programs. Students responded anonymously to a structured written questionnaire. Statistical analyses were conducted to examine (1) differences in knowledge, attitudes, and preventive efforts between smokers and nonsmokers and between men and women; (2) the relationship between smoking by parents, siblings, and friends, and students' knowledge, attitudes, and preventive efforts; and (3) relationships between knowledge, attitudes, and preventive efforts. Peer groups and siblings had a substantial influence on students' attitudes toward passive smoking and their preventive efforts when exposed to passive smoke. A regression analysis revealed a statistically significant linear dependence of preventive efforts on knowledge and attitudes, with the attitude component playing the dominant role. This research suggests that educational efforts on passive smoking, directed toward young college students in developing countries such as Malaysia, should concentrate heavily on changing attitudes and reducing the effects of peer group and sibling influences.

Adult↗
PubMed1992

Membrane potential in myenteric neurons associated with tolerance and dependence to morphine.

Chronic treatment of guinea pigs with morphine produces subsensitivity (tolerance) of the longitudinal smooth muscle-myenteric plexus preparation to a variety of inhibitory agonists (e.g., mu opioid, alpha adrenoceptor and adenosine receptor agonists) and supersensitivity (dependence) to a variety of excitatory agonists (e.g., nicotine, 5-hydroxytryptamine and potassium ions). The present investigation was to determine if these changes in sensitivity could be related to changes in electrical properties of the S and AH neurons in the myenteric plexus. S neurons from morphine-implanted animals were significantly depolarized (7 mV) relative to those from placebo-implanted animals, whereas the membrane potential of AH neurons was unchanged. Approximately 60% of S neurons were hyperpolarized by morphine. In this subset of neurons, membranes were significantly depolarized but the threshold was unchanged in morphine-implanted animals. This means that resting potentials of S neurons from tolerant preparations are closer to threshold. The hyperpolarization produced by morphine (0.1 microM) was similar in preparations from morphine- and placebo-implanted animals. Thus, the partially depolarized state of S neurons in the myenteric plexus is the cause of the subsensitivity and supersensitivity to agonists and can explain both tolerance and dependence. Changes in opioid receptors or their coupling to potassium channels do not appear to contribute to tolerance in the longitudinal smooth muscle-myenteric plexus.

Action Potentials↗
PubMed1992

Stability of ceftazidime in plastic syringes and glass vials under various storage conditions.

The stability of ceftazidime solutions (100 and 200 mg/mL) in plastic syringes and glass vials under various storage conditions was examined. Solutions of ceftazidime 100 and 200 mg/mL in sterile water were placed in polypropylene plastic syringes or glass vials and stored (1) at 21-23 degrees C for up to 8 hours, (2) at 4 degrees C for up to 96 hours, (3) at -20 degrees C for 28 days and then 21-23 degrees C for up to 8 hours, (4) at -20 degrees C for 28 days and then 4 degrees C for up to 96 hours, (5) at -20 degrees C for 91 days and then 21-23 degrees C for up to 8 hours, or (6) at-20 degrees C for 91 days and then 4 degrees C for up to 96 hours. Samples were withdrawn from each syringe and vial at designated times and assayed by high-performance liquid chromatography. Solutions were judged to be stable if drug concentrations remained above 90% of the initial values. The number of particles in each container under each storage condition was also evaluated. Ceftazidime was stable under all storage conditions. In all containers, particulate matter was within USP specifications for small-volume injections, with no change in particle count as a result of the freezing and thawing. Ceftazidime in sterile water in either glass vials or plastic syringes is stable for 8 hours at room temperature or 96 hours at 4 degrees C when such storage occurs (1) immediately after constitution, (2) after 28 days of frozen storage, or (3) after 91 days of frozen storage.

Ceftazidime↗
PubMed1991

The electrophysiological effects of [D-Ala2,N-Me-Phe4,Gly5-ol]enkephalin on guinea-pig myenteric neurons.

The electrophysiological effects of a highly selective mu opioid agonist, [D-Ala2,N-Me-Phe4,Gly5-ol]enkephalin (DAGO) were investigated on S and AH myenteric neurons in the guinea-pig ileum. Administration of DAGO (500 nM) caused a mean membrane hyperpolarization (+/- S.E.M.) of 7.8 +/- 0.5 mV in 58 of 138 S neurons, associated with a decrease in input resistance from 158 +/- 18 to 132 +/- 13 m omega. DAGO also produced a significant decrease in the mean amplitude of the cholinergic fast excitatory postsynaptic potentials (EPSPs), from 12.0 +/- 1.1 to 6.6 +/- 1.4 mV in 13 of 27 S neurons. On the other hand, in AH neurons, DAGO did not significantly affect the membrane potential, input resistance, action potential configuration, slow after-hyperpolarization or the antidromic action potential. The experiments indicate that the acute effects of mu opioids in the guinea-pig ileum are confined to a subpopulation of a single electrophysiological class of myenteric neurons.

Action Potentials↗
PubMed1991

Electrophysiological properties of neurons within the nucleus ambiguus of adult guinea pigs.

1. The purpose of this study was to determine the electrophysiological properties of neurons within the region of the nucleus ambiguus (NA), an area that contains the ventral respiratory group. By the use of an in vitro brain stem slice preparation, intracellular recordings from neurons in this region (to be referred to as NA neurons, n = 235) revealed the following properties: postinhibitory rebound (PIR), delayed excitation (DE), adaptation, and posttetanic hyperpolarization (PTH). NA neurons were separated into three groups on the basis of their expression of PIR and DE: PIR cells (58%), DE cells (31%), and Non cells (10%). Non cells expressed neither PIR nor DE and no cells expressed both PIR and DE. 2. PIR was a transient depolarization that produced a single action potential or a burst of action potentials when the cell was released from hyperpolarization. In the presence of tetrodotoxin (TTX), the maximum magnitude of PIR was 7-12 mV. Under voltage-clamp conditions, hyperpolarizing voltage steps elicited a small inward current during the hyperpolarization and a small inward tail current on release from hyperpolarization. These currents, which mediate PIR, were most likely due to Q-current because they were blocked with extracellular cesium and were insensitive to barium. 3. DE was a delay in the onset of action potential firing when cells were hyperpolarized before application of depolarizing current. When cells were hyperpolarized to -90 mV for greater than or equal to 300 ms, maximum delays ranged from 150 to 450 ms. The transient outward current underlying DE was presumed to be A-current because of the current's activation and inactivation characteristics and its elimination by 4-aminopyridine (4-AP). 4. Adaptation was examined by applying depolarizing current for 2.0 s and measuring the frequency of evoked action potentials. Although there was a large degree of variability in the degree of adaptation, PIR cells tended to express less adaptation than DE and Non cells. Nearly three-fourths of all NA neurons adapted rapidly (i.e., 50% adaptation in less than 200 ms), but PIR cells tended to adapt faster than DE and Non cells. PTH after a train of action potentials was relatively rare and occurred more often in DE cells (43%) and Non cells (33%) than in PIR cells (13%). PTH had a magnitude of up to 18 mV and time constants that reflected the presence of one (1.7 +/- 1.4 s, mean +/- SD) or two components (0.28 +/- 0.13 and 4.1 +/- 2.2 s).(ABSTRACT TRUNCATED AT 400 WORDS)

Action Potentials↗
PubMed1991

Nonspecific tolerance in ileal circular muscle-myenteric plexus preparations from morphine-pretreated guinea pigs.

Guinea pigs were treated for 6 to 8 days by s.c. implantation of pellets, each containing a mixture of morphine base (120 mg) and morphine hydrochloride (35 mg). Each guinea pig received one pellet. Circular muscle-myenteric plexus preparations from the pretreated animals exhibited 6.1-fold tolerance to the inhibitory effects of morphine on nerve-mediated contractions of the circular muscle. Morphine-tolerant tissues were also tolerant to the inhibitory effects of another mu agonist, (D-Ala2-N-Me-Phe4,Gly5- ol)enkephalin (2.7-fold), the selective kappa agonist, dynorphin (4.0-fold), the adrenoceptor agonist, clonidine (22-fold) and the adenosine receptor agonist, 2-chloroadenosine (43-fold). That is, tissues were tolerant to four inhibitory agents that acted via four distinct receptors. Tolerance therefore cannot be explained by a change in the opioid receptor that was occupied chronically by morphine. Nonspecific tolerance would result if an intracellular effector mechanism that was shared by each agonist was altered by morphine pellet implantation. Alternatively, tolerance could be a consequence of the neuronal hyperexcitability that is induced by chronic exposure to morphine. As such, inhibitory agents, irrespective of the receptors or intracellular mechanisms that they activate, may be less effective in reducing the excitability of myenteric neurons and hence less effective in decreasing transmitter release.

2-Chloroadenosine↗