Biomedical subjects

R Baker

Publications and source records attributed to R Baker.

At least 433 records · Page 24Linked to original sources

PubMed1986

Study of sulphamethoxazole in rheumatoid arthritis.

Twenty-three patients with rheumatoid arthritis (RA) entered a single-blind cross-over study of sulphamethoxazole 2 g daily compared to placebo. Sulphamethoxazole was administered for 3 months during the 6-month study. Sulphamethoxazole exhibited properties commensurate with a second-line effect with a significant acute-phase reactant response and a parallel change in the clinical state. Adverse effects were common and resulted in nine drug-related withdrawals, mainly due to nausea and vomiting. There were also reversible abnormalities in liver function tests on the active drug. The role of sulphonamides in treatment of RA requires further exploration.

Adult↗

PubMed1986

New developments for upper rate response in DDD pacing.

Although widely accepted as an effective method of dealing with rapid atrial rates in a DDD pacemaker, Wenckebach-type and multiblock-type upper rate behaviors may exacerbate pacemaker-mediated tachycardia through AV dissociation. In addition, pathologic atrial rates (e.g., atrial fibrillation, atrial flutter, automatic atrial tachycardia, etc.) frequently result in ventricular pacing at inappropriately high rates. New, more sophisticated algorithms available in today's microprocessor-based DDD pacing systems provide the capability to discriminate successfully a normal atrial rate response to exercise from a pathologic atrial rate. These and other improved capabilities allow the clinician to provide safe rate-responsive pacing to patients in whom rate-responsive pacing was previously contraindicated.

Electrocardiography↗

PubMed1986

A validity study of a new rating scale for psychiatric patients.

A criterion validation of a new scale, REHAB (Rehabilitation Evaluation Hall And Baker) (1) is described. Forty-three long-stay psychiatric patients from two wards were observed by a psychologist over a 2-week period using a time sampling procedure. The observed behaviour was coded into predetermined categories based on Blunden & Kushlick's (2) concept of engagement. Also during this period the ward nurses rated the 43 patients using the REHAB assessment. The time sampled observations were correlated with REHAB factors and items. Five hypotheses about the relationship between the two measures were tested. Four of the five hypotheses were supported by the data. Overall, despite certain limitations of the study, it is concluded that evidence is provided for the criterion validity of REHAB.

Activities of Daily Living↗

PubMed1986

Failure to vaccinate against whooping cough.

We describe a prospective study in which we investigated why children fail to get vaccinated against whooping cough, including an assessment of the attitudes of parents and professionals and the impact of different views of the contraindications. There was considerable disagreement among the professionals on the interpretation of the contraindications to immunisation, and the commonest reason for omitting pertussis vaccine was advice from the doctor based on dubious contraindications. When faced with parents anxious about the risks of immunisation health professionals are unable to find reassurance in the list of contraindications to immunisation.

Attitude of Health Personnel↗

PubMed1986

Terfenadine and brompheniramine maleate in urticaria and dermographism.

The effects of brompheniramine maleate (12 mg twice daily in sustained release form) and terfenadine (60 mg twice daily) on the symptoms and well-being of 16 adults with urticaria with or without dermographism were assessed by symptom questionnaire. Following an initial 2-week period without therapy, each drug was taken for 2 weeks in a randomised double-blind cross-over study. Both drugs produced significant relief of itch and rash but only brompheniramine produced significant drowsiness. Brompheniramine maleate was more effective than terfenadine in the patients with dermographism.

Adult↗

PubMed1986

A method for reconstructing patterns of somatosensory cerebral cortical activity.

An interactive graphics package was developed in order to acquire, display, and manipulate images of cerebral cortical autoradiographic data. The primary purpose for development of the system was to reconstruct accurate 2-dimensional maps of the functional activity within the somatosensory cerebral cortex. A Datacube Q-bus graphics module (QVG/QAF-123) was interfaced with the Micro PDP-11/23 to accept a standard RS170 video input signal, and autoradiographs of serial sections (each 20 microns thick) of a cerebral cortex were digitized individually to 768 X 512 X 8 bit resolution. Input look-up tables were used to standardize the autoradiographic data. Boundaries of the somatosensory cortex were entered (with a Summagraphics MM 1201 digitizer), and the image data was stored on disk file (a method of data compression was devised). A method for segmenting the image data for many (sequential) sections was developed that provided arrays from which the maps were generated. Thresholding, histogram equalization, edge detection and edge enhancement, and filters in both the spatial and frequency domains were employed to process the images of the maps. Plots of optical density values along any axis of the maps and gray level histograms of any map region could also be generated. Maps made by the described method are much higher in resolution than those produced by traditional (manual) methods, and permit analysis of the reconstructions in both the frequency and spatial domains.

Animals↗

PubMed1985

Cytology and intrinsic organization of the perihypoglossal nuclei in the cat.

The morphology of the neurons in the perihypoglossal nuclei (nucleus prepositus, nucleus intercalatus, and nucleus of Roller) of the cat was studied in normal Nissl material, and by intracellular injection of horseradish peroxidase. The neurons in the nucleus prepositus were morphologically heterogeneous. Many of the cells in the ventromedial part of the caudal prepositus had relatively large somata, and complex dendritic trees which arose from numerous proximal dendrites and ramified extensively in the ventromedial aspect of the prepositus. These neurons had thick axons which typically did not give rise to local collaterals. The cells in the dorsolateral part of the caudal prepositus tended to have small somata, and dendritic trees which arborized in that region of the nucleus. The axons of these small cells frequently gave rise to local collaterals which terminated in the prepositus. Most of the cells in the prepositus had medium-sized somata and relatively few dendrites which branched in an isodendritic manner and extended for long distances, frequently leaving the nucleus. These "principal" prepositus neurons had axons which arborized unilaterally, and often gave rise to collaterals which terminated in either the ipsilateral or contralateral prepositus. The neurons in the nucleus of Roller and nucleus intercalatus which were intracellularly injected with horseradish peroxidase resembled the multidendritic and small prepositus cells, respectively. The intrinsic connectivity of the perihypoglossal nuclei was also studied by injecting horseradish peroxidase or 3H-leucine into the prepositus nucleus. The results of these experiments suggest that the perihypoglossal nuclei are highly interconnected bilaterally, although the large cells in the ventromedial prepositus and the nucleus of Roller contribute little to these intrinsic connections, and are not major recipients of intrinsic inputs. On the other hand, the magnitude of the reciprocal connections between the prepositus and the nucleus intercalatus suggests that they are functionally related.

Animals↗

PubMed1985

Anatomical connections of the nucleus prepositus of the cat.

The afferent and efferent connections of the nucleus prepositus hypoglossi with brainstem nuclei were studied using anterograde and retrograde axonal transport techniques, and by intracellular recordings and injections of horseradish peroxidase into prepositus hypoglossi neurons. The results of experiments in which horseradish peroxidase was injected into the prepositus hypoglossi suggest that the major inputs to the prepositus hypoglossi arise from the ipsi- and contralateral perihypoglossal nuclei (particularly the prepositus hypoglossi and intercalatus), vestibular nuclei (particularly the medial, inferior, and ventrolateral nuclei), the paramedian medullary and pontine reticular formation, and from the cerebellar cortex (flocculus, paraflocculus, and crus I; the nodulus was not available for study). Regions containing fewer labeled cells included the interstitial n. of Cajal, the rostral interstitial n. of the medial longitudinal fasciculus, the n. of the posterior commissure, the superior colliculus, the n. of the optic tract, the extraocular motor nuclei, the spinal trigeminal n., and the central cervical n. The efferent connections of the prepositus hypoglossi were studied by injecting 3H-leucine into the prepositus hypoglossi, and by following the axons of intracellularly injected prepositus hypoglossi neurons. The results suggest that in addition to the cerebellar cortex, the most important extrinsic targets of prepositus hypoglossi efferents are the vestibular nuclei (particularly the medial, inferior, and ventrolateral nuclei, and the area X), the inferior olive (contralateral dorsal cap of Kooy and ipsilateral subnucleus b of the medial accessory olive), the paramedian medullary and pontine reticular formation, the reticular formation surrounding the parabigeminal n., the contralateral superior colliculus and pretectum, the extraocular motor nuclei (particularly the contralateral abducens nucleus and the ipsilateral medial rectus subdivision of the oculomotor nucleus), the ventral lateral geniculate n., and the central lateral thalamic nucleus. Other areas which were lightly labeled in the autoradiographic experiments were the contralateral spinal trigeminal n., the n. raphe pontis, the Edinger Westphal n., the zona incerta, and the paracentral thalamic n. Many of the efferent connections of the prepositus hypoglossi appear to arise from principal prepositus hypoglossi neurons whose axons collateralize extensively in the brainstem. On the other hand, small prepositus hypoglossi neurons project to the inferior olive, and multidendritic neurons project to the cerebellar flocculus, apparently without collateralizing in the brainstem.(ABSTRACT TRUNCATED AT 400 WORDS)

Afferent Pathways↗

PubMed1985

Inducible aldehyde dehydrogenases from rat liver cytosol.

Two rat hepatic cytoplasmic isozymes of aldehyde dehydrogenase, phi, induced by phenobarbital treatment, and tau, induced by TCDD treatment, have been purified from rat hepatic cytosol by ammonium sulfate fractionation, followed by ion-exchange and affinity chromatography. The specific activities of the two isozymes at pH 9.6 with propionaldehyde as substrate and NAD as cofactor were 2850 and 5250 nmol of NADH/min/mg protein for phi and tau isozymes, respectively. Estimates of molecular weights from gel filtration chromatography gave values of 118,000 Da for phi and 106,000 Da for tau. An isoelectric point for the tau enzyme of 6.5 was determined in an electrofocusing column, and approximately 7.2 for phi by immunoelectrophoresis. Both enzymes can oxidize a wide variety of aldehyde substrates, with Km values ranging from millimolar to micromolar. Long-chain aliphatic and aromatic aldehydes using NAD as cofactor tend to be the best utilized substrates. Only the tau enzyme is able to use NADP as cofactor. The measured Km for phi at pH 7.2 for acetaldehyde was 1.97 mM and for tau, 12.1 mM. Both enzymes showed similar inhibition characteristics with sodium arsenite and disulfiram, although the phi enzyme tended to be slightly more sensitive to all inhibitors.

Aldehyde Dehydrogenase↗

PubMed1985

Natural selection for resistance to mercury pollution.

The survival under conditions of mercury pollution of two natural populations of the marine gastropod Cerithium rupestre, derived from mercury-polluted and mercury-free sites, was tested in the laboratory. The results indicate a significantly higher survival rate for animals derived from the mercury-polluted site, in each of six repetitive experiments. We conclude that mercury resistance in marine organisms is reinforced in mercury polluted sites, presumably by natural selection for increased resistance. The evolution of metal tolerance in marine organisms may be as fast as that of metal tolerance in plants and the evolution of industrial melanisms in moths.

Animals↗

PubMed1985

A split binding site for transcription factor tau on the tRNA3Glu gene.

Yeast transcription factor tau forms a stable complex with tRNA genes. Using this property, the factor could be highly purified on a specific tDNA column. The purified factor was found by DNA footprinting to protect the whole yeast tRNA3Glu gene from position -8 to +81. A DNase-sensitive site was retained in the middle of the gene on both strands. The 3' border of the complex was mapped by exonuclease digestion at +88, just downstream of the termination signal. The 5' limit of the complex was found at position -11. However, upon prolonged incubation with exonuclease, the -11 blockage disappeared and the DNA molecules were digested to position +30 to 38 in the middle of the gene. Contact points at guanine residues were identified by dimethyl sulphate protection experiments. Reduced methylation of G residues in the presence of factor was found solely within the A block and in the B block region. All six invariant GC pairs (i.e., G10, G18, G19 and G53, C56 and C61) were found to have strong contacts with the factor. These results show that tau factor interacts with both the 5' and 3' half of the tRNA3Glu gene, with the B block region being the predominant binding site. The presence of this dual binding site suggests a model in which the factor would bind alternately at the A and B block regions to allow transcription of the internal promoter by RNA polymerase C.

Base Sequence↗

PubMed1985

An intracellular HRP-study of cat tensor tympani motoneurons.

The morphology of single tensor tympani motoneurons was investigated following antidromic identification and intracellular injection of horseradish peroxidase. Eight motoneurons were selected for complete reconstruction and quantitative analysis. The mean size of tensor tympani somata (26.3 +/- 1.8 micron) make this parvocellular cluster of motoneurons below the trigeminal motor nucleus a population of the smallest cranial motoneurons yet described. Axons emerged from either the soma or a primary dendrite. They coursed dorsolaterally frequently through the trigeminal motor nucleus before looping ventrolaterally into the Vth nerve. No collaterals were observed within the brainstem. The 5 primary dendrites of each cell branched heavily and, on average, exhibited 40 terminal branches with an average tree expansion of 1262.5 micron. The dendritic arborization extended far beyond the nuclear boundaries described by the distribution of cell bodies. These data suggest that the overall membrane area for synaptic innervation is large and thus it provides morphological evidence for the hypothesis that tensor tympani motoneurons receive divergent multisensory synaptic input. The latter assumption was supported by morphological and electrophysiological evidence including close the proximity of motoneuronal dendrites to auditory (superior olivary complex) and somatosensory (trigeminal) relay centers. Since no dendrite ever entered the trigeminal motor nucleus proper the tensor motoneuron pool is distinct from the trigeminal not only in terms of soma size, location and function, but also the disposition and expansion of the postsynaptic receptive field. Based on these criteria the tensor tympani motoneuron pool should no longer be regarded as an accessory trigeminal nucleus but be recognized in its own right as the tensor tympani motor nucleus of V.

Animals↗

PubMed1985

Morphology of motoneurons in a mixed motor pool of the cat facial nucleus that innervate orbicularis oculis and quadratus labii superioris, stained intracellularly with horseradish peroxidase.

Retrograde tracing with horseradish peroxidase showed that motoneurons to two distinct muscles, the orbicularis oculis and quadratus labii superioris, are intermixed within the dorsolateral subnucleus of the cat facial nucleus. Intracellular electrodes were used to identify and fill the motoneurons of the dorsolateral subnucleus with horseradish peroxidase. Soma diameters averaged 55 micron. The average number of primary dendrites was 11.6. The area covered by the dendritic trees varied in shape according to the position of the soma within the subnucleus. Axon hillocks were seen arising in many orientations, bearing no apparent relation to subsequent axonal path, cell position within the nucleus or somatic geometry. Motoneurons to the two muscles appeared to be indistinguishable on the basis of morphology, even though they appear to be functionally independent. Their functional differences are not reflected in any measure of somadendritic shape studied here. Of further interest is the variability in shape associated with the neurons's position within the subnucleus. We conclude that many details of dendritic shape do not reflect specific physiological function.

Animals↗

PubMed1985

Assessment of plaque by image analysis.

The uneven distribution and pattern of staining, revealed on root-planed, periodontally-involved root surfaces by the application of a plaque-disclosing solution, precludes the use of conventional plaque scoring indices or other methods of assessment based on planimetric and gravimetric techniques. A method has been developed and evaluated to quantify stained areas using image analysis. The method is reproducible, with an error factor of 1.32%, and represents a comparatively simple, yet effective technique for quantifying plaque on irregular root surface areas.

Dental Plaque↗

PubMed1985

Action of the efferent vestibular system on primary afferents in the toadfish, Opsanus tau.

Spinalized toadfish were held in a lucite chamber and perfused through the mouth with running seawater. Primary vestibular afferents and vestibular efferent axons and somas were studied with glass microelectrodes. Vestibular semicircular canal afferent and efferent axons were visually identified and penetrated with glass microelectrodes. Afferents responded to pulses of injected current with trains of action potentials, whereas efferents responded with only a single spike. This differential response to injected current served to further distinguish these two classes of nerve fibers that share the same canal nerve for part of their course. When current pulses were injected into efferent somadendritic recording sites, cells responded with trains of action potentials similar to those seen in other central nervous system neurons. Semicircular canal afferents were spontaneously active and occupied the same spectrum of regularity as vestibular afferents recorded in other species. Behavioral arousal evoked by lightly touching the fish on the snout or over the eye resembled spontaneous arousal observed in the field and consisted of eye withdrawal, fin erection, and attempted swimming. Efferent vestibular neurons were spontaneously active and increased their frequency of discharge when the fish was behaviorally aroused. Most efferents were briskly activated by behavioral arousal, but the time constant of the decay of their responses was variable ranging from 100 to 600 ms. Not only touch, but multimodal stimuli were capable of increasing the level of spontaneous activity of efferent vestibular neurons. The shortest latency to behavioral activation was 160 ms. Vestibular primary afferents also manifested increase in neuronal activity with behavioral activation. Irregularly discharging afferents were much more responsive than regularly discharging afferents. One rare case of transient inhibition in a regularly discharging afferent is illustrated. Severing the efferent vestibular nerve blocked behavioral activation in vestibular primary afferents. Electrical stimulation of the efferent vestibular nerve produced excitatory postsynaptic potentials (EPSPs) at latencies within the monosynaptic range in vestibular primary afferents. These monosynaptic EPSPs could produce action potentials in primary afferents or could sum with subthreshold depolarizations produced by current passed through the microelectrode to initiate impulses.(ABSTRACT TRUNCATED AT 400 WORDS)

Acoustic Stimulation↗

PubMed1985

The vestibuloocular reflex of the adult flatfish. I. Oculomotor organization.

The flatfish species constitute a natural paradigm for investigating adaptive changes in the vertebrate central nervous system. During metamorphosis all species of flatfish experience a 90 degree change in orientation between their vestibular and extraocular coordinate axes. As a result, the optic axes of both eyes maintain their orientation with respect to earth horizontal, but the horizontal semicircular canals become oriented vertically. Since the flatfish propels its body with the same swimming movements when referenced to the body as a normal fish, the horizontal canals are exposed to identical accelerations, but in the flatfish these accelerations occur in a vertical plane. The appropriate compensatory eye movements are simultaneous rotations of both eyes forward or backward (i.e., parallel), in contrast to the symmetric eye movements in upright fish (i.e., one eye moves forward, the other backward). Therefore, changes in the extraocular muscle arrangement and/or the neuronal connectivity are required. This study describes the peripheral and central oculomotor organization in the adult winter flounder, Pseudopleuronectes americanus. At the level of the peripheral oculomotor apparatus, the sizes of the horizontal extraocular muscles (lateral and medial rectus) were considerably smaller than those of the vertical eye muscles, as quantified by fiber counts and area measurements of cross sections of individual muscles. However, the spatial orientations and the kinematic characteristics of all six extraocular muscles were not different from those described in comparable lateral-eyed animals. There were no detectable asymmetries between the left and the right eye. Central oculomotor organization was investigated by extracellular horseradish peroxidase injections into individual eye muscles. Commonly described distributions of extraocular motor neurons in the oculomotor, trochlear, and abducens nuclei were found. These motor neuron pools consisted of two contralateral (superior rectus and superior oblique) and four ipsilateral populations (inferior oblique, inferior rectus, medial rectus, and lateral rectus). The labeled cells formed distinct motor neuron populations, which overlapped little. As expected, the numbers of labeled motoneurons differed in horizontal and vertical eye movers. The numerical difference was especially prominent in comparing the abducens nucleus with one of the vertical recti subdivisions. Nevertheless, there was bilateral symmetry between the motoneurons projecting to the left and right eyes.(ABSTRACT TRUNCATED AT 400 WORDS)

Abducens Nerve↗

PubMed1985

The vestibuloocular reflex of the adult flatfish. II. Vestibulooculomotor connectivity.

The peripheral and central oculomotor organization of the adult flatfish presents no morphological substrates that suffice to explain adaptive changes in its vestibuloocular reflex system. The necessity for an adaptation occurs because of a 90 degrees displacement of the vestibular with respect to the extraocular coordinate axes during metamorphosis. Since a reorganization of vestibuloocular pathways must be hypothesized (12), the location and termination of electrophysiologically identified secondary vestibular neurons with focus on the horizontal canal system was studied with the intracellular horseradish peroxidase method in adult winter flounders. Pseudopleuronectes americanus. The oculomotor target sites of vertical canal related neurons were similar to those described in mammals. Presumed excitatory anterior canal neurons bifurcated after the main axon had crossed the midline. The descending branch headed toward the spinal cord. The ascending branch reached the oculomotor nucleus via the contralateral medial longitudinal fasciculus and terminated in the superior rectus and inferior oblique subdivisions. Presumed inhibitory posterior canal neurons ascended ipsilaterally in the medial longitudinal fasciculus and terminated mainly in the superior rectus and inferior oblique subdivisions. Horizontal canal neurons exhibited characteristics distinctly different from mammalian ones. Two types of second-order neurons were observed. In the first case, cell bodies were located in the anterior portion of the vestibular nuclear complex. After crossing the midline, the axon ascended in the contralateral medial longitudinal fasciculus. Major termination sites were found in the inferior oblique and superior rectus subdivisions of the oculomotor nucleus. Axonal branches then recrossed the midline and terminated in identical locations on the ipsilateral side. In the second case, cell bodies were located in the descending vestibular nucleus. Their axons crossed the midline and also ascended in the contralateral medial longitudinal fasciculus. Major termination sites were in the trochlear nucleus and in the inferior rectus subdivision of the oculomotor nucleus. As in the first case, axonal branches also recrossed the midline and terminated in identical motoneuron pools on the ipsilateral side. The above target sites were exactly those expected to be used in a reciprocal excitatory-inhibitory fashion during compensatory eye movements. Head-down movement would be excitatory for the lower horizontal canal producing contractions of both superior recti and inferior obliques as well as relaxation of the antagonistic inferior recti and superior obliques.(ABSTRACT TRUNCATED AT 400 WORDS)

Adaptation, Biological↗

PubMed1985

Oxidation of oxalate and polyamines by rat peroxisomes.

During renal failure, polyamines and oxalate levels are elevated in the serum and the glomerular filtrate and are dumped by the kidney. Both of these compounds can be catabolized by oxidative reactions. We have, therefore, investigated the intracellular distribution of oxalate oxidase and of a polyamine oxidase in normal female rat kidney and liver. Polyamine oxidase was demonstrable, using spermidine as substrate in the cerous peroxyhydrate procedure of Briggs et al., in peroxisomes of kidney tubule cells and of hepatocytes. Oxalate oxidase could not be studied with this technique due to precipitation of cerium oxalate in the incubation medium. To demonstrate oxalate oxidase, and to confirm the polyamine oxidase localization, we incubated aldehyde-fixed tissue in a diaminobenzidine medium at pH 8, following the approach of Veenhuis et al., in which oxidases are demonstrated by virtue of their production of H2O2, which then serves as a substrate for endogenous catalase. Using oxalate or spermidine as substrate with this approach, we found reaction product in typical renal peroxisomes; we also found reaction product, with the polyamine substrate, in hepatocyte peroxisomes. To strengthen the conclusion that the oxidases themselves are present in peroxisomes, we used a light microscopic method, based on the tetrazolium procedures of Allen and Beard to demonstrate polyamine and oxalate oxidase activities in bodies with the distribution of renal peroxisomes.

Animals↗